Programs & Examples On #Logged

react hooks useEffect() cleanup for only componentWillUnmount?

function LegoComponent() {

  const [lego, setLegos] = React.useState([])

  React.useEffect(() => {
    let isSubscribed = true
    fetchLegos().then( legos=> {
      if (isSubscribed) {
    return () => isSubscribed = false
  }, []);

  return (
    {> <li>{lego}</li>)}

In the code above, the fetchLegos function returns a promise. We can “cancel” the promise by having a conditional in the scope of useEffect, preventing the app from setting state after the component has unmounted.

Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.

How to post query parameters with Axios?

axios signature for post is[, data[, config]]). So you want to send params object within the third argument:

.post(`/mails/users/sendVerificationMail`, null, { params: {
.then(response => response.status)
.catch(err => console.warn(err));

This will POST an empty body with the two query params:

POST http://localhost:8000/api/mails/users/sendVerificationMail?

Vuex - passing multiple parameters to mutation

Mutations expect two arguments: state and payload, where the current state of the store is passed by Vuex itself as the first argument and the second argument holds any parameters you need to pass.

The easiest way to pass a number of parameters is to destruct them:

mutations: {
    authenticate(state, { token, expiration }) {
        localStorage.setItem('token', token);
        localStorage.setItem('expiration', expiration);

Then later on in your actions you can simply

store.commit('authenticate', {

How to Update a Component without refreshing full page - Angular

One of many solutions is to create an @Injectable() class which holds data that you want to show in the header. Other components can also access this class and alter this data, effectively changing the header.

Another option is to set up @Input() variables and @Output() EventEmitters which you can use to alter the header data.

Edit Examples as you requested:

export class HeaderService {
    private _data;
    set data(value) {
        this._data = value;
    get data() {
        return this._data;

in other component:

constructor(private headerService: HeaderService) {}

// Somewhere = 'abc';

in header component:

let headerData;

constructor(private headerService: HeaderService) {
    this.headerData =;

I haven't actually tried this. If the get/set doesn't work you can change it to use a Subject();

// Simple Subject() example:
let subject = new Subject();
this.subject.subscribe(response => {
  console.log(response); // Logs 'hello'

If condition inside of map() React

You are using both ternary operator and if condition, use any one.

By ternary operator:

.map(id => {
    return this.props.schema.collectionName.length < 0 ?

By if condition:

.map(id => {
    if(this.props.schema.collectionName.length < 0)
        return <Expandable>
    return <h1>hejsan</h1>

How to solve "sign_and_send_pubkey: signing failed: agent refused operation"?

I need to share, as I spent too much time looking for a solution

Here was the solution :

I was using this command :

ssh-keygen -o -t rsa -b 4096 -C "[email protected]"

gnome-keyring does not support the generated key.

Removing the -o argument solved the problem.

React navigation goBack() and update parent state

I would also use navigation.navigate. If someone has the same problem and also uses nested navigators, this is how it would work:

onPress={() =>
        navigation.navigate('MyStackScreen', {
          // Passing params to NESTED navigator screen:
          screen: 'goToScreenA',
          params: { Data: data.item },

How to print a Groovy variable in Jenkins?

The following code worked for me:

echo userInput

How can I manually set an Angular form field as invalid?

Adding to Julia Passynkova's answer

To set validation error in component:

formData.form.controls['email'].setErrors({'incorrect': true});

To unset validation error in component:


Be careful with unsetting the errors using null as this will overwrite all errors. If you want to keep some around you may have to check for the existence of other errors first:

if (isIncorrectOnlyError){

Hibernate Error executing DDL via JDBC Statement

Dialects are removed in recent SQL so use

  <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL57Dialect"/>

How to implement authenticated routes in React Router 4?

const Root = ({ session }) => {
  const isLoggedIn = session && session.getCurrentUser
  return (
      {!isLoggedIn ? (
          <Route path="/signin" component={<Signin />} />
          <Redirect to="/signin" />
      ) : (
          <Route path="/" exact component={Home} />
          <Route path="/about" component={About} />
          <Route path="/something-else" component={SomethingElse} />
          <Redirect to="/" />

Attach Authorization header for all axios requests

The point is to set the token on the interceptors for each request

import axios from "axios";
const httpClient = axios.create({
    baseURL: "http://youradress",
    // baseURL: process.env.APP_API_BASE_URL,

httpClient.interceptors.request.use(function (config) {
    const token = localStorage.getItem('token');
    config.headers.Authorization =  token ? `Bearer ${token}` : '';
    return config;

Tomcat: java.lang.IllegalArgumentException: Invalid character found in method name. HTTP method names must be tokens

This exception can occur when you try to execute HTTPS request from client on endpoint which isn't HTTPS enabled. Client will encrypt request data when server is expecting raw data.

Composer: file_put_contents(./composer.json): failed to open stream: Permission denied

In my case I don't have issues with ~/.composer.
So being inside Laravel app root folder, I did sudo chown -R $USER composer.lock and it was helpful.

Reload child component when variables on parent component changes. Angular2

In case, when we have no control over child component, like a 3rd party library component.

We can use *ngIf and setTimeout to reset the child component from parent without making any change in child component.



show:boolean = true

resetChildForm(){ = false;

   setTimeout(() => { = true
    }, 100);

Angular 2 Checkbox Two Way Data Binding

In Angular p-checkbox,

Use all attributes of p-checkbox

<p-checkbox name="checkbox" value="isAC" 
    label="All Colors" [(ngModel)]="selectedAllColors" 
    [ngModelOptions]="{standalone: true}" id="al" 

And more importantly, don't forget to include [ngModelOptions]="{standalone: true} as well as it SAVED MY DAY.

ASP.NET Core Identity - get current user

private readonly UserManager<AppUser> _userManager;

 public AccountsController(UserManager<AppUser> userManager)
            _userManager = userManager;

[Authorize(Policy = "ApiUser")]
[HttpGet("api/accounts/GetProfile", Name = "GetProfile")]
public async Task<IActionResult> GetProfile()
   var userId = ((ClaimsIdentity)User.Identity).FindFirst("Id").Value;
   var user = await _userManager.FindByIdAsync(userId);

   ProfileUpdateModel model = new ProfileUpdateModel();
   model.Email = user.Email;
   model.FirstName = user.FirstName;
   model.LastName = user.LastName;
   model.PhoneNumber = user.PhoneNumber;

   return new OkObjectResult(model);

ASP.NET Core 1.0 on IIS error 502.5

I changed profile options to this and it's working!!!

enter image description here

Maybe you should change this two options:

  1. Deployment Mode
  2. Target Runtime

How do I detect if a user is already logged in Firebase?

First import the following

import Firebase
import FirebaseAuth


    // Check if logged in
    if (Auth.auth().currentUser != null) {
      // User is logged in   
      // User is not logged in

Firebase FCM force onTokenRefresh() to be called

OnSuccessListener<String>() {
    public void onSuccess(String newToken) {

Firebase cloud messaging notification not received by device

In my case, I just turn on WIFI and mobile data in the emulator and it works like a charm. cause I can't send comments, post a reply. Good luck

Android Studio: /dev/kvm device permission denied

I got this error after updating my ubuntu to 18.04.1. I just download new system image for emulator or you can say that download new emulator and it is worked for me.

How to get current value of RxJS Subject or Observable?

The only way you should be getting values "out of" an Observable/Subject is with subscribe!

If you're using getValue() you're doing something imperative in declarative paradigm. It's there as an escape hatch, but 99.9% of the time you should NOT use getValue(). There are a few interesting things that getValue() will do: It will throw an error if the subject has been unsubscribed, it will prevent you from getting a value if the subject is dead because it's errored, etc. But, again, it's there as an escape hatch for rare circumstances.

There are several ways of getting the latest value from a Subject or Observable in a "Rx-y" way:

  1. Using BehaviorSubject: But actually subscribing to it. When you first subscribe to BehaviorSubject it will synchronously send the previous value it received or was initialized with.
  2. Using a ReplaySubject(N): This will cache N values and replay them to new subscribers.
  3. A.withLatestFrom(B): Use this operator to get the most recent value from observable B when observable A emits. Will give you both values in an array [a, b].
  4. A.combineLatest(B): Use this operator to get the most recent values from A and B every time either A or B emits. Will give you both values in an array.
  5. shareReplay(): Makes an Observable multicast through a ReplaySubject, but allows you to retry the observable on error. (Basically it gives you that promise-y caching behavior).
  6. publishReplay(), publishBehavior(initialValue), multicast(subject: BehaviorSubject | ReplaySubject), etc: Other operators that leverage BehaviorSubject and ReplaySubject. Different flavors of the same thing, they basically multicast the source observable by funneling all notifications through a subject. You need to call connect() to subscribe to the source with the subject.

How to redirect to another page in node.js

The If else statement needs to be wrapped in a .get or a .post to redirect. Such as'/login', function(req, res) {


app.get('/login', function(req, res) {

ReactJS - Add custom event listener to component

If you need to handle DOM events not already provided by React you have to add DOM listeners after the component is mounted:

Update: Between React 13, 14, and 15 changes were made to the API that affect my answer. Below is the latest way using React 15 and ES7. See answer history for older versions.

class MovieItem extends React.Component {

  componentDidMount() {
    // When the component is mounted, add your DOM listener to the "nv" elem.
    // (The "nv" elem is assigned in the render function.)
    this.nv.addEventListener("nv-enter", this.handleNvEnter);

  componentWillUnmount() {
    // Make sure to remove the DOM listener when the component is unmounted.
    this.nv.removeEventListener("nv-enter", this.handleNvEnter);

  // Use a class arrow function (ES7) for the handler. In ES6 you could bind()
  // a handler in the constructor.
  handleNvEnter = (event) => {
    console.log("Nv Enter:", event);

  render() {
    // Here we render a single <div> and toggle the "aria-nv-el-current" attribute
    // using the attribute spread operator. This way only a single <div>
    // is ever mounted and we don't have to worry about adding/removing
    // a DOM listener every time the current index changes. The attrs 
    // are "spread" onto the <div> in the render function: {...attrs}
    const attrs = this.props.index === 0 ? {"aria-nv-el-current": true} : {};

    // Finally, render the div using a "ref" callback which assigns the mounted 
    // elem to a class property "nv" used to add the DOM listener to.
    return (
      <div ref={elem => this.nv = elem} aria-nv-el {...attrs} className="menu_item nv-default">


Example on

How to set default values for Angular 2 component properties?

That is interesting subject. You can play around with two lifecycle hooks to figure out how it works: ngOnChanges and ngOnInit.

Basically when you set default value to Input that's mean it will be used only in case there will be no value coming on that component. And the interesting part it will be changed before component will be initialized.

Let's say we have such components with two lifecycle hooks and one property coming from input.

  selector: 'cmp',
export class Login implements OnChanges, OnInit {
  @Input() property: string = 'default';

  ngOnChanges(changes) {

  ngOnInit() {


Situation 1

Component included in html without defined property value

As result we will see in console: Init default

That's mean onChange was not triggered. Init was triggered and property value is default as expected.

Situation 2

Component included in html with setted property <cmp [property]="'new value'"></cmp>

As result we will see in console:

Changed new value Object {}

Init new value

And this one is interesting. Firstly was triggered onChange hook, which setted property to new value, and previous value was empty object! And only after that onInit hook was triggered with new value of property.

How to know if docker is already logged in to a docker registry server

The docker cli credential scheme is unsurprisingly uncomplicated, just take a look:

cat ~/.docker/config.json

  "auths": {
    "": {},
    "": {}

This exists on Windows (use Get-Content ~\.docker\config.json) and you can also poke around the credential tool which also lists the username ... and I think you can even retrieve the password

. "C:\Program Files\Docker\Docker\resources\bin\docker-credential-wincred.exe" list


Laravel 5.2 Missing required parameters for [Route: user.profile] [URI: user/{nickname}/profile]

My Solution in laravel 5.2

{{ Form::open(['route' => ['votes.submit', $video->id],  'method' => 'POST']) }}
    <button type="submit" class="btn btn-primary">
        <span class="glyphicon glyphicon-thumbs-up"></span> Votar
{{ Form::close() }}

My Routes File (under middleware)

Route::post('votar/{id}', [
    'as' => 'votes.submit',
    'uses' => 'VotesController@submit'

Route::delete('votar/{id}', [
    'as' => 'votes.destroy',
    'uses' => 'VotesController@destroy'

How to get current route in react-router 2.0.0-rc5

You can get the current route using

const currentRoute = this.props.routes[this.props.routes.length - 1];

...which gives you access to the props from the lowest-level active <Route ...> component.


<Route path="childpath" component={ChildComponent} />

currentRoute.path returns 'childpath' and currentRoute.component returns function _class() { ... }.

Can't run Curl command inside my Docker Container

If you are using an Alpine based image, you have to

... \
apk add --no-cache curl \
curl ...

How to fix the error; 'Error: Bootstrap tooltips require Tether ('

I recommend following the instructions in the Bootstrap 4 documentation:

Copy-paste the stylesheet <link> into your <head> before all other stylesheets to load our CSS.

<link rel="stylesheet" href="" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">

Add our JavaScript plugins, jQuery, and Tether near the end of your pages, right before the closing tag. Be sure to place jQuery and Tether first, as our code depends on them. While we use jQuery’s slim build in our docs, the full version is also supported.

<script src="" integrity="sha384-A7FZj7v+d/sdmMqp/nOQwliLvUsJfDHW+k9Omg/a/EheAdgtzNs3hpfag6Ed950n" crossorigin="anonymous"></script>
<script src="" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script>
<script src="" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>

Angular - Set headers for every request

Although I'm answering this very late but if anyone is seeking an easier solution.

We can use angular2-jwt. angular2-jwt is useful automatically attaching a JSON Web Token (JWT) as an Authorization header when making HTTP requests from an Angular 2 app.

We can set global headers with advanced configuration option

export function authHttpServiceFactory(http: Http, options: RequestOptions) {
  return new AuthHttp(new AuthConfig({
    tokenName: 'token',
        tokenGetter: (() => sessionStorage.getItem('token')),
        globalHeaders: [{'Content-Type':'application/json'}],
    }), http, options);

And sending per request token like

    getThing() {
  let myHeader = new Headers();
  myHeader.append('Content-Type', 'application/json');

  this.authHttp.get('', { headers: myHeader })
      data => this.thing = data,
      err => console.log(error),
      () => console.log('Request Complete')

  // Pass it after the body in a POST request'', 'post body', { headers: myHeader })
      data => this.thing = data,
      err => console.log(error),
      () => console.log('Request Complete')

Angular 2 - How to navigate to another route using this.router.parent.navigate('/about')?

Absolute path routing

There are 2 methods for navigation, .navigate() and .navigateByUrl()

You can use the method .navigateByUrl() for absolute path routing:

import {Router} from '@angular/router';

constructor(private router: Router) {}

navigateToLogin() {

You put the absolute path to the URL of the component you want to navigate to.

Note: Always specify the complete absolute path when calling router's navigateByUrl method. Absolute paths must start with a leading /

// Absolute route - Goes up to root level    

// Absolute route - Goes up to root level with route params   

Relative path routing

If you want to use relative path routing, use the .navigate() method.

NOTE: It's a little unintuitive how the routing works, particularly parent, sibling, and child routes:

// Parent route - Goes up one level 
// (notice the how it seems like you're going up 2 levels)
this.router.navigate(['../../parent'], { relativeTo: this.route });

// Sibling route - Stays at the current level and moves laterally, 
// (looks like up to parent then down to sibling)
this.router.navigate(['../sibling'], { relativeTo: this.route });

// Child route - Moves down one level
this.router.navigate(['./child'], { relativeTo: this.route });

// Moves laterally, and also add route parameters
// if you are at the root and = 15, will result in '/sibling/15'
this.router.navigate(['../sibling',], { relativeTo: this.route });

// Moves laterally, and also add multiple route parameters
// will result in '/sibling;id=15;foo=foo'. 
// Note: this does not produce query string URL notation with ? and & ... instead it
// produces a matrix URL notation, an alternative way to pass parameters in a URL.
this.router.navigate(['../sibling', { id:, foo: 'foo' }], { relativeTo: this.route });

Or if you just need to navigate within the current route path, but to a different route parameter:

// If has a value of '15'
// This will take you from `/hero` to `/hero/15`
this.router.navigate([], { relativeTo: this.route });

Link parameters array

A link parameters array holds the following ingredients for router navigation:

  • The path of the route to the destination component. ['/hero']
  • Required and optional route parameters that go into the route URL. ['/hero',] or ['/hero', { id:, foo: baa }]

Directory-like syntax

The router supports directory-like syntax in a link parameters list to help guide route name lookup:

./ or no leading slash is relative to the current level.

../ to go up one level in the route path.

You can combine relative navigation syntax with an ancestor path. If you must navigate to a sibling route, you could use the ../<sibling> convention to go up one level, then over and down the sibling route path.

Important notes about relative nagivation

To navigate a relative path with the Router.navigate method, you must supply the ActivatedRoute to give the router knowledge of where you are in the current route tree.

After the link parameters array, add an object with a relativeTo property set to the ActivatedRoute. The router then calculates the target URL based on the active route's location.

From official Angular Router Documentation

How to detect a route change in Angular?

Angular 8. Check whether the current route is the base route.

  baseroute: boolean;
    private router: Router,
  ) { any) => {
      if (val.url == "/") {
        this.baseroute = true;
      } else {
        this.baseroute = false;

CORS with spring-boot and angularjs not working

Just Make a single class like, everything will be fine with this:

        public class MyCorsConfig implements Filter {

            public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
                final HttpServletResponse response = (HttpServletResponse) res;
                response.setHeader("Access-Control-Allow-Origin", "*");
                response.setHeader("Access-Control-Allow-Methods", "POST, PUT, GET, OPTIONS, DELETE");
                response.setHeader("Access-Control-Allow-Headers", "Authorization, Content-Type, enctype");
                response.setHeader("Access-Control-Max-Age", "3600");
                if ( req).getMethod())) {
                } else {
                    chain.doFilter(req, res);

            public void destroy() {

            public void init(FilterConfig config) throws ServletException {

How do I enable logging for Spring Security?

Spring security logging for webflux reactive apps is now available starting with version 5.4.0-M2 (as mentionned by @bzhu in comment How do I enable logging for Spring Security?)

Until this gets into a GA release, here is how to get this milestone release in gradle

repositories {
    if (!version.endsWith('RELEASE')) {
        maven { url "" }

// Force earlier milestone release to get securing logging preview
dependencyManagement {
    imports {
        mavenBom "${springCloudVersion}"


How to get the current logged in user Id in ASP.NET Core

Make sure that you have enable windows authentication. If you have anonymous authentication enabled you may be getting a null string.

command/usr/bin/codesign failed with exit code 1- code sign error

I had the same error on January 2018 with xcode 8.2.1

Before I try to open xcode I couldn't because the system was updating. I tried sometime later and it let me working on it, and then I got the same error.

I followed most of the solutions described in this article but they didn't work for me.

Then I remembered the message about the system updating and I tried to reboot the machine.

And that did the magic. It worked for me.

recyclerview No adapter attached; skipping layout

I had the same error I fixed it doing this if you are waiting for data like me using retrofit or something like that

Put before Oncreate

private ArtistArrayAdapter adapter;
private RecyclerView recyclerView;

Put them in your Oncreate

 recyclerView = (RecyclerView) findViewById(;
 recyclerView.setLayoutManager(new LinearLayoutManager(this));
 adapter = new ArtistArrayAdapter( artists , R.layout.list_item ,getApplicationContext());

When you receive data put

adapter = new ArtistArrayAdapter( artists , R.layout.list_item ,getApplicationContext());

Now go in your ArtistArrayAdapter class and do this what it will do is if your array is empty or is null it will make GetItemCount return 0 if not it will make it the size of artists array

public int getItemCount() {

    int a ;

    if(artists != null && !artists.isEmpty()) {

        a = artists.size();
    else {

        a = 0;


   return a;

Fatal error: Call to a member function prepare() on null

It looks like your $pdo variable is not initialized. I can't see in the code you've uploaded where you are initializing it.

Make sure you create a new PDO object in the global scope before calling the class methods. (You should declare it in the global scope because of how you implemented the methods inside the Category class).

$pdo = new PDO('mysql:host=localhost;dbname=test', $user, $pass);

android.content.Context.getPackageName()' on a null object reference

android API level 23.



instead of


getActivity() gives the parent Activity, a Context object

Here You can use


instead of

getActivity() / getApplicationContext()

How to extend available properties of User.Identity

Dhaust gives a good way to add the property to the ApplicationUser class. Looking at the OP code it appears they may have done this or were on track to do that. The question asks

How can I retrieve the OrganizationId property of the currently logged in user from within a controller? However, OrganizationId is not a property available in User.Identity. Do I need to extend User.Identity to include the OrganizationId property?

Pawel gives a way to add an extension method that requires using statements or adding the namespace to the web.config file.

However, the question asks if you "need to" extend User.Identity to include the new property. There is an alternative way to access the property without extending User.Identity. If you followed Dhaust method you can then use the following code in your controller to access the new property.

ApplicationDbContext db = new ApplicationDbContext();
var manager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(db));
var currentUser = manager.FindById(User.Identity.GetUserId());
var myNewProperty = currentUser.OrganizationId;

Access denied for user 'root'@'localhost' (using password: YES) after new installation on Ubuntu

Try the command

sudo mysql_secure_installation

press enter and assign a new password for root in mysql/mariadb.

If you get an error like

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock'

enable the service with

service mysql start

now if you re-enter with

mysql -u root -p

if you follow the problem enter with sudo su and mysql -u root -p now apply permissions to root

GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY '<password>';

this fixed my problem in MariaDB.

Good luck

IOS - How to segue programmatically using swift

You can use NSNotification

Add a post method in your custom class:

NSNotificationCenter.defaultCenter().postNotificationName("NotificationIdentifier", object: nil)

Add an observer in your ViewController:

NSNotificationCenter.defaultCenter().addObserver(self, selector: "methodOFReceivedNotication:", name:"NotificationIdentifier", object: nil)

Add function in you ViewController:

func methodOFReceivedNotication(notification: NSNotification){
    self.performSegueWithIdentifier("yourIdentifierInStoryboard", sender: self)

Virtualbox shared folder permissions

Add yourself to the vboxsf group within the guest VM.

Solution 1

Run sudo adduser $USER vboxsf from terminal.
(On Suse it's sudo usermod --append --groups vboxsf $USER)

To take effect you should log out and then log in, or you may need to reboot.

Solution 2

Edit the file /etc/group (you will need root privileges). Look for the line vboxsf:x:999 and add at the end :yourusername -- use this solution if you don't have sudo.

To take effect you should log out and then log in, or you may need to reboot.

React Checkbox not sending onChange

In case someone is looking for a universal event handler the following code can be used more or less (assuming that name property is set for every input):

    this.handleInputChange = (e) => {
        item[] = === "checkbox" ? :;

Resource u'tokenizers/punkt/english.pickle' not found

For me it got solved by using "nltk:"

Failed loading english.pickle with'nltk:tokenizers/punkt/english.pickle')

Command failed due to signal: Segmentation fault: 11

For me this was caused by some of my code. The detailed compiler output in XCode actually pin-pointed the method where it was crashing.

I then commented out all the code in the method, made it return nil, and it did compile. I then re-implemented the method using different and much simpler code, and it worked.

I filed a bug report with Apple. This is the - admittedly somewhat crazy - code that caused the crash in XCode 7 / Swift 2.0.

  func numberAndTitleFromDirectoryName(dirName: String) -> (Int, String)? {
    let components = dirName.characters.split(maxSplit: 1, allowEmptySlices: false) { $0 == " " }.map { String($0) }.map { String($0) }
    if let number = components.first?.toInt() {
        if let title = components.last {
            return (number, title)
    return nil;

I guess I got a little over-excited using the map function there... The new version is a lot simpler and also more human comprehensible. Still the compiler shouldn't crash. At worst it should show some errors. The code as is worked in Swift 1.x

The view didn't return an HttpResponse object. It returned None instead

Because the view must return render, not just call it. Change the last line to

return render(request, 'auth_lifecycle/user_profile.html',

How to redraw DataTable with new data

datatable.rows().iterator('row', function ( context, index ) {
    var data = this.row(index).data();
    var row = $(this.row(index).node());
    data[0] = 'new data';

How to use sudo inside a docker container?

There is no answer on how to do this on CentOS. On Centos, you can add following to Dockerfile

RUN echo "user ALL=(root) NOPASSWD:ALL" > /etc/sudoers.d/user && \
    chmod 0440 /etc/sudoers.d/user

Trusting all certificates with okHttp

You should never look to override certificate validation in code! If you need to do testing, use an internal/test CA and install the CA root certificate on the device or emulator. You can use BurpSuite or Charles Proxy if you don't know how to setup a CA.

How to turn off INFO logging in Spark?

Just execute this command in the spark directory:

cp conf/ conf/


# Set everything to be logged to the console
log4j.rootCategory=INFO, console
log4j.appender.console.layout.ConversionPattern=%d{yy/MM/dd HH:mm:ss} %p %c{1}: %m%n

# Settings to quiet third party logs that are too verbose$exprTyper=INFO$SparkILoopInterpreter=INFO

Replace at the first line:

log4j.rootCategory=INFO, console


log4j.rootCategory=WARN, console

Save and restart your shell. It works for me for Spark 1.1.0 and Spark 1.5.1 on OS X.

Android Studio Google JAR file causing GC overhead limit exceeded error

In my case, to increase the heap-size looks like this:

Using Android Studio 1.1.0

android {
    dexOptions {
        incremental true
        javaMaxHeapSize "2048M"

Put the above code in your Build.gradle file.

Why am I getting a "401 Unauthorized" error in Maven?

