Programs & Examples On #Clicktag

A click tag is a parameter used in Flash banner ads that defines the destination URL from the markup code. By using a click tag, advertisers can easily see and modify the URL without a changing the ActionScript code itself.

In PowerShell, how do I test whether or not a specific variable exists in global scope?

There's an even easier way:

if ($variable)
    Write-Host "bar exist"
    Write-Host "bar does not exists"

How to give a delay in loop execution using Qt

As an update of @Live's answer, for Qt = 5.2 there is no more need to subclass QThread, as now the sleep functions are public:

Static Public Members

  • QThread * currentThread()
  • Qt::HANDLE currentThreadId()
  • int idealThreadCount()
  • void msleep(unsigned long msecs)
  • void sleep(unsigned long secs)
  • void usleep(unsigned long usecs)
  • void yieldCurrentThread()


How to undo 'git reset'?

Short answer:

git reset 'HEAD@{1}'

Long answer:

Git keeps a log of all ref updates (e.g., checkout, reset, commit, merge). You can view it by typing:

git reflog

Somewhere in this list is the commit that you lost. Let's say you just typed git reset HEAD~ and want to undo it. My reflog looks like this:

$ git reflog
3f6db14 HEAD@{0}: HEAD~: updating HEAD
d27924e HEAD@{1}: checkout: moving from d27924e0fe16776f0d0f1ee2933a0334a4787b4c

The first line says that HEAD 0 positions ago (in other words, the current position) is 3f6db14; it was obtained by resetting to HEAD~. The second line says that HEAD 1 position ago (in other words, the state before the reset) is d27924e. It was obtained by checking out a particular commit (though that's not important right now). So, to undo the reset, run git reset HEAD@{1} (or git reset d27924e).

If, on the other hand, you've run some other commands since then that update HEAD, the commit you want won't be at the top of the list, and you'll need to search through the reflog.

One final note: It may be easier to look at the reflog for the specific branch you want to un-reset, say master, rather than HEAD:

$ git reflog show master
c24138b master@{0}: merge origin/master: Fast-forward
90a2bf9 master@{1}: merge origin/master: Fast-forward

This should have less noise it in than the general HEAD reflog.

How to get next/previous record in MySQL?

This is universal solution for conditions wiht more same results.

$your_name1_finded="somethnig searched"; //$your_name1_finded must be finded in previous select

$result = db_query("SELECT your_name1 FROM your_table WHERE your_name=your_condition ORDER BY your_name1, your_name2"); //Get all our ids

while($row = db_fetch_assoc($result)) { //Loop through our rows
    $current_row[$i]=$row['your_name1'];// field with results
    if($row['your_name1'] == $your_name1_finded) {//If we haven't hit our current row yet
if ($current_row[$yid-1]) $out_button.= "<a  class='button' href='/$your_url/".$current_row[$yid-1]."'>BUTTON_PREVIOUS</a>";
if ($current_row[$yid+1]) $out_button.= "<a  class='button' href='/$your_url/".$current_row[$yid+1]."'>BUTTON_NEXT</a>";

echo $out_button;//display buttons

What is the difference between a "line feed" and a "carriage return"?

A line feed means moving one line forward. The code is \n.
A carriage return means moving the cursor to the beginning of the line. The code is \r.

Windows editors often still use the combination of both as \r\n in text files. Unix uses mostly only the \n.

The separation comes from typewriter times, when you turned the wheel to move the paper to change the line and moved the carriage to restart typing on the beginning of a line. This was two steps.

Get element by id - Angular2

(<HTMLInputElement>document.getElementById('loginInput')).value = '123';

Angular cannot take HTML elements directly thereby you need to specify the element type by binding the above generic to it.


This can also be done using ViewChild with #localvariable as shown here, as mentioned in here

<textarea  #someVar  id="tasknote"
                  placeholder="{{ notePlaceholder }}"
                  style="background-color: pink"
                  (blur)="updateNote() ; noteEditMode = false " (click)="noteEditMode = false"> {{ todo.note }} 


import {ElementRef,Renderer2} from '@angular/core';
@ViewChild('someVar') el:ElementRef;

constructor(private rd: Renderer2) {}

ngAfterViewInit() {
      this.el.nativeElement.focus();      //<<<=====same as oldest way

Core Data: Quickest way to delete all instances of an entity

For Swift 2.0:

class func clearCoreData(entity:String) {
  let fetchRequest = NSFetchRequest()
  fetchRequest.entity = NSEntityDescription.entityForName(entity, inManagedObjectContext: moc!)
  fetchRequest.includesPropertyValues = false
  do {
    if let results = try moc!.executeFetchRequest(fetchRequest) as? [NSManagedObject] {
      for result in results {

      try moc!.save()
  } catch {
    LOG.debug("failed to clear core data")

Merging two arrays in .NET

If you don't want to remove duplicates, then try this


var arr1 = new[] { 1, 2, 3, 4, 5 };
var arr2 = new[] { 6, 7, 8, 9, 0 };
var arr = arr1.Concat(arr2).ToArray();

A Space between Inline-Block List Items

I had the same problem, when I used a inline-block on my menu I had the space between each "li" I found a simple solution, I don't remember where I found it, anyway here is what I did.

<li><a href="index.html" title="home" class="active">Home</a></li><!---->
<li><a href="news.html" title="news">News</a></li><!---->
<li><a href="about.html" title="about">About Us</a></li><!---->
<li><a href="contact.html" title="contact">Contact Us</a></li>

You add a comment sign between each end of, and start of : "li" Then the horizontal space disappear. Hope that answer to the question Thanks

Static image src in Vue.js template

You need use just simple code <img alt="img" src="../assets/index.png" />

Do not forgot atribut alt in balise img

Code for Greatest Common Divisor in Python

The algorithms with m-n can runs awfully long.

This one performs much better:

def gcd(x, y):
    while y != 0:
        (x, y) = (y, x % y)
    return x

How to override the path of PHP to use the MAMP path?

I found that on Mavericks 10.8 there wasn't a .bash_profile and my paths were located in /etc/paths

In order to have the new path (whether this is a mamp or brew install of php) take effect it needs to be above the default /usr/bin/php in this paths file. eg.


AFter the change, open a new terminal window and run 'which php' that should now point to your updated path

Java: Array with loop

The Array has declared without intializing the values and if you want to insert values by itterating the loop this code will work.

Public Class Program

public static void main(String args[])

 //Array Intialization
 int my[] = new int[6];

 for(int i=0;i<=5;i++)


//Storing array values in array
my[i]= i;

//Printing array values





How to print variables in Perl

You should always include all relevant code when asking a question. In this case, the print statement that is the center of your question. The print statement is probably the most crucial piece of information. The second most crucial piece of information is the error, which you also did not include. Next time, include both of those.

print $ids should be a fairly hard statement to mess up, but it is possible. Possible reasons:

  1. $ids is undefined. Gives the warning undefined value in print
  2. $ids is out of scope. With use strict, gives fatal warning Global variable $ids needs explicit package name, and otherwise the undefined warning from above.
  3. You forgot a semi-colon at the end of the line.
  4. You tried to do print $ids $nIds, in which case perl thinks that $ids is supposed to be a filehandle, and you get an error such as print to unopened filehandle.


1: Should not happen. It might happen if you do something like this (assuming you are not using strict):

my $var;
while (<>) {
    $Var .= $_;
print $var;

Gives the warning for undefined value, because $Var and $var are two different variables.

2: Might happen, if you do something like this:

if ($something) {
    my $var = "something happened!";
print $var;

my declares the variable inside the current block. Outside the block, it is out of scope.

3: Simple enough, common mistake, easily fixed. Easier to spot with use warnings.

4: Also a common mistake. There are a number of ways to correctly print two variables in the same print statement:

print "$var1 $var2";  # concatenation inside a double quoted string
print $var1 . $var2;  # concatenation
print $var1, $var2;   # supplying print with a list of args

Lastly, some perl magic tips for you:

use strict;
use warnings;

# open with explicit direction '<', check the return value
# to make sure open succeeded. Using a lexical filehandle.
open my $fh, '<', 'file.txt' or die $!;

# read the whole file into an array and
# chomp all the lines at once
chomp(my @file = <$fh>);
close $fh;

my $ids  = join(' ', @file);
my $nIds = scalar @file;
print "Number of lines: $nIds\n";
print "Text:\n$ids\n";

Reading the whole file into an array is suitable for small files only, otherwise it uses a lot of memory. Usually, line-by-line is preferred.


  • print "@file" is equivalent to $ids = join(' ',@file); print $ids;
  • $#file will return the last index in @file. Since arrays usually start at 0, $#file + 1 is equivalent to scalar @file.

You can also do:

my $ids;
do {
    local $/;
    $ids = <$fh>;

By temporarily "turning off" $/, the input record separator, i.e. newline, you will make <$fh> return the entire file. What <$fh> really does is read until it finds $/, then return that string. Note that this will preserve the newlines in $ids.

Line-by-line solution:

open my $fh, '<', 'file.txt' or die $!; # btw, $! contains the most recent error
my $ids;
while (<$fh>) {
    $ids .= "$_ "; # concatenate with string
my $nIds = $.; # $. is Current line number for the last filehandle accessed.

HTML input type=file, get the image before submitting the form

I found This simpler yet powerful tutorial which uses the fileReader Object. It simply creates an img element and, using the fileReader object, assigns its source attribute as the value of the form input

function previewFile() {_x000D_
  var preview = document.querySelector('img');_x000D_
  var file    = document.querySelector('input[type=file]').files[0];_x000D_
  var reader  = new FileReader();_x000D_
  reader.onloadend = function () {_x000D_
    preview.src = reader.result;_x000D_
  if (file) {_x000D_
  } else {_x000D_
    preview.src = "";_x000D_
<input type="file" onchange="previewFile()"><br>_x000D_
<img src="" height="200" alt="Image preview...">

ERROR 1049 (42000): Unknown database

Its a common error which happens when we try to access a database which doesn't exist. So create the database using

CREATE DATABASE blog_development;

The error commonly occours when we have dropped the database using

DROP DATABASE blog_development;

and then try to access the database.

How to obtain the total numbers of rows from a CSV file in Python?

After iterating the whole file with csv.reader() method, you have the total number of lines read, via instance variable line_num:

import csv
with open('csv_path_file') as f:
    csv_reader = csv.reader(f)
    for row in csv_reader:

Quoting the official documentation:


The number of lines read from the source iterator.

Small caveat:

  • total number of lines, includes the header, if the CSV has.

Should a function have only one return statement?

I use multiple exit points for having error-case + handling + return value as close in proximity as possible.

So having to test for conditions a, b, c that have to be true and you need to handle each of them differently:

if (a is false) {
    handle this situation (eg. report, log, message, etc.)
    return some-err-code
if (b is false) {
    handle this situation
    return other-err-code
if (c is false) {
    handle this situation
    return yet-another-err-code

perform any action assured that a, b and c are ok.

The a, b and c might be different things, like a is input parameter check, b is pointer check to newly allocated memory and c is check for a value in 'a' parameter.

How can I get the line number which threw exception?

Extension Method

static class ExceptionHelpers
    public static int LineNumber(this Exception ex)
        int n;
        int i = ex.StackTrace.LastIndexOf(" ");
        if (i > -1)
            string s = ex.StackTrace.Substring(i + 1);
            if (int.TryParse(s, out n))
                return n;
        return -1;


    throw new Exception("A new error happened");
catch (Exception ex)
    //If error in exception LineNumber() will be -1
    System.Diagnostics.Debug.WriteLine("[" + ex.LineNumber() + "] " + ex.Message);

Get first row of dataframe in Python Pandas based on criteria

For existing matches, use query:

df.query(' A > 3' ).head(1)
   A  B  C
2  4  6  3

df.query(' A > 4 and B > 3' ).head(1)
   A  B  C
4  5  4  5

df.query(' A > 3 and (B > 3 or C > 2)' ).head(1)
   A  B  C
2  4  6  3

JUnit tests pass in Eclipse but fail in Maven Surefire

In my case the reason was a bug in the code. The test relied on a certain order of elements in a HashSet, which turned out to be different when run either in Eclipse or in Maven Surefire.

What is the difference between Serializable and Externalizable in Java?

When considering options for improving performance, don't forget custom serialization. You can let Java do what it does well, or at least good enough, for free, and provide custom support for what it does badly. This is usually a lot less code than full Externalizable support.

.Net picking wrong referenced assembly version

In VS2017, have tried all the above solution but nothing works. We are using Azure devops for versioning.

  1. From the teams explorer > Source Control Explorer

enter image description here

  1. Select the project which driving you nuts for a long time

  2. Right click the branch or solution > Advanced > get specific version

enter image description here

  1. Then make sure You have ticked the checkbox of overwrite files as per screenshot

enter image description here

Git ignore file for Xcode projects

The people of GitHub have exhaustive and documented .gitignore files for Xcode projects:



docker : invalid reference format

The first argument after the "run" that is not a flag or parameter to a flag is parsed as an image name. When that parsing fails, it tells you the reference format, aka image name (but could be an image id, pinned image, or other syntax) is invalid. In your command:

 docker run -p 8888:8888 -v `pwd`/../src:/src -v `pwd`/../data:/data -w /src supervisely_anpr --rm -it bash

The image name "supervisely_anpr" is valid, so you need to look earlier in the command. In this case, the error is most likely from pwd outputting a path with a space in it. Everything after the space is no longer a parameter to -v and docker tries to parse it as the image name. The fix is to quote the volume parameters when you cannot guarantee it is free of spaces or other special characters.

