Programs & Examples On #Edge detection

Edge detection is a tool in computer vision used to find discontinuities (edges) in images

Javascript call() & apply() vs bind()?

Call: call invokes the function and allows you to pass arguments one by one

Apply: Apply invokes the function and allows you to pass arguments as an array

Bind: Bind returns a new function, allowing you to pass in a this array and any number of arguments.

var person1 = {firstName: 'Raju', lastName: 'king'};_x000D_
var person2 = {firstName: 'chandu', lastName: 'shekar'};_x000D_
function greet(greeting) {_x000D_
    console.log(greeting + ' ' + this.firstName + ' ' + this.lastName);_x000D_
function greet2(greeting) {_x000D_
        console.log( 'Hello ' + this.firstName + ' ' + this.lastName);_x000D_
_x000D_, 'Hello'); // Hello Raju king_x000D_, 'Hello'); // Hello chandu shekar_x000D_
greet.apply(person1, ['Hello']); // Hello Raju king_x000D_
greet.apply(person2, ['Hello']); // Hello chandu shekar_x000D_
var greetRaju = greet2.bind(person1);_x000D_
var greetChandu = greet2.bind(person2);_x000D_
greetRaju(); // Hello Raju king_x000D_
greetChandu(); // Hello chandu shekar

MySQL select statement with CASE or IF ELSEIF? Not sure how to get the result

Another way of doing this is using nested IF statements. Suppose you have companies table and you want to count number of records in it. A sample query would be something like this

      count(*) > 15,
          count(*) > 10,
      ) as data_count 
      FROM companies

Here second IF condition works when the first IF condition fails. So Sample Syntax of the IF statement would be IF ( CONDITION, THEN, ELSE). Hope it helps someone.

Adding integers to an int array

An array has a fixed length. You cannot 'add' to it. You define at the start how long it will be.

int[] num = new int[5];

This creates an array of integers which has 5 'buckets'. Each bucket contains 1 integer. To begin with these will all be 0.

num[0] = 1;
num[1] = 2;

The two lines above set the first and second values of the array to 1 and 2. Now your array looks like this:


As you can see you set values in it, you don't add them to the end.

If you want to be able to create a list of numbers which you add to, you should use ArrayList.

SSIS expression: convert date to string

If, like me, you are trying to use GETDATE() within an expression and have the seemingly unreasonable requirement (SSIS/SSDT seems very much a work in progress to me, and not a polished offering) of wanting that date to get inserted into SQL Server as a valid date (type = datetime), then I found this expression to work:

@[User::someVar] = (DT_WSTR,4)YEAR(GETDATE()) + "-"  + RIGHT("0" + (DT_WSTR,2)MONTH(GETDATE()), 2) + "-"  + RIGHT("0" + (DT_WSTR,2)DAY( GETDATE()), 2) + " " + RIGHT("0" + (DT_WSTR,2)DATEPART("hh", GETDATE()), 2) + ":" + RIGHT("0" + (DT_WSTR,2)DATEPART("mi", GETDATE()), 2) + ":" + RIGHT("0" + (DT_WSTR,2)DATEPART("ss", GETDATE()), 2)

I found this code snippet HERE

RE error: illegal byte sequence on Mac OS X

You simply have to pipe an iconv command before the sed command. Ex with file.txt input :

iconv -f ISO-8859-1 -t UTF8-MAC file.txt | sed 's/something/àéèêçùû/g' | .....

-f option is the 'from' codeset and -t option is the 'to' codeset conversion.

Take care of case, web pages usually show lowercase like that < charset=iso-8859-1"/> and iconv uses uppercase. You have list of iconv supported codesets in you system with command iconv -l

UTF8-MAC is modern OS Mac codeset for conversion.

How to show SVG file on React Native?

I've tried all the above solutions and other solutions outside of the stack and none of working for me. finally, after long research, I've found one solution for my expo project.

If you need it to work in expo, one workaround might be to use and move the spreading of props to a G element instead of the SVG root like this:

import * as React from 'react';
import Svg, { G, Path } from 'react-native-svg';

function SvgComponent(props) {
  return (
    <Svg viewBox="0 0 511 511">
      <G {...props}>
        <Path d="M131.5 96c-11.537 0-21.955 8.129-29.336 22.891C95.61 132 92 149.263 92 167.5s3.61 35.5 10.164 48.609C109.545 230.871 119.964 239 131.5 239s21.955-8.129 29.336-22.891C167.39 203 171 185.737 171 167.5s-3.61-35.5-10.164-48.609C153.455 104.129 143.037 96 131.5 96zm15.92 113.401C142.78 218.679 136.978 224 131.5 224s-11.28-5.321-15.919-14.599C110.048 198.334 107 183.453 107 167.5s3.047-30.834 8.581-41.901C120.22 116.321 126.022 111 131.5 111s11.28 5.321 15.919 14.599C152.953 136.666 156 151.547 156 167.5s-3.047 30.834-8.58 41.901z" />
        <Path d="M474.852 158.011c-1.263-40.427-10.58-78.216-26.555-107.262C430.298 18.023 405.865 0 379.5 0h-248c-26.365 0-50.798 18.023-68.797 50.749C45.484 82.057 36 123.52 36 167.5s9.483 85.443 26.703 116.751C80.702 316.977 105.135 335 131.5 335a57.57 57.57 0 005.867-.312 7.51 7.51 0 002.133.312h48a7.5 7.5 0 000-15h-16c10.686-8.524 20.436-20.547 28.797-35.749 4.423-8.041 8.331-16.756 11.703-26.007V503.5a7.501 7.501 0 0011.569 6.3l20.704-13.373 20.716 13.374a7.498 7.498 0 008.134 0l20.729-13.376 20.729 13.376a7.49 7.49 0 004.066 1.198c1.416 0 2.832-.4 4.07-1.2l20.699-13.372 20.726 13.374a7.5 7.5 0 008.133 0l20.732-13.377 20.738 13.377a7.5 7.5 0 008.126.003l20.783-13.385 20.783 13.385a7.5 7.5 0 0011.561-6.305v-344a7.377 7.377 0 00-.146-1.488zM187.154 277.023C171.911 304.737 152.146 320 131.5 320s-40.411-15.263-55.654-42.977C59.824 247.891 51 208.995 51 167.5s8.824-80.391 24.846-109.523C91.09 30.263 110.854 15 131.5 15s40.411 15.263 55.654 42.977C203.176 87.109 212 126.005 212 167.5s-8.824 80.391-24.846 109.523zm259.563 204.171a7.5 7.5 0 00-8.122 0l-20.78 13.383-20.742-13.38a7.5 7.5 0 00-8.131 0l-20.732 13.376-20.729-13.376a7.497 7.497 0 00-8.136.002l-20.699 13.373-20.727-13.375a7.498 7.498 0 00-8.133 0l-20.728 13.375-20.718-13.375a7.499 7.499 0 00-8.137.001L227 489.728V271h8.5a7.5 7.5 0 000-15H227v-96.5c0-.521-.054-1.03-.155-1.521-1.267-40.416-10.577-78.192-26.548-107.231C191.936 35.547 182.186 23.524 171.5 15h208c20.646 0 40.411 15.263 55.654 42.977C451.176 87.109 460 126.005 460 167.5V256h-.5a7.5 7.5 0 000 15h.5v218.749l-13.283-8.555z" />
        <Path d="M283.5 256h-16a7.5 7.5 0 000 15h16a7.5 7.5 0 000-15zM331.5 256h-16a7.5 7.5 0 000 15h16a7.5 7.5 0 000-15zM379.5 256h-16a7.5 7.5 0 000 15h16a7.5 7.5 0 000-15zM427.5 256h-16a7.5 7.5 0 000 15h16a7.5 7.5 0 000-15z" />

export default function App() {
  return (
    <SvgComponent width="100%" height="100%" strokeWidth={5} stroke="black" />

AngularJS - Trigger when radio button is selected

Should use ngChange instead of ngClick if trigger source is not from click.

Is the below what you want ? what exactly doesn't work in your case ?

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

function MyCtrl($scope) {
    $scope.value = "none" ;
    $scope.isChecked = false;
    $scope.checkStuff = function () {
        $scope.isChecked = !$scope.isChecked;

<div ng-controller="MyCtrl">
    <input type="radio" ng-model="value" value="one" ng-change="checkStuff()" />
    <span> {{value}} isCheck:{{isChecked}} </span>

jQuery getJSON save result into variable

You can't get value when calling getJSON, only after response.

var myjson;
$.getJSON("", function(json){
    myjson = json;

How to read appSettings section in the web.config file?

    using System.Configuration;

    /// <summary>
    /// For read one setting
    /// </summary>
    /// <param name="key">Key correspondent a your setting</param>
    /// <returns>Return the String contains the value to setting</returns>
    public string ReadSetting(string key)
        var appSettings = ConfigurationManager.AppSettings;
        return appSettings[key] ?? string.Empty;

    /// <summary>
    /// Read all settings for output Dictionary<string,string> 
    /// </summary>        
    /// <returns>Return the Dictionary<string,string> contains all settings</returns>
    public Dictionary<string, string> ReadAllSettings()
        var result = new Dictionary<string, string>();
        foreach (var key in ConfigurationManager.AppSettings.AllKeys)
            result.Add(key, ConfigurationManager.AppSettings[key]);
        return result;

Clear the value of bootstrap-datepicker

You can use this syntax to reset your bootstrap datepicker



PANIC: Cannot find AVD system path. Please define ANDROID_SDK_ROOT (in windows 10)

My problem was solved by creating a Windows user without an accent or special characters and reinstalling android studio on that user. Another change is to change the environment variables:

Left Click in My Computer > Advanced System Settings> Advanced > Environment Variables

ANDROID_HOME = c:\my_sdk_path

ANDROID_SDK_ROOT = c:\my_sdk_path

JAVA_HOME = c:\program files\Java\yourJavaPath

  • the default path of SDK is c:\users\youruser\AppData\LocalAndroid\sdk

Environment variables

Add in Path Variable the values:

  1. %ANDROID_HOME%\platform-tools

  2. %ANDROID_HOME%\tools

path variables

path values

After changes, restart windows and try again!

Python - difference between two strings

What you are asking for is a specialized form of compression. xdelta3 was designed for this particular kind of compression, and there's a python binding for it, but you could probably get away with using zlib directly. You'd want to use zlib.compressobj and zlib.decompressobj with the zdict parameter set to your "base word", e.g. afrykanerskojezyczny.

Caveats are zdict is only supported in python 3.3 and higher, and it's easiest to code if you have the same "base word" for all your diffs, which may or may not be what you want.

Difference between static, auto, global and local variable in the context of c and c++

Difference is static variables are those variables: which allows a value to be retained from one call of the function to another. But in case of local variables the scope is till the block/ function lifetime.

For Example:

#include <stdio.h>

void func() {
    static int x = 0; // x is initialized only once across three calls of func()
    printf("%d\n", x); // outputs the value of x
    x = x + 1;

int main(int argc, char * const argv[]) {
    func(); // prints 0
    func(); // prints 1
    func(); // prints 2
    return 0;

Remove element by id

The ChildNode.remove() method removes the object from the tree it belongs to.

Here is a fiddle that shows how you can call document.getElementById('my-id').remove()


There is no need to extend NodeList. It has been implemented already.


What is two way binding?

Two-way binding means that any data-related changes affecting the model are immediately propagated to the matching view(s), and that any changes made in the view(s) (say, by the user) are immediately reflected in the underlying model. When app data changes, so does the UI, and conversely.

This is a very solid concept to build a web application on top of, because it makes the "Model" abstraction a safe, atomic data source to use everywhere within the application. Say, if a model, bound to a view, changes, then its matching piece of UI (the view) will reflect that, no matter what. And the matching piece of UI (the view) can safely be used as a mean of collecting user inputs/data, so as to maintain the application data up-to-date.

A good two-way binding implementation should obviously make this connection between a model and some view(s) as simple as possible, from a developper point of view.

It is then quite untrue to say that Backbone does not support two-way binding: while not a core feature of the framework, it can be performed quite simply using Backbone's Events though. It costs a few explicit lines of code for the simple cases; and can become quite hazardous for more complex bindings. Here is a simple case (untested code, written on the fly just for the sake of illustration):

Model = Backbone.Model.extend
    data: ''

View = Backbone.View.extend
  template: _.template("Edit the data: <input type='text' value='<%= data %>' />")

    # Listen for user inputs, and edit the model.
    'change input': @setData

  initialize: (options) ->
    # Listen for model's edition, and trigger UI update
    @listenTo @model, 'change:data', @render

  render: ->
    @$el.html @template(@model.attributes)

  setData: (e) =>
    @model.set 'data', $(e.currentTarget).value()

model: new Model()
view = new View {el: $('.someEl'), model: model}

This is a pretty typical pattern in a raw Backbone application. As one can see, it requires a decent amount of (pretty standard) code.

AngularJS and some other alternatives (Ember, Knockout…) provide two-way binding as a first-citizen feature. They abstract many edge-cases under some DSL, and do their best at integrating two-way binding within their ecosystem. Our example would look something like this with AngularJS (untested code, see above):

<div ng-app="app" ng-controller="MainCtrl">
  Edit the data:
  <input name="" ng-model="">
angular.module('app', [])
  .controller 'MainCtrl', ($scope) ->
    $scope.mymodel = {data: ''}

Rather short!

But, be aware that some fully-fledged two-way binding extensions do exist for Backbone as well (in raw, subjective order of decreasing complexity): Epoxy, Stickit, ModelBinder

One cool thing with Epoxy, for instance, is that it allows you to declare your bindings (model attributes <-> view's DOM element) either within the template (DOM), or within the view implementation (JavaScript). Some people strongly dislike adding "directives" to the DOM/template (such as the ng-* attributes required by AngularJS, or the data-bind attributes of Ember).

Taking Epoxy as an example, one can rework the raw Backbone application into something like this (…):

Model = Backbone.Model.extend
    data: ''

View = Backbone.Epoxy.View.extend
  template: _.template("Edit the data: <input type='text' />")
  # or, using the inline form: <input type='text' data-bind='value:data' />

    'input': 'value:data'

  render: ->
    @$el.html @template(@model.attributes)

model: new Model()
view = new View {el: $('.someEl'), model: model}

All in all, pretty much all "mainstream" JS frameworks support two-way binding. Some of them, such as Backbone, do require some extra work to make it work smoothly, but those are the same which do not enforce a specific way to do it, to begin with. So it is really about your state of mind.

Also, you may be interested in Flux, a different architecture for web applications promoting one-way binding through a circular pattern. It is based on the concept of fast, holistic re-rendering of UI components upon any data change to ensure cohesiveness and make it easier to reason about the code/dataflow. In the same trend, you might want to check the concept of MVI (Model-View-Intent), for instance Cycle.

How to check task status in Celery?

You can also create custom states and update it's value duting task execution. This example is from docs:

def upload_files(self, filenames):
    for i, file in enumerate(filenames):
        if not self.request.called_directly:
                meta={'current': i, 'total': len(filenames)})

Is String.Contains() faster than String.IndexOf()?

If you really want to micro optimise your code your best approach is always benchmarking.

