Programs & Examples On #Data sharing

Sync data between Android App and webserver

I'll try to answer all your questions by addressing the larger question: How can I sync data between a webserver and an android app?

Syncing data between your webserver and an android app requires a couple of different components on your android device.

Persistent Storage:

This is how your phone actually stores the data it receives from the webserver. One possible method for accomplishing this is writing your own custom ContentProvider backed by a Sqlite database. A decent tutorial for a content provider can be found here:

A ContentProvider defines a consistent interface to interact with your stored data. It could also allow other applications to interact with your data if you wanted. Behind your ContentProvider could be a Sqlite database, a Cache, or any arbitrary storage mechanism.

While I would certainly recommend using a ContentProvider with a Sqlite database you could use any java based storage mechanism you wanted.

Data Interchange Format:

This is the format you use to send the data between your webserver and your android app. The two most popular formats these days are XML and JSON. When choosing your format, you should think about what sort of serialization libraries are available. I know off-hand that there's a fantastic library for json serialization called gson:, although I'm sure similar libraries exist for XML.

Synchronization Service

You'll want some sort of asynchronous task which can get new data from your server and refresh the mobile content to reflect the content of the server. You'll also want to notify the server whenever you make local changes to content and want to reflect those changes. Android provides the SyncAdapter pattern as a way to easily solve this pattern. You'll need to register user accounts, and then Android will perform lots of magic for you, and allow you to automatically sync. Here's a good tutorial:

As for how you identify if the records are the same, typically you'll create items with a unique id which you store both on the android device and the server. You can use that to make sure you're referring to the same reference. Furthermore, you can store column attributes like "updated_at" to make sure that you're always getting the freshest data, or you don't accidentally write over newly written data.

How do I launch a Git Bash window with particular working directory using a script?

Git Bash uses cmd.exe for its terminal plus extentions from MSYS/MinGW which are provided by sh.exe, a sort of cmd.exe wrapper. In Windows you launch a new terminal using the start command.

Thus a shell script which launches a new Git Bash terminal with a specific working directory is:

(cd C:/path/to/dir1 && start sh --login) &
(cd D:/path/to/dir2 && start sh --login) &

An equivalent Windows batch script is:

cd \path\to\dir1
start "" "%SYSTEMDRIVE%\Program Files (x86)\Git\bin\sh.exe" --login 
cd \path\to\dir2
start "" "%SYSTEMDRIVE%\Program Files (x86)\Git\bin\sh.exe" --login 

To get the same font and window size as the Git Bash launched from the start menu, it is easiest to copy the start menu shortcut settings to the command console defaults (to change defaults, open cmd.exe, left-click the upper left icon, and select Defaults).

Hibernate: get entity by id

In getUserById you shouldn't create a new object (user1) which isn't used. Just assign it to the already (but null) initialized user. Otherwise Hibernate.initialize(user); is actually Hibernate.initialize(null);

Here's the new getUserById (I haven't tested this ;)):

public User getUserById(Long user_id) {
    Session session = null;
    Object user = null;
    try {
        session = HibernateUtil.getSessionFactory().openSession();
        user = (User)session.load(User.class, user_id);
    } catch (Exception e) {
    } finally {
        if (session != null && session.isOpen()) {
    return user;

Recursively add the entire folder to a repository

I simply used this:

git add app/src/release/*

You simply need to specify the folder to add and then use * to add everything that is inside recursively.

Laravel - Form Input - Multiple select for a one to many relationship

I agree with user3158900, and I only differ slightly in the way I use it:

{{Form::label('sports', 'Sports')}}

However, in my experience the 3rd parameter of the select is a string only, so for repopulating data for a multi-select I have had to do something like this:

<select multiple="multiple" name="sports[]" id="sports">
@foreach($aSports as $aKey => $aSport)
    @foreach($aItem->sports as $aItemKey => $aItemSport)
        <option value="{{$aKey}}" @if($aKey == $aItemKey)selected="selected"@endif>{{$aSport}}</option>

Is it valid to replace http:// with // in a <script src="http://...">?

are there any cases where it doesn't work?

Just to throw this in the mix, if you are developing on a local server, it might not work. You need to specify a scheme, otherwise the browser may assume that src="//" is src="file://", which will break since you're not hosting this resource locally.

Microsoft Internet Explorer seem to be particularly sensitive to this, see this question: Not able to load jQuery in Internet Explorer on localhost (WAMP)

You would probably always try to find a solution that works on all your environments with the least amount of modifications needed.

The solution used by HTML5Boilerplate is to have a fallback when the resource is not loaded correctly, but that only works if you incorporate a check:

<script src="//"></script>
<!-- If jQuery is not defined, something went wrong and we'll load the local file -->
<script>window.jQuery || document.write('<script src="js/vendor/jquery-1.10.2.min.js"><\/script>')</script>

UPDATE: HTML5Boilerplate now uses <script src=" after deciding to deprecate protocol relative URLs, see [here][3].

Error :Request header field Content-Type is not allowed by Access-Control-Allow-Headers

For Nginx, the only thing that worked for me was adding this header:

add_header 'Access-Control-Allow-Headers' 'Authorization,Content-Type,Accept,Origin,User-Agent,DNT,Cache-Control,X-Mx-ReqToken,Keep-Alive,X-Requested-With,If-Modified-Since';

Along with the Access-Control-Allow-Origin header:

add_header 'Access-Control-Allow-Origin' '*';

Then reloaded the nginx config and it worked great. Credit

How can I get the IP address from NIC in Python?

Two methods:

Method #1 (use external package)

You need to ask for the IP address that is bound to your eth0 interface. This is available from the netifaces package

import netifaces as ni
ip = ni.ifaddresses('eth0')[ni.AF_INET][0]['addr']
print ip  # should print ""

You can also get a list of all available interfaces via


Method #2 (no external package)

Here's a way to get the IP address without using a python package:

import socket
import fcntl
import struct

def get_ip_address(ifname):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    return socket.inet_ntoa(fcntl.ioctl(
        0x8915,  # SIOCGIFADDR
        struct.pack('256s', ifname[:15])

get_ip_address('eth0')  # ''

Note: detecting the IP address to determine what environment you are using is quite a hack. Almost all frameworks provide a very simple way to set/modify an environment variable to indicate the current environment. Try and take a look at your documentation for this. It should be as simple as doing

if app.config['ENV'] == 'production':
  #send production email
  #send development email

Query to list all stored procedures

The following will Return All Procedures in selected database

SELECT * FROM sys.procedures

.NET DateTime to SqlDateTime Conversion

Also please remember resolutions [quantum of time] are different.

SQL one is 3.33 ms and .net one is 100 ns.

How to disable mouse right click on a web page?

Try this : write below code on body & feel the magic :)

body oncontextmenu="return false"

How to overlay one div over another div

The new Grid CSS specification provides a far more elegant solution. Using position: absolute may lead to overlaps or scaling issues while Grid will save you from dirty CSS hacks.

Most minimal Grid Overlay example:


<div class="container">
  <div class="content">This is the content</div>
  <div class="overlay">Overlay - must be placed under content in the HTML</div>


.container {
  display: grid;

.content, .overlay {
  grid-area: 1 / 1;

That's it. If you don't build for Internet Explorer, your code will most probably work.

Execute jQuery function after another function completes

You could also use custom events:

function Typer() {
    // Some stuff


$(anyDomElement).on("myCustomEvent", function() {
    // Some other stuff

How to open an external file from HTML

Your first idea used to be the way but I've also noticed issues doing this using Firefox, try a straight http:// to the file - href='http://server/directory/file.xlsx'

Check for file exists or not in sql server?

Create a function like so:

CREATE FUNCTION dbo.fn_FileExists(@path varchar(512))
     DECLARE @result INT
     EXEC master.dbo.xp_fileexist @path, @result OUTPUT
     RETURN cast(@result as bit)

Edit your table and add a computed column (IsExists BIT). Set the expression to:


Then just select:

SELECT * FROM dbo.MyTable where IsExists = 1


To use the function outside a computed column:

select id, filename, dbo.fn_FileExists(filename) as IsExists
from dbo.MyTable


If the function returns 0 for a known file, then there is likely a permissions issue. Make sure the SQL Server's account has sufficient permissions to access the folder and files. Read-only should be enough.

And YES, by default, the 'NETWORK SERVICE' account will not have sufficient right into most folders. Right click on the folder in question and select 'Properties', then click on the 'Security' tab. Click 'Edit' and add 'Network Service'. Click 'Apply' and retest.

Should I add the Visual Studio .suo and .user files to source control?

No, you should not add them to source control since - as you said - they're user specific.

SUO (Solution User Options): Records all of the options that you might associate with your solution so that each time you open it, it includes customizations that you have made.

The .user file contains the user options for the project (while SUO is for the solution) and extends the project file name (e.g. anything.csproj.user contains user settings for the anything.csproj project).

Converting a JToken (or string) to a given Type

There is a ToObject method now.

var obj = jsonObject["date_joined"];
var result = obj.ToObject<DateTime>();

It also works with any complex type, and obey to JsonPropertyAttribute rules

var result = obj.ToObject<MyClass>();

public class MyClass 
    public DateTime MyDate {get;set;}

What is the reason behind "non-static method cannot be referenced from a static context"?

The answers so far describe why, but here is a something else you might want to consider:

You can can call a method from an instantiable class by appending a method call to its constructor,

Object instance = new Constuctor().methodCall();


primitive name = new Constuctor().methodCall();

This is useful it you only wish to use a method of an instantiable class once within a single scope. If you are calling multiple methods from an instantiable class within a single scope, definitely create a referable instance.

How can one change the timestamp of an old commit in Git?

To change both the author date and the commit date:

GIT_COMMITTER_DATE="Wed Sep 23 9:40 2015 +0200" git commit --amend --date "Wed Sep 23 9:40 2015 +0200"

How can I split a text into sentences?

No doubt that NLTK is the most suitable for the purpose. But getting started with NLTK is quite painful (But once you install it - you just reap the rewards)

So here is simple re based code available at

# split up a paragraph into sentences
# using regular expressions

def splitParagraphIntoSentences(paragraph):
    ''' break a paragraph into sentences
        and return a list '''
    import re
    # to split by multile characters

    #   regular expressions are easiest (and fastest)
    sentenceEnders = re.compile('[.!?]')
    sentenceList = sentenceEnders.split(paragraph)
    return sentenceList

if __name__ == '__main__':
    p = """This is a sentence.  This is an excited sentence! And do you think this is a question?"""

    sentences = splitParagraphIntoSentences(p)
    for s in sentences:
        print s.strip()

#   This is a sentence
#   This is an excited sentence

#   And do you think this is a question 

How to get pixel data from a UIImage (Cocoa Touch) or CGImage (Core Graphics)?

One way of doing it is to draw the image to a bitmap context that is backed by a given buffer for a given colorspace (in this case it is RGB): (note that this will copy the image data to that buffer, so you do want to cache it instead of doing this operation every time you need to get pixel values)

See below as a sample:

// First get the image into your data buffer
CGImageRef image = [myUIImage CGImage];
NSUInteger width = CGImageGetWidth(image);
NSUInteger height = CGImageGetHeight(image);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = malloc(height * width * 4);
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

CGContextDrawImage(context, CGRectMake(0, 0, width, height));

// Now your rawData contains the image data in the RGBA8888 pixel format.
int byteIndex = (bytesPerRow * yy) + xx * bytesPerPixel;
red = rawData[byteIndex];
green = rawData[byteIndex + 1];
blue = rawData[byteIndex + 2];
alpha = rawData[byteIndex + 3];

What's the difference between '$(this)' and 'this'?

this is the element, $(this) is the jQuery object constructed with that element

 //the iterations current html element 
 //the classic JavaScript API is exposed here (such as .innerHTML and .appendChild)
 var HTMLElement = this;

 //the current HTML element is passed to the jQuery constructor
 //the jQuery API is exposed here (such as .html() and .append())
 var jQueryObject = $(this);

A deeper look

thisMDN is contained in an execution context

The scope refers to the current Execution ContextECMA. In order to understand this, it is important to understand the way execution contexts operate in JavaScript.

execution contexts bind this

When control enters an execution context (code is being executed in that scope) the environment for variables are setup (Lexical and Variable Environments - essentially this sets up an area for variables to enter which were already accessible, and an area for local variables to be stored), and the binding of this occurs.

jQuery binds this

Execution contexts form a logical stack. The result is that contexts deeper in the stack have access to previous variables, but their bindings may have been altered. Every time jQuery calls a callback function, it alters the this binding by using applyMDN.

callback.apply( obj[ i ] )//where obj[i] is the current element

The result of calling apply is that inside of jQuery callback functions, this refers to the current element being used by the callback function.

For example, in .each, the callback function commonly used allows for .each(function(index,element){/*scope*/}). In that scope, this == element is true.

jQuery callbacks use the apply function to bind the function being called with the current element. This element comes from the jQuery object's element array. Each jQuery object constructed contains an array of elements which match the selectorjQuery API that was used to instantiate the jQuery object.

$(selector) calls the jQuery function (remember that $ is a reference to jQuery, code: window.jQuery = window.$ = jQuery;). Internally, the jQuery function instantiates a function object. So while it may not be immediately obvious, using $() internally uses new jQuery(). Part of the construction of this jQuery object is to find all matches of the selector. The constructor will also accept html strings and elements. When you pass this to the jQuery constructor, you are passing the current element for a jQuery object to be constructed with. The jQuery object then contains an array-like structure of the DOM elements matching the selector (or just the single element in the case of this).

Once the jQuery object is constructed, the jQuery API is now exposed. When a jQuery api function is called, it will internally iterate over this array-like structure. For each item in the array, it calls the callback function for the api, binding the callback's this to the current element. This call can be seen in the code snippet above where obj is the array-like structure, and i is the iterator used for the position in the array of the current element.

