Programs & Examples On #Libav

libav (or libav*) is the collective name of the FFmpeg libraries: libavcodec, libavformat, libavfilter, libavutil, etc. The name has also been appropriated by the Libav project–a fork of FFmpeg.

What are the differences and similarities between ffmpeg, libav, and avconv?

Confusing messages

These messages are rather misleading and understandably a source of confusion. Older Ubuntu versions used Libav which is a fork of the FFmpeg project. FFmpeg returned in Ubuntu 15.04 "Vivid Vervet".

The fork was basically a non-amicable result of conflicting personalities and development styles within the FFmpeg community. It is worth noting that the maintainer for Debian/Ubuntu switched from FFmpeg to Libav on his own accord due to being involved with the Libav fork.

The real ffmpeg vs the fake one

For a while both Libav and FFmpeg separately developed their own version of ffmpeg.

Libav then renamed their bizarro ffmpeg to avconv to distance themselves from the FFmpeg project. During the transition period the "not developed anymore" message was displayed to tell users to start using avconv instead of their counterfeit version of ffmpeg. This confused users into thinking that FFmpeg (the project) is dead, which is not true. A bad choice of words, but I can't imagine Libav not expecting such a response by general users.

This message was removed upstream when the fake "ffmpeg" was finally removed from the Libav source, but, depending on your version, it can still show up in Ubuntu because the Libav source Ubuntu uses is from the ffmpeg-to-avconv transition period.

In June 2012, the message was re-worded for the package libav - 4:0.8.3-0ubuntu0.12.04.1. Unfortunately the new "deprecated" message has caused additional user confusion.

Starting with Ubuntu 15.04 "Vivid Vervet", FFmpeg's ffmpeg is back in the repositories again.

libav vs Libav

To further complicate matters, Libav chose a name that was historically used by FFmpeg to refer to its libraries (libavcodec, libavformat, etc). For example the libav-user mailing list, for questions and discussions about using the FFmpeg libraries, is unrelated to the Libav project.

How to tell the difference

If you are using avconv then you are using Libav. If you are using ffmpeg you could be using FFmpeg or Libav. Refer to the first line in the console output to tell the difference: the copyright notice will either mention FFmpeg or Libav.

Secondly, the version numbering schemes differ. Each of the FFmpeg or Libav libraries contains a version.h header which shows a version number. FFmpeg will end in three digits, such as 57.67.100, and Libav will end in one digit such as 57.67.0. You can also view the library version numbers by running ffmpeg or avconv and viewing the console output.

If you want to use the real ffmpeg

Ubuntu 15.04 "Vivid Vervet" or newer

The real ffmpeg is in the repository, so you can install it with:

apt-get install ffmpeg

For older Ubuntu versions

Your options are:

These methods are non-intrusive, reversible, and will not interfere with the system or any repository packages.

Another possible option is to upgrade to Ubuntu 15.04 "Vivid Vervet" or newer and just use ffmpeg from the repository.

Also see

For an interesting blog article on the situation, as well as a discussion about the main technical differences between the projects, see The FFmpeg/Libav situation.

Eclipse: How to install a plugin manually?

  1. Download your plugin
  2. Open Eclipse
  3. From the menu choose: Help / Install New Software...
  4. Click the Add button
  5. In the Add Repository dialog that appears, click the Archive button next to the Location field
  6. Select your plugin file, click OK

You could also just copy plugins to the eclipse/plugins directory, but it's not recommended.

target="_blank" vs. target="_new"

The use of _New is useful when working on pages that are Iframed. Since target="_blank" doesn't do the trick and opens the page on the same iframe... target new is the best solution for Iframe Pages. Just my five cents.

In Perl, how to remove ^M from a file?

To convert DOS style to UNIX style line endings:

for ($line in <FILEHANDLE>) {
   $line =~ s/\r\n$/\n/;

Or, to remove UNIX and/or DOS style line endings:

for ($line in <FILEHANDLE>) {
   $line =~ s/\r?\n$//;

How to get input from user at runtime

you can try this too And it will work:

  a :=: a; --this will take input from user
  b :=: b;
  DBMS_OUTPUT.PUT_LINE('a = '|| a);
  DBMS_OUTPUT.PUT_LINE('b = '|| b);

Cross-Origin Request Blocked

You have to placed this code in application.rb

config.action_dispatch.default_headers = {
        'Access-Control-Allow-Origin' => '*',
        'Access-Control-Request-Method' => %w{GET POST OPTIONS}.join(",")

ORA-06550: line 1, column 7 (PL/SQL: Statement ignored) Error

If the value stored in PropertyLoader.RET_SECONDARY_V_ARRAY is not "V_ARRAY", then you are using different types; even if they are declared identically (e.g. both are table of number) this will not work.

You're hitting this data type compatibility restriction:

You can assign a collection to a collection variable only if they have the same data type. Having the same element type is not enough.

You're trying to call the procedure with a parameter that is a different type to the one it's expecting, which is what the error message is telling you.

How to remove leading and trailing zeros in a string? Python

You can simply do this with a bool:

if int(number) == float(number):

   number = int(number)


   number = float(number)

C function that counts lines in file

You're opening a file, then passing the file pointer to a function that only wants a file name to open the file itself. You can simplify your call to;

void main(void)
  printf("LINES: %d\n",countlines("Test.txt"));

EDIT: You're changing the question around so it's very hard to answer; at first you got your change to main() wrong, you forgot that the first parameter is argc, so it crashed. Now you have the problem of;

if (fp == NULL);   // <-- note the extra semicolon that is the only thing 
                   //     that runs conditionally on the if 
  return 0;        // Always runs and returns 0

which will always return 0. Remove that extra semicolon, and you should get a reasonable count.

How to kill a process running on particular port in Linux?

to build on what @veer7 said:

if you want to know what was on the port, do this before you kill it.

$ sudo netstat -plten |grep java
tcp6       0      0          :::*                    LISTEN      1000       906726      25296/java      
tcp6       0      0 :::8009                 :::*                    LISTEN      1000       907503      25296/java      
tcp6       0      0 :::8080                 :::*                    LISTEN      1000       907499      25296/java      
$ ps 25296
25296 ?        Sl     0:16 /usr/lib/jvm/java-8-openjdk-amd64/bin/java -Dcatalina.base=/hom

Use 'ps' and the number of the process that netstat reported back

How to split a large text file into smaller files with equal number of lines?

HDFS getmerge small file and spilt into property size.

This method will cause line break

split -b 125m compact.file -d -a 3 compact_prefix

I try to getmerge and split into about 128MB every file.

# split into 128m ,judge sizeunit is M or G ,please test before use.

begainsize=`hdfs dfs -du -s -h /externaldata/$table_name/$date/ | awk '{ print $1}' `
sizeunit=`hdfs dfs -du -s -h /externaldata/$table_name/$date/ | awk '{ print $2}' `
if [ $sizeunit = "G" ];then
    res=$(printf "%.f" `echo "scale=5;$begainsize*8 "|bc`)
    res=$(printf "%.f" `echo "scale=5;$begainsize/128 "|bc`)  # celling ref
echo $res
# split into $res files with number suffix.  ref
echo "compact_file_name :"$compact_file_name
split -n l/$res $basedir/$compact_file -d -a 3 $basedir/${compact_file_name}

Finding element in XDocument?

My experience when working with large & complicated XML files is that sometimes neither Elements nor Descendants seem to work in retrieving a specific Element (and I still do not know why).

In such cases, I found that a much safer option is to manually search for the Element, as described by the following MSDN post:

In short, you can create a GetElement function:

private XElement GetElement(XDocument doc,string elementName)
    foreach (XNode node in doc.DescendantNodes())
        if (node is XElement)
            XElement element = (XElement)node;
            if (element.Name.LocalName.Equals(elementName))
                return element;
    return null;

Which you can then call like this:

XElement element = GetElement(doc,"Band");

Note that this will return null if no matching element is found.

How to determine if .NET Core is installed

Run this command

dotnet --list-sdks

enter image description here

How to get a table creation script in MySQL Workbench?

To get an individual table's creation script just right click on the table name and click Copy to Clipboard > Create Statement.

To enable the File > Forward Engineering SQL_CREATE Script.. option and to get the creation script for your entire database :

  1. Database > Reverse Engineer (Ctrl+R)
  2. Go through the steps to create the EER Diagram
  3. When viewing the EER Diagram click File > Forward Engineering SQL_CREATE Script... (Ctrl+Shift+G)

How to get the day of week and the month of the year?

  function currentDate() {
      var monthNames = [ "JANUARY", "FEBRUARY", "MARCH", "APRIL", "MAY", "JUNE",
                     "JULY", "AUGUST", "SEPTEMBER", "OCTOBER", "NOVEMBER", "DECEMBER" ];
      var days = ['SUNDAY','MONDAY','TUESDAY','WEDNESDAY','THURSDAY','FRIDAY','SATURDAY'];                       
      var today = new Date();
      var dd   = today.getDate();
      var mm   = monthNames[today.getMonth()]; 
      var yyyy = today.getFullYear();
      var day  = days[today.getDay()];
      today = 'Date is :' + dd + '-' + mm + '-' + yyyy;
      document.write(today +"<br>");
      document.write('Day is : ' + day );


    itemid INT(10)UNSIGNED,
    itemname VARCHAR(50)





I was confused with CHANGE and MODIFY keywords before too:



While we are there, also note that AUTO_INCREMENT can also start with a predefined number:


How to delete/remove nodes on Firebase

The problem is that you call remove on the root of your Firebase:

ref = new Firebase("")

This will remove the entire Firebase through the API.

You'll typically want to remove specific child nodes under it though, which you do with:


"Cloning" row or column vectors

One clean solution is to use NumPy's outer-product function with a vector of ones:

np.outer(np.ones(n), x)

gives n repeating rows. Switch the argument order to get repeating columns. To get an equal number of rows and columns you might do

np.outer(np.ones_like(x), x)

How to detect Windows 64-bit platform with .NET?

UPDATE: As Joel Coehoorn and others suggest, starting at .NET Framework 4.0, you can just check Environment.Is64BitOperatingSystem.

IntPtr.Size won't return the correct value if running in 32-bit .NET Framework 2.0 on 64-bit Windows (it would return 32-bit).

As Microsoft's Raymond Chen describes, you have to first check if running in a 64-bit process (I think in .NET you can do so by checking IntPtr.Size), and if you are running in a 32-bit process, you still have to call the Win API function IsWow64Process. If this returns true, you are running in a 32-bit process on 64-bit Windows.

Microsoft's Raymond Chen: How to detect programmatically whether you are running on 64-bit Windows

My solution:

static bool is64BitProcess = (IntPtr.Size == 8);
static bool is64BitOperatingSystem = is64BitProcess || InternalCheckIsWow64();

[DllImport("kernel32.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool IsWow64Process(
    [In] IntPtr hProcess,
    [Out] out bool wow64Process

public static bool InternalCheckIsWow64()
    if ((Environment.OSVersion.Version.Major == 5 && Environment.OSVersion.Version.Minor >= 1) ||
        Environment.OSVersion.Version.Major >= 6)
        using (Process p = Process.GetCurrentProcess())
            bool retVal;
            if (!IsWow64Process(p.Handle, out retVal))
                return false;
            return retVal;
        return false;

How to render string with html tags in Angular 4+?

Use one way flow syntax property binding:

<div [innerHTML]="comment"></div>

From angular docs: "Angular recognizes the value as unsafe and automatically sanitizes it, which removes the <script> tag but keeps safe content such as the <b> element."

How to set HTML5 required attribute in Javascript?

And the jquery version:

$('input').attr('required', true)
$('input').attr('required', false)

I know it's beyond the question, but maybe someone will find this helpful :)

LEFT JOIN in LINQ to entities?

You can use this not only in entities but also store procedure or other data source:

var customer = (from cus in _billingCommonservice.BillingUnit.CustomerRepository.GetAll()  
                          join man in _billingCommonservice.BillingUnit.FunctionRepository.ManagersCustomerValue()  
                          on cus.CustomerID equals man.CustomerID  
                          // start left join  
                          into a  
                          from b in a.DefaultIfEmpty(new DJBL_uspGetAllManagerCustomer_Result() )  
                          select new { cus.MobileNo1,b.ActiveStatus });  

Get current date in DD-Mon-YYY format in JavaScript/Jquery

Here's a simple solution, using TypeScript:

  convertDateStringToDate(dateStr) {
    //  Convert a string like '2020-10-04T00:00:00' into '4/Oct/2020'
    let months = ['Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec'];
    let date = new Date(dateStr);
    let str = date.getDate()
                + '/' + months[date.getMonth()]
                + '/' + date.getFullYear()
    return str;

(Yeah, I know the question was about JavaScript, but I'm sure I won't be the only Angular developer coming across this article !)

Adding subscribers to a list using Mailchimp's API v3

These are good answers but detached from a full answer as to how you would get a form to send data and handle that response. This will demonstrate how to add a member to a list with v3.0 of the API from an HTML page via jquery .ajax().

In Mailchimp:

  1. Acquire your API Key and List ID
  2. Make sure you setup your list and what custom fields you want to use with it. In this case, I've set up zipcode as a custom field in the list BEFORE I did the API call.
  3. Check out the API docs on adding members to lists. We are using the create method which requires the use of HTTP POST requests. There are other options in here that require PUT if you want to be able to modify/delete subs.


<form id="pfb-signup-submission" method="post">
  <div class="sign-up-group">
    <input type="text" name="pfb-signup" id="pfb-signup-box-fname" class="pfb-signup-box" placeholder="First Name">
    <input type="text" name="pfb-signup" id="pfb-signup-box-lname" class="pfb-signup-box" placeholder="Last Name">
    <input type="email" name="pfb-signup" id="pfb-signup-box-email" class="pfb-signup-box" placeholder="[email protected]">
    <input type="text" name="pfb-signup" id="pfb-signup-box-zip" class="pfb-signup-box" placeholder="Zip Code">
  <input type="submit" class="submit-button" value="Sign-up" id="pfb-signup-button"></a>
  <div id="pfb-signup-result"></div>

Key things:

  1. Give your <form> a unique ID and don't forget the method="post" attribute so the form works.
  2. Note the last line #signup-result is where you will deposit the feedback from the PHP script.


