Programs & Examples On #Queueuserworkitem

Why am I getting "(304) Not Modified" error on some links when using HttpWebRequest?

This is intended behavior.

When you make an HTTP request, the server normally returns code 200 OK. If you set If-Modified-Since, the server may return 304 Not modified (and the response will not have the content). This is supposed to be your cue that the page has not been modified.

The authors of the class have foolishly decided that 304 should be treated as an error and throw an exception. Now you have to clean up after them by catching the exception every time you try to use If-Modified-Since.

Why I am getting Cannot pass parameter 2 by reference error when I am using bindParam with a constant value?

You need to use bindValue, not bindParam

bindParam takes a variable by reference, and doesn't pull in a value at the time of calling bindParam. I found this in a comment on the PHP docs:

bindValue(':param', null, PDO::PARAM_INT);

P.S. You may be tempted to do this bindValue(':param', null, PDO::PARAM_NULL); but it did not work for everybody (thank you Will Shaver for reporting.)

Cannot implicitly convert type 'System.DateTime?' to 'System.DateTime'. An explicit conversion exists

You have 3 options:

1) Get default value

dt = datetime??DateTime.Now;

it will assign DateTime.Now (or any other value which you want) if datetime is null

2) Check if datetime contains value and if not return empty string

if(!datetime.HasValue) return "";
dt = datetime.Value;

3) Change signature of method to

public string ConvertToPersianToShow(DateTime  datetime)

It's all because DateTime? means it's nullable DateTime so before assigning it to DateTime you need to check if it contains value and only then assign.

Heroku: How to push different local Git branches to Heroku/master

I think it should be

push = refs/heads/*:refs/heads/*


ReferenceError: event is not defined error in Firefox

It is because you forgot to pass in event into the click function:

$('.menuOption').on('click', function (e) { // <-- the "e" for event

    e.preventDefault(); // now it'll work

    var categories = $(this).attr('rel');

On a side note, e is more commonly used as opposed to the word event since Event is a global variable in most browsers.

How do I get a specific range of numbers from rand()?

Updated to not use a #define

double RAND(double min, double max)
    return (double)rand()/(double)RAND_MAX * (max - min) + min;

Resolving IP Address from hostname with PowerShell

Working one liner if you want a single result from the collection:

$ipAddy = [System.Net.Dns]::GetHostAddresses("")[0].IPAddressToString; 


Regex to extract URLs from href attribute in HTML with Python

The best answer is...

Don't use a regex

The expression in the accepted answer misses many cases. Among other things, URLs can have unicode characters in them. The regex you want is here, and after looking at it, you may conclude that you don't really want it after all. The most correct version is ten-thousand characters long.

Admittedly, if you were starting with plain, unstructured text with a bunch of URLs in it, then you might need that ten-thousand-character-long regex. But if your input is structured, use the structure. Your stated aim is to "extract the url, inside the anchor tag's href." Why use a ten-thousand-character-long regex when you can do something much simpler?

Parse the HTML instead

For many tasks, using Beautiful Soup will be far faster and easier to use:

>>> from bs4 import BeautifulSoup as Soup
>>> html = Soup(s, 'html.parser')           # Soup(s, 'lxml') if lxml is installed
>>> [a['href'] for a in html.find_all('a')]
['', '']

If you prefer not to use external tools, you can also directly use Python's own built-in HTML parsing library. Here's a really simple subclass of HTMLParser that does exactly what you want:

from html.parser import HTMLParser

class MyParser(HTMLParser):
    def __init__(self, output_list=None):
        if output_list is None:
            self.output_list = []
            self.output_list = output_list
    def handle_starttag(self, tag, attrs):
        if tag == 'a':


>>> p = MyParser()
>>> p.feed(s)
>>> p.output_list
['', '']

You could even create a new method that accepts a string, calls feed, and returns output_list. This is a vastly more powerful and extensible way than regular expressions to extract information from html.

SQL SERVER: Check if variable is null and then assign statement for Where Clause

is null can be used to check whether null data is coming from a query as in following example:

 declare @Mem varchar(20),@flag int
select @mem=MemberClub from [dbo].[UserMaster] where UserID=@uid
if(@Mem is null)
    set @flag= 0;
    set @flag=1;
return @flag;

Python: Continuing to next iteration in outer loop

In other languages you can label the loop and break from the labelled loop. Python Enhancement Proposal (PEP) 3136 suggested adding these to Python but Guido rejected it:

However, I'm rejecting it on the basis that code so complicated to require this feature is very rare. In most cases there are existing work-arounds that produce clean code, for example using 'return'. While I'm sure there are some (rare) real cases where clarity of the code would suffer from a refactoring that makes it possible to use return, this is offset by two issues:

  1. The complexity added to the language, permanently. This affects not only all Python implementations, but also every source analysis tool, plus of course all documentation for the language.

  2. My expectation that the feature will be abused more than it will be used right, leading to a net decrease in code clarity (measured across all Python code written henceforth). Lazy programmers are everywhere, and before you know it you have an incredible mess on your hands of unintelligible code.

So if that's what you were hoping for you're out of luck, but look at one of the other answers as there are good options there.

Generate a random number in the range 1 - 10

Actually I don't know you want to this.

try this

INSERT INTO my_table (my_column)
    (random() * 10) + 1

How to get a value from a cell of a dataframe?

For pandas 0.10, where iloc is unavalable, filter a DF and get the first row data for the column VALUE:

df_filt = df[df['C1'] == C1val & df['C2'] == C2val]
result = df_filt.get_value(df_filt.index[0],'VALUE')

if there is more then 1 row filtered, obtain the first row value. There will be an exception if the filter result in empty data frame.

How do I disable a Pylint warning?

pylint --generate-rcfile shows it like this:


# Enable the message, report, category or checker with the given id(s). You can
# either give multiple identifier separated by comma (,) or put this option
# multiple time.

# Disable the message, report, category or checker with the given id(s). You
# can either give multiple identifier separated by comma (,) or put this option
# multiple time (only on the command line, not in the configuration file where
# it should appear only once).

So it looks like your ~/.pylintrc should have the disable= line/s in it inside a section [MESSAGES CONTROL].

React passing parameter via onclick event using ES6 syntax

onClick={this.handleRemove.bind(this, id)}

How do you get the file size in C#?

The FileInfo class' Length property returns the size of the file (not the size on disk). If you want a formatted file size (i.e. 15 KB) rather than a long byte value you can use CSharpLib, a package I've made that adds more functionality to the FileInfo class. Here's an example:

using CSharpLib;
FileInfo info = new FileInfo("sample.txt");
Console.WriteLine(info.FormatBytes());  // Output: 15 MB

How to specify an element after which to wrap in css flexbox?

You can accomplish this by setting this on the container:

ul {
    display: flex;
    flex-wrap: wrap;

And on the child you set this:

li:nth-child(2n) {
    flex-basis: 100%;

ul {
  display: flex;
  flex-wrap: wrap;
  list-style: none;

li:nth-child(4n) {
  flex-basis: 100%;

This causes the child to make up 100% of the container width before any other calculation. Since the container is set to break in case there is not enough space it does so before and after this child. So you could use an empty div element to force the wrap between the element before and after it.

How to secure MongoDB with username and password

First run mongoDB on terminal using


now run mongo shell use following commands

    use admin
    user: "myUserAdmin",
    pwd: "abc123",
    roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]

Re-start the MongoDB instance with access control.

mongod --auth

Now authenticate yourself from the command line using

mongo --port 27017 -u "myUserAdmin" -p "abc123" --authenticationDatabase "admin"

I read it from

Python Pandas Counting the Occurrences of a Specific value

Try this:


How to add new DataRow into DataTable?

You have to add the row explicitly to the table


What is move semantics?

If you are really interested in a good, in-depth explanation of move semantics, I'd highly recommend reading the original paper on them, "A Proposal to Add Move Semantics Support to the C++ Language."

It's very accessible and easy to read and it makes an excellent case for the benefits that they offer. There are other more recent and up to date papers about move semantics available on the WG21 website, but this one is probably the most straightforward since it approaches things from a top-level view and doesn't get very much into the gritty language details.

sqlite3.OperationalError: unable to open database file

Make sure you are not editing the file while trying to run syncdb, you will get the same error!!!

self.connection = Database.connect(**kwargs)
sqlite3.OperationalError: unable to open database file

Android AudioRecord example

Here I am posting you the some code example which record good quality of sound using AudioRecord API.

Note: If you use in emulator the sound quality will not much good because we are using sample rate 8k which only supports in emulator. In device use sample rate to 44.1k for better quality.

public class Audio_Record extends Activity {
    private static final int RECORDER_SAMPLERATE = 8000;
    private static final int RECORDER_CHANNELS = AudioFormat.CHANNEL_IN_MONO;
    private static final int RECORDER_AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT;
    private AudioRecord recorder = null;
    private Thread recordingThread = null;
    private boolean isRecording = false;

    public void onCreate(Bundle savedInstanceState) {


        int bufferSize = AudioRecord.getMinBufferSize(RECORDER_SAMPLERATE,

    private void setButtonHandlers() {
        ((Button) findViewById(;
        ((Button) findViewById(;

    private void enableButton(int id, boolean isEnable) {
        ((Button) findViewById(id)).setEnabled(isEnable);

    private void enableButtons(boolean isRecording) {
        enableButton(, !isRecording);
        enableButton(, isRecording);

    int BufferElements2Rec = 1024; // want to play 2048 (2K) since 2 bytes we use only 1024
    int BytesPerElement = 2; // 2 bytes in 16bit format

    private void startRecording() {

        recorder = new AudioRecord(MediaRecorder.AudioSource.MIC,
                RECORDER_AUDIO_ENCODING, BufferElements2Rec * BytesPerElement);

        isRecording = true;
        recordingThread = new Thread(new Runnable() {
            public void run() {
        }, "AudioRecorder Thread");

        //convert short to byte
    private byte[] short2byte(short[] sData) {
        int shortArrsize = sData.length;
        byte[] bytes = new byte[shortArrsize * 2];
        for (int i = 0; i < shortArrsize; i++) {
            bytes[i * 2] = (byte) (sData[i] & 0x00FF);
            bytes[(i * 2) + 1] = (byte) (sData[i] >> 8);
            sData[i] = 0;
        return bytes;


    private void writeAudioDataToFile() {
        // Write the output audio in byte

        String filePath = "/sdcard/voice8K16bitmono.pcm";
        short sData[] = new short[BufferElements2Rec];

        FileOutputStream os = null;
        try {
            os = new FileOutputStream(filePath);
        } catch (FileNotFoundException e) {

        while (isRecording) {
            // gets the voice output from microphone to byte format

  , 0, BufferElements2Rec);
            System.out.println("Short writing to file" + sData.toString());
            try {
                // // writes the data to file from buffer
                // // stores the voice buffer
                byte bData[] = short2byte(sData);
                os.write(bData, 0, BufferElements2Rec * BytesPerElement);
            } catch (IOException e) {
        try {
        } catch (IOException e) {

    private void stopRecording() {
        // stops the recording activity
        if (null != recorder) {
            isRecording = false;
            recorder = null;
            recordingThread = null;

    private View.OnClickListener btnClick = new View.OnClickListener() {
        public void onClick(View v) {
            switch (v.getId()) {
            case {
            case {

    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK) {
        return super.onKeyDown(keyCode, event);

For more detail try this AUDIORECORD BLOG.

Happy Coding !!

Eclipse Workspaces: What for and why?

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

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

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

The character encoding of the HTML document was not declared

You have to change the file from .html to .php.

and add this following line

header('Content-Type: text/html; charset=utf-8');

standard_init_linux.go:190: exec user process caused "no such file or directory" - Docker

in my case I had to change line ending from CRLF to LF for the file and the error was gone.

I hope this helps,

Node.js: Python not found exception due to node-sass and node-gyp

After looking at all the answers, i notice this solution might be very helpful. It explains how to configure "npm" to find your installed python version while installing node-sass. Remember, node-sass requires node-gyp (an npm build-tool) which looks for your python path. Or just install python, and follow the same solution given (in the link). Thanks.

jquery: animate scrollLeft

First off I should point out that css animations would probably work best if you are doing this a lot but I ended getting the desired effect by wrapping .scrollLeft inside .animate


    $('.swipeBox').animate( { scrollLeft: '+=460' }, 1000);

    $('.swipeBox').animate( { scrollLeft: '-=460' }, 1000);

The second parameter is speed, and you can also add a third parameter if you are using smooth scrolling of some sort. Repeater get current index, pointer, or counter

To display the item number on the repeater you can use the Container.ItemIndex property.

<asp:repeater id="rptRepeater" runat="server">
        Item <%# Container.ItemIndex + 1 %>| <%# Eval("Column1") %>
        <br />

How to install and use "make" in Windows?

Another alternative is if you already installed minGW and added the bin folder the to Path environment variable, you can use "mingw32-make" instead of "make".

You can also create a symlink from "make" to "mingw32-make", or copying and changing the name of the file. I would not recommend the options before, they will work until you do changes on the minGW.

Need a query that returns every field that contains a specified letter

All the answers given using LIKEare totally valid, but as all of them noted will be slow. So if you have a lot of queries and not too many changes in the list of keywords, it pays to build a structure that allows for faster querying.

Here are some ideas:

If all you are looking for is the letters a-z and you don't care about uppercase/lowercase, you can add columns containsA .. containsZ and prefill those columns:

UPDATE table
SET containsA = 'X' 
WHERE UPPER(your_field) Like '%A%';

(and so on for all the columns).

Then index the contains.. columns and your query would be

FROM your_table
WHERE containsA = 'X'
AND containsB = 'X'

This may be normalized in an "index table" iTable with the columns your_table_key, letter, index the letter-column and your query becomes something like

FROM your_table 
WHERE <key> in (select a.key
    From iTable a join iTable b and a.key = b.key
    Where a.letter = 'a'
    AND b.letter = 'b');

All of these require some preprocessing (maybe in a trigger or so), but the queries should be a lot faster.

How to view method information in Android Studio?

In addition to the answers here you might want to make sure that the documentation is downloaded. To do that go to SDK Manager

enter image description here

and then the SDK Tools tab and make sure Documentation for Android SDK is installed.

enter image description here

If it isn't check the box and click Apply.

Vim and Ctags tips and tricks

I've encapsulated tags manipulation in an experimental plugin of mine.

Regarding C++ development in vim, I've already answered there: I use my own suite, and a few other plugins.

Sublime Text 2: How do I change the color that the row number is highlighted? seems pretty nice.

