Programs & Examples On #Application server

An application server is a software framework dedicated to the efficient execution of procedures (programs, routines, scripts) for supporting the construction of applications. Normally the term refers to Java application servers. When this is the case, the application server behaves like an extended virtual machine for the running applications, handling transparently connections to the database at one side, and connections to the web client at the other.

What is the difference between application server and web server?

The main difference between Web server and application server is that web server is meant to serve static pages e.g. HTML and CSS, while Application Server is responsible for generating dynamic content by executing server side code e.g. JSP, Servlet or EJB.

Which one should i use?
Once you know the difference between web and application server and web containers, it's easy to figure out when to use them. You need a web server like Apache HTTPD if you are serving static web pages. If you have a Java application with just JSP and Servlet to generate dynamic content then you need web containers like Tomcat or Jetty. While, if you have Java EE application using EJB, distributed transaction, messaging and other fancy features than you need a full fledged application server like JBoss, WebSphere or Oracle's WebLogic.

Web container is a part of Web Server and the Web Server is a part of Application Server.

Application Server

Web Server is composed of web container, while Application Server is composed of web container as well as EJB container.

Difference between web server, web container and application server

A Web application runs within a Web container of a Web server. The Web container provides the runtime environment through components that provide naming context and life cycle management. Some Web servers may also provide additional services such as security and concurrency control. A Web server may work with an EJB server to provide some of those services. A Web server, however, does not need to be located on the same machine as an EJB server.

Web applications are composed of web components and other data such as HTML pages. Web components can be servlets, JSP pages created with the JavaServer Pages™ technology, web filters, and web event listeners. These components typically execute in a web server and may respond to HTTP requests from web clients. Servlets, JSP pages, and filters may be used to generate HTML pages that are an application’s user interface. They may also be used to generate XML or other format data that is consumed by other application components.


Tomcat is web server or application server?

Apache Tomcat is an open source software implementation of the Java Servlet and JavaServer Pages technologies.

Since Tomcat does not implement the full Java EE specification for an application server, it can be considered as a web server.


How to add new activity to existing project in Android Studio?

To add an Activity using Android Studio.

This step is same as adding Fragment, Service, Widget, and etc. Screenshot provided.

[UPDATE] Android Studio 3.5. Note that I have removed the steps for the older version. I assume almost all is using version 3.x.

enter image description here

  1. Right click either java package/java folder/module, I recommend to select a java package then right click it so that the destination of the Activity will be saved there
  2. Select/Click New
  3. Select Activity
  4. Choose an Activity that you want to create, probably the basic one.

To add a Service, or a BroadcastReceiver, just do the same step.

YouTube Autoplay not working

mute=1 or muted=1 as suggested by @Fab will work. However, if you wish to enable autoplay with sound you should add allow="autoplay" to your embedded <iframe>.

<iframe type="text/html" src="" frameborder="0" allow="autoplay"></iframe>

This is officially supported and documented in Google's Autoplay Policy Changes 2017 post

Iframe delegation A feature policy allows developers to selectively enable and disable use of various browser features and APIs. Once an origin has received autoplay permission, it can delegate that permission to cross-origin iframes with a new feature policy for autoplay. Note that autoplay is allowed by default on same-origin iframes.

<!-- Autoplay is allowed. -->
<iframe src="" allow="autoplay">

<!-- Autoplay and Fullscreen are allowed. -->
<iframe src="" allow="autoplay; fullscreen">

When the feature policy for autoplay is disabled, calls to play() without a user gesture will reject the promise with a NotAllowedError DOMException. And the autoplay attribute will also be ignored.

LDAP filter for blank (empty) attribute

The schema definition for an attribute determines whether an attribute must have a value. If the manager attribute in the example given is the attribute defined in RFC4524 with OID 0.9.2342.19200300.100.1.10, then that attribute has DN syntax. DN syntax is a sequence of relative distinguished names and must not be empty. The filter given in the example is used to cause the LDAP directory server to return only entries that do not have a manager attribute to the LDAP client in the search result.

RegEx to make sure that the string contains at least one lower case char, upper case char, digit and symbol

Bart Kiers, your regex has a couple issues. The best way to do that is this:

(.*[a-z].*)       // For lower cases
(.*[A-Z].*)       // For upper cases
(.*\d.*)          // For digits

In this way you are searching no matter if at the beginning, at the end or at the middle. In your have I have a lot of troubles with complex passwords.

Warning: Each child in an array or iterator should have a unique "key" prop. Check the render method of `ListView`

Change your code from:

render() {
    return (
        { => (


render() {
    return (
        { => (
          <li key={}>{result.text}</li>

Then solved.

How to grep a string in a directory and all its subdirectories?

grep -r -e string directory

-r is for recursive; -e is optional but its argument specifies the regex to search for. Interestingly, POSIX grep is not required to support -r (or -R), but I'm practically certain that System V grep did, so in practice they (almost) all do. Some versions of grep support -R as well as (or conceivably instead of) -r; AFAICT, it means the same thing.

Android emulator: How to monitor network traffic?

Yes, wireshark will work.

I don't think there is any easy way to filter out solely emulator traffic, since it is coming from the same src IP.

Perhaps the best way would be to set up a very bare VMware environment and only run the emulator in there, at least that way there wouldn't be too much background traffic.

"element.dispatchEvent is not a function" js error caught in firebug of FF3.0

Change the following line

$(document).ready(function() {


jQuery(document).ready(function($) {

Pythonic way to check if a file exists?

Instead of os.path.isfile, suggested by others, I suggest using os.path.exists, which checks for anything with that name, not just whether it is a regular file.


if not os.path.exists(filename):
    file(filename, 'w').close()


file(filename, 'w+').close()

The latter will create the file if it exists, but not otherwise. It will, however, fail if the file exists, but you don't have permission to write to it. That's why I prefer the first solution.

How to set the JDK Netbeans runs on?

It does not exactly answer your question, but to get around the problem,

  1. you can either create a .cmd file with following content:

    start netbeans --jdkhome c:\path\to\jdk

  2. or in the shortcut of Netbeans set the above option.

Continuous CSS rotation animation on hover, animated back to 0deg on hover out

The solution is to set the default value in your .elem. But this annimation work fine with -moz but not yet implement in -webkit

Look at the fiddle I updated from yours :

It works fine with Firefox but not with Chrome

    position: absolute;_x000D_
    top: 40px;_x000D_
    left: 40px;_x000D_
    width: 0; _x000D_
    height: 0;_x000D_
    border-style: solid;_x000D_
    border-width: 75px;_x000D_
    border-color: red blue green orange;_x000D_
    transition-property: transform;_x000D_
    transition-duration: 1s;_x000D_
.elem:hover {_x000D_
    animation-name: rotate; _x000D_
    animation-duration: 2s; _x000D_
    animation-iteration-count: infinite;_x000D_
    animation-timing-function: linear;_x000D_
@keyframes rotate {_x000D_
    from {transform: rotate(0deg);}_x000D_
    to {transform: rotate(360deg);}_x000D_
<div class="elem"></div>

MySQL Data Source not appearing in Visual Studio

Stuzor and hexcodes solution worked for me as well. However, if you do want the latest connector you have to download another product. From the oracle website:

Starting with version 6.7, Connector/Net will no longer include the MySQL for Visual Studio integration. That functionality is now available in a separate product called MySQL for Visual Studio available using the MySQL Installer for Windows (see

Calling Web API from MVC controller

From my HomeController I want to call this Method and convert Json response to List

No you don't. You really don't want to add the overhead of an HTTP call and (de)serialization when the code is within reach. It's even in the same assembly!

Your ApiController goes against (my preferred) convention anyway. Let it return a concrete type:

public IEnumerable<QDocumentRecord> GetAllRecords()
    listOfFiles = ...
    return listOfFiles;

If you don't want that and you're absolutely sure you need to return HttpResponseMessage, then still there's absolutely no need to bother with calling JsonConvert.SerializeObject() yourself:

return Request.CreateResponse<List<QDocumentRecord>>(HttpStatusCode.OK, listOfFiles);

Then again, you don't want business logic in a controller, so you extract that into a class that does the work for you:

public class FileListGetter
    public IEnumerable<QDocumentRecord> GetAllRecords()
        listOfFiles = ...
        return listOfFiles;

Either way, then you can call this class or the ApiController directly from your MVC controller:

public class HomeController : Controller
    public ActionResult Index()
        var listOfFiles = new DocumentsController().GetAllRecords();
        // OR
        var listOfFiles = new FileListGetter().GetAllRecords();

        return View(listOfFiles);

But if you really, really must do an HTTP request, you can use HttpWebRequest, WebClient, HttpClient or RestSharp, for all of which plenty of tutorials exist.

Android SDK Setup under Windows 7 Pro 64 bit

My problem was installing the Android SDK in Eclipse Helios on Windows 7 Enterprise 64bit, I was getting the following error:

Missing requirement: Android Development Tools 0.9.7.v201005071157-36220 ( 0.9.7.v201005071157-36220) requires 'org.eclipse.jdt.junit 0.0.0' but it could not be found

Having followed the advice above to ensure that the JDK was in my PATH variable (it wasn't), installation went smoothly. I guess the error was somewhat spurious (incidentally if you're looking for the JARs that correspond to that class, they were in my profile rather than the Eclipse installation directory)

So, check that PATH variable!

Why Choose Struct Over Class?

With classes you get inheritance and are passed by reference, structs do not have inheritance and are passed by value.

There are great WWDC sessions on Swift, this specific question is answered in close detail in one of them. Make sure you watch those, as it will get you up to speed much more quickly then the Language guide or the iBook.

HQL "is null" And "!= null" on an Oracle column

No. You have to use is null and is not null in HQL.

Animation fade in and out

we can simply use:

public void animStart(View view) {
        Log.d("count", String.valueOf(count));
        count =1;
    else if(count==1){
        Log.d("count", String.valueOf(count));
        count =0;

where i1 and i2 are defined in the onCreateView() as:

    i1 = (ImageView)findViewById(;
    i2 = (ImageView)findViewById(;

count is a class variable initilaized to 0.

The XML file is :

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android=""
            android:src="@drawable/second" />

          android:src="@drawable/first" />

@drawable/first and @drawable/second are the images in the drawable folder in res.

Reading and displaying data from a .txt file

If you want to take some shortcuts you can use Apache Commons IO:


String data = FileUtils.readFileToString(new File("..."), "UTF-8");


How to create a TextArea in Android

Defining an Android Mulitline EditText Field is done via the inputType=”textMultiline”. Unfortunately the text looks strangely aligned. To solve that also use the gravity=”left|top” attribute.

   android:inputType="textMultiLine" >

   <requestFocus />

check this vogella blog

mailto link with HTML body

Anybody can try the following (mailto function only accepts plaintext but here i show how to use HTML innertext properties and how to add an anchor as mailto body params):

//Create as many html elements you need.

const titleElement = document.createElement("DIV");
titleElement.innerHTML = this.shareInformation.title; // Just some string

//Here I create an <a> so I can use href property
const titleLinkElement = document.createElement("a");
titleLinkElement.href =; // This is a url


let mail = document.createElement("a");

// Using es6 template literals add the html innerText property and anchor element created to mailto body parameter
mail.href = 

// Notice how I use ${titleLinkElement} that is an anchor element, so mailto uses its href and renders the url I needed

Execute Insert command and return inserted Id in Sql

The following solution will work with sql server 2005 and above. You can use output to get the required field. inplace of id you can write your key that you want to return. do it like this

FOR SQL SERVER 2005 and above

    using(SqlCommand cmd=new SqlCommand("INSERT INTO Mem_Basic(Mem_Na,Mem_Occ) output INSERTED.ID VALUES(@na,@occ)",con))
        cmd.Parameters.AddWithValue("@na", Mem_NA);
        cmd.Parameters.AddWithValue("@occ", Mem_Occ);

        int modified =(int)cmd.ExecuteScalar();

        if (con.State == System.Data.ConnectionState.Open) 

        return modified;

FOR previous versions

    using(SqlCommand cmd=new SqlCommand("INSERT INTO Mem_Basic(Mem_Na,Mem_Occ)  VALUES(@na,@occ);SELECT SCOPE_IDENTITY();",con))
        cmd.Parameters.AddWithValue("@na", Mem_NA);
        cmd.Parameters.AddWithValue("@occ", Mem_Occ);

        int modified = Convert.ToInt32(cmd.ExecuteScalar());

        if (con.State == System.Data.ConnectionState.Open) con.Close();
            return modified;

Showing ValueError: shapes (1,3) and (1,3) not aligned: 3 (dim 1) != 1 (dim 0)

The column of the first matrix and the row of the second matrix should be equal and the order should be like this only

column of first matrix = row of second matrix

and do not follow the below step

row of first matrix  = column of second matrix

it will throw an error

Copying a HashMap in Java

If we want to copy an object in Java, there are two possibilities that we need to consider: a shallow copy and a deep copy.

The shallow copy is the approach when we only copy field values. Therefore, the copy might be dependent on the original object. In the deep copy approach, we make sure that all the objects in the tree are deeply copied, so the copy is not dependent on any earlier existing object that might ever change.

This question is the perfect definition for the application of the deep copy approach.

First, if you have a simple HashMap<Integer, List<T>> map then we just create a workaround like this. Creating a new instance of the List<T>.

public static <T> HashMap<Integer, List<T>> deepCopyWorkAround(HashMap<Integer, List<T>> original)
    HashMap<Integer, List<T>> copy = new HashMap<>();
    for (Map.Entry<Integer, List<T>> entry : original.entrySet()) {
        copy.put(entry.getKey(), new ArrayList<>(entry.getValue()));
    return copy;

This one uses Stream.collect() method to create the clone map, but uses the same idea as the previous method.

public static <T> Map<Integer, List<T>> deepCopyStreamWorkAround(Map<Integer, List<T>> original)
    return original
            .collect(Collectors.toMap(Map.Entry::getKey, valueMapper -> new ArrayList<>(valueMapper.getValue())));

But, if the instances inside T are also mutable objects we have a big problem. In this case a real deep copy is an alternative that solves this problem. Its advantage is that at least each mutable object in the object graph is recursively copied. Since the copy is not dependent on any mutable object that was created earlier, it won’t get modified by accident like we saw with the shallow copy.

