Programs & Examples On #Rfc5322

RFC5322 specifies the Internet Message Format (IMF), a syntax for text messages that are sent between computer users, within the framework of "electronic mail" messages.

Get the current language in device

You can use this code to find out keyboard current

InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
InputMethodSubtype ims = imm.getCurrentInputMethodSubtype();
String locale = ims.getLocale();

iOS 7 UIBarButton back button arrow color

If you are using storyboards you could set the navigation bar tint colour.

enter image description here

enter image description here

How to call servlet through a JSP page

You can use RequestDispatcher as you usually use it in Servlet:

<%@ page contentType="text/html"%>
<%@ page import = "javax.servlet.RequestDispatcher" %>
     RequestDispatcher rd = request.getRequestDispatcher("/yourServletUrl");
     request.setAttribute("msg","HI Welcome");
     rd.forward(request, response);

Always be aware that don't commit any response before you use forward, as it will lead to IllegalStateException.

Disable XML validation in Eclipse

You have two options:

  1. Configure Workspace Settings (disable the validation for the current workspace): Go to Window > Preferences > Validation and uncheck the manual and build for: XML Schema Validator, XML Validator

  2. Check enable project specific settings (disable the validation for this project): Right-click on the project, select Properties > Validation and uncheck the manual and build for: XML Schema Validator, XML Validator

Right-click on the project and select Validate to make the errors disappear.

SMTP error 554

To resolve problem go to the MDaemon-->setup-->Miscellaneous options-->Server-->SMTP Server Checks commands and headers for RFC Compliance

Want to upgrade project from Angular v5 to Angular v6

There are few steps to upgrade 2/4/5 to Angular 6.

npm uninstall --save-dev angular-cli
npm install --save-dev @angular/cli@latest
npm install

To fix the issue related to "angular.json" :-

ng update @angular/cli --migrate-only --from=1.7.4



Hoping this will help you :)

fatal error C1083: Cannot open include file: 'xyz.h': No such file or directory?

Either move the xyz.h file somewhere else so the preprocessor can find it, or else change the #include statement so the preprocessor finds it where it already is.

Where the preprocessor looks for included files is described here. One solution is to put the xyz.h file in a folder where the preprocessor is going to find it while following that search pattern.

Alternatively you can change the #include statement so that the preprocessor can find it. You tell us the xyz.cxx file is is in the 'code' folder but you don't tell us where you've put the xyz.h file. Let's say your file structure looks like this...

<some folder>\xyz.h
<some folder>\code\xyz.cxx

In that case the #include statement in xyz.cxx should look something like this..

#include "..\xyz.h"

On the other hand let's say your file structure looks like this...

<some folder>\include\xyz.h
<some folder>\code\xyz.cxx

In that case the #include statement in xyz.cxx should look something like this..

#include "..\include\xyz.h"

Update: On the other other hand as @In silico points out in the comments, if you are using #include <xyz.h> you should probably change it to #include "xyz.h"

Is it possible to run .APK/Android apps on iPad/iPhone devices?

Apple users can download your .apk file, however they cannot run it. It is a different file format than iPhone apps (.ipa)

Python dictionary get multiple values

If the fallback keys are not too many you can do something like this

value = my_dict.get('first_key') or my_dict.get('second_key')

Can't find bundle for base name /Bundle, locale en_US

I was able to resolve the issue, the resource was in my project directories but when the junit utility tries to load it, it was returning an error of MissingResourceException. And the reason was the resource was in the not on the classpath of the test class package so when I added the cfg/ folder to my classpath path entry in eclipse and set the output directory in the build conf to the same class package the issue was resolved.

When you try this approach just make sure, the classpath conf file shows the classpath entry of the resource directory (eg. cfg/)

How to change cursor from pointer to finger using jQuery?

It is very straight forward


<input type="text" placeholder="some text" />
<input type="button" value="button" class="button"/>
<button class="button">Another button</button>


  $('.button').css( 'cursor', 'pointer' );

  // for old IE browsers
  $('.button').css( 'cursor', 'hand' ); 

Check it out on JSfiddle

How do I iterate through table rows and cells in JavaScript?

You can consider using jQuery. With jQuery it's super-easy and might look like this:

$('#mytab1 tr').each(function(){
        //do your stuff, you can use $(this) to get current cell

Make a bucket public in Amazon S3

Amazon provides a policy generator tool:

After that, you can enter the policy requirements for the bucket on the AWS console:

Inserting string at position x of another string

If ES2018's lookbehind is available, one more regexp solution, that makes use of it to "replace" at a zero-width position after the Nth character (similar to @Kamil Kielczewski's, but without storing the initial characters in a capturing group):

"I want apple".replace(/(?<=^.{6})/, " an")

var a = "I want apple";_x000D_
var b = " an";_x000D_
var position = 6;_x000D_
var r= a.replace(new RegExp(`(?<=^.{${position}})`), b);_x000D_
console.log("I want apple".replace(/(?<=^.{6})/, " an"));

Flask Python Buttons

In case anyone was still looking and came across this SO post like I did.

<input type="submit" name="open" value="Open">
<input type="submit" name="close" value="Close">

def contact():
    if "open" in request.form:
    elif "close" in request.form:
    return render_template('contact.html')

Simple, concise, and it works. Don't even need to instantiate a form object.

SQL injection that gets around mysql_real_escape_string()

The short answer is yes, yes there is a way to get around mysql_real_escape_string(). #For Very OBSCURE EDGE CASES!!!

The long answer isn't so easy. It's based off an attack demonstrated here.

The Attack

So, let's start off by showing the attack...

mysql_query('SET NAMES gbk');
$var = mysql_real_escape_string("\xbf\x27 OR 1=1 /*");
mysql_query("SELECT * FROM test WHERE name = '$var' LIMIT 1");

In certain circumstances, that will return more than 1 row. Let's dissect what's going on here:

  1. Selecting a Character Set

    mysql_query('SET NAMES gbk');

    For this attack to work, we need the encoding that the server's expecting on the connection both to encode ' as in ASCII i.e. 0x27 and to have some character whose final byte is an ASCII \ i.e. 0x5c. As it turns out, there are 5 such encodings supported in MySQL 5.6 by default: big5, cp932, gb2312, gbk and sjis. We'll select gbk here.

    Now, it's very important to note the use of SET NAMES here. This sets the character set ON THE SERVER. If we used the call to the C API function mysql_set_charset(), we'd be fine (on MySQL releases since 2006). But more on why in a minute...

  2. The Payload

    The payload we're going to use for this injection starts with the byte sequence 0xbf27. In gbk, that's an invalid multibyte character; in latin1, it's the string ¿'. Note that in latin1 and gbk, 0x27 on its own is a literal ' character.

    We have chosen this payload because, if we called addslashes() on it, we'd insert an ASCII \ i.e. 0x5c, before the ' character. So we'd wind up with 0xbf5c27, which in gbk is a two character sequence: 0xbf5c followed by 0x27. Or in other words, a valid character followed by an unescaped '. But we're not using addslashes(). So on to the next step...

  3. mysql_real_escape_string()

    The C API call to mysql_real_escape_string() differs from addslashes() in that it knows the connection character set. So it can perform the escaping properly for the character set that the server is expecting. However, up to this point, the client thinks that we're still using latin1 for the connection, because we never told it otherwise. We did tell the server we're using gbk, but the client still thinks it's latin1.

    Therefore the call to mysql_real_escape_string() inserts the backslash, and we have a free hanging ' character in our "escaped" content! In fact, if we were to look at $var in the gbk character set, we'd see:

    ?' OR 1=1 /*

    Which is exactly what the attack requires.

  4. The Query

    This part is just a formality, but here's the rendered query:

    SELECT * FROM test WHERE name = '?' OR 1=1 /*' LIMIT 1

Congratulations, you just successfully attacked a program using mysql_real_escape_string()...

The Bad

It gets worse. PDO defaults to emulating prepared statements with MySQL. That means that on the client side, it basically does a sprintf through mysql_real_escape_string() (in the C library), which means the following will result in a successful injection:

$pdo->query('SET NAMES gbk');
$stmt = $pdo->prepare('SELECT * FROM test WHERE name = ? LIMIT 1');
$stmt->execute(array("\xbf\x27 OR 1=1 /*"));

Now, it's worth noting that you can prevent this by disabling emulated prepared statements:

$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);

This will usually result in a true prepared statement (i.e. the data being sent over in a separate packet from the query). However, be aware that PDO will silently fallback to emulating statements that MySQL can't prepare natively: those that it can are listed in the manual, but beware to select the appropriate server version).

The Ugly

I said at the very beginning that we could have prevented all of this if we had used mysql_set_charset('gbk') instead of SET NAMES gbk. And that's true provided you are using a MySQL release since 2006.

If you're using an earlier MySQL release, then a bug in mysql_real_escape_string() meant that invalid multibyte characters such as those in our payload were treated as single bytes for escaping purposes even if the client had been correctly informed of the connection encoding and so this attack would still succeed. The bug was fixed in MySQL 4.1.20, 5.0.22 and 5.1.11.

But the worst part is that PDO didn't expose the C API for mysql_set_charset() until 5.3.6, so in prior versions it cannot prevent this attack for every possible command! It's now exposed as a DSN parameter.

The Saving Grace

As we said at the outset, for this attack to work the database connection must be encoded using a vulnerable character set. utf8mb4 is not vulnerable and yet can support every Unicode character: so you could elect to use that instead—but it has only been available since MySQL 5.5.3. An alternative is utf8, which is also not vulnerable and can support the whole of the Unicode Basic Multilingual Plane.

Alternatively, you can enable the NO_BACKSLASH_ESCAPES SQL mode, which (amongst other things) alters the operation of mysql_real_escape_string(). With this mode enabled, 0x27 will be replaced with 0x2727 rather than 0x5c27 and thus the escaping process cannot create valid characters in any of the vulnerable encodings where they did not exist previously (i.e. 0xbf27 is still 0xbf27 etc.)—so the server will still reject the string as invalid. However, see @eggyal's answer for a different vulnerability that can arise from using this SQL mode.

Safe Examples

The following examples are safe:

mysql_query('SET NAMES utf8');
$var = mysql_real_escape_string("\xbf\x27 OR 1=1 /*");
mysql_query("SELECT * FROM test WHERE name = '$var' LIMIT 1");

Because the server's expecting utf8...

$var = mysql_real_escape_string("\xbf\x27 OR 1=1 /*");
mysql_query("SELECT * FROM test WHERE name = '$var' LIMIT 1");

Because we've properly set the character set so the client and the server match.

$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$pdo->query('SET NAMES gbk');
$stmt = $pdo->prepare('SELECT * FROM test WHERE name = ? LIMIT 1');
$stmt->execute(array("\xbf\x27 OR 1=1 /*"));

Because we've turned off emulated prepared statements.

$pdo = new PDO('mysql:host=localhost;dbname=testdb;charset=gbk', $user, $password);
$stmt = $pdo->prepare('SELECT * FROM test WHERE name = ? LIMIT 1');
$stmt->execute(array("\xbf\x27 OR 1=1 /*"));

Because we've set the character set properly.

$mysqli->query('SET NAMES gbk');
$stmt = $mysqli->prepare('SELECT * FROM test WHERE name = ? LIMIT 1');
$param = "\xbf\x27 OR 1=1 /*";
$stmt->bind_param('s', $param);

Because MySQLi does true prepared statements all the time.

Wrapping Up

If you:

  • Use Modern Versions of MySQL (late 5.1, all 5.5, 5.6, etc) AND mysql_set_charset() / $mysqli->set_charset() / PDO's DSN charset parameter (in PHP = 5.3.6)


  • Don't use a vulnerable character set for connection encoding (you only use utf8 / latin1 / ascii / etc)

You're 100% safe.

Otherwise, you're vulnerable even though you're using mysql_real_escape_string()...

Can I change the color of Font Awesome's icon color?

Is there any possible way to change the color of a font-awesome icon to black?

Yes, there is. See the snipped bellow

<!-- Assuming that you don't have, this needs to be in your HTML file (usually the header) -->
<link rel="stylesheet" href="">

<!-- Here is what you need to use -->
<a href="/users/edit" class="fa fa-cog" style="color:black"> Edit Profile</a>

Font awesome is supposed to be font not image, right?

Yes, it is a font. Therefore, you are able to scale it to any size without losing quality.

Convert a RGB Color Value to a Hexadecimal String

You can use

String hex = String.format("#%02x%02x%02x", r, g, b);  

Use capital X's if you want your resulting hex-digits to be capitalized (#FFFFFF vs. #ffffff).

Inconsistent Accessibility: Parameter type is less accessible than method

parameter type 'support.ACTInterface' is less accessible than method    

The error says 'support.ACTInterface' is less accessible because you have made the interface as private, at least make it internal or make it public.

Print out the values of a (Mat) matrix in OpenCV C++

See the first answer to Accessing a matrix element in the "Mat" object (not the CvMat object) in OpenCV C++
Then just loop over all the elements in cout <<<double>(0,0); rather than just 0,0

Or better still with the C++ interface:

cv::Mat M;
cout << "M = " << endl << " "  << M << endl << endl;

Getting value from appsettings.json in .net core

Program and Startup class

.NET Core 2.x

You don't need to new IConfiguration in the Startup constructor. Its implementation will be injected by the DI system.

