Programs & Examples On #Client templates

Variable might not have been initialized error

You haven't initialised a and b, only declared them. There is a subtle difference.

int a = 0;
int b = 0;

At least this is for C++, I presume Java is the same concept.

List supported SSL/TLS versions for a specific OpenSSL build

Try the following command:

openssl ciphers

This should produce a list of all of the ciphers supported in your version of openssl.

To see just a particular set of ciphers (e.g. just sslv3 ciphers) try:

openssl ciphers -ssl3

See for more info.

How to calculate distance from Wifi router using Signal Strength?

the simple answer to your question would be Triangulation. Which is essentially the concept in all GPS devices, I would give this article a read to learn more about how Google goes about doing this:

From my understanding, they use a service similar to Skyhook, which is a location software that determines your location based on your wifi/cellphone signals. In order to achieve their accuracy, these services have large servers of databases that store location information on these cell towers and wifi access points - they actually survey metropolitan areas to keep it up to date. In order for you to achieve something similar, I would assume you'd have to use a service like Skyhook - you can use their SDK ( ).

However, if you want to do something internal (like using your own routers' locations) - then you'd likely have to create an algorithm that mimics Triangulation. You'll have to find a way to get the signal_strength and mac_address of the device and use that information along with the locations of your routers to come up with the location. You can probably get the information about devices hooked up to your routers by doing something similar to this ( ).

How to use cURL in Java?

You can make use of and/or

URL url = new URL("");

try (BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream(), "UTF-8"))) {
    for (String line; (line = reader.readLine()) != null;) {

Also see the Oracle's simple tutorial on the subject. It's however a bit verbose. To end up with less verbose code, you may want to consider Apache HttpClient instead.

By the way: if your next question is "How to process HTML result?", then the answer is "Use a HTML parser. No, don't use regex for this.".

See also:

Send request to curl with post data sourced from a file

I had to use a HTTP connection, because on HTTPS there is default file size limit.

    curl -i -X 'POST' -F 'file=@/home/testeincremental.xlsx' ''

Request header field Access-Control-Allow-Headers is not allowed by Access-Control-Allow-Headers

You can activate the proper header in PHP with this:

header('Access-Control-Allow-Origin: *');
header("Access-Control-Allow-Methods: GET, POST, OPTIONS, PUT, DELETE");
header("Access-Control-Allow-Headers: Content-Type, Access-Control-Allow-Headers, X-Requested-With");

Trouble Connecting to sql server Login failed. "The login is from an untrusted domain and cannot be used with Windows authentication"

Yet another thing to check:

We had our nightly QA restore job stop working all of a sudden after another developer remoted into the QA server and tried to start the restore job during the middle of the day, which subsequently failed with the "untrusted domain" message. Somehow the server pointed to be the job's maintenance plan was (changed?) using the ip address, instead of the local machine's name. Upon replacing with the machine name the issue was resolved.

Missing Authentication Token while accessing API Gateway?

For the record, if you wouldn't be using credentials, this error also shows when you are setting the request validator in your POST/PUT method to "validate body, query string parameters and HEADERS", or the other option "validate query string parameters and HEADERS" that case it will look for the credentials on the header and reject the request. To sum it up, if you don't intend to send credentials and want to keep it open you should not set that option in request validator(set it to either NONE or to validate body)

Running python script inside ipython

The %run magic has a parameter file_finder that it uses to get the full path to the file to execute (see here); as you note, it just looks in the current directory, appending ".py" if necessary.

There doesn't seem to be a way to specify which file finder to use from the %run magic, but there's nothing to stop you from defining your own magic command that calls into %run with an appropriate file finder.

As a very nasty hack, you could override the default file_finder with your own:[2] = my_file_finder

To be honest, at the rate the IPython API is changing that's as likely to continue to work as defining your own magic is.

How to count rows with SELECT COUNT(*) with SQLAlchemy?

Query for just a single known column:


Is it possible to have different Git configuration for different projects?

You can also point the environment variable GIT_CONFIG to a file that git config should use. With GIT_CONFIG=~/.gitconfig-A git config key value the specified file gets manipulated.

Can't find AVD or SDK manager in Eclipse

I had similar problem after updating SDK from r20 to r21, but all I missed was the SDK/AVD Manager and running into this post while searching for the answer.

I managed to solve it by going to Window -> Customize Perspective, and under Command Groups Availability tab check the Android SDK and AVD Manager (not sure why it became unchecked because it was there before). I'm using Mac by the way, in case the menu option looks different.

'method' object is not subscriptable. Don't know what's wrong

You need to use parentheses: myList.insert([1, 2, 3]). When you leave out the parentheses, python thinks you are trying to access myList.insert at position 1, 2, 3, because that's what brackets are used for when they are right next to a variable.

Angular JS break ForEach

Try this as break;

angular.forEach([0,1,2], function(count){
  if(count == 1){
    return true;

How to compare times in Python?

Inspired by Roger Pate:

import datetime
def todayAt (hr, min=0, sec=0, micros=0):
   now =
   return now.replace(hour=hr, minute=min, second=sec, microsecond=micros)    

# Usage demo1:
print todayAt (17), todayAt (17, 15)

# Usage demo2:    
timeNow =
if timeNow < todayAt (13):
   print "Too Early"

Division of integers in Java

As your output results a double you should cast either completed variable or total variable or both to double while dividing.

So, the correct implmentation will be:


How do I print output in new line in PL/SQL?

In PL/SQL code, you can use: DBMS_OUTPUT.NEW_LINE;

Nested select statement in SQL Server

You need to alias the subquery.

SELECT name FROM (SELECT name FROM agentinformation) a  

or to be more explicit

SELECT FROM (SELECT name FROM agentinformation) a  

Import Error: No module named numpy

pip3 may not refer to the python3 you use. run python3 -m pip install numpy instead.

How to get directory size in PHP

It works perfectly fine .

     public static function folderSize($dir)
        $size = 0;

        foreach (glob(rtrim($dir, '/') . '/*', GLOB_NOSORT) as $each) {
            $func_name = __FUNCTION__;
            $size += is_file($each) ? filesize($each) : static::$func_name($each);

        return $size;

Python class returning value

You are describing a function, not a class.

def Myclass():
    return []

How can I disable a button in a jQuery dialog from a function?

I got this working with the method .dialog("widget") which returns the dialog DIV itself. If you're in the dialog methods:

.addClass("ui-state-disabled") // for the style
.attr("disabled", true);

Include PHP inside JavaScript (.js) files

Because the Javascript executes in the browser, on the client side, and PHP on the server side, what you need is AJAX - in essence, your script makes an HTTP request to a PHP script, passing any required parameters. The script calls your function, and outputs the result, which ultimately gets picked up by the Ajax call. Generally, you don't do this synchronously (waiting for the result) - the 'A' in AJAX stands for asynchronous!

sh: react-scripts: command not found after running npm start

I tried every answer but cleaning my npm cache worked..


  1. Clean cache =====> npm cache clean force.
  2. reinstall create-react-app =====> npm install create-react-app.
  3. npm install.
  4. npm start !!!

PHP preg_match - only allow alphanumeric strings and - _ characters

if(!preg_match('/^[\w-]+$/', $string1)) {
   echo "String 1 not acceptable acceptable";
   // String2 acceptable

Setting up and using environment variables in IntelliJ Idea

Path Variables dialog has nothing to do with the environment variables.

Environment variables can be specified in your OS or customized in the Run configuration:


How to retrieve a single file from a specific revision in Git?

This will help you get all deleted files between commits without specifying the path, useful if there are a lot of files deleted.

git diff --name-only --diff-filter=D $commit~1 $commit | xargs git checkout $commit~1

Getting file names without extensions

As an additional answer (or to compound on the existing answers) you could write an extension method to accomplish this for you within the DirectoryInfo class. Here is a sample that I wrote fairly quickly that could be embellished to provide directory names or other criteria for modification, etc:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace DocumentDistributor.Library
    public static class myExtensions
        public static string[] GetFileNamesWithoutFileExtensions(this DirectoryInfo di)
            FileInfo[] fi = di.GetFiles();
            List<string> returnValue = new List<string>();

            for (int i = 0; i < fi.Length; i++)

            return returnValue.ToArray<string>();

Edit: I also think this method could probably be simplified or awesome-ified if it used LINQ to achieve the construction of the array, but I don't have the experience in LINQ to do it quickly enough for a sample of this kind.

Edit 2 (almost 4 years later): Here is the LINQ-ified method I would use:

public static class myExtensions
    public static IEnumerable<string> GetFileNamesWithoutExtensions(this DirectoryInfo di)
        return di.GetFiles()
            .Select(x => Path.GetFileNameWithoutExtension(x.FullName));

How to search for a string in text files?

Two problems:

  1. Your function does not return anything; a function that does not explicitly return anything returns None (which is falsy)

  2. True is always True - you are not checking the result of your function


def check(fname, txt):
    with open(fname) as dataf:
        return any(txt in line for line in dataf)

if check('example.txt', 'blabla'):
    print "true"
    print "false"

Regular expressions inside SQL Server

In order to match a digit, you can use [0-9].

So you could use 5[0-9][0-9][0-9][0-9][0-9][0-9] and [0-9][0-9][0-9][0-9]7[0-9][0-9][0-9]. I do this a lot for zip codes.

How to process SIGTERM signal gracefully?

Found easiest way for me. Here an example with fork for clarity that this way is useful for flow control.

import signal
import time
import sys
import os

def handle_exit(sig, frame):

def main():

signal.signal(signal.SIGTERM, handle_exit)

p = os.fork()
if p == 0:

    os.waitpid(p, 0)
except (KeyboardInterrupt, SystemExit):
    print('exit handled')
    os.kill(p, 15)
    os.waitpid(p, 0)

ASP.NET Core Web API exception handling

A simple way to handle an exception on any particular method is:

using Microsoft.AspNetCore.Http;

public ActionResult MyAPIMethod()
       var myObject = ... something;

       return Json(myObject);
    catch (Exception ex)
        Log.Error($"Error: {ex.Message}");
        return StatusCode(StatusCodes.Status500InternalServerError);

MS SQL 2008 - get all table names and their row counts in a DB

to get all tables in a database:


to get all columns in a database:

select * from INFORMATION_SCHEMA.columns

to get all views in a db:

select * from INFORMATION_SCHEMA.TABLES where table_type = 'view'

Format JavaScript date as yyyy-mm-dd

If you use momentjs, now they include a constant for that format YYYY-MM-DD:


How to set cache: false in jQuery.get call

Set cache: false in jQuery.get call using Below Method

use new Date().getTime(), which will avoid collisions unless you have multiple requests happening within the same millisecond.


The following will prevent all future AJAX requests from being cached, regardless of which jQuery method you use ($.get, $.ajax, etc.)

$.ajaxSetup({ cache: false });

How to use an environment variable inside a quoted string in Bash

If unsure, you might use the 'cols' request on the terminal, and forget COLUMNS:

COLS=$(tput cols)

How can I color Python logging output?

I modified the original example provided by Sorin and subclassed StreamHandler to a ColorizedConsoleHandler.

The downside of their solution is that it modifies the message, and because that is modifying the actual logmessage any other handlers will get the modified message as well.

This resulted in logfiles with colorcodes in them in our case because we use multiple loggers.

The class below only works on platforms that support ansi, but it should be trivial to add the windows colorcodes to it.

import copy
import logging

class ColoredConsoleHandler(logging.StreamHandler):
    def emit(self, record):
        # Need to make a actual copy of the record
        # to prevent altering the message for other loggers
        myrecord = copy.copy(record)
        levelno = myrecord.levelno
        if(levelno >= 50):  # CRITICAL / FATAL
            color = '\x1b[31m'  # red
        elif(levelno >= 40):  # ERROR
            color = '\x1b[31m'  # red
        elif(levelno >= 30):  # WARNING
            color = '\x1b[33m'  # yellow
        elif(levelno >= 20):  # INFO
            color = '\x1b[32m'  # green
        elif(levelno >= 10):  # DEBUG
            color = '\x1b[35m'  # pink
        else:  # NOTSET and anything else
            color = '\x1b[0m'  # normal
        myrecord.msg = color + str(myrecord.msg) + '\x1b[0m'  # normal
        logging.StreamHandler.emit(self, myrecord)

How can I make a JUnit test wait?

