Programs & Examples On #Input language

How to check if ZooKeeper is running or up from command prompt?

One other way would be to use 4 letter commands to validate if zookeeper service is healthy or not

echo stat | nc <zookeeper ip> 2181
echo mntr | nc <zookeeper ip> 2181
echo isro  | nc <zookeeper ip> 2181

More details on the documentation link below

Dictionary with list of strings as value

I'd wrap the dictionary in another class:

public class MyListDictionary

    private Dictionary<string, List<string>> internalDictionary = new Dictionary<string,List<string>>();

    public void Add(string key, string value)
        if (this.internalDictionary.ContainsKey(key))
            List<string> list = this.internalDictionary[key];
            if (list.Contains(value) == false)
            List<string> list = new List<string>();
            this.internalDictionary.Add(key, list);


Better way to cast object to int

You can first cast object to string and then cast the string to int; for example:

string str_myobject = myobject.ToString();
int int_myobject = int.Parse(str_myobject);

this worked for me.

Error while installing json gem 'mkmf.rb can't find header files for ruby'

Modern era update, as stated by mimoralea:

In case that you are using ruby 2.0 or 2.2 (thanks @patrick-davey).

sudo apt-get install ruby2.0-dev
sudo apt-get install ruby2.2-dev
sudo apt-get install ruby2.3-dev

or, generic way:

sudo apt-get install ruby-dev


sudo apt-get install ruby`ruby -e 'puts RUBY_VERSION[/\d+\.\d+/]'`-dev

The first link you’ve posted is exactly your case: there is no ruby development environment installed. Development env is needed to compile ruby extensions, which are mostly written in C. Proxy has nothing to do with the problem: everything is downloaded fine, just compilation fails.

I would suggest you to install ruby-dev (ruby-devel for rpm-based distros) package onto you target machine.

gcc package might be needed as well.


$ sudo apt-get install ruby-dev

Or, for Redhat distro:

$ sudo yum install ruby-devel

Or, for [open]SuSE:

$ sudo zypper install ruby-devel

Check if a Bash array contains a value

Another one liner without a function:

(for e in "${array[@]}"; do [[ "$e" == "searched_item" ]] && exit 0; done) && echo "found" || echo "not found"

Thanks @Qwerty for the heads up regarding spaces!

corresponding function:

find_in_array() {
  local word=$1
  for e in "$@"; do [[ "$e" == "$word" ]] && return 0; done
  return 1


some_words=( these are some words )
find_in_array word "${some_words[@]}" || echo "expected missing! since words != word"

AngularJS : ng-click not working

Just add the function reference to the $scope in the controller:

for example if you want the function MyFunction to work in ng-click just add to the controller:

app.controller("MyController", ["$scope", function($scope) {
   $scope.MyFunction = MyFunction;

Command to find information about CPUs on a UNIX machine

Try psrinfo to find the processor type and the number of physical processors installed on the system.

Generate your own Error code in swift 3

You can create enums to deal with errors :)

enum RikhError: Error {
    case unknownError
    case connectionError
    case invalidCredentials
    case invalidRequest
    case notFound
    case invalidResponse
    case serverError
    case serverUnavailable
    case timeOut
    case unsuppotedURL

and then create a method inside enum to receive the http response code and return the corresponding error in return :)

static func checkErrorCode(_ errorCode: Int) -> RikhError {
        switch errorCode {
        case 400:
            return .invalidRequest
        case 401:
            return .invalidCredentials
        case 404:
            return .notFound
        //bla bla bla
            return .unknownError

Finally update your failure block to accept single parameter of type RikhError :)

I have a detailed tutorial on how to restructure traditional Objective - C based Object Oriented network model to modern Protocol Oriented model using Swift3 here Have a look :)

Hope it helps :)

Bootstrap number validation

You should use jquery validation because if you use type="number" then you can also enter "E" character in input type, which is not correct.



<input class="form-control floatNumber" name="energy1_total_power_generated" type="text" required="" > 


//integer value validation
$('input.floatNumber').on('input', function() {
    this.value = this.value.replace(/[^0-9.]/g,'').replace(/(\..*)\./g, '$1');

What is the HTML tabindex attribute?

tabindex is a global attribute responsible for two things:

  1. it sets the order of "focusable" elements and
  2. it makes elements "focusable".

In my mind the second thing is even more important than the first one. There are very few elements that are focusable by default (e.g. <a> and form controls). Developers very often add some JavaScript event handlers (like 'onclick') on not focusable elements (<div>, <span> and so on), and the way to make your interface be responsive not only to mouse events but also to keyboard events (e.g. 'onkeypress') is to make such elements focusable. Lastly, if you don't want to set the order but just make your element focusable use tabindex="0" on all such elements:

<div tabindex="0"></div>

Also, if you don't want it to be focusable via the tab key then use tabindex="-1". For example, the below link will not be focused while using tab keys to traverse.

<a href="#" tabindex="-1">Tab key cannot reach here!</a>

How to send authorization header with axios

Rather than adding it to every request, you can just add it as a default config like so.

axios.defaults.headers.common['Authorization'] = `Bearer ${access_token}` 

How to print to console using swift playground?

move you mouse over the "Hello, playground" on the right side bar, you will see an eye icon and a small circle icon next it. Just click on the circle one to show the detail page and console output!

Is there a way to suppress JSHint warning for one given line?

The "evil" answer did not work for me. Instead, I used what was recommended on the JSHints docs page. If you know the warning that is thrown, you can turn it off for a block of code. For example, I am using some third party code that does not use camel case functions, yet my JSHint rules require it, which led to a warning. To silence it, I wrote:

/*jshint -W106 */
/*jshint +W106 */

Column calculated from another column?

You can use generated columns from MYSQL 5.7.

Example Usage:

ALTER TABLE tbl_test
ADD COLUMN calc_val INT 
GENERATED ALWAYS AS (((`column1` - 1) * 16) + `column2`) STORED;


  • Virtual: calculated on the fly when a record is read from a table (default)
  • Stored: calculated when a new record is inserted/updated within the table

Accessing AppDelegate from framework?

If you're creating a framework the whole idea is to make it portable. Tying a framework to the app delegate defeats the purpose of building a framework. What is it you need the app delegate for?

PHP: check if any posted vars are empty - form: all fields required

Something like this:

// Required field names
$required = array('login', 'password', 'confirm', 'name', 'phone', 'email');

// Loop over field names, make sure each one exists and is not empty
$error = false;
foreach($required as $field) {
  if (empty($_POST[$field])) {
    $error = true;

if ($error) {
  echo "All fields are required.";
} else {
  echo "Proceed...";

How to send email attachments?

Another way with python 3 (If someone is searching):

import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.base import MIMEBase
from email import encoders

fromaddr = "sender mail address"
toaddr = "receiver mail address"

msg = MIMEMultipart()

msg['From'] = fromaddr
msg['To'] = toaddr
msg['Subject'] = "SUBJECT OF THE EMAIL"


msg.attach(MIMEText(body, 'plain'))

filename = "fileName"
attachment = open("path of file", "rb")

part = MIMEBase('application', 'octet-stream')
part.add_header('Content-Disposition', "attachment; filename= %s" % filename)


server = smtplib.SMTP('', 587)
server.login(fromaddr, "sender mail password")
text = msg.as_string()
server.sendmail(fromaddr, toaddr, text)

Make sure to allow “less secure apps” on your Gmail account

Fastest way to duplicate an array in JavaScript - slice vs. 'for' loop

Easiest way to deep clone Array or Object:

var dup_array = JSON.parse(JSON.stringify(original_array))

Google Maps API throws "Uncaught ReferenceError: google is not defined" only when using AJAX

At a guess, you're initialising something before your initialize function: var directionsService = new google.maps.DirectionsService();

Move that into the function, so it won't try and execute it before the page is loaded.

var directionsDisplay, directionsService;
var map;
function initialize() {
  directionsService = new google.maps.DirectionsService();
  directionsDisplay = new google.maps.DirectionsRenderer();

CSS display: inline vs inline-block

Inline elements:

  1. respect left & right margins and padding, but not top & bottom
  2. cannot have a width and height set
  3. allow other elements to sit to their left and right.
  4. see very important side notes on this here.

Block elements:

  1. respect all of those
  2. force a line break after the block element
  3. acquires full-width if width not defined

Inline-block elements:

  1. allow other elements to sit to their left and right
  2. respect top & bottom margins and padding
  3. respect height and width

From W3Schools:

  • An inline element has no line break before or after it, and it tolerates HTML elements next to it.

  • A block element has some whitespace above and below it and does not tolerate any HTML elements next to it.

  • An inline-block element is placed as an inline element (on the same line as adjacent content), but it behaves as a block element.

When you visualize this, it looks like this:

CSS block vs inline vs inline-block

The image is taken from this page, which also talks some more about this subject.

Adding a new SQL column with a default value

If you are learning it's helpful to use a GUI like SQLyog, make the changes using the program and then see the History tab for the DDL statements that made those changes.

Showing line numbers in IPython/Jupyter Notebooks

On IPython 2.2.0, just typing l (lowercase L) on command mode (activated by typing Esc) works. See [Help] - [Keyboard Shortcuts] for other shortcuts.

Also, you can set default behavior to display line numbers by editing custom.js.

How to import Maven dependency in Android Studio/IntelliJ?

Try itext. Add dependency to your build.gradle for latest as of this post

Note: special version for android, trailing "g":

dependencies {
    compile 'com.itextpdf:itextg:5.5.9'

Predict() - Maybe I'm not understanding it

First, you want to use

model <- lm(Total ~ Coupon, data=df)

not model <-lm(df$Total ~ df$Coupon, data=df).

Second, by saying lm(Total ~ Coupon), you are fitting a model that uses Total as the response variable, with Coupon as the predictor. That is, your model is of the form Total = a + b*Coupon, with a and b the coefficients to be estimated. Note that the response goes on the left side of the ~, and the predictor(s) on the right.

Because of this, when you ask R to give you predicted values for the model, you have to provide a set of new predictor values, ie new values of Coupon, not Total.

Third, judging by your specification of newdata, it looks like you're actually after a model to fit Coupon as a function of Total, not the other way around. To do this:

model <- lm(Coupon ~ Total, data=df)
new.df <- data.frame(Total=c(79037022, 83100656, 104299800))
predict(model, new.df)

Recursively look for files with a specific extension

find $directory -type f -name "*.in"

is a bit shorter than that whole thing (and safer - deals with whitespace in filenames and directory names).

Your script is probably failing for entries that don't have a . in their name, making $extension empty.

Is there a Java API that can create rich Word documents?

You can use a Java COM bridge like JACOB. If it is from client side, another option would be to use Javascript.

