Programs & Examples On #Qwidget

QWidget is key part of the Qt C++ classes. QWidget is the base class of all the user interface elements in the Qt framework.

"Field has incomplete type" error

The problem is that your ui property uses a forward declaration of class Ui::MainWindowClass, hence the "incomplete type" error.

Including the header file in which this class is declared will fix the problem.


Based on your comment, the following code:

namespace Ui
    class MainWindowClass;

does NOT declare a class. It's a forward declaration, meaning that the class will exist at some point, at link time.
Basically, it just tells the compiler that the type will exist, and that it shouldn't warn about it.

But the class has to be defined somewhere.

Note this can only work if you have a pointer to such a type.
You can't have a statically allocated instance of an incomplete type.

So either you actually want an incomplete type, and then you should declare your ui member as a pointer:

namespace Ui
    // Forward declaration - Class will have to exist at link time
    class MainWindowClass;

class MainWindow : public QMainWindow

        // Member needs to be a pointer, as it's an incomplete type
        Ui::MainWindowClass * ui;

Or you want a statically allocated instance of Ui::MainWindowClass, and then it needs to be declared. You can do it in another header file (usually, there's one header file per class).
But simply changing the code to:

namespace Ui
    // Real class declaration - May/Should be in a specific header file
    class MainWindowClass

class MainWindow : public QMainWindow

        // Member can be statically allocated, as the type is complete
        Ui::MainWindowClass ui;

will also work.

Note the difference between the two declarations. First uses a forward declaration, while the second one actually declares the class (here with no properties nor methods).

How to use QTimer

Other way is using of built-in method start timer & event TimerEvent.



#include <QMainWindow>

namespace Ui {
class MainWindow;

class MainWindow : public QMainWindow

    explicit MainWindow(QWidget *parent = 0);

    Ui::MainWindow *ui;
    int timerId;

    void timerEvent(QTimerEvent *event);

#endif // MAINWINDOW_H


#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
    ui(new Ui::MainWindow)

    timerId = startTimer(1000);

    delete ui;

void MainWindow::timerEvent(QTimerEvent *event)
    qDebug() << "Update...";

Error: expected type-specifier before 'ClassName'

First of all, let's try to make your code a little simpler:

// No need to create a circle unless it is clearly necessary to
// demonstrate the problem

// Your Rect2f defines a default constructor, so let's use it for simplicity.
shared_ptr<Shape> rect(new Rect2f());

Okay, so now we see that the parentheses are clearly balanced. What else could it be? Let's check the following code snippet's error:

int main() {
    delete new T();

This may seem like weird usage, and it is, but I really hate memory leaks. However, the output does seem useful:

In function 'int main()':
Line 2: error: expected type-specifier before 'T'

Aha! Now we're just left with the error about the parentheses. I can't find what causes that; however, I think you are forgetting to include the file that defines Rect2f.

How to make a Qt Widget grow with the window size?

I found it was impossible to assign a layout to the centralwidget until I had added at least one child beneath it. Then I could highlight the tiny icon with the red 'disabled' mark and then click on a layout in the Designer toolbar at top.

grid controls for ASP.NET MVC?

We use Slick Grid in Stack Exchange Data Explorer (example containing 2000 rows).

I found it outperforms jqGrid and flexigrid. It has a very complete feature set and I could not recommend it enough.

Samples of its usage are here.

You can see source samples on how it is integrated to an ASP.NET MVC app here:

How to return temporary table from stored procedure


In your stored procedure, you fill the table @tbRetour.

At the very end of your stored procedure, you write:

SELECT * FROM @tbRetour 

To execute the stored procedure, you write:

USE [...]

DECLARE @return_value int

EXEC @return_value = [dbo].[getEnregistrementWithDetails]
@id_enregistrement_entete = '(guid)'


document.getElementById("remember").visibility = "hidden"; not working on a checkbox

you can use



<asp:TextBox ID="txbProv" runat="server" style="display:none"></asp:TextBox>

Append an empty row in dataframe using pandas

The code below worked for me.

df.append(pd.Series([np.nan]), ignore_index = True)

making a paragraph in html contain a text from a file

You'll want to use either JavaScript or a server-side language like PHP, ASP...etc

(supposedly can be done with HTML <embed> tag, which makes sense, but I haven't used, since PHP...etc is so simple/common)

Javascript can work: Here's a link to someone doing something similar via javascript on stackoverflow: How do I load the contents of a text file into a javascript variable?

PHP (as example of server-side language) is the easiest way to go though:

<div><p><?php include('myFile.txt'); ?></p></div>

To use this (if you're unfamiliar with PHP), you can:

1) check if you have php on your server

2) change the file extension of your .html file to .php

3) paste the code from my PHP example somewhere in the body of your newly-renamed PHP file

install / uninstall APKs programmatically (PackageManager vs Intents)

If you're using Kotlin, API 14+, and just wish to show uninstall dialog for your app:

startActivity(Intent(Intent.ACTION_UNINSTALL_PACKAGE).apply {
    data = Uri.parse("package:$packageName")

You can change packageName to any other package name if you want to prompt the user to uninstall another app on the device

VSCode: How to Split Editor Vertically

Press CMD + SHIFT + P (MAC) and search for Toggle Editor Group

Is it possible to have multiple statements in a python lambda expression?

to demonstrate the lambda x:[f1(),f2()] effect which enables us to execute multiple functions in lambda. it also demonstrates the single line if else conditions if you really want to shrink the code.

  • note that f1() can be a lambda function also(recursive lambda or lambda within lambda). and that inner lambda can be a statement/function of your choice.
  • you can also put exec('statement') for example lambda x:[exec('a=[1]'),exec('b=2')]

a python implementation of touch(linux) command which creates empty files if they are not already existing.

def touch(fpath):
    check= os.path.exists(fpath)
    (lambda fname1:[open(fname1,"w+",errors="ignore").write(""),print('Touched',fname1)] 
    if not check else None) (fpath)

will print [ Touched fpath ] where fpath is file path given as input. will do nothing if file already exist.

the (lambda x: [ f(x), f2(x) ] ) (inp) <- we pass the 'inp' as input to lambda which in this case is the fpath.

How to download a folder from github?

Dependency: cURL and 7-Zip.

curl {url for downloading zip file} | 7z a -tzip {project name}-{branch name}/{folder path in that branch}

for example:

curl | 7z a -tzip flutter_shimmer-master/examples

Delete all rows in an HTML table

I needed to delete all rows except the first and solution posted by @strat but that resulted in uncaught exception (referencing Node in context where it does not exist). The following worked for me.

var myTable = document.getElementById("myTable");
var rowCount = myTable.rows.length;
for (var x=rowCount-1; x>0; x--) {

How to split a dos path into its components in Python

For a somewhat more concise solution, consider the following:

def split_path(p):
    a,b = os.path.split(p)
    return (split_path(a) if len(a) and len(b) else []) + [b]

Difference between static STATIC_URL and STATIC_ROOT on Django

STATICFILES_DIRS: You can keep the static files for your project here e.g. the ones used by your templates.

STATIC_ROOT: leave this empty, when you do collectstatic, it will search for all the static files on your system and move them here. Your static file server is supposed to be mapped to this folder wherever it is located. Check it after running collectstatic and you'll find the directory structure django has built.


As pointed out by @DarkCygnus, STATIC_ROOT should point at a directory on your filesystem, the folder should be empty since it will be populated by Django.

STATIC_ROOT = os.path.join(BASE_DIR, 'staticfiles')


STATIC_ROOT = '/opt/web/project/static_files'

--------End Edit -----------------

STATIC_URL: '/static/' is usually fine, it's just a prefix for static files.

How do I remove documents using Node.js Mongoose?

This for me is the best as of version 3.8.1:

MyModel.findOneAndRemove({field: 'newValue'}, function(err){...});

And it requires only one DB call. Use this given that you don't perform any remove actions pior to the search and removal.

How to show all rows by default in JQuery DataTable


    aLengthMenu: [
        [25, 50, 100, 200, -1],
        [25, 50, 100, 200, "All"]
    iDisplayLength: -1

Or if using 1.10+

    paging: false

The option you should use is iDisplayLength:

  'iDisplayLength': 100

   "lengthMenu": [ [5, 10, 25, 50, -1], [5, 10, 25, 50, "All"] ]

It will Load by default all entries.

    aLengthMenu: [
        [25, 50, 100, 200, -1],
        [25, 50, 100, 200, "All"]
    iDisplayLength: -1

Or if using 1.10+

    paging: false

If you want to load by default 25 not all do this.

    aLengthMenu: [
        [25, 50, 100, 200, -1],
        [25, 50, 100, 200, "All"]

Dealing with multiple Python versions and PIP?

On Windows, you can execute the pip module using a given Python version through the Python launcher, py.exe, if you chose to install it during Python 3 setup.

py -3 -m pip install packagename
py -2 -m pip install packagename

You can be even more specific and request an exact sub-version of Python:

py -3.6 -m pip install packagename

To get a list of all installed Python versions available through the launcher, run:

py --list

Alternatively, you can launch the desired Python executable directly:

C:/path/to/specific/python.exe -m pip install packagename

Refresh Excel VBA Function Results

If you include ALL references to the spreadsheet data in the UDF parameter list, Excel will recalculate your function whenever the referenced data changes:

Public Function doubleMe(d As Variant)
    doubleMe = d * 2
End Function

You can also use Application.Volatile, but this has the disadvantage of making your UDF always recalculate - even when it does not need to because the referenced data has not changed.

Public Function doubleMe()
    doubleMe = Worksheets("Fred").Range("A1") * 2
End Function

C++ inheritance - inaccessible base?

You have to do this:

class Bar : public Foo
    // ...

The default inheritance type of a class in C++ is private, so any public and protected members from the base class are limited to private. struct inheritance on the other hand is public by default.

Converting String to "Character" array in Java

One liner with :

String str = "testString";

//[t, e, s, t, S, t, r, i, n, g]
Character[] charObjectArray = 
    str.chars().mapToObj(c -> (char)c).toArray(Character[]::new); 

What it does is:

  • get an IntStream of the characters (you may want to also look at codePoints())
  • map each 'character' value to Character (you need to cast to actually say that its really a char, and then Java will box it automatically to Character)
  • get the resulting array by calling toArray()

Pip install - Python 2.7 - Windows 7

I've seen this issue before with 2.7.14. Fixed it by :

  1. Re-install python 2.7.14
  2. During the installation, select default path and put a check mark in the installation options to add python to windows path i.e. environmental variables.
  3. After installation is complete, go to System from the Control Panel, select Advanced system settings, and clicking Environment Variables.
  4. Verify that the system variable "path" has "C:\Python\;C:\Python\Scripts;" added to the list.
  5. In cmd, run "where python" and then "where pip". Which will show for example:

    ? where python
    ? where pip
  6. Run pip, then it should show different pip run command options.

Dictionary with list of strings as value

To do this manually, you'd need something like:

List<string> existing;
if (!myDic.TryGetValue(key, out existing)) {
    existing = new List<string>();
    myDic[key] = existing;
// At this point we know that "existing" refers to the relevant list in the 
// dictionary, one way or another.

However, in many cases LINQ can make this trivial using ToLookup. For example, consider a List<Person> which you want to transform into a dictionary of "surname" to "first names for that surname". You could use:

var namesBySurname = people.ToLookup(person => person.Surname,
                                     person => person.FirstName);

How to access the local Django webserver from outside world

For AWS users.

I had to use the following steps to get there.

1) Ensure that pip and django are installed at the sudo level

  • sudo apt-get install python-pip
  • sudo pip install django

2) Ensure that security group in-bound rules includ http on port 80 for

  • configured through AWS console

3) Add Public IP and DNS to ALLOWED_HOSTS

  • ALLOWED_HOSTS is a list object that you can find in
  • ALLOWED_HOSTS = ["",""]

4) Launch development server with sudo on port 80

  • sudo python runserver 0:80

Site now available at either of the following (no need for :80 as that is default for http):

  • [Public DNS] i.e.
  • [Public IP] i.e

How do I quickly rename a MySQL database (change schema name)?

I posted this How do I change the database name using MySQL? today after days of head scratching and hair pulling. The solution is quite simple export a schema to a .sql file and open the file and change the database/schema name in the sql CREAT TABLE section at the top. There are three instances or more and may not be at the top of the page if multible schemas are saved to the file. It is posible to edit the entire database this way but I expect that in large databases it could be quite a pain following all instances of a table property or index.

Make a div fill up the remaining width

Flex-boxes are the solution - and they're fantastic. I've been wanting something like this out of css for a decade. All you need is to add display: flex to your style for "Main" and flex-grow: 100 (where 100 is arbitrary - its not important that it be exactly 100). Try adding this style (colors added to make the effect visible):

    #Main {
        background-color: lightgray;
        display: flex;

    #div1 {
        border: 1px solid green;   
        height: 50px; 
        display: inline-flex; 
    #div2 {
        border: 1px solid blue;    
        height: 50px;
        display: inline-flex;
        flex-grow: 100;
    #div3 {
        border: 1px solid orange;        
        height: 50px;
        display: inline-flex;

More info about flex boxes here:

Using PropertyInfo to find out the property type

Use PropertyInfo.PropertyType to get the type of the property.

public bool ValidateData(object data)
    foreach (PropertyInfo propertyInfo in data.GetType().GetProperties())
        if (propertyInfo.PropertyType == typeof(string))
            string value = propertyInfo.GetValue(data, null);

            if value is not OK
                return false;

    return true;

HTTPS setup in Amazon EC2

This answer is focused to someone that buy a domain in another site (as GoDaddy) and want to use the Amazon free certificate with Certificate Manager

This answer uses Amazon Classic Load Balancer (paid) see the pricing before using it

Step 1 - Request a certificate with Certificate Manager

Go to Certificate Manager > Request Certificate > Request a public certificate

On Domain name you will add and * and go on Next

Chose Email validation and Confirm and Request

Open the email that you have received (on the email account that you have buyed the domain) and aprove the request

After this, check if the validation status of and * is sucess, if is sucess you can continue to Step 2

Step 2 - Create a Security Group to a Load Balancer

On EC2 go to Security Groups > and Create a Security Group and add the http and https inbound

It will be something like: enter image description here

Step 3 - Create the Load Balancer

EC2 > Load Balancer > Create Load Balancer > Classic Load Balancer (Third option)

Create LB inside - the vpc of your project On Load Balancer Protocol add Http and Https enter image description here

Next > Select exiting security group

Choose the security group that you have create in the previous step

Next > Choose certificate from ACM

Select the certificate of the step 1

Next >

on Health check i've used the ping path / (one slash instead of /index.html)

Step 4 - Associate your instance with the security group of load balancer

EC2 > Instances > click on your project > Actions > Networking > Change Security Groups

Add the Security Group of your Load Balancer

Step 5

EC2 > Load Balancer > Click on the load balancer that you have created > copy the DNS Name (A Record), it will be something like

Go to Route 53 > Routes Zones > click on the domain name > Go to Records Sets (If you are don't have your domain here, create a hosted zone with Domain Name: and Type: Public Hosted Zone)

Check if you have a record type A (probably not), create/edit record set with name empty, type A, alias Yes and Target the dns that you have copied

Create also a new Record Set of type A, name *, alias Yes and Target your domain ( This will make possible access your site with and Note: You will need to configure your reverse proxy (Nginx/Apache) to do so.

