Programs & Examples On #Database migration

database-migration is the process of transferring data between storage types, formats, or computer systems. Also refers to migrating the database from one vendor to another, or to upgrading the version of the database software.

How do I enable EF migrations for multiple contexts to separate databases?

If more databases exist use following codes in PowerShell

Add-Migration Starter -context EnrollmentAppContext 
  • 'Starter' is Migration Name

  • 'EnrollmentAppContext' is name of my app Context

You can open PowerShell in VS by doing: Tools->NuGet Package Manager->Package Manager Console

How to export SQL Server database to MySQL?

You can use MySQL Workbench which provides a way to quickly migrate data and applications from Microsoft SQL Server to MySQL employing less time and effort.

This tool has a lot of cool features like:

  • Database migrations - enables migrations from Microsoft SQL Server, Sybase ASE and PostgreSQL.
  • Migration project management - allows migrations to be configured, copied, edited, executed and scheduled.

Read more

Rollback one specific migration in Laravel

better to used refresh migrate

You may rollback & re-migrate a limited number of migrations by providing the step option to the refresh command. For example, the following command will rollback & re-migrate the last two migrations:

php artisan migrate:refresh --step=2

otherwise used rollback migrate

You may rollback a limited number of migrations by providing the step option to the rollback command. For example, the following command will rollback the last three migrations:

php artisan migrate:rollback --step=3

for more detail about migration see

EF Migrations: Rollback last applied migration?

I realised there aren't any good solutions utilizing the CLI dotnet command so here's one:

dotnet ef migrations list
dotnet ef database update NameOfYourMigration

In the place of NameOfYourMigration enter the name of the migration you want to revert to.

How do I move a redis database from one server to another?

redis-dump finally worked for me. Its documentation provides an example how to dump a Redis database and insert the data into another one.

How do I copy SQL Azure database to my local development server?

Use the Import/Export service in SQL Azure to create a .bacpac file.

Then take a look at this method in another Stack Overflow article.

Azure SQL Database Bacpac Local Restore

Access denied for user 'homestead'@'localhost' (using password: YES)

If you have an error returning something like PDOException in Connector.php line 55: SQLSTATE[HY000] [1049] Unknown database 'laravelu' is due to you are changing your batabase config as DB_DATABASE=laravelu. So for now you either:

  1. Change the DB_DATABASE=[yourdatabase] or
  2. create a database called laravelu in your phpmyadmin

this should be able to solve it

Reset Entity-Framework Migrations

Delete the Migrations Folder, Clean then Rebuild the project. This worked for me. Before Clean and Rebuild it was saying the Migration already exists since in its cached memory, it's not yet deleted.

How to add soap header in java

Maven dependency


Configuration class


public class ConfigurationClass{

public Wss4jSecurityInterceptor securityInterceptor() {
    Wss4jSecurityInterceptor wss4jSecurityInterceptor = new Wss4jSecurityInterceptor();
    return wss4jSecurityInterceptor;

Result xml

<SOAP-ENV:Envelope xmlns:SOAP-ENV="">
        <wsse:UsernameToken wsu:Id="UsernameToken-F57F40DC89CD6998E214700450735811">
            <wsse:Password Type="">TestPass123</wsse:Password>

How to know user has clicked "X" or the "Close" button?

if (this.DialogResult == DialogResult.Cancel)

            switch (e.CloseReason)
                case CloseReason.UserClosing:
                    e.Cancel = true;

if condition will execute when user clicks 'X' or close button on form. The else can be used when user clicks Alt+f4 for any other purpose

Get current value selected in dropdown using jQuery

To get the value of a drop-down (select) element, just use val().

$('._someDropDown').live('change', function(e) {

If you want to the text of the selected option, using this:

$('._someDropDown').live('change', function(e) {
  alert($('[value=' + $(this).val() + ']', this).text());

Checking for NULL pointer in C/C++

  • Pointers are not booleans
  • Modern C/C++ compilers emit a warning when you write if (foo = bar) by accident.

Therefore I prefer

if (foo == NULL)
    // null case
    // non null case


if (foo != NULL)
    // non null case
    // null case

However, if I were writing a set of style guidelines I would not be putting things like this in it, I would be putting things like:

Make sure you do a null check on the pointer.

JavaScript ES6 promise for loop

As you already hinted in your question, your code creates all promises synchronously. Instead they should only be created at the time the preceding one resolves.

Secondly, each promise that is created with new Promise needs to be resolved with a call to resolve (or reject). This should be done when the timer expires. That will trigger any then callback you would have on that promise. And such a then callback (or await) is a necessity in order to implement the chain.

With those ingredients, there are several ways to perform this asynchronous chaining:

  1. With a for loop that starts with an immediately resolving promise

  2. With Array#reduce that starts with an immediately resolving promise

  3. With a function that passes itself as resolution callback

  4. With ECMAScript2017's async / await syntax

  5. With ECMAScript2020's for await...of syntax

See a snippet and comments for each of these options below.

1. With for

You can use a for loop, but you must make sure it doesn't execute new Promise synchronously. Instead you create an initial immediately resolving promise, and then chain new promises as the previous ones resolve:

for (let i = 0, p = Promise.resolve(); i < 10; i++) {
    p = p.then(_ => new Promise(resolve =>
        setTimeout(function () {
        }, Math.random() * 1000)

2. With reduce

This is just a more functional approach to the previous strategy. You create an array with the same length as the chain you want to execute, and start out with an immediately resolving promise:

[...Array(10)].reduce( (p, _, i) => 
    p.then(_ => new Promise(resolve =>
        setTimeout(function () {
        }, Math.random() * 1000)
, Promise.resolve() );

This is probably more useful when you actually have an array with data to be used in the promises.

3. With a function passing itself as resolution-callback

Here we create a function and call it immediately. It creates the first promise synchronously. When it resolves, the function is called again:

(function loop(i) {
    if (i < 10) new Promise((resolve, reject) => {
        setTimeout( () => {
        }, Math.random() * 1000);
    }).then(loop.bind(null, i+1));

This creates a function named loop, and at the very end of the code you can see it gets called immediately with argument 0. This is the counter, and the i argument. The function will create a new promise if that counter is still below 10, otherwise the chaining stops.

The call to resolve() will trigger the then callback which will call the function again. loop.bind(null, i+1) is just a different way of saying _ => loop(i+1).

4. With async/await

Modern JS engines support this syntax:

(async function loop() {
    for (let i = 0; i < 10; i++) {
        await new Promise(resolve => setTimeout(resolve, Math.random() * 1000));

It may look strange, as it seems like the new Promise() calls are executed synchronously, but in reality the async function returns when it executes the first await. Every time an awaited promise resolves, the function's running context is restored, and proceeds after the await, until it encounters the next one, and so it continues until the loop finishes.

As it may be a common thing to return a promise based on a timeout, you could create a separate function for generating such a promise. This is called promisifying a function, in this case setTimeout. It may improve the readability of the code:

const delay = ms => new Promise(resolve => setTimeout(resolve, ms));

(async function loop() {
    for (let i = 0; i < 10; i++) {
        await delay(Math.random() * 1000);

5. With for await...of

With EcmaScript 2020, the for await...of found its way to modern JavaScript engines. Although it does not really reduce code in this case, it allows to isolate the definition of the random interval chain from the actual iteration of it:

const delay = ms => new Promise(resolve => setTimeout(resolve, ms));
async function * randomDelays(count ,max) {
    for (let i = 0; i < count; i++) yield delay(Math.random() * max).then(() => i);

(async function loop() {
    for await (let i of randomDelays(10, 1000)) console.log(i);

SQL LEFT JOIN Subquery Alias

You didn't select post_id in the subquery. You have to select it in the subquery like this:

SELECT wp_woocommerce_order_items.order_id As No_Commande
FROM  wp_woocommerce_order_items
        SELECT meta_value As Prenom, post_id  -- <----- this
        FROM wp_postmeta
        WHERE meta_key = '_shipping_first_name'
    ) AS a
ON wp_woocommerce_order_items.order_id = a.post_id
WHERE  wp_woocommerce_order_items.order_id =2198 

How to check if input is numeric in C++

When cin gets input it can't use, it sets failbit:

int n;
cin >> n;
if(!cin) // or if(
    // user didn't input a number
    cin.clear(); // reset failbit
    cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); //skip bad input
    // next, request user reinput

When cin's failbit is set, use cin.clear() to reset the state of the stream, then cin.ignore() to expunge the remaining input, and then request that the user re-input. The stream will misbehave so long as the failure state is set and the stream contains bad input.

What is the --save option for npm install?

Update npm 5:

As of npm 5.0.0, installed modules are added as a dependency by default, so the --save option is no longer needed. The other save options still exist and are listed in the documentation for npm install.

Original answer:

Before version 5, NPM simply installed a package under node_modules by default. When you were trying to install dependencies for your app/module, you would need to first install them, and then add them (along with the appropriate version number) to the dependencies section of your package.json.

The --save option instructed NPM to include the package inside of the dependencies section of your package.json automatically, thus saving you an additional step.

In addition, there are the complementary options --save-dev and --save-optional which save the package under devDependencies and optionalDependencies, respectively. This is useful when installing development-only packages, like grunt or your testing library.

Free ASP.Net and/or CSS Themes

I have used Open source Web Design in the past. They have quite a few css themes, don't know about ASP.Net

No matching client found for package name (Google Analytics) - multiple productFlavors & buildTypes

Check your package name on your google-services.json it should be same with your local package name of your app


"client_info": {
    "mobilesdk_app_id": "1:6596814400689:android:65d6f25f5006145",
    "android_client_info": {
      "package_name": ""

In this case my local package name is so also i have changed my package name in google-services.json with my local package name

Get specific ArrayList item

We print the value using mainList.get(index) where index starts with '0'. For Example: mainList.get(2) prints the 3rd element in the list.

jQuery find file extension (from string)

Yet another way to write it up:

function getExtension(filename) {
    return filename.split('.').pop().toLowerCase();

function openFile(file) { 
    switch(getExtension(file)) {
        //if .jpg/.gif/.png do something
        case 'jpg': case 'gif': case 'png':
            /* handle */
        //if .zip/.rar do something else
        case 'zip': case 'rar':
            /* handle */

        //if .pdf do something else
        case 'pdf':
            /* handle */

What is a Java String's default initial value?

The answer is - it depends.

Is the variable an instance variable / class variable ? See this for more details.

The list of default values can be found here.

What ports need to be open for TortoiseSVN to authenticate (clear text) and commit?

What's the first part of your Subversion repository URL?

  • If your URL looks like: http://subversion/repos/, then you're probably going over Port 80.
  • If your URL looks like: https://subversion/repos/, then you're probably going over Port 443.
  • If your URL looks like: svn://subversion/, then you're probably going over Port 3690.
  • If your URL looks like: svn+ssh://subversion/repos/, then you're probably going over Port 22.
  • If your URL contains a port number like: http://subversion/repos:8080, then you're using that port.

I can't guarantee the first four since it's possible to reconfigure everything to use different ports, of if you go through a proxy of some sort.

If you're using a VPN, you may have to configure your VPN client to reroute these to their correct ports. A lot of places don't configure their correctly VPNs to do this type of proxying. It's either because they have some sort of anal-retentive IT person who's being overly security conscious, or because they simply don't know any better. Even worse, they'll give you a client where this stuff can't be reconfigured.

The only way around that is to log into a local machine over the VPN, and then do everything from that system.

Embed Youtube video inside an Android app

there is an official YouTube Android Player API wich you can use. This is a bit more complicated but it is working better than other solutions using webclients.

First you must register your app in Googles API Console. This is completely free until your app gets over 25k request a month (or something like that). There are complete anf great tutorials under the link. I hope you can understand them. If not, ask! :)

Pandas percentage of total with groupby

As someone who is also learning pandas I found the other answers a bit implicit as pandas hides most of the work behind the scenes. Namely in how the operation works by automatically matching up column and index names. This code should be equivalent to a step by step version of @exp1orer's accepted answer

With the df, I'll call it by the alias state_office_sales:

state office_id        
AZ    2          839507
      4          373917
      6          347225
CA    1          798585
      3          890850
      5          454423
CO    1          819975
      3          202969
      5          614011
WA    2          163942
      4          369858
      6          959285

state_total_sales is state_office_sales grouped by total sums in index level 0 (leftmost).

In:   state_total_sales = df.groupby(level=0).sum()

AZ     2448009
CA     2832270
CO     1495486
WA     595859

Because the two dataframes share an index-name and a column-name pandas will find the appropriate locations through shared indexes like:

In:   state_office_sales / state_total_sales


state   office_id   
AZ      2          0.448640
        4          0.125865
        6          0.425496
CA      1          0.288022
        3          0.322169
        5          0.389809
CO      1          0.206684
        3          0.357891
        5          0.435425
WA      2          0.321689
        4          0.346325
        6          0.331986

To illustrate this even better, here is a partial total with a XX that has no equivalent. Pandas will match the location based on index and column names, where there is no overlap pandas will ignore it:

In:   partial_total = pd.DataFrame(
                      data   =  {'sales' : [2448009, 595859, 99999]},
                      index  =             ['AZ',    'WA',   'XX' ]
                      ) = 'state'

AZ       2448009
WA       595859
XX       99999
In:   state_office_sales / partial_total

state   office_id   
AZ      2          0.448640
        4          0.125865
        6          0.425496
CA      1          NaN
        3          NaN
        5          NaN
CO      1          NaN
        3          NaN
        5          NaN
WA      2          0.321689
        4          0.346325
        6          0.331986

This becomes very clear when there are no shared indexes or columns. Here missing_index_totals is equal to state_total_sales except that it has a no index-name.

In:   missing_index_totals = state_total_sales.rename_axis("")

AZ     2448009
CA     2832270
CO     1495486
WA     595859
In:   state_office_sales / missing_index_totals 

Out:  ValueError: cannot join with no overlapping index names

CodeIgniter 500 Internal Server Error

Just in case somebody else stumbles across this problem, I inherited an older CodeIgniter project and had a lot of trouble getting it to install.

I wasted a ton of time trying to create a local installation of the site and tried everything. In the end, the solution was simple.

The problem is that older CodeIgniter versions (like 1.7 and below), don't work with PHP 5.3. The solution is to switch to PHP 5.2 or something older.

How do I add a foreign key to an existing SQLite table?

You can't.

Although the SQL-92 syntax to add a foreign key to your table would be as follows:

ALTER TABLE child ADD CONSTRAINT fk_child_parent
                  FOREIGN KEY (parent_id) 
                  REFERENCES parent(id);

SQLite doesn't support the ADD CONSTRAINT variant of the ALTER TABLE command ( SQL Features That SQLite Does Not Implement).

