Programs & Examples On #Cppcms

CppCMS is an open source, high performance, model-view-controller, C++ web development framework.

Checking Maven Version

you can use just


How to show full object in Chrome console?

With modern browsers, console.log(functor) works perfectly (behaves the same was a console.dir).

regular expression: match any word until first space

^([^\s]+) use this it correctly matches only the first word you can test this using this link

Hash String via SHA-256 in Java

Java 8: Base64 available:

    MessageDigest md = MessageDigest.getInstance( "SHA-512" );
    md.update( inbytes );
    byte[] aMessageDigest = md.digest();

    String outEncoded = Base64.getEncoder().encodeToString( aMessageDigest );
    return( outEncoded );

angular2: Error: TypeError: Cannot read property '...' of undefined

That's because abc is undefined at the moment of the template rendering. You can use safe navigation operator (?) to "protect" template until HTTP call is completed:


You can read more about safe navigation operator here.


Safe navigation operator can't be used in arrays, you will have to take advantage of NgIf directive to overcome this problem:

<div *ngIf="arr && arr.length > 0">

Read more about NgIf directive here.

EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) on dispatch_semaphore_dispose

I landed here because of an XCTestCase, in which I'd disabled most of the tests by prefixing them with 'no_' as in no_testBackgroundAdding. Once I noticed that most of the answers had something to do with locks and threading, I realized the test contained a few instances of XCTestExpectation with corresponding waitForExpectations. They were all in the disabled tests, but apparently Xcode was still evaluating them at some level.

In the end I found an XCTestExpectation that was defined as @property but lacked the @synthesize. Once I added the synthesize directive, the EXC_BAD_INSTRUCTION disappeared.

add/remove active class for ul list with jquery?

I used this:


Since the active class is in the <li> element and what is clicked is the <a> element, the first line removes .active from all <li> and the second one (again, $(this) represents <a> which is the clicked element) adds .active to the direct parent, which is <li>.

An "and" operator for an "if" statement in Bash


The "-a" operator also doesn't work:

if [ $STATUS -ne 200 ] -a [[ "$STRING" != "$VALUE" ]]

For a more elaborate explanation: [ and ] are not Bash reserved words. The if keyword introduces a conditional to be evaluated by a job (the conditional is true if the job's return value is 0 or false otherwise).

For trivial tests, there is the test program (man test).

As some find lines like if test -f filename; then foo bar; fi, etc. annoying, on most systems you find a program called [ which is in fact only a symlink to the test program. When test is called as [, you have to add ] as the last positional argument.

So if test -f filename is basically the same (in terms of processes spawned) as if [ -f filename ]. In both cases the test program will be started, and both processes should behave identically.

Here's your mistake: if [ $STATUS -ne 200 ] -a [[ "$STRING" != "$VALUE" ]] will parse to if + some job, the job being everything except the if itself. The job is only a simple command (Bash speak for something which results in a single process), which means the first word ([) is the command and the rest its positional arguments. There are remaining arguments after the first ].

Also not, [[ is indeed a Bash keyword, but in this case it's only parsed as a normal command argument, because it's not at the front of the command.

AngularJS - value attribute for select

You can't really do this unless you build them yourself in an ng-repeat.

<select ng-model="foo">
   <option ng-repeat="item in items" value="{{item.code}}">{{}}</option>

BUT... it's probably not worth it. It's better to leave it function as designed and let Angular handle the inner workings. Angular uses the index this way so you can actually use an entire object as a value. So you can use a drop down binding to select a whole value rather than just a string, which is pretty awesome:

<select ng-model="foo" ng-options="item as for item in items"></select>

{{foo | json}}

HTML -- two tables side by side

Depending on your content and space, you can use floats or inline display:

<table style="display: inline-block;">

<table style="float: left;">

Check it out here:


node.js: cannot find module 'request'

Go to directory of your project

mkdir TestProject
cd TestProject

Make this directory a root of your project (this will create a default package.json file)

npm init --yes

Install required npm module and save it as a project dependency (it will appear in package.json)

npm install request --save

Create a test.js file in project directory with code from package example

var request = require('request');
request('', function (error, response, body) {
  if (!error && response.statusCode == 200) {
    console.log(body); // Print the google web page.

Your project directory should look like this

- node_modules/
- package.json
- test.js

Now just run node inside your project directory

node test.js

How do I add a placeholder on a CharField in Django?

Most of the time I just wish to have all placeholders equal to the verbose name of the field defined in my models

I've added a mixin to easily do this to any form that I create,

class ProductForm(PlaceholderMixin, ModelForm):
    class Meta:
        model = Product
        fields = ('name', 'description', 'location', 'store')


class PlaceholderMixin:
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        field_names = [field_name for field_name, _ in self.fields.items()]
        for field_name in field_names:
            field = self.fields.get(field_name)
            field.widget.attrs.update({'placeholder': field.label})

How to print like printf in Python3?

The most recommended way to do is to use format method. Read more about it here

a, b = 1, 2

print("a={0},b={1}".format(a, b))

iOS change navigation bar title font and color

My Swift code for change Navigation Bar title:

let attributes = [NSFontAttributeName : UIFont(name: "Roboto-Medium", size: 16)!, NSForegroundColorAttributeName : UIColor.whiteColor()]
self.navigationController.navigationBar.titleTextAttributes = attributes

And if you want to change background font too then I have this in my AppDelegate:

let attributes = [NSFontAttributeName : UIFont(name: "Roboto-Medium", size: 16)!, NSForegroundColorAttributeName : UIColor.whiteColor()]
UIBarButtonItem.appearance().setTitleTextAttributes(attributes, forState: UIControlState.Normal)

Windows command to convert Unix line endings?

Windows' MORE is not reliable, it destroys TABs inevitably and adds lines.

unix2dos is part also of MinGW/MSYS, Cygutils, GnuWin32 and other unix binary port collections - and may already be installed.

When python is there, this one-liner converts any line endings to current platform - on any platform:

TYPE UNIXFILE.EXT | python -c "import sys; sys.stdout.write(" > MYPLATFILE.EXT


python -c "import sys; sys.stdout.write(open(sys.argv[1]).read())" UNIXFILE.EXT > MYPLATFILE.EXT

Or put the one-liner into a .bat / shell script and on the PATH according to your platform:

@REM This is any2here.bat
python -c "import sys; sys.stdout.write(open(sys.argv[1]).read())" %1

and use that tool like


delete map[key] in go?

Strangely enough,

package main

func main () {
    var sessions = map[string] chan int{};
    delete(sessions, "moo");

seems to work. This seems a poor use of resources though!

Another way is to check for existence and use the value itself:

package main

func main () {
    var sessions = map[string] chan int{};
    sessions["moo"] = make (chan int);
    _, ok := sessions["moo"];
    if ok {
        delete(sessions, "moo");

Numeric for loop in Django templates

For those who are looking to simple answer, just needing to display an amount of values, let say 3 from 100 posts for example just add {% for post in posts|slice:"3" %} and loop it normally and only 3 posts will be added.

How to do a "Save As" in vba code, saving my current Excel workbook with datestamp?

Most likely the path you are trying to access does not exist. It seems you are trying to save to a relative location and you do not have an file extension in that string. If you need to use relative paths you can parse the path from ActiveWorkbook.FullName

EDIT: Better syntax would also be

ActiveWorkbook.SaveAs Filename:=myFileName, FileFormat:=xlWorkbookNormal

Django templates: If false?

This is far easier to check in Python (i.e. your view code) than in the template, because the Python code is simply:

myvar is False


>>> False is False
>>> None is False
>>> [] is False

The problem at the template level is that the template if doesn't parse is (though it does parse in). Also, if you don't mind it, you could try to patch support for is into the template engine; base it on the code for ==.

'Syntax Error: invalid syntax' for no apparent reason

I noticed that invalid syntax error for no apparent reason can be caused by using space in:

print(f'{something something}')

Python IDLE seems to jump and highlight a part of the first line for some reason (even if the first line happens to be a comment), which is misleading.

How to remove specific elements in a numpy array

Not being a numpy person, I took a shot with:

>>> import numpy as np
>>> import itertools
>>> a = np.array([1,2,3,4,5,6,7,8,9])
>>> index=[2,3,6]
>>> a = np.array(list(itertools.compress(a, [i not in index for i in range(len(a))])))
>>> a
array([1, 2, 5, 6, 8, 9])

According to my tests, this outperforms numpy.delete(). I don't know why that would be the case, maybe due to the small size of the initial array?

python -m timeit -s "import numpy as np" -s "import itertools" -s "a = np.array([1,2,3,4,5,6,7,8,9])" -s "index=[2,3,6]" "a = np.array(list(itertools.compress(a, [i not in index for i in range(len(a))])))"
100000 loops, best of 3: 12.9 usec per loop

python -m timeit -s "import numpy as np" -s "a = np.array([1,2,3,4,5,6,7,8,9])" -s "index=[2,3,6]" "np.delete(a, index)"
10000 loops, best of 3: 108 usec per loop

That's a pretty significant difference (in the opposite direction to what I was expecting), anyone have any idea why this would be the case?

Even more weirdly, passing numpy.delete() a list performs worse than looping through the list and giving it single indices.

python -m timeit -s "import numpy as np" -s "a = np.array([1,2,3,4,5,6,7,8,9])" -s "index=[2,3,6]" "for i in index:" "    np.delete(a, i)"
10000 loops, best of 3: 33.8 usec per loop

Edit: It does appear to be to do with the size of the array. With large arrays, numpy.delete() is significantly faster.

python -m timeit -s "import numpy as np" -s "import itertools" -s "a = np.array(list(range(10000)))" -s "index=[i for i in range(10000) if i % 2 == 0]" "a = np.array(list(itertools.compress(a, [i not in index for i in range(len(a))])))"
10 loops, best of 3: 200 msec per loop

python -m timeit -s "import numpy as np" -s "a = np.array(list(range(10000)))" -s "index=[i for i in range(10000) if i % 2 == 0]" "np.delete(a, index)"
1000 loops, best of 3: 1.68 msec per loop

Obviously, this is all pretty irrelevant, as you should always go for clarity and avoid reinventing the wheel, but I found it a little interesting, so I thought I'd leave it here.

How to add an image to a JPanel?

Here's how I do it (with a little more info on how to load an image):

import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JPanel;

public class ImagePanel extends JPanel{

    private BufferedImage image;

    public ImagePanel() {
       try {                
          image = File("image name and path"));
       } catch (IOException ex) {
            // handle exception...

    protected void paintComponent(Graphics g) {
        g.drawImage(image, 0, 0, this); // see javadoc for more info on the parameters            


Why specify @charset "UTF-8"; in your CSS file?

It tells the browser to read the css file as UTF-8. This is handy if your CSS contains unicode characters and not only ASCII.

Using it in the meta tag is fine, but only for pages that include that meta tag.

Read about the rules for character set resolution of CSS files at the w3c spec for CSS 2.

Should I write script in the body or the head of the html?

W3Schools have a nice article on this subject.

Scripts in <head>

Scripts to be executed when they are called, or when an event is triggered, are placed in functions.

Put your functions in the head section, this way they are all in one place, and they do not interfere with page content.

Scripts in <body>

If you don't want your script to be placed inside a function, or if your script should write page content, it should be placed in the body section.

How to plot vectors in python using matplotlib

How about something like

import numpy as np
import matplotlib.pyplot as plt

V = np.array([[1,1], [-2,2], [4,-7]])
origin = np.array([[0, 0, 0],[0, 0, 0]]) # origin point

plt.quiver(*origin, V[:,0], V[:,1], color=['r','b','g'], scale=21)

enter image description here

Then to add up any two vectors and plot them to the same figure, do so before you call Something like:

plt.quiver(*origin, V[:,0], V[:,1], color=['r','b','g'], scale=21)
v12 = V[0] + V[1] # adding up the 1st (red) and 2nd (blue) vectors
plt.quiver(*origin, v12[0], v12[1])

enter image description here

NOTE: in Python2 use origin[0], origin[1] instead of *origin

Import existing source code to GitHub

If you've got local source code you want to add to a new remote new git repository without 'cloning' the remote first, do the following (I often do this - you create your remote empty repository in bitbucket/github, then push up your source)

  1. Create the remote repository, and get the URL such as [email protected]:/youruser/somename.git or

    If your local GIT repo is already set up, skips steps 2 and 3

  2. Locally, at the root directory of your source, git init

    2a. If you initialize the repo with a .gitignore and a you should do a git pull {url from step 1} to ensure you don't commit files to source that you want to ignore ;)

  3. Locally, add and commit what you want in your initial repo (for everything, git add . then git commit -m 'initial commit comment')

  4. to attach your remote repo with the name 'origin' (like cloning would do)
    git remote add origin [URL From Step 1]

  5. Execute git pull origin master to pull the remote branch so that they are in sync.
  6. to push up your master branch (change master to something else for a different branch):
    git push origin master

Difference between acceptance test and functional test?

They are the same thing.

Acceptance testing is performed on the completed system in as identical as possible to the real production/deployement environment before the system is deployed or delivered.

You can do acceptance testing in an automated manner, or manually.

