Programs & Examples On #Msmq transaction

What is pluginManagement in Maven's pom.xml?

pluginManagement: is an element that is seen along side plugins. Plugin Management contains plugin elements in much the same way, except that rather than configuring plugin information for this particular project build, it is intended to configure project builds that inherit from this one. However, this only configures plugins that are actually referenced within the plugins element in the children. The children have every right to override pluginManagement definitions.


Copied from :

Maven2 - problem with pluginManagement and parent-child relationship

Print page numbers on pages when printing html

   **@page {
            margin-top:21% !important; 
            content: element(header);


            @bottom-left {
            content: element(footer
 div.header {

            position: running(header);

            div.footer {

            position: running(footer);
            border-bottom: 2px solid black;

           .pagenumber:before {
            content: counter(page);
            .pagecount:before {
            content: counter(pages);
 <div class="footer" style="font-size:12pt; font-family: Arial; font-family: Arial;">
                <span>Page <span class="pagenumber"/> of <span class="pagecount"/></span>
            </div >**

Display label text with line breaks in c#

Also you can use the following

@"Italian naval...<br><br>"+

Above code you can achieve double space. If you want single one means you simply use

Function to check if a string is a date

If your heart is set on using regEx then is always a good resource:


  $txt='2012-06-14 01:46:28';
  $re1='((?:2|1)\\d{3}(?:-|\\/)(?:(?:0[1-9])|(?:1[0-2]))(?:-|\\/)(?:(?:0[1-9])|(?:[1-2][0-9])|(?:3[0-1]))(?:T|\\s)(?:(?:[0-1][0-9])|(?:2[0-3])):(?:[0-5][0-9]):(?:[0-5][0-9]))';    # Time Stamp 1

  if ($c=preg_match_all ("/".$re1."/is", $txt, $matches))
      print "($timestamp1) \n";


Cannot find a differ supporting object '[object Object]' of type 'object'. NgFor only supports binding to Iterables such as Arrays

<li *ngFor = "let Data of allDataFromAws  | async">
  <pre> {{ Data | json}}</pre>

use async to convert allDataFromAws into Array Object....

Configuring ObjectMapper in Spring

If you want to add custom ObjectMapper for registering custom serializers, try my answer.

In my case (Spring 3.2.4 and Jackson 2.3.1), XML configuration for custom serializer:

    <mvc:message-converters register-defaults="false">
        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <property name="objectMapper">
                <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                    <property name="serializers">
                            <bean class=""/>

was in unexplained way overwritten back to default by something.

This worked for me:

@JsonSerialize(using = CustomObjectSerializer.class)
public class CustomObject {

    private Long value;

    public Long getValue() {
        return value;

    public void setValue(Long value) {
        this.value = value;

public class CustomObjectSerializer extends JsonSerializer<CustomObject> {

    public void serialize(CustomObject value, JsonGenerator jgen,
        SerializerProvider provider) throws IOException,JsonProcessingException {
        jgen.writeNumberField("y", value.getValue());

    public Class<CustomObject> handledType() {
        return CustomObject.class;

No XML configuration (<mvc:message-converters>(...)</mvc:message-converters>) is needed in my solution.

How to get page content using cURL?

this is how:

     * Get a web file (HTML, XHTML, XML, image, etc.) from a URL.  Return an
     * array containing the HTTP server response header fields and content.
    function get_web_page( $url )
        $user_agent='Mozilla/5.0 (Windows NT 6.1; rv:8.0) Gecko/20100101 Firefox/8.0';

        $options = array(

            CURLOPT_CUSTOMREQUEST  =>"GET",        //set request type post or get
            CURLOPT_POST           =>false,        //set to GET
            CURLOPT_USERAGENT      => $user_agent, //set user agent
            CURLOPT_COOKIEFILE     =>"cookie.txt", //set cookie file
            CURLOPT_COOKIEJAR      =>"cookie.txt", //set cookie jar
            CURLOPT_RETURNTRANSFER => true,     // return web page
            CURLOPT_HEADER         => false,    // don't return headers
            CURLOPT_FOLLOWLOCATION => true,     // follow redirects
            CURLOPT_ENCODING       => "",       // handle all encodings
            CURLOPT_AUTOREFERER    => true,     // set referer on redirect
            CURLOPT_CONNECTTIMEOUT => 120,      // timeout on connect
            CURLOPT_TIMEOUT        => 120,      // timeout on response
            CURLOPT_MAXREDIRS      => 10,       // stop after 10 redirects

        $ch      = curl_init( $url );
        curl_setopt_array( $ch, $options );
        $content = curl_exec( $ch );
        $err     = curl_errno( $ch );
        $errmsg  = curl_error( $ch );
        $header  = curl_getinfo( $ch );
        curl_close( $ch );

        $header['errno']   = $err;
        $header['errmsg']  = $errmsg;
        $header['content'] = $content;
        return $header;


//Read a web page and check for errors:

$result = get_web_page( $url );

if ( $result['errno'] != 0 )
    ... error: bad url, timeout, redirect loop ...

if ( $result['http_code'] != 200 )
    ... error: no page, no permissions, no service ...

$page = $result['content'];

Ignore 'Security Warning' running script from command line

For those who want to access a file from an already loaded PowerShell session, either use Unblock-File to mark the file as safe (though you already need to have set a relaxed execution policy like Unrestricted for this to work), or change the execution policy just for the current PowerShell session:

Set-ExecutionPolicy -ExecutionPolicy Bypass -Scope Process

Writing String to Stream and reading it back does not work

You're using message.Length which returns the number of characters in the string, but you should be using the nubmer of bytes to read. You should use something like:

byte[] messageBytes = uniEncoding.GetBytes(message);
stringAsStream.Write(messageBytes, 0, messageBytes.Length);

You're then reading a single byte and expecting to get a character from it just by casting to char. UnicodeEncoding will use two bytes per character.

As Justin says you're also not seeking back to the beginning of the stream.

Basically I'm afraid pretty much everything is wrong here. Please give us the bigger picture and we can help you work out what you should really be doing. Using a StreamWriter to write and then a StreamReader to read is quite possibly what you want, but we can't really tell from just the brief bit of code you've shown.

How to create dynamic href in react render function?

You can use ES6 backtick syntax too

<a href={`/customer/${item._id}`} >{item.get('firstName')} {item.get('lastName')}</a>

More info on es6 template literals

Delete specific line from a text file?

One way to do it if the file is not very big is to load all the lines into an array:

string[] lines = File.ReadAllLines("filename.txt");
string[] newLines = RemoveUnnecessaryLine(lines);
File.WriteAllLines("filename.txt", newLines);

C# with MySQL INSERT parameters

I had the same issue -- Finally tried the ? sigil instead of @, and it worked.

According to the docs:

Note. Prior versions of the provider used the '@' symbol to mark parameters in SQL. This is incompatible with MySQL user variables, so the provider now uses the '?' symbol to locate parameters in SQL. To support older code, you can set 'old syntax=yes' on your connection string. If you do this, please be aware that an exception will not be throw if you fail to define a parameter that you intended to use in your SQL.

Really? Why don't you just throw an exception if someone tries to use the so called old syntax? A few hours down the drain for a 20 line program...


How to control the width of select tag?

You've simply got it backwards. Specifying a minimum width would make the select menu always be at least that width, so it will continue expanding to 90% no matter what the window size is, also being at least the size of its longest option.

You need to use max-width instead. This way, it will let the select menu expand to its longest option, but if that expands past your set maximum of 90% width, crunch it down to that width.

Find duplicate records in MySQL

Powerlord answer is indeed the best and I would recommend one more change: use LIMIT to make sure db would not get overloaded:

SELECT firstname, lastname, list.address FROM list
GROUP BY address HAVING count(id) > 1) dup ON list.address = dup.address

It is a good habit to use LIMIT if there is no WHERE and when making joins. Start with small value, check how heavy the query is and then increase the limit.

how to measure running time of algorithms in python

The programming language doesn't matter; measuring the runtime complexity of an algorithm works the same way regardless of the language. Analysis of Algorithms by Stanford on Google Code University is a very good resource for teaching yourself how to analyze the runtime complexity of algorithms and code.

If all you want to do is measure the elapsed time that a function or section of code took to run in Python, then you can use the timeit or time modules, depending on how long the code needs to run.

How to tell bash that the line continues on the next line

In general, you can use a backslash at the end of a line in order for the command to continue on to the next line. However, there are cases where commands are implicitly continued, namely when the line ends with a token than cannot legally terminate a command. In that case, the shell knows that more is coming, and the backslash can be omitted. Some examples:

# In general
$ echo "foo" \
> "bar"
foo bar

# Pipes
$ echo foo |
> cat

# && and ||
$ echo foo &&
> echo bar
$ false ||
> echo bar

Different, but related, is the implicit continuation inside quotes. In this case, without a backslash, you are simply adding a newline to the string.

$ x="foo
> bar"
$ echo "$x"

With a backslash, you are again splitting the logical line into multiple logical lines.

$ x="foo\
> bar"
$ echo "$x"

Overflow-x:hidden doesn't prevent content from overflowing in mobile browsers

I've just been working on this for a few hours, trying various combinations of things from this and other pages. The thing that worked for me in the end was to make a site wrapper div, as suggested in the accepted answer, but to set both overflows to hidden instead of just the x overflow. If I leave overflow-y at scroll, I end up with a page that only scrolls vertically by a few pixels and then stops.

#all-wrapper {
  overflow: hidden;

Just this was enough, without setting anything on the body or html elements.

How to store Node.js deployment settings/configuration files?

I know this is a really old post. But I want to share my module for configuring environment variables, I think it is very flexible solution. Here is the module json-configurator

var configJson = {
  'baseUrl': '',
  '$prod_baseUrl': '',
  'endpoints': {
    'users': '<%= baseUrl %>/users',
    'accounts': '<%= baseUrl %>/accounts'
  foo: 'bar',
  foobar: 'foobar',
  $prod_foo: 'foo in prod',
  $test_foo: 'foo in test',
    veryDeep: {
      publicKey: 'abc',
      secret: 'secret',
      $prod_secret: 'super secret'

var config = require('json-configurator')(configJson, 'prod');

// super secret 


Then you can use process.env.NODE_ENV to get all the variables for your environment.

Angular 2: How to access an HTTP response body?

Here is an example to access response body using angular2 built in Response

import { Injectable } from '@angular/core';
import {Http,Response} from '@angular/http';

export class SampleService {
  constructor(private http:Http) { }


   .map((res:Response) => (
       res.json() //Convert response to JSON
       res.text() //Convert response to a string
   .subscribe(data => {console.log(data)})


Python re.sub(): how to substitute all 'u' or 'U's with 'you'

it can also be achieved with below code

import re

text = 'how are u? umberella u! u. U. U@ U# u '
print (re.sub (r'[uU] ( [^a-z] )', r' you\1 ', text))


print (re.sub (r'[uU] ( [\s!,.?@#] )', r' you\1 ', text))

how to update spyder on anaconda

This worked for me: conda install --force-reinstall pyqt qt
Based on this

Recommended way to save uploaded files in a servlet application

Store it anywhere in an accessible location except of the IDE's project folder aka the server's deploy folder, for reasons mentioned in the answer to Uploaded image only available after refreshing the page:

  1. Changes in the IDE's project folder does not immediately get reflected in the server's work folder. There's kind of a background job in the IDE which takes care that the server's work folder get synced with last updates (this is in IDE terms called "publishing"). This is the main cause of the problem you're seeing.

  2. In real world code there are circumstances where storing uploaded files in the webapp's deploy folder will not work at all. Some servers do (either by default or by configuration) not expand the deployed WAR file into the local disk file system, but instead fully in the memory. You can't create new files in the memory without basically editing the deployed WAR file and redeploying it.

  3. Even when the server expands the deployed WAR file into the local disk file system, all newly created files will get lost on a redeploy or even a simple restart, simply because those new files are not part of the original WAR file.

It really doesn't matter to me or anyone else where exactly on the local disk file system it will be saved, as long as you do not ever use getRealPath() method. Using that method is in any case alarming.

The path to the storage location can in turn be definied in many ways. You have to do it all by yourself. Perhaps this is where your confusion is caused because you somehow expected that the server does that all automagically. Please note that @MultipartConfig(location) does not specify the final upload destination, but the temporary storage location for the case file size exceeds memory storage threshold.

So, the path to the final storage location can be definied in either of the following ways:

  • Hardcoded:

      File uploads = new File("/path/to/uploads");
  • Environment variable via SET UPLOAD_LOCATION=/path/to/uploads:

      File uploads = new File(System.getenv("UPLOAD_LOCATION"));
  • VM argument during server startup via -Dupload.location="/path/to/uploads":

      File uploads = new File(System.getProperty("upload.location"));
  • *.properties file entry as upload.location=/path/to/uploads:

      File uploads = new File(properties.getProperty("upload.location"));
  • web.xml <context-param> with name upload.location and value /path/to/uploads:

      File uploads = new File(getServletContext().getInitParameter("upload.location"));
  • If any, use the server-provided location, e.g. in JBoss AS/WildFly:

      File uploads = new File(System.getProperty(""), "uploads");

Either way, you can easily reference and save the file as follows:

File file = new File(uploads, "somefilename.ext");

try (InputStream input = part.getInputStream()) {
    Files.copy(input, file.toPath());

Or, when you want to autogenerate an unique file name to prevent users from overwriting existing files with coincidentally the same name:

File file = File.createTempFile("somefilename-", ".ext", uploads);

try (InputStream input = part.getInputStream()) {
    Files.copy(input, file.toPath(), StandardCopyOption.REPLACE_EXISTING);

How to obtain part in JSP/Servlet is answered in How to upload files to server using JSP/Servlet? and how to obtain part in JSF is answered in How to upload file using JSF 2.2 <h:inputFile>? Where is the saved File?

Note: do not use Part#write() as it interprets the path relative to the temporary storage location defined in @MultipartConfig(location).

See also:

How do I align a label and a textarea?

  1. Set the height of your label to the same height as the multiline textbox.
  2. Add the cssClass .alignTop{vertical-align: middle;} for the label control.

