Programs & Examples On #Atomicity

In concurrent programming, an operation (or set of operations) is atomic, linearizable, indivisible or uninterruptible if it appears to the rest of the system to occur instantaneously. Atomicity is a guarantee of isolation from concurrent processes. Additionally, atomic operations commonly have a succeed-or-fail definition — they either successfully change the state of the system, or have no visible effect.

CUDA incompatible with my gcc version

In $CUDA_HOME/include/host_config.h, find lines like these (may slightly vary between different CUDA version):

#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 9)

#error -- unsupported GNU version! gcc versions later than 4.9 are not supported!

#endif [> __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 9) <]

Remove or change them matching your condition.

Note this method is potentially unsafe and may break your build. For example, gcc 5 uses C++11 as default, however this is not the case for nvcc as of CUDA 7.5. A workaround is to add

--Xcompiler="--std=c++98" for CUDA<=6.5


--std=c++11 for CUDA>=7.0.

Explanation of BASE terminology

  • Basic Availability: The database appears to work most of the time.

  • Soft State: Stores don’t have to be write-consistent or mutually consistent all the time.

  • Eventual consistency: Data should always be consistent, with regards how any number of changes are performed.

T-sql - determine if value is integer

Sometimes you don't get to design the database, you just have to work with what you are given. In my case it's a database located on a computer that I only have read access to which has been around since 2008.

I need to select from a column in a poorly designed database which is a varchar with numbers 1-100 but sometimes a random string. I used the following to get around it (although I wish I could have re designed the entire database).

SELECT A from TABLE where isnumeric(A)=1

Error executing command 'ant' on Mac OS X 10.9 Mavericks when building for Android with PhoneGap/Cordova

it don't needed port and brew! because you have android sdk package.

.1 edit your .bash_profile

export ANT_HOME="[your android_sdk_path/eclipse/plugins/org.apache.ant_1.8.3.v201301120609]" 

// its only my org.apache.ant version, check your org.apache.ant version

export PATH=$PATH:$ANT_HOME/bin

.2 make ant command that can executed

chmod 770 [your ANT_HOME/bin/ant]

.3 test if you see below message. that's success!

command line execute: ant

Buildfile: build.xml does not exist!

Build failed

Do you use NULL or 0 (zero) for pointers in C++?

    cerr << sizeof(0) << endl;
    cerr << sizeof(NULL) << endl;
    cerr << sizeof(void*) << endl;

    On a 64-bit gcc RHEL platform you get:

The moral of the story. You should use NULL when you're dealing with pointers.

1) It declares your intent (don't make me search through all your code trying to figure out if a variable is a pointer or some numeric type).

2) In certain API calls that expect variable arguments, they'll use a NULL-pointer to indicate the end of the argument list. In this case, using a '0' instead of NULL can cause problems. On a 64-bit platform, the va_arg call wants a 64-bit pointer, yet you'll be passing only a 32-bit integer. Seems to me like you're relying on the other 32-bits to be zeroed out for you? I've seen certain compilers (e.g. Intel's icpc) that aren't so gracious -- and this has resulted in runtime errors.

Scala list concatenation, ::: vs ++

A different point is that the first sentence is parsed as:

scala> List(1,2,3).++(List(4,5))
res0: List[Int] = List(1, 2, 3, 4, 5)

Whereas the second example is parsed as:

scala> List(4,5).:::(List(1,2,3))
res1: List[Int] = List(1, 2, 3, 4, 5)

So if you are using macros, you should take care.

Besides, ++ for two lists is calling ::: but with more overhead because it is asking for an implicit value to have a builder from List to List. But microbenchmarks did not prove anything useful in that sense, I guess that the compiler optimizes such calls.

Micro-Benchmarks after warming up.

scala>def time(a: => Unit): Long = { val t = System.currentTimeMillis; a; System.currentTimeMillis - t}
scala>def average(a: () => Long) = (for(i<-1 to 100) yield a()).sum/100

scala>average (() => time { (List[Int]() /: (1 to 1000)) { case (l, e) => l ++ List(e) } })
res1: Long = 46
scala>average (() => time { (List[Int]() /: (1 to 1000)) { case (l, e) => l ::: List(e ) } })
res2: Long = 46

As Daniel C. Sobrai said, you can append the content of any collection to a list using ++, whereas with ::: you can only concatenate lists.

What is the difference between readonly="true" & readonly="readonly"?

According to HTML standards, the use of

<input name="TextBox1" type="text" id="TextBox1" readonly/>

is enough to make the input element readonly. But, XHTML standard says that the usage listed above is invalid due to attribute minimization. You can refer to the links below:

How can I get nth element from a list?

An alternative to using (!!) is to use the lens package and its element function and associated operators. The lens provides a uniform interface for accessing a wide variety of structures and nested structures above and beyond lists. Below I will focus on providing examples and will gloss over both the type signatures and the theory behind the lens package. If you want to know more about the theory a good place to start is the readme file at the github repo.

Accessing lists and other datatypes

Getting access to the lens package

At the command line:

$ cabal install lens
$ ghci
GHCi, version 7.6.3:  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
> import Control.Lens

Accessing lists

To access a list with the infix operator

> [1,2,3,4,5] ^? element 2  -- 0 based indexing
Just 3

Unlike the (!!) this will not throw an exception when accessing an element out of bounds and will return Nothing instead. It is often recommend to avoid partial functions like (!!) or head since they have more corner cases and are more likely to cause a run time error. You can read a little more about why to avoid partial functions at this wiki page.

> [1,2,3] !! 9
*** Exception: Prelude.(!!): index too large

> [1,2,3] ^? element 9

You can force the lens technique to be a partial function and throw an exception when out of bounds by using the (^?!) operator instead of the (^?) operator.

> [1,2,3] ^?! element 1
> [1,2,3] ^?! element 9
*** Exception: (^?!): empty Fold

Working with types other than lists

This is not just limited to lists however. For example the same technique works on trees from the standard containers package.

 > import Data.Tree
 > :{
  tree = Node 1 [
       Node 2 [Node 4[], Node 5 []]
     , Node 3 [Node 6 [], Node 7 []]
> putStrLn . drawTree . fmap show $tree
+- 2
|  |
|  +- 4
|  |
|  `- 5
`- 3
   +- 6
   `- 7

We can now access the elements of the tree in depth-first order:

> tree ^? element 0
Just 1
> tree ^? element 1
Just 2
> tree ^? element 2
Just 4
> tree ^? element 3
Just 5
> tree ^? element 4
Just 3
> tree ^? element 5
Just 6
> tree ^? element 6
Just 7

We can also access sequences from the containers package:

> import qualified Data.Sequence as Seq
> Seq.fromList [1,2,3,4] ^? element 3
Just 4

We can access the standard int indexed arrays from the vector package, text from the standard text package, bytestrings fro the standard bytestring package, and many other standard data structures. This standard method of access can be extended to your personal data structures by making them an instance of the typeclass Taversable, see a longer list of example Traversables in the Lens documentation..

Nested structures

Digging down into nested structures is simple with the lens hackage. For example accessing an element in a list of lists:

> [[1,2,3],[4,5,6]] ^? element 0 . element 1
Just 2
> [[1,2,3],[4,5,6]] ^? element 1 . element 2
Just 6

This composition works even when the nested data structures are of different types. So for example if I had a list of trees:

> :{
  tree = Node 1 [
       Node 2 []
     , Node 3 []
> putStrLn . drawTree . fmap show $ tree
+- 2
`- 3
> :{
  listOfTrees = [ tree
      , fmap (*2) tree -- All tree elements times 2
      , fmap (*3) tree -- All tree elements times 3

> listOfTrees ^? element 1 . element 0
Just 2
> listOfTrees ^? element 1 . element 1
Just 4

You can nest arbitrarily deeply with arbitrary types as long as they meet the Traversable requirement. So accessing a list of trees of sequences of text is no sweat.

Changing the nth element

A common operation in many languages is to assign to an indexed position in an array. In python you might:

>>> a = [1,2,3,4,5]
>>> a[3] = 9
>>> a
[1, 2, 3, 9, 5]

The lens package gives this functionality with the (.~) operator. Though unlike in python the original list is not mutated, rather a new list is returned.

> let a = [1,2,3,4,5]
> a & element 3 .~ 9
> a

element 3 .~ 9 is just a function and the (&) operator, part of the lens package, is just reverse function application. Here it is with the more common function application.

> (element 3 .~ 9) [1,2,3,4,5]

Assignment again works perfectly fine with arbitrary nesting of Traversables.

> [[1,2,3],[4,5,6]] & element 0 . element 1 .~ 9

How can I find out what FOREIGN KEY constraint references a table in SQL Server?

The easiest way to get Primary Key and Foreign Key for a table is:

/*  Get primary key and foreign key for a table */
USE DatabaseName;

TABLE_NAME = 'TableName'

TABLE_NAME = 'TableName'

Cannot read property 'map' of undefined

You need to put the data before render

Should be like this:

var data = [
  {author: "Pete Hunt", text: "This is one comment"},
  {author: "Jordan Walke", text: "This is *another* comment"}

  <CommentBox data={data}/>,

Instead of this:

  <CommentBox data={data}/>,

var data = [
  {author: "Pete Hunt", text: "This is one comment"},
  {author: "Jordan Walke", text: "This is *another* comment"}

Output first 100 characters in a string


So If you want to take only 100 first character, use your_string[0:100] or your_string[:100] If you want to take only the character at even position, use your_string[::2] The "default values" for start is 0, for stop - len of string, and for step - 1. So when you don't provide one of its and put ':', it'll use it default value.

Current date and time - Default in MVC razor

Before you return your model from the controller, set your ReturnDate property to DateTime.Now()

myModel.ReturnDate = DateTime.Now()

return View(myModel)

Your view is not the right place to set values on properties so the controller is the better place for this.

You could even have it so that the getter on ReturnDate returns the current date/time.

private DateTime _returnDate = DateTime.MinValue;
public DateTime ReturnDate{
     return (_returnDate == DateTime.MinValue)? DateTime.Now() : _returnDate;
   set{_returnDate = value;}

CSS3 :unchecked pseudo-class

:unchecked is not defined in the Selectors or CSS UI level 3 specs, nor has it appeared in level 4 of Selectors.

In fact, the quote from W3C is taken from the Selectors 4 spec. Since Selectors 4 recommends using :not(:checked), it's safe to assume that there is no corresponding :unchecked pseudo. Browser support for :not() and :checked is identical, so that shouldn't be a problem.

This may seem inconsistent with the :enabled and :disabled states, especially since an element can be neither enabled nor disabled (i.e. the semantics completely do not apply), however there does not appear to be any explanation for this inconsistency.

(:indeterminate does not count, because an element can similarly be neither unchecked, checked nor indeterminate because the semantics don't apply.)

How to break out of nested loops?

Caution: This answer shows a truly obscure construction.

If you are using GCC, check out this library. Like in PHP, break can accept the number of nested loops you want to exit. You can write something like this:

for(int i = 0; i < 1000; i++) {
   for(int j = 0; j < 1000; j++) {
       if(condition) {
            // break two nested enclosing loops

Select value from list of tuples where condition

If you have named tuples you can do this:

results = [t.age for t in mylist if t.person_id == 10]

Otherwise use indexes:

results = [t[1] for t in mylist if t[0] == 10]

Or use tuple unpacking as per Nate's answer. Note that you don't have to give a meaningful name to every item you unpack. You can do (person_id, age, _, _, _, _) to unpack a six item tuple.

How to check the presence of php and apache on ubuntu server through ssh

Try this.

dpkg -s apache2 | grep Status 

dpkg -s php5 | grep Status

Get time in milliseconds using C#

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

File Not Found when running PHP with Nginx

in case it helps someone, my issue seems to be just because I was using a subfolder under my home directory, even though permissions seem correct and I don't have SELinux or anything like that. changing it to be under /var/www/something/something made it work.

(if I ever found the real cause, and remember this answer, I'll update it)

Call a function from another file?

Any of the above solutions didn't work for me. I got ModuleNotFoundError: No module named whtever error. So my solution was importing like below

from . import filename # without .py  

inside my first file I have defined function fun like below

# file name is
def fun():
  print('this is fun')

inside the second file lets say I want to call the function fun

from . import firstFile

def secondFunc(): # calling `fun` from the first file

secondFunc() # calling the function `secondFunc` 

jQuery rotate/transform

I came up with some kind of solution to the problem. It involves jquery and css. This works like toggle but instead of toggling the display of elements it just changes its properties upon alternate clicks. Upon clicking the div it rotates the element with tag 180 degrees and when you click it again the element with tag returns to its original position. If you want to change the animation duration just change transition-duration property.




$(document).ready( function ()  {  var toggle = 1;
  $('div').click( function () {
      if ( (toggle%2)==0){
          $('#example1').css( {'transform': 'rotate(180deg)'});
          $('#example1').css({'transform': 'rotate(0deg)'});


Dynamically adding HTML form field using jQuery

There appears to be a bug with appendTo using a frameset ID appending to a FORM in Chrome. Swapped out the attribute type directly with div and it works.

Stop and Start a service via batch or cmd file?

Syntax always gets me.... so...

Here is explicitly how to add a line to a batch file that will kill a remote service (on another machine) if you are an admin on both machines, run the .bat as an administrator, and the machines are on the same domain. The machine name follows the UNC format \myserver

sc \\ip.ip.ip.ip stop p4_1

In this case... p4_1 was both the Service Name and the Display Name, when you view the Properties for the service in Service Manager. You must use the Service Name.

For your Service Ops junkies... be sure to append your reason code and comment! i.e. '4' which equals 'Planned' and comment 'Stopping server for maintenance'

sc \\ip.ip.ip.ip stop p4_1 4 Stopping server for maintenance

How to convert a Kotlin source file to a Java source file

To convert a Kotlin source file to a Java source file you need to (when you in Android Studio):

  1. Press Cmd-Shift-A on a Mac, or press Ctrl-Shift-A on a Windows machine.

  2. Type the action you're looking for: Kotlin Bytecode and choose Show Kotlin Bytecode from menu.

enter image description here

  1. Press Decompile button on the top of Kotlin Bytecode panel.

enter image description here

  1. Now you get a Decompiled Java file along with Kotlin file in a adjacent tab:

enter image description here

How do I make a file:// hyperlink that works in both IE and Firefox?

file Protocol
Opens a file on a local or network drive.



Specifies the local or network drive.

Optional. Specifies the file to open. If sFile is omitted and the account accessing the drive has permission to browse the directory, a list of accessible files and directories is displayed.


The file protocol and sDrives parameter can be omitted and substituted with just the command line representation of the drive letter and file location. For example, to browse the My Documents directory, the file protocol can be specified as file:///C|/My Documents/ or as C:\My Documents. In addition, a single '\' is equivalent to specifying the root directory on the primary local drive. On most computers, this is C:.

Available as of Microsoft Internet Explorer 3.0 or later.

Note Internet Explorer 6 Service Pack 1 (SP1) no longer allows browsing a local machine from the Internet zone. For instance, if an Internet site contains a link to a local file, Internet Explorer 6 SP1 displays a blank page when a user clicks on the link. Previous versions of Windows Internet Explorer followed the link to the local file.


The following sample demonstrates four ways to use the File protocol.


//Specifying a drive and a file name. 

file:///C|/My Documents/ALetter.html

//Specifying only a drive and a path to browse the directory. 

file:///C|/My Documents/

//Specifying a drive and a directory using the command line representation of the directory location. 

C:\My Documents\

//Specifying only the directory on the local primary drive. 

\My Documents\

Get div tag scroll position using JavaScript

you use the scrollTop attribute

var position = document.getElementById('id').scrollTop;

Is there a Google Chrome-only CSS hack?

Only Chrome CSS hack:

@media all and (-webkit-min-device-pixel-ratio:0) and (min-resolution: .001dpcm) {
    #selector {
        background: red;

MongoDB: exception in initAndListen: 20 Attempted to create a lock file on a read-only directory: /data/db, terminating

The problem is that the directory you created, /data/db is owned by and only writable by the root user, but you are running mongod as yourself. There are several ways to resolve this, but ultimately, you must give the directory in question the right permissions. If this is for production, I would advise you to check the docs and think this over carefully -- you probably want to take special care.

