Programs & Examples On #Mdns

Multicast DNS is a method for (generally) small networks to advertise services without user configuration. The two popular implementations are bonjour (used by Apple systems) avahi (used by linux)

what is the multicast doing on

I deactivated my "Arno's Iptables Firewall" for testing, and then the messages are gone

How to validate an email address using a regular expression?

I know this question is about RegEx, but guessing that 90% of all developers reading these solutions are trying to validate an E-Mail address in an HTML form displayed in a browser.

If this is the case, I'd suggest checking out the new HTML5 <input type="email"> form element:


 <input type="email" required />


 input:required {
      background-color: rgba(255,0,0,0.2);

 input:focus:invalid { 
     box-shadow: 0 0 1em red;
     border-color: red;

 input:focus:valid { 
     box-shadow: 0 0 1em green;
     border-color: green;

This has a couple of advantages:

  1. Automatic validation, no custom solution needed: simple and easy to implement
  2. No JavaScript, no problems if JS has been disabled
  3. No server has to calculate anything for that
  4. The user has an immediate feedback
  5. Old browser should automatically fallback to input type "text"
  6. Mobile browsers can display a specialized keyboard (@-Keyboard)
  7. Form validation feedback is very easy with CSS3

The apparent downside might be missing validation for old browsers, but that'll change over time. I'd prefer this over any of these insane RegEx masterpieces.

also see:

JPA or JDBC, how are they different?

Main difference between JPA and JDBC is level of abstraction.

JDBC is a low level standard for interaction with databases. JPA is higher level standard for the same purpose. JPA allows you to use an object model in your application which can make your life much easier. JDBC allows you to do more things with the Database directly, but it requires more attention. Some tasks can not be solved efficiently using JPA, but may be solved more efficiently with JDBC.

How to prevent column break within an element?

Firefox now supports this:

page-break-inside: avoid;

This solves the problem of elements breaking across columns.

android adb turn on wifi via adb

Unfortunately the only way I could resolve my problem is to root the device.

Here is a good tutorial for Nexus S:

How do Python functions handle the types of the parameters that you pass in?

Python is strongly typed because every object has a type, every object knows its type, it's impossible to accidentally or deliberately use an object of a type "as if" it was an object of a different type, and all elementary operations on the object are delegated to its type.

This has nothing to do with names. A name in Python doesn't "have a type": if and when a name's defined, the name refers to an object, and the object does have a type (but that doesn't in fact force a type on the name: a name is a name).

A name in Python can perfectly well refer to different objects at different times (as in most programming languages, though not all) -- and there is no constraint on the name such that, if it has once referred to an object of type X, it's then forevermore constrained to refer only to other objects of type X. Constraints on names are not part of the concept of "strong typing", though some enthusiasts of static typing (where names do get constrained, and in a static, AKA compile-time, fashion, too) do misuse the term this way.

HTML5 Canvas 100% Width Height of Viewport?

<!DOCTYPE html>

    <canvas id="c"></canvas>


with CSS

body { 
       margin: 0; 
       padding: 0
#c { 
     position: absolute; 
     width: 100%; 
     height: 100%; 
     overflow: hidden

Run parallel multiple commands at once in the same terminal

It can be done with simple Makefile:

        sleep $(subst sleep,,$@)
        @echo $@ done.

Use -j option.

$ make -j sleep3 sleep2 sleep1
sleep 3
sleep 2
sleep 1
sleep1 done.
sleep2 done.
sleep3 done.

Without -j option it executes in serial.

$ make -j sleep3 sleep2 sleep1
sleep 3
sleep3 done.
sleep 2
sleep2 done.
sleep 1
sleep1 done.

You can also do dry run with `-n' option.

$ make -j -n sleep3 sleep2 sleep1
sleep 3
sleep 2
sleep 1

string sanitizer for filename

Well, tempnam() will do it for you.

but that creates an entirely new name.

To sanitize an existing string just restrict what your users can enter and make it letters, numbers, period, hyphen and underscore then sanitize with a simple regex. Check what characters need to be escaped or you could get false positives.

$sanitized = preg_replace('/[^a-zA-Z0-9\-\._]/','', $filename);

fork() and wait() with two child processes

Put your wait() function in a loop and wait for all the child processes. The wait function will return -1 and errno will be equal to ECHILD if no more child processes are available.

Error 80040154 (Class not registered exception) when initializing VCProjectEngineObject (Microsoft.VisualStudio.VCProjectEngine.dll)

There are not many good reasons this would fail, especially the regsvr32 step. Run dumpbin /exports on that dll. If you don't see DllRegisterServer then you've got a corrupt install. It should have more side-effects, you wouldn't be able to build C/C++ projects anymore.

One standard failure mode is running this on a 64-bit operating system. This is 32-bit unmanaged code, you would indeed get the 'class not registered' exception. Project + Properties, Build tab, change Platform Target to x86.

best practice to generate random token for forgot password

You can also use DEV_RANDOM, where 128 = 1/2 the generated token length. Code below generates 256 token.

$token = bin2hex(mcrypt_create_iv(128, MCRYPT_DEV_RANDOM));

How to wait till the response comes from the $http request, in angularjs?

You should use promises for async operations where you don't know when it will be completed. A promise "represents an operation that hasn't completed yet, but is expected in the future." (

An example implementation would be like:

myApp.factory('myService', function($http) {

    var getData = function() {

        // Angular $http() and then() both return promises themselves 
        return $http({method:"GET", url:"/my/url"}).then(function(result){

            // What we return here is the data that will be accessible 
            // to us after the promise resolves

    return { getData: getData };

function myFunction($scope, myService) {
    var myDataPromise = myService.getData();
    myDataPromise.then(function(result) {  

       // this is only run after getData() resolves
       $ = result;

Edit: Regarding Sujoys comment that What do I need to do so that myFuction() call won't return till .then() function finishes execution.

function myFunction($scope, myService) { 
    var myDataPromise = myService.getData(); 
    myDataPromise.then(function(result) { 
         $ = result; 
    console.log("This will get printed before inside then. And I don't want that."); 

Well, let's suppose the call to getData() took 10 seconds to complete. If the function didn't return anything in that time, it would effectively become normal synchronous code and would hang the browser until it completed.

With the promise returning instantly though, the browser is free to continue on with other code in the meantime. Once the promise resolves/fails, the then() call is triggered. So it makes much more sense this way, even if it might make the flow of your code a bit more complex (complexity is a common problem of async/parallel programming in general after all!)

How to use 'git pull' from the command line?

Try setting the HOME environment variable in Windows to your home folder (c:\users\username).

( you can confirm that this is the problem by doing echo $HOME in git bash and echo %HOME% in cmd - latter might not be available )

Is "delete this" allowed in C++?

This is an old, answered, question, but @Alexandre asked "Why would anyone want to do this?", and I thought that I might provide an example usage that I am considering this afternoon.

Legacy code. Uses naked pointers Obj*obj with a delete obj at the end.

Unfortunately I need sometimes, not often, to keep the object alive longer.

I am considering making it a reference counted smart pointer. But there would be lots of code to change, if I was to use ref_cnt_ptr<Obj> everywhere. And if you mix naked Obj* and ref_cnt_ptr, you can get the object implicitly deleted when the last ref_cnt_ptr goes away, even though there are Obj* still alive.

So I am thinking about creating an explicit_delete_ref_cnt_ptr. I.e. a reference counted pointer where the delete is only done in an explicit delete routine. Using it in the one place where the existing code knows the lifetime of the object, as well as in my new code that keeps the object alive longer.

Incrementing and decrementing the reference count as explicit_delete_ref_cnt_ptr get manipulated.

But NOT freeing when the reference count is seen to be zero in the explicit_delete_ref_cnt_ptr destructor.

Only freeing when the reference count is seen to be zero in an explicit delete-like operation. E.g. in something like:

template<typename T> class explicit_delete_ref_cnt_ptr { 
   T* ptr;
   int rc;
   void delete_if_rc0() {
      if( this->ptr ) {
        if( this->rc == 0 ) {
           delete this->ptr;
        this->ptr = 0;

OK, something like that. It's a bit unusual to have a reference counted pointer type not automatically delete the object pointed to in the rc'ed ptr destructor. But it seems like this might make mixing naked pointers and rc'ed pointers a bit safer.

But so far no need for delete this.

But then it occurred to me: if the object pointed to, the pointee, knows that it is being reference counted, e.g. if the count is inside the object (or in some other table), then the routine delete_if_rc0 could be a method of the pointee object, not the (smart) pointer.

class Pointee { 
   int rc;
   void delete_if_rc0() {
        if( this->rc == 0 ) {
           delete this;

Actually, it doesn't need to be a member method at all, but could be a free function:

map<void*,int> keepalive_map;
template<typename T>
void delete_if_rc0(T*ptr) {
        void* tptr = (void*)ptr;
        if( keepalive_map[tptr] == 1 ) {
           delete ptr;

(BTW, I know the code is not quite right - it becomes less readable if I add all the details, so I am leaving it like this.)

Schedule automatic daily upload with FileZilla

FileZilla does not have any command line arguments (nor any other way) that allow an automatic transfer.

Some references:

Though you can use any other client that allows automation.

You have not specified, what protocol you are using. FTP or SFTP? You will definitely be able to use WinSCP, as it supports all protocols that FileZilla does (and more).

Combine WinSCP scripting capabilities with Windows Scheduler:

A typical WinSCP script for upload (with SFTP) looks like:

open sftp://user:[email protected]/ -hostkey="ssh-rsa 2048 xxxxxxxxxxx...="
put c:\mypdfs\*.pdf /home/user/

With FTP, just replace the sftp:// with the ftp:// and remove the -hostkey="..." switch.

Similarly for download: How to schedule an automatic FTP download on Windows?

WinSCP can even generate a script from an imported FileZilla session.

For details, see the guide to FileZilla automation.

(I'm the author of WinSCP)

Another option, if you are using SFTP, is the psftp.exe client from PuTTY suite.

CSS Selector "(A or B) and C"?

Not yet, but there is the experimental :matches() pseudo-class function that does just that:

:matches(.a .b) .c {
  /* stuff goes here */

You can find more info on it here and here. Currently, most browsers support its initial version :any(), which works the same way, but will be replaced by :matches(). We just have to wait a little more before using this everywhere (I surely will).

How to document a method with parameter(s)?

Docstrings are only useful within interactive environments, e.g. the Python shell. When documenting objects that are not going to be used interactively (e.g. internal objects, framework callbacks), you might as well use regular comments. Here’s a style I use for hanging indented comments off items, each on their own line, so you know that the comment is applying to:

def Recomputate \
      # the rotary gyrator to operate on
      # the computrons to perform the recomputation with
      # whether to recomputate forthwith or at one's leisure
  ) :
  # recomputates the specified rotary gyrator with
  # the desired computrons.
#end Recomputate

You can’t do this sort of thing with docstrings.

How to run or debug php on Visual Studio Code (VSCode)

If you don't want to install xDebug or other extensions and just want to run a PHP file without debugging, you can accomplish this using build tasks.

Using Build Tasks

First open the command palette (Ctrl+Shift+P in Windows, ?+Shift+P in Mac), and select "Tasks:Open User Tasks". Now copy my configuration below into your tasks.json file. This creates user-level tasks which can be used any time and in any workspace.

    "version": "2.0.0",
    "tasks": [
            "label": "Start Server",
            "type": "shell",
            "command": "php -S localhost:8080 -t ${fileDirname}",
            "isBackground": true,
            "group": "build",
            "problemMatcher": []
            "label": "Run In Browser",
            "type": "shell",
            "command": "open http://localhost:8080/${fileBasename}",
            "windows": {
                "command": "explorer 'http://localhost:8080/${fileBasename}'"
            "group": "build",
            "problemMatcher": []
            "label": "Run In Terminal",
            "type": "shell",
            "command": "php ${file}",
            "group": "none",
            "problemMatcher": []

If you want to run your php file in the terminal, open the command palette and select "Tasks: Run Task" followed by "Run In Terminal".

If you want to run your code on a webserver which serves a response to a web browser, open the command palette and select "Tasks: Run Task" followed by "Start Server" to run PHP's built-in server, then "Run In Browser" to run the currently open file from your browser.

Note that if you already have a webserver running, you can remove the Start Server task and update the localhost:8080 part to point to whatever URL you are using.

Using PHP Debug

Note: This section was in my original answer. I originally thought that it works without PHP Debug but it looks like PHP Debug actually exposes the php type in the launch configuration. There is no reason to use it over the build task method described above. I'm keeping it here in case it is useful.

Copy the following configuration into your user settings:

    "launch": {
        "version": "0.2.0",
        "configurations": [
            "type": "php",
            "request": "launch",
            "name": "Run using PHP executable",
            "program": "${file}",
            "runtimeExecutable": "/usr/bin/php"
    // all your other user settings...

This creates a global launch configuration that you can use on any PHP file. Note the runtimeExecutable option. You will need to update this with the path to the PHP executable on your machine. After you copy the configuration above, whenever you have a PHP file open, you can press the F5 key to run the PHP code and have the output displayed in the vscode terminal.

How to return a resolved promise from an AngularJS Service using $q?

For shorter JavaScript-Code use this:

myApp.service('userService', [
  '$q', function($q) {
    this.initialized = $q.when();
    this.user = {
      access: false
    this.isAuthenticated = function() {
      this.user = {
        first_name: 'First',
        last_name: 'Last',
        email: '[email protected]',
        access: 'institution'
      return this.initialized;

You know that you loose the binding to userService.user by overwriting it with a new object instead of setting only the objects properties?

Here is what I mean as a example of my example code (Working example:

angular.module('myApp', []).service('userService', [
    '$http', '$q', '$rootScope', '$location', function ($http, $q, $rootScope, $location) {
    this.initialized = $q.when(null);
    this.user = {
        access: false
    this.isAuthenticated = function () {
        this.user.first_name = 'First';
        this.user.last_name = 'Last'; = '[email protected]';
        this.user.access = 'institution';
        return this.initialized;

angular.module('myApp').controller('myCtrl', ['$scope', 'userService', function ($scope, userService) {
    $scope.user = userService.user;
    $scope.callUserService = function () {
        userService.isAuthenticated().then(function () {
            $scope.thencalled = true;

How to check if std::map contains a key without doing insert?

Use my_map.count( key ); it can only return 0 or 1, which is essentially the Boolean result you want.

Alternately my_map.find( key ) != my_map.end() works too.

What is the difference between a static method and a non-static method?