        <asp:Label ID="DescriptionLabel" runat="server" Text="Description: " Width="70px" Height="200px" CssClass="alignTop"></asp:Label>
        <asp:Textbox id="DescriptionTextbox" runat="server" Width="400px" Height="200px" TextMode="MultiLine"></asp:Textbox>
        <asp:RequiredFieldValidator id="DescriptionRequiredFieldValidator" runat="server" ForeColor="Red"
        ControlToValidate="DescriptionTextbox" ErrorMessage="Description is a required field.">    

Format date with Moment.js

The 2nd argument to moment() is a parsing format rather than an display format.

For that, you want the .format() method:


Also note that case does matter. For Month, Day of Month, and Year, the format should be uppercase.

Mysql database sync between two databases

Have a look at Schema and Data Comparison tools in dbForge Studio for MySQL. These tool will help you to compare, to see the differences, generate a synchronization script and synchronize two databases.

How to get the full URL of a Drupal page?

drupal_get_destination() has some internal code that points at the correct place to getthe current internal path. To translate that path into an absolute URL, the url() function should do the trick. If the 'absolute' option is passed in it will generate the full URL, not just the internal path. It will also swap in any path aliases for the current path as well.

$path = isset($_GET['q']) ? $_GET['q'] : '<front>';
$link = url($path, array('absolute' => TRUE));

How do I copy the contents of one stream to another?

The basic questions that differentiate implementations of "CopyStream" are:

  • size of the reading buffer
  • size of the writes
  • Can we use more than one thread (writing while we are reading).

The answers to these questions result in vastly different implementations of CopyStream and are dependent on what kind of streams you have and what you are trying to optimize. The "best" implementation would even need to know what specific hardware the streams were reading and writing to.

How to create streams from string in Node.Js?

Heres a tidy solution in TypeScript:

import { Readable } from 'stream'

class ReadableString extends Readable {
    private sent = false

        private str: string
    ) {

    _read() {
        if (!this.sent) {
            this.sent = true
        else {

const stringStream = new ReadableString('string to be streamed...')

SQL - select distinct only on one column

You will use the following query:


Where [table] is the name of the table.

This provides a unique listing for the NUMBER column however the other columns may be meaningless depending on the vendor implementation; which is to say they may not together correspond to a specific row or rows.

Is it possible to install both 32bit and 64bit Java on Windows 7?

To install 32-bit Java on Windows 7 (64-bit OS + Machine). You can do:

1) Download JDK:
2) Download JRE:

3) System variable create: C:\program files (x86)\java\jre6\bin\

4) Anywhere you type java -version

it use 32-bit on (64-bit). I have to use this because lots of third party libraries do not work with 64-bit. Java wake up from the hell, give us peach :P. Go-language is killer.

Display a loading bar before the entire page is loaded


<div class="preload">
<img src="">

<div class="content">
I would like to display a loading bar before the entire page is loaded. 


$(function() {
    $(".preload").fadeOut(2000, function() {


.content {display:none;}
.preload { 
    height: 100px;
    position: fixed;
    top: 50%;
    left: 50%;


When can I use a forward declaration?

The main rule is that you can only forward-declare classes whose memory layout (and thus member functions and data members) do not need to be known in the file you forward-declare it.

This would rule out base classes and anything but classes used via references and pointers.

Does not contain a definition for and no extension method accepting a first argument of type could be found

There are two cases in which this error is raised.

  1. You didn't declare the variable which is used
  2. You didn't create the instances of the class

why is plotting with Matplotlib so slow?

For the first solution proposed by Joe Kington ( .copy_from_bbox & .draw_artist & canvas.blit), I had to capture the backgrounds after the fig.canvas.draw() line, otherwise the background had no effect and I got the same result as you mentioned. If you put it after the it still does not work as proposed by Michael Browne.

So just put the background line after the canvas.draw():


# We need to draw the canvas before we start animating...

# Let's capture the background of the figure
backgrounds = [fig.canvas.copy_from_bbox(ax.bbox) for ax in axes]

How to check if an element is off-screen

Well... I've found some issues in every proposed solution here.

  • You should be able to choose if you want entire element to be on screen or just any part of it
  • Proposed solutions fails if element is higher/wider than window and kinda covers browser window.

Here is my solution that include jQuery .fn instance function and expression. I've created more variables inside my function than I could, but for complex logical problem I like to divide it into smaller, clearly named pieces.

I'm using getBoundingClientRect method that returns element position relatively to the viewport so I don't need to care about scroll position


$(".some-element").isOnScreen(); // true / false
$(".some-element").isOnScreen(true); // true / false (partially on screen)
$(".some-element").is(":onscreen"); // true / false (partially on screen)
$(".some-element").is(":entireonscreen"); // true / false 


$.fn.isOnScreen = function(partial){

    //let's be sure we're checking only one element (in case function is called on set)
    var t = $(this).first();

    //we're using getBoundingClientRect to get position of element relative to viewport
    //so we dont need to care about scroll position
    var box = t[0].getBoundingClientRect();

    //let's save window size
    var win = {
        h : $(window).height(),
        w : $(window).width()

    //now we check against edges of element

    //firstly we check one axis
    //for example we check if left edge of element is between left and right edge of scree (still might be above/below)
    var topEdgeInRange = >= 0 && <= win.h;
    var bottomEdgeInRange = box.bottom >= 0 && box.bottom <= win.h;

    var leftEdgeInRange = box.left >= 0 && box.left <= win.w;
    var rightEdgeInRange = box.right >= 0 && box.right <= win.w;

    //here we check if element is bigger then window and 'covers' the screen in given axis
    var coverScreenHorizontally = box.left <= 0 && box.right >= win.w;
    var coverScreenVertically = <= 0 && box.bottom >= win.h;

    //now we check 2nd axis
    var topEdgeInScreen = topEdgeInRange && ( leftEdgeInRange || rightEdgeInRange || coverScreenHorizontally );
    var bottomEdgeInScreen = bottomEdgeInRange && ( leftEdgeInRange || rightEdgeInRange || coverScreenHorizontally );

    var leftEdgeInScreen = leftEdgeInRange && ( topEdgeInRange || bottomEdgeInRange || coverScreenVertically );
    var rightEdgeInScreen = rightEdgeInRange && ( topEdgeInRange || bottomEdgeInRange || coverScreenVertically );

    //now knowing presence of each edge on screen, we check if element is partially or entirely present on screen
    var isPartiallyOnScreen = topEdgeInScreen || bottomEdgeInScreen || leftEdgeInScreen || rightEdgeInScreen;
    var isEntirelyOnScreen = topEdgeInScreen && bottomEdgeInScreen && leftEdgeInScreen && rightEdgeInScreen;

    return partial ? isPartiallyOnScreen : isEntirelyOnScreen;


$.expr.filters.onscreen = function(elem) {
  return $(elem).isOnScreen(true);

$.expr.filters.entireonscreen = function(elem) {
  return $(elem).isOnScreen(true);

How to add a downloaded .box file to Vagrant?

You can point to the folder where vagrant and copy the box file to same location. Then after you may run as follows

vagrant box add my-box
vagrant init my-box
vagrant up

Just to check status

vagrant status

Set the default value in dropdownlist using jQuery

$("#dropdownList option[text='it\'s me']").attr("selected","selected"); 

How can one pull the (private) data of one's own Android app?

adb backup will write an Android-specific archive:

adb backup  -f myAndroidBackup.ab  com.corp.appName

This archive can be converted to tar format using:

dd if=myAndroidBackup.ab bs=4K iflag=skip_bytes skip=24 | openssl zlib -d > myAndroidBackup.tar


Search for "Update" at that link.

Alternatively, use Android backup extractor to extract files from the Android backup (.ab) file.

How to navigate back to the last cursor position in Visual Studio Code?

?+U Undo last cursor operation

You can also try ctrl+-

BTW all the shortcuts is here This is really useful!

Div 100% height works on Firefox but not in IE

I've done something very similar to what 'tvanfosson' said, that is, actually using JavaScript to constantly monitor the available height in the window via events like onresize, and use that information to change the container size accordingly (as pixels rather than percentage).

Keep in mind, this does mean a JavaScript dependency, and it isn't as smooth as a CSS solution. You'd also need to ensure that the JavaScript function is capable of correctly returning the window dimensions across all major browsers.

Let us know if one of the previously mentioned CSS solutions work, as it sounds like a better way to fix the problem.

SQL Query for Selecting Multiple Records

You're looking for the IN() clause:

SELECT * FROM `Buses` WHERE `BusID` IN (1,2,3,5,7,9,11,44,88,etc...);

How do I wait for an asynchronously dispatched block to finish?

Generally don't use any of these answers, they often won't scale (there's exceptions here and there, sure)

These approaches are incompatible with how GCD is intended to work and will end up either causing deadlocks and/or killing the battery by nonstop polling.

In other words, rearrange your code so that there is no synchronous waiting for a result, but instead deal with a result being notified of change of state (eg callbacks/delegate protocols, being available, going away, errors, etc.). (These can be refactored into blocks if you don't like callback hell.) Because this is how to expose real behavior to the rest of the app than hide it behind a false façade.

Instead, use NSNotificationCenter, define a custom delegate protocol with callbacks for your class. And if you don't like mucking with delegate callbacks all over, wrap them into a concrete proxy class that implements the custom protocol and saves the various block in properties. Probably also provide convenience constructors as well.

The initial work is slightly more but it will reduce the number of awful race-conditions and battery-murdering polling in the long-run.

(Don't ask for an example, because it's trivial and we had to invest the time to learn objective-c basics too.)

Efficiently test if a port is open on Linux?

nc -l 8000

Where 8000 is the port number. If the port is free, it will start a server that you can close easily. If it isn't it will throw an error:

nc: Address already in use

Convert data file to blob

async function FileToString (file) {
    try {
        let res = await file.raw.text();
    } catch (err) {
        throw err;

How to get a jqGrid selected row cells value

You can use in this manner also

var rowId =$("#list").jqGrid('getGridParam','selrow');  
var rowData = jQuery("#list").getRowData(rowId);
var colData = rowData['UserId'];   // perticuler Column name of jqgrid that you want to access

Twitter bootstrap modal-backdrop doesn't disappear

I had the modal backdrop screen freeze problem but in a slightly different scenario: When 2 back to back modals were being displayed. e.g. The first would ask for confirmation to do something and after the 'confirm' button was clicked, the action would come across an error and the 2nd modal was going to be displayed to popup the error message. The 2nd modal backdrop would freeze the screen. There were no clashes in class names or id's of the elements.

The way the problem was fixed was to give the browser enough time to deal with the modal backdrop. Instead of immediately taking the action after the 'confirm' was clicked, give the browser say 500ms to hide the 1st modal and clean up the backdrop etc - then take the action which would end up in showing the error modal.

<button type="button" class="btn btn-red" data-dismiss="modal" on-tap="_dialogConfirmed">Confirm</button>

The _dialogConfirmed() function has the following code:

    var that = this;

    setTimeout(function () {
      if (that.confirmAction) {
        that.confirmAction = undefined;
    }, 500);

I'm guessing the other solutions worked because they took enough extra time giving the browser the needed cleanup time.

How to scroll to the bottom of a UITableView on the iPhone before the view appears

The accepted answer didn't work with my table (thousands of rows, dynamic loading) but the code below works:

- (void)scrollToBottom:(id)sender {
    if ([self.sections count] > 0) {
        NSInteger idx = [self.sections count] - 1;
        CGRect sectionRect = [self.tableView rectForSection:idx];
        sectionRect.size.height = self.tableView.frame.size.height;
        [self.tableView scrollRectToVisible:sectionRect animated:NO];

Specific Time Range Query in SQL Server

you can try this (I don't have sql server here today so I can't verify syntax, sorry)

select attributeName
  from tableName
 where CONVERT(varchar,attributeName,101) BETWEEN '03/01/2009' AND '03/31/2009'
   and CONVERT(varchar, attributeName,108) BETWEEN '06:00:00' AND '22:00:00'
   and DATEPART(day,attributeName) BETWEEN 2 AND 4

compare two list and return not matching items using linq


  public class Sent
    public int MsgID;
    public string Content;
    public int Status;


public class Messages
    public int MsgID;
    public string Content;

  List<Sent> SentList = new List<Sent>() { new Sent() { MsgID = 1, Content = "aaa", Status = 0 }, new Sent() { MsgID = 3, Content = "ccc", Status = 0 } };
            List<Messages> MsgList = new List<Messages>() { new Messages() { MsgID = 1, Content = "aaa" }, new Messages() { MsgID = 2, Content = "bbb" }, new Messages() { MsgID = 3, Content = "ccc" }, new Messages() { MsgID = 4, Content = "ddd" }, new Messages() { MsgID = 5, Content = "eee" }};

            int [] sentMsgIDs = SentList.Select(v => v.MsgID).ToArray();
            List<Messages> result1 = MsgList.Where(o => !sentMsgIDs.Contains(o.MsgID)).ToList<Messages>();

Hope it should help.

Disabled UIButton not faded or grey

If the UIButton is in the combined state of selected and disabled, its state is UIControlStateSelected | UIControlStateDisabled.

So its state needs to be adjusted like this:

[button setTitleColor:color UIControlStateSelected | UIControlStateDisabled];
[button setImage:image forState:UIControlStateSelected | UIControlStateDisabled];

One approach is to subclass UIButton as follows:

@implementation TTButton
- (void)awakeFromNib {
   [super awakeFromNib];

    //! Fix behavior when `disabled && selected`
    //! Load settings in `xib` or `storyboard`, and apply it again.
    UIColor *color = [self titleColorForState:UIControlStateDisabled];
    [self setTitleColor:color forState:UIControlStateDisabled];

    UIImage *img = [self imageForState:UIControlStateDisabled];
    [self setImage:img forState:UIControlStateDisabled];

- (void)setTitleColor:(UIColor *)color forState:(UIControlState)state {
    [super setTitleColor:color forState:state];

    if (UIControlStateDisabled == state) {
        [super setTitleColor:color forState:UIControlStateSelected | state];
        [super setTitleColor:color forState:UIControlStateHighlighted | state];

- (void)setImage:(UIImage *)image forState:(UIControlState)state {
    [super setImage:image forState:state];

    if (UIControlStateDisabled == state) {
        [super setImage:image forState:UIControlStateSelected | state];
        [super setImage:image forState:UIControlStateHighlighted | state];


Get the first N elements of an array?