Only detect click event on pseudo-element

This works for me:

$('#element').click(function (e) {
        if (e.offsetX > {
            // click on element
           // click on ::before element

matplotlib: how to change data points color based on some variable

If you want to plot lines instead of points, see this example, modified here to plot good/bad points representing a function as a black/red as appropriate:

def plot(xx, yy, good):
    """Plot data

    Good parts are plotted as black, bad parts as red.

    xx, yy : 1D arrays
        Data to plot.
    good : `numpy.ndarray`, boolean
        Boolean array indicating if point is good.
    import numpy as np
    import matplotlib.pyplot as plt
    fig, ax = plt.subplots()
    from matplotlib.colors import from_levels_and_colors
    from matplotlib.collections import LineCollection
    cmap, norm = from_levels_and_colors([0.0, 0.5, 1.5], ['red', 'black'])
    points = np.array([xx, yy]).T.reshape(-1, 1, 2)
    segments = np.concatenate([points[:-1], points[1:]], axis=1)
    lines = LineCollection(segments, cmap=cmap, norm=norm)

NoClassDefFoundError on Maven dependency

when I try to run it, I get NoClassDefFoundError

Run it how? You're probably trying to run it with eclipse without having correctly imported your maven classpath. See the m2eclipse plugin for integrating maven with eclipse for that.

To verify that your maven config is correct, you could run your app with the exec plugin using:

mvn exec:java -D exec.mainClass=<your main class>

Update: First, regarding your error when running exec:java, your main class is When talking about class names, they're (almost) always dot-separated. The simple class name is just the last part: App in your case. The fully-qualified name is the full package plus the simple class name, and that's what you give to maven or java when you want to run something. What you were trying to use was a file system path to a source file. That's an entirely different beast. A class name generally translates directly to a class file that's found in the class path, as compared to a source file in the file system. In your specific case, the class file in question would probably be at target/classes/tr/edu/hacettepe/cs/b21127113/bil138_4/App.class because maven compiles to target/classes, and java traditionally creates a directory for each level of packaging.

Your original problem is simply that you haven't put the Jackson jars on your class path. When you run a java program from the command line, you have to set the class path to let it know where it can load classes from. You've added your own jar, but not the other required ones. Your comment makes me think you don't understand how to manually build a class path. In short, the class path can have two things: directories containing class files and jars containing class files. Directories containing jars won't work. For more details on building a class path, see "Setting the class path" and the java and javac tool documentation.

Your class path would need to be at least, and without the line feeds:


Note that the separator on Windows is a semicolon (;).

I apologize for not noticing it sooner. The problem was sitting there in your original post, but I missed it.

iOS: how to perform a HTTP POST request?

Here is how POST HTTP request works for iOS 8+ using NSURLSession:

- (void)call_PostNetworkingAPI:(NSURL *)url withCompletionBlock:(void(^)(id object,NSError *error,NSURLResponse *response))completion
    NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
    config.requestCachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
    config.URLCache = nil;
    config.timeoutIntervalForRequest = 5.0f;
    config.timeoutIntervalForResource =10.0f;
    NSURLSession *session = [NSURLSession sessionWithConfiguration:config delegate:nil delegateQueue:nil];
    NSMutableURLRequest *Req=[NSMutableURLRequest requestWithURL:url];
    [Req setHTTPMethod:@"POST"];

    NSURLSessionDataTask *task = [session dataTaskWithRequest:Req completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        if (error == nil) {

            NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil];
            if (dict != nil) {
    [task resume];


Hope this will satisfy your following requirement.

"for" vs "each" in Ruby

This is the only difference:


irb> [1,2,3].each { |x| }
  => [1, 2, 3]
irb> x
NameError: undefined local variable or method `x' for main:Object
    from (irb):2
    from :0


irb> for x in [1,2,3]; end
  => [1, 2, 3]
irb> x
  => 3

With the for loop, the iterator variable still lives after the block is done. With the each loop, it doesn't, unless it was already defined as a local variable before the loop started.

Other than that, for is just syntax sugar for the each method.

When @collection is nil both loops throw an exception:

Exception: undefined local variable or method `@collection' for main:Object

Eclipse error: indirectly referenced from required .class files?

In addition to the already suggested cause of missing a class file this error can also indicate a duplicate class file, eclipse reports this error when an class file on the build path uses another class that has multiple definitions in the build path.

sort csv by column

The reader acts like a generator. On a file with some fake data:

>>> import sys, csv
>>> data = csv.reader(open('data.csv'),delimiter=';')
>>> data
<_csv.reader object at 0x1004a11a0>
['a', ' b', ' c']
['x', ' y', ' z']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>

Using operator.itemgetter as Ignacio suggests:

>>> data = csv.reader(open('data.csv'),delimiter=';')
>>> import operator
>>> sortedlist = sorted(data, key=operator.itemgetter(2), reverse=True)
>>> sortedlist
[['x', ' y', ' z'], ['a', ' b', ' c']]

How to copy files across computers using SSH and MAC OS X Terminal

You may also want to look at rsync if you're doing a lot of files.

If you're going to making a lot of changes and want to keep your directories and files in sync, you may want to use a version control system like Subversion or Git. See

How to get directory size in PHP

The following are other solutions offered elsewhere:

If on a Windows Host:

    $f = 'f:/www/docs';
    $obj = new COM ( 'scripting.filesystemobject' );
    if ( is_object ( $obj ) )
        $ref = $obj->getfolder ( $f );
        echo 'Directory: ' . $f . ' => Size: ' . $ref->size;
        $obj = null;
        echo 'can not create object';

Else, if on a Linux Host:

    $f = './path/directory';
    $io = popen ( '/usr/bin/du -sk ' . $f, 'r' );
    $size = fgets ( $io, 4096);
    $size = substr ( $size, 0, strpos ( $size, "\t" ) );
    pclose ( $io );
    echo 'Directory: ' . $f . ' => Size: ' . $size;

Eclipse No tests found using JUnit 5 caused by NoClassDefFoundError for LauncherFactory

Using STS 3.9.1 I got the same problem. However, currently I do not require any new JUnit5 features, so I tried to force using an older version. If using maven, you can add following dependencies to your pom.xml:




This did the trick for me (at least as long as I do not need JUnit5 explicitly).

How to install both Python 2.x and Python 3.x in Windows

If you can't get anything else to work, open an interpreter in whichever version you choose (I prefer using iPython) and:

import subprocess'python -flags')

This uses whichever python version you are currently operating under. Works fine for a single script, but will quickly get out of hand if there are lots of scripts you run, in which case you can always make a batch file with all of these calls inside. Not the most elegant answer, but it works.

Is there a way to make aliases for different python version a la Linux?

Read a file line by line with VB.NET

Replaced the reader declaration with this one and now it works!

Dim reader As New StreamReader(filetoimport.Text, Encoding.Default)

Encoding.Default represents the ANSI code page that is set under Windows Control Panel.

Are there any Java method ordering conventions?

Also, eclipse offers the possibility to sort class members for you, if you for some reason mixed them up:

Open your class file, the go to "Source" in the main menu and select "Sort Members".

taken from here: Sorting methods in Eclipse

pull out p-values and r-squared from a linear regression

I used this lmp function quite a lot of times.

And at one point I decided to add new features to enhance data analysis. I am not in expert in R or statistics but people are usually looking at different information of a linear regression :

  • p-value
  • a and b
  • and of course the aspect of the point distribution

Let's have an example. You have here

Here a reproducible example with different variables:

Ex<-structure(list(X1 = c(-36.8598, -37.1726, -36.4343, -36.8644, 
-37.0599, -34.8818, -31.9907, -37.8304, -34.3367, -31.2984, -33.5731
), X2 = c(64.26, 63.085, 66.36, 61.08, 61.57, 65.04, 72.69, 63.83, 
67.555, 76.06, 68.61), Y1 = c(493.81544, 493.81544, 494.54173, 
494.61364, 494.61381, 494.38717, 494.64122, 493.73265, 494.04246, 
494.92989, 494.98384), Y2 = c(489.704166, 489.704166, 490.710962, 
490.653212, 490.710612, 489.822928, 488.160904, 489.747776, 490.600579, 
488.946738, 490.398958), Y3 = c(-19L, -19L, -19L, -23L, -30L, 
-43L, -43L, -2L, -58L, -47L, -61L)), .Names = c("X1", "X2", "Y1", 
"Y2", "Y3"), row.names = c(NA, 11L), class = "data.frame")



#Use the lmp function

lmp <- function (modelobject) {
  if (class(modelobject) != "lm") stop("Not an object of class 'lm' ")
  f <- summary(modelobject)$fstatistic
    p <- pf(f[1],f[2],f[3],lower.tail=F)
    attributes(p) <- NULL

# create function to extract different informations from lm

lmtable<-function (var1,var2,data,signi=NULL){
  #var1= y data : colnames of data as.character, so "Y1" or c("Y1","Y2") for example
  #var2= x data : colnames of data as.character, so "X1" or c("X1","X2") for example
  #data= data in dataframe, variables in columns
  # if signi TRUE, round p-value with 2 digits and add *** if <0.001, ** if < 0.01, * if < 0.05.

  if (class(data) != "data.frame") stop("Not an object of class 'data.frame' ")
  for (i in 1:length(var2))

  for (n in 1:length(var1))





  for (l in 1:nrow(Tabtemp))


# ------- EXAMPLES ------


There is certainly a faster solution than this function but it works.

How do I center list items inside a UL element?

I have run into this issue before and found that sometimes padding is the issue.

By removing padding from the ul, any li's set to inline-block will be nicely centred:

* {_x000D_
 box-sizing: border-box;_x000D_
ul {_x000D_
 width: 120px;_x000D_
 margin: auto;_x000D_
 text-align: center;_x000D_
 border: 1px solid black;_x000D_
li {_x000D_
 display: inline-block;_x000D_
ul.no_pad {_x000D_
 padding: 0;_x000D_
p {_x000D_
 margin: auto;_x000D_
 text-align: center;_x000D_
.break {_x000D_
 margin: 50px 10px;_x000D_
<div>  _x000D_
  <p>With Padding (Default Style)</p>_x000D_
            <ul class="with_pad">_x000D_
  <div class="break"></div>_x000D_
  <p>No Padding (Padding: 0)</p>_x000D_
   <ul class="no_pad">_x000D_

Hope that helps anyone running into this same issue :)



How best to determine if an argument is not sent to the JavaScript function

There are several different ways to check if an argument was passed to a function. In addition to the two you mentioned in your (original) question - checking arguments.length or using the || operator to provide default values - one can also explicitly check the arguments for undefined via argument2 === undefined or typeof argument2 === 'undefined' if one is paranoid (see comments).

Using the || operator has become standard practice - all the cool kids do it - but be careful: The default value will be triggered if the argument evaluates to false, which means it might actually be undefined, null, false, 0, '' (or anything else for which Boolean(...) returns false).

So the question is when to use which check, as they all yield slightly different results.

Checking arguments.length exhibits the 'most correct' behaviour, but it might not be feasible if there's more than one optional argument.

The test for undefined is next 'best' - it only 'fails' if the function is explicitly called with an undefined value, which in all likelyhood should be treated the same way as omitting the argument.

The use of the || operator might trigger usage of the default value even if a valid argument is provided. On the other hand, its behaviour might actually be desired.

To summarize: Only use it if you know what you're doing!

In my opinion, using || is also the way to go if there's more than one optional argument and one doesn't want to pass an object literal as a workaround for named parameters.

Another nice way to provide default values using arguments.length is possible by falling through the labels of a switch statement:

function test(requiredArg, optionalArg1, optionalArg2, optionalArg3) {
    switch(arguments.length) {
        case 1: optionalArg1 = 'default1';
        case 2: optionalArg2 = 'default2';
        case 3: optionalArg3 = 'default3';
        case 4: break;
        default: throw new Error('illegal argument count')
    // do stuff

This has the downside that the programmer's intention is not (visually) obvious and uses 'magic numbers'; it is therefore possibly error prone.

Selenium WebDriver.get(url) does not open the URL

You need to first declare url as a sting as below:

from selenium import webdriver
from selenium.common.exceptions import TimeoutException
from import WebDriverWait # available since 2.4.0
import time

# Create a new instance of the Firefox driver

String URL = "";

driver = webdriver.Firefox()

# go to the google home page

Check if ADODB connection is open

ADO Recordset has .State property, you can check if its value is adStateClosed or adStateOpen

If Not (rs Is Nothing) Then
  If (rs.State And adStateOpen) = adStateOpen Then rs.Close
  Set rs = Nothing
End If

MSDN about State property

Edit; The reason not to check .State against 1 or 0 is because even if it works 99.99% of the time, it is still possible to have other flags set which will cause the If statement fail the adStateOpen check.


For Late binding without the ActiveX Data Objects referenced, you have few options. Use the value of adStateOpen constant from ObjectStateEnum

If Not (rs Is Nothing) Then
  If (rs.State And 1) = 1 Then rs.Close
  Set rs = Nothing
End If

Or you can define the constant yourself to make your code more readable (defining them all for a good example.)

Const adStateClosed As Long = 0 'Indicates that the object is closed.
Const adStateOpen As Long = 1 'Indicates that the object is open.
Const adStateConnecting As Long = 2 'Indicates that the object is connecting.
Const adStateExecuting As Long = 4 'Indicates that the object is executing a command.
Const adStateFetching As Long = 8 'Indicates that the rows of the object are being retrieved.    