On the mac, the default theme files are in ~/Library/Application\ Support/Sublime\ Text\ 2/Packages/Color\ Scheme\ -\ Default

On Win7, the default theme files are in %appdata%\Sublime Text 2\Packages\Color Scheme - Default

jQuery - Redirect with post data

There is a JQuery plug-in that accomplishes pretty much what you're trying to do:

After including JQuery and the jquery.redirect.min.js plug-in, you can simply do something like this:

$().redirect('demo.php', {'arg1': 'value1', 'arg2': 'value2'});

Use the following code on newer JQuery versions instead:

$.redirect('demo.php', {'arg1': 'value1', 'arg2': 'value2'});

Hope this helps!

How can I select records ONLY from yesterday?

If you want the timestamp for yesterday try something like:


Can I write into the console in a unit test? If yes, why doesn't the console window open?

Someone commented about this apparently new functionality in Visual Studio 2013. I wasn't sure what he meant at first, but now that I do, I think it deserves its own answer.

We can use Console.WriteLine normally and the output is displayed, just not in the Output window, but in a new window after we click "Output" in the test details.

Enter image description here

Setting the height of a SELECT in IE

There is no work-around for this aside from ditching the select element.

Jasmine.js comparing arrays

I had a similar issue where one of the arrays was modified. I was using it for $httpBackend, and the returned object from that was actually a $promise object containing the array (not an Array object).

You can create a jasmine matcher to match the array by creating a toBeArray function:

beforeEach(function() {
  'use strict';
    toBeArray: function(array) {
      this.message = function() {
        return "Expected " + angular.mock.dump(this.actual) + " to be array " + angular.mock.dump(array) + ".";
      var arraysAreSame = function(x, y) {
         var arraysAreSame = true;
         for(var i; i < x.length; i++)
            if(x[i] !== y[i])
               arraysAreSame = false;
         return arraysAreSame;
      return arraysAreSame(this.actual, array);

And then just use it in your tests like the other jasmine matchers:

it('should compare arrays properly', function() {
  var array1, array2;
  /* . . . */

const to Non-const Conversion in C++

The actual code to cast away the const-ness of your pointer would be:

BoxT<T> * nonConstObj = const_cast<BoxT<T> *>(constObj);

But note that this really is cheating. A better solution would either be to figure out why you want to modify a const object, and redesign your code so you don't have to.... or remove the const declaration from your vector, if it turns out you don't really want those items to be read-only after all.

Python PIP Install throws TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'

I also had this issue. Initially, a proxy was set and work fine. Then I connected to a network where it doesn't go through a proxy. After unsetting proxy pip again get works.

unset http_proxy; unset http_prox;  unset HTTP_PROXY; unset HTTPS_PROXY

Resize image proportionally with MaxHeight and MaxWidth constraints

Like this?

public static void Test()
    using (var image = Image.FromFile(@"c:\logo.png"))
    using (var newImage = ScaleImage(image, 300, 400))
        newImage.Save(@"c:\test.png", ImageFormat.Png);

public static Image ScaleImage(Image image, int maxWidth, int maxHeight)
    var ratioX = (double)maxWidth / image.Width;
    var ratioY = (double)maxHeight / image.Height;
    var ratio = Math.Min(ratioX, ratioY);

    var newWidth = (int)(image.Width * ratio);
    var newHeight = (int)(image.Height * ratio);

    var newImage = new Bitmap(newWidth, newHeight);

    using (var graphics = Graphics.FromImage(newImage))
        graphics.DrawImage(image, 0, 0, newWidth, newHeight);

    return newImage;

How to get input text value from inside td

Maybe this will help.

var inputVal = $(this).closest('tr').find("td:eq(x) input").val();

Sql Server trigger insert values from new row into another table

trigger `[dbo].[mytrigger]` on `[dbo].[Patients]` after update , insert as
     --Sql logic
     print 'Hello world'     

Return JSON with error status code MVC

You need to decide if you want "HTTP level error" (that what error codes are for) or "application level error" (that what your custom JSON response is for).

Most high level objects using HTTP will never look into response stream if error code set to something that is not 2xx (success range). In your case you are explicitly setting error code to failure (I think 403 or 500) and force XMLHttp object to ignore body of the response.

To fix - either handle error conditions on client side or not set error code and return JSON with error information (see Sbossb reply for details).

How do I install Eclipse with C++ in Ubuntu 12.10 (Quantal Quetzal)?

There is a package called eclipse-cdt in the Ubuntu 12.10 repositories, this is what you want. If you haven't got g++ already, you need to install that as well, so all you need is:

sudo apt-get install eclipse eclipse-cdt g++

Whether you messed up your system with your previous installation attempts depends heavily on how you did it. If you did it the safe way for trying out new packages not from repositories (i.e., only installed in your home folder, no sudos blindly copied from installation manuals...) you're definitely fine. Otherwise, you may well have thousands of stray files all over your file system now. In that case, run all uninstall scripts you can find for the things you installed, then install using apt-get and hope for the best.

How to Use slideDown (or show) function on a table row?

I'm a bit behind the times on answering this, but I found a way to do it :)

function eventinfo(id) {
    tr = document.getElementById("ei"+id);
    div = document.getElementById("d"+id);
    if ( == "none") {"table-row";
    } else {
        setTimeout(function(){"none";}, 200);

I just put a div element inside the table data tags. when it is set visible, as the div expands, the whole row comes down. then tell it to fade back up (then timeout so you see the effect) before hiding the table row again :)

Hope this helps someone!

What is the meaning of CTOR?

Type "ctor" and press the TAB key twice this will add the default constructor automatically

How can we programmatically detect which iOS version is device running on?

[[UIDevice currentDevice] systemVersion];

or check the version like

You can get the below Macros from here.


        UIImageView *background = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"cs_lines_back.png"]] autorelease];
        theTableView.backgroundView = background;


Hope this helps

Deserializing a JSON file with JavaScriptSerializer()

Assuming you don't want to create another class, you can always let the deserializer give you a dictionary of key-value-pairs, like so:

string s = //{ "user" : {    "id" : 12345,    "screen_name" : "twitpicuser"}};
var serializer = new JavaScriptSerializer();
var result = serializer.DeserializeObject(s);

You'll get back something, where you can do:

var userId = int.Parse(result["user"]["id"]); // or (int)result["user"]["id"] depending on how the JSON is serialized.
// etc.

Look at result in the debugger to see, what's in there.

Setting the default ssh key location

If you are only looking to point to a different location for you identity file, the you can modify your ~/.ssh/config file with the following entry:

IdentityFile ~/.foo/identity

man ssh_config to find other config options.

Why is enum class preferred over plain enum?

C++11 FAQ mentions below points:

conventional enums implicitly convert to int, causing errors when someone does not want an enumeration to act as an integer.

enum color

enum class NewColor

int main()
    //! Implicit conversion is possible
    int i = Red;

    //! Need enum class name followed by access specifier. Ex: NewColor::Red_1
    int j = Red_1; // error C2065: 'Red_1': undeclared identifier

    //! Implicit converison is not possible. Solution Ex: int k = (int)NewColor::Red_1;
    int k = NewColor::Red_1; // error C2440: 'initializing': cannot convert from 'NewColor' to 'int'

    return 0;

conventional enums export their enumerators to the surrounding scope, causing name clashes.

// Header.h

enum vehicle

enum FourWheeler
    Car,        // error C2365: 'Car': redefinition; previous definition was 'enumerator'

enum class Editor

enum class CppEditor
    eclipes,       // No error of redefinitions
    VisualStudio,  // No error of redefinitions

The underlying type of an enum cannot be specified, causing confusion, compatibility problems, and makes forward declaration impossible.

// Header1.h
#include <iostream>

using namespace std;

enum class Port : unsigned char; // Forward declare

class MyClass
    void PrintPort(enum class Port p);

void MyClass::PrintPort(enum class Port p)
    cout << (int)p << endl;


// Header.h
enum class Port : unsigned char // Declare enum type explicitly
    PORT_1 = 0x01,
    PORT_2 = 0x02,
    PORT_3 = 0x04


// Source.cpp
#include "Header1.h"
#include "Header.h"

using namespace std;
int main()
    MyClass m;

    return 0;

How to make bootstrap column height to 100% row height?

You can solve that using display table.

Here is the updated JSFiddle that solves your problem.


.body {
    display: table;
    background-color: green;

.left-side {
    background-color: blue;
    float: none;
    display: table-cell;
    border: 1px solid;

.right-side {
    background-color: red;
    float: none;
    display: table-cell;
    border: 1px solid;


<div class="row body">
        <div class="col-xs-9 left-side">
        <div class="col-xs-3 right-side">

How to restart Jenkins manually?

If you installed as a rpm or deb, then service jenkins restart will work also.

Font awesome is not showing icon

Based on the 5.10.1 version.

My solution (locally):

  1. If you're using "fontawesome.css" or "fontawesome.min.css", try using "all.css" instead (located in the css folder).

  2. The "css" folder and the "webfonts" folder from the fontawesome package that you downloaded must be in the same level as each other.

In my case, I already had a css folder so I just renamed the fontawesome css folder to "css-fa".

With both "css-fa" and "webfonts" in my css folder, simply link it correctly in your text editor and it should work.

Ex: link rel="stylesheet" href="css/css-fa/all.css"

Load jQuery with Javascript and use jQuery

There's a working JSFiddle with a small example here, that demonstrates exactly what you are looking for (unless I've misunderstood your request):

There are a few issues with that method of loading javascript dynamically. When it comes to the very basal frameworks, like jQuery, you actually probably want to load them statically, because otherwise, you would have to write a whole JavaScript loading framework...

You could use some of the existing JavaScript loaders, or write your own by watching for window.jQuery to get defined.

// Immediately-invoked function expression
(function() {
    // Load the script
    var script = document.createElement("SCRIPT");
    script.src = '';
    script.type = 'text/javascript';
    script.onload = function() {
        var $ = window.jQuery;
        // Use $ here...

Just remember that if you need to support really old browsers, like IE8, load event handlers do not execute. In that case, you would need to poll for the existance of window.jQuery using repeated window.setTimeout. There is a working JSFiddle with that method here:

There are lots of people who have already done what you need to do. Check out some of the existing JavaScript Loader frameworks, like:

What is the difference between g++ and gcc?

gcc and g++ are compiler-drivers of the GNU Compiler Collection (which was once upon a time just the GNU C Compiler).

Even though they automatically determine which backends (cc1 cc1plus ...) to call depending on the file-type, unless overridden with -x language, they have some differences.

The probably most important difference in their defaults is which libraries they link against automatically.

According to GCC's online documentation link options and how g++ is invoked, g++ is equivalent to gcc -xc++ -lstdc++ -shared-libgcc (the 1st is a compiler option, the 2nd two are linker options). This can be checked by running both with the -v option (it displays the backend toolchain commands being run).

How do I make Git ignore file mode (chmod) changes?


git config core.fileMode false

From git-config(1):

    Tells Git if the executable bit of files in the working tree
    is to be honored.

    Some filesystems lose the executable bit when a file that is
    marked as executable is checked out, or checks out a
    non-executable file with executable bit on. git-clone(1)
    or git-init(1) probe the filesystem to see if it handles the 
    executable bit correctly and this variable is automatically
    set as necessary.

    A repository, however, may be on a filesystem that handles
    the filemode correctly, and this variable is set to true when
    created, but later may be made accessible from another
    environment that loses the filemode (e.g. exporting ext4
    via CIFS mount, visiting a Cygwin created repository with Git
    for Windows or Eclipse). In such a case it may be necessary
    to set this variable to false. See git-update-index(1).

    The default is true (when core.filemode is not specified
    in the config file).

The -c flag can be used to set this option for one-off commands:

git -c core.fileMode=false diff

And the --global flag will make it be the default behavior for the logged in user.

git config --global core.fileMode false

Changes of the global setting won't be applied to existing repositories. Additionally, git clone and git init explicitly set core.fileMode to true in the repo config as discussed in Git global core.fileMode false overridden locally on clone


core.fileMode is not the best practice and should be used carefully. This setting only covers the executable bit of mode and never the read/write bits. In many cases you think you need this setting because you did something like chmod -R 777, making all your files executable. But in most projects most files don't need and should not be executable for security reasons.

The proper way to solve this kind of situation is to handle folder and file permission separately, with something like:

find . -type d -exec chmod a+rwx {} \; # Make folders traversable and read/write
find . -type f -exec chmod a+rw {} \;  # Make files read/write

If you do that, you'll never need to use core.fileMode, except in very rare environment.

How to highlight text using javascript

The solutions offered here are quite bad.

  1. You can't use regex, because that way, you search/highlight in the html tags.
  2. You can't use regex, because it doesn't work properly with UTF* (anything with non-latin/English characters).
  3. You can't just do an innerHTML.replace, because this doesn't work when the characters have a special HTML notation, e.g. &amp; for &, &lt; for <, &gt; for >, &auml; for ä, &ouml; for ö &uuml; for ü &szlig; for ß, etc.

What you need to do:

Loop through the HTML document, find all text nodes, get the textContent, get the position of the highlight-text with indexOf (with an optional toLowerCase if it should be case-insensitive), append everything before indexof as textNode, append the matched Text with a highlight span, and repeat for the rest of the textnode (the highlight string might occur multiple times in the textContent string).