Thread.sleep() could work in most cases, but usually if you're waiting, you are actually waiting for a particular condition or state to occur. Thread.sleep() does not guarantee that whatever you're waiting for has actually happened.

If you are waiting on a rest request for example maybe it usually return in 5 seconds, but if you set your sleep for 5 seconds the day your request comes back in 10 seconds your test is going to fail.

To remedy this JayWay has a great utility called Awatility which is perfect for ensuring that a specific condition occurs before you move on.

It has a nice fluent api as well

await().until(() -> 
    return yourConditionIsMet();

How can I show a combobox in Android?

Here is an example of custom combobox in android:

package myWidgets;
import android.content.Context;
import android.database.Cursor;
import android.text.InputType;
import android.util.AttributeSet;
import android.view.View;
import android.widget.AutoCompleteTextView;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.SimpleCursorAdapter;

public class ComboBox extends LinearLayout {

   private AutoCompleteTextView _text;
   private ImageButton _button;

   public ComboBox(Context context) {

   public ComboBox(Context context, AttributeSet attrs) {
       super(context, attrs);

 private void createChildControls(Context context) {
    this.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,

   _text = new AutoCompleteTextView(context);
                   | InputType.TYPE_TEXT_VARIATION_NORMAL
                   | InputType.TYPE_TEXT_FLAG_CAP_SENTENCES
                   | InputType.TYPE_TEXT_FLAG_AUTO_COMPLETE
                   | InputType.TYPE_TEXT_FLAG_AUTO_CORRECT);
   this.addView(_text, new LayoutParams(LayoutParams.WRAP_CONTENT,
                   LayoutParams.WRAP_CONTENT, 1));

   _button = new ImageButton(context);
   _button.setOnClickListener(new OnClickListener() {
           public void onClick(View v) {
   this.addView(_button, new LayoutParams(LayoutParams.WRAP_CONTENT,

    * Sets the source for DDLB suggestions.
    * Cursor MUST be managed by supplier!!
    * @param source Source of suggestions.
    * @param column Which column from source to show.
 public void setSuggestionSource(Cursor source, String column) {
    String[] from = new String[] { column };
    int[] to = new int[] { };
    SimpleCursorAdapter cursorAdapter = new SimpleCursorAdapter(this.getContext(),
                   android.R.layout.simple_dropdown_item_1line, source, from, to);
    // this is to ensure that when suggestion is selected
    // it provides the value to the textbox

    * Gets the text in the combo box.
    * @return Text.
public String getText() {
    return _text.getText().toString();

    * Sets the text in combo box.
public void setText(String text) {

Hope it helps!!

Visual Studio "Could not copy" .... during build


A workaround is to put this in the Pre-build event command line property of the >project (In the build Events tab):

Code Snippet

if exist "$(TargetPath).locked" del "$(TargetPath).locked"

if exist "$(TargetPath)" if not exist "$(TargetPath).locked" move "$(TargetPath)" "$(TargetPath).locked"

PG COPY error: invalid input syntax for integer

I had this same error on a postgres .sql file with a COPY statement, but my file was tab-separated instead of comma-separated and quoted.

My mistake was that I eagerly copy/pasted the file contents from github, but in that process all the tabs were converted to spaces, hence the error. I had to download and save the raw file to get a good copy.

Java: Local variable mi defined in an enclosing scope must be final or effectively final

One solution is to create a named class instead of using an anonymous class. Give that named class a constructor that takes whatever parameters you wish and assigns them to class fields:

class MenuActionListener implements ActionListener {
    private Color kolorIkony;

    public MenuActionListener(Color kolorIkony) {
        this.kolorIkony = kolorIkony

    public void actionPerformed(ActionEvent e) {
        JMenuItem item = (JMenuItem) e.getSource();
        IconA icon = (IconA) item.getIcon();
        // Use the class field here

Now you can create an instance of this class as usual:

Jmi.addActionListener(new MenuActionListener(getColor(colors[mi]));

How do I change Bootstrap 3 column order on mobile layout?

Updated 2018

For the original question based on Bootstrap 3, the solution was to use push-pull.

In Bootstrap 4 it's now possible to change the order, even when the columns are full-width stacked vertically, thanks to Bootstrap 4 flexbox. OFC, the push pull method will still work, but now there are other ways to change column order in Bootstrap 4, making it possible to re-order full-width columns.

Method 1 - Use flex-column-reverse for xs screens:

<div class="row flex-column-reverse flex-md-row">
    <div class="col-md-3">
    <div class="col-md-9">

Method 2 - Use order-first for xs screens:

<div class="row">
    <div class="col-md-3">
    <div class="col-md-9 order-first order-md-last">

Bootstrap 4(alpha 6):
Bootstrap 4.1:

Original 3.x Answer

For the original question based on Bootstrap 3, the solution was to use push-pull for the larger widths, and then the columns will show is their natural order on smaller (xs) widths. (A-B reverse to B-A).

<div class="container">
    <div class="row">
        <div class="col-md-9 col-md-push-3">
        <div class="col-md-3 col-md-pull-9">

Bootstrap 3:

@emre stated, "You cannot change the order of columns in smaller screens but you can do that in large screens". However, this should be clarified to state: "You cannot change the order of full-width "stacked" columns.." in Bootstrap 3.

Is it possible to serialize and deserialize a class in C++?

Boost is a good suggestion. But if you would like to roll your own, it's not so hard.

Basically you just need a way to build up a graph of objects and then output them to some structured storage format (JSON, XML, YAML, whatever). Building up the graph is as simple as utilizing a marking recursive decent object algorithm and then outputting all the marked objects.

I wrote an article describing a rudimentary (but still powerful) serialization system. You may find it interesting: Using SQLite as an On-disk File Format, Part 2.

Python Brute Force algorithm

I found another very easy way to create dictionaries using itertools.

generator=itertools.combinations_with_replacement('abcd', 4 )

This will iterate through all combinations of 'a','b','c' and 'd' and create combinations with a total length of 1 to 4. ie. a,b,c,d,aa,ab.........,dddc,dddd. generator is an itertool object and you can loop through normally like this,

for password in generator:

Each password is infact of type tuple and you can work on them as you normally do.

Java JRE 64-bit download for Windows?

Might this be the download you are looking for?

  1. Go to the Java SE Downloads Page.
  2. Scroll down a tad look for the main table with the header of "Java Platform, Standard Edition"
  3. Click the JRE Download Button (JRE is the runtime component. JDK is the developer's kit).
  4. Select the appropriate download (all platforms and 32/64 bit downloads are listed)

How to restrict user to type 10 digit numbers in input element?

Here all of the above outputs are giving a 10 digit number, but along with that the input field is accepting characters also, which is not the full solution. In order to set the 10 digit numbers only, we can use an input tag along with that type as number, and in that we can remove the up-down array by writing some small code in css which is shown below along with the input tag.

 <input name="phone" maxlength="10" pattern="[1-9]{1}[0-9]{9}" class="form-control" id="mobile"  placeholder="Enter your phone Number" type="number">

input[type=number]::-webkit-outer-spin-button { 
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    margin: 0; 

Abstract Class:-Real Time Example

I use often abstract classes in conjuction with Template method pattern.
In main abstract class I wrote the skeleton of main algorithm and make abstract methods as hooks where suclasses can make a specific implementation; I used often when writing data parser (or processor) that need to read data from one different place (file, database or some other sources), have similar processing step (maybe small differences) and different output.
This pattern looks like Strategy pattern but it give you less granularity and can degradated to a difficult mantainable code if main code grow too much or too exceptions from main flow are required (this considerations came from my experience).
Just a small example:

abstract class MainProcess {
  public static class Metrics {
    int skipped;
    int processed;
    int stored;
    int error;
  private Metrics metrics;
  protected abstract Iterator<Item> readObjectsFromSource();
  protected abstract boolean storeItem(Item item);
  protected Item processItem(Item item) {
    /* do something on item and return it to store, or null to skip */
    return item;
  public Metrics getMetrics() {
    return metrics;
  /* Main method */
  final public void process() {
    this.metrics = new Metrics();
    Iterator<Item> items = readObjectsFromSource();
    for(Item item : items) {
      item = processItem(item);
      if(null != item) {

      else {

class ProcessFromDatabase extends MainProcess {
  ProcessFromDatabase(String query) {
    this.query = query;
  protected Iterator<Item> readObjectsFromSource() {
    return sessionFactory.getCurrentSession().query(query).list();
  protected boolean storeItem(Item item) {
    return sessionFactory.getCurrentSession().saveOrUpdate(item);

Here another example.

How to format DateTime columns in DataGridView?

You can set the format in aspx, just add the property "DateFormatString" in your BoundField.

DataFormatString="{0:dd/MM/yyyy hh:mm:ss}"

How do AX, AH, AL map onto EAX?

The below snippet examines EAX using GDB.

    (gdb) info register eax
    eax            0xaa55   43605
    (gdb) info register ax
    ax             0xaa55   -21931
    (gdb) info register ah
    ah             0xaa -86
    (gdb) info register al
    al             0x55 85
  1. EAX - Full 32 bit value
  2. AX - lower 16 bit value
  3. AH - Bits from 8 to 15
  4. AL - lower 8 bits of EAX/AX

wildcard * in CSS for classes

What you need is called attribute selector. An example, using your html structure, is the following:

div[class^="tocolor-"], div[class*=" tocolor-"] {

In the place of div you can add any element or remove it altogether, and in the place of class you can add any attribute of the specified element.

[class^="tocolor-"] — starts with "tocolor-".
[class*=" tocolor-"] — contains the substring "tocolor-" occurring directly after a space character.


More information on CSS attribute selectors, you can find here and here. And from MDN Docs MDN Docs

Get the last 4 characters of a string

str = "aaaaabbbb"
newstr = str[-4:]

See :

How to create NSIndexPath for TableView

For Swift 3 it's now: IndexPath(row: rowIndex, section: sectionIndex)

How many bytes is unsigned long long?

The beauty of C++, like C, is that the sized of these things are implementation-defined, so there's no correct answer without your specifying the compiler you're using. Are those two the same? Yes. "long long" is a synonym for "long long int", for any compiler that will accept both.

Timestamp with a millisecond precision: How to save them in MySQL

CREATE TABLE fractest( c1 TIME(3), c2 DATETIME(3), c3 TIMESTAMP(3) );

('17:51:04.777', '2018-09-08 17:51:04.777', '2018-09-08 17:51:04.777');

Android: long click on a button -> perform actions

Change return false; to return true; in longClickListener

You long click the button, if it returns true then it does the work. If it returns false then it does it's work and also calls the short click and then the onClick also works.

HTML5 : Iframe No scrolling?

In HTML5 there is no scrolling attribute because "its function is better handled by CSS" see for other changes. Well and the CSS solution:

CSS solution:

HTML4's scrolling="no" is kind of an alias of the CSS's overflow: hidden, to do so it is important to set size attributes width/height:

  width: 250px; /*or any other size*/
  height: 300px; /*or any other size*/
  overflow: hidden;

Add this class to your iframe and you're done:

<iframe src="" class="noScrolling"></iframe>

! IMPORTANT NOTE ! : overflow: hidden for <iframe> is not fully supported by all modern browsers yet(even chrome doesn't support it yet) so for now (2013) it's still better to use Transitional version and use scrolling="no" and overflow:hidden at the same time :)

UPDATE 2020: the above is still true, oveflow for iframes is still not supported by all majors

Accessing clicked element in angularjs

While AngularJS allows you to get a hand on a click event (and thus a target of it) with the following syntax (note the $event argument to the setMaster function; documentation here:

function AdminController($scope) {    
  $scope.setMaster = function(obj, $event){

this is not very angular-way of solving this problem. With AngularJS the focus is on the model manipulation. One would mutate a model and let AngularJS figure out rendering.