Quoting backslashes in Python string literals

You're being mislead by output -- the second approach you're taking actually does what you want, you just aren't believing it. :)

>>> foo = 'baz "\\"'
>>> foo
'baz "\\"'
>>> print(foo)
baz "\"

Incidentally, there's another string form which might be a bit clearer:

>>> print(r'baz "\"')
baz "\"

Creating multiline strings in JavaScript

Downvoters: This code is supplied for information only.

This has been tested in Fx 19 and Chrome 24 on Mac


var new_comment; /*<<<EOF _x000D_
    <li class="photobooth-comment">_x000D_
       <span class="username">_x000D_
          <a href="#">You</a>:_x000D_
       <span class="comment-text">_x000D_
       </span> _x000D_
       @<span class="comment-time">_x000D_
       </span> ago_x000D_
// note the script tag here is hardcoded as the FIRST tag _x000D_
new_comment=document.currentScript.innerHTML.split("EOF")[1]; _x000D_
document.querySelector("ul").innerHTML=new_comment.replace('$text','This is a dynamically created text');

Zoom to fit all markers in Mapbox or Leaflet

var markerArray = [];
markerArray.push(L.marker([51.505, -0.09]));
var group = L.featureGroup(markerArray).addTo(map);

npm install vs. update - what's the difference?

The difference between npm install and npm update handling of package versions specified in package.json:

  "name":          "my-project",
  "version":       "1.0",                             // install   update
  "dependencies":  {                                  // ------------------
    "already-installed-versionless-module":  "*",     // ignores   "1.0" -> "1.1"
    "already-installed-semver-module":       "^1.4.3" // ignores   "1.4.3" -> "1.5.2"
    "already-installed-versioned-module":    "3.4.1"  // ignores   ignores
    "not-yet-installed-versionless-module":  "*",     // installs  installs
    "not-yet-installed-semver-module":       "^4.2.1" // installs  installs
    "not-yet-installed-versioned-module":    "2.7.8"  // installs  installs

Summary: The only big difference is that an already installed module with fuzzy versioning ...

  • gets ignored by npm install
  • gets updated by npm update

Additionally: install and update by default handle devDependencies differently

  • npm install will install/update devDependencies unless --production flag is added
  • npm update will ignore devDependencies unless --dev flag is added

Why use npm install at all?

Because npm install does more when you look besides handling your dependencies in package.json. As you can see in npm install you can ...

  • manually install node-modules
  • set them as global (which puts them in the shell's PATH) using npm install -g <name>
  • install certain versions described by git tags
  • install from a git url
  • force a reinstall with --force

Android ListView selected item stay highlighted

To hold the color of listview item when you press it, include the following line in your listview item layout:


Then define bg_key.xml in drawable folder like this:

<?xml version="1.0" encoding="utf-8" ?>
<selector xmlns:android="">
        android:drawable="@color/default_color" />

Finally, include this in your ListView onClickListener:

listView.setOnItemClickListener(new OnItemClickListener() {
    public void onItemClick(AdapterView<?> parent, View view, int position,long arg3) {
        ... // Anything

This way, only one item will be color-selected at any time. You can define your color values in res/values/colors.xml with something like this:

<?xml version="1.0" encoding="utf-8"?>
    <color name="pressed_color">#4d90fe</color>
    <color name="default_color">#ffffff</color>

@Autowired - No qualifying bean of type found for dependency at least 1 bean

Missing the 'implements' keyword in the impl classes might also be the issue

How can I convert string to datetime with format specification in JavaScript?

I think this can help you:

There's a getDateFromFormat() function that you can tweak a little to solve your problem.

Update: there's an updated version of the samples available at

What is the memory consumption of an object in Java?

The question will be a very broad one.

It depends on the class variable or you may call as states memory usage in java.

It also has some additional memory requirement for headers and referencing.

The heap memory used by a Java object includes

  • memory for primitive fields, according to their size (see below for Sizes of primitive types);

  • memory for reference fields (4 bytes each);

  • an object header, consisting of a few bytes of "housekeeping" information;

Objects in java also requires some "housekeeping" information, such as recording an object's class, ID and status flags such as whether the object is currently reachable, currently synchronization-locked etc.

Java object header size varies on 32 and 64 bit jvm.

Although these are the main memory consumers jvm also requires additional fields sometimes like for alignment of the code e.t.c.

Sizes of primitive types

boolean & byte -- 1

char & short -- 2

int & float -- 4

long & double -- 8

React: how to update state.item[1] in state using setState?

Use array map with arrow function, in one line

    items:, index) =>
      index === 1 ? { ...item, name: 'newName' } : item,

Adding an image to a project in Visual Studio

  • You just need to have an existing file, open the context menu on your folder , and then choose Add => Existing item...

    enter image description here

  • If you have the file already placed within your project structure, but it is not yet included, you can do so by making them visible in the solution explorer

    enter image description here

and then include them via the file context menu enter image description here

How to write and read a file with a HashMap?

You can write an object to a file using writeObject in ObjectOutputStream


Twitter bootstrap scrollable modal

In case of using .modal {overflow-y: auto;}, would create additional scroll bar on the right of the page, when body is already overflowed.

The work around for this is to remove overflow from the body tag temporarily and set modal overflow-y to auto.


$('.myModalSelector').on('', function () {

        // Store initial body overflow value
        _initial_body_overflow = $('body').css('overflow');

        // Let modal be scrollable
        $(this).css('overflow-y', 'auto');
        $('body').css('overflow', 'hidden');

    }).on('', function () {

        // Reverse previous initialization
        $(this).css('overflow-y', 'hidden');
        $('body').css('overflow', _initial_body_overflow);

How to dynamically change header based on AngularJS partial view?

Thanks to tosh shimayama for his solution.
I thought it was not so clean to put a service straight into the $scope, so here's my slight variation on that:

The controller (that in original answer seemed to me a little bit too dumb) creates an ActionBar object, and this one is stuffed into $scope.
The object is responsible for actually querying the service. It also hides from the $scope the call to set the template URL, which instead is available to other controllers to set the URL.

Convert date time string to epoch in Bash

What you're looking for is date --date='06/12/2012 07:21:22' +"%s". Keep in mind that this assumes you're using GNU coreutils, as both --date and the %s format string are GNU extensions. POSIX doesn't specify either of those, so there is no portable way of making such conversion even on POSIX compliant systems.

Consult the appropriate manual page for other versions of date.

Note: bash --date and -d option expects the date in US or ISO8601 format, i.e. mm/dd/yyyy or yyyy-mm-dd, not in UK, EU, or any other format.

Set cookies for cross origin requests

Pim's answer is very helpful. In my case, I have to use

Expires / Max-Age: "Session"

If it is a dateTime, even it is not expired, it still won't send the cookie to the backend:

Expires / Max-Age: "Thu, 21 May 2020 09:00:34 GMT"

Hope it is helpful for future people who may meet same issue.

Python read-only property

I know i'm bringing back from the dead this thread, but I was looking at how to make a property read only and after finding this topic, I wasn't satisfied with the solutions already shared.

So, going back to the initial question, if you start with this code:

def x(self):
    return self._x

And you want to make X readonly, you can just add:

def x(self, value):
    raise Exception("Member readonly")

Then, if you run the following:

print (x) # Will print whatever X value is
x = 3 # Will raise exception "Member readonly"

UnicodeDecodeError: 'charmap' codec can't decode byte X in position Y: character maps to <undefined>

For those working in Anaconda in Windows, I had the same problem. Notepad++ help me to solve it.

Open the file in Notepad++. In the bottom right it will tell you the current file encoding. In the top menu, next to "View" locate "Encoding". In "Encoding" go to "character sets" and there with patiente look for the enconding that you need. In my case the encoding "Windows-1252" was found under "Western European"

How to support different screen size in android

You can figure out the dimensions of the screen dynamically

Display mDisplay= activity.getWindowManager().getDefaultDisplay();
int width= mDisplay.getWidth();
int Height= mDisplay.getHeight();

The layout can be set using the width and the height obtained using this method.

Class vs. static method in JavaScript

I use namespaces:

var Foo = {
     element: document.getElementById("id-here"),

     Talk: function(message) {
            alert("talking..." + message);

     ChangeElement: function() {
   = "red";

And to use it:




How to create module-wide variables in Python?

Steveha's answer was helpful to me, but omits an important point (one that I think wisty was getting at). The global keyword is not necessary if you only access but do not assign the variable in the function.

If you assign the variable without the global keyword then Python creates a new local var -- the module variable's value will now be hidden inside the function. Use the global keyword to assign the module var inside a function.

Pylint 1.3.1 under Python 2.7 enforces NOT using global if you don't assign the var.

module_var = '/dev/hello'

def readonly_access():

def readwrite_access():
    global module_var
    module_var = '/dev/hello2'

How can I lookup a Java enum from its String value?

@Lyle's answer is rather dangerous and I have seen it not work particularly if you make the enum a static inner class. Instead I have used something like this which will load the BootstrapSingleton maps before the enums.

Edit this should not be a problem any more with modern JVMs (JVM 1.6 or greater) but I do think there are still issues with JRebel but I haven't had a chance to retest it.

Load me first:

   public final class BootstrapSingleton {

        // Reverse-lookup map for getting a day from an abbreviation
        public static final Map<String, Day> lookup = new HashMap<String, Day>();

Now load it in the enum constructor:

   public enum Day { 
        MONDAY("M"), TUESDAY("T"), WEDNESDAY("W"),
        THURSDAY("R"), FRIDAY("F"), SATURDAY("Sa"), SUNDAY("Su"), ;

        private final String abbreviation;

        private Day(String abbreviation) {
            this.abbreviation = abbreviation;
            BootstrapSingleton.lookup.put(abbreviation, this);

        public String getAbbreviation() {
            return abbreviation;

        public static Day get(String abbreviation) {
            return lookup.get(abbreviation);

If you have an inner enum you can just define the Map above the enum definition and that (in theory) should get loaded before.

How To Execute SSH Commands Via PHP

//Update 2018, works//


Download phpseclib v1 and use this code:

set_include_path(__DIR__ . '/phpseclib1.0.11');

$key ="MyPassword";
  /* ### if using PrivateKey ### 
  $key = new Crypt_RSA();

$ssh = new Net_SSH2('', 22);   // Domain or IP
if (!$ssh->login('your_username', $key))  exit('Login Failed');

echo $ssh->exec('pwd');

or Method2:

Download newest phpseclib v2 (requires composer install at first):


set_include_path($path=__DIR__ . '/phpseclib-master/phpseclib');
include ($path.'/../vendor/autoload.php');

$loader = new \Composer\Autoload\ClassLoader();

use phpseclib\Net\SSH2;

$key ="MyPassword";
  /* ### if using PrivateKey ### 
  use phpseclib\Crypt\RSA;
  $key = new RSA();

$ssh = new SSH2('', 22);   // Domain or IP
if (!$ssh->login('your_username', $key))   exit('Login Failed'); 

echo $ssh->exec('pwd');

p.s. if you get "Connection timed out" then it's probably the issue of HOST/FIREWALL (local or remote) or like that, not a fault of script.

Java 32-bit vs 64-bit compatibility

Yes to the first question and no to the second question; it's a virtual machine. Your problems are probably related to unspecified changes in library implementation between versions. Although it could be, say, a race condition.

There are some hoops the VM has to go through. Notably references are treated in class files as if they took the same space as ints on the stack. double and long take up two reference slots. For instance fields, there's some rearrangement the VM usually goes through anyway. This is all done (relatively) transparently.

Also some 64-bit JVMs use "compressed oops". Because data is aligned to around every 8 or 16 bytes, three or four bits of the address are useless (although a "mark" bit may be stolen for some algorithms). This allows 32-bit address data (therefore using half as much bandwidth, and therefore faster) to use heap sizes of 35- or 36-bits on a 64-bit platform.

Transfer data between databases with PostgreSQL

You can not perform a cross-database query like SQL Server; PostgreSQL does not support this.

The DbLink extension of PostgreSQL is used to connect one database to another database. You have install and configure DbLink to execute a cross-database query.

I have already created a step-by-step script and example for executing cross database query in PostgreSQL. Please visit this post: PostgreSQL [Video]: Cross Database Queries using the DbLink Extension

How to query as GROUP BY in django?

Django does not support free group by queries. I learned it in the very bad way. ORM is not designed to support stuff like what you want to do, without using custom SQL. You are limited to:

  • RAW sql (i.e. MyModel.objects.raw())
  • cr.execute sentences (and a hand-made parsing of the result).
  • .annotate() (the group by sentences are performed in the child model for .annotate(), in examples like aggregating lines_count=Count('lines'))).

Over a queryset qs you can call qs.query.group_by = ['field1', 'field2', ...] but it is risky if you don't know what query are you editing and have no guarantee that it will work and not break internals of the QuerySet object. Besides, it is an internal (undocumented) API you should not access directly without risking the code not being anymore compatible with future Django versions.

Execute external program


public class Code {
  public static void main(String[] args) throws Exception {
    ProcessBuilder builder = new ProcessBuilder("ls", "-ltr");
    Process process = builder.start();

    StringBuilder out = new StringBuilder();
    try (BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()))) {
        String line = null;
      while ((line = reader.readLine()) != null) {

Try online

How to programmatically tell if a Bluetooth device is connected?

