Programs & Examples On #Image resizing

Image resizing is the downscaling or upscaling of an image. Dozens of algorithms exist, all with performance vs. quality tradeoffs.

How to set max width of an image in CSS

You can write like this:


Check this

Resize image in PHP

(IMPORTANT: In the case of animation (animated webp or gif) resizing, the result will be a not animated, but resized image from the first frame! (The original animation remains intact...)

I created this to my php 7.2 project (example imagebmp sure (PHP 7 >= 7.2.0) :php/manual/function.imagebmp) about, with GD2, (so nothing 3rd party library) and very similar to the answer of Nico Bistolfi, but works with the all five basic image mimetype (png, jpeg, webp, bmp and gif), creating a new resized file, without modifying the original one, and the all stuff in one function and ready to use (copy and paste to your project). (You can set the extension of the new file with the fifth parameter, or just leave it, if you want keep the orignal):

function createResizedImage(
    string $imagePath = '',
    string $newPath = '',
    int $newWidth = 0,
    int $newHeight = 0,
    string $outExt = 'DEFAULT'
) : ?string
    if (!$newPath or !file_exists ($imagePath)) {
        return null;

    $type = exif_imagetype ($imagePath);

    if (!in_array ($type, $types)) {
        return null;

    list ($width, $height) = getimagesize ($imagePath);

    $outBool = in_array ($outExt, ['jpg', 'jpeg', 'png', 'gif', 'bmp', 'webp']);

    switch ($type) {
        case IMAGETYPE_JPEG:
            $image = imagecreatefromjpeg ($imagePath);
            if (!$outBool) $outExt = 'jpg';
        case IMAGETYPE_PNG:
            $image = imagecreatefrompng ($imagePath);
            if (!$outBool) $outExt = 'png';
        case IMAGETYPE_GIF:
            $image = imagecreatefromgif ($imagePath);
            if (!$outBool) $outExt = 'gif';
        case IMAGETYPE_BMP:
            $image = imagecreatefrombmp ($imagePath);
            if (!$outBool) $outExt = 'bmp';
        case IMAGETYPE_WEBP:
            $image = imagecreatefromwebp ($imagePath);
            if (!$outBool) $outExt = 'webp';

    $newImage = imagecreatetruecolor ($newWidth, $newHeight);

    $color = imagecolorallocatealpha ($newImage, 0, 0, 0, 127); //fill transparent back
    imagefill ($newImage, 0, 0, $color);
    imagesavealpha ($newImage, true);

    imagecopyresampled ($newImage, $image, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);

    // Rotate image on iOS
    if(function_exists('exif_read_data') && $exif = exif_read_data($imagePath, 'IFD0'))
        if(isset($exif['Orientation']) && isset($exif['Make']) && !empty($exif['Orientation']) && preg_match('/(apple|ios|iphone)/i', $exif['Make'])) {
            switch($exif['Orientation']) {
                case 8:
                    if ($width > $height) $newImage = imagerotate($newImage,90,0);
                case 3:
                    $newImage = imagerotate($newImage,180,0);
                case 6:
                    $newImage = imagerotate($newImage,-90,0);

    switch (true) {
        case in_array ($outExt, ['jpg', 'jpeg']): $success = imagejpeg ($newImage, $newPath);
        case $outExt === 'png': $success = imagepng ($newImage, $newPath);
        case $outExt === 'gif': $success = imagegif ($newImage, $newPath);
        case  $outExt === 'bmp': $success = imagebmp ($newImage, $newPath);
        case  $outExt === 'webp': $success = imagewebp ($newImage, $newPath);

    if (!$success) {
        return null;

    return $newPath;

How to resize an image to a specific size in OpenCV?

Make a useful function like this:

IplImage* img_resize(IplImage* src_img, int new_width,int new_height)
    IplImage* des_img;
    return des_img;

Resize image proportionally with CSS?

You can use object-fit property:

.my-image {
    width: 100px;
    height: 100px;
    object-fit: contain;

This will fit image, without changing the proportionally.

Resizing an image in an HTML5 canvas

So something interesting that I found a while ago while working with canvas that might be helpful:

To resize the canvas control on its own, you need to use the height="" and width="" attributes (or canvas.width/canvas.height elements). If you use CSS to resize the canvas, it will actually stretch (i.e.: resize) the content of the canvas to fit the full canvas (rather than simply increasing or decreasing the area of the canvas.

It'd be worth a shot to try drawing the image into a canvas control with the height and width attributes set to the size of the image and then using CSS to resize the canvas to the size you're looking for. Perhaps this would use a different resizing algorithm.

It should also be noted that canvas has different effects in different browsers (and even different versions of different browsers). The algorithms and techniques used in the browsers is likely to change over time (especially with Firefox 4 and Chrome 6 coming out so soon, which will place heavy emphasis on canvas rendering performance).

In addition, you may want to give SVG a shot, too, as it likely uses a different algorithm as well.

Best of luck!

Resize Google Maps marker icon image

As mentionned in comments, this is the updated solution in favor of Icon object with documentation.

Use Icon object

var icon = {
    url: "../res/sit_marron.png", // url
    scaledSize: new google.maps.Size(50, 50), // scaled size
    origin: new google.maps.Point(0,0), // origin
    anchor: new google.maps.Point(0, 0) // anchor

 posicion = new google.maps.LatLng(latitud,longitud)
 marker = new google.maps.Marker({
  position: posicion,
  map: map,
  icon: icon

Responsive css background images

If you want the entire image to show irrespective of the aspect ratio, then try this:

background-size:100% 100%;

This will show the entire image no matter what the screen size.

Remove plot axis values

Change the axis_colour to match the background and if you are modifying the background dynamically you will need to update the axis_colour simultaneously. * The shared picture shows the graph/plot example using mock data ()

### Main Plotting Function ###
plotXY <- function(time, value){

    ### Plot Style Settings ###

    ### default bg is white, set it the same as the axis-colour 
    background <- "white"

    ### default col.axis is black, set it the same as the background to match
    axis_colour <- "white"

    plot_title <- "Graph it!"
    xlabel <- "Time"
    ylabel <- "Value"
    label_colour <- "black"
    label_scale <- 2
    axis_scale <- 2
    symbol_scale <- 2
    title_scale <- 2
    subtitle_scale <- 2
    # point style 16 is a black dot
    point <- 16 
    # p - points, l - line, b - both
    plot_type <- "b"

    plot(time, value, main=plot_title, cex=symbol_scale, cex.lab=label_scale, cex.axis=axis_scale, cex.main=title_scale, cex.sub=subtitle_scale, xlab=xlabel, ylab=ylabel, col.lab=label_colour, col.axis=axis_colour, bg=background, pch=point, type=plot_type)

plotXY(time, value)

enter image description here

Pass a datetime from javascript to c# (Controller)

The following format should work:

    type: "POST",
    url: "@Url.Action("refresh", "group")",
    contentType: "application/json; charset=utf-8",
    data: JSON.stringify({ 
        myDate: '2011-04-02 17:15:45'
    success: function (result) {
        //do something
    error: function (req, status, error) {

Add rows to CSV File in powershell

Simple to me is like this:

$Time = Get-Date -Format "yyyy-MM-dd HH:mm K"
$Description = "Done on time"

"$Time,$Description"|Add-Content -Path $File # Keep no space between content variables

If you have a lot of columns, then create a variable like $NewRow like:

$Time = Get-Date -Format "yyyy-MM-dd HH:mm K"
$Description = "Done on time"
$NewRow = "$Time,$Description" # No space between variables, just use comma(,).

$NewRow | Add-Content -Path $File # Keep no space between content variables

Please note the difference between Set-Content (overwrites the existing contents) and Add-Content (appends to the existing contents) of the file.

Get index of a key in json

In principle, it is wrong to look for an index of a key. Keys of a hash map are unordered, you should never expect specific order.

Why doesn't adding CORS headers to an OPTIONS route allow browsers to access my API?

I have made a more complete middleware suitable for express or connect. It supports OPTIONS requests for preflight checking. Note that it will allow CORS access to anything, you might want to put in some checks if you want to limit access.

app.use(function(req, res, next) {
    var oneof = false;
    if(req.headers.origin) {
        res.header('Access-Control-Allow-Origin', req.headers.origin);
        oneof = true;
    if(req.headers['access-control-request-method']) {
        res.header('Access-Control-Allow-Methods', req.headers['access-control-request-method']);
        oneof = true;
    if(req.headers['access-control-request-headers']) {
        res.header('Access-Control-Allow-Headers', req.headers['access-control-request-headers']);
        oneof = true;
    if(oneof) {
        res.header('Access-Control-Max-Age', 60 * 60 * 24 * 365);

    // intercept OPTIONS method
    if (oneof && req.method == 'OPTIONS') {
    else {

Use of Greater Than Symbol in XML

You can try to use CDATA to put all your symbols that don't work.

An example of something that will work in XML:

function matchwo(a,b) {
    if (a < b && a < 0) {
        return 1;
   } else {
       return 0;

And of course you can use &lt; and &gt;.

Java 8 - Best way to transform a list: map or foreach?

One of the main benefits of using streams is that it gives the ability to process data in a declarative way, that is, using a functional style of programming. It also gives multi-threading capability for free meaning there is no need to write any extra multi-threaded code to make your stream concurrent.

Assuming the reason you are exploring this style of programming is that you want to exploit these benefits then your first code sample is potentially not functional since the foreach method is classed as being terminal (meaning that it can produce side-effects).

The second way is preferred from functional programming point of view since the map function can accept stateless lambda functions. More explicitly, the lambda passed to the map function should be

  1. Non-interfering, meaning that the function should not alter the source of the stream if it is non-concurrent (e.g. ArrayList).
  2. Stateless to avoid unexpected results when doing parallel processing (caused by thread scheduling differences).

Another benefit with the second approach is if the stream is parallel and the collector is concurrent and unordered then these characteristics can provide useful hints to the reduction operation to do the collecting concurrently.

Update a column value, replacing part of a string

UPDATE yourtable
SET url = REPLACE(url, '', '')
WHERE url LIKE ('');

relevant docs:

bootstrap 3 navbar collapse button not working

In case it might help someone, I had a similar issue after adding Bootstrap 3 to my MVC 4 project. It turned out my problem was that I was referring to bootstrap-min.js instead of bootstrap.js in my BundleConfig.cs.

Didn't work:

bundles.Add(new ScriptBundle("~/bundles/bootstrap").Include(


bundles.Add(new ScriptBundle("~/bundles/bootstrap").Include(

box-shadow on bootstrap 3 container

     @import url("");

.row {
    height: 100px;
    background-color: green;
.container {
    margin-top: 50px;
    box-shadow: 0 0 30px black;
    padding:0 15px 0 15px;

    <div class="container">
        <div class="row">one</div>
        <div class="row">two</div>
        <div class="row">three</div>

Insert new item in array on any position in PHP

Normally, with scalar values:

$elements = array('foo', ...);
array_splice($array, $position, $length, $elements);

To insert a single array element into your array don't forget to wrap the array in an array (as it was a scalar value!):

$element = array('key1'=>'value1');
$elements = array($element);
array_splice($array, $position, $length, $elements);

otherwise all the keys of the array will be added piece by piece.

Pandas read_csv from url

To Import Data through URL in pandas just apply the simple below code it works actually better.

import pandas as pd
train = pd.read_table("")

If you are having issues with a raw data then just put 'r' before URL

import pandas as pd
train = pd.read_table(r"")

Add spaces between the characters of a string in Java?

A simple way can be to split the string on each character and join the parts using space as the delimiter.


public class Main {
    public static void main(String[] args) {
        String s = "JAYARAM";
        s = String.join(" ", s.split(""));



How do I represent a time only value in .NET?

I say use a DateTime. If you don't need the date portion, just ignore it. If you need to display just the time to the user, output it formatted to the user like this:

DateTime.Now.ToString("t");  // outputs 10:00 PM

It seems like all the extra work of making a new class or even using a TimeSpan is unnecessary.

how to convert java string to Date object

You basically effectively converted your date in a string format to a date object. If you print it out at that point, you will get the standard date formatting output. In order to format it after that, you then need to convert it back to a date object with a specified format (already specified previously)

String startDateString = "06/27/2007";
DateFormat df = new SimpleDateFormat("MM/dd/yyyy"); 
Date startDate;
try {
    startDate = df.parse(startDateString);
    String newDateString = df.format(startDate);
} catch (ParseException e) {

Javascript: How to remove the last character from a div or a string?

$('#mainn').text(function (_,txt) {
    return txt.slice(0, -1);

demo -->

Make a bucket public in Amazon S3

You can set a bucket policy as detailed in this blog post:

As per @robbyt's suggestion, create a bucket policy with the following JSON:

  "Version": "2008-10-17",
  "Statement": [{
    "Sid": "AllowPublicRead",
    "Effect": "Allow",
    "Principal": { "AWS": "*" },
    "Action": ["s3:GetObject"],
    "Resource": ["arn:aws:s3:::bucket/*" ]

Important: replace bucket in the Resource line with the name of your bucket.

What does a lazy val do?

The difference between them is, that a val is executed when it is defined whereas a lazy val is executed when it is accessed the first time.

scala> val x = { println("x"); 15 }
x: Int = 15

scala> lazy val y = { println("y"); 13 }
y: Int = <lazy>

scala> x
res2: Int = 15

scala> y
res3: Int = 13

scala> y
res4: Int = 13

In contrast to a method (defined with def) a lazy val is executed once and then never again. This can be useful when an operation takes long time to complete and when it is not sure if it is later used.

scala> class X { val x = { Thread.sleep(2000); 15 } }
defined class X

scala> class Y { lazy val y = { Thread.sleep(2000); 13 } }
defined class Y

scala> new X
res5: X = X@262505b7 // we have to wait two seconds to the result

scala> new Y
res6: Y = Y@1555bd22 // this appears immediately

Here, when the values x and y are never used, only x unnecessarily wasting resources. If we suppose that y has no side effects and that we do not know how often it is accessed (never, once, thousands of times) it is useless to declare it as def since we don't want to execute it several times.

If you want to know how lazy vals are implemented, see this question.

How to remove the border highlight on an input text element

You could use CSS to disable that! This is the code I use for disabling the blue border:

*:focus {
    outline: none;

This is a working example

What's the difference between Apache's Mesos and Google's Kubernetes

Kubernetes and Mesos are a match made in heaven. Kubernetes enables the Pod (group of co-located containers) abstraction, along with Pod labels for service discovery, load-balancing, and replication control. Mesos provides the fine-grained resource allocations for pods across nodes in a cluster, and can make Kubernetes play nicely with other frameworks running on the same cluster resources.

from readme of kubernetes-mesos

How to convert a command-line argument to int?

Note that your main arguments are not correct. The standard form should be:

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

or equivalently:

int main(int argc, char **argv)

There are many ways to achieve the conversion. This is one approach:

#include <sstream>

int main(int argc, char *argv[])
    if (argc >= 2)
        std::istringstream iss( argv[1] );
        int val;

        if (iss >> val)
            // Conversion successful

    return 0;

Angular2 *ngFor in select list, set active based on string from object

Check it out in this demo fiddle, go ahead and change the dropdown or default values in the code.

Setting the passenger.Title with a value that equals to a title.Value should work.


<select [(ngModel)]="passenger.Title">
    <option *ngFor="let title of titleArray" [value]="title.Value">

TypeScript used:

class Passenger {
  constructor(public Title: string) { };
class ValueAndText {
  constructor(public Value: string, public Text: string) { }

export class AppComponent {
    passenger: Passenger = new Passenger("Lord");

    titleArray: ValueAndText[] = [new ValueAndText("Mister", "Mister-Text"),
                                  new ValueAndText("Lord", "Lord-Text")];


What is the Auto-Alignment Shortcut Key in Eclipse?

Auto-alignment? Lawful good?

If you mean formatting, then Ctrl+Shift+F.

How to set a value to a file input in HTML?

Not an answer to your question (which others have answered), but if you want to have some edit functionality of an uploaded file field, what you probably want to do is:

  • show the current value of this field by just printing the filename or URL, a clickable link to download it, or if it's an image: just show it, possibly as thumbnail
  • the <input> tag to upload a new file
  • a checkbox that, when checked, deletes the currently uploaded file. note that there's no way to upload an 'empty' file, so you need something like this to clear out the field's value

Remove leading comma from a string

var s = ",'first string','more','even more'";

var array = s.split(',').slice(1);

That's assuming the string you begin with is in fact a String, like you said, and not an Array of strings.

Why did I get the compile error "Use of unassigned local variable"?

Local variables don't have a default value.

They have to be definitely assigned before you use them. It reduces the chance of using a variable you think you've given a sensible value to, when actually it's got some default value.

How to select a specific node with LINQ-to-XML

I'd use something like:

dim customer = (from c in xmldoc...<Customer> 
                where c.<ID>.Value=22 
                select c).SingleOrDefault 


missed the c# tag, sorry......the example is in VB.NET

Execute stored procedure with an Output parameter?




@parm varchar(10),
**@parm1OUT varchar(30) OUTPUT**,
**@parm2OUT varchar(30) OUTPUT**
  SELECT @parm1OUT='parm 1' + @parm
 SELECT @parm2OUT='parm 2' + @parm


DECLARE @ParmDefinition NVARCHAR(500)

SET @parmIN=' returned'
SET @SQLString=N'EXEC Myproc @parm,
                         @parm1OUT OUTPUT, @parm2OUT OUTPUT'
SET @ParmDefinition=N'@parm varchar(10),
                  @parm1OUT varchar(30) OUTPUT,
                  @parm2OUT varchar(30) OUTPUT'

EXECUTE sp_executesql
@parm1OUT=@parmRET1 OUTPUT,@parm2OUT=@parmRET2 OUTPUT

SELECT @parmRET1 AS "parameter 1", @parmRET2 AS "parameter 2"

Hope this helps!