   * Add a 'member' to a 'list' via mailchimp API v3.x
   * @
   * ================
   * Typical use case is that this code would get run by an .ajax() jQuery call or possibly a form action
   * The live data you need will get transferred via the global $_POST variable
   * That data must be put into an array with keys that match the mailchimp endpoints, check the above link for those
   * You also need to include your API key and list ID for this to work.
   * You'll just have to go get those and type them in here, see
   * ================

  // Set API Key and list ID to add a subscriber
  $api_key = 'your-api-key-here';
  $list_id = 'your-list-id-here';

  /* ================
   * Note: your API URL has a location subdomain at the front of the URL string
   * It can vary depending on where you are in the world
   * To determine yours, check the last 3 digits of your API key
   * ================
  $url = '' . $list_id . '/members/';

  /* ================
   * Encode data into a format that the add subscriber mailchimp end point is looking for
   * Must include 'email_address' and 'status'
   * Statuses: pending = they get an email; subscribed = they don't get an email
   * Custom fields go into the 'merge_fields' as another array
   * More here:
   * ================
  $pfb_data = array(
    'email_address' => $_POST['emailname'],
    'status'        => 'pending',
    'merge_fields'  => array(
      'FNAME'       => $_POST['firstname'],
      'LNAME'       => $_POST['lastname'],
      'ZIPCODE'     => $_POST['zipcode']

  // Encode the data
  $encoded_pfb_data = json_encode($pfb_data);

  // Setup cURL sequence
  $ch = curl_init();

  /* ================
   * The tricky one here is the _USERPWD - this is how you transfer the API key over
   * _RETURNTRANSFER allows us to get the response into a variable which is nice
   * This example just POSTs, we don't edit/modify - just a simple add to a list
   * _POSTFIELDS does the heavy lifting
   * _SSL_VERIFYPEER should probably be set but I didn't do it here
   * ================
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_USERPWD, 'user:' . $api_key);
  curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_TIMEOUT, 10);
  curl_setopt($ch, CURLOPT_POST, 1);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $encoded_pfb_data);
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

  $results = curl_exec($ch); // store response
  $response = curl_getinfo($ch, CURLINFO_HTTP_CODE); // get HTTP CODE
  $errors = curl_error($ch); // store errors


  // Returns info back to jQuery .ajax or just outputs onto the page

  $results = array(
    'results' => $result_info,
    'response' => $response,
    'errors' => $errors

  // Sends data back to the page OR the ajax() in your JS
  echo json_encode($results);

Key things:

  1. CURLOPT_USERPWD handles the API key and Mailchimp doesn't really show you how to do this.
  2. CURLOPT_RETURNTRANSFER gives us the response in such a way that we can send it back into the HTML page with the .ajax() success handler.
  3. Use json_encodeon the data you received.


// Signup form submission
$('#pfb-signup-submission').submit(function(event) {

  // Get data from form and store it
  var pfbSignupFNAME = $('#pfb-signup-box-fname').val();
  var pfbSignupLNAME = $('#pfb-signup-box-lname').val();
  var pfbSignupEMAIL = $('#pfb-signup-box-email').val();
  var pfbSignupZIP = $('#pfb-signup-box-zip').val();

  // Create JSON variable of retreived data
  var pfbSignupData = {
    'firstname': pfbSignupFNAME,
    'lastname': pfbSignupLNAME,
    'email': pfbSignupEMAIL,
    'zipcode': pfbSignupZIP

  // Send data to PHP script via .ajax() of jQuery
    type: 'POST',
    dataType: 'json',
    url: 'mailchimp-signup.php',
    data: pfbSignupData,
    success: function (results) {
      $('#pfb-signup-result').text('Thanks for adding yourself to the email list. We will be in touch.');
    error: function (results) {
      $('#pfb-signup-result').html('<p>Sorry but we were unable to add you into the email list.</p>');

Key things:

  1. JSON data is VERY touchy on transfer. Here, I am putting it into an array and it looks easy. If you are having problems, it is likely because of how your JSON data is structured. Check this out!
  2. The keys for your JSON data will become what you reference in the PHP _POST global variable. In this case it will be _POST['email'], _POST['firstname'], etc. But you could name them whatever you want - just remember what you name the keys of the data part of your JSON transfer is how you access them in PHP.
  3. This obviously requires jQuery ;)

Android Studio Gradle DSL method not found: 'android()' -- Error(17,0)

For some unknown reason, Android Studio incorrectly adds the android() method in the top-level build.gradle file.

Just delete the method and it works for me.

android {
    compileSdkVersion 21
    buildToolsVersion '21.1.2'

read.csv warning 'EOF within quoted string' prevents complete reading of file

I had the similar problem: EOF -warning and only part of data was loading with read.csv(). I tried the quotes="", but it only removed the EOF -warning.

But looking at the first row that was not loading, I found that there was a special character, an arrow ? (hexadecimal value 0x1A) in one of the cells. After deleting the arrow I got the data to load normally.

How to make sql-mode="NO_ENGINE_SUBSTITUTION" permanent in MySQL my.cnf

Just to add my configuration to the mix, I'm using MySQL 5.7.8 which has the same strict sql_mode rules by default.

  • I finally figured the following working in my /etc/mysql/my.conf:


i.e. dash, not underscore and quotes around the value.

  • I have NO other my.conf files other than /etc/mysql/my.conf

  • There are some extra config includes being loaded from /etc/mysql/conf.d/ but they are blank.

And that seems to work for me.

How to start a background process in Python?

While jkp's solution works, the newer way of doing things (and the way the documentation recommends) is to use the subprocess module. For simple commands its equivalent, but it offers more options if you want to do something complicated.

Example for your case:

import subprocess

This will run rm -r some.file in the background. Note that calling .communicate() on the object returned from Popen will block until it completes, so don't do that if you want it to run in the background:

import subprocess
ls_output=subprocess.Popen(["sleep", "30"])
ls_output.communicate()  # Will block for 30 seconds

See the documentation here.

Also, a point of clarification: "Background" as you use it here is purely a shell concept; technically, what you mean is that you want to spawn a process without blocking while you wait for it to complete. However, I've used "background" here to refer to shell-background-like behavior.

Difference between Hashing a Password and Encrypting it

Hashing algorithms are usually cryptographic in nature, but the principal difference is that encryption is reversible through decryption, and hashing is not.

An encryption function typically takes input and produces encrypted output that is the same, or slightly larger size.

A hashing function takes input and produces a typically smaller output, typically of a fixed size as well.

While it isn't possible to take a hashed result and "dehash" it to get back the original input, you can typically brute-force your way to something that produces the same hash.

In other words, if a authentication scheme takes a password, hashes it, and compares it to a hashed version of the requires password, it might not be required that you actually know the original password, only its hash, and you can brute-force your way to something that will match, even if it's a different password.

Hashing functions are typically created to minimize the chance of collisions and make it hard to just calculate something that will produce the same hash as something else.

With form validation: why onsubmit="return functionname()" instead of onsubmit="functionname()"?

HTML event handler code behaves like the body of a JavaScript function. Many languages such as C or Perl implicitly return the value of the last expression evaluated in the function body. JavaScript doesn't, it discards it and returns undefined unless you write an explicit returnEXPR.

Print in Landscape format

you cannot set this in javascript, you have to do this with html/css:

<style type="text/css" media="print">
  @page { size: landscape; }

EDIT: See this Question and the accepted answer for more information on browser support: Is @Page { size:landscape} obsolete?

Symbol for any number of any characters in regex?

You can use this regular expression (any whitespace or any non-whitespace) as many times as possible down to and including 0.


This expression will match as few as possible, but as many as necessary for the rest of the expression.


For example, in this regex [\s\S]*?B will match aB in aBaaaaB. But in this regex [\s\S]*B will match aBaaaaB in aBaaaaB.

Mock MVC - Add Request Parameter to test

When i analyzed your code. I have also faced the same problem but my problem is if i give value for both first and last name means it is working fine. but when i give only one value means it says 400. anyway use the .andDo(print()) method to find out the error

public void testGetUserByName() throws Exception {
    String firstName = "Jack";
    String lastName = "s";       
    this.userClientObject = client.createClient();
            .sessionAttr("userClientObject", this.userClientObject)
            .param("firstName", firstName)
            .param("lastName", lastName)               

If your problem is org.springframework.web.bind.missingservletrequestparameterexception you have to change your code to

@RequestMapping(value = "/byName", method = RequestMethod.GET)
    String getUserByName(
        @RequestParam( value="firstName",required = false) String firstName,
        @RequestParam(value="lastName",required = false) String lastName, 
        @ModelAttribute("userClientObject") UserClient userClient)

        return client.getUserByName(userClient, firstName, lastName);

Call jQuery Ajax Request Each X Minutes

No plugin required. You can use only jquery.

If you want to set something on a timer, you can use JavaScript's setTimeout or setInterval methods:

setTimeout ( expression, timeout );
setInterval ( expression, interval );

Connect Android to WiFi Enterprise network EAP(PEAP)

Thanks for enlightening us Cypawer.

I also tried this app

and it worked flawlessly.

Leap Wifi Connector

How do I get the resource id of an image if I know its name?

Example for a public system resource:

// this will get id for android.R.drawable.ic_dialog_alert
int id = Resources.getSystem().getIdentifier("ic_dialog_alert", "drawable", "android");


Another way is to refer the documentation for android.R.drawable class.

What does random.sample() method in python do?

According to documentation:

random.sample(population, k)

Return a k length list of unique elements chosen from the population sequence. Used for random sampling without replacement.

Basically, it picks k unique random elements, a sample, from a sequence:

>>> import random
>>> c = list(range(0, 15))
>>> c
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
>>> random.sample(c, 5)
[9, 2, 3, 14, 11]

random.sample works also directly from a range:

>>> c = range(0, 15)
>>> c
range(0, 15)
>>> random.sample(c, 5)
[12, 3, 6, 14, 10]

In addition to sequences, random.sample works with sets too:

>>> c = {1, 2, 4}
>>> random.sample(c, 2)
[4, 1]

However, random.sample doesn't work with arbitrary iterators:

>>> c = [1, 3]
>>> random.sample(iter(c), 5)
TypeError: Population must be a sequence or set.  For dicts, use list(d).

POST data with request module on Node.JS

I have to get the data from a POST method of the PHP code. What worked for me was:

const querystring = require('querystring');
const request = require('request');

const link = '';
let params = { 'A': 'a', 'B': 'b' };

params = querystring.stringify(params); // changing into querystring eg 'A=a&B=b'{
  headers: { 'Content-Type': 'application/x-www-form-urlencoded' }, // important to interect with PHP
  url: link,
  body: params,
}, function(error, response, body){

How is attr_accessible used in Rails 4?

We can use

params.require(:person).permit(:name, :age)

where person is Model, you can pass this code on a method person_params & use in place of params[:person] in create method or else method

How To Launch Git Bash from DOS Command Line?

The answer by Endoro has aged and I'm unable to comment;

# if you want to launch from a batch file or the command line:

start "" "%ProgramFiles%\Git\bin\sh.exe" --login

How to save and extract session data in codeigniter

First you have load session library.


You can load it in auto load, which I think is better.

To set session


To extract Data


How to use SearchView in Toolbar Android

If you want to add it directly in the toolbar.

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


            android:layout_centerHorizontal="true" />



Understanding `scale` in R

This is a late addition but I was looking for information on the scale function myself and though it might help somebody else as well.

To modify the response from Ricardo Saporta a little bit.
Scaling is not done using standard deviation, at least not in version 3.6.1 of R, I base this on "Becker, R. (2018). The new S language. CRC Press." and my own experimentation. <- X/sqrt(sum(X^2)/(length(X)-1))
X.aut.scaled <- scale(X, center = F)

The result of these rows are exactly the same, I show it without centering because of simplicity.

I would respond in a comment but did not have enough reputation.

syntaxerror: "unexpected character after line continuation character in python" math

You must press enter after continuation character

Note: Space after continuation character leads to error

cost = {"apples": [3.5, 2.4, 2.3], "bananas": [1.2, 1.8]}

0.9 * average(cost["apples"]) + \ """enter here"""
0.1 * average(cost["bananas"])

Intent.putExtra List

you can do it in two ways using

  • Serializable

  • Parcelable.

This examle will show you how to implement it with serializable

class Customer implements Serializable
   // properties, getter setters & constructor

// This is your custom object
Customer customer = new Customer(name, address, zip);

Intent intent = new Intent();
intent.setClass(SourceActivity.this, TargetActivity.this);
intent.putExtra("customer", customer);

// Now in your TargetActivity
Bundle extras = getIntent().getExtras();
if (extras != null)
    Customer customer = (Customer)extras.getSerializable("customer");
    // do something with the customer

Now have a look at this. This link will give you a brief overview of how to implement it with Parcelable.

Look at this.. This discussion will let you know which is much better way to implement it.


Injecting Mockito mocks into a Spring bean

private MyTestObject testObject;

private MyDependentObject mockedObject;

public void setup() {

This will inject any mocked objects into the test class. In this case it will inject mockedObject into the testObject. This was mentioned above but here is the code.

How to find specific lines in a table using Selenium?

You want:

int rowNumber=...;
string value = driver.findElement(By.xpath("//div[@id='productOrderContainer']/table/tbody/tr[" + rowNumber +"]/div[id='something']")).getText();

In other words, locate <DIV> with the id "something" contained within the rowNumberth <TR> of the <TABLE> contained within the <DIV> with the id "productOrderContainer", and then get its text value (which is what I believe you mean by "get me the value in <div id='something'>"

How to store token in Local or Session Storage in Angular 2?