Therefore, the only way to add a foreign key in sqlite 3.6.1 is during CREATE TABLE as follows:

    id           INTEGER PRIMARY KEY, 
    parent_id    INTEGER, 
    description  TEXT,
    FOREIGN KEY (parent_id) REFERENCES parent(id)

Unfortunately you will have to save the existing data to a temporary table, drop the old table, create the new table with the FK constraint, then copy the data back in from the temporary table. ( - FAQ: Q11)

Append values to query string

The end to all URL query string editing woes

After lots of toil and fiddling with the Uri class, and other solutions, here're my string extension methods to solve my problems.

using System;
using System.Collections.Specialized;
using System.Linq;
using System.Web;

public static class StringExtensions
    public static string AddToQueryString(this string url, params object[] keysAndValues)
        return UpdateQueryString(url, q =>
            for (var i = 0; i < keysAndValues.Length; i += 2)
                q.Set(keysAndValues[i].ToString(), keysAndValues[i + 1].ToString());

    public static string RemoveFromQueryString(this string url, params string[] keys)
        return UpdateQueryString(url, q =>
            foreach (var key in keys)

    public static string UpdateQueryString(string url, Action<NameValueCollection> func)
        var urlWithoutQueryString = url.Contains('?') ? url.Substring(0, url.IndexOf('?')) : url;
        var queryString = url.Contains('?') ? url.Substring(url.IndexOf('?')) : null;
        var query = HttpUtility.ParseQueryString(queryString ?? string.Empty);


        return urlWithoutQueryString + (query.Count > 0 ? "?" : string.Empty) + query;

How to set a timer in android

As I have seen it, java.util.Timer is the most used for implementing a timer.

For a repeating task:

new Timer().scheduleAtFixedRate(task, after, interval);

For a single run of a task:

new Timer().schedule(task, after);

task being the method to be executed
after the time to initial execution
(interval the time for repeating the execution)

Bootstrap push div content to new line

Do a row div.

Like this:

<link href="" rel="stylesheet" integrity="sha384-Zug+QiDoJOrZ5t4lssLdxGhVrurbmBWopoEl+M6BdEfwnCJZtKxi1KgxUyJq13dy" crossorigin="anonymous">_x000D_
<div class="grid">_x000D_
    <div class="row">_x000D_
        <div class="col-lg-3 col-md-3 col-sm-3 col-xs-12 bg-success">Under me should be a DIV</div>_x000D_
        <div class="col-lg-6 col-md-6 col-sm-5 col-xs-12 bg-danger">Under me should be a DIV</div>_x000D_
    <div class="row">_x000D_
        <div class="col-lg-3 col-md-3 col-sm-4 col-xs-12 bg-warning">I am the last DIV</div>_x000D_

WPF What is the correct way of using SVG files as icons in WPF

Another alternative is dotnetprojects SVGImage

This allows native use of .svg files directly in xaml.

The nice part is, it is only one assembly which is about 100k. In comparision to sharpvectors which is much bigger any many files.


<svg1:SVGImage Name="mySVGImage" Source="/MyDemoApp;component/Resources/MyImage.svg"/>

That's all.


How to count duplicate value in an array in javascript

You can solve it without using any for/while loops ou forEach.

function myCounter(inputWords) {        
    return inputWords.reduce( (countWords, word) => {
        countWords[word] = ++countWords[word] || 1;
        return countWords;
    }, {});

Hope it helps you!

If/else else if in Jquery for a condition

See this answer. val() is comparing a string, not a numeric value.

How to pass in password to pg_dump?

@Josue Alexander Ibarra answer works on centos 7 and version 9.5 if --dbname is not passed.

pg_dump postgresql://username:[email protected]:5432/mydatabase 

Spring Could not Resolve placeholder

If your config file is in a different path than classpath, you can add the configuration file path as a system property:

java -Dapp.config.path=path_to_config_file -jar your.jar

Where should I put the CSS and Javascript code in an HTML webpage?

You should put CSS in the <head> because that's what the specification says do to.

If you have more than one CSS file, they will be loaded in the order you put them in the code. If there is style in the second CSS file, it overwrites the style in the first; That will happen by design. Thus, Cascading Style Sheets.

Most browser will still effectivly render CSS files out of the head, but your code is not semantically correct.

You can use JavaScript file links anywhere on the document. There are different reasons to use some in the <head> and some elsewhere on the page. (For example, Google analytic code is instructed to be put at the bottom.)

How to break out from foreach loop in javascript

Use a for loop instead of .forEach()

var myObj = [{"a": "1","b": null},{"a": "2","b": 5}]
var result = false

for(var call of myObj) {
    var a = call['a'], b = call['b']
    if(a == null || b == null) {
        result = false

Default keystore file does not exist?

You must be providing the wrong path to the debug.keystore file.

Follow these steps to get the correct path and complete your command:

  1. In eclipse, click the Window menu -> Preferences -> Expand Android -> Build
  2. In the right panel, look for: Default debug keystore:
  3. Select the entire box next to the label specified in Step 2

And finally, use the path you just copied from Step 3 to construct your command:

For example, in my case, it would be:

C:\Program Files\Java\jre7\bin>keytool -list -v -keystore "C:\Users\Siddharth\debug.keystore" -alias androiddebugkey -storepass android -keypass android


If you had already followed the steps mentioned above, the only other solution is to delete the debug.keystore and let Eclipse recreate it for you.

Step 1: Go to the path where your keystore is stored. In your case, C:\Users\Suresh\.android\debug.keystore

Step 2: Close and restart Eclipse.

Step 3 (Optional): You may need to clean your project before the debug.keystore is created again.


You can refer to this for the part about deleting your debug.keystore file: "Debug certificate expired" error in Eclipse Android plugins

Remove Primary Key in MySQL

I believe Quassnoi has answered your direct question. Just a side note: Maybe this is just some awkward wording on your part, but you seem to be under the impression that you have three primary keys, one on each field. This is not the case. By definition, you can only have one primary key. What you have here is a primary key that is a composite of three fields. Thus, you cannot "drop the primary key on a column". You can drop the primary key, or not drop the primary key. If you want a primary key that only includes one column, you can drop the existing primary key on 3 columns and create a new primary key on 1 column.

Arrow operator (->) usage in C

foo->bar is only shorthand for (*foo).bar. That's all there is to it.

Position one element relative to another in CSS

position: absolute will position the element by coordinates, relative to the closest positioned ancestor, i.e. the closest parent which isn't position: static.

Have your four divs nested inside the target div, give the target div position: relative, and use position: absolute on the others.

Structure your HTML similar to this:

<div id="container">
  <div class="top left"></div>
  <div class="top right"></div>
  <div class="bottom left"></div>
  <div class="bottom right"></div>

And this CSS should work:

#container {
  position: relative;

#container > * {
  position: absolute;

.left {
  left: 0;

.right {
  right: 0;

.top {
  top: 0;

.bottom {
  bottom: 0;


How to store date/time and timestamps in UTC time zone with JPA and Hibernate

There are several timezones in operation here:

  1. Java's Date classes (util and sql), which have implicit timezones of UTC
  2. The timezone your JVM is running in, and
  3. the default timezone of your database server.

All of these can be different. Hibernate/JPA has a severe design deficiency in that a user cannot easily ensure that timezone information is preserved in the database server (which allows reconstruction of correct times and dates in the JVM).

Without the ability to (easily) store timezone using JPA/Hibernate then information is lost and once information is lost it becomes expensive to construct it (if at all possible).

I would argue that it is better to always store timezone information (should be the default) and users should then have the optional ability to optimize the timezone away (although it only really affects display, there is still an implicit timezone in any date).

Sorry, this post doesn't provide a work-around (that's been answered elsewhere) but it is a rationalization of why always storing timezone information around is important. Unfortunately it seems many Computer Scientists and programming practitioners argue against the need for timezones simply because they don't appreciate the "loss of information" perspective and how that makes things like internationalization very difficult - which is very important these days with web sites accessible by clients and people in your organization as they move around the world.

Google map V3 Set Center to specific Marker

To build upon @6twenty's answer...I prefer panTo(LatLng) over setCenter(LatLng) as panTo animates for smoother transition to center "if the change is less than both the width and height of the map".

The below uses Google Maps API v3.

var marker = new google.maps.Marker({
    position: new google.maps.LatLng(latitude, longitude),
    title: markerTitle,
    map: map,
google.maps.event.addListener(marker, 'click', function () {
    //map.setCenter(marker.getPosition()); // sets center without animation

Play infinitely looping video on-load in HTML5

The loop attribute should do it:

<video width="320" height="240" autoplay loop>
  <source src="movie.mp4" type="video/mp4" />
  <source src="movie.ogg" type="video/ogg" />
  Your browser does not support the video tag.

Should you have a problem with the loop attribute (as we had in the past), listen to the videoEnd event and call the play() method when it fires.

Note1: I'm not sure about the behavior on Apple's iPad/iPhone, because they have some restrictions against autoplay.

Note2: loop="true" and autoplay="autoplay" are deprecated

Disable browser's back button

While i'm looking for the answer myself, "Best Practice" is.... outdated... Just like browsers are.(Really browsers are ugly fossils)

The best/safest solution would be for browsers to implement a method/request where the user can grant the page the ability to control the interface.

Why? Because for my current project i'm building a 100% JavaScript built and controlled interface.. And back button's have no place in my project since there is no page change. (Ie bloody fast and no page-flashes because of a refresh.. Just like a real application!)

I know why the ability to "highjack" the interface isn't there, and i understand it. But atleast we should have the ability to request it from the browser! Now that would truly be "best practice" without the highjack dangers.

But browsers being browsers.. I don't expect anything exiting to happen in this regard.

Performing SQL queries on an Excel Table within a Workbook with VBA Macro

One thing you may be able to do is get the address of the dynamic named range, and use that as the input in your SQL string. Something like:


Which will spit out an address string, something like $A$1:$A$8


As I said in my comment below, you can dynamically get the full address (including sheet name) and either use it directly or parse the sheet name for later use:


Which results in a string like =Sheet1!$C$1:$C$4. So for your code example above, your SQL statement could be

strRangeAddress = Mid(ActiveWorkbook.Names.Item("namedRangeName").RefersToLocal,2)

strSQL = "SELECT * FROM [strRangeAddress]"

How to check identical array in most efficient way?

You could compare String representations so:

array1.toString() == array2.toString()
array1.toString() !== array3.toString()

but that would also make

array4 = ['1',2,3,4,5]

equal to array1 if that matters to you

jQuery Determine if a matched class has a given id

$('#' + theMysteryId + '.someClass').each(function() { /* do stuff */ });

Python Requests - No connection adapters

You need to include the protocol scheme:


Without the http:// part, requests has no idea how to connect to the remote server.

Note that the protocol scheme must be all lowercase; if your URL starts with HTTP:// for example, it won’t find the http:// connection adapter either.

Cannot create JDBC driver of class ' ' for connect URL 'null' : I do not understand this exception

I can't see anything obviously wrong, but perhaps a different approach might help you debug it?

You could try specify your datasource in the per-application-context instead of the global tomcat one.

You can do this by creating a src/main/webapp/META-INF/context.xml (I'm assuming you're using the standard maven directory structure - if not, then the META-INF folder should be a sibling of your WEB-INF directory). The contents of the META-INF/context.xml file would look something like:

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

<Context [optional other attributes as required]>

<Resource name="jdbc/PollDatasource" auth="Container"
          type="javax.sql.DataSource" driverClassName="org.apache.derby.jdbc.ClientDriver"
          username="suhail" password="suhail" maxActive="20" maxIdle="10" maxWait="-1"/>

Obviously the path and docBase would need to match your application's specific details.

Using this approach, you don't have to specify the datasource details in Tomcat's context.xml file. Although, if you have multiple applications talking to the same database, then your approach makes more sense.

At any rate, give this a whirl and see if it makes any difference. It might give us a clue as to what is going wrong with your approach.

HTTP Error 500.19 and error code : 0x80070021

If you're running IIS on that computer for the first time, you should try running the ASP.NET IIS registration tool (aspnet_regiis.exe).

Here's how to do that: If you're using .net framework v4, open command prompt as an administrator, and change directory to your .net framework base folder using:

CD C:\Windows\Microsoft.NET\Framework\v4.0.30319

or, if you're using a 64 bit computer, use:

CD C:\Windows\Microsoft.NET\Framework64\v4.0.30319

when you've successfully navigated to the appropriate directory, execute the ASP.NET IIS registration tool using:

aspnet_regiis -i

If you're using a different .NET framework version, simply replace v4.0.30319 with the appropriate folder name.

Hope this helps.

Adding placeholder attribute using Jquery

This line of code might not work in IE 8 because of native support problems.

$(".hidden").attr("placeholder", "Type here to search");

You can try importing a JQuery placeholder plugin for this task. Simply import it to your libraries and initiate from the sample code below.

$('input, textarea').placeholder();

How do you determine the size of a file in C?

And if you're building a Windows app, use the GetFileSizeEx API as CRT file I/O is messy, especially for determining file length, due to peculiarities in file representations on different systems ;)

Can an html element have multiple ids?

You can only have one ID per element, but you can indeed have more than one class. But don't have multiple class attributes, put multiple class values into one attribute.

<div id="foo" class="bar baz bax">

is perfectly legal.

Removing ul indentation with CSS

Remove this from #info:


Add this for your header:

#info p {
    text-align: center;

Do you need the fixed width etc.? I removed the in my opinion not necessary stuff and centered the header with text-align.


Build not visible in itunes connect

Well, in my case I uploaded a build with updated version. like 1.1.0 Build 1.1.0, then I reverted back to 1.0.0 build 1.0.5 and the same build was visible under the 1.0.0 header dropdown.

Hope it helps someone.

How can I add a hint text to WPF textbox?

This is my simple solution, adapted from Microsoft (

    <Grid Background="White" HorizontalAlignment="Right" VerticalAlignment="Top"  >
        <!-- overlay with hint text -->
        <TextBlock Margin="5,2" MinWidth="50" Text="Suche..." 
                   Foreground="LightSteelBlue" Visibility="{Binding ElementName=txtSearchBox, Path=Text.IsEmpty, Converter={StaticResource MyBoolToVisibilityConverter}}" IsHitTestVisible="False"/>
        <!-- enter term here -->
        <TextBox MinWidth="50" Name="txtSearchBox" Background="Transparent" />

Detecting EOF in C

You want to check the result of scanf() to make sure there was a successful conversion; if there wasn't, then one of three things is true:

  1. scanf() is choking on a character that isn't valid for the %f conversion specifier (i.e., something that isn't a digit, dot, 'e', or 'E');
  2. scanf() has detected EOF;
  3. scanf() has detected an error on reading stdin.


int moreData = 1;
printf("Input no: ");
 * Loop while moreData is true
while (moreData)
  errno = 0;
  int itemsRead = scanf("%f", &input);
  if (itemsRead == 1)
    printf("Output: %f\n", input);
    printf("Input no: ");
    if (feof(stdin))
      printf("Hit EOF on stdin; exiting\n");
      moreData = 0;
    else if (ferror(stdin))
       * I *think* scanf() sets errno; if not, replace
       * the line below with a regular printf() and
       * a generic "read error" message.
      perror("error during read");
      moreData = 0;
      printf("Bad character stuck in input stream; clearing to end of line\n");
      while (getchar() != '\n')
        ; /* empty loop */
      printf("Input no: ");

What is the point of the diamond operator (<>) in Java 7?

When you write List<String> list = new LinkedList();, compiler produces an "unchecked" warning. You may ignore it, but if you used to ignore these warnings you may also miss a warning that notifies you about a real type safety problem.

So, it's better to write a code that doesn't generate extra warnings, and diamond operator allows you to do it in convenient way without unnecessary repetition.

Javascript "Cannot read property 'length' of undefined" when checking a variable's length


You asked why it happens, let's see:

The official language specificaion dictates a call to the internal [[GetValue]] method. Your .attr returns undefined and you're trying to access its length.

If Type(V) is not Reference, return V.

This is true, since undefined is not a reference (alongside null, number, string and boolean)

Let base be the result of calling GetBase(V).

This gets the undefined part of myVar.length .

If IsUnresolvableReference(V), throw a ReferenceError exception.

This is not true, since it is resolvable and it resolves to undefined.