In the current order? I'd say array_slice(). Since it's a built in function it will be faster than looping through the array while keeping track of an incrementing index until N.

How to set a ripple effect on textview or imageview on Android?

Ref :,



How can I remove all objects but one from the workspace in R?

From within a function, rm all objects in .GlobalEnv except the function

initialize <- function( {

  if (length(setdiff(ls(pos = .GlobalEnv), "initialize")) > 0) {
    rm(list=setdiff(ls(pos = .GlobalEnv), "initialize"), pos = .GlobalEnv)


Splitting on last delimiter in Python string?

Use .rsplit() or .rpartition() instead:

s.rsplit(',', 1)

str.rsplit() lets you specify how many times to split, while str.rpartition() only splits once but always returns a fixed number of elements (prefix, delimiter & postfix) and is faster for the single split case.


>>> s = "a,b,c,d"
>>> s.rsplit(',', 1)
['a,b,c', 'd']
>>> s.rsplit(',', 2)
['a,b', 'c', 'd']
>>> s.rpartition(',')
('a,b,c', ',', 'd')

Both methods start splitting from the right-hand-side of the string; by giving str.rsplit() a maximum as the second argument, you get to split just the right-hand-most occurrences.

Check if a string matches a regex in Bash script

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

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

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

What is a serialVersionUID and why should I use it?

To understand the significance of field serialVersionUID, one should understand how Serialization/Deserialization works.

When a Serializable class object is serialized Java Runtime associates a serial version no.(called as serialVersionUID) with this serialized object. At the time when you deserialize this serialized object Java Runtime matches the serialVersionUID of serialized object with the serialVersionUID of the class. If both are equal then only it proceeds with the further process of deserialization else throws InvalidClassException.

So we conclude that to make Serialization/Deserialization process successful the serialVersionUID of serialized object must be equivalent to the serialVersionUID of the class. In case if programmer specifies the serialVersionUID value explicitly in the program then the same value will be associated with the serialized object and the class, irrespective of the serialization and deserialzation platform(for ex. serialization might be done on platform like windows by using sun or MS JVM and Deserialization might be on different platform Linux using Zing JVM).

But in case if serialVersionUID is not specified by programmer then while doing Serialization\DeSerialization of any object, Java runtime uses its own algorithm to calculate it. This serialVersionUID calculation algorithm varies from one JRE to another. It is also possible that the environment where the object is serialized is using one JRE (ex: SUN JVM) and the environment where deserialzation happens is using Linux Jvm(zing). In such cases serialVersionUID associated with serialized object will be different than the serialVersionUID of class calculated at deserialzation environment. In turn deserialization will not be successful. So to avoid such situations/issues programmer must always specify serialVersionUID of Serializable class.

How do I make a WinForms app go Full Screen

You need to set your window to be topmost.

Spring JPA @Query with LIKE

@Query("select u from user u where u.username LIKE :username")
List<User> findUserByUsernameLike(@Param("username") String username);

How can I remove a key from a Python dictionary?

del my_dict[key] is slightly faster than my_dict.pop(key) for removing a key from a dictionary when the key exists

>>> import timeit
>>> setup = "d = {i: i for i in range(100000)}"

>>> timeit.timeit("del d[3]", setup=setup, number=1)
>>> timeit.timeit("d.pop(3)", setup=setup, number=1)
>>> timeit.timeit("d2 = {key: val for key, val in d.items() if key != 3}", setup=setup, number=1)

But when the key doesn't exist if key in my_dict: del my_dict[key] is slightly faster than my_dict.pop(key, None). Both are at least three times faster than del in a try/except statement:

>>> timeit.timeit("if 'missing key' in d: del d['missing key']", setup=setup)
>>> timeit.timeit("d.pop('missing key', None)", setup=setup)
>>> try_except = """
... try:
...     del d['missing key']
... except KeyError:
...     pass
... """
>>> timeit.timeit(try_except, setup=setup)

Curl Command to Repeat URL Request

You could use URL sequence substitution with a dummy query string (if you want to use CURL and save a few keystrokes):


If you have other query strings in your URL, assign the sequence to a throwaway variable:


Check out the URL section on the man page:

How can you create multiple cursors in Visual Studio Code

Alt + Click works in OSX. Code Version 1.14.2

Connect Java to a MySQL database

Here's a step by step explanation how to install MySQL and JDBC and how to use it:

  1. Download and install the MySQL server. Just do it the usual way. Remember the port number whenever you've changed it. It's by default 3306.

  2. Download the JDBC driver and put in classpath, extract the ZIP file and put the containing JAR file in the classpath. The vendor-specific JDBC driver is a concrete implementation of the JDBC API (tutorial here).

    If you're using an IDE like Eclipse or Netbeans, then you can add it to the classpath by adding the JAR file as Library to the Build Path in project's properties.

    If you're doing it "plain vanilla" in the command console, then you need to specify the path to the JAR file in the -cp or -classpath argument when executing your Java application.

    java -cp .;/path/to/mysql-connector.jar com.example.YourClass

    The . is just there to add the current directory to the classpath as well so that it can locate com.example.YourClass and the ; is the classpath separator as it is in Windows. In Unix and clones : should be used.

  3. Create a database in MySQL. Let's create a database javabase. You of course want World Domination, so let's use UTF-8 as well.

    CREATE DATABASE javabase DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci;
  4. Create an user for Java and grant it access. Simply because using root is a bad practice.

    CREATE USER 'java'@'localhost' IDENTIFIED BY 'password';
    GRANT ALL ON javabase.* TO 'java'@'localhost' IDENTIFIED BY 'password';

    Yes, java is the username and password is the password here.

  5. Determine the JDBC URL. To connect the MySQL database using Java you need an JDBC URL in the following syntax:

    • hostname: The hostname where MySQL server is installed. If it's installed at the same machine where you run the Java code, then you can just use localhost. It can also be an IP address like If you encounter connectivity problems and using instead of localhost solved it, then you've a problem in your network/DNS/hosts config.

    • port: The TCP/IP port where MySQL server listens on. This is by default 3306.

    • databasename: The name of the database you'd like to connect to. That's javabase.

    So the final URL should look like:

  6. Test the connection to MySQL using Java. Create a simple Java class with a main() method to test the connection.

    String url = "jdbc:mysql://localhost:3306/javabase";
    String username = "java";
    String password = "password";
    System.out.println("Connecting database...");
    try (Connection connection = DriverManager.getConnection(url, username, password)) {
        System.out.println("Database connected!");
    } catch (SQLException e) {
        throw new IllegalStateException("Cannot connect the database!", e);

    If you get a SQLException: No suitable driver, then it means that either the JDBC driver wasn't autoloaded at all or that the JDBC URL is wrong (i.e. it wasn't recognized by any of the loaded drivers). Normally, a JDBC 4.0 driver should be autoloaded when you just drop it in runtime classpath. To exclude one and other, you can always manually load it as below:

    System.out.println("Loading driver...");
    try {
        System.out.println("Driver loaded!");
    } catch (ClassNotFoundException e) {
        throw new IllegalStateException("Cannot find the driver in the classpath!", e);

    Note that the newInstance() call is not needed here. It's just to fix the old and buggy Explanation here. If this line throws ClassNotFoundException, then the JAR file containing the JDBC driver class is simply not been placed in the classpath.

    Note that you don't need to load the driver everytime before connecting. Just only once during application startup is enough.

    If you get a SQLException: Connection refused or Connection timed out or a MySQL specific CommunicationsException: Communications link failure, then it means that the DB isn't reachable at all. This can have one or more of the following causes:

    1. IP address or hostname in JDBC URL is wrong.
    2. Hostname in JDBC URL is not recognized by local DNS server.
    3. Port number is missing or wrong in JDBC URL.
    4. DB server is down.
    5. DB server doesn't accept TCP/IP connections.
    6. DB server has run out of connections.
    7. Something in between Java and DB is blocking connections, e.g. a firewall or proxy.

    To solve the one or the other, follow the following advices:

    1. Verify and test them with ping.
    2. Refresh DNS or use IP address in JDBC URL instead.
    3. Verify it based on my.cnf of MySQL DB.
    4. Start the DB.
    5. Verify if mysqld is started without the --skip-networking option.
    6. Restart the DB and fix your code accordingly that it closes connections in finally.
    7. Disable firewall and/or configure firewall/proxy to allow/forward the port.

    Note that closing the Connection is extremely important. If you don't close connections and keep getting a lot of them in a short time, then the database may run out of connections and your application may break. Always acquire the Connection in a try-with-resources statement. Or if you're not on Java 7 yet, explicitly close it in finally of a try-finally block. Closing in finally is just to ensure that it get closed as well in case of an exception. This also applies to Statement, PreparedStatement and ResultSet.

That was it as far the connectivity concerns. You can find here a more advanced tutorial how to load and store fullworthy Java model objects in a database with help of a basic DAO class.

Using a Singleton Pattern for the DB connection is a bad approach. See among other questions: This is a #1 starters mistake.

How to check if a Docker image with a specific tag exist locally?

for specific tag name

$ docker images  --filter reference='<REPOSITORY>:TAG'

for "like clause" tagname:my_image_tag --> start my_ima*

$ docker images  --filter reference='<REPOSITORY>:my_ima*'

if you want to someting "the image" for example delete all images tag started "my_ima" try this

docker rmi -f $(docker images -q  --filter reference='myreponame:my_ima*')

Any way to limit border length?

This is a CSS trick, not a formal solution. I leave the code with the period black because it helps me position the element. Afterward, color your content (color:white) and (margin-top:-5px or so) to make it as though the period is not there.

div.yourdivname:after {
content: ".";
  border-bottom:1px solid grey;
  margin:0 auto;

jQuery Loop through each div

$('').each(function() {
   /* Measure the width of each image. */
   var test = $(this).find('.scrolling img').width();

   /* Find out how many images there are. */
   var testimg = $(this).find('.scrolling img').length;

   /* Do the maths. */
   var final = (test* testimg)*1.2;

   /* Apply the maths to the CSS. */

Here you loop through all your div's with class target and you do the calculations. Within this loop you can simply use $(this) to indicate the currently selected <div> tag.

How does Python manage int and long?

On my machine:

>>> print type(1<<30)
<type 'int'>
>>> print type(1<<31)
<type 'long'>
>>> print type(0x7FFFFFFF)
<type 'int'>
>>> print type(0x7FFFFFFF+1)
<type 'long'>

Python uses ints (32 bit signed integers, I don't know if they are C ints under the hood or not) for values that fit into 32 bit, but automatically switches to longs (arbitrarily large number of bits - i.e. bignums) for anything larger. I'm guessing this speeds things up for smaller values while avoiding any overflows with a seamless transition to bignums.

app.config for a class library

If you want to configure your project logging using log4Net, while using a class library, There is no actual need of any config file. You can configure your log4net logger in a class and can use that class as library.

As log4net provides all the options to configure it.

Please find the code below.

public static void SetLogger(string pathName, string pattern)
            Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();

            PatternLayout patternLayout = new PatternLayout();
            patternLayout.ConversionPattern = pattern;

            RollingFileAppender roller = new RollingFileAppender();
            roller.AppendToFile = false;
            roller.File = pathName;
            roller.Layout = patternLayout;
            roller.MaxSizeRollBackups = 5;
            roller.MaximumFileSize = "1GB";
            roller.RollingStyle = RollingFileAppender.RollingMode.Size;
            roller.StaticLogFileName = true;

            MemoryAppender memory = new MemoryAppender();

            hierarchy.Root.Level = log4net.Core.Level.Info;
            hierarchy.Configured = true;

Now instead of calling XmlConfigurator.Configure(new FileInfo("app.config")) you can directly call SetLogger with desired path and pattern to set the logger in Global.asax application start function.

And use the below code to log the error.

        public static void getLog(string className, string message)
            log4net.ILog iLOG = LogManager.GetLogger(className);
            iLOG.Error(message);    // Info, Fatal, Warn, Debug

By using following code you need not to write a single line neither in application web.config nor inside the app.config of library.

DateTime "null" value

If you're using .NET 2.0 (or later) you can use the nullable type:

DateTime? dt = null;


Nullable<DateTime> dt = null;

then later:

dt = new DateTime();

And you can check the value with:

if (dt.HasValue)
  // Do something with dt.Value

Or you can use it like:

DateTime dt2 = dt ?? DateTime.MinValue;

You can read more here:

Populating a razor dropdownlist from a List<object> in MVC

Your call to DropDownListFor needs a few more parameters to flesh it out. You need a SelectList as in the following SO question:

MVC3 DropDownListFor - a simple example?

With what you have there, you've only told it where to store the data, not where to load the list from.

Need to navigate to a folder in command prompt

I prefer to use

pushd d:\windows\movie

because it requires no switches yet the working directory will change to the correct drive and path in one step.

Added plus:

  • also works with UNC paths if an unused drive letter is available for automatic drive mapping,
  • easy to go back to the previous working directory: just enter popd.

How to generate random colors in matplotlib?

Improving the answer to work with Python3. That piece of code would sometimes generate numbers greater than 1 and matplotlib would throw an error.

for X,Y in data:
   scatter(X, Y, c=numpy.random.random(3))

Trying to create a file in Android: open failed: EROFS (Read-only file system)

I have tried this with and without the WRITE_INTERNAL_STORAGE permission.

There is no WRITE_INTERNAL_STORAGE permission in Android.

How do I create this file for writing?

You don't, except perhaps on a rooted device, if your app is running with superuser privileges. You are trying to write to the root of internal storage, which apps do not have access to.

Please use the version of the FileOutputStream constructor that takes a File object. Create that File object based off of some location that you can write to, such as:

  • getFilesDir() (called on your Activity or other Context)
  • getExternalFilesDir() (called on your Activity or other Context)

The latter will require WRITE_EXTERNAL_STORAGE as a permission.

Is there an easier way than writing it to a file then reading from it again?