// Program.cs
public class Program
    public static void Main(string[] args)

    public static IWebHost BuildWebHost(string[] args) =>

// Startup.cs
public class Startup
    public IHostingEnvironment HostingEnvironment { get; private set; }
    public IConfiguration Configuration { get; private set; }

    public Startup(IConfiguration configuration, IHostingEnvironment env)
        this.HostingEnvironment = env;
        this.Configuration = configuration;

.NET Core 1.x

You need to tell Startup to load the appsettings files.

// Program.cs
public class Program
    public static void Main(string[] args)
        var host = new WebHostBuilder()


public class Startup
    public IConfigurationRoot Configuration { get; private set; }

    public Startup(IHostingEnvironment env)
        var builder = new ConfigurationBuilder()
            .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
            .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)

        this.Configuration = builder.Build();

Getting Values

There are many ways you can get the value you configure from the app settings:

Let's say your appsettings.json looks like this:

    "ConnectionStrings": {
    "AppIdentitySettings": {
        "User": {
            "RequireUniqueEmail": true
        "Password": {
            "RequiredLength": 6,
            "RequireLowercase": true,
            "RequireUppercase": true,
            "RequireDigit": true,
            "RequireNonAlphanumeric": true
        "Lockout": {
            "AllowedForNewUsers": true,
            "DefaultLockoutTimeSpanInMins": 30,
            "MaxFailedAccessAttempts": 5
    "Recaptcha": { 

Simple Way

You can inject the whole configuration into the constructor of your controller/class (via IConfiguration) and get the value you want with a specified key:

public class AccountController : Controller
    private readonly IConfiguration _config;

    public AccountController(IConfiguration config)
        _config = config;

    public IActionResult ResetPassword(int userId, string code)
        var vm = new ResetPasswordViewModel
            PasswordRequiredLength = _config.GetValue<int>(
            RequireUppercase = _config.GetValue<bool>(

        return View(vm);

Options Pattern

The ConfigurationBuilder.GetValue<T> works great if you only need one or two values from the app settings. But if you want to get multiple values from the app settings, or you don't want to hard code those key strings in multiple places, it might be easier to use Options Pattern. The options pattern uses classes to represent the hierarchy/structure.

To use options pattern:

  1. Define classes to represent the structure
  2. Register the configuration instance which those classes bind against
  3. Inject IOptions<T> into the constructor of the controller/class you want to get values on

1. Define configuration classes to represent the structure

You can define classes with properties that need to exactly match the keys in your app settings. The name of the class does't have to match the name of the section in the app settings:

public class AppIdentitySettings
    public UserSettings User { get; set; }
    public PasswordSettings Password { get; set; }
    public LockoutSettings Lockout { get; set; }

public class UserSettings
    public bool RequireUniqueEmail { get; set; }

public class PasswordSettings
    public int RequiredLength { get; set; }
    public bool RequireLowercase { get; set; }
    public bool RequireUppercase { get; set; }
    public bool RequireDigit { get; set; }
    public bool RequireNonAlphanumeric { get; set; }

public class LockoutSettings
    public bool AllowedForNewUsers { get; set; }
    public int DefaultLockoutTimeSpanInMins { get; set; }
    public int MaxFailedAccessAttempts { get; set; }

2. Register the configuration instance

And then you need to register this configuration instance in ConfigureServices() in the start up:

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace DL.SO.UI.Web
    public class Startup
        public void ConfigureServices(IServiceCollection services)
            var identitySettingsSection = 

3. Inject IOptions

Lastly on the controller/class you want to get the values, you need to inject IOptions<AppIdentitySettings> through constructor:

public class AccountController : Controller
    private readonly AppIdentitySettings _appIdentitySettings;

    public AccountController(IOptions<AppIdentitySettings> appIdentitySettingsAccessor)
        _appIdentitySettings = appIdentitySettingsAccessor.Value;

    public IActionResult ResetPassword(int userId, string code)
        var vm = new ResetPasswordViewModel
            PasswordRequiredLength = _appIdentitySettings.Password.RequiredLength,
            RequireUppercase = _appIdentitySettings.Password.RequireUppercase

        return View(vm);

Have a div cling to top of screen if scrolled down past it

The trick to make infinity's answer work without the flickering is to put the scroll-check on another div then the one you want to have fixed.

Derived from the code uses I ended up using this:

function sticky_relocate() {
    var window_top = $(window).scrollTop();
    var div_top = $('#sticky-anchor').offset().top;
    if (window_top > div_top)

$(function() {

This way the function is only called once the sticky-anchor is reached and thus won't be removing and adding the '.sticky' class on every scroll event.

Now it adds the sticky class when the sticky-anchor reaches the top and removes it once the sticky-anchor return into view.

Just place an empty div with a class acting like an anchor just above the element you want to have fixed.

Like so:

<div id="sticky-anchor"></div>
<div id="sticky-element">Your sticky content</div>

All credit for the code goes to

Add image to layout in ruby on rails

It's working for me:

<%= image_tag( root_url + "images/rss.jpg", size: "50x50", :alt => "rss feed") -%>

How do I append to a table in Lua

You are looking for the insert function, found in the table section of the main library.

foo = {}
table.insert(foo, "bar")
table.insert(foo, "baz")

What's the difference between a method and a function?

To a first order approximation, a method (in C++ style OO) is another word for a member function, that is a function that is part of a class.

In languages like C/C++ you can have functions which are not members of a class; you don't call a function not associated with a class a method.

How to detect IE11?

Get IE Version from the User-Agent

var ie = 0;
try { ie = navigator.userAgent.match( /(MSIE |Trident.*rv[ :])([0-9]+)/ )[ 2 ]; }

How it works: The user-agent string for all IE versions includes a portion "MSIE space version" or "Trident other-text rv space-or-colon version". Knowing this, we grab the version number from a String.match() regular expression. A try-catch block is used to shorten the code, otherwise we'd need to test the array bounds for non-IE browsers.

Note: The user-agent can be spoofed or omitted, sometimes unintentionally if the user has set their browser to a "compatibility mode". Though this doesn't seem like much of an issue in practice.

Get IE Version without the User-Agent

var d = document, w = window;
var ie = ( !!w.MSInputMethodContext ? 11 : !d.all ? 99 : w.atob ? 10 : 
d.addEventListener ? 9 : d.querySelector ? 8 : w.XMLHttpRequest ? 7 : 
d.compatMode ? 6 : w.attachEvent ? 5 : 1 );

How it works: Each version of IE adds support for additional features not found in previous versions. So we can test for the features in a top-down manner. A ternary sequence is used here for brevity, though if-then and switch statements would work just as well. The variable ie is set to an integer 5-11, or 1 for older, or 99 for newer/non-IE. You can set it to 0 if you just want to test for IE 1-11 exactly.

Note: Object detection may break if your code is run on a page with third-party scripts that add polyfills for things like document.addEventListener. In such situations the user-agent is the best option.

Detect if the Browser is Modern

If you're only interested in whether or not a browser supports most HTML 5 and CSS 3 standards, you can reasonably assume that IE 8 and lower remain the primary problem apps. Testing for window.getComputedStyle will give you a fairly good mix of modern browsers, as well (IE 9, FF 4, Chrome 11, Safari 5, Opera 11.5). IE 9 greatly improves on standards support, but native CSS animation requires IE 10.

var isModernBrowser = ( !document.all || ( document.all && document.addEventListener ) ); 

How to get back Lost phpMyAdmin Password, XAMPP

You want to edit this file: "\xampp\phpMyAdmin\"

change this line:

$cfg['Servers'][$i]['password'] = 'WhateverPassword';

to whatever your password is. If you don't remember your password, then run this command in the Shell:

mysqladmin.exe -u root password WhateverPassword

where 'WhateverPassword' is your new password.

How to change TextField's height and width?

If you use "suffixIcon" to collapse the height of the TextField add: suffixIconConstraints

                    style: TextStyle(fontSize: r * 1.8, color: Colors.black87),
                    decoration: InputDecoration(
                      isDense: true,
                      contentPadding: EdgeInsets.symmetric(vertical: r * 1.6, horizontal: r * 1.6),
                      suffixIcon: Icon(, color: Colors.black54),
                      suffixIconConstraints: BoxConstraints(minWidth: 32, minHeight: 32),

Install Windows Service created in Visual Studio

Here is an alternate way to make the installer and get rid of that error message. Also it seems that VS2015 express does not have the "Add Installer" menu item.

You simply need to create a class and add the below code and add the reference System.Configuration.Install.dll.

using System.Configuration.Install;
using System.ServiceProcess;
using System.ComponentModel;

namespace SAS
    public class MyProjectInstaller : Installer
        private ServiceInstaller serviceInstaller1;
        private ServiceProcessInstaller processInstaller;

        public MyProjectInstaller()
            // Instantiate installer for process and service.
            processInstaller = new ServiceProcessInstaller();
            serviceInstaller1 = new ServiceInstaller();

            // The service runs under the system account.
            processInstaller.Account = ServiceAccount.LocalSystem;

            // The service is started manually.
            serviceInstaller1.StartType = ServiceStartMode.Manual;

            // ServiceName must equal those on ServiceBase derived classes.
            serviceInstaller1.ServiceName = "SAS Service";

            // Add installer to collection. Order is not important if more than one service.

Accessing JSON object keys having spaces

The way to do this is via the bracket notation.

var test = {_x000D_
    "id": "109",_x000D_
    "No. of interfaces": "4"_x000D_
alert(test["No. of interfaces"]);

For more info read out here:

getSupportActionBar() The method getSupportActionBar() is undefined for the type TaskActivity. Why?

Here is another solution you could have used. It is working in my app.

      public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState); actionBar =getSupportActionBar();

Then you can get rid of that import for the one line ActionBar use.

How to create a 100% screen width div inside a container in bootstrap?

The reason why your full-width-div doesn't stretch 100% to your screen it's because of its parent "container" which occupies only about 80% of the screen.

If you want to make it stretch 100% to the screen either you make the "full-width-div" position fixed or use the "container-fluid" class instead of "container".

see Bootstrap 3 docs:

Why is there no Constant feature in Java?

The C++ semantics of const are very different from Java final. If the designers had used const it would have been unnecessarily confusing.

The fact that const is a reserved word suggests that the designers had ideas for implementing const, but they have since decided against it; see this closed bug. The stated reasons include that adding support for C++ style const would cause compatibility problems.

youtube: link to display HD video by default

via Is there a way to link someone to a YouTube Video in HD 1080p quality?

Yes there is:

options are:

default|none: vq=auto;
Code for auto: vq=auto;
Code for 2160p: vq=hd2160;
Code for 1440p: vq=hd1440;
Code for 1080p: vq=hd1080;
Code for 720p: vq=hd720;
Code for 480p: vq=large;
Code for 360p: vq=medium;
Code for 240p: vq=small;

As mentioned, you have to use the /embed/ or /v/ URL.

Note: Some copyrighted content doesn't support be played in this way

How to reload a page using Angularjs?

You can also try this, after injecting $window service.


Communication between tabs or windows

There's a tiny open-source component to sync/communicate between tabs/windows of the same origin (disclaimer - I'm one of the contributors!) based around localStorage.

TabUtils.BroadcastMessageToAllTabs("eventName", eventDataString);

TabUtils.OnBroadcastMessage("eventName", function (eventDataString) {

TabUtils.CallOnce("lockname", function () {
    alert("I run only once across multiple tabs");

P.S. I took the liberty to recommend it here since most of the "lock/mutex/sync" components fail on websocket connections when events happen almost simultaneously

HTML5 canvas ctx.fillText won't do line breaks?

I don't think this is possible neither, but a workaround for this is to create a <p>element and position it with Javascript.

Cannot install node modules that require compilation on Windows 7 x64/VS2012

Try that - will set it globally:

npm config set msvs_version 2012 --global

How to check if a Docker image with a specific tag exist locally?

Using test

if test ! -z "$(docker images -q <name:tag>)"; then
  echo "Exist"

or in one line

test ! -z "$(docker images -q <name:tag>)" &&  echo exist

increase the java heap size permanently?

This worked for me:

export _JAVA_OPTIONS="-Xmx1g"

It's important that you have no spaces because for me it did not work. I would suggest just copying and pasting. Then I ran:

java -XshowSettings:vm 

and it will tell you:

Picked up _JAVA_OPTIONS: -Xmx1g

What is the 'realtime' process priority setting for?

A realtime priority thread can never be pre-empted by timer interrupts and runs at a higher priority than any other thread in the system. As such a CPU bound realtime priority thread can totally ruin a machine.

Creating realtime priority threads requires a privilege (SeIncreaseBasePriorityPrivilege) so it can only be done by administrative users.

For Vista and beyond, one option for applications that do require that they run at realtime priorities is to use the Multimedia Class Scheduler Service (MMCSS) and let it manage your threads priority. The MMCSS will prevent your application from using too much CPU time so you don't have to worry about tanking the machine.

How do change the color of the text of an <option> within a <select>?

