Programs & Examples On #Ora 00979

ORA-00979: not a GROUP BY expression


I know I'm late to the party, but try this...

FROM TrainTable

Src: Group Concat Documentation

Edit: fixed sql syntax

ORA-00979 not a group by expression

Too bad Oracle has limitations like these. Sure, the result for a column not in the GROUP BY would be random, but sometimes you want that. Silly Oracle, you can do this in MySQL/MSSQL.

BUT there is a work around for Oracle:

While the following line does not work

SELECT unique_id_col, COUNT(1) AS cnt FROM yourTable GROUP BY col_A;

You can trick Oracle with some 0's like the following, to keep your column in scope, but not group by it (assuming these are numbers, otherwise use CONCAT)

SELECT MAX(unique_id_col) AS unique_id_col, COUNT(1) AS cnt 
FROM yourTable GROUP BY col_A, (unique_id_col*0 + col_A);

How to specify a port to run a create-react-app based project?

In your package.json, go to scripts and use --port 4000 or set PORT=4000, like in the example below:

package.json (Windows):

"scripts": {
    "start": "set PORT=4000 && react-scripts start"

package.json (Ubuntu):

"scripts": {
    "start": "export PORT=4000 && react-scripts start"

Resizing Images in VB.NET

This will re-size any image using the best quality with support for 32bpp with alpha. The new image will have the original image centered inside the new one at the original aspect ratio.

#Region " ResizeImage "
    Public Overloads Shared Function ResizeImage(SourceImage As Drawing.Image, TargetWidth As Int32, TargetHeight As Int32) As Drawing.Bitmap
        Dim bmSource = New Drawing.Bitmap(SourceImage)

        Return ResizeImage(bmSource, TargetWidth, TargetHeight)
    End Function

    Public Overloads Shared Function ResizeImage(bmSource As Drawing.Bitmap, TargetWidth As Int32, TargetHeight As Int32) As Drawing.Bitmap
        Dim bmDest As New Drawing.Bitmap(TargetWidth, TargetHeight, Drawing.Imaging.PixelFormat.Format32bppArgb)

        Dim nSourceAspectRatio = bmSource.Width / bmSource.Height
        Dim nDestAspectRatio = bmDest.Width / bmDest.Height

        Dim NewX = 0
        Dim NewY = 0
        Dim NewWidth = bmDest.Width
        Dim NewHeight = bmDest.Height

        If nDestAspectRatio = nSourceAspectRatio Then
            'same ratio
        ElseIf nDestAspectRatio > nSourceAspectRatio Then
            'Source is taller
            NewWidth = Convert.ToInt32(Math.Floor(nSourceAspectRatio * NewHeight))
            NewX = Convert.ToInt32(Math.Floor((bmDest.Width - NewWidth) / 2))
            'Source is wider
            NewHeight = Convert.ToInt32(Math.Floor((1 / nSourceAspectRatio) * NewWidth))
            NewY = Convert.ToInt32(Math.Floor((bmDest.Height - NewHeight) / 2))
        End If

        Using grDest = Drawing.Graphics.FromImage(bmDest)
            With grDest
                .CompositingQuality = Drawing.Drawing2D.CompositingQuality.HighQuality
                .InterpolationMode = Drawing.Drawing2D.InterpolationMode.HighQualityBicubic
                .PixelOffsetMode = Drawing.Drawing2D.PixelOffsetMode.HighQuality
                .SmoothingMode = Drawing.Drawing2D.SmoothingMode.AntiAlias
                .CompositingMode = Drawing.Drawing2D.CompositingMode.SourceOver

                .DrawImage(bmSource, NewX, NewY, NewWidth, NewHeight)
            End With
        End Using

        Return bmDest
    End Function
#End Region

Limit to 2 decimal places with a simple pipe

It's Works

.ts -> pi = 3.1415

.html -> {{ pi | number : '1.0-2' }}

Ouput -> 3.14
  1. if it has a decimal it only shows one
  2. if it has two decimals it shows both

this works for me!!! thanks!!

How does the "position: sticky;" property work?

Funny moment that wasn't obvious for me: at least in Chrome 70 position: sticky is not applied if you've set it using DevTools.

C# static class constructor

A static constructor looks like this

static class Foo
    static Foo()
         // Static initialization code here

It is executed only once when the type is first used. All classes can have static constructors, not just static classes.

How to get a reversed list view on a list in Java?

I use this:

public class ReversedView<E> extends AbstractList<E>{

    public static <E> List<E> of(List<E> list) {
        return new ReversedView<>(list);

    private final List<E> backingList;

    private ReversedView(List<E> backingList){
        this.backingList = backingList;

    public E get(int i) {
        return backingList.get(backingList.size()-i-1);

    public int size() {
        return backingList.size();


like this:

ReversedView.of(backingList) // is a fully-fledged generic (but read-only) list

Listing all extras of an Intent

private TextView tv;

protected void onCreate(Bundle savedInstanceState) {

    tv = new TextView(this);
    tv.setText("Extras: \n\r");


    StringBuilder str = new StringBuilder();
    Bundle bundle = getIntent().getExtras();
    if (bundle != null) {
        Set<String> keys = bundle.keySet();
        Iterator<String> it = keys.iterator();
        while (it.hasNext()) {
            String key =;

How to update a value in a json file and save it through node.js

Save data after task completion

fs.readFile("./sample.json", 'utf8', function readFileCallback(err, data) {
        if (err) {
        } else {
          fs.writeFile("./sample.json", JSON.stringify(result), 'utf8', err => {
            if (err) throw err;
            console.log('File has been saved!');

Display milliseconds in Excel

First represent the epoch of the millisecond time as a date (usually 1/1/1970), then add your millisecond time divided by the number of milliseconds in a day (86400000):


If your cell is properly formatted, you should see a human-readable date/time.

Bootstrap modal link

Please remove . from your target it should be a id

<a href="#bannerformmodal" data-toggle="modal" data-target="#bannerformmodal">Load me</a>

Also you have to give your modal id like below

<div class="modal fade bannerformmodal" tabindex="-1" role="dialog" aria-labelledby="bannerformmodal" aria-hidden="true" id="bannerformmodal">

Here is the solution in a fiddle.

What does the line "#!/bin/sh" mean in a UNIX shell script?

When you try to execute a program in unix (one with the executable bit set), the operating system will look at the first few bytes of the file. These form the so-called "magic number", which can be used to decide the format of the program and how to execute it.

#! corresponds to the magic number 0x2321 (look it up in an ascii table). When the system sees that the magic number, it knows that it is dealing with a text script and reads until the next \n (there is a limit, but it escapes me atm). Having identified the interpreter (the first argument after the shebang) it will call the interpreter.

Other files also have magic numbers. Try looking at a bitmap (.BMP) file via less and you will see the first two characters are BM. This magic number denotes that the file is indeed a bitmap.

How to make a <div> appear in front of regular text/tables

It moves table down because there is no much space, try to decrease/increase width of certain elements so that it finds some space and does not push the table down. Also you may want to use absolute positioning to position the div at exactly the place you want, for example:

   top:100px; /* set top value */
   left:100px; /* set left value */
   width:100px;  /* set width value */

If you want to appear it over something, you also need to give it z-index, so it might look like this:

   top:100px; /* set top value */
   left:100px; /* set left value */
   width:100px;  /* set width value */

How do I implement IEnumerable<T>

If you work with generics, use List instead of ArrayList. The List has exactly the GetEnumerator method you need.

List<MyObject> myList = new List<MyObject>();

extract month from date in python

import datetime

a = '2010-01-31'

datee = datetime.datetime.strptime(a, "%Y-%m-%d")

Out[9]: 1

Out[10]: 2010
Out[11]: 31

Nginx: Job for nginx.service failed because the control process exited

$ ps ax | grep nginx<br>
$ kill -9 PIDs
$ service nginx start

or set back /etc/nginx/sites-available/default

location / {
     # First attempt to serve request as file, then
     # as directory, then fall back to displaying a 404.

     try_files $uri $uri/ =404;

Openssl : error "self signed certificate in certificate chain"

You have a certificate which is self-signed, so it's non-trusted by default, that's why OpenSSL complains. This warning is actually a good thing, because this scenario might also rise due to a man-in-the-middle attack.

To solve this, you'll need to install it as a trusted server. If it's signed by a non-trusted CA, you'll have to install that CA's certificate as well.

Have a look at this link about installing self-signed certificates.

How to exit an Android app programmatically?

Just call this:


Where is JAVA_HOME on macOS Mojave (10.14) to Lion (10.7)?

Newer Oracle JVMs such as 1.7.0_21-b12 seem to install here:

/Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin/Contents/Home

Map implementation with duplicate keys

If there are duplicate keys then a key may correspond to more than one value. The obvious solution is to map the key to a list of these values.

For example in Python:

map = dict()
map["driver"] = list()
print map["driver"]          # It shows john and mike
print map["driver"][0]       # It shows john
print map["driver"][1]       # It shows mike

Remove commas from the string using JavaScript

Related answer, but if you want to run clean up a user inputting values into a form, here's what you can do:

const numFormatter = new Intl.NumberFormat('en-US', {
  style: "decimal",
  maximumFractionDigits: 2

// Good Inputs
parseFloat(numFormatter.format('1234').replace(/,/g,"")) // 1234
parseFloat(numFormatter.format('123').replace(/,/g,"")) // 123

// 3rd decimal place rounds to nearest
parseFloat(numFormatter.format('1234.233').replace(/,/g,"")); // 1234.23
parseFloat(numFormatter.format('1234.239').replace(/,/g,"")); // 1234.24

// Bad Inputs
parseFloat(numFormatter.format('1234.233a').replace(/,/g,"")); // NaN
parseFloat(numFormatter.format('$1234.23').replace(/,/g,"")); // NaN

// Edge Cases
parseFloat(numFormatter.format(true).replace(/,/g,"")) // 1
parseFloat(numFormatter.format(false).replace(/,/g,"")) // 0
parseFloat(numFormatter.format(NaN).replace(/,/g,"")) // NaN

Use the international date local via format. This cleans up any bad inputs, if there is one it returns a string of NaN you can check for. There's no way currently of removing commas as part of the locale (as of 10/12/19), so you can use a regex command to remove commas using replace.

ParseFloat converts the this type definition from string to number

If you use React, this is what your calculate function could look like:

updateCalculationInput = (e) => {
    let value;
    value = numFormatter.format(; // 123,456.78 - 3rd decimal rounds to nearest number as expected
    if(value === 'NaN') return; // locale returns string of NaN if fail
    value = value.replace(/,/g, ""); // remove commas
    value = parseFloat(value); // now parse to float should always be clean input

    // Do the actual math and setState calls here

WPF Databinding: How do I access the "parent" data context?

This will also work:

<Hyperlink Command="{Binding RelativeSource={RelativeSource AncestorType=ItemsControl},
                             Path=DataContext.AllowItemCommand}" />

ListView will inherit its DataContext from Window, so it's available at this point, too.
And since ListView, just like similar controls (e. g. Gridview, ListBox, etc.), is a subclass of ItemsControl, the Binding for such controls will work perfectly.

How to detect the OS from a Bash script?

I recommend to use this complete bash code

    echo "$1" | sed "y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/abcdefghijklmnopqrstuvwxyz/"

OS=`lowercase \`uname\``
KERNEL=`uname -r`
MACH=`uname -m`

if [ "{$OS}" == "windowsnt" ]; then
elif [ "{$OS}" == "darwin" ]; then
    if [ "${OS}" = "SunOS" ] ; then
        ARCH=`uname -p`
        OSSTR="${OS} ${REV}(${ARCH} `uname -v`)"
    elif [ "${OS}" = "AIX" ] ; then
        OSSTR="${OS} `oslevel` (`oslevel -r`)"
    elif [ "${OS}" = "Linux" ] ; then
        if [ -f /etc/redhat-release ] ; then
            DIST=`cat /etc/redhat-release |sed s/\ release.*//`
            PSUEDONAME=`cat /etc/redhat-release | sed s/.*\(// | sed s/\)//`
            REV=`cat /etc/redhat-release | sed s/.*release\ // | sed s/\ .*//`
        elif [ -f /etc/SuSE-release ] ; then
            PSUEDONAME=`cat /etc/SuSE-release | tr "\n" ' '| sed s/VERSION.*//`
            REV=`cat /etc/SuSE-release | tr "\n" ' ' | sed s/.*=\ //`
        elif [ -f /etc/mandrake-release ] ; then
            PSUEDONAME=`cat /etc/mandrake-release | sed s/.*\(// | sed s/\)//`
            REV=`cat /etc/mandrake-release | sed s/.*release\ // | sed s/\ .*//`
        elif [ -f /etc/debian_version ] ; then
            DIST=`cat /etc/lsb-release | grep '^DISTRIB_ID' | awk -F=  '{ print $2 }'`
            PSUEDONAME=`cat /etc/lsb-release | grep '^DISTRIB_CODENAME' | awk -F=  '{ print $2 }'`
            REV=`cat /etc/lsb-release | grep '^DISTRIB_RELEASE' | awk -F=  '{ print $2 }'`
        if [ -f /etc/UnitedLinux-release ] ; then
            DIST="${DIST}[`cat /etc/UnitedLinux-release | tr "\n" ' ' | sed s/VERSION.*//`]"
        OS=`lowercase $OS`
        DistroBasedOn=`lowercase $DistroBasedOn`
        readonly OS
        readonly DIST
        readonly DistroBasedOn
        readonly PSUEDONAME
        readonly REV
        readonly KERNEL
        readonly MACH

echo $OS
echo $KERNEL
echo $MACH

more examples examples here:

How to use mongoimport to import csv

mongoimport -d test -c test --type csv --file SampleCSVFile_119kb.csv --headerline

check collection data:-

var collections = db.getCollectionNames();_x000D_
for(var i = 0; i< collections.length; i++)_x000D_
{    _x000D_
   print('Collection: ' + collections[i]);_x000D_
   // print the name of each collection_x000D_
   //and then print the json of each of its elements_x000D_

Apply function to each element of a list

Or, alternatively, you can take a list comprehension approach:

>>> mylis = ['this is test', 'another test']
>>> [item.upper() for item in mylis]

How to get video duration, dimension and size in PHP?

getID3 supports video formats. See:

Edit: So, in code format, that'd be like:

$getID3 = new getID3;
$file = $getID3->analyze($filename);
echo("Duration: ".$file['playtime_string'].
" / Dimensions: ".$file['video']['resolution_x']." wide by ".$file['video']['resolution_y']." tall".
" / Filesize: ".$file['filesize']." bytes<br />");

Note: You must include the getID3 classes before this will work! See the above link.

Edit: If you have the ability to modify the PHP installation on your server, a PHP extension for this purpose is ffmpeg-php. See:

Apply global variable to Vuejs

Just Adding Instance Properties

For example, all components can access a global appName, you just write one line code:

Vue.prototype.$appName = 'My App'

$ isn't magic, it's a convention Vue uses for properties that are available to all instances.

Alternatively, you can write a plugin that includes all global methods or properties.

How to temporarily disable a click handler in jQuery?