You can temporarily put it in a static data member.

because many people don't have SD card slots

"SD card slots" are irrelevant, by and large. 99% of Android device users will have external storage -- the exception will be 4+ year old devices where the user removed their SD card. Devices manufactured since mid-2010 have external storage as part of on-board flash, not as removable media.

This declaration has no storage class or type specifier in C++

You can declare an object of a class in another Class,that's possible but you cant initialize that object. For that you need to do something like this :--> (inside main)

Orderbook o1;

but that would be unnecessary. Keeping things short :-

You can't call functions inside a Class

How to perform update operations on columns of type JSONB in Postgres 9.4

Ideally, you don't use JSON documents for structured, regular data that you want to manipulate inside a relational database. Use a normalized relational design instead.

JSON is primarily intended to store whole documents that do not need to be manipulated inside the RDBMS. Related:

Updating a row in Postgres always writes a new version of the whole row. That's the basic principle of Postgres' MVCC model. From a performance perspective, it hardly matters whether you change a single piece of data inside a JSON object or all of it: a new version of the row has to be written.

Thus the advice in the manual:

JSON data is subject to the same concurrency-control considerations as any other data type when stored in a table. Although storing large documents is practicable, keep in mind that any update acquires a row-level lock on the whole row. Consider limiting JSON documents to a manageable size in order to decrease lock contention among updating transactions. Ideally, JSON documents should each represent an atomic datum that business rules dictate cannot reasonably be further subdivided into smaller datums that could be modified independently.

The gist of it: to modify anything inside a JSON object, you have to assign a modified object to the column. Postgres supplies limited means to build and manipulate json data in addition to its storage capabilities. The arsenal of tools has grown substantially with every new release since version 9.2. But the principal remains: You always have to assign a complete modified object to the column and Postgres always writes a new row version for any update.

Some techniques how to work with the tools of Postgres 9.3 or later:

This answer has attracted about as many downvotes as all my other answers on SO together. People don't seem to like the idea: a normalized design is superior for non-dynamic data. This excellent blog post by Craig Ringer explains in more detail:

What is AF_INET, and why do I need it?

it defines the protocols address family.this determines the type of socket created. pocket pc support AF_INET.

the content in the following page is quite decent

How can I setup & run PhantomJS on Ubuntu?

See link Installation guide is in ...

And run in terminal with this command

phantomjs --webdriver=4444

Linux: where are environment variables stored?

Type "set" and you will get a list of all the current variables. If you want something to persist put it in ~/.bashrc or ~/.bash_profile (if you're using bash)

How do I correctly detect orientation change using Phonegap on iOS?

While working with the orientationchange event, I needed a timeout to get the correct dimensions of the elements in the page, but matchMedia worked fine. My final code:

var matchMedia = window.msMatchMedia || window.MozMatchMedia || window.WebkitMatchMedia || window.matchMedia;

if (typeof(matchMedia) !== 'undefined') {
  // use matchMedia function to detect orientationchange
  window.matchMedia('(orientation: portrait)').addListener(function() {
    // your code ...
} else {
  // use orientationchange event with timeout (fires to early)
  $(window).on('orientationchange', function() {
    window.setTimeout(function() {
      // your code ...
    }, 300)

Android Material and appcompat Manifest merger failed

For solving this issue i would recommend to define explicitly the version for the ext variables at the android/build.gradle at your root project

ext {
    googlePlayServicesVersion = "16.1.0" // default: "+"
    firebaseVersion = "15.0.2" // default: "+"

    // Other settings
    compileSdkVersion = <Your compile SDK version> // default: 23
    buildToolsVersion = "<Your build tools version>" // default: "23.0.1"
    targetSdkVersion = <Your target SDK version> // default: 23
    supportLibVersion = "<Your support lib version>" // default: 23.1.1


System.Net.Http: missing from namespace? (using .net 4.5)

How I solved it.

  1. Open project (!) "Properties", choose "Application", select targeting framework ".Net Framework 4.5"
  2. Right click on your project -> Add reference
  3. Make sure that in "Assemblies" -> "Extensions" option "System.Net.Http" is unchecked
  4. Go to "Assemblies" -> "Framework" and select "System.Net.Http" and "System.Net.Http" options
  5. That`s all!

In my case i had at the beginning .Net 4.0 and "Assemblies" -> "Extensions" option "System.Net.Http" with version After my actions "Assemblies" -> "Framework" options "System.Net.Http" and "System.Net.Http" had the same version.

How to call a PHP function on the click of a button

Yes, you need Ajax here. Please refer to the code below for more details.


Change your markup like this

<input type="submit" class="button" name="insert" value="insert" />
<input type="submit" class="button" name="select" value="select" />



        var clickBtnValue = $(this).val();
        var ajaxurl = 'ajax.php',
        data =  {'action': clickBtnValue};
        $.post(ajaxurl, data, function (response) {
            // Response div goes here.
            alert("action performed successfully");

In ajax.php

    if (isset($_POST['action'])) {
        switch ($_POST['action']) {
            case 'insert':
            case 'select':

    function select() {
        echo "The select function is called.";

    function insert() {
        echo "The insert function is called.";

What does Ruby have that Python doesn't, and vice versa?

I'm unsure of this, so I add it as an answer first.

Python treats unbound methods as functions

That means you can call a method either like theobject.themethod() or by TheClass.themethod(anobject).

Edit: Although the difference between methods and functions is small in Python, and non-existant in Python 3, it also doesn't exist in Ruby, simply because Ruby doesn't have functions. When you define functions, you are actually defining methods on Object.

But you still can't take the method of one class and call it as a function, you would have to rebind it to the object you want to call on, which is much more obstuse.

How to initialize array to 0 in C?

If you'd like to initialize the array to values other than 0, with gcc you can do:

int array[1024] = { [ 0 ... 1023 ] = -1 };

This is a GNU extension of C99 Designated Initializers. In older GCC, you may need to use -std=gnu99 to compile your code.

Activity, AppCompatActivity, FragmentActivity, and ActionBarActivity: When to Use Which?

I thought Activity was deprecated


So for API Level 22 (with a minimum support for API Level 15 or 16), what exactly should I use both to host the components, and for the components themselves? Are there uses for all of these, or should I be using one or two almost exclusively?

Activity is the baseline. Every activity inherits from Activity, directly or indirectly.

FragmentActivity is for use with the backport of fragments found in the support-v4 and support-v13 libraries. The native implementation of fragments was added in API Level 11, which is lower than your proposed minSdkVersion values. The only reason why you would need to consider FragmentActivity specifically is if you want to use nested fragments (a fragment holding another fragment), as that was not supported in native fragments until API Level 17.

AppCompatActivity is from the appcompat-v7 library. Principally, this offers a backport of the action bar. Since the native action bar was added in API Level 11, you do not need AppCompatActivity for that. However, current versions of appcompat-v7 also add a limited backport of the Material Design aesthetic, in terms of the action bar and various widgets. There are pros and cons of using appcompat-v7, well beyond the scope of this specific Stack Overflow answer.

ActionBarActivity is the old name of the base activity from appcompat-v7. For various reasons, they wanted to change the name. Unless some third-party library you are using insists upon an ActionBarActivity, you should prefer AppCompatActivity over ActionBarActivity.

So, given your minSdkVersion in the 15-16 range:

  • If you want the backported Material Design look, use AppCompatActivity

  • If not, but you want nested fragments, use FragmentActivity

  • If not, use Activity

Just adding from comment as note: AppCompatActivity extends FragmentActivity, so anyone who needs to use features of FragmentActivity can use AppCompatActivity.

Programmatically trigger "select file" dialog box

Natively the only way is by creating an <input type="file"> element and then simulating a click, unfortunately.

There's a tiny plugin (shameless plug) which will take the pain away of having to do this all the time: file-dialog

    .then(file => {
        const data = new FormData()
        data.append('file', file[0])
        data.append('imageName', 'flower')

        // Post to server
        fetch('/uploadImage', {
            method: 'POST',
            body: data

Set the absolute position of a view

A more cleaner and dynamic way without hardcoding any pixel values in the code.

I wanted to position a dialog (which I inflate on the fly) exactly below a clicked button.

and solved it this way :

    // get the yoffset of the position where your View has to be placed 
    final int yoffset = < calculate the position of the view >

    // position using top margin
    if(myView.getLayoutParams() instanceof MarginLayoutParams) {
        ((MarginLayoutParams) myView.getLayoutParams()).topMargin = yOffset;

However you have to make sure the parent layout of myView is an instance of RelativeLayout.

more complete code :

    // identify the button
    final Button clickedButton = <... code to find the button here ...>

    // inflate the dialog - the following style preserves xml layout params
    final View floatingDialog = 
            this.floatingDialogContainer, false);


    // get the buttons position
    final int[] buttonPos = new int[2];
    final int yOffset =  buttonPos[1] + clickedButton.getHeight();

    // position using top margin
    if(floatingDialog.getLayoutParams() instanceof MarginLayoutParams) {
        ((MarginLayoutParams) floatingDialog.getLayoutParams()).topMargin = yOffset;

This way you can still expect the target view to adjust to any layout parameters set using layout XML files, instead of hardcoding those pixels/dps in your Java code.

PHP json_decode() returns NULL with valid JSON?

This worked for me

json_decode( preg_replace('/[\x00-\x1F\x80-\xFF]/', '', $json_string), true );

JavaScript onclick redirect

There are several issues in your code :

  • You are handling the click event of a submit button, whose default behavior is to post a request to the server and reload the page. You have to inhibit this behavior by returning false from your handler:

    onclick="SubmitFrm(); return false;"
  • value cannot be called because it is a property, not a method:

    var Searchtxt = document.getElementById("txtSearch").value;
  • The search query you are sending in the query string has to be encoded:

    window.location = ""
        + encodeURIComponent(Searchtxt);

How to show empty data message in Datatables

I was finding same but lastly i found an answer. I hope this answer help you so much.

when your array is empty then you can send empty array just like

            echo json_encode($result);
            echo json_encode(array('data'=>''));

Thank you

What does $(function() {} ); do?

This is a shortcut for $(document).ready(), which is executed when the browser has finished loading the page (meaning here, "when the DOM is available"). See If you are trying to call example() before the browser has finished loading the page, it may not work.

Is there an upside down caret character?

There's always a lowercase "v". But seriously, aside from Unicode, all I can find would be &darr, which looks like ↓.

How can I start PostgreSQL server on Mac OS X?

I had the same problem and performed all updates from the first post. But after checking the log file,


I see the true cause:

FATAL:  data directory "/usr/local/var/postgres" has group or world access
DETAIL:  Permissions should be u=rwx (0700).

After changing permissions on this directory,

chmod 0700 /usr/local/var/postgres

the PostgreSQL server started.

Check the log file every time.

Android - set TextView TextStyle programmatically?

This worked for me

textview.setTypeface(textview.getTypeface(), Typeface.BOLD);



Setting width of spreadsheet cell using PHPExcel

setAutoSize method must come before setWidth:


How can I see CakePHP's SQL dump in the controller?

It is greatly frustrating that CakePHP does not have a $this->Model->lastQuery();. Here are two solutions including a modified version of Handsofaten's:

1. Create a Last Query Function

To print the last query run, in your /app_model.php file add:

function lastQuery(){
    $dbo = $this->getDatasource();
    $logs = $dbo->_queriesLog;
    // return the first element of the last array (i.e. the last query)
    return current(end($logs));

Then to print output you can run:

debug($this->lastQuery()); // in model


debug($this->Model->lastQuery()); // in controller

2. Render the SQL View (Not avail within model)

To print out all queries run in a given page request, in your controller (or component, etc) run:


It will likely throw a missing view error, but this is better than no access to recent queries!

(As Handsofaten said, there is the /elements/sql_dump.ctp in cake/libs/view/elements/, but I was able to do the above without creating the sql.ctp view. Can anyone explain that?)

Div table-cell vertical align not working

This is how I do it:


html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    display: table
#content {
    display: table-cell;
    text-align: center;
    vertical-align: middle


<div id="content">
    Content goes here


Example of vertical centering


CSS: centering things.

How to find the files that are created in the last hour in unix

If the dir to search is srch_dir then either

$ find srch_dir -cmin -60 # change time


$ find srch_dir -mmin -60 # modification time


$ find srch_dir -amin -60 # access time

shows files created, modified or accessed in the last hour.

correction :ctime is for change node time (unsure though, please correct me )

Is there way to use two PHP versions in XAMPP?

I just want to share my new finding:

I just used it for 1 hour and it looks promising.

  • You can add and switch PHP versions,
  • it has one-click installers for Wordpress, laravel, etc
  • it autocreates vhosts with the name of each app (eg. appname.test)
  • you can select your current htdocs folder as the root www folder
  • you just add other PHP versions extracting them in folders and selecting them from a list
  • it auto reload apache after each change
  • adding phpMyAdmin is as easy as download it and put it in {LARAGON_DIR}\etc\apps\phpMyAdmin, etc...

Laragon DOCS

How to add another PHP version to Laragon

How to add phpMyAdmin to Laragon

I'm not affiliated in any way with Laragon. Just found it on Google looking for "XAMPP Windows alteratives"

Convert ASCII TO UTF-8 Encoding

Use utf8_encode()

Man page can be found here

Also read this article from Joel on Software. It provides an excellent explanation if what Unicode is and how it works.

How do I convert certain columns of a data frame to become factors?

Here's an example:

#Create a data frame
> d<- data.frame(a=1:3, b=2:4)
> d
  a b
1 1 2
2 2 3
3 3 4

#currently, there are no levels in the `a` column, since it's numeric as you point out.
> levels(d$a)

#Convert that column to a factor
> d$a <- factor(d$a)
> d
  a b
1 1 2
2 2 3
3 3 4

#Now it has levels.
> levels(d$a)
[1] "1" "2" "3"

You can also handle this when reading in your data. See the colClasses and stringsAsFactors parameters in e.g. readCSV().

Note that, computationally, factoring such columns won't help you much, and may actually slow down your program (albeit negligibly). Using a factor will require that all values are mapped to IDs behind the scenes, so any print of your data.frame requires a lookup on those levels -- an extra step which takes time.