Sometimes, you want to have variables that are common to all objects. This is accomplished with the static modifier.

i.e. class human - number of heads (1) is static, same for all humans, however human - haircolor is variable for each human.

Notice that static vars can also be used to share information across all instances

Is there any native DLL export functions viewer?

you can use Dependency Walker to view the function name. you can see the function's parameters only if it's decorated. read the following from the FAQ:

How do I view the parameter and return types of a function? For most functions, this information is simply not present in the module. The Windows' module file format only provides a single text string to identify each function. There is no structured way to list the number of parameters, the parameter types, or the return type. However, some languages do something called function "decoration" or "mangling", which is the process of encoding information into the text string. For example, a function like int Foo(int, int) encoded with simple decoration might be exported as _Foo@8. The 8 refers to the number of bytes used by the parameters. If C++ decoration is used, the function would be exported as ?Foo@@YGHHH@Z, which can be directly decoded back to the function's original prototype: int Foo(int, int). Dependency Walker supports C++ undecoration by using the Undecorate C++ Functions Command.

"%%" and "%/%" for the remainder and the quotient

I think it is because % has often be associated with the modulus operator in many programming languages.

It is the case, e.g., in C, C++, C# and Java, and many other languages which derive their syntax from C (C itself took it from B).

C# - Making a Process.Start wait until the process has start-up

I also needed this once, and I did a check on the window title of the process. If it is the one you expect, you can be sure the application is running. The application I was checking needed some time for startup and this method worked fine for me.

var process = Process.Start("popup.exe");
while(process.MainWindowTitle != "Title")

Cannot insert explicit value for identity column in table 'table' when IDENTITY_INSERT is set to OFF

The best solution is to use annotation GeneratedValue(strategy = ...), i.e.

@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column ...
private int OperationID;

it says, that this column is generated by database using IDENTITY strategy and you don't need to take care of - database will do it.

MVC4 DataType.Date EditorFor won't display date value in Chrome, fine in Internet Explorer

Reply to MVC4 DataType.Date EditorFor won't display date value in Chrome, fine in IE

In the Model you need to have following type of declaration:

public DateTime? DateXYZ { get; set; }


public Nullable<System.DateTime> DateXYZ { get; set; }

You don't need to use following attribute:

[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]

At the Date.cshtml use this template:

@model Nullable<DateTime>
@using System.Globalization;

    DateTime dt = DateTime.Now;
    if (Model != null)
        dt = (System.DateTime)Model;


    if (Request.Browser.Type.ToUpper().Contains("IE") || Request.Browser.Type.Contains("InternetExplorer"))
        @Html.TextBox("", String.Format("{0:d}", dt.ToShortDateString()), new { @class = "datefield", type = "date" })
        //Tested in chrome
        DateTimeFormatInfo dtfi = CultureInfo.CreateSpecificCulture("en-US").DateTimeFormat;
        dtfi.DateSeparator = "-";
        dtfi.ShortDatePattern = @"yyyy/MM/dd"; 
        @Html.TextBox("", String.Format("{0:d}", dt.ToString("d", dtfi)), new { @class = "datefield", type = "date" })

Have fun! Regards, Blerton

SQL Error: ORA-00922: missing or invalid option

The error you're getting appears to be the result of the fact that there is no underscore between "chartered" and "flight" in the table name. I assume you want something like this where the name of the table is chartered_flight.

CREATE TABLE chartered_flight(flight_no NUMBER(4) PRIMARY KEY
, customer_id NUMBER(6) REFERENCES customer(customer_id)
, aircraft_no NUMBER(4) REFERENCES aircraft(aircraft_no)
, flight_type VARCHAR2 (12)
, flight_date DATE NOT NULL
, takeoff_at CHAR (3) NOT NULL
, destination CHAR (3) NOT NULL)

Generally, there is no benefit to declaring a column as CHAR(3) rather than VARCHAR2(3). Declaring a column as CHAR(3) doesn't force there to be three characters of (useful) data. It just tells Oracle to space-pad data with fewer than three characters to three characters. That is unlikely to be helpful if someone inadvertently enters an incorrect code. Potentially, you could declare the column as VARCHAR2(3) and then add a CHECK constraint that LENGTH(takeoff_at) = 3.

CREATE TABLE chartered_flight(flight_no NUMBER(4) PRIMARY KEY
, customer_id NUMBER(6) REFERENCES customer(customer_id)
, aircraft_no NUMBER(4) REFERENCES aircraft(aircraft_no)
, flight_type VARCHAR2 (12)
, flight_date DATE NOT NULL
, takeoff_at CHAR (3) NOT NULL CHECK( length( takeoff_at ) = 3 )
, destination CHAR (3) NOT NULL CHECK( length( destination ) = 3 )

Since both takeoff_at and destination are airport codes, you really ought to have a separate table of valid airport codes and define foreign key constraints between the chartered_flight table and this new airport_code table. That ensures that only valid airport codes are added and makes it much easier in the future if an airport code changes.

And from a naming convention standpoint, since both takeoff_at and destination are airport codes, I would suggest that the names be complementary and indicate that fact. Something like departure_airport_code and arrival_airport_code, for example, would be much more meaningful.

Run chrome in fullscreen mode on Windows

Update 03-Oct-19

new script that displays 10second countdown then launches chrome/chromiumn in fullscreen kiosk mode.

more updates to chrome required script update to allow autoplaying video with audio. Note --overscroll-history-navigation=0 isn't working currently will need to disable this flag by going to chrome://flags/#overscroll-history-navigation in your browser and setting to disabled.

@echo off
echo Countdown to application launch...
timeout /t 10
"C:\Program Files (x86)\chrome-win32\chrome.exe" --chrome --kiosk http://localhost/xxxx --incognito --disable-pinch --no-user-gesture-required --overscroll-history-navigation=0

might need to set chrome://flags/#autoplay-policy if running an older version of chrome (60 below)

Update 11-May-16

There have been many updates to chrome since I posted this and have had to alter the script alot to keep it working as I needed.

Couple of issues with newer versions of chrome:

  • built in pinch to zoom
  • Chrome restore error always showing after forced shutdown
  • auto update popup

Because of the restore error switched out to incognito mode as this launches a clear version all the time and does not save what the user was viewing and so if it crashes there is nothing to restore. Also the auto up in newer versions of chrome being a pain to try and disable I switched out to use chromium as it does not auto update and still gives all the modern features of chrome. Note make sure you download the top version of chromium this comes with all audio and video codecs as the basic version of chromium does not support all codecs.

Chromium download link

@echo off

echo Step 1 of 2: Waiting a few seconds before starting the Kiosk...

"C:\windows\system32\ping" -n 5 -w 1000 >NUL

echo Step 2 of 5: Waiting a few more seconds before starting the browser...

"C:\windows\system32\ping" -n 5 -w 1000 >NUL

echo Final 'invisible' step: Starting the browser, Finally...

"C:\Program Files (x86)\Google\Chromium\chrome.exe" --chrome --kiosk --incognito --disable-pinch --overscroll-history-navigation=0



I use this for exhibitions to lock down screens. I think its what your looking for.

  • Start chrome and go to drag and drop the url out onto the desktop
  • rename it to something handy for this example google_homepage
  • drop this now into your c directory, click on my computer c: and drop this file in there
  • start chrome again go to settings and under on start up select open a specific page and set your home page here.

Next part is the script that I use to start close and restart chrome again in kiosk mode. The locations is where I have chrome installed so it might be abit different for you depending on your install.

Open your text editor of choice or just notepad and past the below code in, make sure its in the same format/order as below. Save it to your desktop as what ever you like so for this example chrome_startup_script.txt next right click it and rename, remove the txt from the end and put in bat instead. double click this to launch the script to see if its working correctly.

A command line box should appear and run through the script, chrome will start and then close down the reason to do this is to remove any error reports such as if the pc crashed, when chrome starts again without this it would show the yellow error bar at the top saying chrome did not shut down properly would you like to restore it. After a few seconds chrome should start again and in kiosk mode and will point to what ever homepage you have set.

@echo off
echo Step 1 of 5: Waiting a few seconds before starting the Kiosk...
"C:\windows\system32\ping" -n 31 -w 1000 >NUL
echo Step 2 of 5: Starting browser as a pre-start to delete error messages...
echo Step 3 of 5: Waiting a few seconds before killing the browser task...
"C:\windows\system32\ping" -n 11 -w 1000 >NUL
echo Step 4 of 5: Killing the browser task gracefully to avoid session restore...
Taskkill /IM chrome.exe
echo Step 5 of 5: Waiting a few seconds before restarting the browser...
"C:\windows\system32\ping" -n 11 -w 1000 >NUL
echo Final 'invisible' step: Starting the browser, Finally...
"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --kiosk --overscroll-history-navigation=0"

Note: The number after the -n of the ping is the amount of seconds (minus one second) to wait before starting the link (or application in the next line)

Finally if this is all working then you can drag and drop the .bat file into the startup folder in windows and this script will launch each time windows starts.


With recent versions of chrome they have really got into enabling touch gestures, this means that swiping left or right on a touchscreen will cause the browser to go forward or backward in history. To prevent this we need to disable the history navigation on the back and forward buttons to do that add the following --overscroll-history-navigation=0 to the end of the script.

invalid use of non-static data member

In C++, nested classes are not connected to any instance of the outer class. If you want bar to access non-static members of foo, then bar needs to have access to an instance of foo. Maybe something like:

class bar {
    int getA(foo & f ) {return foo.a;}

Or maybe

class bar {
    foo & f;

    bar(foo & g)
    : f(g)

    int getA() { return f.a; }

In any case, you need to explicitly make sure you have access to an instance of foo.

adding css file with jquery

Try doing it the other way around.

$('<link rel="stylesheet" href="css/style2.css" type="text/css" />').appendTo('head');

sys.path different in Jupyter and Python - how to import own modules in Jupyter?

Jupyter is base on ipython, a permanent solution could be changing the ipython config options.

Create a config file

$ ipython profile create
$ ipython locate

Edit the config file

$ cd /Users/username/.ipython
$ vi profile_default/

The following lines allow you to add your module path to sys.path

c.InteractiveShellApp.exec_lines = [
    'import sys; sys.path.append("/path/to/your/module")'

At the jupyter startup the previous line will be executed

Here you can find more details about ipython config

Init function in javascript and how it works

The way I usually explain this to people is to show how it's similar to other JavaScript patterns.

First, you should know that there are two ways to declare a function (actually, there's at least five, but these are the two main culprits):

function foo() {/*code*/}


var foo = function() {/*code*/};

Even if this construction looks strange, you probably use it all the time when attaching events:


You should notice that the second form is not much different from a regular variable declaration:

var bar = 5;
var baz = 'some string';
var foo = function() {/*code*/};

But in JavaScript, you always have the choice between using a value directly or through a variable. If bar is 5, then the next two statements are equivalent:

var myVal = bar * 100; // use 'bar'
var myVal = 5 * 100;   // don't use 'bar'

Well, if you can use 5 on its own, why can't you use function() {\*code*\} on its own too? In fact, you can. And that's called an anonymous function. So these two examples are equivalent as well:

var foo = function() {/*code*/}; // use 'foo'

(function(){/*code*/})();        // don't use 'foo' 

The only difference you should see is in the extra brackets. That's simply because if you start a line with the keyword function, the parser will think you are declaring a function using the very first pattern at the top of this answer and throw a syntax error exception. So wrap your entire anonymous function inside a pair of braces and the problem goes away.

In other words, the following three statements are valid:

5;                        // pointless and stupid
'some string';            // pointless and stupid
(function(){/*code*/})(); // wonderfully powerful

[EDIT in 2020]

The previous version of my answer recommended Douglas Crockford's form of parens-wrapping for these "immediately invoked anonymous functions". User @RayLoveless recommended in 2012 to use the version shown now. Back then, before ES6 and arrow functions, there was no obvious idiomatic difference; you simply had to prevent the statement starting with the function keyword. In fact, there were lots of ways to do that. But using parens, these two statements were syntactically and idiomatically equivalent:

( function() { /* code */}() );
( function() { /* code */} )();

But user @zentechinc's comment below reminds me that arrow functions change all this. So now only one of these statements is correct.

( () => { /* code */ }() ); // Syntax error
( () => { /* code */ } )();

Why on earth does this matter? Actually, it's pretty easy to demonstrate. Remember an arrow function can come in two basic forms:

() => { return 5; };       // With a function body
() => { console.log(5); };

() => 5;                   // Or with a single expression
() => console.log(5);

Without parens wrapping this second type of arrow function, you end up with an idiomatic mess:

() => 5();              // How do you invoke a 5?
() => console.log(5)(); // console.log does not return a function!

How do I add an integer value with javascript (jquery) to a value that's returning a string?

Parse int is the tool you should use here, but like any tool it should be used correctly. When using parseInt you should always use the radix parameter to ensure the correct base is used

var currentValue = parseInt($("#replies").text(),10);

How to set the size of a column in a Bootstrap responsive table

you can use the following Bootstrap class with

<tr class="w-25">


for more details check the following page

Are dictionaries ordered in Python 3.6+?

To fully answer this question in 2020, let me quote several statements from official Python docs:

Changed in version 3.7: Dictionary order is guaranteed to be insertion order. This behavior was an implementation detail of CPython from 3.6.

Changed in version 3.7: Dictionary order is guaranteed to be insertion order.

Changed in version 3.8: Dictionaries are now reversible.

Dictionaries and dictionary views are reversible.

A statement regarding OrderedDict vs Dict:

Ordered dictionaries are just like regular dictionaries but have some extra capabilities relating to ordering operations. They have become less important now that the built-in dict class gained the ability to remember insertion order (this new behavior became guaranteed in Python 3.7).

WPF checkbox binding

if you have the property "MyProperty" on your data-class, then you bind the IsChecked like this.... (the converter is optional, but sometimes you need that)

<local:MyBoolConverter x:Key="MyBoolConverterKey"/>
<checkbox IsChecked="{Binding Path=MyProperty, Converter={StaticResource MyBoolConverterKey}}"/>

How do I reload a page without a POSTDATA warning in Javascript?

Just changing window.location in JavaScript is dangerous because the user could still hit the back button and resubmit the post, which could have unexpected results (such as a duplicate purchase). PRG is a much better solution

Use the Post/Redirect/Get (PRG) pattern

To avoid this problem, many web applications use the PRG pattern — instead of returning an HTML page directly, the POST operation returns a redirection command (using the HTTP 303 response code (sometimes 302) together with the HTTP "Location" response header), instructing the browser to load a different page using an HTTP GET request. The result page can then safely be bookmarked or reloaded without unexpected side effects.