If Not (rs Is Nothing) Then

    ' ex. If (0001 And 0001) = 0001 (only open flag) -> true
    ' ex. If (1001 And 0001) = 0001 (open and retrieve) -> true
    '    This second example means it is open, but its value is not 1
    '    and If rs.State = 1 -> false, even though it is open
    If (rs.State And adStateOpen) = adStateOpen Then 
    End If

    Set rs = Nothing
End If

What is the argument for printf that formats a long?

On most platforms, long and int are the same size (32 bits). Still, it does have its own format specifier:

long n;
unsigned long un;
printf("%ld", n); // signed
printf("%lu", un); // unsigned

For 64 bits, you'd want a long long:

long long n;
unsigned long long un;
printf("%lld", n); // signed
printf("%llu", un); // unsigned

Oh, and of course, it's different in Windows:

printf("%l64d", n); // signed
printf("%l64u", un); // unsigned

Frequently, when I'm printing 64-bit values, I find it helpful to print them in hex (usually with numbers that big, they are pointers or bit fields).

unsigned long long n;
printf("0x%016llX", n); // "0x" followed by "0-padded", "16 char wide", "long long", "HEX with 0-9A-F"

will print:


Btw, "long" doesn't mean that much anymore (on mainstream x64). "int" is the platform default int size, typically 32 bits. "long" is usually the same size. However, they have different portability semantics on older platforms (and modern embedded platforms!). "long long" is a 64-bit number and usually what people meant to use unless they really really knew what they were doing editing a piece of x-platform portable code. Even then, they probably would have used a macro instead to capture the semantic meaning of the type (eg uint64_t).

char c;       // 8 bits
short s;      // 16 bits
int i;        // 32 bits (on modern platforms)
long l;       // 32 bits
long long ll; // 64 bits 

Back in the day, "int" was 16 bits. You'd think it would now be 64 bits, but no, that would have caused insane portability issues. Of course, even this is a simplification of the arcane and history-rich truth. See wiki:Integer

Remove stubborn underline from link

text-decoration: none !important should remove it .. Are you sure there isn't a border-bottom: 1px solid lurking about? (Trace the computed style in Firebug/F12 in IE)

PHP - Fatal error: Unsupported operand types

$total_ratings is an array, which you can't use for a division.

From above:

$total_ratings = mysqli_fetch_array($result);

How to pass data from child component to its parent in ReactJS?

To pass data from child component to parent component

In Parent Component:

    // do not forget to bind getData in constructor
 return(<Child sendData={this.getData}/>);

In Child Component:


How to calculate a Mod b in Casio fx-991ES calculator

Here's how I usually do it. For example, to calculate 1717 mod 2:

  • Take 1717 / 2. The answer is 858.5
  • Now take 858 and multiply it by the mod (2) to get 1716
  • Finally, subtract the original number (1717) minus the number you got from the previous step (1716) -- 1717-1716=1.

So 1717 mod 2 is 1.

To sum this up all you have to do is multiply the numbers before the decimal point with the mod then subtract it from the original number.

iOS - Ensure execution on main thread

This will do it:

[[NSOperationQueue mainQueue] addOperationWithBlock:^ {

   //Your code goes in here
   NSLog(@"Main Thread Code");


Hope this helps!

Why is the GETDATE() an invalid identifier

Use ORACLE equivalent of getdate() which is sysdate . Read about here. Getdate() belongs to SQL Server , will not work on Oracle.

Other option is current_date

Find size of an array in Perl

Use int(@array) as it threats the argument as scalar.

Uncaught ReferenceError: function is not defined with onclick

I think you put the function in the $(document).ready....... The functions are always provided out the $(document).ready.......

Remove all child nodes from a parent?

You can use .empty(), like this:


From the docs:

Remove all child nodes of the set of matched elements from the DOM.

Timeout a command in bash without unnecessary delay

There's also cratimeout by Martin Cracauer (written in C for Unix and Linux systems).

# cf.
# usage: cratimeout timeout_in_msec cmd args
cratimeout 5000 sleep 1
cratimeout 5000 sleep 600
cratimeout 5000 tail -f /dev/null
cratimeout 5000 sh -c 'while sleep 1; do date; done'

HTTP Headers for File Downloads

As explained by Alex's link you're probably missing the header Content-Disposition on top of Content-Type.

So something like this:

Content-Disposition: attachment; filename="MyFileName.ext"

Repeating a function every few seconds

For this the System.Timers.Timer works best

// Create a timer
myTimer = new System.Timers.Timer();
// Tell the timer what to do when it elapses
myTimer.Elapsed += new ElapsedEventHandler(myEvent);
// Set it to go off every five seconds
myTimer.Interval = 5000;
// And start it        
myTimer.Enabled = true;

// Implement a call with the right signature for events going off
private void myEvent(object source, ElapsedEventArgs e) { }

See Timer Class (.NET 4.6 and 4.5) for details

Printing tuple with string formatting in Python

Talk is cheap, show you the code:

>>> tup = (10, 20, 30)
>>> i = 50
>>> print '%d      %s'%(i,tup)
50  (10, 20, 30)
>>> print '%s'%(tup,)
(10, 20, 30)

how can I set visible back to true in jquery

Remove the visible="false" attribute and add a CSS class that is not visible by default. Then you should be able to reference the dropdown by the correct id, for example:


Above ID you should serach for in the source of the rendered page in your browser.

How to write LaTeX in IPython Notebook?

You can choose a cell to be markdown, then write latex code which gets interpreted by mathjax, as one of the responders say above.

Alternatively, Latex section of the iPython notebook tutorial explains this well.

You can either do:

from IPython.display import Latex
\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\
\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\
\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\
\nabla \cdot \vec{\mathbf{B}} & = 0 

or do this:

\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\
\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\
\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\
\nabla \cdot \vec{\mathbf{B}} & = 0

More info found in this link

Chrome, Javascript, in new tab

You can't directly control this, because it's an option controlled by Internet Explorer users.

Opening pages using with a different window name will open in a new browser window like a popup, OR open in a new tab, if the user configured the browser to do so.


A more detailed explanation:

1. In modern browsers, will open in a new tab rather than a popup.

2. You can force a browser to use a new window (‘popup’) by specifying options in the 3rd parameter

3. If the call was not part of a user-initiated event, it’ll open in a new window.

4. A “user initiated event” does not have to the same function call – but it must originate in the function invoked by a user click

5. If a user initiated event delegates or defers a function call (in an event listener or delegate not bound to the click event, or by using setTimeout for example), it loses it’s status as “user initiated”

6. Some popup blockers will allow windows opened from user initiated events, but not those opened otherwise.

7. If any popup is blocked, those normally allowed by a blocker (via user initiated events) will sometimes also be blocked. Some examples…

Forcing a window to open in a new browser instance, instead of a new tab:'page.php', '', 'width=1000');

The following would qualify as a user-initiated event, even though it calls another function:

function o(){'page.php');
$('button').addEvent('click', o);

The following would not qualify as a user-initiated event, since the setTimeout defers it:

function g(){
  setTimeout(o, 1);
function o(){'page.php');
$('button').addEvent('click', g);

Why won't my PHP app send a 404 error?

A little bit shorter version. Suppress odd echo.

if (strstr($_SERVER['REQUEST_URI'],'index.php')){
  header('HTTP/1.0 404 Not Found');
  exit("<h1>404 Not Found</h1>\nThe page that you have requested could not be found.");

Line continue character in C#

@"string here
that is long you mean"

But be careful, because

@"string here
           and space before this text
     means the space is also a part of the string"

It also escapes things in the string

@"c:\\folder" // c:\\folder
@"c:\folder" // c:\folder
"c:\\folder" // c:\folder


Reversing a String with Recursion in Java

Because this is recursive your output at each step would be something like this:

  1. "Hello" is entered. The method then calls itself with "ello" and will return the result + "H"
  2. "ello" is entered. The method calls itself with "llo" and will return the result + "e"
  3. "llo" is entered. The method calls itself with "lo" and will return the result + "l"
  4. "lo" is entered. The method calls itself with "o" and will return the result + "l"
  5. "o" is entered. The method will hit the if condition and return "o"

So now on to the results:

The total return value will give you the result of the recursive call's plus the first char

To the return from 5 will be: "o"

The return from 4 will be: "o" + "l"

The return from 3 will be: "ol" + "l"

The return from 2 will be: "oll" + "e"

The return from 1 will be: "olle" + "H"

This will give you the result of "olleH"

How to define a relative path in java

Firstly, see the different between absolute path and relative path here:

An absolute path always contains the root element and the complete directory list required to locate the file.

Alternatively, a relative path needs to be combined with another path in order to access a file.

In constructor File(String pathname), Javadoc's File class said that

A pathname, whether abstract or in string form, may be either absolute or relative.

If you want to get relative path, you must be define the path from the current working directory to file or directory.Try to use system properties to get this.As the pictures that you drew:

String localDir = System.getProperty("user.dir");
File file = new File(localDir + "\\");

Moreover, you should try to avoid using similar ".", "../", "/", and other similar relative to the file location relative path, because when files are moved, it is harder to handle.

Delete column from pandas DataFrame

Another way of Deleting a Column in Pandas DataFrame

if you're not looking for In-Place deletion then you can create a new DataFrame by specifying the columns using DataFrame(...) function as

my_dict = { 'name' : ['a','b','c','d'], 'age' : [10,20,25,22], 'designation' : ['CEO', 'VP', 'MD', 'CEO']}

df = pd.DataFrame(my_dict)

Create a new DataFrame as

newdf = pd.DataFrame(df, columns=['name', 'age'])

You get a result as good as what you get with del / drop

Copy all values in a column to a new column in a pandas dataframe

Following up on these solutions, here is some helpful code illustrating :

# Copying columns in pandas without slice warning
import numpy as np
df = pd.DataFrame(np.random.randn(10, 3), columns=list('ABC'))

# copies column B into new column D
df.loc[:,'D'] = df['B']
print df

# creates new column 'E' with values -99
# But copy command replaces those where 'B'>0 while others become NaN (not copied)
df['E'] = -99
print df
df['E'] = df[df['B']>0]['B'].copy()
print df

# creates new column 'F' with values -99
# Copy command only overwrites values which meet criteria 'B'>0
df.loc[df['B']>0,'F'] = df[df['B']>0]['B'].copy()
print df

Stripping non printable characters from a string in python

Iterating over strings is unfortunately rather slow in Python. Regular expressions are over an order of magnitude faster for this kind of thing. You just have to build the character class yourself. The unicodedata module is quite helpful for this, especially the unicodedata.category() function. See Unicode Character Database for descriptions of the categories.

import unicodedata, re, itertools, sys

all_chars = (chr(i) for i in range(sys.maxunicode))
categories = {'Cc'}
control_chars = ''.join(c for c in all_chars if unicodedata.category(c) in categories)
# or equivalently and much more efficiently
control_chars = ''.join(map(chr, itertools.chain(range(0x00,0x20), range(0x7f,0xa0))))

control_char_re = re.compile('[%s]' % re.escape(control_chars))

def remove_control_chars(s):
    return control_char_re.sub('', s)

For Python2

import unicodedata, re, sys

all_chars = (unichr(i) for i in xrange(sys.maxunicode))
categories = {'Cc'}
control_chars = ''.join(c for c in all_chars if unicodedata.category(c) in categories)
# or equivalently and much more efficiently
control_chars = ''.join(map(unichr, range(0x00,0x20) + range(0x7f,0xa0)))

control_char_re = re.compile('[%s]' % re.escape(control_chars))

def remove_control_chars(s):
    return control_char_re.sub('', s)

For some use-cases, additional categories (e.g. all from the control group might be preferable, although this might slow down the processing time and increase memory usage significantly. Number of characters per category:

  • Cc (control): 65
  • Cf (format): 161
  • Cs (surrogate): 2048
  • Co (private-use): 137468
  • Cn (unassigned): 836601

Edit Adding suggestions from the comments.

nodejs vs node on ubuntu 12.04

Late answer, but for up-to-date info...

If you install node.js using the recommend method from the node github installation readme, it suggests following the instructions on the nodesource blog article, rather than installing from the out of date apt-get repo, node.js should run using the node command, as well as the nodejs command, without having to make a new symlink.

This method from article is:

# Note the new setup script name for Node.js v0.12
curl -sL | sudo bash -

# Then install with:
sudo apt-get install -y nodejs

Note that this is for v0.12, which will get likely become outdated in the not to distant future.

Also, if you're behind a corporate proxy (like me) you'll want to add the -E option to the sudo command, to preserve the env vars required for the proxy:

curl -sL | sudo -E bash -

How to build and fill pandas dataframe from for loop?

