Programs & Examples On #Xargs

xargs is a command on Unix and most Unix-like operating systems used to build and execute command lines from standard input.

Make xargs handle filenames that contain spaces

On macOS 10.12.x (Sierra), if you have spaces in file names or subdirectories, you can use the following:

find . -name '*.swift' -exec echo '"{}"' \; |xargs wc -l

How can I use xargs to copy files that have spaces and quotes in their names?

The easiest way to do what the original poster wants is to change the delimiter from any whitespace to just the end-of-line character like this:

find whatever ... | xargs -d "\n" cp -t /var/tmp

Make xargs execute the command once for each line of input

The following will only work if you do not have spaces in your input:

xargs -L 1
xargs --max-lines=1 # synonym for the -L option

from the man page:

-L max-lines
          Use at most max-lines nonblank input lines per command line.
          Trailing blanks cause an input line to be logically continued  on
          the next input line.  Implies -x.

Using grep to search for hex strings in a file

This seems to work for me:

LANG=C grep --only-matching --byte-offset --binary --text --perl-regexp "<\x-hex pattern>" <file>

short form:

LANG=C grep -obUaP "<\x-hex pattern>" <file>


LANG=C grep -obUaP "\x01\x02" /bin/grep

Output (cygwin binary):

153: <\x01\x02>
33210: <\x01\x02>
53453: <\x01\x02>

So you can grep this again to extract offsets. But don't forget to use binary mode again.

Note: LANG=C is needed to avoid utf8 encoding issues.

Running multiple commands with xargs

Try this:

git config --global alias.all '!f() { find . -d -name ".git" | sed s/\\/\.git//g | xargs -P10 -I{} git --git-dir={}/.git --work-tree={} $1; }; f'

It runs ten threads in parallel and does what ever git command you want to all repos in the folder structure. No matter if the repo is one or n levels deep.

E.g: git all pull

How to enable ASP classic in IIS7.5

I found some detailed instructions here:

The key piece of advice seems to be, don't use the 64-bit ASP.DLL (found in system32) if you've configured the app pool to run 32-bit applications (instead, use the 32-bit ASP.DLL).

Add a script map using the following setting:

Request Path: *.asp
Executable: C:\Windows\system32\inetsrv\asp.dll
Name: whatever you want. I named my Classic ASP

The executable above is 64 BIT ASP handler for your asp script. If you want your ASP script to be handled in 32 bit environment, you need to use executable from this location: C:\Windows\SysWOW64\inetsrv\asp.dll.

Of course, if you don't need to load any 32-bit libraries (or data providers, etc.), just make your life easier by running the 64-bit ASP.DLL!

SQL Server: How to use UNION with two queries that BOTH have a WHERE clause?

select * from 
    select top 2 t1.ID, t1.ReceivedDate
    from Table t1
    where t1.Type = 'TYPE_1'
    order by t1.ReceivedDate de
) t1
select * from 
    select top 2 t2.ID
    from Table t2
    where t2.Type = 'TYPE_2'
    order by t2.ReceivedDate desc
) t2

or using CTE (SQL Server 2005+)

;with One as
    select top 2 t1.ID, t1.ReceivedDate
    from Table t1
    where t1.Type = 'TYPE_1'
    order by t1.ReceivedDate de
,Two as
    select top 2 t2.ID
    from Table t2
    where t2.Type = 'TYPE_2'
    order by t2.ReceivedDate desc
select * from One
select * from Two

You don't have write permissions for the /var/lib/gems/2.3.0 directory

If you want to use the distribution Ruby instead of rb-env/rvm, you can set up a GEM_HOME for your current user. Start by creating a directory to store the Ruby gems for your user:

$ mkdir ~/.ruby

Then update your shell to use that directory for GEM_HOME and to update your PATH variable to include the Ruby gem bin directory.

$ echo 'export GEM_HOME=~/.ruby/' >> ~/.bashrc
$ echo 'export PATH="$PATH:~/.ruby/bin"' >> ~/.bashrc
$ source ~/.bashrc

(That last line will reload the environment variables in your current shell.)

Now you should be able to install Ruby gems under your user using the gem command. I was able to get this working with Ruby 2.5.1 under Ubuntu 18.04. If you are using a shell that is not Bash, then you will need to edit the startup script for that shell instead of bashrc.

Difference between Groovy Binary and Source release?

Binary releases contain computer readable version of the application, meaning it is compiled. Source releases contain human readable version of the application, meaning it has to be compiled before it can be used.

Show how many characters remaining in a HTML text box using JavaScript


  <textarea id='text' maxlength='10'></textarea>
  <div id='msg'>10 characters left</div>
  <div id='lastChar'></div>


function charCount() {
  var textEntered = document.getElementById('text').value;
  var msg = document.getElementById('msg');
  var counter = (10-(textEntered.length));
  msg.textContent = counter+' characters left';

var el = document.getElementById('text');

Is there a download function in jsFiddle?

You have to put /show a after the URL you're working on:

For example:


for Field URL :


after that save the file and go to the show folder(or the file name you have saved with) under that folder u will get a html file show_resource.HTML .that is your actual open it in browser and view the source code. Best of luck--------Ujjwal Gupta

html table span entire width?

Try (in your <head> section, or existing css definitions)...

  body {

How to transfer some data to another Fragment?

From Activity Class:

Send the data using bundle arguments to the fragment and load the fragment

   Fragment fragment = new myFragment();
   Bundle bundle = new Bundle();
   bundle.putString("pName", personName);
   bundle.putString("pEmail", personEmail);
   bundle.putString("pId", personId);


From myFragment Class:

Get the arguments from the bundle and set them to xml

    Bundle arguments = getArguments();
    String personName = arguments.getString("pName");
    String personEmail = arguments.getString("pEmail");
    String personId = arguments.getString("pId");

    nameTV = v.findViewById(;
    emailTV = v.findViewById(;
    idTV = v.findViewById(;

    nameTV.setText("Name: "+ personName);
    emailTV.setText("Email: "+ personEmail);
    idTV.setText("ID: "+ personId);

How to change facet labels?

The labeller function defintion with variable, value as arguments would not work for me. Also if you want to use expression you need to use lapply and can not simply use arr[val], as the argument to the function is a data.frame.

This code did work:

arr <- list('virginica'=TeX("x_1"), "versicolor"=TeX("x_2"), "setosa"=TeX("x_3"))
mylabel <- function(val) { return(lapply(val, function(x) arr[x])) }
ggplot(iris, aes(x=Sepal.Length, y=Sepal.Width)) + geom_line() + facet_wrap(~Species, labeller=mylabel)

Python - OpenCV - imread - Displaying Image

Looks like the image is too big and the window simply doesn't fit the screen. Create window with the cv2.WINDOW_NORMAL flag, it will make it scalable. Then you can resize it to fit your screen like this:

from __future__ import division
import cv2

img = cv2.imread('1.jpg')

screen_res = 1280, 720
scale_width = screen_res[0] / img.shape[1]
scale_height = screen_res[1] / img.shape[0]
scale = min(scale_width, scale_height)
window_width = int(img.shape[1] * scale)
window_height = int(img.shape[0] * scale)

cv2.namedWindow('dst_rt', cv2.WINDOW_NORMAL)
cv2.resizeWindow('dst_rt', window_width, window_height)

cv2.imshow('dst_rt', img)

According to the OpenCV documentation CV_WINDOW_KEEPRATIO flag should do the same, yet it doesn't and it's value not even presented in the python module.

How to include quotes in a string

As well as escaping quotes with backslashes, also see SO question 2911073 which explains how you could alternatively use double-quoting in a @-prefixed string:

string msg = @"I want to learn ""c#""";

Border around each cell in a range

You only need a single line of code to set the border around every cell in the range:

Range("A1:F20").Borders.LineStyle = xlContinuous

It's also easy to apply multiple effects to the border around each cell.

For example:

Sub RedOutlineCells()
    Dim rng As Range

    Set rng = Range("A1:F20")

    With rng.Borders
        .LineStyle = xlContinuous
        .Color = vbRed
        .Weight = xlThin
    End With
End Sub

How to pass datetime from c# to sql correctly?

You've already done it correctly by using a DateTime parameter with the value from the DateTime, so it should already work. Forget about ToString() - since that isn't used here.

If there is a difference, it is most likely to do with different precision between the two environments; maybe choose a rounding (seconds, maybe?) and use that. Also keep in mind UTC/local/unknown (the DB has no concept of the "kind" of date; .NET does).

I have a table and the date-times in it are in the format: 2011-07-01 15:17:33.357

Note that datetimes in the database aren't in any such format; that is just your query-client showing you white lies. It is stored as a number (and even that is an implementation detail), because humans have this odd tendency not to realise that the date you've shown is the same as 40723.6371916281. Stupid humans. By treating it simply as a "datetime" throughout, you shouldn't get any problems.

Using If/Else on a data frame

Use ifelse:

frame$twohouses <- ifelse(frame$data>=2, 2, 1)
   data twohouses
1     0         1
2     1         1
3     2         2
4     3         2
5     4         2
16    0         1
17    2         2
18    1         1
19    2         2
20    0         1
21    4         2

The difference between if and ifelse:

  • if is a control flow statement, taking a single logical value as an argument
  • ifelse is a vectorised function, taking vectors as all its arguments.

The help page for if, accessible via ?"if" will also point you to ?ifelse

what is the differences between sql server authentication and windows authentication..?

SQL Server Authentication Modes

SQL Server 2008 offers two authentication mode options:

Windows authentication mode requires users to provide a valid Windows username and password to access the database server. In enterprise environments, these credentials are normally Active Directory domain credentials.

Mixed authentication mode allows the use of Windows credentials but supplements them with local SQL Server user accounts that the administrator may create and maintain within SQL Server.

Copy entire directory contents to another directory?

Neither FileUtils.copyDirectory() nor Archimedes's answer copy directory attributes (file owner, permissions, modification times, etc). provides a complete JDK7 solution that does precisely that.

Remove element of a regular array

Here's how I did it...

    public static ElementDefinitionImpl[] RemoveElementDefAt(
        ElementDefinition[] oldList,
        int removeIndex
        ElementDefinitionImpl[] newElementDefList = new ElementDefinitionImpl[ oldList.Length - 1 ];

        int offset = 0;
        for ( int index = 0; index < oldList.Length; index++ )
            ElementDefinitionImpl elementDef = oldList[ index ] as ElementDefinitionImpl;
            if ( index == removeIndex )
                //  This is the one we want to remove, so we won't copy it.  But 
                //  every subsequent elementDef will by shifted down by one.
                offset = -1;
                newElementDefList[ index + offset ] = elementDef;
        return newElementDefList;

Regular expression for not allowing spaces in the input field

This will help to find the spaces in the beginning, middle and ending:

var regexp = /\s/g

Fade In Fade Out Android Animation in Java

viewToAnimate.animate().alpha(1).setDuration(1000).setInterpolator(new DecelerateInterpolator()).withEndAction(new Runnable() {
    public void run() {
        viewToAnimate.animate().alpha(0).setDuration(1000).setInterpolator(new AccelerateInterpolator()).start();

What does "Object reference not set to an instance of an object" mean?

Most of the time, when you try to assing value into object, and if the value is null, then this kind of exception occur. Please check this link.

for the sake of self learning, you can put some check condition. like

if (myObj== null)
Console.Write("myObj is NULL");

How can I make a CSS glass/blur effect work for an overlay?

If you're looking for a reliable cross-browser approach today, you won't find a great one. The best option you have is to create two images (this could be automated in some environments), and arrange them such that one overlays the other. I've created a simple example below:

<figure class="js">
    <img src="" />
    <img src="" class="blur" />
figure.js {
    position: relative;
    width: 250px; height: 250px;

figure.js .blur {
    top: 0; left: 0;
    position: absolute;
    clip: rect( 0, 250px, 125px, 0 );

Though effective, even this approach isn't necessarily ideal. That being said, it does yield the desired result.

enter image description here

Non-Static method cannot be referenced from a static context with methods and variables

You should place Scanner input = new Scanner (; into the main method rather than creating the input object outside.

How to convert a GUID to a string in C#?

In Visual Basic, you can call a parameterless method without the braces (()). In C#, they're mandatory. So you should write:

String guid = System.Guid.NewGuid().ToString();

Without the braces, you're assigning the method itself (instead of its result) to the variable guid, and obviously the method cannot be converted to a String, hence the error.

HTML image not showing in Gmail

Late to the party but here goes... I have experienced this problem as well and it was solved with the following:

  • Including the scheme in the src url (using "//" does not work - use full scheme EG: "https://")
  • Including width and height attributes
  • Including style="display:block" attribute
  • Including both alt and title attributes


<img src="" alt="Logo" title="Logo" style="display:block" width="200" height="87" />

Where can I find a list of keyboard keycodes?

I know this was asked awhile back, but I found a comprehensive list of the virtual keyboard key codes right in MSDN, for use in C/C++. This also includes the mouse events. Note it is different than the javascript key codes (I noticed it around the VK_OEM section).

Here's the link:

Hide Signs that Meteor.js was Used

The amount of hacks you would need to go through to completely hide the fact your site is built by Meteor.js is absolutely ridiculous. You would have to strip essentially all core functionality and just serve straight up html, completely defeating the purpose of using the framework anyway.

That being said, I suggest looking at

You enter a url, and it reveals a ton of information about a site. If you only need to "fool" engines like this, there may be simple solutions.

