Programs & Examples On #File processing

Pure CSS scroll animation

Use anchor links and the scroll-behavior property (MDN reference) for the scrolling container:

scroll-behavior: smooth;

Browser support: Firefox 36+, Chrome 61+ (therefore also Edge 79+) and Opera 48+.

Intenet Explorer, non-Chromium Edge and (so far) Safari do not support scroll-behavior and simply "jump" to the link target.

Example usage:

  <style type="text/css">
    html {
      scroll-behavior: smooth;
<body id="body">
  <a href="#foo">Go to foo!</a>

  <!-- Some content -->

  <div id="foo">That's foo.</div>
  <a href="#body">Back to top</a>

Here's a Fiddle.

And here's also a Fiddle with both horizontal and vertical scrolling.

Convert array to string in NodeJS

In node, you can just say


and it will format it as it should.

If you need to use the resulting string you should use


What does "atomic" mean in programming?

"Atomic operation" means an operation that appears to be instantaneous from the perspective of all other threads. You don't need to worry about a partly complete operation when the guarantee applies.

PHP session handling errors

You can fix the issue with the following steps:

  1. Verify the folder exists with sudo cd /var/lib/php/session. If it does not exist then sudo mkdir /var/lib/php/session or double check the logs to make sure you have the correct path.
  2. Give the folder full read and write permissions with sudo chmod 666 /var/lib/php/session.

Rerun you script and it should be working fine, however, it's not recommended to leave the folder with full permissions. For security, files and folders should only have the minimum permissions required. The following steps will fix that:

  1. You should already be in the session folder so just run sudo ls -l to find out the owner of the session file.
  2. Set the correct owner of the session folder with sudo chown user /var/lib/php/session.
  3. Give just the owner full read and write permissions with sudo chmod 600 /var/lib/php/session.


You might not need to use the sudo command.

Send cookies with curl TRUE / FALSE 1560211200 MY_VARIABLE MY_VALUE

The cookies file format apparently consists of a line per cookie and each line consists of the following seven tab-delimited fields:

  • domain - The domain that created AND that can read the variable.
  • flag - A TRUE/FALSE value indicating if all machines within a given domain can access the variable. This value is set automatically by the browser, depending on the value you set for domain.
  • path - The path within the domain that the variable is valid for.
  • secure - A TRUE/FALSE value indicating if a secure connection with the domain is needed to access the variable.
  • expiration - The UNIX time that the variable will expire on. UNIX time is defined as the number of seconds since Jan 1, 1970 00:00:00 GMT.
  • name - The name of the variable.
  • value - The value of the variable.


How to create a project from existing source in Eclipse and then find it?

While creating a project from a full folder may or may not work within the workspace, there's a condition outside of the workspace that prevents starting a new project with a full folder.

This is relevant if you use numerous folder locations for sources, for example an htdocs or www folder for web projects, and a different location for desktop Java applications.

The condition mentioned occurs when Eclipse is told to create a new project, and given a full folder outside the workspace. Eclipse will say the folder isn't empty, and prevent creating a new project within the given folder. I haven't found a way around this, and any solution requires extra steps.

My favorite solution is as follows

  1. Rename the full folder with an appended "Original" or "Backup.
  2. Create the Eclipse project with the name of the full folder before the folder was renamed.
  3. Copy all the relabeled full folders contents into the new project folder.

Eclipse should make a new project, and update that project with the new folder contents as it scans for changes. The existing sources are now part of the new project.

Although you had to perform three extra steps, you now have a backup with the original sources available, and are also able to use a copy of them in an existing project. If storage space is a concern, simply move/cut the source rather than fully copy the original folder contents.

CSS container div not getting height

I ran into this same issue, and I have come up with four total viable solutions:

  1. Make the container display: flex; (this is my favorite solution)
  2. Add overflow: auto; or overflow: hidden; to the container
  3. Add the following CSS for the container:
.c:after {
    clear: both;
    content: "";
    display: block;
  1. Make the following the last item inside the container:
<div style="clear: both;"></div>

Pass path with spaces as parameter to bat file

@echo off
setlocal enableextensions enabledelayedexpansion

if %1=="" (     
        rem Set default path
        set PWA_PATH="C:\Program Files\PWA"
        echo You have not specified your PWA url.
        echo Default will be assumed: C:\Program Files\PWA.     
        choice /C:YN /M:"Do you wish to continue [Y] or cancel the script [N]?"
                IF ERRORLEVEL ==2 GOTO CANCEL
        GOTO END
    ) else (
        set PWA_PATH=%1
        @echo !PWA_PATH! vs. %1
        goto end
echo ok
goto end
echo cancelled
echo. final %PWA_PATH% vs. %1

As VardhanDotNet mentions, %1 is enough.

"%1%" would add quotes around quotes: ""c:\Program Files\xxx"" which means:

  • 'empty string' (""),
  • followed by 'c:\Program',
  • followed by the "unexpected here" 'Files\xxx',
  • followed by an empty string ("")

Note however that if you need to use PWA_PATH within your IF clause, you need to refer if as !PWA_PATH! (hence the enabledelayedexpansion as the beginning of the script)

Deserialize JSON with Jackson into Polymorphic Types - A Complete Example is giving me a compile error

Handling polymorphism is either model-bound or requires lots of code with various custom deserializers. I'm a co-author of a JSON Dynamic Deserialization Library that allows for model-independent json deserialization library. The solution to OP's problem can be found below. Note that the rules are declared in a very brief manner.

public class SOAnswer {
    @ToString @Getter @Setter
    @AllArgsConstructor @NoArgsConstructor
    public static abstract class Animal {
        private String name;    

    @ToString(callSuper = true) @Getter @Setter
    @AllArgsConstructor @NoArgsConstructor
    public static class Dog extends Animal {
        private String breed;

    @ToString(callSuper = true) @Getter @Setter
    @AllArgsConstructor @NoArgsConstructor
    public static class Cat extends Animal {
        private String favoriteToy;
    public static void main(String[] args) {
        String json = "[{"
                + "    \"name\": \"pluto\","
                + "    \"breed\": \"dalmatian\""
                + "},{"
                + "    \"name\": \"whiskers\","
                + "    \"favoriteToy\": \"mouse\""
                + "}]";
        // create a deserializer instance
        DynamicObjectDeserializer deserializer = new DynamicObjectDeserializer();
        // runtime-configure deserialization rules; 
        // condition is bound to the existence of a field, but it could be any Predicate
                (e) -> e.getJsonNode().has("breed"),
                (e) -> e.getJsonNode().has("favoriteToy"),
        List<Animal> deserializedAnimals = deserializer.deserializeArray(json, Animal.class);
        for (Animal animal : deserializedAnimals) {
            System.out.println("Deserialized Animal Class: " + animal.getClass().getSimpleName()+";\t value: "+animal.toString());

Maven depenendency for pretius-jddl (check newest version at


How to modify WooCommerce cart, checkout pages (main theme portion)

Another way to totally override the cart.php is to copy:

woocommerce/templates/cart/cart.php to   

Then do whatever you need at the yourtheme/woocommerce/cart/cart.php

Android: Getting "Manifest merger failed" error after updating to a new version of gradle

The error for me was:

Manifest merger failed : Attribute value=(26.0.2) from [] AndroidManifest.xml:25:13-35
    is also present at [] AndroidManifest.xml:28:13-35 value=(26.1.0).
    Suggestion: add 'tools:replace="android:value"' to <meta-data> element at AndroidManifest.xml:23:9-25:38 to override.

The solution for me was in my project Gradle file I needed to bump my version.

I was using version 3.1.1:

classpath '

And the error resolved after I bumped it to version 3.2.1:

classpath '

I had just upgraded all my libraries to the latest including v27.1.1 of all the support libraries and v15.0.0 of all the Firebase libraries when I saw the error.

How can I change the class of an element with jQuery>

To set a class completely, instead of adding one or removing one, use this:


Advantage of this is that you'll remove any class that might be set in there and reset it to how you like. At least this worked for me in one situation.

Deserialize from string instead TextReader

Shamelessly copied from Generic deserialization of an xml string

    public static T DeserializeFromXmlString<T>(string xmlString)
        var serializer = new XmlSerializer(typeof(T));
        using (TextReader reader = new StringReader(xmlString))
            return (T) serializer.Deserialize(reader);

makefile:4: *** missing separator. Stop

If you are using mcedit for makefile edit. you have to see the following mark. enter image description here

Why can't I call a public method in another class?

It sounds like you're not instantiating your class. That's the primary reason I get the "an object reference is required" error.

MyClass myClass = new MyClass();

once you've added that line you can then call your method


Also, are all of your classes in the same namespace? When I was first learning c# this was a common tripping point for me.

Use C# HttpWebRequest to send json to web service

First of all you missed ScriptService attribute to add in webservice.


After then try following method to call webservice via JSON.

        var webAddr = "http://Domain/VBRService.asmx/callJson";
        var httpWebRequest = (HttpWebRequest)WebRequest.Create(webAddr);
        httpWebRequest.ContentType = "application/json; charset=utf-8";
        httpWebRequest.Method = "POST";            

        using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
            string json = "{\"x\":\"true\"}";


        var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
        using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
            var result = streamReader.ReadToEnd();
            return result;

How to remove only 0 (Zero) values from column in excel 2010

I selected columns that I want to delete 0 values then clicked DATA > FILTER. In column's header there is a filter icon appears. I clicked on that icon and selected only 0 values and clicked OK. Only 0 values becomes selected. Finally clear content OR use DELETE button. Problem Solved!

What is the difference between & vs @ and = in angularJS

It took me a hell of a long time to really get a handle on this. The key to me was in understanding that "@" is for stuff that you want evaluated in situ and passed through into the directive as a constant where "=" actually passes the object itself.

There's a nice blog post that explains this this at:

What's causing my Connection reset?

If you experience this trying to access Web services deployed on a Glassfish3 server, you might want to tune your http-thread-pool settings. That fixed SocketExceptions we had when many concurrent threads was calling the web service.

  1. Go to admin console
  2. Navigate to "Configurations"->"Server config"->"Thread pools"->"http-thread-pool".
  3. Change setting "Max Thread Pool Size" from 5 to 32
  4. Change setting "Min Thread Pool Size" from 2 to 16
  5. Restart Glassfish.

How to do constructor chaining in C#

Are you asking about this?

  public class VariantDate {
    public int day;
    public int month;
    public int year;

    public VariantDate(int day) : this(day, 1) {}

    public VariantDate(int day, int month) : this(day, month,1900){}

    public VariantDate(int day, int month, int year){;


How to type in textbox using Selenium WebDriver (Selenium 2) with Java?

This is simple if you only use Selenium WebDriver, and forget the usage of Selenium-RC. I'd go like this.

WebDriver driver = new FirefoxDriver();
WebElement email = driver.findElement("email"));
email.sendKeys("[email protected]");

The reason for NullPointerException however is that your variable driver has never been started, you start FirefoxDriver in a variable wb thas is never being used.

How to clear a data grid view

private void ClearGrid()
    if(this.InvokeRequired) this.Invoke(new Action(this.ClearGrid));

    this.dataGridView.DataSource = null;

What is the difference between C++ and Visual C++?

What is the difference between c++ and visaul c++?

Visual C++ is an IDE. There's also C++Builder from Embarcadero. (Used to be Borland.) There are also a few other C++ IDE's.

I know that c++ has the portability and all so if you know c++ how is it related to visual c++?

C++ is as portable as the libraries that you use in your C++ application. VC++ has some specialized libraries to use with Windows, so if you use those libraries in your C++ application, you're stuck with Windows. But a simple "Hello, World" application that just uses the console as output can be compiled on Windows, Linux, VMS, AS/400, Smartphones, FreeBSD, MS-DOS, CP80 and almost any other system for which you can find a C++ compiler. Injteresting fact: at you can download the C sourcecode for an almost antique game, where you have to walk through a bunch of mazes, kick some monsters around, find treasures and steal some valuable amulet and bring that amulet back out. (It's also a game where you can encounter your characters from previous, failed attempts to get that amulet. :-) The sourcecode of NetHack is a fine example of how portable C (C++) code can be.