On NS copy the 4 Name Servers values to use on the next Step, it will be something like:

Go to EC2 > Instances > And copy the IPv4 Public IP too

Step 6

On the domain register site that you have buyed the domain (in my case GoDaddy)

Change the routing to http : <Your IPv4 Public IP Number> and select Forward with masking

Change the Name Servers (NS) to the 4 NS that you have copied, this can take 48 hours to make effect

Change GitHub Account username

Yes, it's possible. But first read, "What happens when I change my username?"

To change your username, click your profile picture in the top right corner, then click Settings. On the left side, click Account. Then click Change username.

Using "label for" on radio buttons

(Firstly read the other answers which has explained the for in the <label></label> tags. Well, both the tops answers are correct, but for my challenge, it was when you have several radio boxes, you should select for them a common name like name="r1" but with different ids id="r1_1" ... id="r1_2"

So this way the answer is more clear and removes the conflicts between name and ids as well.

You need different ids for different options of the radio box.

<input type="radio" name="r1" id="r1_1" />_x000D_
       <label for="r1_1">button text one</label>_x000D_
       <input type="radio" name="r1" id="r1_2" />_x000D_
       <label for="r1_2">button text two</label>_x000D_
       <input type="radio" name="r1" id="r1_3" />_x000D_
       <label for="r1_3">button text three</label>

PostgreSQL wildcard LIKE for any of a list of words

All currently supported versions (9.5 and up) allow pattern matching in addition to LIKE.


How to find indices of all occurrences of one string in another in JavaScript?

function countInString(searchFor,searchIn){

 var results=0;
 var a=searchIn.indexOf(searchFor)


return results;


Is there a way to create xxhdpi, xhdpi, hdpi, mdpi and ldpi drawables from a large scale image?

I use a tool called Android Icon Set in the Eclipse for standard icons like Launcher, ActionBar, Tab icons and notification icons. You can launch it from File --> New --> Other.. --> Android --> Android Icon Set. The best part is that you can choose any file from your computer and it will automatically place all the images of standard sizes into your project directory.

enter image description here

ProcessStartInfo hanging on "WaitForExit"? Why?

I think with async, it is possible to have a more elegant solution and not having deadlocks even when using both standardOutput and standardError:

using (Process process = new Process())
    process.StartInfo.FileName = filename;
    process.StartInfo.Arguments = arguments;
    process.StartInfo.UseShellExecute = false;
    process.StartInfo.RedirectStandardOutput = true;
    process.StartInfo.RedirectStandardError = true;


    var tStandardOutput = process.StandardOutput.ReadToEndAsync();
    var tStandardError = process.StandardError.ReadToEndAsync();

    if (process.WaitForExit(timeout))
        string output = await tStandardOutput;
        string errors = await tStandardError;

        // Process completed. Check process.ExitCode here.
        // Timed out.

It is base on Mark Byers answer. If you are not in an async method, you can use string output = tStandardOutput.result; instead of await

Inline CSS styles in React: how to implement a:hover?

Late to party but come with solution. You can use "&" to defines styles for hover nth Child etc:

day: {
    display: "flex",
    flex: "1",
    justifyContent: "center",
    alignItems: "center",
    width: "50px",
    height: "50px",
    transition: "all 0.2s",
    borderLeft: "solid 1px #cccccc",

    "&:hover": {
      background: "#efefef"
    "&:last-child": {
      borderRight: "solid 1px #cccccc"

how to set ASPNETCORE_ENVIRONMENT to be considered for publishing an core application?

With the latest version of dotnet cli (2.1.400 or greater), you can just set this msbuild property $(EnvironmentName) and publish tooling will take care of adding ASPNETCORE_ENVIRONMENT to the web.config with the environment name.

Also, XDT support is available starting 2.2.100-preview1.


What is the difference between a heuristic and an algorithm?

Heuristics are algorithms, so in that sense there is none, however, heuristics take a 'guess' approach to problem solving, yielding a 'good enough' answer, rather than finding a 'best possible' solution.

A good example is where you have a very hard (read NP-complete) problem you want a solution for but don't have the time to arrive to it, so have to use a good enough solution based on a heuristic algorithm, such as finding a solution to a travelling salesman problem using a genetic algorithm.

SimpleXML - I/O warning : failed to load external entity

simplexml_load_file() interprets an XML file (either a file on your disk or a URL) into an object. What you have in $feed is a string.

You have two options:

  • Use file_get_contents() to get the XML feed as a string, and use e simplexml_load_string():

    $feed = file_get_contents('...');
    $items = simplexml_load_string($feed);
  • Load the XML feed directly using simplexml_load_file():

    $items = simplexml_load_file('...');

How to indent a few lines in Markdown markup?

Check if you can use HTML with your markdown. Maybe this works out for you:

  • List entry one<br/>
    Indented line<br/>
    And some more..
  • Second entry
    • Subentry<br/>
      Hello there!

Find row where values for column is maximal in a pandas DataFrame

The direct ".argmax()" solution does not work for me.

The previous example provided by @ely

>>> import pandas
>>> import numpy as np
>>> df = pandas.DataFrame(np.random.randn(5,3),columns=['A','B','C'])
>>> df
      A         B         C
0  1.232853 -1.979459 -0.573626
1  0.140767  0.394940  1.068890
2  0.742023  1.343977 -0.579745
3  2.125299 -0.649328 -0.211692
4 -0.187253  1.908618 -1.862934
>>> df['A'].argmax()
>>> df['B'].argmax()
>>> df['C'].argmax()

returns the following message :

FutureWarning: 'argmax' is deprecated, use 'idxmax' instead. The behavior of 'argmax' 
will be corrected to return the positional maximum in the future.
Use 'series.values.argmax' to get the position of the maximum now.

So that my solution is :


Changing user agent on urllib2.urlopen

there are two properties of urllib.URLopener() namely:
addheaders = [('User-Agent', 'Python-urllib/1.17'), ('Accept', '*/*')] and
version = 'Python-urllib/1.17'.
To fool the website you need to changes both of these values to an accepted User-Agent. for e.g.
Chrome browser : 'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.149 Safari/537.36'
Google bot : 'Googlebot/2.1'
like this

import urllib
page_extractor.addheaders = [('User-Agent', 'Googlebot/2.1'), ('Accept', '*/*')]  
page_extractor.version = 'Googlebot/2.1'
page_extractor.retrieve(<url>, <file_path>)

changing just one property does not work because the website marks it as a suspicious request.

Jackson overcoming underscores in favor of camel-case

There are few answers here indicating both strategies for 2 different versions of Jackson library below:

For Jackson 2.6.*

ObjectMapper objMapper = new ObjectMapper(new JsonFactory()); // or YAMLFactory()

For Jackson 2.7.*

ObjectMapper objMapper = new ObjectMapper(new JsonFactory()); // or YAMLFactory()

Modifying CSS class property values on the fly with JavaScript / jQuery

Use jquery to add a style override in the <head>:

$('<style>.someClass {color: red;} input::-webkit-outer-spin-button: {display: none;}</style>')

SQLSTATE[HY000] [2002] Connection refused within Laravel homestead

The only thing that solved it for me was to put the connection details in config/database.php instead of the .env file. Hope this helps

Temporarily change current working directory in bash to run a command

You can run the cd and the executable in a subshell by enclosing the command line in a pair of parentheses:

(cd SOME_PATH && exec_some_command)


$ pwd
$ (cd /tmp && pwd)  # directory changed in the subshell
$ pwd               # parent shell's pwd is still the same

Why docker container exits immediately

Coming from duplicates, I don't see any answer here which addresses the very common antipattern of running your main workload as a background job, and then wondering why Docker exits.

In simple terms, if you have

my-main-thing &

then either take out the & to run the job in the foreground, or add


at the end of the script to make it wait for all background jobs.

It will then still exit if the main workload exits, so maybe run this in a while true loop to force it to restart forever:

while true; do
    my-main-thing &
    other things which need to happen while the main workload runs in the background
    maybe if you have such things

(Notice also how to write while true. It's common to see silly things like while [ true ] or while [ 1 ] which coincidentally happen to work, but don't mean what the author probably imagined they ought to mean.)

div inside table

You can't put a div directly inside a table, like this:

<!-- INVALID -->
    Hello World

Putting a div inside a td or th element is fine, however:

<!-- VALID -->
        Hello World

Accessing clicked element in angularjs

While AngularJS allows you to get a hand on a click event (and thus a target of it) with the following syntax (note the $event argument to the setMaster function; documentation here:

function AdminController($scope) {    
  $scope.setMaster = function(obj, $event){

this is not very angular-way of solving this problem. With AngularJS the focus is on the model manipulation. One would mutate a model and let AngularJS figure out rendering.

The AngularJS-way of solving this problem (without using jQuery and without the need to pass the $event argument) would be:

<div ng-controller="AdminController">
    <ul class="list-holder">
        <li ng-repeat="section in sections" ng-class="{active : isSelected(section)}">
            <a ng-click="setMaster(section)">{{}}</a>
    {{selected | json}}

where methods in the controller would look like this:

$scope.setMaster = function(section) {
    $scope.selected = section;

$scope.isSelected = function(section) {
    return $scope.selected === section;

Here is the complete jsFiddle:

How to declare an array inside MS SQL Server Stored Procedure?

Great question and great idea, but in SQL you'll need to do this:

For data type datetime, something like this-

declare @BeginDate    datetime = '1/1/2016',
        @EndDate      datetime = '12/1/2016'
create table #months (dates datetime)
declare @var datetime = @BeginDate
   while @var < dateadd(MONTH, +1, @EndDate)
          insert into #months Values(@var)
          set @var = Dateadd(MONTH, +1, @var)

If all you really want is numbers, do this-

create table #numbas (digit int)
declare @var int = 1        --your starting digit
    while @var <= 12        --your ending digit
        insert into #numbas Values(@var)
        set @var = @var +1

How to implement HorizontalScrollView like Gallery?

Here is my layout:

        android:paddingTop="@dimen/padding" >

        android:layout_marginTop="10dp" >

And I populate it in the code with dynamic check-boxes.

How can a web application send push notifications to iOS devices?

Pushbullet is a great alternative for this.

However the user needs to have a Pushbullet account and the app installed (iOS, Android) or plugin installed (Chrome, Opera, Firefox and Windows).

You can use the API by creating a Pushbullet app, and connect your application's user to the Pushbullet user using oAuth2.

Using a library would make it much easier, for PHP I could recommend ivkos/Pushbullet-for-PHP.

android: changing option menu items programmatically

To disable certain items:

MenuItem item = menu.findItem(;

Could not find method compile() for arguments Gradle

Wrong gradle file. The right one is build.gradle in your 'app' folder.

@font-face not working

Not sure exactly what your problem is, but try the following:

  1. Do the font files exist?
  2. Do you need quotes around the URLs?
  3. Are you using a CSS3-enabled browser?

Check here for examples, if they don't work for you then you have another problem


You have a bunch of repeated declarations in your source, does this work?

@font-face { font-family: Gotham; src: url('../fonts/gothammedium.eot'); }

a { font-family:Gotham,Verdana,Arial; }

Change value of input placeholder via model?

You can bind with a variable in the controller:

<input type="text" ng-model="inputText" placeholder="{{somePlaceholder}}" />

In the controller:

$scope.somePlaceholder = 'abc';

C++ String Concatenation operator<<

nametext is an std::string but these do not have the stream insertion operator (<<) like output streams do.

To concatenate strings you can use the append member function (or its equivalent, +=, which works in the exact same way) or the + operator, which creates a new string as a result of concatenating the previous two.

Call Javascript function from URL/address bar

There isn't from a hyperlink, no. Not unless the page has script inside specifically for this and it's checking for some parameter....but for your question, no, there's no built-in support in browsers for this.

There are however bookmarklets you can bookmark to quickly run JavaScript functions from your address bar; not sure if that meets your needs, but it's as close as it gets.

Sum of values in an array using jQuery

You can use reduce which works in all browser except IE8 and lower.

["20","40","80","400"].reduce(function(a, b) {
    return parseInt(a, 10) + parseInt(b, 10);

HTML button opening link in new tab

Try this code.

<input type="button" value="Open Window"

Boto3 Error: botocore.exceptions.NoCredentialsError: Unable to locate credentials

Make sure your ~/.aws/credentials file in Unix looks like this:

aws_access_key_id = yourAccessId
aws_secret_access_key = yourSecretKey

aws_access_key_id = yourAccessId
aws_secret_access_key = yourSecretKey

Your Python script should look like this, and it'll work:

from __future__ import print_function
import boto3
import os

os.environ['AWS_PROFILE'] = "MyProfile1"
os.environ['AWS_DEFAULT_REGION'] = "us-east-1"

ec2 = boto3.client('ec2')

# Retrieves all regions/endpoints that work with EC2
response = ec2.describe_regions()
print('Regions:', response['Regions'])


TypeError: got multiple values for argument

This happens when a keyword argument is specified that overwrites a positional argument. For example, let's imagine a function that draws a colored box. The function selects the color to be used and delegates the drawing of the box to another function, relaying all extra arguments.

def color_box(color, *args, **kwargs):
    painter.draw_box(*args, **kwargs)

Then the call

color_box("blellow", color="green", height=20, width=30)

will fail because two values are assigned to color: "blellow" as positional and "green" as keyword. (painter.draw_box is supposed to accept the height and width arguments).

This is easy to see in the example, but of course if one mixes up the arguments at call, it may not be easy to debug:

# misplaced height and width
color_box(20, 30, color="green")

Here, color is assigned 20, then args=[30] and color is again assigned "green".

How to replace NA values in a table for selected columns

this works fine for me

DataTable DT = new DataTable();

DT = DT.AsEnumerable().Select(R =>
      R["Campo1"] = valor;
      return (R);

Passing just a type as a parameter in C#

You can do this, just wrap it in typeof()


public void GetColumnValues(Type type)

Reading and writing environment variables in Python?

Try using the os module.

import os

os.environ['DEBUSSY'] = '1'
os.environ['FSDB'] = '1'

# Open child processes via os.system(), popen() or fork() and execv()

someVariable = int(os.environ['DEBUSSY'])

See the Python docs on os.environ. Also, for spawning child processes, see Python's subprocess docs.

Test if string is URL encoded in PHP

i have one trick :

you can do this to prevent doubly encode. Every time first decode then again encode;

$string = urldecode($string);

Then do again

$string = urlencode($string);

Performing this way we can avoid double encode :)

T-SQL - function with default parameters

you have to call it like this

SELECT dbo.CheckIfSFExists(23, default)

From Technet:

When a parameter of the function has a default value, the keyword DEFAULT must be specified when the function is called in order to retrieve the default value. This behaviour is different from using parameters with default values in stored procedures in which omitting the parameter also implies the default value. An exception to this behaviour is when invoking a scalar function by using the EXECUTE statement. When using EXECUTE, the DEFAULT keyword is not required.

PDO closing connection

According to documentation you're correct (

The connection remains active for the lifetime of that PDO object. To close the connection, you need to destroy the object by ensuring that all remaining references to it are deleted--you do this by assigning NULL to the variable that holds the object. If you don't do this explicitly, PHP will automatically close the connection when your script ends.

Note that if you initialise the PDO object as a persistent connection it will not automatically close the connection.

How do I install a color theme for IntelliJ IDEA 7.0.x

Take a look here: Third Party Add-ons

You may have to extract the jar using a zip application. Hopefully inside you'll find a collection of XML files.