How to make input type= file Should accept only pdf and xls

You can try following way

<input type= "file" name="Upload" accept = "application/pdf,.csv, application/vnd.openxmlformats-officedocument.spreadsheetml.sheet, application/">

OR (in mvc)

@Html.TextBoxFor(x => x.FileName, new { @id = "doc", @type = "file", @accept = "application/pdf,.csv, application/vnd.openxmlformats-officedocument.spreadsheetml.sheet, application/" })

Android WebView, how to handle redirects in app instead of opening a browser

Create a class that implements webviewclient and add the following code that allows ovveriding the url string as shown below. You can see these [example][1]

public class myWebClient extends WebViewClient {

    public boolean shouldOverrideUrlLoading(WebView view, String url) {
         return true;

On your constructor, create a webview object as shown below.

   web = new WebView(this); web.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.FILL_PARENT)); 

Then add the following code to perform loading of urls inside your app

       WebSettings settings=web.getSettings(); 
    web.setWebViewClient(new myWebClient()); 
 web.setWebChromeClient(new WebChromeClient() {

Make text wrap in a cell with FPDF?

Text Wrap:

The MultiCell is used for print text with multiple lines. It has the same atributes of Cell except for ln and link.

$pdf->MultiCell( 200, 40, $reportSubtitle, 1);

Line Height:

What multiCell does is to spread the given text into multiple cells, this means that the second parameter defines the height of each line (individual cell) and not the height of all cells (collectively).

MultiCell(float w, float h, string txt [, mixed border [, string align [, boolean fill]]])

You can read the full documentation here.

tsconfig.json: Build:No inputs were found in config file

Changing index.js to index.ts fixed this error for me. (I did not have any .ts files before this).

Note: remember to change anywhere you reference index.js to index.ts except of course, where you reference your main file. By convention this is probably in your lib or dist folders. My tsconfig.json:

  "compilerOptions": {
    "target": "es2016",
    "module": "commonjs",
    "outDir": "./dist",
    "strict": true,
    "esModuleInterop": true,
    "inlineSourceMap": true,
    "noImplicitAny": false

My outDir is ./dist so I reference my main in my package.json as "main": "dist/index.js"

enter image description here

How to install JSTL? The absolute uri: cannot be resolved

This workedfor me


Python code to remove HTML tags from a string

global temp

temp =''

s = ' '

def remove_strings(text):

    global temp 

    if text == '':

        return temp

    start = text.find('<')

    end = text.find('>')

    if start == -1 and end == -1 :

        temp = temp + text

    return temp

newstring = text[end+1:]

fresh_start = newstring.find('<')

if newstring[:fresh_start] != '':

    temp += s+newstring[:fresh_start]


return temp

PowerShell - Start-Process and Cmdline Switches

Unless the OP is using PowerShell Community Extensions which does provide a Start-Process cmdlet along with a bunch of others. If this the case then Glennular's solution works a treat since it matches the positional parameters of pscx\start-process : -path (position 1) -arguments (positon 2).

How do I declare a namespace in JavaScript?

I've written another namespacing library that works a bit more like packages / units do in other languages. It allows you to create a package of JavaScript code and the reference that package from other code:

File hello.js

Package("hello", [], function() {
  function greeting() {
    alert("Hello World!");
  // Expose function greeting to other packages
  Export("greeting", greeting);

File Example.js

Package("example", ["hello"], function(greeting) {
  // Greeting is available here
  greeting();  // Alerts: "Hello World!"

Only the second file needs to be included in the page. Its dependencies (file hello.js in this example) will automatically be loaded and the objects exported from those dependencies will be used to populate the arguments of the callback function.

You can find the related project in Packages JS.

Android: show soft keyboard automatically when focus is on an EditText

I created nice kotlin-esqe extension functions incase anyone is interested

fun Activity.hideKeyBoard() {
    val view = this.currentFocus
    val methodManager = this.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
    assert(view != null)
    methodManager.hideSoftInputFromWindow(view!!.windowToken, InputMethodManager.HIDE_NOT_ALWAYS)

fun Activity.showKeyboard() {
    val view = this.currentFocus
    val methodManager = this.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
    assert(view != null)
    methodManager.showSoftInput(view, InputMethodManager.SHOW_IMPLICIT)

How to delete an array element based on key?

this looks like PHP to me. I'll delete if it's some other language.

Simply unset($arr[1]);

How to show a dialog to confirm that the user wishes to exit an Android Activity?

public void onBackPressed() {
    new AlertDialog.Builder(this)
           .setMessage("Are you sure you want to exit?")
           .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
               public void onClick(DialogInterface dialog, int id) {
           .setNegativeButton("No", null)

What is the syntax for Typescript arrow functions with generics?

The language specification says on p.64f

A construct of the form < T > ( ... ) => { ... } could be parsed as an arrow function expression with a type parameter or a type assertion applied to an arrow function with no type parameter. It is resolved as the former[..]


// helper function needed because Backbone-couchdb's sync does not return a jqxhr
let fetched = <
           R extends Backbone.Collection<any> >(c:R) => {
               return new Promise(function (fulfill, reject) {
                   c.fetch({reset: true, success: fulfill, error: reject})

What is the difference between "Class.forName()" and "Class.forName().newInstance()"?

just adding to above answers, when we have a static code (ie code block is instance independent) that needs to be present in memory, we can have the class returned so we'll use Class.forname("someName") else if we dont have static code we can go for Class.forname().newInstance("someName") as it will load object level code blocks(non static) to memory

Convert a String to a byte array and then back to the original String

Use [String.getBytes()][1] to convert to bytes and use [String(byte[] data)][2] constructor to convert back to string.

How to find a min/max with Ruby

You can use




It's a method for Arrays.

String escape into XML

Following functions will do the work. Didn't test against XmlDocument, but I guess this is much faster.

public static string XmlEncode(string value)
    System.Xml.XmlWriterSettings settings = new System.Xml.XmlWriterSettings 
        ConformanceLevel = System.Xml.ConformanceLevel.Fragment

    StringBuilder builder = new StringBuilder();

    using (var writer = System.Xml.XmlWriter.Create(builder, settings))

    return builder.ToString();

public static string XmlDecode(string xmlEncodedValue)
    System.Xml.XmlReaderSettings settings = new System.Xml.XmlReaderSettings
        ConformanceLevel = System.Xml.ConformanceLevel.Fragment

    using (var stringReader = new System.IO.StringReader(xmlEncodedValue))
        using (var xmlReader = System.Xml.XmlReader.Create(stringReader, settings))
            return xmlReader.Value;

Merge two HTML table cells

Set the colspan attribute to 2.

...but please don't use tables for layout.

I/O error(socket error): [Errno 111] Connection refused

Use a packet sniffer like Wireshark to look at what happens. You need to see a SYN-flagged packet outgoing, a SYN+ACK-flagged incoming and then a ACK-flagged outgoing. After that, the port is considered open on the local side.

If you only see the first packet and the error message comes after several seconds of waiting, the other side is not answering at all (like in: unplugged cable, overloaded server, misguided packet was discarded) and your local network stack aborts the connection attempt. If you see RST packets, the host actually denies the connection. If you see "ICMP Port unreachable" or host unreachable packets, a firewall or the target host inform you of the port actually being closed.

Of course you cannot expect the service to be available at all times (consider all the points of failure in between you and the data), so you should try again later.

Git merge master into feature branch

I am on the feature branch and made refactorings. I want to merge the master changes now to my feature branch. I am far behind. Note I do not want to pull the master changes to my local because my feature branch have modules moved from one place to another. I found just performing below without pull does not work. it says "Already up to date."

 //below does not get the latest from remote master to my local feature branch without git pull
    git checkout master 
    git fetch 
    git checkout my-feature-branch 
    git merge master

This below works, note use git merge origin/master:

 git checkout master 
    git fetch 
    git checkout my-feature-branch 
    git merge origin/master

Create a menu Bar in WPF?

Yes, a menu gives you the bar but it doesn't give you any items to put in the bar. You need something like (from one of my own projects):

<!-- Menu. -->
<Menu Width="Auto" Height="20" Background="#FFA9D1F4" DockPanel.Dock="Top">
    <MenuItem Header="_Emulator">
    <MenuItem Header="Load..." Click="MenuItem_Click" />
    <MenuItem Header="Load again" Click="menuEmulLoadLast" />
    <Separator />
    <MenuItem Click="MenuItem_Click">
                <TextBlock Width="10"></TextBlock>
                <TextBlock HorizontalAlignment="Right">F2</TextBlock>

How to get the result of OnPostExecute() to main activity because AsyncTask is a separate class?

Hope you been through this , if not please read.

Depending on the nature of result data, you should choose best possible option you can think of.

It is a great choice to use an Interface

some other options would be..

  • If the AsyncTask class is defined inside the very class you want to use the result in.Use a static global variable or get() , use it from outer class (volatile variable if necessary). but should be aware of the AsyncTask progress or should at least make sure that it have finished the task and result is available through global variable / get() method. you may use polling, onProgressUpdate(Progress...), synchronization or interfaces (Which ever suits best for you)

  • If the Result is compatible to be a sharedPreference entry or it is okay to be saved as a file in the memory you could save it even from the background task itself and could use the onPostExecute() method
    to get notified when the result is available in the memory.

  • If the string is small enough, and is to be used with start of an activity. it is possible to use intents (putExtra()) within onPostExecute() , but remember that static contexts aren't that safe to deal with.

  • If possible, you can call a static method from the onPostExecute() method, with the result being your parameter

What is a unix command for deleting the first N characters of a line?

You can use cut:

cut -c N- file.txt > new_file.txt

-c: characters

file.txt: input file

new_file.txt: output file

N-: Characters from N to end to be cut and output to the new file.

Can also have other args like: 'N' , 'N-M', '-M' meaning nth character, nth to mth character, first to mth character respectively.

This will perform the operation to each line of the input file.

Remove table row after clicking table row delete button

As @gaurang171 mentioned, we can use .closest() which will return the first ancestor, or the closest to our delete button, and use .remove() to remove it.

This is how we can implement it using jQuery click event instead of using JavaScript onclick.


<table id="myTable">
  <th width="30%" style="color:red;">ID</th>
  <th width="25%" style="color:red;">Name</th>
  <th width="25%" style="color:red;">Age</th>
  <th width="1%"></th>

  <td width="30%" style="color:red;">SSS-001</td>
  <td width="25%" style="color:red;">Ben</td>
  <td width="25%" style="color:red;">25</td>
  <td><button type='button' class='btnDelete'>x</button></td>

  <td width="30%" style="color:red;">SSS-002</td>
  <td width="25%" style="color:red;">Anderson</td>
  <td width="25%" style="color:red;">47</td>
  <td><button type='button' class='btnDelete'>x</button></td>

  <td width="30%" style="color:red;">SSS-003</td>
  <td width="25%" style="color:red;">Rocky</td>
  <td width="25%" style="color:red;">32</td>
  <td><button type='button' class='btnDelete'>x</button></td>

  <td width="30%" style="color:red;">SSS-004</td>
  <td width="25%" style="color:red;">Lee</td>
  <td width="25%" style="color:red;">15</td>
  <td><button type='button' class='btnDelete'>x</button></td>



Try in JSFiddle: click here.

Given an RGB value, how do I create a tint (or shade)?

Some definitions

  • A shade is produced by "darkening" a hue or "adding black"
  • A tint is produced by "ligthening" a hue or "adding white"

Creating a tint or a shade

Depending on your Color Model, there are different methods to create a darker (shaded) or lighter (tinted) color:

  • RGB:

    • To shade:

      newR = currentR * (1 - shade_factor)
      newG = currentG * (1 - shade_factor)
      newB = currentB * (1 - shade_factor)
    • To tint:

      newR = currentR + (255 - currentR) * tint_factor
      newG = currentG + (255 - currentG) * tint_factor
      newB = currentB + (255 - currentB) * tint_factor
    • More generally, the color resulting in layering a color RGB(currentR,currentG,currentB) with a color RGBA(aR,aG,aB,alpha) is:

      newR = currentR + (aR - currentR) * alpha
      newG = currentG + (aG - currentG) * alpha
      newB = currentB + (aB - currentB) * alpha

    where (aR,aG,aB) = black = (0,0,0) for shading, and (aR,aG,aB) = white = (255,255,255) for tinting

  • HSV or HSB:

    • To shade: lower the Value / Brightness or increase the Saturation
    • To tint: lower the Saturation or increase the Value / Brightness
  • HSL:
    • To shade: lower the Lightness
    • To tint: increase the Lightness

There exists formulas to convert from one color model to another. As per your initial question, if you are in RGB and want to use the HSV model to shade for example, you can just convert to HSV, do the shading and convert back to RGB. Formula to convert are not trivial but can be found on the internet. Depending on your language, it might also be available as a core function :

Comparing the models

  • RGB has the advantage of being really simple to implement, but:
    • you can only shade or tint your color relatively
    • you have no idea if your color is already tinted or shaded
  • HSV or HSB is kind of complex because you need to play with two parameters to get what you want (Saturation & Value / Brightness)
  • HSL is the best from my point of view:
    • supported by CSS3 (for webapp)
    • simple and accurate:
      • 50% means an unaltered Hue
      • >50% means the Hue is lighter (tint)
      • <50% means the Hue is darker (shade)
    • given a color you can determine if it is already tinted or shaded
    • you can tint or shade a color relatively or absolutely (by just replacing the Lightness part)

How do you set the title color for the new Toolbar?