If IsPropertyReference(V), then

This happens since it's a property reference with the . syntax.

Now it tries to convert undefined to a function which results in a TypeError.

How do I make a delay in Java?

Using TimeUnit.SECONDS.sleep(1); or Thread.sleep(1000); Is acceptable way to do it. In both cases you have to catch InterruptedExceptionwhich makes your code Bulky.There is an Open Source java library called MgntUtils (written by me) that provides utility that already deals with InterruptedException inside. So your code would just include one line:

TimeUtils.sleepFor(1, TimeUnit.SECONDS);

See the javadoc here. You can access library from Maven Central or from Github. The article explaining about the library could be found here

Render HTML string as real HTML in a React component


dangerouslySetInnerHTML is React’s replacement for using innerHTML in the browser DOM. In general, setting HTML from code is risky because it’s easy to inadvertently expose your users to a cross-site scripting (XSS) attack. So, you can set HTML directly from React, but you have to type out dangerouslySetInnerHTML and pass an object with a __html key, to remind yourself that it’s dangerous. For example:

function createMarkup() {
  return {__html: 'First &middot; Second'};

function MyComponent() {
  return <div dangerouslySetInnerHTML={createMarkup()} />;

Truncate with condition

The short answer is no: MySQL does not allow you to add a WHERE clause to the TRUNCATE statement. Here's MySQL's documentation about the TRUNCATE statement.

But the good news is that you can (somewhat) work around this limitation.

Simple, safe, clean but slow solution using DELETE

First of all, if the table is small enough, simply use the DELETE statement (it had to be mentioned):

1. LOCK TABLE my_table WRITE;

The LOCK and UNLOCK statements are not compulsory, but they will speed things up and avoid potential deadlocks.

Unfortunately, this will be very slow if your table is large... and since you are considering using the TRUNCATE statement, I suppose it's because your table is large.

So here's one way to solve your problem using the TRUNCATE statement:

Simple, fast, but unsafe solution using TRUNCATE

1. CREATE TABLE my_table_backup AS
      SELECT * FROM my_table WHERE my_date>=DATE_SUB(NOW(), INTERVAL 1 MONTH);
2. TRUNCATE my_table;
3. LOCK TABLE my_table WRITE, my_table_backup WRITE;
4. INSERT INTO my_table SELECT * FROM my_table_backup;
6. DROP TABLE my_table_backup;

Unfortunately, this solution is a bit unsafe if other processes are inserting records in the table at the same time:

  • any record inserted between steps 1 and 2 will be lost
  • the TRUNCATE statement resets the AUTO-INCREMENT counter to zero. So any record inserted between steps 2 and 3 will have an ID that will be lower than older IDs and that might even conflict with IDs inserted at step 4 (note that the AUTO-INCREMENT counter will be back to it's proper value after step 4).

Unfortunately, it is not possible to lock the table and truncate it. But we can (somehow) work around that limitation using RENAME.

Half-simple, fast, safe but noisy solution using TRUNCATE

1. RENAME TABLE my_table TO my_table_work;
2. CREATE TABLE my_table_backup AS
     SELECT * FROM my_table_work WHERE my_date>DATE_SUB(NOW(), INTERVAL 1 MONTH);
3. TRUNCATE my_table_work;
4. LOCK TABLE my_table_work WRITE, my_table_backup WRITE;
5. INSERT INTO my_table_work SELECT * FROM my_table_backup;
7. RENAME TABLE my_table_work TO my_table;
8. DROP TABLE my_table_backup;

This should be completely safe and quite fast. The only problem is that other processes will see table my_table disappear for a few seconds. This might lead to errors being displayed in logs everywhere. So it's a safe solution, but it's "noisy".

Disclaimer: I am not a MySQL expert, so these solutions might actually be crappy. The only guarantee I can offer is that they work fine for me. If some expert can comment on these solutions, I would be grateful.

What is the best way to get all the divisors of a number?

Here is a smart and fast way to do it for numbers up to and around 10**16 in pure Python 3.6,

from itertools import compress

def primes(n):
    """ Returns  a list of primes < n for n > 2 """
    sieve = bytearray([True]) * (n//2)
    for i in range(3,int(n**0.5)+1,2):
        if sieve[i//2]:
            sieve[i*i//2::i] = bytearray((n-i*i-1)//(2*i)+1)
    return [2,*compress(range(3,n,2), sieve[1:])]

def factorization(n):
    """ Returns a list of the prime factorization of n """
    pf = []
    for p in primeslist:
      if p*p > n : break
      count = 0
      while not n % p:
        n //= p
        count += 1
      if count > 0: pf.append((p, count))
    if n > 1: pf.append((n, 1))
    return pf

def divisors(n):
    """ Returns an unsorted list of the divisors of n """
    divs = [1]
    for p, e in factorization(n):
        divs += [x*p**k for k in range(1,e+1) for x in divs]
    return divs

n = 600851475143
primeslist = primes(int(n**0.5)+1) 

Jinja2 template variable if None Object set a default value

{{p.User['first_name'] or 'My default string'}}

SVG drop shadow using css3

Easiest way I've found is with feDropShadow.

<filter id="shadow" x="0" y="0" width="200%" height="200%">
  <feDropShadow dx="40" dy="40" stdDeviation="35" flood-color="#ff0000" flood-opacity="1" />

On the element:

<path d="..." filter="url(#shadow)"/>

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

To enable msbuild in Command Prompt, you simply have to add the directory of the msbuild.exe install on your machine to the PATH environment variable.

You can access the environment variables by:

  1. Right clicking on Computer
  2. Click Properties
  3. Then click Advanced system settings on the left navigation bar
  4. On the next dialog box click Environment variables
  5. Scroll down to PATH
  6. Edit it to include your path to the framework (don't forget a ";" after the last entry in here).

For reference, my path was C:\Windows\Microsoft.NET\Framework\v4.0.30319

Path Updates:

As of MSBuild 12 (2013)/VS 2013/.NET 4.5.1+ and onward MSBuild is now installed as a part of Visual Studio.

For VS2015 the path was %ProgramFiles(x86)%\MSBuild\14.0\Bin

For VS2017 the path was %ProgramFiles(x86)%\Microsoft Visual Studio\2017\Enterprise\MSBuild\15.0\Bin

For VS2019 the path was %ProgramFiles(x86)%\Microsoft Visual Studio\2019\Community\MSBuild\Current\Bin

Border length smaller than div width?

You can use a linear gradient:

div {_x000D_
    background-image: linear-gradient(to right, #000 1px, rgba(255,255,255,0) 1px), linear-gradient(to left, #000 0.1rem, rgba(255,255,255,0) 1px);_x000D_
 background-position: bottom;_x000D_
 background-size: 100% 25px;_x000D_
 background-repeat: no-repeat;_x000D_
    border-bottom: 1px solid #000;_x000D_
    border-top: 1px solid red;_x000D_

How can I check if a single character appears in a string?

You can use string.indexOf('a').

If the char a is present in string :

it returns the the index of the first occurrence of the character in the character sequence represented by this object, or -1 if the character does not occur.

How can I write to the console in PHP?

For Chrome there is an extension called Chrome Logger allowing to log PHP messages.

The Firefox DevTools even have integrated support for the Chrome Logger protocol.

To enable the logging, you just need to save the 'ChromePhp.php' file in your project. Then it can be used like this:

include 'ChromePhp.php';
ChromePhp::log('Hello console!');
ChromePhp::warn('something went wrong!');

Example taken from the GitHub page.

The output may then look like this:

Server log within Firefox DevTools

How to initialize all the elements of an array to any specific value in java

There's also

int[] array = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1};

C# refresh DataGridView when updating or inserted on another form

putting a quick example, should be a sufficient starting point

Code in Form A

public event EventHandler<EventArgs> RowAdded;

private void btnRowAdded_Click(object sender, EventArgs e)
     // insert data
     // if successful raise event

private void OnRowAddedEvent()
     var listener = RowAdded;
     if (listener != null)
         listener(this, EventArgs.Empty);

Code in Form B

private void button1_Click(object sender, EventArgs e)
     var frm = new Form2();
     frm.RowAdded += new EventHandler<EventArgs>(frm_RowAdded);

void frm_RowAdded(object sender, EventArgs e)
     // retrieve data again

You can even consider creating your own EventArgs class that can contain the newly added data. You can then use this to directly add the data to a new row in DatagridView

Redirect to external URI from ASP.NET MVC controller

Try this (I've used Home controller and Index View):

return RedirectToAction("Index", "Home");

Where can I find the TypeScript version installed in Visual Studio?

The tsc -v command run technically reads the TypeScript compiler version within the SDK directory set within the Windows Path variable. This doesn't necessarily reflect the latest version installed as the Path variable is not updated with subsequent installations.

The version that VS.NET uses to compile the TypeScript is what's in the project's configuration:


To help explain this more in detail I created the following post which has the specifics on the TypeScript versions installed, and which version VS.NET uses to compile the TypeScript files.

Which Version of TypeScript is Installed and Which Version is Visual Studio Using?

I also added a feature request on Microsoft Connect to make viewing and switching the TypeScript targeted version in VS.NET easier. This isn't really a TypeScript feature request as much as it is a VS.NET IDE enhancement.

Allow switching TypeScript configured version from Project Properties IDE

Call a python function from jinja2

There's a much simpler decision.

def x():
    return render_template('test.html', foo=y)

def y(text):
    return text

Then, in test.html:

{{ foo('hi') }}

How to print a int64_t type in C

//VC6.0 (386 & better)

    __int64 my_qw_var = 0x1234567890abcdef;

    __int32 v_dw_h;
    __int32 v_dw_l;

            mov eax,[dword ptr my_qw_var + 4]   //dwh
            mov [dword ptr v_dw_h],eax

            mov eax,[dword ptr my_qw_var]   //dwl
            mov [dword ptr v_dw_l],eax

        //Oops 0.8 format
    printf("val = 0x%0.8x%0.8x\n", (__int32)v_dw_h, (__int32)v_dw_l);


nodeJs callbacks simple example

we are creating a simple function as

callBackFunction (data, function ( err, response ){

// callbackfunction 
function callBackFuntion (data, callback){
    //write your logic and return your result as
callback("",result) //if not error
callback(error, "") //if error

Granting DBA privileges to user in Oracle

You need only to write:


Because this already makes the user a DB Administrator

How to grep (search) committed code in the Git history

Adding more to the answers already present. If you know the file in which you might have made do this:

git log --follow -p -S 'search-string' <file-path>

--follow: lists the history of a file

for loop in Python

Try using this:

for k in range(1,c+1,2):

Using unset vs. setting a variable to empty

Mostly you don't see a difference, unless you are using set -u:

/home/user1> var=""
/home/user1> echo $var

/home/user1> set -u
/home/user1> echo $var

/home/user1> unset var
/home/user1> echo $var
-bash: var: unbound variable

So really, it depends on how you are going to test the variable.

I will add that my preferred way of testing if it is set is:

[[ -n $var ]]  # True if the length of $var is non-zero


[[ -z $var ]]  # True if zero length

Qt Creator color scheme

My Dark Color scheme for QtCreator is at:

To use with Vim (dark) scheme.

Hope it is useful for someone.

How do I convert a double into a string in C++?

You could try a more compact style:

std::string number_in_string;

double number_in_double;

std::ostringstream output;

number_in_string = (dynamic_cast< std::ostringstream*>(&(output << number_in_double <<


Changing CSS for last <li>

I've done this with pure CSS (probably because I come from the future - 3 years later than everyone else :P )

Supposing we have a list:

<ul id="nav">
  <li><span>Category 1</span></li>
  <li><span>Category 2</span></li>
  <li><span>Category 3</span></li>

Then we can easily make the text of the last item red with:

ul#nav li:last-child span {
   color: Red;

How to measure time taken by a function to execute

To extend vsync's code further to have the ability to return the timeEnd as a value in NodeJS use this little piece of code.

console.timeEndValue = function(label) { // Add console.timeEndValue, to add a return value
   var time = this._times[label];
   if (!time) {
     throw new Error('No such label: ' + label);
   var duration = - time;
   return duration;

Now use the code like so:

console.time('someFunction timer');


var executionTime = console.timeEndValue('someFunction timer');
console.log("The execution time is " + executionTime);

This gives you more possibilities. You can store the execution time to be used for more purposes like using it in equations, or stored in a database, sent to a remote client over websockets, served on a webpage, etc.

Getting data from Yahoo Finance

To your first question, you can't really do any query through YQL to get data for all companies. It's more oriented towards obtaining data for a smaller query. (I.e., it's not going to give you a full data dump of the whole Yahoo! Finance database.)

To your second question, here's how you can get started exploring the Yahoo! Finance tables in YQL:

  1. Start at the YQL Console
  2. In the upper left corner, make sure Show Community Tables is checked
  3. Type finance in the search field
  4. You'll see all the Yahoo Finance tables (about 15)

Then you can try some example queries like the following:

select * from where symbol in ("YHOO","AAPL","GOOG","MSFT")

Update 2016-04-04: Here's a current screenshot showing the location of the Show Community Tables checkbox which must be clicked to see these finance tables: enter image description here

How do you implement a circular buffer in C?

@Adam Rosenfield's solution, although correct, could be implemented with a more lightweight circular_buffer structure that does not invlove count and capacity.

The structure could only hold the following 4 pointers:

  • buffer: Points to the start of the buffer in memory.
  • buffer_end: Points to the end of the buffer in memory.
  • head: Points to the end of stored data.
  • tail: Points to the start of stored data.

We could keep the sz attribute to allow the parametrisation of the unit of storage.

Both the count and the capacity values should be derive-able using the above pointers.


capacity is straight forward, as it can be derived by dividing the distance between the buffer_end pointer and the buffer pointer by the unit of storage sz (snippet below is pseudocode):

capacity = (buffer_end - buffer) / sz


For count though, things get a bit more complicated. For example, there is no way to determine whether the buffer is empty or full, in the scenario of head and tail pointing to the same location.

To tackle that, the buffer should allocate memory for an additional element. For example, if the desired capacity of our circular buffer is 10 * sz, then we need to allocate 11 * sz.

Capacity formula will then become (snippet below is pseudocode):

capacity_bytes = buffer_end - buffer - sz
capacity = capacity_bytes / sz

This extra element semantic allows us to construct conditions that evaluate whether the buffer is empty or full.

Empty state conditions

In order for the buffer to be empty, the head pointer points to the same location as the tail pointer:

head == tail

If the above evaluates to true, the buffer is empty.

Full state conditions

In order for the buffer to be full, the head pointer should be 1 element behind the tail pointer. Thus, the space needed to cover in order to jump from the head location to the tail location should be equal to 1 * sz.

if tail is larger that head:

tail - head == sz

If the above evaluates to true, the buffer is full.

if head is larger that tail:

  1. buffer_end - head returns the space to jump from the head to the end of the buffer.
  2. tail - buffer returns the space needed to jump from the start of the buffer to the `tail.
  3. Adding the above 2 should equal to the space needed to jump from the head to the tail
  4. The space derived in step 3, shold not be more than 1 * sz
(buffer_end - head) + (tail - buffer) == sz
=> buffer_end - buffer - head + tail == sz
=> buffer_end - buffer - sz == head - tail
=> head - tail == buffer_end - buffer - sz
=> head - tail == capacity_bytes

If the above evaluates to true, the buffer is full.