When you do that, you'll encounter the next error, "executable not found". Everything after the image name is parsed as the command to run inside the container. In your case, it will try to run the command --rm -it bash which will almost certainly fail since --rm will no exist as a binary inside your image. You need to reorder the parameters to resolve that:

 docker run --rm -it -p 8888:8888 -v "`pwd`/../src:/src" -v "`pwd`/../data:/data" -w /src supervisely_anpr  bash

I've got some more details on these two errors and causes in my slides here:

Callback when DOM is loaded in react.js

What I have found is that simply wrapping code in the componentDidMount or componentDidUpdate with a setTimeout with a time of 0 milliseconds ensures that the browser DOM has been updated with the React changes before executing the setTimeout function.

Like this:

componentDidMount() {
    setTimeout(() => {
        $("myclass") //  $ is available here
    }, 0)

This puts the anonymous function on the JS Event Queue to run immediately after the currently running React stack frame has completed.

Can't bind to 'routerLink' since it isn't a known property

I totally chose another way for this method.


import { Router } from '@angular/router';
export class AppComponent {

        private router: Router,
    ) {}

    routerComment() {


<button (click)="routerComment()">Router Link </button>

android get real path by Uri.getPath()

This is what I do:

Uri selectedImageURI = data.getData();
imageFile = new File(getRealPathFromURI(selectedImageURI));


private String getRealPathFromURI(Uri contentURI) {
    String result;
    Cursor cursor = getContentResolver().query(contentURI, null, null, null, null);
    if (cursor == null) { // Source is Dropbox or other similar local file path
        result = contentURI.getPath();
    } else { 
        int idx = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA); 
        result = cursor.getString(idx);
    return result;

NOTE: managedQuery() method is deprecated, so I am not using it.

Last edit: Improvement. We should close cursor!!

Installing a plain plugin jar in Eclipse 3.5

Since the advent of p2, you should be using the dropins directory instead.

To be completely clear create "plugins" under "/dropins" and make sure to restart eclipse with the "-clean" option.

Change Orientation of Bluestack : portrait/landscape mode

Here are the step:

  1. Install the Nova theme in bluestack
  2. go into Nova setting -> look and feel -> screen orientation -> Force Portrait -> go to Home screen

You are done! :)

Notice: Undefined offset: 0 in

getAllVotes() isn't returning an array with the indexes 0 or 1. Make sure it's returning the data you want by calling var_dump() on the result.

How do I check to see if my array includes an object?

So the question is how can I check if my array already has a "horse" included so that I don't fill it with the same horse?

While the answers are concerned with looking through the array to see if a particular string or object exists, that's really going about it wrong, because, as the array gets larger, the search will take longer.

Instead, use either a Hash, or a Set. Both only allow a single instance of a particular element. Set will behave closer to an Array but only allows a single instance. This is a more preemptive approach which avoids duplication because of the nature of the container.

hash = {}
hash['a'] = nil
hash['b'] = nil
hash # => {"a"=>nil, "b"=>nil}
hash['a'] = nil
hash # => {"a"=>nil, "b"=>nil}

require 'set'
ary = [].to_set
ary << 'a'
ary << 'b'
ary # => #<Set: {"a", "b"}>
ary << 'a'
ary # => #<Set: {"a", "b"}>

Hash uses name/value pairs, which means the values won't be of any real use, but there seems to be a little bit of extra speed using a Hash, based on some tests.

require 'benchmark'
require 'set'

ALPHABET = ('a' .. 'z').to_a
N = 100_000 do |x|'Hash') { 
    N.times {
      h = {}
      ALPHABET.each { |i|
        h[i] = nil
  }'Array') {
    N.times {
      a =
      ALPHABET.each { |i|
        a << i

Which outputs:

            user     system      total        real
Hash    8.140000   0.130000   8.270000 (  8.279462)
Array  10.680000   0.120000  10.800000 ( 10.813385)

PHP Get Highest Value from Array

$a = array(10, 20, 52, 105, 56, 89, 96);
$b = 0;
foreach ($a as $key=>$val) {
    if ($val > $b) {
        $b = $val;
echo $b;

What is process.env.PORT in Node.js?

In many environments (e.g. Heroku), and as a convention, you can set the environment variable PORT to tell your web server what port to listen on.

So process.env.PORT || 3000 means: whatever is in the environment variable PORT, or 3000 if there's nothing there.

So you pass that to app.listen, or to app.set('port', ...), and that makes your server able to accept a "what port to listen on" parameter from the environment.

If you pass 3000 hard-coded to app.listen(), you're always listening on port 3000, which might be just for you, or not, depending on your requirements and the requirements of the environment in which you're running your server.

How can I delete all of my Git stashes at once?

There are two ways to delete a stash:

  1. If you no longer need a particular stash, you can delete it with: $ git stash drop <stash_id>.
  2. You can delete all of your stashes from the repo with: $ git stash clear.

Use both of them with caution, it maybe is difficult to revert the once deleted stashes.

Here is the reference article.

Java ElasticSearch None of the configured nodes are available

I spend days together to figure out this issue. I know its late but this might be helpful:

I resolved this issue by changing the compatible/stable version of:

Spring boot: 2.1.1
Spring Data Elastic: 2.1.4
Elastic: 6.4.0 (default)





You don't need to mention Elastic version. By default it is 6.4.0. But if you want to add a specific verison. Use below snippet inside properties tag and use the compatible version of Spring Boot and Spring Data(if required)


Also, I used the Rest High Level client in ElasticConfiguration :

public String host;

public int port;

@Bean(destroyMethod = "close")
public RestHighLevelClient restClient1() {
    final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
    RestClientBuilder builder = RestClient.builder(new HttpHost(host, port));
    RestHighLevelClient client = new RestHighLevelClient(builder);
    return client;

Important Note: Elastic use 9300 port to communicate between nodes and 9200 as HTTP client. In application properties:
elasticsearch.port=9200 (customized Elastic server) (customized cluster name)

From Postman, you can use:[indexname]/_search

Happy coding :)

TERM environment variable not set

You can see if it's really not set. Run the command set | grep TERM.

If not, you can set it like that: export TERM=xterm

Parse query string in JavaScript

Here is a fast and easy way of parsing query strings in JavaScript:

function getQueryVariable(variable) {
    var query =;
    var vars = query.split('&');
    for (var i = 0; i < vars.length; i++) {
        var pair = vars[i].split('=');
        if (decodeURIComponent(pair[0]) == variable) {
            return decodeURIComponent(pair[1]);
    console.log('Query variable %s not found', variable);

Now make a request to page.html?x=Hello:


(unicode error) 'unicodeescape' codec can't decode bytes in position 2-3: truncated \UXXXXXXXX escape

This error occurs because you are using a normal string as a path. You can use one of the three following solutions to fix your problem:

1: Just put r before your normal string it converts normal string to raw string:






Div Size Automatically size of content

I faced the same issue and I resolved it by using: max-width: fit-content;

Get ID from URL with jQuery

You could just use window.location.hash to grab the id.

var id = window.location.hash;

I don't think you will need that much code to achieve this.

How to implement the --verbose or -v option into a script?

I stole the logging code from virtualenv for a project of mine. Look in main() of to see how it's initialized. The code is sprinkled with logger.notify(),, logger.warn(), and the like. Which methods actually emit output is determined by whether virtualenv was invoked with -v, -vv, -vvv, or -q.

How to convert a 3D point into 2D perspective projection?

You might want to debug your system with spheres to determine whether or not you have a good field of view. If you have it too wide, the spheres with deform at the edges of the screen into more oval forms pointed toward the center of the frame. The solution to this problem is to zoom in on the frame, by multiplying the x and y coordinates for the 3 dimensional point by a scalar and then shrinking your object or world down by a similar factor. Then you get the nice even round sphere across the entire frame.

I'm almost embarrassed that it took me all day to figure this one out and I was almost convinced that there was some spooky mysterious geometric phenomenon going on here that demanded a different approach.

Yet, the importance of calibrating the zoom-frame-of-view coefficient by rendering spheres cannot be overstated. If you do not know where the "habitable zone" of your universe is, you will end up walking on the sun and scrapping the project. You want to be able to render a sphere anywhere in your frame of view an have it appear round. In my project, the unit sphere is massive compared to the region that I'm describing.

Also, the obligatory wikipedia entry: Spherical Coordinate System

.attr("disabled", "disabled") issue

Try this updated code :

  if (something) {
     console.log($target.prev("input")) // gives out the right object
     $target.toggleClass("open").prev("input").attr("disabled", "true");
     $target.toggleClass("open").prev("input").removeAttr("disabled"); //this works

Is there StartsWith or Contains in t sql with variables?


a) left(@edition, 15) = 'Express Edition'
b) charindex('Express Edition', @edition) = 1


charindex('Express Edition', @edition) >= 1


left function

set @isExpress = case when left(@edition, 15) = 'Express Edition' then 1 else 0 end

iif function (starting with SQL Server 2012)

set @isExpress = iif(left(@edition, 15) = 'Express Edition', 1, 0);

charindex function

set @isExpress = iif(charindex('Express Edition', @edition) = 1, 1, 0);

Adding 30 minutes to time formatted as H:i in PHP

What you need is a datetime which is 30 minutes later than your given datetime, and a datetime which is 30 minutes before a given datetime. In other words, you need a future datetime and a past datetime. Hence, classes that achieve that are called Future and Past. What data do they need to calculate what you need? Apparently, they must have a datetime relative to which to count those 30 minutes, and an interval itself -- 30 minutes in your case. Thus, the desired datetime looks like the following:

use Meringue\ISO8601DateTime\FromCustomFormat as DateTimeCreatedFromCustomFormat;

(new Future(
    new DateTimeCreatedFromCustomFormat('H:i', '10:00'),
    new NMinutes(30)

If you want to format it somehow, you can do:

use Meringue\ISO8601DateTime\FromCustomFormat as DateTimeCreatedFromCustomFormat;

(new ISO8601Formatted(
    new Future(
        new DateTimeCreatedFromCustomFormat('H:i', '10:00'),
        new NMinutes(30)

It's more verbose, but I guess it's way less cryptic than built-in php functions.

If you liked this approach, you can learn some more about the meringue library used in this example, and the overall approach.

Jenkins - how to build a specific branch

I can see many good answers to the question, but I still would like to share this method, by using Git parameter as follows:

Add Git parameter

When building the pipeline you will be asked to choose the branch: Choose branch to build

After that through the groovy code you could specify the branch you want to clone:

git branch:BRANCH[7..-1], url: '' , credentialsId: 'github' 

Note that I'm using a slice from 7 to the last character to shrink "origin/" and get the branch name.

Also in case you configured a webhooks trigger it still work and it will take the default branch you specified(master in our case).

less than 10 add 0 to number

$('#detect').html( toGeo(apX, screenX)  + latT +', '+ toGeo(apY, screenY) + lonT  );

function toGeo(d, max) {
   var c = '';

   var r = d/max * 180;
   var deg = Math.floor(r);
   if(deg < 10) deg = '0' + deg;
   c += deg + "° ";

   r = (r - deg) * 60;
   var min = Math.floor(r);
   if(min < 10) min = '0' + min;
   c += min + "' ";

   r = (r - min) * 60;
   var sec = Math.floor(r);
   if(sec < 10) sec = '0' + sec;
   c += sec + """;

   return c;

Indentation Error in Python

You are mixing tabs and spaces.

Find the exact location with:

python -tt

and replace all tabs with spaces. You really want to configure your text editor to only insert spaces for tabs as well.

ArrayIndexOutOfBoundsException when using the ArrayList's iterator

Am I doing that right, as far as iterating through the Arraylist goes?

No: by calling iterator twice in each iteration, you're getting new iterators all the time.

The easiest way to write this loop is using the for-each construct:

for (String s : arrayList)
    if (s.equals(value))
        // ...

As for

java.lang.ArrayIndexOutOfBoundsException: -1

You just tried to get element number -1 from an array. Counting starts at zero.

Cannot find either column "dbo" or the user-defined function or aggregate "dbo.Splitfn", or the name is ambiguous

You need to treat a table valued udf like a table, eg JOIN it

select Emp_Id 
from Employee E JOIN dbo.Splitfn(@Id,',') CSV ON E.Emp_Id = CSV.items 

Android Open External Storage directory(sdcard) for storing file

hope it's worked for you:

File yourFile = new File(Environment.getExternalStorageDirectory(), "textarabics.txt");

This will give u sdcard path:

File path = Environment.getExternalStorageDirectory();

Try this:

String pathName = "/mnt/";

or try this:

String pathName = "/storage/";

How to write logs in text file when using java.util.logging.Logger

import org.apache.log4j.Appender;
import org.apache.log4j.FileAppender;
import org.apache.log4j.Logger;
import org.apache.log4j.SimpleLayout;

 * @author Kiran
public class MyLogger {

    public MyLogger() {

    public static void main(String[] args) {
        Logger logger = Logger.getLogger("MyLog");
        Appender fh = null;
        try {
            fh = new FileAppender(new SimpleLayout(), "MyLogFile.log");
            fh.setLayout(new SimpleLayout());
  "My first log");
        } catch (SecurityException e) {
        } catch (IOException e) {
        }"Hi How r u?");

Oracle "(+)" Operator

That's Oracle specific notation for an OUTER JOIN, because the ANSI-89 format (using a comma in the FROM clause to separate table references) didn't standardize OUTER joins.