However, if this is just for testing and you just need this to work and get on with it, you could try this, which will make the directory writable by everyone:

> sudo chmod -R go+w /data/db

or this, which will make the directory owned by you:

> sudo chown -R $USER /data/db

Using prepared statements with JDBCTemplate

Try the following:

PreparedStatementCreator creator = new PreparedStatementCreator() {
    public PreparedStatement createPreparedStatement(Connection con) throws SQLException {
        PreparedStatement updateSales = con.prepareStatement(
        updateSales.setInt(1, 75); 
        updateSales.setString(2, "Colombian"); 
        return updateSales;

Bootstrap 3 Navbar Collapse

Thanks to Seb33300 I got this working. However, an important part seems to be missing. At least in Bootstrap version 3.1.1.

My problem was that the navbar collapsed accordingly at the correct width, but the menu button didn't work. I couldn't expand and collapse the menu.

This is because the class is overrided by the !important in .navbar-collapse.collapse, and can be solved by also adding the "". Seb33300's example completed below:

@media (max-width: 991px) {
    .navbar-header {
        float: none;
    .navbar-toggle {
        display: block;
    .navbar-collapse {
        border-top: 1px solid transparent;
        box-shadow: inset 0 1px 0 rgba(255,255,255,0.1);
    .navbar-collapse.collapse {
        display: none!important;
    } {
        display: block!important;
    .navbar-nav {
        float: none!important;
        margin: 7.5px -15px;
    .navbar-nav>li {
        float: none;
    .navbar-nav>li>a {
        padding-top: 10px;
        padding-bottom: 10px;

How to create PDF files in Python

I believe that matplotlib has the ability to serialize graphics, text and other objects to a pdf document.

how to save canvas as png image?

Full Working HTML Code. Cut+Paste into new .HTML file:

Contains Two Examples:

  1. Canvas in HTML file.
  2. Canvas dynamically created with Javascript.

Tested In:

  1. Chrome
  2. Internet Explorer
  3. *Edge (title name does not show up)
  4. Firefox
  5. Opera

<html lang="en">
    <meta charset="UTF-8">
    <title> #SAVE_CANVAS_TEST# </title>
        name   ="author" 
        content="John Mark Isaac Madison"
    <!-- EMAIL: J4M4I5M7 -[AT]- -->

<div id="about_the_code">
    <li>How to save a canvas from HTML page.     </li>
    <li>How to save a dynamically created canvas.</li>

<canvas id="DOM_CANVAS" 
        width ="300" 

<div id="controls">
    <button type="button" style="width:300px;"
        SAVE_CANVAS ( Dynamically Made Canvas )

    <button type="button" style="width:300px;"
        SAVE_CANVAS ( Canvas In HTML Code )

var obj = new MyTestCodeClass();
function MyTestCodeClass(){

    //Publically exposed functions:

    var _canvas;
    var _canvas_id = "ID_OF_DYNAMIC_CANVAS";
    var _name_hash_counter = 0;

    //:Create Canvas:
    (function _constructor(){
        var D   = document;
        var CE  = D.createElement.bind(D);
        _canvas = CE("canvas");
        _canvas.width = 300;
        _canvas.height= 300;    = _canvas_id;

    //:Before saving the canvas, fill it so
    //:we can see it. For demonstration of code.
    function _fillCanvas(input_canvas, r,g,b){
        var ctx = input_canvas.getContext("2d");
        var c   = input_canvas;

        ctx.fillStyle = "rgb("+r+","+g+","+b+")";
        ctx.fillRect(0, 0, c.width, c.height);

    //:Saves canvas. If optional_id supplied,
    //:will save canvas off the DOM. If not,
    //:will save the dynamically created canvas.
    function SAVE_CANVAS(optional_id){

        var c = _getCanvas( optional_id );

        //:Debug Code: Color canvas from DOM
        //:green, internal canvas red.
        if( optional_id ){

        _saveCanvas( c );

    //:If optional_id supplied, get canvas
    //:from DOM. Else, get internal dynamically
    //:created canvas.
    function _getCanvas( optional_id ){
        var c = null; //:canvas.
        if( typeof optional_id == "string"){
            var id = optional_id;
            var  d = document;
            var c  = d.getElementById( id );
            c = _canvas; 
        return c;

    function _saveCanvas( canvas ){
        if(!window){ alert("[WINDOW_IS_NULL]"); }

        //:We want to give the window a unique
        //:name so that we can save multiple times
        //:without having to close previous
        _name_hash_counter++              ; 
        var NHC = _name_hash_counter      ;
        var URL = 'about:blank'           ;
        var name= 'UNIQUE_WINDOW_ID' + NHC;
        var URL, name )    ;

        if(!w){ alert("[W_IS_NULL]");}

        //:Create the page contents,
        //:THEN set the tile. Order Matters.
        var DW = ""                        ;
        DW += "<img src='"                 ;
        DW += canvas.toDataURL("image/png");
        DW += "' alt='from canvas'/>"      ;
        w.document.write(DW)               ;
        w.document.title = "NHC"+NHC       ;


}//:end class


<!-- In IE: Script cannot be outside of body.  -->

flutter run: No connected devices

If you are using mobile,

  • Turn on your developer options.

  • Turn on USB debugging option

How to force a hover state with jQuery?

Also, you could try triggering a mouseover.

$("#btn").click(function() {

Not sure if this will work for your specific scenario, but I've had success triggering mouseover instead of hover for various cases.

setting global sql_mode in mysql

Setting sql mode permanently using mysql config file.

In my case i have to change file /etc/mysql/mysql.conf.d/mysqld.cnf as mysql.conf.d is included in /etc/mysql/my.cnf. i change this under [mysqld]


just removed ONLY_FULL_GROUP_BY sql mode cause it was causing issue.

I am using ubuntu 16.04, php 7 and mysql --version give me this mysql Ver 14.14 Distrib 5.7.13, for Linux (x86_64) using EditLine wrapper

After this change run below commands

sudo service mysql stop
sudo service mysql start

Now check sql modes by this query SELECT @@sql_mode and you should get modes that you have just set.

jQuery getJSON save result into variable

$.getJSon expects a callback functions either you pass it to the callback function or in callback function assign it to global variale.

var globalJsonVar;

    $.getJSON("", function(json){
               //do some thing with json  or assign global variable to incoming json. 

IMO best is to call the callback function. which is nicer to eyes, readability aspects.

$.getJSON("", callbackFuncWithData);

function callbackFuncWithData(data)
 // do some thing with data 

How to get a path to the desktop for current user in C#?

 string filePath = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
 string extension = ".log";
 filePath += @"\Error Log\" + extension;
 if (!Directory.Exists(filePath))

Retrofit 2: Get JSON from Response body

You can use it like this.

 public void onResponse(Call<JsonObject> call, Response<JsonObject> response) {
            if (response.isSuccessful()) {
                try {
                    JSONObject jsonObject = new JSONObject(new Gson().toJson(response.body()));
                    msg = jsonObject.getString("msg");
                    status = jsonObject.getBoolean("status");

                    msg = jsonObject.getString("msg");
                    status = jsonObject.getBoolean("status");
                } catch (JSONException e) {

                Toast.makeText(MainActivity.this, msg, Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(MainActivity.this, "Some error occurred...", Toast.LENGTH_LONG).show();

How can I get the image url in a Wordpress theme?

You need to use

 <?php bloginfo('template_directory'); ?>

It returns the directory of the current WordPress theme.

Now for example, if your theme has some image named example.jpg inside some folder name subfolder folder in the images folder.

   |-> your theme
          |-> images
                      |-> examples.jpg

You access it like this

 <img class="article-image" src="<?php bloginfo('template_directory'); ?> /images/subfolder/example.jpg" border="0" alt="">

How to remove trailing whitespaces with sed?

var1="\t\t Test String trimming   "
echo $var1
Var2=$(echo "${var1}" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//')
echo $Var2

How to expand 'select' option width after the user wants to select an option

If you have the option pre-existing in a fixed-with <select>, and you don't want to change the width programmatically, you could be out of luck unless you get a little creative.

  • You could try and set the title attribute to each option. This is non-standard HTML (if you care for this minor infraction here), but IE (and Firefox as well) will display the entire text in a mouse popup on mouse hover.
  • You could use JavaScript to show the text in some positioned DIV when the user selects something. IMHO this is the not-so-nice way to do it, because it requires JavaScript on to work at all, and it works only after something has been selected - before there is a change in value no events fire for the select box.
  • You don't use a select box at all, but implement its functionality using other markup and CSS. Not my favorite but I wanted to mention it.

If you are adding a long option later through JavaScript, look here: How to update HTML “select” box dynamically in IE

Backporting Python 3 open(encoding="utf-8") to Python 2

1. To get an encoding parameter in Python 2:

If you only need to support Python 2.6 and 2.7 you can use instead of open. io is the new io subsystem for Python 3, and it exists in Python 2,6 ans 2.7 as well. Please be aware that in Python 2.6 (as well as 3.0) it's implemented purely in python and very slow, so if you need speed in reading files, it's not a good option.

If you need speed, and you need to support Python 2.6 or earlier, you can use instead. It also has an encoding parameter, and is quite similar to except it handles line-endings differently.

2. To get a Python 3 open() style file handler which streams bytestrings:

open(filename, 'rb')

Note the 'b', meaning 'binary'.

How to do a Postgresql subquery in select clause with join in from clause like SQL Server?

I know this is old, but since Postgresql 9.3 there is an option to use a keyword "LATERAL" to use RELATED subqueries inside of JOINS, so the query from the question would look like:

    name, author_id, count(*),
    names as n1
            count(*) as total
            names as n2
            AND n2.author_id = n1.author_id
    ) as t ON 1=1
GROUP BY, n1.author_id

Conveniently map between enum and int / String

Int -->String :

public enum Country {


    private static Map<Integer, String> domainToCountryMapping; 
    private String country;
    private int domain;

    private Country(String country,int domain){;

    public String getCountry(){
        return country;

    public static String getCountry(String domain) {
        if (domainToCountryMapping == null) {

            return domainToCountryMapping.get(domain);
            return "US";


     private static void initMapping() {
         domainToCountryMapping = new HashMap<Integer, String>();
            for (Country s : values()) {

Why is AJAX returning HTTP status code 0?

In an attempt to win the prize for most dumbest reason for the problem described.

Forgetting to call

xmlhttp.send(); //yes, you need this pivotal line!

Yes, I was still getting status returns of zero from the 'open' call.

What is the best way to ensure only one instance of a Bash script is running?

Ubuntu/Debian distros have the start-stop-daemon tool which is for the same purpose you describe. See also /etc/init.d/skeleton to see how it is used in writing start/stop scripts.

-- Noah

How to get size of mysql database?

Run this query and you'll probably get what you're looking for:

SELECT table_schema "DB Name",
        ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) "DB Size in MB" 
FROM information_schema.tables 
GROUP BY table_schema; 

This query comes from the mysql forums, where there are more comprehensive instructions available.

How to get < span > value?

You can use querySelectorAll to get all span elements and then use new ES2015 (ES6) spread operator convert StaticNodeList that querySelectorAll returns to array of spans, and then use map operator to get list of items.

See example bellow

([...document.querySelectorAll('#test span')]).map(x => console.log(x.innerHTML))
<div id="test">_x000D_

How to Code Double Quotes via HTML Codes

Google recommend that you don't use any of them, source.

There is no need to use entity references like &mdash, &rdquo, or &#x263a, assuming the same encoding (UTF-8) is used for files and editors as well as among teams.

Is there a reason you can't simply use "?

About catching ANY exception

Apart from a bare except: clause (which as others have said you shouldn't use), you can simply catch Exception:

import traceback
import logging

except Exception as e:
    # Logs the error appropriately. 

You would normally only ever consider doing this at the outermost level of your code if for example you wanted to handle any otherwise uncaught exceptions before terminating.

The advantage of except Exception over the bare except is that there are a few exceptions that it wont catch, most obviously KeyboardInterrupt and SystemExit: if you caught and swallowed those then you could make it hard for anyone to exit your script.

How to vertically align elements in a div?

All of them need to be vertically aligned within the div

Aligned how? Tops of the images aligned with the top of the text?

One of the images needs to be absolute positioned within the div.

Absolutely positioned relative to the DIV? Perhaps you could sketch out what you're looking for...?

fd has described the steps for absolute positioning, as well as adjusting the display of the H1 element such that images will appear inline with it. To that, i'll add that you can align the images by use of the vertical-align style:

#header h1 { display: inline; }
#header img { vertical-align: middle; }

...this would put the header and images together, with top edges aligned. Other alignment options exist; see the documentation. You might also find it beneficial to drop the DIV and move the images inside the H1 element - this provides semantic value to the container, and removes the need to adjust the display of the H1:

<h1 id=header">
   <img src=".." ></img>
   <img src="..."></img>

No provider for Router?

I have also received this error when developing automatic tests for components. In this context the following import should be done:

import { RouterTestingModule } from "@angular/router/testing";

const testBedConfiguration = {
  imports: [SharedModule,

Remove the legend on a matplotlib figure

If you want to plot a Pandas dataframe and want to remove the legend, add legend=None as parameter to the plot command.

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

df2 = pd.DataFrame(np.random.randn(10, 5))

Java Loop every minute

Use Thread.sleep(long millis).

Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds, subject to the precision and accuracy of system timers and schedulers. The thread does not lose ownership of any monitors.

One minute would be (60*1000) = 60000 milliseconds.

For example, this loop will print the current time once every 5 seconds:

    try {
        while (true) {
            System.out.println(new Date());
            Thread.sleep(5 * 1000);
    } catch (InterruptedException e) {

If your sleep period becomes too large for int, explicitly compute in long (e.g. 1000L).

Force DOM redraw/refresh on Chrome/Mac

CSS only. This works for situations where a child element is removed or added. In these situations, borders and rounded corners can leave artifacts.

el:after { content: " "; }
el:before { content: " "; }

How to fix IndexError: invalid index to scalar variable

You are trying to index into a scalar (non-iterable) value:

[y[1] for y in y_test]
#  ^ this is the problem

When you call [y for y in test] you are iterating over the values already, so you get a single value in y.

Your code is the same as trying to do the following:

y_test = [1, 2, 3]
y = y_test[0] # y = 1
print(y[0]) # this line will fail

I'm not sure what you're trying to get into your results array, but you need to get rid of [y[1] for y in y_test].

If you want to append each y in y_test to results, you'll need to expand your list comprehension out further to something like this:

[results.append(..., y) for y in y_test]

Or just use a for loop:

for y in y_test:
    results.append(..., y)

How can I use the apply() function for a single column?

For a single column better to use map(), like this:

df = pd.DataFrame([{'a': 15, 'b': 15, 'c': 5}, {'a': 20, 'b': 10, 'c': 7}, {'a': 25, 'b': 30, 'c': 9}])

    a   b  c
0  15  15  5
1  20  10  7
2  25  30  9

df['a'] = df['a'].map(lambda a: a / 2.)

      a   b  c
0   7.5  15  5
1  10.0  10  7
2  12.5  30  9

CentOS: Enabling GD Support in PHP Installation

For PHP7 on CentOS or EC2 Linux AMI:

sudo yum install php70-gd

PostgreSQL: Resetting password of PostgreSQL on Ubuntu

Assuming you're the administrator of the machine, Ubuntu has granted you the right to sudo to run any command as any user.
Also assuming you did not restrict the rights in the pg_hba.conf file (in the /etc/postgresql/9.1/main directory), it should contain this line as the first rule:

# Database administrative login by Unix domain socket  
local   all             postgres                                peer

(About the file location: 9.1 is the major postgres version and main the name of your "cluster". It will differ if using a newer version of postgres or non-default names. Use the pg_lsclusters command to obtain this information for your version/system).