This code is for the headset profiles, probably it will work for other profiles too. First you need to provide profile listener (Kotlin code):

private val mProfileListener = object : BluetoothProfile.ServiceListener {
    override fun onServiceConnected(profile: Int, proxy: BluetoothProfile) {
        if (profile == BluetoothProfile.HEADSET) 
            mBluetoothHeadset = proxy as BluetoothHeadset            

    override fun onServiceDisconnected(profile: Int) {
        if (profile == BluetoothProfile.HEADSET) {
            mBluetoothHeadset = null

Then while checking bluetooth:

mBluetoothAdapter.getProfileProxy(context, mProfileListener, BluetoothProfile.HEADSET)
if (!mBluetoothAdapter.isEnabled) {
    return Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)

It takes a bit of time until onSeviceConnected is called. After that you may get the list of the connected headset devices from:


static and extern global variables in C and C++

Global variables are not extern nor static by default on C and C++. When you declare a variable as static, you are restricting it to the current source file. If you declare it as extern, you are saying that the variable exists, but are defined somewhere else, and if you don't have it defined elsewhere (without the extern keyword) you will get a link error (symbol not found).

Your code will break when you have more source files including that header, on link time you will have multiple references to varGlobal. If you declare it as static, then it will work with multiple sources (I mean, it will compile and link), but each source will have its own varGlobal.

What you can do in C++, that you can't in C, is to declare the variable as const on the header, like this:

const int varGlobal = 7;

And include in multiple sources, without breaking things at link time. The idea is to replace the old C style #define for constants.

If you need a global variable visible on multiple sources and not const, declare it as extern on the header, and then define it, this time without the extern keyword, on a source file:

Header included by multiple files:

extern int varGlobal;

In one of your source files:

int varGlobal = 7;

How to get query string parameter from MVC Razor markup?

Noneof the answers worked for me, I was getting "'HttpRequestBase' does not contain a definition for 'Query'", but this did work:


Delete all the queues from RabbitMQ?

There's a way to remove all queues and exchanges without scripts and full reset. You can just delete and re-create a virtual host from admin interface. This will work even for vhost /.

The only thing you'll need to restore is permissions for the newly created vhost.

LoDash: Get an array of values from an array of object properties

const users = [{
      id: 12,
      name: 'Adam'
      id: 14,
      name: 'Bob'
      id: 16,
      name: 'Charlie'
      id: 18,
      name: 'David'
const userIds = _.values(users);
console.log(userIds); //[12, 14, 16, 18]

Copy Notepad++ text with formatting?

Select the Text

From the menu, go to Plugins > NPPExport > Copy RTF to clipboard

In MS Word go to Edit > Paste Special

This will open the Paste Special dialog box. Select the Paste radio button and from the list select Formatted Text (RTF)

You should be able to see the Formatted Text.

How to get screen dimensions as pixels in Android

Using the following code in Activity.

DisplayMetrics metrics = new DisplayMetrics();
int height = metrics.heightPixels;
int wwidth = metrics.widthPixels;

Getting a directory name from a filename

 auto p = boost::filesystem::path("test/folder/file.txt");
 std::cout << p.parent_path() << '\n';             // test/folder
 std::cout << p.parent_path().filename() << '\n';  // folder
 std::cout << p.filename() << '\n';                // file.txt

You may need p.parent_path().filename() to get name of parent folder.

What requests do browsers' "F5" and "Ctrl + F5" refreshes generate?

Generally speaking:

F5 may give you the same page even if the content is changed, because it may load the page from cache. But Ctrl-F5 forces a cache refresh, and will guarantee that if the content is changed, you will get the new content.

Python loop for inside lambda

If you are like me just want to print a sequence within a lambda, without get the return value (list of None).

x = range(3)
from __future__ import print_function           # if not python 3
pra = lambda seq=x: map(print,seq) and None     # pra for 'print all'

How to select the Date Picker In Selenium WebDriver

Do not inject javascript. That is a bad practice.

I would model the DatePicker as an element like textbox / select as shown below.

For the detailed answer - check here-

public class DatePicker {

    private static final String dateFormat = "dd MMM yyyy";

    @FindBy(css = "a.ui-datepicker-prev")
    private WebElement prev;

    @FindBy(css = "a.ui-datepicker-next")
    private WebElement next;

    @FindBy(css = "div.ui-datepicker-title")
    private WebElement curDate;

    @FindBy(css = "a.ui-state-default")
    private List < WebElement > dates;

    public void setDate(String date) {

        long diff = this.getDateDifferenceInMonths(date);
        int day = this.getDay(date);

        WebElement arrow = diff >= 0 ? next : prev;
        diff = Math.abs(diff);

        //click the arrows
        for (int i = 0; i < diff; i++)

        //select the date
            .filter(ele - > Integer.parseInt(ele.getText()) == day)
            .ifPresent(ele - >;


    private int getDay(String date) {
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern(dateFormat);
        LocalDate dpToDate = LocalDate.parse(date, dtf);
        return dpToDate.getDayOfMonth();

    private long getDateDifferenceInMonths(String date) {
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern(dateFormat);
        LocalDate dpCurDate = LocalDate.parse("01 " + this.getCurrentMonthFromDatePicker(), dtf);
        LocalDate dpToDate = LocalDate.parse(date, dtf);
        return YearMonth.from(dpCurDate).until(dpToDate, ChronoUnit.MONTHS);

    private String getCurrentMonthFromDatePicker() {
        return this.curDate.getText();


JQuery: dynamic height() with window resize()

Okay, how about a CSS answer! We use display: table. Then each of the divs are rows, and finally we apply height of 100% to middle 'row' and voilà.

body { display: table; }
div { display: table-row; }
#content {
    margin:0 auto;
    text-align: center;
    background-color: blue;
    color: white;
    height: 100%;

Finding a substring within a list in Python

All the answers work but they always traverse the whole list. If I understand your question, you only need the first match. So you don't have to consider the rest of the list if you found your first match:

mylist = ['abc123', 'def456', 'ghi789']
sub = 'abc'
next((s for s in mylist if sub in s), None) # returns 'abc123'

If the match is at the end of the list or for very small lists, it doesn't make a difference, but consider this example:

import timeit

mylist = ['abc123'] + ['xyz123']*1000
sub = 'abc'

timeit.timeit('[s for s in mylist if sub in s]', setup='from __main__ import mylist, sub', number=100000)
# for me 7.949463844299316 with Python 2.7, 8.568840944994008 with Python 3.4
timeit.timeit('next((s for s in mylist if sub in s), None)', setup='from __main__ import mylist, sub', number=100000) 
# for me 0.12696599960327148 with Python 2.7, 0.09955992100003641 with Python 3.4

How to output git log with the first line only?

if you only want the first line of the messages (the subject):

git log --pretty=format:"%s"

and if you want all the messages on this branch going back to master:

git log --pretty=format:"%s" master..HEAD

Last but not least, if you want to add little bullets for quick markdown release notes:

git log --pretty=format:"- %s" master..HEAD

Android Emulator: Installation error: INSTALL_FAILED_VERSION_DOWNGRADE

Just uninstall the previous Apk and install the updated APK

Convert XLS to CSV on command line

All of these answers helped me construct the following script which will automatically convert XLS* files to CSV and vice versa, by dropping one or more files on the script (or via command line). Apologies for the janky formatting.


'* Global Settings and Variables
Set args = Wscript.Arguments

For Each sFilename In args
    iErr = ConvertExcelFormat(sFilename)
    ' 0 for normal success
    ' 404 for file not found
    ' 10 for file skipped (or user abort if script returns 10)


Function ConvertExcelFormat(srcFile)

    if IsEmpty(srcFile) OR srcFile = "" Then
        WScript.Echo "Error! Please specify at least one source path. Usage: " & WScript.ScriptName & " SourcePath.xls*|csv"
        ConvertExcelFormat = -1
        Exit Function
    End If

    Set objFSO = CreateObject("Scripting.FileSystemObject")

    srcExt = objFSO.GetExtensionName(srcFile)

    ' the 6 is the constant for 'CSV' format, 51 is for 'xlsx'
    Dim outputFormat, srcDest

    If LCase(Mid(srcExt, 1, 2)) = "xl" Then
        outputFormat = 6
        srcDest = "csv"
        outputFormat = 51
        srcDest = "xlsx"
    End If

    'srcFile = objFSO.GetAbsolutePathName(Wscript.Arguments.Item(0))
    srcFile = objFSO.GetAbsolutePathName(srcFile)
    destFile = Replace(srcFile, srcExt, srcDest)

    Dim oExcel
    Set oExcel = CreateObject("Excel.Application")
    Dim oBook
    Set oBook = oExcel.Workbooks.Open(srcFile)
    ' preserve formatting?
    'oBook.Application.Columns("A:J").NumberFormat = "@"
    oBook.SaveAs destFile, outputFormat
    oBook.Close False
    WScript.Echo "Conversion complete of '" & srcFile & "' to '" & objFSO.GetFileName(destFile) & "'"

End Function

How to list all installed packages and their versions in Python?

yes! you should be using pip as your python package manager ( )

with pip installed packages, you can do a

pip freeze

and it will list all installed packages. You should probably also be using virtualenv and virtualenvwrapper. When you start a new project, you can do

mkvirtualenv my_new_project

and then (inside that virtualenv), do

pip install all_your_stuff

This way, you can workon my_new_project and then pip freeze to see which packages are installed for that virtualenv/project.

for example:

?  ~  mkvirtualenv yo_dude
New python executable in yo_dude/bin/python
Installing setuptools............done.
Installing pip...............done.
virtualenvwrapper.user_scripts creating /Users/aaylward/dev/virtualenvs/yo_dude/bin/predeactivate
virtualenvwrapper.user_scripts creating /Users/aaylward/dev/virtualenvs/yo_dude/bin/postdeactivate
virtualenvwrapper.user_scripts creating /Users/aaylward/dev/virtualenvs/yo_dude/bin/preactivate
virtualenvwrapper.user_scripts creating /Users/aaylward/dev/virtualenvs/yo_dude/bin/postactivate
virtualenvwrapper.user_scripts creating /Users/aaylward/dev/virtualenvs/yo_dude/bin/get_env_details

(yo_dude)?  ~  pip install django
Downloading/unpacking django
  Downloading Django-1.4.1.tar.gz (7.7Mb): 7.7Mb downloaded
  Running egg_info for package django

Installing collected packages: django
  Running install for django
    changing mode of build/scripts-2.7/ from 644 to 755

    changing mode of /Users/aaylward/dev/virtualenvs/yo_dude/bin/ to 755
Successfully installed django
Cleaning up...

(yo_dude)?  ~  pip freeze

(yo_dude)?  ~  

or if you have a python package with a requirements.pip file,

mkvirtualenv my_awesome_project
pip install -r requirements.pip
pip freeze

will do the trick

How to see the changes between two commits without commits in-between?

Suppose you want to see the difference between commits 012345 and abcdef. The following should do what you want:

$ git checkout 012345
$ git cherry-pick -n abcdef
$ git diff --cached

Thread pooling in C++11

This is copied from my answer to another very similar post, hope it can help:

1) Start with maximum number of threads a system can support:

int Num_Threads =  thread::hardware_concurrency();

2) For an efficient threadpool implementation, once threads are created according to Num_Threads, it's better not to create new ones, or destroy old ones (by joining). There will be performance penalty, might even make your application goes slower than the serial version.

Each C++11 thread should be running in their function with an infinite loop, constantly waiting for new tasks to grab and run.

Here is how to attach such function to the thread pool:

int Num_Threads = thread::hardware_concurrency();
vector<thread> Pool;
for(int ii = 0; ii < Num_Threads; ii++)
{  Pool.push_back(thread(Infinite_loop_function));}

3) The Infinite_loop_function

This is a "while(true)" loop waiting for the task queue

void The_Pool:: Infinite_loop_function()
            unique_lock<mutex> lock(Queue_Mutex);

            condition.wait(lock, []{return !Queue.empty() || terminate_pool});
            Job = Queue.front();
        Job(); // function<void()> type

4) Make a function to add job to your Queue

void The_Pool:: Add_Job(function<void()> New_Job)
        unique_lock<mutex> lock(Queue_Mutex);

5) Bind an arbitrary function to your Queue

Pool_Obj.Add_Job(std::bind(&Some_Class::Some_Method, &Some_object));

Once you integrate these ingredients, you have your own dynamic threading pool. These threads always run, waiting for job to do.

I apologize if there are some syntax errors, I typed these code and and I have a bad memory. Sorry that I cannot provide you the complete thread pool code, that would violate my job integrity.

Edit: to terminate the pool, call the shutdown() method:

    unique_lock<mutex> lock(threadpool_mutex);
    terminate_pool = true;} // use this flag in condition.wait

    condition.notify_all(); // wake up all threads.

    // Join all threads.
    for(std::thread &every_thread : thread_vector)
    {   every_thread.join();}

    stopped = true; // use this flag in destructor, if not set, call shutdown() 

How to use unicode characters in Windows command line?

A better cleaner thing to do: Just install the available, free, Microsoft Japanese language pack. (Other oriental language packs will also work, but I have tested the Japanese one.)

This gives you the fonts with the larger sets of glyphs, makes them the default behavior, changes the various Windows tools like cmd, WordPad, etc.

Getting a machine's external IP address with Python

I prefer this Amazon AWS endpoint:

import requests
ip = requests.get('').text.strip()

Check if a String contains numbers Java

ASCII is at the start of UNICODE, so you can do something like this:

(x >= 97 && x <= 122) || (x >= 65 && x <= 90) // 97 == 'a' and 65 = 'A'

I'm sure you can figure out the other values...

How do I remove whitespace from the end of a string in Python?

>>> "    xyz     ".rstrip()
'    xyz'

There is more about rstrip in the documentation.

Where does Android emulator store SQLite database?

The databases are stored as SQLite files in /data/data/PACKAGE/databases/DATABASEFILE where:

You can see (copy from/to filesystem) the database file in the emulator selecting DDMS perspective, in the File Explorer tab.