The query would be re-written in ANSI-92 syntax as:

   SELECT ...
     FROM a

This link is pretty good at explaining the difference between JOINs.

It should also be noted that even though the (+) works, Oracle recommends not using it:

Oracle recommends that you use the FROM clause OUTER JOIN syntax rather than the Oracle join operator. Outer join queries that use the Oracle join operator (+) are subject to the following rules and restrictions, which do not apply to the FROM clause OUTER JOIN syntax:

How to convert file to base64 in JavaScript?

const fileInput = document.querySelector('input');

fileInput.addEventListener('change', (e) => {

// get a reference to the file
const file =[0];

// encode the file using the FileReader API
const reader = new FileReader();
reader.onloadend = () => {

    // use a regex to remove data url part
    const base64String = reader.result
        .replace('data:', '')
        .replace(/^.+,/, '');

    // log to console
    // logs wL2dvYWwgbW9yZ...

How to copy file from host to container using Dockerfile

Use COPY command like this:

COPY foo.txt /data/foo.txt
# where foo.txt is the relative path on host
# and /data/foo.txt is the absolute path in the image

read more details for COPY in the official documentation

An alternative would be to use ADD but this is not the best practise if you dont want to use some advanced features of ADD like decompression of tar.gz files.If you still want to use ADD command, do it like this:

ADD abc.txt /data/abc.txt
# where abc.txt is the relative path on host
# and /data/abc.txt is the absolute path in the image

read more details for ADD in the official documentation

Android: Rotate image in imageview by an angle

Rotate an image in android with delay:

imgSplash.animate().rotationBy(360f).setDuration(3000).setInterpolator(new LinearInterpolator()).start();

Behaviour of increment and decrement operators in Python

While the others answers are correct in so far as they show what a mere + usually does (namely, leave the number as it is, if it is one), they are incomplete in so far as they don't explain what happens.

To be exact, +x evaluates to x.__pos__() and ++x to x.__pos__().__pos__().

I could imagine a VERY weird class structure (Children, don't do this at home!) like this:

class ValueKeeper(object):
    def __init__(self, value): self.value = value
    def __str__(self): return str(self.value)

class A(ValueKeeper):
    def __pos__(self):
        print 'called A.__pos__'
        return B(self.value - 3)

class B(ValueKeeper):
    def __pos__(self):
        print 'called B.__pos__'
        return A(self.value + 19)

x = A(430)
print x, type(x)
print +x, type(+x)
print ++x, type(++x)
print +++x, type(+++x)

Get current date, given a timezone in PHP?

date_default_timezone_set('GMT-5');//Set New York timezone
$today = date("F j, Y")

Ruby replace string with captured regex pattern

Try '\1' for the replacement (single quotes are important, otherwise you need to escape the \):

"foo".gsub(/(o+)/, '\1\1\1')
#=> "foooooo"

But since you only seem to be interested in the capture group, note that you can index a string with a regex:

#=> "oo"
"Z_123: foobar"[/^Z_.*(?=:)/]
#=> "Z_123"

Round number to nearest integer

round(value,significantDigit) is the ordinary solution, however this does not operate as one would expect from a math perspective when round values ending in 5. If the 5 is in the digit just after the one you're rounded to, these values are only sometimes rounded up as expected (i.e. 8.005 rounding to two decimal digits gives 8.01). For certain values due to the quirks of floating point math, they are rounded down instead!


>>> round(1.0005,3)
>>> round(2.0005,3)
>>> round(3.0005,3)
>>> round(4.0005,3)
>>> round(1.005,2)
>>> round(5.005,2)
>>> round(6.005,2)
>>> round(7.005,2)
>>> round(3.005,2)
>>> round(8.005,2)


Assuming your intent is to do the traditional rounding for statistics in the sciences, this is a handy wrapper to get the round function working as expected needing to import extra stuff like Decimal.

>>> round(0.075,2)


>>> round(0.075+10**(-2*5),2)


Aha! So based on this we can make a function...

def roundTraditional(val,digits):
   return round(val+10**(-len(str(val))-1), digits)

Basically this adds a value guaranteed to be smaller than the least given digit of the string you're trying to use round on. By adding that small quantity it preserve's round's behavior in most cases, while now ensuring if the digit inferior to the one being rounded to is 5 it rounds up, and if it is 4 it rounds down.

The approach of using 10**(-len(val)-1) was deliberate, as it the largest small number you can add to force the shift, while also ensuring that the value you add never changes the rounding even if the decimal . is missing. I could use just 10**(-len(val)) with a condiditional if (val>1) to subtract 1 more... but it's simpler to just always subtract the 1 as that won't change much the applicable range of decimal numbers this workaround can properly handle. This approach will fail if your values reaches the limits of the type, this will fail, but for nearly the entire range of valid decimal values it should work.

You can also use the decimal library to accomplish this, but the wrapper I propose is simpler and may be preferred in some cases.

Edit: Thanks Blckknght for pointing out that the 5 fringe case occurs only for certain values. Also an earlier version of this answer wasn't explicit enough that the odd rounding behavior occurs only when the digit immediately inferior to the digit you're rounding to has a 5.

Select row on click react-table

The answer you selected is correct, however if you are using a sorting table it will crash since rowInfo will became undefined as you search, would recommend using this function instead

                getTrGroupProps={(state, rowInfo, column, instance) => {
                    if (rowInfo !== undefined) {
                        return {
                            onClick: (e, handleOriginal) => {
                              console.log('It was in this row:', rowInfo)
                                  firstNameState: rowInfo.row.firstName,
                                  lastNameState: rowInfo.row.lastName,
                            style: {
                                cursor: 'pointer',
                                background: === this.state.selectedIndex ? '#00afec' : 'white',
                                color: === this.state.selectedIndex ? 'white' : 'black'

How are Anonymous inner classes used in Java?

Yes, anonymous inner classes is definitely one of the advantages of Java.

With an anonymous inner class you have access to final and member variables of the surrounding class, and that comes in handy in listeners etc.

But a major advantage is that the inner class code, which is (at least should be) tightly coupled to the surrounding class/method/block, has a specific context (the surrounding class, method, and block).

Passing an Object from an Activity to a Fragment

Get reference from the following example.

1. In fragment: Create a reference variable for the class whose object you want in the fragment. Simply create a setter method for the reference variable and call the setter before replacing fragment from the activity.

 MyEmployee myEmp;
 public void setEmployee(MyEmployee myEmp)
     this.myEmp = myEmp;

2. In activity:

   //we need to pass object myEmp to fragment myFragment

    MyEmployee myEmp = new MyEmployee();

    MyFragment myFragment = new MyFragment();


    FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    ft.replace(, myFragment);

Get average color of image via Javascript

As pointed out in other answers, often what you really want the dominant color as opposed to the average color which tends to be brown. I wrote a script that gets the most common color and posted it on this gist

What's the best way to send a signal to all members of a process group?

If you want to kill a process by name:

killall -9 -g someprocessname


pgrep someprocessname | xargs pkill -9 -g

How to activate virtualenv?

Create your own Python virtual environment called <Your Env _name >:. I have given it VE.

git clone
python VE

To activate your new virtual environment, run (notice it's not ./ here):

. VE/bin/activate

Sample output (note prompt changed):


Once your virtual environment is set, you can remove the Virtualenv repo.

How to give spacing between buttons using bootstrap

You can achieved by use bootstrap Spacing. Bootstrap Spacing includes a wide range of shorthand responsive margin and padding. In below example mr-1 set the margin or padding to $spacer * .25.


<button class="btn btn-outline-primary mr-1" href="#">Sign up</button>
<button class="btn btn-outline-primary" href="#">Login</button>

You can read more at Bootstrap Spacing.

Android Fragment handle back button press

When you are transitioning between Fragments, call addToBackStack() as part of your FragmentTransaction:

FragmentTransaction tx = fragmentManager.beginTransation();
tx.replace(, new MyFragment() ).addToBackStack( "tag" ).commit();

If you require more detailed control (i.e. when some Fragments are visible, you want to suppress the back key) you can set an OnKeyListener on the parent view of your fragment:

//You need to add the following line for this solution to work; thanks skayred
fragment.getView().setOnKeyListener( new OnKeyListener()
    public boolean onKey( View v, int keyCode, KeyEvent event )
        if( keyCode == KeyEvent.KEYCODE_BACK )
            return true;
        return false;
} );

Why shouldn't I use PyPy over CPython if PyPy is 6.3 times faster?

Q: If PyPy can solve these great challenges (speed, memory consumption, parallelism) in comparison to CPython, what are its weaknesses that are preventing wider adoption?

A: First, there is little evidence that the PyPy team can solve the speed problem in general. Long-term evidence is showing that PyPy runs certain Python codes slower than CPython and this drawback seems to be rooted very deeply in PyPy.

Secondly, the current version of PyPy consumes much more memory than CPython in a rather large set of cases. So PyPy didn't solve the memory consumption problem yet.

Whether PyPy solves the mentioned great challenges and will in general be faster, less memory hungry, and more friendly to parallelism than CPython is an open question that cannot be solved in the short term. Some people are betting that PyPy will never be able to offer a general solution enabling it to dominate CPython 2.7 and 3.3 in all cases.

If PyPy succeeds to be better than CPython in general, which is questionable, the main weakness affecting its wider adoption will be its compatibility with CPython. There also exist issues such as the fact that CPython runs on a wider range of CPUs and OSes, but these issues are much less important compared to PyPy's performance and CPython-compatibility goals.

Q: Why can't I do drop in replacement of CPython with PyPy now?

A: PyPy isn't 100% compatible with CPython because it isn't simulating CPython under the hood. Some programs may still depend on CPython's unique features that are absent in PyPy such as C bindings, C implementations of Python object&methods, or the incremental nature of CPython's garbage collector.

Python SQLite: database is locked

Even when I just had one writer and one reader, my issue was that one of the reads was taking too long: longer than the stipulated timeout of 5 seconds. So the writer timed out and caused the error.

So, be careful when reading all entries from a database especially from one which the size of the table grows over time.

java get file size efficiently

Well, I tried to measure it up with the code below:

For runs = 1 and iterations = 1 the URL method is fastest most times followed by channel. I run this with some pause fresh about 10 times. So for one time access, using the URL is the fastest way I can think of:

LENGTH sum: 10626, per Iteration: 10626.0

CHANNEL sum: 5535, per Iteration: 5535.0

URL sum: 660, per Iteration: 660.0

For runs = 5 and iterations = 50 the picture draws different.

LENGTH sum: 39496, per Iteration: 157.984

CHANNEL sum: 74261, per Iteration: 297.044

URL sum: 95534, per Iteration: 382.136

File must be caching the calls to the filesystem, while channels and URL have some overhead.


import java.util.*;

public enum FileSizeBench {

    LENGTH {
        public long getResult() throws Exception {
            File me = new File(FileSizeBench.class.getResource(
            return me.length();
        public long getResult() throws Exception {
            FileInputStream fis = null;
            try {
                File me = new File(FileSizeBench.class.getResource(
                fis = new FileInputStream(me);
                return fis.getChannel().size();
            } finally {
    URL {
        public long getResult() throws Exception {
            InputStream stream = null;
            try {
                URL url = FileSizeBench.class
                stream = url.openStream();
                return stream.available();
            } finally {

    public abstract long getResult() throws Exception;

    public static void main(String[] args) throws Exception {
        int runs = 5;
        int iterations = 50;

        EnumMap<FileSizeBench, Long> durations = new EnumMap<FileSizeBench, Long>(FileSizeBench.class);

        for (int i = 0; i < runs; i++) {
            for (FileSizeBench test : values()) {
                if (!durations.containsKey(test)) {
                    durations.put(test, 0l);
                long duration = testNow(test, iterations);
                durations.put(test, durations.get(test) + duration);
                // System.out.println(test + " took: " + duration + ", per iteration: " + ((double)duration / (double)iterations));

        for (Map.Entry<FileSizeBench, Long> entry : durations.entrySet()) {
            System.out.println(entry.getKey() + " sum: " + entry.getValue() + ", per Iteration: " + ((double)entry.getValue() / (double)(runs * iterations)));


    private static long testNow(FileSizeBench test, int iterations)
            throws Exception {
        long result = -1;
        long before = System.nanoTime();
        for (int i = 0; i < iterations; i++) {
            if (result == -1) {
                result = test.getResult();
            } else if ((result = test.getResult()) != result) {
                 throw new Exception("variance detected!");
        return (System.nanoTime() - before) / 1000;


C++ - How to append a char to char*?