Handling exceptions from Java ExecutorService tasks

This works

  • It is derived from SingleThreadExecutor, but you can adapt it easily
  • Java 8 lamdas code, but easy to fix

It will create a Executor with a single thread, that can get a lot of tasks; and will wait for the current one to end execution to begin with the next

In case of uncaugth error or exception the uncaughtExceptionHandler will catch it

public final class SingleThreadExecutorWithExceptions {

    public static ExecutorService newSingleThreadExecutorWithExceptions(final Thread.UncaughtExceptionHandler uncaughtExceptionHandler) {

        ThreadFactory factory = (Runnable runnable)  -> {
            final Thread newThread = new Thread(runnable, "SingleThreadExecutorWithExceptions");
            newThread.setUncaughtExceptionHandler( (final Thread caugthThread,final Throwable throwable) -> {
                uncaughtExceptionHandler.uncaughtException(caugthThread, throwable);
            return newThread;
        return new FinalizableDelegatedExecutorService
                (new ThreadPoolExecutor(1, 1,
                        0L, TimeUnit.MILLISECONDS,
                        new LinkedBlockingQueue(),

                    protected void afterExecute(Runnable runnable, Throwable throwable) {
                        super.afterExecute(runnable, throwable);
                        if (throwable == null && runnable instanceof Future) {
                            try {
                                Future future = (Future) runnable;
                                if (future.isDone()) {
                            } catch (CancellationException ce) {
                                throwable = ce;
                            } catch (ExecutionException ee) {
                                throwable = ee.getCause();
                            } catch (InterruptedException ie) {
                                Thread.currentThread().interrupt(); // ignore/reset
                        if (throwable != null) {

    private static class FinalizableDelegatedExecutorService
            extends DelegatedExecutorService {
        FinalizableDelegatedExecutorService(ExecutorService executor) {
        protected void finalize() {

     * A wrapper class that exposes only the ExecutorService methods
     * of an ExecutorService implementation.
    private static class DelegatedExecutorService extends AbstractExecutorService {
        private final ExecutorService e;
        DelegatedExecutorService(ExecutorService executor) { e = executor; }
        public void execute(Runnable command) { e.execute(command); }
        public void shutdown() { e.shutdown(); }
        public List shutdownNow() { return e.shutdownNow(); }
        public boolean isShutdown() { return e.isShutdown(); }
        public boolean isTerminated() { return e.isTerminated(); }
        public boolean awaitTermination(long timeout, TimeUnit unit)
                throws InterruptedException {
            return e.awaitTermination(timeout, unit);
        public Future submit(Runnable task) {
            return e.submit(task);
        public  Future submit(Callable task) {
            return e.submit(task);
        public  Future submit(Runnable task, T result) {
            return e.submit(task, result);
        public  List> invokeAll(Collection> tasks)
                throws InterruptedException {
            return e.invokeAll(tasks);
        public  List> invokeAll(Collection> tasks,
                                             long timeout, TimeUnit unit)
                throws InterruptedException {
            return e.invokeAll(tasks, timeout, unit);
        public  T invokeAny(Collection> tasks)
                throws InterruptedException, ExecutionException {
            return e.invokeAny(tasks);
        public  T invokeAny(Collection> tasks,
                               long timeout, TimeUnit unit)
                throws InterruptedException, ExecutionException, TimeoutException {
            return e.invokeAny(tasks, timeout, unit);

    private SingleThreadExecutorWithExceptions() {}

When is del useful in Python?

I would like to elaborate on the accepted answer to highlight the nuance between setting a variable to None versus removing it with del:

Given the variable foo = 'bar', and the following function definition:

def test_var(var):
    if var:
        print('variable tested true')
        print('variable tested false')

Once initially declared, test_var(foo) yields variable tested true as expected.

Now try:

foo = None

which yields variable tested false.

Contrast this behavior with:

del foo

which now raises NameError: name 'foo' is not defined.

How to search in a List of Java object

As your list is an ArrayList, it can be assumed that it is unsorted. Therefore, there is no way to search for your element that is faster than O(n).

If you can, you should think about changing your list into a Set (with HashSet as implementation) with a specific Comparator for your sample class.

Another possibility would be to use a HashMap. You can add your data as Sample (please start class names with an uppercase letter) and use the string you want to search for as key. Then you could simply use

Sample samp = myMap.get(myKey);

If there can be multiple samples per key, use Map<String, List<Sample>>, otherwise use Map<String, Sample>. If you use multiple keys, you will have to create multiple maps that hold the same dataset. As they all point to the same objects, space shouldn't be that much of a problem.

How to move text up using CSS when nothing is working

used the following snippet and it worked fine..

.smallText .bmv-disclaimer {
   height: 40px;

How to create bitmap from byte array?

You'll need to get those bytes into a MemoryStream:

Bitmap bmp;
using (var ms = new MemoryStream(imageData))
    bmp = new Bitmap(ms);

That uses the Bitmap(Stream stream) constructor overload.

UPDATE: keep in mind that according to the documentation, and the source code I've been reading through, an ArgumentException will be thrown on these conditions:

stream does not contain image data or is null.
stream contains a PNG image file with a single dimension greater than 65,535 pixels.

How to stick text to the bottom of the page?


.bottom {
    position: fixed;
    bottom: 0;

Resource blocked due to MIME type mismatch (X-Content-Type-Options: nosniff)

I had this error when i was using the azure storage as a static website, the js files that are copied had the content type as text/plain; charset=utf-8 and i changed the content type to application/javascript

It started working.

How do I remove/delete a virtualenv?

That's it! There is no command for deleting your virtual environment. Simply deactivate it and rid your application of its artifacts by recursively removing it.

Note that this is the same regardless of what kind of virtual environment you are using. virtualenv, venv, Anaconda environment, pyenv, pipenv are all based the same principle here.

How to use double or single brackets, parentheses, curly braces

  1. A single bracket ([) usually actually calls a program named [; man test or man [ for more info. Example:

    $ VARIABLE=abcdef
    $ if [ $VARIABLE == abcdef ] ; then echo yes ; else echo no ; fi
  2. The double bracket ([[) does the same thing (basically) as a single bracket, but is a bash builtin.

    $ VARIABLE=abcdef
    $ if [[ $VARIABLE == 123456 ]] ; then echo yes ; else echo no ; fi
  3. Parentheses (()) are used to create a subshell. For example:

    $ pwd
    $ (cd /tmp; pwd)
    $ pwd

    As you can see, the subshell allowed you to perform operations without affecting the environment of the current shell.

  4. (a) Braces ({}) are used to unambiguously identify variables. Example:

    $ VARIABLE=abcdef
    $ echo Variable: $VARIABLE
    Variable: abcdef
    $ echo Variable: $VARIABLE123456
    $ echo Variable: ${VARIABLE}123456
    Variable: abcdef123456

    (b) Braces are also used to execute a sequence of commands in the current shell context, e.g.

    $ { date; top -b -n1 | head ; } >logfile 
    # 'date' and 'top' output are concatenated, 
    # could be useful sometimes to hunt for a top loader )
    $ { date; make 2>&1; date; } | tee logfile
    # now we can calculate the duration of a build from the logfile

There is a subtle syntactic difference with ( ), though (see bash reference) ; essentially, a semicolon ; after the last command within braces is a must, and the braces {, } must be surrounded by spaces.

get the titles of all open windows

Based on the previous answer that give me some errors, finaly I use this code with GetOpenedWindows function:

public class InfoWindow
            public IntPtr Handle = IntPtr.Zero;
            public FileInfo File = new FileInfo( Application.ExecutablePath );
            public string Title = Application.ProductName;
            public override string ToString() {
                return  File.Name + "\t>\t" + Title;

/// <summary>Contains functionality to get info on the open windows.</summary>
public static class RuningWindows
            internal static event EventHandler WindowActivatedChanged;    
            internal static Timer TimerWatcher = new Timer();    
            internal static InfoWindow WindowActive = new InfoWindow();       
            internal static void DoStartWatcher() {
                TimerWatcher.Interval = 500;
                TimerWatcher.Tick += TimerWatcher_Tick;

            /// <summary>Returns a dictionary that contains the handle and title of all the open windows.</summary>
            /// <returns>A dictionary that contains the handle and title of all the open windows.</returns>
            public static IDictionary<IntPtr , InfoWindow> GetOpenedWindows()
                IntPtr shellWindow = GetShellWindow();
                Dictionary<IntPtr , InfoWindow> windows = new Dictionary<IntPtr , InfoWindow>();

                EnumWindows( new EnumWindowsProc( delegate( IntPtr hWnd , int lParam ) {
                    if ( hWnd == shellWindow ) return true;
                    if ( !IsWindowVisible( hWnd ) ) return true;    
                    int length = GetWindowTextLength( hWnd );
                    if ( length == 0 ) return true;    
                    StringBuilder builder = new StringBuilder( length );
                    GetWindowText( hWnd , builder , length + 1 );    
                    var info = new InfoWindow();
                    info.Handle = hWnd;
                    info.File = new FileInfo( GetProcessPath( hWnd ) );
                    info.Title = builder.ToString();    
                    windows[hWnd] = info;
                    return true;    
                } ) , 0 );    
                return windows;

            private delegate bool EnumWindowsProc( IntPtr hWnd , int lParam );  

            public static string GetProcessPath( IntPtr hwnd )
                uint pid = 0;
                GetWindowThreadProcessId( hwnd , out pid );
                if ( hwnd != IntPtr.Zero ) {
                    if ( pid != 0 ) {
                        var process = Process.GetProcessById( (int) pid );
                        if ( process != null ) {
                            return process.MainModule.FileName.ToString();
                return "";

            [DllImport( "USER32.DLL" )]
            private static extern bool EnumWindows( EnumWindowsProc enumFunc , int lParam );

            [DllImport( "USER32.DLL" )]
            private static extern int GetWindowText( IntPtr hWnd , StringBuilder lpString , int nMaxCount );

            [DllImport( "USER32.DLL" )]
            private static extern int GetWindowTextLength( IntPtr hWnd );

            [DllImport( "USER32.DLL" )]
            private static extern bool IsWindowVisible( IntPtr hWnd );

            [DllImport( "USER32.DLL" )]
            private static extern IntPtr GetShellWindow();

            [DllImport( "user32.dll" )]
            private static extern IntPtr GetForegroundWindow();

            //WARN: Only for "Any CPU":
            [DllImport( "user32.dll" , CharSet = CharSet.Auto , SetLastError = true )]
            private static extern int GetWindowThreadProcessId( IntPtr handle , out uint processId );    

            static void TimerWatcher_Tick( object sender , EventArgs e )
                var windowActive = new InfoWindow();
                windowActive.Handle = GetForegroundWindow();
                string path = GetProcessPath( windowActive.Handle );
                if ( string.IsNullOrEmpty( path ) ) return;
                windowActive.File = new FileInfo( path );
                int length = GetWindowTextLength( windowActive.Handle );
                if ( length == 0 ) return;
                StringBuilder builder = new StringBuilder( length );
                GetWindowText( windowActive.Handle , builder , length + 1 );
                windowActive.Title = builder.ToString();
                if ( windowActive.ToString() != WindowActive.ToString() ) {
                    WindowActive = windowActive;
                    if ( WindowActivatedChanged != null ) WindowActivatedChanged( sender , e );
                    Console.WriteLine( "Window: " + WindowActive.ToString() );


Warning: You can only compil/debug under "Any CPU" to access to 32bits Apps...

SQL update from one Table to another based on a ID match

If above answers not working for you try this

Update Sales_Import A left join RetrieveAccountNumber B on A.LeadID = B.LeadID
Set A.AccountNumber = B.AccountNumber
where A.LeadID = B.LeadID 

TypeError: unhashable type: 'numpy.ndarray'

Your variable energies probably has the wrong shape:

>>> from numpy import array
>>> set([1,2,3]) & set(range(2, 10))
set([2, 3])
>>> set(array([1,2,3])) & set(range(2,10))
set([2, 3])
>>> set(array([[1,2,3],])) & set(range(2,10))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'numpy.ndarray'

And that's what happens if you read columnar data using your approach:

>>> data
array([[  1.,   2.,   3.],
       [  3.,   4.,   5.],
       [  5.,   6.,   7.],
       [  8.,   9.,  10.]])
>>> hsplit(data,3)[0]
array([[ 1.],
       [ 3.],
       [ 5.],
       [ 8.]])

Probably you can simply use

>>> data[:,0]
array([ 1.,  3.,  5.,  8.])