Is visual c++ mostly for online apps?

No. But it can be used for online apps. Actually, C# is used more often for server-side web applications while C++ (VC++) is used for all kinds of (server) components that your application will be depending upon.

Would visual basic be better for desktop applications?

Or Embarcadero Delphi. Delphi and Basic are languages that are easier to learn than C++ and both have very good IDE's to develop GUI applications with. Unfortunately, Visual Basic is now running on .NET only, while there are still many developers who need to create WIN32 applications. Those developers often have to choose between Delphi or C++ or else convince management to move to .NET development.

Nesting queries in SQL

If it has to be "nested", this would be one way, to get your job done:

SELECT AS country, o.headofstate 
FROM   country o
WHERE  o.headofstate like 'A%'
AND   (
    SELECT i.population
    FROM   city i
    WHERE =
    ) > 100000

A JOIN would be more efficient than a correlated subquery, though. Can it be, that who ever gave you that task is not up to speed himself?

Hadoop/Hive : Loading data from .csv on a local machine

There is another way of enabling this,

  1. use hadoop hdfs -copyFromLocal to copy the .csv data file from your local computer to somewhere in HDFS, say '/path/filename'

  2. enter Hive console, run the following script to load from the file to make it as a Hive table. Note that '\054' is the ascii code of 'comma' in octal number, representing fields delimiter.

 COMMENT 'from csv file'
 LOCATION '/path/filename';

How do I POST with multipart form data using fetch?

I was recently working with IPFS and worked this out. A curl example for IPFS to upload a file looks like this:

curl -i -H "Content-Type: multipart/form-data; boundary=CUSTOM" -d $'--CUSTOM\r\nContent-Type: multipart/octet-stream\r\nContent-Disposition: file; filename="test"\r\n\r\nHello World!\n--CUSTOM--' "http://localhost:5001/api/v0/add"

The basic idea is that each part (split by string in boundary with --) has it's own headers (Content-Type in the second part, for example.) The FormData object manages all this for you, so it's a better way to accomplish our goals.

This translates to fetch API like this:

const formData = new FormData()
formData.append('blob', new Blob(['Hello World!\n']), 'test')

fetch('http://localhost:5001/api/v0/add', {
  method: 'POST',
  body: formData
.then(r => r.json())
.then(data => {

How do you push a Git tag to a branch using a refspec?

It is probably failing because 1.0.0 is an annotated tag. Perhaps you saw the following error message:

error: Trying to write non-commit object to branch refs/heads/master

Annotated tags have their own distinct type of object that points to the tagged commit object. Branches can not usefully point to tag objects, only commit objects. You need to “peel” the annotated tag back to commit object and push that instead.

git push production +1.0.0^{commit}:master
git push production +1.0.0~0:master          # shorthand

There is another syntax that would also work in this case, but it means something slightly different if the tag object points to something other than a commit (or a tag object that points to (a tag object that points to a …) a commit).

git push production +1.0.0^{}:master

These tag peeling syntaxes are described in git-rev-parse(1) under Specifying Revisions.

recursion versus iteration

Question :

And if recursion is usually slower what is the technical reason for ever using it over for loop iteration?

Answer :

Because in some algorithms are hard to solve it iteratively. Try to solve depth-first search in both recursively and iteratively. You will get the idea that it is plain hard to solve DFS with iteration.

Another good thing to try out : Try to write Merge sort iteratively. It will take you quite some time.

Question :

Is it correct to say that everywhere recursion is used a for loop could be used?

Answer :

Yes. This thread has a very good answer for this.

Question :

And if it is always possible to convert an recursion into a for loop is there a rule of thumb way to do it?

Answer :

Trust me. Try to write your own version to solve depth-first search iteratively. You will notice that some problems are easier to solve it recursively.

Hint : Recursion is good when you are solving a problem that can be solved by divide and conquer technique.


    TableID     int         IDENTITY,
    FieldValue  varchar(20)

--<< No empty string
    SELECT *
    FROM @t1
    WHERE FieldValue = ''
    SELECT TableID
    FROM @t1
    WHERE FieldValue=''
    INSERT INTO @t1 (FieldValue) VALUES ('')

--<< A record with an empty string already exists
    SELECT *
    FROM @t1
    WHERE FieldValue = ''
    SELECT TableID
    FROM @t1
    WHERE FieldValue=''
    INSERT INTO @t1 (FieldValue) VALUES ('')

Creating instance list of different objects

List anyObject = new ArrayList();


List<Object> anyObject = new ArrayList<Object>();

now anyObject can hold objects of any type.

use instanceof to know what kind of object it is.

How to work on UAC when installing XAMPP

This is a specific issue for Windows Vista, 7, 8 (and presumably newer).

User Account Control (UAC) is a feature in Windows that can help you stay in control of your computer by informing you when a program makes a change that requires administrator-level permission. UAC works by adjusting the permission level of your user account.

This is applied mostly to C:\Program Files. You may have noticed sometimes, that some applications can see files in C:\Program Files that does not exist there. You know why? Windows now tend to have "C:\Program Files" folder customized for every user. For example, old applications store config files (like .ini) in the same folder where the executable files are stored. In the good old days all users had the same configurations for such apps. In nowadays Windows stores configs in the special folder tied to the user account. Thus, now different users may have different configs while application still think that config files are in the same folder with the executables.

XAMPP does not like to have different config for different users. In fact it is not a config file for XAMPP, it is folders where you keep your projects and databases. The idea of XAMPP is to make projects same for all users. This is a source of a conflict with Windows.

All you need is to avoid installing XAMPP into C:\Program Files. Thus XAMPP will always use the original files for all users and there would be no confusion.

I recommend to install XAMPP into the special folder in root directory like in C:\XAMPP. But before you choose the folder you need to click on this warning message.

Check if string ends with certain pattern

You can use the substring method:

   String aString = "";
   String aSubstring = "work";
   String endString = aString.substring(aString.length() - 
        (aSubstring.length() + 1),aString.length() - 1);
   if ( endString.equals(aSubstring) )
       System.out.println("Equal " + aString + " " + aSubstring);
       System.out.println("NOT equal " + aString + " " + aSubstring);

git: How to ignore all present untracked files?

IMHO better than the accepted answer is to use the following:

git config --local status.showUntrackedFiles no

The accepted answer does not work for when new files are added that are not in .gitignore

how to implement Interfaces in C++?

There is no concept of interface in C++,
You can simulate the behavior using an Abstract class.
Abstract class is a class which has atleast one pure virtual function, One cannot create any instances of an abstract class but You could create pointers and references to it. Also each class inheriting from the abstract class must implement the pure virtual functions in order that it's instances can be created.

Print the contents of a DIV

From here


    <script language="javascript">
        function printdiv(printpage) {
            var headstr = "<html><head><title></title></head><body>";
            var footstr = "</body>";
            var newstr = document.all.item(printpage).innerHTML;
            var oldstr = document.body.innerHTML;
            document.body.innerHTML = headstr + newstr + footstr;
            document.body.innerHTML = oldstr;
            return false;
    <title>div print</title>

    //HTML Page //Other content you wouldn't like to print
    <input name="b_print" type="button" class="ipt" onClick="printdiv('div_print');" value=" Print ">

    <div id="div_print">

        <h1 style="Color:Red">The Div content which you want to print</h1>

    //Other content you wouldn't like to print //Other content you wouldn't like to print


Including JavaScript class definition from another file in Node.js

Another way in addition to the ones provided here for ES6

module.exports = class TEST{
    constructor(size) { = new MAp();
        this.size = size;


    get(key) {

    length() {


and include the same as

var TEST= require('./TEST');
var test = new TEST(1);

Finding the average of an array using JS

It can simply be done with a single reduce operation as follows;

var avg = [1,2,3,4].reduce((p,c,_,a) => p + c/a.length,0);_x000D_

keypress, ctrl+c (or some combo like that)

I am a little late to the party but here is my part

$(document).on('keydown', function ( e ) {
    // You may replace `c` with whatever key you want
    if ((e.metaKey || e.ctrlKey) && ( String.fromCharCode(e.which).toLowerCase() === 'c') ) {
        console.log( "You pressed CTRL + C" );

How to start Apache and MySQL automatically when Windows 8 comes up

Copy xampp_start.exe from your XAMPP install directory to C:\Users\YOUR USERNAME\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup.

Replace YOUR USERNAME with your username.

$(window).height() vs $(document).height

AFAIK $(window).height(); returns the height of your window and $(document).height(); returns the height of your document

How to return multiple values in one column (T-SQL)?

DECLARE @Str varchar(500)

SELECT @Str=COALESCE(@Str,'') + CAST(ID as varchar(10)) + ','
FROM dbo.fcUser


MySQL - ERROR 1045 - Access denied

I had the same error, but it was because password_expired was set to Y. You can fix that issue by following the same approach as the currently accepted answer, but instead executing the MySQL query:

UPDATE mysql.user SET password_expired = 'N' WHERE User='root';

Textfield with only bottom border

See this JSFiddle

        border: 0;_x000D_
        border-bottom: 1px solid red;_x000D_
        outline: 0;_x000D_
        <input type="text" value="See! ONLY BOTTOM BORDER!" />_x000D_

jquery remove "selected" attribute of option?

The question is asked in a misleading manner. "Removing the selected attribute" and "deselecting all options" are entirely different things.

To deselect all options in a documented, cross-browser manner use either



// Note the use of .prop instead of .attr
$("select option").prop("selected", false);

Duplicate keys in .NET dictionaries?

I think something like List<KeyValuePair<object, object>> would do the Job.

Where is array's length property defined?

Arrays are special objects in java, they have a simple attribute named length which is final.

There is no "class definition" of an array (you can't find it in any .class file), they're a part of the language itself.

10.7. Array Members

The members of an array type are all of the following:

  • The public final field length, which contains the number of components of the array. length may be positive or zero.
  • The public method clone, which overrides the method of the same name in class Object and throws no checked exceptions. The return type of the clone method of an array type T[] is T[].

    A clone of a multidimensional array is shallow, which is to say that it creates only a single new array. Subarrays are shared.

  • All the members inherited from class Object; the only method of Object that is not inherited is its clone method.


How to upload (FTP) files to server in a bash script?

# $1 is the file name
# usage: this_script  <filename>

echo "
 open $IP_address
 USER $username $password
 put $1
" | ftp -n > ftp_$$.log

MySQL Error #1133 - Can't find any matching row in the user table

This error can occur if trying to grant privileges for a non-existing user.

It is not clear to me what MySQL considers a non-existing user. But I suspect MySQL considers a user to exist if it can be found by a name (column User) and a host (column Host) in the user table.

If trying to grant privileges to a user that can be found with his name (column User) but not by his name and host (columns User and Host), and not provide a password, then the error occurs.

For example, the following statement triggers the error:

grant all privileges on mydb.* to myuser@'';

This is because, with no password being specified, MySQL cannot create a new user, and thus tries to find an existing user. But no user with the name myuser and the host can be found in the user table.

Whereas providing a password, allows the statement to be executed successfully:

grant all privileges on mydb.* to myuser@'' identified by 'mypassword';

Make sure to reuse the same password of that user you consider exists, if that new "MySQL user" is the same "application user".

Complete the operation by flushing the privileges:

flush privileges;

mysql error 1364 Field doesn't have a default values

Its work and tested Copy to Config File: /etc/mysql/my.cnf OR /bin/mysql/my.ini

port = 3306

then restart MySQL

What does %5B and %5D in POST requests stand for?

To take a quick look, you can percent-en/decode using this online tool.

Convert a tensor to numpy array in Tensorflow?

Any tensor returned by or eval is a NumPy array.