Parsing JSON in Excel VBA

This works for me under Excel and a big JSON files using JSON query translated in to native form. I am able parse node like "item.something" and get value using simple command:

MsgBox Json("item")("something")

What's nice.

Hide text within HTML?

You said that you can’t use HTML comments because the CMS filters them out. So I assume that you really want to hide this content and you don’t need to display it ever.

In that case, you shouldn’t use CSS (only), as you’d only play on the presentation level, not affecting the content level. Your content should also be hidden for user-agents ignoring the CSS (people using text browsers, feed readers, screen readers; bots; etc.).

In HTML5 there is the global hidden attribute:

When specified on an element, it indicates that the element is not yet, or is no longer, directly relevant to the page's current state, or that it is being used to declare content to be reused by other parts of the page as opposed to being directly accessed by the user. User agents should not render elements that have the hidden attribute specified.

Example (using the small element here, because it’s an "attribution"):

<small hidden>Thanks to John Doe for this idea.</small>

As a fallback (for user-agents that don’t know the hidden attribute), you can specify in your CSS:

[hidden] {display:none;}

An general element for plain text could be the script element used as "data block":

<script type="text/plain" hidden>
Thanks to John Doe for this idea.

Alternatively, you could also use data-* attributes on existing elements (resp. on new div elements if you want to group some elements for the attribution):

<p data-attribution="Thanks to John Doe for this idea!">This is some visible example content …</p>

How to add text to an existing div with jquery

$(function () {_x000D_
  $('#Add').click(function () {_x000D_
<script src=""></script>_x000D_
 <div id="Content">_x000D_
    <button id="Add">Add<button>_x000D_

How to open warning/information/error dialog in Swing?

See How to Make Dialogs.

You can use:

JOptionPane.showMessageDialog(frame, "Eggs are not supposed to be green.");

And you can also change the symbol to an error message or an warning. E.g see JOptionPane Features.

JavaFX How to set scene background image

In addition to @Elltz answer, we can use both fill and image for background:

            new Background(
                    Collections.singletonList(new BackgroundFill(
                            new CornerRadii(500), 
                            new Insets(10))),
                    Collections.singletonList(new BackgroundImage(
                            new Image("image/logo.png", 100, 100, false, true),


                new Background(
                        Collections.singletonList(new BackgroundFill(
                                new CornerRadii(0),
                                new Insets(0))),
                        Collections.singletonList(new BackgroundImage(
                                new Image("file:clouds.jpg", 100, 100, false, true),
                                new BackgroundSize(1.0, 1.0, true, true, false, false)

(different last argument) to make the image full-window size.

java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1888, result=0, data=null} to activity

Adding this first conditional should work:

protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
    if(resultCode != RESULT_CANCELED){
        if (requestCode == CAMERA_REQUEST) {  
            Bitmap photo = (Bitmap) data.getExtras().get("data"); 

How do I set hostname in docker-compose?

The simplest way I have found is to just set the container name in the docker-compose.yml See container_name documentation. It is applicable to docker-compose v1+. It works for container to container, not from the host machine to container.

    image: phensley/docker-dns
    container_name: affy

Now you should be able to access affy from other containers using the container name. I had to do this for multiple redis servers in a development environment.

NOTE The solution works so long as you don't need to scale. Such as consistant individual developer environments.

How to set $_GET variable

I know this is an old thread, but I wanted to post my 2 cents...

Using Javascript you can achieve this without using $_POST, and thus avoid reloading the page..

function ButtonPressed()
window.location='index.php?view=next'; //this will set $_GET['view']='next'

<button type='button' onClick='ButtonPressed()'>Click me!</button>

          echo "This will display after pressing the 'Click Me' button!";

What version of javac built my jar?

Following up on @David J. Liszewski's answer, I ran the following commands to extract the jar file's manifest on Ubuntu:

# Determine the manifest file name:
$ jar tf LuceneSearch.jar | grep -i manifest

# Extract the file:
$ sudo jar xf LuceneSearch.jar META-INF/MANIFEST.MF

# Print the file's contents:
Manifest-Version: 1.0
Ant-Version: Apache Ant 1.8.2
Created-By: 1.7.0_25-b30 (Oracle Corporation)
Main-Class: org.wikimedia.lsearch.config.StartupManager

Android Studio installation on Windows 7 fails, no JDK found

For me, the problem was that I had changed the GC vm arg to -XX:+UseParallelGC in the C:\Users\<username>\.AndroidStudio2.1\studio64.exe.vmoptions file. That's what I use in Eclipse and I was trying various things to get AndroidStudio half way as efficent as Eclipse. I restored the GC to -XX:+UseConcMarkSweepGC.

Functional, Declarative, and Imperative Programming

Declarative programming is programming by expressing some timeless logic between the input and the output, for instance, in pseudocode, the following example would be declarative:

def factorial(n):
  if n < 2:
    return 1
    return factorial(n-1)

output = factorial(argvec[0])

We just define a relationship called the 'factorial' here, and defined the relationship between the output and the input as the that relationship. As should be evident here, about any structured language allows declarative programming to some extend. A central idea of declarative programming is immutable data, if you assign to a variable, you only do so once, and then never again. Other, stricter definitions entail that there may be no side-effects at all, these languages are some times called 'purely declarative'.

The same result in an imperative style would be:

a = 1
b = argvec[0]
while(b < 2):
  a * b--

output = a

In this example, we expressed no timeless static logical relationship between the input and the output, we changed memory addresses manually until one of them held the desired result. It should be evident that all languages allow declarative semantics to some extend, but not all allow imperative, some 'purely' declarative languages permit side effects and mutation altogether.

Declarative languages are often said to specify 'what must be done', as opposed to 'how to do it', I think that is a misnomer, declarative programs still specify how one must get from input to output, but in another way, the relationship you specify must be effectively computable (important term, look it up if you don't know it). Another approach is nondeterministic programming, that really just specifies what conditions a result much meet, before your implementation just goes to exhaust all paths on trial and error until it succeeds.

Purely declarative languages include Haskell and Pure Prolog. A sliding scale from one and to the other would be: Pure Prolog, Haskell, OCaml, Scheme/Lisp, Python, Javascript, C--, Perl, PHP, C++, Pascall, C, Fortran, Assembly

To show only file name without the entire directory path

I prefer the base name which is already answered by fge. Another way is :

ls /home/user/new/*.txt|awk -F"/" '{print $NF}'

one more ugly way is :

ls /home/user/new/*.txt| perl -pe 's/\//\n/g'|tail -1

Looping over a list in Python

Here is the solution I was looking for. If you would like to create List2 that contains the difference of the number elements in List1.

list1 = [12, 15, 22, 54, 21, 68, 9, 73, 81, 34, 45]
list2 = []
for i in range(1, len(list1)):
  change = list1[i] - list1[i-1]

Note that while len(list1) is 11 (elements), len(list2) will only be 10 elements because we are starting our for loop from element with index 1 in list1 not from element with index 0 in list1

Getting the last n elements of a vector. Is there a better way than using the length() function?

Here is a function to do it and seems reasonably fast.

stop("Length of value greater than length of vector")




                                                    test replications elapsed relative
1                                 expression(tail(x, 5))       100000    5.24    6.469
2 expression(x[ = length(x), length.out = 5)])       100000    0.98    1.210
3                       expression(x[length(x) - (4:0)])       100000    0.81    1.000
4                                 expression(endv(x, 5))       100000    1.37    1.691

Show / hide div on click with CSS

A little hack-ish but it works. Note that the label tag can be placed any where. The key parts are:

  • The css input:checked+div selects the div immediately next to/after the input
  • The label for said checkbox (or hey leave out the label and just have the checkbox)
  • display:none hides stuff


        #sidebar {height:100%; background:blue; width:200px; clear:none; float:left;}
        #content {height:100%; background:green; width:400px; clear:none; float:left;}
        label {background:yellow;float:left;}
<label for="hider">Hide</label>
<input type="checkbox" id="hider">
<div id="sidebar">foo</div>

<div id="content">hello</div>


EDIT: Sorry could have read the question better.

One could also use css3 elements to create the slide/fade effect. I am not familiar enough with them to be much help with that aspect but they do exist. Browser support is iffy though.

You could combine the above effect with javascript to use fancy transitions and still have a fall back. jquery has a css method to override the above and slide and fade for transitions.

  • Tilda(~) mean some sibling after; not next sibling like plus(+).
  • [key="value"] is an attribute selector.
  • Radio buttons must have same name

To string tabs together one could use:

input[value="1"]:checked ~ div[id="1"]{
input[value="2"]:checked ~ div[id="2"]{
<input type="radio" name="hider" value="1">
<input type="radio" name="hider" value="2">
<div id="1">div 1</div>
<div id="2">div 2</div>

Update Row if it Exists Else Insert Logic with Entity Framework

Ladislav's answer was close but I had to made a couple of modifications to get this to work in EF6 (database-first). I extended my data context with my on AddOrUpdate method and so far this appears to be working well with detached objects:

using System.Data.Entity;


public partial class MyDBEntities {

  public void AddOrUpdate(MyDBEntities ctx, DbSet set, Object obj, long ID) {
      if (ID != 0) {
          ctx.Entry(obj).State = EntityState.Modified;
      else {

.NET String.Format() to add commas in thousands place for a number

String.Format("0,###.###"); also works with decimal places

How can I select from list of values in Oracle

There are various ways to take a comma-separated list and parse it into multiple rows of data. In SQL

SQL> ed
Wrote file afiedt.buf

  1  with x as (
  2    select '1,2,3,a,b,c,d' str from dual
  3  )
  4   select regexp_substr(str,'[^,]+',1,level) element
  5     from x
  6* connect by level <= length(regexp_replace(str,'[^,]+')) + 1
SQL> /


7 rows selected.

Or in PL/SQL

SQL> create type str_tbl is table of varchar2(100);
  2  /

Type created.

SQL> create or replace function parse_list( p_list in varchar2 )
  2    return str_tbl
  3    pipelined
  4  is
  5  begin
  6    for x in (select regexp_substr( p_list, '[^,]', 1, level ) element
  7                from dual
  8             connect by level <= length( regexp_replace( p_list, '[^,]+')) + 1)
  9    loop
 10      pipe row( x.element );
 11    end loop
 12    return;
 13  end;
 15  /

Function created.

SQL> select *
  2    from table( parse_list( 'a,b,c,1,2,3,d,e,foo' ));


9 rows selected.

How do I import CSV file into a MySQL table?

Try this, it worked for me


IGNORE 1 ROWS here ignores the first row which contains the fieldnames. Note that for the filename you must type the absolute path of the file.

How to clone object in C++ ? Or Is there another solution?

If your object is not polymorphic (and a stack implementation likely isn't), then as per other answers here, what you want is the copy constructor. Please note that there are differences between copy construction and assignment in C++; if you want both behaviors (and the default versions don't fit your needs), you'll have to implement both functions.

If your object is polymorphic, then slicing can be an issue and you might need to jump through some extra hoops to do proper copying. Sometimes people use as virtual method called clone() as a helper for polymorphic copying.

Finally, note that getting copying and assignment right, if you need to replace the default versions, is actually quite difficult. It is usually better to set up your objects (via RAII) in such a way that the default versions of copy/assign do what you want them to do. I highly recommend you look at Meyer's Effective C++, especially at items 10,11,12.

Trying to get property of non-object - Laravel 5

Is your query returning array or object? If you dump it out, you might find that it's an array and all you need is an array access ([]) instead of an object access (->).

Reset select2 value and show placeholder

I was also having this problem and it stems from val(null).trigger("change"); throwing a No select2/compat/inputData error before the placeholder gets reset. I solved it by catching the error and setting the placeholder directly (along with a width). Note: If you have more than one you will need to catch each one.

$('.select2-search__field')[0].placeholder='All Items';
$('.select2-search__field')[1].placeholder='All Locations';

I'm running Select2 4.0.3

Array slices in C#

Here's a simple extension method that returns a slice as a new array:

public static T[] Slice<T>(this T[] arr, uint indexFrom, uint indexTo) {
    if (indexFrom > indexTo) {
        throw new ArgumentOutOfRangeException("indexFrom is bigger than indexTo!");

    uint length = indexTo - indexFrom;
    T[] result = new T[length];
    Array.Copy(arr, indexFrom, result, 0, length);

    return result;

Then you can use it as:

byte[] slice = foo.Slice(0, 40);

jQuery AJAX file upload PHP

Use pure js

async function saveFile() _x000D_
    let formData = new FormData();           _x000D_
    formData.append("file", sortpicture.files[0]);_x000D_
    await fetch('/uploads', {method: "POST", body: formData});    _x000D_
<input id="sortpicture" type="file" name="sortpic" />_x000D_
<button id="upload" onclick="saveFile()">Upload</button>_x000D_
<br>Before click upload look on chrome>console>network (in this snipped we will see 404)

The filename is automatically included to request and server can read it, the 'content-type' is automatically set to 'multipart/form-data'. Here is more developed example with error handling and additional json sending

async function saveFile(inp) _x000D_
    let user = { name:'john', age:34 };_x000D_
    let formData = new FormData();_x000D_
    let photo = inp.files[0];      _x000D_
    formData.append("photo", photo);_x000D_
    formData.append("user", JSON.stringify(user));  _x000D_
    try {_x000D_
       let r = await fetch('/upload/image', {method: "POST", body: formData}); _x000D_
       console.log('HTTP response code:',r.status); _x000D_
    } catch(e) {_x000D_
       console.log('Huston we have problem...:', e);_x000D_
<input type="file" onchange="saveFile(this)" >_x000D_
Before selecting the file Open chrome console > network tab to see the request details._x000D_
<small>Because in this example we send request to the response code will be 404 ofcourse...</small>

How do I get a background location update every n minutes in my iOS application?

Now that iOS6 is out the best way to have a forever running location services is...

- (void)applicationWillResignActive:(UIApplication *)application
 Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
 Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.

