Programs & Examples On #Properties file

A .properties file is either a simple text file or an XML file containing pairs of keys and values. Java and related technologies frequently use .properties files to store configuration information.

Spring .properties file: get element as an Array

Here is an example of how you can do it in Spring 4.0+ content:


Java Code:

private Environment env;


String[] springRocks = env.getProperty("some.key", String[].class);

adding comment in .properties files

The property file task is for editing properties files. It contains all sorts of nice features that allow you to modify entries. For example:

<propertyfile file="">
    <entry key="build_number"

I've incremented my build_number by one. I have no idea what the value was, but it's now one greater than what it was before.

  • Use the <echo> task to build a property file instead of <propertyfile>. You can easily layout the content and then use <propertyfile> to edit that content later on.


<echo file="">
# Default Configuration
# Source Configuration
  • Create separate properties files for each section. You're allowed a comment header for each type. Then, use to batch them together into one single file:


<propertyfile file=""
    comment="Default Configuration">
    <entry key="source.dir" value="1"/>
    <entry key="dir.publish" value="1"/>

<propertyfile file=""
    comment="Source Configuration">
    <entry key="dir.publish.html" value="1"/>
<concat destfile="">
    <fileset dir="${basedir}">
        <include name=""/>
        <include name=""/>

    <fileset dir="${basedir}">
         <include name=""/>
        <include name=""/>

Loading a properties file from Java package

public class ReadPropertyDemo {
    public static void main(String[] args) {
        Properties properties = new Properties();

        try {
            properties.load(new FileInputStream(
            System.out.println("Domain :- " + properties.getProperty("domain"));
            System.out.println("Website Age :- "
                    + properties.getProperty("website_age"));
            System.out.println("Founder :- " + properties.getProperty("founder"));

            // Display all the values in the form of key value
            for (String key : properties.stringPropertyNames()) {
                String value = properties.getProperty(key);
                System.out.println("Key:- " + key + "Value:- " + value);

        } catch (IOException e) {
            System.out.println("Exception Occurred" + e.getMessage());


How to access a value defined in the file in Spring Boot

Best ways to get property values are using.

1. Using Value annotation

private String propertyKeyVariable;

2. Using Enviornment bean

private Environment env;

public String getValue() {
    return env.getProperty("property.key");

public void display(){
  System.out.println("# Value : "+getValue);

How to read an external properties file in Maven

Using the suggested Maven properties plugin I was able to read in a file that I use to version my builds.


How to read values from properties file?

There are various ways to achieve the same. Below are some commonly used ways in spring-

  1. Using PropertyPlaceholderConfigurer

  2. Using PropertySource

  3. Using ResourceBundleMessageSource

  4. Using PropertiesFactoryBean

    and many more........................

Assuming ds.type is key in your property file.

Using PropertyPlaceholderConfigurer

Register PropertyPlaceholderConfigurer bean-

<context:property-placeholder location="classpath:path/"/>


<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
  <property name="locations" value="classpath:path/" ></property>


public class SampleConfig {
 public static PropertySourcesPlaceholderConfigurer placeHolderConfigurer() {
  return new PropertySourcesPlaceholderConfigurer();
  //set locations as well.

After registering PropertySourcesPlaceholderConfigurer, you can access the value-

@Value("${ds.type}")private String attr; 

Using PropertySource

In the latest spring version you don't need to register PropertyPlaceHolderConfigurer with @PropertySource, I found a good link to understand version compatibility-

public class BeanTester {
    @Autowired Environment environment; 
    public void execute() {
        String attr = this.environment.getProperty("ds.type");

Using ResourceBundleMessageSource

Register Bean-

<bean id="messageSource" class="">
  <property name="basenames">

Access Value-

((ApplicationContext)context).getMessage("ds.type", null, null);


public class BeanTester {
    @Autowired MessageSource messageSource; 
    public void execute() {
        String attr = this.messageSource.getMessage("ds.type", null, null);

Using PropertiesFactoryBean

Register Bean-

<bean id="properties"
  <property name="locations">

Wire Properties instance into your class-

public class BeanTester {
    @Autowired Properties properties; 
    public void execute() {
        String attr = properties.getProperty("ds.type");

Where to place and how to read configuration resource files in servlet based application?

It's your choice. There are basically three ways in a Java web application archive (WAR):

1. Put it in classpath

So that you can load it by ClassLoader#getResourceAsStream() with a classpath-relative path:

ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
InputStream input = classLoader.getResourceAsStream("");
// ...
Properties properties = new Properties();

Here is supposed to be placed in one of the roots which are covered by the default classpath of a webapp, e.g. webapp's /WEB-INF/lib and /WEB-INF/classes, server's /lib, or JDK/JRE's /lib. If the propertiesfile is webapp-specific, best is to place it in /WEB-INF/classes. If you're developing a standard WAR project in an IDE, drop it in src folder (the project's source folder). If you're using a Maven project, drop it in /main/resources folder.

You can alternatively also put it somewhere outside the default classpath and add its path to the classpath of the appserver. In for example Tomcat you can configure it as shared.loader property of Tomcat/conf/

If you have placed the it in a Java package structure like com.example, then you need to load it as below

ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
InputStream input = classLoader.getResourceAsStream("com/example/");
// ...

Note that this path of a context class loader should not start with a /. Only when you're using a "relative" class loader such as SomeClass.class.getClassLoader(), then you indeed need to start it with a /.

ClassLoader classLoader = getClass().getClassLoader();
InputStream input = classLoader.getResourceAsStream("/com/example/");
// ...

However, the visibility of the properties file depends then on the class loader in question. It's only visible to the same class loader as the one which loaded the class. So, if the class is loaded by e.g. server common classloader instead of webapp classloader, and the properties file is inside webapp itself, then it's invisible. The context class loader is your safest bet so you can place the properties file "everywhere" in the classpath and/or you intend to be able to override a server-provided one from the webapp on.

2. Put it in webcontent

So that you can load it by ServletContext#getResourceAsStream() with a webcontent-relative path:

InputStream input = getServletContext().getResourceAsStream("/WEB-INF/");
// ...

Note that I have demonstrated to place the file in /WEB-INF folder, otherwise it would have been public accessible by any webbrowser. Also note that the ServletContext is in any HttpServlet class just accessible by the inherited GenericServlet#getServletContext() and in Filter by FilterConfig#getServletContext(). In case you're not in a servlet class, it's usually just injectable via @Inject.

3. Put it in local disk file system

So that you can load it the usual way with an absolute local disk file system path:

InputStream input = new FileInputStream("/absolute/path/to/");
// ...

Note the importance of using an absolute path. Relative local disk file system paths are an absolute no-go in a Java EE web application. See also the first "See also" link below.

Which to choose?

Just weigh the advantages/disadvantages in your own opinion of maintainability.

If the properties files are "static" and never needs to change during runtime, then you could keep them in the WAR.

If you prefer being able to edit properties files from outside the web application without the need to rebuild and redeploy the WAR every time, then put it in the classpath outside the project (if necessary add the directory to the classpath).

If you prefer being able to edit properties files programmatically from inside the web application using Properties#store() method, put it outside the web application. As the Properties#store() requires a Writer, you can't go around using a disk file system path. That path can in turn be passed to the web application as a VM argument or system property. As a precaution, never use getRealPath(). All changes in deploy folder will get lost on a redeploy for the simple reason that the changes are not reflected back in original WAR file.

See also:

How do I convert strings in a Pandas data frame to a 'date' data type?

Another way to do this and this works well if you have multiple columns to convert to datetime.

cols = ['date1','date2']
df[cols] = df[cols].apply(pd.to_datetime)

Set variable value to array of strings

In SQL you can not have a variable array.
However, the best alternative solution is to use a temporary table.

How can I remove all text after a character in bash?

trim off everything after the last instance of ":"

cat fileListingPathsAndFiles.txt | grep -o '^.*:'

and if you wanted to drop that last ":"

cat file.txt | grep -o '^.*:' | sed 's/:$//'

@kp123: you'd want to replace : with / (where the sed colon should be \/)

Java word count program

You can use this code.It may help you:

public static void main (String[] args)

   System.out.println("Simple Java Word Count Program");

   String str1 = "Today is Holdiay Day";
   int count=0;
   String[] wCount=str1.split(" ");

   for(int i=0;i<wCount.length;i++){

Why maven? What are the benefits?

This should have been a comment, but it wasn't fitting in a comment length, so I posted it as an answer.

All the benefits mentioned in other answers are achievable by simpler means than using maven. If, for-example, you are new to a project, you'll anyway spend more time creating project architecture, joining components, coding than downloading jars and copying them to lib folder. If you are experienced in your domain, then you already know how to start off the project with what libraries. I don't see any benefit of using maven, especially when it poses a lot of problems while automatically doing the "dependency management".

I only have intermediate level knowledge of maven, but I tell you, I have done large projects(like ERPs) without using maven.

String concatenation in Jinja

Just another hack can be like this.

I have Array of strings which I need to concatenate. So I added that array into dictionary and then used it inside for loop which worked.

{% set dict1 = {'e':''} %}
{% for i in list1 %}
{% if dict1.update({'e':dict1.e+":"+i+"/"+i}) %} {% endif %}
{% endfor %}
{% set layer_string = dict1['e'] %}

Repeat a task with a time delay?

In my case, I had to execute a process if one of these conditions were true: if a previous process was completed or if 5 seconds had already passed. So, I did the following and worked pretty well:

private Runnable mStatusChecker;
private Handler mHandler;

class {
method() {
  mStatusChecker = new Runnable() {
            int times = 0;
            public void run() {
                if (times < 5) {
                    if (process1.isRead()) {
                    } else {
                        mHandler.postDelayed(mStatusChecker, 1000);
                } else {

        mHandler = new Handler();

    void startRepeatingTask() {;

    void stopRepeatingTask() {


If process1 is read, it executes process2. If not, it increments the variable times, and make the Handler be executed after one second. It maintains a loop until process1 is read or times is 5. When times is 5, it means that 5 seconds passed and in each second, the if clause of process1.isRead() is executed.

Python Replace \\ with \

You are missing, that \ is the escape character.

Look here: at 2.4.1 "Escape Sequence"

Most importantly \n is a newline character. And \\ is an escaped escape character :D

>>> a = 'a\\\\nb'
>>> a
>>> print a
>>> a.replace('\\\\', '\\')
>>> print a.replace('\\\\', '\\')

Static way to get 'Context' in Android?

I use a variation of the Singleton design pattern to help me with this.

import android.content.Context;

public class ApplicationContextSingleton {
    private static Activity gContext;

    public static void setContext( Activity activity) {
        gContext = activity;

    public static Activity getActivity() {
        return gContext;

    public static Context getContext() {
        return gContext;

I then call ApplicationContextSingleton.setContext( this ); in my activity.onCreate() and ApplicationContextSingleton.setContext( null ); in onDestroy();

Cannot set content-type to 'application/json' in jQuery.ajax

So all you need to do for this to work is add:

headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json'

as a field to your post request and it'll work.

How do I delete specific characters from a particular String in Java?

To remove the last character do as Mark Byers said

s = s.substring(0, s.length() - 1);

Additionally, another way to remove the characters you don't want would be to use the .replace(oldCharacter, newCharacter) method.

as in:

s = s.replace(",","");


s = s.replace(".","");

This view is not constrained vertically. At runtime it will jump to the left unless you add a vertical constraint

for example I have this

< xmlns:android=""

use RelativeLayout layout like this

<RelativeLayout xmlns:android=""

How to configure CORS in a Spring Boot + Spring Security application?

After much searching for the error coming from javascript CORS, the only elegant solution I found for this case was configuring the cors of Spring's own class org.springframework.web.cors.CorsConfiguration.CorsConfiguration()

public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    protected void configure(HttpSecurity http) throws Exception {
        http.cors().configurationSource(request -> new CorsConfiguration().applyPermitDefaultValues());

Socket.IO handling disconnect event

For those like @sha1 wondering why the OP's code doesn't work -

OP's logic for deleting player at server side is in the handler for DelPlayer event, and the code that emits this event (DelPlayer) is in inside disconnected event callback of client.

The server side code that emits this disconnected event is inside the disconnect event callback which is fired when the socket loses connection. Since the socket already lost connection, disconnected event doesn't reach the client.

Accepted solution executes the logic on disconnect event at server side, which is fired when the socket disconnects, hence works.

missing FROM-clause entry for table

   AcId, AcName, PldepPer, RepId, CustCatg, HardCode, BlockCust, CrPeriod, CrLimit, 
   BillLimit, Mode, PNotes, gtab82.memno 
   VCustomer AS v1
   gtab82 ON gtab82.memacid = v1.AcId 
WHERE (AcGrCode = '204' OR CreDebt = 'True') 
AND Masked = 'false'

You typically only use an alias for a table name when you need to prefix a column with the table name due to duplicate column names in the joined tables and the table name is long or when the table is joined to itself. In your case you use an alias for VCustomer but only use it in the ON clause for uncertain reasons. You may want to review that aspect of your code.

MySQL: Selecting multiple fields into multiple variables in a stored procedure

Your syntax isn't quite right: you need to list the fields in order before the INTO, and the corresponding target variables after:

SELECT Id, dateCreated
INTO iId, dCreate
FROM products
WHERE pName = iName

Pipe subprocess standard output to a variable

If you are using python 2.7 or later, the easiest way to do this is to use the subprocess.check_output() command. Here is an example:

output = subprocess.check_output('ls')

To also redirect stderr you can use the following:

output = subprocess.check_output('ls', stderr=subprocess.STDOUT)

In the case that you want to pass parameters to the command, you can either use a list or use invoke a shell and use a single string.

output = subprocess.check_output(['ls', '-a'])
output = subprocess.check_output('ls -a', shell=True)

How to test an SQL Update statement before running it?

Run select query on same table with all where conditions you are applying in update query.

"The page you are requesting cannot be served because of the extension configuration." error message

In case this helps anyone, I was getting this error when attempting to run aspnet_regiis.exe:

Operation failed with 0x8007000B

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

As it turns out, the server was running 2008 64 bit and I was trying to run the 32 bit version of the utility. Running the version found in \Windows\Microsoft.NET\Framework64\v2.0.50727 fixed the issue.

c:\Windows\Microsoft.NET\Framework64\v2.0.50727>aspnet_regiis.exe -i

Add a pipe separator after items in an unordered list unless that item is the last on a line

I came across a solution today that does not appear to be here already and which seems to work quite well so far. The accepted answer does not work as-is on IE10 but this one does. credit to the author of course!