This is a more idiomatic alternative to the artificial state variable solutions:

$("#button_id").one('click', DoSomething);

function DoSomething() {
  // do something.

  $("#button_id").one('click', DoSomething);

One will only execute once (until attached again). More info here:

How to downgrade the installed version of 'pip' on windows?

pip itself is just a normal python package. Thus you can install pip with pip.

Of cource, you don't want to affect the system's pip, install it inside a virtualenv.

pip install pip==1.2.1

How to align text below an image in CSS?

Best way is to wrap the Image and Paragraph text with a DIV and assign a class.


<div class="image1">
    <div class="imgWrapper">
        <img src="images/img1.png" width="250" height="444" alt="Screen 1"/>
        <p>It's my first Image</p>

Check if a class is derived from a generic class

Added to @jaredpar's answer, here's what I use to check for interfaces:

public static bool IsImplementerOfRawGeneric(this Type type, Type toCheck)
    if (toCheck.GetTypeInfo().IsClass)
        return false;

    return type.GetInterfaces().Any(interfaceType =>
        var current = interfaceType.GetTypeInfo().IsGenericType ?
                    interfaceType.GetGenericTypeDefinition() : interfaceType;
        return current == toCheck;

public static bool IsSubTypeOfRawGeneric(this Type type, Type toCheck)
    return type.IsInterface ?
          IsImplementerOfRawGeneric(type, toCheck)
        : IsSubclassOfRawGeneric(type, toCheck);


Console.WriteLine(typeof(IList<>).IsSubTypeOfRawGeneric(typeof(IList<int>))); // true

Gradle Build Android Project "Could not resolve all dependencies" error

Try to turn off your firewall, it works for me. It seems that android studio wants to download some dependencies and our firewall prevents it from downloading it, just be aware that turning your firewall off may lower the security of your computer. If you have more time you can manually allow your android studio to bypass your firewall, this way you can turn on your firewall while allowing android studio to download anything that it wants.

How can I remove a button or make it invisible in Android?

Try This Code :


Converting File to MultiPartFile

It's working for me:

File file = path.toFile();
String mimeType = Files.probeContentType(path);     

DiskFileItem fileItem = new DiskFileItem("file", mimeType, false, file.getName(), (int) file.length(),
MultipartFile multipartFile = new CommonsMultipartFile(fileItem);

How to retrieve the first word of the output of a command in bash?

I wondered how several of the top answers measured up in terms of speed. I tested the following:

1 @mattbh's

echo "..." | awk '{print $1;}'

2 @ghostdog74's

string="..."; set -- $string; echo $1

3 @boontawee-home's

echo "..." | { read -a array ; echo ${array[0]} ; }

and 4 @boontawee-home's

echo "..." | { read first _ ; echo $first ; }

I measured them with Python's timeit in a Bash script in a Zsh terminal on macOS, using a test string with 215 5-letter words. Did each measurement five times (the results were all for 100 loops, best of 3), and averaged the results:

method       time
1. awk       9.2ms
2. set       11.6ms (1.26 * "1")
3. read -a   11.7ms (1.27 * "1")
4. read      13.6ms (1.48 * "1")

Nice job, voters The votes (as of this writing) match the solutions' speed!

How to get selected option using Selenium WebDriver with Java

Completing the answer:

String selectedOption = new Select(driver.findElement(By.xpath("Type the xpath of the drop-down element"))).getFirstSelectedOption().getText();

Assert.assertEquals("Please select any option...", selectedOption);

error: 'Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)' -- Missing /var/run/mysqld/mysqld.sock

This solution can help others, sometimes the fix is very simple.

In your live environment restart mysql server and apache

sudo service mysql restart
sudo apache services restart

this is a common problem when you install a plugin or execute any database commands.

Change directory command in Docker?

RUN git clone http://username:password@url/example.git
WORKDIR /folder
RUN make

Angular.js How to change an elements css class on click and to remove all others

have you tried with a condition in ng-class like here : ?

    <span id='1' ng-class='{"myclass":tog==1}' ng-click='tog=1'>span 1</span>
    <span id='2' ng-class='{"myclass":tog==2}' ng-click='tog=2'>span 2</span>

How to change Apache Tomcat web server port number

Navigate to /tomcat-root/conf folder. Within you will find the server.xml file.

Open the server.xml in your preferred editor. Search the below similar statement (not exactly same as below will differ)

    <Connector port="8080" protocol="HTTP/1.1" 
           redirectPort="8443" />

Going to give the port number to 9090

     <Connector port="9090" protocol="HTTP/1.1" 
           redirectPort="8443" />

Save the file and restart the server. Now the tomcat will listen at port 9090

jQuery when element becomes visible

I like plugin It works without timers!

Simple usage

$('.some:visible').livequery( function(){ ... } );

But you need to fix a mistake. Replace line

$jQlq.registerPlugin('append', 'prepend', 'after', 'before', 'wrap', 'attr', 'removeAttr', 'addClass', 'removeClass', 'toggleClass', 'empty', 'remove', 'html', 'prop', 'removeProp');


$jQlq.registerPlugin('show', 'append', 'prepend', 'after', 'before', 'wrap', 'attr', 'removeAttr', 'addClass', 'removeClass', 'toggleClass', 'empty', 'remove', 'html', 'prop', 'removeProp');

How do I post form data with fetch api?

To post form data with fetch api, try this code it works for me ^_^

function card(fileUri) {
let body = new FormData();
let formData = new FormData();
formData.append('file', fileUri);

      body: formData,
      method: "post"

Angular - res.json() is not a function

Had a similar problem where we wanted to update from deprecated Http module to HttpClient in Angular 7. But the application is large and need to change res.json() in a lot of places. So I did this to have the new module with back support.

return this.http.get(this.BASE_URL + url)
        let res = {'results': JSON.stringify(data),
        'json': ()=>{return data;}
       return res; 
      .catch(error => {
        return Promise.reject(error);

Adding a dummy "json" named function from the central place so that all other services can still execute successfully before updating them to accommodate a new way of response handling i.e. without "json" function.

Return multiple fields as a record in PostgreSQL with PL/pgSQL

You need to define a new type and define your function to return that type.

CREATE TYPE my_type AS (f1 varchar(10), f2 varchar(10) /* , ... */ );

CREATE OR REPLACE FUNCTION get_object_fields(name text) 
RETURNS my_type 

  result_record my_type;

  SELECT f1, f2, f3
  INTO result_record.f1, result_record.f2, result_record.f3
  FROM table1
  WHERE pk_col = 42;

  SELECT f3 
  INTO result_record.f3
  FROM table2
  WHERE pk_col = 24;

  RETURN result_record;

$$ LANGUAGE plpgsql; 

If you want to return more than one record you need to define the function as returns setof my_type


Another option is to use RETURNS TABLE() instead of creating a TYPE which was introduced in Postgres 8.4

CREATE OR REPLACE FUNCTION get_object_fields(name text) 
  RETURNS TABLE (f1 varchar(10), f2 varchar(10) /* , ... */ )

header location not working in my php code

Remove Space

Correct : header("Location: home.php"); or header("Location:home.php");

Incorrect : header("Location :home.php");

Remove space between Location and : --> header("Location(remove space): home.php");

How to add Class in <li> using wp_nav_menu() in Wordpress?

HERE WordPress add custom class in wp_nav_menu links

OR you can add class <li class='my_own_class'><a href=''>Link</a></li> from admin panel:

  1. Go to YOURSITEURL/wp-admin/nav-menus.php


  3. make checked CSS CLASSES, then you will see CSS Classes (optional) field in each menu link.

Should I use JSLint or JSHint JavaScript validation?

This answer has been edited. I'm leaving the original answer below for context (otherwise the comments wouldn't make sense).

When this question was originally asked, JSLint was the main linting tool for JavaScript. JSHint was a new fork of JSLint, but had not yet diverged much from the original.

Since then, JSLint has remained pretty much static, while JSHint has changed a great deal - it has thrown away many of JSLint's more antagonistic rules, has added a whole load of new rules, and has generally become more flexible. Also, another tool ESLint is now available, which is even more flexible and has more rule options.

In my original answer, I said that you should not force yourself to stick to JSLint's rules; as long as you understood why it was throwing a warning, you could make a judgement for yourself about whether to change the code to resolve the warning or not.

With the ultra-strict ruleset of JSLint from 2011, this was reasonable advice -- I've seen very few JavaScript codesets that could pass a JSLint test. However with the more pragmatic rules available in today's JSHint and ESLint tools, it is a much more realistic proposition to try to get your code passing through them with zero warnings.

There may still occasionally be cases where a linter will complain about something that you've done intentionally -- for example, you know that you should always use === but just this one time you have a good reason to use ==. But even then, with ESLint you have the option to specify eslint-disable around the line in question so you can still have a passing lint test with zero warnings, with the rest of your code obeying the rule. (just don't do that kind of thing too often!)


By all means use JSLint. But don't get hung up on the results and on fixing everything that it warns about. It will help you improve your code, and it will help you find potential bugs, but not everything that JSLint complains about turns out to be a real problem, so don't feel like you have to complete the process with zero warnings.

Pretty much any Javascript code with any significant length or complexity will produce warnings in JSLint, no matter how well written it is. If you don't believe me, try running some popular libraries like JQuery through it.

Some JSLint warnings are more valuable than others: learn which ones to watch out for, and which ones are less important. Every warning should be considered, but don't feel obliged to fix your code to clear any given warning; it's perfectly okay to look at the code and decide you're happy with it; there are times when things that JSlint doesn't like are actually the right thing to do.

Is Google Play Store supported in avd emulators?

Easiest way: You should create a new emulator, before opening it for the first time follow these 3 easy steps:

1- go to C:\Users[user].android\avd[your virtual device folder] open "config.ini" with text editor like notepad

2- change

"PlayStore.enabled=false" to "PlayStore.enabled=true"

3- change

mage.sysdir.1 = system-images\android-30\google_apis\x86\


image.sysdir.1 = system-images\android-30\google_apis_playstore\x86\

Why is __dirname not defined in node REPL?

I was running a script from batch file as SYSTEM user and all variables like process.cwd() , path.resolve() and all other methods would give me path to C:\Windows\System32 folder instead of actual path. During experiments I noticed that when an error is thrown the stack contains a true path to the node file.

Here's a very hacky way to get true path by triggering an error and extracting path from e.stack. Do not use.

// this should be the name of currently executed file
const currentFilename = 'index.js';

function veryHackyGetFolder() {
  try {
    throw new Error();
  } catch(e) {
    const fullMsg = e.stack.toString();
    const beginning = fullMsg.indexOf('file:///') + 8;
    const end = fullMsg.indexOf('\/' + currentFilename);
    const dir = fullMsg.substr(beginning, end - beginning).replace(/\//g, '\\');
    return dir;


const dir = veryHackyGetFolder();

Where do alpha testers download Google Play Android apps?

You can use a Google Group and have your alpha testers just join the group. Everything else should just be handled through the Google Play Store App.

Eclipse comment/uncomment shortcut?

For single line comment you can use Ctrl + / and for multiple line comment you can use Ctrl + Shift + / after selecting the lines you want to comment in java editor.

On Mac/OS X you can use ? + / to comment out single lines or selected blocks.

Sending HTML mail using a shell script

I've been trying to just make a simple bash script that emails out html formatted content-type and all these are great but I don't want to be creating local files on the filesystem to be passing into the script and also on our version of mailx(12.5+) the -a parameter for mail doesn't work anymore since it adds an attachment and I couldn't find any replacement parameter for additional headers so the easiest way for me was to use sendmail.

Below is the simplest 1 liner I created to run in our bash script that works for us. It just basically passes the Content-Type: text/html, subject, and the body and works.

printf "Content-Type: text/html\nSubject: Test Email\nHTML BODY<b>test bold</b>" | sendmail <Email Address To>

If you wanted to create an entire html page from a variable an alternative method I used in the bash script was to pass the variable as below.

emailBody="From: <Email Address From>
Subject: Test
Content-Type: text/html; charset=\"us-ascii\"
<b> test bold</b>

echo "$emailBody" | sendmail <Email Address To>

How can I discard remote changes and mark a file as "resolved"?

Make sure of the conflict origin: if it is the result of a git merge, see Brian Campbell's answer.

But if is the result of a git rebase, in order to discard remote (their) changes and use local changes, you would have to do a:

git checkout --theirs -- .

See "Why is the meaning of “ours” and “theirs” reversed"" to see how ours and theirs are swapped during a rebase (because the upstream branch is checked out).

Why does the program give "illegal start of type" error?

You have an extra '{' before return type. You may also want to put '==' instead of '=' in if and else condition.

unknown type name 'uint8_t', MinGW


To Be Clear: If the order of your #includes matters and it is not part of your design pattern (read: you don't know why), then you need to rethink your design. Most likely, this just means you need to add the #include to the header file causing problems.

At this point, I have little interest in discussing/defending the merits of the example but will leave it up as it illustrates some nuances in the compilation process and why they result in errors.


You need to #include the stdint.h BEFORE you #include any other library interfaces that need it.


My LCD library uses uint8_t types. I wrote my library with an interface (Display.h) and an implementation (Display.c)

In display.c, I have the following includes.

#include <stdint.h>
#include <string.h>
#include <avr/io.h>
#include <Display.h>
#include <GlobalTime.h>

And this works.

However, if I re-arrange them like so:

#include <string.h>
#include <avr/io.h>
#include <Display.h>
#include <GlobalTime.h>
#include <stdint.h>

I get the error you describe. This is because Display.h needs things from stdint.h but can't access it because that information is compiled AFTER Display.h is compiled.

So move stdint.h above any library that need it and you shouldn't get the error anymore.

Importing images from a directory (Python) to list or dictionary

from PIL import Image
import os, os.path

imgs = []
path = "/home/tony/pictures"
valid_images = [".jpg",".gif",".png",".tga"]
for f in os.listdir(path):
    ext = os.path.splitext(f)[1]
    if ext.lower() not in valid_images:

How can I make all images of different height and width the same via CSS?

You can do it this way:

position: relative;
width: 100px;
height: 100px;
overflow: hidden;
z-index: 1;

left: 50%;
position: absolute;
top: 50%;
-ms-transform: translate(-50%, -50%);
-webkit-transform: translate(-50%, -50%);
-moz-transform: translate(-50%, -50%);
transform: translate(-50%, -50%);
max-width: 100%;

Convert string date to timestamp in Python

>>> import time
>>> import datetime
>>> s = "01/12/2011"
>>> time.mktime(datetime.datetime.strptime(s, "%d/%m/%Y").timetuple())

GZIPInputStream reading line by line

BufferedReader in = new BufferedReader(new InputStreamReader(
        new GZIPInputStream(new FileInputStream("F:/gawiki-20090614-stub-meta-history.xml.gz"))));

String content;

while ((content = in.readLine()) != null)


How to check 'undefined' value in jQuery

I know I am late to answer the function but jquery have a in build function to do this

if(jQuery.type(val) === "undefined"){
    //Some code goes here

Refer jquery API document of jquery.type for the same.