To solve that this deep copy implementations will do the work.

public class DeepClone
    public static void main(String[] args)
        Map<Long, Item> itemMap = Stream.of(
                entry(0L, new Item(2558584)),
                entry(1L, new Item(254243232)),
                entry(2L, new Item(986786)),
                entry(3L, new Item(672542)),
                entry(4L, new Item(4846)),
                entry(5L, new Item(76867467)),
                entry(6L, new Item(986786)),
                entry(7L, new Item(7969768)),
                entry(8L, new Item(68868486)),
                entry(9L, new Item(923)),
                entry(10L, new Item(986786)),
                entry(11L, new Item(549768)),
                entry(12L, new Item(796168)),
                entry(13L, new Item(868421)),
                entry(14L, new Item(923)),
                entry(15L, new Item(986786)),
                entry(16L, new Item(549768)),
                entry(17L, new Item(4846)),
                entry(18L, new Item(4846)),
                entry(19L, new Item(76867467)),
                entry(20L, new Item(986786)),
                entry(21L, new Item(7969768)),
                entry(22L, new Item(923)),
                entry(23L, new Item(4846)),
                entry(24L, new Item(986786)),
                entry(25L, new Item(549768))

        Map<Long, Item> clone = DeepClone.deepClone(itemMap);


    private DeepClone() {}

    public static <T> T deepClone(final T input)
        if (input == null) return null;

        if (input instanceof Map<?, ?>) {
            return (T) deepCloneMap((Map<?, ?>) input);
        } else if (input instanceof Collection<?>) {
            return (T) deepCloneCollection((Collection<?>) input);
        } else if (input instanceof Object[]) {
            return (T) deepCloneObjectArray((Object[]) input);
        } else if (input.getClass().isArray()) {
            return (T) clonePrimitiveArray((Object) input);

        return input;

    private static Object clonePrimitiveArray(final Object input)
        final int length = Array.getLength(input);
        final Object output = Array.newInstance(input.getClass().getComponentType(), length);
        System.arraycopy(input, 0, output, 0, length);
        return output;

    private static <E> E[] deepCloneObjectArray(final E[] input)
        final E[] clone = (E[]) Array.newInstance(input.getClass().getComponentType(), input.length);
        for (int i = 0; i < input.length; i++) {
            clone[i] = deepClone(input[i]);

        return clone;

    private static <E> Collection<E> deepCloneCollection(final Collection<E> input)
        Collection<E> clone;
        if (input instanceof LinkedList<?>) {
            clone = new LinkedList<>();
        } else if (input instanceof SortedSet<?>) {
            clone = new TreeSet<>();
        } else if (input instanceof Set) {
            clone = new HashSet<>();
        } else {
            clone = new ArrayList<>();

        for (E item : input) {

        return clone;

    private static <K, V> Map<K, V> deepCloneMap(final Map<K, V> map)
        Map<K, V> clone;
        if (map instanceof LinkedHashMap<?, ?>) {
            clone = new LinkedHashMap<>();
        } else if (map instanceof TreeMap<?, ?>) {
            clone = new TreeMap<>();
        } else {
            clone = new HashMap<>();

        for (Map.Entry<K, V> entry : map.entrySet()) {
            clone.put(deepClone(entry.getKey()), deepClone(entry.getValue()));

        return clone;

Get the filePath from Filename using Java

You can use the Path api:

Path p = Paths.get(yourFileNameUri);
Path folder = p.getParent();

Add line break to ::after or ::before pseudo-element content

For people who will going to look for 'How to change dynamically content on pseudo element adding new line sign" here's answer

Html chars like &#13;&#10; will not work appending them to html using JavaScript because those characters are changed on document render

Instead you need to find unicode representation of this characters which are U+000D and U+000A so we can do something like

var el = document.querySelector('div');_x000D_
var string = el.getAttribute('text').replace(/, /, '\u000D\u000A');_x000D_
el.setAttribute('text', string);
   content: attr(text);_x000D_
   white-space: pre;_x000D_
<div text='I want to break it in javascript, after comma sign'></div> 

Hope this save someones time, good luck :)

How to set div's height in css and html

<div style="height: 100px;"> </div>


<div id="foo"/> and set the style as #foo { height: 100px; }
<div class="bar"/> and set the style as .bar{ height: 100px;  }

How to print like printf in Python3?

Python 3.6 introduced f-strings for inline interpolation. What's even nicer is it extended the syntax to also allow format specifiers with interpolation. Something I've been working on while I googled this (and came across this old question!):

print(f'{account:40s} ({ratio:3.2f}) -> AUD {splitAmount}')

PEP 498 has the details. And... it sorted my pet peeve with format specifiers in other langs -- allows for specifiers that themselves can be expressions! Yay! See: Format Specifiers.

Woocommerce, get current product id

2017 Update - since WooCommerce 3:

global $product;
$id = $product->get_id();

Woocommerce doesn't like you accessing those variables directly. This will get rid of any warnings from woocommerce if your wp_debug is true.

Difference between datetime and timestamp in sqlserver?

According to the documentation, timestamp is a synonym for rowversion - it's automatically generated and guaranteed1 to be unique. datetime isn't - it's just a data type which handles dates and times, and can be client-specified on insert etc.

1 Assuming you use it properly, of course. See comments.

LINQ extension methods - Any() vs. Where() vs. Exists()

Any - boolean function that returns true when any of object in list satisfies condition set in function parameters. For example:

List<string> strings = LoadList();
boolean hasNonEmptyObject = strings.Any(s=>string.IsNullOrEmpty(s));

Where - function that returns list with all objects in list that satisfy condition set in function parameters. For example:

IEnumerable<string> nonEmptyStrings = strings.Where(s=> !string.IsNullOrEmpty(s));

Exists - basically the same as any but it's not generic - it's defined in List class, while Any is defined on IEnumerable interface.

Set up a scheduled job?

For simple dockerized projects, I could not really see any existing answer fit.

So I wrote a very barebones solution without the need of external libraries or triggers, which runs on its own. No external os-cron needed, should work in every environment.

It works by adding a middleware:

import threading

def should_run(name, seconds_interval):
    from application.models import CronJob
    from django.utils.timezone import now

        c = CronJob.objects.get(name=name)
    except CronJob.DoesNotExist:
        CronJob(name=name, last_ran=now()).save()
        return True

    if (now() - c.last_ran).total_seconds() >= seconds_interval:
        c.last_ran = now()
        return True

    return False

class CronTask:
    def __init__(self, name, seconds_interval, function): = name
        self.seconds_interval = seconds_interval
        self.function = function

def cron_worker(*_):
    if not should_run("main", 60):

    # customize this part:
    from application.models import Event
    tasks = [
        CronTask("events", 60 * 30, Event.clean_stale_objects),
        # ...

    for task in tasks:
        if should_run(, task.seconds_interval):

def cron_middleware(get_response):

    def middleware(request):
        response = get_response(request)
        return response

    return middleware


from django.db import models

class CronJob(models.Model):
    name = models.CharField(max_length=10, primary_key=True)
    last_ran = models.DateTimeField()


SQL ORDER BY date problem

It sounds to me like your column isn't a date column but a text column (varchar/nvarchar etc). You should store it in the database as a date, not a string.

If you have to store it as a string for some reason, store it in a sortable format e.g. yyyy/MM/dd.

As najmeddine shows, you could convert the column on every access, but I would try very hard not to do that. It will make the database do a lot more work - it won't be able to keep appropriate indexes etc. Whenever possible, store the data in a type appropriate to the data itself.

How to get span tag inside a div in jQuery and assign a text?

Vanilla JS, without jQuery:

document.querySelector('#message span').innerHTML = 'hello world!'

Available in all browsers:

Error: "The sandbox is not in sync with the Podfile.lock..." after installing RestKit with cocoapods

I use the cocoa pods installation from the bundle.

  • Install bundler
  • Add Gemfile in root of project
  • Add required gems in Gemfile
  • bundle install
  • and then always use bundle exec pod install

If you don't know how-tos of one of these steps, searching on google will help :)

Java ArrayList of Arrays?

As already answered, you can create an ArrayList of String Arrays as @Péter Török written;

    //Declaration of an ArrayList of String Arrays
    ArrayList<String[]> listOfArrayList = new ArrayList<String[]>();

When assigning different String Arrays to this ArrayList, each String Array's length will be different.

In the following example, 4 different Array of String added, their lengths are varying.

String Array #1: len: 3
String Array #2: len: 1
String Array #3: len: 4
String Array #4: len: 2

The Demonstration code is as below;

import java.util.ArrayList;

public class TestMultiArray {

    public static void main(String[] args) {
        //Declaration of an ArrayList of String Arrays
        ArrayList<String[]> listOfArrayList = new ArrayList<String[]>();

        //Assignment of 4 different String Arrays with different lengths
        listOfArrayList.add( new String[]{"line1: test String 1","line1: test String 2","line1: test String 3"}  );
        listOfArrayList.add( new String[]{"line2: test String 1"}  );
        listOfArrayList.add( new String[]{"line3: test String 1","line3: test String 2","line3: test String 3", "line3: test String 4"}  );
        listOfArrayList.add( new String[]{"line4: test String 1","line4: test String 2"}  );

        // Printing out the ArrayList Contents of String Arrays
        // '$' is used to indicate the String elements of String Arrays
        for( int i = 0; i < listOfArrayList.size(); i++ ) {
            for( int j = 0; j < listOfArrayList.get(i).length; j++ )
                System.out.printf(" $ " + listOfArrayList.get(i)[j]);



And the output is as follows;

 $ line1: test String 1 $ line1: test String 2 $ line1: test String 3
 $ line2: test String 1
 $ line3: test String 1 $ line3: test String 2 $ line3: test String 3 $ line3: test String 4
 $ line4: test String 1 $ line4: test String 2

Also notify that you can initialize a new Array of Sting as below;

new String[]{ str1, str2, str3,... }; // Assuming str's are String objects

So this is same with;

String[] newStringArray = { str1, str2, str3 }; // Assuming str's are String objects

I've written this demonstration just to show that no theArrayList object, all the elements are references to different instantiations of String Arrays, thus the length of each String Arrays are not have to be the same, neither it is important.

One last note: It will be best practice to use the ArrayList within a List interface, instead of which that you've used in your question.

It will be better to use the List interface as below;

    //Declaration of an ArrayList of String Arrays
    List<String[]> listOfArrayList = new ArrayList<String[]>();

Preloading CSS Images

how about loading that background image somewhere hidden. That way it will be loaded when the page is opened and wont take any time once the form is created using ajax:

body {
background: #ffffff url('img_tree.png') no-repeat -100px -100px;

What is the difference between exit and return?

  • return returns from the current function; it's a language keyword like for or break.
  • exit() terminates the whole program, wherever you call it from. (After flushing stdio buffers and so on).

The only case when both do (nearly) the same thing is in the main() function, as a return from main performs an exit().

In most C implementations, main is a real function called by some startup code that does something like int ret = main(argc, argv); exit(ret);. The C standard guarantees that something equivalent to this happens if main returns, however the implementation handles it.

Example with return:

#include <stdio.h>

void f(){
    printf("Executing f\n");

int main(){
    printf("Back from f\n");

If you execute this program it prints:

Executing f
Back from f

Another example for exit():

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

void f(){
    printf("Executing f\n");

int main(){
    printf("Back from f\n");

If you execute this program it prints:

Executing f

You never get "Back from f". Also notice the #include <stdlib.h> necessary to call the library function exit().

Also notice that the parameter of exit() is an integer (it's the return status of the process that the launcher process can get; the conventional usage is 0 for success or any other value for an error).

The parameter of the return statement is whatever the return type of the function is. If the function returns void, you can omit the return at the end of the function.

Last point, exit() come in two flavors _exit() and exit(). The difference between the forms is that exit() (and return from main) calls functions registered using atexit() or on_exit() before really terminating the process while _exit() (from #include <unistd.h>, or its synonymous _Exit from #include <stdlib.h>) terminates the process immediately.

Now there are also issues that are specific to C++.

C++ performs much more work than C when it is exiting from functions (return-ing). Specifically it calls destructors of local objects going out of scope. In most cases programmers won't care much of the state of a program after the processus stopped, hence it wouldn't make much difference: allocated memory will be freed, file ressource closed and so on. But it may matter if your destructor performs IOs. For instance automatic C++ OStream locally created won't be flushed on a call to exit and you may lose some unflushed data (on the other hand static OStream will be flushed).

This won't happen if you are using the good old C FILE* streams. These will be flushed on exit(). Actually, the rule is the same that for registered exit functions, FILE* will be flushed on all normal terminations, which includes exit(), but not calls to _exit() or abort().

You should also keep in mind that C++ provide a third way to get out of a function: throwing an exception. This way of going out of a function will call destructor. If it is not catched anywhere in the chain of callers, the exception can go up to the main() function and terminate the process.

Destructors of static C++ objects (globals) will be called if you call either return from main() or exit() anywhere in your program. They wont be called if the program is terminated using _exit() or abort(). abort() is mostly useful in debug mode with the purpose to immediately stop the program and get a stack trace (for post mortem analysis). It is usually hidden behind the assert() macro only active in debug mode.

When is exit() useful ?

exit() means you want to immediately stops the current process. It can be of some use for error management when we encounter some kind of irrecoverable issue that won't allow for your code to do anything useful anymore. It is often handy when the control flow is complicated and error codes has to be propagated all way up. But be aware that this is bad coding practice. Silently ending the process is in most case the worse behavior and actual error management should be preferred (or in C++ using exceptions).

Direct calls to exit() are especially bad if done in libraries as it will doom the library user and it should be a library user's choice to implement some kind of error recovery or not. If you want an example of why calling exit() from a library is bad, it leads for instance people to ask this question.

There is an undisputed legitimate use of exit() as the way to end a child process started by fork() on Operating Systems supporting it. Going back to the code before fork() is usually a bad idea. This is the rationale explaining why functions of the exec() family will never return to the caller.

Java: Why is the Date constructor deprecated, and what do I use instead?

The java.util.Date class isn't actually deprecated, just that constructor, along with a couple other constructors/methods are deprecated. It was deprecated because that sort of usage doesn't work well with internationalization. The Calendar class should be used instead:

Calendar cal = Calendar.getInstance();
cal.set(Calendar.YEAR, 1988);
cal.set(Calendar.MONTH, Calendar.JANUARY);
cal.set(Calendar.DAY_OF_MONTH, 1);
Date dateRepresentation = cal.getTime();

Take a look at the date Javadoc:

Spring RestTemplate GET with parameters

If you pass non-parametrized params for RestTemplate, you'll have one Metrics for everyone single different URL that you pass, considering the parameters. You would like to use parametrized urls:


instead of


The second case is what you get by using UriComponentsBuilder class.