The function name does not reflect the semantic of the function. In fact you do not append a character. You create a new character array that contains the original array plus the given character. So if you indeed need a function that appends a character to a character array I would write it the following way

bool AppendCharToCharArray( char *array, size_t n, char c )
    size_t sz = std::strlen( array );

    if ( sz + 1 < n ) 
        array[sz] = c;
        array[sz + 1] = '\0';

    return ( sz + 1 < n );

If you need a function that will contain a copy of the original array plus the given character then it could look the following way

char * CharArrayPlusChar( const char *array, char c )
    size_t sz = std::strlen( array );
    char *s = new char[sz + 2];

    std::strcpy( s, array );
    s[sz] = c;
    s[sz + 1] = '\0';

    return ( s );

Programmatically change input type of the EditText from PASSWORD to NORMAL & vice versa

password.setInputType(InputType.TYPE_CLASS_TEXT | inputType.TYPE_TEXT_VARIATION_PASSWORD);

Method above didn't really work for me. Answer below works for 2.2 sdk.


Set inputType for an EditText?

Is there a foreach in MATLAB? If so, how does it behave if the underlying data changes?

I think this is what the OP really wants:

array = -1:0.1:10

for i=1:numel(array)

What is the best way to left align and right align two div tags?

You can do it with few lines of CSS code. You can align all div's which you want to appear next to each other to right.

<div class="div_r">First Element</div>
<div class="div_r">Second Element</div>


What does set -e mean in a bash script?

Script 1: without setting -e
decho "hi"
echo "hello"
This will throw error in decho and program continuous to next line

Script 2: With setting -e
set -e
decho "hi" 
echo "hello"
# Up to decho "hi" shell will process and program exit, it will not proceed further

Allow multiple roles to access controller action

Better code with adding a subclass AuthorizeRole.cs

    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, Inherited = true, AllowMultiple = true)]
    class AuthorizeRoleAttribute : AuthorizeAttribute
        public AuthorizeRoleAttribute(params Rolenames[] roles)
            this.Roles = string.Join(",", roles.Select(r => Enum.GetName(r.GetType(), r)));
        protected override void HandleUnauthorizedRequest(System.Web.Mvc.AuthorizationContext filterContext)
            if (filterContext.HttpContext.Request.IsAuthenticated)
                filterContext.Result = new RedirectToRouteResult(
                new RouteValueDictionary {
                  { "action", "Unauthorized" },
                  { "controller", "Home" },
                  { "area", "" }
                filterContext.Result = new RedirectToRouteResult(
                new RouteValueDictionary {
                  { "action", "Login" },
                  { "controller", "Account" },
                  { "area", "" },
                  { "returnUrl", HttpContext.Current.Request.Url }

How to use this


public ActionResult Index()
return View();

Trying to detect browser close event

<script type="text/javascript">
window.addEventListener("beforeunload", function (e) {

  var confirmationMessage = "Are you sure you want to leave this page without placing the order ?";
  (e || window.event).returnValue = confirmationMessage;
  return confirmationMessage;


Please try this code, this is working fine for me. This custom message is coming into Chrome browser but in Mozilla this message is not showing.

"The underlying connection was closed: An unexpected error occurred on a send." With SSL Certificate

The below code solved my problem :

request.ProtocolVersion = HttpVersion.Version10; // THIS DOES THE TRICK
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;

C++ printing spaces or tabs given a user input integer

Simply add spaces for { 2 3 4 5 6 } like these:


    cout<<" "<<n;    //n is the element to print !

cout<<" }";

Sending HTML Code Through JSON


$data = "<html>....";

Then you should use AJAX to retrieve the data and do what you want with it. I suggest using JQuery:

Python memory usage of numpy arrays

You can use array.nbytes for numpy arrays, for example:

>>> import numpy as np
>>> from sys import getsizeof
>>> a = [0] * 1024
>>> b = np.array(a)
>>> getsizeof(a)
>>> b.nbytes

Array Size (Length) in C#

You can look at the documentation for Array to find out the answer to this question.

In this particular case you probably need Length:

int sizeOfArray = array.Length;

But since this is such a basic question and you no doubt have many more like this, rather than just telling you the answer I'd rather tell you how to find the answer yourself.

Visual Studio Intellisense

When you type the name of a variable and press the . key it shows you a list of all the methods, properties, events, etc. available on that object. When you highlight a member it gives you a brief description of what it does.

Press F1

If you find a method or property that might do what you want but you're not sure, you can move the cursor over it and press F1 to get help. Here you get a much more detailed description plus links to related information.


The search terms size of array in C# gives many links that tells you the answer to your question and much more. One of the most important skills a programmer must learn is how to find information. It is often faster to find the answer yourself, especially if the same question has been asked before.

Use a tutorial

If you are just beginning to learn C# you will find it easier to follow a tutorial. I can recommend the C# tutorials on MSDN. If you want a book, I'd recommend Essential C#.

Stack Overflow

If you're not able to find the answer on your own, please feel free to post the question on Stack Overflow. But we appreciate it if you show that you have taken the effort to find the answer yourself first.

Find out the history of SQL queries

For recent SQL:

select * from v$sql

For history:

select * from dba_hist_sqltext

Can scrapy be used to scrape dynamic content from websites that are using AJAX?

I was using a custom downloader middleware, but wasn't very happy with it, as I didn't manage to make the cache work with it.

A better approach was to implement a custom download handler.

There is a working example here. It looks like this:

# encoding: utf-8
from __future__ import unicode_literals

from scrapy import signals
from scrapy.signalmanager import SignalManager
from scrapy.responsetypes import responsetypes
from scrapy.xlib.pydispatch import dispatcher
from selenium import webdriver
from six.moves import queue
from twisted.internet import defer, threads
from twisted.python.failure import Failure

class PhantomJSDownloadHandler(object):

    def __init__(self, settings):
        self.options = settings.get('PHANTOMJS_OPTIONS', {})

        max_run = settings.get('PHANTOMJS_MAXRUN', 10)
        self.sem = defer.DeferredSemaphore(max_run)
        self.queue = queue.LifoQueue(max_run)

        SignalManager(dispatcher.Any).connect(self._close, signal=signals.spider_closed)

    def download_request(self, request, spider):
        """use semaphore to guard a phantomjs pool"""
        return, request, spider)

    def _wait_request(self, request, spider):
            driver = self.queue.get_nowait()
        except queue.Empty:
            driver = webdriver.PhantomJS(**self.options)

        # ghostdriver won't response when switch window until page is loaded
        dfd = threads.deferToThread(lambda: driver.switch_to.window(driver.current_window_handle))
        dfd.addCallback(self._response, driver, spider)
        return dfd

    def _response(self, _, driver, spider):
        body = driver.execute_script("return document.documentElement.innerHTML")
        if body.startswith("<head></head>"):  # cannot access response header in Selenium
            body = driver.execute_script("return document.documentElement.textContent")
        url = driver.current_url
        respcls = responsetypes.from_args(url=url, body=body[:100].encode('utf8'))
        resp = respcls(url=url, body=body, encoding="utf-8")

        response_failed = getattr(spider, "response_failed", None)
        if response_failed and callable(response_failed) and response_failed(resp, driver):
            return defer.succeed(resp)

    def _close(self):
        while not self.queue.empty():
            driver = self.queue.get_nowait()

Suppose your scraper is called "scraper". If you put the mentioned code inside a file called on the root of the "scraper" folder, then you could add to your

    'http': 'scraper.handlers.PhantomJSDownloadHandler',
    'https': 'scraper.handlers.PhantomJSDownloadHandler',

And voilà, the JS parsed DOM, with scrapy cache, retries, etc.

ShowAllData method of Worksheet class failed

The simple way to avoid this is not to use the worksheet method ShowAllData

Autofilter has the same ShowAllData method which doesn't throw an error when the filter is enabled but no filter is set

If ActiveSheet.AutoFilterMode Then ActiveSheet.AutoFilter.ShowAllData

HTML 5 video recording and storing a stream

RecordRTC: WebRTC audio/video recording

  • Audio recording both for Chrome and Firefox
  • Video/Gif recording for Chrome; (Firefox has a little bit issues, will be recovered soon)

Demo :

Creating .webm video from getUserMedia()

Demo :

Capturing Audio & Video in HTML5

How a thread should close itself in Java?

If you simply call interrupt(), the thread will not automatically be closed. Instead, the Thread might even continue living, if isInterrupted() is implemented accordingly. The only way to guaranteedly close a thread, as asked for by OP, is


Method is deprecated, however.

Calling return only returns from the current method. This only terminates the thread if you're at its top level.

Nevertheless, you should work with interrupt() and build your code around it.

Woocommerce, get current product id

Since WooCommerce 2.2 you are able to simply use the wc_get_product Method. As an argument you can pass the ID or simply leave it empty if you're already in the loop.


OR with 2 lines

$product = wc_get_product();
$id = $product->get_id();

What is the use of DesiredCapabilities in Selenium WebDriver?

Desired capabilities comes in handy while doing remote or parallel execution using selenium grid. We will be parametrizing the browser details and passing in to selenium server using desired capabilities class.

Another usage is, test automation using Appium as shown below

// Created object of DesiredCapabilities class. 
DesiredCapabilities capabilities = new DesiredCapabilities(); 
// Set android deviceName desired capability. Set your device name. 
capabilities.setCapability("deviceName", "your Device Name"); 
// Set BROWSER_NAME desired capability. 
capabilities.setCapability(CapabilityType.BROWSER_NAME, "Chrome"); 
// Set android VERSION desired capability. Set your mobile device's OS version. 
capabilities.setCapability(CapabilityType.VERSION, "5.1"); 
// Set android platformName desired capability. It's Android in our case here. 
capabilities.setCapability("platformName", "Android"); 

How can I de-install a Perl module installed via `cpan`?

There are scripts on CPAN which attempt to uninstall modules:

ExtUtils::Packlist shows sample module removing code, modrm.

Sending private messages to user

If your looking to type up the message and then your bot will send it to the user, here is the code. It also has a role restriction on it :)

case 'dm':
  mentiondm = message.mentions.users.first();;
  if (!message.member.roles.cache.some(role => === "Owner")) return'Beep Boing: This command is way too powerful for you to use!');
  if (mentiondm == null) return message.reply('Beep Boing: No user to send message to!');
  mentionMessage = message.content.slice(3);
  console.log('Message Sent!')

Export multiple classes in ES6 modules

Hope this helps:

// Export (file name: my-functions.js)
export const MyFunction1 = () => {}
export const MyFunction2 = () => {}
export const MyFunction3 = () => {}

// if using `eslint` (airbnb) then you will see warning, so do this:
const MyFunction1 = () => {}
const MyFunction2 = () => {}
const MyFunction3 = () => {}

export {MyFunction1, MyFunction2, MyFunction3};

// Import
import * as myFns from "./my-functions";


// OR Import it as Destructured
import { MyFunction1, MyFunction2, MyFunction3 } from "./my-functions";

// AND you can use it like below with brackets (Parentheses) if it's a function 
// AND without brackets if it's not function (eg. variables, Objects or Arrays)  

How to replace negative numbers in Pandas Data Frame by zero

Another succinct way of doing this is pandas.DataFrame.clip.

For example:

import pandas as pd

In [20]: df = pd.DataFrame({'a': [-1, 100, -2]})

In [21]: df
0   -1
1  100
2   -2

In [22]: df.clip(lower=0)
0    0
1  100
2    0

There's also df.clip_lower(0).

Webdriver and proxy server for firefox

I just had fun with this issue for a couple of days and it was hard for me to find an answer for HTTPS, so here's my take, for Java:

    FirefoxProfile profile = new FirefoxProfile();
    profile.setPreference("network.proxy.type", 1);
    profile.setPreference("network.proxy.http", "");
    profile.setPreference("network.proxy.http_port", 8080);
    profile.setPreference("network.proxy.ssl", "");
    profile.setPreference("network.proxy.ssl_port", 8080);
    driver = new FirefoxDriver(profile);

Gotchas here: enter just the domain and not, the property name is .ssl and not .https

I'm now having even more fun trying to get it to accept my self signed certificates...

scipy.misc module has no attribute imread?

Install the Pillow library by following commands:

pip install pillow

Note, the selected answer has been outdated. See the docs of SciPy

Note that Pillow ( is not a dependency of SciPy, but the image manipulation functions indicated in the list below are not available without it.

How do I launch the Android emulator from the command line?

open CMD

  1. Open Command Prompt
  2. type the path of emulator in my case

C:\adt-bundle-windows-x86_64-20140702\sdk\tools enter image description here

  1. write "emulator -avd emulatorname" in my case

emulator -avd AdilVD

enter image description here

Default username password for Tomcat Application Manager

To reset your keyring.

  1. Go into your home folder.

  2. Press ctrl & h to show your hidden folders.

  3. Now look in your .gnome2/keyrings directory.

  4. Find the default.keyring file.

  5. Move that file to a different folder.

  6. Once done, reboot your computer.

How to use Class<T> in Java?

From the Java Documentation:

[...] More surprisingly, class Class has been generified. Class literals now function as type tokens, providing both run-time and compile-time type information. This enables a style of static factories exemplified by the getAnnotation method in the new AnnotatedElement interface:

<T extends Annotation> T getAnnotation(Class<T> annotationType); 

This is a generic method. It infers the value of its type parameter T from its argument, and returns an appropriate instance of T, as illustrated by the following snippet:

Author a = Othello.class.getAnnotation(Author.class);

Prior to generics, you would have had to cast the result to Author. Also you would have had no way to make the compiler check that the actual parameter represented a subclass of Annotation. [...]

