Programs & Examples On #Application shutdown

A graceful termination of the application, either in response to some input or by internal logic. Usually applied for applications that need to run certain code in order to terminate in consistent way.

JTable - Selected Row click event

You can use the MouseClicked event:

private void tableMouseClicked(java.awt.event.MouseEvent evt) {
 // Do something.

Java regex email

Try the below code for email is format of

[email protected]

1st part -jsmith 2nd part [email protected]

1. In the 1 part it will allow 0-9,A-Z,dot sign(.),underscore sign(_)
 2. In the 2 part it will allow A-Z, must be @ and .


Sort array of objects by string property value

I will give you a solution implementing selectionSort algorithm ,it is simple and effective

var objs = [ 
{ first_nom: 'Lazslo', last_nom: 'Jamf'     },
{ first_nom: 'Pig',    last_nom: 'Bodine'   },
{ first_nom: 'Pirate', last_nom: 'Prentice' }

function selection_Sort(num) { 
 var temp, index;
 for (var i = 0; i <= num.length - 1; i++) {
index = i;
for (var j = i + 1; j <= num.length - 1; j++) {
 // you can use first_nom/last_nom,any way you choose to sort

  if (num[j]. last_nom < num[index]. last_nom) {
    index = j;

//below is the swapping part
temp = num[i]. last_nom;
num[i]. last_nom = num[index]. last_nom;
num[index]. last_nom = temp;
 return num; 

Great to see such great answers

ffmpeg - Converting MOV files to MP4

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

ffmpeg -i -qscale 0 output.mp4

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

ffmpeg -i -q:v 0 output.mp4

How to format time since xxx e.g. “4 minutes ago” similar to Stack Exchange sites

Changed the function above to

function timeSince(date) {

    var seconds = Math.floor(((new Date().getTime()/1000) - date)),
    interval = Math.floor(seconds / 31536000);

    if (interval > 1) return interval + "y";

    interval = Math.floor(seconds / 2592000);
    if (interval > 1) return interval + "m";

    interval = Math.floor(seconds / 86400);
    if (interval >= 1) return interval + "d";

    interval = Math.floor(seconds / 3600);
    if (interval >= 1) return interval + "h";

    interval = Math.floor(seconds / 60);
    if (interval > 1) return interval + "m ";

    return Math.floor(seconds) + "s";

Otherwise it would show things like "75 minutes" (between 1 and 2 hours). It also now assumes input date is a Unix timestamp.

White spaces are required between publicId and systemId

If you're working from some network that requires you to use a proxy in your browser to connect to the internet (likely an office building), that might be it. I had the same issue and adding the proxy configs to the network settings solved it.

  • Go to your preferences (Eclipse -> Preferences on a Mac, or Window -> Preferences on a Windows)
  • Then -> General -> expand to view the list underneath -> Select Network Connections (don't expand)
  • At the top of the page that appears there is a drop down, select "Manual."
  • Then select "HTTP" in the list directly below the drop down (which now should have all it's options checked) and then click the "Edit" button to the right of the list.
  • Enter in the proxy url and port you need to connect to the internet in your web browser normally.
  • Repeat for "HTTPS."

If you don't know the proxy url and port, talk to your network admin.

How to convert ZonedDateTime to Date?

If you are interested in now only, then simply use:

Date d = new Date();

Field 'id' doesn't have a default value?

I had an issue on AWS with mariadb - This is how I solved the STRICT_TRANS_TABLES issue

SSH into server and chanege to the ect directory

[ec2-user]$ cd /etc

Make a back up of my.cnf

[ec2-user etc]$ sudo cp -a my.cnf{,.strict.bak}

I use nano to edit but there are others

[ec2-user etc]$ sudo nano my.cnf

Add this line in the the my.cnf file


Then exit and save

OR if sql_mode is there something like this:


Change to


exit and save

then restart the database

[ec2-user etc]$ sudo systemctl restart mariadb

PDO closing connection

I created a derived class to have a more self-documented instruction instead of $conn=null;.

class CMyPDO extends PDO {
    public function __construct($dsn, $username = null, $password = null, array $options = null) {
        parent::__construct($dsn, $username, $password, $options);

    static function getNewConnection() {
        try {
            $conn = new CMyPDO("mysql:host=$host;dbname=$dbname",$user,$pass);
        catch (PDOException $exc) {
            echo $exc->getMessage();
        return $conn;

    static function closeConnection(&$conn) {

So I can call my code between:

// my code


PHPSESSID is an auto generated session cookie by the server which contains a random long number which is given out by the server itself

java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader

I use Android Studio 3.0 and encounter this problem. And I'm sure app's build.gradle is OK.

Go to Run -> Edit Configurations -> Profiling, and disable "Enable advanced profiling".

This works for me. Reference answer

CSS last-child selector: select last-element of specific class, not last child inside of parent?

:last-child only works when the element in question is the last child of the container, not the last of a specific type of element. For that, you want :last-of-type

As per @BoltClock's comment, this is only checking for the last article element, not the last element with the class of .comment.

body {_x000D_
  background: black;_x000D_
.comment {_x000D_
  width: 470px;_x000D_
  border-bottom: 1px dotted #f0f0f0;_x000D_
  margin-bottom: 10px;_x000D_
.comment:last-of-type {_x000D_
  border-bottom: none;_x000D_
  margin-bottom: 0;_x000D_
<div class="commentList">_x000D_
  <article class="comment " id="com21"></article>_x000D_
  <article class="comment " id="com20"></article>_x000D_
  <article class="comment " id="com19"></article>_x000D_
  <div class="something"> hello </div>_x000D_

Get a list of all the files in a directory (recursive)

The following works for me in Gradle / Groovy for build.gradle for an Android project, without having to import (NOTE: Does not recurse subdirectories, but when I found this solution I no longer cared about recursion, so you may not either):

FileCollection proGuardFileCollection = files { file('./proguard').listFiles() }
proGuardFileCollection.each {
    println "Proguard file located and processed: " + it

How do I force Internet Explorer to render in Standards Mode and NOT in Quirks?

I know this question was asked over 2 years ago but no one has mentioned this yet.

The best method is to use a http header

Adding the meta tag to the head doesn't always work because IE might have determined the mode before it's read. The best way to make sure IE always uses standards mode is to use a custom http header.


name: X-UA-Compatible  
value: IE=edge

For example in a .NET application you could put this in the web.config file.

        <add name="X-UA-Compatible" value="IE=edge" />

jQuery - Increase the value of a counter when a button is clicked

Several of the suggestions above use global variables. This is not a good solution for the problem. The count is specific to one element, and you can use jQuery's data function to bind an item of data to an element:

$('#counter').data('count', 0);
        var $this = $(this),
            count = $'count') + 1;

        $'count', count);
        return count;

Note also that this uses the callback syntax of html to make the code more fluent and fast.

How to convert an IPv4 address into a integer in C#?

With the UInt32 in the proper little-endian format, here are two simple conversion functions:

public uint GetIpAsUInt32(string ipString)
    IPAddress address = IPAddress.Parse(ipString);

    byte[] ipBytes = address.GetAddressBytes();


    return BitConverter.ToUInt32(ipBytes, 0);

public string GetIpAsString(uint ipVal)
    byte[] ipBytes = BitConverter.GetBytes(ipVal);


    return new IPAddress(ipBytes).ToString();

How to tag docker image with docker-compose

If you specify image as well as build, then Compose names the built image with the webapp and optional tag specified in image:

build: ./dir
image: webapp:tag

This results in an image named webapp and tagged tag, built from ./dir.

Command line: search and replace in all filenames matched by grep

The answer already given of using find and sed

find -name '*.html' -print -exec sed -i.bak 's/foo/bar/g' {} \;

is probably the standard answer. Or you could use perl -pi -e s/foo/bar/g' instead of the sed command.

For most quick uses, you may find the command rpl is easier to remember. Here is replacement (foo -> bar), recursively on all files in the current directory:

rpl -R foo bar .

It's not available by default on most Linux distros but is quick to install (apt-get install rpl or similar).

However, for tougher jobs that involve regular expressions and back substitution, or file renames as well as search-and-replace, the most general and powerful tool I'm aware of is repren, a small Python script I wrote a while back for some thornier renaming and refactoring tasks. The reasons you might prefer it are:

  • Support renaming of files as well as search-and-replace on file contents (including moving files between directories and creating new parent directories).
  • See changes before you commit to performing the search and replace.
  • Support regular expressions with back substitution, whole words, case insensitive, and case preserving (replace foo -> bar, Foo -> Bar, FOO -> BAR) modes.
  • Works with multiple replacements, including swaps (foo -> bar and bar -> foo) or sets of non-unique replacements (foo -> bar, f -> x).

Check the README for examples.

Inserting multiple rows in mysql

INSERT statements that use VALUES syntax can insert multiple rows. To do this, include multiple lists of column values, each enclosed within parentheses and separated by commas.


INSERT INTO tbl_name


ReferenceError: variable is not defined

It's declared inside a closure, which means it can only be accessed there. If you want a variable accessible globally, you can remove the var:

    value = "10";
value; // "10"

This is equivalent to writing window.value = "10";.

Static class initializer in PHP

There is a way to call the init() method once and forbid it's usage, you can turn the function into private initializer and ivoke it after class declaration like this:

class Example {
    private static function init() {
        // do whatever needed for class initialization
(static function () {
})->bindTo(null, Example::class)();

Text on image mouseover?

Here is one way to do this using css


<div class="imageWrapper">
    <img src="" alt="" />
    <a href="" class="cornerLink">Link</a>


.imageWrapper {
    position: relative;
    width: 300px;
    height: 300px;
.imageWrapper img {
    display: block;
.imageWrapper .cornerLink {
    opacity: 0;
    position: absolute;
    bottom: 0px;
    left: 0px;
    right: 0px;
    padding: 2px 0px;
    color: #ffffff;
    background: #000000;
    text-decoration: none;
    text-align: center;
    -webkit-transition: opacity 500ms;
    -moz-transition: opacity 500ms;
    -o-transition: opacity 500ms;
    transition: opacity 500ms;

.imageWrapper:hover .cornerLink {
    opacity: 0.8;


Or if you just want it in the bottom left corner:


How do I sort a list of datetime or date objects?

You're getting None because list.sort() it operates in-place, meaning that it doesn't return anything, but modifies the list itself. You only need to call a.sort() without assigning it to a again.

There is a built in function sorted(), which returns a sorted version of the list - a = sorted(a) will do what you want as well.

Please add a @Pipe/@Directive/@Component annotation. Error

In my case, I accidentally added the package in the declaration but it should be in imports.

How to exit a function in bash


return [n]

From help return

return: return [n]

Return from a shell function.

Causes a function or sourced script to exit with the return value
specified by N.  If N is omitted, the return status is that of the
last command executed within the function or script.

Exit Status:
Returns N, or failure if the shell is not executing a function or script.

Casting to string in JavaScript

Real world example: I've got a log function that can be called with an arbitrary number of parameters: log("foo is {} and bar is {}", param1, param2). If a DEBUG flag is set to true, the brackets get replaced by the given parameters and the string is passed to console.log(msg). Parameters can and will be Strings, Numbers and whatever may be returned by JSON / AJAX calls, maybe even null.

  • arguments[i].toString() is not an option, because of possible null values (see Connell Watkins answer)
  • JSLint will complain about arguments[i] + "". This may or may not influence a decision on what to use. Some folks strictly adhere to JSLint.
  • In some browsers, concatenating empty strings is a little faster than using string function or string constructor (see JSPerf test in Sammys S. answer). In Opera 12 and Firefox 19, concatenating empty strings is rediculously faster (95% in Firefox 19) - or at least JSPerf says so.

jQuery or Javascript - how to disable window scroll without overflow:hidden;

If you want to scroll the element you're over and prevent the window to scroll, here's a really useful function :

$('.Scrollable').on('DOMMouseScroll mousewheel', function(ev) {
    var $this = $(this),
        scrollTop = this.scrollTop,
        scrollHeight = this.scrollHeight,
        height = $this.height(),
        delta = (ev.type == 'DOMMouseScroll' ?
            ev.originalEvent.detail * -40 :
        up = delta > 0;

    var prevent = function() {
        ev.returnValue = false;
        return false;

    if (!up && -delta > scrollHeight - height - scrollTop) {
        // Scrolling down, but this will take us past the bottom.

        return prevent();
    } else if (up && delta > scrollTop) {
        // Scrolling up, but this will take us past the top.
        return prevent();

Apply the class "Scrollable" to your element and that's it!

Removing Java 8 JDK from Mac

I nuked everything Java, JDK, and oracle. I was running Java 8 on OSX El Capitan

Other answers were missing tons of stuff. This answer covers a lot more bases.

Good bye, shovelware.

sudo rm -rf /Library/PreferencePanes/JavaControlPanel.prefPane
sudo rm -rf /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin
sudo rm -rf /Library/LaunchAgents/
sudo rm -rf /Library/LaunchDaemons/
sudo rm -rf /Library/Preferences/
sudo rm -rf /System/Library/Frameworks/JavaVM.framework
sudo rm -rf /var/db/receipts/
sudo rm -rf /var/db/receipts/
sudo rm -rf /var/db/receipts/
sudo rm -rf /var/db/receipts/
sudo rm -rf /var/root/Library/Preferences/
sudo rm -rf ~/Library/Preferences/
sudo rm -rf ~/Library/Preferences/
sudo rm -rf ~/.oracle_jre_usage

Java current machine name and logged in user?

To get the currently logged in user:

System.getProperty(""); //platform independent 

and the hostname of the machine: localMachine =;
System.out.println("Hostname of local machine: " + localMachine.getHostName());

How to import XML file into MySQL database table using XML_LOAD(); function

Since ID is auto increment, you can also specify ID=NULL as,

LOAD XML LOCAL INFILE '/pathtofile/file.xml' INTO TABLE my_tablename SET ID=NULL;

XPath OR operator for different nodes

If you want to select only one of two nodes with union operator, you can use this solution: (//bookstore/book/title | //bookstore/city/zipcode/title)[1]

Where and why do I have to put the "template" and "typename" keywords?

(See here also for my C++11 answer)

In order to parse a C++ program, the compiler needs to know whether certain names are types or not. The following example demonstrates that:

t * f;

How should this be parsed? For many languages a compiler doesn't need to know the meaning of a name in order to parse and basically know what action a line of code does. In C++, the above however can yield vastly different interpretations depending on what t means. If it's a type, then it will be a declaration of a pointer f. However if it's not a type, it will be a multiplication. So the C++ Standard says at paragraph (3/7):

Some names denote types or templates. In general, whenever a name is encountered it is necessary to determine whether that name denotes one of these entities before continuing to parse the program that contains it. The process that determines this is called name lookup.

How will the compiler find out what a name t::x refers to, if t refers to a template type parameter? x could be a static int data member that could be multiplied or could equally well be a nested class or typedef that could yield to a declaration. If a name has this property - that it can't be looked up until the actual template arguments are known - then it's called a dependent name (it "depends" on the template parameters).

You might recommend to just wait till the user instantiates the template:

Let's wait until the user instantiates the template, and then later find out the real meaning of t::x * f;.

This will work and actually is allowed by the Standard as a possible implementation approach. These compilers basically copy the template's text into an internal buffer, and only when an instantiation is needed, they parse the template and possibly detect errors in the definition. But instead of bothering the template's users (poor colleagues!) with errors made by a template's author, other implementations choose to check templates early on and give errors in the definition as soon as possible, before an instantiation even takes place.

