Programs & Examples On #Videochat

Video chat refers to online chatting while video signal is being broadcasted.

Using :: in C++

You're pretty much right about cout and cin. They are objects (not functions) defined inside the std namespace. Here are their declarations as defined by the C++ standard:

Header <iostream> synopsis

#include <ios>
#include <streambuf>
#include <istream>
#include <ostream>

namespace std {
  extern istream cin;
  extern ostream cout;
  extern ostream cerr;
  extern ostream clog;

  extern wistream wcin;
  extern wostream wcout;
  extern wostream wcerr;
  extern wostream wclog;

:: is known as the scope resolution operator. The names cout and cin are defined within std, so we have to qualify their names with std::.

Classes behave a little like namespaces in that the names declared inside the class belong to the class. For example:

class foo
    void bar();

The constructor named foo is a member of the class named foo. They have the same name because its the constructor. The function bar is also a member of foo.

Because they are members of foo, when referring to them from outside the class, we have to qualify their names. After all, they belong to that class. So if you're going to define the constructor and bar outside the class, you need to do it like so:

  // Implement the constructor

void foo::bar()
  // Implement bar

This is because they are being defined outside the class. If you had not put the foo:: qualification on the names, you would be defining some new functions in the global scope, rather than as members of foo. For example, this is entirely different bar:

void bar()
  // Implement different bar

It's allowed to have the same name as the function in the foo class because it's in a different scope. This bar is in the global scope, whereas the other bar belonged to the foo class.

SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo failed: Name or service not known

If you are on production server and the .env file doesn't work at all, go to /bootstrap/cache/config.php and on the line 230 more or less you will find the database data that is beeing cached from the .env file.

'mysql' => 
  array (
    'driver' => 'mysql',
    'host' => '',
    'port' => '3306',
    'database' => 'yorDBname',
    'username' => 'YOURUSERNAME',
    'password' => 'yourpass',
    'unix_socket' => '',
    'charset' => 'utf8mb4',
    'collation' => 'utf8mb4_unicode_ci',
    'prefix' => '',
    'strict' => true,
    'engine' => 'InnoDB ROW_FORMAT=DYNAMIC',

What is the difference between DSA and RSA?

And in addition to the above nice answers.

  • DSA uses Discrete logarithm.
  • RSA uses Integer Factorization.

RSA stands for Ron Rivest, Adi Shamir and Leonard Adleman.

Function to check if a string is a date

I found my answer here, bassically

$d = DateTime::createFromFormat($format, $date);
// The Y ( 4 digits year ) returns TRUE for any integer with any number of digits so changing the comparison from == to === fixes the issue.
if($d && $d->format($format) === $date) {
    //it's a proper date!
else {
    //it's not a proper date

Python conditional assignment operator

I'm surprised no one offered this answer. It's not as "built-in" as Ruby's ||= but it's basically equivalent and still a one-liner:

foo = foo if 'foo' in locals() else 'default'

Of course, locals() is just a dictionary, so you can do:

foo = locals().get('foo', 'default')

How do I update pip itself from inside my virtual environment?

In case you are using venv any update to pip install will result in upgrading the system pip instead of the venv pip. You need to upgrade the pip bootstrapping packages as well.

  python3 -m pip install --upgrade pip setuptools wheel

Catch KeyError in Python

You can also try to use get(), for example:

connection = manager.connect.get("I2Cx")

which won't raise a KeyError in case the key doesn't exist.

You may also use second argument to specify the default value, if the key is not present.

error: command 'gcc' failed with exit status 1 on CentOS

pip install -U pip
pip install -U cython

sql insert into table with select case values

Also you can use COALESCE instead of CASE expression. Because result of concatenating anything to NULL, even itself, is always NULL

INSERT TblStuff(FullName,Address,City,Zip)
SELECT COALESCE(Fname + ' ' + Middle + ' ' + Lname, Fname + LName) AS FullName,
       COALESCE(Address1 + ', ' + Address2, Address1) AS Address, City, Zip
FROM tblImport

Demo on SQLFiddle

How to go back to previous page if back button is pressed in WebView?

here is a code with confirm exit:

    public void onBackPressed()
            new AlertDialog.Builder(this)
            .setMessage("Are you sure you want to close?")
            .setPositiveButton("Yes", new DialogInterface.OnClickListener()
                public void onClick(DialogInterface dialog, int which) {

            .setNegativeButton("No", null)

What is the best way to delete a component with CLI

I am not sure if it is the best way, but it worked for me.

  • First, I deleted the component folder.
  • Then, I cleared app.module.ts, app.component.ts & app.component.html of the imports and declarations related to the component I wanted to delete.
  • Similarly, I cleared main.ts.

I just saved and refreshed the app and it worked.

How to automatically generate getters and setters in Android Studio

You can generate getter and setter by following steps:

  • Declare variables first.
  • click on ALT+Insert on keyboard placing cursor down to variable declaration part
  • now select constructor and press Ctrl+A on keyboard and click on Enter to create constructor.
  • Now again placing cursor at next line of constructor closing brace , click ALT+INSERT and select getter and setter and again press CTRL+A to select all variables and hit Enter.

That's it. Happy coding!!

Running npm command within Visual Studio Code

I installed npm after Visual studio code, closed all visual studio instances and opened again and it started working.

codes for ADD,EDIT,DELETE,SEARCH in vb2010

A good resource start off point would be MSDN as your looking into a microsoft product

Why is $$ returning the same id as the parent process?

You can use one of the following.

  • $! is the PID of the last backgrounded process.
  • kill -0 $PID checks whether it's still running.
  • $$ is the PID of the current shell.

Is there an upper bound to BigInteger?

The number is held in an int[] - the maximum size of an array is Integer.MAX_VALUE. So the maximum BigInteger probably is (2 ^ 32) ^ Integer.MAX_VALUE.

Admittedly, this is implementation dependent, not part of the specification.

In Java 8, some information was added to the BigInteger javadoc, giving a minimum supported range and the actual limit of the current implementation:

BigInteger must support values in the range -2Integer.MAX_VALUE (exclusive) to +2Integer.MAX_VALUE (exclusive) and may support values outside of that range.

Implementation note: BigInteger constructors and operations throw ArithmeticException when the result is out of the supported range of -2Integer.MAX_VALUE (exclusive) to +2Integer.MAX_VALUE (exclusive).

AssertNull should be used or AssertNotNull

I just want to add that if you want to write special text if It null than you make it like that

  Assert.assertNotNull("The object you enter return null", str1)

Html.DropdownListFor selected value not being set

This is CSS issues. I don't know why @Html.DropDownListFor in Bootstrap 4 doest work. Surely this is class design problem. Anyways the work arround is, if your Dropdown input box has CSS Padding: #px, # px; element then disable it. Hope this will work.

Resize image proportionally with CSS?

To resize the image proportionally using CSS:

img.resize {
    width:540px; /* you can use % */
    height: auto;

How can I add an empty directory to a Git repository?

As described in other answers, Git is unable to represent empty directories in its staging area. (See the Git FAQ.) However, if, for your purposes, a directory is empty enough if it contains a .gitignore file only, then you can create .gitignore files in empty directories only via:

find . -type d -empty -exec touch {}/.gitignore \;

Convert a Unix timestamp to time in JavaScript

I'm partial to Jacob Wright's Date.format() library, which implements JavaScript date formatting in the style of PHP's date() function.

new Date(unix_timestamp * 1000).format('h:i:s')

SQL Server 2008 Windows Auth Login Error: The login is from an untrusted domain

in order to enable windows authentication both computers need to be in the same domain. in order to allow managment studios to pass the current credentials and authenticate in the sql box

Read Session Id using Javascript

you can receive the session id by issuing the following regular expression on document.cookie:


in my example the cookie name to store session id is PHPSESSID (php server), just replace the PHPSESSID with the cookie name that holds the session id. (configurable by the web server)

Check if url contains string with JQuery

window.location is an object, not a string so you need to use window.location.href to get the actual string url

if (window.location.href.indexOf("?added-to-cart=555") >= 0) {
    alert("found it");

How to encrypt and decrypt file in Android?

You could use java-aes-crypto or Facebook's Conceal


Quoting from the repo

A simple Android class for encrypting & decrypting strings, aiming to avoid the classic mistakes that most such classes suffer from.

Facebook's conceal

Quoting from the repo

Conceal provides easy Android APIs for performing fast encryption and authentication of data

How to use CSS to surround a number with a circle?

This version does not rely on hard-coded, fixed values but sizes relative to the font-size of the div.

enter image description here


.numberCircle {
    font: 32px Arial, sans-serif;

    width: 2em;
    height: 2em;
    box-sizing: initial;

    background: #fff;
    border: 0.1em solid #666;
    color: #666;
    text-align: center;
    border-radius: 50%;    

    line-height: 2em;
    box-sizing: content-box;   


<div class="numberCircle">30</div>
<div class="numberCircle" style="font-size: 60px">1</div>
<div class="numberCircle" style="font-size: 12px">2</div>

Adding and reading from a Config file

Configuration configManager = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
KeyValueConfigurationCollection confCollection = configManager.AppSettings.Settings;

confCollection["YourKey"].Value = "YourNewKey";


What are the differences between Deferred, Promise and Future in JavaScript?

What really made it all click for me was this presentation by Domenic Denicola.

In a github gist, he gave the description I like most, it's very concise:

The point of promises is to give us back functional composition and error bubbling in the async world.

In other word, promises are a way that lets us write asynchronous code that is almost as easy to write as if it was synchronous.

Consider this example, with promises:

getTweetsFor("domenic") // promise-returning async function
    .then(function (tweets) {
        var shortUrls = parseTweetsForUrls(tweets);
        var mostRecentShortUrl = shortUrls[0];
        return expandUrlUsingTwitterApi(mostRecentShortUrl); // promise-returning async function
    .then(doHttpRequest) // promise-returning async function
        function (responseBody) {
            console.log("Most recent link text:", responseBody);
        function (error) {
            console.error("Error with the twitterverse:", error);

It works as if you were writing this synchronous code:

try {
    var tweets = getTweetsFor("domenic"); // blocking
    var shortUrls = parseTweetsForUrls(tweets);
    var mostRecentShortUrl = shortUrls[0];
    var responseBody = doHttpRequest(expandUrlUsingTwitterApi(mostRecentShortUrl)); // blocking x 2
    console.log("Most recent link text:", responseBody);
} catch (error) {
    console.error("Error with the twitterverse: ", error);

(If this still sounds complicated, watch that presentation!)

Regarding Deferred, it's a way to .resolve() or .reject() promises. In the Promises/B spec, it is called .defer(). In jQuery, it's $.Deferred().

Please note that, as far as I know, the Promise implementation in jQuery is broken (see that gist), at least as of jQuery 1.8.2.
It supposedly implements Promises/A thenables, but you don't get the correct error handling you should, in the sense that the whole "async try/catch" functionality won't work. Which is a pity, because having a "try/catch" with async code is utterly cool.

If you are going to use Promises (you should try them out with your own code!), use Kris Kowal's Q. The jQuery version is just some callback aggregator for writing cleaner jQuery code, but misses the point.

Regarding Future, I have no idea, I haven't seen that in any API.

Edit: Domenic Denicola's youtube talk on Promises from @Farm's comment below.

A quote from Michael Jackson (yes, Michael Jackson) from the video:

I want you to burn this phrase in your mind: A promise is an asynchronous value.

This is an excellent description: a promise is like a variable from the future - a first-class reference to something that, at some point, will exist (or happen).

When to choose mouseover() and hover() function?

You can try it out on the jQuery doc page. It's a nice little, interactive demo that makes it very clear and you can actually see for yourself.

In short, you'll notice that a mouse over event occurs on an element when you are over it - coming from either its child OR parent element, but a mouse enter event only occurs when the mouse moves from the parent element to the element.

Difference between Amazon EC2 and AWS Elastic Beanstalk

First off, EC2 and Elastic Compute Cloud are the same thing.

Next, AWS encompasses the range of Web Services that includes EC2 and Elastic Beanstalk. It also includes many others such as S3, RDS, DynamoDB, and all the others.


EC2 is Amazon's service that allows you to create a server (AWS calls these instances) in the AWS cloud. You pay by the hour and only what you use. You can do whatever you want with this instance as well as launch n number of instances.

Elastic Beanstalk

Elastic Beanstalk is one layer of abstraction away from the EC2 layer. Elastic Beanstalk will setup an "environment" for you that can contain a number of EC2 instances, an optional database, as well as a few other AWS components such as a Elastic Load Balancer, Auto-Scaling Group, Security Group. Then Elastic Beanstalk will manage these items for you whenever you want to update your software running in AWS. Elastic Beanstalk doesn't add any cost on top of these resources that it creates for you. If you have 10 hours of EC2 usage, then all you pay is 10 compute hours.

Running Wordpress

For running Wordpress, it is whatever you are most comfortable with. You could run it straight on a single EC2 instance, you could use a solution from the AWS Marketplace, or you could use Elastic Beanstalk.

What to pick?

In the case that you want to reduce system operations and just focus on the website, then Elastic Beanstalk would be the best choice for that. Elastic Beanstalk supports a PHP stack (as well as others). You can keep your site in version control and easily deploy to your environment whenever you make changes. It will also setup an Autoscaling group which can spawn up more EC2 instances if traffic is growing.

Here's the first result off of Google when searching for "elastic beanstalk wordpress":

What is the meaning of {...this.props} in Reactjs

You will use props in your child component

for example

if your now component props is

   booking: 4,
   isDisable: false

you can use this props in your child compoenet

 <div {...this.props}> ... </div>

in you child component, you will receive all your parent props.

How do I disable a href link in JavaScript?

Install this plugin for jquery and use it

It allows you to disable/enable pretty much any field in the page.