In practice

Modifying @Adam Rosenfield's to use the above circular_buffer structure:

#include <string.h>

#define CB_SUCCESS 0        /* CB operation was successful */
#define CB_MEMORY_ERROR 1   /* Failed to allocate memory */
#define CB_OVERFLOW_ERROR 2 /* CB is full. Cannot push more items. */
#define CB_EMPTY_ERROR 3    /* CB is empty. Cannot pop more items. */

typedef struct circular_buffer {
  void *buffer;
  void *buffer_end;
  size_t sz;
  void *head;
  void *tail;
} circular_buffer;

int cb_init(circular_buffer *cb, size_t capacity, size_t sz) {
  const int incremented_capacity = capacity + 1; // Add extra element to evaluate count
  cb->buffer = malloc(incremented_capacity * sz);
  if (cb->buffer == NULL)
    return CB_MEMORY_ERROR;
  cb->buffer_end = (char *)cb->buffer + incremented_capacity * sz;
  cb->sz = sz;
  cb->head = cb->buffer;
  cb->tail = cb->buffer;
  return CB_SUCCESS;

int cb_free(circular_buffer *cb) {
  return CB_SUCCESS;

const int _cb_length(circular_buffer *cb) {
  return (char *)cb->buffer_end - (char *)cb->buffer;

int cb_push_back(circular_buffer *cb, const void *item) {
  const int buffer_length = _cb_length(cb);
  const int capacity_length = buffer_length - cb->sz;

  if ((char *)cb->tail - (char *)cb->head == cb->sz ||
      (char *)cb->head - (char *)cb->tail == capacity_length)

  memcpy(cb->head, item, cb->sz);

  cb->head = (char*)cb->head + cb->sz;
  if(cb->head == cb->buffer_end)
    cb->head = cb->buffer;

  return CB_SUCCESS;

int cb_pop_front(circular_buffer *cb, void *item) {
  if (cb->head == cb->tail)
    return CB_EMPTY_ERROR;

  memcpy(item, cb->tail, cb->sz);

  cb->tail = (char*)cb->tail + cb->sz;
  if(cb->tail == cb->buffer_end)
    cb->tail = cb->buffer;

  return CB_SUCCESS;

no default constructor exists for class

If you define a class without any constructor, the compiler will synthesize a constructor for you (and that will be a default constructor -- i.e., one that doesn't require any arguments). If, however, you do define a constructor, (even if it does take one or more arguments) the compiler will not synthesize a constructor for you -- at that point, you've taken responsibility for constructing objects of that class, so the compiler "steps back", so to speak, and leaves that job to you.

You have two choices. You need to either provide a default constructor, or you need to supply the correct parameter when you define an object. For example, you could change your constructor to look something like:

Blowfish(BlowfishAlgorithm algorithm = CBC); the ctor could be invoked without (explicitly) specifying an algorithm (in which case it would use CBC as the algorithm).

The other alternative would be to explicitly specify the algorithm when you define a Blowfish object:

class GameCryptography { 
    Blowfish blowfish_;
    GameCryptography() : blowfish_(ECB) {}
    // ...

In C++ 11 (or later) you have one more option available. You can define your constructor that takes an argument, but then tell the compiler to generate the constructor it would have if you didn't define one:

class GameCryptography { 

    // define our ctor that takes an argument

    // Tell the compiler to do what it would have if we didn't define a ctor:
    GameCryptography() = default;

As a final note, I think it's worth mentioning that ECB, CBC, CFB, etc., are modes of operation, not really encryption algorithms themselves. Calling them algorithms won't bother the compiler, but is unreasonably likely to cause a problem for others reading the code.

PHP - define constant inside a class

class Foo {
    const BAR = 'baz';

echo Foo::BAR;

This is the only way to make class constants. These constants are always globally accessible via Foo::BAR, but they're not accessible via just BAR.

To achieve a syntax like Foo::baz()->BAR, you would need to return an object from the function baz() of class Foo that has a property BAR. That's not a constant though. Any constant you define is always globally accessible from anywhere and can't be restricted to function call results.

Unix epoch time to Java Date object

How about just:

Date expiry = new Date(Long.parseLong(date));

EDIT: as per rde6173's answer and taking a closer look at the input specified in the question , "1081157732" appears to be a seconds-based epoch value so you'd want to multiply the long from parseLong() by 1000 to convert to milliseconds, which is what Java's Date constructor uses, so:

Date expiry = new Date(Long.parseLong(date) * 1000);

MySQL Great Circle Distance (Haversine formula)

I have written a procedure that can calculate the same, but you have to enter the latitude and longitude in the respective table.

drop procedure if exists select_lattitude_longitude;

delimiter //

create procedure select_lattitude_longitude(In CityName1 varchar(20) , In CityName2 varchar(20))


    declare origin_lat float(10,2);
    declare origin_long float(10,2);

    declare dest_lat float(10,2);
    declare dest_long float(10,2);

    if CityName1  Not In (select Name from City_lat_lon) OR CityName2  Not In (select Name from City_lat_lon) then 

        select 'The Name Not Exist or Not Valid Please Check the Names given by you' as Message;


        select lattitude into  origin_lat from City_lat_lon where Name=CityName1;

        select longitude into  origin_long  from City_lat_lon where Name=CityName1;

        select lattitude into  dest_lat from City_lat_lon where Name=CityName2;

        select longitude into  dest_long  from City_lat_lon where Name=CityName2;

        select origin_lat as CityName1_lattitude,
               origin_long as CityName1_longitude,
               dest_lat as CityName2_lattitude,
               dest_long as CityName2_longitude;

        SELECT 3956 * 2 * ASIN(SQRT( POWER(SIN((origin_lat - dest_lat) * pi()/180 / 2), 2) + COS(origin_lat * pi()/180) * COS(dest_lat * pi()/180) * POWER(SIN((origin_long-dest_long) * pi()/180 / 2), 2) )) * 1.609344 as Distance_In_Kms ;

    end if;

end ;


delimiter ;

Get the size of a 2D array

Expanding on what Mark Elliot said earlier, the easiest way to get the size of a 2D array given that each array in the array of arrays is of the same size is:

array.length * array[0].length

Detecting locked tables (locked by LOCK TABLE)

You could also get all relevant details from performance_schema:

FROM performance_schema.table_handles 


This works similar as

show open tables WHERE In_use > 0

Android Crop Center of Bitmap

Here a more complete snippet that crops out the center of an [bitmap] of arbitrary dimensions and scales the result to your desired [IMAGE_SIZE]. So you will always get a [croppedBitmap] scaled square of the image center with a fixed size. ideal for thumbnailing and such.

Its a more complete combination of the other solutions.

final int IMAGE_SIZE = 255;
boolean landscape = bitmap.getWidth() > bitmap.getHeight();

float scale_factor;
if (landscape) scale_factor = (float)IMAGE_SIZE / bitmap.getHeight();
else scale_factor = (float)IMAGE_SIZE / bitmap.getWidth();
Matrix matrix = new Matrix();
matrix.postScale(scale_factor, scale_factor);

Bitmap croppedBitmap;
if (landscape){
    int start = (tempBitmap.getWidth() - tempBitmap.getHeight()) / 2;
    croppedBitmap = Bitmap.createBitmap(tempBitmap, start, 0, tempBitmap.getHeight(), tempBitmap.getHeight(), matrix, true);
} else {
    int start = (tempBitmap.getHeight() - tempBitmap.getWidth()) / 2;
    croppedBitmap = Bitmap.createBitmap(tempBitmap, 0, start, tempBitmap.getWidth(), tempBitmap.getWidth(), matrix, true);

How can I detect browser type using jQuery?

The best solution is probably: use Modernizr.

However, if you necessarily want to use $.browser property, you can do it using jQuery Migrate plugin (for JQuery >= 1.9 - in earlier versions you can just use it) and then do something like:

if($ {
} else if ($.browser.mozilla) {
} else if ($.browser.msie) {

And if you need for some reason to use navigator.userAgent, then it would be:

$.browser.msie = /msie/.test(navigator.userAgent.toLowerCase()); 
$.browser.mozilla = /firefox/.test(navigator.userAgent.toLowerCase()); 

Getting all documents from one collection in Firestore

The example in the other answer is unnecessarily complex. This would be more straightforward, if all you want to do is return the raw data objects for each document in a query or collection:

async getMarker() {
    const snapshot = await firebase.firestore().collection('events').get()
    return =>;

Node.js connect only works on localhost


I have a NodeJS server working on Windows 10 PC, but when I put the IP address and port (example into another computer's browser on my local network nothing happened, although it worked OK on the host computer.

(To find your windows IP address run CMD, then IPCONFIG)

Bar Horing Amir's answer points to the Windows firewall settings. On My PC the Windows Firewall was turned off - as McAfee anti-virus has added its own Firewall.

My system started to work on other computers after I added port 5000 to 'Ports and Systems Services' under the McAfee Firewall settings on the computer with NodeJS on it. Other anti-virus software will have similar settings.

I would seriously suggest trying this solution first with Windows.

Getting Error 800a0e7a "Provider cannot be found. It may not be properly installed."

  1. Under Window Administrative Tools, run ODBC Data Sources (32-bit).

  2. Under the Drivers tab, check you have the Microsoft Excel Driver (*.xls, *.xlsx etc...) - the file name is ACEODBC.DLL

  3. If this is missing, you will need to install the Microsoft Access Database Engine 2016 Redistributable.

You'll find the installer here

  1. Your connection should be:
Set objConn1 = Server.CreateObject("ADODB.Connection") 
objConn1.Provider = "Microsoft.ACE.OLEDB.12.0"   
objConn1.ConnectionString = "Data Source=" & pPath & ";Extended Properties=""Excel 12.0 Xml;HDR=YES;IMEX=1""" 

Database cluster and load balancing

From SQL Server point of view:

Clustering will give you an active - passive configuration. Meaning in a 2 node cluster, one of them will be the active (serving) and the other one will be passive (waiting to take over when the active node fails). It's a high availability from hardware point of view.

You can have an active-active cluster, but it will require multiple instances of SQL Server running on each node. (i.e. Instance 1 on Node A failing over to Instance 2 on Node B, and instance 1 on Node B failing over to instance 2 on Node A).

Load balancing (at least from SQL Server point of view) does not exists (at least in the same sense of web server load balancing). You can't balance load that way. However, you can split your application to run on some database on server 1 and also run on some database on server 2, etc. This is the primary mean of "load balancing" in SQL world.

how to apply click event listener to image in android

Try this example.


<LinearLayout xmlns:android=""
    tools:context=".MainActivity" >




<LinearLayout xmlns:android=""
    android:padding="5dp" >





package com.example.lalit.gridtest;

import android.content.Context;
        import android.view.LayoutInflater;
        import android.view.View;
        import android.view.ViewGroup;
        import android.widget.BaseAdapter;
        import android.widget.ImageView;
        import android.widget.TextView;

public class CustomGrid extends BaseAdapter {
    private Context mContext;
    private final String[] web;
    private final int[] Imageid;

    public CustomGrid(Context c, String[] web, int[] Imageid) {
        mContext = c;
        this.Imageid = Imageid;
        this.web = web;

    public int getCount() {
        // TODO Auto-generated method stub
        return web.length;

    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return null;

    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;

    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        View grid;
        LayoutInflater inflater = (LayoutInflater) mContext

        if (convertView == null) {

            grid = new View(mContext);
            grid = inflater.inflate(R.layout.grid_single, null);
            TextView textView = (TextView) grid.findViewById(;
            ImageView imageView = (ImageView) grid.findViewById(;
        } else {
            grid = (View) convertView;

        return grid;

package com.example.lalit.gridtest;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends Activity {
    GridView grid;
    String[] web = {

    int[] imageId = {


    protected void onCreate(Bundle savedInstanceState) {

        final CustomGrid adapter = new CustomGrid(MainActivity.this, web, imageId);
        grid = (GridView) findViewById(;
        grid.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id){

                if (web[position].toString().equals("Mom")) {
                    try {
                        String uri ="te:"+ "**********";

                        Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse(uri));
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), "Your call has failed...",


                    if (web[position].toString().equals("Mahendra")) {
                        try {
                            String uri = "tel:" + "**********";

                            Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse(uri));
                        } catch (Exception e) {
                            Toast.makeText(getApplicationContext(), "Your call has failed...",



                    try {
                        String uri = "tel:" + "**********";

                        Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse(uri));
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), "Your call has failed...",



                    try {
                        String uri = "tel:" + "**********";

                        Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse(uri));
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), "Your call has failed...",




                    try {
                        String uri = "tel:" + "**********";

                        Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse(uri));
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), "Your call has failed...",




                    try {
                        String uri = "tel:" + "**********";

                        Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse(uri));
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), "Your call has failed...",



                    try {
                        String uri = "tel:" + "**********";

                        Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse(uri));
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), "Your call has failed...",



                    try {
                        String uri = "tel:" + "**********";

                        Intent callIntent = new Intent(Intent.ACTION_CALL, Uri.parse(uri));
                    } catch (Exception e) {
                        Toast.makeText(getApplicationContext(), "Your call has failed...",








<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android=""
    package="com.example.lalit.gridtest" >
    <uses-permission android:name="android.permission.CALL_PHONE" />
        android:theme="@style/AppTheme" >
            android:label="@string/app_name" >
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />


Align DIV to bottom of the page

It's a quick fix, I hope it helps.

<div id="content">
content footer...


#content{min-height: calc(100vh - 100px);}

100vh is 100% height of device and 100px is height of footer

If the content is higher than height of device, the footer will stay on bottom. And the content is shorter than height of device, the footer will stay on bottom of screen

Download files from server php

To read directory contents you can use readdir() and use a script, in my example download.php, to download files

if ($handle = opendir('/path/to/your/dir/')) {
    while (false !== ($entry = readdir($handle))) {
        if ($entry != "." && $entry != "..") {
            echo "<a href='download.php?file=".$entry."'>".$entry."</a>\n";

In download.php you can force browser to send download data, and use basename() to make sure client does not pass other file name like ../config.php

$file = basename($_GET['file']);
$file = '/path/to/your/dir/'.$file;

if(!file_exists($file)){ // file does not exist
    die('file not found');
} else {
    header("Cache-Control: public");
    header("Content-Description: File Transfer");
    header("Content-Disposition: attachment; filename=$file");
    header("Content-Type: application/zip");
    header("Content-Transfer-Encoding: binary");

    // read the file from disk

Splitting a string into chunks of a certain size

You can use morelinq by Jon Skeet. Use Batch like:

string str = "1111222233334444";
int chunkSize = 4;
var chunks = str.Batch(chunkSize).Select(r => new String(r.ToArray()));

This will return 4 chunks for the string "1111222233334444". If the string length is less than or equal to the chunk size Batch will return the string as the only element of IEnumerable<string>

For output:

foreach (var chunk in chunks)

and it will give:


how to align all my li on one line?

I think the NOBR tag might be overkill, and as you said, unreliable.

There are 2 options available depending on how you are displaying the text.

If you are displaying text in a table cell you would do Long Text Here. If you are using a div or a span, you can use the style="white-space: nowrap;"

How to check whether a string contains a substring in JavaScript?