I may be wrong, but I think the accepted answer by @amit has a bug.

from pandas import DataFrame as df
x = [1,2,3]
y = [7,8,9,10]

# this gives me a syntax error at 'for' (Python 3.7)
d1 = df[[a, "A", b, "B"] for a in x for b in y]

# this works
d2 = df([a, "A", b, "B"] for a in x for b in y)

# and if you want to add the column names on the fly
# note the additional parentheses
d3 = df(([a, "A", b, "B"] for a in x for b in y), columns = ("l","m","n","o"))

Oracle query execution time

select LAST_LOAD_TIME, ELAPSED_TIME, MODULE, SQL_TEXT elapsed from v$sql
  order by LAST_LOAD_TIME desc

More complicated example (don't forget to delete or to substitute PATTERN):

select * from (
  select LAST_LOAD_TIME, to_char(ELAPSED_TIME/1000, '999,999,999.000') || ' ms' as TIME,
         MODULE, SQL_TEXT from SYS."V_\$SQL"
    where SQL_TEXT like '%PATTERN%'
    order by LAST_LOAD_TIME desc
  ) where ROWNUM <= 5;

Get full path without filename from path that includes filename

Path.GetDirectoryName() returns the directory name, so for what you want (with the trailing reverse solidus character) you could call Path.GetDirectoryName(filePath) + Path.DirectorySeparatorChar.

Calling a JavaScript function returned from an Ajax response

This does not sound like a good idea.

You should abstract out the function to include in the rest of your JavaScript code from the data returned by Ajax methods.

For what it's worth, though, (and I don't understand why you're inserting a script block in a div?) even inline script methods written in a script block will be accessible.

Value does not fall within the expected range

This might be due to the fact that you are trying to add a ListBoxItem with a same name to the page.

If you want to refresh the content of the listbox with the newly retrieved values you will have to first manually remove the content of the listbox other wise your loop will try to create lb_1 again and add it to the same list.

Look at here for a similar problem that occured Silverlight: Value does not fall within the expected range exception


How to convert a private key to an RSA private key?

This may be of some help (do not literally write out the backslashes '\' in the commands, they are meant to indicate that "everything has to be on one line"):

Which Command to Apply When

It seems that all the commands (in grey) take any type of key file (in green) as "in" argument. Which is nice.

Here are the commands again for easier copy-pasting:

openssl rsa                                                -in $FF -out $TF
openssl rsa -aes256                                        -in $FF -out $TF
openssl pkcs8 -topk8 -nocrypt                              -in $FF -out $TF
openssl pkcs8 -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA256 -in $FF -out $TF


openssl rsa -check -in $FF
openssl rsa -text  -in $FF

Show a PDF files in users browser via PHP/Perl

The safest way to have a PDF display instead of download seems to be embedding it using an object or iframe element. There are also 3rd party solutions like Google's PDF viewer.

See Best Way to Embed PDF in HTML for an overview.

There's also DoPDF, a Java based In-browser PDF viewer. I can't speak to its quality but it looks interesting.

How to send a POST request in Go?

You have mostly the right idea, it's just the sending of the form that is wrong. The form belongs in the body of the request.

req, err := http.NewRequest("POST", url, strings.NewReader(form.Encode()))

Query to convert from datetime to date mysql

syntax of date_format:

SELECT date_format(date_born, '%m/%d/%Y' ) as my_date FROM date_tbl

    '%W %D %M %Y %T'    -> Wednesday 5th May 2004 23:56:25
    '%a %b %e %Y %H:%i' -> Wed May 5 2004 23:56
    '%m/%d/%Y %T'       -> 05/05/2004 23:56:25
    '%d/%m/%Y'          -> 05/05/2004
    '%m-%d-%y'          -> 04-08-13

How to get the fragment instance from the FragmentActivity?

To get the fragment instance in a class that extends FragmentActivity:

MyclassFragment instanceFragment=

To get the fragment instance in a class that extends Fragment:

MyclassFragment instanceFragment =  

JavaScript for detecting browser language preference

var language = navigator.languages && navigator.languages[0] || // Chrome / Firefox_x000D_
               navigator.language ||   // All browsers_x000D_
               navigator.userLanguage; // IE <= 10_x000D_

Try PWA Template

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

The best way is to look in your httpd.conf file and see what the default is. It could also be overridden by your specific virtual host. I start by looking at /etc/httpd/conf/httpd.conf or /etc/apache2/httpd.conf and search for error_log. It could be listed as either /var/log/httpd/error_log or /var/log/apache2/error_log but it might also be listed as simply logs/error_log.

In this case it is a relative path, which means it will be under /etc/httpd/logs/error_log. If you still can't find it check the bottom of your httpd.conf file and see where your virtual hosts are included. It might be in /etc/httpd/conf.d/<- as "other" or "extra". Your virtual host could override it then with ErrorLog "/path/to/error_log".

The view 'Index' or its master was not found.

Where this error only occurs when deployed to a web server then the issue could be because the views are not being deployed correctly.

An example of how this can happen is if the build action for the views is set to None rather than Content.

A way to check that the views are deployed correctly is to navigate to the physical path for the site on the web server and confirm that the views are present.


VARCHAR means that it's a variable-length character, so it's only going to take as much space as is necessary. But if you knew something about the underlying structure, it may make sense to restrict VARCHAR to some maximum amount.

For instance, if you were storing comments from the user, you may limit the comment field to only 4000 characters; if so, it doesn't really make any sense to make the sql table have a field that's larger than VARCHAR(4000).

WPF What is the correct way of using SVG files as icons in WPF

Windows 10 build 15063 "Creators Update" natively supports SVG images (though with some gotchas) to UWP/UAP applications targeting Windows 10.

If your application is a WPF app rather than a UWP/UAP, you can still use this API (after jumping through quite a number of hoops): Windows 10 build 17763 "October 2018 Update" introduced the concept of XAML islands (as a "preview" technology but I believe allowed in the app store; in all cases, with Windows 10 build 18362 "May 2019 Update" XAML islands are no longer a preview feature and are fully supported) allowing you to use UWP APIs and controls in your WPF applications.

You need to first add the references to the WinRT APIs, and to use certain Windows 10 APIs that interact with user data or the system (e.g. loading images from disk in a Windows 10 UWP webview or using the toast notification API to show toasts), you also need to associate your WPF application with a package identity, as shown here (immensely easier in Visual Studio 2019). This shouldn't be necessary to use the Windows.UI.Xaml.Media.Imaging.SvgImageSource class, though.

Usage (if you're on UWP or you've followed the directions above and added XAML island support under WPF) is as simple as setting the Source for an <Image /> to the path to the SVG. That is equivalent to using SvgImageSource, as follows:

        <SvgImageSource UriSource="Assets/svg/icon.svg" />

However, SVG images loaded in this way (via XAML) may load jagged/aliased. One workaround is to specify a RasterizePixelHeight or RasterizePixelWidth value that is double+ your actual height/width:

<SvgImageSource RasterizePixelHeight="300" RasterizePixelWidth="300" UriSource="Assets/svg/icon.svg" /> <!-- presuming actual height or width is under 150 -->

This can be worked around dynamically by creating a new SvgImageSource in the ImageOpened event for the base image:

var svgSource = new SvgImageSource(new Uri("ms-appx://" + Icon));
PrayerIcon.ImageOpened += (s, e) =>
    var newSource = new SvgImageSource(svgSource.UriSource);
    newSource.RasterizePixelHeight = PrayerIcon.DesiredSize.Height * 2;
    newSource.RasterizePixelWidth = PrayerIcon.DesiredSize.Width * 2;
    PrayerIcon2.Source = newSource;
PrayerIcon.Source = svgSource;

The aliasing may be hard to see on non high-dpi screens, but here's an attempt to illustrate it.

This is the result of the code above: an Image that uses the initial SvgImageSource, and a second Image below it that uses the SvgImageSource created in the ImageOpened event:

enter image description here

This is a blown up view of the top image:

enter image description here

Whereas this is a blown-up view of the bottom (antialiased, correct) image:

enter image description here

(you'll need to open the images in a new tab and view at full size to appreciate the difference)

How can I make IntelliJ IDEA update my dependencies from Maven?

You need to go to: Maven settings -> Auto-Reload Settings

Auto-Reload Settings

Then check "Any Changes":

enter image description here

PHP - remove all non-numeric characters from a string

You can use preg_replace in this case;

$res = preg_replace("/[^0-9]/", "", "Every 6 Months" );

$res return 6 in this case.

If want also to include decimal separator or thousand separator check this example:

$res = preg_replace("/[^0-9.]/", "", "$ 123.099");

$res returns "123.099" in this case

Include period as decimal separator or thousand separator: "/[^0-9.]/"

Include coma as decimal separator or thousand separator: "/[^0-9,]/"

Include period and coma as decimal separator and thousand separator: "/[^0-9,.]/"

Git push won't do anything (everything up-to-date)

In my case, I had to delete all remotes (there were multiple for some unexplained reason), add the remote again, and commit with -f.

$ git remote

$ git remote remove upstream
$ git remote remove origin
$ git remote add origin <my origin>
$ git push -u -f origin main

I don't know if the -u flag contributed anything, but it doesn't hurt either.

PowerShell on Windows 7: Set-ExecutionPolicy for regular users

Set-ExecutionPolicy Unrestricted -Scope CurrentUser

This will set the execution policy for the current user (stored in HKEY_CURRENT_USER) rather than the local machine (HKEY_LOCAL_MACHINE). This is useful if you don't have administrative control over the computer.

Trigger 404 in Spring-MVC controller?

Configure web.xml with setting



Create new controller

     * Error Controller. handles the calls for 404, 500 and 401 HTTP Status codes.
    @RequestMapping(value = ErrorController.ERROR_URL, produces = MediaType.APPLICATION_XHTML_XML_VALUE)
    public class ErrorController {

         * The constant ERROR_URL.
        public static final String ERROR_URL = "/error";

         * The constant TILE_ERROR.
        public static final String TILE_ERROR = "";

         * Page Not Found.
         * @return Home Page
        @RequestMapping(value = "/404", produces = MediaType.APPLICATION_XHTML_XML_VALUE)
        public ModelAndView notFound() {

            ModelAndView model = new ModelAndView(TILE_ERROR);
            model.addObject("message", "The page you requested could not be found. This location may not be current.");

            return model;

         * Error page.
         * @return the model and view
        @RequestMapping(value = "/500", produces = MediaType.APPLICATION_XHTML_XML_VALUE)
        public ModelAndView errorPage() {
            ModelAndView model = new ModelAndView(TILE_ERROR);
            model.addObject("message", "The page you requested could not be found. This location may not be current, due to the recent site redesign.");

            return model;

How do you use String.substringWithRange? (or, how do Ranges work in Swift?)

The short answer is that this is really hard in Swift right now. My hunch is that there is still a bunch of work for Apple to do on convenience methods for things like this.

String.substringWithRange() is expecting a Range<String.Index> parameter, and as far as I can tell there isn't a generator method for the String.Index type. You can get String.Index values back from aString.startIndex and aString.endIndex and call .succ() or .pred() on them, but that's madness.

How about an extension on the String class that takes good old Ints?

extension String {
    subscript (r: Range<Int>) -> String {
        get {
            let subStart = advance(self.startIndex, r.startIndex, self.endIndex)
            let subEnd = advance(subStart, r.endIndex - r.startIndex, self.endIndex)
            return self.substringWithRange(Range(start: subStart, end: subEnd))
    func substring(from: Int) -> String {
        let end = countElements(self)
        return self[from..<end]
    func substring(from: Int, length: Int) -> String {
        let end = from + length
        return self[from..<end]

let mobyDick = "Call me Ishmael."
println(mobyDick[8...14])             // Ishmael

let dogString = "This 's name is Patch."
println(dogString[5..<6])               // 
println(dogString[5...5])              // 
println(dogString.substring(5))        // 's name is Patch.
println(dogString.substring(5, length: 1))   // 

Update: Swift beta 4 resolves the issues below!

As it stands [in beta 3 and earlier], even Swift-native strings have some issues with handling Unicode characters. The dog icon above worked, but the following doesn't:

let harderString = "1:1??"
for character in harderString {



Convert timedelta to total seconds

You can use mx.DateTime module

import mx.DateTime as mt

t1 = 
t2 =
print int((t2-t1).seconds)

Why maven settings.xml file is not there?

By Installing Maven you can not expect the settings.xml in your .m2 folder(If may be hidden folder, to unhide just press Ctrl+h). You need to place the file explicitly at that location. After placing the file maven plugin for eclipse will start using that file too.

How can I do a BEFORE UPDATED trigger with sql server?

All "normal" triggers in SQL Server are "AFTER ..." triggers. There are no "BEFORE ..." triggers.

To do something before an update, check out INSTEAD OF UPDATE Triggers.

jQuery each loop in table row

In jQuery just use:

$('#tblOne > tbody  > tr').each(function() {...code...});

Using the children selector (>) you will walk over all the children (and not all descendents), example with three rows:

$('table > tbody  > tr').each(function(index, tr) { 



In VanillaJS you can use document.querySelectorAll() and walk over the rows using forEach()

[]'#tblOne > tbody  > tr'), function(index, tr) {
    /* console.log(index); */
    /* console.log(tr); */

How to format a numeric column as phone number in SQL

I'd generally recommend you leave the formatting up to your front-end code and just return the data as-is from SQL. However, to do it in SQL, I'd recommend you create a user-defined function to format it. Something like this:

CREATE FUNCTION [dbo].[fnFormatPhoneNumber](@PhoneNo VARCHAR(20))
DECLARE @Formatted VARCHAR(25)

IF (LEN(@PhoneNo) <> 10)
    SET @Formatted = @PhoneNo
    SET @Formatted = LEFT(@PhoneNo, 3) + '-' + SUBSTRING(@PhoneNo, 4, 3) + '-' + SUBSTRING(@PhoneNo, 7, 4)

RETURN @Formatted

Which you can then use like this:

SELECT [dbo].[fnFormatPhoneNumber](PhoneNumber) AS PhoneNumber
FROM SomeTable

It has a safeguard in, in case the phone number stored isn't the expected number of digits long, is blank, null etc - it won't error.

