Programs & Examples On #Image archive

How to Remove Array Element and Then Re-Index Array?

You better use array_shift(). That will return the first element of the array, remove it from the array and re-index the array. All in one efficient method.

Center an item with position: relative

Alternatively, you may also use the CSS3 Flexible Box Model. It's a great way to create flexible layouts that can also be applied to center content like so:

#parent {

.Net System.Mail.Message adding multiple "To" addresses

I wasn't able to replicate your bug:

var message = new MailMessage();

message.To.Add("[email protected]");
message.To.Add("[email protected]");

message.From = new MailAddress("[email protected]");
message.Subject = "Test";
message.Body = "Test";

var client = new SmtpClient("localhost", 25);

Dumping the contents of the To: MailAddressCollection:

MailAddressCollection (2 items)
DisplayName User Host Address

user [email protected]
user2 [email protected]

And the resulting e-mail as caught by smtp4dev:

Received: from mycomputername (mycomputername [])
     by localhost (Eric Daugherty's C# Email Server)
     3/8/2010 12:50:28 PM
MIME-Version: 1.0
From: [email protected]
To: [email protected], [email protected]
Date: 8 Mar 2010 12:50:28 -0800
Subject: Test
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: quoted-printable


Are you sure there's not some other issue going on with your code or SMTP server?

Issue with parsing the content from json file with Jackson & message- JsonMappingException -Cannot deserialize as out of START_ARRAY token

As said, JsonMappingException: out of START_ARRAY token exception is thrown by Jackson object mapper as it's expecting an Object {} whereas it found an Array [{}] in response.

A simpler solution could be replacing the method getLocations with:

public static List<Location> getLocations(InputStream inputStream) {
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        TypeReference<List<Location>> typeReference = new TypeReference<>() {};
        return objectMapper.readValue(inputStream, typeReference);
    } catch (IOException e) {
    return null;

On the other hand, if you don't have a pojo like Location, you could use:

TypeReference<List<Map<String, Object>>> typeReference = new TypeReference<>() {};
return objectMapper.readValue(inputStream, typeReference);

What's the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL JOIN?

INNER JOIN gets all records that are common between both tables based on the supplied ON clause.

LEFT JOIN gets all records from the LEFT linked and the related record from the right table ,but if you have selected some columns from the RIGHT table, if there is no related records, these columns will contain NULL.

RIGHT JOIN is like the above but gets all records in the RIGHT table.

FULL JOIN gets all records from both tables and puts NULL in the columns where related records do not exist in the opposite table.

Repeat a string in JavaScript a number of times

Another interesting way to quickly repeat n character is to use idea from quick exponentiation algorithm:

var repeatString = function(string, n) {
    var result = '', i;

    for (i = 1; i <= n; i *= 2) {
        if ((n & i) === i) {
            result += string;
        string = string + string;

    return result;

How do you read CSS rule values with JavaScript?

Some browser differences to be aware of:

Given the CSS:

div#a { ... }
div#b, div#c { ... }

and given InsDel's example, classes will have 2 classes in FF and 3 classes in IE7.

My example illustrates this:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<html xmlns="" xml:lang="en" lang="en">
    div#a { }
    div#b, div#c { }
    function PrintRules() {
    var rules = document.styleSheets[0].rules || document.styleSheets[0].cssRules
        for(var x=0;x<rules.length;x++) {
            document.getElementById("rules").innerHTML += rules[x].selectorText + "<br />";
    <input onclick="PrintRules()" type="button" value="Print Rules" /><br />
    <div id="rules"></div>

Python class returning value

I think you are very confused about what is occurring.

In Python, everything is an object:

  • [] (a list) is an object
  • 'abcde' (a string) is an object
  • 1 (an integer) is an object
  • MyClass() (an instance) is an object
  • MyClass (a class) is also an object
  • list (a type--much like a class) is also an object

They are all "values" in the sense that they are a thing and not a name which refers to a thing. (Variables are names which refer to values.) A value is not something different from an object in Python.

When you call a class object (like MyClass() or list()), it returns an instance of that class. (list is really a type and not a class, but I am simplifying a bit here.)

When you print an object (i.e. get a string representation of an object), that object's __str__ or __repr__ magic method is called and the returned value printed.

For example:

>>> class MyClass(object):
...     def __str__(self):
...             return "MyClass([])"
...     def __repr__(self):
...             return "I am an instance of MyClass at address "+hex(id(self))
>>> m = MyClass()
>>> print m
>>> m
I am an instance of MyClass at address 0x108ed5a10

So what you are asking for, "I need that MyClass return a list, like list(), not the instance info," does not make any sense. list() returns a list instance. MyClass() returns a MyClass instance. If you want a list instance, just get a list instance. If the issue instead is what do these objects look like when you print them or look at them in the console, then create a __str__ and __repr__ method which represents them as you want them to be represented.

Update for new question about equality

Once again, __str__ and __repr__ are only for printing, and do not affect the object in any other way. Just because two objects have the same __repr__ value does not mean they are equal!

MyClass() != MyClass() because your class does not define how these would be equal, so it falls back to the default behavior (of the object type), which is that objects are only equal to themselves:

>>> m = MyClass()
>>> m1 = m
>>> m2 = m
>>> m1 == m2
>>> m3 = MyClass()
>>> m1 == m3

If you want to change this, use one of the comparison magic methods

For example, you can have an object that is equal to everything:

>>> class MyClass(object):
...     def __eq__(self, other):
...             return True
>>> m1 = MyClass()
>>> m2 = MyClass()
>>> m1 == m2
>>> m1 == m1
>>> m1 == 1
>>> m1 == None
>>> m1 == []

I think you should do two things:

  1. Take a look at this guide to magic method use in Python.
  2. Justify why you are not subclassing list if what you want is very list-like. If subclassing is not appropriate, you can delegate to a wrapped list instance instead:

    class MyClass(object):
        def __init__(self):
            self._list = []
        def __getattr__(self, name):
            return getattr(self._list, name)
        # __repr__ and __str__ methods are automatically created
        # for every class, so if we want to delegate these we must
        # do so explicitly
        def __repr__(self):
            return "MyClass(%s)" % repr(self._list)
        def __str__(self):
            return "MyClass(%s)" % str(self._list)

    This will now act like a list without being a list (i.e., without subclassing list).

    >>> c = MyClass()
    >>> c.append(1)
    >>> c

Start systemd service after specific service?

In the .service file under the [Unit] section:

Description=My Website mongodb.service

The important part is the mongodb.service

The manpage describes it however due to formatting it's not as clear on first sight

systemd.unit - well formatted

systemd.unit - not so well formatted

How to run html file using node js

Just install http-server globally

npm install -g http-server

where ever you need to run a html file run the command http-server For ex: your html file is in /home/project/index.html you can do /home/project/$ http-server

That will give you a link to accessyour webpages: http-server Starting up http-server, serving ./ Available on:

remove all special characters in java

use [\\W+] or "[^a-zA-Z0-9]" as regex to match any special characters and also use String.replaceAll(regex, String) to replace the spl charecter with an empty string. remember as the first arg of String.replaceAll is a regex you have to escape it with a backslash to treat em as a literal charcter.

          String c= "hjdg$h&jk8^i0ssh6";
        Pattern pt = Pattern.compile("[^a-zA-Z0-9]");
        Matcher match= pt.matcher(c);
            String s=;
        c=c.replaceAll("\\"+s, "");

How to output numbers with leading zeros in JavaScript?

NOTE: Potentially outdated. ECMAScript 2017 includes String.prototype.padStart.

You'll have to convert the number to a string since numbers don't make sense with leading zeros. Something like this:

function pad(num, size) {
    num = num.toString();
    while (num.length < size) num = "0" + num;
    return num;

Or, if you know you'd never be using more than X number of zeros, this might be better. This assumes you'd never want more than 10 digits.

function pad(num, size) {
    var s = "000000000" + num;
    return s.substr(s.length-size);

If you care about negative numbers you'll have to strip the - and read it.

How to delete multiple rows in SQL where id = (x to y)

Please try this:

DELETE FROM `table` WHERE id >=163 and id<= 265

Detecting user leaving page with react-router

For react-router v0.13.x with react v0.13.x:

this is possible with the willTransitionTo() and willTransitionFrom() static methods. For newer versions, see my other answer below.

From the react-router documentation:

You can define some static methods on your route handlers that will be called during route transitions.

willTransitionTo(transition, params, query, callback)

Called when a handler is about to render, giving you the opportunity to abort or redirect the transition. You can pause the transition while you do some asynchonous work and call callback(error) when you're done, or omit the callback in your argument list and it will be called for you.

willTransitionFrom(transition, component, callback)

Called when an active route is being transitioned out giving you an opportunity to abort the transition. The component is the current component, you'll probably need it to check its state to decide if you want to allow the transition (like form fields).


  var Settings = React.createClass({
    statics: {
      willTransitionTo: function (transition, params, query, callback) {
        auth.isLoggedIn((isLoggedIn) => {

      willTransitionFrom: function (transition, component) {
        if (component.formHasUnsavedData()) {
          if (!confirm('You have unsaved information,'+
                       'are you sure you want to leave this page?')) {


For react-router 1.0.0-rc1 with react v0.14.x or later:

this should be possible with the routerWillLeave lifecycle hook. For older versions, see my answer above.

From the react-router documentation:

To install this hook, use the Lifecycle mixin in one of your route components.

  import { Lifecycle } from 'react-router'

  const Home = React.createClass({

    // Assuming Home is a route component, it may use the
    // Lifecycle mixin to get a routerWillLeave method.
    mixins: [ Lifecycle ],

    routerWillLeave(nextLocation) {
      if (!this.state.isSaved)
        return 'Your work is not saved! Are you sure you want to leave?'

    // ...


Things. may change before the final release though.

Meaning of *& and **& in C++

To understand those phrases let's look at the couple of things:

typedef double Foo;
void fooFunc(Foo &_bar){ ... }

So that's passing a double by reference.

typedef double* Foo;
void fooFunc(Foo &_bar){ ... }

now it's passing a pointer to a double by reference.

typedef double** Foo;
void fooFunc(Foo &_bar){ ... }

Finally, it's passing a pointer to a pointer to a double by reference. If you think in terms of typedefs like this you'll understand the proper ordering of the & and * plus what it means.

How to subtract days from a plain Date?

The top answers led to a bug in my code where on the first of the month it would set a future date in the current month. Here is what I did,

curDate = new Date(); // Took current date as an example
prvDate = new Date(0); // Date set to epoch 0
prvDate.setUTCMilliseconds((curDate - (5 * 24 * 60 * 60 * 1000))); //Set epoch time

List View Filter Android

In case anyone are still interested in this subject, I find that the best approach for filtering lists is to create a generic Filter class and use it with some base reflection/generics techniques contained in the Java old school SDK package. Here's what I did:

public class GenericListFilter<T> extends Filter {

     * Copycat constructor
     * @param list  the original list to be used
    public GenericListFilter (List<T> list, String reflectMethodName, ArrayAdapter<T> adapter) {
        super ();

        mInternalList = new ArrayList<>(list);
        mAdapterUsed  = adapter;

        try {
            ParameterizedType stringListType = (ParameterizedType)
            mCompairMethod =
        catch (Exception ex) {
            Log.w("GenericListFilter", ex.getMessage(), ex);

            try {
                if (mInternalList.size() > 0) {
                    T type = mInternalList.get(0);
                    mCompairMethod = type.getClass().getMethod(reflectMethodName);
            catch (Exception e) {
                Log.e("GenericListFilter", e.getMessage(), e);


     * Let's filter the data with the given constraint
     * @param constraint
     * @return
    @Override protected FilterResults performFiltering(CharSequence constraint) {
        FilterResults results = new FilterResults();
        List<T> filteredContents = new ArrayList<>();

        if ( constraint.length() > 0 ) {
            try {
                for (T obj : mInternalList) {
                    String result = (String) mCompairMethod.invoke(obj);
                    if (result.toLowerCase().startsWith(constraint.toString().toLowerCase())) {
            catch (Exception ex) {
                Log.e("GenericListFilter", ex.getMessage(), ex);
        else {

        results.values = filteredContents;
        results.count  = filteredContents.size();
        return results;

     * Publish the filtering adapter list
     * @param constraint
     * @param results
    @Override protected void publishResults(CharSequence constraint, FilterResults results) {
        mAdapterUsed.addAll((List<T>) results.values);

        if ( results.count == 0 ) {
        else {

    // class properties
    private ArrayAdapter<T> mAdapterUsed;
    private List<T> mInternalList;
    private Method  mCompairMethod;

And afterwards, the only thing you need to do is to create the filter as a member class (possibly within the View's "onCreate") passing your adapter reference, your list, and the method to be called for filtering:

this.mFilter = new GenericFilter<MyObjectBean> (list, "getName", adapter);

The only thing missing now, is to override the "getFilter" method in the adapter class:

@Override public Filter getFilter () {
     return MyViewClass.this.mFilter;

All done! You should successfully filter your list - Of course, you should also implement your filter algorithm the best way that describes your need, the code bellow is just an example.. Hope it helped, take care.

Execute PHP function with onclick

You will have to do this via AJAX. I HEAVILY reccommend you use jQuery to make this easier for you....

$("#idOfElement").on('click', function(){

       url: 'pathToPhpFile.php',
       dataType: 'json',
       success: function(data){
            //data returned from php

How to display databases in Oracle 11g using SQL*Plus

SELECT NAME FROM v$database; shows the database name in oracle

JSON ValueError: Expecting property name: line 1 column 2 (char 1)

A different case in which I encountered this was when I was using echo to pipe the JSON into my python script and carelessly wrapped the JSON string in double quotes:

echo "{"thumbnailWidth": 640}" |

Note that the JSON string itself has quotes and I should have done:

echo '{"thumbnailWidth": 640}' |

As it was, this is what the python script received: {thumbnailWidth: 640}; the double quotes were effectively stripped.

Change link color of the current page with CSS

You do not need jQuery just to do this! All you need is a tiny and very light vanilla Javascript and a css class (as in all the answers above) :

  • First define a CSS class in your stylesheet called current.

  • Second add the following pure JavaScript either in your existing JavaScript file or in a separate js script file (but add script tage link to it in the head of the pages) or event just add it in a script tag just before the closing body tag, it will still work in all these cases.

    function highlightCurrent() {
         const curPage = document.URL;
         const links = document.getElementsByTagName('a');
         for (let link of links) {
           if (link.href == curPage) {

       document.onreadystatechange = () => {
         if (document.readyState === 'complete') {

The 'href' attribute of current link should be the absolute path as given by document.URL (console.log it to make sure it is the same)

Update Item to Revision vs Revert to Revision

To understand how the state of your working copy is different in both scenarios, you must understand the concept of the BASE revision:


The revision number of an item in a working copy. If the item has been locally modified, this refers to the way the item appears without those local modifications.