Well, I never had to use this kind of stuff. Anyone?

Split (explode) pandas dataframe string entry to separate rows

I have been struggling with out-of-memory experience using various way to explode my lists so I prepared some benchmarks to help me decide which answers to upvote. I tested five scenarios with varying proportions of the list length to the number of lists. Sharing the results below:

Time: (less is better, click to view large version)


Peak memory usage: (less is better)

Peak memory usage


  • @MaxU's answer (update 2), codename concatenate offers the best speed in almost every case, while keeping the peek memory usage low,
  • see @DMulligan's answer (codename stack) if you need to process lots of rows with relatively small lists and can afford increased peak memory,
  • the accepted @Chang's answer works well for data frames that have a few rows but very large lists.

Full details (functions and benchmarking code) are in this GitHub gist. Please note that the benchmark problem was simplified and did not include splitting of strings into the list - which most solutions performed in a similar fashion.

How to create Gmail filter searching for text only at start of subject line?

I was wondering how to do this myself; it seems Gmail has since silently implemented this feature. I created the following filter:

Matches: subject:([test])
Do this: Skip Inbox

And then I sent a message with the subject

[test] foo

And the message was archived! So it seems all that is necessary is to create a filter for the subject prefix you wish to handle.

JPA & Criteria API - Select only specific columns

First of all, I don't really see why you would want an object having only ID and Version, and all other props to be nulls. However, here is some code which will do that for you (which doesn't use JPA Em, but normal Hibernate. I assume you can find the equivalence in JPA or simply obtain the Hibernate Session obj from the em delegate Accessing Hibernate Session from EJB using EntityManager ):

List<T> results = session.createCriteria(entityClazz)
    .setProjection( Projections.projectionList()
        .add( Property.forName("ID") )
        .add( Property.forName("VERSION") )

This will return a list of Objects having their ID and Version set and all other props to null, as the aliasToBean transformer won't be able to find them. Again, I am uncertain I can think of a situation where I would want to do that.

What do parentheses surrounding an object/function/class declaration mean?

A few considerations on the subject:

  • The parenthesis:

    The browser (engine/parser) associates the keyword function with

    [optional name]([optional parameters]){...code...}

    So in an expression like function(){}() the last parenthesis makes no sense.

    Now think at

    name=function(){} ; name() !?

Yes, the first pair of parenthesis force the anonymous function to turn into a variable (stored expression) and the second launches evaluation/execution, so ( function(){} )() makes sense.

  • The utility: ?

    1. For executing some code on load and isolate the used variables from the rest of the page especially when name conflicts are possible;

    2. Replace eval("string") with

      (new Function("string"))()

    3. Wrap long code for " =?: " operator like:

      result = exp_to_test ? (function(){... long_code ...})() : (function(){...})();

Installing mcrypt extension for PHP on OSX Mountain Lion

I tend to use Homebrew on Mac. It will install and configure all the stuff for you.

Then you should be able to install it with brew install mcrypt php53-mcrypt and it'll Just Work (tm).

You can replace the 53 with whatever version of PHP you're using, such as php56-mcrypt or php70-mcrypt. If you're not sure, use brew search php.

Do also remember that if you are using the built in Mac PHP it's installed into /usr/bin you can see which php you are using with which php at the terminal and it'll return the path.

How to generate a random int in C?

You can use the concept of a dangling pointer.

A pointer pointing to a memory location that has been deleted (or freed) is called dangling pointer.

It will show random values while printing.

How to remove the arrow from a select element in Firefox

Since Firefox 35, "-moz-appearance:none" that you already wrote in your code, finally remove arrow button as desired.

It was a bug solved since that version.

Authenticating in PHP using LDAP through Active Directory

For those looking for a complete example check out

I have tested this connecting to both Windows Server 2003 and Windows Server 2008 R2 domain controllers from a Windows Server 2003 Web Server (IIS6) and from a windows server 2012 enterprise running IIS 8.

Initializing a struct to 0

See §6.7.9 Initialization:

21 If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration.

So, yes both of them work. Note that in C99 a new way of initialization, called designated initialization can be used too:

myStruct _m1 = {.c2 = 0, .c1 = 1};

How can I parse a YAML file from a Linux shell script?

Moving my answer from How to convert a json response into yaml in bash, since this seems to be the authoritative post on dealing with YAML text parsing from command line.

I would like to add details about the yq YAML implementation. Since there are two implementations of this YAML parser lying around, both having the name yq, it is hard to differentiate which one is in use, without looking at the implementations' DSL. There two available implementations are

  1. kislyuk/yq - The more often talked about version, which is a wrapper over jq, written in Python using the PyYAML library for YAML parsing
  2. mikefarah/yq - A Go implementation, with its own dynamic DSL using the go-yaml v3 parser.

Both are available for installation via standard installation package managers on almost all major distributions

  1. kislyuk/yq - Installation instructions
  2. mikefarah/yq - Installation instructions

Both the versions have some pros and cons over the other, but a few valid points to highlight (adopted from their repo instructions)


  1. Since the DSL is the adopted completely from jq, for users familiar with the latter, the parsing and manipulation becomes quite straightforward
  2. Supports mode to preserve YAML tags and styles, but loses comments during the conversion. Since jq doesn't preserve comments, during the round-trip conversion, the comments are lost.
  3. As part of the package, XML support is built in. An executable, xq, which transcodes XML to JSON using xmltodict and pipes it to jq, on which you can apply the same DSL to perform CRUD operations on the objects and round-trip the output back to XML.
  4. Supports in-place edit mode with -i flag (similar to sed -i)


  1. Prone to frequent changes in DSL, migration from 2.x - 3.x
  2. Rich support for anchors, styles and tags. But lookout for bugs once in a while
  3. A relatively simple Path expression syntax to navigate and match yaml nodes
  4. Supports YAML->JSON, JSON->YAML formatting and pretty printing YAML (with comments)
  5. Supports in-place edit mode with -i flag (similar to sed -i)
  6. Supports coloring the output YAML with -C flag (not applicable for JSON output) and indentation of the sub elements (default at 2 spaces)
  7. Supports Shell completion for most shells - Bash, zsh (because of powerful support from spf13/cobra used to generate CLI flags)

My take on the following YAML (referenced in other answer as well) with both the versions

root_key1: this is value one
root_key2: "this is value two"

  state: liquid
    best_served: hot
    colour: brown
    best_served: cold
    colour: orange

  state: solid
    best_served: warm

root_key_3: this is value three

Various actions to be performed with both the implementations (some frequently used operations)

  1. Modifying node value at root level - Change value of root_key2
  2. Modifying array contents, adding value - Add property to coffee
  3. Modifying array contents, deleting value - Delete property from orange_juice
  4. Printing key/value pairs with paths - For all items under food

Using kislyuk/yq

  1. yq -y '.root_key2 |= "this is a new value"' yaml
  2. yq -y ' += { time: "always"}' yaml
  3. yq -y 'del(.drink.orange_juice.colour)' yaml
  4. yq -r '.food|paths(scalars) as $p | [($p|join(".")), (getpath($p)|tojson)] | @tsv' yaml

Which is pretty straightforward. All you need is to transcode jq JSON output back into YAML with the -y flag.

Using mikefarah/yq

  1.  yq w yaml root_key2 "this is a new value"
  2.  yq w yaml "always"
  3.  yq d yaml drink.orange_juice.colour
  4.  yq r yaml --printMode pv "food.**"

As of today Dec 21st 2020, yq v4 is in beta and supports much powerful path expressions and supports DSL similar to using jq. Read the transition notes - Upgrading from V3

Parse (split) a string in C++ using string delimiter (standard C++)

std::vector<std::string> parse(std::string str,std::string delim){
    std::vector<std::string> tokens;
    char *str_c = strdup(str.c_str()); 
    char* token = NULL;

    token = strtok(str_c, delim.c_str()); 
    while (token != NULL) { 
        token = strtok(NULL, delim.c_str()); 

    delete[] str_c;

    return tokens;

Android WebView Cookie Problem

Don't use your raw url

Instead of:

cookieManager.setCookie(myUrl, cookieString); 

use it like this:

cookieManager.setCookie("your url host", cookieString); 

Proper way to initialize a C# dictionary with values?

With C# 6.0, you can create a dictionary in following way:

var dict = new Dictionary<string, int>
    ["one"] = 1,
    ["two"] = 2,
    ["three"] = 3

It even works with custom types.

Simple Android grid example using RecyclerView with GridLayoutManager (like the old GridView)

Set in RecyclerView initialization

recyclerView.setLayoutManager(new GridLayoutManager(this, 4));

IPhone/IPad: How to get screen width programmatically?

Here is a Swift way to get screen sizes, this also takes current interface orientation into account:

var screenWidth: CGFloat {
    if UIInterfaceOrientationIsPortrait(screenOrientation) {
        return UIScreen.mainScreen().bounds.size.width
    } else {
        return UIScreen.mainScreen().bounds.size.height
var screenHeight: CGFloat {
    if UIInterfaceOrientationIsPortrait(screenOrientation) {
        return UIScreen.mainScreen().bounds.size.height
    } else {
        return UIScreen.mainScreen().bounds.size.width
var screenOrientation: UIInterfaceOrientation {
    return UIApplication.sharedApplication().statusBarOrientation

These are included as a standard function in:

DateTime2 vs DateTime in SQL Server

Select ValidUntil + 1
from Documents

The above SQL won't work with a DateTime2 field. It returns and error "Operand type clash: datetime2 is incompatible with int"

Adding 1 to get the next day is something developers have been doing with dates for years. Now Microsoft have a super new datetime2 field that cannot handle this simple functionality.

"Let's use this new type that is worse than the old one", I don't think so!

RESTful web service - how to authenticate requests from other services?

There are several different approaches you can take.

  1. The RESTful purists will want you to use BASIC authentication, and send credentials on every request. Their rationale is that no one is storing any state.

  2. The client service could store a cookie, which maintains a session ID. I don't personally find this as offensive as some of the purists I hear from - it can be expensive to authenticate over and over again. It sounds like you're not too fond of this idea, though.

  3. From your description, it really sounds like you might be interested in OAuth2 My experience so far, from what I've seen, is that it's kind of confusing, and kind of bleeding edge. There are implementations out there, but they're few and far between. In Java, I understand that it has been integrated into Spring3's security modules. (Their tutorial is nicely written.) I've been waiting to see if there will be an extension in Restlet, but so far, although it's been proposed, and may be in the incubator, it's still not been fully incorporated.

What is the difference between synchronous and asynchronous programming (in node.js)

The function makes the second one asynchronous.

The first one forces the program to wait for each line to finish it's run before the next one can continue. The second one allows each line to run together (and independently) at once.

Languages and frameworks (js, node.js) that allow asynchronous or concurrency is great for things that require real time transmission (eg. chat, stock applications).

Get first and last date of current month with JavaScript or jQuery

I fixed it with Datejs

This is alerting the first day:

var fd =;
var firstday = fd.toString("MM/dd/yyyy");

This is for the last day:

var ld =;
var lastday = ld.toString("MM/dd/yyyy");

Using Custom Domains With IIS Express

Like Jessa Flint above, I didn't want to manually edit .vs\config\applicationhost.config because I wanted the changes to persist in source control. I also didn't want to have a separate batch file. I'm using VS 2015.

Project Properties?Build Events?Pre-build event command line: Screenshot of project properties

::The following configures IIS Express to bind to any address at the specified port

::remove binding if it already exists
"%programfiles%\IIS Express\appcmd.exe" set site "MySolution.Web" /-bindings.[protocol='http',bindingInformation='*:1167:'] /apphostconfig:"$(SolutionDir).vs\config\applicationhost.config"

::add the binding
"%programfiles%\IIS Express\appcmd.exe" set site "MySolution.Web" /+bindings.[protocol='http',bindingInformation='*:1167:'] /apphostconfig:"$(SolutionDir).vs\config\applicationhost.config"

Just make sure you change the port number to your desired port.

When to use IMG vs. CSS background-image?

Here's a technical consideration: will the image be generated dynamically? It tends to be a lot easier to generate the <img> tag in HTML than to try to dynamically edit a CSS property.

What does "javax.naming.NoInitialContextException" mean?

Just read the docs:

This exception is thrown when no initial context implementation can be created. The policy of how an initial context implementation is selected is described in the documentation of the InitialContext class.

This exception can be thrown during any interaction with the InitialContext, not only when the InitialContext is constructed. For example, the implementation of the initial context might lazily retrieve the context only when actual methods are invoked on it. The application should not have any dependency on when the existence of an initial context is determined.

But this is explained much better in the docs for InitialContext

How do I obtain the frequencies of each value in an FFT?

The FFT output coefficients (for complex input of size N) are from 0 to N - 1 grouped as [LOW,MID,HI,HI,MID,LOW] frequency.

I would consider that the element at k has the same frequency as the element at N-k since for real data, FFT[N-k] = complex conjugate of FFT[k].