NSLog(@"to background");

app.isInBackground = TRUE;

UIApplication *app = [UIApplication sharedApplication];

// Request permission to run in the background. Provide an
// expiration handler in case the task runs long.
NSAssert(bgTask == UIBackgroundTaskInvalid, nil);

bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
    // Synchronize the cleanup call on the main thread in case
    // the task actually finishes at around the same time.
    dispatch_async(dispatch_get_main_queue(), ^{

        if (bgTask != UIBackgroundTaskInvalid)
            [app endBackgroundTask:bgTask];
            bgTask = UIBackgroundTaskInvalid;

// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    // Do the work associated with the task.

    locationManager.distanceFilter = 100;
    locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
    [locationManager startMonitoringSignificantLocationChanges];
    [locationManager startUpdatingLocation];

    NSLog(@"App staus: applicationDidEnterBackground");
    // Synchronize the cleanup call on the main thread in case
    // the expiration handler is fired at the same time.
    dispatch_async(dispatch_get_main_queue(), ^{
        if (bgTask != UIBackgroundTaskInvalid)
            [app endBackgroundTask:bgTask];
            bgTask = UIBackgroundTaskInvalid;

NSLog(@"backgroundTimeRemaining: %.0f", [[UIApplication sharedApplication] backgroundTimeRemaining]);


Just tested it like that:

I started the app, go background and move in the car by some minutes. Then I go home for 1 hour and start moving again (without opening again the app). Locations started again. Then stopped for two hours and started again. Everything ok again...

DO NOT FORGET USING the new location services in iOS6

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
    CLLocation *loc = [locations lastObject];

    // Lat/Lon
    float latitudeMe = loc.coordinate.latitude;
    float longitudeMe = loc.coordinate.longitude;

Where can I find a list of Mac virtual key codes?

The more canonical reference is in <HIToolbox/Events.h>:


In newer Versions of MacOS the "Events.h" moved to here:


Is it better to use "is" or "==" for number comparison in Python?

Others have answered your question, but I'll go into a little bit more detail:

Python's is compares identity - it asks the question "is this one thing actually the same object as this other thing" (similar to == in Java). So, there are some times when using is makes sense - the most common one being checking for None. Eg, foo is None. But, in general, it isn't what you want.

==, on the other hand, asks the question "is this one thing logically equivalent to this other thing". For example:

>>> [1, 2, 3] == [1, 2, 3]
>>> [1, 2, 3] is [1, 2, 3]

And this is true because classes can define the method they use to test for equality:

>>> class AlwaysEqual(object):
...     def __eq__(self, other):
...         return True
>>> always_equal = AlwaysEqual()
>>> always_equal == 42
>>> always_equal == None

But they cannot define the method used for testing identity (ie, they can't override is).

How can I prevent a window from being resized with tkinter?

This is a variant of an existing solution already provided above:

import tkinter as tk

root = tk.Tk()
root.resizable(0, 0)

The advantage is that you type less.

Ant if else condition?

The quirky syntax using conditions on the target (described by Mads) is the only supported way to perform conditional execution in core ANT.

ANT is not a programming language and when things get complicated I choose to embed a script within my build as follows:

<target name="prepare-copy" description="copy file based on condition">
        if (properties["some.condition"] == "true") {
            ant.copy(file:"${properties["some.dir"]}/true", todir:".")

ANT supports several languages (See script task), my preference is Groovy because of it's terse syntax and because it plays so well with the build.

Apologies, David I am not a fan of ant-contrib.

How to insert text with single quotation sql server 2005

You asked how to escape an Apostrophe character (') in SQL Server. All the answers above do an excellent job of explaining that.

However, depending on the situation, the Right single quotation mark character (’) might be appropriate.

(No escape characters needed)

-- Direct insert
INSERT INTO Table1 (Column1) VALUES ('John’s')

• Apostrophe (U+0027)

Ascii Apostrophe on Wikipedia

• Right single quotation mark (U+2019)

Unicode Right single quotation on Wikipedia

Invariant Violation: Could not find "store" in either the context or props of "Connect(SportsDatabase)"

This happened to me when I upgraded. I had to downgrade back.

react-redux ^5.0.6 ? ^7.1.3

print variable and a string in python

Assuming you use Python 2.7 (not 3):

print "I have", card.price (as mentioned above).

print "I have %s" % card.price (using string formatting)

print " ".join(map(str, ["I have", card.price])) (by joining lists)

There are a lot of ways to do the same, actually. I would prefer the second one.

Google maps responsive resize

After few years, I moved to leaflet map and I have fixed this issue completely, the following could be applied to google maps too:

    var headerHeight = $("#navMap").outerHeight();
    var footerHeight = $("footer").outerHeight();
    var windowHeight = window.innerHeight;
    var mapContainerHeight = headerHeight + footerHeight;
    var totalMapHeight = windowHeight - mapContainerHeight;
    $("#map").css("margin-top", headerHeight);

        var headerHeight = $("#navMap").outerHeight();
        var footerHeight = $("footer").outerHeight();
        var windowHeight = window.innerHeight;
        var mapContainerHeight = headerHeight + footerHeight;
        var totalMapHeight = windowHeight - mapContainerHeight;
        $("#map").css("margin-top", headerHeight);

Declaring and using MySQL varchar variables

This works fine for me using MySQL 5.1.35:


DROP PROCEDURE IF EXISTS `example`.`test` $$
CREATE PROCEDURE `example`.`test` ()

  DECLARE FOO varchar(7);
  DECLARE oldFOO varchar(7);
  SET FOO = '138';
  SET oldFOO = CONCAT('0', FOO);

  update mypermits
     set person = FOO
   where person = oldFOO;

END $$



DROP TABLE IF EXISTS `example`.`mypermits`;
CREATE TABLE  `example`.`mypermits` (
  `person` varchar(7) NOT NULL

INSERT INTO mypermits VALUES ('0138');

CALL test()

Create a branch in Git from another branch

Create a Branch

  • Create branch when master branch is checked out. Here commits in master will be synced to the branch you created.

    $ git branch branch1

  • Create branch when branch1 is checked out . Here commits in branch1 will be synced to branch2

    $ git branch branch2

Checkout a Branch

git checkout command switch branches or restore working tree files

  • $ git checkout branchname

Renaming a Branch

  • $ git branch -m branch1 newbranchname

Delete a Branch

  • $ git branch -d branch-to-delete
  • $ git branch -D branch-to-delete ( force deletion without checking the merged status )

Create and Switch Branch

  • $ git checkout -b branchname

Branches that are completely included

  • $ git branch --merged

************************** Branch Differences [ git diff branch1..branch2 ] ************************

Multiline difference
  • $ git diff master..branch1
Singleline difference
  • $ git diff --color-words branch1..branch2

Export and import table dump (.sql) using pgAdmin

follow he steps. in pgadmin

host-DataBase-Schemas- public (click right) CREATE script- open file -(choose xxx.sql) , then click over the option execute query write result to file -export data file ok- then click in save.its all. it work to me.

note: error in version command script enter image description herede sql over pgadmin can be search, example:

enter image description here

Android - running a method periodically using postDelayed() call

Perhaps involve the activity's life-cycle methods to achieve this:

Handler handler = new Handler();

protected void onCreate(Bundle savedInstanceState) {

protected void onDestroy() {

private final Runnable sendData = new Runnable(){
    public void run(){
        try {
            //prepare and send the data here..

            handler.postDelayed(this, 1000);    
        catch (Exception e) {

In this approach, if you press back-key on your activity or call finish();, it will also stop the postDelayed callings.

How to safely upgrade an Amazon EC2 instance from t1.micro to large?

Use the AWS EC2 console, not ElasticFox.

First Way:

  • Create a new AMI of the instance
  • Launch it

Alternative Way:

  • Make a snapshot of the disk
  • Launch a large EBS instance with the same AMI type (please note that at this point the disk will contain the data that was present when this AMI was created, not your latest changes)
  • Once is fully booted, stop the new instance
  • Detach the root volume from the stopped instance
  • Create a virtual disk from the snapshot created before in the same availability zone of the new instance
  • Attach the root volume to /dev/sda1
  • Start the new instance again

Regex - how to match everything except a particular pattern


then use what group 2 captures...

Java Comparator class to sort arrays

[...] How should Java Comparator class be declared to sort the arrays by their first elements in decreasing order [...]

Here's a complete example using Java 8:

import java.util.*;

public class Test {

    public static void main(String args[]) {

        int[][] twoDim = { {1, 2}, {3, 7}, {8, 9}, {4, 2}, {5, 3} };

        Arrays.sort(twoDim, Comparator.comparingInt(a -> a[0])



[[8, 9], [5, 3], [4, 2], [3, 7], [1, 2]]

For Java 7 you can do:

Arrays.sort(twoDim, new Comparator<int[]>() {
    public int compare(int[] o1, int[] o2) {
        return[0], o1[0]);

If you unfortunate enough to work on Java 6 or older, you'd do:

Arrays.sort(twoDim, new Comparator<int[]>() {
    public int compare(int[] o1, int[] o2) {
        return ((Integer) o2[0]).compareTo(o1[0]);

Slick Carousel Uncaught TypeError: $(...).slick is not a function

I solve this by simply add 'https:' to slick cdn link gotfrom slick

Creating Roles in Identity MVC 5

My application was hanging on startup when I used Peter Stulinski & Dave Gordon's code samples with EF 6.0. I changed:

var roleManager = new RoleManager<Microsoft.AspNet.Identity.EntityFramework.IdentityRole>(new RoleStore<IdentityRole>(new ApplicationDbContext()));


var roleManager = new RoleManager<Microsoft.AspNet.Identity.EntityFramework.IdentityRole>(new RoleStore<IdentityRole>(**context**));

Which makes sense when in the seed method you don't want instantiate another instance of the ApplicationDBContext. This might have been compounded by the fact that I had Database.SetInitializer<ApplicationDbContext>(new ApplicationDbInitializer()); in the constructor of ApplicationDbContext

Why is it that "No HTTP resource was found that matches the request URI" here?

Please check the class you inherited. Whether it is simply Controller or APIController.

By mistake we might create a controller from MVC 5 controller. It should be from Web API Controller.

How to insert date values into table

let suppose we create a table Transactions using SQl server management studio

txn_id int,

txn_type_id varchar(200),

Account_id int,

Amount int,

tDate date


with date datatype we can insert values in simple format: 'yyyy-mm-dd'

INSERT INTO transactions (txn_id,txn_type_id,Account_id,Amount,tDate)
VALUES (978, 'DBT', 103, 100, '2004-01-22');

Moreover we can have differet time formats like

DATE - format YYYY-MM-DD

How do I grep for all non-ASCII characters?

In perl

perl -ane '{ if(m/[[:^ascii:]]/) { print  } }' fileName > newFile

Can I prevent text in a div block from overflowing?

there is another css property :

white-space : normal;

The white-space property controls how text is handled on the element it is applied to.

div {

  /* This is the default, you don't need to
     explicitly declare it unless overriding
     another declaration */
  white-space: normal; 


Multidimensional Lists in C#

Where does the variable results come from?

This block:

foreach (People p in ppl.results) {

Should probably read more like:

foreach (People p in ppl.results) {
    var list = new List<string>();

Convert json data to a html table

Thanks all for your replies. I wrote one myself. Please note that this uses jQuery.

Code snippet:

var myList = [_x000D_
  { "name": "abc", "age": 50 },_x000D_
  { "age": "25", "hobby": "swimming" },_x000D_
  { "name": "xyz", "hobby": "programming" }_x000D_
// Builds the HTML Table out of myList._x000D_
function buildHtmlTable(selector) {_x000D_
  var columns = addAllColumnHeaders(myList, selector);_x000D_
  for (var i = 0; i < myList.length; i++) {_x000D_
    var row$ = $('<tr/>');_x000D_
    for (var colIndex = 0; colIndex < columns.length; colIndex++) {_x000D_
      var cellValue = myList[i][columns[colIndex]];_x000D_
      if (cellValue == null) cellValue = "";_x000D_
// Adds a header row to the table and returns the set of columns._x000D_
// Need to do union of keys from all records as some records may not contain_x000D_
// all records._x000D_
function addAllColumnHeaders(myList, selector) {_x000D_
  var columnSet = [];_x000D_
  var headerTr$ = $('<tr/>');_x000D_
  for (var i = 0; i < myList.length; i++) {_x000D_
    var rowHash = myList[i];_x000D_
    for (var key in rowHash) {_x000D_
      if ($.inArray(key, columnSet) == -1) {_x000D_
  return columnSet;_x000D_
<script src=""></script>_x000D_
<body onLoad="buildHtmlTable('#excelDataTable')">_x000D_
  <table id="excelDataTable" border="1">_x000D_

Get Application Name/ Label via ADB Shell or Terminal

If you know the app id of the package (like org.mozilla.firefox), it is easy. First to get the path of actual package file of the appId,

$  adb shell pm list packages -f

Now you can do some grep|sed magic to extract the path : /data/app/

After that aapt tool comes in handy :

$  adb shell aapt dump badging /data/app/

Again some grep magic to get the Label.

How to handle "Uncaught (in promise) DOMException: play() failed because the user didn't interact with the document first." on Desktop with Chrome 66?

Try to use mousemove event lisentner

var audio = document.createElement("AUDIO")
audio.src = "./audio/rain.m4a"

document.body.addEventListener("mousemove", function () {

How to use OUTPUT parameter in Stored Procedure

There are a several things you need to address to get it working

  1. The name is wrong its not @ouput its @code
  2. You need to set the parameter direction to Output.
  3. Don't use AddWithValue since its not supposed to have a value just you Add.
  4. Use ExecuteNonQuery if you're not returning rows


SqlParameter output = new SqlParameter("@code", SqlDbType.Int);
output.Direction = ParameterDirection.Output;

Insert data to MySql DB and display if insertion is success or failure

$result = mysql_query("INSERT INTO PEOPLE (NAME ) VALUES ('COLE')"));
echo "Success";

echo "Error";


PostgreSQL - query from bash script as database user 'postgres'

PGPASSWORD=$(echo $password) psql -h -U example_user -d example_db -t -c "select * from example_table1" -o example_out.txt 

Using a scanner to accept String input and storing in a String Array

Please correct me if I'm wrong.`

public static void main(String[] args) {

    Scanner na = new Scanner(;
    System.out.println("Please enter the number of contacts: ");
    int num = na.nextInt();

    String[] contactName = new String[num];
    String[] contactPhone = new String[num];
    String[] contactAdd1 = new String[num];
    String[] contactAdd2 = new String[num];

    Scanner input = new Scanner(;

    for (int i = 0; i < num; i++) {

        System.out.println("Enter contacts name: " + (i+1));
        contactName[i] = input.nextLine();

        System.out.println("Enter contacts addressline1: " + (i+1));
        contactAdd1[i] = input.nextLine();

        System.out.println("Enter contacts addressline2: " + (i+1));
        contactAdd2[i] = input.nextLine();

        System.out.println("Enter contact phone number: " + (i+1));
        contactPhone[i] = input.nextLine();


    for (int i = 0; i < num; i++) {
        System.out.println("Contact Name No." + (i+1) + " is "+contactName[i]);
        System.out.println("First Contacts Address No." + (i+1) + " is "+contactAdd1[i]);
        System.out.println("Second Contacts Address No." + (i+1) + " is "+contactAdd2[i]);
        System.out.println("Contact Phone Number No." + (i+1) + " is "+contactPhone[i]);


Mounting multiple volumes on a docker container?

