Programs & Examples On #256color


Change the location of the ~ directory in a Windows install of Git Bash

I don't understand, why you don't want to set the $HOME environment variable since that solves exactly what you're asking for.

cd ~ doesn't mean change to the root directory, but change to the user's home directory, which is set by the $HOME environment variable.

Quick'n'dirty solution

Edit C:\Program Files (x86)\Git\etc\profile and set $HOME variable to whatever you want (add it if it's not there). A good place could be for example right after a condition commented by # Set up USER's home directory. It must be in the MinGW format, for example:


Save it, open Git Bash and execute cd ~. You should be in a directory /c/my/custom/home now.

Everything that accesses the user's profile should go into this directory instead of your Windows' profile on a network drive.

Note: C:\Program Files (x86)\Git\etc\profile is shared by all users, so if the machine is used by multiple users, it's a good idea to set the $HOME dynamically:


Cleaner solution

Set the environment variable HOME in Windows to whatever directory you want. In this case, you have to set it in Windows path format (with backslashes, e.g. c:\my\custom\home), Git Bash will load it and convert it to its format.

If you want to change the home directory for all users on your machine, set it as a system environment variable, where you can use for example %USERNAME% variable so every user will have his own home directory, for example:


If you want to change the home directory just for yourself, set it as a user environment variable, so other users won't be affected. In this case, you can simply hard-code the whole path:


-bash: export: `=': not a valid identifier

I faced the same error and did some research to only see that there could be different scenarios to this error. Let me share my findings.

Scenario 1: There cannot be spaces beside the = (equals) sign

$ export TEMP_ENV = example-value
-bash: export: `=': not a valid identifier
// this is the answer to the question

$ export TEMP_ENV =example-value
-bash: export: `=example-value': not a valid identifier

$ export TEMP_ENV= example-value
-bash: export: `example-value': not a valid identifier

Scenario 2: Object value assignment should not have spaces besides quotes

$ export TEMP_ENV={ "key" : "json example" } 
-bash: export: `:': not a valid identifier
-bash: export: `json example': not a valid identifier
-bash: export: `}': not a valid identifier

Scenario 3: List value assignment should not have spaces between values

$ export TEMP_ENV=[1,2 ,3 ]
-bash: export: `,3': not a valid identifier
-bash: export: `]': not a valid identifier

I'm sharing these, because I was stuck for a couple of hours trying to figure out a workaround. Hopefully, it will help someone in need.

nano error: Error opening terminal: xterm-256color

I hear that this can be fixed by overwriting your /usr/share/terminfo with one from the computer of somebody with a working install of Lion. I can't confirm whether this works or not, and unfortunately I haven't upgraded yet, so I can't provide you with that file.

What is console.log in jQuery?

it will print log messages in your developer console (firebug/webkit dev tools/ie dev tools)

jquery $(window).width() and $(window).height() return different values when viewport has not been resized

I was having a very similar problem. I was getting inconsistent height() values when I refreshed my page. (It wasn't my variable causing the problem, it was the actual height value.)

I noticed that in the head of my page I called my scripts first, then my css file. I switched so that the css file is linked first, then the script files and that seems to have fixed the problem so far.

Hope that helps.

How to deploy a war file in Tomcat 7

This has been working for me:

  1. Create your war file (mysite.war) locally.
  2. Rename it locally to something besides .war, like mysite.www
  3. With tomcat still running, upload mysite.www to webapps directory.
  4. After it finishes uploading, delete the previous version mysite.war
  5. List the directory, watching for the directory /mysite to disappear.
  6. Rename mysite.www to be mysite.war
  7. List the directory, watching for the new /mysite to be created.

If you try uploading the new file as a war file, with tomcat still running, it will attempt to expand it before it is all there. It will fail. Having failed, it will not try again. Thus, uploading a www file, then renaming it, allows the whole war file to be present before tomcat notices it.

Hint, don't forget to check that the war file's owner is tomcat (Use chown)

NoClassDefFoundError on Maven dependency

You have to make classpath in pom file for your dependency. Therefore you have to copy all the dependencies into one place.

Check my blog.

            <mainClass>$fullqualified path to your main Class</mainClass>

UnicodeEncodeError: 'charmap' codec can't encode - character maps to <undefined>, print function

If you use Python 3.6 (possibly 3.5 or later), it doesn't give that error to me anymore. I had a similar issue, because I was using v3.4, but it went away after I uninstalled and reinstalled.

How do you test to see if a double is equal to NaN?

Use the static Double.isNaN(double) method, or your Double's .isNaN() method.

// 1. static method
if (Double.isNaN(doubleValue)) {
// 2. object's method
if (doubleObject.isNaN()) {

Simply doing:

if (var == Double.NaN) {

is not sufficient due to how the IEEE standard for NaN and floating point numbers is defined.

What is the purpose of .PHONY in a Makefile?

.PHONY: install
  • means the word "install" doesn't represent a file name in this Makefile;
  • means the Makefile has nothing to do with a file called "install" in the same directory.

Git Stash vs Shelve in IntelliJ IDEA

git shelve doesn't exist in Git.

Only git stash:

  • when you want to record the current state of the working directory and the index, but want to go back to a clean working directory.
  • which saves your local modifications away and reverts the working directory to match the HEAD commit.

You had a 2008 old project git shelve to isolate modifications in a branch, but that wouldn't be very useful nowadays.

As documented in Intellij IDEA shelve dialog, the feature "shelving and unshelving" is not linked to a VCS (Version Control System tool) but to the IDE itself, to temporarily storing pending changes you have not committed yet in changelist.

Note that since Git 2.13 (Q2 2017), you now can stash individual files too.

How to search through all Git and Mercurial commits in the repository for a certain string?

In addition to richq answer of using git log -g --grep=<regexp> or git grep -e <regexp> $(git log -g --pretty=format:%h): take a look at the following blog posts by Junio C Hamano, current git maintainer


Both git grep and git log --grep are line oriented, in that they look for lines that match specified pattern.

You can use git log --grep=<foo> --grep=<bar> (or git log --author=<foo> --grep=<bar> that internally translates to two --grep) to find commits that match either of patterns (implicit OR semantic).

Because of being line-oriented, the useful AND semantic is to use git log --all-match --grep=<foo> --grep=<bar> to find commit that has both line matching first and line matching second somewhere.

With git grep you can combine multiple patterns (all which must use the -e <regexp> form) with --or (which is the default), --and, --not, ( and ). For grep --all-match means that file must have lines that match each of alternatives.

Find closest previous element jQuery

No, there is no "easy" way. Your best bet would be to do a loop where you first check each previous sibling, then move to the parent node and all of its previous siblings.

You'll need to break the selector into two, 1 to check if the current node could be the top level node in your selector, and 1 to check if it's descendants match.

Edit: This might as well be a plugin. You can use this with any selector in any HTML:

(function($) {
    $.fn.closestPrior = function(selector) {
        selector = selector.replace(/^\s+|\s+$/g, "");
        var combinator =[ +~>]|$/);
        var parent = selector.substr(0, combinator);
        var children = selector.substr(combinator);
        var el = this;
        var match = $();
        while (el.length && !match.length) {
            el = el.prev();
            if (!el.length) {
                var par = el.parent();
                // Don't use the parent - you've already checked all of the previous 
                // elements in this parent, move to its previous sibling, if any.
                while (par.length && !par.prev().length) {
                    par = par.parent();
                el = par.prev();
                if (!el.length) {
            if ( && el.find(children).length) {
                match = el.find(children).last();
            else if (el.find(selector).length) {
                match = el.find(selector).last();
        return match;

Auto increment in phpmyadmin

@AmitKB, Your procedure is correct. Although this error

Query error: #1075 - Incorrect table definition; there can be only one auto column and it must be defined as a key

can be solved by first marking the field as key(using the key icon with label primary),unless you have other key then it may not work.

How do I cancel a build that is in progress in Visual Studio?

I was hit by an unresponsive build and absolutely nothing would allow me to either kill or cancel the build. Even trying to end the task would trigger a user input window, saying that it could not be ended while the build is still going on (quite ironic because that was precisely the intention, to leave that broken state).

The build was taken care of by MSBuild, so the one way I found is to end its task. When forcing MSBuild.exe to end, VS will wake up and finally see the build as cancelled, allowing you to work again.

Hope this helps someone in the same situation.

Tomcat 8 throwing - org.apache.catalina.webresources.Cache.getResource Unable to add the resource

You have more static resources that the cache has room for. You can do one of the following:

  • Increase the size of the cache
  • Decrease the TTL for the cache
  • Disable caching

For more details see the documentation for these configuration options.

How to programmatically determine the current checked out Git branch

That's one solution. If you add it to your .bashrc, it'll display the current branch in the console.

# git branch
parse_git_branch() {
    git branch 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/(\1) /'

However it's pretty limited. But there is a great project called git sh, which is doing exactly that (and much more).

How to set a DateTime variable in SQL Server 2008?

Try using Select instead of Print


SET @Test = '2011-02-15'

Select @Test

Send JSON data via POST (ajax) and receive json response from Controller (MVC)

var SendInfo= { SendInfo: [... your elements ...]};

            type: 'post',
            url: 'Your-URI',
            data: JSON.stringify(SendInfo),
            contentType: "application/json; charset=utf-8",
            traditional: true,
            success: function (data) {

and in action

public ActionResult AddDomain(IEnumerable<PersonSheets> SendInfo){

you can bind your array like this

var SendInfo = [];

$(this).parents('table').find('input:checked').each(function () {
    var domain = {
        name: $("#id-manuf-name").val(),
        address: $("#id-manuf-address").val(),
        phone: $("#id-manuf-phone").val(),


hope this can help you.

how to reset <input type = "file">

Particularly for Angular

document.getElementById('uploadFile').value = "";

Will work, But if you use Angular It will say "Property 'value' does not exist on type 'HTMLElement'.any"

document.getElementById() returns the type HTMLElement which does not contain a value property. So, cast it into HTMLInputElement

(<HTMLInputElement>document.getElementById('uploadFile')).value = "";


However, we should not use DOM manipulation ( in angular.

To do that angular has provided @VIewChild, @ViewChildren, etc which are document.querySelector(), document.queryselectorAll() respectively.

Even I haven't read it. Better to follows expert's blogs

Go through this link1, link2

Default password of mysql in ubuntu server 16.04

Although this is an old question, there are several of us still struggle to find an answer. At least I did. Please don't follow all the lengthy solutions. You could simply login to your mysql as root without providing any password (provided it is a fresh installation or you haven't changed the password since your installation) by adding sudo before your mysql command. $sudo mysql -uroot -p mysql> This is because mysql changed the security model in one of the latest versions.

Hope this helps

Trigger validation of all fields in Angular Form submit

Based on Thilak's answer I was able to come up with this solution...

Since my form fields only show validation messages if a field is invalid, and has been touched by the user I was able to use this code triggered by a button to show my invalid fields:

// Show/trigger any validation errors for this step_x000D_
angular.forEach(vm.rfiForm.stepTwo.$error, function(error) {_x000D_
  angular.forEach(error, function(field) {_x000D_
// Prevent user from going to next step if current step is invalid_x000D_
if (!vm.rfiForm.stepTwo.$valid) {_x000D_
  isValid = false;_x000D_
<!-- form field -->_x000D_
<div class="form-group" ng-class="{ 'has-error': rfi.rfiForm.stepTwo.Parent_Suffix__c.$touched && rfi.rfiForm.stepTwo.Parent_Suffix__c.$invalid }">_x000D_
  <!-- field label -->_x000D_
  <label class="control-label">Suffix</label>_x000D_
  <!-- end field label -->_x000D_
  <!-- field input -->_x000D_
  <select name="Parent_Suffix__c" class="form-control"_x000D_
          ng-options="item.value as item.label for item in"_x000D_
          ng-model="" />_x000D_
  <!-- end field input -->_x000D_
  <!-- field help -->_x000D_
  <span class="help-block" ng-messages="rfi.rfiForm.stepTwo.Parent_Suffix__c.$error" ng-show="rfi.rfiForm.stepTwo.Parent_Suffix__c.$touched">_x000D_
    <span ng-message="required">this field is required</span>_x000D_
  </span>  _x000D_
  <!-- end field help -->_x000D_
<!-- end form field -->

a href link for entire div in HTML/CSS

Going off of what Surreal Dreams said, it's probably best to style the anchor tag in my experience, but it really does depend on what you are doing. Here's an example:


<div class="parent-div">
  <a href="#">Test</a>
  <a href="#">Test</a>
  <a href="#">Test</a>

Then the CSS:

.parent-div {
  width: 200px;
a {
  background-color: #ccc;
  color: #000;
a:hover {
  background-color: #ddd;

Can't operator == be applied to generic types in C#?

Well in my case I wanted to unit-test the equality operator. I needed call the code under the equality operators without explicitly setting the generic type. Advises for EqualityComparer were not helpful as EqualityComparer called Equals method but not the equality operator.

Here is how I've got this working with generic types by building a LINQ. It calls the right code for == and != operators:

/// <summary>
/// Gets the result of "a == b"
/// </summary>
public bool GetEqualityOperatorResult<T>(T a, T b)
    // declare the parameters
    var paramA = Expression.Parameter(typeof(T), nameof(a));
    var paramB = Expression.Parameter(typeof(T), nameof(b));
    // get equality expression for the parameters
    var body = Expression.Equal(paramA, paramB);
    // compile it
    var invokeEqualityOperator = Expression.Lambda<Func<T, T, bool>>(body, paramA, paramB).Compile();
    // call it
    return invokeEqualityOperator(a, b);

/// <summary>
/// Gets the result of "a =! b"
/// </summary>
public bool GetInequalityOperatorResult<T>(T a, T b)
    // declare the parameters
    var paramA = Expression.Parameter(typeof(T), nameof(a));
    var paramB = Expression.Parameter(typeof(T), nameof(b));
    // get equality expression for the parameters
    var body = Expression.NotEqual(paramA, paramB);
    // compile it
    var invokeInequalityOperator = Expression.Lambda<Func<T, T, bool>>(body, paramA, paramB).Compile();
    // call it
    return invokeInequalityOperator(a, b);

Variable interpolation in the shell

Use curly braces around the variable name:

`tail -1 ${filepath}`

adding css class to multiple elements

.button input,
.button a {

When restoring a backup, how do I disconnect all active connections?

SQL Server Management Studio 2005

When you right click on a database and click Tasks and then click Detach Database, it brings up a dialog with the active connections.

Detach Screen

By clicking on the hyperlink under "Messages" you can kill the active connections.

You can then kill those connections without detaching the database.

More information here.