EDIT: Just clocked on you want to update your existing data. The main bit that's relevant from my answer then is that you need to protect against "dodgy"/incomplete data (i.e. what if some existing values are only 5 characters long)

How do you deploy Angular apps?

I would say a lot of people with Web experience prior to angular, are use to deploying their web artifacts inside a war (i.e. jquery and html inside a Java/Spring project). I ended up doing this to get around CORS issue, after attempting to keep my angular and REST projects separate.

My solution was to move all angular (4) contents, generated with CLI, from my-app to MyJavaApplication/angular. Then I modifed my Maven build to use maven-resources-plugin to move the contents from /angular/dist to the root of my distribution (i.e. $}/MyJavaApplication). Angular loads resources from root of the war by default.

When I started to add routing to my angular project, I further modifed maven build to copy index.html from /dist to WEB-INF/app. And, added a Java controller that redirects all server side rest calls to index.

Vertically centering Bootstrap modal window

Vertically centered Add .modal-dialog-centered to .modal-dialog to vertically center the modal

Launch demo modal

<!-- Modal -->
<div class="modal fade" id="exampleModalCenter" tabindex="-1" role="dialog" aria-labelledby="exampleModalCenterTitle" aria-hidden="true">
  <div class="modal-dialog modal-dialog-centered" role="document">
    <div class="modal-content">
      <div class="modal-header">
        <h5 class="modal-title" id="exampleModalCenterTitle">Modal title</h5>
        <button type="button" class="close" data-dismiss="modal" aria-label="Close">
          <span aria-hidden="true">&times;</span>
      <div class="modal-body">
      <div class="modal-footer">
        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
        <button type="button" class="btn btn-primary">Save changes</button>

How to manually trigger validation with jQuery validate?

My approach was as below. Now I just wanted my form to be validated when one specific checkbox was clicked/changed:

$('#myForm input:checkbox[name=yourChkBxName]').click(

DataGridView AutoFit and Fill

public static void Fill(DataGridView dgv2)
            dgv = dgv2;
            foreach (DataGridViewColumn GridCol in dgv.Columns)
                for (int j = 0; j < GridCol.DataGridView.ColumnCount; j++)
                    GridCol.DataGridView.Columns[j].AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;
                    GridCol.DataGridView.Columns[j].AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells;
                    GridCol.DataGridView.Columns[j].FillWeight = 1;
        catch (Exception ex)
            MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);

Making a Bootstrap table column fit to content

Add w-auto native bootstrap 4 class to the table element and your table will fit its content.

enter image description here

Running bash script from within python

If someone looking for calling a script with arguments

import subprocess

val = subprocess.check_call("./ '%s'" % arg, shell=True)

Remember to convert the args to string before passing, using str(arg).

This can be used to pass as many arguments as desired:

subprocess.check_call("./script.ksh %s %s %s" % (arg1, str(arg2), arg3), shell=True)

Can't access Tomcat using IP address

If you are not able to access tomcat from remote, there might be reason that taken port is not open in your machine. Suppose you have taken 8081 port.

On Your windows machine:

Open Control panel-> windows Firewall-> Advance setting->Inbound Rules

Create a new rule: mention Port


Configure your port and then shutdown and start your tomcat and it will be accessible from remote as well.

That port issue majorly comes in AWS machines.

If it is still not working then please check with your administrator that selected port is open for public access or not, if not then open it.

how to rename an index in a cluster?

Just in case someone still needs it. The successful, not official, way to rename indexes are:

  1. Close indexes that need to be renamed
  2. Rename indexes' folders in all data directories of master and data nodes.
  3. Reopen old closed indexes (I use kofp plugin). Old indexes will be reopened but stay unassigned. New indexes will appear in closed state
  4. Reopen new indexes
  5. Delete old indexes

If you happen to get this error "dangled index directory name is", remove index folder in all master nodes (not data nodes), and restart one of the data nodes.

How to implode array with key and value without foreach in PHP

For debugging purposes. Recursive write an array of nested arrays to a string. Used foreach. Function stores National Language characters.

function q($input)
    $glue = ', ';
    $function = function ($v, $k) use (&$function, $glue) {
        if (is_array($v)) {
            $arr = [];
            foreach ($v as $key => $value) {
                $arr[] = $function($value, $key);
            $result = "{" . implode($glue, $arr) . "}";
        } else {
            $result = sprintf("%s=\"%s\"", $k, var_export($v, true));
        return $result;
    return implode($glue, array_map($function, $input, array_keys($input))) . "\n";

Aligning a button to the center

Add width:100px, margin:50%. Now the left side of the button is set to the center.
Finally add half of the width of the button in our case 50px.
The middle of the button is in the center.

<input type='submit' style='width:100px;margin:0 50%;position:relative;left:-50px;'>

C convert floating point to int

If you want to round it to lower, just cast it.

float my_float = 42.8f;
int my_int;
my_int = (int)my_float;          // => my_int=42

For other purpose, if you want to round it to nearest, you can make a little function or a define like this:

#define FLOAT_TO_INT(x) ((x)>=0?(int)((x)+0.5):(int)((x)-0.5))

float my_float = 42.8f;
int my_int;
my_int = FLOAT_TO_INT(my_float); // => my_int=43

Be careful, ideally you should verify float is between INT_MIN and INT_MAX before casting it.

A good Sorted List for Java

This is the SortedList implementation I am using. Maybe this helps with your problem:

import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
 * This class is a List implementation which sorts the elements using the
 * comparator specified when constructing a new instance.
 * @param <T>
public class SortedList<T> extends ArrayList<T> {
     * Needed for serialization.
    private static final long serialVersionUID = 1L;
     * Comparator used to sort the list.
    private Comparator<? super T> comparator = null;
     * Construct a new instance with the list elements sorted in their
     * {@link java.lang.Comparable} natural ordering.
    public SortedList() {
     * Construct a new instance using the given comparator.
     * @param comparator
    public SortedList(Comparator<? super T> comparator) {
        this.comparator = comparator;
     * Construct a new instance containing the elements of the specified
     * collection with the list elements sorted in their
     * {@link java.lang.Comparable} natural ordering.
     * @param collection
    public SortedList(Collection<? extends T> collection) {
     * Construct a new instance containing the elements of the specified
     * collection with the list elements sorted using the given comparator.
     * @param collection
     * @param comparator
    public SortedList(Collection<? extends T> collection, Comparator<? super T> comparator) {
     * Add a new entry to the list. The insertion point is calculated using the
     * comparator.
     * @param paramT
     * @return <code>true</code> if this collection changed as a result of the call.
    public boolean add(T paramT) {
        int initialSize = this.size();
        // Retrieves the position of an existing, equal element or the 
        // insertion position for new elements (negative).
        int insertionPoint = Collections.binarySearch(this, paramT, comparator);
        super.add((insertionPoint > -1) ? insertionPoint : (-insertionPoint) - 1, paramT);
        return (this.size() != initialSize);
     * Adds all elements in the specified collection to the list. Each element
     * will be inserted at the correct position to keep the list sorted.
     * @param paramCollection
     * @return <code>true</code> if this collection changed as a result of the call.
    public boolean addAll(Collection<? extends T> paramCollection) {
        boolean result = false;
        if (paramCollection.size() > 4) {
            result = super.addAll(paramCollection);
            Collections.sort(this, comparator);
        else {
            for (T paramT:paramCollection) {
                result |= add(paramT);
        return result;
     * Check, if this list contains the given Element. This is faster than the
     * {@link #contains(Object)} method, since it is based on binary search.
     * @param paramT
     * @return <code>true</code>, if the element is contained in this list;
     * <code>false</code>, otherwise.
    public boolean containsElement(T paramT) {
        return (Collections.binarySearch(this, paramT, comparator) > -1);
     * @return The comparator used for sorting this list.
    public Comparator<? super T> getComparator() {
        return comparator;
     * Assign a new comparator and sort the list using this new comparator.
     * @param comparator
    public void setComparator(Comparator<? super T> comparator) {
        this.comparator = comparator;
        Collections.sort(this, comparator);

This solution is very flexible and uses existing Java functions:

  • Completely based on generics
  • Uses java.util.Collections for finding and inserting list elements
  • Option to use a custom Comparator for list sorting

Some notes:

  • This sorted list is not synchronized since it inherits from java.util.ArrayList. Use Collections.synchronizedList if you need this (refer to the Java documentation for java.util.ArrayList for details).
  • The initial solution was based on java.util.LinkedList. For better performance, specifically for finding the insertion point (Logan's comment) and quicker get operations (, this has been changed to java.util.ArrayList.

Can't import javax.servlet.annotation.WebServlet

Check that the version number of your servlet-api.jar is at least 3.0. There is a version number inside the jar in the META-INF/ file:

Implementation-Version: 3.0.1

If it's less than 3.0 download the 3.0.1 from Maven Central:|javax.servlet|javax.servlet-api|3.0.1|jar

Former servlet specifications (2.5, 2.4 etc.) do not support annotations.

SQL Server stored procedure parameters

SQL Server doesn't allow you to pass parameters to a procedure that you haven't defined. I think the closest you can get to this sort of design is to use optional parameters like so:

    @TaskName varchar(50),
    @ID int = NULL
-- SP Logic

You would need to include every possible parameter that you might use in the definition. Then you'd be free to call the procedure either way:

EXEC GetTaskEvents @TaskName = 'TESTTASK', @ID = 2;
EXEC GetTaskEvents @TaskName = 'TESTTASK'; -- @ID gets NULL here

Page redirect after certain time PHP

header( "refresh:5;url=wherever.php" );

indeed you can use this code as teneff said, but you don't have to necessarily put the header before any sent output (this would output a "cannot relocate header.... :3 error").

To solve this use the php function ob_start(); before any html is outputed.

To terminate the ob just put ob_end_flush(); after you don't have any html output.


Why do I need to override the equals and hashCode methods in Java?

Java puts a rule that

"If two objects are equal using Object class equals method, then the hashcode method should give the same value for these two objects."

So, if in our class we override equals() we should override hashcode() method also to follow this rule. Both methods, equals() and hashcode(), are used in Hashtable, for example, to store values as key-value pairs. If we override one and not the other, there is a possibility that the Hashtable may not work as we want, if we use such object as a key.

How to move screen without moving cursor in Vim?

I'm surprised no one is using the Scrolloff option which keeps the cursor in the middle of the page. Try it with:

:set so=999

It's the first recommended method on the Vim wiki and works well.

how to parse JSON file with GSON

You have to fetch the whole data in the list and then do the iteration as it is a file and will become inefficient otherwise.

private static final Type REVIEW_TYPE = new TypeToken<List<Review>>() {
Gson gson = new Gson();
JsonReader reader = new JsonReader(new FileReader(filename));
List<Review> data = gson.fromJson(reader, REVIEW_TYPE); // contains the whole reviews list
data.toScreen(); // prints to screen some values

How to set the size of button in HTML

button { 

or even

 button { 
    width:1000px !important

If thats what you mean

PHP with MySQL 8.0+ error: The server requested authentication method unknown to the client

You have to change MySQL settings. Edit my.cnf file and put this setting in mysqld section:

default_authentication_plugin= mysql_native_password

Then run following command:


Above command will bring into effect the changes of default authentication mechanism.

How can I pad a value with leading zeros?

just wanted to make the comment (but i don't have enough points) that the highest voted answer fails with negative numbers and decimals

function padNumber(n,pad) {
    p = Math.pow(10,pad);
    a = Math.abs(n);
    g = (n<0);
    return (a < p) ?  ((g ? '-' : '') + (p+a).toString().substring(1)) : n;

padNumber( -31.235, 5);


psql: server closed the connection unexepectedly

In my case I was making an connection through pgAdmin with ssh tunneling and set to host field ip address but it was necessary to set localhost

What is the purpose of shuffling and sorting phase in the reducer in Map Reduce Programming?

Well, In Mapreduce there are two important phrases called Mapper and reducer both are too important, but Reducer is mandatory. In some programs reducers are optional. Now come to your question. Shuffling and sorting are two important operations in Mapreduce. First Hadoop framework takes structured/unstructured data and separate the data into Key, Value.

Now Mapper program separate and arrange the data into keys and values to be processed. Generate Key 2 and value 2 values. This values should process and re arrange in proper order to get desired solution. Now this shuffle and sorting done in your local system (Framework take care it) and process in local system after process framework cleanup the data in local system. Ok

Here we use combiner and partition also to optimize this shuffle and sort process. After proper arrangement, those key values passes to Reducer to get desired Client's output. Finally Reducer get desired output.

K1, V1 -> K2, V2 (we will write program Mapper), -> K2, V' (here shuffle and soft the data) -> K3, V3 Generate the output. K4,V4.