Your working copy contains a snapshot of each file (hidden in a .svn folder) in this BASE revision, meaning as it was when last retrieved from the repository. This explains why working copies take 2x the space and how it is possible that you can examine and even revert local modifications without a network connection.

Update item to Revision changes this base revision, making BASE out of date. When you try to commit local modifications, SVN will notice that your BASE does not match the repository HEAD. The commit will be refused until you do an update (and possibly a merge) to fix this.

Revert to revision does not change BASE. It is conceptually almost the same as manually editing the file to match an earlier revision.

jQuery remove options from select

$('.ct option').each(function() {
    if ( $(this).val() == 'X' ) {

Or just

$('.ct option[value="X"]').remove();

Main point is that find takes a selector string, by feeding it x you are looking for elements named x.

Is there a <meta> tag to turn off caching in all browsers?

I noticed some caching issues with service calls when repeating the same service call (long polling). Adding metadata didn't help. One solution is to pass a timestamp to ensure ie thinks it's a different http service request. That worked for me, so adding a server side scripting code snippet to automatically update this tag wouldn't hurt:

<meta http-equiv="expires" content="timestamp">

How can I use the HTML5 canvas element in IE?

I just used flashcanvas, and I got that working. If you encounter problems, just make sure to read the caveats and whatnot. Particularly, if you create canvas elements dynamically, you need to initialize them explicitly:

if (typeof FlashCanvas != "undefined") {

Finding second occurrence of a substring in a string in Java

Use overloaded version of indexOf(), which takes the starting index (fromIndex) as 2nd parameter:

str.indexOf("is", str.indexOf("is") + 1);

cmd line rename file with date and time

Animuson gives a decent way to do it, but no help on understanding it. I kept looking and came across a forum thread with this commands:

Echo Off
IF Not EXIST n:\dbfs\doekasp.txt GOTO DoNothing

copy n:\dbfs\doekasp.txt n:\history\doekasp.txt

Rem rename command is done twice (2) to allow for 1 or 2 digit hour,
Rem If before 10am (1digit) hour Rename starting at location (0) for (2) chars,
Rem will error out, as location (0) will have a space
Rem and space is invalid character for file name,
Rem so second remame will be used.
Rem if equal 10am or later (2 digit hour) then first remame will work and second will not
Rem as doekasp.txt will not be found (remamed)

ren n:\history\doekasp.txt doekasp-%date:~4,2%-%date:~7,2%-%date:~10,4%_@_%time:~0,2%h%time:~3,2%m%time:~6,2%s%.txt
ren n:\history\doekasp.txt doekasp-%date:~4,2%-%date:~7,2%-%date:~10,4%_@_%time:~1,1%h%time:~3,2%m%time:~6,2%s%.txt

I always name year first YYYYMMDD, but wanted to add time. Here you will see that he has given a reason why 0,2 will not work and 1,1 will, because (space) is an invalid character. This opened my eyes to the issue. Also, by default you're in 24hr mode.

I ended up with:

ren Logs.txt Logs-%date:~10,4%%date:~7,2%%date:~4,2%_%time:~0,2%%time:~3,2%.txt
ren Logs.txt Logs-%date:~10,4%%date:~7,2%%date:~4,2%_%time:~1,1%%time:~3,2%.txt



Possible cases for Javascript error: "Expected identifier, string or number"

Maybe you've got an object having a method 'constructor' and try to invoke that one.

C non-blocking keyboard input

Here's a function to do this for you. You need termios.h which comes with POSIX systems.

#include <termios.h>
void stdin_set(int cmd)
    struct termios t;
    switch (cmd) {
    case 1:
            t.c_lflag &= ~ICANON;
            t.c_lflag |= ICANON;

Breaking this down: tcgetattr gets the current terminal information and stores it in t. If cmd is 1, the local input flag in t is set to non-blocking input. Otherwise it is reset. Then tcsetattr changes standard input to t.

If you don't reset standard input at the end of your program you will have problems in your shell.

jQuery, simple polling example

function doPoll(){
    $.post('ajax/test.html', function(data) {
        alert(data);  // process results here

What are major differences between C# and Java?

Comparing Java 7 and C# 3

(Some features of Java 7 aren't mentioned here, but the using statement advantage of all versions of C# over Java 1-6 has been removed.)

Not all of your summary is correct:

  • In Java methods are virtual by default but you can make them final. (In C# they're sealed by default, but you can make them virtual.)
  • There are plenty of IDEs for Java, both free (e.g. Eclipse, Netbeans) and commercial (e.g. IntelliJ IDEA)

Beyond that (and what's in your summary already):

  • Generics are completely different between the two; Java generics are just a compile-time "trick" (but a useful one at that). In C# and .NET generics are maintained at execution time too, and work for value types as well as reference types, keeping the appropriate efficiency (e.g. a List<byte> as a byte[] backing it, rather than an array of boxed bytes.)
  • C# doesn't have checked exceptions
  • Java doesn't allow the creation of user-defined value types
  • Java doesn't have operator and conversion overloading
  • Java doesn't have iterator blocks for simple implemetation of iterators
  • Java doesn't have anything like LINQ
  • Partly due to not having delegates, Java doesn't have anything quite like anonymous methods and lambda expressions. Anonymous inner classes usually fill these roles, but clunkily.
  • Java doesn't have expression trees
  • C# doesn't have anonymous inner classes
  • C# doesn't have Java's inner classes at all, in fact - all nested classes in C# are like Java's static nested classes
  • Java doesn't have static classes (which don't have any instance constructors, and can't be used for variables, parameters etc)
  • Java doesn't have any equivalent to the C# 3.0 anonymous types
  • Java doesn't have implicitly typed local variables
  • Java doesn't have extension methods
  • Java doesn't have object and collection initializer expressions
  • The access modifiers are somewhat different - in Java there's (currently) no direct equivalent of an assembly, so no idea of "internal" visibility; in C# there's no equivalent to the "default" visibility in Java which takes account of namespace (and inheritance)
  • The order of initialization in Java and C# is subtly different (C# executes variable initializers before the chained call to the base type's constructor)
  • Java doesn't have properties as part of the language; they're a convention of get/set/is methods
  • Java doesn't have the equivalent of "unsafe" code
  • Interop is easier in C# (and .NET in general) than Java's JNI
  • Java and C# have somewhat different ideas of enums. Java's are much more object-oriented.
  • Java has no preprocessor directives (#define, #if etc in C#).
  • Java has no equivalent of C#'s ref and out for passing parameters by reference
  • Java has no equivalent of partial types
  • C# interfaces cannot declare fields
  • Java has no unsigned integer types
  • Java has no language support for a decimal type. (java.math.BigDecimal provides something like System.Decimal - with differences - but there's no language support)
  • Java has no equivalent of nullable value types
  • Boxing in Java uses predefined (but "normal") reference types with particular operations on them. Boxing in C# and .NET is a more transparent affair, with a reference type being created for boxing by the CLR for any value type.

This is not exhaustive, but it covers everything I can think of off-hand.

HTML-5 date field shows as "mm/dd/yyyy" in Chrome, even when valid date is set

I was having the same problem, with a value like 2016-08-8, then I solved adding a zero to have two digits days, and it works. Tested in chrome, firefox, and Edge

   var today = new Date();
   var d = (today.getDate() < 10 ? '0' : '' )+ today.getDate();
   var m = ((today.getMonth() + 1) < 10 ? '0' :'') + (today.getMonth() + 1);
   var y = today.getFullYear();
   var x = String(y+"-"+m+"-"+d); 
   return x;

How to create multiple page app using react


This answer uses the dynamic routing approach embraced in react-router v4+. Other answers may reference the previously-used "static routing" approach that has been abandoned by react-router.


react-router is a great solution. You create your pages as Components and the router swaps out the pages according to the current URL. In other words, it replaces your original page with your new page dynamically instead of asking the server for a new page.

For web apps I recommend you read these two things first:

Summary of the general approach:

1 - Add react-router-dom to your project:


yarn add react-router-dom

or NPM

npm install react-router-dom

2 - Update your index.js file to something like:

import { BrowserRouter } from 'react-router-dom';

    <App /> {/* The various pages will be displayed by the `Main` component. */}
  ), document.getElementById('root')

3 - Create a Main component that will show your pages according to the current URL:

import React from 'react';
import { Switch, Route } from 'react-router-dom';

import Home from '../pages/Home';
import Signup from '../pages/Signup';

const Main = () => {
  return (
    <Switch> {/* The Switch decides which component to show based on the current URL.*/}
      <Route exact path='/' component={Home}></Route>
      <Route exact path='/signup' component={Signup}></Route>

export default Main;

4 - Add the Main component inside of the App.js file:

function App() {
  return (
    <div className="App">
      <Navbar />
      <Main />

5 - Add Links to your pages.

(You must use Link from react-router-dom instead of just a plain old <a> in order for the router to work properly.)

import { Link } from "react-router-dom";
<Link to="/signup">
  <button variant="outlined">
    Sign up

Unix tail equivalent command in Windows Powershell

Very basic, but does what you need without any addon modules or PS version requirements:

while ($true) {Clear-Host; gc E:\test.txt | select -last 3; sleep 2 }

How to send password using sftp batch file

You need to use the command pscp and forcing it to pass through sftp protocol. pscp is automatically installed when you install PuttY, a software to connect to a linux server through ssh.

When you have your pscp command here is the command line:

pscp -sftp -pw <yourPassword> "<pathToYourFile(s)>" <username>@<serverIP>:<PathInTheServerFromTheHomeDirectory>

These parameters (-sftp and -pw) are only available with pscp and not scp. You can also add -r if you want to upload everything in a folder in a recursive way.

DataGridView changing cell background color

I finally managed to get it working. Here the code :

private void dgvStatus_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
    if (e.ColumnIndex != color.Index)

    e.CellStyle.BackColor = Color.FromArgb(int.Parse(((DataRowView)dgvStatus.Rows[e.RowIndex].DataBoundItem).Row[4].ToString()));

if anyone know a better to do this please don't hesitate to post it. I'm open to suggestion

Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<AnonymousType#1>' to 'System.Collections.Generic.List<string>

If you want it to be List<string>, get rid of the anonymous type and add a .ToList() call:

List<string> list = (from char c in source
                     select c.ToString()).ToList();

Where to find free public Web Services? -- Great collection of all category API's across web. It not only show cases the API's , but also Developers who use those API's in their applications and code samples, rating of the API and much more. They have more than apis they also have sdk and libraries too.

The requested operation cannot be performed on a file with a user-mapped section open

My issue was also solved by sifting through the Process Explorer. However, the process I had to kill was the MySQL Notifier.exe that was still running after closing all VS and SQL applications.

Getting multiple values with scanf()

int a[1000] ;
for(int i = 0 ; i <= 3 , i++)
scanf("%d" , &a[i]) ;

`IF` statement with 3 possible answers each based on 3 different ranges

This is what I did:

Very simply put:

=IF(C7>100,"Profit",IF(C7=100,"Quota Met","Loss"))

The first IF Statement, if true will input Profit, and if false will lead on to the next IF statement and so forth :)

I only have basic formula knowledge but it's working so I will accept I am right!

Turn ON/OFF Camera LED/flash light in Samsung Galaxy Ace 2.2.1 & Galaxy Tab

I will soon released a new version of my app to support to galaxy ace.

You can download here:

In order to solve your problem you should do this:

this._camera =;     
this._camera.autoFocus(new AutoFocusCallback() {
public void onAutoFocus(boolean success, Camera camera) {

Parameters params = this._camera.getParameters();

params = this._camera.getParameters();

don't worry about FLASH_MODE_OFF because this will keep the light on, strange but it's true

to turn off the led just release the camera

UnicodeEncodeError: 'ascii' codec can't encode character u'\xa0' in position 20: ordinal not in range(128)

I always put the code below in the first two lines of the python files:

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

MySQL search and replace some text in a field

And if you want to search and replace based on the value of another field you could do a CONCAT:

update table_name set `field_name` = replace(`field_name`,'YOUR_OLD_STRING',CONCAT('NEW_STRING',`OTHER_FIELD_VALUE`,'AFTER_IF_NEEDED'));

Just to have this one here so that others will find it at once.

Replace one substring for another string in shell script

To replace the first occurrence of a pattern with a given string, use ${parameter/pattern/string}:

firstString="I love Suzi and Marry"
echo "${firstString/Suzi/$secondString}"    
# prints 'I love Sara and Marry'

To replace all occurrences, use ${parameter//pattern/string}:

message='The secret code is 12345'
echo "${message//[0-9]/X}"           
# prints 'The secret code is XXXXX'

(This is documented in the Bash Reference Manual, §3.5.3 "Shell Parameter Expansion".)

Note that this feature is not specified by POSIX — it's a Bash extension — so not all Unix shells implement it. For the relevant POSIX documentation, see The Open Group Technical Standard Base Specifications, Issue 7, the Shell & Utilities volume, §2.6.2 "Parameter Expansion".

libstdc++-6.dll not found

If you are using MingW to compile C++ code on Windows, you may like to add the options -static-libgcc and -static-libstdc++ to link the C and C++ standard libraries statically and thus remove the need to carry around any separate copies of those. Version management of libraries is a pain in Windows, so I've found this approach the quickest and cleanest solution to creating Windows binaries.

How to tell Jackson to ignore a field during serialization if its value is null?

You can set


or application.yaml:

    default-property-inclusion: non_null

Difference between Static methods and Instance methods

Methods and variables that are not declared as static are known as instance methods and instance variables. To refer to instance methods and variables, you must instantiate the class first means you should create an object of that class first.For static you don't need to instantiate the class u can access the methods and variables with the class name using period sign which is in (.)

for example:

Person.staticMethod();           //accessing static method.

for non-static method you must instantiate the class.

Person person1 = new Person();   //instantiating
person1.nonStaticMethod();       //accessing non-static method.

Java: Literal percent sign in printf statement

You can use StringEscapeUtils from Apache Commons Logging utility or escape manually using code for each character.

Generate C# class from XML

You can use xsd as suggested by Darin.