Here is the code for this:

var InstantSearch = {

    "highlight": function (container, highlightText)
        var internalHighlighter = function (options)

            var id = {
                container: "container",
                tokens: "tokens",
                all: "all",
                token: "token",
                className: "className",
                sensitiveSearch: "sensitiveSearch"
            tokens = options[id.tokens],
            allClassName = options[id.all][id.className],
            allSensitiveSearch = options[id.all][id.sensitiveSearch];

            function checkAndReplace(node, tokenArr, classNameAll, sensitiveSearchAll)
                var nodeVal = node.nodeValue, parentNode = node.parentNode,
                    i, j, curToken, myToken, myClassName, mySensitiveSearch,
                    finalClassName, finalSensitiveSearch,
                    foundIndex, begin, matched, end,
                    textNode, span, isFirst;

                for (i = 0, j = tokenArr.length; i < j; i++)
                    curToken = tokenArr[i];
                    myToken = curToken[id.token];
                    myClassName = curToken[id.className];
                    mySensitiveSearch = curToken[id.sensitiveSearch];

                    finalClassName = (classNameAll ? myClassName + " " + classNameAll : myClassName);

                    finalSensitiveSearch = (typeof sensitiveSearchAll !== "undefined" ? sensitiveSearchAll : mySensitiveSearch);

                    isFirst = true;
                    while (true)
                        if (finalSensitiveSearch)
                            foundIndex = nodeVal.indexOf(myToken);
                            foundIndex = nodeVal.toLowerCase().indexOf(myToken.toLowerCase());

                        if (foundIndex < 0)
                            if (isFirst)

                            if (nodeVal)
                                textNode = document.createTextNode(nodeVal);
                                parentNode.insertBefore(textNode, node);
                            } // End if (nodeVal)

                        } // End if (foundIndex < 0)

                        isFirst = false;

                        begin = nodeVal.substring(0, foundIndex);
                        matched = nodeVal.substr(foundIndex, myToken.length);

                        if (begin)
                            textNode = document.createTextNode(begin);
                            parentNode.insertBefore(textNode, node);
                        } // End if (begin)

                        span = document.createElement("span");
                        span.className += finalClassName;
                        parentNode.insertBefore(span, node);

                        nodeVal = nodeVal.substring(foundIndex + myToken.length);
                    } // Whend

                } // Next i 
            }; // End Function checkAndReplace 

            function iterator(p)
                if (p === null) return;

                var children =, i, cur;

                if (children.length)
                    for (i = 0; i < children.length; i++)
                        cur = children[i];
                        if (cur.nodeType === 3)
                            checkAndReplace(cur, tokens, allClassName, allSensitiveSearch);
                        else if (cur.nodeType === 1)
            }; // End Function iterator

        } // End Function highlighter

                container: container
                , all:
                        className: "highlighter"
                , tokens: [
                        token: highlightText
                        , className: "highlight"
                        , sensitiveSearch: false
        ); // End Call internalHighlighter 

    } // End Function highlight


Then you can use it like this:

function TestTextHighlighting(highlightText)
    var container = document.getElementById("testDocument");
    InstantSearch.highlight(container, highlightText);

Here's an example HTML document

<!DOCTYPE html>
        <title>Example of Text Highlight</title>
        <style type="text/css" media="screen">
            .highlight{ background: #D3E18A;}
            .light{ background-color: yellow;}
        <div id="testDocument">
            This is a test
            <span> This is another test</span>

By the way, if you search in a database with LIKE,
e.g. WHERE textField LIKE CONCAT('%', @query, '%') [which you shouldn't do, you should use fulltext-search or Lucene], then you can escape every character with \ and add an SQL-escape-statement, that way you'll find special characters that are LIKE-expressions.


WHERE textField LIKE CONCAT('%', @query, '%') ESCAPE '\'

and the value of @query is not '%completed%' but '%\c\o\m\p\l\e\t\e\d%'

(tested, works with SQL-Server and PostgreSQL, and every other RDBMS system that supports ESCAPE)

A revised typescript-version:

namespace SearchTools 

    export interface IToken
        token: string;
        className: string;
        sensitiveSearch: boolean;

    export class InstantSearch 

        protected m_container: Node;
        protected m_defaultClassName: string;
        protected m_defaultCaseSensitivity: boolean;
        protected m_highlightTokens: IToken[];

        constructor(container: Node, tokens: IToken[], defaultClassName?: string, defaultCaseSensitivity?: boolean)
            this.iterator = this.iterator.bind(this);
            this.checkAndReplace = this.checkAndReplace.bind(this);
            this.highlight = this.highlight.bind(this);
            this.highlightNode = this.highlightNode.bind(this);    

            this.m_container = container;
            this.m_defaultClassName = defaultClassName || "highlight";
            this.m_defaultCaseSensitivity = defaultCaseSensitivity || false;
            this.m_highlightTokens = tokens || [{
                token: "test",
                className: this.m_defaultClassName,
                sensitiveSearch: this.m_defaultCaseSensitivity

        protected checkAndReplace(node: Node)
            let nodeVal: string = node.nodeValue;
            let parentNode: Node = node.parentNode;
            let textNode: Text = null;

            for (let i = 0, j = this.m_highlightTokens.length; i < j; i++)
                let curToken: IToken = this.m_highlightTokens[i];
                let textToHighlight: string = curToken.token;
                let highlightClassName: string = curToken.className || this.m_defaultClassName;
                let caseSensitive: boolean = curToken.sensitiveSearch || this.m_defaultCaseSensitivity;

                let isFirst: boolean = true;
                while (true)
                    let foundIndex: number = caseSensitive ?
                        : nodeVal.toLowerCase().indexOf(textToHighlight.toLowerCase());

                    if (foundIndex < 0)
                        if (isFirst)

                        if (nodeVal)
                            textNode = document.createTextNode(nodeVal);
                            parentNode.insertBefore(textNode, node);
                        } // End if (nodeVal)

                    } // End if (foundIndex < 0)

                    isFirst = false;

                    let begin: string = nodeVal.substring(0, foundIndex);
                    let matched: string = nodeVal.substr(foundIndex, textToHighlight.length);

                    if (begin)
                        textNode = document.createTextNode(begin);
                        parentNode.insertBefore(textNode, node);
                    } // End if (begin)

                    let span: HTMLSpanElement = document.createElement("span");

                    if (!span.classList.contains(highlightClassName))

                    parentNode.insertBefore(span, node);

                    nodeVal = nodeVal.substring(foundIndex + textToHighlight.length);
                } // Whend

            } // Next i 

        } // End Sub checkAndReplace 

        protected iterator(p: Node)
            if (p == null)

            let children: Node[] =;

            if (children.length)
                for (let i = 0; i < children.length; i++)
                    let cur: Node = children[i];

                    if (cur.nodeType === Node.TEXT_NODE) 
                    else if (cur.nodeType === Node.ELEMENT_NODE) 
                } // Next i 

            } // End if (children.length) 

        } // End Sub iterator

        public highlightNode(n:Node)
        } // End Sub highlight 

        public highlight()
        } // End Sub highlight 

    } // End Class InstantSearch 

} // End Namespace SearchTools 


let searchText = document.getElementById("txtSearchText");
let searchContainer = document.body; // document.getElementById("someTable");
let highlighter = new SearchTools.InstantSearch(searchContainer, [
        token: "this is the text to highlight" // searchText.value,
        className: "highlight", // this is the individual highlight class
        sensitiveSearch: false

// highlighter.highlight(); // this would highlight in the entire table
// foreach tr - for each td2 
highlighter.highlightNode(td2); // this highlights in the second column of table

How to import module when module name has a '-' dash or hyphen in it?

If you can't rename the module to match Python naming conventions, create a new module to act as an intermediary:

 ---- ----
 tmp = __import__('foo-bar')

 ---- ----
 from foo_proxy import * 

How to add parameters into a WebRequest?

The code below differs from all other code because at the end it prints the response string in the console that the request returns. I learned in previous posts that the user doesn't get the response Stream and displays it.

//Visual Basic Implementation Request and Response String
  Dim params = "key1=value1&key2=value2"
    Dim byteArray = UTF8.GetBytes(params)
    Dim url = ""
    Dim client = WebRequest.Create(url)
    client.Method = "POST"
    client.ContentType = "application/x-www-form-urlencoded"
    client.ContentLength = byteArray.Length
    Dim stream = client.GetRequestStream()

    //sending the data
    stream.Write(byteArray, 0, byteArray.Length)

//getting the full response in a stream        
Dim response = client.GetResponse().GetResponseStream()

//reading the response 
Dim result = New StreamReader(response)

//Writes response string to Console

Objective-C - Remove last character from string

The documentation is your friend, NSString supports a call substringWithRange that can shorten the string that you have an return the shortened String. You cannot modify an instance of NSString it is immutable. If you have an NSMutableString is has a method called deleteCharactersInRange that can modify the string in place

NSRange r;
r.location = 0;
r.size = [mutable length]-1;
NSString* shorted = [stringValue substringWithRange:r];

How do I force my .NET application to run as administrator?

The detailed steps are as follow.

  1. Add application manifest file to solution
  2. Change application setting to "app.manifest"
  3. Update tag of "requestedExecutionLevel" to requireAdministrator.

Adding file in Solution

Select Application Manifest File

Select Manifest option

Update Manifest file

Note that using this code you need to turn off the security settings of ClickOnce, for do this, go inside Properties -> Security -> ClickOnce Security

how to modify the size of a column

Regardless of what error Oracle SQL Developer may indicate in the syntax highlighting, actually running your alter statement exactly the way you originally had it works perfectly:


You only need to add parenthesis if you need to alter more than one column at once, such as:

ALTER TABLE TEST_PROJECT2 MODIFY (proj_name VARCHAR2(400), proj_desc VARCHAR2(400));

Error: Expression must have integral or unscoped enum type

Your variable size is declared as: float size;

You can't use a floating point variable as the size of an array - it needs to be an integer value.

You could cast it to convert to an integer:

float *temp = new float[(int)size];

Your other problem is likely because you're writing outside of the bounds of the array:

   float *temp = new float[size];

    //Getting input from the user
    for (int x = 1; x <= size; x++){
        cout << "Enter temperature " << x << ": ";

        // cin >> temp[x];
        // This should be:
        cin >> temp[x - 1];

Arrays are zero based in C++, so this is going to write beyond the end and never write the first element in your original code.

jQuery: Check if special characters exists in string

If you really want to check for all those special characters, it's easier to use a regular expression:

var str = $('#Search').val();
if(/^[a-zA-Z0-9- ]*$/.test(str) == false) {
    alert('Your search string contains illegal characters.');

The above will only allow strings consisting entirely of characters on the ranges a-z, A-Z, 0-9, plus the hyphen an space characters. A string containing any other character will cause the alert.

How to check if a value exists in an object using JavaScript

if( myObj.hasOwnProperty('key') && myObj['key'] === value ){

Using Node.js require vs. ES6 import/export

The most important thing to know is that ES6 modules are, indeed, an official standard, while CommonJS (Node.js) modules are not.

In 2019, ES6 modules are supported by 84% of browsers. While Node.js puts them behind an --experimental-modules flag, there is also a convenient node package called esm, which makes the integration smooth.

Another issue you're likely to run into between these module systems is code location. Node.js assumes source is kept in a node_modules directory, while most ES6 modules are deployed in a flat directory structure. These are not easy to reconcile, but it can be done by hacking your package.json file with pre and post installation scripts. Here is an example isomorphic module and an article explaining how it works.

javascript - replace dash (hyphen) with a space

var str = "This-is-a-news-item-";
while (str.contains("-")) {
  str = str.replace("-", ' ');

I found that one use of str.replace() would only replace the first hyphen, so I looped thru while the input string still contained any hyphens, and replaced them all.

PHP, display image with Header()

There is a better why to determine type of an image. with exif_imagetype

If you use this function, you can tell image's real extension.

with this function filename's extension is completely irrelevant, which is good.

function setHeaderContentType(string $filePath): void
    $numberToContentTypeMap = [
        '1' => 'image/gif',
        '2' => 'image/jpeg',
        '3' => 'image/png',
        '6' => 'image/bmp',
        '17' => 'image/ico'

    $contentType = $numberToContentTypeMap[exif_imagetype($filePath)] ?? null;
    if ($contentType === null) {
        throw new Exception('Unable to determine content type of file.');

    header("Content-type: $contentType");

You can add more types from the link.

Hope it helps.

Can I make a <button> not submit a form?

Just use good old HTML:

<input type="button" value="Submit" />

Wrap it as the subject of a link, if you so desire:

<a href=""><input type="button" value="Submit" /></a>

Or if you decide you want javascript to provide some other functionality:

<input type="button" value="Cancel" onclick="javascript: someFunctionThatCouldIncludeRedirect();"/>

How do I iterate over a range of numbers defined by variables in Bash?

If you're on BSD / OS X you can use jot instead of seq:

for i in $(jot $END); do echo $i; done

The import cannot be resolved

This issue may also occur if you have multiple versions of the same support library android-support-v4.jar. If your project is using other library projects that contain different-2 versions of the support library. To resolve the issue keep the same version of support library at each place.

How to change dataframe column names in pyspark?

We can use various approaches to rename the column name.

First, let create a simple DataFrame.

df = spark.createDataFrame([("x", 1), ("y", 2)], 
                                  ["col_1", "col_2"])

Now let's try to rename col_1 to col_3. PFB a few approaches to do the same.

# Approach - 1 : using withColumnRenamed function.
df.withColumnRenamed("col_1", "col_3").show()

# Approach - 2 : using alias function.["col_1"].alias("col3"), "col_2").show()

# Approach - 3 : using selectExpr function.
df.selectExpr("col_1 as col_3", "col_2").show()

# Rename all columns
# Approach - 4 : using toDF function. Here you need to pass the list of all columns present in DataFrame.
df.toDF("col_3", "col_2").show()

Here is the output.

|    x|    1|
|    y|    2|

I hope this helps.

Why GDB jumps unpredictably between lines and prints variables as "<value optimized out>"?

Im using QtCreator with gdb.



Works well for me

Background color on input type=button :hover state sticks in IE

There might be a fix to <input type="button"> - but if there is, I don't know it.

Otherwise, a good option seems to be to replace it with a carefully styled a element.


.button {
    background-color: #E3E1B8; 
    padding: 2px 4px;
    font: 13px sans-serif;
    text-decoration: none;
    border: 1px solid #000;
    border-color: #aaa #444 #444 #aaa;
    color: #000

Upsides include that the a element will style consistently between different (older) versions of Internet Explorer without any extra work, and I think my link looks nicer than that button :)

How to use Git?

git clone your-url local-dir

to checkout source code;

git pull

to update source code in local-dir;

Get selected item value from Bootstrap DropDown with specific ID

Design code using Bootstrap

<div class="dropdown-menu" id="demolist">_x000D_
  <a class="dropdown-item" h ref="#">Cricket</a>_x000D_
  <a class="dropdown-item" href="#">UFC</a>_x000D_
  <a class="dropdown-item" href="#">Football</a>_x000D_
  <a class="dropdown-item" href="#">Basketball</a>_x000D_

  • jquery Code

<script src=""></script>_x000D_
  $(document).ready(function () {_x000D_
    $('#demolist a').on('click', function () {_x000D_
      var txt= ($(this).text());_x000D_
      alert("Your Favourite Sports is "+txt);_x000D_

In Tkinter is there any way to make a widget not visible?

One option, as explained in another answer, is to use pack_forget or grid_forget. Another option is to use lift and lower. This changes the stacking order of widgets. The net effect is that you can hide widgets behind sibling widgets (or descendants of siblings). When you want them to be visible you lift them, and when you want them to be invisible you lower them.

The advantage (or disadvantage...) is that they still take up space in their master. If you "forget" a widget, the other widgets might readjust their size or orientation, but if you raise or lower them they will not.