String MinLength and MaxLength validation don't work ( mvc)

They do now, with latest version of MVC (and jquery validate packages). mvc51-release-notes#Unobtrusive

Thanks to this answer for pointing it out!

ORA-00979 not a group by expression

Same error also come when UPPER or LOWER keyword not used in both place in select expression and group by expression .

Wrong :-

select a , count(*) from my_table group by UPPER(a) .

Right :-

select UPPER(a) , count(*) from my_table group by UPPER(a) .

Java Synchronized list

synchronized(list) {
    for (Object o : list) {}

Custom alert and confirm box in jquery

I made custom messagebox using jquery UI component. Here is demo

You have to pass just the parameters like caption name, message, button's text. You can specify trigger function on any button click. This will helpful for you.

How to create materialized views in SQL Server?

You might need a bit more background on what a Materialized View actually is. In Oracle these are an object that consists of a number of elements when you try to build it elsewhere.

An MVIEW is essentially a snapshot of data from another source. Unlike a view the data is not found when you query the view it is stored locally in a form of table. The MVIEW is refreshed using a background procedure that kicks off at regular intervals or when the source data changes. Oracle allows for full or partial refreshes.

In SQL Server, I would use the following to create a basic MVIEW to (complete) refresh regularly.

First, a view. This should be easy for most since views are quite common in any database Next, a table. This should be identical to the view in columns and data. This will store a snapshot of the view data. Then, a procedure that truncates the table, and reloads it based on the current data in the view. Finally, a job that triggers the procedure to start it's work.

Everything else is experimentation.

How to change resolution (DPI) of an image?

You have to copy the bits over a new image with the target resolution, like this:

    using (Bitmap bitmap = (Bitmap)Image.FromFile("file.jpg"))
        using (Bitmap newBitmap = new Bitmap(bitmap))
            newBitmap.SetResolution(300, 300);
            newBitmap.Save("file300.jpg", ImageFormat.Jpeg);

SyntaxError: unexpected EOF while parsing

Maybe this is what you mean to do:

import random

x = 0
z = input('Please Enter an integer: ')
z = int(z) # you need to capture the result of the expressioin: int(z) and assign it backk to z

def main():
    for i in range(x,z):
        n1 = random.randrange(1,3)
        n2 = random.randrange(1,3)
        t1 = n1+n2

  1. do z = int(z)
  2. Add the missing closing parenthesis on the last line of code in your listing.
  3. And have a for-loop that will iterate from x to z-1

Here's a link on the range() function:

How to hide image broken Icon using only CSS/HTML?

I liked the answer by Nick and was playing around with this solution. Found a cleaner method. Since ::before/::after pseudos don't work on replaced elements like img and object they will only work if the object data (src) is not loaded. It keeps the HTML more clean and will only add the pseudo if the object fails to load.

object {_x000D_
  position: relative;_x000D_
  float: left;_x000D_
  display: block;_x000D_
  width: 200px;_x000D_
  height: 200px;_x000D_
  margin-right: 20px;_x000D_
  border: 1px solid black;_x000D_
object::after {_x000D_
  position: absolute;_x000D_
  top: 0;_x000D_
  left: 0;_x000D_
  display: block;_x000D_
  width: 100%;_x000D_
  height: 100%;_x000D_
  content: '';_x000D_
  background: red url("");_x000D_
<object data="" type="image/png"></object>_x000D_
<object data="http://broken.img/url" type="image/png"></object>

Generate 'n' unique random numbers within a range

If you just need sampling without replacement:

>>> import random
>>> random.sample(range(1, 100), 3)
[77, 52, 45]

random.sample takes a population and a sample size k and returns k random members of the population.

If you have to control for the case where k is larger than len(population), you need to be prepared to catch a ValueError:

>>> try:
...   random.sample(range(1, 2), 3)
... except ValueError:
...   print('Sample size exceeded population size.')
Sample size exceeded population size

pandas get column average/mean

Do note that it needs to be in the numeric data type in the first place.

 import pandas as pd
 df['column'] = pd.to_numeric(df['column'], errors='coerce')

Next find the mean on one column or for all numeric columns using describe().


Example of result from describe:

count    62.000000 
mean     84.678548 
std     216.694615 
min      13.100000 
25%      27.012500 
50%      41.220000 
75%      70.817500 
max    1666.860000

Read a text file line by line in Qt

Use this code:

QFile inputFile(fileName);
if (
   QTextStream in(&inputFile);
   while (!in.atEnd())
      QString line = in.readLine();

how to find array size in angularjs

Just use the length property of a JavaScript array like so:


Also, I don't see a starting <script> tag in your code.

If you want the length inside your view, do it like so:

{{ names.length }}

How should I edit an Entity Framework connection string?

Follow the next steps:

  1. Open the app.config and comment on the connection string (save file)
  2. Open the edmx (go to properties, the connection string should be blank), close the edmx file again
  3. Open the app.config and uncomment the connection string (save file)
  4. Open the edmx, go to properties, you should see the connection string uptated!!

How to use OpenSSL to encrypt/decrypt files?

Short Answer:

You likely want to use gpg instead of openssl so see "Additional Notes" at the end of this answer. But to answer the question using openssl:

To Encrypt:

openssl enc -aes-256-cbc -in -out

To Decrypt:

openssl enc -d -aes-256-cbc -in -out

Note: You will be prompted for a password when encrypting or decrypt.

Long Answer:

Your best source of information for openssl enc would probably be:

Command line: openssl enc takes the following form:

openssl enc -ciphername [-in filename] [-out filename] [-pass arg]
[-e] [-d] [-a/-base64] [-A] [-k password] [-kfile filename] 
[-K key] [-iv IV] [-S salt] [-salt] [-nosalt] [-z] [-md] [-p] [-P] 
[-bufsize number] [-nopad] [-debug] [-none] [-engine id]

Explanation of most useful parameters with regards to your question:

    Encrypt the input data: this is the default.

    Decrypt the input data.

-k <password>
    Only use this if you want to pass the password as an argument. 
    Usually you can leave this out and you will be prompted for a 
    password. The password is used to derive the actual key which 
    is used to encrypt your data. Using this parameter is typically
    not considered secure because your password appears in 
    plain-text on the command line and will likely be recorded in 
    bash history.

-kfile <filename>
    Read the password from the first line of <filename> instead of
    from the command line as above.

    base64 process the data. This means that if encryption is taking 
    place the data is base64 encoded after encryption. If decryption 
    is set then the input data is base64 decoded before being 
    You likely DON'T need to use this. This will likely increase the
    file size for non-text data. Only use this if you need to send 
    data in the form of text format via email etc.

    To use a salt (randomly generated) when encrypting. You always
    want to use a salt while encrypting. This parameter is actually
    redundant because a salt is used whether you use this or not 
    which is why it was not used in the "Short Answer" above!

-K key    
    The actual key to use: this must be represented as a string
    comprised only of hex digits. If only the key is specified, the
    IV must additionally be specified using the -iv option. When 
    both a key and a password are specified, the key given with the
    -K option will be used and the IV generated from the password 
    will be taken. It probably does not make much sense to specify 
    both key and password.

-iv IV
    The actual IV to use: this must be represented as a string 
    comprised only of hex digits. When only the key is specified 
    using the -K option, the IV must explicitly be defined. When a
    password is being specified using one of the other options, the 
    IV is generated from this password.

-md digest
    Use the specified digest to create the key from the passphrase.
    The default algorithm as of this writing is sha-256. But this 
    has changed over time. It was md5 in the past. So you might want
    to specify this parameter every time to alleviate problems when
    moving your encrypted data from one system to another or when
    updating openssl to a newer version.

Additional Notes:

Though you have specifically asked about OpenSSL you might want to consider using GPG instead for the purpose of encryption based on this article OpenSSL vs GPG for encrypting off-site backups?

To use GPG to do the same you would use the following commands:

To Encrypt:

gpg --output --symmetric --cipher-algo AES256

To Decrypt:

gpg --output --decrypt

Note: You will be prompted for a password when encrypting or decrypt.

jQuery limit to 2 decimal places

Here is a working example in both Javascript and jQuery:

//In jQuery
$("#calculate").click(function() {
    var num = parseFloat($("#textbox").val());
    var new_num = $("#textbox").val(num.toFixed(2));

// In javascript
document.getElementById('calculate').onclick = function() {
    var num = parseFloat(document.getElementById('textbox').value);
    var new_num = num.toFixed(2);
    document.getElementById('textbox').value = new_num;

AngularJS 1.2 $injector:modulerr

The problem was caused by missing inclusion of ngRoute module. Since version 1.1.6 it's a separate part:

<script src=""></script>

var app = angular.module('myapp', ['ngRoute']);

PHP, display image with Header()

if you know the file name, but don't know the file extention you can use this function:

public function showImage($name)

         $types = [
             'gif'=> 'image/gif',
             'png'=> 'image/png',
             'jpeg'=> 'image/jpeg',
             'jpg'=> 'image/jpeg',
         $root_path  = '/var/www/my_app'; //use your framework to get this properly ..
         foreach($types as $type=>$meta){
             if(file_exists($root_path .'/uploads/'.$name  .'.'. $type)){
                 header('Content-type: ' . $meta);
                 readfile($root_path .'/uploads/'.$name .'.'. $type);

Note: the correct content-type for JPG files is image/jpeg.

Set a persistent environment variable from cmd.exe

Use the SETX command (note the 'x' suffix) to set variables that persist after the cmd window has been closed.

For example, to set an env var "foo" with value of "bar":

setx foo bar

Though it's worth reading the 'notes' that are displayed if you print the usage (setx /?), in particular:

2) On a local system, variables created or modified by this tool will be available in future command windows but not in the current CMD.exe command window.

3) On a remote system, variables created or modified by this tool will be available at the next logon session.

In PowerShell, the [Environment]::SetEnvironmentVariable command.

How could I use requests in asyncio?

The answers above are still using the old Python 3.4 style coroutines. Here is what you would write if you got Python 3.5+.

aiohttp supports http proxy now

import aiohttp
import asyncio

async def fetch(session, url):
    async with session.get(url) as response:
        return await response.text()

async def main():
    urls = [
    tasks = []
    async with aiohttp.ClientSession() as session:
        for url in urls:
            tasks.append(fetch(session, url))
        htmls = await asyncio.gather(*tasks)
        for html in htmls:

if __name__ == '__main__':
    loop = asyncio.get_event_loop()

Adding value to input field with jQuery

You have to escape [ and ]. Try this:

    var fieldID = $(this).prev().attr("id");
    fieldID = fieldID.replace(/([\[\]]+)/g, "\\$1");
    $('#' + fieldID).val("hello world");


How to scan multiple paths using the @ComponentScan annotation?

@ComponentScan uses string array, like this:


When you provide multiple package names in only one string, Spring interprets this as one package name, and thus can't find it.

Random number between 0 and 1 in python

random.random() does exactly that

>>> import random
>>> for i in range(10):
...     print(random.random())

If you want really random numbers, and to cover the range [0, 1]:

>>> import os
>>> int.from_bytes(os.urandom(8), byteorder="big") / ((1 << 64) - 1)

Enable/Disable Anchor Tags using AngularJS

My problem was slightly different: I have anchor tags that define an href, and I want to use ng-disabled to prevent the link from going anywhere when clicked. The solution is to un-set the href when the link is disabled, like this:

<a ng-href="{{isDisabled ? '' : '#/foo'}}"

In this case, ng-disabled is only used for styling the element.

If you want to avoid using unofficial attributes, you'll need to style it yourself:

a.disabled {
    color: #888;
<a ng-href="{{isDisabled ? '' : '#/foo'}}"
   ng-class="{disabled: isDisabled}">Foo</a>

Unit testing click event in Angular

My objective is to check if the 'onEditButtonClick' is getting invoked when the user clicks the edit button and not checking just the console.log being printed.

You will need to first set up the test using the Angular TestBed. This way you can actually grab the button and click it. What you will do is configure a module, just like you would an @NgModule, just for the testing environment

import { TestBed, async, ComponentFixture } from '@angular/core/testing';

describe('', () => {
  let fixture: ComponentFixture<TestComponent>;
  let component: TestComponent;

  beforeEach(async(() => {
      imports: [ ],
      declarations: [ TestComponent ],
      providers: [  ]
    }).compileComponents().then(() => {
      fixture = TestBed.createComponent(TestComponent);
      component = fixture.componentInstance;

Then you need to spy on the onEditButtonClick method, click the button, and check that the method was called

it('should', async(() => {
  spyOn(component, 'onEditButtonClick');

  let button = fixture.debugElement.nativeElement.querySelector('button');;

  fixture.whenStable().then(() => {

Here we need to run an async test as the button click contains asynchronous event handling, and need to wait for the event to process by calling fixture.whenStable()


It is now preferred to use fakeAsync/tick combo as opposed to the async/whenStable combo. The latter should be used if there is an XHR call made, as fakeAsync does not support it. So instead of the above code, refactored, it would look like

it('should', fakeAsync(() => {
  spyOn(component, 'onEditButtonClick');

  let button = fixture.debugElement.nativeElement.querySelector('button');;


Don't forget to import fakeAsync and tick.

See also:

How to check for a valid URL in Java?

I'd love to post this as a comment to Tendayi Mawushe's answer, but I'm afraid there is not enough space ;)

This is the relevant part from the Apache Commons UrlValidator source:

 * This expression derived/taken from the BNF for URI (RFC2396).
private static final String URL_PATTERN =
//         12            3  4          5       6   7        8 9

 * Schema/Protocol (ie. http:, ftp:, file:, etc).
private static final int PARSE_URL_SCHEME = 2;

 * Includes hostname/ip and port number.
private static final int PARSE_URL_AUTHORITY = 4;

private static final int PARSE_URL_PATH = 5;

private static final int PARSE_URL_QUERY = 7;

private static final int PARSE_URL_FRAGMENT = 9;

You can easily build your own validator from there.

Java, How to implement a Shift Cipher (Caesar Cipher)

Java Shift Caesar Cipher by shift spaces.


  1. Only works with a positive number in the shift parameter.
  2. Only works with shift less than 26.
  3. Does a += which will bog the computer down for bodies of text longer than a few thousand characters.
  4. Does a cast number to character, so it will fail with anything but ascii letters.
  5. Only tolerates letters a through z. Cannot handle spaces, numbers, symbols or unicode.
  6. Code violates the DRY (don't repeat yourself) principle by repeating the calculation more than it has to.


  1. Loop through each character in the string.
  2. Add shift to the character and if it falls off the end of the alphabet then subtract shift from the number of letters in the alphabet (26)
  3. If the shift does not make the character fall off the end of the alphabet, then add the shift to the character.
  4. Append the character onto a new string. Return the string.


String cipher(String msg, int shift){
    String s = "";
    int len = msg.length();
    for(int x = 0; x < len; x++){
        char c = (char)(msg.charAt(x) + shift);
        if (c > 'z')
            s += (char)(msg.charAt(x) - (26-shift));
            s += (char)(msg.charAt(x) + shift);
    return s;

How to invoke it:

System.out.println(cipher("abc", 3));  //prints def
System.out.println(cipher("xyz", 3));  //prints abc

Disable ScrollView Programmatically?