Escaping Double Quotes in Batch Script

eplawless's own answer simply and effectively solves his specific problem: it replaces all " instances in the entire argument list with \", which is how Bash requires double-quotes inside a double-quoted string to be represented.

To generally answer the question of how to escape double-quotes inside a double-quoted string using cmd.exe, the Windows command-line interpreter (whether on the command line - often still mistakenly called the "DOS prompt" - or in a batch file):See bottom for a look at PowerShell.


  • You must use "" when passing a string to a(nother) batch file and you may use "" with applications created with Microsoft's C/C++/.NET compilers (which also accept \"), which on Windows includes Python and Node.js:

    • Example: foo.bat "We had 3"" of rain."

    • The following applies to batch files only:

      • "" is the only way to get the command interpreter (cmd.exe) to treat the whole double-quoted string as a single argument.

      • Sadly, however, not only are the enclosing double-quotes retained (as usual), but so are the doubled escaped ones, so obtaining the intended string is a two-step process; e.g., assuming that the double-quoted string is passed as the 1st argument, %1:

      • set "str=%~1" removes the enclosing double-quotes; set "str=%str:""="%" then converts the doubled double-quotes to single ones.
        Be sure to use the enclosing double-quotes around the assignment parts to prevent unwanted interpretation of the values.

  • \" is required - as the only option - by many other programs, (e.g., Ruby, Perl, and even Microsoft's own Windows PowerShell(!)), but ITS USE IS NOT SAFE:

    • \" is what many executables and interpreters either require - including Windows PowerShell - when passed strings from the outside - or, in the case of Microsoft's compilers, support as an alternative to "" - ultimately, though, it's up to the target program to parse the argument list.
      • Example: foo.exe "We had 3\" of rain."
      • The following characters present this risk: & | < >
      • For instance, the following results in unintended execution of the ver command; see further below for an explanation and the next bullet point for a workaround:
        • foo.exe "3\" of snow" "& ver."
    • For Windows PowerShell, \"" and "^"" are robust, but limited alternatives (see section "Calling PowerShell's CLI ..." below).
  • If you must use \", there are only 3 safe approaches, which are, however quite cumbersome: Tip of the hat to T S for his help.

    • Using (possibly selective) delayed variable expansion in your batch file, you can store literal \" in a variable and reference that variable inside a "..." string using !var! syntax - see T S's helpful answer.

      • The above approach, despite being cumbersome, has the advantage that you can apply it methodically and that it works robustly, with any input.
    • Only with LITERAL strings - ones NOT involving VARIABLES - do you get a similarly methodical approach: categorically ^-escape all cmd.exe metacharacters: " & | < > and - if you also want to suppress variable expansion - %:
      foo.exe ^"3\^" of snow^" ^"^& ver.^"

    • Otherwise, you must formulate your string based on recognizing which portions of the string cmd.exe considers unquoted due to misinterpreting \" as closing delimiters:

      • in literal portions containing shell metacharacters: ^-escape them; using the example above, it is & that must be ^-escaped:
        foo.exe "3\" of snow" "^& ver."

      • in portions with %...%-style variable references: ensure that cmd.exe considers them part of a "..." string and that that the variable values do not themselves have embedded, unbalanced quotes - which is not even always possible.

For background information, read on.


Note: This is based on my own experiments. Do let me know if I'm wrong.

POSIX-like shells such as Bash on Unix-like systems tokenize the argument list (string) before passing arguments individually to the target program: among other expansions, they split the argument list into individual words (word splitting) and remove quoting characters from the resulting words (quote removal). The target program is handed an array of individual arguments, with syntactic quotes removed.

By contrast, the Windows command interpreter apparently does not tokenize the argument list and simply passes the single string comprising all arguments - including quoting chars. - to the target program.
However, some preprocessing takes place before the single string is passed to the target program: ^ escape chars. outside of double-quoted strings are removed (they escape the following char.), and variable references (e.g., %USERNAME%) are interpolated first.

Thus, unlike in Unix, it is the target program's responsibility to parse to parse the arguments string and break it down into individual arguments with quotes removed. Thus, different programs can hypothetically require differing escaping methods and there's no single escaping mechanism that is guaranteed to work with all programs - contains excellent background on the anarchy that is Windows command-line parsing.

In practice, \" is very common, but NOT SAFE, as mentioned above:

Since cmd.exe itself doesn't recognize \" as an escaped double-quote, it can misconstrue later tokens on the command line as unquoted and potentially interpret them as commands and/or input/output redirections.
In a nutshell: the problem surfaces, if any of the following characters follow an opening or unbalanced \": & | < >; for example:

foo.exe "3\" of snow" "& ver."

cmd.exe sees the following tokens, resulting from misinterpreting \" as a regular double-quote:

  • "3\"
  • of
  • snow" "
  • rest: & ver.

Since cmd.exe thinks that & ver. is unquoted, it interprets it as & (the command-sequencing operator), followed by the name of a command to execute (ver. - the . is ignored; ver reports cmd.exe's version information).
The overall effect is:

  • First, foo.exe is invoked with the first 3 tokens only.
  • Then, command ver is executed.

Even in cases where the accidental command does no harm, your overall command won't work as designed, given that not all arguments are passed to it.

Many compilers / interpreters recognize ONLY \" - e.g., the GNU C/C++ compiler, Python, Perl, Ruby, even Microsoft's own Windows PowerShell when invoked from cmd.exe - and, except (with limitations) for Windows PowerShell with \"", for them there is no simple solution to this problem.
Essentially, you'd have to know in advance which portions of your command line are misinterpreted as unquoted, and selectively ^-escape all instances of & | < > in those portions.

By contrast, use of "" is SAFE, but is regrettably only supported by Microsoft-compiler-based executables and batch files (in the case of batch files, with the quirks discussed above), which notable excludes PowerShell - see next section.

Calling PowerShell's CLI from cmd.exe or POSIX-like shells:

Note: See the bottom section for how quoting is handled inside PowerShell.

When invoked from the outside - e.g., from cmd.exe, whether from the command line or a batch file:

  • PowerShell [Core] v6+ now properly recognizes "" (in addition to \"), which is both safe to use and whitespace-preserving.

    • pwsh -c " ""a & c"".length " doesn't break and correctly yields 6
  • Windows PowerShell (the legacy edition whose last version is 5.1) recognizes only \" and, on Windows also """ and the more robust \"" / "^"" (even though internally PowerShell uses ` as the escape character in double-quoted strings and also accepts "" - see bottom section):

Calling Windows PowerShell from cmd.exe / a batch file:

  • "" breaks, because it is fundamentally unsupported:

    • powershell -c " ""ab c"".length " -> error "The string is missing the terminator"
  • \" and """ work in principle, but aren't safe:

    • powershell -c " \"ab c\".length " works as intended: it outputs 5 (note the 2 spaces)
    • But it isn't safe, because cmd.exe metacharacters break the command, unless escaped:
      powershell -c " \"a& c\".length " breaks, due to the &, which would have to be escaped as ^&
  • \"" is safe, but normalize interior whitespace, which can be undesired:

    • powershell -c " \""a& c\"".length " outputs 4(!), because the 2 spaces are normalized to 1.
  • "^"" is the best choice for Windows PowerShell specifically, where it is both safe and whitespace-preserving, but with PowerShell Core (on Windows) it is the same as \"", i.e, whitespace-normalizing. Credit goes to Venryx for discovering this approach.

    • powershell -c " "^""a& c"^"".length " works: doesn't break - despite & - and outputs 5, i.e., correctly preserved whitespace.

    • PowerShell Core: pwsh -c " "^""a& c"^"".length " works, but outputs 4, i.e. normalizes whitespace, as \"" does.

On Unix-like platforms (Linux, macOS), when calling PowerShell [Core]'s CLI, pwsh, from a POSIX-like shell such as bash:

You must use \", which, however is both safe and whitespace-preserving:

$ pwsh -c " \"a&  c|\".length" # OK: 5

Related information

  • ^ can only be used as the escape character in unquoted strings - inside double-quoted strings, ^ is not special and treated as a literal.

    • CAVEAT: Use of ^ in parameters passed to the call statement is broken (this applies to both uses of call: invoking another batch file or binary, and calling a subroutine in the same batch file):
      • ^ instances in double-quoted values are inexplicably doubled, altering the value being passed: e.g., if variable %v% contains literal value a^b, call :foo "%v%" assigns "a^^b"(!) to %1 (the first parameter) in subroutine :foo.
      • Unquoted use of ^ with call is broken altogether in that ^ can no longer be used to escape special characters: e.g., call foo.cmd a^&b quietly breaks (instead of passing literal a&b too foo.cmd, as would be the case without call) - foo.cmd is never even invoked(!), at least on Windows 7.
  • Escaping a literal % is a special case, unfortunately, which requires distinct syntax depending on whether a string is specified on the command line vs. inside a batch file; see

    • The short of it: Inside a batch file, use %%. On the command line, % cannot be escaped, but if you place a ^ at the start, end, or inside a variable name in an unquoted string (e.g., echo %^foo%), you can prevent variable expansion (interpolation); % instances on the command line that are not part of a variable reference are treated as literals (e.g, 100%).
  • Generally, to safely work with variable values that may contain spaces and special characters:

    • Assignment: Enclose both the variable name and the value in a single pair of double-quotes; e.g., set "v=a & b" assigns literal value a & b to variable %v% (by contrast, set v="a & b" would make the double-quotes part of the value). Escape literal % instances as %% (works only in batch files - see above).
    • Reference: Double-quote variable references to make sure their value is not interpolated; e.g., echo "%v%" does not subject the value of %v% to interpolation and prints "a & b" (but note that the double-quotes are invariably printed too). By contrast, echo %v% passes literal a to echo, interprets & as the command-sequencing operator, and therefore tries to execute a command named b.
      Also note the above caveat re use of ^ with the call statement.
    • External programs typically take care of removing enclosing double-quotes around parameters, but, as noted, in batch files you have to do it yourself (e.g., %~1 to remove enclosing double-quotes from the 1st parameter) and, sadly, there is no direct way that I know of to get echo to print a variable value faithfully without the enclosing double-quotes.
      • Neil offers a for-based workaround that works as long as the value has no embedded double quotes; e.g.:
        set "var=^&')|;,%!" for /f "delims=" %%v in ("%var%") do echo %%~v
  • cmd.exe does not recognize single-quotes as string delimiters - they are treated as literals and cannot generally be used to delimit strings with embedded whitespace; also, it follows that the tokens abutting the single-quotes and any tokens in between are treated as unquoted by cmd.exe and interpreted accordingly.

    • However, given that target programs ultimately perform their own argument parsing, some programs such as Ruby do recognize single-quoted strings even on Windows; by contrast, C/C++ executables, Perl and Python do not recognize them.
      Even if supported by the target program, however, it is not advisable to use single-quoted strings, given that their contents are not protected from potentially unwanted interpretation by cmd.exe.

Quoting from within PowerShell:

Windows PowerShell is a much more advanced shell than cmd.exe, and it has been a part of Windows for many years now (and PowerShell Core brought the PowerShell experience to macOS and Linux as well).

PowerShell works consistently internally with respect to quoting:

  • inside double-quoted strings, use `" or "" to escape double-quotes
  • inside single-quoted strings, use '' to escape single-quotes

This works on the PowerShell command line and when passing parameters to PowerShell scripts or functions from within PowerShell.

(As discussed above, passing an escaped double-quote to PowerShell from the outside requires \" or, more robustly, \"" - nothing else works).

Sadly, when invoking external programs from PowerShell, you're faced with the need to both accommodate PowerShell's own quoting rules and to escape for the target program:

This problematic behavior is also discussed and summarized in this answer

Double-quotes inside double-quoted strings:

Consider string "3`" of rain", which PowerShell-internally translates to literal 3" of rain.

If you want to pass this string to an external program, you have to apply the target program's escaping in addition to PowerShell's; say you want to pass the string to a C program, which expects embedded double-quotes to be escaped as \":

foo.exe "3\`" of rain"

Note how both `" - to make PowerShell happy - and the \ - to make the target program happy - must be present.

The same logic applies to invoking a batch file, where "" must be used:

foo.bat "3`"`" of rain"

By contrast, embedding single-quotes in a double-quoted string requires no escaping at all.

Single-quotes inside single-quoted strings do not require extra escaping; consider '2'' of snow', which is PowerShell' representation of 2' of snow.

foo.exe '2'' of snow'
foo.bat '2'' of snow'

PowerShell translates single-quoted strings to double-quoted ones before passing them to the target program.

However, double-quotes inside single-quoted strings, which do not need escaping for PowerShell, do still need to be escaped for the target program:

foo.exe '3\" of rain'
foo.bat '3"" of rain'

PowerShell v3 introduced the magic --% option, called the stop-parsing symbol, which alleviates some of the pain, by passing anything after it uninterpreted to the target program, save for cmd.exe-style environment-variable references (e.g., %USERNAME%), which are expanded; e.g.:

foo.exe --% "3\" of rain" -u %USERNAME%

Note how escaping the embedded " as \" for the target program only (and not also for PowerShell as \`") is sufficient.

However, this approach:

  • does not allow for escaping % characters in order to avoid environment-variable expansions.
  • precludes direct use of PowerShell variables and expressions; instead, the command line must be built in a string variable in a first step, and then invoked with Invoke-Expression in a second.

Thus, despite its many advancements, PowerShell has not made escaping much easier when calling external programs. It has, however, introduced support for single-quoted strings.

I wonder if it's fundamentally possible in the Windows world to ever switch to the Unix model of letting the shell do all the tokenization and quote removal predictably, up front, irrespective of the target program, and then invoke the target program by passing the resulting tokens.

Is there a Wikipedia API?

JWPL - Java-based Wikipedia Library -- An application programming interface for Wikipedia

How to download image using requests

Get a file-like object from the request and copy it to a file. This will also avoid reading the whole thing into memory at once.

import shutil

import requests

url = ''
response = requests.get(url, stream=True)
with open('img.png', 'wb') as out_file:
    shutil.copyfileobj(response.raw, out_file)
del response

How can I create a blank/hardcoded column in a sql query?

Thank you, in PostgreSQL this works for boolean

false as placeholder

Bash script prints "Command Not Found" on empty lines

for executing that you must provide full path of that for example


LINQ: When to use SingleOrDefault vs. FirstOrDefault() with filtering criteria

Nobody has mentioned that FirstOrDefault translated in SQL does TOP 1 record, and SingleOrDefault does TOP 2, because it needs to know is there more than 1 record.

Overflow-x:hidden doesn't prevent content from overflowing in mobile browsers

I've just been working on this for a few hours, trying various combinations of things from this and other pages. The thing that worked for me in the end was to make a site wrapper div, as suggested in the accepted answer, but to set both overflows to hidden instead of just the x overflow. If I leave overflow-y at scroll, I end up with a page that only scrolls vertically by a few pixels and then stops.

#all-wrapper {
  overflow: hidden;

Just this was enough, without setting anything on the body or html elements.

How to recover MySQL database from .myd, .myi, .frm files

You can copy the files into an appropriately named subdirectory directory of the data folder as long as it is the EXACT same version of mySQL and you have retained all of the associated files in that directory. If you don't have all the files, I'm pretty sure you're going to have issues.

How to export plots from matplotlib with transparent background?

Png files can handle transparency. So you could use this question Save plot to image file instead of displaying it using Matplotlib so as to save you graph as a png file.

And if you want to turn all white pixel transparent, there's this other question : Using PIL to make all white pixels transparent?

If you want to turn an entire area to transparent, then there's this question: And then use the PIL library like in this question Python PIL: how to make area transparent in PNG? so as to make your graph transparent.

How to implement a binary search tree in Python?

The Op's Tree.insert method qualifies for the "Gross Misnomer of the Week" award -- it doesn't insert anything. It creates a node which is not attached to any other node (not that there are any nodes to attach it to) and then the created node is trashed when the method returns.

For the edification of @Hugh Bothwell:

>>> class Foo(object):
...    bar = None
>>> a = Foo()
>>> b = Foo()
>>> = 42
>>> = 666

VB.NET: how to prevent user input in a ComboBox

this is the most simple way but it works for me with a ComboBox1 name


step 1.

Declare a variable at the beginning of your form which will hold the original text value of the ComboBox. Example:

     Dim xCurrentTextValue as string

step 2.

Create the event combobox1 key down and Assign to xCurrentTextValue variable the current text of the combobox if any key diferrent than "ENTER" is pressed the combobox text value keeps the original text value


Private Sub ComboBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles ComboBox1.KeyDown

    xCurrentTextValue = ComboBox1.Text

    If e.KeyCode <> Keys.Enter Then
        Me.ComboBox1.Text = xCmbItem
    End If

End Sub

step 3.