That totally depends of what do you need exactly. If you just need to store and retrieve a token in order to use it in your http requests, i suggest you to simply create a service and use it in your whole project.

example of basic integration:

import {Injectable} from 'angular@core'

export class TokenManager {

    private tokenKey:string = 'app_token';

    private store(content:Object) {
        localStorage.setItem(this.tokenKey, JSON.stringify(content));

    private retrieve() {
        let storedToken:string = localStorage.getItem(this.tokenKey);
        if(!storedToken) throw 'no token found';
        return storedToken;

    public generateNewToken() {
        let token:string = '...';//custom token generation;
        let currentTime:number = (new Date()).getTime() + ttl;{ttl: currentTime, token});

    public retrieveToken() {

        let currentTime:number = (new Date()).getTime(), token = null;
        try {
            let storedToken = JSON.parse(this.retrieve());
            if(storedToken.ttl < currentTime) throw 'invalid token found';
            token = storedToken.token;
        catch(err) {
        return token;



However if you need to use the local storage more often, by using the stored values in your app views for example. You can use one of the libraries that provides a wrapper of the webstorages like you did with angular2-localstorage.

I created some months ago ng2-webstorage that should respond to your needs. It provides two ng2 services and two decorators to sync the webstorage's values and the service/component's attributes.

import {Component} from '@angular/core';
import {LocalStorageService, LocalStorage} from 'ng2-webstorage';

    selector: 'foo',
    template: `
        <section><input type="text" [(ngModel)]="attribute"/></section>
        <section><button (click)="saveValue()">Save</button></section>
export class FooComponent {

    boundValue; // attribute bound to the localStorage

    constructor(private storage:LocalStorageService) {
        this.localSt.observe('boundValue')// triggers the callback each time a new value is set
            .subscribe((newValue) => console.log('new value', newValue));

    saveValue() {'boundValue', this.value); // store the given value


Easiest way to copy a table from one database to another?

use below steps to copy and insert some columns from one database table to another database table-

  1. CREATE TABLE tablename ( columnname datatype (size), columnname datatype (size));

2.INSERT INTO db2.tablename SELECT columnname1,columnname2 FROM db1.tablename;

Find if variable is divisible by 2

Seriously, there's no jQuery plugin for odd/even checks?

Well, not anymore - releasing "Oven" a jQuery plugin under the MIT license to test if a given number is Odd/Even.

Source code is also available at

Test-suites are available at

(function() {
     * isEven(n)
     * @args number n
     * @return boolean returns whether the given number is even
    jQuery.isEven = function(number) {
        return number % 2 == 0;

    /* isOdd(n)
     * @args number n
     * @return boolean returns whether the given number is odd
    jQuery.isOdd = function(number) {
        return !jQuery.isEven(number);

Int to byte array

This may be OT but if you are serializing a lot of primitive types or POD structures, Google Protocol Buffers for .Net might be useful to you. This addresses the endianness issue @Marc raised above, among other useful features.

Android How to adjust layout in Full Screen Mode when softkeyboard is visible

Based on yghm's workaround, I coded up a convenience class that allows me to solve the problem with a one-liner (after adding the new class to my source code of course). The one-liner is:


And the implementation class is:

public class AndroidBug5497Workaround {

    // For more information, see
    // To use this class, simply invoke assistActivity() on an Activity that already has its content view set.

    public static void assistActivity (Activity activity) {
        new AndroidBug5497Workaround(activity);

    private View mChildOfContent;
    private int usableHeightPrevious;
    private FrameLayout.LayoutParams frameLayoutParams;

    private AndroidBug5497Workaround(Activity activity) {
        FrameLayout content = (FrameLayout) activity.findViewById(;
        mChildOfContent = content.getChildAt(0);
        mChildOfContent.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            public void onGlobalLayout() {
        frameLayoutParams = (FrameLayout.LayoutParams) mChildOfContent.getLayoutParams();

    private void possiblyResizeChildOfContent() {
        int usableHeightNow = computeUsableHeight();
        if (usableHeightNow != usableHeightPrevious) {
            int usableHeightSansKeyboard = mChildOfContent.getRootView().getHeight();
            int heightDifference = usableHeightSansKeyboard - usableHeightNow;
            if (heightDifference > (usableHeightSansKeyboard/4)) {
                // keyboard probably just became visible
                frameLayoutParams.height = usableHeightSansKeyboard - heightDifference;
            } else {
                // keyboard probably just became hidden
                frameLayoutParams.height = usableHeightSansKeyboard;
            usableHeightPrevious = usableHeightNow;

    private int computeUsableHeight() {
        Rect r = new Rect();
        return (r.bottom -;

Hope this helps someone.

Android: Reverse geocoding - getFromLocation

It looks like there's two things happening here.

1) You've missed the new keyword from before calling the constructor.

2) The parameter you're passing in to the Geocoder constructor is incorrect. You're passing in a Locale where it's expecting a Context.

There are two Geocoder constructors, both of which require a Context, and one also taking a Locale:

Geocoder(Context context, Locale locale)
Geocoder(Context context)


Modify your code to pass in a valid Context and include new and you should be good to go.

Geocoder myLocation = new Geocoder(getApplicationContext(), Locale.getDefault());   
List<Address> myList = myLocation.getFromLocation(latPoint, lngPoint, 1);


If you're still having problems it may be a permissioning issue. Geocoding implicitly uses the Internet to perform the lookups, so your application will require an INTERNET uses-permission tag in your manifest.

Add the following uses-permission node within the manifest node of your manifest.

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

MySQL SELECT WHERE datetime matches day (and not necessarily time)

... WHERE date_column >='2012-12-25' AND date_column <'2012-12-26' may potentially work better(if you have an index on date_column) than DATE.

Microsoft Visual C++ Compiler for Python 3.4

Unfortunately to be able to use the extension modules provided by others you'll be forced to use the official compiler to compile Python. These are:

Alternatively, you can use MinGw to compile extensions in a way that won't depend on others.

See: or

This allows you to have one compiler to build your extensions for both versions of Python, Python 2.x and Python 3.x.

Get a Windows Forms control by name in C#

Assuming you have Windows.Form Form1 as the parent form which owns the menu you've created. One of the form's attributes is named .Menu. If the menu was created programmatically, it should be the same, and it would be recognized as a menu and placed in the Menu attribute of the Form.

In this case, I had a main menu called File. A sub menu, called a MenuItem under File contained the tag Open and was named menu_File_Open. The following worked. Assuming you

// So you don't have to fully reference the objects.
using System.Windows.Forms;

// More stuff before the real code line, but irrelevant to this discussion.

MenuItem my_menuItem = (MenuItem)Form1.Menu.MenuItems["menu_File_Open"];

// Now you can do what you like with my_menuItem;

"java.lang.OutOfMemoryError: PermGen space" in Maven build

If you want to make this part of your POM for a repeatable build, you can use the fork-variant of a few of the plugins (especially compiler:compile and surefire:test):


        <argLine>-Xmx1024m -XX:MaxPermSize=256m</argLine>

Why do I always get the same sequence of random numbers with rand()?

If I remember the quote from Knuth's seminal work "The Art of Computer Programming" at the beginning of the chapter on Random Number Generation, it goes like this:

"Anyone who attempts to generate random numbers by mathematical means is, technically speaking, in a state of sin".

Simply put, the stock random number generators are algorithms, mathematical and 100% predictable. This is actually a good thing in a lot of situations, where a repeatable sequence of "random" numbers is desirable - for example for certain statistical exercises, where you don't want the "wobble" in results that truly random data introduces thanks to clustering effects.

Although grabbing bits of "random" data from the computer's hardware is a popular second alternative, it's not truly random either - although the more complex the operating environment, the more possibilities for randomness - or at least unpredictability.

Truly random data generators tend to look to outside sources. Radioactive decay is a favorite, as is the behavior of quasars. Anything whose roots are in quantum effects is effectively random - much to Einstein's annoyance.

The provider is not compatible with the version of Oracle client

For Oracle 11g ( I had to add the following dlls along with my Exe to work.

  1. oci.dll
  2. OraOps11w.dll
  3. oraociicus11.dll (pretty huge close to 30mb)
  4. Oracle.DataAccess.dll

With Twitter Bootstrap, how can I customize the h1 text color of one page and leave the other pages to be default?

You can add your own id or class to the body tag of your index page to target all elements on that page with a custom style like so:

<body id="index">

Then you can target the elements you wish to modify with your class or id like so:

#index h1 {

Get IPv4 addresses from Dns.GetHostEntry()

To find all valid address list this is the code I have used

public static IEnumerable<string> GetAddresses()
      var host = Dns.GetHostEntry(Dns.GetHostName());
      return (from ip in host.AddressList where ip.AddressFamily == AddressFamily.lo select ip.ToString()).ToList();

Why do I get PLS-00302: component must be declared when it exists?

You can get that error if you have an object with the same name as the schema. For example:

create sequence s2;


ORA-06550: line 2, column 6:
PLS-00302: component 'A' must be declared
ORA-06550: line 2, column 3:
PL/SQL: Statement ignored

When you refer to S2.MY_FUNC2 the object name is being resolved so it doesn't try to evaluate S2 as a schema name. When you just call it as MY_FUNC2 there is no confusion, so it works.

The documentation explains name resolution. The first piece of the qualified object name - S2 here - is evaluated as an object on the current schema before it is evaluated as a different schema.

It might not be a sequence; other objects can cause the same error. You can check for the existence of objects with the same name by querying the data dictionary.

select owner, object_type, object_name
from all_objects
where object_name = 'S2';

What are the retransmission rules for TCP?

What exactly are the rules for requesting retransmission of lost data?

The receiver does not request the retransmission. The sender waits for an ACK for the byte-range sent to the client and when not received, resends the packets, after a particular interval. This is ARQ (Automatic Repeat reQuest). There are several ways in which this is implemented.

Stop-and-wait ARQ
Go-Back-N ARQ
Selective Repeat ARQ

are detailed in the RFC 3366.

At what time frequency are the retransmission requests performed?

The retransmissions-times and the number of attempts isn't enforced by the standard. It is implemented differently by different operating systems, but the methodology is fixed. (One of the ways to fingerprint OSs perhaps?)

The timeouts are measured in terms of the RTT (Round Trip Time) times. But this isn't needed very often due to Fast-retransmit which kicks in when 3 Duplicate ACKs are received.

Is there an upper bound on the number?

Yes there is. After a certain number of retries, the host is considered to be "down" and the sender gives up and tears down the TCP connection.

Is there functionality for the client to indicate to the server to forget about the whole TCP segment for which part went missing when the IP packet went missing?

The whole point is reliable communication. If you wanted the client to forget about some part, you wouldn't be using TCP in the first place. (UDP perhaps?)

Getting the error "Java.lang.IllegalStateException Activity has been destroyed" when using tabs with ViewPager

I encountered the same issue when calling super.onCreate() at the end of my method. The reason: attachActivity() is called in onCreate() of FragmentActivity. When overriding onCreate() and, for example, creating tabs, the Tab manager will try to switch to a fragment while not having the activity attached to the FragmentManager.

Simple solution: Move the call to super.onCreate() to the head of the function body.

In general, it seems there are loads of reasons this issue may occur. This is just another one ...


Can I change the scroll speed using css or jQuery?

I just made a pure Javascript function based on that code. Javascript only version demo:

That is the independent code from jQuery

if (window.addEventListener) {window.addEventListener('DOMMouseScroll', wheel, false); 
window.onmousewheel = document.onmousewheel = wheel;}

function wheel(event) {
    var delta = 0;
    if (event.wheelDelta) delta = (event.wheelDelta)/120 ;
    else if (event.detail) delta = -(event.detail)/3;

    if (event.preventDefault) event.preventDefault();
    event.returnValue = false;

function handle(sentido) {
    var inicial = document.body.scrollTop;
    var time = 1000;
    var distance = 200;
    delay: 0,
    duration: time,
    delta: function(p) {return p;},
    step: function(delta) {
window.scrollTo(0, inicial-distance*delta*sentido);   

function animate(opts) {
  var start = new Date();
  var id = setInterval(function() {
    var timePassed = new Date() - start;
    var progress = (timePassed / opts.duration);
    if (progress > 1) {progress = 1;}
    var delta =;
    if (progress == 1) {clearInterval(id);}}, opts.delay || 10);

Using two values for one switch case statement

The case values are just codeless "goto" points that can share the same entry point:

case text1:
case text4: 

Note that the braces are redundant.

Background color not showing in print preview

I used purgatory101's answer but had trouble keeping all colours (icons, backgrounds, text colours etc...), especially that CSS stylesheets cannot be used with libraries which dynamically change DOM element's colours. Therefore here is a script that changes element's styles (background-colour and colour) before printing and clears styles once printing is done. It is useful to avoid writing a lot of CSS in a @media print stylesheet as it works whatever the page structure.

There is a part of the script that is specially made to keep FontAwesome icons color (or any element that uses a :before selector to insert coloured content).