SQL Server Management Studio 2008

The interface has changed for SQL Server Management studio 2008, here are the steps (via: Tim Leung)

  1. Right-click the server in Object Explorer and select 'Activity Monitor'.
  2. When this opens, expand the Processes group.
  3. Now use the drop-down to filter the results by database name.
  4. Kill off the server connections by selecting the right-click 'Kill Process' option.

display HTML page after loading complete

Hide the body initially, and then show it with jQuery after it has loaded.

body {
    display: none;

$(function () {
}); // end ready

Also, it would be best to have $('body').show(); as the last line in your last and main .js file.

HTTP 401 - what's an appropriate WWW-Authenticate header value?

When indicating HTTP Basic Authentication we return something like:

WWW-Authenticate: Basic realm="myRealm"

Whereas Basic is the scheme and the remainder is very much dependent on that scheme. In this case realm just provides the browser a literal that can be displayed to the user when prompting for the user id and password.

You're obviously not using Basic however since there is no point having session expiry when Basic Auth is used. I assume you're using some form of Forms based authentication.

From recollection, Windows Challenge Response uses a different scheme and different arguments.

The trick is that it's up to the browser to determine what schemes it supports and how it responds to them.

My gut feel if you are using forms based authentication is to stay with the 200 + relogin page but add a custom header that the browser will ignore but your AJAX can identify.

For a really good User + AJAX experience, get the script to hang on to the AJAX request that found the session expired, fire off a relogin request via a popup, and on success, resubmit the original AJAX request and carry on as normal.

Avoid the cheat that just gets the script to hit the site every 5 mins to keep the session alive cause that just defeats the point of session expiry.

The other alternative is burn the AJAX request but that's a poor user experience.

Convert INT to FLOAT in SQL

In oracle db there is a trick for casting int to float (I suppose, it should also work in mysql):

select myintfield + 0.0 as myfloatfield from mytable

While @Heximal's answer works, I don't personally recommend it.

This is because it uses implicit casting. Although you didn't type CAST, either the SUM() or the 0.0 need to be cast to be the same data-types, before the + can happen. In this case the order of precedence is in your favour, and you get a float on both sides, and a float as a result of the +. But SUM(aFloatField) + 0 does not yield an INT, because the 0 is being implicitly cast to a FLOAT.

I find that in most programming cases, it is much preferable to be explicit. Don't leave things to chance, confusion, or interpretation.

If you want to be explicit, I would use the following.

CAST(SUM( AS FLOAT) * cp.price
-- using MySQL CAST FLOAT  requires 8.0

I won't discuss whether NUMERIC or FLOAT *(fixed point, instead of floating point)* is more appropriate, when it comes to rounding errors, etc. I'll just let you google that if you need to, but FLOAT is so massively misused that there is a lot to read about the subject already out there.

You can try the following to see what happens...

CAST(SUM( AS NUMERIC(10,4)) * CAST(cp.price AS NUMERIC(10,4))

How can I quickly sum all numbers in a file?

Another for fun

sum=0;for i in $(cat file);do sum=$((sum+$i));done;echo $sum

or another bash only

s=0;while read l; do s=$((s+$l));done<file;echo $s

But awk solution is probably best as it's most compact.

What is the MySQL VARCHAR max size?


A BLOB type in MySQL can store up to 65,534 bytes, if you try to store more than this much data MySQL will truncate the data. MEDIUMBLOB can store up to 16,777,213 bytes, and LONGBLOB can store up to 4,294,967,292 bytes.

SQL Left Join first match only

Try this

 FROM people P 
              FROM people)

How do I make a simple crawler in PHP?

I created a small class to grab data from the provided url, then extract html elements of your choice. The class makes use of CURL and DOMDocument.

php class:

class crawler {

   public static $timeout = 2;
   public static $agent   = 'Mozilla/5.0 (compatible; Googlebot/2.1; +';

   public static function http_request($url) {
      $ch = curl_init();
      curl_setopt($ch, CURLOPT_URL,            $url);
      curl_setopt($ch, CURLOPT_USERAGENT,      self::$agent);
      curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, self::$timeout);
      curl_setopt($ch, CURLOPT_TIMEOUT,        self::$timeout);
      curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
      $response = curl_exec($ch);
      return $response;

   public static function strip_whitespace($data) {
      $data = preg_replace('/\s+/', ' ', $data);
      return trim($data);

   public static function extract_elements($tag, $data) {
      $response = array();
      $dom      = new DOMDocument;
      foreach ( $dom->getElementsByTagName($tag) as $index => $element ) {
         $response[$index]['text'] = self::strip_whitespace($element->nodeValue);
         foreach ( $element->attributes as $attribute ) {
            $response[$index]['attributes'][strtolower($attribute->nodeName)] = self::strip_whitespace($attribute->nodeValue);
      return $response;


example usage:

$data  = crawler::http_request('');
$links = crawler::extract_elements('a', $data);
if ( count($links) > 0 ) {
   file_put_contents('links.json', json_encode($links, JSON_PRETTY_PRINT));

example response:

        "text": "Stack Overflow",
        "attributes": {
            "href": "https:\/\/",
            "class": "-logo js-gps-track",
            "data-gps-track": "{is_current:false, location:2, destination:8})"
        "text": "Questions",
        "attributes": {
            "id": "nav-questions",
            "href": "\/questions",
            "class": "-link js-gps-track",
            "data-gps-track": "{is_current:true, location:2, destination:1})"
        "text": "Developer Jobs",
        "attributes": {
            "id": "nav-jobs",
            "href": "\/jobs?med=site-ui&ref=jobs-tab",
            "class": "-link js-gps-track",
            "data-gps-track": "{is_current:false, location:2, destination:6})"

Is "delete this" allowed in C++?

Well, in Component Object Model (COM) delete this construction can be a part of Release method that is called whenever you want to release aquisited object:

void IMyInterface::Release()
    if(instanceCount == 0)
        delete this;

SQL Server dynamic PIVOT query?

Dynamic SQL PIVOT:

create table temp
    date datetime,
    category varchar(3),
    amount money

insert into temp values ('1/1/2012', 'ABC', 1000.00)
insert into temp values ('2/1/2012', 'DEF', 500.00)
insert into temp values ('2/1/2012', 'GHI', 800.00)
insert into temp values ('2/10/2012', 'DEF', 700.00)
insert into temp values ('3/1/2012', 'ABC', 1100.00)

    @query  AS NVARCHAR(MAX);

SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.category) 
            FROM temp c
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 

set @query = 'SELECT date, ' + @cols + ' from 
                select date
                    , amount
                    , category
                from temp
           ) x
                for category in (' + @cols + ')
            ) p '


drop table temp


Date                        ABC         DEF    GHI
2012-01-01 00:00:00.000     1000.00     NULL    NULL
2012-02-01 00:00:00.000     NULL        500.00  800.00
2012-02-10 00:00:00.000     NULL        700.00  NULL
2012-03-01 00:00:00.000     1100.00     NULL    NULL

Redirecting to a page after submitting form in HTML

You need to use the jQuery AJAX or XMLHttpRequest() for post the data to the server. After data posting you can redirect your page to another page by window.location.href.


 var xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      window.location.href = '';
  };"POST", "demo_post.asp", true);

Java SSLException: hostname in certificate didn't match

Updating the java version from 1.8.0_40 to 1.8.0_181 resolved the issue.

Get records with max value for each group of grouped SQL results

You can join against a subquery that pulls the MAX(Group) and Age. This method is portable across most RDBMS.

FROM yourTable t1
    SELECT `Group`, MAX(Age) AS max_age
    FROM yourTable
    GROUP BY `Group`
) t2
    ON t1.`Group` = t2.`Group` AND t1.Age = t2.max_age;

Change User Agent in UIWebView

I faced the same question. I want to add some info to the user-agent, also need to keep the original user-agent of webview. I solved it by using the code below:

    //get the original user-agent of webview
UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectZero];
NSString *oldAgent = [webView stringByEvaluatingJavaScriptFromString:@"navigator.userAgent"];
NSLog(@"old agent :%@", oldAgent);

//add my info to the new agent
NSString *newAgent = [oldAgent stringByAppendingString:@" Jiecao/2.4.7 ch_appstore"];
NSLog(@"new agent :%@", newAgent);

//regist the new agent
NSDictionary *dictionnary = [[NSDictionary alloc] initWithObjectsAndKeys:newAgent, @"UserAgent", nil];
[[NSUserDefaults standardUserDefaults] registerDefaults:dictionnary];

Use it before you instancing webview.

How to set a timer in android

As I have seen it, java.util.Timer is the most used for implementing a timer.

For a repeating task:

new Timer().scheduleAtFixedRate(task, after, interval);

For a single run of a task:

new Timer().schedule(task, after);

task being the method to be executed
after the time to initial execution
(interval the time for repeating the execution)

Bootstrap with jQuery Validation Plugin

this is the solution you need, you can use the errorPlacement method to override where to put the error message

    rules: {
        firstname: {
            minlength: 3,
            maxlength: 15,
            required: true
        lastname: {
            minlength: 3,
            maxlength: 15,
            required: true
    errorPlacement: function(error, element) {
        error.insertAfter('.form-group'); //So i putted it after the .form-group so it will not include to your append/prepend group.
    highlight: function(element) {
    unhighlight: function(element) {

it's works for me like magic. Cheers

How do you use global variables or constant values in Ruby?

Variable scope in Ruby is controlled by sigils to some degree. Variables starting with $ are global, variables with @ are instance variables, @@ means class variables, and names starting with a capital letter are constants. All other variables are locals. When you open a class or method, that's a new scope, and locals available in the previous scope aren't available.

I generally prefer to avoid creating global variables. There are two techniques that generally achieve the same purpose that I consider cleaner:

  1. Create a constant in a module. So in this case, you would put all the classes that need the offset in the module Foo and create a constant Offset, so then all the classes could access Foo::Offset.

  2. Define a method to access the value. You can define the method globally, but again, I think it's better to encapsulate it in a module or class. This way the data is available where you need it and you can even alter it if you need to, but the structure of your program and the ownership of the data will be clearer. This is more in line with OO design principles.

How to get the selected value from RadioButtonList?

string radioListValue = RadioButtonList.Text;

Enabling WiFi on Android Emulator

Apparently it does not and I didn't quite expect it would. HOWEVER Ivan brings up a good possibility that has escaped Android people.

What is the purpose of an emulator? to EMULATE, right? I don't see why for testing purposes -provided the tester understands the limitations- the emulator might not add a Wifi emulator.

It could for example emulate WiFi access by using the underlying internet connection of the host. Obviously testing WPA/WEP differencess would not make sense but at least it could toggle access via WiFi.

Or some sort of emulator plugin where there would be a base WiFi emulator that would emulate WiFi access via the underlying connection but then via configuration it could emulate WPA/WEP by providing a list of fake WiFi networks and their corresponding fake passwords that would be matched against a configurable list of credentials.

After all the idea is to do initial testing on the emulator and then move on to the actual device.

What is the difference between `let` and `var` in swift?

let keyword defines a constant

let myNum = 7

so myNum can't be changed afterwards;

But var defines an ordinary variable.

The value of a constant doesn’t need to be known at compile time, but you must assign it a value exactly once.

You can use almost any character you like for constant and variable names, including Unicode characters;


var x = 7 // here x is instantiated with 7 
x = 99 // now x is 99 it means it has been changed.

But if we take let then...

let x = 7 // here also x is instantiated with 7 
x = 99 // this will a compile time error

PHP Constants Containing Arrays?

You can define like this


$domains = json_decode(GENERIC_DOMAIN);

How to detect scroll position of page using jQuery

$('.div').scroll(function (event) {
 var scroll = $(this).scrollTop();
 if(scroll == 0){

This code for chat_boxes for loading previous messages

What does the "+=" operator do in Java?

^ = (bitwise XOR)


Binary XOR Operator copies the bit if it is set in one operand but not both.


(A ^ B) will give 49 which is 0011 0001

hidden field in php

You absolutely can, I use this approach a lot w/ both JavaScript and PHP.

Field definition:

<input type="hidden" name="foo" value="<?php echo $var;?>" />

Access w/ PHP:

$_GET['foo'] or $_POST['foo']

Also: Don't forget to sanitize your inputs if they are going into a database. Feel free to use my routine:


How to round the corners of a button

You may want to check out my library called DCKit. It's written on the latest version of Swift.

You'd be able to make a rounded corner button/text field from the Interface builder directly:

DCKit: rounded button

It also has many other cool features, such as text fields with validation, controls with borders, dashed borders, circle and hairline views etc.

SQL to search objects, including stored procedures, in Oracle

In Oracle 11g, if you want to search any text in whole database or procedure below mentioned query can be used:

select * from user_source WHERE UPPER(text) LIKE '%YOUR SAGE%'

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 can one develop iPhone apps in Java?

Perhaps you should consider Android applications instead of iPhone applications if you really want to develop in Java for smartphones. Android natively uses Java for it's applications; so perhaps this might be a better option?

As for iPhone, I would recommend you to look into Obj-C or C/C++ depending on the type of applications you want to make. Should be fun to dabble into a new language! :)

Check the current number of connections to MongoDb

Connect to MongoDB using mongo-shell and run following command.



mongo> db.serverStatus().connections
{ "current" : 3, "available" : 816, "totalCreated" : NumberLong(1270) }

Get the previous month's first and last day dates in c#

DateTime LastMonthLastDate = DateTime.Today.AddDays(0 - DateTime.Today.Day);
DateTime LastMonthFirstDate = LastMonthLastDate.AddDays(1 - LastMonthLastDate.Day);

How to call stopservice() method of Service class from the calling activity class

That looks like it should stop the service when you uncheck the checkbox. Are there any exceptions in the log? stopService returns a boolean indicating whether or not it was able to stop the service.

If you are starting your service by Intents, then you may want to extend IntentService instead of Service. That class will stop the service on its own when it has no more work to do.


class AutoService extends IntentService {
     private static final String TAG = "AutoService";
     private Timer timer;    
     private TimerTask task;

     public onCreate() {
          timer = new Timer();
          timer = new TimerTask() {
            public void run() 

     protected void onHandleIntent(Intent i) {
        Log.d(TAG, "onHandleIntent");     

        int delay = 5000; // delay for 5 sec.
        int period = 5000; // repeat every sec.

        timer.scheduleAtFixedRate(timerTask, delay, period);

     public boolean stopService(Intent name) {
        // TODO Auto-generated method stub
        return super.stopService(name);


Can I have H2 autocreate a schema in an in-memory database?

Yes, H2 supports executing SQL statements when connecting. You could run a script, or just a statement or two:

String url = "jdbc:h2:mem:test;" + 
String url = "jdbc:h2:mem:test;" + 
                  "SET SCHEMA TEST";
String url = "jdbc:h2:mem;" + 
             "INIT=RUNSCRIPT FROM '~/create.sql'\\;" + 
                  "RUNSCRIPT FROM '~/populate.sql'";

Please note the double backslash (\\) is only required within Java. The backslash(es) before ; within the INIT is required.