Anyway, if the pg_hba.conf file does not have that line, edit the file, add it, and reload the service with sudo service postgresql reload.

Then you should be able to log in with psql as the postgres superuser with this shell command:

sudo -u postgres psql

Once inside psql, issue the SQL command:

ALTER USER postgres PASSWORD 'newpassword';

In this command, postgres is the name of a superuser. If the user whose password is forgotten was ritesh, the command would be:

ALTER USER ritesh PASSWORD 'newpassword';

References: PostgreSQL 9.1.13 Documentation, Chapter 19. Client Authentication

Keep in mind that you need to type postgres with a single S at the end

If leaving the password in clear text in the history of commands or the server log is a problem, psql provides an interactive meta-command to avoid that, as an alternative to ALTER USER ... PASSWORD:

\password username

It asks for the password with a double blind input, then hashes it according to the password_encryption setting and issue the ALTER USER command to the server with the hashed version of the password, instead of the clear text version.

How to get the selected date of a MonthCalendar control in C#

For those who are still trying, this link helped me out, too; it just puts it all together:

private void MonthCalendar1_DateChanged(object sender, System.Windows.Forms.DateRangeEventArgs e)
//Display the dates for selected range
Label1.Text = "Dates Selected from :" + (MonthCalendar1.SelectionRange.Start() + " to " + MonthCalendar1.SelectionRange.End);

//To display single selected of date
//MonthCalendar1.MaxSelectionCount = 1;

//To display single selected of date use MonthCalendar1.SelectionRange.Start/ MonthCalendarSelectionRange.End
Label2.Text = "Date Selected :" + MonthCalendar1.SelectionRange.Start;

How can I check whether an array is null / empty?

if you are trying to check that in spring frame work then isEmpty method in objectUtils class helps,

public static boolean isEmpty(@Nullable Object[] array) {
        return (array == null || array.length == 0);

How does one target IE7 and IE8 with valid CSS?

Explicitly Target IE versions without hacks using HTML and CSS

Use this approach if you don't want hacks in your CSS. Add a browser-unique class to the <html> element so you can select based on browser later.


<!doctype html>
<!--[if IE]><![endif]-->
<!--[if lt IE 7 ]> <html lang="en" class="ie6">    <![endif]-->
<!--[if IE 7 ]>    <html lang="en" class="ie7">    <![endif]-->
<!--[if IE 8 ]>    <html lang="en" class="ie8">    <![endif]-->
<!--[if IE 9 ]>    <html lang="en" class="ie9">    <![endif]-->
<!--[if (gt IE 9)|!(IE)]><!--><html lang="en"><!--<![endif]-->

Then in your CSS you can very strictly access your target browser.


.ie6 body { 
    border:1px solid red;
.ie7 body { 
    border:1px solid blue;

For more information check out

Target IE versions with CSS "Hacks"

More to your point, here are the hacks that let you target IE versions.

Use "\9" to target IE8 and below.
Use "*" to target IE7 and below.
Use "_" to target IE6.


body { 
border:1px solid red; /* standard */
border:1px solid blue\9; /* IE8 and below */
*border:1px solid orange; /* IE7 and below */
_border:1px solid blue; /* IE6 */

Update: Target IE10

IE10 does not recognize the conditional statements so you can use this to apply an "ie10" class to the <html> element

<!doctype html>
    <html lang="en">
    <!--[if !IE]><!--><script>if (/*@cc_on!@*/false) {document.documentElement.className+=' ie10';}</script><!--<![endif]-->

Detect when a window is resized using JavaScript ?

If You want to check only when scroll ended, in Vanilla JS, You can come up with a solution like this:

Super Super compact

var t
window.onresize = () => { clearTimeout(t) t = setTimeout(() => { resEnded() }, 500) }
function resEnded() { console.log('ended') }

All 3 possible combinations together (ES6)

var t
window.onresize = () => {
    resizing(this, this.innerWidth, this.innerHeight) //1
    if (typeof t == 'undefined') resStarted() //2
    clearTimeout(t); t = setTimeout(() => { t = undefined; resEnded() }, 500) //3

function resizing(target, w, h) {
    console.log(`Youre resizing: width ${w} height ${h}`)
function resStarted() { 
    console.log('Resize Started') 
function resEnded() { 
    console.log('Resize Ended') 

adb is not recognized as internal or external command on windows

If you get your adb from Android Studio (which most will nowadays since Android is deprecated on Eclipse), your adb program will most likely be located here:


Where %USERPROFILE% represents something like C:\Users\yourName.

If you go into your computer's environmental variables and add %USERPROFILE%\AppData\Local\Android\sdk\platform-tools to the PATH (just copy-paste that line, even with the % --- it will work fine, at least on Windows, you don't need to hardcode your username) then it should work now. Open a new command prompt and type adb to check.

Another git process seems to be running in this repository

  • My Mac is slow so I ran 2 git commits: one executed and the second was blocked by the first.
  • I tried rm -f .git/index.lock
    • rm .git/refs/heads/[your-branch-name].lock
  • <path to your repo>/.git/index.lock
  • <path to your repo>/.git/modules/<path to your submodule>/index.lock


  1. find | grep '\.lock$'
  2. rm -f ./.git/index.lock this was useful to check - no .lock file was lurking

I did what @Chole did - checked out of my IDE exited and looked at a git-status once more. Then ran a $git add . $git commit -m'msg' $git push

It cleared the 2 terminals that were running commands and solved the problem. Hope this helps someone - the diagnostics were good so thanks all, very helpful.

A slow Mac has caused this problem before - so now I just wait for a bit before running a second commit that conflicts with the first.

Where are logs located?

In Laravel 6, by default the logs are in:


Nginx upstream prematurely closed connection while reading response header from upstream, for large requests

I got the same error, here is how I resolved it:

  • Downloaded logs from AWS.
  • Reviewed Nginx logs, no additional details as above.
  • Reviewed node.js logs, AccessDenied AWS SDK permissions error.
  • Checked the S3 bucket that AWS was trying to read from.
  • Added additional bucket with read permission to correct server role.

Even though I was processing large files there were no other errors or settings I had to change once I corrected the missing S3 access.

How to join (merge) data frames (inner, outer, left, right)

For the case of a left join with a 0..*:0..1 cardinality or a right join with a 0..1:0..* cardinality it is possible to assign in-place the unilateral columns from the joiner (the 0..1 table) directly onto the joinee (the 0..* table), and thereby avoid the creation of an entirely new table of data. This requires matching the key columns from the joinee into the joiner and indexing+ordering the joiner's rows accordingly for the assignment.

If the key is a single column, then we can use a single call to match() to do the matching. This is the case I'll cover in this answer.

Here's an example based on the OP, except I've added an extra row to df2 with an id of 7 to test the case of a non-matching key in the joiner. This is effectively df1 left join df2:

df1 <- data.frame(CustomerId=1:6,Product=c(rep('Toaster',3L),rep('Radio',3L)));
df2 <- data.frame(CustomerId=c(2L,4L,6L,7L),State=c(rep('Alabama',2L),'Ohio','Texas'));
df1[names(df2)[-1L]] <- df2[match(df1[,1L],df2[,1L]),-1L];
##   CustomerId Product   State
## 1          1 Toaster    <NA>
## 2          2 Toaster Alabama
## 3          3 Toaster    <NA>
## 4          4   Radio Alabama
## 5          5   Radio    <NA>
## 6          6   Radio    Ohio

In the above I hard-coded an assumption that the key column is the first column of both input tables. I would argue that, in general, this is not an unreasonable assumption, since, if you have a data.frame with a key column, it would be strange if it had not been set up as the first column of the data.frame from the outset. And you can always reorder the columns to make it so. An advantageous consequence of this assumption is that the name of the key column does not have to be hard-coded, although I suppose it's just replacing one assumption with another. Concision is another advantage of integer indexing, as well as speed. In the benchmarks below I'll change the implementation to use string name indexing to match the competing implementations.

I think this is a particularly appropriate solution if you have several tables that you want to left join against a single large table. Repeatedly rebuilding the entire table for each merge would be unnecessary and inefficient.

On the other hand, if you need the joinee to remain unaltered through this operation for whatever reason, then this solution cannot be used, since it modifies the joinee directly. Although in that case you could simply make a copy and perform the in-place assignment(s) on the copy.

As a side note, I briefly looked into possible matching solutions for multicolumn keys. Unfortunately, the only matching solutions I found were:

  • inefficient concatenations. e.g. match(interaction(df1$a,df1$b),interaction(df2$a,df2$b)), or the same idea with paste().
  • inefficient cartesian conjunctions, e.g. outer(df1$a,df2$a,`==`) & outer(df1$b,df2$b,`==`).
  • base R merge() and equivalent package-based merge functions, which always allocate a new table to return the merged result, and thus are not suitable for an in-place assignment-based solution.

For example, see Matching multiple columns on different data frames and getting other column as result, match two columns with two other columns, Matching on multiple columns, and the dupe of this question where I originally came up with the in-place solution, Combine two data frames with different number of rows in R.


I decided to do my own benchmarking to see how the in-place assignment approach compares to the other solutions that have been offered in this question.

Testing code:


solSpecs <- list(
        inner=function(df1,df2,key) merge(df1,df2,key),
        left =function(df1,df2,key) merge(df1,df2,key,all.x=T),
        right=function(df1,df2,key) merge(df1,df2,key,all.y=T),
        full =function(df1,df2,key) merge(df1,df2,key,all=T)
        inner=function(dt1,dt2,key) dt1[dt2,on=key,nomatch=0L,allow.cartesian=T],
        left =function(dt1,dt2,key) dt2[dt1,on=key,allow.cartesian=T],
        right=function(dt1,dt2,key) dt1[dt2,on=key,allow.cartesian=T],
        full =function(dt1,dt2,key) merge(dt1,dt2,key,all=T,allow.cartesian=T) ## calls
        inner=function(dt1,dt2) dt1[dt2,nomatch=0L,allow.cartesian=T],
        left =function(dt1,dt2) dt2[dt1,allow.cartesian=T],
        right=function(dt1,dt2) dt1[dt2,allow.cartesian=T],
        full =function(dt1,dt2) merge(dt1,dt2,all=T,allow.cartesian=T) ## calls
    sqldf.unindexed=list(testFuncs=list( ## note: must pass connection=NULL to avoid running against the live DB connection, which would result in collisions with the residual tables from the last query upload
        inner=function(df1,df2,key) sqldf(paste0('select * from df1 inner join df2 using(',paste(collapse=',',key),')'),connection=NULL),
        left =function(df1,df2,key) sqldf(paste0('select * from df1 left join df2 using(',paste(collapse=',',key),')'),connection=NULL),
        right=function(df1,df2,key) sqldf(paste0('select * from df2 left join df1 using(',paste(collapse=',',key),')'),connection=NULL) ## can't do right join proper, not yet supported; inverted left join is equivalent
        ##full =function(df1,df2,key) sqldf(paste0('select * from df1 full join df2 using(',paste(collapse=',',key),')'),connection=NULL) ## can't do full join proper, not yet supported; possible to hack it with a union of left joins, but too unreasonable to include in testing
    sqldf.indexed=list(testFuncs=list( ## important: requires an active DB connection with preindexed main.df1 and main.df2 ready to go; arguments are actually ignored
        inner=function(df1,df2,key) sqldf(paste0('select * from main.df1 inner join main.df2 using(',paste(collapse=',',key),')')),
        left =function(df1,df2,key) sqldf(paste0('select * from main.df1 left join main.df2 using(',paste(collapse=',',key),')')),
        right=function(df1,df2,key) sqldf(paste0('select * from main.df2 left join main.df1 using(',paste(collapse=',',key),')')) ## can't do right join proper, not yet supported; inverted left join is equivalent
        ##full =function(df1,df2,key) sqldf(paste0('select * from main.df1 full join main.df2 using(',paste(collapse=',',key),')')) ## can't do full join proper, not yet supported; possible to hack it with a union of left joins, but too unreasonable to include in testing
        inner=function(df1,df2,key) join(df1,df2,key,'inner'),
        left =function(df1,df2,key) join(df1,df2,key,'left'),
        right=function(df1,df2,key) join(df1,df2,key,'right'),
        full =function(df1,df2,key) join(df1,df2,key,'full')
        inner=function(df1,df2,key) inner_join(df1,df2,key),
        left =function(df1,df2,key) left_join(df1,df2,key),
        right=function(df1,df2,key) right_join(df1,df2,key),
        full =function(df1,df2,key) full_join(df1,df2,key)
        left =function(df1,df2,key) { cns <- setdiff(names(df2),key); df1[cns] <- df2[match(df1[,key],df2[,key]),cns]; df1; },
        right=function(df1,df2,key) { cns <- setdiff(names(df1),key); df2[cns] <- df1[match(df2[,key],df1[,key]),cns]; df2; }

getSolTypes <- function() names(solSpecs);
getJoinTypes <- function() unique(unlist(lapply(solSpecs,function(x) names(x$testFuncs))));
getArgSpec <- function(argSpecs,key=NULL) if (is.null(key)) argSpecs$default else argSpecs[[key]];

initSqldf <- function() {
    sqldf(); ## creates sqlite connection on first run, cleans up and closes existing connection otherwise
    if (exists('sqldfInitFlag',envir=globalenv(),inherits=F) && sqldfInitFlag) { ## false only on first run
        sqldf(); ## creates a new connection
    } else {
        assign('sqldfInitFlag',T,envir=globalenv()); ## set to true for the one and only time
    }; ## end if
}; ## end initSqldf()

setUpBenchmarkCall <- function(argSpecs,joinType,solTypes=getSolTypes(),env=parent.frame()) {
    ## builds and returns a list of expressions suitable for passing to the list argument of microbenchmark(), and assigns variables to resolve symbol references in those expressions
    callExpressions <- list();
    nms <- character();
    for (solType in solTypes) {
        testFunc <- solSpecs[[solType]]$testFuncs[[joinType]];
        if (is.null(testFunc)) next; ## this join type is not defined for this solution type
        testFuncName <- paste0('tf.',solType);
        argSpecKey <- solSpecs[[solType]]$argSpec;
        argSpec <- getArgSpec(argSpecs,argSpecKey);
        argList <- setNames(nm=names(argSpec$args),vector('list',length(argSpec$args)));
        for (i in seq_along(argSpec$args)) {
            argName <- paste0('tfa.',argSpecKey,i);
            argList[[i]] <- if (i%in%argSpec$copySpec) call('copy',as.symbol(argName)) else as.symbol(argName);
        }; ## end for
        callExpressions[[length(callExpressions)+1L]] <-,c(list(testFuncName),argList),quote=T);
        nms[length(nms)+1L] <- solType;
    }; ## end for
    names(callExpressions) <- nms;
}; ## end setUpBenchmarkCall()

harmonize <- function(res) {
    res <-; ## coerce to data.frame
    for (ci in which(sapply(res,is.factor))) res[[ci]] <- as.character(res[[ci]]); ## coerce factor columns to character
    for (ci in which(sapply(res,is.logical))) res[[ci]] <- as.integer(res[[ci]]); ## coerce logical columns to integer (works around sqldf quirk of munging logicals to integers)
    ##for (ci in which(sapply(res,inherits,'POSIXct'))) res[[ci]] <- as.double(res[[ci]]); ## coerce POSIXct columns to double (works around sqldf quirk of losing POSIXct class) ----- POSIXct doesn't work at all in sqldf.indexed
    res <- res[order(names(res))]; ## order columns
    res <- res[,res),]; ## order rows
}; ## end harmonize()

checkIdentical <- function(argSpecs,solTypes=getSolTypes()) {
    for (joinType in getJoinTypes()) {
        callExpressions <- setUpBenchmarkCall(argSpecs,joinType,solTypes);
        if (length(callExpressions)<2L) next;
        ex <- harmonize(eval(callExpressions[[1L]]));
        for (i in seq(2L,len=length(callExpressions)-1L)) {
            y <- harmonize(eval(callExpressions[[i]]));
            if (!isTRUE(all.equal(ex,y,check.attributes=F))) {
                ex <<- ex;
                y <<- y;
                solType <- names(callExpressions)[i];
                stop(paste0('non-identical: ',solType,' ',joinType,'.'));
            }; ## end if
        }; ## end for
    }; ## end for
}; ## end checkIdentical()

testJoinType <- function(argSpecs,joinType,solTypes=getSolTypes(),metric=NULL,times=100L) {
    callExpressions <- setUpBenchmarkCall(argSpecs,joinType,solTypes);
    bm <- microbenchmark(list=callExpressions,times=times);
    if (is.null(metric)) return(bm);
    bm <- summary(bm);
    res <- setNames(nm=names(callExpressions),bm[[metric]]);
    attr(res,'unit') <- attr(bm,'unit');
}; ## end testJoinType()

testAllJoinTypes <- function(argSpecs,solTypes=getSolTypes(),metric=NULL,times=100L) {
    joinTypes <- getJoinTypes();
    resList <- setNames(nm=joinTypes,lapply(joinTypes,function(joinType) testJoinType(argSpecs,joinType,solTypes,metric,times)));
    if (is.null(metric)) return(resList);
    units <- unname(unlist(lapply(resList,attr,'unit')));
    res <-,c(list(join=joinTypes),setNames(nm=solTypes,rep(list(rep(NA_real_,length(joinTypes))),length(solTypes))),list(unit=units,stringsAsFactors=F)));
    for (i in seq_along(resList)) res[i,match(names(resList[[i]]),names(res))] <- resList[[i]];
}; ## end testAllJoinTypes()

testGrid <- function(makeArgSpecsFunc,sizes,overlaps,solTypes=getSolTypes(),joinTypes=getJoinTypes(),metric='median',times=100L) {

    res <- expand.grid(size=sizes,overlap=overlaps,joinType=joinTypes,stringsAsFactors=F);
    res[solTypes] <- NA_real_;
    res$unit <- NA_character_;
    for (ri in seq_len(nrow(res))) {

        size <- res$size[ri];
        overlap <- res$overlap[ri];
        joinType <- res$joinType[ri];

        argSpecs <- makeArgSpecsFunc(size,overlap);


        cur <- testJoinType(argSpecs,joinType,solTypes,metric,times);
        res[ri,match(names(cur),names(res))] <- cur;
        res$unit[ri] <- attr(cur,'unit');