I had the same error. I tried and rechecked everything. I was so focused in the Stack trace that I didn't read the last lines of the build before the Reactor summary and the stack trace:

[DEBUG] Using connector AetherRepositoryConnector with priority 3.4028235E38 for http://www:8081/nexus/content/repositories/snapshots/
[INFO] Downloading: http://www:8081/nexus/content/repositories/snapshots/com/wdsuite/com.wdsuite.server.product/1.0.0-SNAPSHOT/maven-metadata.xml
[DEBUG] Could not find metadata in nexus (http://www:8081/nexus/content/repositories/snapshots/)
[DEBUG] Writing tracking file /home/me/.m2/repository/com/group/project/version-SNAPSHOT/
[INFO] Uploading: http://www:8081/nexus/content/repositories/snapshots/com/
[INFO] Uploading: http://www:8081/nexus/content/repositories/snapshots/com/...-1.0.0-20141118.124526-1.pom
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:

This was the key : "Could not find metadata". Although it said that it was an authentication error actually it got fixed doing a "rebuild metadata" in the nexus repository.

Hope it helps.

Using $window or $location to Redirect in AngularJS

I believe the way to do this is $location.url('/RouteTo/Login');

Edit for Clarity

Say my route for my login view was /Login, I would say $location.url('/Login') to navigate to that route.

For locations outside of the Angular app (i.e. no route defined), plain old JavaScript will serve:

window.location = ""

TypeError: Cannot read property 'then' of undefined

You need to return your promise to the calling function.

    var cUid=sessionService.get('uid');
    alert("in loginServce, cuid is "+cUid);
    var $checkSessionServer=$'data/check_session.php?cUid='+cUid);
        alert("session check returned!");
        console.log("checkSessionServer is "+$checkSessionServer);
    return $checkSessionServer; // <-- return your promise to the calling function

Filezilla FTP Server Fails to Retrieve Directory Listing

I also had the problem after upgrading to 3.10. I had versoin 3.6.02 hanging around and installed that. Problem solved.

Click a button programmatically - JS

The other answers here rely on the user making an initial click (on the image). This is fine for the specifics of the OP detail but not necessarily the question title.

There is an answer here explaining how to do it by firing a click event on the button ( or any element ).

creating custom tableview cells in swift

This is for who are working custom cell with .xib

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell{

    let identifier = "Custom"

    var cell: CustomCell! = tableView.dequeueReusableCellWithIdentifier(identifier) as? CustomCel  

      if cell == nil {
            tableView.registerNib(UINib(nibName: "CustomCell", bundle: nil), forCellReuseIdentifier: identifier)
           cell =tableView.dequeueReusableCellWithIdentifier(identifier) as? CustomCell
        }return cell}

SSIS Excel Connection Manager failed to Connect to the Source

After researching everywhere finally i have found out temporary solution. Because i have try all the solution installing access drivers but still i am facing same issues.

For excel source, Before this step you need to change the setting. Save excel file as 2010 format.xlsx

Also set Project Configuration Properties for Debugging Run64BitRuntime = False

  1. Drag and drop the excel source
  2. Double click on the excel source and connect excel. Any way you will get an same error no table or view cannot load....
  3. Click ok
  4. Right click on excel source, click on show advanced edit.
  5. In that click on component properties.
  6. You can see openrowset. In that right side you need to enter you excel sheet name example: if in excel sheet1 then you need to enter sheet1$. I.e end with dollar symbol. And click ok.
  7. Now you can do other works connecting to destination.

I am using visual studio 2017, sql server 2017, office 2016, and Microsoft access database 2010 engine 32bit. Os windows 10 64 bit.

This is temporary solution. Because many peoples are searching for this type of question. Finally I figured out and this solution is not available in any of the website.

Get ALL User Friends Using Facebook Graph API - Android

In v2.0 of the Graph API, calling /me/friends returns the person's friends who also use the app.

In addition, in v2.0, you must request the user_friends permission from each user. user_friends is no longer included by default in every login. Each user must grant the user_friends permission in order to appear in the response to /me/friends. See the Facebook upgrade guide for more detailed information, or review the summary below.

The /me/friendlists endpoint and user_friendlists permission are not what you're after. This endpoint does not return the users friends - its lets you access the lists a person has made to organize their friends. It does not return the friends in each of these lists. This API and permission is useful to allow you to render a custom privacy selector when giving people the opportunity to publish back to Facebook.

If you want to access a list of non-app-using friends, there are two options:

  1. If you want to let your people tag their friends in stories that they publish to Facebook using your App, you can use the /me/taggable_friends API. Use of this endpoint requires review by Facebook and should only be used for the case where you're rendering a list of friends in order to let the user tag them in a post.

  2. If your App is a Game AND your Game supports Facebook Canvas, you can use the /me/invitable_friends endpoint in order to render a custom invite dialog, then pass the tokens returned by this API to the standard Requests Dialog.

In other cases, apps are no longer able to retrieve the full list of a user's friends (only those friends who have specifically authorized your app using the user_friends permission).

For apps wanting allow people to invite friends to use an app, you can still use the Send Dialog on Web or the new Message Dialog on iOS and Android.

upstream sent too big header while reading response header from upstream

This is still the highest SO-question on Google when searching for this error, so let's bump it.

When getting this error and not wanting to deep-dive into the NGINX settings immediately, you might want to check your outputs to the debug console. In my case I was outputting loads of text to the FirePHP / Chromelogger console, and since this is all sent as a header, it was causing the overflow.

It might not be needed to change the webserver settings if this error is caused by just sending insane amounts of log messages.

Get Current Session Value in JavaScript?

this is how i used ->

<body  onkeypress='myFunction(event)'>

<input type='hidden' id='homepage' value='$_SESSION[homepage]'>

    function myFunction(event){var x = event.which;if(x == 13){var homepage 
    document.getElementById("h1").innerHTML = "<h1> Press <i> ENTER </i> to go back... </h1>";}}

Start redis-server with config file

I think that you should make the reference to your config file

26399:C 16 Jan 08:51:13.413 # Warning: no config file specified, using the default config. In order to specify a config file use ./redis-server /path/to/redis.conf

you can try to start your redis server like

./redis-server /path/to/redis-stable/redis.conf

Powershell script to see currently logged in users (domain and machine) + status (active, idle, away)

If you want to find interactively logged on users, I found a great tip here : (Win32_ComputerSystem did not help me)

$explorerprocesses = @(Get-WmiObject -Query "Select * FROM Win32_Process WHERE Name='explorer.exe'" -ErrorAction SilentlyContinue)
If ($explorerprocesses.Count -eq 0)
    "No explorer process found / Nobody interactively logged on"
    ForEach ($i in $explorerprocesses)
        $Username = $i.GetOwner().User
        $Domain = $i.GetOwner().Domain
        Write-Host "$Domain\$Username logged on since: $($i.ConvertToDateTime($i.CreationDate))"

Ignore fields from Java object dynamically while sending as JSON from Spring MVC

I know I'm a bit late to the party, but I actually ran into this as well a few months back. All of the available solutions weren't very appealing to me (mixins? ugh!), so I ended up creating a new library to make this process cleaner. It's available here if anyone would like to try it out:

The basic usage is pretty simple, you use the JsonView object in your controller methods like so:

import com.monitorjbl.json.JsonView;
import static com.monitorjbl.json.Match.match;

@RequestMapping(method = RequestMethod.GET, value = "/myObject")
public void getMyObjects() {
    //get a list of the objects
    List<MyObject> list = myObjectService.list();

    //exclude expensive field
    JsonView.with(list).onClass(MyObject.class, match().exclude("contains"));

You can also use it outside of Spring:

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import static com.monitorjbl.json.Match.match;

ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.addSerializer(JsonView.class, new JsonViewSerializer());

      .onClass(MyObject.class, match()
      .onClass(MySmallObject.class, match()

How to fix Hibernate LazyInitializationException: failed to lazily initialize a collection of roles, could not initialize proxy - no Session

There are cases where you don't need to put @Transactional annotation to your service method, like integration testing. I was getting this org.hibernate.LazyInitializationException when testing a method that just selects from database, which did not need to be transactional. The entity class I try to load has a lazy fetch relation that caused this

@OneToMany(mappedBy = "parent", fetch = FetchType.LAZY)
private List<Item> items;

so I ended up adding the @Transactional to only to the test method.

public void verifySomethingTestSomething()  {

Get current user id in ASP.NET Identity 2.0

I had the same issue. I am currently using Core 2.2. I solved this problem with the following piece of code.

using Microsoft.AspNetCore.Identity;
var user = await _userManager.FindByEmailAsync(User.Identity.Name);

I hope this will be useful to someone.

Failed to build gem native extension (installing Compass)

you must have gcc,json_pure

i collect some information from several post

sudo gem uninstall sass_x000D_
sudo gem uninstall compass_x000D_
sudo gem update --system_x000D_
gem install json_pure   (if you have already have continued to next step)_x000D_
sudo yum install gcc gcc-c++   (if you have already have continued to next step)_x000D_
sudo gem install sass_x000D_
sudo gem install compass

Hi if ** sudo gem update --system ** not working you got an error in the update then use

sudo gem update --system 2.7.8

Npm Please try using this command again as root/administrator


I ran Command Prompt as Administrator. This helped partially - as I no longer got the error, "Please try using this command again as root/administrator". I was trying to install Cordova. To do it successfully, I also had to do the following:

(1) "npm update node", plus...