Find the directory part (minus the filename) of a full path in access 97


vDirFile = Replace(vFilename, Dir(vFileName, vbDirectory), "")

' Result=C:\Informes\Indicadores_Contraloria\Programa\Versiones anteriores\

How to embed small icon in UILabel

Your reference image looks like a button. Try (can also be done in Interface Builder):

enter image description here

UIButton* button = [UIButton buttonWithType:UIButtonTypeCustom];
[button setFrame:CGRectMake(50, 50, 100, 44)];
[button setImage:[UIImage imageNamed:@"img"] forState:UIControlStateNormal];
[button setImageEdgeInsets:UIEdgeInsetsMake(0, -30, 0, 0)];
[button setTitle:@"Abc" forState:UIControlStateNormal];
[button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[button setBackgroundColor:[UIColor yellowColor]];
[view addSubview:button];

How do I pass an object to HttpClient.PostAsync and serialize as a JSON body?

There's now a simpler way with .NET Standard or .NET Core:

var client = new HttpClient();
var response = await client.PostAsync(uri, myRequestObject, new JsonMediaTypeFormatter());

NOTE: In order to use the JsonMediaTypeFormatter class, you will need to install the Microsoft.AspNet.WebApi.Client NuGet package, which can be installed directly, or via another such as Microsoft.AspNetCore.App.

Using this signature of HttpClient.PostAsync, you can pass in any object and the JsonMediaTypeFormatter will automatically take care of serialization etc.

With the response, you can use HttpContent.ReadAsAsync<T> to deserialize the response content to the type that you are expecting:

var responseObject = await response.Content.ReadAsAsync<MyResponseType>();

Oracle Error ORA-06512

I also had the same error. In my case reason was I have created a update trigger on a table and under that trigger I am again updating the same table. And when I have removed the update statement from the trigger my problem has been resolved.

How do I upgrade the Python installation in Windows 10?

Python 2.x and Python 3.x are different. If you would like to download a newer version of Python 2, you could just download and install the newer version.

If you want to install Python 3, you could install Python 3 separately then change the path for Python 2.x to Python 3.x in Control Panel > All Control Panel Items > System > Advanced System Settings > Environment Variables.

File changed listener in Java

Since JDK 1.7, the canonical way to have an application be notified of changes to a file is using the WatchService API. The WatchService is event-driven. The official tutorial provides an example:

 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.

import java.nio.file.*;
import static java.nio.file.StandardWatchEventKinds.*;
import static java.nio.file.LinkOption.*;
import java.nio.file.attribute.*;
import java.util.*;

 * Example to watch a directory (or tree) for changes to files.

public class WatchDir {

    private final WatchService watcher;
    private final Map<WatchKey,Path> keys;
    private final boolean recursive;
    private boolean trace = false;

    static <T> WatchEvent<T> cast(WatchEvent<?> event) {
        return (WatchEvent<T>)event;

     * Register the given directory with the WatchService
    private void register(Path dir) throws IOException {
        WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
        if (trace) {
            Path prev = keys.get(key);
            if (prev == null) {
                System.out.format("register: %s\n", dir);
            } else {
                if (!dir.equals(prev)) {
                    System.out.format("update: %s -> %s\n", prev, dir);
        keys.put(key, dir);

     * Register the given directory, and all its sub-directories, with the
     * WatchService.
    private void registerAll(final Path start) throws IOException {
        // register directory and sub-directories
        Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
                throws IOException
                return FileVisitResult.CONTINUE;

     * Creates a WatchService and registers the given directory
    WatchDir(Path dir, boolean recursive) throws IOException {
        this.watcher = FileSystems.getDefault().newWatchService();
        this.keys = new HashMap<WatchKey,Path>();
        this.recursive = recursive;

        if (recursive) {
            System.out.format("Scanning %s ...\n", dir);
        } else {

        // enable trace after initial registration
        this.trace = true;

     * Process all events for keys queued to the watcher
    void processEvents() {
        for (;;) {

            // wait for key to be signalled
            WatchKey key;
            try {
                key = watcher.take();
            } catch (InterruptedException x) {

            Path dir = keys.get(key);
            if (dir == null) {
                System.err.println("WatchKey not recognized!!");

            for (WatchEvent<?> event: key.pollEvents()) {
                WatchEvent.Kind kind = event.kind();

                // TBD - provide example of how OVERFLOW event is handled
                if (kind == OVERFLOW) {

                // Context for directory entry event is the file name of entry
                WatchEvent<Path> ev = cast(event);
                Path name = ev.context();
                Path child = dir.resolve(name);

                // print out event
                System.out.format("%s: %s\n", event.kind().name(), child);

                // if directory is created, and watching recursively, then
                // register it and its sub-directories
                if (recursive && (kind == ENTRY_CREATE)) {
                    try {
                        if (Files.isDirectory(child, NOFOLLOW_LINKS)) {
                    } catch (IOException x) {
                        // ignore to keep sample readbale

            // reset key and remove from set if directory no longer accessible
            boolean valid = key.reset();
            if (!valid) {

                // all directories are inaccessible
                if (keys.isEmpty()) {

    static void usage() {
        System.err.println("usage: java WatchDir [-r] dir");

    public static void main(String[] args) throws IOException {
        // parse arguments
        if (args.length == 0 || args.length > 2)
        boolean recursive = false;
        int dirArg = 0;
        if (args[0].equals("-r")) {
            if (args.length < 2)
            recursive = true;

        // register directory and process its events
        Path dir = Paths.get(args[dirArg]);
        new WatchDir(dir, recursive).processEvents();

For individual files, various solutions exist, such as:

Note that Apache VFS uses a polling algorithm, although it may offer greater functionality. Also note that the API does not offer a way to determine whether a file has been closed.

Eclipse Workspaces: What for and why?

The whole point of a workspace is to group a set of related projects together that usually make up an application. The workspace framework comes down to the eclipse.core.resources plugin and it naturally by design makes sense.

Projects have natures, builders are attached to specific projects and as you change resources in one project you can see in real time compile or other issues in projects that are in the same workspace. So the strategy I suggest is have different workspaces for different projects you work on but without a workspace in eclipse there would be no concept of a collection of projects and configurations and after all it's an IDE tool.

If that does not make sense ask how Net Beans or Visual Studio addresses this? It's the same theme. Maven is a good example, checking out a group of related maven projects into a workspace lets you develop and see errors in real time. If not a workspace what else would you suggest? An RCP application can be a different beast depending on what its used for but in the true IDE sense I don't know what would be a better solution than a workspace or context of projects. Just my thoughts. - Duncan

Find something in column A then show the value of B for that row in Excel 2010

Guys Its very interesting to know that many of us face the problem of replication of lookup value while using the Vlookup/Index with Match or Hlookup.... If we have duplicate value in a cell we all know, Vlookup will pick up against the first item would be matching in loopkup array....So here is solution for you all...


in Column A we have field called company....

Column A                             Column B            Column C

Company_Name                         Value        
Monster                              25000                              
Naukri                               30000  
WNS                                  80000  
American Express                     40000  
Bank of America                      50000  
Alcatel Lucent                       35000  
Google                               75000  
Microsoft                            60000  
Monster                              35000  
Bank of America                      15000 

Now if you lookup the above dataset, you would see the duplicity is in Company Name at Row No# 10 & 11. So if you put the vlookup, the data will be picking up which comes first..But if you use the below formula, you can make your lookup value Unique and can pick any data easily without having any dispute or facing any problem

Put the formula in C2.........A2&"_"&COUNTIF(A2:$A$2,A2)..........Result will be Monster_1 for first line item and for row no 10 & 11.....Monster_2, Bank of America_2 respectively....Here you go now you have the unique value so now you can pick any data easily now..

Cheers!!! Anil Dhawan

Map.Entry: How to use it?

A Map is a collection of Key + Value pairs, which is visualized like this:


The Map interface allows a few options for accessing this collection: The Key set [fooKey, barKey,quxKey], the Value set [fooValue, barValue, quxValue] and finally entry Set [fooKey=fooValue],barKey=barValue],[quxKey=quxValue].

Entry set is simply a convenience to iterate over the key value pairs in the map, the Map.Entry is the representation of each key value pair. An equivalent way to do your last loop would be:

for (String buttonKey: listbouton.keySet()) {
    this.add(listbouton.get(buttonKey)) ;


for (JButton button: listbouton.values()) {
    this.add(button) ;

PDF Blob - Pop up window not showing content

I use AngularJS v1.3.4


<button ng-click="downloadPdf()" class="btn btn-primary">download PDF</button>

JS controller:

'use strict';
    .controller('MathController', function ($scope, MathServicePDF) {
        $scope.downloadPdf = function () {
            var fileName = "test.pdf";
            var a = document.createElement("a");
            MathServicePDF.downloadPdf().then(function (result) {
                var file = new Blob([], {type: 'application/pdf'});
                var fileURL = window.URL.createObjectURL(file);
                a.href = fileURL;
       = fileName;

JS services:

    .factory('MathServicePDF', function ($http) {
        return {
            downloadPdf: function () {
            return $http.get('api/downloadPDF', { responseType: 'arraybuffer' }).then(function (response) {
                return response;

Java REST Web Services - Spring MVC:

@RequestMapping(value = "/downloadPDF", method = RequestMethod.GET, produces = "application/pdf")
    public ResponseEntity<byte[]> getPDF() {
        FileInputStream fileStream;
        try {
            fileStream = new FileInputStream(new File("C:\\xxxxx\\xxxxxx\\test.pdf"));
            byte[] contents = IOUtils.toByteArray(fileStream);
            HttpHeaders headers = new HttpHeaders();
            String filename = "test.pdf";
            headers.setContentDispositionFormData(filename, filename);
            ResponseEntity<byte[]> response = new ResponseEntity<byte[]>(contents, headers, HttpStatus.OK);
            return response;
        } catch (FileNotFoundException e) {
        } catch (IOException e) {
        return null;

What is the most useful script you've written for everyday life?

A Greasemonkey script which removes obviously stupid[*] comments from gaming site

[*] As identified by common spelling mistakes, all-caps writing, excessive use of "LOL" and similar heuristics.

Tell Ruby Program to Wait some amount of time

Use sleep like so:

sleep 2

That'll sleep for 2 seconds.

Be careful to give an argument. If you just run sleep, the process will sleep forever. (This is useful when you want a thread to sleep until it's woken.)

How can I get the current network interface throughput statistics on Linux/UNIX?

nload is a great tool for monitoring bandwidth in real time and easily installed in Ubuntu or Debian with sudo apt-get install nload.

Device eth0 [] (1/2):

                               .         ...|    
                               #         ####|   
                           .. |#|  ...   #####.         ..          Curr: 2.07 MBit/s
                          ###.###  #### #######|.     . ##      |   Avg: 1.41 MBit/s
                         ########|#########################.   ###  Min: 1.12 kBit/s
             ........    ###################################  .###  Max: 4.49 MBit/s
           .##########. |###################################|#####  Ttl: 1.94 GByte
            ##########  ###########    ###########################
            ##########  ###########    ###########################
            ##########. ###########   .###########################
            ########### ###########  #############################
            ########### ###########..#############################
           ############ ##########################################
           ############ ##########################################
           ############ ##########################################  Curr: 63.88 MBit/s
           ############ ##########################################  Avg: 32.04 MBit/s
           ############ ##########################################  Min: 0.00 Bit/s
           ############ ##########################################  Max: 93.23 MBit/s
         ############## ##########################################  Ttl: 2.49 GByte

Another excellent tool is iftop, also easily apt-get'able:

             191Mb      381Mb                 572Mb       763Mb             954Mb     
box4.local            => box-2.local                      91.0Mb  27.0Mb  15.1Mb
                      <=                                  1.59Mb   761kb   452kb
box4.local            => box.local                         560b   26.8kb  27.7kb
                      <=                                   880b   31.3kb  32.1kb
box4.local            =>                         0b   11.4kb  8.01kb
                      <=                                  1.17kb  2.39kb  1.75kb
box4.local            =>              0b     58b    168b
                      <=                                     0b     83b    288b
box4.local            =>                   0b     42b     21b
                      <=                                     0b     42b     21b
box4.local            =>                         0b      0b    179b
                      <=                                     0b      0b      0b           => box-2.local                         0b      0b      0b
                      <=                                     0b      0b     36b           => box.local                           0b      0b      0b
                      <=                                     0b      0b     35b

TX:           cum:   37.9MB   peak:   91.0Mb     rates:   91.0Mb  27.1Mb  15.2Mb
RX:                  1.19MB           1.89Mb              1.59Mb   795kb   486kb
TOTAL:               39.1MB           92.6Mb              92.6Mb  27.9Mb  15.6Mb

Don't forget about the classic and powerful sar and netstat utilities on older *nix!

Reading binary file and looping over each byte

If the file is not too big that holding it in memory is a problem:

with open("filename", "rb") as f:
    bytes_read =
for b in bytes_read:

where process_byte represents some operation you want to perform on the passed-in byte.

If you want to process a chunk at a time:

with open("filename", "rb") as f:
    bytes_read =
    while bytes_read:
        for b in bytes_read:
        bytes_read =

The with statement is available in Python 2.5 and greater.

SQL left join vs multiple tables on FROM line?

I hear a lot of people complain the first one is too difficult to understand and that it is unclear. I don't see a problem with it, but after having that discussion, I use the second one even on INNER JOINS for clarity.

How do I ALTER a PostgreSQL table and make a column unique?

Or, have the DB automatically assign a constraint name using:

ALTER TABLE foo ADD UNIQUE (thecolumn);

TypeError: 'NoneType' object is not iterable in Python

Explanation of error: 'NoneType' object is not iterable

In python2, NoneType is the type of None. In Python3 NoneType is the class of None, for example:

>>> print(type(None))     #Python2
<type 'NoneType'>         #In Python2 the type of None is the 'NoneType' type.

>>> print(type(None))     #Python3
<class 'NoneType'>        #In Python3, the type of None is the 'NoneType' class.

Iterating over a variable that has value None fails:

for a in None:
    print("k")     #TypeError: 'NoneType' object is not iterable

Python methods return NoneType if they don't return a value:

def foo():
a, b = foo()      #TypeError: 'NoneType' object is not iterable

You need to check your looping constructs for NoneType like this:

a = None 
print(a is None)              #prints True
print(a is not None)          #prints False
print(a == None)              #prints True
print(a != None)              #prints False
print(isinstance(a, object))  #prints True
print(isinstance(a, str))     #prints False

Guido says only use is to check for None because is is more robust to identity checking. Don't use equality operations because those can spit bubble-up implementationitis of their own. Python's Coding Style Guidelines - PEP-008

NoneTypes are Sneaky, and can sneak in from lambdas:

import sys
b = lambda x : sys.stdout.write("k") 
for a in b(10): 
    pass            #TypeError: 'NoneType' object is not iterable 

NoneType is not a valid keyword:

a = NoneType     #NameError: name 'NoneType' is not defined

Concatenation of None and a string:

bar = "something"
foo = None
print foo + bar    #TypeError: cannot concatenate 'str' and 'NoneType' objects

What's going on here?