Please note all these steps are logical operation only, not change the original data.

Your question: What is the purpose of shuffling and sorting phase in the reducer in Map Reduce Programming?

Short answer: To process the data to get desired output. Shuffling is aggregate the data, reduce is get expected output.

Singleton: How should it be used

The problem with singletons is not their implementation. It is that they conflate two different concepts, neither of which is obviously desirable.

1) Singletons provide a global access mechanism to an object. Although they might be marginally more threadsafe or marginally more reliable in languages without a well-defined initialization order, this usage is still the moral equivalent of a global variable. It's a global variable dressed up in some awkward syntax (foo::get_instance() instead of g_foo, say), but it serves the exact same purpose (a single object accessible across the entire program) and has the exact same drawbacks.

2) Singletons prevent multiple instantiations of a class. It's rare, IME, that this kind of feature should be baked into a class. It's normally a much more contextual thing; a lot of the things that are regarded as one-and-only-one are really just happens-to-be-only-one. IMO a more appropriate solution is to just create only one instance--until you realize that you need more than one instance.

Ruby function to remove all white spaces?

Also don't forget:

$ s = "   I have white space   ".split
=> ["I", "have", "white", "space"]

Django: Display Choice Value

For every field that has choices set, the object will have a get_FOO_display() method, where FOO is the name of the field. This method returns the “human-readable” value of the field.

In Views

person = Person.objects.filter(to_be_listed=True)
context['gender'] = person.get_gender_display()

In Template

{{ person.get_gender_display }}

Documentation of get_FOO_display()

How To limit the number of characters in JTextField?

If you wanna have everything into one only piece of code, then you can mix tim's answer with the example's approach found on the API for JTextField, and you'll get something like this:

public class JTextFieldLimit extends JTextField {
    private int limit;

    public JTextFieldLimit(int limit) {
        this.limit = limit;

    protected Document createDefaultModel() {
        return new LimitDocument();

    private class LimitDocument extends PlainDocument {

        public void insertString( int offset, String  str, AttributeSet attr ) throws BadLocationException {
            if (str == null) return;

            if ((getLength() + str.length()) <= limit) {
                super.insertString(offset, str, attr);



Then there is no need to add a Document to the JTextFieldLimit due to JTextFieldLimit already have the functionality inside.

Adding items to an object through the .push() method

.push() is a method of the Built-in Array Object

It is not related to jQuery in any way.

You are defining a literal Object with

// Object
var stuff = {};

You can define a literal Array like this

// Array
var stuff = [];



Arrays actually get their bracket syntax stuff[index] inherited from their parent, the Object. This is why you are able to use it the way you are in your first example.

This is often used for effortless reflection for dynamically accessing properties

stuff = {}; // Object

stuff['prop'] = 'value'; // assign property of an 
                         // Object via bracket syntax

stuff.prop === stuff['prop']; // true

How do you select a particular option in a SELECT element in jQuery?

Using jquery-2.1.4, I found the following answer to work for me:


If you have a string value try the following:

$('#MySelectionBox').val("extra thing").change();

Other examples did not work for me so that's why I'm adding this answer.

I found the original answer at:


UPDATE will not do anything if the row does not exist.

Where as the INSERT OR REPLACE would insert if the row does not exist, or replace the values if it does.

How to get the version of ionic framework?

Run from your project folder:

$ ionic info

Cordova CLI: 5.0.0
Ionic Version: 1.0.1
Ionic CLI Version: 1.6.1
Ionic App Lib Version: 0.3.3
OS: Windows 7 SP1
Node Version: v0.12.2

If your CLI is old enough, it will say "info is not a valid task" and you can use this:

$ ionic lib

Local Ionic version: 1.0.1  (C:\stuff\july21app\www\lib\ionic\version.json)
Latest Ionic version: 1.0.1  (released 2015-06-30)
* Local version up to date

How to get size in bytes of a CLOB column in Oracle?

I'm adding my comment as an answer because it solves the original problem for a wider range of cases than the accepted answer. Note: you must still know the maximum length and the approximate proportion of multi-byte characters that your data will have.

If you have a CLOB greater than 4000 bytes, you need to use DBMS_LOB.SUBSTR rather than SUBSTR. Note that the amount and offset parameters are reversed in DBMS_LOB.SUBSTR.

Next, you may need to substring an amount less than 4000, because this parameter is the number of characters, and if you have multi-byte characters then 4000 characters will be more than 4000 bytes long, and you'll get ORA-06502: PL/SQL: numeric or value error: character string buffer too small because the substring result needs to fit in a VARCHAR2 which has a 4000 byte limit. Exactly how many characters you can retrieve depends on the average number of bytes per character in your data.

So my answer is:


where you add as many chunks as you need to cover your longest CLOB, and adjust the chunk size according to average bytes-per-character of your data.

How do I use select with date condition?

Select * from Users where RegistrationDate >= CONVERT(datetime, '01/20/2009', 103)

is safe to use, independent of the date settings on the server.

The full list of styles can be found here.

Iframe positioning

you have to use this css property,


use it for your #contentframe div tag

Preventing SQL injection in Node.js

The node-mysql library automatically performs escaping when used as you are already doing. See

XSD - how to allow elements in any order any number of times?

This is what finally worked for me:

<xsd:element name="bar">
      <!--  Permit any of these tags in any order in any number     -->
      <xsd:choice minOccurs="0" maxOccurs="unbounded">
        <xsd:element name="child1" type="xsd:string" />
        <xsd:element name="child2" type="xsd:string" />
        <xsd:element name="child3" type="xsd:string" />

How do I output text without a newline in PowerShell?

Write-Host -NoNewline "Enabling feature XYZ......."

Location of sqlite database on the device

Do not hardcode path like //data/data/<Your-Application-Package-Name>/databases/<your-database-name>. Well it does work in most cases, but this one is not working in devices where device can support multiple users. The path can be like //data/user/10/<Your-Application-Package-Name>/databases/<your-database-name>. Possible solution to this is using context.getDatabasePath(<your-database-name>).

What's the meaning of System.out.println in Java?

System is a class in java.lang package. And out is a PrintStream object. Nice explanation @

What is the difference between Sublime text and Github's Atom

I'm working in little extreme environment; edit files on remote filesystem (external network, surely) that is mounted on my Laptop thru ssh(aka. sshfs). Regardless why I'm doing like this, also though its cumbersome responsiveness, it's fairly edible when I'm using Sublime Text 2.

I tried on Atom after reading this post, but it turned out to be somewhat painful to me; Atom seems that it doesn't cache directory structure so efficiently. Every time I expand a folder on Tree View, the UI froze for a short time, 2~3 seconds, maybe fetching file system info. Yes, it's because I'm using remote filesystem. But Sublime handles this more efficient, at least it doesn't freeze every time I expand a folder, so less painful.

I think Atom is hell nice for free, and my story is trivial that might be enhanced someday, but it would be helpful to someone at this time.


added on 8/26/2014

Recently, I changed my laptop from Macbook Air 2010 late to Macbook Pro 13" 2013 late. It has likely 4 times faster CPU and much enhancements in performance. I want to mention my opinion is about in the case WHEN YOU MOUNT REMOTE FILE SYSTEM. (using OS X Mavericks, most recent version of Atom, FUSE 2.7.3 / OSXFUSE 2.6.4 / sshfs 2.5.0, and remote system is Ubuntu server) Eventually, UI freeze gets pretty shorter, but it is still there. Specifically, to open a folder with many folder/files in it and index it is requires certain amount of time. Also, if you expand a folder full of files, it just falters. (when collapsing the folder, it doesn't)

According to @EliDuenisch , it seems not happen on Linux Mint. I'm not sure but it might be from difference between OSes. Surely, if you work on local file system, you don't have to care about this issue at all.

Get all files that have been modified in git branch

Update Nov 2020:

To get the list of files modified (and committed!) in the current branch you can use the shortest console command using standard git:

git diff --name-only master...

  • If your local "master" branch is outdated (behind the remote), add a remote name (assuming its "origin") git diff --name-only origin/master...

  • If you want to include uncommitted changes as well, remove the ...:

    git diff --name-only master

  • If you use different main branch name (eg: "main"), substitute it:

    git diff --name-only origin/main...

  • If your want to output to stdout (so its copyable)

    git diff --name-only master... | cat

per really nice detailed explanation of different options

Search and replace a particular string in a file using Perl

You could also do this:


use strict;
use warnings;

$^I = '.bak'; # create a backup copy 

while (<>) {
   s/<PREF>/ABCD/g; # do the replacement
   print; # print to the modified file

Invoke the script with by

./ input_file

You will get a file named input_file, containing your changes, and a file named input_file.bak, which is simply a copy of the original file.

Save and retrieve image (binary) from SQL Server using Entity Framework 6

Convert the image to a byte[] and store that in the database.

Add this column to your model:

public byte[] Content { get; set; }

Then convert your image to a byte array and store that like you would any other data:

public byte[] ImageToByteArray(System.Drawing.Image imageIn)
    using(var ms = new MemoryStream())
        imageIn.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);

        return ms.ToArray();

public Image ByteArrayToImage(byte[] byteArrayIn)
     using(var ms = new MemoryStream(byteArrayIn))
         var returnImage = Image.FromStream(ms);

         return returnImage;

Source: Fastest way to convert Image to Byte array

var image = new ImageEntity()
   Content = ImageToByteArray(image)


When you want to get the image back, get the byte array from the database and use the ByteArrayToImage and do what you wish with the Image

This stops working when the byte[] gets to big. It will work for files under 100Mb

How to detect input type=file "change" for the same file?

Probably the easiest thing you can do is set the value to an empty string. This forces it to 'change' the file each time even if the same file is selected again.

<input type="file" value="" />

Tomcat is web server or application server?

It runs Java compiled code, it can maintain database connection pools, it can log errors of various types. I'd call it an application server, in fact I do. In our environment we have Apache as the webserver fronting a number of different application servers, including Tomcat and Coldfusion, and others.

Can the Android drawable directory contain subdirectories?

Use assets folder.

sample code:

InputStream is = null;
try {
    is = this.getResources().getAssets().open("test/sample.png");
} catch (IOException e) {

image = BitmapFactory.decodeStream(is);

Adding a 'share by email' link to website

Something like this might be the easiest way.

<a href="mailto:?subject=I wanted you to see this site&amp;body=Check out this site"
   title="Share by Email">
  <img src="">

You could find another email image and add that if you wanted.

SQL Server "AFTER INSERT" trigger doesn't see the just-inserted row

Your "trigger" is doing something that a "trigger" is not suppose to be doing. You can simple have your Sql Server Agent run

WHERE ISNUMERIC(someField) = 1

every 1 second or so. While you're at it, how about writing a nice little SP to stop the programming folk from inserting errors into your table. One good thing about SP's is that the parameters are type safe.

Catch error if iframe src fails to load . Error :-"Refused to display '' in a frame.."

I faced similar problem. I solved it without using onload handler.I was working on AngularJs project so i used $interval and $ timeout. U can also use setTimeout and setInterval.Here's the code:

 var stopPolling;
 var doIframePolling;
 $scope.showIframe = true;
 doIframePolling = $interval(function () {
    if(document.getElementById('UrlIframe') && document.getElementById('UrlIframe').contentDocument.head && document.getElementById('UrlIframe').contentDocument.head.innerHTML != ''){
        doIframePolling = undefined;
        stopPolling = undefined;
        $scope.showIframe = true;

stopPolling = $timeout(function () {
        doIframePolling = undefined;
        stopPolling = undefined;
        $scope.showIframe = false;     

 $scope.$on("$destroy",function() {

Every 0.4 Seconds keep checking the head of iFrame Document. I somthing is present.Loading was not stopped by CORS as CORS error shows blank page. If nothing is present after 5 seconds there was some error (Cors policy) etc.. Show suitable message.Thanks. I hope it solves your problem.

Using PowerShell to remove lines from a text file if it contains a string

Suppose you want to write that in the same file, you can do as follows:

Set-Content -Path "C:\temp\Newtext.txt" -Value (get-content -Path "c:\Temp\Newtext.txt" | Select-String -Pattern 'H\|159' -NotMatch)

Refused to display in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'

Ran into this similar issue while using iframe to logout of sub sites with different domains. The solution I used was to load the iframe first, then update the source after the frame is loaded.

var frame = document.createElement('iframe');_x000D_ = 'none';_x000D_
frame.setAttribute('src', 'about:blank');_x000D_
frame.addEventListener('load', () => {_x000D_
  frame.setAttribute('src', url);_x000D_

React - how to pass state to another component

Move all of your state and your handleClick function from Header to your MainWrapper component.

Then pass values as props to all components that need to share this functionality.

class MainWrapper extends React.Component {
    constructor() {
        this.state = {
            sidbarPushCollapsed: false,
            profileCollapsed: false
        this.handleClick = this.handleClick.bind(this);
    handleClick() {
            sidbarPushCollapsed: !this.state.sidbarPushCollapsed,
            profileCollapsed: !this.state.profileCollapsed

    render() {
        return (
               profileCollapsed={this.state.profileCollapsed} />

Then in your Header's render() method, you'd use this.props:

<button type="button" id="sidbarPush" onClick={this.props.handleClick} profile={this.props.profileCollapsed}>

IsNothing versus Is Nothing

VB is full of things like that trying to make it both "like English" and comfortable for people who are used to languages that use () and {} a lot. And on the other side, as you already probably know, most of the time you can use () with function calls if you want to, but don't have to.