The .net framework has an excellent stopwatch implementation - System.Diagnostics.Stopwatch

How to get the selected row values of DevExpress XtraGrid?

Here is the way that I've followed,

int[] selRows = ((GridView)gridControl1.MainView).GetSelectedRows();
DataRowView selRow = (DataRowView)(((GridView)gridControl1.MainView).GetRow(selRows[0]));
txtName.Text = selRow["name"].ToString();

Also you can iterate through selected rows using the selRows array. Here the code describes how to get data only from first selected row. You can insert these code lines to click event of the grid.

Is there 'byte' data type in C++?

No there is no byte data type in C++. However you could always include the bitset header from the standard library and create a typedef for byte:

typedef bitset<8> BYTE;

NB: Given that WinDef.h defines BYTE for windows code, you may want to use something other than BYTE if your intending to target Windows.

Edit: In response to the suggestion that the answer is wrong. The answer is not wrong. The question was "Is there a 'byte' data type in C++?". The answer was and is: "No there is no byte data type in C++" as answered.

With regards to the suggested possible alternative for which it was asked why is the suggested alternative better?

According to my copy of the C++ standard, at the time:

"Objects declared as characters (char) shall be large enough to store any member of the implementations basic character set":

I read that to suggest that if a compiler implementation requires 16 bits to store a member of the basic character set then the size of a char would be 16 bits. That today's compilers tend to use 8 bits for a char is one thing, but as far as I can tell there is certainly no guarantee that it will be 8 bits.

On the other hand, "the class template bitset<N> describes an object that can store a sequence consisting of a fixed number of bits, N." : 20.5.1. In otherwords by specifying 8 as the template parameter I end up with an object that can store a sequence consisting of 8 bits.

Whether or not the alternative is better to char, in the context of the program being written, therefore depends, as far as I understand, although I may be wrong, upon your compiler and your requirements at the time. It was therefore upto the individual writing the code, as far as I'm concerned, to do determine whether the suggested alternative was appropriate for their requirements/wants/needs.

SQL/mysql - Select distinct/UNIQUE but return all columns?

That's a really good question. I have read some useful answers here already, but probably I can add a more precise explanation.

Reducing the number of query results with a GROUP BY statement is easy as long as you don't query additional information. Let's assume you got the following table 'locations'.

--country-- --city--
 France      Lyon
 Poland      Krakow
 France      Paris
 France      Marseille
 Italy       Milano

Now the query

SELECT country FROM locations
GROUP BY country

will result in:


However, the following query

SELECT country, city FROM locations
GROUP BY country

...throws an error in MS SQL, because how could your computer know which of the three French cities "Lyon", "Paris" or "Marseille" you want to read in the field to the right of "France"?

In order to correct the second query, you must add this information. One way to do this is to use the functions MAX() or MIN(), selecting the biggest or smallest value among all candidates. MAX() and MIN() are not only applicable to numeric values, but also compare the alphabetical order of string values.

SELECT country, MAX(city) FROM locations
GROUP BY country

will result in:

--country-- --city--
 France      Paris
 Poland      Krakow
 Italy       Milano


SELECT country, MIN(city) FROM locations
GROUP BY country

will result in:

--country-- --city--
 France      Lyon
 Poland      Krakow
 Italy       Milano

These functions are a good solution as long as you are fine with selecting your value from the either ends of the alphabetical (or numeric) order. But what if this is not the case? Let us assume that you need a value with a certain characteristic, e.g. starting with the letter 'M'. Now things get complicated.

The only solution I could find so far is to put your whole query into a subquery, and to construct the additional column outside of it by hands:

     (SELECT TOP 1 city
     FROM locations
          country =
          AND city like 'M%'
(SELECT country FROM locations
GROUP BY country) countrylist

will result in:

--country-- --city--
 France      Marseille
 Poland      NULL
 Italy       Milano

Place input box at the center of div

The catch is that input elements are inline. We have to make it block (display:block) before positioning it to center : margin : 0 auto. Please see the code below :

        div.wrapper {
            width: 300px;
            border:1px solid black;

        input[type="text"] {
             display: block;
             margin : 0 auto;


    <div class='wrapper'>
        <input type='text' name='ok' value='ok'>


But if you have a div which is positioned = absolute then we need to do the things little bit differently.Now see this!

        div.wrapper {
            position:  absolute;
            top : 200px;
            left: 300px;
            width: 300px;
            border:1px solid black;

        input[type="text"] {
             position: relative;
             display: block;
             margin : 0 auto;


    <div class='wrapper'>
        <input type='text' name='ok' value='ok'>


Hoping this can be helpful.Thank you.

How can I set size of a button?

This is how I did it.

            JFrame frame = new JFrame("SAP Multiple Entries");
            JPanel panel = new JPanel(new GridLayout(10,10,10,10));
            frame.setLayout(new FlowLayout());
            frame.setSize(512, 512);
            JButton button = new JButton("Select File");
            button.setPreferredSize(new Dimension(256, 256));

            button.addActionListener(new ActionListener() {

                public void actionPerformed(ActionEvent ae) {
                    JFileChooser fileChooser = new JFileChooser();
                    int returnValue = fileChooser.showOpenDialog(null);
                    if (returnValue == JFileChooser.APPROVE_OPTION) {
                        File selectedFile = fileChooser.getSelectedFile();

                        keep = selectedFile.getAbsolutePath();

                       // System.out.println(keep);
                       if(file.flag==true) {
                           JOptionPane.showMessageDialog(null, "It is done! \nLocation: " + file.path , "Success Message", JOptionPane.INFORMATION_MESSAGE);
                           JOptionPane.showMessageDialog(null, "failure", "not okay", JOptionPane.INFORMATION_MESSAGE);

VirtualBox: mount.vboxsf: mounting failed with the error: No such device

This was resolved by:

yum install gcc kernel-devel make

workaround is here:

How are ssl certificates verified?

You said that

the browser gets the certificate's issuer information from that certificate, then uses that to contact the issuerer, and somehow compares certificates for validity.

The client doesn't have to check with the issuer because two things :

  1. all browsers have a pre-installed list of all major CAs public keys
  2. the certificate is signed, and that signature itself is enough proof that the certificate is valid because the client can make sure, by his own, and without contacting the issuer's server, that that certificate is authentic. That's the beauty of asymmetric encryption.

Notice that 2. can't be done without 1.

This is better explained in this big diagram I made some time ago

(skip to "what's a signature ?" at the bottom)


Eclipse Java error: This selection cannot be launched and there are no recent launches

It happens when sometimes we copy or import the project from somewhere. The source folder is a big thing to concern about.

One simple technique is, create a new project, inside the source folder, create a new class and paste the content over there.

It will work...

Hope it helps.

How to establish a connection pool in JDBC?


It's modern, it's fast, it's simple. I use it for every new project. I prefer it a lot over C3P0, don't know the other pools too well.

How to run python script with elevated privilege on windows

I found a very easy solution to this problem.

  1. Create a shortcut for python.exe
  2. Change the shortcut target into something like C:\xxx\...\python.exe
  3. Click "advance..." in the property panel of the shortcut, and click the option "run as administrator"

I'm not sure whether the spells of these options are right, since I'm using Chinese version of Windows.

C++ display stack trace on exception

I have a similar problem, and though I like portability, I only need gcc support. In gcc, execinfo.h and the backtrace calls are available. To demangle the function names, Mr. Bingmann has a nice piece of code. To dump a backtrace on an exception, I create an exception that prints the backtrace in the constructor. If I were expecting this to work with an exception thrown in a library, it might require rebuilding/linking so that the backtracing exception is used.

#Makefile with flags for printing backtrace with function names
# compile with symbols for backtrace
# add symbols to dynamic symbol table for backtrace

#include <cstdio>
#include <stdexcept>
#include <execinfo.h>
#include "stacktrace.h" /* */

// simple exception that prints backtrace when constructed
class btoverflow_error: public std::overflow_error
    btoverflow_error( const std::string& arg ) :
        std::overflow_error( arg )

void chicken(void)
    throw btoverflow_error( "too big" );

void duck(void)

void turkey(void)

int main( int argc, char *argv[])
    catch( btoverflow_error e)
        printf( "caught exception: %s\n", e.what() );

Compiling and running this with gcc 4.8.4 yields a backtrace with nicely unmangled C++ function names:

stack trace:
 ./turducken : btoverflow_error::btoverflow_error(std::string const&)+0x43
 ./turducken : chicken()+0x48
 ./turducken : duck()+0x9
 ./turducken : turkey()+0x9
 ./turducken : main()+0x15
 /lib/x86_64-linux-gnu/ : __libc_start_main()+0xf5
 ./turducken() [0x401629]

CSV new-line character seen in unquoted field error

Try to run dos2unix on your windows imported files first

How to insert DECIMAL into MySQL database

I noticed something else about your coding.... look

INSERT INTO reports_services (id,title,description,cost) VALUES (0, 'test title', 'test decription ', '3.80')

in your "CREATE TABLE" code you have the id set to "AUTO_INCREMENT" which means it's automatically generating a result for that field.... but in your above code you include it as one of the insertions and in the "VALUES" you have a 0 there... idk if that's your way of telling us you left it blank because it's set to AUTO_INC. or if that's the actual code you have... if it's the code you have not only should you not be trying to send data to a field set to generate it automatically, but the RIGHT WAY to do it WRONG would be


you put

0, that might be causing some of the problem... I also just noticed in the code after "test description" you have a space before the '.... that might be throwing something off too.... idk.. I hope this helps n maybe resolves some other problem you might be pulling your hair out about now.... speaking of which.... I need to figure out my problem before I tear all my hair out..... good luck.. :)


I almost forgot... if you have the 0 there to show that it's blank... you could be entering "test title" as the id and "test description" as the title then "3.whatever cents" for the description leaving "cost" empty...... which could be why it maxed out because if I'm not mistaking you have it set to NOT NULL.... and you left it null... so it forced something... maybe.... lol

How to Alter Constraint

No. We cannot alter the constraint, only thing we can do is drop and recreate it


Foreign Key Constraint

Alter Table Table1 Add Constraint [CONSTRAINTNAME] Foreign Key (Column) References Table2 (Column) On Update Cascade On Delete Cascade

Primary Key constraint

Alter Table Table add constraint [Primary Key] Primary key(Column1,Column2,.....)

Unrecognized escape sequence for path string containing backslashes

string foo = "D:\\Projects\\Some\\Kind\\Of\\Pathproblem\\wuhoo.xml";

This will work, or the previous examples will, too. @"..." means treat everything between the quote marks literally, so you can do


To include a literal newline. I'm more old school and prefer to escape "\" with "\\"

How do I append to a table in Lua

I'd personally make use of the table.insert function:


This saves you from having to iterate over the whole table therefore saving valuable resources such as memory and time.

How to get a ListBox ItemTemplate to stretch horizontally the full width of the ListBox?

If your items are wider than the ListBox, the other answers here won't help: the items in the ItemTemplate remain wider than the ListBox.

The fix that worked for me was to disable the horizontal scrollbar, which, apparently, also tells the container of all those items to remain only as wide as the list box.

Hence the combined fix to get ListBox items that are as wide as the list box, whether they are smaller and need stretching, or wider and need wrapping, is as follows:

<ListBox HorizontalContentAlignment="Stretch" 

(credits for the scroll bar idea)

Sum rows in data.frame or matrix

The rowSums function (as Greg mentions) will do what you want, but you are mixing subsetting techniques in your answer, do not use "$" when using "[]", your code should look something more like:

data$new <- rowSums( data[,43:167] )

If you want to use a function other than sum, then look at ?apply for applying general functions accross rows or columns.

Commands out of sync; you can't run this command now

I think the problem is that you're making a new connection in the function, and then not closing it at the end. Why don't you try passing in the existing connection and re-using it?

Another possibility is that you're returning out of the middle of a while loop fetching. You never complete that outer fetch.

How to make php display \t \n as tab and new line instead of characters

"\t" not '\t', php doesnt escape in single quotes

Regular expression for matching HH:MM time format

check this masterfull timestamp detector regex I built to look for a user-specified timestamp, examples of what it will pickup include, but is most definitely NOT limited to;

09:40-09 : 50
09 : 40-09 : 50
09:40 - 09 : 50
08 : 00to05 : 00
08:00 to 05:00
08h00 till 17h00
06pm untill 9am

It'll also pickup many more, as long as the times include digits

Why does pycharm propose to change method to static

It might be a bit messy, but sometimes you just don't need to access self, but you would prefer to keep the method in the class and not make it static. Or you just want to avoid adding a bunch of unsightly decorators. Here are some potential workarounds for that situation.

If your method only has side effects and you don't care about what it returns:

def bar(self):
    return self

If you do need the return value:

def bar(self):
    result = doing_something_without_self()
    if self:
        return result

Now your method is using self, and the warning goes away!

c#: getter/setter

You can also use a lambda expression

public string Type
    get => _type;
    set => _type = value;

Replace Div Content onclick

Here's an approach:


<div id="1">
    My Content 1

<div id="2" style="display:none;">
    My Dynamic Content
<button id="btnClick">Click me!</button>


    $('#2').html('Here is my dynamic content').show().siblings('div').hide();
    }else if($('#2').css('display')!='none'){

JsFiddle: <--- Commented

SQL Server stored procedure creating temp table and inserting value

A SELECT INTO statement creates the table for you. There is no need for the CREATE TABLE statement before hand.

What is happening is that you create #ivmy_cash_temp1 in your CREATE statement, then the DB tries to create it for you when you do a SELECT INTO. This causes an error as it is trying to create a table that you have already created.

Either eliminate the CREATE TABLE statement or alter your query that fills it to use INSERT INTO SELECT format.

If you need a unique ID added to your new row then it's best to use SELECT INTO... since IDENTITY() only works with this syntax.

How to pass values arguments to function in Bootstrap


$(document).ready(function() {
    $('#createFormId').on('', function(event) {

C#: Looping through lines of multiline string

Here's a quick code snippet that will find the first non-empty line in a string:

string line1;
while (
    ((line1 = sr.ReadLine()) != null) &&
    ((line1 = line1.Trim()).Length == 0)
{ /* Do nothing - just trying to find first non-empty line*/ }

if(line1 == null){ /* Error - no non-empty lines in string */ }

Pandas split DataFrame by column value

Using "groupby" and list comprehension:

Storing all the split dataframe in list variable and accessing each of the seprated dataframe by their index.

DF = pd.DataFrame({'chr':["chr3","chr3","chr7","chr6","chr1"],'pos':[10,20,30,40,50],})
ans = [pd.DataFrame(y) for x, y in DF.groupby('chr', as_index=False)]

accessing the separated DF like this:

ans[len(ans)-1] # this is the last separated DF

accessing the column value of the separated DF like this:


How to open an external file from HTML

If your web server is IIS, you need to make sure that the new Office 2007 (I see the xlsx suffix) mime types are added to the list of mime types in IIS, otherwise it will refuse to serve the unknown file type.

Here's one link to tell you how:

Configuring IIS 6 for Office 2007

PermGen elimination in JDK 8

Oracle's JVM implementation for Java 8 got rid of the PermGen model and replaced it with Metaspace.