>>> print(type(tf.Session().run(tf.constant([1,2,3]))))
<class 'numpy.ndarray'>


>>> sess = tf.InteractiveSession()
>>> print(type(tf.constant([1,2,3]).eval()))
<class 'numpy.ndarray'>

Or, equivalently:

>>> sess = tf.Session()
>>> with sess.as_default():
>>>    print(type(tf.constant([1,2,3]).eval()))
<class 'numpy.ndarray'>

EDIT: Not any tensor returned by or eval() is a NumPy array. Sparse Tensors for example are returned as SparseTensorValue:

>>> print(type(tf.Session().run(tf.SparseTensor([[0, 0]],[1],[1,2]))))
<class 'tensorflow.python.framework.sparse_tensor.SparseTensorValue'>

Removing duplicate characters from a string

from collections import OrderedDict
def remove_duplicates(value):
        for i in m:
        return s

Can you use a trailing comma in a JSON object?

Use JSON5. Don't use JSON.

  • Objects and arrays can have trailing commas
  • Object keys can be unquoted if they're valid identifiers
  • Strings can be single-quoted
  • Strings can be split across multiple lines
  • Numbers can be hexadecimal (base 16)
  • Numbers can begin or end with a (leading or trailing) decimal point.
  • Numbers can include Infinity and -Infinity.
  • Numbers can begin with an explicit plus (+) sign.
  • Both inline (single-line) and block (multi-line) comments are allowed.

What is your single most favorite command-line trick using Bash?

When downloading a large file I quite often do:

while ls -la <filename>; do sleep 5; done

And then just ctrl+c when I'm done (or if ls returns non-zero). It's similar to the watch program but it uses the shell instead, so it works on platforms without watch.

Another useful tool is netcat, or nc. If you do:

nc -l -p 9100 > printjob.prn

Then you can set up a printer on another computer but instead use the IP address of the computer running netcat. When the print job is sent, it is received by the computer running netcat and dumped into printjob.prn.

How do I get the current timezone name in Postgres 9.3?

I don't think this is possible using PostgreSQL alone in the most general case. When you install PostgreSQL, you pick a time zone. I'm pretty sure the default is to use the operating system's timezone. That will usually be reflected in postgresql.conf as the value of the parameter "timezone". But the value ends up as "localtime". You can see this setting with the SQL statement.

show timezone;

But if you change the timezone in postgresql.conf to something like "Europe/Berlin", then show timezone; will return that value instead of "localtime".

So I think your solution will involve setting "timezone" in postgresql.conf to an explicit value rather than the default "localtime".

Convert .pfx to .cer

PFX files are PKCS#12 Personal Information Exchange Syntax Standard bundles. They can include arbitrary number of private keys with accompanying X.509 certificates and a certificate authority chain (set certificates).

If you want to extract client certificates, you can use OpenSSL's PKCS12 tool.

openssl pkcs12 -in input.pfx -out mycerts.crt -nokeys -clcerts

The command above will output certificate(s) in PEM format. The ".crt" file extension is handled by both macOS and Window.

You mention ".cer" extension in the question which is conventionally used for the DER encoded files. A binary encoding. Try the ".crt" file first and if it's not accepted, easy to convert from PEM to DER:

openssl x509 -inform pem -in mycerts.crt -outform der -out mycerts.cer

Purpose of "%matplotlib inline"

Provided you are running Jupyter Notebook, the %matplotlib inline command will make your plot outputs appear in the notebook, also can be stored.

Use sudo with password as parameter

echo -e "YOURPASSWORD\n" | sudo -S yourcommand

How to use Oracle ORDER BY and ROWNUM correctly?

Use ROW_NUMBER() instead. ROWNUM is a pseudocolumn and ROW_NUMBER() is a function. You can read about difference between them and see the difference in output of below queries:

SELECT * FROM (SELECT rownum, deptno, ename
           FROM scott.emp
        ORDER BY deptno
 WHERE rownum <= 3

 7        10    CLARK
 14       10    MILLER
 9        10    KING

  SELECT deptno, ename
       , ROW_NUMBER() OVER (ORDER BY deptno) rno
  FROM scott.emp
 ORDER BY deptno
WHERE rno <= 3

10    CLARK        1
10    MILLER       2
10    KING         3

Failed to load ApplicationContext from Unit Test: FileNotFound

Add in in pom.xml give the following plugin:


How do I delete specific lines in Notepad++?

Using regex and find&replace, you can delete all the lines containing #region without leaving empty lines. Because for some reason Ray's method didn't work on my machine I searched for (.*#region.*\n)|(\n.*#region.*) and left the replace box empty.

That regex ensures that the if #region is found on the first line, the ending newline is deleted, and if it is found on the last line the preceding newline is deleted.

Still, Ray's solution is the better one if it works for you.

java.sql.SQLException: - ORA-01000: maximum open cursors exceeded

I faced the same problem (ORA-01000) today. I had a for loop in the try{}, to execute a SELECT statement in an Oracle DB many times, (each time changing a parameter), and in the finally{} I had my code to close Resultset, PreparedStatement and Connection as usual. But as soon as I reached a specific amount of loops (1000) I got the Oracle error about too many open cursors.

Based on the post by Andrew Alcock above, I made changes so that inside the loop, I closed each resultset and each statement after getting the data and before looping again, and that solved the problem.

Additionaly, the exact same problem occured in another loop of Insert Statements, in another Oracle DB (ORA-01000), this time after 300 statements. Again it was solved in the same way, so either the PreparedStatement or the ResultSet or both, count as open cursors until they are closed.

Return array in a function

int *fillarr(int arr[])

You can still use the result like

int *returned_array = fillarr(some_other_array);
if(returned_array[0] == 3)

Laravel - Route::resource vs Route::controller

RESTful Resource controller

A RESTful resource controller sets up some default routes for you and even names them.

Route::resource('users', 'UsersController');

Gives you these named routes:

Verb          Path                        Action  Route Name
GET           /users                      index   users.index
GET           /users/create               create  users.create
POST          /users                      store
GET           /users/{user}               show
GET           /users/{user}/edit          edit    users.edit
PUT|PATCH     /users/{user}               update  users.update
DELETE        /users/{user}               destroy users.destroy

And you would set up your controller something like this (actions = methods)

class UsersController extends BaseController {

    public function index() {}

    public function show($id) {}

    public function store() {}


You can also choose what actions are included or excluded like this:

Route::resource('users', 'UsersController', [
    'only' => ['index', 'show']

Route::resource('monkeys', 'MonkeysController', [
    'except' => ['edit', 'create']

API Resource controller

Laravel 5.5 added another method for dealing with routes for resource controllers. API Resource Controller acts exactly like shown above, but does not register create and edit routes. It is meant to be used for ease of mapping routes used in RESTful APIs - where you typically do not have any kind of data located in create nor edit methods.

Route::apiResource('users', 'UsersController');

RESTful Resource Controller documentation

Implicit controller

An Implicit controller is more flexible. You get routed to your controller methods based on the HTTP request type and name. However, you don't have route names defined for you and it will catch all subfolders for the same route.

Route::controller('users', 'UserController');

Would lead you to set up the controller with a sort of RESTful naming scheme:

class UserController extends BaseController {

    public function getIndex()
        // GET request to index

    public function getShow($id)
        // get request to 'users/show/{id}'

    public function postStore()
        // POST request to 'users/store'


Implicit Controller documentation

It is good practice to use what you need, as per your preference. I personally don't like the Implicit controllers, because they can be messy, don't provide names and can be confusing when using php artisan routes. I typically use RESTful Resource controllers in combination with explicit routes.

Event when window.location.href changes

You can't avoid polling, there isn't any event for href change.

Using intervals is quite light anyways if you don't go overboard. Checking the href every 50ms or so will not have any significant effect on performance if you're worried about that.

Increasing nesting function calls limit

Personally I would suggest this is an error as opposed to a setting that needs adjusting. In my code it was because I had a class that had the same name as a library within one of my controllers and it seemed to trip it up.

Output errors and see where this is being triggered.

Replace a value in a data frame based on a conditional (`if`) statement

You have created a factor variable in nm so you either need to avoid doing so or add an additional level to the factor attributes. You should also avoid using <- in the arguments to data.frame()

Option 1:

junk <- data.frame(x = rep(LETTERS[1:4], 3), y =letters[1:12], stringsAsFactors=FALSE)
junk$nm[junk$nm == "B"] <- "b"

Option 2:

levels(junk$nm) <- c(levels(junk$nm), "b")
junk$nm[junk$nm == "B"] <- "b"

ASP.NET set hiddenfield a value in Javascript

  • First you need to create the Hidden Field properly

    <asp:HiddenField ID="hdntxtbxTaksit" runat="server"></asp:HiddenField>

  • Then you need to set value to the hidden field

    If you aren't using Jquery you should use it:

    document.getElementById("<%= hdntxtbxTaksit.ClientID %>").value = "test";

    If you are using Jquery, this is how it should be:

    $("#<%= hdntxtbxTaksit.ClientID %>").val("test");

CSS Selector that applies to elements with two classes

Chain both class selectors (without a space in between): {
    /* Styles for element(s) with foo AND bar classes */

If you still have to deal with ancient browsers like IE6, be aware that it doesn't read chained class selectors correctly: it'll only read the last class selector (.bar in this case) instead, regardless of what other classes you list.

To illustrate how other browsers and IE6 interpret this, consider this CSS:

* {
    color: black;
} {
    color: red;

Output on supported browsers is:

<div class="foo">Hello Foo</div>       <!-- Not selected, black text [1] -->
<div class="foo bar">Hello World</div> <!-- Selected, red text [2] -->
<div class="bar">Hello Bar</div>       <!-- Not selected, black text [3] -->

Output on IE6 is:

<div class="foo">Hello Foo</div>       <!-- Not selected, black text [1] -->
<div class="foo bar">Hello World</div> <!-- Selected, red text [2] -->
<div class="bar">Hello Bar</div>       <!-- Selected, red text [2] -->


  • Supported browsers:
    1. Not selected as this element only has class foo.
    2. Selected as this element has both classes foo and bar.
    3. Not selected as this element only has class bar.

  • IE6:
    1. Not selected as this element doesn't have class bar.
    2. Selected as this element has class bar, regardless of any other classes listed.

How to determine programmatically the current active profile using Spring boot

It doesn't matter is your app Boot or just raw Spring. There is just enough to inject org.springframework.core.env.Environment to your bean.

private Environment environment;


How to write a unit test for a Spring Boot Controller endpoint

Here is another answer using Spring MVC's standaloneSetup. Using this way you can either autowire the controller class or Mock it.

    import static org.mockito.Mockito.mock;
    import static org.springframework.test.web.server.request.MockMvcRequestBuilders.get;
    import static org.springframework.test.web.server.result.MockMvcResultMatchers.content;
    import static org.springframework.test.web.server.result.MockMvcResultMatchers.status;

    import org.junit.Before;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.http.MediaType;
    import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    import org.springframework.test.web.server.MockMvc;
    import org.springframework.test.web.server.setup.MockMvcBuilders;

    @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
    public class DemoApplicationTests {

        final String BASE_URL = "http://localhost:8080/";

        private HelloWorld controllerToTest;

        private MockMvc mockMvc;

        public void setup() {
            this.mockMvc = MockMvcBuilders.standaloneSetup(controllerToTest).build();

        public void testSayHelloWorld() throws Exception{
            //Mocking Controller
            controllerToTest = mock(HelloWorld.class);


        public void contextLoads() {


splitting a number into the integer and decimal parts

This also works for me

>>> val_int = int(a)
>>> val_fract = a - val_int

How do I prevent and/or handle a StackOverflowException?

From Microsoft:

Starting with the .NET Framework version 2.0, a StackOverflowException object cannot be caught by a try-catch block and the corresponding process is terminated by default. Consequently, users are advised to write their code to detect and prevent a stack overflow. For example, if your application depends on recursion, use a counter or a state condition to terminate the recursive loop.

I'm assuming the exception is happening within an internal .NET method, and not in your code.

You can do a couple things.