So there has to be a way to tell the compiler that certain names are types and that certain names aren't.

The "typename" keyword

The answer is: We decide how the compiler should parse this. If t::x is a dependent name, then we need to prefix it by typename to tell the compiler to parse it in a certain way. The Standard says at (14.6/2):

A name used in a template declaration or definition and that is dependent on a template-parameter is assumed not to name a type unless the applicable name lookup finds a type name or the name is qualified by the keyword typename.

There are many names for which typename is not necessary, because the compiler can, with the applicable name lookup in the template definition, figure out how to parse a construct itself - for example with T *f;, when T is a type template parameter. But for t::x * f; to be a declaration, it must be written as typename t::x *f;. If you omit the keyword and the name is taken to be a non-type, but when instantiation finds it denotes a type, the usual error messages are emitted by the compiler. Sometimes, the error consequently is given at definition time:

// t::x is taken as non-type, but as an expression the following misses an
// operator between the two names or a semicolon separating them.
t::x f;

The syntax allows typename only before qualified names - it is therefor taken as granted that unqualified names are always known to refer to types if they do so.

A similar gotcha exists for names that denote templates, as hinted at by the introductory text.

The "template" keyword

Remember the initial quote above and how the Standard requires special handling for templates as well? Let's take the following innocent-looking example:

boost::function< int() > f;

It might look obvious to a human reader. Not so for the compiler. Imagine the following arbitrary definition of boost::function and f:

namespace boost { int function = 0; }
int main() { 
  int f = 0;
  boost::function< int() > f; 

That's actually a valid expression! It uses the less-than operator to compare boost::function against zero (int()), and then uses the greater-than operator to compare the resulting bool against f. However as you might well know, boost::function in real life is a template, so the compiler knows (14.2/3):

After name lookup (3.4) finds that a name is a template-name, if this name is followed by a <, the < is always taken as the beginning of a template-argument-list and never as a name followed by the less-than operator.

Now we are back to the same problem as with typename. What if we can't know yet whether the name is a template when parsing the code? We will need to insert template immediately before the template name, as specified by 14.2/4. This looks like:

t::template f<int>(); // call a function template

Template names can not only occur after a :: but also after a -> or . in a class member access. You need to insert the keyword there too:

this->template f<int>(); // call a function template


For the people that have thick Standardese books on their shelf and that want to know what exactly I was talking about, I'll talk a bit about how this is specified in the Standard.

In template declarations some constructs have different meanings depending on what template arguments you use to instantiate the template: Expressions may have different types or values, variables may have different types or function calls might end up calling different functions. Such constructs are generally said to depend on template parameters.

The Standard defines precisely the rules by whether a construct is dependent or not. It separates them into logically different groups: One catches types, another catches expressions. Expressions may depend by their value and/or their type. So we have, with typical examples appended:

  • Dependent types (e.g: a type template parameter T)
  • Value-dependent expressions (e.g: a non-type template parameter N)
  • Type-dependent expressions (e.g: a cast to a type template parameter (T)0)

Most of the rules are intuitive and are built up recursively: For example, a type constructed as T[N] is a dependent type if N is a value-dependent expression or T is a dependent type. The details of this can be read in section (14.6.2/1) for dependent types, ( for type-dependent expressions and ( for value-dependent expressions.

Dependent names

The Standard is a bit unclear about what exactly is a dependent name. On a simple read (you know, the principle of least surprise), all it defines as a dependent name is the special case for function names below. But since clearly T::x also needs to be looked up in the instantiation context, it also needs to be a dependent name (fortunately, as of mid C++14 the committee has started to look into how to fix this confusing definition).

To avoid this problem, I have resorted to a simple interpretation of the Standard text. Of all the constructs that denote dependent types or expressions, a subset of them represent names. Those names are therefore "dependent names". A name can take different forms - the Standard says:

A name is a use of an identifier (2.11), operator-function-id (13.5), conversion-function-id (12.3.2), or template-id (14.2) that denotes an entity or label (6.6.4, 6.1)

An identifier is just a plain sequence of characters / digits, while the next two are the operator + and operator type form. The last form is template-name <argument list>. All these are names, and by conventional use in the Standard, a name can also include qualifiers that say what namespace or class a name should be looked up in.

A value dependent expression 1 + N is not a name, but N is. The subset of all dependent constructs that are names is called dependent name. Function names, however, may have different meaning in different instantiations of a template, but unfortunately are not caught by this general rule.

Dependent function names

Not primarily a concern of this article, but still worth mentioning: Function names are an exception that are handled separately. An identifier function name is dependent not by itself, but by the type dependent argument expressions used in a call. In the example f((T)0), f is a dependent name. In the Standard, this is specified at (14.6.2/1).

Additional notes and examples

In enough cases we need both of typename and template. Your code should look like the following

template <typename T, typename Tail>
struct UnionNode : public Tail {
    // ...
    template<typename U> struct inUnion {
        typedef typename Tail::template inUnion<U> dummy;
    // ...

The keyword template doesn't always have to appear in the last part of a name. It can appear in the middle before a class name that's used as a scope, like in the following example

typename t::template iterator<int>::value_type v;

In some cases, the keywords are forbidden, as detailed below

  • On the name of a dependent base class you are not allowed to write typename. It's assumed that the name given is a class type name. This is true for both names in the base-class list and the constructor initializer list:

     template <typename T>
     struct derive_from_Has_type : /* typename */ SomeBase<T>::type 
     { };
  • In using-declarations it's not possible to use template after the last ::, and the C++ committee said not to work on a solution.

     template <typename T>
     struct derive_from_Has_type : SomeBase<T> {
        using SomeBase<T>::template type; // error
        using typename SomeBase<T>::type; // typename *is* allowed

Including an anchor tag in an ASP.NET MVC Html.ActionLink

I would probably build the link manually, like this:

<a href="<%=Url.Action("Subcategory", "Category", new { categoryID = parent.ID }) %>#section12">link text</a>

How to check if the URL contains a given string?

You need add href property and check indexOf instead of contains

<script src=""></script>_x000D_
<script type="text/javascript">_x000D_
  $(document).ready(function() {_x000D_
    if (window.location.href.indexOf("franky") > -1) {_x000D_
      alert("your url contains the name franky");_x000D_

Revert to a commit by a SHA hash in Git?


This answer is simpler than my answer:

Original answer:

# Create a backup of master branch
git branch backup_master

# Point master to '56e05fce' and
# make working directory the same with '56e05fce'
git reset --hard 56e05fce

# Point master back to 'backup_master' and
# leave working directory the same with '56e05fce'.
git reset --soft backup_master

# Now working directory is the same '56e05fce' and
# master points to the original revision. Then we create a commit.
git commit -a -m "Revert to 56e05fce"

# Delete unused branch
git branch -d backup_master

The two commands git reset --hard and git reset --soft are magic here. The first one changes the working directory, but it also changes head (the current branch) too. We fix the head by the second one.

How do I apply a CSS class to Html.ActionLink in ASP.NET MVC?

It is:

<%=Html.ActionLink("Home", "Index", MyRouteValObj, new with {.class = "tab" })%>

In you set an anonymous type using

new with {.class = "tab" }

and, as other point out, your third parameter should be an object (could be an anonymous type, also).

using if else with eval in aspx page

 <%if (System.Configuration.ConfigurationManager.AppSettings["OperationalMode"] != "live") {%>

Restful API service

Robby provides a great answer, though I can see you still looking for more information. I implemented REST api calls the easy BUT wrong way. It wasn't until watching this Google I/O video that I understood where I went wrong. It's not as simple as putting together an AsyncTask with a HttpUrlConnection get/put call.

How to prevent null values inside a Map and null fields inside a bean from getting serialized through Jackson

For Jackson versions < 2.0 use this annotation on the class being serialized:


IntelliJ IDEA "The selected directory is not a valid home for JDK"

It got this error because I had managed to clobber jdk1.8.0_60 with the jre!

Generic deep diff between two objects

Here is a modified version of something found on gisthub.

isNullBlankOrUndefined = function (o) {
    return (typeof o === "undefined" || o == null || o === "");

 * Deep diff between two object, using lodash
 * @param  {Object} object Object compared
 * @param  {Object} base   Object to compare with
 * @param  {Object} ignoreBlanks will not include properties whose value is null, undefined, etc.
 * @return {Object}        Return a new object who represent the diff
objectDifference = function (object, base, ignoreBlanks = false) {
    if (!lodash.isObject(object) || lodash.isDate(object)) return object            // special case dates
    return lodash.transform(object, (result, value, key) => {
        if (!lodash.isEqual(value, base[key])) {
            if (ignoreBlanks && du.isNullBlankOrUndefined(value) && isNullBlankOrUndefined( base[key])) return;
            result[key] = lodash.isObject(value) && lodash.isObject(base[key]) ? objectDifference(value, base[key]) : value;

css - position div to bottom of containing div

.outside {
    width: 200px;
    height: 200px;
    background-color: #EEE; /*to make it visible*/

Needs to be

.outside {
    position: relative;
    width: 200px;
    height: 200px;
    background-color: #EEE; /*to make it visible*/

Absolute positioning looks for the nearest relatively positioned parent within the DOM, if one isn't defined it will use the body.

Android emulator not able to access the internet

[UPDATE 2020] for Mac Users

  1. System Preferences
  2. Network
  3. WiFi > Select Advanced
  4. From Advanced Choose DNS tab
  5. Add DNS Server

Sending Windows key using SendKeys

Alt+F4 is working only in brackets


Change Timezone in Lumen or Laravel 5

Please try this - Create a directory 'config' in your lumen setup, and then create app.php file inside this 'config' dir. it will look like this -

<?php return ['app.timezone' => 'America/Los_Angeles'];

Then you can access its value anywhere like this -

$value = config('app.timezone');

If it doesn't work, you can add this lines in routes.php


This worked for me!

printf %f with only 2 numbers after the decimal point?

You can use something like this:

printf("%.2f", number);

If you need to use the string for something other than printing out, use the NumberFormat class:

NumberFormat formatter = new DecimalFormatter("#.##");
String s = formatter.format(3.14159265); // Creates a string containing "3.14"

Sibling package imports

I made a sample project to demonstrate how I handled this, which is indeed another sys.path hack as indicated above. Python Sibling Import Example, which relies on:

if __name__ == '__main__': import os import sys sys.path.append(os.getcwd())

This seems to be pretty effective so long as your working directory remains at the root of the Python project. If anyone deploys this in a real production environment it'd be great to hear if it works there as well.

Are duplicate keys allowed in the definition of binary search trees?

I just want to add some more information to what @Robert Paulson answered.

Let's assume that node contains key & data. So nodes with the same key might contain different data.
(So the search must find all nodes with the same key)

  1. left <= cur < right
  1. left < cur <= right
  1. left <= cur <= right
  1. left < cur < right && cur contain sibling nodes with the same key.
  1. left < cur < right, such that no duplicate keys exist.

1 & 2. works fine if the tree does not have any rotation-related functions to prevent skewness.
But this form doesn't work with AVL tree or Red-Black tree, because rotation will break the principal.
And even if search() finds the node with the key, it must traverse down to the leaf node for the nodes with duplicate key.
Making time complexity for search = theta(logN)

3. will work well with any form of BST with rotation-related functions.
But the search will take O(n), ruining the purpose of using BST.
Say we have the tree as below, with 3) principal.

       /    \
     10     20
    /  \    /
   9   11  12 
      /      \
    10       12

If we do search(12) on this tree, even tho we found 12 at the root, we must keep search both left & right child to seek for the duplicate key.
This takes O(n) time as I've told.

4. is my personal favorite. Let's say sibling means the node with the same key.
We can change above tree into below.

         12 - 12 - 12
       /    \
10 - 10     20
    /  \
   9   11

Now any search will take O(logN) because we don't have to traverse children for the duplicate key.
And this principal also works well with AVL or RB tree.

Head and tail in one line

>>> mylist = [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
>>> head, tail = mylist[0], mylist[1:]
>>> head
>>> tail
[1, 2, 3, 5, 8, 13, 21, 34, 55]

Make <body> fill entire screen?

This works for me:

<!doctype html>
  <meta charset="utf-8" />
  <title> Fullscreen Div </title>
    position: fixed;
    width: 100%;
    height: 100%;
    left: 0;
    top: 0;
    z-index: 10;
  <div class='test'>Some text</div>

Why is there an unexplainable gap between these inline-block div elements?

Found a solution not involving Flex, because Flex doesn't work in older Browsers. Example:

.container {
    margin:0 auto;

.cols {
    margin:0 auto;

.cols:last-child {

How to get text with Selenium WebDriver in Python

This is the correct answer. It worked!!

from selenium import webdriver
from import WebDriverWait

driver = webdriver.Chrome("E:\\Python\\selenium\\webdriver\\chromedriver.exe")
print ("Executed Successfully")
driver.find_element_by_xpath("//div[@class='pdp-promo-title pdp-title']").click()
SpecialPrice = driver.find_element_by_xpath("//div[@class='pdp-promo-title pdp-title']").text

Bypass popup blocker on when JQuery event.preventDefault() is set

Try using an a link element and click it with javascriipt

<a id="SimulateOpenLink" href="#" target="_blank" rel="noopener noreferrer"></a>

and the script

function openURL(url) {
    document.getElementById("SimulateOpenLink").href = url

Use it like this

//do stuff
var id = 123123141;
openURL("/api/user/" + id + "/print") //this open webpage bypassing pop-up blocker
openURL("") //Another link

How can I format bytes a cell in Excel as KB, MB, GB etc?

The above formatting approach works but only for three levels. The above used KB, MB, and GB. Here I've expanded it to six. Right-click on the cell(s) and select Format Cells. Under the Number tab, select Custom. Then in the Type: box, put the following:

[<1000]##0.00"  B";[<1000000]##0.00," KB";##0.00,," MB"

Then select OK. This covers B, KB, and MB. Then, with the same cells selected, click Home ribbon, Conditional Formatting, New Rule. Select Format only cells that contain. Then below in the rule description, Format only cells with, Cell Value, greater than or equal to, 1000000000 (that's 9 zeros.) Then click on Format, Number tab, Custom, and in the Type: box, put the following:

[<1000000000000]##0.00,,," GB";[<1000000000000000]##0.00,,,," TB";#,##0.00,,,,," PB"

Select OK, and OK. This conditional formatting will take over only if the value is bigger than 1,000,000,000. And it will take care of the GB, TB, and PB ranges.

567.00  B
  5.67 KB
 56.70 KB
567.00 KB
  5.67 MB
 56.70 MB
567.00 MB
  5.67 GB
 56.70 GB
567.00 GB
  5.67 TB
 56.70 TB
567.00 TB
  5.67 PB
 56.70 PB

Anything bigger than PB will just show up as a bigger PB, e.g. 56,700 PB. You could add another conditional formatting to handle even bigger values, EB, and so on.

Can you call Directory.GetFiles() with multiple filters?