(2) I also added the " -g " in the >>npm install cordova<<. In other words, type this: >>npm install -g cordova<<

~~~ FOR WINDOWS 8.1 ~~~


For windows 8.1, I don't have an ACCESSORIES group when I click START > ALL PROGRAMS. But I do have that older -- but trusty and reliable -- START BUTTON and START MENU - thanks to the free Classic Start Menu app. So, with that installed....


1. Type "cmd" in the SEARCH BOX at the bottom of the START menu.  
2. When cmd.exe shows up in the top of the search results, right click it and select RUN AS ADMINISTRATOR.

ALTERNATIVE #2 If you already have a Command Prompt window open and running - and you want to open another one to Run As Administrator:

1. Locate the Command Prompt app icon in the Taskbar (usually along the bottom of you screen unless you have moved it a different dock/location).
2. Right click the app icon.
3. Now, right click "COMMAND PROMPT" and select RUN AS ADMINISTRATOR. 

Hope this helps someone.

How to send data with angularjs $http.delete() request?

A many to many relationship normally has a linking table. Consider this "link" as an entity in its own right and give it a unique id, then send that id in the delete request.

You would have a a REST resource URL like /user/role to handle operations on a user-role "link" entity.

changing the owner of folder in linux

Use chown to change ownership and chmod to change rights.

use the -R option to apply the rights for all files inside of a directory too.

Note that both these commands just work for directories too. The -R option makes them also change the permissions for all files and directories inside of the directory.

For example

sudo chown -R username:group directory

will change ownership (both user and group) of all files and directories inside of directory and directory itself.

sudo chown username:group directory

will only change the permission of the folder directory but will leave the files and folders inside the directory alone.

you need to use sudo to change the ownership from root to yourself.


Note that if you use chown user: file (Note the left-out group), it will use the default group for that user.

Also You can change the group ownership of a file or directory with the command:

chgrp group_name file/directory_name

You must be a member of the group to which you are changing ownership to.

You can find group of file as follows

# ls -l file
-rw-r--r-- 1 root family 0 2012-05-22 20:03 file

# chown sujit:friends file

User 500 is just a normal user. Typically user 500 was the first user on the system, recent changes (to /etc/login.defs) has altered the minimum user id to 1000 in many distributions, so typically 1000 is now the first (non root) user.

What you may be seeing is a system which has been upgraded from the old state to the new state and still has some processes knocking about on uid 500. You can likely change it by first checking if your distro should indeed now use 1000, and if so alter the login.defs file yourself, the renumber the user account in /etc/passwd and chown/chgrp all their files, usually in /home/, then reboot.

But in answer to your question, no, you should not really be worried about this in all likelihood. It'll be showing as "500" instead of a username because o user in /etc/passwd has a uid set of 500, that's all.

Also you can show your current numbers using id i'm willing to bet it comes back as 1000 for you.

Using $state methods with $stateChangeStart toState and fromState in Angular ui-router

Suggestion 1

When you add an object to $stateProvider.state that object is then passed with the state. So you can add additional properties which you can read later on when needed.

Example route configuration

.state('public', {
    abstract: true,
    module: 'public'
.state('public.login', {
    url: '/login',
    module: 'public'
.state('tool', {
    abstract: true,
    module: 'private'
.state('tool.suggestions', {
    url: '/suggestions',
    module: 'private'

The $stateChangeStart event gives you acces to the toState and fromState objects. These state objects will contain the configuration properties.

Example check for the custom module property

$rootScope.$on('$stateChangeStart', function(e, toState, toParams, fromState, fromParams) {
    if (toState.module === 'private' && !$cookies.Session) {
        // If logged out and transitioning to a logged in page:
    } else if (toState.module === 'public' && $cookies.Session) {
        // If logged in and transitioning to a logged out page:

I didn't change the logic of the cookies because I think that is out of scope for your question.

Suggestion 2

You can create a Helper to get you this to work more modular.

Value publicStates

myApp.value('publicStates', function(){
    return {
      module: 'public',
      routes: [{
        name: 'login', 
        config: { 
          url: '/login'

Value privateStates

myApp.value('privateStates', function(){
    return {
      module: 'private',
      routes: [{
        name: 'suggestions', 
        config: { 
          url: '/suggestions'

The Helper

myApp.provider('stateshelperConfig', function () {
  this.config = {
    // These are the properties we need to set
    // $stateProvider: undefined
    process: function (stateConfigs){
      var module = stateConfigs.module;
      $stateProvider = this.$stateProvider;
      $stateProvider.state(module, {
        abstract: true,
        module: module
      angular.forEach(stateConfigs, function (route){
        route.config.module = module;
        $stateProvider.state(module +, route.config);

  this.$get = function () {
    return {
      config: this.config

Now you can use the helper to add the state configuration to your state configuration.

myApp.config(['$stateProvider', '$urlRouterProvider', 
    'stateshelperConfigProvider', 'publicStates', 'privateStates',
  function ($stateProvider, $urlRouterProvider, helper, publicStates, privateStates) {
    helper.config.$stateProvider = $stateProvider;

This way you can abstract the repeated code, and come up with a more modular solution.

Note: the code above isn't tested

ERROR 1044 (42000): Access denied for 'root' With All Privileges

If you get an error 1044 (42000) when you try to run SQL commands in MySQL (which installed along XAMPP server) cmd prompt, then here's the solution:

  1. Close your MySQL command prompt.

  2. Open your cmd prompt (from Start menu -> run -> cmd) which will show: C:\Users\User>_

  3. Go to MySQL.exe by Typing the following commands:

C:\Users\User>cd\ C:\>cd xampp C:\xampp>cd mysql C:\xxampp\mysql>cd bin C:\xampp\mysql\bin>mysql -u root

  1. Now try creating a new database by typing:

    mysql> create database employee;

    if it shows:

    Query OK, 1 row affected (0.00 sec)

    Then congrats ! You are good to go...

AngularJS $http, CORS and http authentication

No you don't have to put credentials, You have to put headers on client side eg:

        url: 'url of service',
        method: "POST",
        data: {test :  name },
        withCredentials: true,
        headers: {
                    'Content-Type': 'application/json; charset=utf-8'

And and on server side you have to put headers to this is example for nodejs:

 * On all requests add headers
app.all('*', function(req, res,next) {

     * Response settings
     * @type {Object}
    var responseSettings = {
        "AccessControlAllowOrigin": req.headers.origin,
        "AccessControlAllowHeaders": "Content-Type,X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5,  Date, X-Api-Version, X-File-Name",
        "AccessControlAllowMethods": "POST, GET, PUT, DELETE, OPTIONS",
        "AccessControlAllowCredentials": true

     * Headers
    res.header("Access-Control-Allow-Credentials", responseSettings.AccessControlAllowCredentials);
    res.header("Access-Control-Allow-Origin",  responseSettings.AccessControlAllowOrigin);
    res.header("Access-Control-Allow-Headers", (req.headers['access-control-request-headers']) ? req.headers['access-control-request-headers'] : "x-requested-with");
    res.header("Access-Control-Allow-Methods", (req.headers['access-control-request-method']) ? req.headers['access-control-request-method'] : responseSettings.AccessControlAllowMethods);

    if ('OPTIONS' == req.method) {
    else {


Can not run Java Applets in Internet Explorer 11 using JRE 7u51

Try this. It worked for me.

Go to RUN and type gpedit.msc then completely disable Onedrive. Have you noticed that the problem only existed after the last large download from Microsoft? It contained this package. I also removed it from the Start menu.

This appears to be the cause of the issue. Something to do with downloading temporary files, which of course an applet is.

Once done everything went back to normal.


Hi all I had the same issue that was being caused by a duplicate support version 4 file that I had included while trying to get parse integrated. Deleted the extra inclusion from the libs directory and it works fine now!

JNI and Gradle in Android Studio

In my case, I'm on Windows and following the answer by Cameron above only works if you use the full name of the ndk-build which is ndk-build.cmd. I have to clean and rebuild the project, then restart the emulator before getting the app to work (Actually I imported the sample HelloJni from NDK, into Android Studio). However, make sure the path to NDK does not contain space.

Finally, my build.gradle is full listed as below:

apply plugin: ''

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "com.example.hellojni"
        minSdkVersion 4
        targetSdkVersion 4

        ndk {
            moduleName "hello-jni"

        testApplicationId "com.example.hellojni.tests"
        testInstrumentationRunner "android.test.InstrumentationTestRunner"
    sourceSets.main {
        jni.srcDirs = [] // This prevents the auto generation of
//        sourceSets.main.jni.srcDirs = []
        jniLibs.srcDir 'src/main/libs' // This is not necessary unless you have precompiled libraries in your project.

    task buildNative(type: Exec, description: 'Compile JNI source via NDK') {
        def ndkDir = android.plugin.ndkFolder
        commandLine "$ndkDir/ndk-build.cmd",
                '-C', file('src/main/jni').absolutePath, // Change src/main/jni the relative path to your jni source
                '-j', Runtime.runtime.availableProcessors(),

    task cleanNative(type: Exec, description: 'Clean JNI object files') {
        def ndkDir = android.plugin.ndkFolder
        commandLine "$ndkDir/ndk-build.cmd",
                '-C', file('src/main/jni').absolutePath, // Change src/main/jni the relative path to your jni source

    clean.dependsOn 'cleanNative'

    tasks.withType(JavaCompile) {
        compileTask -> compileTask.dependsOn buildNative


dependencies {
    compile ''

How to Avoid Response.End() "Thread was being aborted" Exception during the Excel file download

I researched online and saw that the Response.End() always throws an exception.

Replace this: HttpContext.Current.Response.End();

With this:

HttpContext.Current.Response.Flush(); // Sends all currently buffered output to the client.
HttpContext.Current.Response.SuppressContent = true;  // Gets or sets a value indicating whether to send HTTP content to the client.
HttpContext.Current.ApplicationInstance.CompleteRequest(); // Causes ASP.NET to bypass all events and filtering in the HTTP pipeline chain of execution and directly execute the EndRequest event.

AngularJS- Login and Authentication in each route and controller


'use strict';
// Declare app level module which depends on filters, and services
var app= angular.module('myApp', ['ngRoute','angularUtils.directives.dirPagination','ngLoadingSpinner']);
app.config(['$routeProvider', function($routeProvider) {
  $routeProvider.when('/login', {templateUrl: 'partials/login.html', controller: 'loginCtrl'});
  $routeProvider.when('/home', {templateUrl: 'partials/home.html', controller: 'homeCtrl'});
  $routeProvider.when('/salesnew', {templateUrl: 'partials/salesnew.html', controller: 'salesnewCtrl'});
  $routeProvider.when('/salesview', {templateUrl: 'partials/salesview.html', controller: 'salesviewCtrl'});
  $routeProvider.when('/users', {templateUrl: 'partials/users.html', controller: 'usersCtrl'});
    $routeProvider.when('/forgot', {templateUrl: 'partials/forgot.html', controller: 'forgotCtrl'});

  $routeProvider.otherwise({redirectTo: '/login'});

}]);$rootScope, $location, loginService){
    var routespermission=['/home'];  //route that require login
    var salesnew=['/salesnew'];
    var salesview=['/salesview'];
    var users=['/users'];
    $rootScope.$on('$routeChangeStart', function(){
        if( routespermission.indexOf($location.path()) !=-1
        || salesview.indexOf($location.path()) !=-1
        || salesnew.indexOf($location.path()) !=-1
        || users.indexOf($location.path()) !=-1)
            var connected=loginService.islogged();



'use strict';
app.factory('loginService',function($http, $location, sessionService){
            var $promise=$'data/user.php',data); //send data to user.php
                    scope.msgtxt='Correct information';
                else  {
                    scope.msgtxt='incorrect information';
            var $checkSessionServer=$'data/check_session.php');
            return $checkSessionServer;
            if(sessionService.get('user')) return true;
            else return false;



'use strict';

app.factory('sessionService', ['$http', function($http){
            return sessionStorage.setItem(key,value);
            return sessionStorage.getItem(key);
            return sessionStorage.removeItem(key);


'use strict';

app.controller('loginCtrl', ['$scope','loginService', function ($scope,loginService) {
        loginService.login(data,$scope); //call login service


ASP.NET MVC 5 - Identity. How to get current ApplicationUser

As of ASP.NET Identity 3.0.0, This has been refactored into

//returns the userid claim value if present, otherwise returns null

Putty: Getting Server refused our key Error

In the case of mine it was a wrong user:group attribution. I solved setting the right user and group:

sudo chown [user]:[group] -R /home/[user]

Execution failed app:processDebugResources Android Studio

I got this problem after deleting the logs I resolved this by rebuilding the project

phpmyadmin.pma_table_uiprefs doesn't exist

I had to change this rows:

$cfg['Servers'][$i]['pma__bookmarktable'] = 'pma__bookmark';
$cfg['Servers'][$i]['pma__relation'] = 'pma__relation';
$cfg['Servers'][$i]['pma__table_info'] = 'pma__table_info';
$cfg['Servers'][$i]['pma__table_coords'] = 'pma__table_coords';
$cfg['Servers'][$i]['pma__pdf_pages'] = 'pma__pdf_pages';
$cfg['Servers'][$i]['pma__column_info'] = 'pma__column_info';
$cfg['Servers'][$i]['pma__history'] = 'pma__history';
$cfg['Servers'][$i]['pma__table_uiprefs'] = 'pma__table_uiprefs';
$cfg['Servers'][$i]['pma__designer_coords'] = 'pma__designer_coords';
$cfg['Servers'][$i]['pma__tracking'] = 'pma__tracking';
$cfg['Servers'][$i]['pma__userconfig'] = 'pma__userconfig';
$cfg['Servers'][$i]['pma__recent'] = 'pma__recent';
$cfg['Servers'][$i]['pma__table_uiprefs'] = 'pma__table_uiprefs';

add: "pma__" to ['bookmarktable'] and "_" to 'pma_bookmark'

Error while installing json gem 'mkmf.rb can't find header files for ruby'

You may need to install gcc after install ruby-devel

Refused to display in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'

I found a better solution, maybe it can help somebody replace "watch?v=" by "v/" and it will work

var url = url.replace("watch?v=", "v/");

ECONNREFUSED error when connecting to mongodb from node.js

Use this code to setup your mongodb connection:

var mongoose = require('mongoose');

var mongoURI = "mongodb://localhost:27017/test";
var MongoDB = mongoose.connect(mongoURI).connection;
MongoDB.on('error', function(err) { console.log(err.message); });
MongoDB.once('open', function() {
  console.log("mongodb connection open");

Make sure mongod is running while you start the server. Are you using Express or just a simple node.js server? What is the error message you get with the above code?

How to write log file in c#?

if(!File.Exists(filename)) //No File? Create
    fs = File.Create(filename);
if(File.ReadAllBytes().Length >= 100*1024*1024) // (100mB) File to big? Create new
    string filenamebase = "myLogFile"; //Insert the base form of the log file, the same as the 1st filename without .log at the end
    if(filename.contains("-")) //Check if older log contained -x
         int lognumber = Int32.Parse(filename.substring(filename.lastIndexOf("-")+1, filename.Length-4); //Get old number, Can cause exception if the last digits aren't numbers
         lognumber++; //Increment lognumber by 1
         filename = filenamebase + "-" + lognumber + ".log"; //Override filename
         filename = filenamebase + "-1.log"; //Override filename
    fs = File.Create(filename);

Refer link:

What is the height of Navigation Bar in iOS 7?

There is a difference between the navigation bar and the status bar. The confusing part is that it looks like one solid feature at the top of the screen, but the areas can actually be separated into two distinct views; a status bar and a navigation bar. The status bar spans from y=0 to y=20 points and the navigation bar spans from y=20 to y=64 points. So the navigation bar (which is where the page title and navigation buttons go) has a height of 44 points, but the status bar and navigation bar together have a total height of 64 points.

Here is a great resource that addresses this question along with a number of other sizing idiosyncrasies in iOS7:

Error 1920 service failed to start. Verify that you have sufficient privileges to start system services

In my case, the service failed to start because I didn't set Platform='x64' in the wix file.

I saw these errors in Event Viewer:

Service cannot be started.

System.BadImageFormatException: Could not load file or assembly 'SOME_LIBRARY_FILE, Version=, Culture=neutral, PublicKeyToken=33345856ad364e35' or one of its dependencies.

I tried checking the bitness of all service related files using CorFlags.exe. When I changed my installer to be 64 bit, everything started working fine.

Best practices for Storyboard login screen, handling clearing of data upon logout

Create **LoginViewController** and **TabBarController**.

After creating the LoginViewController and TabBarController, we need to add a StoryboardID as “loginViewController” and “tabBarController” respectively.

Then I prefer to create the Constant struct:

struct Constants {
    struct StoryboardID {
        static let signInViewController = "SignInViewController"
        static let mainTabBarController = "MainTabBarController"

    struct kUserDefaults {
        static let isSignIn = "isSignIn"

In LoginViewController add IBAction:

@IBAction func tapSignInButton(_ sender: UIButton) {
    UserDefaults.standard.set(true, forKey: Constants.kUserDefaults.isSignIn)

In ProfileViewController add IBAction:

@IBAction func tapSignOutButton(_ sender: UIButton) {
    UserDefaults.standard.set(false, forKey: Constants.kUserDefaults.isSignIn)

In AppDelegate add line of code in didFinishLaunchingWithOptions:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {


    return true

Finally create Switcher class:

import UIKit

class Switcher {

    static func updateRootViewController() {

        let status = UserDefaults.standard.bool(forKey: Constants.kUserDefaults.isSignIn)
        var rootViewController : UIViewController?

        #if DEBUG

        if (status == true) {
            let mainStoryBoard = UIStoryboard(name: "Main", bundle: nil)
            let mainTabBarController = mainStoryBoard.instantiateViewController(withIdentifier: Constants.StoryboardID.mainTabBarController) as! MainTabBarController
            rootViewController = mainTabBarController
        } else {
            let mainStoryBoard = UIStoryboard(name: "Main", bundle: nil)
            let signInViewController = mainStoryBoard.instantiateViewController(withIdentifier: Constants.StoryboardID.signInViewController) as! SignInViewController
            rootViewController = signInViewController

        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        appDelegate.window?.rootViewController = rootViewController



That is all!

WordPress - Check if user is logged in

Example: Display different output depending on whether the user is logged in or not.


if ( is_user_logged_in() ) {
    echo 'Welcome, registered user!';
} else {
    echo 'Welcome, visitor!';


how to create a logfile in php?

You could use built-in function trigger_error() to trigger user errors/warnings/notices and set_error_handler() to handle them. Inside your error handler you might want to use error_log() or file_put_contents() to store all records on files. To have a single file for every day just use something like sprintf('%s.log', date('Y-m-d')) as filename. And now you should know where to start... :)

Session variables not working php

The other important reason sessions can not work is playing with the session cookie settings, eg. setting session cookie lifetime to 0 or other low values because of simple mistake or by other developer for a reason.


Access denied for user 'root'@'localhost' (using password: Yes) after password reset LINUX

You have to reset the password! steps for mac osx(tested and working) and ubuntu

Stop MySQL

$ sudo /usr/local/mysql/support-files/mysql.server stop

Start it in safe mode:

$ sudo mysqld_safe --skip-grant-tables

(above line is the whole command)

This will be an ongoing command until the process is finished so open another shell/terminal window, log in without a password:

$ mysql -u root

mysql> UPDATE mysql.user SET Password=PASSWORD('password') WHERE User='root';

Start MySQL

sudo /usr/local/mysql/support-files/mysql.server start

your new password is 'password'.

Installing PG gem on OS X - failure to build native extension


gem install pg -- --with-pg-config=`which pg_config`

TypeError: Cannot read property "0" from undefined

Looks like what you're trying to do is access property '0' of an undefined value in your 'data' array. If you look at your while statement, it appears this is happening because you are incrementing 'i' by 1 for each loop. Thus, the first time through, you will access, 'data[1]', but on the next loop, you'll access 'data[2]' and so on and so forth, regardless of the length of the array. This will cause you to eventually hit an array element which is undefined, if you never find an item in your array with property '0' which is equal to 'name'.

Ammend your while statement to this...

for(var iIndex = 1; iIndex <= data.length; iIndex++){
    if (data[iIndex][0] === name){

JDBC connection failed, error: TCP/IP connection to host failed

  1. Open SQL Server Configuration Manager, and then expand SQL Server 2012 Network Configuration.
  2. Click Protocols for InstanceName, and then make sure TCP/IP is enabled in the right panel and double-click TCP/IP.
  3. On the Protocol tab, notice the value of the Listen All item.
  4. Click the IP Addresses tab: If the value of Listen All is yes, the TCP/IP port number for this instance of SQL Server 2012 is the value of the TCP Dynamic Ports item under IPAll. If the value of Listen All is no, the TCP/IP port number for this instance of SQL Server 2012 is the value of the TCP Dynamic Ports item for a specific IP address.
  5. Make sure the TCP Port is 1433.
  6. Click OK.

If there are any more questions, please let me know.


Tomcat 7.0.43 "INFO: Error parsing HTTP request header"

My problem occurs when I try to open https. I don't use SSL.

It's Tomcat bug.

Today 12/02/2017 newest official version from Debian repositories is Tomcat 8.0.14

Solution is to download from official site and install newest package of Tomcat 8, 8.5, 9 or upgrade to newest version(8.5.x) from jessie-backports

Debian 8

Add to /etc/apt/sources.list

deb jessie-backports main

Then update and install Tomcat from jessie-backports

sudo apt-get update && sudo apt-get -t jessie-backports install tomcat8

SSH -L connection successful, but localhost port forwarding not working "channel 3: open failed: connect failed: Connection refused"

Posting this to help someone.


channel 2: open failed: connect failed: Connection refused
debug1: channel 2: free: direct-tcpip:
   listening port 8890 for port 8890,
   connect from ::1 port 52337 to ::1 port 8890, nchannels 8

My scenario; i had to use the remote server as a bastion host to connect elsewhere. Final Destination/Target:, port 8890. Through intermediary server with public ip:

SSH local port forwarding command:

ssh -i ~/keys/dev.tst -vnNT -L :8890:
[email protected]

What the problem was: There was no service bound on port 8890 in the target host. i had forgotten to start the service.

How did i trouble shoot:

SSH into bastion host and then do curl.

Hope this helps.

How to pass parameters to a modal?

If you're not using AngularJS UI Bootstrap, here's how I did it.

I created a directive that will hold that entire element of your modal, and recompile the element to inject your scope into it.

angular.module('yourApp', []).
function($rootScope,  $log,  $compile) {
    var _scope = null;
    var _element = null;
    var _onModalShow = function(event) {

    return {
        link: function(scope, element, attributes) {
            _scope = scope;
            _element = element;

I'm assuming your modal template is inside the scope of your controller, then add directive my-modal to your template. If you saved the clicked user to $scope.aModel, the original template will now work.

Note: The entire scope is now visible to your modal so you can also access $scope.users in it.

<div my-modal id="encouragementModal" class="modal hide fade">
  <div class="modal-header">
    <button type="button" class="close" data-dismiss="modal"
    <h3>Confirm encouragement?</h3>
  <div class="modal-body">
      Do you really want to encourage <b>{{aModel.userName}}</b>?
  <div class="modal-footer">
    <button class="btn btn-info"
      ng-click="encourage('${createLink(uri: '/encourage/')}',{{aModel.userName}})">
    <button class="btn" data-dismiss="modal" aria-hidden="true">Never Mind</button>

How to get current user, and how to use User class in MVC5?

Getting the Id is pretty straight forward and you've solved that.

Your second question though is a little more involved.

So, this is all prerelease stuff right now, but the common problem you're facing is where you're extending the user with new properties ( or an Items collection in you're question).

Out of the box you'll get a file called IdentityModel under the Models folder (at the time of writing). In there you have a couple of classes; ApplicationUser and ApplicationDbContext. To add your collection of Items you'll want to modify the ApplicationUser class, just like you would if this were a normal class you were using with Entity Framework. In fact, if you take a quick look under the hood you'll find that all the identity related classes (User, Role etc...) are just POCOs now with the appropriate data annotations so they play nice with EF6.

Next, you'll need to make some changes to the AccountController constructor so that it knows to use your DbContext.

public AccountController()
    IdentityManager = new AuthenticationIdentityManager(
    new IdentityStore(new ApplicationDbContext()));

Now getting the whole user object for your logged in user is a little esoteric to be honest.

    var userWithItems = (ApplicationUser)await IdentityManager.Store.Users
    .FindAsync(User.Identity.GetUserId(), CancellationToken.None);

That line will get the job done and you'll be able to access userWithItems.Items like you want.


Pass variable to function in jquery AJAX success callback

You can't pass parameters like this - the success object maps to an anonymous function with one parameter and that's the received data. Create a function outside of the for loop which takes (data, i) as parameters and perform the code there:

function image_link(data, i) {
       new Image().src = url[i] + $(this).attr("href");
success: function(data){
    image_link(data, i)

Windows Scheduled task succeeds but returns result 0x1

Just had the same problem here. In my case, the bat files had space " " After getting rid of spaces from filename and change into underscore, bat file worked

sample before it wont start

"x:\Update & pull.bat"

after rename


TypeError: $.ajax(...) is not a function?

Neither of the answers here helped me. The problem was: I was using the slim build of jQuery, which had some things removed, ajax being one of them.

The solution: Just download the regular (compressed or not) version of jQuery here and include it in your project.

Access Denied for User 'root'@'localhost' (using password: YES) - No Privileges?

I faced this problem while installing Testlink on Ubuntu server, I followed these steps

mysql -u root
use mysql;
update user set password=PASSWORD("root") where User='root';
flush privileges;

Now stop the instance and start again i.e

sudo /etc/init.d/mysql stop
sudo /etc/init.d/mysql start

Use dynamic (variable) string as regex pattern in JavaScript

var string = "Hi welcome to stack overflow"
var toSearch = "stack"

//case insensitive search

var result = RegExp(toSearch, "i")) > 0 ? 'Matched' : 'notMatched'

Hope this helps

Allow anything through CORS Policy

I have had a similar problem before where it turned out to be the web brower (chrome in my case) that was the issue.

If you are using chrome, try launching it so:

For Windows:

1) Create a shortcut to Chrome on your desktop. Right-click on the shortcut and choose Properties, then switch to “Shortcut” tab.

2) In the “Target” field, append the following: –args –disable-web-security

For Mac, Open a terminal window and run this from command-line: open ~/Applications/Google\ –args –disable-web-security

Above info from:

Laravel: Auth::user()->id trying to get a property of a non-object

Check your route for the function in which you are using Auth::user(), For getting Auth::user() data the function should be inside web middleware Route::group(['middleware' => 'web'], function () {}); .

Heroku 'Permission denied (publickey) fatal: Could not read from remote repository' woes

I got the same error, and because I have 4 ssh-keys, so I tried follow:

ssh-keygen -t rsa
heroku keys:add

then, four options show:


I choose 3), the newest one

Then, I fix the error.

How to save and extract session data in codeigniter

First you have load session library.


You can load it in auto load, which I think is better.

To set session


To extract Data


How can I get a user's media from Instagram without authenticating as a user?

The Instagram API requires user authentication through OAuth to access the recent media endpoint for a user. There doesn't appear to be any other way right now to get all media for a user.

Createuser: could not connect to database postgres: FATAL: role "tom" does not exist

You mentioned Ubuntu so I'm going to guess you installed the PostgreSQL packages from Ubuntu through apt.

If so, the postgres PostgreSQL user account already exists and is configured to be accessible via peer authentication for unix sockets in pg_hba.conf. You get to it by running commands as the postgres unix user, eg:

sudo -u postgres createuser owning_user
sudo -u postgres createdb -O owning_user dbname

This is all in the Ubuntu PostgreSQL documentation that's the first Google hit for "Ubuntu PostgreSQL" and is covered in numerous Stack Overflow questions.

(You've made this question a lot harder to answer by omitting details like the OS and version you're on, how you installed PostgreSQL, etc.)

How can I get the username of the logged-in user in Django?

request.user.get_username() will return a string of the users email.

request.user.username will return a method.

How to get a list of programs running with nohup

When I started with $ nohup storm dev-zookeper ,

METHOD1 : using jobs,

prayagupd@prayagupd:/home/vmfest# jobs -l
[1]+ 11129 Running                 nohup ~/bin/storm/bin/storm dev-zookeeper &

METHOD2 : using ps command.

$ ps xw
1031 tty1     Ss+    0:00 /sbin/getty -8 38400 tty1
10582 ?        S      0:01 [kworker/0:0]
10826 ?        Sl     0:18 java -server -Dstorm.options= -Dstorm.home=/root/bin/storm -Djava.library.path=/usr/local/lib:/opt/local/lib:/usr/lib -Dsto
10853 ?        Ss     0:00 sshd: vmfest [priv] 

TTY column with ? => nohup running programs.


  • TTY column = the terminal associated with the process
  • STAT column = state of a process
    • S = interruptible sleep (waiting for an event to complete)
    • l = is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)


$ man ps # then search /PROCESS STATE CODES

HTTP get with headers using RestTemplate

Take a look at the JavaDoc for RestTemplate.

There is the corresponding getForObject methods that are the HTTP GET equivalents of postForObject, but they doesn't appear to fulfil your requirements of "GET with headers", as there is no way to specify headers on any of the calls.