    }; ## end for


}; ## end testGrid()

Here's a benchmark of the example based on the OP that I demonstrated earlier:

## OP's example, supplemented with a non-matching row in df2
argSpecs <- list(
        df1 <- data.frame(CustomerId=1:6,Product=c(rep('Toaster',3L),rep('Radio',3L))),
        df2 <- data.frame(CustomerId=c(2L,4L,6L,7L),State=c(rep('Alabama',2L),'Ohio','Texas')),
## prepare sqldf
sqldf('create index df1_key on df1(CustomerId);'); ## upload and create an sqlite index on df1
sqldf('create index df2_key on df2(CustomerId);'); ## upload and create an sqlite index on df2


##    join    merge data.table.unkeyed data.table.keyed sqldf.unindexed sqldf.indexed      plyr    dplyr         unit
## 1 inner  644.259           861.9345          923.516        9157.752      1580.390  959.2250 270.9190       NA microseconds
## 2  left  713.539           888.0205          910.045        8820.334      1529.714  968.4195 270.9185 224.3045 microseconds
## 3 right 1221.804           909.1900          923.944        8930.668      1533.135 1063.7860 269.8495 218.1035 microseconds
## 4  full 1302.203          3107.5380         3184.729              NA            NA 1593.6475 270.7055       NA microseconds

Here I benchmark on random input data, trying different scales and different patterns of key overlap between the two input tables. This benchmark is still restricted to the case of a single-column integer key. As well, to ensure that the in-place solution would work for both left and right joins of the same tables, all random test data uses 0..1:0..1 cardinality. This is implemented by sampling without replacement the key column of the first data.frame when generating the key column of the second data.frame.

makeArgSpecs.singleIntegerKey.optionalOneToOne <- function(size,overlap) {

    com <- as.integer(size*overlap);

    argSpecs <- list(
            df1 <- data.frame(id=sample(size),y1=rnorm(size),y2=rnorm(size)),
            df2 <- data.frame(id=sample(c(if (com>0L) sample(df1$id,com) else integer(),seq(size+1L,len=size-com))),y3=rnorm(size),y4=rnorm(size)),
    ## prepare sqldf
    sqldf('create index df1_key on df1(id);'); ## upload and create an sqlite index on df1
    sqldf('create index df2_key on df2(id);'); ## upload and create an sqlite index on df2


}; ## end makeArgSpecs.singleIntegerKey.optionalOneToOne()

## cross of various input sizes and key overlaps
sizes <- c(1e1L,1e3L,1e6L);
overlaps <- c(0.99,0.5,0.01);
system.time({ res <- testGrid(makeArgSpecs.singleIntegerKey.optionalOneToOne,sizes,overlaps); });
##     user   system  elapsed
## 22024.65 12308.63 34493.19

I wrote some code to create log-log plots of the above results. I generated a separate plot for each overlap percentage. It's a little bit cluttered, but I like having all the solution types and join types represented in the same plot.

I used spline interpolation to show a smooth curve for each solution/join type combination, drawn with individual pch symbols. The join type is captured by the pch symbol, using a dot for inner, left and right angle brackets for left and right, and a diamond for full. The solution type is captured by the color as shown in the legend.

plotRes <- function(res,titleFunc,useFloor=F) {
    solTypes <- setdiff(names(res),c('size','overlap','joinType','unit')); ## derive from res
    normMult <- c(microseconds=1e-3,milliseconds=1); ## normalize to milliseconds
    joinTypes <- getJoinTypes();
    cols <- c(merge='purple',data.table.unkeyed='blue',data.table.keyed='#00DDDD',sqldf.unindexed='brown',sqldf.indexed='orange',plyr='red',dplyr='#00BB00','magenta');
    pchs <- list(inner=20L,left='<',right='>',full=23L);
    cexs <- c(inner=0.7,left=1,right=1,full=0.7);
    NP <- 60L;
    ord <- order(decreasing=T,colMeans(res[res$size==max(res$size),solTypes],na.rm=T));
    ymajors <- data.frame(y=c(1,1e3),label=c('1ms','1s'),stringsAsFactors=F);
    for (overlap in unique(res$overlap)) {
        x1 <- res[res$overlap==overlap,];
        x1[solTypes] <- x1[solTypes]*normMult[x1$unit]; x1$unit <- NULL;
        xlim <- c(1e1,max(x1$size));
        xticks <- 10^seq(log10(xlim[1L]),log10(xlim[2L]));
        ylim <- c(1e-1,10^((if (useFloor) floor else ceiling)(log10(max(x1[solTypes],na.rm=T))))); ## use floor() to zoom in a little more, only sqldf.unindexed will break above, but xpd=NA will keep it visible
        yticks <- 10^seq(log10(ylim[1L]),log10(ylim[2L]));
        yticks.minor <- rep(yticks[-length(yticks)],each=9L)*1:9;
        plot(NA,xlim=xlim,ylim=ylim,xaxs='i',yaxs='i',axes=F,xlab='size (rows)',ylab='time (ms)',log='xy');
        for (joinType in rev(joinTypes)) { ## reverse to draw full first, since it's larger and would be more obtrusive if drawn last
            x2 <- x1[x1$joinType==joinType,];
            for (solType in solTypes) {
                if (any(![[solType]]))) {
                    xy <- spline(x2$size,x2[[solType]],xout=10^(seq(log10(x2$size[1L]),log10(x2$size[nrow(x2)]),len=NP)));
                }; ## end if
            }; ## end for
        }; ## end for
        ## custom legend
        ## due to logarithmic skew, must do all distance calcs in inches, and convert to user coords afterward
        ## the bottom-left corner of the legend will be defined in normalized figure coords, although we can convert to inches immediately
        leg.cex <- 0.7; <- grconvertX(0.275,'nfc','in'); <- grconvertY(0.6,'nfc','in');
        leg.x.user <- grconvertX(,'in');
        leg.y.user <- grconvertY(,'in'); <- 0.1; <- 0.1; <- 0.1; <- 0.1; <- max(strwidth(solTypes,'in',leg.cex)); <- max(strheight(solTypes,'in',leg.cex))*1.5; ## multiplication factor for greater line height <- max(strheight(joinTypes,'in',leg.cex))*1.5; ## ditto <- max(strwidth(joinTypes,'in',leg.cex)); <-*length(joinTypes); <-*length(solTypes);
        leg.x2.user <- grconvertX(*,'in');
        leg.y2.user <- grconvertY(*,'in');
        leg.cols.x.user <- grconvertX(*(0.5+seq(0L,length(joinTypes)-1L)),'in');
        leg.lines.y.user <- grconvertY(*(0.5+seq(0L,length(solTypes)-1L)),'in');
        leg.sol.x.user <- grconvertX(,'in');
        leg.join.y.user <- grconvertY(,'in');
        text(leg.cols.x.user,leg.join.y.user,joinTypes,cex=leg.cex,pos=4L,offset=0,srt=90); ## srt rotation applies *after* pos/offset positioning
        for (i in seq_along(joinTypes)) {
            joinType <- joinTypes[i];
        }; ## end for
        readline(sprintf('overlap %.02f',overlap));
    }; ## end for
}; ## end plotRes()

titleFunc <- function(overlap) sprintf('R merge solutions: single-column integer key, 0..1:0..1 cardinality, %d%% overlap',as.integer(overlap*100));




Here's a second large-scale benchmark that's more heavy-duty, with respect to the number and types of key columns, as well as cardinality. For this benchmark I use three key columns: one character, one integer, and one logical, with no restrictions on cardinality (that is, 0..*:0..*). (In general it's not advisable to define key columns with double or complex values due to floating-point comparison complications, and basically no one ever uses the raw type, much less for key columns, so I haven't included those types in the key columns. Also, for information's sake, I initially tried to use four key columns by including a POSIXct key column, but the POSIXct type didn't play well with the sqldf.indexed solution for some reason, possibly due to floating-point comparison anomalies, so I removed it.)

makeArgSpecs.assortedKey.optionalManyToMany <- function(size,overlap,uniquePct=75) {

    ## number of unique keys in df1
    u1Size <- as.integer(size*uniquePct/100);

    ## (roughly) divide u1Size into bases, so we can use expand.grid() to produce the required number of unique key values with repetitions within individual key columns
    ## use ceiling() to ensure we cover u1Size; will truncate afterward
    u1SizePerKeyColumn <- as.integer(ceiling(u1Size^(1/3)));

    ## generate the unique key values for df1
    keys1 <- expand.grid(stringsAsFactors=F,
        ##idPOSIXct=as.POSIXct('2016-01-01 00:00:00','UTC')+sample(u1SizePerKeyColumn)

    ## rbind some repetitions of the unique keys; this will prepare one side of the many-to-many relationship
    ## also scramble the order afterward
    keys1 <- rbind(keys1,keys1[sample(nrow(keys1),size-u1Size,T),])[sample(size),];

    ## common and unilateral key counts
    com <- as.integer(size*overlap);
    uni <- size-com;

    ## generate some unilateral keys for df2 by synthesizing outside of the idInteger range of df1
    keys2 <- data.frame(stringsAsFactors=F,
        ##idPOSIXct=as.POSIXct('2016-01-01 00:00:00','UTC')+u1SizePerKeyColumn+sample(uni)

    ## rbind random keys from df1; this will complete the many-to-many relationship
    ## also scramble the order afterward
    keys2 <- rbind(keys2,keys1[sample(nrow(keys1),com,T),])[sample(size),];

    ##keyNames <- c('idCharacter','idInteger','idLogical','idPOSIXct');
    keyNames <- c('idCharacter','idInteger','idLogical');
    ## note: was going to use raw and complex type for two of the non-key columns, but data.table doesn't seem to fully support them
    argSpecs <- list(
            df1 <- cbind(stringsAsFactors=F,keys1,y1=sample(c(F,T),size,T),y2=sample(size),y3=rnorm(size),y4=replicate(size,paste(collapse='',sample(letters,sample(4:12,1L),T)))),
            df2 <- cbind(stringsAsFactors=F,keys2,y5=sample(c(F,T),size,T),y6=sample(size),y7=rnorm(size),y8=replicate(size,paste(collapse='',sample(letters,sample(4:12,1L),T)))),
    ## prepare sqldf
    sqldf(paste0('create index df1_key on df1(',paste(collapse=',',keyNames),');')); ## upload and create an sqlite index on df1
    sqldf(paste0('create index df2_key on df2(',paste(collapse=',',keyNames),');')); ## upload and create an sqlite index on df2


}; ## end makeArgSpecs.assortedKey.optionalManyToMany()

sizes <- c(1e1L,1e3L,1e5L); ## 1e5L instead of 1e6L to respect more heavy-duty inputs
overlaps <- c(0.99,0.5,0.01);
solTypes <- setdiff(getSolTypes(),'');
system.time({ res <- testGrid(makeArgSpecs.assortedKey.optionalManyToMany,sizes,overlaps,solTypes); });
##     user   system  elapsed
## 38895.50   784.19 39745.53

The resulting plots, using the same plotting code given above:

titleFunc <- function(overlap) sprintf('R merge solutions: character/integer/logical key, 0..*:0..* cardinality, %d%% overlap',as.integer(overlap*100));




Replace words in the body text

I had the same problem. I wrote my own function using replace on innerHTML, but it would screw up anchor links and such.

To make it work correctly I used a library to get this done.

The library has an awesome API. After including the script I called it like this:

findAndReplaceDOMText(document.body, {
  find: 'texttofind',
  replace: 'texttoreplace'

How can I set the PATH variable for javac so I can manually compile my .java works?

Typing the SET PATH command into the command shell every time you fire it up could get old for you pretty fast. Three alternatives:

  1. Run javac from a batch (.CMD) file. Then you can just put the SET PATH into that file before your javac execution. Or you could do without the SET PATH if you simply code the explicit path to javac.exe
  2. Set your enhanced, improved PATH in the "environment variables" configuration of your system.
  3. In the long run you'll want to automate your Java compiling with Ant. But that will require yet another extension to PATH first, which brings us back to (1) and (2).

How to align center the text in html table row?

<td align="center"valign="center">textgoeshere</td>

more on valign

What's the difference between Cache-Control: max-age=0 and no-cache?

By the way, it's worth noting that some mobile devices, particularly Apple products like iPhone/iPad completely ignore headers like no-cache, no-store, Expires: 0, or whatever else you may try to force them to not re-use expired form pages.

This has caused us no end of headaches as we try to get the issue of a user's iPad say, being left asleep on a page they have reached through a form process, say step 2 of 3, and then the device totally ignores the store/cache directives, and as far as I can tell, simply takes what is a virtual snapshot of the page from its last state, that is, ignoring what it was told explicitly, and, not only that, taking a page that should not be stored, and storing it without actually checking it again, which leads to all kinds of strange Session issues, among other things.

I'm just adding this in case someone comes along and can't figure out why they are getting session errors with particularly iphones and ipads, which seem by far to be the worst offenders in this area.

I've done fairly extensive debugger testing with this issue, and this is my conclusion, the devices ignore these directives completely.

Even in regular use, I've found that some mobiles also totally fail to check for new versions via say, Expires: 0 then checking last modified dates to determine if it should get a new one.

It simply doesn't happen, so what I was forced to do was add query strings to the css/js files I needed to force updates on, which tricks the stupid mobile devices into thinking it's a file it does not have, like: my.css?v=1, then v=2 for a css/js update. This largely works.

User browsers also, by the way, if left to their defaults, as of 2016, as I continuously discover (we do a LOT of changes and updates to our site) also fail to check for last modified dates on such files, but the query string method fixes that issue. This is something I've noticed with clients and office people who tend to use basic normal user defaults on their browsers, and have no awareness of caching issues with css/js etc, almost invariably fail to get the new css/js on change, which means the defaults for their browsers, mostly MSIE / Firefox, are not doing what they are told to do, they ignore changes and ignore last modified dates and do not validate, even with Expires: 0 set explicitly.

