Programs & Examples On #Carrington

Create a custom callback in JavaScript

Actually, your code will pretty much work as is, just declare your callback as an argument and you can call it directly using the argument name.

The basics

function doSomething(callback) {
    // ...

    // Call the callback
    callback('stuff', 'goes', 'here');

function foo(a, b, c) {
    // I'm the callback
    alert(a + " " + b + " " + c);


That will call doSomething, which will call foo, which will alert "stuff goes here".

Note that it's very important to pass the function reference (foo), rather than calling the function and passing its result (foo()). In your question, you do it properly, but it's just worth pointing out because it's a common error.

More advanced stuff

Sometimes you want to call the callback so it sees a specific value for this. You can easily do that with the JavaScript call function:

function Thing(name) { = name;
Thing.prototype.doSomething = function(callback) {
    // Call our callback, but using our own instance as the context;

function foo() {

var t = new Thing('Joe');
t.doSomething(foo);  // Alerts "Joe" via `foo`

You can also pass arguments:

function Thing(name) { = name;
Thing.prototype.doSomething = function(callback, salutation) {
    // Call our callback, but using our own instance as the context, salutation);

function foo(salutation) {
    alert(salutation + " " +;

var t = new Thing('Joe');
t.doSomething(foo, 'Hi');  // Alerts "Hi Joe" via `foo`

Sometimes it's useful to pass the arguments you want to give the callback as an array, rather than individually. You can use apply to do that:

function Thing(name) { = name;
Thing.prototype.doSomething = function(callback) {
    // Call our callback, but using our own instance as the context
    callback.apply(this, ['Hi', 3, 2, 1]);

function foo(salutation, three, two, one) {
    alert(salutation + " " + + " - " + three + " " + two + " " + one);

var t = new Thing('Joe');
t.doSomething(foo);  // Alerts "Hi Joe - 3 2 1" via `foo`

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

How To Auto-Format / Indent XML/HTML in Notepad++

It's been the third time that I install Windows and npp and after some time I realize the tidy function no longer work. So I google for a solution, come to this thread, then with the help of few more so threads I finally fix it. I'll put a summary of all my actions once and for all.

  1. Install TextFX plugin: Plugins -> Plugin Manager -> Show Plugin Manager. Select TextFX Characters and install. After a restart of npp, the menu 'TextFX' should be visible. (credits: @remipod).

  2. Install libtidy.dll by pasting the Config folder from an old npp package: Follow instructions in this answer.

  3. After having a Config folder in your latest npp installation destination (typically C:\Program Files (x86)\Notepad++\plugins), npp needs write access to that folder. Right click Config folder -> Properties -> Security tab -> select Users, click Edit -> check Full control to allow read/write access. Note that you need administrator privileges to do that.

  4. Restart npp and verify TextFX -> TextFX HTML Tidy -> Tidy: Reindent XML works.

Best practices to test protected methods with PHPUnit

I'd like to propose a slight variation to getMethod() defined in uckelman's answer.

This version changes getMethod() by removing hard-coded values and simplifying usage a little. I recommend adding it to your PHPUnitUtil class as in the example below or to your PHPUnit_Framework_TestCase-extending class (or, I suppose, globally to your PHPUnitUtil file).

Since MyClass is being instantiated anyways and ReflectionClass can take a string or an object...

class PHPUnitUtil {
     * Get a private or protected method for testing/documentation purposes.
     * How to use for MyClass->foo():
     *      $cls = new MyClass();
     *      $foo = PHPUnitUtil::getPrivateMethod($cls, 'foo');
     *      $foo->invoke($cls, $...);
     * @param object $obj The instantiated instance of your class
     * @param string $name The name of your private/protected method
     * @return ReflectionMethod The method you asked for
    public static function getPrivateMethod($obj, $name) {
      $class = new ReflectionClass($obj);
      $method = $class->getMethod($name);
      return $method;
    // ... some other functions

I also created an alias function getProtectedMethod() to be explicit what is expected, but that one's up to you.

Convert a date format in PHP

You can try the strftime() function. Simple example: strftime($time, '%d %m %Y');

Flask ImportError: No Module Named Flask

This is what worked for me when I got a similar error in Windows; 1. Install virtualenv

pip install virtualenve
  1. Create a virtualenv

    virtualenv flask

  2. Navigate to Scripts and activate the virtualenv


  3. Install Flask

    python -m pip install flask

  4. Check if flask is installed

    python -m pip list

How can I determine if a variable is 'undefined' or 'null'?

I still think the best/safe way to test these two conditions is to cast the value to a string:

var EmpName = $("div#esd-names div#name").attr('class');

// Undefined check
if ( === '[object Undefined]'){
    // Do something with your code

// Nullcheck
if ( === '[object Null]'){
    // Do something with your code

Android: How to Enable/Disable Wifi or Internet Connection Programmatically

I know of enabling or disabling wifi:

WifiManager wifiManager = (WifiManager)this.context.getSystemService(Context.WIFI_SERVICE);

where status may be true or false as per requirement.


You also need the following permissions in your manifest file:

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

How to open local files in Swagger-UI

I had that issue and here is much simpler solution:

  • Make a dir (eg: swagger-ui) in your public dir (static path: no route is required) and copy dist from swagger-ui into that directory and open localhost/swagger-ui
  • You will see swagger-ui with default petstore example
  • Replace default petstore url in dist/index.html with your localhost/api-docs or to make it more generalized, replace with this:

    location.protocol+'//' + location.hostname+(location.port ? ':' + location.port: '') + "/api-docs";

  • Hit again localhost/swagger-ui

Voila! You local swagger implementation is ready

How do I fix the "You don't have write permissions into the /usr/bin directory" error when installing Rails?

To fix your specific error you need to run that command as sudo, ie:

sudo gem install rails --pre

Inserting one list into another list in java?

no... Once u have executed the statement anotherList.addAll(list) and after that if u change some list data it does not carry to another list

How to delete only the content of file in python

What could be easier than something like this:

import tempfile

for i in range(400):
    with tempfile.TemporaryFile() as tf:
        for j in range(1000):
            tf.write('Line {} of file {}'.format(j,i))

That creates 400 temp files and writes 1000 lines to each temp file. It executes in less than 1/2 second on my unremarkable machine. Each temp file of the total is created and deleted as the context manager opens and closes in this case. It is fast, secure, and cross platform.

Using tempfile is a lot better than trying to reinvent it.

NSPhotoLibraryUsageDescription key must be present in Info.plist to use camera roll

In order to save or retrieve an image from the camera roll. Additionally, you need to ask the user for the permission otherwise you'll get this error or your app may get crashed. To save yourself from this add this into your info.plist

<string>This app requires read and write permission from the user.</string>

In the case of Xamarin.iOS

 if you're adding it from the generic editor then "Privacy - Photo Library Additions Usage Description" will be the given option you will find out instead of "NSPhotoLibraryAddUsageDescription".

error: This is probably not a problem with npm. There is likely additional logging output above

Novice mistake. Make sure your package.json file is coded correctly. I had:

"start": "index node.js"
instead of:
"start": "node index.js"


Delete your package-lock.json file and node_modules folder. Then do npm cache clean

npm cache clean --force do npm install

Efficient way to rotate a list in python

Another alternative:

def move(arr, n):
    return [arr[(idx-n) % len(arr)] for idx,_ in enumerate(arr)]

How to specify table's height such that a vertical scroll bar appears?

Try using the overflow CSS property. There are also separate properties to define the behaviour of just horizontal overflow (overflow-x) and vertical overflow (overflow-y).

Since you only want the vertical scroll, try this:

table {
  height: 500px;
  overflow-y: scroll;


Apparently <table> elements don't respect the overflow property. This appears to be because <table> elements are not rendered as display: block by default (they actually have their own display type). You can force the overflow property to work by setting the <table> element to be a block type:

table {
  display: block;
  height: 500px;
  overflow-y: scroll;

Note that this will cause the element to have 100% width, so if you don't want it to take up the entire horizontal width of the page, you need to specify an explicit width for the element as well.

How to change an element's title attribute using jQuery

If you are creating a div and trying to add a title to it.


var myDiv= document.createElement("div");

Oracle 11g SQL to get unique values in one column of a multi-column query

Eric Petroelje almost has it right:


Note: using ROWID (row unique id), not ROWNUM (which gives the row number within the result set)

How to save a data frame as CSV to a user selected location using tcltk

Take a look at the write.csv or the write.table functions. You just have to supply the file name the user selects to the file parameter, and the dataframe to the x parameter:

write.csv(x=df, file="myFileName")

Setting JDK in Eclipse

Eclipse's compiler can assure that your java sources conform to a given JDK version even if you don't have that version installed. This feature is useful for ensuring backwards compatibility of your code.

Your code will still be compiled and run by the JDK you've selected.

Make view 80% width of parent in React Native

That should fit your needs:

var yourComponent = React.createClass({
    render: function () {
        return (
            <View style={{flex:1, flexDirection:'column', justifyContent:'center'}}>
                <View style={{flexDirection:'row'}}>
                    <TextInput style={{flex:0.8, borderWidth:1, height:20}}></TextInput>
                    <View style={{flex:0.2}}></View> // spacer

How do I execute external program within C code in linux with arguments?

In C

#include <stdlib.h>

system("./foo 1 2 3");

In C++

#include <cstdlib>

std::system("./foo 1 2 3");

Then open and read the file as usual.

ADB not responding. You can wait more,or kill "adb.exe" process manually and click 'Restart'

Go to

Tools > Android > (Uncheck) Enable ADB Integration (if studio hangs/gets stuck end adb process manually)


Tools > Android > (Check) Enable ADB Integration

Tick symbol in HTML/XHTML

I think you're using less-well-supported Unicode values, which don't always have glyphs for all the code points.
Try the following characters:

  • ? (0x2610 in Unicode hexadecimal [HTML decimal: &#9744;]): an empty (unchecked) checkbox
  • ? (0x2611 [HTML decimal: &#9745;]): the checked version of the previous checkbox
  • ? (0x2713 [HTML decimal: &#10003;])
  • ? (0x2714 [HTML decimal: &#10004;])

Edit: There seems to be some confusion about the first symbol here, ? / 0x2610. This is an empty (unchecked) checkbox, so if you see a box, that's the way it's supposed to look. It's the counterpart to ? / 0x2611, which is the checked version.

Difference between array_push() and $array[] =

When you call a function in PHP (such as array_push()), there are overheads to the call, as PHP has to look up the function reference, find its position in memory and execute whatever code it defines.

Using $arr[] = 'some value'; does not require a function call, and implements the addition straight into the data structure. Thus, when adding a lot of data it is a lot quicker and resource-efficient to use $arr[].

Deny direct access to all .php files except index.php

place all files in one folder. place a .htaccess file in that folder and give it the value deny all. then in index.php thats placed outside of the folder have it echo out the right pages based on user input or event

Ruby: Merging variables in to a string

You can use sprintf-like formatting to inject values into the string. For that the string must include placeholders. Put your arguments into an array and use on of these ways: (For more info look at the documentation for Kernel::sprintf.)

fmt = 'The %s %s the %s'
res = fmt % [animal, action, other_animal]  # using %-operator
res = sprintf(fmt, animal, action, other_animal)  # call Kernel.sprintf

You can even explicitly specify the argument number and shuffle them around:

'The %3$s %2$s the %1$s' % ['cat', 'eats', 'mouse']

Or specify the argument using hash keys:

'The %{animal} %{action} the %{second_animal}' %
  { :animal => 'cat', :action=> 'eats', :second_animal => 'mouse'}

Note that you must provide a value for all arguments to the % operator. For instance, you cannot avoid defining animal.

Merge r brings error "'by' must specify uniquely valid columns"

This is what I tried for a right outer join [as per my requirement]:

m1 <- merge(x=companies, y=rounds2, by.x=companies$permalink, 
            by.y=rounds2$company_permalink, all.y=TRUE)
# Error in, x) : 'by' must specify uniquely valid columns
m1 <- merge(x=companies, y=rounds2, by.x=c("permalink"), 
            by.y=c("company_permalink"), all.y=TRUE)

This worked.

Pass Array Parameter in SqlCommand

Passing an array of items as a collapsed parameter to the WHERE..IN clause will fail since query will take form of WHERE Age IN ("11, 13, 14, 16").

But you can pass your parameter as an array serialized to XML or JSON:

Using nodes() method:

StringBuilder sb = new StringBuilder();

foreach (ListItem item in ddlAge.Items)
  if (item.Selected)
    sb.Append("<age>" + item.Text + "</age>"); // actually it's xml-ish

sqlComm.CommandText = @"SELECT * from TableA WHERE Age IN (
    SELECT Tab.col.value('.', 'int') as Age from @Ages.nodes('/age') as Tab(col))";
sqlComm.Parameters.Add("@Ages", SqlDbType.NVarChar);
sqlComm.Parameters["@Ages"].Value = sb.ToString();

Using OPENXML method:

using System.Xml.Linq;
XElement xml = new XElement("Ages");

foreach (ListItem item in ddlAge.Items)
  if (item.Selected)
    xml.Add(new XElement("age", item.Text);

sqlComm.CommandText = @"DECLARE @idoc int;
    EXEC sp_xml_preparedocument @idoc OUTPUT, @Ages;
    SELECT * from TableA WHERE Age IN (
    SELECT Age from OPENXML(@idoc, '/Ages/age') with (Age int 'text()')
    EXEC sp_xml_removedocument @idoc";
sqlComm.Parameters.Add("@Ages", SqlDbType.Xml);
sqlComm.Parameters["@Ages"].Value = xml.ToString();

That's a bit more on the SQL side and you need a proper XML (with root).

Using OPENJSON method (SQL Server 2016+):

using Newtonsoft.Json;
List<string> ages = new List<string>();

foreach (ListItem item in ddlAge.Items)
  if (item.Selected)

sqlComm.CommandText = @"SELECT * from TableA WHERE Age IN (
    select value from OPENJSON(@Ages))";
sqlComm.Parameters.Add("@Ages", SqlDbType.NVarChar);
sqlComm.Parameters["@Ages"].Value = JsonConvert.SerializeObject(ages);

Note that for the last method you also need to have Compatibility Level at 130+.