Here is my demo with jQuery

<!doctype html>
    option:not(first-child) {
        color: #000;
<script type="text/javascript" src=""></script>
            if ($(this).val()=="") $(this).css({color: "#aaa"});
            else $(this).css({color: "#000"});
<meta charset="utf-8">
    <option disable hidden value="">CHOOSE</option>

How to drop a database with Mongoose?

The difficulty I've had with the other solutions is they rely on restarting your application if you want to get the indexes working again.

For my needs (i.e. being able to run a unit test the nukes all collections, then recreates them along with their indexes), I ended up implementing this solution:

This relies on the underscore.js and async.js libraries to assemble the indexes in parellel, it could be unwound if you're against that library but I leave that as an exerciser for the developer.

mongoose.connection.db.executeDbCommand( {dropDatabase:1}, function(err, result) {
  var mongoPath = mongoose.connections[0].host + ':' + mongoose.connections[0].port + '/' + mongoose.connections[0].name
  //Kill the current connection, then re-establish it
  mongoose.connect('mongodb://' + mongoPath, function(err){
    var asyncFunctions = []

    //Loop through all the known schemas, and execute an ensureIndex to make sure we're clean
    _.each(mongoose.connections[0].base.modelSchemas, function(schema, key) {
        mongoose.model(key, schema).ensureIndexes(function(){
          return cb()

    async.parallel(asyncFunctions, function(err) {
      console.log('Done dumping all collections and recreating indexes')

"Untrusted App Developer" message when installing enterprise iOS Application

You absolutely can avoid this issue if you manage the device with MDM or have access to Apple Configurator.

The solution is to push either the Developer or iOS Distribution certificate to the device via MDM or Apple Configurator. Once you do that, any application signed by that cert will be trusted.

When you click on "Do you trust this developer", you're essentially adding that certificate manually on a per-app basis.

biggest integer that can be stored in a double

9007199254740992 (that's 9,007,199,254,740,992) with no guarantees :)


#include <math.h>
#include <stdio.h>

int main(void) {
  double dbl = 0; /* I started with 9007199254000000, a little less than 2^53 */
  while (dbl + 1 != dbl) dbl++;
  printf("%.0f\n", dbl - 1);
  printf("%.0f\n", dbl);
  printf("%.0f\n", dbl + 1);
  return 0;



PHP: convert spaces in string into %20?

Use the rawurlencode function instead.

Automatic creation date for Django model form objects?

You can use the auto_now and auto_now_add options for updated_at and created_at respectively.

class MyModel(models.Model):
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

Slide a layout up from bottom of screen

Try this below code, Its very short and simple.


<?xml version="1.0" encoding="utf-8"?><!-- Copyright (C) 2013 The Android Open Source Project

     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
     You may obtain a copy of the License at

     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
<set xmlns:android="">
        android:toYDelta="-90%p" />

    <alpha xmlns:android=""
        android:toAlpha="1.0" />


<?xml version="1.0" encoding="utf-8"?>
< xmlns:android=""

        app:srcCompat="@drawable/balloons" />

public class MainActivity extends AppCompatActivity {

    protected void onCreate(Bundle savedInstanceState) {
        final ImageView imageView1 = (ImageView) findViewById(;
        imageView1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {


    private void startBottomToTopAnimation(View view) {
        view.startAnimation(AnimationUtils.loadAnimation(this, R.anim.translate_anim));

bottom_up_navigation of image

Replace all whitespace characters

We can also use this if we want to change all multiple joined blank spaces with a single character:


See it in action here:


/ \s+ / g

  • \s+ matches any whitespace character (equal to [\r\n\t\f\v ])
  • + Quantifier — Matches between one and unlimited times, as many times as possible, giving back as needed (greedy)

  • Global pattern flags
    • g modifier: global. All matches (don't return after first match)

Why use a READ UNCOMMITTED isolation level?

The advantage is that it can be faster in some situations. The disadvantage is the result can be wrong (data which hasn't been committed yet could be returned) and there is no guarantee that the result is repeatable.

If you care about accuracy, don't use this.

More information is on MSDN:

Implements dirty read, or isolation level 0 locking, which means that no shared locks are issued and no exclusive locks are honored. When this option is set, it is possible to read uncommitted or dirty data; values in the data can be changed and rows can appear or disappear in the data set before the end of the transaction. This option has the same effect as setting NOLOCK on all tables in all SELECT statements in a transaction. This is the least restrictive of the four isolation levels.

How can I verify if a Windows Service is running

I guess something like this would work:

Add System.ServiceProcess to your project references (It's on the .NET tab).

using System.ServiceProcess;

ServiceController sc = new ServiceController(SERVICENAME);

switch (sc.Status)
    case ServiceControllerStatus.Running:
        return "Running";
    case ServiceControllerStatus.Stopped:
        return "Stopped";
    case ServiceControllerStatus.Paused:
        return "Paused";
    case ServiceControllerStatus.StopPending:
        return "Stopping";
    case ServiceControllerStatus.StartPending:
        return "Starting";
        return "Status Changing";

Edit: There is also a method sc.WaitforStatus() that takes a desired status and a timeout, never used it but it may suit your needs.

Edit: Once you get the status, to get the status again you will need to call sc.Refresh() first.

Reference: ServiceController object in .NET.

Java: Check the date format of current string is according to required format or not

DateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
try {
    Date date= formatter.parse("02/03/2010");
} catch (ParseException e) {
    //If input date is in different format or invalid.

formatter.setLenient(false) will enforce strict matching.

If you are using Joda-Time -

private boolean isValidDate(String dateOfBirth) {
        boolean valid = true;
        try {
            DateTimeFormatter formatter = DateTimeFormat.forPattern("dd/MM/yyyy");
            DateTime dob = formatter.parseDateTime(dateOfBirth);
        } catch (Exception e) {
            valid = false;
        return valid;

Does Hibernate create tables in the database automatically

Hibernate can create a table, hibernate sequence and tables used for many-to-many mapping on your behalf but you have to explicitly configure it by calling setProperty("", "create") of the Configuration object. By Default, it just validates the schema with DB and fails if anything not already exists by giving error "ORA-00942: table or view does not exist".

If you do above configuration then order of performed actions will be:- a) Drop all tables and sequence and do not give an error if they are not already present. b) create all table and sequence c) alter tables with constraints d) insert data into it.

android - setting LayoutParams programmatically

after creating the view we have to add layout parameters .

change like this

TextView tv = new TextView(this);
tv.setLayoutParams(new ViewGroup.LayoutParams(

if (mine) {
    leftMargin = 5;
else {
    leftMargin = 50;
final ViewGroup.MarginLayoutParams lpt =(MarginLayoutParams)tv.getLayoutParams();

Assign multiple values to array in C

If you are doing these same assignments a lot in your program and want a shortcut, the most straightforward solution might be to just add a function

static inline void set_coordinates(
        GLfloat coordinates[static 8],
        GLfloat c0, GLfloat c1, GLfloat c2, GLfloat c3,
        GLfloat c4, GLfloat c5, GLfloat c6, GLfloat c7)
    coordinates[0] = c0;
    coordinates[1] = c1;
    coordinates[2] = c2;
    coordinates[3] = c3;
    coordinates[4] = c4;
    coordinates[5] = c5;
    coordinates[6] = c6;
    coordinates[7] = c7;

and then simply call

GLfloat coordinates[8];
// ...
set_coordinates(coordinates, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f);

How to count the number of columns in a table using SQL?

Old question - but I recently needed this along with the row count... here is a query for both - sorted by row count desc:

SELECT t.owner, 
FROM   all_tables t 
       LEFT JOIN all_tab_columns c 
              ON t.table_name = c.table_name 
WHERE  num_rows IS NOT NULL 
GROUP  BY t.owner, 
ORDER  BY t.num_rows DESC; 

How do I specify unique constraint for multiple columns in MySQL?

For PostgreSQL... It didn't work for me with index; it gave me an error, so I did this:

alter table table_name
add unique(column_name_1,column_name_2);

PostgreSQL gave unique index its own name. I guess you can change the name of index in the options for the table, if it is needed to be changed...

how to set value of a input hidden field through javascript?

The first thing I will try - determine if your code with alerts is actually rendered. I see some server "if" code in what you posted, so may be condition to render javascript is not satisfied. So, on the page you working on, right-click -> view source. Try to find the js code there. Please tell us if you found the code on the page.

How to use terminal commands with Github?

git add myfile.h
git commit -m "your commit message"
git push -u origin master

if you don't remember all the files you need to update, use

git status

Converting camel case to underscore case in ruby

The ruby core itself has no support to convert a string from (upper) camel case to (also known as pascal case) to underscore (also known as snake case).

So you need either to make your own implementation or use an existing gem.

There is a small ruby gem called lucky_case which allows you to convert a string from any of the 10+ supported cases to another case easily:

require 'lucky_case'

# convert to snake case string
LuckyCase.snake_case('CamelCaseString')      # => 'camel_case_string'
# or the opposite way
LuckyCase.pascal_case('camel_case_string')   # => 'CamelCaseString'

You can even monkey patch the String class if you want to:

require 'lucky_case/string'

'CamelCaseString'.snake_case  # => 'camel_case_string'
'CamelCaseString'.snake_case! # => 'camel_case_string' and overwriting original

Have a look at the offical repository for more examples and documentation:

Equivalent of shell 'cd' command to change the working directory?

If you're using a relatively new version of Python, you can also use a context manager, such as this one:

from __future__ import with_statement
from grizzled.os import working_directory

with working_directory(path_to_directory):
    # code in here occurs within the directory

# code here is in the original directory


If you prefer to roll your own:

import os
from contextlib import contextmanager

def working_directory(directory):
    owd = os.getcwd()
        yield directory

IndentationError: unindent does not match any outer indentation level

Other posters are probably correct...there might be spaces mixed in with your tabs. Try doing a search & replace to replace all tabs with a few spaces.

Try this:

import sys

def Factorial(n): # return factorial
    result = 1
    for i in range (1,n):
        result = result * i
    print "factorial is ",result
    return result

print Factorial(10)

How does "make" app know default target to build if no target is specified?

GNU Make also allows you to specify the default make target using a special variable called .DEFAULT_GOAL. You can even unset this variable in the middle of the Makefile, causing the next target in the file to become the default target.

Ref: The Gnu Make manual - Special Variables

TypeError: expected a character buffer object - while trying to save integer to textfile

from __future__ import with_statement
with open('file.txt','r+') as f:
    counter = str(int(

Having both a Created and Last Updated timestamp columns in MySQL 4.0

There is a trick to have both timestamps, but with a little limitation.

You can use only one of the definitions in one table. Create both timestamp columns like so:

create table test_table( 
  id integer not null auto_increment primary key, 
  stamp_created timestamp default '0000-00-00 00:00:00', 
  stamp_updated timestamp default now() on update now() 

Note that it is necessary to enter null into both columns during insert:

mysql> insert into test_table(stamp_created, stamp_updated) values(null, null); 
Query OK, 1 row affected (0.06 sec)

mysql> select * from test_table; 
| id | stamp_created       | stamp_updated       |
|  2 | 2009-04-30 09:44:35 | 2009-04-30 09:44:35 |
2 rows in set (0.00 sec)  

mysql> update test_table set id = 3 where id = 2; 
Query OK, 1 row affected (0.05 sec) Rows matched: 1  Changed: 1  Warnings: 0  

mysql> select * from test_table;
| id | stamp_created       | stamp_updated       | 
|  3 | 2009-04-30 09:44:35 | 2009-04-30 09:46:59 | 
2 rows in set (0.00 sec)  

How to implement "confirmation" dialog in Jquery UI dialog?

Simple and short solution that i just tried and it works

  $('.confirm').click(function() {
    return false;

then just add the class="confirm" to your a link and it works!