Angular 4 HttpClient Query Parameters

If you have an object that can be converted to {key: 'stringValue'} pairs, you can use this shortcut to convert it:

this._Http.get(myUrlString, {params: {...myParamsObject}});

I just love the spread syntax!

How to use Angular2 templates with *ngFor to create a table out of nested arrays?

it's not exact output that you wanted but maybe something like this will do. Parent cmp:

  <item *ngFor="#i of items" [data]="i"></item>

Child cmp

import {Component} from 'angular2/core';

  selector: `item`,
  inputs: ['data'],
  template: `
    <tr *ngFor="#i of data.items">
export default class Item {


Route.get() requires callback functions but got a "object Undefined"

check your closing tags in your model, it may be that you have defined a callback in another callback

How to turn off magic quotes on shared hosting?

How about $_SERVER ?

if (get_magic_quotes_gpc() === 1) {

    $_GET = json_decode(stripslashes(json_encode($_GET, JSON_HEX_APOS)), true);
    $_POST = json_decode(stripslashes(json_encode($_POST, JSON_HEX_APOS)), true);
    $_COOKIE = json_decode(stripslashes(json_encode($_COOKIE, JSON_HEX_APOS)), true);
    $_REQUEST = json_decode(stripslashes(json_encode($_REQUEST, JSON_HEX_APOS)), true); 
    $_SERVER = json_decode( stripslashes(json_encode($_SERVER,JSON_HEX_APOS)), true); 

Run class in Jar file

This is the right way to execute a .jar, and whatever one class in that .jar should have main() and the following are the parameters to it :

java -DLB="uk" -DType="CLIENT_IND" -jar com.fbi.rrm.rrm-batchy-1.5.jar

Draw a curve with css

@Navaneeth and @Antfish, no need to transform you can do like this also because in above solution only top border is visible so for inside curve you can use bottom border.

.box {_x000D_
  width: 500px;_x000D_
  height: 100px;_x000D_
  border: solid 5px #000;_x000D_
  border-color: transparent transparent #000 transparent;_x000D_
  border-radius: 0 0 240px 50%/60px;_x000D_
<div class="box"></div>

angular.service vs angular.factory

Simply put ..

const user = {
  firstName: 'john'

// Factory
const addLastNameFactory = (user, lastName) => ({

console.log(addLastNameFactory(user, 'doe'));

// Service
const addLastNameService = (user, lastName) => {
  user.lastName = lastName; // BAD! Mutation
  return user;

console.log(addLastNameService(user, 'doe'));

How do I go about adding an image into a java project with eclipse?

Place the image in a source folder, not a regular folder. That is: right-click on project -> New -> Source Folder. Place the image in that source folder. Then:

InputStream input = classLoader.getResourceAsStream("image.jpg");

Note that the path is omitted. That's because the image is directly in the root of the path. You can add folders under your source folder to break it down further if you like. Or you can put the image under your existing source folder (usually called src).

Why emulator is very slow in Android Studio?

For those who enabled HAXM and the emulator still works slow here is what you should do:

  1. If Avast antivirus is running on your computer, it is most likely the culprit.

as per HAXM Release_Notes.txt (Version 7.5.2):

  • On Windows, Avast Antivirus may interfere with HAXM and cause Android Emulator or QEMU to run very slowly. A workaround is to uncheck "Use nested virtualization where available" in Avast Settings > Troubleshooting.

So open your Avast dashboard > Menu > Settings > Troubleshooting and disable "Enable hardware-assisted virtualization"

enter image description here

  1. Give a higher priority to your emulator's process in the Task Manager:

    Locate your emulator's process in the Task Manager > Details tab:

    Right-click on it and Set Priority -> Above normal enter image description here

Sorry that the screenshot is not in English but you got the point, right? That helped me significantly! I hope it will help you as well.

Also, one thing as per the Release Notes:

  • On Windows 8, 8.1 and 10, it is recommended to disable Hyper-V from Windows Features in order for the HAXM driver to properly function.

In my case, I didn't have any "Hyper-V" feature on my Windows 8.1 but you probably should try it, just in case. To locate and disable that feature see this article:

How can I convert a string to a float in mysql?

This will convert to a numeric value without the need to cast or specify length or digits:


If your column is an INT, can leave off the .0 to avoid decimals:


NSURLSession/NSURLConnection HTTP load failed on iOS 9

If you're having this problem with Amazon S3 as me, try to paste this on your info.plist as a direct child of your top level tag


You can find more info at:

Pointer-to-pointer dynamic two-dimensional array

In both cases your inner dimension may be dynamically specified (i.e. taken from a variable), but the difference is in the outer dimension.

This question is basically equivalent to the following:

Is int* x = new int[4]; "better" than int x[4]?

The answer is: "no, unless you need to choose that array dimension dynamically."

Multiline text in JLabel

This is horrifying. All these answers suggesting adding to the start of the label text, and there is not one word in the Java 11 (or earlier) documentation for JLabel to suggest that the text of a label is handled differently if it happens to start with <html>. Who says that works everywhere and always will? And you can get big, big surprises wrapping arbitrary text in and handing it to an html layout engine.

I've upvoted the answer that suggests JTextArea. But I'll note that JTextArea isn't a drop-in replacement; by default it expands to fill rows, which is not how JLabel acts. I haven't come up with a solution to that yet.

Advantages of using display:inline-block vs float:left in CSS

If you want to align the div with pixel accurate, then use float. inline-block seems to always requires you to chop off a few pixels (at least in IE)

Get number days in a specified month using JavaScript?

// Month here is 1-indexed (January is 1, February is 2, etc). This is
// because we're using 0 as the day so that it returns the last day
// of the last month, so you have to add 1 to the month number 
// so it returns the correct amount of days
function daysInMonth (month, year) {
    return new Date(year, month, 0).getDate();

// July
daysInMonth(7,2009); // 31
// February
daysInMonth(2,2009); // 28
daysInMonth(2,2008); // 29

Localhost : 404 not found

open D:\xampp\apache\conf\extra\httpd-vhosts.conf

ServerName localhost DocumentRoot "D:\xampp\htdocs" SetEnv APPLICATION_ENV "development"
DirectoryIndex index.php AllowOverride FileInfo Require all granted

Restart Apache server

and then refresh your given url

Inserting image into IPython notebook markdown

Getting an image into Jupyter NB is a much simpler operation than most people have alluded to here.

1) Simply create an empty Markdown cell. 2) Then drag-and-drop the image file into the empty Markdown cell.

The Markdown code that will insert the image then appears.

For example, a string shown highlighted in gray below will appear in the Jupyter cell:


3) Then execute the Markdown cell by hitting Shift-Enter. The Jupyter server will then insert the image, and the image will then appear.

I am running Jupyter notebook server is: 5.7.4 with Python 3.7.0 on Windows 7.

This is so simple !!

Connecting to MySQL from Android with JDBC

If u need to connect your application to a server you can do it through PHP/MySQL and JSON .Mysql Connection code should be in AsynTask class. Dont run it in Main Thread.

Getting "net::ERR_BLOCKED_BY_CLIENT" error on some AJAX calls

AdBlockers usually have some rules, i.e. they match the URIs against some type of expression (sometimes they also match the DOM against expressions, not that this matters in this case).

Having rules and expressions that just operate on a tiny bit of text (the URI) is prone to create some false-positives...

Besides instructing your users to disable their extensions (at least on your site) you can also get the extension and test which of the rules/expressions blocked your stuff, provided the extension provides enough details about that. Once you identified the culprit, you can either try to avoid triggering the rule by using different URIs, report the rule as incorrect or overly-broad to the team that created it, or both. Check the docs for a particular add-on on how to do that.

For example, AdBlock Plus has a Blockable items view that shows all blocked items on a page and the rules that triggered the block. And those items also including XHR requests.

Blockable items

Append date to filename in linux

There's two problems here.

1. Get the date as a string

This is pretty easy. Just use the date command with the + option. We can use backticks to capture the value in a variable.

$ DATE=`date +%d-%m-%y` 

You can change the date format by using different % options as detailed on the date man page.

2. Split a file into name and extension.

This is a bit trickier. If we think they'll be only one . in the filename we can use cut with . as the delimiter.

$ NAME=`echo $FILE | cut -d. -f1
$ EXT=`echo $FILE | cut -d. -f2`

However, this won't work with multiple . in the file name. If we're using bash - which you probably are - we can use some bash magic that allows us to match patterns when we do variable expansion:

$ NAME=${FILE%.*}
$ EXT=${FILE#*.} 

Putting them together we get:

$ FILE=somefile.txt             
$ NAME=${FILE%.*}
$ EXT=${FILE#*.} 
$ DATE=`date +%d-%m-%y`         
$ echo $NEWFILE                 

And if we're less worried about readability we do all the work on one line (with a different date format):

$ FILE=somefile.txt  
$ FILE=${FILE%.*}_`date +%d%b%y`.${FILE#*.}
$ echo $FILE                                 

How to layout multiple panels on a jFrame? (java)

You'll want to use a number of layout managers to help you achieve the basic results you want.

Check out A Visual Guide to Layout Managers for a comparision.

You could use a GridBagLayout but that's one of the most complex (and powerful) layout managers available in the JDK.

You could use a series of compound layout managers instead.

I'd place the graphics component and text area on a single JPanel, using a BorderLayout, with the graphics component in the CENTER and the text area in the SOUTH position.

I'd place the text field and button on a separate JPanel using a GridBagLayout (because it's the simplest I can think of to achieve the over result you want)

I'd place these two panels onto a third, master, panel, using a BorderLayout, with the first panel in the CENTER and the second at the SOUTH position.

But that's me

Extract data from log file in specified range of time

You can use this for getting current and log times:


while read line
  current_hours=`date | awk 'BEGIN{FS="[ :]+"}; {print $4}'`
  current_minutes=`date | awk 'BEGIN{FS="[ :]+"}; {print $5}'`
  current_seconds=`date | awk 'BEGIN{FS="[ :]+"}; {print $6}'`

  log_file_hours=`echo $line | awk 'BEGIN{FS="[ [/:]+"}; {print  $7}'`
  log_file_minutes=`echo $line | awk 'BEGIN{FS="[ [/:]+"}; {print  $8}'`
  log_file_seconds=`echo $line | awk 'BEGIN{FS="[ [/:]+"}; {print  $9}'`    
done < $log

And compare log_file_* and current_* variables.

Difference between \b and \B in regex

\b matches a word-boundary. \B matches non-word-boundaries, and is equivalent to [^\b](?!\b) (thanks to @Alan Moore for the correction!). Both are zero-width.

See for details. The site is extremely useful for many basic regex questions.

How to loop through file names returned by find?

# Doesn't handle whitespace
for x in `find . -name "*.txt" -print`; do
  process_one $x


# Handles whitespace and newlines
find . -name "*.txt" -print0 | xargs -0 -n 1 process_one

What is the difference between Python's list methods append and extend?

Append and extend are one of the extensibility mechanisms in python.

Append: Adds an element to the end of the list.

my_list = [1,2,3,4]

To add a new element to the list, we can use append method in the following way.


The default location that the new element will be added is always in the (length+1) position.

Insert: The insert method was used to overcome the limitations of append. With insert, we can explicitly define the exact position we want our new element to be inserted at.

Method descriptor of insert(index, object). It takes two arguments, first being the index we want to insert our element and second the element itself.

Example: my_list = [1,2,3,4]
my_list[4, 'a']

Extend: This is very useful when we want to join two or more lists into a single list. Without extend, if we want to join two lists, the resulting object will contain a list of lists.

a = [1,2]
b = [3]
print (a)

If we try to access the element at pos 2, we get a list ([3]), instead of the element. To join two lists, we'll have to use append.

a = [1,2]
b = [3]
print (a)

To join multiple lists

a = [1]
b = [2]
c = [3]
print (a)

Proper way to handle multiple forms on one page in Django

A method for future reference is something like this. bannedphraseform is the first form and expectedphraseform is the second. If the first one is hit, the second one is skipped (which is a reasonable assumption in this case):

if request.method == 'POST':
    bannedphraseform = BannedPhraseForm(request.POST, prefix='banned')
    if bannedphraseform.is_valid():
    bannedphraseform = BannedPhraseForm(prefix='banned')

if request.method == 'POST' and not bannedphraseform.is_valid():
    expectedphraseform = ExpectedPhraseForm(request.POST, prefix='expected')
    bannedphraseform = BannedPhraseForm(prefix='banned')
    if expectedphraseform.is_valid():

    expectedphraseform = ExpectedPhraseForm(prefix='expected')

Use string value from a cell to access worksheet of same name

By using the ROW() function I can drag this formula vertically. It can also be dragged horizontally since there is no $ before the D.

= INDIRECT("'"&D$2&"'!$B"&ROW())

My layout has sheet names as column headers (B2, C2, D2, etc.) and maps multiple row values from Column B in each sheet.

Getting Integer value from a String using javascript/jquery

just do this , you need to remove char other than "numeric" and "." form your string will do work for you

yourString = yourString.replace ( /[^\d.]/g, '' );

your final code will be

  str1 = "test123.00".replace ( /[^\d.]/g, '' );
  str2 = "yes50.00".replace ( /[^\d.]/g, '' );
  total = parseInt(str1, 10) + parseInt(str2, 10);


Is there a Boolean data type in Microsoft SQL Server like there is in MySQL?

You are looking for a bit. It stores 1 or 0 (or NULL).

Alternatively, you could use the strings 'true' and 'false' in place of 1 or 0, like so-

declare @b1 bit = 'false'
print @b1                    --prints 0

declare @b2 bit = 'true'
print @b2                    --prints 1

Also, any non 0 value (either positive or negative) evaluates to (or converts to in some cases) a 1.

declare @i int = -42
print cast(@i as bit)    --will print 1, because @i is not 0

Note that SQL Server uses three valued logic (true, false, and NULL), since NULL is a possible value of the bit data type. Here are the relevant truth tables -

enter image description here

More information on three valued logic-

Example of three valued logic in SQL Server

Add (insert) a column between two columns in a data.frame

R has no functionality to specify where a new column is added. E.g., mtcars$mycol<-'foo'. It always is added as last column. Using other means (e.g., dplyr's select()) you can move the mycol to a desired position. This is not ideal and R may want to try to change that in the future.

Pointers in JavaScript?

Late answer but I have come across a way of passing primitive values by reference by means of closures. It is rather complicated to create a pointer, but it works.

function ptr(get, set) {
    return { get: get, set: set };

function helloWorld(namePtr) {

var myName = 'joe';
var myNamePtr = ptr(
    function () { return myName; },
    function (value) { myName = value; }

helloWorld(myNamePtr); // joe, jack
console.log(myName); // jack

In ES6, the code can be shortened to use lambda expressions:

var myName = 'joe';
var myNamePtr = ptr(=> myName, v => myName = v);

helloWorld(myNamePtr); // joe, jack
console.log(myName); // jack

Length of string in bash

To get the length of a string stored in a variable, say:

myvar="some string"

To confirm it was properly saved, echo it:

$ echo "$size"

Use find command but exclude files in two directories

for me, this solution didn't worked on a command exec with find, don't really know why, so my solution is

find . -type f -path "./a/*" -prune -o -path "./b/*" -prune -o -exec gzip -f -v {} \;

Explanation: same as sampson-chen one with the additions of

-prune - ignore the proceding path of ...