One way to implement the first behavior is the following:

Map<String, Object> params = new HashMap<>();
params.put("param1", "XXXX");
params.put("param2", "YYYY");

String url = "http://my-url/action?%s";

String parametrizedArgs = params.keySet().stream().map(k ->
    String.format("%s={%s}", k, k)

HttpHeaders headers = new HttpHeaders();
headers.set("Accept", MediaType.APPLICATION_JSON_VALUE);
HttpEntity<String> entity = new HttpEntity<>(headers);, parametrizedArgs), HttpMethod.GET, entity, String.class, params);

Create dynamic variable name

Variable names should be known at compile time. If you intend to populate those names dynamically at runtime you could use a List<T>

 var variables = List<Variable>();
 variables.Add(new Variable { Name = inputStr1 });
 variables.Add(new Variable { Name = inputStr2 });

here input string maybe any text or any list

- java.lang.NullPointerException - setText on null object reference

Here lies your problem:

private void fillTextView (int id, String text) {
    TextView tv = (TextView) findViewById(id);
    tv.setText(text); // tv is null

--> (TextView) findViewById(id); // returns null But from your code, I can't find why this method returns null. Try to track down, what id you give as a parameter and if this view with the specified id exists.

The error message is very clear and even tells you at what method. From the documentation:

public final View findViewById (int id)
    Look for a child view with the given id. If this view has the given id, return this view.
        id  The id to search for.
        The view that has the given id in the hierarchy or null

In other words: You have no view with the id you give as a parameter.

SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax — PHP — PDO

ALTER TABLE `{$installer->getTable('sales/quote_payment')}`
ADD `custom_field_one` VARCHAR( 255 ) NOT NULL,
    ADD `custom_field_two` VARCHAR( 255 ) NOT NULL;

Add backtick i.e. " ` " properly. Write your getTable name and column name between backtick.

Finding Android SDK on Mac and adding to PATH

Find the Android SDK location

Android Studio 
  > Preferences
  > Appearance & Behaviour
  > System Settings 
  > Android SDK
  > Android SDK Location

Create a .bash_profile file for your environment variables

  • Open the Terminal app
  • Go to your home directory via cd ~
  • Create the file with touch .bash_profile

Add the PATH variable to your .bash_profile

  • Open the file via open .bash_profile
  • Add export PATH=$PATH: [your SDK location] /platform-tools to the file and hit ?s to save it. By default it's:

    export PATH=$PATH:/Users/yourUserName/Library/Android/sdk/platform-tools

  • Go back to your Terminal App and load the variable with source ~/.bash_profile

How can I change the default credentials used to connect to Visual Studio Online (TFSPreview) when loading Visual Studio up?

You can also try to reset visual studio setting

  1. Open Visual Studio Command Prompt

  2. Enter command Devenv /ResetSettings

It will remove already saved TFS account and ask for credentials

What is the difference between dim and set in vba

Dim is short for Dimension and is used in VBA and VB6 to declare local variables.

Set on the other hand, has nothing to do with variable declarations. The Set keyword is used to assign an object variable to a new object.

Hope that clarifies the difference for you.

<!--[if !IE]> not working

This is for until IE9

<!--[if IE ]>
<style> .someclass{
    text-align: center;
    background: #00ADEF;
    color: #fff;
    visibility:hidden;  // in case of hiding
    display: block !important;
    visibility:visible; // in case of visible


This is for after IE9

  @media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {enter your CSS here}

The term 'ng' is not recognized as the name of a cmdlet

Changing the policy to Unrestricted worked for me:

Set-ExecutionPolicy Unrestricted -Scope CurrentUser

Request is not available in this context

You can get around the problem without switching to classic mode and still use Application_Start

public class Global : HttpApplication
   private static HttpRequest initialRequest;

   static Global()
      initialRequest = HttpContext.Current.Request;       

   void Application_Start(object sender, EventArgs e)
      //access the initial request here

For some reason, the static type is created with a request in its HTTPContext, allowing you to store it and reuse it immediately in the Application_Start event

Add to python path mac os x

Setting the $PYTHONPATH environment variable does not seem to affect the Spyder IDE's iPython terminals on a Mac. However, Spyder's application menu contains a "PYTHONPATH manager." Adding my path here solved my problem. The "PYTHONPATH manager" is also persistent across application restarts.

This is specific to a Mac, because setting the PYTHONPATH environment variable on my Windows PC gives the expected behavior (modules are found) without using the PYTHONPATH manager in Spyder.

Command for restarting all running docker containers?

To start multiple containers with the only particular container id's $ docker restart contianer-id1 container-id2 container-id3 ...

How do I compile jrxml to get jasper?

If you are using iReport you can easily do it.

  1. When you click preview it will automatically compile.
  2. There is an option to make it complie. You can compile by selecting the page then right click you will get the compile option.

Query to get all rows from previous month

Here's another alternative. Assuming you have an indexed DATE or DATETIME type field, this should use the index as the formatted dates will be type converted before the index is used. You should then see a range query rather than an index query when viewed with EXPLAIN.

    date_created >= DATE_FORMAT( CURRENT_DATE - INTERVAL 1 MONTH, '%Y/%m/01' ) 
    date_created < DATE_FORMAT( CURRENT_DATE, '%Y/%m/01' )

Can an interface extend multiple interfaces in Java?

An interface can extend multiple interfaces.

A class can implement multiple interfaces.

However, a class can only extend a single class.

Careful how you use the words extends and implements when talking about interface and class.

how to open a page in new tab on button click in

In either on button click or on link button click, this will work.

System.Web.UI.ScriptManager.RegisterClientScriptBlock(Me, Me.GetType(), "openModal", "'CertificatePrintViewAll.aspx' ,'_blank');", True)

How do I import from Excel to a DataSet using Microsoft.Office.Interop.Excel?

Have you seen this one? From

public DataTable Import(String path)
    Microsoft.Office.Interop.Excel.Application app = new Microsoft.Office.Interop.Excel.Application();
    Microsoft.Office.Interop.Excel.Workbook workBook = app.Workbooks.Open(path, 0, true, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);

    Microsoft.Office.Interop.Excel.Worksheet workSheet = (Microsoft.Office.Interop.Excel.Worksheet)workBook.ActiveSheet;

    int index = 0;
    object rowIndex = 2;

    DataTable dt = new DataTable();

    DataRow row;

    while (((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, 1]).Value2 != null)

        row = dt.NewRow();
        row[0] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, 1]).Value2);
        row[1] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, 2]).Value2);
        row[2] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, 3]).Value2);
        row[3] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, 4]).Value2);
        row[4] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, 5]).Value2);

        rowIndex = 2 + index;
    return dt;

Removing empty lines in Notepad++

  1. notepad++
  2. Ctrl-H
  3. Select Regular Expression
  4. Enter ^[ \t]*$\r?\n into find what, leave replace empty. This will match all lines starting with white space and ending with carriage return (in this case a windows crlf)
  5. Click the Find Next button to see for yourself how it matches only empty lines.

Check for special characters in string

I suggest using RegExp .test() function to check for a pattern match, and the only thing you need to change is remove the start/end of line anchors (and the * quantifier is also redundant) in the regex:

var format = /[ `!@#$%^&*()_+\-=\[\]{};':"\\|,.<>\/?~]/;_x000D_
//            ^                                       ^   _x000D_
document.write(format.test("My@string-with(some%text)") + "<br/>");_x000D_
document.write(format.test("My string with spaces") + "<br/>");_x000D_

The anchors (like ^ start of string/line, $ end od string/line and \b word boundaries) can restrict matches at specific places in a string. When using ^ the regex engine checks if the next subpattern appears right at the start of the string (or line if /m modifier is declared in the regex). Same case with $: the preceding subpattern should match right at the end of the string.

In your case, you want to check the existence of the special character from the set anywhere in the string. Even if it is only one, you want to return false. Thus, you should remove the anchors, and the quantifier *. The * quantifier would match even an empty string, thus we must remove it in order to actually check for the presence of at least 1 special character (actually, without any quantifiers we check for exactly one occurrence, same as if we were using {1} limiting quantifier).

More specific solutions

What characters are "special" for you?

  • All chars other than ASCII chars: /[^\x00-\x7F]/ (demo)
  • All chars other than printable ASCII chars: /[^ -~]/ (demo)
  • Any printable ASCII chars other than space, letters and digits: /[!-\/:-@[-`{-~]/ (demo)
  • Any Unicode punctuation proper chars, the \p{P} Unicode property class:
    • ECMAScript 2018: /\p{P}/u
    • ES6+:

         ? ES5 (demo):

  • All Unicode symbols (not punctuation proper), \p{S}:
    • ECMAScript 2018: /\p{S}/u
    • ES6+:

         ? ES5 (demo):

  • All Unicode punctuation and symbols, \p{P} and \p{S}:
    • ECMAScript 2018: /[\p{P}\p{S}]/u
    • ES6+:

         ? ES5 (demo):


How to extract the decision rules from scikit-learn decision-tree?

from StringIO import StringIO
out = StringIO()
out = tree.export_graphviz(clf, out_file=out)
print out.getvalue()

You can see a digraph Tree. Then, clf.tree_.feature and clf.tree_.value are array of nodes splitting feature and array of nodes values respectively. You can refer to more details from this github source.

Create a date time with month and day only, no year

Anyway you need 'Year'.

In some engineering fields, you have fixed day and month and year can be variable. But that day and month are important for beginning calculation without considering which year you are. Your user, for example, only should select a day and a month and providing year is up to you.

You can create a custom combobox using this: Customizable ComboBox Drop-Down.

1- In VS create a user control.

2- See the code in the link above for impelemnting that control.

3- Create another user control and place in it 31 button or label and above them place a label to show months.

4- Place the control in step 3 in your custom combobox.

5- Place the control in setp 4 in step 1.

You now have a control with only days and months. You can use any year that you have in your database or ....

Javascript Uncaught TypeError: Cannot read property '0' of undefined

The error is here:


You are passing the first item of words, instead of the array.

Instead, pass the array to the function:


Problem solved!

Here's a breakdown of what the problem was:

I'm guessing in your browser (chrome throws a different error), words[] == words[0], so when you call hasLetter("a",words[]);, you are actually calling hasLetter("a",words[0]);. So, in essence, you are passing the first item of words to your function, not the array as a whole.

Of course, because words is just an empty array, words[0] is undefined. Therefore, your function call is actually:

hasLetter("a", undefined);

which means that, when you try to access d[ascii], you are actually trying to access undefined[0], hence the error.

Verify if file exists or not in C#

I have written this code in vb and its is working fine to check weather a file is exists or not for fileupload control. try it

FOR VB CODE ============

    If FileUpload1.HasFile = True Then
        Dim FileExtension As String = System.IO.Path.GetExtension(FileUpload1.FileName)

        If FileExtension.ToLower <> ".jpg" Then
            lblMessage.ForeColor = System.Drawing.Color.Red
            lblMessage.Text = "Please select .jpg image file to upload"
            Dim FileSize As Integer = FileUpload1.PostedFile.ContentLength

            If FileSize > 1048576 Then
                lblMessage.ForeColor = System.Drawing.Color.Red
                lblMessage.Text = "File size (1MB) exceeded"
                Dim FileName As String = System.IO.Path.GetFileName(FileUpload1.FileName)

                Dim ServerFileName As String = Server.MapPath("~/Images/Folder1/" + FileName)

                If System.IO.File.Exists(ServerFileName) = False Then
                    FileUpload1.SaveAs(Server.MapPath("~/Images/Folder1/") + FileUpload1.FileName)
                    lblMessage.ForeColor = System.Drawing.Color.Green
                    lblMessage.Text = "File : " + FileUpload1.FileName + " uploaded successfully"
                    lblMessage.ForeColor = System.Drawing.Color.Red
                    lblMessage.Text = "File : " + FileName.ToString() + " already exsist"
                End If
            End If
        End If
        lblMessage.ForeColor = System.Drawing.Color.Red
        lblMessage.Text = "Please select a file to upload"
    End If

FOR C# CODE ======================

if (FileUpload1.HasFile == true) {
    string FileExtension = System.IO.Path.GetExtension(FileUpload1.FileName);

    if (FileExtension.ToLower != ".jpg") {
        lblMessage.ForeColor = System.Drawing.Color.Red;
        lblMessage.Text = "Please select .jpg image file to upload";
    } else {
        int FileSize = FileUpload1.PostedFile.ContentLength;

        if (FileSize > 1048576) {
            lblMessage.ForeColor = System.Drawing.Color.Red;
            lblMessage.Text = "File size (1MB) exceeded";
        } else {
            string FileName = System.IO.Path.GetFileName(FileUpload1.FileName);

            string ServerFileName = Server.MapPath("~/Images/Folder1/" + FileName);

            if (System.IO.File.Exists(ServerFileName) == false) {
                FileUpload1.SaveAs(Server.MapPath("~/Images/Folder1/") + FileUpload1.FileName);
                lblMessage.ForeColor = System.Drawing.Color.Green;
                lblMessage.Text = "File : " + FileUpload1.FileName + " uploaded successfully";
            } else {
                lblMessage.ForeColor = System.Drawing.Color.Red;
                lblMessage.Text = "File : " + FileName.ToString() + " already exsist";
} else {
    lblMessage.ForeColor = System.Drawing.Color.Red;
    lblMessage.Text = "Please select a file to upload";

Laravel 5 not finding css files

In the root path create a .htaccess file with

<IfModule mod_rewrite.c>
Options +FollowSymLinks
RewriteEngine On

RewriteCond %{REQUEST_URI} !^/public/ 

RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f

RewriteRule ^(.*)$ /public/$1 
#RewriteRule ^ index.php [L]
RewriteRule ^(/)?$ public/index.php [L] 

In public directory create a .htaccess file

<IfModule mod_rewrite.c>
    <IfModule mod_negotiation.c>
        Options -MultiViews -Indexes

    RewriteEngine On

    # Handle Authorization Header
    RewriteCond %{HTTP:Authorization} .
    RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]

    # Redirect Trailing Slashes If Not A Folder...
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_URI} (.+)/$
    RewriteRule ^ %1 [L,R=301]

    # Handle Front Controller...
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^ index.php [L]

if you have done any changes in public/index.php file correct them with the right path then your site will be live.

what will solve with this?

  • Hosting issue of laravel project.
  • Css not work on laravel.
  • Laravel site not work.
  • laravel site load with domain/public/index.php
  • laravel project does not redirect correctly

Removing all empty elements from a hash / YAML?

Could be done with facets library (a missing features from standard library), like that:

require 'hash/compact'
require 'enumerable/recursively'
hash.recursively { |v| v.compact! }

Works with any Enumerable (including Array, Hash).

Look how recursively method is implemented.

How to download HTTP directory with all files and sub-directories as they appear on the online files/folders list?

I was able to get this to work thanks to this post utilizing VisualWGet. It worked great for me. The important part seems to be to check the -recursive flag (see image).