Here is a simple example:

import Tkinter as tk

class SampleApp(tk.Tk):
    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)
        self.frame = tk.Frame(self)
        self.frame.pack(side="top", fill="both", expand=True)
        self.label = tk.Label(self, text="Hello, world")
        button1 = tk.Button(self, text="Click to hide label",
        button2 = tk.Button(self, text="Click to show label",

    def show_label(self, event=None):

    def hide_label(self, event=None):

if __name__ == "__main__":
    app = SampleApp()

Can "list_display" in a Django ModelAdmin display attributes of ForeignKey fields?

You can show whatever you want in list display by using a callable. It would look like this:

def book_author(object):

class PersonAdmin(admin.ModelAdmin):
  list_display = [book_author,]

What is the use of the init() usage in JavaScript?

JavaScript doesn't have a built-in init() function, that is, it's not a part of the language. But it's not uncommon (in a lot of languages) for individual programmers to create their own init() function for initialisation stuff.

A particular init() function may be used to initialise the whole webpage, in which case it would probably be called from document.ready or onload processing, or it may be to initialise a particular type of object, or...well, you name it.

What any given init() does specifically is really up to whatever the person who wrote it needed it to do. Some types of code don't need any initialisation.

function init() {
  // initialisation stuff here

// elsewhere in code

Accessing @attribute from SimpleXML

$xml = <<<XML
<elem attrib="value" />

$sxml = simplexml_load_string($xml);
$attrs = $sxml->elem->attributes();
echo $attrs["attrib"]; //or just $sxml->elem["attrib"]

Use SimpleXMLElement::attributes.

Truth is, the SimpleXMLElement get_properties handler lies big time. There's no property named "@attributes", so you can't do $sxml->elem->{"@attributes"}["attrib"].

Git Cherry-pick vs Merge Workflow

Both rebase (and cherry-pick) and merge have their advantages and disadvantages. I argue for merge here, but it's worth understanding both. (Look here for an alternate, well-argued answer enumerating cases where rebase is preferred.)

merge is preferred over cherry-pick and rebase for a couple of reasons.

  1. Robustness. The SHA1 identifier of a commit identifies it not just in and of itself but also in relation to all other commits that precede it. This offers you a guarantee that the state of the repository at a given SHA1 is identical across all clones. There is (in theory) no chance that someone has done what looks like the same change but is actually corrupting or hijacking your repository. You can cherry-pick in individual changes and they are likely the same, but you have no guarantee. (As a minor secondary issue the new cherry-picked commits will take up extra space if someone else cherry-picks in the same commit again, as they will both be present in the history even if your working copies end up being identical.)
  2. Ease of use. People tend to understand the merge workflow fairly easily. rebase tends to be considered more advanced. It's best to understand both, but people who do not want to be experts in version control (which in my experience has included many colleagues who are damn good at what they do, but don't want to spend the extra time) have an easier time just merging.

Even with a merge-heavy workflow rebase and cherry-pick are still useful for particular cases:

  1. One downside to merge is cluttered history. rebase prevents a long series of commits from being scattered about in your history, as they would be if you periodically merged in others' changes. That is in fact its main purpose as I use it. What you want to be very careful of, is never to rebase code that you have shared with other repositories. Once a commit is pushed someone else might have committed on top of it, and rebasing will at best cause the kind of duplication discussed above. At worst you can end up with a very confused repository and subtle errors it will take you a long time to ferret out.
  2. cherry-pick is useful for sampling out a small subset of changes from a topic branch you've basically decided to discard, but realized there are a couple of useful pieces on.

As for preferring merging many changes over one: it's just a lot simpler. It can get very tedious to do merges of individual changesets once you start having a lot of them. The merge resolution in git (and in Mercurial, and in Bazaar) is very very good. You won't run into major problems merging even long branches most of the time. I generally merge everything all at once and only if I get a large number of conflicts do I back up and re-run the merge piecemeal. Even then I do it in large chunks. As a very real example I had a colleague who had 3 months worth of changes to merge, and got some 9000 conflicts in 250000 line code-base. What we did to fix is do the merge one month's worth at a time: conflicts do not build up linearly, and doing it in pieces results in far fewer than 9000 conflicts. It was still a lot of work, but not as much as trying to do it one commit at a time.

Html.EditorFor Set Default Value

Shove it in the ViewBag:


ViewBag.ProductId = 1;


@Html.TextBoxFor(c => c.Propertyname, new {@Value = ViewBag.ProductId})

Visual Studio - How to change a project's folder name and solution name without breaking the solution

You could open the SLN file in any text editor (Notepad, etc.) and simply change the project path there.

Firebase (FCM) how to get token

You can use the following in Firebase (FCM) to get the token:


How to loop through a HashMap in JSP?

Below code works for me

first I defined the partnerTypesMap like below in the server side,

Map<String, String> partnerTypes = new HashMap<>();

after adding values to it I added the object to model,

model.addAttribute("partnerTypesMap", partnerTypes);

When rendering the page I use below foreach to print them one by one.

<c:forEach items="${partnerTypesMap}" var="partnerTypesMap">
      <form:option value="${partnerTypesMap['value']}">${partnerTypesMap['key']}</form:option>

How to position the div popup dialog to the center of browser screen?

Its a classical problem, when you scroll the modal popup generated on the screen stays at it place and does not scroll along, so the user might be blocked as he might not see the popup on his viewable screen.

The following link also provides CSS only code for generating a modal box along with its absolute position.

Is it possible to clone html element objects in JavaScript / JQuery?

It's actually very easy in jQuery:


Change .appendTo() of course...

Best way to use multiple SSH private keys on one client

For me, the only working solution was to simply add this in file ~/.ssh/config:

Host *
  IdentityFile ~/.ssh/your_ssh_key
  IdentityFile ~/.ssh/your_ssh_key2
  IdentityFile ~/.ssh/your_ssh_key3
  AddKeysToAgent yes

your_ssh_key is without any extension. Don't use .pub.

__proto__ VS. prototype in JavaScript

Prototype or Object.prototype is a property of an object literal. It represents the Object prototype object which you can override to add more properties or methods further along the prototype chain.

__proto__ is an accessor property (get and set function) that exposes the internal prototype of an object thru which it is accessed.




Get a list of all threads currently running in Java

Have you taken a look at jconsole?

This will list all threads running for a particular Java process.

You can start jconsole from the JDK bin folder.

You can also get a full stack trace for all threads by hitting Ctrl+Break in Windows or by sending kill pid --QUIT in Linux.

Unable to find the requested .Net Framework Data Provider. It may not be installed. - when following mvc3 tutorial

In my case, the issue was caused by a connection problem to the SQL database. I just disconnected and then reconnected the SQL datasource from the design view. I am back up and running. Hope this works for everyone.

How to secure RESTful web services?

If choosing between OAuth versions, go with OAuth 2.0.

OAuth bearer tokens should only be used with a secure transport.

OAuth bearer tokens are only as secure or insecure as the transport that encrypts the conversation. HTTPS takes care of protecting against replay attacks, so it isn't necessary for the bearer token to also guard against replay.

While it is true that if someone intercepts your bearer token they can impersonate you when calling the API, there are plenty of ways to mitigate that risk. If you give your tokens a long expiration period and expect your clients to store the tokens locally, you have a greater risk of tokens being intercepted and misused than if you give your tokens a short expiration, require clients to acquire new tokens for every session, and advise clients not to persist tokens.

If you need to secure payloads that pass through multiple participants, then you need something more than HTTPS/SSL, since HTTPS/SSL only encrypts one link of the graph. This is not a fault of OAuth.

Bearer tokens are easy to for clients to obtain, easy for clients to use for API calls and are widely used (with HTTPS) to secure public facing APIs from Google, Facebook, and many other services.

Java reflection: how to get field value from an object, not knowing its class

I strongly recommend using Java generics to specify what type of object is in that List, ie. List<Car>. If you have Cars and Trucks you can use a common superclass/interface like this List<Vehicle>.

However, you can use Spring's ReflectionUtils to make fields accessible, even if they are private like the below runnable example:

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

list.add("some value");

for(Object obj : list)
    Class<?> clazz = obj.getClass();

    Field field = org.springframework.util.ReflectionUtils.findField(clazz, "value");

    System.out.println("value=" + field.get(obj));

Running this has an output of:


Capture the screen shot using .NET

It's certainly possible to grab a screenshot using the .NET Framework. The simplest way is to create a new Bitmap object and draw into that using the Graphics.CopyFromScreen method.

Sample code:

using (Bitmap bmpScreenCapture = new Bitmap(Screen.PrimaryScreen.Bounds.Width, 
using (Graphics g = Graphics.FromImage(bmpScreenCapture))
                     0, 0,

Caveat: This method doesn't work properly for layered windows. Hans Passant's answer here explains the more complicated method required to get those in your screen shots.

concatenate variables

If you need to concatenate paths with quotes, you can use = to replace quotes in a variable. This does not require you to know if the path already contains quotes or not. If there are no quotes, nothing is changed.

@echo off
rem Paths to combine
set DIRECTORY="C:\Directory with spaces"
set FILENAME="sub directory\filename.txt"

rem Combine two paths

rem This is just to illustrate how the = operator works

Python urllib2: Receive JSON response from url

resource_url = 'http://localhost:8080/service/'
response = json.loads(urllib2.urlopen(resource_url).read())

Bootstrap center heading

.text-left {
  text-align: left;

.text-right {
  text-align: right;

.text-center {
  text-align: center;

bootstrap has added three css classes for text align.

What's the syntax for mod in java

Another way is:

boolean isEven = false;
if((a % 2) == 0)
    isEven = true;

But easiest way is still:

boolean isEven = (a % 2) == 0;

Like @Steve Kuo said.

Moving matplotlib legend outside of the axis makes it cutoff by the figure box

Added: I found something that should do the trick right away, but the rest of the code below also offers an alternative.

Use the subplots_adjust() function to move the bottom of the subplot up:

fig.subplots_adjust(bottom=0.2) # <-- Change the 0.02 to work for your plot.

Then play with the offset in the legend bbox_to_anchor part of the legend command, to get the legend box where you want it. Some combination of setting the figsize and using the subplots_adjust(bottom=...) should produce a quality plot for you.

Alternative: I simply changed the line:

fig = plt.figure(1)


fig = plt.figure(num=1, figsize=(13, 13), dpi=80, facecolor='w', edgecolor='k')

and changed

lgd = ax.legend(loc=9, bbox_to_anchor=(0.5,0))


lgd = ax.legend(loc=9, bbox_to_anchor=(0.5,-0.02))

and it shows up fine on my screen (a 24-inch CRT monitor).

Here figsize=(M,N) sets the figure window to be M inches by N inches. Just play with this until it looks right for you. Convert it to a more scalable image format and use GIMP to edit if necessary, or just crop with the LaTeX viewport option when including graphics.

Change the selected value of a drop-down list with jQuery

I know this is a old question and the above solutions works fine except in some cases.


<select id="select_selector">
<option value="1">Item1</option>
<option value="2">Item2</option>
<option value="3">Item3</option>
<option value="4" selected="selected">Item4</option>
<option value="5">Item5</option>

So Item 4 will show as "Selected" in the browser and now you want to change the value as 3 and show "Item3" as selected instead of Item4.So as per the above solutions,if you use


You will see that Item 3 as selected in browser.But when you process the data either in php or asp , you will find the selected value as "4".The reason is that , your html will look like this.

<select id="select_selector">
<option value="1">Item1</option>
<option value="2">Item2</option>
<option value="3" selected="selected">Item3</option>
<option value="4" selected="selected">Item4</option>
<option value="5">Item5</option>

and it gets the last value as "4" in sever side language.


newselectedIndex = 3;
jQuery("#select_selector option:selected").removeAttr("selected");
jQuery("#select_selector option[value='"+newselectedIndex +"']").attr('selected', 'selected');  

EDIT: Add single quote around "+newselectedIndex+" so that the same functionality can be used for non-numerical values.

So what I do is actually ,removed the selected attribute and then make the new one as selected.

I would appreciate comments on this from senior programmers like @strager , @y0mbo , @ISIK and others

How to convert SSH keypairs generated using PuTTYgen (Windows) into key-pairs used by ssh-agent and Keychain (Linux)

PPK ? OpenSSH RSA with PuttyGen & Docker.

Private key:

docker run --rm -v $(pwd):/app zinuzoid/puttygen private.ppk -O private-openssh -o my-openssh-key

Public key:

docker run --rm -v $(pwd):/app zinuzoid/puttygen private.ppk -L -o

See also

.ps1 cannot be loaded because the execution of scripts is disabled on this system

There are certain scenarios in which you can follow the steps suggested in the other answers, verify that Execution Policy is set correctly, and still have your scripts fail. If this happens to you, you are probably on a 64-bit machine with both 32-bit and 64-bit versions of PowerShell, and the failure is happening on the version that doesn't have Execution Policy set. The setting does not apply to both versions, so you have to explicitly set it twice.

Look in your Windows directory for System32 and SysWOW64.

Repeat these steps for each directory:

  1. Navigate to WindowsPowerShell\v1.0 and launch powershell.exe
  2. Check the current setting for ExecutionPolicy:

    Get-ExecutionPolicy -List

  3. Set the ExecutionPolicy for the level and scope you want, for example:

    Set-ExecutionPolicy -Scope LocalMachine Unrestricted

Note that you may need to run PowerShell as administrator depending on the scope you are trying to set the policy for.

You can read a lot more here: Running Windows PowerShell Scripts

Adding CSRFToken to Ajax request

From JSP

<form method="post" id="myForm" action="someURL">
    <input name="csrfToken" value="5965f0d244b7d32b334eff840...etc" type="hidden">    

This is the simplest way that worked for me after struggling for 3hrs, just get the token from input hidden field like this and while doing the AJAX request to just need to pass this token in header as follows:-

From Jquery

var token =  $('input[name="csrfToken"]').attr('value'); 

From plain Javascript

var token = document.getElementsByName("csrfToken").value;

Final AJAX Request

      url: route.url,
      data : JSON.stringify(data),
      method : 'POST',
      headers: {
                    'X-CSRF-Token': token 
      success: function (data) { ...      },
      error: function (data) { ...  }


Now you don't need to disable crsf security in web config, and also this will not give you 405( Method Not Allowed) error on console.

Hope this will help people..!!

How to force a view refresh without having it trigger automatically from an observable?

You can't call something on the entire viewModel, but on an individual observable you can call myObservable.valueHasMutated() to notify subscribers that they should re-evaluate. This is generally not necessary in KO, as you mentioned.

ESLint Parsing error: Unexpected token

Just for the record, if you are using eslint-plugin-vue, the correct place to add 'parser': 'babel-eslint' is inside parserOptions param.