In addition to that it is recommended to edit the test.xsd-file to create a more reasonable schema.

type="xs:string" can be changed to type="xs:int" for integer values
minOccurs="0" can be changed to minOccurs="1" where the field is required
maxOccurs="unbounded" can be changed to maxOccurs="1" where only one item is allowed

You can create more advanced xsd-s if you want to validate your data further, but this will at least give you reasonable data types in the generated c#.

how to convert string into time format and add two hours

This will give you the time you want (eg: 21:31 PM)

//Add 2 Hours to just TIME
SimpleDateFormat formatter = new SimpleDateFormat("HH:mm:ss a");
Date date2 = formatter.parse("19:31:51 PM");
Calendar cal2 = Calendar.getInstance();
cal2.add(Calendar.HOUR_OF_DAY, 2);
SimpleDateFormat printTimeFormat = new SimpleDateFormat("HH:mm a");

AngularJS: how to implement a simple file upload with multipart form?

I know this is a late entry but I have created a simple upload directive. Which you can get working in no time!

<input type="file" multiple ng-simple-upload web-api-url="/api/post"
       callback-fn="myCallback" />

ng-simple-upload more on Github with an example using Web API.

How to use WHERE IN with Doctrine 2

The easiest way to do that is by binding the array itself as a parameter:

$queryBuilder->andWhere('r.winner IN (:ids)')
             ->setParameter('ids', $ids);

How to change color in circular progress bar?

You can change color programmatically by using this code :

ProgressBar v = (ProgressBar) findViewById(;

If you want to change ProgressDialog's progressbar color, u can use this :

mDilog.setOnShowListener(new OnShowListener() {
        public void onShow(DialogInterface dialog) {
            ProgressBar v = (ProgressBar)mDilog.findViewById(;


Add Variables to Tuple

You can start with a blank tuple with something like t = (). You can add with +, but you have to add another tuple. If you want to add a single element, make it a singleton: t = t + (element,). You can add a tuple of multiple elements with or without that trailing comma.

>>> t = ()
>>> t = t + (1,)
>>> t
>>> t = t + (2,)
>>> t
(1, 2)
>>> t = t + (3, 4, 5)
>>> t
(1, 2, 3, 4, 5)
>>> t = t + (6, 7, 8,)
>>> t
(1, 2, 3, 4, 5, 6, 7, 8)

SQL Server dynamic PIVOT query?

There's my solution cleaning up the unnecesary null values

@maxcols AS NVARCHAR(MAX),

select @cols = STUFF((SELECT ',' + QUOTENAME(CodigoFormaPago) 
                from PO_FormasPago
                order by CodigoFormaPago
        FOR XML PATH(''), TYPE
        ).value('.', 'NVARCHAR(MAX)') 

select @maxcols = STUFF((SELECT ',MAX(' + QUOTENAME(CodigoFormaPago) + ') as ' + QUOTENAME(CodigoFormaPago)
                from PO_FormasPago
                order by CodigoFormaPago
        FOR XML PATH(''), TYPE
        ).value('.', 'NVARCHAR(MAX)')

set @query = 'SELECT CodigoProducto, DenominacionProducto, ' + @maxcols + '
                CodigoProducto, DenominacionProducto,
                ' + @cols + ' from 
                        p.CodigoProducto as CodigoProducto,
                        p.DenominacionProducto as DenominacionProducto,
                        fpp.CantidadCuotas as CantidadCuotas,
                        fpp.IdFormaPago as IdFormaPago,
                        fp.CodigoFormaPago as CodigoFormaPago
                        PR_Producto p
                        LEFT JOIN PR_FormasPagoProducto fpp
                            ON fpp.IdProducto = p.IdProducto
                        LEFT JOIN PO_FormasPago fp
                            ON fpp.IdFormaPago = fp.IdFormaPago
                ) xp
                    for CodigoFormaPago in (' + @cols + ')
                ) p 
            )  xx 
            GROUP BY CodigoProducto, DenominacionProducto'

t @query;


How can I escape white space in a bash loop list?

find . -type d | while read file; do echo $file; done

However, doesn't work if the file-name contains newlines. The above is the only solution i know of when you actually want to have the directory name in a variable. If you just want to execute some command, use xargs.

find . -type d -print0 | xargs -0 echo 'The directory is: '

How do I debug "Error: spawn ENOENT" on node.js?

Before anyone spends to much time debugging this problem, most of the time it can be resolved by deleting node_modules and reinstalling the packages.

To Install:

If a lockfile exists you might use

yarn install --frozen-lockfile


npm ci

respectivly. if not then

yarn install


npm i

How to convert nanoseconds to seconds using the TimeUnit enum?

To reduce verbosity, you can use a static import:

import static java.util.concurrent.TimeUnit.NANOSECONDS;

-and henceforth just type


regex with space and letters only?

Try this demo please:

Thanks Jan for spaces \s rest there is some good detail in this link:

Hope it fits your need :)


 $(function() {

    $("#field").bind("keyup", function(event) {
        var regex = /^[a-zA-Z\s]+$/;
        if (regex.test($("#field").val())) {
        } else {
            $('.validation').html("FAIL regex");

How do I delete from multiple tables using INNER JOIN in SQL server

All has been pointed out. Just use either DELETE ON CASCADE on the parent table or delete from the child-table and then parent.

Android: show/hide a view using an animation

Try this.

    .setListener(new AnimatorListenerAdapter() {
        public void onAnimationEnd(Animator animation) {

how to get the one entry from hashmap without iterating

auto it=m.begin();//get iterator to the first element of map(m)
return m->first;//return first string(1st string in map<string,string>m)
//Incase you want the second string 
//you can use return m->second(2st string in map<string,string>m)
//if you want to iterate the whole map you can use loop
for(auto it:m)//m is a map

EF Migrations: Rollback last applied migration?

In EF Core you can enter the command Remove-Migration in the package manager console after you've added your erroneous migration.

The console suggests you do so if your migration could involve a loss of data:

An operation was scaffolded that may result in the loss of data. Please review the migration for accuracy. To undo this action, use Remove-Migration.

MySQL limit from descending order

No, you shouldn't do this. Without an ORDER BY clause you shouldn't rely on the order of the results being the same from query to query. It might work nicely during testing but the order is indeterminate and could break later. Use an order by.


By the way, another way of getting the last 3 rows is to reverse the order and select the first three rows:


This will always work even if the number of rows in the result set isn't always 8.

Change the Bootstrap Modal effect

I copied model code from w3school bootstrap model and added following css. This code provides beautiful animation. You can try it.

.modal.fade .modal-dialog {
     -webkit-transform: scale(0.1);
     -moz-transform: scale(0.1);
     -ms-transform: scale(0.1);
     transform: scale(0.1);
     top: 300px;
     opacity: 0;
     -webkit-transition: all 0.3s;
     -moz-transition: all 0.3s;
     transition: all 0.3s;
} .modal-dialog {
    -webkit-transform: scale(1);
    -moz-transform: scale(1);
    -ms-transform: scale(1);
    transform: scale(1);
    -webkit-transform: translate3d(0, -300px, 0);
    transform: translate3d(0, -300px, 0);
    opacity: 1;

How to convert column with dtype as object to string in Pandas Dataframe

Not answering the question directly, but it might help someone else.

I have a column called Volume, having both - (invalid/NaN) and numbers formatted with ,

df['Volume'] = df['Volume'].astype('str')
df['Volume'] = df['Volume'].str.replace(',', '')
df['Volume'] = pd.to_numeric(df['Volume'], errors='coerce')

Casting to string is required for it to apply to str.replace


How do I change the font-size of an <option> element within <select>?

.service-small option {
    font-size: 14px;
    padding: 5px;
    background: #5c5c5c;

I think it because you used .styled-select in start of the class code.

How to convert these strange characters? (ë, Ã, ì, ù, Ã)

If you see those characters you probably just didn’t specify the character encoding properly. Because those characters are the result when an UTF-8 multi-byte string is interpreted with a single-byte encoding like ISO 8859-1 or Windows-1252.

In this case ë could be encoded with 0xC3 0xAB that represents the Unicode character ë (U+00EB) in UTF-8.

Detecting when Iframe content has loaded (Cross browser)

For those using React, detecting a same-origin iframe load event is as simple as setting onLoad event listener on iframe element.

<iframe src={'path-to-iframe-source'} onLoad={this.loadListener} frameBorder={0} />

C++ int float casting

Because (a.y - b.y) is probably less then (a.x - b.x) and in your code the casting is done after the divide operation so the result is an integer so 0.

You should cast to float before the / operation

View the change history of a file using Git versioning

git diff -U <filename> give you a unified diff.

It should be colored on red and green. If it's not, run: git config color.ui auto first.

PHP Parse HTML code

Use PHP Document Object Model:

   $str = '<h1>T1</h1>Lorem ipsum.<h1>T2</h1>The quick red fox...<h1>T3</h1>... jumps over the lazy brown FROG';
   $DOM = new DOMDocument;

   //get all H1
   $items = $DOM->getElementsByTagName('h1');

   //display all H1 text
   for ($i = 0; $i < $items->length; $i++)
        echo $items->item($i)->nodeValue . "<br/>";

This outputs as:


[EDIT]: After OP Clarification:

If you want the content like Lorem ipsum. etc, you can directly use this regex:

   $str = '<h1>T1</h1>Lorem ipsum.<h1>T2</h1>The quick red fox...<h1>T3</h1>... jumps over the lazy brown FROG';
   echo preg_replace("#<h1.*?>.*?</h1>#", "", $str);

this outputs:

Lorem ipsum.The quick red fox...... jumps over the lazy brown FROG

Javascript replace with reference to matched group?

"hello _there_".replace(/_(.*?)_/, function(a, b){
    return '<div>' + b + '</div>';

Oh, or you could also:

"hello _there_".replace(/_(.*?)_/, "<div>$1</div>")

EDIT by Liran H: For six other people including myself, $1 did not work, whereas \1 did.

How can I read SMS messages from the device programmatically in Android?

        final String myPackageName = getPackageName();
        if (!Telephony.Sms.getDefaultSmsPackage(this).equals(myPackageName)) {

            Intent intent = new Intent(Telephony.Sms.Intents.ACTION_CHANGE_DEFAULT);
            intent.putExtra(Telephony.Sms.Intents.EXTRA_PACKAGE_NAME, myPackageName);
            startActivityForResult(intent, 1);
        }else {
            List<Sms> lst = getAllSms();
    }else {
        List<Sms> lst = getAllSms();

Set app as default SMS app

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 1) {
    if (resultCode == RESULT_OK) {

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            final String myPackageName = getPackageName();
            if (Telephony.Sms.getDefaultSmsPackage(mActivity).equals(myPackageName)) {

                List<Sms> lst = getAllSms();

Function to get SMS

public List<Sms> getAllSms() {
    List<Sms> lstSms = new ArrayList<Sms>();
    Sms objSms = new Sms();
    Uri message = Uri.parse("content://sms/");
    ContentResolver cr = mActivity.getContentResolver();

    Cursor c = cr.query(message, null, null, null, null);
    int totalSMS = c.getCount();

    if (c.moveToFirst()) {
        for (int i = 0; i < totalSMS; i++) {

            objSms = new Sms();
            if (c.getString(c.getColumnIndexOrThrow("type")).contains("1")) {
            } else {

    // else {
    // throw new RuntimeException("You have no SMS");
    // }

    return lstSms;

Sms class is below:

public class Sms{
private String _id;
private String _address;
private String _msg;
private String _readState; //"0" for have not read sms and "1" for have read sms
private String _time;
private String _folderName;

public String getId(){
return _id;
public String getAddress(){
return _address;
public String getMsg(){
return _msg;
public String getReadState(){
return _readState;
public String getTime(){
return _time;
public String getFolderName(){
return _folderName;

public void setId(String id){
_id = id;
public void setAddress(String address){
_address = address;
public void setMsg(String msg){
_msg = msg;
public void setReadState(String readState){
_readState = readState;
public void setTime(String time){
_time = time;
public void setFolderName(String folderName){
_folderName = folderName;


Don't forget to define permission in your AndroidManifest.xml

<uses-permission android:name="android.permission.READ_SMS" />

MySQL - How to increase varchar size of an existing column in a database without breaking existing data?

I normally use this statement:

ALTER TABLE `table_name`
  CHANGE COLUMN `col_name` `col_name` VARCHAR(10000);

But, I think SET will work too, never have tried it. :)

How to get the android Path string to a file on Assets folder?

You can use this method.

    public static File getRobotCacheFile(Context context) throws IOException {
        File cacheFile = new File(context.getCacheDir(), "robot.png");
        try {
            InputStream inputStream = context.getAssets().open("robot.png");
            try {
                FileOutputStream outputStream = new FileOutputStream(cacheFile);
                try {
                    byte[] buf = new byte[1024];
                    int len;
                    while ((len = > 0) {
                        outputStream.write(buf, 0, len);
                } finally {
            } finally {
        } catch (IOException e) {
            throw new IOException("Could not open robot png", e);
        return cacheFile;

You should never use InputStream.available() in such cases. It returns only bytes that are buffered. Method with .available() will never work with bigger files and will not work on some devices at all.

In Kotlin (;D):

fun getRobotCacheFile(context: Context): File = File(context.cacheDir, "robot.png")
    .also {
        it.outputStream().use { cache ->"robot.png").use { it.copyTo(cache) } }

python NameError: name 'file' is not defined

file is not defined in Python3, which you are using apparently. The package you're instaling is not suitable for Python 3, instead, you should install Python 2.7 and try again.


conversion from string to json object android

Using Kotlin

    val data = "{\"ApiInfo\":{\"description\":\"userDetails\",\"status\":\"success\"},\"userDetails\":{\"Name\":\"somename\",\"userName\":\"value\"},\"pendingPushDetails\":[]}\n"
try {
      val jsonObject = JSONObject(data)
      val infoObj = jsonObject.getJSONObject("ApiInfo")
    } catch (e: Exception) {

Convert a binary NodeJS Buffer to JavaScript ArrayBuffer

No dependencies, fastest, Node.js 4.x and later

Buffers are Uint8Arrays, so you just need to slice (copy) its region of the backing ArrayBuffer.

// Original Buffer
let b = Buffer.alloc(512);
// Slice (copy) its segment of the underlying ArrayBuffer
let ab = b.buffer.slice(b.byteOffset, b.byteOffset + b.byteLength);

The slice and offset stuff is required because small Buffers (less than 4 kB by default, half the pool size) can be views on a shared ArrayBuffer. Without slicing, you can end up with an ArrayBuffer containing data from another Buffer. See explanation in the docs.