Save text file UTF-8 encoded with VBA

Here is another way to do this - using the API function WideCharToMultiByte:

Option Explicit

Private Declare Function WideCharToMultiByte Lib "kernel32.dll" ( _
  ByVal CodePage As Long, _
  ByVal dwFlags As Long, _
  ByVal lpWideCharStr As Long, _
  ByVal cchWideChar As Long, _
  ByVal lpMultiByteStr As Long, _
  ByVal cbMultiByte As Long, _
  ByVal lpDefaultChar As Long, _
  ByVal lpUsedDefaultChar As Long) As Long

Private Sub getUtf8(ByRef s As String, ByRef b() As Byte)
Const CP_UTF8 As Long = 65001
Dim len_s As Long
Dim ptr_s As Long
Dim size As Long
  Erase b
  len_s = Len(s)
  If len_s = 0 Then _
    Err.Raise 30030, , "Len(WideChars) = 0"
  ptr_s = StrPtr(s)
  size = WideCharToMultiByte(CP_UTF8, 0, ptr_s, len_s, 0, 0, 0, 0)
  If size = 0 Then _
    Err.Raise 30030, , "WideCharToMultiByte() = 0"
  ReDim b(0 To size - 1)
  If WideCharToMultiByte(CP_UTF8, 0, ptr_s, len_s, VarPtr(b(0)), size, 0, 0) = 0 Then _
    Err.Raise 30030, , "WideCharToMultiByte(" & Format$(size) & ") = 0"
End Sub

Public Sub writeUtf()
Dim file As Integer
Dim s As String
Dim b() As Byte
  s = "äöüßµ@€|~{}[]²³\ .." & _
    " OMEGA" & ChrW$(937) & ", SIGMA" & ChrW$(931) & _
    ", alpha" & ChrW$(945) & ", beta" & ChrW$(946) & ", pi" & ChrW$(960) & vbCrLf
  file = FreeFile
  Open "C:\Temp\TestUtf8.txt" For Binary Access Write Lock Read Write As #file
  getUtf8 s, b
  Put #file, , b
  Close #file
End Sub

Send and Receive a file in socket programming in Linux with C/C++ (GCC/G++)

The most portable solution is just to read the file in chunks, and then write the data out to the socket, in a loop (and likewise, the other way around when receiving the file). You allocate a buffer, read into that buffer, and write from that buffer into your socket (you could also use send and recv, which are socket-specific ways of writing and reading data). The outline would look something like this:

while (1) {
    // Read data into buffer.  We may not have enough to fill up buffer, so we
    // store how many bytes were actually read in bytes_read.
    int bytes_read = read(input_file, buffer, sizeof(buffer));
    if (bytes_read == 0) // We're done reading from the file

    if (bytes_read < 0) {
        // handle errors

    // You need a loop for the write, because not all of the data may be written
    // in one call; write will return how many bytes were written. p keeps
    // track of where in the buffer we are, while we decrement bytes_read
    // to keep track of how many bytes are left to write.
    void *p = buffer;
    while (bytes_read > 0) {
        int bytes_written = write(output_socket, p, bytes_read);
        if (bytes_written <= 0) {
            // handle errors
        bytes_read -= bytes_written;
        p += bytes_written;

Make sure to read the documentation for read and write carefully, especially when handling errors. Some of the error codes mean that you should just try again, for instance just looping again with a continue statement, while others mean something is broken and you need to stop.

For sending the file to a socket, there is a system call, sendfile that does just what you want. It tells the kernel to send a file from one file descriptor to another, and then the kernel can take care of the rest. There is a caveat that the source file descriptor must support mmap (as in, be an actual file, not a socket), and the destination must be a socket (so you can't use it to copy files, or send data directly from one socket to another); it is designed to support the usage you describe, of sending a file to a socket. It doesn't help with receiving the file, however; you would need to do the loop yourself for that. I cannot tell you why there is a sendfile call but no analogous recvfile.

Beware that sendfile is Linux specific; it is not portable to other systems. Other systems frequently have their own version of sendfile, but the exact interface may vary (FreeBSD, Mac OS X, Solaris).

In Linux 2.6.17, the splice system call was introduced, and as of 2.6.23 is used internally to implement sendfile. splice is a more general purpose API than sendfile. For a good description of splice and tee, see the rather good explanation from Linus himself. He points out how using splice is basically just like the loop above, using read and write, except that the buffer is in the kernel, so the data doesn't have to transferred between the kernel and user space, or may not even ever pass through the CPU (known as "zero-copy I/O").

Show Youtube video source into HTML5 video tag?

With the new iframe tag embedded in your website, the code will automatically detect whether you are using a browser that supports HTML5 or not.

The iframe code for embedding YouTube videos is as follows, simply copy the Video ID and replace in the code below:

<iframe type="text/html" 

plot with custom text for x axis points

This worked for me. Each month on X axis

str_month_list = ['January','February','March','April','May','June','July','August','September','October','November','December']

How to add a Hint in spinner in XML

This can be done in a very simple way. Instead of setting the adapter using the built-in values (android.R.layout.simple_list_item_1), create your own xml layout for both TextView and DropDown, and use them. In the TextView layout, define Hint text and Hint color. Last step, create and empty item as the first item in the item array defined in Strings.

<string-array name="professional_qualification_array">

Create XML layout for Spinner TextView (spnr_qualification.xml)

<TextView xmlns:android=""
    android:textColor="@color/blue_black" />

Create XML layout for spinner DropDown.(drpdn_qual.xml)

<CheckedTextView xmlns:android=""

Define spinner in the main XML layout


And finally in the code, while setting adapter for the spinner, use your custom XML layout.

ArrayAdapter<CharSequence> qual_adapter = ArrayAdapter.createFromResource(this, R.array.professional_qualification_array,R.layout.spnr_qualification);



How do I write a batch script that copies one directory to another, replaces old files?

In your batch file do this

set source=C:\Users\Habib\test
set destination=C:\Users\Habib\testdest\
xcopy %source% %destination% /y

If you want to copy the sub directories including empty directories then do:

xcopy %source% %destination% /E /y

If you only want to copy sub directories and not empty directories then use /s like:

xcopy %source% %destination% /s /y

How to use a TRIM function in SQL Server

You are missing two closing parentheses...and I am not sure an ampersand works as a string concatenation operator. Try '+'

SELECT dbo.COL_V_Cost_GEMS_Detail.TNG_SYS_NR AS [EHP Code], 
dbo.COL_TBL_VCOURSE.TNG_NA AS [Course Title], 
LTRIM(RTRIM(FCT_TYP_CD)) + ') AND (' + LTRIM(RTRIM(DEP_TYP_ID)) + ')' AS [Course Owner]

Debugging WebSocket in Google Chrome

If you don't have a page which is accessing the websocket, you can open up the Chrome console and type your JavaScript in:

var webSocket = new WebSocket('ws://address:port');
webSocket.onmessage = function(data) { console.log(data); }

This will open up the web socket so you can see it in the network tab and in the console.

Is the practice of returning a C++ reference variable evil?

I ran into a real problem where it was indeed evil. Essentially a developer returned a reference to an object in a vector. That was Bad!!!

The full details I wrote about in Janurary:

What is the correct way to restore a deleted file from SVN?

You should be able to just check out the one file you want to restore. Try something like svn co svn://your_repos/path/to/file/you/want/to/restore@rev where rev is the last revision at which the file existed.

I had to do exactly this a little while ago and if I remember correctly, using the -r option to svn didn't work; I had to use the :rev syntax. (Although I might have remembered it backwards...)

Connecting PostgreSQL 9.2.1 with Hibernate

If the project is maven placed it in src/main/resources, in the package phase it will copy it in ../WEB-INF/classes/hibernate.cfg.xml

Dealing with HTTP content in HTTPS pages

Your worst case scenario isn't as bad as you think.

You are already parsing the RSS feed, so you already have the image URLs. Say you have an image URL like You rewrite this URL as This way, the browser always makes request over https, so you get rid of the problems.

The next part - create a proxy page or servlet that does the following -

  1. Read the url parameter from the query string, and verify the hash
  2. Download the image from the server, and proxy it back to the browser
  3. Optionally, cache the image on disk

This solution has some advantages. You don't have to download the image at the time of creating the html. You don't have to store the images locally. Also, you are stateless; the url contains all the information necessary to serve the image.

Finally, the hash parameter is for security; you only want your servlet to serve images for urls you have constructed. So, when you create the url, compute md5(image_url + secret_key) and append it as the hash parameter. Before you serve the request, recompute the hash and compare it to what was passed to you. Since the secret_key is only known to you, nobody else can construct valid urls.

If you are developing in java, the Servlet is just a few lines of code. You should be able to port the code below on any other back-end technology.

targetURL is the url you get from RSS feeds
request and response are wrt to the browser
Assumes you have commons-io in your classpath

protected void proxyResponse (String targetURL, HttpServletRequest request,
 HttpServletResponse response) throws IOException {
    GetMethod get = new GetMethod(targetURL);
     * Proxy the request headers from the browser to the target server
    Enumeration headers = request.getHeaderNames();
    while(headers!=null && headers.hasMoreElements())
        String headerName = (String)headers.nextElement();

        String headerValue = request.getHeader(headerName);

        if(headerValue != null)
            get.addRequestHeader(headerName, headerValue);

    /*Make a request to the target server*/
     * Set the status code

     * proxy the response headers to the browser
    Header responseHeaders[] = get.getResponseHeaders();
    for(int i=0; i<responseHeaders.length; i++)
        String headerName = responseHeaders[i].getName();
        String headerValue = responseHeaders[i].getValue();

        if(headerValue != null)
            response.addHeader(headerName, headerValue);

     * Proxy the response body to the browser
    InputStream in = get.getResponseBodyAsStream();
    OutputStream out = response.getOutputStream();

     * If the server sends a 204 not-modified response, the InputStream will be null.
    if (in !=null) {
        IOUtils.copy(in, out);

Setting selected option in laravel form

If anyone is still here, here is my simple version.

<select name="status" class="js-example-basic-single w-100">
              <option value="" @if($brand->status == '') ? selected : null @endif disabled>Choose what to be seen on brand section</option>
              <option value="TA" @if($brand->status == 'TA') ? selected : null @endif>Title Active</option>
              <option value="ITA" @if($brand->status == 'ITA') ? selected : null @endif>Image Title Active</option>

How to instantiate a javascript class in another js file?

Possible Suggestions to make it work:

Some modifications (U forgot to include a semicolon in the statement this.getName=function(){...} it should be this.getName=function(){...};)

function Customer(){"Jhon";

(This might be one of the problem.)


Make sure U Link the JS files in the correct order

<script src="file1.js" type="text/javascript"></script>
<script src="file2.js" type="text/javascript"></script>

Android: Tabs at the BOTTOM

There are two ways to display tabs at the bottom of a tab activity.

  1. Using relative layout
  2. Using Layout_weight attribute

Please check the link for more details.

Android studio logcat nothing to show

Run this command in terminal. It will start working again.

adb kill-server && adb start-server

PDF files do not open in Internet Explorer with Adobe Reader 10.0 - users get an empty gray screen. How can I fix this for my users?

I had this problem. Reinstalling the latest version of Adobe Reader did nothing. Adobe Reader worked in Chrome but not in IE. This worked for me ...

1) Go to IE's Tools-->Compatibility View menu.
2) Enter a website that has the PDF you wish to see. Click OK.
3) Restart IE 4) Go to the website you entered and select the PDF. It should come up.
5) Go back to Compatibility View and delete the entry you made.
6) Adobe Reader works OK now in IE on all websites.

It's a strange fix, but it worked for me. I needed to go through an Adobe acceptance screen after reinstall that only appeared after I did the Compatibility View trick. Once accepted, it seemed to work everywhere. Pretty flaky stuff. Hope this helps someone.

Reading specific columns from a text file in python

First of all we open the file and as datafile then we apply .read() method reads the file contents and then we split the data which returns something like: ['5', '10', '6', '6', '20', '1', '7', '30', '4', '8', '40', '3', '9', '23', '1', '4', '13', '6'] and the we applied list slicing on this list to start from the element at index position 1 and skip next 3 elements untill it hits the end of the loop.

with open("sample.txt", "r") as datafile:


['10', '20', '30', '40', '23', '13']

Java logical operator short-circuiting

Java provides two interesting Boolean operators not found in most other computer languages. These secondary versions of AND and OR are known as short-circuit logical operators. As you can see from the preceding table, the OR operator results in true when A is true, no matter what B is.

Similarly, the AND operator results in false when A is false, no matter what B is. If you use the || and && forms, rather than the | and & forms of these operators, Java will not bother to evaluate the right-hand operand alone. This is very useful when the right-hand operand depends on the left one being true or false in order to function properly.

For example, the following code fragment shows how you can take advantage of short-circuit logical evaluation to be sure that a division operation will be valid before evaluating it:

if ( denom != 0 && num / denom >10)

Since the short-circuit form of AND (&&) is used, there is no risk of causing a run-time exception from dividing by zero. If this line of code were written using the single & version of AND, both sides would have to be evaluated, causing a run-time exception when denom is zero.

It is standard practice to use the short-circuit forms of AND and OR in cases involving Boolean logic, leaving the single-character versions exclusively for bitwise operations. However, there are exceptions to this rule. For example, consider the following statement:

 if ( c==1 & e++ < 100 ) d = 100;

Here, using a single & ensures that the increment operation will be applied to e whether c is equal to 1 or not.

how to empty recyclebin through command prompt?

Yes, you can Make a Batch file with the following code:

cd \Desktop

echo $Shell = New-Object -ComObject Shell.Application >>FILENAME.ps1
echo $RecBin = $Shell.Namespace(0xA) >>FILENAME.ps1
echo $RecBin.Items() ^| %%{Remove-Item $_.Path -Recurse -Confirm:$false} >>FILENAME.ps1

REM The actual lines being writen are right, exept for the last one, the actual thigs being writen are "$RecBin.Items() | %{Remove-Item $_.Path -Recurse -Confirm:$false}"   
But since | and % screw things up, i had to make some changes.

Powershell.exe -executionpolicy remotesigned -File  C:\Desktop\FILENAME.ps1

This basically creates a powershell script that empties the trash in the \Desktop directory, then runs it.

Java web start - Unable to load resource

I've changed the java proxy settings to direct connection - and it works.

