Programs & Examples On #Cups

CUPS is the standards-based, open source printing system for Mac OS X and other UNIX®-like operating systems.

Content Security Policy "data" not working for base64 Images in Chrome 28

According to the grammar in the CSP spec, you need to specify schemes as scheme:, not just scheme. So, you need to change the image source directive to:

img-src 'self' data:;

How to take input in an array + PYTHON?

You want this - enter N and then take N number of elements.I am considering your input case is just like this

2 3 6 6 5

have this in this way in python 3.x (for python 2.x use raw_input() instead if input())

Python 3

n = int(input())
arr = input()   # takes the whole line of n numbers
l = list(map(int,arr.split(' '))) # split those numbers with space( becomes ['2','3','6','6','5']) and then map every element into int (becomes [2,3,6,6,5])

Python 2

n = int(raw_input())
arr = raw_input()   # takes the whole line of n numbers
l = list(map(int,arr.split(' '))) # split those numbers with space( becomes ['2','3','6','6','5']) and then map every element into int (becomes [2,3,6,6,5])

How do you execute an arbitrary native command from a string?

Invoke-Expression, also aliased as iex. The following will work on your examples #2 and #3:

iex $command

Some strings won't run as-is, such as your example #1 because the exe is in quotes. This will work as-is, because the contents of the string are exactly how you would run it straight from a Powershell command prompt:

$command = 'C:\somepath\someexe.exe somearg'
iex $command

However, if the exe is in quotes, you need the help of & to get it running, as in this example, as run from the commandline:

>> &"C:\Program Files\Some Product\SomeExe.exe" "C:\some other path\file.ext"

And then in the script:

$command = '"C:\Program Files\Some Product\SomeExe.exe" "C:\some other path\file.ext"'
iex "& $command"

Likely, you could handle nearly all cases by detecting if the first character of the command string is ", like in this naive implementation:

function myeval($command) {
    if ($command[0] -eq '"') { iex "& $command" }
    else { iex $command }

But you may find some other cases that have to be invoked in a different way. In that case, you will need to either use try{}catch{}, perhaps for specific exception types/messages, or examine the command string.

If you always receive absolute paths instead of relative paths, you shouldn't have many special cases, if any, outside of the 2 above.

Error: Address already in use while binding socket with address but the port number is shown free by `netstat`

the error i received was:

cockpit.socket: Failed to listen on sockets: Address already in use

the fix I discovered is:

  1. I had to disable selinux
  2. in /usr/lib/systemd/system/cockpit service i changed the line :

    #ExecStartPre=/usr/sbin/remotectl certificate --ensure --user=root --group=cockpit-ws --selinux-type=etc_t


    #ExecStartPre=/usr/sbin/remotectl certificate --ensure --user=root --group=cockpit-ws 

so as you can see i took out the argument about selinux then i ran:

systemctl daemon-reload
systemctl start cockpit.service

then I browsed to:

I accepted the self-signed certificate and was able to login successfully to cockpit and use it normally.

this is all on a fedora25 machine. the 9090 port had already been added using firewall-cmd

How can I fix MySQL error #1064?


Error #1064 means that MySQL can't understand your command. To fix it:

  • Read the error message. It tells you exactly where in your command MySQL got confused.

  • Examine your command. If you use a programming language to create your command, use echo, console.log(), or its equivalent to show the entire command so you can see it.

  • Check the manual. By comparing against what MySQL expected at that point, the problem is often obvious.

  • Check for reserved words. If the error occurred on an object identifier, check that it isn't a reserved word (and, if it is, ensure that it's properly quoted).

  1. Aaaagh!! What does #1064 mean?

    Error messages may look like gobbledygook, but they're (often) incredibly informative and provide sufficient detail to pinpoint what went wrong. By understanding exactly what MySQL is telling you, you can arm yourself to fix any problem of this sort in the future.

    As in many programs, MySQL errors are coded according to the type of problem that occurred. Error #1064 is a syntax error.

    • What is this "syntax" of which you speak? Is it witchcraft?