Looking at the JavaDoc, no method that is HTTP GET specific allows you to also provide header information. There are alternatives though, one of which you have found and are using. The exchange methods allow you to provide an HttpEntity object representing the details of the request (including headers). The execute methods allow you to specify a RequestCallback from which you can add the headers upon its invocation.

Difference between "module.exports" and "exports" in the CommonJs Module System

Rene's answer about the relationship between exports and module.exports is quite clear, it's all about javascript references. Just want to add that:

We see this in many node modules:

var app = exports = module.exports = {};

This will make sure that even if we changed module.exports, we can still use exports by making those two variables point to the same object.

error: package javax.servlet does not exist

I got here with a similar problem with my Gradle build and fixed it in a similar way:

Unable to load class hudson.model.User due to missing dependency javax/servlet/ServletException

fixed with:

dependencies {

Close Window from ViewModel

It's simple. You can create your own ViewModel class for Login - LoginViewModel. You can create view var dialog = new UserView(); inside your LoginViewModel. And you can set-up Command LoginCommand into button.

<Button Name="btnLogin" IsDefault="True" Content="Login" Command="{Binding LoginCommand}" />


<Button Name="btnCancel" IsDefault="True" Content="Login" Command="{Binding CancelCommand}" />

ViewModel class:

public class LoginViewModel
    Window dialog;
    public bool ShowLogin()
       dialog = new UserView();
       dialog.DataContext = this; // set up ViewModel into View
       if (dialog.ShowDialog() == true)
         return true;

       return false;

    ICommand _loginCommand
    public ICommand LoginCommand
            if (_loginCommand == null)
                _loginCommand = new RelayCommand(param => this.Login());

            return _loginCommand;

    public void CloseLoginView()
            if (dialog != null)

    public void Login()
          // write error message

    public bool CheckLogin()
      // ... check login code
      return true;

How to ftp with a batch file?

If you need to pass variables to the txt file you can create in on the fly and remove after.

This is example is a batch script running as administrator. It creates a zip file using some date & time variables. Then it creates a ftp text file on the fly with some variables. Then it deletes the zip, folder and ftp text file.

set YYYY=%DATE:~10,4%
set MM=%DATE:~4,2%
set DD=%DATE:~7,2%

set HH=%TIME: =0%
set HH=%HH:~0,2%
set MI=%TIME:~3,2%
set SS=%TIME:~6,2%
set FF=%TIME:~9,2%

set dirName=%YYYY%%MM%%DD%

echo %fileName%

"C:\Program Files\7-Zip\7z.exe" a -tzip C:\%dirName%\%fileName% -r "C:\tozip\*.*" -mx5

    echo open 198.123.456.789
    echo [email protected]
    echo yourpassword
    echo lcd "C:/%dirName%"
    echo cd  theremotedir
    echo binary
    echo mput *.zip
    echo disconnect
    echo bye
) > C:\ftp.details.txt

cd C:\
FTP -v -i -s:"ftp.details.txt"

del C:\ftp.details.txt /f

AngularJS: Basic example to use authentication in Single Page Application

var _login = function (loginData) {_x000D_
        var data = "grant_type=password&username=" + loginData.userName + "&password=" + loginData.password;_x000D_
        var deferred = $q.defer();_x000D_
        $ + 'token', data, { headers: { 'Content-Type': 'application/x-www-form-urlencoded' } }).success(function (response) {_x000D_
            localStorageService.set('authorizationData', { token: response.access_token, userName: loginData.userName });_x000D_
            _authentication.isAuth = true;_x000D_
            _authentication.userName = loginData.userName;_x000D_
        }).error(function (err, status) {_x000D_
        return deferred.promise;_x000D_

Jackson serialization: ignore empty values (or null)

You have the annotation in the wrong place - it needs to be on the class, not the field. i.e:

@JsonInclude(Include.NON_NULL) //or Include.NON_EMPTY, if that fits your use case 
public static class Request {
  // ...

As noted in comments, in versions below 2.x the syntax for this annotation is:

@JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL) // or JsonSerialize.Inclusion.NON_EMPTY

The other option is to configure the ObjectMapper directly, simply by calling mapper.setSerializationInclusion(Include.NON_NULL);

(for the record, I think the popularity of this answer is an indication that this annotation should be applicable on a field-by-field basis, @fasterxml)

Webclient / HttpWebRequest with Basic Authentication returns 404 not found for valid URL

If its working when you are using a browser and then passing on your username and password for the first time - then this means that once authentication is done Request header of your browser is set with required authentication values, which is then passed on each time a request is made to hosting server.

So start with inspecting Request Header (this could be done using Web Developers tools), Once you established whats required in header then you could pass this within your HttpWebRequest Header.

Example with Digest Authentication:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;
using System.Text.RegularExpressions;
using System.Net;
using System.IO;

namespace NUI
    public class DigestAuthFixer
        private static string _host;
        private static string _user;
        private static string _password;
        private static string _realm;
        private static string _nonce;
        private static string _qop;
        private static string _cnonce;
        private static DateTime _cnonceDate;
        private static int _nc;

public DigestAuthFixer(string host, string user, string password)
    // TODO: Complete member initialization
    _host = host;
    _user = user;
    _password = password;

private string CalculateMd5Hash(
    string input)
    var inputBytes = Encoding.ASCII.GetBytes(input);
    var hash = MD5.Create().ComputeHash(inputBytes);
    var sb = new StringBuilder();
    foreach (var b in hash)
    return sb.ToString();

private string GrabHeaderVar(
    string varName,
    string header)
    var regHeader = new Regex(string.Format(@"{0}=""([^""]*)""", varName));
    var matchHeader = regHeader.Match(header);
    if (matchHeader.Success)
        return matchHeader.Groups[1].Value;
    throw new ApplicationException(string.Format("Header {0} not found", varName));

private string GetDigestHeader(
    string dir)
    _nc = _nc + 1;

    var ha1 = CalculateMd5Hash(string.Format("{0}:{1}:{2}", _user, _realm, _password));
    var ha2 = CalculateMd5Hash(string.Format("{0}:{1}", "GET", dir));
    var digestResponse =
        CalculateMd5Hash(string.Format("{0}:{1}:{2:00000000}:{3}:{4}:{5}", ha1, _nonce, _nc, _cnonce, _qop, ha2));

    return string.Format("Digest username=\"{0}\", realm=\"{1}\", nonce=\"{2}\", uri=\"{3}\", " +
        "algorithm=MD5, response=\"{4}\", qop={5}, nc={6:00000000}, cnonce=\"{7}\"",
        _user, _realm, _nonce, dir, digestResponse, _qop, _nc, _cnonce);

public string GrabResponse(
    string dir)
    var url = _host + dir;
    var uri = new Uri(url);

    var request = (HttpWebRequest)WebRequest.Create(uri);

    // If we've got a recent Auth header, re-use it!
    if (!string.IsNullOrEmpty(_cnonce) &&
        DateTime.Now.Subtract(_cnonceDate).TotalHours < 1.0)
        request.Headers.Add("Authorization", GetDigestHeader(dir));

    HttpWebResponse response;
        response = (HttpWebResponse)request.GetResponse();
    catch (WebException ex)
        // Try to fix a 401 exception by adding a Authorization header
        if (ex.Response == null || ((HttpWebResponse)ex.Response).StatusCode != HttpStatusCode.Unauthorized)

        var wwwAuthenticateHeader = ex.Response.Headers["WWW-Authenticate"];
        _realm = GrabHeaderVar("realm", wwwAuthenticateHeader);
        _nonce = GrabHeaderVar("nonce", wwwAuthenticateHeader);
        _qop = GrabHeaderVar("qop", wwwAuthenticateHeader);

        _nc = 0;
        _cnonce = new Random().Next(123400, 9999999).ToString();
        _cnonceDate = DateTime.Now;

        var request2 = (HttpWebRequest)WebRequest.Create(uri);
        request2.Headers.Add("Authorization", GetDigestHeader(dir));
        response = (HttpWebResponse)request2.GetResponse();
    var reader = new StreamReader(response.GetResponseStream());
    return reader.ReadToEnd();


Then you could call it:

DigestAuthFixer digest = new DigestAuthFixer(domain, username, password);
string strReturn = digest.GrabResponse(dir);

if Url is: then domain: (domain part) dir: /folder/rss (rest of the url)

you could also return it as stream and use XmlDocument Load() method.

HTML5 LocalStorage: Checking if a key exists

The MDN documentation shows how the getItem method is implementated:

Object.defineProperty(oStorage, "getItem", {
      value: function (sKey) { return sKey ? this[sKey] : null; },
      writable: false,
      configurable: false,
      enumerable: false

If the value isn't set, it returns null. You are testing to see if it is undefined. Check to see if it is null instead.

if(localStorage.getItem("username") === null){

The operation couldn’t be completed. (com.facebook.sdk error 2.) ios6

check your Bundle identifier for your project and you give Bundle identifier for your app which create on that they are same or not.

List of all users that can connect via SSH

Read man sshd_config for more details, but you can use the AllowUsers directive in /etc/ssh/sshd_config to limit the set of users who can login.


AllowUsers boris

would mean that only the boris user could login via ssh.

Why does the preflight OPTIONS request of an authenticated CORS request work in Chrome but not Firefox?

It was particular for me. I am sending a header named 'SESSIONHASH'. No problem for Chrome and Opera, but Firefox also wants this header in the list "Access-Control-Allow-Headers". Otherwise, Firefox will throw the CORS error.

Parse error: syntax error, unexpected T_ECHO in

Missing ; after var_dump($row)

An Authentication object was not found in the SecurityContext - Spring 3.2.2

I encountered the same error while using SpringBoot 2.1.4, along with Spring Security 5 (I believe). After one day of trying everything that Google had to offer, I discovered the cause of error in my case. I had a setup of micro-services, with the Auth server being different from the Resource Server. I had the following lines in my application.yml which prevented 'auto-configuration' despite of having included dependencies spring-boot-starter-security, spring-security-oauth2 and spring-security-jwt. I had included the following in the properties (during development) which caused the error.


Commenting it out solved it for me.

#  autoconfigure:
#    exclude:

Hope, it helps someone.

There has been an error processing your request, Error log record number

Clear your cache and your website will be work well.

how to kill the tty in unix

Try this:

skill -KILL -v pts/6

skill -KILL -v pts/9

skill -KILL -v pts/10

Redirecting to a new page after successful login

Javascript redirection generated with php code:

 if($match > 0){
     $msg = 'Login Complete! Thanks';
     echo "<script> window.location.assign('index.php'); </script>";
     $msg = 'Login Failed!<br /> Please make sure that you enter the correct  details and that you have activated your account.';

Php redirection only:

    header("Location: index.php"); 

Create intermediate folders if one doesn't exist

You have to actually call some method to create the directories. Just creating a file object will not create the corresponding file or directory on the file system.

You can use File#mkdirs() method to create the directory: -


Difference between File#mkdir() and File#mkdirs() is that, the later will create any intermediate directory if it does not exist.

How to log as much information as possible for a Java Exception?

Something that I do is to have a static method that handles all exceptions and I add the log to a JOptionPane to show it to the user, but you could write the result to a file in FileWriter wraped in a BufeeredWriter. For the main static method, to catch the Uncaught Exceptions I do:

SwingUtilities.invokeLater( new Runnable() {
    public void run() {

    new Thread.UncaughtExceptionHandler() {
        public void uncaughtException( Thread t, Throwable ex ) {
            handleExceptions( ex, true );

And as for the method:

public static void handleExceptions( Throwable ex, boolean shutDown ) {
    JOptionPane.showMessageDialog( null,
        "SYSTEM FAIL",
        JOptionPane.ERROR_MESSAGE );

    StringBuilder sb = new StringBuilder(ex.toString());
    for (StackTraceElement ste : ex.getStackTrace()) {
        sb.append("\n\tat ").append(ste);

    while( (ex = ex.getCause()) != null ) {
        for (StackTraceElement ste : ex.getStackTrace()) {
            sb.append("\n\tat ").append(ste);

    String trace = sb.toString();

    JOptionPane.showMessageDialog( null,
        "SYSTEM FAIL",

    if( shutDown ) {
        Runtime.getRuntime().exit( 0 );

In you case, instead of "screaming" to the user, you could write a log like I told you before:

String trace = sb.toString();

File file = new File("mylog.txt");
FileWriter myFileWriter = null;
BufferedWriter myBufferedWriter = null;

try {
    //with FileWriter(File file, boolean append) you can writer to 
    //the end of the file
    myFileWriter = new FileWriter( file, true );
    myBufferedWriter = new BufferedWriter( myFileWriter );

    myBufferedWriter.write( trace );
catch ( IOException ex1 ) {
    //Do as you want. Do you want to use recursive to handle 
    //this exception? I don't advise that. Trust me...
finally {
    try {
    catch ( IOException ex1 ) {

    try {
    catch ( IOException ex1 ) {

I hope I have helped.

Have a nice day. :)

Spring Security redirect to previous page after successful login

I have following solution and it worked for me.

Whenever login page is requested, write the referer value to the session:

@RequestMapping(value="/login", method = RequestMethod.GET)
public String login(ModelMap model,HttpServletRequest request) {

    String referrer = request.getHeader("Referer");
        request.getSession().setAttribute("url_prior_login", referrer);
    return "user/login";

Then, after successful login custom implementation of SavedRequestAwareAuthenticationSuccessHandler will redirect user to the previous page:

HttpSession session = request.getSession(false);
if (session != null) {
    url = (String) request.getSession().getAttribute("url_prior_login");

Redirect the user:

if (url != null) {

Redirecting to previous page after login? PHP

A common way to do this is to pass the user's current page to the Login form via a $_GET variable.

For example: if you are reading an Article, and you want to leave a comment. The URL for comments is comment.php?articleid=17. While comment.php is loading, it notices that you are not logged in. It wants to send you to login.php, like you showed earlier. However, we're going to change your script so that is also tells the login page to remember where you are:

header("Location:login.php?location=" . urlencode($_SERVER['REQUEST_URI']));
// Note: $_SERVER['REQUEST_URI'] is your current page

This should send the user to: login.php?location=comment.php%3Farticleid%3D17. login.php should now check to see if $_GET['location'] is populated. If it is populated, then send the user to this location (in this case, comment.php?articleid=17). For example:

//  login.php
echo '<input type="hidden" name="location" value="';
if(isset($_GET['location'])) {
    echo htmlspecialchars($_GET['location']);
echo '" />';
//  Will show something like this:
//  <input type="hidden" name="location" value="comment.php?articleid=17" />


//  login-check.php

//  our url is now stored as $_POST['location'] (posted from login.php). If it's blank, let's ignore it. Otherwise, let's do something with it.
$redirect = NULL;
if($_POST['location'] != '') {
    $redirect = $_POST['location'];

if((empty($username) OR empty($password) AND !isset($_SESSION['id_login']))) {
    $url = 'login.php?p=1';
    // if we have a redirect URL, pass it back to login.php so we don't forget it
    if(isset($redirect)) {
        $url .= '&location=' . urlencode($redirect);
   header("Location: " . $url);
elseif (!user_exists($username,$password) AND !isset($_SESSION['id_login'])) {
    $url = 'login.php?p=2';
    if(isset($redirect)) {
        $url .= '&location=' . urlencode($redirect);
   header("Location:" . $url);
elseif(isset($_SESSION['id_login'])) {
    // if login is successful and there is a redirect address, send the user directly there
    if($redirect) {
        header("Location:". $redirect);
    } else {


You should run some validation against $_GET['location'] before sending the user there. For example, if I tell people who use your site to click on this link: login.php? then they will be sent to a foreign URL that will try to do something bad.

Always make sure to use urlencode when passing URLs as $_GET parameters. This encodes special URL characters (such as ?, &, and %) so that they don't break your url (e.g.: login.php?location=comment.php?id=17 <- this has two ?'s and will not work correctly)

How to programmatically log out from Facebook SDK 3.0 without using Facebook login/logout button?

Since Facebook's Android SDK v4.0 (see changelog) you need to execute the following:


C# ASP.NET Single Sign-On Implementation

[disclaimer: I'm one of the contributors]

We built a very simple free/opensource component that adds SAML support for ASP.NET apps

Basically it's just one short C# file you can throw into your project (or install via Nuget) and use it with your app

Windows task scheduler error 101 launch failure code 2147943785

The user that is configured to run this scheduled task must have "Log on as a batch job" rights on the computer that hosts the exe you are launching. This can be configured on the local security policy of the computer that hosts the exe. You can change the policy (on the server hosting the exe) under

Administrative Tools -> Local Security Policy -> Local Policies -> User Rights Assignment -> Log On As Batch Job

Add your user to this list (you could also make the user account a local admin on the machine hosting the exe).

Finally, you could also simply copy your exe from the network location to your local computer and run it from there instead.

Note also that a domain policy could be restricting "Log on as a batch job" rights at your organization.

Getting time difference between two times in PHP

$start = strtotime("12:00");
$end = // Run query to get datetime value from db
$elapsed = $end - $start;
echo date("H:i", $elapsed);

Socket File "/var/pgsql_socket/.s.PGSQL.5432" Missing In Mountain Lion (OS X Server)

Check for the status of the database:

service postgresql status

If the database is not running, start the db:

sudo service postgresql start

setValue:forUndefinedKey: this class is not key value coding-compliant for the key

For me I switched a call for my collection view header where I was registering the nib to registering the class. That fixed it.

Unable to install gem - Failed to build gem native extension - cannot load such file -- mkmf (LoadError)

For WSL (Windows Subsystem for Linux) you need install build-essential package:

sudo apt install build-essential

Pass array to where in Codeigniter Active Record

Use where_in()

$ids = array('20', '15', '22', '46', '86');
$this->db->where_in('id', $ids );

why windows 7 task scheduler task fails with error 2147942667

I had this same issue.

The solution for me was found in the Microsoft KB Article 2452723:

Windows Vista onwards scheduled tasks fail to run if the path in "Start in (Optional)" field has quotes

Basically, edit your scheduled task and take the Quotes out of the Start In field:

  1. Open your Scheduled Task
  2. Switch to "Actions" tab
  3. Open your Action
  4. Remove Quotes (") from the field "Start in (optional)"
  5. Save and close all open dialogs

Edit Action Dialog Box

To get the relevant error message:

1) Convert 2147942667 to hex: 8007010B
2) Take last 4 digits (010B) and convert to decimal: 267
3) Run: net helpmsg 267
4) Result: "The directory name is invalid."

Command Prompt Window

PermissionError: [Errno 13] in python

When doing;

a_file = open('E:\Python Win7-64-AMD 3.3\Test', encoding='utf-8')'re trying to open a directory as a file, which may (and on most non UNIX file systems will) fail.

Your other example though;

a_file = open('E:\Python Win7-64-AMD 3.3\Test\a.txt', encoding='utf-8')

should work well if you just have the permission on a.txt. You may want to use a raw (r-prefixed) string though, to make sure your path does not contain any escape characters like \n that will be translated to special characters.

a_file = open(r'E:\Python Win7-64-AMD 3.3\Test\a.txt', encoding='utf-8')

How to populate a sub-document in mongoose after creating it?

I faced the same problem,but after hours of efforts i find the solution.It can be without using any external plugin:)

applicantListToExport: function (query, callback) {
   .find(query).select({'advtId': 0})
      path: 'influId',
      model: 'influencer',
      select: { '_id': 1,'user':1},
      populate: {
        path: 'userid',
        model: 'User'

Keeping session alive with Curl and PHP

You have correctly used "CURLOPT_COOKIEJAR" (writing) but you also need to set "CURLOPT_COOKIEFILE" (reading)


At least one JAR was scanned for TLDs yet contained no TLDs

For anyone trying to get this working using the Sysdeo Eclipse Tomcat plugin, try the following steps (I used Sysdeo Tomcat Plugin 3.3.0, Eclipse Kepler, and Tomcat 7.0.53 to construct these steps):

  1. Window --> Preferences --> Expand the Tomcat node in the tree --> JVM Settings
  2. Under "Append to JVM Parameters", click the "Add" button.
  3. In the "New Tomcat JVM parameter" popup, enter -Djava.util.logging.config.file="{TOMCAT_HOME}\conf\", where {TOMCAT_HOME} is the path to your Tomcat directory (example: C:\Tomcat\apache-tomcat-7.0.53\conf\ Click OK.
  4. Under "Append to JVM Parameters", click the "Add" button again.
  5. In the "New Tomcat JVM parameter" popup, enter -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager. Click OK.
  6. Click OK in the Preferences window.
  7. Make the adjustments to the {TOMCAT_HOME}\conf\ file as specified in the question above.
  8. The next time you start Tomcat in Eclipse, you should see the scanned .jars listed in the Eclipse Console instead of the "Enable debug logging for this logger" message. The information should also be logged in {TOMCAT_HOME}\logs\catalina.yyyy-mm-dd.log.

403 - Forbidden: Access is denied. You do not have permission to view this directory or page using the credentials that you supplied

You can get the same error in MVC5 if you have a class name and a folder with a matching name Example : If you have class lands where when you want to see view/lands/index.cshtml file, if you also have a folder with name 'lands' you get the error as it first try the lands folder

MySQL Error #1133 - Can't find any matching row in the user table

I encountered this error using MySQL in a different context (not within phpMyAdmin). GRANT and SET PASSWORD commands failed on a particular existing user, who was listed in the mysql.user table. In my case, it was fixed by running


The documentation for this command says

Reloads the privileges from the grant tables in the mysql database.

The server caches information in memory as a result of GRANT and CREATE USER statements. This memory is not released by the corresponding REVOKE and DROP USER statements, so for a server that executes many instances of the statements that cause caching, there will be an increase in memory use. This cached memory can be freed with FLUSH PRIVILEGES.

Apparently the user table cache had reached an inconsistent state, causing this weird error message. More information is available here.

Error TF30063: You are not authorized to access ... \DefaultCollection

Disconnect from Team Fountation Server under Team Menu and reconnect it from Connect Tab under Team Explorer Window

enter image description here enter image description here

How to SELECT in Oracle using a DBLINK located in a different schema?

I had the same problem I used the solution offered above - I dropped the SYNONYM, created a VIEW with the same name as the synonym. it had a select using the dblink , and gave GRANT SELECT to the other schema It worked great.

How to get the currently logged in user's user id in Django?

Assuming you are referring to Django's Auth User, in your view:

def game(request):
  user = request.user

  gta = Game.objects.create(name="gta", owner=user)

Failed to build gem native extension — Rails install

sudo apt-get install ruby-dev

worked for me

Taskkill /f doesn't kill a process

In my case, after several days of fighting with this problem (it was happening to VirtualBox and µTorrent processes), I discovered it was caused by a network driver issue, provoked by Windows Update patch KB4338818 (Windows 7 x64). After uninstalling that patch everything went back to normal. I just thought it could be useful for others.

How to fix 'Microsoft Excel cannot open or save any more documents'

Go to this key on Registry Editor (Run | Regedit) HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders

change key Cache to something like C:\Windows\Temp

My similar problem was solved like this.



Logout button php

When you want to destroy a session completely, you need to do more then just


First, you should unset any session variables. Then you should destroy the session followed by closing the write of the session. This can be done by the following:

header('Location: /');

The reason you want have a separate script for a logout is so that you do not accidently execute it on the page. So make a link to your logout script, then the header will redirect to the root of your site.


You need to remove the () from your exit code near the top of your script. it should just be


What's the difference between console.dir and console.log?

Following Felix Klings advice I tried it out in my chrome browser.

console.dir([1,2]) gives the following output:

 0: 1
 1: 2
 length: 2
 __proto__: Array[0]

While console.log([1,2]) gives the following output:

[1, 2]

So I believe console.dir() should be used to get more information like prototype etc in arrays and objects.

How to "log in" to a website using Python's Requests module?

If the information you want is on the page you are directed to immediately after login...

Lets call your ck variable payload instead, like in the python-requests docs:

payload = {'inUserName': 'USERNAME/EMAIL', 'inUserPass': 'PASSWORD'}
url = '', data=payload)


See below.

Calling a JSON API with Node.js

Another solution is to user axios:

npm install axios

Code will be like:

const url = `${this.env.someMicroservice.address}/v1/my-end-point`;

const { data } = await axios.get<MyInterface>(url, {
  auth: {
    username: this.env.auth.user,
    password: this.env.auth.pass

return data;

Chrome javascript debugger breakpoints don't do anything?

So, in addition to Adam Rackis' answer, if you have errors in your javascript file above the breakpoint, you won't reach it regardless if you flag it, or put in debugger;.

Here's an example:

if (nonExistentVar === "something") {
  console.log("this won't happen as the above errors out");
console.log("this won't print either")

Access denied for root user in MySQL command-line

I had the same issue, and it turned out to be that MariaDB was set to allow only root to log in locally via the unix_socket plug-in, so clearing that setting allowed successfully logging in with the user specified on the command line, provided a correct password is entered, of course. See this answer on Ask Ubuntu

Remove multiple objects with rm()

Make the list a character vector (not a vector of names)

rm(list = c('temp1','temp2'))


rm(temp1, temp2)

Notice: Array to string conversion in

Store the Value of $_SESSION['username'] into a variable such as $username


$get = @mysql_query("SELECT money FROM players WHERE username = 

it should work!

Redirecting to a certain route based on condition

 .when('/main' , {templateUrl: 'partials/main.html',  controller: MainController})
 .when('/login', {templateUrl: 'partials/login.html', controller: LoginController}).
 .when('/login', {templateUrl: 'partials/index.html', controller: IndexController})
 .otherwise({redirectTo: '/index'});

phpMyAdmin says no privilege to create database, despite logged in as root user

It appears to be a transient issue and fixed itself afterwards. Thanks for everyone's attention.

Enable remote connections for SQL Server Express 2012

I had to add a firewall inbound port rule to open UDP port 1434. This is the one Sql Server Browser listens on.

rsync - mkstemp failed: Permission denied (13)

I have Centos 7 server with rsyncd on board: /etc/rsyncd.conf

path = /files

By default selinux blocks access for rsyncd to /files folder

# this sets needed context to my /files folder
sudo semanage fcontext -a -t rsync_data_t '/files(/.*)?'
sudo restorecon -Rv '/files'
# sets needed booleans
sudo setsebool -P rsync_client 1

Disabling selinux is an easy but not a good solution

Error 6 (net::ERR_FILE_NOT_FOUND): The files c or directory could not be found

Big one I see that causes this is filename. If you have a SPACE then any number such as 'Site 2' the file path with look like something/Site%202/index.html This is because spaces or rendered as %20, and if another number is immediately following that it will try to read it as %202. Fix is you never use spaces in your filenames.

Could not complete the operation due to error 80020101. IE

when do you call timerReset()? Perhaps you get that error when trying to call it after setTimeout() has already done its thing?

wrap it in

if (window.myTimeout) { 
  myTimeout = setTimeout("timerDone()", 1000 * 1440);

edit: Actually, upon further reflection, since you did mention jQuery (and yet don't have any actual jQuery code here... I wonder if you have this nested within some jQuery (like inside a $(document).ready(.. and this is a matter of variable scope. If so, try this:

window.message="Logged in";
window.myTimeout = setTimeout("timerDone()",1000 * 1440);
function timerDone()
    window.message="Logged out";   
function timerReset()

    window.myTimeout = setTimeout("timerDone()", 1000 * 1440);

Error message "Forbidden You don't have permission to access / on this server"

If you are using MAMP Pro the way to fix this is by checking the Indexes checkbox under the Hosts - Extended tab.

In MAMP Pro v3.0.3 this is what that looks like: enter image description here

Append an int to a std::string

I have a feeling that your ClientID is not of a string type (zero-terminated char* or std::string) but some integral type (e.g. int) so you need to convert number to the string first:

std::stringstream ss;
ss << ClientID;

But you can use operator+ as well (instead of append):

query += ss.str();

How to tell if node.js is installed or not

Open the command prompt in Windows or terminal in Linux and Mac.Type

node -v

If node is install it will show its version.For eg.,


Else download it from

How to check if an user is logged in Symfony2 inside a controller?

Try this:

if( $this->container->get('security.context')->isGranted('IS_AUTHENTICATED_FULLY') ){
    // authenticated (NON anonymous)

Further information:

"Anonymous users are technically authenticated, meaning that the isAuthenticated() method of an anonymous user object will return true. To check if your user is actually authenticated, check for the IS_AUTHENTICATED_FULLY role."


Issue with Task Scheduler launching a task

  • Right Click on the Task in Task Scheduler
  • Click on the Actions tab
  • Click on Edit
  • Remove the quotes around the path in the "Starts In" textbox.

Using sessions & session variables in a PHP Login Script


//extract data from submit post 


if($user=="user" && $pass=="pass")


$_SESSION['user']= $user;   

//if correct password and name store in session 

else {

echo "Invalid user and password";





//your home page code here


PHP sessions default timeout

It depends on the server configuration or the relevant directives session.gc_maxlifetime in php.ini.

Typically the default is 24 minutes (1440 seconds), but your webhost may have altered the default to something else.

Displaying all table names in php from MySQL database

The brackets that are commonly used in the mysql documentation for examples should be ommitted in a 'real' query.

It also doesn't appear that you're echoing the result of the mysql query anywhere. mysql_query returns a mysql resource on success. The php manual page also includes instructions on how to load the mysql result resource into an array for echoing and other manipulation.

Can't change table design in SQL Server 2008

The answer is on the MSDN site:

The Save (Not Permitted) dialog box warns you that saving changes is not permitted because the changes you have made require the listed tables to be dropped and re-created.

The following actions might require a table to be re-created:

  • Adding a new column to the middle of the table
  • Dropping a column
  • Changing column nullability