  'parserOptions': {
    'parser': 'babel-eslint',
    'ecmaVersion': 2018,
    'sourceType': 'module'

How to select only the first rows for each unique value of a column?

In SQL 2k5+, you can do something like:

;with cte as (
  select CName, AddressLine,
  rank() over (partition by CName order by AddressLine) as [r]
  from MyTable
select CName, AddressLine
from cte
where [r] = 1

Kubernetes Pod fails with CrashLoopBackOff

I ran into the same error.

NAME         READY   STATUS             RESTARTS   AGE
pod/webapp   0/1     CrashLoopBackOff   5          47h

My problem was that I was trying to run two different pods with the same metadata name.

kind: Pod metadata: name: webapp labels: ...

To find all the names of your pods run: kubectl get pods

webapp       1/1     Running   15         47h

then I changed the conflicting pod name and everything worked just fine.

NAME                 READY   STATUS    RESTARTS   AGE
webapp               1/1     Running   17         2d
webapp-release-0-5   1/1     Running   0          13m

How do I create a MongoDB dump of my database?

to export

mongodump -d <database name> <backup-folder>

to import

mongorestore -d <database name> <backup-folder>

npm global path prefix

Spent a while on this issue, and the PATH switch wasn't helping. My problem was the Homebrew/node/npm bug found here -

If you've already installed node using Homebrew, try ****Note per comments that this might not be safe. It worked for me but could have unintended consequences. It also appears that latest version of Homebrew properly installs npm. So likely I would try brew update, brew doctor, brew upgrade node etc before trying****:

npm update -gf

Or, if you want to install node with Homebrew and have npm work, use:

brew install node --without-npm
curl -L | sh

powerpoint loop a series of animation

Unfortunately you're probably done with the animation and presentation already. In the hopes this answer can help future questioners, however, this blog post has a walkthrough of steps that can loop a single slide as a sort of sub-presentation.

First, click Slide Show > Set Up Show.

Put a checkmark to Loop continuously until 'Esc'.

Click Ok. Now, Click Slide Show > Custom Shows. Click New.

Select the slide you are looping, click Add. Click Ok and Close.

Click on the slide you are looping. Click Slide Show > Slide Transition. Under Advance slide, put a checkmark to Automatically After. This will allow the slide to loop automatically. Do NOT Apply to all slides.

Right click on the thumbnail of the current slide, select Hide Slide.

Now, you will need to insert a new slide just before the slide you are looping. On the new slide, insert an action button. Set the hyperlink to the custom show you have created. Put a checkmark on "Show and Return"

This has worked for me.

ASP.NET Background image

resize your background image in an image editor to the size you want related to your login box, which should help page loading and preserve image quality...

hard-size your DIV relative to your image

position your asp:login control where needed...

Hibernate: How to fix "identifier of an instance altered from X to Y"?

Also ran into this error message, but the root cause was of a different flavor from those referenced in the other answers here.

Generic answer: Make sure that once hibernate loads an entity, no code changes the primary key value in that object in any way. When hibernate flushes all changes back to the database, it throws this exception because the primary key changed. If you don't do it explicitly, look for places where this may happen unintentionally, perhaps on related entities that only have LAZY loading configured.

In my case, I am using a mapping framework (MapStruct) to update an entity. In the process, also other referenced entities were being updates as mapping frameworks tend to do that by default. I was later replacing the original entity with new one (in DB terms, changed the value of the foreign key to reference a different row in the related table), the primary key of the previously-referenced entity was already updated, and hibernate attempted to persist this update on flush.

How to get package name from anywhere?

Use: BuildConfig.APPLICATION_ID to get PACKAGE NAME anywhere( ie; services, receiver, activity, fragment, etc )

Example: String PackageName = BuildConfig.APPLICATION_ID;

How to pop an alert message box using PHP?

PHP renders HTML and Javascript to send to the client's browser. PHP is a server-side language. This is what allows it do things like INSERT something into a database on the server.

But an alert is rendered by the browser of the client. You would have to work through javascript to get an alert.

Error 'LINK : fatal error LNK1123: failure during conversion to COFF: file invalid or corrupt' after installing Visual Studio 2012 Release Preview

The issue was magically resolved for me by removing .NET 4.5, and replacing it with .NET 4.0. I then had to repair Visual Studio 2010 - it being corrupted along the way somehow.

I had previously installed, and then un-installed, Visual Studio 2012 - which may be related to the issue.

How to get the concrete class name as a string?



>>> class A():
>>> a = A()
>>> a.__class__.__name__

Undefined reference to `pow' and `floor'

You need to compile with the link flag -lm, like this:

gcc fib.c -lm -o fibo

This will tell gcc to link your code against the math lib. Just be sure to put the flag after the objects you want to link.

Find kth smallest element in a binary search tree in Optimum way

Here's a concise version in C# that returns the k-th smallest element, but requires passing k in as a ref argument (it's the same approach as @prasadvk):

Node FindSmall(Node root, ref int k)
    if (root == null || k < 1)
        return null;

    Node node = FindSmall(root.LeftChild, ref k);
    if (node != null)
        return node;

    if (--k == 0)
        return node ?? root;
    return FindSmall(root.RightChild, ref k);

It's O(log n) to find the smallest node, and then O(k) to traverse to k-th node, so it's O(k + log n).

C# Test if user has write access to a folder

Try this:

    DirectoryInfo di = new DirectoryInfo(path);
    DirectorySecurity acl = di.GetAccessControl();
    AuthorizationRuleCollection rules = acl.GetAccessRules(true, true, typeof(NTAccount));

    WindowsIdentity currentUser = WindowsIdentity.GetCurrent();
    WindowsPrincipal principal = new WindowsPrincipal(currentUser);
    foreach (AuthorizationRule rule in rules)
        FileSystemAccessRule fsAccessRule = rule as FileSystemAccessRule;
        if (fsAccessRule == null)

        if ((fsAccessRule.FileSystemRights & FileSystemRights.WriteData) > 0)
            NTAccount ntAccount = rule.IdentityReference as NTAccount;
            if (ntAccount == null)

            if (principal.IsInRole(ntAccount.Value))
                Console.WriteLine("Current user is in role of {0}, has write access", ntAccount.Value);
            Console.WriteLine("Current user is not in role of {0}, does not have write access", ntAccount.Value);                        
catch (UnauthorizedAccessException)
    Console.WriteLine("does not have write access");

Convert timedelta to total seconds

Use timedelta.total_seconds().

>>> import datetime
>>> datetime.timedelta(seconds=24*60*60).total_seconds()

error LNK2005, already defined?

Presence of int k; in the header file causes symbol k to be defined within each translation unit this header is included to while linker expects it to be defined only once (aka One Definition Rule Violation).

While suggestion involving extern are not wrong, extern is a C-ism and should not be used.

Pre C++17 solution that would allow variable in header file to be defined in multiple translation units without causing ODR violation would be conversion to template:

template<typename x_Dummy = void> class
    public: static int s_k;

template<typename x_Dummy> int t_HeaderVariableHolder<x_Dummy>::s_k{};

// Getter is necessary to decouple variable storage implementation details from access to it.
inline int & Get_K() noexcept
    return t_HeaderVariableHolder<>::s_k;

With C++17 things become much simpler as it allows inline variables:

inline int g_k{};

// Getter is necessary to decouple variable storage implementation details from access to it.
inline int & Get_K() noexcept
    return g_k;

Jenkins: Can comments be added to a Jenkinsfile?

You can use block (/***/) or single line comment (//) for each line. You should use "#" in sh command.

Block comment

/*  _x000D_
post {_x000D_
    success {_x000D_
      mail to: "[email protected]", _x000D_
      subject:"SUCCESS: ${currentBuild.fullDisplayName}", _x000D_
      body: "Yay, we passed."_x000D_
    failure {_x000D_
      mail to: "[email protected]", _x000D_
      subject:"FAILURE: ${currentBuild.fullDisplayName}", _x000D_
      body: "Boo, we failed."_x000D_

Single Line

// post {_x000D_
//     success {_x000D_
//       mail to: "[email protected]", _x000D_
//       subject:"SUCCESS: ${currentBuild.fullDisplayName}", _x000D_
//       body: "Yay, we passed."_x000D_
//     }_x000D_
//     failure {_x000D_
//       mail to: "[email protected]", _x000D_
//       subject:"FAILURE: ${currentBuild.fullDisplayName}", _x000D_
//       body: "Boo, we failed."_x000D_
//     }_x000D_
// }

Comment in 'sh' command

        stage('Unit Test') {_x000D_
            steps {_x000D_
                  sh '''_x000D_
                  npm test_x000D_
                  # this is a comment in sh_x000D_

Log4Net configuring log level

you can use log4net.Filter.LevelMatchFilter. other options can be found at log4net tutorial - filters

in ur appender section add

<filter type="log4net.Filter.LevelMatchFilter">
    <levelToMatch value="Info" />
    <acceptOnMatch value="true" />

the accept on match default is true so u can leave it out but if u set it to false u can filter out log4net filters

How do getters and setters work?

You may also want to read "Why getter and setter methods are evil":

Though getter/setter methods are commonplace in Java, they are not particularly object oriented (OO). In fact, they can damage your code's maintainability. Moreover, the presence of numerous getter and setter methods is a red flag that the program isn't necessarily well designed from an OO perspective.

This article explains why you shouldn't use getters and setters (and when you can use them) and suggests a design methodology that will help you break out of the getter/setter mentality.

How to write to Console.Out during execution of an MSTest test

The Console output is not appearing is because the backend code is not running in the context of the test.

You're probably better off using Trace.WriteLine (In System.Diagnostics) and then adding a trace listener which writes to a file.

This topic from MSDN shows a way of doing this.

According to Marty Neal's and Dave Anderson's comments:

using System;
using System.Diagnostics;


Trace.Listeners.Add(new TextWriterTraceListener(Console.Out));
// or Trace.Listeners.Add(new ConsoleTraceListener());
Trace.WriteLine("Hello World");

How to set ANDROID_HOME path in ubuntu?

Had the same issue, in the terminal you can type:

export ANDROID_HOME=$HOME/Android/Sdk

or any other location depending on where you installed the sdk.

export PATH=$PATH:$ANDROID_HOME/platform-tools

Hope it helps!

Is a slash ("/") equivalent to an encoded slash ("%2F") in the path portion of an HTTP URL

What to do if :foo in its natural form contains slashes? You wouldn't want it to Isn't that the distinction the recommendation is attempting to preserve? It specifically notes,

The similarity to unix and other disk operating system filename conventions should be taken as purely coincidental, and should not be taken to indicate that URIs should be interpreted as file names.

If one was building an online interface to a backup program, and wished to express the path as a part of the URL path, it would make sense to encode the slashes in the file path, as that is not really part of the hierarchy of the resource - and more importantly, the route. /backups/2016-07-28content//home/dan/ loses the root of the filesystem in the double slash. Escaping the slashes is the appropriate way to distinguish, as I read it.

Comparing strings in Java

Using the == operator will compare the references to the strings not the string themselves.

Ok, you have to toString() the Editable. I loaded up some of the code I had before that dealt with this situation.

String passwd1Text = passw1.getText().toString();
String passwd2Text = passw2.getText().toString();

if (passwd1Text.equals(passwd2Text))

java.lang.IllegalAccessError: tried to access method

I was getting similar exception but at class level

e.g. Caused by: java.lang.IllegalAccessError: tried to access class ....

I fixed this by making my class public.

How to choose an AES encryption mode (CBC ECB CTR OCB CFB)?

A formal analysis has been done by Phil Rogaway in 2011, here. Section 1.6 gives a summary that I transcribe here, adding my own emphasis in bold (if you are impatient, then his recommendation is use CTR mode, but I suggest that you read my paragraphs about message integrity versus encryption below).

Note that most of these require the IV to be random, which means non-predictable and therefore should be generated with cryptographic security. However, some require only a "nonce", which does not demand that property but instead only requires that it is not re-used. Therefore designs that rely on a nonce are less error prone than designs that do not (and believe me, I have seen many cases where CBC is not implemented with proper IV selection). So you will see that I have added bold when Rogaway says something like "confidentiality is not achieved when the IV is a nonce", it means that if you choose your IV cryptographically secure (unpredictable), then no problem. But if you do not, then you are losing the good security properties. Never re-use an IV for any of these modes.

Also, it is important to understand the difference between message integrity and encryption. Encryption hides data, but an attacker might be able to modify the encrypted data, and the results can potentially be accepted by your software if you do not check message integrity. While the developer will say "but the modified data will come back as garbage after decryption", a good security engineer will find the probability that the garbage causes adverse behaviour in the software, and then he will turn that analysis into a real attack. I have seen many cases where encryption was used but message integrity was really needed more than the encryption. Understand what you need.

I should say that although GCM has both encryption and message integrity, it is a very fragile design: if you re-use an IV, you are screwed -- the attacker can recover your key. Other designs are less fragile, so I personally am afraid to recommend GCM based upon the amount of poor encryption code that I have seen in practice.

If you need both, message integrity and encryption, you can combine two algorithms: usually we see CBC with HMAC, but no reason to tie yourself to CBC. The important thing to know is encrypt first, then MAC the encrypted content, not the other way around. Also, the IV needs to be part of the MAC calculation.

I am not aware of IP issues.

Now to the good stuff from Professor Rogaway:

Block ciphers modes, encryption but not message integrity

ECB: A blockcipher, the mode enciphers messages that are a multiple of n bits by separately enciphering each n-bit piece. The security properties are weak, the method leaking equality of blocks across both block positions and time. Of considerable legacy value, and of value as a building block for other schemes, but the mode does not achieve any generally desirable security goal in its own right and must be used with considerable caution; ECB should not be regarded as a “general-purpose” confidentiality mode.

CBC: An IV-based encryption scheme, the mode is secure as a probabilistic encryption scheme, achieving indistinguishability from random bits, assuming a random IV. Confidentiality is not achieved if the IV is merely a nonce, nor if it is a nonce enciphered under the same key used by the scheme, as the standard incorrectly suggests to do. Ciphertexts are highly malleable. No chosen ciphertext attack (CCA) security. Confidentiality is forfeit in the presence of a correct-padding oracle for many padding methods. Encryption inefficient from being inherently serial. Widely used, the mode’s privacy-only security properties result in frequent misuse. Can be used as a building block for CBC-MAC algorithms. I can identify no important advantages over CTR mode.