List<string> FileList = new List<string>();
DirectoryInfo di = new DirectoryInfo("C:\\DirName");

IEnumerable<FileInfo> fileList = di.GetFiles("*.*");

//Create the query
IEnumerable<FileInfo> fileQuery = from file in fileList
                                  where (file.Extension.ToLower() == ".jpg" || file.Extension.ToLower() == ".png")
                                  orderby file.LastWriteTime
                                  select file;

foreach (System.IO.FileInfo fi in fileQuery)
    fi.Attributes = FileAttributes.Normal;

hash function for string

Wikipedia shows a nice string hash function called Jenkins One At A Time Hash. It also quotes improved versions of this hash.

uint32_t jenkins_one_at_a_time_hash(char *key, size_t len)
    uint32_t hash, i;
    for(hash = i = 0; i < len; ++i)
        hash += key[i];
        hash += (hash << 10);
        hash ^= (hash >> 6);
    hash += (hash << 3);
    hash ^= (hash >> 11);
    hash += (hash << 15);
    return hash;

How to write a JSON file in C#?

Update 2020: It's been 7 years since I wrote this answer. It still seems to be getting a lot of attention. In 2013 Newtonsoft Json.Net was THE answer to this problem. Now it's still a good answer to this problem but it's no longer the the only viable option. To add some up-to-date caveats to this answer:

  • .Net Core now has the spookily similar System.Text.Json serialiser (see below)
  • The days of the JavaScriptSerializer have thankfully passed and this class isn't even in .Net Core. This invalidates a lot of the comparisons ran by Newtonsoft.
  • It's also recently come to my attention, via some vulnerability scanning software we use in work that Json.Net hasn't had an update in some time. Updates in 2020 have dried up and the latest version, 12.0.3, is over a year old.
  • The speed tests quoted below are comparing an older version of Json.Nt (version 6.0 and like I said the latest is 12.0.3) with an outdated .Net Framework serialiser.

Are Json.Net's days numbered? It's still used a LOT and it's still used by MS librarties. So probably not. But this does feel like the beginning of the end for this library that may well of just run it's course.

Update since .Net Core 3.0

A new kid on the block since writing this is System.Text.Json which has been added to .Net Core 3.0. Microsoft makes several claims to how this is, now, better than Newtonsoft. Including that it is faster than Newtonsoft. as below, I'd advise you to test this yourself .

I would recommend Json.Net, see example below:

List<data> _data = new List<data>();
_data.Add(new data()
    Id = 1,
    SSN = 2,
    Message = "A Message"

string json = JsonConvert.SerializeObject(_data.ToArray());

//write string to file
System.IO.File.WriteAllText(@"D:\path.txt", json);

Or the slightly more efficient version of the above code (doesn't use a string as a buffer):

//open file stream
using (StreamWriter file = File.CreateText(@"D:\path.txt"))
     JsonSerializer serializer = new JsonSerializer();
     //serialize object directly into file stream
     serializer.Serialize(file, _data);

Documentation: Serialize JSON to a file

Why? Here's a feature comparison between common serialisers as well as benchmark tests .

Below is a graph of performance taken from the linked article:

enter image description here

This separate post, states that:

Json.NET has always been memory efficient, streaming the reading and writing large documents rather than loading them entirely into memory, but I was able to find a couple of key places where object allocations could be reduced...... (now) Json.Net (6.0) allocates 8 times less memory than JavaScriptSerializer

Benchmarks appear to be Json.Net 5, the current version (on writing) is 10. What version of standard .Net serialisers used is not mentioned

These tests are obviously from the developers who maintain the library. I have not verified their claims. If in doubt test them yourself.

jQuery validation: change default error message

To remove all default error messages use

$.validator.messages.required = "";

How to split the screen with two equal LinearLayouts?

To Split a layout to equal parts

Use Layout Weights. Keep in mind that it is important to set layout_width as 0dp on children to make it work as intended.

on parent layout:

  1. Set weightSum of parent Layout as 1 (android:weightSum="1")

on the child layout:

  1. Set layout_width as 0dp (android:layout_width="0dp")
  2. Set layout_weight as 0.5 [half of weight sum fr equal two] (android:layout_weight="0.5")

To split layout to three equal parts:

  • parent: weightSum 3
  • child: layout_weight: 1

To split layout to four equal parts:

  • parent: weightSum 1
  • child: layout_weight: 0.25

To split layout to n equal parts:

  • parent: weightSum n
  • child: layout_weight: 1

Below is an example layout for splitting layout to two equal parts.



        <TextView .. />

        <EditText .../>



        <TextView ../>

        <EditText ../>



How to set selected item of Spinner by value, not by position?

here is my solution

List<Country> list = CountryBO.GetCountries(0);
CountriesAdapter dataAdapter = new CountriesAdapter(this,list);

and getItemIndexById below

public int getItemIndexById(String id) {
    for (Country item : this.items) {
            return this.items.indexOf(item);
    return 0;

Hope this help!

resize2fs: Bad magic number in super-block while trying to open

resize2fs Command will not work for all file systems.

Please confirm the file system of your instance using below command. enter image description here

Please follow the procedure to expand volume by following the steps mentioned in Amazon official document for different file systems.

Default file system in Centos is xfs, use the following command for xfs file system to increase partition size.

sudo xfs_growfs -d /

then "df -h" to check.

PHP Warning: mysqli_connect(): (HY000/2002): Connection refused

For me to make it work again I just deleted the files





from :


Mac 10.13.3
MAMP:Version 4.3 (853)

Is optimisation level -O3 dangerous in g++?

In the early days of gcc (2.8 etc.) and in the times of egcs, and redhat 2.96 -O3 was quite buggy sometimes. But this is over a decade ago, and -O3 is not much different than other levels of optimizations (in buggyness).

It does however tend to reveal cases where people rely on undefined behavior, due to relying more strictly on the rules, and especially corner cases, of the language(s).

As a personal note, I am running production software in the financial sector for many years now with -O3 and have not yet encountered a bug that would not have been there if I would have used -O2.

By popular demand, here an addition:

-O3 and especially additional flags like -funroll-loops (not enabled by -O3) can sometimes lead to more machine code being generated. Under certain circumstances (e.g. on a cpu with exceptionally small L1 instruction cache) this can cause a slowdown due to all the code of e.g. some inner loop now not fitting anymore into L1I. Generally gcc tries quite hard to not to generate so much code, but since it usually optimizes the generic case, this can happen. Options especially prone to this (like loop unrolling) are normally not included in -O3 and are marked accordingly in the manpage. As such it is generally a good idea to use -O3 for generating fast code, and only fall back to -O2 or -Os (which tries to optimize for code size) when appropriate (e.g. when a profiler indicates L1I misses).

If you want to take optimization into the extreme, you can tweak in gcc via --param the costs associated with certain optimizations. Additionally note that gcc now has the ability to put attributes at functions that control optimization settings just for these functions, so when you find you have a problem with -O3 in one function (or want to try out special flags for just that function), you don't need to compile the whole file or even whole project with O2.

otoh it seems that care must be taken when using -Ofast, which states:

-Ofast enables all -O3 optimizations. It also enables optimizations that are not valid for all standard compliant programs.

which makes me conclude that -O3 is intended to be fully standards compliant.

How to show live preview in a small popup of linked page on mouse over on link?

You can display a live preview of a link using javascript using the code below.

<embed src="" width="60" height="40" />_x000D_
<p id="p1"><a href="">Cnet</a></p>_x000D_
<p id="p2"><a href="">Codegena</a></p>_x000D_
<p id="p3"><a href="">Apple</a></p>_x000D_
<script src=""></script>_x000D_
  <link href="" rel="stylesheet">     _x000D_
  <script type="text/javascript">_x000D_
    $(function() {_x000D_
                $('#p1 a').miniPreview({ prefetch: 'pageload' });_x000D_
                $('#p2 a').miniPreview({ prefetch: 'parenthover' });_x000D_
                $('#p3 a').miniPreview({ prefetch: 'none' });_x000D_
  </script> <script src=""></script>

Learn more about it at Codegena

id="p1" - Fetch image preview on page load.
id="p2" - Fetch preview on hover.
id="p3" - Fetch preview image each time you hover.

setOnItemClickListener on custom ListView

If it helps anyone, I found that the problem was I already had an android:onClick event in my layout file (which I inflated for the ListView rows). This was superseding the onItemClick event.

How can I access getSupportFragmentManager() in a fragment?

getActivity().getFragmentManager() This worked or me.

Also take a look at here.

Post-increment and pre-increment within a 'for' loop produce same output

If you wrote it like this then it would matter :

for(i=0; i<5; i=j++) {

Would iterate once more than if written like this :

for(i=0; i<5; i=++j) {

How to predict input image using trained model in Keras?

If someone is still struggling to make predictions on images, here is the optimized code to load the saved model and make predictions:

# Modify 'test1.jpg' and 'test2.jpg' to the images you want to predict on

from keras.models import load_model
from keras.preprocessing import image
import numpy as np

# dimensions of our images
img_width, img_height = 320, 240

# load the model we saved
model = load_model('model.h5')

# predicting images
img = image.load_img('test1.jpg', target_size=(img_width, img_height))
x = image.img_to_array(img)
x = np.expand_dims(x, axis=0)

images = np.vstack([x])
classes = model.predict_classes(images, batch_size=10)
print classes

# predicting multiple images at once
img = image.load_img('test2.jpg', target_size=(img_width, img_height))
y = image.img_to_array(img)
y = np.expand_dims(y, axis=0)

# pass the list of multiple images np.vstack()
images = np.vstack([x, y])
classes = model.predict_classes(images, batch_size=10)

# print the classes, the images belong to
print classes
print classes[0]
print classes[0][0]

What type of hash does WordPress use?

The best way to do this is using WordPress class to authenticate users. Here is my solutions:

1. Include following WordPress PHP file:

include_once(dirname(dirname(dirname(__FILE__))) . DIRECTORY_SEPARATOR . "wp-includes" . DIRECTORY_SEPARATOR . "class-phpass.php");

2. Create an object of PasswordHash class:

$wp_hasher = new PasswordHash(8, true);

3. call CheckPassword function to authenticate user:

$check = $wp_hasher->CheckPassword($password, $row['user_pass']);

4. check $check variable:

if($check) {
   echo "password is correct";
} else {
   echo "password is incorrect";

Please Note that: $password is the un-hashed password in clear text whereas $row['user_pass'] is the hashed password that you need to fetch from the database.

How to read PDF files using Java?

PDFBox is the best library I've found for this purpose, it's comprehensive and really quite easy to use if you're just doing basic text extraction. Examples can be found here.

It explains it on the page, but one thing to watch out for is that the start and end indexes when using setStartPage() and setEndPage() are both inclusive. I skipped over that explanation first time round and then it took me a while to realise why I was getting more than one page back with each call!

Itext is another alternative that also works with C#, though I've personally never used it. It's more low level than PDFBox, so less suited to the job if all you need is basic text extraction.

Can a Windows batch file determine its own file name?


Use the special %0 variable to get the path to the current file.

Write %~n0 to get just the filename without the extension.

Write %~n0%~x0 to get the filename and extension.

Also possible to write %~nx0 to get the filename and extension.

Uncaught ReferenceError: angular is not defined - AngularJS not working

As you know angular.module( declared under angular.js file.So before accessing angular.module, you must have make it available by using <script src="lib/angular/angular.js"></script>(In your case) after then you can call angular.module. It will work.


<html lang="en">
  <meta charset="utf-8">
  <title>My AngularJS App</title>
  <link rel="stylesheet" href="css/app.css"/>
<!-- In production use:
  <script src="//"></script>
  <script src="lib/angular/angular.js"></script>
  <script src="lib/angular/angular-route.js"></script>
  <script src="js/app.js"></script>
  <script src="js/services.js"></script>
  <script src="js/controllers.js"></script>
  <script src="js/filters.js"></script>
  <script src="js/directives.js"></script>

        var app = angular.module('myApp',[]);


            return function(scope, element,attrs) {
                element.bind('click',function() {alert('click')});

<body ng-app="myApp">
    <div >
        <button my-directive>Click Me!</button>


How do I write a backslash (\) in a string?

even though this post is quite old I tried something that worked for my case .

I wanted to create a string variable with the value below:


so my approach was like that:

  • build the string using verbatim

    string substring = @"21541_12_1_13\"":null";

  • and then remove the unwanted backslashes using Remove function

    string newsubstring = substring.Remove(13, 1);

Hope that helps. Cheers

Delay/Wait in a test case of Xcode UI testing

Asynchronous UI Testing was introduced in Xcode 7 Beta 4. To wait for a label with the text "Hello, world!" to appear you can do the following:

let app = XCUIApplication()

let label = app.staticTexts["Hello, world!"]
let exists = NSPredicate(format: "exists == 1")

expectationForPredicate(exists, evaluatedWithObject: label, handler: nil)
waitForExpectationsWithTimeout(5, handler: nil)

More details about UI Testing can be found on my blog.

error: Libtool library used but 'LIBTOOL' is undefined

For people using Tiny Core Linux, you also need to install libtool-dev as it has the *.m4 files needed for libtoolize.

How do I include negative decimal numbers in this regular expression?

I have some experiments about regex in django url, which required from negative to positive numbers


Let's we focused on this (\-\d+|\d+) part and ignoring others, this semicolon | means OR in regex, then the negative value will match with this \-\d+ part, and positive value into this \d+

Python: How to pip install opencv2 with specific version 2.4.9?

cv2 vs. "opencv3"

To get a potential misunderstanding out of the way: The python OpenCV module is named and imported via import cv2 in all versions > 2.0, including > 3.0. If you want to work with cv2, installing OpenCV versions > 3 is fine - unless you're looking for specific compatibility with older versions or are a fan of the 2.4.x versions. The switch from 2.4.x to 3.x was in 2015 and in terms of features, speed and transparency, it makes much sense to use the newer versions. You can read here and here about major differences. 2.4.x versions are still supported though, current release is

Installing a specific version, e.g. OpenCV 2.4.9

That said: If you want to install a specific version that neither pip install opencv-python==2.4.X, sudo apt-get install opencv nor conda install opencv=2.4.x provide (as explained by other answers here), you can always install from sources. In the sourceforge repository you can find all major versions for each operating system. Although for unxeperienced users this might be scary, it is well explained in some tutorials. E.g. here for 2.4.9 on Ubuntu 14.04. Or here is the official Linux install doc for the latest release

In essence, the install process boils down to:

  1. install dependencies, refer to docs (e.g. here) for required packages

  2. get sources from OpenCVs sourceforge

    e.g. wget

  3. unzip sources and prepare build by creating build directory and running cmake

    mkdir build
    cd build
    cmake (... your build options ...)
  4. build in the created build directory with:

    sudo make install

How do I use valgrind to find memory leaks?

You can create an alias in .bashrc file as follows

alias vg='valgrind --leak-check=full -v --track-origins=yes --log-file=vg_logfile.out'

So whenever you want to check memory leaks, just do simply

vg ./<name of your executable> <command line parameters to your executable>

This will generate a Valgrind log file in the current directory.

Is it possible to disable floating headers in UITableView with UITableViewStylePlain?


let tableView = UITableView(frame: .zero, style: .grouped)


func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
    if section == 0 {
        return 40
        tableView.sectionHeaderHeight = 0

    return 0

This helped to use header space

How to remove default mouse-over effect on WPF buttons?

Using a template trigger:

<Style x:Key="ButtonStyle" TargetType="{x:Type Button}">
    <Setter Property="Background" Value="White"></Setter>
    <Setter Property="Template">
            <ControlTemplate TargetType="{x:Type Button}">
                <Border Background="{TemplateBinding Background}">
                    <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
                    <Trigger Property="IsMouseOver" Value="True">
                        <Setter Property="Background" Value="White"/>

How does functools partial do what it does?

partials are incredibly useful.