The order of scanning from LOW to HIGH frequency is





 [N/2] - 1,
 N - ([N/2] - 1) = [N/2]+1,


There are [N/2]+1 groups of frequency from index i = 0 to [N/2], each having the frequency = i * SamplingFrequency / N

So the frequency at bin FFT[k] is:

if k <= [N/2] then k * SamplingFrequency / N
if k >= [N/2] then (N-k) * SamplingFrequency / N

Save file Javascript with file name

function saveAs(uri, filename) {
    var link = document.createElement('a');
    if (typeof === 'string') {
        document.body.appendChild(link); // Firefox requires the link to be in the body = filename;
        link.href = uri;;
        document.body.removeChild(link); // remove the link when done
    } else {

Regex for checking if a string is strictly alphanumeric

It's 2016 or later and things have progressed. This matches Unicode alphanumeric strings:


See the reference (section "Classes for Unicode scripts, blocks, categories and binary properties"). There's also this answer that I found helpful.

PHP Get Site URL Protocol - http vs https

Some changes:

function siteURL() {
  $protocol = ((!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != 'off') || 
    $_SERVER['SERVER_PORT'] == 443) ? "https://" : "http://";
  $domainName = $_SERVER['HTTP_HOST'];
  return $protocol.$domainName;

How can I install pip on Windows?

Here how to install pip the easy way.

  1. Copy and paste this content in a file as
  2. Copy and paste into the Python folder.C:\Python27.
  3. Double click on file. It will install pip on your computer.
  4. Now you have to add C:\Python27\Scripts path to your environment variable. Because it includes the pip.exe file.
  5. Now you are ready to use pip. Open cmd and type as
    pip install package_name

Creating a jQuery object from a big HTML-string

You can try something like below

$($.parseHTML(<<table html string variable here>>)).find("td:contains('<<some text to find>>')").first().prev().text();

How to use background thread in swift?

The best practice is to define a reusable function that can be accessed multiple times.


e.g. somewhere like AppDelegate.swift as a Global Function.

func backgroundThread(_ delay: Double = 0.0, background: (() -> Void)? = nil, completion: (() -> Void)? = nil) {
    dispatch_async(dispatch_get_global_queue(Int(QOS_CLASS_USER_INITIATED.value), 0)) {

        let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
        dispatch_after(popTime, dispatch_get_main_queue()) {

Note: in Swift 2.0, replace QOS_CLASS_USER_INITIATED.value above with QOS_CLASS_USER_INITIATED.rawValue instead


A. To run a process in the background with a delay of 3 seconds:

    backgroundThread(3.0, background: {
            // Your background function here

B. To run a process in the background then run a completion in the foreground:

    backgroundThread(background: {
            // Your function here to run in the background
    completion: {
            // A function to run in the foreground when the background thread is complete

C. To delay by 3 seconds - note use of completion parameter without background parameter:

    backgroundThread(3.0, completion: {
            // Your delayed function here to be run in the foreground

Disable the postback on an <ASP:LinkButton>

Why not use an empty ajax update panel and wire the linkbutton's click event to it? This way only the update panel will get updated, thus avoiding a postback and allowing you to run your javascript

C++ code file extension? .cc vs .cpp

.C and .cc seem to be standard for the (few) Unix-oriented C++ programs I've seen. I've always used .cpp myself, since I only really work on Windows and that's been the standard there since like forever.

I recommend .cpp personally, because... it stands for "C Plus Plus". It is of course vitally important that file extensions are acronyms, but should this rationale prove insufficiently compelling other important things are non-use of the shift key (which rules out .C and .c++) and avoidance of regular expression metacharacters where possible (which rules out .c++ -- unfortunately you can't really avoid the . of course.).

This doesn't rule out .cc, so even though it doesn't really stand for anything (or does it?) it is probably a good choice for Linux-oriented code.

How to convert 'binary string' to normal string in Python3?

Decode it.

>>> b'a string'.decode('ascii')
'a string'

To get bytes from string, encode it.

>>> 'a string'.encode('ascii')
b'a string'

How can a add a row to a data frame in R?

Not terribly elegant, but:

data.frame(rbind(as.matrix(df), as.matrix(de)))

From documentation of the rbind function:

For rbind column names are taken from the first argument with appropriate names: colnames for a matrix...

How to stick <footer> element at the bottom of the page (HTML5 and CSS3)?

I would use this in HTML 5... Just sayin

#footer {
  position: absolute;
  bottom: 0;
  width: 100%;
  height: 60px;
  background-color: #f5f5f5;

Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.10:test

I had same issue, I resolved from below steps:

  1. Right click on project->maven->Update project
  2. Here I selected "force update for snapshot/release"
  3. After that I compiled again my project and issue got fixed

How to Test Facebook Connect Locally

Create 2 apps and

In /initializers/env_variables.rb

if Rails.env == 'development'
    ENV['FB_APP_ID'] = "HERE"
    ENV['FB_APP_ID'] = "HERE"

Looping through the content of a file in Bash

Option 1a: While loop: Single line at a time: Input redirection

echo Start
while read p; do 
    echo $p
done < $filename

Option 1b: While loop: Single line at a time:
Open the file, read from a file descriptor (in this case file descriptor #4).

exec 4<$filename
echo Start
while read -u4 p ; do
    echo $p

UnicodeEncodeError: 'latin-1' codec can't encode character

Latin-1 (aka ISO 8859-1) is a single octet character encoding scheme, and you can't fit \u201c () into a byte.

Did you mean to use UTF-8 encoding?

Disable form autofill in Chrome without disabling autocomplete

Autofill works with name attribute of the input, so if you set a name for an input like "firstname", chrome will fill it.

If you want to disable it, use an odd name like "supermanname".

Javascript can't solve your problem.

Second solution: You can make your inputs hidden with the same names, and set their values with other inputs. I simplified the Js with jQUery.

<form action="handlerfile.php" method="post">
<input type="text" id="1" onclick="$("#2").val($("#1").val())"/>
<input type="hidden" name="username" id="2">

Find and Replace text in the entire table using a MySQL query

Running an SQL query in PHPmyadmin to find and replace text in all wordpress blog posts, such as finding and replacing that with Table in this example is tj_posts

UPDATE `tj_posts`
SET `post_content` = replace(post_content, '', '')

Checking for directory and file write permissions in .NET

Deny takes precedence over Allow. Local rules take precedence over inherited rules. I have seen many solutions (including some answers shown here), but none of them takes into account whether rules are inherited or not. Therefore I suggest the following approach that considers rule inheritance (neatly wrapped into a class):

public class CurrentUserSecurity
    WindowsIdentity _currentUser;
    WindowsPrincipal _currentPrincipal;

    public CurrentUserSecurity()
        _currentUser = WindowsIdentity.GetCurrent();
        _currentPrincipal = new WindowsPrincipal(_currentUser);

    public bool HasAccess(DirectoryInfo directory, FileSystemRights right)
        // Get the collection of authorization rules that apply to the directory.
        AuthorizationRuleCollection acl = directory.GetAccessControl()
            .GetAccessRules(true, true, typeof(SecurityIdentifier));
        return HasFileOrDirectoryAccess(right, acl);

    public bool HasAccess(FileInfo file, FileSystemRights right)
        // Get the collection of authorization rules that apply to the file.
        AuthorizationRuleCollection acl = file.GetAccessControl()
            .GetAccessRules(true, true, typeof(SecurityIdentifier));
        return HasFileOrDirectoryAccess(right, acl);

    private bool HasFileOrDirectoryAccess(FileSystemRights right,
                                          AuthorizationRuleCollection acl)
        bool allow = false;
        bool inheritedAllow = false;
        bool inheritedDeny = false;

        for (int i = 0; i < acl.Count; i++) {
            var currentRule = (FileSystemAccessRule)acl[i];
            // If the current rule applies to the current user.
            if (_currentUser.User.Equals(currentRule.IdentityReference) ||
                                (SecurityIdentifier)currentRule.IdentityReference)) {

                if (currentRule.AccessControlType.Equals(AccessControlType.Deny)) {
                    if ((currentRule.FileSystemRights & right) == right) {
                        if (currentRule.IsInherited) {
                            inheritedDeny = true;
                        } else { // Non inherited "deny" takes overall precedence.
                            return false;
                } else if (currentRule.AccessControlType
                                                  .Equals(AccessControlType.Allow)) {
                    if ((currentRule.FileSystemRights & right) == right) {
                        if (currentRule.IsInherited) {
                            inheritedAllow = true;
                        } else {
                            allow = true;

        if (allow) { // Non inherited "allow" takes precedence over inherited rules.
            return true;
        return inheritedAllow && !inheritedDeny;

However, I made the experience that this does not always work on remote computers as you will not always have the right to query the file access rights there. The solution in that case is to try; possibly even by just trying to create a temporary file, if you need to know the access right before working with the "real" files.

500.19 - Internal Server Error - The requested page cannot be accessed because the related configuration data for the page is invalid

I had this error with Visual Studion 2019, my project was NopCommerce 4.30 which is an ASP.Net Core 3.1 project. I added page "gouden-munten-buitenland" to be the starting page and I only got the error when going to that page. Turned out that Visual Studio generated an invalid applicationHost.config :

    <add name="gouden-munten-buitenland AppPool" autoStart="true" />
    <add name="gouden-munten-buitenland AppPool 2" autoStart="true" /> <!-- WRONG -->
    <add name="Nop.Web AppPool" managedRuntimeVersion="" />
    <applicationPoolDefaults managedRuntimeVersion="v4.0">
    <processModel loadUserProfile="true" setProfileEnvironment="false" />


    <site name="Nop.Web" id="2">
    <application path="/gouden-munten-buitenland/gouden-munten-buitenland" applicationPool="gouden-munten-buitenland AppPool">
        <virtualDirectory path="/" physicalPath="C:\Usr\Stephan\Wrk\Kevelam\kNop.430\Presentation\Nop.Web" />
    <application path="/gouden-munten-buitenland" applicationPool="gouden-munten-buitenland AppPool 2">
        <virtualDirectory path="/" physicalPath="C:\Usr\Stephan\Wrk\Kevelam\kNop.430\Presentation\Nop.Web" />
    </application> <!-- WRONG -->

I removed the nodes identified as 'WRONG' and then it worked.

Java rounding up to an int using Math.ceil

There are two methods by which you can round up your double value.

  1. Math.ceil
  2. Math.floor

If you want your answer 4.90625 as 4 then you should use Math.floor and if you want your answer 4.90625 as 5 then you can use Math.ceil

You can refer following code for that.

public class TestClass {

    public static void main(String[] args) {
        int floorValue = (int) Math.floor((double)157 / 32);
        int ceilValue = (int) Math.ceil((double)157 / 32);
        System.out.println("Floor: "+floorValue);
        System.out.println("Ceil: "+ceilValue);



Alternate table with new not null Column in existing table in SQL

There are two ways to add the NOT NULL Columns to the table :

  1. ALTER the table by adding the column with NULL constraint. Fill the column with some data. Ex: column can be updated with ''

  2. ALTER the table by adding the column with NOT NULL constraint by giving DEFAULT values. ALTER table TableName ADD NewColumn DataType NOT NULL DEFAULT ''

php.ini & SMTP= - how do you pass username & password

  1. Install Postfix (Sendmail-compatible).
  2. Edit /etc/postfix/ to read:
#Relay config
relayhost =
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_tls_CAfile = /etc/postfix/cacert.pem
smtp_sasl_security_options = noanonymous
  1. Create /etc/postfix/sasl_passwd, enter: username:password
  1. Type # /usr/sbin/postmap sasl_passwd

  2. Then run: service postfix reload

Now PHP will run mail as usual with the sendmail -t -i command and Postfix will intercept it and relay it to your SMTP server that you provided.

Can scripts be inserted with innerHTML?

Gabriel Garcia's mention of MutationObservers is on the right track, but didn't quite work for me. I am not sure if that was because of a browser quirk or due to a mistake on my end, but the version that ended up working for me was the following:

document.addEventListener("DOMContentLoaded", function(event) {
    var observer = new MutationObserver(mutations=>{>{
                if (node.tagName === "SCRIPT") {
                    var s = document.createElement("script");
                    if (typeof(node.parentElement.added) === 'undefined')
                        node.parentElement.added = [];
                    node.parentElement.added[node.parentElement.added.length] = s;
    observer.observe(document.getElementById("element_to_watch"), {childList: true, subtree: true,attributes: false});

Of course, you should replace element_to_watch with the name of the element that is being modified.

node.parentElement.added is used to store the script tags that are added to document.head. In the function used to load the external page, you can use something like the following to remove no longer relevant script tags:

function freeScripts(node){
    if (node === null)
    if (typeof(node.added) === 'object') {
        for (var script in node.added) {
        node.added = {};
    for (var child in node.children) {

And an example of the beginning of a load function:

function load(url, id, replace) {
    if (document.getElementById(id) === null) {
        console.error("Element of ID "+id + " does not exist!");
    var xhttp = new XMLHttpRequest();
    // proceed to load in the page and modify innerHTML

Googlemaps API Key for Localhost

You can follow this way. It works at least for me :

in Credential page :

  1. Select option with IP address ( option no. 3 ).

  2. Put your IP address from your provider. If you don't it, search your IP address by using this link :

  3. Save it.

  4. Change your google map link as follow between the scrip tag :"

  5. Wait for about 5 minutes or more to let your API key to propagate.

Now your google map should works.