Python's interpreter converted your code to pyc bytecode. The Python virtual machine processed the bytecode, it encountered a looping construct which said iterate over a variable containing None. The operation was performed by invoking the __iter__ method on the None.

None has no __iter__ method defined, so Python's virtual machine tells you what it sees: that NoneType has no __iter__ method.

This is why Python's duck-typing ideology is considered bad. The programmer does something completely reasonable with a variable and at runtime it gets contaminated by None, the python virtual machine attempts to soldier on, and pukes up a bunch of unrelated nonsense all over the carpet.

Java or C++ doesn't have these problems because such a program wouldn't be allowed to compile since you haven't defined what to do when None occurs. Python gives the programmer lots of rope to hang himself by allowing you to do lots of things that should cannot be expected to work under exceptional circumstances. Python is a yes-man, saying yes-sir when it out to be stopping you from harming yourself, like Java and C++ does.

Using success/error/finally/catch with Promises in AngularJS

What type of granularity are you looking for? You can typically get by with:

  //success function
  function(results) {
    //do something w/
  //error function
  function(err) {
    //handle error

I've found that "finally" and "catch" are better off when chaining multiple promises.

Error With Port 8080 already in use

It has been long time, but I faced the same Issue, and solved it as follow: 1. tried shutting down the application server using the shutdown.bat/.bash which might be in your application Server / bin/shutdown..

  1. My Issue, was that more than 1 instance of java was running, I was changing ports, and not looking back, so it kept running other java processes, with that specific port. for windows users, : ALT+Shift+Esc, and end java processes that you are not using and now you should be able to re-use your port 8080

How to free memory in Java?

I have done experimentation on this.

It's true that System.gc(); only suggests to run the Garbage Collector.

But calling System.gc(); after setting all references to null, will improve performance and memory occupation.

C# SQL Server - Passing a list to a stored procedure

No, arrays/lists can't be passed to SQL Server directly.

The following options are available:

  1. Passing a comma-delimited list and then having a function in SQL split the list. The comma delimited list will most likely be passed as an Nvarchar()
  2. Pass xml and have a function in SQL Server parse the XML for each value in the list
  3. Use the new defined User Defined table type (SQL 2008)
  4. Dynamically build the SQL and pass in the raw list as "1,2,3,4" and build the SQL statement. This is prone to SQL injection attacks, but it will work.

Shell script - remove first and last quote (") from a variable

The shortest way around - try:

echo $opt | sed "s/\"//g"

It actually removes all "s (double quotes) from opt (are there really going to be any more double quotes other than in the beginning and the end though? So it's actually the same thing, and much more brief ;-))

List of ANSI color escape sequences

How about:

ECMA-48 - Control Functions for Coded Character Sets, 5th edition (June 1991) - A standard defining the color control codes, that is apparently supported also by xterm.

SGR 38 and 48 were originally reserved by ECMA-48, but were fleshed out a few years later in a joint ITU, IEC, and ISO standard, which comes in several parts and which (amongst a whole lot of other things) documents the SGR 38/48 control sequences for direct colour and indexed colour:

There's a column for xterm in this table on the Wikipedia page for ANSI escape codes

How to make bootstrap 3 fluid layout without horizontal scrollbar

This was introduced in v3.1.0:

Commit #62736046 added ".container-fluid variation for full-width containers and layouts".

Android Studio Gradle Already disposed Module

I was having this issue because gradle and Android Studio were using a different path for the jvm. In the Event Log there was an option for AS and gradle to use the same path. Selecting this and then doing an invalidate cache & restart resolved the issue for me.

How can I kill whatever process is using port 8080 so that I can vagrant up?

I needed to run this command

sudo lsof -i :80 # checks port 8080

Then i got

acwebseca 312 root   36u  IPv4 0x34ae935da20560c1      0t0  TCP> (ESTABLISHED)

show which service is using the PID

ps -ef 312

Then I got this

  UID   PID  PPID   C STIME   TTY           TIME CMD
    0   312    58   0  9:32PM ??         0:02.70 /opt/cisco/anyconnect/bin/acwebsecagent -console

To uninstall cisco web security agent run

sudo /opt/cisco/anyconnect/bin/

credits to:

Executing a shell script from a PHP script

It's a simple problem. When you are running from terminal, you are running the php file from terminal as a privileged user. When you go to the php from your web browser, the php script is being run as the web server user which does not have permissions to execute files in your home directory. In Ubuntu, the www-data user is the apache web server user. If you're on ubuntu you would have to do the following: chown yourusername:www-data /home/testuser/testscript chmod g+x /home/testuser/testscript

what the above does is transfers user ownership of the file to you, and gives the webserver group ownership of it. the next command gives the group executable permission to the file. Now the next time you go ahead and do it from the browser, it should work.

How can I print each command before executing?

set -x is fine.

Another way to print each executed command is to use trap with DEBUG. Put this line at the beginning of your script :

trap 'echo "# $BASH_COMMAND"' DEBUG

You can find a lot of other trap usages here.

Creating a comma separated list from IList<string> or IEnumerable<string>

Specific need when we should surround by ', by ex:

        string[] arr = { "jj", "laa", "123" };
        List<string> myList = arr.ToList();

        // 'jj', 'laa', '123'
        Console.WriteLine(string.Join(", ",
            myList.ConvertAll(m =>
                string.Format("'{0}'", m)).ToArray()));

Wampserver icon not going green fully, mysql services not starting up?

I had the same issue, to resolve it I added the following line to my.ini

innodb_force_recovery = 1

How to find out what group a given user has?

On Linux/OS X/Unix to display the groups to which you (or the optionally specified user) belong, use:

id -Gn [user]

which is equivalent to groups [user] utility which has been obsoleted on Unix.

On OS X/Unix, the command id -p [user] is suggested for normal interactive.

Explanation on the parameters:

-G, --groups - print all group IDs

-n, --name - print a name instead of a number, for -ugG

-p - Make the output human-readable.

trigger click event from angularjs directive

This is how I was able to trigger a button click when the page loads.

<li ng-repeat="a in array">
  <a class="button" id="btn" ng-click="function(a)" index="$index" on-load-clicker>

A simple directive that takes the index from the ng-repeat and uses a condition to call the first button in the index and click it when the page loads.

        .directive('onLoadClicker', function ($timeout) {
            return {
                restrict: 'A',
                scope: {
                    index: '=index'
                link: function($scope, iElm) {
                    if ($scope.index == 0) {
                        $timeout(function() {


                        }, 0);

This was the only way I was able to even trigger an auto click programmatically in the first place. angular.element(document.querySelector('#btn')).click(); Did not work from the controller so making this simple directive seems most effective if you are trying to run a click on page load and you can specify which button to click by passing in the index. I got help through this stack-overflow answer from another post reference: onLoadClicker Directive.

Index was out of range. Must be non-negative and less than the size of the collection parameter name:index

The error says "The index is out of range". That means you were trying to index an object with a value that was not valid. If you have two books, and I ask you to give me your third book, you will look at me funny. This is the computer looking at you funny. You said - "create a collection". So it did. But initially the collection is empty: not only is there nothing in it - it has no space to hold anything. "It has no hands".

Then you said "the first element of the collection is now 'ItemID'". And the computer says "I never was asked to create space for a 'first item'." I have no hands to hold this item you are giving me.

In terms of your code, you created a view, but never specified the size. You need a

dataGridView1.ColumnCount = 5;

Before trying to access any columns. Modify

DataGridView dataGridView1 = new DataGridView();

dataGridView1.Columns[0].Name = "ItemID";


DataGridView dataGridView1 = new DataGridView();
dataGridView1.ColumnCount = 5;
dataGridView1.Columns[0].Name = "ItemID";


Gradle failed to resolve library in Android Studio

Solved by using "" instead of "".

repositories {
    jcenter( { url "" } )

Get the element with the highest occurrence in an array

function mode(array){
    var set = Array.from(new Set(array));
    var counts =>array.filter(b=>b==a).length);
    var indices =,b)=>Math.max(...counts)===a?b:0).filter(b=>b!==0);
    var mode =>set[a]);
    return mode;

How to correctly implement custom iterators and const_iterators?

There are plenty of good answers but I created a template header I use that is quite concise and easy to use.

To add an iterator to your class it is only necessary to write a small class to represent the state of the iterator with 7 small functions, of which 2 are optional:

#include <iostream>
#include <vector>
#include "iterator_tpl.h"

struct myClass {
  std::vector<float> vec;

  // Add some sane typedefs for STL compliance:

  struct it_state {
    int pos;
    inline void begin(const myClass* ref) { pos = 0; }
    inline void next(const myClass* ref) { ++pos; }
    inline void end(const myClass* ref) { pos = ref->vec.size(); }
    inline float& get(myClass* ref) { return ref->vec[pos]; }
    inline bool cmp(const it_state& s) const { return pos != s.pos; }

    // Optional to allow operator--() and reverse iterators:
    inline void prev(const myClass* ref) { --pos; }
    // Optional to allow `const_iterator`:
    inline const float& get(const myClass* ref) const { return ref->vec[pos]; }
  // Declare typedef ... iterator;, begin() and end() functions:
  SETUP_ITERATORS(myClass, float&, it_state);
  // Declare typedef ... reverse_iterator;, rbegin() and rend() functions:
  SETUP_REVERSE_ITERATORS(myClass, float&, it_state);

Then you can use it as you would expect from an STL iterator:

int main() {
  myClass c1;

  std::cout << "iterator:" << std::endl;
  for (float& val : c1) {
    std::cout << val << " "; // 1.0 2.0 3.0

  std::cout << "reverse iterator:" << std::endl;
  for (auto it = c1.rbegin(); it != c1.rend(); ++it) {
    std::cout << *it << " "; // 3.0 2.0 1.0

I hope it helps.

Difference between DTO, VO, POJO, JavaBeans?

Java Beans are not the same thing as EJBs.

The JavaBeans specification in Java 1.0 was Sun's attempt to allow Java objects to be manipulated in an IDE that looked like VB. There were rules laid down for objects that qualified as "Java Beans":

  1. Default constructor
  2. Getters and setters for private data members that followed the proper naming convention
  3. Serializable
  4. Maybe others that I'm forgetting.

EJBs came later. They combine distributed components and a transactional model, running in a container that manages threads, pooling, life cycle, and provides services. They are a far cry from Java Beans.

DTOs came about in the Java context because people found out that the EJB 1.0 spec was too "chatty" with the database. Rather than make a roundtrip for every data element, people would package them into Java Beans in bulk and ship them around.

POJOs were a reaction against EJBs.

Vertically align text next to an image?

Here are some simple techniques for vertical-align:

One-line vertical-align:middle

This one is easy: set the line-height of the text element to equal that of the container

  <img style="width:30px; height:30px;">
  <span style="line-height:30px;">Doesn't work.</span>

Multiple-lines vertical-align:bottom

Absolutely position an inner div relative to its container

<div style="position:relative;width:30px;height:60px;">
  <div style="position:absolute;bottom:0">This is positioned on the bottom</div>

Multiple-lines vertical-align:middle

<div style="display:table;width:30px;height:60px;">
  <div style="display:table-cell;height:30px;">This is positioned in the middle</div>

If you must support ancient versions of IE <= 7

In order to get this to work correctly across the board, you'll have to hack the CSS a bit. Luckily, there is an IE bug that works in our favor. Setting top:50% on the container and top:-50% on the inner div, you can achieve the same result. We can combine the two using another feature IE doesn't support: advanced CSS selectors.

<style type="text/css">
  #container {
    width: 30px;
    height: 60px;
    position: relative;
  #wrapper > #container {
    display: table;
    position: static;
  #container div {
    position: absolute;
    top: 50%;
  #container div div {
    position: relative;
    top: -50%;
  #container > div {
    display: table-cell;
    vertical-align: middle;
    position: static;

<div id="wrapper">
  <div id="container">
    <div><div><p>Works in everything!</p></div></div>

Variable container height vertical-align:middle

This solution requires a slightly more modern browser than the other solutions, as it makes use of the transform: translateY property. (

Applying the following 3 lines of CSS to an element will vertically centre it within its parent regardless of the height of the parent element:

position: relative;
top: 50%;
transform: translateY(-50%);

Getting "file not found" in Bridging Header when importing Objective-C frameworks into Swift project

This happened to me after adding/renaming current configurations and it makes sense.

Every configuration makes use of Configurations Set generated by cocoapods so these things needs to match.

So if you add/rename configurations, these will need to use the right configuration sets, and for that running pod install will do it.

Overlay a background-image with an rgba background-color

The solution by PeterVR has the disadvantage that the additional color displays on top of the entire HTML block - meaning that it also shows up on top of div content, not just on top of the background image. This is fine if your div is empty, but if it is not using a linear gradient might be a better solution:

<div class="the-div">Red text</div>

<style type="text/css">
    background-image: url("the-image.png");
    color: #f00;
    margin: 10px;
    width: 200px;
    height: 80px;
    background-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.1), rgba(0, 0, 0, 0.1)), url("the-image.png");
    background-image: -moz-linear-gradient(top, rgba(0, 0, 0, 0.1), rgba(0, 0, 0, 0.1)), url("the-image.png");
    background-image: -o-linear-gradient(top, rgba(0, 0, 0, 0.1), rgba(0, 0, 0, 0.1)), url("the-image.png");
    background-image: -ms-linear-gradient(top, rgba(0, 0, 0, 0.1), rgba(0, 0, 0, 0.1)), url("the-image.png");
    background-image: -webkit-gradient(linear, left top, left bottom, from(rgba(0, 0, 0, 0.1)), to(rgba(0, 0, 0, 0.1))), url("the-image.png");
    background-image: -webkit-linear-gradient(top, rgba(0, 0, 0, 0.1), rgba(0, 0, 0, 0.1)), url("the-image.png");

See fiddle. Too bad that gradient specifications are currently a mess. See compatibility table, the code above should work in any browser with a noteworthy market share - with the exception of MSIE 9.0 and older.

Edit (March 2017): The state of the web got far less messy by now. So the linear-gradient (supported by Firefox and Internet Explorer) and -webkit-linear-gradient (supported by Chrome, Opera and Safari) lines are sufficient, additional prefixed versions are no longer necessary.