For instance, in a 'pipe-lined' sequence of function calls (in which the returned value from one function is the argument passed to the next).

Sometimes a function in such a pipeline requires a single argument, but the function immediately upstream from it returns two values.

In this scenario, functools.partial might allow you to keep this function pipeline intact.

Here's a specific, isolated example: suppose you want to sort some data by each data point's distance from some target:

# create some data
import random as RND
fnx = lambda: RND.randint(0, 10)
data = [ (fnx(), fnx()) for c in range(10) ]
target = (2, 4)

import math
def euclid_dist(v1, v2):
    x1, y1 = v1
    x2, y2 = v2
    return math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

To sort this data by distance from the target, what you would like to do of course is this:


but you can't--the sort method's key parameter only accepts functions that take a single argument.

so re-write euclid_dist as a function taking a single parameter:

from functools import partial

p_euclid_dist = partial(euclid_dist, target)

p_euclid_dist now accepts a single argument,

>>> p_euclid_dist((3, 3))

so now you can sort your data by passing in the partial function for the sort method's key argument:


# verify that it works:
for p in data:
    print(round(p_euclid_dist(p), 3))


Or for instance, one of the function's arguments changes in an outer loop but is fixed during iteration in the inner loop. By using a partial, you don't have to pass in the additional parameter during iteration of the inner loop, because the modified (partial) function doesn't require it.

>>> from functools import partial

>>> def fnx(a, b, c):
      return a + b + c

>>> fnx(3, 4, 5)

create a partial function (using keyword arg)

>>> pfnx = partial(fnx, a=12)

>>> pfnx(b=4, c=5)

you can also create a partial function with a positional argument

>>> pfnx = partial(fnx, 12)

>>> pfnx(4, 5)

but this will throw (e.g., creating partial with keyword argument then calling using positional arguments)

>>> pfnx = partial(fnx, a=12)

>>> pfnx(4, 5)
      Traceback (most recent call last):
      File "<pyshell#80>", line 1, in <module>
      pfnx(4, 5)
      TypeError: fnx() got multiple values for keyword argument 'a'

another use case: writing distributed code using python's multiprocessing library. A pool of processes is created using the Pool method:

>>> import multiprocessing as MP

>>> # create a process pool:
>>> ppool = MP.Pool()

Pool has a map method, but it only takes a single iterable, so if you need to pass in a function with a longer parameter list, re-define the function as a partial, to fix all but one:

>>>, [4, 6, 7, 8])

How to check whether a given string is valid JSON in Java

The answers are partially correct. I also faced the same problem. Parsing the json and checking for exception seems the usual way but the solution fails for the input json something like

{"outputValueSchemaFormat": "","sortByIndexInRecord": 0,"sortOrder":847874874387209"descending"}kajhfsadkjh

As you can see the json is invalid as there are trailing garbage characters. But if you try to parse the above json using jackson or gson then you will get the parsed map of the valid json and garbage trailing characters are ignored. Which is not the required solution when you are using the parser for checking json validity.

For solution to this problem see here.

PS: This question was asked and answered by me.

Check if object value exists within a Javascript array of objects and if not add a new object to array

xorWith in Lodash can be used to achieve this

let objects = [ { id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 2, username: 'ted' } ]
let existingObject = { id: 1, username: 'fred' };
let newObject = { id: 1729, username: 'Ramanujan' }

_.xorWith(objects, [existingObject], _.isEqual)
// returns [ { id: 2, username: 'bill' }, { id: 2, username: 'ted' } ]

_.xorWith(objects, [newObject], _.isEqual)
// returns [ { id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 2, username: 'ted' } ,{ id: 1729, username: 'Ramanujan' } ]

Create a file if it doesn't exist

w  write mode
r  read mode
a  append mode

w+  create file if it doesn't exist and open it in (over)write mode
    [it overwrites the file if it already exists]
r+  open an existing file in read+write mode
a+  create file if it doesn't exist and open it in append mode


file_name = 'my_file.txt'
f = open(file_name, 'a+')  # open file in append mode
f.write('python rules')

I hope this helps. [FYI am using python version 3.6.2]

SQL How to replace values of select return?

You have a number of choices:

  1. Join with a domain table with TRUE, FALSE Boolean value.
  2. Use (as pointed in this answer)


    Or if Boolean is not supported:

    SELECT CASE WHEN hide = 0 THEN 'false' ELSE 'true' END FROM

How to redirect to action from JavaScript method?

function DeleteJob() {
    if (confirm("Do you really want to delete selected job/s?"))
        window.location.href = "/{controller}/{action}/{params}";
        return false;

Regular expression for floating point numbers


[+-]? - optional leading sign

(([1-9][0-9]*)|(0)) - integer without leading zero, including single zero

([.,][0-9]+)? - optional fractional part

Array of char* should end at '\0' or "\0"?

Well, technically '\0' is a character while "\0" is a string, so if you're checking for the null termination character the former is correct. However, as Chris Lutz points out in his answer, your comparison won't work in it's current form.

How to make Python script run as service?

for my script of python, I use...

To START python script :

start-stop-daemon --start --background --pidfile $PIDFILE --make-pidfile --exec $DAEMON

To STOP python script :

kill -9 $PID
rm -f $PIDFILE

P.S.: sorry for poor English, I'm from CHILE :D

Replace missing values with column mean

Go simply with Zoo, it will simply replace all NA values with mean of the column values:


Postgres: How to convert a json string to text?

In 9.4.4 using the #>> operator works for me:

select to_json('test'::text) #>> '{}';

To use with a table column:

select jsoncol #>> '{}' from mytable;

How to submit an HTML form on loading the page?

You can do it by using simple one line JavaScript code and also be careful that if JavaScript is turned off it will not work. The below code will do it's job if JavaScript is turned off.

Turn off JavaScript and run the code on you own file to know it's full function.(If you turn off JavaScript here, the below Code Snippet will not work)

.noscript-error {_x000D_
  color: red;_x000D_
<body onload="document.getElementById('payment-form').submit();">_x000D_
  <div align="center">_x000D_
      Please Waite... You Will be Redirected Shortly<br/>_x000D_
      Don't Refresh or Press Back _x000D_
  <form method='post' action='acction.php' id='payment-form'>_x000D_
    <input type='hidden' name='field-name' value='field-value'>_x000D_
     <input type='hidden' name='field-name2' value='field-value2'>_x000D_
      <div align="center" class="noscript-error">Sorry, your browser does not support JavaScript!._x000D_
        <br>Kindly submit it manually_x000D_
        <input type='submit' value='Submit Now' />_x000D_

java.lang.ClassNotFoundException: org.apache.xmlbeans.XmlObject Error

I was working with talend V7.3.1 and I had poi version "4.1.0" and including xml-beans from the list of dependencies didnt fix my problem (i.e: 2.3.0 and 2.6.0).

It was fixed by downloading the jar "xmlbeans-3.0.1.jar" and adding it to the project

enter image description here

Data at the root level is invalid

For the record:

"Data at the root level is invalid" means that you have attempted to parse something that is not an XML document. It doesn't even start to look like an XML document. It usually means just what you found: you're parsing something like the string "C:\inetpub\wwwroot\mysite\officelist.xml".

How does Zalgo text work?

Zalgo text works because of combining characters. These are special characters that allow to modify character that comes before.

enter image description here


y + ̆ = y̆ which actually is

y + &#x0306; = y&#x0306;

Since you can stack them one atop the other you can produce the following:


which actually is:


The same goes for putting stuff underneath:


that in fact is:


In Unicode, the main block of combining diacritics for European languages and the International Phonetic Alphabet is U+0300–U+036F.

More about it here

To produce a list of combining diacritical marks you can use the following script (since links keep on dying)

for(var i=768; i<879; i++){console.log(new DOMParser().parseFromString("&#"+i+";", "text/html").documentElement.textContent +"  "+"&#"+i+";");}

Also check em out

Mͣͭͣ̾ Vͣͥͭ͛ͤͮͥͨͥͧ̾

How to get an ASP.NET MVC Ajax response to redirect to new page instead of inserting view into UpdateTargetId?

The accepted answer works well except for the fact that the javascript is briefly displayed in whatever the ajax target element is. To get around this, create a partial view called _Redirect with the following code:

@model string
   window.location = '@Model';

Then, in the controller replace

return Redirect(Url.Action("Index", "Home"));


return PartialView("_Redirect",Url.Action("Index", "Home"));

The effect is the same as the accepted answer, but without the brief artifact in the display. Place the _Redirect.cshtml in the shared folder so it can be used from anywhere.

What's the console.log() of java?

Use the Android logging utility.

Log has a bunch of static methods for accessing the different log levels. The common thread is that they always accept at least a tag and a log message.

Tags are a way of filtering output in your log messages. You can use them to wade through the thousands of log messages you'll see and find the ones you're specifically looking for.

You use the Log functions in Android by accessing the Log.x objects (where the x method is the log level). For example:

Log.d("MyTagGoesHere", "This is my log message at the debug level here");
Log.e("MyTagGoesHere", "This is my log message at the error level here");

I usually make it a point to make the tag my class name so I know where the log message was generated too. Saves a lot of time later on in the game.

You can see your log messages using the logcat tool for android:

adb logcat

Or by opening the eclipse Logcat view by going to the menu bar

Window->Show View->Other then select the Android menu and the LogCat view

How to upgrade pip3?

What worked for me was the following command:

python -m pip install --upgrade pip

How do I get the selected element by name and then get the selected value from a dropdown using jQuery?

Your selector is a little off, it's missing the trailing ]

var mySelect = $('select[name=' + name + ']')

you may also need to put quotes around the name, like so:

var mySelect = $('select[name="' + name + '"]')

QR Code encoding and decoding using zxing

I tried using ISO-8859-1 as said in the first answer. All went ok on encoding, but when I tried to get the byte[] using result string on decoding, all negative bytes became the character 63 (question mark). The following code does not work:

// Encoding works great
byte[] contents = new byte[]{-1};
QRCodeWriter codeWriter = new QRCodeWriter();
BitMatrix bitMatrix = codeWriter.encode(new String(contents, Charset.forName("ISO-8859-1")), BarcodeFormat.QR_CODE, w, h);

// Decodes like this fails
LuminanceSource ls = new BufferedImageLuminanceSource(encodedBufferedImage);
Result result = new QRCodeReader().decode(new BinaryBitmap( new HybridBinarizer(ls)));
byte[] resultBytes = result.getText().getBytes(Charset.forName("ISO-8859-1")); // a byte[] with byte 63 is given
return resultBytes;

It looks so strange because the API in a very old version (don't know exactly) had a method thar works well:

Vector byteSegments = result.getByteSegments();

So I tried to search why this method was removed and realized that there is a way to get ByteSegments, through metadata. So my decode method looks like:

// Decodes like this works perfectly
LuminanceSource ls = new BufferedImageLuminanceSource(encodedBufferedImage);
Result result = new QRCodeReader().decode(new BinaryBitmap( new HybridBinarizer(ls)));
Vector byteSegments = (Vector) result.getResultMetadata().get(ResultMetadataType.BYTE_SEGMENTS);  
int i = 0;
int tam = 0;
for (Object o : byteSegments) {
    byte[] bs = (byte[])o;
    tam += bs.length;
byte[] resultBytes = new byte[tam];
i = 0;
for (Object o : byteSegments) {
    byte[] bs = (byte[])o;
    for (byte b : bs) {
        resultBytes[i++] = b;
return resultBytes;

Getting data from Yahoo Finance

Since Yahoo Finances API was disabled, I found Alpha Vantage API

This a stock query sample that I'm using with Excel's Power Query:

Assignment makes pointer from integer without cast

strToLower should return a char * instead of a char. Something like this would do.

char *strToLower(char *cString)

How to close a window using jQuery

You can only use the window.close function when you have opened the window using, so I use the following function:

function close_window(url){
    var newWindow ='', '_self', ''); //open the current window

What is an MvcHtmlString and when should I use it?

ASP.NET 4 introduces a new code nugget syntax <%: %>. Essentially, <%: foo %> translates to <%= HttpUtility.HtmlEncode(foo) %>. The team is trying to get developers to use <%: %> instead of <%= %> wherever possible to prevent XSS.

However, this introduces the problem that if a code nugget already encodes its result, the <%: %> syntax will re-encode it. This is solved by the introduction of the IHtmlString interface (new in .NET 4). If the foo() in <%: foo() %> returns an IHtmlString, the <%: %> syntax will not re-encode it.

MVC 2's helpers return MvcHtmlString, which on ASP.NET 4 implements the interface IHtmlString. Therefore when developers use <%: Html.*() %> in ASP.NET 4, the result won't be double-encoded.


An immediate benefit of this new syntax is that your views are a little cleaner. For example, you can write <%: ViewData["anything"] %> instead of <%= Html.Encode(ViewData["anything"]) %>.

"The specified Android SDK Build Tools version (26.0.0) is ignored..."

Open app/build.gradle file

Change buildToolsVersion to buildToolsVersion "26.0.2"

change compile ' to compile ''

Run php function on button click

I tried the code of William, Thanks brother.

but it's not working as a simple button I have to add form with method="post". Also I have to write submit instead of button.

here is my code below..

<form method="post">
    <input type="submit" name="test" id="test" value="RUN" /><br/>


function testfun()
   echo "Your test function on button click is working";



What is a deadlock?

A deadlock occurs when there is a circular chain of threads or processes which each hold a locked resource and are trying to lock a resource held by the next element in the chain. For example, two threads that hold respectively lock A and lock B, and are both trying to acquire the other lock.

How to convert const char* to char* in C?

First of all you should do such things only if it is really necessary - e.g. to use some old-style API with char* arguments which are not modified. If an API function modifies the string which was const originally, then this is unspecified behaviour, very likely crash.

Use cast:


How to get Tensorflow tensor dimensions (shape) as int values?

Another simple solution is to use map() as follows:

tensor_shape = map(int, my_tensor.shape)

This converts all the Dimension objects to int

Convert a negative number to a positive one in JavaScript

I know another way to do it. This technique works negative to positive & Vice Versa

var x = -24;
var result = x * -1;

Vice Versa:

var x = 58;
var result = x * -1;


// NEGATIVE TO POSITIVE: ******************************************_x000D_
var x = -24;_x000D_
var result = x * -1;_x000D_
// VICE VERSA: ****************************************************_x000D_
var x = 58;_x000D_
var result = x * -1;_x000D_
// FLOATING POINTS: ***********************************************_x000D_
var x = 42.8;_x000D_
var result = x * -1;_x000D_
// FLOATING POINTS VICE VERSA: ************************************_x000D_
var x = -76.8;_x000D_
var result = x * -1;_x000D_

Drawing circles with System.Drawing

There is no DrawCircle method; use DrawEllipse instead. I have a static class with handy graphics extension methods. The following ones draw and fill circles. They are wrappers around DrawEllipse and FillEllipse:

public static class GraphicsExtensions
    public static void DrawCircle(this Graphics g, Pen pen,
                                  float centerX, float centerY, float radius)
        g.DrawEllipse(pen, centerX - radius, centerY - radius,
                      radius + radius, radius + radius);

    public static void FillCircle(this Graphics g, Brush brush,
                                  float centerX, float centerY, float radius)
        g.FillEllipse(brush, centerX - radius, centerY - radius,
                      radius + radius, radius + radius);

You can call them like this:

g.FillCircle(myBrush, centerX, centerY, radius);
g.DrawCircle(myPen, centerX, centerY, radius);

Rolling back local and remote git repository by 1 commit

I solved problem like yours by this commands:

git reset --hard HEAD^
git push -f <remote> <local branch>:<remote branch> 

how to use math.pi in java

You're missing the multiplication operator. Also, you want to do 4/3 in floating point, not integer math.

volume = (4.0 / 3) * Math.PI * Math.pow(radius, 3);
           ^^      ^

JS: Failed to execute 'getComputedStyle' on 'Window': parameter is not of type 'Element'

In my case I was using ClassName.

getComputedStyle( document.getElementsByClassName(this_id)) //error

It will also work without 2nd argument " ".