Also found that the -no-parent flag is important, othewise it will try to download everything.

enter image description here enter image description here

Getting SyntaxError for print with keyword argument end=' '

In python 2.7 here is how you do it

mantra = 'Always look on the bright side of life'
for c in mantra: print c,

A l w a y s   l o o k   o n   t h e   b r i g h t   s i d e   o f   l i f e

In python 3.x

myjob= 'hacker'
for c in myjob: print (c, end=' ')
h a c k e r 

Passing bash variable to jq

It's a quote issue, you need :

  cat file.json | jq -r ".resource[] | select(.username=='$EMAILID') | .id"

If you put single quotes to delimit the main string, the shell takes $EMAILID literally.

"Double quote" every literal that contains spaces/metacharacters and every expansion: "$var", "$(command "$var")", "${array[@]}", "a & b". Use 'single quotes' for code or literal $'s: 'Costs $5 US', ssh host 'echo "$HOSTNAME"'. See

Elasticsearch: Failed to connect to localhost port 9200 - Connection refused

Tried everything on this page, and only instructions from here helped.

in /etc/default/elasticsearch, make sure these are un-commented:


make sure /var/lib/elasticsearch is owned by elasticsearch user:

chown -R elasticsearch:elasticsearch /var/lib/elasticsearch/

How to change a string into uppercase

To get upper case version of a string you can use str.upper:

s = 'sdsd'
#=> 'SDSD'

On the other hand string.ascii_uppercase is a string containing all ASCII letters in upper case:

import string

HTTPS setup in Amazon EC2

An old question but worth mentioning another option in the answers. In case the DNS system of your domain has been defined in Amazon Route 53, you can use Amazon CloudFront service in front of your EC2 and attach a free Amazon SSL certificate to it. This way you will benefit from both having a CDN for a faster content delivery and also securing you domain with HTTPS protocol.

Batch file include external file for variables

The best option according to me is to have key/value pairs file as it could be read from other scripting languages.

Other thing is I would prefer to have an option for comments in the values file - which can be easy achieved with eol option in for /f command.

Here's the example

values file:

;;;;;; file with example values ;;;;;;;;

;; Will be processed by a .bat file
;; ';' can be used for commenting a line


;;Do not let spaces arround the equal sign
;; As this makes the processing much easier
;; and reliable


;;as call set will be used in reading script
;; refering another variables will be possible.


;;; end

Reading script:

@echo off

set "VALUES_FILE=E:\scripts\example.values"

FOR /F "usebackq eol=; tokens=* delims=" %%# in (
) do (
    call set "%%#"

echo %First_Value% -- %Second_Value% -- %Third_Value%

How do I delete multiple rows in Entity Framework (without foreach)

Still seems crazy to have to pull anything back from the server just to delete it, but at least getting back just the IDs is a lot leaner than pulling down the full entities:

var ids = from w in context.Widgets where w.WidgetId == widgetId select w.Id;
context.Widgets.RemoveRange(from id in ids.AsEnumerable() select new Widget { Id = id });

How can I undo git reset --hard HEAD~1?

It is possible to recover it if Git hasn't garbage collected yet.

Get an overview of dangling commits with fsck:

$ git fsck --lost-found
dangling commit b72e67a9bb3f1fc1b64528bcce031af4f0d6fcbf

Recover the dangling commit with rebase:

$ git rebase b72e67a9bb3f1fc1b64528bcce031af4f0d6fcbf

Reverse the ordering of words in a string

public class manip{

public static char[] rev(char[] a,int left,int right) {
    char temp;
    for (int i=0;i<(right - left)/2;i++)    {
        temp = a[i + left];
        a[i + left] = a[right -i -1];
        a[right -i -1] = temp;

    return a;
public static void main(String[] args) throws IOException {

    String s= "i think this works";
    char[] str = s.toCharArray();       
    int i=0;
    int j=0;
    while(j < str.length) {
        if (str[j] != ' ' && j != str.length -1) {
        } else
            if (j == (str.length -1))   {

Using Sockets to send and receive data

the easiest way to do this is to wrap your sockets in ObjectInput/OutputStreams and send serialized java objects. you can create classes which contain the relevant data, and then you don't need to worry about the nitty gritty details of handling binary protocols. just make sure that you flush your object streams after you write each object "message".

Order of items in classes: Fields, Properties, Constructors, Methods

I would recommend using the coding standards from IDesign or the ones listed on Brad Abram's website. Those are the best two that I have found.

Brad would say...

Classes member should be alphabetized, and grouped into sections (Fields, Constructors, Properties, Events, Methods, Private interface implementations, Nested types)

Matching strings with wildcard

A wildcard * can be translated as .* or .*? regex pattern.

You might need to use a singleline mode to match newline symbols, and in this case, you can use (?s) as part of the regex pattern.

You can set it for the whole or part of the pattern:

X* = > @"X(?s:.*)"
*X = > @"(?s:.*)X"
*X* = > @"(?s).*X.*"
*X*YZ* = > @"(?s).*X.*YZ.*"
X*YZ*P = > @"(?s:X.*YZ.*P)"

Javascript: getFullyear() is not a function

One way to get this error is to forget to use the 'new' keyword when instantiating your Date in javascript like this:

> d = Date();
'Tue Mar 15 2016 20:05:53 GMT-0400 (EDT)'
> typeof(d);
> d.getFullYear();
TypeError: undefined is not a function

Had you used the 'new' keyword, it would have looked like this:

> el@defiant $ node
> d = new Date();
Tue Mar 15 2016 20:08:58 GMT-0400 (EDT)
> typeof(d);
> d.getFullYear(0);

Another way to get that error is to accidentally re-instantiate a variable in javascript between when you set it and when you use it, like this:

el@defiant $ node
> d = new Date();
Tue Mar 15 2016 20:12:13 GMT-0400 (EDT)
> d.getFullYear();
> d = 57 + 23;
> d.getFullYear();
TypeError: undefined is not a function

convert htaccess to nginx

Use this:

Online converter, nice way and time saver ;)

Component based game engine design

While not a complete tutorial on the subject of game engine design, I have found that this page has some good detail and examples on use of the component architecture for games.

How can I change all input values to uppercase using Jquery?

Use css text-transform to display text in all input type text. In Jquery you can then transform the value to uppercase on blur event.


input[type=text] {
    text-transform: uppercase;


$(document).on('blur', "input[type=text]", function () {
    $(this).val(function (_, val) {
        return val.toUpperCase();

Set Encoding of File to UTF8 With BOM in Sublime Text 3

By default, Sublime Text set 'UTF8 without BOM', but that wasn't specified.

The only specicified things is 'UTF8 with BOM'.

Hope this help :)

Printing newlines with print() in R

You can also use a combination of cat and paste0

cat(paste0("File not supplied.\n", "Usage: ./program F=filename"))

I find this to be more useful when incorporating variables into the printout. For example:

file <- "myfile.txt"
cat(paste0("File not supplied.\n", "Usage: ./program F=", file))

jQuery counting elements by class - what is the best way to implement this?


    <img src='' class='class' />
    <img src='' class='class' />
    <img src='' class='class' />



var numItems = $('.class').length; 

Fiddle demo for inside only div

How to create full compressed tar file using Python?

Previous answers advise using the tarfile Python module for creating a .tar.gz file in Python. That's obviously a good and Python-style solution, but it has serious drawback in speed of the archiving. This question mentions that tarfile is approximately two times slower than the tar utility in Linux. According to my experience this estimation is pretty correct.

So for faster archiving you can use the tar command using subprocess module:['tar', '-czf', output_filename, file_to_archive])

How to display pie chart data values of each slice in chart.js

You can make use of PieceLabel plugin for Chart.js.

{ pieceLabel: { mode: 'percentage', precision: 2 } }

Demo | Documentation

The plugin appears to have a new location (and name): Demo Docs.

"Line contains NULL byte" in CSV reader (Python)

It is very simple.

don't make a csv file by "create new excel" or save as ".csv" from window.

simply import csv module, write a dummy csv file, and then paste your data in that.

csv made by python csv module itself will no longer show you encoding or blank line error.

SQL Server NOLOCK and joins

I was pretty sure that you need to specify the NOLOCK for each JOIN in the query. But my experience was limited to SQL Server 2005.

When I looked up MSDN just to confirm, I couldn't find anything definite. The below statements do seem to make me think, that for 2008, your two statements above are equivalent though for 2005 it is not the case:

[SQL Server 2008 R2]

All lock hints are propagated to all the tables and views that are accessed by the query plan, including tables and views referenced in a view. Also, SQL Server performs the corresponding lock consistency checks.

[SQL Server 2005]

In SQL Server 2005, all lock hints are propagated to all the tables and views that are referenced in a view. Also, SQL Server performs the corresponding lock consistency checks.

Additionally, point to note - and this applies to both 2005 and 2008:

The table hints are ignored if the table is not accessed by the query plan. This may be caused by the optimizer choosing not to access the table at all, or because an indexed view is accessed instead. In the latter case, accessing an indexed view can be prevented by using the OPTION (EXPAND VIEWS) query hint.

UIView frame, bounds and center

I think if you think it from the point of CALayer, everything is more clear.

Frame is not really a distinct property of the view or layer at all, it is a virtual property, computed from the bounds, position(UIView's center), and transform.

So basically how the layer/view layouts is really decided by these three property(and anchorPoint), and either of these three property won't change any other property, like changing transform doesn't change bounds.

How to set the "Content-Type ... charset" in the request header using a HTML link

This is not possible from HTML on. The closest what you can get is the accept-charset attribute of the <form>. Only MSIE browser adheres that, but even then it is doing it wrong (e.g. CP1252 is actually been used when it says that it has sent ISO-8859-1). Other browsers are fully ignoring it and they are using the charset as specified in the Content-Type header of the response. Setting the character encoding right is basically fully the responsiblity of the server side. The client side should just send it back in the same charset as the server has sent the response in.

To the point, you should really configure the character encoding stuff entirely from the server side on. To overcome the inability to edit URIEncoding attribute, someone here on SO wrote a (complex) filter: Detect the URI encoding automatically in Tomcat. You may find it useful as well (note: I haven't tested it).

Update: Noted should be that the meta tag as given in your question is ignored when the content is been transferred over HTTP. Instead, the HTTP response Content-Type header will be used to determine the content type and character encoding. You can determine the HTTP header with for example Firebug, in the Net panel.

alt text

how to fix Cannot call sendRedirect() after the response has been committed?

you have already forwarded the response in catch block:

RequestDispatcher dd = request.getRequestDispatcher("error.jsp");

dd.forward(request, response);

so, you can not again call the :


because it is already forwarded (committed).

So what you can do is: keep a string to assign where you need to forward the response.

    String page = "";
    try {

    } catch (Exception e) {
      page = "error.jsp";
    } finally {
      page = "usertaskpage.jsp";

RequestDispatcher dd=request.getRequestDispatcher(page);
dd.forward(request, response);

How to represent matrices in python


Using tuples instead of lists makes it marginally harder to change the data structure in unwanted ways.

If you are going to do extensive use of those, you are best off wrapping a true number array in a class, so you can define methods and properties on them. (Or, you could NumPy, SciPy, ... if you are going to do your processing with those libraries.)

Remove CSS class from element with JavaScript (no jQuery)


Okay, complete re-write. It's been a while, I've learned a bit and the comments have helped.

Node.prototype.hasClass = function (className) {
    if (this.classList) {
        return this.classList.contains(className);
    } else {
        return (-1 < this.className.indexOf(className));

Node.prototype.addClass = function (className) {
    if (this.classList) {
    } else if (!this.hasClass(className)) {
        var classes = this.className.split(" ");
        this.className = classes.join(" ");
    return this;

Node.prototype.removeClass = function (className) {
    if (this.classList) {
    } else {
        var classes = this.className.split(" ");
        classes.splice(classes.indexOf(className), 1);
        this.className = classes.join(" ");
    return this;

Old Post
I was just working with something like this. Here's a solution I came up with...

// Some browsers don't have a native trim() function
if(!String.prototype.trim) {
    Object.defineProperty(String.prototype,'trim', {
        value: function() {
            return this.replace(/^\s+|\s+$/g,'');
// addClass()
// first checks if the class name already exists, if not, it adds the class.
Object.defineProperty(Node.prototype,'addClass', {
    value: function(c) {
        if(this.className.indexOf(c)<0) {
            this.className=this.className+=' '+c;
        return this;
// removeClass()
// removes the class and cleans up the className value by changing double 
// spacing to single spacing and trimming any leading or trailing spaces
Object.defineProperty(Node.prototype,'removeClass', {
    value: function(c) {
        this.className=this.className.replace(c,'').replace('  ',' ').trim();
        return this;

Now you can call myElement.removeClass('myClass')

or chain it: myElement.removeClass("oldClass").addClass("newClass");

Git Cherry-Pick and Conflicts

Do, I need to resolve all the conflicts before proceeding to next cherry -pick

Yes, at least with the standard git setup. You cannot cherry-pick while there are conflicts.

Furthermore, in general conflicts get harder to resolve the more you have, so it's generally better to resolve them one by one.

That said, you can cherry-pick multiple commits at once, which would do what you are asking for. See e.g. How to cherry-pick multiple commits . This is useful if for example some commits undo earlier commits. Then you'd want to cherry-pick all in one go, so you don't have to resolve conflicts for changes that are undone by later commits.

Further, is it suggested to do cherry-pick or branch merge in this case?

Generally, if you want to keep a feature branch up to date with main development, you just merge master -> feature branch. The main advantage is that a later merge feature branch -> master will be much less painful.

Cherry-picking is only useful if you must exclude some changes in master from your feature branch. Still, this will be painful so I'd try to avoid it.

Determine whether a key is present in a dictionary

if 'name' in mydict:

is the preferred, pythonic version. Use of has_key() is discouraged, and this method has been removed in Python 3.

What exactly does the T and Z mean in timestamp?

The T doesn't really stand for anything. It is just the separator that the ISO 8601 combined date-time format requires. You can read it as an abbreviation for Time.

The Z stands for the Zero timezone, as it is offset by 0 from the Coordinated Universal Time (UTC).

Both characters are just static letters in the format, which is why they are not documented by the datetime.strftime() method. You could have used Q or M or Monty Python and the method would have returned them unchanged as well; the method only looks for patterns starting with % to replace those with information from the datetime object.

How to skip over an element in .map()?

TLDR: You can first filter your array and then perform your map but this would require two passes on the array (filter returns an array to map). Since this array is small, it is a very small performance cost. You can also do a simple reduce. However if you want to re-imagine how this can be done with a single pass over the array (or any datatype), you can use an idea called "transducers" made popular by Rich Hickey.


We should not require increasing dot chaining and operating on the array [].map(fn1).filter(f2)... since this approach creates intermediate arrays in memory on every reducing function.

The best approach operates on the actual reducing function so there is only one pass of data and no extra arrays.