If you ultimately need a TypedArray, you can create one without copying the data:

// Create a new view of the ArrayBuffer without copying
let ui32 = new Uint32Array(b.buffer, b.byteOffset, b.byteLength / Uint32Array.BYTES_PER_ELEMENT);

No dependencies, moderate speed, any version of Node.js

Use Martin Thomson's answer, which runs in O(n) time. (See also my replies to comments on his answer about non-optimizations. Using a DataView is slow. Even if you need to flip bytes, there are faster ways to do so.)

Dependency, fast, Node.js = 0.12 or iojs 3.x

You can use to go in either direction (Buffer to ArrayBuffer and back). It's faster than the other answers posted here and is a well-written library. Node 0.12 through iojs 3.x require ngossen's fork (see this).

How to connect to a docker container from outside the host (same network) [Windows]

This is the most common issue faced by Windows users for running Docker Containers. IMO this is the "million dollar question on Docker"; @"Rocco Smit" has rightly pointed out "inbound traffic for it was disabled by default on my host machine's firewall"; in my case, my McAfee Anti Virus software. I added additional ports to be allowed for inbound traffic from other computers on the same Wifi LAN in the Firewall Settings of McAfee; then it was magic. I had struggled for more than a week browsing all over internet, SO, Docker documentations, Tutorials after Tutorials related to the Networking of Docker, and the many illustrations of "not supported on Windows" for "macvlan", "ipvlan", "user defined bridge" and even this same SO thread couple of times. I even started browsing google with "anybody using Docker in Production?", (yes I know Linux is more popular for Prod workloads compared to Windows servers) as I was not able to access (from my mobile in the same Home wifi) an nginx app deployed in Docker Container on Windows. After all, what good it is, if you cannot access the application (deployed on a Docker Container) from other computers / devices in the same LAN at-least; Ultimately in my case, the issue was just with a firewall blocking inbound traffic;

How to respond with HTTP 400 error in a Spring MVC @ResponseBody method returning String?

You also could just throw new HttpMessageNotReadableException("error description") to benefit from Spring's default error handling.

However, just as is the case with those default errors, no response body will be set.

I find these useful when rejecting requests that could reasonably only have been handcrafted, potentially indicating a malevolent intent, since they obscure the fact that the request was rejected based on a deeper, custom validation and its criteria.

Hth, dtk

How to launch Safari and open URL from iOS app

Swift 4 solution:"http://yo.lo")! as URL, options: [String : Any](), completionHandler: nil)

How to add 10 minutes to my (String) time?

I would use Joda Time, parse the time as a LocalTime, and then use

time = time.plusMinutes(10);

Short but complete program to demonstrate this:

import org.joda.time.*;
import org.joda.time.format.*;

public class Test {
    public static void main(String[] args) {
        DateTimeFormatter formatter = DateTimeFormat.forPattern("HH:mm");
        LocalTime time = formatter.parseLocalTime("14:10");
        time = time.plusMinutes(10);

Note that I would definitely use Joda Time instead of java.util.Date/Calendar if you possibly can - it's a much nicer API.

Remove end of line characters from Java string

You can use unescapeJava from org.apache.commons.text.StringEscapeUtils like below

str = "hello\r\njava\r\nbook";

Parse date without timezone javascript

simple solution

const handler1 = {
  construct(target, args) {
    let newDate = new target(...args);
    var tzDifference = newDate.getTimezoneOffset();
    return new target(newDate.getTime() + tzDifference * 60 * 1000);

Date = new Proxy(Date, handler1);

Error: Tablespace for table xxx exists. Please DISCARD the tablespace before IMPORT

The only way it worked for me was:

  1. Create a similar table
  2. Copy the .frm and .idb files of the new similar table to the name of the corrupt table.
  3. Fix permissions
  4. Restart MariaDB
  5. Drop the corrupt table

Triggering a checkbox value changed event in DataGridView

I use the CellContentClick event, which makes sure the user clicked the checkbox. It DOES fire multiple times even if the user stays in the same cell. The one issue is that the Value does not get updated, and always returns "false" for unchecked. The trick is to use the .EditedFormattedValue property of the cell instead of the Value property. The EditedFormattedValue will track with the check mark and is what one wishes the Value had in it when the CellContentClick is fired.

No need for a timer, no need for any fancy stuff, just use CellContentClick event and inspect the EditedFormattedValue to tell what state the checkbox is going into / just went into. If EditedFormattedValue = true, the checkbox is getting checked.

How to make a website secured with https

I think you are getting confused with your site Authentication and SSL.

If you need to get your site into SSL, then you would need to install a SSL certificate into your web server. You can buy a certificate for yourself from one of the places like Symantec etc. The certificate would contain your public/private key pair, along with other things.

You wont need to do anything in your source code, and you can still continue to use your Form Authntication (or any other) in your site. Its just that, any data communication that takes place between the web server and the client will encrypted and signed using your certificate. People would use secure-HTTP (https://) to access your site.

View this for more info -->

How to set a Fragment tag by code?

You can add the tag as a property for the Fragment arguments. It will be automatically restored if the fragment is destroyed and then recreated by the OS.


    final Bundle args = new Bundle();
    args.putString("TAG", "my tag");

IIS error, Unable to start debugging on the webserver

For who has same issue on VS Professional 2019. I Installed Xamarin bundle and after that this IIS error starts. I have tried all solutions above without any luck. What I did to fix it is :

  • From Visual Studio Installer check Development time IIS support from web & Cloud - ASP.NET and web development. enter image description here

  • Restart IIS

  • Open solution - Issue fixed.

Loop over array dimension in plpgsql

Since PostgreSQL 9.1 there is the convenient FOREACH:

   m   varchar[];
   arr varchar[] := array[['key1','val1'],['key2','val2']];
      RAISE NOTICE 'another_func(%,%)',m[1], m[2];

Solution for older versions:

   arr varchar[] := '{{key1,val1},{key2,val2}}';
   FOR i IN array_lower(arr, 1) .. array_upper(arr, 1)
      RAISE NOTICE 'another_func(%,%)',arr[i][1], arr[i][2];

Also, there is no difference between varchar[] and varchar[][] for the PostgreSQL type system. I explain in more detail here.

The DO statement requires at least PostgreSQL 9.0, and LANGUAGE plpgsql is the default (so you can omit the declaration).

What is the best free SQL GUI for Linux for various DBMS systems

For Oracle, I highly recommend the free Oracle SQL Developer

The doucmentation states it also works with non-oracle databases - i've never tried that feature myself, but I do know that it works really well with Oracle

How to directly initialize a HashMap (in a literal way)?

Unfortunately, using varargs if the type of the keys and values are not the same is not very reasonable as you'd have to use Object... and lose type safety completely. If you always want to create e.g. a Map<String, String>, of course a toMap(String... args) would be possible though, but not very pretty as it would be easy to mix up keys and values, and an odd number of arguments would be invalid.

You could create a sub-class of HashMap that has a chainable method like

public class ChainableMap<K, V> extends HashMap<K, V> {
  public ChainableMap<K, V> set(K k, V v) {
    put(k, v);
    return this;

and use it like new ChainableMap<String, Object>().set("a", 1).set("b", "foo")

Another approach is to use the common builder pattern:

public class MapBuilder<K, V> {
  private Map<K, V> mMap = new HashMap<>();

  public MapBuilder<K, V> put(K k, V v) {
    mMap.put(k, v);
    return this;

  public Map<K, V> build() {
    return mMap;

and use it like new MapBuilder<String, Object>().put("a", 1).put("b", "foo").build();

However, the solution I've used now and then utilizes varargs and the Pair class:

public class Maps {
  public static <K, V> Map<K, V> of(Pair<K, V>... pairs) {
    Map<K, V> = new HashMap<>();

    for (Pair<K, V> pair : pairs) {
      map.put(pair.first, pair.second);

    return map;

Map<String, Object> map = Maps.of(Pair.create("a", 1), Pair.create("b", "foo");

The verbosity of Pair.create() bothers me a bit, but this works quite fine. If you don't mind static imports you could of course create a helper:

public <K, V> Pair<K, V> p(K k, V v) {
  return Pair.create(k, v);

Map<String, Object> map = Maps.of(p("a", 1), p("b", "foo");

(Instead of Pair one could imagine using Map.Entry, but since it's an interface it requires an implementing class and/or a helper factory method. It's also not immutable, and contains other logic not useful for this task.)

Assign static IP to Docker container

This works for me.

Create a network with docker network create --subnet= selnet

Run docker image docker run --net selnet --ip hub

At first, I got

docker: Error response from daemon: Invalid address It does not belong to any of this network's subnets.
ERRO[0000] error waiting for container: context canceled

Solution: Increased the 2nd quadruple of the IP [.18. instead of .17.]

How do I remove a single breakpoint with GDB?

Try these (reference):

clear linenum
clear filename:linenum

Is it possible to style a select box?

this on uses the twitter-bootstrap styles to turn selectin dropdown menu

How to pass in a react component into another react component to transclude the first component's content?

Actually, your question is how to write a Higher Order Component (HOC). The main goal of using HOC is preventing copy-pasting. You can write your HOC as a purely functional component or as a class here is an example:

    class Child extends Component {
    render() {
        return (

If you want to write your parent component as a class-based component:

    class Parent extends Component {
    render() {
        return (

If you want to write your parent as a functional component:

    const Parent=props=>{

#1071 - Specified key was too long; max key length is 1000 bytes

run this query before creating or altering table.

SET @@global.innodb_large_prefix = 1;

this will set max key length to 3072 bytes

submitting a form when a checkbox is checked

Yes, this is possible.

<form id="formName" action="<?php echo $_SERVER['PHP_SELF'];?>" method="get">
    <input type ="checkbox" name="cBox[]" value = "3" onchange="document.getElementById('formName').submit()">3</input>
    <input type ="checkbox" name="cBox[]" value = "4" onchange="document.getElementById('formName').submit()">4</input>
    <input type ="checkbox" name="cBox[]" value = "5" onchange="document.getElementById('formName').submit()">5</input>
    <input type="submit" name="submit" value="Search" />

By adding onchange="document.getElementById('formName').submit()" to each checkbox, you'll submit any time a checkbox is changed.

If you're OK with jQuery, it's even easier (and unobtrusive):

    $("#formname").on("change", "input:checkbox", function(){

For any number of checkboxes in your form, when the "change" event happens, the form is submitted. This will even work if you dynamically create more checkboxes thanks to the .on() method.

How to select first and last TD in a row?

If you use sass(scss) you can use the following snippet:

tr > td{
   /* styles for all td*/
     /* styles for first */ 
    /* styles for last*/

How to convert DOS/Windows newline (CRLF) to Unix newline (LF) in a Bash script?

This worked for me

tr "\r" "\n" < sampledata.csv > sampledata2.csv 

Adding placeholder attribute using Jquery

Try something like the following if you want to use pure JavaScript:

document.getElementsByName('link')[0].placeholder='Type here to search';

Round up value to nearest whole number in SQL UPDATE

You could use the ceiling function; this portion of SQL code :

select ceiling(45.01), ceiling(45.49), ceiling(45.99);

will get you "46" each time.

For your update, so, I'd say :

Update product SET price = ceiling(45.01)

BTW : On MySQL, ceil is an alias to ceiling ; not sure about other DB systems, so you might have to use one or the other, depending on the DB you are using...

Quoting the documentation :


Returns the smallest integer value not less than X.

And the given example :

mysql> SELECT CEILING(1.23);
        -> 2
mysql> SELECT CEILING(-1.23);
        -> -1

How many bytes in a JavaScript string?

You can use the Blob to get the string size in bytes.


  new Blob(['']).size,                             // 4_x000D_
  new Blob(['']).size,                             // 4_x000D_
  new Blob(['']).size,                           // 8_x000D_
  new Blob(['']).size,                           // 8_x000D_
  new Blob(['I\'m a string']).size,                  // 12_x000D_
  // from Premasagar correction of Lauri's answer for_x000D_
  // strings containing lone characters in the surrogate pair range:_x000D_
  new Blob([String.fromCharCode(55555)]).size,       // 3_x000D_
  new Blob([String.fromCharCode(55555, 57000)]).size // 4 (not 6)_x000D_

How would I run an async Task<T> method synchronously?

use below code snip

Task.WaitAll(Task.Run(async () => await service.myAsyncMethod()));

SQL LIKE condition to check for integer?

PostgreSQL supports regular expressions matching.

So, your example would look like

SELECT * FROM books WHERE title ~ '^\d+ ?' 

This will match a title starting with one or more digits and an optional space

How can I add the sqlite3 module to Python?

Normally, it is included. However, as @ngn999 said, if your python has been built from source manually, you'll have to add it.

Here is an example of a script that will setup an encapsulated version (virtual environment) of Python3 in your user directory with an encapsulated version of sqlite3.

cd ~
mkdir build
cd build
[ -f Python-3.6.2.tgz ] || wget
tar -zxvf Python-3.6.2.tgz

[ -f sqlite-autoconf-3240000.tar.gz ] || wget
tar -zxvf sqlite-autoconf-3240000.tar.gz

cd sqlite-autoconf-3240000
./configure --prefix=${INSTALL_BASE_PATH}
make install

cd ../Python-3.6.2
./configure --prefix=${INSTALL_BASE_PATH}
make install

cd ~
if grep -q -v "${LINE_TO_ADD}" $HOME/.bash_profile; then echo "${LINE_TO_ADD}" >> $HOME/.bash_profile; fi
source $HOME/.bash_profile

Why do this? You might want a modular python environment that you can completely destroy and rebuild without affecting your managed package installation. This would give you an independent development environment. In this case, the solution is to install sqlite3 modularly too.

using href links inside <option> tag

Try this Code

<select name="forma" onchange="location = this.options[this.selectedIndex].value;">
 <option value="Home.php">Home</option>
 <option value="Contact.php">Contact</option>
 <option value="Sitemap.php">Sitemap</option>

Hide options in a select list using jQuery

I know this question has been answered. But my requirement was slightly different. Instead of value I wanted to filter by text. So i modified the answer by @William Herry like this.

var array = ['Administration', 'Finance', 'HR', 'IT', 'Marketing', 'Materials', 'Reception', 'Support'];
if (somecondition) {
   $(array).each(function () {
       $("div#deprtmnts option:contains(" + this + ")").unwrap();
   $(array).each(function () {
       $("div#deprtmnts option:contains(" + this + ")").wrap('<span/>');

This way you can use value also by replacing contains like this

 $("div#ovrcateg option[value=" + this + "]").wrap('<span/>');

not finding android sdk (Unity)

The issue is due to incompatibility of unity with latest Android build tools. For MacOS here's a one liner that will get it working for you:

cd $ANDROID_HOME; rm -rf tools; wget; unzip

How do I create 7-Zip archives with .NET?