How to get an array of unique values from an array containing duplicates in JavaScript?

function array_unique(nav_array) {
    nav_array = nav_array.sort(function (a, b) { return a*1 - b*1; });      
    var ret = [nav_array[0]];       
    // Start loop at 1 as element 0 can never be a duplicate
    for (var i = 1; i < nav_array.length; i++) { 
        if (nav_array[i-1] !== nav_array[i]) {              
    return ret;     

Check if a value exists in ArrayList

public static void linktest()
    driver=new ChromeDriver();
    //List<WebElement> allLinkElements=(List<WebElement>) driver.findElement(By.xpath("//a"));
    //int linkcount=allLinkElements.size();
    List<WebElement> link = driver.findElements(By.tagName("a"));
    String data="HOME";
    int linkcount=link.size();
    for(int i=0;i<link.size();i++) { 
        if(link.get(i).getText().contains(data)) {

How to duplicate a git repository? (without forking)

If you are copying to GitHub, you may use the GitHub Importer to do that for you. The original repo can even be from other version control systems.

Gradient text color

You can achieve that effect using a combination of CSS linear-gradient and mix-blend-mode.


    Enter your message here... 
    To be or not to be, 
    that is the question...
    maybe, I think, 
    I'm not sure
    wait, you're still reading this?
    Type a good message already!


p {
    width: 300px;
    position: relative;

p::after {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(45deg, red, orange, yellow, green, blue, purple);
    mix-blend-mode: screen;

What this does is add a linear gradient on the paragraph's ::after pseudo-element and make it cover the whole paragraph element. But with mix-blend-mode: screen, the gradient will only show on parts where there is text.

Here's a jsfiddle to show this at work. Just modify the linear-gradient values to achieve what you want.

How can I access my localhost from my Android device?

"Port forwarding on Chrome for Android makes it easy to test your development site on mobile. It works by creating a listening TCP port on your mobile device that maps to a particular TCP port on your development machine. Traffic between these ports travels through USB, so the connection doesn't depend on your network configuration."

More details here:

How can I use external JARs in an Android project?

Goto Current Project

RightClick->Properties->Java Build Path->Add Jar Files into Libraries -> Click OK

Then it is added into the Referenced Libraries File in your Current Project .

List of swagger UI alternatives

Yes, there are a few of them.

Hosted solutions that support swagger:

Check the following articles for more details:

Requested bean is currently in creation: Is there an unresolvable circular reference?

@Resource annotation on field level also could be used to declare look up at runtime

SQL Case Sensitive String Compare

You can also convert that attribute as case sensitive using this syntax :

COLLATE SQL_Latin1_General_CP1_CS_AS

Now your search will be case sensitive.

If you want to make that column case insensitive again, then use

COLLATE SQL_Latin1_General_CP1_CI_AS

Create a BufferedImage from file and make it TYPE_INT_ARGB

BufferedImage in =;

BufferedImage newImage = new BufferedImage(
    in.getWidth(), in.getHeight(), BufferedImage.TYPE_INT_ARGB);

Graphics2D g = newImage.createGraphics();
g.drawImage(in, 0, 0, null);

RelativeLayout center vertical

I have edited your layout. Check this code now.

<RelativeLayout xmlns:android=""
android:padding="5dp" >

    android:background="@android:drawable/ic_lock_lock" />

    android:text="This is my test string............"
    android:textColor="#FFFFFF" />

    android:src="@android:drawable/ic_media_next" />


Can't find file executable in your configured search path for gnc gcc compiler

ComboBox.SelectedText doesn't give me the SelectedText

I think you dont need SelectedText but you may need

String status = "The status of my combobox is " + comboBoxTest.Text;

Can constructors throw exceptions in Java?

Yes, it can throw an exception and you can declare that in the signature of the constructor too as shown in the example below:

public class ConstructorTest
    public ConstructorTest() throws InterruptedException
        System.out.println("Preparing object....");
        System.out.println("Object ready");

    public static void main(String ... args)
            ConstructorTest test = new ConstructorTest();
        catch (InterruptedException e)
            System.out.println("Got interrupted...");

UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 23: ordinal not in range(128)

I was getting this error when executing in python3,I got the same program working by simply executing in python2

How do I properly compare strings in C?

    int main()
        char s1[50],s2[50];
        printf("Enter the character of strings: ");
        printf("\nEnter different character of string to repeat: \n");
        return 0;

This is very simple solution in which you will get your output as you want.

How to join entries in a set into one string?

You have the join statement backwards try:

print ', '.join(set_3)

How to implement Android Pull-to-Refresh

To implement android Pull-to-Refresh try this piece of code,


        android:layout_height="match_parent" >


Activity class:

ListView lv = (ListView) findViewById(;
SwipeRefreshLayout pullToRefresh = (SwipeRefreshLayout) findViewById(;


pullToRefresh.setOnRefreshListener(new OnRefreshListener() {

        public void onRefresh() {
            // TODO Auto-generated method stub



private void refreshContent(){ 

     new Handler().postDelayed(new Runnable() {
            @Override public void run() {
        }, 5000);


How to make a vertical SeekBar in Android?

Wrap it inside a FrameLayout so that there is no Size issue.


                    android:rotation="270" />

Extract the maximum value within each group in a dataframe

There are many possibilities to do this in R. Here are some of them:

df <- read.table(header = TRUE, text = 'Gene   Value
A      12
A      10
B      3
B      5
B      6
C      1
D      3
D      4')

# aggregate
aggregate(df$Value, by = list(df$Gene), max)
aggregate(Value ~ Gene, data = df, max)

# tapply
tapply(df$Value, df$Gene, max)

# split + lapply
lapply(split(df, df$Gene), function(y) max(y$Value))

# plyr
ddply(df, .(Gene), summarise, Value = max(Value))

# dplyr
df %>% group_by(Gene) %>% summarise(Value = max(Value))

# data.table
dt <- data.table(df)
dt[ , max(Value), by = Gene]

# doBy
summaryBy(Value~Gene, data = df, FUN = max)

# sqldf
sqldf("select Gene, max(Value) as Value from df group by Gene", drv = 'SQLite')

# ave
df[as.logical(ave(df$Value, df$Gene, FUN = function(x) x == max(x))),]

Combine two ActiveRecord::Relation objects

This is how I've "handled" it if you use pluck to get an identifier for each of the records, join the arrays together and then finally do a query for those joined ids:

  transaction_ids = @club.type_a_trans.pluck(:id) + @club.type_b_transactions.pluck(:id) + @club.type_c_transactions.pluck(:id)
  @transactions = Transaction.where(id: transaction_ids).limit(100)

How to make a HTML Page in A4 paper size page(s)?

Many ways to do:



    height: 842px;
    width: 595px;

How do I add indices to MySQL tables?

A better option is to add the constraints directly during CREATE TABLE query (assuming you have the information about the tables)

CREATE TABLE products(
    productName varchar(100) not null,
    categoryId INT NOT NULL,
    CONSTRAINT fk_category
    FOREIGN KEY (categoryId) 
    REFERENCES categories(categoryId)

Creating a procedure in mySql with parameters

(IN @brugernavn varchar(64)**)**,IN @password varchar(64))

The problem is the )

How can I make SQL case sensitive string comparison on MySQL?

You can use BINARY to case sensitive like this

select * from tb_app where BINARY android_package='com.Mtime';

unfortunately this sql can't use index, you will suffer a performance hit on queries reliant on that index

mysql> explain select * from tb_app where BINARY android_package='com.Mtime';
| id | select_type | table  | partitions | type | possible_keys | key  | key_len | ref  | rows    | filtered | Extra       |
|  1 | SIMPLE      | tb_app | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 1590351 |   100.00 | Using where |

Fortunately, I have a few tricks to solve this problem

mysql> explain select * from tb_app where android_package='com.Mtime' and BINARY android_package='com.Mtime';
| id | select_type | table  | partitions | type | possible_keys             | key                       | key_len | ref   | rows | filtered | Extra                 |
|  1 | SIMPLE      | tb_app | NULL       | ref  | idx_android_pkg           | idx_android_pkg           | 771     | const |    1 |   100.00 | Using index condition |

Pass C# ASP.NET array to Javascript array


The array of integers is quite simple to pass. However this solution works for more complex data as well. In your model:

public int[] Numbers => new int[5];

In your view:

numbers = @(new HtmlString(JsonSerializer.Serialize(Model.Numbers)))


A tip for passing strings. You may want JSON encoder to not escape some symbols in your strings. In this example I want raw unescaped cyrillic letters. In your view:

strings = @(
new HtmlString(
    JsonSerializer.Serialize(Model.Strings, new JsonSerializerOptions
        Encoder = JavaScriptEncoder.Create(

jQuery - setting the selected value of a select control via its text description

To avoid all jQuery version complications, I honestly recommend using one of these really simple javascript functions...

function setSelectByValue(eID,val)
{ //Loop through sequentially//
  var ele=document.getElementById(eID);
  for(var ii=0; ii<ele.length; ii++)
    if(ele.options[ii].value==val) { //Found!
      return true;
  return false;

function setSelectByText(eID,text)
{ //Loop through sequentially//
  var ele=document.getElementById(eID);
  for(var ii=0; ii<ele.length; ii++)
    if(ele.options[ii].text==text) { //Found!
      return true;
  return false;

How can I get (query string) parameters from the URL in Next.js?

For those looking for a solution that works with static exports, try the solution listed here:

In a nutshell, router.query works only with SSR applications, but router.asPath still works.

So can either configure the query pre-export in next.config.js with exportPathMap (not dynamic):

    return {
      '/': { page: '/' },
      '/about': { page: '/about', query: { title: 'about-us' } }

Or use router.asPath and parse the query yourself with a library like query-string:

import { withRouter } from "next/router";
import queryString from "query-string";

export const withPageRouter = Component => {
  return withRouter(({ router, ...props }) => {
    router.query = queryString.parse(router.asPath.split(/\?/)[1]);

    return <Component {...props} router={router} />;

Negative list index?

Negative numbers mean that you count from the right instead of the left. So, list[-1] refers to the last element, list[-2] is the second-last, and so on.

List<Object> and List<?>

Why cant I do this:

List<Object> object = new List<Object>();

You can't do this because List is an interface, and interfaces cannot be instantiated. Only (concrete) classes can be. Examples of concrete classes implementing List include ArrayList, LinkedList etc.

Here is how one would create an instance of ArrayList:

List<Object> object = new ArrayList<Object>();

I have a method that returns a List<?>, how would I turn that into a List<Object>

Show us the relevant code and I'll update the answer.

C# Switch-case string starting with

If you knew that the length of conditions you would care about would all be the same length then you could:

switch(mystring.substring(0, Math.Min(3, mystring.Length))
  case "abc":
    //do something
  case "xyz":
    //do something else
    //do a different thing

The Math.Min(3, mystring.Length) is there so that a string of less than 3 characters won't throw an exception on the sub-string operation.

There are extensions of this technique to match e.g. a bunch of 2-char strings and a bunch of 3-char strings, where some 2-char comparisons matching are then followed by 3-char comparisons. Unless you've a very large number of such strings though, it quickly becomes less efficient than simple if-else chaining for both the running code and the person who has to maintain it.

Edit: Added since you've now stated they will be of different lengths. You could do the pattern I mentioned of checking the first X chars and then the next Y chars and so on, but unless there's a pattern where most of the strings are the same length this will be both inefficient and horrible to maintain (a classic case of premature pessimisation).

The command pattern is mentioned in another answer, so I won't give details of that, as is that where you map string patterns to IDs, but they are option.

I would not change from if-else chains to command or mapping patterns to gain the efficiency switch sometimes has over if-else, as you lose more in the comparisons for the command or obtaining the ID pattern. I would though do so if it made code clearer.

A chain of if-else's can work pretty well, either with string comparisons or with regular expressions (the latter if you have comparisons more complicated than the prefix-matches so far, which would probably be simpler and faster, I'm mentioning reg-ex's just because they do sometimes work well with more general cases of this sort of pattern).

If you go for if-elses, try to consider which cases are going to happen most often, and make those tests happen before those for less-common cases (though of course if "starts with abcd" is a case to look for it would have to be checked before "starts with abc").

How to add new elements to an array?

String[] source = new String[] { "a", "b", "c", "d" };
String[] destination = new String[source.length + 2];
destination[0] = "/bin/sh";
destination[1] = "-c";
System.arraycopy(source, 0, destination, 2, source.length);

for (String parts : destination) {

Error:Execution failed for task ':ProjectName:mergeDebugResources'. > Crunching Cruncher *some file* failed, see logs

I have tried methods mentioned above, restarting the AS didn't work for me, and rebuilding didn't work either. Finally I found the problem was with the .9.png files, I deleted them and rebuilt the project, and it worked fine! Try it.

Calling an executable program using awk

I was able to have this done via below method

cat ../logs/em2.log.1 |grep -i |awk '{system(`date`); print $1}'

awk has a function called system it enables you to execute any linux bash command within the output of awk.

img onclick call to JavaScript function

This should work(with or without 'javascript:' part):

<img onclick="javascript:exportToForm('1.6','55','10','50','1')" src="China-Flag-256.png" />
function exportToForm(a, b, c, d, e) {
     alert(a, b);

How can I define an array of objects?

 var xxxx : { [key:number]: MyType };

The transaction manager has disabled its support for remote/network transactions

I had the same error message. For me changing pooling=False to ;pooling=true;Max Pool Size=200 in the connection string fixed the problem.