  • Write code that checks the xsl for infinite recursion and notifies the user prior to applying a transform (Ugh).
  • Load the XslTransform code into a separate process (Hacky, but less work).

You can use the Process class to load the assembly that will apply the transform into a separate process, and alert the user of the failure if it dies, without killing your main app.

EDIT: I just tested, here is how to do it:


// This is just an example, obviously you'll want to pass args to this.
Process p1 = new Process();
p1.StartInfo.FileName = "ApplyTransform.exe";
p1.StartInfo.UseShellExecute = false;
p1.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;


if (p1.ExitCode == 1)    
   Console.WriteLine("StackOverflow was thrown");

ApplyTransform Process:

class Program
    static void Main(string[] args)
        AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException);
        throw new StackOverflowException();

    // We trap this, we can't save the process, 
    // but we can prevent the "ILLEGAL OPERATION" window 
    static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
        if (e.IsTerminating)

JQuery .each() backwards

$($("li").get().reverse()).each(function() { /* ... */ });

Invalid URI: The format of the URI could not be determined

I worked around this by using UriBuilder instead.

UriBuilder builder = new UriBuilder(slct.Text);

if (DeleteFileOnServer(builder.Uri))

What is /var/www/html?

/var/www/html is just the default root folder of the web server. You can change that to be whatever folder you want by editing your apache.conf file (usually located in /etc/apache/conf) and changing the DocumentRoot attribute (see for info on that)

Many hosts don't let you change these things yourself, so your mileage may vary. Some let you change them, but only with the built in admin tools (cPanel, for example) instead of via a command line or editing the raw config files.

Sorting 1 million 8-decimal-digit numbers with 1 MB of RAM

If the range of the numbers is limited (there can be only mod 2 8 digit numbers, or only 10 different 8 digit numbers for example), then you could write an optimized sorting algorithm. But if you want to sort all possible 8 digit numbers, this is not possible with that low amount of memory.

How can I setup & run PhantomJS on Ubuntu?

Or the latest - 32bit version Linux

sudo wget

sudo ln -s /usr/local/share/phantomjs-1.9.2-linux-i686/bin/phantomjs /usr/local/share/phantomjs

sudo ln -s /usr/local/share/phantomjs-1.9.2-linux-i686/bin/phantomjs /usr/local/bin/phantomjs

sudo ln -s /usr/local/share/phantomjs-1.9.2-linux-i686/bin/phantomjs /usr/bin/phantomjs

TypeError: unhashable type: 'dict', when dict used as a key for another dict

What it seems like to me is that by calling the keys method you're returning to python a dictionary object when it's looking for a list or a tuple. So try taking all of the keys in the dictionary, putting them into a list and then using the for loop.

CSS3 selector :first-of-type with class name?

Simply :first works for me, why isn't this mentioned yet?

How to increase image size of pandas.DataFrame.plot in jupyter notebook?

If you want to make a change global to the whole notebook:

import matplotlib.pyplot as plt
%matplotlib inline
plt.rcParams["figure.figsize"] = [10, 5]

jQuery change event on dropdown

You should've kept that DOM ready function

$(function() {
    $("#projectKey").change(function() {
        alert( $('option:selected', this).text() );

The document isn't ready if you added the javascript before the elements in the DOM, you have to either use a DOM ready function or add the javascript after the elements, the usual place is right before the </body> tag

How to load a jar file at runtime

Use org.openide.util.Lookup and ClassLoader to dynamically load the Jar plugin, as shown here.

public LoadEngine() {
    Lookup ocrengineLookup;
    Collection<OCREngine> ocrengines;
    Template ocrengineTemplate;
    Result ocrengineResults;
    try {
        //ocrengineLookup = Lookup.getDefault(); this only load OCREngine in classpath of  application
        ocrengineLookup = Lookups.metaInfServices(getClassLoaderForExtraModule());//this load the OCREngine in the extra module as well
        ocrengineTemplate = new Template(OCREngine.class);
        ocrengineResults = ocrengineLookup.lookup(ocrengineTemplate); 
        ocrengines = ocrengineResults.allInstances();//all OCREngines must implement the defined interface in OCREngine. Reference to guideline of implement org.openide.util.Lookup for more information

    } catch (Exception ex) {

public ClassLoader getClassLoaderForExtraModule() throws IOException {

    List<URL> urls = new ArrayList<URL>(5);
    //foreach( filepath: external file *.JAR) with each external file *.JAR, do as follows
    File jar = new File(filepath);
    JarFile jf = new JarFile(jar);
    Manifest mf = jf.getManifest(); // If the jar has a class-path in it's manifest add it's entries
    if (mf
            != null) {
        String cp =
        if (cp
                != null) {
            for (String cpe : cp.split("\\s+")) {
                File lib =
                        new File(jar.getParentFile(), cpe);
    ClassLoader cl = ClassLoader.getSystemClassLoader();
    if (urls.size() > 0) {
        cl = new URLClassLoader(urls.toArray(new URL[urls.size()]), ClassLoader.getSystemClassLoader());
    return cl;

How do you check if a JavaScript Object is a DOM Object?

Not to hammer on this or anything but for ES5-compliant browsers why not just:

function isDOM(e) {
  return (/HTML(?:.*)Element/).test(, -1));

Won't work on TextNodes and not sure about Shadow DOM or DocumentFragments etc. but will work on almost all HTML tag elements.

System.BadImageFormatException An attempt was made to load a program with an incorrect format

i have same problem what i did i just downloaded 32-bit dll and added it to my bin folder this is solved my problem

Cannot create cache directory .. or directory is not writable. Proceeding without cache in Laravel

Give full access of .composer to user.

sudo chown -R 'user-name' /home/'user-name'/.composer


sudo chmod 777 -R /home/'user-name'/.composer

user-name is your system user-name.

to get user-name type "whoami" in terminal:

enter image description here

Read file content from S3 bucket with boto3

boto3 offers a resource model that makes tasks like iterating through objects easier. Unfortunately, StreamingBody doesn't provide readline or readlines.

s3 = boto3.resource('s3')
bucket = s3.Bucket('test-bucket')
# Iterates through all the objects, doing the pagination for you. Each obj
# is an ObjectSummary, so it doesn't contain the body. You'll need to call
# get to get the whole body.
for obj in bucket.objects.all():
    key = obj.key
    body = obj.get()['Body'].read()

Difference between "managed" and "unmanaged"

This is more general than .NET and Windows. Managed is an environment where you have automatic memory management, garbage collection, type safety, ... unmanaged is everything else. So for example .NET is a managed environment and C/C++ is unmanaged.

Class has been compiled by a more recent version of the Java Environment

This is just a version mismatch. You have compiled your code using java version 9 and your current JRE is version 8. Try upgrading your JRE to 9.

49 = Java 5
50 = Java 6
51 = Java 7
52 = Java 8
53 = Java 9
54 = Java 10
55 = Java 11
56 = Java 12
57 = Java 13
58 = Java 14

How can I submit a form using JavaScript?

You can use the below code to submit the form using JavaScript:


Is it possible to make desktop GUI application in .NET Core?

I have been searching for this for ages now and none of the solution above are to my satisfaction.

I ended up working with for now.

I can confirm it works at least across macos and win10 and claims to be compatible with linux.

Leaving this here in case it can help someone.

enter image description here

Send array with Ajax to PHP script

 dataString = [];
        type: "POST",
        url: "script.php",
        data:{data: $(dataString).serializeArray()}, 
        cache: false,

        success: function(){

SSIS Excel Connection Manager failed to Connect to the Source

I found that my excel file that was created in Excel 365 was incompatible with any of the versions available. I re-saved the excel file in 97-2003 version and of course chose that version in the dropdown list and it read the file OK.

How to get rid of "Unnamed: 0" column in a pandas DataFrame?

To get ride of all Unnamed columns, you can also use regex such as df.drop(df.filter(regex="Unname"),axis=1, inplace=True)

go get results in 'terminal prompts disabled' error for github private repo

If you configure your gitconfig with this option, you will later have a problem cloning other repos of GitHub

git config --global --add url. "[email protected]". Instead, ""

Instead, I recommend that you use this option

echo "export GIT_TERMINAL_PROMPT=1" >> ~/.bashrc || ~/.zshrc

and do not forget to generate an access token from your private repository. When prompted to enter your password, just paste the access token. Happy clone :)

How do I line up 3 divs on the same row?

Check out the foundation rapid prototyping framework they handled this quite nicely, basically they allow you to use HTML like this:

<div class="row">
    <div class="four columns">
    <div class="four columns">
    <div class="four columns">

This is the simplest HTML/CSS grid system that I've come across, it's based on 12 column grid.

Basically the columns are given a % width and left margin relative to the parent row. They columns have float set to left, position set to relative, and display set to block.

The row has several properties set on it that care core of an issue that normally causes the containing div to collapse to height of 0 preventing the following divs from getting 'pushed' down as they should.

You can find examples of using the foundation grid system here:

If you don't want to use the entire framework the following CSS should do the trick with the example code I provided:

.row:after {
    content: "";
    clear: both;
    display: table;

.four.column {
    float: left;
    width: 33%;

If you really specifically want a left center and right columns then use code like this:


.row:after {
    content: "";
    clear: both;
    display: table;

.left {
    float: left;
    width: 100px;

.center {
    margin: 0 auto;
    width: 100px;

.right {
    float: right;
    width: 100px;


<div class="row">
    <div class="left">left</div>
    <div class="right">right</div>
    <div class="center">center</div>

How to determine if Javascript array contains an object with an attribute that equals a given value?

const check = vendors.find((item)=>item.Name==='Magenic')


Try this code.

If the item or element is present then the output will show you that element. If it is not present then the output will be 'undefined'.

How to get the current time in Google spreadsheet using script editor?

use the JavaScript Date() object. There are a number of ways to get the time, date, timestamps, etc from the object. (Reference)

function myFunction() {
  var d = new Date();
  var timeStamp = d.getTime();  // Number of ms since Jan 1, 1970

  // OR:

  var currentTime = d.toLocaleTimeString(); // "12:35 PM", for instance

How to put individual tags for a scatter plot

Perhaps use plt.annotate:

import numpy as np
import matplotlib.pyplot as plt

N = 10
data = np.random.random((N, 4))
labels = ['point{0}'.format(i) for i in range(N)]

plt.subplots_adjust(bottom = 0.1)
    data[:, 0], data[:, 1], marker='o', c=data[:, 2], s=data[:, 3] * 1500,

for label, x, y in zip(labels, data[:, 0], data[:, 1]):
        xy=(x, y), xytext=(-20, 20),
        textcoords='offset points', ha='right', va='bottom',
        bbox=dict(boxstyle='round,pad=0.5', fc='yellow', alpha=0.5),
        arrowprops=dict(arrowstyle = '->', connectionstyle='arc3,rad=0'))

enter image description here

'const string' vs. 'static readonly string' in C#


public const string MyStr;

is a compile time constant (you can use it as the default parameter for a method parameter for example), and it will not be obfuscated if you use such technology

static readonly

public static readonly string MyStr;

is runtime constant. It means that it is evaluated when the application is launched and not before. This is why it can't be used as the default parameter for a method (compilation error) for example. The value stored in it can be obfuscated.

Simple CSS: Text won't center in a button

Usualy, your code should work...

But here is a way to center text in css:

    margin-left: auto;
    margin-right: auto;

This has proved to be bulletproof to me whenever I want to center text with css.

Get folder up one level

You can try

echo realpath(__DIR__ . DIRECTORY_SEPARATOR . '..'); 

Unable to capture screenshot. Prevented by security policy. Galaxy S6. Android 6.0

Go to Phone Settings --> Developer Options --> Simulate Secondary Displays and turn it to None. If you don't see Developer Options in the settings menu (it should be at the bottom, go Settings ==> About phone and tap on the Build number a lot of times)

Set the value of an input field

if your form contains an input field like

<input type='text' id='id1' />

then you can write the code in javascript as given below to set its value as

document.getElementById('id1').value='text to be displayed' ; 

Nginx no-www to www and www to no-www

Actually you don't even need a rewrite.

server {
    #listen 80 is default
    return 301 $scheme://$request_uri;

server {
    #listen 80 is default
    ## here goes the rest of your conf...