CFB: An IV-based encryption scheme, the mode is secure as a probabilistic encryption scheme, achieving indistinguishability from random bits, assuming a random IV. Confidentiality is not achieved if the IV is predictable, nor if it is made by a nonce enciphered under the same key used by the scheme, as the standard incorrectly suggests to do. Ciphertexts are malleable. No CCA-security. Encryption inefficient from being inherently serial. Scheme depends on a parameter s, 1 = s = n, typically s = 1 or s = 8. Inefficient for needing one blockcipher call to process only s bits . The mode achieves an interesting “self-synchronization” property; insertion or deletion of any number of s-bit characters into the ciphertext only temporarily disrupts correct decryption.

OFB: An IV-based encryption scheme, the mode is secure as a probabilistic encryption scheme, achieving indistinguishability from random bits, assuming a random IV. Confidentiality is not achieved if the IV is a nonce, although a fixed sequence of IVs (eg, a counter) does work fine. Ciphertexts are highly malleable. No CCA security. Encryption and decryption inefficient from being inherently serial. Natively encrypts strings of any bit length (no padding needed). I can identify no important advantages over CTR mode.

CTR: An IV-based encryption scheme, the mode achieves indistinguishability from random bits assuming a nonce IV. As a secure nonce-based scheme, the mode can also be used as a probabilistic encryption scheme, with a random IV. Complete failure of privacy if a nonce gets reused on encryption or decryption. The parallelizability of the mode often makes it faster, in some settings much faster, than other confidentiality modes. An important building block for authenticated-encryption schemes. Overall, usually the best and most modern way to achieve privacy-only encryption.

XTS: An IV-based encryption scheme, the mode works by applying a tweakable blockcipher (secure as a strong-PRP) to each n-bit chunk. For messages with lengths not divisible by n, the last two blocks are treated specially. The only allowed use of the mode is for encrypting data on a block-structured storage device. The narrow width of the underlying PRP and the poor treatment of fractional final blocks are problems. More efficient but less desirable than a (wide-block) PRP-secure blockcipher would be.

MACs (message integrity but not encryption)

ALG1–6: A collection of MACs, all of them based on the CBC-MAC. Too many schemes. Some are provably secure as VIL PRFs, some as FIL PRFs, and some have no provable security. Some of the schemes admit damaging attacks. Some of the modes are dated. Key-separation is inadequately attended to for the modes that have it. Should not be adopted en masse, but selectively choosing the “best” schemes is possible. It would also be fine to adopt none of these modes, in favor of CMAC. Some of the ISO 9797-1 MACs are widely standardized and used, especially in banking. A revised version of the standard (ISO/IEC FDIS 9797-1:2010) will soon be released [93].

CMAC: A MAC based on the CBC-MAC, the mode is provably secure (up to the birthday bound) as a (VIL) PRF (assuming the underlying blockcipher is a good PRP). Essentially minimal overhead for a CBCMAC-based scheme. Inherently serial nature a problem in some application domains, and use with a 64-bit blockcipher would necessitate occasional re-keying. Cleaner than the ISO 9797-1 collection of MACs.

HMAC: A MAC based on a cryptographic hash function rather than a blockcipher (although most cryptographic hash functions are themselves based on blockciphers). Mechanism enjoys strong provable-security bounds, albeit not from preferred assumptions. Multiple closely-related variants in the literature complicate gaining an understanding of what is known. No damaging attacks have ever been suggested. Widely standardized and used.

GMAC: A nonce-based MAC that is a special case of GCM. Inherits many of the good and bad characteristics of GCM. But nonce-requirement is unnecessary for a MAC, and here it buys little benefit. Practical attacks if tags are truncated to = 64 bits and extent of decryption is not monitored and curtailed. Complete failure on nonce-reuse. Use is implicit anyway if GCM is adopted. Not recommended for separate standardization.

authenticated encryption (both encryption and message integrity)

CCM: A nonce-based AEAD scheme that combines CTR mode encryption and the raw CBC-MAC. Inherently serial, limiting speed in some contexts. Provably secure, with good bounds, assuming the underlying blockcipher is a good PRP. Ungainly construction that demonstrably does the job. Simpler to implement than GCM. Can be used as a nonce-based MAC. Widely standardized and used.

GCM: A nonce-based AEAD scheme that combines CTR mode encryption and a GF(2128)-based universal hash function. Good efficiency characteristics for some implementation environments. Good provably-secure results assuming minimal tag truncation. Attacks and poor provable-security bounds in the presence of substantial tag truncation. Can be used as a nonce-based MAC, which is then called GMAC. Questionable choice to allow nonces other than 96-bits. Recommend restricting nonces to 96-bits and tags to at least 96 bits. Widely standardized and used.

How to convert a file into a dictionary?

def get_pair(line):
    key, sep, value = line.strip().partition(" ")
    return int(key), value

with open("file.txt") as fd:    
    d = dict(get_pair(line) for line in fd)

Empty ArrayList equals null

If you want to check whether the array contains items with null values, use this:

private boolean isListOfNulls(ArrayList<String> stringList){
    for (String s: stringList)
        if( s != null) return false;
    return true;

You could replace <String> with the corresponding type for your ArrayList

The type List is not generic; it cannot be parameterized with arguments [HTTPClient]

I got the same error, but when i did as below, it resolved the issue.
Instead of writing like this:

List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1);

use the below one:

ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1);

Django CSRF check failing with an Ajax POST request

I have a solution. in my JS I have two functions. First to get Cookies (ie. csrftoken):

function getCookie(name) {
let cookieValue = null;
if (document.cookie && document.cookie !== '') {
    const cookies = document.cookie.split(';');
    for (let i = 0; i < cookies.length; i++) {
        const cookie = cookies[i].trim();
        // Does this cookie string begin with the name we want?
        if (cookie.substring(0, name.length + 1) === (name + '=')) {
            cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
return cookieValue;


Second one is my ajax function. in this case it's for login and in fact doesn't return any thing, just pass values to set a session:

function LoginAjax() {

    //get scrftoken:
    const csrftoken = getCookie('csrftoken');

    var req = new XMLHttpRequest();
    var userName = document.getElementById("Login-Username");
    var password = document.getElementById("Login-Password");

    req.onreadystatechange = function () {
        if (this.readyState == 4 && this.status == 200) {            
            //read response loggedIn JSON show me if user logged in or not
            var respond = JSON.parse(this.responseText);            

    }"POST", "login", true);

    //following header set scrftoken to resolve problem
    req.setRequestHeader('X-CSRFToken', csrftoken);

    req.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    req.send("UserName=" + userName.value + "&Password=" + password.value);

Where can I download JSTL jar

It's been split into two separate JAR files: jstl-api.jar and jstl-impl.jar.

What's the difference between ngOnInit and ngAfterViewInit of Angular2?

Content is what is passed as children. View is the template of the current component.

The view is initialized before the content and ngAfterViewInit() is therefore called before ngAfterContentInit().

** ngAfterViewInit() is called when the bindings of the children directives (or components) have been checked for the first time. Hence its perfect for accessing and manipulating DOM with Angular 2 components. As @Günter Zöchbauer mentioned before is correct @ViewChild() hence runs fine inside it.


    selector: 'widget-three',
    template: `<input #input1 type="text">`
export class WidgetThree{
    @ViewChild('input1') input1;

    constructor(private renderer:Renderer){}


Import an existing git project into GitLab?

Add the new gitlab remote to your existing repository and push:

git remote add gitlab url-to-gitlab-repo
git push gitlab master

ArrayList of String Arrays

You can't force the String arrays to have a specific size. You can do this:

private List<String[]> addresses = new ArrayList<String[]>();

but an array of any size can be added to this list.

However, as others have mentioned, the correct thing to do here is to create a separate class representing addresses. Then you would have something like:

private List<Address> addresses = new ArrayList<Address>();

How can I read and parse CSV files in C++?

You could also take a look at capabilities of Qt library.

It has regular expressions support and QString class has nice methods, e.g. split() returning QStringList, list of strings obtained by splitting the original string with a provided delimiter. Should suffice for csv file..

To get a column with a given header name I use following: c++ inheritance Qt problem qstring

How to install mongoDB on windows?

Its very simple to install Mongo DB on windows 7 ( i used 32 bit win7 OS)

  1. Install the correct version of Mongodb ( according to ur bit 32/64 .. imp :- 64 bit is not compatible with 32 bit and vice versa)

2.u can install Mongodb from thius website ( acc to ur OS)

  1. DOWNLOAD THE .MSI OR zip file .. and install with proper privellages

4.copy the mongodb folder from c:programfiles to d: [optional]

5.After installation open command prompt ( as administrator .. right click on cmd and u will find the option)

  1. navigate to D:\MongoDB 2.6 Standard\bin

  2. run mongo.exe ... you might get this error you might get this error

  3. If you get then no isse you just need to do following steps

i) try the coomand in following image yo will get to know the error enter image description here

ii)This means that u neeed to create a directory \data\db

iii) now you have two options either create above directory in c drive or create any "xyz" name directory somewhere else ( doesnot make and diffrence) .. lets create a directory of mongodata in d:

enter image description here

  1. Now lets rerun the command but now like this :- mongod --dbpath d:\mongodata [shown in fig] this time you will not get and error

enter image description here

  1. Hope everything is fine till this point .. open new command propmt [sufficent privellages (admin)]

colured in orange will be the command u need to run .. it will open the new command propmt which we known as mongo shell (or mongodb shell)

enter image description here

11.dont close the shell[any of command promt as well] as in this we will create /delete/insert our databse operations

  1. Lets perform basic operation

a) show databases b) show current databse c) creation of collection / inserting data into it (name will be test) d) show data of collection

12.please find scrren shot of results of our operation .. please not :- dont close any command propmt

enter image description here

  1. a diffrent structure type of number is object id :- which is created automatically

  2. Hope you get some important info for installing mongodb DB.

Python Prime number checker

The two main problems with your code are:

  1. After designating a number not prime, you continue to check the rest of the divisors even though you already know it is not prime, which can lead to it printing "prime" after printing "not prime". Hint: use the `break' statement.
  2. You designate a number prime before you have checked all the divisors you need to check, because you are printing "prime" inside the loop. So you get "prime" multiple times, once for each divisor that doesn't go evenly into the number being tested. Hint: use an else clause with the loop to print "prime" only if the loop exits without breaking.

A couple pretty significant inefficiencies:

  1. You should keep track of the numbers you have already found that are prime and only divide by those. Why divide by 4 when you have already divided by 2? If a number is divisible by 4 it is also divisible by 2, so you would have already caught it and there is no need to divide by 4.
  2. You need only to test up to the square root of the number being tested because any factor larger than that would need to be multiplied with a number smaller than that, and that would already have been tested by the time you get to the larger one.

Change File Extension Using C#

try this.

filename = Path.ChangeExtension(".blah") 

in you Case:

myfile= c:/my documents/my images/cars/a.jpg;
string extension = Path.GetExtension(myffile);
filename = Path.ChangeExtension(myfile,".blah") 

You should look this post too:

Send email by using codeigniter library via localhost

I had the same problem and I solved by using the postcast server. You can install it locally and use it.

Can I force pip to reinstall the current version?

If you want to reinstall packages specified in a requirements.txt file, without upgrading, so just reinstall the specific versions specified in the requirements.txt file:

pip install -r requirements.txt --ignore-installed

Python threading. How do I lock a thread?

You can see that your locks are pretty much working as you are using them, if you slow down the process and make them block a bit more. You had the right idea, where you surround critical pieces of code with the lock. Here is a small adjustment to your example to show you how each waits on the other to release the lock.

import threading
import time
import inspect

class Thread(threading.Thread):
    def __init__(self, t, *args):
        threading.Thread.__init__(self, target=t, args=args)

count = 0
lock = threading.Lock()

def incre():
    global count
    caller = inspect.getouterframes(inspect.currentframe())[1][3]
    print "Inside %s()" % caller
    print "Acquiring lock"
    with lock:
        print "Lock Acquired"
        count += 1  

def bye():
    while count < 5:

def hello_there():
    while count < 5:

def main():    
    hello = Thread(hello_there)
    goodbye = Thread(bye)

if __name__ == '__main__':

Sample output:

Inside hello_there()
Acquiring lock
Lock Acquired
Inside bye()
Acquiring lock
Lock Acquired

' << ' operator in verilog

1 << ADDR_WIDTH means 1 will be shifted 8 bits to the left and will be assigned as the value for RAM_DEPTH.

In addition, 1 << ADDR_WIDTH also means 2^ADDR_WIDTH.

Given ADDR_WIDTH = 8, then 2^8 = 256 and that will be the value for RAM_DEPTH

Change value in a cell based on value in another cell


How to create a pulse effect using -webkit-animation - outward rings

You have a lot of unnecessary keyframes. Don't think of keyframes as individual frames, think of them as "steps" in your animation and the computer fills in the frames between the keyframes.

Here is a solution that cleans up a lot of code and makes the animation start from the center:

.gps_ring {
    border: 3px solid #999;
    -webkit-border-radius: 30px;
    height: 18px;
    width: 18px;
    position: absolute;
    -webkit-animation: pulsate 1s ease-out;
    -webkit-animation-iteration-count: infinite; 
    opacity: 0.0
@-webkit-keyframes pulsate {
    0% {-webkit-transform: scale(0.1, 0.1); opacity: 0.0;}
    50% {opacity: 1.0;}
    100% {-webkit-transform: scale(1.2, 1.2); opacity: 0.0;}

You can see it in action here:

Coerce multiple columns to factors at once

and, for completeness and with regards to this question asking about changing string columns only, there's mutate_if:

data <- cbind(stringVar = sample(c("foo","bar"),10,replace=TRUE),
              data.frame(matrix(sample(1:40), 10, 10, dimnames = list(1:10, LETTERS[1:10]))),stringsAsFactors=FALSE)     

factoredData = data %>% mutate_if(is.character,funs(factor(.)))

Raw SQL Query without DbSet - Entity Framework Core

This solution leans heavily on the solution from @pius. I wanted to add the option to support query parameters to help mitigate SQL injection and I also wanted to make it an extension off of the DbContext DatabaseFacade for Entity Framework Core to make it a little more integrated.

First create a new class with the extension:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Metadata;
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Linq;
using System.Threading.Tasks;

namespace EF.Extend

    public static class ExecuteSqlExt
        /// <summary>
        /// Execute raw SQL query with query parameters
        /// </summary>
        /// <typeparam name="T">the return type</typeparam>
        /// <param name="db">the database context database, usually _context.Database</param>
        /// <param name="query">the query string</param>
        /// <param name="map">the map to map the result to the object of type T</param>
        /// <param name="queryParameters">the collection of query parameters, if any</param>
        /// <returns></returns>
        public static List<T> ExecuteSqlRawExt<T, P>(this DatabaseFacade db, string query, Func<DbDataReader, T> map, IEnumerable<P> queryParameters = null)
            using (var command = db.GetDbConnection().CreateCommand())
                if((queryParameters?.Any() ?? false))

                command.CommandText = query;
                command.CommandType = CommandType.Text;


                using (var result = command.ExecuteReader())
                    var entities = new List<T>();

                    while (result.Read())

                    return entities;


Note in the above that "T" is the type for the return and "P" is the type of your query parameters which will vary based on if you are using MySql, Sql, so on.