IntelliJ IDEA Plugins

How to unmount, unrender or remove a component, from itself in a React/Redux/Typescript notification message

I've been to this post about 10 times now and I just wanted to leave my two cents here. You can just unmount it conditionally.

if (renderMyComponent) {
  <MyComponent props={...} />

All you have to do is remove it from the DOM in order to unmount it.

As long as renderMyComponent = true, the component will render. If you set renderMyComponent = false, it will unmount from the DOM.

Can I give the col-md-1.5 in bootstrap?

According to Rex Bloom response I have write a bootstrap helper:

//8,33333333% col-1

.extra-col {
  position: relative;
  width: 100%;
  padding-right: 15px;
  padding-left: 15px;

.col-0-5 {
  @extend .extra-col;
  flex: 0 0 4.16666667%;
  max-width: 4.16666667%;

.col-1-5 {
  @extend .extra-col;
  flex: 0 0 12.5%;
  max-width: 12.5%;

.col-2-5 {
  @extend .extra-col;
  flex: 0 0 20.833333325%;
  max-width: 20.833333325%;

.col-3-5 {
  @extend .extra-col;
  flex: 0 0 29.166666655%;
  max-width: 29.166666655%;

.col-4-5 {
  @extend .extra-col;
  flex: 0 0 37.499999985%;
  max-width: 37.499999985%;

.col-5-5 {
  @extend .extra-col;
  flex: 0 0 45.833333315%;
  max-width: 45.833333315%;

.col-6-5 {
  @extend .extra-col;
  flex: 0 0 54.166666645%;
  max-width: 54.166666645%;

.col-7-5 {
  @extend .extra-col;
  flex: 0 0 62.499999975%;
  max-width: 62.499999975%;

.col-8-5 {
  @extend .extra-col;
  flex: 0 0 70.833333305%;
  max-width: 70.833333305%;

.col-9-5 {
  @extend .extra-col;
  flex: 0 0 79.166666635%;
  max-width: 79.166666635%;

.col-10-5 {
  @extend .extra-col;
  flex: 0 0 87.499999965%;
  max-width: 87.499999965%;

.col-11-5 {
  @extend .extra-col;
  flex: 0 0 95.8333333%;
  max-width: 95.8333333%;

Get sum of MySQL column in PHP

$query = "SELECT * FROM tableName";
$query_run = mysql_query($query);

$qty= 0;
while ($num = mysql_fetch_assoc ($query_run)) {
    $qty += $num['ColumnName'];
echo $qty;

Android: Align button to bottom-right of screen using FrameLayout?

Actually it's possible, despite what's being said in other answers. If you have a FrameLayout, and want to position a child item to the bottom, you can use android:layout_gravity="bottom" and that is going to align that child to the bottom of the FrameLayout.

I know it works because I'm using it. I know is late, but it might come handy to others since this ranks in the top positions on google

round a single column in pandas

You are very close. You applied the round to the series of values given by df.value1. The return type is thus a Series. You need to assign that series back to the dataframe (or another dataframe with the same Index).

Also, there is a pandas.Series.round method which is basically a short hand for pandas.Series.apply(np.round).

    df.value1 = df.value1.round()
    print df

    item  value1  value2
    0    a       1     1.3
    1    a       2     2.5
    2    a       0     0.0
    3    b       3    -1.0
    4    b       5    -1.0

Display string multiple times

The accepted answer is short and sweet, but here is an alternate syntax allowing to provide a separator in Python 3.x.

print(*3*('-',), sep='_')

Adding a module (Specifically pymorph) to Spyder (Python IDE)

just use '!' before the pip command in spyder terminal and it will be fine


!pip install imutils

Counting number of characters in a file through shell script

This will do it:

wc -c filename

If you want only the count without the filename being repeated in the output:

wc -c < filename


Use -m to count character instead of bytes (as shown in Sébastien's answer).

Android: Background Image Size (in Pixel) which Support All Devices

The following are the best dimensions for the app to run in all devices. For understanding multiple supporting screens you have to read

xxxhdpi: 1280x1920 px
xxhdpi: 960x1600 px
xhdpi: 640x960 px
hdpi: 480x800 px
mdpi: 320x480 px
ldpi: 240x320 px

How to debug JavaScript / jQuery event bindings with Firebug or similar tools?

jQuery stores events in the following:


Doing a console.log($("a#somefoo").data("events")) should list the events attached to that element.

Get current cursor position in a textbox

Here's one possible method.

function isMouseInBox(e) {
  var textbox = document.getElementById('textbox');

  // Box position & sizes
  var boxX = textbox.offsetLeft;
  var boxY = textbox.offsetTop;
  var boxWidth = textbox.offsetWidth;
  var boxHeight = textbox.offsetHeight;

  // Mouse position comes from the 'mousemove' event
  var mouseX = e.pageX;
  var mouseY = e.pageY;
  if(mouseX>=boxX && mouseX<=boxX+boxWidth) {
    if(mouseY>=boxY && mouseY<=boxY+boxHeight){
       // Mouse is in the box
       return true;

document.addEventListener('mousemove', function(e){

Calling a function within a Class method?

class test {
    public newTest(){

    private  function bigTest(){
        //Big Test Here

    private function smallTest(){
       //Small Test Here

    public scoreTest(){
      //Scoring code here;

Accessing Imap in C#

I've been searching for an IMAP solution for a while now, and after trying quite a few, I'm going with AE.Net.Mail.

You can download the code by going to the Code tab and click the small 'Download' icon. As the author does not provide any pre-built downloads, you must compile it yourself. (I believe you can get it through NuGet though). There is no longer a .dll in the bin/ folder.

There is no documentation, which I consider a downside, but I was able to whip this up by looking at the source code (yay for open source!) and using Intellisense. The below code connects specifically to Gmail's IMAP server:

// Connect to the IMAP server. The 'true' parameter specifies to use SSL
// which is important (for Gmail at least)
ImapClient ic = new ImapClient("", "[email protected]", "pass",
                ImapClient.AuthMethods.Login, 993, true);
// Select a mailbox. Case-insensitive
// Get the first *11* messages. 0 is the first message;
// and it also includes the 10th message, which is really the eleventh ;)
// MailMessage represents, well, a message in your mailbox
MailMessage[] mm = ic.GetMessages(0, 10);
foreach (MailMessage m in mm)
// Probably wiser to use a using statement

Make sure you checkout the Github page for the newest version and some better code examples.

Query an object array using linq


using System.Linq;

to the top of your file.

And then:

Car[] carList = ...
var carMake = 
    from item in carList
    where item.Model == "bmw" 
    select item.Make;

or if you prefer the fluent syntax:

var carMake = carList
    .Where(item => item.Model == "bmw")
    .Select(item => item.Make);

Things to pay attention to:

  • The usage of item.Make in the select clause instead if s.Make as in your code.
  • You have a whitespace between item and .Model in your where clause

HTTP status code 0 - Error Domain=NSURLErrorDomain?

CORS in my case.

I had such response in a iOS app once. The solution was the missing Access-Control-Allow-Origin: * in the headers.


C char array initialization

This is not how you initialize an array, but for:

  1. The first declaration:

    char buf[10] = "";

    is equivalent to

    char buf[10] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
  2. The second declaration:

    char buf[10] = " ";

    is equivalent to

    char buf[10] = {' ', 0, 0, 0, 0, 0, 0, 0, 0, 0};
  3. The third declaration:

    char buf[10] = "a";

    is equivalent to

    char buf[10] = {'a', 0, 0, 0, 0, 0, 0, 0, 0, 0};

As you can see, no random content: if there are fewer initializers, the remaining of the array is initialized with 0. This the case even if the array is declared inside a function.

Scala vs. Groovy vs. Clojure


Scala evolved out of a pure functional language known as Funnel and represents a clean-room implementation of almost all Java's syntax, differing only where a clear improvement could be made or where it would compromise the functional nature of the language. Such differences include singleton objects instead of static methods, and type inference.

Much of this was based on Martin Odersky's prior work with the Pizza language. The OO/FP integration goes far beyond mere closures and has led to the language being described as post-functional.

Despite this, it's the closest to Java in many ways. Mainly due to a combination of OO support and static typing, but also due to a explicit goal in the language design that it should integrate very tightly with Java.


Groovy explicitly tackles two of Java's biggest criticisms by

  • being dynamically typed, which removes a lot of boilerplate and
  • adding closures to the language.

It's perhaps syntactically closest to Java, not offering some of the richer functional constructs that Clojure and Scala provide, but still offering a definite evolutionary improvement - especially for writing script-syle programs.

Groovy has the strongest commercial backing of the three languages, mostly via springsource.


Clojure is a functional language in the LISP family, it's also dynamically typed.

Features such as STM support give it some of the best out-of-the-box concurrency support, whereas Scala requires a 3rd-party library such as Akka to duplicate this.

Syntactically, it's also the furthest of the three languages from typical Java code.

I also have to disclose that I'm most acquainted with Scala :)

Scraping html tables into R data frames using the XML package

Another option using Xpath.


theurl <- ""
webpage <- getURL(theurl)
webpage <- readLines(tc <- textConnection(webpage)); close(tc)

pagetree <- htmlTreeParse(webpage, error=function(...){}, useInternalNodes = TRUE)

# Extract table header and contents
tablehead <- xpathSApply(pagetree, "//*/table[@class='wikitable sortable']/tr/th", xmlValue)
results <- xpathSApply(pagetree, "//*/table[@class='wikitable sortable']/tr/td", xmlValue)

# Convert character vector to dataframe
content <-, ncol = 8, byrow = TRUE))

# Clean up the results
content[,1] <- gsub(" ", "", content[,1])
tablehead <- gsub(" ", "", tablehead)
names(content) <- tablehead

Produces this result

> head(content)
   Opponent Played Won Drawn Lost Goals for Goals against % Won
1 Argentina     94  36    24   34       148           150 38.3%
2  Paraguay     72  44    17   11       160            61 61.1%
3   Uruguay     72  33    19   20       127            93 45.8%
4     Chile     64  45    12    7       147            53 70.3%
5      Peru     39  27     9    3        83            27 69.2%
6    Mexico     36  21     6    9        69            34 58.3%

How to apply a low-pass or high-pass filter to an array in Matlab?

You can design a lowpass Butterworth filter in runtime, using butter() function, and then apply that to the signal.

fc = 300; % Cut off frequency
fs = 1000; % Sampling rate

[b,a] = butter(6,fc/(fs/2)); % Butterworth filter of order 6
x = filter(b,a,signal); % Will be the filtered signal

Highpass and bandpass filters are also possible with this method. See

How to have conditional elements and keep DRY with Facebook React's JSX?

As already mentioned in the answers, JSX presents you with two options

  • Ternary operator

    { this.state.price ? <div>{this.state.price}</div> : null }

  • Logical conjunction

    { this.state.price && <div>{this.state.price}</div> }

However, those don't work for price == 0.

JSX will render the false branch in the first case and in case of logical conjunction, nothing will be rendered. If the property may be 0, just use if statements outside of your JSX.

NameError: name 'self' is not defined

For cases where you also wish to have the option of setting 'b' to None:

def p(self, **kwargs):
    b = kwargs.get('b', self.a)
    print b

How do I get a decimal value when using the division operator in Python?

Add the following function in your code with its callback.

# Starting of the function
def divide(number_one, number_two, decimal_place = 4):
    quotient = number_one/number_two
    remainder = number_one % number_two
    if remainder != 0:
        quotient_str = str(quotient)
        for loop in range(0, decimal_place):
            if loop == 0:
                quotient_str += "."
            surplus_quotient = (remainder * 10) / number_two
            quotient_str += str(surplus_quotient)
            remainder = (remainder * 10) % number_two
            if remainder == 0:
        return float(quotient_str)
        return quotient
#Ending of the function

# Calling back the above function
# Structure : divide(<divident>, <divisor>, <decimal place(optional)>)
divide(1, 7, 10) # Output : 0.1428571428
# OR
divide(1, 7) # Output : 0.1428

This function works on the basis of "Euclid Division Algorithm". This function is very useful if you don't want to import any external header files in your project.

Syntex : divide([divident], [divisor], [decimal place(optional))

Code : divide(1, 7, 10) OR divide(1, 7)

Comment below for any queries.

PostgreSQL column 'foo' does not exist

It could be quotes themselves that are the entire problem. I had a similar problem and it was due to quotes around the column name in the CREATE TABLE statement. Note there were no whitespace issues, just quotes causing problems.

The column looked like it was called anID but was really called "anID". The quotes don't appear in typical queries so it was hard to detect (for this postgres rookie). This is on postgres 9.4.1

Some more detail:

Doing postgres=# SELECT * FROM test; gave:

  anID | value 
     1 | hello
     2 | baz
     3 | foo (3 rows)

but trying to select just the first column SELECT anID FROM test; resulted in an error:

ERROR:  column "anid" does not exist 

Just looking at the column names didn't help: postgres=# \d test;

          Table "public.test"
 Column |       Type        | Modifiers 
 anID   | integer           | not null
 value  | character varying | 
    "PK on ID" PRIMARY KEY, btree ("anID")

but in pgAdmin if you click on the column name and look in the SQL pane it populated with:

ALTER TABLE test ADD COLUMN "anID" integer;

and lo and behold there are the quoutes around the column name. So then ultimately postgres=# select "anID" FROM test; works fine:

(3 rows)

Same moral, don't use quotes.

Is there a difference between PhoneGap and Cordova commands?

This first choice might be a confusing one but it’s really very simple. PhoneGap is a product owned by Adobe which currently includes additional build services, and it may or may not eventually offer additional services and/or charge payments for use in the future. Cordova is owned and maintained by Apache, and will always be maintained as an open source project. Currently they both have a very similar API. I would recommend going with Cordova, unless you require the additional PhoneGap build services.

How do I compare two variables containing strings in JavaScript?

instead of using the == sign, more safer use the === sign when compare, the code that you post is work well

Min/Max-value validators in mvc

jQuery Validation Plugin already implements min and max rules, we just need to create an adapter for our custom attribute:

public class MaxAttribute : ValidationAttribute, IClientValidatable
    private readonly int maxValue;

    public MaxAttribute(int maxValue)
        this.maxValue = maxValue;

    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
        var rule = new ModelClientValidationRule();

        rule.ErrorMessage = ErrorMessageString, maxValue;

        rule.ValidationType = "max";
        rule.ValidationParameters.Add("max", maxValue);
        yield return rule;

    public override bool IsValid(object value)
        return (int)value <= maxValue;


   function (options) {
       options.rules['max'] = parseInt(options.params['max'], 10);
       options.messages['max'] = options.message;

Min attribute would be very similar. error in opening zip file

I've seen this exception before when whatever the JVM considers to be a temp directory is not accessible due to not being there or not having permission to write.

CSS transition with visibility not working

Visibility is an animatable property according to the spec, but transitions on visibility do not work gradually, as one might expect. Instead transitions on visibility delay hiding an element. On the other hand making an element visible works immediately. This is as it is defined by the spec (in the case of the default timing function) and as it is implemented in the browsers.