MongoDb shuts down with Code 100

MongoDB needs a folder to store the database. Create a C:\data\db\ directory:

mkdir C:\data\db

and then start MongoDB:

C:\Program Files\MongoDB\Server\3.4\bin\mongod.exe

Sometimes C:\data\db folder already exists due to previous installation. So if for this reason mongod.exe does not work, you may delete all the contents from C:\data\db folder and execute mongod.exeagain.

Handling Dialogs in WPF with MVVM

A good MVVM dialog should:

  1. Be declared with only XAML.
  2. Get all of it's behavior from databinding.

Unfortunately, WPF doesn't provide these features. Showing a dialog requires a code-behind call to ShowDialog(). The Window class, which supports dialogs, can't be declared in XAML so it can't easily be databound to the DataContext.

To solve this, I wrote a XAML stub control that sits in the logical tree and relays databinding to a Window and handles showing and hiding the dialog. You can find it here:

It's really simply to use and doesn't require any strange changes to your ViewModel and doesn't require events or messages. The basic call looks like this:

<dialog:Dialog Content="{Binding Path=DialogViewModel}" Showing="True" />

You probably want to add a style that sets Showing. I explain it in my article. I hope this helps you.

Including external HTML file to another HTML file

The iframe element.

<iframe src="name.html"></iframe>

But content that you way to have appear on multiple pages is better handled using templates.

Call a stored procedure with another in Oracle

@Michael Lockwood - you don't need to use the keyword "CALL" anywhere. You just need to mention the procedure call directly.

That is

   proc1(input1, input2);

instead of

   call proc1(input1, input2);

How do I add an element to a list in Groovy?

From the documentation:

We can add to a list in many ways:

assert [1,2] + 3 + [4,5] + 6 == [1, 2, 3, 4, 5, 6]
assert [1,2].plus(3).plus([4,5]).plus(6) == [1, 2, 3, 4, 5, 6]
    //equivalent method for +
def a= [1,2,3]; a += 4; a += [5,6]; assert a == [1,2,3,4,5,6]
assert [1, *[222, 333], 456] == [1, 222, 333, 456]
assert [ *[1,2,3] ] == [1,2,3]
assert [ 1, [2,3,[4,5],6], 7, [8,9] ].flatten() == [1, 2, 3, 4, 5, 6, 7, 8, 9]

def list= [1,2]
list.add(3) //alternative method name
list.addAll([5,4]) //alternative method name
assert list == [1,2,3,5,4]

list= [1,2]
list.add(1,3) //add 3 just before index 1
assert list == [1,3,2]
list.addAll(2,[5,4]) //add [5,4] just before index 2
assert list == [1,3,5,4,2]

list = ['a', 'b', 'z', 'e', 'u', 'v', 'g']
list[8] = 'x'
assert list == ['a', 'b', 'z', 'e', 'u', 'v', 'g', null, 'x']

You can also do:

def myNewList = myList << "fifth"

Pandas "Can only compare identically-labeled DataFrame objects" error

You can also try dropping the index column if it is not needed to compare:

print(df1.reset_index(drop=True) == df2.reset_index(drop=True))

I have used this same technique in a unit test like so:

from pandas.util.testing import assert_frame_equal

assert_frame_equal(actual.reset_index(drop=True), expected.reset_index(drop=True))

C# Clear all items in ListView

My guess is that Clear() causes a Changed event to be sent, which in turn triggers an automatic update of your listview from the data source. So this is a feature, not a bug ;-)

Have you tried myListView.Clear() instead of myListView.Items.Clear()? Maybe that works better.

How can I determine if a date is between two dates in Java?

This might be a bit more readable:

Date min, max;   // assume these are set to something
Date d;          // the date in question

return d.after(min) && d.before(max);

Provide static IP to docker containers via docker-compose

I was facing some difficulties with an environment variable that is with custom name (not with container name /port convention for KAPACITOR_BASE_URL and KAPACITOR_ALERTS_ENDPOINT). If we give service name in this case it wouldn't resolve the ip as

KAPACITOR_BASE_URL:  http://kapacitor:9092

In above http://[**kapacitor**]:9092 would not resolve to

I resolved the static IPs issues using subnetting configurations.

version: "3.3"

        - subnet:
        image: postgres:9.4.4
            - "5432:5432"
            - postgres_data:/var/lib/postgresql/data

        image: redis:latest
            - "6379"

        image: influxdb:latest
            - "8086:8086"
            - "8083:8083"
            - ../influxdb/influxdb.conf:/etc/influxdb/influxdb.conf
            - ../influxdb/inxdb:/var/lib/influxdb
          INFLUXDB_ADMIN_ENABLED: "true"
          INFLUXDB_USERNAME: "db_username"
          INFLUXDB_PASSWORD: "12345678"
          INFLUXDB_DB: db_customers

        image: kapacitor:latest
            - "9092:9092"
            - influxdb
            - ../kapacitor/kapacitor.conf:/etc/kapacitor/kapacitor.conf
            - ../kapacitor/kapdb:/var/lib/kapacitor
          KAPACITOR_INFLUXDB_0_URLS_0: http://influxdb:8086

        build: .
        command: bundle exec rails s -b
            - "3000:3000"
            - db
            - kapacitor
            - db
            - .:/var/app/current
          DATABASE_URL: postgres://postgres@db
          DATABASE_USERNAME: postgres
          DATABASE_PASSWORD: postgres
          INFLUX_URL: http://influxdb:8086
          INFLUX_USER: db_username
          INFLUX_PWD: 12345678


How do you create vectors with specific intervals in R?

In R the equivalent function is seq and you can use it with the option by:

seq(from = 5, to = 100, by = 5)
# [1]   5  10  15  20  25  30  35  40  45  50  55  60  65  70  75  80  85  90  95 100

In addition to by you can also have other options such as length.out and along.with.

length.out: If you want to get a total of 10 numbers between 0 and 1, for example:

seq(0, 1, length.out = 10)
# gives 10 equally spaced numbers from 0 to 1

along.with: It takes the length of the vector you supply as input and provides a vector from 1:length(input).

# [1] 1 2 3

Although, instead of using the along.with option, it is recommended to use seq_along in this case. From the documentation for ?seq

seq is generic, and only the default method is described here. Note that it dispatches on the class of the first argument irrespective of argument names. This can have unintended consequences if it is called with just one argument intending this to be taken as along.with: it is much better to use seq_along in that case.

seq_along: Instead of seq(along.with(.))

# [1] 1 2 3

Hope this helps.

How to extract text from a PDF?

For image extraction, pdfimages is a free command line tool for Linux or Windows (win32):

pdfimages: Extract and Save Images From A Portable Document Format ( PDF ) File

What's the difference between a mock & stub?

A fake is a generic term that can be used to describe either a stub or a mock object (handwritten or otherwise), because they both look like the real object.

Whether a fake is a stub or a mock depends on how it’s used in the current test. If it’s used to check an interaction (asserted against), it’s a mock object. Otherwise, it’s a stub.

Fakes makes sure test runs smoothly. It means that reader of your future test will understand what will be the behavior of the fake object, without needing to read its source code (without needing to depend on external resource).

What does test run smoothly mean?
Forexample in below code:

 public void Analyze(string filename)
                    errorService.LogError("long file entered named:" + filename);
                catch (Exception e)
                    mailService.SendEMail("[email protected]", "ErrorOnWebService", "someerror");

You want to test mailService.SendEMail() method, to do that you need to simulate an Exception in you test method, so you just need to create a Fake Stub errorService class to simulate that result, then your test code will be able to test mailService.SendEMail() method. As you see you need to simulate a result which is from an another External Dependency ErrorService class.

Delete commits from a branch in Git

I'm appending this answer because I don't see why anyone who has just tried to commit work would want to delete all that work because of some mistake using Git!

If you want to keep your work and just 'undo' that commit command (you caught before pushing to repo):

git reset --soft HEAD~1

Do not use the --hard flag unless you want to destroy your work in progress since the last commit.

You don't have write permissions for the /Library/Ruby/Gems/2.3.0 directory. (mac user)

Solution for MAC. run the command

sudo gem update    

then type your Mac password when prompted

Convert Word doc, docx and Excel xls, xlsx to PDF with PHP

Step 1. Install "Apache_OpenOffice_4.1.2" in your system Step 2. Download "unoconv" library from github or any where else.

-> C:\Program Files (x86)\OpenOffice 4\program\python.exe = Path of open office install directory

-> D:\wamp\www\doc_to_pdf\libobasis4.4-pyuno\unoconv = Path of library folder

-> D:/wamp/www/doc_to_pdf/files/'.$pdf_File_name.' = path and file name of pdf

-> D:/wamp/www/doc_to_pdf/files/'.$doc_file_name = Path of your document file.

If pdf not created than last step is Go to ->Control Panel\All Control Panel Items\Administrative Tools-> services-> find "wampapache" -> right click and click on property -> click on logon tab Than check checkbox of allow service to interact with desktop

Create sample .php file and put below code and run on wamp or xampp server

$result = exec('"C:\Program Files (x86)\OpenOffice 4\program\python.exe" D:\wamp\www\doc_to_pdf\libobasis4.4-pyuno\unoconv -f pdf -o D:/wamp/www/doc_to_pdf/files/'.$pdf_File_name.' D:/wamp/www/doc_to_pdf/files/'.$doc_file_name);

This code working for me in windows-8 operating system

Better solution without exluding fields from Binding

You should not use your domain models in your views. ViewModels are the correct way to do it.

You need to map your domain model's necessary fields to viewmodel and then use this viewmodel in your controllers. This way you will have the necessery abstraction in your application.

If you never heard of viewmodels, take a look at this.

Webpack - webpack-dev-server: command not found

I found the accepted answer does not work in all scenarios. To ensure it 100% works one must ALSO clear the npm cache. Either directly Goto the cache and clear locks, caches, anonymous-cli-metrics.json; or one can try npm cache clean.

Since the author had cleared the cache before trying the recommended solution its possible that failed to make it part of the pre-requisites.

Can I execute a function after setState is finished updating?

render will be called every time you setState to re-render the component if there are changes. If you move your call to drawGrid there rather than calling it in your update* methods, you shouldn't have a problem.

If that doesn't work for you, there is also an overload of setState that takes a callback as a second parameter. You should be able to take advantage of that as a last resort.

Padding or margin value in pixels as integer using jQuery

You could also extend the jquery framework yourself with something like:

jQuery.fn.margin = function() {
var marginTop = this.outerHeight(true) - this.outerHeight();
var marginLeft = this.outerWidth(true) - this.outerWidth();

return {
    top: marginTop,
    left: marginLeft

Thereby adding a function on your jquery objects called margin(), which returns a collection like the offset function.



How do I store data in local storage using Angularjs?

One should use a third party script for this called called ngStorage here is a example how to use.It updates localstorage with change in scope/view.

    <!DOCTYPE html>

<head lang="en">
    <meta charset="UTF-8">
    <!-- CDN Link -->
    <script src="angular.min.js"></script>
    <script src="ngStorage.min.js"></script>
        var app = angular.module('app', ['ngStorage']);
        app.factory("myfactory", function() {
            return {
                data: ["ram", "shyam"]
        app.controller('Ctrl', function($scope, $localStorage, $sessionStorage, myfactory) {

            $scope.abcd = $localStorage; //Pass $localStorage (or $sessionStorage) by reference to a hook under $scope
            // Delete from Local Storage
            //delete $scope.abcd.counter;
            // delete $localStorage.counter;
            // $localStorage.$reset(); // clear the localstorage
            /* $localStorage.$reset({
                 counter: 42   // reset with default value
            // $;

<body ng-app="app" ng-controller="Ctrl">

    <button ng-click="abcd.counter = abcd.counter + 1">{{abcd.counter}}</button>


Python:Efficient way to check if dictionary is empty or not

I just wanted to know if the dictionary i was going to try to pull data from had data in it in the first place, this seems to be simplest way.

d = {}


#should return

d = {'hello':'world'}


#should return

MySQL INNER JOIN select only one row from second table

This is quite simple do The inner join and then group by user_id and use max aggregate function in payment_id assuming your table being user and payment query can be

select, max( from user inner join payment on ( = payment.user_id) group by

How to set breakpoints in inline Javascript in Google Chrome?

I was having the same problem too, how to debug JavaScript that is inside <script> tags. But then I found it under the Sources tab, called "(index)", with parenthesis. Click the line number to set breakpoints.

enter image description here

This is Chrome 71.

Mongoose: CastError: Cast to ObjectId failed for value "[object Object]" at path "_id"

If you are having this issue and you are performing a populate somewhere along the lines, see this Mongoose issue.

Update to Mongoose 4.0 and the issue has been fixed.

Query to display all tablespaces in a database and datafiles

SELECT a.file_name,
       substr(A.tablespace_name,1,14) tablespace_name,
       trunc(decode(A.autoextensible,'YES',,'NO', free_mb,
       trunc(a.bytes/1024/1024) allocated_mb,
       trunc(A.MAXSIZE/1024/1024) capacity,
       a.autoextensible ae
     SELECT file_id, file_name,
            decode(autoextensible,'YES',maxbytes,bytes) maxsize
     FROM   dba_data_files
     GROUP BY file_id, file_name,
     ) a,
     (SELECT file_id,
             sum(bytes) free
      FROM   dba_free_space
      GROUP BY file_id,
      ) b
WHERE a.file_id=b.file_id(+)
AND A.tablespace_name=b.tablespace_name(+)
ORDER BY A.tablespace_name ASC; 

Counting inversions in an array

Here is O(n*log(n)) perl implementation:

sub sort_and_count {
    my ($arr, $n) = @_;
    return ($arr, 0) unless $n > 1;

    my $mid = $n % 2 == 1 ? ($n-1)/2 : $n/2;
    my @left = @$arr[0..$mid-1];
    my @right = @$arr[$mid..$n-1];

    my ($sleft, $x) = sort_and_count( \@left, $mid );
    my ($sright, $y) = sort_and_count( \@right, $n-$mid);
    my ($merged, $z) = merge_and_countsplitinv( $sleft, $sright, $n );

    return ($merged, $x+$y+$z);

sub merge_and_countsplitinv {
    my ($left, $right, $n) = @_;

    my ($l_c, $r_c) = ($#$left+1, $#$right+1);
    my ($i, $j) = (0, 0);
    my @merged;
    my $inv = 0;

    for my $k (0..$n-1) {
        if ($i<$l_c && $j<$r_c) {
            if ( $left->[$i] < $right->[$j]) {
                push @merged, $left->[$i];
            } else {
                push @merged, $right->[$j];
                $inv += $l_c - $i;
        } else {
            if ($i>=$l_c) {
                push @merged, @$right[ $j..$#$right ];
            } else {
                push @merged, @$left[ $i..$#$left ];

    return (\@merged, $inv);

How to trap the backspace key using jQuery?