-o - Then if no match print the results, (prune the directories and print the remaining results)

18:12 $ mkdir a b c d e
18:13 $ touch a/1 b/2 c/3 d/4 e/5 e/a e/b
18:13 $ find . -type f -path "./a/*" -prune -o -path "./b/*" -prune -o -exec gzip -f -v {} \;

gzip: . is a directory -- ignored
gzip: ./a is a directory -- ignored
gzip: ./b is a directory -- ignored
gzip: ./c is a directory -- ignored
./c/3:    0.0% -- replaced with ./c/3.gz
gzip: ./d is a directory -- ignored
./d/4:    0.0% -- replaced with ./d/4.gz
gzip: ./e is a directory -- ignored
./e/5:    0.0% -- replaced with ./e/5.gz
./e/a:    0.0% -- replaced with ./e/a.gz
./e/b:    0.0% -- replaced with ./e/b.gz

What does 'stale file handle' in Linux mean?

When the directory is deleted, the inode for that directory (and the inodes for its contents) are recycled. The pointer your shell has to that directory's inode (and its contents's inodes) are now no longer valid. When the directory is restored from backup, the old inodes are not (necessarily) reused; the directory and its contents are stored on random inodes. The only thing that stays the same is that the parent directory reuses the same name for the restored directory (because you told it to).

Now if you attempt to access the contents of the directory that your original shell is still pointing to, it communicates that request to the file system as a request for the original inode, which has since been recycled (and may even be in use for something entirely different now). So you get a stale file handle message because you asked for some nonexistent data.

When you perform a cd operation, the shell reevaluates the inode location of whatever destination you give it. Now that your shell knows the new inode for the directory (and the new inodes for its contents), future requests for its contents will be valid.

How can I extract all values from a dictionary in Python?

Call the values() method on the dict.

How to detect orientation change?

Swift 4:

override func viewWillAppear(_ animated: Bool) {
    NotificationCenter.default.addObserver(self, selector: #selector(deviceRotated), name: UIDevice.orientationDidChangeNotification, object: nil)

override func viewWillDisappear(_ animated: Bool) {
    NotificationCenter.default.removeObserver(self, name: UIDevice.orientationDidChangeNotification, object: nil)

@objc func deviceRotated(){
    if UIDevice.current.orientation.isLandscape {
        //Code here
    } else {
        //Code here

A lot of answers dont help when needing to detect across various view controllers. This one does the trick.

Reading DataSet

If ds is the DataSet, you can access the CustomerID column of the first row in the first table with something like:

DataRow dr = ds.Tables[0].Rows[0];

Submit form and stay on same page?

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

PHP function to get the subdomain of a URL

Here's a one line solution:

array_shift((explode('.', $_SERVER['HTTP_HOST'])));

Or using your example:

array_shift((explode('.', '')));

EDIT: Fixed "only variables should be passed by reference" by adding double parenthesis.

EDIT 2: Starting from PHP 5.4 you can simply do:

explode('.', '')[0];

Automating running command on Linux from Windows using PuTTY

There could be security issues with common methods for auto-login. One of the most easiest ways is documented below:

And as for the part the executes the command In putty UI, Connection>SSH> there's a field for remote command.

4.17 The SSH panel

The SSH panel allows you to configure options that only apply to SSH sessions.

4.17.1 Executing a specific command on the server

In SSH, you don't have to run a general shell session on the server. Instead, you can choose to run a single specific command (such as a mail user agent, for example). If you want to do this, enter the command in the "Remote command" box.

in short, your answers might just as well be similar to the text below:

How to overcome "datetime.datetime not JSON serializable"?

The json.dumps method can accept an optional parameter called default which is expected to be a function. Every time JSON tries to convert a value it does not know how to convert it will call the function we passed to it. The function will receive the object in question, and it is expected to return the JSON representation of the object.

def myconverter(o):
 if isinstance(o, datetime.datetime):
    return o.__str__()

print(json.dumps(d, default = myconverter)) 

How can I enable CORS on Django REST Framework

Django=2.2.12 django-cors-headers=3.2.1 djangorestframework=3.11.0

Follow the official instruction doesn't work

Finally use the old way to figure it out.


# proj/
from rest_framework.authentication import SessionAuthentication

class CsrfExemptSessionAuthentication(SessionAuthentication):

    def enforce_csrf(self, request):
        return  # To not perform the csrf check previously happening



Firefox Add-on RESTclient - How to input POST parameters?

If you want to submit a POST request

  1. You have to set the “request header” section of the Firefox plugin to have a “name” = “Content-Type” and “value” = “application/x-www-form-urlencoded
  2. Now, you are able to submit parameter like “name=mynamehere&title=TA” in the “request body” text area field

How do I tell Python to convert integers into words

The inflect package can do this.

$ pip install inflect

and then:

>>>import inflect
>>>p = inflect.engine()

HttpListener Access Denied

As an alternative that doesn't require elevation or netsh you could also use TcpListener for instance.

The following is a modified excerpt of this sample:

// Generates state and PKCE values.
string state = randomDataBase64url(32);
string code_verifier = randomDataBase64url(32);
string code_challenge = base64urlencodeNoPadding(sha256(code_verifier));
const string code_challenge_method = "S256";

// Creates a redirect URI using an available port on the loopback address.
var listener = new TcpListener(IPAddress.Loopback, 0);
string redirectURI = string.Format("http://{0}:{1}/", IPAddress.Loopback, ((IPEndPoint)listener.LocalEndpoint).Port);
output("redirect URI: " + redirectURI);

// Creates the OAuth 2.0 authorization request.
string authorizationRequest = string.Format("{0}?response_type=code&scope=openid%20profile&redirect_uri={1}&client_id={2}&state={3}&code_challenge={4}&code_challenge_method={5}",

// Opens request in the browser.

// Waits for the OAuth authorization response.
var client = await listener.AcceptTcpClientAsync();

// Read response.
var response = ReadString(client);

// Brings this app back to the foreground.

// Sends an HTTP response to the browser.
WriteStringAsync(client, "<html><head><meta http-equiv='refresh' content='10;url='></head><body>Please close this window and return to the app.</body></html>").ContinueWith(t =>

    Console.WriteLine("HTTP server stopped.");

// TODO: Check the response here to get the authorization code and verify the code challenge

The read and write methods being:

private string ReadString(TcpClient client)
    var readBuffer = new byte[client.ReceiveBufferSize];
    string fullServerReply = null;

    using (var inStream = new MemoryStream())
        var stream = client.GetStream();

        while (stream.DataAvailable)
            var numberOfBytesRead = stream.Read(readBuffer, 0, readBuffer.Length);
            if (numberOfBytesRead <= 0)

            inStream.Write(readBuffer, 0, numberOfBytesRead);

        fullServerReply = Encoding.UTF8.GetString(inStream.ToArray());

    return fullServerReply;

private Task WriteStringAsync(TcpClient client, string str)
    return Task.Run(() =>
        using (var writer = new StreamWriter(client.GetStream(), new UTF8Encoding(false)))
            writer.Write("HTTP/1.0 200 OK");
            writer.Write("Content-Type: text/html; charset=UTF-8");
            writer.Write("Content-Length: " + str.Length);

Excel: Creating a dropdown using a list in another sheet?

Yes it is. Use Data Validation from the Data panel. Select Allow: List and pick those cells on the other sheet as your source.

Node.js: Python not found exception due to node-sass and node-gyp

Node-sass tries to download the binary for you platform when installing. Node 5 is supported by 3.8 If your Jenkins can't download the prebuilt binary, then you need to follow the platform requirements on Node-gyp README (Python2, VS or MSBuild, ...) If possible I'd suggest updating your Node to at least 6 since 5 isn't supported by Node anymore. If you want to upgrade to 8, you'll need to update node-sass to 4.5.3

How do you make an array of structs in C?

That error means that the compiler is not able to find the definition of the type of your struct before the declaration of the array of structs, since you're saying you have the definition of the struct in a header file and the error is in nbody.c then you should check if you're including correctly the header file. Check your #include's and make sure the definition of the struct is done before declaring any variable of that type.

SQL grammar for SELECT MIN(DATE)

You need to use GROUP BY instead of DISTINCT if you want to use aggregation functions.

SELECT title, MIN(date)
FROM table
GROUP BY title

How to install easy_install in Python 2.7.1 on Windows 7

for 32-bit Python, the installer is here. after you run the installer, you will have easy_install.exe in your \Python27\Scripts directory

if you are looking for 64-bit installers, this is an excellent resource:

the author has installers for both Setuptools and Distribute. Either one will give you easy_install.exe

The resource could not be loaded because the App Transport Security policy requires the use of a secure connection

Transport security is provided in iOS 9.0 or later, and in OS X v10.11 and later.

So by default only https calls only allowed in apps. To turn off App Transport Security add following lines in info.plist file...


For more info:

How to rsync only a specific list of files?

$ date
  Wed 24 Apr 2019 09:54:53 AM PDT
$ rsync --version
  rsync  version 3.1.3  protocol version 31

Syntax: rsync <file_/_folder_list> <source> <target>

Folder names (here, WITH a trailing /; e.g. Cancer - Evolution/) are in a folder list file (e.g.: cm_folder_list_test):

# /mnt/Vancouver/projects/ie/claws/data/cm_folder_list_test
# test file: 2019-04-24
Cancer - Evolution/
Cancer - Genomic Variants/
Cancer - Metastasis (EMT Transition ...)/
Cancer Pathways, Networks/
Catabolism - Autophagy; Phagosomes; Mitophagy/
Catabolism - Lysosomes/

If you don't include those trailing /, the rsync'd target folders are created, but are empty.

Those folder names are appended to the rest of their path (/home/victoria/Mail/2_RESEARCH - NEWS), thus providing the complete folder path to rsync; e.g.: /home/victoria/Mail/2_RESEARCH - NEWS/Cancer - Evolution/.

Note that you also need to use --files-from= ..., NOT --include-from= ...

rsync -aqP --delete --files-from=/mnt/Vancouver/projects/ie/claws/data/cm_folder_list_test "/home/victoria/Mail/2_RESEARCH - NEWS" $IN/

(In my BASH script, I defined variable $IN as follows.)


rsync options used:

 -a  :   archive: equals -rlptgoD (no -H,-A,-X)
    -r  :   recursive
    -l  :   copy symlinks as symlinks
    -p  :   preserve permissions
    -t  :   preserve modification times 
    -g  :   preserve group 
    -o  :   preserve owner (super-user only) 
    -D  :   same as --devices --specials 
  -q  :   quiet (

    This  tells  rsync to delete extraneous files from the RECEIVING SIDE (ones
    that AREN’T ON THE SENDING SIDE), but only for the directories that are
    being synchronized.  You must have asked rsync to send the whole directory
    (e.g.  "dir" or "dir/") without using a wildcard for the directory’s contents
    (e.g. "dir/*") since the wildcard is expanded by the shell and rsync thus
    gets a request to transfer individual files, not the files’ parent directory.
    Files  that  are  excluded  from  the transfer are also excluded from being
    deleted unless you use the --delete-excluded option or mark the rules as
    only matching on the sending side (see the include/exclude modifiers in the
    FILTER RULES section).  ...

error: expected primary-expression before ')' token (C)

You're passing a type as an argument, not an object. You need to do characterSelection(screen, test); where test is of type SelectionneNonSelectionne.

Warning: Permanently added the RSA host key for IP address

I solved it by using git push -u origin master

c# Image resizing to different size while preserving aspect ratio

Maintain aspect Ration and eliminate letterbox and Pillarbox.

static Image FixedSize(Image imgPhoto, int Width, int Height)
        int sourceWidth = imgPhoto.Width;
        int sourceHeight = imgPhoto.Height;
        int X = 0;
        int Y = 0;

        float nPercent = 0;
        float nPercentW = 0;
        float nPercentH = 0;

        nPercentW = ((float)Width / (float)sourceWidth);
        nPercentH = ((float)Height / (float)sourceHeight);
        if (nPercentH < nPercentW)
            nPercent = nPercentH;
            nPercent = nPercentW;

        int destWidth = (int)(sourceWidth * nPercent);
        int destHeight = (int)(sourceHeight * nPercent);

        Bitmap bmPhoto = new Bitmap(destWidth, destHeight, PixelFormat.Format24bppRgb);


        Graphics grPhoto = Graphics.FromImage(bmPhoto);

                new Rectangle(X, Y, destWidth, destHeight),
                new Rectangle(X, Y, sourceWidth, sourceHeight),

        return bmPhoto;

HTML - Alert Box when loading page

If you use jqueryui (or another toolset) this is the way you do it


<div id="hw" title="Empty the recycle bin?">The new way</div>


        alert('the old way')

UPDATE : how to include jqueryui by pointing to cdn

<link rel="stylesheet" type="text/css" href="">
<script src=""></script>
<script src=""></script>

What is a correct MIME type for .docx, .pptx, etc.?

This post will explore various approaches of fetching MIME Type across various programming languages with their CONS in one-line description as header. So, use them accordingly and the one which works for you.

For eg. the code below is especially helpful when user may supply either of .xls, .xlsx or .xlsm and you don't want to write code testing extension and supplying MIME-type for each of them. Let the system do this job.

Python 3

Using python-magic

>>> pip install python-magic
>>> import magic
>>> magic.from_file("Employee.pdf", mime=True)

Using built-in mimeypes module - Map filenames to MimeTypes modules

>>> import mimetypes
>>> mimetypes.init()
>>> mimetypes.knownfiles
['/etc/mime.types', '/etc/httpd/mime.types', ... ]
>>> mimetypes.suffix_map['.tgz']
>>> mimetypes.encodings_map['.gz']
>>> mimetypes.types_map['.tgz']


Source: Baeldung's blog on File MIME Types in Java

Operating System dependent

public void get_JAVA7_mimetype() {
    Path path = new File("Employee.xlsx").toPath();
    String mimeType = Files.probeContentType(path);

    assertEquals(mimeType, "application/");

It will use FileTypeDetector implementations to probe the MIME type and invokes the probeContentType of each implementation to resolve the type. Hence, if the file is known to the implementations then the content type is returned. However, if that doesn’t happen, a system-default file type detector is invoked.

Resolve using first few characters of the input stream

public void getMIMEType_from_Extension(){
    File file = new File("Employee.xlsx");
    String mimeType = URLConnection.guessContentTypeFromName(file.getName());

    assertEquals(mimeType, "application/");

Using built-in table of MIME types

public void getMIMEType_UsingGetFileNameMap(){
    File file = new File("Employee.xlsx");
    FileNameMap fileNameMap = URLConnection.getFileNameMap();
    String mimeType = fileNameMap.getContentTypeFor(file.getName());

    assertEquals(mimeType, "image/png");

It returns the matrix of MIME types used by all instances of URLConnection which then is used to resolve the input file type. However, this matrix of MIME types is very limited when it comes to URLConnection.