As my answer is getting more and more up votes but the above as well. You should never use a rewrite in this context. Why? Because nginx has to process and start a search. If you use return (which should be available in any nginx version) it directly stops execution. This is preferred in any context.

Redirect both, non-SSL and SSL to their non-www counterpart:

server {
    listen               80;
    listen               443 ssl;
    ssl_certificate      path/to/cert;
    ssl_certificate_key  path/to/key;

    return 301 $scheme://$request_uri;

server {
    listen               80;
    listen               443 ssl;
    ssl_certificate      path/to/cert;
    ssl_certificate_key  path/to/key;

    # rest goes here...

The $scheme variable will only contain http if your server is only listening on port 80 (default) and the listen option does not contain the ssl keyword. Not using the variable will not gain you any performance.

Note that you need even more server blocks if you use HSTS, because the HSTS headers should not be sent over non-encrypted connections. Hence, you need unencrypted server blocks with redirects and encrypted server blocks with redirects and HSTS headers.

Redirect everything to SSL (personal config on UNIX with IPv4, IPv6, SPDY, ...):

# Redirect all www to non-www
server {
    ssl_certificate      ssl/;
    ssl_certificate_key  ssl/;
    listen               *:80;
    listen               *:443 ssl spdy;
    listen               [::]:80 ipv6only=on;
    listen               [::]:443 ssl spdy ipv6only=on;

    return 301$request_uri;

# Redirect all non-encrypted to encrypted
server {
    listen               *:80;
    listen               [::]:80;

    return 301$request_uri;

# There we go!
server {
    ssl_certificate      ssl/;
    ssl_certificate_key  ssl/;
    listen               *:443 ssl spdy;
    listen               [::]:443 ssl spdy;

    # rest goes here...

I guess you can imagine other compounds with this pattern now by yourself.

More of my configs? Go here and here.

How do I hide javascript code in a webpage?

You could use document.write.

Without jQuery

<!DOCTYPE html>
<head><meta charset=utf-8></head>
<body onload="document.write('<!doctype html><html><head><meta charset=utf-8></head><body><p>You cannot find this in the page source. (Your page needs to be in this document.write argument.)</p></body></html>');">

Or with jQuery

$(function () {
  document.write("<!doctype html><html><head><meta charset=utf-8></head><body><p>You cannot find this in the page source. (Your page needs to be in this document.write argument.)</p></body></html>")

How to automatically reload a page after a given period of inactivity

If you want to refresh the page if there is no activity then you need to figure out how to define activity. Let's say we refresh the page every minute unless someone presses a key or moves the mouse. This uses jQuery for event binding:

     var time = new Date().getTime();
     $(document.body).bind("mousemove keypress", function(e) {
         time = new Date().getTime();

     function refresh() {
         if(new Date().getTime() - time >= 60000) 
             setTimeout(refresh, 10000);

     setTimeout(refresh, 10000);

rejected master -> master (non-fast-forward)

You need to do

git branch

if the output is something like:

* (no branch)

then do

git checkout master

Make sure you do not have any pending commits as checking out will lose all non-committed changes.

How to join multiple collections with $lookup in mongodb

The join feature supported by Mongodb 3.2 and later versions. You can use joins by using aggregate query.
You can do it using below example :


    // Join with user_info table
            from: "userinfo",       // other table name
            localField: "userId",   // name of users table field
            foreignField: "userId", // name of userinfo table field
            as: "user_info"         // alias for userinfo table
    {   $unwind:"$user_info" },     // $unwind used for getting data in object or for one record only

    // Join with user_role table
            from: "userrole", 
            localField: "userId", 
            foreignField: "userId",
            as: "user_role"
    {   $unwind:"$user_role" },

    // define some conditions here 
            $and:[{"userName" : "admin"}]

    // define which fields are you want to fetch
            _id : 1,
            email : 1,
            userName : 1,
            userPhone : "$",
            role : "$user_role.role",

This will give result like this:

    "_id" : ObjectId("5684f3c454b1fd6926c324fd"),
    "email" : "[email protected]",
    "userName" : "admin",
    "userPhone" : "0000000000",
    "role" : "admin"

Hope this will help you or someone else.


Is there a format code shortcut for Visual Studio?

Right click on the code, and you have "Format Document". In my case it is Ctrl+Shift+I

enter image description here

PHP date() with timezone?

It should like this:


Hibernate Criteria for Dates

By using this way you can get the list of selected records.

GregorianCalendar gregorianCalendar = new GregorianCalendar();
Criteria cri = session.createCriteria(ProjectActivities.class);
cri.add("EffectiveFrom", gregorianCalendar.getTime()));
List list = cri.list();

All the Records will be generated into list which are greater than or equal to '08-Oct-2012' or else pass the date of user acceptance date at 2nd parameter of Restrictions (gregorianCalendar.getTime()) of criteria to get the records.

How to configure SSL certificates with Charles Web Proxy and the latest Android Emulator on Windows?

Things have changed a little in the way Charles provides HTTPS proxying.

First the certificates installation options have been moved to the help menu.

Help -> SSL Proxying -> Install Charles Root Certificate
Help -> SSL Proxying -> Install Charles Root Certificate in iOS Simulators

Charles SSL Proxying

Second, starting in iOS 9 you must provide a NSAppTransportSecurity option in your Info.plist and if you want Charles to work properly as a man in the middle, you must add:


as part of the your domains see full example:


The reason being (I guess) that Charles at some point communicates in clear http after acting as the man in the middle https server.

Last step is to activate SSL Proxying for this domain in Charles (right click on domain and select Enable SSL Proxying)

enable HTTP Proxying

How to convert datatype:object to float64 in python?

Or you can use regular expression to handle multiple items as the general case of this issue,

df['2nd'] = pd.to_numeric(df['2nd'].str.replace(r'[,.%]','')) 
df['CTR'] = pd.to_numeric(df['CTR'].str.replace(r'[^\d%]',''))

Is < faster than <=?

Only if the people who created the computers are bad with boolean logic. Which they shouldn't be.

Every comparison (>= <= > <) can be done in the same speed.

What every comparison is, is just a subtraction (the difference) and seeing if it's positive/negative.
(If the msb is set, the number is negative)

How to check a >= b? Sub a-b >= 0 Check if a-b is positive.
How to check a <= b? Sub 0 <= b-a Check if b-a is positive.
How to check a < b? Sub a-b < 0 Check if a-b is negative.
How to check a > b? Sub 0 > b-a Check if b-a is negative.

Simply put, the computer can just do this underneath the hood for the given op:

a >= b == msb(a-b)==0
a <= b == msb(b-a)==0
a > b == msb(b-a)==1
a < b == msb(a-b)==1

and of course the computer wouldn't actually need to do the ==0 or ==1 either.
for the ==0 it could just invert the msb from the circuit.

Anyway, they most certainly wouldn't have made a >= b be calculated as a>b || a==b lol

Remove last character of a StringBuilder?

if(sb.length() > 0){
    sb.deleteCharAt(sb.length() - 1);

How to repeat last command in python interpreter shell?

On Mac with Python 2.x

? ~ brew install rlwrap

Start with rlwrap

? ~ rlwrap python

vertical alignment of text element in SVG

If you're testing this in IE, dominant-baseline and alignment-baseline are not supported.

The most effective way to center text in IE is to use something like this with "dy":

<text font-size="ANY SIZE" text-anchor="middle" "dy"="-.4em"> Ya Text </text>

The negative value will shift it up and a positive value of dy will shift it down. I've found using -.4em seems a bit more centered vertically to me than -.5em, but you'll be the judge of that.

Code for best fit straight line of a scatter plot in python

Assuming line of best fit for a set of points is:

y = a + b * x
b = ( sum(xi * yi) - n * xbar * ybar ) / sum((xi - xbar)^2)
a = ybar - b * xbar

Code and plot

# sample points 
X = [0, 5, 10, 15, 20]
Y = [0, 7, 10, 13, 20]

# solve for a and b
def best_fit(X, Y):

    xbar = sum(X)/len(X)
    ybar = sum(Y)/len(Y)
    n = len(X) # or len(Y)

    numer = sum([xi*yi for xi,yi in zip(X, Y)]) - n * xbar * ybar
    denum = sum([xi**2 for xi in X]) - n * xbar**2

    b = numer / denum
    a = ybar - b * xbar

    print('best fit line:\ny = {:.2f} + {:.2f}x'.format(a, b))

    return a, b

# solution
a, b = best_fit(X, Y)
#best fit line:
#y = 0.80 + 0.92x

# plot points and fit line
import matplotlib.pyplot as plt
plt.scatter(X, Y)
yfit = [a + b * xi for xi in X]
plt.plot(X, yfit)

enter image description here


notebook version

Remove duplicates from a dataframe in PySpark

if you have a data frame and want to remove all duplicates -- with reference to duplicates in a specific column (called 'colName'):

count before dedupe:


do the de-dupe (convert the column you are de-duping to string type):

from pyspark.sql.functions import col
df = df.withColumn('colName',col('colName').cast('string'))


can use a sorted groupby to check to see that duplicates have been removed:


Get the current date and time

Try this one:

System.DateTime.Now.ToString("yyyy/MM/dd HH:mm:ss")

How do I commit only some files?

I suppose you want to commit the changes to one branch and then make those changes visible in the other branch. In git you should have no changes on top of HEAD when changing branches.

You commit only the changed files by:

git commit [some files]

Or if you are sure that you have a clean staging area you can

git add [some files]       # add [some files] to staging area
git add [some more files]  # add [some more files] to staging area
git commit                 # commit [some files] and [some more files]

If you want to make that commit available on both branches you do

git stash                     # remove all changes from HEAD and save them somewhere else
git checkout <other-project>  # change branches
git cherry-pick <commit-id>   # pick a commit from ANY branch and apply it to the current
git checkout <first-project>  # change to the other branch
git stash pop                 # restore all changes again

jQuery - Dynamically Create Button and Attach Event Handler

Your problem is that you're converting the button into an HTML snippet when you add it to the table, but that snippet is not the same object as the one that has the click handler on it.

$("#myButton").click(function () {
    var test = $('<button>Test</button>').click(function () {

    $("#nodeAttributeHeader").css('display', 'table-row'); // NB: changed

    var tr = $('<tr>').insertBefore('#addNodeTable tr:last');
    var td = $('<td>').append(test).appendTo(tr);

Conversion failed when converting the varchar value 'simple, ' to data type int

If you are converting a varchar to int make sure you do not have decimal places.

For example, if you are converting a varchar field with value (12345.0) to an integer then you get this conversion error. In my case I had all my fields with .0 as ending so I used the following statement to globally fix the problem.