If you want to open a page on some condition write a java script function and call it from href. If the condition satisfied you open page otherwise just do nothing.

code looks like this:

<a href="javascript: openPage()" >Click here</a>

and function:
function openPage()
if(some conditon)
opener.document.location = "";

You can also put the link in a div and set the display property of the Style attribute to none. this will hide the div. For eg.,

<div id="divid" style="display:none">
<a href="Hiding Link" />

This will hide the link. Use a button or an image to make this div visible now by calling this function in onclick as:

<a href="Visible Link" onclick="showDiv()">

and write the js code as:

function showDiv(){

You can also put an id tag to the html tag, so it would be

<a id="myATag" href="whatever"></a>

And get this id on your javascript by using


One of this must work for sure haha

Convert negative data into positive data in SQL Server

The best solution is: from positive to negative or from negative to positive

For negative:

SELECT ABS(a) * -1 AS AbsoluteA, ABS(b) * -1 AS AbsoluteB
FROM YourTable

For positive:

SELECT ABS(a) AS AbsoluteA, ABS(b)  AS AbsoluteB
FROM YourTable

Is there a splice method for strings?

It is faster to slice the string twice, like this:

function spliceSlice(str, index, count, add) {
  // We cannot pass negative indexes directly to the 2nd slicing operation.
  if (index < 0) {
    index = str.length + index;
    if (index < 0) {
      index = 0;

  return str.slice(0, index) + (add || "") + str.slice(index + count);

than using a split followed by a join (Kumar Harsh's method), like this:

function spliceSplit(str, index, count, add) {
  var ar = str.split('');
  ar.splice(index, count, add);
  return ar.join('');

Here's a jsperf that compares the two and a couple other methods. (jsperf has been down for a few months now. Please suggest alternatives in comments.)

Although the code above implements functions that reproduce the general functionality of splice, optimizing the code for the case presented by the asker (that is, adding nothing to the modified string) does not change the relative performance of the various methods.

SyntaxError: Unexpected Identifier in Chrome's Javascript console

The comma got eaten by the quotes!

This part:

("username," visitorName);

Should be this:

("username", visitorName);

Aside: For pasting code into the console, you can paste them in one line at a time to help you pinpoint where things went wrong ;-)

How Do I Get the Query Builder to Output Its Raw SQL Query as a String?

There is a method in eloquent for getting query string.


in our case,



select * from users

is the exact solution that return the SQL query string..Hope this helpful...

Get paragraph text inside an element

Try this:

<li onclick="myfunction(this)">

function myfunction(li) {
    var TextInsideLi = li.getElementsByTagName('p')[0].innerHTML;

Live demo

Request exceeded the limit of 10 internal redirects due to probable configuration error

This error occurred to me when I was debugging the PHP header() function:

header('Location: /aaa/bbb/ccc'); // error

If I use a relative path it works:

header('Location: aaa/bbb/ccc'); // success, but not what I wanted

However when I use an absolute path like /aaa/bbb/ccc, it gives the exact error:

Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace.

It appears the header function redirects internally without going HTTP at all which is weird. After some tests and trials, I found the solution of adding exit after header():

header('Location: /aaa/bbb/ccc');

And it works properly.

How do I automatically play a Youtube video (IFrame API) muted?

Update 2021 to loop and autoplay video on desktop/mobile devices (tested on iPhone X - Safari).

I am using the onPlayerStateChange event and if the video end, I play the video again. Refference to onPlayerStateChange event in YouTube API.

<div id="player"></div>
  var tag = document.createElement('script');

  tag.src = "";
  var firstScriptTag = document.getElementsByTagName('script')[0];
  firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);

  var player;

  function onYouTubeIframeAPIReady() {
    player = new YT.Player('player', {
      height: '100%',
      width: '100%',
      playerVars: {
        autoplay: 1,
        loop: 1,
        controls: 0,
        showinfo: 0,
        autohide: 1,
        playsinline: 1,
        mute: 1,
        modestbranding: 1,
        vq: 'hd1080'
      videoId: 'ScMzIvxBSi4',
      events: {
        'onReady': onPlayerReady,
        'onStateChange': onPlayerStateChange

  function onPlayerReady(event) {;

    setTimeout(function() {;
    }, 0);

  function onPlayerStateChange(event) {
    if ( == 0) {
      setTimeout(function() {;
      }, 0);

How to compare two double values in Java?

Instead of using doubles for decimal arithemetic, please use java.math.BigDecimal. It would produce the expected results.

For reference take a look at this stackoverflow question

How to set True as default value for BooleanField on Django?

from django.db import models

class Foo(models.Model):
    any_field = models.BooleanField(default=True)

How to convert java.sql.timestamp to LocalDate (java8) java.time?

You can do:


Note that timestamp.toLocalDateTime() will use the Clock.systemDefaultZone() time zone to make the conversion. This may or may not be what you want.

Remove row lines in twitter bootstrap

The other way around, if you have problems ADDING the lines to your panel dont forget to add the to your TABLE. By default (, it is suppose to add the line but It helped me to add the tag so now the row lines are shown.

The following example "probably" wont display the lines between rows:

<div class="panel panel-default">
    <!-- Default panel contents -->
    <div class="panel-heading">Panel heading</div>
    <!-- Table -->
    <table class="table">
        <tr><td> Hi 1! </td></tr>
        <tr><td> Hi 2! </td></tr>

The following example WILL display the lines between rows:

<div class="panel panel-default">
    <!-- Default panel contents -->
    <div class="panel-heading">Panel heading</div>
    <!-- Table -->
    <table class="table">
        <tr><td> Hi 1! </td></tr>
        <tr><td> Hi 2! </td></tr>

get UTC timestamp in python with datetime

Also note the calendar.timegm() function as described by this blog entry:

import calendar

The output should agree with the solution of vaab.

"detached entity passed to persist error" with JPA/EJB code

I had this problem and it was caused by the second level cache:

  1. I persisted an entity using hibernate
  2. Then I deleted the row created from a separate process that didn't interact with the second level cache
  3. I persisted another entity with the same identifier (my identifier values are not auto-generated)

Hence, because the cache wasn't invalidated, hibernate assumed that it was dealing with a detached instance of the same entity.

How to show current time in JavaScript in the format HH:MM:SS?

You can use native function Date.toLocaleTimeString():

var d = new Date();
var n = d.toLocaleTimeString();

This will display e.g.:


I found it on

var d = new Date();_x000D_
var n = d.toLocaleTimeString();_x000D_
alert("The time is: \n"+n);

How to return multiple values?

You can only return one value, but it can be an object that has multiple fields - ie a "value object". Eg

public class MyResult {
    int returnCode;
    String errorMessage;
    // etc

public MyResult someMethod() {
    // impl here

Check if instance is of a type

As others have mentioned, the "is" keyword. However, if you're going to later cast it to that type, eg.

TForm t = (TForm)c;

Then you should use the "as" keyword.

e.g. TForm t = c as TForm.

Then you can check

if(t != null)
 // put TForm specific stuff here

Don't combine as with is because it's a duplicate check.

MySql server startup error 'The server quit without updating PID file '

In my case, the problem was, that mysql data directory was moved by accident to wrong directory (/var/log, and not to /var/lib). After moving data back to /var/lib/mysql and restarting server, all everything went back to normal again.

Finding first and last index of some value in a list in Python

As a small helper function:

def rindex(mylist, myvalue):
    return len(mylist) - mylist[::-1].index(myvalue) - 1

Run Bash Command from PHP

Check if have not set a open_basedir in php.ini or .htaccess of domain what you use. That will jail you in directory of your domain and php will get only access to execute inside this directory.

How can I subset rows in a data frame in R based on a vector of values?

This will give you what you want:

eg2011cleaned <- eg2011[!eg2011$ID %in% bg2011missingFromBeg, ]

The error in your second attempt is because you forgot the ,

In general, for convenience, the specification object[index] subsets columns for a 2d object. If you want to subset rows and keep all columns you have to use the specification object[index_rows, index_columns], while index_cols can be left blank, which will use all columns by default.

However, you still need to include the , to indicate that you want to get a subset of rows instead of a subset of columns.

What is the difference between an int and a long in C++?

The only guarantee you have are:

sizeof(char) == 1
sizeof(char) <= sizeof(short) <= sizeof(int) <= sizeof(long) <= sizeof(long long)

// FROM @KTC. The C++ standard also has:
sizeof(signed char)   == 1
sizeof(unsigned char) == 1

// NOTE: These size are not specified explicitly in the standard.
//       They are implied by the minimum/maximum values that MUST be supported
//       for the type. These limits are defined in limits.h
sizeof(short)     * CHAR_BIT >= 16
sizeof(int)       * CHAR_BIT >= 16
sizeof(long)      * CHAR_BIT >= 32
sizeof(long long) * CHAR_BIT >= 64
CHAR_BIT         >= 8   // Number of bits in a byte

Also see: Is long guaranteed to be at least 32 bits?

Loop through files in a directory using PowerShell

Give this a try:

Get-ChildItem "C:\Users\gerhardl\Documents\My Received Files" -Filter *.log | 
Foreach-Object {
    $content = Get-Content $_.FullName

    #filter and save content to the original file
    $content | Where-Object {$_ -match 'step[49]'} | Set-Content $_.FullName

    #filter and save content to a new file 
    $content | Where-Object {$_ -match 'step[49]'} | Set-Content ($_.BaseName + '_out.log')

auto refresh for every 5 mins

Install an interval:

<script type="text/javascript">    
    setInterval(page_refresh, 5*60000); //NOTE: period is passed in milliseconds

How to catch a unique constraint error in a PL/SQL block?

I'm sure you have your reasons, but just in case... you should also consider using a "merge" query instead:

    merge into some_table st
    using (select 'some' name, 'values' value from dual) v
    on (
    when matched then update set st.value=v.value
    when not matched then insert (name, value) values (, v.value);

(modified the above to be in the begin/end block; obviously you can run it independantly of the procedure too).

Return only string message from Spring MVC 3 Controller

Annotate your method in controller with @ResponseBody:

@RequestMapping(value="/controller", method=GET)
public String foo() {
    return "Response!";

From: Mapping the response body with the @ResponseBody annotation:

The @ResponseBody annotation [...] can be put on a method and indicates that the return type should be written straight to the HTTP response body (and not placed in a Model, or interpreted as a view name).

How can I change the Bootstrap default font family using font from Google?

Another way is to download source code then change following vaiables in variables.less

@font-family-sans-serif:  "Helvetica Neue", Helvetica, Arial, sans-serif;
@font-family-serif:       Georgia, "Times New Roman", Times, serif;
//** Default monospace fonts for `<code>`, `<kbd>`, and `<pre>`.
@font-family-monospace:   Menlo, Monaco, Consolas, "Courier New", monospace;
@font-family-base:        @font-family-sans-serif;

And then compile it to .css file

High-precision clock in Python

I observed that the resolution of time.time() is different between Windows 10 Professional and Education versions.

On a Windows 10 Professional machine, the resolution is 1 ms. On a Windows 10 Education machine, the resolution is 16 ms.

Fortunately, there's a tool that increases Python's time resolution in Windows:

With this tool, I was able to achieve 1 ms resolution regardless of Windows version. You will need to be keep it running while executing your Python codes.

How do you run multiple programs in parallel from a bash script?

How about:

prog1 & prog2 && fg

This will:

  1. Start prog1.
  2. Send it to background, but keep printing its output.
  3. Start prog2, and keep it in foreground, so you can close it with ctrl-c.
  4. When you close prog2, you'll return to prog1's foreground, so you can also close it with ctrl-c.

Java - How to create a custom dialog box?

Well, you essentially create a JDialog, add your text components and make it visible. It might help if you narrow down which specific bit you're having trouble with.

jQuery Mobile Page refresh mechanism

function refreshPage()
{, {
        allowSamePageTransition: true,
        transition: 'none',
        reloadPage: true

Taken from here also tested on jQuery Mobile 1.2.0

Most efficient solution for reading CLOB to String, and String to CLOB in Java?

private String convertToString(java.sql.Clob data)
    final StringBuilder builder= new StringBuilder();

        final Reader         reader = data.getCharacterStream();
        final BufferedReader br     = new BufferedReader(reader);

        int b;
        while(-1 != (b =

    catch (SQLException e)
        log.error("Within SQLException, Could not convert CLOB to string",e);
        return e.toString();
    catch (IOException e)
        log.error("Within IOException, Could not convert CLOB to string",e);
        return e.toString();
    //enter code here
    return builder.toString();

Moving Average Pandas

A moving average can also be calculated and visualized directly in a line chart by using the following code:

Example using stock price data:

import as web
import matplotlib.pyplot as plt
import datetime'ggplot')

# Input variables
start = datetime.datetime(2016, 1, 01)
end = datetime.datetime(2018, 3, 29)
stock = 'WFC'

# Extrating data
df = web.DataReader(stock,'morningstar', start, end)
df = df['Close']

print df 

plt.plot(df['WFC'],label= 'Close')
plt.plot(df['WFC'].rolling(9).mean(),label= 'MA 9 days')
plt.plot(df['WFC'].rolling(21).mean(),label= 'MA 21 days')
plt.title('Wells Fargo\nClose and Moving Averages')

Tutorial on how to do this:

How to do a "Save As" in vba code, saving my current Excel workbook with datestamp?

Most likely the path you are trying to access does not exist. It seems you are trying to save to a relative location and you do not have an file extension in that string. If you need to use relative paths you can parse the path from ActiveWorkbook.FullName

EDIT: Better syntax would also be

ActiveWorkbook.SaveAs Filename:=myFileName, FileFormat:=xlWorkbookNormal

If Python is interpreted, what are .pyc files?