Test if a string contains any of the strings from an array

EDIT: Here is an update using the Java 8 Streaming API. So much cleaner. Can still be combined with regular expressions too.

public static boolean stringContainsItemFromList(String inputStr, String[] items) {

Also, if we change the input type to a List instead of an array we can use

You can also use .filter(inputStr::contains).findAny() if you wish to return the matching string.

Important: the above code can be done using parallelStream() but most of the time this will actually hinder performance. See this question for more details on parallel streaming.

Original slightly dated answer:

Here is a (VERY BASIC) static method. Note that it is case sensitive on the comparison strings. A primitive way to make it case insensitive would be to call toLowerCase() or toUpperCase() on both the input and test strings.

If you need to do anything more complicated than this, I would recommend looking at the Pattern and Matcher classes and learning how to do some regular expressions. Once you understand those, you can use those classes or the String.matches() helper method.

public static boolean stringContainsItemFromList(String inputStr, String[] items)
    for(int i =0; i < items.length; i++)
            return true;
    return false;

How can I create a Windows .exe (standalone executable) using Java/Eclipse?

Creating .exe distributions isn't typical for Java. While such wrappers do exist, the normal mode of operation is to create a .jar file.

To create a .jar file from a Java project in Eclipse, use file->export->java->Jar file. This will create an archive with all your classes.

On the command prompt, use invocation like the following:

java -cp myapp.jar

Unable to set data attribute using jQuery Data() API

Had the same problem. Since you can still get data using the .data() method, you only have to figure out a way to write to the elements. This is the helper method I use. Like most people have said, you will have to use .attr. I have it replacing any _ with - as I know it does that. I'm not aware of any other characters it replaces...however I have not researched that.

function ExtendElementData(element, object){
    //element is what you want to set data on
    //object is a hash/js-object
    var keys = Object.keys(object);
    for (var i = 0; i < keys.length; i++){
        var key = keys[i];
        $(element).attr('data-'+key.replace("_", "-"), object[key]);

EDIT: 5/1/2017

I found there were still instances where you could not get the correct data using built in methods so what I use now is as follows:

function setDomData(element, object){
    //object is a hash

    var keys = Object.keys(object);
    for (var i = 0; i < keys.length; i++){
        var key = keys[i];
        $(element).attr('data-'+key.replace("_", "-"), object[key]);

function getDomData(element, key){
    var domObject = $(element).get(0);
    var attKeys = Object.keys(domObject.attributes);

    var values = null;
    if (key != null){
        values = $(element).attr('data-' + key);
    } else {
        values = {};

        var keys = [];
        for (var i = 0; i < attKeys.length; i++) {

        for (var i = 0; i < keys.length; i++){
                values[keys[i]] = $(element).attr(keys[i]);
    return values;

Measuring text height to be drawn on Canvas ( Android )

@bramp's answer is correct - partially, in that it does not mention that the calculated boundaries will be the minimum rectangle that contains the text fully with implicit start coordinates of 0, 0.

This means, that the height of, for example "Py" will be different from the height of "py" or "hi" or "oi" or "aw" because pixel-wise they require different heights.

This by no means is an equivalent to FontMetrics in classic java.

While width of a text is not much of a pain, height is.

In particular, if you need to vertically center-align the drawn text, try getting the boundaries of the text "a" (without quotes), instead of using the text you intend to draw. Works for me...

Here's what I mean:

Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.LINEAR_TEXT_FLAG);


Rect bounds = new Rect();
paint.getTextBounds("a", 0, 1, bounds);

buffer.drawText(this.myText, canvasWidth >> 1, (canvasHeight + bounds.height()) >> 1, paint);
// remember x >> 1 is equivalent to x / 2, but works much much faster

Vertically center aligning the text means vertically center align the bounding rectangle - which is different for different texts (caps, long letters etc). But what we actually want to do is to also align the baselines of rendered texts, such that they did not appear elevated or grooved. So, as long as we know the center of the smallest letter ("a" for example) we then can reuse its alignment for the rest of the texts. This will center align all the texts as well as baseline-align them.

Scanner is skipping nextLine() after using next() or nextFoo()?

Use 2 scanner objects instead of one

Scanner input = new Scanner(;
System.out.println("Enter numerical value");    
int option;
Scanner input2 = new Scanner(;
option = input2.nextInt();

Can a table have two foreign keys?

Yes, a table have one or many foreign keys and each foreign keys hava a different parent table.

How to turn off word wrapping in HTML?

white-space: nowrap;: Will never break text, will keep other defaults

white-space: pre;: Will never break text, will keep multiple spaces after one another as multiple spaces, will break if explicitly written to break(pressing enter in html etc)

Calculate the mean by group

We already have tons of options to get mean by group, adding one more from mosaic package.

mosaic::mean(speed~dive, data = df)
#dive1 dive2 
#0.579 0.440 

This returns a named numeric vector, if needed a dataframe we can wrap it in stack

stack(mosaic::mean(speed~dive, data = df))

#  values   ind
#1  0.579 dive1
#2  0.440 dive2


df <- data.frame(dive=factor(sample(c("dive1","dive2"),10,replace=TRUE)),

Using number as "index" (JSON)

When a Javascript object property's name doesn't begin with either an underscore or a letter, you cant use the dot notation (like Game.status[0].0), and you must use the alternative notation, which is Game.status[0][0].

One different note, do you really need it to be an object inside the status array? If you're using the object like an array, why not use a real array instead?

iOS app with framework crashed on device, dyld: Library not loaded, Xcode 6 Beta

For iOS greater than or equal to 8

Under the target's General tab, in the Embedded Binaries section add the framework. This will copy the framework into the compiled so that it can be linked to at runtime.

enter image description here

Why is this happening? : because the framework you are linking to is compiled as a dynamically linked framework and thus is linked to at runtime.

** Note:** Embedding custom frameworks is only supported in iOS > 8 and thus an alternative solution that works on older versions of iOS follows.

For iOS less than 8

If you influence this framework (have access to the source code/build process) you may change this framework to be statically linked rather than dynamically linked. This will cause the code to be included in your compiled app rather than linked to at runtime and thus the framework will not have to be embedded.

** How:** Under the framework's Build Setting tab, in the Linking section, change the Mach-O Type to Static Library. You should now not need to include the framework under embedded binaries.

Static Framework

Including Assets: To include things such as images, audio, or xib/nib files I recommend creating a bundle (essentially a directory, more info here and then load the assets from the bundle using NSBundle.

What is the difference between getText() and getAttribute() in Selenium WebDriver?

getText(): Get the visible (i.e. not hidden by CSS) innerText of this element, including sub-elements, without any leading or trailing whitespace.

getAttribute(String attrName): Get the value of a the given attribute of the element. Will return the current value, even if this has been modified after the page has been loaded. More exactly, this method will return the value of the given attribute, unless that attribute is not present, in which case the value of the property with the same name is returned (for example for the "value" property of a textarea element). If neither value is set, null is returned. The "style" attribute is converted as best can be to a text representation with a trailing semi-colon. The following are deemed to be "boolean" attributes, and will return either "true" or null: async, autofocus, autoplay, checked, compact, complete, controls, declare, defaultchecked, defaultselected, defer, disabled, draggable, ended, formnovalidate, hidden, indeterminate, iscontenteditable, ismap, itemscope, loop, multiple, muted, nohref, noresize, noshade, novalidate, nowrap, open, paused, pubdate, readonly, required, reversed, scoped, seamless, seeking, selected, spellcheck, truespeed, willvalidate Finally, the following commonly mis-capitalized attribute/property names are evaluated as expected: "class" "readonly"

getText() return the visible text of the element.

getAttribute(String attrName) returns the value of the attribute passed as parameter.

Converting between java.time.LocalDateTime and java.util.Date

Everything is here :

The answer with "round-tripping" is not exact : when you do

LocalDateTime ldt = LocalDateTime.ofInstant(instant, ZoneOffset.UTC);

if your system timezone is not UTC/GMT, you change the time !

Why does Java have an "unreachable statement" compiler error?

While I think this compiler error is a good thing, there is a way you can work around it. Use a condition you know will be true:

public void myMethod(){


    if(1 < 2) return; // compiler isn't smart enough to complain about this



The compiler is not smart enough to complain about that.

Creating an empty list in Python

Just to highlight @Darkonaut answer because I think it should be more visible.

new_list = [] or new_list = list() are both fine (ignoring performance), but append() returns None, as result you can't do new_list = new_list.append(something).

center MessageBox in parent form

From a comment on Joel Spolsky's blog:

A Messagebox is always centered on the screen. You can provide an owner, but that is just for Z-order, not centering. The only way is to use Win32 hooks and center it yourself. You can find code doing that online if you search for it.

Much easier is to just write your own message box class and add centering functionality. Then you can also add default captioning, Do not show again-checkbox and making them modeless.

"Win32 hooks" probably refers to using SetWindowsHookEx as shown in this example.

Difference between the Apache HTTP Server and Apache Tomcat?

Apache Tomcat is used to deploy your Java Servlets and JSPs. So in your Java project you can build your WAR (short for Web ARchive) file, and just drop it in the deploy directory in Tomcat.

So basically Apache is an HTTP Server, serving HTTP. Tomcat is a Servlet and JSP Server serving Java technologies.

Tomcat includes Catalina, which is a servlet container. A servlet, at the end, is a Java class. JSP files (which are similar to PHP, and older ASP files) are generated into Java code (HttpServlet), which is then compiled to .class files by the server and executed by the Java virtual machine.

VBA for filtering columns

Here's a different approach. The heart of it was created by turning on the Macro Recorder and filtering the columns per your specifications. Then there's a bit of code to copy the results. It will run faster than looping through each row and column:

Sub FilterAndCopy()
Dim LastRow As Long

With Worksheets("Sheet1")
    .Range("$A:$E").AutoFilter field:=1, Criteria1:="#N/A"
    .Range("$A:$E").AutoFilter field:=2, Criteria1:="=String1", Operator:=xlOr, Criteria2:="=string2"
    .Range("$A:$E").AutoFilter field:=3, Criteria1:=">0"
    .Range("$A:$E").AutoFilter field:=5, Criteria1:="Number"
    LastRow = .Range("A" & .Rows.Count).End(xlUp).Row
    .Range("A1:A" & LastRow).SpecialCells(xlCellTypeVisible).EntireRow.Copy _
End With
End Sub

As a side note, your code has more loops and counter variables than necessary. You wouldn't need to loop through the columns, just through the rows. You'd then check the various cells of interest in that row, much like you did.

here-document gives 'unexpected end of file' error

Along with the other answers mentioned by Barmar and Joni, I've noticed that I sometimes have to leave a blank line before and after my EOF when using <<-EOF.

post checkbox value

You should use

<input type="submit" value="submit" />

inside your form.

and add action into your form tag for example:

<form action="booking.php" method="post">

It's post your form into action which you choose.

From php you can get this value by


CSS: Responsive way to center a fluid div (without px width) while limiting the maximum width?

Centering both horizontally and vertically

Actually, having the height and width in percents makes centering it even easier. You just offset the left and top by half of the area not occupied by the div.

So if you height is 40%, 100% - 40% = 60%. So you want 30% above and below. Then top: 30% does the trick.

See the example here:

Centering only horizontally

Use inline-block. The other answer here will not work for IE 8 and below, however. You must use a CSS hack or conditional styles for that. Here is the hack version:

See the example here:

.inlineblock { 
    display: inline-block;
    zoom: 1;
    display*: inline; /* ie hack */


By using media queries you can combine two techniques to achive the effect you want. The only complication is height. You use a nested div to switch between % width and

@media (max-width: 1000px) {
@media (min-width: 1000px) {

Sort Java Collection

SortedSet and Comparator. Comparator should honour the id field.

SQL Server 2008- Get table constraints

I used the following query to retrieve the information of constraints in the SQL Server 2012, and works perfectly. I hope it would be useful for you.

    , AS [Table Id]
    , AS [Constraint Name]
    ,constr.xtype AS [Constraint Type]
    ,CASE constr.xtype WHEN 'PK' THEN 'Primary Key' WHEN 'UQ' THEN 'Unique' ELSE '' END AS [Constraint Name]
    ,i.index_id AS [Index ID]
    ,ic.column_id AS [Column ID]
    , AS [Column Name]
    ,clmns.max_length AS [Column Max Length]
    ,clmns.precision AS [Column Precision]
    ,CASE WHEN clmns.is_nullable = 0 THEN 'NO' ELSE 'YES' END AS [Column Nullable]
    ,CASE WHEN clmns.is_identity = 0 THEN 'NO' ELSE 'YES' END AS [Column IS IDENTITY]
FROM SysObjects AS tab
INNER JOIN SysObjects AS constr ON(constr.parent_obj = AND constr.type = 'K')
INNER JOIN sys.indexes AS i ON( (i.index_id > 0 and i.is_hypothetical = 0) AND ( AND = )
INNER JOIN sys.index_columns AS ic ON (ic.column_id > 0 and (ic.key_ordinal > 0 or ic.partition_ordinal = 0 or ic.is_included_column != 0)) 
                                    AND (ic.index_id=CAST(i.index_id AS int) 
                                    AND ic.object_id=i.object_id)
INNER JOIN sys.columns AS clmns ON clmns.object_id = ic.object_id and clmns.column_id = ic.column_id
WHERE tab.xtype = 'U'

printf a variable in C

As Shafik already wrote you need to use the right format because scanf gets you a char. Don't hesitate to look here if u aren't sure about the usage:

Hint: It's faster/nicer to write x=x+1; the shorter way: x++;

Sorry for answering what's answered just wanted to give him the link - the site was really useful to me all the time dealing with C.