You can make a CustomScrollView, for which you can disable its interference with other views. Though this can be sometimes irritating for the end user. Use it with caution.

This is the code:

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ViewParent;

public class CustomScrollView extends android.widget.ScrollView {

    public CustomScrollView(Context context) {

    public CustomScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);

    public CustomScrollView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

    public boolean onInterceptTouchEvent(MotionEvent ev)
        /* Prevent parent controls from stealing our events once we've gotten a touch down */
        if (ev.getActionMasked() == MotionEvent.ACTION_DOWN)
            ViewParent p = getParent();
            if (p != null)

        return false;

How to use the CustomScrollView?

You can add CustomScrollView as a parent to the screen in which you want to add another Scrollview as a child view, and the whole screen is scrollable. I used this for a RelativeLayout.

<?xml version="1.0" encoding="utf-8"?>
    #**Inside this I had a TableLayout and TableRow. Inside the TableRow,**
    #**I had a TextView which I made scrollable from Java Code.**
    #**textView.setMovementMethod(new ScrollingMovementMethod());**

It worked for my case.

How to create a simple map using JavaScript/JQuery

This is an old question, but because the existing answers could be very dangerous, I wanted to leave this answer for future folks who might stumble in here...

The answers based on using an Object as a HashMap are broken and can cause extremely nasty consequences if you use anything other than a String as the key. The problem is that Object properties are coerced to Strings using the .toString method. This can lead to the following nastiness:

function MyObject(name) { = name;
var key1 = new MyObject("one");
var key2 = new MyObject("two");

var map = {};
map[key1] = 1;
map[key2] = 2;

If you were expecting that Object would behave in the same way as a Java Map here, you would be rather miffed to discover that map only contains one entry with the String key [object Object]:

> JSON.stringify(map);
{"[object Object]": 2}

This is clearly not a replacement for Java's HashMap. Bizarrely, given it's age, Javascript does not currently have a general purpose map object. There is hope on the horizon, though: although a glance at the Browser Compatability table there will show that this isn't ready to used in general purpose web apps yet.

In the meantime, the best you can do is:

  • Deliberately use Strings as keys. I.e. use explicit strings as keys rather than relying on the implicit .toString-ing of the keys you use.
  • Ensure that the objects you are using as keys have a well-defined .toString() method that suits your understanding of uniqueness for these objects.
  • If you cannot/don't want to change the .toString of the key Objects, when storing and retrieving the entries, convert the objects to a string which represents your understanding of uniqueness. E.g. map[toUniqueString(key1)] = 1

Sometimes, though, that is not possible. If you want to map data based on, for example File objects, there is no reliable way to do this because the attributes that the File object exposes are not enough to ensure its uniqueness. (You may have two File objects that represent different files on disk, but there is no way to distinguish between them in JS in the browser). In these cases, unfortunately, all that you can do is refactor your code to eliminate the need for storing these in a may; perhaps, by using an array instead and referencing them exclusively by index.

How to execute a java .class from the command line

If you have in your java source

package mypackage;

and your class is with

public class hello {

and in that you have

 public static void main(String[] args) {

Then (after compilation) changeDir (cd) to the directory where your hello.class is. Then

java -cp . mypackage.hello

Mind the current directory and the package name before the class name. It works for my on linux mint and i hope on the other os's also

Thanks Stack overflow for a wealth of info.

How do I redirect users after submit button click?



or simply window.location("login.php");

It is better than using window.location.href =, because replace() does not put the originating page in the session history, meaning the user won't get stuck in a never-ending back-button fiasco. If you want to simulate someone clicking on a link, use location.href. If you want to simulate an HTTP redirect, use location.replace.

How to install a private NPM module without my own registry?

cd somedir
npm install .


npm install path/to/somedir

somedir must contain the package.json inside it.

It knows about git too:

npm install git://

How to Update Multiple Array Elements in mongodb

This does in fact relate to the long standing issue at where there are in fact a number of challenges to a clear syntax that supports "all cases" where mutiple array matches are found. There are in fact methods already in place that "aid" in solutions to this problem, such as Bulk Operations which have been implemented after this original post.

It is still not possible to update more than a single matched array element in a single update statement, so even with a "multi" update all you will ever be able to update is just one mathed element in the array for each document in that single statement.

The best possible solution at present is to find and loop all matched documents and process Bulk updates which will at least allow many operations to be sent in a single request with a singular response. You can optionally use .aggregate() to reduce the array content returned in the search result to just those that match the conditions for the update selection:

    { "$match": { "events.handled": 1 } },
    { "$project": {
        "events": {
            "$setDifference": [
               { "$map": {
                   "input": "$events",
                   "as": "event",
                   "in": {
                       "$cond": [
                           { "$eq": [ "$$event.handled", 1 ] },
]).forEach(function(doc) { {
        bulk.find({ "_id": doc._id, "events.handled": 1  }).updateOne({
            "$set": { "events.$.handled": 0 }

        if ( count % 1000 == 0 ) {
            bulk = db.collection.initializeOrderedBulkOp();

if ( count % 1000 != 0 )

The .aggregate() portion there will work when there is a "unique" identifier for the array or all content for each element forms a "unique" element itself. This is due to the "set" operator in $setDifference used to filter any false values returned from the $map operation used to process the array for matches.

If your array content does not have unique elements you can try an alternate approach with $redact:

    { "$match": { "events.handled": 1 } },
    { "$redact": {
        "$cond": {
            "if": {
                "$eq": [ { "$ifNull": [ "$handled", 1 ] }, 1 ]
            "then": "$$DESCEND",
            "else": "$$PRUNE"

Where it's limitation is that if "handled" was in fact a field meant to be present at other document levels then you are likely going to get unexepected results, but is fine where that field appears only in one document position and is an equality match.

Future releases ( post 3.1 MongoDB ) as of writing will have a $filter operation that is simpler:

    { "$match": { "events.handled": 1 } },
    { "$project": {
        "events": {
            "$filter": {
                "input": "$events",
                "as": "event",
                "cond": { "$eq": [ "$$event.handled", 1 ] }

And all releases that support .aggregate() can use the following approach with $unwind, but the usage of that operator makes it the least efficient approach due to the array expansion in the pipeline:

    { "$match": { "events.handled": 1 } },
    { "$unwind": "$events" },
    { "$match": { "events.handled": 1 } },
    { "$group": {
        "_id": "$_id",
        "events": { "$push": "$events" }

In all cases where the MongoDB version supports a "cursor" from aggregate output, then this is just a matter of choosing an approach and iterating the results with the same block of code shown to process the Bulk update statements. Bulk Operations and "cursors" from aggregate output are introduced in the same version ( MongoDB 2.6 ) and therefore usually work hand in hand for processing.

In even earlier versions then it is probably best to just use .find() to return the cursor, and filter out the execution of statements to just the number of times the array element is matched for the .update() iterations:

db.collection.find({ "events.handled": 1 }).forEach(function(doc){{ return event.handled == 1 }).forEach(function(event){
        db.collection.update({ "_id": doc._id },{ "$set": { "events.$.handled": 0 }});

If you are aboslutely determined to do "multi" updates or deem that to be ultimately more efficient than processing multiple updates for each matched document, then you can always determine the maximum number of possible array matches and just execute a "multi" update that many times, until basically there are no more documents to update.

A valid approach for MongoDB 2.4 and 2.2 versions could also use .aggregate() to find this value:

var result = db.collection.aggregate([
    { "$match": { "events.handled": 1 } },
    { "$unwind": "$events" },
    { "$match": { "events.handled": 1 } },
    { "$group": {
        "_id": "$_id",
        "count": { "$sum": 1 }
    { "$group": {
        "_id": null,
        "count": { "$max": "$count" }

var max = result.result[0].count;

while ( max-- ) {
    db.collection.update({ "events.handled": 1},{ "$set": { "events.$.handled": 0 }},{ "multi": true })

Whatever the case, there are certain things you do not want to do within the update:

  1. Do not "one shot" update the array: Where if you think it might be more efficient to update the whole array content in code and then just $set the whole array in each document. This might seem faster to process, but there is no guarantee that the array content has not changed since it was read and the update is performed. Though $set is still an atomic operator, it will only update the array with what it "thinks" is the correct data, and thus is likely to overwrite any changes occurring between read and write.

  2. Do not calculate index values to update: Where similar to the "one shot" approach you just work out that position 0 and position 2 ( and so on ) are the elements to update and code these in with and eventual statement like:

    { "$set": {
        "events.0.handled": 0,
        "events.2.handled": 0

    Again the problem here is the "presumption" that those index values found when the document was read are the same index values in th array at the time of update. If new items are added to the array in a way that changes the order then those positions are not longer valid and the wrong items are in fact updated.

So until there is a reasonable syntax determined for allowing multiple matched array elements to be processed in single update statement then the basic approach is to either update each matched array element in an indvidual statement ( ideally in Bulk ) or essentially work out the maximum array elements to update or keep updating until no more modified results are returned. At any rate, you should "always" be processing positional $ updates on the matched array element, even if that is only updating one element per statement.

Bulk Operations are in fact the "generalized" solution to processing any operations that work out to be "multiple operations", and since there are more applications for this than merely updating mutiple array elements with the same value, then it has of course been implemented already, and it is presently the best approach to solve this problem.

HTML radio buttons allowing multiple selections

The name of the inputs must be the same to belong to the same group. Then the others will be automatically deselected when one is clicked.

Angular - ng: command not found

>> npm uninstall -g angular-cli
>> npm uninstall -g @angular/cli

>> npm cache clean

Restart you machine

then >> npm install -g @angular/cli@latest

set Path : C:\Users\admin\AppData\Roaming\npm\node_modules@angular\cli

Hope you never get 'ng' not found Connection reset

Whenever I have had odd issues like this, I usually sit down with a tool like WireShark and look at the raw data being passed back and forth. You might be surprised where things are being disconnected, and you are only being notified when you try and read.

How to assign execute permission to a .sh file in windows to be executed in linux

As far as I know the permission system in Linux is set up in such a way to prevent exactly what you are trying to accomplish.

I think the best you can do is to give your Linux user a custom unzip one-liner to run on the prompt:

unzip && chmod +x

If there are multiple scripts that you need to give execute permission to, write a as follows:

# file:

chmod +x
chmod +x
chmod +x

(You can put the scripts all on one line for chmod, but I found separate lines easier to work with in vim and with shell script commands.)

And now your unzip one-liner becomes:

unzip && source

Note that since you are using source to run, it doesn't need execute permission

getting the screen density programmatically in android?

I am using following code to access DPI from modules (no need for having access to a context object):


How to set delay in vbscript

better use timer:

Sub wait (sec)
    dim temp
    do while timer-temp<sec
end Sub

What do Push and Pop mean for Stacks?

Hopefully this will help you visualize a Stack, and how it works.

Empty Stack:

|     |
|     |
|     |

After Pushing A, you get:

|     |
|     |
|  A  |

After Pushing B, you get:

|     |
|  B  |
|  A  |

After Popping, you get:

|     |
|     |
|  A  |

After Pushing C, you get:

|     |
|  C  |
|  A  |

After Popping, you get:

|     |
|     |
|  A  |

After Popping, you get:

|     |
|     |
|     |

Reading and writing to serial port in C on Linux

1) I'd add a /n after init. i.e. write( USB, "init\n", 5);

2) Double check the serial port configuration. Odds are something is incorrect in there. Just because you don't use ^Q/^S or hardware flow control doesn't mean the other side isn't expecting it.

3) Most likely: Add a "usleep(100000); after the write(). The file-descriptor is set not to block or wait, right? How long does it take to get a response back before you can call read? (It has to be received and buffered by the kernel, through system hardware interrupts, before you can read() it.) Have you considered using select() to wait for something to read()? Perhaps with a timeout?

Edited to Add:

Do you need the DTR/RTS lines? Hardware flow control that tells the other side to send the computer data? e.g.

int tmp, serialLines;

cout << "Dropping Reading DTR and RTS\n";
ioctl ( readFd, TIOCMGET, & serialLines );
serialLines &= ~TIOCM_DTR;
serialLines &= ~TIOCM_RTS;
ioctl ( readFd, TIOCMSET, & serialLines );
ioctl ( readFd, TIOCMGET, & tmp );
cout << "Reading DTR status: " << (tmp & TIOCM_DTR) << endl;
sleep (2);

cout << "Setting Reading DTR and RTS\n";
serialLines |= TIOCM_DTR;
serialLines |= TIOCM_RTS;
ioctl ( readFd, TIOCMSET, & serialLines );
ioctl ( readFd, TIOCMGET, & tmp );
cout << "Reading DTR status: " << (tmp & TIOCM_DTR) << endl;

Clear ComboBox selected text

Try specifying the actual index of the item you want erase the text from and set it's Text equal to "".

myComboBox[this.SelectedIndex].Text = ""


myComboBox.selectedIndex.Text = ""

I don't remember the exact syntax but it's something along those lines.

Is there a simple way to delete a list element by value?

With a for loop and a condition:

def cleaner(seq, value):    
    temp = []                      
    for number in seq:
        if number != value:
    return temp

And if you want to remove some, but not all:

def cleaner(seq, value, occ):
    temp = []
    for number in seq:
        if number == value and occ:
            occ -= 1
    return temp

In Python, how to check if a string only contains certain characters?

Here's a simple, pure-Python implementation. It should be used when performance is not critical (included for future Googlers).

import string
allowed = set(string.ascii_lowercase + string.digits + '.')

def check(test_str):
    set(test_str) <= allowed

Regarding performance, iteration will probably be the fastest method. Regexes have to iterate through a state machine, and the set equality solution has to build a temporary set. However, the difference is unlikely to matter much. If performance of this function is very important, write it as a C extension module with a switch statement (which will be compiled to a jump table).

Here's a C implementation, which uses if statements due to space constraints. If you absolutely need the tiny bit of extra speed, write out the switch-case. In my tests, it performs very well (2 seconds vs 9 seconds in benchmarks against the regex).

#include <Python.h>

static PyObject *check(PyObject *self, PyObject *args)
        const char *s;
        Py_ssize_t count, ii;
        char c;
        if (0 == PyArg_ParseTuple (args, "s#", &s, &count)) {
                return NULL;
        for (ii = 0; ii < count; ii++) {
                c = s[ii];
                if ((c < '0' && c != '.') || c > 'z') {
                if (c > '9' && c < 'a') {


PyDoc_STRVAR (DOC, "Fast stringcheck");
static PyMethodDef PROCEDURES[] = {
        {"check", (PyCFunction) (check), METH_VARARGS, NULL},
        {NULL, NULL}
initstringcheck (void) {
        Py_InitModule3 ("stringcheck", PROCEDURES, DOC);

Include it in your

from distutils.core import setup, Extension
ext_modules = [
    Extension ('stringcheck', ['stringcheck.c']),

Use as:

>>> from stringcheck import check
>>> check("abc")
>>> check("ABC")

What is a web service endpoint?

A endpoint is a URL for web service.And Endpoints also is a distributed API.