They contain byte code, which is what the Python interpreter compiles the source to. This code is then executed by Python's virtual machine.

Python's documentation explains the definition like this:

Python is an interpreted language, as opposed to a compiled one, though the distinction can be blurry because of the presence of the bytecode compiler. This means that source files can be run directly without explicitly creating an executable which is then run.

How can I open Java .class files in a human-readable way?

If you don't mind reading bytecode, javap should work fine. It's part of the standard JDK installation.

Usage: javap <options> <classes>...

where options include:
   -c                        Disassemble the code
   -classpath <pathlist>     Specify where to find user class files
   -extdirs <dirs>           Override location of installed extensions
   -help                     Print this usage message
   -J<flag>                  Pass <flag> directly to the runtime system
   -l                        Print line number and local variable tables
   -public                   Show only public classes and members
   -protected                Show protected/public classes and members
   -package                  Show package/protected/public classes
                             and members (default)
   -private                  Show all classes and members
   -s                        Print internal type signatures
   -bootclasspath <pathlist> Override location of class files loaded
                             by the bootstrap class loader
   -verbose                  Print stack size, number of locals and args for methods
                             If verifying, print reasons for failure

How to write the code for the back button?

In my application,above javascript function didnt work,because i had many procrosses inside one following code worked for me hope it helps you guys.

  function redirection()
           <?php $send=$_SERVER['HTTP_REFERER'];?> 
            var redirect_to="<?php echo $send;?>";             
            window.location = redirect_to;


org.glassfish.jersey.servlet.ServletContainer ClassNotFoundException

Suppose you are usin Jersey 2.25.1, this worked for me - I am using Apache Tomcat web container:


NB: Replace version with the version you are using

Convert dd-mm-yyyy string to date

The accepted answer kinda has a bug

var from = $("#datepicker").val().split("-")
var f = new Date(from[2], from[1] - 1, from[0])

Consider if the datepicker contains "77-78-7980" which is obviously not a valid date. This would result in:

var f = new Date(7980, 77, 77);
=> Date 7986-08-15T22:00:00.000Z

Which is probably not the desired result.

The reason for this is explained on the MDN site:

Where Date is called as a constructor with more than one argument, if values are greater than their logical range (e.g. 13 is provided as the month value or 70 for the minute value), the adjacent value will be adjusted. E.g. new Date(2013, 13, 1) is equivalent to new Date(2014, 1, 1).

A better way to solve the problem is:

const stringToDate = function(dateString) {
  const [dd, mm, yyyy] = dateString.split("-");
  return new Date(`${yyyy}-${mm}-${dd}`);

// Date 2019-04-04T00:00:00.000Z

// Invalid Date

This gives you the possibility to handle invalid input.

For example:

const date = stringToDate("77-78-7980");

if (date === "Invalid Date" || isNaN(date)) {
  console.log("It's all gone bad");
} else {
  // Do something with your valid date here

Android Studio marks R in red with error message "cannot resolve symbol R", but build succeeds

Had the same problem with android studio, I found out that build/generated/source/r contained only release folder and not debug. So for some reason debug build did not generate usable R class.

I solved it by opening the project iml file and fixed this line

<option name="RES_FOLDERS_RELATIVE_PATH" value="" />


<option name="RES_FOLDERS_RELATIVE_PATH" value="file://$MODULE_DIR$/src/main/res" />

resynced with gradle, commented out lines using R, run debug to generate the R, uncommented lines using R and run the debug again, fixed.

What is the difference between concurrent programming and parallel programming?

I will try to explain it in my own style, it might not be in computer terms but it gives you the general idea.

Let's take an example, say Household chores: cleaning dishes, taking out trash, mowing the lawn etc, also we have 3 people(threads) A, B, C to do them

Concurrent: The three individuals start different tasks independently i.e.,

A --> cleaning dishes
B --> taking out trash 
C --> mowing the lawn 

Here, the order of tasks are indeterministic and responses depends on the amount of work

Parallel: Here if we want to improve the throughput we can assign multiple people to the single task, for example, cleaning dishes we assign two people, A soaping the dishes and B washing the dishes which might improve the throughput.

cleaning the dishes:

A --> soaping the dishes
B --> washing the dishes

so on

Hope this gives an idea! now move on to the technical terms which are explained in the other answers ;)

When to catch java.lang.Error?

And there are a couple of other cases where if you catch an Error, you have to rethrow it. For example ThreadDeath should never be caught, it can cause big problem is you catch it in a contained environment (eg. an application server) :

An application should catch instances of this class only if it must clean up after being terminated asynchronously. If ThreadDeath is caught by a method, it is important that it be rethrown so that the thread actually dies.

nginx missing sites-available directory

I tried sudo apt install nginx-full. You will get all the required packages.

How to install Android SDK Build Tools on the command line?

The "android" command is deprecated.

For command-line tools, use tools/bin/sdkmanager and tools/bin/avdmanager

If you do not need Android Studio, you can download the basic Android command line tools from in section Command line tools only.

from CLI it should be somfing like:

curl --output


wget --output-document

After that just unpack the archive to the target folder


And now we can install everything you need...

./tools/bin/sdkmanager --install 'build-tools;29.0.2' 'platform-tools' 'platforms;android-29' 'tools'

You can get a complete list of packages using the command ./tools/bin/sdkmanager --list

Some packages require acceptance of the license agreement. you can accept it interactively or just pass "y" to the input stream, like this(two agreements in case):

echo -ne "y\ny" | ./tools/bin/sdkmanager --install 'system-images;android-29;default;x86_64'

And of course, for your convenience, you can export variables such as ANDROID_HOME or ANDROID_SDK_ROOT (including doing it in ~/.profile or ~/.bash_profile) or patch the PATH variable - all this is at your discretion.

Script example:

mkdir /opt/android-sdk
cd /opt/android-sdk
curl --output
echo -ne "y" | ./tools/bin/sdkmanager --install 'build-tools;29.0.2' 'platform-tools' 'platforms;android-29' 'tools'

Requirements: curl(or wget) and unzip


if you see Warning: Could not create settings, you need to have the tools directory inside the cmdline-tools directory inside the ANDROID_HOME (create it if needed with this exact name) see Android Command line tools sdkmanager always shows: Warning: Could not create settings

Unable to convert MySQL date/time value to System.DateTime

You must add Convert Zero Datetime=True to your connection string, for example:

server=localhost;User Id=root;password=mautauaja;Persist Security Info=True;database=test;Convert Zero Datetime=True

Collection was modified; enumeration operation may not execute in ArrayList

You are removing the item during a foreach, yes? Simply, you can't. There are a few common options here:

  • use List<T> and RemoveAll with a predicate
  • iterate backwards by index, removing matching items

    for(int i = list.Count - 1; i >= 0; i--) {
        if({some test}) list.RemoveAt(i);
  • use foreach, and put matching items into a second list; now enumerate the second list and remove those items from the first (if you see what I mean)

How to add Action bar options menu in Android Fragments

in AndroidManifest.xml set theme holo like this:

android:name="your Fragment or activity"
android:theme="@android:style/Theme.Holo" >

How to create user for a db in postgresql?

From CLI:

$ su - postgres 
$ psql template1
template1=# CREATE USER tester WITH PASSWORD 'test_password';
template1=# GRANT ALL PRIVILEGES ON DATABASE "test_database" to tester;
template1=# \q

PHP (as tested on localhost, it works as expected):

  $connString = 'port=5432 dbname=test_database user=tester password=test_password';
  $connHandler = pg_connect($connString);
  echo 'Connected to '.pg_dbname($connHandler);

Passing event and argument to v-on in Vue.js

Depending on what arguments you need to pass, especially for custom event handlers, you can do something like this:

<div @customEvent='(arg1) => myCallback(arg1, arg2)'>Hello!</div>

Calculate RSA key fingerprint

To see your key on Ubuntu, just enter the following command on your terminal:

ssh-add -l

You will get an output like this: 2568 0j:20:4b:88:a7:9t:wd:19:f0:d4:4y:9g:27:cf:97:23 yourName@ubuntu (RSA)

If however you get an error like; Could not open a connection to your authentication agent.
Then it means that ssh-agent is not running. You can start/run it with: ssh-agent bash (thanks to @Richard in the comments) and then re-run ssh-add -l

How does the @property decorator work in Python?

Let's start with Python decorators.

A Python decorator is a function that helps to add some additional functionalities to an already defined function.

In Python, everything is an object. Functions in Python are first-class objects which means that they can be referenced by a variable, added in the lists, passed as arguments to another function etc.

Consider the following code snippet.

def decorator_func(fun):
    def wrapper_func():
        print("Wrapper function started")
        print("Given function decorated")
        # Wrapper function add something to the passed function and decorator 
        # returns the wrapper function
    return wrapper_func

def say_bye():

say_bye = decorator_func(say_bye)

# Output:
#  Wrapper function started
#  bye
#  Given function decorated

Here, we can say that decorator function modified our say_hello function and added some extra lines of code in it.

Python syntax for decorator

def decorator_func(fun):
    def wrapper_func():
        print("Wrapper function started")
        print("Given function decorated")
        # Wrapper function add something to the passed function and decorator 
        # returns the wrapper function
    return wrapper_func

def say_bye():


Let's Concluded everything than with a case scenario, but before that let's talk about some oops priniciples.

Getters and setters are used in many object oriented programming languages to ensure the principle of data encapsulation(is seen as the bundling of data with the methods that operate on these data.)

These methods are of course the getter for retrieving the data and the setter for changing the data.

According to this principle, the attributes of a class are made private to hide and protect them from other code.

Yup, @property is basically a pythonic way to use getters and setters.

Python has a great concept called property which makes the life of an object-oriented programmer much simpler.

Let us assume that you decide to make a class that could store the temperature in degree Celsius.

class Celsius:
def __init__(self, temperature = 0):

def to_fahrenheit(self):
    return (self.get_temperature() * 1.8) + 32

def get_temperature(self):
    return self._temperature

def set_temperature(self, value):
    if value < -273:
        raise ValueError("Temperature below -273 is not possible")
    self._temperature = value

Refactored Code, Here is how we could have achieved it with property.

In Python, property() is a built-in function that creates and returns a property object.

A property object has three methods, getter(), setter(), and delete().

class Celsius:
def __init__(self, temperature = 0):
    self.temperature = temperature

def to_fahrenheit(self):
    return (self.temperature * 1.8) + 32

def get_temperature(self):
    print("Getting value")
    return self.temperature

def set_temperature(self, value):
    if value < -273:
        raise ValueError("Temperature below -273 is not possible")
    print("Setting value")
    self.temperature = value

temperature = property(get_temperature,set_temperature)


temperature = property(get_temperature,set_temperature)

could have been broken down as,

# make empty property
temperature = property()
# assign fget
temperature = temperature.getter(get_temperature)
# assign fset
temperature = temperature.setter(set_temperature)

Point To Note:

  • get_temperature remains a property instead of a method.

Now you can access the value of temperature by writing.

C = Celsius()
# instead of writing C.get_temperature()

We can further go on and not define names get_temperature and set_temperature as they are unnecessary and pollute the class namespace.

The pythonic way to deal with the above problem is to use @property.

class Celsius:
    def __init__(self, temperature = 0):
        self.temperature = temperature

    def to_fahrenheit(self):
        return (self.temperature * 1.8) + 32

    def temperature(self):
        print("Getting value")
        return self.temperature

    def temperature(self, value):
        if value < -273:
            raise ValueError("Temperature below -273 is not possible")
        print("Setting value")
        self.temperature = value

Points to Note -

  1. A method which is used for getting a value is decorated with "@property".
  2. The method which has to function as the setter is decorated with "@temperature.setter", If the function had been called "x", we would have to decorate it with "@x.setter".
  3. We wrote "two" methods with the same name and a different number of parameters "def temperature(self)" and "def temperature(self,x)".

As you can see, the code is definitely less elegant.

Now,let's talk about one real-life practical scenerio.

Let's say you have designed a class as follows:

class OurClass:

    def __init__(self, a):
        self.x = a

y = OurClass(10)

Now, let's further assume that our class got popular among clients and they started using it in their programs, They did all kinds of assignments to the object.

And One fateful day, a trusted client came to us and suggested that "x" has to be a value between 0 and 1000, this is really a horrible scenario!

Due to properties it's easy: We create a property version of "x".

class OurClass:

    def __init__(self,x):
        self.x = x

    def x(self):
        return self.__x

    def x(self, x):
        if x < 0:
            self.__x = 0
        elif x > 1000:
            self.__x = 1000
            self.__x = x

This is great, isn't it: You can start with the simplest implementation imaginable, and you are free to later migrate to a property version without having to change the interface! So properties are not just a replacement for getters and setter!

You can check this Implementation here

Get the first element of each tuple in a list in Python

The functional way of achieving this is to unzip the list using:

sample = [(2, 9), (2, 9), (8, 9), (10, 9), (23, 26), (1, 9), (43, 44)]
first,snd = zip(*sample)

(2, 2, 8, 10, 23, 1, 43) (9, 9, 9, 9, 26, 9, 44)

What port is a given program using?

Windows 8 (and likely 7 + Vista) also provide a view in Resource Monitor. If you select the Network tab, there's a section called 'Listening Ports'. Can sort by port number, and see which process is using it.

Convert DataTable to CSV stream

Update 1

I have modified it to use StreamWriter instead, add an option to check if you need column headers in your output.

public static bool DataTableToCSV(DataTable dtSource, StreamWriter writer, bool includeHeader)
    if (dtSource == null || writer == null) return false;

    if (includeHeader)
        string[] columnNames = dtSource.Columns.Cast<DataColumn>().Select(column => "\"" + column.ColumnName.Replace("\"", "\"\"") + "\"").ToArray<string>();
        writer.WriteLine(String.Join(",", columnNames));

    foreach (DataRow row in dtSource.Rows)
        string[] fields = row.ItemArray.Select(field => "\"" + field.ToString().Replace("\"", "\"\"") + "\"").ToArray<string>();
        writer.WriteLine(String.Join(",", fields));

    return true;

As you can see, you can choose the output by initial StreamWriter, if you use StreamWriter(Stream BaseStream), you can write csv into MemeryStream, FileStream, etc.