Here is my complete running code :

function changeFontSize(target) {

  var minmax = document.getElementById("minmax");

  var computedStyle = window.getComputedStyle
        ? getComputedStyle(minmax) // Standards
        : minmax.currentStyle;     // Old IE

  var fontSize;

  if (computedStyle) { // This will be true on nearly all browsers
      fontSize = parseFloat(computedStyle && computedStyle.fontSize);

      if (target == "sizePlus") {
        fontSize += 5;

      } else if (target == "sizeMinus") {
        fontSize -= 5;
      } = fontSize + "px";

onclick= "changeFontSize("

Using querySelectorAll to retrieve direct children

Well we can easily get all the direct children of an element using childNodes and we can select ancestors with a specific class with querySelectorAll, so it's not hard to imagine we could create a new function that gets both and compares the two.

HTMLElement.prototype.queryDirectChildren = function(selector){
  var direct = [] || []); // Cast to Array
  var queried = [] || []); // Cast to Array
  var both = [];
  // I choose to loop through the direct children because it is guaranteed to be smaller
  for(var i=0; i<direct.length; i++){
  return both;

Note: This will return an Array of Nodes, not a NodeList.



Reading CSV files using C#

Another one to this list, Cinchoo ETL - an open source library to read and write CSV files

For a sample CSV file below

Id, Name
1, Tom
2, Mark

Quickly you can load them using library as below

using (var reader = new ChoCSVReader("test.csv").WithFirstLineHeader())
   foreach (dynamic item in reader)

If you have POCO class matching the CSV file

public class Employee
   public int Id { get; set; }
   public string Name { get; set; }

You can use it to load the CSV file as below

using (var reader = new ChoCSVReader<Employee>("test.csv").WithFirstLineHeader())
   foreach (var item in reader)

Please check out articles at CodeProject on how to use it.

Disclaimer: I'm the author of this library

Where can I find a list of Mac virtual key codes?

Below is a list of the common key codes for quick reference, taken from Events.h.

If you need to use these keycodes in an application, you should include the Carbon framework:

#include <Carbon/Carbon.h>

import Carbon.HIToolbox

You can then use the kVK_ANSI_A constants directly.


The key constants reference physical keys on the keyboard. Their output changes if the typist is using a different keyboard layout. The letters in the constants correspond only to the U.S. QWERTY keyboard layout.

For example, the left ring-finger key on the homerow:

QWERTY keyboard layout > s > kVK_ANSI_S > "s"
Dvorak keyboard layout > o > kVK_ANSI_S > "o"

Strategies for layout-agnostic conversion of keycode to string, and vice versa, are discussed here:

How to convert ASCII character to CGKeyCode?

From Events.h:

 *  Summary:
 *    Virtual keycodes
 *  Discussion:
 *    These constants are the virtual keycodes defined originally in
 *    Inside Mac Volume V, pg. V-191. They identify physical keys on a
 *    keyboard. Those constants with "ANSI" in the name are labeled
 *    according to the key position on an ANSI-standard US keyboard.
 *    For example, kVK_ANSI_A indicates the virtual keycode for the key
 *    with the letter 'A' in the US keyboard layout. Other keyboard
 *    layouts may have the 'A' key label on a different physical key;
 *    in this case, pressing 'A' will generate a different virtual
 *    keycode.
enum {
  kVK_ANSI_A                    = 0x00,
  kVK_ANSI_S                    = 0x01,
  kVK_ANSI_D                    = 0x02,
  kVK_ANSI_F                    = 0x03,
  kVK_ANSI_H                    = 0x04,
  kVK_ANSI_G                    = 0x05,
  kVK_ANSI_Z                    = 0x06,
  kVK_ANSI_X                    = 0x07,
  kVK_ANSI_C                    = 0x08,
  kVK_ANSI_V                    = 0x09,
  kVK_ANSI_B                    = 0x0B,
  kVK_ANSI_Q                    = 0x0C,
  kVK_ANSI_W                    = 0x0D,
  kVK_ANSI_E                    = 0x0E,
  kVK_ANSI_R                    = 0x0F,
  kVK_ANSI_Y                    = 0x10,
  kVK_ANSI_T                    = 0x11,
  kVK_ANSI_1                    = 0x12,
  kVK_ANSI_2                    = 0x13,
  kVK_ANSI_3                    = 0x14,
  kVK_ANSI_4                    = 0x15,
  kVK_ANSI_6                    = 0x16,
  kVK_ANSI_5                    = 0x17,
  kVK_ANSI_Equal                = 0x18,
  kVK_ANSI_9                    = 0x19,
  kVK_ANSI_7                    = 0x1A,
  kVK_ANSI_Minus                = 0x1B,
  kVK_ANSI_8                    = 0x1C,
  kVK_ANSI_0                    = 0x1D,
  kVK_ANSI_RightBracket         = 0x1E,
  kVK_ANSI_O                    = 0x1F,
  kVK_ANSI_U                    = 0x20,
  kVK_ANSI_LeftBracket          = 0x21,
  kVK_ANSI_I                    = 0x22,
  kVK_ANSI_P                    = 0x23,
  kVK_ANSI_L                    = 0x25,
  kVK_ANSI_J                    = 0x26,
  kVK_ANSI_Quote                = 0x27,
  kVK_ANSI_K                    = 0x28,
  kVK_ANSI_Semicolon            = 0x29,
  kVK_ANSI_Backslash            = 0x2A,
  kVK_ANSI_Comma                = 0x2B,
  kVK_ANSI_Slash                = 0x2C,
  kVK_ANSI_N                    = 0x2D,
  kVK_ANSI_M                    = 0x2E,
  kVK_ANSI_Period               = 0x2F,
  kVK_ANSI_Grave                = 0x32,
  kVK_ANSI_KeypadDecimal        = 0x41,
  kVK_ANSI_KeypadMultiply       = 0x43,
  kVK_ANSI_KeypadPlus           = 0x45,
  kVK_ANSI_KeypadClear          = 0x47,
  kVK_ANSI_KeypadDivide         = 0x4B,
  kVK_ANSI_KeypadEnter          = 0x4C,
  kVK_ANSI_KeypadMinus          = 0x4E,
  kVK_ANSI_KeypadEquals         = 0x51,
  kVK_ANSI_Keypad0              = 0x52,
  kVK_ANSI_Keypad1              = 0x53,
  kVK_ANSI_Keypad2              = 0x54,
  kVK_ANSI_Keypad3              = 0x55,
  kVK_ANSI_Keypad4              = 0x56,
  kVK_ANSI_Keypad5              = 0x57,
  kVK_ANSI_Keypad6              = 0x58,
  kVK_ANSI_Keypad7              = 0x59,
  kVK_ANSI_Keypad8              = 0x5B,
  kVK_ANSI_Keypad9              = 0x5C

/* keycodes for keys that are independent of keyboard layout*/
enum {
  kVK_Return                    = 0x24,
  kVK_Tab                       = 0x30,
  kVK_Space                     = 0x31,
  kVK_Delete                    = 0x33,
  kVK_Escape                    = 0x35,
  kVK_Command                   = 0x37,
  kVK_Shift                     = 0x38,
  kVK_CapsLock                  = 0x39,
  kVK_Option                    = 0x3A,
  kVK_Control                   = 0x3B,
  kVK_RightShift                = 0x3C,
  kVK_RightOption               = 0x3D,
  kVK_RightControl              = 0x3E,
  kVK_Function                  = 0x3F,
  kVK_F17                       = 0x40,
  kVK_VolumeUp                  = 0x48,
  kVK_VolumeDown                = 0x49,
  kVK_Mute                      = 0x4A,
  kVK_F18                       = 0x4F,
  kVK_F19                       = 0x50,
  kVK_F20                       = 0x5A,
  kVK_F5                        = 0x60,
  kVK_F6                        = 0x61,
  kVK_F7                        = 0x62,
  kVK_F3                        = 0x63,
  kVK_F8                        = 0x64,
  kVK_F9                        = 0x65,
  kVK_F11                       = 0x67,
  kVK_F13                       = 0x69,
  kVK_F16                       = 0x6A,
  kVK_F14                       = 0x6B,
  kVK_F10                       = 0x6D,
  kVK_F12                       = 0x6F,
  kVK_F15                       = 0x71,
  kVK_Help                      = 0x72,
  kVK_Home                      = 0x73,
  kVK_PageUp                    = 0x74,
  kVK_ForwardDelete             = 0x75,
  kVK_F4                        = 0x76,
  kVK_End                       = 0x77,
  kVK_F2                        = 0x78,
  kVK_PageDown                  = 0x79,
  kVK_F1                        = 0x7A,
  kVK_LeftArrow                 = 0x7B,
  kVK_RightArrow                = 0x7C,
  kVK_DownArrow                 = 0x7D,
  kVK_UpArrow                   = 0x7E

Macintosh Toolbox Essentials illustrates the physical locations of these virtual key codes for the Apple Extended Keyboard II in Figure 2-10:

Virtual key codes for the Apple Extended Keyboard II

Determining image file size + dimensions via Javascript?

Getting the Original Dimensions of the Image

If you need to get the original image dimensions (not in the browser context), clientWidth and clientHeight properties do not work since they return incorrect values if the image is stretched/shrunk via css.

To get original image dimensions, use naturalHeight and naturalWidth properties.

var img = document.getElementById('imageId'); 

var width = img.naturalWidth;
var height = img.naturalHeight;

p.s. This does not answer the original question as the accepted answer does the job. This, instead, serves like addition to it.

Git - Ignore files during merge

You could start by using git merge --no-commit, and then edit the merge however you like i.e. by unstaging config.xml or any other file, then commit. I suspect you'd want to automate it further after that using hooks, but I think it'd be worth going through manually at least once.

How to do a deep comparison between 2 objects with lodash?

For anyone stumbling upon this thread, here's a more complete solution. It will compare two objects and give you the key of all properties that are either only in object1, only in object2, or are both in object1 and object2 but have different values:

 * Compare two objects by reducing an array of keys in obj1, having the
 * keys in obj2 as the intial value of the result. Key points:
 * - All keys of obj2 are initially in the result.
 * - If the loop finds a key (from obj1, remember) not in obj2, it adds
 *   it to the result.
 * - If the loop finds a key that are both in obj1 and obj2, it compares
 *   the value. If it's the same value, the key is removed from the result.
function getObjectDiff(obj1, obj2) {
    const diff = Object.keys(obj1).reduce((result, key) => {
        if (!obj2.hasOwnProperty(key)) {
        } else if (_.isEqual(obj1[key], obj2[key])) {
            const resultKeyIndex = result.indexOf(key);
            result.splice(resultKeyIndex, 1);
        return result;
    }, Object.keys(obj2));

    return diff;

Here's an example output:

// Test
let obj1 = {
    a: 1,
    b: 2,
    c: { foo: 1, bar: 2},
    d: { baz: 1, bat: 2 }

let obj2 = {
    b: 2, 
    c: { foo: 1, bar: 'monkey'}, 
    d: { baz: 1, bat: 2 }
    e: 1
getObjectDiff(obj1, obj2)
// ["c", "e", "a"]

If you don't care about nested objects and want to skip lodash, you can substitute the _.isEqual for a normal value comparison, e.g. obj1[key] === obj2[key].

How to stop Python closing immediately when executed in Microsoft Windows

I think I am too late to answer this question but anyways here goes nothing.

I have run in to the same problem before and I think there are two alternative solutions you can choose from.

  1. using sleep(_sometime)

from time import * sleep(10)

  1. using a prompt message (note that I am using python 2.7)

exit_now = raw_input("Do you like to exit now (Y)es (N)o ? ")'

if exit_now.lower() = 'n'

//more processing here

Alternatively you can use a hybrid of those two methods as well where you can prompt for a message and use sleep(sometime) to delay the window closing as well. choice is yours.

please note the above are just ideas and if you want to use any of those in practice you might have to think about your application logic a bit.

How do I get some variable from another class in Java?

I am trying to get int x equal to 5 (as seen in the setNum() method) but when it prints it gives me 0.

To run the code in setNum you have to call it. If you don't call it, the default value is 0.

PowerShell: Store Entire Text File Contents in Variable

Powershell 2.0:

(see detailed explanation here)

$text = Get-Content $filePath | Out-String

The IO.File.ReadAllText didn't work for me with a relative path, it looks for the file in %USERPROFILE%\$filePath instead of the current directory (when running from Powershell ISE at least):

$text = [IO.File]::ReadAllText($filePath)

Powershell 3+:

$text = Get-Content $filePath -Raw

Replace and overwrite instead of appending

You need seek to the beginning of the file before writing and then use file.truncate() if you want to do inplace replace:

import re

myfile = "path/test.xml"

with open(myfile, "r+") as f:
    data =
    f.write(re.sub(r"<string>ABC</string>(\s+)<string>(.*)</string>", r"<xyz>ABC</xyz>\1<xyz>\2</xyz>", data))

The other way is to read the file then open it again with open(myfile, 'w'):

with open(myfile, "r") as f:
    data =

with open(myfile, "w") as f:
    f.write(re.sub(r"<string>ABC</string>(\s+)<string>(.*)</string>", r"<xyz>ABC</xyz>\1<xyz>\2</xyz>", data))

Neither truncate nor open(..., 'w') will change the inode number of the file (I tested twice, once with Ubuntu 12.04 NFS and once with ext4).

By the way, this is not really related to Python. The interpreter calls the corresponding low level API. The method truncate() works the same in the C programming language: See

Split string using a newline delimiter with Python

data = """a,b,c

print(data.split())       # ['a,b,c', 'd,e,f', 'g,h,i', 'j,k,l']

str.split, by default, splits by all the whitespace characters. If the actual string has any other whitespace characters, you might want to use

print(data.split("\n"))   # ['a,b,c', 'd,e,f', 'g,h,i', 'j,k,l']

Or as @Ashwini Chaudhary suggested in the comments, you can use


How to get UTC timestamp in Ruby?

time =

Rationale: In my eyes a timestamp is exactly that: A point in time. This can be accurately represented with an object. If you need anything else, a scalar value, e.g. seconds since the Unix epoch, 100-ns intervals since 1601 or maybe a string for display purposes or storing the timestamp in a database, you can readily get that from the object. But that depends very much on your intended use.

Saying that »a true timestamp is the number of seconds since the Unix epoch« is a little missing the point, as that is one way of representing a point in time, but it also needs additional information to even know that you're dealing with a time and not a number. A Time object solves this problem nicely by representing a point in time and also being explicit about what it is.

How to hide a View programmatically?

You can call view.setVisibility(View.GONE) if you want to remove it from the layout.

Or view.setVisibility(View.INVISIBLE) if you just want to hide it.