What does 'wb' mean in this code, using Python?

File mode, write and binary. Since you are writing a .jpg file, it looks fine.

But if you supposed to read that jpg file you need to use 'rb'

More info

On Windows, 'b' appended to the mode opens the file in binary mode, so there are also modes like 'rb', 'wb', and 'r+b'. Python on Windows makes a distinction between text and binary files; the end-of-line characters in text files are automatically altered slightly when data is read or written. This behind-the-scenes modification to file data is fine for ASCII text files, but it’ll corrupt binary data like that in JPEG or EXE files.

How do I enable php to work with postgresql?

  • SO: Windows/Linux
  • HTTP Web Server: Apache
  • Programming language: PHP

Enable PHP to work with PostgreSQL in Apache

In Apache I edit the following configuration file: C:\xampp\php.ini

I make sure to have the following lines uncommented:


Finally restart Apache before attempting a new connection to the database engine.

Also, I leave my code that ensures that the connection is unique:

private static $pdo = null;

public static function provideDataBaseInstance() {
    if (self::$pdo == null) {
        $dsn = "pgsql:host=" . HOST .
               ";port=5432;dbname=" . DATABASE .
               ";user=" . POSTGRESQL_USER .
               ";password=" . POSTGRESQL_PASSWORD;
        try {
            self::$pdo = new PDO($dsn);
        } catch (PDOException $exception) {
            $msg = $exception->getMessage();
            echo $msg . 
                 ". Do not forget to enable in the web server the database 
                  manager for php and in the database instance authorize the 
                  ip of the server instance if they not in the same 
    return self::$pdo;


How to read/write files in .Net Core?

Works in Net Core 2.1

    var file = Path.Combine(Directory.GetCurrentDirectory(), "wwwroot", "email", "EmailRegister.htm");

    string SendData = System.IO.File.ReadAllText(file);

System.BadImageFormatException: Could not load file or assembly (from installutil.exe)

The problem is that every System.BadImageFormatException: Could not load file or assembly including the ones not associated with installutil.exe at all point to this very thread.

  1. If your issue is related to WindowsBase or PresentationFramework dlls and you got analyzers installed make sure to either have them installed for all of the projects in your solution or for none of them.

    enter image description here

  2. Reference the entire framework in .csproj file of your library rather than just the two dlls:

    <Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
  3. Remove bin and obj dirs, clean solution and rebuild.

'Found the synthetic property @panelState. Please include either "BrowserAnimationsModule" or "NoopAnimationsModule" in your application.'

Simply add .. import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

imports: [ .. BrowserAnimationsModule


in app.module.ts file.

make sure you have installed .. npm install @angular/animations@latest --save

Should 'using' directives be inside or outside the namespace?

There is actually a (subtle) difference between the two. Imagine you have the following code in File1.cs:

// File1.cs
using System;
namespace Outer.Inner
    class Foo
        static void Bar()
            double d = Math.PI;

Now imagine that someone adds another file (File2.cs) to the project that looks like this:

// File2.cs
namespace Outer
    class Math

The compiler searches Outer before looking at those using directives outside the namespace, so it finds Outer.Math instead of System.Math. Unfortunately (or perhaps fortunately?), Outer.Math has no PI member, so File1 is now broken.

This changes if you put the using inside your namespace declaration, as follows:

// File1b.cs
namespace Outer.Inner
    using System;
    class Foo
        static void Bar()
            double d = Math.PI;

Now the compiler searches System before searching Outer, finds System.Math, and all is well.

Some would argue that Math might be a bad name for a user-defined class, since there's already one in System; the point here is just that there is a difference, and it affects the maintainability of your code.

It's also interesting to note what happens if Foo is in namespace Outer, rather than Outer.Inner. In that case, adding Outer.Math in File2 breaks File1 regardless of where the using goes. This implies that the compiler searches the innermost enclosing namespace before it looks at any using directive.

'str' object has no attribute 'decode'. Python 3 error?

If you land here using jwt authentication after the PyJWT v2.0.0 release (22/12/2020), you might want to freeze your version of PyJWT to the previous release in your requirements.txt file.


mysqldump exports only one table

Quoting this link:

  • Exporting the Table

To export the table run the following command from the command line:

mysqldump -p --user=username dbname tableName > tableName.sql

This will export the tableName to the file tableName.sql.

  • Importing the Table

To import the table run the following command from the command line:

mysql -u username -p -D dbname < tableName.sql

The path to the tableName.sql needs to be prepended with the absolute path to that file. At this point the table will be imported into the DB.

Not unique table/alias

 select persons.personsid,name,,address
    -> from persons
    -> inner join persons on info.infoid =;

Where IN clause in LINQ

This little bit different idea. But it will useful to you. I have used sub query to inside the linq main query.


Let say we have document table. Schema as follows schema : document(name,version,auther,modifieddate) composite Keys : name,version

So we need to get latest versions of all documents.


 var result = (from t in Context.document
                          where ((from tt in Context.document where t.Name == tt.Name
                                orderby tt.Version descending select new {Vesion=tt.Version}).FirstOrDefault()).Vesion.Contains(t.Version)
                          select t).ToList();

How to get JavaScript caller function line number? How to get JavaScript caller source URL?

the following code works for me in Mozilla and Chrome.

Its log function that shows the file's name and the line of the caller.

log: function (arg) {
    var toPrint = [];
    for (var i = 0; i < arguments.length; ++i) {

    function getErrorObject(){
        try { throw Error('') } catch(err) { return err; }

    var err = getErrorObject(),

    if ($.browser.mozilla) {
        caller = err.stack.split("\n")[2];
    } else {
        caller = err.stack.split("\n")[4];

    var index = caller.indexOf('.js');

    var str = caller.substr(0, index + 3);
    index = str.lastIndexOf('/');
    str = str.substr(index + 1, str.length);

    var info = "\t\tFile: " + str;

    if ($.browser.mozilla) {
        str = caller;
    } else {
        index = caller.lastIndexOf(':');
        str = caller.substr(0, index);
    index = str.lastIndexOf(':');
    str = str.substr(index + 1, str.length);
    info += " Line: " + str;

    console.log.apply(console, toPrint);

dyld: Library not loaded: /usr/local/opt/openssl/lib/libssl.1.0.0.dylib

Switch to an older openssl package

brew switch openssl 1.0.2s

Or, depending on your exact system configuration, you may need to switch to a different version. Check the output of ls -al /usr/local/Cellar/openssl for the version number to switch to.

brew switch openssl 1.0.2q
# or
brew switch openssl 1.0.2r
# or 
brew switch openssl 1.0.2s
# or
brew switch openssl 1.0.2t
# etc...

Clear the form field after successful submission of php form

You can use .reset() on your form.


"NoClassDefFoundError: Could not initialize class" error

NoClassDefFound error is a nebulous error and is often hiding a more serious issue. It is not the same as ClassNotFoundException (which is thrown when the class is just plain not there).

NoClassDefFound may indicate the class is not there, as the javadocs indicate, but it is typically thrown when, after the classloader has loaded the bytes for the class and calls "defineClass" on them. Also carefully check your full stack trace for other clues or possible "cause" Exceptions (though your particular backtrace shows none).

The first place to look when you get a NoClassDefFoundError is in the static bits of your class i.e. any initialization that takes place during the defining of the class. If this fails it will throw a NoClassDefFoundError - it's supposed to throw an ExceptionInInitializerError and indicate the details of the problem but in my experience, these are rare. It will only do the ExceptionInInitializerError the first time it tries to define the class, after that it will just throw NoClassDefFound. So look at earlier logs.

I would thus suggest looking at the code in that HibernateTransactionInterceptor line and seeing what it is requiring. It seems that it is unable to define the class SpringFactory. So maybe check the initialization code in that class, that might help. If you can debug it, stop it at the last line above (17) and debug into so you can try find the exact line that is causing the exception. Also check higher up in the log, if you very lucky there might be an ExceptionInInitializerError.

How to call a function after a div is ready?

Thus far, the only way to "listen" on DOM events, like inserting or modifying Elements, was to use the such called Mutation Events. For instance

document.body.addEventListener('DOMNodeInserted', function( event ) {
    console.log('whoot! a new Element was inserted, see my event object for details!');
}, false);

Further reading on that: MDN

The Problem with Mutation Events was (is) they never really made their way into any official spec because of inconcistencies and stuff. After a while, this events were implemented in all modern browser, but they were declared as deprecated, in other words you don't want to use them.

The official replacement for the Mutation Events is the MutationObserver() object.

Further reading on that: MDN

The syntax at present looks like

var observer = new MutationObserver(function( mutations ) {
    mutations.forEach(function( mutation ) {
         console.log( mutation.type );

var config = { childList: true };

observer.observe( document.body, config );

At this time, the API has been implemented in newer Firefox, Chrome and Safari versions. I'm not sure about IE and Opera. So the tradeoff here is definitely that you can only target for topnotch browsers.

How to put a div in center of browser using CSS?


html, body


    margin:0 auto;
    border: solid 1px #993333;
    z-index: 0;

/* for Internet Explorer */
* html #something{
height: 600px;


<div id="distance"></div>

<div id="something">


Tested in FF2-3, IE6-7, Opera and works well!

How to add include path in Qt Creator?

If you use custom Makefiles, you can double click on the .includes file and add it there.

Select All distinct values in a column using LINQ

To have unique Categories:

var uniqueCategories =  repository.GetAllProducts()

What's the C++ version of Java's ArrayList

A couple of additional points re use of vector here.

Unlike ArrayList and Array in Java, you don't need to do anything special to treat a vector as an array - the underlying storage in C++ is guaranteed to be contiguous and efficiently indexable.

Unlike ArrayList, a vector can efficiently hold primitive types without encapsulation as a full-fledged object.

When removing items from a vector, be aware that the items above the removed item have to be moved down to preserve contiguous storage. This can get expensive for large containers.

Make sure if you store complex objects in the vector that their copy constructor and assignment operators are efficient. Under the covers, C++ STL uses these during container housekeeping.

Advice about reserve()ing storage upfront (ie. at vector construction or initialilzation time) to minimize memory reallocation on later extension carries over from Java to C++.

How do I make Java register a string input with spaces?

I found a very weird thing in Java today, so it goes like -

If you are inputting more than 1 thing from the user, say

Scanner sc = new Scanner(;
int i = sc.nextInt();
double d = sc.nextDouble();
String s = sc.nextLine();


So, it might look like if we run this program, it will ask for these 3 inputs and say our input values are 10, 2.5, "Welcome to java" The program should print these 3 values as it is, as we have used nextLine() so it shouldn't ignore the text after spaces that we have entered in our variable s

But, the output that you will get is -


And that's it, it doesn't even prompt for the String input. Now I was reading about it and to be very honest there are still some gaps in my understanding, all I could figure out was after taking the int input and then the double input when we press enter, it considers that as the prompt and ignores the nextLine().

So changing my code to something like this -

Scanner sc = new Scanner(;
int i = sc.nextInt();
double d = sc.nextDouble();
String s = sc.nextLine();


does the job perfectly, so it is related to something like "\n" being stored in the keyboard buffer in the previous example which we can bypass using this.

Please if anybody knows help me with an explanation for this.

SELECT last id, without INSERT

I think to add timestamp to every record and get the latest. In this situation you can get any ids, pack rows and other ops.

Role/Purpose of ContextLoaderListener in Spring?

When you want to put your Servlet file in your custom location or with custom name, rather than the default naming convention [servletname]-servlet.xml and path under Web-INF/ ,then you can use ContextLoaderListener.

How to check a not-defined variable in JavaScript

An even easier and more shorthand version would be:

if (!x) {


if (typeof x !== "undefined") {
    //Do something since x is defined.

How to delete a cookie?

I had trouble deleting a cookie made via JavaScript and after I added the host it worked (scroll the code below to the right to see the After clearing the cookies on a domain try the following to see the results:

if (document.cookie.length==0)
 document.cookie = 'name=example; expires='+new Date((new Date()).valueOf()+1000*60*60*24*15)+'; path=/; domain=';

 if (document.cookie.length==0) {alert('Cookies disabled');}
  document.cookie = 'name=example; expires=Thu, 01 Jan 1970 00:00:00 GMT; path=/; domain=';

  if (document.cookie.length==0) {alert('Created AND deleted cookie successfully.');}
  else {alert('document.cookies.length = '+document.cookies.length);}

What does the "$" sign mean in jQuery or JavaScript?

In JavaScript it has no special significance (no more than a or Q anyway). It is just an uninformative variable name.

In jQuery the variable is assigned a copy of the jQuery function. This function is heavily overloaded and means half a dozen different things depending on what arguments it is passed. In this particular example you are passing it a string that contains a selector, so the function means "Create a jQuery object containing the element with the id Text".

How to add url parameters to Django template url tag?

Simply add Templates URL:

<a href="{% url 'service_data' %}">

Used in django 2.0

Adding Apostrophe in every field in particular column for excel

i use concantenate. works for me.

  1. fill j2-j14 with '(appostrophe)
  2. enter L2 with formula =concantenate(j2,k2)
  3. copy L2 to L3-L14

7-zip commandline

Instead of the option a use option x, this will create the directories but only for extraction, not compression.

Find records from one table which don't exist in another

There's several different ways of doing this, with varying efficiency, depending on how good your query optimiser is, and the relative size of your two tables:

This is the shortest statement, and may be quickest if your phone book is very short:

FROM    Call
WHERE   phone_number NOT IN (SELECT phone_number FROM Phone_book)

alternatively (thanks to Alterlife)

FROM   Call
   FROM   Phone_book
   WHERE  Phone_book.phone_number = Call.phone_number)

or (thanks to WOPR)

FROM   Call
  ON (Call.phone_number = Phone_book.phone_number)
  WHERE Phone_book.phone_number IS NULL

(ignoring that, as others have said, it's normally best to select just the columns you want, not '*')

Any way (or shortcut) to auto import the classes in IntelliJ IDEA like in Eclipse?