How can I pass a username/password in the header to a SOAP WCF Service

Obviously it has been some years this post has been alive - but the fact is I did find it when looking for a similar issue. In our case, we had to add the username / password info to the Security header. This is different from adding header info outside of the Security headers.

The correct way to do this (for custom bindings / authenticationMode="CertificateOverTransport") (as on the .Net framework version 4.6.1), is to add the Client Credentials as usual :

    client.ClientCredentials.UserName.UserName = "[username]";
    client.ClientCredentials.UserName.Password = "[password]";

and then add a "token" in the security binding element - as the username / pwd credentials would not be included by default when the authentication mode is set to certificate.

You can set this token like so:

    //Get the current binding 
    System.ServiceModel.Channels.Binding binding = client.Endpoint.Binding;
    //Get the binding elements 
    BindingElementCollection elements = binding.CreateBindingElements();
    //Locate the Security binding element
    SecurityBindingElement security = elements.Find<SecurityBindingElement>();

    //This should not be null - as we are using Certificate authentication anyway
    if (security != null)
    UserNameSecurityTokenParameters uTokenParams = new UserNameSecurityTokenParameters();
    uTokenParams.InclusionMode = SecurityTokenInclusionMode.AlwaysToRecipient;

   client.Endpoint.Binding = new CustomBinding(elements.ToArray());

That should do it. Without the above code (to explicitly add the username token), even setting the username info in the client credentials may not result in those credentials passed to the Service.

Convert wchar_t to char

In general, no. int(wchar_t(255)) == int(char(255)) of course, but that just means they have the same int value. They may not represent the same characters.

You would see such a discrepancy in the majority of Windows PCs, even. For instance, on Windows Code page 1250, char(0xFF) is the same character as wchar_t(0x02D9) (dot above), not wchar_t(0x00FF) (small y with diaeresis).

Note that it does not even hold for the ASCII range, as C++ doesn't even require ASCII. On IBM systems in particular you may see that 'A' != 65

Can't ping a local VM from the host

Try dropping all the firewall, the one from your VM and the one from you Laptop, or add the rule in your firewall where you can ping

How to import JsonConvert in C# application?

Or if you're using dotnet Core,

add to your .csproj file

    <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />


dotnet restore

How to pad zeroes to a string?

>>> '99'.zfill(5)
>>> '99'.rjust(5,'0')

if you want the opposite:

>>> '99'.ljust(5,'0')

Add colorbar to existing axis

The colorbar has to have its own axes. However, you can create an axes that overlaps with the previous one. Then use the cax kwarg to tell fig.colorbar to use the new axes.

For example:

import numpy as np
import matplotlib.pyplot as plt

data = np.arange(100, 0, -1).reshape(10, 10)

fig, ax = plt.subplots()
cax = fig.add_axes([0.27, 0.8, 0.5, 0.05])

im = ax.imshow(data, cmap='gist_earth')
fig.colorbar(im, cax=cax, orientation='horizontal')

enter image description here

How to change the type of a field?

Starting Mongo 4.2, db.collection.update() can accept an aggregation pipeline, finally allowing the update of a field based on its own value:

// { a: "45", b: "x" }
// { a:  53,  b: "y" }
  { a : { $type: 1 } },
  [{ $set: { a: { $toString: "$a" } } }],
  { multi: true }
// { a: "45", b: "x" }
// { a: "53", b: "y" }
  • The first part { a : { $type: 1 } } is the match query:

    • It filters which documents to update.
    • In this case, since we want to convert "a" to string when its value is a double, this matches elements for which "a" is of type 1 (double)).
    • This table provides the codes representing the different possible types.
  • The second part [{ $set: { a: { $toString: "$a" } } }] is the update aggregation pipeline:

    • Note the squared brackets signifying that this update query uses an aggregation pipeline.
    • $set is a new aggregation operator (Mongo 4.2) which in this case modifies a field.
    • This can be simply read as "$set" the value of "a" to "$a" converted "$toString".
    • What's really new here, is being able in Mongo 4.2 to reference the document itself when updating it: the new value for "a" is based on the existing value of "$a".
    • Also note "$toString" which is a new aggregation operator introduced in Mongo 4.0.
  • Don't forget { multi: true }, otherwise only the first matching document will be updated.

In case your cast isn't from double to string, you have the choice between different conversion operators introduced in Mongo 4.0 such as $toBool, $toInt, ...

And if there isn't a dedicated converter for your targeted type, you can replace { $toString: "$a" } with a $convert operation: { $convert: { input: "$a", to: 2 } } where the value for to can be found in this table:

  { a : { $type: 1 } },
  [{ $set: { a: { $convert: { input: "$a", to: 2 } } } }],
  { multi: true }

Is it possible to create a File object from InputStream

Since Java 7, you can do it in one line even without using any external libraries:

Files.copy(inputStream, outputPath, StandardCopyOption.REPLACE_EXISTING);

See the API docs.

What does #defining WIN32_LEAN_AND_MEAN exclude exactly?

Complementing the above answers and also "Parroting" from the Windows Dev Center documentation,

The Winsock2.h header file internally includes core elements from the Windows.h header file, so there is not usually an #include line for the Windows.h header file in Winsock applications. If an #include line is needed for the Windows.h header file, this should be preceded with the #define WIN32_LEAN_AND_MEAN macro. For historical reasons, the Windows.h header defaults to including the Winsock.h header file for Windows Sockets 1.1. The declarations in the Winsock.h header file will conflict with the declarations in the Winsock2.h header file required by Windows Sockets 2.0. The WIN32_LEAN_AND_MEAN macro prevents the Winsock.h from being included by the Windows.h header ..

Differences between Octave and MATLAB?

Octave is basically an open source version of MATLAB. It was written to be just that. MATLAB has a very nice GUI which makes it a bit easier to use but the next stable release of OCTAVE will also have a GUI, which I have tested in the unstable release, and looks fantastic. Octave is much more buggy because it was developed and maintained by a group of volunteers, where the development of MATLAB is funded by millions of dollars by industry. I'm still a student and am using a student version of MATLAB, but I am thinking of going over to Octave once the stable version with the GUI is released.

MATLAB is probably a lot more powerful than Octave, and the algorithms run faster, but for most applications, Octave is more than adequate and is, in my opinion' an amazing tool that is completely free, where Octave is completely free.

I would say use MATLAB while you can use the academic version, but the switch to Octave should be seamless as they use the exact same syntax.

Lastly, there is the issue of SIMULINK. If you want to do simulation or control system design (there are probably a million other uses) SIMULINK is fantastic and comes with MATLAB. I don't think any other comes close to this, although Scilab is apparently a 'good' open source alternative, I haven't tried it.


How and when to use SLEEP() correctly in MySQL?


But what are you using this for? Are you trying to circumvent/reinvent mutexes or transactions?

.NET Core vs Mono

You have chosen not only a realistic path, but arguably one of the best ecosystems strongly backed(also X-platforms) by MS. Still you should consider following points:

  • Update: Main doc about .Net platform standard is here:
  • Update: Current Mono 4.4.1 cannot run latest Asp.Net core 1.0 RTM
  • Although mono is more feature complete, its future is unclear, because MS owns it for some months now and its a duplicate work for them to support it. But MS is definitely committed to .Net Core and betting big on it.
  • Although .Net core is released, the 3rd party ecosystem is not quite there. For example Nhibernate, Umbraco etc cannot run over .Net core yet. But they have a plan.
  • There are some features missing in .Net Core like System.Drawing, you should look for 3rd party libraries
  • You should use nginx as front server with kestrelserver for apps, because kestrelserver is not quite ready for production. For example HTTP/2 is not implemented.

I hope it helps

Remove CSS class from element with JavaScript (no jQuery)


Okay, complete re-write. It's been a while, I've learned a bit and the comments have helped.

Node.prototype.hasClass = function (className) {
    if (this.classList) {
        return this.classList.contains(className);
    } else {
        return (-1 < this.className.indexOf(className));

Node.prototype.addClass = function (className) {
    if (this.classList) {
    } else if (!this.hasClass(className)) {
        var classes = this.className.split(" ");
        this.className = classes.join(" ");
    return this;

Node.prototype.removeClass = function (className) {
    if (this.classList) {
    } else {
        var classes = this.className.split(" ");
        classes.splice(classes.indexOf(className), 1);
        this.className = classes.join(" ");
    return this;

Old Post
I was just working with something like this. Here's a solution I came up with...

// Some browsers don't have a native trim() function
if(!String.prototype.trim) {
    Object.defineProperty(String.prototype,'trim', {
        value: function() {
            return this.replace(/^\s+|\s+$/g,'');
// addClass()
// first checks if the class name already exists, if not, it adds the class.
Object.defineProperty(Node.prototype,'addClass', {
    value: function(c) {
        if(this.className.indexOf(c)<0) {
            this.className=this.className+=' '+c;
        return this;
// removeClass()
// removes the class and cleans up the className value by changing double 
// spacing to single spacing and trimming any leading or trailing spaces
Object.defineProperty(Node.prototype,'removeClass', {
    value: function(c) {
        this.className=this.className.replace(c,'').replace('  ',' ').trim();
        return this;

Now you can call myElement.removeClass('myClass')

or chain it: myElement.removeClass("oldClass").addClass("newClass");

unbound method f() must be called with fibo_ instance as first argument (got classobj instance instead)

OK, first of all, you don't have to get a reference to the module into a different name; you already have a reference (from the import) and you can just use it. If you want a different name just use import swineflu as f.

Second, you are getting a reference to the class rather than instantiating the class.

So this should be:

import swineflu

fibo = swineflu.fibo()  # get an instance of the class
fibo.f()                # call the method f of the instance

A bound method is one that is attached to an instance of an object. An unbound method is, of course, one that is not attached to an instance. The error usually means you are calling the method on the class rather than on an instance, which is exactly what was happening in this case because you hadn't instantiated the class.

How do I extend a class with c# extension methods?

Unfortunately, you can't do that. I believe it would be useful, though. It is more natural to type:




With a Util class, you have to check for the existence of a static method in two different classes, instead of one.

The service cannot accept control messages at this time

I forgot I had mine attached to Visual Studio debugger. Be sure to disconnect from there, and then wait a moment. Otherwise killing the process viewing the PID from the Worker Processes functionality of IIS manager will work too.

What is the difference between `git merge` and `git merge --no-ff`?

This is an old question, and this is somewhat subtly mentioned in the other posts, but the explanation that made this click for me is that non fast forward merges will require a separate commit.

Using lodash to compare jagged arrays (items existence without order)

There are already answers here, but here's my pure JS implementation. I'm not sure if it's optimal, but it sure is transparent, readable, and simple.

// Does array a contain elements of array b?
const contains = (a, b) => new Set([...a, ...b]).size === a.length
const isEqualSet = (a, b) => contains(a, b) && contains(b, a)

The rationale in contains() is that if a does contain all the elements of b, then putting them into the same set would not change the size.

For example, if const a = [1,2,3,4] and const b = [1,2], then new Set([...a, ...b]) === {1,2,3,4}. As you can see, the resulting set has the same elements as a.

From there, to make it more concise, we can boil it down to the following:

const isEqualSet = (a, b) => {
  const unionSize = new Set([...a, ...b])
  return unionSize === a.length && unionSize === b.length

error TS2339: Property 'x' does not exist on type 'Y'

I was getting this error on Vue 3. It was because defineComponent must be imported like this:

<script lang="ts">
import { defineComponent } from "vue";

export default defineComponent({
    name: "HelloWorld",
    props: {
        msg: String,
    created() {
    methods: {
        testF() {

Custom toast on Android: a simple example

For all Kotlin Users

You can create an Extension like following:

fun FragmentActivity.showCustomToast(message : String,color : Int) {
 val toastView = findViewById<TextView>(
 toastView.text = message
 toastView.visibility = View.VISIBLE

 // create a daemon thread
 val timer = Timer("schedule", true)

 // schedule a single event
 timer.schedule(2000) {
    runOnUiThread { toastView.visibility = View.GONE }

How to create multiple output paths in Webpack config

I'm not sure if we have the same problem since webpack only support one output per configuration as of Jun 2016. I guess you already seen the issue on Github.