  • Changing the order of the columns
  • Changing the data type of a column


Additional useful informations from here:

To change the Prevent saving changes that require the table re-creation option, follow these steps:

  1. Open SQL Server Management Studio (SSMS).
  2. On the Tools menu, click Options.
  3. In the navigation pane of the Options window, click Designers.
  4. Select or clear the Prevent saving changes that require the table re-creation check box, and then click OK.

Note If you disable this option, you are not warned when you save the table that the changes that you made have changed the metadata structure of the table. In this case, data loss may occur when you save the table.

Risk of turning off the "Prevent saving changes that require table re-creation" option

Although turning off this option can help you avoid re-creating a table, it can also lead to changes being lost. For example, suppose that you enable the Change Tracking feature in SQL Server 2008 to track changes to the table. When you perform an operation that causes the table to be re-created, you receive the error message that is mentioned in the "Symptoms" section. However, if you turn off this option, the existing change tracking information is deleted when the table is re-created. Therefore, we recommend that you do not work around this problem by turning off the option.

Settings, screen shot

Sending data through POST request from a node.js server to a node.js server

Posting data is a matter of sending a query string (just like the way you would send it with an URL after the ?) as the request body.

This requires Content-Type and Content-Length headers, so the receiving server knows how to interpret the incoming data. (*)

var querystring = require('querystring');
var http = require('http');

var data = querystring.stringify({
      username: yourUsernameValue,
      password: yourPasswordValue

var options = {
    host: 'my.url',
    port: 80,
    path: '/login',
    method: 'POST',
    headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
        'Content-Length': Buffer.byteLength(data)

var req = http.request(options, function(res) {
    res.on('data', function (chunk) {
        console.log("body: " + chunk);


(*) Sending data requires the Content-Type header to be set correctly, i.e. application/x-www-form-urlencoded for the traditional format that a standard HTML form would use.

It's easy to send JSON (application/json) in exactly the same manner; just JSON.stringify() the data beforehand.

URL-encoded data supports one level of structure (i.e. key and value). JSON is useful when it comes to exchanging data that has a nested structure.

The bottom line is: The server must be able to interpret the content type in question. It could be text/plain or anything else; there is no need to convert data if the receiving server understands it as it is.

Add a charset parameter (e.g. application/json; charset=Windows-1252) if your data is in an unusual character set, i.e. not UTF-8. This can be necessary if you read it from a file, for example.

How to update SQLAlchemy row entry?

I wrote telegram bot, and have some problem with update rows. Use this example, if you have Model

def update_state(chat_id, state):
        value = Users.query.filter(Users.chat_id == str(chat_id)).first()
        value.state = str(state)
        print('Error in def update_state')

Why use db.session.flush()? That's why >>> SQLAlchemy: What's the difference between flush() and commit()?

How do I run Visual Studio as an administrator by default?


"W7 prompts everytime to run this program "devenv.exe" , anyway to get rid of that ?"

Yes. You can prevent Windows from prompting you by going to Control Panel/User Accounts/Change User Account Control settings and move the slider down.

Unable to add window -- token android.os.BinderProxy is not valid; is your activity running?

This can occur when you are showing the dialog for a context that no longer exists. A common case - if the 'show dialog' operation is after an asynchronous operation, and during that operation the original activity (that is to be the parent of your dialog) is destroyed. For a good description, see this blog post and comments:

From the stack trace above, it appears that the facebook library spins off the auth operation asynchronously, and you have a Handler - Callback mechanism (onComplete called on a listener) that could easily create this scenario.

When I've seen this reported in my app, its pretty rare and matches the experience in the blog post. Something went wrong for the activity/it was destroyed during the work of the the AsyncTask. I don't know how your modification could result in this every time, but perhaps you are referencing an Activity as the context for the dialog that is always destroyed by the time your code executes?

Also, while I'm not sure if this is the best way to tell if your activity is running, see this answer for one method of doing so:

Check whether activity is active

Why do I get permission denied when I try use "make" to install something?

I had a very similar error message as you, although listing a particular file:

$ make
make: execvp: ../HoughLineExtractor/houghlineextractor.hh: Permission denied
make: *** [../HoughLineAccumulator/houghlineaccumulator.o] Error 127

$ sudo make
make: execvp: ../HoughLineExtractor/houghlineextractor.hh: Permission denied
make: *** [../HoughLineAccumulator/houghlineaccumulator.o] Error 127

In my case, I forgot to add a trailing slash to indicate continuation of the line as shown:

    ../HoughLineAccumulator/houghlineaccumulator.hh  # <-- missing slash!!

Hope that helps someone else who lands here from a search engine.

How to run batch file from network share without "UNC path are not supported" message?

My env windows10 2019 lts version and I add this two binray data ,fix this error

Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Command Processor DisableUNCCheck value 1 Computer\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Command Processor DisableUNCCheck value 1

How to use the onClick event for Hyperlink using C# code?

this may help you.

In .cs page,

//Declare a string
   public string usertypeurl = "";
  //check who is the user
       //place your code to check who is the user
       //if it is admin
       usertypeurl = "help/AdminTutorial.html";
       //if it is other 
        usertypeurl = "help/UserTutorial.html";

In .aspx age pass this variabe

  <a href='<%=usertypeurl%>'>Tutorial</a>

check if variable empty

you can use isset() routine .

also additionaly you can refer an range of is_type () functions like

is_string(), is_float(),is_int() etc to further specificaly test

How to get active user's UserDetails

And if you need authorized user in templates (e.g. JSP) use

<%@ taglib prefix="sec" uri="" %>
<sec:authentication property="principal.yourCustomField"/>

together with


How to view the stored procedure code in SQL Server Management Studio

This is another way of viewing definition of stored procedure


Access denied for user 'root'@'localhost' while attempting to grant privileges. How do I grant privileges?

You may have come to this question with MySQL version 8 installed (like me) and not found a satisfactory answer. You can no longer create users like this in version 8:


The rather confusing error message that you get back is: ERROR 1410 (42000): You are not allowed to create a user with GRANT

In order to create users in version 8 you have to do it in two steps:

CREATE USER 'steves'@'[hostname].com' IDENTIFIED BY '[OBSCURED]';
GRANT ALL PRIVILEGES ON *.* TO 'steves'@'[hostname].com' WITH GRANT OPTION;

Of course, if you prefer, you can also supply a limited number of privileges (instead of GRANT ALL PRIVILEGES), e.g. GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, ALTER

What does "if (" mean?

The next() moves the cursor froward one row from its current position in the resultset. so its evident that if( means that if the next row is not null (means if it exist), Go Ahead.

Now w.r.t your problem,

ResultSet rs = stmt.executeQuery(sql);  //This is wrong

note that executeQuery(String) is used in case you use a sql-query as string.

Whereas when you use a PreparedStatement, use executeQuery() which executes the SQL query in this PreparedStatement object and returns the ResultSet object generated by the query.

Solution :

Use : ResultSet rs = stmt.executeQuery();

No suitable driver found for 'jdbc:mysql://localhost:3306/mysql

i had same problem i fix this using if developing jsp, put mysql connetor into WEB-INF->lib folder after puting that in eclipse right click and go build-path -> configure build patha in library tab add external jar file give location where lib folder is

REST API Authentication

For e.g. when a user has login.Now lets say the user want to create a forum topic, How will I know that the user is already logged in?

Think about it - there must be some handshake that tells your "Create Forum" API that this current request is from an authenticated user. Since REST APIs are typically stateless, the state must be persisted somewhere. Your client consuming the REST APIs is responsible for maintaining that state. Usually, it is in the form of some token that gets passed around since the time the user was logged in. If the token is good, your request is good.

Check how Amazon AWS does authentications. That's a perfect example of "passing the buck" around from one API to another.

*I thought of adding some practical response to my previous answer. Try Apache Shiro (or any authentication/authorization library). Bottom line, try and avoid custom coding. Once you have integrated your favorite library (I use Apache Shiro, btw) you can then do the following:

  1. Create a Login/logout API like: /api/v1/login and api/v1/logout
  2. In these Login and Logout APIs, perform the authentication with your user store
  3. The outcome is a token (usually, JSESSIONID) that is sent back to the client (web, mobile, whatever)
  4. From this point onwards, all subsequent calls made by your client will include this token
  5. Let's say your next call is made to an API called /api/v1/findUser
  6. The first thing this API code will do is to check for the token ("is this user authenticated?")
  7. If the answer comes back as NO, then you throw a HTTP 401 Status back at the client. Let them handle it.
  8. If the answer is YES, then proceed to return the requested User

That's all. Hope this helps.

Logging levels - Logback - rule-of-thumb to assign log levels

My approach, i think coming more from an development than an operations point of view, is:

  • Error means that the execution of some task could not be completed; an email couldn't be sent, a page couldn't be rendered, some data couldn't be stored to a database, something like that. Something has definitively gone wrong.
  • Warning means that something unexpected happened, but that execution can continue, perhaps in a degraded mode; a configuration file was missing but defaults were used, a price was calculated as negative, so it was clamped to zero, etc. Something is not right, but it hasn't gone properly wrong yet - warnings are often a sign that there will be an error very soon.
  • Info means that something normal but significant happened; the system started, the system stopped, the daily inventory update job ran, etc. There shouldn't be a continual torrent of these, otherwise there's just too much to read.
  • Debug means that something normal and insignificant happened; a new user came to the site, a page was rendered, an order was taken, a price was updated. This is the stuff excluded from info because there would be too much of it.
  • Trace is something i have never actually used.

Android - Start service on boot

Just to make searching easier, as mentioned in comments, this is not possible since 3.1

`require': no such file to load -- mkmf (LoadError)

This is the answer that worked for me. Was in the comments above, but deserves its rightful place as answer for ubuntu 12.04 ruby 1.8.7

sudo apt-get install ruby-dev
# if above doesnt work make sure you have build essential
sudo apt-get install build-essential

How to redirect both stdout and stderr to a file


command >>log_file 2>>log_file

Specify path to node_modules in package.json

I'm not sure if this is what you had in mind, but I ended up on this question because I was unable to install node_modules inside my project dir as it was mounted on a filesystem that did not support symlinks (a VM "shared" folder).

I found the following workaround:

  1. Copy the package.json file to a temp folder on a different filesystem
  2. Run npm install there
  3. Copy the resulting node_modules directory back into the project dir, using cp -r --dereference to expand symlinks into copies.

I hope this helps someone else who ends up on this question when looking for a way to move node_modules to a different filesystem.

Other options

There is another workaround, which I found on the github issue that @Charminbear linked to, but this doesn't work with grunt because it does not support NODE_PATH as per

lets say you have /media/sf_shared and you can't install symlinks in there, which means you can't actually npm install from /media/sf_shared/myproject because some modules use symlinks.

  • $ mkdir /home/dan/myproject && cd /home/dan/myproject
  • $ ln -s /media/sf_shared/myproject/package.json (you can symlink in this direction, just can't create one inside of /media/sf_shared)
  • $ npm install
  • $ cd /media/sf_shared/myproject
  • $ NODE_PATH=/home/dan/myproject/node_modules node index.js

All libraries must use the exact same version specification

The best way to solve the problem is implement all '' suggested by Android Studio

(Doesn't matter which support versions you are using – 27.1.1, 28.0.0 etc.)

Place the cursor to the error line e.g.

implementation ''

Android Studio will suggest you which '' is different version than ''


All libraries must use the exact same version specification (mixing versions can lead to runtime crashes). Found versions 28.0.0, 27.1.0, 27.0.2. Examples include and

So add & Now sync gradle file.

One by one try to implement all the suggested '' until there is no error in this line implementation ''

In my case, I added

implementation ''

implementation ''
implementation ''
implementation ''
implementation ''
implementation ''
implementation ''

All these dependencies, it could be different for you.

The database cannot be opened because it is version 782. This server supports version 706 and earlier. A downgrade path is not supported

Another solution is to migrate the database to e.g 2012 when you "export" the DB from e.g. Sql Server manager 2014. This is done in menu Tasks-> generate scripts when right-click on DB. Just follow this instruction:

It generates an scripts with everything and then in your SQL server manager e.g. 2012 run the script as specified in the instruction. I have performed the test with success.

How to read file binary in C#?

using (FileStream fs = File.OpenRead(binarySourceFile.Path))
    using (BinaryReader reader = new BinaryReader(fs))
        // Read in all pairs.
        while (reader.BaseStream.Position != reader.BaseStream.Length)
            Item item = new Item();
            item.UniqueId = reader.ReadString();
            item.StringUnique = reader.ReadString();
    return result;  

Binary Data Posting with curl

You don't need --header "Content-Length: $LENGTH".

curl --request POST --data-binary "@template_entry.xml" $URL

Note that GET request does not support content body widely.

Also remember that POST request have 2 different coding schema. This is first form:

  $ nc -l -p 6666 &
  $ curl  --request POST --data-binary "@README" http://localhost:6666

User-Agent: curl/7.21.0 (x86_64-pc-linux-gnu) libcurl/7.21.0 OpenSSL/0.9.8o zlib/ libidn/1.15 libssh2/1.2.6
Host: localhost:6666
Accept: */*
Content-Length: 9309
Content-Type: application/x-www-form-urlencoded
Expect: 100-continue

.. -*- mode: rst; coding: cp1251; fill-column: 80 -*-
.. contents::

You probably request this:

-F/--form name=content
           (HTTP) This lets curl emulate a filled-in form in
              which a user has pressed the submit button. This
              causes curl to POST data using the Content- Type
              multipart/form-data according to RFC2388. This
              enables uploading of binary files etc. To force the
              'content' part to be a file, prefix the file name
              with an @ sign. To just get the content part from a
              file, prefix the file name with the symbol <. The
              difference between @ and < is then that @ makes a
              file get attached in the post as a file upload,
              while the < makes a text field and just get the
              contents for that text field from a file.

vim - How to delete a large block of text without counting the lines?

Alongside with other motions that are already mentioned here, there is also /{pattern}<CR> motion, so if you know that you want to delete to line that contains foo, you could do dV/foo<CR>. V is here to force motion be line-wise because by default / is characterwise.

How to get the parent dir location

os.path.abspath doesn't validate anything, so if we're already appending strings to __file__ there's no need to bother with dirname or joining or any of that. Just treat __file__ as a directory and start climbing:

# climb to __file__'s parent's parent:
os.path.abspath(__file__ + "/../../")

That's far less convoluted than os.path.abspath(os.path.join(os.path.dirname(__file__),"..")) and about as manageable as dirname(dirname(__file__)). Climbing more than two levels starts to get ridiculous.

But, since we know how many levels to climb, we could clean this up with a simple little function:

uppath = lambda _path, n: os.sep.join(_path.split(os.sep)[:-n])

# __file__ = "/aParent/templates/blog1/page.html"
>>> uppath(__file__, 1)
>>> uppath(__file__, 2)
>>> uppath(__file__, 3)

How to add a set path only for that batch file executing?

There is an important detail:

set PATH="C:\linutils;C:\wingit\bin;%PATH%"

does not work, while

set PATH=C:\linutils;C:\wingit\bin;%PATH%

works. The difference is the quotes!

UPD also see the comment by venimus

Best method for reading newline delimited files and discarding the newlines?

I use this

def cleaned( aFile ):
    for line in aFile:
        yield line.strip()

Then I can do things like this.

lines = list( cleaned( open("file","r") ) )

Or, I can extend cleaned with extra functions to, for example, drop blank lines or skip comment lines or whatever.

Does GPS require Internet?

There are two issues:

  1. Getting the current coordinates (longitude, latitude, perhaps altitude) based on some external signals received by your device, and
  2. Deriving a human-readable position (address) from the coordinates.

To get the coordinates you don't need the Internet. GPS is satellite-based. But to derive street/city information from the coordinates, you'd need either to implement the map and the corresponding algorithms yourself on the device (a lot of work!) or to rely on proven services, e.g. by Google, in which case you'd need an Internet connection.

As of recently, Google allows for caching the maps, which would at least allow you to show your current position on the map even without a data connection, provided, you had cached the map in advance, when you could access the Internet.

SQL Server convert string to datetime

UPDATE MyTable SET MyDate = CONVERT(datetime, '2009/07/16 08:28:01', 120)

For a full discussion of CAST and CONVERT, including the different date formatting options, see the MSDN Library Link below:

How to convert DOS/Windows newline (CRLF) to Unix newline (LF) in a Bash script?

This worked for me

tr "\r" "\n" < sampledata.csv > sampledata2.csv 

Downloading a picture via urllib and python

Python 3 version of @DiGMi's answer:

from urllib import request
f = open('00000001.jpg', 'wb')

Disabling Controls in Bootstrap

No, Bootstrap does not introduce special considerations for disabling a drop-down.

<select id="xxx" name="xxx" class="input-medium" disabled>


<select id="xxx" name="xxx" class="input-medium" disabled="disabled">

will work. I prefer to give attributes values (as in the second form; in XHTML, attributes must have a value), but the HTML spec says:

The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.


The key differences between read-only and disabled:*

The Disabled attribute

  • Values for disabled form elements are not passed to the processor method. The W3C calls this a successful element.(This works similar to form check boxes that are not checked.)
  • Some browsers may override or provide default styling for disabled form elements. (Gray out or emboss text) Internet Explorer 5.5 is particularly nasty about this.
  • Disabled form elements do not receive focus.
  • Disabled form elements are skipped in tabbing navigation.

The Read Only Attribute

  • Not all form elements have a readonly attribute. Most notable, the <SELECT>, <OPTION>, and <BUTTON> elements do not have readonly attributes (although thy both have disabled attributes)
  • Browsers provide no default overridden visual feedback that the form element is read only
  • Form elements with the readonly attribute set will get passed to the form processor.
  • Read only form elements can receive the focus
  • Read only form elements are included in tabbed navigation.

*-blatant plagiarism from

Cannot bulk load. Operating system error code 5 (Access is denied.)

In our case it ended up being a Kerberos issue. I followed the steps in this article to resolve the issue:

It came down to configuring delegation on the machine account of the SQL Server where the BULK INSERT statement is running. The machine account needs to be able to delegate via the "cifs" service to the file server where the files are located. If you are using constrained delegation make sure to specify "Use any authenication protocol".

If DFS is involved you can execute the following Powershell command to get the name of the file server:

Get-DfsnFolderTarget -Path "\\dfsnamespace\share"

How do I check whether a file exists without exceptions?

How do I check whether a file exists, without using the try statement?

In 2016, this is still arguably the easiest way to check if both a file exists and if it is a file:

import os
os.path.isfile('./file.txt')    # Returns True if exists, else False

isfile is actually just a helper method that internally uses os.stat and stat.S_ISREG(mode) underneath. This os.stat is a lower-level method that will provide you with detailed information about files, directories, sockets, buffers, and more. More about os.stat here

Note: However, this approach will not lock the file in any way and therefore your code can become vulnerable to "time of check to time of use" (TOCTTOU) bugs.

So raising exceptions is considered to be an acceptable, and Pythonic, approach for flow control in your program. And one should consider handling missing files with IOErrors, rather than if statements (just an advice).

How to run a subprocess with Python, wait for it to exit and get the full stdout as a string?

I'd try something like:

from __future__ import print_function

import shlex
from subprocess import Popen, PIPE

def shlep(cmd):
    '''shlex split and popen
    parsed_cmd = shlex.split(cmd)
    ## if parsed_cmd[0] not in approved_commands:
    ##    raise ValueError, "Bad User!  No output for you!"
    proc = Popen(parsed_command, stdout=PIPE, stderr=PIPE)
    out, err = proc.communicate()
    return (proc.returncode, out, err)

... In other words let shlex.split() do most of the work. I would NOT attempt to parse the shell's command line, find pipe operators and set up your own pipeline. If you're going to do that then you'll basically have to write a complete shell syntax parser and you'll end up doing an awful lot of plumbing.

Of course this raises the question, why not just use Popen with the shell=True (keyword) option? This will let you pass a string (no splitting nor parsing) to the shell and still gather up the results to handle as you wish. My example here won't process any pipelines, backticks, file descriptor redirection, etc that might be in the command, they'll all appear as literal arguments to the command. Thus it is still safer then running with shell=True ... I've given a silly example of checking the command against some sort of "approved command" dictionary or set --- through it would make more sense to normalize that into an absolute path unless you intend to require that the arguments be normalized prior to passing the command string to this function.

dotnet ef not found in .NET Core 3

I had the same problem. I resolved, uninstalling all de the versions in my pc and then reinstall dotnet.

How do I enumerate through a JObject?

For people like me, linq addicts, and based on svick's answer, here a linq approach:

using System.Linq;
//make it linq iterable. 
var obj_linq = Response.Cast<KeyValuePair<string, JToken>>();

Now you can make linq expressions like:

JToken x = obj_linq
          .Where( d => d.Key == "my_key")
          .Select(v => v)
string y = ((JValue)x).Value;

Or just:

var y = obj_linq
       .Where(d => d.Key == "my_key")
       .Select(v => ((JValue)v.Value).Value)

Or this one to iterate over all data:

obj_linq.ToList().ForEach( x => { do stuff } ); 

Detect all Firefox versions in JS

here it it

var ffversion = '18';
var is_firefox = navigator.userAgent.toLowerCase().indexOf('firefox/'+ffversion) > -1;

Vim: insert the same characters across multiple lines

Updated January 2016

Whilst the accepted answer is a great solution, this is actually slightly fewer keystrokes, and scales better - based in principle on the accepted answer.

  1. Move the cursor to the n in name.
  2. Enter visual block mode (ctrlv).
  3. Press 3j
  4. Press I.
  5. Type in vendor_.
  6. Press esc.

visual illustration

Note, this has fewer keystrokes than the accepted answer provided (compare Step 3). We just count the number of j actions to perform.

If you have line numbers enabled (as illustrated above), and know the line number you wish to move to, then step 3 can be changed to #G where # is the wanted line number.

In our example above, this would be 4G. However when dealing with just a few line numbers an explicit count works well.

(grep) Regex to match non-ASCII characters?

To Validate Text Box Accept Ascii Only use this Pattern


how to convert a string date into datetime format in python?

The particular format for strptime:

datetime.datetime.strptime(string_date, "%Y-%m-%d %H:%M:%S.%f")
#>>> datetime.datetime(2013, 9, 28, 20, 30, 55, 782000)

Is unsigned integer subtraction defined behavior?

The result of a subtraction generating a negative number in an unsigned type is well-defined:

  1. [...] A computation involving unsigned operands can never overflow, because a result that cannot be represented by the resulting unsigned integer type is reduced modulo the number that is one greater than the largest value that can be represented by the resulting type. (ISO/IEC 9899:1999 (E) §6.2.5/9)

As you can see, (unsigned)0 - (unsigned)1 equals -1 modulo UINT_MAX+1, or in other words, UINT_MAX.

Note that although it does say "A computation involving unsigned operands can never overflow", which might lead you to believe that it applies only for exceeding the upper limit, this is presented as a motivation for the actual binding part of the sentence: "a result that cannot be represented by the resulting unsigned integer type is reduced modulo the number that is one greater than the largest value that can be represented by the resulting type." This phrase is not restricted to overflow of the upper bound of the type, and applies equally to values too low to be represented.

How to generate Entity Relationship (ER) Diagram of a database using Microsoft SQL Server Management Studio?

As of Oct 2019, SQL Server Management Studio, they did not upgraded the SSMS to add create ER Diagram feature.

I would suggest try using DBWeaver from here :

I am using Mac and Windows both and I was able to download the community edition and logged into my SQL server database and was able to create the ER diagram using the DB Weaver.

ER Diagram using the Community Version Db Viewer

Oracle "(+)" Operator

In Oracle, (+) denotes the "optional" table in the JOIN. So in your query,

SELECT,, a.col_2, b.col_2, ...
FROM a,b

it's a LEFT OUTER JOIN of table 'b' to table 'a'. It will return all data of table 'a' without losing its data when the other side (optional table 'b') has no data.

Diagram of Left Outer Join

The modern standard syntax for the same query would be

SELECT,, a.col_2, b.col_2, ...

or with a shorthand for (not supported by all databases):

SELECT,, a.col_2, b.col_2, ...

If you remove (+) then it will be normal inner join query

Older syntax, in both Oracle and other databases:

SELECT,, a.col_2, b.col_2, ...
FROM a,b

More modern syntax:

SELECT,, a.col_2, b.col_2, ...

Or simply:

SELECT,, a.col_2, b.col_2, ...

Diagram of Inner Join

It will only return all data where both 'a' & 'b' tables 'id' value is same, means common part.

If you want to make your query a Right Join

This is just the same as a LEFT JOIN, but switches which table is optional.

Diagram of Right Outer Join

Old Oracle syntax:

SELECT,, a.col_2, b.col_2, ...
FROM a,b

Modern standard syntax:

SELECT,, a.col_2, b.col_2, ...

Ref & help:

Left Outer Join using + sign in Oracle 11g

HTML display result in text (input) field?

Do you really want the result to come up in an input box? If not, consider a table with borders set to other than transparent and use

document.getElementById('sum').innerHTML = sum;

Return multiple values from a SQL Server function

Change it to a table-valued function

Please refer to the following link, for example.

error: Your local changes to the following files would be overwritten by checkout

I encountered the same problem and solved it by

git checkout -f branch

and its specification is rather clear.

-f, --force

When switching branches, proceed even if the index or the working tree differs from HEAD. This is used to throw away local changes.

When checking out paths from the index, do not fail upon unmerged entries; instead, unmerged entries are ignored.

How do you find the row count for all your tables in Postgres

I usually don't rely on statistics, especially in PostgreSQL.

SELECT table_name, dsql2('select count(*) from '||table_name) as rownum
FROM information_schema.tables
WHERE table_type='BASE TABLE'
    AND table_schema='livescreen'
  v_val int;
  execute i_text into v_val;
  return v_val;
  COST 100;

Removing multiple keys from a dictionary safely

Some timing tests for cpython 3 shows that a simple for loop is the fastest way, and it's quite readable. Adding in a function doesn't cause much overhead either:

timeit results (10k iterations):

  • all(x.pop(v) for v in r) # 0.85
  • all(map(x.pop, r)) # 0.60
  • list(map(x.pop, r)) # 0.70
  • all(map(x.__delitem__, r)) # 0.44
  • del_all(x, r) # 0.40
  • <inline for loop>(x, r) # 0.35
def del_all(mapping, to_remove):
      """Remove list of elements from mapping."""
      for key in to_remove:
          del mapping[key]

For small iterations, doing that 'inline' was a bit faster, because of the overhead of the function call. But del_all is lint-safe, reusable, and faster than all the python comprehension and mapping constructs.

Merge/flatten an array of arrays

I think array.flat(Infinity) is a perfect solution. But flat function is a relatively new function and may not run in older versions of browsers. We can use recursive function for solving this.

const arr = ["A", ["B", [["B11", "B12", ["B131", "B132"]], "B2"]], "C", ["D", "E", "F", ["G", "H", "I"]]]_x000D_
const flatArray = (arr) => {_x000D_
    const res = []_x000D_
    for (const item of arr) {_x000D_
        if (Array.isArray(item)) {_x000D_
            const subRes = flatArray(item)_x000D_
        } else {_x000D_
    return res_x000D_

Tkinter module not found on Ubuntu

Adding solution for CentOs 7 (python 3.6.x)

yum install python36-tkinter

I had tried about every version possible, hopefully this helps out others.

nvm is not compatible with the npm config "prefix" option:

This may be a conflict with your local installation of Node (if you had it installed via another way than NVM in the past). You should delete this instance of node:

  1. remove node_modules sudo rm -rf /usr/local/lib/node_modules
  2. remove node sudo rm /usr/local/bin/node
  3. remove node link cd /usr/local/bin && ls -l | grep "../lib/node_modules/" | awk '{print $9}'| xargs rm

After you cant install nvm

Using Selenium Web Driver to retrieve value of a HTML input

If the input value gets populated by a script that has some latency involved (e.g. AJAX call) then you need to wait until the input has been populated. E.g.

var w = new WebDriverWait(WebBrowser, TimeSpan.FromSeconds(10));
            w.Until((d) => {
                // Wait until the input has a value...

                var elements = d.FindElements(By.Name(name));

                var ele = elements.SingleOrDefault();