(P.S. Your code looks like it's undecided about whether it's data or elementdata. I've assumed it's simply a typo.)

Correct modification of state arrays in React.js

If you are using functional component please use this as below.

const [chatHistory, setChatHistory] = useState([]); // define the state

const chatHistoryList = [...chatHistory, {'from':'me', 'message'}]; // new array need to update
setChatHistory(chatHistoryList); // update the state

How can I get current date in Android?

CharSequence s  = DateFormat.getDateInstance().format("MMMM d, yyyy ");

You need an instance first

Execute a command line binary with Node.js

You are looking for child_process.exec

Here is the example:

const exec = require('child_process').exec;
const child = exec('cat *.js bad_file | wc -l',
    (error, stdout, stderr) => {
        console.log(`stdout: ${stdout}`);
        console.log(`stderr: ${stderr}`);
        if (error !== null) {
            console.log(`exec error: ${error}`);

Android, Java: HTTP POST Request

You can reuse the implementation I added to ACRA:

(See the doPost(Map, Url) method, working over http and https even with self signed certs)

How do I select an entire row which has the largest ID in the table?

FROM table 

jquery stop child triggering parent event

I stumbled upon this question, looking for another answer.

I wanted to prevent all children from triggering the parent.


document.getElementById("parent").addEventListener("click",  function (e) {
    if (this !== return;
    // Do something


$("#parent").click(function () {
    // Do something
}).children().on("click", function (e) {

Is there a format code shortcut for Visual Studio?

Select all text in the document and press Ctrl + E + D.

git: How to ignore all present untracked files?

Two ways:

  • use the argument -uno to git-status. Here's an example:

    [jenny@jenny_vmware:ft]$ git status
    # On branch ft
    # Untracked files:
    #   (use "git add <file>..." to include in what will be committed)
    #       foo
    nothing added to commit but untracked files present (use "git add" to track)
    [jenny@jenny_vmware:ft]$ git status -uno
    # On branch ft
    nothing to commit (working directory clean)
  • Or you can add the files and directories to .gitignore, in which case they will never show up.

Can JavaScript connect with MySQL?

Depending on your environment, you could use Rhino to do this, see Rhino website. This gives you access to all of the Java libraries from within JavaScript.

Deleting rows with Python in a CSV file

You should have if row[2] != "0". Otherwise it's not checking to see if the string value is equal to 0.

I need to convert an int variable to double

You have to cast one (or both) of the arguments to the division operator to double:

double firstSolution = (b1 * a22 - b2 * a12) / (double)(a11 * a22 - a12 * a21);

Since you are performing the same calculation twice I'd recommend refactoring your code:

double determinant = a11 * a22 - a12 * a21;
double firstSolution = (b1 * a22 - b2 * a12) / determinant;
double secondSolution = (b2 * a11 - b1 * a21) / determinant;

This works in the same way, but now there is an implicit cast to double. This conversion from int to double is an example of a widening primitive conversion.

How can I add raw data body to an axios request?

The only solution I found that would work is the transformRequest property which allows you to override the extra data prep axios does before sending off the request.

        method: 'post',
        url: '',
        data: {},
        headers: {
            'Content-Type': 'application/x-www-form-urlencoded',
        transformRequest: [(data, header) => {
            data = 'grant_type=client_credentials'
            return data

How to find sitemap.xml path on websites?

According to protocol documentation there are at least three options website designers can use to inform sitemap.xml location to search engines:

  • Informing each search engine of the location through their provided interface
  • Adding url to the robots.txt file
  • Submiting url to search engines through http

So, unless they have chosen to publish the sitemap location on their robots.txt file, you cannot really know where they have put their sitemap.xml files.

iPhone SDK on Windows (alternative solutions)

There is another solution if you want to develop in C/C++. will allow you to build iPhone applications in Visual Studio on Windows. It's worth a look-see for sure.

VBA Copy Sheet to End of Workbook (with Hidden Worksheets)

Answer : I found this and wants to share it with you.

Sub Copier4()
   Dim x As Integer

   For x = 1 To ActiveWorkbook.Sheets.Count
      'Loop through each of the sheets in the workbook
      'by using x as the sheet index number.
      ActiveWorkbook.Sheets(x).Copy _
         'Puts all copies after the last existing sheet.
End Sub

But the question, can we use it with following code to rename the sheets, if yes, how can we do so?

Sub CreateSheetsFromAList()
Dim MyCell As Range, MyRange As Range
Set MyRange = Sheets("Summary").Range("A10")
Set MyRange = Range(MyRange, MyRange.End(xlDown))
For Each MyCell In MyRange
Sheets.Add After:=Sheets(Sheets.Count) 'creates a new worksheet
Sheets(Sheets.Count).Name = MyCell.Value ' renames the new worksheet
Next MyCell
End Sub

Unable to add window -- token null is not valid; is your activity running?

If you're using getApplicationContext() as Context in Activity for the dialog like this

Dialog dialog = new Dialog(getApplicationContext());

then use YourActivityName.this

Dialog dialog = new Dialog(YourActivityName.this);

NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver

In my case none of the above solutions didn't help:

Root cause: incompatible version of gcc


1. sudo apt install --reinstall gcc
2. sudo apt-get --purge -y remove 'nvidia*'
3  sudo apt install nvidia-driver-450 
4. sudo reboot

System: AWS EC2 18.04 instance

Solution source:

How to create <input type=“text”/> dynamically

Using Javascript, all you need is document.createElement and setAttribute.

var input = document.createElement("input");
input.setAttribute('type', 'text');

Then you can use appendChild to append the created element to the desired parent element.

var parent = document.getElementById("parentDiv");

What is the best way to paginate results in SQL Server

This is a duplicate of the 2012 old SO question: efficient way to implement paging


Here the topic is discussed in greater details, and with alternate approaches.

Access the css ":after" selector with jQuery

You can add style for :after a like html code.
For example:

var value = 22;
body.append('<style>.wrapper:after{border-top-width: ' + value + 'px;}</style>');

How to quickly edit values in table in SQL Server Management Studio?

In Mgmt Studio, when you are editing the top 200, you can view the SQL pane - either by right clicking in the grid and choosing Pane->SQL or by the button in the upper left. This will allow you to write a custom query to drill down to the row(s) you want to edit.

But ultimately mgmt studio isn't a data entry/update tool which is why this is a little cumbersome.

If statement for strings in python?

Python is case sensitive and needs proper indentation. You need to use lowercase "if", indent your conditions properly and the code has a bug. proceed will evaluate to y

Change an image with onclick()

To change image onclik with javascript you need to have image with id:

        <img alt="" src="" 
            style="height: 85px; width: 198px" id="imgClickAndChange" onclick="changeImage()"  />

Then you could call javascript function when image is clicked:

<script language="javascript">
    function changeImage() {

        if (document.getElementById("imgClickAndChange").src == "") 
            document.getElementById("imgClickAndChange").src = "";
            document.getElementById("imgClickAndChange").src = "";

This code will set image to maximize.png if current img.src is set to minimize.png and vice versa. For more details visit: Change image onclick with javascript link

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

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

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

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

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

Why do I have to define LD_LIBRARY_PATH with an export every time I run my application?

Did you 'export' in your .bashrc?

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:"/path/to/library"

pandas read_csv and filter columns with usecols

This code achieves what you want --- also its weird and certainly buggy:

I observed that it works when:

a) you specify the index_col rel. to the number of columns you really use -- so its three columns in this example, not four (you drop dummy and start counting from then onwards)

b) same for parse_dates

c) not so for usecols ;) for obvious reasons

d) here I adapted the names to mirror this behaviour

import pandas as pd
from StringIO import StringIO

csv = """dummy,date,loc,x

df = pd.read_csv(StringIO(csv),
        names=["date", "loc", "", "x"])

print df

which prints

date       loc   
2009-01-01 a    1
2009-01-02 a    3
2009-01-03 a    5
2009-01-01 b    1
2009-01-02 b    3
2009-01-03 b    5

TypeError: can't pickle _thread.lock objects

I had the same problem with Pool() in Python 3.6.3.

Error received: TypeError: can't pickle _thread.RLock objects

Let's say we want to add some number num_to_add to each element of some list num_list in parallel. The code is schematically like this:

class DataGenerator:
    def __init__(self, num_list, num_to_add)
        self.num_list = num_list # e.g. [4,2,5,7]
        self.num_to_add = num_to_add # e.g. 1 

    def run(self):
        new_num_list = Manager().list()

        pool = Pool(processes=50)
        results = [pool.apply_async(run_parallel, (num, new_num_list)) 
                      for num in num_list]
        roots = [r.get() for r in results]

    def run_parallel(self, num, shared_new_num_list):
        new_num = num + self.num_to_add # uses class parameter

The problem here is that self in function run_parallel() can't be pickled as it is a class instance. Moving this parallelized function run_parallel() out of the class helped. But it's not the best solution as this function probably needs to use class parameters like self.num_to_add and then you have to pass it as an argument.


def run_parallel(num, shared_new_num_list, to_add): # to_add is passed as an argument
    new_num = num + to_add

class DataGenerator:
    def __init__(self, num_list, num_to_add)
        self.num_list = num_list # e.g. [4,2,5,7]
        self.num_to_add = num_to_add # e.g. 1

    def run(self):
        new_num_list = Manager().list()

        pool = Pool(processes=50)
        results = [pool.apply_async(run_parallel, (num, new_num_list, self.num_to_add)) # num_to_add is passed as an argument
                      for num in num_list]
        roots = [r.get() for r in results]

Other suggestions above didn't help me.

How to call jQuery function onclick?

try this:

    // this function will be raised when submit button is clicked.
    // perform submit operations here

NodeJs : TypeError: require(...) is not a function

I think this means that module.exports in your ./app/routes module is not assigned to be a function so therefore require('./app/routes') does not resolve to a function so therefore, you cannot call it as a function like this require('./app/routes')(app, passport).

Show us ./app/routes if you want us to comment further on that.

It should look something like this;

module.exports = function(app, passport) {
    // code here

You are exporting a function that can then be called like require('./app/routes')(app, passport).

One other reason a similar error could occur is if you have a circular module dependency where module A is trying to require(B) and module B is trying to require(A). When this happens, it will be detected by the require() sub-system and one of them will come back as null and thus trying to call that as a function will not work. The fix in that case is to remove the circular dependency, usually by breaking common code into a third module that both can separately load though the specifics of fixing a circular dependency are unique for each situation.

relative path in BAT script

I have found that %CD% gives the path the script was called from and not the path of the script, however, %~dp0 will give the path of the script itself.

Multiple rows to one comma-separated value in Sql Server

Test Data

INSERT INTO @Table1 VALUES (1,100),(1,200),(1,300),(1,400)


       ,STUFF((SELECT ', ' + CAST(Value AS VARCHAR(10)) [text()]
         FROM @Table1 
         WHERE ID = t.ID
         FOR XML PATH(''), TYPE)
        .value('.','NVARCHAR(MAX)'),1,2,' ') List_Output
FROM @Table1 t

Result Set

¦ ID ¦     List_Output     ¦
¦  1 ¦  100, 200, 300, 400 ¦

SQL Server 2017 and Later Versions

If you are working on SQL Server 2017 or later versions, you can use built-in SQL Server Function STRING_AGG to create the comma delimited list:

INSERT INTO @Table1 VALUES (1,100),(1,200),(1,300),(1,400);

SELECT ID , STRING_AGG([Value], ', ') AS List_Output
FROM @Table1

Result Set

¦ ID ¦     List_Output     ¦
¦  1 ¦  100, 200, 300, 400 ¦

transform object to array with lodash

For me, this worked:, d => _.fromPairs([d]));

It turns

{"a":"b", "c":"d", "e":"f"} 


[{"a":"b"}, {"c":"d"}, {"e":"f"}]

How to Save Console.WriteLine Output to Text File

For the question:

How to save Console.Writeline Outputs to text file?