Factors are great when storing strings which you don't want to store repeatedly, but would rather reference by their ID. Consider storing a more friendly name in such columns to fully benefit from factors.

Getting value from table cell in JavaScript...not jQuery

confer below code


    function addRow(){
 var table = document.getElementById('myTable');
//var row = document.getElementById("myTable");
var x = table.insertRow(0);
var e =table.rows.length-1;
var l =table.rows[e].cells.length;
//x.innerHTML = "&nbsp;";
 for (var c =0,  m=l; c < m; c++) {
   table.rows[0].cells[c].innerHTML  = "&nbsp;&nbsp;";


function addColumn(){
       var table = document.getElementById('myTable');
        for (var r = 0, n = table.rows.length; r < n; r++) {
                table.rows[r].cells[0].innerHTML =  "&nbsp;&nbsp;" ;



function deleteRow() {


function deleteColumn() {
   // var row = document.getElementById("myRow");
 var table = document.getElementById('myTable');
 for (var r = 0, n = table.rows.length; r < n; r++) {
    table.rows[r].deleteCell(0);//var table handle 

<input type="button" value="row +" onClick="addRow()" border=0       style='cursor:hand'>
    <input type="button" value="row -" onClick='deleteRow()' border=0 style='cursor:hand'>
    <input type="button" value="column +" onClick="addColumn()" border=0 style='cursor:hand'>
    <input type="button" value="column -" onClick='deleteColumn()' border=0 style='cursor:hand'>

    <table  id='myTable' border=1 cellpadding=0 cellspacing=0>
 <tr id='myRow'>          



What causes the Broken Pipe Error?

Maybe the 40 bytes fits into the pipe buffer, and the 40000 bytes doesn't?


The sending process is sent a SIGPIPE signal when you try to write to a closed pipe. I don't know exactly when the signal is sent, or what effect the pipe buffer has on this. You may be able to recover by trapping the signal with the sigaction call.

Add image to left of text via css

This works great

    content: "";
    display: block;
    background: url('somewhere.jpg') no-repeat;
    width: 25px;
    height: 25px;
    float: left;

Word wrap for a label in Windows Forms

If you are entering text into the label beforehand, you can do this.

  1. In the designer, Right-Click on the label and click Properties.
  2. In Properties, search for text tab.
  3. Click in the tab and click on the arrow button next to it.
  4. A box will popup on top of it.
  5. You can press enter in the popup box to add lines and type as in notepad! (PRESS ENTER WHERE YOU WANT TO WRAP THE LABEL TEXT)

Laravel Eloquent limit and offset

Maybe this

$products = $art->products->take($limit)->skip($offset)->get();

Responsive background image in div full width

When you use background-size: cover the background image will automatically be stretched to cover the entire container. Aspect ratio is maintained however, so you will always lose part of the image, unless the aspect ratio of the image and the element it is applied to are identical.

I see two ways you could solve this:

  • Do not maintain the aspect ratio of the image by setting background-size: 100% 100% This will also make the image cover the entire container, but the ratio will not be maintained. Disadvantage is that this distorts your image, and therefore may look very weird, depending on the image. With the image you are using in the fiddle, I think you could get away with it though.

  • You could also calculate and set the height of the element with javascript, based on its width, so it gets the same ratio as the image. This calculation would have to be done on load and on resize. It should be easy enough with a few lines of code (feel free to ask if you want an example). Disadvantage of this method is that your width may become very small (on mobile devices), and therfore the calculated height also, which may cause the content of the container to overflow. This could be solved by changing the size of the content as well or something, but it adds some complexity to the solution/

Check if a Bash array contains a value

Borrowing from Dennis Williamson's answer, the following solution combines arrays, shell-safe quoting, and regular expressions to avoid the need for: iterating over loops; using pipes or other sub-processes; or using non-bash utilities.

declare -a array=('hello, stack' one 'two words' words last)
printf -v array_str -- ',,%q' "${array[@]}"

if [[ "${array_str},," =~ ,,words,, ]]
   echo 'Matches'
   echo "Doesn't match"

The above code works by using Bash regular expressions to match against a stringified version of the array contents. There are six important steps to ensure that the regular expression match can't be fooled by clever combinations of values within the array:

  1. Construct the comparison string by using Bash's built-in printf shell-quoting, %q. Shell-quoting will ensure that special characters become "shell-safe" by being escaped with backslash \.
  2. Choose a special character to serve as a value delimiter. The delimiter HAS to be one of the special characters that will become escaped when using %q; that's the only way to guarantee that values within the array can't be constructed in clever ways to fool the regular expression match. I choose comma , because that character is the safest when eval'd or misused in an otherwise unexpected way.
  3. Combine all array elements into a single string, using two instances of the special character to serve as delimiter. Using comma as an example, I used ,,%q as the argument to printf. This is important because two instances of the special character can only appear next to each other when they appear as the delimiter; all other instances of the special character will be escaped.
  4. Append two trailing instances of the delimiter to the string, to allow matches against the last element of the array. Thus, instead of comparing against ${array_str}, compare against ${array_str},,.
  5. If the target string you're searching for is supplied by a user variable, you must escape all instances of the special character with a backslash. Otherwise, the regular expression match becomes vulnerable to being fooled by cleverly-crafted array elements.
  6. Perform a Bash regular expression match against the string.

convert htaccess to nginx

You can easily make a Php script to parse your old htaccess, I am using this one for PRestashop rules :

$content = $_POST['content'];

    $lines   = explode(PHP_EOL, $content);
    $results = '';

    foreach($lines as $line)
        $items = explode(' ', $line);

        $q = str_replace("^", "^/", $items[1]);

        if (substr($q, strlen($q) - 1) !== '$') $q .= '$';

        $buffer = 'rewrite "'.$q.'" "'.$items[2].'" last;';

        $results .= $buffer.PHP_EOL;


How to add a JAR in NetBeans

Right click 'libraries' in the project list, then click add.

"Invalid signature file" when attempting to run a .jar

Some of your dependencies are likely signed jarfiles. When you combine them all into one big jarfile, the corresponding signature files are still present, and no longer match the "big combined" jarfile, so the runtime halts thinking the jar file has been tampered with (which it...has so to speak).

Assuming you're using ant, you can solve the problem by eliminating the signature files from your jarfile dependencies. Unfortunately, it's not possible to do this in one step in ant.

However, I was able to get this working with Ant in two steps, without specifically naming each jarfile dependency, by using:

<target name="jar" depends="compile" description="Create one big jarfile.">
    <jar jarfile="${output.dir}/deps.jar">
        <zipgroupfileset dir="jars">
            <include name="**/*.jar" />
    <sleep seconds="1" />
    <jar jarfile="${output.dir}/myjar.jar" basedir="${classes.dir}">
        <zipfileset src="${output.dir}/deps.jar" excludes="META-INF/*.SF" />
            <attribute name="Main-Class" value="com.mycompany.MyMain" />

The sleep element is supposed to prevent errors about files with modification dates in the future.

Other variations I found in the linked threads didn't work for me.

How do I update an entity using spring-data-jpa?

You can simply use this function with save() JPAfunction, but the object sent as parameter must contain an existing id in the database otherwise it will not work, because save() when we send an object without id, it adds directly a row in database, but if we send an object with an existing id, it changes the columns already found in the database.

public void updateUser(Userinfos u) {
    User userFromDb = userRepository.findById(u.getid());
    // crush the variables of the object found

How to list all files in a directory and its subdirectories in hadoop hdfs

Code snippet for both recursive and non-recursive approaches:

//helper method to get the list of files from the HDFS path
public static List<String>
    listFilesFromHDFSPath(Configuration hadoopConfiguration,
                          String hdfsPath,
                          boolean recursive) throws IOException,
    //resulting list of files
    List<String> filePaths = new ArrayList<String>();

    //get path from string and then the filesystem
    Path path = new Path(hdfsPath);  //throws IllegalArgumentException
    FileSystem fs = path.getFileSystem(hadoopConfiguration);

    //if recursive approach is requested
        //(heap issues with recursive approach) => using a queue
        Queue<Path> fileQueue = new LinkedList<Path>();

        //add the obtained path to the queue

        //while the fileQueue is not empty
        while (!fileQueue.isEmpty())
            //get the file path from queue
            Path filePath = fileQueue.remove();

            //filePath refers to a file
            if (fs.isFile(filePath))
            else   //else filePath refers to a directory
                //list paths in the directory and add to the queue
                FileStatus[] fileStatuses = fs.listStatus(filePath);
                for (FileStatus fileStatus : fileStatuses)
                } // for
            } // else

        } // while

    } // if
    else        //non-recursive approach => no heap overhead
        //if the given hdfsPath is actually directory
            FileStatus[] fileStatuses = fs.listStatus(path);

            //loop all file statuses
            for(FileStatus fileStatus : fileStatuses)
                //if the given status is a file, then update the resulting list
            } // for
        } // if
        else        //it is a file then
            //return the one and only file path to the resulting list
        } // else

    } // else

    //close filesystem; no more operations

    //return the resulting list
    return filePaths;
} // listFilesFromHDFSPath

Select Top and Last rows in a table (SQL server)

To get the bottom 1000 you will want to order it by a column in descending order, and still take the top 1000.

FROM [SomeTable]

If you care for it to be in the same order as before you can use a common table expression for that:

    SELECT TOP 1000 *
    FROM [SomeTable]
    ORDER BY MySortColumn DESC

ORDER BY MySortColumn

Select subset of columns in data.table R

You can do

dt[, !c("V1","V2","V3","V5")]

to get

            V4         V6         V7        V8         V9        V10
 1: 0.88612076 0.94727825 0.50502208 0.6702523 0.24186706 0.96263313
 2: 0.11121752 0.13969145 0.19092645 0.9589867 0.27968190 0.07796870
 3: 0.50179822 0.10641301 0.08540322 0.3297847 0.03643195 0.18082180
 4: 0.09787517 0.07312777 0.88077548 0.3218041 0.75826099 0.55847774
 5: 0.73475574 0.96644484 0.58261312 0.9921499 0.78962675 0.04976212
 6: 0.88861117 0.85690337 0.27723130 0.3662264 0.50881663 0.67402625
 7: 0.33933983 0.83392047 0.30701697 0.6138122 0.85107176 0.58609504
 8: 0.89907094 0.61389815 0.19957386 0.3968331 0.78876682 0.90546328
 9: 0.54136123 0.08274569 0.25190790 0.1920462 0.15142604 0.12134807
10: 0.36511064 0.88117171 0.05730210 0.9441072 0.40125023 0.62828674

How many significant digits do floats and doubles have in java?

A normal math answer.

Understanding that a floating point number is implemented as some bits representing the exponent and the rest, most for the digits (in the binary system), one has the following situation:

With a high exponent, say 10²³ if the least significant bit is changed, a large difference between two adjacent distinghuishable numbers appear. Furthermore the base 2 decimal point makes that many base 10 numbers can only be approximated; 1/5, 1/10 being endless numbers.

So in general: floating point numbers should not be used if you care about significant digits. For monetary amounts with calculation, e,a, best use BigDecimal.

For physics floating point doubles are adequate, floats almost never. Furthermore the floating point part of processors, the FPU, can even use a bit more precission internally.

What order are the Junit @Before/@After called?

One potential gotcha that has bitten me before:

I like to have at most one @Before method in each test class, because order of running the @Before methods defined within a class is not guaranteed. Typically, I will call such a method setUpTest().

But, although @Before is documented as The @Before methods of superclasses will be run before those of the current class. No other ordering is defined., this only applies if each method marked with @Before has a unique name in the class hierarchy.

For example, I had the following:

public class AbstractFooTest {
  public void setUpTest() { 

public void FooTest extends AbstractFooTest {
  public void setUpTest() { 

I expected AbstractFooTest.setUpTest() to run before FooTest.setUpTest(), but only FooTest.setupTest() was executed. AbstractFooTest.setUpTest() was not called at all.

The code must be modified as follows to work:

public void FooTest extends AbstractFooTest {
  public void setUpTest() {

check null,empty or undefined angularjs

You can use angular's function called angular.isUndefined(value) returns boolean.

You may read more about angular's functions here: AngularJS Functions (isUndefined)

Difference between application/x-javascript and text/javascript content types

text/javascript is obsolete, and application/x-javascript was experimental (hence the x- prefix) for a transitional period until application/javascript could be standardised.

You should use application/javascript. This is documented in the RFC.

As far a browsers are concerned, there is no difference (at least in HTTP headers). This was just a change so that the text/* and application/* MIME type groups had a consistent meaning where possible. (text/* MIME types are intended for human readable content, JavaScript is not designed to directly convey meaning to humans).

Note that using application/javascript in the type attribute of a script element will cause the script to be ignored (as being in an unknown language) in some older browsers. Either continue to use text/javascript there or omit the attribute entirely (which is permitted in HTML 5).

This isn't a problem in HTTP headers as browsers universally (as far as I'm aware) either ignore the HTTP content-type of scripts entirely, or are modern enough to recognise application/javascript.

Optimal way to concatenate/aggregate strings

Are methods using FOR XML PATH like below really that slow? Itzik Ben-Gan writes that this method has good performance in his T-SQL Querying book (Mr. Ben-Gan is a trustworthy source, in my view).

create table #t (id int, name varchar(20))

insert into #t
values (1, 'Matt'), (1, 'Rocks'), (2, 'Stylus')

select  id
        ,Names = stuff((select ', ' + name as [text()]
        from #t xt
        where =
        for xml path('')), 1, 2, '')
from #t t
group by id

show icon in actionbar/toolbar with AppCompat-v7 21

In Xamarin.Android you can use these:


using Android.Support.V7.App.AppCompatActivity is required.

How to toggle a boolean?

bool = !bool;

This holds true in most languages.

How do I include a newline character in a string in Delphi?

On the side, a trick that can be useful:
If you hold your multiple strings in a TStrings, you just have to use the Text property of the TStrings like in the following example.

Label1.Caption := Memo1.Lines.Text;

And you'll get your multi-line label...