There is a String.prototype.includes in ES6:

> true

Note that this does not work in Internet Explorer or some other old browsers with no or incomplete ES6 support. To make it work in old browsers, you may wish to use a transpiler like Babel, a shim library like es6-shim, or this polyfill from MDN:

if (!String.prototype.includes) {
  String.prototype.includes = function(search, start) {
    'use strict';
    if (typeof start !== 'number') {
      start = 0;

    if (start + search.length > this.length) {
      return false;
    } else {
      return this.indexOf(search, start) !== -1;

FFmpeg on Android

First, add the dependency of FFmpeg library

implementation 'com.writingminds:FFmpegAndroid:0.3.2'

Then load in activity

FFmpeg ffmpeg;
    private void trimVideo(ProgressDialog progressDialog) {

    outputAudioMux = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MOVIES).getAbsolutePath()
            + "/VidEffectsFilter" + "/" + new SimpleDateFormat("ddMMyyyy_HHmmss").format(new Date())
            + "filter_apply.mp4";

    if (startTrim.equals("")) {
        startTrim = "00:00:00";

    if (endTrim.equals("")) {
        endTrim = timeTrim(player.getDuration());

    String[] cmd = new String[]{"-ss", startTrim + ".00", "-t", endTrim + ".00", "-noaccurate_seek", "-i", videoPath, "-codec", "copy", "-avoid_negative_ts", "1", outputAudioMux};

    execFFmpegBinary1(cmd, progressDialog);

    private void execFFmpegBinary1(final String[] command, ProgressDialog prpg) {

    ProgressDialog progressDialog = prpg;

    try {
        ffmpeg.execute(command, new ExecuteBinaryResponseHandler() {
            public void onFailure(String s) {
                Toast.makeText(PlayerTestActivity.this, "Fail to generate video", Toast.LENGTH_SHORT).show();
                Log.d(TAG, "FAILED with output : " + s);

            public void onSuccess(String s) {
                Log.d(TAG, "SUCCESS wgith output : " + s);

//                    pathVideo = outputAudioMux;
                String finalPath = outputAudioMux;
                videoPath = outputAudioMux;
                Toast.makeText(PlayerTestActivity.this, "Storage Path =" + finalPath, Toast.LENGTH_SHORT).show();

                Intent intent = new Intent(PlayerTestActivity.this, ShareVideoActivity.class);
                intent.putExtra("pathGPU", finalPath);
                MediaScannerConnection.scanFile(PlayerTestActivity.this, new String[]{finalPath}, new String[]{"mp4"}, null);


            public void onProgress(String s) {
                Log.d(TAG, "Started gcommand : ffmpeg " + command);
                progressDialog.setMessage("Please Wait video triming...");

            public void onStart() {
                Log.d(TAG, "Startedf command : ffmpeg " + command);


            public void onFinish() {
                Log.d(TAG, "Finished f command : ffmpeg " + command);
    } catch (FFmpegCommandAlreadyRunningException e) {
        // do nothing for now

  private void loadFFMpegBinary() {
    try {
        if (ffmpeg == null) {
            ffmpeg = FFmpeg.getInstance(this);
        ffmpeg.loadBinary(new LoadBinaryResponseHandler() {
            public void onFailure() {

            public void onSuccess() {
                Log.d("dd", "ffmpeg : correct Loaded");
    } catch (FFmpegNotSupportedException e) {
    } catch (Exception e) {
        Log.d("dd", "EXception no controlada : " + e);

private void showUnsupportedExceptionDialog() {
    new AlertDialog.Builder(this)
            .setTitle("Not Supported")
            .setMessage("Device Not Supported")
            .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {

    public String timeTrim(long milliseconds) {
        String finalTimerString = "";
        String minutString = "";
        String secondsString = "";

        // Convert total duration into time
        int hours = (int) (milliseconds / (1000 * 60 * 60));
        int minutes = (int) (milliseconds % (1000 * 60 * 60)) / (1000 * 60);
        int seconds = (int) ((milliseconds % (1000 * 60 * 60)) % (1000 * 60) / 1000);
        // Add hours if there

        if (hours < 10) {
            finalTimerString = "0" + hours + ":";
        } else {
            finalTimerString = hours + ":";

        if (minutes < 10) {
            minutString = "0" + minutes;
        } else {
            minutString = "" + minutes;

        // Prepending 0 to seconds if it is one digit
        if (seconds < 10) {
            secondsString = "0" + seconds;
        } else {
            secondsString = "" + seconds;

        finalTimerString = finalTimerString + minutString + ":" + secondsString;

        // return timer string
        return finalTimerString;

Also use another feature by FFmpeg

===> merge audio to video
String[] cmd = new String[]{"-i", yourRealPath, "-i", arrayList.get(posmusic).getPath(), "-map", "1:a", "-map", "0:v", "-codec", "copy", "-shortest", outputcrop};

===> Flip vertical :
String[] cm = new String[]{"-i", yourRealPath, "-vf", "vflip", "-codec:v", "libx264", "-preset", "ultrafast", "-codec:a", "copy", outputcrop1};

===> Flip horizontally :  
String[] cm = new String[]{"-i", yourRealPath, "-vf", "hflip", "-codec:v", "libx264", "-preset", "ultrafast", "-codec:a", "copy", outputcrop1};

===> Rotate 90 degrees clockwise:
String[] cm=new String[]{"-i", yourRealPath, "-c", "copy", "-metadata:s:v:0", "rotate=90", outputcrop1};

===> Compress Video
String[] complexCommand = {"-y", "-i", yourRealPath, "-strict", "experimental", "-vcodec", "libx264", "-preset", "ultrafast", "-crf", "24", "-acodec", "aac", "-ar", "22050", "-ac", "2", "-b", "360k", "-s", "1280x720", outputcrop1};

===> Speed up down video
String[] complexCommand = {"-y", "-i", yourRealPath, "-filter_complex", "[0:v]setpts=2.0*PTS[v];[0:a]atempo=0.5[a]", "-map", "[v]", "-map", "[a]", "-b:v", "2097k", "-r", "60", "-vcodec", "mpeg4", outputcrop1};
String[] complexCommand = {"-y", "-i", yourRealPath, "-filter_complex", "[0:v]setpts=1.0*PTS[v];[0:a]atempo=1.0[a]", "-map", "[v]", "-map", "[a]", "-b:v", "2097k", "-r", "60", "-vcodec", "mpeg4", outputcrop1};
String[] complexCommand = {"-y", "-i", yourRealPath, "-filter_complex", "[0:v]setpts=0.75*PTS[v];[0:a]atempo=1.5[a]", "-map", "[v]", "-map", "[a]", "-b:v", "2097k", "-r", "60", "-vcodec", "mpeg4", outputcrop1};
String[] complexCommand = {"-y", "-i", yourRealPath, "-filter_complex", "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]", "-map", "[v]", "-map", "[a]", "-b:v", "2097k", "-r", "60", "-vcodec", "mpeg4", outputcrop1};

===> Add two mp3 files 

StringBuilder sb = new StringBuilder();
sb.append("-i ");
sb.append(" -i ");
sb.append(" -filter_complex [0:0][1:0]concat=n=2:v=0:a=1[out] -map [out] ");
---> ffmpeg.execute(sb.toString().split(" "), new ExecuteBinaryResponseHandler()

===> Add three mp3 files

StringBuilder sb = new StringBuilder();
sb.append("-i ");
sb.append(" -i ");
sb.append(" -i ");
sb.append(" -filter_complex [0:0][1:0][2:0]concat=n=3:v=0:a=1[out] -map [out] ");
---> ffmpeg.execute(sb.toString().split(" "), new ExecuteBinaryResponseHandler()

Difference between left join and right join in SQL Server

select fields 
from tableA --left
left join tableB --right
on tableA.key = tableB.key

The table in the from in this example tableA, is on the left side of relation.

tableA <- tableB

So if you want to take all rows from the left table (tableA), even if there are no matches in the right table (tableB), you'll use the "left join".

And if you want to take all rows from the right table (tableB), even if there are no matches in the left table (tableA), you will use the right join.

Thus, the following query is equivalent to that used above.

select fields
from tableB 
right join tableA on tableB.key = tableA.key

Url decode UTF-8 in Python

If you are using Python 3, you can use urllib.parse

url = """"""

import urllib.parse



How to remove all the null elements inside a generic list in one go?

I do not know of any in-built method, but you could just use linq:

parameterList = parameterList.Where(x => x != null).ToList();

Time complexity of Euclid's Algorithm

Here's intuitive understanding of runtime complexity of Euclid's algorithm. The formal proofs are covered in various texts such as Introduction to Algorithms and TAOCP Vol 2.

First think about what if we tried to take gcd of two Fibonacci numbers F(k+1) and F(k). You might quickly observe that Euclid's algorithm iterates on to F(k) and F(k-1). That is, with each iteration we move down one number in Fibonacci series. As Fibonacci numbers are O(Phi ^ k) where Phi is golden ratio, we can see that runtime of GCD was O(log n) where n=max(a, b) and log has base of Phi. Next, we can prove that this would be the worst case by observing that Fibonacci numbers consistently produces pairs where the remainders remains large enough in each iteration and never become zero until you have arrived at the start of the series.

We can make O(log n) where n=max(a, b) bound even more tighter. Assume that b >= a so we can write bound at O(log b). First, observe that GCD(ka, kb) = GCD(a, b). As biggest values of k is gcd(a,c), we can replace b with b/gcd(a,b) in our runtime leading to more tighter bound of O(log b/gcd(a,b)).

Compiled vs. Interpreted Languages

It's rather difficult to give a practical answer because the difference is about the language definition itself. It's possible to build an interpreter for every compiled language, but it's not possible to build an compiler for every interpreted language. It's very much about the formal definition of a language. So that theoretical informatics stuff noboby likes at university.

Determine if char is a num or letter

If (theChar >= '0' && theChar <='9') it's a digit. You get the idea.

How to make a promise from setTimeout

const setTimeoutAsync = (cb, delay) =>
  new Promise((resolve) => {
    setTimeout(() => {
    }, delay);

We can pass custom 'cb fxn' like this one

SessionTimeout: web.xml vs session.maxInactiveInterval()

Now, i'm being told that this will terminate the session (or is it all sessions?) in the 15th minute of use, regardless their activity.

No, that's not true. The session-timeout configures a per session timeout in case of inactivity.

Are these methods equivalent? Should I favour the web.xml config?

The setting in the web.xml is global, it applies to all sessions of a given context. Programatically, you can change this for a particular session.

axios post request to send form data

2020 ES6 way of doing

Having the form in html I binded in data like so:


form: {
   name: 'Joan Cap de porc',
   email: '[email protected]',
   phone: 2323,
   query: 'cap d\ou'
   file: null,
   legal: false


async submitForm() {
  const formData = new FormData()
  Object.keys(this.form).forEach((key) => {
    formData.append(key, this.form[key])

  try {
    await this.$'/ajax/contact/contact-us', formData)
  } catch (err) {

How to write connection string in web.config file and read from it?

Try this After open web.config file in application and add sample db connection in connectionStrings section like this

<add name="yourconnectinstringName" connectionString="Data Source= DatabaseServerName; Integrated Security=true;Initial Catalog= YourDatabaseName; uid=YourUserName; Password=yourpassword; " providerName="System.Data.SqlClient"/>
</connectionStrings >

jQuery Toggle Text?

Perhaps I'm oversimplifying the problem, but this is what I use.

    toggleText: function(a, b) {
        $.trim(this.html()) == a ? this.html(b) : this.html(a);

What is object slicing?

class A 
    int x; 

class B 
    B( ) : x(1), c('a') { } 
    int x; 
    char c; 

int main( ) 
    A a; 
    B b; 
    a = b;     // b.c == 'a' is "sliced" off
    return 0; 

iPhone/iOS JSON parsing tutorial

Here's a link to my tutorial, which walks you through :

  • creating a JSON WCF Web Service from scratch (and the problems you'll want to avoid)
  • adapting it to read/write SQL Server data
  • getting an iOS 6 app to use the JSON servies.
  • using the JSON web services with JavaScript

All source code is provided, free of charge. Enjoy.

Pretty-Print JSON Data to a File using Python

import json
def writeToFile(logData, fileName, openOption="w"):
  file = open(fileName, openOption)
  file.write(json.dumps(json.loads(logData), indent=4)) 

Add content to a new open window

When you call document.write after a page has loaded it will eliminate all content and replace it with the parameter you provide. Instead use DOM methods to add content, for example:

var OpenWindow ='mypage.html','_blank','width=335,height=330,resizable=1');
var text = document.createTextNode('hi');

If you want to use jQuery you get some better APIs to deal with. For example:

var OpenWindow ='mypage.html','_blank','width=335,height=330,resizable=1');

If you need the code to run after the new window's DOM is ready try:

var OpenWindow ='mypage.html','_blank','width=335,height=330,resizable=1');
$(OpenWindow.document.body).ready(function() {

How do I auto size columns through the Excel interop objects?

This might be too late but if you add




it also works.

How to prevent form resubmission when page is refreshed (F5 / CTRL+R)

I found next workaround. You may escape the redirection after processing POST request by manipulating history object.

So you have the HTML form:

<form method=POST action='/process.php'>
 <input type=submit value=OK>

When you process this form on your server you instead of redirecting user to /the/result/page by setting up the Location header like this:

$cat process.php
     process POST data here
     header('Location: /the/result/page');

enter image description here

After processing POSTed data you render small <script> and the result /the/result/page

     process POST data here
     render the <script>         // see below
     render `/the/result/page`   // OK

The <script> you should render:

    window.onload = function() {
        history.replaceState("", "", "/the/result/page");

The result is:

enter image description here

as you can see the form data is POSTed to process.php script.
This script process POSTed data and rendering /the/result/page at once with:

  1. no redirection
  2. no rePOST data when you refresh page (F5)
  3. no rePOST when you navigate to previous/next page through the browser history


As another solution I ask feature request the Mozilla FireFox team to allow users to setup NextPage header which will work like Location header and make post/redirect/get pattern obsolete.

In short. When server process form POST data successfully it:

  1. Setup NextPage header instead of Location
  2. Render the result of processing POST form data as it would render for GET request in post/redirect/get pattern

The browser in turn when see the NextPage header:

  1. Adjust window.location with NextPage value
  2. When user refresh the page the browser will negotiate GET request to NextPage instead of rePOST form data

I think this would be excelent if implemented, would not? =)

How to get a specific column value from a DataTable in c#

The table normally contains multiple rows. Use a loop and use row.Field<string>(0) to access the value of each row.

foreach(DataRow row in dt.Rows)
    string file = row.Field<string>("File");

You can also access it via index:

foreach(DataRow row in dt.Rows)
    string file = row.Field<string>(0);

If you expect only one row, you can also use the indexer of DataRowCollection:

string file = dt.Rows[0].Field<string>(0); 

Since this fails if the table is empty, use dt.Rows.Count to check if there is a row:

if(dt.Rows.Count > 0)
    file = dt.Rows[0].Field<string>(0);

How to find integer array size in java

Integer Array doesn't contain size() or length() method. Try the below code, it'll work. ArrayList contains size() method. String contains length(). Since you have used int array[], so it will be array.length

public class Example {

    int array[] = {1, 99, 10000, 84849, 111, 212, 314, 21, 442, 455, 244, 554, 22, 22, 211};

    public void Printrange() {

        for (int i = 0; i < array.length; i++) {
            if (array[i] > 100 && array[i] < 500) {
                System.out.println("numbers with in range" + i);

Html table with button on each row

Pretty sure this solves what you're looking for:


    <tr><td><button class="editbtn">edit</button></td></tr>
    <tr><td><button class="editbtn">edit</button></td></tr>
    <tr><td><button class="editbtn">edit</button></td></tr>
    <tr><td><button class="editbtn">edit</button></td></tr>

Javascript (using jQuery):

        $(this).html($(this).html() == 'edit' ? 'modify' : 'edit');


Apparently I should have looked at your sample code first ;)

You need to change (at least) the ID attribute of each element. The ID is the unique identifier for each element on the page, meaning that if you have multiple items with the same ID, you'll get conflicts.