The reducing function is the function passed into reduce and takes an accumulator and input from the source and returns something that looks like the accumulator

// 1. create a concat reducing function that can be passed into `reduce`
const concat = (acc, input) => acc.concat([input])

// note that [1,2,3].reduce(concat, []) would return [1,2,3]

// transforming your reducing function by mapping
// 2. create a generic mapping function that can take a reducing function and return another reducing function
const mapping = (changeInput) => (reducing) => (acc, input) => reducing(acc, changeInput(input))

// 3. create your map function that operates on an input
const getSrc = (x) => x.src
const mappingSrc = mapping(getSrc)

// 4. now we can use our `mapSrc` function to transform our original function `concat` to get another reducing function
const inputSources = [{src:'one.html'}, {src:'two.txt'}, {src:'three.json'}]
inputSources.reduce(mappingSrc(concat), [])
// -> ['one.html', 'two.txt', 'three.json']

// remember this is really essentially just
// inputSources.reduce((acc, x) => acc.concat([x.src]), [])

// transforming your reducing function by filtering
// 5. create a generic filtering function that can take a reducing function and return another reducing function
const filtering = (predicate) => (reducing) => (acc, input) => (predicate(input) ? reducing(acc, input): acc)

// 6. create your filter function that operate on an input
const filterJsonAndLoad = (img) => {
  if(img.src.split('.').pop() === 'json') {
    // game.loadSprite(...);
    return false;
  } else {
    return true;
const filteringJson = filtering(filterJsonAndLoad)

// 7. notice the type of input and output of these functions
// concat is a reducing function,
// mapSrc transforms and returns a reducing function
// filterJsonAndLoad transforms and returns a reducing function
// these functions that transform reducing functions are "transducers", termed by Rich Hickey
// source:
// we can pass this all into reduce! and without any intermediate arrays

const sources = inputSources.reduce(filteringJson(mappingSrc(concat)), []);
// [ 'one.html', 'two.txt' ]

// ==================================
// 8. BONUS: compose all the functions
// You can decide to create a composing function which takes an infinite number of transducers to
// operate on your reducing function to compose a computed accumulator without ever creating that
// intermediate array
const composeAll = (...args) => (x) => {
  const fns = args
  var i = fns.length
  while (i--) {
    x = fns[i].call(this, x);
  return x

const doABunchOfStuff = composeAll(
    filtering((x) => x.src.split('.').pop() !== 'json'),
    mapping((x) => x.src),
    mapping((x) => x.toUpperCase()),
    mapping((x) => x + '!!!')

const sources2 = inputSources.reduce(doABunchOfStuff(concat), [])
// ['ONE.HTML!!!', 'TWO.TXT!!!']

Resources: rich hickey transducers post

2D array values C++

Just want to point out you do not need to specify all dimensions of the array.

The leftmost dimension can be 'guessed' by the compiler.

#include <stdio.h>
int main(void) {
  int arr[][5] = {{1,2,3,4,5}, {5,6,7,8,9}, {6,5,4,3,2}};
  printf("sizeof arr is %d bytes\n", (int)sizeof arr);
  printf("number of elements: %d\n", (int)(sizeof arr/sizeof arr[0]));
  return 0;

Fixed footer in Bootstrap

To get a footer that sticks to the bottom of your viewport, give it a fixed position like this:

footer {
    position: fixed;
    height: 100px;
    bottom: 0;
    width: 100%;

Bootstrap includes this CSS in the Navbar > Placement section with the class fixed-bottom. Just add this class to your footer element:

<footer class="fixed-bottom">

Bootstrap docs:

How can I use ":" as an AWK field separator?

You can also use a regular expression as a field separator. The following will print "bar" by using a regular expression to set the number "10" as a separator.

echo "foo 10 bar" | awk -F'[0-9][0-9]' '{print $2}'

Dynamic variable names in Bash

Beyond associative arrays, there are several ways of achieving dynamic variables in Bash. Note that all these techniques present risks, which are discussed at the end of this answer.

In the following examples I will assume that i=37 and that you want to alias the variable named var_37 whose initial value is lolilol.

Method 1. Using a “pointer” variable

You can simply store the name of the variable in an indirection variable, not unlike a C pointer. Bash then has a syntax for reading the aliased variable: ${!name} expands to the value of the variable whose name is the value of the variable name. You can think of it as a two-stage expansion: ${!name} expands to $var_37, which expands to lolilol.

echo "$name"         # outputs “var_37”
echo "${!name}"      # outputs “lolilol”
echo "${!name%lol}"  # outputs “loli”
# etc.

Unfortunately, there is no counterpart syntax for modifying the aliased variable. Instead, you can achieve assignment with one of the following tricks.

1a. Assigning with eval

eval is evil, but is also the simplest and most portable way of achieving our goal. You have to carefully escape the right-hand side of the assignment, as it will be evaluated twice. An easy and systematic way of doing this is to evaluate the right-hand side beforehand (or to use printf %q).

And you should check manually that the left-hand side is a valid variable name, or a name with index (what if it was evil_code # ?). By contrast, all other methods below enforce it automatically.

# check that name is a valid variable name:
# note: this code does not support variable_name[index]
shopt -s globasciiranges
[[ "$name" == [a-zA-Z_]*([a-zA-Z_0-9]) ]] || exit

eval "$name"='$value'  # carefully escape the right-hand side!
echo "$var_37"  # outputs “babibab”


  • does not check the validity of the variable name.
  • eval is evil.
  • eval is evil.
  • eval is evil.

1b. Assigning with read

The read builtin lets you assign values to a variable of which you give the name, a fact which can be exploited in conjunction with here-strings:

IFS= read -r -d '' "$name" <<< 'babibab'
echo "$var_37"  # outputs “babibab\n”

The IFS part and the option -r make sure that the value is assigned as-is, while the option -d '' allows to assign multi-line values. Because of this last option, the command returns with an non-zero exit code.

Note that, since we are using a here-string, a newline character is appended to the value.


  • somewhat obscure;
  • returns with a non-zero exit code;
  • appends a newline to the value.

1c. Assigning with printf

Since Bash 3.1 (released 2005), the printf builtin can also assign its result to a variable whose name is given. By contrast with the previous solutions, it just works, no extra effort is needed to escape things, to prevent splitting and so on.

printf -v "$name" '%s' 'babibab'
echo "$var_37"  # outputs “babibab”


  • Less portable (but, well).

Method 2. Using a “reference” variable

Since Bash 4.3 (released 2014), the declare builtin has an option -n for creating a variable which is a “name reference” to another variable, much like C++ references. Just as in Method 1, the reference stores the name of the aliased variable, but each time the reference is accessed (either for reading or assigning), Bash automatically resolves the indirection.

In addition, Bash has a special and very confusing syntax for getting the value of the reference itself, judge by yourself: ${!ref}.

declare -n ref="var_$i"
echo "${!ref}"  # outputs “var_37”
echo "$ref"     # outputs “lolilol”
echo "$var_37"  # outputs “babibab”

This does not avoid the pitfalls explained below, but at least it makes the syntax straightforward.


  • Not portable.


All these aliasing techniques present several risks. The first one is executing arbitrary code each time you resolve the indirection (either for reading or for assigning). Indeed, instead of a scalar variable name, like var_37, you may as well alias an array subscript, like arr[42]. But Bash evaluates the contents of the square brackets each time it is needed, so aliasing arr[$(do_evil)] will have unexpected effects… As a consequence, only use these techniques when you control the provenance of the alias.

function guillemots() {
  declare -n var="$1"

arr=( aaa bbb ccc )
guillemots 'arr[1]'  # modifies the second cell of the array, as expected
guillemots 'arr[$(date>>date.out)1]'  # writes twice into date.out
            # (once when expanding var, once when assigning to it)

The second risk is creating a cyclic alias. As Bash variables are identified by their name and not by their scope, you may inadvertently create an alias to itself (while thinking it would alias a variable from an enclosing scope). This may happen in particular when using common variable names (like var). As a consequence, only use these techniques when you control the name of the aliased variable.

function guillemots() {
  # var is intended to be local to the function,
  # aliasing a variable which comes from outside
  declare -n var="$1"

guillemots var  # Bash warnings: “var: circular name reference”
echo "$var"     # outputs anything!


where is create-react-app webpack config and files?

If you want to find webpack files and configurations go to your package.json file and look for scripts


You will find that scripts object is using a library react-scripts

Now go to node_modules and look for react-scripts folder react-script-in-node-modules

This react-scripts/scripts and react-scripts/config folder contains all the webpack configurations.

How do I delete all messages from a single queue using the CLI?

rabbitmqadmin is the perfect tool for this

rabbitmqadmin purge queue name=name_of_the_queue_to_be_purged

Angular-Material DateTime Picker Component?

Angular Material 10 now includes a new date range picker.

To use the new date range picker, you can use the mat-date-range-input and mat-date-range-picker components.



  <mat-label>Enter a date range</mat-label>
  <mat-date-range-input [rangePicker]="picker">
    <input matStartDate matInput placeholder="Start date">
    <input matEndDate matInput placeholder="End date">
  <mat-datepicker-toggle matSuffix [for]="picker"></mat-datepicker-toggle>
  <mat-date-range-picker #picker></mat-date-range-picker>

You can read and learn more about this in their official documentation.

Unfortunately, they still haven't build a timepicker on this release.

Apache: client denied by server configuration

This code worked for me..

 <Location />
Allow from all
Order Deny,Allow

Hope this helps others

The type initializer for 'CrystalDecisions.CrystalReports.Engine.ReportDocument' threw an exception

I faced the same issue. The target platform was Any CPU in my case. But the checkbox "Prefer-32Bit" was checked.. Unchecking the same resolved the issue.

Difference between two DateTimes C#?

var theDiff24 = (b-a).Hours

Can I do a max(count(*)) in SQL?

Just order by count(*) desc and you'll get the highest (if you combine it with limit 1)

Capturing TAB key in text box

The previous answer is fine, but I'm one of those guys that's firmly against mixing behavior with presentation (putting JavaScript in my HTML) so I prefer to put my event handling logic in my JavaScript files. Additionally, not all browsers implement event (or e) the same way. You may want to do a check prior to running any logic:

document.onkeydown = TabExample;

function TabExample(evt) {
  var evt = (evt) ? evt : ((event) ? event : null);
  var tabKey = 9;
  if(evt.keyCode == tabKey) {
    // do work

MySQL dump by query

mysql Export the query results command line:

mysql -h120.26.133.63 -umiyadb -proot123 miya -e "select * from user where id=1" > mydumpfile.txt

How do I clone into a non-empty directory?

In the following shell commands existing-dir is a directory whose contents match the tracked files in the repo-to-clone git repository.

# Clone just the repository's .git folder (excluding files as they are already in
# `existing-dir`) into an empty temporary directory
git clone --no-checkout repo-to-clone existing-dir/existing-dir.tmp # might want --no-hardlinks for cloning local repo

# Move the .git folder to the directory with the files.
# This makes `existing-dir` a git repo.
mv existing-dir/existing-dir.tmp/.git existing-dir/

# Delete the temporary directory
rmdir existing-dir/existing-dir.tmp
cd existing-dir

# git thinks all files are deleted, this reverts the state of the repo to HEAD.
# WARNING: any local changes to the files will be lost.
git reset --hard HEAD

How do I list / export private keys from a keystore?

If you don't need to do it programatically, but just want to manage your keys, then I've used IBM's free KeyMan tool for a long time now. Very nice for exporting a private key to a PFX file (then you can easily use OpenSSL to manipulate it, extract it, change pwds, etc).

Select your keystore, select the private key entry, then File->Save to a pkcs12 file (*.pfx, typically). You can then view the contents with:

$ openssl pkcs12 -in mykeyfile.pfx -info

How do I access my SSH public key?

In UBUNTU +18.04

         ssh-keygen -o -t rsa -b 4096 -C "[email protected]" 

And After that Just Copy And Paste

         cat ~/.ssh/ 


         cat ~/.ssh/

installing vmware tools: location of GCC binary?

Install prerequisites VMware Tools for LinuxOS:

If you have RHEL/CentOS:

yum install perl gcc make kernel-headers kernel-devel -y

If you have Ubuntu/Debian:

sudo apt-get -y install linux-headers-server build-essential
  • build-essential, also install: dpkg-dev, g++, gcc, lib6-dev, libc-dev, make

Extracted from:

Android set bitmap to Imageview

Please try this:

byte[] decodedString = Base64.decode(person_object.getPhoto(),Base64.NO_WRAP);
InputStream inputStream  = new ByteArrayInputStream(decodedString);
Bitmap bitmap  = BitmapFactory.decodeStream(inputStream);

"Invalid form control" only in Google Chrome

I was getting this error, and determined it was actually on a field that was not hidden.

In this case, it was a type="number" field, that is required. When no value has ever been entered into this field, the error message is shown in the console, and the form is not submitted. Entering a value, and then removing it means that the validation error is shown as expected.

I believe this is a bug in Chrome: my workaround for now was to come up with an initial/default value.

Generate random numbers using C++11 random library

Here is some resource you can read about pseudo-random number generator.

Basically, random numbers in computer need a seed (this number can be the current system time).


std::default_random_engine generator;


std::default_random_engine generator(<some seed number>);

How to set a DateTime variable in SQL Server 2008?

Check This:

    @_month TINYINT         = 5,
    @_year SMALLINT         = 2020,
    @date_ref DATETIME      = NULL 

    IF @_year IS NULL
        SET @date_ref = GETDATE() - 430
        SELECT @date_ref = CAST ( CAST ( @_year AS VARCHAR (4)) 
                WHEN @_month < 10 THEN '0' + CAST ( @_month AS VARCHAR(1)) 
                ELSE CAST ( @_month AS VARCHAR(2)) 
            '01' AS DATETIME )

Google MAP API v3: Center & Zoom on displayed markers

Try this works...

$(function() {
        var myOptions = {
            zoom: 10,
            center: latlng,
            mapTypeId: google.maps.MapTypeId.ROADMAP
        var map = new google.maps.Map(document.getElementById("map_canvas"),myOptions);
        var latlng_pos=[];
        var j=0;
            latlng_pos[j]=new google.maps.LatLng($(this).find(".latitude").val(),$(this).find(".longitude").val());
            var marker = new google.maps.Marker({
                position: new google.maps.LatLng($(this).find(".latitude").val(),$(this).find(".longitude").val()),
                // position: new google.maps.LatLng(-35.397, 150.640),
                map: map
        // map: an instance of google.maps.Map object
        // latlng: an array of google.maps.LatLng objects
        var latlngbounds = new google.maps.LatLngBounds( );
        for ( var i = 0; i < latlng_pos.length; i++ ) {
            latlngbounds.extend( latlng_pos[ i ] );
        map.fitBounds( latlngbounds );


How can I run a html file from terminal?