IntelliJ IDEA does not have an action to add imports. Rather it has the ability to do such as you type. If you enable the "Add unambiguous imports on the fly" in Settings > Editor > General > Auto Import, IntelliJ IDEA will add them as you type without the need for any shortcuts. You can also add classes and packages to exclude from auto importing to make a class you use heavily, that clashes with other classes of the same name, unambiguous.

For classes that are ambiguous (or is you prefer to have the "Add unambiguous imports on the fly" option turned off), just type the name of the class (just the name is OK, no need to fully qualify). Use code completion and select the particular class you want:

enter image description here

Notice the fully qualified names to the right. When I select the one I want and hit enter, IDEA will automatically add the import statement. This works the same if I was typing the name of a constructor. For static methods, you can even just keep typing the method you want. In the following screenshot, no "StringUtils" class is imported yet.

enter image description here

Alternatively, type the class name and then hit Alt+Enter or ?+Enter to "Show intention actions and quick-fixes" and then select the import option.

Although I've never used it, I think the Eclipse Code Formatter third party plug-in will do what you want. It lists "emulates Eclipse's imports optimizing" as a feature. See its instructions for more information. But in the end, I suspect you'll find the built in IDEA features work fine once you get use to their paradigm. In general, IDEA uses a "develop by intentions" concept. So rather than interrupting my development work to add an import statement, I just type the class I want (my intention) and IDEA automatically adds the import statement for the class for me.

Removing empty lines in Notepad++

There is now a built-in way to do this as of version 6.5.2

Edit -> Line Operations -> Remove Empty Lines or Remove Empty Lines (Containing Blank characters)

Screenshot of removing empty lines

jQuery How to Get Element's Margin and Padding?

var bordT = $('img').outerWidth() - $('img').innerWidth();
var paddT = $('img').innerWidth() - $('img').width();
var margT = $('img').outerWidth(true) - $('img').outerWidth();

var formattedBord = bordT + 'px';
var formattedPadd = paddT + 'px';
var formattedMarg = margT + 'px';

Check the jQuery API docs for information on each:

Here's the edited jsFiddle showing the result.

You can perform the same type of operations for the Height to get its margin, border, and padding.

TypeScript typed array usage

You have an error in your syntax here:

this._possessions = new Thing[100]();

This doesn't create an "array of things". To create an array of things, you can simply use the array literal expression:

this._possessions = [];

Of the array constructor if you want to set the length:

this._possessions = new Array(100);

I have created a brief working example you can try in the playground.

module Entities {  

    class Thing {


    export class Person {
        private _name: string;
        private _possessions: Thing[];
        private _mostPrecious: Thing;

        constructor (name: string) {
            this._name = name;
            this._possessions = [];
            this._possessions.push(new Thing())
            this._possessions[100] = new Thing();

What's the easiest way to escape HTML in Python?

cgi.escape is fine. It escapes:

  • < to &lt;
  • > to &gt;
  • & to &amp;

That is enough for all HTML.

EDIT: If you have non-ascii chars you also want to escape, for inclusion in another encoded document that uses a different encoding, like Craig says, just use:

data.encode('ascii', 'xmlcharrefreplace')

Don't forget to decode data to unicode first, using whatever encoding it was encoded.

However in my experience that kind of encoding is useless if you just work with unicode all the time from start. Just encode at the end to the encoding specified in the document header (utf-8 for maximum compatibility).


>>> cgi.escape(u'<a>bá</a>').encode('ascii', 'xmlcharrefreplace')

Also worth of note (thanks Greg) is the extra quote parameter cgi.escape takes. With it set to True, cgi.escape also escapes double quote chars (") so you can use the resulting value in a XML/HTML attribute.

EDIT: Note that cgi.escape has been deprecated in Python 3.2 in favor of html.escape, which does the same except that quote defaults to True.

nginx showing blank PHP pages

None of the above answers worked for me - PHP was properly rendering everything except pages that relied on mysqli, for which it was sending a blank page with a 200 response code and not throwing any errors. As I'm on OS X, the fix was simply

sudo port install php56-mysql

followed by a restart of PHP-FPM and nginx.

I was migrating from an older Apache/PHP setup to nginx, and failed to notice the version mismatch in the driver for php-mysql and php-fpm.

Trimming text strings in SQL Server 2008

You do have an RTRIM and an LTRIM function. You can combine them to get the trim function you want.


Computed / calculated / virtual / derived columns in PostgreSQL

PostgreSQL 12 supports generated columns:

PostgreSQL 12 Beta 1 Released!

Generated Columns

PostgreSQL 12 allows the creation of generated columns that compute their values with an expression using the contents of other columns. This feature provides stored generated columns, which are computed on inserts and updates and are saved on disk. Virtual generated columns, which are computed only when a column is read as part of a query, are not implemented yet.

Generated Columns

A generated column is a special column that is always computed from other columns. Thus, it is for columns what a view is for tables.

    height_cm numeric,
    height_in numeric GENERATED ALWAYS AS (height_cm * 2.54) STORED

db<>fiddle demo

how to POST/Submit an Input Checkbox that is disabled?

Adding onclick="this.checked=true"Solve my problem:

<input type="checkbox" id="scales" name="feature[]" value="scales" checked="checked" onclick="this.checked=true" />

Convert Json String to C# Object List

Please make sure that all properties are both the getter and setter. In case, any property is getter only, it will cause the reverting the List to original data as the JSON string is typed.

Please refer to the following code snippet for the same: Model:

 public class Person
    public int ID { get; set; }
    // following 2 lines are cause of error
    //public string Name { get { return string.Format("{0} {1}", First, Last); } }
    //public string Country { get { return Countries[CountryID]; } }
    public int CountryID { get; set; }
    public bool Active { get; set; }
    public string First { get; set; }
    public string Last { get; set; }
    public DateTime Hired { get; set; }
public class ModelObj
        public string Str { get; set; }
        public List<Person> Persons { get; set; }


    public ActionResult Index(FormCollection collection)
        var data = new ModelObj();
        data.Str = (string)collection.GetValue("Str").ConvertTo(typeof(string));
        var personsString = (string)collection.GetValue("Persons").ConvertTo(typeof(string));
        using (var textReader = new StringReader(personsString))
            using (var reader = new JsonTextReader(textReader))
                data.Persons = new JsonSerializer().Deserialize(reader, typeof(List<Person>)) as List<Person>; 

        return View(data);

How to pass data from 2nd activity to 1st activity when pressed back? - android

Take This as an alternate to startActivityforResult.But keep in mind that for such cases this approach can be expensive in terms of performance but in some cases you might need to use.

In Activity2,

public void onBackPressed() {
String data = mEditText.getText();
SharedPreferences sp = getSharedPreferences("LoginInfos", 0);
Editor editor = sp.edit();

In Activity1,

public void onResume() {
SharedPreferences sp = getSharedPreferences("LoginInfos", 0);
String  dataFromOtherAct= sp.getString("email", "no email");

getting the index of a row in a pandas apply function

To answer the original question: yes, you can access the index value of a row in apply(). It is available under the key name and requires that you specify axis=1 (because the lambda processes the columns of a row and not the rows of a column).

Working example (pandas 0.23.4):

>>> import pandas as pd
>>> df = pd.DataFrame([[1,2,3],[4,5,6]], columns=['a','b','c'])
>>> df.set_index('a', inplace=True)
>>> df
   b  c
1  2  3
4  5  6
>>> df['index_x10'] = df.apply(lambda row: 10*, axis=1)
>>> df
   b  c  index_x10
1  2  3         10
4  5  6         40

Where does Oracle SQL Developer store connections?

On linux systems:


Getting a POST variable

Use the


for POST variables,


for GET.

Is the size of C "int" 2 bytes or 4 bytes?

Is the size of C “int” 2 bytes or 4 bytes?

The answer is "yes" / "no" / "maybe" / "maybe not".

The C programming language specifies the following: the smallest addressable unit, known by char and also called "byte", is exactly CHAR_BIT bits wide, where CHAR_BIT is at least 8.

So, one byte in C is not necessarily an octet, i.e. 8 bits. In the past one of the first platforms to run C code (and Unix) had 4-byte int - but in total int had 36 bits, because CHAR_BIT was 9!

int is supposed to be the natural integer size for the platform that has range of at least -32767 ... 32767. You can get the size of int in the platform bytes with sizeof(int); when you multiply this value by CHAR_BIT you will know how wide it is in bits.

While 36-bit machines are mostly dead, there are still platforms with non-8-bit bytes. Just yesterday there was a question about a Texas Instruments MCU with 16-bit bytes, that has a C99, C11-compliant compiler.

On TMS320C28x it seems that char, short and int are all 16 bits wide, and hence one byte. long int is 2 bytes and long long int is 4 bytes. The beauty of C is that one can still write an efficient program for a platform like this, and even do it in a portable manner!

What is the purpose of .PHONY in a Makefile?

There's also one important tricky treat of ".PHONY" - when a physical target depends on phony target that depends on another physical target:


You'd simply expect that if you updated TARGET2, then TARGET1 should be considered stale against TARGET1, so TARGET1 should be rebuild. And it really works this way.

The tricky part is when TARGET2 isn't stale against TARGET1 - in which case you should expect that TARGET1 shouldn't be rebuild.

This surprisingly doesn't work because: the phony target was run anyway (as phony targets normally do), which means that the phony target was considered updated. And because of that TARGET1 is considered stale against the phony target.


all: fileall

fileall: file2 filefwd
    echo file2 file1 >fileall

file2: file2.src
    echo file2.src >file2

file1: file1.src
    echo file1.src >file1
    echo file1.src >>file1

.PHONY: filefwd
.PHONY: filefwd2

filefwd: filefwd2

filefwd2: file1
    @echo "Produced target file1"

    echo "Some text 1" >> file1.src
    echo "Some text 2" >> file2.src

You can play around with this:

  • first do 'make prepare' to prepare the "source files"
  • play around with that by touching particular files to see them updated

You can see that fileall depends on file1 indirectly through a phony target - but it always gets rebuilt due to this dependency. If you change the dependency in fileall from filefwd to file, now fileall does not get rebuilt every time, but only when any of dependent targets is stale against it as a file.

Difference between char* and const char*?

char* is a mutable pointer to a mutable character/string.

const char* is a mutable pointer to an immutable character/string. You cannot change the contents of the location(s) this pointer points to. Also, compilers are required to give error messages when you try to do so. For the same reason, conversion from const char * to char* is deprecated.

char* const is an immutable pointer (it cannot point to any other location) but the contents of location at which it points are mutable.

const char* const is an immutable pointer to an immutable character/string.

Call to undefined function oci_connect()

Alright, folks.

First, use


and determine your PHP Version (located at the very top, e.g. and also, your PHP Version architecture: x64 or x86 and also, Thread Safe or Not THread Safe (located in the first table as "Thread Safety".) "Disabled" obviously means "Not Thread Safe".

It is absolutely critical that the following three pieces of software that you will need are:

  1. for the same major version of PHP (7.0 for
  2. same version of Oracle as the version you are accessing (11g, 12g, etc)
  3. the same Not Thread Safe / Thread Safe version of PHP
  4. all for the same architecture.

If any of the following are for a different architecture, Not Thread Safe/Thread Safe version, PHP major version number, or database version, you'll get errors:

 1. PHP for Windows
 2. OCI8 PECL Drivers for PHP (
 3. Oracle Instant Client

Remember: If you are connecting to an 11g Oracle instance, you need an 11g driver.

Second, install the correct PHP, OCI8 PECL Driver, and instant client.

I chose:

d:\php\ for php
d:\oci\ for instant client
unzip the contents of the OCI8 PECL Driver into d:\php\ext\

Third, modify d:\php\php.ini according the instructions given by Oracle:

1. set the extension directory
2. set only one of the following:
  a. for 11g drivers, use extension=php_oci8_11g.dll
  b. for 12c drivers, use extension=php_oci8_12c.dll
  c. for other oracle DB drivers, use the correct oracle extension.

Fourth: Add d:\oci\ (or whatever your instant client install location is) to your system PATH.

Fifth: reboot your PC.

Sixth, on a command prompt, type "where oci*" and verify that your Instant Client install path version of oci.dll is present.

Seventh, go to d:\php\ and type "php -m" and you should see OCI8 in the list.

If you do not see OCI8 in the list of modules after typing "php -m", open up d:\php\errorlog.txt

If you see something like:

PHP Warning:  PHP Startup: Unable to load dynamic library 'ext\php_oci8_11g.dll' - %1 is not a valid Win32 application.

then either instant client or your PECL driver download is not the same architecture as your PHP version.

If you see something like:

PHP Warning:  PHP Startup: Unable to load dynamic library 'ext\php_oci8_12c.dll' - The specified procedure could not be found.

then you are using the wrong OCI8 PECL driver for your version of instant client.

Hope this helps.

Print new output on same line

>>> for i in range(1, 11):
...     print(i, end=' ')
...     if i==len(range(1, 11)): print()
1 2 3 4 5 6 7 8 9 10 

This is how to do it so that the printing does not run behind the prompt on the next line.

Correctly Parsing JSON in Swift 3

First of all never load data synchronously from a remote URL, use always asynchronous methods like URLSession.

'Any' has no subscript members

occurs because the compiler has no idea of what type the intermediate objects are (for example currently in ["currently"]!["temperature"]) and since you are using Foundation collection types like NSDictionary the compiler has no idea at all about the type.

Additionally in Swift 3 it's required to inform the compiler about the type of all subscripted objects.

You have to cast the result of the JSON serialization to the actual type.