JSFiddle showing the script in action

Compatibility: works in Chrome, I did not test other browsers.

function setColors(selector) {
  var elements = $(selector);
  for (var i = 0; i < elements.length; i++) {
    var eltBackground = $(elements[i]).css('background-color');
    var eltColor = $(elements[i]).css('color');

    var elementStyle = elements[i].style;
    if (eltBackground) {
      elementStyle.oldBackgroundColor = {
        value: elementStyle.backgroundColor,
        importance: elementStyle.getPropertyPriority('background-color'),
      elementStyle.setProperty('background-color', eltBackground, 'important');
    if (eltColor) {
      elementStyle.oldColor = {
        value: elementStyle.color,
        importance: elementStyle.getPropertyPriority('color'),
      elementStyle.setProperty('color', eltColor, 'important');

function resetColors(selector) {
  var elements = $(selector);
  for (var i = 0; i < elements.length; i++) {
    var elementStyle = elements[i].style;

    if (elementStyle.oldBackgroundColor) {
      elementStyle.setProperty('background-color', elementStyle.oldBackgroundColor.value, elementStyle.oldBackgroundColor.importance);
      delete elementStyle.oldBackgroundColor;
    } else {
      elementStyle.setProperty('background-color', '', '');
    if (elementStyle.oldColor) {
      elementStyle.setProperty('color', elementStyle.oldColor.value, elementStyle.oldColor.importance);
      delete elementStyle.oldColor;
    } else {
      elementStyle.setProperty('color', '', '');

function setIconColors(icons) {
  var css = '';
  $(icons).each(function (k, elt) {
    var selector = $(elt)
      .map(function () { return this.tagName; })

    var id = $(elt).attr('id');
    if (id) {
      selector += '#' + id;

    var classNames = $(elt).attr('class');
    if (classNames) {
      selector += '.' + $.trim(classNames).replace(/\s/gi, '.');

    css += selector + ':before { color: ' + $(elt).css('color') + ' !important; }';
  $('head').append('<style id="print-icons-style">' + css + '</style>');

function resetIconColors() {

And then modify the window.print function to make it set the styles before printing and resetting them after.

window._originalPrint = window.print;
window.print = function() {
  setColors('body *');
  setIconColors('body .fa');
  setTimeout(function () {
    resetColors('body *');
  }, 100);

The part that finds icons paths to create CSS for :before elements is a copy from this SO answer

Java Compare Two Lists

If you are looking for a handy way to test the equality of two collections, you can use org.apache.commons.collections.CollectionUtils.isEqualCollection, which compares two collections regardless of the ordering.

replacing text in a file with Python

I might consider using a dict and re.sub for something like this:

import re
repldict = {'zero':'0', 'one':'1' ,'temp':'bob','garage':'nothing'}
def replfunc(match):
    return repldict[]

regex = re.compile('|'.join(re.escape(x) for x in repldict))
with open('file.txt') as fin, open('fout.txt','w') as fout:
    for line in fin:

This has a slight advantage to replace in that it is a bit more robust to overlapping matches.

Permission denied on accessing host directory in Docker

I resolved that issue by using a data container, this also has the advantage of isolating the data from the application layer. You could run it like this:

docker run --volumes-from=<container-data-name> ubuntu

This tutorial provides a good explanation on the use of data containers.

How to improve performance of ngRepeat over a huge dataset (angular.js)?

Sometimes what happened,you get the data from server (or back-end) in few ms (for example I'm I am assuming it 100ms) but it takes more time to display in our web page (let's say it is taking 900ms to display).

So, What is happening here is 800ms It is taking just to render web page.

What I have done in my web application is, I have used pagination (or you can use infinite scrolling also) to display list of data. Let's say I am showing 50 data/page.

So I will not load render all the data at once,only 50 data I am loading initially which takes only 50ms (I'm assuming here).

so total time here decreased from 900ms to 150ms, once user request next page then display next 50 data and so on.

Hope this will help you to improve the performance. All the best

What are all the user accounts for IIS/ASP.NET and how do they differ?

This is a very good question and sadly many developers don't ask enough questions about IIS/ASP.NET security in the context of being a web developer and setting up IIS. So here goes....

To cover the identities listed:


This is analogous to the old IIS6 IIS_WPG group. It's a built-in group with it's security configured such that any member of this group can act as an application pool identity.


This account is analogous to the old IUSR_<MACHINE_NAME> local account that was the default anonymous user for IIS5 and IIS6 websites (i.e. the one configured via the Directory Security tab of a site's properties).

For more information about IIS_IUSRS and IUSR see:

Understanding Built-In User and Group Accounts in IIS 7


If an application pool is configured to run using the Application Pool Identity feature then a "synthesised" account called IIS AppPool\<pool name> will be created on the fly to used as the pool identity. In this case there will be a synthesised account called IIS AppPool\DefaultAppPool created for the life time of the pool. If you delete the pool then this account will no longer exist. When applying permissions to files and folders these must be added using IIS AppPool\<pool name>. You also won't see these pool accounts in your computers User Manager. See the following for more information:

Application Pool Identities

ASP.NET v4.0: -

This will be the Application Pool Identity for the ASP.NET v4.0 Application Pool. See DefaultAppPool above.


The NETWORK SERVICE account is a built-in identity introduced on Windows 2003. NETWORK SERVICE is a low privileged account under which you can run your application pools and websites. A website running in a Windows 2003 pool can still impersonate the site's anonymous account (IUSR_ or whatever you configured as the anonymous identity).

In ASP.NET prior to Windows 2008 you could have ASP.NET execute requests under the Application Pool account (usually NETWORK SERVICE). Alternatively you could configure ASP.NET to impersonate the site's anonymous account via the <identity impersonate="true" /> setting in web.config file locally (if that setting is locked then it would need to be done by an admin in the machine.config file).

Setting <identity impersonate="true"> is common in shared hosting environments where shared application pools are used (in conjunction with partial trust settings to prevent unwinding of the impersonated account).

In IIS7.x/ASP.NET impersonation control is now configured via the Authentication configuration feature of a site. So you can configure to run as the pool identity, IUSR or a specific custom anonymous account.


The LOCAL SERVICE account is a built-in account used by the service control manager. It has a minimum set of privileges on the local computer. It has a fairly limited scope of use:

LocalService Account


You didn't ask about this one but I'm adding for completeness. This is a local built-in account. It has fairly extensive privileges and trust. You should never configure a website or application pool to run under this identity.

LocalSystem Account

In Practice:

In practice the preferred approach to securing a website (if the site gets its own application pool - which is the default for a new site in IIS7's MMC) is to run under Application Pool Identity. This means setting the site's Identity in its Application Pool's Advanced Settings to Application Pool Identity:

enter image description here

In the website you should then configure the Authentication feature:

enter image description here

Right click and edit the Anonymous Authentication entry:

enter image description here

Ensure that "Application pool identity" is selected:

enter image description here

When you come to apply file and folder permissions you grant the Application Pool identity whatever rights are required. For example if you are granting the application pool identity for the ASP.NET v4.0 pool permissions then you can either do this via Explorer:

enter image description here

Click the "Check Names" button:

enter image description here

Or you can do this using the ICACLS.EXE utility:

icacls c:\wwwroot\mysite /grant "IIS AppPool\ASP.NET v4.0":(CI)(OI)(M)

...or...if you site's application pool is called BobsCatPicBlogthen:

icacls c:\wwwroot\mysite /grant "IIS AppPool\BobsCatPicBlog":(CI)(OI)(M)

I hope this helps clear things up.


I just bumped into this excellent answer from 2009 which contains a bunch of useful information, well worth a read:

The difference between the 'Local System' account and the 'Network Service' account?

How do I make curl ignore the proxy?

Add your proxy preferences into .curlrc

proxy =
noproxy = .dev,localhost,

This make all dev domains and local machine request ignore the proxy.

Getting URL parameter in java and extract a specific text from that URL

Using pure Java 8

Assumming you want to extract param "v" from url:

             String paramV = Stream.of(url.split("?")[1].split("&"))
                        .map(kv -> kv.split("="))
                        .filter(kv -> "v".equalsIgnoreCase(kv[0]))
                        .map(kv -> kv[1])

Change onclick action with a Javascript function

You could try changing the button attribute like this:

element.setAttribute( "onClick", "javascript: Boo();" );

What does (function($) {})(jQuery); mean?

Type 3, in order to work would have to look like this:

    //Attach this new method to jQuery
        //This is where you write your plugin's name
        'pluginname': function(_options) {
            // Put defaults inline, no need for another variable...
            var options =  $.extend({
                'defaults': "go here..."
            }, _options);

            //Iterate over the current set of matched elements
            return this.each(function() {

                //code to be inserted here


I am unsure why someone would use extend over just directly setting the property in the jQuery prototype, it is doing the same exact thing only in more operations and more clutter.

Dynamically Add Images React Webpack

here is the code

    import React, { Component } from 'react';
    import logo from './logo.svg';
    import './image.css';
    import Dropdown from 'react-dropdown';
    import axios from 'axios';

    let obj = {};

    class App extends Component {
        this.state = {
          selectedFiles: []
        this.fileUploadHandler = this.fileUploadHandler.bind(this);

        let selectedFiles_ = this.state.selectedFiles;
        this.setState({selectedFiles: selectedFiles_});

      render() {
        let Images = => {
          <div className = "image_parent">

              <img src={require(image.src)}

        return (
            <div className="image-upload images_main">

            <input type="file" onClick={this.fileUploadHandler}/>


    export default App;

Read text file into string array (and write)

func readToDisplayUsingFile1(f *os.File){
    defer f.Close()
    reader := bufio.NewReader(f)
    contents, _ := ioutil.ReadAll(reader)
    lines := strings.Split(string(contents), '\n')


func readToDisplayUsingFile1(f *os.File){
    defer f.Close()
    slice := make([]string,0)

    reader := bufio.NewReader(f)


    str, err := reader.ReadString('\n')
    if err == io.EOF{

        slice = append(slice, str)

What is Python buffer type for?

An example usage:

>>> s = 'Hello world'
>>> t = buffer(s, 6, 5)
>>> t
<read-only buffer for 0x10064a4b0, size 5, offset 6 at 0x100634ab0>
>>> print t

The buffer in this case is a sub-string, starting at position 6 with length 5, and it doesn't take extra storage space - it references a slice of the string.

This isn't very useful for short strings like this, but it can be necessary when using large amounts of data. This example uses a mutable bytearray:

>>> s = bytearray(1000000)   # a million zeroed bytes
>>> t = buffer(s, 1)         # slice cuts off the first byte
>>> s[1] = 5                 # set the second element in s
>>> t[0]                     # which is now also the first element in t!

This can be very helpful if you want to have more than one view on the data and don't want to (or can't) hold multiple copies in memory.

Note that buffer has been replaced by the better named memoryview in Python 3, though you can use either in Python 2.7.

Note also that you can't implement a buffer interface for your own objects without delving into the C API, i.e. you can't do it in pure Python.

How can I pass command-line arguments to a Perl program?

You can access them directly, by assigning the special variable @ARGV to a list of variables. So, for example:

( $st, $prod, $ar, $file, $chart, $e, $max, $flag ,$id) = @ARGV;

perl 1 2 3 4 5

enter image description here

How to emit an event from parent to child?

Within the parent, you can reference the child using @ViewChild. When needed (i.e. when the event would be fired), you can just execute a method in the child from the parent using the @ViewChild reference.

Android Material: Status bar color won't change

Status bar coloring is not supported in AppCompat v7:21.0.0.

From the Android developers blog post

On older platforms, AppCompat emulates the color theming where possible. At the moment this is limited to coloring the action bar and some widgets.

This means the AppCompat lib will only color status bars on Lollipop and above.

Mask for an Input to allow phone numbers?

I do this using the TextMaskModule from 'angular2-text-mask'

Mine are split but you can get the idea

Package using NPM NodeJS

"dependencies": {
    "angular2-text-mask": "8.0.0",


<input *ngIf="column?.type =='areaCode'" type="text" [textMask]="{mask: areaCodeMask}" [(ngModel)]="areaCodeModel">

<input *ngIf="column?.type =='phone'" type="text" [textMask]="{mask: phoneMask}" [(ngModel)]="phoneModel"> 

Inside Component

public areaCodeModel = '';
public areaCodeMask = ['(', /[1-9]/, /\d/, /\d/, ')'];

public phoneModel = '';
public phoneMask = [/\d/, /\d/, /\d/, '-', /\d/, /\d/, /\d/, /\d/];

How to parse freeform street/postal address out of text, and into components

There are many street address parsers. They come in two basic flavors - ones that have databases of place names and street names, and ones that don't.

A regular expression street address parser can get up to about a 95% success rate without much trouble. Then you start hitting the unusual cases. The Perl one in CPAN, "Geo::StreetAddress::US", is about that good. There are Python and Javascript ports of that, all open source. I have an improved version in Python which moves the success rate up slightly by handling more cases. To get the last 3% right, though, you need databases to help with disambiguation.

A database with 3-digit ZIP codes and US state names and abbreviations is a big help. When a parser sees a consistent postal code and state name, it can start to lock on to the format. This works very well for the US and UK.

Proper street address parsing starts from the end and works backwards. That's how the USPS systems do it. Addresses are least ambiguous at the end, where country names, city names, and postal codes are relatively easy to recognize. Street names can usually be isolated. Locations on streets are the most complex to parse; there you encounter things such as "Fifth Floor" and "Staples Pavillion". That's when a database is a big help.

Unable to compile class for JSP: The type java.util.Map$Entry cannot be resolved. It is indirectly referenced from required .class files

There are a lot of correct/same answers, but for future references:

Same stands for Tomcat 7. Be aware that updating only your used frameworks' versions (as proposed in other similar questions) isn't enough.

You also have to update Tomcat plugin's version. What worked for me, using Java 7, was upgrading to version 2.2 of tomcat7-maven-plugin (= Tomcat 7.0.47).

WAMP server, localhost is not working

Wamp Server localhost not working. problems port 80 is closed. Icon Color Yellow


wamp icon click > Apache > Service > Service Install

wamp icon click > All Services Restart

Icon Green its Work

How to center links in HTML

Since you have a list of links, you should be marking them up as a list (and not as paragraphs).

Listamatic has a bunch of examples of how you can style lists of links, including a number that are vertical lists with each link being centred (which is what you appear to be after). It also has a tutorial which explains the principles.

That part of the styling essentially boils down to "Set text-align: center on an element that is displaying as a block which contains the link text" (that could be the anchor itself (if you make it display as a block) or the list item containing it.

How to detect the physical connected state of a network cable/connector?

You can use ethtool:

$ sudo ethtool eth0
Settings for eth0:
    Supported ports: [ TP ]
    Supported link modes:   10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
    Supports auto-negotiation: Yes
    Advertised link modes:  10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
    Advertised auto-negotiation: Yes
    Speed: 1000Mb/s
    Duplex: Full
    Port: Twisted Pair
    PHYAD: 0
    Transceiver: internal
    Auto-negotiation: on
    Supports Wake-on: umbg
    Wake-on: g
    Current message level: 0x00000007 (7)
    Link detected: yes

To only get the Link status you can use grep:

$ sudo ethtool eth0 | grep Link
    Link detected: yes

Convert List<T> to ObservableCollection<T> in WP7

The answer provided by Zin Min solved my problem with a single line of code. Excellent!