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

    android:background="@color/green" />

How to change the session timeout in PHP?

Session timeout is a notion that has to be implemented in code if you want strict guarantees; that's the only way you can be absolutely certain that no session ever will survive after X minutes of inactivity.

If relaxing this requirement a little is acceptable and you are fine with placing a lower bound instead of a strict limit to the duration, you can do so easily and without writing custom logic.

Convenience in relaxed environments: how and why

If your sessions are implemented with cookies (which they probably are), and if the clients are not malicious, you can set an upper bound on the session duration by tweaking certain parameters. If you are using PHP's default session handling with cookies, setting session.gc_maxlifetime along with session_set_cookie_params should work for you like this:

// server should keep session data for AT LEAST 1 hour
ini_set('session.gc_maxlifetime', 3600);

// each client should remember their session id for EXACTLY 1 hour

session_start(); // ready to go!

This works by configuring the server to keep session data around for at least one hour of inactivity and instructing your clients that they should "forget" their session id after the same time span. Both of these steps are required to achieve the expected result.

  • If you don't tell the clients to forget their session id after an hour (or if the clients are malicious and choose to ignore your instructions) they will keep using the same session id and its effective duration will be non-deterministic. That is because sessions whose lifetime has expired on the server side are not garbage-collected immediately but only whenever the session GC kicks in.

    GC is a potentially expensive process, so typically the probability is rather small or even zero (a website getting huge numbers of hits will probably forgo probabilistic GC entirely and schedule it to happen in the background every X minutes). In both cases (assuming non-cooperating clients) the lower bound for effective session lifetimes will be session.gc_maxlifetime, but the upper bound will be unpredictable.

  • If you don't set session.gc_maxlifetime to the same time span then the server might discard idle session data earlier than that; in this case, a client that still remembers their session id will present it but the server will find no data associated with that session, effectively behaving as if the session had just started.

Certainty in critical environments

You can make things completely controllable by using custom logic to also place an upper bound on session inactivity; together with the lower bound from above this results in a strict setting.

Do this by saving the upper bound together with the rest of the session data:

session_start(); // ready to go!

$now = time();
if (isset($_SESSION['discard_after']) && $now > $_SESSION['discard_after']) {
    // this session has worn out its welcome; kill it and start a brand new one

// either new or old, it should live at most for another hour
$_SESSION['discard_after'] = $now + 3600;

Session id persistence

So far we have not been concerned at all with the exact values of each session id, only with the requirement that the data should exist as long as we need them to. Be aware that in the (unlikely) case that session ids matter to you, care must be taken to regenerate them with session_regenerate_id when required.

package does not exist ; in Android studio 0.8



Then sync gradle to build project.

PostgreSQL Exception Handling

Use the DO statement, a new option in version 9.0:

CREATE TABLE "Logs"."Events"
        PrimaryKeyId bigint NOT NULL,
        EventDateTime date NOT NULL DEFAULT(now()),
        Action varchar(12) NOT NULL,
        UserId integer NOT NULL REFERENCES "Office"."Users"(UserId),
        PrincipalUserId varchar(50) NOT NULL DEFAULT(user)

    CREATE TABLE "Logs"."EventDetails"
        EventId bigint NOT NULL REFERENCES "Logs"."Events"(EventId),
        Resource varchar(64) NOT NULL,
        OldVal varchar(4000) NOT NULL,
        NewVal varchar(4000) NOT NULL

    RAISE NOTICE 'Task completed sucessfully.';    

Compare two DataFrames and output their differences side-by-side

This answer simply extends @Andy Hayden's, making it resilient to when numeric fields are nan, and wrapping it up into a function.

import pandas as pd
import numpy as np

def diff_pd(df1, df2):
    """Identify differences between two pandas DataFrames"""
    assert (df1.columns == df2.columns).all(), \
        "DataFrame column names are different"
    if any(df1.dtypes != df2.dtypes):
        "Data Types are different, trying to convert"
        df2 = df2.astype(df1.dtypes)
    if df1.equals(df2):
        return None
        # need to account for np.nan != np.nan returning True
        diff_mask = (df1 != df2) & ~(df1.isnull() & df2.isnull())
        ne_stacked = diff_mask.stack()
        changed = ne_stacked[ne_stacked]
        changed.index.names = ['id', 'col']
        difference_locations = np.where(diff_mask)
        changed_from = df1.values[difference_locations]
        changed_to = df2.values[difference_locations]
        return pd.DataFrame({'from': changed_from, 'to': changed_to},

So with your data (slightly edited to have a NaN in the score column):

import sys
if sys.version_info[0] < 3:
    from StringIO import StringIO
    from io import StringIO

DF1 = StringIO("""id   Name   score                    isEnrolled           Comment
111  Jack   2.17                     True                 "He was late to class"
112  Nick   1.11                     False                "Graduated"
113  Zoe    NaN                     True                  " "
DF2 = StringIO("""id   Name   score                    isEnrolled           Comment
111  Jack   2.17                     True                 "He was late to class"
112  Nick   1.21                     False                "Graduated"
113  Zoe    NaN                     False                "On vacation" """)
df1 = pd.read_table(DF1, sep='\s+', index_col='id')
df2 = pd.read_table(DF2, sep='\s+', index_col='id')
diff_pd(df1, df2)


                from           to
id  col                          
112 score       1.11         1.21
113 isEnrolled  True        False
    Comment           On vacation

How to submit a form using Enter key in react.js?

It's been quite a few years since this question was last answered. React introduced "Hooks" back in 2017, and "keyCode" has been deprecated.

Now we can write this:

  useEffect(() => {
    const listener = event => {
      if (event.code === "Enter" || event.code === "NumpadEnter") {
        console.log("Enter key was pressed. Run your function.");
        // callMyFunction();
    document.addEventListener("keydown", listener);
    return () => {
      document.removeEventListener("keydown", listener);
  }, []);

This registers a listener on the keydown event, when the component is loaded for the first time. It removes the event listener when the component is destroyed.

Regex to match 2 digits, optional decimal, two digits

EDIT: Changed to fit other feedback.

I understood you to mean that if there is no decimal point, then there shouldn't be two more digits. So this should be it:


That should do the trick in most implementations. If not, you can use:


And that should work on every implementation I've seen.

Iterating over a numpy array

I think you're looking for the ndenumerate.

>>> a =numpy.array([[1,2],[3,4],[5,6]])
>>> for (x,y), value in numpy.ndenumerate(a):
...  print x,y
0 0
0 1
1 0
1 1
2 0
2 1

Regarding the performance. It is a bit slower than a list comprehension.

X = np.zeros((100, 100, 100))

%timeit list([((i,j,k), X[i,j,k]) for i in range(X.shape[0]) for j in range(X.shape[1]) for k in range(X.shape[2])])
1 loop, best of 3: 376 ms per loop

%timeit list(np.ndenumerate(X))
1 loop, best of 3: 570 ms per loop

If you are worried about the performance you could optimise a bit further by looking at the implementation of ndenumerate, which does 2 things, converting to an array and looping. If you know you have an array, you can call the .coords attribute of the flat iterator.

a = X.flat
%timeit list([(a.coords, x) for x in a.flat])
1 loop, best of 3: 305 ms per loop

JSON character encoding - is UTF-8 well-supported by browsers or should I use numeric escape sequences?

Reading the json rfc ( it is clear that the preferred encoding is utf-8.

FYI, RFC 4627 is no longer the official JSON spec. It was obsoleted in 2014 by RFC 7159, which was then obsoleted in 2017 by RFC 8259, which is the current spec.

RFC 8259 states:

8.1. Character Encoding

JSON text exchanged between systems that are not part of a closed ecosystem MUST be encoded using UTF-8 [RFC3629].

Previous specifications of JSON have not required the use of UTF-8 when transmitting JSON text. However, the vast majority of JSON-based software implementations have chosen to use the UTF-8 encoding, to the extent that it is the only encoding that achieves interoperability.

Implementations MUST NOT add a byte order mark (U+FEFF) to the beginning of a networked-transmitted JSON text. In the interests of interoperability, implementations that parse JSON texts MAY ignore the presence of a byte order mark rather than treating it as an error.

jQuery Validate - Enable validation for hidden fields

The plugin's author says you should use "square brackets without the quotes", []

Release: Validation Plugin 1.9.0: "...Another change should make the setup of forms with hidden elements easier, these are now ignored by default (option “ignore” has “:hidden” now as default). In theory, this could break an existing setup. In the unlikely case that it actually does, you can fix it by setting the ignore-option to “[]” (square brackets without the quotes)."

To change this setting for all forms:

    ignore: [],
    // any other default options and/or rules

(It is not required that .setDefaults() be within the document.ready function)

OR for one specific form:

$(document).ready(function() {

        ignore: [],
        // any other options and/or rules



See this answer for how to enable validation on some hidden fields but still ignore others.


Before leaving comments that "this does not work", keep in mind that the OP is simply asking about the jQuery Validate plugin and his question has nothing to do with how ASP.NET, MVC, or any other Microsoft framework can alter this plugin's normal expected behavior. If you're using a Microsoft framework, the default functioning of the jQuery Validate plugin is over-written by Microsoft's unobtrusive-validation plugin.

If you're struggling with the unobtrusive-validation plugin, then please refer to this answer instead:

How can I regenerate ios folder in React Native project?

Remove the ios folder first

 react-native eject 
 cd ios/ 
 pod init 
 pod install 
 cd .. 
 react-native link 
 cd ios 
 open *.xcworkspace/

Which browser has the best support for HTML 5 currently?

To test your browser, go to The code is being maintained at: github dot com slash NielsLeenheer slash html5test.

AcquireConnection method call to the connection manager <Excel Connection Manager> failed with error code 0xC0202009

I don't think it's 64/32 bit error. My Dev machine and DB server are 32bit. But I could make it work. I had to set Delay Validation property of Data Flow tasks to TRUE.


The canonical T-SQL (SqlServer) answer is to use a DELETE with JOIN as such

FROM Orders o
INNER JOIN Customers c
    ON o.CustomerId = c.CustomerId
WHERE c.FirstName = 'sklivvz'

This will delete all orders which have a customer with first name Sklivvz.

How can I list all cookies for the current page with Javascript?


The only API browsers give you for handling cookies is getting and setting them via key-value pairs. All browsers handle cookies by domain name only.

Accessing all cookies for current domain is done via document.cookie.

Vertical Align text in a Label

If your label is in table, padding may cause it to expand. To avoid this you may use margin:

div label {
    display: block;
    text-align: left;
    margin-bottom: -0.2%;

How to align content of a div to the bottom

If you have multiple, dynamic height items, use the CSS display values of table and table-cell:



  <div class="valign bottom">

      <div>my bottom aligned div 1</div>
      <div>my bottom aligned div 2</div>
      <div>my bottom aligned div 3</div>




body {
  width: 100%;
  height: 100%;
.valign {
  display: table;
  width: 100%;
  height: 100%;
.valign > div {
  display: table-cell;
  width: 100%;
  height: 100%;
.valign.bottom > div {
  vertical-align: bottom;

I've created a JSBin demo here:

The demo also has an example how to vertically center align using the same technique.

json.dump throwing "TypeError: {...} is not JSON serializable" on seemingly valid object?

Because it's not actually a dictionary; it's another mapping type that looks like a dictionary. Use type() to verify. Pass it to dict() to get a real dictionary from it.

Python Pip install Error: Unable to find vcvarsall.bat. Tried all solutions

I have tried all suggestions and found my own simple solution.

The problem is that codes written in external environment like C need compiler. Look for its own VS environment, i.e. VS 2008.

Currently my machine runs VS 2012 and faces Unable to find vcvarsall.bat. I studied codes that i want to install to find the VS version. It was VS 2008. i have add to system variable VS90COMNTOOLS as variable name and gave the value of VS120COMNTOOLS.

You can find my step by step solution below:

  1. Right click on My Computer.
  2. Click Properties
  3. Advanced system settings
  4. Environment variables
  5. Add New system variable
  6. Enter VS90COMNTOOLS to the variable name
  7. Enter the value of current version to the new variable.
  8. Close all windows

Now open a new session and pip install your-package

How do I determine file encoding in OS X?

Which LaTeX are you using? When I was using teTeX, I had to manually download the unicode package and add this to my .tex files:

% UTF-8 stuff

Now, I've switched over to XeTeX from the TeXlive 2008 package (here), it is even more simple:

% UTF-8 stuff

As for detection of a file's encoding, you could play with file(1) (but it is rather limited) but like someone else said, it is difficult.

Why does DEBUG=False setting make my django Static Files Access fail?

Support for string view arguments to url() is deprecated and will be removed in Django 1.10

My solution is just small correction to Conrado solution above.

from django.conf import settings
import os
from django.views.static import serve as staticserve

if settings.DEBUG404:
    urlpatterns += patterns('',
        (r'^static/(?P<path>.*)$', staticserve,
            {'document_root': os.path.join(os.path.dirname(__file__), 'static')} ),

XAMPP on Windows - Apache not starting

my friend this the will fix ur problem ;)

in root of folder ( xampp ) just run this file ( setup_xampp.bat ) then press enter

and try to start the apache server

every things will work like charm ;)

change text of button and disable button in iOS

Assuming that the button is a UIButton:

UIButton *button = …;
[button setEnabled:NO]; // disables
[button setTitle:@"Foo" forState:UIControlStateNormal]; // sets text

See the documentation for UIButton.