By default, the class uses file in JRE_HOME/lib. We can, however, extend it, by specifying a user-specific table using the content.types.user.table property:



Source: FileReader API & Medium's article on using Magic Numbers in JavaScript to get Mime Types

Interpret the Magic Number fetched using FileReader API

Final result looks something like this when one use javaScript to fetch the MimeType based on filestream. Open the embedded jsFiddle to see and understand this approach.

Bonus: It's accessible for most of the MIME Types and also you can add custom Mime Types in the getMimetype function. Also, it has FULL SUPPORT for MS Office Files Mime Types.

FileReader API Result

The steps to calculate mime type for a file in this example would be:

  1. The user selects a file.
  2. Take the first 4 bytes of the file using the slice method.
  3. Create a new FileReader instance
  4. Use the FileReader to read the 4 bytes you sliced out as an array buffer.
  5. Since the array buffer is just a generic way to represent a binary buffer we need to create a TypedArray, in this case an Uint8Array.
  6. With a TypedArray at our hands we can retrieve every byte and transform it to hexadecimal (by using toString(16)).
  7. We now have a way to get the magic numbers from a file by reading the first four bytes. The final step is to map it to a real mime type.

Browser Support (Above 95% overall and Close to 100% in all modern browsers): FileReader API

File Reader API Browser Support

const uploads = []_x000D_
const fileSelector = document.getElementById('file-selector')_x000D_
fileSelector.addEventListener('change', (event) => {_x000D_
  const file =[0]_x000D_
  const filereader = new FileReader()_x000D_
  filereader.onloadend = function(evt) {_x000D_
    if ( === FileReader.DONE) {_x000D_
      const uint = new Uint8Array(
      let bytes = []_x000D_
      uint.forEach((byte) => {_x000D_
      const hex = bytes.join('').toUpperCase()_x000D_
        filetype: file.type ? file.type : 'Unknown/Extension missing',_x000D_
        binaryFileType: getMimetype(hex),_x000D_
        hex: hex_x000D_
  const blob = file.slice(0, 4);_x000D_
const render = () => {_x000D_
  const container = document.getElementById('files')_x000D_
  const uploadedFiles = => {_x000D_
    return `<div class=result><hr />_x000D_
                    <span class=filename>Filename: <strong>${file.filename}</strong></span><br>_x000D_
                    <span class=fileObject>File Object (Mime Type):<strong> ${file.filetype}</strong></span><br>_x000D_
                    <span class=binaryObject>Binary (Mime Type):<strong> ${file.binaryFileType}</strong></span><br>_x000D_
                    <span class=HexCode>Hex Code (Magic Number):<strong> <em>${file.hex}</strong></span></em>_x000D_
  container.innerHTML = uploadedFiles.join('')_x000D_
const getMimetype = (signature) => {_x000D_
  switch (signature) {_x000D_
    case '89504E47':_x000D_
      return 'image/png'_x000D_
    case '47494638':_x000D_
      return 'image/gif'_x000D_
    case '25504446':_x000D_
      return 'application/pdf'_x000D_
    case 'FFD8FFDB':_x000D_
    case 'FFD8FFE0':_x000D_
    case 'FFD8FFE1':_x000D_
      return 'image/jpeg'_x000D_
    case '504B0304':_x000D_
      return 'application/zip'_x000D_
    case '504B34':_x000D_
      return 'application/'_x000D_
      return 'Unknown filetype'_x000D_
.result {_x000D_
  font-family: Palatino, "Palatino Linotype", "Palatino LT STD", "Book Antiqua", Georgia, serif;_x000D_
  line-height: 20px;_x000D_
  font-size: 14px;_x000D_
  margin: 10px 0;_x000D_
.filename {_x000D_
  color: #333;_x000D_
  font-size: 16px;_x000D_
.fileObject {_x000D_
  color: #a53;_x000D_
.binaryObject {_x000D_
  color: #63f;_x000D_
.HexCode {_x000D_
  color: #262;_x000D_
em {_x000D_
  padding: 2px 4px;_x000D_
  background-color: #efefef;_x000D_
  font-style: normal;_x000D_
input[type=file] {_x000D_
  background-color: #4CAF50;_x000D_
  border: none;_x000D_
  color: white;_x000D_
  padding: 8px 16px;_x000D_
  text-decoration: none;_x000D_
  margin: 4px 2px;_x000D_
  cursor: pointer;_x000D_
  <input type="file" id="file-selector">_x000D_
  <div id="files"></div>

Download single files from GitHub

  1. The page you linked to answers the first question.

  2. GitHub also has a download facility for things like releases.

  3. Google Code does not have Git at all.

  4. GitHub, Google Code and SourceForge, just to start, are free hosting. SourceForge might still do CVS.

Can not get a simple bootstrap modal to work

A simple way to use modals is with eModal!

Ex from github:

  1. Link to eModal.js <script src="//"></script>
  2. use eModal to display a modal for alert, ajax, prompt or confirm

    // Display an alert modal with default title (Attention)
    eModal.alert('You shall not pass!');

Change name of folder when cloning from GitHub?

git clone <Repo> <DestinationDirectory>

Clone the repository located at Repo into the folder called DestinationDirectory on the local machine.

LINQ: When to use SingleOrDefault vs. FirstOrDefault() with filtering criteria

Nobody has mentioned that FirstOrDefault translated in SQL does TOP 1 record, and SingleOrDefault does TOP 2, because it needs to know is there more than 1 record.

What is the standard way to add N seconds to datetime.time in Python?

Old question, but I figured I'd throw in a function that handles timezones. The key parts are passing the datetime.time object's tzinfo attribute into combine, and then using timetz() instead of time() on the resulting dummy datetime. This answer partly inspired by the other answers here.

def add_timedelta_to_time(t, td):
    """Add a timedelta object to a time object using a dummy datetime.

    :param t: datetime.time object.
    :param td: datetime.timedelta object.

    :returns: datetime.time object, representing the result of t + td.

    NOTE: Using a gigantic td may result in an overflow. You've been
    # Create a dummy date object.
    dummy_date = date(year=100, month=1, day=1)

    # Combine the dummy date with the given time.
    dummy_datetime = datetime.combine(date=dummy_date, time=t, tzinfo=t.tzinfo)

    # Add the timedelta to the dummy datetime.
    new_datetime = dummy_datetime + td

    # Return the resulting time, including timezone information.
    return new_datetime.timetz()

And here's a really simple test case class (using built-in unittest):

import unittest
from datetime import datetime, timezone, timedelta, time

class AddTimedeltaToTimeTestCase(unittest.TestCase):
    """Test add_timedelta_to_time."""

    def test_wraps(self):
        t = time(hour=23, minute=59)
        td = timedelta(minutes=2)
        t_expected = time(hour=0, minute=1)
        t_actual = add_timedelta_to_time(t=t, td=td)
        self.assertEqual(t_expected, t_actual)

    def test_tz(self):
        t = time(hour=4, minute=16, tzinfo=timezone.utc)
        td = timedelta(hours=10, minutes=4)
        t_expected = time(hour=14, minute=20, tzinfo=timezone.utc)
        t_actual = add_timedelta_to_time(t=t, td=td)
        self.assertEqual(t_expected, t_actual)

if __name__ == '__main__':

How to escape a JSON string containing newline characters using JavaScript?

Use json_encode() if your server side scripting lang is PHP, json_encode() escapes the newline & other unexpected tokens for you (if not using PHP look for similar function for your scripting language)

then use $.parseJSON() in your JavaScript, done!

jQuery: Clearing Form Inputs

Demo :

  .not(':button, :submit, :reset, :hidden')

Original Answer: Resetting a multi-stage form with jQuery

Mike's suggestion (from the comments) to keep checkbox and selects intact!

Warning: If you're creating elements (so they're not in the dom), replace :hidden with [type=hidden] or all fields will be ignored!

  .not(':button, :submit, :reset, :hidden, :radio, :checkbox')

Gradle: How to Display Test Results in the Console in Real Time?

As a follow up to Shubham's great answer I like to suggest using enum values instead of strings. Please take a look at the documentation of the TestLogging class.

import org.gradle.api.tasks.testing.logging.TestExceptionFormat
import org.gradle.api.tasks.testing.logging.TestLogEvent

tasks.withType(Test) {
    testLogging {
        events TestLogEvent.FAILED,
        exceptionFormat TestExceptionFormat.FULL
        showCauses true
        showExceptions true
        showStackTraces true

Run local java applet in browser (chrome/firefox) "Your security settings have blocked a local application from running"

Go to java control tab>java control pannel>click security tab>down the security level to medium. Then applet progrramme after 2to 3 security promt it will run.

How can I customize the tab-to-space conversion factor?

When using TypeScript, the default tab width is always two regardless of what it says in the toolbar. You have to set "prettier.tabWidth" in your user settings to change it.

Ctrl + P, Type ? user settings, add:

"prettier.tabWidth": 4

set font size in jquery

You can try another way like that:

<div class="content">

jQuery code:

    background: "#d1d1d1",
    fontSize: "30px"

Now you can add more css property as you want.

Bootstrap 4 - Glyphicons migration?

Bootstrap 4 files do not come with the glyphicon support. But you can simply open up your bootstrap.css or bootstrap.min.css and paste this code which I came across here.

@font-face{font-family:'Glyphicons Halflings';src:url('');src:url('') format('embedded-opentype'),url('') format('woff'),url('') format('truetype'),url('') format('svg');}.glyphicon{position:relative;top:1px;display:inline-block;font-family:'Glyphicons Halflings';font-style:normal;font-weight:normal;line-height:1;-webkit-font-smoothing:antialiased;}

How to debug in Android Studio using adb over WiFi

if adb command not found.


Install homebrew

 /bin/bash -c "$(curl -fsSL"

Install adb

brew install android-platform-tools


Connect the device now.

  • Enable USB debugging in the Android device
  • Enable Allow ADB debugging in charge only mode
  • Connect the device to the computer via a USB port.

Start using adb

adb devices

List of devices attached
DUM0219A21000314 device

the first item is device id.

adb -s <device id> tcpip 5555

adb -s DUM0219A21000314 tcpip 5555

restarting in TCP mode port: 5555

Find the local IP address of your Android device. You can find this information in the quick settings drop-down menu by pressing / long pressing the WiFi icon and then clicking on the WiFi network you are connected to.

adb connect <IP address>:5555
adb connect

connected to

Don't forget! Allow ADB debugging in charge only mode enabled before connecting the device

HTML/Javascript change div content

Assuming you're not using jQuery or some other library that makes this sort of thing easier for you, you can just use the element's innerHTML property.

document.getElementById("content").innerHTML = "whatever";

Alert after page load

There are three ways.
The first is to put the script tag on the bottom of the page:

<!--Body content-->
<script type="text/javascript">
alert('<%: TempData["Resultat"]%>');

The second way is to create an onload event:

<script type="text/javascript">
window.onload = function(){//window.addEventListener('load',function(){...}); (for Netscape) and window.attachEvent('onload',function(){...}); (for IE and Opera) also work
    alert('<%: TempData["Resultat"]%>');

It will execute a function when the window loads.
Finally, the third way is to create a readystatechange event and check the current document.readystate:

<script type="text/javascript">
document.onreadystatechange = function(){//window.addEventListener('readystatechange',function(){...}); (for Netscape) and window.attachEvent('onreadystatechange',function(){...}); (for IE and Opera) also work
    if(document.readyState=='loaded' || document.readyState=='complete')
        alert('<%: TempData["Resultat"]%>');

How to import large sql file in phpmyadmin

For that you will have to edit php.ini file, If you are using the ubuntu server this is link Upload large file in phpMyAdmin might help you.

Convert PDF to image with high resolution

I use pdftoppm on the command line to get the initial image, typically with a resolution of 300dpi, so pdftoppm -r 300, then use convert to do the trimming and PNG conversion.

PHP namespaces and "use"

The use operator is for giving aliases to names of classes, interfaces or other namespaces. Most use statements refer to a namespace or class that you'd like to shorten:

use My\Full\Namespace;

is equivalent to:

use My\Full\Namespace as Namespace;
// Namespace\Foo is now shorthand for My\Full\Namespace\Foo

If the use operator is used with a class or interface name, it has the following uses:

// after this, "new DifferentName();" would instantiate a My\Full\Classname
use My\Full\Classname as DifferentName;

// global class - making "new ArrayObject()" and "new \ArrayObject()" equivalent
use ArrayObject;

The use operator is not to be confused with autoloading. A class is autoloaded (negating the need for include) by registering an autoloader (e.g. with spl_autoload_register). You might want to read PSR-4 to see a suitable autoloader implementation.

How enable auto-format code for Intellij IDEA?

You can do this with Save Actions plugin Refer This article on how to configure the plugin.

Save Actions plugin Supports configurable, Eclipse like, save actions, including "optimize imports", "reformat code", "rearrange code", "compile file" and some quick fixes for Java like "add / remove 'this' qualifier", etc. The plugin executes the configured actions when the file is synchronised (or saved) on disk.

  1. Install the plugin
  2. Go to Settings > Other settings > Save actions
  3. Tick Activate save actions on save
  4. Tick Reformat file
  5. Apply > OK

enter image description here

I prefer the hot-keys though, For Mac,

To format the code : Ctrl+Alt(Option)+L

And additionally I do,: Ctrl+Alt(Option)+O , This will remove unused imports and format the import list as well.

Where is Android Studio layout preview?

Several people seem to have the same problem. The issue is that the IDE only displays the preview if editing a layout file in the res/layout* directory of an Android project.

In particular, it won't show if editing a file in build/res/layout* since those are not source directory but output directory. In your case, you are editing a file in the build/ directory...

The Resource folder is set automatically, and can be viewed (and changed) in Project Structure > Modules > [Module name] > Android > Resources directory.

how to convert numeric to nvarchar in sql command

select convert(nvarchar(255), 4343)

Should do the trick.

How to count number of files in each directory?

THis could be another way to browse through the directory structures and provide depth results.

find . -type d  | awk '{print "echo -n \""$0"  \";ls -l "$0" | grep -v total | wc -l" }' | sh 

what is the difference between const_iterator and iterator?

Performance wise there is no difference. The only purpose of having const_iterator over iterator is to manage the accessesibility of the container on which the respective iterator runs. You can understand it more clearly with an example:

std::vector<int> integers{ 3, 4, 56, 6, 778 };

If we were to read & write the members of a container we will use iterator:

for( std::vector<int>::iterator it = integers.begin() ; it != integers.end() ; ++it )
       {*it = 4;  std::cout << *it << std::endl; }

If we were to only read the members of the container integers you might wanna use const_iterator which doesn't allow to write or modify members of container.

for( std::vector<int>::const_iterator it = integers.begin() ; it != integers.end() ; ++it )
       { cout << *it << endl; }

NOTE: if you try to modify the content using *it in second case you will get an error because its read-only.

How to customize the back button on ActionBar

I have checked the question. Here is the steps that I follow. The source code is hosted on GitHub:

Override the actual style for the pre-v11 devices.

Copy and paste the follow code in the file styles.xml of the default values folder.

    <style name="MyCustomTheme" parent="Theme.Sherlock.Light">
    <item name="homeAsUpIndicator">@drawable/ic_home_up</item>

Note that the parent could be changed to any Sherlock theme.