Validate the when the combo text is changed if len(xcurrenttextvalue)> 0 or is different than nothing then the combobox1 takes the xcurrenttextvalue variable value

Private Sub ComboBox1_TextChanged(sender As Object, e As EventArgs) Handles ComboBox1.TextChanged
    If Len(xCurrentTextValue) > 0 Then
        Me.ComboBox1.Text = xCurrentTextValue

    End If
End Sub

========================================================== that's it,

Originally I only tried the step number 2, but I have problems when you press the DEL key and DOWN arrow key, also for some reason it didn't validate the keydown event unless I display any message box

!Sorry, this is a correction on step number 2, I forgot to change the variable xCmbItem to xCurrentTextValue, xCmbItem it was used for my personal use


xCurrentTextValue = ComboBox1.Text

If e.KeyCode <> Keys.Enter Then
    Me.ComboBox1.Text = xCurrentTextValue
End If

System has not been booted with systemd as init system (PID 1). Can't operate

For WSL2, I had to install cgroupfs-mount, than start the daemon, as described here:

sudo apt-get install cgroupfs-mount
sudo cgroupfs-mount
sudo service docker start

Save file Javascript with file name

Use the filename property like this:

uriContent = "data:application/octet-stream;filename=filename.txt," + 
              encodeURIComponent(codeMirror.getValue());, 'filename.txt');


Apparently, there is no reliable way to do this. See: Is there any way to specify a suggested filename when using data: URI?

How to check if an element is off-screen

There's a jQuery plugin here which allows users to test whether an element falls within the visible viewport of the browser, taking the browsers scroll position into account.


You can also check for partial visibility:

$('#element').visible( true);

One drawback is that it only works with vertical positioning / scrolling, although it should be easy enough to add horizontal positioning into the mix.

How to get first and last day of previous month (with timestamp) in SQL Server

From SQL2012, there is a new function introduced called EOMONTH. Using this function the first and last day of the last month can be easily found.

select DATEADD(DD,1,EOMONTH(Getdate(),-2)) firstdayoflastmonth, EOMONTH(Getdate(), -1) lastdayoflastmonth

Entity Framework: "Store update, insert, or delete statement affected an unexpected number of rows (0)."

While editing include the id or primary key of the entity as a hidden field in the view


      @Html.HiddenFor(m => m.Id)

that solves the problem.

Also if your model includes non-used item include that too and post that to the controller

Add new column in Pandas DataFrame Python

You just do an opposite comparison. if Col2 <= 1. This will return a boolean Series with False values for those greater than 1 and True values for the other. If you convert it to an int64 dtype, True becomes 1 and False become 0,

df['Col3'] = (df['Col2'] <= 1).astype(int)

If you want a more general solution, where you can assign any number to Col3 depending on the value of Col2 you should do something like:

df['Col3'] = df['Col2'].map(lambda x: 42 if x > 1 else 55)


df['Col3'] = 0
condition = df['Col2'] > 1
df.loc[condition, 'Col3'] = 42
df.loc[~condition, 'Col3'] = 55

How to find index of list item in Swift?

Swift 4. If your array contains elements of type [String: AnyObject]. So to find the index of element use the below code

var array = [[String: AnyObject]]()// Save your data in array
let objectAtZero = array[0] // get first object
let index = (self.array as NSArray).index(of: objectAtZero)

Or If you want to found index on the basis of key from Dictionary. Here array contains Objects of Model class and I am matching id property.

   let userId = 20
    if let index = array.index(where: { (dict) -> Bool in
           return == userId // Will found index of matched id
    }) {
    print("Index found")
      let storeId = Int(surveyCurrent.store_id) // Accessing model key value
      indexArrUpTo = self.arrEarnUpTo.index { Int($0.store_id) == storeId }! // Array contains models and finding specific one

Insert results of a stored procedure into a temporary table

I met the same problem and here is what I did for this from Paul's suggestion. The main part is here is to use NEWID() to avoid multiple users run the store procedures/scripts at the same time, the pain for global temporary table.

DECLARE @sql varchar(max) = '', 
@tmp_global_table varchar(255) = '##global_tmp_' + CONVERT(varchar(36), NEWID())
SET @sql = @sql + 'select * into [' + @tmp_global_table + '] from YOURTABLE'

EXEC('SELECT * FROM [' + @tmp_global_table + ']')

C++ vector's insert & push_back difference

The biggest difference is their functionality. push_back always puts a new element at the end of the vector and insert allows you to select new element's position. This impacts the performance. vector elements are moved in the memory only when it's necessary to increase it's length because too little memory was allocated for it. On the other hand insert forces to move all elements after the selected position of a new element. You simply have to make a place for it. This is why insert might often be less efficient than push_back.

Catching access violation exceptions?

Nope. C++ does not throw an exception when you do something bad, that would incur a performance hit. Things like access violations or division by zero errors are more like "machine" exceptions, rather than language-level things that you can catch.

"CSV file does not exist" for a filename with embedded quotes

I also experienced the same problem I solved as follows:

dataset = pd.read_csv('C:\\Users\\path\\to\\file.csv')

How to declare global variables in Android?

I wrote this answer back in '09 when Android was relatively new, and there were many not well established areas in Android development. I have added a long addendum at the bottom of this post, addressing some criticism, and detailing a philosophical disagreement I have with the use of Singletons rather than subclassing Application. Read it at your own risk.


The more general problem you are encountering is how to save state across several Activities and all parts of your application. A static variable (for instance, a singleton) is a common Java way of achieving this. I have found however, that a more elegant way in Android is to associate your state with the Application context.

As you know, each Activity is also a Context, which is information about its execution environment in the broadest sense. Your application also has a context, and Android guarantees that it will exist as a single instance across your application.

The way to do this is to create your own subclass of, and then specify that class in the application tag in your manifest. Now Android will automatically create an instance of that class and make it available for your entire application. You can access it from any context using the Context.getApplicationContext() method (Activity also provides a method getApplication() which has the exact same effect). Following is an extremely simplified example, with caveats to follow:

class MyApp extends Application {

  private String myState;

  public String getState(){
    return myState;
  public void setState(String s){
    myState = s;

class Blah extends Activity {

  public void onCreate(Bundle b){
    MyApp appState = ((MyApp)getApplicationContext());
    String state = appState.getState();

This has essentially the same effect as using a static variable or singleton, but integrates quite well into the existing Android framework. Note that this will not work across processes (should your app be one of the rare ones that has multiple processes).

Something to note from the example above; suppose we had instead done something like:

class MyApp extends Application {

  private String myState = /* complicated and slow initialization */;

  public String getState(){
    return myState;

Now this slow initialization (such as hitting disk, hitting network, anything blocking, etc) will be performed every time Application is instantiated! You may think, well, this is only once for the process and I'll have to pay the cost anyways, right? For instance, as Dianne Hackborn mentions below, it is entirely possible for your process to be instantiated -just- to handle a background broadcast event. If your broadcast processing has no need for this state you have potentially just done a whole series of complicated and slow operations for nothing. Lazy instantiation is the name of the game here. The following is a slightly more complicated way of using Application which makes more sense for anything but the simplest of uses:

class MyApp extends Application {

  private MyStateManager myStateManager = new MyStateManager();

  public MyStateManager getStateManager(){
    return myStateManager ;

class MyStateManager {

  MyStateManager() {
    /* this should be fast */

  String getState() {
    /* if necessary, perform blocking calls here */
    /* make sure to deal with any multithreading/synchronicity issues */


    return state;

class Blah extends Activity {

  public void onCreate(Bundle b){
    MyStateManager stateManager = ((MyApp)getApplicationContext()).getStateManager();
    String state = stateManager.getState();

While I prefer Application subclassing to using singletons here as the more elegant solution, I would rather developers use singletons if really necessary over not thinking at all through the performance and multithreading implications of associating state with the Application subclass.

NOTE 1: Also as anticafe commented, in order to correctly tie your Application override to your application a tag is necessary in the manifest file. Again, see the Android docs for more info. An example:


NOTE 2: user608578 asks below how this works with managing native object lifecycles. I am not up to speed on using native code with Android in the slightest, and I am not qualified to answer how that would interact with my solution. If someone does have an answer to this, I am willing to credit them and put the information in this post for maximum visibility.


As some people have noted, this is not a solution for persistent state, something I perhaps should have emphasized more in the original answer. I.e. this is not meant to be a solution for saving user or other information that is meant to be persisted across application lifetimes. Thus, I consider most criticism below related to Applications being killed at any time, etc..., moot, as anything that ever needed to be persisted to disk should not be stored through an Application subclass. It is meant to be a solution for storing temporary, easily re-creatable application state (whether a user is logged in for example) and components which are single instance (application network manager for example) (NOT singleton!) in nature.

Dayerman has been kind enough to point out an interesting conversation with Reto Meier and Dianne Hackborn in which use of Application subclasses is discouraged in favor of Singleton patterns. Somatik also pointed out something of this nature earlier, although I didn't see it at the time. Because of Reto and Dianne's roles in maintaining the Android platform, I cannot in good faith recommend ignoring their advice. What they say, goes. I do wish to disagree with the opinions, expressed with regards to preferring Singleton over Application subclasses. In my disagreement I will be making use of concepts best explained in this StackExchange explanation of the Singleton design pattern, so that I do not have to define terms in this answer. I highly encourage skimming the link before continuing. Point by point:

Dianne states, "There is no reason to subclass from Application. It is no different than making a singleton..." This first claim is incorrect. There are two main reasons for this. 1) The Application class provides a better lifetime guarantee for an application developer; it is guaranteed to have the lifetime of the application. A singleton is not EXPLICITLY tied to the lifetime of the application (although it is effectively). This may be a non-issue for your average application developer, but I would argue this is exactly the type of contract the Android API should be offering, and it provides much more flexibility to the Android system as well, by minimizing the lifetime of associated data. 2) The Application class provides the application developer with a single instance holder for state, which is very different from a Singleton holder of state. For a list of the differences, see the Singleton explanation link above.

Dianne continues, "...just likely to be something you regret in the future as you find your Application object becoming this big tangled mess of what should be independent application logic." This is certainly not incorrect, but this is not a reason for choosing Singleton over Application subclass. None of Diane's arguments provide a reason that using a Singleton is better than an Application subclass, all she attempts to establish is that using a Singleton is no worse than an Application subclass, which I believe is false.

She continues, "And this leads more naturally to how you should be managing these things -- initializing them on demand." This ignores the fact that there is no reason you cannot initialize on demand using an Application subclass as well. Again there is no difference.

Dianne ends with "The framework itself has tons and tons of singletons for all the little shared data it maintains for the app, such as caches of loaded resources, pools of objects, etc. It works great." I am not arguing that using Singletons cannot work fine or are not a legitimate alternative. I am arguing that Singletons do not provide as strong a contract with the Android system as using an Application subclass, and further that using Singletons generally points to inflexible design, which is not easily modified, and leads to many problems down the road. IMHO, the strong contract the Android API offers to developer applications is one of the most appealing and pleasing aspects of programming with Android, and helped lead to early developer adoption which drove the Android platform to the success it has today. Suggesting using Singletons is implicitly moving away from a strong API contract, and in my opinion, weakens the Android framework.

Dianne has commented below as well, mentioning an additional downside to using Application subclasses, they may encourage or make it easier to write less performance code. This is very true, and I have edited this answer to emphasize the importance of considering perf here, and taking the correct approach if you're using Application subclassing. As Dianne states, it is important to remember that your Application class will be instantiated every time your process is loaded (could be multiple times at once if your application runs in multiple processes!) even if the process is only being loaded for a background broadcast event. It is therefore important to use the Application class more as a repository for pointers to shared components of your application rather than as a place to do any processing!

I leave you with the following list of downsides to Singletons, as stolen from the earlier StackExchange link:

  • Inability to use abstract or interface classes;
  • Inability to subclass;
  • High coupling across the application (difficult to modify);
  • Difficult to test (can't fake/mock in unit tests);
  • Difficult to parallelize in the case of mutable state (requires extensive locking);

and add my own:

  • Unclear and unmanageable lifetime contract unsuited for Android (or most other) development;

How to convert IPython notebooks to PDF and HTML?

Also pass the --execute flag to generate the output cells

jupyter nbconvert --execute --to html notebook.ipynb
jupyter nbconvert --execute --to pdf notebook.ipynb

The best practice is to keep the output out of the notebook for version control, see: Using IPython notebooks under version control

But then, if you don't pass --execute, the output won't be present in the HTML, see also: How to run an .ipynb Jupyter Notebook from terminal?

For an HTML fragment without header: How to export an IPython notebook to HTML for a blog post?

Tested in Jupyter 4.4.0.

sorting a List of Map<String, String>

if you want to make use of lamdas and make it a bit easier to read

  List<Map<String,String>> results;

  Comparator<Map<String,String>> sortByName = Comparator.comparing(x -> x.get("Name"));

  public void doSomething(){

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

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

from __future__ import with_statement
from grizzled.os import working_directory

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

# code here is in the original directory


If you prefer to roll your own:

import os
from contextlib import contextmanager

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

Unsupported method: BaseConfig.getApplicationIdSuffix()

You can do this by changing the gradle file.

 build.gradle > change
    dependencies {
    classpath ''
    } > update

Mongodb find() query : return only unique values (no duplicates)

I think you can use db.collection.distinct(fields,query)

You will be able to get the distinct values in your case for NetworkID.

It should be something like this :


Difference between x86, x32, and x64 architectures?

As the 64bit version is an x86 architecture and was accordingly first called x86-64, that would be the most appropriate name, IMO. Also, x32 is a thing (as mentioned before)—‘x64’, however, is not a continuation of that, so is (theoretically) missleading (even though many people will know what you are talking about) and should thus only be recognised as a marketing thing, not an ‘official’ architecture (again, IMO–obviously, others disagree).

Delete a closed pull request from GitHub

This is the reply I received from Github when I asked them to delete a pull request:

"Thanks for getting in touch! Pull requests can't be deleted through the UI at the moment and we'll only delete pull requests when they contain sensitive information like passwords or other credentials."

Reactjs - Form input validation

Try this, example, the required property in below input tag will ensure that the name field should be submitted empty.

<input type="text" placeholder="Your Name" required />

What does 'synchronized' mean?

synchronized simple means no two threads can access the block/method simultaneously. When we say any block/method of a class is synchronized it means only one thread can access them at a time. Internally the thread which tries to access it first take a lock on that object and as long as this lock is not available no other thread can access any of the synchronized methods/blocks of that instance of the class.

Note another thread can access a method of the same object which is not defined to be synchronized. A thread can release the lock by calling


What is App.config in C#.NET? How to use it?

You can access keys in the App.Config using:


Take alook at this Thread

What are the true benefits of ExpandoObject?

After valueTuples, what's the use of ExpandoObject class? this 6 lines code with ExpandoObject:

dynamic T = new ExpandoObject();
T.x = 1;
T.y = 2;
T.z = new ExpandoObject();
T.z.a = 3;
T.b= 4;

can be written in one line with tuples:

var T = (x: 1, y: 2, z: (a: 3, b: 4));

besides with tuple syntax you have strong type inference and intlisense support

What's the difference of $host and $http_host in Nginx

$host is a variable of the Core module.


This variable is equal to line Host in the header of request or name of the server processing the request if the Host header is not available.

This variable may have a different value from $http_host in such cases: 1) when the Host input header is absent or has an empty value, $host equals to the value of server_name directive; 2)when the value of Host contains port number, $host doesn't include that port number. $host's value is always lowercase since 0.8.17.

$http_host is also a variable of the same module but you won't find it with that name because it is defined generically as $http_HEADER (ref).


The value of the HTTP request header HEADER when converted to lowercase and with 'dashes' converted to 'underscores', e.g. $http_user_agent, $http_referer...;


  • $http_host equals always the HTTP_HOST request header.
  • $host equals $http_host, lowercase and without the port number (if present), except when HTTP_HOST is absent or is an empty value. In that case, $host equals the value of the server_name directive of the server which processed the request.

Insert some string into given string at given index in Python

An important point that often bites new Python programmers but the other posters haven't made explicit is that strings in Python are immutable -- you can't ever modify them in place.

You need to retrain yourself when working with strings in Python so that instead of thinking, "How can I modify this string?" instead you're thinking "how can I create a new string that has some pieces from this one I've already gotten?"

Must issue a STARTTLS command first

smtp port and socketFactory has to be change

    String to = "[email protected]";
    String subject = "subject"
    String msg ="email text...."
    final String from ="[email protected]"
    final  String password ="senderPassword"

    Properties props = new Properties();  
    props.setProperty("mail.transport.protocol", "smtp");     
    props.setProperty("", "");  
    props.put("mail.smtp.auth", "true");  
    props.put("mail.smtp.port", "465");  
    props.put("mail.debug", "true");  
    props.put("mail.smtp.socketFactory.port", "465");  
    props.put("mail.smtp.socketFactory.fallback", "false");  
    Session session = Session.getDefaultInstance(props,  
    new javax.mail.Authenticator() {
       protected PasswordAuthentication getPasswordAuthentication() {  
       return new PasswordAuthentication(from,password);  

   Transport transport = session.getTransport();  
   InternetAddress addressFrom = new InternetAddress(from);  

   MimeMessage message = new MimeMessage(session);  
   message.setContent(msg, "text/plain");  
   message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));  


hope it will work for you..

Eclipse : Maven search dependencies doesn't work

For me for this issue worked to:

  • remove ~/.m2
  • enable "Full Index Enabled" in maven repository view on central repository
  • "Rebuild Index" on central maven repository

After eclipse restart everything worked well.

HTTPS connections over proxy servers

I don't think "have HTTPS connections over proxy servers" means the Man-in-the-Middle attack type of proxy server. I think it's asking whether one can connect to a http proxy server over TLS. And the answer is yes.

Is it possible to have HTTPS connections over proxy servers?

Yes, see my question and answer here. HTTPs proxy server only works in SwitchOmega

If yes, what kind of proxy server allows this?

The kind of proxy server deploys SSL certificates, like how ordinary websites do. But you need a pac file for the brower to configure proxy connection over SSL.