This code uses URLSession and exclusively Swift native types

let urlString = ",122.048951"

let url = URL(string: urlString)
URLSession.shared.dataTask(with:url!) { (data, response, error) in
  if error != nil {
  } else {
    do {

      let parsedData = try JSONSerialization.jsonObject(with: data!) as! [String:Any]
      let currentConditions = parsedData["currently"] as! [String:Any]


      let currentTemperatureF = currentConditions["temperature"] as! Double
    } catch let error as NSError {


To print all key / value pairs of currentConditions you could write

 let currentConditions = parsedData["currently"] as! [String:Any]

  for (key, value) in currentConditions {
    print("\(key) - \(value) ")

A note regarding jsonObject(with data:

Many (it seems all) tutorials suggest .mutableContainers or .mutableLeaves options which is completely nonsense in Swift. The two options are legacy Objective-C options to assign the result to NSMutable... objects. In Swift any variable is mutable by default and passing any of those options and assigning the result to a let constant has no effect at all. Further most of the implementations are never mutating the deserialized JSON anyway.

The only (rare) option which is useful in Swift is .allowFragments which is required if if the JSON root object could be a value type(String, Number, Bool or null) rather than one of the collection types (array or dictionary). But normally omit the options parameter which means No options.


Some general considerations to parse JSON

JSON is a well-arranged text format. It's very easy to read a JSON string. Read the string carefully. There are only six different types – two collection types and four value types.

The collection types are

  • Array - JSON: objects in square brackets [] - Swift: [Any] but in most cases [[String:Any]]
  • Dictionary - JSON: objects in curly braces {} - Swift: [String:Any]

The value types are

  • String - JSON: any value in double quotes "Foo", even "123"or "false" – Swift: String
  • Number - JSON: numeric values not in double quotes 123 or 123.0 – Swift: Int or Double
  • Bool - JSON: true or false not in double quotes – Swift: true or false
  • null - JSON: null – Swift: NSNull

According to the JSON specification all keys in dictionaries are required to be String.

Basically it's always recommeded to use optional bindings to unwrap optionals safely

If the root object is a dictionary ({}) cast the type to [String:Any]

if let parsedData = try JSONSerialization.jsonObject(with: data!) as? [String:Any] { ...

and retrieve values by keys with (OneOfSupportedJSONTypes is either JSON collection or value type as described above.)

if let foo = parsedData["foo"] as? OneOfSupportedJSONTypes {

If the root object is an array ([]) cast the type to [[String:Any]]

if let parsedData = try JSONSerialization.jsonObject(with: data!) as? [[String:Any]] { ...

and iterate through the array with

for item in parsedData {

If you need an item at specific index check also if the index exists

if let parsedData = try JSONSerialization.jsonObject(with: data!) as? [[String:Any]], parsedData.count > 2,
   let item = parsedData[2] as? OneOfSupportedJSONTypes {

In the rare case that the JSON is simply one of the value types – rather than a collection type – you have to pass the .allowFragments option and cast the result to the appropriate value type for example

if let parsedData = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as? String { ...

Apple has published a comprehensive article in the Swift Blog: Working with JSON in Swift


In Swift 4+ the Codable protocol provides a more convenient way to parse JSON directly into structs / classes.

For example the given JSON sample in the question (slightly modified)

let jsonString = """
{"icon": "partly-cloudy-night", "precipProbability": 0, "pressure": 1015.39, "humidity": 0.75, "precip_intensity": 0, "wind_speed": 6.04, "summary": "Partly Cloudy", "ozone": 321.13, "temperature": 49.45, "dew_point": 41.75, "apparent_temperature": 47, "wind_bearing": 332, "cloud_cover": 0.28, "time": 1480846460}

can be decoded into the struct Weather. The Swift types are the same as described above. There are a few additional options:

  • Strings representing an URL can be decoded directly as URL.
  • The time integer can be decoded as Date with the dateDecodingStrategy .secondsSince1970.
  • snaked_cased JSON keys can be converted to camelCase with the keyDecodingStrategy .convertFromSnakeCase

struct Weather: Decodable {
    let icon, summary: String
    let pressure: Double, humidity, windSpeed : Double
    let ozone, temperature, dewPoint, cloudCover: Double
    let precipProbability, precipIntensity, apparentTemperature, windBearing : Int
    let time: Date

let data = Data(jsonString.utf8)
do {
    let decoder = JSONDecoder()
    decoder.dateDecodingStrategy = .secondsSince1970
    decoder.keyDecodingStrategy = .convertFromSnakeCase
    let result = try decoder.decode(Weather.self, from: data)
} catch {

Other Codable sources:

JS strings "+" vs concat method

  • We can't concatenate a string variable to an integer variable using concat() function because this function only applies to a string, not on a integer. but we can concatenate a string to a number(integer) using + operator.
  • As we know, functions are pretty slower than operators. functions needs to pass values to the predefined functions and need to gather the results of the functions. which is slower than doing operations using operators because operators performs operations in-line but, functions used to jump to appropriate memory locations... So, As mentioned in previous answers the other difference is obviously the speed of operation.

<!DOCTYPE html>_x000D_
<p>The concat() method joins two or more strings</p>_x000D_
<p id="demo"></p>_x000D_
<p id="demo1"></p>_x000D_
var text1 = 4;_x000D_
var text2 = "World!";_x000D_
document.getElementById("demo").innerHTML = text1 + text2;_x000D_
//Below Line can't produce result_x000D_
document.getElementById("demo1").innerHTML = text1.concat(text2);_x000D_
<p><strong>The Concat() method can't concatenate a string with a integer </strong></p>_x000D_

How to convert std::chrono::time_point to calendar datetime string with fractional seconds?

In my case I use chrono and c function localtime_r which is thread-safe (in opposition to std::localtime).

#include <iostream>
#include <chrono>
#include <ctime>
#include <time.h>
#include <iomanip>

int main() {
  std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
  std::time_t currentTime = std::chrono::system_clock::to_time_t(now);
  std::chrono::milliseconds now2 = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch());
  struct tm currentLocalTime;
  localtime_r(&currentTime, &currentLocalTime);
  char timeBuffer[80];
  std::size_t charCount { std::strftime( timeBuffer, 80,
                                         "%b %d %T",

  if (charCount == 0) return -1;

  std::cout << timeBuffer << "." << std::setfill('0') << std::setw(3) << now2.count() % 1000 << std::endl;
  return 0;

Reorder / reset auto increment primary key

Even though this question seems to be quite old, will post an answer for someone who reaches in here searching.

SET @count = 0;
UPDATE `users` SET `users`.`id` = @count:= @count + 1;

If the column is used as a foreign key in other tables, make sure you use ON UPDATE CASCADE instead of the default ON UPDATE NO ACTION for the foreign key relationship in those tables.

Further, in order to reset the AUTO_INCREMENT count, you can immediately issue the following statement.


For MySQLs it will reset the value to MAX(id) + 1.

Ubuntu, how do you remove all Python 3 but not 2

neither try any above ways nor sudo apt autoremove python3 because it will remove all gnome based applications from your system including gnome-terminal. In case if you have done that mistake and left with kernal only than trysudo apt install gnome on kernal.

try to change your default python version instead removing it. you can do this through bashrc file or export path command.

How do I prevent Conda from activating the base environment by default?

I faced the same problem. Initially I deleted the .bash_profile but this is not the right way. After installing anaconda it is showing the instructions clearly for this problem. Please check the image for solution provided by Anaconda

Convert command line argument to string

I'm not sure if this is 100% portable but the way the OS SHOULD parse the args is to scan through the console command string and insert a nil-term char at the end of each token, and int main(int,char**) doesn't use const char** so we can just iterate through the args starting from the third argument (@note the first arg is the working directory) and scan backward to the nil-term char and turn it into a space rather than start from beginning of the second argument and scanning forward to the nil-term char. Here is the function with test script, and if you do need to un-nil-ify more than one nil-term char then please comment so I can fix it; thanks.

#include <cstdio>
#include <iostream>

using namespace std;

namespace _ {
/* Converts int main(int,char**) arguments back into a string.
@return false if there are no args to convert.
@param arg_count The number of arguments.
@param args      The arguments. */
bool ArgsToString(int args_count, char** args) {
  if (args_count <= 1) return false;
  if (args_count == 2) return true;
  for (int i = 2; i < args_count; ++i) {
    char* cursor = args[i];
    while (*cursor) --cursor;
    *cursor = ' ';
  return true;
}  // namespace _

int main(int args_count, char** args) {
  cout << "\n\nTesting ArgsToString...\n";

  if (args_count <= 1) return 1;
  cout << "\nArguments:\n";
  for (int i = 0; i < args_count; ++i) {
    char* arg = args[i];
    printf("\ni:%i\"%s\" 0x%p", i, arg, arg);
  cout << "\n\nContiguous Args:\n";
  char* end = args[args_count - 1];
  while (*end) ++end;
  cout << "\n\nContiguous Args:\n";
  char* cursor = args[0];
  while (cursor != end) {
    char c = *cursor++;
    if (c == 0)
      cout << '`';
    else if (c < ' ')
      cout << '~';
      cout << c;
  cout << "\n\nPrinting argument string...\n";
  _::ArgsToString(args_count, args);
  cout << "\n" << args[1];
  return 0;

How to get response as String using retrofit without using GSON or any other library in android

** Update ** A scalars converter has been added to retrofit that allows for a String response with less ceremony than my original answer below.

Example interface --

public interface GitHubService {
    Call<String> listRepos(@Path("user") String user);

Add the ScalarsConverterFactory to your retrofit builder. Note: If using ScalarsConverterFactory and another factory, add the scalars factory first.

Retrofit retrofit = new Retrofit.Builder()
    // add other factories here, if needed.

You will also need to include the scalars converter in your gradle file --

implementation 'com.squareup.retrofit2:converter-scalars:2.1.0'

--- Original Answer (still works, just more code) ---

I agree with @CommonsWare that it seems a bit odd that you want to intercept the request to process the JSON yourself. Most of the time the POJO has all the data you need, so no need to mess around in JSONObject land. I suspect your specific problem might be better solved using a custom gson TypeAdapter or a retrofit Converter if you need to manipulate the JSON. However, retrofit provides more the just JSON parsing via Gson. It also manages a lot of the other tedious tasks involved in REST requests. Just because you don't want to use one of the features, doesn't mean you have to throw the whole thing out. There are times you just want to get the raw stream, so here is how to do it -

First, if you are using Retrofit 2, you should start using the Call API. Instead of sending an object to convert as the type parameter, use ResponseBody from okhttp --

public interface GitHubService {
    Call<ResponseBody> listRepos(@Path("user") String user);

then you can create and execute your call --

GitHubService service = retrofit.create(GitHubService.class);
Call<ResponseBody> result = service.listRepos(username);
result.enqueue(new Callback<ResponseBody>() {
    public void onResponse(Response<ResponseBody> response) {
        try {
        } catch (IOException e) {

    public void onFailure(Throwable t) {

Note The code above calls string() on the response object, which reads the entire response into a String. If you are passing the body off to something that can ingest streams, you can call charStream() instead. See the ResponseBody docs.

Looping through JSON with node.js

Not sure if it helps, but it looks like there might be a library for async iteration in node hosted here:

Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript. Although originally designed for use with node.js, it can also be used directly in the browser.

Async provides around 20 functions that include the usual 'functional' suspects (map, reduce, filter, forEach…) as well as some common patterns for asynchronous control flow (parallel, series, waterfall…). All these functions assume you follow the node.js convention of providing a single callback as the last argument of your async function.

How can I remove all my changes in my SVN working directory?

None of the answers here were quite what I wanted. Here's what I came up with:

# Recursively revert any locally-changed files
svn revert -R .

# Delete any other files in the sandbox (including ignored files),
# being careful to handle files with spaces in the name
svn status --no-ignore | grep '^\?' | \
    perl -ne 'print "$1\n" if $_ =~ /^\S+\s+(.*)$/' | \
    tr '\n' '\0' | xargs -0 rm -rf

Tested on Linux; may work in Cygwin, but relies on (I believe) a GNU-specific extension which allows xargs to split based on '\0' instead of whitespace.

The advantage to the above command is that it does not require any network activity to reset the sandbox. You get exactly what you had before, and you lose all your changes. (disclaimer before someone blames me for this code destroying their work) ;-)

I use this script on a continuous integration system where I want to make sure a clean build is performed after running some tests.

Edit: I'm not sure this works with all versions of Subversion. It's not clear if the svn status command is always formatted consistently. Use at your own risk, as with any command that uses such a blanket rm command.

How to check if running as root in a bash script

As far as I know the correct way to check it is:

if [ $(id -u) = "0" ]; then
    echo "You are root"
    echo "You are NOT root"

See "Testing For Root" section here:

What does the line "#!/bin/sh" mean in a UNIX shell script?

It's called a shebang, and tells the parent shell which interpreter should be used to execute the script.

#!/bin/sh <--------- bourne shell compatible script
#!/usr/bin/perl  <-- perl script
#!/usr/bin/php  <--- php script
#!/bin/false <------ do-nothing script, because false returns immediately anyways.

Most scripting languages tend to interpret a line starting with # as comment and will ignore the following !/usr/bin/whatever portion, which might otherwise cause a syntax error in the interpreted language.

What does !important mean in CSS?

!important is a part of CSS1.

Browsers supporting it: IE5.5+, Firefox 1+, Safari 3+, Chrome 1+.

It means, something like:

Use me, if there is nothing important else around!

Cant say it better.

How do ports work with IPv6?

I would say the best reference is Format for Literal IPv6 Addresses in URL's where usage of [] is defined.

Also, if it is for programming and code, specifically Java, I would suggest this readsClass for Inet6Address java/net/URL definition where usage of Inet4 address in Inet6 connotation and other cases are presented in details. For my case, IPv4-mapped address Of the form::ffff:w.x.y.z, for IPv6 address is used to represent an IPv4 address also solved my problem. It allows the native program to use the same address data structure and also the same socket when communicating with both IPv4 and IPv6 nodes. This is the case on Amazon cloud Linux boxes default setup.