From Android Docs:


This view is invisible, but it still takes up space for layout purposes. Use with setVisibility(int) and android:visibility.


This view is invisible, and it doesn't take any space for layout purposes. Use with setVisibility(int) and android:visibility.

Console logging for react?

If you want to log inside JSX you can create a dummy component
which plugs where you wish to log:

const Console = prop => (
  ,null // ? React components must return something 

// Some component with JSX and a logger inside
const App = () => 
    <p>imagine this is some component</p>
    <Console log='foo' />
    <p>imagine another component</p>
    <Console warn='bar' />

// Render 
  <App />,
<script src=""></script>
<script src=""></script>
<div id="react"></div>

How to fix Broken pipe?

I noticed I was using the incorrect HTTP request url while making it, later which i changed that it resolved my problem. my upload url was : while i was using that was a get call. and got a Broken pipe? exception.

That was my reason. might lead you to check one more point when this issue

  public void postRequest()  {

        Security.insertProviderAt(Conscrypt.newProvider(), 1);

        System.out.println("mediafilename-->>" + mediaFileName);
        String[] dirarray = mediaFileName.split("/");
        String file_name = dirarray[6];

        RequestBody requestBody = new MultipartBody.Builder()
                    .addFormDataPart("file",file_name, RequestBody.create(MediaType.parse("video/mp4"), new File(mediaFileName))).build();
        OkHttpClient okHttpClient = new OkHttpClient();
//        ExecutorService executor = newFixedThreadPool(20);
//        Request request = new Request.Builder().post(requestBody).url("").build();
        Request request = new Request.Builder().url("").post(requestBody).build();
//        Request request = new Request.Builder().url("").build();
        okHttpClient.newCall(request).enqueue(new Callback() {
            public void onFailure(@NotNull Call call, @NotNull IOException e) {



                runOnUiThread(new Runnable() {
                    public void run() {
                        Toast.makeText(getApplicationContext(),"Something went wrong:" + " ", Toast.LENGTH_SHORT).show();



            public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {

                runOnUiThread(new Runnable() {
                    public void run() {

                        try {
                        } catch (IOException e) {

                System.out.println("Response ; " + response.body().toString());
//                Toast.makeText(getApplicationContext(), response.body().toString(),Toast.LENGTH_LONG).show();


Is there any way to start with a POST request using Selenium?

Well, i agree with the @Mishkin Berteig - Agile Coach answer. Using the form is the quick way to use the POST features.

Anyway, i see some mention about javascript, but no code. I have that for my own needs, which includes jquery for easy POST plus others.

Basically, using the driver.execute_script() you can send any javascript, including Ajax queries.

# -*- coding: utf8 -*-
# proxy is used to inspect data involved on the request without so much code.
# using a basic http written in python. u can found it there:

import selenium
from selenium import webdriver
import requests
from selenium.webdriver.common.proxy import Proxy, ProxyType

jquery = open("jquery.min.js", "r").read()
#print jquery

proxy = Proxy()
proxy.proxy_type = ProxyType.MANUAL
proxy.http_proxy = ""
proxy.socks_proxy = ""
proxy.ssl_proxy = ""

capabilities = webdriver.DesiredCapabilities.PHANTOMJS

driver = webdriver.PhantomJS(desired_capabilities=capabilities)

driver.execute_script(jquery) # ensure we have jquery

ajax_query = '''
            $.post( "post", {
                "a" : "%s",
                "b" : "%s"
            ''' % (1,2)

ajax_query = ajax_query.replace(" ", "").replace("\n", "")
print ajax_query

result = driver.execute_script("return " + ajax_query)
#print result

#print driver.page_source


# this retuns that from the proxy, and is OK
Accept: */*
X-Requested-With: XMLHttpRequest
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/538.1 (KHTML, like Gecko) PhantomJS/2.0.0 Safari/538.1
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Content-Length: 7
Cookie: _ga=GAxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx; _gat=1
Connection: Keep-Alive
Accept-Encoding: gzip, deflate
Accept-Language: es-ES,en,*

a=1&b=2  <<---- that is OK, is the data contained into the POST

Pass C# ASP.NET array to Javascript array

I came up with this similar situation and I resolved it quiet easily.Here is what I did. Assuming you already have the value in array at your aspx.cs page.

1)Put a hidden field in your aspx page and us the hidden field ID to store the array value.

 HiddenField2.Value = string.Join(",", myarray);

2)Now that the hidden field has the value stored, just separated by commas. Use this hidden field in JavaScript like this. Simply create an array in JavaScript and then store the value in that array by removing the commas.

var hiddenfield2 = new Array();

This should solve your problem.

Value does not fall within the expected range

In case of WSS 3.0 recently I experienced same issue. It was because of column that was accessed from code was not present in the wss list.

What is the default lifetime of a session?

You can use something like ini_set('session.gc_maxlifetime', 28800); // 8 * 60 * 60 too.

How to display a JSON representation and not [Object Object] on the screen

  .subscribe(response => 
  this.records=JSON.stringify(response) // impoprtant

Shortcut to create properties in Visual Studio?

Go to

Tools >> Options >> Text Editor >> C# >> IntelliSense

Under the Snippets behaviour section:

Make sure "Always include snippets" is selected.

I hope it works for you too.

Adding event listeners to dynamically added elements using jQuery

Using .on() you can define your function once, and it will execute for any dynamically added elements.

for example

$('#staticDiv').on('click', 'yourSelector', function() {
  //do something

Who is listening on a given TCP port on Mac OS X?


sudo lsof -n -i -P | grep TCP

For the LISTEN ports only

sudo lsof -n -i -P | grep LISTEN

For a specific LISTEN port, ex: port 80

sudo lsof -n -i -P | grep ':80 (LISTEN)'

Or if you just want a compact summary [no service/apps described], go by NETSTAT. The good side here is, no sudo needed

netstat -a -n | grep 'LISTEN '

Explaining the items used:

-n suppress the host name

-i for IPv4 and IPv6 protocols

-P omit port names

-a [over netstat] for all sockets

-n [over netstat] don't resolve names, show network addresses as numbers

Tested on High Sierra 10.13.3 and Mojave 10.14.3

  • the last syntax netstat works on linux too

Uninstalling an MSI file from the command line without using msiexec

Short answer: you can't. Use MSIEXEC /x

Long answer: When you run the MSI file directly at the command line, all that's happening is that it runs MSIEXEC for you. This association is stored in the registry. You can see a list of associations by (in Windows Explorer) going to Tools / Folder Options / File Types.

For example, you can run a .DOC file from the command line, and WordPad or WinWord will open it for you.

If you look in the registry under HKEY_CLASSES_ROOT\.msi, you'll see that .MSI files are associated with the ProgID "Msi.Package". If you look in HKEY_CLASSES_ROOT\Msi.Package\shell\Open\command, you'll see the command line that Windows actually uses when you "run" a .MSI file.

Sending email through Gmail SMTP server with C#

Simple steps to fix this:

1)Sign in to your Gmail

2)Navigate to this page & set to "Turn On"

Check if element found in array c++

In C++ you would use std::find, and check if the resultant pointer points to the end of the range, like this:

Foo array[10];
... // Init the array here
Foo *foo = std::find(std::begin(array), std::end(array), someObject);
// When the element is not found, std::find returns the end of the range
if (foo != std::end(array)) {
    cerr << "Found at position " << std::distance(array, foo) << endl;
} else {
    cerr << "Not found" << endl;

keytool error bash: keytool: command not found

If you are not using openjdk, use the below commands to set your keytool.

sudo update-alternatives --install "/usr/bin/keytool" "keytool" "/usr/lib/jvm/java8/jdk1.8.0_251/bin/keytool" 1


sudo update-alternatives --set keytool /usr/lib/jvm/java8/jdk1.8.0_251/bin/keytool

This worked for me!

How to create full compressed tar file using Python?

In addition to @Aleksandr Tukallo's answer, you could also obtain the output and error message (if occurs). Compressing a folder using tar is explained pretty well on the following answer.

import traceback
import subprocess

    cmd = ['tar', 'czfj', output_filename, file_to_archive]
    output = subprocess.check_output(cmd).decode("utf-8").strip() 
except Exception:       
    print(f"E: {traceback.format_exc()}")       

How is a JavaScript hash map implemented?

<script type="text/javascript">
function test(){
var map= {'m1': 12,'m2': 13,'m3': 14,'m4': 15}
<input type="button" value="click" onclick="test()"/>

End of File (EOF) in C

That's a lot of questions.

  1. Why EOF is -1: usually -1 in POSIX system calls is returned on error, so i guess the idea is "EOF is kind of error"

  2. any boolean operation (including !=) returns 1 in case it's TRUE, and 0 in case it's FALSE, so getchar() != EOF is 0 when it's FALSE, meaning getchar() returned EOF.

  3. in order to emulate EOF when reading from stdin press Ctrl+D

SSRS the definition of the report is invalid

I got this error on a report I copied from another project and changed the data source. I solved it by opening the properties of my dataset, going to the Parameters section, and literally just reselecting all the parameters in the right column, like I just clicked the dropdown and selected the same column. Then I hit preview, and it worked!

Create a new database with MySQL Workbench

This answer is for Ubuntu users looking for a solution without writing SQL queries.

The following is the initial screen you'll get after opening it

Initial screen

In the top right, where it says Administration, click in the arrow to the right

From Administration to Schemas

This will show Schema (instead of Administration) and it's possible to see a sys database.

Schema menu with databases

Right click in the grey area after functions and click Create Schema...

Create Schema

This will open the following where I'm creating a table named StackOverflow_db

Create new Schema

Clicking in the bottom right button that says "Apply",

Create a new Schema in Workbench

And in this new view click in "Apply" too. In the end you'll get a database called StackOverflow_db

Database created

Fatal error: Call to undefined function mysql_connect() in C:\Apache\htdocs\test.php on line 2

Change the database.php file from

$db['default']['dbdriver'] = 'mysql';


$db['default']['dbdriver'] = 'mysqli';

When does System.gc() do something?

You need to be very careful if you call System.gc(). Calling it can add unnecessary performance issues to your application, and it is not guaranteed to actually perform a collection. It is actually possible to disable explicit System.gc() via the java argument -XX:+DisableExplicitGC.

I'd highly recommend reading through the documents available at Java HotSpot Garbage Collection for more in depth details about garbage collection.

Using Apache POI how to read a specific excel column

Here is the code to read the excel data by column.

public ArrayList<String> extractExcelContentByColumnIndex(int columnIndex){
        ArrayList<String> columndata = null;
        try {
            File f = new File("sample.xlsx")
            FileInputStream ios = new FileInputStream(f);
            XSSFWorkbook workbook = new XSSFWorkbook(ios);
            XSSFSheet sheet = workbook.getSheetAt(0);
            Iterator<Row> rowIterator = sheet.iterator();
            columndata = new ArrayList<>();

            while (rowIterator.hasNext()) {
                Row row =;
                Iterator<Cell> cellIterator = row.cellIterator();
                while (cellIterator.hasNext()) {
                    Cell cell =;

                    if(row.getRowNum() > 0){ //To filter column headings
                        if(cell.getColumnIndex() == columnIndex){// To match column index
                            switch (cell.getCellType()) {
                            case Cell.CELL_TYPE_NUMERIC:
                            case Cell.CELL_TYPE_STRING:
        } catch (Exception e) {
        return columndata;

Android studio logcat nothing to show

You may put some text in the search and filter out the Logcat result.
That was the reason for my problem :)

Adding new files to a subversion repository

  • Checkout a working copy of the repository (or at least the subdirectory that you want to add the files to): svn checkout
  • Copy the files over there.
  • svn add file1 file2...
  • svn commit

I am not aware of a quicker option.

Note: if you are on the same machine as your Subversion repository, the URL can use the file: specifier with a path in place of https: in the svn checkout command. For example svn checkout file:///path/to/repo/bleh.

PS. as pointed out in the comments and other answers, you can use something like svn import . <URL> if you want to recursively import everything in the current directory. With this option, however, you can't skip over some of the files; it's all or nothing.

box-shadow on bootstrap 3 container

Add an additional div around all container divs you want the drop shadow to encapsulate. Add the classes drop-shadow and container to the additional div. The class .container will keep the fluidity. Use the class .drop-shadow (or whatever you like) to add the box-shadow property. Then target the .drop-shadow div and negate the unwanted styles .container adds--such as left & right padding.


It'll be something like:

<div class="container drop-shadow">
    <div class="container">
        <div class="row">
            <div class="col-md-8">Main Area</div>
            <div class="col-md-4">Side Area</div>

And your CSS:

    .drop-shadow {
        -webkit-box-shadow: 0 0 5px 2px rgba(0, 0, 0, .5);
        box-shadow: 0 0 5px 2px rgba(0, 0, 0, .5);
    .container.drop-shadow {

What does the return keyword do in a void method in Java?

See this example, you want to add to the list conditionally. Without the word "return", all ifs will be executed and add to the ArrayList!

    Arraylist<String> list =  new ArrayList<>();

    public void addingToTheList() {

    if(isSunday()) {
        list.add("Pray today")

    if(isMonday()) {
        list.add("Work today"

    if(isTuesday()) {
        list.add("Tr today")

How to add text inside the doughnut chart using Chart.js?

None of the other answers resize the text based off the amount of text and the size of the doughnut. Here is a small script you can use to dynamically place any amount of text in the middle, and it will automatically resize it.


Doughnut With Dynamic Text in the Middle

It will take any amount of text in the doughnut sized perfect for the doughnut. To avoid touching the edges you can set a side-padding as a percentage of the diameter of the inside of the circle. If you don't set it, it will default to 20. You also the color, the font, and the text. The plugin takes care of the rest.

The plugin code will start with a base font size of 30px. From there it will check the width of the text and compare it against the radius of the circle and resize it based off the circle/text width ratio.

It has a default minimum font size of 20px. If the text would exceed the bounds at the minimum font size, it will wrap the text. The default line height when wrapping the text is 25px, but you can change it. If you set the default minimum font size to false, the text will become infinitely small and will not wrap.

It also has a default max font size of 75px in case there is not enough text and the lettering would be too big.