Sort array of objects by single key with date value

Sorting by an ISO formatted date can be expensive, unless you limit the clients to the latest and best browsers, which can create the correct timestamp by Date-parsing the string.

If you are sure of your input, and you know it will always be yyyy-mm-ddThh:mm:ss and GMT (Z) you can extract the digits from each member and compare them like integers

    return a.updated_at.replace(/\D+/g,'')-b.updated_at.replace(/\D+/g,'');

If the date could be formatted differently, you may need to add something for iso challenged folks:

Date.fromISO: function(s){
    var day, tz,
    rx=/^(\d{4}\-\d\d\-\d\d([tT ][\d:\.]*)?)([zZ]|([+\-])(\d\d):(\d\d))?$/,
    p= rx.exec(s) || [];
        day= p[1].split(/\D/).map(function(itm){
            return parseInt(itm, 10) || 0;
        day[1]-= 1;
        day= new Date(Date.UTC.apply(Date, day));
        if(!day.getDate()) return NaN;
            tz= (parseInt(p[5], 10)*60);
            if(p[6]) tz+= parseInt(p[6], 10);
            if(p[4]== '+') tz*= -1;
            if(tz) day.setUTCMinutes(day.getUTCMinutes()+ tz);
        return day;
    return NaN;
if(!{ function(fun, scope){
        var T= this, L= T.length, A= Array(L), i= 0;
        if(typeof fun== 'function'){
            while(i< L){
                if(i in T){
                    A[i]=, T[i], i, T);
            return A;

Ship an application with a database

The SQLiteAssetHelper library makes this task really simple.

It's easy to add as a gradle dependency (but a Jar is also available for Ant/Eclipse), and together with the documentation it can be found at:

Note: This project is no longer maintained as stated on above Github link.

As explained in documentation:

  1. Add the dependency to your module's gradle build file:

    dependencies {
        compile 'com.readystatesoftware.sqliteasset:sqliteassethelper:+'
  2. Copy the database into the assets directory, in a subdirectory called assets/databases. For instance:

    (Optionally, you may compress the database in a zip file such as assets/databases/ This isn't needed, since the APK is compressed as a whole already.)

  3. Create a class, for example:

    public class MyDatabase extends SQLiteAssetHelper {
        private static final String DATABASE_NAME = "my_database.db";
        private static final int DATABASE_VERSION = 1;
        public MyDatabase(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);

Calculate the number of business days between two dates?

Since I can't comment. There is one more issue with the accepted solution where bank holidays are subtracted even when they are situated in the weekend. Seeing how other input is checked, it is only fitting that this is as well.

The foreach should therefore be:

    // subtract the number of bank holidays during the time interval
    foreach (DateTime bankHoliday in bankHolidays)
        DateTime bh = bankHoliday.Date;

        // Do not subtract bank holidays when they fall in the weekend to avoid double subtraction
        if (bh.DayOfWeek == DayOfWeek.Saturday || bh.DayOfWeek == DayOfWeek.Sunday)

        if (firstDay <= bh && bh <= lastDay)

The relationship could not be changed because one or more of the foreign-key properties is non-nullable

If you are using Auto mapper and facing the the issue following is the good solution, it work for me

Since the problem is that we're mapping null navigation properties, and we actually don't need them to be updated on the Entity since they didn't changed on the Contract, we need to ignore them on the mapping definition:

ForMember(dest => dest.RefundType, opt => opt.Ignore())

So my code ended up like this:

Mapper.CreateMap<MyDataContract, MyEntity>
ForMember(dest => dest.NavigationProperty1, opt => opt.Ignore())
ForMember(dest => dest.NavigationProperty2, opt => opt.Ignore())

How can I make a checkbox readonly? not disabled?

document.getElementById("your checkbox id").disabled=true;

Check folder size in Bash

Use a summary (-s) and bytes (-b). You can cut the first field of the summary with cut. Putting it all together:

CHECK=$(du -sb /data/sflow_log | cut -f1)

jQuery: select all elements of a given class, except for a particular Id

You could use the .not function like the following examples to remove items that have an exact id, id containing a specific word, id starting with a word, etc... see for more information on jQuery selectors.

Ignore by Exact ID:


Ignore ID's that contains the word "Id"


Ignore ID's that start with "my"


$('body').on('click', '.anything', function(){})

You should use $(document). It is a function trigger for any click event in the document. Then inside you can use the jquery on("click","body *",somefunction), where the second argument specifies which specific element to target. In this case every element inside the body.

$(document).on('click','body *',function(){
    //  $(this) = your current element that clicked.
    // additional code

How to find a string inside a entire database?

I think you have to options:

  1. Build a dynamic SQL using sys.tables and sys.columns to perform the search (example here).

  2. Use any program that have this function. An example of this is SQL Workbench (free).

how to get session id of client in Client

Try this way.

                var socket = io.connect('http://...');

How to use QueryPerformanceCounter?

I use these defines:

/** Use to init the clock */
#define TIMER_INIT \
    LARGE_INTEGER frequency; \
    LARGE_INTEGER t1,t2; \
    double elapsedTime; \

/** Use to start the performance timer */
#define TIMER_START QueryPerformanceCounter(&t1);

/** Use to stop the performance timer and output the result to the standard stream. Less verbose than \c TIMER_STOP_VERBOSE */
#define TIMER_STOP \
    QueryPerformanceCounter(&t2); \
    elapsedTime=(float)(t2.QuadPart-t1.QuadPart)/frequency.QuadPart; \
    std::wcout<<elapsedTime<<L" sec"<<endl;

Usage (brackets to prevent redefines):




Output from usage example:

1.00003 sec
1.23407 sec

Android - How to regenerate R class?

You can just delete the file from your project and it will regenerate assuming you have build automatically enabled. If you do not have build automatically enabled simply goto project->build all

How to get label text value form a html page?

The best way to get the text value from a <label> element is as follows.

if you will be getting element ids frequently it's best to have a function to return the ids:

function id(e){return document.getElementById(e)}

Assume the following structure: <label for='phone'>Phone number</label> <input type='text' id='phone' placeholder='Mobile or landline numbers...'>

This code will extract the text value 'Phone number' from the<label>: var text = id('phone').previousElementSibling.innerHTML;

This code works on all browsers, and you don't have to give each<label>element a unique id.

AngularJS: factory $http.get JSON file

++ This worked for me. It's vanilla javascirpt and good for use cases such as de-cluttering when testing with ngMocks library:

<!-- specRunner.html - keep this at the top of your <script> asset loading so that it is available readily -->
<!--  Frienly tip - have all JSON files in a json-data folder for keeping things organized-->
<script src="json-data/findByIdResults.js" charset="utf-8"></script>
<script src="json-data/movieResults.js" charset="utf-8"></script>

This is your javascript file that contains the JSON data

// json-data/JSONFindByIdResults.js
var JSONFindByIdResults = {
     "Title": "Star Wars",
     "Year": "1983",
     "Rated": "N/A",
     "Released": "01 May 1983",
     "Runtime": "N/A",
     "Genre": "Action, Adventure, Sci-Fi",
     "Director": "N/A",
     "Writer": "N/A",
     "Actors": "Harrison Ford, Alec Guinness, Mark Hamill, James Earl Jones",
     "Plot": "N/A",
     "Language": "English",
     "Country": "USA",
     "Awards": "N/A",
     "Poster": "N/A",
     "Metascore": "N/A",
     "imdbRating": "7.9",
     "imdbVotes": "342",
     "imdbID": "tt0251413",
     "Type": "game",
     "Response": "True"

Finally, work with the JSON data anywhere in your code

// working with JSON data in code
var findByIdResults = window.JSONFindByIdResults;

Note:- This is great for testing and even karma.conf.js accepts these files for running tests as seen below. Also, I recommend this only for de-cluttering data and testing/development environment.

// extract from karma.conf.js
files: [

Hope this helps.

++ Built on top of this answer


An easier way that worked for me is just include a function at the bottom of the code returning whatever JSON.

// within test code
let movies = getMovieSearchJSON();
// way down below in the code
function getMovieSearchJSON() {
      return {
         "Title": "Bri Squared",
         "Year": "2011",
         "Rated": "N/A",
         "Released": "N/A",
         "Runtime": "N/A",
         "Genre": "Comedy",
         "Director": "Joy Gohring",
         "Writer": "Briana Lane",
         "Actors": "Brianne Davis, Briana Lane, Jorge Garcia, Gabriel Tigerman",
         "Plot": "N/A",
         "Language": "English",
         "Country": "USA",
         "Awards": "N/A",
         "Poster": "",
         "Metascore": "N/A",
         "imdbRating": "8.2",
         "imdbVotes": "5",
         "imdbID": "tt1937109",
         "Type": "movie",
         "Response": "True"

What is the difference between README and in GitHub projects?

.md is markdown. is used to generate the html summary you see at the bottom of projects. Github has their own flavor of Markdown.

Order of Preference: If you have two files named README and, the file named is preferred, and it will be used to generate github's html summary.

FWIW, Stack Overflow uses local Markdown modifications as well (also see Stack Overflow's C# Markdown Processor)

regex match any single character (one character only)

Match any single character

  • Use the dot . character as a wildcard to match any single character.

Example regex: a.c

abc   // match
a c   // match
azc   // match
ac    // no match
abbc  // no match

Match any specific character in a set

  • Use square brackets [] to match any characters in a set.
  • Use \w to match any single alphanumeric character: 0-9, a-z, A-Z, and _ (underscore).
  • Use \d to match any single digit.
  • Use \s to match any single whitespace character.

Example 1 regex: a[bcd]c

abc   // match
acc   // match
adc   // match
ac    // no match
abbc  // no match

Example 2 regex: a[0-7]c

a0c   // match
a3c   // match
a7c   // match
a8c   // no match
ac    // no match
a55c  // no match

Match any character except ...

Use the hat in square brackets [^] to match any single character except for any of the characters that come after the hat ^.

Example regex: a[^abc]c

aac   // no match
abc   // no match
acc   // no match
a c   // match
azc   // match
ac    // no match
azzc  // no match

(Don't confuse the ^ here in [^] with its other usage as the start of line character: ^ = line start, $ = line end.)

Match any character optionally

Use the optional character ? after any character to specify zero or one occurrence of that character. Thus, you would use .? to match any single character optionally.

Example regex: a.?c

abc   // match
a c   // match
azc   // match
ac    // match
abbc  // no match

See also

rsync: how can I configure it to create target directory on server?

this worked for me:

 rsync /dev/null node:existing-dir/new-dir/

I do get this message :

skipping non-regular file "null"

but I don't have to worry about having an empty directory hanging around.

Get current batchfile directory

Very simple:

cd /d %~dp0

Where can I find the Tomcat 7 installation folder on Linux AMI in Elastic Beanstalk?

Following environment variables worked for me on Debian Wheezy 7 and Tomcat 7:


(I did create /tmp/tomcat7 manually)

Programmatically set left drawable in a TextView

there are two ways of doing it either you can use XML or Java for it. If it's static and requires no changes then you can initialize in XML.


Now if you need to change the icons dynamically then you can do it by calling the icons based on the events

       textViewContext.setText("File Uploaded");
textViewContext.setCompoundDrawablesWithIntrinsicBounds(R.drawable.uploaded, 0, 0, 0);

ImportError: cannot open shared object file: No such file or directory

There is now a headless version of opencv-python which removes the graphical dependencies (like libSM). You can see the normal / headless version on the releases page (and the GitHub issue leading to this); just add -headless when installing, e.g.,

pip install opencv-python-headless
# also contrib, if needed
pip install opencv-contrib-python-headless

How to force garbage collection in Java?

To manually Request GC (not from System.gc()) :

  1. Go To : bin folder in JDK eg.-C:\Program Files\Java\jdk1.6.0_31\bin
  2. Open jconsole.exe
  3. Connect to the desired local Process.
  4. Go To memory tab and click perform GC.

Setting the selected attribute on a select list using jQuery


var select = function(dropdown, selectedValue) {
    var options = $(dropdown).find("option");
    var matches = $.grep(options,
        function(n) { return $(n).text() == selectedValue; });
    $(matches).attr("selected", "selected");


select("#dropdown", "B");

Node.js on multi-core machines

The cluster module allows you to utilise all cores of your machine. In fact you can take advantage of this in just 2 commands and without touching your code using a very popular process manager pm2.

npm i -g pm2
pm2 start app.js -i max

Run a PHP file in a cron job using CPanel

This cron line worked for me on hostgator VPS using cpanel.

/usr/bin/php -q /home/username/public_html/scriptname.php

Tab separated values in awk

You can set the Field Separator:

... | awk 'BEGIN {FS="\t"}; {print $1}'

Excellent read:

Python: Ignore 'Incorrect padding' error when base64 decoding

You can simply use base64.urlsafe_b64decode(data) if you are trying to decode a web image. It will automatically take care of the padding.

What does it mean "No Launcher activity found!"