But I separate the output path by using the multi-compiler. (i.e. separating the configuration object of webpack.config.js).

var config = {
    // TODO: Add common Configuration
    module: {},

var fooConfig = Object.assign({}, config, {
    name: "a",
    entry: "./a/app",
    output: {
       path: "./a",
       filename: "bundle.js"
var barConfig = Object.assign({}, config,{
    name: "b",
    entry: "./b/app",
    output: {
       path: "./b",
       filename: "bundle.js"

// Return Array of Configurations
module.exports = [
    fooConfig, barConfig,       

If you have common configuration among them, you could use the extend library or Object.assign in ES6 or {...} spread operator in ES7.

How to return value from an asynchronous callback function?

If you happen to be using jQuery, you might want to give this a shot:

It allows you to defer the execution of your callback function until the ajax request (or any async operation) is completed. This can also be used to call a callback once several ajax requests have all completed.

Loop through a comma-separated shell variable

If you set a different field separator, you can directly use a for loop:

for v in $variable
   # things with "$v" ...

You can also store the values in an array and then loop through it as indicated in How do I split a string on a delimiter in Bash?:

IFS=, read -ra values <<< "$variable"
for v in "${values[@]}"
   # things with "$v"


$ variable="abc,def,ghij"
$ IFS=","
$ for v in $variable
> do
> echo "var is $v"
> done
var is abc
var is def
var is ghij

You can find a broader approach in this solution to How to iterate through a comma-separated list and execute a command for each entry.

Examples on the second approach:

$ IFS=, read -ra vals <<< "abc,def,ghij"
$ printf "%s\n" "${vals[@]}"
$ for v in "${vals[@]}"; do echo "$v --"; done
abc --
def --
ghij --

Nginx not running with no error message

Check the daemon option in nginx.conf file. It has to be ON. Or you can simply rip out this line from config file. This option is fully described here

postgres default timezone

Choose a timezone from:

SELECT * FROM pg_timezone_names;

And set as below given example:

ALTER DATABASE postgres SET timezone TO 'Europe/Berlin';

Use your DB name in place of postgres in above statement.

Why use pointers?

Here's a slightly different, but insightful take on why many features of C make sense:

Basically, the standard CPU architecture is a Von Neumann architecture, and it's tremendously useful to be able to refer to the location of a data item in memory, and do arithmetic with it, on such a machine. If you know any variant of assembly language, you will quickly see how crucial this is at the low level.

C++ makes pointers a bit confusing, since it sometimes manages them for you and hides their effect in the form of "references." If you use straight C, the need for pointers is much more obvious: there's no other way to do call-by-reference, it's the best way to store a string, it's the best way to iterate through an array, etc.

What's the difference between :: (double colon) and -> (arrow) in PHP?

:: is used in static context, ie. when some method or property is declared as static:

class Math {
    public static function sin($angle) {
        return ...;

$result = Math::sin(123);

Also, the :: operator (the Scope Resolution Operator, a.k.a Paamayim Nekudotayim) is used in dynamic context when you invoke a method/property of a parent class:

class Rectangle {
     protected $x, $y;

     public function __construct($x, $y) {
         $this->x = $x;
         $this->y = $y;

class Square extends Rectangle {
    public function __construct($x) {
        parent::__construct($x, $x);

-> is used in dynamic context, ie. when you deal with some instance of some class:

class Hello {
    public function say() {
       echo 'hello!';

$h = new Hello();

By the way: I don't think that using Symfony is a good idea when you don't have any OOP experience.

Javascript communication between browser tabs/windows

I don't think you need cookies. Each document's js code can access the other document elements. So you can use them directly to share data. Your first window w1 opens w2 and save the reference

var w2 = 

In w2 you can access w1 using the opener property of window.

How do I quickly rename a MySQL database (change schema name)?

For your convenience, below is a small shellscript that has to be executed with two parameters: db-name and new db-name.

You might need to add login-parameters to the mysql-lines if you don't use the .my.cnf-file in your home-directory. Please make a backup before executing this script.

#!/usr/bin/env bash

mysql -e "CREATE DATABASE $2 DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;"
for i in $(mysql -Ns $1 -e "show tables");do
    echo "$1.$i -> $2.$i"
    mysql -e "rename TABLE $1.$i to $2.$i"
mysql -e "DROP DATABASE $1"

How to count number of records per day?

select DateAdded, count(CustID)
from tbl
group by DateAdded

about 7-days interval it's DB-depending question

How to encrypt a large file in openssl using public key

Solution for safe and high secured encode anyone file in OpenSSL and command-line:

You should have ready some X.509 certificate for encrypt files in PEM format.

Encrypt file:

openssl smime -encrypt -binary -aes-256-cbc -in -out -outform DER yourSslCertificate.pem

What is what:

  • smime - ssl command for S/MIME utility (smime(1))
  • -encrypt - chosen method for file process
  • -binary - use safe file process. Normally the input message is converted to "canonical" format as required by the S/MIME specification, this switch disable it. It is necessary for all binary files (like a images, sounds, ZIP archives).
  • -aes-256-cbc - chosen cipher AES in 256 bit for encryption (strong). If not specified 40 bit RC2 is used (very weak). (Supported ciphers)
  • -in - input file name
  • -out - output file name
  • -outform DER - encode output file as binary. If is not specified, file is encoded by base64 and file size will be increased by 30%.
  • yourSslCertificate.pem - file name of your certificate's. That should be in PEM format.

That command can very effectively a strongly encrypt big files regardless of its format.
Known issue: Something wrong happens when you try encrypt huge file (>600MB). No error thrown, but encrypted file will be corrupted. Always verify each file! (or use PGP - that has bigger support for files encryption with public key)

Decrypt file:

openssl smime -decrypt -binary -in -inform DER -out -inkey private.key -passin pass:your_password

What is what:

  • -inform DER - same as -outform above
  • -inkey private.key - file name of your private key. That should be in PEM format and can be encrypted by password.
  • -passin pass:your_password - your password for private key encrypt. (passphrase arguments)

Bad operand type for unary +: 'str'

The code works for me. (after adding missing except clause / import statements)

Did you put \ in the original code?

urlToVisit = '' \
              + stock + '/chartdata;type=quote;range=5d/csv'

If you omit it, it could be a cause of the exception:

>>> stock = 'GOOG'
>>> urlToVisit = ''
>>> + stock + '/chartdata;type=quote;range=5d/csv'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: bad operand type for unary +: 'str'

BTW, string(e) should be str(e).

Spring Boot REST API - request timeout?

The @Transactional annotation takes a timeout parameter where you can specify timeout in seconds for a specific method in the @RestController

@RequestMapping(value = "/method",
    method = RequestMethod.POST,
    produces = MediaType.APPLICATION_JSON_VALUE)
@Transactional(timeout = 120)

writing a batch file that opens a chrome URL

start "Chrome" "C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --profile-directory="Profile 2"

start "webpage name" ""

start "Chrome" "C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --profile-directory="Profile 3"

start "webpage name" ""

Dismissing a Presented View Controller

In my experience, it comes in handy when you need to dismiss it from any ViewController you want and perform different tasks for each viewcontroller that dismisses it. Any viewController that adopts the protocol can dismiss the view in it's own way. (ipad vs iphone, or passing different data when dismissing from different views, calling different methods when dismissing, etc..)


So, to clarify, if all you ever want to do is dismiss the view, I see no need to setup the delegate protocol. If you need to do different things after you dismiss it from different presenting view controllers, It would be your best way to go using the delegate.

How to test if a string is JSON or not?

var parsedData;

try {
    parsedData = JSON.parse(data)
} catch (e) {
    // is not a valid JSON string

However, I will suggest to you that your http call / service should return always a data in the same format. So if you have an error, than you should have a JSON object that wrap this error:

{"error" : { "code" : 123, "message" : "Foo not supported" } } 

And maybe use as well as HTTP status a 5xx code.

Extracting specific selected columns to new DataFrame as a copy

columns by index:

# selected column index: 1, 6, 7
new = old.iloc[: , [1, 6, 7]].copy() 

Creating a Facebook share button with customized url, title and image

Crude, but it works on our system:

<div class="block-share spread-share p-t-md">
  <a href="!" 
    <button class="btn btn-social btn-facebook">
      <span class="icon icon-facebook">
      Share on Facebook

  <a href="" target="_blank">
    <button class="btn btn-social btn-facebook">
      <span class="icon icon-facebook">
      Like  on Facebook

Predict() - Maybe I'm not understanding it

To avoid error, an important point about the new dataset is the name of independent variable. It must be the same as reported in the model. Another way is to nest the two function without creating a new dataset

model <- lm(Coupon ~ Total, data=df)
predict(model, data.frame(Total=c(79037022, 83100656, 104299800)))

Pay attention on the model. The next two commands are similar, but for predict function, the first work the second don't work.

model <- lm(Coupon ~ Total, data=df) #Ok
model <- lm(df$Coupon ~ df$Total) #Ko

How to check if there exists a process with a given pid in Python?

The following code works on both Linux and Windows, and not depending on external modules

import os
import subprocess
import platform
import re

def pid_alive(pid:int):
    """ Check For whether a pid is alive """

    system = platform.uname().system
    if'Linux', system, re.IGNORECASE):
            os.kill(pid, 0)
        except OSError:
            return False
            return True
    elif'Windows', system, re.IGNORECASE):
        out = subprocess.check_output(["tasklist","/fi",f"PID eq {pid}"]).strip()
        # b'INFO: No tasks are running which match the specified criteria.'

        if'No tasks', out, re.IGNORECASE):
            return False
            return True
        raise RuntimeError(f"unsupported system={system}")

It can be easily enhanced in case you need

  1. other platforms
  2. other language

Binary numbers in Python

I think you're confused about what binary is. Binary and decimal are just different representations of a number - e.g. 101 base 2 and 5 base 10 are the same number. The operations add, subtract, and compare operate on numbers - 101 base 2 == 5 base 10 and addition is the same logical operation no matter what base you're working in.

Replace one substring for another string in shell script

echo [string] | sed "s/[original]/[target]/g"
  • "s" means "substitute"
  • "g" means "global, all matching occurrences"

Switch case with fallthrough?

  • Do not use () behind function names in bash unless you like to define them.
  • use [23] in case to match 2 or 3
  • static string cases should be enclosed by '' instead of ""

If enclosed in "", the interpreter (needlessly) tries to expand possible variables in the value before matching.

case "$C" in

For case insensitive matching, you can use character classes (like [23]):

case "$C" in

# will match C='Abra' and C='abra'

# will match all letter cases at any char like `abra`, `ABRA` or `AbRa`


But abra didn't hit anytime because it will be matched by the first case.

If needed, you can omit ;; in the first case to continue testing for matches in following cases too. (;; jumps to esac)

Retrieving JSON Object Literal from HttpServletRequest

If you're trying to get data out of the request body, the code above works. But, I think you are having the same problem I was..

If the data in the body is in JSON form, and you want it as a Java object, you'll need to parse it yourself, or use a library like google-gson to handle it for you. You should look at the docs and examples at the project's website to know how to use it. It's fairly simple.

jquery <a> tag click event

<a href="javascript:void(0)" class="aaf" id="users_id">add as a friend</a>

on jquery

  var usersid =  $(this).attr("id");
  //post code

//other method is to use the data attribute

<a href="javascript:void(0)" class="aaf" data-id="102" data-username="sample_username">add as a friend</a>

on jquery

    var usersid =  $(this).data("id");
    var username = $(this).data("username");

How do I fix twitter-bootstrap on IE?

If you are within the intranet and the settings are set to compatibility mode, then proper doctypes and respond.js is not enough.

Please refer to this link for more info: Force IE8 or IE9 document mode to standards and see Ralph Bacon's answer.

It would be same as this:

<!DOCTYPE html>
<meta http-equiv="X-UA-Compatible" content="IE=edge">

Java - Writing strings to a CSV file

 private static final String FILE_HEADER ="meter_Number,latestDate";
    private static final String COMMA_DELIMITER = ",";
    private static final String NEW_LINE_SEPARATOR = "\n";
    static SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:m m:ss");

    private void writeToCsv(Map<String, Date> meterMap) {
        try {
            Iterator<Map.Entry<String, Date>> iter = meterMap.entrySet().iterator();
            FileWriter fw = new FileWriter("smaple.csv");
            while (iter.hasNext()) {
                Map.Entry<String, Date> entry =;
                try {
                } catch (Exception e) {
                } finally {
        } catch (Exception e) {

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space

There is a another best/effective way to solve this error,

for example, let's take a loop which counts till 10 thousand, here you may get the error Out of memory, do to solve it you can give the computer time to recover.

So, you can sleep for 400-500ms before you're loop counts the next number :

new Thread(new Runnable() {
            public void run() {
                try {
                    sleep(550); // 550 ms (milli seconds)
                } catch (InterruptedException e) {

By doing this, will make you're program slower but you don't get any error till the heap space is full again, so by waiting some ms, you can prevent that error.

You can apply this method other than loop.

Hope it helped you, :D

C/C++ NaN constant (literal)?

yes, by the concept of pointer you can do it like this for an int variable:

int *a;
int b=0;
a=NULL; // or a=&b; for giving the value of b to a

it is very simple and straitforward. it worked for me in Arduino IDE.

The absolute uri: cannot be resolved in either web.xml or the jar files deployed with this application

This might be because of the transitive dependencies.

Try to add/ remove the scope from the JSTL library.

This worked for me!