How to size an Android view based on its parent's dimensions

If the other side is empty. I guess the simplest way would be to add an empty view (e.g. a linear layout) then set both views' widths to fill_parent and both their weights to 1.

This works in a LinearLayout...

Is it possible to use Visual Studio on macOS?

Yes, you can! There's a Visual Studio for macs and there's Visual Studio Code if you only need a text editor like Sublime Text.

Warning: A non-numeric value encountered

$sn = 0;//increment the serial number, then add the sn to job
for($x = 0; $x<20; $x++)
$added_date = "10/10/10";
$job_title = "new job";
$salary = $sn*1000;
$cd = "27/10/2017";//the closing date
$ins = "some institution";//the institution for the vacancy 
$notes = "some notes here";//any notes about the jobs

$sn_div = "<div class='sn_div'>".$sn."</div>";
$ad_div = "<div class='ad_div'>".$added_date."</div>";
$job_div = "<div class='job_div'>".$job_title."</div>";
$salary_div = "<div class='salary_div'>".$salary."</div>";
$cd_div = "<div class='cd_div'>".$cd."</div>";//cd means closing date
$ins_div = "<div class='ins_div'>".$ins."</div>";//ins means institution
$notes_div = "<div class='notes_div'>".$notes."</div>";

/*erroneous line*/$job_no = "job"+$sn;//to create the job rows
$$job_no = "<div class='job_wrapper'>".$sn_div.$ad_div.$job_div.$salary_div.$cd_div.$ins_div.$notes_div."</div>";

echo $$job_no;//and then echo each job


that's the code I had which looped and created new html div elements. The code worked fine and the elements were formed, but i got the same warning in the error_log.

After reading the useful other answers, I figured that I was summing up a string and a number in the erroneous line. So I changed the code at that line to

/*erroneous line*/$job_no = "job"&&$sn;//this is the new variable that will create the job rows

Now the code works as earlier but with no warnings this time. Hope this example would be useful to someone.

Update Item to Revision vs Revert to Revision

Update to revision will only update files of your workingcopy to your choosen revision. But you cannot continue to work on this revision, as SVN will complain that your workingcopy is out of date.

revert to this revision will undo all changes in your working copy which were made after the selected revision (in your example rev. 96,97,98,99,100) Your working copy is now in modified state.

The file content of both scenarions is same, however in first case you have an unmodified working copy and you cannot commit your changes(as your workingcopy is not pointing to HEAD rev 100) in second case you have a modified working copy pointing to head and you can continue to work and commit

Convert char to int in C#

char c = '1';
int i = (int)(c-'0');

and you can create a static method out of it:

static int ToInt(this char c)
    return (int)(c - '0');

C: socket connection timeout

Here is a modern connect_with_timeout implementation, using poll, with proper error and signal handling:

#include <sys/socket.h>
#include <fcntl.h>
#include <poll.h>
#include <time.h>

int connect_with_timeout(int sockfd, const struct sockaddr *addr, socklen_t addrlen, unsigned int timeout_ms) {
    int rc = 0;
    // Set O_NONBLOCK
    int sockfd_flags_before;
    if((sockfd_flags_before=fcntl(sockfd,F_GETFL,0)<0)) return -1;
    if(fcntl(sockfd,F_SETFL,sockfd_flags_before | O_NONBLOCK)<0) return -1;
    // Start connecting (asynchronously)
    do {
        if (connect(sockfd, addr, addrlen)<0) {
            // Did connect return an error? If so, we'll fail.
            if ((errno != EWOULDBLOCK) && (errno != EINPROGRESS)) {
                rc = -1;
            // Otherwise, we'll wait for it to complete.
            else {
                // Set a deadline timestamp 'timeout' ms from now (needed b/c poll can be interrupted)
                struct timespec now;
                if(clock_gettime(CLOCK_MONOTONIC, &now)<0) { rc=-1; break; }
                struct timespec deadline = { .tv_sec = now.tv_sec,
                                             .tv_nsec = now.tv_nsec + timeout_ms*1000000l};
                // Wait for the connection to complete.
                do {
                    // Calculate how long until the deadline
                    if(clock_gettime(CLOCK_MONOTONIC, &now)<0) { rc=-1; break; }
                    int ms_until_deadline = (int)(  (deadline.tv_sec  - now.tv_sec)*1000l
                                                  + (deadline.tv_nsec - now.tv_nsec)/1000000l);
                    if(ms_until_deadline<0) { rc=0; break; }
                    // Wait for connect to complete (or for the timeout deadline)
                    struct pollfd pfds[] = { { .fd = sockfd, .events = POLLOUT } };
                    rc = poll(pfds, 1, ms_until_deadline);
                    // If poll 'succeeded', make sure it *really* succeeded
                    if(rc>0) {
                        int error = 0; socklen_t len = sizeof(error);
                        int retval = getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &error, &len);
                        if(retval==0) errno = error;
                        if(error!=0) rc=-1;
                // If poll was interrupted, try again.
                while(rc==-1 && errno==EINTR);
                // Did poll timeout? If so, fail.
                if(rc==0) {
                    errno = ETIMEDOUT;
    } while(0);
    // Restore original O_NONBLOCK state
    if(fcntl(sockfd,F_SETFL,sockfd_flags_before)<0) return -1;
    // Success
    return rc;

Explanation on Integer.MAX_VALUE and Integer.MIN_VALUE to find min and max value in an array

By initializing the min/max values to their extreme opposite, you avoid any edge cases of values in the input: Either one of min/max is in fact one of those values (in the case where the input consists of only one of those values), or the correct min/max will be found.

It should be noted that primitive types must have a value. If you used Objects (ie Integer), you could initialize value to null and handle that special case for the first comparison, but that creates extra (needless) code. However, by using these values, the loop code doesn't need to worry about the edge case of the first comparison.

Another alternative is to set both initial values to the first value of the input array (never a problem - see below) and iterate from the 2nd element onward, since this is the only correct state of min/max after one iteration. You could iterate from the 1st element too - it would make no difference, other than doing one extra (needless) iteration over the first element.

The only sane way of dealing with inout of size zero is simple: throw an IllegalArgumentException, because min/max is undefined in this case.

Creating your own header file in C


#ifndef FOO_H_   /* Include guard */
#define FOO_H_

int foo(int x);  /* An example function declaration */

#endif // FOO_H_


#include "foo.h"  /* Include the header (not strictly necessary here) */

int foo(int x)    /* Function definition */
    return x + 5;


#include <stdio.h>
#include "foo.h"  /* Include the header here, to obtain the function declaration */

int main(void)
    int y = foo(3);  /* Use the function here */
    printf("%d\n", y);
    return 0;

To compile using GCC

gcc -o my_app main.c foo.c

How to list files in a directory in a C program?

Below code will only print files within directory and exclude directories within given directory while traversing.

#include <dirent.h>
#include <stdio.h>
#include <errno.h>
#include <sys/stat.h>
int main(void)
    DIR *d;
    struct dirent *dir;
    char path[1000]="/home/joy/Downloads";
    d = opendir(path);
    char full_path[1000];
    if (d)
        while ((dir = readdir(d)) != NULL)
            //Condition to check regular file.

PDO mysql: How to know if insert was successful

PDOStatement->execute() can throw an exception

so what you can do is

//record inserted
catch(Exception $e)
//Some error occured. (i.e. violation of constraints)

How can I control the width of a label tag?

Using CSS, of course...

label { display: block; width: 100px; }

The width attribute is deprecated, and CSS should always be used to control these kinds of presentational styles.

Windows command prompt log to a file

You can redirect the output of a cmd prompt to a file using > or >> to append to a file.


echo Hello World >C:\output.txt
echo Hello again! >>C:\output.txt


mybatchfile.bat >C:\output.txt

Note that using > will automatically overwrite the file if it already exists.

You also have the option of redirecting stdin, stdout and stderr.

See here for a complete list of options.

Why does CreateProcess give error 193 (%1 is not a valid Win32 app)

Your Button2Click and Button3Click functions pass klad.xls and smimime.txt. These files most likely aren't actual executables indeed.

In order to open arbitrary files using the application associated with them, use ShellExecute

R Markdown - changing font size and font type in html output

I had the same issue and solved by making sure that 1. when you make the style.css file, make sure you didn't just rename a text file as "style.css", make sure it's really the .css format (e.g, use visual studio code); 2. put that style.css file in the same folder with your .rmd file. Hopefully this works for you.

CSS :not(:last-child):after selector

You can try this, I know is not the answers you are looking for but the concept is the same.

Where you are setting the styles for all the children and then removing it from the last child.

Code Snippet

  margin-right: 10px

    margin-right: 0


enter image description here

How to find the port for MS SQL Server 2008?

Try this (requires access to sys.dm_exec_connections):

FROM sys.dm_exec_connections 
WHERE local_tcp_port IS NOT NULL

How do I read an image file using Python?

The word "read" is vague, but here is an example which reads a jpeg file using the Image class, and prints information about it.

from PIL import Image
jpgfile ="picture.jpg")

print(jpgfile.bits, jpgfile.size, jpgfile.format)

How do you determine what SQL Tables have an identity column programmatically

sys.columns.is_identity = 1


from sys.objects o inner join sys.columns c on o.object_id = c.object_id
where c.is_identity = 1

Pass arguments into C program from command line

Instead of getopt(), you may also consider using argp_parse() (an alternative interface to the same library).

From libc manual:

getopt is more standard (the short-option only version of it is a part of the POSIX standard), but using argp_parse is often easier, both for very simple and very complex option structures, because it does more of the dirty work for you.

But I was always happy with the standard getopt.

N.B. GNU getopt with getopt_long is GNU LGPL.

How to initialize array to 0 in C?

Global variables and static variables are automatically initialized to zero. If you have simply

char ZEROARRAY[1024];

at global scope it will be all zeros at runtime. But actually there is a shorthand syntax if you had a local array. If an array is partially initialized, elements that are not initialized receive the value 0 of the appropriate type. You could write:

char ZEROARRAY[1024] = {0};

The compiler would fill the unwritten entries with zeros. Alternatively you could use memset to initialize the array at program startup:

memset(ZEROARRAY, 0, 1024);

That would be useful if you had changed it and wanted to reset it back to all zeros.

Vim: insert the same characters across multiple lines

I would use a macro to record my actions and would then repeat it.

  1. Put your cursor on the first letter in name.
  2. Hit qq to start recording into the q buffer.
  3. Hit i to go into insert mode, type vector_, and then hit Esc to leave insert mode.
  4. Now hit 0 to go back to the beginning of the line.
  5. Now hit j to go down.
  6. Now hit q again to stop recording.

You now have a nice macro.

Type 3@q to execute your macro three times to do the rest of the lines.

Converting double to string

How about when you do the


You just do

totalCost.setText( "" + total );

Where the "" + < variable > will convert it to string automaticly

Using DataContractSerializer to serialize, but can't deserialize back

Other solution is:

public static T Deserialize<T>(string rawXml)
    using (XmlReader reader = XmlReader.Create(new StringReader(rawXml)))
        DataContractSerializer formatter0 = 
            new DataContractSerializer(typeof(T));
        return (T)formatter0.ReadObject(reader);

One remark: sometimes it happens that raw xml contains e.g.:

<?xml version="1.0" encoding="utf-16"?>

then of course you can't use UTF8 encoding used in other examples..

Autoplay an audio with HTML5 embed tag while the player is invisible

You Could use this code, It's Works with me

<div style="visibility:hidden">
    <audio autoplay loop>
        <source src="../audio/audio.mp3">

CSS Input Type Selectors - Possible to have an "or" or "not" syntax?

CSS3 has a pseudo-class called :not()

input:not([type='checkbox']) {    
    visibility: hidden;
<p>If <code>:not()</code> is supported, you'll only see the checkbox.</p>
  <li>text: (<input type="text">)</li>  
  <li>password (<input type="password">)</li>       
  <li>checkbox (<input type="checkbox">)</li> 

Multiple selectors

As Vincent mentioned, it's possible to string multiple :not()s together:


CSS4, which is supported in many of the latest browser releases, allows multiple selectors in a :not()


Legacy support

All modern browsers support the CSS3 syntax. At the time this question was asked, we needed a fall-back for IE7 and IE8. One option was to use a polyfill like IE9.js. Another was to exploit the cascade in CSS:

input {
   // styles for most inputs

input[type=checkbox] {
  // revert back to the original style

input.checkbox {
  // for completeness, this would have worked even in IE3!

Does JavaScript pass by reference?

Objects are always pass by reference and primitives by value. Just keep that parameter at the same address for objects.

Here's some code to illustrate what I mean (try it in a JavaScript sandbox such as

Unfortunately you can't only retain the address of the parameter; you retain all the original member values as well.

a = { key: 'bevmo' };
document.write(' after function ');

function testRetain (b)
    document.write(' arg0 is ');
    b.key = 'passed by reference';
    var retain = b; // Retaining the original address of the parameter

    // Address of left set to address of right, changes address of parameter
    b = {key: 'vons'}; // Right is a new object with a new address
    document.write(' arg0 is ');

    // Now retrieve the original address of the parameter for pass by reference
    b = retain;
    document.write(' arg0 is ');


arg0 is bevmo arg0 is vons arg0 is passed by reference after function passed by reference

How to increase apache timeout directive in .htaccess?

if you have long processing server side code, I don't think it does fall into 404 as you said ("it goes to a webpage is not found error page")

Browser should report request timeout error.

You may do 2 things:

Based on CGI/Server side engine increase timeout there

PHP : - default is 30 seconds

In php.ini:

max_execution_time 60

Increase apache timeout - default is 300 (in version 2.4 it is 60).

In your httpd.conf (in server config or vhost config)

TimeOut 600

Note that first setting allows your PHP script to run longer, it will not interferre with network timeout.

Second setting modify maximum amount of time the server will wait for certain events before failing a request

Sorry, I'm not sure if you are using PHP as server side processing, but if you provide more info I will be more accurate.

ASP.NET MVC View Engine Comparison

I think this list should also include samples of each view engine so users can get a flavour of each without having to visit every website.

Pictures say a thousand words and markup samples are like screenshots for view engines :) So here's one from my favourite Spark View Engine

<viewdata products="IEnumerable[[Product]]"/>
<ul if="products.Any()">
  <li each="var p in products">${p.Name}</li>
  <p>No products available</p>

Convert Year/Month/Day to Day of Year in Python

Just subtract january 1 from the date:

import datetime
today =
day_of_year = (today - datetime.datetime(today.year, 1, 1)).days + 1

How to change an Eclipse default project into a Java project

Using project Project facets we can configure characteristics and requirements for projects.