For those like me, who have reached this thread because they want to serve an html file from linux terminal or want to view it using a terminal command, use these steps:-

1)If you want to view your html using a browser:-
Navigate to the directory containing the html file
If you have chrome installed, Use:-

google-chrome <filename>.html


firefox <filename>.html

2)If you want to serve html file and view it using a browser
Navigate to the directory containing the html file
And Simply type the following on the Terminal:-

pushd <filename>.html; python3 -m http.server 9999; popd;

Then click the I.P. address OR localhost:9999 (Whatever is the result after executing the above commands). Or type on the terminal :-


Using the second method, anyone else connected to the same network can also view your file by using the URL:- ""

How to get the current loop index when using Iterator?

I had the same question and found using a ListIterator worked. Similar to the test above:

List<String> list = Arrays.asList("zero", "one", "two");

ListIterator iter = list.listIterator();
while (iter.hasNext()) {
    System.out.println("index: " + iter.nextIndex() + " value: " +;

Make sure you call the nextIndex() before you actually get the next().

Python script to do something at the same time every day

You can do that like this:

from datetime import datetime
from threading import Timer
y=x.replace(, hour=1, minute=0, second=0, microsecond=0)


def hello_world():
    print "hello world"

t = Timer(secs, hello_world)

This will execute a function (eg. hello_world) in the next day at 1a.m.


As suggested by @PaulMag, more generally, in order to detect if the day of the month must be reset due to the reaching of the end of the month, the definition of y in this context shall be the following:

y = x.replace(, hour=1, minute=0, second=0, microsecond=0) + timedelta(days=1)

With this fix, it is also needed to add timedelta to the imports. The other code lines maintain the same. The full solution, using also the total_seconds() function, is therefore:

from datetime import datetime, timedelta
from threading import Timer
y = x.replace(, hour=1, minute=0, second=0, microsecond=0) + timedelta(days=1)


def hello_world():
    print "hello world"

t = Timer(secs, hello_world)

How to use a ViewBag to create a dropdownlist?

@Html.DropDownListFor(m =>, (SelectList)ViewBag.Department, "Select", htmlAttributes: new { @class = "form-control" })

UPDATE with CASE and IN - Oracle

"The list are variables/paramaters that is pre-defined as comma separated lists". Do you mean that your query is actually

UPDATE tab1   SET budgpost_gr1=     
CASE  WHEN (budgpost in ('1001,1012,50055'))  THEN 'BP_GR_A'   
      WHEN (budgpost in ('5,10,98,0'))  THEN 'BP_GR_B'  
      WHEN (budgpost in ('11,876,7976,67465'))     
      ELSE 'Missing' END`

If so, you need a function to take a string and parse it into a list of numbers.

create type tab_num is table of number;

create or replace function f_str_to_nums (i_str in varchar2) return tab_num is
  v_tab_num tab_num := tab_num();
  v_start   number := 1;
  v_end     number;
  v_delim   VARCHAR2(1) := ',';
  v_cnt     number(1) := 1;
  v_end := instr(i_str||v_delim,v_delim,1, v_start);
  WHILE v_end > 0 LOOP
    v_cnt := v_cnt + 1;
    v_tab_num(v_tab_num.count) := 
    v_start := v_end + 1;
    v_end := instr(i_str||v_delim,v_delim,v_start);
  RETURN v_tab_num;

Then you can use the function like so:

select column_id, 
   case when column_id in 
     (select column_value from table(f_str_to_nums('1,2,3,4'))) then 'red' 
   else 'blue' end
from  user_tab_columns
where table_name = 'EMP'

Calculating how many minutes there are between two times

In your quesion code you are using TimeSpan.FromMinutes incorrectly. Please see the MSDN Documentation for TimeSpan.FromMinutes, which gives the following method signature:

public static TimeSpan FromMinutes(double value)

hence, the following code won't compile

var intMinutes = TimeSpan.FromMinutes(varTime); // won't compile

Instead, you can use the TimeSpan.TotalMinutes property to perform this arithmetic. For instance:

TimeSpan varTime = (DateTime)varFinish - (DateTime)varValue; 
double fractionalMinutes = varTime.TotalMinutes;
int wholeMinutes = (int)fractionalMinutes;

Setting background color for a JFrame

you can override the paint method of JFrame and then fill that by your favorite color like this:

public void paint(Graphics g) {
    g.fillRect(0, 0, this.getWidth(), this.getHeight());

How to get a right click mouse event? Changing EventArgs to MouseEventArgs causes an error in Form1Designer?

You need MouseClick instead of Click event handler, reference.

switch (e.Button) {

    case MouseButtons.Left:
    // Left click

    case MouseButtons.Right:
    // Right click

Bootstrap modal opening on page load

Use a document.ready() event around your call.

$(document).ready(function () {



jsFiddle updated -

Format price in the current locale and currency

try this:

<?php echo Mage::app()->getLocale()->currency(Mage::app()->getStore()->getCurrentCurrencyCode())->getSymbol(); ?>

Creating and Naming Worksheet in Excel VBA

Dim WS as Worksheet
Set WS = Sheets.Add

You don't have to know where it's located, or what it's name is, you just refer to it as WS.
If you still want to do this the "old fashioned" way, try this:

Sheets.Add.Name = "Test"

Abort Ajax requests using jQuery

I was doing a live search solution and needed to cancel pending requests that may have taken longer than the latest/most current request.

In my case I used something like this:

//On document ready
var ajax_inprocess = false;

$(document).ajaxStart(function() {
ajax_inprocess = true;

$(document).ajaxStop(function() {
ajax_inprocess = false;

//Snippet from live search function
if (ajax_inprocess == true)
//Call for new request 

Difference between F5, Ctrl + F5 and click on refresh button?

CTRL+F5 Reloads the current page, ignoring cached content and generating the expected result.

How do I set up Eclipse/EGit with GitHub?

Make sure your refs for pushing are correct. This tutorial is pretty great, right from the documentation:

You can clone directly from GitHub, you choose where you clone that repository. And when you import that repository to Eclipse, you choose what refspec to push into upstream.

Click on the Git Repository workspace view, and make sure your remote refs are valid. Make sure you are pointing to the right local branch and pushing to the correct remote branch.

VBA Macro to compare all cells of two Excel files

A very simple check you can do with Cell formulas:

Sheet 1 (new - old)


Sheet 2 (old - new)


This formulas should work for an ENGLISH Excel. For other languages they need to be translated. (For German i can assist)

You need to open all three Excel Documents, then copy the first formula into A1 of your sheet 1 and the second into A1 of sheet 2. Now click in A1 of the first cell and mark "Ref_New", now you can select your reference, go to the new file and click in the A1, go back to sheet1 and do the same for "Ref_Old" with the old file. Replace also the other "Ref_New".

Doe the same for Sheet two.

Now copy the formaula form A1 over the complete range where zour data is in the old and the new file.

But two cases are not covered here:

  1. In the compared cell of New and Old is the same data (Resulting Cell will be empty)
  2. In the compared cell of New and Old is diffe data (Resulting Cell will be empty)

To cover this two cases also, you should create your own function, means learn VBA. A very useful Excel page is

Use a.any() or a.all()

If you take a look at the result of valeur <= 0.6, you can see what’s causing this ambiguity:

>>> valeur <= 0.6
array([ True, False, False, False], dtype=bool)

So the result is another array that has in this case 4 boolean values. Now what should the result be? Should the condition be true when one value is true? Should the condition be true only when all values are true?

That’s exactly what numpy.any and numpy.all do. The former requires at least one true value, the latter requires that all values are true:

>>> np.any(valeur <= 0.6)
>>> np.all(valeur <= 0.6)

Setting Timeout Value For .NET Web Service

Try setting the timeout value in your web service proxy class:

WebReference.ProxyClass myProxy = new WebReference.ProxyClass();
myProxy.Timeout = 100000; //in milliseconds, e.g. 100 seconds

How to check if a std::string is set or not?

As several answers pointed out, std::string has no concept of 'nullness' for its value. If using the empty string as such a value isn't good enough (ie., you need to distinguish between a string that has no characters and a string that has no value), you can use a std::string* and set it to NULL or to a valid std::string instance as appropriate.

You may want to use some sort of smart pointer type (boost::scoped_ptr or something) to help manage the lifetime of any std::string object that you set the pointer to.

How to style an menu with CSS

You can try styling with LevelSubMenuStyles

            <asp:Menu ID="mainMenu" runat="server" Orientation="Horizontal" 
                <StaticMenuStyle CssClass="test" />
                    <asp:SubMenuStyle BackColor="#33CCFF" BorderColor="#FF9999" 
                        Font-Underline="False" />
                    <asp:SubMenuStyle BackColor="#FF99FF" Font-Underline="False" />
                <StaticMenuItemStyle CssClass="main-nav-item" />

Can Twitter Bootstrap alerts fade in as well as out?

You can fade-in a box using jquery. Use bootstraps built in 'hide' class to effectively set display:none on the div element:

<div id="saveAlert" class="alert alert-success hide" data-alert="alert" style="top:0">
            <a class="close" href="#">×</a>
            <p><strong>Well done!</strong> You successfully read this alert message.</p>

and then use the fadeIn function in jquery, like so:


There are also specify a duration for the fadeIn function, e.g: $("#saveAlert").fadeIn(400);

Full details on using the fadeIn function can be found on the official jQuery documentation site:

Just a sidenote as well, if you arent using jquery, you can either add the 'hide' class to your own CSS file, or just add this to your div:

 <div style="display:none;" id="saveAlert">

Your div will then basically be set to hidden as default, and then jQuery will perform the fadeIn action, forcing the div to be displayed.

How to use Google Translate API in my Java application?

I’m tired of looking for free translators and the best option for me was Selenium (more precisely selenide and webdrivermanager) and

import io.github.bonigarcia.wdm.ChromeDriverManager;
import com.codeborne.selenide.Configuration;
import io.github.bonigarcia.wdm.DriverManagerType;
import static com.codeborne.selenide.Selenide.*;

public class Main {

    public static void main(String[] args) throws IOException, ParseException {

        Configuration.startMaximized = true;
        String[] strings = /some strings to translate
        for (String data: strings) {
            String translation = $x("//span[@class='tlid-translation translation']").getText();

Opacity of div's background without affecting contained element in IE 8?

Use RGBA or if you hex code then change it into rgba. No need to do some presodu element css.

function hexaChangeRGB(hex, alpha) {
    var r = parseInt(hex.slice(1, 3), 16),
        g = parseInt(hex.slice(3, 5), 16),
        b = parseInt(hex.slice(5, 7), 16);

    if (alpha) {
        return "rgba(" + r + ", " + g + ", " + b + ", " + alpha + ")";
    } else {
        return "rgb(" + r + ", " + g + ", " + b + ")";

hexaChangeRGB('#FF0000', 0.2);

css ---------

background-color: #fff;
opacity: 0.8;


mycolor = hexaChangeRGB('#FF0000', 0.2);
document.getElementById("myP").style.background-color = mycolor;

JavaFX - create custom button with image

There are a few different ways to accomplish this, I'll outline my favourites.

Use a ToggleButton and apply a custom style to it. I suggest this because your required control is "like a toggle button" but just looks different from the default toggle button styling.

My preferred method is to define a graphic for the button in css:

.toggle-button {
  -fx-graphic: url('');

.toggle-button:selected {
  -fx-graphic: url('');

OR use the attached css to define a background image.

// file imagetogglebutton.css deployed in the same package as ToggleButtonImage.class
.toggle-button {
  -fx-background-image: url('');
  -fx-background-repeat: no-repeat;
  -fx-background-position: center;

.toggle-button:selected {
  -fx-background-image: url('');

I prefer the -fx-graphic specification over the -fx-background-* specifications as the rules for styling background images are tricky and setting the background does not automatically size the button to the image, whereas setting the graphic does.

And some sample code:

import javafx.application.Application;
import javafx.scene.*;
import javafx.scene.control.ToggleButton;
import javafx.scene.layout.StackPaneBuilder;
import javafx.stage.Stage;

public class ToggleButtonImage extends Application {
  public static void main(String[] args) throws Exception { launch(args); }
  @Override public void start(final Stage stage) throws Exception {
    final ToggleButton toggle = new ToggleButton();
    toggle.setMinSize(148, 148); toggle.setMaxSize(148, 148);
    stage.setScene(new Scene(
        .style("-fx-padding:10; -fx-background-color: cornsilk;")

Some advantages of doing this are:

  1. You get the default toggle button behavior and don't have to re-implement it yourself by adding your own focus styling, mouse and key handlers etc.
  2. If your app gets ported to different platform such as a mobile device, it will work out of the box responding to touch events rather than mouse events, etc.
  3. Your styling is separated from your application logic so it is easier to restyle your application.

An alternate is to not use css and still use a ToggleButton, but set the image graphic in code:

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.scene.*;
import javafx.scene.control.ToggleButton;
import javafx.scene.image.*;
import javafx.scene.layout.StackPaneBuilder;
import javafx.stage.Stage;

public class ToggleButtonImageViaGraphic extends Application {
  public static void main(String[] args) throws Exception { launch(args); }
  @Override public void start(final Stage stage) throws Exception {
    final ToggleButton toggle      = new ToggleButton();
    final Image        unselected  = new Image(
    final Image        selected    = new Image(
    final ImageView    toggleImage = new ImageView();

    stage.setScene(new Scene(
        .style("-fx-padding:10; -fx-background-color: cornsilk;")

The code based approach has the advantage that you don't have to use css if you are unfamilar with it.

For best performance and ease of porting to unsigned applet and webstart sandboxes, bundle the images with your app and reference them by relative path urls rather than downloading them off the net.

When should I use double or single quotes in JavaScript?

As stated by other replies, they are almost the same. But I will try to add more.

  1. Some efficient algorithms use character arrays to process strings. Those algorithms (browser compiler, etc.) would see " (#34) first before ' (#39) therefore saving several CPU cycles depending on your data structure.
  2. " is escaped by anti-XSS engines

Url decode UTF-8 in Python

The data is UTF-8 encoded bytes escaped with URL quoting, so you want to decode, with urllib.parse.unquote(), which handles decoding from percent-encoded data to UTF-8 bytes and then to text, transparently:

from urllib.parse import unquote

url = unquote(url)


>>> from urllib.parse import unquote
>>> url = ''
>>> unquote(url)

The Python 2 equivalent is urllib.unquote(), but this returns a bytestring, so you'd have to decode manually:

from urllib import unquote

url = unquote(url).decode('utf8')

Where does System.Diagnostics.Debug.Write output appear?

The Diagnostics messages are displayed in the Output Window.

What is the difference between and localhost

Wikipedia sums this up well:

On modern computer systems, localhost as a hostname translates to an IPv4 address in the (loopback) net block, usually, or ::1 in IPv6.