I prefer IsNothing()... but I use C and C#, so that's just what is comfortable. And I think it's more readable. But go with whatever feels more comfortable to you.

expand/collapse table rows with JQuery

using jQuery it's easy...

 $('YOUR CLASS SELECTOR').click(function(){


Failed loading english.pickle with

In Spyder, go to your active shell and download nltk using below 2 commands. import nltk Then you should see NLTK downloader window open as below, Go to 'Models' tab in this window and click on 'punkt' and download 'punkt'


Creating all possible k combinations of n items in C++

In Python, this is implemented as itertools.combinations

In C++, such combination function could be implemented based on permutation function.

The basic idea is to use a vector of size n, and set only k item to 1 inside, then all combinations of nchoosek could obtained by collecting the k items in each permutation. Though it might not be the most efficient way require large space, as combination is usually a very large number. It's better to be implemented as a generator or put working codes into do_sth().

Code sample:

#include <vector>
#include <iostream>
#include <iterator>
#include <algorithm>

using namespace std;

int main(void) {

  int n=5, k=3;

  // vector<vector<int> > combinations;
 vector<int> selected;
 vector<int> selector(n);
 fill(selector.begin(), selector.begin() + k, 1);
 do {
     for (int i = 0; i < n; i++) {
      if (selector[i]) {
     //     combinations.push_back(selected);
     copy(selected.begin(), selected.end(), ostream_iterator<int>(cout, " "));
     cout << endl;
 while (prev_permutation(selector.begin(), selector.end()));

  return 0;

and the output is

0 1 2 
0 1 3 
0 1 4 
0 2 3 
0 2 4 
0 3 4 
1 2 3 
1 2 4 
1 3 4 
2 3 4 

This solution is actually a duplicate with Generating combinations in c++

How to execute two mysql queries as one in PHP/MYSQL?

Update: Apparently possible by passing a flag to mysql_connect(). See Executing multiple SQL queries in one statement with PHP Nevertheless, any current reader should avoid using the mysql_-class of functions and prefer PDO.

You can't do that using the regular mysql-api in PHP. Just execute two queries. The second one will be so fast that it won't matter. This is a typical example of micro optimization. Don't worry about it.

For the record, it can be done using mysqli and the mysqli_multi_query-function.

How do I escape only single quotes?

I wrote the following function. It replaces the following:

Single quote ['] with a slash and a single quote [\'].

Backslash [\] with two backslashes [\\]

function escapePhpString($target) {
    $replacements = array(
            "'" => '\\\'',
            "\\" => '\\\\'
    return strtr($target, $replacements);

You can modify it to add or remove character replacements in the $replacements array. For example, to replace \r\n, it becomes "\r\n" => "\r\n" and "\n" => "\n".

 * With new line replacements too
function escapePhpString($target) {
    $replacements = array(
            "'" => '\\\'',
            "\\" => '\\\\',
            "\r\n" => "\\r\\n",
            "\n" => "\\n"
    return strtr($target, $replacements);

The neat feature about strtr is that it will prefer long replacements.

Example, "Cool\r\nFeature" will escape \r\n rather than escaping \n along.

How to iterate through a table rows and get the cell values using jQuery

Hello every one thanks for the help below is the working code for my question

$("#TableView tr.item").each(function() { 
    var quantity1=$(this).find("").val(); 
    var quantity2=$(this).find("").val(); 

Return HTTP status code 201 in flask

Ripping off Luc's comment here, but to return a blank response, like a 201 the simplest option is to use the following return in your route.

return "", 201

So for example:

    @app.route('/database', methods=["PUT"])
    def database():
        return "", 201

JavaScript window resize event

Never override the window.onresize function.

Instead, create a function to add an Event Listener to the object or element. This checks and incase the listeners don't work, then it overrides the object's function as a last resort. This is the preferred method used in libraries such as jQuery.

object: the element or window object
type: resize, scroll (event type)
callback: the function reference

var addEvent = function(object, type, callback) {
    if (object == null || typeof(object) == 'undefined') return;
    if (object.addEventListener) {
        object.addEventListener(type, callback, false);
    } else if (object.attachEvent) {
        object.attachEvent("on" + type, callback);
    } else {
        object["on"+type] = callback;

Then use is like this:

addEvent(window, "resize", function_reference);

or with an anonymous function:

addEvent(window, "resize", function(event) {

Setting up a JavaScript variable from Spring model by using Thymeleaf

If you need to display your variable unescaped, use this format:

<script th:inline="javascript">

    var message = /*[(${message})]*/ 'default';


Note the [( brackets which wrap the variable.

Why use Select Top 100 Percent?

No reason but indifference, I'd guess.

Such query strings are usually generated by a graphical query tool. The user joins a few tables, adds a filter, a sort order, and tests the results. Since the user may want to save the query as a view, the tool adds a TOP 100 PERCENT. In this case, though, the user copies the SQL into his code, parameterized the WHERE clause, and hides everything in a data access layer. Out of mind, out of sight.

Run on server option not appearing in Eclipse

I had a similar issue. The Maven projects have different structure than "Dynamic Web Projects". Eclipse knows only how to deploy the Dynamic Web Projects (project structure used by Web Tools Platform).

In order to solve this and tell Eclipse how to deploy a "maven style" projects, you have to install the M2E Eclipse WTP plugin (I suppose you are already using the m2e plugin).

To install: Preferences->Maven->Discovery->Open Catalog and choose the WTP plugin.

After reinstalling, you will be able to "run on server" those projects which are maven web projects.

Hope that helps,

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

Casting a Context object to an Activity object compiles fine.

Try this:

((Activity) mContext).getApplication(...)

CSS ''background-color" attribute not working on checkbox inside <div>

After so much trouble i got it.

.purple_checkbox:after {
  content: " ";
  background-color: #5C2799;
  display: inline-block;
  visibility: visible;

.purple_checkbox:checked:after {
  content: "\2714";
  box-shadow: 0px 2px 4px rgba(155, 155, 155, 0.15);
  border-radius: 3px;
  height: 12px;
  display: block;
  width: 12px;
  text-align: center;
  font-size: 9px;
  color: white;

It will be like this when checked with this code. enter image description here

What is "Connect Timeout" in sql server connection string?

How a connection works in a nutshell

A connection between a program and a database server relies on a handshake.

What this means is that when a connection is opened then the thread establishing the connection will send network packets to the database server. This thread will then pause until either network packets about this connection are received from the database server or when the connection timeout expires.

The connection timeout

The connection timeout is measured in seconds from the point the connection is opened.

When the timeout expires then the thread will continue, but it will do so having reported a connection failure.

  • If there is no value specified for connection timeout in the connection string then the default value is 30.

  • A value greater than zero means how many seconds before it gives up e.g. a value of 10 means to wait 10 seconds.

  • A value of 0 means to never give up waiting for the connection

Note: A value of 0 is not advised since it is possible for either the connection request packets or the server response packets to get lost. Will you seriously be prepared to wait even a day for a response that may never come?

What should I set my Connection Timeout value to?

This setting should depend on the speed of your network and how long you are prepared to allow a thread to wait for a response.

As an example, on a task that repeats hourly during the day, I know my network has always responded within one second so I set the connection timeout to a value of 2 just to be safe. I will then try again three times before giving up and either raising a support ticket or escalating a similar existing support ticket.

Test your own network speed and consider what to do when a connection fails as a one off, and also when it fails repeatedly and sporadically.

Trying Gradle build - "Task 'build' not found in root project"

You didn't do what you're being asked to do.

What is asked:

I have to execute ../gradlew build

What you do

cd ..
gradlew build

That's not the same thing.

The first one will use the gradlew command found in the .. directory (mdeinum...), and look for the build file to execute in the current directory, which is (for example) chapter1-bookstore.

The second one will execute the gradlew command found in the current directory (mdeinum...), and look for the build file to execute in the current directory, which is mdeinum....

So the build file executed is not the same.

How to center the content inside a linear layout?

Here's some sample code. This worked for me.


So you're designing the Linear Layout to place all its contents (TextView and Button) in its center, and then the TextView and Button are placed relative to the center of the Linear Layout.

Pandas/Python: Set value of one column based on value in another column

one way to do this would be to use indexing with .loc.


In the absence of an example dataframe, I'll make one up here:

import numpy as np
import pandas as pd

df = pd.DataFrame({'c1': list('abcdefg')})
df.loc[5, 'c1'] = 'Value'

>>> df
0      a
1      b
2      c
3      d
4      e
5  Value
6      g

Assuming you wanted to create a new column c2, equivalent to c1 except where c1 is Value, in which case, you would like to assign it to 10:

First, you could create a new column c2, and set it to equivalent as c1, using one of the following two lines (they essentially do the same thing):

df = df.assign(c2 = df['c1'])
# OR:
df['c2'] = df['c1']

Then, find all the indices where c1 is equal to 'Value' using .loc, and assign your desired value in c2 at those indices:

df.loc[df['c1'] == 'Value', 'c2'] = 10

And you end up with this:

>>> df
      c1  c2
0      a   a
1      b   b
2      c   c
3      d   d
4      e   e
5  Value  10
6      g   g

If, as you suggested in your question, you would perhaps sometimes just want to replace the values in the column you already have, rather than create a new column, then just skip the column creation, and do the following:

df['c1'].loc[df['c1'] == 'Value'] = 10
# or:
df.loc[df['c1'] == 'Value', 'c1'] = 10

Giving you:

>>> df
0      a
1      b
2      c
3      d
4      e
5     10
6      g

How to display an alert box from C# in ASP.NET?

After insertion code,

ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Record Inserted Successfully')", true);

Getting a timestamp for today at midnight?

You are looking to calculate the time of the most recent celestial event where the sun has passed directly below your feet, adjusted for local conventions of marking high noon and also potentially adjusting so that people have enough daylight left after returning home from work, and for other political considerations.

Daunting right? Actually this is a common problem but the complete answer is location-dependent:

$zone = new \DateTimeZone('America/New_York'); // Or your own definition of “here”
$todayStart = new \DateTime('today midnight', $zone);
$timestamp = $todayStart->getTimestamp();

Potential definitions of “here” are listed at

How do I change Bootstrap 3 column order on mobile layout?

October 2017

I would like to add another Bootstrap 4 solution. One that worked for me.

The CSS "Order" property, combined with a media query, can be used to re-order columns when they get stacked in smaller screens.

Something like this:

@media only screen and (max-width: 768px) {
    #first {
        order: 2;
    #second {
        order: 4;
    #third {
        order: 1;
    #fourth {
        order: 3;

CodePen Link:

Adjust the screen size and you'll see the columns get stacked in a different order.

I'll tie this in with the original poster's question. With CSS, the navbar, sidebar, and content can be targeted and then order properties applied within a media query.

C++ program converts fahrenheit to celsius

The answer has already been found although I would also like to share my answer:

int main(void)
using namespace std;

short tempC;
cout << "Please enter a Celsius value: ";
cin >> tempC;
double tempF = convert(tempC);
cout << tempC << " degrees Celsius is " << tempF << " degrees Fahrenheit." << endl;
return 0;


int convert(short nT)
return nT * 1.8 + 32;

This is a more proper way to do this; however, it is slightly more complex then what you were going for.

Connect different Windows User in SQL Server Management Studio (2005 or later)

The runas /netonly /user:domain\username program.exe command only worked for me on Windows 10

  • saving it as a batch file
  • running it as an administrator,

when running the command batch as regular user I got the wrong password issue mentioned by some users on previous comments.

In Python try until no error

Many different answers here but I used a combination of a few of the brilliant answers and threw in my own not-so-secret sauce to come up with the following recipe:

def actioin_one(self):
    action = # define attempted action here
    failure = bool(action.status_code != 200) # example ... replace this.
    self.attempt_action_repeatedly(action, 5, failure)

def action_two(self):
    action = # define attempted action here
    failure = bool(action.status_code != 200) # example ... replace this.
    self.attempt_action_repeatedly(action, 5, failure)

def attempt_action_repeatedly(self, action, authorized_attempts, failure):
    attempts = 0
    sleep_time = 2 # seconds
    more_attempts_left = bool(attempts < authorized_attempts)
    while failure and more_attempts_left:
        attempts += 1

    if not more_attempts_left:
        print("Max number of attempts exceeded. Attempts failed because:")
        data = action.json() # customize this 
        print(data['detail']) # customize this       

Couldn't load memtrack module Logcat Error

I had the same error. Creating a new AVD with the appropriate API level solved my problem.

How to launch PowerShell (not a script) from the command line

The color and window sizing are defined by the shortcut LNK file. I think I found a way that will do what you need, try this:

explorer.exe "Windows PowerShell.lnk"

The LNK file is in the all user start menu which is located in different places depending whether your on XP or Windows 7. In 7 the LNK file is here:

C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessories\Windows PowerShell

org.postgresql.util.PSQLException: FATAL: sorry, too many clients already

An explanation of the following error:

org.postgresql.util.PSQLException: FATAL: sorry, too many clients already.