Install the NuGet package called SevenZipSharp.Interop


var compressor = new SevenZip.SevenZipCompressor();
var filesToCompress = Directory.GetFiles(@"D:\data\");
compressor.CompressFiles(@"C:\archive\abc.7z", filesToCompress);

Jquery Hide table rows

If the label is in a table row you can do this to hide the row:


You can refine your selector as you need and then get the table row that contains that element.

JQuery Selectors help:

EDIT This is the correct way to do it.


How can I print using JQuery

function printResult() {
    var DocumentContainer = document.getElementById('your_div_id');
    var WindowObject ='', "PrintWindow", "width=750,height=650,top=50,left=50,toolbars=no,scrollbars=yes,status=no,resizable=yes");

What is the cleanest way to ssh and run multiple commands in Bash?

The posted answers using multiline strings and multiple bash scripts did not work for me.

  • Long multiline strings are hard to maintain.
  • Separate bash scripts do not maintain local variables.

Here is a functional way to ssh and run multiple commands while keeping local context.


run_remote() {
    echo "$LOCAL_VARIABLE"
    ls some_folder; 
    ./ 'some params'
    ./some_other_action 'other params'

ssh otherhost "$(set); run_remote"

How to call a function from a string stored in a variable?

My favorite version is the inline version:

${"variableName"} = 12;



You can place variables or expressions inside the brackets too!

How to duplicate a git repository? (without forking)

If you just want to create a new repository using all or most of the files from an existing one (i.e., as a kind of template), I find the easiest approach is to make a new repo with the desired name etc, clone it to your desktop, then just add the files and folders you want in it.

You don't get all the history etc, but you probably don't want that in this case.

How to check if any flags of a flag combination are set?

You could just check if the value is not zero.

if ((Int32)(letter & Letters.AB) != 0) { }

But I would consider it a better solution to introduce a new enumeration value with value zero and compare agains this enumeration value (if possible because you must be able to modify the enumeration).

enum Letters
    None = 0,
    A    = 1,
    B    = 2,
    C    = 4,
    AB   =  A | B,
    All  = AB | C

if (letter != Letters.None) { }


Missread the question - fixed the first suggestion and just ignore the second suggestion.

How to use SQL LIKE condition with multiple values in PostgreSQL?

You might be able to use IN, if you don't actually need wildcards.

SELECT * from table WHERE column IN ('AAA', 'BBB', 'CCC')

Display number with leading zeros

Use a format string -

For example:

python -c 'print "%(num)02d" % {"num":5}'


Is NDEBUG standard?

Yes it is a standard macro with the semantic "Not Debug" for C89, C99, C++98, C++2003, C++2011, C++2014 standards. There are no _DEBUG macros in the standards.

C++2003 standard send the reader at "page 326" at " Headers" to standard C.

That NDEBUG is similar as This is the same as the Standard C library.

In C89 (C programmers called this standard as standard C) in "4.2 DIAGNOSTICS" section it was said

If NDEBUG is defined as a macro name at the point in the source file where is included, the assert macro is defined simply as

     #define assert(ignore) ((void)0)

If look at the meaning of _DEBUG macros in Visual Studio then it will be seen, that this macro is automatically defined by your ?hoice of language runtime library version.

Export HTML page to PDF on user click using JavaScript

This is because you define your "doc" variable outside of your click event. The first time you click the button the doc variable contains a new jsPDF object. But when you click for a second time, this variable can't be used in the same way anymore. As it is already defined and used the previous time.

change it to:

$(function () {

    var specialElementHandlers = {
        '#editor': function (element,renderer) {
            return true;
 $('#cmd').click(function () {
        var doc = new jsPDF();
            $('#target').html(), 15, 15, 
            { 'width': 170, 'elementHandlers': specialElementHandlers }, 
            function(){'sample-file.pdf'); }


and it will work.

Ordering by specific field value first

Generally you can do

select * from your_table
order by case when name = 'core' then 1 else 2 end,

Especially in MySQL you can also do

select * from your_table
order by name <> 'core',

Since the result of a comparision in MySQL is either 0 or 1 and you can sort by that result.

Laravel Rule Validation for Numbers

Also, there was just a typo in your original post.

'min:2|max5' should have been 'min:2|max:5'.
Notice the ":" for the "max" rule.

CSS rounded corners in IE8

Rounded corners in IE8

Internet Explorer 8 (and earlier versions) doesn't support rounded corners, however there are few other solutions you may consider:

  • Use Rounded Corners Images instead (this generator is a good resource)

  • Use a jQuery Corner plugin from here

  • Use a very good script called CSS3 PIE from here (Pro's & Con's here)

  • Checkout CSS Juice from here

  • Another good script is IE-CSS3 from here

Even though CSS PIE is the most popular solution, I'm suggesting you to review all other solutions and choose what works best for your needs.

Hope it was useful. Good Luck!

How do I horizontally center an absolute positioned element inside a 100% width div?

here is the best practiced method to center a div as position absolute


code --

#header {
position:relative; // you forgot this, this is very important

#logo {
margin: auto; // margin auto works just you need to put top left bottom right as 0

Centering in CSS Grid

Try using flex:

Plunker demo :

/* Styles go here */

body {
  margin: 0;
  padding: 0;

.container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  grid-template-rows: 100vh;
  grid-gap: 0px 0px;

.left_bg {
  background-color: #3498db;
  grid-column: 1 / 1;
  grid-row: 1 / 1;
  z-index: 0;
  display: flex;
  justify-content: center;
  align-items: center;


.right_bg {
  background-color: #ecf0f1;
  grid-column: 2 / 2;
  grid_row: 1 / 1;
  z-index: 0;
  display: flex;
  justify-content: center;
  align-items: center;

.text {
  font-family: Raleway;
  font-size: large;
  text-align: center;


    <div class="container">
  <!--everything on the page-->

  <div class="left_bg">
    <!--left background color of the page-->
    <div class="text">
      <!--left side text content-->
      <p>Review my stuff</p>

  <div class="right_bg">
    <!--right background color of the page-->
    <div class="text">
      <!--right side text content-->
      <p>Hire me!</p>

Vertically align text to top within a UILabel

I've found the answers on this question are now a bit out-of-date, so adding this for the auto layout fans out there.

Auto layout makes this issue pretty trivial. Assuming we're adding the label to UIView *view, the following code will accomplish this:

UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];
[label setText:@"Some text here"];
[label setTranslatesAutoresizingMaskIntoConstraints:NO];
[view addSubview:label];

[view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[label]|" options:0 metrics:nil views:@{@"label": label}]];
[view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[label]" options:0 metrics:nil views:@{@"label": label}]];

The label's height will be calculated automatically (using it's intrinsicContentSize) and the label will be positioned edge-to-edge horizontally, at the top of the view.

Cannot find libcrypto in Ubuntu

I solved this on 12.10 by installing libssl-dev.

sudo apt-get install libssl-dev

JavaScript Object Id

If you want to lookup/associate an object with a unique identifier without modifying the underlying object, you can use a WeakMap:

// Note that object must be an object or array,
// NOT a primitive value like string, number, etc.
var objIdMap=new WeakMap, objectCount = 0;
function objectId(object){
  if (!objIdMap.has(object)) objIdMap.set(object,++objectCount);
  return objIdMap.get(object);

var o1={}, o2={}, o3={a:1}, o4={a:1};
console.log( objectId(o1) ) // 1
console.log( objectId(o2) ) // 2
console.log( objectId(o1) ) // 1
console.log( objectId(o3) ) // 3
console.log( objectId(o4) ) // 4
console.log( objectId(o3) ) // 3

Using a WeakMap instead of Map ensures that the objects can still be garbage-collected.

How to center the content inside a linear layout?

android:gravity handles the alignment of its children,

android:layout_gravity handles the alignment of itself.

So use one of these.

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

        android:gravity="center" >

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

        android:gravity="center" >

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



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

        android:layout_weight="1" >

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

        android:layout_weight="1" >

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


Tooltips for cells in HTML table (no Javascript)

The highest-ranked answer by Mudassar Bashir using the "title" attribute seems the easiest way to do this, but it gives you less control over how the comment/tooltip is displayed.

I found that The answer by Christophe for a custom tooltip class seems to give much more control over the behavior of the comment/tooltip. Since the provided demo does not include a table, as per the question, here is a demo that includes a table.

Note that the "position" style for the parent element of the span (a in this case), must be set to "relative" so that the comment does not push the table contents around when it is displayed. It took me a little while to figure that out.

#MyTable td{_x000D_
  position:absolute; _x000D_
  color:red; _x000D_
  top:20px; _x000D_
.CellWithComment:hover span.CellComment{_x000D_
<table id="MyTable">_x000D_
  <caption>Cell 1,2 Has a Comment</caption>_x000D_
      <td>Heading 1</td>_x000D_
      <td>Heading 2</td>_x000D_
      <td>Heading 3</td>_x000D_
      <td>Cell 1,1</td>_x000D_
      <td class="CellWithComment">Cell 1,2_x000D_
        <span class="CellComment">Here is a comment</span>_x000D_
      <td>Cell 1,3</td>_x000D_
      <td>Cell 2,1</td>_x000D_
      <td>Cell 2,2</td>_x000D_
      <td>Cell 2,3</td>_x000D_

find filenames NOT ending in specific extensions on Unix?

find  /data1/batch/source/export   -type f -not  -name "*.dll" -not -name "*.exe"

How do I POST JSON data with cURL?

If you configure the SWAGGER to your spring boot application, and invoke any API from your application there you can see that CURL Request as well.

I think this is the easy way of generating the requests through the CURL.

SQL QUERY replace NULL value in a row with a value from the previous known value

The following script solves this problem and only uses plain ANSI SQL. I tested this solution on SQL2008, SQLite3 and Oracle11g.

CREATE TABLE test(mysequence INT, mynumber INT);


SELECT t1.mysequence, t1.mynumber AS ORIGINAL
, (
    SELECT t2.mynumber
    FROM test t2
    WHERE t2.mysequence = (
        SELECT MAX(t3.mysequence)
        FROM test t3
        WHERE t3.mysequence <= t1.mysequence
        AND mynumber IS NOT NULL
FROM test t1;

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

function validateAttrs(arg1, arg2, arg3,arg4){
    var args = Object.values(arguments);
    return (args.filter(x=> x===null || !x)).length<=0
console.log(validateAttrs('1',2, 3, 4));
console.log(validateAttrs('1',2, 3, null));
console.log(validateAttrs('1',undefined, 3, 4));
console.log(validateAttrs('1',2, '', 4));
console.log(validateAttrs('1',2, 3, null));

NSNotificationCenter addObserver in Swift

  1. Declare a notification name

    extension Notification.Name {
        static let purchaseDidFinish = Notification.Name("purchaseDidFinish")
  2. You can add observer in two ways:

    Using Selector

    NotificationCenter.default.addObserver(self, selector: #selector(myFunction), name: .purchaseDidFinish, object: nil)
    @objc func myFunction(notification: Notification) {
        print(notification.object ?? "") //myObject
        print(notification.userInfo ?? "") //[AnyHashable("key"): "Value"]

    or using block

    NotificationCenter.default.addObserver(forName: .purchaseDidFinish, object: nil, queue: nil) { [weak self] (notification) in
        guard let strongSelf = self else {
        strongSelf.myFunction(notification: notification)
    func myFunction(notification: Notification) {
        print(notification.object ?? "") //myObject
        print(notification.userInfo ?? "") //[AnyHashable("key"): "Value"]
  3. Post your notification .purchaseDidFinish, object: "myObject", userInfo: ["key": "Value"])

from iOS 9 and OS X 10.11. It is no longer necessary for an NSNotificationCenter observer to un-register itself when being deallocated. more info

For a block based implementation you need to do a weak-strong dance if you want to use self inside the block. more info

Block based observers need to be removed more info

let center = NSNotificationCenter.defaultCenter()

How is TeamViewer so fast?

would take time to route through TeamViewer's servers (TeamViewer bypasses corporate Symmetric NATs by simply proxying traffic through their servers)

You'll find that TeamViewer rarely needs to relay traffic through their own servers. TeamViewer penetrates NAT and networks complicated by NAT using NAT traversal (I think it is UDP hole-punching, like Google's libjingle).

They do use their own servers to middle-man in order to do the handshake and connection set-up, but most of the time the relationship between client and server will be P2P (best case, when the hand-shake is successful). If NAT traversal fails, then TeamViewer will indeed relay traffic through its own servers.

I've only ever seen it do this when a client has been behind double-NAT, though.

iPhone and WireShark

The following worked for iPhone 4S (iOS 5) and Macbook Pro (10.8.2)

  1. On your Mac, go to System Preferences > Sharing > Internet Sharing internetSharing

  2. On your iPhone, go to Settings > Wifi and choose your Mac as the Wifi Access Point. Press the blue detail disclosure next to it to and note down the IP Address ( in my case). At this point, the wifi icon on Mac's your taskbar should change to the following: wifi

  3. Open wireshark. Click on start capture, and use the new bridge interface that should now be available among the options. wshark

  4. ???

  5. Profit!

As with all stuff networking related, you might have to restart wifi etc and repeat steps and invoke your favorite deity to get this incantation working :)

Listing only directories using ls in Bash?

Four ways to get this done, each with a different output format

1. Using echo

Example: echo */, echo */*/
Here is what I got:

cs/ draft/ files/ hacks/ masters/ static/  
cs/code/ files/images/ static/images/ static/stylesheets/  

2. Using ls only

Example: ls -d */
Here is exactly what I got:

cs/     files/      masters/  
draft/  hacks/      static/  

Or as list (with detail info): ls -dl */

3. Using ls and grep

Example: ls -l | grep "^d" Here is what I got:

drwxr-xr-x  24 h  staff     816 Jun  8 10:55 cs  
drwxr-xr-x   6 h  staff     204 Jun  8 10:55 draft  
drwxr-xr-x   9 h  staff     306 Jun  8 10:55 files  
drwxr-xr-x   2 h  staff      68 Jun  9 13:19 hacks  
drwxr-xr-x   6 h  staff     204 Jun  8 10:55 masters  
drwxr-xr-x   4 h  staff     136 Jun  8 10:55 static  

4. Bash Script (Not recommended for filename containing spaces)

Example: for i in $(ls -d */); do echo ${i%%/}; done
Here is what I got:


If you like to have '/' as ending character, the command will be: for i in $(ls -d */); do echo ${i}; done


How can I go back/route-back on vue-router?