This was a good thread with a lot of good technical information, but it's also important to note how bad the support for this stuff is in particularly mobile devices. Every few months I have to add more layers of protection against their failure to follow the header commands they receive, or to properly interpet those commands.

How to convert php array to utf8?

In case of a PDO connection, the following might help, but the database should be in UTF-8:

$db = new PDO(
    'mysql:host=localhost;dbname=database_name;', 'dbuser', 'dbpassword',
$db->query("SET CHARACTER SET utf8");

Hiding button using jQuery

jQuery offers the .hide() method for this purpose. Simply select the element of your choice and call this method afterward. For example:


One can also determine how fast the transition runs by providing a duration parameter in miliseconds or string (possible values being 'fast', and 'slow'):


In case you want to do something just after the element hid, you must provide a callback as a parameter too:

$('#comanda').hide('fast', function() {
  alert('It is hidden now!');

Check if a string has white space

You can simply use the indexOf method on the input string:

function hasWhiteSpace(s) {
  return s.indexOf(' ') >= 0;

Or you can use the test method, on a simple RegEx:

function hasWhiteSpace(s) {
  return /\s/g.test(s);

This will also check for other white space characters like Tab.

Parsing JSON objects for HTML table

Loop over each object, push in string array and join them. Append in target table, it is better.

$(document).ready(function () {
function (json) {
    var tr=[];
    for (var i = 0; i < json.length; i++) {
        tr.push("<td>" + json[i].User_Name + "</td>");
        tr.push("<td>" + json[i].score + "</td>");
        tr.push("<td>" + json[i].team + "</td>");

Android Studio Run/Debug configuration error: Module not specified

check your build.gradle file and make sure that use apply plugin: '' istead of apply plugin: ''

it worked for me

How do I print bytes as hexadecimal?

This is a modified version of the Nibble to Hex method

void hexArrayToStr(unsigned char* info, unsigned int infoLength, char **buffer) {
    const char* pszNibbleToHex = {"0123456789ABCDEF"};
    int nNibble, i;
    if (infoLength > 0) {
        if (info != NULL) {
            *buffer = (char *) malloc((infoLength * 2) + 1);
            buffer[0][(infoLength * 2)] = 0;
            for (i = 0; i < infoLength; i++) {
                nNibble = info[i] >> 4;
                buffer[0][2 * i] = pszNibbleToHex[nNibble];
                nNibble = info[i] & 0x0F;
                buffer[0][2 * i + 1] = pszNibbleToHex[nNibble];
        } else {
            *buffer = NULL;
    } else {
        *buffer = NULL;

How does the FetchMode work in Spring Data JPA

Spring-jpa creates the query using the entity manager, and Hibernate will ignore the fetch mode if the query was built by the entity manager.

The following is the work around that I used:

  1. Implement a custom repository which inherits from SimpleJpaRepository

  2. Override the method getQuery(Specification<T> spec, Sort sort):

    protected TypedQuery<T> getQuery(Specification<T> spec, Sort sort) { 
        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
        CriteriaQuery<T> query = builder.createQuery(getDomainClass());
        Root<T> root = applySpecificationToCriteria(spec, query);;
        if (sort != null) {
            query.orderBy(toOrders(sort, root, builder));
        return applyRepositoryMethodMetadata(entityManager.createQuery(query));

    In the middle of the method, add applyFetchMode(root); to apply the fetch mode, to make Hibernate create the query with the correct join.

    (Unfortunately we need to copy the whole method and related private methods from the base class because there was no other extension point.)

  3. Implement applyFetchMode:

    private void applyFetchMode(Root<T> root) {
        for (Field field : getDomainClass().getDeclaredFields()) {
            Fetch fetch = field.getAnnotation(Fetch.class);
            if (fetch != null && fetch.value() == FetchMode.JOIN) {
                root.fetch(field.getName(), JoinType.LEFT);

How do you create a hidden div that doesn't create a line break or horizontal space?

Use style="display: none;". Also, you probably don't need to have the DIV, just setting the style to display: none on the checkbox would probably be sufficient.

How to connect to MySQL Database?

you can use Package Manager to add it as package and it is the easiest way to do. You don't need anything else to work with mysql database.

Or you can run below command in Package Manager Console

PM> Install-Package MySql.Data

NUGET Mysql.Data

Tomcat won't stop or restart

It seems Tomcat was actually stopped. I started it and it started fine. Thanks all.

Insert an item into sorted list in Python

You should use the bisect module. Also, the list needs to be sorted before using bisect.insort_left

It's a pretty big difference.

>>> l = [0, 2, 4, 5, 9]
>>> bisect.insort_left(l,8)
>>> l
[0, 2, 4, 5, 8, 9]

timeit.timeit("l.append(8); l = sorted(l)",setup="l = [4,2,0,9,5]; import bisect; l = sorted(l)",number=10000)

timeit.timeit("bisect.insort_left(l,8)",setup="l = [4,2,0,9,5]; import bisect; l=sorted(l)",number=10000)

Naming conventions for Java methods that return boolean

The convention is to ask a question in the name.

Here are a few examples that can be found in the JDK:



That way, the names are read like they would have a question mark on the end.

Is the Collection empty?
Does this Node have children?

And, then, true means yes, and false means no.

Or, you could read it like an assertion:

The Collection is empty.
The node has children

Sometimes you may want to name a method something like createFreshSnapshot?. Without the question mark, the name implies that the method should be creating a snapshot, instead of checking to see if one is required.

In this case you should rethink what you are actually asking. Something like isSnapshotExpired is a much better name, and conveys what the method will tell you when it is called. Following a pattern like this can also help keep more of your functions pure and without side effects.

If you do a Google Search for isEmpty() in the Java API, you get lots of results.

Random row selection in Pandas dataframe

The best way to do this is with the sample function from the random module,

import numpy as np
import pandas as pd
from random import sample

# given data frame df

# create random index
rindex =  np.array(sample(xrange(len(df)), 10))

# get 10 random rows from df
dfr = df.ix[rindex]

ReferenceError: Invalid left-hand side in assignment

You have to use == to compare (or even ===, if you want to compare types). A single = is for assignment.

if (one == 'rock' && two == 'rock') {
    console.log('Tie! Try again!');

Compiling a java program into an executable

You can convert .jar file to .exe on these ways:
alt text

1- JSmooth .exe wrapper:
JSmooth is a Java Executable Wrapper. It creates native Windows launchers (standard .exe) for your java applications. It makes java deployment much smoother and user-friendly, as it is able to find any installed Java VM by itself. When no VM is available, the wrapper can automatically download and install a suitable JVM, or simply display a message or redirect the user to a web site.

JSmooth provides a variety of wrappers for your java application, each of them having their own behaviour: Choose your flavour!


2- JarToExe 1.8
Jar2Exe is a tool to convert jar files into exe files. Following are the main features as describe in their website:

  • Can generate “Console”, “Windows GUI”, “Windows Service” three types of exe files.
  • Generated exe files can add program icons and version information.
  • Generated exe files can encrypt and protect java programs, no temporary files will be generated when program runs.
  • Generated exe files provide system tray icon support.
  • Generated exe files provide record system event log support.
  • Generated windows service exe files are able to install/uninstall itself, and support service pause/continue.
  • New release of x64 version, can create 64 bits executives. (May 18, 2008)
  • Both wizard mode and command line mode supported. (May 18, 2008)


3- Executor
Package your Java application as a jar, and Executor will turn the jar into a Windows exe file, indistinguishable from a native application. Simply double-clicking the exe file will invoke the Java Runtime Environment and launch your application.


EDIT: The above link is broken, but here is the page (with working download) from the Internet Archive.

4- Advanced Installer
Advanced Installer lets you create Windows MSI installs in minutes. This also has Windows Vista support and also helps to create MSI packages in other languages.
Download: Let me know other tools that you have used to convert JAR to EXE.

Get value of Span Text

<script type="text/javascript">
document.getElementById('button1').onChange = function () {
    document.getElementById('hidden_field_id').value = document.getElementById('span_id').innerHTML;

How to add form validation pattern in Angular 2?

custom validation step by step

Html template

  <form [ngFormModel]="demoForm">
  [ngFormControl] ="demoForm.controls['spec']"

 <div class='error' *ngIf="demo.control.touched">
   <div *ngIf="demo.control.hasError('required')"> field  is required.</div>
   <div *ngIf="demo.control.hasError('invalidChar')">Special Characters are not Allowed</div>

Component App.ts

import {Control, ControlGroup, FormBuilder, Validators, NgForm, NgClass} from 'angular2/common';
import {CustomValidator} from '../../yourServices/validatorService';

under class define

 demoForm: ControlGroup;
constructor( @Inject(FormBuilder) private Fb: FormBuilder ) {
    this.demoForm ={
       spec: new Control('', Validators.compose([Validators.required,   CustomValidator.specialCharValidator])),

under {../../yourServices/validatorService.ts}

export class CustomValidator {
    static specialCharValidator(control: Control): { [key: string]: any } {
   if (control.value) {
       if (!control.value.match(/[-!$%^&*()_+|~=`{}\[\]:";#@'<>?,.\/]/)) {            
           return null;
       else {            
           return { 'invalidChar': true };



What are the lengths of Location Coordinates, latitude and longitude?

Google Maps actually uses signed values to represent the position:

  • Latitude : max/min 90.0000000 to -90.0000000

  • Longitude : max/min 180.0000000 to -180.0000000

So if you want to work with Coordinates in your projects you would need DECIMAL(10,7) ie. for SQL.

Gather multiple sets of columns

It's not at all related to "tidyr" and "dplyr", but here's another option to consider: merged.stack from my "splitstackshape" package, V1.4.0 and above.

merged.stack(df, id.vars = c("id", "time"), 
             var.stubs = c("Q3.2.", "Q3.3."),
             sep = "var.stubs")
#     id       time .time_1       Q3.2.       Q3.3.
#  1:  1 2009-01-01      1. -0.62645381  1.35867955
#  2:  1 2009-01-01      2.  1.51178117 -0.16452360
#  3:  1 2009-01-01      3.  0.91897737  0.39810588
#  4:  2 2009-01-02      1.  0.18364332 -0.10278773
#  5:  2 2009-01-02      2.  0.38984324 -0.25336168
#  6:  2 2009-01-02      3.  0.78213630 -0.61202639
#  7:  3 2009-01-03      1. -0.83562861  0.38767161
# <<:::SNIP:::>>
# 24:  8 2009-01-08      3. -1.47075238 -1.04413463
# 25:  9 2009-01-09      1.  0.57578135  1.10002537
# 26:  9 2009-01-09      2.  0.82122120 -0.11234621
# 27:  9 2009-01-09      3. -0.47815006  0.56971963
# 28: 10 2009-01-10      1. -0.30538839  0.76317575
# 29: 10 2009-01-10      2.  0.59390132  0.88110773
# 30: 10 2009-01-10      3.  0.41794156 -0.13505460
#     id       time .time_1       Q3.2.       Q3.3.

ERROR 1064 (42000): You have an error in your SQL syntax;

It is varchar and not var_char


USE courses;

    name VARCHAR(50) NOT NULL,
    addr VARCHAR(255) NOT NULL,
    phone INT NOT NULL

You should use a SQL tool to visualize possbile errors like MySQL Workbench.

Removing App ID from Developer Connection

As @AlexanderN pointed out, you can now delete App IDs.

  1. In your Member Center go to the Certificates, Identifiers & Profiles section.
  2. Go to Identifiers folder.
  3. Select the App ID you want to delete and click Settings
  4. Scroll down and click Delete.

Client to send SOAP request and receive response

So this is my final code after googling for 2 days on how to add a namespace and make soap request along with the SOAP envelope without adding proxy/Service Reference

class Request
    public static void Execute(string XML)
            HttpWebRequest request = CreateWebRequest();
            XmlDocument soapEnvelopeXml = new XmlDocument();

            using (Stream stream = request.GetRequestStream())

            using (WebResponse response = request.GetResponse())
                using (StreamReader rd = new StreamReader(response.GetResponseStream()))
                    string soapResult = rd.ReadToEnd();
        catch (Exception ex)

    private static HttpWebRequest CreateWebRequest()
        string ICMURL = System.Configuration.ConfigurationManager.AppSettings.Get("ICMUrl");
        HttpWebRequest webRequest = null;

            webRequest = (HttpWebRequest)WebRequest.Create(ICMURL);
            webRequest.ContentType = "text/xml;charset=\"utf-8\"";
            webRequest.Accept = "text/xml";
            webRequest.Method = "POST";
        catch (Exception ex)
        return webRequest;

    private static string AddNamespace(string XML)
        string result = string.Empty;

            XmlDocument xdoc = new XmlDocument();

            XmlElement temproot = xdoc.CreateElement("ws", "Request", "");
            temproot.InnerXml = xdoc.DocumentElement.InnerXml;
            result = temproot.OuterXml;

        catch (Exception ex)

        return result;

    private static string AppendEnvelope(string data)
        string head= @"<soapenv:Envelope xmlns:soapenv="""" ><soapenv:Header/><soapenv:Body>";
        string end = @"</soapenv:Body></soapenv:Envelope>";
        return head + data + end;

How to send objects through bundle

You could use the global application state.


Customize and then add this to your AndroidManifest.xml :

<application android:label="@string/app_name" android:debuggable="true" android:name=".CustomApplication"

And then have a class in your project like this :

package com.example;


public class CustomApplication extends Application {
    public int someVariable = -1;

And because "It can be accessed via getApplication() from any Activity or Service", you use it like this:

CustomApplication application = (CustomApplication)getApplication();
application.someVariable = 123; 

Hope that helps.

Rounding integer division (instead of truncating)

I ran into the same difficulty. The code below should work for positive integers.

I haven't compiled it yet but I tested the algorithm on a google spreadsheet (I know, wtf) and it was working.

unsigned int integer_div_round_nearest(unsigned int numerator, unsigned int denominator)
    unsigned int rem;
    unsigned int floor;
    unsigned int denom_div_2;

    // check error cases
    if(denominator == 0)
        return 0;

    if(denominator == 1)
        return numerator;

    // Compute integer division and remainder
    floor = numerator/denominator;
    rem = numerator%denominator;

    // Get the rounded value of the denominator divided by two
    denom_div_2 = denominator/2;

    // If the remainder is bigger than half of the denominator, adjust value
    if(rem >= denom_div_2)
        return floor+1;
        return floor;

select2 changing items dynamically

I've made an example for you showing how this could be done.

Notice the js but also that I changed #value into an input element

<input id="value" type="hidden" style="width:300px"/>

and that I am triggering the change event for getting the initial values

$('#attribute').select2().on('change', function() {

Code Example


In the current version of select2 the class attribute is being transferred from the hidden input into the root element created by select2, even the select2-offscreen class which positions the element way outside the page limits.

To fix this problem all that's needed is to add removeClass('select2-offscreen') before applying select2 a second time on the same element.

$('#attribute').select2().on('change', function() {

I've added a new Code Example to address this issue.

How to change JAVA.HOME for Eclipse/ANT

For me, ant apparently refuses to listen to any configuration for eclipse default, project JDK, and the suggestion of "Ant Home Entries" just didn't have traction - there was nothing there referring to JDK.

However, this works:

Menu "Run" -> "External Tools" -> "External Tools Configuration".
  Goto the node "Ant build", choose the ant buildfile in question.
     Choose tab "JRE".
        Select e.g. "Run in same JRE as workspace", or whatever you want.

How to detect online/offline event cross-browser?

navigator.onLine is a mess

I face this when trying to make an ajax call to the server.