Here's an example from AndroidManifest.xml. You need to specify the MAIN and LAUNCHER in the intent filter for the activity you want to start on launch

<application android:label="@string/app_name" android:icon="@drawable/icon">
    <activity android:name="ExampleActivity"
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />

Internet Explorer 11- issue with security certificate error prompt

This behavior is related to Zone that is set - Internet/Intranet/etc and corresponding Security Level

You can change this by setting less secure Security Level (not recommended) or by customizing Display Mixed Content property

You can do that by following steps:

  1. Click on Gear icon at the top of the browser window.
  2. Select Internet Options.
  3. Select the Security tab at the top.
  4. Click the Custom Level... button.
  5. Scroll about halfway down to the Miscellaneous heading (denoted by a "blank page" icon).
  6. Under this heading is the option Display Mixed Content; set this to Enable/Prompt.
  7. Click OK, then Yes when prompted to confirm the change, then OK to close the Options window.
  8. Close and restart the browser.

enter image description here

Mongoose limit/offset and count query

There is a library that will do all of this for you, check out mongoose-paginate-v2

Class is inaccessible due to its protection level

All your classes are internal by default

Marking public did not do the trick.

Are you sure you do not have two classes named Method, and perhaps are including the wrong Method class?

justify-content property isn't working


Go to inspect element and check if .justify-content-center is listed as a class name under 'Styles' tab. If not, probably you are using bootstrap v3 in which justify-content-center is not defined.

If so, please update bootstrap, worked for me.

How to choose the id generation strategy when using JPA and Hibernate

I find this lecture very valuable, in point 3 it summarizes these generators and also gives some performance analysis and guideline one when you use each one.

Can I restore a single table from a full mysql mysqldump file?

You can use vi editor. Type:

vi -o mysql.dump mytable.dump

to open both whole dump mysql.dump and a new file mytable.dump. Find the appropriate insert into line by pressing / and then type a phrase, for example: "insert into `mytable`", then copy that line using yy. Switch to next file by ctrl+w then down arrow key, paste the copied line with pp. Finally save the new file by typing :wq and quite vi editor by :q.

Note that if you have dumped the data using multiple inserts you can copy (yank) all of them at once using Nyy in which N is the number of lines to be copied.

I have done it with a file of 920 MB size.

What's an object file in C?

An object file is the real output from the compilation phase. It's mostly machine code, but has info that allows a linker to see what symbols are in it as well as symbols it requires in order to work. (For reference, "symbols" are basically names of global objects, functions, etc.)

A linker takes all these object files and combines them to form one executable (assuming that it can, ie: that there aren't any duplicate or undefined symbols). A lot of compilers will do this for you (read: they run the linker on their own) if you don't tell them to "just compile" using command-line options. (-c is a common "just compile; don't link" option.)

How to disable Google asking permission to regularly check installed apps on my phone?

It is also available in general settings

Settings -> Security -> Verify Apps

Just un-check it.

( I am running 4.2.2 but most probably it should be available in 4.0 and higher. Cant say about previous versions ... )

Change NULL values in Datetime format to empty string

CASE and CAST should work:

CASE WHEN mycol IS NULL THEN '' ELSE CONVERT(varchar(50), mycol, 121) END

How to repair COMException error 80040154?

To find the DLL, go to your 64-bit machine and open the registry. Find the key called HKEY_CLASSES_ROOT\CLSID\{681EF637-F129-4AE9-94BB-618937E3F6B6}\InprocServer32. This key will have the filename of the DLL as its default value.

If you solved the problem on your 64-bit machine by recompiling your project for x86, then you'll need to look in the 32-bit portion of the registry instead of in the normal place. This is HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Classes\CLSID\{681EF637-F129-4AE9-94BB-618937E3F6B6}\InprocServer32.

If the DLL is built for 32 bits then you can use it directly on your 32-bit machine. If it's built for 64 bits then you'll have to contact the vendor and get a 32-bit version from them.

When you have the DLL, register it by running c:\windows\system32\regsvr32.exe.

How can I remove file extension from a website address?

For those who are still looking for a simple answer to this; You can remove your file extension by using .htaccessbut this solution is just saving the day maybe even not. Because when user copies the URL from address bar or tries to reload or even coming back from history, your standart Apache Router will not be able to realize what are you looking for and throw you a 404 Error. You need a dedicated Router for this purpose to make your app understand what does the URL actually means by saying something Server and File System has no idea about.

I leave here my solution for this. This is tested and used many times for my clients and for my projects too. It supports multi language and language detection too. Read Readme file is recommended. It also provides you a good structure to have a tidy project with differenciated language files (you can even have different designs for each language) and separated css,js and phpfiles even more like images or whatever you have.

Cr8Router - Simple PHP Router

What is the proper #include for the function 'sleep()'?

sleep(3) is in unistd.h, not stdlib.h. Type man 3 sleep on your command line to confirm for your machine, but I presume you're on a Mac since you're learning Objective-C, and on a Mac, you need unistd.h.

How to convert String to long in Java?

It's quite simple, use Long.valueOf(String s);

For example:

String s;
long l;

Scanner sc=new Scanner(;;

You're done!!!

How can I get terminal output in python?

You can use Popen in subprocess as they suggest.

with os, which is not recomment, it's like below:

import os
a  = os.popen('pwd').readlines()

Gulp command not found after install

If you're using tcsh (which is my default shell on Mac OS X), you probably just need to type rehash into the shell just after the install completes:

npm install -g gulp

followed immediately by:


Otherwise, if this is your very first time installing gulp, your shell may not recognize that there's a new executable installed -- so you either need to start a new shell, or type rehash in the current shell.

(This is basically a one-time thing for each command you install globally.)

Why aren't variable-length arrays part of the C++ standard?

This was considered for inclusion in C++/1x, but was dropped (this is a correction to what I said earlier).

It would be less useful in C++ anyway since we already have std::vector to fill this role.

CSS vertical-align: text-bottom;

if your text doesn't spill over two rows then you can do line-height: ; in your CSS, the more line-height you give, the lower on the container it will hold.

"Unable to find remote helper for 'https'" during git clone

I landed here once because I was working with git itself. When I built it the default makefile installed the binary in ~/bin/git. Since my PATH had ~/bin first when I ran 'git pull --rebase' it used the one in ~/bin and consequently could not locate the helpers.

I worked around the issue by running '/usr/bin/git ...' with a full path (alternatively I could have adjusted my PATH).

In Ruby, how do I skip a loop in a .each loop, similar to 'continue'

next - it's like return, but for blocks! (So you can use this in any proc/lambda too.)

That means you can also say next n to "return" n from the block. For instance:

puts [1, 2, 3].map do |e|
  next 42 if e == 2

This will yield 46.

Note that return always returns from the closest def, and never a block; if there's no surrounding def, returning is an error.

Using return from within a block intentionally can be confusing. For instance:

def my_fun
  [1, 2, 3].map do |e|
    return "Hello." if e == 2

my_fun will result in "Hello.", not [1, "Hello.", 2], because the return keyword pertains to the outer def, not the inner block.

Convert Mercurial project to Git

Some notes of my experience converting Mercurial to Git.

1. hg-fast-export

Using hg-fast-export failed and I needed --force as noted above. Next I got this error:

error: cannot lock ref 'refs/heads/stable': 'refs/heads/stable/sub-branch-name' exists; cannot create 'refs/heads/stable'

Upon completion of the hg-fast-export I ended up with an amputated repo. I think that this repo had a good few orphaned branches and that hg-fast-export needs a somewhat idealised repo. This all seemed a bit rough around the edges, so I moved on to Kiln Harmony (

2. Kiln

Kiln Harmony does not appear to exist on a free tier account as suggested above. I could choose between Git-only and Mercurial-only repos and there is no option to switch. I raised a support ticket and will share the result if they reply.

3. hg-git

The Hg-Git mercurial plugin ( did work for me. FYI on Mac OSX I installed hg-git via macports as follows:

  • sudo port install python27
  • sudo port select --set python python27
  • sudo port install py27-hggit
  • vi ~/.hgrc

.hgrc needs these lines:

username = Name Surname <[email protected]>

hgext.bookmarks =
hggit = 

I then had success with:

hg push git+ssh://[email protected]:myaccount/myrepo.git

4. Caveat: Know your repo

All the above are blunt instruments and I only pushed ahead because it took enough time to get the team to use git properly.

Upon first pushing the project per (3) I ended up with all new changes missing. This is because this line of code must be viewed as a guide only:

$ hg bookmark -r default master # make a bookmark of master for default, so a ref gets created

The theory is that the default branch can be deemed to be master when pushing to git, and in my case I inherited a repo where they used 'stable' as the equivalent of master. Moreover, I also discovered that the tip of the repo was a hotfix not yet merged with the 'stable' branch.

Without properly understanding both Mercurial and the repo to be converted, you are probably better off not doing the conversion.

I did the following in order to get the repo ready for a second conversion attempt:

hg update -C stable
hg merge stable/hotfix-feature
hg ci -m "Merge with stable branch"
hg push git+ssh://[email protected]:myaccount/myrepo.git

After this I had a verifiably equivalent project in git, however all the orphaned branches I mentioned earlier are gone. I don't think that is too serious, but I may well live to regret this as an oversight. Therefore my final thought is to keep the original anyway.

Edit: If you just want the latest commit in git, this is simpler than the above merge:

hg book -r tip master
hg push git+ssh://[email protected]:myaccount/myrepo.git

What is the difference between a candidate key and a primary key?

John Woo's answer is correct, as far as it goes. Here are a few additional points.

A primary key is always one of the candidate keys. Fairly often, it's the only candidate.

A table with no candidate keys does not represent a relation. If you're using the relational model to help you build a good database, then every table you design will have at least one candidate key.

The relational model would be complete without the concept of primary key. It wasn't in the original presentation of the relational model. As a practical matter, the use of foreign key references without a declared primary key leads to a mess. It could be a logically correct mess, but it's a mess nonetheless. Declaring a primary key lets the DBMS help you enforce the data rules. Most of the time, having the DBMS help you enforce the data rules is a good thing, and well worth the cost.

Some database designers and some users have some mental confusion about whether the primary key identifies a row (record) in a table or an instance of an entity in the subject matter that the table represents. In an ideal world, it's supposed to do both, and there should be a one-for-one correspondence between rows in an entity table and instances of the corresponding entity.

In the real world, things get screwed up. Somebody enters the same new employee twice, and the employee ends up with two ids. Somebody gets hired, but the data entry slips through the cracks in some manual process, and the employee doesn't get an id, until the omission is corrected. A database that does not collapse the first time things get screwed up is more robust than one that does.

How to handle a lost KeyStore password in Android?

Open taskHistory.bin and search for storePassword

How to link 2 cell of excel sheet?

The simplest solution is to select the second cell, and press =. This will begin the fomula creation process. Now either type in the 1st cell reference (eg, A1) or click on the first cell and press enter. This should make the second cell reference the value of the first cell.

To read up more on different options for referencing see - This Article.

Get only the Date part of DateTime in mssql

Another nifty way is:

DATEADD(dd, 0, DATEDIFF(dd, 0, [YourDate]))

Which gets the number of days from DAY 0 to YourDate and the adds it to DAY 0 to set the baseline again. This method (or "derivatives" hereof) can be used for a bunch of other date manipulation.

Edit - other date calculations:

First Day of Month:

DATEADD(mm, DATEDIFF(mm, 0, getdate()), 0)

First Day of the Year:

DATEADD(yy, DATEDIFF(yy, 0, getdate()), 0)

First Day of the Quarter:

DATEADD(qq, DATEDIFF(qq, 0, getdate()), 0)

Last Day of Prior Month:

DATEADD(ms, -3, DATEADD(mm, DATEDIFF(mm, 0, getdate()), 0))

Last Day of Current Month:

DATEADD(ms, -3, DATEADD(mm, DATEDIFF(m, 0, getdate()) + 1, 0))

Last Day of Current Year:

DATEADD(ms, -3, DATEADD(yy, DATEDIFF(yy, 0, getdate()) + 1, 0))

First Monday of the Month:

DATEADD(wk, DATEDIFF(wk, 0, DATEADD(dd, 6 - DATEPART(day, getdate()), getdate())), 0)        

Edit: True, Joe, it does not add it to DAY 0, it adds 0 (days) to the number of days which basically just converts it back to a datetime.

How to declare std::unique_ptr and what is the use of it?

Unique pointers are guaranteed to destroy the object they manage when they go out of scope.

In this case:

unique_ptr<double> uptr2 (pd);

pd will be destroyed when uptr2 goes out of scope. This facilitates memory management by automatic deletion.

The case of unique_ptr<int> uptr (new int(3)); is not different, except that the raw pointer is not assigned to any variable here.

Vertically aligning CSS :before and :after content

This is what worked for me:

.pdf::before {
    content: url('path/to/image.png');
    display: flex;
    align-items: center;
    justify-content: center;
    height: inherit;

Convert a negative number to a positive one in JavaScript

If you want the number to always be positive no matter what you can do this.

function toPositive(n){
    if(n < 0){
        n = n * -1;
    return n;
var a = toPositive(2);  // 2
var b = toPositive(-2); // 2

You could also try this, but i don't recommended it:

function makePositive(n){
    return Number((n*-n).toString().replace('-','')); 
var a = makePositive(2);  // 2
var b = makePositive(-2); // 2

The problem with this is that you could be changing the number to negative, then converting to string and removing the - from the string, then converting back to int. Which I would guess would take more processing then just using the other function.

I have tested this in php and the first function is faster, but sometimes JS does some crazy things, so I can't say for sure.

How to convert a structure to a byte array in C#?