The AngularJS-way of solving this problem (without using jQuery and without the need to pass the $event argument) would be:

<div ng-controller="AdminController">
    <ul class="list-holder">
        <li ng-repeat="section in sections" ng-class="{active : isSelected(section)}">
            <a ng-click="setMaster(section)">{{}}</a>
    {{selected | json}}

where methods in the controller would look like this:

$scope.setMaster = function(section) {
    $scope.selected = section;

$scope.isSelected = function(section) {
    return $scope.selected === section;

Here is the complete jsFiddle:

Meaning of = delete after function declaration

Deleting a function is a C++11 feature:

The common idiom of "prohibiting copying" can now be expressed directly:

class X {
    // ...
    X& operator=(const X&) = delete;  // Disallow copying
    X(const X&) = delete;


The "delete" mechanism can be used for any function. For example, we can eliminate an undesired conversion like this:

struct Z {
    // ...

    Z(long long);     // can initialize with an long long         
    Z(long) = delete; // but not anything less

Removing duplicate objects with Underscore for Javascript

Implementation of Shiplu's answer.

var foo = [ { "a" : "1" }, { "b" : "2" }, { "a" : "1" } ];

var x = _.uniq( _.collect( foo, function( x ){
    return JSON.stringify( x );

console.log( x ); // returns [ { "a" : "1" }, { "b" : "2" } ]

How to set default value to all keys of a dict object in python?

You can use the following class. Just change zero to any default value you like. The solution was tested in Python 2.7.

class cDefaultDict(dict):
    # dictionary that returns zero for missing keys
    # keys with zero values are not stored

    def __missing__(self,key):
        return 0

    def __setitem__(self, key, value):
        if value==0:
            if key in self:  # returns zero anyway, so no need to store it
                del self[key]
            dict.__setitem__(self, key, value)

How to set iframe size dynamically

If you use jquery, it can be done by using $(window).height();

<iframe src="html_intro.asp" width="100%" class="myIframe">
<p>Hi SOF</p>

<script type="text/javascript" language="javascript"> 
$('.myIframe').css('height', $(window).height()+'px');

When should null values of Boolean be used?

Use boolean rather than Boolean every time you can. This will avoid many NullPointerExceptions and make your code more robust.

Boolean is useful, for example

  • to store booleans in a collection (List, Map, etc.)
  • to represent a nullable boolean (coming from a nullable boolean column in a database, for example). The null value might mean "we don't know if it's true or false" in this context.
  • each time a method needs an Object as argument, and you need to pass a boolean value. For example, when using reflection or methods like MessageFormat.format().

Passing structs to functions

Passing structs to functions by reference: simply :)

#define maxn 1000

struct solotion
    int sol[maxn];
    int arry_h[maxn];
    int cat[maxn];
    int scor[maxn];


void inser(solotion &come){

void initial(solotion &come){
    for(int i=0;i<maxn;i++)

int main()
    solotion sol1;
    solotion sol2;

OPENSSL file_get_contents(): Failed to enable crypto

Had same problem - it was somewhere in the ca certificate, so I used the ca bundle used for curl, and it worked. You can download the curl ca bundle here:

For encryption and security issues see this helpful article:

Here is the example:

    $url = '';
    $cn_match = '';

    $data = array (     
        'apikey' => '[example api key here]',               
        'limit' => intval($limit),
        'offset' => intval($offset)

    // use key 'http' even if you send the request to https://...
    $options = array(
        'http' => array(
            'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
            'method'  => 'POST',                
            'content' => http_build_query($data)                
        , 'ssl' => array(
            'verify_peer' => true,
            'cafile' => [path to file] . "cacert.pem",
            'ciphers' => 'HIGH:TLSv1.2:TLSv1.1:TLSv1.0:!SSLv3:!SSLv2',
            'CN_match' => $cn_match,
            'disable_compression' => true,

    $context  = stream_context_create($options);
    $response = file_get_contents($url, false, $context);

Hope that helps

How to implement WiX installer upgrade?

The Upgrade element inside the Product element, combined with proper scheduling of the action will perform the uninstall you're after. Be sure to list the upgrade codes of all the products you want to remove.

<Property Id="PREVIOUSVERSIONSINSTALLED" Secure="yes" />
<Upgrade Id="00000000-0000-0000-0000-000000000000">
  <UpgradeVersion Minimum="" Maximum="" Property="PREVIOUSVERSIONSINSTALLED" IncludeMinimum="yes" IncludeMaximum="no" />

Note that, if you're careful with your builds, you can prevent people from accidentally installing an older version of your product over a newer one. That's what the Maximum field is for. When we build installers, we set UpgradeVersion Maximum to the version being built, but IncludeMaximum="no" to prevent this scenario.

You have choices regarding the scheduling of RemoveExistingProducts. I prefer scheduling it after InstallFinalize (rather than after InstallInitialize as others have recommended):

  <RemoveExistingProducts After="InstallFinalize"></RemoveExistingProducts>

This leaves the previous version of the product installed until after the new files and registry keys are copied. This lets me migrate data from the old version to the new (for example, you've switched storage of user preferences from the registry to an XML file, but you want to be polite and migrate their settings). This migration is done in a deferred custom action just before InstallFinalize.

Another benefit is efficiency: if there are unchanged files, Windows Installer doesn't bother copying them again when you schedule after InstallFinalize. If you schedule after InstallInitialize, the previous version is completely removed first, and then the new version is installed. This results in unnecessary deletion and recopying of files.

For other scheduling options, see the RemoveExistingProducts help topic in MSDN. This week, the link is:

php timeout - set_time_limit(0); - don't work

Checkout this, This is from PHP MANUAL, This may help you.

If you're using PHP_CLI SAPI and getting error "Maximum execution time of N seconds exceeded" where N is an integer value, try to call set_time_limit(0) every M seconds or every iteration. For example:



$stmt = $db->query($sql);

while ($row = $stmt->fetchRow()) {
    // your code here


font-weight is not working properly?

For me the bold work when I change the font style from font-family: 'Open Sans', sans-serif; to Arial

SELECTING with multiple WHERE conditions on same column

Change AND to OR. Simple mistake. Think of it like plain English, I want to select anything with that equals this or that.

Open a new tab on button click in AngularJS

Proper HTML way: just surround your button with anchor element and add attribute target="_blank". It is as simple as that:

<a ng-href="{{yourDynamicURL}}" target="_blank">
    <h1>Open me in new Tab</h1>

where you can set in the controller:

$scope.yourDynamicURL = '';

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

dynamic MsgResult = this.ShowMessageBox("Do you want to cancel all pending changes ?", "Cancel Changes", MessageBoxOption.YesNo);

if (MsgResult == System.Windows.MessageBoxResult.Yes)
    enter code here
    enter code here

Check more detail from here

Safari 3rd party cookie iframe trick no longer working?

Here's some code that I use. I found that if I set any cookie from my site, then cookies magically work in the iframe from then on.

 if (isset($_GET['setdefaultcookie'])) {
        // top level page, set default cookie then redirect back to canvas page
        setcookie ('default',"1",0,"/");
        $url = substr($_SERVER['REQUEST_URI'],strrpos($_SERVER['REQUEST_URI'],"/")+1);
        $url = str_replace("setdefaultcookie","defaultcookieset",$url);
        $url = $facebookapp->getCanvasUrl($url);
        echo "<html>\n<body>\n<script>\ntop.location.href='".$url."';\n</script></body></html>";
    } else if ((!isset($_COOKIE['default'])) && (!isset($_GET['defaultcookieset']))) {
        // no default cookie, so we need to redirect to top level and set
        $url = $_SERVER['REQUEST_URI'];
        if (strpos($url,"?") === false) $url .= "?";
        else $url .= "&";
        $url .= "setdefaultcookie=1";
        echo "<html>\n<body>\n<script>\ntop.location.href='".$url."';\n</script></body></html>";

How to do select from where x is equal to multiple values?

And even simpler using IN:

SELECT ads.*, location.county 
  FROM ads
  LEFT JOIN location ON location.county = ads.county_id
  WHERE ads.published = 1 
        AND ads.type = 13
        AND ads.county_id IN (2,5,7,9)

SQL Server - stop or break execution of a SQL script

None of these works with 'GO' statements. In this code, regardless of whether the severity is 10 or 11, you get the final PRINT statement.

Test Script:

-- =================================
PRINT 'Start Test 1 - RAISERROR'

IF 1 = 1 BEGIN
    RAISERROR('Error 1, level 11', 11, 1)

IF 1 = 1 BEGIN
    RAISERROR('Error 2, level 11', 11, 1)

PRINT 'Test 1 - After GO'

-- =================================
PRINT 'Start Test 2 - Try/Catch'

    SELECT (1 / 0) AS CauseError
    RAISERROR('Error in TRY, level 11', 11, 1)

PRINT 'Test 2 - After GO'


Start Test 1 - RAISERROR
Msg 50000, Level 11, State 1, Line 5
Error 1, level 11
Test 1 - After GO
Start Test 2 - Try/Catch

Divide by zero error encountered.

Msg 50000, Level 11, State 1, Line 10
Error in TRY, level 11
Test 2 - After GO

The only way to make this work is to write the script without GO statements. Sometimes that's easy. Sometimes it's quite difficult. (Use something like IF @error <> 0 BEGIN ....)

Uncaught TypeError: Cannot set property 'onclick' of null

So I was having a similar issue and I managed to solve it by putting the script tag with my JS file after the closing body tag.

I assume it's because it makes sure there's something to reference, but I am not entirely sure.

Calling pylab.savefig without display in ipython

We don't need to plt.ioff() or (if we use %matplotlib inline). You can test above code without plt.ioff(). plt.close() has the essential role. Try this one:

%matplotlib inline
import pylab as plt

# It doesn't matter you add line below. You can even replace it by 'plt.ion()', but you will see no changes.
## plt.ioff()

# Create a new figure, plot into it, then close it so it never gets displayed
fig = plt.figure()

# Create a new figure, plot into it, then don't close it so it does get displayed
fig2 = plt.figure()

If you run this code in iPython, it will display a second plot, and if you add plt.close(fig2) to the end of it, you will see nothing.

In conclusion, if you close figure by plt.close(fig), it won't be displayed.

How to use .htaccess in WAMP Server?

if it related to hosting site then ask to your hosting to enable url writing or if you want to enable it in local machine then check this youtube step by step tutorial related to enabling rewrite module in wamp apache
Wamp server icon -> Apache -> Apache Modules and check the rewrite module option it should be checked Note its very important that after enable rewrite module you should require to restart all services of wamp server

How to send an HTTP request using Telnet

telnet ServerName 80

GET /index.html?

? means 'return', you need to hit return twice

Could not locate Gemfile

Here is something you could try.

Add this to any config files you use to run your app.

ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)
require 'bundler/setup' # Set up gems listed in the Gemfile.

Rails and other Rack based apps use this scheme. It happens sometimes that you are trying to run things which are some directories deeper than your root where your Gemfile normally is located. Of course you solved this problem for now but occasionally we all get into trouble with this finding the Gemfile. I sometimes like when you can have all you gems in the .bundle directory also. It never hurts to keep this site address under your pillow.

Remove white space below image

.youtube-thumb img {display:block;} or .youtube-thumb img {float:left;}

using awk with column value conditions

please try this

echo $VAR | grep ClNonZ | awk '{print $3}';


echo cat filename | grep ClNonZ | awk '{print $3}';

Check if element at position [x] exists in the list

int? here = (list.ElementAtOrDefault(2) != 0 ? list[2]:(int?) null);

CORS with spring-boot and angularjs not working

This is what has worked for me in order to disable CORS between Spring boot and React

public class CorsConfig implements WebMvcConfigurer {

     * Overriding the CORS configuration to exposed required header for ussd to work
     * @param registry CorsRegistry

    public void addCorsMappings(CorsRegistry registry) {

I had to modify the Security configuration also like below:

        protected void configure(HttpSecurity http) throws Exception {
                    .cors().configurationSource(new CorsConfigurationSource() {

                public CorsConfiguration getCorsConfiguration(HttpServletRequest request) {
                    CorsConfiguration config = new CorsConfiguration();
                    return config;

How to add 'ON DELETE CASCADE' in ALTER TABLE statement

For anyone using MySQL:

If you head into your PHPMYADMIN webpage and navigate to the table that has the foreign key you want to update, all you have to do is click the Relational view located in the Structure tab and change the On delete select menu option to Cascade.