The Simple Object Access Protocol (SOAP) endpoint is a URL. It identifies the location on the built-in HTTP service where the web services listener listens for incoming requests.



Try this:

select CONVERT(datetime, convert(varchar(10), 20120103))

What is the difference between Step Into and Step Over in a debugger

When debugging lines of code, here are the usual scenarios:

  • (Step Into) A method is about to be invoked, and you want to debug into the code of that method, so the next step is to go into that method and continue debugging step-by-step.
  • (Step Over) A method is about to be invoked, but you're not interested in debugging this particular invocation, so you want the debugger to execute that method completely as one entire step.
  • (Step Return) You're done debugging this method step-by-step, and you just want the debugger to run the entire method until it returns as one entire step.
  • (Resume) You want the debugger to resume "normal" execution instead of step-by-step
  • (Line Breakpoint) You don't care how it got there, but if execution reaches a particular line of code, you want the debugger to temporarily pause execution there so you can decide what to do.

Eclipse has other advanced debugging features, but these are the basic fundamentals.

See also

Git - Undo pushed commits

Here is my way:

Let's say the branch name is develop.

# Create a new temp branch based on one history commit
git checkout <last_known_good_commit_hash>
git checkout -b develop-temp

# Delete the original develop branch and 
# create a new branch with the same name based on the develop-temp branch
git branch -D develop
git checkout -b develop

# Force update this new branch
git push -f origin develop

# Remove the temp branch
git branch -D develop-temp

C++ class forward declaration

To perform *new tile_tree_apple the constructor of tile_tree_apple should be called, but in this place compiler knows nothing about tile_tree_apple, so it can't use the constructor.

If you put

tile tile_tree::tick() {if (rand()%20==0) return *new tile_tree_apple;};

in separate cpp file which has the definition of class tile_tree_apple or includes the header file which has the definition everything will work fine.

How to update TypeScript to latest version with npm?

Try npm install -g typescript@latest. You can also use npm update instead of install, without the latest modifier.

Transition color fade on hover?

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

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

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

.clicker:hover { 
    background: #eee;

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

Broadcast Receiver within a Service

as your service is already setup, simply add a broadcast receiver in your service:

private final BroadcastReceiver receiver = new BroadcastReceiver() {
   public void onReceive(Context context, Intent intent) {
      String action = intent.getAction();
        //action for sms received
      else if(action.equals(android.telephony.TelephonyManager.ACTION_PHONE_STATE_CHANGED)){
           //action for phone state changed

in your service's onCreate do this:

IntentFilter filter = new IntentFilter();
filter.addAction("your_action_strings"); //further more
filter.addAction("your_action_strings"); //further more

registerReceiver(receiver, filter);

and in your service's onDestroy:


and you are good to go to receive broadcast for what ever filters you mention in onCreate. Make sure to add any permission if required. for e.g.

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

TortoiseGit-git did not exit cleanly (exit code 1)

first login on git then before push take the pull. issue will be resolved

How can I revert a single file to a previous version?

Git is very flexible. You shouldn't need hundreds of branches to do what you are asking. If you want to revert the state all the way back to the 2nd change (and it is indeed a change that was already committed and pushed), use git revert. Something like:

git revert a4r9593432 

where a4r9593432 is the starting characters of the hash of the commit you want to back out.

If the commit contains changes to many files, but you just want to revert just one of the files, you can use git reset (the 2nd or 3rd form):

git reset a4r9593432 -- path/to/file.txt
# the reverted state is added to the staging area, ready for commit
git diff --cached path/to/file.txt        # view the changes
git commit
git checkout HEAD path/to/file.txt        # make the working tree match HEAD           

But this is pretty complex, and git reset is dangerous. Use git checkout <hash> <file path> instead, as Jefromi suggests.

If you just want to view what the file looked like in commit x, you can use git show:

git show a4r9593432:path/to/file.txt

For all of the commands, there are many ways to refer to a commit other than via the commit hash (see Naming Commits in the Git User Manual).

How to get the Touch position in android?

Supplemental answer

Given an OnTouchListener

private View.OnTouchListener handleTouch = new View.OnTouchListener() {

    public boolean onTouch(View v, MotionEvent event) {

        int x = (int) event.getX();
        int y = (int) event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                Log.i("TAG", "touched down");
            case MotionEvent.ACTION_MOVE:
                Log.i("TAG", "moving: (" + x + ", " + y + ")");
            case MotionEvent.ACTION_UP:
                Log.i("TAG", "touched up");

        return true;

set on some view:


This gives you the touch event coordinates relative to the view that has the touch listener assigned to it. The top left corner of the view is (0, 0). If you move your finger above the view, then y will be negative. If you move your finger left of the view, then x will be negative.

int x = (int)event.getX();
int y = (int)event.getY();

If you want the coordinates relative to the top left corner of the device screen, then use the raw values.

int x = (int)event.getRawX();
int y = (int)event.getRawY();


Excel formula to get week number in month (having Monday)

If week 1 always starts on the first Monday of the month try this formula for week number


That gets the week number from the date in A1 with no intermediate calculations - if you want to use your "Monday's date" in B1 you can use this version


Continue For loop

I sometimes do a double do loop:



        If I_Don't_Want_to_Finish_This_Loop Then Exit Do

        Exit Do


Loop Until Done

This avoids having "goto spaghetti"

Changing Java Date one hour back

Or using the famous Joda Time library:

DateTime dateTime = new DateTime();
dateTime = dateTime.minusHours(1);
Date modifiedDate = dateTime.toDate();

How can I change the font-size of a select option?

check this fiddle,

i just edited the above fiddle, its working

.selectDefault, .selectDiv option

How to count total lines changed by a specific author in a Git repository?

I wrote this Perl script to accomplish that task.

#!/usr/bin/env perl

use strict;
use warnings;

# save the args to pass to the git log command
my $ARGS = join(' ', @ARGV);

#get the repo slug
my $NAME = _get_repo_slug();

#get list of authors
my @authors = _get_authors();
my ($projectFiles, $projectInsertions, $projectDeletions) = (0,0,0);
#for each author
foreach my $author (@authors) {
  my $command = qq{git log $ARGS --author="$author" --oneline --shortstat --no-merges};
  my ($files, $insertions, $deletions) = (0,0,0);
  my @lines = `$command`;
  foreach my $line (@lines) {
    if ($line =~ m/^\s(\d+)\s\w+\s\w+,\s(\d+)\s\w+\([\+|\-]\),\s(\d+)\s\w+\([\+|\-]\)$|^\s(\d+)\s\w+\s\w+,\s(\d+)\s\w+\(([\+|\-])\)$/) {
      my $lineFiles = $1 ? $1 : $4;
      my $lineInsertions = (defined $6 && $6 eq '+') ? $5 : (defined $2) ? $2 : 0;
      my $lineDeletions = (defined $6 && $6 eq '-') ? $5 : (defined $3) ? $3 : 0;
      $files += $lineFiles;
      $insertions += $lineInsertions;
      $deletions += $lineDeletions;
      $projectFiles += $lineFiles;
      $projectInsertions += $lineInsertions;
      $projectDeletions += $lineDeletions;
  if ($files || $insertions || $deletions) {
      $insertions - $deletions

  $projectInsertions - $projectDeletions

exit 0;

#get the remote.origin.url joins that last two pieces (project and repo folder)
#and removes any .git from the results. 
sub _get_repo_slug {
  my $get_remote_url = "git config --get remote.origin.url";
  my $remote_url = `$get_remote_url`;
  chomp $remote_url;

  my @parts = split('/', $remote_url);

  my $slug = join('-', @parts[-2..-1]);
  $slug =~ s/\.git//;

  return $slug;

sub _get_authors {
  my $git_authors = 'git shortlog -s | cut -c8-';
  my @authors = `$git_authors`;
  chomp @authors;

  return @authors;

I named it git-line-changes-by-author and put into /usr/local/bin. Because it is saved in my path, I can issue the command git line-changes-by-author --before 2018-12-31 --after 2020-01-01 to get the report for the 2019 year. As an example. And if I were to misspell the name git will suggest the proper spelling.

You may want to adjust the _get_repo_slug sub to only include the last portion of the remote.origin.url as my repos are saved as project/repo and your might not be.

Does Typescript support the ?. operator? (And, what's it called?)

This is defined in the ECMAScript Optional Chaining specification, so we should probably refer to optional chaining when we discuss this. Likely implementation:

const result = a?.b?.c;

The long and short of this one is that the TypeScript team are waiting for the ECMAScript specification to get tightened up, so their implementation can be non-breaking in the future. If they implemented something now, it would end up needing major changes if ECMAScript redefine their specification.

See Optional Chaining Specification

Where something is never going to be standard JavaScript, the TypeScript team can implement as they see fit, but for future ECMAScript additions, they want to preserve semantics even if they give early access, as they have for so many other features.

Short Cuts

So all of JavaScripts funky operators are available, including the type conversions such as...

var n: number = +myString; // convert to number
var b: bool = !!myString; // convert to bool

Manual Solution

But back to the question. I have an obtuse example of how you can do a similar thing in JavaScript (and therefore TypeScript) although I'm definitely not suggesting it is a graceful as the feature you are really after.


So if foo is undefined the result is undefined and if foo is defined and has a property named bar that has a value, the result is that value.

I put an example on JSFiddle.

This looks quite sketchy for longer examples.

var postCode = ((person||{}).address||{}).postcode;

Chain Function

If you are desperate for a shorter version while the specification is still up in the air, I use this method in some cases. It evaluates the expression and returns a default if the chain can't be satisfied or ends up null/undefined (note the != is important here, we don't want to use !== as we want a bit of positive juggling here).

function chain<T>(exp: () => T, d: T) {
    try {
        let val = exp();
        if (val != null) {
            return val;
    } catch { }
    return d;

let obj1: { a?: { b?: string }} = {
    a: {
        b: 'c'

// 'c'
console.log(chain(() => obj1.a.b, 'Nothing'));

obj1 = {
    a: {}

// 'Nothing'
console.log(chain(() => obj1.a.b, 'Nothing'));

obj1 = {};

// 'Nothing'
console.log(chain(() => obj1.a.b, 'Nothing'));

obj1 = null;

// 'Nothing'
console.log(chain(() => obj1.a.b, 'Nothing'));

How to log PostgreSQL queries?

In your data/postgresql.conf file, change the log_statement setting to 'all'.


Looking at your new information, I'd say there may be a few other settings to verify:

  • make sure you have turned on the log_destination variable
  • make sure you turn on the logging_collector
  • also make sure that the log_directory directory already exists inside of the data directory, and that the postgres user can write to it.

What does this symbol mean in JavaScript?

See the documentation on MDN about expressions and operators and statements.

Basic keywords and general expressions

this keyword:

var x = function() vs. function x() — Function declaration syntax

(function(){})() — IIFE (Immediately Invoked Function Expression)

someFunction()() — Functions which return other functions

=> — Equal sign, greater than: arrow function expression syntax

|> — Pipe, greater than: Pipeline operator

function*, yield, yield* — Star after function or yield: generator functions

[], Array() — Square brackets: array notation

If the square brackets appear on the left side of an assignment ([a] = ...), or inside a function's parameters, it's a destructuring assignment.

{key: value} — Curly brackets: object literal syntax (not to be confused with blocks)

If the curly brackets appear on the left side of an assignment ({ a } = ...) or inside a function's parameters, it's a destructuring assignment.

`${}` — Backticks, dollar sign with curly brackets: template literals

// — Slashes: regular expression literals

$ — Dollar sign in regex replace patterns: $$, $&, $`, $', $n

() — Parentheses: grouping operator

Property-related expressions

obj.prop, obj[prop], obj["prop"] — Square brackets or dot: property accessors

?., ?.[], ?.() — Question mark, dot: optional chaining operator

:: — Double colon: bind operator

new operator

...iter — Three dots: spread syntax; rest parameters

Increment and decrement

++, -- — Double plus or minus: pre- / post-increment / -decrement operators

Unary and binary (arithmetic, logical, bitwise) operators

delete operator

void operator

+, - — Plus and minus: addition or concatenation, and subtraction operators; unary sign operators

|, &, ^, ~ — Single pipe, ampersand, circumflex, tilde: bitwise OR, AND, XOR, & NOT operators

% — Percent sign: remainder operator

&&, ||, ! — Double ampersand, double pipe, exclamation point: logical operators

?? — Double question mark: nullish-coalescing operator

** — Double star: power operator (exponentiation)

Equality operators

==, === — Equal signs: equality operators

!=, !== — Exclamation point and equal signs: inequality operators

Bit shift operators

<<, >>, >>> — Two or three angle brackets: bit shift operators

Conditional operator

?:… — Question mark and colon: conditional (ternary) operator

Assignment operators

= — Equal sign: assignment operator

%= — Percent equals: remainder assignment

+= — Plus equals: addition assignment operator

&&=, ||=, ??= — Double ampersand, pipe, or question mark, followed by equal sign: logical assignments


Comma operator

, — Comma operator

Control flow

{} — Curly brackets: blocks (not to be confused with object literal syntax)


var, let, const — Declaring variables


label: — Colon: labels

# — Hash (number sign): Private methods or private fields

How to read data when some numbers contain commas as thousand separator?

I want to use R rather than pre-processing the data as it makes it easier when the data are revised. Following Shane's suggestion of using gsub, I think this is about as neat as I can do:

x <- read.csv("file.csv",header=TRUE,colClasses="character")
col2cvt <- 15:41
x[,col2cvt] <- lapply(x[,col2cvt],function(x){as.numeric(gsub(",", "", x))})

Excel function to get first word from sentence in other cell

Generic solution extracting the first "n" words of refcell string into a new string of "x" number of characters

=LEFT(SUBSTITUTE(***refcell***&" "," ",REPT(" ",***x***),***n***),***x***)

Assuming A1 has text string to extract, the 1st word extracted to a 15 character result

=LEFT(SUBSTITUTE(A1&" "," ",REPT(" ",15),1),15)

This would result in "Toronto" being returned to a 15 character string. 1st 2 words extracted to a 30 character result

=LEFT(SUBSTITUTE(A1&" "," ",REPT(" ",30),2),30)

would result in "Toronto is" being returned to a 30 character string

python "TypeError: 'numpy.float64' object cannot be interpreted as an integer"

Similar situation. It was working. Then, I started to include pytables. At first view, no reason to errors. I decided to use another function, that has a domain constraint (elipse) and received the following error:

TypeError: 'numpy.float64' object cannot be interpreted as an integer


TypeError: 'numpy.float64' object is not iterable

The crazy thing: the previous function I was using, no code changed, started to return the same error. My intermediary function, already used was:

def MinMax(x, mini=0, maxi=1)
    return max(min(x,mini), maxi)

The solution was avoid numpy or math:

def MinMax(x, mini=0, maxi=1)
    x = [x_aux if x_aux > mini else mini for x_aux in x]
    x = [x_aux if x_aux < maxi else maxi for x_aux in x]
    return max(min(x,mini), maxi)

Then, everything calm again. It was like one library possessed max and min!

How to draw a graph in PHP?