Or you can do

docker run -v /var/volume1 -v /var/volume2 DATA busybox true

How to clear gradle cache?

there seems to be incorrect info posted here. some people report on how to clear the Android builder cache (with task cleanBuildCache) but do not seem to realize that said cache is independent of Gradle's build cache, AFAIK.

my understanding is that Android's cache predates (and inspired) Gradle's, but i could be wrong. whether the Android builder will be/was updated to use Gradle's cache and retire its own, i do not know.

EDIT: the Android builder cache is obsolete and has been eliminated. the Android Gradle plugin now uses Gradle's build cache instead. to control this cache you must now interact with Gradle's generic cache infrastructure.

TIP: search for Gradle's cache help online without mentioning the keyword 'android' to get help for the currently relevant cache.

EDIT 2: due to tir38's question in a comment below, i am testing using an Android Gradle plugin v3.4.2 project. the gradle cache is enabled by org.gradle.caching=true in i do a couple of clean build and the second time most tasks show FROM-CACHE as their status, showing that the cache is working.

surprisingly, i have a cleanBuildCache gradle task and a <user-home>/.android/build-cache/3.4.2/ directory, both hinting the existence of an Android builder cache.

i execute cleanBuildCache and the 3.4.2/ directory is gone. next i do another clean build:

  • nothing changed: most tasks show FROM-CACHE as their status and the build completed at cache-enabled speeds.
  • the 3.4.2/ directory is recreated.
  • the 3.4.2/ directory is empty (save for 2 hidden, zero length marker files).


  1. caching of all normal Android builder tasks is handled by Gradle.
  2. executing cleanBuildCache does not clear or affect the build cache in any way.
  3. there is still an Android builder cache there. this could be vestigial code that the Android build team forgot to remove, or it could actually cache something strange that for whatever reason has not or cannot be ported to using the Gradle cache. (the 'cannot' option being highly improvable, IMHO.)

next, i disable the Gradle cache by removing org.gradle.caching=true from and i try a couple of clean build:

  • the builds are slow.
  • all tasks show their status as being executed and not cached or up to date.
  • the 3.4.2/ directory continues to be empty.

more conclusions:

  1. there is no Android builder cache fallback for when the Gradle cache fails to hit.
  2. the Android builder cache, at least for common tasks, has indeed been eliminated as i stated before.
  3. the relevant android doc contains outdated info. in particular the cache is not enabled by default as stated there, and the Gradle cache has to be enabled manually.

EDIT 3: user tir38 confirmed that the Android builder cache is obsolete and has been eliminated with this find. tir38 also created this issue. thanks!

Daylight saving time and time zone best practices

Just one example to prove that handling time is the huge mess described, and that you can never be complacent. In several spots on this page leap-seconds have been ignored.

Several years ago, the Android operating system used GPS satellites to get a UTC time reference, but ignored the fact that GPS satellites do not use leap-seconds. No one noticed until there was confusion on New Year's Eve, when the Apple phone users and Android phone users did their count-downs about 15 seconds apart.

I think it has since been fixed, but you never know when these 'minor details' will come back to haunt you.

POST request with a simple string in body with Alamofire

If you use Alamofire, it is enough to encoding type to "URLEncoding.httpBody"

With that, you can send your data as a string in the httpbody allthough you defined it json in your code.

It worked for me..


  var url = "http://..."
    let _headers : HTTPHeaders = ["Content-Type":"application/x-www-form-urlencoded"]
    let params : Parameters = ["grant_type":"password","username":"mail","password":"pass"]

    let url =  NSURL(string:"url" as String)

    request(url, method: .post, parameters: params, encoding: URLEncoding.httpBody , headers: _headers).responseJSON(completionHandler: {
        response in response

        let jsonResponse = response.result.value as! NSDictionary

        if jsonResponse["access_token"] != nil
            access_token = String(describing: jsonResponse["accesstoken"]!)



Can (domain name) subdomains have an underscore "_" in it?

I followed the link to RFC1034 and read most of it and was surprised to see this:

The labels must follow the rules for ARPANET host names. They must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphen. There are also some restrictions on the length. Labels must be 63 characters or less.

For clarification, a domain names are made up of labels which are separated by dots ".". This spec must be outdated because it doesn't mention the use of underscores. I can understand the confusion if anybody stumbles over this spec without knowing it is obsolete. It is obsolete, isn't it?

I followed the link to RFC2181 and read some of it. Especially where it pertains to the issue of what is an authoritative, or canonical, name and the issue of what makes a valid DNS label.

As posted earlier it states there's only a length restriction then to sum it up it reads:

(about names and valid labels)

These are already adequately specified, however the specifications seem to be sometimes ignored. We seek to reinforce the existing specifications.

Kind of leaves me wondering if "a length only restriction" is "adequate". Are we going to start seeing domain names like @#$%!! soon? Isn't the internet screwed up enough?

How do you check what version of SQL Server for a database using TSQL?


SELECT @@MICROSOFTVERSION / 0x01000000 AS MajorVersionNumber

For more information see: Querying for version/edition info

Error launching Eclipse 4.4 "Version 1.6.0_65 of the JVM is not suitable for this product."

Please check if you got the x64 edition of eclipse. Someone answered this just a few hours ago.

TypeError: '<=' not supported between instances of 'str' and 'int'


vote = input('Enter the name of the player you wish to vote for')


vote = int(input('Enter the name of the player you wish to vote for'))

You are getting the input from the console as a string, so you must cast that input string to an int object in order to do numerical operations.

ORA-00984: column not allowed here

Replace double quotes with single ones:

       '2013-06-11 17:16:31',

In SQL, double quotes are used to mark identifiers, not string constants.

Excel VBA - Pass a Row of Cell Values to an Array and then Paste that Array to a Relative Reference of Cells

When i Tried your Code i got en Error when i wanted to fill the Array.

you can try to fill the Array like This.

Sub Testing_Data()
Dim k As Long, S2 As Worksheet, VArray

Application.ScreenUpdating = False
Set S2 = ThisWorkbook.Sheets("Sheet1")
With S2
    VArray = .Range("A1:A" & .Cells(Rows.Count, "A").End(xlUp).Row)
End With
For k = 2 To UBound(VArray, 1)
    S2.Cells(k, "B") = VArray(k, 1) / 100
    S2.Cells(k, "C") = VArray(k, 1) * S2.Cells(k, "B")

End Sub

How to export database schema in Oracle to a dump file

It depends on which version of Oracle? Older versions require exp (export), newer versions use expdp (data pump); exp was deprecated but still works most of the time.

Before starting, note that Data Pump exports to the server-side Oracle "directory", which is an Oracle symbolic location mapped in the database to a physical location. There may be a default directory (DATA_PUMP_DIR), check by querying DBA_DIRECTORIES:

  SQL> select * from dba_directories;

... and if not, create one

  SQL> create directory DATA_PUMP_DIR as '/oracle/dumps';
  SQL> grant all on directory DATA_PUMP_DIR to myuser;    -- DBAs dont need this grant

Assuming you can connect as the SYSTEM user, or another DBA, you can export any schema like so, to the default directory:

 $ expdp system/manager schemas=user1 dumpfile=user1.dpdmp

Or specifying a specific directory, add directory=<directory name>:

 C:\> expdp system/manager schemas=user1 dumpfile=user1.dpdmp directory=DUMPDIR

With older export utility, you can export to your working directory, and even on a client machine that is remote from the server, using:

 $ exp system/manager owner=user1 file=user1.dmp

Make sure the export is done in the correct charset. If you haven't setup your environment, the Oracle client charset may not match the DB charset, and Oracle will do charset conversion, which may not be what you want. You'll see a warning, if so, then you'll want to repeat the export after setting NLS_LANG environment variable so the client charset matches the database charset. This will cause Oracle to skip charset conversion.

Example for American UTF8 (UNIX):


Windows uses SET, example using Japanese UTF8:

 C:\> set NLS_LANG=Japanese_Japan.AL32UTF8

More info on Data Pump here:

Using FileUtils in eclipse

For selenium automation users

  1. Download Library file from
  2. Extract
  3. Right click on the proj name from the explorer >> Build path >>Config Build Path

pandas dataframe groupby datetime month

(update: 2018)

Note that pd.Timegrouper is depreciated and will be removed. Use instead:


jQuery events .load(), .ready(), .unload()

If both "document.ready" variants are used they will both fire, in the order of appearance

    alert('shorthand document.ready');

//try changing places

Gradle: Execution failed for task ':processDebugManifest'

I also faced this error when I was adding firebase push notifications in my app. but in my case I was doing a very silly mistake which i noticed after some time. I declared below code in manifest two times. After removing duplicate declaration. my issue solved.

        <service   android:name="com.evampsaanga.mytelenor.firebase.MyFirebaseInstanceIDService">
            <action android:name="" />

so you also check if there is anything duplicate in your app manifest file.

Memory address of an object in C#

Instead of this code, you should call GetHashCode(), which will return a (hopefully-)unique value for each instance.

You can also use the ObjectIDGenerator class, which is guaranteed to be unique.

How to downgrade Node version

In Mac there is a fast method with brew:

brew search node

You see some version, for example: node@10 node@12 ... Then

brew unlink node

And now select a before version for example node@12

brew link --overwrite --force node@12

Ready, you have downgraded you node version.

Read all files in a folder and apply a function to each data frame

usually i don't use for loop in R, but here is my solution using for loops and two packages : plyr and dostats

plyr is on cran and you can download dostats on (may be using install_github from Hadley devtools package)

Assuming that i have your first two data.frame (Df.1 and Df.2) in csv files, you can do something like this.


files <- list.files(pattern = ".csv")

for (i in seq_along(files)) {

    assign(paste("Df", i, sep = "."), read.csv(files[i]))

    assign(paste(paste("Df", i, sep = ""), "summary", sep = "."), 
           ldply(get(paste("Df", i, sep = ".")), dostats, sum, min, mean, median, max))


Here is the output

R> Df1.summary
  .id sum min   mean median max
1   A  34   4 5.6667    5.5   8
2   B  22   1 3.6667    3.0   9
R> Df2.summary
  .id sum min   mean median max
1   A  21   1 3.5000    3.5   6
2   B  16   1 2.6667    2.5   5

Gradients on UIView and UILabels On iPhone

Note: The results below apply to older versions of iOS, but when testing on iOS 13 the stepping doesn't occur. I don't know for which version of iOS the stepping was removed.

When using CAGradientLayer, as opposed to CGGradient, the gradient is not smooth, but has noticeable stepping to it. See this example:

To get more attractive results it is better to use CGGradient.

How to manually set an authenticated user in Spring Security / SpringMVC

The new filtering feature in Servlet 2.4 basically alleviates the restriction that filters can only operate in the request flow before and after the actual request processing by the application server. Instead, Servlet 2.4 filters can now interact with the request dispatcher at every dispatch point. This means that when a Web resource forwards a request to another resource (for instance, a servlet forwarding the request to a JSP page in the same application), a filter can be operating before the request is handled by the targeted resource. It also means that should a Web resource include the output or function from other Web resources (for instance, a JSP page including the output from multiple other JSP pages), Servlet 2.4 filters can work before and after each of the included resources. .

To turn on that feature you need:




return "forward:/login?j_username=" + registrationModel.getUserEmail()
        + "&j_password=" + registrationModel.getPassword();

const char* concatenation

Connecting two constant char pointer without using strcpy command in the dynamic allocation of memory:

const char* one = "Hello ";
const char* two = "World!";

char* three = new char[strlen(one) + strlen(two) + 1] {'\0'};

strcat_s(three, strlen(one) + 1, one);
strcat_s(three, strlen(one) + strlen(two) + 1, two);

cout << three << endl;

delete[] three;
three = nullptr;

Is Laravel really this slow?

Laravel is slow, because in most cases, using PHP for web pages is slow.

With Laravel, the entire framework is rebuilt on every invocation - that is why all pages point to index.php. Since the entire framework is PHP scripts, they all need to go through the PHP interpreter - each time. The larger the framework, the longer this takes.

Contrast this with a "server environment" (e.g. tomcat) where the server runs the initialization code once, and eventually all pages will be in native code (after JIT).

As a reference example, using the same hardware, OS, etc. a simple 'hello world' using JSP on this hardware is 3000 rps, the same hello world on laravel is 51 rps.

The easiest way to test framework overhead, and the resulting maximum RPS per core, is to use Apache AB and a concurrency value of 1, with a simple 'hello world' that is dynamic (to avoid static page caching).

I need to know how to get my program to output the word i typed in and also the new rearranged word using a 2D array

  1. What exactly doesn't work?
  2. Why are you using a 2d array?
  3. If you must use a 2d array:

    int numOfPairs = 10;  String[][] array = new String[numOfPairs][2]; for(int i = 0; i < array.length; i++){     for(int j = 0; j < array[i].length; j++){         array[i] = new String[2];         array[i][0] = "original word";         array[i][1] = "rearranged word";     }    } 

Does this give you a hint?

ViewDidAppear is not called when opening app from background

Using Objective-C

You should register a UIApplicationWillEnterForegroundNotification in your ViewController's viewDidLoad method and whenever app comes back from background you can do whatever you want to do in the method registered for notification. ViewController's viewWillAppear or viewDidAppear won't be called when app comes back from background to foreground.


[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(doYourStuff)

  name:UIApplicationWillEnterForegroundNotification object:nil];


   // do whatever you want to do when app comes back from background.

Don't forget to unregister the notification you are registered for.

-(void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];

Note if you register your viewController for UIApplicationDidBecomeActiveNotification then your method would be called every time your app becomes active, It is not recommended to register viewController for this notification .

Using Swift

For adding observer you can use the following code

 override func viewDidLoad() {

     NotificationCenter.default.addObserver(self, selector: "doYourStuff", name: UIApplication.willEnterForegroundNotification, object: nil)

 func doYourStuff(){
     // your code

To remove observer you can use deinit function of swift.

deinit {

How can I clone a JavaScript object except for one key?

If you're dealing with a huge variable, you don't want to copy it and then delete it, as this would be inefficient.