Deprecation warning in Moment.js - Not in a recognized ISO format

Parsing string with moment.js.

const date = '1231231231231' //Example String date
const parsed = moment(+date);

How can I hide the Adobe Reader toolbar when displaying a PDF in the .NET WebBrowser control?

It appears the default setting for Adobe Reader X is for the toolbars not to be shown by default unless they are explicitly turned on by the user. And even when I turn them back on during a session, they don't show up automatically next time. As such, I suspect you have a preference set contrary to the default.

The state you desire, with the top and left toolbars not shown, is called "Read Mode". If you right-click on the document itself, and then click "Page Display Preferences" in the context menu that is shown, you'll be presented with the Adobe Reader Preferences dialog. (This is the same dialog you can access by opening the Adobe Reader application, and selecting "Preferences" from the "Edit" menu.) In the list shown in the left-hand column of the Preferences dialog, select "Internet". Finally, on the right, ensure that you have the "Display in Read Mode by default" box checked:

   Adobe Reader Preferences dialog

You can also turn off the toolbars temporarily by clicking the button at the right of the top toolbar that depicts arrows pointing to opposing corners:

   Adobe Reader Read Mode toolbar button

Finally, if you have "Display in Read Mode by default" turned off, but want to instruct the page you're loading not to display the toolbars (i.e., override the user's current preferences), you can append the following to the URL:


So, for example, the following code will disable both the top toolbar (called "toolbar") and the left-hand toolbar (called "navpane"). However, if the user knows the keyboard combination (F8, and perhaps other methods as well), they will still be able to turn them back on.

string url = @"";

You can read more about the parameters that are available for customizing the way PDF files open here on Adobe's developer website.

Downloading a large file using curl

You can use this function, which creates a tempfile in the filesystem and returns the path to the downloaded file if everything worked fine:

function getFileContents($url)
    // Workaround: Save temp file
    $img = tempnam(sys_get_temp_dir(), 'pdf-');
    $img .= '.' . pathinfo($url, PATHINFO_EXTENSION);

    $fp = fopen($img, 'w+');

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);

    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_FILE, $fp);
    curl_setopt($ch, CURLOPT_HEADER, false);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);

    $result = curl_exec($ch);


    return $result ? $img : false;

View stored procedure/function definition in MySQL

An alternative quick and hacky solution if you want to get an overview of all the produres there are, or run into the issue of only getting the procedure header shown by SHOW CREATE PROCEDURE:

mysqldump --user=<user> -p --no-data --routines <database>

It will export the table descriptions as well, but no data. Works well for sniffing around unknown or forgotten schemas... ;)

Get date from input form within PHP

if (isset($_POST['birthdate'])) {
    $timestamp = strtotime($_POST['birthdate']); 

Flexbox: how to get divs to fill up 100% of the container width without wrapping?

You can use the shorthand flex property and set it to

flex: 0 0 100%;

That's flex-grow, flex-shrink, and flex-basis in one line. Flex shrink was described above, flex grow is the opposite, and flex basis is the size of the container.

Node.js throws "btoa is not defined" error

Maybe you don't need it anymore but if someone needs this using node:

How to make Visual Studio copy a DLL file to the output directory?

Use a post-build action in your project, and add the commands to copy the offending DLL. The post-build action are written as a batch script.

The output directory can be referenced as $(OutDir). The project directory is available as $(ProjDir). Try to use relative pathes where applicable, so that you can copy or move your project folder without breaking the post-build action.

How to get a value from the last inserted row?

Use sequences in postgres for id columns:

INSERT mytable(myid) VALUES (nextval('MySequence'));

SELECT currval('MySequence');

currval will return the current value of the sequence in the same session.

(In MS SQL, you would use @@identity or SCOPE_IDENTITY())

How to fix homebrew permissions?

On MacOS Mojave, I did not have permission to chown the /usr/local folder either (sudo chown -R "$USER":admin /usr/local).

sudo chown -R "$USER":admin /usr/local/* did work for me however, altering the permissions of everything within the local folder.

Hopefully this will help others with the same issue.

Applications are expected to have a root view controller at the end of application launch

I ran into this in an iPad application targeting iOS 5.1 in Xcode 4.5.1. The app uses UITabBarController. I needed a new section within the tab bar controller, so I created a new view controller and xib. Once I added the new view controller to the tab bar controller, none of my on-screen controls worked anymore, and I got the "expected to have a root view controller" log.

Somehow the top-level object in the new xib was UIWindow instead of UIView. When I dropped a UIView into the XIB, had the view outlet point to it, moved all the subviews into the new UIView, and removed the UIWindow instance, the problem was fixed.

How do I change selected value of select2 dropdown with JqGrid?

Looking at the select2 docs you use the below to get/set the value.

$("#select").select2("val"); //get the value
$("#select").select2("val", "CA"); //set the value

@PanPipes has pointed out that this has changed for 4.x (go toss him an upvote below). val is now called directly


So within the loadComplete of the jqGrid you can get whatever value you are looking for then set the selectbox value.

Notice from the docs

Notice that in order to use this method you must define the initSelection function in the options so Select2 knows how to transform the id of the object you pass in val() to the full object it needs to render selection. If you are attaching to a select element this function is already provided for you.

"find: paths must precede expression:" How do I specify a recursive search that also finds files in the current directory?

Try putting it in quotes -- you're running into the shell's wildcard expansion, so what you're acually passing to find will look like:

find . -name bobtest.c cattest.c snowtest.c

...causing the syntax error. So try this instead:

find . -name '*test.c'

Note the single quotes around your file expression -- these will stop the shell (bash) expanding your wildcards.

How to recover deleted rows from SQL server table?

It is possible using Apex Recovery Tool,i have successfully recovered my table rows which i accidentally deleted

if you download the trial version it will recover only 10th row

check here

Should we @Override an interface's method implementation?

If the class that is implementing the interface is an abstract class, @Override is useful to ensure that the implementation is for an interface method; without the @Override an abstract class would just compile fine even if the implementation method signature does not match the method declared in the interface; the mismatched interface method would remain as unimplemented. The Java doc cited by @Zhao

The method does override or implement a method declared in a supertype

is clearly referring to an abstract super class; an interface can not be called the supertype. So, @Override is redundant and not sensible for interface method implementations in concrete classes.

Android: failed to convert @drawable/picture into a drawable

In my case I had an image in different folders (with same name) for supporting different dpi and device sizes. All images had same name except one of them. It was mistyped and once I renamed it like other names, it resolved my issue.

How to handle the `onKeyPress` event in ReactJS?

Late to the party, but I was trying to get this done in TypeScript and came up with this:

<div onKeyPress={(e: KeyboardEvent<HTMLDivElement>) => console.log(e.key)}

This prints the exact key pressed to the screen. So if you want to respond to all "a" presses when the div is in focus, you'd compare e.key to "a" - literally if(e.key === "a").

How is a tag different from a branch in Git? Which should I use, here?

Branches are made of wood and grow from the trunk of the tree. Tags are made of paper (derivative of wood) and hang like Christmas Ornaments from various places in the tree.

Your project is the tree, and your feature that will be added to the project will grow on a branch. The answer is branch.

Injection of autowired dependencies failed;

The error shows that is not a registered bean. Add the packages in which you have beans that will be autowired in your application context:

<context:component-scan base-package=""/>
<context:component-scan base-package=""/>

Alternatively, if you want to include all subpackages in

<context:component-scan base-package="">
     <context:include-filter type="aspectj" expression="*" />

As a side note, if you're using Spring 3.1 or later, you can take advantage of the @ComponentScan annotation, so that you don't have to use any xml configuration regarding component-scan. Use it in conjunction with @Configuration.

@ComponentScan("") // No need to include component-scan in xml
public class ArticleControleur {

    ArticleService articleService;

You might find this Spring in depth section on Autowiring useful.

What are the git concepts of HEAD, master, origin?

I highly recommend the book "Pro Git" by Scott Chacon. Take time and really read it, while exploring an actual git repo as you do.

HEAD: the current commit your repo is on. Most of the time HEAD points to the latest commit in your current branch, but that doesn't have to be the case. HEAD really just means "what is my repo currently pointing at".

In the event that the commit HEAD refers to is not the tip of any branch, this is called a "detached head".

master: the name of the default branch that git creates for you when first creating a repo. In most cases, "master" means "the main branch". Most shops have everyone pushing to master, and master is considered the definitive view of the repo. But it's also common for release branches to be made off of master for releasing. Your local repo has its own master branch, that almost always follows the master of a remote repo.

origin: the default name that git gives to your main remote repo. Your box has its own repo, and you most likely push out to some remote repo that you and all your coworkers push to. That remote repo is almost always called origin, but it doesn't have to be.

HEAD is an official notion in git. HEAD always has a well-defined meaning. master and origin are common names usually used in git, but they don't have to be.

How to get array keys in Javascript?

I wrote a function what works fine with every instance of Objects (Arrays are those).

Object.prototype.toArray = function()
      return null;

    var c = [];

    for (var key in this) 
        if ( ( this instanceof Array && this.constructor === Array && key === 'length' ) || !this.hasOwnProperty(key) ) 


    return c;


var a   = [ 1, 2, 3 ];
a[11]   = 4;
a["js"] = 5;


var b = { one: 1, two: 2, three: 3, f: function() { return 4; }, five: 5 };
b[7] = 7;



> [ 1, 2, 3, 4, 5 ]
> [ 7, 1, 2, 3, function () { return 4; }, 5 ]

It may be useful for anyone.

Render Content Dynamically from an array map function in React Native

lapsList() {

    return => {
      return (

You forgot to return the map. this code will resolve the issue.

what is <meta charset="utf-8">?

That meta tag basically specifies which character set a website is written with.

Here is a definition of UTF-8:

UTF-8 (U from Universal Character Set + Transformation Format—8-bit) is a character encoding capable of encoding all possible characters (called code points) in Unicode. The encoding is variable-length and uses 8-bit code units.

Detect click inside/outside of element with single event handler

Rather than using the jQuery .parents function (as suggested in the accepted answer), it's better to use .closest for this purpose. As explained in the jQuery api docs, .closest checks the element passed and all its parents, whereas .parents just checks the parents. Consequently, this works:

$(function() {
    $("body").click(function(e) {
        if ($("#myDiv").length) {
            alert("Clicked inside #myDiv");
        } else { 
            alert("Clicked outside #myDiv");

How to change the data type of a column without dropping the column with query?

ALTER TABLE YourTableNameHere ALTER COLUMN YourColumnNameHere VARCHAR(20)

How to inflate one view with a layout

If you want to add a single view multiple time then you have to use

   layoutInflaterForButton = getActivity().getLayoutInflater();

 for (int noOfButton = 0; noOfButton < 5; noOfButton++) {
        FrameLayout btnView = (FrameLayout) layoutInflaterForButton.inflate(R.layout.poll_button, null);

If you do like

   layoutInflaterForButton = getActivity().getLayoutInflater();
    FrameLayout btnView = (FrameLayout) layoutInflaterForButton.inflate(R.layout.poll_button, null);


for (int noOfButton = 0; noOfButton < 5; noOfButton++) {

then it will throw exception of all ready added view.

Converting BigDecimal to Integer

I found that the above did not work for me. I was pulling a cell value from a JTable but could not cast to double or int etc. My solution:

Object obj = getTable().getValueAt(row, 0);

where row 0 would always be a number. Hope this helps anyone still scrolling!

How to change a TextView's style at runtime

TextView tvCompany = (TextView)findViewById(R.layout.tvCompany);

You an set it from code. Typeface

clear data inside text file in c++

As far as I am aware, simply opening the file in write mode without append mode will erase the contents of the file.

ofstream file("filename.txt"); // Without append
ofstream file("filename.txt", ios::app); // with append

The first one will place the position bit at the beginning erasing all contents while the second version will place the position bit at the end-of-file bit and write from there.

How to disable HTML links

To disable link to access another page on touch device:

if (control == false)
  document.getElementById('id_link').setAttribute('href', '#');
  document.getElementById('id_link').setAttribute('href', 'page/link.html');
end if;

How do you create a Marker with a custom icon for google maps API v3?

Symbol You Want on Color You Want!

I was looking for this answer for days and here it is the right and easy way to create a custom marker:

'' where xxx is the text and 5680fc is the hexadecimal color code of the background and 000000 is the hexadecimal color code of the text.

Theses markers are totally dynamic and you can create whatever balloon icon you want. Just change the URL.

apache mod_rewrite is not working or not enabled

Try setting: "AllowOverride All".

Unable to run Java code with Intellij IDEA

If you are just opened a new java project then create a new folder src/ in the man project location.

Then cut and paste all your package in that folder.

Then Right click on src directory and select option Mark Directory As > Sources Root.

Move_uploaded_file() function is not working

This is a working example.

HTML Form :

<form enctype="multipart/form-data" action="upload.php" method="POST">
    <input type="hidden" name="MAX_FILE_SIZE" value="512000" />
    Send this file: <input name="userfile" type="file" />
    <input type="submit" value="Send File" />

PHP Code :

    $uploaddir = '/var/www/uploads/';
    $uploadfile = $uploaddir . basename($_FILES['userfile']['name']);

    echo "<p>";

    if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) {
        echo "File is valid, and was successfully uploaded.\n";
    } else {
        echo "Upload failed";

    echo "</p>";
    echo '<pre>';
    echo 'Here is some more debugging info:';
    print "</pre>";

Cannot drop database because it is currently in use

Someone connected to the database. Try to switch to another database and then, to drop it:


SP_WHO to see who connected

and KILL if needed

What is a NoReverseMatch error, and how do I fix it?

The NoReverseMatch error is saying that Django cannot find a matching url pattern for the url you've provided in any of your installed app's urls.

The NoReverseMatch exception is raised by django.core.urlresolvers when a matching URL in your URLconf cannot be identified based on the parameters supplied.

To start debugging it, you need to start by disecting the error message given to you.

  • NoReverseMatch at /my_url/

    This is the url that is currently being rendered, it is this url that your application is currently trying to access but it contains a url that cannot be matched

  • Reverse for 'my_url_name'

    This is the name of the url that it cannot find

  • with arguments '()' and

    These are the non-keyword arguments its providing to the url

  • keyword arguments '{}' not found.