# ------- The graph values in the form of associative array
    "Jan" => 110,
    "Feb" => 130,
    "Mar" => 215,
    "Apr" => 81,
    "May" => 310,
    "Jun" => 110,
    "Jul" => 190,
    "Aug" => 175,
    "Sep" => 390,
    "Oct" => 286,
    "Nov" => 150,
    "Dec" => 196


# ---- Find the size of graph by substracting the size of borders
$graph_width=$img_width - $margins * 2;
$graph_height=$img_height - $margins * 2; 

$gap= ($graph_width- $total_bars * $bar_width ) / ($total_bars +1);

# -------  Define Colors ----------------

# ------ Create the border around the graph ------


# ------- Max value is required to adjust the scale -------
$ratio= $graph_height/$max_value;

# -------- Create scale and draw horizontal lines  --------

    $y=$img_height - $margins - $horizontal_gap * $i ;
    $v=intval($horizontal_gap * $i /$ratio);


# ----------- Draw the bars here ------
for($i=0;$i< $total_bars; $i++){ 
    # ------ Extract key and value pair from the current pointer position
    $x1= $margins + $gap + $i * ($gap+$bar_width) ;
    $x2= $x1 + $bar_width; 
    $y1=$margins +$graph_height- intval($value * $ratio) ;


Swipe ListView item From right to left show delete button

An app is available that demonstrates a listview that combines both swiping-to-delete and dragging to reorder items. The code is based on Chet Haase's code for swiping-to-delete and Daniel Olshansky's code for dragging-to-reorder.

Chet's code deletes an item immediately. I improved on this by making it function more like Gmail where swiping reveals a bottom view that indicates that the item is deleted but provides an Undo button where the user has the possibility to undo the deletion. Chet's code also has a bug in it. If you have less items in the listview than the height of the listview is and you delete the last item, the last item appears to not be deleted. This was fixed in my code.

Daniel's code requires pressing long on an item. Many users find this unintuitive as it tends to be a hidden function. Instead, I modified the code to allow for a "Move" button. You simply press on the button and drag the item. This is more in line with the way the Google News app works when you reorder news topics.

The source code along with a demo app is available at:

Chet and Daniel are both from Google.

Chet's video on deleting items can be viewed at:

Daniel's video on reordering items can be viewed at:

A considerable amount of work went into gluing all this together to provide a seemless UI experience, so I'd appreciate a Like or Up Vote. Please also star the project in Github.

How can I set a cookie in react?

I set cookies in React using the react-cookie library, it has options you can pass in options to set expiration time.

Check it out here

An example of its use for your case:

import cookie from "react-cookie";

setCookie() => {
  let d = new Date();
  d.setTime(d.getTime() + (minutes*60*1000));

  cookie.set("onboarded", true, {path: "/", expires: d});

Store a closure as a variable in Swift

This works too:

var exeBlk = {
    () -> Void in
exeBlk = {
    //do something
//instead of nil:
exeBlk = {}

Error:could not create the Java Virtual Machine Error:A fatal exception has occured.Program will exit

Try executing below command,

java -help

It gives option as,

-version print product version and exit

java -version is the correct command to execute

Can't import Numpy in Python

I was trying to import numpy in python 3.2.1 on windows 7.

Followed suggestions in above answer for as below after unzipping it

cd numpy-1.6
python install

but got an error with a statement as below

unable to find vcvarsall.bat

For this error I found a related question here which suggested installing mingW. MingW was taking some time to install.

In the meanwhile tried to install numpy 1.6 again using the direct windows installer available at this link the file name is "numpy-1.6.1-win32-superpack-python3.2.exe"

Installation went smoothly and now I am able to import numpy without using mingW.

Long story short try using windows installer for numpy, if one is available.

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

you can use



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

Simulate a click on 'a' element using javascript/jquery

Try adding a function inside the click() method.

  //do something here

It worked for me with a function assigned inside the click() method rather than keeping it empty.

"Parameter not valid" exception loading System.Drawing.Image

Just Follow this to Insert values into database

//Connection String


sqlQuery = "INSERT INTO [dbo].[Client] ([Client_ID],[Client_Name],[Phone],[Address],[Image]) VALUES('" + txtClientID.Text + "','" + txtClientName.Text + "','" + txtPhoneno.Text + "','" + txtaddress.Text + "',@image)";

                cmd = new SqlCommand(sqlQuery, con);
                cmd.Parameters.Add("@image", SqlDbType.Image);
                cmd.Parameters["@image"].Value = img;
            //img is a byte object
           ** /*MemoryStream ms = new MemoryStream();
            byte[] img = ms.ToArray();*/**


How to auto-scroll to end of div when data is added?

var objDiv = document.getElementById("divExample");
objDiv.scrollTop = objDiv.scrollHeight;

How to upgrade rubygems

For me it sufficed to simply run

gem update

Javascript Thousand Separator / string format

You can use ngx-format-field. It is a directive to format the input value which will appear in the view. It will not manipulate the Input value which will be saved in the backend. See link here!



<input type="text" formControlName="currency" [appFormatFields]="CURRENCY"


onChangeCurrency() {

To see the demo: here!

Print array elements on separate lines in Bash?

Try doing this :

$ printf '%s\n' "${my_array[@]}"

The difference between $@ and $*:

  • Unquoted, the results are unspecified. In Bash, both expand to separate args and then wordsplit and globbed.

  • Quoted, "$@" expands each element as a separate argument, while "$*" expands to the args merged into one argument: "$1c$2c..." (where c is the first char of IFS).

You almost always want "$@". Same goes for "${arr[@]}".

Always quote them!

How to change Vagrant 'default' machine name?

I found the multiple options confusing, so I decided to test all of them to see exactly what they do.

I'm using VirtualBox 4.2.16-r86992 and Vagrant 1.3.3.

I created a directory called nametest and ran

vagrant init precise64

to generate a default Vagrantfile. Then I opened the VirtualBox GUI so I could see what names the boxes I create would show up as.

  1. Default Vagrantfile

    Vagrant.configure('2') do |config| = "precise64"
        config.vm.box_url = ""

    VirtualBox GUI Name: "nametest_default_1386347922"

    Comments: The name defaults to the format DIRECTORY_default_TIMESTAMP.

  2. Define VM

    Vagrant.configure('2') do |config| = "precise64"
        config.vm.box_url = ""
        config.vm.define "foohost"

    VirtualBox GUI Name: "nametest_foohost_1386347922"

    Comments: If you explicitly define a VM, the name used replaces the token 'default'. This is the name vagrant outputs on the console. Simplifying based on zook's (commenter) input

  3. Set Provider Name

    Vagrant.configure('2') do |config| = "precise64"
        config.vm.box_url = ""
        config.vm.provider :virtualbox do |vb|
   = "foohost"

    VirtualBox GUI Name: "foohost"

    Comments: If you set the name attribute in a provider configuration block, that name will become the entire name displayed in the VirtualBox GUI.

    Combined Example: Define VM -and- Set Provider Name

    Vagrant.configure('2') do |config| = "precise64"
        config.vm.box_url = ""
        config.vm.define "foohost"
        config.vm.provider :virtualbox do |vb|
   = "barhost"

    VirtualBox GUI Name: "barhost"

    Comments: If you use both methods at the same time, the value assigned to name in the provider configuration block wins. Simplifying based on zook's (commenter) input

  4. Set hostname (BONUS)

    Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
      config.vm.hostname = "buzbar"

    Comments: This sets the hostname inside the VM. This would be the output of hostname command in the VM and also this is what's visible in the prompt like vagrant@<hostname>, here it will look like vagrant@buzbar

Final Code

    Vagrant.configure('2') do |config| = "precise64"
        config.vm.box_url = ""
        config.vm.hostname = "buzbar"
        config.vm.define "foohost"
        config.vm.provider :virtualbox do |vb|
   = "barhost"

So there it is. You now know 3 different options you can set and the effects they have. I guess it's a matter of preference at this point? (I'm new to Vagrant, so I can't speak to best practices yet.)

Binding value to style

Try []="changeBackground()"

javascript compare strings without being case sensitive

Try this...

if(string1.toLowerCase() == string2.toLowerCase()){
    return true;

Also, it's not a loop, it's a block of code. Loops are generally repeated (although they can possibly execute only once), whereas a block of code never repeats.

I read your note about not using toLowerCase, but can't see why it would be a problem.

What is the most efficient way of finding all the factors of a number in Python?

 import math

    I applied finding prime factorization to solve this. (Trial Division)
    It's not complicated

    def generate_factors(n):
        lower_bound_check = int(math.sqrt(n))  # determine lowest bound divisor range [16 = 4]
        factors = set()  # store factors
        for divisors in range(1, lower_bound_check + 1):  # loop [1 .. 4]
            if n % divisors == 0:
                factors.add(divisors)  # lower bound divisor is found 16 [ 1, 2, 4]
                factors.add(n // divisors)  # get upper divisor from lower [ 16 / 1 = 16, 16 / 2 = 8, 16 / 4 = 4]
        return factors  # [1, 2, 4, 8 16]

    print(generate_factors(12)) # {1, 2, 3, 4, 6, 12} -> pycharm output

 Pierre Vriens hopefully this makes more sense. this is an O(nlogn) solution. 

'DataFrame' object has no attribute 'sort'

Pandas Sorting 101

sort has been replaced in v0.20 by DataFrame.sort_values and DataFrame.sort_index. Aside from this, we also have argsort.

Here are some common use cases in sorting, and how to solve them using the sorting functions in the current API. First, the setup.

# Setup
df = pd.DataFrame({'A': list('accab'), 'B': np.random.choice(10, 5)})    
   A  B
0  a  7
1  c  9
2  c  3
3  a  5
4  b  2

Sort by Single Column

For example, to sort df by column "A", use sort_values with a single column name:


   A  B
0  a  7
3  a  5
4  b  2
1  c  9
2  c  3

If you need a fresh RangeIndex, use DataFrame.reset_index.

Sort by Multiple Columns

For example, to sort by both col "A" and "B" in df, you can pass a list to sort_values:

df.sort_values(by=['A', 'B'])

   A  B
3  a  5
0  a  7
4  b  2
2  c  3
1  c  9

Sort By DataFrame Index

df2 = df.sample(frac=1)

   A  B
1  c  9
0  a  7
2  c  3
3  a  5
4  b  2

You can do this using sort_index:


   A  B
0  a  7
1  c  9
2  c  3
3  a  5
4  b  2

# False
# True

Here are some comparable methods with their performance:

%timeit df2.sort_index()                                                                                                                  
%timeit df2.iloc[df2.index.argsort()]                                                                                                     
%timeit df2.reindex(np.sort(df2.index))                                                                                                   

605 µs ± 13.6 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
610 µs ± 24.2 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
581 µs ± 7.63 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

Sort by List of Indices

For example,

idx = df2.index.argsort()
# array([0, 7, 2, 3, 9, 4, 5, 6, 8, 1])

This "sorting" problem is actually a simple indexing problem. Just passing integer labels to iloc will do.


   A  B
1  c  9
0  a  7
2  c  3
3  a  5
4  b  2

How to resolve ambiguous column names when retrieving results?

I had this same issue with dynamic tables. (Tables that are assumed to have an id to be able to join but without any assumption for the rest of the fields.) In this case you don't know the aliases before hand.

In such cases you can first get the table column names for all dynamic tables:

$tblFields = array_keys($zendDbInstance->describeTable($tableName));

Where $zendDbInstance is an instance of Zend_Db or you can use one of the functions here to not rely on Zend php pdo: get the columns name of a table

Then for all dynamic tables you can get the aliases and use $tableName.* for the ones you don't need aliases:

$aliases = "";
foreach($tblKeys as $field)
    $aliases .= $tableName . '.' . $field . ' AS ' . $tableName . '_' . $field . ',' ;
$aliases = trim($aliases, ',');

You can wrap this whole process up into one generic function and just have cleaner code or get more lazy if you wish :)

remote rejected master -> master (pre-receive hook declined)

I had the same issue.

Look at your git ignore and check if .env is not ignored.

It was my problem and resolved to my case.

MySQL Select Date Equal to Today

You can use the CONCAT with CURDATE() to the entire time of the day and then filter by using the BETWEEN in WHERE condition:

SELECT, DATE_FORMAT(users.signup_date, '%Y-%m-%d') 
FROM users 
WHERE (users.signup_date BETWEEN CONCAT(CURDATE(), ' 00:00:00') AND CONCAT(CURDATE(), ' 23:59:59'))

Error pushing to GitHub - insufficient permission for adding an object to repository database

Since the error deals with permissions on the object folder, I did a chown directly on the objects folder and it worked for me.

Is there a way to view two blocks of code from the same file simultaneously in Sublime Text?

In the nav go View => Layout => Columns:2 (alt+shift+2) and open your file again in the other pane (i.e. click the other pane and use ctrl+p

It appears you can also reopen the file using the command File -> New View into File which will open the current file in a new tab

jQuery delete confirmation box

Try with below code:

var checkstr =  confirm('are you sure you want to delete this?');
if(checkstr == true){
  // do your code
return false;


function deleteItem(){
    var checkstr =  confirm('are you sure you want to delete this?');
    if(checkstr == true){
      // do your code
    return false;

This may work for you..


Android Respond To URL in Intent

You might need to allow different combinations of data in your intent filter to get it to work in different cases (http/ vs https/, www. vs no www., etc).

For example, I had to do the following for an app which would open when the user opened a link to Google Drive forms (

Note that path prefix is optional.

            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.DEFAULT" />
            <category android:name="android.intent.category.BROWSABLE" />

            <data android:scheme="http" />
            <data android:scheme="https" />

            <data android:host="" />
            <data android:host="" />

            <data android:pathPrefix="/forms" />

Unable to import path from django.urls

How to use url both app(pages) and in the project.

entire project url configuration root/

 from django.conf.urls import url, include
 from django.contrib import admin
 urlpatterns = [
     url('', include('pages.urls')),

app pages url configuration root/pages/

# pages/
from django.conf.urls import url
from . import views
urlpatterns = [
url('', views.homePageView, name='home')

How can I compare strings in C using a `switch` statement?

My preferred method for doing this is via a hash function (borrowed from here). This allows you to utilize the efficiency of a switch statement even when working with char *'s:

#include "stdio.h"

#define LS 5863588
#define CD 5863276
#define MKDIR 210720772860
#define PWD 193502992

const unsigned long hash(const char *str) {
    unsigned long hash = 5381;  
    int c;

    while ((c = *str++))
        hash = ((hash << 5) + hash) + c;
    return hash;

int main(int argc, char *argv[]) {
    char *p_command = argv[1];
    switch(hash(p_command)) {
    case LS:
        printf("Running ls...\n");
    case CD:
        printf("Running cd...\n");
    case MKDIR:
        printf("Running mkdir...\n");
    case PWD:
        printf("Running pwd...\n");
        printf("[ERROR] '%s' is not a valid command.\n", p_command);

Of course, this approach requires that the hash values for all possible accepted char *'s are calculated in advance. I don't think this is too much of an issue; however, since the switch statement operates on fixed values regardless. A simple program can be made to pass char *'s through the hash function and output their results. These results can then be defined via macros as I have done above.