      Whilst "syntax" is a word that many programmers only encounter in the context of computers, it is in fact borrowed from wider linguistics. It refers to sentence structure: i.e. the rules of grammar; or, in other words, the rules that define what constitutes a valid sentence within the language.

      For example, the following English sentence contains a syntax error (because the indefinite article "a" must always precede a noun):

      This sentence contains syntax error a.

    • What does that have to do with MySQL?

      Whenever one issues a command to a computer, one of the very first things that it must do is "parse" that command in order to make sense of it. A "syntax error" means that the parser is unable to understand what is being asked because it does not constitute a valid command within the language: in other words, the command violates the grammar of the programming language.

      It's important to note that the computer must understand the command before it can do anything with it. Because there is a syntax error, MySQL has no idea what one is after and therefore gives up before it even looks at the database and therefore the schema or table contents are not relevant.

  2. How do I fix it?

    Obviously, one needs to determine how it is that the command violates MySQL's grammar. This may sound pretty impenetrable, but MySQL is trying really hard to help us here. All we need to do is…

    • Read the message!

      MySQL not only tells us exactly where the parser encountered the syntax error, but also makes a suggestion for fixing it. For example, consider the following SQL command:

      UPDATE my_table WHERE id=101 SET name='foo'

      That command yields the following error message:

      ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE id=101 SET name='foo'' at line 1

      MySQL is telling us that everything seemed fine up to the word WHERE, but then a problem was encountered. In other words, it wasn't expecting to encounter WHERE at that point.

      Messages that say ...near '' at line... simply mean that the end of command was encountered unexpectedly: that is, something else should appear before the command ends.

    • Examine the actual text of your command!

      Programmers often create SQL commands using a programming language. For example a php program might have a (wrong) line like this:

      $result = $mysqli->query("UPDATE " . $tablename ."SET name='foo' WHERE id=101");

      If you write this this in two lines

      $query = "UPDATE " . $tablename ."SET name='foo' WHERE id=101"
      $result = $mysqli->query($query);

      then you can add echo $query; or var_dump($query) to see that the query actually says

      UPDATE userSET name='foo' WHERE id=101

      Often you'll see your error immediately and be able to fix it.

    • Obey orders!

      MySQL is also recommending that we "check the manual that corresponds to our MySQL version for the right syntax to use". Let's do that.

      I'm using MySQL v5.6, so I'll turn to that version's manual entry for an UPDATE command. The very first thing on the page is the command's grammar (this is true for every command):

      UPDATE [LOW_PRIORITY] [IGNORE] table_reference
          SET col_name1={expr1|DEFAULT} [, col_name2={expr2|DEFAULT}] ...
          [WHERE where_condition]
          [ORDER BY ...]
          [LIMIT row_count]

      The manual explains how to interpret this syntax under Typographical and Syntax Conventions, but for our purposes it's enough to recognise that: clauses contained within square brackets [ and ] are optional; vertical bars | indicate alternatives; and ellipses ... denote either an omission for brevity, or that the preceding clause may be repeated.

      We already know that the parser believed everything in our command was okay prior to the WHERE keyword, or in other words up to and including the table reference. Looking at the grammar, we see that table_reference must be followed by the SET keyword: whereas in our command it was actually followed by the WHERE keyword. This explains why the parser reports that a problem was encountered at that point.

    A note of reservation

    Of course, this was a simple example. However, by following the two steps outlined above (i.e. observing exactly where in the command the parser found the grammar to be violated and comparing against the manual's description of what was expected at that point), virtually every syntax error can be readily identified.

    I say "virtually all", because there's a small class of problems that aren't quite so easy to spot—and that is where the parser believes that the language element encountered means one thing whereas you intend it to mean another. Take the following example:

    UPDATE my_table SET where='foo'

    Again, the parser does not expect to encounter WHERE at this point and so will raise a similar syntax error—but you hadn't intended for that where to be an SQL keyword: you had intended for it to identify a column for updating! However, as documented under Schema Object Names:

    If an identifier contains special characters or is a reserved word, you must quote it whenever you refer to it. (Exception: A reserved word that follows a period in a qualified name must be an identifier, so it need not be quoted.) Reserved words are listed at Section 9.3, “Keywords and Reserved Words”.