I would use Console.SetOut as others have mentioned.

However, it looks more like you are keeping track of your program flow. I would consider using Debug or Trace for keeping track of the program state.

It works similar the console except you have more control over your input such as WriteLineIf.

Debug will only operate when in debug mode where as Trace will operate in both debug or release mode.

They both allow for listeners such as output files or the console.

TextWriterTraceListener tr1 = new TextWriterTraceListener(System.Console.Out);

TextWriterTraceListener tr2 = new TextWriterTraceListener(System.IO.File.CreateText("Output.txt"));


How to generate entire DDL of an Oracle schema (scriptable)?

The get_ddl procedure for a PACKAGE will return both spec AND body, so it will be better to change the query on the all_objects so the package bodies are not returned on the select.

So far I changed the query to this:

SELECT DBMS_METADATA.GET_DDL(REPLACE(object_type, ' ', '_'), object_name, owner)
and object_type not like '%PARTITION'
and object_type not like '%BODY'
order by object_type, object_name;

Although other changes might be needed depending on the object types you are getting...

Is there any sed like utility for cmd.exe?

Try fart.exe. It's a Find-and-replace-text utility that can be used in command batch programs.

Problems after upgrading to Xcode 10: Build input file cannot be found

I ran into this error after renaming a file. Somehow Xcode didn't correctly rename the actual file on disk.

So it wasn't able to find the file. Sometimes the files gets highlights with a red text color. At other times the Swift icon in front of the file was getting a gray overlay.

The fix was simple.

  • Look into the error and see exactly which file it's unable to find.
  • Select the file that can't be found.
  • Go to the 'File Inspector'. It's on Xcode's right navigation pane.
  • Click on the folder icon.
  • Select the correct file.
  • Clean build and run it again.

Free easy way to draw graphs and charts in C++?

My favourite has always been gnuplot. It's very extensive, so it might be a bit too complex for your needs though. It is cross-platform and there is a C++ API.

How could I create a function with a completion handler in Swift?

We can use Closures for this purpose. Try the following

func loadHealthCareList(completionClosure: (indexes: NSMutableArray)-> ()) {
      //some code here
      completionClosure(indexes: list)

At some point we can call this function as given below.

healthIndexManager.loadHealthCareList { (indexes) -> () in

Please refer the following link for more information regarding Closures.

How to add color to Github's file

As an alternative to rendering a raster image, you can embed a SVG file:

<a><img src=""/></a>

You can then add color text to the SVG file as usual:

<?xml version="1.0" encoding="utf-8"?>
<svg version="1.1" 
     width="100" height="50"
  <text font-size="16" x="10" y="20">
    <tspan fill="red">Hello</tspan>,
    <tspan fill="green">world</tspan>!

Unfortunately, even though you can select and copy text when you open the .svg file, the text is not selectable when the SVG image is embedded.


Print a file, skipping the first X lines, in Bash

Easiest way I found to remove the first ten lines of a file:

$ sed 1,10d file.txt

In the general case (where X is the number of initial lines to delete, credit to commenters and editors for this):

$ sed 1,Xd file.txt

What does it mean when a PostgreSQL process is "idle in transaction"?

The PostgreSQL manual indicates that this means the transaction is open (inside BEGIN) and idle. It's most likely a user connected using the monitor who is thinking or typing. I have plenty of those on my system, too.

If you're using Slony for replication, however, the Slony-I FAQ suggests idle in transaction may mean that the network connection was terminated abruptly. Check out the discussion in that FAQ for more details.

What are the differences between .gitignore and .gitkeep?

Many people prefer to use just .keep since the convention has nothing to do with git.

How to remove a package from Laravel using composer?

you can remove any package just by typing follwing command in terminal, and just remove the providers and alias you provided at the time of installing the package, if any and update the composer,

composer remove vendor/your_package_name
composer update

Negative regex for Perl string pattern match

What's wrong with using two regexs (or three)? This makes your intentions more clear and may even improve your performance:

if ($string =~ /^(Clinton|Reagan)/i && $string !~ /Bush/i) { ... }

if (($string =~ /^Clinton/i || $string =~ /^Reagan/i)
        && $string !~ /Bush/i) {
    print "$string\n"

Why does range(start, end) not include end?

The length of the range is the top value minus the bottom value.

It's very similar to something like:

for (var i = 1; i < 11; i++) {
    //i goes from 1 to 10 in here

in a C-style language.

Also like Ruby's range:

1...11 #this is a range from 1 to 10

However, Ruby recognises that many times you'll want to include the terminal value and offers the alternative syntax:

1..10 #this is also a range from 1 to 10

MySql Error: 1364 Field 'display_name' doesn't have default value

All of these answers are a good way, but I don't think you want to always go to your DB and modify the default value that you have set to NULL.

I suggest you go to the app/User.php and modify the protected $fillable so it will take your new fields in the data array used to register.

Let's say you add a new input field called "first_name", your $fillable should be something like this :

protected $fillable = [ 'first_name', 'email', 'password',]; 

This did it for me. Good luck!

Convert timestamp to date in Oracle SQL

Try using TRUNC and TO_DATE instead

    TRUNC(start_ts) = TO_DATE('2016-05-13', 'YYYY-MM-DD')

Alternatively, you can use >= and < instead to avoid use of function in the start_ts column:

   start_ts >= TO_DATE('2016-05-13', 'YYYY-MM-DD')
   AND start_ts < TO_DATE('2016-05-14', 'YYYY-MM-DD')

URL Encode a string in jQuery for an AJAX request

Better way:

encodeURIComponent escapes all characters except the following: alphabetic, decimal digits, - _ . ! ~ * ' ( )

To avoid unexpected requests to the server, you should call encodeURIComponent on any user-entered parameters that will be passed as part of a URI. For example, a user could type "Thyme &time=again" for a variable comment. Not using encodeURIComponent on this variable will give comment=Thyme%20&time=again. Note that the ampersand and the equal sign mark a new key and value pair. So instead of having a POST comment key equal to "Thyme &time=again", you have two POST keys, one equal to "Thyme " and another (time) equal to again.

For application/x-www-form-urlencoded (POST), per, spaces are to be replaced by '+', so one may wish to follow a encodeURIComponent replacement with an additional replacement of "%20" with "+".

If one wishes to be more stringent in adhering to RFC 3986 (which reserves !, ', (, ), and *), even though these characters have no formalized URI delimiting uses, the following can be safely used:

function fixedEncodeURIComponent (str) {
  return encodeURIComponent(str).replace(/[!'()]/g, escape).replace(/\*/g, "%2A");

How do I make a column unique and index it in a Ruby on Rails migration?

You might want to add name for the unique key as many times the default unique_key name by rails can be too long for which the DB can throw the error.

To add name for your index just use the name: option. The migration query might look something like this -

add_index :table_name, [:column_name_a, :column_name_b, ... :column_name_n], unique: true, name: 'my_custom_index_name'

More info -

CSS 100% height with padding/margin

The better way is with the calc() property. So your case would look like:

#myDiv {
    width: calc(100% - 5px);
    height: calc(100% - 5px);
    padding: 5px;

Simple, clean, no workarounds. Just make sure you don't forget the space between the values and the operator (eg (100%-5px) that will break the syntax. Enjoy!

How to substring in jquery

How about the following?

<script charset='utf-8' type='text/javascript'>
  jQuery(function($) { var a=$; a.noConflict();
    //assumming that you are using an input text 
    //  element with the text "nameGorge"
    var itext_target = a("input[type='text']:contains('nameGorge')");
    //gives the second part of the split which is 'Gorge'

Using JsonConvert.DeserializeObject to deserialize Json to a C# POCO class

Here is a working example.

Keypoints are:

  • Declaration of Accounts
  • Use of JsonProperty attribute


using (WebClient wc = new WebClient())
    var json = wc.DownloadString("");
    var user = JsonConvert.DeserializeObject<User>(json);


public class User
    /// <summary>
    /// A User's username. eg: "sergiotapia, mrkibbles, matumbo"
    /// </summary>
    public string Username { get; set; }

    /// <summary>
    /// A User's name. eg: "Sergio Tapia, John Cosack, Lucy McMillan"
    /// </summary>
    public string Name { get; set; }

    /// <summary>
    /// A User's location. eh: "Bolivia, USA, France, Italy"
    /// </summary>
    public string Location { get; set; }

    public int Endorsements { get; set; } //Todo.

    public string Team { get; set; } //Todo.

    /// <summary>
    /// A collection of the User's linked accounts.
    /// </summary>
    public Account Accounts { get; set; }

    /// <summary>
    /// A collection of the User's awarded badges.
    /// </summary>
    public List<Badge> Badges { get; set; }

public class Account
    public string github;

public class Badge
    public string Name;
    public string Description;
    public string Created;
    public string BadgeUrl;

Python 3 TypeError: must be str, not bytes with sys.stdout.write()

Python 3 handles strings a bit different. Originally there was just one type for strings: str. When unicode gained traction in the '90s the new unicode type was added to handle Unicode without breaking pre-existing code1. This is effectively the same as str but with multibyte support.

In Python 3 there are two different types:

  • The bytes type. This is just a sequence of bytes, Python doesn't know anything about how to interpret this as characters.
  • The str type. This is also a sequence of bytes, but Python knows how to interpret those bytes as characters.
  • The separate unicode type was dropped. str now supports unicode.

In Python 2 implicitly assuming an encoding could cause a lot of problems; you could end up using the wrong encoding, or the data may not have an encoding at all (e.g. it’s a PNG image).
Explicitly telling Python which encoding to use (or explicitly telling it to guess) is often a lot better and much more in line with the "Python philosophy" of "explicit is better than implicit".

This change is incompatible with Python 2 as many return values have changed, leading to subtle problems like this one; it's probably the main reason why Python 3 adoption has been so slow. Since Python doesn't have static typing2 it's impossible to change this automatically with a script (such as the bundled 2to3).

  • You can convert str to bytes with bytes('h€llo', 'utf-8'); this should produce b'H\xe2\x82\xacllo'. Note how one character was converted to three bytes.
  • You can convert bytes to str with b'H\xe2\x82\xacllo'.decode('utf-8').

Of course, UTF-8 may not be the correct character set in your case, so be sure to use the correct one.

In your specific piece of code, nextline is of type bytes, not str, reading stdout and stdin from subprocess changed in Python 3 from str to bytes. This is because Python can't be sure which encoding this uses. It probably uses the same as sys.stdin.encoding (the encoding of your system), but it can't be sure.

You need to replace:




or maybe:


You will also need to modify if nextline == '' to if nextline == b'' since:

>>> '' == b''

Also see the Python 3 ChangeLog, PEP 358, and PEP 3112.

1 There are some neat tricks you can do with ASCII that you can't do with multibyte character sets; the most famous example is the "xor with space to switch case" (e.g. chr(ord('a') ^ ord(' ')) == 'A') and "set 6th bit to make a control character" (e.g. ord('\t') + ord('@') == ord('I')). ASCII was designed in a time when manipulating individual bits was an operation with a non-negligible performance impact.

2 Yes, you can use function annotations, but it's a comparatively new feature and little used.

android set button background programmatically

Using setBackgroundColor() affects the style. So, declare a new style of the same properties with respect to the previous button, with a a different color.