This works like a clock for me:

methods: {
 hasHistory () { return window.history.length > 2 }

Then, in the template:

    ? $router.go(-1) 
    : $router.push('/')" class="my-5 btn btn-outline-success">&laquo; 

Add column in dataframe from list

Old question; but I always try to use fastest code!

I had a huge list with 69 millions of uint64. np.array() was fastest for me.

df['hashes'] = hashes
Time spent: 17.034842014312744

df['hashes'] = pd.Series(hashes).values
Time spent: 17.141014337539673

df['key'] = np.array(hashes)
Time spent: 10.724546194076538

How to dynamically set bootstrap-datepicker's date value?

the Format should be like Year-Month-Day
It worked well for me ...

Storing SHA1 hash values in MySQL

Output size of sha1 is 160 bits. Which is 160/8 == 20 chars (if you use 8-bit chars) or 160/16 = 10 (if you use 16-bit chars).

How to check if a line has one of the strings in a list?

One approach is to combine the search strings into a regex pattern as in this answer.

What is the difference between __init__ and __call__?

__init__ would be treated as Constructor where as __call__ methods can be called with objects any number of times. Both __init__ and __call__ functions do take default arguments.

Java random numbers using a seed

That's the principle of a Pseudo-RNG. The numbers are not really random. They are generated using a deterministic algorithm, but depending on the seed, the sequence of generated numbers vary. Since you always use the same seed, you always get the same sequence.

How to get df linux command output always in GB

If you also want it to be a command you can reference without remembering the arguments, you could simply alias it:

alias df-gb='df -BG'

So if you type:


into a terminal, you'll get your intended output of the disk usage in GB.

EDIT: or even use just df -h to get it in a standard, human readable format.

Mac zip compress without __MACOSX folder?

Do you mean the zip command-line tool or the Finder's Compress command?

For zip, you can try the --data-fork option. If that doesn't do it, you might try --no-extra, although that seems to ignore other file metadata that might be valuable, like uid/gid and file times.

For the Finder's Compress command, I don't believe there are any options to control its behavior. It's for the simple case.

The other tool, and maybe the one that the Finder actually uses under the hood, is ditto. With the -c -k options, it creates zip archives. With this tool, you can experiment with --norsrc, --noextattr, --noqtn, --noacl and/or simply leave off the --sequesterRsrc option (which, according to the man page, may be responsible for the __MACOSX subdirectory). Although, perhaps the absence of --sequesterRsrc simply means to use AppleDouble format, which would create ._ files all over the place instead of one __MACOSX directory.

SQL SERVER: Check if variable is null and then assign statement for Where Clause

Try the following:

if ((select VisitCount from PageImage where PID=@pid and PageNumber=5) is NULL)
    update PageImage
    set VisitCount=1
    where PID=@pid and PageNumber=@pageno
    update PageImage 
    set VisitCount=VisitCount+1
    where PID=@pid and PageNumber=@pageno

MVC Razor Hidden input and passing values

If you are using Razor, you cannot access the field directly, but you can manage its value.

The idea is that the first Microsoft approach drive the developers away from Web Development and make it easy for Desktop programmers (for example) to make web applications.

Meanwhile, the web developers, did not understand this tricky strange way of ASP.NET.

Actually this hidden input is rendered on client-side, and the ASP has no access to it (it never had). However, in time you will see its a piratical way and you may rely on it, when you get use with it. The web development differs from the Desktop or Mobile.

The model is your logical unit, and the hidden field (and the whole view page) is just a representative view of the data. So you can dedicate your work on the application or domain logic and the view simply just serves it to the consumer - which means you need no detailed access and "brainstorming" functionality in the view.

The controller actually does work you need for manage the hidden or general setup. The model serves specific logical unit properties and functionality and the view just renders it to the end user, simply said. Read more about MVC.


public class MyClassModel
    public int Id { get; set; }
    public string Name { get; set; }
    public string MyPropertyForHidden { get; set; }

This is the controller aciton

public ActionResult MyPageView()
    MyClassModel model = new MyClassModel(); // Single entity, strongly-typed
    // IList model = new List<MyClassModel>(); // or List, strongly-typed
    // ViewBag.MyHiddenInputValue = "Something to pass"; // ...or using ViewBag

    return View(model);

The view is below

//This will make a Model property of the View to be of MyClassModel
@model MyNamespace.Models.MyClassModel // strongly-typed view
// @model IList<MyNamespace.Models.MyClassModel> // list, strongly-typed view

// ... Some Other Code ...

@using(Html.BeginForm()) // Creates <form>
    // Renders hidden field for your model property (strongly-typed)
    // The field rendered to server your model property (Address, Phone, etc.)
    Html.HiddenFor(model => Model.MyPropertyForHidden); 

    // For list you may use foreach on Model
    // foreach(var item in Model) or foreach(MyClassModel item in Model)

// ... Some Other Code ...

The view with ViewBag:

// ... Some Other Code ...

@using(Html.BeginForm()) // Creates <form>
        new { @class = "hiddencss", maxlength = 255 /*, etc... */ }

// ... Some Other Code ...

We are using Html Helper to render the Hidden field or we could write it by hand - <input name=".." id=".." value="ViewBag.MyHiddenInputValue"> also.

The ViewBag is some sort of data carrier to the view. It does not restrict you with model - you can place whatever you like.

Android Studio shortcuts like Eclipse

If you use Android Studio with Mac OS X these are some shortcuts:

- Compile java sources SHF+CMD+F9

- Build the project CMD+F9

- Run the current configuration CTR+R

- Run in debugger CTR+D

- Open project properties CMD++;

- Open Android Studio preferences CMD++,

- Find any command SHF+CMD+A

- Auto-format code OPT+CMD+L

- Delete line CMD+DELETE or CMD+Backspace

- Duplicate line/selection CMD+D

- Copy line CMD+C (with nothing selected)

- Select next occurance(s) CTR+G

Scope based selection

  • Select next higher scope Option+UP

  • Select next lower scope Option+DOWN

enter image description here

Navigating the code

- Open class CMD+O

- Open file SHF+CMD+O

- Navigate back to last position CMD+[

- Navigate forward to previous position CMD+]

- Switch to recently used files CRT+TAB

Intention Actions

  • If/Switch actions Option+RETURN

enter image description here

Create method CMD+N


enter image description here

Loop an array of ints

enter image description here

  • Generate Logs usin logd, loge, logi, logt, logm and logr

enter image description here

- Project quick fix ALT+ENTER

- Show docs for selected API F1

- Jump to source CMD+down-arrow

Most of them I found on this really good article and Android Studio Tips and Tricks

How do I get the entity that represents the current user in Symfony2?

Symfony 4+, 2019+ Approach

In symfony 4 (probably 3.3 also, but only real-tested in 4) you can inject the Security service via auto-wiring in the controller like this:


use Symfony\Component\Security\Core\Security;

class SomeClass
     * @var Security
    private $security;

    public function __construct(Security $security)
       $this->security = $security;

    public function privatePage() : Response
        $user = $this->security->getUser(); // null or UserInterface, if logged in
        // ... do whatever you want with $user

Symfony 2- Approach

As @ktolis says, you first have to configure your /app/config/security.yml.

Then with

$user = $this->get('security.token_storage')->getToken()->getUser();

should be enougth!

$user is your User Object! You don't need to query it again.

Find out the way to set up your providers in security.yml from Sf2 Documentation and try again.

Best luck!

Set width of a "Position: fixed" div relative to parent div

Fixed positioning is supposed to define everything in relation to the viewport, so position:fixed is always going to do that. Try using position:relative on the child div instead. (I realize you might need the fixed positioning for other reasons, but if so - you can't really make the width match it's parent with out JS without inherit)

TimeStamp on file name using PowerShell

Thanks for the above script. One little modification to add in the file ending correctly. Try this ...

$filenameFormat = "MyFileName" + " " + (Get-Date -Format "yyyy-MM-dd") **+ ".txt"**

Rename-Item -Path "C:\temp\MyFileName.txt" -NewName $filenameFormat

What are queues in jQuery?

This thread helped me a lot with my problem, but I've used $.queue in a different way and thought I would post what I came up with here. What I needed was a sequence of events (frames) to be triggered, but the sequence to be built dynamically. I have a variable number of placeholders, each of which should contain an animated sequence of images. The data is held in an array of arrays, so I loop through the arrays to build each sequence for each of the placeholders like this:

/* create an empty queue */
var theQueue = $({});
/* loop through the data array */
for (var i = 0; i < ph.length; i++) {
    for (var l = 0; l < ph[i].length; l++) {
        /* create a function which swaps an image, and calls the next function in the queue */
        theQueue.queue("anim", new Function("cb", "$('ph_"+i+"' img').attr('src', '/images/"+i+"/"+l+".png');cb();"));
        /* set the animation speed */
/* start the animation */

This is a simplified version of the script I have arrived at, but should show the principle - when a function is added to the queue, it is added using the Function constructor - this way the function can be written dynamically using variables from the loop(s). Note the way the function is passed the argument for the next() call, and this is invoked at the end. The function in this case has no time dependency (it doesn't use $.fadeIn or anything like that), so I stagger the frames using $.delay.

how to sync windows time from a ntp time server in command

If you just need to resync windows time, open an elevated command prompt and type:

w32tm /resync

C:\WINDOWS\system32>w32tm /resync 
Sending resync command to local computer 
The command completed successfully.

How to alias a table in Laravel Eloquent queries (or using Query Builder)?

To use aliases on eloquent models modify your code like this:

    ::from( 'items as items_alias' )
    ->join( 'attachments as att', DB::raw( 'att.item_id' ), '=', DB::raw( '' ) )
    ->select( DB::raw( 'items_alias.*' ) )

This will automatically add table prefix to table names and returns an instance of Items model. not a bare query result. Adding DB::raw prevents laravel from adding table prefixes to aliases.

Do Swift-based applications work on OS X 10.9/iOS 7 and lower?

Yes, in fact Apple has announced that Swift apps will be backward compatible with iOS 7 and OS X Mavericks. Furthermore the WWDC app is written in the Swift programming language.

Split string with delimiters in C

My approach is to scan the string and let the pointers point to every character after the deliminators(and the first character), at the same time assign the appearances of deliminator in string to '\0'.
First make a copy of original string(since it's constant), then get the number of splits by scan it pass it to pointer parameter len. After that, point the first result pointer to the copy string pointer, then scan the copy string: once encounter a deliminator, assign it to '\0' thus the previous result string is terminated, and point the next result string pointer to the next character pointer.

char** split(char* a_str, const char a_delim, int* len){
    char* s = (char*)malloc(sizeof(char) * strlen(a_str));
    strcpy(s, a_str);
    char* tmp = a_str;
    int count = 0;
    while (*tmp != '\0'){
        if (*tmp == a_delim) count += 1;
        tmp += 1;
    *len = count;
    char** results = (char**)malloc(count * sizeof(char*));
    results[0] = s;
    int i = 1;
    while (*s!='\0'){
        if (*s == a_delim){
            *s = '\0';
            s += 1;
            results[i++] = s;
        else s += 1;
    return results;

Python function to convert seconds into minutes, hours, and days

Do it the other way around subtracting the secs as needed, and don't call it time; there's a package with that name:

def sec_to_time():
    sec = int( input ('Enter the number of seconds:'.strip()) )

    days = sec / 86400
    sec -= 86400*days

    hrs = sec / 3600
    sec -= 3600*hrs

    mins = sec / 60
    sec -= 60*mins
    print days, ':', hrs, ':', mins, ':', sec

How to get first two characters of a string in oracle query?

Just use SUBSTR function. It takes 3 parameters: String column name, starting index and length of substring:

select SUBSTR(OrderNo, 1, 2) FROM shipment;

NuGet behind a proxy

I could be wrong but I thought it used IE's proxy settings.

If it sees that you need to login it opens a dialog and asks you to do so (login that is).

Please see the description of this here ->

Spring Boot, Spring Data JPA with multiple DataSources

I checked the source code you provided on GitHub. There were several mistakes / typos in the configuration.

In CustomerDbConfig / OrderDbConfig you should refer to customerEntityManager and packages should point at existing packages:

    entityManagerFactoryRef = "customerEntityManager",
    transactionManagerRef = "customerTransactionManager",
    basePackages = {""})
public class CustomerDbConfig {

The packages to scan in customerEntityManager and orderEntityManager were both not pointing at proper package:


Also the injection of proper EntityManagerFactory did not work. It should be:

@Bean(name = "customerTransactionManager")
public PlatformTransactionManager transactionManager(EntityManagerFactory customerEntityManager){


The above was causing the issue and the exception. While providing the name in a @Bean method you are sure you get proper EMF injected.

The last thing I have done was to disable to automatic configuration of JpaRepositories:

@EnableAutoConfiguration(exclude = JpaRepositoriesAutoConfiguration.class)

And with all fixes the application starts as you probably expect!

PSQLException: current transaction is aborted, commands ignored until end of transaction block

I think that the best solution is to use java.sql.Savepoint.

Before you execute a query which can throw SQLException, use the method Connection.setSavepoint(), and if an exception is thrown you only rollback to this savepoint, not the whole transaction.

Example code:

Connection conn = null;
Savepoint savepoint = null;
try {
    conn = getConnection();
    savepoint = conn.setSavepoint();
    //execute some query
} catch(SQLException e) {
    if(conn != null && savepoint != null) {
} finally {
   if(conn != null) {
      try {
      } catch(SQLException e) {}


Insert HTML from CSS

This can be done. For example with Firefox


#hlinks {
  -moz-binding: url(stackexchange.xml#hlinks);


<bindings xmlns=""
  <binding id="hlinks">
      <html:a href="/privileges">privileges</html:a>
      <html:span class="lsep"> | </html:span>
      <html:a href="/users/logout">log out</html:a>

ref 1

ref 2

How to use environment variables in docker compose

Since 1.25.4, docker-compose supports the option --env-file that enables you to specify a file containing variables.

Yours should look like this:


And the command:

docker-compose --env-file /path/to/my-env-file config

Get operating system info

If you want very few info like a class in your html for common browsers for instance, you could use:

function get_browser()
    $browser = '';
    $ua = strtolower($_SERVER['HTTP_USER_AGENT']);
    if (preg_match('~(?:msie ?|trident.+?; ?rv: ?)(\d+)~', $ua, $matches)) $browser = 'ie ie'.$matches[1];
    elseif (preg_match('~(safari|chrome|firefox)~', $ua, $matches)) $browser = $matches[1];

    return $browser;

which will return 'safari' or 'firefox' or 'chrome', or 'ie ie8', 'ie ie9', 'ie ie10', 'ie ie11'.