This also is a useful behavior, since in fact one can imagine various visual effects to hide an element. Fading out an element is just one kind of visual effect that is specified using opacity. Other visual effects might move away the element using e.g. the transform property, also see

It is often useful to combine the opacity transition with a visibility transition! Although opacity appears to do the right thing, fully transparent elements (with opacity:0) still receive mouse events. So e.g. links on an element that was faded out with an opacity transition alone, still respond to clicks (although not visible) and links behind the faded element do not work (although being visible through the faded element). See

This strange behavior can be avoided by just using both transitions, the transition on visibility and the transition on opacity. Thereby the visibility property is used to disable mouse events for the element while opacity is used for the visual effect. However care must be taken not to hide the element while the visual effect is playing, which would otherwise not be visible. Here the special semantics of the visibility transition becomes handy. When hiding an element the element stays visible while playing the visual effect and is hidden afterwards. On the other hand when revealing an element, the visibility transition makes the element visible immediately, i.e. before playing the visual effect.

How to protect Excel workbook using VBA?

  1. in your sample code you must remove the brackets, because it's not a functional assignment; also for documentary reasons I would suggest you use the := notation (see code sample below)

    1. Application.Thisworkbook refers to the book containing the VBA code, not necessarily the book containing the data, so be cautious.

Express the sheet you're working on as a sheet object and pass it, together with a logical variable to the following sub:

Sub SetProtectionMode(MySheet As Worksheet, ProtectionMode As Boolean)

    If ProtectionMode Then
        MySheet.Protect DrawingObjects:=True, Contents:=True, _
                        AllowSorting:=True, AllowFiltering:=True
    End If
End Sub

Within the .Protect method you can define what you want to allow/disallow. This code block will switch protection on/off - without password in this example, you can add it as a parameter or hardcoded within the Sub. Anyway somewhere the PW will be hardcoded. If you don't want this, just call the Protection Dialog window and let the user decide what to do:


Hope that helps

Good luck - MikeD

Using Font Awesome icon for bullet points, with a single list item element

I'd like to build upon some of the answers above and given elsewhere and suggest using absolute positioning along with the :before pseudo class. A lot of the examples above (and in similar questions) are utilizing custom HTML markup, including Font Awesome's method of handling. This goes against the original question, and isn't strictly necessary.


ul {
  list-style-type: none;
  padding-left: 20px;

li {
  position: relative;
  padding-left: 20px;
  margin-bottom: 10px

li:before {
  position: absolute;
  top: 0;
  left: 0;
  font-family: FontAwesome;
  content: "\f058";
  color: green;

That's basically it. You can get the ISO value for use in CSS content on the Font Awesome cheatsheet. Simply use the last 4 alphanumerics prefixed with a backslash. So [&#xf058;] becomes \f058

Access parent DataContext from DataTemplate

I was searching how to do something similar in WPF and I got this solution:

<ItemsControl ItemsSource="{Binding MyItems,Mode=OneWay}">
        <StackPanel Orientation="Vertical" />
            Command="{Binding Path=DataContext.CustomCommand, 
                        RelativeSource={RelativeSource Mode=FindAncestor,      
                        AncestorType={x:Type ItemsControl}} }"
            CommandParameter="{Binding}" />

I hope this works for somebody else. I have a data context which is set automatically to the ItemsControls, and this data context has two properties: MyItems -which is a collection-, and one command 'CustomCommand'. Because of the ItemTemplate is using a DataTemplate, the DataContext of upper levels is not directly accessible. Then the workaround to get the DC of the parent is use a relative path and filter by ItemsControl type.

MySQL search and replace some text in a field

In my experience, the fastest method is

UPDATE table_name SET field = REPLACE(field, 'foo', 'bar') WHERE field LIKE '%foo%';

The INSTR() way is the second-fastest and omitting the WHERE clause altogether is slowest, even if the column is not indexed.

SQL Query to find missing rows between two related tables






Please note that these queries do not require that ABC_ID be in table B at all. I think that does what you want.

SQL Query - how do filter by null or not null

set ansi_nulls off go select * from table t inner join otherTable o on t.statusid = o.statusid go set ansi_nulls on go

Creating a new directory in C

You can use mkdir:

$ man 2 mkdir

#include <sys/stat.h>
#include <sys/types.h>

int result = mkdir("/home/me/test.txt", 0777);

Unable to cast object of type 'System.DBNull' to type 'System.String`

This is the generic method that I use to convert any object that might be a DBNull.Value:

public static T ConvertDBNull<T>(object value, Func<object, T> conversionFunction)
    return conversionFunction(value == DBNull.Value ? null : value);


var result = command.ExecuteScalar();

return result.ConvertDBNull(Convert.ToInt32);


return command

Javascript to check whether a checkbox is being checked or unchecked

I am not sure what the problem is, but I am pretty sure this will fix it.

for (i=0; i<arrChecks.length; i++)
        var attribute = arrChecks[i].getAttribute("xid")
        if (attribute == elementName)
            if (arrChecks[i].checked == 0)  
                arrChecks[i].checked = 1;
            } else {
                arrChecks[i].checked = 0;

        } else {
            arrChecks[i].checked = 0;

Align an element to bottom with flexbox

You can use display: flex to position an element to the bottom, but I do not think you want to use flex in this case, as it will affect all of your elements.

To position an element to the bottom using flex try this:

.container {
  display: flex;

.button {
  align-self: flex-end;

Your best bet is to set position: absolute to the button and set it to bottom: 0, or you can place the button outside the container and use negative transform: translateY(-100%) to bring it in the container like this:

.content {
    height: 400px;
    background: #000;
    color: #fff;
.button {
    transform: translateY(-100%);
    display: inline-block;

Check this JSFiddle

How to manually set an authenticated user in Spring Security / SpringMVC

I couldn't find any other full solutions so I thought I would post mine. This may be a bit of a hack, but it resolved the issue to the above problem:

public void login(HttpServletRequest request, String userName, String password)

    UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(userName, password);

    // Authenticate the user
    Authentication authentication = authenticationManager.authenticate(authRequest);
    SecurityContext securityContext = SecurityContextHolder.getContext();

    // Create a new session and add the security context.
    HttpSession session = request.getSession(true);
    session.setAttribute("SPRING_SECURITY_CONTEXT", securityContext);

CodeIgniter removing index.php from url

Step 1 => Place your .htaccess file in root folder where application and system folders exist.

Step 2 => If your web path using sub-folder like - - then use following code in htaccess file

RewriteEngine on
RewriteBase    /project/
RewriteCond $1 !^(index\.php|images|robots\.txt)
RewriteRule ^(.*)$ /project/index.php/$1 [L]

If your web path using root-folder like - - then use following code in htaccess file

RewriteEngine on
RewriteBase    /
RewriteCond $1 !^(index\.php|images|robots\.txt)
RewriteRule ^(.*)$ /index.php/$1 [L]

How do I set the default Java installation/runtime (Windows)?

I have several JDK (1.4, 1.5, 1.6) installed in C:\Java with their JREs. Then I let Sun update the public JRE in C:\Program Files\Java.
Lately there is an improvement, installing in jre6. Previously, there was a different folder per new version (1.5.0_4, 1.5.0_5, etc.), which was taking lot of space

Dockerfile if else condition with external arguments

Exactly as others told, shell script would help.

Just an additional case, IMHO it's worth mentioning (for someone else who stumble upon here, looking for an easier case), that is Environment replacement.

Environment variables (declared with the ENV statement) can also be used in certain instructions as variables to be interpreted by the Dockerfile.

The ${variable_name} syntax also supports a few of the standard bash modifiers as specified below:

  • ${variable:-word} indicates that if variable is set then the result will be that value. If variable is not set then word will be the result.

  • ${variable:+word} indicates that if variable is set then word will be the result, otherwise the result is the empty string.

Use of var keyword in C#

If you know the type, use the type. If you don't know the type, why not? If you can't know the type, that's okay -- you've found the only valid use.

And I'm sorry, but if the best you can do is "it makes the code all line up", that's not a good answer. Find a different way to format your code.

Unable to start debugging on the web server. Could not start ASP.NET debugging VS 2010, II7, Win 7 x64

I had this error come up today due to a defect in code that was posting back a tremendous amount of times causing IIS to be flooded with requests. This essentially locked up IIS and so when I tried to debug, it 'timed out' trying to start the debugger. I simply restarted IIS, which took a few minutes, and it solved the issue.

I sure do wish this error was less generic, seems like there are several different ways to produce it.

jQuery hide and show toggle div with plus and minus icon

this works:


.show_hide {
.plus:after {
    content:" +";
.minus:after {
    content:" -";




<a href="#" class="show_hide">Show/hide</a>

<div class="slidingDiv" style="display: block;">
Check out the updated jQuery plugin for doing this: <a href="" class="show_hide" target="_blank" style="display: inline;">jQuery Show / Hide Plugin</a>

in the CSS, instead of content:" +"; You can put an background-image (with background-position:right center; and background-repeat:no-repeat and maybe making the .show_hide displayed as block and give him a width, so that the bg-image is not overlayed by the link-text itself).

Split files using tar, gz, zip, or bzip2

If you are splitting from Linux, you can still reassemble in Windows.

copy /b file1 + file2 + file3 + file4 filetogether

Why maven settings.xml file is not there?

I also underwent the same issue as Maven doesn't create the settings.xml file under .m2 folder. What I did was the following and it works smoothly without any issues.

Go to the location where you maven was unzipped.

Direct to following path,

\apache-maven-3.0.4\conf\ and copy the settings.xml file and paste it inside your .m2 folder.

Now create a maven project.

'0000-00-00 00:00:00' can not be represented as java.sql.Timestamp error

Instead of using fake dates like 0000-00-00 00:00:00 or 0001-01-01 00:00:00 (the latter should be accepted as it is a valid date), change your database schema, to allow NULL values.


How to do this using jQuery - document.getElementById("selectlist").value

In some cases of which I can't remember why but $('#selectlist').val() won't always return the correct item value, so I use $('#selectlist option:selected').val() instead.

C# - How to convert string to char?

Your question is a bit unclear, but I think you want (requires using System.Linq;):

var result = yourArrayOfStrings.SelectMany(s => s).ToArray();

Another solution is:

var result = string.Concat(yourArrayOfStrings).ToCharArray();

HTML if image is not found

For the alternative, if the image doesn't exist - show nothing at all. (what I was looking for)

You can swap the function from Robby Shaw's answer in the "onerror" attribute to "this.remove()".

<img id="currentPhoto" src="SomeImage.jpg" alt='1' width="100" height="120">_x000D_
<img id="currentPhoto" src="SomeImage.jpg" onerror="this.onerror=null; this.remove();" alt="2" width="100" height="120">

Resize image with javascript canvas (smoothly)

You can use down-stepping to achieve better results. Most browsers seem to use linear interpolation rather than bi-cubic when resizing images.

(Update There has been added a quality property to the specs, imageSmoothingQuality which is currently available in Chrome only.)

Unless one chooses no smoothing or nearest neighbor the browser will always interpolate the image after down-scaling it as this function as a low-pass filter to avoid aliasing.

Bi-linear uses 2x2 pixels to do the interpolation while bi-cubic uses 4x4 so by doing it in steps you can get close to bi-cubic result while using bi-linear interpolation as seen in the resulting images.

var canvas = document.getElementById("canvas");_x000D_
var ctx = canvas.getContext("2d");_x000D_
var img = new Image();_x000D_
img.onload = function () {_x000D_
    // set size proportional to image_x000D_
    canvas.height = canvas.width * (img.height / img.width);_x000D_
    // step 1 - resize to 50%_x000D_
    var oc = document.createElement('canvas'),_x000D_
        octx = oc.getContext('2d');_x000D_
    oc.width = img.width * 0.5;_x000D_
    oc.height = img.height * 0.5;_x000D_
    octx.drawImage(img, 0, 0, oc.width, oc.height);_x000D_
    // step 2_x000D_
    octx.drawImage(oc, 0, 0, oc.width * 0.5, oc.height * 0.5);_x000D_
    // step 3, resize to final size_x000D_
    ctx.drawImage(oc, 0, 0, oc.width * 0.5, oc.height * 0.5,_x000D_
    0, 0, canvas.width, canvas.height);_x000D_
img.src = "//";
<img src="//" width="300" height="234">_x000D_
<canvas id="canvas" width=300></canvas>

Depending on how drastic your resize is you can might skip step 2 if the difference is less.

In the demo you can see the new result is now much similar to the image element.

Android Emulator sdcard push error: Read-only file system

Android studio version 0.8.9 and above has a bug creating AVDs.

See Issue 78434.


  • go to your ADV folder in .android folder and find your AVD config.ini
  • open it with a text editor that can handle unix newlines. (Notepad will run the lines together since they don't have CR-LFs.)
  • change hw.sdCard=no to hw.sdCard=yes

this should work for everyone in new builds

Define global variable with webpack

There are several way to approach globals:

  1. Put your variables in a module.

Webpack evaluates modules only once, so your instance remains global and carries changes through from module to module. So if you create something like a globals.js and export an object of all your globals then you can import './globals' and read/write to these globals. You can import into one module, make changes to the object from a function and import into another module and read those changes in a function. Also remember the order things happen. Webpack will first take all the imports and load them up in order starting in your entry.js. Then it will execute entry.js. So where you read/write to globals is important. Is it from the root scope of a module or in a function called later?


export default {
    FOO: 'bar'


import CONFIG from './config.js'
console.log(`FOO: ${CONFIG.FOO}`)

Note: If you want the instance to be new each time, then use an ES6 class. Traditionally in JS you would capitalize classes (as opposed to the lowercase for objects) like
import FooBar from './foo-bar' // <-- Usage: myFooBar = new FooBar()

  1. Webpack's ProvidePlugin

Here's how you can do it using Webpack's ProvidePlugin (which makes a module available as a variable in every module and only those modules where you actually use it). This is useful when you don't want to keep typing import Bar from 'foo' again and again. Or you can bring in a package like jQuery or lodash as global here (although you might take a look at Webpack's Externals).

Step 1) Create any module. For example, a global set of utilities would be handy:


export function sayHello () {

Step 2) Alias the module and add to ProvidePlugin:


var webpack = require("webpack");
var path = require("path");

// ...

module.exports = {

  // ...

  resolve: {
    extensions: ['', '.js'],
    alias: {
      'utils': path.resolve(__dirname, './utils')  // <-- When you build or restart dev-server, you'll get an error if the path to your utils.js file is incorrect.

  plugins: [

    // ...

    new webpack.ProvidePlugin({
      'utils': 'utils'


Now just call utils.sayHello() in any js file and it should work. Make sure you restart your dev-server if you are using that with Webpack.

Note: Don't forget to tell your linter about the global, so it won't complain. For example, see my answer for ESLint here.

  1. Use Webpack's DefinePlugin

If you just want to use const with string values for your globals, then you can add this plugin to your list of Webpack plugins:

new webpack.DefinePlugin({
  PRODUCTION: JSON.stringify(true),
  VERSION: JSON.stringify("5fa3b9"),
  TWO: "1+1",
  "typeof window": JSON.stringify("object")

Use it like:

console.log("Running App version " + VERSION);
if(!BROWSER_SUPPORTS_HTML5) require("html5shiv");
  1. Use the global window object (or Node's global) = 'bar'  // For SPA's, browser environment. = 'bar'  // Webpack will automatically convert this to window if your project is targeted for web (default), read more here:

You'll see this commonly used for polyfills, for example: window.Promise = Bluebird

  1. Use a package like dotenv

(For server side projects) The dotenv package will take a local configuration file (which you could add to your .gitignore if there are any keys/credentials) and adds your configuration variables to Node's process.env object.

// As early as possible in your application, require and configure dotenv.    