    [ deletia ]

    The identifier quote character is the backtick (“`”):

    mysql> SELECT * FROM `select` WHERE `select`.id > 100;

    If the ANSI_QUOTES SQL mode is enabled, it is also permissible to quote identifiers within double quotation marks:

    mysql> CREATE TABLE "test" (col INT);
    ERROR 1064: You have an error in your SQL syntax...
    mysql> SET sql_mode='ANSI_QUOTES';
    mysql> CREATE TABLE "test" (col INT);
    Query OK, 0 rows affected (0.00 sec)

How to filter a RecyclerView with a SearchView

With Android Architecture Components through the use of LiveData this can be easily implemented with any type of Adapter. You simply have to do the following steps:

1. Setup your data to return from the Room Database as LiveData as in the example below:

public interface CustomDAO{

@Query("SELECT * FROM words_table WHERE column LIKE :searchquery")
    public LiveData<List<Word>> searchFor(String searchquery);

2. Create a ViewModel object to update your data live through a method that will connect your DAO and your UI

public class CustomViewModel extends AndroidViewModel {

    private final AppDatabase mAppDatabase;

    public WordListViewModel(@NonNull Application application) {
        this.mAppDatabase = AppDatabase.getInstance(application.getApplicationContext());

    public LiveData<List<Word>> searchQuery(String query) {
        return mAppDatabase.mWordDAO().searchFor(query);


3. Call your data from the ViewModel on the fly by passing in the query through onQueryTextListener as below:

Inside onCreateOptionsMenu set your listener as follows


Setup your query listener somewhere in your SearchActivity class as follows

private onQueryTextListener =
            new {
                public boolean onQueryTextSubmit(String query) {
                    return true;

                public boolean onQueryTextChange(String newText) {
                    return true;

                private void getResults(String newText) {
                    String queryText = "%" + newText + "%";
                            SearchResultsActivity.this, new Observer<List<Word>>() {
                                public void onChanged(@Nullable List<Word> words) {
                                    if (words == null) return;

Note: Steps (1.) and (2.) are standard AAC ViewModel and DAO implementation, the only real "magic" going on here is in the OnQueryTextListener which will update the results of your list dynamically as the query text changes.

If you need more clarification on the matter please don't hesitate to ask. I hope this helped :).

How do I temporarily disable triggers in PostgreSQL?

SET session_replication_role = replica;  

also dosent work for me in Postgres 9.1. i use the two function described by bartolo-otrit with some modification. I modified the first function to make it work for me because the namespace or the schema must be present to identify the table correctly. The new code is :

CREATE OR REPLACE FUNCTION disable_triggers(a boolean, nsp character varying)
act character varying;
r record;
    if(a is true) then
        act = 'disable';
        act = 'enable';
    end if;

    for r in select c.relname from pg_namespace n
        join pg_class c on c.relnamespace = n.oid and c.relhastriggers = true
        where n.nspname = nsp
        execute format('alter table %I.%I %s trigger all', nsp,r.relname, act); 
    end loop;
  COST 100;
ALTER FUNCTION disable_triggers(boolean, character varying)
  OWNER TO postgres;

then i simply do a select query for every schema :

SELECT disable_triggers(true,'public');
SELECT disable_triggers(true,'Adempiere');

Handling key-press events (F1-F12) using JavaScript and jQuery, cross-browser

Try this solution if works.

window.onkeypress = function(e) {
    if ((e.which || e.keyCode) == 116) {

JBoss AS 7: How to clean up tmp?

I do not have experience with version 7 of JBoss but with 5 I often had issues when redeploying apps which went away when I cleaned the work and tmp folder. I wrote a script for that which was executed everytime the server shut down. Maybe executing it before startup is better considering abnormal shutdowns (which weren't uncommon with Jboss 5 :))

MSSQL Error 'The underlying provider failed on Open'

The SQL Server Express service were not set tostart automatically.