Image shown below:

enter image description here

SQL DATEPART(dw,date) need monday = 1 and sunday = 7

I think this could work:

    case when datepart(dw,[Date]) = 1 then 7 else DATEPART(DW,[Date])-1 end as WeekDay

HTML button to NOT submit form

By default, html buttons submit a form.

This is due to the fact that even buttons located outside of a form act as submitters (see the W3Schools website:

In other words, the button type is "submit" by default

<button type="submit">Button Text</button>

Therefore an easy way to get around this is to use the button type.

<button type="button">Button Text</button>

Other options include returning false at the end of the onclick or any other handler for when the button is clicked, or to using an < input> tag instead

To find out more, check out the Mozilla Developer Network's information on buttons:

Run a single migration file

If you're having trouble with paths you can use

require Rails.root + 'db/migrate/20090408054532_add_foos.rb'

Are there any Open Source alternatives to Crystal Reports?

Report Manager has been around for quite a few years. It's written in Delphi (at least it was originally) and has components that can be used in Delphi, but is usable via ActiveX or dll from just about any language. Now has a native .NET library too. Has a nifty report-serving webserver you can set up too. The designer gui looks and feels a little rough around the edges but it works.

Node.js get file extension


Since the original answer, extname() has been added to the path module, see Snowfish answer

Original answer:

I'm using this function to get a file extension, because I didn't find a way to do it in an easier way (but I think there is) :

function getExtension(filename) {
    var ext = path.extname(filename||'').split('.');
    return ext[ext.length - 1];

you must require 'path' to use it.

another method which does not use the path module :

function getExtension(filename) {
    var i = filename.lastIndexOf('.');
    return (i < 0) ? '' : filename.substr(i);

Android: How to add R.raw to project?

Here is the string to access files in raw folder. Replace filename with name of your file.

android.resource://" + getPackageName() + "/" + R.raw.filename

Pylint "unresolved import" error in Visual Studio Code

Conda environment

pylint error: "Unable to import 'django.X'"

After activating the desired Python interpreter in your conda environment, VS Code will sometimes continue to use pylint from the default conda environment. For example:


1. Install pylint in your target conda environment

$ conda activate <target environment>
$ conda install pylint

2. Update VS Code Settings

  • In VS Code Settings, search for "pylint path"
  • Click the Workspace tab (instead of the default User)
  • Under "Extensions (##)", click "Python (#)"
  • Scroll down to Python > Linting: Pylint Path
  • Enter the pylint path pointing to the copy of pylint that was just installed, for example:

/home/<username>/anaconda3/envs/<target environment>/bin/pylint

Replace <username> and <target environment> according to your system configuration.

Now pylint will find the installed libraries, including Django, presuming that Django has been installed in <target environment>.

3. Install the Django pylint plugin

$ conda install pylint-django

Update the VS Code Settings to use the plugin:

  • Search VS Code settings for "pylint args"
  • Under Python > Linting: Pylint Args, click "Add Item"
  • Enter: --load-plugins=pylint_django
  • Click "OK"
  • Click "Add Item"
  • Enter: --django-settings-module=<PROJECT FOLDER>.settings
    • Replace <PROJECT FOLDER> with the folder containing the "" Django configuration file.
  • Click "OK"
  • Restart VS Code

matplotlib colorbar for scatter

If you're looking to scatter by two variables and color by the third, Altair can be a great choice.

Creating the dataset

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

df = pd.DataFrame(40*np.random.randn(10, 3), columns=['A', 'B','C'])

Altair plot

from altair import *
Chart(df).mark_circle().encode(x='A',y='B', color='C').configure_cell(width=200, height=150)


enter image description here

PHP Array to CSV

I know this is old, I had a case where I needed the array key to be included in the CSV also, so I updated the script by Jesse Q to do that. I used a string as output, as implode can't add new line (new line is something I added, and should really be there).

Please note, this only works with single value arrays (key, value). but could easily be updated to handle multi-dimensional (key, array()).

function arrayToCsv( array &$fields, $delimiter = ',', $enclosure = '"', $encloseAll = false, $nullToMysqlNull = false ) {
    $delimiter_esc = preg_quote($delimiter, '/');
    $enclosure_esc = preg_quote($enclosure, '/');

    $output = '';
    foreach ( $fields as $key => $field ) {
        if ($field === null && $nullToMysqlNull) {
            $output = '';

        // Enclose fields containing $delimiter, $enclosure or whitespace
        if ( $encloseAll || preg_match( "/(?:${delimiter_esc}|${enclosure_esc}|\s)/", $field ) ) {
            $output .= $key;
            $output .= $delimiter;
            $output .= $enclosure . str_replace($enclosure, $enclosure . $enclosure,     $field) . $enclosure;
            $output .= PHP_EOL;
        else {
            $output .= $key;
            $output .= $delimiter;
            $output .= $field;
            $output .= PHP_EOL;

    return  $output ;

How to printf uint64_t? Fails with: "spurious trailing ‘%’ in format"

When compiling memcached under Centos 5.x i got the same problem.

The solution is to upgrade gcc and g++ to version 4.4 at least.

Make sure your CC/CXX is set (exported) to right binaries before compiling.

Is there a constraint that restricts my generic method to numeric types?

This question is a bit of a FAQ one, so I'm posting this as wiki (since I've posted similar before, but this is an older one); anyway...

What version of .NET are you using? If you are using .NET 3.5, then I have a generic operators implementation in MiscUtil (free etc).

This has methods like T Add<T>(T x, T y), and other variants for arithmetic on different types (like DateTime + TimeSpan).

Additionally, this works for all the inbuilt, lifted and bespoke operators, and caches the delegate for performance.

Some additional background on why this is tricky is here.

You may also want to know that dynamic (4.0) sort-of solves this issue indirectly too - i.e.

dynamic x = ..., y = ...
dynamic result = x + y; // does what you expect runserver

I was struggling with the same problem and found one solution. I guess it can help you. when you run python runserver, it will take as default ip address and 8000. is the same as localhost which can be accessed locally. to access it from cross origin you need to run it on your system ip or can be accessed from any origin in the network. for port number, you need to set inbound and outbound policy of your system if you want to use your own port number not the default one.

To do this you need to run server with command python runserver<your port> as mentioned above

or, set a default ip and port in your python environment. For this see my answer on django change default runserver port

Enjoy coding .....

Using sessions & session variables in a PHP Login Script

You need to begin the session at the top of a page or before you call session code


SQL using sp_HelpText to view a stored procedure on a linked server

Instead of invoking the sp_helptext locally with a remote argument, invoke it remotely with a local argument:

EXEC  [ServerName].[DatabaseName].dbo.sp_HelpText 'storedProcName'

MySQL date format DD/MM/YYYY select query?

If the hour is important, I used str_to_date(date, '%d/%m/%Y %T' ), the %T shows the hour in the format hh:mm:ss.

link with target="_blank" does not open in new tab in Chrome

Learn from another guy:

<a onclick=",'_blank');return false;" href="">Some Other Site</a>

It makes sense to me.

Difference between and logger.debug

Just a clarification about the set of all possible levels, that are:


How to programmatically disable page scrolling with jQuery

Try this code:

    $(function() { 
        // ...

        var $body = $(document);
        $body.bind('scroll', function() {
            if ($body.scrollLeft() !== 0) {

        // ...

What's the difference between "end" and "exit sub" in VBA?

This is a bit outside the scope of your question, but to avoid any potential confusion for readers who are new to VBA: End and End Sub are not the same. They don't perform the same task.

End puts a stop to ALL code execution and you should almost always use Exit Sub (or Exit Function, respectively).

End halts ALL exectution. While this sounds tempting to do it also clears all global and static variables. (source)

See also the MSDN dox for the End Statement

When executed, the End statement resets allmodule-level variables and all static local variables in allmodules. To preserve the value of these variables, use the Stop statement instead. You can then resume execution while preserving the value of those variables.

Note The End statement stops code execution abruptly, without invoking the Unload, QueryUnload, or Terminate event, or any other Visual Basic code. Code you have placed in the Unload, QueryUnload, and Terminate events offorms andclass modules is not executed. Objects created from class modules are destroyed, files opened using the Open statement are closed, and memory used by your program is freed. Object references held by other programs are invalidated.

Nor is End Sub and Exit Sub the same. End Sub can't be called in the same way Exit Sub can be, because the compiler doesn't allow it.

enter image description here

This again means you have to Exit Sub, which is a perfectly legal operation:

Exit Sub
Immediately exits the Sub procedure in which it appears. Execution continues with the statement following the statement that called the Sub procedure. Exit Sub can be used only inside a Sub procedure.

Additionally, and once you get the feel for how procedures work, obviously, End Sub does not clear any global variables. But it does clear local (Dim'd) variables:

End Sub
Terminates the definition of this procedure.

How do I run msbuild from the command line using Windows SDK 7.1?

Using the "Developer Command Prompt for Visual Studio 20XX" instead of "cmd" will set the path for msbuild automatically without having to add it to your environment variables.

Simulate a click on 'a' element using javascript/jquery

Try to use document.createEvent described here

The code for function that simulates click should look something like this:

function simulateClick() {
  var evt = document.createEvent("MouseEvents");
  evt.initMouseEvent("click", true, true, window,
    0, 0, 0, 0, 0, false, false, false, false, 0, null);
  var a = document.getElementById("gift-close"); 

Swift how to sort array of custom objects by property value

Two alternatives

1) Ordering the original array with sortInPlace

self.assignments.sortInPlace({ $0.order < $1.order })

2) Using an alternative array to store the ordered array

var assignmentsO = [Assignment] ()
assignmentsO = self.assignments.sort({ $0.order < $1.order })

Visual Studio Expand/Collapse keyboard shortcuts

Go to Tools->Options->Text Editor->c#->Advanced and uncheck the first checkbox Enter outlining mode when files open.

This will solve this problem forever

How do I style radio buttons with images - laughing smiley for good, sad smiley for bad?

You cannot style things like radio buttons, checkboxes, scrollsbars (etc.) at all. These are native to the OS and the browser and not something you can manipulate.

You can simulate this, however by hiding the radio buttons and only showing an image instead as in.

<input type="radio" style="display: none;" id="sad" /><label for="sad"><img class="sad_image" /></label>

Cannot change version of project facet Dynamic Web Module to 3.0?

For a maven eclipse web project, changing dynamic web module version needs to check three places. If one uses eclipse, and after you have checked the following: 1) web.xml

<web-app xmlns=""

2) maven:

      <scope>provided</scope>   ## ensure you have tomcat 7 not other version

            <source>1.7</source> ## at least 6

3) eclipse build path and compiler version is 1.7

you still have an error marker at maven:

cannot change version of project facet dynamic web module to 3.0 one or more constrants have not been satisfied

Then you can: uncheck the dynamic web module, and recheck it. I think it is because .settings of eclipse file is corrupted somehow. About the second tip tomcat which version is a good note.

Android button with icon and text

You can use the Material Components Library and the MaterialButton component.
Use the app:icon and app:iconGravity="start" attributes.

Something like:


enter image description here

Step-by-step debugging with IPython

If you type exit() in embed() console the code continue and go to the next embed() line.

Execution failed for task 'app:mergeDebugResources' Crunching Cruncher....png failed

  1. Look at the folders drawable-hdpi, drawable-mdpi, drawable-xhdpi and so on.
  2. If there is a wrong bitmap file, Delete it and resave.
  3. Go to Build->Rebuild Project

SSIS Convert Between Unicode and Non-Unicode Error

  1. First, add a data conversion block into your data flow diagram.

  2. Open the data conversion block and tick the column for which the error is showing. Below change its data type to unicode string(DT_WSTR) or whatever datatype is expected and save.