.pipe-separated-list-container {_x000D_
  overflow-x: hidden;_x000D_
.pipe-separated-list-container ul {_x000D_
  list-style-type: none;_x000D_
  position: relative;_x000D_
  left: -1px;_x000D_
  padding: 0;_x000D_
.pipe-separated-list-container ul li {_x000D_
  display: inline-block;_x000D_
  line-height: 1;_x000D_
  padding: 0 1em;_x000D_
  margin-bottom: 1em;_x000D_
  border-left: 1px solid;_x000D_
<div class="pipe-separated-list-container">_x000D_
    <li>Twenty One</li>_x000D_
    <li>Twenty Two</li>_x000D_
    <li>Twenty Three</li>_x000D_
    <li>Twenty Four</li>_x000D_
    <li>Twenty Five</li>_x000D_
    <li>Twenty Six</li>_x000D_
    <li>Twenty Seven</li>_x000D_
    <li>Twenty Eight</li>_x000D_
    <li>Twenty Nine</li>_x000D_

Checking if a textbox is empty in Javascript

onchange will work only if the value of the textbox changed compared to the value it had before, so for the first time it won't work because the state didn't change.

So it is better to use onblur event or on submitting the form.

function checkTextField(field) {_x000D_
  document.getElementById("error").innerText =_x000D_
    (field.value === "") ? "Field is empty." : "Field is filled.";_x000D_
<input type="text" onblur="checkTextField(this);" />_x000D_
<p id="error"></p>

(Or old live demo.)

Understanding __get__ and __set__ and Python descriptors

Why do I need the descriptor class?

Inspired by Fluent Python by Buciano Ramalho

Imaging you have a class like this

class LineItem:
     price = 10.9
     weight = 2.1
     def __init__(self, name, price, weight):
 = name
          self.price = price
          self.weight = weight

item = LineItem("apple", 2.9, 2.1)
item.price = -0.9  # it's price is negative, you need to refund to your customer even you delivered the apple :(
item.weight = -0.8 # negative weight, it doesn't make sense

We should validate the weight and price in avoid to assign them a negative number, we can write less code if we use descriptor as a proxy as this

class Quantity(object):
    __index = 0

    def __init__(self):
        self.__index = self.__class__.__index
        self._storage_name = "quantity#{}".format(self.__index)
        self.__class__.__index += 1

    def __set__(self, instance, value):
        if value > 0:
            setattr(instance, self._storage_name, value)
           raise ValueError('value should >0')

   def __get__(self, instance, owner):
        return getattr(instance, self._storage_name)

then define class LineItem like this:

class LineItem(object):
     weight = Quantity()
     price = Quantity()

     def __init__(self, name, weight, price): = name
         self.weight = weight
         self.price = price

and we can extend the Quantity class to do more common validating

How do I activate a virtualenv inside PyCharm's terminal?


The preferences in Settings (Preferences) | Tools | Terminal are global.
If you use a venv for each project, remember to use current path variable and a default venv name:

"cmd.exe" /k ""%CD%\venv\Scripts\activate"" 

For Windows users: when using PyCharm with a virtual environment, you can use the /K parameter to cmd.exe to set the virtual environment automatically.

PyCharm 3 or 4: Settings, Terminal, Default shell and add /K <path-to-your-activate.bat>.

PyCharm 5: Settings, Tools, Terminal, and add /K <path-to-your-activate.bat> to Shell path.

PyCharm 2016.1 or 2016.2: Settings, Tools, Terminal, and add ""/K <path-to-your-activate.bat>"" to Shell path and add (mind the quotes). Also add quotes around cmd.exe, resulting in:

"cmd.exe" /k ""C:\mypath\my-venv\Scripts\activate.bat""

Windows service start failure: Cannot start service from the command line or debugger

Watch this video, I had the same question. He shows you how to debug the service as well.

Here are his instructions using the basic C# Windows Service template in Visual Studio 2010/2012.

You add this to the Service1.cs file:

public void onDebug()

You change your Main() to call your service this way if you are in the DEBUG Active Solution Configuration.

static void Main()
    #if DEBUG
    //While debugging this section is used.
    Service1 myService = new Service1();

    //In Release this section is used. This is the "normal" way.
    ServiceBase[] ServicesToRun;
    ServicesToRun = new ServiceBase[] 
        new Service1() 

Keep in mind that while this is an awesome way to debug your service. It doesn't call OnStop() unless you explicitly call it similar to the way we called OnStart(null) in the onDebug() function.

Remove substring from the string

here's what I'd do

2.2.1 :015 > class String; def remove!(start_index, end_index) (end_index - start_index + 1).times{ self.slice! start_index }; self end; end;
2.2.1 :016 >   "idliketodeleteHEREallthewaytoHEREplease".remove! 14, 32
 => "idliketodeleteplease" 
2.2.1 :017 > ":)".remove! 1,1
 => ":" 
2.2.1 :018 > "ohnoe!".remove! 2,4
 => "oh!" 

Formatted on multiple lines:

class String
    def remove!(start_index, end_index)
        (end_index - start_index + 1).times{ self.slice! start_index }

Center an element in Bootstrap 4 Navbar

Updated for Bootstrap 4.1+

Bootstrap 4 the navbar now uses flexbox so the Website Name can be centered using mx-auto. The left and right side menus don't require floats.

<nav class="navbar navbar-expand-md navbar-fixed-top navbar-dark bg-dark main-nav">
    <div class="container">
        <ul class="nav navbar-nav">
            <li class="nav-item active">
                <a class="nav-link" href="#">Home</a>
            <li class="nav-item">
                <a class="nav-link" href="#">Download</a>
            <li class="nav-item">
                <a class="nav-link" href="#">Register</a>
        <ul class="nav navbar-nav mx-auto">
            <li class="nav-item"><a class="nav-link" href="#">Website Name</a></li>
        <ul class="nav navbar-nav">
            <li class="nav-item">
                <a class="nav-link" href="#">Rates</a>
            <li class="nav-item">
                <a class="nav-link" href="#">Help</a>
            <li class="nav-item">
                <a class="nav-link" href="#">Contact</a>

Navbar center with mx-auto Demo

If the Navbar only has a single navbar-nav, then justify-content-center can also be used to center.


In the solution above, the Website Name is centered relative to the left and right navbar-nav so if the width of these adjacent navs are different the Website Name is no longer centered.

enter image description here

To resolve this, one of the flexbox workarounds for absolute centering can be used...

Option 1 - Use position:absolute;

Since it's ok to use absolute positioning in flexbox, one option is to use this on the item to be centered.

.abs-center-x {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);

Navbar center with absolute position Demo

Option 2 - Use flexbox nesting

Finally, another option is to make the centered item also display:flexbox (using d-flex) and center justified. In this case each navbar component must have flex-grow:1

As of Bootstrap 4 Beta, the Navbar is now display:flex. Bootstrap 4.1.0 includes a new flex-fill class to make each nav section fill the width:

<nav class="navbar navbar-expand-sm navbar-dark bg-dark main-nav">
    <div class="container justify-content-center">
        <ul class="nav navbar-nav flex-fill w-100 flex-nowrap">
            <li class="nav-item active">
                <a class="nav-link" href="#">Home</a>
            <li class="nav-item">
                <a class="nav-link" href="#">Download</a>
            <li class="nav-item">
                <a class="nav-link" href="#">Register</a>
            <li class="nav-item">
                <a class="nav-link" href="#">More</a>
        <ul class="nav navbar-nav flex-fill justify-content-center">
            <li class="nav-item"><a class="nav-link" href="#">Center</a></li>
        <ul class="nav navbar-nav flex-fill w-100 justify-content-end">
            <li class="nav-item">
                <a class="nav-link" href="#">Help</a>
            <li class="nav-item">
                <a class="nav-link" href="#">Contact</a>

Navbar center with flexbox nesting Demo

Prior to Bootstrap 4.1.0 you can add the flex-fill class like this...

.flex-fill {

As of 4.1 flex-fill is included in Bootstrap.

Bootstrap 4 Navbar center demos
More centering demos
Center links on desktop, left align on mobile

How to center nav-items in Bootstrap?
Bootstrap NavBar with left, center or right aligned items
How move 'nav' element under 'navbar-brand' in my Navbar

enter image description here

How to set a Header field on POST a form?

In fact a better way to do it to save a cookie on the client side. Then the cookie is automatically sent with every page header for that particular domain.

In node-js, you can set up and use cookies with cookie-parser.

an example:

res.cookie('token', "xyz....", { httpOnly: true });

Now you can access this :

app.get('/',function(req, res){
 var token = req.cookies.token

Note that httpOnly:true ensures that the cookie is usually not accessible manually or through javascript and only browser can access it. If you want to send some headers or security tokens with a form post, and not through ajax, in most situation this can be considered a secure way. Although make sure that the data is sent over secure protocol /ssl if you are storing some sensitive user related info which is usually the case.

Execute a shell function with timeout

if you just want to add timeout as an additional option for the entire existing script, you can make it test for the timeout-option, and then make it call it self recursively without that option.

if [ "$1" == "-t" ]; then
  timeout 1m $0 $2
  #the original script
  echo $1
  sleep 2m
  echo YAWN...

running this script without timeout:

$./ -other_option # -other_option
                            # YAWN...

running it with a one minute timeout:

$./ -t -other_option # -other_option

How to remove all of the data in a table using Django

Using shell,

1) For Deleting the table:

python dbshell
>> DROP TABLE {app_name}_{model_name}

2) For removing all data from table:

python shell
>> from {app_name}.models import {model_name}
>> {model_name}.objects.all().delete()

How to get the primary IP address of the local machine on Linux and OS X?

For linux machines (not OS X) :

hostname --ip-address

How can I import data into mysql database via mysql workbench?

  • Under Server Administration on the Home window select the server instance you want to restore database to (Create New Server Instance if doing it first time).
  • Click on Manage Import/Export
  • Click on Data Import/Restore on the left side of the screen.
  • Select Import from Self-Contained File radio button (right side of screen)
  • Select the path of .sql
  • Click Start Import button at the right bottom corner of window.

Hope it helps.

---Edited answer---

Regarding selection of the schema. MySQL Workbench (5.2.47 CE Rev1039) does not yet support exporting to the user defined schema. It will create only the schema for which you exported the .sql... In 5.2.47 we see "New" target schema. But it does not work. I use MySQL Administrator (the old pre-Oracle MySQL Admin beauty) for my work for backup/restore. You can still download it from Googled trustable sources (search MySQL Administrator 1.2.17).

How to execute shell command in Javascript

Here is simple command that executes ifconfig shell command of Linux

var process = require('child_process');
process.exec('ifconfig',function (err,stdout,stderr) {
    if (err) {
    } else {

How do I do redo (i.e. "undo undo") in Vim?

Refer to the "undo" and "redo" part of Vim document.

:red[o] (Redo one change which was undone) and {count} Ctrl+r (Redo {count} changes which were undone) are both ok.

Also, the :earlier {count} (go to older text state {count} times) could always be a substitute for undo and redo.

Convert IEnumerable to DataTable

A 2019 answer if you're using .NET Core - use the Nuget ToDataTable library. Advantages:

Disclaimer - I'm the author of ToDataTable

Performance - I span up some Benchmark .Net tests and included them in the ToDataTable repo. The results were as follows:

Creating a 100,000 Row Datatable:

Reflection                 818.5 ms
DataTableProxy           1,068.8 ms
ToDataTable                449.0 ms

How to hide element label by element id in CSS?

This is worked for me.

        display: none;
    label[for="_account_id"] { display: none !important; }

auto refresh for every 5 mins

Refresh document every 300 seconds using HTML Meta tag add this inside the head tag of the page

 <meta http-equiv="refresh" content="300">

Using Script:

            setInterval(function() {
                }, 300000); 

How to get Spinner value?

add setOnItemSelectedListener to spinner reference and get the data like that`

 mSizeSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        public void onItemSelected(AdapterView<?> adapterView, View view, int position, long l) {

Get current category ID of the active page

Alternative -

 $catID = the_category_ID($echo=false);

EDIT: Above function is deprecated please use get_the_category()

jQuery document.createElement equivalent?

I've just made a small jQuery plugin for that:

It follows your syntax:

var myDiv = $.create("div");

DOM node ID can be specified as second parameter:

var secondItem = $.create("div","item2");

Is it serious? No. But this syntax is better than $("<div></div>"), and it's a very good value for that money.

I'm a new jQuery user, switching from DOMAssistant, which has a similar function:

My plugin is simpler, I think attrs and content is better to add by chaining methods:

$("#container").append( $.create("div").addClass("box").html("Hello, world!") );

Also, it's a good example for a simple jQuery-plugin (the 100th one).

Converting Hexadecimal String to Decimal Integer

This is my solution:

public static int hex2decimal(String s) {
    int val = 0;
    for (int i = 0; i < s.length(); i++) {
        char c = s.charAt(i);
        int num = (int) c;
        val = 256*val + num;
    return val;

For example to convert 3E8 to 1000:

StringBuffer sb = new StringBuffer();
sb.append((char) 0x03);
sb.append((char) 0xE8);
int n = hex2decimal(sb.toString());
System.out.println(n); //will print 1000.

React.js create loop through Array

In CurrentGame component you need to change initial state because you are trying use loop for participants but this property is undefined that's why you get error.,

getInitialState: function(){
    return {
       data: {
          participants: [] 

also, as player in .map is Object you should get properties from it {
   return <li key={player.championId}>{player.summonerName}</li>
   // -------------------^^^^^^^^^^^---------^^^^^^^^^^^^^^


ggplot geom_text font size control

Here are a few options for changing text / label sizes


# Example data using mtcars

a <- aggregate(mpg ~ vs + am , mtcars, function(i) round(mean(i)))

p <- ggplot(mtcars, aes(factor(vs), y=mpg, fill=factor(am))) + 
            geom_bar(stat="identity",position="dodge") + 
            geom_text(data = a, aes(label = mpg), 
                            position = position_dodge(width=0.9),  size=20)

The size in the geom_text changes the size of the geom_text labels.

p <- p + theme(axis.text = element_text(size = 15)) # changes axis labels

p <- p + theme(axis.title = element_text(size = 25)) # change axis titles

p <- p + theme(text = element_text(size = 10)) # this will change all text size 
                                                             # (except geom_text)

For this And why size of 10 in geom_text() is different from that in theme(text=element_text()) ?