I have an easy datatable to csv function, it serves me well:

    public static void DataTableToCsv(DataTable dt, string csvFile)
        StringBuilder sb = new StringBuilder();

        var columnNames = dt.Columns.Cast<DataColumn>().Select(column => "\"" + column.ColumnName.Replace("\"", "\"\"") + "\"").ToArray();
        sb.AppendLine(string.Join(",", columnNames));

        foreach (DataRow row in dt.Rows)
            var fields = row.ItemArray.Select(field => "\"" + field.ToString().Replace("\"", "\"\"") + "\"").ToArray();
            sb.AppendLine(string.Join(",", fields));

        File.WriteAllText(csvFile, sb.ToString(), Encoding.Default);

Partly JSON unmarshal into a map in Go

This can be accomplished by Unmarshaling into a map[string]json.RawMessage.

var objmap map[string]json.RawMessage
err := json.Unmarshal(data, &objmap)

To further parse sendMsg, you could then do something like:

var s sendMsg
err = json.Unmarshal(objmap["sendMsg"], &s)

For say, you can do the same thing and unmarshal into a string:

var str string
err = json.Unmarshal(objmap["say"], &str)

EDIT: Keep in mind you will also need to export the variables in your sendMsg struct to unmarshal correctly. So your struct definition would be:

type sendMsg struct {
    User string
    Msg  string


How do I make bootstrap table rows clickable?

Using jQuery it's quite trivial. v2.0 uses the table class on all tables.

$('.table > tbody > tr').click(function() {
    // row was clicked

How to read user input into a variable in Bash?

Use read -p:

# fullname="USER INPUT"
read -p "Enter fullname: " fullname
# user="USER INPUT"
read -p "Enter user: " user

If you like to confirm:

read -p "Continue? (Y/N): " confirm && [[ $confirm == [yY] || $confirm == [yY][eE][sS] ]] || exit 1

You should also quote your variables to prevent pathname expansion and word splitting with spaces:

# passwd "$user"
# mkdir "$home"
# chown "$user:$group" "$home"

Android: converting String to int

Use regular expression:

int i=Integer.parseInt("hello123".replaceAll("[\\D]",""));
int j=Integer.parseInt("123hello".replaceAll("[\\D]",""));
int k=Integer.parseInt("1h2el3lo".replaceAll("[\\D]",""));



Using two values for one switch case statement

With the integration of JEP 325: Switch Expressions (Preview) in JDK-12 early access builds, one can now make use of the new form of the switch label as :-

case text1, text4 -> {

or to rephrase the demo from one of the answers, something like :-

public class RephraseDemo {

    public static void main(String[] args) {
        int month = 9;
        int year = 2018;
        int numDays = 0;

        switch (month) {
            case 1, 3, 5, 7, 8, 10, 12 ->{
                numDays = 31;
            case 4, 6, 9, 11 ->{
                numDays = 30;
            case 2 ->{
                if (((year % 4 == 0) &&
                        !(year % 100 == 0))
                        || (year % 400 == 0))
                    numDays = 29;
                    numDays = 28;
            default ->{
                System.out.println("Invalid month.");

        System.out.println("Number of Days = " + numDays);

Here is how you can give it a try - Compile a JDK12 preview feature with Maven

Automatic confirmation of deletion in powershell

Add -confirm:$false to suppress confirmation.

How to check if array element exists or not in javascript?

var fruits = ["Banana", "Orange", "Apple", "Mango"];_x000D_
if(fruits.indexOf("Banana") == -1){_x000D_
    console.log('item not exist')_x000D_
} else {_x000D_
 console.log('item exist')_x000D_

Why is "npm install" really slow?

I was having the same problem, i am on the nodejs version: 8.9.4 and npm version: 5.6.0. I tried a lot solutions online, including the ones on this post, none worked for me, then i found about yarn package manager which solved the problem for me, so if all fails, i think "yarn" is worth checking out.


It seems npm has problems when it is outdated, updating it has helped me as well.

How to set DOM element as the first child?

2017 version

You can use

targetElement.insertAdjacentElement('afterbegin', newFirstElement)

From MDN :

The insertAdjacentElement() method inserts a given element node at a given position relative to the element it is invoked upon.

A DOMString representing the position relative to the element; must be one of the following strings:
beforebegin: Before the element itself.
afterbegin: Just inside the element, before its first child.
beforeend: Just inside the element, after its last child.
afterend: After the element itself.

The element to be inserted into the tree.

Also in the family of insertAdjacent there is the sibling methods:

element.insertAdjacentHTML('afterbegin','htmlText') for inject html string directly, like innerHTML but without overide everything , so you can jump oppressive process of document.createElement and even build whole componet with string manipulation process

element.insertAdjacentText for inject sanitize string into element . no more encode/decode

jQuery append() vs appendChild()

append is a jQuery method to append some content or HTML to an element.

$('#example').append('Some text or HTML');

appendChild is a pure DOM method for adding a child element.


enable or disable checkbox in html

According the W3Schools you might use JavaScript for disabled checkbox.

<!-- Checkbox who determine if the other checkbox must be disabled -->
<input type="checkbox" id="checkboxDetermine">
<!-- The other checkbox conditionned by the first checkbox -->
<input type="checkbox" id="checkboxConditioned">
<!-- JS Script -->
<script type="text/javascript">
    // Get your checkbox who determine the condition
    var determine = document.getElementById("checkboxDetermine");
    // Make a function who disabled or enabled your conditioned checkbox
    var disableCheckboxConditioned = function () {
        if(determine.checked) {
            document.getElementById("checkboxConditioned").disabled = true;
        else {
            document.getElementById("checkboxConditioned").disabled = false;
    // On click active your function
    determine.onclick = disableCheckboxConditioned;

You can see the demo working here :

Access to ES6 array element index inside for-of loop

Also you can use JavaScript to solve your problem

iterate(item, index) {
    console.log(`${item} has index ${index}`);
    //Do what you want...

readJsonList() {    
    //it could be any array list.

Removing leading zeroes from a field in a SQL statement

select substring(substring('B10000N0Z', patindex('%[0]%','B10000N0Z'), 20), 
    patindex('%[^0]%',substring('B10000N0Z', patindex('%[0]%','B10000N0Z'), 
    20)), 20)

returns N0Z, that is, will get rid of leading zeroes and anything that comes before them.

Is there a "previous sibling" selector?

You could use double negation


Replace SELECTOR with either the TAG or .CLASS ( Using #ID is probably too specific ). Replace FILTER with some other :PSUEDO-SELECTOR (I've only tried :hover) or .CLASS (More for toggling through Javascript).

Since the typical usage will probably rely upon hovering (See example that follows)

/* Effect only limited when hovering */
TAG.CLASS:not(TAG.CLASS:hover):not(TAG.CLASS:hover + TAG.CLASS) {}
/* Effect only applied when hovering */

/* Solution */
div.parent:hover > div.child:not(:hover):not(:hover ~ .child)  {
div.parent:hover > div.child:not(:hover):not(:hover ~ .child) > div {

/* Make pretty (kinda) */
div.parent {
  /* Layout */
  grid-template-columns : auto auto auto;
  grid-template-rows : auto auto auto;
div.child {
  /* Dimensions */
  /* Layout */
  /* Cursor */
  cursor: pointer;
  /* Presentation */
  border: 1px black solid;
.star {
  /* Dimensions */
  width: 2.5em;
  height: 2.5em;
  /* Placement */
  top: 50%;
  left: 50%;
  /* Geometry */
  -webkit-clip-path: polygon(
    50% 0%,
    63% 38%,
    100% 38%,
    69% 59%,
    82% 100%,
    50% 75%,
    18% 100%,
    31% 59%,
    0% 38%,
    37% 38%
  clip-path: polygon(
    50% 0%,
    63% 38%,
    100% 38%,
    69% 59%,
    82% 100%,
    50% 75%,
    18% 100%,
    31% 59%,
    0% 38%,
    37% 38%
  /* Presentation */
  background-color: lightgrey;
div.child:hover {
    /* Presentation */
div.child:hover > {
    /* Presentation */
<div class="parent">
  <div class="child" href="#"><div class="star"></div></div>
  <div class="child" href="#"><div class="star"></div></div>
  <div class="child" href="#"><div class="star"></div></div>
  <div class="child" href="#"><div class="star"></div></div>
  <div class="child" href="#"><div class="star"></div></div>
  <div class="child" href="#"><div class="star"></div></div>
  <div class="child" href="#"><div class="star"></div></div>
  <div class="child" href="#"><div class="star"></div></div>
  <div class="child" href="#"><div class="star"></div></div>

SVN Error: Commit blocked by pre-commit hook (exit code 1) with output: Error: n/a (6)

Could it be that you have not entered a commit message? According to their twitter feed: "New functionality added. Block users from committing work without writing a log message. Find in the resources section of your control panel".

Execute write on doc: It isn't possible to write into a document from an asynchronously-loaded external script unless it is explicitly opened.

In case this is useful to anyone I had this same issue. I was bringing in a footer into a web page via jQuery. Inside that footer were some Google scripts for ads and retargeting. I had to move those scripts from the footer and place them directly in the page and that eliminated the notice.

How to insert 1000 rows at a time

I create a student table with three column id, student,age. show you this example

declare @id int 
select @id = 1
while @id >=1 and @id <= 1000
    insert into student values(@id, 'jack' + convert(varchar(5), @id), 12)
    select @id = @id + 1

this is the result about the example enter image description here

How to add "active" class to Html.ActionLink in ASP.NET MVC

I did this:

Made a helper in menu partial view

 @helper RouterLink(string action, string controller)
    var IsActive = ViewContext.RouteData.Values["Controller"].ToString() == controller && ViewContext.RouteData.Values["Action"].ToString() == action;
    <text>href="@Url.Action(action, controller)"</text>if (IsActive){ <text>class="active"</text>}

Then used it in the anchor tag like this:

<li><a @RouterLink("Index","Home")>Home</a></li>

My application had no areas but it can also be included as another variable in the helper function. And I had to pass the active class to the anchor tag in my view. But li can also be configured like this.

git clone through ssh

Upfront, I am a bit lacking in my GIT skills.

That is going to clone a bare repository on your machine, which only contains the folders within .git which is a hidden directory. execute ls -al and you should see .git or cd .git inside your repository.

Can you add a description of your intent so that someone with more GIT skills can help? What is it you really want to do not how you plan on doing it?

Using the passwd command from within a shell script

Sometimes it is useful to set a password which nobody knows. This seems to work:

tr -dc A-Za-z0-9 < /dev/urandom | head -c44 | passwd --stdin $user

How to set shadows in React Native for android?

Generating shadows for a circle, react native, android

Based on the answers here, and on text that I found in github (react-native-shadow), I made few tests and thought that some people may find the following helpful.

Here is how the screen looks like:

enter image description here


import React, { Component } from 'react';
import { View, TouchableHighlight, Text } from 'react-native';
import { BoxShadow } from 'react-native-shadow'

export default class ShadowsTest extends Component {

  render() {
    const shadowOpt = {
      width: 100,
      height: 100,
      color: "#000",
      border: 2,
      radius: 50,
      opacity: 0.8,
      x: 3,
      y: 3,
      //style: { marginVertical: 5 }

    return (
      <View style={{ flex: 1 }}>
          text={"Shadows Test"} />

        <View style={{ flexDirection: 'row', justifyContent: 'center' }}>
          <View style={{ margin: 10, alignItems: 'center',
              justifyContent: 'center' }}>
            <TouchableHighlight style={{
              position: 'relative',
              width: 100,
              height: 100,
              backgroundColor: "#fff",
              borderRadius: 50,
              borderWidth: 0.8,
              borderColor: '#000',
              // marginVertical:5,
              alignItems: 'center',
              justifyContent: 'center',
              overflow: "hidden" }}>
              <Text style={{ textAlign: 'center' }}>
                0: plain border

          <View style={{ margin: 10, alignItems: 'center',
              justifyContent: 'center' }}>
            <BoxShadow setting={ shadowOpt }>
              <TouchableHighlight style={{
                position: 'relative',
                width: 100,
                height: 100,
                backgroundColor: "#fff",
                borderRadius: 50,
                borderWidth: 1,
                borderColor: '#aaa',
                // marginVertical:5,
                alignItems: 'center',
                justifyContent: 'center',
                overflow: "hidden" }}>
                <Text style={{ textAlign: 'center' }}>
                  1: RN shadow package

        <View style={{ flexDirection: 'row', justifyContent: 'center' }}>
          <View style={{ margin: 10, alignItems: 'center',
              justifyContent: 'center' }}>
              <TouchableHighlight style={{
                position: 'relative',
                width: 100,
                height: 100,
                backgroundColor: "#fff",
                borderRadius: 50,
                borderWidth: 1,
                borderColor: '#aaa',
                // marginVertical:5,
                alignItems: 'center',
                justifyContent: 'center',
                overflow: "hidden",
                shadowOffset: { width: 15, height: 15 },
                shadowColor: "black",
                shadowOpacity: 0.9,
                shadowRadius: 10,
                <Text style={{ textAlign: 'center' }}>
                  2: vanilla RN: shadow (may work on iOS)
          <View style={{ margin: 10, alignItems: 'center',
              justifyContent: 'center' }}>
              <TouchableHighlight style={{
                position: 'relative',
                width: 100,
                height: 100,
                backgroundColor: "#fff",
                borderRadius: 50,
                borderWidth: 1,
                borderColor: '#aaa',
                // marginVertical:5,
                alignItems: 'center',
                justifyContent: 'center',
                overflow: "hidden",
                elevation: 15,
                <Text style={{ textAlign: 'center' }}>
                  3: vanilla RN: elevation only (15)

        <View style={{ flexDirection: 'row', justifyContent: 'center', marginBottom: 30 }}>
          <View style={{ margin: 10, alignItems: 'center',
              justifyContent: 'center' }}>
              <TouchableHighlight style={{
                position: 'relative',
                width: 100,
                height: 100,
                backgroundColor: "#fff",
                borderRadius: 50,
                borderWidth: 1,
                borderColor: '#aaa',
                // marginVertical:5,
                alignItems: 'center',
                justifyContent: 'center',
                overflow: "hidden",
                elevation: 5,
                <Text style={{ textAlign: 'center' }}>
                  4: vanilla RN: elevation only (5)
          <View style={{ margin: 10, alignItems: 'center',
              justifyContent: 'center' }}>
              <TouchableHighlight style={{
                position: 'relative',
                width: 100,
                height: 100,
                backgroundColor: "#fff",
                borderRadius: 50,
                borderWidth: 1,
                borderColor: '#aaa',
                // marginVertical:5,
                alignItems: 'center',
                justifyContent: 'center',
                overflow: "hidden",
                elevation: 50,
                <Text style={{ textAlign: 'center' }}>
                  5: vanilla RN: elevation only (50)

JavaScript DOM remove element

In most browsers, there's a slightly more succinct way of removing an element from the DOM than calling .removeChild(element) on its parent, which is to just call element.remove(). In due course, this will probably become the standard and idiomatic way of removing an element from the DOM.