Why extend the Android Application class?

Not an answer but an observation: keep in mind that the data in the extended application object should not be tied to an instance of an activity, as it is possible that you have two instances of the same activity running at the same time (one in the foreground and one not being visible).

For example, you start your activity normally through the launcher, then "minimize" it. You then start another app (ie Tasker) which starts another instance of your activitiy, for example in order to create a shortcut, because your app supports android.intent.action.CREATE_SHORTCUT. If the shortcut is then created and this shortcut-creating invocation of the activity modified the data the application object, then the activity running in the background will start to use this modified application object once it is brought back to the foreground.

How Stuff and 'For Xml Path' work in SQL Server?

I did debugging and finally returned my 'stuffed' query to it it's normal way.


select * from myTable for xml path('myTable')

gives me contents of the table to write to a log table from a trigger I debug.

What does Html.HiddenFor do?

Like a lot of functions, this one can be used in many different ways to solve many different problems, I think of it as yet another tool in our toolbelts.

So far, the discussion has focused heavily on simply hiding an ID, but that is only one value, why not use it for lots of values! That is what I am doing, I use it to load up the values in a class only one view at a time, because html.beginform creates a new object and if your model object for that view already had some values passed to it, those values will be lost unless you provide a reference to those values in the beginform.

To see a great motivation for the html.hiddenfor, I recommend you see Passing data from a View to a Controller in .NET MVC - "@model" not highlighting

Display Animated GIF

I think the better library to handle gif files is this one: by koral

Used it and i'm successful and this library is dedicated to GIF'S; but where as the picasso and glide are general purpose image framework; so i think the developers of this library have entirely concentrated on gif files

Read a file line by line assigning the value to a variable

Using the following Bash template should allow you to read one value at a time from a file and process it.

while read name; do
    # Do what you want to $name
done < filename

SOAP-ERROR: Parsing WSDL: Couldn't load from - but works on WAMP

After hours of analysis reading tons of logs and internet, finally found problem.

If you use docker and php 7.4 (my case) you probably get error because default security level in OpenSSL it too high for wsdl cert. Even if you disable verify and allow self-signed in SoapClient options.

You need lower seclevel in /etc/ssl/openssl.cnf from DEFAULT@SECLEVEL=2 to


Or just add into Dockerfile

RUN sed -i "s|DEFAULT@SECLEVEL=2|DEFAULT@SECLEVEL=1|g" /etc/ssl/openssl.cnf


You can verify it by run on container

curl -A 'cURL User Agent' -4

Before that change I got error:

SSL routines:tls_process_ske_dhe:dh key too small

Svn switch from trunk to branch

  • Short version of (correct) tzaman answer will be (for fresh SVN)

    svn switch ^/branches/v1p2p3
  • --relocate switch is deprecated anyway, when it needed you'll have to use svn relocate command

  • Instead of creating snapshot-branch (ReadOnly) you can use tags (conventional RO labels for history)

On Windows, the caret character (^) must be escaped:

svn switch ^^/branches/v1p2p3

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

Mac OS X and some other Unixes at least have the user path compiled into sshd for security reasons so those of us that install git as /usr/local/git/{bin,lib,...} can run into trouble as the git executables are not in the precompiled path. To override this I prefer to edit my /etc/sshd_config changing:

#PermitUserEnvironment no


PermitUserEnvironment yes

and then create ~/.ssh/environment files as needed. My git users have the following in their ~/.ssh/environment file:


Note variable expansion does not occur when the ~/.ssh/environment file is read so:


will not work.

Optimal number of threads per core

One example of lots of threads ("thread pool") vs one per core is that of implementing a web-server in Linux or in Windows.

Since sockets are polled in Linux a lot of threads may increase the likelihood of one of them polling the right socket at the right time - but the overall processing cost will be very high.

In Windows the server will be implemented using I/O Completion Ports - IOCPs - which will make the application event driven: if an I/O completes the OS launches a stand-by thread to process it. When the processing has completed (usually with another I/O operation as in a request-response pair) the thread returns to the IOCP port (queue) to wait for the next completion.

If no I/O has completed there is no processing to be done and no thread is launched.

Indeed, Microsoft recommends no more than one thread per core in IOCP implementations. Any I/O may be attached to the IOCP mechanism. IOCs may also be posted by the application, if necessary.

How to change HTML Object element data attribute value in javascript

The following code works if you use jquery

$( "object" ).replaceWith('<object data=""></object>');

Is it not possible to define multiple constructors in Python?

For the example you gave, use default values:

class City:
    def __init__(self, name="Default City Name"):

In general, you have two options:

1) Do if-elif blocks based on the type:

def __init__(self, name):
    if isinstance(name, str):
    elif isinstance(name, City):

2) Use duck typing --- that is, assume the user of your class is intelligent enough to use it correctly. This is typically the preferred option.

How to add an existing folder with files to SVN?

I don't use commands. You should be able to do this using the GUI:

  • Right-click an empty space in your My Documents folder, select TortoiseSVN > Repo-browser.
  • Enter http://subversion... (your URL path to your Subversion server/directory you will save to) as your path and select OK
  • Right-click the root directory in Repo and select Add folder. Give it the name of your project and create it.
  • Right-click the project folder in the Repo-browser and select Checkout. The Checkout directory will be your Visual Studio\Projects\{your project} folder. Select OK.
  • You will receive a warning that the folder is not empty. Say Yes to checkout/export to that folder - it will not overwrite your project files.
  • Open your project folder. You will see question marks on folders that are associated with your VS project that have not yet been added to Subversion. Select those folders using Ctrl + Click, then right-click one of the selected items and select TortoiseSVN > Add
  • Select OK on the prompt
  • Your files should add. Select OK on the Add Finished! dialog
  • Right-click in an empty area of the folder and select Refresh. You’ll see “+” icons on the folders/files, now
  • Right-click an empty area in the folder once again and select SVN Commit
  • Add a message regarding what you are committing and click OK

change PATH permanently on Ubuntu

Try to add export PATH=$PATH:/home/me/play in ~/.bashrc file.

jQuery keypress() event not firing?

e.which doesn't work in IE try e.keyCode, also you probably want to use keydown() instead of keypress() if you are targeting IE.

See for more information.

How do I edit a file after I shell to a Docker container?

After you shelled to the Docker container, just type:

apt-get update
apt-get install nano

AutoComplete TextBox Control

Check out the AutoCompleteSource, AutoCompleteCustomSource and AutoCompleteMode properties.

textBox1.AutoCompleteMode = AutoCompleteMode.Suggest;
textBox1.AutoCompleteSource = AutoCompleteSource.CustomSource;
AutoCompleteStringCollection col = new AutoCompleteStringCollection();
textBox1.AutoCompleteCustomSource = col;

Note that the designer allows you to do that without writing any code...

How to find out whether a file is at its `eof`?

This code will work for python 3 and above

f=file.readlines()   #reads all lines from the file
EOF=-1   #represents end of file
for k in range(len(f)-1,-1,-1):
    if temp==0:
        if f[k]=="\n":
print("Given file has",EOF,"lines")

How can I get the application's path in a .NET console application?

You can simply add to your project references System.Windows.Forms and then use the System.Windows.Forms.Application.StartupPath as usual .

So, not need for more complicated methods or using the reflection.

Reduce left and right margins in matplotlib plot

All you need is


before your output.

In addition to cutting down the margins, this also tightly groups the space between any subplots:

x = [1,2,3]
y = [1,4,9]
import matplotlib.pyplot as plt
fig = plt.figure()
subplot1 = fig.add_subplot(121)
subplot2 = fig.add_subplot(122)

Accessing elements by type in javascript

If you are lucky and need to care only for recent browsers, you can use:


"recent" means not IE6 and IE7

How to run Gradle from the command line on Mac bash


Your directory with gradlew is not included in the PATH, so you must specify path to the gradlew. . means "current directory".

How can I pass a member function where a free function is expected?

If you actually don't need to use the instance a (i.e. you can make it static like @mathengineer 's answer) you can simply pass in a non-capture lambda. (which decay to function pointer)

#include <iostream>

class aClass
   void aTest(int a, int b)
      printf("%d + %d = %d", a, b, a + b);

void function1(void (*function)(int, int))
    function(1, 1);

int main()
   //note: you don't need the `+`
   function1(+[](int a,int b){return aClass{}.aTest(a,b);}); 


note: if aClass is costly to construct or has side effect, this may not be a good way.

Jquery Validate custom error message location


<form ... id ="GoogleMapsApiKeyForm">
    <input name="GoogleMapsAPIKey" type="text" class="form-control" placeholder="Enter Google maps API key" />
    <span class="text-danger" id="GoogleMapsAPIKey-errorMsg"></span>'
    <button type="submit" class="btn btn-primary">Save</button>


$(function () {
      rules: {
          GoogleMapsAPIKey: {
              required: true
        messages: {
            GoogleMapsAPIKey: 'Google maps api key is required',
        errorPlacement: function (error, element) {
            if (element.attr("name") == "GoogleMapsAPIKey")
        submitHandler: function (form) {
           // form.submit(); //if you need Ajax submit follow for rest of code below

    //If you want to use ajax
    $("#GoogleMapsApiKeyForm").submit(function (e) {
        if (!$("#GoogleMapsApiKeyForm").valid())

       //Put your ajax call here

How to get file URL using Storage facade in laravel 5?

Edit: Solution for L5.2+

There's a better and more straightforward solution.

Use Storage::url($filename) to get the full path/URL of a given file. Note that you need to set S3 as your storage filesystem in config/filesystems.php: 'default' => 's3'

Of course, you can also do Storage::disk('s3')->url($filename) in the same way.

As you can see in config/filesystems.php there's also a parameter 'cloud' => 's3' defined, that refers to the Cloud filesystem. In case you want to mantain the storage folder in the local server but retrieve/store some files in the cloud use Storage::cloud(), which also has the same filesystem methods, i.e. Storage::cloud()->url($filename).

The Laravel documentation doesn't mention this method, but if you want to know more about it you can check its source code here.

System.IO.FileNotFoundException: Could not load file or assembly 'X' or one of its dependencies when deploying the application

... Could not load file or assembly 'X' or one of its dependencies ...

Most likely it fails to load another dependency.

you could try to check the dependencies with a dependency walker.


Also check your build configuration (x86 / 64)

Edit: I also had this problem once when I was copying dlls in zip from a "untrusted" network share. The file was locked by Windows and the FileNotFoundException was raised.

See here: Detected DLLs that are from the internet and "blocked" by CASPOL

How to check if a file exists from inside a batch file

C:\>help if

Performs conditional processing in batch programs.

IF [NOT] ERRORLEVEL number command

IF [NOT] string1==string2 command

IF [NOT] EXIST filename command

Composer killed while updating

composer 2 update have reduced the memory usage

composer self-update
composer update
composer require xxx

Error creating bean with name

I think it comes from this line in your XML file:

<context:component-scan base-package="" />

Replace it by:

<context:component-scan base-package="" />

It is because your Autowired service is not scanned by Spring since it is not in the right package.

WebView and Cookies on Android

I figured out what's going on.

When I load a page through a server side action (a url visit), and view the html returned from that action inside a Webview, that first action/page runs inside that Webview. However, when you click on any link that are action commands in your web app, these actions start a new browser. That is why cookie info gets lost because the first cookie information you set for Webview is gone, we have a seperate program here.

You have to intercept clicks on Webview so that browsing never leaves the app, everything stays inside the same Webview.

  WebView webview = new WebView(this);      
  webview.setWebViewClient(new WebViewClient() {  
      public boolean shouldOverrideUrlLoading(WebView view, String url)  
        view.loadUrl(url); //this is controversial - see comments and other answers
        return true;  
  webview.loadUrl([MY URL]);

This fixes the problem.

Auto-indent in Notepad++

In the latest version (at least), you can find it through:

  • Settings (menu)
  • Preferences...
  • MISC (tab)
  • lower-left checkbox list
  • "Auto-indent" is the 2nd option in this group

[EDIT] Though, I don't think it's had the best implementation of Auto-indent. So, check to make sure you have version 5.1 -- auto-indent got an overhaul recently, so it auto-corrects your indenting.

Do also note that you're missing the block for the 2nd if:

void main(){
    if() { }  # here

Using group by on multiple columns

Here I am going to explain not only the GROUP clause use, but also the Aggregate functions use.

The GROUP BY clause is used in conjunction with the aggregate functions to group the result-set by one or more columns. e.g.:

-- GROUP BY with one parameter:
SELECT column_name, AGGREGATE_FUNCTION(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name;

-- GROUP BY with two parameters:

Remember this order:

  1. SELECT (is used to select data from a database)

  2. FROM (clause is used to list the tables)

  3. WHERE (clause is used to filter records)

  4. GROUP BY (clause can be used in a SELECT statement to collect data across multiple records and group the results by one or more columns)

  5. HAVING (clause is used in combination with the GROUP BY clause to restrict the groups of returned rows to only those whose the condition is TRUE)

  6. ORDER BY (keyword is used to sort the result-set)

You can use all of these if you are using aggregate functions, and this is the order that they must be set, otherwise you can get an error.

Aggregate Functions are:

MIN() returns the smallest value in a given column

MAX() returns the maximum value in a given column.

SUM() returns the sum of the numeric values in a given column

AVG() returns the average value of a given column

COUNT() returns the total number of values in a given column

COUNT(*) returns the number of rows in a table

SQL script examples about using aggregate functions:

Let's say we need to find the sale orders whose total sale is greater than $950. We combine the HAVING clause and the GROUP BY clause to accomplish this:

    orderId, SUM(unitPrice * qty) Total
GROUP BY orderId
HAVING Total > 950;

Counting all orders and grouping them customerID and sorting the result ascendant. We combine the COUNT function and the GROUP BY, ORDER BY clauses and ASC:

    customerId, COUNT(*)
GROUP BY customerId

Retrieve the category that has an average Unit Price greater than $10, using AVG function combine with GROUP BY and HAVING clauses:

    categoryName, AVG(unitPrice)
    Products p
    Categories c ON c.categoryId = p.categoryId
GROUP BY categoryName
HAVING AVG(unitPrice) > 10;

Getting the less expensive product by each category, using the MIN function in a subquery:

SELECT categoryId,
FROM Products p1
WHERE unitPrice = (
                SELECT MIN(unitPrice)
                FROM Products p2
                WHERE p2.categoryId = p1.categoryId)

The following statement groups rows with the same values in both categoryId and productId columns:

    categoryId, categoryName, productId, SUM(unitPrice)
    Products p
    Categories c ON c.categoryId = p.categoryId
GROUP BY categoryId, productId

Bootstrap Modal before form Submit

It is easy to solve, only create an hidden submit:

<button id="submitCadastro" type="button">ENVIAR</button>
<input type="submit" id="submitCadastroHidden" style="display: none;" >

with jQuery you click the submit:

    if($("#checkDocumentos").prop("checked") == false){
        //alert("Aceite os termos e condições primeiro!.");

HTML 5 Favicon - Support?