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android=""
<solid android:color="@color/green"/>
<corners android:radius="10dp"/>

Now, use OnClick method.

location.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {



this changes the button but looks similar to changing the background.

How do I create a readable diff of two spreadsheets using git diff?

I have found xdocdiff WinMerge Plugin. It is a plugin for WinMerge (both OpenSource and Freeware, you doesn't need to write a VBA nor save an excel to csv or xml). It works just for the celd's contains.

This plugin supports also:

  • .rtf Rich Text
  • .docx/.docm Microsoft WORD 2007(OOXML)
  • .xlsx/.xlsm Microsoft Excel 2007(OOXML)
  • .pptx/.pptm Microsoft PowerPoint 2007(OOXML)
  • .doc Microsoft WORD ver5.0/95/97/2000/XP/2003
  • .xls Microsoft Excel ver5.0/95/97/2000/XP/2003
  • .ppt Microsoft PowerPoint 97/2000/XP/2003
  • .sxw/.sxc/.sxi/.sxd
  • .odt/.ods/.odp/.odg Open Document
  • .wj2/wj3/wk3/wk4/123 Lotus 123
  • .wri Windows3.1 Write
  • .pdf Adobe PDF
  • .mht Web Archive
  • .eml Exported files from OutlookExpress

Regard, Andres

Access index of last element in data frame


seems the most readable

how to display data values on Chart.js

I'd recommend using this plugin:

Labels can be added to your charts simply by importing the plugin to the js file e.g.:

import 'chartjs-plugin-datalabels'

And can be fine tuned using these docs:

What's the fastest way to loop through an array in JavaScript?

It's the year 2017.

I made some tests.

Looks like the while method is the fastest on Chrome.

Looks like the left decrement (--i) is much faster than the others (++i, i--, i++) on Firefox.

This approach is the fasted on average. But it iterates the array in reversed order.

let i = array.length;
while (--i >= 0) {

If the forward order is important, use this approach.

let ii = array.length;
let i = 0;
while (i < ii) {

How to parse a CSV file in Bash?

We can parse csv files with quoted strings and delimited by say | with following code

while read -r line
    field1=$(echo "$line" | awk -F'|' '{printf "%s", $1}' | tr -d '"')
    field2=$(echo "$line" | awk -F'|' '{printf "%s", $2}' | tr -d '"')

    echo "$field1 $field2"
done < "$csvFile"

awk parses the string fields to variables and tr removes the quote.

Slightly slower as awk is executed for each field.

Replace a string in shell script using a variable

I prefer to use double quotes , as single quptes are very powerful as we used them if dont able to change anything inside it or can invoke the variable substituion .

so use double quotes instaed.

echo $LINE | sed -e "s/12345678/$replace/g"

What's the difference between SoftReference and WeakReference in Java?

Weak references are collected eagerly. If GC finds that an object is weakly reachable (reachable only through weak references), it'll clear the weak references to that object immediately. As such, they're good for keeping a reference to an object for which your program also keeps (strongly referenced) "associated information" somewere, like cached reflection information about a class, or a wrapper for an object, etc. Anything that makes no sense to keep after the object it is associated with is GC-ed. When the weak reference gets cleared, it gets enqueued in a reference queue that your code polls somewhere, and it discards the associated objects as well. That is, you keep extra information about an object, but that information is not needed once the object it refers to goes away. Actually, in certain situations you can even subclass WeakReference and keep the associated extra information about the object in the fields of the WeakReference subclass. Another typical use of WeakReference is in conjunction with Maps for keeping canonical instances.

SoftReferences on the other hand are good for caching external, recreatable resources as the GC typically delays clearing them. It is guaranteed though that all SoftReferences will get cleared before OutOfMemoryError is thrown, so they theoretically can't cause an OOME[*].

Typical use case example is keeping a parsed form of a contents from a file. You'd implement a system where you'd load a file, parse it, and keep a SoftReference to the root object of the parsed representation. Next time you need the file, you'll try to retrieve it through the SoftReference. If you can retrieve it, you spared yourself another load/parse, and if the GC cleared it in the meantime, you reload it. That way, you utilize free memory for performance optimization, but don't risk an OOME.

Now for the [*]. Keeping a SoftReference can't cause an OOME in itself. If on the other hand you mistakenly use SoftReference for a task a WeakReference is meant to be used (namely, you keep information associated with an Object somehow strongly referenced, and discard it when the Reference object gets cleared), you can run into OOME as your code that polls the ReferenceQueue and discards the associated objects might happen to not run in a timely fashion.

So, the decision depends on usage - if you're caching information that is expensive to construct, but nonetheless reconstructible from other data, use soft references - if you're keeping a reference to a canonical instance of some data, or you want to have a reference to an object without "owning" it (thus preventing it from being GC'd), use a weak reference.

Run git pull over all subdirectories

A bit more low-tech than leo's solution:

for i in */.git; do ( echo $i; cd $i/..; git pull; ); done

This will update all Git repositories in your working directory. No need to explicitly list their names ("cms", "admin", "chart"). The "cd" command only affects a subshell (spawned using the parenthesis).

How to print pthread_t

On Centos 5.4 x86_64, pthread_t is a typedef to a unsigned long.

Therefore, we could do this...

#include <iostream>
#include <pthread.h>

int main() {
    pthread_t x;
    printf("%li\n", (unsigned long int) x);
    std::cout << (unsigned long int) x << "\n";

How do I set/unset a cookie with jQuery?

Try (doc here, SO snippet not works so run this one)

document.cookie = "test=1"             // set
document.cookie = "test=1;max-age=0"   // unset

What is the SQL command to return the field names of a table?

For IBM DB2 (will double check this on Monday to be sure.)


What's the difference between a null pointer and a void pointer?

Both void and null pointers point to a memory location in the end.

A null pointer points to place (in a memory segment) which is usually the 0th address of memory segment. It is almost all about how the underlying OS treat that "reserved" memory location (an implementation detail) when you try to access it to read/write or dereference. For example, that particular memory location can be marked as "non-accessible" and throws an expection when it's accessed.

A void pointer can point to anywhere and potentially represent any type (primitive, reference-type, and including null).

As someone nicely put above, null pointer represents a value whereas void* represents a type more than a value.

"CAUTION: provisional headers are shown" in Chrome debugger

I got this error when I tried to print a page in a popup. The print dialog was show and it still waiting my acceptance or cancellation of the printing in the popup while in the master page also was waiting in the background showing the message CAUTION provisional headers are shown when I tried to click another link.

In my case the solution was to remove the window.print (); script that it was executing on the <body> of the popup window to prevent the print dialog.

Getting "project" nuget configuration is invalid error

NOTE: This is mentioned in the question but restarting Visual Studio fixes the issue in most cases.

Updating Visual Studio to 'Update 2' got it working again.

Tools -> Extensions and Updates ->Visual Studio Update 2

As mentioned in the question and the link i posted therein, I'd already updated NuGet Package Manager to 3.4.4 prior to this and restarted to no avail, so I don't know if the combination of both these actions worked.

How to use AND in IF Statement

Brief syntax lesson

Cells(Row, Column) identifies a cell. Row must be an integer between 1 and the maximum for version of Excel you are using. Column must be a identifier (for example: "A", "IV", "XFD") or a number (for example: 1, 256, 16384)

.Cells(Row, Column) identifies a cell within a sheet identified in a earlier With statement:

With ActiveSheet
End With

If you omit the dot, Cells(Row,Column) is within the active worksheet. So wsh = ActiveWorkbook wsh.Range is not strictly necessary. However, I always use a With statement so I do not wonder which sheet I meant when I return to my code in six months time. So, I would write:

With ActiveSheet
End With

Actually, I would not write the above unless I really did want the code to work on the active sheet. What if the user has the wrong sheet active when they started the macro. I would write:

With Sheets("xxxx")
End With

because my code only works on sheet xxxx.

Cells(Row,Column) identifies a cell. Cells(Row,Column).xxxx identifies a property of the cell. Value is a property. Value is the default property so you can usually omit it and the compiler will know what you mean. But in certain situations the compiler can be confused so the advice to include the .Value is good.

Cells(Row,Column) like "*Miami*" will give True if the cell is "Miami", "South Miami", "Miami, North" or anything similar.

Cells(Row,Column).Value = "Miami" will give True if the cell is exactly equal to "Miami". "MIAMI" for example will give False. If you want to accept MIAMI, use the lower case function:

Lcase(Cells(Row,Column).Value) = "miami"  

My suggestions

Your sample code keeps changing as you try different suggestions which I find confusing. You were using Cells(Row,Column) <> "Miami" when I started typing this.


If Cells(i, "A").Value like "*Miami*" And Cells(i, "D").Value like "*Florida*" Then
  Cells(i, "C").Value = "BA"

if you want to accept, for example, "South Miami" and "Miami, North".


If Cells(i, "A").Value = "Miami" And Cells(i, "D").Value like "Florida" Then
  Cells(i, "C").Value = "BA"

if you want to accept, exactly, "Miami" and "Florida".


If Lcase(Cells(i, "A").Value) = "miami" And _
   Lcase(Cells(i, "D").Value) = "florida" Then
  Cells(i, "C").Value = "BA"

if you don't care about case.

Saving numpy array to txt file row wise


' '.join(a)

and write this output to a file.

How to determine whether an object has a given property in JavaScript


There is a new feature on ES6+ that you can check it like below:

if (x?.y)

Actually, the interpretor checks the existence of x and then call the y and because of putting inside if parentheses the coercion happens and x?.y converted to boolean.

Changing image size in Markdown

For those intereseted in an rmarkdown and knitr solution. There are some ways to resize images in an .rmd file without the use of html:

You can simply specify a width for an image by adding {width=123px}. Don't introduce whitespace in between the brackets:

![image description]('your-image.png'){width=250px}

Another option is to use knitr::include_graphics:

```{r, fig.cap="image description", out.width = '50%'}

Sending HTTP POST Request In Java

I recomend use http-request built on apache http api.

HttpRequest<String> httpRequest = HttpRequestBuilder.createPost("", String.class)

public void send(){
   String response = httpRequest.execute("id", "10").get();

How do I make a composite key with SQL Server Management Studio?

Open up the table designer in SQL Server Management Studio (right-click table and select 'Design')

Holding down the Ctrl key highlight two or more columns in the left hand table margin

Hit the little 'Key' on the standard menu bar at the top

You're done..


The equivalent of a GOTO in python

Gotos are universally reviled in computer science and programming as they lead to very unstructured code.

Python (like almost every programming language today) supports structured programming which controls flow using if/then/else, loop and subroutines.

The key to thinking in a structured way is to understand how and why you are branching on code.

For example, lets pretend Python had a goto and corresponding label statement shudder. Look at the following code. In it if a number is greater than or equal to 0 we print if it

number = input()
if number < 0: goto negative
if number % 2 == 0:
   print "even"
   print "odd"
goto end
label: negative
print "negative"
label: end
print "all done"

If we want to know when a piece of code is executed, we need to carefully traceback in the program, and examine how a label was arrived at - which is something that can't really be done.

For example, we can rewrite the above as:

number = input()
goto check

label: negative
print "negative"
goto end

label: check
if number < 0: goto negative
if number % 2 == 0:
   print "even"
   print "odd"
goto end

label: end
print "all done"

Here, there are two possible ways to arrive at the "end", and we can't know which one was chosen. As programs get large this kind of problem gets worse and results in spaghetti code

In comparison, below is how you would write this program in Python:

number = input()
if number >= 0:
   if number % 2 == 0:
       print "even"
       print "odd"
   print "negative"
print "all done"

I can look at a particular line of code, and know under what conditions it is met by tracing back the tree of if/then/else blocks it is in. For example, I know that the line print "odd" will be run when a ((number >= 0) == True) and ((number % 2 == 0) == False).

setTimeout in React Native

const getData = () => {
// some functionality

const that = this;
   setTimeout(() => {
   // write your functions    

Simple, Settimout function get triggered after 6000 milliseonds

Add content to a new open window

If you want to open a page or window with sending data POST or GET method you can use a code like this:

    type: "get",  // or post method, your choice
    url: yourFileForInclude.php, // any url in same origin
    data: data,  // data if you need send some data to page
    success: function(msg){
                console.log(msg); // for checking
      'about:blank').document.body.innerHTML = msg;  

How to change onClick handler dynamically?

Use .onclick (all lowercase). Like so:

document.getElementById("foo").onclick = function () {
  alert('foo'); // do your stuff
  return false; // <-- to suppress the default link behaviour

Actually, you'll probably find yourself way better off using some good library (I recommend jQuery for several reasons) to get you up and running, and writing clean javascript.

Cross-browser (in)compatibilities are a right hell to deal with for anyone - let alone someone who's just starting.

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

Print a div using javascript in angularJS single page application

Two conditional functions are needed: one for Google Chrome, and a second for the remaining browsers.

$scope.printDiv = function (divName) {

    var printContents = document.getElementById(divName).innerHTML; 

    if (navigator.userAgent.toLowerCase().indexOf('chrome') > -1) {
        var popupWin ='', '_blank', 'width=600,height=600,scrollbars=no,menubar=no,toolbar=no,location=no,status=no,titlebar=no');
        popupWin.document.write('<!DOCTYPE html><html><head>' +
            '<link rel="stylesheet" type="text/css" href="style.css" />' +
            '</head><body onload="window.print()"><div class="reward-body">' + printContents + '</div></body></html>');
        popupWin.onbeforeunload = function (event) {
            return '.\n';
        popupWin.onabort = function (event) {
    } else {
        var popupWin ='', '_blank', 'width=800,height=600');;
        popupWin.document.write('<html><head><link rel="stylesheet" type="text/css" href="style.css" /></head><body onload="window.print()">' + printContents + '</body></html>');

    return true;

Node.js ES6 classes with require

In class file you can either use:

module.exports = class ClassNameHere {
 print() {
  console.log('In print function');

or you can use this syntax

class ClassNameHere{
  console.log('In print function');

module.exports = ClassNameHere;

On the other hand to use this class in any other file you need to do these steps. First require that file using this syntax: const anyVariableNameHere = require('filePathHere');

Then create an object const classObject = new anyVariableNameHere();

After this you can use classObject to access the actual class variables

Using Thymeleaf when the value is null

Also worth to look at documentation for #objects build-in helper:

There is useful: ${#objects.nullSafe(obj, default)}

Modifying the "Path to executable" of a windows service

You could also do it with PowerShell:

Get-WmiObject win32_service -filter "Name='My Service'" `
    | Invoke-WmiMethod -Name Change `
    -ArgumentList @($null,$null,$null,$null,$null, `
    "C:\Program Files (x86)\My Service\NewName.EXE")


Set-ItemProperty -Path "HKLM:\System\CurrentControlSet\Services\My Service" `
    -Name ImagePath -Value "C:\Program Files (x86)\My Service\NewName.EXE"

How do I use regex in a SQLite query?

You could use a regular expression with REGEXP, but that is a silly way to do an exact match.

You should just say WHERE x = '3'.

Div not expanding even with content inside

There are two solutions to fix this:

  1. Use clear:both after the last floated tag. This works good.
  2. If you have fixed height for your div or clipping of content is fine, go with: overflow: hidden

Django 1.7 throws django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet

This is what solved it for us and these folks:

Our project started with Django 1.4, we went to 1.5 and then to 1.7. Our looked like this:

import os

from django.core.handlers.wsgi import WSGIHandler

os.environ['DJANGO_SETTINGS_MODULE'] = 'myapp.settings'
application = WSGIHandler()

When I updated to the 1.7 style WSGI handler:

import os

from django.core.wsgi import get_wsgi_application

os.environ['DJANGO_SETTINGS_MODULE'] = 'myapp.settings'
application = get_wsgi_application()

Everything works now.

How to validate array in Laravel?

I have this array as my request data from a HTML+Vue.js data grid/table:

[0] => Array
        [item_id] => 1
        [item_no] => 3123
        [size] => 3e
[1] => Array
        [item_id] => 2
        [item_no] => 7688
        [size] => 5b

And use this to validate which works properly:

$this->validate($request, [
    '*.item_id' => 'required|integer',
    '*.item_no' => 'required|integer',
    '*.size'    => 'required|max:191',

gradle build fails on lint task

Got same error on AndroidStudio version 0.51

Build was working fine and suddenly, after only changing the version code value, I got a Lint related build error.

Tried to change build.gradle, cleared AndroidStudio cache and restart, but no change.

Finally I returned to original code (causing the error), and removed android:debuggable="false" from AndroidManifest.xml, causing the build to succeed.

I added it again and it still works... Don't ask me why :S

How to check if a value is not null and not empty string in JS

if (data?.trim().length > 0) {
   //use data

the ?. optional chaining operator will short-circuit and return undefined if data is nullish (null or undefined) which will evaluate to false in the if expression.

How to extract numbers from string in c?

void main(int argc,char *argv[])
char *str ="ab234cid*(s349*(20kd", *ptr = str;
while (*ptr) { // While there are more characters to process...
    if ( isdigit(*ptr) ) {
        // Found a number
        int val = (int)strtol(ptr,&ptr, 10); // Read number
        printf("%d\n", val); // and print it.
    } else {
        // Otherwise, move on to the next character.


mappedBy reference an unknown target entity property

I know the answer by @Pascal Thivent has solved the issue. I would like to add a bit more to his answer to others who might be surfing this thread.

If you are like me in the initial days of learning and wrapping your head around the concept of using the @OneToMany annotation with the 'mappedBy' property, it also means that the other side holding the @ManyToOne annotation with the @JoinColumn is the 'owner' of this bi-directional relationship.

Also, mappedBy takes in the instance name (mCustomer in this example) of the Class variable as an input and not the Class-Type (ex:Customer) or the entity name(Ex:customer).

BONUS : Also, look into the orphanRemoval property of @OneToMany annotation. If it is set to true, then if a parent is deleted in a bi-directional relationship, Hibernate automatically deletes it's children.

ASP.NET 2.0 - How to use app_offline.htm

Make sure filename extensions are visible in explorer and filename is actually




Automatically resize jQuery UI dialog to the width of the content loaded by ajax

I have the same problem and having position: absolute in your .ui-dialog{} css was not enough. I noticed that position: relative was being set on the actual element's direct style, so the .ui-dialog css definition was getting overwritten. Setting position: absolute on the div I was going to make a dialog statically also did not work.

In the end I changed two placed in my local jQuery to make this work.

I changed the following line in jQuery to be: = "absolute";


Also, since my dialog was set to draggable, I had to change this line as well in jQuery-ui to be:

this.element[0].style.position = 'absolute';


Perhaps going through the style I have more thoroughly would fix things, but thought I'd share how I got this working.

Using the star sign in grep

This worked for me:

grep ".*${expr}" - with double-quotes, preceded by the dot. Where "expr" is whatever string you need in the end of the line.

Standard unix grep w/out additional switches.

How do I convert Int/Decimal to float in C#?

You can just do a cast

int val1 = 1;
float val2 = (float)val1;


decimal val3 = 3;
float val4 = (float)val3;

C# : "A first chance exception of type 'System.InvalidOperationException'"

The problem here is that your timer starts a thread and when it runs the callback function, the callback function ( updatelistview) is accessing controls on UI thread so this can not be done becuase of this

for-in statement

edit 2018: This is outdated, js and typescript now have for..of loops.

The book "TypeScript Revealed" says

"You can iterate through the items in an array by using either for or loops as demonstrated here:

// standard for loop
for (var i = 0; i < actors.length; i++)

// loop
for (var actor in actors)


Turns out, the second loop does not pass the actors in the loop. So would say this is plain wrong. Sadly it is as above, loops are untouched by typescript.

map and forEach often help me and are due to typescripts enhancements on function definitions more approachable, lke at the very moment:

this.notes = => new Note(state));

My wish list to TypeScript;

  1. Generic collections
  2. Iterators (IEnumerable, IEnumerator interfaces would be best)

Exception : peer not authenticated

You can get this if the client specifies "https" but the server is only running "http". So, the server isn't expecting to make a secure connection.

Rounding integer division (instead of truncating)

The following correctly rounds the quotient to the nearest integer for both positive and negative operands WITHOUT floating point or conditional branches (see assembly output below). Assumes N-bit 2's complement integers.

#define ASR(x) ((x) < 0 ? -1 : 0)  // Compiles into a (N-1)-bit arithmetic shift right
#define ROUNDING(x,y) ( (y)/2 - (ASR((x)^(y)) & (y)))

int RoundedQuotient(int x, int y)
   return (x + ROUNDING(x,y)) / y ;

The value of ROUNDING will have the same sign as the dividend (x) and half the magnitude of the divisor (y). Adding ROUNDING to the dividend thus increases its magnitude before the integer division truncates the resulting quotient. Here's the output of the gcc compiler with -O3 optimization for a 32-bit ARM Cortex-M4 processor:

RoundedQuotient:                // Input parameters: r0 = x, r1 = y
    eor     r2, r1, r0          // r2 = x^y
    and     r2, r1, r2, asr #31 // r2 = ASR(x^y) & y
    add     r3, r1, r1, lsr #31 // r3 = (y < 0) ? y + 1 : y
    rsb     r3, r2, r3, asr #1  // r3 = y/2 - (ASR(x^y) & y)
    add     r0, r0, r3          // r0 = x + (y/2 - (ASR(x^y) & y)
    sdiv    r0, r0, r1          // r0 = (x + ROUNDING(x,y)) / y
    bx      lr                  // Returns r0 = rounded quotient

How to increment a number by 2 in a PHP For Loop

     $x = 1;

     for($x = 1; $x < 8; $x++) {
       $x = $x + 2;
       echo $x;

How can one use multi threading in PHP applications

Threading isn't available in stock PHP, but concurrent programming is possible by using HTTP requests as asynchronous calls.