To find Project facets on eclipse:

  • Step 1: Right click on the project and choose properties from the menu.
  • Step 2:Select project facets option. Click on Convert to faceted form... enter image description here

  • Step 3: We can find all available facets you can select and change their settings. enter image description here

Convert web page to image

I'm not sure if this is quite what you're looking for but I've had a lot of success using an HTML to Postscript converter html2ps to create postscript copies of web pages, which I then convert to .gif or .pngs

This doesn't produce exact screenshot quality that you'd get from a web browser and doesn't handle complicated things like flash or css all that well, but the advantage is that you can run it on the web server.

(I use it to create thumbnails of user created content, for navigation)

Project vs Repository in GitHub

In general, on GitHub, 1 repository = 1 project. For example: . But it isn't a hard rule.

1 repository = many projects. For example:

1 projects = many repositories. For example: (1 project named Zend Framework 3 has 61 + 1 = 62 repositories, don't believe? let count Zend Frameworks' modules + main repository)

I totally agree with @Brandon Ibbotson's comment:

A GitHub repository is just a "directory" where folders and files can exist.

Check if datetime instance falls in between other two datetime objects

Do simple compare > and <.

if (dateA>dateB && dateA<dateC)
    //do something

If you care only on time:

if (dateA.TimeOfDay>dateB.TimeOfDay && dateA.TimeOfDay<dateC.TimeOfDay)
    //do something

How to install crontab on Centos

As seen in Install crontab on CentOS, the crontab package in CentOS is vixie-cron. Hence, do install it with:

yum install vixie-cron

And then start it with:

service crond start

To make it persistent, so that it starts on boot, use:

chkconfig crond on

On CentOS 7 you need to use cronie:

yum install cronie

On CentOS 6 you can install vixie-cron, but the real package is cronie:

yum install vixie-cron


yum install cronie

In both cases you get the same output:

 Package         Arch       Version         Repository      Size
 cronie          x86_64     1.4.4-12.el6    base             73 k
Installing for dependencies:
 cronie-anacron  x86_64     1.4.4-12.el6    base             30 k
 crontabs        noarch     1.10-33.el6     base             10 k
 exim            x86_64     4.72-6.el6      epel            1.2 M

Transaction Summary
Install       4 Package(s)

Can not find module “@angular-devkit/build-angular”

I've just encountered this problem and fixed it. I think the root cause of this problem is ng and current version of node.js (10.6.0) and accompanying npm are not in sync. I've installed the LTS version of node.js (8.11.3) and the problem disappeared.

React-Native: Module AppRegistry is not a registered callable module

The one main reason of this problem could be where you would have installed a plugin and forget to link it.

try this:

react-native link

Re-run your app.

Hope this will help. Please let me know in comments. Thanks.

check if a file is open in Python

None of the other provided examples would work for me when dealing with this specific issue with excel on windows 10. The only other option I could think of was to try and rename the file or directory containing the file temporarily, then rename it back.

import os

    os.rename('file.xls', 'tempfile.xls')
    os.rename('tempfile.xls', 'file.xls')
except OSError:
    print('File is still open.')

HTML 5 video recording and storing a stream

Here is an elegant library that records video in all supported browsers and supports uploading:

How can I generate an MD5 hash?

I do not know if this is relevant for anyone reading this, but I just had the problem that I wanted to

  • download a file from a given URL and
  • compare its MD5 to a known value.

I wanted to do it with JRE classes only (no Apache Commons or similar). A quick web search did not show me sample code snippets doing both at the same time, only each task separately. Because this requires to read the same file twice, I figured it might be worth the while to write some code which unifies both tasks, calculating the checksum on the fly while downloading the file. This is my result (sorry if it is not perfect Java, but I guess you get the idea anyway):

import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import;        // new

void downloadFile(String fromURL, String toFile, BigInteger md5)
    throws IOException, NoSuchAlgorithmException
    ReadableByteChannel in = Channels.newChannel(new URL(fromURL).openStream());
    MessageDigest md5Digest = MessageDigest.getInstance("MD5");
    WritableByteChannel out = Channels.newChannel(
        //new FileOutputStream(toFile));  // old
        new DigestOutputStream(new FileOutputStream(toFile), md5Digest));  // new
    ByteBuffer buffer = ByteBuffer.allocate(1024 * 1024);  // 1 MB

    while ( != -1) {
        //md5Digest.update(buffer.asReadOnlyBuffer());  // old

    BigInteger md5Actual = new BigInteger(1, md5Digest.digest()); 
    if (! md5Actual.equals(md5))
        throw new RuntimeException(
            "MD5 mismatch for file " + toFile +
            ": expected " + md5.toString(16) +
            ", got " + md5Actual.toString(16)

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

What is JNDI? What is its basic use? When is it used?

The best explanation to me is given here

What is JNDI

It is an API to providing access to a directory service, that is, a service mapping name (strings) with objects, reference to remote objects or simple data. This is called binding. The set of bindings is called the context. Applications use the JNDI interface to access resources.

To put it very simply, it is like a hashmap with a String key and Object values representing resources on the web.

What Issues Does JNDI Solve

Without JNDI, the location or access information of remote resources would have to be hard-coded in applications or made available in a configuration. Maintaining this information is quite tedious and error prone.

If a resources has been relocated on another server, with another IP address, for example, all applications using this resource would have to be updated with this new information. With JNDI, this is not necessary. Only the corresponding resource binding has to be updated. Applications can still access it with its name and the relocation is transparent.

Jenkins/Hudson - accessing the current build number?

Jenkins Pipeline also provides the current build number as the property number of the currentBuild. It can be read as currentBuild.number.

For example:

// Scripted pipeline
def buildNumber = currentBuild.number
// Declarative pipeline
echo "Build number is ${currentBuild.number}"

Other properties of currentBuild are described in the Pipeline Syntax: Global Variables page that is included on each Pipeline job page. That page describes the global variables available in the Jenkins instance based on the current plugins.

MySql difference between two timestamps in days?

If you're happy to ignore the time portion in the columns, DATEDIFF() will give you the difference you're looking for in days.

SELECT DATEDIFF('2010-10-08 18:23:13', '2010-09-21 21:40:36') AS days;
| days |
|   17 |

error: ORA-65096: invalid common user or role name in oracle

Might be, more safe alternative to "_ORACLE_SCRIPT"=true is to change "_common_user_prefix" from C## to an empty string. When it's null - any name can be used for common user. Found there.

During changing that value you may face another issue - ORA-02095 - parameter cannot be modified, that can be fixed in a several ways, based on your configuration (source).

So for me worked that:

alter system set _common_user_prefix = ''; scope=spfile;

What's the best practice using a settings file in Python?

You can have a regular Python module, say, like this:

truck = dict(
    color = 'blue',
    brand = 'ford',
city = 'new york'
cabriolet = dict(
    color = 'black',
    engine = dict(
        cylinders = 8,
        placement = 'mid',
    doors = 2,

and use it like this:

import config

How to add number of days in postgresql datetime

This will give you the deadline :

select id,  
       created_at + interval '1' day * claim_window as deadline
from projects

Alternatively the function make_interval can be used:

select id,  
       created_at + make_interval(days => claim_window) as deadline
from projects

To get all projects where the deadline is over, use:

select *
from (
  select id, 
         created_at + interval '1' day * claim_window as deadline
  from projects
) t
where localtimestamp at time zone 'UTC' > deadline

how to add the missing RANDR extension

First off, Xvfb doesn't read configuration from xorg.conf. Xvfb is a variant of the KDrive X servers and like all members of that family gets its configuration from the command line.

It is true that XRandR and Xinerama are mutually exclusive, but in the case of Xvfb there's no Xinerama in the first place. You can enable the XRandR extension by starting Xvfb using at least the following command line options

Xvfb +extension RANDR [further options]

tkinter: how to use after method

You need to give a function to be called after the time delay as the second argument to after:

after(delay_ms, callback=None, *args)

Registers an alarm callback that is called after a given time.

So what you really want to do is this:

tiles_letter = ['a', 'b', 'c', 'd', 'e']

def add_letter():
    rand = random.choice(tiles_letter)
    tile_frame = Label(frame, text=rand)
    root.after(500, add_letter)
    tiles_letter.remove(rand)  # remove that tile from list of tiles

root.after(0, add_letter)  # add_letter will run as soon as the mainloop starts.

You also need to schedule the function to be called again by repeating the call to after inside the callback function, since after only executes the given function once. This is also noted in the documentation:

The callback is only called once for each call to this method. To keep calling the callback, you need to reregister the callback inside itself

Note that your example will throw an exception as soon as you've exhausted all the entries in tiles_letter, so you need to change your logic to handle that case whichever way you want. The simplest thing would be to add a check at the beginning of add_letter to make sure the list isn't empty, and just return if it is:

def add_letter():
    if not tiles_letter:
    rand = random.choice(tiles_letter)
    tile_frame = Label(frame, text=rand)
    root.after(500, add_letter)
    tiles_letter.remove(rand)  # remove that tile from list of tiles


How to add composite primary key to table

The ALTER TABLE statement presented by Chris should work, but first you need to declare the columns NOT NULL. All parts of a primary key need to be NOT NULL.

How to grep and replace

Usually not with grep, but rather with sed -i 's/string_to_find/another_string/g' or perl -i.bak -pe 's/string_to_find/another_string/g'.

jQuery checkbox change and click event

simply just use click event my check box id is CheckAll

     $('#CheckAll').click(function () {

        if ($('#CheckAll').is(':checked') == true) {


How can I undo a `git commit` locally and on a remote after `git push`

Try using

git reset --hard <commit id> 

Please Note : Here commit id will the id of the commit you want to go to but not the id you want to reset. this was the only point where i also got stucked.

then push

git push -f <remote> <branch>

Difference between IsNullOrEmpty and IsNullOrWhiteSpace in C#

This is implementation of methods after decompiling.

    public static bool IsNullOrEmpty(String value) 
        return (value == null || value.Length == 0); 

    public static bool IsNullOrWhiteSpace(String value) 
        if (value == null) return true; 

        for(int i = 0; i < value.Length; i++) { 
            if(!Char.IsWhiteSpace(value[i])) return false; 

        return true;

So it is obvious that IsNullOrWhiteSpace method also checks if value that is being passed contain white spaces.

Whitespaces refer :

Tracking changes in Windows registry

PhiLho has mentioned AutoRuns in passing, but I think it deserves elaboration.

It doesn't scan the whole registry, just the parts containing references to things which get loaded automatically (EXEs, DLLs, drivers etc.) which is probably what you are interested in. It doesn't track changes but can export to a text file, so you can run it before and after installation and do a diff.

An error occurred while executing the command definition. See the inner exception for details

I've just run into this issue and it was because I had updated a view in my DB and not refreshed the schema in my mapping.

How do you uninstall a python package that was installed using distutils?

install --record + xargs rm

sudo python install --record files.txt
xargs sudo rm -rf < files.txt

removes all files and but leaves empty directories behind.

That is not ideal, it should be enough to avoid package conflicts.

And then you can finish the job manually if you want by reading files.txt, or be braver and automate empty directory removal as well.

A safe helper would be:

python-setup-uninstall() (
  sudo rm -f files.txt
  sudo python install --record files.txt && \
  xargs rm -rf < files.txt
  sudo rm -f files.txt

Tested in Python 2.7.6, Ubuntu 14.04.

How do I clone a generic List in Java?

To clone a generic interface like java.util.List you will just need to cast it. here you are an example:

List list = new ArrayList();
List list2 = ((List) ( (ArrayList) list).clone());

It is a bit tricky, but it works, if you are limited to return a List interface, so anyone after you can implement your list whenever he wants.

I know this answer is close to the final answer, but my answer answers how to do all of that while you are working with List -the generic parent- not ArrayList

How to install mechanize for Python 2.7?

You need to follow the installation instructions and not just download the files into your Python27 directory. It has to be installed in the site-packages directory properly, which the directions tell you how to do.

git push says "everything up-to-date" even though I have local changes

I ran into this myself when I merged a branch on Github and continued to develop in it locally. My fix was a little different than the others that have been suggested.

First I branched a new local branch off my old local branch (that I couldn't push). Then I pushed the new local branch to the origin server (Github). I.e.

$ git checkout -b newlocalbranch oldlocalbranch
$ git push origin newlocalbranch

This got the changes to show up on Github, albeit in newlocalbranch rather than oldlocalbranch.

How to count number of records per day?

You could also try this:

SELECT DISTINCT (DATE(dateadded)) AS unique_date, COUNT(*) AS amount
FROM table
GROUP BY unique_date
ORDER BY unique_date ASC

How do I "break" out of an if statement?

if (test)
    goto jmp;

Oh why not :)

How to use sed/grep to extract text between two words?

GNU grep can also support positive & negative look-ahead & look-back: For your case, the command would be:

echo "Here is a string" | grep -o -P '(?<=Here).*(?=string)'

If there are multiple occurrences of Here and string, you can choose whether you want to match from the first Here and last string or match them individually. In terms of regex, it is called as greedy match (first case) or non-greedy match (second case)

$ echo 'Here is a string, and Here is another string.' | grep -oP '(?<=Here).*(?=string)' # Greedy match
 is a string, and Here is another 
$ echo 'Here is a string, and Here is another string.' | grep -oP '(?<=Here).*?(?=string)' # Non-greedy match (Notice the '?' after '*' in .*)
 is a 
 is another 

django change default runserver port

In Pycharm you can simply add the port to the parameters

enter image description here

What are the calling conventions for UNIX & Linux system calls (and user-space functions) on i386 and x86-64

Calling conventions defines how parameters are passed in the registers when calling or being called by other program. And the best source of these convention is in the form of ABI standards defined for each these hardware. For ease of compilation, the same ABI is also used by userspace and kernel program. Linux/Freebsd follow the same ABI for x86-64 and another set for 32-bit. But x86-64 ABI for Windows is different from Linux/FreeBSD. And generally ABI does not differentiate system call vs normal "functions calls". Ie, here is a particular example of x86_64 calling conventions and it is the same for both Linux userspace and kernel: (note the sequence a,b,c,d,e,f of parameters):

A good rendering of calling conventions vs registers usage

Performance is one of the reasons for these ABI (eg, passing parameters via registers instead of saving into memory stacks)

For ARM there is various ABI:

ARM64 convention:

For Linux on PowerPC:

And for embedded there is the PPC EABI:

This document is good overview of all the different conventions:

Linux command (like cat) to read a specified quantity of characters

Here's a simple script that wraps up using the dd approach mentioned here:

#!/usr/bin/env bash

function show_help()
extracts characters X to Y from stdin or FILE
usage: X Y {FILE}


2 10 /tmp/it     => extract chars 2-10 from /tmp/it
  echo "$IT"

if [ "$1" == "help" ]
if [ -z "$1" ]

COUNT=`expr $TO - $FROM + 1`

if [ -z "$3" ]
  dd skip=$FROM count=$COUNT bs=1 2>/dev/null
  dd skip=$FROM count=$COUNT bs=1 if=$3 2>/dev/null 

Excel VBA Automation Error: The object invoked has disconnected from its clients

The error in the below line of code (as mentioned by the requestor-William) is due to the following reason:

fromBook.Sheets("Report").Copy Before:=newBook.Sheets("Sheet1")

The destination sheet you are trying to copy to is closed. (Here newbook.Sheets("Sheet1")). Add the below statement just before copying to destination.