CONVERT(int, replace(FIELD_NAME,'.0',''))

Keep CMD open after BAT file executes

When the .bat file is started not from within the command line (e.g. double-clicking).

echo The echoed text


echo The echoed text


echo The echoed text
cmd /k

cmd k

echo The echoed text & pause


Passing a string with spaces as a function argument in bash

I'm 9 years late but a more dynamic way would be

function myFunction {
   for i in "$*"; do echo "$i"; done;

Deleting row from datatable in C#

There several different ways to do it. But You can use the following approach:

List<DataRow> RowsToDelete = new List<DataRow>();

for (int i = 0; i < drr.Length; i++) 
   if(condition to delete the row) 

foreach(var dr in RowsToDelete) 

Download file of any type in Asp.Net MVC using FileResult?

its simple just give your physical path in directoryPath with file name

public FilePathResult GetFileFromDisk(string fileName)
    return File(directoryPath, "multipart/form-data", fileName);

script to map network drive

Here a JScript variant of JohnB's answer

// Below the MSDN page for MapNetworkDrive Method with link and in case if Microsoft breaks it like every now and then the path to the documentation of now.
// MSDN Library -> Web Development -> Scripting -> JScript and VBScript -> Windows Scripting -> Windows Script Host -> Reference (Windows Script Host) -> Methods (Windows Script Host) -> MapNetworkDrive Method

var WshNetwork = WScript.CreateObject('WScript.Network');
function localNameInUse(localName) {
    var driveIterator = WshNetwork.EnumNetworkDrives();
    for (var i=0, l=driveIterator.length; i < l; i += 2) {
        if (driveIterator.Item(i) == localName) {
            return true;
    return false;

function mount(localName, remoteName) {
    if (localNameInUse(localName)) {
        WScript.Echo('"' + localName + '" drive letter already in use.');
    } else {
        WshNetwork.MapNetworkDrive(localName, remoteName);

function unmount(localName) {
    if (localNameInUse(localName)) {

ORDER BY the IN value list

SELECT * FROM "comments" JOIN (
  SELECT 1 as "id",1 as "order" UNION ALL 
) j ON "comments"."id" = j."id" ORDER BY j.ORDER

or if you prefer evil over good:

SELECT * FROM "comments" WHERE ("comments"."id" IN (1,3,2,4))
ORDER BY POSITION(','+"comments"."id"+',' IN ',1,3,2,4,')

How to enable back/left swipe gesture in UINavigationController after setting leftBarButtonItem?

it works for me Swift 3:

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return true

and in ViewDidLoad:

    self.navigationController?.interactivePopGestureRecognizer?.delegate = self
    self.navigationController?.interactivePopGestureRecognizer?.isEnabled = true

Maven2: Best practice for Enterprise Project (EAR file)

This is a good example of the maven-ear-plugin part.

You can also check the maven archetypes that are available as an example. If you just runt mvn archetype:generate you'll get a list of available archetypes. One of them is


Jupyter Notebook not saving: '_xsrf' argument missing from post

I use jupyter notebooks daily and had never experienced this issue before... until today. I had the notebook open all day but it wasn't running anything and then for no apparent reason stopped auto-saving with the '_xsrf' argument missing from POST error message in the top right. FYI - this is a python3 notebook.

I don't know the cause of this problem but I have recently upgraded my python3 version to 3.7.2 and upgraded all of my site-packages to their latest version as of a few days ago which could possibly be the cause.

As for a solution, as suggested in the comment by @AlexK, I opened the same notebook in a new window (different browser in fact), using

jupyter notebook list

in the terminal to get the URL with login token.

This resulted in me having the notebook open and savable again but the information I had entered since the last successful auto-save was missing. Thankfully, my broken instance was still open and working apart from saving so I was able to simply copy and paste the information across then hit save. So, keep the broken instance open if you try this!

how to set the background image fit to browser using html

add this css in your stylesheet

        background:url(Desert.jpg) no-repeat center center fixed;
        background-size: cover;
        -webkit-background-size: cover;
        -moz-background-size: cover;
        -o-background-size: cover;
        margin: 0;
        padding: 0;


DateTimePicker: pick both date and time

You can get it to display time. From that you will probably have to have two controls (one date, one time) the accomplish what you want.

go to character in vim

:goto 21490 will take you to the 21490th byte in the buffer.

update to python 3.7 using anaconda

The September 4th release for 3.7 recommends the following:

conda install python=3.7 anaconda=custom

If you want to create a new environment, they recommend:

conda create -n example_env numpy scipy pandas scikit-learn notebook
conda activate example_env

How can I do a case insensitive string comparison?

This is not the best practice in .NET framework (4 & +) to check equality

String.Compare(x.Username, (string)drUser["Username"], 
                  StringComparison.OrdinalIgnoreCase) == 0

Use the following instead

String.Equals(x.Username, (string)drUser["Username"], 

MSDN recommends:

  • Use an overload of the String.Equals method to test whether two strings are equal.
  • Use the String.Compare and String.CompareTo methods to sort strings, not to check for equality.

How do I right align div elements?

If you have multiple divs that you want aligned side by side at the right end of the parent div, set text-align: right; on the parent div.

How to set JAVA_HOME for multiple Tomcat instances?

If you are a Windows user, put the content below in a setenv.bat file that you must create in Tomcat bin directory.

set JAVA_HOME=C:\Program Files\Java\jdk1.6.x

If you are a Linux user, put the content below in a file that you must create in Tomcat bin directory.


How to search a Git repository by commit message?

git log --grep=<pattern>
            Limit the commits output to ones with log message that matches the
            specified pattern (regular expression).

Change background position with jQuery

Sets new value for backgroundPosition on the carousel div when a li in the submenu div is hovered. Removes the backgroundPosition when hovering ends and resets backgroundPosition to old value.

$('#submenu li').hover(function() {
    if ($('#carousel').data('oldbackgroundPosition')==undefined) {
        $('#carousel').data('oldbackgroundPosition', $('#carousel').css('backgroundPosition'));
    $('#carousel').css('backgroundPosition', [enternewvaluehere]);
function() {
    var reset = '';
    if ($('#carousel').data('oldbackgroundPosition') != undefined) {
        reset = $('#carousel').data('oldbackgroundPosition');
    $('#carousel').css('backgroundPosition', reset);

Converting .NET DateTime to JSON

var date = eval(data.Data.Entity.Slrq.replace(/\/Date\((\d )\)\//gi, "new Date($1)"));  
alert(date.format("yyyy-MM-dd HH:mm:ss"));  
alert(dateFormat(date, "yyyy-MM-dd HH:mm:ss"));  

Expression must be a modifiable L-value

lvalue means "left value" -- it should be assignable. You cannot change the value of text since it is an array, not a pointer.

Either declare it as char pointer (in this case it's better to declare it as const char*):

const char *text;
if(number == 2) 
    text = "awesome"; 
    text = "you fail";

Or use strcpy:

char text[60];
if(number == 2) 
    strcpy(text, "awesome"); 
    strcpy(text, "you fail");

Oracle SQL Where clause to find date records older than 30 days


 WHERE creation_date <= TRUNC(SYSDATE) - 30

SYSDATE returns the date & time; TRUNC resets the date to being as of midnight so you can omit it if you want the creation_date that is 30 days previous including the current time.

Depending on your needs, you could also look at using ADD_MONTHS:

 WHERE creation_date <= ADD_MONTHS(TRUNC(SYSDATE), -1)

How to add parameters into a WebRequest?

For doing FORM posts, the best way is to use WebClient.UploadValues() with a POST method.

Reading from stdin

You can do something like this to read 10 bytes:

char buffer[10];
read(STDIN_FILENO, buffer, 10);

remember read() doesn't add '\0' to terminate to make it string (just gives raw buffer).

To read 1 byte at a time:

char ch;
while(read(STDIN_FILENO, &ch, 1) > 0)
 //do stuff

and don't forget to #include <unistd.h>, STDIN_FILENO defined as macro in this file.

There are three standard POSIX file descriptors, corresponding to the three standard streams, which presumably every process should expect to have:

Integer value   Name
       0        Standard input (stdin)
       1        Standard output (stdout)
       2        Standard error (stderr)

So instead STDIN_FILENO you can use 0.

In Linux System you can find this using following command:

$ sudo grep 'STDIN_FILENO' /usr/include/* -R | grep 'define'
/usr/include/unistd.h:#define   STDIN_FILENO    0   /* Standard input.  */

Notice the comment /* Standard input. */

How to specify the private SSH-key to use when executing shell command on Git?

If SSH port number is not 22(default), add Port xx in ~/.ssh/config

In my case (synology),

Host my_synology
    IdentityFile ~/.ssh/id_rsa_xxxx
    User myname
    Port xx

Then clone using Host title in config. ("my_synology". to avoid @chopstik 's "*")

git clone my_synology:path/to/repo.git

Parse error: syntax error, unexpected [

Are you using php 5.4 on your local? the render line is using the new way of initializing arrays. Try replacing ["title" => "Welcome "] with array("title" => "Welcome ")

correct way to define class variables in Python

I think this sample explains the difference between the styles:

#!/usr/bin/env python

class MyClass:
    element1 = "Hello"

    def __init__(self):
        self.element2 = "World"

obj = MyClass()

print dir(MyClass)
print "--"
print dir(obj)
print "--"
print obj.element1 
print obj.element2
print MyClass.element1 + " " + MyClass.element2
['__doc__', '__init__', '__module__', 'element1']
['__doc__', '__init__', '__module__', 'element1', 'element2']
Hello World
Traceback (most recent call last):
  File "./", line 17, in <module>
    print MyClass.element2
AttributeError: class MyClass has no attribute 'element2'

element1 is bound to the class, element2 is bound to an instance of the class.

MySQL Daemon Failed to Start - centos 6

Try restarting apache sudo service httpd restart. Worked for me.

check if array is empty (vba excel)

The problem with VBA is that there are both dynamic and static arrays...

Dynamic Array Example

Dim myDynamicArray() as Variant

Static Array Example

Dim myStaticArray(10) as Variant
Dim myOtherStaticArray(0 To 10) as Variant

Using error handling to check if the array is empty works for a Dynamic Array, but a static array is by definition not empty, there are entries in the array, even if all those entries are empty.

So for clarity's sake, I named my function "IsZeroLengthArray".

    Public Function IsZeroLengthArray(ByRef subject() As Variant) As Boolean
        'Tell VBA to proceed if there is an error to the next line.
        On Error Resume Next
        Dim UpperBound As Integer
        Dim ErrorNumber As Long
        Dim ErrorDescription As String
        Dim ErrorSource As String
        'If the array is empty this will throw an error because a zero-length 
          'array has no UpperBound (or LowerBound).
        'This only works for dynamic arrays.  If this was a static array there 
          'would be both an upper and lower bound.
        UpperBound = UBound(subject)

        'Store the Error Number and then clear the Error object 
         'because we want VBA to treat unintended errors normally
        ErrorNumber = Err.Number
        ErrorDescription = Err.Description
        ErrorSource = Err.Source
        On Error GoTo 0
        'Check the Error Object to see if we have a "subscript out of range" error.  
          'If we do (the number is 9) then we can assume that the array is zero-length.
        If ErrorNumber = 9 Then
            IsZeroLengthArray = True

        'If the Error number is something else then 9 we want to raise 
        'that error again...
        ElseIf ErrorNumber <> 0 Then
            Err.Raise ErrorNumber, ErrorSource, ErrorDescription

        'If the Error number is 0 then we have no error and can assume that the
         'array is not of zero-length
        ElseIf ErrorNumber = 0 Then
            IsZeroLengthArray = False
        End If
    End Function

I hope that this helps others as it helped me.

Append column to pandas dataframe

Both join() and concat() way could solve the problem. However, there is one warning I have to mention: Reset the index before you join() or concat() if you trying to deal with some data frame by selecting some rows from another DataFrame.

One example below shows some interesting behavior of join and concat:

dat1 = pd.DataFrame({'dat1': range(4)})
dat2 = pd.DataFrame({'dat2': range(4,8)})
dat1.index = [1,3,5,7]
dat2.index = [2,4,6,8]

# way1 join 2 DataFrames
# output
   dat1  dat2
1     0   NaN
3     1   NaN
5     2   NaN
7     3   NaN

# way2 concat 2 DataFrames
   dat1  dat2
1   0.0   NaN
2   NaN   4.0
3   1.0   NaN
4   NaN   5.0
5   2.0   NaN
6   NaN   6.0
7   3.0   NaN
8   NaN   7.0

#reset index 
dat1 = dat1.reset_index(drop=True)
dat2 = dat2.reset_index(drop=True)
#both 2 ways to get the same result

   dat1  dat2
0     0     4
1     1     5
2     2     6
3     3     7

   dat1  dat2
0     0     4
1     1     5
2     2     6
3     3     7

How to add a linked source folder in Android Studio?