Create a .env file in the root directory of your project. Add environment-specific variables on new lines in the form of NAME=VALUE. For example:


That's it.

process.env now has the keys and values you defined in your .env file.

var db = require('db')
  host: process.env.DB_HOST,
  username: process.env.DB_USER,
  password: process.env.DB_PASS


Regarding Webpack's Externals, use it if you want to exclude some modules from being included in your built bundle. Webpack will make the module globally available but won't put it in your bundle. This is handy for big libraries like jQuery (because tree shaking external packages doesn't work in Webpack) where you have these loaded on your page already in separate script tags (perhaps from a CDN).

How to add java plugin for Firefox on Linux?

Do you want the JDK or the JRE? Anyways, I had this problem too, a few weeks ago. I followed the instructions here and it worked:

NOTE: Before installing Java make sure you kill Firefox.

root@bt:~# killall -9 /opt/firefox/firefox-bin

You can download java from the official website. (Download tar.gz version)

We first create the directory and place java there:

root@bt:~# mkdir /opt/java

root@bt:~# mv -f jre1.7.0_05/ /opt/java/

Final changes.

root@bt:~# update-alternatives --install /usr/bin/java java /opt/java/jre1.7.0_05/bin/java 1

root@bt:~# update-alternatives --set java /opt/java/jre1.7.0_05/bin/java

root@bt:~# export JAVA_HOME="/opt/java/jre1.7.0_05"

Adding the plugin to Firefox.

For Java 7 (32 bit)

root@bt:~# ln -sf $JAVA_HOME/lib/i386/ /usr/lib/mozilla/plugins/

For Java 8 (64 bit)

root@bt:~# ln -sf $JAVA_HOME/jre/lib/amd64/ /usr/lib/mozilla/plugins/

Testing the plugin.

root@bt:~# firefox

Rollback transaction after @Test

I know, I am tooooo late to post an answer, but hoping that it might help someone. Plus, I just solved this issue I had with my tests. This is what I had in my test:

My test class

@ContextConfiguration(locations = { "path-to-context" })
public class MyIntegrationTest 

Context xml

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
   <property name="driverClassName" value="${jdbc.driverClassName}" />
   <property name="url" value="${jdbc.url}" />
   <property name="username" value="${jdbc.username}" />
   <property name="password" value="${jdbc.password}" />

I still had the problem that, the database was not being cleaned up automatically.

Issue was resolved when I added following property to BasicDataSource

<property name="defaultAutoCommit" value="false" />

Hope it helps.

Where is the Java SDK folder in my computer? Ubuntu 12.04

WAY-1 : Updated for the shortest and easy way

Below command will give you the path, But it will only work if java command is working in other words if java path is configured.

readlink -f $(which java) 

Read more at Where can I find the Java SDK in Linux?

WAY-2 (Better than WAY-1) : Below answer is still working and try it if above command is not working for you.

You need to dig into symbolic links. Below is steps to get Java directory

Step 1:

$ whereis java
java: /usr/bin/java /etc/java /usr/share/java

That tells the command java resides in /usr/bin/java.

Dig again:

Step 2:

$ ls -l /usr/bin/java
lrwxrwxrwx 1 root root 22 2009-01-15 18:34 /usr/bin/java -> /etc/alternatives/java

So, now we know that /usr/bin/java is actually a symbolic link to /etc/alternatives/java.

Dig deeper using the same method above:

Step 3:

$ ls -l /etc/alternatives/java
lrwxrwxrwx 1 root root 31 2009-01-15 18:34 /etc/alternatives/java -> /usr/local/jre1.6.0_07/bin/java

So, thats the actual location of java: /usr/local/jre.....

You could still dig deeper to find other symbolic links.

Reference : where is java's home dir?

Git - push current branch shortcut

With the help of ceztko's answer I wrote this little helper function to make my life easier:

function gpu()
    if git rev-parse --abbrev-ref --symbolic-full-name @{u} > /dev/null 2>&1; then
        git push origin HEAD
        git push -u origin HEAD

It pushes the current branch to origin and also sets the remote tracking branch if it hasn't been setup yet.

Replacing some characters in a string with another character

echo "$string" | tr xyz _

would replace each occurrence of x, y, or z with _, giving A__BC___DEF__LMN in your example.

echo "$string" | sed -r 's/[xyz]+/_/g'

would replace repeating occurrences of x, y, or z with a single _, giving A_BC_DEF_LMN in your example.

How do I use a char as the case in a switch-case?

Here's an example:

public class Main {

    public static void main(String[] args) {

        double val1 = 100;
        double val2 = 10;
        char operation = 'd';
        double result = 0;

        switch (operation) {

            case 'a':
                result = val1 + val2; break;

            case 's':
                result = val1 - val2; break;
            case 'd':
                if (val2 != 0)
                    result = val1 / val2; break;
            case 'm':
                result = val1 * val2; break;

            default: System.out.println("Not a defined operation");



Select a random sample of results from a query result

This in not a perfect answer but will get much better performance.

FROM    (
    SELECT  *
    FROM    mytable sample (0.01)
WHERE rownum <= 1000

Sample will give you a percent of your actual table, if you really wanted a 1000 rows you would need to adjust that number. More often I just need an arbitrary number of rows anyway so I don't limit my results. On my database with 2 million rows I get 2 seconds vs 60 seconds.

select * from mytable sample (0.01)

Find the directory part (minus the filename) of a full path in access 97

If you are confident in your input parameters, you can use this single line of code which uses the native Split and Join functions and Excel native Application.pathSeparator.

Split(Join(Split(strPath, "."), Application.pathSeparator), Application.pathSeparator)

If you want a more extensive function, the code below is tested in Windows and should also work on Mac (though not tested). Be sure to also copy the supporting function GetPathSeparator, or modify the code to use Application.pathSeparator. Note, this is a first draft; I should really refactor it to be more concise.

Private Sub ParsePath2Test()
    'ParsePath2(DrivePathFileExt, -2) returns a multi-line string for debugging.
    Dim p As String, n As Integer

    Debug.Print String(2, vbCrLf)

    If True Then
        Debug.Print String(2, vbCrLf)
        Debug.Print ParsePath2("", -2)
        Debug.Print ParsePath2("C:", -2)
        Debug.Print ParsePath2("C:\", -2)
        Debug.Print ParsePath2("C:\Windows", -2)
        Debug.Print ParsePath2("C:\Windows\notepad.exe", -2)
        Debug.Print ParsePath2("C:\Windows\SysWOW64", -2)
        Debug.Print ParsePath2("C:\Windows\SysWOW64\", -2)
        Debug.Print ParsePath2("C:\Windows\SysWOW64\AcLayers.dll", -2)
        Debug.Print ParsePath2("C:\Windows\SysWOW64\.fakedir", -2)
        Debug.Print ParsePath2("C:\Windows\SysWOW64\fakefile.ext", -2)
    End If

    If True Then
        Debug.Print String(1, vbCrLf)
        Debug.Print ParsePath2("\Windows", -2)
        Debug.Print ParsePath2("\Windows\notepad.exe", -2)
        Debug.Print ParsePath2("\Windows\SysWOW64", -2)
        Debug.Print ParsePath2("\Windows\SysWOW64\", -2)
        Debug.Print ParsePath2("\Windows\SysWOW64\AcLayers.dll", -2)
        Debug.Print ParsePath2("\Windows\SysWOW64\.fakedir", -2)
        Debug.Print ParsePath2("\Windows\SysWOW64\fakefile.ext", -2)
    End If

    If True Then
        Debug.Print String(1, vbCrLf)
        Debug.Print ParsePath2("Windows\notepad.exe", -2)
        Debug.Print ParsePath2("Windows\SysWOW64", -2)
        Debug.Print ParsePath2("Windows\SysWOW64\", -2)
        Debug.Print ParsePath2("Windows\SysWOW64\AcLayers.dll", -2)
        Debug.Print ParsePath2("Windows\SysWOW64\.fakedir", -2)
        Debug.Print ParsePath2("Windows\SysWOW64\fakefile.ext", -2)
        Debug.Print ParsePath2(".fakedir", -2)
        Debug.Print ParsePath2("fakefile.txt", -2)
        Debug.Print ParsePath2("fakefile.onenote", -2)
        Debug.Print ParsePath2("C:\Personal\Workspace\Code\PythonVenvs\xlwings_test\.idea", -2)
        Debug.Print ParsePath2("Windows", -2)   ' Expected to raise error 52
    End If

    If True Then
        Debug.Print String(2, vbCrLf)
        Debug.Print "ParsePath2 ""\Windows\SysWOW64\fakefile.ext"" with different ReturnType values"
        Debug.Print , "{empty}", "D", ParsePath2("Windows\SysWOW64\fakefile.ext")(1)
        Debug.Print , "0", "D", ParsePath2("Windows\SysWOW64\fakefile.ext", 0)(1)
        Debug.Print , "1", "ext", ParsePath2("Windows\SysWOW64\fakefile.ext", 1)
        Debug.Print , "10", "file", ParsePath2("Windows\SysWOW64\fakefile.ext", 10)
        Debug.Print , "11", "file.ext", ParsePath2("Windows\SysWOW64\fakefile.ext", 11)
        Debug.Print , "100", "path", ParsePath2("Windows\SysWOW64\fakefile.ext", 100)
        Debug.Print , "110", "path\file", ParsePath2("Windows\SysWOW64\fakefile.ext", 110)
        Debug.Print , "111", "path\file.ext", ParsePath2("Windows\SysWOW64\fakefile.ext", 111)
        Debug.Print , "1000", "D", ParsePath2("Windows\SysWOW64\fakefile.ext", 1000)
        Debug.Print , "1100", "D:\path", ParsePath2("Windows\SysWOW64\fakefile.ext", 1100)
        Debug.Print , "1110", "D:\p\file", ParsePath2("Windows\SysWOW64\fakefile.ext", 1110)
        Debug.Print , "1111", "D:\p\f.ext", ParsePath2("Windows\SysWOW64\fakefile.ext", 1111)
        On Error GoTo EH:
        ' This is expected to presetn an error:
        p = "Windows\SysWOW64\fakefile.ext"
        n = 1010
        Debug.Print "1010", "D:\p\file.ext", ParsePath2("Windows\SysWOW64\fakefile.ext", 1010)
        On Error GoTo 0
    End If
Exit Sub
    Debug.Print , CStr(n), "Error: "; Err.Number, Err.Description
    Resume Next
End Sub
Public Function ParsePath2(ByVal DrivePathFileExt As String _
                         , Optional ReturnType As Integer = 0)
' Writen by Chris Advena.  You may modify and use this code provided you leave
' this credit in the code.
' Parses the input DrivePathFileExt string into individual components (drive
' letter, folders, filename and extension) and returns the portions you wish
' based on ReturnType.
' Returns either an array of strings (ReturnType = 0) or an individual string
' (all other defined ReturnType values).
' Parameters:
'   DrivePathFileExt: The full drive letter, path, filename and extension
'   ReturnType: -2 or a string up of to 4 ones with leading or lagging zeros
'              (e.g., 0001)
'      -2: special code for debugging use in ParsePath2Test().
'          Results in printing verbose information to the Immediate window.
'       0: default: Array(driveStr, pathStr, fileStr, extStr)
'       1: extension
'      10: filename stripped of extension
'      11: filename.extension, excluding drive and folders
'     100: folders, excluding drive letter filename and extension
'     111: folders\filename.extension, excluding drive letter
'    1000: drive leter only
'    1100: drive:\folders,  excluding filename and extension
'    1110: drive:\folders\filename, excluding extension
'    1010, 0101, 1001: invalid ReturnTypes.  Will result raise error 380, Value
'          is not valid.

    Dim driveStr As String, pathStr As String
    Dim fileStr As String, extStr As String
    Dim drivePathStr As String
    Dim pathFileExtStr As String, fileExtStr As String
    Dim s As String, cnt As Integer
    Dim i As Integer, slashStr As String
    Dim dotLoc As Integer, slashLoc As Integer, colonLoc As Integer
    Dim extLen As Integer, fileLen As Integer, pathLen As Integer
    Dim errStr As String

    DrivePathFileExt = Trim(DrivePathFileExt)

    If DrivePathFileExt = "" Then
        fileStr = ""
        extStr = ""
        fileExtStr = ""
        pathStr = ""
        pathFileExtStr = ""
        drivePathStr = ""
        GoTo ReturnResults
    End If

    ' Determine if Dos(/) or UNIX(\) slash is used
    slashStr = GetPathSeparator(DrivePathFileExt)

' Find location of colon, rightmost slash and dot.
    ' COLON: colonLoc and driveStr
    colonLoc = 0
    driveStr = ""
    If Mid(DrivePathFileExt, 2, 1) = ":" Then
        colonLoc = 2
        driveStr = Left(DrivePathFileExt, 1)
    End If
    #If Mac Then
        pathFileExtStr = DrivePathFileExt
    #Else ' Windows
        pathFileExtStr = ""
        If Len(DrivePathFileExt) > colonLoc _
        Then pathFileExtStr = Mid(DrivePathFileExt, colonLoc + 1)
    #End If

    ' SLASH: slashLoc, fileExtStr and fileStr
    ' Find the rightmost path separator (Win backslash or Mac Fwdslash).
    slashLoc = InStrRev(DrivePathFileExt, slashStr, -1, vbBinaryCompare)

    ' DOT: dotLoc and extStr
    ' Find rightmost dot.  If that dot is not part of a relative reference,
    ' then set dotLoc.  dotLoc is meant to apply to the dot before an extension,
    ' NOT relative path reference dots.  REl ref dots appear as "." or ".." at
    ' the very leftmost of the path string.
    dotLoc = InStrRev(DrivePathFileExt, ".", -1, vbTextCompare)
    If Left(DrivePathFileExt, 1) = "." And dotLoc <= 2 Then dotLoc = 0
    If slashLoc + 1 = dotLoc Then
        dotLoc = 0
        If Len(extStr) = 0 And Right(pathFileExtStr, 1) <> slashStr _
        Then pathFileExtStr = pathFileExtStr & slashStr
    End If
    #If Not Mac Then
        ' In windows, filenames cannot end with a dot (".").
        If dotLoc = Len(DrivePathFileExt) Then
            s = "Error in FileManagementMod.ParsePath2 function.  " _
                & "DrivePathFileExt " & DrivePathFileExt _
                & " cannot end iwth a dot ('.')."
            Err.Raise 52, "FileManagementMod.ParsePath2", s
        End If
    #End If

    ' extStr
    extStr = ""
    If dotLoc > 0 And (dotLoc < Len(DrivePathFileExt)) _
    Then extStr = Mid(DrivePathFileExt, dotLoc + 1)

    ' fileExtStr
    fileExtStr = ""
    If slashLoc > 0 _
    And slashLoc < Len(DrivePathFileExt) _
    And dotLoc > slashLoc Then
        fileExtStr = Mid(DrivePathFileExt, slashLoc + 1)
    End If