By using classes, you can apply the same logic to multiple elements without any conflicts.

JSFiddle sample

PHP equivalent of .NET/Java's toString()

How do I convert the value of a PHP variable to string?

A value can be converted to a string using the (string) cast or the strval() function. (Edit: As Thomas also stated).

It also should be automatically casted for you when you use it as a string.

Is there a MessageBox equivalent in WPF?

You can use this:

MessageBoxResult result = MessageBox.Show("Do you want to close this window?",
if (result == MessageBoxResult.Yes)

For more information, visit MessageBox in WPF.

How to open a web page automatically in full screen mode

It's better to try to simulate a webbrowser by yourself.You don't have to stick with Chrome or IE or else thing.

If you're using Python,you can try package pyQt4 which helps you to simulate a webbrowser. By doing this,there will not be any security reasons and you can set the webbrowser to show in full screen mode automatically.

What is the proper REST response code for a valid request but an empty data?

In this scenario Ruby on Rails responses with 404 Not Found.

404 Not Found is more appropriate.

C - freeing structs

Simple answer : free(testPerson) is enough .

Remember you can use free() only when you have allocated memory using malloc, calloc or realloc.

In your case you have only malloced memory for testPerson so freeing that is sufficient.

If you have used char * firstname , *last surName then in that case to store name you must have allocated the memory and that's why you had to free each member individually.

Here is also a point it should be in the reverse order; that means, the memory allocated for elements is done later so free() it first then free the pointer to object.

Freeing each element you can see the demo shown below:

typedef struct Person
char * firstname , *last surName;
Person *ptrobj =malloc(sizeof(Person)); // memory allocation for struct
ptrobj->firstname = malloc(n); // memory allocation for firstname
ptrobj->surName = malloc(m); // memory allocation for surName

. // do whatever you want


The reason behind this is, if you free the ptrobj first, then there will be memory leaked which is the memory allocated by firstname and suName pointers.

Python: Binary To Decimal Conversion

You can use int casting which allows the base specification.

int(b, 2)  # Convert a binary string to a decimal int.

REST, HTTP DELETE and parameters

It's an old question, but here are some comments...

  1. In SQL, the DELETE command accepts a parameter "CASCADE", which allows you to specify that dependent objects should also be deleted. This is an example of a DELETE parameter that makes sense, but 'man rm' could provide others. How would these cases possibly be implemented in REST/HTTP without a parameter?
  2. @Jan, it seems to be a well-established convention that the path part of the URL identifies a resource, whereas the querystring does not (at least not necessarily). Examples abound: getting the same resource but in a different format, getting specific fields of a resource, etc. If we consider the querystring as part of the resource identifier, it is impossible to have a concept of "different views of the same resource" without turning to non-RESTful mechanisms such as HTTP content negotiation (which can be undesirable for many reasons).

PHP get dropdown value and text

$animals = array('--Select Animal--', 'Cat', 'Dog', 'Cow');
$selected_key = $_POST['animal'];
$selected_val = $animals[$_POST['animal']];

Use your $animals list to generate your dropdown list; you now can get the key & the value of that key.

Parsing json and searching through it

You can use jsonpipe if you just need the output (and more comfortable with command line):

cat bookmarks.json | jsonpipe |grep uri

How to obtain the query string from the current URL with JavaScript?

Have a look at the MDN article about window.location.

The QueryString is available in

Solution that work in legacy browsers as well

MDN provide an example (no longer available in the above referenced article) of how to the get value of a single key available in the QueryString. Something like this:

function getQueryStringValue (key) {  
  return decodeURIComponent( RegExp("^(?:.*[&\\?]" + encodeURIComponent(key).replace(/[\.\+\*]/g, "\\$&") + "(?:\\=([^&]*))?)?.*$", "i"), "$1"));  

// Would write the value of the QueryString-variable called name to the console  

In modern browsers

In modern browsers you have the searchParams property of the URL interface, which returns a URLSearchParams object. The returned object has a number of convenient methods, including a get-method. So the equivalent of the above example would be:

let params = (new URL(document.location)).searchParams;
let name = params.get("name");

The URLSearchParams interface can also be used to parse strings in a querystring format, and turn them into a handy URLSearchParams object.

let paramsString = "name=foo&age=1337"
let searchParams = new URLSearchParams(paramsString);

searchParams.has("name") === true; // true
searchParams.get("age") === "1337"; // true

Notice that the browser support is still limited on this interface, so if you need to support legacy browsers, stick with the first example or use a polyfill.

How to resolve the "ADB server didn't ACK" error?

On my end, I used Resource Monitor to see which application was still listening to port 5037 after all the Eclipse and adb restart were unsuccessful for me.

Start > All Programs > Accessories > System Tools >
Resource Monitor > Network > Listening Ports

This eventually showed that java.exe was listening to port 5037, hence, preventing adb from doing so. I killed java.exe, immediately start adb (with adb start-server) and received a confirmation that adb was able to start:

android-sdks\platform-tools>adb start-server
* daemon not running. starting it now on port 5037 *
* daemon started successfully *

How do I reverse an int array in Java?

There are two ways to have a solution for the problem:

1. Reverse an array in space.

Step 1. Swap the elements at the start and the end index.

Step 2. Increment the start index decrement the end index.

Step 3. Iterate Step 1 and Step 2 till start index < end index

For this, the time complexity will be O(n) and the space complexity will be O(1)

Sample code for reversing an array in space is like:

public static int[] reverseAnArrayInSpace(int[] array) {
    int startIndex = 0;
    int endIndex = array.length - 1;
    while(startIndex < endIndex) {
        int temp = array[endIndex];
        array[endIndex] = array[startIndex];
        array[startIndex] = temp;
    return array;

2. Reverse an array using an auxiliary array.

Step 1. Create a new array of size equal to the given array.

Step 2. Insert elements to the new array starting from the start index, from the given array starting from end index.

For this, the time complexity will be O(n) and the space complexity will be O(n)

Sample code for reversing an array with auxiliary array is like:

public static int[] reverseAnArrayWithAuxiliaryArray(int[] array) {
    int[] reversedArray = new int[array.length];
    for(int index = 0; index < array.length; index++) {
        reversedArray[index] = array[array.length - index -1]; 
    return reversedArray;

Also, we can use the Collections API from Java to do this.

The Collections API internally uses the same reverse in space approach.

Sample code for using the Collections API is like:

public static Integer[] reverseAnArrayWithCollections(Integer[] array) {
    List<Integer> arrayList = Arrays.asList(array);
    return arrayList.toArray(array);

Difference between maven scope compile and provided for JAR packaging

If jar file is like executable spring boot jar file then scope of all dependencies must be compile to include all jar files.

But if jar file used in other packages or applications then it does not need to include all dependencies in jar file because these packages or applications can provide other dependencies themselves.

How to run script as another user without password?

`su -c "Your command right here" -s /bin/sh username`

The above command is correct, but on Red Hat if selinux is enforcing it will not allow cron to execute scripts as another user. example; execl: couldn't exec /bin/sh execl: Permission denied

I had to install setroubleshoot and setools and run the following to allow it:

yum install setroubleshoot setools
sealert -a /var/log/audit/audit.log
grep crond /var/log/audit/audit.log | audit2allow -M mypol
semodule -i mypol.p

Automatically enter SSH password with script

You could use an expects script. I have not written one in quite some time but it should look like below. You will need to head the script with #!/usr/bin/expect

#!/usr/bin/expect -f
spawn ssh HOSTNAME
expect "login:" 
send "username\r"
expect "Password:"
send "password\r"

installation app blocked by play protect

If you are using some trackers like google analytics or amplitude and you are trying to release your app in another platforms other than Google Play, this errors appears for users. So there are two possible solutions:

  1. Use special trackers in your app (firebase and appmetrica are tested and are ok)
  2. Release your app in Google Play

Clear an input field with Reactjs?

Let me assume that you have done the 'this' binding of 'sendThru' function.

The below functions clears the input fields when the method is triggered.

sendThru() {
    this.inputTitle.value = "";
    this.inputEntry.value = "";

Refs can be written as inline function expression:

ref={el => this.inputTitle = el}

where el refers to the component.

When refs are written like above, React sees a different function object each time so on every update, ref will be called with null immediately before it's called with the component instance.

Read more about it here.

Using a RegEx to match IP addresses in Python

You have to modify your regex in the following way

pat = re.compile("^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$")

that's because . is a wildcard that stands for "every character"

How to break out of nested loops?

I note that the question is simply, "Is there any other way to break all of the loops?" I don't see any qualification but that it not be goto, in particular the OP didn't ask for a good way. So, how about we longjmp out of the inner loop? :-)

#include <stdio.h>
#include <setjmp.h>

int main(int argc, char* argv[]) {
  int counter = 0;
  jmp_buf look_ma_no_goto;
  if (!setjmp(look_ma_no_goto)) {
    for (int i = 0; i < 1000; i++) {
      for (int j = 0; j < 1000; j++) {
        if (i == 500 && j == 500) {
          longjmp(look_ma_no_goto, 1);
  printf("counter=%d\n", counter);

The setjmp function returns twice. The first time, it returns 0 and the program executes the nested for loops. Then when the both i and j are 500, it executes longjmp, which causes setjmp to return again with the value 1, skipping over the loop.

Not only will longjmp get you out of nested loops, it works with nested functions too!

Is there a way to specify which pytest tests to run from a file?

Specifying tests / selecting tests

Pytest supports several ways to run and select tests from the command-line.

Run tests in a module


Run tests in a directory

pytest testing/

Run tests by keyword expressions

pytest -k "MyClass and not method"

This will run tests which contain names that match the given string expression, which can include Python operators that use filenames, class names and function names as variables. The example above will run TestMyClass.test_something but not TestMyClass.test_method_simple.

Run tests by node ids

Each collected test is assigned a unique nodeid which consist of the module filename followed by specifiers like class names, function names and parameters from parametrization, separated by :: characters.

To run a specific test within a module:


Another example specifying a test method in the command line:


Run tests by marker expressions

pytest -m slow

Will run all tests which are decorated with the @pytest.mark.slow decorator.

For more information see marks.

Run tests from packages

pytest --pyargs pkg.testing

This will import pkg.testing and use its filesystem location to find and run tests from.


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

Many times as API's are updated. We forgot to update SDK Managers. For accessing recent API's one should always have highest API Level updated if possible should also have other regularly used lower level APIs to accommodate backward compatibility.
Go to build.gradle ( file change compileSdkVersion buildToolsVersion targetSdkVersion, all should have the highest level of API.

Converting list to numpy array

If you have a list of lists, you only needed to use ...

import numpy as np
npa = np.asarray(someListOfLists, dtype=np.float32)

per this LINK in the scipy / numpy documentation. You just needed to define dtype inside the call to asarray.

Uploading Laravel Project onto Web Server

If you are trying to host your Laravel app on a shared hosting, this may help you.

Hosting Laravel on shared hosting #1

Hosting Laravel on shared hosting #2

If you want PHP 5.4 add this line to your .htaccess file or call your hosting provider.

AddType application/x-httpd-php54 .php

Finding a substring within a list in Python

print [s for s in list if sub in s]

If you want them separated by newlines:

print "\n".join(s for s in list if sub in s)

Full example, with case insensitivity:

mylist = ['abc123', 'def456', 'ghi789', 'ABC987', 'aBc654']
sub = 'abc'

print "\n".join(s for s in mylist if sub.lower() in s.lower())

How to set JAVA_HOME path on Ubuntu?

I normally set paths in


However for Java, I followed instructions at

and it was sufficient for me.

you can also define multiple java_home's and have only one of them active (rest commented).

suppose in your bashrc file, you have

export JAVA_HOME=......jdk1.7

#export JAVA_HOME=......jdk1.8

notice 1.8 is commented. Once you do

source ~/.bashrc

jdk1.7 will be in path.

you can switch them fairly easily this way. There are other more permanent solutions too. The link I posted has that info.

How to restart service using command prompt?

This is my code, to start/stop a Windows service using SC command. If the service fails to start/stop, it will print a log info. You can try it by Inno Setup.

{ start a service }
Exec(ExpandConstant('{cmd}'), '/C sc start ServiceName', '',
     SW_HIDE, ewWaitUntilTerminated, ResultCode);
Log('sc start ServiceName:'+SysErrorMessage(ResultCode));
{ stop a service }
Exec(ExpandConstant('{cmd}'), '/C sc stop ServiceName', '',
     SW_HIDE, ewWaitUntilTerminated, ResultCode);
Log('sc stop ServiceName:'+SysErrorMessage(ResultCode));

Android : Fill Spinner From Java Code Programmatically

// you need to have a list of data that you want the spinner to display
List<String> spinnerArray =  new ArrayList<String>();

ArrayAdapter<String> adapter = new ArrayAdapter<String>(
    this, android.R.layout.simple_spinner_item, spinnerArray);

Spinner sItems = (Spinner) findViewById(;

also to find out what is selected you could do something like this

String selected = sItems.getSelectedItem().toString();
if (selected.equals("what ever the option was")) {

SQL select everything in an array

while ($i<length($cat)-1)

$SQL="SELECT * FROM products WHERE catid IN "+$SQL_Part;

It's more generic and will fit for any array!!

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

This did what I needed.

ps -eaf | grep `lsof -t -i:$PORT`

What is the bower (and npm) version syntax?

Bower uses semver syntax, but here are a few quick examples:

You can install a specific version:

$ bower install jquery#1.11.1

You can use ~ to specify 'any version that starts with this':

$ bower install jquery#~1.11

You can specify multiple version requirements together:

$ bower install "jquery#<2.0 >1.10"

Bin size in Matplotlib (Histogram)

For N bins, the bin edges are specified by list of N+1 values where the first N give the lower bin edges and the +1 gives the upper edge of the last bin.


from numpy import np; from pylab import *

bin_size = 0.1; min_edge = 0; max_edge = 2.5
N = (max_edge-min_edge)/bin_size; Nplus1 = N + 1
bin_list = np.linspace(min_edge, max_edge, Nplus1)

Note that linspace produces array from min_edge to max_edge broken into N+1 values or N bins

Refresh Page C# ASP.NET

You can just do a regular postback to refresh the page if you don't want to redirect. Posting back from any control will run the page lifecycle and refresh the page.

To do it from javascript, you can just call the __doPostBack() function.

Python import csv to list

You can use the list() function to convert csv reader object to list

import csv

with open('input.csv') as csv_file:
    reader = csv.reader(csv_file, delimiter=',')
    rows = list(reader)

'int' object has no attribute '__getitem__'

The error:

'int' object has no attribute '__getitem__'

means that you're attempting to apply the index operator [] on an int, not a list. So is col not a list, even when it should be? Let's start from that.

Look here:

col = [[0 for col in range(5)] for row in range(6)]

Use a different variable name inside, looks like the list comprehension overwrites the col variable during iteration. (Not during the iteration when you set col, but during the following ones.)