This is the plugin code

  beforeDraw: function(chart) {
    if ( {
      // Get ctx from string
      var ctx = chart.chart.ctx;

      // Get options from the center object in options
      var centerConfig =;
      var fontStyle = centerConfig.fontStyle || 'Arial';
      var txt = centerConfig.text;
      var color = centerConfig.color || '#000';
      var maxFontSize = centerConfig.maxFontSize || 75;
      var sidePadding = centerConfig.sidePadding || 20;
      var sidePaddingCalculated = (sidePadding / 100) * (chart.innerRadius * 2)
      // Start with a base font of 30px
      ctx.font = "30px " + fontStyle;

      // Get the width of the string and also the width of the element minus 10 to give it 5px side padding
      var stringWidth = ctx.measureText(txt).width;
      var elementWidth = (chart.innerRadius * 2) - sidePaddingCalculated;

      // Find out how much the font can grow in width.
      var widthRatio = elementWidth / stringWidth;
      var newFontSize = Math.floor(30 * widthRatio);
      var elementHeight = (chart.innerRadius * 2);

      // Pick a new font size so it will not be larger than the height of label.
      var fontSizeToUse = Math.min(newFontSize, elementHeight, maxFontSize);
      var minFontSize = centerConfig.minFontSize;
      var lineHeight = centerConfig.lineHeight || 25;
      var wrapText = false;

      if (minFontSize === undefined) {
        minFontSize = 20;

      if (minFontSize && fontSizeToUse < minFontSize) {
        fontSizeToUse = minFontSize;
        wrapText = true;

      // Set font settings to draw it correctly.
      ctx.textAlign = 'center';
      ctx.textBaseline = 'middle';
      var centerX = ((chart.chartArea.left + chart.chartArea.right) / 2);
      var centerY = (( + chart.chartArea.bottom) / 2);
      ctx.font = fontSizeToUse + "px " + fontStyle;
      ctx.fillStyle = color;

      if (!wrapText) {
        ctx.fillText(txt, centerX, centerY);

      var words = txt.split(' ');
      var line = '';
      var lines = [];

      // Break words up into multiple lines if necessary
      for (var n = 0; n < words.length; n++) {
        var testLine = line + words[n] + ' ';
        var metrics = ctx.measureText(testLine);
        var testWidth = metrics.width;
        if (testWidth > elementWidth && n > 0) {
          line = words[n] + ' ';
        } else {
          line = testLine;

      // Move the center up depending on line height and number of lines
      centerY -= (lines.length / 2) * lineHeight;

      for (var n = 0; n < lines.length; n++) {
        ctx.fillText(lines[n], centerX, centerY);
        centerY += lineHeight;
      //Draw text in center
      ctx.fillText(line, centerX, centerY);

And you use the following options in your chart object

options: {
  elements: {
    center: {
      text: 'Red is 2/3 the total numbers',
      color: '#FF6384', // Default is #000000
      fontStyle: 'Arial', // Default is Arial
      sidePadding: 20, // Default is 20 (as a percentage)
      minFontSize: 20, // Default is 20 (in px), set to false and text will not wrap.
      lineHeight: 25 // Default is 25 (in px), used for when text wraps

Credit to @Jenna Sloan for help with the math used in this solution.

Specifying width and height as percentages without skewing photo proportions in HTML

Note: it is invalid to provide percentages directly as <img> width or height attribute unless you're using HTML 4.01 (see current spec, obsolete spec and this answer for more details). That being said, browsers will often tolerate such behaviour to support backwards-compatibility.

Those percentage widths in your 2nd example are actually applying to the container your <img> is in, and not the image's actual size. Say you have the following markup:

<div style="width: 1000px; height: 600px;">
    <img src="#" width="50%" height="50%">

Your resulting image will be 500px wide and 300px tall.

jQuery Resize

If you're trying to reduce an image to 50% of its width, you can do it with a snippet of jQuery:

$( "img" ).each( function() {
    var $img = $( this );
    $img.width( $img.width() * .5 );

Just make sure you take off any height/width = 50% attributes first.

When should I use GET or POST method? What's the difference between them?

It's not a matter of security. The HTTP protocol defines GET-type requests as being idempotent, while POSTs may have side effects. In plain English, that means that GET is used for viewing something, without changing it, while POST is used for changing something. For example, a search page should use GET, while a form that changes your password should use POST.

Also, note that PHP confuses the concepts a bit. A POST request gets input from the query string and through the request body. A GET request just gets input from the query string. So a POST request is a superset of a GET request; you can use $_GET in a POST request, and it may even make sense to have parameters with the same name in $_POST and $_GET that mean different things.

For example, let's say you have a form for editing an article. The article-id may be in the query string (and, so, available through $_GET['id']), but let's say that you want to change the article-id. The new id may then be present in the request body ($_POST['id']). OK, perhaps that's not the best example, but I hope it illustrates the difference between the two.


This terminal command:

open /Applications/Python\ 3.7/Install\ Certificates.command

Found here:

Resolved it for me. With my config

pip install --upgrade certifi

had no impact.

webpack: Module not found: Error: Can't resolve (with relative path)

while importing libraries use the exact path to a file, including the directory relative to the current file, for example:

import Footer from './Footer/index.jsx'
import AddTodo from '../containers/AddTodo/index.jsx'
import VisibleTodoList from '../containers/VisibleTodoList/index.jsx'

Hope this may help

How can I pretty-print JSON using Go?

Here's what I use. If it fails to pretty print the JSON it just returns the original string. Useful for printing HTTP responses that should contain JSON.

import (

func jsonPrettyPrint(in string) string {
    var out bytes.Buffer
    err := json.Indent(&out, []byte(in), "", "\t")
    if err != nil {
        return in
    return out.String()

MVC 4 @Scripts "does not exist"

I had the same problem and I used WinMerge to help me track this down. But as I researched it more, I found that Rick has the perfect blog post for it.


  • Add <add namespace="System.Web.Optimization"/> to both web.config files
  • Run Install-Package -IncludePrerelease Microsoft.AspNet.Web.Optimization
  • Update Bundling code
  • Update Layout file
  • The last step is to update 10 other libraries. I didn't and it worked fine. So looks like you can procrastinate this one (unless I already updated 1 or more of them). :)

Speed comparison with Project Euler: C vs Python vs Erlang vs Haskell

Trying GO:

package main

import "fmt"
import "math"

func main() {
    var n, m, c int
    for i := 1; ; i++ {
        n, m, c = i * (i + 1) / 2, int(math.Sqrt(float64(n))), 0
        for f := 1; f < m; f++ {
            if n % f == 0 { c++ }
    c *= 2
    if m * m == n { c ++ }
    if c > 1001 {

I get:

original c version: 9.1690 100%
go: 8.2520 111%

But using:

package main

import (

// Sieve of Eratosthenes
func PrimesBelow(limit int) []int {
    switch {
        case limit < 2:
            return []int{}
        case limit == 2:
            return []int{2}
    sievebound := (limit - 1) / 2
    sieve := make([]bool, sievebound+1)
    crosslimit := int(math.Sqrt(float64(limit))-1) / 2
    for i := 1; i <= crosslimit; i++ {
        if !sieve[i] {
            for j := 2 * i * (i + 1); j <= sievebound; j += 2*i + 1 {
                sieve[j] = true
    plimit := int(1.3*float64(limit)) / int(math.Log(float64(limit)))
    primes := make([]int, plimit)
    p := 1
    primes[0] = 2
    for i := 1; i <= sievebound; i++ {
        if !sieve[i] {
            primes[p] = 2*i + 1
            if p >= plimit {
    last := len(primes) - 1
    for i := last; i > 0; i-- {
        if primes[i] != 0 {
        last = i
    return primes[0:last]

func main() {
// Requires PrimesBelow from utils.go
func p12() int {
    n, dn, cnt := 3, 2, 0
    primearray := PrimesBelow(1000000)
    for cnt <= 1001 {
        n1 := n
        if n1%2 == 0 {
            n1 /= 2
        dn1 := 1
        for i := 0; i < len(primearray); i++ {
            if primearray[i]*primearray[i] > n1 {
                dn1 *= 2
            exponent := 1
            for n1%primearray[i] == 0 {
                n1 /= primearray[i]
            if exponent > 1 {
                dn1 *= exponent
            if n1 == 1 {
        cnt = dn * dn1
        dn = dn1
    return n * (n - 1) / 2

I get:

original c version: 9.1690 100%
thaumkid's c version: 0.1060 8650%
first go version: 8.2520 111%
second go version: 0.0230 39865%

I also tried Python3.6 and pypy3.3-5.5-alpha:

original c version: 8.629 100%
thaumkid's c version: 0.109 7916%
Python3.6: 54.795 16%
pypy3.3-5.5-alpha: 13.291 65%

and then with following code I got:

original c version: 8.629 100%
thaumkid's c version: 0.109 8650%
Python3.6: 1.489 580%
pypy3.3-5.5-alpha: 0.582 1483%

def D(N):
    if N == 1: return 1
    sqrtN = int(N ** 0.5)
    nf = 1
    for d in range(2, sqrtN + 1):
        if N % d == 0:
            nf = nf + 1
    return 2 * nf - (1 if sqrtN**2 == N else 0)

L = 1000
Dt, n = 0, 0

while Dt <= L:
    t = n * (n + 1) // 2
    Dt = D(n/2)*D(n+1) if n%2 == 0 else D(n)*D((n+1)/2)
    n = n + 1

print (t)

Maven: Non-resolvable parent POM

I had the issue that two reactor build pom.xml files had the same artefactId.

Using Excel VBA to run SQL query

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

References required for SQL

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

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

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

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

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

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

jQuery remove selected option from this

This is a simpler one


How to persist a property of type List<String> in JPA?

Ok i know its bit late. But for those brave souls that will see this as time passes.

As written in documentation:

@Basic: The simplest type of mapping to a database column. The Basic annotation can be applied to a persistent property or instance variable of any of the following types: Java primitive types, [...], enums, and any other type that implements

The important part is type that implements Serializable

So by far the most simple and easiest to use solution is simply using ArrayList instead of List (or any serializable container):

ArrayList<Color> lovedColors;

ArrayList<String> catNames;

Remember however that this will use system serialization, so it will come with some price, such as:

  • if serialized object model will change, u might not be able to restore data

  • small overhead is added for each element stored.

In short

it is quite simple to store flags or few elements, but i would not recomend it to store data that might grow big.

How do I subscribe to all topics of a MQTT broker

Use the wildcard "#" but beware that at some point you will have to somehow understand the data passing through the bus!

Using lodash to compare jagged arrays (items existence without order)

There are already answers here, but here's my pure JS implementation. I'm not sure if it's optimal, but it sure is transparent, readable, and simple.

// Does array a contain elements of array b?
const contains = (a, b) => new Set([...a, ...b]).size === a.length
const isEqualSet = (a, b) => contains(a, b) && contains(b, a)

The rationale in contains() is that if a does contain all the elements of b, then putting them into the same set would not change the size.

For example, if const a = [1,2,3,4] and const b = [1,2], then new Set([...a, ...b]) === {1,2,3,4}. As you can see, the resulting set has the same elements as a.

From there, to make it more concise, we can boil it down to the following:

const isEqualSet = (a, b) => {
  const unionSize = new Set([...a, ...b])
  return unionSize === a.length && unionSize === b.length

How to set a default Value of a UIPickerView

In normal case, you can do something like this in viewDidLoad method;

[_picker selectRow:1 inComponent:0 animated:YES];

In my case, I'd like to fetch data from api server and display them onto UIPickerView then I want the picker to select the first item by default.

The UIPickerView will look like it selected the first item after it was created, but when you try to get the selected index by using selectedRowInComponent, you will get NSNull. That's because it detected nothing changed by the user (select 0 from 0 ).

Following is my solution (in viewWillAppear, after I fetched the data)

[_picker selectRow:1 inComponent:0 animated:NO];
[_picker selectRow:0 inComponent:0 animated:NO];

Its a bit dirty, but dont worry, the UI rendering in iOS is very fast ;)

Calculate relative time in C#

 * {@code date1} has to be earlier than {@code date2}.
public static String relativize(Date date1, Date date2) {
    assert date2.getTime() >= date1.getTime();

    long duration = date2.getTime() - date1.getTime();
    long converted;

    if ((converted = TimeUnit.MILLISECONDS.toDays(duration)) > 0) {
        return String.format("%d %s ago", converted, converted == 1 ? "day" : "days");
    } else if ((converted = TimeUnit.MILLISECONDS.toHours(duration)) > 0) {
        return String.format("%d %s ago", converted, converted == 1 ? "hour" : "hours");
    } else if ((converted = TimeUnit.MILLISECONDS.toMinutes(duration)) > 0) {
        return String.format("%d %s ago", converted, converted == 1 ? "minute" : "minutes");
    } else if ((converted = TimeUnit.MILLISECONDS.toSeconds(duration)) > 0) {
        return String.format("%d %s ago", converted, converted == 1 ? "second" : "seconds");
    } else {
        return "just now";

How to determine if a list of polygon points are in clockwise order?

For what it is worth, I used this mixin to calculate the winding order for Google Maps API v3 apps.

The code leverages the side effect of polygon areas: a clockwise winding order of vertexes yields a positive area, while a counter-clockwise winding order of the same vertexes produces the same area as a negative value. The code also uses a sort of private API in the Google Maps geometry library. I felt comfortable using it - use at your own risk.

Sample usage:

var myPolygon = new google.maps.Polygon({/*options*/});
var isCW = myPolygon.isPathClockwise();

Full example with unit tests @

/** Mixin to extend the behavior of the Google Maps JS API Polygon type
 *  to determine if a polygon path has clockwise of counter-clockwise winding order.
 *  Tested against v3.14 of the GMaps API.
 *  @author  [email protected]
 *  @license
 *  @version 1.0
 *  @mixin
 *  @param {(number|Array|google.maps.MVCArray)} [path] - an optional polygon path; defaults to the first path of the polygon
 *  @returns {boolean} true if the path is clockwise; false if the path is counter-clockwise
(function() {
  var category = 'google.maps.Polygon.isPathClockwise';
     // check that the GMaps API was already loaded
  if (null == google || null == google.maps || null == google.maps.Polygon) {
    console.error(category, 'Google Maps API not found');
  if (typeof(google.maps.geometry.spherical.computeArea) !== 'function') {
    console.error(category, 'Google Maps geometry library not found');

  if (typeof(google.maps.geometry.spherical.computeSignedArea) !== 'function') {
    console.error(category, 'Google Maps geometry library private function computeSignedArea() is missing; this may break this mixin');

  function isPathClockwise(path) {
    var self = this,

    if (null === path)
      throw new Error('Path is optional, but cannot be null');

    // default to the first path
    if (arguments.length === 0)
        path = self.getPath();

    // support for passing an index number to a path
    if (typeof(path) === 'number')
        path = self.getPaths().getAt(path);

    if (!path instanceof Array && !path instanceof google.maps.MVCArray)
      throw new Error('Path must be an Array or MVCArray');

    // negative polygon areas have counter-clockwise paths
    isCounterClockwise = (google.maps.geometry.spherical.computeSignedArea(path) < 0);

    return (!isCounterClockwise);

  if (typeof(google.maps.Polygon.prototype.isPathClockwise) !== 'function') {
    google.maps.Polygon.prototype.isPathClockwise = isPathClockwise;

Responsive css background images

#container {
    background-image: url("../images/layout/bg.png");
    background-repeat: no-repeat;
    background-size: 100% 100%;
    height: 100vh;
    margin: 3px auto 0;
    position: relative;

CSS Div width percentage and padding without breaking layout

If you want the #header to be the same width as your container, with 10px of padding, you can leave out its width declaration. That will cause it to implicitly take up its entire parent's width (since a div is by default a block level element).

Then, since you haven't defined a width on it, the 10px of padding will be properly applied inside the element, rather than adding to its width:

#container {
    position: relative;
    width: 80%;

#header {
    position: relative;
    height: 50px;
    padding: 10px;

You can see it in action here.

The key when using percentage widths and pixel padding/margins is not to define them on the same element (if you want to accurately control the size). Apply the percentage width to the parent and then the pixel padding/margin to a display: block child with no width set.


Another option for dealing with this is to use the box-sizing CSS rule:

#container { 
    -webkit-box-sizing: border-box; /* Safari/Chrome, other WebKit */
    -moz-box-sizing: border-box;    /* Firefox, other Gecko */
    box-sizing: border-box;         /* Opera/IE 8+ */

    /* Since this element now uses border-box sizing, the 10px of horizontal
       padding will be drawn inside the 80% width */
    width: 80%;
    padding: 0 10px;

Here's a post talking about how box-sizing works.

chart.js load totally new data

The only solution I can find so far for myself is to re-initialize the chart from scratch:

var myLineChart = new Chart(ctx).Line(data, options);

However this seems a bit hokey to me. Any better, more standard solution anybody?