' Validate the input: DrivePathFileExt
    s = ""
    #If Mac Then
        If InStr(1, DrivePathFileExt, ":") > 0 Then
            s = "DrivePathFileExt ('" & DrivePathFileExt _
                & "')has invalid format.  " _
                & "UNIX/Mac filenames cannot contain a colon ('.')."
        End If
    #End If
    If Not colonLoc = 0 And slashLoc = 0 And dotLoc = 0 _
    And Left(DrivePathFileExt, 1) <> slashStr _
    And Left(DrivePathFileExt, 1) <> "." Then
        s = "DrivePathFileExt ('" & DrivePathFileExt _
            & "') has invalid format.  " _
            & "Good example: 'C:\folder\file.txt'"
    ElseIf colonLoc <> 0 And colonLoc <> 2 Then
        ' We are on Windows and there is a colon; it can only be
        ' in position 2.
        s = "DrivePathFileExt ('" & DrivePathFileExt _
            & "') has invalid format.  " _
            & "In the  Windows operating system, " _
            & "a colon (':') can only be the second character '" _
            & "of a valid file path. "
    ElseIf Left(DrivePathFileExt, 1) = ":" _
    Or InStr(3, DrivePathFileExt, ":", vbTextCompare) > 0 Then
        'If path contains a drive letter, it must contain at least one slash.
        s = "DrivePathFileExt ('" & DrivePathFileExt _
            & "') has invalid format.  " _
            & "Colon can only appear in the second character position." _
            & slashStr & "')."
    ElseIf colonLoc > 0 And slashLoc = 0 _
    And Len(DrivePathFileExt) > 2 Then
        'If path contains a drive letter, it must contain at least one slash.
        s = "DrivePathFileExt ('" & DrivePathFileExt _
            & "') has invalid format.  " _
            & "The last dot ('.') cannot be before the last file separator '" _
            & slashStr & "')."
    ElseIf colonLoc = 2 _
    And InStr(1, DrivePathFileExt, slashStr, vbTextCompare) = 0 _
    And Len(DrivePathFileExt) > 2 Then
        ' There is a colon, but no file separator (slash).  This is invalid.
        s = "DrivePathFileExt ('" & DrivePathFileExt _
            & "') has invalid format.  " _
            & "If a drive letter is included, then there must be at " _
            & "least one file separator character ('" & slashStr & "')."
    ElseIf Len(driveStr) > 0 And Len(DrivePathFileExt) > 2 And slashLoc = 0 Then
        ' If path contains a drive letter and is more than 2 character long
        ' (e.g., 'C:'), it must contain at least one slash.
        s = "DrivePathFileExt cannot contain a drive letter but no path separator."
    End If
    If Len(s) > 0 Then
    End If

' Determine if DrivePathFileExt = DrivePath
' or  = Path (with no fileStr or extStr components).
    If Right(DrivePathFileExt, 1) = slashStr _
    Or slashLoc = 0 _
    Or dotLoc = 0 _
    Or (dotLoc > 0 And dotLoc <= slashLoc + 1) Then
        ' If rightmost character is the slashStr, then no fileExt exists, just drivePath
        ' If no dot found, then no extension.  Assume a folder is after the last slashstr,
        ' not a filename.
        ' If a dot is found (extension exists),
        ' If a rightmost dot appears one-char to the right of the rightmost slash
        '    or anywhere before (left) of that, it is not a file/ext separator. Exmaple:
        '    'C:\folder1\.folder2' Then
        ' If no slashes, then no fileExt exists.  It must just be a driveletter.
        ' DrivePathFileExt contains no file or ext name.
        fileStr = ""
        extStr = ""
        fileExtStr = ""
        pathStr = pathFileExtStr
        drivePathStr = DrivePathFileExt
        GoTo ReturnResults
        ' fileStr
        fileStr = ""
        If slashLoc > 0 Then
            If Len(extStr) = 0 Then
                fileStr = fileExtStr
                ' length of filename excluding dot and extension.
                i = Len(fileExtStr) - Len(extStr) - 1
                fileStr = Left(fileExtStr, i)
            End If
                s = "Error in FileManagementMod.ParsePath2 function. " _
                    & "*** Unhandled scenario: find fileStr when slashLoc = 0. *** "
                Err.Raise 52, "FileManagementMod.ParsePath2", s
        End If

        ' pathStr
        pathStr = ""
        ' length of pathFileExtStr excluding fileExt.
        i = Len(pathFileExtStr) - Len(fileExtStr)
        pathStr = Left(pathFileExtStr, i)

        ' drivePathStr
        drivePathStr = ""
        ' length of DrivePathFileExt excluding dot and extension.
        i = Len(DrivePathFileExt) - Len(fileExtStr)
        drivePathStr = Left(DrivePathFileExt, i)
    End If

    ' ReturnType uses a 4-digit binary code: dpfe = drive path file extension,
    ' where 1 = return in array and 0 = do not return in array
    ' -2, and 0 are special cases that do not follow the code.

    ' Note: pathstr is determined with the tailing slashstr
    If Len(drivePathStr) > 0 And Right(drivePathStr, 1) <> slashStr _
    Then drivePathStr = drivePathStr & slashStr
    If Len(pathStr) > 0 And Right(pathStr, 1) <> slashStr _
    Then pathStr = pathStr & slashStr
    #If Not Mac Then
        ' Including this code add a slash to the beginnning where missing.
        ' the downside is that it would create an absolute path where a
        ' sub-path of the current folder is intended.
        'If colonLoc = 0 Then
        '    If Len(drivePathStr) > 0 And Not IsIn(Left(drivePathStr, 1), slashStr, ".") _
             Then drivePathStr = slashStr & drivePathStr
        '    If Len(pathStr) > 0 And Not IsIn(Left(pathStr, 1), slashStr, ".") _
             Then pathStr = slashStr & pathStr
        '    If Len(pathFileExtStr) > 0 And Not IsIn(Left(pathFileExtStr, 1), slashStr, ".") _
             Then pathFileExtStr = slashStr & pathFileExtStr
        'End If
    #End If
    Select Case ReturnType
        Case -2  ' used for ParsePath2Test() only.
            ParsePath2 = "DrivePathFileExt          " _
                        & CStr(Nz(DrivePathFileExt, "{empty string}")) _
                        & vbCrLf & "        " _
                        & "--------------    -----------------------------------------" _
                        & vbCrLf & "        " & "D:\Path\          " & drivePathStr _
                        & vbCrLf & "        " & "\path[\file.ext]  " & pathFileExtStr _
                        & vbCrLf & "        " & "\path\            " & pathStr _
                        & vbCrLf & "        " & "file.ext          " & fileExtStr _
                        & vbCrLf & "        " & "file              " & fileStr _
                        & vbCrLf & "        " & "ext               " & extStr _
                        & vbCrLf & "        " & "D                 " & driveStr _
                        & vbCrLf & vbCrLf
            ' My custom debug printer prints to Immediate winodw and log file.
            ' Dbg.Prnt 2, ParsePath2
            Debug.Print ParsePath2
        Case 1      '0001: ext
            ParsePath2 = extStr
        Case 10     '0010: file
            ParsePath2 = fileStr
        Case 11     '0011: file.ext
            ParsePath2 = fileExtStr
        Case 100    '0100: path
            ParsePath2 = pathStr
        Case 110    '0110: (path, file)
            ParsePath2 = pathStr & fileStr
        Case 111    '0111:
            ParsePath2 = pathFileExtStr
        Case 1000
            ParsePath2 = driveStr
        Case 1100
            ParsePath2 = drivePathStr
        Case 1110
            ParsePath2 = drivePathStr & fileStr
        Case 1111
            ParsePath2 = DrivePathFileExt
        Case 1010, 101, 1001
            s = "Error in FileManagementMod.ParsePath2 function.  " _
                & "Value of Paramter (ReturnType = " _
                & CStr(ReturnType) & ") is not valid."
            Err.Raise 380, "FileManagementMod.ParsePath2", s
        Case Else   '   default: 0
            ParsePath2 = Array(driveStr, pathStr, fileStr, extStr)
    End Select

End Function

Supporting function GetPathSeparatorTest extends the native Application.pathSeparator (or bypasses when needed) to work on Mac and Win. It can also takes an optional path string and will try to determine the path separator used in the string (favoring the OS native path separator).

Private Sub GetPathSeparatorTest()
    Dim s As String
    Debug.Print "GetPathSeparator(s):"
    Debug.Print "s not provided: ", GetPathSeparator
    s = "C:\folder1\folder2\file.ext"
    Debug.Print "s = "; s, GetPathSeparator(DrivePathFileExt:=s)
    s = "C:/folder1/folder2/file.ext"
    Debug.Print "s = "; s, GetPathSeparator(DrivePathFileExt:=s)
End Sub
Function GetPathSeparator(Optional DrivePathFileExt As String = "") As String
' by Chris Advena
' Finds the path separator from a string, DrivePathFileExt.
' If DrivePathFileExt is not provided, return the operating system path separator
' (Windows = backslash, Mac = forwardslash).
' Mac/Win compatible.

    ' Initialize
    Dim retStr As String: retStr = ""
    Dim OSSlash As String: OSSlash = ""
    Dim OSOppositeSlash As String: OSOppositeSlash = ""
        Dim PathFileExtSlash As String

    GetPathSeparator = ""
    retStr = ""

    ' Determine if OS expects fwd or back slash ("/" or "\").
    On Error GoTo EH
    OSSlash = Application.pathSeparator

    If DrivePathFileExt = "" Then
    ' Input parameter DrivePathFileExt is empty, so use OS file separator.
        retStr = OSSlash
    ' Input parameter DrivePathFileExt provided.  See if it contains / or \.
        ' Set OSOppositeSlash to the opposite slash the OS expects.
        OSOppositeSlash = "\"
        If OSSlash = "\" Then OSOppositeSlash = "/"

        ' If DrivePathFileExt does NOT contain OSSlash
        ' and DOES contain OSOppositeSlash, return OSOppositeSlash.
        ' Otherwise, assume OSSlash is correct.
        retStr = OSSlash
        If InStr(1, DrivePathFileExt, OSSlash, vbTextCompare) = 0 _
        And InStr(1, DrivePathFileExt, OSOppositeSlash, vbTextCompare) > 0 Then
            retStr = OSOppositeSlash
        End If
    End If

    GetPathSeparator = retStr
Exit Function
    ' Application.PathSeparator property does not exist in Access,
    ' so get it the slightly less easy way.
    #If Mac Then ' Application.PathSeparator doesn't seem to exist in Access...
        OSSlash = "/"
        OSSlash = "\"
    #End If
    Resume Next
End Function

Supporting function (actually commented out, so you can skip this if you don't plan to use it).

Sub IsInTest()
' IsIn2 is case insensitive
    Dim StrToFind As String, arr As Variant
    arr = Array("Me", "You", "Dog", "Boo")

    StrToFind = "doG"
    Debug.Print "Is '" & CStr(StrToFind) & "' in list (expect True): " _
                , IsIn(StrToFind, "Me", "You", "Dog", "Boo")

    StrToFind = "Porcupine"
    Debug.Print "Is '" & CStr(StrToFind) & "' in list (expect False): " _
                , IsIn(StrToFind, "Me", "You", "Dog", "Boo")
End Sub
Function IsIn(ByVal StrToFind, ParamArray StringArgs() As Variant) As Boolean
' StrToFind: the string to find in the list of StringArgs()
' StringArgs: 1-dimensional array containing string values.
' Built for Strings, but actually works with other data types.
    Dim arr As Variant
    arr = StringArgs
    IsIn = Not IsError(Application.Match(StrToFind, arr, False))
End Function

How to access parent scope from within a custom directive *with own scope* in AngularJS?

If you are using ES6 Classes and ControllerAs syntax, you need to do something slightly different.

See the snippet below and note that vm is the ControllerAs value of the parent Controller as used in the parent HTML

myApp.directive('name', function() {
  return {
    // no scope definition
    link : function(scope, element, attrs, ngModel) {


OpenCV !_src.empty() in function 'cvtColor' error

In my case it was a permission issue. I had to:

  • chmod a+wrx the image,

then it worked.

Matlab: Running an m-file from command-line

cat 1.m | matlab -nodesktop -nosplash

And I use Ubuntu

Replace all spaces in a string with '+'

Use a regular expression with the g modifier:

var replaced = str.replace(/ /g, '+');

From Using Regular Expressions with JavaScript and ActionScript:

/g enables "global" matching. When using the replace() method, specify this modifier to replace all matches, rather than only the first one.

How do I download NLTK data?

I had the similar issue. Probably check if you are using proxy.

If yes, set up the proxy before doing download:

nltk.set_proxy('', ('USERNAME', 'PASSWORD'))

Best way to verify string is empty or null

.map(string -> !label.isEmpty)



the last solution will check if not null and trimm the str at the same time

Variable is accessed within inner class. Needs to be declared final

Here's a funny answer.

You can declare a final one-element array and change the elements of the array all you want apparently. I'm sure it breaks the very reason why this compiler rule was implemented in the first place but it's handy when you're in a time-bind as I was today.

I actually can't claim credit for this one. It was IntelliJ's recommendation! Feels a bit hacky. But doesn't seem as bad as a global variable so I thought it worth mentioning here. It's just one solution to the problem. Not necessarily the best one.

final int[] tapCount = {0};

addSiteButton.setOnClickListener(new View.OnClickListener() {

    public void onClick(View v) {


How to examine processes in OS X's Terminal?

Using top and ps is okay, but I find that using htop is far better & clearer than the standard tools Mac OS X uses. My fave use is to hit the T key while it is running to view processes in tree view (see screenshot). Shows you what processes are co-dependent on other processes.

htop on OSX

You can install it from Homebrew using:

brew install htop

And if you have Xcode and related tools such as git installed on your system and you want to install the latest development code from the official source repository—just follow these steps.

First clone the source code from the htop GitHub repository:

git clone [email protected]:hishamhm/htop.git

Now go into the repository directory:

cd htop



Run this configure command:


Once the configure process completes, run make:


Finally install it by running sudo make install:

sudo make install

Create a zip file and download it

Add Content-length header describing size of zip file in bytes.

header("Content-type: application/zip"); 
header("Content-Disposition: attachment; filename=$archive_file_name");
header("Content-length: " . filesize($archive_file_name));
header("Pragma: no-cache"); 
header("Expires: 0"); 

Also make sure that there is absolutely no white space before <? and after ?>. I see a space here:


$file_names = array('iMUST Operating Manual V1.3a.pdf','iMUST Product Information Sheet.pdf');

Tomcat is not deploying my web project from Eclipse

I have the same problem, my solution is:

  • Install WTP Maven integration (don't know if this is necessary)
  • Project -> Run Configurations (Select your tomcat server) -> Run

For a few hours I tried to deploy and start application using Servers window but it didn't worked. My war was not placed in wptwebapps folder, manually deplying war to webapps worked.

Using Run Configurations made my app finally deployable...

VBA - how to conditionally skip a for loop iteration

Continue For isn't valid in VBA or VB6.

From this MSDN page it looks to have been introduced into VB.Net in VS 2005./Net 2.

As the others have said there's not really an option other than to use Goto or an Else.

What are Java command line options to set to allow JVM to be remotely debugged?

I have this article bookmarked on setting this up for Java 5 and below.

Basically run it with:

-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=1044

For Java 5 and above, run it with:


Element-wise addition of 2 lists?

The others gave examples how to do this in pure python. If you want to do this with arrays with 100.000 elements, you should use numpy:

In [1]: import numpy as np
In [2]: vector1 = np.array([1, 2, 3])
In [3]: vector2 = np.array([4, 5, 6])

Doing the element-wise addition is now as trivial as

In [4]: sum_vector = vector1 + vector2
In [5]: print sum_vector
[5 7 9]

just like in Matlab.