How to find the size of an int[]?

when u pass any array to some function. u are just passing it's starting address, so for it to work u have to pass it size also for it to work properly. it's the same reason why we pass argc with argv[] in command line arguement.

Renaming columns in Pandas

Here's a nifty little function I like to use to cut down on typing:

def rename(data, oldnames, newname):
    if type(oldnames) == str: # Input can be a string or list of strings
        oldnames = [oldnames] # When renaming multiple columns
        newname = [newname] # Make sure you pass the corresponding list of new names
    i = 0
    for name in oldnames:
        oldvar = [c for c in data.columns if name in c]
        if len(oldvar) == 0:
            raise ValueError("Sorry, couldn't find that column in the dataset")
        if len(oldvar) > 1: # Doesn't have to be an exact match
            print("Found multiple columns that matched " + str(name) + ": ")
            for c in oldvar:
                print(str(oldvar.index(c)) + ": " + str(c))
            ind = input('Please enter the index of the column you would like to rename: ')
            oldvar = oldvar[int(ind)]
        if len(oldvar) == 1:
            oldvar = oldvar[0]
        data = data.rename(columns = {oldvar : newname[i]})
        i += 1
    return data

Here is an example of how it works:

In [2]: df = pd.DataFrame(np.random.randint(0, 10, size=(10, 4)), columns = ['col1', 'col2', 'omg', 'idk'])
# First list = existing variables
# Second list = new names for those variables
In [3]: df = rename(df, ['col', 'omg'],['first', 'ohmy'])
Found multiple columns that matched col:
0: col1
1: col2

Please enter the index of the column you would like to rename: 0

In [4]: df.columns
Out[5]: Index(['first', 'col2', 'ohmy', 'idk'], dtype='object')

Work on a remote project with Eclipse via SSH

I had the same problem 2 years ago and I solved it in the following way:

1) I build my projects with makefiles, not managed by eclipse 2) I use a SAMBA connection to edit the files inside Eclipse 3) Building the project: Eclipse calles a "local" make with a makefile which opens a SSH connection to the Linux Host. On the SSH command line you can give parameters which are executed on the Linux host. I use for that parameter a shell script which call the "real" make on the linux host. The different targets for building you can give also by parameters from the local makefile --> --> makefile on linux host.

jQuery: Handle fallback for failed AJAX Request

Yes, it's built in to jQuery. See the docs at jquery documentation.

ajaxError may be what you want.

What is the Sign Off feature in Git for?

Sign-off is a requirement for getting patches into the Linux kernel and a few other projects, but most projects don't actually use it.

It was introduced in the wake of the SCO lawsuit, (and other accusations of copyright infringement from SCO, most of which they never actually took to court), as a Developers Certificate of Origin. It is used to say that you certify that you have created the patch in question, or that you certify that to the best of your knowledge, it was created under an appropriate open-source license, or that it has been provided to you by someone else under those terms. This can help establish a chain of people who take responsibility for the copyright status of the code in question, to help ensure that copyrighted code not released under an appropriate free software (open source) license is not included in the kernel.

How to create a library project in Android Studio and an application project that uses the library project

Don't forget to use apply plugin: '' in your build.gradle instead of apply plugin: ''

Python 3 print without parenthesis

I finally figured out the regex to change these all in old Python2 example scripts. Otherwise use

Try it out on, doesn't work in NP++(?):

find:     (?<=print)( ')(.*)(')
replace: ('$2')

for variables:

(?<=print)( )(.*)(\n)

for label and variable:

(?<=print)( ')(.*)(',)(.*)(\n)

How to assert two list contain the same elements in Python?

As of Python 3.2 unittest.TestCase.assertItemsEqual(doc) has been replaced by unittest.TestCase.assertCountEqual(doc) which does exactly what you are looking for, as you can read from the python standard library documentation. The method is somewhat misleadingly named but it does exactly what you are looking for.

a and b have the same elements in the same number, regardless of their order

Here a simple example which compares two lists having the same elements but in a different order.

  • using assertCountEqual the test will succeed
  • using assertListEqual the test will fail due to the order difference of the two lists

Here a little example script.

import unittest

class TestListElements(unittest.TestCase):
    def setUp(self):
        self.expected = ['foo', 'bar', 'baz']
        self.result = ['baz', 'foo', 'bar']

    def test_count_eq(self):
        """Will succeed"""
        self.assertCountEqual(self.result, self.expected)

    def test_list_eq(self):
        """Will fail"""
        self.assertListEqual(self.result, self.expected)

if __name__ == "__main__":

Side Note : Please make sure that the elements in the lists you are comparing are sortable.

Arithmetic overflow error converting numeric to data type numeric

I feel I need to clarify one very important thing, for others (like my co-worker) who came across this thread and got the wrong information.

The answer given ("Try decimal(9,2) or decimal(10,2) or whatever.") is correct, but the reason ("increase the number of digits before the decimal") is wrong.

decimal(p,s) and numeric(p,s) both specify a Precision and a Scale. The "precision" is not the number of digits to the left of the decimal, but instead is the total precision of the number.

For example: decimal(2,1) covers 0.0 to 9.9, because the precision is 2 digits (00 to 99) and the scale is 1. decimal(4,1) covers 000.0 to 999.9 decimal(4,2) covers 00.00 to 99.99 decimal(4,3) covers 0.000 to 9.999

How can I echo a newline in a batch file?

Ken and Jeb solutions works well.

But the new lines are generated with only an LF character and I need CRLF characters (Windows version).

To this, at the end of the script, I have converted LF to CRLF.


TYPE file.txt | FIND "" /V > file_win.txt
del file.txt
rename file_win.txt file.txt

Delete files older than 3 months old in a directory using .NET

An SSIS type of example .. (if this helps anyone)

          public void Main()
                 // TODO: Add your code here
        // Author: Allan F 10th May 2019

        //first part of process .. put any files of last Qtr (or older) in Archive area 
        //e.g. if today is 10May2019 then last quarter is 1Jan2019 to 31March2019 .. any files earlier than 31March2019 will be archived

        //string SourceFileFolder = "\\\\adlsaasf11\\users$\\aford05\\Downloads\\stage\\";
        string SourceFilesFolder = (string)Dts.Variables["SourceFilesFolder"].Value;
        string ArchiveFolder = (string)Dts.Variables["ArchiveFolder"].Value;
        string FilePattern = (string)Dts.Variables["FilePattern"].Value;
        string[] files = Directory.GetFiles(SourceFilesFolder, FilePattern);

        //DateTime date = new DateTime(2019, 2, 15);//commented out line .. just for testing the dates .. 

        DateTime date = DateTime.Now;
        int quarterNumber = (date.Month - 1) / 3 + 1;
        DateTime firstDayOfQuarter = new DateTime(date.Year, (quarterNumber - 1) * 3 + 1, 1);
        DateTime lastDayOfQuarter = firstDayOfQuarter.AddMonths(3).AddDays(-1);

        DateTime LastDayOfPriorQuarter = firstDayOfQuarter.AddDays(-1);
        int PrevQuarterNumber = (LastDayOfPriorQuarter.Month - 1) / 3 + 1;
        DateTime firstDayOfLastQuarter = new DateTime(LastDayOfPriorQuarter.Year, (PrevQuarterNumber - 1) * 3 + 1, 1);
        DateTime lastDayOfLastQuarter = firstDayOfLastQuarter.AddMonths(3).AddDays(-1);

        //MessageBox.Show("debug pt2: firstDayOfQuarter" + firstDayOfQuarter.ToString("dd/MM/yyyy"));
        //MessageBox.Show("debug pt2: firstDayOfLastQuarter" + firstDayOfLastQuarter.ToString("dd/MM/yyyy"));

        foreach (string file in files)
            FileInfo fi = new FileInfo(file);

            //MessageBox.Show("debug pt2:" + fi.Name + " " + fi.CreationTime.ToString("dd/MM/yyyy HH:mm") + " " + fi.LastAccessTime.ToString("dd/MM/yyyy HH:mm") + " " + fi.LastWriteTime.ToString("dd/MM/yyyy HH:mm"));
            if (fi.LastWriteTime < firstDayOfQuarter)


                    FileInfo fi2 = new FileInfo(ArchiveFolder);

                    //Ensure that the target does not exist.

                    //Copy the file.
                    fi.CopyTo(ArchiveFolder + fi.Name);
                    //Console.WriteLine("{0} was copied to {1}.", path, ArchiveFolder);

                    //Delete the old location file.
                    //Console.WriteLine("{0} was successfully deleted.", ArchiveFolder);

                catch (Exception e)
                    //do nothing
                    //Console.WriteLine("The process failed: {0}", e.ToString());

        //second part of process .. delete any files in Archive area dated earlier than last qtr ..
        //e.g. if today is 10May2019 then last quarter is 1Jan2019 to 31March2019 .. any files earlier than 1Jan2019 will be deleted

        string[] archivefiles = Directory.GetFiles(ArchiveFolder, FilePattern);
        foreach (string archivefile in archivefiles)
            FileInfo fi = new FileInfo(archivefile);
            if (fi.LastWriteTime < firstDayOfLastQuarter )
                catch (Exception e)
                    //do nothing

                 Dts.TaskResult = (int)ScriptResults.Success;

The executable was signed with invalid entitlements

I have found that "get-task-allow" needs to be checked for Development builds but unchecked for Distribution builds. The easiest way to accomplish this (AFAIK) is to have two entitlements files in your project: Entitlements.plist and EntitlementsDebug.plist - and to reference the proper one in the build project settings for the various configurations in your project.

Warning: #1265 Data truncated for column 'pdd' at row 1

As the message error says, you need to Increase the length of your column to fit the length of the data you are trying to insert (0000-00-00)


Following your comment, I run a test table:

mysql> create table testDate(id int(2) not null auto_increment, pdd date default null, primary key(id));
Query OK, 0 rows affected (0.20 sec)


mysql> insert into testDate values(1,'0000-00-00');
Query OK, 1 row affected (0.06 sec)


So, aparently you want to insert a NULL value to pdd field as your comment states ? You can do that in 2 ways like this:

Method 1:

mysql> insert into testDate values(2,'');
Query OK, 1 row affected, 1 warning (0.06 sec)

Method 2:

mysql> insert into testDate values(3,NULL);
Query OK, 1 row affected (0.07 sec)


You failed to change the default value of pdd field. Here is the syntax how to do it (in my case, I set it to NULL in the start, now I will change it to NOT NULL)

mysql> alter table testDate modify pdd date not null;
Query OK, 3 rows affected, 1 warning (0.60 sec)
Records: 3  Duplicates: 0  Warnings: 1

Convert Rows to columns using 'Pivot' in SQL Server

I've achieved the same thing before by using subqueries. So if your original table was called StoreCountsByWeek, and you had a separate table that listed the Store IDs, then it would look like this:

    Week1=(SELECT ISNULL(SUM(xCount),0) FROM StoreCountsByWeek WHERE StoreCountsByWeek.StoreID=Store.StoreID AND Week=1),
    Week2=(SELECT ISNULL(SUM(xCount),0) FROM StoreCountsByWeek WHERE StoreCountsByWeek.StoreID=Store.StoreID AND Week=2),
    Week3=(SELECT ISNULL(SUM(xCount),0) FROM StoreCountsByWeek WHERE StoreCountsByWeek.StoreID=Store.StoreID AND Week=3)
FROM Store

One advantage to this method is that the syntax is more clear and it makes it easier to join to other tables to pull other fields into the results too.

My anecdotal results are that running this query over a couple of thousand rows completed in less than one second, and I actually had 7 subqueries. But as noted in the comments, it is more computationally expensive to do it this way, so be careful about using this method if you expect it to run on large amounts of data .

How to remove application from app listings on Android Developer Console

There is strictly no service provided yet from Google Store to delete/remove production app and also you can't change production build for best test.

Pass variables by reference in JavaScript

I personally dislike the "pass by reference" functionality offered by various programming languages. Perhaps that's because I am just discovering the concepts of functional programming, but I always get goosebumps when I see functions that cause side effects (like manipulating parameters passed by reference). I personally strongly embrace the "single responsibility" principle.

IMHO, a function should return just one result/value using the return keyword. Instead of modifying a parameter/argument, I would just return the modified parameter/argument value and leave any desired reassignments up to the calling code.

But sometimes (hopefully very rarely), it is necessary to return two or more result values from the same function. In that case, I would opt to include all those resulting values in a single structure or object. Again, processing any reassignments should be up to the calling code.


Suppose passing parameters would be supported by using a special keyword like 'ref' in the argument list. My code might look something like this:

//The Function
function doSomething(ref value) {
    value = "Bar";

//The Calling Code
var value = "Foo";
console.log(value); //Bar

Instead, I would actually prefer to do something like this:

//The Function
function doSomething(value) {
    value = "Bar";
    return value;

//The Calling Code:
var value = "Foo";
value = doSomething(value); //Reassignment
console.log(value); //Bar

When I would need to write a function that returns multiple values, I would not use parameters passed by reference either. So I would avoid code like this:

//The Function
function doSomething(ref value) {
    value = "Bar";

    //Do other work
    var otherValue = "Something else";

    return otherValue;

//The Calling Code
var value = "Foo";
var otherValue = doSomething(value);
console.log(value); //Bar
console.log(otherValue); //Something else

Instead, I would actually prefer to return both new values inside an object, like this:

//The Function
function doSomething(value) {
    value = "Bar";

    //Do more work
    var otherValue = "Something else";

    return {
        value: value,
        otherValue: otherValue

//The Calling Code:
var value = "Foo";
var result = doSomething(value);
value = result.value; //Reassignment
console.log(value); //Bar

These code examples are quite simplified, but it roughly demonstrates how I personally would handle such stuff. It helps me to keep various responsibilities in the correct place.

Happy coding. :)

ReactJs: What should the PropTypes be for this.props.children?

Try a custom propTypes :

 const  childrenPropTypeLogic = (props, propName, componentName) => {
          const prop = props[propName];
          return React.Children
                   .find(child => child.type !== 'div') && new Error(`${componentName} only accepts "div" elements`);

static propTypes = {

   children : childrenPropTypeLogic



const {Component, PropTypes} = React;_x000D_
 const  childrenPropTypeLogic = (props, propName, componentName) => {_x000D_
             var error;_x000D_
          var prop = props[propName];_x000D_
          React.Children.forEach(prop, function (child) {_x000D_
            if (child.type !== 'div') {_x000D_
              error = new Error(_x000D_
                '`' + componentName + '` only accepts children of type `div`.'_x000D_
          return error;_x000D_
class ContainerComponent extends Component {_x000D_
  static propTypes = {_x000D_
    children: childrenPropTypeLogic,_x000D_
  render() {_x000D_
    return (_x000D_
class App extends Component {_x000D_
    return (_x000D_
ReactDOM.render(<App /> , document.querySelector('section'))
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<section />

Concatenate rows of two dataframes in pandas

call concat and pass param axis=1 to concatenate column-wise:

In [5]:

pd.concat([df_a,df_b], axis=1)
        AAseq Biorep  Techrep Treatment     mz      AAseq1 Biorep1  Techrep1  \
0  ELVISLIVES      A        1         C  500.0  ELVISLIVES       A         1   
1  ELVISLIVES      A        1         C  500.5  ELVISLIVES       A         1   
2  ELVISLIVES      A        1         C  501.0  ELVISLIVES       A         1   

  Treatment1  inte1  
0          C   1100  
1          C   1050  
2          C   1010  

There is a useful guide to the various methods of merging, joining and concatenating online.

For example, as you have no clashing columns you can merge and use the indices as they have the same number of rows:

In [6]:

df_a.merge(df_b, left_index=True, right_index=True)
        AAseq Biorep  Techrep Treatment     mz      AAseq1 Biorep1  Techrep1  \
0  ELVISLIVES      A        1         C  500.0  ELVISLIVES       A         1   
1  ELVISLIVES      A        1         C  500.5  ELVISLIVES       A         1   
2  ELVISLIVES      A        1         C  501.0  ELVISLIVES       A         1   

  Treatment1  inte1  
0          C   1100  
1          C   1050  
2          C   1010  

And for the same reasons as above a simple join works too:

In [7]:

        AAseq Biorep  Techrep Treatment     mz      AAseq1 Biorep1  Techrep1  \
0  ELVISLIVES      A        1         C  500.0  ELVISLIVES       A         1   
1  ELVISLIVES      A        1         C  500.5  ELVISLIVES       A         1   
2  ELVISLIVES      A        1         C  501.0  ELVISLIVES       A         1   

  Treatment1  inte1  
0          C   1100  
1          C   1050  
2          C   1010  

Most efficient way to map function over numpy array


As noted by @user2357112, a "direct" method of applying the function is always the fastest and simplest way to map a function over Numpy arrays:

import numpy as np
x = np.array([1, 2, 3, 4, 5])
f = lambda x: x ** 2
squares = f(x)

Generally avoid np.vectorize, as it does not perform well, and has (or had) a number of issues. If you are handling other data types, you may want to investigate the other methods shown below.