Yes, they are different. I did a quick manual check and they appear to be in the ratio of ~ (14/5) for geom_text sizes to theme sizes.

So a horrible fix for uniform sizes is to scale by this ratio

geom.text.size = 7
theme.size = (14/5) * geom.text.size

ggplot(mtcars, aes(factor(vs), y=mpg, fill=factor(am))) + 
  geom_bar(stat="identity",position="dodge") + 
  geom_text(data = a, aes(label = mpg), 
            position = position_dodge(width=0.9),  size=geom.text.size) + 
  theme(axis.text = element_text(size = theme.size, colour="black")) 

This of course doesn't explain why? and is a pita (and i assume there is a more sensible way to do this)

How to Automatically Start a Download in PHP?

Send the following headers before outputting the file:

header("Content-Disposition: attachment; filename=\"" . basename($File) . "\"");
header("Content-Type: application/octet-stream");
header("Content-Length: " . filesize($File));
header("Connection: close");

@grom: Interesting about the 'application/octet-stream' MIME type. I wasn't aware of that, have always just used 'application/force-download' :)

CSS: create white glow around image

Depends on what your target browsers are. In newer ones it's as simple as:

   -moz-box-shadow: 0 0 5px #fff;
-webkit-box-shadow: 0 0 5px #fff;
        box-shadow: 0 0 5px #fff;

For older browsers you have to implement workarounds, e.g., based on this example, but you will most probably need extra mark-up.

ERROR 2003 (HY000): Can't connect to MySQL server on '' (111)

I just have this problem.... running in Win7 and wamp server ... after reading this

Found that Antivirus Firewall has caused the problem.

How do I get the selected element by name and then get the selected value from a dropdown using jQuery?

Remove the onchange event from the HTML Markup and bind it in your document ready event

<select  name="a[b]" >
     <option value='Choice 1'>Choice 1</option>
     <option value='Choice 2'>Choice 2</option>

and Script


Working sample :

T-SQL: How to Select Values in Value List that are NOT IN the Table?

For SQL Server 2008

SELECT email,
                     FROM   Users U
                     WHERE = THEN 'Exist'
         ELSE 'Not Exist'
       END AS [Status]
FROM   (VALUES('email1'),
              ('email4')) E(email)  

For previous versions you can do something similar with a derived table UNION ALL-ing the constants.

/*The SELECT list is the same as previously*/
SELECT 'email4'
)  E(email)

Or if you want just the non-existing ones (as implied by the title) rather than the exact resultset given in the question, you can simply do this

SELECT email
FROM   (VALUES('email1'),
              ('email4')) E(email)  
SELECT email
FROM Users

How to change button color with tkinter

When you do self.button = Button(...).grid(...), what gets assigned to self.button is the result of the grid() command, not a reference to the Button object created.

You need to assign your self.button variable before packing/griding it. It should look something like this:

self.button = Button(self,text="Click Me",command=self.color_change,bg="blue")
self.button.grid(row = 2, column = 2, sticky = W)

How to replace part of string by position?

You could try something link this:

string str = "ABCDEFGHIJ";
str = str.Substring(0, 2) + "ZX" + str.Substring(5);

if...else within JSP or JSTL

In case you want to compare strings, write the following JSTL :

    <c:when test="${myvar.equals('foo')}">
    <c:when test="${myvar.equals('bar')}">

How to get the string size in bytes?

I like to use:

(strlen(string) + 1 ) * sizeof(char)

This will give you the buffer size in bytes. You can use this with snprintf() may help:

const char* message = "%s, World!";
char* string = (char*)malloc((strlen(message)+1))*sizeof(char));
snprintf(string, (strlen(message)+1))*sizeof(char), message, "Hello");

Cheers! Function: size_t strlen (const char *s)

gzip: stdin: not in gzip format tar: Child returned status 1 tar: Error is not recoverable: exiting now

cd /Whatever/Directory/Path/The/File/Is/In

chmod +x

sudo ./

It works

For more information refer

What's the difference between Instant and LocalDateTime?

Instant corresponds to time on the prime meridian (Greenwich).

Whereas LocalDateTime relative to OS time zone settings, and

cannot represent an instant without additional information such as an offset or time-zone.

How do I get list of all tables in a database using TSQL?


Average of multiple columns

This works in MariaDB:

SELECT Req_ID, (R1+R2+R3+R4+R5)/5 AS Average
FROM Request

How do I make a placeholder for a 'select' box?

A non-CSS - no JavaScript/jQuery answer:

    <option value="" disabled selected>Select your option</option>_x000D_
    <option value="hurr">Durr</option>_x000D_

How to append data to a json file?

I have some code which is similar, but does not rewrite the entire contents each time. This is meant to run periodically and append a JSON entry at the end of an array.

If the file doesn't exist yet, it creates it and dumps the JSON into an array. If the file has already been created, it goes to the end, replaces the ] with a , drops the new JSON object in, and then closes it up again with another ]

# Append JSON object to output file JSON array
fname = "somefile.txt"
if os.path.isfile(fname):
    # File exists
    with open(fname, 'a+') as outfile:, os.SEEK_END)
        json.dump(data_dict, outfile)
    # Create file
    with open(fname, 'w') as outfile:
        array = []
        json.dump(array, outfile)

How do I enable TODO/FIXME/XXX task tags in Eclipse?

For me, such tags are enabled by default. You can configure which task tags should be used in the workspace options: Java > Compiler > Task tags

alt text

Check if they are enabled in this location, and that should be enough to have them appear in the Task list (or the Markers view).

Extra note: reinstalling Eclipse won't change anything most of the time if you work on the same workspace. Most settings used by Eclipse are stored in the .metadata folder, in your workspace folder.

How to cherry pick from 1 branch to another

When you cherry-pick, it creates a new commit with a new SHA. If you do:

git cherry-pick -x <sha>

then at least you'll get the commit message from the original commit appended to your new commit, along with the original SHA, which is very useful for tracking cherry-picks.

Child element click event trigger the parent click event

The stopPropagation() method stops the bubbling of an event to parent elements, preventing any parent handlers from being notified of the event.

You can use the method event.isPropagationStopped() to know whether this method was ever called (on that event object).


Here is the simple syntax to use this method:



$("div").click(function(event) {
    alert("This is : " + $(this).prop('id'));

    // Comment the following to see the difference

Android Material and appcompat Manifest merger failed

I had this same problem for three days.

It is like android wants us to either use Kotlin Or AndroidX, they are doing away with Android.

But this is how I solved it.

  • I migrated my project to AndroidX. This does not bring in any errors related to this issue in question, It updates files respectively. No method, class or variable name needs to be changed in your application.

NB: You must be using the latest Libraries (build.grudle file) in the latest stable version of android studio 3.4.1

How to change color in markdown cells ipython/jupyter notebook?

You can simply use raw html tags like

foo <font color='red'>bar</font> foo

Be aware that this will not survive a conversion of the notebook to latex.

As there are some complaints about the deprecation of the proposed solution. They are totally valid and Scott has already answered the question with a more recent, i.e. CSS based approach. Nevertheless, this answer shows some general approach to use html tags within IPython to style markdown cell content beyond the available pure markdown capabilities.

How do I run Java .class files?

You have to put java in lower case and you have to add .class!

java HelloWorld2.class

where is gacutil.exe?

On Windows 2012 R2, you can't install Visual Studio or SDK. You can use powershell to register assemblies into GAC. It didn't need any special installation for me.

Set-location "C:\Temp"
[System.Reflection.Assembly]::Load("System.EnterpriseServices, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")
$publish = New-Object System.EnterpriseServices.Internal.Publish

If you need to get the name and PublicKeyToken see this question.

Pip freeze vs. pip list

The main difference is that the output of pip freeze can be dumped into a requirements.txt file and used later to re-construct the "frozen" environment.

In other words you can run: pip freeze > frozen-requirements.txt on one machine and then later on a different machine or on a clean environment you can do: pip install -r frozen-requirements.txt and you'll get the an identical environment with the exact same dependencies installed as you had in the original environment where you generated the frozen-requirements.txt.

How to change background color in the Notepad++ text editor?

Notepad++ changed in the past couple of years, and it requires a few extra steps to set up a dark theme.

The answer by Amit-IO is good, but the example theme that is needed has stopped being maintained. The DraculaTheme is active. Just download the XML and put it in a themes folder. You may need Admin access in Windows.


Loop over array dimension in plpgsql

Since PostgreSQL 9.1 there is the convenient FOREACH:

   m   varchar[];
   arr varchar[] := array[['key1','val1'],['key2','val2']];
      RAISE NOTICE 'another_func(%,%)',m[1], m[2];

Solution for older versions:

   arr varchar[] := '{{key1,val1},{key2,val2}}';
   FOR i IN array_lower(arr, 1) .. array_upper(arr, 1)
      RAISE NOTICE 'another_func(%,%)',arr[i][1], arr[i][2];

Also, there is no difference between varchar[] and varchar[][] for the PostgreSQL type system. I explain in more detail here.

The DO statement requires at least PostgreSQL 9.0, and LANGUAGE plpgsql is the default (so you can omit the declaration).

How do I set the icon for my application in visual studio 2008?

The important thing is that the icon you want to be displayed as the application icon ( in the title bar and in the task bar ) must be the FIRST icon in the resource script file

The file is in the res folder and is named (applicationName).rc

// Icon

// Icon with lowest ID value placed first to ensure application icon
// remains consistent on all systems.
(icon ID )          ICON                    "res\\filename.ico"

How to set width of a div in percent in JavaScript?


    $(document).ready(function() { 
        rules: { 
          name: "required", //simple rule, converted to {required:true} 
          email: { //compound rule 
          required: true, 
          email: true 
        url: { 
          url: true 
        comment: { 
          required: true 
        messages: { 
          comment: "Please enter a comment." 

    var ok=confirm('Click "OK" to go to yahoo, "CANCEL" to go to hotmail')
    if (ok)

    function changeWidth(){
    var e1 = document.getElementById("e1"); = 400;


  <style type="text/css"> 
    * { font-family: Verdana; font-size: 11px; line-height: 14px; } 
    .submit { margin-left: 125px; margin-top: 10px;} 
    .label { display: block; float: left; width: 120px; text-align: right; margin-right: 5px; } 
    .form-row { padding: 5px 0; clear: both; width: 700px; } 
    .label.error { width: 250px; display: block; float: left; color: red; padding-left: 10px; } 
    .input[type=text], textarea { width: 250px; float: left; } 
    .textarea { height: 50px; } 


    <form id="form1" method="post" action=""> 
      <div class="form-row"><span class="label">Name *</span><input type="text" name="name" /></div> 
      <div class="form-row"><span class="label">E-Mail *</span><input type="text" name="email" /></div> 
      <div class="form-row"><span class="label">URL </span><input type="text" name="url" /></div> 
      <div class="form-row"><span class="label">Your comment *</span><textarea name="comment" ></textarea></div> 
      <div class="form-row"><input class="submit" type="submit" value="Submit"></div> 
      <input type="button" value="change width" onclick="changeWidth()"/>
      <div id="e1" style="width:20px;height:20px; background-color:#096"></div>


C# switch on type

See gjvdkamp's answer below; this feature now exists in C#

I usually use a dictionary of types and delegates.
var @switch = new Dictionary<Type, Action> {
    { typeof(Type1), () => ... },
    { typeof(Type2), () => ... },
    { typeof(Type3), () => ... },


It's a little less flexible as you can't fall through cases, continue etc. But I rarely do so anyway.

Is it possible to return empty in react render function?

Yes you can return an empty value from a React render method.

You can return any of the following: false, null, undefined, or true

According to the docs:

false, null, undefined, and true are valid children. They simply don’t render.

You could write

return null; or
return false; or
return true; or
return <div>{undefined}</div>; 

However return null is the most preferred as it signifies that nothing is returned

How do I abort/cancel TPL Tasks?

I use a mixed approach to cancel a task.

  • Firstly, I'm trying to Cancel it politely with using the Cancellation.
  • If it's still running (e.g. due to a developer's mistake), then misbehave and kill it using an old-school Abort method.

Checkout an example below:

private CancellationTokenSource taskToken;
private AutoResetEvent awaitReplyOnRequestEvent = new AutoResetEvent(false);

void Main()
    // Start a task which is doing nothing but sleeps 1s
    // Stop the task

/// <summary>
///     Launch task in a new thread
/// </summary>
void LaunchTaskAsync()
    taskToken = new CancellationTokenSource();
    Task.Factory.StartNew(() =>
            {   //Capture the thread
                runningTaskThread = Thread.CurrentThread;
                // Run the task
                if (taskToken.IsCancellationRequested || !awaitReplyOnRequestEvent.WaitOne(10000))
                Console.WriteLine("Task finished!");
            catch (Exception exc)
                // Handle exception
        }, taskToken.Token);

/// <summary>
///     Stop running task
/// </summary>
void StopTask()
    // Attempt to cancel the task politely
    if (taskToken != null)
        if (taskToken.IsCancellationRequested)

    // Notify a waiting thread that an event has occurred
    if (awaitReplyOnRequestEvent != null)

    // If 1 sec later the task is still running, kill it cruelly
    if (runningTaskThread != null)
        catch (Exception ex)

Set the selected index of a Dropdown using jQuery

I'm using


to select the option element that has value='xyz'

Why isn't Python very good for functional programming?

The question you reference asks which languages promote both OO and functional programming. Python does not promote functional programming even though it works fairly well.

The best argument against functional programming in Python is that imperative/OO use cases are carefully considered by Guido, while functional programming use cases are not. When I write imperative Python, it's one of the prettiest languages I know. When I write functional Python, it becomes as ugly and unpleasant as your average language that doesn't have a BDFL.