The .remove() method was added to the DOM Living Standard in 2011 (commit), and has since been implemented by Chrome, Firefox, Safari, Opera, and Edge. It was not supported in any version of Internet Explorer.

If you want to support older browsers, you'll need to shim it. This turns out to be a little irritating, both because nobody seems to have made a all-purpose DOM shim that contains these methods, and because we're not just adding the method to a single prototype; it's a method of ChildNode, which is just an interface defined by the spec and isn't accessible to JavaScript, so we can't add anything to its prototype. So we need to find all the prototypes that inherit from ChildNode and are actually defined in the browser, and add .remove to them.

Here's the shim I came up with, which I've confirmed works in IE 8.

(function () {
    var typesToPatch = ['DocumentType', 'Element', 'CharacterData'],
        remove = function () {
            // The check here seems pointless, since we're not adding this
            // method to the prototypes of any any elements that CAN be the
            // root of the DOM. However, it's required by spec (see point 1 of
            // and would
            // theoretically make a difference if somebody .apply()ed this
            // method to the DOM's root node, so let's roll with it.
            if (this.parentNode != null) {

    for (var i=0; i<typesToPatch.length; i++) {
        var type = typesToPatch[i];
        if (window[type] && !window[type].prototype.remove) {
            window[type].prototype.remove = remove;

This won't work in IE 7 or lower, since extending DOM prototypes isn't possible before IE 8. I figure, though, that on the verge of 2015 most people needn't care about such things.

Once you've included them shim, you'll be able to remove a DOM element element from the DOM by simply calling


Change line width of lines in matplotlib pyplot legend

@ImportanceOfBeingErnest 's answer is good if you only want to change the linewidth inside the legend box. But I think it is a bit more complex since you have to copy the handles before changing legend linewidth. Besides, it can not change the legend label fontsize. The following two methods can not only change the linewidth but also the legend label text font size in a more concise way.

Method 1

import numpy as np
import matplotlib.pyplot as plt

# make some data
x = np.linspace(0, 2*np.pi)

y1 = np.sin(x)
y2 = np.cos(x)

# plot sin(x) and cos(x)
fig = plt.figure()
ax  = fig.add_subplot(111)
ax.plot(x, y1, c='b', label='y1')
ax.plot(x, y2, c='r', label='y2')

leg = plt.legend()
# get the individual lines inside legend and set line width
for line in leg.get_lines():
# get label texts inside legend and set font size
for text in leg.get_texts():


Method 2

import numpy as np
import matplotlib.pyplot as plt

# make some data
x = np.linspace(0, 2*np.pi)

y1 = np.sin(x)
y2 = np.cos(x)

# plot sin(x) and cos(x)
fig = plt.figure()
ax  = fig.add_subplot(111)
ax.plot(x, y1, c='b', label='y1')
ax.plot(x, y2, c='r', label='y2')

leg = plt.legend()
# get the lines and texts inside legend box
leg_lines = leg.get_lines()
leg_texts = leg.get_texts()
# bulk-set the properties of all lines and texts
plt.setp(leg_lines, linewidth=4)
plt.setp(leg_texts, fontsize='x-large')

The above two methods produce the same output image:

output image

Maven compile: package does not exist

You have to add the following dependency to your build:


Furthermore i would suggest to take a deep look into the documentation about how to use the lib.

C# - using List<T>.Find() with custom objects

It's easy, just use list.Find(x => == "stringNameOfObjectToFind");

CSS Border Not Working

AFAIK, there's no such shorthand for border. You have to define each border separately:

border: 0 solid #000;
border-left: 1px solid #000;
border-right: 1px solid #000;

How to do error logging in CodeIgniter (PHP)

To simply put a line in the server's error log, use PHP's error_log() function. However, that method will not send an e-mail.

First, to trigger an error:

trigger_error("Error message here", E_USER_ERROR);

By default, this will go in the server's error log file. See the ErrorLog directive for Apache. To set your own log file:

ini_set('error_log', 'path/to/log/file');

Note that the log file you choose must already exist and be writable by the server process. The simplest way to make the file writable is to make the server user the owner of the file. (The server user may be nobody, _www, apache, or something else, depending on your OS distribution.)

To e-mail the error, you need to set up a custom error handler:

function mail_error($errno, $errstr, $errfile, $errline) {
  $message = "[Error $errno] $errstr - Error on line $errline in file $errfile";
  error_log($message); // writes the error to the log file
  mail('[email protected]', 'I have an error', $message);
set_error_handler('mail_error', E_ALL^E_NOTICE);

Please see the relevant PHP documentation for more info.

Launch an app from within another (iPhone)

The lee answer is absolutely correct for iOS prior to 8.

In iOS 9+ you must whitelist any URL schemes your App wants to query in Info.plist under the LSApplicationQueriesSchemes key (an array of strings):

enter image description here

How does += (plus equal) work?

1 += 2 is a syntax error (left-side must be a variable).

x += y is shorthand for x = x + y.

Tools to selectively Copy HTML+CSS+JS From A Specific Element of DOM

Just copy the part you want from the webpage and paste it in the wysiwyg editor. Check the html source by clicking on the "source" button on the editor toolbar.

I've found this most easiest way when I was working on a Drupal site. I use wysiwyg CKeditor.

Chrome extension: accessing localStorage in content script

Sometimes it may be better to use API. It's better then localStorage because you can:

  • store information from your content script without the need for message passing between content script and extension;
  • store your data as JavaScript objects without serializing them to JSON (localStorage only stores strings).

Here's a simple code demonstrating the use of Content script gets the url of visited page and timestamp and stores it, popup.js gets it from storage area.


(function () {
    var visited = window.location.href;
    var time = +new Date();{'visitedPages':{pageUrl:visited,time:time}}, function () {
        console.log("Just visited",visited)


(function () { (changes,areaName) {
        console.log("New item in storage",changes.visitedPages.newValue);

"Changes" here is an object that contains old and new value for a given key. "AreaName" argument refers to name of storage area, either 'local', 'sync' or 'managed'.

Remember to declare storage permission in manifest.json.


"permissions": [

JSON and XML comparison

I found this article at digital bazaar really interesting. Quoting their quotations from Norm:

About JSON pros:

If all you want to pass around are atomic values or lists or hashes of atomic values, JSON has many of the advantages of XML: it’s straightforwardly usable over the Internet, supports a wide variety of applications, it’s easy to write programs to process JSON, it has few optional features, it’s human-legible and reasonably clear, its design is formal and concise, JSON documents are easy to create, and it uses Unicode. ...

About XML pros:

XML deals remarkably well with the full richness of unstructured data. I’m not worried about the future of XML at all even if its death is gleefully celebrated by a cadre of web API designers.

And I can’t resist tucking an "I told you so!" token away in my desk. I look forward to seeing what the JSON folks do when they are asked to develop richer APIs. When they want to exchange less well strucured data, will they shoehorn it into JSON? I see occasional mentions of a schema language for JSON, will other languages follow? ...

I personally agree with Norm. I think that most attacks to XML come from Web Developers for typical applications, and not really from integration developers. But that's my opinion! ;)

Extract value of attribute node via XPath

@ryenus, You need to loop through the result. This is how I'd do it in vbscript;

Set xmlDoc = CreateObject("Msxml2.DOMDocument")
xmlDoc.setProperty "SelectionLanguage", "XPath"

'Remove the id=1 attribute on Parent to return all child names for all Parent nodes
For Each c In xmlDoc.selectNodes ("//Parent[@id='1']/Children/child/@name")
    Wscript.Echo c.text

PostgreSQL error: Fatal: role "username" does not exist

Installing postgres using apt-get does not create a user role or a database.

To create a superuser role and a database for your personal user account:

sudo -u postgres createuser -s $(whoami); createdb $(whoami)

Using 24 hour time in bootstrap timepicker

And this works for me:

$(function () {
        format: 'HH:mm'

Angular File Upload

Try this


npm install primeng --save


import {FileUploadModule} from 'primeng/primeng';


<p-fileUpload name="myfile[]" url="./upload.php" multiple="multiple"
    accept="image/*" auto="auto"></p-fileUpload>

How to create <input type=“text”/> dynamically

You could use createElement() method for creating that textbox

How to count the number of observations in R like Stata command count

The with function will let you use shorthand column references and sum will count TRUE results from the expression(s).

sum(with(aaa, sex==1 & group1==2))
## [1] 3

sum(with(aaa, sex==1 & group2=="A"))
## [1] 2

As @mnel pointed out, you can also do:

nrow(aaa[aaa$sex==1 & aaa$group1==2,])
## [1] 3

nrow(aaa[aaa$sex==1 & aaa$group2=="A",])
## [1] 2

The benefit of that is that you can do:

## [1] 6

And, the behaviour matches Stata's count almost exactly (syntax notwithstanding).

Git: Could not resolve host error while cloning remote repository in git

All, I want to let you all know that I was having this same issue. I solve it by resetting my remote URL git remote set-url origin I found how to do this from this answer but I had to change hit to https: Change the URI (URL) for a remote Git repository

BAT file to open CMD in current directory

this code works for me name it cmd.bat

@echo off
title This is Only A Test
set /p the="%cd%"
goto loop

Laravel 5 route not defined, while it is?

i had the same issue and find the solution lately.

you should check if your route is rather inside a route::group

like here:

Route::group(['prefix' => 'Auth', 'as' => 'Auth.', 'namespace' => 'Auth', 'middleware' => 'Auth']

if so you should use it in the view file. like here:

!! Form::model(Auth::user(), ['method' => 'PATCH', 'route' => 'Auth.preferences/' . Auth::user()->id]) !!}

How to JSON decode array elements in JavaScript?

If you get this text in an alert:

function(){return JSON.encode(this);}

when you try alert(myArray[i]), then there are a few possibilities:

  • myArray[i] is a function (most likely)
  • myArray[i] is the literal string "function(){return JSON.encode(this);}"
  • myArray[i] has a .toString() method that returns that function or that string. This is the least likely of the three.

The simplest way to tell would be to check typeof(myArray[i]).

Missing artifact com.sun:tools:jar

Add this dependecy in pom.xml file. Hope this help.
In <systemPath> property you have to write your jdk lib path..

        <systemPath>C:/Program Files/Java/jdk1.6.0_30/lib/tools.jar</systemPath>

Format a BigDecimal as String with max 2 decimal digits, removing 0 on decimal part

If its money use:


How to fix Uncaught InvalidValueError: setPosition: not a LatLng or LatLngLiteral: in property lat: not a number?

I had the same problem when setting the center of the map with map.setCenter(). Using Number() solved for me. Had to use parseFloat to truncate the data.

code snippet:

 var centerLat = parseFloat(;
 var centerLng = parseFloat(data.long).toFixed(0);
      lat: Number(centerLat),
      lng: Number(centerLng)

How can I get the application's path in a .NET console application?

None of these methods work in special cases like using a symbolic link to the exe, they will return the location of the link not the actual exe.

So can use QueryFullProcessImageName to get around that:

using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using System.Diagnostics;

internal static class NativeMethods
    [DllImport("kernel32.dll", SetLastError = true)]
    internal static extern bool QueryFullProcessImageName([In]IntPtr hProcess, [In]int dwFlags, [Out]StringBuilder lpExeName, ref int lpdwSize);

    [DllImport("kernel32.dll", SetLastError = true)]
    internal static extern IntPtr OpenProcess(
        UInt32 dwDesiredAccess,
        Boolean bInheritHandle,
        Int32 dwProcessId

public static class utils

    private const UInt32 PROCESS_QUERY_INFORMATION = 0x400;
    private const UInt32 PROCESS_VM_READ = 0x010;

    public static string getfolder()
        Int32 pid = Process.GetCurrentProcess().Id;
        int capacity = 2000;
        StringBuilder sb = new StringBuilder(capacity);
        IntPtr proc;

        if ((proc = NativeMethods.OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, false, pid)) == IntPtr.Zero)
            return "";

        NativeMethods.QueryFullProcessImageName(proc, 0, sb, ref capacity);

        string fullPath = sb.ToString(0, capacity);

        return Path.GetDirectoryName(fullPath) + @"\";

NodeJS / Express: what is "app.use"?