Comparison of methods

Here are some simple tests to compare three methods to map a function, this example using with Python 3.6 and NumPy 1.15.4. First, the set-up functions for testing:

import timeit
import numpy as np

f = lambda x: x ** 2
vf = np.vectorize(f)

def test_array(x, n):
    t = timeit.timeit(
        'np.array([f(xi) for xi in x])',
        'from __main__ import np, x, f', number=n)
    print('array: {0:.3f}'.format(t))

def test_fromiter(x, n):
    t = timeit.timeit(
        'np.fromiter((f(xi) for xi in x), x.dtype, count=len(x))',
        'from __main__ import np, x, f', number=n)
    print('fromiter: {0:.3f}'.format(t))

def test_direct(x, n):
    t = timeit.timeit(
        'from __main__ import x, f', number=n)
    print('direct: {0:.3f}'.format(t))

def test_vectorized(x, n):
    t = timeit.timeit(
        'from __main__ import x, vf', number=n)
    print('vectorized: {0:.3f}'.format(t))

Testing with five elements (sorted from fastest to slowest):

x = np.array([1, 2, 3, 4, 5])
n = 100000
test_direct(x, n)      # 0.265
test_fromiter(x, n)    # 0.479
test_array(x, n)       # 0.865
test_vectorized(x, n)  # 2.906

With 100s of elements:

x = np.arange(100)
n = 10000
test_direct(x, n)      # 0.030
test_array(x, n)       # 0.501
test_vectorized(x, n)  # 0.670
test_fromiter(x, n)    # 0.883

And with 1000s of array elements or more:

x = np.arange(1000)
n = 1000
test_direct(x, n)      # 0.007
test_fromiter(x, n)    # 0.479
test_array(x, n)       # 0.516
test_vectorized(x, n)  # 0.945

Different versions of Python/NumPy and compiler optimization will have different results, so do a similar test for your environment.

How to preserve request url with nginx proxy_pass

I think the proxy_set_header directive could help:

location / {
    proxy_pass http://my_app_upstream;
    proxy_set_header Host $host;
    # ...

How do you round a floating point number in Perl?

If you are only concerned with getting an integer value out of a whole floating point number (i.e. 12347.9999 or 54321.0001), this approach (borrowed and modified from above) will do the trick:

my $rounded = floor($float + 0.1); 

JAVA_HOME should point to a JDK not a JRE

Make sure that you do NOT have a JRE path, if you have delete it.

  1. Add JAVA_HOME in the System variable. Variable value: C:\Program Files\Java\jdk-10.0.2 (location of JDK without bin)
  2. Add M2 in the System variable. Variable value: C:\dev\maven\apache-maven-3.5.4\bin (location of maven with bin)
  3. Add M2_HOME in the System variable. Variable value: C:\dev\maven\apache-maven-3.5.4 (location of maven without bin)
  4. Add %JAVA_HOME% and %M2% in Path System Variable or C:\Program Files\Java\jdk-10.0.2 and C:\dev\maven\apache-maven-3.5.4\bin --> For windows 10, just add the location. For other version, at the end of the Variable Value field add semicolon then the location Ex: ;%JAVA_HOME%;%M2%

I did not check if the addition or removal of bin changes the result but nonetheless this works for me.

support FragmentPagerAdapter holds reference to old fragments

You are running into a problem because you are instantiating and keeping references to your fragments outside of PagerAdapter.getItem, and are trying to use those references independently of the ViewPager. As Seraph says, you do have guarantees that a fragment has been instantiated/added in a ViewPager at a particular time - this should be considered an implementation detail. A ViewPager does lazy loading of its pages; by default it only loads the current page, and the one to the left and right.

If you put your app into the background, the fragments that have been added to the fragment manager are saved automatically. Even if your app is killed, this information is restored when you relaunch your app.

Now consider that you have viewed a few pages, Fragments A, B and C. You know that these have been added to the fragment manager. Because you are using FragmentPagerAdapter and not FragmentStatePagerAdapter, these fragments will still be added (but potentially detached) when you scroll to other pages.

Consider that you then background your application, and then it gets killed. When you come back, Android will remember that you used to have Fragments A, B and C in the fragment manager and so it recreates them for you and then adds them. However, the ones that are added to the fragment manager now are NOT the ones you have in your fragments list in your Activity.

The FragmentPagerAdapter will not try to call getPosition if there is already a fragment added for that particular page position. In fact, since the fragment recreated by Android will never be removed, you have no hope of replacing it with a call to getPosition. Getting a handle on it is also pretty difficult to obtain a reference to it because it was added with a tag that is unknown to you. This is by design; you are discouraged from messing with the fragments that the view pager is managing. You should be performing all your actions within a fragment, communicating with the activity, and requesting to switch to a particular page, if necessary.

Now, back to your problem with the missing activity. Calling pagerAdapter.getItem(1)).update(id, name) after all of this has happened returns you the fragment in your list, which has yet to be added to the fragment manager, and so it will not have an Activity reference. I would that suggest your update method should modify some shared data structure (possibly managed by the activity), and then when you move to a particular page it can draw itself based on this updated data.

How to downgrade Xcode to previous version?

I'm assuming you are having at least OSX 10.7, so go ahead into the applications folder (Click on Finder icon > On the Sidebar, you'll find "Applications", click on it ), delete the "Xcode" icon. That will remove Xcode from your system completely. Restart your mac.

Now go to and download an older version of Xcode, as needed and install. You need an Apple ID to login to that portal.

Write a function that returns the longest palindrome in a given string


The best algorithm i have ever found, with complexity O(N)

 import java.util.Arrays;

 public class ManachersAlgorithm {

  public static String findLongestPalindrome(String s) {
    if (s==null || s.length()==0)
      return "";

    char[] s2 = addBoundaries(s.toCharArray());
    int[] p = new int[s2.length]; 
    int c = 0, r = 0; // Here the first element in s2 has been processed.
    int m = 0, n = 0; // The walking indices to compare if two elements are the same
    for (int i = 1; i<s2.length; i++) {
      if (i>r) {
        p[i] = 0; m = i-1; n = i+1;
      } else {
        int i2 = c*2-i;
        if (p[i2]<(r-i)) {
          p[i] = p[i2];
          m = -1; // This signals bypassing the while loop below. 
        } else {
          p[i] = r-i;
          n = r+1; m = i*2-n;
      while (m>=0 && n<s2.length && s2[m]==s2[n]) {
        p[i]++; m--; n++;
      if ((i+p[i])>r) {
        c = i; r = i+p[i];
    int len = 0; c = 0;
    for (int i = 1; i<s2.length; i++) {
      if (len<p[i]) {
        len = p[i]; c = i;
    char[] ss = Arrays.copyOfRange(s2, c-len, c+len+1);
    return String.valueOf(removeBoundaries(ss));

  private static char[] addBoundaries(char[] cs) {
    if (cs==null || cs.length==0)
      return "||".toCharArray();

    char[] cs2 = new char[cs.length*2+1];
    for (int i = 0; i<(cs2.length-1); i = i+2) {
      cs2[i] = '|';
      cs2[i+1] = cs[i/2];
    cs2[cs2.length-1] = '|';
    return cs2;

  private static char[] removeBoundaries(char[] cs) {
    if (cs==null || cs.length<3)
      return "".toCharArray();

    char[] cs2 = new char[(cs.length-1)/2];
    for (int i = 0; i<cs2.length; i++) {
      cs2[i] = cs[i*2+1];
    return cs2;

Angular 4 setting selected option in Dropdown

To preselect an option when the form is initialized, the value of the select element must be set to an element attribute of the array you are iterating over and setting the value of option to. Which is the key attribute in this case.

From your example.

<select [id]="question.key" [formControlName]="question.key">
  <option *ngFor="let opt of question.options" [value]="opt.key"</option>

You are iterating over 'options' to create the select options. So the value of select must be set to the key attribute of an item in options(the one you want to display on initialization). This will display the default of select as the option whose value matches the value you set for select.

You can achieve this by setting the value of the select element in the onInit method like so.

ngOnInit(): void{
    myForm : new FormGroup({
       question.key : new FormControl(null)
    // Get desired initial value to display on <select>
    desiredValue = question.options.find(opt => opt === initialValue)

NoSql vs Relational database

Not all data is relational. For those situations, NoSQL can be helpful.

With that said, NoSQL stands for "Not Only SQL". It's not intended to knock SQL or supplant it.

SQL has several very big advantages:

  1. Strong mathematical basis.
  2. Declarative syntax.
  3. A well-known language in Structured Query Language (SQL).

Those haven't gone away.

It's a mistake to think about this as an either/or argument. NoSQL is an alternative that people need to consider when it fits, that's all.

Documents can be stored in non-relational databases, like CouchDB.

Maybe reading this will help.

How do I get the number of elements in a list?

There is an inbuilt function called len() in python which will help in these conditions.

print(len(a))     #Here the len() function counts the number of items in the list.


>>> 6

This will work slightly different in the case of string (below):

print(len(a)) #Here the len() function counts the alphabets or characters in the list.


>>> 5

This is because variable (a) is a string and not a list, so it will count the number of characters or alphabets in the string and then print the output.

Prevent direct access to a php include file

Do something like:

if ($_SERVER['SCRIPT_FILENAME'] == '<path to php include file>') {
    header('HTTP/1.0 403 Forbidden');

My httpd.conf is empty

The /etc/apache2/httpd.conf is empty in Ubuntu, because the Apache configuration resides in /etc/apache2/apache2.conf!

“httpd.conf is for user options.” No it isn't, it's there for historic reasons.

Using Apache server, all user options should go into a new *.conf-file inside /etc/apache2/conf.d/. This method should be "update-safe", as httpd.conf or apache2.conf may get overwritten on the next server update.

Inside /etc/apache2/apache2.conf, you will find the following line, which includes those files:

# Include generic snippets of statements
Include conf.d/

As of Apache 2.4+ the user configuration directory is /etc/apache2/conf-available/. Use a2enconf FILENAME_WITHOUT_SUFFIX to enable the new configuration file or manually create a symlink in /etc/apache2/conf-enabled/. Be aware that as of Apache 2.4 the configuration files must have the suffix .conf (e.g. conf-available/my-settings.conf);

Display images in mvc

Make sure you image is a relative path such as:



<img src="~/Content/images/myimage.png" />

You could convert the byte[] into a Base64 string on the fly.

string base64String = Convert.ToBase64String(imageBytes);

<img src="@String.Format("data:image/png;base64,{0}", base64string)" />

Curl command without using cache

The -H 'Cache-Control: no-cache' argument is not guaranteed to work because the remote server or any proxy layers in between can ignore it. If it doesn't work, you can do it the old-fashioned way, by adding a unique querystring parameter. Usually, the servers/proxies will think it's a unique URL and not use the cache.

curl ""

You have to use a different querystring value every time, though. Otherwise, the server/proxies will match the cache again. To automatically generate a different querystring parameter every time, you can use date +%s, which will return the seconds since epoch.

curl "$(date +%s)"

How to redirect the output of print to a TXT file

To redirect output for all prints, you can do this:

import sys
with open('c:\\goat.txt', 'w') as f:
    sys.stdout = f
    print "test"

How can I convert a PFX certificate file for use with Apache on a linux server?

To get it to work with Apache, we needed one extra step.

openssl pkcs12 -in domain.pfx -clcerts -nokeys -out domain.cer
openssl pkcs12 -in domain.pfx -nocerts -nodes  -out domain_encrypted.key
openssl rsa -in domain_encrypted.key -out domain.key

The final command decrypts the key for use with Apache. The domain.key file should look like this:


Using Excel VBA to run SQL query

Below is code that I currently use to pull data from a MS SQL Server 2008 into VBA. You need to make sure you have the proper ADODB reference [VBA Editor->Tools->References] and make sure you have Microsoft ActiveX Data Objects 2.8 Library checked, which is the second from the bottom row that is checked (I'm using Excel 2010 on Windows 7; you might have a slightly different ActiveX version, but it will still begin with Microsoft ActiveX):

References required for SQL

Sub Module for Connecting to MS SQL with Remote Host & Username/Password

Sub Download_Standard_BOM()
'Initializes variables
Dim cnn As New ADODB.Connection
Dim rst As New ADODB.Recordset
Dim ConnectionString As String
Dim StrQuery As String

'Setup the connection string for accessing MS SQL database
   'Make sure to change:
       '1: PASSWORD
       '2: USERNAME
       '4: DATABASE
    ConnectionString = "Provider=SQLOLEDB.1;Password=PASSWORD;Persist Security Info=True;User ID=USERNAME;Data Source=REMOTE_IP_ADDRESS;Use Procedure for Prepare=1;Auto Translate=True;Packet Size=4096;Use Encryption for Data=False;Tag with column collation when possible=False;Initial Catalog=DATABASE"

    'Opens connection to the database
    cnn.Open ConnectionString
    'Timeout error in seconds for executing the entire query; this will run for 15 minutes before VBA timesout, but your database might timeout before this value
    cnn.CommandTimeout = 900

    'This is your actual MS SQL query that you need to run; you should check this query first using a more robust SQL editor (such as HeidiSQL) to ensure your query is valid
    StrQuery = "SELECT TOP 10 * FROM tbl_table"

    'Performs the actual query
    rst.Open StrQuery, cnn
    'Dumps all the results from the StrQuery into cell A2 of the first sheet in the active workbook
    Sheets(1).Range("A2").CopyFromRecordset rst
End Sub

Primefaces valueChangeListener or <p:ajax listener not firing for p:selectOneMenu

Another solution is to mix valueChangeListener, ajax and process:

<p:selectManyCheckbox id="employees" value="#{employees}" columns="1" layout="grid" valueChangeListener="#{mybean.fireSelection}"   >
    <f:selectItems var="employee" value="#{employeesSI}" />
    <p:ajax event="valueChange" immediate="true" process="@this"/>

Method in mybean is just :

public void fireSelection(ValueChangeEvent event) {
    log.debug("New: "+event.getNewValue()+", Old: "+event.getOldValue());

Like this, valueChangeEvent is very light !

PS: Works fine with PrimeFaces 5.0

Android ListView Selector Color

The list selector drawable is a StateListDrawable — it contains reference to multiple drawables for each state the list can be, like selected, focused, pressed, disabled...

While you can retrieve the drawable using getSelector(), I don't believe you can retrieve a specific Drawable from a StateListDrawable, nor does it seem possible to programmatically retrieve the colour directly from a ColorDrawable anyway.

As for setting the colour, you need a StateListDrawable as described above. You can set this on your list using the android:listSelector attribute, defining the drawable in XML like this:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="">
  <item android:state_enabled="false" android:state_focused="true"
        android:drawable="@drawable/item_disabled" />
  <item android:state_pressed="true"
        android:drawable="@drawable/item_pressed" />
  <item android:state_focused="true"
        android:drawable="@drawable/item_focused" />

How to serve .html files with Spring

Background of the problem

First thing to understand is following: it is NOT spring which renders the jsp files. It is JspServlet (org.apache.jasper.servlet.JspServlet) which does it. This servlet comes with Tomcat (jasper compiler) not with spring. This JspServlet is aware how to compile jsp page and how to return it as html text to the client. The JspServlet in tomcat by default only handles requests matching two patterns: *.jsp and *.jspx.

Now when spring renders the view with InternalResourceView (or JstlView), three things really takes place:

  1. get all the model parameters from model (returned by your controller handler method i.e. "public ModelAndView doSomething() { return new ModelAndView("home") }")
  2. expose these model parameters as request attributes (so that it can be read by JspServlet)
  3. forward request to JspServlet. RequestDispatcher knows that each *.jsp request should be forwarded to JspServlet (because this is default tomcat's configuration)

When you simply change the view name to home.html tomcat will not know how to handle the request. This is because there is no servlet handling *.html requests.


How to solve this. There are three most obvious solutions:

  1. expose the html as a resource file
  2. instruct the JspServlet to also handle *.html requests
  3. write your own servlet (or pass to another existing servlet requests to *.html).

For complete code examples how to achieve this please reffer to my answer in another post: How to map requests to HTML file in Spring MVC?

How to permanently export a variable in Linux?

A particular example: I have Java 7 and Java 6 installed, I need to run some builds with 6, others with 7. Therefore I need to dynamically alter JAVA_HOME so that maven picks up what I want for each build. I did the following:

  • created script which simply does export JAVA_HOME=... path to j6 install...
  • then, as suggested by one of the comments above, whenever I need J6 for a build, I run source in that respective command terminal. By default, my JAVA_HOME is set to J7.

Hope this helps.

Store List to session

YourListType ListName = (List<YourListType>)Session["SessionName"];

Darkening an image with CSS (In any shape)

Easy as

img {
  filter: brightness(50%);

Retrieve column values of the selected row of a multicolumn Access listbox

Just a little addition. If you've only selected 1 row then the code below will select the value of a column (index of 4, but 5th column) for the selected row:


This saves having to use the ItemsSelected property.


how to create a window with two buttons that will open a new window

You add your ActionListener twice to button. So correct your code for button2 to

  JButton button2 = new JButton("hello agin2");
  button2.addActionListener (new Action2());//note the button2 here instead of button

Furthermore, perform your Swing operations on the correct thread by using EventQueue.invokeLater

Why doesn't calling a Python string method do anything unless you assign its output?

Example for String Methods

Given a list of filenames, we want to rename all the files with extension hpp to the extension h. To do this, we would like to generate a new list called newfilenames, consisting of the new filenames. Fill in the blanks in the code using any of the methods you’ve learned thus far, like a for loop or a list comprehension.

filenames = ["program.c", "stdio.hpp", "sample.hpp", "a.out", "math.hpp", "hpp.out"]
# Generate newfilenames as a list containing the new filenames
# using as many lines of code as your chosen method requires.
newfilenames = []
for i in filenames:
    if i.endswith(".hpp"):
        x = i.replace("hpp", "h")

# Should be ["program.c", "stdio.h", "sample.h", "a.out", "math.h", "hpp.out"]

Video auto play is not working in Safari and Chrome desktop browser

None of the other answers worked for me. My workaround was to trigger a click on the video itself; hacky (because of the timeout that is needed) but it works fine:

function startVideoIfNotStarted () {
    $(".id_of_video_tag").ready(function () {
        }, 1000);

Trying to get property of non-object MySQLi result

I have been working on to write a custom module in Drupal 7 and got the same error:

Notice: Trying to get property of non-object

My code is something like this:

function example_node_access($node, $op, $account) {
  if ($node->type == 'page' && $op == 'update') {
    drupal_set_message('This poll has been published, you may not make changes to it.','error');
    return NODE_ACCESS_DENY;    

Solution: I just added a condition if (is_object($sqlResult)), and everything went fine.