  3. Go to the destination block. Go to mapping in it and map the newly created element to its corresponding address and save.

  4. Right click your project in the solution properties. Select configuration properties and select debugging in it. In this, set the Run64BitRunTime option to false (as excel does not handle the 64 bit application very well).

How to comment and uncomment blocks of code in the Office VBA Editor

With MZ-Tools installed, I comment/uncomment blocks in VBE by using the keyboard shortcut
Ctrl+Alt+C (MZ-Tools default)

PHP: Possible to automatically get all POSTed data?

As long as you don't want any special formatting: yes.

foreach ($_POST as $key => $value) 
    $body .= $key . ' -> ' . $value . '<br>';

Obviously, more formatting would be necessary, however that's the "easy" way. Unless I misunderstood the question.

You could also do something like this (and if you like the format, it's certainly easier):

$body = print_r($_POST, true);

Access Database opens as read only

If someone else has the database open, then ask them to close it. If the database was not closed cleanly (Access or a computer crashed), then you can try to Compact and Repair the file.

I have also noticed that if the file is opened or put in a read-only state at any time, it might get 'stuck' like that. So try this:

  1. Open Access, but no database
  2. Open the file in question, but explicitly open it in read-only mode (the 'Open' button is actually a dropdown button. Use the button to open read-only
  3. Close the file (but not Access)
  4. Open the file again, but open normally.

Not sure it that's a bug or a feature, but I've seen it frustrate many a user.

How do you overcome the svn 'out of date' error?

In my case only deleting of the local version and re checkout of fresh copy was a solution.

Set the absolute position of a view

Try below code to set view on specific location :-

            TextView textView = new TextView(getActivity());
            textView.setText(count + "");
            textView.setTextSize(TypedValue.COMPLEX_UNIT_SP, 12);
            textView.setOnClickListener(new OnClickListener() {
                public void onClick(View v) {
                    // to handle click 
            // set background 

            // set apear

                    .setInterpolator(new BounceInterpolator()).start();
            FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(
            layoutParams.topMargin = 100; // margin in pixels, not dps
            layoutParams.leftMargin = 100; // margin in pixels, not dps

            // add into my parent view

Bootstrap 4 - Responsive cards in card-columns

Bootstrap 4 (4.0.0-alpha.2) uses the css property column-count in the card-columns class to define how many columns of cards would be displayed inside the div element.
But this property has only two values:

  • The default value 1 for small screens (max-width: 34em)
  • The value 3 for all other sizes (min-width: 34em)

Here's how it is implemented in bootstrap.min.css :

@media (min-width: 34em) {
    .card-columns {

To make the card stacking responsive, you can add the following media queries to your css file and modify the values for min-width as per your requirements :

@media (min-width: 34em) {
    .card-columns {
        -webkit-column-count: 2;
        -moz-column-count: 2;
        column-count: 2;

@media (min-width: 48em) {
    .card-columns {
        -webkit-column-count: 3;
        -moz-column-count: 3;
        column-count: 3;

@media (min-width: 62em) {
    .card-columns {
        -webkit-column-count: 4;
        -moz-column-count: 4;
        column-count: 4;

@media (min-width: 75em) {
    .card-columns {
        -webkit-column-count: 5;
        -moz-column-count: 5;
        column-count: 5;

Format an Excel column (or cell) as Text in C#?

Before your write to Excel need to change the format:

xlApp = New Excel.Application
xlWorkSheet = xlWorkBook.Sheets("Sheet1")

Dim cells As Excel.Range = xlWorkSheet.Cells

'set each cell's format to Text
cells.NumberFormat = "@"

'reset horizontal alignment to the right
cells.HorizontalAlignment = Excel.XlHAlign.xlHAlignRight

How can I detect the touch event of an UIImageView?

First, you should place an UIButton and then either you can add a background image for this button, or you need to place an UIImageView over the button.


You can add the tap gesture to a UIImageView so that get the click action when tap on the UIImageView.

hadoop No FileSystem for scheme: file

For maven, just add the maven dependency for hadoop-hdfs (refer to the link below) will solve the issue.

How to terminate script execution when debugging in Google Chrome?

If you are encountering this while using the debugger statement,


... then I think the page will continue running forever until the js runtime yields, or the next break. Assuming you're in break-on-error mode (the pause-icon toggle), you can ensure a break happens by instead doing something like:

debugger;throw 1;

or maybe call a non-existent function:


(Of course this doesn't help if you are trying to step through functions, though perhaps you could dynamically add in a throw 1 or z() or somesuch in the Sources panel, ctrl-S to save, and then ctrl-R to refresh... this may however skip one breakpoint, but may work if you're in a loop.)

If you are doing a loop and expect to trigger the debugger statement again, you could just type throw 1 instead.

throw 1;

Then when you hit ctrl-R, the next throw will be hit, and the page will refresh.

(tested with Chrome v38, circa Apr 2017)

Oracle "Partition By" Keyword

The concept is very well explained by the accepted answer, but I find that the more example one sees, the better it sinks in. Here's an incremental example:

1) Boss says "get me number of items we have in stock grouped by brand"

You say: "no problem"



|  Brand       |   Count       | 
| H&M          |     50        |
| Hugo Boss    |     100       |
| No brand     |     22        |

2) The boss says "Now get me a list of all items, with their brand AND number of items that the respective brand has"

You may try:


But you get:

ORA-00979: not a GROUP BY expression 

This is where the OVER (PARTITION BY BRAND) comes in:


Whic means:

  • COUNT(ITEM_ID) - get the number of items
  • OVER - Over the set of rows
  • (PARTITION BY BRAND) - that have the same brand

And the result is:

|  Items       |  Brand        | Count()  |
|  Item 1      |  Hugo Boss    |   100    | 
|  Item 2      |  Hugo Boss    |   100    | 
|  Item 3      |  No brand     |   22     | 
|  Item 4      |  No brand     |   22     | 
|  Item 5      |  H&M          |   50     | 


How to quickly clear a JavaScript Object?

You can delete the props, but don't delete variables. delete abc; is invalid in ES5 (and throws with use strict).

You can assign it to null to set it for deletion to the GC (it won't if you have other references to properties)

Setting length property on an object does not change anything. (it only, well, sets the property)

Ajax request returns 200 OK, but an error event is fired instead of success

I had the same problem. It was because my JSON response contains some special characters and the server file was not encoded with UTF-8, so the Ajax call considered that this was not a valid JSON response.

How to hide a TemplateField column in a GridView

try this


add following code on RowCreated Event of GridView

protected void OnRowCreated(object sender, GridViewRowEventArgs e)
     if (e.Row.RowType == DataControlRowType.DataRow)
         e.Row.Cells[0].CssClass = "hiddencol";
     else if (e.Row.RowType == DataControlRowType.Header)
         e.Row.Cells[0].CssClass = "hiddencol";

Comment out HTML and PHP together

I found the following solution pretty effective if you need to comment a lot of nested HTML + PHP code.

Wrap all the content in this:


Here goes your PHP + HTML code


Mongod complains that there is no /data/db folder

This works for me, found in comments:

sudo chown -R $USER /data/db

How to convert List<Integer> to int[] in Java?

int[] toIntArray(List<Integer> list)  {
    int[] ret = new int[list.size()];
    int i = 0;
    for (Integer e : list)  
        ret[i++] = e;
    return ret;

Slight change to your code to avoid expensive list indexing (since a List is not necessarily an ArrayList, but could be a linked list, for which random access is expensive)

Rollback one specific migration in Laravel

It might be a little late to answer this question but here's a very good, clean and efficient way to do it I feel. I'll try to be as thorough as possible.

Before creating your migrations create different directories like so:


Then, when creating your migrations run the following command (using your tables as an example):

     php artisan make:migration alter_table_web_directories --path=database/migrations/batch_1


     php artisan make:migration alter_table_web_directories --path=database/migrations/batch_2


     php artisan make:migration alter_table_web_directories --path=database/migrations/batch_3

The commands above will make the migration file within the given directory path. Then you can simply run the following command to migrate your files via their assigned directories.

    php artisan migrate alter_table_web_directories --path=database/migrations/batch_1

*Note: You can change batch_1 to batch_2 or batch_3 or whatever folder name you're storing the migration files in. As long as it remains within the database/migrations directory or some specified directory.

Next if you need to rollback your specific migrations you can rollback by batch as shown below:

    php artisan migrate:rollback --step=1
                    or try
php artisan migrate:rollback alter_table_web_directories --path=database/migrations/batch_1


    php artisan migrate:rollback --step=2
                    or try
php artisan migrate:rollback alter_table_web_directories --path=database/migrations/batch_2


    php artisan migrate:rollback --step=3
                    or try
php artisan migrate:rollback alter_table_web_directories --path=database/migrations/batch_3

Using these techniques will allow you more flexibility and control over your database(s) and any modifications made to your schema.

What does the servlet <load-on-startup> value signify

Servlet Life Cycle

The lifecycle of a servlet is controlled by the container in which the servlet has been deployed. When a request is mapped to a servlet, the container performs the following steps.

  1. If an instance of the servlet does not exist, the web container:

    a. Loads the servlet class

    b. Creates an instance of the servlet class

    c. Initializes the servlet instance by calling the init method (initialization is covered in Creating and Initializing a Servlet)

  2. The container invokes the service method, passing request and response objects. Service methods are discussed in Writing Service Methods.

A 0 value on load-on-startup means that point 1 is executed when a request comes to that servlet. Other values means that point 1 is executed at container startup.

Should I use alias or alias_method?

The rubocop gem contributors propose in their Ruby Style Guide:

Prefer alias when aliasing methods in lexical class scope as the resolution of self in this context is also lexical, and it communicates clearly to the user that the indirection of your alias will not be altered at runtime or by any subclass unless made explicit.

class Westerner
  def first_name

 alias given_name first_name

Always use alias_method when aliasing methods of modules, classes, or singleton classes at runtime, as the lexical scope of alias leads to unpredictability in these cases

module Mononymous
  def self.included(other)
    other.class_eval { alias_method :full_name, :given_name }

class Sting < Westerner
  include Mononymous

How to colorize diff on the command line?

Character-level color diff: Install ccdiff

ccdiff -r /usr/share/dict/words /tmp/new-dict

Output of ccdiff

Media Player called in state 0, error (-38,0)

Some times file are encoded in a way that Android can't decode. Even some mp4 files can not be played. Please try a different file format (.3gp are played most of the time) and see..

How to convert a JSON string to a Map<String, String> with Jackson JSON

Warning you get is done by compiler, not by library (or utility method).

Simplest way using Jackson directly would be:

HashMap<String,Object> props;

// src is a File, InputStream, String or such
props = new ObjectMapper().readValue(src, new TypeReference<HashMap<String,Object>>() {});
// or:
props = (HashMap<String,Object>) new ObjectMapper().readValue(src, HashMap.class);
// or even just:
@SuppressWarnings("unchecked") // suppresses typed/untype mismatch warnings, which is harmless
props = new ObjectMapper().readValue(src, HashMap.class);

Utility method you call probably just does something similar to this.

How can I check if mysql is installed on ubuntu?

With this command:

 dpkg -s mysql-server | grep Status

How can I make SMTP authenticated in C#

To send a message through TLS/SSL, you need to set Ssl of the SmtpClient class to true.

string to = "[email protected]";
string from = "[email protected]";
MailMessage message = new MailMessage(from, to);
message.Subject = "Using the new SMTP client.";
message.Body = @"Using this new feature, you can send an e-mail message from an application very easily.";
SmtpClient client = new SmtpClient(server);
// Credentials are necessary if the server requires the client 
// to authenticate before it will send e-mail on the client's behalf.
client.UseDefaultCredentials = true;
client.EnableSsl = true;

How to set URL query params in Vue with Vue-Router

this.$router.push({ query: Object.assign(this.$route.query, { new: 'param' }) })

<hr> tag in Twitter Bootstrap not functioning correctly?

Instead of writing



<hr class="col-xs-12">

And it will display full width as normal.