Working on the same idea as above , but generalizing a bit . Since the backspace should work fine on the input elements , but should not work if the focus is a paragraph or something , since it is there where the page tends to go back to the previous page in history .

$('html').on('keydown' , function(event) {

        if(! $('input')) {
           if(event.which == 8) {
            //  alert('backspace pressed');
            return false;

returning false => both event.preventDefault and event.stopPropagation are in effect .

How to reload apache configuration for a site without restarting apache?

It should be possible using the command

sudo /etc/init.d/apache2 reload

I hope that helps.

How can I check if a checkbox is checked?

use like this

<script type=text/javascript>
function validate(){
if (document.getElementById('remember').checked){
          alert("checked") ;
alert("You didn't check it! Let me check it for you.")

<input id="remember" name="remember" type="checkbox" onclick="validate()" />

SSIS Convert Between Unicode and Non-Unicode Error

Instead of adding an earlier suggested Data Conversion you can cast the nvarchar column to a varchar column. This prevents you from having an unnecessary step and has a higher performance then the alternative.

In the select of your SQL statement replace date with CAST(date AS varchar([size])). For some reason this does not yet change the output data type. To do this do the following:

  1. Right click your OLE DB Source step and open the advanced editor.
  2. Go to Input and Output Properties
  3. Select Output Columns
  4. Select your column
  5. Under Data Type Properties change DataType to string [DT_STR]
  6. Change Length to the length you specified in your CAST statement

After doing this your source data will be output as a varchar and your error will disappear.


Enum Naming Convention - Plural

I started out naming enums in the plural but have since changed to singular. Just seems to make more sense in the context of where they're used.

enum Status { Unknown = 0, Incomplete, Ready }

Status myStatus = Status.Ready;

Compare to:

Statuses myStatus = Statuses.Ready;

I find the singular form to sound more natural in context. We are in agreement that when declaring the enum, which happens in one place, we're thinking "this is a group of whatevers", but when using it, presumably in many places, that we're thinking "this is one whatever".

How to format date in angularjs

Angular.js has a built-in date filter.


// in your controller:
$ = '20140313T00:00:00';

// in your view, date property, filtered with date filter and format 'MM/dd/yyyy'
<p ng-bind="date | date:'MM/dd/yyyy'"></p>

// produces

You can see the supported date formats in the source for the date filter.


If you're trying to get the correct format in the datepicker (not clear if you're using datepicker or just trying to use it's formatter), those supported format strings are here:

Select query to get data from SQL Server

you have to add parameter also @zip

 SqlConnection conn = new SqlConnection("Data Source=;Initial Catalog=;Persist Security Info=True;User ID=;Password=");
      SqlCommand command = new SqlCommand("Select id from [table1] where name=@zip", conn);
    // Add new SqlParameter to the command.
      int result = (Int32) (command.ExecuteScalar());
      using (SqlDataReader reader = command.ExecuteReader())
          // iterate your results here


How do I add records to a DataGridView in VB.Net?

I think you should build a dataset/datatable in code and bind the grid to that.

Redirect using AngularJS

It is hard to say without knowing your code. My best guess is that the onchange event is not firing when you change your textbox value from JavaScript code.

There are two ways for this to work; the first is to call onchange by yourself, and the second is to wait for the textbox to lose focus.

Check this question; same issue, different framework.

How to install a specific JDK on Mac OS X?

JDK is the Java Development Kit (used to develop Java software).

JRE is the Java Runtime Environment (used to run any .jar file 'Java software').

The JDK contains a JRE inside it.

On Windows when you update Java, it updates the JRE automatically.

On Mac you do not have a JRE separated you have it, but inside the JDK, so when you update Java it will update your JRE which is inside your JDK; it doesn't install an JDK for you. You need to get it from somewhere else.

String date to xmlgregoriancalendar conversion

GregorianCalendar c = GregorianCalendar.from((LocalDate.parse("2016-06-22")).atStartOfDay(ZoneId.systemDefault()));
XMLGregorianCalendar date2 = DatatypeFactory.newInstance().newXMLGregorianCalendar(c);

spring PropertyPlaceholderConfigurer and context:property-placeholder

Following worked for me:
<context:property-placeholder location="file:src/resources/spring/"/>

Somehow "classpath:xxx" is not picking the file.

Checking for directory and file write permissions in .NET

The accepted answer by Kev to this question doesn't actually give any code, it just points to other resources that I don't have access to. So here's my best attempt at the function. It actually checks that the permission it's looking at is a "Write" permission and that the current user belongs to the appropriate group.

It might not be complete with regard to network paths or whatever, but it's good enough for my purpose, checking local configuration files under "Program Files" for writability:

using System.Security.Principal;
using System.Security.AccessControl;

private static bool HasWritePermission(string FilePath)
        FileSystemSecurity security;
        if (File.Exists(FilePath))
            security = File.GetAccessControl(FilePath);
            security = Directory.GetAccessControl(Path.GetDirectoryName(FilePath));
        var rules = security.GetAccessRules(true, true, typeof(NTAccount));

        var currentuser = new WindowsPrincipal(WindowsIdentity.GetCurrent());
        bool result = false;
        foreach (FileSystemAccessRule rule in rules)
            if (0 == (rule.FileSystemRights &
                (FileSystemRights.WriteData | FileSystemRights.Write)))

            if (rule.IdentityReference.Value.StartsWith("S-1-"))
                var sid = new SecurityIdentifier(rule.IdentityReference.Value);
                if (!currentuser.IsInRole(sid))
                if (!currentuser.IsInRole(rule.IdentityReference.Value))

            if (rule.AccessControlType == AccessControlType.Deny)
                return false;
            if (rule.AccessControlType == AccessControlType.Allow)
                result = true;
        return result;
        return false;

Empty responseText from XMLHttpRequest


In my case the problem was that I do the ajax call (with $.ajax, $.get or $.getJSON methods from jQuery) with full path in the url param:

url: ""

But the correct way is to pass the value of url as:

url: "site/cgi-bin/serverApp.php"

Some browser don't conflict and make no distiction between one text or another, but in Firefox 3.6 for Mac OS take this full path as "cross site scripting"... another thing, in the same browser there is a distinction between:

And put

In fact it is the correct point view, but most implementations make no distinction, so the solution was to remove all the text that specify the full path to the script in the methods that do the ajax request AND.... remove any BASE tag in the index.html file

base href="" <--- bad idea, remove it!

If you don't remove it, this version of browser for this system may take your ajax request like if it is a cross site request!

I have the same problem but only on the Mac OS machine. The problem is that Firefox treat the ajax response as an "cross site" call, in any other machine/browser it works fine. I didn't found any help about this (I think that is a firefox implementation issue), but I'm going to prove the next code at the server side:

header('Content-type: application/json');

to ensure that browser get the data as "json data" ...

Reading string from input with space character?


fgets (name, 100, stdin);

100 is the max length of the buffer. You should adjust it as per your need.


scanf ("%[^\n]%*c", name);

The [] is the scanset character. [^\n] tells that while the input is not a newline ('\n') take input. Then with the %*c it reads the newline character from the input buffer (which is not read), and the * indicates that this read in input is discarded (assignment suppression), as you do not need it, and this newline in the buffer does not create any problem for next inputs that you might take.

Read here about the scanset and the assignment suppression operators.

Note you can also use gets but ....

Never use gets(). Because it is impossible to tell without knowing the data in advance how many characters gets() will read, and because gets() will continue to store characters past the end of the buffer, it is extremely dangerous to use. It has been used to break computer security. Use fgets() instead.

How to POST URL in data of a curl request

Perhaps you don't have to include the single quotes:

curl --request POST 'http://localhost/Service' --data "path=/xyz/pqr/test/&fileName=1.doc"

Update: Reading curl's manual, you could actually separate both fields with two --data:

curl --request POST 'http://localhost/Service' --data "path=/xyz/pqr/test/" --data "fileName=1.doc"

You could also try --data-binary:

curl --request POST 'http://localhost/Service' --data-binary "path=/xyz/pqr/test/" --data-binary "fileName=1.doc"

And --data-urlencode:

curl --request POST 'http://localhost/Service' --data-urlencode "path=/xyz/pqr/test/" --data-urlencode "fileName=1.doc"

Does a `+` in a URL scheme/host/path represent a space?

Thou shalt always encode URLs.

Here is how Ruby encodes your URL:

irb(main):008:0> CGI.escape ""
=> ""

Android Studio cannot resolve R in imported project?

I solve that problem setting JAVA_HOME, CLASSPATH.

People sometimes skip JAVA_HOME and CLASSPATH when setting Java_path.

So try to check Environment Variable.


JAVA_HOME -> C:\Program Files\Java\jdk(version) or where Java installed

and then check the xml file which can have error(Do not naming well-known things such as button,text etc)

Hibernate: failed to lazily initialize a collection of role, no session or session was closed

for me it worked the approach that I used in eclipselink as well. Just call the size() of the collection that should be loaded before using it as parameter to pages.

for (Entity e : entityListKeeper.getEntityList()) {

Here entityListKeeper has List of Entity that has list of LazyLoadedEntity. If you have just therelation Entity has list of LazyLoadedEntity then the solution is:


Edit line thickness of CSS 'underline' attribute

Here is one way of achieving this :


<h4>This is a heading</h4>

<h4><u>This is another heading</u></h4>

?CSS :

 u {
    text-decoration: none;
    border-bottom: 10px solid black;

Here is an example:

Finding the indices of matching elements in list in Python

>>> average =  [1,3,2,1,1,0,24,23,7,2,727,2,7,68,7,83,2]
>>> matches = [i for i in range(0,len(average)) if average[i]<2 or average[i]>4]
>>> matches
[0, 3, 4, 5, 6, 7, 8, 10, 12, 13, 14, 15]

How to read all files in a folder from Java?

You can put the file path to argument and create a list with all the filepaths and not put it the list manually. Then use a for loop and a reader. Example for txt files:

public static void main(String[] args) throws IOException{    
File[] files = new File(args[0].replace("\\", "\\\\")).listFiles(new FilenameFilter() { @Override public boolean accept(File dir, String name) { return name.endsWith(".txt"); } });
    ArrayList<String> filedir = new ArrayList<String>();
    String FILE_TEST = null;
    for (i=0; i<files.length; i++){

        try(Reader testreader = Files.newBufferedReader(Paths.get(FILE_TEST));
              //write your stuff

Can I store images in MySQL

Yes, you can store images in the database, but it's not advisable in my opinion, and it's not general practice.

A general practice is to store images in directories on the file system and store references to the images in the database. e.g. path to the image,the image name, etc.. Or alternatively, you may even store images on a content delivery network (CDN) or numerous hosts across some great expanse of physical territory, and store references to access those resources in the database.

Images can get quite large, greater than 1MB. And so storing images in a database can potentially put unnecessary load on your database and the network between your database and your web server if they're on different hosts.

I've worked at startups, mid-size companies and large technology companies with 400K+ employees. In my 13 years of professional experience, I've never seen anyone store images in a database. I say this to support the statement it is an uncommon practice.

Send and Receive a file in socket programming in Linux with C/C++ (GCC/G++)

Do aman 2 sendfile. You only need to open the source file on the client and destination file on the server, then call sendfile and the kernel will chop and move the data.

load Js file in HTML

If this is your detail.html I don't see where do you load detail.js? Maybe this

<script src="js/index.js"></script>

should be this

<script src="js/detail.js"></script>


Move to next item using Java 8 foreach loop in stream

You can use a simple if statement instead of continue. So instead of the way you have your code, you can try:

try(Stream<String> lines = Files.lines(path, StandardCharsets.ISO_8859_1)){
            filteredLines = lines.filter(...).foreach(line -> {
           if(!...) {
              // Code you want to run
           // Once the code runs, it will continue anyway

The predicate in the if statement will just be the opposite of the predicate in your if(pred) continue; statement, so just use ! (logical not).

How to set Highcharts chart maximum yAxis value

Alternatively one can use the setExtremes method also,

yAxis.setExtremes(0, 100);

Or if only one value is needed to be set, just leave other as null

yAxis.setExtremes(null, 100);

Custom ImageView with drop shadow

I believe this answer from UIFuel

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="">

     <!-- Drop Shadow Stack -->
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#00CCCCCC" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#10CCCCCC" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#20CCCCCC" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#30CCCCCC" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#50CCCCCC" />

    <!-- Background -->
            <solid android:color="@color/white" />
        <corners android:radius="3dp" />

MySQL dump by query

not mysqldump, but mysql cli...

mysql -e "select * from myTable" -u myuser -pxxxxxxxxx mydatabase

you can redirect it out to a file if you want :

mysql -e "select * from myTable" -u myuser -pxxxxxxxx mydatabase > mydumpfile.txt

Update: Original post asked if he could dump from the database by query. What he asked and what he meant were different. He really wanted to just mysqldump all tables.

mysqldump --tables myTable --where="id < 1000"

Replace part of a string with another string

With C++11 you can use std::regex like so:

#include <regex>
std::string string("hello $name");
string = std::regex_replace(string, std::regex("\\$name"), "Somename");

The double backslash is required for escaping an escape character.