                if (ele != null)
                    // Found a single element

                    if (ele.GetAttribute("value") != "")
                        // We have a value now
                        return true;

                return false;

        var e = WebBrowser.Current.FindElement(By.Name(name));

        if (e.GetAttribute("value") != value)
            Assert.Fail("Result contains a field named '{0}', but its value is '{1}', not '{2}' as expected", name, e.GetAttribute("value"), value);

Insert default value when parameter is null

This is the best I can come up with. It prevents sql injection uses only one insert statement and can ge extended with more case statements.

CREATE PROCEDURE t_insert (     @value varchar(50) = null )
SET @sQuery = N'
insert into __t (value) values ( '+
CASE WHEN @value IS NULL THEN ' default ' ELSE ' @value ' END +' );';

EXEC sp_executesql 
@stmt = @sQuery, 
@params = N'@value varchar(50)',
@value = @value;


How to jquery alert confirm box "yes" & "no"

I won't write your code but what you looking for is something like a jquery dialog

take a look here

jQuery modal-confirmation

$(function() {
    $( "#dialog-confirm" ).dialog({
      resizable: false,
      modal: true,
      buttons: {
        "Delete all items": function() {
          $( this ).dialog( "close" );
        Cancel: function() {
          $( this ).dialog( "close" );

<div id="dialog-confirm" title="Empty the recycle bin?">
    <span class="ui-icon ui-icon-alert" style="float:left; margin:0 7px 20px 0;"></span>
    These items will be permanently deleted and cannot be recovered. Are you sure?

React.js, wait for setState to finish before triggering a function?

Why not one more answer? setState() and the setState()-triggered render() have both completed executing when you call componentDidMount() (the first time render() is executed) and/or componentDidUpdate() (any time after render() is executed). (Links are to docs.)

Example with componentDidUpdate()

Caller, set reference and set state...

<Cmp ref={(inst) => {this.parent=inst}}>;

Render parent...

componentDidMount() {           // componentDidMount() gets called after first state set
    console.log(;   // output: "hello!"
componentDidUpdate() {          // componentDidUpdate() gets called after all other states set
    console.log(;   // output: "hello!"

Example with componentDidMount()

Caller, set reference and set state...

<Cmp ref={(inst) => {this.parent=inst}}>

Render parent...

render() {              // render() gets called anytime setState() is called
    return (

After parent rerenders child, see state in componentDidUpdate().

componentDidMount() {           // componentDidMount() gets called anytime setState()/render() finish
console.log(; // output: "hello!"

Regex to test if string begins with http:// or https://

^https?:\/\/(.*) where (.*) is match everything else after https://

How to resolve TypeError: can only concatenate str (not "int") to str

Use f-strings to resolve the TypeError

# the following line causes a TypeError
# test = 'Here is a test that can be run' + 15 + 'times'

# same intent with a f-string
i = 15

test = f'Here is a test that can be run {i} times'


# output
'Here is a test that can be run 15 times'
i = 15
# t = 'test' + i  # will cause a TypeError

# should be
t = f'test{i}'


# output
  • The issue may be attempting to evaluate an expression where a variable is the string of a numeric.
  • Convert the string to an int.
  • This scenario is specific to this question
  • When iterating, it's important to be aware of the dtype
i = '15'
# t = 15 + i  # will cause a TypeError

# convert the string to int
t = 15 + int(i)

# output


  • The preceding part of the answer addresses the TypeError shown in the question title, which is why people seem to be coming to this question.
  • However, this doesn't resolve the issue in relation to the example provided by the OP, which is addressed below.

Original Code Issues

  • TypeError is caused because message type is a str.
  • The code iterates each character and attempts to add char, a str type, to an int
  • That issue can be resolved by converting char to an int
  • As the code is presented, secret_string needs to be initialized with 0 instead of "".
  • The code also results in a ValueError: chr() arg not in range(0x110000) because 7429146 is out of range for chr().
  • Resolved by using a smaller number
  • The output is not a string, as was intended, which leads to the Updated Code in the question.
message = input("Enter a message you want to be revealed: ")

secret_string = 0

for char in message:
    char = int(char)
    value = char + 742146
    secret_string += ord(chr(value))
print(f'\nRevealed: {secret_string}')

# Output
Enter a message you want to be revealed:  999

Revealed: 2226465

Updated Code Issues

  • message is now an int type, so for char in message: causes TypeError: 'int' object is not iterable
  • message is converted to int to make sure the input is an int.
  • Set the type with str()
  • Only convert value to Unicode with chr
  • Don't use ord
while True:
        message = str(int(input("Enter a message you want to be decrypt: ")))
    except ValueError:
        print("Error, it must be an integer")
secret_string = ""
for char in message:
    value = int(char) + 10000
    secret_string += chr(value)

print("Decrypted", secret_string)

# output
Enter a message you want to be decrypt:  999
Decrypted ???

Enter a message you want to be decrypt:  100
Decrypted ???

git: can't push (unpacker error) related to permission issues

For me its a permissions issue:

On the git server run this command on the repo directory

sudo chmod -R 777 theDirectory/

Why does an SSH remote command get fewer environment variables then when run manually?

I had similar issue, but in the end I found out that ~/.bashrc was all I needed.

However, in Ubuntu, I had to comment the line that stops processing ~/.bashrc :

#If not running interactively, don't do anything
[ -z "$PS1" ] && return

Creating a file only if it doesn't exist in Node.js

What about using the a option?

According to the docs:

'a+' - Open file for reading and appending. The file is created if it does not exist.

It seems to work perfectly with createWriteStream

How to parse string into date?

Although the CONVERT thing works, you actually shouldn't use it. You should ask yourself why you are parsing string values in SQL-Server. If this is a one-time job where you are manually fixing some data you won't get that data another time, this is ok, but if any application is using this, you should change something. Best way would be to use the "date" data type. If this is user input, this is even worse. Then you should first do some checking in the client. If you really want to pass string values where SQL-Server expects a date, you can always use ISO format ('YYYYMMDD') and it should convert automatically.

filtering NSArray into a new NSArray in Objective-C

Assuming that your objects are all of a similar type you could add a method as a category of their base class that calls the function you're using for your criteria. Then create an NSPredicate object that refers to that method.

In some category define your method that uses your function

@implementation BaseClass (SomeCategory)
- (BOOL)myMethod {
    return someComparisonFunction(self, whatever);

Then wherever you'll be filtering:

- (NSArray *)myFilteredObjects {
    NSPredicate *pred = [NSPredicate predicateWithFormat:@"myMethod = TRUE"];
    return [myArray filteredArrayUsingPredicate:pred];

Of course, if your function only compares against properties reachable from within your class it may just be easier to convert the function's conditions to a predicate string.

Where is Developer Command Prompt for VS2013?

For some reason, it doesn't properly add an icon when running Windows 8+. Here's how I solved it:

Using Windows Explorer, navigate to:

C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Visual Studio 2013

In that folder, you'll see a shortcut named Visual Studio Tools that maps to (assuming default installation):

C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\Tools\Shortcuts

Double-click the shortcut (or go to the folder above).

From that folder, copy the shortcut named Developer Command Prompt for VS2013 (and any others you find useful) to the first directory (for the Start Menu). You'll likely be prompted for administrative access (do so).

Once you've done that, you'll now have an icon available for the 2013 command prompt.

How to list the files in current directory?

Your code gives expected result,if you compile and run your code standalone(from commandline). As in eclipse for each project by default working directory is project directory that's why you are getting this result.

You can set user.dir property in java as:

   System.setProperty("user.dir", "absolute path of src folder");

then it will give expected result.

Elasticsearch query to return all records

use server:9200/_stats also to get statistics about all your aliases.. like size and number of elements per alias, that's very useful and provides helpful information

angular js unknown provider

I got that error because I was passing an incorrect parameter to the factory definition. I had:

myModule.factory('myService', function($scope, $http)...

It worked when I removed the $scope and changed the factory definition to:

myModule.factory('myService', function( $http)...

In case you need to inject $scope, use:

myModule.factory('myService', function($rootScope, $http)...

jQuery animated number counter from zero to value

This worked for me


<span class="number-count">841</span>

jQuery Code

$('.number-count').each(function () {
        Counter: $(this).text()
    }, {
        duration: 4000,
        easing: 'swing',
        step: function (now) {

How do I check how many options there are in a dropdown menu?

With pure javascript you can just call the length on the id of the select box. It will be more faster. Typically with everything native javascript is performing better and better with modern browsers

This can be achieved in javascript by

     var dropdownFilterSite = document.querySelector( '#dropDownId' );  //Similar to jQuery

var length = dropdownFilterSite.length.

Good website for some learning

A good video to watch by Todd Motto

When should you NOT use a Rules Engine?

I'm a big fan of Business Rules Engines, since it can help you make your life much easier as a programmer. One of the first experiences I've had while working on a Data Warehouse project was to find Stored Procedures containing complicated CASE structures stretching over entire pages. It was a nightmare to debug, since it was very difficult to understand the logic applied in such long CASE structures, and to determine if you have an overlapping between a rule at page 1 of the code and another from page 5. Overall, we had more than 300 such rules embedded in the code.

When we've received a new development requirement, for something called Accounting Destination, which was involving treating more than 3000 rules, i knew something had to change. Back then I've been working on a prototype which later on become the parent of what now is a Custom Business Rule engine, capable of handling all SQL standard operators. Initially we've been using Excel as an authoring tool and , later on, we've created an application which will allow the Business Users to define their own business rules, without the need of writing code. Now the system works fine, with very few bugs, and contains over 7000 rules for calculating this Accounting Destination. I don't think such scenario would have been possible by just hard-coding. And the users are pretty happy that they can define their own rules without IT becoming their bottleneck.

Still, there are limits to such approach:

  • You need to have capable business users which have an excellent understanding of the company business.
  • There is a significant workload on searching the entire system (in our case a Data Warehouse), in order to determine all hard-coded conditions which make sense to translate into rules to be handled by a Business Rule Engine. We've also had to take good care that these initial templates to be fully understandable by Business Users.
  • You need to have an application used for rules authoring, in which algorithms for detection of overlapping business rules is implemented. Otherwise you'll end up with a big mess, where no one understands anymore the results they get. When you have a bug in a generic component like a Custom Business Rule Engine, it can be very difficult to debug and involve extensive tests to make sure that things that worked before also work now.

More details on this topic can be found on a post I've written:

Overall, the biggest advantage of using a Business Rule Engines is that it allows the users to take back control over the Business Rule definitions and authoring, without the need of going to the IT department each time they need to modify something. It also the reduces the workload over IT development teams, which can now focus on building stuff with more added value.



How can I break from a try/catch block without throwing an exception in Java

In this sample in catch block i change the value of counter and it will break while block:

class TestBreak {
    public static void main(String[] a) {
        int counter = 0;

        while(counter<5) {
            try {
                int x = counter/0;
            catch(Exception e) {
                counter = 1000;    

Select2 open dropdown on focus

Somehow select2Focus didn't work here with empty selection, couldn't figured out the issue, therefore I added manual control when after focus event auto open get's triggered.

Here is coffeescript:

  .on 'select2-blur', ->
    $(this).data('select2-auto-open', 'true')
  .on 'select2-focus', ->
    $(this).data('select2').open() if $(this).data('select2-auto-open') != 'false'
  .on 'select2-selecting', ->
    $(this).data('select2-auto-open', 'false')

Creating virtual directories in IIS express

IIS express configuration is managed by applicationhost.config.
You can find it in

Users\<username>\Documents\IISExpress\config folder.

Inside you can find the sites section that hold a section for each IIS Express configured site.

Add (or modify) a site section like this:

<site name="WebSiteWithVirtualDirectory" id="20">
   <application path="/" applicationPool="Clr4IntegratedAppPool">
     <virtualDirectory path="/" physicalPath="c:\temp\website1" />
   <application path="/OffSiteStuff" applicationPool="Clr4IntegratedAppPool">
     <virtualDirectory path="/" physicalPath="d:\temp\SubFolderApp" />
      <binding protocol="http" bindingInformation="*:1132:localhost" />

Practically you need to add a new application tag in your site for each virtual directory. You get a lot of flexibility because you can set different configuration for the virtual directory (for example a different .Net Framework version)

EDIT Thanks to Fevzi Apaydin to point to a more elegant solution.

You can achieve same result by adding one or more virtualDirectory tag to the Application tag:

<site name="WebSiteWithVirtualDirectory" id="20">
   <application path="/" applicationPool="Clr4IntegratedAppPool">
     <virtualDirectory path="/" physicalPath="c:\temp\website1" />
     <virtualDirectory path="/OffSiteStuff" physicalPath="d:\temp\SubFolderApp" />
      <binding protocol="http" bindingInformation="*:1132:localhost" />


Git on Windows: How do you set up a mergetool?

I found two ways to configure "SourceGear DiffMerge" as difftool and mergetool in github Windows.

The following commands in a Command Prompt window will update your .gitconfig to configure GIT use DiffMerge:

git config --global diff.tool diffmerge
git config --global difftool.diffmerge.cmd 'C:/Program\ Files/SourceGear/Common/DiffMerge/sgdm.exe  \"$LOCAL\" \"$REMOTE\"'

git config --global merge.tool diffmerge
git config --global mergetool.diffmerge.cmd  'C:/Program\ Files/SourceGear/Common/DiffMerge/sgdm.exe  -merge  -result=\"$MERGED\" \"$LOCAL\" \"$BASE\" \"$REMOTE\"'


Add the following lines to your .gitconfig. This file should be in your home directory in C:\Users\UserName:

    tool = diffmerge
[difftool "diffmerge"]
    cmd = C:/Program\\ Files/SourceGear/Common/DiffMerge/sgdm.exe \"$LOCAL\" \"$REMOTE\"

    tool = diffmerge
[mergetool "diffmerge"]
    trustExitCode = true
    cmd = C:/Program\\ Files/SourceGear/Common/DiffMerge/sgdm.exe -merge -result=\"$MERGED\" \"$LOCAL\" \"$BASE\" \"$REMOTE\"

Twitter Bootstrap Button Text Word Wrap

Try this: add white-space: normal; to the style definition of the Bootstrap Button or you can replace the code you displayed with the one below

<div class="col-lg-3"> <!-- FIRST COL -->
  <div class="panel panel-default">
    <div class="panel-body"> 
    <h4>Posted on</h4>
    <p>22nd September 2013</p>
    <a href="#" class="btn btn-primary btn-xs col-lg-12" style="margin-bottom:4px;white-space: normal;">Lorem ipsum dolor sit amet, consectetur adipiscing elit.</a>
   <a href="#" class="btn btn-primary btn-xs col-lg-12" style="margin-bottom:4px;white-space: normal;">Lorem ipsum dolor sit amet, consectetur adipiscing elit.</a>
   <a href="#" class="btn btn-primary btn-xs col-lg-12" style="margin-bottom:4px;white-space: normal;">Lorem ipsum dolor sit amet, consectetur adipiscing elit.</a>

I have updated your fiddle here to show how it comes out.

Is it possible to append to innerHTML without destroying descendants' event listeners?

Now, it is 2012, and jQuery has append and prepend functions that do exactly this, add content without effecting current content. Very useful.

Connect to Oracle DB using sqlplus

Different ways to connect Oracle Database from Unix user are:

[oracle@OLE1 ~]$ sqlplus scott/tiger

[oracle@OLE1 ~]$ sqlplus scott/tiger@orcl

[oracle@OLE1 ~]$ sqlplus scott/[email protected]:1521/orcl

[oracle@OLE1 ~]$ sqlplus scott/tiger@//


Please see the explanation at link:


Center a DIV horizontally and vertically

Here's a demo:

A method (JSFiddle example)


html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    display: table
#content {
    display: table-cell;
    text-align: center;
    vertical-align: middle;


<div id="content">
    Content goes here

Another method (JSFiddle example)


body, html, #wrapper {
    width: 100%;
    height: 100%
#wrapper {
    display: table
#main {
    display: table-cell;
    vertical-align: middle;


<div id="wrapper">
<div id="main">
    Content goes here

Can you remove elements from a std::list while iterating through it?

If you think of the std::list like a queue, then you can dequeue and enqueue all the items that you want to keep, but only dequeue (and not enqueue) the item you want to remove. Here's an example where I want to remove 5 from a list containing the numbers 1-10...

std::list<int> myList;

int size = myList.size(); // The size needs to be saved to iterate through the whole thing

for (int i = 0; i < size; ++i)
    int val = myList.back()
    myList.pop_back() // dequeue
    if (val != 5)
         myList.push_front(val) // enqueue if not 5

myList will now only have numbers 1-4 and 6-10.

Array formula on Excel for Mac

  1. Select the desired range of cells
  2. Press Fn + F2 or CONTROL + U
  3. Paste in your array value
  4. Press COMMAND (?) + SHIFT + RETURN

Datanode process not running in Hadoop

I ran into the same issue. I have created a hdfs folder '/home/username/hdfs' with sub-directories name, data, and tmp which were referenced in config xml files of hadoop/conf.

When I started hadoop and did jps, I couldn't find datanode so I tried to manually start datanode using bin/hadoop datanode. Then I realized from error message that it has permissions issue accessing the which was referenced in one of the hadoop config files. All I had to do was stop hadoop, delete the contents of /home/username/hdfs/tmp/* directory and then try this command - chmod -R 755 /home/username/hdfs/ and then start hadoop. I could find the datanode!

Transparent CSS background color

In this case background-color:rgba(0,0,0,0.5); is the best way. For example: background-color:rgba(0,0,0,opacity option);

Delete last char of string

In C# 8 ranges and indices were introduced, giving us a new more succinct solution:

strgroupids = strgroupids[..^1];

Find if a String is present in an array

This can be done in java 8 using Stream.


String[] stringList = {"Red", "Orange", "Yellow", "Green", "Blue", "Violet", "Orange", "Blue"};

boolean contains = Stream.of(stringList).anyMatch(x -> x.equals(say.getText());

How do I get the day of week given a date?

datetime library sometimes gives errors with strptime() so I switched to dateutil library. Here's an example of how you can use it :

from dateutil import parser
parser.parse('January 11, 2010').strftime("%a")

The output that you get from this is 'Mon'. If you want the output as 'Monday', use the following :

parser.parse('January 11, 2010').strftime("%A")

This worked for me pretty quickly. I was having problems while using the datetime library because I wanted to store the weekday name instead of weekday number and the format from using the datetime library was causing problems. If you're not having problems with this, great! If you are, you cand efinitely go for this as it has a simpler syntax as well. Hope this helps.

Calling async method synchronously

If you have an async method called " RefreshList " then, you can call that async method from a non-async method like below.

Task.Run(async () => { await RefreshList(); });

xlrd.biffh.XLRDError: Excel xlsx file; not supported

The previous version, xlrd 1.2.0, may appear to work, but it could also expose you to potential security vulnerabilities. With that warning out of the way, if you still want to give it a go, type the following command:

pip install xlrd==1.2.0

How to know if two arrays have the same values

If you want to compare two arrays and check if any object is same in both arrays it will works. Example :

Array1 = [a,b,c,d]
Array2 = [d,e,f,g]

Here, 'd' is common in both array so this function will return true value.

  cehckArray(array1, array2) {
    for (let i = 0; i < array1.length; i++) {
      for (let j = 0; j < array2.length; j++) {
        if (array1[i] === array2[j]) {
          return true;
    // Return if no common element exist 
    return false;

JavaScript or jQuery browser back button click detector

suppose you have a button:

<button onclick="backBtn();">Back...</button>

Here the code of the backBtn method:

  function backBtn(){
                    return false;

Pad a number with leading zeros in JavaScript

function padToFour(number) {
  if (number<=9999) { number = ("000"+number).slice(-4); }
  return number;

Something like that?

Bonus incomprehensible-but-slicker single-line ES6 version:

let padToFour = number => number <= 9999 ? `000${number}`.slice(-4) : number;


  • let is a block scoped variable (as opposed to var’s functional scoping)
  • => is an arrow function that among other things replaces function and is prepended by its parameters
  • If a arrow function takes a single parameter you can omit the parentheses (hence number =>)
  • If an arrow function body has a single line that starts with return you can omit the braces and the return keyword and simply use the expression
  • To get the function body down to a single line I cheated and used a ternary expression

Unsafe JavaScript attempt to access frame with URL

I found that using the XFBML version of the Facebook like button instead of the HTML5 version fixed this problem. Add the below code where you want the button to appear:

<div id="fb-root"></div>
<script>(function (d, s, id) {
    var js, fjs = d.getElementsByTagName(s)[0];
    if (d.getElementById(id)) return;
    js = d.createElement(s); = id;
    js.src = "//";
    fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>

<fb:like send="true" layout="button_count" width="50" show_faces="false" font="arial"></fb:like>

Then add this to your HTML tag:


Try/catch does not seem to have an effect

I was able to duplicate your result when trying to run a remote WMI query. The exception thrown is not caught by the Try/Catch, nor will a Trap catch it, since it is not a "terminating error". In PowerShell, there are terminating errors and non-terminating errors . It appears that Try/Catch/Finally and Trap only works with terminating errors.

It is logged to the $error automatic variable and you can test for these type of non-terminating errors by looking at the $? automatic variable, which will let you know if the last operation succeeded ($true) or failed ($false).

From the appearance of the error generated, it appears that the error is returned and not wrapped in a catchable exception. Below is a trace of the error generated.

PS C:\scripts\PowerShell> Trace-Command -Name errorrecord  -Expression {Get-WmiObject win32_bios -ComputerName HostThatIsNotThere}  -PSHost
DEBUG: InternalCommand Information: 0 :  Constructor Enter Ctor
Microsoft.PowerShell.Commands.GetWmiObjectCommand: 25857563
DEBUG: InternalCommand Information: 0 :  Constructor Leave Ctor
Microsoft.PowerShell.Commands.GetWmiObjectCommand: 25857563
DEBUG: ErrorRecord Information: 0 :  Constructor Enter Ctor
System.Management.Automation.ErrorRecord: 19621801 exception =
System.Runtime.InteropServices.COMException (0x800706BA): The RPC
server is unavailable. (Exception from HRESULT: 0x800706BA)
System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo)
   at System.Management.ManagementScope.InitializeGuts(Object o)
   at System.Management.ManagementScope.Initialize()
   at System.Management.ManagementObjectSearcher.Initialize()
   at System.Management.ManagementObjectSearcher.Get()
   at Microsoft.PowerShell.Commands.GetWmiObjectCommand.BeginProcessing()
errorId = GetWMICOMException errorCategory = InvalidOperation
targetObject =
DEBUG: ErrorRecord Information: 0 :  Constructor Leave Ctor
System.Management.Automation.ErrorRecord: 19621801

A work around for your code could be:

    $colItems = get-wmiobject -class "Win32_PhysicalMemory" -namespace "root\CIMV2" -computername $strComputerName -Credential $credentials
    if ($?)
      foreach ($objItem in $colItems) 
          write-host "Bank Label: " $objItem.BankLabel
          write-host "Capacity: " ($objItem.Capacity / 1024 / 1024)
          write-host "Caption: " $objItem.Caption
          write-host "Creation Class Name: " $objItem.CreationClassName      
       throw $error[0].Exception

Python - use list as function parameters

You can do this using the splat operator:


This causes the function to receive each list item as a separate parameter. There's a description here:

Add a column with a default value to an existing table in SQL Server




        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.


Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerate
    a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6

Optional With-Values Statement:
The WITH VALUES is only needed when your Column is Nullable
    and you want the Default Value used for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
    for all Existing Records, whether you specify WITH VALUES or not.

How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0.
If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls),
    then the Default-Constraint will not be used and NULL will be inserted as the Value.

Notes were based on everyone's great feedback below.
Special Thanks to:
    @Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.

Why use 'virtual' for class properties in Entity Framework model definitions?

The virtual keyword in C# enables a method or property to be overridden by child classes. For more information please refer to the MSDN documentation on the 'virtual' keyword

UPDATE: This doesn't answer the question as currently asked, but I'll leave it here for anyone looking for a simple answer to the original, non-descriptive question asked.

error: command 'gcc' failed with exit status 1 while installing eventlet

Your install is failing because you don't have the python development headers installed. You can do this through apt on ubuntu/debian with:

sudo apt-get install python-dev 

for python3 use:

sudo apt-get install python3-dev

For eventlet you might also need the libevent libraries installed so if you get an error talking about that you can install libevent with:

sudo apt-get install libevent-dev

IBOutlet and IBAction

Ran into the diagram while looking at key-value coding, thought it might help someone. It helps with understanding of what IBOutlet is.

By looking at the flow, one could see that IBOutlets are only there to match the property name with a control name in the Nib file.

How nib file is loaded, screenshot of Matt's online book for iOS6

What is the best way to delete a value from an array in Perl?

if you change

my @del_indexes = grep { $arr[$_] eq 'foo' } 0..$#arr;


my @del_indexes = reverse(grep { $arr[$_] eq 'foo' } 0..$#arr);

This avoids the array renumbering issue by removing elements from the back of the array first. Putting a splice() in a foreach loop cleans up @arr. Relatively simple and readable...

foreach $item (@del_indexes) {
   splice (@arr,$item,1);

Draw on HTML5 Canvas using a mouse

I think, other examples here are too complicated. This one is simpler and JS only...

// create canvas element and append it to document body_x000D_
var canvas = document.createElement('canvas');_x000D_
// some hotfixes... ( ?_?)_x000D_ = 0;_x000D_ = 'fixed';_x000D_
// get canvas 2D context and set him correct size_x000D_
var ctx = canvas.getContext('2d');_x000D_
// last known position_x000D_
var pos = { x: 0, y: 0 };_x000D_
window.addEventListener('resize', resize);_x000D_
document.addEventListener('mousemove', draw);_x000D_
document.addEventListener('mousedown', setPosition);_x000D_
document.addEventListener('mouseenter', setPosition);_x000D_
// new position from mouse event_x000D_
function setPosition(e) {_x000D_
  pos.x = e.clientX;_x000D_
  pos.y = e.clientY;_x000D_
// resize canvas_x000D_
function resize() {_x000D_
  ctx.canvas.width = window.innerWidth;_x000D_
  ctx.canvas.height = window.innerHeight;_x000D_
function draw(e) {_x000D_
  // mouse left button must be pressed_x000D_
  if (e.buttons !== 1) return;_x000D_
  ctx.beginPath(); // begin_x000D_
  ctx.lineWidth = 5;_x000D_
  ctx.lineCap = 'round';_x000D_
  ctx.strokeStyle = '#c0392b';_x000D_
  ctx.moveTo(pos.x, pos.y); // from_x000D_
  ctx.lineTo(pos.x, pos.y); // to_x000D_
  ctx.stroke(); // draw it!_x000D_

Unity Scripts edited in Visual studio don't provide autocomplete

one of the above methods are worked for me and I just found a solution to this problem,
1. First, go to the project directory and delete .sln file
2. Second, go to unity and double click your script. Then Visual Studio will be open with an error, enter image description here

  1. Then click ok and close Visual Studio editor.
  2. Finally, turn off your Windows Defender and then go to your project directory and there will be .csproj file. Just double click and open this from your Visual Studio editor and open the scripts folder inside the assets folder and open the scripts and autocompletion will be working perfectly fine.

How to test a variable is null in python

You can do this in a try and catch block:

    if val is None:
except NameError:
    # throw an exception or do something else

Populating a dictionary using for loops (python)

dicts = {}
keys = range(4)
values = ["Hi", "I", "am", "John"]
for i in keys:
        dicts[i] = values[i]


In [7]: dict(list(enumerate(values)))
Out[7]: {0: 'Hi', 1: 'I', 2: 'am', 3: 'John'}

CSS Custom Dropdown Select that works across all browsers IE7+ FF Webkit

<select class="dropdownmenu" name="drop-down">
    <option class="dropdownmenu_list1" value="select-option">Choose ...</option>
    <option class="dropdownmenu_list2" value="Topic 1">Option 1</option>
    <option class="dropdownmenu_list3" value="Topic 2">Option 2</option>

This works best in Firefox. Too bad that Chrome and Safari do not support this rather easy CSS styling.

How to receive POST data in django

res = request.GET['paymentid'] will raise a KeyError if paymentid is not in the GET data.

Your sample php code checks to see if paymentid is in the POST data, and sets $payID to '' otherwise:

$payID = isset($_POST['paymentid']) ? $_POST['paymentid'] : ''

The equivalent in python is to use the get() method with a default argument:

payment_id = request.POST.get('payment_id', '')

while debugging, this is what I see in the response.GET: <QueryDict: {}>, request.POST: <QueryDict: {}>

It looks as if the problem is not accessing the POST data, but that there is no POST data. How are you are debugging? Are you using your browser, or is it the payment gateway accessing your page? It would be helpful if you shared your view.

Once you are managing to submit some post data to your page, it shouldn't be too tricky to convert the sample php to python.

How to normalize an array in NumPy to a unit vector?

If you work with multidimensional array following fast solution is possible.

Say we have 2D array, which we want to normalize by last axis, while some rows have zero norm.

import numpy as np