I was having the same issue of converting a generic List to a generic ObservableCollection to use the values from my List to populate a ComboBox that is participating in binding via a factory class for a WPF Window.

_expediteStatuses = new ObservableCollection<ExpediteStatus>(_db.getExpediteStatuses());

Here is the signature for the getExpediteStatuses method:

public List<ExpediteStatus> getExpediteStatuses()

How to respond to clicks on a checkbox in an AngularJS directive?

I prefer to use the ngModel and ngChange directives when dealing with checkboxes. ngModel allows you to bind the checked/unchecked state of the checkbox to a property on the entity:

<input type="checkbox" ng-model="entity.isChecked">

Whenever the user checks or unchecks the checkbox the entity.isChecked value will change too.

If this is all you need then you don't even need the ngClick or ngChange directives. Since you have the "Check All" checkbox, you obviously need to do more than just set the value of the property when someone checks a checkbox.

When using ngModel with a checkbox, it's best to use ngChange rather than ngClick for handling checked and unchecked events. ngChange is made for just this kind of scenario. It makes use of the ngModelController for data-binding (it adds a listener to the ngModelController's $viewChangeListeners array. The listeners in this array get called after the model value has been set, avoiding this problem).

<input type="checkbox" ng-model="entity.isChecked" ng-change="selectEntity()">

... and in the controller ...

var model = {};
$scope.model = model;

// This property is bound to the checkbox in the table header
model.allItemsSelected = false;

// Fired when an entity in the table is checked
$scope.selectEntity = function () {
    // If any entity is not checked, then uncheck the "allItemsSelected" checkbox
    for (var i = 0; i < model.entities.length; i++) {
        if (!model.entities[i].isChecked) {
            model.allItemsSelected = false;

    // ... otherwise ensure that the "allItemsSelected" checkbox is checked
    model.allItemsSelected = true;

Similarly, the "Check All" checkbox in the header:

    <input type="checkbox" ng-model="model.allItemsSelected" ng-change="selectAll()">

... and ...

// Fired when the checkbox in the table header is checked
$scope.selectAll = function () {
    // Loop through all the entities and set their isChecked property
    for (var i = 0; i < model.entities.length; i++) {
        model.entities[i].isChecked = model.allItemsSelected;


What is the best way to... add a CSS class to the <tr> containing the entity to reflect its selected state?

If you use the ngModel approach for the data-binding, all you need to do is add the ngClass directive to the <tr> element to dynamically add or remove the class whenever the entity property changes:

<tr ng-repeat="entity in model.entities" ng-class="{selected: entity.isChecked}">

See the full Plunker here.

How can I throw a general exception in Java?

It depends. You can throw a more general exception, or a more specific exception. For simpler methods, more general exceptions are enough. If the method is complex, then, throwing a more specific exception will be reliable.

MySQL remove all whitespaces from the entire column

Working Query:

SELECT replace(col_name , ' ','') FROM table_name;

While this doesn't :

SELECT trim(col_name) FROM table_name;

Select distinct values from a list using LINQ in C#


var newList = 
from x in empCollection
select new {Loc = x.empLoc, PL = x.empPL, Shift = x.empShift}

Replacement for "rename" in dplyr

I tried to use dplyr::rename and I get an error:

occ_5d <- dplyr::rename(occ_5d, rowname='code_5d')
Error: Unknown column `code_5d` 
Call `rlang::last_error()` to see a backtrace

I instead used the base R function which turns out to be quite simple and effective:

names(occ_5d)[1] = "code_5d"

How to use addTarget method in swift 3

the Demo from Apple document.

import UIKit
class MyViewController: UIViewController {
    let myButton = UIButton(frame: CGRect(x: 0, y: 0, width: 100, height: 50))

    override init(nibName nibNameOrNil: NSNib.Name?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
        // without parameter style
        let action = #selector(MyViewController.tappedButton)
        // with parameter style
        // #selector(MyViewController.tappedButton(_:))
        myButton.addTarget(self, action: action, forControlEvents: .touchUpInside)

    @objc func tappedButton(_ sender: UIButton?) {
        print("tapped button")

    required init?(coder: NSCoder) {
        super.init(coder: coder)

How to find an object in an ArrayList by property

For finding objects which are meaningfully equal, you need to override equals and hashcode methods for the class. You can find a good tutorial here.

How to get process ID of background process?

You can use the jobs -l command to get to a particular jobL

[1]+  Stopped                 guard

my_mac:workspace r$ jobs -l
[1]+ 46841 Suspended: 18           guard

In this case, 46841 is the PID.

From help jobs:

-l Report the process group ID and working directory of the jobs.

jobs -p is another option which shows just the PIDs.

Transition color fade on hover?

What do you want to fade? The background or color attribute?

Currently you're changing the background color, but telling it to transition the color property. You can use all to transition all properties.

.clicker { 
    -moz-transition: all .2s ease-in;
    -o-transition: all .2s ease-in;
    -webkit-transition: all .2s ease-in;
    transition: all .2s ease-in;
    background: #f5f5f5; 
    padding: 20px;

.clicker:hover { 
    background: #eee;

Otherwise just use transition: background .2s ease-in.

The conversion of the varchar value overflowed an int column

Declare @phoneNumber int

select @phoneNumber=Isnull('08041159620',0);

Give error :

The conversion of the varchar value '8041159620' overflowed an int column.: select cast('8041159620' as int)


Integer is defined as :

Integer (whole number) data from -2^31 (-2,147,483,648) through 2^31 - 1 (2,147,483,647). Storage size is 4 bytes. The SQL-92 synonym for int is integer.


Declare @phoneNumber bigint


Cannot use a CONTAINS or FREETEXT predicate on table or indexed view because it is not full-text indexed

You must define Full-Text-Index on all tables in database where you require to use a query with CONTAINS which will take sometime.

Instead you can use the LIKE which will give you instant results without the need to adjust any settings for the tables.


SELECT * FROM ChartOfAccounts WHERE AccountName LIKE '%Tax%'

The same result obtained with CONTAINS can be obtained with LIKE.

see the result: enter image description here

Rollback a Git merge

From here:

git revert -m 1 <merge commit hash>

Git revert adds a new commit that rolls back the specified commit.

Using -m 1 tells it that this is a merge and we want to roll back to the parent commit on the master branch. You would use -m 2 to specify the develop branch.

In DB2 Display a table's definition

DB2 Version 11.0


        ON I.NAME = P.IXNAME
WHERE I.TBcreator ='ME' and I.TBNAME ='MY_TABLE'

Cast Object to Generic Type for returning

I stumble upon this question and it grabbed my interest. The accepted answer is completely correct, but I thought I do provide my findings at JVM byte code level to explain why the OP encounter the ClassCastException.

I have the code which is pretty much the same as OP's code:

public static <T> T convertInstanceOfObject(Object o) {
    try {
       return (T) o;
    } catch (ClassCastException e) {
        return null;

public static void main(String[] args) {
    String k = convertInstanceOfObject(345435.34);

and the corresponding byte code is:

public static <T> T convertInstanceOfObject(java.lang.Object);
       0: aload_0
       1: areturn
       2: astore_1
       3: aconst_null
       4: areturn
    Exception table:
       from    to  target type
           0     1     2   Class java/lang/ClassCastException

  public static void main(java.lang.String[]);
       0: ldc2_w        #3                  // double 345435.34d
       3: invokestatic  #5                  // Method java/lang/Double.valueOf:(D)Ljava/lang/Double;
       6: invokestatic  #6                  // Method convertInstanceOfObject:(Ljava/lang/Object;)Ljava/lang/Object;
       9: checkcast     #7                  // class java/lang/String
      12: astore_1
      13: getstatic     #8                  // Field java/lang/System.out:Ljava/io/PrintStream;
      16: aload_1
      17: invokevirtual #9                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V
      20: return

Notice that checkcast byte code instruction happens in the main method not the convertInstanceOfObject and convertInstanceOfObject method does not have any instruction that can throw ClassCastException. Because the main method does not catch the ClassCastException hence when you execute the main method you will get a ClassCastException and not the expectation of printing null.

Now I modify the code to the accepted answer:

public static <T> T convertInstanceOfObject(Object o, Class<T> clazz) {
        try {
            return clazz.cast(o);
        } catch (ClassCastException e) {
            return null;
    public static void main(String[] args) {
        String k = convertInstanceOfObject(345435.34, String.class);

The corresponding byte code is:

public static <T> T convertInstanceOfObject(java.lang.Object, java.lang.Class<T>);
       0: aload_1
       1: aload_0
       2: invokevirtual #2                  // Method java/lang/Class.cast:(Ljava/lang/Object;)Ljava/lang/Object;
       5: areturn
       6: astore_2
       7: aconst_null
       8: areturn
    Exception table:
       from    to  target type
           0     5     6   Class java/lang/ClassCastException

  public static void main(java.lang.String[]);
       0: ldc2_w        #4                  // double 345435.34d
       3: invokestatic  #6                  // Method java/lang/Double.valueOf:(D)Ljava/lang/Double;
       6: ldc           #7                  // class java/lang/String
       8: invokestatic  #8                  // Method convertInstanceOfObject:(Ljava/lang/Object;Ljava/lang/Class;)Ljava/lang/Object;
      11: checkcast     #7                  // class java/lang/String
      14: astore_1
      15: getstatic     #9                  // Field java/lang/System.out:Ljava/io/PrintStream;
      18: aload_1
      19: invokevirtual #10                 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
      22: return

Notice that there is an invokevirtual instruction in the convertInstanceOfObject method that calls Class.cast() method which throws ClassCastException which will be catch by the catch(ClassCastException e) bock and return null; hence, "null" is printed to console without any exception.

Send file using POST from a Python script

I am trying to test django rest api and its working for me:

def test_upload_file(self):
        filename = "/Users/Ranvijay/tests/test_price_matrix.csv"
        data = {'file': open(filename, 'rb')}
        client = APIClient()
        # client.credentials(HTTP_AUTHORIZATION='Token ' + token.key)
        response ='price-matrix-csv'), data, format='multipart')

        print response
        self.assertEqual(response.status_code, status.HTTP_200_OK)

jQuery .val change doesn't change input value

to expand a bit on Ricardo's answer:

about val()

Setting values using this method (or using the native value property) does not cause the dispatch of the change event. For this reason, the relevant event handlers will not be executed. If you want to execute them, you should call .trigger( "change" ) after setting the value.

What is the best/safest way to reinstall Homebrew?

Try running the command brew doctor and let us know what sort of output you get

edit: And to answer the title question, this is from their FAQ :

Homebrew doesn’t write files outside its prefix. So generally you can just rm -rf the folder you installed it in.

So following that up with a clean re-install (following their latest recommended steps) should be your best bet.

Difference between parameter and argument

Argument is often used in the sense of actual argument vs. formal parameter.

The formal parameter is what is given in the function declaration/definition/prototype, while the actual argument is what is passed when calling the function — an instance of a formal parameter, if you will.

That being said, they are often used interchangeably, their exact use depending on different programming languages and their communities. For example, I have also heard actual parameter etc.

So here, x and y would be formal parameters:

int foo(int x, int y) {

Whereas here, in the function call, 5 and z are the actual arguments:

foo(5, z);

Could not open ServletContext resource

I think currently the application-context.xml file is into src/main/resources AND the file is into src/main/java... so when you package (mvn package) or when you run tomcat (mvn tomcat:run) your disappeared (I know you said when you checked into the .war the files are here... but your exception says the opposite).

The solution is simply to put all your configuration files (application-context.xml and into src/main/resources to follow the maven standard structure.

java - iterating a linked list

I found 5 main ways to iterate over a Linked List in Java (including the Java 8 way):

  1. For Loop
  2. Enhanced For Loop
  3. While Loop
  4. Iterator
  5. Collections’s stream() util (Java8)

For loop

LinkedList<String> linkedList = new LinkedList<>();
System.out.println("==> For Loop Example.");
for (int i = 0; i < linkedList.size(); i++) {

Enhanced for loop

for (String temp : linkedList) {

While loop

int i = 0;
while (i < linkedList.size()) {


Iterator<String> iterator = linkedList.iterator();
while (iterator.hasNext()) {

collection stream() util (Java 8)

linkedList.forEach((temp) -> {

One thing should be pointed out is that the running time of For Loop or While Loop is O(n square) because get(i) operation takes O(n) time(see this for details). The other 3 ways take linear time and performs better.

Most concise way to convert a Set<T> to a List<T>

Considering that we have Set<String> stringSet we can use following:

Plain Java

List<String> strList = new ArrayList<>(stringSet);


List<String> strList = Lists.newArrayList(stringSet);

Apache Commons

List<String> strList = new ArrayList<>();
CollectionUtils.addAll(strList, stringSet);

Java 10 (Unmodifiable List)

List<String> strList = List.copyOf(stringSet);
List<String> strList =;

Java 8 (Modifiable Lists)

import static*;
List<String> stringList1 =;

As per the doc for the method toList()

There are no guarantees on the type, mutability, serializability, or thread-safety of the List returned; if more control over the returned List is required, use toCollection(Supplier).

So if we need a specific implementation e.g. ArrayList we can get it this way:

List<String> stringList2 =

Java 8 (Unmodifiable Lists)

We can make use of Collections::unmodifiableList method and wrap the list returned in previous examples. We can also write our own custom method as:

class ImmutableCollector {
    public static <T> Collector<T, List<T>, List<T>> toImmutableList(Supplier<List<T>> supplier) {
            return Collector.of( supplier, List::add, (left, right) -> {
                        return left;
                    }, Collections::unmodifiableList);

And then use it as:

List<String> stringList3 =

Another possibility is to make use of collectingAndThen method which allows some final transformation to be done before returning result:

    List<String> stringList4 =

One point to note is that the method Collections::unmodifiableList returns an unmodifiable view of the specified list, as per doc. An unmodifiable view collection is a collection that is unmodifiable and is also a view onto a backing collection. Note that changes to the backing collection might still be possible, and if they occur, they are visible through the unmodifiable view. But the collector method Collectors.unmodifiableList returns truly immutable list in Java 10.