Timing to compare with Ashwini's fastest version:

In [16]: from operator import add
In [17]: n = 10**5
In [18]: vector2 = np.tile([4,5,6], n)
In [19]: vector1 = np.tile([1,2,3], n)
In [20]: list1 = [1,2,3]*n
In [21]: list2 = [4,5,6]*n
In [22]: timeit map(add, list1, list2)
10 loops, best of 3: 26.9 ms per loop

In [23]: timeit vector1 + vector2
1000 loops, best of 3: 1.06 ms per loop

So this is a factor 25 faster! But use what suits your situation. For a simple program, you probably don't want to install numpy, so use standard python (and I find Henry's version the most Pythonic one). If you are into serious number crunching, let numpy do the heavy lifting. For the speed freaks: it seems that the numpy solution is faster starting around n = 8.

Is "&#160;" a replacement of "&nbsp;"?

  • &nbsp; is the character entity reference (meant to be easily parseable by humans).
  • &#160; is the numeric entity reference (meant to be easily parseable by machines).

They are the same except for the fact that the latter does not need another lookup table to find its actual value. The lookup table is called a DTD, by the way.

You can read more about character entity references in the offical W3C documents.

Are HTTPS headers encrypted?

HTTP version 1.1 added a special HTTP method, CONNECT - intended to create the SSL tunnel, including the necessary protocol handshake and cryptographic setup.
The regular requests thereafter all get sent wrapped in the SSL tunnel, headers and body inclusive.

How to add /usr/local/bin in $PATH on Mac

To make the edited value of path persists in the next sessions

cd ~/
touch .bash_profile
open .bash_profile

That will open the .bash_profile in editor, write inside the following after adding what you want to the path separating each value by column.

export PATH=$PATH:/usr/local/git/bin:/usr/local/bin:

Save, exit, restart your terminal and enjoy

SQL Server find and replace specific word in all rows of specific column

SET number = REPLACE(number, 'KIT', 'CH')
WHERE number like 'KIT%'

or simply this if you are sure that you have no values like this CKIT002

SET number = REPLACE(number, 'KIT', 'CH')

How do I update the element at a certain position in an ArrayList?


and if u want to update it then add this line also


How to create a file in memory for user to download, but not through server?

The following method works in IE10+, Edge, Opera, FF and Chrome:

const saveDownloadedData = (fileName, data) => {
    if(~navigator.userAgent.indexOf('MSIE') || ~navigator.appVersion.indexOf('Trident/')) { /* IE9-11 */
        const blob = new Blob([data], { type: 'text/csv;charset=utf-8;' });
        navigator.msSaveBlob(blob, fileName);
    } else {
        const link = document.createElement('a')
        link.setAttribute('target', '_blank');
        if(Blob !== undefined) {
            const blob = new Blob([data], { type: 'text/plain' });
            link.setAttribute('href', URL.createObjectURL(blob));
        } else {
            link.setAttribute('href', 'data:text/plain,' + encodeURIComponent(data));

            && (fileName = fileName.replace(/[&\/\\#,+$~%.'':*?<>{}]/g, '_')); /* Edge */

        link.setAttribute('download', fileName);

So, just call the function:

saveDownloadedData('test.txt', 'Lorem ipsum');

Git keeps prompting me for a password

I feel like the answer provided by static_rtti is hacky in some sense. I don't know if this was available earlier, but Git tools now provide credential storage.

Cache Mode

$ git config --global credential.helper cache

Use the “cache” mode to keep credentials in memory for a certain period of time. None of the passwords are ever stored on disk, and they are purged from the cache after 15 minutes.

Store Mode

$ git config --global credential.helper 'store --file ~/.my-credentials'

Use the “store” mode to save the credentials to a plain-text file on disk, and they never expire.

I personally used the store mode. I deleted my repository, cloned it, and then had to enter my credentials once.

Reference: 7.14 Git Tools - Credential Storage

How to Auto-start an Android Application?

You have to add a manifest permission entry:

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

(of course you should list all other permissions that your app uses).

Then, implement BroadcastReceiver class, it should be simple and fast executable. The best approach is to set an alarm in this receiver to wake up your service (if it's not necessary to keep it running ale the time as Prahast wrote).

public class BootUpReceiver extends BroadcastReceiver {
    public void onReceive(Context context, Intent intent) {
        AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
        PendingIntent pi = PendingIntent.getService(context, 0, new Intent(context, MyService.class), PendingIntent.FLAG_UPDATE_CURRENT);
        am.setInexactRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + interval, interval, pi);

Then, add a Receiver class to your manifest file:

<receiver android:enabled="true" android:name=".receivers.BootUpReceiver"
        <action android:name="android.intent.action.BOOT_COMPLETED" />
        <category android:name="android.intent.category.DEFAULT" />

How to tell if homebrew is installed on Mac OS X

The standard way of figuring out if something is installed is to use which.

If Brew is installed.

>>> which brew

If Brew is not installed.

>>> which brew
brew not found

Note: The "not installed" message depends on your shell. zsh is shown above. bash will just not print anything. csh will say brew: Command not found. In the "installed" case, all shells will print the path.)

It works with all command line programs. Try which grep or which python. Since it tells you the program that you're running, it's helpful when debugging as well.

How do I force files to open in the browser instead of downloading (PDF)?

If you link to a .PDF it will open in the browser.
If the box is unchecked it should link to a .zip to force the download.

If a .zip is not an option, then use headers in PHP to force the download

header('Content-Type: application/force-download'); 
header('Content-Description: File Transfer'); 

How can I export a GridView.DataSource to a datatable or dataset?

You should convert first DataSource in BindingSource, look example

BindingSource bs = (BindingSource)dgrid.DataSource; // Se convierte el DataSource 
DataTable tCxC = (DataTable) bs.DataSource;

With the data of tCxC you can do anything.

How to run (not only install) an android application using .apk file?

This is a solution in shell script:


1. Install apk

adb install "$apk"
sleep 1

2. Get package name

pkg_info=`aapt dump badging "$apk" | head -1 | awk -F " " '{print $2}'`
eval $pkg_info > /dev/null

3. Start app

adb shell monkey -p "${pkg_name}" -c android.intent.category.LAUNCHER 1

How to center a Window in Java?

The following code center the Window in the center of the current monitor (ie where the mouse pointer is located).

public static final void centerWindow(final Window window) {
    GraphicsDevice screen = MouseInfo.getPointerInfo().getDevice();
    Rectangle r = screen.getDefaultConfiguration().getBounds();
    int x = (r.width - window.getWidth()) / 2 + r.x;
    int y = (r.height - window.getHeight()) / 2 + r.y;
    window.setLocation(x, y);

Upload video files via PHP and save them in appropriate folder and have a database entry





<form action="upload.php" method="post" enctype="multipart/form-data">
    <label for="file"><span>Filename:</span></label>
    <input type="file" name="file" id="file" /> 
    <br />
<input type="submit" name="submit" value="Submit" />


    //============================= DATABASE CONNECTIVITY d ====================
    $servername = "localhost";
    $username = "root";
    $password = "";
    $dbname = "test";

    // Create connection
    $conn = new mysqli($servername, $username, $password, $dbname);
    // Check connection
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);

    //============================= DATABASE CONNECTIVITY u ====================
    //============================= Retrieve data from DB d ====================
    $sql = "SELECT name, size, type FROM videos";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) 
        $path = "uploaded/" . $row["name"];

            echo $path . "<br>";

    } else {
        echo "0 results";
    //============================= Retrieve data from DB d ====================



Get first element of Series without knowing the index

Use iloc to access by position (rather than label):

In [11]: df = pd.DataFrame([[1, 2], [3, 4]], ['a', 'b'], ['A', 'B'])

In [12]: df
   A  B
a  1  2
b  3  4

In [13]: df.iloc[0]  # first row in a DataFrame
A    1
B    2
Name: a, dtype: int64

In [14]: df['A'].iloc[0]  # first item in a Series (Column)
Out[14]: 1

Easiest way to copy a single file from host to Vagrant guest?

Go to the directory where you have your Vagrantfile
Then, edit your Vagrantfile and add the following:

config.vm.synced_folder ".", "/vagrant", :mount_options => ['dmode=774','fmode=775']

"." means the directory you are currently in on your host machine
"/vagrant" refers to "/home/vagrant" on the guest machine(Vagrant machine).

Copy the files you need to send to guest machine to the folder where you have your Vagrantfile Then open Git Bash and cd to the directory where you have your Vagrantfile and type:

vagrant scp config.json XXXXXXX:/home/vagrant/

where XXXXXXX is your vm name. You can get your vm name by running

vagrant global-status

ReactJS - Call One Component Method From Another Component

Well, actually, React is not suitable for calling child methods from the parent. Some frameworks, like Cycle.js, allow easily access data both from parent and child, and react to it.

Also, there is a good chance you don't really need it. Consider calling it into existing component, it is much more independent solution. But sometimes you still need it, and then you have few choices:

  • Pass method down, if it is a child (the easiest one, and it is one of the passed properties)
  • add events library; in React ecosystem Flux approach is the most known, with Redux library. You separate all events into separated state and actions, and dispatch them from components
  • if you need to use function from the child in a parent component, you can wrap in a third component, and clone parent with augmented props.

UPD: if you need to share some functionality which doesn't involve any state (like static functions in OOP), then there is no need to contain it inside components. Just declare it separately and invoke when need:

let counter = 0;
function handleInstantiate() {

constructor(props) {

How to disable SSL certificate checking with Spring RestTemplate?

Here's a solution where security checking is disabled (for example, conversing with the localhost) Also, some of the solutions I've seen now contain deprecated methods and such.

 * @param configFilePath
 * @param ipAddress
 * @param userId
 * @param password
 * @throws MalformedURLException
public Upgrade(String aConfigFilePath, String ipAddress, String userId, String password) {
    configFilePath = aConfigFilePath;
    baseUri = "https://" + ipAddress + ":" + PORT + "/";

    restTemplate = new RestTemplate(createSecureTransport(userId, password, ipAddress, PORT));
    restTemplate.getMessageConverters().add(new MappingJacksonHttpMessageConverter());
    restTemplate.getMessageConverters().add(new StringHttpMessageConverter());

ClientHttpRequestFactory createSecureTransport(String username,
        String password, String host, int port) {
    HostnameVerifier nullHostnameVerifier = new HostnameVerifier() {
        public boolean verify(String hostname, SSLSession session) {
            return true;
    UsernamePasswordCredentials credentials = new UsernamePasswordCredentials(username, password);
    CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
            new AuthScope(AuthScope.ANY_HOST, AuthScope.ANY_PORT, AuthScope.ANY_REALM), credentials);

    HttpClient client = HttpClientBuilder.create()

    HttpComponentsClientHttpRequestFactory requestFactory = 
            new HttpComponentsClientHttpRequestFactory(client);

    return requestFactory;

private SSLContext createContext() {
    TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() {
        public[] getAcceptedIssuers() {
            return null;

        public void checkClientTrusted(
      [] certs, String authType) {

        public void checkServerTrusted(
      [] certs, String authType) {
    } };

    try {
        SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, trustAllCerts, null);
        HttpsURLConnection.setDefaultHostnameVerifier(new HostnameVerifier() {
            public boolean verify(String hostname, SSLSession session) {
                    return true;
        return sc;

    } catch (Exception e) {
    return null;

How to verify if $_GET exists?

You are use PHP isset


if (isset($_GET["id"])) {
    echo $_GET["id"];

How to print all key and values from HashMap in Android?

for (Map.Entry<String,String> entry : map.entrySet()) {
  String key = entry.getKey();
  String value = entry.getValue();
  // do stuff

What is a None value?

All of these are good answers but I think there's more to explain why None is useful.

Imagine you collecting RSVPs to a wedding. You want to record whether each person will attend. If they are attending, you set person.attending = True. If they are not attending you set person.attending = False. If you have not received any RSVP, then person.attending = None. That way you can distinguish between no information - None - and a negative answer.

How to fix docker: Got permission denied issue

In Linux environment, after installing docker and docker-compose reboot is required for work docker better.

$ reboot

OR restart the docker

$ sudo systemctl restart docker

Display Back Arrow on Toolbar

In your manifest file for the activity where you want to add a back button, we will use the property android:parentActivityName


P.S. This attribute was introduced in API Level 16.

How do I enable --enable-soap in php on linux?

As far as your question goes: no, if activating from .ini is not enough and you can't upgrade PHP, there's not much you can do. Some modules, but not all, can be added without recompilation (zypper install php5-soap, yum install php-soap). If it is not enough, try installing some PEAR class for interpreted SOAP support (NuSOAP, etc.).

In general, the double-dash --switches are designed to be used when recompiling PHP from scratch.

You would download the PHP source package (as a compressed .tgz tarball, say), expand it somewhere and then, e.g. under Linux, run the configure script

./configure --prefix ...

The configure command used by your PHP may be shown with phpinfo(). Repeating it identical should give you an exact copy of the PHP you now have installed. Adding --enable-soap will then enable SOAP in addition to everything else.

That said, if you aren't familiar with PHP recompilation, don't do it. It also requires several ancillary libraries that you might, or might not, have available - freetype, gd, libjpeg, XML, expat, and so on and so forth (it's not enough they are installed; they must be a developer version, i.e. with headers and so on; in most distributions, having libjpeg installed might not be enough, and you might need libjpeg-dev also).

I have to keep a separate virtual machine with everything installed for my recompilation purposes.

Change a Git remote HEAD to point to something besides master

Simple just log into your GitHub account and on the far right side in the navigation menu choose Settings, in the Settings Tab choose Default Branch and return back to main page of your repository that did the trick for me.

HttpServletRequest - Get query string parameters, no form data

As the other answers state there is no way getting query string parameters using servlet api.

So, I think the best way to get query parameters is parsing the query string yourself. ( It is more complicated iterating over parameters and checking if query string contains the parameter)

I wrote below code to get query string parameters. Using apache StringUtils and ArrayUtils which supports CSV separated query param values as well.

Example: username=james&username=smith&password=pwd1,pwd2 will return

password : [pwd1, pwd2] (length = 2)

username : [james, smith] (length = 2)

public static Map<String, String[]> getQueryParameters(HttpServletRequest request) throws UnsupportedEncodingException {
    Map<String, String[]> queryParameters = new HashMap<>();
    String queryString = request.getQueryString();
    if (StringUtils.isNotEmpty(queryString)) {
        queryString = URLDecoder.decode(queryString, StandardCharsets.UTF_8.toString());
        String[] parameters = queryString.split("&");
        for (String parameter : parameters) {
            String[] keyValuePair = parameter.split("=");
            String[] values = queryParameters.get(keyValuePair[0]);
            //length is one if no value is available.
            values = keyValuePair.length == 1 ? ArrayUtils.add(values, "") :
                    ArrayUtils.addAll(values, keyValuePair[1].split(",")); //handles CSV separated query param values.
            queryParameters.put(keyValuePair[0], values);
    return queryParameters;

Converting from longitude\latitude to Cartesian coordinates

Here's the answer I found:

Just to make the definition complete, in the Cartesian coordinate system:

  • the x-axis goes through long,lat (0,0), so longitude 0 meets the equator;
  • the y-axis goes through (0,90);
  • and the z-axis goes through the poles.

The conversion is:

x = R * cos(lat) * cos(lon)

y = R * cos(lat) * sin(lon)

z = R *sin(lat)

Where R is the approximate radius of earth (e.g. 6371 km).

If your trigonometric functions expect radians (which they probably do), you will need to convert your longitude and latitude to radians first. You obviously need a decimal representation, not degrees\minutes\seconds (see e.g. here about conversion).