Printing hexadecimal characters in C

You are seeing the ffffff because char is signed on your system. In C, vararg functions such as printf will promote all integers smaller than int to int. Since char is an integer (8-bit signed integer in your case), your chars are being promoted to int via sign-extension.

Since c0 and 80 have a leading 1-bit (and are negative as an 8-bit integer), they are being sign-extended while the others in your sample don't.

char    int
c0 -> ffffffc0
80 -> ffffff80
61 -> 00000061

Here's a solution:

char ch = 0xC0;
printf("%x", ch & 0xff);

This will mask out the upper bits and keep only the lower 8 bits that you want.

select records from postgres where timestamp is in certain range

FROM reservations 
WHERE arrival >= '2012-01-01'
AND arrival < '2013-01-01'

BTW if the distribution of values indicates that an index scan will not be the worth (for example if all the values are in 2012), the optimiser could still choose a full table scan. YMMV. Explain is your friend.

Regular Expression to get a string between parentheses in Javascript

let str = "Before brackets (Inside brackets) After brackets".replace(/.*\(|\).*/g, '');_x000D_
console.log(str) // Inside brackets

Inserting a string into a list without getting split into characters

You have to add another list:


Toolbar navigation icon never set

Remove this line from activity if you have added

    protected void onPostCreate(Bundle savedInstanceState) {
        // Sync the toggle state after onRestoreInstanceState has occurred.

Then set icon


Is it ok to scrape data from Google results?

Google will eventually block your IP when you exceed a certain amount of requests.

What is the difference between the | and || or operators?

Just like the & and && operator, the double Operator is a "short-circuit" operator.

For example:

if(condition1 || condition2 || condition3)

If condition1 is true, condition 2 and 3 will NOT be checked.

if(condition1 | condition2 | condition3)

This will check conditions 2 and 3, even if 1 is already true. As your conditions can be quite expensive functions, you can get a good performance boost by using them.

There is one big caveat, NullReferences or similar problems. For example:

if(class != null && class.someVar < 20)

If class is null, the if-statement will stop after class != null is false. If you only use &, it will try to check class.someVar and you get a nice NullReferenceException. With the Or-Operator that may not be that much of a trap as it's unlikely that you trigger something bad, but it's something to keep in mind.

No one ever uses the single & or | operators though, unless you have a design where each condition is a function that HAS to be executed. Sounds like a design smell, but sometimes (rarely) it's a clean way to do stuff. The & operator does "run these 3 functions, and if one of them returns false, execute the else block", while the | does "only run the else block if none return false" - can be useful, but as said, often it's a design smell.

There is a Second use of the | and & operator though: Bitwise Operations.

Get List of connected USB Devices

To see the devices I was interested in, I had replace Win32_USBHub by Win32_PnPEntity in Adel Hazzah's code, based on this post. This works for me:

namespace ConsoleApplication1
  using System;
  using System.Collections.Generic;
  using System.Management; // need to add System.Management to your project references.

  class Program
    static void Main(string[] args)
      var usbDevices = GetUSBDevices();

      foreach (var usbDevice in usbDevices)
        Console.WriteLine("Device ID: {0}, PNP Device ID: {1}, Description: {2}",
            usbDevice.DeviceID, usbDevice.PnpDeviceID, usbDevice.Description);


    static List<USBDeviceInfo> GetUSBDevices()
      List<USBDeviceInfo> devices = new List<USBDeviceInfo>();

      ManagementObjectCollection collection;
      using (var searcher = new ManagementObjectSearcher(@"Select * From Win32_PnPEntity"))
        collection = searcher.Get();      

      foreach (var device in collection)
        devices.Add(new USBDeviceInfo(

      return devices;

  class USBDeviceInfo
    public USBDeviceInfo(string deviceID, string pnpDeviceID, string description)
      this.DeviceID = deviceID;
      this.PnpDeviceID = pnpDeviceID;
      this.Description = description;
    public string DeviceID { get; private set; }
    public string PnpDeviceID { get; private set; }
    public string Description { get; private set; }

How to get Spinner value?

If you already know the item is a String, I prefer:

String itemText = (String) mySpinner.getSelectedItem();

Calling toString() on an Object that you know is a String seems like a more roundabout path than just casting the Object to String.

jQuery: Count number of list elements?

var listItems = $("#myList").children();

var count = listItems.length;

Of course you can condense this with

var count = $("#myList").children().length;

For more help with jQuery, is a good place to start.

How to easily import multiple sql files into a MySQL database?

Save this file as .bat and run it , change variables inside parenthesis ...

@echo off
title Mysql Import Script
cd (Folder Name)
 for %%a in (*) do (
     echo Importing File  : %%a 
     mysql -u(username) -p(password)  %%~na < %%a

if it's only one database modify (%%~na) with the database name .

jQuery object equality

Since jQuery 1.6, you can use .is. Below is the answer from over a year ago...

var a = $('#foo');
var b = a;

if ( {
    // the same object!

If you want to see if two variables are actually the same object, eg:

var a = $('#foo');
var b = a;

...then you can check their unique IDs. Every time you create a new jQuery object it gets an id.

if ($.data(a) == $.data(b)) {
    // the same object!

Though, the same could be achieved with a simple a === b, the above might at least show the next developer exactly what you're testing for.

In any case, that's probably not what you're after. If you wanted to check if two different jQuery objects contain the same set of elements, the you could use this:

$.fn.equals = function(compareTo) {
  if (!compareTo || this.length != compareTo.length) {
    return false;
  for (var i = 0; i < this.length; ++i) {
    if (this[i] !== compareTo[i]) {
      return false;
  return true;


var a = $('p');
var b = $('p');
if (a.equals(b)) {
    // same set

How to highlight text using javascript

Since HTML5 you can use the <mark></mark> tags to highlight text. You can use javascript to wrap some text/keyword between these tags. Here is a little example of how to mark and unmark text.


How do you concatenate Lists in C#?

targetList = list1.Concat(list2).ToList();

It's working fine I think so. As previously said, Concat returns a new sequence and while converting the result to List, it does the job perfectly.

How to change port for jenkins window service when 8080 is being used

Restart Jenkins service

Just restart the Jenkins service after you changed the port in jenkins.xml.

  1. Press Win + R
  2. Type "services.msc"
  3. Right click on the "Jenkins" line > Restart

    Restart Jenkins

  4. Type http://localhost:8081/ in your browser to test the change.

Convert a space delimited string to list

Use string's split() method.


Checking if a variable is an integer in PHP

All $_GET parameters have a string datatype, therefore, is_int will always return false.

You can see this by calling var_dump:

var_dump($_GET['p']); // string(2) "54"

Using is_numeric will provide the desired result (mind you, that allows values such as: 0x24).

"Exception has been thrown by the target of an invocation" error (mscorlib)

I know its kind of odd but I experienced this error for a c# application and finally I found out the problem is the Icon of the form! when I changed it everything just worked fine.

I should say that I had this error just in XP not in 7 or 8 .

How to debug heap corruption errors?

I'd like to add my experience. In the last few days, I solved an instance of this error in my application. In my particular case, the errors in the code were:

  • Removing elements from an STL collection while iterating over it (I believe there are debug flags in Visual Studio to catch these things; I caught it during code review)
  • This one is more complex, I'll divide it in steps:
    • From a native C++ thread, call back into managed code
    • In managed land, call Control.Invoke and dispose a managed object which wraps the native object to which the callback belongs.
    • Since the object is still alive inside the native thread (it will remain blocked in the callback call until Control.Invoke ends). I should clarify that I use boost::thread, so I use a member function as the thread function.
    • Solution: Use Control.BeginInvoke (my GUI is made with Winforms) instead so that the native thread can end before the object is destroyed (the callback's purpose is precisely notifying that the thread ended and the object can be destroyed).

Javascript : natural sort of alphanumerical strings

So you need a natural sort ?

If so, than maybe this script by Brian Huisman based on David koelle's work would be what you need.

It seems like Brian Huisman's solution is now directly hosted on David Koelle's blog:

How do you check if a string is not equal to an object or other string value in java?

Change your || to && so it will only exit if the answer is NEITHER "AM" nor "PM".

Shuffling a list of objects

from random import random
my_list = range(10)
shuffled_list = sorted(my_list, key=lambda x: random())

This alternative may be useful for some applications where you want to swap the ordering function.

How Spring Security Filter Chain works

The Spring security filter chain is a very complex and flexible engine.

Key filters in the chain are (in the order)

  • SecurityContextPersistenceFilter (restores Authentication from JSESSIONID)
  • UsernamePasswordAuthenticationFilter (performs authentication)
  • ExceptionTranslationFilter (catch security exceptions from FilterSecurityInterceptor)
  • FilterSecurityInterceptor (may throw authentication and authorization exceptions)

Looking at the current stable release 4.2.1 documentation, section 13.3 Filter Ordering you could see the whole filter chain's filter organization:

13.3 Filter Ordering

The order that filters are defined in the chain is very important. Irrespective of which filters you are actually using, the order should be as follows:

  1. ChannelProcessingFilter, because it might need to redirect to a different protocol

  2. SecurityContextPersistenceFilter, so a SecurityContext can be set up in the SecurityContextHolder at the beginning of a web request, and any changes to the SecurityContext can be copied to the HttpSession when the web request ends (ready for use with the next web request)

  3. ConcurrentSessionFilter, because it uses the SecurityContextHolder functionality and needs to update the SessionRegistry to reflect ongoing requests from the principal

  4. Authentication processing mechanisms - UsernamePasswordAuthenticationFilter, CasAuthenticationFilter, BasicAuthenticationFilter etc - so that the SecurityContextHolder can be modified to contain a valid Authentication request token

  5. The SecurityContextHolderAwareRequestFilter, if you are using it to install a Spring Security aware HttpServletRequestWrapper into your servlet container

  6. The JaasApiIntegrationFilter, if a JaasAuthenticationToken is in the SecurityContextHolder this will process the FilterChain as the Subject in the JaasAuthenticationToken

  7. RememberMeAuthenticationFilter, so that if no earlier authentication processing mechanism updated the SecurityContextHolder, and the request presents a cookie that enables remember-me services to take place, a suitable remembered Authentication object will be put there

  8. AnonymousAuthenticationFilter, so that if no earlier authentication processing mechanism updated the SecurityContextHolder, an anonymous Authentication object will be put there

  9. ExceptionTranslationFilter, to catch any Spring Security exceptions so that either an HTTP error response can be returned or an appropriate AuthenticationEntryPoint can be launched

  10. FilterSecurityInterceptor, to protect web URIs and raise exceptions when access is denied

Now, I'll try to go on by your questions one by one:

I'm confused how these filters are used. Is it that for the spring provided form-login, UsernamePasswordAuthenticationFilter is only used for /login, and latter filters are not? Does the form-login namespace element auto-configure these filters? Does every request (authenticated or not) reach FilterSecurityInterceptor for non-login url?

Once you are configuring a <security-http> section, for each one you must at least provide one authentication mechanism. This must be one of the filters which match group 4 in the 13.3 Filter Ordering section from the Spring Security documentation I've just referenced.

This is the minimum valid security:http element which can be configured:

<security:http authentication-manager-ref="mainAuthenticationManager" 
    <security:intercept-url pattern="/sectest/zone1/**" access="hasRole('ROLE_ADMIN')"/>

Just doing it, these filters are configured in the filter chain proxy:

        "1": "",
        "2": "",
        "3": "",
        "4": "",
        "5": "",
        "6": "",
        "7": "",
        "8": "",
        "9": "",
        "10": ""

Note: I get them by creating a simple RestController which @Autowires the FilterChainProxy and returns it's contents:

    private FilterChainProxy filterChainProxy;

    public @ResponseBody Map<Integer, Map<Integer, String>> getSecurityFilterChainProxy(){
        return this.getSecurityFilterChainProxy();

    public Map<Integer, Map<Integer, String>> getSecurityFilterChainProxy(){
        Map<Integer, Map<Integer, String>> filterChains= new HashMap<Integer, Map<Integer, String>>();
        int i = 1;
        for(SecurityFilterChain secfc :  this.filterChainProxy.getFilterChains()){
            //filters.put(i++, secfc.getClass().getName());
            Map<Integer, String> filters = new HashMap<Integer, String>();
            int j = 1;
            for(Filter filter : secfc.getFilters()){
                filters.put(j++, filter.getClass().getName());
            filterChains.put(i++, filters);
        return filterChains;

Here we could see that just by declaring the <security:http> element with one minimum configuration, all the default filters are included, but none of them is of a Authentication type (4th group in 13.3 Filter Ordering section). So it actually means that just by declaring the security:http element, the SecurityContextPersistenceFilter, the ExceptionTranslationFilter and the FilterSecurityInterceptor are auto-configured.