The only difference is that it would be looking up in the DNS for the system what localhost resolves to. This lookup is really, really quick. For instance, to get to you typed in that to the address bar (or used a bookmarklet that pointed here). Either way, you got here through a hostname. localhost provides a similar functionality.

chai test array equality doesn't work as expected

import chai from 'chai';
const arr1 = [2, 1];
const arr2 = [2, 1];
chai.expect(arr1).to.eql(arr2); // Will pass. `eql` is data compare instead of object compare.

Querying date field in MongoDB with Mongoose

{ "date" : "1000000" } in your Mongo doc seems suspect. Since it's a number, it should be { date : 1000000 }

It's probably a type mismatch. Try post.findOne({date: "1000000"}, callback) and if that works, you have a typing issue.

Plugin is too old, please update to a more recent version, or set ANDROID_DAILY_OVERRIDE environment variable to

This is android's way of telling you to upgrade gradle to the most recent version. You can do two things-

  1. Upgrade to the newer version of gradle. You may face new errors after the upgrade (eg, if you are upgrading to 4.1, you will have to adapt to new syntax - "compile" is no longer valid, use "implementation").
  2. Update your ANDROID_DAILY_OVERRIDE variable to the value given. Go to Computer -> Properties -> Advanced System Settings -> Environment Variables, and create a new variable or update value of existing ANDROID_DAILY_OVERRIDE. As the name suggests, this value is only valid for one day and next day you will again have to override the variable.

javax.mail.AuthenticationFailedException: failed to connect, no password specified?

First of all, enable the less secure app in your Gmail account from which you will send emails using this link:-

Then you simply add the following code in your session creation. It will work fine then.

Session mailSession = Session.getInstance(props, new javax.mail.Authenticator(){
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(
                    "your_email", "your_password");// Specify the Username and the PassWord

if you want the more elaborated one use the following:-

import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.NoSuchProviderException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class MailSender {

    public Properties mailProperties() {
        Properties props = new Properties();

        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("", "");
        props.setProperty("mail.smtp.port", "587");
        props.setProperty("mail.smtp.user", "your_email");
        props.setProperty("mail.smtp.password", "your_password");
        props.setProperty("mail.smtp.starttls.enable", "true");
        props.setProperty("mail.smtp.auth", "true");

        return props;

    public String sendMail(String from, String to, String subject, String msgBody) {
        Properties props = mailProperties();
        Session mailSession = Session.getInstance(props, new javax.mail.Authenticator(){
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(
                    "your_email", "your_password");// Specify the Username and the PassWord


        try {
            Transport transport = mailSession.getTransport();

            MimeMessage message = new MimeMessage(mailSession);
            message.setFrom(new InternetAddress(from));
            message.addRecipients(Message.RecipientType.TO, to);

            MimeMultipart multipart = new MimeMultipart();

            MimeBodyPart messageBodyPart = new MimeBodyPart();

            messageBodyPart.setContent(msgBody, "text/html");


            transport.sendMessage(message, message.getRecipients(Message.RecipientType.TO));
            return "SUCCESS";
        } catch (NoSuchProviderException e) {
            return "INVALID_EMAIL";
        } catch (MessagingException e) {
        return "ERROR";

    public static void main(String args[]) {
        System.out.println(new MailSender().sendMail("your_email/from_email", "to_email", "Subject", "Message"));

Hope! it helps. Thanks!

Open directory using C

Here is a simple way to implement ls command using c. To run use for example ./xls /tmp

    #include <dirent.h>
    void main(int argc,char *argv[])
   DIR *dir;
   struct dirent *dent;
   dir = opendir(argv[1]);   

        if((strcmp(dent->d_name,".")==0 || strcmp(dent->d_name,"..")==0 || (*dent->d_name) == '.' ))

Shuffle DataFrame rows

Here is another way:

df['rnd'] = np.random.rand(len(df)) df = df.sort_values(by='rnd', inplace=True).drop('rnd', axis=1)

Boxplot show the value of mean

You can also use a function within stat_summary to calculate the mean and the hjust argument to place the text, you need a additional function but no additional data frame:

fun_mean <- function(x){

ggplot(PlantGrowth,aes(x=group,y=weight)) +
geom_boxplot(aes(fill=group)) +
stat_summary(fun.y = mean, geom="point",colour="darkred", size=3) +
stat_summary( = fun_mean, geom="text", vjust=-0.7)

enter image description here

Regular Expression for alphanumeric and underscores

I believe you are not taking Latin and Unicode characters in your matches. For example, if you need to take "ã" or "ü" chars, the use of "\w" won't work.

You can, alternatively, use this approach:


Hope it helps!

Make one div visible and another invisible

If u want to use display=block it will make the content reader jump, so instead of using display you can set the left attribute to a negative value which does not exist in your html page to be displayed but actually it do.

I hope you must be understanding my point, if I am unable to make u understand u can message me back.

Stop a gif animation onload, on mouseover start the activation

The best option is probably to have a still image which you replace the gif with when you want to stop it.

<img src="gif/1303552574110.1.gif" alt="" class="anim" >
<img src="gif/1302919192204.gif" alt="" class="anim" >
<img src="gif/1303642234740.gif" alt="" class="anim" >
<img src="gif/1303822879528.gif" alt="" class="anim" >
<img src="gif/1303825584512.gif" alt="" class="anim" >

$(window).load(function() {

$(".anim").mouseover(function {

$(".anim").mouseout(function {

You probably want to have two arrays containing paths to the still and animated gifs which you can assign to each image.

Backup a single table with its data from a database in sql server 2008

Another approach you can take if you need to back up a single table out of multiple tables in a database is:

  1. Generate script of specific table(s) from a database (Right-click database, click Task > Generate Scripts...

  2. Run the script in the query editor. You must change/add the first line (USE DatabaseName) in the script to a new database, to avoid getting the "Database already exists" error.

  3. Right-click on the newly created database, and click on Task > Back Up... The backup will contain the selected table(s) from the original database.

Overriding fields or properties in subclasses

The example implementation when you want to have an abstract class with implementation. Subclasses must:

  1. Parameterize the implementation of an abstract class.
  2. Fully inherit the implementation of the abstract class;
  3. Have your own implementation.

In this case, the properties that are necessary for the implementation should not be available for use except for the abstract class and its own subclass.

    internal abstract class AbstractClass
        //Properties for parameterization from concrete class
        protected abstract string Param1 { get; }
        protected abstract string Param2 { get; }

        //Internal fields need for manage state of object
        private string var1;
        private string var2;

        internal AbstractClass(string _var1, string _var2)
            this.var1 = _var1;
            this.var2 = _var2;

        internal void CalcResult()
            //The result calculation uses Param1, Param2, var1, var2;

    internal class ConcreteClassFirst : AbstractClass
        private string param1;
        private string param2;
        protected override string Param1 { get { return param1; } }
        protected override string Param2 { get { return param2; } }

        public ConcreteClassFirst(string _var1, string _var2) : base(_var1, _var2) { }

        internal void CalcParams()
            //The calculation param1 and param2

    internal class ConcreteClassSecond : AbstractClass
        private string param1;
        private string param2;

        protected override string Param1 { get { return param1; } }

        protected override string Param2 { get { return param2; } }

        public ConcreteClassSecond(string _var1, string _var2) : base(_var1, _var2) { }

        internal void CalcParams()
            //The calculation param1 and param2

    static void Main(string[] args)
        string var1_1 = "val1_1";
        string var1_2 = "val1_2";

        ConcreteClassFirst concreteClassFirst = new ConcreteClassFirst(var1_1, var1_2);

        string var2_1 = "val2_1";
        string var2_2 = "val2_2";

        ConcreteClassSecond concreteClassSecond = new ConcreteClassSecond(var2_1, var2_2);

        //Param1 and Param2 are not visible in main method

No appenders could be found for logger(log4j)?

If you are using Eclipse and this problem appeared out of nowhere after everything worked fine beforehand, try going to Project - Clean - Clean.

How to force a component's re-rendering in Angular 2?

ChangeDetectorRef.detectChanges() is usually the most focused way of doing this. ApplicationRef.tick() is usually too much of a sledgehammer approach.

To use ChangeDetectorRef.detectChanges(), you'll need this at the top of your component:

import {  ChangeDetectorRef } from '@angular/core';

... then, usually you alias that when you inject it in your constructor like this:

constructor( private cdr: ChangeDetectorRef ) { ... }

Then, in the appropriate place, you call it like this:


Where you call ChangeDetectorRef.detectChanges() can be highly significant. You need to completely understand the life cycle and exactly how your application is functioning and rendering its components. There's no substitute here for completely doing your homework and making sure you understand the Angular lifecycle inside out. Then, once you understand that, you can use ChangeDetectorRef.detectChanges() appropriately (sometimes it's very easy to understand where you should use it, other times it can be very complex).

Wait until all promises complete even if some rejected

You can execute your logic sequentially via synchronous executor nsynjs. It will pause on each promise, wait for resolution/rejection, and either assign resolve's result to data property, or throw an exception (for handling that you will need try/catch block). Here is an example:

function synchronousCode() {_x000D_
    function myFetch(url) {_x000D_
        try {_x000D_
            return window.fetch(url).data;_x000D_
        catch (e) {_x000D_
            return {status: 'failed:'+e};_x000D_
    var arr=[_x000D_
    console.log('array is ready:',arr[0].status,arr[1].status,arr[2].status);_x000D_
<script src=""></script>

Strange "java.lang.NoClassDefFoundError" in Eclipse

Doing Project->Clean… in Eclipse solved this problem for me.

How can I get relative path of the folders in my android project?

In Android, application-level meta data is accessed through the Context reference, which an activity is a descendant of.

For example, you can get the source directory via the getApplicationInfo().sourceDir property. There are methods for other folders as well (assets directory, data dir, database dir, etc.).

Splitting strings in PHP and get last part

As has been mentioned by others, if you don't assign the result of explode() to a variable, you get the message:

E_STRICT: Strict standards: Only variables should be passed by reference

The correct way is:

$words = explode('-', 'hello-world-123');
$id = array_pop($words); // 123
$slug = implode('-', $words); // hello-world

What's the point of the X-Requested-With header?

Make sure you read SilverlightFox's answer. It highlights a more important reason.

The reason is mostly that if you know the source of a request you may want to customize it a little bit.

For instance lets say you have a website which has many recipes. And you use a custom jQuery framework to slide recipes into a container based on a link they click. The link may be

Now normally that returns a full page, header, footer, recipe content and ads. But if someone is browsing your website some of those parts are already loaded. So you can use an AJAX to get the recipe the user has selected but to save time and bandwidth don't load the header/footer/ads.

Now you can just write a secondary endpoint for the data like but that's harder to maintain and share to other people.

But it's easier to just detect that it is an ajax request making the request and then returning only a part of the data. That way the user wastes less bandwidth and the site appears more responsive.

The frameworks just add the header because some may find it useful to keep track of which requests are ajax and which are not. But it's entirely dependent on the developer to use such techniques.

It's actually kind of similar to the Accept-Language header. A browser can request a website please show me a Russian version of this website without having to insert /ru/ or similar in the URL.

Jquery post, response in new window

I did it with an ajax post and then returned using a data url:

$(document).ready(function () {
    var exportClick = function () {
           url: "/api/test.php",
           type: "POST",
           dataType: "text",
           data: {
              action: "getCSV",
              filter: "name = 'smith'",
           success: function(data) {
              var w ='data:text/csv;charset=utf-8,' + encodeURIComponent(data));
           error: function () {
              alert('Problem getting data');

Oracle SQL Where clause to find date records older than 30 days


 WHERE creation_date <= TRUNC(SYSDATE) - 30

SYSDATE returns the date & time; TRUNC resets the date to being as of midnight so you can omit it if you want the creation_date that is 30 days previous including the current time.

Depending on your needs, you could also look at using ADD_MONTHS:

 WHERE creation_date <= ADD_MONTHS(TRUNC(SYSDATE), -1)

Pushing from local repository to GitHub hosted remote

You push your local repository to the remote repository using the git push command after first establishing a relationship between the two with the git remote add [alias] [url] command. If you visit your Github repository, it will show you the URL to use for pushing. You'll first enter something like:

git remote add origin [email protected]:username/reponame.git

Unless you started by running git clone against the remote repository, in which case this step has been done for you already.

And after that, you'll type:

git push origin master

After your first push, you can simply type:

git push

when you want to update the remote repository in the future.

invalid new-expression of abstract class type

invalid new-expression of abstract class type 'box'

There is nothing unclear about the error message. Your class box has at least one member that is not implemented, which means it is abstract. You cannot instantiate an abstract class.

If this is a bug, fix your box class by implementing the missing member(s).

If it's by design, derive from box, implement the missing member(s) and use the derived class.

Creating a custom JButton in Java

You could always try the Synth look & feel. You provide an xml file that acts as a sort of stylesheet, along with any images you want to use. The code might look like this:

try {
    SynthLookAndFeel synth = new SynthLookAndFeel();
    Class aClass = MainFrame.class;
    InputStream stream = aClass.getResourceAsStream("\\default.xml");

    if (stream == null) {
        System.err.println("Missing configuration file");

    synth.load(stream, aClass);

} catch (ParseException pe) {
    System.err.println("Bad configuration file");
} catch (UnsupportedLookAndFeelException ulfe) {
    System.err.println("Old JRE in use. Get a new one");

From there, go on and add your JButton like you normally would. The only change is that you use the setName(string) method to identify what the button should map to in the xml file.

The xml file might look like this:

    <style id="button">
        <font name="DIALOG" size="12" style="BOLD"/>
        <state value="MOUSE_OVER">
            <imagePainter method="buttonBackground" path="dirt.png" sourceInsets="2 2 2 2"/>
            <insets top="2" botton="2" right="2" left="2"/>
        <state value="ENABLED">
            <imagePainter method="buttonBackground" path="dirt.png" sourceInsets="2 2 2 2"/>
            <insets top="2" botton="2" right="2" left="2"/>
    <bind style="button" type="name" key="dirt"/>

The bind element there specifies what to map to (in this example, it will apply that styling to any buttons whose name property has been set to "dirt").

And a couple of useful links:

Package php5 have no installation candidate (Ubuntu 16.04)

Currently, I am using Ubuntu 16.04 LTS. Me too was facing same problem while Fetching the Postgress Database values using Php so i resolved it by using the below commands.

Mine PHP version is 7.0, so i tried the below command.

apt-get install php-pgsql

Remember to restart Apache.

/etc/init.d/apache2 restart

loop through json array jquery

You have to parse the string as JSON (data[0] == "[" is an indication that data is actually a string, not an object):

data = $.parseJSON(data);
$.each(data, function(i, item) {

How can I get a list of all classes within current module in Python?