Middleware is a general term for software that serves to "glue together" so app.use is a method to configure the middleware, for example: to parse and handle the body of request: app.use(bodyParser.urlencoded({ extended: true })); app.use(bodyParser.json()); there are many middlewares you can use in your express application just read the doc :

How to convert rdd object to dataframe in spark

Note: This answer was originally posted here

I am posting this answer because I would like to share additional details about the available options that I did not find in the other answers

To create a DataFrame from an RDD of Rows, there are two main options:

1) As already pointed out, you could use toDF() which can be imported by import sqlContext.implicits._. However, this approach only works for the following types of RDDs:

  • RDD[Int]
  • RDD[Long]
  • RDD[String]
  • RDD[T <: scala.Product]

(source: Scaladoc of the SQLContext.implicits object)

The last signature actually means that it can work for an RDD of tuples or an RDD of case classes (because tuples and case classes are subclasses of scala.Product).

So, to use this approach for an RDD[Row], you have to map it to an RDD[T <: scala.Product]. This can be done by mapping each row to a custom case class or to a tuple, as in the following code snippets:

val df ={ 
  case Row(val1: String, ..., valN: Long) => (val1, ..., valN)
}).toDF("col1_name", ..., "colN_name")


case class MyClass(val1: String, ..., valN: Long = 0L)
val df ={ 
  case Row(val1: String, ..., valN: Long) => MyClass(val1, ..., valN)
}).toDF("col1_name", ..., "colN_name")

The main drawback of this approach (in my opinion) is that you have to explicitly set the schema of the resulting DataFrame in the map function, column by column. Maybe this can be done programatically if you don't know the schema in advance, but things can get a little messy there. So, alternatively, there is another option:

2) You can use createDataFrame(rowRDD: RDD[Row], schema: StructType) as in the accepted answer, which is available in the SQLContext object. Example for converting an RDD of an old DataFrame:

val rdd = oldDF.rdd
val newDF = oldDF.sqlContext.createDataFrame(rdd, oldDF.schema)

Note that there is no need to explicitly set any schema column. We reuse the old DF's schema, which is of StructType class and can be easily extended. However, this approach sometimes is not possible, and in some cases can be less efficient than the first one.

Oracle Differences between NVL and Coalesce

NVL: Replace the null with value.

COALESCE: Return the first non-null expression from expression list.


| Purchase_Price | Min_Price |
| 10             | null      |
| 20             |           |
| 50             | 30        |
| 100            | 80        |
| null           | null      |

Below is the example of

[1] Set sales price with adding 10% profit to all products.
[2] If there is no purchase list price, then the sale price is the minimum price. For clearance sale.
[3] If there is no minimum price also, then set the sale price as default price "50".

     NVL(Purchase_Price + (Purchase_Price * 0.10), Min_Price)    AS NVL_Sales_Price,
COALESCE(Purchase_Price + (Purchase_Price * 0.10), Min_Price,50) AS Coalesce_Sales_Price

Explain with real life practical example.

| Purchase_Price | Min_Price | NVL_Sales_Price | Coalesce_Sales_Price |
| 10             | null      | 11              |                   11 |
| null           | 20        | 20              |                   20 |
| 50             | 30        | 55              |                   55 |
| 100            | 80        | 110             |                  110 |
| null           | null      | null            |                   50 |

You can see that with NVL we can achieve rules [1],[2]
But with COALSECE we can achieve all three rules.

'dict' object has no attribute 'has_key'

In python3, has_key(key) is replaced by __contains__(key)

Tested in python3.7:

a = {'a':1, 'b':2, 'c':3}

List of zeros in python

$ python3
>>> from itertools import repeat
>>> list(repeat(0, 7))
[0, 0, 0, 0, 0, 0, 0]

Can I add extension methods to an existing static class?

You can't add static methods to a type. You can only add (pseudo-)instance methods to an instance of a type.

The point of the this modifier is to tell the C# compiler to pass the instance on the left-side of the . as the first parameter of the static/extension method.

In the case of adding static methods to a type, there is no instance to pass for the first parameter.

What is this property in Spring Boot?

This property will register an OpenEntityManagerInViewInterceptor, which registers an EntityManager to the current thread, so you will have the same EntityManager until the web request is finished. It has nothing to do with a Hibernate SessionFactory etc.

Linear regression with matplotlib / numpy

arange generates lists (well, numpy arrays); type help(np.arange) for the details. You don't need to call it on existing lists.

>>> x = [1,2,3,4]
>>> y = [3,5,7,9] 
>>> m,b = np.polyfit(x, y, 1)
>>> m
>>> b

I should add that I tend to use poly1d here rather than write out "m*x+b" and the higher-order equivalents, so my version of your code would look something like this:

import numpy as np
import matplotlib.pyplot as plt

x = [1,2,3,4]
y = [3,5,7,10] # 10, not 9, so the fit isn't perfect

coef = np.polyfit(x,y,1)
poly1d_fn = np.poly1d(coef) 
# poly1d_fn is now a function which takes in x and returns an estimate for y

plt.plot(x,y, 'yo', x, poly1d_fn(x), '--k')
plt.xlim(0, 5)
plt.ylim(0, 12)

enter image description here

Using Intent in an Android application to show another activity

When you create any activity in android file you have to specify it in AndroidManifest.xml like

<uses-sdk android:minSdkVersion="8" />

    android:label="@string/app_name" >
        android:label="@string/app_name" >
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />

     <activity android:name=".OrderScreen"></activity>


Loop Through All Subfolders Using VBA

And to complement Rich's recursive answer, a non-recursive method.

Public Sub NonRecursiveMethod()
    Dim fso, oFolder, oSubfolder, oFile, queue As Collection

    Set fso = CreateObject("Scripting.FileSystemObject")
    Set queue = New Collection
    queue.Add fso.GetFolder("your folder path variable") 'obviously replace

    Do While queue.Count > 0
        Set oFolder = queue(1)
        queue.Remove 1 'dequeue
        '...insert any folder processing code here...
        For Each oSubfolder In oFolder.SubFolders
            queue.Add oSubfolder 'enqueue
        Next oSubfolder
        For Each oFile In oFolder.Files
            '...insert any file processing code here...
        Next oFile

End Sub

You can use a queue for FIFO behaviour (shown above), or you can use a stack for LIFO behaviour which would process in the same order as a recursive approach (replace Set oFolder = queue(1) with Set oFolder = queue(queue.Count) and replace queue.Remove(1) with queue.Remove(queue.Count), and probably rename the variable...)

Maven fails to find local artifact

Even in offline mode, maven will check remote repositories if there is a _remote.repositories marker for the dependency. If you need to operate in offline mode, you may need to delete these files.

The simple shell command below deletes these marker files. This is safe to do if you only use offline mode for the machine. I would NOT do this on a machine that needs to pull files down from the web.

I have used this strategy on a build server that is disconnected from the web. We have to transfer the repository to it, delete the marker files and then run in offline mode.

On Linux / Unix you can delete the remote repository marker files this way:

cd ~/.m2
find . -name "_remote.repositories" -type f -delete

How to get UTC time in Python?

you could use datetime library to get UTC time even local time.

import datetime

utc_time = datetime.datetime.utcnow() 
print(utc_time.strftime('%Y%m%d %H%M%S'))

How to search by key=>value in a multidimensional array in PHP

How about the SPL version instead? It'll save you some typing:

// I changed your input example to make it harder and
// to show it works at lower depths:

$arr = array(0 => array('id'=>1,'name'=>"cat 1"),
             1 => array(array('id'=>3,'name'=>"cat 1")),
             2 => array('id'=>2,'name'=>"cat 2")

//here's the code:

    $arrIt = new RecursiveIteratorIterator(new RecursiveArrayIterator($arr));

 foreach ($arrIt as $sub) {
    $subArray = $arrIt->getSubIterator();
    if ($subArray['name'] === 'cat 1') {
        $outputArray[] = iterator_to_array($subArray);

What's great is that basically the same code will iterate through a directory for you, by using a RecursiveDirectoryIterator instead of a RecursiveArrayIterator. SPL is the roxor.

The only bummer about SPL is that it's badly documented on the web. But several PHP books go into some useful detail, particularly Pro PHP; and you can probably google for more info, too.

What is the meaning of "this" in Java?

As everyone said, this represents the current object / current instance. I understand it this way, if its just "this" - it returns class object, in below ex: Dog if it has this.something, something is a method in that class or a variable

class Dog {
private String breed;
private String name;

Dog(String breed, String name) {
    this.breed = breed; = name;

public Dog getDog() {
    // return Dog type
    return this;


enter image description here

Set width of dropdown element in HTML select dropdown options


<select class="shortenedSelect">
    <option value="0" disabled>Please select an item</option>
    <option value="1">Item text goes in here but it is way too long to fit inside a select option that has a fixed width adding more</option>


.shortenedSelect {
    max-width: 350px;


// Shorten select option text if it stretches beyond max-width of select element
$.each($('.shortenedSelect option'), function(key, optionElement) {
    var curText = $(optionElement).text();
    $(this).attr('title', curText);

    // Tip: parseInt('350px', 10) removes the 'px' by forcing parseInt to use a base ten numbering system.
    var lengthToShortenTo = Math.round(parseInt($(this).parent('select').css('max-width'), 10) / 7.3);

    if (curText.length > lengthToShortenTo) {
        $(this).text('... ' + curText.substring((curText.length - lengthToShortenTo), curText.length));

// Show full name in tooltip after choosing an option
$('.shortenedSelect').change(function() {
    $(this).attr('title', ($(this).find('option:eq('+$(this).get(0).selectedIndex +')').attr('title')));

Works perfectly. I had the same issue myself. Check out this JSFiddle

What's the correct way to convert bytes to a hex string in Python 3?

The method binascii.hexlify() will convert bytes to a bytes representing the ascii hex string. That means that each byte in the input will get converted to two ascii characters. If you want a true str out then you can .decode("ascii") the result.

I included an snippet that illustrates it.

import binascii

with open("addressbook.bin", "rb") as f: # or any binary file like '/bin/ls'
    in_bytes =
    print(in_bytes) # b'\n\x16\n\x04'
    hex_bytes = binascii.hexlify(in_bytes) 
    print(hex_bytes) # b'0a160a04' which is twice as long as in_bytes
    hex_str = hex_bytes.decode("ascii")
    print(hex_str) # 0a160a04

from the hex string "0a160a04" to can come back to the bytes with binascii.unhexlify("0a160a04") which gives back b'\n\x16\n\x04'

Change a Nullable column to NOT NULL with Default Value

If its SQL Server you can do it on the column properties within design view

Try this?:

ALTER TABLE dbo.TableName 
  ADD CONSTRAINT DF_TableName_ColumnName
    DEFAULT '01/01/2000' FOR ColumnName

How to add a recyclerView inside another recyclerView

I ran into similar problem a while back and what was happening in my case was the outer recycler view was working perfectly fine but the the adapter of inner/second recycler view had minor issues all the methods like constructor got initiated and even getCount() method was being called, although the final methods responsible to generate view ie..

1. onBindViewHolder() methods never got called. --> Problem 1.

2. When it got called finally it never show the list items/rows of recycler view. --> Problem 2.

Reason why this happened :: When you put a recycler view inside another recycler view, then height of the first/outer recycler view is not auto adjusted. It is defined when the first/outer view is created and then it remains fixed. At that point your second/inner recycler view has not yet loaded its items and thus its height is set as zero and never changes even when it gets data. Then when onBindViewHolder() in your second/inner recycler view is called, it gets items but it doesn't have the space to show them because its height is still zero. So the items in the second recycler view are never shown even when the onBindViewHolder() has added them to it.

Solution :: you have to create your custom LinearLayoutManager for the second recycler view and that is it. To create your own LinearLayoutManager: Create a Java class with the name CustomLinearLayoutManager and paste the code below into it. NO CHANGES REQUIRED

public class CustomLinearLayoutManager extends LinearLayoutManager {

    private static final String TAG = CustomLinearLayoutManager.class.getSimpleName();

    public CustomLinearLayoutManager(Context context) {


    public CustomLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);

    private int[] mMeasuredDimension = new int[2];

    public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) {

        final int widthMode = View.MeasureSpec.getMode(widthSpec);
        final int heightMode = View.MeasureSpec.getMode(heightSpec);
        final int widthSize = View.MeasureSpec.getSize(widthSpec);
        final int heightSize = View.MeasureSpec.getSize(heightSpec);

        int width = 0;
        int height = 0;
        for (int i = 0; i < getItemCount(); i++) {
            measureScrapChild(recycler, i, View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
                    View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),

            if (getOrientation() == HORIZONTAL) {
                width = width + mMeasuredDimension[0];
                if (i == 0) {
                    height = mMeasuredDimension[1];
            } else {
                height = height + mMeasuredDimension[1];
                if (i == 0) {
                    width = mMeasuredDimension[0];
        switch (widthMode) {
            case View.MeasureSpec.EXACTLY:
                width = widthSize;
            case View.MeasureSpec.AT_MOST:
            case View.MeasureSpec.UNSPECIFIED:

        switch (heightMode) {
            case View.MeasureSpec.EXACTLY:
                height = heightSize;
            case View.MeasureSpec.AT_MOST:
            case View.MeasureSpec.UNSPECIFIED:

        setMeasuredDimension(width, height);

    private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
                                   int heightSpec, int[] measuredDimension) {
        try {
            View view = recycler.getViewForPosition(position);

            if (view != null) {
                RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();

                int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
                        getPaddingLeft() + getPaddingRight(), p.width);

                int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
                        getPaddingTop() + getPaddingBottom(), p.height);

                view.measure(childWidthSpec, childHeightSpec);
                measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;
                measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;
        } catch (Exception e) {

How to solve ' a 'type', which is not valid in the given context'? (C#)


private void Form1_Load(object sender, EventArgs e) 
        CERas.CERAS = new CERas.CERAS(); 


private void Form1_Load(object sender, EventArgs e) 
        CERas.CERAS c = new CERas.CERAS(); 

Or if you wish to use it later again

change it to

using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Windows.Forms; 

namespace WinApp_WMI2 
    public partial class Form1 : Form 
        CERas.CERAS m_CERAS;

        public Form1() 

    private void Form1_Load(object sender, EventArgs e) 
        m_CERAS = new CERas.CERAS(); 


UICollectionView - dynamic cell height?