In fact, one authentication processing mechanism should be configured, and even security namespace beans processing claims for that, throwing an error during startup, but it can be bypassed adding an entry-point-ref attribute in <http:security>

If I add a basic <form-login> to the configuration, this way:

<security:http authentication-manager-ref="mainAuthenticationManager">
    <security:intercept-url pattern="/sectest/zone1/**" access="hasRole('ROLE_ADMIN')"/>
    <security:form-login />

Now, the filterChain will be like this:

        "1": "",
        "2": "",
        "3": "",
        "4": "",
        "5": "",
        "6": "",
        "7": "",
        "8": "",
        "9": "",
        "10": "",
        "11": "",
        "12": ""

Now, this two filters and are created and configured in the FilterChainProxy.

So, now, the questions:

Is it that for the spring provided form-login, UsernamePasswordAuthenticationFilter is only used for /login, and latter filters are not?

Yes, it is used to try to complete a login processing mechanism in case the request matches the UsernamePasswordAuthenticationFilter url. This url can be configured or even changed it's behaviour to match every request.

You could too have more than one Authentication processing mechanisms configured in the same FilterchainProxy (such as HttpBasic, CAS, etc).

Does the form-login namespace element auto-configure these filters?

No, the form-login element configures the UsernamePasswordAUthenticationFilter, and in case you don't provide a login-page url, it also configures the, which ends in a simple autogenerated login page.

The other filters are auto-configured by default just by creating a <security:http> element with no security:"none" attribute.

Does every request (authenticated or not) reach FilterSecurityInterceptor for non-login url?

Every request should reach it, as it is the element which takes care of whether the request has the rights to reach the requested url. But some of the filters processed before might stop the filter chain processing just not calling FilterChain.doFilter(request, response);. For example, a CSRF filter might stop the filter chain processing if the request has not the csrf parameter.

What if I want to secure my REST API with JWT-token, which is retrieved from login? I must configure two namespace configuration http tags, rights? Other one for /login with UsernamePasswordAuthenticationFilter, and another one for REST url's, with custom JwtAuthenticationFilter.

No, you are not forced to do this way. You could declare both UsernamePasswordAuthenticationFilter and the JwtAuthenticationFilter in the same http element, but it depends on the concrete behaviour of each of this filters. Both approaches are possible, and which one to choose finnally depends on own preferences.

Does configuring two http elements create two springSecurityFitlerChains?

Yes, that's true

Is UsernamePasswordAuthenticationFilter turned off by default, until I declare form-login?

Yes, you could see it in the filters raised in each one of the configs I posted

How do I replace SecurityContextPersistenceFilter with one, which will obtain Authentication from existing JWT-token rather than JSESSIONID?

You could avoid SecurityContextPersistenceFilter, just configuring session strategy in <http:element>. Just configure like this:

<security:http create-session="stateless" >

Or, In this case you could overwrite it with another filter, this way inside the <security:http> element:

<security:http ...>  
   <security:custom-filter ref="myCustomFilter" position="SECURITY_CONTEXT_FILTER"/>    
<beans:bean id="myCustomFilter" class="" />


One question about "You could too have more than one Authentication processing mechanisms configured in the same FilterchainProxy". Will the latter overwrite the authentication performed by first one, if declaring multiple (Spring implementation) authentication filters? How this relates to having multiple authentication providers?

This finally depends on the implementation of each filter itself, but it's true the fact that the latter authentication filters at least are able to overwrite any prior authentication eventually made by preceding filters.

But this won't necesarily happen. I have some production cases in secured REST services where I use a kind of authorization token which can be provided both as a Http header or inside the request body. So I configure two filters which recover that token, in one case from the Http Header and the other from the request body of the own rest request. It's true the fact that if one http request provides that authentication token both as Http header and inside the request body, both filters will try to execute the authentication mechanism delegating it to the manager, but it could be easily avoided simply checking if the request is already authenticated just at the begining of the doFilter() method of each filter.

Having more than one authentication filter is related to having more than one authentication providers, but don't force it. In the case I exposed before, I have two authentication filter but I only have one authentication provider, as both of the filters create the same type of Authentication object so in both cases the authentication manager delegates it to the same provider.

And opposite to this, I too have a scenario where I publish just one UsernamePasswordAuthenticationFilter but the user credentials both can be contained in DB or LDAP, so I have two UsernamePasswordAuthenticationToken supporting providers, and the AuthenticationManager delegates any authentication attempt from the filter to the providers secuentially to validate the credentials.

So, I think it's clear that neither the amount of authentication filters determine the amount of authentication providers nor the amount of provider determine the amount of filters.

Also, documentation states SecurityContextPersistenceFilter is responsible of cleaning the SecurityContext, which is important due thread pooling. If I omit it or provide custom implementation, I have to implement the cleaning manually, right? Are there more similar gotcha's when customizing the chain?

I did not look carefully into this filter before, but after your last question I've been checking it's implementation, and as usually in Spring, nearly everything could be configured, extended or overwrited.

The SecurityContextPersistenceFilter delegates in a SecurityContextRepository implementation the search for the SecurityContext. By default, a HttpSessionSecurityContextRepository is used, but this could be changed using one of the constructors of the filter. So it may be better to write an SecurityContextRepository which fits your needs and just configure it in the SecurityContextPersistenceFilter, trusting in it's proved behaviour rather than start making all from scratch.

What's the best way to parse a JSON response from the requests library?

Since you're using requests, you should use the response's json method.

import requests

response = requests.get(...)
data = response.json()

It autodetects which decoder to use.

Catch a thread's exception in the caller thread in Python

Although it is not possible to directly catch an exception thrown in a different thread, here's a code to quite transparently obtain something very close to this functionality. Your child thread must subclass the ExThread class instead of threading.Thread and the parent thread must call the child_thread.join_with_exception() method instead of child_thread.join() when waiting for the thread to finish its job.

Technical details of this implementation: when the child thread throws an exception, it is passed to the parent through a Queue and thrown again in the parent thread. Notice that there's no busy waiting in this approach .

#!/usr/bin/env python

import sys
import threading
import Queue

class ExThread(threading.Thread):
    def __init__(self):
        self.__status_queue = Queue.Queue()

    def run_with_exception(self):
        """This method should be overriden."""
        raise NotImplementedError

    def run(self):
        """This method should NOT be overriden."""
        except BaseException:

    def wait_for_exc_info(self):
        return self.__status_queue.get()

    def join_with_exception(self):
        ex_info = self.wait_for_exc_info()
        if ex_info is None:
            raise ex_info[1]

class MyException(Exception):

class MyThread(ExThread):
    def __init__(self):

    def run_with_exception(self):
        thread_name = threading.current_thread().name
        raise MyException("An error in thread '{}'.".format(thread_name))

def main():
    t = MyThread()
    except MyException as ex:
        thread_name = threading.current_thread().name
        print "Caught a MyException in thread '{}': {}".format(thread_name, ex)

if __name__ == '__main__':

Check if a string matches a regex in Bash script

Where the usage of a regex can be helpful to determine if the character sequence of a date is correct, it cannot be used easily to determine if the date is valid. The following examples will pass the regular expression, but are all invalid dates: 20180231, 20190229, 20190431

So if you want to validate if your date string (let's call it datestr) is in the correct format, it is best to parse it with date and ask date to convert the string to the correct format. If both strings are identical, you have a valid format and valid date.

if [[ "$datestr" == $(date -d "$datestr" "+%Y%m%d" 2>/dev/null) ]]; then
     echo "Valid date"
     echo "Invalid date"

Facebook OAuth "The domain of this URL isn't included in the app's domain"

This same Facebook error happened to me in the Production environment. The reason was I had 2 apps registered with Facebook (Local, Production) but I hardcoded the Local app ID into the source code and forgot to switch it out for the Production app ID before deployment.

Best practice dictates you shouldn't have the app ID hardcoded into the source code but if you do, do not mismatch your various Facebook app IDs like I mistakenly did.

How can I get the assembly file version

There are three versions: assembly, file, and product. They are used by different features and take on different default values if you don't explicit specify them.

string assemblyVersion = Assembly.GetExecutingAssembly().GetName().Version.ToString(); 
string assemblyVersion = Assembly.LoadFile("your assembly file").GetName().Version.ToString(); 
string fileVersion = FileVersionInfo.GetVersionInfo(Assembly.GetExecutingAssembly().Location).FileVersion; 
string productVersion = FileVersionInfo.GetVersionInfo(Assembly.GetExecutingAssembly().Location).ProductVersion;

Forcing to download a file using PHP

Configure your server to send the file with the media type application/octet-stream.

All ASP.NET Web API controllers return 404


Should be first in App_start event. I have tried it at last position in APP_start event, but that did not work.

How can I select rows with most recent timestamp for each key value?

There is one common answer I haven't see here yet, which is the Window Function. It is an alternative to the correlated sub-query, if your DB supports it.

SELECT sensorID,timestamp,sensorField1,sensorField2 
    SELECT sensorID,timestamp,sensorField1,sensorField2
        , ROW_NUMBER() OVER(
            PARTITION BY sensorID
            ORDER BY timestamp
        ) AS rn
    FROM sensorTable s1
WHERE rn = 1
ORDER BY sensorID, timestamp;

I acually use this more than correlated sub-queries. Feel free to bust me in the comments over effeciancy, I'm not too sure how it stacks up in that regard.

How to run a subprocess with Python, wait for it to exit and get the full stdout as a string?

With Python 3.8 this workes for me. For instance to execute a python script within the venv:

    import subprocess
    import sys
    res =[
              sys.executable,            # venv3.8/bin/python
              '', '--help',], 

How to update an "array of objects" with Firestore?

Firestore now has two functions that allow you to update an array without re-writing the entire thing.

Link:, specifically

Update elements in an array

If your document contains an array field, you can use arrayUnion() and arrayRemove() to add and remove elements. arrayUnion() adds elements to an array but only elements not already present. arrayRemove() removes all instances of each given element.

php execute a background process

Thanks to this answer: A perfect tool to run a background process would be Symfony Process Component, which is based on proc_* functions, but it's much easier to use. See its documentation for more information.

Cloning an Object in Node.js

You can use the extend function from JQuery:

var newClone= jQuery.extend({}, oldObject);  
var deepClone = jQuery.extend(true, {}, oldObject); 

There is a Node.js Plugin too:

To do it without JQuery or Plugin read this here:

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

To be safe you don't break stuff (for example when these strings are changed in your code or further up), or crash you program (in case the returned string was literal for example like "hello I'm a literal string" and you start to edit it), make a copy of the returned string.

You could use strdup() for this, but read the small print. Or you can of course create your own version if it's not there on your platform.

How to replace (null) values with 0 output in PIVOT

To modify the results under pivot, you can put the columns in the selected fields and then modify them accordingly. May be you can use DECODE for the columns you have built using pivot function.

  • Kranti A

Connect to docker container as user other than root

Execute command as www-data user: docker exec -t --user www-data container bash -c "ls -la"

jQuery: selecting each td in a tr

Fully example to demonstrate how jQuery query all data in HTML table.

Assume there is a table like the following in your HTML code.