Which is not to say that it's bad, just that you have to work harder than you would if you switched to a language that promotes functional programming or switched to writing OO Python.

Here are the functional things I miss in Python:

  • No pattern matching and no tail recursion mean your basic algorithms have to be written imperatively. Recursion is ugly and slow in Python.
  • A small list library and no functional dictionaries mean that you have to write a lot of stuff yourself.
  • No syntax for currying or composition means that point-free style is about as full of punctuation as explicitly passing arguments.
  • Iterators instead of lazy lists means that you have to know whether you want efficiency or persistence, and to scatter calls to list around if you want persistence. (Iterators are use-once)
  • Python's simple imperative syntax, along with its simple LL1 parser, mean that a better syntax for if-expressions and lambda-expressions is basically impossible. Guido likes it this way, and I think he's right.

C#: how to get first char of a string?

Following example for getting first character from a string might help someone

string anyNameForString = "" + stringVariableName[0];

How do I convert an array object to a string in PowerShell?

You could specify type like this:

[string[]] $a = "This", "Is", "a", "cat"

Checking the type:



    IsPublic IsSerial Name                                     BaseType
    -------- -------- ----                                     --------
    True     True     String[]                                 System.Array

Outputting $a:

PS C:\> $a 

WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for jquery

Further to the accepted answer, I ran into issues with code elsewhere on my site requiring jQuery along with the Migrate Plugin.

When the required mapping is added to Global.asax, when loading a page requiring unobtrusive validation (for example a page with the ChangePassword ASP control), the mapped script resource conflicts with the already-loaded jQuery and migrate scripts.

Adding the migrate plugin as a second mapping solves the issue:

// required for UnobtrusiveValidationMode introduced since ASP.NET 4.5
var jQueryScriptDefinition = new ScriptResourceDefinition
    Path = "~/Plugins/Common/jquery-3.3.1.min.js", DebugPath = "~/Plugins/Common/jquery-3.3.1.js", LoadSuccessExpression = "typeof(window.jQuery) !== 'undefined'"
var jQueryMigrateScriptDefinition = new ScriptResourceDefinition
    Path = "~/Plugins/Common/jquery-migrate-3.0.1.min.js", DebugPath = "~/Plugins/Common/jquery-migrate-3.0.1.js", LoadSuccessExpression = "typeof(window.jQuery) !== 'undefined'"
ScriptManager.ScriptResourceMapping.AddDefinition("jquery", jQueryScriptDefinition);
ScriptManager.ScriptResourceMapping.AddDefinition("jquery", jQueryMigrateScriptDefinition);

How can I parse a YAML file from a Linux shell script?

Moving my answer from How to convert a json response into yaml in bash, since this seems to be the authoritative post on dealing with YAML text parsing from command line.

I would like to add details about the yq YAML implementation. Since there are two implementations of this YAML parser lying around, both having the name yq, it is hard to differentiate which one is in use, without looking at the implementations' DSL. There two available implementations are

  1. kislyuk/yq - The more often talked about version, which is a wrapper over jq, written in Python using the PyYAML library for YAML parsing
  2. mikefarah/yq - A Go implementation, with its own dynamic DSL using the go-yaml v3 parser.

Both are available for installation via standard installation package managers on almost all major distributions

  1. kislyuk/yq - Installation instructions
  2. mikefarah/yq - Installation instructions

Both the versions have some pros and cons over the other, but a few valid points to highlight (adopted from their repo instructions)


  1. Since the DSL is the adopted completely from jq, for users familiar with the latter, the parsing and manipulation becomes quite straightforward
  2. Supports mode to preserve YAML tags and styles, but loses comments during the conversion. Since jq doesn't preserve comments, during the round-trip conversion, the comments are lost.
  3. As part of the package, XML support is built in. An executable, xq, which transcodes XML to JSON using xmltodict and pipes it to jq, on which you can apply the same DSL to perform CRUD operations on the objects and round-trip the output back to XML.
  4. Supports in-place edit mode with -i flag (similar to sed -i)


  1. Prone to frequent changes in DSL, migration from 2.x - 3.x
  2. Rich support for anchors, styles and tags. But lookout for bugs once in a while
  3. A relatively simple Path expression syntax to navigate and match yaml nodes
  4. Supports YAML->JSON, JSON->YAML formatting and pretty printing YAML (with comments)
  5. Supports in-place edit mode with -i flag (similar to sed -i)
  6. Supports coloring the output YAML with -C flag (not applicable for JSON output) and indentation of the sub elements (default at 2 spaces)
  7. Supports Shell completion for most shells - Bash, zsh (because of powerful support from spf13/cobra used to generate CLI flags)

My take on the following YAML (referenced in other answer as well) with both the versions

root_key1: this is value one
root_key2: "this is value two"

  state: liquid
    best_served: hot
    colour: brown
    best_served: cold
    colour: orange

  state: solid
    best_served: warm

root_key_3: this is value three

Various actions to be performed with both the implementations (some frequently used operations)

  1. Modifying node value at root level - Change value of root_key2
  2. Modifying array contents, adding value - Add property to coffee
  3. Modifying array contents, deleting value - Delete property from orange_juice
  4. Printing key/value pairs with paths - For all items under food

Using kislyuk/yq

  1. yq -y '.root_key2 |= "this is a new value"' yaml
  2. yq -y ' += { time: "always"}' yaml
  3. yq -y 'del(.drink.orange_juice.colour)' yaml
  4. yq -r '.food|paths(scalars) as $p | [($p|join(".")), (getpath($p)|tojson)] | @tsv' yaml

Which is pretty straightforward. All you need is to transcode jq JSON output back into YAML with the -y flag.

Using mikefarah/yq

  1.  yq w yaml root_key2 "this is a new value"
  2.  yq w yaml "always"
  3.  yq d yaml drink.orange_juice.colour
  4.  yq r yaml --printMode pv "food.**"

As of today Dec 21st 2020, yq v4 is in beta and supports much powerful path expressions and supports DSL similar to using jq. Read the transition notes - Upgrading from V3

How to implement the Softmax function in Python

I needed something compatible with the output of a dense layer from Tensorflow.

The solution from @desertnaut does not work in this case because I have batches of data. Therefore, I came with another solution that should work in both cases:

def softmax(x, axis=-1):
    e_x = np.exp(x - np.max(x)) # same code
    return e_x / e_x.sum(axis=axis, keepdims=True)


logits = np.asarray([
    [-0.0052024,  -0.00770216,  0.01360943, -0.008921], # 1
    [-0.0052024,  -0.00770216,  0.01360943, -0.008921]  # 2


#[[0.2492037  0.24858153 0.25393605 0.24827873]
# [0.2492037  0.24858153 0.25393605 0.24827873]]

Ref: Tensorflow softmax

How to insert a newline in front of a pattern?

In vi on Red Hat, I was able to insert carriage returns using just the \r character. I believe this internally executes 'ex' instead of 'sed', but it's similar, and vi can be another way to do bulk edits such as code patches. For example. I am surrounding a search term with an if statement that insists on carriage returns after the braces:


Note that I also had it insert some tabs to make things align better.

"Application tried to present modally an active controller"?

Assume you have three view controllers instantiated like so:

UIViewController* vc1 = [[UIViewController alloc] init];
UIViewController* vc2 = [[UIViewController alloc] init];
UIViewController* vc3 = [[UIViewController alloc] init];

You have added them to a tab bar like this:

UITabBarController* tabBarController = [[UITabBarController alloc] init];
[tabBarController setViewControllers:[NSArray arrayWithObjects:vc1, vc2, vc3, nil]];

Now you are trying to do something like this:

[tabBarController presentModalViewController:vc3];

This will give you an error because that Tab Bar Controller has a death grip on the view controller that you gave it. You can either not add it to the array of view controllers on the tab bar, or you can not present it modally.

Apple expects you to treat their UI elements in a certain way. This is probably buried in the Human Interface Guidelines somewhere as a "don't do this because we aren't expecting you to ever want to do this".

Multiple submit buttons on HTML form – designate one button as default

My suggestion is don't fight this behaviour. You can effectively alter the order using floats. For example:

<p id="buttons">
<input type="submit" name="next" value="Next">
<input type="submit" name="prev" value="Previous">


#buttons { overflow: hidden; }
#buttons input { float: right; }

will effectively reverse the order and thus the "Next" button will be the value triggered by hitting enter.

This kind of technique will cover many circumstances without having to resort to more hacky JavaScript methods.

Default passwords of Oracle 11g?

Once installed in windows Followed the instructions starting from Run SQL Command Line (command prompt)

then... v. SQL> connect /as sysdba

Connected. [SQL prompt response]

vi. SQL> alter user SYS identified by "newpassword";

User altered. [SQL prompt response]

Thank you. This minimized a headache

Spring Data JPA find by embedded object property

According to me, Spring doesn't handle all the cases with ease. In your case the following should do the trick

Page<QueuedBook> findByBookIdRegion(Region region, Pageable pageable);  


Page<QueuedBook> findByBookId_Region(Region region, Pageable pageable);

However, it also depends on the naming convention of fields that you have in your @Embeddable class,

e.g. the following field might not work in any of the styles that mentioned above

private String cRcdDel;

I tried with both the cases (as follows) and it didn't work (it seems like Spring doesn't handle this type of naming conventions(i.e. to many Caps , especially in the beginning - 2nd letter (not sure about if this is the only case though)

Page<QueuedBook> findByBookIdCRcdDel(String cRcdDel, Pageable pageable); 


Page<QueuedBook> findByBookIdCRcdDel(String cRcdDel, Pageable pageable);

When I renamed column to

private String rcdDel;

my following solutions work fine without any issue:

Page<QueuedBook> findByBookIdRcdDel(String rcdDel, Pageable pageable); 


Page<QueuedBook> findByBookIdRcdDel(String rcdDel, Pageable pageable);

How to pause for specific amount of time? (Excel/VBA)

Just a cleaned up version of clemo's code - works in Access, which doesn't have the Application.Wait function.

Public Sub Pause(sngSecs As Single)
    Dim sngEnd As Single
    sngEnd = Timer + sngSecs
    While Timer < sngEnd
End Sub

Public Sub TestPause()
    Pause 1
    MsgBox "done"
End Sub

Laravel 5 - How to access image uploaded in storage within View?

If you want to load a small number of Private images You can encode the images to base64 and echo them into <img src="{{$image_data}}"> directly:

$path = image.png
$full_path = Storage::path($path);
$base64 = base64_encode(Storage::get($path));
$image_data = 'data:'.mime_content_type($full_path) . ';base64,' . $base64;

I mentioned private because you should only use these methods if you do not want to store images publicly accessible through url ,instead you Must always use the standard way (link storage/public folder and serve images with HTTP server).

Beware encoding to base64() have two important down sides:

  1. This will increase image size by ~30%.
  2. You combine all of the images sizes in one request, instead of loading them in parallel, this should not be a problem for some small thumbnails but for many images avoid using this method.

%i or %d to print integer in C using printf()?

They are completely equivalent when used with printf(). Personally, I prefer %d, it's used more often (should I say "it's the idiomatic conversion specifier for int"?).

(One difference between %i and %d is that when used with scanf(), then %d always expects a decimal integer, whereas %i recognizes the 0 and 0x prefixes as octal and hexadecimal, but no sane programmer uses scanf() anyway so this should not be a concern.)

How to index an element of a list object in R

Indexing a list is done using double bracket, i.e. hypo_list[[1]] (e.g. have a look here: BTW: read.table does not return a table but a dataframe (see value section in ?read.table). So you will have a list of dataframes, rather than a list of table objects. The principal mechanism is identical for tables and dataframes though.

Note: In R, the index for the first entry is a 1 (not 0 like in some other languages).


l <- list(anscombe, iris)   # put dfs in list
l[[1]]             # returns anscombe dataframe

anscombe[1:2, 2]   # access first two rows and second column of dataset
[1] 10  8

l[[1]][1:2, 2]     # the same but selecting the dataframe from the list first
[1] 10  8

Table objects

tbl1 <- table(sample(1:5, 50, rep=T))
tbl2 <- table(sample(1:5, 50, rep=T))
l <- list(tbl1, tbl2)  # put tables in a list

tbl1[1:2]              # access first two elements of table 1 

Now with the list

l[[1]]                 # access first table from the list

1  2  3  4  5 
9 11 12  9  9 

l[[1]][1:2]            # access first two elements in first table

1  2 
9 11 

How to add number of days in postgresql datetime

For me I had to put the whole interval in single quotes not just the value of the interval.

select id,  
   created_at + interval '1 day' * claim_window as deadline from projects   

Instead of

select id,  
   created_at + interval '1' day * claim_window as deadline from projects   

Postgres Date/Time Functions

HTML email in outlook table width issue - content is wider than the specified table width

I guess problem is in width attributes in table and td remove 'px' for example

<table border="0" cellpadding="0" cellspacing="0" width="580px" style="background-color: #0290ba;">

Should be

<table border="0" cellpadding="0" cellspacing="0" width="580" style="background-color: #0290ba;">

Manually raising (throwing) an exception in Python

For the common case where you need to throw an exception in response to some unexpected conditions, and that you never intend to catch, but simply to fail fast to enable you to debug from there if it ever happens — the most logical one seems to be AssertionError:

if 0 < distance <= RADIUS:
    #Do something.
elif RADIUS < distance:
    #Do something.
    raise AssertionError("Unexpected value of 'distance'!", distance)

Search and replace part of string in database

You can do it with an UPDATE statement setting the value with a REPLACE

    Column = Replace(Column, 'find value', 'replacement value')

You will want to be extremely careful when doing this! I highly recommend doing a backup first.

Stylesheet not loaded because of MIME-type

I have used virtual domain in my XAMPP and got this issue. So in httpd-vshosts.conf file when I checked, I had explicitly pointed to index.php file and this had caused the issue.

So I changed this:

<VirtualHost *:80>
    DocumentRoot "C:/xampp/htdocs/cv/index.php"
    ServerName cv.dv

to this:

<VirtualHost *:80>
    DocumentRoot "C:/xampp/htdocs/cv/"
    ServerName cv.dv

and then the files were loaded without issues.

Clicking submit button of an HTML form by a Javascript code


or, use the same code as the onclick handler:


(Though that onclick handler is kind of stupidly-written: document.forms['loginForm'] could be replaced with this.)