Variant of the code of Vicent with one less memory allocation:

public static byte[] GetBytes<T>(T str)
    int size = Marshal.SizeOf(str);

    byte[] arr = new byte[size];

    GCHandle h = default(GCHandle);

        h = GCHandle.Alloc(arr, GCHandleType.Pinned);

        Marshal.StructureToPtr<T>(str, h.AddrOfPinnedObject(), false);
        if (h.IsAllocated)

    return arr;

public static T FromBytes<T>(byte[] arr) where T : struct
    T str = default(T);

    GCHandle h = default(GCHandle);

        h = GCHandle.Alloc(arr, GCHandleType.Pinned);

        str = Marshal.PtrToStructure<T>(h.AddrOfPinnedObject());

        if (h.IsAllocated)

    return str;

I use GCHandle to "pin" the memory and then I use directly its address with h.AddrOfPinnedObject().

How can I remove time from date with Moment.js?

Whenever I use the moment.js library I specify the desired format this way:

moment(<your Date goes here>).format("DD-MMM-YYYY")


moment(<your Date goes here>).format("DD/MMM/YYYY")

... etc I hope you get the idea

Inside the format function, you put the desired format. The example above will get rid of all unwanted elements from the date such as minutes and seconds

JavaScript Uncaught ReferenceError: jQuery is not defined; Uncaught ReferenceError: $ is not defined

Cause you need to add jQuery library to your file:

jQuery UI is just an addon to jQuery which means that
first you need to include the jQuery library → and then the UI.

<script src="path/to/your/jquery.min.js"></script>
<script src="path/to/your/jquery.ui.min.js"></script>

Argument Exception "Item with Same Key has already been added"

To illustrate the problem you are having, let's look at some code...

Dictionary<string, string> test = new Dictionary<string, string>();

test.Add("Key1", "Value1");  // Works fine
test.Add("Key2", "Value2");  // Works fine
test.Add("Key1", "Value3");  // Fails because of duplicate key

The reason that a dictionary has a key/value pair is a feature so you can do this...

var myString = test["Key2"];  // myString is now Value2.

If Dictionary had 2 Key2's, it wouldn't know which one to return, so it limits you to a unique key.

Append to string variable

var str1 = 'abc';
var str2 = str1+' def'; // str2 is now 'abc def'

How to JOIN three tables in Codeigniter

Try this one for data...

function get_album_data() {
    $this->db->select ( 'album.*,cat.*,s_track.*' )
        ->from ( 'albums as album' );
        ->join ( 'categories cat', 'cat.cat_id = album.cat_id')
        ->join ( 'soundtracks s_tracks ', 's_tracks.album_id = album.album_id');
    $query = $this->db->get ();
    return $query->result ();

while for datum try this...

function get_album_datum($album_id) {
    $this->db->select ( 'album.*,cat.*,s_track.*' )
        ->from ( 'albums as album' );
        ->join ( 'categories cat', 'cat.cat_id = album.cat_id')
        ->join ( 'soundtracks s_tracks ', 's_tracks.album_id = album.album_id');
    $this->db->where ( 'album.album_id', $album_id);
    $query = $this->db->get ();
    return $query->row();


Checking from shell script if a directory contains files

How about the following:

if find /some/dir/ -maxdepth 0 -empty | read v; then echo "Empty dir"; fi

This way there is no need for generating a complete listing of the contents of the directory. The read is both to discard the output and make the expression evaluate to true only when something is read (i.e. /some/dir/ is found empty by find).

how to convert a string to a bool

I used the below code to convert a string to boolean.


Laravel Eloquent limit and offset

laravel have own function skip for offset and take for limit. just like below example of laravel query :-


How can I output a UTF-8 CSV in PHP that Excel will read properly?

I have the same (or similar) problem.

In my case, if I add a BOM to the output, it works:

header('Content-Encoding: UTF-8');
header('Content-type: text/csv; charset=UTF-8');
header('Content-Disposition: attachment; filename=Customers_Export.csv');
echo "\xEF\xBB\xBF"; // UTF-8 BOM

I believe this is a pretty ugly hack, but it worked for me, at least for Excel 2007 Windows. Not sure it'll work on Mac.

CSS div element - how to show horizontal scroll bars only?

you can also make it overflow: auto and give a maximum fixed height and width that way, when the text or whatever is in there, overflows it'll show only the required scrollbar

How to use Git Revert

The question is quite old but revert is still confusing people (like me)

As a beginner, after some trial and error (more errors than trials) I've got an important point:

  • git revert requires the id of the commit you want to remove keeping it into your history

  • git reset requires the commit you want to keep, and will consequentially remove anything after that from history.

That is, if you use revert with the first commit id, you'll find yourself into an empty directory and an additional commit in history, while with reset your directory will be.. reverted back to the initial commit and your history will get as if the last commit(s) never happened.

To be even more clear, with a log like this:

# git log --oneline

cb76ee4 wrong
01b56c6 test
2e407ce first commit

Using git revert cb76ee4 will by default bring your files back to 01b56c6 and will add a further commit to your history:

8d4406b Revert "wrong"
cb76ee4 wrong
01b56c6 test
2e407ce first commit

git reset 01b56c6 will instead bring your files back to 01b56c6 and will clean up any other commit after that from your history :

01b56c6 test
2e407ce first commit

I know these are "the basis" but it was quite confusing for me, by running revert on first id ('first commit') I was expecting to find my initial files, it taken a while to understand, that if you need your files back as 'first commit' you need to use the next id.

How to pass model attributes from one Spring MVC controller to another controller?

Using just redirectAttributes.addFlashAttribute(...) -> "redirect:..." worked as well, didn't have to "reinsert" the model attribute.

Thanks, aborskiy!

How to store a list in a column of a database table

Only one option doesn't mentioned in the answers. You can de-normalize your DB design. So you need two tables. One table contains proper list, one item per row, another table contains whole list in one column (coma-separated, for example).

Here it is 'traditional' DB design:

List(ListID, ListName) 
List_Item(ListID, ItemID, SortOrder)

Here it is de-normalized table:

Lists(ListID, ListContent)

The idea here - you maintain Lists table using triggers or application code. Every time you modify List_Item content, appropriate rows in Lists get updated automatically. If you mostly read lists it could work quite fine. Pros - you can read lists in one statement. Cons - updates take more time and efforts.

Proper way to renew distribution certificate for iOS

Very simple was to renew your certificate. Go to your developer member centre and go to your Provisioning profile and see what are the certificate Active and InActive and select Inactive certificate and hit Edit button then hit generate button. Now your certificate successful renewal for another 1 year. Thanks

Adding a column after another column within SQL

It depends on what database you are using. In MySQL, you would use the "ALTER TABLE" syntax. I don't remember exactly how, but it would go something like this if you wanted to add a column called 'newcol' that was a 200 character varchar:

ALTER TABLE example ADD newCol VARCHAR(200) AFTER otherCol;

Adding Permissions in AndroidManifest.xml in Android Studio?

You can add manually in the manifest file within manifest tag by:

<uses-permission android:name="android.permission.CAMERA"/>

This permission is required to be able to access the camera device.

How to adjust gutter in Bootstrap 3 grid system?

(Posted on behalf of the OP).

I believe I figured it out.

In my case, I added [class*="col-"] {padding: 0 7.5px;};.

Then added .row {margin: 0 -7.5px;}.

This works pretty well, except there is 1px margin on both sides. So I just make .row {margin: 0 -7.5px;} to .row {margin: 0 -8.5px;}, then it works perfectly.

I have no idea why there is a 1px margin. Maybe someone can explain it?

See the sample I created:

Code error adding symbols: DSO missing from command line

You should mention the library on the command line after the object files being compiled:

 gcc -Wstrict-prototypes -Wall -Wno-sign-compare -Wpointer-arith -Wdeclaration-after-statement -Wformat-security -Wswitch-enum -Wunused-parameter -Wstrict-aliasing -Wbad-function-cast -Wcast-align -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-field-initializers -Wno-override-init \
     -g -O2 -export-dynamic -o utilities/ovs-dpctl utilities/ovs-dpctl.o \
     lib/libopenvswitch.a \
     /home/jyyoo/src/dpdk/build/lib/librte_eal.a /home/jyyoo/src/dpdk/build/lib/libethdev.a /home/jyyoo/src/dpdk/build/lib/librte_cmdline.a /home/jyyoo/src/dpdk/build/lib/librte_hash.a /home/jyyoo/src/dpdk/build/lib/librte_lpm.a /home/jyyoo/src/dpdk/build/lib/librte_mbuf.a /home/jyyoo/src/dpdk/build/lib/librte_ring.a /home/jyyoo/src/dpdk/build/lib/librte_mempool.a /home/jyyoo/src/dpdk/build/lib/librte_malloc.a \
     -lrt -lm -lpthread 

Explanation: the linking is dependent on the order of modules. Symbols are first requested, and then linked in from a library that has them. So you have to specify modules that use libraries first, and libraries after them. Like this:

gcc x.o y.o z.o -la -lb -lc

Moreover, in case there's a circular dependency, you should specify the same library on the command line several times. So in case libb needs symbol from libc and libc needs symbol from libb, the command line should be:

gcc x.o y.o z.o -la -lb -lc -lb

What is the "continue" keyword and how does it work in Java?

Basically in java, continue is a statement. So continue statement is normally used with the loops to skip the current iteration.

For how and when it is used in java, refer link below. It has got explanation with example.

Hope it helps !!

How can I split this comma-delimited string in Python?

Question is a little vague.

list_of_lines = multiple_lines.split("\n")
for line in list_of_lines:
    list_of_items_in_line = line.split(",")
    first_int = int(list_of_items_in_line[0])


How to specify font attributes for all elements on an html web page?

* {
 font-size: 100%;
 font-family: Arial;

The asterisk implies all elements.

How do I check out an SVN project into Eclipse as a Java project?

I had to add the .classpath too, form a java project. I made a dummy java project and looked in the workspace for this dummy java project to see what is required. I transferred the two files. profile and .claspath to my checked out, and disconnected source from my subversion server. From then on it turned to a java project from just a plain old project.

Extract elements of list at odd positions

You can make use of bitwise AND operator &. Let's see below:

x = [1, 2, 3, 4, 5, 6, 7]
y = [i for i in x if i&1]
[1, 3, 5, 7]

Bitwise AND operator is used with 1, and the reason it works because, odd number when written in binary must have its first digit as 1. Let's check

23 = 1 * (2**4) + 0 * (2**3) + 1 * (2**2) + 1 * (2**1) + 1 * (2**0) = 10111
14 = 1 * (2**3) + 1 * (2**2) + 1 * (2**1) + 0 * (2**0) = 1110

AND operation with 1 will only return 1 (1 in binary will also have last digit 1), iff the value is odd.

Check the Python Bitwise Operator page for more.

P.S: You can tactically use this method if you want to select odd and even columns in a dataframe. Let's say x and y coordinates of facial key-points are given as columns x1, y1, x2, etc... To normalize the x and y coordinates with width and height values of each image you can simply perform

for i in range(df.shape[1]):
    if i&1:
        df.iloc[:, i] /= heights
        df.iloc[:, i] /= widths

This is not exactly related to the question but for data scientists and computer vision engineers this method could be useful.


How to overlay one div over another div

I am not much of a coder nor an expert in CSS, but I am still using your idea in my web designs. I have tried different resolutions too:

#wrapper {_x000D_
  margin: 0 auto;_x000D_
  width: 901px;_x000D_
  height: 100%;_x000D_
  background-color: #f7f7f7;_x000D_
  background-image: url(images/wrapperback.gif);_x000D_
  color: #000;_x000D_
#header {_x000D_
  float: left;_x000D_
  width: 100.00%;_x000D_
  height: 122px;_x000D_
  background-color: #00314e;_x000D_
  background-image: url(images/header.jpg);_x000D_
  color: #fff;_x000D_
#menu {_x000D_
  float: left;_x000D_
  padding-top: 20px;_x000D_
  margin-left: 495px;_x000D_
  width: 390px;_x000D_
  color: #f1f1f1;_x000D_
<div id="wrapper">_x000D_
  <div id="header">_x000D_
    <div id="menu">_x000D_
      menu will go here_x000D_

Of course there will be a wrapper around both of them. You can control the location of the menu div which will be displayed within the header div with left margins and top positions. You can also set the div menu to float right if you like.

glob exclude pattern

As mentioned by the accepted answer, you can't exclude patterns with glob, so the following is a method to filter your glob result.

The accepted answer is probably the best pythonic way to do things but if you think list comprehensions look a bit ugly and want to make your code maximally numpythonic anyway (like I did) then you can do this (but note that this is probably less efficient than the list comprehension method):

import glob

data_files = glob.glob("path_to_files/*.fits")

light_files = np.setdiff1d( data_files, glob.glob("*BIAS*"))
light_files = np.setdiff1d(light_files, glob.glob("*FLAT*"))

(In my case, I had some image frames, bias frames, and flat frames all in one directory and I just wanted the image frames)

Mysql where id is in array


$array=array_map('intval', explode(',', $string));


$array= implode(',', array_map('intval', explode(',', $string)));

array_map returns an array, not a string. You need to convert the array to a comma separated string in order to use in the WHERE clause.

Android RecyclerView addition & removal of items

first of all, item should be removed from the list!




"webxml attribute is required" error in Maven

This is an old question, and there are many answers, most of which will be more or less helpful; however, there is one, very important and still relevant point, which none of the answers touch (providing, instead, different hacks to make build possible), and which, I think, in no way has a less importance.. on the contrary.

According to your log message, you are using Maven, which is a Project Management tool, firmly following the conventions, over configuration principle.

When Maven builds the project:

  1. it expects your project to have a particular directory structure, so that it knows where to expect what. This is called a Maven's Standard Directory Layout;
  2. during the build, it creates also proper directory structure and places files into corresponding locations/directories, and this, in compliance with the Sun Microsystems Directory Structure Standard for Java EE [web] applications.