A simple for-loop with a hasOwnProperty check should work, and it is much more adaptable to future needs :

for(var key in someObject) {
        if(someObject.hasOwnProperty(key) && key != 'undesiredkey') {
                copyOfObject[key] = someObject[key];

Limiting number of displayed results when using ngRepeat

Slightly more "Angular way" would be to use the straightforward limitTo filter, as natively provided by Angular:

<ul class="phones">
  <li ng-repeat="phone in phones | filter:query | orderBy:orderProp | limitTo:quantity">
app.controller('PhoneListCtrl', function($scope, $http) {
        $scope.phones =;
    $scope.orderProp = 'age';
    $scope.quantity = 5;


How to send 100,000 emails weekly?

Short answer: While it's technically possible to send 100k e-mails each week yourself, the simplest, easiest and cheapest solution is to outsource this to one of the companies that specialize in it (I did say "cheapest": there's no limit to the amount of development time (and therefore money) that you can sink into this when trying to DIY).

Long answer: If you decide that you absolutely want to do this yourself, prepare for a world of hurt (after all, this is e-mail/e-fail we're talking about). You'll need:

  • e-mail content that is not spam (otherwise you'll run into additional major roadblocks on every step, even legal repercussions)
  • in addition, your content should be easy to distinguish from spam - that may be a bit hard to do in some cases (I heard that a certain pharmaceutical company had to all but abandon e-mail, as their brand names are quite common in spams)
  • a configurable SMTP server of your own, one which won't buckle when you dump 100k e-mails onto it (your ISP's upstream server won't be sufficient here and you'll make the ISP violently unhappy; we used two dedicated boxes)
  • some mail wrapper (e.g. PhpMailer if PHP's your poison of choice; using PHP's mail() is horrible enough by itself)
  • your own sender function to run in a loop, create the mails and pass them to the wrapper (note that you may run into PHP's memory limits if your app has a memory leak; you may need to recycle the sending process periodically, or even better, decouple the "creating e-mails" and "sending e-mails" altogether)

Surprisingly, that was the easy part. The hard part is actually sending it:

  • some servers will ban you when you send too many mails close together, so you need to shuffle and watch your queue (e.g. send one mail to [email protected], then three to other domains, only then another to [email protected])
  • you need to have correct PTR, SPF, DKIM records
  • handling remote server timeouts, misconfigured DNS records and other network pleasantries
  • handling invalid e-mails (and no, regex is the wrong tool for that)
  • handling unsubscriptions (many legitimate newsletters have been reclassified as spam due to many frustrated users who couldn't unsubscribe in one step and instead chose to "mark as spam" - the spam filters do learn, esp. with large e-mail providers)
  • handling bounces and rejects ("no such mailbox [email protected]","mailbox [email protected] full")
  • handling blacklisting and removal from blacklists (Sure, you're not sending spam. Some recipients won't be so sure - with such large list, it will happen sometimes, no matter what precautions you take. Some people (e.g. your not-so-scrupulous competitors) might even go as far to falsely report your mailings as spam - it does happen. On average, it takes weeks to get yourself removed from a blacklist.)

And to top it off, you'll have to manage the legal part of it (various federal, state, and local laws; and even different tangles of laws once you send outside the U.S. (note: you have no way of finding if [email protected] lives in Southwest Elbonia, the country with world's most draconian antispam laws)).

I'm pretty sure I missed a few heads of this hydra - are you still sure you want to do this yourself? If so, there'll be another wave, this time merely the annoying problems inherent in sending an e-mail. (You see, SMTP is a store-and-forward protocol, which means that your e-mail will be shuffled across many SMTP servers around the Internet, in the hope that the next one is a bit closer to the final recipient. Basically, the e-mail is sent to an SMTP server, which puts it into its forward queue; when time comes, it will forward it further to a different SMTP server, until it reaches the SMTP server for the given domain. This forward could happen immediately, or in a few minutes, or hours, or days, or never.) Thus, you'll see the following issues - most of which could happen en route as well as at the destination:

  • the remote SMTP servers don't want to talk to your SMTP server
  • your mails are getting marked as spam (<blink> is not your friend here, nor is <font color=...>)
  • your mails are delivered days, even weeks late (contrary to popular opinion, SMTP is designed to make a best effort to deliver the message sometime in the future - not to deliver it now)
  • your mails are not delivered at all (already sent from e-mail server on hop #4, not sent yet from server on hop #5, the server that currently holds the message crashes, data is lost)
  • your mails are mangled by some braindead server en route (this one is somewhat solvable with base64 encoding, but then the size goes up and the e-mail looks more suspicious)
  • your mails are delivered and the recipients seem not to want them ("I'm sure I didn't sign up for this, I remember exactly what I did a year ago" (of course you do, sir))
  • users with various versions of Microsoft Outlook and its special handling of Internet mail
  • wizard's apprentice mode (a self-reinforcing positive feedback loop - in other words, automated e-mails as replies to automated e-mails as replies to...; you really don't want to be the one to set this off, as you'd anger half the internet at yourself)

and it'll be your job to troubleshoot and solve this (hint: you can't, mostly). The people who run a legit mass-mailing businesses know that in the end you can't solve it, and that they can't solve it either - and they have the reasons well researched, documented and outlined (maybe even as a Powerpoint presentation - complete with sounds and cool transitions - that your bosses can understand), as they've had to explain this a million times before. Plus, for the problems that are actually solvable, they know very well how to solve them.

If, after all this, you are not discouraged and still want to do this, go right ahead: it's even possible that you'll find a better way to do this. Just know that the road ahead won't be easy - sending e-mail is trivial, getting it delivered is hard.

How can I use Bash syntax in Makefile targets?

You can call bash directly, use the -c flag:

bash -c "diff <(sort file1) <(sort file2) > $@"

Of course, you may not be able to redirect to the variable $@, but when I tried to do this, I got -bash: $@: ambiguous redirect as an error message, so you may want to look into that before you get too into this (though I'm using bash 3.2.something, so maybe yours works differently).

Gradle's dependency cache may be corrupt (this sometimes occurs after a network connection timeout.)

If you using Ubuntu, So firstly you have unhide all files from your home directory or where located your android studio folder :

  1. Go to your home directory and unhide all files by using ctrl+h
  2. You found .gradle folder
  3. Inside .gradle -> wrapper
  4. You can found dists folder, So delete this dists folder
  5. Create a New Project than your Gradle file re-downloaded
  6. Congo you successfully build project

HRESULT: 0x800A03EC on Worksheet.range

Just FYI, got the error trying to apply row style....

wSheet.Rows(y).Style = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Red)

NuGet Package Restore Not Working

Did you enable package restore mode in the project that has the missing packages/binaries ? There's a known issue that requires the packages to be correctly installed when enabling the restore mode :

Original link is dead; this might be a replacement:

Reverting single file in SVN to a particular revision

svn cat takes a revision arg too!

svn cat -r 175 mydir/myfile > mydir/myfile

How does one capture a Mac's command key via JavaScript?

For people using jQuery, there is an excellent plugin for handling key events:

jQuery hotkeys on GitHub

For capturing ?+S and Ctrl+S I'm using this:

$(window).bind('keydown.ctrl_s keydown.meta_s', function(event) {
    // Do something here

connecting MySQL server to NetBeans

in my cases, i found my password in glassfish-recources.xml under WEB-INF

Why does AngularJS include an empty option in select?

Maybe useful for someone:

If you want to use plain options instead of ng-options, you could do like below:

<select ng-model="sortorder" ng-init="sortorder='publish_date'">
  <option value="publish_date">Ascending</option>
  <option value="-publish_date">Descending</option>

Set the model inline. Use ng-init to get rid of empty option

Java: parse int value from a char

That's probably the best from the performance point of view, but it's rough:

String element = "el5";
String s;
int x = element.charAt(2)-'0';

It works if you assume your character is a digit, and only in languages always using Unicode, like Java...

org.hibernate.MappingException: Unknown entity: annotations.Users

Define the Entity class in Hibernate.cfg.xml

<mapping class="com.supernt.Department"/>

While creating the sessionFactory object Load the Configuration file Like

SessionFactory factory = new AnnotationConfiguration().configure("hibernate.cfg.xml").buildSessionFactory();

PHP/MySQL: How to create a comment section in your website

I'm working on this right now as well. You should also add a datetime of the comment. You'll need this later when you want to sort by most recent.

Here are some of the db fields i'm using.

id (auto incremented)

Change color of Label in C#

I am going to assume this is a WinForms questions (which it feels like, based on it being a "program" rather than a website/app). In which case you can simple do the following to change the text colour of a label:

myLabel.ForeColor = System.Drawing.Color.Red;

Or any other colour of your choice. If you want to be more specific you can use an RGB value like so:

myLabel.ForeColor = Color.FromArgb(0, 0, 0);//(R, G, B) (0, 0, 0 = black)

Having different colours for different users can be done a number of ways. For example, you could allow each user to specify their own RGB value colours, store these somewhere and then load them when the user "connects".

An alternative method could be to just use 2 colours - 1 for the current user (running the app) and another colour for everyone else. This would help the user quickly identify their own messages above others.

A third approach could be to generate the colour randomly - however you will likely get conflicting values that do not show well against your background, so I would suggest not taking this approach. You could have a pre-defined list of "acceptable" colours and just pop one from that list for each user that joins.

How do I make a matrix from a list of vectors in R?

simplify2array is a base function that is fairly intuitive. However, since R's default is to fill in data by columns first, you will need to transpose the output. (sapply uses simplify2array, as documented in help(sapply).)

> t(simplify2array(a))
      [,1] [,2] [,3] [,4] [,5] [,6]
 [1,]    1    1    2    3    4    5
 [2,]    2    1    2    3    4    5
 [3,]    3    1    2    3    4    5
 [4,]    4    1    2    3    4    5
 [5,]    5    1    2    3    4    5
 [6,]    6    1    2    3    4    5
 [7,]    7    1    2    3    4    5
 [8,]    8    1    2    3    4    5
 [9,]    9    1    2    3    4    5
[10,]   10    1    2    3    4    5

Use jQuery to change a second select list based on the first select list option

I built on sabithpocker's idea and made a more generalized version that lets you control more than one selectbox from a given trigger.

I assigned the selectboxes I wanted to be controlled the classname "switchable," and cloned them all like this:

$j(this).data('options',$j('select.switchable option').clone());

and used a specific naming convention for the switchable selects, which could also translate into classes. In my case, "category" and "issuer" were the select names, and "category_2" and "issuer_1" the class names.

Then I ran an $.each on the select.switchable groups, after making a copy of $(this) for use inside the function:

var that = this;
$j("select.switchable").each(function() { 
    var thisname = $j(this).attr('name');
    var theseoptions = $j(that).data('options').filter( '.' + thisname + '_' + id );

By using a classname on the ones you want to control, the function will safely ignore other selects elsewhere on the page (such as the last one in the example on Fiddle).

Here's a Fiddle with the complete code:

Adding a new value to an existing ENUM Type

NOTE if you're using PostgreSQL 9.1 or later, and you are ok with making changes outside of a transaction, see this answer for a simpler approach.

I had the same problem few days ago and found this post. So my answer can be helpful for someone who is looking for solution :)

If you have only one or two columns which use the enum type you want to change, you can try this. Also you can change the order of values in the new type.

-- 1. rename the enum type you want to change
alter type some_enum_type rename to _some_enum_type;
-- 2. create new type
create type some_enum_type as enum ('old', 'values', 'and', 'new', 'ones');
-- 3. rename column(s) which uses our enum type
alter table some_table rename column some_column to _some_column;
-- 4. add new column of new type
alter table some_table add some_column some_enum_type not null default 'new';
-- 5. copy values to the new column
update some_table set some_column = _some_column::text::some_enum_type;
-- 6. remove old column and type
alter table some_table drop column _some_column;
drop type _some_enum_type;

3-6 should be repeated if there is more than 1 column.

How to fix C++ error: expected unqualified-id

For anyone with this situation: I saw this error when I accidentally used my_first_scope::my_second_scope::true in place of simply true, like this:

bool my_var = my_first_scope::my_second_scope::true;

instead of:

bool my_var = true;

This is because I had a macro which caused MY_MACRO(true) to expand into my_first_scope::my_second_scope::true, by mistake, and I was actually calling bool my_var = MY_MACRO(true);.

Here's a quick demo of this type of scoping error:

Program (you can run it online here:

#include <iostream>
#include <cstdio>

namespace my_first_scope 
namespace my_second_scope
} // namespace my_second_scope
} // namespace my_first_scope

int main()
    printf("Hello World\n");
    bool my_var = my_first_scope::my_second_scope::true;
    std::cout << my_var << std::endl;

    return 0;

Output (build error):

main.cpp: In function ‘int main()’:
main.cpp:27:52: error: expected unqualified-id before ‘true’
     bool my_var = my_first_scope::my_second_scope::true;

Notice the error: error: expected unqualified-id before ‘true’, and where the arrow under the error is pointing. Apparently the "unqualified-id" in my case is the double colon (::) scope operator I have just before true.

When I add in the macro and use it (run this new code here:

#define MY_MACRO(input) my_first_scope::my_second_scope::input


bool my_var = MY_MACRO(true);

I get this new error instead:

main.cpp: In function ‘int main()’:
main.cpp:29:28: error: expected unqualified-id before ‘true’
     bool my_var = MY_MACRO(true);
main.cpp:16:58: note: in definition of macro ‘MY_MACRO’
 #define MY_MACRO(input) my_first_scope::my_second_scope::input

How to replace local branch with remote branch entirely in Git?

git branch -D <branch-name>
git fetch <remote> <branch-name>
git checkout -b <branch-name> --track <remote>/<branch-name>

Proper way to set response status and JSON content in a REST API made with nodejs and express

try {
  var data = {foo: "bar"};
catch (e) {

Rename multiple files based on pattern in Unix

It was much easier (on my Mac) to do this in Ruby. Here are 2 examples:

# for your fgh example. renames all files from "fgh..." to "jkl..."
files = Dir['fgh*']

files.each do |f|
  f2 = f.gsub('fgh', 'jkl')
  system("mv #{f} #{f2}")

# renames all files in directory from "021roman.rb" to "021_roman.rb"
files = Dir['*rb'].select {|f| f =~ /^[0-9]{3}[a-zA-Z]+/}

files.each do |f|
  f1 = f.clone
  f2 = f.insert(3, '_')
  system("mv #{f1} #{f2}")

How to open a local disk file with JavaScript?

The HTML5 fileReader facility does allow you to process local files, but these MUST be selected by the user, you cannot go rooting about the users disk looking for files.

I currently use this with development versions of Chrome (6.x). I don't know what other browsers support it.

Authentication plugin 'caching_sha2_password' cannot be loaded

Currently (on 2018/04/23), you need to download a development release. The GA ones do not work.