There are several possible situations when the client is offline:

  • the ajax call timouts and you receive error
  • the ajax call returns success, but the msg is null
  • the ajax call is not executed because browser decides so (may be this is when navigator.onLine becomes false after a while)

The solution I am using is to control the status myself with javascript. I set the condition of a successful call, in any other case I assume the client is offline. Something like this:

var offline;
pendingItems.push(item);//add another item for processing
updatePendingInterval = setInterval("tryUpdatePending()",30000);

    function tryUpdatePending() {

        offline = setTimeout("$('#offline').show()", 10000);
        $.ajax({ data: JSON.stringify({ items: pendingItems }), url: "WebMethods.aspx/UpdatePendingItems", type: "POST", dataType: "json", contentType: "application/json; charset=utf-8",
          success: function (msg) {
            if ((!msg) || msg.d != "ok")
            pending = new Array(); //empty the pending array

How to get full file path from file name?

You Can use:

string path = Path.GetFullPath(FileName);

it will return the Full path of that mentioned file.

How to skip "are you sure Y/N" when deleting files in batch files

You have the following options on Windows command line:

net use [DeviceName [/home[{Password | *}] [/delete:{yes | no}]]

Try like:

net use H: /delete /y

How to enable bulk permission in SQL Server

Try this:

USE master;


python pip on Windows - command 'cl.exe' failed

I was facing the same problem with visual studio 2017.

you can find cl.exe in C:\Program Files(x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023\bin\Hostx86\x86.

just set the environment variable as the able address and run the command in anaconda, it worked for me.

What is perm space?

What exists under PremGen : Class Area comes under PremGen area. Static fields are also developed at class loading time, so they also exist in PremGen. Constant Pool area having all immutable fields that are pooled like String are kept here. In addition to that, class data loaded by class loaders, Object arrays, internal objects used by jvm are also located.

Best C++ IDE or Editor for Windows

VIsual studio is by far the best IDE but you can also take a look at Code::Blocks

No 'Access-Control-Allow-Origin' header is present on the requested resource- AngularJS

Use this extension for chrome. Allows to you request any site with ajax from any source. Adds to response 'Allow-Control-Allow-Origin: *' header

How to prevent favicon.ico requests?

The easiest way to block these temporarily for testing purposes is to open up the inspect page in chrome by right-clicking anywhere on the page and clicking inspect or by pressing Ctrl+Shift+j and then going to the networking tab and then reloading the page which will send all the requests your page is supposed to make including that annoying favicon.ico. You can now simply right click the favicon.ico request and click "Block request URL".

screenshot of blocking a specific request URL for Chrome browser

All of the above answers are for devs who control the app source code. If you are a sysadmin, who's figuring our load-balancer or proxying configuration and is annoyed by this favicon.ico shenanigans, this simple trick does a better job. This answer is for Chrome, but I think there should be a similar alternative which you would figure out for Firefox/Opera/Tor/any other browser :)

How to make background of table cell transparent

Transparent background will help you see what behind the element, in this case what behind your td is in fact the parent table. So we have no way to achieve what you want using pure CSS. Even using script can't solve it in a direct way. We can just have a workaround using script based on the idea of using the same background for both the body and the td. However we have to update the background-position accordingly whenver the window is resized. Here is the code you can use with the default background position of body (which is left top, otherwise you have to change the code to update the background-position of the td correctly):


<table id = "MainTable">
    <td width = "20%"></td>
    <td width = "80%" id='test'>
        <tr><td>something interesting here</td></tr>
        <tr><td>another thing also interesting out there</td></tr>


/* use the same background for the td #test and the body */
#test {
body {

JS (better use jQuery):

//code placed in onload event handler
function updateBackgroundPos(){
  var pos = $('#test').offset();
                            -pos.left + 'px' + " " + ( + 'px'));


Try resizing the viewport, you'll see the background-position updated correctly, which will make an effect looking like the background of the td is transparent to the body.

How do I enable php to work with postgresql?

I have to add in httpd.conf this line (Windows):

LoadFile "C:/Program Files (x86)/PostgreSQL/8.3/bin/libpq.dll"

How get total sum from input box values using Javascript?

I need to sum the span elements so I edited Akhil Sekharan's answer below.

var arr = document.querySelectorAll('span[id^="score"]');
var total=0;
    for(var i=0;i<arr.length;i++){
            total+= parseInt(arr[i].innerHTML);

You can change the elements with other elements link will guide you with editing.

Docker: "no matching manifest for windows/amd64 in the manifest list entries"

You need to pull with the Linux platform first, then you can run on Windows:

docker pull --platform linux php
docker run -it php

See blog post Docker for Windows Desktop 18.02 with Windows 10 Fall Creators Update.

Unzip a file with php

Please, don't do it like that (passing GET var to be a part of a system call). Use ZipArchive instead.

So, your code should look like:

$zipArchive = new ZipArchive();
$result = $zipArchive->open($_GET["master"]);
if ($result === TRUE) {
    $zipArchive ->extractTo("my_dir");
    $zipArchive ->close();
    // Do something else on success
} else {
    // Do something on error

And to answer your question, your error is 'something $var something else' should be "something $var something else" (in double quotes).

URL Encoding using C#

Edit: Note that this answer is now out of date. See Siarhei Kuchuk's answer below for a better fix

UrlEncoding will do what you are suggesting here. With C#, you simply use HttpUtility, as mentioned.

You can also Regex the illegal characters and then replace, but this gets far more complex, as you will have to have some form of state machine (switch ... case, for example) to replace with the correct characters. Since UrlEncode does this up front, it is rather easy.

As for Linux versus windows, there are some characters that are acceptable in Linux that are not in Windows, but I would not worry about that, as the folder name can be returned by decoding the Url string, using UrlDecode, so you can round trip the changes.

Relative imports - ModuleNotFoundError: No module named x

TL;DR: You can't do relative imports from the file you execute since __main__ module is not a part of a package.

Absolute imports - import something available on sys.path

Relative imports - import something relative to the current module, must be a part of a package

If you're running both variants in exactly the same way, one of them should work. Here is an example that should help you understand what's going on. Let's add another file with the overall directory structure like this:


And let's update to see what's going on:

debug = True

    # Trying to find module in the parent package
    from . import config
    del config
except ImportError:
    print('Relative import failed')

    # Trying to find module on sys.path
    import config
except ModuleNotFoundError:
    print('Absolute import failed')
import ryan.test

Let's run first:

$ python ryan/
Relative import failed

Here "test" is the __main__ module and doesn't know anything about belonging to a package. However import config should work, since the ryan folder will be added to sys.path.

Let's run instead:

$ python
Absolute import failed

And here test is inside of the "ryan" package and can perform relative imports. import config fails since implicit relative imports are not allowed in Python 3.

Hope this helped.

P.S.: If you're sticking with Python 3 there is no more need for files.

How to create a .NET DateTime from ISO 8601 format

DateTime.ParseExact(...) allows you to tell the parser what each character represents.

Convert Year/Month/Day to Day of Year in Python

If you have reason to avoid the use of the datetime module, then these functions will work.

def is_leap_year(year):
    """ if year is a leap year return True
        else return False """
    if year % 100 == 0:
        return year % 400 == 0
    return year % 4 == 0

def doy(Y,M,D):
    """ given year, month, day return day of year
        Astronomical Algorithms, Jean Meeus, 2d ed, 1998, chap 7 """
    if is_leap_year(Y):
        K = 1
        K = 2
    N = int((275 * M) / 9.0) - K * int((M + 9) / 12.0) + D - 30
    return N

def ymd(Y,N):
    """ given year = Y and day of year = N, return year, month, day
        Astronomical Algorithms, Jean Meeus, 2d ed, 1998, chap 7 """    
    if is_leap_year(Y):
        K = 1
        K = 2
    M = int((9 * (K + N)) / 275.0 + 0.98)
    if N < 32:
        M = 1
    D = N - int((275 * M) / 9.0) + K * int((M + 9) / 12.0) + 30
    return Y, M, D

Is there a way to @Autowire a bean that requires constructor arguments?

An alternative would be instead of passing the parameters to the constructor you might have them as getter and setters and then in a @PostConstruct initialize the values as you want. In this case Spring will create the bean using the default constructor. An example is below

public class MyConstructorClass{

  String var;

  public void setVar(String var){
     this.var = var;

  public void getVar(){
    return var;

  public void init(){

public class MyBeanService{
  //field autowiring
  MyConstructorClass myConstructorClass;


Can you get a Windows (AD) username in PHP?

No. But what you can do is have your Active Directory admin enable LDAP so that users can maintain one set of credentials

Most efficient way to check if a file is empty in Java on Windows

Try FileReader, this reader is meant to read stream of character, while FileInputStream is meant to read raw data.

From the Javadoc:

FileReader is meant for reading streams of characters. For reading streams of raw bytes, consider using a FileInputStream.

Since you wanna read a log file, FileReader is the class to use IMO.

How to compile .c file with OpenSSL includes?

You need to include the library path (-L/usr/local/lib/)

gcc -o Opentest Opentest.c -L/usr/local/lib/ -lssl -lcrypto

It works for me.

XSD - how to allow elements in any order any number of times?

You should find that the following schema allows the what you have proposed.

  <xs:element name="foo">
      <xs:sequence minOccurs="0" maxOccurs="unbounded">
          <xs:element maxOccurs="unbounded" name="child1" type="xs:unsignedByte" />
          <xs:element maxOccurs="unbounded" name="child2" type="xs:string" />

This will allow you to create a file such as:

<?xml version="1.0" encoding="utf-8" ?>

Which seems to match your question.

Can I remove the URL from my print css, so the web address doesn't print?

I am not sure but the URL is added by a browser when you want to print. It is not part of the page so can not be affected by CSS. Maybe there is a way but it will be browser dependent.

Excel function to get first word from sentence in other cell

A1                   A2 
Toronto<b> is nice   =LEFT(A1,(FIND("<",A1,1)-1))

Not sure if the syntax is correct but the forumla in A2 will work for you,

How to check if variable is array?... or something array-like

You can check instance of Traversable with a simple function. This would work for all this of Iterator because Iterator extends Traversable

function canLoop($mixed) {
    return is_array($mixed) || $mixed instanceof Traversable ? true : false;

How can I create a temp file with a specific extension with .NET?

I think you should try this:

string path = Path.GetRandomFileName();
path = Path.Combine(@"c:\temp", path);
path = Path.ChangeExtension(path, ".tmp");

It generates a unique filename and creates a file with that file name at a specified location.

checked = "checked" vs checked = true

The element has both an attribute and a property named checked. The property determines the current state.

The attribute is a string, and the property is a boolean. When the element is created from the HTML code, the attribute is set from the markup, and the property is set depending on the value of the attribute.

If there is no value for the attribute in the markup, the attribute becomes null, but the property is always either true or false, so it becomes false.

When you set the property, you should use a boolean value:

document.getElementById('myRadio').checked = true;

If you set the attribute, you use a string:

document.getElementById('myRadio').setAttribute('checked', 'checked');

Note that setting the attribute also changes the property, but setting the property doesn't change the attribute.

Note also that whatever value you set the attribute to, the property becomes true. Even if you use an empty string or null, setting the attribute means that it's checked. Use removeAttribute to uncheck the element using the attribute:


Passing a variable to a powershell script via command line

Declare the parameter in test.ps1:

                [switch]$force = $false

Run the script from Run OR Windows Task Scheduler:

powershell.exe -command "& C:\FTP_DATA\test.ps1 -input_dir C:\FTP_DATA\IN -output_dir C:\FTP_DATA\OUT"


 powershell.exe -command "& 'C:\FTP DATA\test.ps1' -input_dir 'C:\FTP DATA\IN' -output_dir 'C:\FTP DATA\OUT'"

Using :before and :after CSS selector to insert Html

content doesn't support HTML, only text. You should probably use javascript, jQuery or something like that.

Another problem with your code is " inside a " block. You should mix ' and " (class='headingDetail').

If content did support HTML you could end up in an infinite loop where content is added inside content.

How to get the focused element with jQuery?

$( document.activeElement )

Will retrieve it without having to search the whole DOM tree as recommended on the jQuery documentation

Asking the user for input until they give a valid response

Try this one:-

def takeInput(required):
  print 'ooo or OOO to exit'
  ans = raw_input('Enter: ')

  if not ans:
      print "You entered nothing...!"
      return takeInput(required) 

      ##  FOR Exit  ## 
  elif ans in ['ooo', 'OOO']:
    print "Closing instance."

    if ans.isdigit():
      current = 'int'
    elif set('[~!@#$%^&*()_+{}":/\']+$').intersection(ans):
      current = 'other'
    elif isinstance(ans,basestring):
      current = 'str'        
      current = 'none'

  if required == current :
    return ans
    return takeInput(required)

## pass the value in which type you want [str/int/special character(as other )]
print "input: ", takeInput('str')

SQL update trigger only when column is modified

Whenever a record has updated a record is "deleted". Here is my example:

ALTER TRIGGER [dbo].[UpdatePhyDate]
   ON  [dbo].[M_ContractDT1]
    -- on ContarctDT1 PhyQty is updated 
    -- I want system date in Phytate automatically saved

    declare @dt1ky as int   

        select @dt1ky = dt1ky from deleted

        update M_ContractDT1 set PhyDate=GETDATE() where Dt1Ky=  @dt1ky     



It works fine

Regex lookahead, lookbehind and atomic groups

Lookarounds are zero width assertions. They check for a regex (towards right or left of the current position - based on ahead or behind), succeeds or fails when a match is found (based on if it is positive or negative) and discards the matched portion. They don't consume any character - the matching for regex following them (if any), will start at the same cursor position.

Read for more details.

  • Positive lookahead:



Match only if REGEX_1 matches; after matching REGEX_1, the match is discarded and searching for REGEX_2 starts at the same position.



REGEX_1 is [a-z0-9]{4}$ which matches four alphanumeric chars followed by end of line.
REGEX_2 is [a-z]{1,2}[0-9]{2,3} which matches one or two letters followed by two or three digits.

REGEX_1 makes sure that the length of string is indeed 4, but doesn't consume any characters so that search for REGEX_2 starts at the same location. Now REGEX_2 makes sure that the string matches some other rules. Without look-ahead it would match strings of length three or five.

  • Negative lookahead



Match only if REGEX_1 does not match; after checking REGEX_1, the search for REGEX_2 starts at the same position.



The look-ahead part checks for the FWORD in the string and fails if it finds it. If it doesn't find FWORD, the look-ahead succeeds and the following part verifies that the string's length is between 10 and 30 and that it contains only word characters a-zA-Z0-9_

Look-behind is similar to look-ahead: it just looks behind the current cursor position. Some regex flavors like javascript doesn't support look-behind assertions. And most flavors that support it (PHP, Python etc) require that look-behind portion to have a fixed length.

  • Atomic groups basically discards/forgets the subsequent tokens in the group once a token matches. Check this page for examples of atomic groups

Jump to function definition in vim

Another common technique is to place the function name in the first column. This allows the definition to be found with a simple search.

main(int argc, char *argv[])

The above function could then be found with /^main inside the file or with :grep -r '^main' *.c in a directory. As long as code is properly indented the only time the identifier will occur at the beginning of a line is at the function definition.

Of course, if you aren't using ctags from this point on you should be ashamed of yourself! However, I find this coding standard a helpful addition as well.

VSCode single to double quote automatic replace

For JSX use:

{"jsxSingleQuote": false}

JavaScript: Object Rename Key

const data = res
const lista = []
let newElement: any

if (data && data.length > 0) {

  data.forEach(element => {
      newElement = element

      Object.entries(newElement).map(([key, value]) =>
        Object.assign(newElement, {
          [key.toLowerCase()]: value
        }, delete newElement[key], delete newElement['_id'])
return lista

Python Socket Multiple Clients

def get_clients():
    first_run = True
    startMainMenu = False

    while True:
        if first_run:
            global done
            done = False
            Thread(target=animate, args=("Waiting For Connection",)).start()

        Client, address = objSocket.accept()
        global menuIsOn
        if menuIsOn:
            menuIsOn = False  # will stop main menu
            startMainMenu = True

        done = True

        # Get Current Directory in Client Machine
        current_client_directory = Client.recv(1024).decode("utf-8", errors="ignore")

        # beep on connection
        print(f"{bcolors.OKBLUE}\n***** Incoming Connection *****{bcolors.OKGREEN}")
        print('* Connected to: ' + address[0] + ':' + str(address[1]))
            get_client_info(Client, first_run)
        except Exception as e:
            print("Error data received is not a json!")
        now =
        current_time = now.strftime("%D %H:%M:%S")
        print("* Current Time =", current_time)

        print("* Current Folder in Client: " + current_client_directory + bcolors.WARNING)



        if first_run:
            Thread(target=threaded_main_menu, daemon=True).start()

            first_run = False
            print(f"{bcolors.OKBLUE}* Hit Enter To Continue.{bcolors.WARNING}\n#>", end="")
        if startMainMenu == True:
            Thread(target=threaded_main_menu, daemon=True).start()
            startMainMenu = False

Vue 'export default' vs 'new Vue'

export default is used to create local registration for Vue component.