You may incorporate many things, including maven plugins, changing/reconfiguring project root directory, etc., but better and easier is to follow the default conventions over configuration, according to which, (now is the answer to your problem) there is one simple step that can make your project work: Just place your web.xml under src\main\webapp\WEB-INF\ and try to build the project with mvn package.

How to enable zoom controls and pinch zoom in a WebView?

Strange. Inside OnCreate method, I'm using


And it's working fine here. Anything particular in your webview ?

How to remove array element in mongodb?

In Mongoose: from the document:

To remove a document from a subdocument array we may pass an object with a matching _id.{ _id: itemId }) // remove; // this also works

See Leonid Beschastny's answer for the correct answer.

Unloading classes in java?

The only way that a Class can be unloaded is if the Classloader used is garbage collected. This means, references to every single class and to the classloader itself need to go the way of the dodo.

One possible solution to your problem is to have a Classloader for every jar file, and a Classloader for each of the AppServers that delegates the actual loading of classes to specific Jar classloaders. That way, you can point to different versions of the jar file for every App server.

This is not trivial, though. The OSGi platform strives to do just this, as each bundle has a different classloader and dependencies are resolved by the platform. Maybe a good solution would be to take a look at it.

If you don't want to use OSGI, one possible implementation could be to use one instance of JarClassloader class for every JAR file.

And create a new, MultiClassloader class that extends Classloader. This class internally would have an array (or List) of JarClassloaders, and in the defineClass() method would iterate through all the internal classloaders until a definition can be found, or a NoClassDefFoundException is thrown. A couple of accessor methods can be provided to add new JarClassloaders to the class. There is several possible implementations on the net for a MultiClassLoader, so you might not even need to write your own.

If you instanciate a MultiClassloader for every connection to the server, in principle it is possible that every server uses a different version of the same class.

I've used the MultiClassloader idea in a project, where classes that contained user-defined scripts had to be loaded and unloaded from memory and it worked quite well.

Simplest way to do a recursive self-join?

The Quassnoi query with a change for large table. Parents with more childs then 10: Formating as str(5) the row_number()

WITH    q AS 
        SELECT  m.*, CAST(str(ROW_NUMBER() OVER (ORDER BY m.ordernum),5) AS VARCHAR(MAX)) COLLATE Latin1_General_BIN AS bc
        FROM    #t m
        WHERE   ParentID =0
        UNION ALL
        SELECT  m.*,  q.bc + '.' + str(ROW_NUMBER()  OVER (PARTITION BY m.ParentID ORDER BY m.ordernum),5) COLLATE Latin1_General_BIN
        FROM    #t m
        JOIN    q
        ON      m.parentID = q.DBID
FROM    q

OS X Bash, 'watch' command

Try this:

# usage: watch [-n integer] COMMAND

case $# in
        echo "Usage $0 [-n int] COMMAND"

if [ "$1" == "-n" ]; then
    shift; shift

while :; 
    echo "$(date) every ${sleep}s $@"; echo 
    sleep $sleep; 

How to position text over an image in css

How about something like this:

Its done by using position:absolute and z-index to place the text over the image.

#container {_x000D_
  height: 400px;_x000D_
  width: 400px;_x000D_
  position: relative;_x000D_
#image {_x000D_
  position: absolute;_x000D_
  left: 0;_x000D_
  top: 0;_x000D_
#text {_x000D_
  z-index: 100;_x000D_
  position: absolute;_x000D_
  color: white;_x000D_
  font-size: 24px;_x000D_
  font-weight: bold;_x000D_
  left: 150px;_x000D_
  top: 350px;_x000D_
<div id="container">_x000D_
  <img id="image" src="" />_x000D_
  <p id="text">_x000D_
    Hello World!_x000D_

How to find files recursively by file type and copy them to a directory while in ssh?

Try this:

find . -name "*.pdf" -type f -exec cp {} ./pdfsfolder \;

Using Mysql WHERE IN clause in codeigniter

Try this one:

$this->db->where_in("(SELECT trans_id FROM myTable WHERE code = 'B')");
$this->db->where('code !=', 'B');

Note: $this->db->select("*"); is optional when you are selecting all columns from table

How can I get the executing assembly version?

I finally settled on typeof(MyClass).GetTypeInfo().Assembly.GetName().Version for a netstandard1.6 app. All of the other proposed answers presented a partial solution. This is the only thing that got me exactly what I needed.

Sourced from a combination of places:

How to create JSON string in C#

This code snippet uses the DataContractJsonSerializer from System.Runtime.Serialization.Json in .NET 3.5.

public static string ToJson<T>(/* this */ T value, Encoding encoding)
    var serializer = new DataContractJsonSerializer(typeof(T));

    using (var stream = new MemoryStream())
        using (var writer = JsonReaderWriterFactory.CreateJsonWriter(stream, encoding))
            serializer.WriteObject(writer, value);

        return encoding.GetString(stream.ToArray());

How to run a python script from IDLE interactive shell?

execFile('') does the job for me. A thing to note is to enter the complete directory name of the .py file if it isnt in the Python folder itself (atleast this is the case on Windows)

For example, execFile('C:/')

How to use a variable for a key in a JavaScript object literal?

If you want object key to be same as variable name, there's a short hand in ES 2015. New notations in ECMAScript 2015

var thetop = 10;
var obj = { thetop };
console.log(obj.thetop); // print 10

Python script to convert from UTF-8 to ASCII

UTF-8 is a superset of ASCII. Either your UTF-8 file is ASCII, or it can't be converted without loss.

CSS content generation before or after 'input' elements

fyi <form> supports :before / :after as well, might be of help if you wrap your <input> element with it... (got myself a design issue with that too)

Calling @Html.Partial to display a partial view belonging to a different controller

As GvS said, but I also find it useful to use strongly typed views so that I can write something like

@Html.Partial(MVC.Student.Index(), model)

without magic strings.

Calculate days between two Dates in Java 8

You can use until():

LocalDate independenceDay = LocalDate.of(2014, Month.JULY, 4);
LocalDate christmas = LocalDate.of(2014, Month.DECEMBER, 25);

System.out.println("Until christmas: " + independenceDay.until(christmas));
System.out.println("Until christmas (with crono): " + independenceDay.until(christmas, ChronoUnit.DAYS));

Can I set up HTML/Email Templates with ASP.NET?

@bardev provides a good solution, but unfortunately it's not ideal in all cases. Mine was one of them.

I'm using WebForms in a Website (I swear I'll never use a Website again--what a PITA) in VS 2013.

I tried the Razor suggestion, but mine being a Website I didn't get the all-important IntelliSense that the IDE delivers in an MVC project. I also like to use the designer for my templates--a perfect spot for a UserControl.

Nix on Razor again.

So I came up with this little framework instead (hat tips to @mun for UserControl and @imatoria for Strong Typing). Just about the only potential trouble spot I can see is that you have to be careful to keep your .ASCX filename in sync with its class name. If you stray, you'll get a runtime error.

FWIW: In my testing at least the RenderControl() call doesn't like a Page control, so I went with UserControl.

I'm pretty sure I've included everything here; let me know if I left something out.



Partial Class Purchase
  Inherits UserControl

  Private Sub SendReceipt()
    Dim oTemplate As MailTemplates.PurchaseReceipt

    oTemplate = MailTemplates.Templates.PurchaseReceipt(Me)
    oTemplate.Name = "James Bond"
    oTemplate.OrderTotal = 3500000
    oTemplate.OrderDescription = "Q-Stuff"

    Utils.SendMail("{0} <[email protected]>".ToFormat(oTemplate.Name), "Purchase Receipt", oTemplate.ToHtml)
  End Sub
End Class

Base Class:

Namespace MailTemplates
  Public MustInherit Class BaseTemplate
    Inherits UserControl

    Public Shared Function GetTemplate(Caller As TemplateControl, Template As Type) As BaseTemplate
      Return Caller.LoadControl("~/MailTemplates/{0}.ascx".ToFormat(Template.Name))
    End Function

    Public Sub InjectCss(FileName As String)
      If Me.Styler IsNot Nothing Then
        Me.Styler.Controls.Add(New Controls.Styler(FileName))
      End If
    End Sub

    Private ReadOnly Property Styler As PlaceHolder
        If _Styler Is Nothing Then
          _Styler = Me.FindNestedControl(GetType(PlaceHolder))
        End If

        Return _Styler
      End Get
    End Property
    Private _Styler As PlaceHolder
  End Class
End Namespace

"Factory" Class:

Namespace MailTemplates
  Public Class Templates
    Public Shared ReadOnly Property PurchaseReceipt(Caller As TemplateControl) As PurchaseReceipt
        Return BaseTemplate.GetTemplate(Caller, GetType(PurchaseReceipt))
      End Get
    End Property
  End Class
End Namespace

Template Class:

Namespace MailTemplates
  Public MustInherit Class PurchaseReceipt
    Inherits BaseTemplate

    Public MustOverride WriteOnly Property Name As String
    Public MustOverride WriteOnly Property OrderTotal As Decimal
    Public MustOverride WriteOnly Property OrderDescription As String
  End Class
End Namespace

ASCX Header:

<%@ Control Language="VB" ClassName="_Header" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional //EN" "">

  See for discussion of DocType in HTML Email

<html xmlns="">
  <asp:PlaceHolder ID="plcStyler" runat="server"></asp:PlaceHolder>

ASCX Footer:

<%@ Control Language="VB" ClassName="_Footer" %>


ASCX Template:

<%@ Control Language="VB" AutoEventWireup="false" CodeFile="PurchaseReceipt.ascx.vb" Inherits="PurchaseReceipt" %>

<%@ Register Src="_Header.ascx" TagName="Header" TagPrefix="uc" %>
<%@ Register Src="_Footer.ascx" TagName="Footer" TagPrefix="uc" %>

<uc:Header ID="ctlHeader" runat="server" />

  <p>Name: <asp:Label ID="lblName" runat="server"></asp:Label></p>
  <p>Order Total: <asp:Label ID="lblOrderTotal" runat="server"></asp:Label></p>
  <p>Order Description: <asp:Label ID="lblOrderDescription" runat="server"></asp:Label></p>

<uc:Footer ID="ctlFooter" runat="server" />

ASCX Template CodeFile:

Partial Class PurchaseReceipt
  Inherits MailTemplates.PurchaseReceipt

  Public Overrides WriteOnly Property Name As String
    Set(Value As String)
      lblName.Text = Value
    End Set
  End Property

  Public Overrides WriteOnly Property OrderTotal As Decimal
    Set(Value As Boolean)
      lblOrderTotal.Text = Value
    End Set
  End Property

  Public Overrides WriteOnly Property OrderDescription As Decimal
    Set(Value As Boolean)
      lblOrderDescription.Text = Value
    End Set
  End Property
End Class


' FindNestedControl helpers based on tip by @andleer
' at

Public Module Helpers
  Public Function AllControls(Control As Control) As List(Of Control)
    Return Control.Controls.Flatten
  End Function

  Public Function FindNestedControl(Control As Control, Id As String) As Control
    Return Control.Controls.Flatten(Function(C) C.ID = Id).SingleOrDefault
  End Function

  Public Function FindNestedControl(Control As Control, Type As Type) As Control
    Return Control.Controls.Flatten(Function(C) C.GetType = Type).SingleOrDefault
  End Function

  Public Function Flatten(Controls As ControlCollection) As List(Of Control)
    Flatten = New List(Of Control)

    Controls.Traverse(Sub(Control) Flatten.Add(Control))
  End Function

  Public Function Flatten(Controls As ControlCollection, Predicate As Func(Of Control, Boolean)) As List(Of Control)
    Flatten = New List(Of Control)

                        If Predicate(Control) Then
                        End If
                      End Sub)
  End Function

  Public Sub Traverse(Controls As ControlCollection, Action As Action(Of Control))
    Controls.Cast(Of Control).ToList.ForEach(Sub(Control As Control)

                                               If Control.HasControls Then
                                               End If
                                             End Sub)
  End Sub

  Public Function ToFormat(Template As String, ParamArray Values As Object()) As String
    Return String.Format(Template, Values)
  End Function

  Public Function ToHtml(Control As Control) As String
    Dim oSb As StringBuilder

    oSb = New StringBuilder

    Using oSw As New StringWriter(oSb)
      Using oTw As New HtmlTextWriter(oSw)
        Return oSb.ToString
      End Using
    End Using
  End Function
End Module

Namespace Controls
  Public Class Styler
    Inherits LiteralControl

    Public Sub New(FileName As String)
      Dim _
        sFilePath As String

      sFileName = Path.GetFileNameWithoutExtension(FileName)
      sFilePath = HttpContext.Current.Server.MapPath("~/Styles/{0}.css".ToFormat(sFileName))

      If File.Exists(sFilePath) Then
        Me.Text = "{0}<style type=""text/css"">{0}{1}</style>{0}".ToFormat(vbCrLf, File.ReadAllText(sFilePath))
        Me.Text = String.Empty
      End If
    End Sub
  End Class
End Namespace

Public Class Utils
  Public Shared Sub SendMail(Recipient As MailAddress, Subject As String, HtmlBody As String)
    Using oMessage As New MailMessage
      oMessage.IsBodyHtml = True
      oMessage.Subject = Subject.Trim
      oMessage.Body = HtmlBody.Trim

      Using oClient As New SmtpClient
      End Using
    End Using
  End Sub
End Class

How do I load the contents of a text file into a javascript variable?