How to output an Excel *.xls file from classic ASP

It's AddHeader, not AppendHeader.

<%@ Language=VBScript %>
<%  Option Explicit

Response.ContentType = "application/"
Response.AddHeader "Content-Disposition", "attachment; filename=excelTest.xls"

Update: I've written a blog post about how to generate Excel files in ASP Classic. It contains a rather useful piece of code to generate both xls and csv files.

Setting up SSL on a local xampp/apache server

I did most of the suggested stuff here, still didnt work. Tried this and it worked: Open your XAMPP Control Panel, locate the Config button for the Apache module. Click on the Config button and Select PHP (php.ini). Open with any text editor and remove the semi-column before php_openssl. Save and Restart Apache. That should do!

How to return a part of an array in Ruby?

Ruby 2.6 Beginless/Endless Ranges

# or

# or

=> [1, 2, 3, 4]

 => [1, 2, 3]

ROLES = %w[superadmin manager admin contact user]
=> ["admin", "contact", "user"]

Oracle pl-sql escape character (for a " ' ")

Here is a way to easily escape & char in oracle DB

set escape '\\'

and within query write like


Get first element in PHP stdObject

Update PHP 7.4

Curly brace access syntax is deprecated since PHP 7.4

Update 2019

Moving on to the best practices of OOPS, @MrTrick's answer must be marked as correct, although my answer provides a hacked solution its not the best method.

Simply iterate its using {}



This way your object is not destroyed and you can easily iterate through object.

For PHP 5.6 and below use this


Both array() and the stdClass objects can be accessed using the current() key() next() prev() reset() end() functions.

So, if your object looks like

object(stdClass)#19 (3) {
  object(stdClass)#20 (22) {
    string(1) "123"

Then you can just do;

$id = reset($obj)->id; //Gets the 'id' attr of the first entry in the object

If you need the key for some reason, you can do;

reset($obj); //Ensure that we're at the first element
$key = key($obj);

Hope that works for you. :-) No errors, even in super-strict mode, on PHP 5.4

2022 Update:
After PHP 7.4, using current(), end(), etc functions on objects is deprecated.

In newer versions of PHP, use the ArrayIterator class:

$objIterator = new ArrayIterator($obj);

$id = $objIterator->current()->id; // Gets the 'id' attr of the first entry in the object

$key = $objIterator->key(); // and gets the key

Catching access violation exceptions?

This type of situation is implementation dependent and consequently it will require a vendor specific mechanism in order to trap. With Microsoft this will involve SEH, and *nix will involve a signal

In general though catching an Access Violation exception is a very bad idea. There is almost no way to recover from an AV exception and attempting to do so will just lead to harder to find bugs in your program.

Best way to structure a tkinter application?

Probably the best way to learn how to structure your program is by reading other people's code, especially if it's a large program to which many people have contributed. After looking at the code of many projects, you should get an idea of what the consensus style should be.

Python, as a language, is special in that there are some strong guidelines as to how you should format your code. The first is the so-called "Zen of Python":

  • Beautiful is better than ugly.
  • Explicit is better than implicit.
  • Simple is better than complex.
  • Complex is better than complicated.
  • Flat is better than nested.
  • Sparse is better than dense.
  • Readability counts.
  • Special cases aren't special enough to break the rules.
  • Although practicality beats purity.
  • Errors should never pass silently.
  • Unless explicitly silenced.
  • In the face of ambiguity, refuse the temptation to guess.
  • There should be one-- and preferably only one --obvious way to do it.
  • Although that way may not be obvious at first unless you're Dutch.
  • Now is better than never.
  • Although never is often better than right now.
  • If the implementation is hard to explain, it's a bad idea.
  • If the implementation is easy to explain, it may be a good idea.
  • Namespaces are one honking great idea -- let's do more of those!

On a more practical level, there is PEP8, the style guide for Python.

With those in mind, I would say that your code style doesn't really fit, particularly the nested functions. Find a way to flatten those out, either by using classes or moving them into separate modules. This will make the structure of your program much easier to understand.

Which version of MVC am I using?

Select the System.Web.Mvc assembly in the "References" folder in the solution explorer. Bring up the properties window (F4) and check the Version

Reference Properties

CSS selector for text input fields?


or, to restrict to text inputs inside forms

form input[type=text]

or, to restrict further to a certain form, assuming it has id myForm

#myForm input[type=text]

Notice: This is not supported by IE6, so if you want to develop for IE6 either use IE7.js (as Yi Jiang suggested) or start adding classes to all your text inputs.


Because it is specified that default attribute values may not always be selectable with attribute selectors, one could try to cover other cases of markup for which text inputs are rendered:

input:not([type]), // type attribute not present in markup
input[type=""], // type attribute present, but empty
input[type=text] // type is explicitly defined as 'text'

Still this leaves the case when the type is defined, but has an invalid value and that still falls back to type="text". To cover that we could use select all inputs that are not one of the other known types


But this selector would be quite ridiculous and also the list of possible types is growing with new features being added to HTML.

Notice: the :not pseudo-class is only supported starting with IE9.

cannot download, $GOPATH not set

Watch a Video

In general, I always recommend this official video from Go to get a quick overview on the matter:

It's easier to be shown than to be told.

@jwfearn paraphrased the important part of the video:

export GOPATH="${HOME}/gocode"; export PATH="${PATH}:${GOPATH}/bin"; mkdir -p "${GOPATH}"

Boxplot show the value of mean

You can also use a function within stat_summary to calculate the mean and the hjust argument to place the text, you need a additional function but no additional data frame:

fun_mean <- function(x){

ggplot(PlantGrowth,aes(x=group,y=weight)) +
geom_boxplot(aes(fill=group)) +
stat_summary(fun.y = mean, geom="point",colour="darkred", size=3) +
stat_summary( = fun_mean, geom="text", vjust=-0.7)

enter image description here

Why and when to use angular.copy? (Deep Copy)

When using angular.copy, instead of updating the reference, a new object is created and assigned to the destination(if a destination is provided). But there's more. There's this cool thing that happens after a deep copy.

Say you have a factory service which has methods which updates factory variables.

angular.module('test').factory('TestService', [function () {
    var o = {
        shallow: [0,1], // initial value(for demonstration)
        deep: [0,2] // initial value(for demonstration)
    o.shallowCopy = function () {
        o.shallow = [1,2,3]
    o.deepCopy = function () {
        angular.copy([4,5,6], o.deep);
    return o;

and a controller which uses this service,

angular.module('test').controller('Ctrl', ['TestService', function (TestService) {
     var shallow = TestService.shallow;
     var deep = TestService.deep;

     console.log('****Printing initial values');


     console.log('****Printing values after service method execution');

     console.log('****Printing service variables directly');

When the above program is run the output will be as follows,

****Printing initial values

****Printing values after service method execution

****Printing service variables directly

Thus the cool thing about using angular copy is that, the references of the destination are reflected with the change of values, without having to re-assign the values manually, again.

Python socket connection timeout

You just need to use the socket settimeout() method before attempting the connect(), please note that after connecting you must settimeout(None) to set the socket into blocking mode, such is required for the makefile . Here is the code I am using:

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
fileobj = sock.makefile('rb', 0)

Django templates: If false?

For posterity, I have a few NullBooleanFields and here's what I do:

To check if it's True:

{% if variable %}True{% endif %}

To check if it's False (note this works because there's only 3 values -- True/False/None):

{% if variable != None %}False{% endif %}

To check if it's None:

{% if variable == None %}None{% endif %}

I'm not sure why, but I can't do variable == False, but I can do variable == None.

How do I force Kubernetes to re-pull an image?

Now, the command kubectl rollout restart deploy YOUR-DEPLOYMENT combined with a imagePullPolicy: Always policy will allow you to restart all your pods with a latest version of your image.

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

PHPMYADMIN - Cannot connect: invalid settings.

I also faced similar issue but now I found a fix.

For wamp server:

IN: C:\wamp\apps\phpmyadminVERSION\

$cfg['Servers'][$i]['AllowNoPasswordRoot'] = true; 

$cfg['Servers'][$i]['AllowNoPasswordRoot'] = false; 

For xampp server:

because of xampp server had the following settings.


$cfg['Servers'][$i]['user'] = 'root';

$cfg['Servers'][$i]['password'] = ''; // which is default setting in xampp server

$cfg['Servers'][$i]['password'] = 'your password';//type your password you have changed Button OnClick event not firing

If you are using updatepanel on onclick event, this may happen.

Use 'EnableEventValidation="false"' in your page markup like this :

<%@ Page Language="C#" MasterPageFile="~/ars_home.master" AutoEventWireup="true" CodeFile="Transaction_Window.aspx.cs" Inherits="Transaction_Window" EnableEventValidation="false" %>

Hope this helps

Convert JSON String to Pretty Print JSON output using Jackson

This looks like it might be the answer to your question. It says it's using Spring, but I think that should still help you in your case. Let me inline the code here so it's more convenient:



public class Foo
  public static void main(String[] args) throws Exception
    ObjectMapper mapper = new ObjectMapper();
    MyClass myObject = mapper.readValue(new FileReader("input.json"), MyClass.class);
    // this is Jackson 1.x API only: 
    ObjectWriter writer = mapper.defaultPrettyPrintingWriter();
    // ***IMPORTANT!!!*** for Jackson 2.x use the line below instead of the one above: 
    // ObjectWriter writer = mapper.writer().withDefaultPrettyPrinter();

class MyClass
  String one;
  String[] two;
  MyOtherClass three;

  public String getOne() {return one;}
  void setOne(String one) { = one;}
  public String[] getTwo() {return two;}
  void setTwo(String[] two) {this.two = two;}
  public MyOtherClass getThree() {return three;}
  void setThree(MyOtherClass three) {this.three = three;}

class MyOtherClass
  String four;
  String[] five;

  public String getFour() {return four;}
  void setFour(String four) {this.four = four;}
  public String[] getFive() {return five;}
  void setFive(String[] five) {this.five = five;}

Print array elements on separate lines in Bash?

Just quote the argument to echo:

( IFS=$'\n'; echo "${my_array[*]}" )

the sub shell helps restoring the IFS after use

NuGet Packages are missing

I solved my issue by removing this code from .csproj file:

<Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
    <ErrorText>This project references NuGet package(s) that are missing on this computer. Enable NuGet Package Restore to download them.  For more information, see The missing file is {0}.</ErrorText>
  <Error Condition="!Exists('$(SolutionDir)\.nuget\NuGet.targets')" Text="$([System.String]::Format('$(ErrorText)', '$(SolutionDir)\.nuget\NuGet.targets'))" />

tr:hover not working

Like @wesley says, you have not closed your first <td>. You opened it two times.

<table class="list1">


.list1 tr:hover{

There is no JavaScript needed, just complete your HTML code

IF... OR IF... in a windows batch file

There is no IF <arg> OR or ELIF or ELSE IF in Batch, however...

Try nesting the other IF's inside the ELSE of the previous IF.

IF <arg> (
) ELSE (
    IF <arg> (
    ) ELSE (
        IF <arg> (
        ) ELSE (

LaTeX: Prevent line break in a span of text

Use \nolinebreak


The \nolinebreak command prevents LaTeX from breaking the current line at the point of the command. With the optional argument, number, you can convert the \nolinebreak command from a demand to a request. The number must be a number from 0 to 4. The higher the number, the more insistent the request is.


HttpURLConnection timeout settings

If the HTTP Connection doesn't timeout, You can implement the timeout checker in the background thread itself (AsyncTask, Service, etc), the following class is an example for Customize AsyncTask which timeout after certain period

public abstract class AsyncTaskWithTimer<Params, Progress, Result> extends
    AsyncTask<Params, Progress, Result> {

private static final int HTTP_REQUEST_TIMEOUT = 30000;

protected Result doInBackground(Params... params) {
    return doInBackgroundImpl(params);

private void createTimeoutListener() {
    Thread timeout = new Thread() {
        public void run() {

            final Handler handler = new Handler();
            handler.postDelayed(new Runnable() {
                public void run() {

                    if (AsyncTaskWithTimer.this != null
                            && AsyncTaskWithTimer.this.getStatus() != Status.FINISHED)
            }, HTTP_REQUEST_TIMEOUT);


abstract protected Result doInBackgroundImpl(Params... params);

A Sample for this

public class AsyncTaskWithTimerSample extends AsyncTaskWithTimer<Void, Void, Void> {

    protected void onCancelled(Void void) {
        Log.d(TAG, "Async Task onCancelled With Result");

    protected void onCancelled() {
        Log.d(TAG, "Async Task onCancelled");

    protected Void doInBackgroundImpl(Void... params) {
        // Do background work
        return null;

How do I handle a click anywhere in the page, even when a certain element stops the propagation?

this is the key (vs See example.

document.body.addEventListener("click", function (evt) {_x000D_
    //note can be a nested element, not the body element, resulting in misfires_x000D_
    alert("body clicked");_x000D_
<h4>This is a heading.</h4>_x000D_
<p>this is a paragraph.</p>

Force an Android activity to always use landscape mode

use Only
android:screenOrientation="portrait" tools:ignore="LockedOrientationActivity"

Log exception with traceback

What I was looking for:

import sys
import traceback

exc_type, exc_value, exc_traceback = sys.exc_info()
traceback_in_var = traceback.format_tb(exc_traceback)


git-upload-pack: command not found, when cloning remote Git repo

For zsh you need to put it in this file: ~/.zshenv

For example, on OS X using the git-core package from MacPorts:

$ echo 'export PATH=/opt/local/sbin:/opt/local/bin:$PATH' > ~/.zshenv

Bootstrap 3.0 - Fluid Grid that includes Fixed Column Sizes

There's really no easy way to mix fluid and fixed widths with Bootstrap 3. It's meant to be like this, as the grid system is designed to be a fluid, responsive thing. You could try hacking something up, but it would go against what the Responsive Grid system is trying to do, the intent of which is to make that layout flow across different device types.