    These are the keyword arguments its providing to the url

  • n pattern(s) tried: []

    These are the patterns that it was able to find in your files that it tried to match against

Start by locating the code in your source relevant to the url that is currently being rendered - the url, the view, and any templates involved. In most cases, this will be the part of the code you're currently developing.

Once you've done this, read through the code in the order that django would be following until you reach the line of code that is trying to construct a url for your my_url_name. Again, this is probably in a place you've recently changed.

Now that you've discovered where the error is occuring, use the other parts of the error message to work out the issue.

The url name

  • Are there any typos?
  • Have you provided the url you're trying to access the given name?
  • If you have set app_name in the app's (e.g. app_name = 'my_app') or if you included the app with a namespace (e.g. include('myapp.urls', namespace='myapp'), then you need to include the namespace when reversing, e.g. {% url 'myapp:my_url_name' %} or reverse('myapp:my_url_name').

Arguments and Keyword Arguments

The arguments and keyword arguments are used to match against any capture groups that are present within the given url which can be identified by the surrounding () brackets in the url pattern.

Assuming the url you're matching requires additional arguments, take a look in the error message and first take a look if the value for the given arguments look to be correct.

If they aren't correct:

  • The value is missing or an empty string

    This generally means that the value you're passing in doesn't contain the value you expect it to be. Take a look where you assign the value for it, set breakpoints, and you'll need to figure out why this value doesn't get passed through correctly.

  • The keyword argument has a typo

    Correct this either in the url pattern, or in the url you're constructing.

If they are correct:

  • Debug the regex

    You can use a website such as regexr to quickly test whether your pattern matches the url you think you're creating, Copy the url pattern into the regex field at the top, and then use the text area to include any urls that you think it should match against.

    Common Mistakes:

    • Matching against the . wild card character or any other regex characters

      Remember to escape the specific characters with a \ prefix

    • Only matching against lower/upper case characters

      Try using either a-Z or \w instead of a-z or A-Z

  • Check that pattern you're matching is included within the patterns tried

    If it isn't here then its possible that you have forgotten to include your app within the INSTALLED_APPS setting (or the ordering of the apps within INSTALLED_APPS may need looking at)

Django Version

In Django 1.10, the ability to reverse a url by its python path was removed. The named path should be used instead.

If you're still unable to track down the problem, then feel free to ask a new question that includes what you've tried, what you've researched (You can link to this question), and then include the relevant code to the issue - the url that you're matching, any relevant url patterns, the part of the error message that shows what django tried to match, and possibly the INSTALLED_APPS setting if applicable.

.war vs .ear file

JAR Files

A JAR (short for Java Archive) file permits the combination of several files into a single one. Files with the '.jar'; extension are utilized by software developers to distribute Java classes and various metadata. These also hold libraries and resource files, as well as accessory files (such as property files).

Users can extract and create JAR files with Java Development Kit's (JDK) '.jar' command. ZIP tools may also be used.

JAR files have optional manifest files. Entries within the manifest file prescribe the JAR file's use. A 'main' class specification for a file class denotes the file as a detached or ‘stand-alone' program.

WAR Files

A WAR (or Web Application archive) files can comprise XML (extensible Markup Language) files, Java classes, as well as Java Server pages for purposes of Internet application. It is also employed to mark libraries and Web pages which make up a Web application. Files with the ‘.war' extension contain the Web app for use with server or JSP (Java Server Page) containers. It has JSP, HTML (Hypertext Markup Language), JavaScript, and various files for creating the aforementioned Web apps.

A WAR file is structured as such to allow for special directories and files. It may also have a digital signature (much like that of a JAR file) to show the veracity of the code.

EAR Files

An EAR (Enterprise Archive) file merges JAR and WAR files into a single archive. These files with the ‘.ear' extension have a directory for metadata. The modules are packaged into on archive for smooth and simultaneous operation of the different modules within an app server.

The EAR file also has deployment descriptors (which are XML files) which effectively dictate the deployment of the different modules.

enter image description here

How to end a session in ExpressJS

The question didn't clarify what type of session store was being used. Both answers seem to be correct.

For cookie based sessions:


req.session = null // Deletes the cookie.

For Redis, etc based sessions:

req.session.destroy // Deletes the session in the database.

Multiple actions were found that match the request in Web Api

It is possible due to using MVC controller instead of Web API controller. Check the namespace in Web API controller it should be as following

using System.Net;
using System.Net.Http;
using System.Web.Http;

If the namespace are as following then it is give above error in web api controller method calling

using System.Web;
using System.Web.Mvc;

UTC Date/Time String to Timezone

How about:

$timezone = new DateTimeZone('UTC');
$date = new DateTime('2011-04-21 13:14', $timezone);
echo $date->format;

The PowerShell -and conditional operator

Another option:

if( ![string]::IsNullOrEmpty($user_sam) -and ![string]::IsNullOrEmpty($user_case) )

How do I lowercase a string in Python?

Also, you can overwrite some variables:

s = input('UPPER CASE')
lower = s.lower()

If you use like this:

s = "Kilometer"
print(s.lower())     - kilometer
print(s)             - Kilometer

It will work just when called.

Using Node.JS, how do I read a JSON file into (server) memory?

Asynchronous is there for a reason! Throws stone at @mihai

Otherwise, here is the code he used with the asynchronous version:

// Declare variables
var fs = require('fs'),

// Read the file and send to the callback
fs.readFile('path/to/file', handleFile)

// Write the callback function
function handleFile(err, data) {
    if (err) throw err
    obj = JSON.parse(data)
    // You can now play with your datas

Format an Integer using Java String Format

String.format("%03d", 1)  // => "001"
//              ¦¦¦   +-- print the number one
//              ¦¦+------ ... as a decimal integer
//              ¦+------- ... minimum of 3 characters wide
//              +-------- ... pad with zeroes instead of spaces

See java.util.Formatter for more information.

Rails Active Record find(:all, :order => ) issue

The problem is that date is a reserved sqlite3 keyword. I had a similar problem with time, also a reserved keyword, which worked fine in PostgreSQL, but not in sqlite3. The solution is renaming the column.

See this: Sqlite3 activerecord :order => "time DESC" doesn't sort

What's the shebang/hashbang (#!) in Facebook and new Twitter URLs for?

The octothorpe/number-sign/hashmark has a special significance in an URL, it normally identifies the name of a section of a document. The precise term is that the text following the hash is the anchor portion of an URL. If you use Wikipedia, you will see that most pages have a table of contents and you can jump to sections within the document with an anchor, such as: identifies the page and Early_computers_and_the_Turing_test is the anchor. The reason that Facebook and other Javascript-driven applications (like my own Wood & Stones) use anchors is that they want to make pages bookmarkable (as suggested by a comment on that answer) or support the back button without reloading the entire page from the server.

In order to support bookmarking and the back button, you need to change the URL. However, if you change the page portion (with something like window.location = '';) to a different URL or without specifying an anchor, the browser will load the entire page from the URL. Try this in Firebug or Safari's Javascript console. Load Now in the Javascript console, type:

window.location = '';

You will see the page refresh from the server. Now type:

window.location = '';

Aha! No page refresh! Type:

window.location = '';

Still no refresh. Use the back button to see that these URLs are in the browser history. The browser notices that we are on the same page but just changing the anchor, so it doesn't reload. Thanks to this behaviour, we can have a single Javascript application that appears to the browser to be on one 'page' but to have many bookmarkable sections that respect the back button. The application must change the anchor when a user enters different 'states', and likewise if a user uses the back button or a bookmark or a link to load the application with an anchor included, the application must restore the appropriate state.

So there you have it: Anchors provide Javascript programmers with a mechanism for making bookmarkable, indexable, and back-button-friendly applications. This technique has a name: It is a Single Page Interface.

p.s. There is a fourth benefit to this technique: Loading page content through AJAX and then injecting it into the current DOM can be much faster than loading a new page. In addition to the speed increase, further tricks like loading certain portions in the background can be performed under the programmer's control.

p.p.s. Given all of that, the 'bang' or exclamation mark is a further hint to Google's web crawler that the exact same page can be loaded from the server at a slightly different URL. See Ajax Crawling. Another technique is to make each link point to a server-accessible URL and then use unobtrusive Javascript to change it into an SPI with an anchor.

Here's the key link again: The Single Page Interface Manifesto

Change a HTML5 input's placeholder color with CSS

In the html file:

<input type="text" placeholder="placeholder" class="redPlaceHolder">

In the css file:

   color: #ff0000;

Why compile Python code?

It's compiled to bytecode which can be used much, much, much faster.

The reason some files aren't compiled is that the main script, which you invoke with python is recompiled every time you run the script. All imported scripts will be compiled and stored on the disk.

Important addition by Ben Blank:

It's worth noting that while running a compiled script has a faster startup time (as it doesn't need to be compiled), it doesn't run any faster.

Does a foreign key automatically create an index?

A foreign key is a constraint, a relationship between two tables - that has nothing to do with an index per se.

But it is a known fact that it makes a lot of sense to index all the columns that are part of any foreign key relationship, because through a FK-relationship, you'll often need to lookup a relating table and extract certain rows based on a single value or a range of values.

So it makes good sense to index any columns involved in a FK, but a FK per se is not an index.

Check out Kimberly Tripp's excellent article "When did SQL Server stop putting indexes on Foreign Key columns?".

Listing all permutations of a string/integer

If performance and memory is an issue, I suggest this very efficient implementation. According to Heap's algorithm in Wikipedia, it should be the fastest. Hope it will fits your need :-) !

Just as comparison of this with a Linq implementation for 10! (code included):

  • This: 36288000 items in 235 millisecs
  • Linq: 36288000 items in 50051 millisecs

    using System;
    using System.Collections.Generic;
    using System.Diagnostics;
    using System.Linq;
    using System.Runtime.CompilerServices;
    using System.Text;
    namespace WpfPermutations
        /// <summary>
        /// EO: 2016-04-14
        /// Generator of all permutations of an array of anything.
        /// Base on Heap's Algorithm. See:
        /// </summary>
        public static class Permutations
            /// <summary>
            /// Heap's algorithm to find all pmermutations. Non recursive, more efficient.
            /// </summary>
            /// <param name="items">Items to permute in each possible ways</param>
            /// <param name="funcExecuteAndTellIfShouldStop"></param>
            /// <returns>Return true if cancelled</returns> 
            public static bool ForAllPermutation<T>(T[] items, Func<T[], bool> funcExecuteAndTellIfShouldStop)
                int countOfItem = items.Length;
                if (countOfItem <= 1)
                    return funcExecuteAndTellIfShouldStop(items);
                var indexes = new int[countOfItem];
                for (int i = 0; i < countOfItem; i++)
                    indexes[i] = 0;
                if (funcExecuteAndTellIfShouldStop(items))
                    return true;
                for (int i = 1; i < countOfItem;)
                    if (indexes[i] < i)
                    { // On the web there is an implementation with a multiplication which should be less efficient.
                        if ((i & 1) == 1) // if (i % 2 == 1)  ... more efficient ??? At least the same.
                            Swap(ref items[i], ref items[indexes[i]]);
                            Swap(ref items[i], ref items[0]);
                        if (funcExecuteAndTellIfShouldStop(items))
                            return true;
                        i = 1;
                        indexes[i++] = 0;
                return false;
            /// <summary>
            /// This function is to show a linq way but is far less efficient
            /// </summary>
            /// <typeparam name="T"></typeparam>
            /// <param name="list"></param>
            /// <param name="length"></param>
            /// <returns></returns>
            static IEnumerable<IEnumerable<T>> GetPermutations<T>(IEnumerable<T> list, int length)
                if (length == 1) return list.Select(t => new T[] { t });
                return GetPermutations(list, length - 1)
                    .SelectMany(t => list.Where(e => !t.Contains(e)),
                        (t1, t2) => t1.Concat(new T[] { t2 }));
            /// <summary>
            /// Swap 2 elements of same type
            /// </summary>
            /// <typeparam name="T"></typeparam>
            /// <param name="a"></param>
            /// <param name="b"></param>
            static void Swap<T>(ref T a, ref T b)
                T temp = a;
                a = b;
                b = temp;
            /// <summary>
            /// Func to show how to call. It does a little test for an array of 4 items.
            /// </summary>
            public static void Test()
                ForAllPermutation("123".ToCharArray(), (vals) =>
                    Debug.Print(String.Join("", vals));
                    return false;
                int[] values = new int[] { 0, 1, 2, 4 };
                Debug.Print("Non Linq");
                ForAllPermutation(values, (vals) =>
                    Debug.Print(String.Join("", vals));
                    return false;
                foreach(var v in GetPermutations(values, values.Length))
                    Debug.Print(String.Join("", v));
                // Performance
                int count = 0;
                values = new int[10];
                for(int n = 0; n < values.Length; n++)
                    values[n] = n;
                Stopwatch stopWatch = new Stopwatch();
                ForAllPermutation(values, (vals) =>
                    foreach(var v in vals)
                    return false;
                Debug.Print($"Non Linq {count} items in {stopWatch.ElapsedMilliseconds} millisecs");
                count = 0;
                foreach (var vals in GetPermutations(values, values.Length))
                    foreach (var v in vals)
                Debug.Print($"Linq {count} items in {stopWatch.ElapsedMilliseconds} millisecs");

JavaScript Nested function

Functions are another type of variable in JavaScript (with some nuances of course). Creating a function within another function changes the scope of the function in the same way it would change the scope of a variable. This is especially important for use with closures to reduce total global namespace pollution.

The functions defined within another function won't be accessible outside the function unless they have been attached to an object that is accessible outside the function:

function foo(doBar)
  function bar()
    console.log( 'bar' );

  function baz()
    console.log( 'baz' );

  window.baz = baz;
  if ( doBar ) bar();

In this example, the baz function will be available for use after the foo function has been run, as it's overridden window.baz. The bar function will not be available to any context other than scopes contained within the foo function.

as a different example:

function Fizz(qux)
{ = function(){
    console.log( qux );

The Fizz function is designed as a constructor so that, when run, it assigns a buzz function to the newly created object.

Is null reference possible?

References are not pointers.