Angular Material: mat-select not selecting default

A comparison between a number and a string use to be false, so, cast you selected value to a string within ngOnInit and it will work.

I had same issue, I filled the mat-select with an enum, using

Object.keys(MyAwesomeEnum).filter(k => !isNaN(Number(k)));

and I had the enum value I wanted to select...

I spent few hours struggling my mind trying to identify why it wasn't working. And I did it just after rendering all the variables being used in the mat-select, the keys collection and the selected... if you have ["0","1","2"] and you want to select 1 (which is a number) 1=="1" is false and because of that nothing is selected.

so, the solution is to cast you selected value to a string within ngOnInit and it will work.

Convert Variable Name to String?

I'd like to point out a use case for this that is not an anti-pattern, and there is no better way to do it.

This seems to be a missing feature in python.

There are a number of functions, like patch.object, that take the name of a method or property to be patched or accessed.

Consider this:

patch.object(obj, "method_name", new_reg)

This can potentially start "false succeeding" when you change the name of a method. IE: you can ship a bug, you thought you were testing.... simply because of a bad method name refactor.

Now consider: varname. This could be an efficient, built-in function. But for now it can work by iterating an object or the caller's frame:

Now your call can be:

patch.member(obj, obj.method_name, new_reg)

And the patch function can call:

varname(var, obj=obj)

This would: assert that the var is bound to the obj and return the name of the member. Or if the obj is not specified, use the callers stack frame to derive it, etc.

Could be made an efficient built in at some point, but here's a definition that works. I deliberately didn't support builtins, easy to add tho:

Feel free to stick this in a package called, and use it in your patch.object calls:

patch.object(obj, varname(obj, obj.method_name), new_reg)

Note: this was written for python 3.

import inspect

def _varname_dict(var, dct):
    key_name = None
    for key, val in dct.items():
        if val is var:
            if key_name is not None:
                raise NotImplementedError("Duplicate names not supported %s, %s" % (key_name, key))
            key_name = key
    return key_name

def _varname_obj(var, obj):
    key_name = None
    for key in dir(obj):
        val = getattr(obj, key)
        equal = val is var
        if equal:
            if key_name is not None:
                raise NotImplementedError("Duplicate names not supported %s, %s" % (key_name, key))
            key_name = key
    return key_name

def varname(var, obj=None):
    if obj is None:
        if hasattr(var, "__self__"):
            return var.__name__
        caller_frame = inspect.currentframe().f_back
            ret = _varname_dict(var, caller_frame.f_locals)
        except NameError:
            ret = _varname_dict(var, caller_frame.f_globals)
        ret = _varname_obj(var, obj)
    if ret is None:
        raise NameError("Name not found. (Note: builtins not supported)")
    return ret

What is the most appropriate way to store user settings in Android application

In general SharedPreferences are your best bet for storing preferences, so in general I'd recommend that approach for saving application and user settings.

The only area of concern here is what you're saving. Passwords are always a tricky thing to store, and I'd be particularly wary of storing them as clear text. The Android architecture is such that your application's SharedPreferences are sandboxed to prevent other applications from being able to access the values so there's some security there, but physical access to a phone could potentially allow access to the values.

If possible I'd consider modifying the server to use a negotiated token for providing access, something like OAuth. Alternatively you may need to construct some sort of cryptographic store, though that's non-trivial. At the very least, make sure you're encrypting the password before writing it to disk.

Deleting folders in python recursively

For Linux users, you can simply run the shell command in a pythonic way

import os
os.system("rm -r /home/user/folder1  /home/user/folder2  ...")

If facing any issue then instead of rm -r use rm -rf but remember f will delete the directory forcefully.

Where rm stands for remove, -r for recursively and -rf for recursively + forcefully.

Note: It doesn't matter either the directories are empty or not, they'll get deleted.

Create new XML file and write data to it?

With FluidXML you can generate and store an XML document very easily.

$doc = fluidxml();

$doc->add('Album', true)
        ->add('Track', 'Track Title');


Loading a document from a file is equally simple.

$doc = fluidify('album.xml');

        ->attr('id', 123);

jquery data selector

I've created a new data selector that should enable you to do nested querying and AND conditions. Usage:


The pattern is:

:data( {namespace} [{operator} {check}]  )

"operator" and "check" are optional. So, if you only have :data(a.b.c) it will simply check for the truthiness of a.b.c.

You can see the available operators in the code below. Amongst them is ~= which allows regex testing:


I've tested it with a few variations and it seems to work quite well. I'll probably add this as a Github repo soon (with a full test suite), so keep a look out!

The code:


    var matcher = /\s*(?:((?:(?:\\\.|[^.,])+\.?)+)\s*([!~><=]=|[><])\s*("|')?((?:\\\3|.)*?)\3|(.+?))\s*(?:,|$)/g;

    function resolve(element, data) {

        data = data.match(/(?:\\\.|[^.])+(?=\.|$)/g);

        var cur =[data.shift()];

        while (cur && data[0]) {
            cur = cur[data.shift()];

        return cur || undefined;


    jQuery.expr[':'].data = function(el, i, match) {

        matcher.lastIndex = 0;

        var expr = match[3],
            check, val,
            allMatch = null,
            foundMatch = false;

        while (m = matcher.exec(expr)) {

            check = m[4];
            val = resolve(el, m[1] || m[5]);

            switch (m[2]) {
                case '==': foundMatch = val == check; break;
                case '!=': foundMatch = val != check; break;
                case '<=': foundMatch = val <= check; break;
                case '>=': foundMatch = val >= check; break;
                case '~=': foundMatch = RegExp(check).test(val); break;
                case '>': foundMatch = val > check; break;
                case '<': foundMatch = val < check; break;
                default: if (m[5]) foundMatch = !!val;

            allMatch = allMatch === null ? foundMatch : allMatch && foundMatch;


        return allMatch;



Split string in Lua?

If you program in Lua, you are out of luck here. Lua is THE one programming language that just happens to be notoriously infamous because its authors never implemented "the" split function in the standard library, and instead wrote 16 screenfulls of explanations and lame excuses as to why they didn't and wouldn't, interspersed with numerous half-working examples that are virtually guaranteed to work for almost everyone but break in your corner case. This is just Lua state of the art, and everyone who programs in Lua simply ends up clenching their teeth and iterating over characters. There are lots of solutions in existence that are sometimes better, but exactly zero solutions that are reliably better.

Bootstrap 4 - Responsive cards in card-columns

Bootstrap 4 (4.0.0-alpha.2) uses the css property column-count in the card-columns class to define how many columns of cards would be displayed inside the div element.
But this property has only two values:

  • The default value 1 for small screens (max-width: 34em)
  • The value 3 for all other sizes (min-width: 34em)

Here's how it is implemented in bootstrap.min.css :

@media (min-width: 34em) {
    .card-columns {

To make the card stacking responsive, you can add the following media queries to your css file and modify the values for min-width as per your requirements :

@media (min-width: 34em) {
    .card-columns {
        -webkit-column-count: 2;
        -moz-column-count: 2;
        column-count: 2;

@media (min-width: 48em) {
    .card-columns {
        -webkit-column-count: 3;
        -moz-column-count: 3;
        column-count: 3;

@media (min-width: 62em) {
    .card-columns {
        -webkit-column-count: 4;
        -moz-column-count: 4;
        column-count: 4;

@media (min-width: 75em) {
    .card-columns {
        -webkit-column-count: 5;
        -moz-column-count: 5;
        column-count: 5;

IntelliJ does not show project folders

I encountered this problem when the .idea folder was accidentally added to SVN version control. When I took an update --- blooey! I subsequently removed the .idea folder from version control.

Remove all special characters, punctuation and spaces from string

Shorter way :

import re
cleanString = re.sub('\W+','', string )

If you want spaces between words and numbers substitute '' with ' '

Setting up FTP on Amazon Cloud Server

In case you are getting 530 password incorrect

1 more step needed

in file /etc/shells

Add the following line


Difference between arguments and parameters in Java

The term parameter refers to any declaration within the parentheses following the method/function name in a method/function declaration or definition; the term argument refers to any expression within the parentheses of a method/function call. i.e.

  1. parameter used in function/method definition.
  2. arguments used in function/method call.

Please have a look at the below example for better understanding:


public class ArithmeticOperations {

    public static int add(int x, int y) { //x, y are parameters here
        return x + y;

    public static void main(String[] args) {
        int x = 10;
        int y = 20;
        int sum = add(x, y); //x, y are arguments here
        System.out.println("SUM IS: " +sum);


Thank you!

Replace all elements of Python NumPy Array that are greater than some value

You can consider using numpy.putmask:

np.putmask(arr, arr>=T, 255.0)

Here is a performance comparison with the Numpy's builtin indexing:

In [1]: import numpy as np
In [2]: A = np.random.rand(500, 500)

In [3]: timeit np.putmask(A, A>0.5, 5)
1000 loops, best of 3: 1.34 ms per loop

In [4]: timeit A[A > 0.5] = 5
1000 loops, best of 3: 1.82 ms per loop

How to split a long array into smaller arrays, with JavaScript

If you want a method that doesn't modify the existing array, try this:

let oldArray = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
let newArray = [];
let size = 3; // Size of chunks you are after
let j = 0; // This helps us keep track of the child arrays

for (var i = 0; i < oldArray.length; i++) {
  if (i % size === 0) {
  if(!newArray[j]) newArray[j] = [];

Value Change Listener to JTextField

Add a listener to the underlying Document, which is automatically created for you.

// Listen for changes in the text
textField.getDocument().addDocumentListener(new DocumentListener() {
  public void changedUpdate(DocumentEvent e) {
  public void removeUpdate(DocumentEvent e) {
  public void insertUpdate(DocumentEvent e) {

  public void warn() {
     if (Integer.parseInt(textField.getText())<=0){
          "Error: Please enter number bigger than 0", "Error Message",

Counter exit code 139 when running, but gdb make it through

this error is also caused by null pointer reference. if you are using a pointer who is not initialized then it causes this error.

to check either a pointer is initialized or not you can try something like

Class *pointer = new Class();

Why dict.get(key) instead of dict[key]?

get takes a second optional value. If the specified key does not exist in your dictionary, then this value will be returned.

dictionary = {"Name": "Harry", "Age": 17}
dictionary.get('Year', 'No available data')
>> 'No available data'

If you do not give the second parameter, None will be returned.

If you use indexing as in dictionary['Year'], nonexistent keys will raise KeyError.

Numpy: Divide each row by a vector element

Here you go. You just need to use None (or alternatively np.newaxis) combined with broadcasting:

In [6]: data - vector[:,None]
array([[0, 0, 0],
       [0, 0, 0],
       [0, 0, 0]])

In [7]: data / vector[:,None]
array([[1, 1, 1],
       [1, 1, 1],
       [1, 1, 1]])

How to easily import multiple sql files into a MySQL database?

in windows open windows powershell and go to the folder where sql files are then run this command

cat *.sql |  C:\xampp\mysql\bin\mysql.exe -u username -p databasename

How do I get monitor resolution in Python?

Taken directly from an answer to this post: How to get the screen size in Tkinter?

import tkinter as tk

root = tk.Tk()

screen_width = root.winfo_screenwidth()
screen_height = root.winfo_screenheight()

Login failed for user 'DOMAIN\MACHINENAME$'

Basically to resolve this we need to have some set up like

  • Web App Running under ApplicationPoolIdentity
  • Web Application connecting to databases through ADO.Net using Windows Authentication in the connection string

The connection string used with Windows authentication include either Trusted_Connection=Yesattribute or the equivalent attribute Integrated Security=SSPI in Web.config file

My database connection is in Windows Authentication mode. So I resolved it by simply changing the Application Pools Identity from ApplicationPoolIdentity to my domain log in credentials DomainName\MyloginId


  1. Click on Application Pools
  2. Select Name of your application

  3. Go to Advanced Setting

  4. Expand Process Model and click Identity. Click three dot on right end.
  5. Click Set... button and Provide your domain log in credentials

For me it was resolved.

Note: In Production or IT environment, you might have service account under same domain for app pool identity. If so, use service account instead of your login.

Auto expand a textarea using jQuery

Let's say you're trying to accomplish this using Knockout... here's how:

In page:

<textarea data-bind="event: { keyup: $root.GrowTextArea }"></textarea>

In view model:

self.GrowTextArea = function (data, event) {
    $('#' +;

This should work even if you have multiple textareas created by a Knockout foreach like I do.

Why are only a few video games written in Java?

.NET definitely has some of the same issues that Java has when it comes to intense 3D performance. Microsoft has also invested a lot more time and money in the development of the libraries when it comes to working with 3D heavy operations.

(...personally, I also think they had a leg up when it comes to the magic between DirectX and .NET)

Appending to list in Python dictionary

list.append returns None, since it is an in-place operation and you are assigning it back to dates_dict[key]. So, the next time when you do dates_dict.get(key, []).append you are actually doing None.append. That is why it is failing. Instead, you can simply do

dates_dict.setdefault(key, []).append(date)

But, we have collections.defaultdict for this purpose only. You can do something like this

from collections import defaultdict
dates_dict = defaultdict(list)
for key, date in cur:

This will create a new list object, if the key is not found in the dictionary.

Note: Since the defaultdict will create a new list if the key is not found in the dictionary, this will have unintented side-effects. For example, if you simply want to retrieve a value for the key, which is not there, it will create a new list and return it.

ImportError: No Module Named bs4 (BeautifulSoup)

Try reinstalling the module OR Try installing with beautiful soup with the below command

pip install --ignore-installed BeautifulSoup4

How to instantiate a javascript class in another js file?

It is saying the value is undefined because it is a constructor function, not a class with a constructor. In order to use it, you would need to use Customer() or customer().