How to find the logs on android studio?

On toolbar -> Help Menu -> Show log in explorer.

It opens log folder, where you can find all logs

How to get cell value from DataGridView in VB.Net?

To get the value of cell, use the following syntax,

datagridviewName(columnFirst, rowSecond).value

But the intellisense and MSDN documentation is wrongly saying rowFirst, colSecond approach...

How to know installed Oracle Client is 32 bit or 64 bit?

For Unix

grep "ARCHITECTURE" $ORACLE_HOME/inventory/ContentsXML/oraclehomeproperties.xml

And the output is:


For Windows

findstr "ARCHITECTURE" %ORACLE_HOME%\inventory\ContentsXML\oraclehomeproperties.xml

And the output can be:


If statements for Checkboxes

Your going to use the checkbox1.checked property in your if statement, this returns true or false depending on weather it is checked or not.

How to see query history in SQL Server Management Studio

I use the below query for tracing application activity on a SQL server that does not have trace profiler enabled. The method uses Query Store (SQL Server 2016+) instead of the DMV's. This gives better ability to look into historical data, as well as faster lookups. It is very efficient to capture short-running queries that can't be captured by sp_who/sp_whoisactive.

/* Adjust script to your needs.
    Run full script (F5) -> Interact with UI -> Run full script again (F5)
    Output will contain the queries completed in that timeframe.

/* Requires Query Store to be enabled:

USE <db> /* Select your DB */

IF OBJECT_ID('tempdb..#lastendtime') IS NULL
    SELECT GETUTCDATE() AS dt INTO #lastendtime

    DB_NAME() AS DBName
    , + '.' + AS ObjectName
    , qt.query_sql_text
    , rs.runtime_stats_id
    , p.query_id
    , p.plan_id
    , CAST(p.last_execution_time AS DATETIME) AS last_execution_time
    , CASE WHEN p.last_execution_time > #lastendtime.dt THEN 'X' ELSE '' END AS New
    , CAST(rs.last_duration / 1.0e6 AS DECIMAL(9,3)) last_duration_s
    , rs.count_executions
    , rs.last_rowcount
    , rs.last_logical_io_reads
    , rs.last_physical_io_reads
    , q.query_parameterization_type_desc
    SELECT *, ROW_NUMBER() OVER (PARTITION BY plan_id, runtime_stats_id ORDER BY runtime_stats_id DESC) AS recent_stats_in_current_priod
    FROM sys.query_store_runtime_stats 
    ) AS rs
INNER JOIN sys.query_store_runtime_stats_interval AS rsi ON rsi.runtime_stats_interval_id = rs.runtime_stats_interval_id
INNER JOIN sys.query_store_plan AS p ON p.plan_id = rs.plan_id
INNER JOIN sys.query_store_query AS q ON q.query_id = p.query_id
INNER JOIN sys.query_store_query_text AS qt ON qt.query_text_id = q.query_text_id
LEFT OUTER JOIN sys.objects AS o ON o.object_id = q.object_id
LEFT OUTER JOIN sys.schemas AS s ON s.schema_id = o.schema_id
CROSS APPLY #lastendtime
WHERE rsi.start_time <= GETUTCDATE() AND GETUTCDATE() < rsi.end_time
    AND recent_stats_in_current_priod = 1
    /* Adjust your filters: */
    -- AND ( IN ('<myschema>') OR IS NULL)
FROM #lastendtime
WHERE T.query_sql_text IS NULL OR T.query_sql_text NOT LIKE '%#lastendtime%' -- do not show myself
ORDER BY last_execution_time DESC

TRUNCATE TABLE #lastendtime

Multiple file upload in php

Nice link on:

PHP Single File Uploading with vary basic explanation.

PHP file uploading with the Validation

PHP Multiple Files Upload With Validation Click here to download source code

PHP/jQuery Multiple Files Upload With The ProgressBar And Validation (Click here to download source code)

How To Upload Files In PHP And Store In MySql Database (Click here to download source code)

    foreach($_FILES["files"]["tmp_name"] as $key=>$tmp_name)
                    array_push($error,"$file_name, ");

and you must check your HTML code

<form action="create_photo_gallery.php" method="post" enctype="multipart/form-data">
    <table width="100%">
            <td>Select Photo (one or multiple):</td>
            <td><input type="file" name="files[]" multiple/></td>
            <td colspan="2" align="center">Note: Supported image format: .jpeg, .jpg, .png, .gif</td>
            <td colspan="2" align="center"><input type="submit" value="Create Gallery" id="selectedButton"/></td>

Nice link on:

PHP Single File Uploading with vary basic explanation.

PHP file uploading with the Validation

PHP Multiple Files Upload With Validation Click here to download source code

PHP/jQuery Multiple Files Upload With The ProgressBar And Validation (Click here to download source code)

How To Upload Files In PHP And Store In MySql Database (Click here to download source code)

Is there a GUI design app for the Tkinter / grid geometry?

The best tool for doing layouts using grid, IMHO, is graph paper and a pencil. I know you're asking for some type of program, but it really does work. I've been doing Tk programming for a couple of decades so layout comes quite easily for me, yet I still break out graph paper when I have a complex GUI.

Another thing to think about is this: The real power of Tkinter geometry managers comes from using them together*. If you set out to use only grid, or only pack, you're doing it wrong. Instead, design your GUI on paper first, then look for patterns that are best solved by one or the other. Pack is the right choice for certain types of layouts, and grid is the right choice for others. For a very small set of problems, place is the right choice. Don't limit your thinking to using only one of the geometry managers.

* The only caveat to using both geometry managers is that you should only use one per container (a container can be any widget, but typically it will be a frame).

Changing Font Size For UITableView Section Headers

Swift 3:

Simplest way to adjust only size:

func tableView(_ tableView: UITableView, willDisplayHeaderView view: UIView, forSection section: Int) {

    let header = view as! UITableViewHeaderFooterView

    if let textlabel = header.textLabel {
        textlabel.font = textlabel.font.withSize(15)

Disable webkit's spin buttons on input type="number"?

The below css works for both Chrome and Firefox

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

input[type=number] {

How do I handle the window close event in Tkinter?

Depending on the Tkinter activity, and especially when using Tkinter.after, stopping this activity with destroy() -- even by using protocol(), a button, etc. -- will disturb this activity ("while executing" error) rather than just terminate it. The best solution in almost every case is to use a flag. Here is a simple, silly example of how to use it (although I am certain that most of you don't need it! :)

from Tkinter import *

def close_window():
  global running
  running = False  # turn off while loop
  print( "Window closed")

root = Tk()
root.protocol("WM_DELETE_WINDOW", close_window)
cv = Canvas(root, width=200, height=200)

running = True;
# This is an endless loop stopped only by setting 'running' to 'False'
while running: 
  for i in range(200): 
    if not running: 
    cv.create_oval(i, i, i+1, i+1)

This terminates graphics activity nicely. You only need to check running at the right place(s).

How to include js and CSS in JSP with spring MVC

In a situation where you are using just spring and not spring mvc, take the following approach.

Place the following in servlet dispatcher

<mvc:annotation-driven />               
<mvc:resources mapping="/css/**" location="/WEB-INF/assets/css/"/>
<mvc:resources mapping="/js/**" location="/WEB-INF/assets/js/"/>

As you will notice /css for stylesheet location, doesn't have to be in /resources folder if you don't have the folder structure required for spring mvc as is the case with a spring application.Same applies to javascript files, fonts if you need them etc.

You can then access the resources as you need them like so

<link rel="stylesheet" href="css/vendor/swiper.min.css" type="text/css" />
<link rel="stylesheet" href="css/styles.css" type="text/css" />

I am sure someone will find this useful as most examples are with spring mvc

Remove grid, background color, and top and right borders from ggplot2

Simplification from the above Andrew's answer leads to this key theme to generate the half border.

theme (panel.border = element_blank(),
       axis.line    = element_line(color='black'))

Disabling contextual LOB creation as createClob() method threw error

In order to hide the exception:

For Hibernate 5.2 (and Spring Boot 2.0), you can either use the use_jdbc_metadata_defaults property that the others pointed out:

# Meant to hide HHH000424: Disabling contextual LOB creation as createClob() method threw error false

Or, if you want to not have any side effects from the above setting (there's a comment warning us about some Oracle side effects, I don't know if it's valid or not), you can just disable the logging of the exception like this:

      # Hides HHH000424: Disabling contextual LOB creation as createClob() method threw error 
      org.hibernate.engine.jdbc.env.internal.LobCreatorBuilderImpl: WARN

How to secure phpMyAdmin

You can use the following command :

$ grep "phpmyadmin" $path_to_access.log | grep -Po "^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}" | sort | uniq | xargs -I% sudo iptables -A INPUT -s % -j DROP 


Make sure your IP isn't listed before piping through iptables drop!!

This will first find all lines in $path_to_access.log that have phpmyadmin in them,

then grep out the ip address from the start of the line,

then sort and unique them,

then add a rule to drop them in iptables

Again, just edit in echo % at the end instead of the iptables command to make sure your IP isn't in there. Don't inadvertently ban your access to the server!


You may need to change the grep part of the command if you're on mac or any system that doesn't have grep -P. I'm not sure if all systems start with xargs, so that might need to be installed too. It's super useful anyway if you do a lot of bash.

How to show progress dialog in Android?

This is the good way to use dialog

private class YourAsyncTask extends AsyncTask<Void, Void, Void> {

   ProgressDialog dialog = new ProgressDialog(IncidentFormActivity.this);

    protected void onPreExecute() {
        //set message of the dialog
        //show dialog;

   protected Void doInBackground(Void... args) {
    // do background work here
    return null;

   protected void onPostExecute(Void result) {
     // do UI work here
     if(dialog != null && dialog.isShowing()){


How to use MySQLdb with Python and Django in OSX 10.6?

For me the problem got solved by simply reinstalling mysql-python

pip uninstall mysql-python
pip install mysql-python

Is it better to use C void arguments "void foo(void)" or not "void foo()"?

There are two ways for specifying parameters in C. One is using an identifier list, and the other is using a parameter type list. The identifier list can be omitted, but the type list can not. So, to say that one function takes no arguments in a function definition you do this with an (omitted) identifier list

void f() {
    /* do something ... */

And this with a parameter type list:

void f(void) {
    /* do something ... */

If in a parameter type list the only one parameter type is void (it must have no name then), then that means the function takes no arguments. But those two ways of defining a function have a difference regarding what they declare.

Identifier lists

The first defines that the function takes a specific number of arguments, but neither the count is communicated nor the types of what is needed - as with all function declarations that use identifier lists. So the caller has to know the types and the count precisely before-hand. So if the caller calls the function giving it some argument, the behavior is undefined. The stack could become corrupted for example, because the called function expects a different layout when it gains control.

Using identifier lists in function parameters is deprecated. It was used in old days and is still present in lots of production code. They can cause severe danger because of those argument promotions (if the promoted argument type do not match the parameter type of the function definition, behavior is undefined either!) and are much less safe, of course. So always use the void thingy for functions without parameters, in both only-declarations and definitions of functions.

Parameter type list

The second one defines that the function takes zero arguments and also communicates that - like with all cases where the function is declared using a parameter type list, which is called a prototype. If the caller calls the function and gives it some argument, that is an error and the compiler spits out an appropriate error.

The second way of declaring a function has plenty of benefits. One of course is that amount and types of parameters are checked. Another difference is that because the compiler knows the parameter types, it can apply implicit conversions of the arguments to the type of the parameters. If no parameter type list is present, that can't be done, and arguments are converted to promoted types (that is called the default argument promotion). char will become int, for example, while float will become double.

Composite type for functions

By the way, if a file contains both an omitted identifier list and a parameter type list, the parameter type list "wins". The type of the function at the end contains a prototype:

void f();
void f(int a) {
    printf("%d", a);

// f has now a prototype. 

That is because both declarations do not say anything contradictory. The second, however, had something to say in addition. Which is that one argument is accepted. The same can be done in reverse

void f(a) 
  int a;
    printf("%d", a);

void f(int);

The first defines a function using an identifier list, while the second then provides a prototype for it, using a declaration containing a parameter type list.

How to catch and print the full exception traceback without halting/exiting the program?

How to print the full traceback without halting the program?

When you don't want to halt your program on an error, you need to handle that error with a try/except:

except Exception as error:

To extract the full traceback, we'll use the traceback module from the standard library:

import traceback

And to create a decently complicated stacktrace to demonstrate that we get the full stacktrace:

def raise_error():
    raise RuntimeError('something bad happened!')

def do_something_that_might_error():


To print the full traceback, use the traceback.print_exc method:

except Exception as error:

Which prints:

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 2, in do_something_that_might_error
  File "<stdin>", line 2, in raise_error
RuntimeError: something bad happened!

Better than printing, logging:

However, a best practice is to have a logger set up for your module. It will know the name of the module and be able to change levels (among other attributes, such as handlers)

import logging
logger = logging.getLogger(__name__)

In which case, you'll want the logger.exception function instead:

except Exception as error:

Which logs:

ERROR:__main__:something bad happened!
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 2, in do_something_that_might_error
  File "<stdin>", line 2, in raise_error
RuntimeError: something bad happened!

Or perhaps you just want the string, in which case, you'll want the traceback.format_exc function instead:

except Exception as error:

Which logs:

DEBUG:__main__:Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "<stdin>", line 2, in do_something_that_might_error
  File "<stdin>", line 2, in raise_error
RuntimeError: something bad happened!


And for all three options, we see we get the same output as when we have an error:

>>> do_something_that_might_error()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in do_something_that_might_error
  File "<stdin>", line 2, in raise_error
RuntimeError: something bad happened!

Which to use

Performance concerns aren't important here as IO usually dominates. I'd prefer, since it does precisely what's being requested in a forward compatible way:


Logging levels and outputs can be adjusted, making it easy to turn off without touching the code. And usually doing what's directly needed is the most efficient way to do it.

How to properly and completely close/reset a TcpClient connection?

Have you tried calling TcpClient.Dispose() explicitly?

And are you sure that you have TcpClient.Close() and TcpClient.Dispose()-ed ALL connections?

Are the PUT, DELETE, HEAD, etc methods available in most web browsers?

HTML forms support GET and POST. (HTML5 at one point added PUT/DELETE, but those were dropped.)

XMLHttpRequest supports every method, including CHICKEN, though some method names are matched against case-insensitively (methods are case-sensitive per HTTP) and some method names are not supported at all for security reasons (e.g. CONNECT).