<table id="someTable">
      <td>title 0</td>
      <td>title 1</td>
      <td>title 2</td>
      <td>row 0 td 0</td>
      <td>row 0 td 1</td>
      <td>row 0 td 2</td>
      <td>row 1 td 0</td>
      <td>row 1 td 1</td>
      <td>row 1 td 2</td>
      <td>row 2 td 0</td>
      <td>row 2 td 1</td>
      <td>row 2 td 2</td>
    <tr> ... </tr>
    <tr> ... </tr>
    <tr> ... </tr>
      <td>row n td 0</td>
      <td>row n td 1</td>
      <td>row n td 2</td>

Then, The Answer, the code to print all row all column, should like this

$('#someTable tbody tr').each( (tr_idx,tr) => {
    $(tr).children('td').each( (td_idx, td) => {
        console.log( '[' +tr_idx+ ',' +td_idx+ '] => ' + $(td).text());

After running the code, the result will show

[0,0] => row 0 td 0
[0,1] => row 0 td 1
[0,2] => row 0 td 2
[1,0] => row 1 td 0
[1,1] => row 1 td 1
[1,2] => row 1 td 2
[2,0] => row 2 td 0
[2,1] => row 2 td 1
[2,2] => row 2 td 2
[n,0] => row n td 0
[n,1] => row n td 1
[n,2] => row n td 2

In the code,
tr_idx is the row index start from 0.
td_idx is the column index start from 0.

From this double-loop code,
you can get all loop-index and data in each td cell after comparing the Answer's source code and the output result.

How to Display Selected Item in Bootstrap Button Dropdown Title

Another simple way (Bootstrap 4) to work with multiple dropdowns

    $('.dropdown-item').on('click',  function(){
        var btnObj = $(this).parent().siblings('button');

Type or namespace name does not exist

And if all else fails, such as ensuring that the target frameworks are the same, and you are dealing with a WPF class library in VS2010, simply restart Visual Studio. That did it for me.

How to "EXPIRE" the "HSET" child key in redis?

We had the same problem discussed here.

We have a Redis hash, a key to hash entries (name/value pairs), and we needed to hold individual expiration times on each hash entry.

We implemented this by adding n bytes of prefix data containing encoded expiration information when we write the hash entry values, we also set the key to expire at the time contained in the value being written.

Then, on read, we decode the prefix and check for expiration. This is additional overhead, however, the reads are still O(n) and the entire key will expire when the last hash entry has expired.

R dplyr: Drop multiple columns

Another way is to mutate the undesired columns to NULL, this avoids the embedded parentheses :

head(iris,2) %>% mutate_at(drop.cols, ~NULL)
#   Petal.Length Petal.Width Species
# 1          1.4         0.2  setosa
# 2          1.4         0.2  setosa

What is the difference between id and class in CSS, and when should I use them?

For more info on this click here.


<div id="header_id" class="header_class">Text</div>

#header_id {font-color:#fff}
.header_class {font-color:#000}

(Note that CSS uses the prefix # for IDs and . for Classes.)

However color was an HTML 4.01 <font> tag attribute deprecated in HTML 5. In CSS there is no "font-color", the style is color so the above should read:


<div id="header_id" class="header_class">Text</div>

#header_id {color:#fff}
.header_class {color:#000}

The text would be white.

Node.js res.setHeader('content-type', 'text/javascript'); pushing the response javascript as file download

You can directly set the content type like below:

res.writeHead(200, {'Content-Type': 'text/plain'});

For reference go through the nodejs Docs link.

Change span text?

document.getElementById("serverTime").innerHTML = ...;

How do I perform a JAVA callback between classes?

I don't know if this is what you are looking for, but you can achieve this by passing a callback to the child class.

first define a generic callback:

public interface ITypedCallback<T> {
    void execute(T type);

create a new ITypedCallback instance on ServerConnections instantiation:

public Server(int _address) {
    serverConnectionHandler = new ServerConnections(new ITypedCallback<Socket>() {
        public void execute(Socket socket) {
            // do something with your socket here

call the execute methode on the callback object.

public class ServerConnections implements Runnable {

    private ITypedCallback<Socket> callback;

    public ServerConnections(ITypedCallback<Socket> _callback) {
        callback = _callback;

    public void run() {   
        try {
            mainSocket = new ServerSocket(serverPort);
            while (true) {
        } catch (IOException ex) {
            Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);

btw: I didn't check if it's 100% correct, directly coded it here.

How can I sanitize user input with PHP?

Do not try to prevent SQL injection by sanitizing input data.

Instead, do not allow data to be used in creating your SQL code. Use Prepared Statements (i.e. using parameters in a template query) that uses bound variables. It is the only way to be guaranteed against SQL injection.

Please see my website for more about preventing SQL injection.

Setting up an MS-Access DB for multi-user access

Access is a great multi-user database. It has lots of built in features to handle the multi-user situation. In fact, it is so very popular because it is such a great multi-user database. There is an upper limit on how many users can all use the database at the same time doing updates and edits - depending on how knowledgeable the developer is about access and how the database has been designed - anywhere from 20 users to approx 50 users. Some access databases can be built to handle up to 50 concurrent users, while many others can handle 20 or 25 concurrent users updating the database. These figures have been observed for databases that have been in use for several or more years and have been discussed many times on the access newsgroups.

VB.NET Empty String Array

The array you created by Dim s(0) As String IS NOT EMPTY

In VB.Net, the subscript you use in the array is index of the last element. VB.Net by default starts indexing at 0, so you have an array that already has one element.

You should instead try using System.Collections.Specialized.StringCollection or (even better) System.Collections.Generic.List(Of String). They amount to pretty much the same thing as an array of string, except they're loads better for adding and removing items. And let's be honest: you'll rarely create an empty string array without wanting to add at least one element to it.

If you really want an empty string array, declare it like this:

Dim s As String()


Dim t() As String

Ubuntu: OpenJDK 8 - Unable to locate package

UPDATE: installation without root privileges below

I advise you to not install packages manually on ubuntu system if there is already a (semi-official) repository able to solve your problem. Further, use Oracle JDK for development, just to avoid (very sporadic) compatibility issues (i've tried many years ago, it's surely better now).

Add the webupd8 repo to your system:

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update

Install your preferred version of jdk (versions from java-6 to java-9 available):

sudo apt-get install oracle-java8-installer

You can also install multiple version of jdk, mixing openjdk and oracle versions. Then you can use the command update-java-alternatives to switch between installed version:

# list available jdk
update-java-alternatives --list

# use jdk7
sudo update-java-alternatives --set java-7-oracle

# use jdk8
sudo update-java-alternatives --set java-8-oracle


If you get add-apt-repository: command not found be sure to have software-properties-common installed:

sudo apt-get install software-properties-common

If you're using an older version Ubuntu:

sudo apt-get install python-software-properties

JDK installation without root privileges

If you haven't administrator rights on your target machine your simplest bet is to use sdkman to install the zulu certified openjdk:

curl -s "" | bash
source "$HOME/.sdkman/bin/"
sdk install java

NOTE: sdkman allow to install also the official Oracle JDK, although it's not a the default option. View available versions with:

sdk ls java

Install the chosen version with:

sdk install java <version>

For example:

sdk install java 9.0.1-oracle

Glossary of commands

  • sudo <command> [command_arguments]: execute a command with the superuser privilege.

  • add-apt-repository <PPA_id>: Ubuntu (just like every Debian derivatives and generally speaking every Linux distribution) has a main repository of packages that handle things like package dependencies and updating. In Ubuntu is possible to extend the main repository using a PPA (Personal Package Archive) that usually contains packages not available in the system (just like oracle jdk) or updated versions of available ones (example: LibreOffice 5 in LTS is available only through this PPA).

  • apt-get [install|update|upgrade|purge|...]: it's "the" command-line package handler used to manipulate the state of every repository on the system (installing / updating / upgrading can be viewed as an alteration of the repository current state).

In our case: with the command sudo add-apt-repository ppa:webupd8team/java we inform the system that the next repository update must retrieve packages information also from webupd8 repo.

With sudo apt-get update we actually update the system repository (all this operations requires superuser privileges, so we prepend sudo to the commands).

sudo apt-get install oracle-java8-installer

  • update-java-alternatives (a specific java version of update-alternatives): in Ubuntu several packages provides the same functionality (browse the internet, compile mails, edit a text file or provides java/javac executables...). To allows the system to choose the user favourites tool given a specific task a mechanism using symlinks under /etc/alternatives/ is used. Try to update the jdk as indicated above (switch between java 7 and java 8) and view how change the output of this command:

    ls -l /etc/alternatives/java*

In our case: sudo update-java-alternatives --set java-8-oracle update symlinks under /etc/alternatives to point to java-8-oracle executables.


  • man <command>: start using man to read a really well written and detailed help on (almost) every shell command and its options (every command i mention in this little answer has a man page, try man update-java-alternatives).

  • apt-cache search <search_key>: query the APT cache to search for a package related with the search_key provided (can be the package name or some word in package description).

  • apt-cache show <package>: provides APT information for a specific package (package version, installed or not, description).

Oracle: what is the situation to use RAISE_APPLICATION_ERROR?

if your application accepts errors raise from Oracle, then you can use it. we have an application, each time when an error happens, we call raise_application_error, the application will popup a red box to show the error message we provide through this method.

When using dotnet code, I just use "raise", dotnet exception mechanisim will automatically capture the error passed by Oracle ODP and shown inside my catch exception code.

VBScript - How to make program wait until process has finished?

You need to tell the run to wait until the process is finished. Something like:

const DontWaitUntilFinished = false, ShowWindow = 1, DontShowWindow = 0, WaitUntilFinished = true
set oShell = WScript.CreateObject("WScript.Shell")
command = "cmd /c C:\windows\system32\wscript.exe <path>\myScript.vbs " & args
oShell.Run command, DontShowWindow, WaitUntilFinished

In the script itself, start Excel like so. While debugging start visible:

File = "c:\test\myfile.xls" """C:\Program Files\Microsoft Office\Office14\EXCEL.EXE"" " & File, 1, true

SQL Server Script to create a new user

You can use:

CREATE LOGIN <login name> WITH PASSWORD = '<password>' ; GO 

To create the login (See here for more details).

Then you may need to use:

CREATE USER user_name 

To create the user associated with the login for the specific database you want to grant them access too.

(See here for details)

You can also use:

GRANT permission  [ ,...n ] ON SCHEMA :: schema_name

To set up the permissions for the schema's that you assigned the users to.

(See here for details)

Two other commands you might find useful are ALTER USER and ALTER LOGIN.

Generic htaccess redirect www to non-www

There can be a lot of misinformation out there about htaccess redirects, I find. First off, make sure your site is running on Unix using Apache and not on a Windows host if you expect this code to work.

RewriteEngine On

RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]

RewriteRule ^(.*)$ http://%1/$1 [R=301,L] 

(Make sure there are no line spaces between each line of text, though; I have added an extra space between lines so it renders okay in this window.)

This is one snippet of code that can be used to direct the www version of your site to the http:// version. There are other similar codes that can be used, too.

How to close current tab in a browser window?

It is possible. I searched the whole net for this, but once when i took one of microsoft's survey, I finally got the answer.

try this:;

this will close the current tab for you.

useState set method not reflecting change immediately

Much like setState in Class components created by extending React.Component or React.PureComponent, the state update using the updater provided by useState hook is also asynchronous, and will not be reflected immediately.

Also, the main issue here is not just the asynchronous nature but the fact that state values are used by functions based on their current closures, and state updates will reflect in the next re-render by which the existing closures are not affected, but new ones are created. Now in the current state, the values within hooks are obtained by existing closures, and when a re-render happens, the closures are updated based on whether the function is recreated again or not.

Even if you add a setTimeout the function, though the timeout will run after some time by which the re-render would have happened, the setTimeout will still use the value from its previous closure and not the updated one.

console.log(movies) // movies here will not be updated

If you want to perform an action on state update, you need to use the useEffect hook, much like using componentDidUpdate in class components since the setter returned by useState doesn't have a callback pattern

useEffect(() => {
    // action on update of movies
}, [movies]);

As far as the syntax to update state is concerned, setMovies(result) will replace the previous movies value in the state with those available from the async request.

However, if you want to merge the response with the previously existing values, you must use the callback syntax of state updation along with the correct use of spread syntax like

setMovies(prevMovies => ([...prevMovies, ...result]));