Here is a Ray Wenderlich tutorial that shows you how to use AutoLayout to dynamically size UITableViewCells. I would think it would be the same for UICollectionViewCell.

Basically, though, you end up dequeueing and configuring a prototype cell and grabbing its height. After reading this article, I decided to NOT implement this method and just write some clear, explicit sizing code.

Here's what I consider the "secret sauce" for the entire article:

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    return [self heightForBasicCellAtIndexPath:indexPath];

- (CGFloat)heightForBasicCellAtIndexPath:(NSIndexPath *)indexPath {
    static RWBasicCell *sizingCell = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sizingCell = [self.tableView dequeueReusableCellWithIdentifier:RWBasicCellIdentifier];

    [self configureBasicCell:sizingCell atIndexPath:indexPath];
    return [self calculateHeightForConfiguredSizingCell:sizingCell];

- (CGFloat)calculateHeightForConfiguredSizingCell:(UITableViewCell *)sizingCell {
    [sizingCell setNeedsLayout];
    [sizingCell layoutIfNeeded];

    CGSize size = [sizingCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
    return size.height + 1.0f; // Add 1.0f for the cell separator height

EDIT: I did some research into your crash and decided that there is no way to get this done without a custom XIB. While that is a bit frustrating, you should be able to cut and paste from your Storyboard to a custom, empty XIB.

Once you've done that, code like the following will get you going:

//  ViewController.m
#import "ViewController.h"
#import "CollectionViewCell.h"
@interface ViewController () <UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout> {

@property (weak, nonatomic) IBOutlet CollectionViewCell *cell;
@property (weak, nonatomic) IBOutlet UICollectionView   *collectionView;
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor lightGrayColor];
    [self.collectionView registerNib:[UINib nibWithNibName:@"CollectionViewCell" bundle:nil] forCellWithReuseIdentifier:@"cell"];
- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return 50;
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section {
    return 10.0f;
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section {
    return 10.0f;
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    return [self sizingForRowAtIndexPath:indexPath];
- (CGSize)sizingForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *title                  = @"This is a long title that will cause some wrapping to occur. This is a long title that will cause some wrapping to occur.";
    static NSString *subtitle               = @"This is a long subtitle that will cause some wrapping to occur. This is a long subtitle that will cause some wrapping to occur.";
    static NSString *buttonTitle            = @"This is a really long button title that will cause some wrapping to occur.";
    static CollectionViewCell *sizingCell   = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sizingCell                          = [[NSBundle mainBundle] loadNibNamed:@"CollectionViewCell" owner:self options:nil][0];
    [sizingCell configureWithTitle:title subtitle:[NSString stringWithFormat:@"%@: Number %d.", subtitle, (int)indexPath.row] buttonTitle:buttonTitle];
    [sizingCell setNeedsLayout];
    [sizingCell layoutIfNeeded];
    CGSize cellSize = [sizingCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
    NSLog(@"cellSize: %@", NSStringFromCGSize(cellSize));
    return cellSize;
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *title                  = @"This is a long title that will cause some wrapping to occur. This is a long title that will cause some wrapping to occur.";
    static NSString *subtitle               = @"This is a long subtitle that will cause some wrapping to occur. This is a long subtitle that will cause some wrapping to occur.";
    static NSString *buttonTitle            = @"This is a really long button title that will cause some wrapping to occur.";
    CollectionViewCell *cell                = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    [cell configureWithTitle:title subtitle:[NSString stringWithFormat:@"%@: Number %d.", subtitle, (int)indexPath.row] buttonTitle:buttonTitle];
    return cell;

The code above (along with a very basic UICollectionViewCell subclass and associated XIB) gives me this:

enter image description here

PHPMyAdmin Default login password

I just installed Fedora 16 (yea, I know it's old and not supported but, I had the CD burnt :) )

Anyway, coming to the solution, this is what I was required to do:

su -
gedit /etc/phpMyAdmin/

if not found... try phpmyadmin - all small caps.

gedit /etc/phpmyadmin/



and set it to:

$cfg['Servers'][$i]['AllowNoPassword'] = TRUE;

Save it.

Illegal mix of collations error in MySql

You need to change each column Collation from latin1_general_ci to latin1_swedish_ci


The my.cnf file you should edit is the /etc/mysql/my.cnf file. Just:

sudo nano /etc/mysql/my.cnf

Then add:



The headers [mysqld] and [mysql] are already given, just locate them in the file and add local-infile underneath each of them.

It works for me on MySQL 5.5 on Ubuntu 12.04 LTS.

SVN checkout the contents of a folder, not the folder itself

Provide the directory on the command line:

svn checkout file:///home/landonwinters/svn/waterproject/trunk public_html

XPath: How to select elements based on their value?

The condition below:

//Element[@attribute1="abc" and @attribute2="xyz" and Data]

checks for the existence of the element Data within Element and not for element value Data.

Instead you can use

//Element[@attribute1="abc" and @attribute2="xyz" and text()="Data"]

How to get the current time in Google spreadsheet using script editor?

I considered with timezone in my Google Docs like this:

timezone = "GMT+" + new Date().getTimezoneOffset()/60
var date = Utilities.formatDate(new Date(), timezone, "yyyy-MM-dd HH:mm"); // "yyyy-MM-dd'T'HH:mm:ss'Z'"

my script for Google docs

Open directory using C

Some feedback on the segment of code, though for the most part, it should work...

void main(int c,char **args)
  • int main - the standard defines main as returning an int.
  • c and args are typically named argc and argv, respectfully, but you are allowed to name them anything


DIR *dir;
struct dirent *dent;
char buffer[50];
  • You have a buffer overflow here: If args[1] is longer than 50 bytes, buffer will not be able to hold it, and you will write to memory that you shouldn't. There's no reason I can see to copy the buffer here, so you can sidestep these issues by just not using strcpy...


dir=opendir(buffer);   //this part

If this returning NULL, it can be for a few reasons:

  • The directory didn't exist. (Did you type it right? Did it have a space in it, and you typed ./your_program my directory, which will fail, because it tries to opendir("my"))
  • You lack permissions to the directory
  • There's insufficient memory. (This is unlikely.)

Get the device width in javascript

Just as an FYI, there is a library called breakpoints which detects the max-width as set in CSS and allows you to use it in JS if-else conditions using <=, <, >, >= and == signs. I found it quite useful. The payload size is under 3 KB.

Regex: Use start of line/end of line signs (^ or $) in different context

Just use look-arounds to solve this:


The difference with look-arounds and just regular groups are that with regular groups the comma would be part of the match, and with look-arounds it wouldn't. In this case it doesn't make a difference though.

How do I rotate text in css?

In your case, it's the best to use rotate option from transform property as mentioned before. There is also writing-mode property and it works like rotate(90deg) so in your case, it should be rotated after it's applied. Even it's not the right solution in this case but you should be aware of this property.



More about transform:

More about writing-mode:

Convert string to datetime

I have had success with:

require 'time'
t = Time.parse(some_string)

How to update/modify an XML file in python?

To make this process more robust, you could consider using the SAX parser (that way you don't have to hold the whole file in memory), read & write till the end of tree and then start appending.

What is the difference between atomic / volatile / synchronized?


volatile is a keyword. volatile forces all threads to get latest value of the variable from main memory instead of cache. No locking is required to access volatile variables. All threads can access volatile variable value at same time.

Using volatile variables reduces the risk of memory consistency errors, because any write to a volatile variable establishes a happens-before relationship with subsequent reads of that same variable.

This means that changes to a volatile variable are always visible to other threads. What's more, it also means that when a thread reads a volatile variable, it sees not just the latest change to the volatile, but also the side effects of the code that led up the change.

When to use: One thread modifies the data and other threads have to read latest value of data. Other threads will take some action but they won't update data.


AtomicXXX classes support lock-free thread-safe programming on single variables. These AtomicXXX classes (like AtomicInteger) resolves memory inconsistency errors / side effects of modification of volatile variables, which have been accessed in multiple threads.

When to use: Multiple threads can read and modify data.


synchronized is keyword used to guard a method or code block. By making method as synchronized has two effects:

  1. First, it is not possible for two invocations of synchronized methods on the same object to interleave. When one thread is executing a synchronized method for an object, all other threads that invoke synchronized methods for the same object block (suspend execution) until the first thread is done with the object.

  2. Second, when a synchronized method exits, it automatically establishes a happens-before relationship with any subsequent invocation of a synchronized method for the same object. This guarantees that changes to the state of the object are visible to all threads.

When to use: Multiple threads can read and modify data. Your business logic not only update the data but also executes atomic operations

AtomicXXX is equivalent of volatile + synchronized even though the implementation is different. AmtomicXXX extends volatile variables + compareAndSet methods but does not use synchronization.

Related SE questions:

Difference between volatile and synchronized in Java

Volatile boolean vs AtomicBoolean

Good articles to read: ( Above content is taken from these documentation pages)

How to get char from string by index?

This should further clarify the points:

a = int(raw_input('Enter the index'))
str1 = 'Example'
leng = len(str1)
if (a < (len-1)) and (a > (-len)):
    print str1[a]
    print('Index overflow')

Input 3 Output m

Input -3 Output p

Best way to check if object exists in Entity Framework?

From a performance point of view, I guess that a direct SQL query using the EXISTS command would be appropriate. See here for how to execute SQL directly in Entity Framework:

Android - Pulling SQlite database android device

For debuggable apps1 on non-rooted devices, you could use following command:

adb shell run-as chmod 666 /data/data/
adb pull /data/data/


adb shell run-as chmod 666 /data/data/
adb pull /data/data/

Set PATH adb for Enviroment Variables or use cd command to android sdk folder platform-tools.


cd /folder/android-sdk/platform-tools/

then use above command

1 Note that most apps in Play store are not debuggable since it requires setting the debuggable flag in the manifest.

SQL for ordering by number - 1,2,3,4 etc instead of 1,10,11,12

ORDER_BY cast(registration_no as unsigned) ASC

gives the desired result with warnings.

Hence, better to go for

ORDER_BY registration_no + 0 ASC

for a clean result without any SQL warnings.

MongoDB "root" user

The best superuser role would be the root.The Syntax is:

use admin

    user: "root",
    pwd: "password",
    roles: [ "root" ]

For more details look at built-in roles.

Hope this helps !!!

How does Python manage int and long?

Python 2.7.9 auto promotes numbers. For a case where one is unsure to use int() or long().

>>> a = int("123")
>>> type(a)
<type 'int'>
>>> a = int("111111111111111111111111111111111111111111111111111")
>>> type(a)
<type 'long'>

CSS width of a <span> tag

Like in other answers, start your span attributes with this:


Now you can use padding more than width:


When you use padding, your color expands to both side (right and left), not just right (like in widht).

Rewrite left outer join involving multiple tables from Informix to Oracle

I'm guessing that you want something like

SELECT tab1.a, tab2.b, tab3.c, tab4.d
  FROM table1 tab1 
       JOIN table2 tab2 ON (tab1.fg = tab2.fg)
       LEFT OUTER JOIN table4 tab4 ON ( =
       LEFT OUTER JOIN table3 tab3 ON (tab4.xya = tab3.xya and tab3.desc = 'XYZ')
       LEFT OUTER JOIN table5 tab5 on (tab4.kk = tab5.kk AND
                                       tab3.dd = tab5.dd)

Definition of "downstream" and "upstream"

When you read in git tag man page:

One important aspect of git is it is distributed, and being distributed largely means there is no inherent "upstream" or "downstream" in the system.

, that simply means there is no absolute upstream repo or downstream repo.
Those notions are always relative between two repos and depends on the way data flows:

If "yourRepo" has declared "otherRepo" as a remote one, then:

  • you are pulling from upstream "otherRepo" ("otherRepo" is "upstream from you", and you are "downstream for otherRepo").
  • you are pushing to upstream ("otherRepo" is still "upstream", where the information now goes back to).

Note the "from" and "for": you are not just "downstream", you are "downstream from/for", hence the relative aspect.

The DVCS (Distributed Version Control System) twist is: you have no idea what downstream actually is, beside your own repo relative to the remote repos you have declared.

  • you know what upstream is (the repos you are pulling from or pushing to)
  • you don't know what downstream is made of (the other repos pulling from or pushing to your repo).


In term of "flow of data", your repo is at the bottom ("downstream") of a flow coming from upstream repos ("pull from") and going back to (the same or other) upstream repos ("push to").

You can see an illustration in the git-rebase man page with the paragraph "RECOVERING FROM UPSTREAM REBASE":

It means you are pulling from an "upstream" repo where a rebase took place, and you (the "downstream" repo) is stuck with the consequence (lots of duplicate commits, because the branch rebased upstream recreated the commits of the same branch you have locally).

That is bad because for one "upstream" repo, there can be many downstream repos (i.e. repos pulling from the upstream one, with the rebased branch), all of them having potentially to deal with the duplicate commits.