First, you need to load file1.js before file2.js, like slebetman said:

<script defer src="file1.js" type="module"></script>
<script defer src="file2.js" type="module"></script>

Then, you could change your file1.js as follows:

export default class Customer(){

And the file2.js as follows:

import { Customer } from "./file1";
var customer=new Customer();

Please correct me if I am wrong.

Upload folder with subfolders using S3 and the AWS console

It's worth mentioning that if you are simply using S3 for backups, you should just zip the folder and then upload that. This Will save you upload time and costs.

If you are not sure how to do efficient zipping from the terminal have a look here for OSX.

And $ zip -r folder_to_compress for Windows. Alternatively a client such as 7-Zip would be sufficient for Windows users

How do I use Safe Area Layout programmatically?

I'm actually using an extension for it and controlling if it is ios 11 or not.

extension UIView {

  var safeTopAnchor: NSLayoutYAxisAnchor {
    if #available(iOS 11.0, *) {
      return self.safeAreaLayoutGuide.topAnchor
    return self.topAnchor

  var safeLeftAnchor: NSLayoutXAxisAnchor {
    if #available(iOS 11.0, *){
      return self.safeAreaLayoutGuide.leftAnchor
    return self.leftAnchor

  var safeRightAnchor: NSLayoutXAxisAnchor {
    if #available(iOS 11.0, *){
      return self.safeAreaLayoutGuide.rightAnchor
    return self.rightAnchor

  var safeBottomAnchor: NSLayoutYAxisAnchor {
    if #available(iOS 11.0, *) {
      return self.safeAreaLayoutGuide.bottomAnchor
    return self.bottomAnchor

Including a css file in a blade template?

As you said this is a very bad way to do so laravel doesn't have that functionality AFAIK.

However blade can run plain php so you can do like this if you really need to:

<?php include public_path('css/styles.css') ?>

GUI Tool for PostgreSQL

Postgres Enterprise Manager from EnterpriseDB is probably the most advanced you'll find. It includes all the features of pgAdmin, plus monitoring of your hosts and database servers, predictive reporting, alerting and a SQL Profiler.

Ninja edit disclaimer/notice: it seems that this user is affiliated with EnterpriseDB, as the linked Postgres Enterprise Manager website contains a video of one Dave Page.

Can I use git diff on untracked files?

With recent git versions you can git add -N the file (or --intent-to-add), which adds a zero-length blob to the index at that location. The upshot is that your "untracked" file now becomes a modification to add all the content to this zero-length file, and that shows up in the "git diff" output.

git diff

echo "this is a new file" > new.txt
git diff

git add -N new.txt
git diff
diff --git a/new.txt b/new.txt
index e69de29..3b2aed8 100644
--- a/new.txt
+++ b/new.txt
@@ -0,0 +1 @@
+this is a new file

Sadly, as pointed out, you can't git stash while you have an --intent-to-add file pending like this. Although if you need to stash, you just add the new files and then stash them. Or you can use the emulation workaround:

git update-index --add --cacheinfo \
100644 e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 new.txt

(setting up an alias is your friend here).

Returning JSON object as response in Spring Boot

The reason why your current approach doesn't work is because Jackson is used by default to serialize and to deserialize objects. However, it doesn't know how to serialize the JSONObject. If you want to create a dynamic JSON structure, you can use a Map, for example:

public Map<String, String> sayHello() {
    HashMap<String, String> map = new HashMap<>();
    map.put("key", "value");
    map.put("foo", "bar");
    map.put("aa", "bb");
    return map;

This will lead to the following JSON response:

{ "key": "value", "foo": "bar", "aa": "bb" }

This is a bit limited, since it may become a bit more difficult to add child objects. Jackson has its own mechanism though, using ObjectNode and ArrayNode. To use it, you have to autowire ObjectMapper in your service/controller. Then you can use:

public ObjectNode sayHello() {
    ObjectNode objectNode = mapper.createObjectNode();
    objectNode.put("key", "value");
    objectNode.put("foo", "bar");
    objectNode.put("number", 42);
    return objectNode;

This approach allows you to add child objects, arrays, and use all various types.

Invalid CSRF Token 'null' was found on the request parameter '_csrf' or header 'X-CSRF-TOKEN'

i think csrf only works with spring forms

<%@ taglib prefix="form" uri="" %>

change to form:form tag and see it that works.

Oracle SQL - DATE greater than statement

You need to convert the string to date using the to_date() function

SELECT * FROM OrderArchive
WHERE OrderDate <= to_date('31-Dec-2014','DD-MON-YYYY');


SELECT * FROM OrderArchive
WHERE OrderDate <= to_date('31 Dec 2014','DD MON YYYY');


SELECT * FROM OrderArchive
WHERE OrderDate <= to_date('2014-12-31','yyyy-MM-dd');

This will work only if OrderDate is stored in Date format. If it is Varchar you should apply to_date() func on that column also like

 SELECT * FROM OrderArchive
    WHERE to_date(OrderDate,'yyyy-Mm-dd') <= to_date('2014-12-31','yyyy-MM-dd');

Repair all tables in one go

from command line you can use:

mysqlcheck -A --auto-repair

Should image size be defined in the img tag height/width attributes or in CSS?

Definitely not both. Other than that I'd have to say it's a personal preference. I'd use css if I had many images the same size to reduce code.

.my_images img {width: 20px; height:20px}

In the long term CSS may win out due to HTML attribute deprecation and more likely due to the growth of vector image formats like SVG where it can actually make sense to scale images using non-pixel based units like % or em.

What is a plain English explanation of "Big O" notation?

Big O notation is a way of describing the upper bound of an algorithm in terms of space or running time. The n is the number of elements in the the problem (i.e size of an array, number of nodes in a tree, etc.) We are interested in describing the running time as n gets big.

When we say some algorithm is O(f(n)) we are saying that the running time (or space required) by that algorithm is always lower than some constant times f(n).

To say that binary search has a running time of O(logn) is to say that there exists some constant c which you can multiply log(n) by that will always be larger than the running time of binary search. In this case you will always have some constant factor of log(n) comparisons.

In other words where g(n) is the running time of your algorithm, we say that g(n) = O(f(n)) when g(n) <= c*f(n) when n > k, where c and k are some constants.

HTML table headers always visible at top of window when viewing a large table

It's frustrating that what works great in one browser doesn't work in others. The following works in Firefox, but not in Chrome or IE:

<table width="80%">


  <th>Column 1</th>
  <th>Column 2</th>
  <th>Column 3</th>


 <tbody style="height:50px; overflow:auto">

    <td>Cell A1</td>
    <td>Cell B1</td>
    <td>Cell C1</td>

    <td>Cell A2</td>
    <td>Cell B2</td>
    <td>Cell C2</td>

    <td>Cell A3</td>
    <td>Cell B3</td>
    <td>Cell C3</td>



Valid to use <a> (anchor tag) without href attribute?

Yes, it is valid to use the anchor tag without a href attribute.

If the a element has no href attribute, then the element represents a placeholder for where a link might otherwise have been placed, if it had been relevant, consisting of just the element's contents.

Yes, you can use class and other attributes, but you can not use target, download, rel, hreflang, and type.

The target, download, rel, hreflang, and type attributes must be omitted if the href attribute is not present.

As for the "Should I?" part, see the first citation: "where a link might otherwise have been placed if it had been relevant". So I would ask "If I had no JavaScript, would I use this tag as a link?". If the answer is yes, then yes, you should use <a> without href. If no, then I would still use it, because productivity is more important for me than edge case semantics, but this is just my personal opinion.

Additionally, you should watch out for different behaviour and styling (e.g. no underline, no pointer cursor, not a :link).

Source: W3C HTML5 Recommendation

ASP.NET MVC 3 Razor: Include JavaScript file in the head tag

You can use Named Sections.


    <script type="text/javascript" src="@Url.Content("/Scripts/jquery-1.6.2.min.js")"></script>
    @RenderSection("JavaScript", required: false)


@section JavaScript
   <script type="text/javascript" src="@Url.Content("/Scripts/SomeScript.js")"></script>
   <script type="text/javascript" src="@Url.Content("/Scripts/AnotherScript.js")"></script>

Remove the complete styling of an HTML button/submit

Your question says "Internet Explorer," but for those interested in other browsers, you can now use all: unset on buttons to unstyle them.

It doesn't work in IE, but it's well-supported everywhere else.

Old Safari color warning: Setting the text color of the button after using all: unset can fail in Safari 13.1, due to a bug in WebKit. (The bug is fixed in Safari 14 and up.) "all: unset is setting -webkit-text-fill-color to black, and that overrides color." If you need to set text color after using all: unset, be sure to set both the color and the -webkit-text-fill-color to the same color.

Accessibility warning: For the sake of users who aren't using a mouse pointer, be sure to re-add some :focus styling, e.g. button:focus { outline: orange auto 5px } for keyboard accessibility.

And don't forget cursor: pointer. all: unset removes all styling, including the cursor: pointer, which makes your mouse cursor look like a pointing hand when you hover over the button. You almost certainly want to bring that back.

button {
  all: unset;
  color: blue;
  -webkit-text-fill-color: blue;
  cursor: pointer;

button:focus {
  outline: orange 5px auto;
<button>check it out</button>

Is it possible to opt-out of dark mode on iOS 13?

Just add these line in info.plist file:


This will force app to run in light mode only.

Setting new value for an attribute using jQuery

It is working you have to check attr after assigning value


$('#amount').attr( 'datamin','1000');

alert($('#amount').attr( 'datamin'));?

How to close a GUI when I push a JButton?

In Java 8, you can use Lambda expressions to make it simpler.

Close application

JButton btnClose = new JButton("Close");
btnClose.addActionListener(e -> System.exit(0));

Close window

JButton btnClose = new JButton("Close");
btnClose.addActionListener(e -> this.dispose());

How to hide collapsible Bootstrap 4 navbar on click

I am using Angular 5 with Boostrap 4. It works for me in this way.

 $(document).on('click', '.navbar-nav>li>a, .navbar-brand, .dropdown-menu>a', function (e) {_x000D_
      if ( $('a') && $('class') != 'nav-link dropdown-toggle' ) {_x000D_
<nav class="navbar navbar-expand-lg navbar-dark bg-primary">_x000D_
  <a class="navbar-brand" [routerLink]="['/home']">FbShareTool</a>_x000D_
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarColor01" aria-controls="navbarColor01" aria-expanded="false" aria-label="Toggle navigation" style="">_x000D_
    <span class="navbar-toggler-icon"></span>_x000D_
  <div class="collapse navbar-collapse" id="navbarColor01">_x000D_
    <ul class="navbar-nav mr-auto">_x000D_
      <li class="nav-item active" *ngIf="_myAuthService.isAuthenticated()">_x000D_
        <a class="nav-link" [routerLink]="['/dashboard']">Dashboard <span class="sr-only">(current)</span></a>_x000D_
      <li class="nav-item dropdown" *ngIf="_myAuthService.isAuthenticated()">_x000D_
          <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">_x000D_
          <div class="dropdown-menu" aria-labelledby="navbarDropdown">_x000D_
            <a class="dropdown-item" [routerLink]="['/fbgroup']">Facebook Group</a>_x000D_
            <div class="dropdown-divider"></div>_x000D_
            <a class="dropdown-item" href="#">Fetch Data</a>_x000D_
    <ul class="navbar-nav navbar-right navbar-right-link">_x000D_
        <li class="nav-item" *ngIf="!_myAuthService.isAuthenticated()" >_x000D_
            <a class="nav-link" (click)="logIn()">Login</a>_x000D_
        <li class="nav-item" *ngIf="_myAuthService.isAuthenticated()">_x000D_
           <a class="nav-link">{{ _myAuthService.userDetails.displayName }}</a>_x000D_
        <li class="nav-item" *ngIf="_myAuthService.isAuthenticated() && _myAuthService.userDetails.photoURL">_x000D_
              <img [src]="_myAuthService.userDetails.photoURL" alt="profile-photo" class="img-fluid rounded" width="40px;">_x000D_
        <li class="nav-item" *ngIf="_myAuthService.isAuthenticated()">_x000D_
            <a class="nav-link" (click)="logOut()">Logout</a>_x000D_

How to run function in AngularJS controller on document ready?

I had a similar situation where I needed to execute a controller function after the view was loaded and also after a particular 3rd-party component within the view was loaded, initialized, and had placed a reference to itself on $scope. What ended up working for me was to setup a watch on this scope property and firing my function only after it was initialized.

// $scope.myGrid property will be created by the grid itself
// The grid will have a loadedRows property once initialized

$scope.$watch('myGrid', function(newValue, oldValue) {
    if (newValue && newValue.loadedRows && !oldValue) {

The watcher is called a couple of times with undefined values. Then when the grid is created and has the expected property, the initialization function may be safely called. The first time the watcher is called with a non-undefined newValue, oldValue will still be undefined.

Escaping Double Quotes in Batch Script

The escape character in batch scripts is ^. But for double-quoted strings, double up the quotes:

"string with an embedded "" character"

How can you customize the numbers in an ordered list?

I suggest playing with the :before attribute and seeing what you can achieve with it. It will mean your code really is limited to nice new browsers, and excludes the (annoyingly large) section of the market still using rubbish old browsers,

Something like the following, which forces a fixed with on the items. Yes, I know it's less elegant to have to choose the width yourself, but using CSS for your layout is like undercover police work: however good your motives, it always gets messy.

li:before {
  content: counter(item) ") ";
  counter-increment: item;
  display: marker;
  width: 2em;

But you're going to have to experiment to find the exact solution.

Can I create view with parameter in MySQL?

I previously came up with a different workaround that doesn't use stored procedures, but instead uses a parameter table and some connection_id() magic.

EDIT (Copied up from comments)

create a table that contains a column called connection_id (make it a bigint). Place columns in that table for parameters for the view. Put a primary key on the connection_id. replace into the parameter table and use CONNECTION_ID() to populate the connection_id value. In the view use a cross join to the parameter table and put WHERE param_table.connection_id = CONNECTION_ID(). This will cross join with only one row from the parameter table which is what you want. You can then use the other columns in the where clause for example where orders.order_id = param_table.order_id.