Browsers are slowly converging on the rules specified by XMLHttpRequest, but as the other comment pointed out there are still some differences.

How do I count unique visitors to my site?

Here is a nice tutorial, it is what you need. (Source:

Register and show online users and visitors

Count Online users and visitors using a MySQL table

In this tutorial you can learn how to register, to count, and display in your webpage the number of online users and visitors. The principle is this: each user / visitor is registered in a text file or database. Every time a page of the website is accessed, the php script deletes all records older than a certain time (eg 2 minutes), adds the current user / visitor and takes the number of records left to display.

You can store the online users and visitors in a file on the server, or in a MySQL table. In this case, I think that using a text file to add and read the records is faster than storing them into a MySQL table, which requires more requests.

First it's presented the method with recording in a text file on the server, than the method with MySQL table.

To download the files with the scripts presented in this tutorial, click -> Count Online Users and Visitors.

• Both scripts can be included in ".php" files (with include()), or in ".html" files (with <script>), as you can see in the examples presented at the bottom of this page; but the server must run PHP.

Storing online users and visitors in a text file

To add records in a file on the server with PHP you must set CHMOD 0766 (or CHMOD 0777) permissions to that file, so the PHP can write data in it.

  1. Create a text file on your server (for example, named userson.txt) and give it CHMOD 0777 permissions (in your FTP application, right click on that file, choose Properties, then select Read, Write, and Execute options).
  2. Create a PHP file (named usersontxt.php) having the code below, then copy this php file in the same directory as userson.txt.

The code for usersontxt.php;

// Script Online Users and Visitors -
if(!isset($_SESSION)) session_start();        // start Session, if not already started

$filetxt = 'userson.txt';  // the file in which the online users /visitors are stored
$timeon = 120;             // number of secconds to keep a user online
$sep = '^^';               // characters used to separate the user name and date-time
$vst_id = '-vst-';        // an identifier to know that it is a visitor, not logged user

 If you have an user registration script,
 replace $_SESSION['nume'] with the variable in which the user name is stored.
 You can get a free registration script from:

// get the user name if it is logged, or the visitors IP (and add the identifier)

    $uvon = isset($_SESSION['nume']) ? $_SESSION['nume'] : $_SERVER['SERVER_ADDR']. $vst_id;

$rgxvst = '/^([0-9\.]*)'. $vst_id. '/i';         // regexp to recognize the line with visitors
$nrvst = 0;                                       // to store the number of visitors

// sets the row with the current user /visitor that must be added in $filetxt (and current timestamp)

    $addrow[] = $uvon. $sep. time();

// check if the file from $filetxt exists and is writable

    if(is_writable($filetxt)) {
      // get into an array the lines added in $filetxt
      $ar_rows = file($filetxt, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
      $nrrows = count($ar_rows);

            // number of rows

  // if there is at least one line, parse the $ar_rows array

      if($nrrows>0) {
        for($i=0; $i<$nrrows; $i++) {
          // get each line and separate the user /visitor and the timestamp
          $ar_line = explode($sep, $ar_rows[$i]);
      // add in $addrow array the records in last $timeon seconds
          if($ar_line[0]!=$uvon && (intval($ar_line[1])+$timeon)>=time()) {
            $addrow[] = $ar_rows[$i];

$nruvon = count($addrow);                   // total online
$usron = '';                                    // to store the name of logged users
// traverse $addrow to get the number of visitors and users
for($i=0; $i<$nruvon; $i++) {
 if(preg_match($rgxvst, $addrow[$i])) $nrvst++;       // increment the visitors
 else {
   // gets and stores the user's name
   $ar_usron = explode($sep, $addrow[$i]);
   $usron .= '<br/> - <i>'. $ar_usron[0]. '</i>';
$nrusr = $nruvon - $nrvst;              // gets the users (total - visitors)

// the HTML code with data to be displayed
$reout = '<div id="uvon"><h4>Online: '. $nruvon. '</h4>Visitors: '. $nrvst. '<br/>Users: '. $nrusr. $usron. '</div>';

// write data in $filetxt
if(!file_put_contents($filetxt, implode("\n", $addrow))) $reout = 'Error: Recording file not exists, or is not writable';

// if access from <script>, with GET 'uvon=showon', adds the string to return into a JS statement
// in this way the script can also be included in .html files
if(isset($_GET['uvon']) && $_GET['uvon']=='showon') $reout = "document.write('$reout');";

echo $reout;             // output /display the result
  1. If you want to include the script above in a ".php" file, add the following code in the place you want to show the number of online users and visitors:

4.To show the number of online visitors /users in a ".html" file, use this code:

<script type="text/javascript" src="usersontxt.php?uvon=showon"></script>

This script (and the other presented below) works with $_SESSION. At the beginning of the PHP file in which you use it, you must add: session_start();. Count Online users and visitors using a MySQL table

To register, count and show the number of online visitors and users in a MySQL table, require to perform three SQL queries: Delete the records older than a certain time. Insert a row with the new user /visitor, or, if it is already inserted, Update the timestamp in its column. Select the remaining rows. Here's the code for a script that uses a MySQL table (named "userson") to store and display the Online Users and Visitors.

  1. First we create the "userson" table, with 2 columns (uvon, dt). In the "uvon" column is stored the name of the user (if logged in) or the visitor's IP. In the "dt" column is stored a number with the timestamp (Unix time) when the page is accessed.
  • Add the following code in a php file (for example, named "create_userson.php"):

The code for create_userson.php:

header('Content-type: text/html; charset=utf-8');

// HERE add your data for connecting to MySQ database
$host = 'localhost';           // MySQL server address
$user = 'root';                // User name
$pass = 'password';            // User`s password
$dbname = 'database';          // Database name

// connect to the MySQL server
$conn = new mysqli($host, $user, $pass, $dbname);

// check connection
if (mysqli_connect_errno()) exit('Connect failed: '. mysqli_connect_error());

// sql query for CREATE "userson" TABLE
$sql = "CREATE TABLE `userson` (
 ) CHARACTER SET utf8 COLLATE utf8_general_ci"; 

// Performs the $sql query on the server to create the table
if ($conn->query($sql) === TRUE) echo 'Table "userson" successfully created';
else echo 'Error: '. $conn->error;

  1. Now we create the script that Inserts, Deletes, and Selects data in the userson table (For explanations about the code, see the comments in script).
  • Add the code below in another php file (named usersmysql.php): In both file you must add your personal data for connecting to MySQL database, in the variables: $host, $user, $pass, and $dbname .

The code for usersmysql.php:

// Script Online Users and Visitors -
if(!isset($_SESSION)) session_start();         // start Session, if not already started

// HERE add your data for connecting to MySQ database
$host = 'localhost';           // MySQL server address
$user = 'root';                // User name
$pass = 'password';            // User`s password
$dbname = 'database';          // Database name

 If you have an user registration script,
 replace $_SESSION['nume'] with the variable in which the user name is stored.
 You can get a free registration script from:

// get the user name if it is logged, or the visitors IP (and add the identifier)
$vst_id = '-vst-';         // an identifier to know that it is a visitor, not logged user
$uvon = isset($_SESSION['nume']) ? $_SESSION['nume'] : $_SERVER['SERVER_ADDR']. $vst_id;

$rgxvst = '/^([0-9\.]*)'. $vst_id. '/i';         // regexp to recognize the rows with visitors
$dt = time();                                    // current timestamp
$timeon = 120;             // number of secconds to keep a user online
$nrvst = 0;                                     // to store the number of visitors
$nrusr = 0;                                     // to store the number of usersrs
$usron = '';                                    // to store the name of logged users

// connect to the MySQL server
$conn = new mysqli($host, $user, $pass, $dbname);

// Define and execute the Delete, Insert/Update, and Select queries
$sqldel = "DELETE FROM `userson` WHERE `dt`<". ($dt - $timeon);
$sqliu = "INSERT INTO `userson` (`uvon`, `dt`) VALUES ('$uvon', $dt) ON DUPLICATE KEY UPDATE `dt`=$dt";
$sqlsel = "SELECT * FROM `userson`";

// Execute each query
if(!$conn->query($sqldel)) echo 'Error: '. $conn->error;
if(!$conn->query($sqliu)) echo 'Error: '. $conn->error;
$result = $conn->query($sqlsel);

// if the $result contains at least one row
if ($result->num_rows > 0) {
  // traverse the sets of results and set the number of online visitors and users ($nrvst, $nrusr)
  while($row = $result->fetch_assoc()) {
    if(preg_match($rgxvst, $row['uvon'])) $nrvst++;       // increment the visitors
    else {
      $nrusr++;                   // increment the users
      $usron .= '<br/> - <i>'.$row['uvon']. '</i>';          // stores the user's name

$conn->close();                  // close the MySQL connection

// the HTML code with data to be displayed
$reout = '<div id="uvon"><h4>Online: '. ($nrusr+$nrvst). '</h4>Visitors: '. $nrvst. '<br/>Users: '. $nrusr. $usron. '</div>';

// if access from <script>, with GET 'uvon=showon', adds the string to return into a JS statement
// in this way the script can also be included in .html files
if(isset($_GET['uvon']) && $_GET['uvon']=='showon') $reout = "document.write('$reout');";

echo $reout;             // output /display the result
  1. After you have created these two php files on your server, run the "create_userson.php" on your browser to create the "userson" table.

  2. Include the usersmysql.php file in the php file in which you want to display the number of online users and visitors.

  3. Or, if you want to insert it in a ".html" file, add this code:

Examples using these scripts

• Including the "usersontxt.php` in a php file:

<!doctype html>

Counter Online Users and Visitors

• Including the "usersmysql.php" in a html file:

<!doctype html>
 <meta charset="utf-8" />
 <title>Counter Online Users and Visitors</title>
 <meta name="description" content="PHP script to count and show the number of online users and visitors" />
 <meta name="keywords" content="online users, online visitors" />

<!-- Includes the script ("usersontxt.php", or "usersmysql.php") -->
<script type="text/javascript" src="usersmysql.php?uvon=showon"></script>


Both scripts (with storing data in a text file on the server, or into a MySQL table) will display a result like this: Online: 5

Visitors: 3 Users: 2

  • MarPlo
  • Marius

What is the purpose of using -pedantic in GCC/G++ compiler?

Pedantic makes it so that the gcc compiler rejects all GNU C extensions not just the ones that make it ANSI compatible.

How to calculate time elapsed in bash script?

Another option is to use datediff from dateutils (

$ datediff 10:33:56 10:36:10
$ datediff 10:33:56 10:36:10 -f%H:%M:%S
$ datediff 10:33:56 10:36:10 -f%0H:%0M:%0S

You could also use gawk. mawk 1.3.4 also has strftime and mktime but older versions of mawk and nawk don't.

$ TZ=UTC0 awk 'BEGIN{print strftime("%T",mktime("1970 1 1 10 36 10")-mktime("1970 1 1 10 33 56"))}'

Or here's another way to do it with GNU date:

$ date -ud@$(($(date -ud'1970-01-01 10:36:10' +%s)-$(date -ud'1970-01-01 10:33:56' +%s))) +%T

Killing a process using Java

It might be a java interpreter defect, but java on HPUX does not do a kill -9, but only a kill -TERM.

I did a small test

ProcessBuilder pb = new ProcessBuilder(args);
Process process = pb.start();

And the invocation:

$ tusc -f -p -s signal,kill -e /opt/java1.5/bin/java testDestroy sh -c 'trap "echo TERM" TERM; sleep 10'

dies after 10s (not killed after 1s as expected) and shows:

[19999]   Received signal 15, SIGTERM, in waitpid(), [caught], no siginfo
[19998] kill(19999, SIGTERM) ............................................................................. = 0

Doing the same on windows seems to kill the process fine even if signal is handled (but that might be due to windows not using signals to destroy).

Actually i found Java - Process.destroy() source code for Linux related thread and openjava implementation seems to use -TERM as well, which seems very wrong.

Correct way to handle conditional styling in React

Another way, using inline style and the spread operator

  ...completed ? { textDecoration: completed } : {}

That way be useful in some situations where you want to add a bunch of properties at the same time base on the condition.

Javascript querySelector vs. getElementById

The functions getElementById and getElementsByClassName are very specific, while querySelector and querySelectorAll are more elaborate. My guess is that they will actually have a worse performance.

Also, you need to check for the support of each function in the browsers you are targetting. The newer it is, the higher probability of lack of support or the function being "buggy".

How to display multiple notifications in android

Below is the code for pass unique notification id:

//"CommonUtilities.getValudeFromOreference" is the method created by me to get value from savedPreferences.
String notificationId = CommonUtilities.getValueFromPreference(context, Global.NOTIFICATION_ID, "0");
int notificationIdinInt = Integer.parseInt(notificationId);

notificationManager.notify(notificationIdinInt, notification);

// will increment notification id for uniqueness
notificationIdinInt = notificationIdinInt + 1;
CommonUtilities.saveValueToPreference(context, Global.NOTIFICATION_ID, notificationIdinInt + "");
//Above "CommonUtilities.saveValueToPreference" is the method created by me to save new value in savePreferences.

Reset notificationId in savedPreferences at specific range like I have did it at 1000. So it will not create any issues in future. Let me know if you need more detail information or any query. :)

C# function to return array

You're trying to return variable Labels of type ArtworkData instead of array, therefore this needs to be in the method signature as its return type. You need to modify your code as such:

public static ArtworkData[] GetDataRecords(int UsersID)
    ArtworkData[] Labels;
    Labels = new ArtworkData[3];

    return Labels;

Array[] is actually an array of Array, if that makes sense.

Android: how to parse URL String with spaces to URI object?

URL url = Test.class.getResource(args[0]);  // reading demo file path from                                                   
                                            // same location where class                                    
File input=null;
try {
    input = new File(url.toURI());
} catch (URISyntaxException e1) {
    // TODO Auto-generated catch block

How to Detect cause of 503 Service Temporarily Unavailable error and handle it?

There is of course some apache log files. Search in your apache configuration files for 'Log' keyword, you'll certainly find plenty of them. Depending on your OS and installation places may vary (in a Typical Linux server it would be /var/log/apache2/[access|error].log).

Having a 503 error in Apache usually means the proxied page/service is not available. I assume you're using tomcat and that means tomcat is either not responding to apache (timeout?) or not even available (down? crashed?). So chances are that it's a configuration error in the way to connect apache and tomcat or an application inside tomcat that is not even sending a response for apache.

Sometimes, in production servers, it can as well be that you get too much traffic for the tomcat server, apache handle more request than the proxyied service (tomcat) can accept so the backend became unavailable.