Again, with the "flow of data" analogy, in a DVCS, one bad command "upstream" can have a "ripple effect" downstream.

Note: this is not limited to data.
It also applies to parameters, as git commands (like the "porcelain" ones) often call internally other git commands (the "plumbing" ones). See rev-parse man page:

Many git porcelainish commands take mixture of flags (i.e. parameters that begin with a dash '-') and parameters meant for the underlying git rev-list command they use internally and flags and parameters for the other commands they use downstream of git rev-list. This command is used to distinguish between them.

Sort a List of Object in VB.NET

To sort by a property in the object, you have to specify a comparer or a method to get that property.

Using the List.Sort method:

theList.Sort(Function(x, y) x.age.CompareTo(y.age))

Using the OrderBy extension method:

theList = theList.OrderBy(Function(x) x.age).ToList()

PHP 5 disable strict standards error

In php.ini set :

error_reporting = E_ALL & ~E_NOTICE & ~E_STRICT

How to get the correct range to set the value to a cell?

Use setValue method of Range class to set the value of particular cell.

function storeValue() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  // ss is now the spreadsheet the script is associated with
  var sheet = ss.getSheets()[0]; // sheets are counted starting from 0
  // sheet is the first worksheet in the spreadsheet
  var cell = sheet.getRange("B2"); 

You can also select a cell using row and column numbers.

var cell = sheet.getRange(2, 3); // here cell is C2

It's also possible to set value of multiple cells at once.

var values = [
  ["2.000", "1,000,000", "$2.99"]

var range = sheet.getRange("B2:D2");

Sort array by value alphabetically php

asort() - Maintains key association: yes.

sort() - Maintains key association: no.


Hashmap does not work with int, char

Generic parameters can only bind to reference types, not primitive types, so you need to use the corresponding wrapper types. Try HashMap<Character, Integer> instead.

However, I'm having trouble figuring out why HashMap fails to be able to deal with primitive data types.

This is due to type erasure. Java didn't have generics from the beginning so a HashMap<Character, Integer> is really a HashMap<Object, Object>. The compiler does a bunch of additional checks and implicit casts to make sure you don't put the wrong type of value in or get the wrong type out, but at runtime there is only one HashMap class and it stores objects.

Other languages "specialize" types so in C++, a vector<bool> is very different from a vector<my_class> internally and they share no common vector<?> super-type. Java defines things though so that a List<T> is a List regardless of what T is for backwards compatibility with pre-generic code. This backwards-compatibility requirement that there has to be a single implementation class for all parameterizations of a generic type prevents the kind of template specialization which would allow generic parameters to bind to primitives.

Uncaught Invariant Violation: Too many re-renders. React limits the number of renders to prevent an infinite loop

In SnackbarContentWrapper you need to change



          onClick={() => onClose}

so that it only fires the action when you click.

Instead, you could just curry the handleClose in SingInContainer to

const handleClose = () => (reason) => {
        if (reason === 'clickaway') {


It's the same.

Quickly create a large file on a Linux system

This is the fastest I could do (which is not fast) with the following constraints:

  • The goal of the large file is to fill a disk, so can't be compressible.
  • Using ext3 filesystem. (fallocate not available)

This is the gist of it...

// include stdlib.h, stdio.h, and stdint.h
int32_t buf[256]; // Block size.
for (int i = 0; i < 256; ++i)
    buf[i] = rand(); // random to be non-compressible.
FILE* file = fopen("/file/on/your/system", "wb");
int blocksToWrite = 1024 * 1024; // 1 GB
for (int i = 0; i < blocksToWrite; ++i)
   fwrite(buf, sizeof(int32_t), 256, file);

In our case this is for an embedded linux system and this works well enough, but would prefer something faster.

FYI the command dd if=/dev/urandom of=outputfile bs=1024 count = XX was so slow as to be unusable.

Getting cursor position in Python

Using pyautogui

To install

pip install pyautogui

and to find the location of the mouse pointer

import pyautogui

This will give the pixel location to which mouse pointer is at.

Create an array of strings

Another option:

names = repmat({'Sample Text'}, 10, 1)

How to make a shape with left-top round rounded corner and left-bottom rounded corner?

From the documentation:

NOTE: Every corner must (initially) be provided a corner radius greater than 1, or else no corners are rounded. If you want specific corners to not be rounded, a work-around is to use android:radius to set a default corner radius greater than 1, but then override each and every corner with the values you really want, providing zero ("0dp") where you don't want rounded corners.

E.g. you have to set an android:radius="<bigger than 1dp>" to be able to do what you want:


How can I display a tooltip on an HTML "option" tag?

If increasing the number of visible options is available, the following might work for you:

        <title>Select Option Tooltip Test</title>
            function showIETooltip(e){
                if(!e){var e = window.event;}
                var obj = e.srcElement;
                var objHeight = obj.offsetHeight;
                var optionCount = obj.options.length;
                var eX = e.offsetX;
                var eY = e.offsetY;

                //vertical position within select will roughly give the moused over option...
                var hoverOptionIndex = Math.floor(eY / (objHeight / optionCount));

                var tooltip = document.getElementById('dvDiv');
                tooltip.innerHTML = obj.options[hoverOptionIndex].title;



       = 'block';

                var frm = document.getElementById("frm");
       = tooltip.offsetHeight;
       = tooltip.offsetWidth;
       = "block";
            function hideIETooltip(e){
                var tooltip = document.getElementById('dvDiv');
                var iFrm = document.getElementById('frm');
                tooltip.innerHTML = '';
       = 'none';
       = 'none';
        <select onmousemove="showIETooltip();" onmouseout="hideIETooltip();" size="10">
            <option title="Option #1" value="1">Option #1</option>
            <option title="Option #2" value="2">Option #2</option>
            <option title="Option #3" value="3">Option #3</option>
            <option title="Option #4" value="4">Option #4</option>
            <option title="Option #5" value="5">Option #5</option>
            <option title="Option #6" value="6">Option #6</option>
            <option title="Option #7" value="7">Option #7</option>
            <option title="Option #8" value="8">Option #8</option>
            <option title="Option #9" value="9">Option #9</option>
            <option title="Option #10" value="10">Option #10</option>
        <div id="dvDiv" style="display:none;position:absolute;padding:1px;border:1px solid #333333;;background-color:#fffedf;font-size:smaller;z-index:999;"></div>
        <iframe id="frm" style="display:none;position:absolute;z-index:998"></iframe>

HTML select dropdown list

Have <option value="">- Please select a name -</option> as the first option and use JavaScript (and backend validation) to ensure the user has selected something other than an empty value.

Using union and order by clause in mysql

I got this working on a join plus union.

 FROM table1, table2, foo1, table5
 WHERE table5.somerecord = table1.column1
 ORDER BY table1.column1 ASC, table1.column2 DESC


    ... Another complex query as above

ORDER BY column1 DESC, column2 ASC

How to add footnotes to GitHub-flavoured Markdown?

I used a variant of Mateo's solution. I'm using this in Rmd files written in github flavored markdown (gfm) for a Jekyll powered website but the same Rmd files are being used to produce pdfs in various contexts. The Rmd files are math heavy and the math is displayed with MathJax on the website. So I needed a solution that works with gfm that is processed via Jekyll, works with pandoc->pdflatex, and is compatible with MathJax.

snippet from Rmd file (which is gfm)

Here is a paragraph with an footnote <span id="a1">[[1]](#f1)</span>.


1. <span id="f1"></span> This is a footnote. [$\hookleftarrow$](#a1)

$\hookleftarrow$ is latex, which works for me since I always have MathJax enabled. I use that to make sure it shows up correctly in my pdfs. I put my footnotes in square brackets because superscript is confusing if I am putting a footnote on some inline math.

Here it is in action:

These notes can be put anywhere in the Rmd. I am putting in a list at the end so they are technically endnotes.

NodeJS - What does "socket hang up" actually mean?

Also reason can be because of using app instance of express instead of server from const server = http.createServer(app) while creating server socket .


const express = require('express');
const http = require('http');
const WebSocket = require('ws');

const app = express();

app.use(function (req, res) {
  res.send({ msg: "hello" });

const wss = new WebSocket.Server({ server: app }); // will throw error while connecting from client socket

app.listen(8080, function listening() {
  console.log('Listening on %d', server.address().port);


const express = require('express');
const http = require('http');
const WebSocket = require('ws');

const app = express();

app.use(function (req, res) {
  res.send({ msg: "hello" });

const server = http.createServer(app);
const wss = new WebSocket.Server({ server });

server.listen(8080, function listening() {
  console.log('Listening on %d', server.address().port);

Setting timezone to UTC (0) in PHP

In PHP DateTime (PHP >= 5.3)

$dt = new DateTime();
$dt->setTimezone(new DateTimeZone('UTC'));
echo $dt->getTimestamp();

CSS3 Rotate Animation

Here is a demo. The correct animation CSS:

.image {_x000D_
    position: absolute;_x000D_
    top: 50%;_x000D_
    left: 50%;_x000D_
    width: 120px;_x000D_
    height: 120px;_x000D_
    margin:-60px 0 0 -60px;_x000D_
    -webkit-animation:spin 4s linear infinite;_x000D_
    -moz-animation:spin 4s linear infinite;_x000D_
    animation:spin 4s linear infinite;_x000D_
@-moz-keyframes spin { 100% { -moz-transform: rotate(360deg); } }_x000D_
@-webkit-keyframes spin { 100% { -webkit-transform: rotate(360deg); } }_x000D_
@keyframes spin { 100% { -webkit-transform: rotate(360deg); transform:rotate(360deg); } }
<img class="image" src="" alt="" width="120" height="120">

Some notes on your code:

  1. You've nested the keyframes inside the .image rule, and that's incorrect
  2. float:left won't work on absolutely positioned elements
  3. Have a look at caniuse: IE10 doesn't need the -ms- prefix

How can I use numpy.correlate to do autocorrelation?

Your question 1 has been already extensively discussed in several excellent answers here.

I thought to share with you a few lines of code that allow you to compute the autocorrelation of a signal based only on the mathematical properties of the autocorrelation. That is, the autocorrelation may be computed in the following way:

  1. subtract the mean from the signal and obtain an unbiased signal

  2. compute the Fourier transform of the unbiased signal

  3. compute the power spectral density of the signal, by taking the square norm of each value of the Fourier transform of the unbiased signal

  4. compute the inverse Fourier transform of the power spectral density

  5. normalize the inverse Fourier transform of the power spectral density by the sum of the squares of the unbiased signal, and take only half of the resulting vector

The code to do this is the following:

def autocorrelation (x) :
    Compute the autocorrelation of the signal, based on the properties of the
    power spectral density of the signal.
    xp = x-np.mean(x)
    f = np.fft.fft(xp)
    p = np.array([np.real(v)**2+np.imag(v)**2 for v in f])
    pi = np.fft.ifft(p)
    return np.real(pi)[:x.size/2]/np.sum(xp**2)

jQuery: Handle fallback for failed AJAX Request

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

ajaxError may be what you want.

How to get progress from XMLHttpRequest

If you have access to your apache install and trust third-party code, you can use the apache upload progress module (if you use apache; there's also a nginx upload progress module).

Otherwise, you'd have to write a script that you can hit out of band to request the status of the file (checking the filesize of the tmp file for instance).

There's some work going on in firefox 3 I believe to add upload progress support to the browser, but that's not going to get into all the browsers and be widely adopted for a while (more's the pity).

Windows service on Local Computer started and then stopped error

Use Timer and tick event to copy your files.

On start the service, start the time and specify the interval in the time.

So the service is keep running and copy the files ontick.

Hope it help.

How to call a method daily, at specific time, in C#?

This little program should be the solution ;-)

I hope this helps everyone.

using System;
using System.Threading;
using System.Threading.Tasks;

namespace DailyWorker
    class Program
        static void Main(string[] args)
            var cancellationSource = new CancellationTokenSource();

            var utils = new Utils();
            var task = Task.Run(
                () => utils.DailyWorker(12, 30, 00, () => DoWork(cancellationSource.Token), cancellationSource.Token));

            Console.WriteLine("Hit [return] to close!");


        private static void DoWork(CancellationToken token)
            while (!token.IsCancellationRequested)
                Console.CursorLeft = 0;

    public class Utils
        public void DailyWorker(int hour, int min, int sec, Action someWork, CancellationToken token)
            while (!token.IsCancellationRequested)
                var dateTimeNow = DateTime.Now;
                var scanDateTime = new DateTime(
                    hour,       // <-- Hour when the method should be started.
                    min,  // <-- Minutes when the method should be started.
                    sec); // <-- Seconds when the method should be started.

                TimeSpan ts;
                if (scanDateTime > dateTimeNow)
                    ts = scanDateTime - dateTimeNow;
                    scanDateTime = scanDateTime.AddDays(1);
                    ts           = scanDateTime - dateTimeNow;

                catch (OperationCanceledException)

                // Method to start

Zsh: Conda/Pip installs command not found

MAC OS Users:

  1. brew install anaconda
  2. Add export PATH="/usr/local/anaconda3/bin:$PATH" to top of ~/.zshrc
  3. source ~/.zshrc OR restart terminal

Test it. Bingo Bango.

Modifying a subset of rows in a pandas dataframe

To replace multiples columns convert to numpy array using .values:

df.loc[df.A==0, ['B', 'C']] = df.loc[df.A==0, ['B', 'C']].values / 2

How to create a dump with Oracle PL/SQL Developer?

Just as an update this can be done by using Toad 9 also.Goto Database>Export>Data Pump Export wizard.At the desitination directory window if you dont find any directory in the dropdown,then you probably have to create a directory object.

CREATE OR REPLACE DIRECTORY data_pmp_dir_test AS '/u01/app/oracle/oradata/pmp_dir_test'; 

See this for an example.