1) Go to control panel 2) Administrative Tools 3) Service 4) Set SQL Server express to start automatically by clicking on it 5) Right click and start the service

I hope that will help.

How do I extract value from Json

we can use the below to get key as string from JSON OBJECT

JsonObject json = new JsonObject(); 

this gives the string without double quotes " " in the string

How do I write JSON data to a file?

I don't have enough reputation to add in comments, so I just write some of my findings of this annoying TypeError here:

Basically, I think it's a bug in the json.dump() function in Python 2 only - It can't dump a Python (dictionary / list) data containing non-ASCII characters, even you open the file with the encoding = 'utf-8' parameter. (i.e. No matter what you do). But, json.dumps() works on both Python 2 and 3.

To illustrate this, following up phihag's answer: the code in his answer breaks in Python 2 with exception TypeError: must be unicode, not str, if data contains non-ASCII characters. (Python 2.7.6, Debian):

import json
data = {u'\u0430\u0431\u0432\u0433\u0434': 1} #{u'?????': 1}
with open('data.txt', 'w') as outfile:
    json.dump(data, outfile)

It however works fine in Python 3.

How do implement a breadth first traversal?

Breadth first is a queue, depth first is a stack.

For breadth first, add all children to the queue, then pull the head and do a breadth first search on it, using the same queue.

For depth first, add all children to the stack, then pop and do a depth first on that node, using the same stack.

How to use paginator from material angular?

I'm struggling with the same here. But I can show you what I've got doing some research. Basically, you first start adding the page @Output event in the foo.template.ts:

 <md-paginator #paginator
                [pageSizeOptions]="[5, 10, 25, 100]"
                (page)="pageEvent = getServerData($event)"

And later, you have to add the pageEvent attribute in the foo.component.ts class and the others to handle paginator requirements:

pageEvent: PageEvent;
datasource: null;

And add the method that will fetch the server data:

ngOnInit() {
   getServerData(null) ...

public getServerData(event?:PageEvent){
    response =>{
      if(response.error) {
        // handle error
      } else {
        this.datasource =;
        this.pageIndex = response.pageIndex;
        this.pageSize = response.pageSize;
        this.length = response.length;
    error =>{
      // handle error
  return event;

So, basically every time you click the paginator, you'll activate getServerData(..) method that will call foo.service.ts getting all data required. In this case, you do not need to handle nextPage and nextXXX events because it will be automatically calculated upon view rendering.

Hope this can help you. Let me know if you had success. =]

How to display loading image while actual image is downloading

Instead of just doing this quoted method from,

You can do something like this:

// show loading image

// main image loaded ?
$('#main_img').on('load', function(){
  // hide/remove the loading image

You assign load event to the image which fires when image has finished loading. Before that, you can show your loader image.

you can use a different jQuery function to make the loading image fade away, then be hidden:

// Show the loading image.

// When main image loads:
$('#main_img').on('load', function(){
  // Fade out and hide the loading image.
  $('#loader_img').fadeOut(100); // Time in milliseconds.

"Once the opacity reaches 0, the display style property is set to none."

Or you could not use the jQuery library because there are already simple cross-browser JavaScript methods.

Html.fromHtml deprecated in Android N

Just to extend the answer from @Rockney and @k2col the improved code can look like:

public static Spanned fromHtml(@NonNull String html) {
    if (CompatUtils.isApiNonLowerThan(VERSION_CODES.N)) {
        return Html.fromHtml(html, Html.FROM_HTML_MODE_LEGACY);
    } else {
        //noinspection deprecation
        return Html.fromHtml(html);

Where the CompatUtils.isApiNonLowerThan:

public static boolean isApiNonLowerThan(int versionCode) {
    return Build.VERSION.SDK_INT >= versionCode;

The difference is that there are no extra local variable and the deprecation is only in else branch. So this will not suppress all method but single branch.

It can help when the Google will decide in some future versions of Android to deprecate even the fromHtml(String source, int flags) method.