C# How do I click a button by hitting Enter whilst textbox has focus?

The simple option is just to set the forms's AcceptButton to the button you want pressed (usually "OK" etc):

    TextBox tb = new TextBox();
    Button btn = new Button { Dock = DockStyle.Bottom };
    btn.Click += delegate { Debug.WriteLine("Submit: " + tb.Text); };
    Application.Run(new Form { AcceptButton = btn, Controls = { tb, btn } });

If this isn't an option, you can look at the KeyDown event etc, but that is more work...

    TextBox tb = new TextBox();
    Button btn = new Button { Dock = DockStyle.Bottom };
    btn.Click += delegate { Debug.WriteLine("Submit: " + tb.Text); };
    tb.KeyDown += (sender,args) => {
        if (args.KeyCode == Keys.Return)
    Application.Run(new Form { Controls = { tb, btn } });

Trigger change() event when setting <select>'s value with val() function

As jQuery won't trigger native change event but only triggers its own change event. If you bind event without jQuery and then use jQuery to trigger it the callbacks you bound won't run !

The solution is then like below (100% working) :

var sortBySelect = document.querySelector("select.your-class"); 
sortBySelect.value = "new value"; 
sortBySelect.dispatchEvent(new Event("change"));

Excel 2013 VBA Clear All Filters macro

ShowAllData will throw an error if a filter isn't currently applied. This will work:

Sub ResetFilters()
    On Error Resume Next
End Sub

How to set thymeleaf th:field value from other variable

If you don't have to come back on the page with keeping form's value, you can do that :

<form method="post" th:action="@{''}" th:object="${form}">
    <input class="form-control"

It's some kind of magic :

  • it will set the value =
  • it will send back the value in the form, as 'name' field. So you would have to change your form field, 'clientName' to 'name'

If you matter keeping you form's input values, like a back on the page with an user input mistake, then you will have to do that :

<form method="post" th:action="@{''}" th:object="${form}">
    <input class="form-control"
           th:value="${ != null} ? ${} : ${}"/>

That means :

  • The form field name is 'name'
  • The value is taken from the form if it exists, else from the client bean. Which matches the first arrival on the page with initial value, then the forms input values if there is an error.

Without having to map your client bean to your form bean. And it works because once you submitted the form, the value arn't null but "" (empty)

Get elements by attribute when querySelectorAll is not available without using libraries?

That works too:




Deserializing JSON data to C# using JSON.NET

I found my I had built my object incorrectly. I used to generate me my object class from the JSON. Once I had the correct Oject I was able to cast without issue. Norbit, Noob mistake. Thought I'd add it in case you have the same issue.

Can't import javax.servlet.annotation.WebServlet

Simply add the below to your maven project pom.xml flie:


Postgresql column reference "id" is ambiguous

You need the table name/alias in the SELECT part (maybe (, name)) :

SELECT (, name) FROM v_groups vg 
inner join people2v_groups p2vg on = p2vg.v_group_id
where p2vg.people_id =0;

Can't import Numpy in Python

The following command worked for me:

python.exe -m pip install numpy

Javascript seconds to minutes and seconds

I prefer thinking of Millisecond as its own unit, rather than as a subunit of something else. In that sense, it will have values of 0-999, so youre going to want to Pad three instead of two like I have seen with other answers. Here is an implementation:

function format(n) {
   let mil_s = String(n % 1000).padStart(3, '0');
   n = Math.trunc(n / 1000);
   let sec_s = String(n % 60).padStart(2, '0');
   n = Math.trunc(n / 60);
   return String(n) + ' m ' + sec_s + ' s ' + mil_s + ' ms';

HTML button opening link in new tab

You can also add this to your form:

<form ... target="_blank">

PHPMailer character encoding issues

To avoid problems of character encoding in sending emails using the class PHPMailer we can configure it to send it with UTF-8 character encoding using the "CharSet" parameter, as we can see in the following Php code:

$mail = new PHPMailer();
$mail->From = '[email protected]';
$mail->FromName = 'Mi nombre';
$mail->AddAddress('[email protected]');
$mail->Subject = 'Prueba';
$mail->Body = '';

// Active condition utf-8
$mail->CharSet = 'UTF-8';

// Send mail

How do I send email with JavaScript without opening the mail client?

There needs to be some type of backend framework to send the email. This can be done via PHP/ASP.NET, or with the local mail client. If you want the user to see nothing, the best way is to tap into those by an AJAX call to a separate send_email file.

Python class returning value

I think you are very confused about what is occurring.

In Python, everything is an object:

  • [] (a list) is an object
  • 'abcde' (a string) is an object
  • 1 (an integer) is an object
  • MyClass() (an instance) is an object
  • MyClass (a class) is also an object
  • list (a type--much like a class) is also an object

They are all "values" in the sense that they are a thing and not a name which refers to a thing. (Variables are names which refer to values.) A value is not something different from an object in Python.

When you call a class object (like MyClass() or list()), it returns an instance of that class. (list is really a type and not a class, but I am simplifying a bit here.)

When you print an object (i.e. get a string representation of an object), that object's __str__ or __repr__ magic method is called and the returned value printed.

For example:

>>> class MyClass(object):
...     def __str__(self):
...             return "MyClass([])"
...     def __repr__(self):
...             return "I am an instance of MyClass at address "+hex(id(self))
>>> m = MyClass()
>>> print m
>>> m
I am an instance of MyClass at address 0x108ed5a10

So what you are asking for, "I need that MyClass return a list, like list(), not the instance info," does not make any sense. list() returns a list instance. MyClass() returns a MyClass instance. If you want a list instance, just get a list instance. If the issue instead is what do these objects look like when you print them or look at them in the console, then create a __str__ and __repr__ method which represents them as you want them to be represented.

Update for new question about equality

Once again, __str__ and __repr__ are only for printing, and do not affect the object in any other way. Just because two objects have the same __repr__ value does not mean they are equal!

MyClass() != MyClass() because your class does not define how these would be equal, so it falls back to the default behavior (of the object type), which is that objects are only equal to themselves:

>>> m = MyClass()
>>> m1 = m
>>> m2 = m
>>> m1 == m2
>>> m3 = MyClass()
>>> m1 == m3

If you want to change this, use one of the comparison magic methods

For example, you can have an object that is equal to everything:

>>> class MyClass(object):
...     def __eq__(self, other):
...             return True
>>> m1 = MyClass()
>>> m2 = MyClass()
>>> m1 == m2
>>> m1 == m1
>>> m1 == 1
>>> m1 == None
>>> m1 == []

I think you should do two things:

  1. Take a look at this guide to magic method use in Python.
  2. Justify why you are not subclassing list if what you want is very list-like. If subclassing is not appropriate, you can delegate to a wrapped list instance instead:

    class MyClass(object):
        def __init__(self):
            self._list = []
        def __getattr__(self, name):
            return getattr(self._list, name)
        # __repr__ and __str__ methods are automatically created
        # for every class, so if we want to delegate these we must
        # do so explicitly
        def __repr__(self):
            return "MyClass(%s)" % repr(self._list)
        def __str__(self):
            return "MyClass(%s)" % str(self._list)

    This will now act like a list without being a list (i.e., without subclassing list).

    >>> c = MyClass()
    >>> c.append(1)
    >>> c

How can I see the entire HTTP request that's being sent by my Python application?

The verbose configuration option might allow you to see what you want. There is an example in the documentation.

NOTE: Read the comments below: The verbose config options doesn't seem to be available anymore.

Cannot find firefox binary in PATH. Make sure firefox is installed. OS appears to be: VISTA

you have to add vm argument while running the program. This should be like


In IntelliJ IDE much simpler Goto Run ? Edit Configurations... In VM options add the above.

IntelliJ Run Configurations

Eclipse also have the options to give vm argument while running. This way I am using portable Firefox with selenium.

Adding multiple class using ng-class

An incredibly powerful alternative to other answers here:

ng-class="[  { key: resulting-class-expression }[ key-matching-expression ], ..  ]"

Some examples:

1. Simply adds 'class1 class2 class3' to the div:

<div ng-class="[{true: 'class1'}[true], {true: 'class2 class3'}[true]]"></div>

2. Adds 'odd' or 'even' classes to div, depending on the $index:

<div ng-class="[{0:'even', 1:'odd'}[ $index % 2]]"></div>

3. Dynamically creates a class for each div based on $index

<div ng-class="[{true:'index'+$index}[true]]"></div>

If $index=5 this will result in:

<div class="index5"></div>

Here's a code sample you can run:

var app = angular.module('app', []); _x000D_
app.controller('MyCtrl', function($scope){_x000D_
  $scope.items = 'abcdefg'.split('');_x000D_
.odd  { background-color: #eee; }_x000D_
.even { background-color: #fff; }_x000D_
.index5 {background-color: #0095ff; color: white; font-weight: bold; }_x000D_
* { font-family: "Courier New", Courier, monospace; }
<script src=""></script>_x000D_
<div ng-app="app" ng-controller="MyCtrl">_x000D_
  <div ng-repeat="item in items"_x000D_
    ng-class="[{true:'index'+$index}[true], {0:'even', 1:'odd'}[ $index % 2 ]]">_x000D_
    index {{$index}} = "{{item}}" ng-class="{{[{true:'index'+$index}[true], {0:'even', 1:'odd'}[ $index % 2 ]].join(' ')}}"_x000D_

How to set the height of table header in UITableView?

With autolayout you could do something like:

tableView.sectionHeaderHeight = UITableViewAutomaticDimension
tableView.estimatedSectionHeaderHeight = <your-header-height>

or if your headers are of different heights, go ahead and implement:

func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
    return <your-header-height>

How do I find the version of Apache running without access to the command line?

Telnet to the host at port 80.


get / http1.1

It is kind of an HTTP request, but it's not valid so the 500 error it gives you will probably give you the information you want. The blank lines at the end are important otherwise it will just seem to hang.

Could not connect to React Native development server on Android

Make sure NPM server is running. Else run it again. It will solve the issue.

Python, how to read bytes from file and save it?

Here's how to do it with the basic file operations in Python. This opens one file, reads the data into memory, then opens the second file and writes it out.

in_file = open("in-file", "rb") # opening for [r]eading as [b]inary
data = # if you only wanted to read 512 bytes, do .read(512)

out_file = open("out-file", "wb") # open for [w]riting as [b]inary

We can do this more succinctly by using the with keyboard to handle closing the file.

with open("in-file", "rb") as in_file, open("out-file", "wb") as out_file:

If you don't want to store the entire file in memory, you can transfer it in pieces.

piece_size = 4096 # 4 KiB

with open("in-file", "rb") as in_file, open("out-file", "wb") as out_file:
    while True:
        piece =

        if piece == "":
            break # end of file


Postman - How to see request with headers and body data with variables substituted

As of now, Postman comes with its own "Console." Click the terminal-like icon on the bottom left to open the console. Send a request, and you can inspect the request from within Postman's console.

enter image description here

What is the most effective way to get the index of an iterator of an std::vector?

Beside int float string etc., you can put extra data to .second when using diff. types like:

std::map<unsigned long long int, glm::ivec2> voxels_corners;
std::map<unsigned long long int, glm::ivec2>::iterator it_corners;


struct voxel_map {
    int x,i;

std::map<unsigned long long int, voxel_map> voxels_corners;
std::map<unsigned long long int, voxel_map>::iterator it_corners;


long long unsigned int index_first=some_key; // llu in this case...
int i=0;


long long unsigned int index_first=some_key;
int index_counter=0;
voxel_map one;


with right type || structure you can put anything in the .second including a index number that is incremented when doing an insert.

instead of

it_corners - _corners.begin()


std::distance(it_corners.begin(), it_corners)


it_corners = voxels_corners.find(index_first+bdif_x+x_z);

the index is simply:

int vertice_index = it_corners->second.y;

when using the glm::ivec2 type


int vertice_index = it_corners->second.i;

in case of the structure data type

Lowercase and Uppercase with jQuery

Try this:

var jIsHasKids = $('#chkIsHasKids').attr('checked');
jIsHasKids = jIsHasKids.toString().toLowerCase();
jIsHasKids = jIsHasKids.val().toLowerCase();

Possible duplicate with: How do I use jQuery to ignore case when selecting

MySQL vs MySQLi when using PHP

for me, prepared statements is a must-have feature. more exactly, parameter binding (which only works on prepared statements). it's the only really sane way to insert strings into SQL commands. i really don't trust the 'escaping' functions. the DB connection is a binary protocol, why use an ASCII-limited sub-protocol for parameters?

Print range of numbers on same line

1 2 3 4 5 6 7 8 9 10

Python one liner to print the range

Should I use px or rem value units in my CSS?

josh3736's answer is a good one, but to provide a counterpoint 3 years later:

I recommend using rem units for fonts, if only because it makes it easier for you, the developer, to change sizes. It's true that users very rarely change the default font size in their browsers, and that modern browser zoom will scale up px units. But what if your boss comes to you and says "don't enlarge the images or icons, but make all the fonts bigger". It's much easier to just change the root font size and let all the other fonts scale relative to that, then to change px sizes in dozens or hundreds of css rules.

I think it still makes sense to use px units for some images, or for certain layout elements that should always be the same size regardless of the scale of the design. may have said that only 75% of browsers when josh3736 posted his answer in 2012, but as of March 27 they claim 93.78% support. Only IE8 doesn't support it among the browsers they track.

Parsing JSON Object in Java

Thank you so much to @Code in another answer. I can read any JSON file thanks to your code. Now, I'm trying to organize all the elements by levels, for could use them!