arr = np.array([
    [1, 2, 3], 
    [0, 0, 0],
    [5, 6, 7]
], dtype=np.float)

lengths = np.linalg.norm(arr, axis=-1)
print(lengths)  # [ 3.74165739  0.         10.48808848]
arr[lengths > 0] = arr[lengths > 0] / lengths[lengths > 0][:, np.newaxis]
# [[0.26726124 0.53452248 0.80178373]
# [0.         0.         0.        ]
# [0.47673129 0.57207755 0.66742381]]

What should I use to open a url instead of urlopen in urllib3

You should use urllib.reuqest, not urllib3.

import urllib.request   # not urllib - important!

How to return a table from a Stored Procedure?

Where is your problem??

For the stored procedure, just create:

   SELECT *  -- I would *strongly* recommend specifying the columns EXPLICITLY
   FROM dbo.Emp
   WHERE ID = @EmpID

That's all there is.

From your ASP.NET application, just create a SqlConnection and a SqlCommand (don't forget to set the CommandType = CommandType.StoredProcedure)

DataTable tblEmployees = new DataTable();

using(SqlConnection _con = new SqlConnection("your-connection-string-here"))
using(SqlCommand _cmd = new SqlCommand("ReadEmployees", _con))
    _cmd.CommandType = CommandType.StoredProcedure;

    _cmd.Parameters.Add(new SqlParameter("@EmpID", SqlDbType.Int));
    _cmd.Parameters["@EmpID"].Value = 42;

    SqlDataAdapter _dap = new SqlDataAdapter(_cmd);


YourGridView.DataSource = tblEmployees;

and then fill e.g. a DataTable with that data and bind it to e.g. a GridView.

Difference between "Complete binary tree", "strict binary tree","full binary Tree"?

Let us consider a binary tree of height 'h'. A binary tree is called a complete binary tree if all the leaves are present at height 'h' or 'h-1' without any missing numbers in the sequence.

                 /   \
              2       3
            /    \         
         4        5

It is a complete binary tree.

                 /   \
              2       3
            /        /    
         4         6    

It is not a complete binary tree as the node of number 5 is missing in the sequence

Metadata file '.dll' could not be found

Removing the packages folder containing NuGet in the solution folder worked for me. After rebuilding everything worked again. Check References in the solution and check for references that have a yellow triangle.

Example picture:

Enter image description here

Video auto play is not working in Safari and Chrome desktop browser

Adding the below code at the bottom of the page worked for me . I dont know why it works :(


How can I set a cookie in react?

Use vanilla js, example

document.cookie = `referral_key=hello;max-age=604800;`

Read more at:

postgres default timezone

The time zone is a session parameter. So, you can change the timezone for the current session.

See the doc.

set timezone TO 'GMT';

Or, more closely following the SQL standard, use the SET TIME ZONE command. Notice two words for "TIME ZONE" where the code above uses a single word "timezone".


The doc explains the difference:

SET TIME ZONE extends syntax defined in the SQL standard. The standard allows only numeric time zone offsets while PostgreSQL allows more flexible time-zone specifications. All other SET features are PostgreSQL extensions.

Windows command prompt log to a file

In cmd when you use > or >> the output will be only written on the file. Is it possible to see the output in the cmd windows and also save it in a file. Something similar if you use teraterm, when you can start saving all the log in a file meanwhile you use the console and view it (only for ssh, telnet and serial).

Using Chrome, how to find to which events are bound to an element

findEventHandlers is a jquery plugin, the raw code is here:


  1. Paste the raw code directely into chrome's console(note:must have jquery loaded already)

  2. Use the following function call: findEventHandlers(eventType, selector);
    to find the corresponding's selector specified element's eventType handler.


findEventHandlers("click", "#clickThis");

Then if any, the available event handler will show bellow, you need to expand to find the handler, right click the function and select show function definition


Initialize a byte array to a certain value, other than the default null?

Just to expand on my answer a neater way of doing this multiple times would probably be:

PopulateByteArray(UserCode, 0x20);

which calls:

public static void PopulateByteArray(byte[] byteArray, byte value)
    for (int i = 0; i < byteArray.Length; i++)
        byteArray[i] = value;

This has the advantage of a nice efficient for loop (mention to gwiazdorrr's answer) as well as a nice neat looking call if it is being used a lot. And a lot mroe at a glance readable than the enumeration one I personally think. :)

Newline character in StringBuilder

For multiple lines the best way I find is to do this:

        IEnumerable<string> lines = new List<string>
            string.Format("{{ line with formatting... {0} }}", id),
            "line 2",
            "line 3"
        StringBuilder sb = new StringBuilder();
        foreach(var line in lines)

In this way you don't have to clutter the screen with the Environment.NewLine or AppendLine() repeated multiple times. It will also be less error prone than having to remember to type them.

wget can't download - 404 error

You will also get a 404 error if you are using ipv6 and the server only accepts ipv4.

To use ipv4, make a request adding -4:

wget -4

Break a previous commit into multiple commits

It's been more than 8 years, but maybe someone will find it helpful anyway. I was able to do the trick without rebase -i. The idea is to lead git to the same state it was before you did git commit:

# first rewind back (mind the dot,
# though it can be any valid path,
# for instance if you want to apply only a subset of the commit)
git reset --hard <previous-commit> .

# apply the changes
git checkout <commit-you-want-to-split>

# we're almost there, but the changes are in the index at the moment,
# hence one more step (exactly as git gently suggests):
# (use "git reset HEAD <file>..." to unstage)
git reset

After this you'll see this shiny Unstaged changes after reset: and your repo is in a state like you're about to commit all these files. From now on you can easily commit it again like you usually do. Hope it helps.

How to check if a file exists from a url

You have to use CURL

function does_url_exists($url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_NOBODY, true);
    $code = curl_getinfo($ch, CURLINFO_HTTP_CODE);

    if ($code == 200) {
        $status = true;
    } else {
        $status = false;
    return $status;

Excel VBA date formats

It's important to distinguish between the content of cells, their display format, the data type read from cells by VBA, and the data type written to cells from VBA and how Excel automatically interprets this. (See e.g. this previous answer.) The relationship between these can be a bit complicated, because Excel will do things like interpret values of one type (e.g. string) as being a certain other data type (e.g. date) and then automatically change the display format based on this. Your safest bet it do everything explicitly and not to rely on this automatic stuff.

I ran your experiment and I don't get the same results as you do. My cell A1 stays a Date the whole time, and B1 stays 41575. So I can't answer your question #1. Results probably depend on how your Excel version/settings choose to automatically detect/change a cell's number format based on its content.

Question #2, "How can I ensure that a cell will return a date value": well, not sure what you mean by "return" a date value, but if you want it to contain a numerical value that is displayed as a date, based on what you write to it from VBA, then you can either:

  • Write to the cell a string value that you hope Excel will automatically interpret as a date and format as such. Cross fingers. Obviously this is not very robust. Or,

  • Write a numerical value to the cell from VBA (obviously a Date type is the intended type, but an Integer, Long, Single, or Double could do as well) and explicitly set the cells' number format to your desired date format using the .NumberFormat property (or manually in Excel). This is much more robust.

If you want to check that existing cell contents can be displayed as a date, then here's a function that will help:

Function CellContentCanBeInterpretedAsADate(cell As Range) As Boolean
    Dim d As Date
    On Error Resume Next
    d = CDate(cell.Value)
    If Err.Number <> 0 Then
        CellContentCanBeInterpretedAsADate = False
        CellContentCanBeInterpretedAsADate = True
    End If
    On Error GoTo 0
End Function

Example usage:

Dim cell As Range
Set cell = Range("A1")

If CellContentCanBeInterpretedAsADate(cell) Then
    cell.NumberFormat = "mm/dd/yyyy hh:mm"
    cell.NumberFormat = "General"
End If

How do I call a JavaScript function on page load?

For detect loaded html (from server) inserted into DOM use MutationObserver or detect moment in your loadContent function when data are ready to use

let ignoreFirstChange = 0;_x000D_
let observer = (new MutationObserver((m, ob)=>_x000D_
  if(ignoreFirstChange++ > 0) console.log('Element added on', new Date());_x000D_
)).observe(content, {childList: true, subtree:true });_x000D_
// TEST: simulate element loading_x000D_
let tmp=1;_x000D_
function loadContent(name) {  _x000D_
    console.log(`Element ${name} loaded`)_x000D_
    content.innerHTML += `<div>My name is ${name}</div>`; _x000D_
}; _x000D_
<div id="content"><div>

How to get the height of a body element


html { height: 100%; }
body { min-height: 100%; }

instead of height: 100%.

The result jQuery returns is correct, because you've set the height of the body to 100%, and that's probably the height of the viewport. These three DIVs were causing an overflow, because there weren't enough space for them in the BODY element. To see what I mean, set a border to the BODY tag and check where the border ends.

How to pass datetime from c# to sql correctly?

I had many issues involving C# and SqlServer. I ended up doing the following:

  1. On SQL Server I use the DateTime column type
  2. On c# I use the .ToString("yyyy-MM-dd HH:mm:ss") method

Also make sure that all your machines run on the same timezone.

Regarding the different result sets you get, your first example is "July First" while the second is "4th of July" ...

Also, the second example can be also interpreted as "April 7th", it depends on your server localization configuration (my solution doesn't suffer from this issue).

EDIT: hh was replaced with HH, as it doesn't seem to capture the correct hour on systems with AM/PM as opposed to systems with 24h clock. See the comments below.

TypeScript error TS1005: ';' expected (II)

You don't have the last version of typescript.

Running :

npm install -g typescript

npm checks if tsc command is already installed.

And it might be, by another software like Visual Studio. If so, npm doesn't override it. So you have to remove the previous deprecated tsc installed command.

Run where tsc to know its bin location. It should be in C:\Program Files (x86)\Microsoft SDKs\TypeScript\1.0\ in windows. Once found, delete the folder, and re-run npm install -g typescript. This should now install the last version of typescript.

PHP Parse HTML code

Use PHP Document Object Model:

   $str = '<h1>T1</h1>Lorem ipsum.<h1>T2</h1>The quick red fox...<h1>T3</h1>... jumps over the lazy brown FROG';
   $DOM = new DOMDocument;

   //get all H1
   $items = $DOM->getElementsByTagName('h1');

   //display all H1 text
   for ($i = 0; $i < $items->length; $i++)
        echo $items->item($i)->nodeValue . "<br/>";

This outputs as:


[EDIT]: After OP Clarification:

If you want the content like Lorem ipsum. etc, you can directly use this regex:

   $str = '<h1>T1</h1>Lorem ipsum.<h1>T2</h1>The quick red fox...<h1>T3</h1>... jumps over the lazy brown FROG';
   echo preg_replace("#<h1.*?>.*?</h1>#", "", $str);

this outputs:

Lorem ipsum.The quick red fox...... jumps over the lazy brown FROG

TortoiseSVN icons not showing up under Windows 7

In my case, Dropbox overlays were starting with a " (quoted identifier) in the registry. I deleted all the " prefixes and restarted explorer.exe.


Edit: I installed Windows 10 and this solution didn't work for me. So I just went to the same registry location and deleted all Google and SkyDrive records and restarted explorer.exe.

Second edit: After installing TortoiseGit it fixed everything without any customisation.

Where does Console.WriteLine go in ASP.NET?

If you look at the Console class in .NET Reflector, you'll find that if a process doesn't have an associated console, Console.Out and Console.Error are backed by Stream.Null (wrapped inside a TextWriter), which is a dummy implementation of Stream that basically ignores all input, and gives no output.

So it is conceptually equivalent to /dev/null, but the implementation is more streamlined: there's no actual I/O taking place with the null device.

Also, apart from calling SetOut, there is no way to configure the default.

Update 2020-11-02: As this answer is still gathering votes in 2020, it should probably be noted that under ASP.NET Core, there usually is a console attached. You can configure the ASP.NET Core IIS Module to redirect all stdout and stderr output to a log file via the stdoutLogEnabled and stdoutLogFile settings:

  <aspNetCore processPath="dotnet"
              stdoutLogFile=".\logs\stdout" />

Fastest way to determine if an integer's square root is an integer

Calculating square roots by Newton's method is horrendously fast ... provided that the starting value is reasonable. However there is no reasonable starting value, and in practice we end with bisection and log(2^64) behaviour.
To be really fast we need a fast way to get at a reasonable starting value, and that means we need to descend into machine language. If a processor provides an instruction like POPCNT in the Pentium, that counts the leading zeroes we can use that to have a starting value with half the significant bits. With care we can find a a fixed number of Newton steps that will always suffice. (Thus foregoing the need to loop and have very fast execution.)

A second solution is going via the floating point facility, which may have a fast sqrt calculation (like the i87 coprocessor.) Even an excursion via exp() and log() may be faster than Newton degenerated into a binary search. There is a tricky aspect to this, a processor dependant analysis of what and if refinement afterwards is necessary.

A third solution solves a slightly different problem, but is well worth mentionning because the situation is described in the question. If you want to calculate a great many square roots for numbers that differ slightly, you can use Newton iteration, if you never reinitialise the starting value, but just leave it where the previous calculation left off. I've used this with success in at least one Euler problem.

Declare global variables in Visual Studio 2010 and VB.NET

A global variable could be accessible in all your forms in your project if you use the keyword public shared if it is in a class. It will also work if you use the keyword "public" if it is under a Module, but it is not the best practice for many reasons.

(... Yes, I somewhat repeating what "Cody Gray" and "RBarryYoung" said.)

One of the problems is when you have two threads that call the same global variable at the same time. You will have some surprises. You might have unexpected reactions if you don't know their limitations. Take a look at the post Global Variables in Visual Basic .NET and download the sample project!

Installation error: INSTALL_FAILED_OLDER_SDK

I am on Android Studio. I got this error when min/targetSDKVersion were set to 17. While looking thro this thread, I tried to change the minSDKVersion, voila..problem fixed. Go figure.. :(

    android:targetSdkVersion="17" />

Add an index (numeric ID) column to large data frame

If your data.frame is a data.table, you can use special symbol .I:

data[, ID := .I]

Effective swapping of elements of an array in Java

If you're swapping numbers and want a concise way to write the code without creating a separate function or using a confusing XOR hack, I find this is much easier to understand and it's also a one liner.

public static void swap(int[] arr, int i, int j) {
    arr[i] = (arr[i] + arr[j]) - (arr[j] = arr[i]);

What I've seen from some primitive benchmarks is that the performance difference is basically negligible as well.

This is one of the standard ways for swapping array elements without using a temporary variable, at least for integers.

how to do "press enter to exit" in batch

Default interpreters from Microsoft are done in a way, that causes them exit when they reach EOF. If rake is another batch file, command interpreter switches to it and exits when rake interpretation is finished. To prevent this write:

@echo off
call rake

IMHO, call operator will lauch another instance of intepretator thereby preventing the current one interpreter from switching to another input file.

How can I commit a single file using SVN over a network?

  1. svn add filename.html
  2. svn commit -m"your comment"
  3. You dont have to push

How to call a .NET Webservice from Android using KSOAP2?

How does your .NET Webservice look like?

I had the same effect using ksoap 2.3 from I followed the tutorial on The Code Project (which is great BTW.)

And everytime I used

    Integer result = (Integer)envelope.getResponse();

to get the result of a my webservice (regardless of the type, I tried Object, String, int) I ran into the org.ksoap2.serialization.SoapPrimitive exception.

I found a solution (workaround). The first thing I had to do was to remove the "SoapRpcMethod() attribute from my webservice methods.

    [SoapRpcMethod(), WebMethod]
    public Object GetInteger1(int i)
        // android device will throw exception
        return 0;

    public Object GetInteger2(int i)
        // android device will get the value
        return 0;

Then I changed my Android code to:

    SoapPrimitive result = (SoapPrimitive)envelope.getResponse();

However, I get a SoapPrimitive object, which has a "value" filed that is private. Luckily the value is passed through the toString() method, so I use Integer.parseInt(result.toString()) to get my value, which is enough for me, because I don't have any complex types that I need to get from my Web service.

Here is the full source:

private static final String SOAP_ACTION = "";
private static final String METHOD_NAME = "GetInteger2";
private static final String NAMESPACE = "";
private static final String URL = "";

public int GetInteger2() throws IOException, XmlPullParserException {
    SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);

    PropertyInfo pi = new PropertyInfo();

    SoapSerializationEnvelope envelope =
        new SoapSerializationEnvelope(SoapEnvelope.VER11);
    envelope.dotNet = true;

    AndroidHttpTransport androidHttpTransport = new AndroidHttpTransport(URL);, envelope);

    SoapPrimitive result = (SoapPrimitive)envelope.getResponse();
    return Integer.parseInt(result.toString());

JFrame.dispose() vs System.exit()

JFrame.dispose() affects only to this frame (release all of the native screen resources used by this component, its subcomponents, and all children). System.exit() affects to entire JVM.

If you want to close all JFrame or all Window (since Frames extend Windows) to terminate the application in an ordered mode, you can do some like this:

Arrays.asList(Window.getWindows()).forEach(e -> e.dispose()); // or JFrame.getFrames()

Usage of $broadcast(), $emit() And $on() in AngularJS

This little example shows how the $rootScope emit a event that will be listen by a children scope in another controller.



  .controller('ExampleController1', Controller1);

Controller1.$inject = ['$rootScope'];

function Controller1($rootScope) {
  var vm = this, 
      message = 'Hi my children scope boy';

  vm.sayHi = sayHi;

  function sayHi(){
    $rootScope.$broadcast('greeting', message);


  .controller('ExampleController2', Controller2);

Controller2.$inject = ['$scope'];

function Controller2($scope) {
  var vm = this;

  $scope.$on('greeting', listenGreeting)

  function listenGreeting($event, message){
    alert(['Message received',message].join(' : '));



The answer of @gayathri bottom explain technically the differences of all those methods in the scope angular concept and their implementations $scope and $rootScope.

user authentication libraries for node.js?

I was basically looking for the same thing. Specifically, I wanted the following:

  1. To use express.js, which wraps Connect's middleware capability
  2. "Form based" authentication
  3. Granular control over which routes are authenticated
  4. A database back-end for users/passwords
  5. Use sessions

What I ended up doing was creating my own middleware function check_auth that I pass as an argument to each route I want authenticated. check_auth merely checks the session and if the user is not logged in, then redirects them to the login page, like so:

function check_auth(req, res, next) {

  //  if the user isn't logged in, redirect them to a login page
  if(!req.session.login) {
    return; // the buck stops here... we do not call next(), because
            // we don't want to proceed; instead we want to show a login page

  //  the user is logged in, so call next()

Then for each route, I ensure this function is passed as middleware. For example:

app.get('/tasks', check_auth, function(req, res) {
    // snip

Finally, we need to actually handle the login process. This is straightforward:

app.get('/login', function(req, res) {
  res.render("login", {layout:false});
});'/login', function(req, res) {

  // here, I'm using mongoose.js to search for the user in mongodb
  var user_query = UserModel.findOne({}, function(err, user){
    if(err) {
      res.render("login", {layout:false, locals:{ error:err } });

    if(!user || user.password != req.body.password) {
          locals:{ error:"Invalid login!", }
    } else {
      // successful login; store the session info
      req.session.login =;

At any rate, this approach was mostly designed to be flexible and simple. I'm sure there are numerous ways to improve it. If you have any, I'd very much like your feedback.

EDIT: This is a simplified example. In a production system, you'd never want to store & compare passwords in plain text. As a commenter points out, there are libs that can help manage password security.

How do I tell if a variable has a numeric value in Perl?

Personally I think that the way to go is to rely on Perl's internal context to make the solution bullet-proof. A good regexp could match all the valid numeric values and none of the non-numeric ones (or vice versa), but as there is a way of employing the same logic the interpreter is using it should be safer to rely on that directly.

As I tend to run my scripts with -w, I had to combine the idea of comparing the result of "value plus zero" to the original value with the no warnings based approach of @ysth:

do { 
    no warnings "numeric";
    if ($x + 0 ne $x) { return "not numeric"; } else { return "numeric"; }

Convert iterator to pointer?

A safe version to convert an iterator to a pointer (exactly what that means regardless of the implications) and by safe I mean no worries about having to dereference the iterator and cause possible exceptions / errors due to end() / other situations

#include <iostream>
#include <vector>
#include <string.h>

int main()
    std::vector<int> vec;

    char itPtr[25];
    long long itPtrDec;
    std::vector<int>::iterator it = vec.begin();
    memset(&itPtr, 0, 25);
    sprintf(itPtr, "%llu", it);
    itPtrDec = atoll(itPtr);
    printf("it = 0x%X\n", itPtrDec);
    it = vec.begin();
    memset(&itPtr, 0, 25);
    sprintf(itPtr, "%llu", it);
    itPtrDec = atoll(itPtr);
    printf("it = 0x%X\n", itPtrDec);

will print something like

it = 0x0

it = 0x2202E10

It's an incredibly hacky way to do it, but if you need it, it does the job. You will receive some compiler warnings which, if really bothering you, can be removed with #pragma

Run class in Jar file

Assuming you are in the directory where myJar.jar file is and that myClass has a public static void main() method on it:

You use the following command line:

java -cp ./myJar.jar myClass


  1. myJar.jar is in the current path, note that . isn't in the current path on most systems. A fully qualified path is preferred here as well.

  2. myClass is a fully qualified package path to the class, the example assumes that myClass is in the default package which is bad practice, if it is in a nested package it would be com.mycompany.mycode.myClass.

How do I open a URL from C++?

Here's an example in windows code using winsock.

#include <winsock2.h>
#include <windows.h>
#include <iostream>
#include <string>
#include <locale>
#pragma comment(lib,"ws2_32.lib")
using namespace std;

string website_HTML;
locale local;

void get_Website(char *url );

int main ()
    //open website
    get_Website("" );

    //format website HTML
    for (size_t i=0; i<website_HTML.length(); ++i) 
        website_HTML[i]= tolower(website_HTML[i],local);

    //display HTML
    cout <<website_HTML;


    return 0;

void get_Website(char *url )
    WSADATA wsaData;
    SOCKET Socket;
    SOCKADDR_IN SockAddr;

    int lineCount=0;
    int rowCount=0;

    struct hostent *host;
    char *get_http= new char[256];

        memset(get_http,' ', sizeof(get_http) );
        strcpy(get_http,"GET / HTTP/1.1\r\nHost: ");
        strcat(get_http,"\r\nConnection: close\r\n\r\n");

        if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0) 
            cout << "WSAStartup failed.\n";
            //return 1;

        host = gethostbyname(url);

        SockAddr.sin_addr.s_addr = *((unsigned long*)host->h_addr);

        cout << "Connecting to "<< url<<" ...\n";

        if(connect(Socket,(SOCKADDR*)(&SockAddr),sizeof(SockAddr)) != 0)
            cout << "Could not connect";
            //return 1;

        cout << "Connected.\n";     
        send(Socket,get_http, strlen(get_http),0 );

        char buffer[10000];

        int nDataLength;
            while ((nDataLength = recv(Socket,buffer,10000,0)) > 0)
                int i = 0;

                while (buffer[i] >= 32 || buffer[i] == '\n' || buffer[i] == '\r') 
                    i += 1;

            delete[] get_http;

Example of multipart/form-data

EDIT: I am maintaining a similar, but more in-depth answer at:

To see exactly what is happening, use nc -l or an ECHO server and an user agent like a browser or cURL.

Save the form to an .html file:

<form action="http://localhost:8000" method="post" enctype="multipart/form-data">
  <p><input type="text" name="text" value="text default">
  <p><input type="file" name="file1">
  <p><input type="file" name="file2">
  <p><button type="submit">Submit</button>

Create files to upload:

echo 'Content of a.txt.' > a.txt
echo '<!DOCTYPE html><title>Content of a.html.</title>' > a.html


nc -l localhost 8000

Open the HTML on your browser, select the files and click on submit and check the terminal.

nc prints the request received. Firefox sent:

Host: localhost:8000
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:29.0) Gecko/20100101 Firefox/29.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Cookie: __atuvc=34%7C7; permanent=0; _gitlab_session=226ad8a0be43681acf38c2fab9497240; __profilin=p%3Dt; request_method=GET
Connection: keep-alive
Content-Type: multipart/form-data; boundary=---------------------------9051914041544843365972754266
Content-Length: 554

Content-Disposition: form-data; name="text"

text default
Content-Disposition: form-data; name="file1"; filename="a.txt"
Content-Type: text/plain

Content of a.txt.

Content-Disposition: form-data; name="file2"; filename="a.html"
Content-Type: text/html

<!DOCTYPE html><title>Content of a.html.</title>


Aternativelly, cURL should send the same POST request as your a browser form:

nc -l localhost 8000
curl -F "text=default" -F "[email protected]" -F "[email protected]" localhost:8000

You can do multiple tests with:

while true; do printf '' | nc -l localhost 8000; done

Making the Android emulator run faster

Enable GPU Hardware Acceleration (in addition to Intel's HAXM), if you are using API 15 v3 or newer and SDK Tools v17+. Graphics acceleration for the emulator takes advantage of your development computer's graphics hardware, specifically its graphics processing unit (GPU), to make screen drawing faster. This gives a noticeable boost in speed.

To enable graphics acceleration enabled by default on your emulator: when creating the AVD, in the Hardware section, click New, select GPU emulation and set the value to Yes.

To enable acceleration only at runtime: use the -gpu flag while starting the emulator like this:

emulator -avd <avd_name> -gpu on

Source: Google's Using the Emulator tutorial.

Android ListView with Checkbox and all clickable

this code works on my proyect and i can select the listview item and checkbox

<?xml version="1.0" encoding="utf-8"?>
<!-- Single List Item Design -->
<LinearLayout xmlns:android=""
    android:clickable="true" >

        android:layout_weight="4" />

        android:text="" >


Where is adb.exe in windows 10 located?

if you know SDK'path on your system, (by default, it's in /users/appdata/local/Android/...

then, open platform-tools or platform/platform-tools and launch cmd...

it's there you can write adb

Java, How to get number of messages in a topic in apache kafka

Apache Kafka command to get un handled messages on all partitions of a topic:

    --topic test --zookeeper localhost:2181 
    --group test_group


Group      Topic        Pid Offset          logSize         Lag             Owner
test_group test         0   11051           11053           2               none
test_group test         1   10810           10812           2               none
test_group test         2   11027           11028           1               none

Column 6 is the un-handled messages. Add them up like this:

    --topic test --zookeeper localhost:2181 
    --group test_group 2>/dev/null | awk 'NR>1 {sum += $6} 
    END {print sum}'

awk reads the rows, skips the header line and adds up the 6th column and at the end prints the sum.



How do I join two lists in Java?

You can do a oneliner if the target list is predeclared.

(newList = new ArrayList<String>(list1)).addAll(list2);

How to error handle 1004 Error with WorksheetFunction.VLookup?

From my limited experience, this happens for two main reasons:

  1. The lookup_value (arg1) is not present in the table_array (arg2)

The simple solution here is to use an error handler ending with Resume Next

  1. The formats of arg1 and arg2 are not interpreted correctly

If your lookup_value is a variable you can enclose it with TRIM()

cellNum = wsFunc.VLookup(TRIM(currName), rngLook, 13, False)

ADB not responding. You can wait more,or kill "adb.exe" process manually and click 'Restart'

None of the above helped me completely. Although Oventoaster made me think. I had a couple of adb on my system. Removed them almost all.

I am running android studio on ubuntu 14.04 64 bit.

So I checked manually /home/xxxxx/Android/Sdk/platform-tools/adb

where xxxxx was my linux username

this gave

/home/xxxxx/Android/Sdk/platform-tools/adb: error while loading shared libraries: cannot open shared object file: No such file or directory

solved it for me.

How to pass query parameters with a routerLink

<a [routerLink]="['../']" [queryParams]="{name: 'ferret'}" [fragment]="nose">Ferret Nose</a>
\_/   \______________/\_________/ \_________/ \__/
 |           |            |            |        |
scheme    authority      path        query   fragment

For more info -

Dynamically load JS inside JS

I need to do this frequently, so I use this:

var loadJS = function(url, implementationCode, location){
    //url is URL of external file, implementationCode is the code
    //to be called from the file, location is the location to 
    //insert the <script> element

    var scriptTag = document.createElement('script');
    scriptTag.src = url;

    scriptTag.onload = implementationCode;
    scriptTag.onreadystatechange = implementationCode;

var yourCodeToBeCalled = function(){
//your code goes here
loadJS('yourcode.js', yourCodeToBeCalled, document.body);

For more information, see this site How do I include a JavaScript file in another JavaScript file?, which is the source of my function idea.

How to create a drop shadow only on one side of an element?

It's always better to read the specs. There is no box-shadow-bottom property, and as Lea points out you should always place the un-prefixed property at the bottom, after the prefixed ones.

So it's:

.shadow {_x000D_
  -webkit-box-shadow: 0px 2px 4px #000000;_x000D_
  -moz-box-shadow: 0px 2px 4px #000000;_x000D_
  box-shadow: 0px 2px 4px #000000;_x000D_
<div class="shadow">Some content</div>

org.glassfish.jersey.servlet.ServletContainer ClassNotFoundException

I had the same problem with eclipse, the WA solution was to copy the libs to WEB-INF/lib

What is the JUnit XML format specification that Hudson supports?