With the curl's timeout setting set to 1 and using the same session_id for the processes you want to be associated with each other, you can communicate with session variables as in my example below. With this method you can even close your browser and the concurrent process still exists on the server.

Don't forget to verify the correct session ID like this:

http://localhost/test/verifysession.php?sessionid=[the correct id]


$request = "http://localhost/test/process1.php?sessionid=".$_REQUEST["PHPSESSID"];
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $request);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_TIMEOUT, 1);



if ($_REQUEST["sessionid"])

function checkclose()
   global $_SESSION;
   if ($_SESSION["closesession"])

   $_SESSION["test"] = rand();


if ($_REQUEST["sessionid"])



if ($_REQUEST["sessionid"])

$_SESSION["closesession"] = true;

How can I delay a method call for 1 second?

Use in Swift 3

perform(<Selector>, with: <object>, afterDelay: <Time in Seconds>)

UICollectionView current visible cell index

Just want to add for others : for some reason, I didnt not get the cell that was visible to the user when I was scrolling to previous cell in collectionView with pagingEnabled.

So I insert the code inside dispatch_async to give it some "air" and this works for me.

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
    dispatch_async(dispatch_get_main_queue(), ^{
            UICollectionViewCell * visibleCell= [[self.collectionView visibleCells] objectAtIndex:0];

            [visibleCell doSomthing];

SQL Plus change current directory

I don't think that you can change the directory in SQL*Plus.

Instead of changing directory, you can use @@filename, which reads in another script whose location is relative to the directory the current script is running in. For example, if you have two scripts


then script1.sql can run script2.sql if it contains the line


See this for more info about @@.

How to rollback everything to previous commit

If you have pushed the commits upstream...

Select the commit you would like to roll back to and reverse the changes by clicking Reverse File, Reverse Hunk or Reverse Selected Lines. Do this for all the commits after the commit you would like to roll back to also.

reverse stuff reverse commit

If you have not pushed the commits upstream...

Right click on the commit and click on Reset current branch to this commit.

reset branch to commit

How to start/stop/restart a thread in Java?

You can start a thread like:

    Thread thread=new Thread(new Runnable() {
                public void run() {
                    try {
                        //Do you task
                    }catch (Exception ex){

To stop a Thread:

   thread.join();//it will kill you thread

   //if you want to know whether your thread is alive or dead you can use
System.out.println("Thread is "+thread.isAlive());

Its advisable to create a new thread rather than restarting it.

how to use the Box-Cox power transformation in R

According to the Box-cox transformation formula in the paper Box,George E. P.; Cox,D.R.(1964). "An analysis of transformations", I think mlegge's post might need to be slightly edited.The transformed y should be (y^(lambda)-1)/lambda instead of y^(lambda). (Actually, y^(lambda) is called Tukey transformation, which is another distinct transformation formula.)
So, the code should be:

(trans <- bc$x[which.max(bc$y)])
[1] 0.4242424
# re-run with transformation
mnew <- lm(((y^trans-1)/trans) ~ x) # Instead of mnew <- lm(y^trans ~ x) 

More information

Please correct me if I misunderstood it.

How to check the first character in a string in Bash or UNIX shell?

Consider the case statement as well which is compatible with most sh-based shells:

case $str in
    echo 1
    echo 0

How do I drag and drop files into an application?

Yet another gotcha:

The framework code that calls the Drag-events swallow all exceptions. You might think your event code is running smoothly, while it is gushing exceptions all over the place. You can't see them because the framework steals them.

That's why I always put a try/catch in these event handlers, just so I know if they throw any exceptions. I usually put a Debugger.Break(); in the catch part.

Before release, after testing, if everything seems to behave, I remove or replace these with real exception handling.

How to use the PI constant in C++

Since the official standard library doesn't define a constant PI you would have to define it yourself. So the answer to your question "How can I get PI without defining it manually?" is "You don't -- or you rely on some compiler-specific extensions.". If you're not concerned about portability you could check your compiler's manual for this.

C++ allows you to write

const double PI = std::atan(1.0)*4;

but the initialization of this constant is not guaranteed to be static. The G++ compiler however handles those math functions as intrinsics and is able to compute this constant expression at compile-time.

Getting value of HTML Checkbox from onclick/onchange events

Use this

<input type="checkbox" onclick="onClickHandler()" id="box" />

function onClickHandler(){
    var chk=document.getElementById("box").value;

    //use this value


/exclude in xcopy just for a file type

For excluding multiple file types, you can use '+' to concatenate other lists. For example:

xcopy /r /d /i /s /y /exclude:excludedfileslist1.txt+excludedfileslist2.txt C:\dev\apan C:\web\apan


Redirect to an external URL from controller action in Spring MVC

For me works fine:

@RequestMapping (value = "/{id}", method = RequestMethod.GET)
public ResponseEntity<Object> redirectToExternalUrl() throws URISyntaxException {
    URI uri = new URI("");
    HttpHeaders httpHeaders = new HttpHeaders();
    return new ResponseEntity<>(httpHeaders, HttpStatus.SEE_OTHER);

How do I draw a set of vertical lines in gnuplot?

Here is a snippet from my perl script to do this:

print OUTPUT "set arrow from $x1,$y1 to $x1,$y2 nohead lc rgb \'red\'\n";

As you might guess from above, it's actually drawn as a "headless" arrow.

What is the difference between float and double?

Unlike an int (whole number), a float have a decimal point, and so can a double. But the difference between the two is that a double is twice as detailed as a float, meaning that it can have double the amount of numbers after the decimal point.

How can I print out all possible letter combinations a given phone number can represent?

This is a recursive algorithm in C++11.

#include <iostream>
#include <array>
#include <list>

std::array<std::string, 10> pm = {
    "0", "1", "ABC", "DEF", "GHI", "JKL", "MNO", "PQRS", "TUV", "WXYZ"

void generate_mnemonic(const std::string& numbers, size_t i, std::string& m,
    std::list<std::string>& mnemonics)
    // Base case
    if (numbers.size() == i) {

    for (char c : pm[numbers[i] - '0']) {
        m[i] = c;
        generate_mnemonic(numbers, i + 1, m, mnemonics);

std::list<std::string> phone_number_mnemonics(const std::string& numbers)
    std::list<std::string> mnemonics;
    std::string m(numbers.size(), 0);
    generate_mnemonic(numbers, 0, m, mnemonics);
    return mnemonics;

int main() {
    std::list<std::string> result = phone_number_mnemonics("2276696");
    for (const std::string& s : result) {
        std::cout << s << std::endl;
    return 0;

Run php function on button click

Do this:

<input type="button" name="test" id="test" value="RUN" /><br/>


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

Grant execute permission for a user on all stored procedures in database?

This is a solution that means that as you add new stored procedures to the schema, users can execute them without having to call grant execute on the new stored procedure:

IF  EXISTS (SELECT * FROM sys.database_principals WHERE name = N'asp_net')
DROP USER asp_net

IF  EXISTS (SELECT * FROM sys.database_principals 
WHERE name = N'db_execproc' AND type = 'R')
DROP ROLE [db_execproc]

--Create a database role....

--...with EXECUTE permission at the schema level...
GRANT EXECUTE ON SCHEMA::dbo TO db_execproc;

--Any stored procedures that are created in the dbo schema can be 
--executed by users who are members of the db_execproc database role

--...add a user e.g. for the NETWORK SERVICE login that uses
CREATE USER asp_net 

--...and add them to the roles you need
EXEC sp_addrolemember N'db_execproc', 'asp_net';
EXEC sp_addrolemember N'db_datareader', 'asp_net';
EXEC sp_addrolemember N'db_datawriter', 'asp_net';

Reference: Grant Execute Permission on All Stored Procedures

JavaScript Number Split into individual digits

A functional approach in order to get digits from a number would be to get a string from your number, split it into an array (of characters) and map each element back into a number.

For example:

var number = 123456;

var array = number.toString()
.map(function(item, index) {
   return parseInt(item);

console.log(array); // returns [1, 2, 3, 4, 5, 6]

If you also need to sum all digits, you can append the reduce() method to the previous code:

var num = 123456;

var array = num.toString()
.map(function(item, index) {
   return parseInt(item);
.reduce(function(previousValue, currentValue, index, array) {
  return previousValue + currentValue;
}, 0);

console.log(array); // returns 21

As an alternative, with ECMAScript 2015 (6th Edition), you can use arrow functions:

var number = 123456;
var array = number.toString().split('').map((item, index) => parseInt(item));
console.log(array); // returns [1, 2, 3, 4, 5, 6]

If you need to sum all digits, you can append the reduce() method to the previous code:

var num = 123456;

var result = num.toString()
.map((item, index) => parseInt(item))
.reduce((previousValue, currentValue) => previousValue + currentValue, 0);

console.log(result); // returns 21

python 2.7: cannot pip on windows "bash: pip: command not found"

The problem is that your Python version and the library you want to use are not same versionally (Python). Even if you install Python's latest version, your PATH might not change properly and automatically. Thus, you should change it manually.After matching their version, it will work.

Ex: When I tried to install Django3, I got same error. I noticed that my PATH still seems C:\python27\Scripts though I already install Python3.8, so that I manually edited my PATH C:\python38\Scripts and reinstalled pip install Django and everything worked well.

Java regular expression OR operator

You can just use the pipe on its own:


for example:

String s = "string1, string2, string3";
System.out.println(s.replaceAll("string1|string2", "blah"));


blah, blah, string3

The main reason to use parentheses is to limit the scope of the alternatives:

String s = "string1, string2, string3";
System.out.println(s.replaceAll("string(1|2)", "blah"));

has the same output. but if you just do this:

String s = "string1, string2, string3";
System.out.println(s.replaceAll("string1|2", "blah"));

you get:

blah, stringblah, string3

because you've said "string1" or "2".

If you don't want to capture that part of the expression use ?::

String s = "string1, string2, string3";
System.out.println(s.replaceAll("string(?:1|2)", "blah"));

Efficient iteration with index in Scala

How about this?

val a = Array("One", "Two", "Three")
a.foldLeft(0) ((i, x) => {println(i + ": " + x); i + 1;} )


0: One
1: Two
2: Three

String to LocalDate

You may have to go from DateTime to LocalDate.

Using Joda Time:

DateTimeFormatter FORMATTER = DateTimeFormat.forPattern("yyyy-MMM-dd");
DateTime dateTime = FORMATTER.parseDateTime("2005-nov-12");
LocalDate localDate = dateTime.toLocalDate();

Retrieve column values of the selected row of a multicolumn Access listbox

Just a little addition. If you've only selected 1 row then the code below will select the value of a column (index of 4, but 5th column) for the selected row:


This saves having to use the ItemsSelected property.


Count words in a string method?

lambda, in which splitting and storing of the counted words is dispensed with
and only counting is done

String text = "counting w/o apostrophe's problems or consecutive   spaces";

int count = text.codePoints().boxed().collect(
        () -> new int[] {0, 0},
        (a, c) -> {
          if( ".,; \t".indexOf( c ) >= 0 )
            a[1] = 0;
          else if( a[1]++ == 0 ) a[0]++;
        }, (a, b) -> {a[0] += b[0]; return( a );},
        a -> a[0] ) );

gets: 7
works as a status machine that counts the transitions from spacing characters .,; \t to words

C programming: Dereferencing pointer to incomplete type error

How did you actually define the structure? If

struct {
  char name[32];
  int  size;
  int  start;
  int  popularity;
} stasher_file;

is to be taken as type definition, it's missing a typedef. When written as above, you actually define a variable called stasher_file, whose type is some anonymous struct type.


typedef struct { ... } stasher_file;

(or, as already mentioned by others):

struct stasher_file { ... };

The latter actually matches your use of the type. The first form would require that you remove the struct before variable declarations.

How to remove all null elements from a ArrayList or String Array?

I played around with this and found out that trimToSize() seems to work. I am working on the Android platform so it might be different.

No notification sound when sending notification from firebase in android

I am able to play notification sound even if I send it from firebase console. To do that you just need to add key "sound" with value "default" in advance option.

How to change my Git username in terminal?

If you have created a new Github account and you want to push commits with your new account instead of your previous account then the .gitconfig must be updated, otherwise, you will push with the already owned Github account to the new account.