Here is a great article that explain more about components

how to convert string to numerical values in mongodb

MongoDB aggregation not allowed to change existing data type of given fields. In this case you should create some programming code to convert string to int. Check below code

db.collectionName.find().forEach(function(data) {
        "_id": data._id,
        "moop": data.moop
    }, {
        "$set": {
            "PartnerID": parseInt(data.PartnerID)

If your collections size more then above script will slow down the performance, for perfomace mongo provide mongo bulk operations, using mongo bulk operations also updated data type

var bulk = db.collectionName.initializeOrderedBulkOp();
var counter = 0;
db.collectionName.find().forEach(function(data) {
    var updoc = {
        "$set": {}
    var myKey = "PartnerID";
    updoc["$set"][myKey] = parseInt(data.PartnerID);
    // queue the update
        "_id": data._id
    // Drain and re-initialize every 1000 update statements
    if (counter % 1000 == 0) {
        bulk = db.collectionName.initializeOrderedBulkOp();
    // Add the rest in the queue
if (counter % 1000 != 0) bulk.execute();

This basically reduces the amount of operations statements sent to the sever to only sending once every 1000 queued operations.

How to go up a level in the src path of a URL in HTML?

Here is all you need to know about relative file paths:

  • Starting with / returns to the root directory and starts there

  • Starting with ../ moves one directory backward and starts there

  • Starting with ../../ moves two directories backward and starts there (and so on...)

  • To move forward, just start with the first sub directory and keep moving forward.

Click here for more details!

td widths, not working?

You can use within <td> tag css : display:inline-block

Like: <td style="display:inline-block">

preg_match in JavaScript?

Some Googling brought me to this :

function preg_match (regex, str) {
  return (new RegExp(regex).test(str))
console.log(preg_match("^[a-zA-Z0-9._-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,6}$","[email protected]"))

See for more info.

View tabular file such as CSV from command line

I wrote this to format CSVs from the command line, this reads the entire file to figure out the optimal width of each column (requires perl, assumes there are no commas in fields, also uses less):


perl -we '
  sub max( @ ) {
    my $max = shift;

    map { $max = $_ if $_ > $max } @_;
    return $max;

  sub transpose( @ ) {
    my @matrix = @_;
    my $width  = scalar @{ $matrix[ 0 ] };
    my $height = scalar @matrix;

    return map { my $x = $_; [ map { $matrix[ $_ ][ $x ] } 0 .. $height - 1 ] } 0 .. $width - 1;

  # Read all lines, as arrays of fields
  my @lines = map { s/\r?\n$//; [ split /,/ ] } ;

  my $widths =
    # Build a pack expression based on column lengths
    join "",

    # For each column get the longest length plus 1
    map { 'A' . ( 1 + max map { length } @$_ ) }

    # Get arrays of columns


  # Format all lines with pack
  map { print pack( $widths, @$_ ) . "\n" } @lines;
' $1 | less -NS

When is JavaScript synchronous?

To someone who really understands how JS works this question might seem off, however most people who use JS do not have such a deep level of insight (and don't necessarily need it) and to them this is a fairly confusing point, I will try to answer from that perspective.

JS is synchronous in the way its code is executed. each line only runs after the line before it has completed and if that line calls a function after that is complete etc...

The main point of confusion arises from the fact that your browser is able to tell JS to execute more code at anytime (similar to how you can execute more JS code on a page from the console). As an example JS has Callback functions who's purpose is to allow JS to BEHAVE asynchronously so further parts of JS can run while waiting for a JS function that has been executed (I.E. a GET call) to return back an answer, JS will continue to run until the browser has an answer at that point the event loop (browser) will execute the JS code that calls the callback function.

Since the event loop (browser) can input more JS to be executed at any point in that sense JS is asynchronous (the primary things that will cause a browser to input JS code are timeouts, callbacks and events)

I hope this is clear enough to be helpful to somebody.

jquery .live('click') vs .click()

There might be times when you explicitly want to only assign the click handler to objects which already exist, and handle new objects differently. But more commonly, live doesn't always work. It doesn't work with chained jQuery statements such as:


It needs a selector to work properly because of the way events bubble up the DOM tree.

Edit: Someone just upvoted this, so obviously people are still looking at it. I should point out that live and bind are both deprecated. You can perform both with .on(), which IMO is a much clearer syntax. To replace bind:

$(selector).on('click', function () {

and to replace live:

$(document).on('click', selector, function () {

Instead of using $(document), you can use any jQuery object which contains all the elements you're monitoring the clicks on, but the corresponding element must exist when you call it.

VS 2017 Git Local Commit DB.lock error on every commit

For me steps below helped:

  • Close Visual Studio 2019
  • Delete .vs folder in the Project
  • Reopen the Project, .vs folder is automatically created
  • Done

Bootstrap 3 Horizontal Divider (not in a dropdown)

As I found the default Bootstrap <hr/> size unsightly, here's some simple HTML and CSS to balance out the element visually:


<hr class="half-rule"/>


.half-rule { 
    margin-left: 0;
    text-align: left;
    width: 50%;

How can I run another application within a panel of my C# program?

I notice that all the prior answers use older Win32 User library functions to accomplish this. I think this will work in most cases, but will work less reliably over time.

Now, not having done this, I can't tell you how well it will work, but I do know that a current Windows technology might be a better solution: the Desktop Windows Manager API.

DWM is the same technology that lets you see live thumbnail previews of apps using the taskbar and task switcher UI. I believe it is closely related to Remote Terminal services.

I think that a probable problem that might happen when you force an app to be a child of a parent window that is not the desktop window is that some application developers will make assumptions about the device context (DC), pointer (mouse) position, screen widths, etc., which may cause erratic or problematic behavior when it is "embedded" in the main window.

I suspect that you can largely eliminate these problems by relying on DWM to help you manage the translations necessary to have an application's windows reliably be presented and interacted with inside another application's container window.

The documentation assumes C++ programming, but I found one person who has produced what he claims is an open source C# wrapper library: The post is old, and the source is not on a big repository like GitHub, bitbucket, or sourceforge, so I don't know how current it is.

Eclipse: The resource is not on the build path of a Java project

You can add the src folder to build path by:

  1. Select Java perspective.
  2. Right click on src folder.
  3. Select Build Path > Use a source folder.

And you are done. Hope this help.

EDIT: Refer to the Eclipse documentation

generate random string for div id

I really like this function:

function guidGenerator() {
    var S4 = function() {
       return (((1+Math.random())*0x10000)|0).toString(16).substring(1);
    return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4());

From Create GUID / UUID in JavaScript?

Converting a Date object to a calendar object

Here's your method:

public static Calendar toCalendar(Date date){ 
  Calendar cal = Calendar.getInstance();
  return cal;

Everything else you are doing is both wrong and unnecessary.

BTW, Java Naming conventions suggest that method names start with a lower case letter, so it should be: dateToCalendar or toCalendar (as shown).

OK, let's milk your code, shall we?

DateFormat formatter = new SimpleDateFormat("yyyyMMdd");
date = (Date)formatter.parse(date.toString()); 

DateFormat is used to convert Strings to Dates (parse()) or Dates to Strings (format()). You are using it to parse the String representation of a Date back to a Date. This can't be right, can it?

Get the current language in device

My solution is like this

public String getCurrentLocale2() {
    return Resources.getSystem().getConfiguration().locale.getLanguage();

public Locale getCurrentLocale() {
    return Resources.getSystem().getConfiguration().getLocales().get(0);

and then

                Log.e("Locale", getCurrentLocale().getLanguage());
            } else {
                Log.e("Locale", getCurrentLocale2().toString());

shown ---> en

div hover background-color change?

if you want the color to change when you have simply add the :hover pseudo

div.e:hover {

Android - Best and safe way to stop thread

You should make your thread support interrupts. Basically, you can call yourThread.interrupt() to stop the thread and, in your run() method you'd need to periodically check the status of Thread.interrupted()

There is a good tutorial here.

What is the order of precedence for CSS?

First of all, based on your @extend directive, it seems you're not using pure CSS, but a preprocessor such as SASS os Stylus.

Now, when we talk about "order of precedence" in CSS, there is a general rule involved: whatever rules set after other rules (in a top-down fashion) are applied. In your case, just by specifying .smallbox after .smallbox-paysummary you would be able to change the precedence of your rules.

However, if you wanna go a bit further, I suggest this reading: CSS cascade W3C specification. You will find that the precedence of a rule is based on:

  1. The current media type;
  2. Importance;
  3. Origin;
  4. Specificity of the selector, and finally our well-known rule:
  5. Which one is latter specified.

Can I execute a function after setState is finished updating?

With hooks in React 16.8 onward, it's easy to do this with useEffect

I've created a CodeSandbox to demonstrate this.

useEffect(() => {
  // code to be run when state variables in
  // dependency array changes
}, [stateVariables, thatShould, triggerChange])

Basically, useEffect synchronises with state changes and this can be used to render the canvas

import React, { useState, useEffect, useRef } from "react";
import { Stage, Shape } from "@createjs/easeljs";
import "./styles.css";

export default function App() {
  const [rows, setRows] = useState(10);
  const [columns, setColumns] = useState(10);
  let stage = useRef()

  useEffect(() => {
    stage.current = new Stage("canvas");
    var rectangles = [];
    var rectangle;
    for (var x = 0; x < rows; x++) {
      // Columns
      for (var y = 0; y < columns; y++) {
        var color = "Green";
        rectangle = new Shape();;, 0, 32, 44);
        rectangle.x = y * 33;
        rectangle.y = x * 45;


        var id = rectangle.x + "_" + rectangle.y;
        rectangles[id] = rectangle;
  }, [rows, columns]);

  return (
      <div className="canvas-wrapper">
        <canvas id="canvas" width="400" height="300"></canvas>
        <p>Rows: {rows}</p>
        <p>Columns: {columns}</p>
      <div className="array-form">
          <label>Number of Rows</label>
            onChange={(e) => setRows(}
          <label>Number of Columns</label>
            onChange={(e) => setColumns(}

const getOptions = () => {
  const options = [1, 2, 5, 10, 12, 15, 20];
  return (
      { => (
        <option key={option} value={option}>

Passing vector by reference

You can pass the container by reference in order to modify it in the function. What other answers haven’t addressed is that std::vector does not have a push_front member function. You can use the insert() member function on vector for O(n) insertion:

void do_something(int el, std::vector<int> &arr){
    arr.insert(arr.begin(), el);

Or use std::deque instead for amortised O(1) insertion:

void do_something(int el, std::deque<int> &arr){

Apply multiple functions to multiple groupby columns

New in version 0.25.0.

To support column-specific aggregation with control over the output column names, pandas accepts the special syntax in GroupBy.agg(), known as “named aggregation”, where

  • The keywords are the output column names
  • The values are tuples whose first element is the column to select and the second element is the aggregation to apply to that column. Pandas provides the pandas.NamedAgg namedtuple with the fields ['column', 'aggfunc'] to make it clearer what the arguments are. As usual, the aggregation can be a callable or a string alias.
    In [79]: animals = pd.DataFrame({'kind': ['cat', 'dog', 'cat', 'dog'],
       ....:                         'height': [9.1, 6.0, 9.5, 34.0],
       ....:                         'weight': [7.9, 7.5, 9.9, 198.0]})

    In [80]: animals
      kind  height  weight
    0  cat     9.1     7.9
    1  dog     6.0     7.5
    2  cat     9.5     9.9
    3  dog    34.0   198.0

    In [81]: animals.groupby("kind").agg(
       ....:     min_height=pd.NamedAgg(column='height', aggfunc='min'),
       ....:     max_height=pd.NamedAgg(column='height', aggfunc='max'),
       ....:     average_weight=pd.NamedAgg(column='weight', aggfunc=np.mean),
       ....: )
          min_height  max_height  average_weight
    cat          9.1         9.5            8.90
    dog          6.0        34.0          102.75

pandas.NamedAgg is just a namedtuple. Plain tuples are allowed as well.

    In [82]: animals.groupby("kind").agg(
       ....:     min_height=('height', 'min'),
       ....:     max_height=('height', 'max'),
       ....:     average_weight=('weight', np.mean),
       ....: )
          min_height  max_height  average_weight
    cat          9.1         9.5            8.90
    dog          6.0        34.0          102.75

Additional keyword arguments are not passed through to the aggregation functions. Only pairs of (column, aggfunc) should be passed as **kwargs. If your aggregation functions requires additional arguments, partially apply them with functools.partial().

Named aggregation is also valid for Series groupby aggregations. In this case there’s no column selection, so the values are just the functions.

    In [84]: animals.groupby("kind").height.agg(
       ....:     min_height='min',
       ....:     max_height='max',
       ....: )
          min_height  max_height
    cat          9.1         9.5
    dog          6.0        34.0

How to upload folders on GitHub

I've just gone through that process again. Always end up cloning the repo locally, upload the folder I want to have in that repo to that cloned location, commit the changes and then push it.

Note that if you're dealing with large files, you'll need to consider using something like Git LFS.

Integrate ZXing in Android Studio

this tutorial help me to integrate to android studio: if down try THIS

just add to AndroidManifest.xml

         android:windowSoftInputMode="stateAlwaysHidden" >
             <action android:name="" />
             <category android:name="android.intent.category.DEFAULT" />

Hope this help!.

base_url() function not working in codeigniter

Question -I wanted to load my css file but it was not working even though i autoload and manual laod why ? i found the solution => here is my solution : application>config>config.php $config['base_url'] = 'http://localhost/CodeIgniter/'; //paste the link to base url

question explanation:

" > i had my bootstrap.min.css file inside assets/css folder where assets is root directory which i was created.But it was not working even though when i loaded ? 1. $autoload['helper'] = array('url'); 2. $this->load->helper('url'); in my controllar then i go to my

Why Doesn't C# Allow Static Methods to Implement an Interface?

When a class implements an interface,it is creating instance for the interface members. While a static type doesnt have an instance,there is no point in having static signatures in an interface.

laravel Unable to prepare route ... for serialization. Uses Closure

If none of your routes contain closures, but you are still getting this error, please check


Laravel has a default auth api route in the above file.

Route::middleware('auth:api')->get('/user', function (Request $request) {
    return $request->user();

which can be commented or replaced with a call to controller method if required.

virtualbox Raw-mode is unavailable courtesy of Hyper-V windows 10

In my case, the problem was with the specific box I was trying to use ubuntu/xenial64, I just had to switch to centos/7 and all those errors disappeared.

Hope this helps someone.

Datetime format Issue: String was not recognized as a valid DateTime

try this:

string strTime = "04/30/2013 23:00";
DateTime dtTime;
if(DateTime.TryParseExact(strTime, "MM/dd/yyyy HH:mm",  
   System.Globalization.DateTimeStyles.None, out dtTime))

MVC pattern on Android

Model View Controller (MVC)

enter image description here


  • When we have to main large projects in the software development, MVC is generally used because it’s a universal way of organizing the projects.
  • New developers can quickly adapt to the project
  • Helps in development of big projects and cross platform too.