I was working with Android reading a JSON from an URL and the only I had to change was the lines

Set<Object> set = jsonObject.keySet(); Iterator<Object> iterator = set.iterator();


Iterator<?> iterator = jsonObject.keys();

I share my implementation, to help someone:

public void parseJson(JSONObject jsonObject) throws ParseException, JSONException {

    Iterator<?> iterator = jsonObject.keys();
    while (iterator.hasNext()) {
        String obj =;

        if (jsonObject.get(obj) instanceof JSONArray) {
            //Toast.makeText(MainActivity.this, "Objeto: JSONArray", Toast.LENGTH_SHORT).show();
            TextView txtView = new TextView(this);
        } else {
            if (jsonObject.get(obj) instanceof JSONObject) {
                //Toast.makeText(MainActivity.this, "Objeto: JSONObject", Toast.LENGTH_SHORT).show();
                parseJson((JSONObject) jsonObject.get(obj));
            } else {
                //Toast.makeText(MainActivity.this, "Objeto: Value", Toast.LENGTH_SHORT).show();
                //System.out.println(obj.toString() + "\t"+ jsonObject.get(obj));
                TextView txtView = new TextView(this);
                txtView.setText(obj.toString() + "\t"+ jsonObject.get(obj));

How to add a string to a string[] array? There's no .Add function

Why don't you use a for loop instead of using foreach. In this scenario, there is no way you can get the index of the current iteration of the foreach loop.

The name of the file can be added to the string[] in this way,

private string[] ColeccionDeCortes(string Path)
  DirectoryInfo X = new DirectoryInfo(Path);
  FileInfo[] listaDeArchivos = X.GetFiles();
  string[] Coleccion=new string[listaDeArchivos.Length];

  for (int i = 0; i < listaDeArchivos.Length; i++)
     Coleccion[i] = listaDeArchivos[i].Name;

  return Coleccion;

Change Color of Fonts in DIV (CSS)

To do links, you can do

.social h2 a:link {
  color: pink;
  font-size: 14px;   

You can change the hover, visited, and active link styling too. Just replace "link" with what you want to style. You can learn more at the w3schools page CSS Links.

Unexpected character encountered while parsing value

When I encountered a similar problem, I fixed it by substituting &mode=xml for &mode=json in the request.

What does mscorlib stand for?

Microsoft Core Library, ie they are at the heart of everything.

There is a more "massaged" explanation you may prefer:

"When Microsoft first started working on the .NET Framework, MSCorLib.dll was an acronym for Microsoft Common Object Runtime Library. Once ECMA started to standardize the CLR and parts of the FCL, MSCorLib.dll officially became the acronym for Multilanguage Standard Common Object Runtime Library."


Around 1999, to my personal memory, .Net was known as "COOL", so I am a little suspicious of this derivation. I never heard it called "COR", which is a silly-sounding name to a native English speaker.

How is the default max Java heap size determined?

For Java SE 5: According to Garbage Collector Ergonomics [Oracle]:

initial heap size:

Larger of 1/64th of the machine's physical memory on the machine or some reasonable minimum. Before J2SE 5.0, the default initial heap size was a reasonable minimum, which varies by platform. You can override this default using the -Xms command-line option.

maximum heap size:

Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0, the default maximum heap size was 64MB. You can override this default using the -Xmx command-line option.


As pointed out by Tom Anderson in his comment, the above is for server-class machines. From Ergonomics in the 5.0 JavaTM Virtual Machine:

In the J2SE platform version 5.0 a class of machine referred to as a server-class machine has been defined as a machine with

  • 2 or more physical processors
  • 2 or more Gbytes of physical memory

with the exception of 32 bit platforms running a version of the Windows operating system. On all other platforms the default values are the same as the default values for version 1.4.2.

In the J2SE platform version 1.4.2 by default the following selections were made

  • initial heap size of 4 Mbyte
  • maximum heap size of 64 Mbyte

ValueError: Wrong number of items passed - Meaning and suggestions?

Not sure if this is relevant to your question but it might be relevant to someone else in the future: I had a similar error. Turned out that the df was empty (had zero rows) and that is what was causing the error in my command.

How to validate phone number using PHP?

I depends heavily on which number formats you aim to support, and how strict you want to enforce number grouping, use of whitespace and other separators etc....

Take a look at this similar question to get some ideas.

Then there is E.164 which is a numbering standard recommendation from ITU-T

I want to vertical-align text in select box

So far this is working fine for me:

line-height: 100%;

How to get the command line args passed to a running process on unix/linux systems?

There are several options:

ps -fp <pid>
cat /proc/<pid>/cmdline | sed -e "s/\x00/ /g"; echo

There is more info in /proc/<pid> on Linux, just have a look.

On other Unixes things might be different. The ps command will work everywhere, the /proc stuff is OS specific. For example on AIX there is no cmdline in /proc.

HTML5 Audio Looping

Your code works for me on Chrome (5.0.375), and Safari (5.0). Doesn't loop on Firefox (3.6).

See example.

var song = new Audio("file");
song.loop = true;

Simplest way to detect a pinch

Think about what a pinch event is: two fingers on an element, moving toward or away from each other. Gesture events are, to my knowledge, a fairly new standard, so probably the safest way to go about this is to use touch events like so:

(ontouchstart event)

if (e.touches.length === 2) {
    scaling = true;

(ontouchmove event)

if (scaling) {

(ontouchend event)

if (scaling) {
    scaling = false;

To get the distance between the two fingers, use the hypot function:

var dist = Math.hypot(
    e.touches[0].pageX - e.touches[1].pageX,
    e.touches[0].pageY - e.touches[1].pageY);

REST API - Bulk Create or Update in single request

You probably will need to use POST or PATCH, because it is unlikely that a single request that updates and creates multiple resources will be idempotent.

Doing PATCH /docs is definitely a valid option. You might find using the standard patch formats tricky for your particular scenario. Not sure about this.

You could use 200. You could also use 207 - Multi Status

This can be done in a RESTful way. The key, in my opinion, is to have some resource that is designed to accept a set of documents to update/create.

If you use the PATCH method I would think your operation should be atomic. i.e. I wouldn't use the 207 status code and then report successes and failures in the response body. If you use the POST operation then the 207 approach is viable. You will have to design your own response body for communicating which operations succeeded and which failed. I'm not aware of a standardized one.

Calculate row means on subset of columns

Calculate row means on a subset of columns:

Create a new data.frame which specifies the first column from DF as an column called ID and calculates the mean of all the other fields on that row, and puts that into column entitled 'Means':

data.frame(ID=DF[,1], Means=rowMeans(DF[,-1]))
  ID    Means
1  A 3.666667
2  B 4.333333
3  C 3.333333
4  D 4.666667
5  E 4.333333

Best HTML5 markup for sidebar

The book HTML5 Guidelines for Web Developers: Structure and Semantics for Documents suggested this way (option 1):

<aside id="sidebar">
    <section id="widget_1"></section>
    <section id="widget_2"></section>
    <section id="widget_3"></section>

It also points out that you can use sections in the footer. So section can be used outside of the actual page content.

Flask-SQLAlchemy how to delete all rows in a single table

Try delete:


From the docs: Returns the number of rows deleted, excluding any cascades.

What's the difference between MyISAM and InnoDB?

The main differences between InnoDB and MyISAM ("with respect to designing a table or database" you asked about) are support for "referential integrity" and "transactions".

If you need the database to enforce foreign key constraints, or you need the database to support transactions (i.e. changes made by two or more DML operations handled as single unit of work, with all of the changes either applied, or all the changes reverted) then you would choose the InnoDB engine, since these features are absent from the MyISAM engine.

Those are the two biggest differences. Another big difference is concurrency. With MyISAM, a DML statement will obtain an exclusive lock on the table, and while that lock is held, no other session can perform a SELECT or a DML operation on the table.

Those two specific engines you asked about (InnoDB and MyISAM) have different design goals. MySQL also has other storage engines, with their own design goals.

So, in choosing between InnoDB and MyISAM, the first step is in determining if you need the features provided by InnoDB. If not, then MyISAM is up for consideration.

A more detailed discussion of differences is rather impractical (in this forum) absent a more detailed discussion of the problem space... how the application will use the database, how many tables, size of the tables, the transaction load, volumes of select, insert, updates, concurrency requirements, replication features, etc.

The logical design of the database should be centered around data analysis and user requirements; the choice to use a relational database would come later, and even later would the choice of MySQL as a relational database management system, and then the selection of a storage engine for each table.

How do I create a local database inside of Microsoft SQL Server 2014?

As per comments, First you need to install an instance of SQL Server if you don't already have one -

Once this is installed you must connect to this instance (server) and then you can create a database here -

How to insert a picture into Excel at a specified cell position with VBA

Looking at posted answers I think this code would be also an alternative for someone. Nobody above used .Shapes.AddPicture in their code, only .Pictures.Insert()

Dim myPic As Object
Dim picpath As String

picpath = "C:\Users\photo.jpg" 'example photo path

Set myPic = ws.Shapes.AddPicture(picpath, False, True, 20, 20, -1, -1)

With myPic
    .Width = 25
    .Height = 25
    .Top = xlApp.Cells(i, 20).Top 'according to variables from correct answer
    .Left = xlApp.Cells(i, 20).Left
    .LockAspectRatio = msoFalse
End With

I'm working in Excel 2013. Also realized that You need to fill all the parameters in .AddPicture, because of error "Argument not optional". Looking at this You may ask why I set Height and Width as -1, but that doesn't matter cause of those parameters are set underneath between With brackets.

Hope it may be also useful for someone :)

Difference between SET autocommit=1 and START TRANSACTION in mysql (Have I missed something?)

The correct way to use LOCK TABLES and UNLOCK TABLES with transactional tables, such as InnoDB tables, is to begin a transaction with SET autocommit = 0 (not START TRANSACTION) followed by LOCK TABLES, and to not call UNLOCK TABLES until you commit the transaction explicitly. For example, if you need to write to table t1 and read from table t2, you can do this:

SET autocommit=0;
LOCK TABLES t1 WRITE, t2 READ, ...;... do something with tables t1 and t2 here ...

Undoing a git rebase

Charles's answer works, but you may want to do this:

git rebase --abort

to clean up after the reset.

Otherwise, you may get the message “Interactive rebase already started”.

How to get every first element in 2 dimensional list

You can get it like

[ x[0] for x in a]

which will return a list of the first element of each list in a

You cannot call a method on a null-valued expression

The simple answer for this one is that you have an undeclared (null) variable. In this case it is $md5. From the comment you put this needed to be declared elsewhere in your code

$md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider

The error was because you are trying to execute a method that does not exist.

PS C:\Users\Matt> $md5 | gm

   TypeName: System.Security.Cryptography.MD5CryptoServiceProvider

Name                       MemberType Definition                                                                                                                            
----                       ---------- ----------                                                                                                                            
Clear                      Method     void Clear()                                                                                                                          
ComputeHash                Method     byte[] ComputeHash(System.IO.Stream inputStream), byte[] ComputeHash(byte[] buffer), byte[] ComputeHash(byte[] buffer, int offset, ...

The .ComputeHash() of $md5.ComputeHash() was the null valued expression. Typing in gibberish would create the same effect.

PS C:\Users\Matt> $bagel.MakeMeABagel()
You cannot call a method on a null-valued expression.
At line:1 char:1
+ $bagel.MakeMeABagel()
+ ~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

PowerShell by default allows this to happen as defined its StrictMode

When Set-StrictMode is off, uninitialized variables (Version 1) are assumed to have a value of 0 (zero) or $Null, depending on type. References to non-existent properties return $Null, and the results of function syntax that is not valid vary with the error. Unnamed variables are not permitted.

What is the backslash character (\\)?

If double backslash looks weird to you, C# also allows verbatim string literals where the escaping is not required.

Console.WriteLine(@"Mango \ Nightangle");

Don't you just wish Java had something like this ;-)

Check if a value exists in ArrayList

Just use ArrayList.contains(desiredElement). For example, if you're looking for the conta1 account from your example, you could use something like:

if (lista.contains(conta1)) {
    System.out.println("Account found");
} else {
    System.out.println("Account not found");

Edit: Note that in order for this to work, you will need to properly override the equals() and hashCode() methods. If you are using Eclipse IDE, then you can have these methods generated by first opening the source file for your CurrentAccount object and the selecting Source > Generate hashCode() and equals()...

Python - PIP install trouble shooting - PermissionError: [WinError 5] Access is denied

As of upgrading from pip 7.x.x to 8.x.x on Python 3.4 (for *.whl support).

Wrong command: pip install --upgrade pip (can't move pip.exe to temporary folder, permisson denied)

OK variant: py -3.4 -m pip install --upgrade pip (do not execute pip.exe)

How can I parse a CSV string with JavaScript, which contains comma in data?

I had a very specific use case where I wanted to copy cells from Google Sheets into my web app. Cells could include double-quotes and new-line characters. Using copy and paste, the cells are delimited by a tab characters, and cells with odd data are double quoted. I tried this main solution, the linked article using regexp, and Jquery-CSV, and CSVToArray. Is the only one that worked out of the box. Copy and paste is seamless with Google Sheets with default auto-detect options.

Run a command shell in jenkins

As far as I know, Windows will not support shell scripts out of the box. You can install Cygwin or Git for Windows, go to Manage Jenkins > Configure System Shell and point it to the location of sh.exe file found in their installation. For example:

C:\Program Files\Git\bin\sh.exe

There is another option I've discovered. This one is better because it allowed me to use shell in pipeline scripts with simple sh "something".

Add the folder to system PATH. Right click on Computer, click properties > advanced system settings > environmental variables, add C:\Program Files\Git\bin\ to your system Path property.

IMPORTANT note: for some reason I had to add it to the system wide Path, adding to user Path didn't work, even though Jenkins was running on this user.

An important note (thanks bugfixr!):

This works. It should be noted that you will need to restart Jenkins in order for it to pick up the new PATH variable. I just went to my services and restated it from there.

Disclaimer: the names may differ slightly as I'm not using English Windows.

How to tell if a JavaScript function is defined

I was looking for how to check if a jQuery function was defined and I didn't find it easily.

Perhaps might need it ;)

if(typeof jQuery.fn.datepicker !== "undefined")

How to add an extra column to a NumPy array

Assuming M is a (100,3) ndarray and y is a (100,) ndarray append can be used as follows:


The trick is to use

y[:, None]

This converts y to a (100, 1) 2D array.


now gives

(100, 4)

PostgreSQL - max number of parameters in "IN" clause?

There is no limit to the number of elements that you are passing to IN clause. If there are more elements it will consider it as array and then for each scan in the database it will check if it is contained in the array or not. This approach is not so scalable. Instead of using IN clause try using INNER JOIN with temp table. Refer for more info. Using INNER JOIN scales well as query optimizer can make use of hash join and other optimization. Whereas with IN clause there is no way for the optimizer to optimize the query. I have noticed speedup of at least 2x with this change.