How do I check whether an array contains a string in TypeScript?

Also note that "in" keyword does not work on arrays. It works on objects only.

propName in myObject

Array inclusion test is


Moment.js transform to date object

To convert any date, for example utc:

moment( moment().utc().format( "YYYY-MM-DD HH:mm:ss" )).toDate()

How to query MongoDB with "like"?

Above answers are perfectly answering the questions about core mongodb query. But when using pattern based search query such as:

{"keywords":{ "$regex": "^toron.*"}}


{"keywords":{ "$regex": "^toron"}}

in spring boot jpa repository query with @Query annotation, use query something like:

@Query(value = "{ keyword : { $regex : ?0 }  }")
List<SomeResponse> findByKeywordContainingRegex(String keyword);

and call should be either of:

List<SomeResponse> someResponseList =    someRepository.findByKeywordsContainingRegex("^toron");

List<SomeResponse> someResponseList =    someRepository.findByKeywordsContainingRegex("^toron.*");

But Never use:

List<SomeResponse> someResponseList = someRepository.findByKeywordsContainingRegex("/^toron/");

List<SomeResponse> someResponseList =someRepository.findByKeywordsContainingRegex("/^toron.*/");

Important point to note: each time ?0 field in @Query statement is replaced with double quoted string. so forwardslash(/)should not be used in these cases! always go for pattern using double quotes in searching pattern!! eg. use "^toron" or "^toron.*" over /^toron/ or /^toron.*/

How to disable CSS in Browser for testing purposes

Actually, it's easier than you think. In any browsers press F12 to bring up the debug console. This works for IE, Firefox, and Chrome. Not sure about Opera. Then comment out the CSS in the element windows. That's it.

How do I erase an element from std::vector<> by index?

If you have an unordered vector you can take advantage of the fact that it's unordered and use something I saw from Dan Higgins at CPPCON

template< typename TContainer >
static bool EraseFromUnorderedByIndex( TContainer& inContainer, size_t inIndex )
    if ( inIndex < inContainer.size() )
        if ( inIndex != inContainer.size() - 1 )
            inContainer[inIndex] = inContainer.back();
        return true;
    return false;

Since the list order doesn't matter, just take the last element in the list and copy it over the top of the item you want to remove, then pop and delete the last item.

Angular 2: import external js file into component

The following approach worked in Angular 5 CLI.

For sake of simplicity, I used similar d3gauge.js demo created and provided by oliverbinns - which you may easily find on Github.

So first, I simply created a new folder named externalJS on same level as the assets folder. I then copied the 2 following .js files.

  • d3.v3.min.js
  • d3gauge.js

I then made sure to declare both linked directives in main index.html

<script src="./externalJS/d3.v3.min.js"></script>
<script src="./externalJS/d3gauge.js"></script>

I then added a similar code in a gauge.component.ts component as followed:

import { Component, OnInit } from '@angular/core';

declare var d3gauge:any; <----- !
declare var drawGauge: any; <-----!

  selector: 'app-gauge',
  templateUrl: './gauge.component.html'

export class GaugeComponent implements OnInit {
   constructor() { }

   ngOnInit() {

   createD3Gauge() { 
      let gauges = []
      document.addEventListener("DOMContentLoaded", function (event) {      
      let opt = {
         gaugeRadius: 160,
         minVal: 0,
         maxVal: 100,
         needleVal: Math.round(30),
         tickSpaceMinVal: 1,
         tickSpaceMajVal: 10,
         divID: "gaugeBox",
         gaugeUnits: "%"

    gauges[0] = new drawGauge(opt);


and finally, I simply added a div in corresponding gauge.component.html

<div id="gaugeBox"></div>

et voilà ! :)

enter image description here

Alternative to a goto statement in Java

Use a labeled break as an alternative to goto.

Truncate (not round) decimal places in SQL Server

I know this is pretty late but I don't see it as an answer and have been using this trick for years.

Simply subtract .005 from your value and use Round(@num,2).

Your example:

declare @num decimal(9,5) = 123.456

select round(@num-.005,2)

returns 123.45

It will automatically adjust the rounding to the correct value you are looking for.

By the way, are you recreating the program from the movie Office Space?

How can I create an Asynchronous function in Javascript?

Here is a function that takes in another function and outputs a version that runs async.

var async = function (func) {
  return function () {
    var args = arguments;
    setTimeout(function () {
      func.apply(this, args);
    }, 0);

It is used as a simple way to make an async function:

var anyncFunction = async(function (callback) {

This is different from @fider's answer because the function itself has its own structure (no callback added on, it's already in the function) and also because it creates a new function that can be used.

How to do Base64 encoding in node.js?

crypto now supports base64 (reference):'base64') 

So you could simply do:

var cipher = crypto.createCipheriv('des-ede3-cbc', encryption_key, iv);
var ciph = cipher.update(plaintext, 'utf8', 'base64');
ciph +='base64');

var decipher = crypto.createDecipheriv('des-ede3-cbc', encryption_key, iv);
var txt = decipher.update(ciph, 'base64', 'utf8');
txt +='utf8');

Failed to connect to mysql at with user root access denied for user 'root'@'localhost'(using password:YES)

I faced this issue after using Vast cleanup. Basically mysql instance starts on PC startup and it is active in background all the time even when not in use.

Mistakenly I've stopped it

Failed to connect to mysql at with user root access denied for user 'root'@'localhost'(using password:YES)

Solution which worked for me:

type in mysql command line client. As soon as you open you will be prompted with password

-> mysql -u root -p -h -P 3306

and finally it works even when you switch back to workbench.

How to use background thread in swift?

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


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

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

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

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


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

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

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

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

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

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

sendmail: how to configure sendmail on ubuntu?

Combine two answers above, I finally make it work. Just be careful that the first single quote for each string is a backtick (`) in file

#Change to your mail config directory:
cd /etc/mail

#Make a auth subdirectory
mkdir auth
chmod 700 auth  #maybe not, because I cannot apply cmd "cd auth" if I do so.

#Create a file with your auth information to the smtp server
cd auth
touch client-info

#In the file, put the following, matching up to your smtp server: "U:root" "I:user" "P:password"

#Generate the Authentication database, make both files readable only by root
makemap hash client-info < client-info
chmod 600 client-info
cd ..

#Add the following lines to Make sure you update your smtp server
#The first single quote for each string should be changed to a backtick (`) like this:
FEATURE(`authinfo',`hash /etc/mail/auth/client-info')dnl

sudo sendmailconfig

Spring RestTemplate GET with parameters

Converting of a hash map to a string of query parameters:

Map<String, String> params = new HashMap<>();
params.put("msisdn", msisdn);
params.put("email", email);
params.put("clientVersion", clientVersion);
params.put("clientType", clientType);
params.put("issuerName", issuerName);
params.put("applicationName", applicationName);

UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl(url);
for (Map.Entry<String, String> entry : params.entrySet()) {
    builder.queryParam(entry.getKey(), entry.getValue());

HttpHeaders headers = new HttpHeaders();
headers.set("Accept", "application/json");

HttpEntity<String> response =, HttpMethod.GET, new HttpEntity(headers), String.class);

Error #2032: Stream Error

Just to clarify my comment (it's illegible in a single line)

I think the best answer is the comment by Mike Chambers in this link ( by Hunter McMillen.

A note from Mike Chambers:

If you run into this using URLLoader, listen for the:

and in AIR :

It should give you some more information (such as the status code being returned from the server).

how to view the contents of a .pem certificate

Use the -printcert command like this:

keytool -printcert -file certificate.pem

How to install PyQt4 on Windows using pip?

Try this for PyQt5:

pip install PyQt5

Use the operating system on this link for PyQt4.

Or download the supported wheel for your platform on this link.

Else use this link for the windows executable installer. Hopefully this helps you to install either PyQt4 or PyQt5.

std::wstring VS std::string

1) As mentioned by Greg, wstring is helpful for internationalization, that's when you will be releasing your product in languages other than english

4) Check this out for wide character

How to align text below an image in CSS?

You can use the HTML5 Caption feature.

How to read keyboard-input?

Non-blocking, multi-threaded example:

As blocking on keyboard input (since the input() function blocks) is frequently not what we want to do (we'd frequently like to keep doing other stuff), here's a very-stripped-down multi-threaded example to demonstrate how to keep running your main application while still reading in keyboard inputs whenever they arrive.

This works by creating one thread to run in the background, continually calling input() and then passing any data it receives to a queue.

In this way, your main thread is left to do anything it wants, receiving the keyboard input data from the first thread whenever there is something in the queue.

1. Bare Python 3 code example (no comments):

import threading
import queue
import time

def read_kbd_input(inputQueue):
    print('Ready for keyboard input:')
    while (True):
        input_str = input()

def main():
    EXIT_COMMAND = "exit"
    inputQueue = queue.Queue()

    inputThread = threading.Thread(target=read_kbd_input, args=(inputQueue,), daemon=True)

    while (True):
        if (inputQueue.qsize() > 0):
            input_str = inputQueue.get()
            print("input_str = {}".format(input_str))

            if (input_str == EXIT_COMMAND):
                print("Exiting serial terminal.")
            # Insert your code here to do whatever you want with the input_str.

        # The rest of your program goes here.


if (__name__ == '__main__'): 

2. Same Python 3 code as above, but with extensive explanatory comments:


Gabriel Staples
14 Nov. 2018

- *****
- *****

To install PySerial: `sudo python3 -m pip install pyserial`

To run this program: `python3`


import threading
import queue
import time

def read_kbd_input(inputQueue):
    print('Ready for keyboard input:')
    while (True):
        # Receive keyboard input from user.
        input_str = input()
        # Enqueue this input string.
        # Note: Lock not required here since we are only calling a single Queue method, not a sequence of them 
        # which would otherwise need to be treated as one atomic operation.

def main():

    EXIT_COMMAND = "exit" # Command to exit this program

    # The following threading lock is required only if you need to enforce atomic access to a chunk of multiple queue
    # method calls in a row.  Use this if you have such a need, as follows:
    # 1. Pass queueLock as an input parameter to whichever function requires it.
    # 2. Call queueLock.acquire() to obtain the lock.
    # 3. Do your series of queue calls which need to be treated as one big atomic operation, such as calling
    # inputQueue.qsize(), followed by inputQueue.put(), for example.
    # 4. Call queueLock.release() to release the lock.
    # queueLock = threading.Lock() 

    #Keyboard input queue to pass data from the thread reading the keyboard inputs to the main thread.
    inputQueue = queue.Queue()

    # Create & start a thread to read keyboard inputs.
    # Set daemon to True to auto-kill this thread when all other non-daemonic threads are exited. This is desired since
    # this thread has no cleanup to do, which would otherwise require a more graceful approach to clean up then exit.
    inputThread = threading.Thread(target=read_kbd_input, args=(inputQueue,), daemon=True)

    # Main loop
    while (True):

        # Read keyboard inputs
        # Note: if this queue were being read in multiple places we would need to use the queueLock above to ensure
        # multi-method-call atomic access. Since this is the only place we are removing from the queue, however, in this
        # example program, no locks are required.
        if (inputQueue.qsize() > 0):
            input_str = inputQueue.get()
            print("input_str = {}".format(input_str))

            if (input_str == EXIT_COMMAND):
                print("Exiting serial terminal.")
                break # exit the while loop
            # Insert your code here to do whatever you want with the input_str.

        # The rest of your program goes here.

        # Sleep for a short time to prevent this thread from sucking up all of your CPU resources on your PC.

# If you run this Python file directly (ex: via `python3`), do the following:
if (__name__ == '__main__'): 

Sample output:

$ python3
Ready for keyboard input:
input_str = hey
input_str = hello
input_str = 7000
input_str = exit
Exiting serial terminal.

The Python Queue library is thread-safe:

Note that Queue.put() and Queue.get() and other Queue class methods are thread-safe! That means they implement all the internal locking semantics required for inter-thread operations, so each function call in the queue class can be considered as a single, atomic operation. See the notes at the top of the documentation: (emphasis added):

The queue module implements multi-producer, multi-consumer queues. It is especially useful in threaded programming when information must be exchanged safely between multiple threads. The Queue class in this module implements all the required locking semantics.


  2. *****
  3. *****
  4. Python: How do I make a subclass from a superclass?


  1. PySerial non-blocking read loop

.gitignore for Visual Studio Projects and Solutions

For those interested in what Microsoft thinks should be included in the gitignore, here's the default one which Visual Studio 2013 RTM automatically generates when creating a new Git-Repository:

## Ignore Visual Studio temporary files, build results, and
## files generated by popular Visual Studio add-ons.

# User-specific files

# Build results


# Enable "build/" folder in the NuGet Packages folder since NuGet packages use it for MSBuild targets

# MSTest test Results


# Visual C++ cache files

# Visual Studio profiler

# Guidance Automation Toolkit

# ReSharper is a .NET coding add-in

# TeamCity is a build add-in

# DotCover is a Code Coverage Tool

# NCrunch

# Installshield output folder

# DocProject is a documentation generator add-in

# Click-Once directory

# Publish Web Output

# NuGet Packages Directory
## TODO: If you have NuGet Package Restore enabled, uncomment the next line

# Windows Azure Build Output

# Windows Store app package directory

# Others

# RIA/Silverlight projects

# Backup & report files from converting an old project file to a newer
# Visual Studio version. Backup files are not needed, because we have git ;-)

# SQL Server files

#LightSwitch generated files

# =========================
# Windows detritus
# =========================

# Windows image file caches

# Folder config file

# Recycle Bin used on file shares

# Mac desktop service store files

See: Add a default .gitignore file on MSDN

Where's my JSON data in my incoming Django request?

The HTTP POST payload is just a flat bunch of bytes. Django (like most frameworks) decodes it into a dictionary from either URL encoded parameters, or MIME-multipart encoding. If you just dump the JSON data in the POST content, Django won't decode it. Either do the JSON decoding from the full POST content (not the dictionary); or put the JSON data into a MIME-multipart wrapper.