If you need to stick with this layout, I'd consider laying out your page with custom CSS and not using the grid.

How do you access the matched groups in a JavaScript regular expression?

There is no need to invoke the exec method! You can use "match" method directly on the string. Just don't forget the parentheses.

var str = "This is cool";
var matches = str.match(/(This is)( cool)$/);
console.log( JSON.stringify(matches) ); // will print ["This is cool","This is"," cool"] or something like that...

Position 0 has a string with all the results. Position 1 has the first match represented by parentheses, and position 2 has the second match isolated in your parentheses. Nested parentheses are tricky, so beware!

Git and nasty "error: cannot lock existing info/refs fatal"

Running command git update-ref -d refs/heads/origin/branch fixed it.

remove borders around html input


Will work fine.

Fixed header, footer with scrollable content

Now we've got CSS grid. Welcome to 2019.

/* Required */_x000D_
body {_x000D_
   margin: 0;_x000D_
   height: 100%;_x000D_
#wrapper {_x000D_
   height: 100vh;_x000D_
   display: grid;_x000D_
   grid-template-rows: 30px 1fr 30px;_x000D_
#content {_x000D_
   overflow-y: scroll;_x000D_
/* Optional */_x000D_
#wrapper > * {_x000D_
   padding: 5px;_x000D_
#header {_x000D_
   background-color: #ff0000ff;_x000D_
#content {_x000D_
   background-color: #00ff00ff;_x000D_
#footer {_x000D_
   background-color: #0000ffff;_x000D_
   <div id="wrapper">_x000D_
      <div id="header">Header Content</div>_x000D_
      <div id="content">_x000D_
         Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum._x000D_
      <div id="footer">Footer Content</div>_x000D_

Regex: ignore case sensitivity

In JavaScript you should pass the i flag to the RegExp constructor as stated in MDN:

const regex = new RegExp('(abc)', 'i');

regex.test('ABc'); // true

Bulk Insert to Oracle using .NET

I guess that OracleBulkCopy is one of the fastest ways. I had some trouble to learn, that I needed a new ODAC version. Cf. Where is type [Oracle.DataAccess.Client.OracleBulkCopy] ?

Here is the complete PowerShell code to copy from a query into a suited existing Oracle table. I tried Sql-Server a datasource, but other valid OLE-DB sources will go to.

if ($ora_dll -eq $null)
    "Load Oracle dll"
    $ora_dll = [System.Reflection.Assembly]::LoadWithPartialName("Oracle.DataAccess") 

# sql-server or Oracle source example is sql-server
$ConnectionString ="server=localhost;database=myDatabase;trusted_connection=yes;Provider=SQLNCLI10;"

# Oracle destination
$oraClientConnString = "Data Source=myTNS;User ID=myUser;Password=myPassword"

$tableName = "mytable"
$sql = "select * from $tableName"

$OLEDBConn = New-Object System.Data.OleDb.OleDbConnection($ConnectionString)
$readcmd = New-Object system.Data.OleDb.OleDbCommand($sql,$OLEDBConn)
$readcmd.CommandTimeout = '300'
$da = New-Object system.Data.OleDb.OleDbDataAdapter($readcmd)
$dt = New-Object system.Data.datatable
#Write-Output $dt

if ($dt)
        $bulkCopy = new-object ("Oracle.DataAccess.Client.OracleBulkCopy") $oraClientConnString
        $bulkCopy.DestinationTableName = $tableName
        $bulkCopy.BatchSize = 5000
        $bulkCopy.BulkCopyTimeout = 10000
        $ex = $_.Exception
        Write-Error "Write-DataTable$($connectionName):$ex.Message"

BTW: I use this to copy table with CLOB columns. I didn't get that to work using linked servers cf. question on dba. I didn't retry linked serves with the new ODAC.

python's re: return True if string contains regex pattern

The best one by far is

bool('ba[rzd]', 'foobarrrr'))

Returns True

Insert content into iFrame

This should do what you want:

$("#iframe").ready(function() {
    var body = $("#iframe").contents().find("body");

Check this JSFiddle for working demo.

Edit: You can of course do it one line style:


subsetting a Python DataFrame

I'll assume that Time and Product are columns in a DataFrame, df is an instance of DataFrame, and that other variables are scalar values:

For now, you'll have to reference the DataFrame instance:

k1 = df.loc[(df.Product == p_id) & (df.Time >= start_time) & (df.Time < end_time), ['Time', 'Product']]

The parentheses are also necessary, because of the precedence of the & operator vs. the comparison operators. The & operator is actually an overloaded bitwise operator which has the same precedence as arithmetic operators which in turn have a higher precedence than comparison operators.

In pandas 0.13 a new experimental DataFrame.query() method will be available. It's extremely similar to subset modulo the select argument:

With query() you'd do it like this:

df[['Time', 'Product']].query('Product == p_id and Month < mn and Year == yr')

Here's a simple example:

In [9]: df = DataFrame({'gender': np.random.choice(['m', 'f'], size=10), 'price': poisson(100, size=10)})

In [10]: df
  gender  price
0      m     89
1      f    123
2      f    100
3      m    104
4      m     98
5      m    103
6      f    100
7      f    109
8      f     95
9      m     87

In [11]: df.query('gender == "m" and price < 100')
  gender  price
0      m     89
4      m     98
9      m     87

The final query that you're interested will even be able to take advantage of chained comparisons, like this:

k1 = df[['Time', 'Product']].query('Product == p_id and start_time <= Time < end_time')

CSS3 Transition - Fade out effect

You forgot to add a position property to the .dummy-wrap class, and the top/left/bottom/right values don't apply to statically positioned elements (the default)

Eclipse - Installing a new JRE (Java SE 8 1.8.0)

You can have many java versions in your system.

I think you should add the java 8 in yours JREs installed or edit.

Take a look my screen:

enter image description here

If you click in edit (check your java 8 path):

enter image description here

Can't access RabbitMQ web management interface after fresh install

It's new features since the version 3.3.0


25603 prevent access using the default guest/guest credentials except via

If you want enable the guest user read this or this RabbitMQ 3.3.1 can not login with guest/guest

# remove guest from loopback_users in rabbitmq.config like this
[{rabbit, [{loopback_users, []}]}].
# It is danger for default user and default password for remote access
# better to change password 
rabbitmqctl  change_password guest NEWPASSWORD

If you want create a new user with admin grants:

rabbitmqctl add_user test test
rabbitmqctl set_user_tags test administrator
rabbitmqctl set_permissions -p / test ".*" ".*" ".*"

Now you can access using test test.

Can a java lambda have more than 1 parameter?

You could also use jOOL library -

It has already prepared function interfaces with different number of parameters. For instance, you could use org.jooq.lambda.function.Function3, etc from Function0 up to Function16.

Regex for quoted string with escaping quotes

As provided by ePharaoh, the answer is


To have the above apply to either single quoted or double quoted strings, use


Access parent DataContext from DataTemplate

the issue is that a DataTemplate isn't part of an element its applied to it.

this means if you bind to the template you're binding to something that has no context.

however if you put a element inside the template then when that element is applied to the parent it gains a context and the binding then works

so this will not work

<DataTemplate >
        <CollectionViewSource x:Key="projects" Source="{Binding Projects}" >

but this works perfectly

<DataTemplate >
    <GroupBox Header="Projects">
            <CollectionViewSource x:Key="projects" Source="{Binding Projects}" >

because after the datatemplate is applied the groupbox is placed in the parent and will have access to its Context

so all you have to do is remove the style from the template and move it into an element in the template

note that the context for a itemscontrol is the item not the control ie ComboBoxItem for ComboBox not the ComboBox itself in which case you should use the controls ItemContainerStyle instead

how to get rid of notification circle in right side of the screen?

This stuff comes from ES file explorer

Just go into this app > settings

Then there is an option that says logging floating window, you just need to disable that and you will get rid of this infernal bubble for good

How can I get current location from user in iOS

iOS 11.x Swift 4.0 Info.plist needs these two properties

<string>We're watching you</string>
<string>Watch Out</string>

And this code ... making sure of course your a CLLocationManagerDelegate

let locationManager = CLLocationManager()

// MARK location Manager delegate code + more

func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
    switch status {
    case .notDetermined:
        print("User still thinking")
    case .denied:
        print("User hates you")
    case .authorizedWhenInUse:
    case .authorizedAlways:
    case .restricted:
        print("User dislikes you")

And of course this code too which you can put in viewDidLoad().

locationManager.delegate = self
locationManager.distanceFilter = kCLDistanceFilterNone
locationManager.desiredAccuracy = kCLLocationAccuracyBest

And these two for the requestLocation to get you going, aka save you having to get out of your seat :)

func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {

Reading values from DataTable

You can do it using the foreach loop

DataTable dr_art_line_2 = ds.Tables["QuantityInIssueUnit"];

  foreach(DataRow row in dr_art_line_2.Rows)
     QuantityInIssueUnit_value = Convert.ToInt32(row["columnname"]);

How to get equal width of input and select fields

Add this code in css:

 select, input[type="text"]{

Curl command line for consuming webServices?

Wrong. That doesn't work for me.

For me this one works:

-H 'SOAPACTION: ""'   
-H 'Content-type: text/xml'   
-d @/tmp/pinrequest.xml

UITableView with fixed section headers

You can also set the tableview's bounces property to NO. This will keep the section headers non-floating/static, but then you also lose the bounce property of the tableview.

Label python data points on plot

I had a similar issue and ended up with this:

enter image description here

For me this has the advantage that data and annotation are not overlapping.

from matplotlib import pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.add_subplot(111)

A = -0.75, -0.25, 0, 0.25, 0.5, 0.75, 1.0
B = 0.73, 0.97, 1.0, 0.97, 0.88, 0.73, 0.54


# annotations at the side (ordered by B values)
for ii, ind in enumerate(np.argsort(B)):
    x = A[ind]
    y = B[ind]
    xPos = x1 + .02 * (x1 - x0)
    yPos = y0 + ii * (y1 - y0)/(len(B) - 1)
          xy=(x, y), xycoords='data',
          xytext=(xPos, yPos), textcoords='data',
                          shrinkA=0, shrinkB=10,
                          arrowstyle= '-|>', ls= '-', linewidth=2
          va='bottom', ha='left', zorder=19
    ax.text(xPos + .01 * (x1 - x0), yPos,
            '({:.2f}, {:.2f})'.format(x,y),
            transform=ax.transData, va='center')


Using the text argument in .annotate ended up with unfavorable text positions. Drawing lines between a legend and the data points is a mess, as the location of the legend is hard to address.

How to manage Angular2 "expression has changed after it was checked" exception when a component property depends on current datetime


ngAfterViewInit() {
    setTimeout(() => {
        this.dateNow = new Date();

Although this is a workaround, sometimes it's really hard to solve this issue in any nicer way, so don't blame yourself if you are using this approach. That's okay.

Examples: The initial issue [link], Solved with setTimeout() [link]

How to avoid

In general this error usually happens after you add somewhere (even in parent/child components) ngAfterViewInit. So first question is to ask yourself - can I live without ngAfterViewInit? Perhaps you move the code somewhere ( ngAfterViewChecked might be an alternative).

Example: [link]


Also async stuff in ngAfterViewInit that affects DOM might cause this. Also can be solved via setTimeout or by adding the delay(0) operator in the pipe:

ngAfterViewInit() {$
    .pipe(delay(0)) //"delay" here is an alternative to setTimeout()

Example: [link]

Nice Reading

Good article about how to debug this and why it happens: link

What's the best practice using a settings file in Python?

You can have a regular Python module, say, like this:

truck = dict(
    color = 'blue',
    brand = 'ford',
city = 'new york'
cabriolet = dict(
    color = 'black',
    engine = dict(
        cylinders = 8,
        placement = 'mid',
    doors = 2,

and use it like this:

import config

Javascript reduce() on Object

What you actually want in this case are the Object.values. Here is a concise ES6 implementation with that in mind:

const add = {
  a: {value:1},
  b: {value:2},
  c: {value:3}

const total = Object.values(add).reduce((t, {value}) => t + value, 0)

console.log(total) // 6

or simply:

const add = {
  a: 1,
  b: 2,
  c: 3

const total = Object.values(add).reduce((t, n) => t + n)

console.log(total) // 6

Java: Insert multiple rows into MySQL with PreparedStatement

we can be submit multiple updates together in JDBC to submit batch updates.

we can use Statement, PreparedStatement, and CallableStatement objects for bacth update with disable autocommit

addBatch() and executeBatch() functions are available with all statement objects to have BatchUpdate

here addBatch() method adds a set of statements or parameters to the current batch.

How to customize the back button on ActionBar

I did the below code onCreate() and worked with me


How do I set the selected item in a comboBox to match my string using C#?

SelectedText is to get or set the actual text in the string editor for the selected item in the combobox as documented here . This goes uneditable if you set:

comboBox1.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDownList;


comboBox1.SelectedItem = "test1";


comboBox1.SelectedIndex = comboBox1.Items.IndexOf("test1");

How to set a default value with Html.TextBoxFor?

value="0" will set defualt value for @Html.TextBoxfor

its case sensitive "v" should be capital

Below is working example:

@Html.TextBoxFor(m => m.Nights, 
    new { @min = "1", @max = "10", @type = "number", @id = "Nights", @name = "Nights", Value = "1" })

Is there a better way to compare dictionary values

Not sure if this helps but in my app I had to check if a dictionary has changed.