Which concurrent Queue implementation should I use in Java?

ConcurrentLinkedQueue means no locks are taken (i.e. no synchronized(this) or Lock.lock calls). It will use a CAS - Compare and Swap operation during modifications to see if the head/tail node is still the same as when it started. If so, the operation succeeds. If the head/tail node is different, it will spin around and try again.

LinkedBlockingQueue will take a lock before any modification. So your offer calls would block until they get the lock. You can use the offer overload that takes a TimeUnit to say you are only willing to wait X amount of time before abandoning the add (usually good for message type queues where the message is stale after X number of milliseconds).

Fairness means that the Lock implementation will keep the threads ordered. Meaning if Thread A enters and then Thread B enters, Thread A will get the lock first. With no fairness, it is undefined really what happens. It will most likely be the next thread that gets scheduled.

As for which one to use, it depends. I tend to use ConcurrentLinkedQueue because the time it takes my producers to get work to put onto the queue is diverse. I don't have a lot of producers producing at the exact same moment. But the consumer side is more complicated because poll won't go into a nice sleep state. You have to handle that yourself.

TypeScript - Append HTML to container element in Angular 2

There is a better solution to this answer that is more Angular based.

  1. Save your string in a variable in the .ts file

    MyStrings = ["one","two","three"]

  2. In the html file use *ngFor.

    <div class="one" *ngFor="let string of MyStrings; let i = index"> <div class="two">{{string}}</div> </div>

  3. if you want to dynamically insert the div element, just push more strings into the MyStrings array

    myFunction(nextString){ this.MyString.push(nextString) }

this way every time you click the button containing the myFunction(nextString) you effectively add another class="two" div which acts the same way as inserting it into the DOM with pure javascript.

doGet and doPost in Servlets

The servlet container's implementation of HttpServlet.service() method will automatically forward to doGet() or doPost() as necessary, so you shouldn't need to override the service method.

Call asynchronous method in constructor?

Try to replace this:

myLongList.ItemsSource = writings;

with this

Dispatcher.BeginInvoke(() => myLongList.ItemsSource = writings);

ASP MVC in IIS 7 results in: HTTP Error 403.14 - Forbidden

Also one more things can be possible

install .net framework 4.0 manually

This solution is for IIS7 on window 7

open cmd with administration previleges

go to directory "C:\Windows\Microsoft.NET\Framework\v4.0.30319"

type aspnet_regiis.exe -i

got to your inet manager by typing in run command "inetmgr"

refresh your IIS7

reload the site.

Latex Multiple Linebreaks

Maybe try inserting lines with only a space?

\ \\
\ \\

Reading InputStream as UTF-8

String file = "";

try {

    InputStream is = new FileInputStream(filename);
    String UTF8 = "utf8";
    int BUFFER_SIZE = 8192;

    BufferedReader br = new BufferedReader(new InputStreamReader(is,
            UTF8), BUFFER_SIZE);
    String str;
    while ((str = br.readLine()) != null) {
        file += str;
} catch (Exception e) {


Try this,.. :-)

WCF named pipe minimal example

I just found this excellent little tutorial. broken link (Cached version)

I also followed Microsoft's tutorial which is nice, but I only needed pipes as well.

As you can see, you don't need configuration files and all that messy stuff.

By the way, he uses both HTTP and pipes. Just remove all code lines related to HTTP, and you'll get a pure pipe example.

Twitter API returns error 215, Bad Authentication Data

This might help someone who use Zend_Oauth_Client to work with twitter api. This working config:

$accessToken = new Zend_Oauth_Token_Access();

$client = $accessToken->getHttpClient(array(
    'requestScheme' => Zend_Oauth::REQUEST_SCHEME_HEADER,
    'version' => '1.0', // it was 1.1 and I got 215 error.
    'signatureMethod' => 'HMAC-SHA1',
    'consumerKey' => 'foo',
    'consumerSecret' => 'bar',
    'requestTokenUrl' => '',
    'authorizeUrl' => '',
    'accessTokenUrl' => '',
    'timeout' => 30

It look like twitter api 1.0 allows oauth version to be 1.1 and 1.0, where twitter api 1.1 require only oauth version to be 1.0.

P.S We do not use Zend_Service_Twitter as it does not allow send custom params on status update.

How to check if an object implements an interface?

For an instance

Character.Gorgon gor = new Character.Gorgon();

Then do

gor instanceof Monster

For a Class instance do

Class<?> clazz = Character.Gorgon.class;

How to print the ld(linker) search path

The question is tagged Linux, but maybe this works as well under Linux?

gcc -Xlinker -v

Under Mac OS X, this prints:

@(#)PROGRAM:ld  PROJECT:ld64-224.1
configured to support archs: armv6 armv7 armv7s arm64 i386 x86_64 armv6m armv7m armv7em
Library search paths:
Framework search paths:

The -Xlinker option of gcc above just passes -v to ld. However:

ld -v

doesn't print the search path.

ASP.NET MVC Global Variables

The steel is far from hot, but I combined @abatishchev's solution with the answer from this post and got to this result. Hope it's useful:

public static class GlobalVars
    private const string GlobalKey = "AllMyVars";

    static GlobalVars()
        Hashtable table = HttpContext.Current.Application[GlobalKey] as Hashtable;

        if (table == null)
            table = new Hashtable();
            HttpContext.Current.Application[GlobalKey] = table;

    public static Hashtable Vars
        get { return HttpContext.Current.Application[GlobalKey] as Hashtable; }

    public static IEnumerable<SomeClass> SomeCollection
        get { return GetVar("SomeCollection") as IEnumerable<SomeClass>; }
        set { WriteVar("SomeCollection", value); }

    internal static DateTime SomeDate
        get { return (DateTime)GetVar("SomeDate"); }
        set { WriteVar("SomeDate", value); }

    private static object GetVar(string varName)
        if (Vars.ContainsKey(varName))
            return Vars[varName];

        return null;

    private static void WriteVar(string varName, object value)
        if (value == null)
            if (Vars.ContainsKey(varName))

        if (Vars[varName] == null)
            Vars.Add(varName, value);
            Vars[varName] = value;

How to find topmost view controller on iOS

you could find the top most view controller by using

NSArray *arrViewControllers=[[self navigationController] viewControllers];
UIViewController *topMostViewController=(UIViewController *)[arrViewControllers objectAtIndex:[arrViewControllers count]-1];

Swift apply .uppercaseString to only the first letter of a string

I'm getting the first character duplicated with Kirsteins' solution. This will capitalise the first character, without seeing double:

var s: String = "hello world"
s = prefix(s, 1).capitalizedString + suffix(s, countElements(s) - 1)

I don't know whether it's more or less efficient, I just know that it gives me the desired result.

What is the proper declaration of main in C++?

The main function must be declared as a non-member function in the global namespace. This means that it cannot be a static or non-static member function of a class, nor can it be placed in a namespace (even the unnamed namespace).

The name main is not reserved in C++ except as a function in the global namespace. You are free to declare other entities named main, including among other things, classes, variables, enumerations, member functions, and non-member functions not in the global namespace.

You can declare a function named main as a member function or in a namespace, but such a function would not be the main function that designates where the program starts.

The main function cannot be declared as static or inline. It also cannot be overloaded; there can be only one function named main in the global namespace.

The main function cannot be used in your program: you are not allowed to call the main function from anywhere in your code, nor are you allowed to take its address.

The return type of main must be int. No other return type is allowed (this rule is in bold because it is very common to see incorrect programs that declare main with a return type of void; this is probably the most frequently violated rule concerning the main function).

There are two declarations of main that must be allowed:

int main()               // (1)
int main(int, char*[])   // (2)

In (1), there are no parameters.

In (2), there are two parameters and they are conventionally named argc and argv, respectively. argv is a pointer to an array of C strings representing the arguments to the program. argc is the number of arguments in the argv array.

Usually, argv[0] contains the name of the program, but this is not always the case. argv[argc] is guaranteed to be a null pointer.

Note that since an array type argument (like char*[]) is really just a pointer type argument in disguise, the following two are both valid ways to write (2) and they both mean exactly the same thing:

int main(int argc, char* argv[])
int main(int argc, char** argv)

Some implementations may allow other types and numbers of parameters; you'd have to check the documentation of your implementation to see what it supports.

main() is expected to return zero to indicate success and non-zero to indicate failure. You are not required to explicitly write a return statement in main(): if you let main() return without an explicit return statement, it's the same as if you had written return 0;. The following two main() functions have the same behavior:

int main() { }
int main() { return 0; }

There are two macros, EXIT_SUCCESS and EXIT_FAILURE, defined in <cstdlib> that can also be returned from main() to indicate success and failure, respectively.

The value returned by main() is passed to the exit() function, which terminates the program.

Note that all of this applies only when compiling for a hosted environment (informally, an environment where you have a full standard library and there's an OS running your program). It is also possible to compile a C++ program for a freestanding environment (for example, some types of embedded systems), in which case startup and termination are wholly implementation-defined and a main() function may not even be required. If you're writing C++ for a modern desktop OS, though, you're compiling for a hosted environment.

vertical-align: middle doesn't work

You must wrap your element in a table-cell, within a table using display.

Like this:

  <span class='twoline'>Two line text</span>
  <span class='float'>Float right</span>


.float {
    display: table-cell;
    vertical-align: middle;
    text-align: right;
.twoline {
    width: 50px;
    display: table-cell;
div {
    display: table;
    border: solid 1px blue;
    width: 500px;
    height: 100px;

Shown here:

How to check whether a file is empty or not?

Since you have not defined what an empty file is. Some might consider a file with just blank lines also an empty file. So if you want to check if your file contains only blank lines (any whitespace character, '\r', '\n', '\t'), you can follow the example below:


import re

def whitespace_only(file):
    content = open(file, 'r').read()
    if'^\s*$', content):
        return True

Explain: the example above uses regular expression (regex) to match the content (content) of the file.
Specifically: for regex of: ^\s*$ as a whole means if the file contains only blank lines and/or blank spaces.
- ^ asserts position at start of a line
- \s matches any whitespace character (equal to [\r\n\t\f\v ])
- * Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
- $ asserts position at the end of a line

Get random sample from list while maintaining ordering of items?

Apparently random.sample was introduced in python 2.3

so for version under that, we can use shuffle (example for 4 items):

myRange =  range(0,len(mylist)) 
coupons = [ bestCoupons[i] for i in sorted(myRange[:4]) ]

How can I make XSLT work in chrome?

Well it does not work if the XML file (starting by the standard PI:

<?xml-stylesheet type="text/xsl" href="..."?>

for referencing the XSL stylesheet) is served as "application/xml". In that case, Chrome will still download the referenced XSL stylesheet, but nothing will be rendered, as it will silently change the document types from "application/xml" into "Document" (!??) and "text/xsl" into "Stylesheet" (!??), and then will attempt to render the XML document as if it was an HTML(5) document, without running first its XSLT processor. And Nothing at all will be displayed in the screen (whose content will continue to show the previous page from which the XML page was referenced, and will continue spinning the icon, as if the document was never completely loaded.

You can perfectly use the Chrome console, that shows that all resources are loaded, but they are incorrectly interpreted.

So yes, Chrome currently only render XML files (with its optional leading XSL stylesheet declaration), only if it is served as "text/xml", but not as "application/xml" as it should for client-side rendered XML with an XSL declaration.

For XML files served as "text/xml" or "application/xml" and that do not contain an XSL stylesheet declaration, Chrome should still use a default stylesheet to render it as a DOM tree, or at least as its text source. But it does not, and here again it attempts to render it as if it was HTML, and bugs immediately on many scripts (including a default internal one) that attempt to access to "document.body" for handling onLoad events and inject some javascript handler in it.

An example of site that does not work as expected (the Common Lisp documentation) in Chrome, but works in IE which supports client-side XSLT:

This index page above is displayed correctly, but all links will drive to XML documents with a basic XSL declaration to an existing XSL stylesheet document, and you can wait indefinitely, thinking that the chapters have problems to be downloaded. All you can do to read the docuemntation is to open the console and read the source code in the Resources tab.

How to delete multiple files at once in Bash on Linux?

A wild card would work nicely for this, although to be safe it would be best to make the use of the wild card as minimal as possible, so something along the lines of this:

rm -rf abc.log.2012-*

Although from the looks of it, are those just single files? The recursive option should not be necessary if none of those items are directories, so best to not use that, just for safety.

C++, What does the colon after a constructor mean?

It's called an initialization list. It initializes members before the body of the constructor executes.

How can Perl's print add a newline by default?

Here's what I found at

$\ The output record separator for the print operator. If defined, this value is printed after the last of print's arguments. Default is undef.

You cannot call output_record_separator() on a handle, only as a static method. See IO::Handle.

Mnemonic: you set $\ instead of adding "\n" at the end of the print. Also, it's just like $/ , but it's what you get "back" from Perl.