Redis strings vs Redis hashes to represent JSON: efficiency?

Some additions to a given set of answers:

First of all if you going to use Redis hash efficiently you must know a keys count max number and values max size - otherwise if they break out hash-max-ziplist-value or hash-max-ziplist-entries Redis will convert it to practically usual key/value pairs under a hood. ( see hash-max-ziplist-value, hash-max-ziplist-entries ) And breaking under a hood from a hash options IS REALLY BAD, because each usual key/value pair inside Redis use +90 bytes per pair.

It means that if you start with option two and accidentally break out of max-hash-ziplist-value you will get +90 bytes per EACH ATTRIBUTE you have inside user model! ( actually not the +90 but +70 see console output below )

 # you need me-redis and awesome-print gems to run exact code
 redis = Redis.include(MeRedis).configure( hash_max_ziplist_value: 64, hash_max_ziplist_entries: 512 ).new 
  => #<Redis client v4.0.1 for redis://> 
 > redis.flushdb
  => "OK" 
 > ap
                "used_memory" => "529512",
          **"used_memory_human" => "517.10K"**,
  => nil 
 # me_set( 't:i' ... ) same as hset( 't:i/512', i % 512 ... )    
 # txt is some english fictionary book around 56K length, 
 # so we just take some random 63-symbols string from it 
 > redis.pipelined{ 10000.times{ |i| redis.me_set( "t:#{i}", txt[rand(50000), 63] ) } }; :done
 => :done 
 > ap
               "used_memory" => "1251944",
         **"used_memory_human" => "1.19M"**, # ~ 72b per key/value
  > redis.flushdb
  => "OK" 
  # setting **only one value** +1 byte per hash of 512 values equal to set them all +1 byte 
  > redis.pipelined{ 10000.times{ |i| redis.me_set( "t:#{i}", txt[rand(50000), i % 512 == 0 ? 65 : 63] ) } }; :done 
  > ap
               "used_memory" => "1876064",
         "used_memory_human" => "1.79M",   # ~ 134 bytes per pair  
    redis.pipelined{ 10000.times{ |i| redis.set( "t:#{i}", txt[rand(50000), 65] ) } };
             "used_memory" => "2262312",
          "used_memory_human" => "2.16M", #~155 byte per pair i.e. +90 bytes    

For TheHippo answer, comments on Option one are misleading:

hgetall/hmset/hmget to the rescue if you need all fields or multiple get/set operation.

For BMiner answer.

Third option is actually really fun, for dataset with max(id) < has-max-ziplist-value this solution has O(N) complexity, because, surprise, Reddis store small hashes as array-like container of length/key/value objects!

But many times hashes contain just a few fields. When hashes are small we can instead just encode them in an O(N) data structure, like a linear array with length-prefixed key value pairs. Since we do this only when N is small, the amortized time for HGET and HSET commands is still O(1): the hash will be converted into a real hash table as soon as the number of elements it contains will grow too much

But you should not worry, you'll break hash-max-ziplist-entries very fast and there you go you are now actually at solution number 1.

Second option will most likely go to the fourth solution under a hood because as question states:

Keep in mind that if I use a hash, the value length isn't predictable. They're not all short such as the bio example above.

And as you already said: the fourth solution is the most expensive +70 byte per each attribute for sure.

My suggestion how to optimize such dataset:

You've got two options:

  1. If you cannot guarantee max size of some user attributes than you go for first solution and if memory matter is crucial than compress user json before store in redis.

  2. If you can force max size of all attributes. Than you can set hash-max-ziplist-entries/value and use hashes either as one hash per user representation OR as hash memory optimization from this topic of a Redis guide: and store user as json string. Either way you may also compress long user attributes.

org.apache.catalina.LifecycleException: Failed to start component [StandardServer[8005]]A child container failed during start

I had a similar error and fixed it by following steps: 1. Under Servers project (which gets created itself when you add Apache Tomcat Server in Eclipse), open server.xml 2. Comment out the line

<Context docBase=... />

JavaScript - XMLHttpRequest, Access-Control-Allow-Origin errors

I think you've missed the point of access control.

A quick recap on why CORS exists: Since JS code from a website can execute XHR, that site could potentially send requests to other sites, masquerading as you and exploiting the trust those sites have in you(e.g. if you have logged in, a malicious site could attempt to extract information or execute actions you never wanted) - this is called a CSRF attack. To prevent that, web browsers have very stringent limitations on what XHR you can send - you are generally limited to just your domain, and so on.

Now, sometimes it's useful for a site to allow other sites to contact it - sites that provide APIs or services, like the one you're trying to access, would be prime candidates. CORS was developed to allow site A(e.g. to say "I trust site B, so you can send XHR from it to me". This is specified by site A sending "Access-Control-Allow-Origin" headers in its responses.

In your specific case, it seems that doesn't bother to use CORS. Your best bet is to contact the site owner and find out why, if you want to use with a browser script. Alternatively, you could try using an extension(those should have higher XHR privileges).

Sort array of objects by string property value


Based on this excellent tutorial I would like to develop Vlad Bezden answer and explain why localeCompare is better than standard comarison method like strA > strB. Lets run this example

console.log( 'Österreich' > 'Zealand' );  // We expect false
console.log( 'a' > 'Z' );                 // We expect false

The reason is that in JS all strings are encoded using UTF-16 and

let str = '';

// order of characters in JS
for (let i = 65; i <= 220; i++) {
  str += String.fromCodePoint(i); // code to character


Capital letters go first (have small codes) and then go small letters and then go character Ö (after z). This is reason why we get true in first snippet - becasue operator > compare characters codes.

As you can see compare characters in diffrent languages is non trivial task - but luckily, modern browsers support the internationalization standard ECMA-402. So in JS we have strA.localeCompare(strB) which do the job (-1 means strA is less than strB; 1 means opposite; 0 means equal)

console.log( 'Österreich'.localeCompare('Zealand') ); // We expect -1
console.log( 'a'.localeCompare('Z') );                // We expect -1

I would like to add that localeCompare supports two parameters: language and additional rules

var objs = [ 
    { first_nom: 'Lazslo', last_nom: 'Jamf'     },
    { first_nom: 'Pig',    last_nom: 'Bodine'   },
    { first_nom: 'Pirate', last_nom: 'Prentice' },
    { first_nom: 'Test',   last_nom: 'jamf'     } 

objs.sort((a,b)=> a.last_nom.localeCompare(b.last_nom,'en',{sensitivity:'case'}))


// in '>' comparison 'Jamf' will NOT be next to 'jamf'

What is __stdcall?

__stdcall is used to put the function arguments in the stack. After the completion of the function it automatically deallocates the memory. This is used for fixed arguments.

void __stdcall fnname ( int, int* )

int main()
    CreateThread ( NULL, 0, fnname, int, int*...... )

Here the fnname has args it directly push into the stack.

Explanation on Integer.MAX_VALUE and Integer.MIN_VALUE to find min and max value in an array

but as for this method, I don't understand the purpose of Integer.MAX_VALUE and Integer.MIN_VALUE.

By starting out with smallest set to Integer.MAX_VALUE and largest set to Integer.MIN_VALUE, they don't have to worry later about the special case where smallest and largest don't have a value yet. If the data I'm looking through has a 10 as the first value, then numbers[i]<smallest will be true (because 10 is < Integer.MAX_VALUE) and we'll update smallest to be 10. Similarly, numbers[i]>largest will be true because 10 is > Integer.MIN_VALUE and we'll update largest. And so on.

Of course, when doing this, you must ensure that you have at least one value in the data you're looking at. Otherwise, you end up with apocryphal numbers in smallest and largest.

Note the point Onome Sotu makes in the comments:

...if the first item in the array is larger than the rest, then the largest item will always be Integer.MIN_VALUE because of the else-if statement.

Which is true; here's a simpler example demonstrating the problem (live copy):

public class Example
    public static void main(String[] args) throws Exception {
        int[] values = {5, 1, 2};
        int smallest = Integer.MAX_VALUE;
        int largest  = Integer.MIN_VALUE;
        for (int value : values) {
            if (value < smallest) {
                smallest = value;
            } else if (value > largest) {
                largest = value;
        System.out.println(smallest + ", " + largest); // 1, 2 -- WRONG

To fix it, either:

  1. Don't use else, or

  2. Start with smallest and largest equal to the first element, and then loop the remaining elements, keeping the else if.

Here's an example of that second one (live copy):

public class Example
    public static void main(String[] args) throws Exception {
        int[] values = {5, 1, 2};
        int smallest = values[0];
        int largest  = values[0];
        for (int n = 1; n < values.length; ++n) {
            int value = values[n];
            if (value < smallest) {
                smallest = value;
            } else if (value > largest) {
                largest = value;
        System.out.println(smallest + ", " + largest); // 1, 5

matching query does not exist Error in Django

As mentioned in Django docs, when get method finds no entry or finds multiple entries, it raises an exception, this is the expected behavior:

get() raises MultipleObjectsReturned if more than one object was found. The MultipleObjectsReturned exception is an attribute of the model class.

get() raises a DoesNotExist exception if an object wasn’t found for the given parameters. This exception is an attribute of the model class.

Using exceptions is a way to handle this problem, but I actually don't like the ugly try-except block. An alternative solution, and cleaner to me, is to use the combination of filter + first.

user = UniversityDetails.objects.filter(email=email).first()

When you do .first() to an empty queryset it returns None. This way you can have the same effect in a single line.

The only difference between catching the exception and using this method occurs when you have multiple entries, the former will raise an exception while the latter will set the first element, but as you are using get I may assume we won't fall on this situation.

Note that first method was added on Django 1.6.

The operation cannot be completed because the DbContext has been disposed error

Here you are trying to execute IQueryable object on inactive DBContext. your DBcontext is already disposed of. you can only execute IQueryable object before DBContext is disposed of. Means you need to write users.Select(x => x.ToInfo()).ToList() statement inside using scope

How to setup FTP on xampp

XAMPP comes preloaded with the FileZilla FTP server. Here is how to setup the service, and create an account.

  1. Enable the FileZilla FTP Service through the XAMPP Control Panel to make it startup automatically (check the checkbox next to filezilla to install the service). Then manually start the service.

  2. Create an ftp account through the FileZilla Server Interface (its the essentially the filezilla control panel). There is a link to it Start Menu in XAMPP folder. Then go to Users->Add User->Stuff->Done.

  3. Try connecting to the server (localhost, port 21).

How to show particular image as thumbnail while implementing share on Facebook?

The easiest way I found to set Facebook Open Graph to every Joomla article, was to place in com_content/article/default.php override, next code:

$app    = JFactory::getApplication();
$path   = JURI::root();

$document = JFactory::getDocument();
$document->addCustomTag('<meta property="og:title" content="YOUR SITE TITLE" />');
$document->addCustomTag('<meta property="og:name" content="YOUR SITE NAME" />');
$document->addCustomTag('<meta property="og:description" content="YOUR SITE DESCRIPTION" />');
$document->addCustomTag('<meta property="og:site_name" content="YOUR SITE NAME" />');
if (isset($images->image_fulltext) and !empty($images->image_fulltext)) : 
    $document->addCustomTag('<meta property="og:image" content="'.$path.'<?php echo htmlspecialchars($images->image_fulltext); ?>" />');
else :
    $document->addCustomTag('<meta property="og:image" content="'.$path.'images/logo.png" />');

This will place meta og tags in the head with details from current article.

What are all the escape characters?

These are escape characters which are used to manipulate string.

\t  Insert a tab in the text at this point.
\b  Insert a backspace in the text at this point.
\n  Insert a newline in the text at this point.
\r  Insert a carriage return in the text at this point.
\f  Insert a form feed in the text at this point.
\'  Insert a single quote character in the text at this point.
\"  Insert a double quote character in the text at this point.
\\  Insert a backslash character in the text at this point.

Read more about them from here.

How do I properly clean up Excel interop objects?

I think that some of that is just the way that the framework handles Office applications, but I could be wrong. On some days, some applications clean up the processes immediately, and other days it seems to wait until the application closes. In general, I quit paying attention to the details and just make sure that there aren't any extra processes floating around at the end of the day.

Also, and maybe I'm over simplifying things, but I think you can just...

objExcel = new Excel.Application();
objBook = (Excel.Workbook)(objExcel.Workbooks.Add(Type.Missing));
objBook.Close(false, Type.Missing, Type.Missing);

Like I said earlier, I don't tend to pay attention to the details of when the Excel process appears or disappears, but that usually works for me. I also don't like to keep Excel processes around for anything other than the minimal amount of time, but I'm probably just being paranoid on that.

Python3: ImportError: No module named '_ctypes' when using Value from module multiprocessing

Refer to this thread or this thread, for customized installation of libffi, it is difficult for Python3.7 to find the library location of libffi. An alternative method is to set the CONFIGURE_LDFLAGS variable in the Makefile, for example CONFIGURE_LDFLAGS="-L/path/to/libffi-3.2.1/lib64".

Non-resolvable parent POM using Maven 3.0.3 and relativePath notation

Please check in logs if you have http.HttpWagon$__sisu1:Cannot find 'basicAuthScope' this error or warning also, if so you need to use maven 3.2.5 version, which will resolve error.

How to get a float result by dividing two integer values using T-SQL?

It's not necessary to cast both of them. Result datatype for a division is always the one with the higher data type precedence. Thus the solution must be:

SELECT CAST(1 AS float) / 3


SELECT 1 / CAST(3 AS float)

Import Python Script Into Another?

I highly recommend the reading of a lecture in SciPy-lectures organization:

It explains all the commented doubts.