You opened up more than the allowed limit of connections to the database. You ran something like this: Connection conn = myconn.Open(); inside of a loop, and forgot to run conn.close();. Just because your class is destroyed and garbage collected does not release the connection to the database. The quickest fix to this is to make sure you have the following code with whatever class that creates a connection:

protected void finalize() throws Throwable  
    try { your_connection.close(); } 
    catch (SQLException e) { 

Place that code in any class where you create a Connection. Then when your class is garbage collected, your connection will be released.

Run this SQL to see postgresql max connections allowed:

show max_connections;

The default is 100. PostgreSQL on good hardware can support a few hundred connections at a time. If you want to have thousands, you should consider using connection pooling software to reduce the connection overhead.

Take a look at exactly who/what/when/where is holding open your connections:

SELECT * FROM pg_stat_activity;

The number of connections currently used is:

SELECT COUNT(*) from pg_stat_activity;

Debugging strategy

  1. You could give different usernames/passwords to the programs that might not be releasing the connections to find out which one it is, and then look in pg_stat_activity to find out which one is not cleaning up after itself.

  2. Do a full exception stack trace when the connections could not be created and follow the code back up to where you create a new Connection, make sure every code line where you create a connection ends with a connection.close();

How to set the max_connections higher:

max_connections in the postgresql.conf sets the maximum number of concurrent connections to the database server.

  1. First find your postgresql.conf file
  2. If you don't know where it is, query the database with the sql: SHOW config_file;
  3. Mine is in: /var/lib/pgsql/data/postgresql.conf
  4. Login as root and edit that file.
  5. Search for the string: "max_connections".
  6. You'll see a line that says max_connections=100.
  7. Set that number bigger, check the limit for your postgresql version.
  8. Restart the postgresql database for the changes to take effect.

What's the maximum max_connections?

Use this query:

select min_val, max_val from pg_settings where name='max_connections';

I get the value 8388607, in theory that's the most you are allowed to have, but then a runaway process can eat up thousands of connections, and surprise, your database is unresponsive until reboot. If you had a sensible max_connections like 100. The offending program would be denied a new connection.

Windows batch: echo without new line

DIY cw.exe (console write) utility

If you don't find it out-of-the-box, off-the-shelf, you can DIY. With this cw utility you can use every kind of characters. At least, I'd like to think so. Please stress-test it and let me know.


All you need is .NET installed, which is very common nowadays.


Some characters typed/copy-pasted.


  1. Create .bat file with the following content.
/* >nul 2>&1

@echo off

set exe=cw
for /f "tokens=* delims=" %%v in ('dir /b /s /a:-d  /o:-n "%SystemRoot%\Microsoft.NET\Framework\*csc.exe"') do set "csc=%%v"

"%csc%" -nologo -out:"%exe%.exe" "%~f0"

exit /b %errorlevel%


using System;

namespace cw {
    class Program {
        static void Main() {
            var exe = Environment.GetCommandLineArgs()[0];
            var rawCmd = Environment.CommandLine;
            var line = rawCmd.Remove(rawCmd.IndexOf(exe),exe.Length).TrimStart('"');
            line = line.Length < 2 ? "\r" : line.Substring(2) ;
  1. Run it.

  2. Now you have a nice 4KB utility so you can delete the .bat.

Alternatively, you can insert this code as a subroutine in any batch, send the resulting .exe to %temp%, use it in your batch and delete it when you're done.

How to use

If you want write something without new line:
cw Whatever you want, even with "", but remember to escape ^|, ^^, ^&, etc. unless double-quoted, like in "| ^ &".

If you want a carriage return (going to the beginning of the line), run just

So try this from command line:

for /l %a in (1,1,1000) do @(cw ^|&cw&cw /&cw&cw -&cw&cw \&cw)

Avoid web.config inheritance in child web application using inheritInChildApplications

If (as I understand) you're trying to completely block inheritance in the web config of your child application, I suggest you to avoid using the tag in web.config. Instead create a new apppool and edit the applicationHost.config file (located in %WINDIR%\System32\inetsrv\Config and %WINDIR%\SysWOW64\inetsrv\config). You just have to find the entry for your apppool and add the attribute enableConfigurationOverride="false" like in the following example:

<add name="MyAppPool" autoStart="true" managedRuntimeVersion="v4.0" managedPipelineMode="Integrated" enableConfigurationOverride="false">
    <processModel identityType="NetworkService" />

This will avoid configuration inheritance in the applications served by MyAppPool.


Set value to currency in <input type="number" />

Add step="0.01" to the <input type="number" /> parameters:

<input type="number" min="0.01" step="0.01" max="2500" value="25.67" />


But the Dollar sign must stay outside the textbox... every non-numeric or separator charachter will be cropped automatically.

Otherwise you could use a classic textbox, like described here.

What is the difference between XML and XSD?



XSD OF ABOVE XML(Explained):

<xs:element name="school">
      <xs:element name="firstname" type="xs:string"/>
      <xs:element name="lastname" type="xs:string"/>


xs:element : Defines an element.

xs:sequence : Denotes child elements only appear in the order mentioned.

xs:complexType : Denotes it contains other elements.

xs:simpleType : Denotes they do not contain other elements.

type: string, decimal, integer, boolean, date, time,

  • In simple words, xsd is another way to represent and validate XML data with the specific type.
  • With the help of extra attributes, we can perform multiple operations.

  • Performing any task on xsd is simpler than xml.

Python: convert string from UTF-8 to Latin-1

Can you provide more details about what you are trying to do? In general, if you have a unicode string, you can use encode to convert it into string with appropriate encoding. Eg:

>>> a = u"\u00E1"
>>> type(a)
<type 'unicode'>
>>> a.encode('utf-8')
>>> a.encode('latin-1')

Read all contacts' phone numbers in android

Here's how to use ContentsContract API to fetch your contacts in your Phone Book. You'll need to add these permissions in your AndroidManifest.xml

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

Then, you can run this method to loop through all your contacts.

Here's an example to query fields like Name and Phone Number, you can configure yourself to use CommonDataKinds, it query other fields in your Contact.

private fun readContactsOnDevice() {
    val context = requireContext()
    if (ContextCompat.checkSelfPermission(
            context, Manifest.permission.WRITE_CONTACTS
        ) != PackageManager.PERMISSION_GRANTED &&
            context, Manifest.permission.READ_CONTACTS
        ) != PackageManager.PERMISSION_GRANTED
    ) {
            arrayOf(Manifest.permission.READ_CONTACTS, Manifest.permission.WRITE_CONTACTS), 1

    val contentResolver = context.contentResolver
    val contacts = contentResolver.query(
        null, null, null, null

    while (contacts?.moveToNext() == true) {
        val name = contacts.getString(
        val phoneNumber = contacts.getString(
        Timber.i("Name: $name, Phone Number: $phoneNumber")

Bootstrap 4 dropdown with search

As of version 1.13.1 there is support for Bootstrap 4:

The implementation remains exactly the same as it was in Bootstrap 3:

  • add class="selectpicker" and data-live-search="true"to your select
  • add data-tokens to your options. The live search will look into these data-token element when performing the search.

This is an example, taken from the site of the link above:

<select class="selectpicker" data-live-search="true">
  <option data-tokens="ketchup mustard">Hot Dog, Fries and a Soda</option>
  <option data-tokens="mustard">Burger, Shake and a Smile</option>
  <option data-tokens="frosting">Sugar, Spice and all things nice</option>

Live search for the search term 'fro' will only leave the third option visible (because of the data-tokens "frosting").

Don't forget to include the bootstrap-select CDN .css and .js in your project. I am very glad to see this live search become available again, because it comes in very handy when presenting large dropdown lists to the user.

Where are static variables stored in C and C++?

Where your statics go depends on whether they are zero-initialized. zero-initialized static data goes in .BSS (Block Started by Symbol), non-zero-initialized data goes in .DATA

Using IF ELSE statement based on Count to execute different Insert statements

If this is in SQL Server, your syntax is correct; however, you need to reference the COUNT(*) as the Total Count from your nested query. This should give you what you need:

  SELECT [Some Column], COUNT(*) TotalCount
  WHERE [Some Column] = 'Target Data'
  GROUP BY [Some Column]
) DerivedTable

Using this, you could assign TotalCount to a variable and then use an IF ELSE statement to execute your INSERT statements:

DECLARE @TotalCount int
SELECT @TotalCount = TotalCount FROM
  SELECT [Some Column], COUNT(*) TotalCount
  WHERE [Some Column] = 'Target Data'
  GROUP BY [Some Column]
) DerivedTable
IF @TotalCount > 0

Java NoSuchAlgorithmException - SunJSSE,$DefaultSSLContext

Well after doing some more searching I discovered the error may be related to other issues as invalid keystores, passwords etc.

I then remembered that I had set two VM arguments for when I was testing SSL for my network connectivity.

I removed the following VM arguments to fix the problem:

Note: this keystore no longer exists so that's probably why the Exception.

Linq on DataTable: select specific column into datatable, not whole table

Try Access DataTable easiest way which can help you for getting perfect idea for accessing DataTable, DataSet using Linq...

Consider following example, suppose we have DataTable like below.

DataTable ObjDt = new DataTable("List");
ObjDt.Columns.Add("WorkName", typeof(string));
ObjDt.Columns.Add("Price", typeof(decimal));
ObjDt.Columns.Add("Area", typeof(string));

Here above is the code for DatTable, here we assume that there are some data are available in this DataTable, and we have to bind Grid view of particular by processing some data as shown below.

Area | Quantity | Breath | Length | Price = Quantity * breath *Length

Than we have to fire following query which will give us exact result as we want.

var data = ObjDt.AsEnumerable().Select
            (r => new
                Area = r.Field<string>("Area"),
                Que = r.Field<int>("Quantity"),
                Breath = r.Field<decimal>("Breath"),
                Length = r.Field<decimal>("Length"),
                totLen = r.Field<int>("Quantity") * (r.Field<decimal>("Breath") * r.Field<decimal>("Length"))

We just have to assign this data variable as Data Source.

By using this simple Linq query we can get all our accepts, and also we can perform all other LINQ queries with this…

How to log PostgreSQL queries?

You also need add these lines in PostgreSQL and restart the server:

log_directory = 'pg_log'                    
log_filename = 'postgresql-dateformat.log'
log_statement = 'all'
logging_collector = on

Prevent screen rotation on Android

Use AsyncTaskLoader to keep your data safe even if the activity changes, instead of using AsyncTask that is a better way to build apps than preventing screen rotation.

HTML not loading CSS file

I have struggled with this same problem (Ubuntu 16.04, Bluefish editor, FireFox, Google Chrome.

Solution: Clear browsing data in Chrome "Settings > Advanced Settings > Clear Browsing Data", In Firefox, "Open Menu image top right tool bar 'Preferences' > Advanced ", look for this image in the menu: Cached Web Content click the button "Clear Now". Browser's cache the .css file and if it has not changed they usually won't reload it. So when you change your .css file clear this web cache and it should work unless a problem exists in your .css file. Peace, Stan

Reading an image file into bitmap from sdcard, why am I getting a NullPointerException?

Try this code:

Bitmap bitmap = null;
File f = new File(_path);
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
try {
    bitmap = BitmapFactory.decodeStream(new FileInputStream(f), null, options);
} catch (FileNotFoundException e) {

How to allow download of .json file with ASP.NET

When adding support for mimetype (as suggested by @ProVega) then it is also best practice to remove the type before adding it - this is to prevent unexpected errors when deploying to servers where support for the type already exists, for example:

    <remove fileExtension=".json" />
    <mimeMap fileExtension=".json" mimeType="application/json" />

keycloak Invalid parameter: redirect_uri

This error is also thrown when your User does not have the expected Role delegated in User definition(Set role for the Realm in drop down).

Difference between web reference and service reference?

The service reference is the newer interface for adding references to all manner of WCF services (they may not be web services) whereas Web reference is specifically concerned with ASMX web references.

You can access web references via the advanced options in add service reference (if I recall correctly).

I'd use service reference because as I understand it, it's the newer mechanism of the two.

Console errors. Failed to load resource: net::ERR_INSECURE_RESPONSE

I had this problem with chrome when I was working on a WordPress site. I added this code

$_SERVER['HTTPS'] = false;

into the theme's functions.php file - it asks you to log in again when you save the file but once it's logged in it works straight away.

Turn Pandas Multi-Index into column

As @cs95 mentioned in a comment, to drop only one level, use:


This avoids having to redefine your desired index after reset.

How to add "active" class to wp_nav_menu() current menu item (simple way)

If you want the 'active' in the html:

header with html and php:

        $menu_items = wp_get_nav_menu_items( 'main_nav' ); // id or name of menu
        foreach ( (array) $menu_items as $key => $menu_item ) {
            if ( ! $menu_item->menu_item_parent ) {
                echo "<li class=" . vince_check_active_menu($menu_item) . "><a href='$menu_item->url'>";
                echo $menu_item->title;
                echo "</a></li>";


function vince_check_active_menu( $menu_item ) {
    $actual_link = ( isset( $_SERVER['HTTPS'] ) ? "https" : "http" ) . "://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";
    if ( $actual_link == $menu_item->url ) {
        return 'active';
    return '';