The answers provided (at the time of this post) are link only answers so I thought I would summarize the links into an answer and what I will be using.

When working to create Cross Browser Favicons (including touch icons) there are several things to consider.

The first (of course) is Internet Explorer. IE does not support PNG favicons until version 11. So our first line is a conditional comment for favicons in IE 9 and below:

<!--[if IE]><link rel="shortcut icon" href="path/to/favicon.ico"><![endif]-->

To cover the uses of the icon create it at 32x32 pixels. Notice the rel="shortcut icon" for IE to recognize the icon it needs the word shortcut which is not standard. Also we wrap the .ico favicon in a IE conditional comment because Chrome and Safari will use the .ico file if it is present, despite other options available, not what we would like.

The above covers IE up to IE 9. IE 11 accepts PNG favicons, however, IE 10 does not. Also IE 10 does not read conditional comments thus IE 10 won't show a favicon. With IE 11 and Edge available I don't see IE 10 in widespread use, so I ignore this browser.

For the rest of the browsers we are going to use the standard way to cite a favicon:

<link rel="icon" href="path/to/favicon.png">

This icon should be 196x196 pixels in size to cover all devices that may use this icon.

To cover touch icons on mobile devices we are going to use Apple's proprietary way to cite a touch icon:

<link rel="apple-touch-icon-precomposed" href="apple-touch-icon-precomposed.png">

Using rel="apple-touch-icon-precomposed" will not apply the reflective shine when bookmarked on iOS. To have iOS apply the shine use rel="apple-touch-icon". This icon should be sized to 180x180 pixels as that is the current size recommend by Apple for the latest iPhones and iPads. I have read Blackberry will also use rel="apple-touch-icon-precomposed".

As a note: Chrome for Android states:

The apple-touch-* are deprecated, and will be supported only for a short time. (Written as of beta for m31 of Chrome).

Custom Tiles for IE 11+ on Windows 8.1+

IE 11+ on Windows 8.1+ does offer a way to create pinned tiles for your site.

Microsoft recommends creating a few tiles at the following size:

Small: 128 x 128

Medium: 270 x 270

Wide: 558 x 270

Large: 558 x 558

These should be transparent images as we will define a color background next.

Once these images are created you should create an xml file called browserconfig.xml with the following code:

<?xml version="1.0" encoding="utf-8"?>
      <square70x70logo src="images/smalltile.png"/>
      <square150x150logo src="images/mediumtile.png"/>
      <wide310x150logo src="images/widetile.png"/>
      <square310x310logo src="images/largetile.png"/>

Save this xml file in the root of your site. When a site is pinned IE will look for this file. If you want to name the xml file something different or have it in a different location add this meta tag to the head:

<meta name="msapplication-config" content="path-to-browserconfig/custom-name.xml" />

For additional information on IE 11+ custom tiles and using the XML file visit Microsoft's website.

Putting it all together:

To put it all together the above code would look like this:

<!-- For IE 9 and below. ICO should be 32x32 pixels in size -->
<!--[if IE]><link rel="shortcut icon" href="path/to/favicon.ico"><![endif]-->

<!-- Touch Icons - iOS and Android 2.1+ 180x180 pixels in size. --> 
<link rel="apple-touch-icon-precomposed" href="apple-touch-icon-precomposed.png">

<!-- Firefox, Chrome, Safari, IE 11+ and Opera. 196x196 pixels in size. -->
<link rel="icon" href="path/to/favicon.png">

Windows Phone Live Tiles

If a user is using a Windows Phone they can pin a website to the start screen of their phone. Unfortunately, when they do this it displays a screenshot of your phone, not a favicon (not even the MS specific code referenced above). To make a "Live Tile" for Windows Phone Users for your website one must use the following code:

Here are detailed instructions from Microsoft but here is a synopsis:

Step 1

Create a square image for your website, to support hi-res screens create it at 768x768 pixels in size.

Step 2

Add a hidden overlay of this image. Here is example code from Microsoft:

<div id="TileOverlay" onclick="ToggleTileOverlay()" style='background-color: Highlight; height: 100%; width: 100%; top: 0px; left: 0px; position: fixed; color: black; visibility: hidden'>
  <img src="customtile.png" width="320" height="320" />
  <div style='margin-top: 40px'>
     Add text/graphic asking user to pin to start using the menu...

Step 3

You then can add thew following line to add a pin to start link:

<a href="javascript:ToggleTileOverlay()">Pin this site to your start screen</a>

Microsoft recommends that you detect windows phone and only show that link to those users since it won't work for other users.

Step 4

Next you add some JS to toggle the overlay visibility

function ToggleTileOverlay() {
 var newVisibility =     (document.getElementById('TileOverlay').style.visibility == 'visible') ? 'hidden' : 'visible';
 document.getElementById('TileOverlay').style.visibility =    newVisibility;

Note on Sizes

I am using one size as every browser will scale down the image as necessary. I could add more HTML to specify multiple sizes if desired for those with a lower bandwidth but I am already compressing the PNG files heavily using TinyPNG and I find this unnecessary for my purposes. Also, according to philippe_b's answer Chrome and Firefox have bugs that cause the browser to load all sizes of icons. Using one large icon may be better than multiple smaller ones because of this.

Further Reading

For those who would like more details see the links below:

How do I position one image on top of another in HTML?

The easy way to do it is to use background-image then just put an <img> in that element.

The other way to do is using css layers. There is a ton a resources available to help you with this, just search for css layers.

How to send 100,000 emails weekly?

Short answer: While it's technically possible to send 100k e-mails each week yourself, the simplest, easiest and cheapest solution is to outsource this to one of the companies that specialize in it (I did say "cheapest": there's no limit to the amount of development time (and therefore money) that you can sink into this when trying to DIY).

Long answer: If you decide that you absolutely want to do this yourself, prepare for a world of hurt (after all, this is e-mail/e-fail we're talking about). You'll need:

  • e-mail content that is not spam (otherwise you'll run into additional major roadblocks on every step, even legal repercussions)
  • in addition, your content should be easy to distinguish from spam - that may be a bit hard to do in some cases (I heard that a certain pharmaceutical company had to all but abandon e-mail, as their brand names are quite common in spams)
  • a configurable SMTP server of your own, one which won't buckle when you dump 100k e-mails onto it (your ISP's upstream server won't be sufficient here and you'll make the ISP violently unhappy; we used two dedicated boxes)
  • some mail wrapper (e.g. PhpMailer if PHP's your poison of choice; using PHP's mail() is horrible enough by itself)
  • your own sender function to run in a loop, create the mails and pass them to the wrapper (note that you may run into PHP's memory limits if your app has a memory leak; you may need to recycle the sending process periodically, or even better, decouple the "creating e-mails" and "sending e-mails" altogether)

Surprisingly, that was the easy part. The hard part is actually sending it:

  • some servers will ban you when you send too many mails close together, so you need to shuffle and watch your queue (e.g. send one mail to [email protected], then three to other domains, only then another to [email protected])
  • you need to have correct PTR, SPF, DKIM records
  • handling remote server timeouts, misconfigured DNS records and other network pleasantries
  • handling invalid e-mails (and no, regex is the wrong tool for that)
  • handling unsubscriptions (many legitimate newsletters have been reclassified as spam due to many frustrated users who couldn't unsubscribe in one step and instead chose to "mark as spam" - the spam filters do learn, esp. with large e-mail providers)
  • handling bounces and rejects ("no such mailbox [email protected]","mailbox [email protected] full")
  • handling blacklisting and removal from blacklists (Sure, you're not sending spam. Some recipients won't be so sure - with such large list, it will happen sometimes, no matter what precautions you take. Some people (e.g. your not-so-scrupulous competitors) might even go as far to falsely report your mailings as spam - it does happen. On average, it takes weeks to get yourself removed from a blacklist.)

And to top it off, you'll have to manage the legal part of it (various federal, state, and local laws; and even different tangles of laws once you send outside the U.S. (note: you have no way of finding if [email protected] lives in Southwest Elbonia, the country with world's most draconian antispam laws)).

I'm pretty sure I missed a few heads of this hydra - are you still sure you want to do this yourself? If so, there'll be another wave, this time merely the annoying problems inherent in sending an e-mail. (You see, SMTP is a store-and-forward protocol, which means that your e-mail will be shuffled across many SMTP servers around the Internet, in the hope that the next one is a bit closer to the final recipient. Basically, the e-mail is sent to an SMTP server, which puts it into its forward queue; when time comes, it will forward it further to a different SMTP server, until it reaches the SMTP server for the given domain. This forward could happen immediately, or in a few minutes, or hours, or days, or never.) Thus, you'll see the following issues - most of which could happen en route as well as at the destination:

  • the remote SMTP servers don't want to talk to your SMTP server
  • your mails are getting marked as spam (<blink> is not your friend here, nor is <font color=...>)
  • your mails are delivered days, even weeks late (contrary to popular opinion, SMTP is designed to make a best effort to deliver the message sometime in the future - not to deliver it now)
  • your mails are not delivered at all (already sent from e-mail server on hop #4, not sent yet from server on hop #5, the server that currently holds the message crashes, data is lost)
  • your mails are mangled by some braindead server en route (this one is somewhat solvable with base64 encoding, but then the size goes up and the e-mail looks more suspicious)
  • your mails are delivered and the recipients seem not to want them ("I'm sure I didn't sign up for this, I remember exactly what I did a year ago" (of course you do, sir))
  • users with various versions of Microsoft Outlook and its special handling of Internet mail
  • wizard's apprentice mode (a self-reinforcing positive feedback loop - in other words, automated e-mails as replies to automated e-mails as replies to...; you really don't want to be the one to set this off, as you'd anger half the internet at yourself)

and it'll be your job to troubleshoot and solve this (hint: you can't, mostly). The people who run a legit mass-mailing businesses know that in the end you can't solve it, and that they can't solve it either - and they have the reasons well researched, documented and outlined (maybe even as a Powerpoint presentation - complete with sounds and cool transitions - that your bosses can understand), as they've had to explain this a million times before. Plus, for the problems that are actually solvable, they know very well how to solve them.

If, after all this, you are not discouraged and still want to do this, go right ahead: it's even possible that you'll find a better way to do this. Just know that the road ahead won't be easy - sending e-mail is trivial, getting it delivered is hard.

When do I use super()?

super is used to call the constructor, methods and properties of parent class.

How to get an enum value from a string value in Java?

You should also be careful with your case. Let me explain: doing Blah.valueOf("A") works, but Blah.valueOf("a") will not work. Then again Blah.valueOf("a".toUpperCase(Locale.ENGLISH)) would work.

Changed toUpperCase to toUpperCase(Locale.ENGLISH) based on tc. comment and the java docs

edit2 On android you should use Locale.US, as sulai points out.

CSS Flex Box Layout: full-width row and columns

This is copied from above, but condensed slightly and re-written in semantic terms. Note: #Container has display: flex; and flex-direction: column;, while the columns have flex: 3; and flex: 2; (where "One value, unitless number" determines the flex-grow property) per MDN flex docs.

#Container {_x000D_
  display: flex;_x000D_
  flex-direction: column;_x000D_
  height: 600px;_x000D_
  width: 580px;_x000D_
.Content {_x000D_
  display: flex;_x000D_
  flex: 1;_x000D_
#Detail {_x000D_
  flex: 3;_x000D_
  background-color: lime;_x000D_
#ThumbnailContainer {_x000D_
  flex: 2;_x000D_
  background-color: black;_x000D_
<div id="Container">_x000D_
  <div class="Content">_x000D_
    <div id="Detail"></div>_x000D_
    <div id="ThumbnailContainer"></div>_x000D_

Is JavaScript object-oriented?

This is of course subjective and an academic question. Some people argue whether an OO language has to implement classes and inheritance, others write programs that change your life. ;-)

(But really, why should an OO language have to implement classes? I'd think objects were the key components. How you create and then use them is another matter.)

How to get key names from JSON using jq

To get the keys on a deeper node in an JSON:

echo '{"data": "1", "user": { "name": 2, "phone": 3 } }' | jq '.user | keys[]'

How do I programmatically set device orientation in iOS 7?

here it is a FULL WORKING example for iOS 7, 8, 9, 10 how to change app orientation to its current opposite


- (void)flipOrientation
    NSNumber *value;
    UIInterfaceOrientation currentOrientation = [[UIApplication sharedApplication] statusBarOrientation];
        if(currentOrientation == UIInterfaceOrientationPortrait)
            value = [NSNumber numberWithInt:UIInterfaceOrientationPortraitUpsideDown];
        else //if(currentOrientation == UIInterfaceOrientationPortraitUpsideDown)
            value = [NSNumber numberWithInt:UIInterfaceOrientationPortrait];
        if(currentOrientation == UIInterfaceOrientationLandscapeRight)
            value = [NSNumber numberWithInt:UIInterfaceOrientationLandscapeLeft];
        else //if(currentOrientation == UIInterfaceOrientationLandscapeLeft)
            value = [NSNumber numberWithInt:UIInterfaceOrientationLandscapeRight];
    [[UIDevice currentDevice] setValue:value forKey:@"orientation"];
    [UIViewController attemptRotationToDeviceOrientation];

Swift 3

func flipOrientation() -> Void
    let currentOrientation : UIInterfaceOrientation = UIApplication.shared.statusBarOrientation
    var value : Int = 0;
        if(currentOrientation == UIInterfaceOrientation.portrait)
            value = UIInterfaceOrientation.portraitUpsideDown.rawValue
        else //if(currentOrientation == UIInterfaceOrientation.portraitUpsideDown)
            value = UIInterfaceOrientation.portrait.rawValue
        if(currentOrientation == UIInterfaceOrientation.landscapeRight)
            value = UIInterfaceOrientation.landscapeLeft.rawValue
        else //if(currentOrientation == UIInterfaceOrientation.landscapeLeft)
            value = UIInterfaceOrientation.landscapeRight.rawValue
    UIDevice.current.setValue(value, forKey: "orientation")

ImageMagick security policy 'PDF' blocking conversion

As pointed out in some comments, you need to edit the policies of ImageMagick in /etc/ImageMagick-7/policy.xml. More particularly, in ArchLinux at the time of writing (05/01/2019) the following line is uncommented:

<policy domain="coder" rights="none" pattern="{PS,PS2,PS3,EPS,PDF,XPS}" />

Just wrap it between <!-- and --> to comment it, and pdf conversion should work again.

How can I force browsers to print background images in CSS?

Use psuedo-elements. While many browsers will ignore background images, psuedo-elements with their content set to an image are technically NOT background images. You can then position the background image roughly where the image should have gone (though it's not as easy or precise as the original image).

One drawback is that for this to work in Chrome, you need to specify this behavior outside of your print media query, and then make it visible in the print media query block. So, something like this...

        content: url("your/image/path");

@media print {

The drawback is that the image will often be downloaded on normal page loads, adding unnecessary bulk. You can avoid that by just using the same image/path you'd already used for the original, visible image.

Display a float with two decimal places in Python

You could use the string formatting operator for that:

>>> '%.2f' % 1.234
>>> '%.2f' % 5.0

The result of the operator is a string, so you can store it in a variable, print etc.