Here is my final code:

function mediaten_node_access($node, $op, $account) {

    if (is_object($node)){

     if ($node->type == 'page' && $op == 'update') {
       drupal_set_message('This poll has been published, you may not make changes.','error');
       return NODE_ACCESS_DENY;    



How to get Enum Value from index in Java?

I recently had the same problem and used the solution provided by Harry Joy. That solution only works with with zero-based enumaration though. I also wouldn't consider it save as it doesn't deal with indexes that are out of range.

The solution I ended up using might not be as simple but it's completely save and won't hurt the performance of your code even with big enums:

public enum Example {

    UNKNOWN(0, "unknown"), ENUM1(1, "enum1"), ENUM2(2, "enum2"), ENUM3(3, "enum3");

    private static HashMap<Integer, Example> enumById = new HashMap<>();
    static { -> enumById.put(e.getId(), e));

    public static Example getById(int id) {
        return enumById.getOrDefault(id, UNKNOWN);

    private int id;
    private String description;

    private Example(int id, String description) { = id;
        this.description= description;

    public String getDescription() {
        return description;

    public int getId() {
        return id;

If you are sure that you will never be out of range with your index and you don't want to use UNKNOWN like I did above you can of course also do:

public static Example getById(int id) {
        return enumById.get(id);

How to get a function name as a string?

import inspect

def my_first_function():
    func_name = inspect.stack()[0][3]
    print(func_name)  # my_first_function


import sys

def my_second_function():
    func_name = sys._getframe().f_code.co_name
    print(func_name)  # my_second_function

How to create my json string by using C#?

No real need for the JSON.NET package. You could use JavaScriptSerializer. The Serialize method will turn a managed type instance into a JSON string.

var serializer = new JavaScriptSerializer();
var json = serializer.Serialize(instanceOfThing);

WPF Datagrid Get Selected Cell Value

you can also use this function.

 public static void GetGridSelectedView(out string tuid, ref DataGrid dataGrid,string Column)
            // grid selected row values
            var item = dataGrid.SelectedItem as DataRowView;
            if (null == item) tuid = null;
            if (item.DataView.Count > 0)
                tuid =  item.DataView[dataGrid.SelectedIndex][Column].ToString().Trim();
            else { tuid = null; }
        catch (Exception exc) { System.Windows.MessageBox.Show(exc.Message); tuid = null; }

prevent property from being serialized in web API

Works fine by just adding the: [IgnoreDataMember]

On top of the propertyp, like:

public class UserSettingsModel
    public string UserName { get; set; }
    public DateTime Created { get; set; }

This works with ApiController. The code:

    [HttpGet, HttpPost]
    public UserSettingsModel UserSettings()
        return _contextService.GetUserSettings();

Android - Share on Facebook, Twitter, Mail, ecc

I think the following code will help....

public void btnShareClick(View v) {
    // shareBtnFlag = 1;
    Dialog d = new Dialog(DrawAppActivity.this);


    final Button btnFacebook = (Button) d.findViewById(;
    final Button btnEmail = (Button) d.findViewById(;

    btnEmail.setOnClickListener(new OnClickListener() {

        public void onClick(View arg0) {
            if (!btnEmail.isSelected()) {
            } else {
            saveBtnFlag = 1;
            // Check if email id is available-------------
            AccountManager manager = AccountManager
            Account[] accounts = manager.getAccountsByType("");
            Account account = CommonFunctions.getAccount(manager);
            if ( != null) {
                emailSendingTask eTask = new emailSendingTask();
                if (CommonFunctions.createDirIfNotExists(getResources()


                Intent sendIntent;
                sendIntent = new Intent(Intent.ACTION_SEND);
                        new String[] { });
                sendIntent.putExtra(Intent.EXTRA_SUBJECT, "Drawing App");
                sendIntent.putExtra(Intent.EXTRA_TEXT, "Check This Image");
                        Uri.parse("file://" + tempPath.getPath()));

                List<ResolveInfo> list = getPackageManager()

                if (list.size() != 0) {

                            "Send Email Using:"));


                else {
                    AlertDialog.Builder confirm = new AlertDialog.Builder(
                    confirm.setMessage("No Email Sending App Available");
                    confirm.setPositiveButton("Set Account",
                            new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog,
                                        int which) {
            } else {
                AlertDialog.Builder confirm = new AlertDialog.Builder(
                confirm.setMessage("No Email Account Available!");
                confirm.setPositiveButton("Set Account",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,
                                    int which) {
                                Intent i = new Intent(
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,
                                    int which) {



    btnFacebook.setOnClickListener(new OnClickListener() {

        public void onClick(View arg0) {
            if (!btnFacebook.isSelected()) {
            } else {
            saveBtnFlag = 1;
            // if (connection.isInternetOn()) {

            if (android.os.Environment.getExternalStorageState().equals(
                    android.os.Environment.MEDIA_MOUNTED)) {
                Intent i = new Intent(DrawAppActivity.this,

            else {
                        R.string.app_name, R.string.Sd_card,


public void tempImageSaving(String tmpPath, byte[] image) {
    Random rand = new Random();

    tempfile = new File(Environment.getExternalStorageDirectory(), tmpPath);
    if (!tempfile.exists()) {

    tempPath = new File(tempfile.getPath(), "DrawApp" + rand.nextInt()
            + ".jpg");
    try {
        FileOutputStream fos1 = new FileOutputStream(tempPath.getPath());


    } catch (FileNotFoundException e) {
    } catch (Exception e) {
    sendBroadcast(new Intent(
            Uri.parse("file://" + Environment.getExternalStorageDirectory())));

public byte[] getCurrentImage() {

    Bitmap b = drawingSurface.getBitmap();
    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    b.compress(Bitmap.CompressFormat.PNG, 100, stream);

    byteArray = stream.toByteArray();

    return byteArray;

private class emailSendingTask extends AsyncTask<String, Void, String> {
    protected void onPreExecute() {
        progressDialog = new ProgressDialog(DrawAppActivity.this);
        progressDialog.setMessage("Saving..Please Wait..");
        // progressDialog.setIcon(R.drawable.icon);;


    protected String doInBackground(String... urls) {

        String response = "";
        try {

            if (android.os.Environment.getExternalStorageState().equals(
                    android.os.Environment.MEDIA_MOUNTED)) {

                response = "Yes";

            } else {
                        R.string.app_name, R.string.Sd_card,


        } catch (Exception e) {


        return response;


    protected void onPostExecute(String result) {

        if (result.contains("Yes")) {

        sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED,
                        + Environment.getExternalStorageDirectory())));


private class ImageSavingTask extends AsyncTask<String, Void, String> {
    protected void onPreExecute() {
        progressDialog = new ProgressDialog(DrawAppActivity.this);
        progressDialog.setMessage("Saving..Please Wait..");
        // progressDialog.setIcon(R.drawable.icon);;


    protected String doInBackground(String... urls) {

        String response = "";
        try {

            if (android.os.Environment.getExternalStorageState().equals(
                    android.os.Environment.MEDIA_MOUNTED)) {

                response = "Yes";

            } else {
                        R.string.app_name, R.string.Sd_card,


        } catch (Exception e) {


        return response;


    protected void onPostExecute(String result) {

        if (result.contains("Yes")) {

            if (CommonFunctions.createDirIfNotExists(getResources()

        sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED,
                        + Environment.getExternalStorageDirectory())));


For facebook application use facebook SDK

How can I compare time in SQL Server?

below query gives you time of the date

select DateAdd(day,-DateDiff(day,0,YourDateTime),YourDateTime) As NewTime from Table

What does from __future__ import absolute_import actually do?

The difference between absolute and relative imports come into play only when you import a module from a package and that module imports an other submodule from that package. See the difference:

$ mkdir pkg
$ touch pkg/
$ touch pkg/
$ echo 'import string;print(string.ascii_uppercase)' > pkg/
$ python2
Python 2.7.9 (default, Dec 13 2014, 18:02:08) [GCC] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg.main1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pkg/", line 1, in <module>
    import string;print(string.ascii_uppercase)
AttributeError: 'module' object has no attribute 'ascii_uppercase'
$ echo 'from __future__ import absolute_import;import string;print(string.ascii_uppercase)' > pkg/
$ python2
Python 2.7.9 (default, Dec 13 2014, 18:02:08) [GCC] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg.main2

In particular:

$ python2 pkg/
Traceback (most recent call last):
  File "pkg/", line 1, in <module>
    from __future__ import absolute_import;import string;print(string.ascii_uppercase)
AttributeError: 'module' object has no attribute 'ascii_uppercase'
$ python2
Python 2.7.9 (default, Dec 13 2014, 18:02:08) [GCC] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg.main2
$ python2 -m pkg.main2

Note that python2 pkg/ has a different behaviour then launching python2 and then importing pkg.main2 (which is equivalent to using the -m switch).

If you ever want to run a submodule of a package always use the -m switch which prevents the interpreter for chaining the sys.path list and correctly handles the semantics of the submodule.

Also, I much prefer using explicit relative imports for package submodules since they provide more semantics and better error messages in case of failure.

iptables LOG and DROP in one rule

At work, I needed to log and block SSLv3 connections on ports 993 (IMAPS) and 995 (POP3S) using iptables. So, I combined Gert van Dijk's How to take down SSLv3 in your network using iptables firewall? (POODLE) with Prevok's answer and came up with this:

iptables -N SSLv3
iptables -A SSLv3 -j LOG --log-prefix "SSLv3 Client Hello detected: "
iptables -A SSLv3 -j DROP
iptables -A INPUT \
  -p tcp \! -f -m multiport --dports 993,995 \
  -m state --state ESTABLISHED -m u32 --u32 \
  "0>>22&0x3C@ 12>>26&0x3C@ 0 & 0xFFFFFF00=0x16030000 && \
   0>>22&0x3C@ 12>>26&0x3C@ 2 & 0xFF=0x01 && \
   0>>22&0x3C@ 12>>26&0x3C@ 7 & 0xFFFF=0x0300" \
  -j SSLv3


  1. To LOG and DROP, create a custom chain (e.g. SSLv3):

    iptables -N SSLv3
    iptables -A SSLv3 -j LOG --log-prefix "SSLv3 Client Hello detected: "
    iptables -A SSLv3 -j DROP
  2. Then, redirect what you want to LOG and DROP to that chain (see -j SSLv3):

    iptables -A INPUT \
      -p tcp \! -f -m multiport --dports 993,995 \
      -m state --state ESTABLISHED -m u32 --u32 \
      "0>>22&0x3C@ 12>>26&0x3C@ 0 & 0xFFFFFF00=0x16030000 && \
       0>>22&0x3C@ 12>>26&0x3C@ 2 & 0xFF=0x01 && \
       0>>22&0x3C@ 12>>26&0x3C@ 7 & 0xFFFF=0x0300" \
      -j SSLv3

Note: mind the order of the rules. Those rules did not work for me until I put them above this one I had on my firewall script:

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

Concatenating date with a string in Excel

Don't know if it's the best way but I'd do this:

=A1 & TEXT(A2,"mm/dd/yyyy")

That should format your date into your desired string.

Edit: That funny number you saw is the number of days between December 31st 1899 and your date. That's how Excel stores dates.

Use of "instanceof" in Java

instanceof is used to check if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface.

Read more from the Oracle language definition here.

width:auto for <input> fields

The only option I can think of is using width:100%. If you want to have a padding on the input field too, than just place a container label around it, move the formatting to that label instead, while also specify the padding to the label. Input fields are rigid.

PDO support for multiple queries (PDO_MYSQL, PDO_MYSQLND)

After half a day of fiddling with this, found out that PDO had a bug where...


//This would run as expected:
$pdo->exec("valid-stmt1; valid-stmt2;");


//This would error out, as expected:
$pdo->exec("non-sense; valid-stmt1;");


//Here is the bug:
$pdo->exec("valid-stmt1; non-sense; valid-stmt3;");

It would execute the "valid-stmt1;", stop on "non-sense;" and never throw an error. Will not run the "valid-stmt3;", return true and lie that everything ran good.

I would expect it to error out on the "non-sense;" but it doesn't.

Here is where I found this info: Invalid PDO query does not return an error

Here is the bug:

So, I tried doing this with mysqli and haven't really found any solid answer on how it works so I thought I's just leave it here for those who want to use it..

    // db connection
    $mysqli = new mysqli("host", "user" , "password", "database");
        throw new Exception("Connection Failed: [".$mysqli->connect_errno. "] : ".$mysqli->connect_error );

    // read file.
    // This file has multiple sql statements.
    $file_sql = file_get_contents("filename.sql");

    if($file_sql == "null" || empty($file_sql) || strlen($file_sql) <= 0){
        throw new Exception("File is empty. I wont run it..");

    //run the sql file contents through the mysqli's multi_query function.
    // here is where it gets complicated...
    // if the first query has errors, here is where you get it.
    $sqlFileResult = $mysqli->multi_query($file_sql);
    // this returns false only if there are errros on first sql statement, it doesn't care about the rest of the sql statements.

    $sqlCount = 1;
    if( $sqlFileResult == false ){
        throw new Exception("File: '".$fullpath."' , Query#[".$sqlCount."], [".$mysqli->errno."]: '".$mysqli->error."' }");

    // so handle the errors on the subsequent statements like this.
    // while I have more results. This will start from the second sql statement. The first statement errors are thrown above on the $mysqli->multi_query("SQL"); line
        // load the next result set into mysqli's active buffer. if this fails the $mysqli->error, $mysqli->errno will have appropriate error info.
        if($mysqli->next_result() == false){
            throw new Exception("File: '".$fullpath."' , Query#[".$sqlCount."], Error No: [".$mysqli->errno."]: '".$mysqli->error."' }");
catch(Exception $e){
    echo $e->getMessage(). " <pre>".$e->getTraceAsString()."</pre>";

String in function parameter

Inside the function parameter list, char arr[] is absolutely equivalent to char *arr, so the pair of definitions and the pair of declarations are equivalent.

void function(char arr[]) { ... }
void function(char *arr)  { ... }

void function(char arr[]);
void function(char *arr);

The issue is the calling context. You provided a string literal to the function; string literals may not be modified; your function attempted to modify the string literal it was given; your program invoked undefined behaviour and crashed. All completely kosher.

Treat string literals as if they were static const char literal[] = "string literal"; and do not attempt to modify them.

Getting full JS autocompletion under Sublime Text

As already mentioned, tern.js is a new and promising project with plugins for Sublime Text, Vim and Emacs. I´ve been using TernJS for Sublime for a while and the suggestions I get are way better than the standard ones:

enter image description here

Tern scans all .js files in your project. You can get support for DOM, nodejs, jQuery, and more by adding "libs" in your .sublime-project file:

"ternjs": {
    "exclude": ["wordpress/**", "node_modules/**"],
    "libs": ["browser", "jquery"],
    "plugins": {
        "requirejs": {
            "baseURL": "./js"

enter image description here

How to manually send HTTP POST requests from Firefox or Chrome browser?

Just to give my 2 cents to this answer, there have been some other clients born since the raise of Postman that worth mentioning here:

What USB driver should we use for the Nexus 5?

While Nexus 5 owners wait for a dedicated driver, you could try this driver, which is the one for the LG G2, from LG Electronics' website, since usually USB drivers are not limited to one particular model. This one, for example, seems like a generic USB driver. You are prompted to download the same one for quite a few models on LG Electronics' website.

I hope this helps you ;)

TypeScript: Property does not exist on type '{}'

You can assign the any type to the object:

let bar: any = {}; = "foobar"; 

How to disable a particular checkstyle rule for a particular line of code?

<module name="Checker">
    <module name="SuppressionCommentFilter"/>
    <module name="TreeWalker">
        <module name="FileContentsHolder"/>

To configure a filter to suppress audit events between a comment containing line BEGIN GENERATED CODE and a comment containing line END GENERATED CODE:

<module name="SuppressionCommentFilter">
  <property name="offCommentFormat" value="BEGIN GENERATED CODE"/>
  <property name="onCommentFormat" value="END GENERATED CODE"/>

public boolean equals(Object obj) { ... } // No violation events will be reported

public int hashCode() { ... } // No violation events will be reported

See more

Testing Private method using mockito

Put your test in the same package, but a different source folder (src/main/java vs. src/test/java) and make those methods package-private. Imo testability is more important than privacy.

C# ASP.NET Single Sign-On Implementation

There are multiple options to implement SSO for a .NET application.

Check out the following tutorials online:

Basics of Single Sign on, July 2012

GaryMcAllisterOnline: ASP.NET MVC 4, ADFS 2.0 and 3rd party STS integration (IdentityServer2), Jan 2013

The first one uses ASP.NET Web Forms, while the second one uses ASP.NET MVC4.

If your requirements allow you to use a third-party solution, also consider OpenID. There's an open source library called DotNetOpenAuth.

For further information, read MSDN blog post Integrate OpenAuth/OpenID with your existing ASP.NET application using Universal Providers.

Hope this helps!

How do you import an Eclipse project into Android Studio now?