Application.Workbooks.Open ("YOUR SHEET NAME")

This will solve the problem!!

How do I enumerate through a JObject?

JObjects can be enumerated via JProperty objects by casting it to a JToken:

foreach (JProperty x in (JToken)obj) { // if 'obj' is a JObject
    string name = x.Name;
    JToken value = x.Value;

If you have a nested JObject inside of another JObject, you don't need to cast because the accessor will return a JToken:

foreach (JProperty x in obj["otherObject"]) { // Where 'obj' and 'obj["otherObject"]' are both JObjects
    string name = x.Name;
    JToken value = x.Value;

How can the size of an input text box be defined in HTML?

You can set the width in pixels via inline styling:

<input type="text" name="text" style="width: 195px;">

You can also set the width with a visible character length:

<input type="text" name="text" size="35">

Wait some seconds without blocking UI execution

If you do not want to block things and also not want to use multi threading, here is the solution for you:

The UI Thread is not blocked and the timer waits for 2 seconds before doing something.

Here is the code coming from the link above:

        // Create a timer with a two second interval.
    aTimer = new System.Timers.Timer(2000);
    // Hook up the Elapsed event for the timer. 
    aTimer.Elapsed += OnTimedEvent;
    aTimer.Enabled = true;

    Console.WriteLine("Press the Enter key to exit the program... ");
    Console.WriteLine("Terminating the application...");

Possible reason for NGINX 499 error codes

As you point 499 a connection abortion logged by the nginx. But usually this is produced when your backend server is being too slow, and another proxy timeouts first or the user software aborts the connection. So check if uWSGI is answering fast or not of if there is any load on uWSGI / Database server.

In many cases there are some other proxies between the user and nginx. Some can be in your infrastructure like maybe a CDN, Load Balacer, a Varnish cache etc. Others can be in user side like a caching proxy etc.

If there are proxies on your side like a LoadBalancer / CDN ... you should set the timeouts to timeout first your backend and progressively the other proxies to the user.

If you have:

user >>> CDN >>> Load Balancer >>> Nginx >>> uWSGI

I'll recommend you to set:

  • n seconds to uWSGI timeout
  • n+1 seconds to nginx timeout
  • n+2 senconds to timeout to Load Balancer
  • n+3 seconds of timeout to the CDN.

If you can't set some of the timeouts (like CDN) find whats is its timeout and adjust the others according to it (n, n-1...).

This provides a correct chain of timeouts. and you'll find really whose giving the timeout and return the right response code to the user.

android button selector

Create custom_selector.xml in drawable folder

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="">
   <item android:drawable="@drawable/unselected" android:state_pressed="true" />
   <item android:drawable="@drawable/selected" />

Create selected.xml shape in drawable folder

<shape xmlns:android="" android:shape="rectangle" android:padding="90dp">
   <solid android:color="@color/selected"/>
   <padding />
   <stroke android:color="#000" android:width="1dp"/>
   <corners android:bottomRightRadius="15dp" android:bottomLeftRadius="15dp" android:topLeftRadius="15dp" android:topRightRadius="15dp"/>

Create unselected.xml shape in drawable folder

<shape xmlns:android="" android:shape="rectangle" android:padding="90dp">
   <solid android:color="@color/unselected"/>
   <padding />
   <stroke android:color="#000" android:width="1dp"/>
   <corners android:bottomRightRadius="15dp" android:bottomLeftRadius="15dp" android:topLeftRadius="15dp" android:topRightRadius="15dp"/>

Add following colors for selected/unselected state in color.xml of values folder

<color name="selected">#a8cf45</color>
<color name="unselected">#ff8cae3b</color>

you can check complete solution from here

How can I find the link URL by link text with XPath?

Think of the phrase in the square brackets as a WHERE clause in SQL.

So this query says, "select the "href" attribute (@) of an "a" tag that appears anywhere (//), but only where (the bracketed phrase) the textual contents of the "a" tag is equal to 'programming questions site'".

Insert auto increment primary key to existing table

An ALTER TABLE statement adding the PRIMARY KEY column works correctly in my testing:


On a temporary table created for testing purposes, the above statement created the AUTO_INCREMENT id column and inserted auto-increment values for each existing row in the table, starting with 1.

What encoding/code page is cmd.exe using?

To answer your second query re. how encoding works, Joel Spolsky wrote a great introductory article on this. Strongly recommended.

PHP decoding and encoding json with unicode characters

A hacky way of doing JSON_UNESCAPED_UNICODE in PHP 5.3. Really disappointed by PHP json support. Maybe this will help someone else.

$array = some_json();
// Encode all string children in the array to html entities.
array_walk_recursive($array, function(&$item, $key) {
    if(is_string($item)) {
        $item = htmlentities($item);
$json = json_encode($array);

// Decode the html entities and end up with unicode again.
$json = html_entity_decode($rson);

Java synchronized block vs. Collections.synchronizedMap

If you are using JDK 6 then you might want to check out ConcurrentHashMap

Note the putIfAbsent method in that class.

HTML span align center not working?

span.login-text {
    font-size: 22px;
    margin-left: auto;
    margin-right: auto;

<span class="login-text">Welcome To .....CMP</span>

For me it worked very well. try this also

How can I convert a char to int in Java?

The ASCII table is arranged so that the value of the character '9' is nine greater than the value of '0'; the value of the character '8' is eight greater than the value of '0'; and so on.

So you can get the int value of a decimal digit char by subtracting '0'.

char x = '9';
int y = x - '0'; // gives the int value 9

Pass by pointer & Pass by reference

Pass by pointer is the only way you could pass "by reference" in C, so you still see it used quite a bit.

The NULL pointer is a handy convention for saying a parameter is unused or not valid, so use a pointer in that case.

References can't be updated once they're set, so use a pointer if you ever need to reassign it.

Prefer a reference in every case where there isn't a good reason not to. Make it const if you can.

How to position a table at the center of div horizontally & vertically

Additionally, if you want to center both horizontally and vertically -instead of having a flow-design (in such cases, the previous solutions apply)- you could do:

  1. Declare the main div as absolute or relative positioning (I call it content).
  2. Declare an inner div, which will actually hold the table (I call it wrapper).
  3. Declare the table itself, inside wrapper div.
  4. Apply CSS transform to change the "registration point" of the wrapper object to it's center.
  5. Move the wrapper object to the center of the parent object.

#content {_x000D_
  width: 5em;_x000D_
  height: 5em;_x000D_
  border: 1px solid;_x000D_
  border-color: red;_x000D_
  position: relative;_x000D_
#wrapper {_x000D_
  width: 4em;_x000D_
  height: 4em;_x000D_
  border: 3px solid;_x000D_
  border-color: black;_x000D_
  position: absolute;_x000D_
  left: 50%; top: 50%; /*move the object to the center of the parent object*/_x000D_
  -webkit-transform: translate(-50%, -50%);_x000D_
  -moz-transform: translate(-50%, -50%);_x000D_
  -ms-transform: translate(-50%, -50%);_x000D_
  -o-transform: translate(-50%, -50%);_x000D_
  transform: translate(-50%, -50%);_x000D_
  /*these 5 settings change the base (or registration) point of the wrapper object to it's own center - so we align child center with parent center*/_x000D_
table {_x000D_
  width: 100%;_x000D_
  height: 100%;_x000D_
  border: 1px solid;_x000D_
  border-color: yellow;_x000D_
  display: inline-block;_x000D_
<div id="content">_x000D_
    <div id="wrapper">_x000D_

Note: You cannot get rid of the wrapper div, since this style does not work directly on tables, so I use a div to wrap it and position it, while the table is flowed inside the div.

How to use a servlet filter in Java to change an incoming servlet request url?

You could use the ready to use Url Rewrite Filter with a rule like this one:


Check the Examples for more... examples.

Appending a list or series to a pandas DataFrame as a row?

If you want to add a Series and use the Series' index as columns of the DataFrame, you only need to append the Series between brackets:

In [1]: import pandas as pd

In [2]: df = pd.DataFrame()

In [3]: row=pd.Series([1,2,3],["A","B","C"])

In [4]: row
A    1
B    2
C    3
dtype: int64

In [5]: df.append([row],ignore_index=True)
   A  B  C
0  1  2  3

[1 rows x 3 columns]

Whitout the ignore_index=True you don't get proper index.

How to solve java.lang.NullPointerException error?

This error occures when you try to refer to a null object instance. I can`t tell you what causes this error by your given information, but you can debug it easily in your IDE. I strongly recommend you that use exception handling to avoid unexpected program behavior.

org.apache.catalina.core.StandardContext startInternal SEVERE: Error listenerStart

Select "all project" and right click

Maven-> Update project

How to get value from form field in django framework?

It is easy if you are using django version 3.1 and above

def login_view(request):
        yourForm= YourForm(request.POST)
        itemValue = yourForm['your_filed_name'].value()
        # Check if you get the value
        return HttpResponse(itemValue )
        return render(request, "base.html")

Understanding PIVOT function in T-SQL

FOR XML PATH might not work on Microsoft Azure Synapse Serve. A possible alternative, following @Taryn dynamic generated cols approach, same results is obtained by using STRING_AGG.


SELECT @cols = STRING_AGG(QUOTENAME(c.phaseid),', ')
/*OPTIONAL: within group (order by cast(t1.[FLOW_SP_SLPM] as INT) asc)*/
FROM (SELECT phaseid FROM temp
GROUP BY phaseid) c

set @query = 'SELECT elementid,' + @cols + ' from 
                select elementid,
                from temp
            ) x
                for phaseid in (' + @cols + ')
            ) p '


C# Clear Session

In ASP.NET, when should I use Session.Clear() rather than Session.Abandon()?

Session.Abandon() destroys the session and the Session_OnEnd event is triggered.

Session.Clear() just removes all values (content) from the Object. The session with the same key is still alive.

So, if you use Session.Abandon(), you lose that specific session and the user will get a new session key. You could use it for example when the user logs out.

Use Session.Clear(), if you want that the user remaining in the same session (if you don't want him to relogin for example) and reset all his session specific data.

What is the difference between Session.Abandon() and Session.Clear()

Clear - Removes all keys and values from the session-state collection.

Abandon - removes all the objects stored in a Session. If you do not call the Abandon method explicitly, the server removes these objects and destroys the session when the session times out. It also raises events like Session_End.

Session.Clear can be compared to removing all books from the shelf, while Session.Abandon is more like throwing away the whole shelf.


Generally, in most cases you need to use Session.Clear. You can use Session.Abandon if you are sure the user is going to leave your site.

So back to the differences:

  • Abandon raises Session_End request.
  • Clear removes items immediately, Abandon does not.
  • Abandon releases the SessionState object and its items so it can garbage collected.
  • Clear keeps SessionState and resources associated with it.

Session.Clear() or Session.Abandon() ?

You use Session.Clear() when you don't want to end the session but rather just clear all the keys in the session and reinitialize the session.

Session.Clear() will not cause the Session_End eventhandler in your Global.asax file to execute.

But on the other hand Session.Abandon() will remove the session altogether and will execute Session_End eventhandler.

Session.Clear() is like removing books from the bookshelf

Session.Abandon() is like throwing the bookshelf itself.


I check on some sessions if not equal null in the page load. if one of them equal null i wanna to clear all the sessions and redirect to the login page?


If you want the user to login again, use Session.Abandon.

How to clear APC cache entries?

I don't believe any of these answers actually work for clearing the APC cache from the command line. As Frank Farmer commented above, the CLI runs in a process separate from Apache.

My solution for clearing from the command line was to write a script that copies an APC clearing script to the web directory and accesses it and then deletes it. The script is restricted to being accessed from the localhost.

  1. apc_clear.php

    This is the file that the script copies to the web directory, accesses, and deletes.

    if (in_array(@$_SERVER['REMOTE_ADDR'], array('', '::1')))
      echo json_encode(array('success' => true));
      die('SUPER TOP SECRET');
  2. Cache clearing script

    This script copies apc_clear.php to the web directory, accesses it, then deletes it. This is based off of a Symfony task. In the Symfony version, calls are made to the Symfony form of copy and unlink, which handle errors. You may want to add checks that they succeed.

    copy($apcPaths['data'], $apcPaths['web']); //'data' is a non web accessable directory
    $url = 'http://localhost/apc_clear.php'; //use domain name as necessary
    $result = json_decode(file_get_contents($url));
    if (isset($result['success']) && $result['success'])
      //handle success
      //handle failure

ElasticSearch: Unassigned Shards, how to fix?

I was having this issue as well, and I found an easy way to resolve it.

  • Get the index of unassigned shards

    $ curl -XGET
  • Install curator Tools, and use it to delete index

    $ curator --host delete indices --older-than 1 \
           --timestring '%Y.%m.%d' --time-unit days --prefix logstash

    NOTE: In my case, the index is logstash of the day 2016-04-21

  • Then check the shards again, all the unassigned shards go away!