Next we will show an example. I'm using the MySql EF Core capability, so we'll see how we can use the generic extension above with this more specific MySql implementation:

//add your using statement for the extension at the top of your Controller
//with all your other using statements
using EF.Extend;

//then your your Controller looks something like this
namespace Car.Api.Controllers

    //Define a quick Car class for the custom return type
    //you would want to put this in it's own class file probably
    public class Car
        public string Make { get; set; }
        public string Model { get; set; }
        public string DisplayTitle { get; set; }

    public class CarController : ControllerBase
        private readonly ILogger<CarController> _logger;
        //this would be your Entity Framework Core context
        private readonly CarContext _context;

        public CarController(ILogger<CarController> logger, CarContext context)
            _logger = logger;
            _context = context;

        //... more stuff here ...

       /// <summary>
       /// Get car example
       /// </summary>
       public IEnumerable<Car> Get()
           //instantiate three query parameters to pass with the query
           //note the MySqlParameter type is because I'm using MySql
           MySqlParameter p1 = new MySqlParameter
               ParameterName = "id1",
               Value = "25"

           MySqlParameter p2 = new MySqlParameter
               ParameterName = "id2",
               Value = "26"

           MySqlParameter p3 = new MySqlParameter
               ParameterName = "id3",
               Value = "27"

           //add the 3 query parameters to an IEnumerable compatible list object
           List<MySqlParameter> queryParameters = new List<MySqlParameter>() { p1, p2, p3 };

           //note the extension is now easily accessed off the _context.Database object
           //also note for ExecuteSqlRawExt<Car, MySqlParameter>
           //Car is my return type "T"
           //MySqlParameter is the specific DbParameter type MySqlParameter type "P"
           List<Car> result = _context.Database.ExecuteSqlRawExt<Car, MySqlParameter>(
        "SELECT Car.Make, Car.Model, CONCAT_WS('', Car.Make, ' ', Car.Model) As DisplayTitle FROM Car WHERE Car.Id IN(@id1, @id2, @id3)",
        x => new Car { Make = (string)x[0], Model = (string)x[1], DisplayTitle = (string)x[2] }, 

           return result;

The query would return rows like:
"Ford", "Explorer", "Ford Explorer"
"Tesla", "Model X", "Tesla Model X"

The display title is not defined as a database column, so it wouldn't be part of the EF Car model by default. I like this approach as one of many possible solutions. The other answers on this page reference other ways to address this issue with the [NotMapped] decorator, which depending on your use case could be the more appropriate approach.

Note the code in this example is obviously more verbose than it needs to be, but I thought it made the example clearer.

How to get image size (height & width) using JavaScript?

With jQuery library-

Use .width() and .height().

More in jQuery width and jQuery heigth.

Example Code-

        alert("Width of image: " + $("#img_exmpl").width());_x000D_
        alert("Height of image: " + $("#img_exmpl").height());_x000D_
<script src=""></script>_x000D_
<img id="img_exmpl" src="">_x000D_
<button>Display dimensions of img</button>

org.springframework.beans.factory.BeanCreationException: Error creating bean with name

According to the stack trace, your issue is that your app cannot find org.apache.commons.dbcp.BasicDataSource, as per this line:

java.lang.ClassNotFoundException: org.apache.commons.dbcp.BasicDataSource

I see that you have commons-dbcp in your list of jars, but for whatever reason, your app is not finding the BasicDataSource class in it.

How to push object into an array using AngularJS

Please check this -


var app= angular.module('app', []);

app.controller('TestController', function($scope) {
    this.arrayText = [{text:'Hello',},{text: 'world'}];

    this.addText = function(text) {

      if(text) {
        var obj = {
          text: text
          this.myText = '';


<form ng-controller="TestController as testCtrl" ng-submit="testCtrl.addText(testCtrl.myText)">
        <input type="text" ng-model="testCtrl.myText" value="Lets go">
        <button type="submit">Add</button>
        <div ng-repeat="item in testCtrl.arrayText">

Android EditText view Floating Hint in Material Design

@andruboy's suggestion of is probably your best bet. kind of works with appcompat-v7 v21.0.0, but since v21.0.0 does not support accent colors with subclasses of EditText, the underline of the FloatingHintEditText will be the default solid black or white. Also the padding is not optimized for the Material style EditText, so you may need to adjust it.

Error CS2001: Source file '.cs' could not be found

In my case, I add file as Link from another project and then rename file in source project that cause problem in destination project. I delete linked file in destination and add again with new name.

Set HTML dropdown selected option using JSTL

Assuming that you have a collection ${roles} of the elements to put in the combo, and ${selected} the selected element, It would go like this:

<select name='role'>
    <option value="${selected}" selected>${selected}</option>
    <c:forEach items="${roles}" var="role">
        <c:if test="${role != selected}">
            <option value="${role}">${role}</option>

UPDATE (next question)

You are overwriting the attribute "productSubCategoryName". At the end of the for loop, the last productSubCategoryName.

Because of the limitations of the expression language, I think the best way to deal with this is to use a map:

Map<String,Boolean> map = new HashMap<String,Boolean>();
for(int i=0;i<userProductData.size();i++){
    String productSubCategoryName=userProductData.get(i).getProductSubCategory();
    map.put(productSubCategoryName, true);
request.setAttribute("productSubCategoryMap", map);

And then in the JSP:

<select multiple="multiple" name="prodSKUs">
    <c:forEach items="${productSubCategoryList}" var="productSubCategoryList">
        <option value="${productSubCategoryList}" ${not empty productSubCategoryMap[productSubCategoryList] ? 'selected' : ''}>${productSubCategoryList}</option>

Calculate difference between two datetimes in MySQL

USE TIMESTAMPDIFF MySQL function. For example, you can use:

SELECT TIMESTAMPDIFF(SECOND, '2012-06-06 13:13:55', '2012-06-06 15:20:18')

In your case, the third parameter of TIMSTAMPDIFF function would be the current login time (NOW()). Second parameter would be the last login time, which is already in the database.

console.log timestamps in Chrome?

Try this also:

this.log = console.log.bind( console, '[' + new Date().toUTCString() + ']' );

This function puts timestamp, filename and line number as same of built-in console.log.

Ant if else condition?

<project name="Build" basedir="." default="clean">
    <property name="" value ="Release"/>

    <target name="clean">
    <echo>Value Buld is now  ${PARAM_BUILD_TYPE} is set</echo>
        <condition property="build.type" value="${PARAM_BUILD_TYPE}" else="${}">
            <isset property="PARAM_BUILD_TYPE"/>

       <echo>Value Buld is now  ${PARAM_BUILD_TYPE} is set</echo>
       <echo>Value Buld is now  ${build.type} is set</echo>

In my Case DPARAM_BUILD_TYPE=Debug if it is supplied than, I need to build for for Debug otherwise i need to go for building Release build. I write like above condition it worked and i have tested as below it is working fine for me.

And property ${build.type} we can pass this to other target or macrodef for processing which i am doing in my other ant macrodef.

Buildfile: D:\build.xml
     [echo] Value Buld is now  Debug is set
     [echo] Value Buld is now  Debug is set
     [echo] Value Buld is now  Debug is set
Total time: 0 seconds
Buildfile: D:\build.xml
     [echo] Value Buld is now  ${PARAM_BUILD_TYPE} is set
     [echo] Value Buld is now  ${PARAM_BUILD_TYPE} is set
     [echo] Value Buld is now  Release is set
Total time: 0 seconds

It work for me to implement condition so posted hope it will helpful.

':app:lintVitalRelease' error when generating signed apk

Just find the error reason in here and fix it.


How to get the nvidia driver version from the command line?

Using nvidia-smi should tell you that:

bwood@mybox:~$ nvidia-smi 
Mon Oct 29 12:30:02 2012       
| NVIDIA-SMI 3.295.41   Driver Version: 295.41         |                       
| Nb.  Name                     | Bus Id        Disp.  | Volatile ECC SB / DB |
| Fan   Temp   Power Usage /Cap | Memory Usage         | GPU Util. Compute M. |
| 0.  GeForce GTX 580           | 0000:25:00.0  N/A    |       N/A        N/A |
|  54%   70 C  N/A   N/A /  N/A |  25%  383MB / 1535MB |  N/A      Default    |
| Compute processes:                                               GPU Memory |
|  GPU  PID     Process name                                       Usage      |
|  0.           Not Supported                                                 |

XmlSerializer giving FileNotFoundException at constructor

Function XmlSerializer.FromTypes does not throw the exception, but it leaks the memory. Thats why you need to cache such serializer for every type to avoid memory leaking for every instance created.

Create your own XmlSerializer factory and use it simply:

XmlSerializer serializer = XmlSerializerFactoryNoThrow.Create(typeof(MyType));

The factory looks likes:

public static class XmlSerializerFactoryNoThrow
    public static Dictionary<Type, XmlSerializer> _cache = new Dictionary<Type, XmlSerializer>();

    private static object SyncRootCache = new object();        

    /// <summary>
    /// //the constructor XmlSerializer.FromTypes does not throw exception, but it is said that it causes memory leaks
    /// That is why I use dictionary to cache the serializers my self.
    /// </summary>
    public static XmlSerializer Create(Type type)
        XmlSerializer serializer;

        lock (SyncRootCache)
            if (_cache.TryGetValue(type, out serializer))
                return serializer;

        lock (type) //multiple variable of type of one type is same instance
            //constructor XmlSerializer.FromTypes does not throw the first chance exception           
            serializer = XmlSerializer.FromTypes(new[] { type })[0];
            //serializer = XmlSerializerFactoryNoThrow.Create(type);

        lock (SyncRootCache)
            _cache[type] = serializer;
        return serializer;

More complicated version without possibility of memory leak (please someone review the code):

    public static XmlSerializer Create(Type type)
        XmlSerializer serializer;

        lock (SyncRootCache)
            if (_cache.TryGetValue(type, out serializer))
                return serializer;

        lock (type) //multiple variable of type of one type is same instance
            lock (SyncRootCache)
                if (_cache.TryGetValue(type, out serializer))
                    return serializer;
            serializer = XmlSerializer.FromTypes(new[] { type })[0];
            lock (SyncRootCache)
                _cache[type] = serializer;
        return serializer;

How to generate .NET 4.0 classes from xsd?

The command that worked in my case was:

xsd /c your.xsd 

Ignore files that have already been committed to a Git repository

i followed these steps

git rm -r --cached .
git add .
git reset HEAD

after that, git delete all files (*.swp in my case) that should be ignoring.

How to get the last five characters of a string using Substring() in C#?

// Get first three characters
string sub = input.Substring(0, 3);
Console.WriteLine("Substring: {0}", sub); // Output One. 

string sub = input.Substring(6, 5);
Console.WriteLine("Substring: {0}", sub); //You'll get output: Three

How to get the 'height' of the screen using jquery

$(window).height();   // returns height of browser viewport
$(document).height(); // returns height of HTML document

As documented here:

How do you determine the size of a file in C?

If you're fine with using the std c library:

#include <sys/stat.h>
off_t fsize(char *file) {
    struct stat filestat;
    if (stat(file, &filestat) == 0) {
        return filestat.st_size;
    return 0;

Are types like uint32, int32, uint64, int64 defined in any stdlib header?

If you are using C99 just include stdint.h. BTW, the 64bit types are there iff the processor supports them.

Concatenate two string literals

Your second example does not work because there is no operator + for two string literals. Note that a string literal is not of type string, but instead is of type const char *. Your second example will work if you revise it like this:

const string message = string("Hello") + ",world" + exclam;

Does Python have “private” variables in classes?

As mentioned earlier, you can indicate that a variable or method is private by prefixing it with an underscore. If you don't feel like this is enough, you can always use the property decorator. Here's an example:

class Foo:

    def __init__(self, bar):
        self._bar = bar

    def bar(self):
        """Getter for '_bar'."""
        return self._bar

This way, someone or something that references bar is actually referencing the return value of the bar function rather than the variable itself, and therefore it can be accessed but not changed. However, if someone really wanted to, they could simply use _bar and assign a new value to it. There is no surefire way to prevent someone from accessing variables and methods that you wish to hide, as has been said repeatedly. However, using property is the clearest message you can send that a variable is not to be edited. property can also be used for more complex getter/setter/deleter access paths, as explained here: get file names in directory?

You will need to use the IO.Directory.GetFiles function.

Dim files() As String = IO.Directory.GetFiles("c:\")

For Each file As String In files
  ' Do work, example
  Dim text As String = IO.File.ReadAllText(file)

JavaScript Form Submit - Confirm or Cancel Submission Dialog Box

OK, just change your code to something like this:

function submit() {
   return confirm('Do you really want to submit the form?');

<form onsubmit="return submit(this);">
   <input type="image" src="xxx" border="0" name="submit" onclick="show_alert();"
      alt="PayPal - The safer, easier way to pay online!" value="Submit">

Also this is the code in run, just I make it easier to see how it works, just run the code below to see the result:

function submitForm() {_x000D_
  return confirm('Do you really want to submit the form?');_x000D_
<form onsubmit="return submitForm(this);">_x000D_
  <input type="text" border="0" name="submit" />_x000D_
  <button value="submit">submit</button>_x000D_

++i or i++ in for loops ??

For integers, there is no difference between pre- and post-increment.

If i is an object of a non-trivial class, then ++i is generally preferred, because the object is modified and then evaluated, whereas i++ modifies after evaluation, so requires a copy to be made.

Is it possible to animate scrollTop with jQuery?

But if you really want to add some animation while scrolling, you can try my simple plugin (AnimateScroll) which currently supports more than 30 easing styles

Reference - What does this error mean in PHP?

Parse error: syntax error, unexpected '['

This error comes in two variatians:

Variation 1

$arr = [1, 2, 3];

This array initializer syntax was only introduced in PHP 5.4; it will raise a parser error on versions before that. If possible, upgrade your installation or use the old syntax:

$arr = array(1, 2, 3);

See also this example from the manual.

Variation 2

$suffix = explode(',', 'foo,bar')[1];

Array dereferencing function results was also introduced in PHP 5.4. If it's not possible to upgrade you need to use a (temporary) variable:

$parts = explode(',', 'foo,bar');
$suffix = $parts[1];

See also this example from the manual.