The formula for back conversion:

   lat = asin(z / R)
   lon = atan2(y, x)

asin is of course arc sine. read about atan2 in wikipedia. Don’t forget to convert back from radians to degrees.

This page gives c# code for this (note that it is very different from the formulas), and also some explanation and nice diagram of why this is correct,

How to get just the responsive grid from Bootstrap 3?

It's been a while since this question was asked, but maybe now you can forego Bootstrap altogether and use CSS Grid! (it's simpler, neater, more flexible and faster). See this cool article: Stop using Bootstrap — create a practical CSS Grid template for your component based UI

How to request Administrator access inside a batch file

Ben Gripka's solution causes infinite loops. His batch works like this (pseudo code):

IF "no admin privileges?"
    "write a VBS that calls this batch with admin privileges"
    "execute actual commands that require admin privileges"

As you can see, this causes an infinite loop, if the VBS fails requesting admin privileges.

However, the infinite loop can occur, although admin priviliges have been requested successfully.

The check in Ben Gripka's batch file is just error-prone. I played around with the batch and observed that admin privileges are available although the check failed. Interestingly, the check worked as expected, if I started the batch file from windows explorer, but it didn't when I started it from my IDE.

So I suggest to use two separate batch files. The first generates the VBS that calls the second batch file:

@echo off

echo Set UAC = CreateObject^("Shell.Application"^) > "%temp%\getadmin.vbs"
set params = %*:"=""
echo UAC.ShellExecute "cmd.exe", "/c ""%~dp0\my_commands.bat"" %params%", "", "runas", 1 >> "%temp%\getadmin.vbs"

del "%temp%\getadmin.vbs"

The second, named "my_commands.bat" and located in the same directory as the first contains your actual commands:

pushd "%CD%"
CD /D "%~dp0"
REM Your commands which require admin privileges here

This causes no infinite loops and also removes the error-prone admin privilege check.

How do I load a PHP file into a variable?

Theoretically you could just use fopen, then use stream_get_contents.

$stream = fopen("file.php","r");
$string = stream_get_contents($stream);

That should read the entire file into $string for you, and should not evaluate it. Though I'm surprised that file_get_contents didn't work when you specified the local path....

How to implement one-to-one, one-to-many and many-to-many relationships while designing tables?


The one-to-many table relationship looks as follows:


In a relational database system, a one-to-many table relationship links two tables based on a Foreign Key column in the child which references the Primary Key of the parent table row.

In the table diagram above, the post_id column in the post_comment table has a Foreign Key relationship with the post table id Primary Key column:



The one-to-one table relationship looks as follows:


In a relational database system, a one-to-one table relationship links two tables based on a Primary Key column in the child which is also a Foreign Key referencing the Primary Key of the parent table row.

Therefore, we can say that the child table shares the Primary Key with the parent table.

In the table diagram above, the id column in the post_details table has also a Foreign Key relationship with the post table id Primary Key column:



The many-to-many table relationship looks as follows:


In a relational database system, a many-to-many table relationship links two parent tables via a child table which contains two Foreign Key columns referencing the Primary Key columns of the two parent tables.

In the table diagram above, the post_id column in the post_tag table has also a Foreign Key relationship with the post table id Primary Key column:


And, the tag_id column in the post_tag table has a Foreign Key relationship with the tag table id Primary Key column:


Count all values in a matrix greater than a value

This is very straightforward with boolean arrays:

p31 = numpy.asarray(o31)
za = (p31 < 200).sum() # p31<200 is a boolean array, so `sum` counts the number of True elements

How to execute shell command in Javascript

With nashorn you can write a script like this:

$EXEC('find -type f');
var files = $OUT.split('\n');

and run it:

jjs -scripting each_file.js

How to cin to a vector

using namespace std;

int main()
    vector<string> v;
    string line,t;
    istringstream iss(line);

    vector<string>::iterator it;
    return 0;

OpenCV & Python - Image too big to display

Looks like opencv lib is pretty sensitive to parameters passed to the methods. The following code worked for me using opencv 4.3.0:

win_name = "visualization"  #  1. use var to specify window name everywhere
cv2.namedWindow(win_name, cv2.WINDOW_NORMAL)  #  2. use 'normal' flag
img = cv2.imread(filename)
h,w = img.shape[:2]  #  suits for image containing any amount of channels
h = int(h / resize_factor)  #  one must compute beforehand
w = int(w / resize_factor)  #  and convert to INT
cv2.resizeWindow(win_name, w, h)  #  use variables defined/computed BEFOREHAND
cv2.imshow(win_name, img)

Receiver not registered exception error?

Be careful, when you register by


you can't unregister by


you must use


or app will crash, log as follow:

09-30 14:00:55.458 19064-19064/com.jialan.guangdian.view E/AndroidRuntime: FATAL EXCEPTION: main Process: com.jialan.guangdian.view, PID: 19064 java.lang.RuntimeException: Unable to stop service java.lang.IllegalArgumentException: Receiver not registered:$PlayStatusReceiver@19538584 at at$2200( at$H.handleMessage( at android.os.Handler.dispatchMessage( at android.os.Looper.loop( at at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke( at$ at Caused by: java.lang.IllegalArgumentException: Receiver not registered:$PlayStatusReceiver@19538584 at at at android.content.ContextWrapper.unregisterReceiver( at at at$2200(  at$H.handleMessage(  at android.os.Handler.dispatchMessage(  at android.os.Looper.loop(  at  at java.lang.reflect.Method.invoke(Native Method)  at java.lang.reflect.Method.invoke(  at$  at 

Subtract two variables in Bash

You can use:

((count = FIRSTV - SECONDV))

to avoid invoking a separate process, as per the following transcript:

pax:~$ FIRSTV=7
pax:~$ SECONDV=2
pax:~$ ((count = FIRSTV - SECONDV))
pax:~$ echo $count

How do you redirect HTTPS to HTTP?

It is better to avoid using mod_rewrite when you can.

In your case I would replace the Rewrite with this:

    <If "%{HTTPS} == 'on'" >
            Redirect permanent / http://production_server/

The <If> directive is only available in Apache 2.4+ as per this blog here.

Adding horizontal spacing between divs in Bootstrap 3

The best solution is not to use the same element for column and panel:

<div class="row">
    <div class="col-md-3">
        <div class="panel" id="gameplay-away-team">Away Team</div>
    <div class="col-md-6">
        <div class="panel" id="gameplay-baseball-field">Baseball Field</div>
    <div class="col-md-3">
        <div class="panel" id="gameplay-home-team">Home Team</div>

and some more styles:

#gameplay-baseball-field {
  padding-right: 10px;
  padding-left: 10px;

tmux set -g mouse-mode on doesn't work

As @Graham42 noted, mouse option has changed in version 2.1. Scrolling now requires for you to enter copy mode first. To enable scrolling almost identical to how it was before 2.1 add following to your .tmux.conf.

set-option -g mouse on

# make scrolling with wheels work
bind -n WheelUpPane if-shell -F -t = "#{mouse_any_flag}" "send-keys -M" "if -Ft= '#{pane_in_mode}' 'send-keys -M' 'select-pane -t=; copy-mode -e; send-keys -M'"
bind -n WheelDownPane select-pane -t= \; send-keys -M

This will enable scrolling on hover over a pane and you will be able to scroll that pane line by line.


Curl GET request with json parameter

This should work :

  curl -i -H "Accept: application/json" 'server:5050/a/c/getName{"param0":"pradeep"}'

use option -i instead of x.

Windows shell command to get the full path to the current directory?

This has always worked for me:

SET CurrentDir="%~dp0"

ECHO The current file path this bat file is executing in is the following:

ECHO %CurrentDir%


MySQL LEFT JOIN 3 tables

Try this definitely work.

SELECT p.PersonID AS person_id,
   p.Name, p.SS, 
   f.FearID AS fear_id,
   FROM person_fear AS pf 
      LEFT JOIN persons AS p ON pf.PersonID = p.PersonID 
      LEFT JOIN fears AS f ON pf.PersonID = f.FearID 
   WHERE f.FearID = pf.FearID AND p.PersonID = pf.PersonID

Batch File; List files in directory, only filenames?

create a batch-file with the following code:

dir %1 /b /a-d > list.txt

Then drag & drop a directory on it and the files inside the directory will be listed in list.txt

Access-Control-Allow-Origin wildcard subdomains, ports and protocols

EDIT: Use @Noyo's solution instead of this one. It's simpler, clearer and likely a lot more performant under load.


I did some playing around with this issue and came up with this reusable .htaccess (or httpd.conf) solution that works with Apache:

<IfModule mod_rewrite.c>
<IfModule mod_headers.c>
    # Define the root domain that is allowed
    SetEnvIf Origin .+

    # Check that the Origin: matches the defined root domain and capture it in
    # an environment var if it does
    RewriteEngine On
    RewriteCond %{ENV:ACCESS_CONTROL_ROOT} !=""
    RewriteCond %{ENV:ACCESS_CONTROL_ORIGIN} =""
    RewriteCond %{ENV:ACCESS_CONTROL_ROOT}&%{HTTP:Origin} ^([^&]+)&(https?://(?:.+?\.)?\1(?::\d{1,5})?)$
    RewriteRule .* - [E=ACCESS_CONTROL_ORIGIN:%2]

    # Set the response header to the captured value if there was a match
    Header set Access-Control-Allow-Origin %{ACCESS_CONTROL_ORIGIN}e env=ACCESS_CONTROL_ORIGIN

Just set the ACCESS_CONTROL_ROOT variable at the top of the block to your root domain and it will echo the Origin: request header value back to the client in the Access-Control-Allow-Origin: response header value if it matches your domain.

Note also that you can use as the ACCESS_CONTROL_ROOT and it will limit origins to and * (i.e. it doesn't have to be the domain root). The elements that are allowed to vary (protocol, port) can be controlled by modifying the URI matching portion of the regex.

How to call a Web Service Method?

In visual studio, use the "Add Web Reference" feature and then enter in the URL of your web service.

By adding a reference to the DLL, you not referencing it as a web service, but simply as an assembly.

When you add a web reference it create a proxy class in your project that has the same or similar methods/arguments as your web service. That proxy class communicates with your web service via SOAP but hides all of the communications protocol stuff so you don't have to worry about it.

How to use 'hover' in CSS

You need to concatenate the selector and pseudo selector. You'll also need a style element to contain your styles. Most people use an external stylesheet, for lots of benefits (caching for one).

<a class="hover">click</a>

<style type="text/css">

    a.hover:hover {
        text-decoration: underline;



Just a note: the hover class is not necessary, unless you are defining only certain links to have this behavior (which may be the case)

How can I turn a string into a list in Python?

The list() function [docs] will convert a string into a list of single-character strings.

>>> list('hello')
['h', 'e', 'l', 'l', 'o']

Even without converting them to lists, strings already behave like lists in several ways. For example, you can access individual characters (as single-character strings) using brackets:

>>> s = "hello"
>>> s[1]
>>> s[4]

You can also loop over the characters in the string as you can loop over the elements of a list:

>>> for c in 'hello':
...     print c + c,
hh ee ll ll oo

How do I capture all of my compiler's output to a file?

The compiler warnings happen on stderr, not stdout, which is why you don't see them when you just redirect make somewhere else. Instead, try this if you're using Bash:

$ make &> results.txt

The & means "redirect stdout and stderr to this location". Other shells often have similar constructs.

How to make g++ search for header files in a specific directory?

gcc -I/path -L/path
  • -I /path path to include, gcc will find .h files in this path

  • -L /path contains library files, .a, .so

JavaScript to get rows count of a HTML table

This is another option, using jQuery and getting only tbody rows (with the data) and desconsidering thead/tfoot.

$("#tableId > tbody > tr").length

console.log($("#myTableId > tbody > tr").length);
.demo {
   border:1px solid #C0C0C0;

.demo caption {

.demo th {
   border:1px solid #C0C0C0;

.demo td {
   border:1px solid #C0C0C0;
<script src=""></script>
<table id="myTableId" class="demo">
   <caption>Table 1</caption>
         <th>Header 1</th>
         <th>Header 2</th>
         <th>Header 3</th>
         <th>Header 4</th>
         <td colspan=4 style="background:#F0F0F0">&nbsp; </td>

Checking if a character is a special character in Java

You can use regular expressions.

String input = ...
if (input.matches("[^a-zA-Z0-9 ]"))

If your definition of a 'special character' is simply anything that doesn't apply to your other filters that you already have, then you can simply add an else. Also note that you have to use else if in this case:

if(c == ' ') {
} else if (Character.isDigit(c)) {
} else if (Character.isLetter(c)) {
} else { 

How to get the request parameters in Symfony 2?

For symfony 4 users:

$query = $request->query->get('query');

UnicodeEncodeError: 'ascii' codec can't encode character at special name

Try setting the system default encoding as utf-8 at the start of the script, so that all strings are encoded using that.

Example -

import sys

The above should set the default encoding as utf-8 .

How to increase the max upload file size in ASP.NET?

You can write that block of code in your application web.config file.

<httpRuntime maxRequestLength="2048576000" />
<sessionState timeout="3600"  />

By writing that code you can upload a larger file than now

Casting objects in Java

Sometimes you will like to receive as argument a Parent reference and inside you probably want to do something specific of a child.

abstract class Animal{
 public abstract void move();
class Shark extends Animal{
 public void move(){
 public void swim(){}
 public void bite(){}
class Dog extends Animal{
 public void move(){
 public void run(){}
 public void bark(){}


void somethingSpecific(Animal animal){
 // Here you don't know and may don't care which animal enters
 animal.move(); // You can call parent methods but you can't call bark or bite.
 if(animal instanceof Shark){
  Shark shark = (Shark)animal;
  shark.bite(); // Now you can call bite!
 //doSomethingSharky(animal); // You cannot call this method.


In above's method you can pass either Shark or Dog, but what if you have something like this:

void doSomethingSharky(Shark shark){
 //Here you cannot receive an Animal reference

That method can only be called by passing shark references So if you have an Animal (and it is deeply a Shark) you can call it like this:

Animal animal...
doSomethingSharky((Shark) animal)

Bottom line, you can use Parent references and it is usually better when you don't care about the implementation of the parent and use casting to use the Child as an specific object, it will be exactly the same object, but your reference know it, if you don't cast it, your reference will point to the same object but cannot be sure what kind of Animal would it be, therefore will only allow you to call known methods.

std::thread calling method of class

Not so hard:

#include <thread>

void Test::runMultiThread()
    std::thread t1(&Test::calculate, this,  0, 10);
    std::thread t2(&Test::calculate, this, 11, 20);

If the result of the computation is still needed, use a future instead:

#include <future>

void Test::runMultiThread()
     auto f1 = std::async(&Test::calculate, this,  0, 10);
     auto f2 = std::async(&Test::calculate, this, 11, 20);

     auto res1 = f1.get();
     auto res2 = f2.get();

Which ChromeDriver version is compatible with which Chrome Browser version?

In case of mine, I solved it just by npm install protractor@latest -g and npm install webdriver-manager@latest. I am using chrome 80.x version. It worked for me in both Angular 4 & 6

How can I use querySelector on to pick an input element by name?

You can try 'input[name="pwd"]':

function checkForm(){
     var form = document.forms[0];
     var selectElement = form.querySelector('input[name="pwd"]');
     var selectedValue = selectElement.value;

take a look a this