If your input was structured as XML, you could use the importXML function. (More info here at quirksmode).

If it isn't XML, and there isn't an equivalent function for importing plain text, then you could open it in a hidden iframe and then read the contents from there.

Split string in C every white space

you can scan the char array looking for the token if you found it just print new line else print the char.

    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>

    int main()
        char *s;
        s = malloc(1024 * sizeof(char));
        scanf("%[^\n]", s);
        s = realloc(s, strlen(s) + 1);
        int len = strlen(s);
        char delim =' ';
        for(int i = 0; i < len; i++) {
            if(s[i] == delim) {
            else {
                printf("%c", s[i]);
        return 0;

Rename specific column(s) in pandas

data.rename(columns={'gdp':'log(gdp)'}, inplace=True)

The rename show that it accepts a dict as a param for columns so you just pass a dict with a single entry.

Also see related

Simple pthread! C++

From the pthread function prototype:

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
    void *(*start_routine)(void*), void *arg);

The function passed to pthread_create must have a prototype of

void* name(void *arg)

What is the usefulness of PUT and DELETE HTTP request methods?

DELETE is for deleting the request resource:

The DELETE method requests that the origin server delete the resource identified by the Request-URI. This method MAY be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation has been carried out, even if the status code returned from the origin server indicates that the action has been completed successfully …

PUT is for putting or updating a resource on the server:

The PUT method requests that the enclosed entity be stored under the supplied Request-URI. If the Request-URI refers to an already existing resource, the enclosed entity SHOULD be considered as a modified version of the one residing on the origin server. If the Request-URI does not point to an existing resource, and that URI is capable of being defined as a new resource by the requesting user agent, the origin server can create the resource with that URI …

For the full specification visit:

Since current browsers unfortunately do not support any other verbs than POST and GET in HTML forms, you usually cannot utilize HTTP to it's full extent with them (you can still hijack their submission via JavaScript though). The absence of support for these methods in HTML forms led to URIs containing verbs, like for instance


or even worse


effectively tunneling CRUD semantics over HTTP. But verbs were never meant to be part of the URI. Instead HTTP already provides the mechanism and semantics to CRUD a Resource (e.g. an order) through the HTTP methods. HTTP is a protocol and not just some data tunneling service.

So to delete a Resource on the webserver, you'd call


and to update it you'd call


and provide the updated Resource Representation in the PUT body for the webserver to apply then.

So, if you are building some sort of client for a REST API, you will likely make it send PUT and DELETE requests. This could be a client built inside a browser, e.g. sending requests via JavaScript or it could be some tool running on a server, etc.

For some more details visit:

How to execute a JavaScript function when I have its name as a string

The answer to this other question shows you how to do that: Javascript equivalent of Python's locals()?

Basically, you can say

window["foo"](arg1, arg2);

or as many others have suggested, you can just use eval:

eval(fname)(arg1, arg2);

although this is extremely unsafe unless you're absolutely sure about what you're eval-ing.

Converting a JToken (or string) to a given Type

var i2 = JsonConvert.DeserializeObject(obj["id"].ToString(), type);

throws a parsing exception due to missing quotes around the first argument (I think). I got it to work by adding the quotes:

var i2 = JsonConvert.DeserializeObject("\"" + obj["id"].ToString() + "\"", type);

Difference between "process.stdout.write" and "console.log" in node.js?

Console.log implement process.sdout.write, process.sdout.write is a buffer/stream that will directly output in your console.

According to my puglin serverline : console = new Console(consoleOptions) you can rewrite Console class with your own readline system.

You can see code source of console.log:

See more :

Column order manipulation using col-lg-push and col-lg-pull in Twitter Bootstrap 3

Pull "pulls" the div towards the left of the browser and and Push "pushes" the div away from left of browser.

Like: enter image description here

So basically in a 3 column layout of any web page the "Main Body" appears at the "Center" and in "Mobile" view the "Main Body" appears at the "Top" of the page. This is mostly desired by everyone with 3 column layout.

<div class="container">
    <div class="row">
        <div id="content" class="col-lg-4 col-lg-push-4 col-sm-12">
        <h2>This is Content</h2>
        <p>orem Ipsum ...</p>

        <div id="sidebar-left" class="col-lg-4  col-sm-6 col-lg-pull-4">
        <h2>This is Left Sidebar</h2>
        <p>orem Ipsum...</p>

        <div id="sidebar-right" class="col-lg-4 col-sm-6">
        <h2>This is Right Sidebar</h2>
        <p>orem Ipsum.... </p>

You can view it here:

Hope it helps

NUnit vs. MbUnit vs. MSTest vs.

It's not a big deal, it's pretty easy to switch between them. MSTest being integrated isn't a big deal either, just grab

Like the previous person said pick a mocking framework, my favourite at the moment is Moq.

Pro JavaScript programmer interview questions (with answers)

Because JavaScript is such a small language, yet with incredible complexity, you should be able to ask relatively basic questions and find out if they are really that good based on their answers. For instance, my standard first question to gauge the rest of the interview is:

In JavaScript, what is the difference between var x = 1 and x = 1? Answer in as much or as little detail as you feel comfortable.

Novice JS programmers might have a basic answer about locals vs globals. Intermediate JS guys should definitely have that answer, and should probably mention function-level scope. Anyone calling themselves an "advanced" JS programmer should be prepared to talk about locals, implied globals, the window object, function-scope, declaration hoisting, and scope chains. Furthermore, I'd love to hear about [[DontDelete]], hoisting precedence (parameters vs var vs function), and undefined.

Another good question is to ask them to write a sum() function that accepts any number of arguments, and returns their sum. Then, ask them to use that function (without modification) to sum all the values in an array. They should write a function that looks like this:

function sum() {
  var i, l, result = 0;
  for (i = 0, l = arguments.length; i < l; i++) {
    result += arguments[i];
  return result;
sum(1,2,3); // 6

And they should invoke it on your array like this (context for apply can be whatever, I usually use null in that case):

var data = [1,2,3];
sum.apply(null, data); // 6

If they've got those answers, they probably know their JavaScript. You should then proceed to asking them about non-JS specific stuff like testing, workflows, version control, etc. to find out if they're a good programmer.

How to increment variable under DOS?

I built my answer thanks to previous contributors.

Not having time for a custom counter.exe, I downloaded sed for FREEDOS.

And then the batch code could be, emulating "wc -l" with the utility sed, something like this according to your loop (I just use it to increment through executions starting from "1" to n+1):

Just remember to manually create a file "test.txt" with written on the first row


sed -n '$=' test.txt > counter.txt
set /P Var=< counter.txt
echo 0 >> test.txt

Refresh DataGridView when updating data source

Observablecollection :Represents a dynamic data collection that provides notifications when items get added, removed, or when the whole list is refreshed. You can enumerate over any collection that implements the IEnumerable interface. However, to set up dynamic bindings so that insertions or deletions in the collection update the UI automatically, the collection must implement the INotifyCollectionChanged interface. This interface exposes the CollectionChanged event, an event that should be raised whenever the underlying collection changes.

Observablecollection<ItemState> itemStates = new Observablecollection<ItemState>();

for (int i = 0; i < 10; i++) { 
    itemStates.Add(new ItemState { Id = i.ToString() });
 dataGridView1.DataSource = itemStates;

How can I determine browser window size on server side C#

I went with using the regex from to check against the user-agent string. Even tho it says it was last updated in 2014 it was accurate on the devices I tested.

Here is the C# code I got from them at the time of submitting this answer:

<%@ Page Language="C#" %> 
<%@ Import Namespace="System.Text.RegularExpressions" %>
    string u = Request.ServerVariables["HTTP_USER_AGENT"];
    Regex b = new Regex(@"(android|bb\d+|meego).+mobile|avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|mobile.+firefox|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)\/|plucker|pocket|psp|series(4|6)0|symbian|treo|up\.(browser|link)|vodafone|wap|windows ce|xda|xiino", RegexOptions.IgnoreCase | RegexOptions.Multiline);
    Regex v = new Regex(@"1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s\-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|as(te|us)|attw|au(di|\-m|r |s )|avan|be(ck|ll|nq)|bi(lb|rd)|bl(ac|az)|br(e|v)w|bumb|bw\-(n|u)|c55\/|capi|ccwa|cdm\-|cell|chtm|cldc|cmd\-|co(mp|nd)|craw|da(it|ll|ng)|dbte|dc\-s|devi|dica|dmob|do(c|p)o|ds(12|\-d)|el(49|ai)|em(l2|ul)|er(ic|k0)|esl8|ez([4-7]0|os|wa|ze)|fetc|fly(\-|_)|g1 u|g560|gene|gf\-5|g\-mo|go(\.w|od)|gr(ad|un)|haie|hcit|hd\-(m|p|t)|hei\-|hi(pt|ta)|hp( i|ip)|hs\-c|ht(c(\-| |_|a|g|p|s|t)|tp)|hu(aw|tc)|i\-(20|go|ma)|i230|iac( |\-|\/)|ibro|idea|ig01|ikom|im1k|inno|ipaq|iris|ja(t|v)a|jbro|jemu|jigs|kddi|keji|kgt( |\/)|klon|kpt |kwc\-|kyo(c|k)|le(no|xi)|lg( g|\/(k|l|u)|50|54|\-[a-w])|libw|lynx|m1\-w|m3ga|m50\/|ma(te|ui|xo)|mc(01|21|ca)|m\-cr|me(rc|ri)|mi(o8|oa|ts)|mmef|mo(01|02|bi|de|do|t(\-| |o|v)|zz)|mt(50|p1|v )|mwbp|mywa|n10[0-2]|n20[2-3]|n30(0|2)|n50(0|2|5)|n7(0(0|1)|10)|ne((c|m)\-|on|tf|wf|wg|wt)|nok(6|i)|nzph|o2im|op(ti|wv)|oran|owg1|p800|pan(a|d|t)|pdxg|pg(13|\-([1-8]|c))|phil|pire|pl(ay|uc)|pn\-2|po(ck|rt|se)|prox|psio|pt\-g|qa\-a|qc(07|12|21|32|60|\-[2-7]|i\-)|qtek|r380|r600|raks|rim9|ro(ve|zo)|s55\/|sa(ge|ma|mm|ms|ny|va)|sc(01|h\-|oo|p\-)|sdk\/|se(c(\-|0|1)|47|mc|nd|ri)|sgh\-|shar|sie(\-|m)|sk\-0|sl(45|id)|sm(al|ar|b3|it|t5)|so(ft|ny)|sp(01|h\-|v\-|v )|sy(01|mb)|t2(18|50)|t6(00|10|18)|ta(gt|lk)|tcl\-|tdg\-|tel(i|m)|tim\-|t\-mo|to(pl|sh)|ts(70|m\-|m3|m5)|tx\-9|up(\.b|g1|si)|utst|v400|v750|veri|vi(rg|te)|vk(40|5[0-3]|\-v)|vm40|voda|vulc|vx(52|53|60|61|70|80|81|83|85|98)|w3c(\-| )|webc|whit|wi(g |nc|nw)|wmlb|wonu|x700|yas\-|your|zeto|zte\-", RegexOptions.IgnoreCase | RegexOptions.Multiline);
    if ((b.IsMatch(u) || v.IsMatch(u.Substring(0, 4)))) {

How to Generate Unique Public and Private Key via RSA

The RSACryptoServiceProvider(CspParameters) constructor creates a keypair which is stored in the keystore on the local machine. If you already have a keypair with the specified name, it uses the existing keypair.

It sounds as if you are not interested in having the key stored on the machine.

So use the RSACryptoServiceProvider(Int32) constructor:

public static void AssignNewKey(){
    RSA rsa = new RSACryptoServiceProvider(2048); // Generate a new 2048 bit RSA key

    string publicPrivateKeyXML = rsa.ToXmlString(true);
    string publicOnlyKeyXML = rsa.ToXmlString(false);
    // do stuff with keys...


Alternatively try setting the PersistKeyInCsp to false:

public static void AssignNewKey(){
    const int PROVIDER_RSA_FULL = 1;
    const string CONTAINER_NAME = "KeyContainer";
    CspParameters cspParams;
    cspParams = new CspParameters(PROVIDER_RSA_FULL);
    cspParams.KeyContainerName = CONTAINER_NAME;
    cspParams.Flags = CspProviderFlags.UseMachineKeyStore;
    cspParams.ProviderName = "Microsoft Strong Cryptographic Provider";
    rsa = new RSACryptoServiceProvider(cspParams);

    rsa.PersistKeyInCsp = false;

    string publicPrivateKeyXML = rsa.ToXmlString(true);
    string publicOnlyKeyXML = rsa.ToXmlString(false);
    // do stuff with keys...

Get Country of IP Address with PHP

I see there are a lot of answers, but no one of them mentions

You're allowed up to 15,000 queries per hour. I think that's enough in most of the cases. Otherwise, you should think about using local databases from MaxMind GeoIP.

Freegeoip is open-source and you can find sources on github, deploy it locally and get rid of the query limits.

Also, service provides latitude/longitude/timezone and other useful stuff.

How can I convert a stack trace to a string?

My oneliner to convert stack trace to the enclosed multi-line string:

Stream.of(e.getStackTrace()).map((a) -> a.toString()).collect(Collectors.joining("\n", "[", "]"))

Easy to pass to the logger "as is".