Is it possible to use JS to open an HTML select to show its option list?

This works on Google Chrome

dropDown = function (elementId) {
    var dropdown = document.getElementById(elementId);
    try {
    } catch(e) {

    return false;

showDropdown = function (element) {
    var event;
    event = document.createEvent('MouseEvents');
    event.initMouseEvent('mousedown', true, true, window);

Anaconda Installed but Cannot Launch Navigator

In my case; it was available in the anaconda folder in "All App" from main menu

When to use reinterpret_cast?

One case when reinterpret_cast is necessary is when interfacing with opaque data types. This occurs frequently in vendor APIs over which the programmer has no control. Here's a contrived example where a vendor provides an API for storing and retrieving arbitrary global data:

// vendor.hpp
typedef struct _Opaque * VendorGlobalUserData;
void VendorSetUserData(VendorGlobalUserData p);
VendorGlobalUserData VendorGetUserData();

To use this API, the programmer must cast their data to VendorGlobalUserData and back again. static_cast won't work, one must use reinterpret_cast:

// main.cpp
#include "vendor.hpp"
#include <iostream>
using namespace std;

struct MyUserData {
    MyUserData() : m(42) {}
    int m;

int main() {
    MyUserData u;

        // store global data
    VendorGlobalUserData d1;
//  d1 = &u;                                          // compile error
//  d1 = static_cast<VendorGlobalUserData>(&u);       // compile error
    d1 = reinterpret_cast<VendorGlobalUserData>(&u);  // ok

        // do other stuff...

        // retrieve global data
    VendorGlobalUserData d2 = VendorGetUserData();
    MyUserData * p = 0;
//  p = d2;                                           // compile error
//  p = static_cast<MyUserData *>(d2);                // compile error
    p = reinterpret_cast<MyUserData *>(d2);           // ok

    if (p) { cout << p->m << endl; }
    return 0;

Below is a contrived implementation of the sample API:

// vendor.cpp
static VendorGlobalUserData g = 0;
void VendorSetUserData(VendorGlobalUserData p) { g = p; }
VendorGlobalUserData VendorGetUserData() { return g; }

Plotting lines connecting points

I think you're going to need separate lines for each segment:

import numpy as np
import matplotlib.pyplot as plt

x, y = np.random.random(size=(2,10))

for i in range(0, len(x), 2):
    plt.plot(x[i:i+2], y[i:i+2], 'ro-')

(The numpy import is just to set up some random 2x10 sample data)

enter image description here

How to get the android Path string to a file on Assets folder?

Have a look at the from API samples that come with the SDK.

       try {
        InputStream is = getAssets().open("read_asset.txt");

        // We guarantee that the available method returns the total
        // size of the asset...  of course, this does mean that a single
        // asset can't be more than 2 gigs.
        int size = is.available();

        // Read the entire asset into a local byte buffer.
        byte[] buffer = new byte[size];;

        // Convert the buffer into a string.
        String text = new String(buffer);

        // Finally stick the string into the text view.
        TextView tv = (TextView)findViewById(;
    } catch (IOException e) {
        // Should never happen!
        throw new RuntimeException(e);

Replacing from match to end-of-line

This should do what you want:

sed 's/two.*/BLAH/'

$ echo "   one  two  three  five
>    four two  five five six
>    six  one  two seven four" | sed 's/two.*/BLAH/'
   one  BLAH
   four BLAH
   six  one  BLAH

The $ is unnecessary because the .* will finish at the end of the line anyways, and the g at the end is unnecessary because your first match will be the first two to the end of the line.

How do I set browser width and height in Selenium WebDriver?

Here is firefox profile default prefs from python selenium 2.31.0

and type "about:config" in firefox address bar to see all prefs

reference to the entries in about:config:

    "": "false",
    "app.update.enabled": "false",
    "": "false",
    "browser.EULA.override": "true",
    "browser.EULA.3.accepted": "true",
    "": "2",
    "": "2",
    "browser.offline": "false",
    "browser.safebrowsing.enabled": "false",
    "": "false",
    "extensions.blocklist.enabled": "false",
    "browser.sessionstore.resume_from_crash": "false",
    "": "false",
    "browser.tabs.warnOnClose": "false",
    "browser.tabs.warnOnOpen": "false",
    "": "0",
    "browser.safebrowsing.malware.enabled": "false",
    "startup.homepage_welcome_url": "\"about:blank\"",
    "devtools.errorconsole.enabled": "true",
    "dom.disable_open_during_load": "false",
    "extensions.autoDisableScopes" : 10,
    "extensions.logging.enabled": "true",
    "extensions.update.enabled": "false",
    "extensions.update.notifyUser": "false",
    "network.manage-offline-status": "false",
    "network.http.max-connections-per-server": "10",
    "network.http.phishy-userpass-length": "255",
    "offline-apps.allow_by_default": "true",
    "prompts.tab_modal.enabled": "false",
    "security.fileuri.origin_policy": "3",
    "security.fileuri.strict_origin_policy": "false",
    "security.warn_entering_secure": "false",
    "security.warn_entering_secure.show_once": "false",
    "security.warn_entering_weak": "false",
    "security.warn_entering_weak.show_once": "false",
    "security.warn_leaving_secure": "false",
    "security.warn_leaving_secure.show_once": "false",
    "security.warn_submit_insecure": "false",
    "security.warn_viewing_mixed": "false",
    "security.warn_viewing_mixed.show_once": "false",
    "signon.rememberSignons": "false",
    "toolkit.networkmanager.disable": "true",
    "toolkit.telemetry.enabled": "false",
    "toolkit.telemetry.prompted": "2",
    "toolkit.telemetry.rejected": "true",
    "javascript.options.showInConsole": "true",
    "browser.dom.window.dump.enabled": "true",
    "webdriver_accept_untrusted_certs": "true",
    "webdriver_enable_native_events": "true",
    "webdriver_assume_untrusted_issuer": "true",
    "dom.max_script_run_time": "30",

Auto detect mobile browser (via user-agent?)

I put this demo with scripts and examples included together:

This example utilizes php functions for user agent detection and offers the additional benefit of permitting users to state a preference for a version of the site which would not typically be the default based on their browser or device type. This is done with cookies (maintained using php on the server-side as opposed to javascript.)

Be sure to check out the download link in the article for the examples.

Hope you enjoy!

Return a `struct` from a function in C

There is no issue in passing back a struct. It will be passed by value

But, what if the struct contains any member which has a address of a local variable

struct emp {
    int id;
    char *name;

struct emp get() {
    char *name = "John";

    struct emp e1 = {100, name};

    return (e1);

int main() {

    struct emp e2 = get();


Now, here contains a memory address local to the function get(). Once get() returns, the local address for name would have been freed up. SO, in the caller if we try to access that address, it may cause segmentation fault, as we are trying a freed address. That is bad..

Where as the will be perfectly valid as its value will be copied to

So, we should always try to avoid returning local memory addresses of a function.

Anything malloced can be returned as and when wanted

NoClassDefFoundError on Maven dependency

Choosing to Project -> Clean should resolve this

How can you create multiple cursors in Visual Studio Code

Same issue on Ubuntu-MATE, but here you resolve it by:

gsettings set org.mate.Marco.general mouse-button-modifier "<Super>"

Stretch and scale CSS background

Scaling an image with CSS is not quite possible, but a similar effect can be achieved in the following manner, though.

Use this markup:

<div id="background">
    <img src="img.jpg" class="stretch" alt="" />

with the following CSS:

#background {
    width: 100%; 
    height: 100%; 
    position: absolute; 
    left: 0px; 
    top: 0px; 
    z-index: 0;

.stretch {

and you should be done!

In order to scale the image to be "full bleed" and maintain the aspect ratio, you can do this instead:

.stretch { min-width:100%; min-height:100%; width:auto; height:auto; }

It works out quite nicely! If one dimension is cropped, however, it will be cropped on only one side of the image, rather than being evenly cropped on both sides (and centered). I've tested it in Firefox, Webkit, and Internet Explorer 8.

SQL Server: What is the difference between CROSS JOIN and FULL OUTER JOIN?


  • The FULL OUTER JOIN returns all rows from the left table (table1) and from the right table (table2) irrespective of the match.

  • The FULL OUTER JOIN keyword combines the result of both LEFT OUTER JOIN and RIGHT OUTER JOIN

  • SQL full outer join is also known as FULL JOIN

Reference :


  • In SQL CROSS JOIN Each Row of first table is mapped with the each and every row of second table.

  • Number of rows produced by a result set of CROSS JOIN operation is equal to number of rows in the first table multiplied by the number of rows in the second table.

  • CROSS JOIN is also known as Cartesian product / Cartesian join

  • Number of rows in table A is m, Number of rows in table B is n and resultant table will have m*n rows


Add params to given URL in Python

There are a couple of quirks with the urllib and urlparse modules. Here's a working example:

    import urlparse
    from urllib import urlencode
except: # For Python 3
    import urllib.parse as urlparse
    from urllib.parse import urlencode

url = ""
params = {'lang':'en','tag':'python'}

url_parts = list(urlparse.urlparse(url))
query = dict(urlparse.parse_qsl(url_parts[4]))

url_parts[4] = urlencode(query)


ParseResult, the result of urlparse(), is read-only and we need to convert it to a list before we can attempt to modify its data.

Populate dropdown select with array using jQuery

The solution I used was to create a javascript function that uses jquery:

This will populate a dropdown object on the HTML page. Please let me know where this can be optimized - but works fine as is.

function util_PopulateDropDownListAndSelect(sourceListObject, sourceListTextFieldName, targetDropDownName, valueToSelect)
    var options = '';

    // Create the list of HTML Options
    for (i = 0; i < sourceListObject.List.length; i++)
        options += "<option value='" + sourceListObject.List[i][sourceListTextFieldName] + "'>" + sourceListObject.List[i][sourceListTextFieldName] + "</option>\r\n";

    // Assign the options to the HTML Select container
    $('select#' + targetDropDownName)[0].innerHTML = options;

    // Set the option to be Selected
    $('#' + targetDropDownName).val(valueToSelect);

    // Refresh the HTML Select so it displays the Selected option
    $('#' + targetDropDownName).selectmenu('refresh')

<script src=""></script>

How do I move to end of line in Vim?

Just the $ (dollar sign) key. You can use A to move to the end of the line and switch to editing mode (Append). To jump the last non-blank character, you can press g then _ keys.

The opposite of A is I (Insert mode at beginning of line), as an aside. Pressing just the ^ will place your cursor at the first non-white-space character of the line.

How to handle button clicks using the XML onClick within Fragments

I've recently solved this issue without having to add a method to the context Activity or having to implement OnClickListener. I'm not sure if it is a "valid" solution neither, but it works.

Based on:

It can be done with data bindings: Just add your fragment instance as a variable, then you can link any method with onClick.

<layout xmlns:android=""

        <variable android:name="fragment" android:type="com.example.testapp.fragments.CustomFragment"/>

            android:onClick="@{() -> fragment.buttonClicked()}"/>

And the fragment linking code would be...

public class CustomFragment extends Fragment {


    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_person_profile, container, false);
        FragmentCustomBinding binding = DataBindingUtil.bind(view);
        return view;



How do I use the new computeIfAbsent function?


This is really helpful if you want to create a multimap without resorting to the Google Guava library for its implementation of MultiMap.

For example, suppose you want to store a list of students who enrolled for a particular subject.

The normal solution for this using JDK library is:

Map<String,List<String>> studentListSubjectWise = new TreeMap<>();
List<String>lis = studentListSubjectWise.get("a");
if(lis == null) {
    lis = new ArrayList<>();


Since it have some boilerplate code, people tend to use Guava Mutltimap.

Using Map.computeIfAbsent, we can write in a single line without guava Multimap as follows.

studentListSubjectWise.computeIfAbsent("a", (x -> new ArrayList<>())).add("John");

Stuart Marks & Brian Goetz did a good talk about this

grep output to show only matching file

grep -l 

(That's a lowercase L)

Getting JSONObject from JSONArray

JSONArray objects have a function getJSONObject(int index), you can loop through all of the JSONObjects by writing a simple for-loop:

JSONArray array;
for(int n = 0; n < array.length(); n++)
    JSONObject object = array.getJSONObject(n);
    // do some stuff....

List columns with indexes in PostgreSQL

When playing around with indexes the order of which columns are constructed in the index is as important as the columns themselves.

The following query lists all indexes for a given table and all their columns in a sorted fashion.

  string_agg(column_name, ',')
         t.relname AS table_name,
         i.relname AS index_name,
         a.attname AS column_name,
         (SELECT i
          FROM (SELECT
                  OVER () i
                FROM unnest(indkey) WITH ORDINALITY AS a(v)) a
          WHERE v = attnum)
         pg_class t,
         pg_class i,
         pg_index ix,
         pg_attribute a
         t.oid = ix.indrelid
         AND i.oid = ix.indexrelid
         AND a.attrelid = t.oid
         AND a.attnum = ANY (ix.indkey)
         AND t.relkind = 'r'
         AND t.relname LIKE 'tablename'
       ORDER BY table_name, index_name, i
     ) raw
GROUP BY table_name, index_name

macOS on VMware doesn't recognize iOS device

If you went throught alot of pain installing macos on vmware I recommend this tutorial which also provides you with all the file you need. it's straight forward tutorial and works all the way without any problem.

Web API Put Request generates an Http 405 Method Not Allowed error

This simple problem can cause a real headache!

I can see your controller EDIT (PUT) method expects 2 parameters: a) an int id, and b) a department object.

It is the default code when you generate this from VS > add controller with read/write options. However, you have to remember to consume this service using the two parameters, otherwise you will get the error 405.

In my case, I did not need the id parameter for PUT, so I just dropped it from the header... after a few hours of not noticing it there! If you keep it there, then the name must also be retained as id, unless you go on to make necessary changes to your configurations.

How do you copy the contents of an array to a std::vector in C++ without looping?

int dataArray[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };//source

unsigned dataArraySize = sizeof(dataArray) / sizeof(int);

std::vector<int> myvector (dataArraySize );//target

std::copy ( myints, myints+dataArraySize , myvector.begin() );

//myvector now has 1,2,3,...10 :-)

Regular cast vs. static_cast vs. dynamic_cast

FYI, I believe Bjarne Stroustrup is quoted as saying that C-style casts are to be avoided and that you should use static_cast or dynamic_cast if at all possible.

Barne Stroustrup's C++ style FAQ

Take that advice for what you will. I'm far from being a C++ guru.