Override the actual style for the v11+ devices.

On the same folder where the folder values is, create a new folder called values-v11. Android will automatically look for the content of this folder for devices with API or above.

Create a new file called styles.xml and paste the follow code into the file:

<?xml version="1.0" encoding="utf-8"?>
    <style name="MyCustomTheme" parent="Theme.Sherlock.Light">
    <item name="android:homeAsUpIndicator">@drawable/ic_home_up</item>

Note tha the name of the style must be the same as the file in the default values folder and instead of the item homeAsUpIndicator, it is called android:homeAsUpIndicator.

The item issue is because for devices with API 11 or above, Sherlock Action Bar use the default Action Bar which comes with Android, which the key name is android:homeAsUpIndicator. But for the devices with API 10 or lower, Sherlock Action Bar uses its own ActionBar, which the home as up indicator is called simple "homeAsUpIndicator".

Use the new theme in the manifest

Replace the theme for the application/activity in the AndroidManifest file:

    android:theme="@style/MyCustomTheme" >

Java Project: Failed to load ApplicationContext

I faced this issue, and that is when a Bean (@Bean) was not instantiated properly as it was not given the correct parameters in my test class.

How do I deserialize a JSON string into an NSDictionary? (For iOS 5+)

With Swift 3 and Swift 4, String has a method called data(using:allowLossyConversion:). data(using:allowLossyConversion:) has the following declaration:

func data(using encoding: String.Encoding, allowLossyConversion: Bool = default) -> Data?

Returns a Data containing a representation of the String encoded using a given encoding.

With Swift 4, String's data(using:allowLossyConversion:) can be used in conjunction with JSONDecoder's decode(_:from:) in order to deserialize a JSON string into a dictionary.

Furthermore, with Swift 3 and Swift 4, String's data(using:allowLossyConversion:) can also be used in conjunction with JSONSerialization's json?Object(with:?options:?) in order to deserialize a JSON string into a dictionary.

#1. Swift 4 solution

With Swift 4, JSONDecoder has a method called decode(_:from:). decode(_:from:) has the following declaration:

func decode<T>(_ type: T.Type, from data: Data) throws -> T where T : Decodable

Decodes a top-level value of the given type from the given JSON representation.

The Playground code below shows how to use data(using:allowLossyConversion:) and decode(_:from:) in order to get a Dictionary from a JSON formatted String:

let jsonString = """
{"password" : "1234",  "user" : "andreas"}

if let data = String.Encoding.utf8) {
    do {
        let decoder = JSONDecoder()
        let jsonDictionary = try decoder.decode(Dictionary<String, String>.self, from: data)
        print(jsonDictionary) // prints: ["user": "andreas", "password": "1234"]
    } catch {
        // Handle error

#2. Swift 3 and Swift 4 solution

With Swift 3 and Swift 4, JSONSerialization has a method called json?Object(with:?options:?). json?Object(with:?options:?) has the following declaration:

class func jsonObject(with data: Data, options opt: JSONSerialization.ReadingOptions = []) throws -> Any

Returns a Foundation object from given JSON data.

The Playground code below shows how to use data(using:allowLossyConversion:) and json?Object(with:?options:?) in order to get a Dictionary from a JSON formatted String:

import Foundation

let jsonString = "{\"password\" : \"1234\",  \"user\" : \"andreas\"}"

if let data = String.Encoding.utf8) {
    do {
        let jsonDictionary = try JSONSerialization.jsonObject(with: data, options: []) as? [String : String]
        print(String(describing: jsonDictionary)) // prints: Optional(["user": "andreas", "password": "1234"])
    } catch {
        // Handle error

Django REST Framework: adding additional field to ModelSerializer

My response to a similar question (here) might be useful.

If you have a Model Method defined in the following way:

class MyModel(models.Model):

    def model_method(self):
        return "some_calculated_result"

You can add the result of calling said method to your serializer like so:

class MyModelSerializer(serializers.ModelSerializer):
    model_method_field = serializers.CharField(source='model_method')

p.s. Since the custom field isn't really a field in your model, you'll usually want to make it read-only, like so:

class Meta:
    model = MyModel
    read_only_fields = (
        ) using a form to insert data into an sql server table

Simple, make a simple asp page with the designer (just for the beginning) Lets say the body is something like this:

    <form id="form1" runat="server">
        <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
        <br />
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        <asp:Button ID="Button1" runat="server" Text="Button" />

Great, now every asp object IS an object. So you can access it in the asp's CS code. The asp's CS code is triggered by events (mostly). The class will probably inherit from System.Web.UI.Page

If you go to the cs file of the asp page, you'll see a protected void Page_Load(object sender, EventArgs e) ... That's the load event, you can use that to populate data into your objects when the page loads.

Now, go to the button in your designer (Button1) and look at its properties, you can design it, or add events from there. Just change to the events view, and create a method for the event.

The button is a web control Button Add a Click event to the button call it Button1Click:

void Button1Click(Object sender,EventArgs e) { }

Now when you click the button, this method will be called. Because ASP is object oriented, you can think of the page as the actual class, and the objects will hold the actual current data.

So if for example you want to access the text in TextBox1 you just need to call that object in the C# code:

String firstBox = TextBox1.Text;

In the same way you can populate the objects when event occur.

Now that you have the data the user posted in the textboxes , you can use regular C# SQL connections to add the data to your database.

Cannot push to GitHub - keeps saying need merge

Another option: locally rename your branch to something new.

You will then be able to push it to the remote repository, for example if that is your way of keeping a copy (backup) and making sure nothing gets lost.

You can fetch the remote branch to have a local copy and examine the differences between (i) what the remote had (with the old branch name) and (ii) what you have (with the new branch name), and decide what to do. Since you weren't aware of the remote's differences in the first place (hence the problem), simply merging or forcing changes somewhere is far too brutal.

Look at the differences, pick which branch you want to work on, cherry pick changes you want from the other branch, or revert changes you don't want on the branch you've got etc.

Then you should be in a position to decide whether you want to force your clean version onto the remote, or add new changes, or whatever.

how to get the current working directory's absolute path from irb

This will give you the working directory of the current file.



current_file: "/Users/nemrow/SITM/folder1/folder2/amazon.rb"

result: "/Users/nemrow/SITM/folder1/folder2"

Does Visual Studio Code have box select/multi-line edit?

For multiple select in Visual Studio Code, hold down the Alt key and starting clicking wherever you want to edit.

Visual Studio Code supports multiple line edit.

How to join multiple collections with $lookup in mongodb

First add the collections and then apply lookup on these collections. Don't use $unwind as unwind will simply separate all the documents of each collections. So apply simple lookup and then use $project for projection. Here is mongoDB query:

        $lookup: {
           from: "userRole",
           localField: "userId",
           foreignField: "userId",
           as: "userRole"
        $lookup: {
            from: "userInfo",
            localField: "userId",
            foreignField: "userId",
            as: "userInfo"
    {$project: {
        } ])

Here is the output:

/* 1 */ {
    "userId" : "AD",
    "phone" : "0000000000",
    "userRole" : [ 
            "userId" : "AD",
            "role" : "admin"
    "userInfo" : [ 
            "userId" : "AD",
            "phone" : "0000000000"
    ] }


Create a nonclustered non-unique index within the CREATE TABLE statement with SQL Server

It's a separate statement.

It's also not possible to insert into a table and select from it and build an index in the same statement either.

The BOL entry contains the information you need:

Indicate that a clustered or a nonclustered index is created for the PRIMARY KEY or UNIQUE constraint. PRIMARY KEY constraints default to CLUSTERED, and UNIQUE constraints default to NONCLUSTERED.

In a CREATE TABLE statement, CLUSTERED can be specified for only one constraint. If CLUSTERED is specified for a UNIQUE constraint and a PRIMARY KEY constraint is also specified, the PRIMARY KEY defaults to NONCLUSTERED.

You can create an index on a PK field, but not a non-clustered index on a non-pk non-unique-constrained field.

A NCL index is not relevant to the structure of the table, and is not a constraint on the data inside the table. It's a separate entity that supports the table but is not integral to it's functionality or design.

That's why it's a separate statement. The NCL index is irrelevant to the table from a design perspective (query optimization notwithstanding).

How can I implement custom Action Bar with custom buttons in Android?

Please write following code in menu.xml file:

<menu xmlns:android=""
<item android:id="@+id/item_one"
      android:title="Item One"
          <item android:id="@+id/sub_one"
                android:title="Sub-menu item one" />
          <item android:id="@+id/sub_two"
                android:title="Sub-menu item two" />

Also write this java code in activity class file:

public boolean onOptionsItemSelected(MenuItem item)
    Toast.makeText(this, "Menus item selected: " +
        item.getTitle(), Toast.LENGTH_SHORT).show();
    switch (item.getItemId())
            isItemOneSelected = true;
            return true;
        case MENU_ITEM + 1:
            isRemoveItem = true;
            return true;
            return false;

This is the easiest way to display menus in action bar.

MSBuild doesn't copy references (DLL files) if using project dependencies in solution

I just deal with it like this. Go to the properties of your reference and do this:

Set "Copy local = false"
Set "Copy local = true"

and that's it.

Visual Studio 2010 doesn't initially put: <private>True</private> in the reference tag and setting "copy local" to false causes it to create the tag. Afterwards it will set it to true and false accordingly.

How do I rename a file using VBScript?

You can rename the file using FSO by moving it: MoveFile Method.

Dim Fso
Set Fso = WScript.CreateObject("Scripting.FileSystemObject")
Fso.MoveFile "A.txt", "B.txt"

Bad Gateway 502 error with Apache mod_proxy and Tomcat

I know this does not answer this question, but I came here because I had the same error with nodeJS server. I am stuck a long time until I found the solution. My solution just adds slash or /in end of proxyreserve apache.

my old code is:

ProxyPass /
ProxyPassReverse /

the correct code is:

ProxyPass /
ProxyPassReverse /

How can I search (case-insensitive) in a column using LIKE wildcard?

You don't need to ALTER any table. Just use the following queries, prior to the actual SELECT query that you want to use the wildcard:

    set names `utf8`;
    SET COLLATION_CONNECTION=utf8_general_ci;

Select top 2 rows in Hive

select * from employee_list order by salary desc limit 2;

Rest-assured. Is it possible to extract value from request json?

JsonPath jsonPathEvaluator = response.jsonPath();
return jsonPathEvaluator.get("user_id").toString();

Fatal error: Call to undefined function mb_detect_encoding()

There's a much easier way than recompiling PHP. Just yum install the required mbstring library:

Example: How to install PHP mbstring on CentOS 6.2

yum --enablerepo=remi install php-mbstring

Oh, and don't forget to restart apache afterward.

Hiding elements in responsive layout?

I have a couple of clarifications to add here:

1) The list shown (visible-phone, visible-tablet, etc.) is deprecated in Bootstrap 3. The new values are:

  • visible-xs-*
  • visible-sm-*
  • visible-md-*
  • visible-lg-*
  • hidden-xs-*
  • hidden-sm-*
  • hidden-md-*
  • hidden-lg-*

The asterisk translates to the following for each (I show only visible-xs-* below):

  • visible-xs-block
  • visible-xs-inline
  • visible-xs-inline-block

2) When you use these classes, you don't add a period in front (as confusingly shown in part of the answer above).

For example:

<div class="visible-md-block col-md-6 text-right text-muted">
   <h5>Copyright &copy; 2014 Jazimov</h5>

3) You can use visible-* and hidden-* (for example, visible-xs and hidden-xs) but these have been deprecated in Bootstrap 3.2.0.

For more details and the latest specs, go here and search for "visible":

Correct use for angular-translate in controllers

Recommended: don't translate in the controller, translate in your view

I'd recommend to keep your controller free from translation logic and translate your strings directly inside your view like this:

<h1>{{ 'TITLE.HELLO_WORLD' | translate }}</h1>

Using the provided service

Angular Translate provides the $translate service which you can use in your Controllers.

An example usage of the $translate service can be:

.controller('TranslateMe', ['$scope', '$translate', function ($scope, $translate) {
        .then(function (translatedValue) {
            $scope.pageTitle = translatedValue;

The translate service also has a method for directly translating strings without the need to handle a promise, using $translate.instant():

.controller('TranslateMe', ['$scope', '$translate', function ($scope, $translate) {
    $scope.pageTitle = $translate.instant('TITLE.DASHBOARD'); // Assuming TITLE.DASHBOARD is defined

The downside with using $translate.instant() could be that the language file isn't loaded yet if you are loading it async.

Using the provided filter

This is my preferred way since I don't have to handle promises this way. The output of the filter can be directly set to a scope variable.

.controller('TranslateMe', ['$scope', '$filter', function ($scope, $filter) {
    var $translate = $filter('translate');

    $scope.pageTitle = $translate('TITLE.DASHBOARD'); // Assuming TITLE.DASHBOARD is defined

Using the provided directive

Since @PascalPrecht is the creator of this awesome library, I'd recommend going with his advise (see his answer below) and use the provided directive which seems to handle translations very intelligent.

The directive takes care of asynchronous execution and is also clever enough to unwatch translation ids on the scope if the translation has no dynamic values.

intellij incorrectly saying no beans of type found for autowired repository

just add below two annotations to your POJO.

public class YourClass {

How to read barcodes with the camera on Android?

There are two parts in building barcode scanning feature, one capturing barcode image using camera and second extracting barcode value from the image.

Barcode image can be captured from your app using camera app and barcode value can be extracted using Firebase Machine Learning Kit barcode scanning API.

Here is an example app

Cross-thread operation not valid: Control 'textBox1' accessed from a thread other than the thread it was created on

Use the following extensions and just pass the action like:

_frmx.PerformSafely(() => _frmx.Show());
_frmx.PerformSafely(() => _frmx.Location = new Point(x,y));

Extension class:

public static class CrossThreadExtensions
    public static void PerformSafely(this Control target, Action action)
        if (target.InvokeRequired)

    public static void PerformSafely<T1>(this Control target, Action<T1> action,T1 parameter)
        if (target.InvokeRequired)
            target.Invoke(action, parameter);

    public static void PerformSafely<T1,T2>(this Control target, Action<T1,T2> action, T1 p1,T2 p2)
        if (target.InvokeRequired)
            target.Invoke(action, p1,p2);

Python csv string to array

Panda is quite powerful and smart library reading CSV in Python

A simple example here, I have file with four files in it.
 -- example1.csv
 -- example1.txt
 -- example2.csv
 -- example2.txt

from zipfile import ZipFile
import pandas as pd

filepath = ''
file_prefix = filepath[:-4].lower()

zipfile = ZipFile(filepath)
target_file = ''.join([file_prefix, '/', file_prefix, 1 , '.csv'])

df = pd.read_csv(

print(df.head()) # print first five row of csv
print(df[COL_NAME]) # fetch the col_name data

Once you have data you can manipulate to play with a list or other formats.

IIS error, Unable to start debugging on the webserver

Just had the same issue after VS crashed and Rahul's comment regarding the application pool pointed me in the right direction. In my case recycling the app pool did the trick (IIS Manager => App Pools => right click on ap in question and recycle).

postgresql - add boolean column to table set default


you can also directly specify NOT NULL


UPDATE: following is only true for versions before postgresql 11.