Deleting multiple elements from a list

To generalize the comment from @sth. Item deletion in any class, that implements abc.MutableSequence, and in list in particular, is done via __delitem__ magic method. This method works similar to __getitem__, meaning it can accept either an integer or a slice. Here is an example:

class MyList(list):
    def __delitem__(self, item):
        if isinstance(item, slice):
            for i in range(*item.indices(len(self))):
                self[i] = 'null'
            self[item] = 'null'

l = MyList(range(10))
del l[5:8]

This will output

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[0, 1, 2, 3, 4, 'null', 'null', 'null', 8, 9]

How can I troubleshoot Python "Could not find platform independent libraries <prefix>"

I had this issue while using Python installed with sudo make altinstall on Opensuse linux. It seems that the compiled libraries are installed in /usr/local/lib64 but Python is looking for them in /usr/local/lib.

I solved it by creating a dynamic link to the relevant directory in /usr/local/lib

sudo ln -s /usr/local/lib64/python3.8/lib-dynload/ /usr/local/lib/python3.8/lib-dynload

I suspect the better thing to do would be to specify libdir as an argument to configure (at the start of the build process) but I haven't tested it that way.

Is there a Social Security Number reserved for testing/examples?

I used this 457-55-5462 as testing SSN and it worked for me. I used it at paypal sandbox account. Hope it helps somebody

"Press Any Key to Continue" function in C

You can try more system indeppended method: system("pause");

How does Content Security Policy (CSP) work?

Apache 2 mod_headers

You could also enable Apache 2 mod_headers. On Fedora it's already enabled by default. If you use Ubuntu/Debian, enable it like this:

# First enable headers module for Apache 2,
# and then restart the Apache2 service
a2enmod headers
apache2 -k graceful

On Ubuntu/Debian you can configure headers in the file /etc/apache2/conf-enabled/security.conf

# Setting this header will prevent MSIE from interpreting files as something
# else than declared by the content type in the HTTP headers.
# Requires mod_headers to be enabled.
#Header set X-Content-Type-Options: "nosniff"

# Setting this header will prevent other sites from embedding pages from this
# site as frames. This defends against clickjacking attacks.
# Requires mod_headers to be enabled.
Header always set X-Frame-Options: "sameorigin"
Header always set X-Content-Type-Options nosniff
Header always set X-XSS-Protection "1; mode=block"
Header always set X-Permitted-Cross-Domain-Policies "master-only"
Header always set Cache-Control "no-cache, no-store, must-revalidate"
Header always set Pragma "no-cache"
Header always set Expires "-1"
Header always set Content-Security-Policy: "default-src 'none';"
Header always set Content-Security-Policy: "script-src 'self';"
Header always set Content-Security-Policy: "style-src 'self';"

Note: This is the bottom part of the file. Only the last three entries are CSP settings.

The first parameter is the directive, the second is the sources to be white-listed. I've added Google analytics and an adserver, which you might have. Furthermore, I found that if you have aliases, e.g, and configured in Apache 2 you should add them to the white-list as well.

Inline code is considered harmful, and you should avoid it. Copy all the JavaScript code and CSS to separate files and add them to the white-list.

While you're at it you could take a look at the other header settings and install mod_security

Further reading:

How to add include and lib paths to configure/make cycle?

This took a while to get right. I had this issue when cross-compiling in Ubuntu for an ARM target. I solved it with:

PATH=$PATH:/ccpath/bin CC=ccname-gcc AR=ccname-ar LD=ccname-ld CPPFLAGS="-nostdinc -I/ccrootfs/usr/include ..." LDFLAGS=-L/ccrootfs/usr/lib ./ --build=`config.guess` --host=armv5tejl-unknown-linux-gnueabihf

Notice CFLAGS is not used with, using it gave me the error: "configure: error: C compiler cannot create executables". In the build environment I was using an script was provided, if you don't have an script substitute ./ with ./configure in the command above. I ran config.guess on the target system to get the --host parameter.

After successfully running, compile with:

PATH=$PATH:/ccpath/bin CC=ccname-gcc AR=ccname-ar LD=ccname-ld CPPFLAGS="-nostdinc -I/ccrootfs/usr/include ..." LDFLAGS=-L/ccrootfs/usr/lib CFLAGS="-march=... -mcpu=... etc." make

The CFLAGS I chose to use were: "-march=armv5te -fno-tree-vectorize -mthumb-interwork -mcpu=arm926ej-s". It will take a while to get all of the include directories set up correctly: you might want some includes pointing to your cross-compiler and some pointing to your root file system includes, and there will likely be some conflicts.

I'm sure this is not the perfect answer. And I am still seeing some include directories pointing to / and not /ccrootfs in the Makefiles. Would love to know how to correct this. Hope this helps someone.

Winforms issue - Error creating window handle

I think it's normally related to the computer running out of memory so it's not able to create any more window handles. Normally windows starts to show some strange behavior at this point as well.

Display Bootstrap Modal using javascript onClick

You don't need an onclick. Assuming you're using Bootstrap 3 Bootstrap 3 Documentation

<div class="span4 proj-div" data-toggle="modal" data-target="#GSCCModal">Clickable content, graphics, whatever</div>

<div id="GSCCModal" class="modal fade" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
 <div class="modal-dialog">
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;  </button>
        <h4 class="modal-title" id="myModalLabel">Modal title</h4>
      <div class="modal-body">
      <div class="modal-footer">
        <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
        <button type="button" class="btn btn-primary">Save changes</button>

If you're using Bootstrap 2, you'd follow the markup here:

Link entire table row?

Unfortunately, no. Not with HTML and CSS. You need an a element to make a link, and you can't wrap an entire table row in one.

The closest you can get is linking every table cell. Personally I'd just link one cell and use JavaScript to make the rest clickable. It's good to have at least one cell that really looks like a link, underlined and all, for clarity anyways.

Here's a simple jQuery snippet to make all table rows with links clickable (it looks for the first link and "clicks" it)

$("table").on("click", "tr", function(e) {
    if ($("a,input")) // anything else you don't want to trigger the click

    location.href = $(this).find("a").attr("href");

Selecting multiple columns with linq query and lambda expression

Not sure what you table structure is like but see below.

public NamePriceModel[] AllProducts()
        using (UserDataDataContext db = new UserDataDataContext())
            return db.mrobProducts
                .Where(x => x.Status == 1)
                .Select(x => new NamePriceModel { 
                    Name = x.Name, 
                    Id = x.Id, 
                    Price = x.Price
                .OrderBy(x => x.Id)
         return null;

This would return an array of type anonymous with the members you require.


Create a new class.

public class NamePriceModel 
    public string Name {get; set;}
    public decimal? Price {get; set;}
    public int Id {get; set;}

I've modified the query above to return this as well and you should change your method from returning string[] to returning NamePriceModel[].

Google Maps API v3: How do I dynamically change the marker icon?

This thread might be dead, but StyledMarker is available for API v3. Just bind the color change you want to the correct DOM event using the addDomListener() method. This example is pretty close to what you want to do. If you look at the page source, change:

google.maps.event.addDomListener(document.getElementById("changeButton"),"click",function() {

to something like:

google.maps.event.addDomListener("mouseover",function() {

That should be enough to get you moving along.

The Wikipedia page on DOM Events will also help you target the event that you want to capture on the client-side.

Good luck (if you still need it)

How do I check if a property exists on a dynamic anonymous type in c#?

Merging and fixing answers from Serj-TM and user3359453 so that it works with both ExpandoObject and DynamicJsonObject. This works for me.

public static bool HasPropertyExist(dynamic settings, string name)
    if (settings is System.Dynamic.ExpandoObject)
        return ((IDictionary<string, object>)settings).ContainsKey(name);

    if (settings is System.Web.Helpers.DynamicJsonObject)
        return settings[name] != null;
    catch (KeyNotFoundException)
        return false;

    return settings.GetType().GetProperty(name) != null;

Google Play on Android 4.0 emulator

For future visitors.

As of now Android 4.2.2 platform includes Google Play services. Just use an emulator running Jelly Bean. Details can be found here:

Setup Google Play Services SDK


Another option is to use Genymotion (runs way faster)


As @gdw2 commented: "setting up the Google Play Services SDK does not install a working Google Play app -- it just enables certain services provided by the SDK"

After version 2.0 Genymotion does not come with Play Services by default, but it can be easily installed manually. Just download the right version from here and drag and drop into the virtual device (emulador).

Total memory used by Python process?

Even easier to use than /proc/self/status: /proc/self/statm. It's just a space delimited list of several statistics. I haven't been able to tell if both files are always present.


Provides information about memory usage, measured in pages. The columns are:

  • size (1) total program size (same as VmSize in /proc/[pid]/status)
  • resident (2) resident set size (same as VmRSS in /proc/[pid]/status)
  • shared (3) number of resident shared pages (i.e., backed by a file) (same as RssFile+RssShmem in /proc/[pid]/status)
  • text (4) text (code)
  • lib (5) library (unused since Linux 2.6; always 0)
  • data (6) data + stack
  • dt (7) dirty pages (unused since Linux 2.6; always 0)

Here's a simple example:

from pathlib import Path
from resource import getpagesize

PAGESIZE = getpagesize()
PATH = Path('/proc/self/statm')

def get_resident_set_size() -> int:
    """Return the current resident set size in bytes."""
    # statm columns are: size resident shared text lib data dt
    statm = PATH.read_text()
    fields = statm.split()
    return int(fields[1]) * PAGESIZE

data = []
start_memory = get_resident_set_size()
for _ in range(10):
    data.append('X' * 100000)
    print(get_resident_set_size() - start_memory)

That produces a list that looks something like this:


You can see that it jumps by about 300,000 bytes after roughly 3 allocations of 100,000 bytes.

How to check if an item is selected from an HTML drop down list?

function check(selId) {
  var sel = document.getElementById(selId);
  var dropDown_sel = sel.options[sel.selectedIndex].text;
  if (dropDown_sel != "none") {


     //state is a Global variable initially it is set to 0

function checkstatevalue() {
      if (state==1) {
           return 1;
      return false;

and html is for example

<form name="droptest" onSubmit="return checkstatevalue()">

<select id='Sel1' onchange='check("Sel1");'>
  <option value='junaid'>Junaid</option>
  <option value='none'>none</option>
  <option value='ali'>Ali</option>


Now when submitting a form first check what is the value of state if it is 0 it means that no item has been selected.

how to do "press enter to exit" in batch

Use this snippet:

@echo off
echo something
echo press enter to exit
pause >nul

CMD command to check connected USB devices

You could use wmic command:

wmic logicaldisk where drivetype=2 get <DeviceID, VolumeName, Description, ...>

Drivetype 2 indicates that its a removable disk.

Output ("echo") a variable to a text file

Note: The answer below is written from the perspective of Windows PowerShell.
However, it applies to the cross-platform PowerShell Core edition (v6+) as well, except that the latter - commendably - consistently defaults to BOM-less UTF-8 character encoding, which is the most widely compatible one across platforms and cultures.

To complement bigtv's helpful answer helpful answer with a more concise alternative and background information:

# > $file is effectively the same as | Out-File $file
# Objects are written the same way they display in the console.
# Default character encoding is UTF-16LE (mostly 2 bytes per char.), with BOM.
# Use Out-File -Encoding <name> to change the encoding.
$env:computername > $file

# Set-Content calls .ToString() on each object to output.
# Default character encoding is "ANSI" (culture-specific, single-byte).
# Use Set-Content -Encoding <name> to change the encoding.
# Use Set-Content rather than Add-Content; the latter is for *appending* to a file.
$env:computername | Set-Content $file 

When outputting to a text file, you have 2 fundamental choices that use different object representations and, in Windows PowerShell (as opposed to PowerShell Core), also employ different default character encodings:

  • Out-File (or >) / Out-File -Append (or >>):

    • Suitable for output objects of any type, because PowerShell's default output formatting is applied to the output objects.

      • In other words: you get the same output as when printing to the console.
    • The default encoding, which can be changed with the -Encoding parameter, is Unicode, which is UTF-16LE in which most characters are encoded as 2 bytes. The advantage of a Unicode encoding such as UTF-16LE is that it is a global alphabet, capable of encoding all characters from all human languages.

      • In PSv5.1+, you can change the encoding used by > and >>, via the $PSDefaultParameterValues preference variable, taking advantage of the fact that > and >> are now effectively aliases of Out-File and Out-File -Append. To change to UTF-8, for instance, use:
  • Set-Content / Add-Content:

    • For writing strings and instances of types known to have meaningful string representations, such as the .NET primitive data types (Booleans, integers, ...).

      • .psobject.ToString() method is called on each output object, which results in meaningless representations for types that don't explicitly implement a meaningful representation; [hashtable] instances are an example:
        @{ one = 1 } | Set-Content t.txt writes literal System.Collections.Hashtable to t.txt, which is the result of @{ one = 1 }.ToString().
    • The default encoding, which can be changed with the -Encoding parameter, is Default, which is the system's "ANSI" code page, a the single-byte culture-specific legacy encoding for non-Unicode applications, most commonly Windows-1252.
      Note that the documentation currently incorrectly claims that ASCII is the default encoding.

    • Note that Add-Content's purpose is to append content to an existing file, and it is only equivalent to Set-Content if the target file doesn't exist yet.
      Furthermore, the default or specified encoding is blindly applied, irrespective of the file's existing contents' encoding.

Out-File / > / Set-Content / Add-Content all act culture-sensitively, i.e., they produce representations suitable for the current culture (locale), if available (though custom formatting data is free to define its own, culture-invariant representation - see Get-Help about_format.ps1xml). This contrasts with PowerShell's string expansion (string interpolation in double-quoted strings), which is culture-invariant - see this answer of mine.

As for performance: Since Set-Content doesn't have to apply default formatting to its input, it performs better.

As for the OP's symptom with Add-Content:

Since $env:COMPUTERNAME cannot contain non-ASCII characters, Add-Content's output, using "ANSI" encoding, should not result in ? characters in the output, and the likeliest explanation is that the ? were part of the preexisting content in output file $file, which Add-Content appended to.

React - how to pass state to another component

Move all of your state and your handleClick function from Header to your MainWrapper component.

Then pass values as props to all components that need to share this functionality.

class MainWrapper extends React.Component {
    constructor() {
        this.state = {
            sidbarPushCollapsed: false,
            profileCollapsed: false
        this.handleClick = this.handleClick.bind(this);
    handleClick() {
            sidbarPushCollapsed: !this.state.sidbarPushCollapsed,
            profileCollapsed: !this.state.profileCollapsed

    render() {
        return (
               profileCollapsed={this.state.profileCollapsed} />

Then in your Header's render() method, you'd use this.props:

<button type="button" id="sidbarPush" onClick={this.props.handleClick} profile={this.props.profileCollapsed}>

Get a pixel from HTML Canvas?

Yup, check out getImageData(). Here's an example of breaking CAPTCHA with JavaScript using canvas:

OCR and Neural Nets in JavaScript

Custom UITableViewCell from nib in Swift

With Swift 5 and iOS 12.2, you should try the following code in order to solve your problem:


import UIKit

class CustomCell: UITableViewCell {

    // Link those IBOutlets with the UILabels in your .XIB file
    @IBOutlet weak var middleLabel: UILabel!
    @IBOutlet weak var leftLabel: UILabel!
    @IBOutlet weak var rightLabel: UILabel!



import UIKit

class TableViewController: UITableViewController {

    let items = ["Item 1", "Item2", "Item3", "Item4"]

    override func viewDidLoad() {
        tableView.register(UINib(nibName: "CustomCell", bundle: nil), forCellReuseIdentifier: "CustomCell")

    // MARK: - UITableViewDataSource

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "CustomCell", for: indexPath) as! CustomCell

        cell.middleLabel.text = items[indexPath.row]
        cell.leftLabel.text = items[indexPath.row]
        cell.rightLabel.text = items[indexPath.row]

        return cell


The image below shows a set of constraints that work with the provided code without any constraints ambiguity message from Xcode:

enter image description here

git rebase fatal: Needed a single revision

You need to provide the name of a branch (or other commit identifier), not the name of a remote to git rebase.


git rebase origin/master


git rebase origin

Note, although origin should resolve to the the ref origin/HEAD when used as an argument where a commit reference is required, it seems that not every repository gains such a reference so it may not (and in your case doesn't) work. It pays to be explicit.