The right answer is:

android {

    sourceSets { += 'src/main/<YOUR DIRECTORY>'

Furthermore, if your external source directory is not under src/main, you could use a relative path like this:

sourceSets { += 'src/main/../../../<YOUR DIRECTORY>'

How to create a GUID/UUID in Python

This function is fully configurable and generates unique uid based on the format specified

eg:- [8, 4, 4, 4, 12] , this is the format mentioned and it will generate the following uuid


 import random as r

 def generate_uuid():
        random_string = ''
        random_str_seq = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
        uuid_format = [8, 4, 4, 4, 12]
        for n in uuid_format:
            for i in range(0,n):
                random_string += str(random_str_seq[r.randint(0, len(random_str_seq) - 1)])
            if n != 12:
                random_string += '-'
        return random_string

Add a border outside of a UIView (instead of inside)

With the above accepted best answer i made experiences with such not nice results and unsightly edges:

border without bezier path

So i will share my UIView Swift extension with you, that uses a UIBezierPath instead as border outline – without unsightly edges (inspired by @Fattie):

border with bezier path

//  UIView+BezierPathBorder.swift

import UIKit

extension UIView {

    fileprivate var bezierPathIdentifier:String { return "bezierPathBorderLayer" }

    fileprivate var bezierPathBorder:CAShapeLayer? {
        return (self.layer.sublayers?.filter({ (layer) -> Bool in
            return == self.bezierPathIdentifier && (layer as? CAShapeLayer) != nil
        }) as? [CAShapeLayer])?.first

    func bezierPathBorder(_ color:UIColor = .white, width:CGFloat = 1) {

        var border = self.bezierPathBorder
        let path = UIBezierPath(roundedRect: self.bounds, cornerRadius:self.layer.cornerRadius)
        let mask = CAShapeLayer()
        mask.path = path.cgPath
        self.layer.mask = mask

        if (border == nil) {
            border = CAShapeLayer()
            border!.name = self.bezierPathIdentifier

        border!.frame = self.bounds
        let pathUsingCorrectInsetIfAny =
            UIBezierPath(roundedRect: border!.bounds, cornerRadius:self.layer.cornerRadius)

        border!.path = pathUsingCorrectInsetIfAny.cgPath
        border!.fillColor = UIColor.clear.cgColor
        border!.strokeColor = color.cgColor
        border!.lineWidth = width * 2

    func removeBezierPathBorder() {
        self.layer.mask = nil



let view = UIView(frame: CGRect(x: 20, y: 20, width: 100, height: 100))
view.layer.cornerRadius = view.frame.width / 2
view.backgroundColor = .red

//add white 2 pixel border outline
view.bezierPathBorder(.white, width: 2)

//remove border outline (optional)

How to compress an image via Javascript in the browser?

For JPG Image compression you can use the best compression technique called JIC (Javascript Image Compression)This will definitely help you -->

Change event on select with knockout binding, how can I know if it is a real change?

If you are working using Knockout, use the key functionality of observable functionality knockout.
Use ko.computed() method and do and trigger ajax call within that function.

Error when deploying an artifact in Nexus

Cause of problem for me was -source.jars was getting uploaded twice (with maven-source-plugin) as mentioned as one of the cause in accepted answer. Redirecting to answer that I referred: Maven release plugin fails : source artifacts getting deployed twice

How to write log to file

os.Open() must have worked differently in the past, but this works for me:

f, err := os.OpenFile("testlogfile", os.O_RDWR | os.O_CREATE | os.O_APPEND, 0666)
if err != nil {
    log.Fatalf("error opening file: %v", err)
defer f.Close()

log.Println("This is a test log entry")

Based on the Go docs, os.Open() can't work for log.SetOutput, because it opens the file "for reading:"

func Open

func Open(name string) (file *File, err error) Open opens the named file for reading. If successful, methods on the returned file can be used for reading; the associated file descriptor has mode O_RDONLY. If there is an error, it will be of type *PathError.


Moved defer f.Close() to after if err != nil check

"Error: Main method not found in class MyClass, please define the main method as..."

When you use the java command to run a Java application from the command line, e.g.,

java some.AppName arg1 arg2 ...

the command loads the class that you nominated and then looks for the entry point method called main. More specifically, it is looking for a method that is declared as follows:

package some;
public class AppName {
    public static void main(final String[] args) {
        // body of main method follows

The specific requirements for the entry point method are:

  1. The method must be in the nominated class.
  2. The name of the method must be "main" with exactly that capitalization1.
  3. The method must be public.
  4. The method must be static 2.
  5. The method's return type must be void.
  6. The method must have exactly one argument and argument's type must be String[] 3.

(The argument may be declared using varargs syntax; e.g. String... args. See this question for more information. The String[] argument is used to pass the arguments from the command line, and is required even if your application takes no command-line arguments.)

If anyone of the above requirements is not satisfied, the java command will fail with some variant of the message:

Error: Main method not found in class MyClass, please define the main method as:
   public static void main(String[] args)
or a JavaFX application class must extend javafx.application.Application

Or, if you are running an extremely old version of Java:

java.lang.NoSuchMethodError: main
Exception in thread "main"

If you encounter this error, check that you have a main method and that it satisfies all of the six requirements listed above.

1 - One really obscure variation of this is when one or more of the characters in "main" is NOT a LATIN-1 character … but a Unicode character that looks like the corresponding LATIN-1 character when displayed.

2 - Here is an explanation of why the method is required to be static.

3 - String must correspond to java.lang.String and not to a custom class named String hiding it.

Get top n records for each group of grouped results

How about using self-joining:

CREATE TABLE mytable (person, groupname, age);
INSERT INTO mytable VALUES('Bob',1,32);
INSERT INTO mytable VALUES('Jill',1,34);
INSERT INTO mytable VALUES('Shawn',1,42);
INSERT INTO mytable VALUES('Jake',2,29);
INSERT INTO mytable VALUES('Paul',2,36);
INSERT INTO mytable VALUES('Laura',2,39);

SELECT a.* FROM mytable AS a
  LEFT JOIN mytable AS a2 
    ON a.groupname = a2.groupname AND a.age <= a2.age
GROUP BY a.person
ORDER BY a.groupname, a.age DESC;

gives me:

a.person    a.groupname  a.age     
----------  -----------  ----------
Shawn       1            42        
Jill        1            34        
Laura       2            39        
Paul        2            36      

I was strongly inspired by the answer from Bill Karwin to Select top 10 records for each category

Also, I'm using SQLite, but this should work on MySQL.

Another thing: in the above, I replaced the group column with a groupname column for convenience.


Following-up on the OP's comment regarding missing tie results, I incremented on snuffin's answer to show all the ties. This means that if the last ones are ties, more than 2 rows can be returned, as shown below:

.headers on
.mode column

CREATE TABLE foo (person, groupname, age);
INSERT INTO foo VALUES('Paul',2,36);
INSERT INTO foo VALUES('Laura',2,39);
INSERT INTO foo VALUES('Joe',2,36);
INSERT INTO foo VALUES('Bob',1,32);
INSERT INTO foo VALUES('Jill',1,34);
INSERT INTO foo VALUES('Shawn',1,42);
INSERT INTO foo VALUES('Jake',2,29);
INSERT INTO foo VALUES('James',2,15);
INSERT INTO foo VALUES('Fred',1,12);
INSERT INTO foo VALUES('Chuck',3,112);

SELECT a.person, a.groupname, a.age 
FROM foo AS a 
WHERE a.age >= (SELECT MIN(b.age)
                FROM foo AS b 
                WHERE (SELECT COUNT(*)
                       FROM foo AS c
                       WHERE c.groupname = b.groupname AND c.age >= b.age) <= 2
                GROUP BY b.groupname)
ORDER BY a.groupname ASC, a.age DESC;

gives me:

person      groupname   age       
----------  ----------  ----------
Shawn       1           42        
Jill        1           34        
Laura       2           39        
Paul        2           36        
Joe         2           36        
Chuck       3           112      

What is the difference between H.264 video and MPEG-4 video?

H.264 is a new standard for video compression which has more advanced compression methods than the basic MPEG-4 compression. One of the advantages of H.264 is the high compression rate. It is about 1.5 to 2 times more efficient than MPEG-4 encoding. This high compression rate makes it possible to record more information on the same hard disk.
The image quality is also better and playback is more fluent than with basic MPEG-4 compression. The most interesting feature however is the lower bit-rate required for network transmission.
So the 3 main advantages of H.264 over MPEG-4 compression are:
- Small file size for longer recording time and better network transmission.
- Fluent and better video quality for real time playback
- More efficient mobile surveillance application

H264 is now enshrined in MPEG4 as part 10 also known as AVC

Refer to:

Hope this helps.

Prevent redirect after form is submitted

The design of HTTP means that making a POST with data will return a page. The original designers probably intended for that to be a "result" page of your POST.

It is normal for a PHP application to POST back to the same page as it can not only process the POST request, but it can generate an updated page based on the original GET but with the new information from the POST. However, there's nothing stopping your server code from providing completely different output. Alternatively, you could POST to an entirely different page.

If you don't want the output, one method that I've seen before AJAX took off was for the server to return a HTTP response code of (I think) 250. This is called "No Content" and this should make the browser ignore the data.

Of course, the third method is to make an AJAX call with your submitted data, instead.

DNS problem, nslookup works, ping doesn't

I think this behavior can be turned off, but Window's online help wasn't extremely clear:

If you disable NetBIOS over TCP/IP, you cannot use broadcast-based NetBIOS name resolution to resolve computer names to IP addresses for computers on the same network segment. If your computers are on the same network segment, and NetBIOS over TCP/IP is disabled, you must install a DNS server and either have the computers register with DNS (or manually configure DNS records) or configure entries in the local Hosts file for each computer.

In Windows XP, there is a checkbox:

Advanced TCP/IP Settings

[ ] Enable LMHOSTS lookup

There is also a book that covers this at length, "Networking Personal Computers with TCP/IP: Building TCP/IP Networks (old O'Reilly book)". Unfortunately, I cannot look it up because I disposed of my copy a while ago.

android: how to use getApplication and getApplicationContext from non activity / service class

Sending your activity context to other classes could cause memoryleaks because holding that context alive is the reason that the GC can't dispose the object

Get random item from array

If you don't mind picking the same item again at some other time:

$items[rand(0, count($items) - 1)];

How to play videos in android from assets folder or raw folder?

I found it :

Uri raw_uri = Uri.parse(<package_name>/+R.raw.<video_file_name>);

Personnaly Android found the resource, but can't play it for now. My file is a .m4v

Function to convert column number to letter?

Easy way to get the column name

Sub column()

column = Replace(cell.Address(False, False), cell.Row, "")
msgbox column

End Sub

I hope it helps =)

AttributeError: 'str' object has no attribute

The problem is in your playerMovement method. You are creating the string name of your room variables (ID1, ID2, ID3):

letsago = "ID" + str(self.dirDesc.values())

However, what you create is just a str. It is not the variable. Plus, I do not think it is doing what you think its doing:


If you REALLY needed to find the variable this way, you could use the eval function:

>>>foo = 'Hello World!'
'Hello World!'

or the globals function:

class Foo(object):
    def __init__(self):
        super(Foo, self).__init__()
    def test(self, name):

foo = Foo()
bar = 'Hello World!'

However, instead I would strongly recommend you rethink you class(es). Your userInterface class is essentially a Room. It shouldn't handle player movement. This should be within another class, maybe GameManager or something like that.

How to convert a String to CharSequence?

You can use

CharSequence[] cs = String[] {"String to CharSequence"};

git pull error :error: remote ref is at but expected

Use the below two commands one by one.

git gc --prune=now

git remote prune origin

This will resolve your issue.

How to set OnClickListener on a RadioButton in Android?