But, new paths can be easily added and avoiding duplication with the following code:

import sys
new_path = 'insert here the new path'

if new_path not in sys.path:
import funcoes_python #Useful python functions saved in a different script

Remove all html tags from php string

For my this is best solution.

function strip_tags_content($string) { 
    // ----- remove HTML TAGs ----- 
    $string = preg_replace ('/<[^>]*>/', ' ', $string); 
    // ----- remove control characters ----- 
    $string = str_replace("\r", '', $string);
    $string = str_replace("\n", ' ', $string);
    $string = str_replace("\t", ' ', $string);
    // ----- remove multiple spaces ----- 
    $string = trim(preg_replace('/ {2,}/', ' ', $string));
    return $string; 


webpack is not recognized as a internal or external command,operable program or batch file

Webpack CLI is now in a separate package and must be installed globally in order to use the 'webpack' command:

npm install -g webpack-cli

EDIT: Much has changed. Webpack folks do not recommend installing the CLI globally (or separately for that matter). This issue should be fixed now but the proper install command is:

npm install --save-dev webpack

This answer was originally intended as a "work-around" for the OPs problem.

Currency formatting in Python

This is an ancient post, but I just implemented the following solution which:

  • Doesn't require external modules
  • Doesn't require creating a new function
  • Can be done in-line
  • Handles multiple variables
  • Handles negative dollar amounts


num1 = 4153.53
num2 = -23159.398598

print 'This: ${:0,.0f} and this: ${:0,.2f}'.format(num1, num2).replace('$-','-$')


This: $4,154 and this: -$23,159.40

And for the original poster, obviously, just switch $ for £

When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used?

static_cast is the first cast you should attempt to use. It does things like implicit conversions between types (such as int to float, or pointer to void*), and it can also call explicit conversion functions (or implicit ones). In many cases, explicitly stating static_cast isn't necessary, but it's important to note that the T(something) syntax is equivalent to (T)something and should be avoided (more on that later). A T(something, something_else) is safe, however, and guaranteed to call the constructor.

static_cast can also cast through inheritance hierarchies. It is unnecessary when casting upwards (towards a base class), but when casting downwards it can be used as long as it doesn't cast through virtual inheritance. It does not do checking, however, and it is undefined behavior to static_cast down a hierarchy to a type that isn't actually the type of the object.

const_cast can be used to remove or add const to a variable; no other C++ cast is capable of removing it (not even reinterpret_cast). It is important to note that modifying a formerly const value is only undefined if the original variable is const; if you use it to take the const off a reference to something that wasn't declared with const, it is safe. This can be useful when overloading member functions based on const, for instance. It can also be used to add const to an object, such as to call a member function overload.

const_cast also works similarly on volatile, though that's less common.

dynamic_cast is exclusively used for handling polymorphism. You can cast a pointer or reference to any polymorphic type to any other class type (a polymorphic type has at least one virtual function, declared or inherited). You can use it for more than just casting downwards – you can cast sideways or even up another chain. The dynamic_cast will seek out the desired object and return it if possible. If it can't, it will return nullptr in the case of a pointer, or throw std::bad_cast in the case of a reference.

dynamic_cast has some limitations, though. It doesn't work if there are multiple objects of the same type in the inheritance hierarchy (the so-called 'dreaded diamond') and you aren't using virtual inheritance. It also can only go through public inheritance - it will always fail to travel through protected or private inheritance. This is rarely an issue, however, as such forms of inheritance are rare.

reinterpret_cast is the most dangerous cast, and should be used very sparingly. It turns one type directly into another — such as casting the value from one pointer to another, or storing a pointer in an int, or all sorts of other nasty things. Largely, the only guarantee you get with reinterpret_cast is that normally if you cast the result back to the original type, you will get the exact same value (but not if the intermediate type is smaller than the original type). There are a number of conversions that reinterpret_cast cannot do, too. It's used primarily for particularly weird conversions and bit manipulations, like turning a raw data stream into actual data, or storing data in the low bits of a pointer to aligned data.

C-style cast and function-style cast are casts using (type)object or type(object), respectively, and are functionally equivalent. They are defined as the first of the following which succeeds:

  • const_cast
  • static_cast (though ignoring access restrictions)
  • static_cast (see above), then const_cast
  • reinterpret_cast
  • reinterpret_cast, then const_cast

It can therefore be used as a replacement for other casts in some instances, but can be extremely dangerous because of the ability to devolve into a reinterpret_cast, and the latter should be preferred when explicit casting is needed, unless you are sure static_cast will succeed or reinterpret_cast will fail. Even then, consider the longer, more explicit option.

C-style casts also ignore access control when performing a static_cast, which means that they have the ability to perform an operation that no other cast can. This is mostly a kludge, though, and in my mind is just another reason to avoid C-style casts.

How to use OAuth2RestTemplate?

You can find examples for writing OAuth clients here:

In your case you can't just use default or base classes for everything, you have a multiple classes Implementing OAuth2ProtectedResourceDetails. The configuration depends of how you configured your OAuth service but assuming from your curl connections I would recommend:

class MyConfig{

    private String baseUrl;
    private String authorizeUrl;
    private String tokenUrl;

    protected OAuth2ProtectedResourceDetails resource() {
        ResourceOwnerPasswordResourceDetails resource;
        resource = new ResourceOwnerPasswordResourceDetails();

        List scopes = new ArrayList<String>(2);
        return resource;

    public OAuth2RestOperations restTemplate() {
        AccessTokenRequest atr = new DefaultAccessTokenRequest();
        return new OAuth2RestTemplate(resource(), new DefaultOAuth2ClientContext(atr));

class MyService {

    private OAuth2RestOperations restTemplate;

    public MyService() {

Do not forget about @EnableOAuth2Client on your config class, also I would suggest to try that the urls you are using are working with curl first, also try to trace it with the debugger because lot of exceptions are just consumed and never printed out due security reasons, so it gets little hard to find where the issue is. You should use logger with debug enabled set. Good luck

I uploaded sample springboot app on github to depict your situation because I could not find any samples for your scenario .

Read/Parse text file line by line in VBA

The below is my code from reading text file to excel file.

Sub openteatfile()
Dim i As Long, j As Long
Dim filepath As String
filepath = "C:\Users\TarunReddyNuthula\Desktop\sample.ctxt"
Open filepath For Input As #1
i = l
Do Until EOF(1)
Line Input #1, linefromfile
lineitems = Split(linefromfile, "|")
        For j = LBound(lineitems) To UBound(lineitems)
            ThisWorkbook.Worksheets("Sheet4").Cells(i, j + 1).value = lineitems(j)
        Next j
    i = i + 1 
Close #1
End Sub

Apple Cover-flow effect using jQuery or other library?

  • is the best I ever found. a true 'CoverFlow', highly configurable, cross-browser, very smooth action, has relections and supports scroll wheel + keyboard control. - has to be what your looking for!

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

Try using this attribute, for example for password min length:

[StringLength(100, ErrorMessage = "???????????? ????? ?????? 20 ????????", MinimumLength = User.PasswordMinLength)]

"Unable to locate tools.jar" when running ant

Make sure you use the root folder of the JDK. Don't add "\lib" to the end of the path, where tools.jar is physically located. It took me an hour to figure that one out. Also, this post will help show you where Ant is looking for tools.jar:

Why does ANT tell me that JAVA_HOME is wrong when it is not?

PHP output showing little black diamonds with a question mark

You can also change the caracter set in your browser. Just for debug reasons.

Refresh a page using PHP

You can do it with PHP:


It refreshes your current page, and if you need to redirect it to another page, use following:

header("Refresh:0; url=page2.php");

Using different Web.config in development and production environment

You can also use the extension "Configuration Transform" works the same as "SlowCheetah",

file_get_contents behind a proxy?

There's a similar post here: which explains how to do it.

function file_get_contents_proxy($url,$proxy){

    // Create context stream
    $context_array = array('http'=>array('proxy'=>$proxy,'request_fulluri'=>true));
    $context = stream_context_create($context_array);

    // Use context stream with file_get_contents
    $data = file_get_contents($url,false,$context);

    // Return data via proxy
    return $data;


Ansible: Store command's stdout in new variable?

There's no need to set a fact.

    - shell: cat "hello"
      register: cat_contents

    - shell: echo "I cat hello"
      when: cat_contents.stdout == "hello"

How to Get a Specific Column Value from a DataTable?

As per the title of the post I just needed to get all values from a specific column. Here is the code I used to achieve that.

    public static IEnumerable<T> ColumnValues<T>(this DataColumn self)
        return self.Table.Select().Select(dr => (T)Convert.ChangeType(dr[self], typeof(T)));

How to get Client location using Google Maps API v3?

No need to do your own implementation. I can recommend using geolocationmarker from google-maps-utility-library-v3.

ng-options with simple array init

You can use ng-repeat with option like this:

    <select ng-model="yourSelect" 
        ng-options="option as option for option in ['var1', 'var2', 'var3']"
    <input type="hidden" name="yourSelect" value="{{yourSelect}}" />

When you submit your form you can get value of input hidden.


ng-selected ng-repeat

Multiple Forms or Multiple Submits in a Page?

Best practice: one form per product is definitely the way to go.


  • It will save you the hassle of having to parse the data to figure out which product was clicked
  • It will reduce the size of data being posted

In your specific situation

If you only ever intend to have one form element, in this case a submit button, one form for all should work just fine.

My recommendation Do one form per product, and change your markup to something like:

<form method="post" action="">
    <input type="hidden" name="product_id" value="123">
    <button type="submit" name="action" value="add_to_cart">Add to Cart</button>

This will give you a much cleaner and usable POST. No parsing. And it will allow you to add more parameters in the future (size, color, quantity, etc).

Note: There's no technical benefit to using <button> vs. <input>, but as a programmer I find it cooler to work with action=='add_to_cart' than action=='Add to Cart'. Besides, I hate mixing presentation with logic. If one day you decide that it makes more sense for the button to say "Add" or if you want to use different languages, you could do so freely without having to worry about your back-end code.

convert string date to java.sql.Date

worked for me too:

SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
    Date parsed = null;
    try {
        parsed = sdf.parse("02/01/2014");
    } catch (ParseException e1) {
        // TODO Auto-generated catch block
    java.sql.Date data = new java.sql.Date(parsed.getTime());
    contato.setDataNascimento( data);

    // Contato DataNascimento era Calendar

    // grave nessa conexão!!! 
    ContatoDao dao = new ContatoDao("mysql");           

    // método elegante 
    System.out.println("Banco: ["+dao.getNome()+"] Gravado! Data: "+contato.getDataNascimento());

How to avoid pressing Enter with getchar() for reading a single character only?

This code worked for me. Attention : this is not part of the standard library, even if most compilers (I use GCC) supports it.

#include <stdio.h>
#include <conio.h>
int main(int argc, char const *argv[]) {
    char a = getch();
    printf("You typed a char with an ASCII value of %d, printable as '%c'\n", a, a);
    return 0;

This code detects the first key press.

Update multiple rows with different values in a single SQL query

Yes, you can do this, but I doubt that it would improve performances, unless your query has a real large latency.

You could do:

      WHEN id=id[1] THEN posX[1]
      WHEN id=id[2] THEN posX[2]
      ELSE posX END, posY = CASE ... END
 WHERE id IN (id[1], id[2], id[3]...);

The total cost is given more or less by: NUM_QUERIES * ( COST_QUERY_SETUP + COST_QUERY_PERFORMANCE ). This way, you knock down a bit on NUM_QUERIES, but COST_QUERY_PERFORMANCE goes up bigtime. If COST_QUERY_SETUP is really huge (e.g., you're calling some network service which is real slow) then, yes, you might still end up on top.

Otherwise, I'd try with indexing on id, or modifying the architecture.

In MySQL I think you could do this more easily with a multiple INSERT ON DUPLICATE KEY UPDATE (but am not sure, never tried).

How to compare two dates to find time difference in SQL Server 2005, date manipulation

Declare the Start and End date DECLARE @SDATE AS DATETIME

DECLARE @END_-- Set Start and End date

-- Get the Result in HH:MI:SS:MMM(24H) format SELECT CONVERT(VARCHAR(12), DATEADD(MS, DATEDIFF(MS, @START_DATE, @END_DATE), 0), 114) AS TimeDiff

Android Button Onclick

this will sort it for you

protected void onCreate(Bundle savedInstanceState) {

    Button but1=(Button)findViewById(;

    but1.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {

            Intent int1= new Intent(MainActivity.this,xxactivity.class);

You just need to amend the xxactivity to the name of your second activity

JavaScript loop through json array?

your data snippet need to be expanded a little, and it has to be this way to be proper json. notice I just include the array name attribute "item"

  "id": "1",
  "msg": "hi",
  "tid": "2013-05-05 23:35",
  "fromWho": "[email protected]"
}, {
  "id": "2",
  "msg": "there",
  "tid": "2013-05-05 23:45",
  "fromWho": "[email protected]"

your java script is simply

var objCount = json.item.length;
for ( var x=0; x < objCount ; xx++ ) {
    var curitem = json.item[x];

How to install PyQt4 in anaconda?

It looks like the latest version of anaconda forces install of pyqt5.6 over any pyqt build, which will be fatal for your applications. In a terminal, Try:

conda install -c anaconda pyqt=4.11.4

It will prompt to downgrade conda client. After that, it should be good.

UPDATE: If you want to know what pyqt versions are available for install, try:

conda search pyqt

UPDATE: The most recent version of conda installs anaconda-navigator. This depends on qt5, and should first be removed:

conda uninstall anaconda-navigator

Then install "newest" qt4:

conda install qt=4

jQuery vs. javascript?

Personally i think you should learn the hard way first. It will make you a better programmer and you will be able to solve that one of a kind issue when it comes up. After you can do it with pure JavaScript then using jQuery to speed up development is just an added bonus.

If you can do it the hard way then you can do it the easy way, it doesn't work the other way around. That applies to any programming paradigm.

What tools do you use to test your public REST API?

We're planning to use FitNesse, with the RestFixture. We haven't started writing our tests yet, our newest tester got things up and running last week, however he has used FitNesse for this in his last company, so we know it's a reasonable setup for what we want to do.

More info available here:

Can someone explain the dollar sign in Javascript?

The $ sign is an identifier for variables and functions.

That has a clear explanation of what the dollar sign is for.

Here's an alternative explanation:

CSS background image alt attribute

Here's my solution to this type of problem:

Create a new class in CSS and position off screen. Then put your alt text in HTML right before the property that calls your background image. Can be any tag, H1, H2, p, etc.


<style type="text/css">
  .offleft {
    margin-left: -9000px;
    position: absolute;


<h1 class="offleft">put your alt text here</h1>
<div class or id that calls your bg image>  </div>