Connect to SQL Server 2012 Database with C# (Visual Studio 2012)


SqlConnection myConnection = new SqlConnection("Database=testDB;Server=Paul-PC\\SQLEXPRESS;Integrated Security=True;connect timeout = 30");

How to get height of <div> in px dimension

Although they vary slightly as to how they retrieve a height value, i.e some would calculate the whole element including padding, margin, scrollbar, etc and others would just calculate the element in its raw form.
You can try these ones:


var myDiv = document.getElementById("myDiv");

or in jquery:


How can I get session id in php and show it?

In the PHP file first you need to register the session

 <? session_start();
     $_SESSION['id'] = $userData['user_id'];?>

And in each page of your php application you can retrive the session id

 <? session_start()
    id =  $_SESSION['id'];

How do I call paint event?

Refresh would probably also make for much more readable code, depending on context.

How do I change the data type for a column in MySQL?

You can also set a default value for the column just add the DEFAULT keyword followed by the value.

ALTER TABLE [table_name] MODIFY [column_name] [NEW DATA TYPE] DEFAULT [VALUE];

This is also working for MariaDB (tested version 10.2)

How can I turn a List of Lists into a List in Java 8?

Just as @Saravana mentioned:

flatmap is better but there are other ways to achieve the same

 listStream.reduce(new ArrayList<>(), (l1, l2) -> {
        return l1;

To sum up, there are several ways to achieve the same as follows:

private <T> List<T> mergeOne(Stream<List<T>> listStream) {
    return listStream.flatMap(List::stream).collect(toList());

private <T> List<T> mergeTwo(Stream<List<T>> listStream) {
    List<T> result = new ArrayList<>();
    return result;

private <T> List<T> mergeThree(Stream<List<T>> listStream) {
    return listStream.reduce(new ArrayList<>(), (l1, l2) -> {
        return l1;

private <T> List<T> mergeFour(Stream<List<T>> listStream) {
    return listStream.reduce((l1, l2) -> {
        List<T> l = new ArrayList<>(l1);
        return l;
    }).orElse(new ArrayList<>());

private <T> List<T> mergeFive(Stream<List<T>> listStream) {
    return listStream.collect(ArrayList::new, List::addAll, List::addAll);

.htaccess - how to force "www." in a generic way?

This is an older question, and there are many different ways to do this. The most complete answer, IMHO, is found here: . (Pasting and formatting the code here didn't work for me)

Best way to pass parameters to jQuery's .load()

In the first case, the data are passed to the script via GET, in the second via POST.

I don't think there are limits to the data size, but the completition of the remote call will of course take longer with great amount of data.

How do I protect Python code?

Use the same way to protect binary file of c/c++, that is, obfuscate each function body in executable or library binary file, insert an instruction "jump" at the begin of each function entry, jump to special function to restore obfuscated code. Byte-code is binary code of Python script, so

  • First compile python script to code object
  • Then iterate each code object, obfuscate co_code of each code object as the following
    0   JUMP_ABSOLUTE            n = 3 + len(bytecode)

    ... Here it's obfuscated bytecode

    n   LOAD_GLOBAL              ? (__pyarmor__)
    n+3 CALL_FUNCTION            0
    n+6 POP_TOP
    n+7 JUMP_ABSOLUTE            0
  • Save obfuscated code object as .pyc or .pyo file

Those obfuscated file (.pyc or .pyo) can be used by normal python interpreter, when those code object is called first time

  • First op is JUMP_ABSOLUTE, it will jump to offset n

  • At offset n, the instruction is to call a PyCFunction. This function will restore those obfuscated bytecode between offset 3 and n, and put the original byte-code at offset 0. The obfuscated code can be got by the following code

        char *obfucated_bytecode;
        Py_ssize_t len;
        PyFrameObject* frame = PyEval_GetFrame();
        PyCodeObject *f_code = frame->f_code;
        PyObject *co_code = f_code->co_code;      
        PyBytes_AsStringAndSize(co_code, &obfucated_bytecode, &len)
  • After this function returns, the last instruction is to jump to offset 0. The really byte-code now is executed.