A reference shall be initialized to refer to a valid object or function. [Note: in particular, a null reference cannot exist in a well-defined program, because the only way to create such a reference would be to bind it to the “object” obtained by dereferencing a null pointer, which causes undefined behavior. As described in 9.6, a reference cannot be bound directly to a bit-field. ]


Certain other operations are described in this International Standard as undefined (for example, the effect of dereferencing the null pointer)

As Johannes says in a deleted answer, there's some doubt whether "dereferencing a null pointer" should be categorically stated to be undefined behavior. But this isn't one of the cases that raise doubts, since a null pointer certainly does not point to a "valid object or function", and there is no desire within the standards committee to introduce null references.

Use curly braces to initialize a Set in Python

Compare also the difference between {} and set() with a single word argument.

>>> a = set('aardvark')
>>> a
{'d', 'v', 'a', 'r', 'k'} 
>>> b = {'aardvark'}
>>> b

but both a and b are sets of course.

Find all tables containing column with specified name - MS SQL Server

i have just tried it and this works perfectly

USE YourDatabseName
SELECT AS table_name,
SCHEMA_NAME(schema_id) AS schema_name, AS column_name
FROM sys.tables AS t
WHERE LIKE '%YourColumnName%'
ORDER BY schema_name, table_name;

Only change YourDatbaseName to your database and YourcolumnName to your column name that you are looking for the rest keep it as it is.

Hope this has helped

How to create cron job using PHP?

Added to Alister, you can edit the crontab usually (not always the case) by entering crontab -e in a ssh session on the server.

The stars represent (* means every of this unit):

[Minute] [Hour] [Day] [Month] [Day of week (0 =sunday to 6 =saturday)] [Command]

You could read some more about this here.

How to use shell commands in Makefile


FILES = $(shell ls)

indented underneath all like that, it's a build command. So this expands $(shell ls), then tries to run the command FILES ....

If FILES is supposed to be a make variable, these variables need to be assigned outside the recipe portion, e.g.:

FILES = $(shell ls)
        echo $(FILES)

Of course, that means that FILES will be set to "output from ls" before running any of the commands that create the .tgz files. (Though as Kaz notes the variable is re-expanded each time, so eventually it will include the .tgz files; some make variants have FILES := ... to avoid this, for efficiency and/or correctness.1)

If FILES is supposed to be a shell variable, you can set it but you need to do it in shell-ese, with no spaces, and quoted:

        FILES="$(shell ls)"

However, each line is run by a separate shell, so this variable will not survive to the next line, so you must then use it immediately:

        FILES="$(shell ls)"; echo $$FILES

This is all a bit silly since the shell will expand * (and other shell glob expressions) for you in the first place, so you can just:

        echo *

as your shell command.

Finally, as a general rule (not really applicable to this example): as esperanto notes in comments, using the output from ls is not completely reliable (some details depend on file names and sometimes even the version of ls; some versions of ls attempt to sanitize output in some cases). Thus, as l0b0 and idelic note, if you're using GNU make you can use $(wildcard) and $(subst ...) to accomplish everything inside make itself (avoiding any "weird characters in file name" issues). (In sh scripts, including the recipe portion of makefiles, another method is to use find ... -print0 | xargs -0 to avoid tripping over blanks, newlines, control characters, and so on.)

1The GNU Make documentation notes further that POSIX make added ::= assignment in 2012. I have not found a quick reference link to a POSIX document for this, nor do I know off-hand which make variants support ::= assignment, although GNU make does today, with the same meaning as :=, i.e., do the assignment right now with expansion.

Note that VAR := $(shell command args...) can also be spelled VAR != command args... in several make variants, including all modern GNU and BSD variants as far as I know. These other variants do not have $(shell) so using VAR != command args... is superior in both being shorter and working in more variants.

Sort array of objects by object fields

You can use usort, like this:

    return strcmp($first->name, $second->name);

How to override the [] operator in Python?

You need to use the __getitem__ method.

class MyClass:
    def __getitem__(self, key):
        return key * 2

myobj = MyClass()
myobj[3] #Output: 6

And if you're going to be setting values you'll need to implement the __setitem__ method too, otherwise this will happen:

>>> myobj[5] = 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: MyClass instance has no attribute '__setitem__'

How do I remove leading whitespace in Python?

The lstrip() method will remove leading whitespaces, newline and tab characters on a string beginning:

>>> '     hello world!'.lstrip()
'hello world!'


As balpha pointed out in the comments, in order to remove only spaces from the beginning of the string, lstrip(' ') should be used:

>>> '   hello world with 2 spaces and a tab!'.lstrip(' ')
'\thello world with 2 spaces and a tab!'

Related question:

When should I use curly braces for ES6 import?

If you think of import as just syntax sugar for Node.js modules, objects, and destructuring, I find it's pretty intuitive.

// bar.js
module = {};

module.exports = {
  functionA: () => {},
  functionB: ()=> {}

 // Really all that is is this:
 var module = {
   exports: {
      functionA, functionB

// Then, over in foo.js

// The whole exported object:
var fump = require('./bar.js'); //= { functionA, functionB }
// Or
import fump from './bar' // The same thing - object functionA and functionB properties

// Just one property of the object
var fump = require('./bar.js').functionA;

// Same as this, right?
var fump = { functionA, functionB }.functionA;

// And if we use ES6 destructuring:
var { functionA } =  { functionA, functionB };
// We get same result

// So, in import syntax:
import { functionA } from './bar';

PHP mPDF save file as PDF

The mPDF docs state that the first argument of Output() is the file path, second is the saving mode - you need to set it to 'F'.


How can I change the text color with jQuery?

Or you may do the following


But you need to download the color plugin from here.

c++ array - expression must have a constant value

When creating an array like that, its size must be constant. If you want a dynamically sized array, you need to allocate memory for it on the heap and you'll also need to free it with delete when you're done:

//allocate the array
int** arr = new int*[row];
for(int i = 0; i < row; i++)
    arr[i] = new int[col];

// use the array

//deallocate the array
for(int i = 0; i < row; i++)
    delete[] arr[i];
delete[] arr;

If you want a fixed size, then they must be declared const:

const int row = 8;
const int col = 8;
int arr[row][col];


int [row][col];

doesn't even provide a variable name.

Write to custom log file from a Bash script

I did it by using a filter. Most linux systems use rsyslog these days. The config files are located at /etc/rsyslog.conf and /etc/rsyslog.d.

Whenever I run the command logger -t SRI some message, I want "some message" to only show up in /var/log/sri.log.

To do this I added the file /etc/rsyslog.d/00-sri.conf with the following content.

# Filter all messages whose tag starts with SRI
# Note that 'isequal, "SRI:"' or 'isequal "SRI"' will not work.
:syslogtag, startswith, "SRI" /var/log/sri.log

# The stop command prevents this message from getting processed any further.
# Thus the message will not show up in /var/log/messages.
& stop

Then restart the rsyslogd service:

systemctl restart rsyslog.service

Here is a shell session showing the results:

[root@rpm-server html]# logger -t SRI Hello World!
[root@rpm-server html]# cat /var/log/sri.log
Jun  5 10:33:01 rpm-server SRI[11785]: Hello World!
[root@rpm-server html]#
[root@rpm-server html]# # see that nothing shows up in /var/log/messages
[root@rpm-server html]# tail -10 /var/log/messages | grep SRI
[root@rpm-server html]#

End of File (EOF) in C

That's a lot of questions.

  1. Why EOF is -1: usually -1 in POSIX system calls is returned on error, so i guess the idea is "EOF is kind of error"

  2. any boolean operation (including !=) returns 1 in case it's TRUE, and 0 in case it's FALSE, so getchar() != EOF is 0 when it's FALSE, meaning getchar() returned EOF.

  3. in order to emulate EOF when reading from stdin press Ctrl+D

How to restrict UITextField to take only numbers in Swift?

I have edited Raj Joshi's version to allow one dot or one comma:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let inverseSet = CharacterSet(charactersIn:"0123456789").inverted
    let components = string.components(separatedBy: inverseSet)
    let filtered = components.joined(separator: "")

    if filtered == string {
        return true
    } else {
        if string == "." || string == "," {
            let countDots = textField.text!.components(separatedBy:".").count - 1
            let countCommas = textField.text!.components(separatedBy:",").count - 1

            if countDots == 0 && countCommas == 0 {
                return true
            } else {
                return false
        } else  {
            return false

Import CSV to mysql table

First create a table in the database with same numbers of columns that are in the csv file.

Then use following query

LOAD DATA INFILE 'D:/Projects/testImport.csv' INTO TABLE cardinfo

100% width table overflowing div container

Well, given your constraints, I think setting overflow: scroll; on the .page div is probably your only option. 280 px is pretty narrow, and given your font size, word wrapping alone isn't going to do it. Some words are just long and can't be wrapped. You can either reduce your font size drastically or go with overflow: scroll.

How to convert image file data in a byte array to a Bitmap?

Just try this:

Bitmap bitmap = BitmapFactory.decodeFile("/path/images/image.jpg");
ByteArrayOutputStream blob = new ByteArrayOutputStream();
bitmap.compress(CompressFormat.PNG, 0 /* Ignored for PNGs */, blob);
byte[] bitmapdata = blob.toByteArray();

If bitmapdata is the byte array then getting Bitmap is done like this:

Bitmap bitmap = BitmapFactory.decodeByteArray(bitmapdata, 0, bitmapdata.length);

Returns the decoded Bitmap, or null if the image could not be decoded.

How to configure PHP to send e-mail?

To fix this, you must review your PHP.INI, and the mail services setup you have in your server.

But my best advice for you is to forget about the mail() function. It depends on PHP.INI settings, it's configuration is different depending on the platform (Linux or Windows), and it can't handle SMTP authentication, which is a big trouble in current days. Too much headache.

Use "PHP Mailer" instead (, it's a PHP class available for free, and it can handle almost any SMTP server, internal or external, with or without authentication, it works exactly the same way on Linux and Windows, and it won't depend on PHP.INI settings. It comes with many examples, it's very powerful and easy to use.

How to copy a file along with directory structure/path using python?

To create all intermediate-level destination directories you could use os.makedirs() before copying:

import os
import shutil

srcfile = 'a/long/long/path/to/'
dstroot = '/home/myhome/new_folder'

assert not os.path.isabs(srcfile)
dstdir =  os.path.join(dstroot, os.path.dirname(srcfile))

os.makedirs(dstdir) # create all directories, raise an error if it already exists
shutil.copy(srcfile, dstdir)

Convert string to date in Swift

  • Convert the ISO8601 string to date

    let isoDate = "2016-04-14T10:44:00+0000"
    let dateFormatter = DateFormatter()
    dateFormatter.locale = Locale(identifier: "en_US_POSIX") // set locale to reliable US_POSIX
    dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
    let date =!
  • Get the date components for year, month, day and hour from the date

    let calendar = Calendar.current
    let components = calendar.dateComponents([.year, .month, .day, .hour], from: date)
  • Finally create a new Date object and strip minutes and seconds

    let finalDate =

Consider also the convenience formatter ISO8601DateFormatter introduced in iOS 10 / macOS 12:

let isoDate = "2016-04-14T10:44:00+0000"

let dateFormatter = ISO8601DateFormatter()
let date =!

How can I get input radio elements to horizontally align?

This also works like a charm

    <label class="radio-inline">_x000D_
      <input type="radio" name="optradio" checked>Option 1_x000D_
    <label class="radio-inline">_x000D_
      <input type="radio" name="optradio">Option 2_x000D_
    <label class="radio-inline">_x000D_
      <input type="radio" name="optradio">Option 3_x000D_

How to show the "Are you sure you want to navigate away from this page?" when changes committed?

The standard states that prompting can be controlled by canceling the beforeunload event or setting the return value to a non-null value. It also states that authors should use Event.preventDefault() instead of returnValue, and the message shown to the user is not customizable.

As of 69.0.3497.92, Chrome has not met the standard. However, there is a bug report filed, and a review is in progress. Chrome requires returnValue to be set by reference to the event object, not the value returned by the handler.

It is the author's responsibility to track whether changes have been made; it can be done with a variable or by ensuring the event is only handled when necessary.

window.addEventListener('beforeunload', function (e) {_x000D_
    // Cancel the event as stated by the standard._x000D_
    // Chrome requires returnValue to be set._x000D_
    e.returnValue = '';_x000D_
window.location = 'about:blank';

Error related to only_full_group_by when executing a query in MySql

I am using Laravel 5.3, mysql 5.7.12, on laravel homestead (0.5.0, I believe)

Even after explicitly setting editing /etc/mysql/my.cnf to reflect:


I was still receiving the error.

I had to change config/database.php from true to false:

    'mysql' => [
        'strict' => false, //behave like 5.6
        //'strict' => true //behave like 5.7

Further reading:

Top 5 time-consuming SQL queries in Oracle

You could find disk intensive full table scans with something like this:

SELECT Disk_Reads DiskReads, Executions, SQL_ID, SQL_Text SQLText, 
   SQL_FullText SQLFullText 
   SELECT Disk_Reads, Executions, SQL_ID, LTRIM(SQL_Text) SQL_Text, 
      SQL_FullText, Operation, Options, 
      Row_Number() OVER 
         (Partition By sql_text ORDER BY Disk_Reads * Executions DESC) 
       SELECT Avg(Disk_Reads) OVER (Partition By sql_text) Disk_Reads, 
          Max(Executions) OVER (Partition By sql_text) Executions, 
          t.SQL_ID, sql_text, sql_fulltext, p.operation,p.options
       FROM v$sql t, v$sql_plan p
       WHERE t.hash_value=p.hash_value AND p.operation='TABLE ACCESS' 
       AND p.options='FULL' AND p.object_owner NOT IN ('SYS','SYSTEM')
       AND t.Executions > 1
WHERE KeepHighSQL = 1
AND rownum <=5;

Composer install error - requires ext_curl when it's actually enabled

I have Archlinux with php 7.2, which has Curl integrated, so no amount of configuration voodoo would make Composer see ext-curl, that PHP could see and work with happily. Work around is to use Composer with --ignore-platform-reqs.

eg composer update --ignore-platform-reqs

Reference =