As Craig mentioned on filled tables it is more efficient to split it into steps:

UPDATE users SET priv_user = 'f';

R data formats: RData, Rda, Rds etc

In addition to @KenM's answer, another important distinction is that, when loading in a saved object, you can assign the contents of an Rds file. Not so for Rda

> x <- 1:5
> save(x, file="x.Rda")
> saveRDS(x, file="x.Rds")
> rm(x)

> new_x1 <- readRDS("x.Rds")
> new_x1
[1] 1 2 3 4 5

## 'ASSIGN' USING load -- note the result
> new_x2 <- load("x.Rda")
loading in to  <environment: R_GlobalEnv> 
> new_x2
[1] "x"
# NOTE: `load()` simply returns the name of the objects loaded. Not the values. 
> x
[1] 1 2 3 4 5

URL encoding the space character: + or %20?

I would recommend %20.

Are you hard-coding them?

This is not very consistent across languages, though. If I'm not mistaken, in PHP urlencode() treats spaces as + whereas Python's urlencode() treats them as %20.


It seems I'm mistaken. Python's urlencode() (at least in 2.7.2) uses quote_plus() instead of quote() and thus encodes spaces as "+". It seems also that the W3C recommendation is the "+" as per here:

And in fact, you can follow this interesting debate on Python's own issue tracker about what to use to encode spaces:

EDIT #2:

I understand that the most common way of encoding " " is as "+", but just a note, it may be just me, but I find this a bit confusing:

import urllib
print(urllib.urlencode({' ' : '+ '})

>>> '+=%2B+'

Error:Execution failed for task ':app:transformClassesWithDexForDebug'

add multiDexEnabled true in default config file of build.gradle like this

    defaultConfig {
        multiDexEnabled true

How does Python return multiple values from a function?

Here It is actually returning tuple.

If you execute this code in Python 3:

def get():
    a = 3
    b = 5
    return a,b
number = get()

Output :

<class 'tuple'>
(3, 5)

But if you change the code line return [a,b] instead of return a,b and execute :

def get():
    a = 3
    b = 5
    return [a,b]
number = get()

Output :

<class 'list'>
[3, 5]

It is only returning single object which contains multiple values.

There is another alternative to return statement for returning multiple values, use yield( to check in details see this What does the "yield" keyword do in Python?)

Sample Example :

def get():
    for i in range(5):
        yield i
number = get()
for i in number:

Output :

<class 'generator'>
<generator object get at 0x7fbe5a1698b8>

Removing array item by value

w/o flip:

foreach ($items as $key => $value) {
    if ($id === $value) {

XDocument or XmlDocument

I believe that XDocument makes a lot more object creation calls. I suspect that for when you're handling a lot of XML documents, XMLDocument will be faster.

One place this happens is in managing scan data. Many scan tools output their data in XML (for obvious reasons). If you have to process a lot of these scan files, I think you'll have better performance with XMLDocument.

SQL Server String Concatenation with Null

This example will help you to handle various types while creating insert statements

'insert into doc(Id, CDate, Str, Code, Price, Tag )' + 
'values(' +
      '''' + convert(nvarchar(50), Id) + ''',' -- uniqueidentifier
    + '''' + LEFT(CONVERT(VARCHAR, CDate, 120), 10) + ''',' -- date
    + '''' + Str+ ''',' -- string
    + '''' + convert(nvarchar(50), Code)  + ''',' -- int
    + convert(nvarchar(50), Price) + ',' -- decimal
    + '''' + ISNULL(Tag, '''''') + '''' + ')'  -- nullable string

 from doc
 where CDate> '2019-01-01 00:00:00.000'

Soft keyboard open and close listener in an activity in Android

Piece of cake with the awesome KeyboardVisibilityEvent library

    new KeyboardVisibilityEventListener() {
        public void onVisibilityChanged(boolean isOpen) {
            // Ah... at last. do your thing :)

Credits for Yasuhiro SHIMIZU

summing two columns in a pandas dataframe

df['variance'] = df.loc[:,['budget','actual']].sum(axis=1)

Recursive search and replace in text files on Mac and Linux

The command on OSX should be exactly the same as it is Unix under the pretty UI.

jQuery Show-Hide DIV based on Checkbox Value

A tip to all people that use flat-red, flat-green plugin, because of this plugin the answers above wont work!

In that case, use onchange="do_your_stuff();" on the label, for example: Your checkbox here

The reason why it doesn't work is that this Jquery creates a lot of objects around the real checkbox, so you can't see if it's changed or not.

But if someone click straight on checkbox, won't work :'(

Add a border outside of a UIView (instead of inside)

Increase the width and height of view's frame with border width before adding the border:

float borderWidth = 2.0f
CGRect frame = self.frame;
frame.width += borderWidth;
frame.height += borderWidth;
 self.layer.borderColor = [UIColor yellowColor].CGColor;
 self.layer.borderWidth = 2.0f;

Git keeps prompting me for a password

I think you may have the wrong Git repository URL.

Open .git/config and find the [remote "origin"] section. Make sure you're using the SSH one:

ssh://[email protected]/username/repo.git

You can see the SSH URL in the main page of your repository if you click Clone or download and choose ssh.

And NOT the https or git one:

You can now validate with just the SSH key instead of the username and password.

If Git complains that 'origin' has already been added, open the .config file and edit the url = "..." part after [remote origin] as url = ssh://github/username/repo.git

The same goes for other services. Make sure the address looks like: protocol://something@url

E.g. .git/config for Azure DevOps:

[remote "origin"]
    url = https://[email protected]/mystore/myproject/
    fetch = +refs/heads/*:refs/remotes/origin/*

SQL ROWNUM how to return rows between a specific range

I know this is an old question, however, it is useful to mention the new features in the latest version.

From Oracle 12c onwards, you could use the new Top-n Row limiting feature. No need to write a subquery, no dependency on ROWNUM.

For example, the below query would return the employees between 4th highest till 7th highest salaries in ascending order:

SQL> SELECT empno, sal
  2  FROM   emp
  3  ORDER BY sal

     EMPNO        SAL
---------- ----------
      7654       1250
      7934       1300
      7844       1500
      7499       1600


Setting up FTP on Amazon Cloud Server

Thanks @clone45 for the nice solution. But I had just one important problem with Appendix b of his solution. Immediately after I changed the home directory to var/www/html then I couldn't connect to server through ssh and sftp because it always shows following errors

permission denied (public key)

or in FileZilla I received this error:

No supported authentication methods available (server: public key)

But I could access the server through normal FTP connection.

If you encountered to the same error then just undo the appendix b of @clone45 solution by set the default home directory for the user:

sudo usermod -d /home/username/ username

But when you set user's default home directory then the user have access to many other folders outside /var/www/http. So to secure your server then follow these steps:

1- Make sftponly group Make a group for all users you want to restrict their access to only ftp and sftp access to var/www/html. to make the group:

sudo groupadd sftponly

2- Jail the chroot To restrict access of this group to the server via sftp you must jail the chroot to not to let group's users to access any folder except html folder inside its home directory. to do this open /etc/ssh/sshd.config in the vim with sudo. At the end of the file please comment this line:

Subsystem sftp /usr/libexec/openssh/sftp-server

And then add this line below that:

Subsystem sftp internal-sftp

So we replaced subsystem with internal-sftp. Then add following lines below it:

 Match Group sftponly
        ChrootDirectory /var/www
        ForceCommand internal-sftp
        AllowTcpForwarding no

After adding this line I saved my changes and then restart ssh service by:

sudo service sshd restart

3- Add the user to sftponly group Any user you want to restrict their access must be a member of sftponly group. Therefore we join it to sftponly by: sudo usermod -G sftponly username

4- Restrict user access to just var/www/html To restrict user access to just var/www/html folder we need to make a directory in the home directory (with name of 'html') of that user and then mount /var/www to /home/username/html as follow:

sudo mkdir /home/username/html
sudo mount --bind /var/www /home/username/html

5- Set write access If the user needs write access to /var/www/html, then you must jail the user at /var/www which must have root:root ownership and permissions of 755. You then need to give /var/www/html ownership of root:sftponly and permissions of 775 by adding following lines:

sudo chmod 755 /var/www
sudo chown root:root /var/www
sudo chmod 775 /var/www/html
sudo chown root:www /var/www/html

6- Block shell access If you want restrict access to not access to shell to make it more secure then just change the default shell to bin/false as follow:

sudo usermod -s /bin/false username

Getting attributes of Enum's value

I implemented this extension method to get the description from enum values. It works for all kind of enums.

public static class EnumExtension
    public static string ToDescription(this System.Enum value)
        FieldInfo fi = value.GetType().GetField(value.ToString());
        var attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
        return attributes.Length > 0 ? attributes[0].Description : value.ToString();

What is web.xml file and what are all things can I do with it?

If using Struts, we disable direct access to the JSP files by using this tag in web.xml


Best place to insert the Google Analytics code

Google used to recommend putting it just before the </body> tag, because the original method they provided for loading ga.js was blocking. The newer async syntax, though, can safely be put in the head with minimal blockage, so the current recommendation is just before the </head> tag.

<head> will add a little latency; in the footer will reduce the number of pageviews recorded at some small margin. It's a tradeoff. ga.js is heavily cached and present on a large percentage of sites across the web, so its often served from the cache, reducing latency to almost nil.

As a matter of personal preference, I like to include it in the <head>, but its really a matter of preference.

Get bitcoin historical data

In case, you would like to collect bitstamp trade data form their websocket in higher resolution over longer time period you could use script below.

The script uses python websocket-client and pusher_client_python libraries, so install them.


import pusherclient
import time
import logging
import sys
import datetime
import signal
import os

log_file_fd = None

def sigint_and_sigterm_handler(signal, frame):
    global log_file_fd

class BitstampLogger:

    def __init__(self, log_file_path, log_file_reload_path, pusher_key, channel, event): = channel
        self.event = event
        self.log_file_fd = open(log_file_path, "a")
        self.log_file_reload_path = log_file_reload_path
        self.pusher = pusherclient.Pusher(pusher_key)
        self.pusher.connection.bind('pusher:connection_established', self.connect_handler)

    def callback(self, data):
        utc_timestamp = time.mktime(datetime.datetime.utcnow().timetuple())
        line = str(utc_timestamp) + " " + data + "\n"
        if os.path.exists(self.log_file_reload_path):
            self.log_file_fd = open(log_file_path, "a")

    def connect_handler(self, data):
        channel = self.pusher.subscribe(
        channel.bind(self.event, self.callback)

def main(log_file_path, log_file_reload_path):
    global log_file_fd
    bitstamp_logger = BitstampLogger(
    log_file_fd = bitstamp_logger.log_file_fd
    signal.signal(signal.SIGINT, sigint_and_sigterm_handler)
    signal.signal(signal.SIGTERM, sigint_and_sigterm_handler)
    while True:

if __name__ == '__main__':
    log_file_path = sys.argv[1]
    log_file_reload_path = sys.argv[2]
    main(log_file_path, log_file_reload_path

and logrotate file config

    rotate 10000000000
    minsize 10M
        touch /mnt/data/bitstamp_logs/reload_log > /dev/null

then you can run it on background

nohup ./ /mnt/data/bitstamp_logs/bitstamp-trade.log /mnt/data/bitstamp_logs/reload_log &

Converting dd/mm/yyyy formatted string to Datetime

You can use "dd/MM/yyyy" format for using it in DateTime.ParseExact.

Converts the specified string representation of a date and time to its DateTime equivalent using the specified format and culture-specific format information. The format of the string representation must match the specified format exactly.

DateTime date = DateTime.ParseExact("24/01/2013", "dd/MM/yyyy", CultureInfo.InvariantCulture);

Here is a DEMO.

For more informations, check out Custom Date and Time Format Strings

Get Unix timestamp with C++

C++20 introduced a guarantee that time_since_epoch is relative to the UNIX epoch, and gives an example that I've distilled to the relevant code, and changed to units of seconds rather than hours:

#include <iostream>
#include <chrono>
int main()
    const auto p1 = std::chrono::system_clock::now();
    std::cout << "seconds since epoch: "
              << std::chrono::duration_cast<std::chrono::seconds>(
                   p1.time_since_epoch()).count() << '\n';

Using C++17 or earlier, time() is the simplest function - seconds since Epoch, which for Linux and UNIX at least would be the UNIX epoch. Linux manpage here.

The cppreference page linked above gives this example:

#include <ctime>
#include <iostream>
int main()
    std::time_t result = std::time(nullptr);
    std::cout << std::asctime(std::localtime(&result))
              << result << " seconds since the Epoch\n";

How to use an output parameter in Java?

Thank you. I use passing in an object as a parameter. My Android code is below

    String oPerson= null;
    if (CheckAddress("5556", oPerson))
                "It's Match! " + oPerson,                   

    private boolean CheckAddress(String iAddress, String oPerson)
    Cursor cAddress = mDbHelper.getAllContacts();
    String address = "";        
    if (cAddress.getCount() > 0) {
        while (cAddress.isAfterLast() == false) {
            address = cAddress.getString(2).toString();
            oPerson = cAddress.getString(1).toString(); 
            if(iAddress.indexOf(address) != -1)
                        "Person : " + oPerson,                  
                return true;                    
            else cAddress.moveToNext();
    return false;

The result is

Person : John

It's Match! null

Actually, "It's Match! John"

Please check my mistake.

How to "flatten" a multi-dimensional array to simple one in PHP?

function flatten_array($array, $preserve_keys = 0, &$out = array()) {
    # Flatten a multidimensional array to one dimension, optionally preserving keys.
    # $array - the array to flatten
    # $preserve_keys - 0 (default) to not preserve keys, 1 to preserve string keys only, 2 to preserve all keys
    # $out - internal use argument for recursion
    foreach($array as $key => $child)
            $out = flatten_array($child, $preserve_keys, $out);
        elseif($preserve_keys + is_string($key) > 1)
            $out[$key] = $child;
            $out[] = $child;
    return $out;

jQuery - Click event on <tr> elements with in a table and getting <td> element values

Try jQuery's delegate() function, like so:

    $("div.custList table").delegate('tr', 'click', function() {
        alert("You clicked my <tr>!");
        //get <td> element values here!!??

A delegate works in the same way as live() except that live() cannot be applied to chained items, whereas delegate() allows you to specify an element within an element to act on.

How to find all trigger associated with a table with SQL Server?

find triggers on table:

select, text
from sysobjects so, syscomments sc
where type = 'TR'
and =
and text like '%TableName%'

and you can find store procedure which has reference of table:

FROM sys.procedures

Use -notlike to filter out multiple strings in PowerShell

In order to support "matches any of ..." scenarios, I created a function that is pretty easy to read. My version has a lot more to it because its a PowerShell 2.0 cmdlet but the version I'm pasting below should work in 1.0 and has no frills.