I was not able to connect with the latest GA version (6.3.10).

It worked with mysql-workbench-community-8.0.11-rc-winx64.msi (from, tab Development Releases).

Adjust width and height of iframe to fit with content in it

In jQuery, this is the best option to me, that really help me!! I wait that help you!


<iframe src="" frameborder="0" id="iframe" width="100%"></iframe>


        var valueSize = $( "#iframe" ).offset();
        var totalsize = ( * 2) + valueSize.left;

        $( "#iframe" ).height(totalsize);            


Remove all the elements that occur in one list from another

Alternate Solution :

reduce(lambda x,y : filter(lambda z: z!=y,x) ,[2,3,5,8],[1,2,6,8])

How do you strip a character out of a column in SQL Server?

This is done using the REPLACE function

To strip out "somestring" from "SomeColumn" in "SomeTable" in the SELECT query:

SELECT REPLACE([SomeColumn],'somestring','') AS [SomeColumn]  FROM [SomeTable]

To update the table and strip out "somestring" from "SomeColumn" in "SomeTable"

UPDATE [SomeTable] SET [SomeColumn] = REPLACE([SomeColumn], 'somestring', '')

How to remove Left property when position: absolute?

In the future one would use left: unset; for unsetting the value of left.

As of today 4 nov 2014 unset is only supported in Firefox.

Read more about unset in MDN.

My guess is we'll be able to use it around year 2022 when IE 11 is properly phased out.

error_reporting(E_ALL) does not produce error

That error is a parse error. The parser is throwing it while going through the code, trying to understand it. No code is being executed yet in the parsing stage. Because of that it hasn't yet executed the error_reporting line, therefore the error reporting settings aren't changed yet.

You cannot change error reporting settings (or really, do anything) in a file with syntax errors.

How to display tables on mobile using Bootstrap?

After researching for almost 1 month i found the below code which is working very beautifully and 100% perfectly on my website. To check the preview how it is working you can check from the link.


@media only screen and (max-width: 500px)  {
    .resp table  { 
        display: block ; 
    .resp th  { 
        position: absolute;
        top: -9999px;
        left: -9999px;
        display:block ;
     .resp tr { 
    border: 1px solid #ccc;
    .resp td  { 
        /* Behave  like a "row" */
        border: none;
        border-bottom: 1px solid #eee; 
        position: relative;
        text-indent: 50%; 
        padding-left: 0px;
    .resp  td:nth-child(1)  {
        border: none;
        border-bottom: 1px solid #eee; 
        position: relative;
        text-indent: 0%;
    .resp td:before  { 
        /* Now like a table header */
        position: absolute;
        /* Top/left values mimic padding */
        top: 6px;
        left: 6px;
        width: 45%; 
        text-indent: 0%;
        white-space: nowrap;
    Label the data
    .resp td:nth-of-type(2):before  { content: attr(data-th) }
    .resp td:nth-of-type(3):before  { content: attr(data-th) }
    .resp td:nth-of-type(4):before  { content: attr(data-th) }
    .resp td:nth-of-type(5):before  { content: attr(data-th) }
    .resp td:nth-of-type(6):before  { content: attr(data-th) }
    .resp td:nth-of-type(7):before  { content: attr(data-th) }
    .resp td:nth-of-type(8):before  { content: attr(data-th) }
    .resp td:nth-of-type(9):before  { content: attr(data-th) }
    .resp td:nth-of-type(10):before  { content: attr(data-th) }


<td data-th="Heading 1"></td>
<td data-th="Heading 2"></td>
<td data-th="Heading 3"></td>
<td data-th="Heading 4"></td>
<td data-th="Heading 5"></td>

How to send email attachments?

from email.mime.multipart import MIMEMultipart
from email.mime.image import MIMEImage
from email.mime.text import MIMEText
import smtplib

msg = MIMEMultipart()

password = "password"
msg['From'] = "from_address"
msg['To'] = "to_address"
msg['Subject'] = "Attached Photo"
file = "file path"
fp = open(file, 'rb')
img = MIMEImage(
server = smtplib.SMTP(' 587')
server.login(msg['From'], password)
server.sendmail(msg['From'], msg['To'], msg.as_string())

Making text bold using attributed string in swift

Swift 3.0

Convert html to string and font change as per your requirement.

do {

     let str = try NSAttributedString(data: ("I'm a normal text and <b>this is my bold part . </b>And I'm again in the normal text".data(using: String.Encoding.unicode, allowLossyConversion: true)!), options: [ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil)

     myLabel.attributedText = str
     myLabel.font =  MONTSERRAT_BOLD(23)
     myLabel.textAlignment = NSTextAlignment.left
} catch {

func MONTSERRAT_BOLD(_ size: CGFloat) -> UIFont
    return UIFont(name: "MONTSERRAT-BOLD", size: size)!

MySQL: ALTER TABLE if column not exists

Add field if not exist:

CALL addFieldIfNotExists ('settings', 'multi_user', 'TINYINT(1) NOT NULL DEFAULT 1');

addFieldIfNotExists code:




CREATE FUNCTION isFieldExisting (table_name_IN VARCHAR(100), field_name_IN VARCHAR(100)) 
    AND TABLE_NAME = table_name_IN 
    AND COLUMN_NAME = field_name_IN

CREATE PROCEDURE addFieldIfNotExists (
    IN table_name_IN VARCHAR(100)
    , IN field_name_IN VARCHAR(100)
    , IN field_definition_IN VARCHAR(100)

    SET @isFieldThere = isFieldExisting(table_name_IN, field_name_IN);
    IF (@isFieldThere = 0) THEN

        SET @ddl = CONCAT('ALTER TABLE ', table_name_IN);
        SET @ddl = CONCAT(@ddl, ' ', 'ADD COLUMN') ;
        SET @ddl = CONCAT(@ddl, ' ', field_name_IN);
        SET @ddl = CONCAT(@ddl, ' ', field_definition_IN);

        PREPARE stmt FROM @ddl;
        EXECUTE stmt;

    END IF;


How do I remove packages installed with Python's easy_install?

If the problem is a serious-enough annoyance to you, you might consider virtualenv. It allows you to create an environment that encapsulates python libraries. You install packages there rather than in the global site-packages directory. Any scripts you run in that environment have access to those packages (and optionally, your global ones as well). I use this a lot when evaluating packages that I am not sure I want/need to install globally. If you decide you don't need the package, it's easy enough to just blow that virtual environment away. It's pretty easy to use. Make a new env:

$>virtualenv /path/to/your/new/ENV

virtual_envt installs setuptools for you in the new environment, so you can do:


You can even create your own boostrap scripts that setup your new environment. So, with one command, you can create a new virtual env with, say, python 2.6, psycopg2 and django installed by default (you can can install an env-specific version of python if you want).

REST API - file (ie images) processing - best practices

There's no easy solution. Each way has their pros and cons . But the canonical way is using the first option: multipart/form-data. As W3 recommendation guide says

The content type "multipart/form-data" should be used for submitting forms that contain files, non-ASCII data, and binary data.

We aren't sending forms,really, but the implicit principle still applies. Using base64 as a binary representation, is incorrect because you're using the incorrect tool for accomplish your goal, in other hand, the second option forces your API clients to do more job in order to consume your API service. You should do the hard work in the server side in order to supply an easy-to-consume API. The first option is not easy to debug, but when you do it, it probably never changes.

Using multipart/form-data you're sticked with the REST/http philosophy. You can view an answer to similar question here.

Another option if mixing the alternatives, you can use multipart/form-data but instead of send every value separate, you can send a value named payload with the json payload inside it. (I tried this approach using ASP.NET WebAPI 2 and works fine).

ERROR: Google Maps API error: MissingKeyMapError

The script element that loads the API is missing the required authentication parameter. If you are using the standard Maps JavaScript API, you must use a key parameter with a valid API key. If you are a Premium Plan customer, you must use either a client parameter with your client ID or a key parameter with a valid API key.

See the guide to API keys and client IDs.

Math operations from string

Warning: this way is not a safe way, but is very easy to use. Use it wisely.

Use the eval function.

print eval('2 + 4')



You can even use variables or regular python code.

a = 5
print eval('a + 4')



You also can get return values:

d = eval('4 + 5')
print d



Or call functions:

def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

a = 20
b = 10    
print eval('add(a, b)')
print eval('subtract(a, b)')



In case you want to write a parser, maybe instead you can built a python code generator if that is easier and use eval to run the code. With eval you can execute any Python evalution.

Why eval is unsafe?

Since you can put literally anything in the eval, e.g. if the input argument is:

os.system(‘rm -rf /’)

It will remove all files on your system (at least on Linux/Unix). So only use eval when you trust the input.

How to make code wait while calling asynchronous calls like Ajax

Why didn't it work for you using Deferred Objects? Unless I misunderstood something this may work for you.

/* AJAX success handler */
var echo = function() {

var pass = function() {
    /* AJAX requests */
    $.post("/echo/json/", { delay: 1 }, echo),
    $.post("/echo/json/", { delay: 2 }, echo),
    $.post("/echo/json/", { delay: 3 }, echo)
  ).then(function() {
    /* Run after all AJAX */

See it here.


Based on your input it seems what your quickest alternative is to use synchronous requests. You can set the property async to false in your $.ajax requests to make them blocking. This will hang your browser until the request is finished though.

Notice I don't recommend this and I still consider you should fix your code in an event-based workflow to not depend on it.

Image Greyscale with CSS & re-color on mouse-over?

I use the following code on

Smooth transition from b/w to color with magnifying effect (scale)

    img.color_flip {
      filter: url(filters.svg#grayscale); /* Firefox 3.5+ */
      filter: gray; /* IE5+ */
      -webkit-filter: grayscale(1); /* Webkit Nightlies & Chrome Canary */
      -webkit-transition: all .5s ease-in-out;

    img.color_flip:hover {
      filter: none;
      -webkit-filter: grayscale(0);
      -webkit-transform: scale(1.1);

Set timeout for webClient.DownloadFile()

My answer comes from here

You can make a derived class, which will set the timeout property of the base WebRequest class:

using System;
using System.Net;

public class WebDownload : WebClient
    /// <summary>
    /// Time in milliseconds
    /// </summary>
    public int Timeout { get; set; }

    public WebDownload() : this(60000) { }

    public WebDownload(int timeout)
        this.Timeout = timeout;

    protected override WebRequest GetWebRequest(Uri address)
        var request = base.GetWebRequest(address);
        if (request != null)
            request.Timeout = this.Timeout;
        return request;

and you can use it just like the base WebClient class.

Execute command without keeping it in history

In any given Bash session, set the history file to /dev/null by typing:

export HISTFILE=/dev/null

Note that, as pointed out in the comments, this will not write any commands in that session to the history!

Just don't mess with your system administrator's hard work, please ;)

Doodad's solution is more elegant. Simply unset the variable: unset HISTFILE (thanks!)

How to add images to on GitHub?

I am just extending or adding an example to the already accepted answer.

Once you have put the image on your Github repo.


  • Open the corresponding Github repo on your browser.
  • Navigate to the target image file Then just open the image in a new tab. Opening the image in a new tab
  • Copy the url Copy the url from the browser tab
  • And finally insert the url to the following pattern ![alt text](

On my case it is

![In a single picture](


  • shadmazumder is my username
  • Xcode is the projectname
  • master is the branch
  • InOnePicture.png is the image, On my case InOnePicture.png is in the root directory.

SyntaxError of Non-ASCII character

You should define source code encoding, add this to the top of your script:

# -*- coding: utf-8 -*-

The reason why it works differently in console and in the IDE is, likely, because of different default encodings set. You can check it by running:

import sys
print sys.getdefaultencoding()

Also see:

How do I reformat HTML code using Sublime Text 2?

For me, the HTML Prettify solution was extremely simple. I went to the HTML Prettify page.

  1. Needed the Sublime Package Manager
  2. Followed the Instructions for installing the package manager here
  3. typed cmd + shift + p to bring up the menu
  4. Typed prettify
  5. Chose the HTML prettify selection in the menu

Boom. Done. Looks great

iOS: UIButton resize according to text length

If your button was made with Interface Builder, and you're changing the title in code, you can do this:

[self.button setTitle:@"Button Title" forState:UIControlStateNormal];
[self.button sizeToFit];

Generating random integer from a range

In this thread rejection sampling was already discussed, but I wanted to suggest one optimization based on the fact that rand() % 2^something does not introduce any bias as already mentioned above.

The algorithm is really simple:

  • calculate the smallest power of 2 greater than the interval length
  • randomize one number in that "new" interval
  • return that number if it is less than the length of the original interval
    • reject otherwise

Here's my sample code:

int randInInterval(int min, int max) {
    int intervalLen = max - min + 1;
    //now calculate the smallest power of 2 that is >= than `intervalLen`
    int ceilingPowerOf2 = pow(2, ceil(log2(intervalLen)));

    int randomNumber = rand() % ceilingPowerOf2; //this is "as uniform as rand()"

    if (randomNumber < intervalLen)
        return min + randomNumber;      //ok!
    return randInInterval(min, max);    //reject sample and try again

This works well especially for small intervals, because the power of 2 will be "nearer" to the real interval length, and so the number of misses will be smaller.

Obviously avoiding the recursion would be more efficient (no need to calculate over and over the log ceiling..) but I thought it was more readable for this example.

How to restart a node.js server

Using "kill -9 [PID]" or "killall -9 node" worked for me where "kill -2 [PID]" did not work.

A message body writer for Java type, class myPackage.B, and MIME media type, application/octet-stream, was not found

This can also happen if you've recently upgraded Ant. I was using Ant 1.8.4 on a project, and upgraded Ant to 1.9.4, and started to get this error when building a fat jar using Ant.

The solution for me was to downgrade back to Ant 1.8.4 for the command line and Eclipse using the process detailed here

JavaScript check if variable exists (is defined/initialized)

My preference is typeof(elem) != 'undefined' && elem != null.

However you choose, consider putting the check in a function like so

function existy (x) {
    return typeof (x) != 'undefined' && x != null;

If you don't know the variable is declared then continue with typeof (x) != 'undefined' && x != null;

Where you know the variable is declared but may not be existy, you could use

existy(elem) && doSomething(elem);

The variable you are checking may be a nested property sometimes. You can use prop || {} to go down the line checking existance to the property in question:

var exists = ((((existy(myObj).prop1||{}).prop2||{}).prop3||{})[1]||{}).prop4;

After each property use (...' || {}').nextProp so that a missing property won't throw an error.