Check if an array contains any element of another array in JavaScript

When I looked at your answers, I could not find the answer I wanted. I did something myself and I want to share this with you.

It will be true only if the words entered (array) are correct.

function contains(a,b) {
    let counter = 0;
    for(var i = 0; i < b.length; i++) {;
        if(a.includes(b[i])) counter++;
    if(counter === b.length) return true;
    return false;

let main_array = ['foo','bar','baz'];
let sub_array_a = ['foo','foobar'];
let sub_array_b = ['foo','bar'];

console.log(contains(main_array, sub_array_a)); // returns false
console.log(contains(main_array,sub_array_b )); // returns true

While loop to test if a file exists in bash

When you say "doesn't work", how do you know it doesn't work?

You might try to figure out if the file actually exists by adding:

while [ ! -f /tmp/list.txt ]
  sleep 2 # or less like 0.2
ls -l /tmp/list.txt

You might also make sure that you're using a Bash (or related) shell by typing 'echo $SHELL'. I think that CSH and TCSH use a slightly different semantic for this loop.

What character represents a new line in a text area

It seems that, according to the HTML5 spec, the value property of the textarea element should return '\r\n' for a newline:

The element's value is defined to be the element's raw value with the following transformation applied:

Replace every occurrence of a "CR" (U+000D) character not followed by a "LF" (U+000A) character, and every occurrence of a "LF" (U+000A) character not preceded by a "CR" (U+000D) character, by a two-character string consisting of a U+000D CARRIAGE RETURN "CRLF" (U+000A) character pair.

Following the link to 'value' makes it clear that it refers to the value property accessed in javascript:

Form controls have a value and a checkedness. (The latter is only used by input elements.) These are used to describe how the user interacts with the control.

However, in all five major browsers (using Windows, 11/27/2015), if '\r\n' is written to a textarea, the '\r' is stripped. (To test: var e=document.createElement('textarea'); e.value='\r\n'; alert(e.value=='\n');) This is true of IE since v9. Before that, IE was returning '\r\n' and converting both '\r' and '\n' to '\r\n' (which is the HTML5 spec). So... I'm confused.

To be safe, it's usually enough to use '\r?\n' in regular expressions instead of just '\n', but if the newline sequence must be known, a test like the above can be performed in the app.

Getting value from JQUERY datepicker

You could do it as follows - with validation just to ensure that the datepicker is bound to the element.

var dt;

if ($("div#someID").is('.hasDatepicker')) {
    dt = $("div#someID").datepicker('getDate');

How to get client's IP address using JavaScript?

You can use web services like:


<script type="text/javascript" src="">
    function foo(json) {

additional example:    

PHP __get and __set magic methods

From the PHP manual:

  • __set() is run when writing data to inaccessible properties.
  • __get() is utilized for reading data from inaccessible properties.

This is only called on reading/writing inaccessible properties. Your property however is public, which means it is accessible. Changing the access modifier to protected solves the issue.

PivotTable to show values, not sum of values

I fear this might turn out to BE the long way round but could depend on how big your data set is – presumably more than four months for example.

Assuming your data is in ColumnA:C and has column labels in Row 1, also that Month is formatted mmm(this last for ease of sorting):

  1. Sort the data by Name then Month
  2. Enter in D2 =IF(AND(A2=A1,C2=C1),D1+1,1) (One way to deal with what is the tricky issue of multiple entries for the same person for the same month).
  3. Create a pivot table from A1:D(last occupied row no.)
  4. Say insert in F1.
  5. Layout as in screenshot.

SO12803305 example

I’m hoping this would be adequate for your needs because pivot table should automatically update (provided range is appropriate) in response to additional data with refresh. If not (you hard taskmaster), continue but beware that the following steps would need to be repeated each time the source data changes.

  1. Copy pivot table and Paste Special/Values to, say, L1.
  2. Delete top row of copied range with shift cells up.
  3. Insert new cell at L1 and shift down.
  4. Key 'Name' into L1.
  5. Filter copied range and for ColumnL, select Row Labels and numeric values.
  6. Delete contents of L2:L(last selected cell)
  7. Delete blank rows in copied range with shift cells up (may best via adding a column that counts all 12 months). Hopefully result should be as highlighted in yellow.

Happy to explain further/try again (I've not really tested this) if does not suit.

EDIT (To avoid second block of steps above and facilitate updating for source data changes)

.0. Before first step 2. add a blank row at the very top and move A2:D2 up.
.2. Adjust cell references accordingly (in D3 =IF(AND(A3=A2,C3=C2),D2+1,1).
.3. Create pivot table from A:D

.6. Overwrite Row Labels with Name.
.7. PivotTable Tools, Design, Report Layout, Show in Tabular Form and sort rows and columns A>Z.
.8. Hide Row1, ColumnG and rows and columns that show (blank).

additional example

Steps .0. and .2. in the edit are not required if the pivot table is in a different sheet from the source data (recommended).

Step .3. in the edit is a change to simplify the consequences of expanding the source data set. However introduces (blank) into pivot table that if to be hidden may need adjustment on refresh. So may be better to adjust source data range each time that changes instead: PivotTable Tools, Options, Change Data Source, Change Data Source, Select a table or range). In which case copy rather than move in .0.

selecting rows with id from another table

Try this (subquery):

   (SELECT term_id FROM terms_relation WHERE taxonomy = "categ")

Or you can try this (JOIN):

SELECT t.* FROM terms AS t 
   INNER JOIN terms_relation AS tr 
   ON = tr.term_id AND tr.taxonomy = "categ"

If you want to receive all fields from two tables:

SELECT,, t.slug, tr.description, tr.created_at, tr.updated_at 
  FROM terms AS t 
   INNER JOIN terms_relation AS tr 
   ON = tr.term_id AND tr.taxonomy = "categ"

How do I format date in jQuery datetimepicker?

Here you go.

   // dateFormat: 'dd-mm-yy',
   format:'DD/MM/YYYY HH:mm:ss',
    minDate: getFormattedDate(new Date())

function getFormattedDate(date) {
    var day = date.getDate();
    var month = date.getMonth() + 1;
    var year = date.getFullYear().toString().slice(2);
    return day + '-' + month + '-' + year;

You need to pass datepicker() the date formatted correctly.

Python: Figure out local timezone

The following appears to work for 3.7+, using standard libs:

from datetime import timedelta
from datetime import timezone
import time

def currenttz():
    if time.daylight:
        return timezone(timedelta(seconds=-time.altzone),time.tzname[1])
        return timezone(timedelta(seconds=-time.timezone),time.tzname[0])

Parsing a comma-delimited std::string

#include <sstream>
#include <vector>

const char *input = "1,1,1,1,2,1,1,1,0";

int main() {
    std::stringstream ss(input);
    std::vector<int> output;
    int i;
    while (ss >> i) {

Bad input (for instance consecutive separators) will mess this up, but you did say simple.

Getting the thread ID from a thread

For those about to hack:

    public static int GetNativeThreadId(Thread thread)
        var f = typeof(Thread).GetField("DONT_USE_InternalThread",
            BindingFlags.GetField | BindingFlags.NonPublic | BindingFlags.Instance);

        var pInternalThread = (IntPtr)f.GetValue(thread);
        var nativeId = Marshal.ReadInt32(pInternalThread, (IntPtr.Size == 8) ? 548 : 348); // found by analyzing the memory
        return nativeId;

Show Current Location and Nearby Places and Route between two places using Google Maps API in Android

You have two options for displaying the Map

  1. Use Maps Library for Android to render the Map
  2. Use Maps API V3 inside a web view

For showing local POIs around a Lat, Long use Places APIs

How to use the gecko executable with Selenium

I'm using FirefoxOptions class to set the binary location with Firefox 52.0, GeckoDriver v0.15.0 and Selenium 3.3.1 as mentioned in this article -

The java code that I used -

FirefoxOptions options = new FirefoxOptions();
options.setBinary("C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe"); //location of FF exe

FirefoxDriver driver = new FirefoxDriver(options);

Parsing ISO 8601 date in Javascript

datejs could parse following, you might want to try out.

Date.parse('1997-07-16T19:20:15')           // ISO 8601 Formats
Date.parse('1997-07-16T19:20:30+01:00')     // ISO 8601 with Timezone offset

Edit: Regex version

x = "2011-01-28T19:30:00EST"

MM = ["January", "February","March","April","May","June","July","August","September","October","November", "December"]

xx = x.replace(
        return MM[$2-1]+" "+$3+", "+$1+" - "+$4%12+":"+$5+(+$4>12?"PM":"AM")+" "+$6


January 28, 2011 - 7:30PM EST

Edit2: I changed my timezone to EST and now I got following

x = "2011-01-28T19:30:00-05:00"

MM = {Jan:"January", Feb:"February", Mar:"March", Apr:"April", May:"May", Jun:"June", Jul:"July", Aug:"August", Sep:"September", Oct:"October", Nov:"November", Dec:"December"}

xx = String(new Date(x)).replace(
    /\w{3} (\w{3}) (\d{2}) (\d{4}) (\d{2}):(\d{2}):[^(]+\(([A-Z]{3})\)/,
        return MM[$1]+" "+$2+", "+$3+" - "+$4%12+":"+$5+(+$4>12?"PM":"AM")+" "+$6 


January 28, 2011 - 7:30PM EST


String(new Date(x))


Fri Jan 28 2011 19:30:00 GMT-0500 (EST)

regex parts just converting above string to your required format.

January 28, 2011 - 7:30PM EST

Good Java graph algorithm library?

Try Annas its an open source graph package which is easy to get to grips with

How to store file name in database, with other info while uploading image to server using PHP?

Your part:

$result = mysql_connect("localhost", "******", "*****") or die ("Could not save image name

Error: " . mysql_error());

mysql_select_db("project") or die("Could not select database");
mysql_query("INSERT into dbProfiles (photo) VALUES('".$_FILES['filep']['name']."')");
if($result) { echo "Image name saved into database


Doesn't make much sense, your connection shouldn't be named $result but that is a naming issue not a coding one.

What is a coding issue is if($result), your saying if you can connect to the database regardless of the insert query failing or succeeding you will output "Image saved into database".

Try adding do

$realresult = mysql_query("INSERT into dbProfiles (photo) VALUES('".$_FILES['filep']['name']."')");

and change the if($result) to $realresult

I suspect your query is failing, perhaps you have additional columns or something?

Try copy/pasting your query, replacing the ".$_FILES['filep']['name']." with test and running it in your query browser and see if it goes in.

jQuery - Add ID instead of Class

$('selector').attr( 'id', 'yourId' );

Disabling Chrome Autofill

The only way that works for me was:(jQuery required)

$(document).ready(function(e) {
    if ($.browser.webkit) {
        $('#input_id').val(' ').val('');

what is the difference between uint16_t and unsigned short int incase of 64 bit processor?

uint16_t is unsigned 16-bit integer.

unsigned short int is unsigned short integer, but the size is implementation dependent. The standard only says it's at least 16-bit (i.e, minimum value of UINT_MAX is 65535). In practice, it usually is 16-bit, but you can't take that as guaranteed.


  1. If you want a portable unsigned 16-bit integer, use uint16_t.
  2. inttypes.h and stdint.h are both introduced in C99. If you are using C89, define your own type.
  3. uint16_t may not be provided in certain implementation(See reference below), but unsigned short int is always available.

Reference: C11(ISO/IEC 9899:201x) §7.20 Integer types

For each type described herein that the implementation provides) shall declare that typedef name and define the associated macros. Conversely, for each type described herein that the implementation does not provide, shall not declare that typedef name nor shall it define the associated macros. An implementation shall provide those types described as ‘‘required’’, but need not provide any of the others (described as ‘optional’’).

C# loop - break vs. continue

Please let me state the obvious: note that adding neither break nor continue, will resume your program; i.e. I trapped for a certain error, then after logging it, I wanted to resume processing, and there were more code tasks in between the next row, so I just let it fall through.

Java substring: 'string index out of range'

Java's substring method fails when you try and get a substring starting at an index which is longer than the string.

An easy alternative is to use Apache Commons StringUtils.substring:

public static String substring(String str, int start)

Gets a substring from the specified String avoiding exceptions.

A negative start position can be used to start n characters from the end of the String.

A null String will return null. An empty ("") String will return "".

 StringUtils.substring(null, *)   = null
 StringUtils.substring("", *)     = ""
 StringUtils.substring("abc", 0)  = "abc"
 StringUtils.substring("abc", 2)  = "c"
 StringUtils.substring("abc", 4)  = ""
 StringUtils.substring("abc", -2) = "bc"
 StringUtils.substring("abc", -4) = "abc"

str - the String to get the substring from, may be null
start - the position to start from, negative means count back from the end of the String by this many characters

substring from start position, null if null String input

Note, if you can't use Apache Commons lib for some reason, you could just grab the parts you need from the source

// Substring
 * <p>Gets a substring from the specified String avoiding exceptions.</p>
 * <p>A negative start position can be used to start {@code n}
 * characters from the end of the String.</p>
 * <p>A {@code null} String will return {@code null}.
 * An empty ("") String will return "".</p>
 * <pre>
 * StringUtils.substring(null, *)   = null
 * StringUtils.substring("", *)     = ""
 * StringUtils.substring("abc", 0)  = "abc"
 * StringUtils.substring("abc", 2)  = "c"
 * StringUtils.substring("abc", 4)  = ""
 * StringUtils.substring("abc", -2) = "bc"
 * StringUtils.substring("abc", -4) = "abc"
 * </pre>
 * @param str  the String to get the substring from, may be null
 * @param start  the position to start from, negative means
 *  count back from the end of the String by this many characters
 * @return substring from start position, {@code null} if null String input
public static String substring(final String str, int start) {
    if (str == null) {
        return null;

    // handle negatives, which means last n characters
    if (start < 0) {
        start = str.length() + start; // remember start is negative

    if (start < 0) {
        start = 0;
    if (start > str.length()) {
        return EMPTY;

    return str.substring(start);

How much data / information can we save / store in a QR code?

QR codes have three parameters: Datatype, size (number of 'pixels') and error correction level. How much information can be stored there also depends on these parameters. For example the lower the error correction level, the more information that can be stored, but the harder the code is to recognize for readers.

The maximum size and the lowest error correction give the following values:
Numeric only Max. 7,089 characters
Alphanumeric Max. 4,296 characters
Binary/byte Max. 2,953 characters (8-bit bytes)

Excel formula to search if all cells in a range read "True", if not, then show "False"

As it appears you have the values as text, and not the numeric True/False, then you can use either COUNTIF or SUMPRODUCT


Getting a machine's external IP address with Python

Use this script :

import urllib, json

data = json.loads(urllib.urlopen("").read())
print data["ip"]

Without json :

import urllib, re

data ='"([0-9.]*)"', urllib.urlopen("").read()).group(1)
print data

Using Laravel Homestead: 'no input file specified'

After I renamed some directories, I had to destroy and rerun vagrant. None of the solutions here worked.

This worked for me:

vagrant destroy
vagrant up