You call it like so:

Get-Process | Where-Match Company -Like '*VMWare*','*Microsoft*'
Get-Process | Where-Match Company -Regex '^Microsoft.*'

filter Where-Match($Selector,[String[]]$Like,[String[]]$Regex) {

    if ($Selector -is [String]) { $Value = $_.$Selector }
    elseif ($Selector -is [ScriptBlock]) { $Value = &$Selector }
    else { throw 'Selector must be a ScriptBlock or property name' }

    if ($Like.Length) {
        foreach ($Pattern in $Like) {
            if ($Value -like $Pattern) { return $_ }

    if ($Regex.Length) {
        foreach ($Pattern in $Regex) {
            if ($Value -match $Pattern) { return $_ }


filter Where-NotMatch($Selector,[String[]]$Like,[String[]]$Regex) {

    if ($Selector -is [String]) { $Value = $_.$Selector }
    elseif ($Selector -is [ScriptBlock]) { $Value = &$Selector }
    else { throw 'Selector must be a ScriptBlock or property name' }

    if ($Like.Length) {
        foreach ($Pattern in $Like) {
            if ($Value -like $Pattern) { return }

    if ($Regex.Length) {
        foreach ($Pattern in $Regex) {
            if ($Value -match $Pattern) { return }

    return $_


C# ASP.NET MVC Return to Previous Page

For ASP.NET Core You can use asp-route-* attribute:

<form asp-action="Login" asp-route-previous="@Model.ReturnUrl">

An example: Imagine that you have a Vehicle Controller with actions




and you can edit any vehicle from Index or from Details, so if you clicked edit from index you must return to index after edit and if you clicked edit from details you must return to details after edit.

//In your viewmodel add the ReturnUrl Property
public class VehicleViewModel
     public string ReturnUrl {get;set;}

<a asp-action="Edit" asp-route-previous="Details" asp-route-id="@Model.CarId">Edit</a>

<a asp-action="Edit" asp-route-previous="Index" asp-route-id="@item.CarId">Edit</a>

<form asp-action="Edit" asp-route-previous="@Model.ReturnUrl" class="form-horizontal">
        <div class="box-footer">
            <a asp-action="@Model.ReturnUrl" class="btn btn-default">Back to List</a>
            <button type="submit" value="Save" class="btn btn-warning pull-right">Save</button>

In your controller:

// GET: Vehicle/Edit/5
    public ActionResult Edit(int id,string previous)
            var model = this.UnitOfWork.CarsRepository.GetAllByCarId(id).FirstOrDefault();
            var viewModel = this.Mapper.Map<VehicleViewModel>(model);//if you using automapper
    //or by this code if you are not use automapper
    var viewModel = new VehicleViewModel();

    if (!string.IsNullOrWhiteSpace(previous)
                viewModel.ReturnUrl = previous;
                viewModel.ReturnUrl = "Index";
            return View(viewModel);

    public IActionResult Edit(VehicleViewModel model, string previous)
            if (!string.IsNullOrWhiteSpace(previous))
                model.ReturnUrl = previous;
                model.ReturnUrl = "Index";
            return RedirectToAction(model.ReturnUrl);

What is the difference between a pandas Series and a single-column DataFrame?

Series is a one-dimensional object that can hold any data type such as integers, floats and strings e.g

   import pandas as pd
   x = pd.Series([A,B,C]) 

0 A
1 B
2 C

The first column of Series is known as index i.e 0,1,2 the second column is your actual data i.e A,B,C

DataFrames is two-dimensional object that can hold series, list, dictionary


How to make a link open multiple pages when clicked

I did it in a simple way:

    <a href="" onclick="'');
return true;">multiopen</a>

It'll open runningrss in a new window and virtual-doctor in same window.

java.lang.NoClassDefFoundError:failed resolution of :Lorg/apache/http/ProtocolVersion

If you are using or below and your app is targeting API level 28 (Android 9.0) or above, you must include the following declaration within the element of AndroidManifest.xml.

      android:required="false" />

This is handled for you if you are using and is not necessary if your app is targeting a lower API level.

Convert interface{} to int

You need to do type assertion for converting your interface{} to int value.

iAreaId := val.(int)
iAreaId, ok := val.(int)

More information is available.

Eclipse DDMS error "Can't bind to local 8600 for debugger"

On Windows 8 I was batteling with this for some time:
do you have AVG installed? uninstalling AVG did the trick for me

How to make a div have a fixed size?

Thats the natural behavior of the buttons. You could try putting a max-width/max-height on the parent container, but I'm not sure if that would do it.

max-width:something px;
max-height:something px;

The other option would be to use the devlopr tools and see if you can remove the natural padding.

padding: 0;

How to change the status bar color in Android?

Android 5.0 Lollipop introduced Material Design theme which automatically colors the status bar based on the colorPrimaryDark value of the theme.

This is supported on device pre-lollipop thanks to the library support-v7-appcompat starting from version 21. Blogpost about support appcompat v21 from Chris Banes

enter image description here

Read more about the Material Theme on the official Android Developers website

Why does the Google Play store say my Android app is incompatible with my own device?

I have a couple of suggestions:

  1. First of all, you seem to be using API 4 as your target. AFAIK, it's good practice to always compile against the latest SDK and setup your android:minSdkVersion accordingly.

  2. With that in mind, remember that android:required attribute was added in API 5:

The feature declaration can include an android:required=["true" | "false"] attribute (if you are compiling against API level 5 or higher), which lets you specify whether the application (...)

Thus, I'd suggest that you compile against SDK 15, set targetSdkVersion to 15 as well, and provide that functionality.

It also shows here, on the Play site, as incompatible with any device that I have that is (coincidence?) Gingerbread (Galaxy Ace and Galaxy Y here). But it shows as compatible with my Galaxy Tab 10.1 (Honeycomb), Nexus S and Galaxy Nexus (both on ICS).

That also left me wondering, and this is a very wild guess, but since android.hardware.faketouch is API11+, why don't you try removing it just to see if it works? Or perhaps that's all related anyway, since you're trying to use features (faketouch) and the required attribute that are not available in API 4. And in this case you should compile against the latest API.

I would try that first, and remove the faketouch requirement only as last resort (of course) --- since it works when developing, I'd say it's just a matter of the compiled app not recognizing the feature (due to the SDK requirements), thus leaving unexpected filtering issues on Play.

Sorry if this guess doesn't answer your question, but it's very difficult to diagnose those kind of problems and pinpoint the solution without actually testing. Or at least for me without all the proper knowledge of how Play really filters apps.

Good luck.

How to change Apache Tomcat web server port number

Simple !!... you can do it easily via server.xml

  • Go to tomcat>conf folder
  • Edit server.xml
  • Search "Connector port"
  • Replace "8080" by your port number
  • Restart tomcat server.

You are done!.

How can I do an OrderBy with a dynamic string parameter?

If you are using plain LINQ-to-objects and don't want to take a dependency on an external library it is not hard to achieve what you want.

The OrderBy() clause accepts a Func<TSource, TKey> that gets a sort key from a source element. You can define the function outside the OrderBy() clause:

Func<Item, Object> orderByFunc = null;

You can then assign it to different values depending on the sort criteria:

if (sortOrder == SortOrder.SortByName)
  orderByFunc = item => item.Name;
else if (sortOrder == SortOrder.SortByRank)
  orderByFunc = item => item.Rank;

Then you can sort:

var sortedItems = items.OrderBy(orderByFunc);

This example assumes that the source type is Item that have properties Name and Rank.

Note that in this example TKey is Object to not constrain the property types that can be sorted on. If the func returns a value type (like Int32) it will get boxed when sorting and that is somewhat inefficient. If you can constrain TKey to a specific value type you can work around this problem.

Android: How to change the ActionBar "Home" Icon to be something other than the app icon?

In AndroidManifest.xml:


In styles.xml: (See android:icon)

<style name="Theme" parent="@android:style/Theme.Holo.Light">
    <item name="android:actionBarStyle">@style/ActionBar</item>
<style name="ActionBar" parent="@android:style/Widget.Holo.Light.ActionBar">
    <item name="android:icon">@drawable/icon</item>

Why do we not have a virtual constructor in C++?

C++ virtual constructor is not possible.For example you can not mark a constructor as virtual.Try this code

using namespace std;
class aClass
        virtual aClass()
int main()
    aClass a; 

It causes an error.This code is trying to declare a constructor as virtual. Now let us try to understand why we use virtual keyword. Virtual keyword is used to provide run time polymorphism. For example try this code.

using namespace std;
class aClass
            cout<<"aClass contructor\n";
            cout<<"aClass destructor\n";

class anotherClass:public aClass

            cout<<"anotherClass Constructor\n";
            cout<<"anotherClass destructor\n";

int main()
    aClass* a;
    a=new anotherClass;
    delete a;   

In main a=new anotherClass; allocates a memory for anotherClass in a pointer a declared as type of aClass.This causes both the constructor (In aClass and anotherClass) to call automatically.So we do not need to mark constructor as virtual.Because when an object is created it must follow the chain of creation (i.e first the base and then the derived classes). But when we try to delete a delete a; it causes to call only the base destructor.So we have to handle the destructor using virtual keyword. So virtual constructor is not possible but virtual destructor is.Thanks

Error message: (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe.)

You should enable the Server authentication mode to mixed mode as following: In SQL Studio, select YourServer -> Property -> Security -> Select SqlServer and Window Authentication mode.

C: socket connection timeout

This article might help:

Connect with timeout (or another use for select() )

Looks like you put the socket into non-blocking mode until you've connected, and then put it back into blocking mode once the connection's established.

void connect_w_to(void) { 
  int res; 
  struct sockaddr_in addr; 
  long arg; 
  fd_set myset; 
  struct timeval tv; 
  int valopt; 
  socklen_t lon; 

  // Create socket 
  soc = socket(AF_INET, SOCK_STREAM, 0); 
  if (soc < 0) { 
     fprintf(stderr, "Error creating socket (%d %s)\n", errno, strerror(errno)); 

  addr.sin_family = AF_INET; 
  addr.sin_port = htons(2000); 
  addr.sin_addr.s_addr = inet_addr(""); 

  // Set non-blocking 
  if( (arg = fcntl(soc, F_GETFL, NULL)) < 0) { 
     fprintf(stderr, "Error fcntl(..., F_GETFL) (%s)\n", strerror(errno)); 
  arg |= O_NONBLOCK; 
  if( fcntl(soc, F_SETFL, arg) < 0) { 
     fprintf(stderr, "Error fcntl(..., F_SETFL) (%s)\n", strerror(errno)); 
  // Trying to connect with timeout 
  res = connect(soc, (struct sockaddr *)&addr, sizeof(addr)); 
  if (res < 0) { 
     if (errno == EINPROGRESS) { 
        fprintf(stderr, "EINPROGRESS in connect() - selecting\n"); 
        do { 
           tv.tv_sec = 15; 
           tv.tv_usec = 0; 
           FD_SET(soc, &myset); 
           res = select(soc+1, NULL, &myset, NULL, &tv); 
           if (res < 0 && errno != EINTR) { 
              fprintf(stderr, "Error connecting %d - %s\n", errno, strerror(errno)); 
           else if (res > 0) { 
              // Socket selected for write 
              lon = sizeof(int); 
              if (getsockopt(soc, SOL_SOCKET, SO_ERROR, (void*)(&valopt), &lon) < 0) { 
                 fprintf(stderr, "Error in getsockopt() %d - %s\n", errno, strerror(errno)); 
              // Check the value returned... 
              if (valopt) { 
                 fprintf(stderr, "Error in delayed connection() %d - %s\n", valopt, strerror(valopt) 
           else { 
              fprintf(stderr, "Timeout in select() - Cancelling!\n"); 
        } while (1); 
     else { 
        fprintf(stderr, "Error connecting %d - %s\n", errno, strerror(errno)); 
  // Set to blocking mode again... 
  if( (arg = fcntl(soc, F_GETFL, NULL)) < 0) { 
     fprintf(stderr, "Error fcntl(..., F_GETFL) (%s)\n", strerror(errno)); 
  arg &= (~O_NONBLOCK); 
  if( fcntl(soc, F_SETFL, arg) < 0) { 
     fprintf(stderr, "Error fcntl(..., F_SETFL) (%s)\n", strerror(errno)); 
  // I hope that is all 

Android: How do bluetooth UUIDs work?

The UUID stands for Universally Unique Identifier. UUID is an simple 128 bit digit which uniquely distributed across the world.

Bluetooth sends data over air and all nearby device can receive it. Let's suppose, sometimes you have to send some important files via Bluetooth and all near by devices can access it in range. So when you pair with the other devices, they simply share the UUID number and match before sharing the files. When you send any file then your device encrypt that file with appropriate device UUID and share over the network. Now all Bluetooth devices in the range can access the encrypt file but they required right UUID number. So Only right UUID devices have access to encrypt the file and others will reject cause of wrong UUID.

In short, you can use UUID as a secret password for sharing files between any two Bluetooth devices.

How do I fix a merge conflict due to removal of a file in a branch?

If you are using Git Gui on windows,

  1. Abort the merge
  2. Make sure you are on your target branch
  3. Delete the conflicting file from explorer
  4. Rescan for changes in Git Gui (F5)
  5. Notice that conflicting file is deleted
  6. Select Stage Changed Files To Commit (Ctrl-I) from Commit menu
  7. Enter a commit comment like "deleted conflicting file"
  8. Commit (ctrl-enter)
  9. Now if you restart the merge it will (hopefully) work.

How to generate JAXB classes from XSD?

1) You can use standard java utility xjc - ([your java home dir]\bin\xjc.exe). But you need to create .bat (or .sh) script for using it.

e.g. generate.bat:

[your java home dir]\bin\xjc.exe %1 %2 %3

e.g. test-scheme.xsd:

<?xml version="1.0"?>
<xs:schema version="1.0"
    <xs:element name="employee" type="PersonInfoType"/>

    <xs:complexType name="PersonInfoType">
            <xs:element name="firstname" type="xs:string"/>
            <xs:element name="lastname" type="xs:string"/>

Run .bat file with parameters: generate.bat test-scheme.xsd -d [your src dir]

For more info use this documentation -

and this -

2) JAXB (xjc utility) is installed together with JDK6 by default.

How to set up gradle and android studio to do release build?

To activate the installRelease task, you simply need a signingConfig. That is all.


Finally, the plugin creates install/uninstall tasks for all build types (debug, release, test), as long as they can be installed (which requires signing).

Here is what you want:

Install tasks
installDebug - Installs the Debug build
installDebugTest - Installs the Test build for the Debug build
installRelease - Installs the Release build
uninstallAll - Uninstall all applications.
uninstallDebug - Uninstalls the Debug build
uninstallDebugTest - Uninstalls the Test build for the Debug build
uninstallRelease - Uninstalls the Release build   <--- release

Here is how to obtain the installRelease task:

Example build.gradle:

buildscript {
    repositories {

    dependencies {
        classpath ''

apply plugin: ''

android {
  compileSdkVersion 22
  buildToolsVersion '22.0.1'

  defaultConfig {
    applicationId 'demo'
    minSdkVersion 15
    targetSdkVersion 22
    versionCode 1
    versionName '1.0'

  signingConfigs {
      release {
          storeFile <file>
          storePassword <password>
          keyAlias <alias>
          keyPassword <password>

  buildTypes {
    release {
        signingConfig signingConfigs.release