Or you could use existy like existy(o) && existy(o.p) && existy(o.p.q) && doSomething(o.p.q)

How to change the text color of first select option

If the first item is to be used as a placeholder (empty value) and your select is required then you can use the :invalid pseudo-class to target it.

select {_x000D_
  -webkit-appearance: menulist-button;_x000D_
  color: black;_x000D_
select:invalid {_x000D_
  color: green;_x000D_
<select required>_x000D_
  <option value="">Item1</option>_x000D_
  <option value="Item2">Item2</option>_x000D_
  <option value="Item3">Item3</option>_x000D_

Java out.println() how is this possible?

@sfussenegger's answer explains how to make this work. But I'd say don't do it!

Experienced Java programmers use, and expect to see


and not


A static import of System.out or System.err is (IMO) bad style because:

  • it breaks the accepted idiom, and
  • it makes it harder to track down unwanted trace prints that were added during testing and not removed.

If you find yourself doing lots of output to System.out or System.err, I think it is a better to abstract the streams into attributes, local variables or methods. This will make your application more reusable.

How to create a zip archive with PowerShell?

A pure PowerShell alternative that works with PowerShell 3 and .NET 4.5 (if you can use it):

function ZipFiles( $zipfilename, $sourcedir )
   Add-Type -Assembly System.IO.Compression.FileSystem
   $compressionLevel = [System.IO.Compression.CompressionLevel]::Optimal
        $zipfilename, $compressionLevel, $false)

Just pass in the full path to the zip archive you would like to create and the full path to the directory containing the files you would like to zip.

Uninstall / remove a Homebrew package including all its dependencies

The answer of @jfmercer must be modified slightly to work with current brew, because the output of brew missing has changed:

brew deps [FORMULA] | xargs brew remove --ignore-dependencies && brew missing | cut -f1 -d: | xargs brew install

How to get bitmap from a url in android?

This is a simple one line way to do it:

    try {
        URL url = new URL("http://....");
        Bitmap image = BitmapFactory.decodeStream(url.openConnection().getInputStream());
    } catch(IOException e) {

Resizing SVG in html?

I have an SVG file in HTML [....] IS there any way to specify that you want an SVG image displayed smaller or larger than it actually is stored in the file system?

SVG graphics, like other creative works, are protected under copyright law in most countries. Depending on jurisdiction, license of the work or whether or not you are the copyright holder you may not be able to modify the SVG without violating copyright law, believe it or not.

But laws are tricky topics and sometimes you just want to get shit done. Therefore you may adjust the scale of the graphic without modifying the work itself using the img tag with width attribute within your HTML.

Using an external HTTP request to specify the size:

<img width="96" src="/path/to/image.svg">

Specifying size in markup using a Data URI:

<img width="96" src="data:image/svg+xml,...">

SVGs can be Optimized for Data URIs to create SVG Favicon images suitable for any size:

<link rel="icon" sizes="any" href="data:image/svg+xml,%3Csvg%20viewBox='0%200%2046%2045'%20xmlns=''%3E%3Ctitle%3EAfter%20Dark%3C/title%3E%3Cpath%20d='M.708%2045L23%20.416%2045.292%2045H.708zM35%2038L23%2019%2011%2038h24z'%20fill='%23000'/%3E%3C/svg%3E">

Unity Scripts edited in Visual studio don't provide autocomplete

The issue I faced was that the C# Project was targeting a different .NET Framework (4.7.2), whereas the Unity project had a different target (.NET 3.5).

I fixed this by changing the target in Unity as-

File -> Build Settings -> Player Settings -> Other Settings -> API Compatibility Level : Set it to the .NET version you already have installed (Check your .NET Version here). In my case, it was 4.x

After this, Visual Studio worked perfectly and autocorrect was fixed too.

CURL and HTTPS, "Cannot resolve host"

There is a current bug in glibc on Ubuntu which can have this effect:

To resolve it, update libc and all related (Packages that will be upgraded: libc-bin libc-dev-bin libc6 libc6-dev libfreetype6 libfreetype6-dev locales multiarch-support) and restart the server.

How to import cv2 in python3?

Make a virtual enviroment using python3

virtualenv env_name --python="python3"

and run the following command

pip3 install opencv-python

How do I compare two strings in Perl?

And if you'd like to extract the differences between the two strings, you can use String::Diff.

How can I force input to uppercase in an ASP.NET textbox?

I just did something similar today. Here is the modified version:

<asp:TextBox ID="txtInput" runat="server"></asp:TextBox>
<script type="text/javascript">
    function setFormat() {
        var inp = document.getElementById('ctl00_MainContent_txtInput');
        var x = inp.value;
        inp.value = x.toUpperCase();

    var inp = document.getElementById('ctl00_MainContent_txtInput');
    inp.onblur = function(evt) {

Basically, the script attaches an event that fires when the text box loses focus.

How to get number of rows using SqlDataReader in C#

I also face a situation when I needed to return a top result but also wanted to get the total rows that where matching the query. i finaly get to this solution:

   public string Format(SelectQuery selectQuery)
      string result;

      if (string.IsNullOrWhiteSpace(selectQuery.WherePart))
        result = string.Format(
declare @maxResult  int;
set @maxResult = {0};

SELECT count(*) as [Count] FROM {2}
SELECT top (@maxResult) Total.[Count], {1} FROM Total, {2}", m_limit.To, selectQuery.SelectPart, selectQuery.FromPart);
        result = string.Format(
declare @maxResult  int;
set @maxResult = {0};

SELECT count(*) as [Count] FROM {2} WHERE {3}
SELECT top (@maxResult) Total.[Count], {1} FROM Total, {2} WHERE {3}", m_limit.To, selectQuery.SelectPart, selectQuery.FromPart, selectQuery.WherePart);

      if (!string.IsNullOrWhiteSpace(selectQuery.OrderPart))
        result = string.Format("{0} ORDER BY {1}", result, selectQuery.OrderPart);

      return result;

?: ?? Operators Instead Of IF|ELSE

The "do nothing" doesn't really work for ?

if by // Return Nothing you actually mean return null then write

return Source;

if you mean, ignore the codepath then write

 if ( Source != null )
                return Source;
// source is null so continue on.

And for the last

 if ( Source != value )
            { Source = value;
                RaisePropertyChanged ( "Source" );

// nothing done.

Can I force a UITableView to hide the separator between empty cells?

Setting the table's separatorStyle to UITableViewCellSeparatorStyleNone (in code or in IB) should do the trick.

How to find out when a particular table was created in Oracle?

Try this query:

SELECT sysdate FROM schema_name.table_name;

This should display the timestamp that you might need.

Run cron job only if it isn't already running

It's suprising that no one mentioned about run-one. I've solved my problem with this.

 apt-get install run-one

then add run-one before your crontab script

*/20 * * * * * run-one python /script/to/run/

Check out this askubuntu SE answer. You can find link to a detailed information there as well.

How do you simulate Mouse Click in C#?

I use the InvokeOnClick() method. It takes two arguments: Control and EventArgs. If you need the EventArgs, then create an instance of it and pass it in, else use InvokeOnClick(controlToClick, null);. You can use a variety of Mouse event related arguments that derive from EventArgs such as MouseEventArgs.

"Could not find a part of the path" error message

The error is self explanatory. The path you are trying to access is not present.

string source_dir = "E:\\Debug\\VipBat\\{0}";

I'm sure that this is not the correct path. Debug folder directly in E: drive looks wrong to me. I guess there must be the project name folder directory present.

Second thing; what is {0} in your string. I am sure that it is an argument placeholder because folder name cannot contains {0} such name. So you need to use String.Format() to replace the actual value.

string source_dir = String.Format("E:\\Debug\\VipBat\\{0}",variableName);

But first check the path existence that you are trying to access.

What is ".NET Core"?

.NET Core is a free and open-source, managed computer software framework for Windows, Linux, and macOS operating systems. It is an open source, cross platform successor to .NET Framework.

.NET Core applications are supported on Windows, Linux, and macOS. In a nutshell .NET Core is similar to .NET framework, but it is cross-platform, i.e., it allows the .NET applications to run on Windows, Linux and MacOS. .NET framework applications can only run on the Windows system. So the basic difference between .NET framework and .NET core is that .NET Core is cross platform and .NET framework only runs on Windows.

Furthermore, .NET Core has built-in dependency injection by Microsoft and you do not have to use third-party software/DLL files for dependency injection.

JSON library for C#

To give a more up to date answer to this question: yes, .Net includes JSON seriliazer/deserliazer since version 3.5 through the System.Runtime.Serialization.Json Namespace:

But according to the creator of JSON.Net, the .Net Framework compared to his open source implementation is very much slower.

How to check if a file exists in a shell script

If you're using a NFS, "test" is a better solution, because you can add a timeout to it, in case your NFS is down:

time timeout 3 test -f 
real    0m3.004s <<== timeout is taken into account
user    0m0.001s
sys     0m0.004s
echo $?
124   <= 124 means the timeout has been reached

A "[ -e my_file ]" construct will freeze until the NFS is functional again:

if [ -e /nfs/my_nfs_is_currently_down ]; then echo "ok" else echo "ko" ; fi

<no answer from the system, my session is "frozen">

How can I check if a MySQL table exists with PHP?


If you have ANY results, the table exists.

To use this approach in PDO:

$pdo         = new \PDO(/*...*/);
$result      = $pdo->query("SHOW TABLES LIKE 'tableName'");
$tableExists = $result !== false && $result->rowCount() > 0;

To use this approach with DEPRECATED mysql_query

$result      = mysql_query("SHOW TABLES LIKE 'tableName'");
$tableExists = mysql_num_rows($result) > 0;

How to change file encoding in NetBeans?

Go to etc folder in Netbeans home --> open netbeans.conf file and add on netbeans_default_options following line:


Restart Netbeans and it should be in UTF-8

To check go to help --> about and check System: Windows Vista version 6.0 running on x86; UTF-8; nl_NL (nb)

Using Tempdata in ASP.NET MVC - Best practice

Please note that MVC 3 onwards the persistence behavior of TempData has changed, now the value in TempData is persisted until it is read, and not just for the next request.

The value of TempData persists until it is read or until the session times out. Persisting TempData in this way enables scenarios such as redirection, because the values in TempData are available beyond a single request.

Finding the max/min value in an array of primitives using Java

The basic way to get the min/max value of an Array. If you need the unsorted array, you may create a copy or pass it to a method that returns the min or max. If not, sorted array is better since it performs faster in some cases.

public class MinMaxValueOfArray {
    public static void main(String[] args) {
        int[] A = {2, 4, 3, 5, 5};
        int min = A[0];
        int max = A[A.length -1];
        System.out.println("Min Value = " + min);        
        System.out.println("Max Value = " + max);

Receiving JSON data back from HTTP request

If you are referring to the System.Net.HttpClient in .NET 4.5, you can get the content returned by GetAsync using the HttpResponseMessage.Content property as an HttpContent-derived object. You can then read the contents to a string using the HttpContent.ReadAsStringAsync method or as a stream using the ReadAsStreamAsync method.

The HttpClient class documentation includes this example:

  HttpClient client = new HttpClient();
  HttpResponseMessage response = await client.GetAsync("");
  string responseBody = await response.Content.ReadAsStringAsync();

Why is Ant giving me a Unsupported major.minor version error

  1. Check whether u have jdk installed in the path "C:\Program Files\Java" If not Install the JDK in your machine

  2. In Eclipse, right click on "build.xml" then select Run As > External Tools Configuration

  3. Click on "JRE" tab then click on "Installed JREs" > "ADD" > "Standard VM" > Click "Next

  4. Select the Directory "C:\Program Files\Java\jdk1.7.x_xx" and the directory will be added to the "installed jres"

  5. Select the new JDK directory and Click "OK"

  6. Click on "Seperate JRE" dropdown and select the JDK version "jdk1.7.x_xx" and click on "Run"

This would help:)

How to get next/previous record in MySQL?

There's another trick you can use to show columns from previous rows, using any ordering you want, using a variable similar to the @row trick:

SELECT @prev_col_a, @prev_col_b, @prev_col_c,
   @prev_col_a := col_a AS col_a,
   @prev_col_b := col_b AS col_b,
   @prev_col_c := col_c AS col_c
FROM table, (SELECT @prev_col_a := NULL, @prev_col_b := NULL, @prev_col_c := NULL) prv
ORDER BY whatever

Apparently, the select columns are evaluated in order, so this will first select the saved variables, and then update the variables to the new row (selecting them in the process).

NB: I'm not sure that this is defined behaviour, but I've used it and it works.

How to get an MD5 checksum in PowerShell

Here's a function I use that handles relative and absolute paths:

function md5hash($path)
    $fullPath = Resolve-Path $path
    $md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
    $file = [System.IO.File]::Open($fullPath,[System.IO.Filemode]::Open, [System.IO.FileAccess]::Read)
    try {
    } finally {

Thanks to @davor above for the suggestion to use Open() instead of ReadAllBytes() and to @jpmc26 for the suggestion to use a finally block.

Data at the root level is invalid



should be:


LoadXml() is for loading an XML string, not a file name.

Is there a way to create and run javascript in Chrome?

Usually one uses text editor to create source files (like JavaScript). I use VisualStudio which have intellisence supprt for JavaScript, but any other editor will do (vim or notepad on Windows are both fine).

To run JavaScript by itself you need something that can do that. I.e. on Windows you can directly run script from console using CScript script.js command. There are other ways to run JavaScript on Windows and other OS.

Browsers (like Chrome) do not run JavaScript by itself, only as part of a page or extensions. It is unclear what one would expect of browser to do with JavaScript by itself.

Keystore change passwords

For a full programmatic change (e.g. install program) and no prompting

#!/bin/bash -eu


keytool -storepasswd -new "${NEWPASSWORD}" \
  -storepass "${OLDPASSWORD}" \
  -keystore /path/to/keystore

Full disclosure: I DO NOT recommend running this command line in a shell, as the old and new passwords will be saved in the shell's history, and visible in console.

How to install and run Typescript locally in npm?

You can now use ts-node, which makes your life as simple as

npm install -D ts-node
npm install -D typescript

ts-node script.ts

Taskkill /f doesn't kill a process

I've seen this a few times and my only solution was a re-boot.

You could try using PowerShell: Get-Process devenv | kill

But if the other methods failed, this probably will too. :-(

Which characters are valid/invalid in a JSON key name?

It is worth mentioning that while starting the keys with numbers is valid, it could cause some unintended issues.


var testObject = {
    "1tile": "test value"
console.log(testObject.1tile); // fails, invalid syntax
console.log(testObject["1tile"]; // workaround