In order to fix this, you have to navigate to your home directory and open the .gitconfig with an editor. The editor can be vim, notepad++, or even notepad.

Once you have the .gitconfig open, just modify the "name" with your new Github account username that you want to push with.

Pass a password to ssh in pure bash

You can not specify the password from the command line but you can do either using ssh keys or using sshpass as suggested by John C. or using a expect script.

To use sshpass, you need to install it first. Then

sshpass -f <(printf '%s\n' your_password) ssh user@hostname

instead of using sshpass -p your_password. As mentioned by Charles Duffy in the comments, it is safer to supply the password from a file or from a variable instead of from command line.

BTW, a little explanation for the <(command) syntax. The shell executes the command inside the parentheses and replaces the whole thing with a file descriptor, which is connected to the command's stdout. You can find more from this answer

How to fix symbol lookup error: undefined symbol errors in a cluster environment

yum update

helped me out. After I had

wget: symbol lookup error: wget: undefined symbol: psl_latest

Import file size limit in PHPMyAdmin

For uploading large files through PHPMyAdmin, follow these steps:

Step 1: Open your php.ini file.

Step 2: Upgrading Memory Limit:

memory_limit = 750M

Step 3: Upgrading Maximum size to post:

post_max_size = 750M

Step 4: Upgrading Maximum file-size to upload:

upload_max_filesize = 1000M

Step 5: Upgrading Maximum Execution Time:

max_execution_time = 5000

Step 6: Upgrading Maximum Input Time:

max_input_time = 3000

Step 7: Restart your xampp control panel.

How to open up a form from another form in VB.NET?

You can also use showdialog

Private Sub Button3_Click(sender As System.Object, e As System.EventArgs) _
                      Handles Button3.Click

     dim mydialogbox as new aboutbox1

End Sub

How might I find the largest number contained in a JavaScript array?

The easiest syntax, with the new spread operator:

var arr = [1, 2, 3];
var max = Math.max(...arr);

Source : Mozilla MDN

How to remove from a map while iterating it?

Assuming C++11, here is a one-liner loop body, if this is consistent with your programming style:

using Map = std::map<K,V>;
Map map;

// Erase members that satisfy needs_removing(itr)
for (Map::const_iterator itr = map.cbegin() ; itr != map.cend() ; )
  itr = needs_removing(itr) ? map.erase(itr) : std::next(itr);

A couple of other minor style changes:

  • Show declared type (Map::const_iterator) when possible/convenient, over using auto.
  • Use using for template types, to make ancillary types (Map::const_iterator) easier to read/maintain.

How to open a new form from another form

You could try adding a bool so the algorithm would know when the button was activated. When it's clicked, the bool checks true, the new form shows and the last gets closed.

It's important to know that forms consume some ram (at least a little bit), so it's a good idea to close those you're not gonna use, instead of just hiding it. Makes the difference in big projects.

Responsive design with media query : screen size?

Take a look at this...

For big websites I use Bootstrap and sometimes (for simple websites) I create all the style with some @mediaqueries. It's very simple, just think all the code in percentage.

.container {
max-width: 1200px;
width: 100%;
margin: 0 auto;

Inside the container, your structure must have widths in percentage like this...

.col-1 {
width: 40%;
float: left;

.col-2 {
width: 60%;
float: left;

@media screen and (max-width: 320px) {
.col-1, .col-2 { width: 100%; }

In some simple interfaces, if you start to develop the project in this way, you will have great chances to have a fully responsive site using break points only to adjust the flow of objects.

How to make a launcher

Just develop a normal app and then add a couple of lines to the app's manifest file.

First you need to add the following attribute to your activity:


Then add two categories to the intent filter :

            <category android:name="android.intent.category.DEFAULT" />
            <category android:name="android.intent.category.HOME" />

The result could look something like this:

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android=""
        android:versionName="1.0" >

            android:targetSdkVersion="19" />

            android:theme="@style/AppTheme" >
                android:label="@string/app_name" >
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                    <category android:name="android.intent.category.DEFAULT" />
                    <category android:name="android.intent.category.HOME" />


It's that simple!

StringLength vs MaxLength attributes ASP.NET MVC with Entity Framework EF Code First

MaxLengthAttribute means Max. length of array or string data allowed

StringLengthAttribute means Min. and max. length of characters that are allowed in a data field


Rendering React Components from Array of Objects presumably contains all the data, so you would need to do something like this:

var stations = [];
var stationData =;

for (var i = 0; i < stationData.length; i++) {
        <div key={stationData[i].call} className="station">
            Call: {stationData[i].call}, Freq: {stationData[i].frequency}

render() {
  return (
    <div className="stations">{stations}</div>

Or you can use map and arrow functions if you're using ES6:

const stations = =>
    <div key={} className="station">
      Call: {}, Freq: {station.frequency}

Running a command in a new Mac OS X Terminal window

A colleague asked me how to open A LOT of ssh sessions at once. I used cobbal's answer to write this script:

tmpdir=$( mktemp -d )
trap '$DEBUG rm -rf $tmpdir ' EXIT

ssh user1@host1
ssh user2@host2
} | while read command
  index=$(( index + 1 ))
  echo $command > $COMMAND_FILE
  chmod +x  $COMMAND_FILE
sleep 60

By updating the list of commands ( they don't have to be ssh invocations ), you will get an additional open window for every command executed. The sleep 60 at the end is there to keep the .command files around while they are being executed. Otherwise, the shell completes too quickly, executing the trap to delete the temp directory ( created by mktemp ) before the launched sessions have an opportunity to read the files.

How can I select the first day of a month in SQL?

If you are looking at this today, and using SQL server 2012 or newer you have the EOMONTH function which makes things easier:

SELECT DATEADD(day, 1, EOMONTH(DATEADD(month, -1, GETDATE()))) as firstdateofmonth

You can change GETDATE() with whatever date variable you want.

Convert SVG image to PNG with PHP

When converting SVG to transparent PNG, don't forget to put this BEFORE $imagick->readImageBlob():

$imagick->setBackgroundColor(new ImagickPixel('transparent'));

Unzip files (7-zip) via cmd command

make sure that your path is pointing to .exe file in C:\Program Files\7-Zip (may in bin directory)

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

Try this query -

  CASE status
      WHEN 'New' THEN t2.expose_new
      WHEN 'Used' THEN t2.expose_used
  END as 'expose'
  `products` t1
JOIN manufacturers t2
  ON = t1.seller
  t1.seller = 4238

Changing the width of Bootstrap popover

Try this:

var popover_size=($('.popover').css('width'));
var string=(popover_size).split('px');
popover_size = ((parseInt(string[0])+350));

Select * from subquery

You can select every column from that sub-query by aliasing it and adding the alias before the *:

SELECT t.*, a+b AS total_sum
   SELECT SUM(column1) AS a, SUM(column2) AS b
   FROM table
) t

How to pass Multiple Parameters from ajax call to MVC Controller

You're making an HTTP POST, but trying to pass parameters with the GET query string syntax. In a POST, the data are passed as named parameters and do not use the param=value&foo=bar syntax. Using jQuery's ajax method lets you create a javascript object with the named parameters, like so:

  url: '/Home/SaveChart',
  type: 'POST',
  async: false,
  dataType: 'text',
  processData: false,    
  data: { 
      input: JSON.stringify(, 
      name: $("#wrkname").val()
  success: function (data) { }

Can you disable tabs in Bootstrap?

No Need Any Jquery, Just One Line CSS

.nav-tabs li.disabled a {
    pointer-events: none;

What does the @Valid annotation indicate in Spring?

Adding to above answers, take a look at following. AppointmentForm's date column is annotated with couple of annotations. By having @Valid annotation that triggers validations on the AppointmentForm (in this case @NotNull and @Future). These annotations could come from different JSR-303 providers (e.g, Hibernate, Spring..etc).

    @RequestMapping(value = "/appointments", method = RequestMethod.POST)
    public String add(@Valid AppointmentForm form, BindingResult result) {

    static class AppointmentForm {

        @NotNull @Future
        private Date date;

Is floating point math broken?

The kind of floating-point math that can be implemented in a digital computer necessarily uses an approximation of the real numbers and operations on them. (The standard version runs to over fifty pages of documentation and has a committee to deal with its errata and further refinement.)

This approximation is a mixture of approximations of different kinds, each of which can either be ignored or carefully accounted for due to its specific manner of deviation from exactitude. It also involves a number of explicit exceptional cases at both the hardware and software levels that most people walk right past while pretending not to notice.

If you need infinite precision (using the number p, for example, instead of one of its many shorter stand-ins), you should write or use a symbolic math program instead.

But if you're okay with the idea that sometimes floating-point math is fuzzy in value and logic and errors can accumulate quickly, and you can write your requirements and tests to allow for that, then your code can frequently get by with what's in your FPU.

Distinct() with lambda?

You can use LambdaEqualityComparer:

var distinctValues
    = myCustomerList.Distinct(new LambdaEqualityComparer<OurType>((c1, c2) => c1.CustomerId == c2.CustomerId));

public class LambdaEqualityComparer<T> : IEqualityComparer<T>
        public LambdaEqualityComparer(Func<T, T, bool> equalsFunction)
            _equalsFunction = equalsFunction;

        public bool Equals(T x, T y)
            return _equalsFunction(x, y);

        public int GetHashCode(T obj)
            return obj.GetHashCode();

        private readonly Func<T, T, bool> _equalsFunction;

How can I format a decimal to always show 2 decimal places?

.format is a more readable way to handle variable formatting:

'{:.{prec}f}'.format(26.034, prec=2)

Select Specific Columns from Spark DataFrame

If you want to split you dataframe into two different ones, do two selects on it with the different columns you want.

 val sourceDf =
 val df1 ="first column", "second column", "third column")
 val df2 ="first column", "second column", "third column")

Note that this of course means that the sourceDf would be evaluated twice, so if it can fit into distributed memory and you use most of the columns across both dataframes it might be a good idea to cache it. It it has many extra columns that you don't need, then you can do a select on it first to select on the columns you will need so it would store all that extra data in memory.

Difference between 2 dates in SQLite

The SQLite documentation is a great reference and the DateAndTimeFunctions page is a good one to bookmark.

It's also helpful to remember that it's pretty easy to play with queries with the sqlite command line utility:

sqlite> select julianday(datetime('now'));
sqlite> select datetime(julianday(datetime('now')));
2008-11-17 14:13:55

Auto insert date and time in form input field?

<input id="date" name="date" />
<script type="text/javascript">
document.getElementById("date").value = new Date();

Is it possible to display my iPhone on my computer monitor?

Many screencasts displaying an iPhone application simply use the iPhone Simulator, which is one option.

You can also take screenshots on the phone by quickly pressing the menu and the power/sleep button at the same time. The image is then saved to your "Camera Roll" and easily transferable to the computer

The other way is only possible with a Jailbroken phone - Veency is a VNC server for the iPhone, which you can connect to with a regular VNC client.

Find specific string in a text file with VBS script

I'd recommend using a regular expressions instead of string operations for this:

Set fso = CreateObject("Scripting.FileSystemObject")

filename = "C:\VBS\filediprova.txt"

newtext = vbLf & "<tr><td><a href=""..."">Beginning_of_DD_TC5</a></td></tr>"

Set re = New RegExp
re.Pattern = "(\n.*?Test Case \d)"
re.Global  = False
re.IgnoreCase = True

text = f.OpenTextFile(filename).ReadAll
f.OpenTextFile(filename, 2).Write re.Replace(text, newText & "$1")

The regular expression will match a line feed (\n) followed by a line containing the string Test Case followed by a number (\d), and the replacement will prepend that with the text you want to insert (variable newtext). Setting re.Global = False makes the replacement stop after the first match.

If the line breaks in your text file are encoded as CR-LF (carriage return + line feed) you'll have to change \n into \r\n and vbLf into vbCrLf.

If you have to modify several text files, you could do it in a loop like this:

For Each f In fso.GetFolder("C:\VBS").Files
  If LCase(fso.GetExtensionName(f.Name)) = "txt" Then
    text = f.OpenAsTextStream.ReadAll
    f.OpenAsTextStream(2).Write re.Replace(text, newText & "$1")
  End If