In short, show the JavaScript code. The problem seems to be there.

ActiveRecord find and only return selected columns

My answer comes quite late because I'm a pretty new developer. This is what you can do:, :website, :city).find(

Btw, this is Rails 4

Sum across multiple columns with dplyr

I encounter this problem often, and the easiest way to do this is to use the apply() function within a mutate command.


df %>%
  mutate(sum = select(., x1:x5) %>% apply(1, sum, na.rm=TRUE))

Here you could use whatever you want to select the columns using the standard dplyr tricks (e.g. starts_with() or contains()). By doing all the work within a single mutate command, this action can occur anywhere within a dplyr stream of processing steps. Finally, by using the apply() function, you have the flexibility to use whatever summary you need, including your own purpose built summarization function.

Alternatively, if the idea of using a non-tidyverse function is unappealing, then you could gather up the columns, summarize them and finally join the result back to the original data frame.

df <- df %>% mutate( id = 1:n() )   # Need some ID column for this to work

df <- df %>%
  group_by(id) %>%
  gather('Key', 'value', starts_with('x')) %>%
  summarise( Key.Sum = sum(value) ) %>%
  left_join( df, . )

Here I used the starts_with() function to select the columns and calculated the sum and you can do whatever you want with NA values. The downside to this approach is that while it is pretty flexible, it doesn't really fit into a dplyr stream of data cleaning steps.

How to get filename without extension from file path in Ruby

You can get directory path to current script with:

File.dirname __FILE__

Remove HTML tags from string including &nbsp in C#

var noHtml = Regex.Replace(inputHTML, @"<[^>]*(>|$)|&nbsp;|&zwnj;|&raquo;|&laquo;", string.Empty).Trim();

Class name does not name a type in C++

Aren't you missing the #include "B.h" in A.h?

encrypt and decrypt md5

This question is tagged with PHP. But many people are using Laravel framework now. It might help somebody in future. That's why I answering for Laravel. It's more easy to encrypt and decrypt with internal functions.

$string = 'c4ca4238a0b923820dcc';
$encrypted = \Illuminate\Support\Facades\Crypt::encrypt($string);
$decrypted_string = \Illuminate\Support\Facades\Crypt::decrypt($encrypted);


Note: Be sure to set a 16, 24, or 32 character random string in the key option of the config/app.php file. Otherwise, encrypted values will not be secure.

But you should not use encrypt and decrypt for authentication. Rather you should use hash make and check.

To store password in database, make hash of password and then save.

$password = Input::get('password_from_user'); 
$hashed = Hash::make($password); // save $hashed value

To verify password, get password stored of account from database

// $user is database object
// $inputs is Input from user
if( \Illuminate\Support\Facades\Hash::check( $inputs['password'], $user['password']) == false) {
  // Password is not matching 
} else {
  // Password is matching 

Looping through all rows in a table column, Excel-VBA

You can search column before assignments:

Dim col_n as long
for i = 1 to NumCols
    if Cells(1, i).Value = "column header you are looking for" Then col_n = i

for i = 1 to NumRows
    Cells(i, col_n).Value = "PHEV"
next i

Capture iOS Simulator video for App Preview

I was facing the same problem. It has a very simple solution that worked for me. Just follow these steps:

1.Make a preview video in iMovie.

2.Export video using share file option. Choose 1920x1080 as it can be used for 5S, and 6 plus.

3.Download Appshow for Mac by techsmith ( It is specially made for making app preview videos. But i don't recommend it for making videos but rather just for exporting.

4.Choose a new App Preview video and customise it by choosing fewer frames which you can later delete.

5.Import your iMovie video into this template. On the top right corner you can choose any resolution you want, appshow has all the resolutions required for app preview.

6.Finally, just choose the device and export the video in your selected resolution.

How to fix "unable to open stdio.h in Turbo C" error?

Well, I've been working backshift just spent about 6 hours trying to figure this out.

All of the above information led to this conclusion along with a single line in dos prompt screen, when I exited the editor, go to the dos prompt my C: drive is mounted.

I did a dir search and what I found was: the way in which I had mounted the C drive initially looked like this

mount c: /

and my dir did not list all files on the C drive only files within the turboc++ folder. From that I had drawn the conclusion that my directories should look like:






The real problem was the nature in which I had mounted the drive.

Hope this helps someone.


html cellpadding the left side of a cell

I choose to use both methods. Cellpadding on the table as a fallback in case the inline style doesn't stick and inline style for most clients.

<table cellpadding="5">_x000D_
    <td style='padding:5px 10px 5px 5px'>Content</td>_x000D_
    <td style='padding:5px 10px 5px 5px'>Content</td>_x000D_

Difference between natural join and inner join

Inner join, join two table where column name is same.

Natural join, join two table where column name and data types are same.

How to edit CSS style of a div using C# in .NET

To expand on Peri's post & why we may not want to use viewstate the following code:

style="<%= _myCSS %>"

Protected _myCSS As String = "display: none"
Is the approach to look at if you're using AJAX, it allows for manipulating the display via back end code rather than jquery/jscript.

How to remove the hash from window.location (URL) with JavaScript without page refresh?

I think, it would be more safe

if (window.history) {
    window.history.pushState('', document.title, window.location.href.replace(window.location.hash, ''));
} else {
    window.location.hash = '';

sql how to cast a select query

You just CAST() this way

SELECT cast(yourNumber as varchar(10))
FROM yourTable

Then if you want to JOIN based on it, you can use:

FROM yourTable t1
INNER JOIN yourOtherTable t2
    on cast(t1.yourNumber as varchar(10)) = t2.yourString

error LNK2038: mismatch detected for '_ITERATOR_DEBUG_LEVEL': value '0' doesn't match value '2' in main.obj

Try this: Goto project property -> C/C++ -> Code generation -> Runtime Library Select from combobox value : Multi-threaded DLL (/MD) It work for me :)

browser sessionStorage. share between tabs?

  1. You can just use localStorage and remember the date it was first created in session cookie. When localStorage "session" is older than the value of cookie then you may clear the localStorage

    Cons of this is that someone can still read the data after the browser is closed so it's not a good solution if your data is private and confidental.

  2. You can store your data to localStorage for a couple of seconds and add event listener for a storage event. This way you will know when any of the tabs wrote something to the localStorage and you can copy its content to the sessionStorage, then just clear the localStorage

In Matplotlib, what does the argument mean in fig.add_subplot(111)?

enter image description here

import matplotlib.pyplot as plt

The first code creates the first subplot in a layout that has 3 rows and 2 columns.

The three graphs in the first column denote the 3 rows. The second plot comes just below the first plot in the same column and so on.

The last two plots have arguments (2, 2) denoting that the second column has only two rows, the position parameters move row wise.

How to use Elasticsearch with MongoDB?

River is a good solution once you want to have a almost real time synchronization and general solution.

If you have data in MongoDB already and want to ship it very easily to Elasticsearch like "one-shot" you can try my package in Node.js

It's using Node.js streams so you can import data from everything what is supporting streams (i.e. MongoDB, PostgreSQL, MySQL, JSON files, etc)

Example for MongoDB to Elasticsearch:

Install packages:

npm install elasticbulk
npm install mongoose
npm install bluebird

Create script i.e. script.js:

const elasticbulk = require('elasticbulk');
const mongoose = require('mongoose');
const Promise = require('bluebird');
mongoose.connect('mongodb://localhost/your_database_name', {
  useMongoClient: true

mongoose.Promise = Promise;

var Page = mongoose.model('Page', new mongoose.Schema({
  title: String,
  categories: Array
}), 'your_collection_name');

// stream query 
var stream = Page.find({
}, {title: 1, _id: 0, categories: 1}).limit(1500000).skip(0).batchSize(500).stream();

elasticbulk.import(stream, {
  index: 'my_index_name',
  type: 'my_type_name',
  host: 'localhost:9200',
.then(function(res) {
  console.log('Importing finished');

Ship your data:

node script.js

It's not extremely fast but it's working for millions of records (thanks to streams).

Should you use .htm or .html file extension? What is the difference, and which file is correct?

The short answer

There is none. They are exactly the same.

The long answer

Both .htm and .html are exactly the same and will work in the same way. The choice is down to personal preference, provided you’re consistent with your file naming you won’t have a problem with either.

Depending on the configuration of the web server, one of the file types will take precedence over the other. This should not be an issue since it’s unlikely that you’ll have both index.htm and index.html sitting in the same folder.

We always use the shorter .htm for our file names since file extensions are typically 3 characters long.


I think I should add this part here:
There is one single slight difference between .htm and .html files. Consider a path in your server like: If you create an index.htm file inside that folder and you open that like, it will goes crazy and spit out your files as it is in your server,enter image description here
but if you create an index.html file in there and open that directory in your browser, it will load that file. I tested this on my VPS and found this Maybe you could somehow set your server to load index.htm files by default, but I guess the .html file is the default file type for browsers to open in each directory.

jQuery add image inside of div tag

If we want to change the content of <div> tag whenever the function image()is called, we have to do like this:


function image() {
    var img = document.createElement("IMG");
    img.src = "/images/img1.gif";


<div id="image"></div>
<div><a href="javascript:image();">First Image</a></div>

How to use multiple databases in Laravel

Also you can use postgres fdw system

You will be able to connect different db in postgres. After that, in one query, you can access tables that are in different databases.

Strip double quotes from a string in .NET

s = s.Replace("\"", "");

You need to use the \ to escape the double quote character in a string.

Running bash script from within python

If chmod not working then you also try

import os
#you can also use bash instead of sh

test by me thanks

How does Tomcat locate the webapps directory?

I'm using Tomcat through XAMPP which might have been the cause of this problem. When I changed appBase="C:/Java Project/", for example, I kept getting "This localhost page can't be found" in the browser.

I had to add a folder called ROOT inside the Java Project folder and then it worked. Any files you're working on have to be inside this ROOT folder but you need to leave appBase="C:/Java Project/" as changing it to appBase="C:/Java Project/ROOT" will cause "This localhost page can't be found" to be displayed again.

Maybe needing the ROOT folder is obvious to more experienced Java developers but it wasn't for me so hopefully this helps anyone else encountering the same problem.

How can I check if a program exists from a Bash script?

It depends on whether you want to know whether it exists in one of the directories in the $PATH variable or whether you know the absolute location of it. If you want to know if it is in the $PATH variable, use

if which programname >/dev/null; then
    echo exists
    echo does not exist

otherwise use

if [ -x /path/to/programname ]; then
    echo exists
    echo does not exist

The redirection to /dev/null/ in the first example suppresses the output of the which program.

Convert char* to string C++

std::string str(buffer, buffer + length);

Or, if the string already exists:

str.assign(buffer, buffer + length);

Edit: I'm still not completely sure I understand the question. But if it's something like what JoshG is suggesting, that you want up to length characters, or until a null terminator, whichever comes first, then you can use this:

std::string str(buffer, std::find(buffer, buffer + length, '\0'));

Archive the artifacts in Jenkins

An artifact can be any result of your build process. The important thing is that it doesn't matter on which client it was built it will be tranfered from the workspace back to the master (server) and stored there with a link to the build. The advantage is that it is versionized this way, you only have to setup backup on your master and that all artifacts are accesible via the web interface even if all build clients are offline.

It is possible to define a regular expression as the artifact name. In my case I zipped all the files I wanted to store in one file with a constant name during the build.

how to set ASPNETCORE_ENVIRONMENT to be considered for publishing an core application?

This is how we can set it in run-time:

public class Program
    public static void Main(string[] args)
        Environment.SetEnvironmentVariable("ASPNETCORE_ENVIRONMENT", "Development");


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

Creating JSON on the fly with JObject

Sooner or later you will have property with special character. You can either use index or combination of index and property.

dynamic jsonObject = new JObject();
jsonObject["Create-Date"] = DateTime.Now; //<-Index use
jsonObject.Album = "Me Against the world"; //<- Property use
jsonObject["Create-Year"] = 1995; //<-Index use
jsonObject.Artist = "2Pac"; //<-Property use

Why doesn't C++ have a garbage collector?

When we compare C++ with Java, we see that C++ was not designed with implicit Garbage Collection in mind, while Java was.

Having things like arbitrary pointers in C-Style is not only bad for GC-implementations, but it would also destroy backward compatibility for a large amount of C++-legacy-code.

In addition to that, C++ is a language that is intended to run as standalone executable instead of having a complex run-time environment.

All in all: Yes it might be possible to add Garbage Collection to C++, but for the sake of continuity it is better not to do so.

converting numbers in to words C#

When I had to solve this problem, I created a hard-coded data dictionary to map between numbers and their associated words. For example, the following might represent a few entries in the dictionary:

{1, "one"}
{2, "two"}
{30, "thirty"}

You really only need to worry about mapping numbers in the 10^0 (1,2,3, etc.) and 10^1 (10,20,30) positions because once you get to 100, you simply have to know when to use words like hundred, thousand, million, etc. in combination with your map. For example, when you have a number like 3,240,123, you get: three million two hundred forty thousand one hundred twenty three.

After you build your map, you need to work through each digit in your number and figure out the appropriate nomenclature to go with it.

Transpose a data frame

Take advantage of as.matrix:

# keep the first column 
names <-  df.aree[,1]

# Transpose everything other than the first column
df.aree.T <-[,-1])))

# Assign first column as the column names of the transposed dataframe
colnames(df.aree.T) <- names

npm ERR! network getaddrinfo ENOTFOUND

Make sure to use the latest npm version while installing packages using npm.

While installing JavaScript, mention the latest version of NodeJS. For example, while installing JavaScript using devtools, use the below code:

devtools i --javascript nodejs:10.15.1

This will download and install the mentioned NodeJS version. Try installing the packages with npm after updating the version. This worked for me.

How do you get the footer to stay at the bottom of a Web page?