Another solution which works in Python 2 and 3:
import sys

class Foo(object):

def print_classes():
    current_module = sys.modules[__name__]
    for key in dir(current_module):
        if isinstance( getattr(current_module, key), type ):

import foo

What is the meaning of prepended double colon "::"?

:: is the scope resolution operator. It's used to specify the scope of something.

For example, :: alone is the global scope, outside all other namespaces.

some::thing can be interpreted in any of the following ways:

  • some is a namespace (in the global scope, or an outer scope than the current one) and thing is a type, a function, an object or a nested namespace;
  • some is a class available in the current scope and thing is a member object, function or type of the some class;
  • in a class member function, some can be a base type of the current type (or the current type itself) and thing is then one member of this class, a type, function or object.

You can also have nested scope, as in some::thing::bad. Here each name could be a type, an object or a namespace. In addition, the last one, bad, could also be a function. The others could not, since functions can't expose anything within their internal scope.

So, back to your example, ::thing can be only something in the global scope: a type, a function, an object or a namespace.

The way you use it suggests (used in a pointer declaration) that it's a type in the global scope.

I hope this answer is complete and correct enough to help you understand scope resolution.

What is the use of the JavaScript 'bind' method?

bind is a function which is available in java script prototype, as the name suggest bind is used to bind your function call to the context whichever you are dealing with for eg:

    var rateOfInterest='4%';_x000D_
    var axisBank=_x000D_
    return this.rateOfInterest;_x000D_
    axisBank.getRateOfInterest() //'10%' _x000D_
    let knowAxisBankInterest=axisBank.getRateOfInterest // when you want to assign the function call to a varaible we use this syntax_x000D_
    knowAxisBankInterest(); // you will get output as '4%' here by default the function is called wrt global context_x000D_
let knowExactAxisBankInterest=knowAxisBankInterest.bind(axisBank);     //so here we need bind function call  to its local context_x000D_
    knowExactAxisBankInterest() // '10%' 

How to force Laravel Project to use HTTPS for all routes?

I used this at the end of the web.php or api.php file and it worked perfectly:


What is the use of verbose in Keras while validating the model?

The order of details provided with verbose flag are as

Less details.... More details

0 < 2 < 1

Default is 1

For production environment, 2 is recommended

How to scanf only integer?

I know how this can be done using fgets and strtol, I would like to know how this can be done using scanf() (if possible).

As the other answers say, scanf isn't really suitable for this, fgets and strtol is an alternative (though fgets has the drawback that it's hard to detect a 0-byte in the input and impossible to tell what has been input after a 0-byte, if any).

For sake of completeness (and assuming valid input is an integer followed by a newline):

while(scanf("%d%1[\n]", &n, (char [2]){ 0 }) < 2)

Alternatively, use %n before and after %*1[\n] with assignment-suppression. Note, however (from the Debian manpage):

This is not a conversion, although it can be suppressed with the * assignment-suppression character. The C standard says: "Execution of a %n directive does not increment the assignment count returned at the completion of execution" but the Corrigendum seems to contradict this. Probably it is wise not to make any assumptions on the effect of %n conversions on the return value.

Conversion of a datetime2 data type to a datetime data type results out-of-range value

Check the req format in DB. eg my DB have Default value or Binding (((1)/(1))/(1900))

System.DateTime MyDate = new System.DateTime( 1900 ,1, 1);

enter image description here

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

You can't. This is an intentional design decision by the Git maintainers. Basically, the purpose of a Source Code Management System like Git is managing source code and empty directories aren't source code. Git is also often described as a content tracker, and again, empty directories aren't content (quite the opposite, actually), so they are not tracked.

Seeing the underlying SQL in the Spring JdbcTemplate?

This works for me with org.springframework.jdbc-3.0.6.RELEASE.jar. I could not find this anywhere in the Spring docs (maybe I'm just lazy) but I found (trial and error) that the TRACE level did the magic.

I'm using log4j-1.2.15 along with slf4j (1.6.4) and properties file to configure the log4j: = TRACE

This displays both the SQL statement and bound parameters like this:

Executing prepared SQL statement [select HEADLINE_TEXT, NEWS_DATE_TIME from MY_TABLE where PRODUCT_KEY = ? and NEWS_DATE_TIME between ? and ? order by NEWS_DATE_TIME]
Setting SQL statement parameter value: column index 1, parameter value [aaa], value class [java.lang.String], SQL type unknown
Setting SQL statement parameter value: column index 2, parameter value [Thu Oct 11 08:00:00 CEST 2012], value class [java.util.Date], SQL type unknown
Setting SQL statement parameter value: column index 3, parameter value [Thu Oct 11 08:00:10 CEST 2012], value class [java.util.Date], SQL type unknown

Not sure about the SQL type unknown but I guess we can ignore it here

For just an SQL (i.e. if you're not interested in bound parameter values) DEBUG should be enough.

Create text file and fill it using bash

Your question is a a bit vague. This is a shell command that does what I think you want to do:

echo >> name_of_file

Where do I find old versions of Android NDK?

A way to find out old download links is to use internet archive tools like "Way back machine", You can browse older web pages versions and get the links you want.

For example, I needed to download the NDK rev 9, so I used this tool to access the NDK download page ( from March and the download link in March pointed to NDK rev 9.

Reset the Value of a Select Box

neRok touched on this answer above and I'm just expanding on it.

According to the slightly dated, but handy O'Reilly reference book, Javascript: The Definitive Guide:

The selectedIndex property of the Select object is an integer that specifies the index of the selected option within the Select object. If no option is selected, selectedIndex is -1.

As such, the following javascript code will "reset" the Select object to no options selected:

select_box = document.getElementById("myselectbox");
select_box.selectedIndex = -1;

Note that changing the selection in this way does not trigger the onchange() event handler.

R Markdown - changing font size and font type in html output

I had the same issue and solved by making sure that 1. when you make the style.css file, make sure you didn't just rename a text file as "style.css", make sure it's really the .css format (e.g, use visual studio code); 2. put that style.css file in the same folder with your .rmd file. Hopefully this works for you.

Constructors in Go

another way is;

package person

type Person struct {
    Name string
    Old  int

func New(name string, old int) *Person {
    // set only specific field value with field key
    return &Person{
        Name: name,

Graphviz: How to go from .dot to a graph?

This should combine a lot of answers.

# Convert dot to png via graphviz
dot -Tpng -o filename.png

# Convert dot to svg via graphviz
dot -Tsvg -o filename.svg

# Convert dot to eps via graphviz
dot -Tps -o filename.eps

Keep in mind that on OSX (MAC), you need to install homebrew to install graphviz to be able to use the dot commands above.

brew install graphviz

It is also possible to install Graphviz (and use the commands above) through the package manager functionality of conda if you have Anaconda installed.

conda install python-graphviz

passing JSON data to a Spring MVC controller

Add the following dependencies



Modify request as follows

    contentType: "application/json; charset=utf-8",
    data: jsonString, //Stringified Json Object
    async: false,    //Cross-domain requests and dataType: "jsonp" requests do not support synchronous operation
    cache: false,    //This will force requested pages not to be cached by the browser          
    processData:false, //To avoid making query String instead of JSON
    success: function(resposeJsonObject){
        // Success Message Handler

Controller side

@RequestMapping(value = urlPattern , method = RequestMethod.POST)
public @ResponseBody Person save(@RequestBody Person jsonString) {

   Person person=personService.savedata(jsonString);
   return person;

@RequestBody - Covert Json object to java
@ResponseBody- convert Java object to json

What is setContentView(R.layout.main)?

As per the documentation :

Set the activity content from a layout resource. The resource will be inflated, adding all top-level views to the activity.

Your Launcher activity in the manifest first gets called and it set the layout view as specified in respective java files setContentView(R.layout.main);. Now this activity uses setContentView(R.layout.main) to set xml layout to that activity which will actually render as the UI of your activity.

How do I print the percent sign(%) in c

Your problem is that you have to change:




Or you could use ASCII code and write:

printf("%c", 37);


What is the python "with" statement designed for?

Another example for out-of-the-box support, and one that might be a bit baffling at first when you are used to the way built-in open() behaves, are connection objects of popular database modules such as:

The connection objects are context managers and as such can be used out-of-the-box in a with-statement, however when using the above note that:

When the with-block is finished, either with an exception or without, the connection is not closed. In case the with-block finishes with an exception, the transaction is rolled back, otherwise the transaction is commited.

This means that the programmer has to take care to close the connection themselves, but allows to acquire a connection, and use it in multiple with-statements, as shown in the psycopg2 docs:

conn = psycopg2.connect(DSN)

with conn:
    with conn.cursor() as curs:

with conn:
    with conn.cursor() as curs:


In the example above, you'll note that the cursor objects of psycopg2 also are context managers. From the relevant documentation on the behavior:

When a cursor exits the with-block it is closed, releasing any resource eventually associated with it. The state of the transaction is not affected.

Passing parameters to a JDBC PreparedStatement

You should use the setString() method to set the userID. This both ensures that the statement is formatted properly, and prevents SQL injection:

statement =con.prepareStatement("SELECT * from employee WHERE  userID = ?");
statement.setString(1, userID);

There is a nice tutorial on how to use PreparedStatements properly in the Java Tutorials.

Change visibility of ASP.NET label with JavaScript

Try this.

<asp:Button id="myButton" runat="server" style="display:none" Text="Click Me" />

<script type="text/javascript">
    function ShowButton() {
        var buttonID = '<%= myButton.ClientID %>';
        var button = document.getElementById(buttonID);
        if(button) { = 'inherit'; }

Don't use server-side code to do this because that would require a postback. Instead of using Visibility="false", you can just set a CSS property that hides the button. Then, in javascript, switch that property back whenever you want to show the button again.

The ClientID is used because it can be different from the server ID if the button is inside a Naming Container control. These include Panels of various sorts.

How to read values from properties file?

If you need to manually read a properties file without using @Value.

Thanks for the well written page by Lokesh Gupta : Blog

enter image description here

package utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.ResourceUtils;

import java.util.Properties;

public class Utils {

    private static final Logger LOGGER = LoggerFactory.getLogger(Utils.class.getName());

    public static Properties fetchProperties(){
        Properties properties = new Properties();
        try {
            File file = ResourceUtils.getFile("");
            InputStream in = new FileInputStream(file);
        } catch (IOException e) {
        return properties;

How are SSL certificate server names resolved/Can I add alternative names using keytool?

How host name verification should be done is defined in RFC 6125, which is quite recent and generalises the practice to all protocols, and replaces RFC 2818, which was specific to HTTPS. (I'm not even sure Java 7 uses RFC 6125, which might be too recent for this.)

From RFC 2818 (Section 3.1):

If a subjectAltName extension of type dNSName is present, that MUST be used as the identity. Otherwise, the (most specific) Common Name field in the Subject field of the certificate MUST be used. Although the use of the Common Name is existing practice, it is deprecated and Certification Authorities are encouraged to use the dNSName instead.


In some cases, the URI is specified as an IP address rather than a hostname. In this case, the iPAddress subjectAltName must be present in the certificate and must exactly match the IP in the URI.

Essentially, the specific problem you have comes from the fact that you're using IP addresses in your CN and not a host name. Some browsers might work because not all tools follow this specification strictly, in particular because "most specific" in RFC 2818 isn't clearly defined (see discussions in RFC 6215).

If you're using keytool, as of Java 7, keytool has an option to include a Subject Alternative Name (see the table in the documentation for -ext): you could use -ext or -ext san=ip:


You can request a SAN in OpenSSL by changing openssl.cnf (it will pick the copy in the current directory if you don't want to edit the global configuration, as far as I remember, or you can choose an explicit location using the OPENSSL_CONF environment variable).

Set the following options (find the appropriate sections within brackets first):

req_extensions = v3_req

[ v3_req ]
# or

There's also a nice trick to use an environment variable for this (rather in than fixing it in a configuration file) here:

Display A Popup Only Once Per User

The best solution is to save a Boolean value in the database and then obtain that value and validate whether or not the modal was opened for that user, this value could be in the user table for example.

Parse query string into an array

Sometimes parse_str() alone is note accurate, it could display for example:

$url = "somepage?id=123&lang=gr&size=300";

parse_str() would return:

Array ( 
    [somepage?id] => 123 
    [lang] => gr 
    [size] => 300 

It would be better to combine parse_str() with parse_url() like so:

$url = "somepage?id=123&lang=gr&size=300";
parse_str( parse_url( $url, PHP_URL_QUERY), $array );
print_r( $array );

Remove padding or margins from Google Charts

I arrived here like most people with this same issue, and left shocked that none of the answer even remotely worked.

For anyone interested, here is the actual solution:

... //rest of options
width: '100%',
height: '350',
    top: 20,
    width: '100%',
    height: '350',
... //rest of options

The key here has nothing to do with the "left" or "top" values. But rather that the:

Dimensions of both the chart and chart-area are SET and set to the SAME VALUE

As an amendment to my answer. The above will indeed solve the "excessive" padding/margin/whitespace problem. However, if you wish to include axes labels and/or a legend you will need to reduce the height & width of the chart area so something slightly below the outer width/height. This will "tell" the chart API that there is sufficient room to display these properties. Otherwise it will happily exclude them.

Resetting a form in Angular 2 after submit

I'm using reactive forms in angular 4 and this approach works for me:


see reset the form flags in the Fundamentals doc

Difference between res.send and res.json in Express.js

The methods are identical when an object or array is passed, but res.json() will also convert non-objects, such as null and undefined, which are not valid JSON.

The method also uses the json replacer and json spaces application settings, so you can format JSON with more options. Those options are set like so:

app.set('json spaces', 2);
app.set('json replacer', replacer);

And passed to a JSON.stringify() like so:

JSON.stringify(value, replacer, spacing);
// value: object to format
// replacer: rules for transforming properties encountered during stringifying
// spacing: the number of spaces for indentation

This is the code in the res.json() method that the send method doesn't have:

var app =;
var replacer = app.get('json replacer');
var spaces = app.get('json spaces');
var body = JSON.stringify(obj, replacer, spaces);

The method ends up as a res.send() in the end:

this.charset = this.charset || 'utf-8';
this.get('Content-Type') || this.set('Content-Type', 'application/json');

return this.send(body);

Concatenate in jQuery Selector

Your concatenation syntax is correct.

Most likely the callback function isn't even being called. You can test that by putting an alert(), console.log() or debugger line in that function.

If it isn't being called, most likely there's an AJAX error. Look at chaining a .fail() handler after $.post() to find out what the error is, e.g.:

$.post('ajaxskeleton.php', {
    red: text       
}, function(){
    $('#part' + number).html(text);
}).fail(function(jqXHR, textStatus, errorThrown) {