Android open camera from button

I have created a libray for pick image from camera or galley and cropping also

Try this,


public class ImagePro
    public static String TAG = "ImagePro";
    Activity activity;
    Uri mImageCaptureUri;
    public static int CAMERA_CODE = 64;
    public static int GALLERY_CODE = 74;
    public static int CROPPING_CODE = 84;
    private final static int REQUEST_PERMISSION_REQ_CODE = 704;

    public ImagePro(Activity activity) {

        this.activity = activity;
        this.outPutFile = new File(android.os.Environment.getExternalStorageDirectory(), "temp.jpg");

        if (ContextCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {

            ActivityCompat.requestPermissions(activity, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_PERMISSION_REQ_CODE);

    private void LogToast(String message) {

        try {
            Toast.makeText(activity, message, Toast.LENGTH_SHORT).show();
        } catch (Exception e) {

        Log.d(TAG, message);

    private void Toast(String message) {

        try {
            Toast.makeText(activity, message, Toast.LENGTH_SHORT).show();
        } catch (Exception e) {

    private void Log(String message) {

        Log.d(TAG, message);

     * This function return captured image path
     * @param requestCode on activity result requestCode
     * @param resultCode on activity result resultCode
     * @param intent on activity result intent
     * @return ImageDetails values
    public ImageDetails getImagePath(int requestCode, int resultCode, Intent intent) {

        ImageDetails imageDetails = new ImageDetails();

        if(resultCode == Activity.RESULT_OK) {

            if(requestCode == CAMERA_CODE) {
                Bitmap bitmap = null;

                try {
                    bitmap = MediaStore.Images.Media.getBitmap(activity.getContentResolver(), mImageCaptureUri);
                } catch (IOException e) {
                imageDetails.setFile(new File(mImageCaptureUri.getPath()));

            } else if(requestCode == GALLERY_CODE) {

                Uri uri = intent.getData();

                Bitmap bitmap = null;

                try {
                    bitmap = MediaStore.Images.Media.getBitmap(activity.getContentResolver(), uri);
                } catch (IOException e) {

                imageDetails.setFile(new File(uri.getPath()));

            } else if(requestCode == CROPPING_CODE) {
                try {

                        Bitmap photo = decodeFile(outPutFile);
                    else {
                        LogToast("Error while save image");
                } catch (Exception e) {


        } else {
            LogToast("user cancelled.");

        return imageDetails;

     * Open image pick dialog.<br/>
     * CAMERA_CODE</br>
    public void openImagePickOption() {

        final CharSequence[] items = { "Capture Photo", "Choose from Gallery", "Cancel" };

        AlertDialog.Builder builder = new AlertDialog.Builder(activity);
        builder.setTitle("Add Photo!");
        builder.setItems(items, new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int item) {

                if (items[item].equals("Capture Photo")) {


                } else if (items[item].equals("Choose from Gallery")) {


                } else if (items[item].equals("Cancel")) {

     * decode from file to bitmap
     * @param f file
     * @return Bitmap data
    private Bitmap decodeFile(File f) {
        try {
            // decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f), null, o);

            // Find the correct scale value. It should be the power of 2.
            final int REQUIRED_SIZE = 512;
            int width_tmp = o.outWidth, height_tmp = o.outHeight;
            int scale = 1;
            while (true) {
                if (width_tmp / 2 < REQUIRED_SIZE || height_tmp / 2 < REQUIRED_SIZE)
                width_tmp /= 2;
                height_tmp /= 2;
                scale *= 2;

            // decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize = scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {

        return null;

     * Capture image using camera <br/>
    public void captureImage() {

        if(activity != null) {

            Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            File f = new File(android.os.Environment.getExternalStorageDirectory(), "temp1.jpg");
            mImageCaptureUri = Uri.fromFile(f);
            intent.putExtra(MediaStore.EXTRA_OUTPUT, mImageCaptureUri);
            activity.startActivityForResult(intent, CAMERA_CODE);

        } else {

            LogToast("Activity not assigned");

     * pick image from gallery
    public void pickImage() {

        Intent i = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        activity.startActivityForResult(i, GALLERY_CODE);

     * cropping the uri image
     * @param uri - open cropping dialog using the uri data
    public void croppingImage(Uri uri) {


    int CROP_IMG_X=512;
    int CROP_IMG_Y=512;

    public void croppingImage(Uri uri, int cropX, int cropY) {

        CROP_IMG_X = cropX;
        CROP_IMG_Y = cropY;


    File outPutFile=null;

    private void CroppingIMG(Uri uri) {

        final ArrayList<CroppingOption> cropOptions = new ArrayList<>();

        Intent intent = new Intent("");

        List<ResolveInfo> list = activity.getPackageManager().queryIntentActivities( intent, 0 );
        int size = list.size();
        if (size == 0) {
            LogToast("Can't find image croping app");
        } else {
            intent.putExtra("outputX", CROP_IMG_X);
            intent.putExtra("outputY", CROP_IMG_Y);
            intent.putExtra("aspectX", 1);
            intent.putExtra("aspectY", 1);
            intent.putExtra("scale", true);

            //Create output file here
            intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(outPutFile));

            if (size == 1) {
                Intent i   = new Intent(intent);
                ResolveInfo res = list.get(0);

                i.setComponent( new ComponentName(res.activityInfo.packageName,;

                activity.startActivityForResult(i, CROPPING_CODE);
            } else {
                for (ResolveInfo res : list) {
                    final CroppingOption co = new CroppingOption();

                    co.title = activity.getPackageManager().getApplicationLabel(res.activityInfo.applicationInfo);
                    co.icon = activity.getPackageManager().getApplicationIcon(res.activityInfo.applicationInfo);
                    co.appIntent = new Intent(intent);
                    co.appIntent.setComponent( new ComponentName(res.activityInfo.packageName,;

                CropingOptionAdapter adapter = new CropingOptionAdapter(activity.getApplicationContext(), cropOptions);

                AlertDialog.Builder builder = new AlertDialog.Builder(activity);
                builder.setTitle("Choose Cropping App");
                builder.setAdapter( adapter, new DialogInterface.OnClickListener() {
                    public void onClick( DialogInterface dialog, int item ) {
                        activity.startActivityForResult( cropOptions.get(item).appIntent, CROPPING_CODE);

                builder.setOnCancelListener( new DialogInterface.OnCancelListener() {
                    public void onCancel( DialogInterface dialog ) {

                        if (mImageCaptureUri != null ) {
                            activity.getContentResolver().delete(mImageCaptureUri, null, null );
                            mImageCaptureUri = null;
                } );

                AlertDialog alert = builder.create();

     * Capture image using camera<br/>
     * REQUEST_CODE = User defined code<br/>
     * <br/>
     * @param iRequestCode User defined code
    public void captureImage(int iRequestCode) {

        CAMERA_CODE = iRequestCode;

     * get path, bitmap, file and uri from image details object
    public class ImageDetails {

        String path="";
        Bitmap bitmap=null;
        File file=null;
        Uri uri=null;

        public Uri getUri() {
            return uri;

        public void setUri(Uri uri) {
            this.uri = uri;

        public String getPath() {
            return path;

        public void setPath(String path) {
            this.path = path;

        public Bitmap getBitmap() {
            return bitmap;

        public void setBitmap(Bitmap bitmap) {
            this.bitmap = bitmap;

        public File getFile() {
            return file;

        public void setFile(File file) {
            this.file = file;

     * Created by DP on 7/12/2016.
    public class CroppingOption {
        public CharSequence title;
        public Drawable icon;
        public Intent appIntent;

    public class CropingOptionAdapter extends ArrayAdapter {
        private ArrayList<CroppingOption> mOptions;
        private LayoutInflater mInflater;

        public CropingOptionAdapter(Context context, ArrayList<CroppingOption> options) {

            super(context, R.layout.croping_selector, options);
            mOptions  = options;
            mInflater = LayoutInflater.from(context);

        public View getView(int position, View convertView, ViewGroup group) {
            if (convertView == null)
                convertView = mInflater.inflate(R.layout.croping_selector, null);

            CroppingOption item = mOptions.get(position);

            if (item != null) {
                ((ImageView) convertView.findViewById(;
                ((TextView) convertView.findViewById(;

                return convertView;

            return null;

ImagePro imagePro;

    protected void onCreate(Bundle savedInstanceState) {
        imagePro = new ImagePro(this);

    public void onClickUploadImageButton(View view) {



if(requestCode == CAMERA_CODE && resultCode == RESULT_OK) {

            imageDetails = imagePro.getImagePath(CAMERA_CODE, RESULT_OK, data);
//imageDetails.getPath(), imageDetails.getBitmap(), imageDetails.getUri(), imageDetails.getFile

slf4j: how to log formatted message, object array, exception

In addition to @Ceki 's answer, If you are using logback and setup a config file in your project (usually logback.xml), you can define the log to plot the stack trace as well using

    <pattern>%date |%-5level| [%thread] [%file:%line] - %msg%n%ex{full}</pattern> 

the %ex in pattern is what makes the difference

Why are elementwise additions much faster in separate loops than in a combined loop?

Imagine you are working on a machine where n was just the right value for it only to be possible to hold two of your arrays in memory at one time, but the total memory available, via disk caching, was still sufficient to hold all four.

Assuming a simple LIFO caching policy, this code:

for(int j=0;j<n;j++){
    a[j] += b[j];
for(int j=0;j<n;j++){
    c[j] += d[j];

would first cause a and b to be loaded into RAM and then be worked on entirely in RAM. When the second loop starts, c and d would then be loaded from disk into RAM and operated on.

the other loop

for(int j=0;j<n;j++){
    a[j] += b[j];
    c[j] += d[j];

will page out two arrays and page in the other two every time around the loop. This would obviously be much slower.

You are probably not seeing disk caching in your tests but you are probably seeing the side effects of some other form of caching.

There seems to be a little confusion/misunderstanding here so I will try to elaborate a little using an example.

Say n = 2 and we are working with bytes. In my scenario we thus have just 4 bytes of RAM and the rest of our memory is significantly slower (say 100 times longer access).

Assuming a fairly dumb caching policy of if the byte is not in the cache, put it there and get the following byte too while we are at it you will get a scenario something like this:

  • With

    for(int j=0;j<n;j++){
     a[j] += b[j];
    for(int j=0;j<n;j++){
     c[j] += d[j];
  • cache a[0] and a[1] then b[0] and b[1] and set a[0] = a[0] + b[0] in cache - there are now four bytes in cache, a[0], a[1] and b[0], b[1]. Cost = 100 + 100.

  • set a[1] = a[1] + b[1] in cache. Cost = 1 + 1.
  • Repeat for c and d.
  • Total cost = (100 + 100 + 1 + 1) * 2 = 404

  • With

    for(int j=0;j<n;j++){
     a[j] += b[j];
     c[j] += d[j];
  • cache a[0] and a[1] then b[0] and b[1] and set a[0] = a[0] + b[0] in cache - there are now four bytes in cache, a[0], a[1] and b[0], b[1]. Cost = 100 + 100.

  • eject a[0], a[1], b[0], b[1] from cache and cache c[0] and c[1] then d[0] and d[1] and set c[0] = c[0] + d[0] in cache. Cost = 100 + 100.
  • I suspect you are beginning to see where I am going.
  • Total cost = (100 + 100 + 100 + 100) * 2 = 800

This is a classic cache thrash scenario.

Bootstrap 4 File Input

Here is the answer with blue box-shadow,border,outline removed with file name fix in custom-file input of bootstrap appear on choose filename and if you not choose any file then show No file chosen.

    $(document).on('change', 'input[type="file"]', function (event) { _x000D_
        var filename = $(this).val();_x000D_
        if (filename == undefined || filename == ""){_x000D_
        $(this).next('.custom-file-label').html('No file chosen');_x000D_
        else _x000D_
        { $(this).next('.custom-file-label').html([0].name); }_x000D_
    input[type=file]:focus,.custom-file-input:focus~.custom-file-label {_x000D_
        border-color: transparent;_x000D_
        box-shadow: none!important;_x000D_
    .custom-file-input {_x000D_
        cursor: pointer;_x000D_
    <script src=""></script>_x000D_
    <link href="" rel="stylesheet"/>_x000D_
    <div class="container py-5">_x000D_
    <div class="input-group mb-3">_x000D_
      <div class="input-group-prepend">_x000D_
        <span class="input-group-text">Upload</span>_x000D_
      <div class="custom-file">_x000D_
        <input type="file" class="custom-file-input" id="inputGroupFile01">_x000D_
        <label class="custom-file-label" for="inputGroupFile01">Choose file</label>_x000D_

Renaming Columns in an SQL SELECT Statement

You can alias the column names one by one, like so

SELECT col1 as `MyNameForCol1`, col2 as `MyNameForCol2` 
FROM `foobar`

Edit You can access INFORMATION_SCHEMA.COLUMNS directly to mangle a new alias like so. However, how you fit this into a query is beyond my MySql skills :(

select CONCAT('Foobar_', COLUMN_NAME)
where TABLE_NAME = 'Foobar'

Save each sheet in a workbook to separate CSV files

And here's my solution should work with Excel > 2000, but tested only on 2007:

Private Sub SaveAllSheetsAsCSV()
On Error GoTo Heaven

' each sheet reference
Dim Sheet As Worksheet
' path to output to
Dim OutputPath As String
' name of each csv
Dim OutputFile As String

Application.ScreenUpdating = False
Application.DisplayAlerts = False
Application.EnableEvents = False

' ask the user where to save
OutputPath = InputBox("Enter a directory to save to", "Save to directory", Path)

If OutputPath <> "" Then

    ' save for each sheet
    For Each Sheet In Sheets

        OutputFile = OutputPath & "\" & Sheet.Name & ".csv"

        ' make a copy to create a new book with this sheet
        ' otherwise you will always only get the first sheet
        ' this copy will now become active
        ActiveWorkbook.SaveAs FileName:=OutputFile, FileFormat:=xlCSV, CreateBackup:=False

End If

Application.ScreenUpdating = True
Application.DisplayAlerts = True
Application.EnableEvents = True

Exit Sub

MsgBox "Couldn't save all sheets to CSV." & vbCrLf & _
        "Source: " & Err.Source & " " & vbCrLf & _
        "Number: " & Err.Number & " " & vbCrLf & _
        "Description: " & Err.Description & " " & vbCrLf

GoTo Finally
End Sub

(OT: I wonder if SO will replace some of my minor blogging)

Concatenating strings in Razor

You can give like this....

<a href="@(IsProduction.IsProductionUrl)Index/LogOut">

How to recover stashed uncommitted changes

To make this simple, you have two options to reapply your stash:

  1. git stash pop - Restore back to the saved state, but it deletes the stash from the temporary storage.
  2. git stash apply - Restore back to the saved state and leaves the stash list for possible later reuse.

You can read in more detail about git stashes in this article.

Detecting a mobile browser

Once the element gains focus, you immediately blur it. Bootstrap-datepicker, which is a very popular and well-maintained component with almost 10,000 stars in GitHub, uses this approach:

if (window.navigator.maxTouchPoints || 'ontouchstart' in document) {

Thanks to Tigger for assistance.

how to change class name of an element by jquery


Your code has two problems:

  1. The selector .IsBestAnswe does not match what you thought
  2. It's addClass(), not addclass().

Also, I'm not sure whether you want to replace the class or add it. The above will replace, but remove the .removeClass('IsBestAnswer') part to add only:


You should decide whether to use camelCase or all-lowercase in your CSS classes too (e.g. bestAnswer vs. bestanswer).

Does --disable-web-security Work In Chrome Anymore?

The new tag for recent Chrome and Chromium browsers is :

--disable-web-security --user-data-dir=c:\my\data

Move SQL data from one table to another

If the two tables use the same ID or have a common UNIQUE key:

1) Insert the selected record in table 2

INSERT INTO table2 SELECT * FROM table1 WHERE (conditions)

2) delete the selected record from table1 if presents in table2

DELETE FROM table1 as A, table2 as B WHERE (A.conditions) AND  (A.ID = B.ID)