Export from Eclipse

  1. Update your Eclipse ADT Plugin to 22.0 or higher, then go to File | Export

  2. Go to Android now then click on Generate Gradle build files, then it would generate gradle file for you.

    enter image description here

  3. Select your project you want to export

    enter image description here

  4. Click on finish now

    enter image description here

Import into Android Studio

  1. In Android Studio, close any projects currently open. You should see the Welcome to Android Studio window.

  2. Click Import Project.

  3. Locate the project you exported from Eclipse, expand it, select it and click OK.

Calling a user defined function in jQuery

function hello(){_x000D_
<script src=""></script>_x000D_
<input type="text" id="event-on-keyup">

No matching client found for package name (Google Analytics) - multiple productFlavors & buildTypes

Whenever you create or update package name Make sure your package name is exactly the same [Upper case and lower case matters]

Do below step.

1). Check applicationId in App level gradle file,

2). Check package_name in your google-services.json file,

3). Check package in your AndroidManifest file

and for full confirmation make sure that your working package directory name i.e.("") is also the same.

EDIT [ Any one who is facing this issue in productFlavour scenario, go check out Droid Chris's Solution ]

Using global variables between files?

You can think of Python global variables as "module" variables - and as such they are much more useful than the traditional "global variables" from C.

A global variable is actually defined in a module's __dict__ and can be accessed from outside that module as a module attribute.

So, in your example:

# ../myproject/

# Define global myList
# global myList  - there is no "global" declaration at module level. Just inside
# function and methods
myList = []

# Imports
import subfile

# Do something


# ../myproject/

# Save "hey" into myList
def stuff():
     # You have to make the module main available for the 
     # code here.
     # Placing the import inside the function body will
     # usually avoid import cycles - 
     # unless you happen to call this function from 
     # either main or subfile's body (i.e. not from inside a function or method)
     import main

How to put a UserControl into Visual Studio toolBox

Using VS 2010:

Let's say you have a Windows.Forms project. You add a UserControl (say MyControl) to the project, and design it all up. Now you want to add it to your toolbox.

As soon as the project is successfully built once, it will appear in your Framework Components. Right click the Toolbox to get the context menu, select "Choose Items...", and browse to the name of your control (MyControl) under the ".NET Framework Components" tab.

Advantage over using dlls: you can edit the controls in the same project as your form, and the form will build with the new controls. However, the control will only be avilable to this project.

Note: If the control has build errors, resolve them before moving on to the containing forms, or the designer has a heart attack.

Calling multiple JavaScript functions on a button click

Try this .... I got it... onClientClick="var b=validateView();if(b) var b=ShowDiv1();return b;"

how to generate web service out of wsdl

You cannot guarantee that the automatically-generated WSDL will match the WSDL from which you create the service interface.

In your scenario, you should place the WSDL file on your web site somewhere, and have consumers use that URL. You should disable the Documentation protocol in the web.config so that "?wsdl" does not return a WSDL. See <protocols> Element.

Also, note the first paragraph of that article:

This topic is specific to a legacy technology. XML Web services and XML Web service clients should now be created using Windows Communication Foundation (WCF).

How to set up Android emulator proxy settings

Easiest way is to delete default APN from emulator(in my case its T- mobile) and create new APN with your proxy settings.

Note: i have tried all command line options and also tried setting the proxy for emulators default APN but nothing worked.

DateTimeFormat in TypeScript

This should work...

var displayDate = new Date().toLocaleDateString();


But I suspect you are trying it on something else, for example:

var displayDate =; // No!


Error inflating class fragment

Check you class path, this could be the view inflator could not find your class definition as defined in your xml class="de.androidbuch.activiti.task.TaskDetailsFragment" the above path could be wrong.

How to output something in PowerShell

Write-Host "Found file - " + $File.FullName -ForegroundColor Magenta

Magenta can be one of the "System.ConsoleColor" enumerator values - Black, DarkBlue, DarkGreen, DarkCyan, DarkRed, DarkMagenta, DarkYellow, Gray, DarkGray, Blue, Green, Cyan, Red, Magenta, Yellow, White.

The + $File.FullName is optional, and shows how to put a variable into the string.

Angular ng-if="" with multiple arguments

It is possible.

<span ng-if="checked && checked2">
  I'm removed when the checkbox is unchecked.

More than one file was found with OS independent path 'META-INF/LICENSE'

In my case this exception was caused by jupiter

implementation 'org.junit.jupiter:junit-jupiter:5.6.2'

Check if something is (not) in a list in Python

How do I check if something is (not) in a list in Python?

The cheapest and most readable solution is using the in operator (or in your specific case, not in). As mentioned in the documentation,

The operators in and not in test for membership. x in s evaluates to True if x is a member of s, and False otherwise. x not in s returns the negation of x in s.


The operator not in is defined to have the inverse true value of in.

y not in x is logically the same as not y in x.

Here are a few examples:

'a' in [1, 2, 3]
# False

'c' in ['a', 'b', 'c']
# True

'a' not in [1, 2, 3]
# True

'c' not in ['a', 'b', 'c']
# False

This also works with tuples, since tuples are hashable (as a consequence of the fact that they are also immutable):

(1, 2) in [(3, 4), (1, 2)]
#  True

If the object on the RHS defines a __contains__() method, in will internally call it, as noted in the last paragraph of the Comparisons section of the docs.

... in and not in, are supported by types that are iterable or implement the __contains__() method. For example, you could (but shouldn't) do this:

[3, 2, 1].__contains__(1)
# True

in short-circuits, so if your element is at the start of the list, in evaluates faster:

lst = list(range(10001))
%timeit 1 in lst
%timeit 10000 in lst  # Expected to take longer time.

68.9 ns ± 0.613 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
178 µs ± 5.01 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

If you want to do more than just check whether an item is in a list, there are options:

  • list.index can be used to retrieve the index of an item. If that element does not exist, a ValueError is raised.
  • list.count can be used if you want to count the occurrences.

The XY Problem: Have you considered sets?

Ask yourself these questions:

  • do you need to check whether an item is in a list more than once?
  • Is this check done inside a loop, or a function called repeatedly?
  • Are the items you're storing on your list hashable? IOW, can you call hash on them?

If you answered "yes" to these questions, you should be using a set instead. An in membership test on lists is O(n) time complexity. This means that python has to do a linear scan of your list, visiting each element and comparing it against the search item. If you're doing this repeatedly, or if the lists are large, this operation will incur an overhead.

set objects, on the other hand, hash their values for constant time membership check. The check is also done using in:

1 in {1, 2, 3} 
# True

'a' not in {'a', 'b', 'c'}
# False

(1, 2) in {('a', 'c'), (1, 2)}
# True

If you're unfortunate enough that the element you're searching/not searching for is at the end of your list, python will have scanned the list upto the end. This is evident from the timings below:

l = list(range(100001))
s = set(l)

%timeit 100000 in l
%timeit 100000 in s

2.58 ms ± 58.9 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
101 ns ± 9.53 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)

As a reminder, this is a suitable option as long as the elements you're storing and looking up are hashable. IOW, they would either have to be immutable types, or objects that implement __hash__.

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

You can try this:

You must follow the following format

    $('element,id,class').on('click', function(){....});

*JQuery code*

    $('body').addClass('.anything').on('click', function(){
      //do some code here i.e

Find row number of matching value

For your first method change ws.Range("A") to ws.Range("A:A") which will search the entirety of column a, like so:

Sub Find_Bingo()

        Dim wb As Workbook
        Dim ws As Worksheet
        Dim FoundCell As Range
        Set wb = ActiveWorkbook
        Set ws = ActiveSheet

            Const WHAT_TO_FIND As String = "Bingo"

            Set FoundCell = ws.Range("A:A").Find(What:=WHAT_TO_FIND)
            If Not FoundCell Is Nothing Then
                MsgBox (WHAT_TO_FIND & " found in row: " & FoundCell.Row)
                MsgBox (WHAT_TO_FIND & " not found")
            End If
End Sub

For your second method, you are using Bingo as a variable instead of a string literal. This is a good example of why I add Option Explicit to the top of all of my code modules, as when you try to run the code it will direct you to this "variable" which is undefined and not intended to be a variable at all.

Additionally, when you are using With...End With you need a period . before you reference Cells, so Cells should be .Cells. This mimics the normal qualifying behavior (i.e. Sheet1.Cells.Find..)

Change Bingo to "Bingo" and change Cells to .Cells

With Sheet1
        Set FoundCell = .Cells.Find(What:="Bingo", After:=.Cells(1, 1), _
        LookIn:=xlValues, lookat:=xlPart, SearchOrder:=xlByRows, _
        SearchDirection:=xlNext, MatchCase:=False, SearchFormat:=False)
    End With

If Not FoundCell Is Nothing Then
        MsgBox ("""Bingo"" found in row " & FoundCell.Row)
        MsgBox ("Bingo not found")
End If


In my

With Sheet1
End With

The Sheet1 refers to a worksheet's code name, not the name of the worksheet itself. For example, say I open a new blank Excel workbook. The default worksheet is just Sheet1. I can refer to that in code either with the code name of Sheet1 or I can refer to it with the index of Sheets("Sheet1"). The advantage to using a codename is that it does not change if you change the name of the worksheet.

Continuing this example, let's say I renamed Sheet1 to Data. Using Sheet1 would continue to work, as the code name doesn't change, but now using Sheets("Sheet1") would return an error and that syntax must be updated to the new name of the sheet, so it would need to be Sheets("Data").

In the VB Editor you would see something like this:

code object explorer example

Notice how, even though I changed the name to Data, there is still a Sheet1 to the left. That is what I mean by codename.

The Data worksheet can be referenced in two ways:

Debug.Print Sheet1.Name
Debug.Print Sheets("Data").Name

Both should return Data

More discussion on worksheet code names can be found here.

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

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

Now we can write this:

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

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

Angularjs action on click of button

The calculation occurs immediately since the calculation call is bound in the template, which displays its result when quantity changes.

Instead you could try the following approach. Change your markup to the following:

<div ng-controller="myAppController" style="text-align:center">
  <p style="font-size:28px;">Enter Quantity:
      <input type="text" ng-model="quantity"/>
  <button ng-click="calculateQuantity()">Calculate</button>
  <h2>Total Cost: Rs.{{quantityResult}}</h2>

Next, update your controller:

myAppModule.controller('myAppController', function($scope,calculateService) {
  $scope.quantityResult = 0;

  $scope.calculateQuantity = function() {
    $scope.quantityResult = calculateService.calculate($scope.quantity, 10);

Here's a JSBin example that demonstrates the above approach.

The problem with this approach is the calculated result remains visible with the old value till the button is clicked. To address this, you could hide the result whenever the quantity changes.

This would involve updating the template to add an ng-change on the input, and an ng-if on the result:

<input type="text" ng-change="hideQuantityResult()" ng-model="quantity"/>


<h2 ng-if="showQuantityResult">Total Cost: Rs.{{quantityResult}}</h2>

In the controller add:

$scope.showQuantityResult = false;

$scope.calculateQuantity = function() {
  $scope.quantityResult = calculateService.calculate($scope.quantity, 10);
  $scope.showQuantityResult = true;

$scope.hideQuantityResult = function() {
  $scope.showQuantityResult = false;

These updates can be seen in this JSBin demo.

ASP.NET MVC - Extract parameter of an URL

public ActionResult Index(int id,string value)

This function get values form URL After that you can use below function

Request.RawUrl - Return complete URL of Current page

RouteData.Values - Return Collection of Values of URL

Request.Params - Return Name Value Collections

SQL: parse the first, middle and last name from a fullname field

Here's a stored procedure that will put the first word found into First Name, the last word into Last Name and everything in between into Middle Name.

create procedure [dbo].[import_ParseName]
    @FullName nvarchar(max),
    @FirstName nvarchar(255) output,
    @MiddleName nvarchar(255) output,
    @LastName nvarchar(255)  output

set @FirstName = ''
set @MiddleName = ''
set @LastName = ''  
set @FullName = ltrim(rtrim(@FullName))

declare @ReverseFullName nvarchar(max)
set @ReverseFullName = reverse(@FullName)

declare @lengthOfFullName int
declare @endOfFirstName int
declare @beginningOfLastName int

set @lengthOfFullName = len(@FullName)
set @endOfFirstName = charindex(' ', @FullName)
set @beginningOfLastName = @lengthOfFullName - charindex(' ', @ReverseFullName) + 1

set @FirstName = case when @endOfFirstName <> 0 
                      then substring(@FullName, 1, @endOfFirstName - 1) 
                      else ''

set @MiddleName = case when (@endOfFirstName <> 0 and @beginningOfLastName <> 0 and @beginningOfLastName > @endOfFirstName)
                       then ltrim(rtrim(substring(@FullName, @endOfFirstName , @beginningOfLastName - @endOfFirstName))) 
                       else ''

set @LastName = case when @beginningOfLastName <> 0 
                     then substring(@FullName, @beginningOfLastName + 1 , @lengthOfFullName - @beginningOfLastName)
                     else ''



And here's me calling it.

DECLARE @FirstName nvarchar(255),
        @MiddleName nvarchar(255),
        @LastName nvarchar(255)

EXEC    [dbo].[import_ParseName]
        @FullName = N'Scott The Other Scott Kowalczyk',
        @FirstName = @FirstName OUTPUT,
        @MiddleName = @MiddleName OUTPUT,
        @LastName = @LastName OUTPUT

print   @FirstName 
print   @MiddleName
print   @LastName 


The Other Scott

Warning: The method assertEquals from the type Assert is deprecated

When I use Junit4, import junit.framework.Assert; import junit.framework.TestCase; the warning info is :The type of Assert is deprecated

when import like this: import org.junit.Assert; import org.junit.Test; the warning has disappeared

possible duplicate of differences between 2 JUnit Assert classes

Java AES and using my own Key

You should use a KeyGenerator to generate the Key,

AES key lengths are 128, 192, and 256 bit depending on the cipher you want to use.

Take a look at the tutorial here

Here is the code for Password Based Encryption, this has the password being entered through you can change that to use a stored password if you want.

        PBEKeySpec pbeKeySpec;
        PBEParameterSpec pbeParamSpec;
        SecretKeyFactory keyFac;

        // Salt
        byte[] salt = {
            (byte)0xc7, (byte)0x73, (byte)0x21, (byte)0x8c,
            (byte)0x7e, (byte)0xc8, (byte)0xee, (byte)0x99

        // Iteration count
        int count = 20;

        // Create PBE parameter set
        pbeParamSpec = new PBEParameterSpec(salt, count);

        // Prompt user for encryption password.
        // Collect user password as char array (using the
        // "readPassword" method from above), and convert
        // it into a SecretKey object, using a PBE key
        // factory.
        System.out.print("Enter encryption password:  ");
        pbeKeySpec = new PBEKeySpec(readPassword(;
        keyFac = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
        SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);

        // Create PBE Cipher
        Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");

        // Initialize PBE Cipher with key and parameters
        pbeCipher.init(Cipher.ENCRYPT_MODE, pbeKey, pbeParamSpec);

        // Our cleartext
        byte[] cleartext = "This is another example".getBytes();

        // Encrypt the cleartext
        byte[] ciphertext = pbeCipher.doFinal(cleartext);

Is there a standardized method to swap two variables in Python?

Does not work for multidimensional arrays, because references are used here.

import numpy as np

# swaps
data = np.random.random(2)
data[0], data[1] = data[1], data[0]

# does not swap
data = np.random.random((2, 2))
data[0], data[1] = data[1], data[0]

See also Swap slices of Numpy arrays

Performance of Java matrix math libraries?

I'm the main author of jblas and wanted to point out that I've released Version 1.0 in late December 2009. I worked a lot on the packaging, meaning that you can now just download a "fat jar" with ATLAS and JNI libraries for Windows, Linux, Mac OS X, 32 and 64 bit (except for Windows). This way you will get the native performance just by adding the jar file to your classpath. Check it out at!

jQuery table sort

My vote! jquery.sortElements.js and simple jquery
Very simple, very easy, thanks nandhp...

            $('th').live('click', function(){

            var th = $(this), thIndex = th.index(), var table = $(this).parent().parent();

                case 'false': inverse = true; break;
                case 'true:': inverse = false; break;
                default: inverse = false; break;

                return $(this).index() === thIndex;
            }).sortElements(function(a, b){
                return $.text([a]) > $.text([b]) ?
                    inverse ? -1 : 1
                    : inverse ? 1 : -1;
            }, function(){
                // parentNode is the element we want to move
                return this.parentNode; 
            inverse = !inverse;     

Dei uma melhorada do código
One cod better! Function for All tables in all Th in all time... Look it!

How to increase code font size in IntelliJ?

On Intellij Idea 3.3(Ultimate) System : Mac

IntelliJ Idea ? Preferences (CMD + ,) ? Editor ? General(Main) : Uncheck/Check "Change font size(Zoon) with Command + Mouse Wheel"

What are the differences between Abstract Factory and Factory design patterns?