What can <f:metadata>, <f:viewParam> and <f:viewAction> be used for?

Process GET parameters

The <f:viewParam> manages the setting, conversion and validation of GET parameters. It's like the <h:inputText>, but then for GET parameters.

The following example

    <f:viewParam name="id" value="#{}" />

does basically the following:

  • Get the request parameter value by name id.
  • Convert and validate it if necessary (you can use required, validator and converter attributes and nest a <f:converter> and <f:validator> in it like as with <h:inputText>)
  • If conversion and validation succeeds, then set it as a bean property represented by #{} value, or if the value attribute is absent, then set it as request attribtue on name id so that it's available by #{id} in the view.

So when you open the page as foo.xhtml?id=10 then the parameter value 10 get set in the bean this way, right before the view is rendered.

As to validation, the following example sets the param to required="true" and allows only values between 10 and 20. Any validation failure will result in a message being displayed.

    <f:viewParam id="id" name="id" value="#{}" required="true">
        <f:validateLongRange minimum="10" maximum="20" />
<h:message for="id" />

Performing business action on GET parameters

You can use the <f:viewAction> for this.

    <f:viewParam id="id" name="id" value="#{}" required="true">
        <f:validateLongRange minimum="10" maximum="20" />
    <f:viewAction action="#{bean.onload}" />
<h:message for="id" />


public void onload() {
    // ...

The <f:viewAction> is however new since JSF 2.2 (the <f:viewParam> already exists since JSF 2.0). If you can't upgrade, then your best bet is using <f:event> instead.

<f:event type="preRenderView" listener="#{bean.onload}" />

This is however invoked on every request. You need to explicitly check if the request isn't a postback:

public void onload() {
    if (!FacesContext.getCurrentInstance().isPostback()) {
        // ...

When you would like to skip "Conversion/Validation failed" cases as well, then do as follows:

public void onload() {
    FacesContext facesContext = FacesContext.getCurrentInstance();
    if (!facesContext.isPostback() && !facesContext.isValidationFailed()) {
        // ...

Using <f:event> this way is in essence a workaround/hack, that's exactly why the <f:viewAction> was introduced in JSF 2.2.

Pass view parameters to next view

You can "pass-through" the view parameters in navigation links by setting includeViewParams attribute to true or by adding includeViewParams=true request parameter.

<h:link outcome="next" includeViewParams="true">
<!-- Or -->
<h:link outcome="next?includeViewParams=true">

which generates with the above <f:metadata> example basically the following link

<a href="next.xhtml?id=10">

with the original parameter value.

This approach only requires that next.xhtml has also a <f:viewParam> on the very same parameter, otherwise it won't be passed through.

Use GET forms in JSF

The <f:viewParam> can also be used in combination with "plain HTML" GET forms.

    <f:viewParam id="query" name="query" value="#{bean.query}" />
    <f:viewAction action="#{}" />
    <label for="query">Query</label>
    <input type="text" name="query" value="#{empty bean.query ? param.query : bean.query}" />
    <input type="submit" value="Search" />
    <h:message for="query" />
<h:dataTable value="#{bean.results}" var="result" rendered="#{not empty bean.results}">

With basically this @RequestScoped bean:

private String query;
private List<Result> results;

public void search() {
    results =;

Note that the <h:message> is for the <f:viewParam>, not the plain HTML <input type="text">! Also note that the input value displays #{param.query} when #{bean.query} is empty, because the submitted value would otherwise not show up at all when there's a validation or conversion error. Please note that this construct is invalid for JSF input components (it is doing that "under the covers" already).

See also:

Submit form and stay on same page?

When you hit on the submit button, the page is sent to the server. If you want to send it async, you can do it with ajax.

newline in <td title="">

If you're looking to put line breaks into the tooltip that appears on mouseover, there's no reliable crossbrowser way to do that. You'd have to fall back to one of the many Javascript tooltip code samples

Convert pyspark string to date format

The strptime() approach does not work for me. I get another cleaner solution, using cast:

from pyspark.sql.types import DateType
spark_df1 = spark_df.withColumn("record_date",spark_df['order_submitted_date'].cast(DateType()))
#below is the result'order_submitted_date','record_date').show(10,False)

|order_submitted_date |record_date|
|2015-08-19 12:54:16.0|2015-08-19 |
|2016-04-14 13:55:50.0|2016-04-14 |
|2013-10-11 18:23:36.0|2013-10-11 |
|2015-08-19 20:18:55.0|2015-08-19 |
|2015-08-20 12:07:40.0|2015-08-20 |
|2013-10-11 21:24:12.0|2013-10-11 |
|2013-10-11 23:29:28.0|2013-10-11 |
|2015-08-20 16:59:35.0|2015-08-20 |
|2015-08-20 17:32:03.0|2015-08-20 |
|2016-04-13 16:56:21.0|2016-04-13 |

Date constructor returns NaN in IE, but works in Firefox and Chrome

You can use the following code to parse ISO8601 date string:

function parseISO8601(d) {
    var timestamp = d;
    if (typeof (d) !== 'number') {
        timestamp = Date.parse(d);
    return new Date(timestamp);

Display html text in uitextview

Use a UIWebView on iOS 5-.

On iOS 6+ you can use UITextView.attributedString, see for how.

There's also an undocumented -[UITextView setContentToHTMLString:] method. Do not use this if you want to submit to AppStore.

Get the name of a pandas DataFrame

From here what I understand DataFrames are:

DataFrame is a 2-dimensional labeled data structure with columns of potentially different types. You can think of it like a spreadsheet or SQL table, or a dict of Series objects.

And Series are:

Series is a one-dimensional labeled array capable of holding any data type (integers, strings, floating point numbers, Python objects, etc.).

Series have a name attribute which can be accessed like so:

 In [27]: s = pd.Series(np.random.randn(5), name='something')

 In [28]: s
 0    0.541
 1   -1.175
 2    0.129
 3    0.043
 4   -0.429
 Name: something, dtype: float64

 In [29]:
 Out[29]: 'something'

EDIT: Based on OP's comments, I think OP was looking for something like:

 >>> df = pd.DataFrame(...)
 >>> = 'df' # making a custom attribute that DataFrame doesn't intrinsically have
 >>> print(

Pandas - replacing column values

Can try this too!
Create a dictionary of replacement values.

import pandas as pd
data = pd.DataFrame([[1,0],[0,1],[1,0],[0,1]], columns=["sex", "split"])

enter image description here

replace_dict= {0:'Female',1:'Male'}

enter image description here

Use the map function for replacing values


Output after replacing
enter image description here

Using Keras & Tensorflow with AMD GPU

If you have access to other AMD gpu's please see here:

This should get you going in the right direction for tensorflow on the ROCm platform, but Selly's post about is the deal with this route. That page is not an exhaustive list, I found out on my own that the Xeon E5 v2 Ivy Bridge works fine with ROCm even though they list v3 or newer, graphics cards however are a bit more picky. gfx8 or newer with a few small exceptions, polaris and maybe others as time goes on.

UPDATE - It looks like hiptensorflow has an option for opencl support during configure. I would say investigate the link even if you don't have gfx8+ or polaris gpu if the opencl implementation works. It is a long winded process but an hour or three (depending on hardware) following a well written instruction isn't too much to lose to find out.

jquery, selector for class within id

Also $( "#container" ).find( "div.robotarm" );
is equal to: $( "div.robotarm", "#container" )


CREATE TABLE new_table LIKE old_table;

or u can use this

CREATE TABLE new_table as SELECT * FROM old_table WHERE 1 GROUP BY [column to remove duplicates by];

Playing .mp3 and .wav in Java?

I would recommend using the BasicPlayerAPI. It's open source, very simple and it doesn't require JavaFX.

After downloading and extracting the zip-file one should add the following jar-files to the build path of the project:

  • basicplayer3.0.jar
  • all the jars from the lib directory (inside BasicPlayer3.0)

Here is a minimalistic usage example:

String songName = "HungryKidsofHungary-ScatteredDiamonds.mp3";
String pathToMp3 = System.getProperty("user.dir") +"/"+ songName;
BasicPlayer player = new BasicPlayer();
try { URL("file:///" + pathToMp3));;
} catch (BasicPlayerException | MalformedURLException e) {

Required imports:

import javazoom.jlgui.basicplayer.BasicPlayer;
import javazoom.jlgui.basicplayer.BasicPlayerException;

That's all you need to start playing music. The Player is starting and managing his own playback thread and provides play, pause, resume, stop and seek functionality.

For a more advanced usage you may take a look at the jlGui Music Player. It's an open source WinAmp clone:

The first class to look at would be PlayerUI (inside the package javazoom.jlgui.player.amp). It demonstrates the advanced features of the BasicPlayer pretty well.

Vagrant stuck connection timeout retrying

If you're using a wrapper layer (like Kitchen CI) and you're running a 32b host, you'll have to preempt the installation of Vagrant boxes. Their default provider is the opscode "family" of binaries.

So before kitchen create default-ubuntu-1204 make sure you use:

vagrant box add default-ubuntu-1204

for using the 32b image if your host doesn't support word size virtualization

If else in stored procedure sql server

Try this with join query statements

CREATE PROCEDURE [dbo].[deleteItem]
@ItemId int = 0 
 DECLARE @cnt int;

SELECT @cnt =COUNT(ttm.Id) 
    from ItemTransaction itr INNER JOIN ItemUnitMeasurement ium 
        ON itr.Id = ium.ItemTransactionId  INNER JOIN ItemMaster im 
        ON itr.ItemId = im.Id INNER JOIN TransactionTypeMaster ttm 
        ON itr.TransactionTypeMasterId = ttm.Id 
        where im.Id = @ItemId

if(@cnt = 1)
    DECLARE @transactionType varchar(255);
    DECLARE @mesurementAmount float;
    DECLARE @itemTransactionId int;
    DECLARE @itemUnitMeasurementId int;

        SELECT @transactionType = ttm.TransactionType,  @mesurementAmount = ium.Amount, @itemTransactionId = itr.Id, @itemUnitMeasurementId = ium.Id
        from ItemTransaction itr INNER JOIN ItemUnitMeasurement ium 
            ON itr.Id = ium.ItemTransactionId INNER JOIN TransactionTypeMaster ttm 
            ON itr.TransactionTypeMasterId = ttm.Id 
            where itr.ItemId = @ItemId  
        if(@transactionType = 'Close' and @mesurementAmount = 0)
                delete from ItemUnitMeasurement where Id = @itemUnitMeasurementId;

                delete from ItemTransaction where Id = @itemTransactionId;
    delete from ItemMaster where Id = @ItemId;

Bold black cursor in Eclipse deletes code, and I don't know how to get rid of it

This issue can happen not only in but also in any of the .

On systems, in my case, this issue arose when the shift and insert key was pressed in tandem unintentionally which takes the user to the overwrite mode.

To get back to insert mode you need to press shift and insert in tandem again.

Where is after pip install?

On Mac OS


u got


and u can

sudo ln /Library/Frameworks/Python.framework/Versions/2.7/bin/ /usr/local/bin/

and in your .bash_profile

source /usr/local/bin/

or u can

source /Library/Frameworks/Python.framework/Versions/2.7/bin/

Java - Abstract class to contain variables?

Of course. The whole idea of abstract classes is that they can contain some behaviour or data which you require all sub-classes to contain. Think of the simple example of WheeledVehicle - it should have a numWheels member variable. You want all sub classes to have this variable. Remember that abstract classes are a very useful feature when developing APIs, as they can ensure that people who extend your API won't break it.

How do I get a div to float to the bottom of its container?

Stu's answer comes the closest to working so far, but it still doesn't take into account the fact that your outer div's height may change, based on the way the text wraps inside of it. So, repositioning the inner div (by changing the height of the "pipe") only once won't be enough. That change has to occur inside of a loop, so you can continually check whether you've achieved the right positioning yet, and readjust if needed.

The CSS from the previous answer is still perfectly valid:

#outer {
    position: relative; 

#inner {

.pipe {


However, the Javascript should look more like this:

var innerBottom;
var totalHeight;
var hadToReduce = false;
var i = 0;
while(true) {

    // Prevent endless loop
    if (i > 5000) { break; }

    totalHeight = jQuery('#outer').outerHeight();
    innerBottom = jQuery("#inner").position().top + jQuery("#inner").outerHeight();
    if (innerBottom < totalHeight) {
        if (hadToReduce !== true) { 
            jQuery(".pipe").css('height', '' + (jQuery(".pipe").height() + 1) + 'px');
        } else { break; }
    } else if (innerBottom > totalHeight) {
        jQuery(".pipe").css('height', '' + (jQuery(".pipe").height() - 1) + 'px');
        hadToReduce = true;
    } else { break; }

How to remove youtube branding after embedding video in web page?

The only way to remove the YouTube branding (while keeping the video clickable) is to place the embed iFrame inside a container that has overflow set to hidden and has a slightly smaller height than the iFrame.

Of course this means the bottom of your video gets chopped off.

Also, you will be most likely breaching YouTube's Terms of Service.


.videoWrapper {
  width: 550px;
  height: 250px;
  overflow: hidden;


<div class="videoWrapper">
  <iframe width="550" height="314" src=";rel=0&amp;showinfo=0" frameborder="0" allowfullscreen></iframe>

Rename MySQL database

You can create a new database exactly as the previous database existed and then drop the old database when you're done. Use the mysqldump tool to create a .sql backup of the database via mysqldump orig_db > orig_db.sql or if you need to use a username and password then run mysqldump -u root -p orig_db > orig_db.sql. orig_db is the name of the database you want to "rename", root would be the user you're logging in as and orig_db.sql would be the file created containing the backup. Now create a new, empty database with the name you want for the database. For example, mysql -u root -p -e "create database new_db". Once that's done, then run mysql -u root -p new_db < orig_db.sql. new_db now exists as a perfect copy of orig_db. You can then drop the original database as you now have it existing in the new database with the database name you wanted.

The short, quick steps without all the above explanation are:

  1. mysqldump -u root -p original_database > original_database.sql
  2. mysql -u root -p -e "create database my_new_database"
  3. mysql -u root -p my_new_database < original_database.sql
  4. mysql -u root -p -e drop database originl_database

Hope this helps and this is a reliable means to accomplish it without using some ad-hoc method that will corrupt your data and create inconsistencies.

Editor does not contain a main type

The correct answer is: the Scala library needs to before the JRE library in the buildpath.

Go to Java Buildpath > Order and Export and move Scala library to the top

Throw HttpResponseException or return Request.CreateErrorResponse?

As far as I can tell, whether you throw an exception, or you return Request.CreateErrorResponse, the result is the same. If you look at the source code for System.Web.Http.dll, you will see as much. Take a look at this general summary, and a very similar solution that I have made: Web Api, HttpError, and the behavior of exceptions

How to read from input until newline is found using scanf()?

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>

int main(void)
  int i = 0;
  char *a = (char *) malloc(sizeof(char) * 1024);
  while (1) {
    scanf("%c", &a[i]);
    if (a[i] == '\n') {
    else {
  a[i] = '\0';
  i = 0;
  while (a[i] != '\0') {
    printf("%c", a[i]);
  return 0;