$\ = "\n";
print "a newline will be appended to the end of this line automatically";

Finding all the subsets of a set

In case anyone else comes by and was still wondering, here's a function using Michael's explanation in C++

vector< vector<int> > getAllSubsets(vector<int> set)
    vector< vector<int> > subset;
    vector<int> empty;
    subset.push_back( empty );

    for (int i = 0; i < set.size(); i++)
        vector< vector<int> > subsetTemp = subset;  //making a copy of given 2-d vector.

        for (int j = 0; j < subsetTemp.size(); j++)
            subsetTemp[j].push_back( set[i] );   // adding set[i] element to each subset of subsetTemp. like adding {2}(in 2nd iteration  to {{},{1}} which gives {{2},{1,2}}.

        for (int j = 0; j < subsetTemp.size(); j++)
            subset.push_back( subsetTemp[j] );  //now adding modified subsetTemp to original subset (before{{},{1}} , after{{},{1},{2},{1,2}}) 
    return subset;

Take into account though, that this will return a set of size 2^N with ALL possible subsets, meaning there will possibly be duplicates. If you don't want this, I would suggest actually using a set instead of a vector(which I used to avoid iterators in the code).

Jquery change <p> text programmatically

It seems you have the click event wrapped around a custom event name "pageinit", are you sure you're triggered the event before you click the button?

something like this:


change background image in body

You would need to use Javascript for this. You can set the style of the background-image for the body like so.

var body = document.getElementsByTagName('body')[0]; = 'url(http://localhost/background.png)';

Just make sure you replace the URL with the actual URL.

What is the syntax for adding an element to a scala.collection.mutable.Map?

When you say

val map = scala.collection.mutable.Map

you are not creating a map instance, but instead aliasing the Map type.

map: collection.mutable.Map.type = scala.collection.mutable.Map$@fae93e

Try instead the following:

scala> val map = scala.collection.mutable.Map[String, Int]()
map: scala.collection.mutable.Map[String,Int] = Map()

scala> map("asdf") = 9

scala> map
res6: scala.collection.mutable.Map[String,Int] = Map((asdf,9))

How to update parent's state in React?

As per your question, I understand that you need to display some conditional data in Component 3 which is based on state of Component 5. Approach :

  1. State of Component 3 will hold a variable to check whether Component 5's state has that data
  2. Arrow Function which will change Component 3's state variable.
  3. Passing arrow function to Component 5 with props.
  4. Component 5 has an arrow function which will change Component 3's state variable
  5. Arrow function of Component 5 called on loading itself

<script src=""></script>
<script src=""></script>
Class Component3 extends React.Component {
    state = {
        someData = true

    checkForData = (result) => {
        this.setState({someData : result})

    render() {
        if(this.state.someData) {
                <Component5 hasData = {this.checkForData} />
                //Other Data
        else {
                //Other Data

export default Component3;

class Component5 extends React.Component {
    state = {
        dataValue = "XYZ"
    checkForData = () => {
        if(this.state.dataValue === "XYZ") {
        else {
    render() {
            <div onLoad = {this.checkForData}>
                //Conditional Data
export default Component5;

SQL Server : export query as a .txt file

This is quite simple to do and the answer is available in other queries. For those of you who are viewing this:

select entries from my_entries where id='42' INTO OUTFILE 'bishwas.txt';

How can I get the current user's username in Bash?

When the following is invoked within a shell script, the terminal prompt will appear just like many other unix commands do when they are run with sudo:

# get superuser password
stty -echo
read -p "[sudo] password for $user: " password
stty echo
echo ""

Then you can use $password as needed.

Linq Select Group By

    from p in PriceLog
    group p by p.LogDateTime.ToString("MMM") into g
    select new 
        LogDate = g.Key.ToString("MMM yyyy"),
        GoldPrice = (int)dateGroup.Average(p => p.GoldPrice), 
        SilverPrice = (int)dateGroup.Average(p => p.SilverPrice) 

I just discovered why all ASP.Net websites are slow, and I am trying to work out what to do about it

Unless your application has specially needs, I think you have 2 approaches:

  1. Do not use session at all
  2. Use session as is and perform fine tuning as joel mentioned.

Session is not only thread-safe but also state-safe, in a way that you know that until the current request is completed, every session variable wont change from another active request. In order for this to happen you must ensure that session WILL BE LOCKED until the current request have completed.

You can create a session like behavior by many ways, but if it does not lock the current session, it wont be 'session'.

For the specific problems you mentioned I think you should check HttpContext.Current.Response.IsClientConnected. This can be useful to to prevent unnecessary executions and waits on the client, although it cannot solve this problem entirely, as this can be used only by a pooling way and not async.

Set the text in a span

This is because you have wrong selector. According to your markup, .ui-icon and .ui-icon-circle-triangle-w" should point to the same <span> element. So you should use:



$(".ui-datepicker-prev .ui-icon").html("<<");


$(".ui-datepicker-prev span").html("<<");

Can vue-router open a link in a new tab?

It seems like this is now possible in newer versions (Vue Router 3.0.1):

<router-link :to="{ name: 'fooRoute'}" target="_blank">
  Link Text

Adding days to a date in Python

If you happen to already be using pandas, you can save a little space by not specifying the format:

import pandas as pd
startdate = "10/10/2011"
enddate = pd.to_datetime(startdate) + pd.DateOffset(days=5)

Adding placeholder attribute using Jquery

This line of code might not work in IE 8 because of native support problems.

$(".hidden").attr("placeholder", "Type here to search");

You can try importing a JQuery placeholder plugin for this task. Simply import it to your libraries and initiate from the sample code below.

$('input, textarea').placeholder();

ffmpeg - Converting MOV files to MP4

The command to just stream it to a new container (mp4) needed by some applications like Adobe Premiere Pro without encoding (fast) is:

ffmpeg -i -qscale 0 output.mp4

Alternative as mentioned in the comments, which re-encodes with best quaility (-qscale 0):

ffmpeg -i -q:v 0 output.mp4

Tomcat 404 error: The origin server did not find a current representation for the target resource or is not willing to disclose that one exists

Hope this helps. From eclipse, you right click the project -> Run As -> Run on Server and then it worked for me. I used Eclipse Jee Neon and Apache Tomcat 9.0. :)

I just removed the head portion in index.html file and it worked fine.This is the head tag in html file

How can I make a TextBox be a "password box" and display stars when using MVVM?

Send the passwordbox control as a parameter to your login command.

<Button Command="{Binding LoginCommand}" CommandParameter="{Binding ElementName=PasswordBox}"...>

Then you can call CType(parameter, PasswordBox).Password in your viewmodel.

How exactly does __attribute__((constructor)) work?

Here is a "concrete" (and possibly useful) example of how, why, and when to use these handy, yet unsightly constructs...

Xcode uses a "global" "user default" to decide which XCTestObserver class spews it's heart out to the beleaguered console.

In this example... when I implicitly load this psuedo-library, let's call it... libdemure.a, via a flag in my test target á la..

OTHER_LDFLAGS = -ldemure

I want to..

  1. At load (ie. when XCTest loads my test bundle), override the "default" XCTest "observer" class... (via the constructor function) PS: As far as I can tell.. anything done here could be done with equivalent effect inside my class' + (void) load { ... } method.

  2. run my tests.... in this case, with less inane verbosity in the logs (implementation upon request)

  3. Return the "global" XCTestObserver class to it's pristine state.. so as not to foul up other XCTest runs which haven't gotten on the bandwagon (aka. linked to libdemure.a). I guess this historically was done in dealloc.. but I'm not about to start messing with that old hag.


#define USER_DEFS NSUserDefaults.standardUserDefaults

@interface      DemureTestObserver : XCTestObserver @end
@implementation DemureTestObserver

__attribute__((constructor)) static void hijack_observer() {

/*! here I totally hijack the default logging, but you CAN
    use multiple observers, just CSV them, 
    i.e. "@"DemureTestObserverm,XCTestLog"
  [USER_DEFS setObject:@"DemureTestObserver" 
  [USER_DEFS synchronize];

__attribute__((destructor)) static void reset_observer()  {

  // Clean up, and it's as if we had never been here.
  [USER_DEFS setObject:@"XCTestLog" 
  [USER_DEFS synchronize];


Without the linker flag... (Fashion-police swarm Cupertino demanding retribution, yet Apple's default prevails, as is desired, here)

enter image description here

WITH the -ldemure.a linker flag... (Comprehensible results, gasp... "thanks constructor/destructor"... Crowd cheers) enter image description here

Is multiplication and division using shift operators in C actually faster?

Shifting is generally a lot faster than multiplying at an instruction level but you may well be wasting your time doing premature optimisations. The compiler may well perform these optimisations at compiletime. Doing it yourself will affect readability and possibly have no effect on performance. It's probably only worth it to do things like this if you have profiled and found this to be a bottleneck.

Actually the division trick, known as 'magic division' can actually yield huge payoffs. Again you should profile first to see if it's needed. But if you do use it there are useful programs around to help you figure out what instructions are needed for the same division semantics. Here is an example :

An example which I have lifted from the OP's thread on MASM32:

mov eax,9999999
; divide eax by 100000
cdiv 100000
; edx = quotient

Would generate:

mov eax,9999999
mov edx,0A7C5AC47h
add eax,1
.if !CARRY?
    mul edx
shr edx,16

No found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations:

I just solved this error happening in my tests.

Just make sure your test class has all dependencies in the attributes of the class being tested annotated with @MockBean so SpringBoot test context can wire your classes correctly.

Only if you are testing controller: you need also class annotations to load the Controller context propertly.

Check it out:

@DisplayName("UserController Adapter Test")
@AutoConfigureMockMvc(addFilters = false)
public class UserControllerTest {

private MockMvc mockMvc;

private ObjectMapper objectMapper;

private CreateUserCommand createUserCommand;

private GetUserListQuery getUserListQuery;

private GetUserQuery getUserQuery;

Can we write our own iterator in Java?

This is the complete code to write an iterator such that it iterates over elements that begin with 'a':

import java.util.Iterator;

public class AppDemo {

    public static void main(String args[]) {

        Bag<String> bag1 = new Bag<>();


        for (Iterator<String> it1 = bag1.iterator(); it1.hasNext();) {

            String s =;
            if (s != null)

Custom Iterator class

import java.util.ArrayList;
import java.util.Iterator;

public class Bag<T> {

    private ArrayList<T> data;

    public Bag() {

        data = new ArrayList<>();

    public void add(T e) {


    public Iterator<T> iterator() {

        return new BagIterator();

    public class BagIterator<T> implements Iterator<T> {

        private int index; 
        private String str;

        public BagIterator() {

            index = 0;

        public boolean hasNext() {

             return index < data.size();  

        public T next() {

            str = (String) data.get(index); 
            if (str.startsWith("a"))
                return (T) data.get(index++); 
            return null; 

How to get a List<string> collection of values from app.config in WPF?

You can create your own custom config section in the app.config file. There are quite a few tutorials around to get you started. Ultimately, you could have something like this:

    <section name="backupDirectories" type="TestReadMultipler2343.BackupDirectoriesSection, TestReadMultipler2343" />

   <directory location="C:\test1" />
   <directory location="C:\test2" />
   <directory location="C:\test3" />

To complement Richard's answer, this is the C# you could use with his sample configuration:

using System.Collections.Generic;
using System.Configuration;
using System.Xml;

namespace TestReadMultipler2343
    public class BackupDirectoriesSection : IConfigurationSectionHandler
        public object Create(object parent, object configContext, XmlNode section)
            List<directory> myConfigObject = new List<directory>();

            foreach (XmlNode childNode in section.ChildNodes)
                foreach (XmlAttribute attrib in childNode.Attributes)
                    myConfigObject.Add(new directory() { location = attrib.Value });
            return myConfigObject;

    public class directory
        public string location { get; set; }

Then you can access the backupDirectories configuration section as follows:

List<directory> dirs = ConfigurationManager.GetSection("backupDirectories") as List<directory>;

how to change php version in htaccess in server

just FYI in GoDaddy it's this:

AddHandler x-httpd-php5-3 .php

Multiple variables in a 'with' statement?

In Python 3.1+ you can specify multiple context expressions, and they will be processed as if multiple with statements were nested:

with A() as a, B() as b:

is equivalent to

with A() as a:
    with B() as b:

This also means that you can use the alias from the first expression in the second (useful when working with db connections/cursors):

with get_conn() as conn, conn.cursor() as cursor:

Get the Selected value from the Drop down box in PHP

You need to set a name on the <select> tag like so:

<select name="select_catalog" id="select_catalog">

You can get it in php with this:


How do I completely remove root password

Did you try passwd -d root? Most likely, this will do what you want.

You can also manually edit /etc/shadow: (Create a backup copy. Be sure that you can log even if you mess up, for example from a rescue system.) Search for "root". Typically, the root entry looks similar to


There, delete the second field (everything between the first and second colon):


Some systems will make you put an asterisk (*) in the password field instead of blank, where a blank field would allow no password (CentOS 8 for example)


Save the file, and try logging in as root. It should skip the password prompt. (Like passwd -d, this is a "no password" solution. If you are really looking for a "blank password", that is "ask for a password, but accept if the user just presses Enter", look at the manpage of mkpasswd, and use mkpasswd to create the second field for the /etc/shadow.)

How can I check if mysql is installed on ubuntu?

Try executing 'mysql' or 'mysql -- version' without quotes on terminal. it will prompt version otherwise Command Not Found

Finding last occurrence of substring in string, replacing that

I would use a regex:

import re
new_list = [re.sub(r"\.(?=[^.]*$)", r". - ", s) for s in old_list]