To make it very simple with minimum interface & please focus "//1":

class FactoryProgram
        static void Main()
            object myType = Program.MyFactory("byte");

            myType = Program.MyFactory("float"); //3


        static object MyFactory(string typeName)
            object desiredType = null; //1
            switch (typeName)
                case "byte": desiredType = new System.Byte(); break; //2
                case "long": desiredType = new System.Int64(); break;
                case "float": desiredType = new System.Single(); break;
                default: throw new System.NotImplementedException();
            return desiredType;

Here important points: 1. Factory & AbstractFactory mechanisms must use inheritance (System.Object-> byte, float ...); so if you have inheritance in program then Factory(Abstract Factory would not be there most probably) is already there by design 2. Creator (MyFactory) knows about concrete type so returns concrete type object to caller(Main); In abstract factory return type would be an Interface.

interface IVehicle { string VehicleName { get; set; } }
interface IVehicleFactory
        IVehicle CreateSingleVehicle(string vehicleType);
class HondaFactory : IVehicleFactory
        public IVehicle CreateSingleVehicle(string vehicleType)
            switch (vehicleType)
                case "Sports": return new SportsBike();
                case "Regular":return new RegularBike();
                default: throw new ApplicationException(string.Format("Vehicle '{0}' cannot be created", vehicleType));
class HeroFactory : IVehicleFactory
        public IVehicle CreateSingleVehicle(string vehicleType)
            switch (vehicleType)
                case "Sports":  return new SportsBike();
                case "Scooty": return new Scooty();
                case "DarkHorse":return new DarkHorseBike();
                default: throw new ApplicationException(string.Format("Vehicle '{0}' cannot be created", vehicleType));

class RegularBike : IVehicle { public string VehicleName { get { return "Regular Bike- Name"; } set { VehicleName = value; } } }
class SportsBike : IVehicle { public string VehicleName { get { return "Sports Bike- Name"; } set { VehicleName = value; } } }
class RegularScooter : IVehicle { public string VehicleName { get { return "Regular Scooter- Name"; } set { VehicleName = value; } } }
class Scooty : IVehicle { public string VehicleName { get { return "Scooty- Name"; } set { VehicleName = value; } } }
class DarkHorseBike : IVehicle { public string VehicleName { get { return "DarkHorse Bike- Name"; } set { VehicleName = value; } } }

class Program
    static void Main(string[] args)
        IVehicleFactory honda = new HondaFactory(); //1
        RegularBike hondaRegularBike = (RegularBike)honda.CreateSingleVehicle("Regular"); //2
        SportsBike hondaSportsBike = (SportsBike)honda.CreateSingleVehicle("Sports");
        Console.WriteLine("******* Honda **********"+hondaRegularBike.VehicleName+ hondaSportsBike.VehicleName);

        IVehicleFactory hero = new HeroFactory();
        DarkHorseBike heroDarkHorseBike = (DarkHorseBike)hero.CreateSingleVehicle("DarkHorse");
        SportsBike heroSportsBike = (SportsBike)hero.CreateSingleVehicle("Sports");
        Scooty heroScooty = (Scooty)hero.CreateSingleVehicle("Scooty");
        Console.WriteLine("******* Hero **********"+heroDarkHorseBike.VehicleName + heroScooty.VehicleName+ heroSportsBike.VehicleName);


Important points: 1. Requirement: Honda would create "Regular", "Sports" but Hero would create "DarkHorse", "Sports" and "Scooty". 2. why two interfaces? One for manufacturer type(IVehicleFactory) and another for product factory(IVehicle); other way to understand 2 interfaces is abstract factory is all about creating related objects 2. The catch is the IVehicleFactory's children returning and IVehicle(instead of concrete in factory); so I get parent variable(IVehicle); then I create actual concrete type by calling CreateSingleVehicle and then casting parent object to actual child object. What would happen if I do RegularBike heroRegularBike = (RegularBike)hero.CreateSingleVehicle("Regular");; you will get ApplicationException and that's why we need generic abstract factory which I would explain if required. Hope it helps from beginner to intermediate audience.

Combine two integer arrays

I think you have to allocate a new array and put the values into the new array. For example:

int[] array1and2 = new int[array1.length + array2.length];
int currentPosition = 0;

for( int i = 0; i < array1.length; i++) {
    array1and2[currentPosition] = array1[i];

for( int j = 0; j < array2.length; j++) {
    array1and2[currentPosition] = array2[j];

As far as I can tell just looking at it, this code should work.

How can I revert multiple Git commits (already pushed) to a published repository?

The Problem

There are a number of work-flows you can use. The main point is not to break history in a published branch unless you've communicated with everyone who might consume the branch and are willing to do surgery on everyone's clones. It's best not to do that if you can avoid it.

Solutions for Published Branches

Your outlined steps have merit. If you need the dev branch to be stable right away, do it that way. You have a number of tools for Debugging with Git that will help you find the right branch point, and then you can revert all the commits between your last stable commit and HEAD.

Either revert commits one at a time, in reverse order, or use the <first_bad_commit>..<last_bad_commit> range. Hashes are the simplest way to specify the commit range, but there are other notations. For example, if you've pushed 5 bad commits, you could revert them with:

# Revert a series using ancestor notation.
git revert --no-edit

# Revert a series using commit hashes.
git revert --no-edit ffffffff..12345678

This will apply reversed patches to your working directory in sequence, working backwards towards your known-good commit. With the --no-edit flag, the changes to your working directory will be automatically committed after each reversed patch is applied.

See man 1 git-revert for more options, and man 7 gitrevisions for different ways to specify the commits to be reverted.

Alternatively, you can branch off your HEAD, fix things the way they need to be, and re-merge. Your build will be broken in the meantime, but this may make sense in some situations.

The Danger Zone

Of course, if you're absolutely sure that no one has pulled from the repository since your bad pushes, and if the remote is a bare repository, then you can do a non-fast-forward commit.

git reset --hard <last_good_commit>
git push --force

This will leave the reflog intact on your system and the upstream host, but your bad commits will disappear from the directly-accessible history and won't propagate on pulls. Your old changes will hang around until the repositories are pruned, but only Git ninjas will be able to see or recover the commits you made by mistake.

Handle file download from ajax post

This is a 3 years old question but I had the same problem today. I looked your edited solution but I think that it can sacrifice the performance because it has to make a double request. So if anyone needs another solution that doesn't imply to call the service twice then this is the way I did it:

<form id="export-csv-form" method="POST" action="/the/path/to/file">
    <input type="hidden" name="anyValueToPassTheServer" value="">

This form is just used to call the service and avoid to use a window.location(). After that you just simply have to make a form submit from jquery in order to call the service and get the file. It's pretty simple but this way you can make a download using a POST. I now that this could be easier if the service you're calling is a GET, but that's not my case.

What are some alternatives to ReSharper?

CodeRush. Also, Scott Hanselman has a nice post comparing them, ReSharper vs. CodeRush.

A more up-to-date comparison is in Coderush vs Resharper by Jason Irwin.

How do I use a 32-bit ODBC driver on 64-bit Server 2008 when the installer doesn't create a standard DSN?

It turns out that you can create 32-bit ODBC connections using C:\Windows\SysWOW64\odbcad32.exe. My solution was to create the 32-bit ODBC connection as a System DSN. This still didn't allow me to connect to it since .NET couldn't look it up. After significant and fruitless searching to find how to get the OdbcConnection class to look for the DSN in the right place, I stumbled upon a web site that suggested modifying the registry to solve a different problem.

I ended up creating the ODBC connection directly under HKLM\Software\ODBC. I looked in the SysWOW6432 key to find the parameters that were set up using the 32-bit version of the ODBC administration tool and recreated this in the standard location. I didn't add an entry for the driver, however, as that was not installed by the standard installer for the app either.

After creating the entry (by hand), I fired up my windows service and everything was happy.

difference between primary key and unique key

Simply Primary Key is a unique and can't be null, unique can be null and may not be unique.

How do I change the font color in an html table?

if you need to change specific option from the select menu you can do it like this

option[value="Basic"] {

or you can change them all

select {

How to change pivot table data source in Excel?

right click on the pivot table in excel choose wizard click 'back' click 'get data...' in the query window File - Table Definition

then you can create a new or choose a different connection

worked perfectly.

the get data button is next to the tiny button with a red arrow next to the range text input box.

Excel Date Conversion from yyyymmdd to mm/dd/yyyy

Here is a bare bones version:

Let's say that you have a date in Cell A1 in the format you described. For example: 19760210.

Then this formula will give you the date you want:


On my system (Excel 2010) it works with strings or floats.

How do I directly modify a Google Chrome Extension File? (.CRX)

Installed Chrome extension directories are listed below:

  1. Copy the folder of the extension you wish to modify. ( Named according to the extension ID, to find the ID of the extension, go to chrome://extensions/). Once copied, you have to remove the _metadata folder.

  2. From chrome://extensions in Developer mode select Load unpacked extension... and select your copied extension folder, if it contains a subfolder this is named by the version, select this version folder where there is a manifest file, this file is necessary for Chrome.

  3. Make your changes, then select reload and refresh the page for your extension to see your changes.

Chrome extension directories


/Users/username/Library/Application Support/Google/Chrome/Default/Extensions

Windows 7:

C:\Users\username\AppData\Local\Google\Chrome\User Data\Default\Extensions

Windows XP:

C:\Documents and Settings\YourUserName\Local Settings\Application Data\Google\Chrome\User Data\Default

Ubuntu 14.04:


HTML Input Type Date, Open Calendar by default

This is not possible with native HTML input elements. You can use webshim polyfill, which gives you this option by using this markup.

<input type="date" data-date-inline-picker="true" />

Here is a small demo

'uint32_t' does not name a type

I had tha same problem trying to compile a lib I download from the internet. In my case, there was already a #include <cstdint> in the code. I solved it adding a:

using std::uint32_t;

ssh connection refused on Raspberry Pi

I think pi has ssh server enabled by default. Mine have always worked out of the box. Depends which operating system version maybe.

Most of the time when it fails for me it is because the ip address has been changed. Perhaps you are pinging something else now? Also sometimes they just refuse to connect and need a restart.

Hidden Columns in jqGrid

This thread is pretty old I suppose, but in case anyone else stumbles across this question... I had to grab a value from the selected row of a table, but I didn't want to show the column that row was from. I used hideCol, but had the same problem as Andy where it looked messy. To fix it (call it a hack) I just re-set the width of the grid.

jQuery(document).ready(function() {

                width: 700,

Since my row widths are automatic, when I reset the width of the table it reset the column widths but excluded the hidden one, so they filled in the gap.

How to execute raw queries with Laravel 5.1?

    DB::statement("your query")

I used it for add index to column in migration

Automatically deleting related rows in Laravel (Eloquent ORM)

You can actually set this up in your migrations:



You may also specify the desired action for the "on delete" and "on update" properties of the constraint:


how to add new <li> to <ul> onclick with javascript

There is nothing much to add to your code except appending the li tag to the ul


and there you go just add this to your function and then it should work.

Calculating days between two dates with Java

Simplest way:

public static long getDifferenceDays(Date d1, Date d2) {
    long diff = d2.getTime() - d1.getTime();
    return TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS);

Declare variable in table valued function

There are two flavors of table valued functions. One that is just a select statement and one that can have more rows than just a select statement.

This can not have a variable:

create function Func() returns table
select 10 as ColName

You have to do like this instead:

create function Func()
returns @T table(ColName int)
  declare @Var int
  set @Var = 10
  insert into @T(ColName) values (@Var)

Elegant way to create empty pandas DataFrame with NaN of type float

Simply pass the desired value as first argument, like 0, math.inf or, here, np.nan. The constructor then initializes and fills the value array to the size specified by arguments index and columns:

>>> import numpy as np
>>> import pandas as pd
>>> df = pd.DataFrame(np.nan, index=[0, 1, 2, 3], columns=['A', 'B'])

>>> df.dtypes
A    float64
B    float64
dtype: object

>>> df.values
array([[nan, nan],
       [nan, nan],
       [nan, nan],
       [nan, nan]])

How to overlay image with color in CSS?

#header.overlay {
    background-color: SlateGray;
    width: 100%;
    height: 100%;
    opacity: 0.20;
    -moz-opacity: 20%;
    -webkit-opacity: 20%;
    z-index: 2;

Something like this. Just add the overlay class to the header, obviously.

Break when a value changes using the Visual Studio debugger

You can use a memory watchpoint in unmanaged code. Not sure if these are available in managed code though.

Set Content-Type to application/json in jsp file

@Petr Mensik & kensen john

Thanks, I could not used the page directive because I have to set a different content type according to some URL parameter. I will paste my code here since it's something quite common with JSON:

        String callback = request.getParameter("callback");
        if (callback != null) {
            // Equivalent to: <@page contentType="text/javascript" pageEncoding="UTF-8">
        } else {
            // Equivalent to: <@page contentType="application/json" pageEncoding="UTF-8">


        String output = "";

        if (callback != null) {
            output += callback + "(";

        output += jsonObj.toString();

        if (callback != null) {
            output += ");";
    <%=output %>

When callback is supplied, returns:

    callback({...JSON stuff...});

with content-type "text/javascript"

When callback is NOT supplied, returns:

    {...JSON stuff...}

with content-type "application/json"

Creating a singleton in Python

Well, other than agreeing with the general Pythonic suggestion on having module-level global, how about this:

def singleton(class_):
    class class_w(class_):
        _instance = None
        def __new__(class2, *args, **kwargs):
            if class_w._instance is None:
                class_w._instance = super(class_w, class2).__new__(class2, *args, **kwargs)
                class_w._instance._sealed = False
            return class_w._instance
        def __init__(self, *args, **kwargs):
            if self._sealed:
            super(class_w, self).__init__(*args, **kwargs)
            self._sealed = True
    class_w.__name__ = class_.__name__
    return class_w

class MyClass(object):
    def __init__(self, text):
        print text
    def name(class_):
        print class_.__name__

x = MyClass(111)
y = MyClass(222)
print id(x) == id(y)

Output is:

111     # the __init__ is called only on the 1st time
MyClass # the __name__ is preserved
True    # this is actually the same instance

How to get an isoformat datetime string including the default timezone?

To get the current time in UTC in Python 3.2+:

>>> from datetime import datetime, timezone

To get local time in Python 3.3+:

>>> from datetime import datetime, timezone

Explanation: produces a timezone aware datetime object in UTC time. astimezone() then changes the timezone of the datetime object, to the system's locale timezone if called with no arguments. Timezone aware datetime objects then produce the correct ISO format automatically.

How to concatenate two strings in C++?

Since it's C++ why not to use std::string instead of char*? Concatenation will be trivial:

std::string str = "abc";
str += "another";

Join vs. sub-query

Run on a very large database from an old Mambo CMS:

SELECT id, alias
  id IN (
      DISTINCT catid
    FROM mos_content

0 seconds

  DISTINCT mos_content.catid,
  mos_content, mos_categories
  mos_content.catid =;

~3 seconds

An EXPLAIN shows that they examine the exact same number of rows, but one takes 3 seconds and one is near instant. Moral of the story? If performance is important (when isn't it?), try it multiple ways and see which one is fastest.


  mos_content, mos_categories
  mos_content.catid =;

0 seconds

Again, same results, same number of rows examined. My guess is that DISTINCT mos_content.catid takes far longer to figure out than DISTINCT does.

jquery beforeunload when closing (not leaving) the page?

As indicated here, you can implement it by "filtering" what is originating the exit of this page.

As mentionned in the comments, here's a new version of the code in the other question, which also include the ajax request you make in your question :

var canExit = true;

// For every function that will call an ajax query, you need to set the var "canExit" to false, then set it to false once the ajax is finished.

function checkCart() {
  canExit = false;
    url : 'index.php?route=module/cart/check',
    type : 'POST',
    dataType : 'json',
    success : function (result) {
       if (result) {
        canExit = true;

$(document).on('click', 'a', function() {canExit = true;}); // can exit if it's a link
$(window).on('beforeunload', function() {
    if (canExit) return null; // null will allow exit without a question
    // Else, just return the message you want to display
    return "Do you really want to close?";

Important: You shouldn't have a global variable defined (here canExit), this is here for simpler version.

Note that you can't override completely the confirm message (at least in chrome). The message you return will only be prepended to the one given by Chrome. Here's the reason : How can I override the OnBeforeUnload dialog and replace it with my own?

How to convert hex strings to byte values in Java

Convert string to Byte-Array:

byte[] theByteArray = stringToConvert.getBytes();

Convert String to Byte:

 String str = "aa";

 byte b = Byte.valueOf(str);

Hidden Features of C#?

How about the FlagsAttribute on an enumeration? It allows you to perform bitwise operations... took me forever to find out how to do bitwise operations in .NET nicely.

PHP to write Tab Characters inside a file?

Use \t and enclose the string with double-quotes:

$chunk = "abc\tdef\tghi";

Sorting a Dictionary in place with respect to keys

By design, dictionaries are not sortable. If you need this capability in a dictionary, look at SortedDictionary instead.

How do I change the UUID of a virtual disk?

Even though this question asked is old, note that changing a UUID on a virtual HDD in a windows system will make windows treat it as a not activated machine (as it notices the disk change) and will ask for reactivation !

Connect Bluestacks to Android Studio

  1. Goto Blustacks settings > Preferences > Check Enable Android Debug Bridge (ADB)
  2. Restart Bluestacks and Start Android Studio
  3. Done

Using getline() with file input in C++

getline, as it name states, read a whole line, or at least till a delimiter that can be specified.

So the answer is "no", getlinedoes not match your need.

But you can do something like:

inFile >> first_name >> last_name >> age;
name = first_name + " " + last_name;

How to convert a date to milliseconds

The 2017 answer is: Use the date and time classes introduced in Java 8 (and also backported to Java 6 and 7 in the ThreeTen Backport).

If you want to interpret the date-time string in the computer’s time zone:

    long millisSinceEpoch = LocalDateTime.parse(myDate, DateTimeFormatter.ofPattern("uuuu/MM/dd HH:mm:ss"))

If another time zone, fill that zone in instead of ZoneId.systemDefault(). If UTC, use

    long millisSinceEpoch = LocalDateTime.parse(myDate, DateTimeFormatter.ofPattern("uuuu/MM/dd HH:mm:ss"))