I did a similar thing a few months ago, and it turned out this simple format was enough for Hudson to accept it as a test protocol:

<testsuite tests="3">
    <testcase classname="foo1" name="ASuccessfulTest"/>
    <testcase classname="foo2" name="AnotherSuccessfulTest"/>
    <testcase classname="foo3" name="AFailingTest">
        <failure type="NotEnoughFoo"> details about failure </failure>

This question has answers with more details: Spec. for JUnit XML Output

What is an opaque response, and what purpose does it serve?

Consider the case in which a service worker acts as an agnostic cache. Your only goal is serve the same resources that you would get from the network, but faster. Of course you can't ensure all the resources will be part of your origin (consider libraries served from CDNs, for instance). As the service worker has the potential of altering network responses, you need to guarantee you are not interested in the contents of the response, nor on its headers, nor even on the result. You're only interested on the response as a black box to possibly cache it and serve it faster.

This is what { mode: 'no-cors' } was made for.

Choosing the correct upper and lower HSV boundaries for color detection with`cv::inRange` (OpenCV)

Here's a simple HSV color thresholder script to determine the lower/upper color ranges using trackbars for any image on the disk. Simply change the image path in cv2.imread()

enter image description here

import cv2
import numpy as np

def nothing(x):

# Load image
image = cv2.imread('1.jpg')

# Create a window

# Create trackbars for color change
# Hue is from 0-179 for Opencv
cv2.createTrackbar('HMin', 'image', 0, 179, nothing)
cv2.createTrackbar('SMin', 'image', 0, 255, nothing)
cv2.createTrackbar('VMin', 'image', 0, 255, nothing)
cv2.createTrackbar('HMax', 'image', 0, 179, nothing)
cv2.createTrackbar('SMax', 'image', 0, 255, nothing)
cv2.createTrackbar('VMax', 'image', 0, 255, nothing)

# Set default value for Max HSV trackbars
cv2.setTrackbarPos('HMax', 'image', 179)
cv2.setTrackbarPos('SMax', 'image', 255)
cv2.setTrackbarPos('VMax', 'image', 255)

# Initialize HSV min/max values
hMin = sMin = vMin = hMax = sMax = vMax = 0
phMin = psMin = pvMin = phMax = psMax = pvMax = 0

    # Get current positions of all trackbars
    hMin = cv2.getTrackbarPos('HMin', 'image')
    sMin = cv2.getTrackbarPos('SMin', 'image')
    vMin = cv2.getTrackbarPos('VMin', 'image')
    hMax = cv2.getTrackbarPos('HMax', 'image')
    sMax = cv2.getTrackbarPos('SMax', 'image')
    vMax = cv2.getTrackbarPos('VMax', 'image')

    # Set minimum and maximum HSV values to display
    lower = np.array([hMin, sMin, vMin])
    upper = np.array([hMax, sMax, vMax])

    # Convert to HSV format and color threshold
    hsv = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
    mask = cv2.inRange(hsv, lower, upper)
    result = cv2.bitwise_and(image, image, mask=mask)

    # Print if there is a change in HSV value
    if((phMin != hMin) | (psMin != sMin) | (pvMin != vMin) | (phMax != hMax) | (psMax != sMax) | (pvMax != vMax) ):
        print("(hMin = %d , sMin = %d, vMin = %d), (hMax = %d , sMax = %d, vMax = %d)" % (hMin , sMin , vMin, hMax, sMax , vMax))
        phMin = hMin
        psMin = sMin
        pvMin = vMin
        phMax = hMax
        psMax = sMax
        pvMax = vMax

    # Display result image
    cv2.imshow('image', result)
    if cv2.waitKey(10) & 0xFF == ord('q'):


How to add headers to a multicolumn listbox in an Excel userform using VBA

I was searching for quite a while for a solution to add a header without using a separate sheet and copy everything into the userform.

My solution is to use the first row as header and run it through an if condition and add additional items underneath.

Like that:

If lborowcount = 0 Then_x000D_
 With lboorder_x000D_
 .ColumnCount = 5_x000D_
 .Column(0, lborowcount) = "Item"_x000D_
 .Column(1, lborowcount) = "Description"_x000D_
 .Column(2, lborowcount) = "Ordered"_x000D_
 .Column(3, lborowcount) = "Rate"_x000D_
 .Column(4, lborowcount) = "Amount"_x000D_
 End With_x000D_
 lborowcount = lborowcount + 1_x000D_
End If_x000D_
With lboorder_x000D_
 .ColumnCount = 5_x000D_
 .Column(0, lborowcount) = itemselected_x000D_
 .Column(1, lborowcount) = descriptionselected_x000D_
 .Column(2, lborowcount) = orderedselected_x000D_
 .Column(3, lborowcount) = rateselected_x000D_
 .Column(4, lborowcount) = amountselected_x000D_
 End With_x000D_
lborowcount = lborowcount + 1

in that example lboorder is the listbox, lborowcount counts at which row to add the next listbox item. It's a 5 column listbox. Not ideal but it works and when you have to scroll horizontally the "header" stays above the row.

Copy and paste content from one file to another file in vi

Use the variations of d like dd to cut.

To write a range of lines to another file you can use:

:<n>,<m> w filename

Where <n> and <m> are numbers (or symbols) that designate a range of lines.

For using the desktop clipboard, take a look at the +g commands.

Indentation Error in Python

This has happened with me too, python is space sensitive, so after " : "(colon) you might have left a space,
for example: [space is represented by "."]

`if command == 'HOWMANY':.
     opcodegroupr = "A0"
     opcoder = "85"
 elif command == 'IDENTIFY':.
     opcodegroupr = "A0"
     opcoder = "81"`

so try removing the unnecessary spaces,if you open it in IDE your cursor will be displayed away from ":" something like :- "if command == 'HOWMANY': |"
....whereas it should be:- "if command == 'HOWMANY':| "

Import an existing git project into GitLab?

I was able to fully export my project along with all commits, branches and tags to gitlab via following commands run locally on my computer:

To illustrate my example, I will be using as the source repository that I want to import into gitlab. I created an empty project named Kint (under namespace raveren) in gitlab beforehand and it told me the http git url of the newly created project there is

The commands are OS agnostic.

In a new directory:

git clone --mirror
cd kint.git
git remote add gitlab
git push gitlab --mirror

Now if you have a locally cloned repository that you want to keep using with the new remote, just run the following commands* there:

git remote remove origin
git remote add origin
git fetch --all

*This assumes that you did not rename your remote master from origin, otherwise, change the first two lines to reflect it.

No connection could be made because the target machine actively refused it

With this error I was able to trace it, thanks to @Yaur, you need to basically check the service (WCF) if it's running and also check the outbound and inbound TCP properties on your advance firewall settings.

ERROR Source option 1.5 is no longer supported. Use 1.6 or later

I think this means that

  • You are using JDK9 or later
  • Your project uses maven-compiler-plugin with an old version which defaults to Java 5.

You have three options to solve this

  1. Downgrade to JDK7 or JDK8 (meh)
  2. Use maven-compiler-plugin version or later, because

    NOTE: Since 3.8.0 the default value has changed from 1.5 to 1.6 See

  3. Indicate to the maven-compiler-plugin to use source level 6 and target 6 (or later).

    Best practice recommended by

    Also note that at present the default source setting is 1.6 and the default target setting is 1.6, independently of the JDK you run Maven with. You are highly encouraged to change these defaults by setting source and target as described in Setting the -source and -target of the Java Compiler.


    or use


Disabling Chrome cache for website development

One more option for disabling the cache is provided by my 3rd Chrome extension Page Size Inspector that disables the cache exactly the same way as Devtools does.

In addition, the extension quickly reports page size, cache usage, network requests and load time of a web page in a convenient way. Plus its open source at Github.

Screenshot - Page Size Inspector

Is there a way to pass javascript variables in url?

Try this:

 window.location.href = ""+elemA+"&lon="+elemB+"&setLatLon=Set";

To put a variable in a string enclose the variable in quotes and addition signs like this:

var myname = "BOB";
var mystring = "Hi there "+myname+"!"; 

Just remember that one rule!

Split string using a newline delimiter with Python

str.splitlines method should give you exactly that.

>>> data = """a,b,c
... d,e,f
... g,h,i
... j,k,l"""
>>> data.splitlines()
['a,b,c', 'd,e,f', 'g,h,i', 'j,k,l']

Is there a way to get a <button> element to link to a location without wrapping it in an <a href ... tag?

Inline Javascript:

<button onclick="window.location='';">Visit Page Now</button>

Defining a function in Javascript:

    function visitPage(){
<button onclick="visitPage();">Visit Page Now</button>

or in Jquery

<button id="some_id">Visit Page Now</button>

$('#some_id').click(function() {

Division in Python 2.7. and 3.3

In Python 3, / is float division

In Python 2, / is integer division (assuming int inputs)

In both 2 and 3, // is integer division

(To get float division in Python 2 requires either of the operands be a float, either as 20. or float(20))

git: fatal: I don't handle protocol '??http'

I used double quotes for the URL and it worked. So something like

git clone "??"

works.. single quotes dont help. It has to be double quotes.

Java - Access is denied

You need to set permission for the user controls .

  1. Goto C:\Program Files\
  2. Right click java folder, click properties. Select the security tab.
  3. There, click on "Edit" button, which will pop up PERMISSIONS FOR JAVA window.
  4. Click on Add, which will pop up a new window. In that, in the "Enter object name" box, Enter your user account name, and click okay(if already exist, skip this step).
  5. Now in "PERMISSIONS OF JAVA" window, you will see several clickable options like CREATOR OWNER, SYSTEM, among them is your username. Click on it, and check mark the FULL CONTROL option in Permissions for sub window.
  6. Finally, Hit apply and okay.

Converting JSON data to Java object

I looked at Google's Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?

Google Gson supports generics and nested beans. The [] in JSON represents an array and should map to a Java collection such as List or just a plain Java array. The {} in JSON represents an object and should map to a Java Map or just some JavaBean class.

You have a JSON object with several properties of which the groups property represents an array of nested objects of the very same type. This can be parsed with Gson the following way:

package com.stackoverflow.q1688099;

import java.util.List;

public class Test {

    public static void main(String... args) throws Exception {
        String json = 
                + "'title': 'Computing and Information systems',"
                + "'id' : 1,"
                + "'children' : 'true',"
                + "'groups' : [{"
                    + "'title' : 'Level one CIS',"
                    + "'id' : 2,"
                    + "'children' : 'true',"
                    + "'groups' : [{"
                        + "'title' : 'Intro To Computing and Internet',"
                        + "'id' : 3,"
                        + "'children': 'false',"
                        + "'groups':[]"
                    + "}]" 
                + "}]"
            + "}";

        // Now do the magic.
        Data data = new Gson().fromJson(json, Data.class);

        // Show it.


class Data {
    private String title;
    private Long id;
    private Boolean children;
    private List<Data> groups;

    public String getTitle() { return title; }
    public Long getId() { return id; }
    public Boolean getChildren() { return children; }
    public List<Data> getGroups() { return groups; }

    public void setTitle(String title) { this.title = title; }
    public void setId(Long id) { = id; }
    public void setChildren(Boolean children) { this.children = children; }
    public void setGroups(List<Data> groups) { this.groups = groups; }
    public String toString() {
        return String.format("title:%s,id:%d,children:%s,groups:%s", title, id, children, groups);

Fairly simple, isn't it? Just have a suitable JavaBean and call Gson#fromJson().

See also:

Python speed testing - Time Difference - milliseconds

You could simply print the difference:

print tend - tstart

List<T> OrderBy Alphabetical Order

You can use this code snippet:

var New1 = EmpList.OrderBy(z => z.Age).ToList();

where New1 is a List<Employee>.

EmpList is variable of a List<Employee>.

z is a variable of Employee type.

Angular 6: How to set response type as text while making http call

By Default angular return responseType as Json, but we can configure below types according to your requirement.

responseType: 'arraybuffer'|'blob'|'json'|'text'

    { dealerId: 13, createdBy: "-1", productId, quantity }, 
    { headers, responseType: 'text'});

Flutter- wrapping text

You can use Flexible, in this case the could be a long name (Labels and BlankSpace are custom classes that return widgets) :

new Column(
  crossAxisAlignment: CrossAxisAlignment.start,
  children: <Widget>[
   new Row(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      children: <Widget>[
        new Flexible(
            child: Labels.getTitle_2(,
            color: StyleColors.COLOR_BLACK)),

Datatable select method ORDER BY clause

Use"col1='test'","col1 ASC")

Then before binding your data to the grid or repeater etc, use this


That will solve your problem.

slf4j: how to log formatted message, object array, exception

As of SLF4J 1.6.0, in the presence of multiple parameters and if the last argument in a logging statement is an exception, then SLF4J will presume that the user wants the last argument to be treated as an exception and not a simple parameter. See also the relevant FAQ entry.

So, writing (in SLF4J version 1.7.x and later)

 logger.error("one two three: {} {} {}", "a", "b", 
              "c", new Exception("something went wrong"));

or writing (in SLF4J version 1.6.x)

 logger.error("one two three: {} {} {}", new Object[] {"a", "b", 
              "c", new Exception("something went wrong")});

will yield

one two three: a b c
java.lang.Exception: something went wrong
    at Example.main(
    at java.lang.reflect.Method.invoke(
    at ...

The exact output will depend on the underlying framework (e.g. logback, log4j, etc) as well on how the underlying framework is configured. However, if the last parameter is an exception it will be interpreted as such regardless of the underlying framework.

rsync copy over only certain types of files using include option

I think --include is used to include a subset of files that are otherwise excluded by --exclude, rather than including only those files. In other words: you have to think about include meaning don't exclude.

Try instead:

rsync -zarv  --include "*/" --exclude="*" --include="*.sh" "$from" "$to"

For rsync version 3.0.6 or higher, the order needs to be modified as follows (see comments):

rsync -zarv --include="*/" --include="*.sh" --exclude="*" "$from" "$to"

Adding the -m flag will avoid creating empty directory structures in the destination. Tested in version 3.1.2.

So if we only want *.sh files we have to exclude all files --exclude="*", include all directories --include="*/" and include all *.sh files --include="*.sh".

You can find some good examples in the section Include/Exclude Pattern Rules of the man page

What causes a TCP/IP reset (RST) flag to be sent?

RST is sent by the side doing the active close because it is the side which sends the last ACK. So if it receives FIN from the side doing the passive close in a wrong state, it sends a RST packet which indicates other side that an error has occured.

String contains another string

You can use .indexOf():

if(str.indexOf(substr) > -1) {


XSLT getting last element

You need to put the last() indexing on the nodelist result, rather than as part of the selection criteria. Try:


sublime text2 python error message /usr/bin/python: can't find '__main__' module in ''

I got the same error as I didn't save the script before executing it. Check to see if you have saved it!

ImportError: No module named sqlalchemy

So here is an idea!

Since it seemed to work somewhere else.

install python-virtualenv and optionally you can install virtualenv-wrapper (which is pretty cool to create projects and so on)

In each env, you might have different versions of eggs. In other word, you could have sqlalchemy 1 and sqlaclhemy 1.5 in two different envs and they won't conflict with each others. It seems that you have a problem with your currently installed eggs.

So here we go:

virtualenv --no-site-packages foo
source foo/bin/activate

The parameter --no-site-packages will create a virtualenv and not use the packages already installed on your computer. It's pretty much like a bare python install.

source foo/bin/activate loads the virtualenv.

It's not that really userfriendly. And that's why exists.

That said, you should see somthing like thant in your terminal "(foo)user@domain$:" once your virtualenv is activated. It means that you can go on!

Then you have to do.

python develop of your project. It should download and install dependencies of your project in the virtualenv located in foo. If you need to install anything else, please use pip or easy_install without using sudo. When using virtualenv, you almost never need to use sudo. Sudo will install package in your global python install while it's not required and not really desirable.

If something happens in your virtualenv, you can always delete it and create a new one. This is no big deal. No need to mess with anything. Doesn't work? start over, do pip install -U if needed, define the versions if needed and so on.

Last but not least, in the other answers, it seems that the import changed. If the new versions for flask-sqlalchemy is located somewhere else, you should update your import or install the version you used to use.

How to fix: "UnicodeDecodeError: 'ascii' codec can't decode byte"

I had the same problem but it didn't work for Python 3. I followed this and it solved my problem:

enc = sys.getdefaultencoding()
file = open(menu, "r", encoding = enc)

You have to set the encoding when you are reading/writing the file.

how to delete the content of text file without deleting itself

Write an empty string to the file, flush, and close. Make sure that the file writer is not in append-mode. I think that should do the trick.

ListBox with ItemTemplate (and ScrollBar!)

I pasted your code into test project, added about 20 items and I get usable scroll bars, no problem, and they work as expected. When I only add a couple items (such that scrolling is unnecessary) I get no usable scrollbar. Could this be the case? that you are not adding enough items?

If you remove the ScrollViewer.VerticalScrollBarVisibility="Visible" then the scroll bars only appear when you have need of them.

How to temporarily exit Vim and go back

Assuming terminal Vim on a flavor of *nix:

To suspend your running Vim

Ctrl + Z

will suspend the process and get back to your shell


will resume (bring to foreground) your suspended Vim.

To start a new shell

Start a subshell using:


(as configured by)

:set shell?



followed by:

Ctrl+D (or exit, but why type so much?)

to kill the shell and return to Vim.

Dataset - Vehicle make/model/year (free)

How about Freebase? I think they have an API available, too.

What should be the package name of android app?

Package name is the reversed domain name, it is a unique name for each application on Playstore. You can't upload two apps with the same package name. You can check package name of the app from playstore url

so you can easily check on playstore that this package name is in used by some other app or not before uploading it.

Write a mode method in Java to find the most frequently occurring element in an array

public int mode(int[] array) {
    int mode = array[0];
    int maxCount = 0;
    for (int i = 0; i < array.length; i++) {
        int value = array[i];
        int count = 1;
        for (int j = 0; j < array.length; j++) {
            if (array[j] == value) count++;
            if (count > maxCount) {
                mode = value;
                maxCount = count;
    return mode;

Reading HTML content from a UIWebView

To read:-

NSString *html = [myWebView stringByEvaluatingJavaScriptFromString: @"document.getElementById('your div id').textContent"];

To modify:-

html = [myWebView stringByEvaluatingJavaScriptFromString: @"document.getElementById('your div id').textContent=''"];

Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on

I know its too late now. However even today if you are having trouble accessing cross thread controls? This is the shortest answer till date :P

Invoke(new Action(() =>
                    label1.Text = "WooHoo!!!";

This is how i access any form control from a thread.

CS0120: An object reference is required for the nonstatic field, method, or property 'foo'

It looks like you are calling a non static member (a property or method, specifically setTextboxText) from a static method (specifically SumData). You will need to either:

  1. Make the called member static also:

    static void setTextboxText(int result)
        // Write static logic for setTextboxText.  
        // This may require a static singleton instance of Form1.
  2. Create an instance of Form1 within the calling method:

    private static void SumData(object state)
        int result = 0;
        //int[] icount = (int[])state;
        int icount = (int)state;
        for (int i = icount; i > 0; i--)
            result += i;
        Form1 frm1 = new Form1();

    Passing in an instance of Form1 would be an option also.

  3. Make the calling method a non-static instance method (of Form1):

    private void SumData(object state)
        int result = 0;
        //int[] icount = (int[])state;
        int icount = (int)state;
        for (int i = icount; i > 0; i--)
            result += i;

More info about this error can be found on MSDN.

How to assert two list contain the same elements in Python?

Converting your lists to sets will tell you that they contain the same elements. But this method cannot confirm that they contain the same number of all elements. For example, your method will fail in this case:

L1 = [1,2,2,3]
L2 = [1,2,3,3]

You are likely better off sorting the two lists and comparing them:

def checkEqual(L1, L2):
    if sorted(L1) == sorted(L2):
        print "the two lists are the same"
        return True
        print "the two lists are not the same"
        return False

Note that this does not alter the structure/contents of the two lists. Rather, the sorting creates two new lists

jQuery deferreds and promises - .then() vs .done()

In addition to the answers above:

The real power of .then is the possibility to chain ajax calls in a fluent way, and thus avoiding callback hell.

For example:

$.getJSON( 'dataservice/General', {action:'getSessionUser'} )
    .then( function( user ) {
        console.log( user );
        return $.getJSON( 'dataservice/Address', {action:'getFirstAddress'} );
    .then( function( address ) {
        console.log( address );

Here the second .then follows the returned $.getJSON

How to send an email from JavaScript'mailto:[email protected]'); as above does nothing to hide the "[email protected]" email address from being harvested by spambots. I used to constantly run into this problem.

var recipient="test";
var at = String.fromCharCode(64);
var dotcom="";
var mail="mailto:";;

Go build: "Cannot find package" (even though GOPATH is set)

Have you tried adding the absolute directory of go to your 'path'?

export PATH=$PATH:/directory/to/go/

Directory Chooser in HTML page

Try this, I think it will work for you:

<input type="file" webkitdirectory directory multiple/>

You can find the demo of this at , and if you need further information you can find it here.

How to check certificate name and alias in keystore files?

In order to get all the details I had to add the -v option to romaintaz answer:

keytool -v -list -keystore <FileName>.keystore

Jquery- Get the value of first td in table

This should work:

   var value=$(this).closest('tr').children('td:first').text();


  • .closest('tr') gets the nearest ancestor that is a <tr> element (so in this case the row where the <a> element is in).
  • .children('td:first') gets all the children of this element, but with the :first selector we reduce it to the first <td> element.
  • .text() gets the text inside the element

As you can see from the other answers, there is more than only one way to do this.

cURL equivalent in Node.js?

you can easily use request module:

Sample code:

var request = require('request');
request('', function (error, response, body) {
  if (!error && response.statusCode == 200) {
    console.log(body) // Show the HTML for the Google homepage. 
  else {
    console.log("Error "+response.statusCode)

Sum all the elements java arraylist

I haven't tested it but it should work.

public double incassoMargherita()
    double sum = 0;
    for(int i = 0; i < m.size(); i++)
        sum = sum + m.get(i);
    return sum;

Setting the selected attribute on a select list using jQuery

You can follow the .selectedIndex strategy of danielrmt, but determine the index based on the text within the option tags like this:

$('#dropdown')[0].selectedIndex = $('#dropdown option').toArray().map(jQuery.text).indexOf('B');

This works on the original HTML without using value attributes.

How to stop event bubbling on checkbox click

This is an excellent example for understanding event bubbling concept. Based on the above answers, the final code will look like as mentioned below. Where the user Clicks on checkbox the event propagation to its parent element 'header' will be stopped using event.stopPropagation();.

$(document).ready(function() {
            $('#header').click(function() {
                if($('#container').hasClass('hidden')) {
                } else {
          $('#header input[type=checkbox]').click(function(event) {
              if (event.stopPropagation) {    // standard
               } else {    // IE6-8
                    event.cancelBubble = true;

Java Date vs Calendar

I generally use Date if possible. Although it is mutable, the mutators are actually deprecated. In the end it basically wraps a long that would represent the date/time. Conversely, I would use Calendars if I have to manipulate the values.

You can think of it this way: you only use StringBuffer only when you need to have Strings that you can easily manipulate and then convert them into Strings using toString() method. In the same way, I only use Calendar if I need to manipulate temporal data.

For best practice, I tend to use immutable objects as much as possible outside of the domain model. It significantly reduces the chances of any side effects and it is done for you by the compiler, rather than a JUnit test. You use this technique by creating private final fields in your class.

And coming back to the StringBuffer analogy. Here is some code that shows you how to convert between Calendar and Date

String s = "someString"; // immutable string
StringBuffer buf = new StringBuffer(s); // mutable "string" via StringBuffer
assertEquals("someStringx", buf.toString()); // convert to immutable String

// immutable date with hard coded format.  If you are hard
// coding the format, best practice is to hard code the locale
// of the format string, otherwise people in some parts of Europe
// are going to be mad at you.
Date date =     new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH).parse("2001-01-02");

// Convert Date to a Calendar
Calendar cal = Calendar.getInstance();

// mutate the value
cal.add(Calendar.YEAR, 1);

// convert back to Date
Date newDate = cal.getTime();

assertEquals(new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH).parse("2002-01-02"), newDate);

C# int to enum conversion

It's fine just to cast your int to Foo:

int i = 1;
Foo f = (Foo)i;

If you try to cast a value that's not defined it will still work. The only harm that may come from this is in how you use the value later on.

If you really want to make sure your value is defined in the enum, you can use Enum.IsDefined:

int i = 1;
if (Enum.IsDefined(typeof(Foo), i))
    Foo f = (Foo)i;
   // Throw exception, etc.

However, using IsDefined costs more than just casting. Which you use depends on your implemenation. You might consider restricting user input, or handling a default case when you use the enum.

Also note that you don't have to specify that your enum inherits from int; this is the default behavior.

Handling click events on a drawable within an EditText

for left drawable click listener

txt.setOnTouchListener(new View.OnTouchListener() {
        public boolean onTouch(View v, MotionEvent event) {
            final int DRAWABLE_LEFT = 0;

            if (event.getAction() == MotionEvent.ACTION_UP) {
                if (event.getRawX() <= (txt
                        .getCompoundDrawables()[DRAWABLE_LEFT].getBounds().width() +
                        txt.getPaddingLeft() +
                        txt.getLeft())) {

                          //TODO do code here
                    return true;
            return false;

How to extract request http headers from a request using NodeJS connect

var host = req.headers['host']; 

The headers are stored in a JavaScript object, with the header strings as object keys.

Likewise, the user-agent header could be obtained with

var userAgent = req.headers['user-agent']; 

How to Scroll Down - JQuery

$('.btnMedio').click(function(event) {
    // Preventing default action of the event
    // Getting the height of the document
    var n = $(document).height();
    $('html, body').animate({ scrollTop: n }, 50);
//                                       |    |
//                                       |    --- duration (milliseconds) 
//                                       ---- distance from the top

Uncaught SyntaxError: Failed to execute 'querySelector' on 'Document'

Although this is valid in HTML, you can't use an ID starting with an integer in CSS selectors.

As pointed out, you can use getElementById instead, but you can also still achieve the same with a querySelector:


How do I compile C++ with Clang?

Open a Terminal window and navigate to your project directory. Run these sets of commands, depending on which compiler you have installed:

To compile multiple C++ files using clang++:

$ clang++ *.cpp 
$ ./a.out 

To compile multiple C++ files using g++:

$ g++ -c *.cpp 
$ g++ -o temp.exe *.o
$ ./temp.exe

Javascript to display the current date and time

You can try the below:

function formatAMPM() {
    var date = new Date();
    var currDate = date.getDate();
    var hours = date.getHours();
    var dayName = getDayName(date.getDay());
    var minutes = date.getMinutes();
    var monthName = getMonthName(date.getMonth());
    var year = date.getFullYear();
    var ampm = hours >= 12 ? 'pm' : 'am';
    hours = hours % 12;
    hours = hours ? hours : 12; // the hour '0' should be '12'
    minutes = minutes < 10 ? '0' + minutes : minutes;
    var strTime = dayName + ' ' + monthName + ' ' + currDate + ' ' + year + ' ' + hours + ':' + minutes + ' ' + ampm;

function getMonthName(month) {
    var ar = new Array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December");
    return ar[month];

function getDayName(day) {
    var ar1 = new Array("Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat");
    return ar1[day];

EDIT: Refer here for a working demo.

How to exit if a command failed?

If you want that behavior for all commands in your script, just add

  set -e 
  set -o pipefail

at the beginning of the script. This pair of options tell the bash interpreter to exit whenever a command returns with a non-zero exit code.

This does not allow you to print an exit message, though.

How to create a drop-down list?

In Kotlin you can do as:

First, put this code in your layout


Then you can do in onCreate() in Activity as ->

   val spinner = findViewById<Spinner>(
    val items = arrayOf("500g", "1kg", "2kg")
    val adapter = ArrayAdapter<String>(

You can get listener from dropdown as:

 spinner.onItemSelectedListener = object : OnItemSelectedListener {
        override fun onItemSelected(
            arg0: AdapterView<*>?,
            arg1: View?,
            arg2: Int,
            arg3: Long
        ) {
            // Do what you want
            val items = spinner.selectedItem.toString()

        override fun onNothingSelected(arg0: AdapterView<*>?) {}

MySQL show current connection info

There are MYSQL functions you can use. Like this one that resolves the user:


This will return something like root@localhost so you get the host and the user.

To get the current database run this statement:


Other useful functions can be found here:

How can I call PHP functions by JavaScript?

If you actually want to send data to a php script for example you can do this:

The php:

$a = $_REQUEST['a'];
$b = $_REQUEST['b']; //totally sanitized

echo $a + $b;

Js (using jquery):

$.post("/path/to/above.php", {a: something, b: something}, function(data){