A similar solution to @gcedo but without the need of adding an intermediate content in order to push the footer down. We can simply add margin-top:auto to the footer and it will be pushed to the bottom of the page regardless his height or the height of the content above.

body {_x000D_
  display: flex;_x000D_
  flex-direction: column;_x000D_
  min-height: 100vh;_x000D_
.content {_x000D_
  padding: 50px;_x000D_
  background: red;_x000D_
.footer {_x000D_
  margin-top: auto;_x000D_
  background: green;_x000D_
<div class="content">_x000D_
  some content here_x000D_
<footer class="footer">_x000D_
  some content_x000D_

Add UIPickerView & a Button in Action sheet - How?

Update for iOS 7

Apple docs for UIActionSheet: UIActionSheet is not designed to be subclassed, nor should you add views to its hierarchy

I recommend against trying to customize the contents of an ActionSheet, as it can lead to serious invalid context errors in iOS 7. I just spent a few hours working through this problem and ultimately decided to take a different approach. I replaced the call to show the action sheet with a modal view controller containing a simple tableview.

There are many ways to accomplish this. Here's one way that I just implemented in a current project. It's nice because I can reuse it between 5 or 6 different screens where I all users to select from a list of options.

  1. Create a new UITableViewController subclass, SimpleTableViewController.
  2. Create a UITableViewController in your storyboard (embedded in a navigation controller) and set its custom class to SimpleTableViewController.
  3. Give the navigation controller for SimpleTableViewController a Storyboard ID of "SimpleTableVC".
  4. In SimpleTableViewController.h, create an NSArray property that will represent the data in the table.
  5. Also in SimpleTableViewController.h, create a protocol SimpleTableViewControllerDelegate with a required method itemSelectedatRow:, and a weak property called delegate of type id<SimpleTableViewControllerDelegate>. This is how we will pass the selection back to the parent controller.
  6. In SimpleTableViewController.m, implement the tableview data source and delegate methods, calling itemSelectedatRow: in tableView:didSelectRowAtIndexPath:.

This approach has the added benefit of being fairly reusable. To use, import the SimpleTableViewController class in your ViewController.h, conform to the SimpleTableViewDelegate, and implement the itemSelectedAtRow: method. Then, to open the modal just instantiate a new SimpleTableViewController, set the table data and delegate, and present it.

UINavigationController *navigationController = (UINavigationController *)[self.storyboard instantiateViewControllerWithIdentifier:@"SimpleTableVC"];
SimpleTableViewController *tableViewController = (SimpleTableViewController *)[[navigationController viewControllers] objectAtIndex:0];
tableViewController.tableData = self.statesArray;
tableViewController.navigationItem.title = @"States";
tableViewController.delegate = self;
[self presentViewController:navigationController animated:YES completion:nil];

I create a simple example and posted it on github.

Also see Showing actionsheet causes CGContext invalid context errors.

How to print Unicode character in Python?

I use Portable winpython in Windows, it includes IPython QT console, I could achieve the following.

>>>print ("??")

>>>print ("????")

>>>str = "??"

>>>print (str)

your console interpreter should support unicode in order to show unicode characters.

JavaScript string with new line - but not using \n

Check for \n or \r or \r\n.

There are several representations of newlines, see

CSS Circular Cropping of Rectangle Image

insert the image and then backhand all you need is:

img {
  border-radius: 50%;

** the image code will be here automatically**

IntelliJ: Working on multiple projects

you can use import module option which will open it just like eclipse in the same navigator.

Overflow Scroll css is not working in the div

The solution is to add height:100%; to all the parent elements of your .wrapper-div as well. So:

    height: 100%;


    margin:0 auto;

Where are the python modules stored?

1) Using the help function

Get into the python prompt and type the following command:


This will list all the modules installed in the system. You don't need to install any additional packages to list them, but you need to manually search or filter the required module from the list.

2) Using pip freeze

sudo apt-get install python-pip
pip freeze

Even though you need to install additional packages to use this, this method allows you to easily search or filter the result with grep command. e.g. pip freeze | grep feed.

You can use whichever method is convenient for you.

Array of Matrices in MATLAB

If all of the matrices are going to be the same size (i.e. 500x800), then you can just make a 3D array:

nUnknown;  % The number of unknown arrays
myArray = zeros(500,800,nUnknown);

To access one array, you would use the following syntax:

subMatrix = myArray(:,:,3);  % Gets the third matrix

You can add more matrices to myArray in a couple of ways:

myArray = cat(3,myArray,zeros(500,800));
% OR
myArray(:,:,nUnknown+1) = zeros(500,800);

If each matrix is not going to be the same size, you would need to use cell arrays like Hosam suggested.

EDIT: I missed the part about running out of memory. I'm guessing your nUnknown is fairly large. You may have to switch the data type of the matrices (single or even a uintXX type if you are using integers). You can do this in the call to zeros:

myArray = zeros(500,800,nUnknown,'single');

Error: select command denied to user '<userid>'@'<ip-address>' for table '<table-name>'

try grant privileges again.

GRANT ALL PRIVILEGES ON the_database.* TO 'the_user'@'%' WITH GRANT OPTION;

How to use the read command in Bash?

Other bash alternatives that do not involve a subshell:

read str <<END             # here-doc

read str <<< "hello"       # here-string

read str < <(echo hello)   # process substitution

How to run only one task in ansible playbook?

This can be easily done using the tags

The example of tags is defined below:

hosts: localhost
 - name: Creating s3Bucket
        name: ansiblebucket1234567890
       - createbucket

 - name: Simple PUT operation
       bucket: ansiblebucket1234567890
       object: /my/desired/key.txt
       src: /etc/ansible/myfile.txt
       mode: put
      - putfile

 - name: Create an empty bucket
       bucket: ansiblebucket12345678901234
       mode: create
       permission: private
       - emptybucket

to execute the tags we use the command

ansible-playbook creates3bucket.yml --tags "createbucket,putfile"

SQL Server - calculate elapsed time between two datetime stamps in HH:MM:SS format

SQL Server doesn't support the SQL standard interval data type. Your best bet is to calculate the difference in seconds, and use a function to format the result. The native function CONVERT() might appear to work fine as long as your interval is less than 24 hours. But CONVERT() isn't a good solution for this.

create table test (
  id integer not null,
  ts datetime not null

insert into test values (1, '2012-01-01 08:00');
insert into test values (1, '2012-01-01 09:00');
insert into test values (1, '2012-01-01 08:30');
insert into test values (2, '2012-01-01 08:30');
insert into test values (2, '2012-01-01 10:30');
insert into test values (2, '2012-01-01 09:00');
insert into test values (3, '2012-01-01 09:00');
insert into test values (3, '2012-01-02 12:00');

Values were chosen in such a way that for

  • id = 1, elapsed time is 1 hour
  • id = 2, elapsed time is 2 hours, and
  • id = 3, elapsed time is 3 hours.

This SELECT statement includes one column that calculates seconds, and one that uses CONVERT() with subtraction.

       min(ts) start_time,
       max(ts) end_time,
       datediff(second, min(ts),max(ts)) elapsed_sec,
       convert(varchar, max(ts) - min(ts), 108) do_not_use
from test t
group by;

ID  START_TIME                 END_TIME                   ELAPSED_SEC  DO_NOT_USE
1   January, 01 2012 08:00:00  January, 01 2012 09:00:00  3600         01:00:00
2   January, 01 2012 08:30:00  January, 01 2012 10:30:00  7200         02:00:00
3   January, 01 2012 09:00:00  January, 02 2012 12:00:00  97200        03:00:00

Note the misleading "03:00:00" for the 27-hour difference on id number 3.

Function to format elapsed time in SQL Server

CSS transition between left -> right and top -> bottom positions

You can animate the position (top, bottom, left, right) and then subtract the element's width or height through a CSS transformation.


$('.animate').on('click', function(){
     .animate {
        height: 100px;
        width: 100px;
        background-color: #c00;
        transition: all 1s ease;
        position: absolute;
        cursor: pointer;
        font: 13px/100px sans-serif;
        color: white;
        text-align: center;

                               /* ? just to position things  */
      .animate.left   { left: 0;   top: 50%;  margin-top: -100px;}
      .animate.right  { right: 0;  top: 50%;  }    { top: 0;    left: 50%; }
      .animate.bottom { bottom: 0; left: 50%; margin-left: -100px;}

      .animate.left.move {
        left: 100%; 
        transform: translate(-100%, 0);

      .animate.right.move {
        right: 100%; 
        transform: translate(100%, 0);
      } {
        top: 100%; 
        transform: translate(0, -100%);

      .animate.bottom.move {
        bottom: 100%; 
        transform: translate(0, 100%);
<script src=""></script>
Click to animate
<div class="animate left">left</div>
<div class="animate top">top</div>
<div class="animate bottom">bottom</div>
<div class="animate right">right</div>

And then animate depending on the position...

Image resizing client-side with JavaScript before upload to the server

In modern browser you can use canvas to load/save image data. But you should keep in mind several things if you resize image on the client:

  1. You will have only 8bits per channel (jpeg can have better dynamic range, about 12 bits). If you don't upload professional photos, that should not be a problem.
  2. Be careful about resize algorithm. The most of client side resizers use trivial math, and result is worse than it could be.
  3. You may need to sharpen downscaled image.
  4. If you wish do reuse metadata (exif and other) from original - don't forget to strip color profile info. Because it's applied when you load image to canvas.

Custom checkbox image android

Based on the Enselic and Rahul answers.

It works for me (before and after API 21):


    app:buttonCompat="@null" />

Get time in milliseconds using C#

Use System.DateTime.Now.ToUniversalTime(). That puts your reading in a known reference-based millisecond format that totally eliminates day change, etc.

iOS Launching Settings -> Restrictions URL Scheme

Here is something else I found:

  1. After I have the "prefs" URL Scheme defined, "prefs:root=Safari&path=ContentBlockers" is working on Simulator (iOS 9.1 English), but not working on Simulator (Simplified Chinese). It just jump to Safari, but not Content Blockers. If your app is international, be careful.
    Update: Don't know why, now I can't jump into ContentBlockers anymore, the same code, the same version, doesn't work now. :(

  2. On real devcies (mine is iPhone 6S & iPad mini 2), "Safari" should be "SAFARI", "Safari" not working on real device, "SAFARI" now working on simulator:

    #if arch(i386) || arch(x86_64)
        // Simulator
        let url = NSURL(string: "prefs:root=Safari")!
        // Device
        let url = NSURL(string: "prefs:root=SAFARI")!
    if UIApplication.sharedApplication().canOpenURL(url) {
  3. So far, did not find any differences between iPhone and iPad.

How do I determine the size of my array in C?

You can use sizeof operator but it will not work for functions because it will take the reference of pointer you can do the following to find the length of an array:

len = sizeof(arr)/sizeof(arr[0])

Code originally found here: C program to find the number of elements in an array

how to run a command at terminal from java program?

I know this question is quite old, but here's a library that encapsulates the ProcessBuilder api.

How to support UTF-8 encoding in Eclipse

I tried all settings mentioned in this post to build my project successfully however that didn't work for me. At last I was able to build my project successfully with mvn -DargLine=-Dfile.encoding=UTF-8 clean insall command.

How is Perl's @INC constructed? (aka What are all the ways of affecting where Perl modules are searched for?)

As it was said already @INC is an array and you're free to add anything you want.

My CGI REST script looks like:

use strict;
use warnings;
    push @INC, '';
use Modules::Rest;

Subroutine gone is exported by

Return value using String result=Command.ExecuteScalar() error occurs when result returns null

try this :

 string getValue = Convert.ToString(cmd.ExecuteScalar());

Compare two data.frames to find the rows in data.frame 1 that are not present in data.frame 2

I wrote a package ( since I had the same issue.

  > df1 <- data.frame(a = 1:5, b=letters[1:5], row = 1:5)
  > df2 <- data.frame(a = 1:3, b=letters[1:3], row = 1:3)
  > df_compare = compare_df(df1, df2, "row")

  > df_compare$comparison_df
    row chng_type a b
  1   4         + 4 d
  2   5         + 5 e

A more complicated example:

df1 = data.frame(id1 = c("Mazda RX4", "Mazda RX4 Wag", "Datsun 710",
                         "Hornet 4 Drive", "Duster 360", "Merc 240D"),
                 id2 = c("Maz", "Maz", "Dat", "Hor", "Dus", "Mer"),
                 hp = c(110, 110, 181, 110, 245, 62),
                 cyl = c(6, 6, 4, 6, 8, 4),
                 qsec = c(16.46, 17.02, 33.00, 19.44, 15.84, 20.00))

df2 = data.frame(id1 = c("Mazda RX4", "Mazda RX4 Wag", "Datsun 710",
                         "Hornet 4 Drive", " Hornet Sportabout", "Valiant"),
                 id2 = c("Maz", "Maz", "Dat", "Hor", "Dus", "Val"),
                 hp = c(110, 110, 93, 110, 175, 105),
                 cyl = c(6, 6, 4, 6, 8, 6),
                 qsec = c(16.46, 17.02, 18.61, 19.44, 17.02, 20.22))

> df_compare$comparison_df
    grp chng_type                id1 id2  hp cyl  qsec
  1   1         -  Hornet Sportabout Dus 175   8 17.02
  2   2         +         Datsun 710 Dat 181   4 33.00
  3   2         -         Datsun 710 Dat  93   4 18.61
  4   3         +         Duster 360 Dus 245   8 15.84
  5   7         +          Merc 240D Mer  62   4 20.00
  6   8         -            Valiant Val 105   6 20.22

The package also has an html_output command for quick checking

df_compare$html_output enter image description here

"Unable to acquire application service" error while launching Eclipse

This error happen cause you deleted the config.ini file while you deleted the plugins. So, when it can not find configuration in config.ini when eclipse lauching, then it use default configuration which is not fit with your os. The following steps solve you problem:

  1. Delete setting in configuration folder.

  2. create a new config.ini file.