Doing this will not work since basically it's still the same object:


if old_val != val:

Using copy/deepcopy works:

import copy

if old_val != val:

Xcode variables

Here's a list of the environment variables. I think you might want CURRENT_VARIANT. See also BUILD_VARIANTS.

Receive JSON POST with PHP

Use $HTTP_RAW_POST_DATA instead of $_POST.

It will give you POST data as is.

You will be able to decode it using json_decode() later.

Add values to app.config and retrieve them

Try adding a Reference to System.Configuration, you get some of the configuration namespace by referencing the System namespace, adding the reference to System.Configuration should allow you to access ConfigurationManager.

Python function global variables?

As others have noted, you need to declare a variable global in a function when you want that function to be able to modify the global variable. If you only want to access it, then you don't need global.

To go into a bit more detail on that, what "modify" means is this: if you want to re-bind the global name so it points to a different object, the name must be declared global in the function.

Many operations that modify (mutate) an object do not re-bind the global name to point to a different object, and so they are all valid without declaring the name global in the function.

d = {}
l = []
o = type("object", (object,), {})()

def valid():     # these are all valid without declaring any names global!
   d[0] = 1      # changes what's in d, but d still points to the same object
   d[0] += 1     # ditto
   d.clear()     # ditto! d is now empty but it`s still the same object!
   l.append(0)   # l is still the same list but has an additional member
   o.test = 1    # creating new attribute on o, but o is still the same object

Why is Visual Studio 2010 not able to find/open PDB files?

Had the same problem here but a different solution worked.

First, I tried the following, none of which worked:

  1. Load symbols as suggested by seanlitow

  2. Remove/Add reference to PresentationFramework and PresentationCore

  3. Restart system

The solution was to undo the last few changes I had made to my code. I had just added a couple radio buttons and event handlers for checked and unchecked events. After removing my recent changes everything compiled. I then added my exact changes back and everything compiled properly. I don't understand why this worked - only thing I can think of is a problem with my VS Solution. Anyway, if none of the other suggestions work, you might try reverting back your most recent changes. NOTE: if you close & re-open Visual Studio your undo history is lost.. so you might try this before you close VS.

Set QLineEdit to accept only numbers

The Regex Validator

So far, the other answers provide solutions for only a relatively finite number of digits. However, if you're concerned with an arbitrary or a variable number of digits you can use a QRegExpValidator, passing a regex that only accepts digits (as noted by user2962533's comment). Here's a minimal, complete example:

#include <QApplication>
#include <QLineEdit>
#include <QRegExpValidator>

int main(int argc, char *argv[])
    QApplication app(argc, argv);

    QLineEdit le;
    le.setValidator(new QRegExpValidator(QRegExp("[0-9]*"), &le));;

    return app.exec();

The QRegExpValidator has its merits (and that's only an understatement). It allows for a bunch of other useful validations:

QRegExp("[1-9][0-9]*")    //  leading digit must be 1 to 9 (prevents leading zeroes).
QRegExp("\\d*")           //  allows matching for unicode digits (e.g. for 
                          //    Arabic-Indic numerals such as ???).
QRegExp("[0-9]+")         //  input must have at least 1 digit.
QRegExp("[0-9]{8,32}")    //  input must be between 8 to 32 digits (e.g. for some basic
                          //    password/special-code checks).
QRegExp("[0-1]{,4}")      //  matches at most four 0s and 1s.
QRegExp("0x[0-9a-fA-F]")  //  matches a hexadecimal number with one hex digit.
QRegExp("[0-9]{13}")      //  matches exactly 13 digits (e.g. perhaps for ISBN?).
                          //  matches a format similar to an ip address.
                          //    N.B. invalid addresses can still be entered: "999.999.999.999".     

More On Line-edit Behaviour

According to documentation:

Note that if there is a validator set on the line edit, the returnPressed()/editingFinished() signals will only be emitted if the validator returns QValidator::Acceptable.

Thus, the line-edit will allow the user to input digits even if the minimum amount has not yet been reached. For example, even if the user hasn't inputted any text against the regex "[0-9]{3,}" (which requires at least 3 digits), the line-edit still allows the user to type input to reach that minimum requirement. However, if the user finishes editing without satsifying the requirement of "at least 3 digits", the input would be invalid; the signals returnPressed() and editingFinished() won't be emitted.

If the regex had a maximum-bound (e.g. "[0-1]{,4}"), then the line-edit will stop any input past 4 characters. Additionally, for character sets (i.e. [0-9], [0-1], [0-9A-F], etc.) the line-edit only allows characters from that particular set to be inputted.

Note that I've only tested this with Qt 5.11 on a macOS, not on other Qt versions or operating systems. But given Qt's cross-platform schema...

Demo: Regex Validators Showcase

How do servlets work? Instantiation, sessions, shared variables and multithreading


When the servlet container (like Apache Tomcat) starts up, it will deploy and load all its web applications. When a web application is loaded, the servlet container creates the ServletContext once and keeps it in the server's memory. The web app's web.xml and all of included web-fragment.xml files is parsed, and each <servlet>, <filter> and <listener> found (or each class annotated with @WebServlet, @WebFilter and @WebListener respectively) is instantiated once and kept in the server's memory as well. For each instantiated filter, its init() method is invoked with a new FilterConfig.

When a Servlet has a <servlet><load-on-startup> or @WebServlet(loadOnStartup) value greater than 0, then its init() method is also invoked during startup with a new ServletConfig. Those servlets are initialized in the same order specified by that value (1 is 1st, 2 is 2nd, etc). If the same value is specified for more than one servlet, then each of those servlets is loaded in the same order as they appear in the web.xml, web-fragment.xml, or @WebServlet classloading. In the event the "load-on-startup" value is absent, the init() method will be invoked whenever the HTTP request hits that servlet for the very first time.

When the servlet container is finished with all of the above described initialization steps, then the ServletContextListener#contextInitialized() will be invoked.

When the servlet container shuts down, it unloads all web applications, invokes the destroy() method of all its initialized servlets and filters, and all ServletContext, Servlet, Filter and Listener instances are trashed. Finally the ServletContextListener#contextDestroyed() will be invoked.

HttpServletRequest and HttpServletResponse

The servlet container is attached to a web server that listens for HTTP requests on a certain port number (port 8080 is usually used during development and port 80 in production). When a client (e.g. user with a web browser, or programmatically using URLConnection) sends an HTTP request, the servlet container creates new HttpServletRequest and HttpServletResponse objects and passes them through any defined Filter in the chain and, eventually, the Servlet instance.

In the case of filters, the doFilter() method is invoked. When the servlet container's code calls chain.doFilter(request, response), the request and response continue on to the next filter, or hit the servlet if there are no remaining filters.

In the case of servlets, the service() method is invoked. By default, this method determines which one of the doXxx() methods to invoke based off of request.getMethod(). If the determined method is absent from the servlet, then an HTTP 405 error is returned in the response.

The request object provides access to all of the information about the HTTP request, such as its URL, headers, query string and body. The response object provides the ability to control and send the HTTP response the way you want by, for instance, allowing you to set the headers and the body (usually with generated HTML content from a JSP file). When the HTTP response is committed and finished, both the request and response objects are recycled and made available for reuse.


When a client visits the webapp for the first time and/or the HttpSession is obtained for the first time via request.getSession(), the servlet container creates a new HttpSession object, generates a long and unique ID (which you can get by session.getId()), and stores it in the server's memory. The servlet container also sets a Cookie in the Set-Cookie header of the HTTP response with JSESSIONID as its name and the unique session ID as its value.

As per the HTTP cookie specification (a contract any decent web browser and web server must adhere to), the client (the web browser) is required to send this cookie back in subsequent requests in the Cookie header for as long as the cookie is valid (i.e. the unique ID must refer to an unexpired session and the domain and path are correct). Using your browser's built-in HTTP traffic monitor, you can verify that the cookie is valid (press F12 in Chrome / Firefox 23+ / IE9+, and check the Net/Network tab). The servlet container will check the Cookie header of every incoming HTTP request for the presence of the cookie with the name JSESSIONID and use its value (the session ID) to get the associated HttpSession from server's memory.

The HttpSession stays alive until it has been idle (i.e. not used in a request) for more than the timeout value specified in <session-timeout>, a setting in web.xml. The timeout value defaults to 30 minutes. So, when the client doesn't visit the web app for longer than the time specified, the servlet container trashes the session. Every subsequent request, even with the cookie specified, will not have access to the same session anymore; the servlet container will create a new session.

On the client side, the session cookie stays alive for as long as the browser instance is running. So, if the client closes the browser instance (all tabs/windows), then the session is trashed on the client's side. In a new browser instance, the cookie associated with the session wouldn't exist, so it would no longer be sent. This causes an entirely new HttpSession to be created, with an entirely new session cookie being used.

In a nutshell

  • The ServletContext lives for as long as the web app lives. It is shared among all requests in all sessions.
  • The HttpSession lives for as long as the client is interacting with the web app with the same browser instance, and the session hasn't timed out at the server side. It is shared among all requests in the same session.
  • The HttpServletRequest and HttpServletResponse live from the time the servlet receives an HTTP request from the client, until the complete response (the web page) has arrived. It is not shared elsewhere.
  • All Servlet, Filter and Listener instances live as long as the web app lives. They are shared among all requests in all sessions.
  • Any attribute that is defined in ServletContext, HttpServletRequest and HttpSession will live as long as the object in question lives. The object itself represents the "scope" in bean management frameworks such as JSF, CDI, Spring, etc. Those frameworks store their scoped beans as an attribute of its closest matching scope.

Thread Safety

That said, your major concern is possibly thread safety. You should now know that servlets and filters are shared among all requests. That's the nice thing about Java, it's multithreaded and different threads (read: HTTP requests) can make use of the same instance. It would otherwise be too expensive to recreate, init() and destroy() them for every single request.

You should also realize that you should never assign any request or session scoped data as an instance variable of a servlet or filter. It will be shared among all other requests in other sessions. That's not thread-safe! The below example illustrates this:

public class ExampleServlet extends HttpServlet {

    private Object thisIsNOTThreadSafe;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Object thisIsThreadSafe;

        thisIsNOTThreadSafe = request.getParameter("foo"); // BAD!! Shared among all requests!
        thisIsThreadSafe = request.getParameter("foo"); // OK, this is thread safe.

See also:

C++ Remove new line from multiline string

About answer 3 removing only the last \n off string code :

if (!s.empty() && s[s.length()-1] == '\n') {

Will the if condition not fail if the string is really empty ?

Is it not better to do :

if (!s.empty())
    if (s[s.length()-1] == '\n')

When should I use the Visitor Design Pattern?

One way to look at it is that the visitor pattern is a way of letting your clients add additional methods to all of your classes in a particular class hierarchy.

It is useful when you have a fairly stable class hierarchy, but you have changing requirements of what needs to be done with that hierarchy.

The classic example is for compilers and the like. An Abstract Syntax Tree (AST) can accurately define the structure of the programming language, but the operations you might want to do on the AST will change as your project advances: code-generators, pretty-printers, debuggers, complexity metrics analysis.

Without the Visitor Pattern, every time a developer wanted to add a new feature, they would need to add that method to every feature in the base class. This is particularly hard when the base classes appear in a separate library, or are produced by a separate team.

(I have heard it argued that the Visitor pattern is in conflict with good OO practices, because it moves the operations of the data away from the data. The Visitor pattern is useful in precisely the situation that the normal OO practices fail.)

How do I position a div at the bottom center of the screen

If you aren't comfortable with using negative margins, check this out.

div {
  position: fixed;
  left: 50%;
  bottom: 20px;
  transform: translate(-50%, -50%);
  margin: 0 auto;
  Your Text

Especially useful when you don't know the width of the div.

align="center" has no effect.

Since you have position:absolute, I would recommend positioning it 50% from the left and then subtracting half of its width from its left margin.

#manipulate {

Convert Numeric value to Varchar

First convert the numeric value then add the 'S':

 select convert(varchar(10),StandardCost) +'S'
 from DimProduct where ProductKey = 212

Change the jquery show()/hide() animation?

There are the slideDown, slideUp, and slideToggle functions native to jquery 1.3+, and they work quite nicely...

You can use slideDown just like this:


And if you want to combine effects and really go nuts I'd take a look at the animate function which allows you to specify a number of CSS properties to shape tween or morph into. Pretty fancy stuff, that.

How to make div's percentage width relative to parent div and not viewport

Specifying a non-static position, e.g., position: absolute/relative on a node means that it will be used as the reference for absolutely positioned elements within it


We can change the positioning context — which element the absolutely positioned element is positioned relative to. This is done by setting positioning on one of the element's ancestors.

#outer {_x000D_
  min-width: 2000px; _x000D_
  min-height: 1000px; _x000D_
  background: #3e3e3e; _x000D_
#inner {_x000D_
  left: 1%; _x000D_
  top: 45px; _x000D_
  width: 50%; _x000D_
  height: auto; _x000D_
  position: absolute; _x000D_
  z-index: 1;_x000D_
#inner-inner {_x000D_
  background: #efffef;_x000D_
  position: absolute; _x000D_
  height: 400px; _x000D_
  right: 0px; _x000D_
  left: 0px;_x000D_
<div id="outer">_x000D_
  <div id="inner">_x000D_
    <div id="inner-inner"></div>_x000D_

I am getting an "Invalid Host header" message when connecting to webpack-dev-server remotely

If you have not ejected from CRA yet, you can't easily modify your webpack config. The config file is hidden in node_modules/react_scripts/config/webpackDevServer.config.js. You are discouraged to change that config.

Instead, you can just set the environment variable DANGEROUSLY_DISABLE_HOST_CHECK to true to disable the host check:

# or the equivalent npm command