Just in case someone else was struggeling with the accepted answer:

There are different OnCheckedChangeListener-Interfaces. I added to first one to see if a CheckBox was changed.

import android.widget.CompoundButton.OnCheckedChangeListener;


import android.widget.RadioGroup.OnCheckedChangeListener;

When adding the snippet from Ricky I had errors:

The method setOnCheckedChangeListener(RadioGroup.OnCheckedChangeListener) in the type RadioGroup is not applicable for the arguments (new CompoundButton.OnCheckedChangeListener(){})

Can be fixed with answer from Ali :

new RadioGroup.OnCheckedChangeListener()

No function matches the given name and argument types

That error means that a function call is only matched by an existing function if all its arguments are of the same type and passed in same order. So if the next f() function

create function f() returns integer as $$ 
    select 1;
$$ language sql;

is called as

select f(1);

It will error out with

ERROR:  function f(integer) does not exist
LINE 1: select f(1);
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.

because there is no f() function that takes an integer as argument.

So you need to carefully compare what you are passing to the function to what it is expecting. That long list of table columns looks like bad design.

phpMyAdmin - can't connect - invalid setings - ever since I added a root password - locked out

This works for me:


$cfg['Servers'][$i]['password'] = 'secret';

Edit: Before you got this error it is most likely that from phpmyadmin->Users you have added password for the root user. In my case that was "secret" so the above primer works for me BUT for you will work this:

$cfg['Servers'][$i]['password'] = 'Enter the password for root you have added before you got this error';

Which sort algorithm works best on mostly sorted data?

well it depends on use case. If you know which elements is changed, remove and insert will be the best case as far as I am concerned.

How to do the equivalent of pass by reference for primitives in Java

public static void main(String[] args) {
    int[] toyNumber = new int[] {5};
    NewClass temp = new NewClass();;
    System.out.println("Toy number in main " + toyNumber[0]);

void play(int[] toyNumber){
    System.out.println("Toy number in play " + toyNumber[0]);
    System.out.println("Toy number in play after increement " + toyNumber[0]);

What causes signal 'SIGILL'?

It means the CPU attempted to execute an instruction it didn't understand. This could be caused by corruption I guess, or maybe it's been compiled for the wrong architecture (in which case I would have thought the O/S would refuse to run the executable). Not entirely sure what the root issue is.

Getting Cannot bind argument to parameter 'Path' because it is null error in powershell

  1. PM>Uninstall-Package EntityFramework -Force
  2. PM>Iinstall-Package EntityFramework -Pre -Version 6.0.0

I solve this problem with this code in NugetPackageConsole.and it works.The problem was in the version. i thikn it will help others.

JavaScript check if variable exists (is defined/initialized)

In the majority of cases you would use:

elem != null

Unlike a simple if (elem), it allows 0, false, NaN and '', but rejects null or undefined, making it a good, general test for the presence of an argument, or property of an object.

The other checks are not incorrect either, they just have different uses:

  • if (elem): can be used if elem is guaranteed to be an object, or if false, 0, etc. are considered "default" values (hence equivalent to undefined or null).

  • typeof elem == 'undefined' can be used in cases where a specified null has a distinct meaning to an uninitialised variable or property.

    • This is the only check that won't throw an error if elem is not declared (i.e. no var statement, not a property of window, or not a function argument). This is, in my opinion, rather dangerous as it allows typos to slip by unnoticed. To avoid this, see the below method.

Also useful is a strict comparison against undefined:

if (elem === undefined) ...

However, because the global undefined can be overridden with another value, it is best to declare the variable undefined in the current scope before using it:

var undefined; // really undefined
if (elem === undefined) ...


(function (undefined) {
    if (elem === undefined) ...

A secondary advantage of this method is that JS minifiers can reduce the undefined variable to a single character, saving you a few bytes every time.

Where does PHP store the error log? (php5, apache, fastcgi, cpanel)

cPanel Error logs are located in:



By default Apche logs are located inside:




If anyone is using custom log location then you can check it by running this command:

cat /etc/apache2/conf/httpd.conf | grep ErrorLog

If you are getting error that apache2 directory does not exist then you can run this command to find correct location by:

whereis apache


whereis apache2

Order of execution of tests in TestNG

In TestNG, you use dependsOnMethods and/or dependsOnGroups:

@Test(groups = "a")
public void f1() {}

@Test(groups = "a")
public void f2() {}

@Test(dependsOnGroups = "a")
public void g() {}

In this case, g() will only run after f1() and f2() have completed and succeeded.

You will find a lot of examples in the documentation:

No internet on Android emulator - why and how to fix?

If by "use internet", you mean you can not access the internet from an activity while testing on the emulator, make sure you have set the internet permission in your AndroidManifest.xml

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

If you are using the web browser, refer to Donal's post

How to make my layout able to scroll down?

For using scroll view along with Relative layout :

    android:fillViewport="true"> <!--IMPORTANT otherwise backgrnd img. will not fill the whole screen -->


    <!-- Bla Bla Bla i.e. Your Textviews/Buttons etc. -->

Get pixel color from canvas, on mousemove

Merging various references found here in StackOverflow (including the article above) and in other sites, I did so using javascript and JQuery:

<canvas id="myCanvas" width="400" height="400" style="border:1px solid #c3c3c3;">
Your browser does not support the canvas element.
<script src="jquery.js"></script>
<script type="text/javascript">
    window.onload = function(){
        var canvas = document.getElementById('myCanvas');
        var context = canvas.getContext('2d');
        var img = new Image();
        img.src = 'photo_apple.jpg';
        context.drawImage(img, 0, 0);

    function findPos(obj){
    var current_left = 0, current_top = 0;
    if (obj.offsetParent){
            current_left += obj.offsetLeft;
            current_top += obj.offsetTop;
        }while(obj = obj.offsetParent);
        return {x: current_left, y: current_top};
    return undefined;

    function rgbToHex(r, g, b){
    if (r > 255 || g > 255 || b > 255)
        throw "Invalid color component";
    return ((r << 16) | (g << 8) | b).toString(16);

    var position = findPos(this);
    var x = e.pageX - position.x;
    var y = e.pageY - position.y;
    var coordinate = "x=" + x + ", y=" + y;
    var canvas = this.getContext('2d');
    var p = canvas.getImageData(x, y, 1, 1).data;
    var hex = "#" + ("000000" + rgbToHex(p[0], p[1], p[2])).slice(-6);
    alert("HEX: " + hex);
<img src="photo_apple.jpg"/>

This is my complete solution. Here I only used canvas and one image, but if you need to use <map> over the image, it's possible too.

Why I cannot cout a string?

You do not have to reference std::cout or std::endl explicitly.
They are both included in the namespace std. using namespace std instead of using scope resolution operator :: every time makes is easier and cleaner.

using namespace std;

change type of input field with jQuery

heres a DOM solution


How to set xlim and ylim for a subplot in matplotlib

You should use the OO interface to matplotlib, rather than the state machine interface. Almost all of the plt.* function are thin wrappers that basically do gca().*.

plt.subplot returns an axes object. Once you have a reference to the axes object you can plot directly to it, change its limits, etc.

import matplotlib.pyplot as plt

ax1 = plt.subplot(131)
ax1.scatter([1, 2], [3, 4])
ax1.set_xlim([0, 5])
ax1.set_ylim([0, 5])

ax2 = plt.subplot(132)
ax2.scatter([1, 2],[3, 4])
ax2.set_xlim([0, 5])
ax2.set_ylim([0, 5])

and so on for as many axes as you want.

or better, wrap it all up in a loop:

import matplotlib.pyplot as plt

DATA_x = ([1, 2],
          [2, 3],
          [3, 4])

DATA_y = DATA_x[::-1]

XLIMS = [[0, 10]] * 3
YLIMS = [[0, 10]] * 3

for j, (x, y, xlim, ylim) in enumerate(zip(DATA_x, DATA_y, XLIMS, YLIMS)):
    ax = plt.subplot(1, 3, j + 1)
    ax.scatter(x, y)

How to find the operating system version using JavaScript?

If you list all of window.navigator's properties using


You'll see something like this

# platform = Win32
# appCodeName = Mozilla
# appName = Netscape
# appVersion = 5.0 (Windows; en-US)
# language = en-US
# mimeTypes = [object MimeTypeArray]
# oscpu = Windows NT 5.1
# vendor = Firefox
# vendorSub = 1.0.7
# product = Gecko
# productSub = 20050915
# plugins = [object PluginArray]
# securityPolicy =
# userAgent = Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12) Gecko/20050915 Firefox/1.0.7
# cookieEnabled = true
# javaEnabled = function javaEnabled() { [native code] }
# taintEnabled = function taintEnabled() { [native code] }
# preference = function preference() { [native code] }

Note that oscpu attribute gives you the Windows version. Also, you should know that:

'Windows 3.11' => 'Win16',
'Windows 95' => '(Windows 95)|(Win95)|(Windows_95)',
'Windows 98' => '(Windows 98)|(Win98)',
'Windows 2000' => '(Windows NT 5.0)|(Windows 2000)',
'Windows XP' => '(Windows NT 5.1)|(Windows XP)',
'Windows Server 2003' => '(Windows NT 5.2)',
'Windows Vista' => '(Windows NT 6.0)',
'Windows 7' => '(Windows NT 6.1)',
'Windows 8' => '(Windows NT 6.2)|(WOW64)',
'Windows 10' => '(Windows 10.0)|(Windows NT 10.0)',
'Windows NT 4.0' => '(Windows NT 4.0)|(WinNT4.0)|(WinNT)|(Windows NT)',
'Windows ME' => 'Windows ME',
'Open BSD' => 'OpenBSD',
'Sun OS' => 'SunOS',
'Linux' => '(Linux)|(X11)',
'Mac OS' => '(Mac_PowerPC)|(Macintosh)',
'QNX' => 'QNX',
'BeOS' => 'BeOS',
'OS/2' => 'OS/2',
'Search Bot'=>'(nuhk)|(Googlebot)|(Yammybot)|(Openbot)|(Slurp)|(MSNBot)|(Ask Jeeves/Teoma)|(ia_archiver)'

Apache 2.4.3 (with XAMPP 1.8.1) not starting in windows 8

I had the same problem and error, I tried changing the ports for http port from 80 to 81 and ssl port from 443 to 444 but still received the same error so I reverted the ports to default and ran setup_xampp.bat which solve the problem in seconds.

Setting selection to Nothing when programming Excel

None of the many answers with Application.CutCopyMode or .Select worked for me.

But I did find a solution not posted here, which worked fantastically for me!

From StackExchange SuperUser: Excel VBA “Unselect” wanted

If you are really wanting 'nothing selected`, you can use VBA to protect the sheet at the end of your code execution, which will cause nothing to be selected. You can either add this to a macro or put it into your VBA directly.

Sub NoSelect()
   With ActiveSheet
   .EnableSelection = xlNoSelection
   End With
End Sub

As soon as the sheet is unprotected, the cursor will activate a cell.

Hope this helps someone with the same problem!

BLOB to String, SQL Server

          l_data long;
         select XXXXXX into l_data from XXXXX where rowid = p_rowid;
         return substr( l_data, 1, 4000);
  end getlabrapor1;

How to add \newpage in Rmarkdown in a smart way?

Simply \newpage or \pagebreak will work, e.g.

hello world
```{r, echo=FALSE}
```{r, echo=FALSE}

This solution assumes you are knitting PDF. For HTML, you can achieve a similar effect by adding a tag <P style="page-break-before: always">. Note that you likely won't see a page break in your browser (HTMLs don't have pages per se), but the printing layout will have it.

Sharing a variable between multiple different threads

In addition to the other suggestions - you can also wrap the flag in a control class and make a final instance of it in your parent class:

public class Test {
  class Control {
    public volatile boolean flag = false;
  final Control control = new Control();

  class T1 implements Runnable {
    public void run() {
      while ( !control.flag ) {


  class T2 implements Runnable {
    public void run() {
      while ( !control.flag ) {


  private void test() {
    T1 main = new T1();
    T2 help = new T2();

    new Thread(main).start();
    new Thread(help).start();

  public static void main(String[] args) throws InterruptedException {
    try {
      Test test = new Test();
    } catch (Exception e) {