Laravel PDOException SQLSTATE[HY000] [1049] Unknown database 'forge'

Encountered this issue quite a few times, note that I'm running laravel via Vagrant. So here are the fixes that work for me:

  • Try again several times (refresh page)
  • Reload vagrant (vagrant reload)

You may try reloading your server instead of vagrant (ie MAMP)

What does operator "dot" (.) mean?

The dot itself is not an operator, .^ is.

The .^ is a pointwise¹ (i.e. element-wise) power, as .* is the pointwise product.

.^ Array power. A.^B is the matrix with elements A(i,j) to the B(i,j) power. The sizes of A and B must be the same or be compatible.


¹) Hence the dot.

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

Parentheses in function definition

Parentheses () are being used in function definition:

function_name () { command1 ; command2 ; }

That is the reason you have to escape parentheses even in command parameters:

$ echo (
bash: syntax error near unexpected token `newline'

$ echo \(

$ echo () { command echo The command echo was redefined. ; }
$ echo anything
The command echo was redefined.

How to force reloading a page when using browser back button?

An alternative that solved the problem to me is to disable cache for the page. That make the browser to get the page from the server instead of using a cached version:

Response.AppendHeader("Cache-Control","no-cache, no-store, must-revalidate");
Response.AppendHeader("Pragma", "no-cache");
Response.AppendHeader("Expires", "0");

Searching for file in directories recursively

Try the following method:

public static IEnumerable<string> GetXMLFiles(string directory)
    List<string> files = new List<string>();

        files.AddRange(Directory.GetFiles(directory, "*.xml", SearchOption.AllDirectories));
    catch (Exception ex)

    return files;

Removing certain characters from a string in R

try: gsub('\\$', '', '$5.00$')

JQuery: dynamic height() with window resize()

To see the window height while (or after) it is resized, try it:

$(window).resize(function() {
$('body').prepend('<div>' + $(window).height() - 46 + '</div>');

Visual Studio Code pylint: Unable to import 'protorpc'

Changing the library path worked for me. Hitting Ctrl + Shift + P and typing python interpreter and choosing one of the available shown. One was familiar (as pointed to a virtualenv that was working fine earlier) and it worked. Take note of the version of python you are working with, either 2.7 or 3.x and choose accordingly

Is there a free GUI management tool for Oracle Database Express?

Try odbTools at - it is free.

odbTools is set of integrated GUI tools to manage, administer, monitor and tune the Oracle database.

How to remove space from string?

You can also use echo to remove blank spaces, either at the beginning or at the end of the string, but also repeating spaces inside the string.

$ myVar="    kokor    iiij     ook      "
$ echo "$myVar"
    kokor    iiij     ook      
$ myVar=`echo $myVar`
$ # myVar is not set to "kokor iiij ook"
$ echo "$myVar"
kokor iiij ook

Finding the second highest number in array

import java.util.*;
public class SecondLargestNew
    public static void main(String args[])
        int[] array = {0,12,74,26,82,3,89,8,94,3};  

    int highest = Integer.MIN_VALUE;
    int secondHighest = Integer.MIN_VALUE;

    for (int i = 0; i < array.length; i++) 
        if (array[i] > highest) 
            // ...shift the current highest number to second highest
            secondHighest = highest;
            // ...and set the new highest.
            highest = array[i];
        } else if (array[i] > secondHighest)
            // Just replace the second highest
            secondHighest = array[i];
    System.out.println("second largest is "+secondHighest );
    System.out.println("largest is "+ highest);

enter image description here

Break a previous commit into multiple commits

It's been more than 8 years, but maybe someone will find it helpful anyway. I was able to do the trick without rebase -i. The idea is to lead git to the same state it was before you did git commit:

# first rewind back (mind the dot,
# though it can be any valid path,
# for instance if you want to apply only a subset of the commit)
git reset --hard <previous-commit> .

# apply the changes
git checkout <commit-you-want-to-split>

# we're almost there, but the changes are in the index at the moment,
# hence one more step (exactly as git gently suggests):
# (use "git reset HEAD <file>..." to unstage)
git reset

After this you'll see this shiny Unstaged changes after reset: and your repo is in a state like you're about to commit all these files. From now on you can easily commit it again like you usually do. Hope it helps.

How to tackle daylight savings using TimeZone in Java

This is the problem to start with:

Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("EST"));

The 3-letter abbreviations should be wholeheartedly avoided in favour of TZDB zone IDs. EST is Eastern Standard Time - and Standard time never observes DST; it's not really a full time zone name. It's the name used for part of a time zone. (Unfortunately I haven't come across a good term for this "half time zone" concept.)

You want a full time zone name. For example, America/New_York is in the Eastern time zone:

TimeZone zone = TimeZone.getTimeZone("America/New_York");
DateFormat format = DateFormat.getDateTimeInstance();

System.out.println(format.format(new Date()));

How can I access Oracle from Python?

In addition to the Oracle instant client, you may also need to install the Oracle ODAC components and put the path to them into your system path. cx_Oracle seems to need access to the oci.dll file that is installed with them.

Also check that you get the correct version (32bit or 64bit) of them that matches your: python, cx_Oracle, and instant client versions.

Converting Object to JSON and JSON to Object in PHP, (library like Gson for Java)

I made a method to solve this. My approach is:

1 - Create a abstract class that have a method to convert Objects to Array (including private attr) using Regex. 2 - Convert the returned array to json.

I use this Abstract class as parent of all my domain classes

Class code:

namespace Project\core;

abstract class AbstractEntity {
    public function getAvoidedFields() {
        return array ();
    public function toArray() {
        $temp = ( array ) $this;

        $array = array ();

        foreach ( $temp as $k => $v ) {
            $k = preg_match ( '/^\x00(?:.*?)\x00(.+)/', $k, $matches ) ? $matches [1] : $k;
            if (in_array ( $k, $this->getAvoidedFields () )) {
                $array [$k] = "";
            } else {

                // if it is an object recursive call
                if (is_object ( $v ) && $v instanceof AbstractEntity) {
                    $array [$k] = $v->toArray();
                // if its an array pass por each item
                if (is_array ( $v )) {

                    foreach ( $v as $key => $value ) {
                        if (is_object ( $value ) && $value instanceof AbstractEntity) {
                            $arrayReturn [$key] = $value->toArray();
                        } else {
                            $arrayReturn [$key] = $value;
                    $array [$k] = $arrayReturn;
                // if it is not a array and a object return it
                if (! is_object ( $v ) && !is_array ( $v )) {
                    $array [$k] = $v;

        return $array;

Changing :hover to touch/click for mobile devices

I am a CSS noob but I have noticed that hover will work for touch screens so long as it's a "hoverable" element: image, link, button. You can do it all with CSS using the following trick.

Change your div background to an actual image tag within the div or create a dummy link around the entire div, it will then register as a hover when you touch the image.

Doing this will mean that you need the rest of your page to also be "hoverable" so when you touch outside of the image it recognizes that info-slide:hover has ended. My trick is to make all of my other content dummy links.

It's not very elegant but it works.

Get value of a merged cell of an excel from its cell address in vba

Even if it is really discouraged to use merge cells in Excel (use Center Across Selection for instance if needed), the cell that "contains" the value is the one on the top left (at least, that's a way to express it).

Hence, you can get the value of merged cells in range B4:B11 in several ways:

  • Range("B4").Value
  • Range("B4:B11").Cells(1).Value
  • Range("B4:B11").Cells(1,1).Value

You can also note that all the other cells have no value in them. While debugging, you can see that the value is empty.

Also note that Range("B4:B11").Value won't work (raises an execution error number 13 if you try to Debug.Print it) because it returns an array.

What does "exec sp_reset_connection" mean in Sql Server Profiler?

It's an indication that connection pooling is being used (which is a good thing).

Java Programming: call an exe from Java and passing parameters

You're on the right track. The two constructors accept arguments, or you can specify them post-construction with ProcessBuilder#command(java.util.List) and ProcessBuilder#command(String...).

Difference between & and && in Java?

'&' performs both tests, while '&&' only performs the 2nd test if the first is also true. This is known as shortcircuiting and may be considered as an optimization. This is especially useful in guarding against nullness(NullPointerException).

if( x != null && x.equals("*BINGO*") {
  then do something with x...

Validate phone number using angular js

<div ng-class="{'has-error': userForm.mobileno.$error.pattern ,'has-success': userForm.mobileno.$valid}">

              <input type="text" name="mobileno" ng-model="mobileno" ng-pattern="/^[7-9][0-9]{9}$/"  required>

Here "userForm" is my form name.

how to use python2.7 pip instead of default pip

There should be a binary called "pip2.7" installed at some location included within your $PATH variable.

You can find that out by typing

which pip2.7

This should print something like '/usr/local/bin/pip2.7' to your stdout. If it does not print anything like this, it is not installed. In that case, install it by running

$ wget
$ sudo python2.7

Now, you should be all set, and

which pip2.7

should return the correct output.

How do I get the key at a specific index from a Dictionary in Swift?

Swift 3 : Array() can be useful to do this .

Get Key :

let index = 5 // Int Value

Get Value :


Maven Unable to locate the Javac Compiler in:

It was an Eclipse problem. When I tried to build it from the command line using

mvn package

it worked fine.

Why did Servlet.service() for servlet jsp throw this exception?

It can be caused by a classpath contamination. Check that you /WEB-INF/lib doesn't contain something like jsp-api-*.jar.

How do you check if a variable is an array in JavaScript?

The universal solution is below:'[object Array]'

Starting from ECMAScript 5, a formal solution is :


Also, for old JavaScript libs, you can find below solution although it's not accurate enough:

var is_array = function (value) {
    return value &&
    typeof value === 'object' &&
    typeof value.length === 'number' &&
    typeof value.splice === 'function' &&

The solutions are from

What tools do you use to test your public REST API?

Postman in the chrome store is simple but powerful.

IF statement: how to leave cell blank if condition is false ("" does not work)

Try this instead


This will return true for cells that are either truly blank, or contain nothing but white space.

See this post for a few other options.


To reflect the comments and what you ended up doing: Instead of evaluating to "" enter another value such as 'deleteme' and then search for 'deleteme' instead of blanks.


Best way to save a trained model in PyTorch?

A common PyTorch convention is to save models using either a .pt or .pth file extension.

Save/Load Entire Model Save:

path = "username/directory/lstmmodelgpu.pth", path)


Model class must be defined somewhere

model = torch.load(PATH)

Eclipse does not highlight matching variables

I wish I could have read the response by @Ján Lazár.

In addition to all the configurations mentioned in the accepted answer, below setting solved my misery:

For large files the scalability mode must be turned off. Enabling scalability mode will disable reference highlighting.

enter image description here

PS: @Rob Hruska It would be great if this point is added in the accepted answer. Most of the readers do not bother to read the last response.

catch forEach last iteration

Updated answer for ES6+ is here.

arr = [1, 2, 3]; 

arr.forEach(function(i, idx, array){
   if (idx === array.length - 1){ 
       console.log("Last callback call at index " + idx + " with value " + i ); 

would output:

Last callback call at index 2 with value 3

The way this works is testing arr.length against the current index of the array, passed to the callback function.

How do you set the max number of characters for an EditText in Android?

Obviously you can use maxLength in xml or InputFilter.LengthFilter as answered above. But for me in some cases, it was not enough. I created a class for more flexible settings of EditText: It is implementation only for numbers input, but you can change it for any of the types.

How much overhead does SSL impose?

Order of magnitude: zero.

In other words, you won't see your throughput cut in half, or anything like it, when you add TLS. Answers to the "duplicate" question focus heavily on application performance, and how that compares to SSL overhead. This question specifically excludes application processing, and seeks to compare non-SSL to SSL only. While it makes sense to take a global view of performance when optimizing, that is not what this question is asking.

The main overhead of SSL is the handshake. That's where the expensive asymmetric cryptography happens. After negotiation, relatively efficient symmetric ciphers are used. That's why it can be very helpful to enable SSL sessions for your HTTPS service, where many connections are made. For a long-lived connection, this "end-effect" isn't as significant, and sessions aren't as useful.

Here's an interesting anecdote. When Google switched Gmail to use HTTPS, no additional resources were required; no network hardware, no new hosts. It only increased CPU load by about 1%.

How to convert a python numpy array to an RGB image with Opencv 2.4?

If anyone else simply wants to display a black image as a background, here e.g. for 500x500 px:

import cv2
import numpy as np

black_screen  = np.zeros([500,500,3])
cv2.imshow("Simple_black", black_screen)

can't start MySql in Mac OS 10.6 Snow Leopard

YOU MUST REINSTALL mySQL after upgrading to Snow Leopard and remove any previous versions as well as previous startup from the preference panel. install 86_64 10.5...I find the others did not work for me.

  1. Download MySQL version Mac OS X 10.5 (x86_64) located at
  2. Install startup Item (follow instructions)
  3. Then install the beta version (follow instructions)
  4. If you want the start up in the Preference Panel...install mySQL.prefpane I find that SQL does not run from the terminal unless you start mySQL in the preference panel.

Java random numbers using a seed

Problem is that you seed the random generator again. Every time you seed it the initial state of the random number generator gets reset and the first random number you generate will be the first random number after the initial state

How to fire a change event on a HTMLSelectElement if the new value is the same as the old?

JavaScript code:

  • on mousedown event: set selectedIndex property value to -1
  • on change event: handle event

The only drawback is that when the user clicks on the dropdown list, the currently selected item does not appear selected

Formatting Numbers by padding with leading zeros in SQL Server

You can change your procedure in this way

SELECT Right('000000' + CONVERT(NVARCHAR, EmployeeID), 6) AS EmpIDText, 
FROM dbo.RequestItems 

However this assumes that your EmployeeID is a numeric value and this code change the result to a string, I suggest to add again the original numeric value

EDIT Of course I have not read carefully the question above. It says that the field is a char(6) so EmployeeID is not a numeric value. While this answer has still a value per se, it is not the correct answer to the question above.