The MVC pattern is essentially this:

  • Model: What to display. This can be the data source (Ex: Server, Raw data in the app)
  • View: How it’s displayed. This can be the xml. It is thus acting as a presentation filter. A view is attached to its model (or model part) and gets the data necessary for the presentation.
  • Controller: Handling events like user input. This be the activity

Important feature of MVC: We can modify Either the Model or View or Controller still not affecting the other ones

  • Say we change the color in the view, size of the view or the position of the view. By doing so it won’t affect the model or the controller
  • Say we change the model (instead of data fetched from the server fetch data from assets ) still it won’t affect the view and controller
  • Say we change the Controller(Logic in the activity) it won’t affect the model and the view

:last-child not working as expected?

:last-child will not work if the element is not the VERY LAST element

In addition to Harry's answer, I think it's crucial to add/emphasize that :last-child will not work if the element is not the VERY LAST element in a container. For whatever reason it took me hours to realize that, and even though Harry's answer is very thorough I couldn't extract that information from "The last-child selector is used to select the last child element of a parent."

Suppose this is my selector: a:last-child {}

This works:

    <a>This will be selected</a>

This doesn't:

    <a>This will no longer be selected</a>
    <div>This is now the last child :'( </div>

It doesn't because the a element is not the last element inside its parent.

It may be obvious, but it was not for me...

How to select only 1 row from oracle sql?

The answer is:

You should use nested query as:


=> In PL/SQL "ROWNUM = 1" is NOT equal to "TOP 1" of TSQL.

So you can't use a query like this: "select * from any_table_x where rownum=1 order by any_column_x;" Because oracle gets first row then applies order by clause.

How to redirect both stdout and stderr to a file

If you want to log to the same file:

command1 >> log_file 2>&1

If you want different files:

command1 >> log_file 2>> err_file

Checking if a variable is not nil and not zero in ruby

unless [nil, 0].include?(discount) 
  # ...

Get a CSS value with JavaScript

Cross-browser solution to checking CSS values without DOM manipulation:

function get_style_rule_value(selector, style)
 for (var i = 0; i < document.styleSheets.length; i++)
  var mysheet = document.styleSheets[i];
  var myrules = mysheet.cssRules ? mysheet.cssRules : mysheet.rules;

  for (var j = 0; j < myrules.length; j++)
   if (myrules[j].selectorText && myrules[j].selectorText.toLowerCase() === selector)
    return myrules[j].style[style];


get_style_rule_value('.chart-color', 'backgroundColor')

Sanitized version (forces selector input to lowercase, and allows for use case without leading ".")

function get_style_rule_value(selector, style)
 var selector_compare=selector.toLowerCase();
 var selector_compare2= selector_compare.substr(0,1)==='.' ?  selector_compare.substr(1) : '.'+selector_compare;

 for (var i = 0; i < document.styleSheets.length; i++)
  var mysheet = document.styleSheets[i];
  var myrules = mysheet.cssRules ? mysheet.cssRules : mysheet.rules;

  for (var j = 0; j < myrules.length; j++)
    if (myrules[j].selectorText)
     var check = myrules[j].selectorText.toLowerCase();
     switch (check)
      case selector_compare  :
      case selector_compare2 : return myrules[j].style[style];

Go to Matching Brace in Visual Studio?

On my Dutch (Belgian) keyboard, it's CTRL + ^.

Read only file system on Android

it sames that must extract and repack initrc.img and edit init file with the code of mount /system

Uncaught ReferenceError: $ is not defined

If you are doing this in .Net and have the script file referenced properly and you jQuery looks fine, make sure that your users have access to the script file. The project I was working on (a coworker) had their web.config denying access to anonymous users. The page I was working on was accessible to anonymous users therefore they didn't have access to the script file. Dropped the following into the web.config and all was right in the world:

  <location path="Scripts">
        <allow users="*"/>

FirebaseInstanceIdService is deprecated

getInstance().getInstanceId() is also now deprecated and FirebaseMessaging is being used now.

FirebaseMessaging.getInstance().token.addOnCompleteListener { task ->
    if (task.isSuccessful) {
        val token = task.result
    } else {

Platform.runLater and Task in JavaFX

  • Platform.runLater: If you need to update a GUI component from a non-GUI thread, you can use that to put your update in a queue and it will be handled by the GUI thread as soon as possible.
  • Task implements the Worker interface which is used when you need to run a long task outside the GUI thread (to avoid freezing your application) but still need to interact with the GUI at some stage.

If you are familiar with Swing, the former is equivalent to SwingUtilities.invokeLater and the latter to the concept of SwingWorker.

The javadoc of Task gives many examples which should clarify how they can be used. You can also refer to the tutorial on concurrency. cannot open shared object file

I had to do the following (in Kubuntu 16.04.3):

  1. Install the libraries: sudo apt-get install libaio1 libaio-dev
  2. Find where the library is installed: sudo find / -iname 'libaio.a' -type f --> resulted in /usr/lib/x86_64-linux-gnu/libaio.a
  3. Add result to environment variable: export LD_LIBRARY_PATH="/usr/lib/oracle/12.2/client64/lib:/usr/lib/x86_64-linux-gnu"

Clearing all cookies with JavaScript

If you have access to the jquery.cookie plugin, you can erase all cookies this way:

for (var it in $.cookie()) $.removeCookie(it);

Find a file by name in Visual Studio Code

Press Ctl+T will open a search box. Delete # symbol and enter your file name.

reading a line from ifstream into a string variable

Use the std::getline() from <string>.

 istream & getline(istream & is,std::string& str)

So, for your case it would be:


Press any key to continue

I've created a little Powershell function to emulate MSDOS pause. This handles whether running Powershell ISE or non ISE. (ReadKey does not work in powershell ISE). When running Powershell ISE, this function opens a Windows MessageBox. This can sometimes be confusing, because the MessageBox does not always come to the forefront. Anyway, here it goes:

Usage: pause "Press any key to continue"

Function definition:

Function pause ($message)
    # Check if running Powershell ISE
    if ($psISE)
        Add-Type -AssemblyName System.Windows.Forms
        Write-Host "$message" -ForegroundColor Yellow
        $x = $host.ui.RawUI.ReadKey("NoEcho,IncludeKeyDown")

What is the time complexity of indexing, inserting and removing from common data structures?

Keep in mind that unless you're writing your own data structure (e.g. linked list in C), it can depend dramatically on the implementation of data structures in your language/framework of choice. As an example, take a look at the benchmarks of Apple's CFArray over at Ridiculous Fish. In this case, the data type, a CFArray from Apple's CoreFoundation framework, actually changes data structures depending on how many objects are actually in the array - changing from linear time to constant time at around 30,000 objects.

This is actually one of the beautiful things about object-oriented programming - you don't need to know how it works, just that it works, and the 'how it works' can change depending on requirements.

What is difference between sjlj vs dwarf vs seh?

SJLJ (setjmp/longjmp): – available for 32 bit and 64 bit – not “zero-cost”: even if an exception isn’t thrown, it incurs a minor performance penalty (~15% in exception heavy code) – allows exceptions to traverse through e.g. windows callbacks

DWARF (DW2, dwarf-2) – available for 32 bit only – no permanent runtime overhead – needs whole call stack to be dwarf-enabled, which means exceptions cannot be thrown over e.g. Windows system DLLs.

SEH (zero overhead exception) – will be available for 64-bit GCC 4.8.


Deserializing a JSON into a JavaScript object

Do like jQuery does! (the essence)

function parseJSON(data) {
    return window.JSON && window.JSON.parse ? window.JSON.parse( data ) : (new Function("return " + data))(); 
// testing
obj = parseJSON('{"name":"John"}');

This way you don't need any external library and it still works on old browsers.

Scatter plot and Color mapping in Python

Subplot Colorbar

For subplots with scatter, you can trick a colorbar onto your axes by building the "mappable" with the help of a secondary figure and then adding it to your original plot.

As a continuation of the above example:

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(10)
y = x
t = x
fig, (ax1, ax2) = plt.subplots(1, 2)
ax1.scatter(x, y, c=t, cmap='viridis')
ax2.scatter(x, y, c=t, cmap='viridis_r')

# Build your secondary mirror axes:
fig2, (ax3, ax4) = plt.subplots(1, 2)

# Build maps that parallel the color-coded data
# NOTE 1: imshow requires a 2-D array as input
# NOTE 2: You must use the same cmap tag as above for it match
map1 = ax3.imshow(np.stack([t, t]),cmap='viridis')
map2 = ax4.imshow(np.stack([t, t]),cmap='viridis_r')

# Add your maps onto your original figure/axes
fig.colorbar(map1, ax=ax1)
fig.colorbar(map2, ax=ax2)

Scatter subplots with COLORBAR

Note that you will also output a secondary figure that you can ignore.

git: Switch branch and ignore any changes without committing

Close terminal, delete the folder where your project is, then clone again your project and voilá.

Replace X-axis with own values

Yo could also set labels = FALSE inside axis(...) and print the labels in a separate command with Text. With this option you can rotate the text the text in case you need it

axis(1, at=seq(1, 10, by=1), labels = FALSE)
text(seq(1, 10, by=1), par("usr")[3] - 0.2, labels = lablist, srt = 45, pos = 1, xpd = TRUE)

Detailed explanation here

Image with rotated labels

How to add image background to btn-default twitter-bootstrap button?

This works with font awesome:

<button class="btn btn-outline-success">
   <i class="fa fa-print" aria-hidden="true"></i>

How get permission for camera in android.(Specifically Marshmallow)

Requesting Permissions In the following code, we will ask for camera permission:

in java

EasyPermissions is a wrapper library to simplify basic system permissions logic when targeting Android M or higher.

Installation EasyPermissions is installed by adding the following dependency to your build.gradle file:

dependencies {

    // For developers using AndroidX in their applications
    implementation 'pub.devrel:easypermissions:3.0.0'

    // For developers using the Android Support Library
    implementation 'pub.devrel:easypermissions:2.0.1'


private void askAboutCamera(){

                "A partir deste ponto a permissão de câmera é necessária.",
                Manifest.permission.CAMERA );

XAMPP MySQL password setting (Can not enter in PHPMYADMIN)

MySQL multiple instances present on Ubuntu.

step 1 : if it's listed as installed, you got it. Else you need to get it.

sudo ps -A | grep mysql

step 2 : remove the one MySQL

sudo apt-get remove mysql

sudo service mysql restart

step 3 : restart lamp

sudo /opt/lampp/lampp restart

C++ int float casting

You need to use cast. I see the other answers, and they will really work, but as the tag is C++ I'd suggest you to use static_cast:

float m = static_cast< float >( a.y - b.y ) / static_cast< float >( a.x - b.x );

JQuery - Call the jquery button click event based on name property

You can use the name property for that particular element. For example to set a border of 2px around an input element with name xyz, you can use;

$(function() {
    $("input[name = 'xyz']").css("border","2px solid red");


Disabling tab focus on form elements

You have to disable or enable the individual elements. This is how I did it:

     var allowTab = true; 
     var id = $(this).attr('name');

     // insert your form fields here -- (:'') is required after
     var inputArr = {username:'', email:'', password:'', address:''}

     // allow or disable the fields in inputArr by changing true / false
     if(id in inputArr) allowTab = false; 

     if(e.keyCode==9 && allowTab==false) e.preventDefault();

Must JDBC Resultsets and Statements be closed separately although the Connection is closed afterwards?

What you have done is perfect and very good practice.

The reason I say its good practice... For example, if for some reason you are using a "primitive" type of database pooling and you call connection.close(), the connection will be returned to the pool and the ResultSet/Statement will never be closed and then you will run into many different new problems!

So you can't always count on connection.close() to clean up.

I hope this helps :)

Android turn On/Off WiFi HotSpot programmatically

Applies to Oreo+ only...

I made an app with code here on GitHub which uses reflection and DexMaker to 'get at' Oreo's tethering functionality, which is now in ConnectionManager, rather than WifiManager.

The stuff in WifiManager is good only for a closed wifi network (which explained the Closed bit in the class names!).

More explanation

How do I center an SVG in a div?

None of these answers worked for me. This is how I did it.

position: relative;
left: 50%;
-webkit-transform: translateX(-50%);
-ms-transform: translateX(-50%);
transform: translateX(-50%);

How do I create a message box with "Yes", "No" choices and a DialogResult?

Try this:

if (MessageBox.Show("Are you sure", "Title_here", MessageBoxButton.YesNo) == MessageBoxResult.Yes)
    Do something here for 'Yes'...

Regex to get the words after matching string

This might work out for you depending on which language you are using:

(?<=Object Name:).*

It's a positive lookbehind assertion. More information could be found here.

It won't work with JavaScript though. In your comment I read that you're using it for logstash. If you are using GROK parsing for logstash then it would work. You can verify it yourself here:

Enter image description here

Change a HTML5 input's placeholder color with CSS

try this will help you this will work in all your fav browsers :

::-webkit-input-placeholder { 
    /* Chrome/Opera/Safari */
      color: pink;
    ::-moz-placeholder { 
    /* Firefox 19+ */
      color: pink;

    :-moz-placeholder { 
    /* Firefox 18- */
      color: pink;

What are all the uses of an underscore in Scala?

From (my entry) in the FAQ, which I certainly do not guarantee to be complete (I added two entries just two days ago):

import scala._    // Wild card -- all of Scala is imported
import scala.{ Predef => _, _ } // Exception, everything except Predef
def f[M[_]]       // Higher kinded type parameter
def f(m: M[_])    // Existential type
_ + _             // Anonymous function placeholder parameter
m _               // Eta expansion of method into method value
m(_)              // Partial function application
_ => 5            // Discarded parameter
case _ =>         // Wild card pattern -- matches anything
val (a, _) = (1, 2) // same thing
for (_ <- 1 to 10)  // same thing
f(xs: _*)         // Sequence xs is passed as multiple parameters to f(ys: T*)
case Seq(xs @ _*) // Identifier xs is bound to the whole matched sequence
var i: Int = _    // Initialization to the default value
def abc_<>!       // An underscore must separate alphanumerics from symbols on identifiers
t._2              // Part of a method name, such as tuple getters
1_000_000         // Numeric literal separator (Scala 2.13+)

This is also part of this question.

Writing html form data to a txt file without the use of a webserver

I know this is old, but it's the first example of saving form data to a txt file I found in a quick search. So I've made a couple edits to the above code that makes it work more smoothly. It's now easier to add more fields, including the radio button as @user6573234 requested.

<!DOCTYPE html>
form * {
  display: block;
  margin: 10px;
<script language="Javascript" >
function download() {
  var filename = window.document.myform.docname.value;
  var name =;
  var text =  window.document.myform.text.value;
  var problem =  window.document.myform.problem.value;
  var pom = document.createElement('a');
  pom.setAttribute('href', 'data:text/plain;charset=utf-8,' + 
    "Your Name: " + encodeURIComponent(name) + "\n\n" +
    "Problem: " + encodeURIComponent(problem) + "\n\n" +

  pom.setAttribute('download', filename); = 'none';

<form name="myform" method="post" >
  <input type="text" id="docname" value="test.txt" />
  <input type="text" id="name" placeholder="Your Name" />
  <div style="display:unblock">
    Option 1 <input type="radio" value="Option 1" onclick="getElementById('problem').value=this.value; getElementById('problem').show()" style="display:inline" />
    Option 2 <input type="radio" value="Option 2" onclick="getElementById('problem').value=this.value;" style="display:inline" />
    <input type="text" id="problem" />
  <textarea rows=3 cols=50 id="text" />Please type in this box. 
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Propagation Delay vs Transmission delay

Transmission Delay:

This is the amount of time required to transmit all of the packet's bits into the link. Transmission delays are typically on the order of microseconds or less in practice. 

L: packet length (bits)
R: link bandwidth (bps)
so transmission delay is = L/R

Propagation Delay:

Is the time it takes a bit to propagate over the transmission medium from the source router to the destination router; it is a function of the distance between the two routers, but has nothing to do with the packet's length or the transmission rate of the link. 

d: length of physical link
S: propagation speed in medium (~2x108m/sec, for copper wires & ~3x108m/sec, for wireless media)
so propagation delay is = d/s