  3. copy following setting and save:

  4. osgi.splashPath = platform:/base/plugins/org.eclipse.platform  
    osgi.bundles=org.eclipse.equinox.common@2:start, org.eclipse.update.configurator@3:start, org.eclipse.core.runtime@start  
    [email protected]/workspace  
  5. restart eclipse.

Android Studio - Importing external Library/Jar

Easy way and it works for me. Using Android Studio 0.8.2.

  1. Drag jar file under libs.
  2. Press "Sync Project with Gradle Files" button.

enter image description here

How to ping ubuntu guest on VirtualBox

Using NAT (the default) this is not possible. Bridged Networking should allow it. If bridged does not work for you (this may be the case when your network adminstration does not allow multiple IP addresses on one physical interface), you could try 'Host-only networking' instead.

For configuration of Host-only here is a quote from the vbox manual(which is pretty good).

For host-only networking, like with internal networking, you may find the DHCP server useful that is built into VirtualBox. This can be enabled to then manage the IP addresses in the host-only network since otherwise you would need to configure all IP addresses statically.

In the VirtualBox graphical user interface, you can configure all these items in the global settings via "File" -> "Settings" -> "Network", which lists all host-only networks which are presently in use. Click on the network name and then on the "Edit" button to the right, and you can modify the adapter and DHCP settings.

Pressing Ctrl + A in Selenium WebDriver

The simplest answer in C# (if you are C# inclined).

Actions action = new Actions(); 

This answer is almost given by Hari Reddy, but I have fixed the case which he'd got wrong on some keywords, added the KeyUp or you get in a mess leaving the control key down.

I've also added the clarification on OpenQA.Selenium.Keys, because you may also be using Windows.Forms on the same class as I was an require this clarity.

Lastly, I type "a" because I found that to be the simplest way and I can see no suggestion from the OP that they don't want the simplest answer.

Many thanks to Hari Reddy though as I was a novice in Actions class usage and I was writing many different commands. Chaining them together the way he showed is quicker :-)

How to convert string to double with proper cultureinfo

You can change your UI culture to anything you want, but you should change the number separator like this:

CultureInfo info = new CultureInfo("fa-IR");
info.NumberFormat.NumberDecimalSeparator = ".";
Thread.CurrentThread.CurrentCulture = info;
Thread.CurrentThread.CurrentUICulture = Thread.CurrentThread.CurrentCulture;

With this, your strings converts like this: "12.49" instead of "12,49" or "12/49"

How can I tell when HttpClient has timed out?

Basically, you need to catch the OperationCanceledException and check the state of the cancellation token that was passed to SendAsync (or GetAsync, or whatever HttpClient method you're using):

  • if it was canceled (IsCancellationRequested is true), it means the request really was canceled
  • if not, it means the request timed out

Of course, this isn't very convenient... it would be better to receive a TimeoutException in case of timeout. I propose a solution here based on a custom HTTP message handler: Better timeout handling with HttpClient

AngularJs ReferenceError: angular is not defined

I think this will happen if you'll use 'async defer' for (the file that contains the filter) while working with angularjs:

<script src="js/filter.js" type="text/javascript" async defer></script>

if you do, just remove 'async defer'.

APR based Apache Tomcat Native library was not found on the java.library.path?

For Ubntu Users

 1. Install compilers
    #sudo apt-get install make
    #sudo apt-get install gcc

    2. Install openssl and development libraries
    #sudo apt-get install openssl
    #sudo apt-get install libssl-dev
    3. Install the APR package (Downloaded from

    #tar -xzf apr-1.4.6.tar.gz
    #cd apr-1.4.6/
    #sudo ./configure
    #sudo make
    #sudo make install

    You should see the compiled file as

    4. Download, compile and install Tomcat Native sourse package

    Extract the archive into some folder

    #tar -xzf tomcat-native-1.1.27-src.tar.gz
    #cd tomcat-native-1.1.27-src/jni/native
    #sudo ./configure --with-apr=/usr/local/apr --with-java-home=$JAVA_HOME
    #sudo make
    #sudo make install

    Now I have compiled Tomcat Native library in /usr/local/apr/ and symbolic link file /usr/local/apr/ pointed to the library

    5. Create or edit the $CATALINA_HOME/bin/ file with following lines :
    export LD_LIBRARY_PATH='$LD_LIBRARY_PATH:/usr/local/apr/lib'

    6. Restart tomcat and see the desired result:

How do you unit test private methods?

You could generate the test method for the private method from Visual studio 2008. When you create a unit test for a private method, a Test References folder is added to your test project and an accessor is added to that folder. The accessor is also referred to in the logic of the unit test method. This accessor allows your unit test to call private methods in the code that you are testing. For details have a look at

jQuery remove options from select

Try this:

$(".ct option[value='X']").each(function() {

Or to be more terse, this will work just as well:

$(".ct option[value='X']").remove();

Get a specific bit from byte

This is works faster than 0.1 milliseconds.

return (b >> bitNumber) & 1;

How to get the range of occupied cells in excel sheet

See the Range.SpecialCells method. For example, to get cells with constant values or formulas use:

        Microsoft.Office.Interop.Excel.XlCellType.xlCellTypeConstants |

PostgreSQL Crosstab Query

Install the additional module tablefunc once per database, which provides the function crosstab(). Since Postgres 9.1 you can use CREATE EXTENSION for that:


Improved test case

   section   text
 , status    text
 , ct        integer  -- "count" is a reserved word in standard SQL

  ('A', 'Active', 1), ('A', 'Inactive', 2)
, ('B', 'Active', 4), ('B', 'Inactive', 5)
                    , ('C', 'Inactive', 7);  -- ('C', 'Active') is missing

Simple form - not fit for missing attributes

crosstab(text) with 1 input parameter:

FROM   crosstab(
   'SELECT section, status, ct
    FROM   tbl
    ORDER  BY 1,2'  -- needs to be "ORDER BY 1,2" here
   ) AS ct ("Section" text, "Active" int, "Inactive" int);


 Section | Active | Inactive
 A       |      1 |        2
 B       |      4 |        5
 C       |      7 |           -- !!
  • No need for casting and renaming.
  • Note the incorrect result for C: the value 7 is filled in for the first column. Sometimes, this behavior is desirable, but not for this use case.
  • The simple form is also limited to exactly three columns in the provided input query: row_name, category, value. There is no room for extra columns like in the 2-parameter alternative below.

Safe form

crosstab(text, text) with 2 input parameters:

FROM   crosstab(
   'SELECT section, status, ct
    FROM   tbl
    ORDER  BY 1,2'  -- could also just be "ORDER BY 1" here

  , $$VALUES ('Active'::text), ('Inactive')$$
   ) AS ct ("Section" text, "Active" int, "Inactive" int);


 Section | Active | Inactive
 A       |      1 |        2
 B       |      4 |        5
 C       |        |        7  -- !!
  • Note the correct result for C.

  • The second parameter can be any query that returns one row per attribute matching the order of the column definition at the end. Often you will want to query distinct attributes from the underlying table like this:

    'SELECT DISTINCT attribute FROM tbl ORDER BY 1'

    That's in the manual.

    Since you have to spell out all columns in a column definition list anyway (except for pre-defined crosstabN() variants), it is typically more efficient to provide a short list in a VALUES expression like demonstrated:

    $$VALUES ('Active'::text), ('Inactive')$$)

    Or (not in the manual):

    $$SELECT unnest('{Active,Inactive}'::text[])$$  -- short syntax for long lists
  • I used dollar quoting to make quoting easier.

  • You can even output columns with different data types with crosstab(text, text) - as long as the text representation of the value column is valid input for the target type. This way you might have attributes of different kind and output text, date, numeric etc. for respective attributes. There is a code example at the end of the chapter crosstab(text, text) in the manual.

db<>fiddle here

Advanced examples

\crosstabview in psql

Postgres 9.6 added this meta-command to its default interactive terminal psql. You can run the query you would use as first crosstab() parameter and feed it to \crosstabview (immediately or in the next step). Like:

db=> SELECT section, status, ct FROM tbl \crosstabview

Similar result as above, but it's a representation feature on the client side exclusively. Input rows are treated slightly differently, hence ORDER BY is not required. Details for \crosstabview in the manual. There are more code examples at the bottom of that page.

Related answer on dba.SE by Daniel Vérité (the author of the psql feature):

The previously accepted answer is outdated.

  • The variant of the function crosstab(text, integer) is outdated. The second integer parameter is ignored. I quote the current manual:

    crosstab(text sql, int N) ...

    Obsolete version of crosstab(text). The parameter N is now ignored, since the number of value columns is always determined by the calling query

  • Needless casting and renaming.

  • It fails if a row does not have all attributes. See safe variant with two input parameters above to handle missing attributes properly.

  • ORDER BY is required in the one-parameter form of crosstab(). The manual:

    In practice the SQL query should always specify ORDER BY 1,2 to ensure that the input rows are properly ordered

What is log4j's default log file dumping path

You have copy this sample code from Here,right?
now, as you can see there property file they have define, have you done same thing? if not then add below code in your project with property file for log4j

So the content of file would be as follows:

# Define the root logger with appender file
log = /usr/home/log4j
log4j.rootLogger = DEBUG, FILE

# Define the file appender

# Define the layout for file appender

make changes as per your requirement like log path

How do I capture the output into a variable from an external process in PowerShell?

Or try this. It will capture output into variable $scriptOutput:

& "netdom.exe" $params | Tee-Object -Variable scriptOutput | Out-Null


How to change the background color of the options menu?

 <style name="AppThemeLight" parent="Theme.AppCompat.Light.NoActionBar">
    <item name="android:itemBackground">#000000</item>

this works fine for me

Visual Studio SignTool.exe Not Found

Here is a solution for Visual Studio 2017. The installer looks a littlebit different from the VS 2015 version and the name of the installation packages are different.

Jquery how to find an Object by attribute in an Array

I personally use a more generic function that works for any property of any array:

function lookup(array, prop, value) {
    for (var i = 0, len = array.length; i < len; i++)
        if (array[i] && array[i][prop] === value) return array[i];

You just call it like this:

lookup(purposeObjects, "purpose", "daily");

Copying files from server to local computer using SSH

that scp command must be issued on the local command-line, for putty the command is pscp.

C:\something> pscp [email protected]:/dir/of/file.txt \local\dir\

Contains case insensitive

It's 2016, and there's no clear way of how to do this? I was hoping for some copypasta. I'll have a go.

Design notes: I wanted to minimize memory usage, and therefore improve speed - so there is no copying/mutating of strings. I assume V8 (and other engines) can optimise this function.

//TODO: Performance testing
String.prototype.naturalIndexOf = function(needle) {
    //TODO: guard conditions here
    var haystack = this; //You can replace `haystack` for `this` below but I wan't to make the algorithm more readable for the answer
    var needleIndex = 0;
    var foundAt = 0;
    for (var haystackIndex = 0; haystackIndex < haystack.length; haystackIndex++) {
        var needleCode = needle.charCodeAt(needleIndex);
        if (needleCode >= 65 && needleCode <= 90) needleCode += 32; //ToLower. I could have made this a function, but hopefully inline is faster and terser
        var haystackCode = haystack.charCodeAt(haystackIndex);
        if (haystackCode >= 65 && haystackCode <= 90) haystackCode += 32; //ToLower. I could have made this a function, but hopefully inline is faster and terser
        //TODO: code to detect unicode characters and fallback to toLowerCase - when > 128?
        //if (needleCode > 128 || haystackCode > 128) return haystack.toLocaleLowerCase().indexOf(needle.toLocaleLowerCase();
        if (haystackCode !== needleCode)
            foundAt = haystackIndex;
            needleIndex = 0; //Start again
        if (needleIndex == needle.length)
            return foundAt;
    return -1;

My reason for the name:

  • Should have IndexOf in the name
  • Don't add a suffix word - IndexOf refers to the following parameter. So prefix something instead.
  • Don't use "caseInsensitive" prefix would be sooooo long
  • "natural" is a good candidate, because default case sensitive comparisons are not natural to humans in the first place.

Why not...:

  • toLowerCase() - potential repeated calls to toLowerCase on the same string.
  • RegExp - awkward to search with variable. Even the RegExp object is awkward having to escape characters

PHP MySQL Query Where x = $variable

$result = mysqli_query($con,"SELECT `note` FROM `glogin_users` WHERE email = '".$email."'");
while($row = mysqli_fetch_array($result))
echo $row['note'];

FirstOrDefault: Default value other than null

Copied over from comment by @sloth

Instead of YourCollection.FirstOrDefault(), you could use YourCollection.DefaultIfEmpty(YourDefault).First() for example.


var viewModel = new CustomerDetailsViewModel
            MainResidenceAddressSection = (MainResidenceAddressSection)addresses.DefaultIfEmpty(new MainResidenceAddressSection()).FirstOrDefault( o => o is MainResidenceAddressSection),
            RiskAddressSection = addresses.DefaultIfEmpty(new RiskAddressSection()).FirstOrDefault(o => !(o is MainResidenceAddressSection)),

Counter in foreach loop in C#

Not all collections have indexes. For instance, I can use a Dictionary with foreach (and iterate through all the keys and values), but I can't write get at individual elements using dictionary[0], dictionary[1] etc.

If I did want to iterate through a dictionary and keep track of an index, I'd have to use a separate variable that I incremented myself.

Change Primary Key

Assuming that your table name is city and your existing Primary Key is pk_city, you should be able to do the following:


ADD CONSTRAINT pk_city PRIMARY KEY (city_id, buildtime, time);

Make sure that there are no records where time is NULL, otherwise you won't be able to re-create the constraint.

How to commit to remote git repository

You just need to make sure you have the rights to push to the remote repository and do

git push origin master

or simply

git push

Rails: update_attribute vs update_attributes

update_attribute simply updates only one attribute of a model, but we can pass multiple attributes in update_attributes method.


user = User.last

user.update_attribute(:status, "active")

It pass the validation

user.update_attributes(first_name: 'update name', status: "active")

it doesn't update if validation fails.