There is a tool Pyarmor to obfuscate python scripts by this way.

Ansible playbook shell output

I found using the minimal stdout_callback with ansible-playbook gave similar output to using ad-hoc ansible.

In your ansible.cfg (Note that I'm on OS X so modify the callback_plugins path to suit your install)

stdout_callback     = minimal
callback_plugins    = /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/ansible/plugins/callback

So that a ansible-playbook task like yours

  hosts: example
  gather_facts: no
    - shell: ps -eo pcpu,user,args | sort -r -k1 | head -n5

Gives output like this, like an ad-hoc command would

example | SUCCESS | rc=0 >>
 0.2 root     sshd: root@pts/3
 0.1 root     /usr/sbin/CROND -n
 0.0 root     [xfs-reclaim/vda]
 0.0 root     [xfs_mru_cache]

I'm using ansible-playbook

jQuery .live() vs .on() method for adding a click event after loading dynamic html

I know it's a little late for an answer, but I've created a polyfill for the .live() method. I've tested it in jQuery 1.11, and it seems to work pretty well. I know that we're supposed to implement the .on() method wherever possible, but in big projects, where it's not possible to convert all .live() calls to the equivalent .on() calls for whatever reason, the following might work:

if(jQuery && ! { = function(evt, func) {
        $('body').on(evt, this.selector, func);

Just include it after you load jQuery and before you call live().

How to fix "Root element is missing." when doing a Visual Studio (VS) Build?

In my case, when I opened the .csproj file, it was empty so I went to my previous commit in git and copied the contents of that file and pasted it my current .csproj file. After which I deleted the .csproj.user file, reloaded my project, and everything started working again.

MySQL JOIN with LIMIT 1 on joined table

Replace the tables with yours:

SELECT * FROM works w 
(SELECT photoPath, photoUrl, videoUrl FROM workmedias LIMIT 1) AS wm ON wm.idWork = w.idWork

How can I find the location of origin/master in git, and how do I change it?

I was wondering the same thing about my repo. In my case I had an old remote that I wasn't pushing to anymore so I needed to remove it.

Get list of remotes:

git remote

Remove the one that you don't need

git remote rm {insert remote to remove}

How to display HTML in TextView?

Simply use:

String variable="StackOverflow";
textView.setText(Html.fromHtml("<b>Hello : </b>"+ variable));

How do you remove an array element in a foreach loop?

As has already been mentioned, you’d want to do a foreach with the key, and unset using the key – but note that mutating an array during iteration is in general a bad idea, though I’m not sure on PHP’s rules on this offhand.

vagrant login as root by default

This works if you are on ubuntu/trusty64 box:

vagrant ssh

Once you are in the ubuntu box:

sudo su

Now you are root user. You can update root password as shown below:

sudo -i

Now edit the below line in the file /etc/ssh/sshd_config

PermitRootLogin yes

Also, it is convenient to create your own alternate username:

adduser johndoe

Wait until it asks for password.

What's the equivalent of Java's Thread.sleep() in JavaScript?

There's no direct equivalent, as it'd pause a webpage. However there is a setTimeout(), e.g.:

function doSomething() {
  thing = thing + 1;
  setTimeout(doSomething, 500);

Closure example (thanks Daniel):

function doSomething(val) {
  thing = thing + 1;
  setTimeout(function() { doSomething(val) }, 500);

The second argument is milliseconds before firing, you can use this for time events or waiting before performing an operation.

Edit: Updated based on comments for a cleaner result.

How to instantiate a javascript class in another js file?

It is saying the value is undefined because it is a constructor function, not a class with a constructor. In order to use it, you would need to use Customer() or customer().

First, you need to load file1.js before file2.js, like slebetman said:

<script defer src="file1.js" type="module"></script>
<script defer src="file2.js" type="module"></script>

Then, you could change your file1.js as follows:

export default class Customer(){

And the file2.js as follows:

import { Customer } from "./file1";
var customer=new Customer();

Please correct me if I am wrong.

How do I update a Linq to SQL dbml file?

You could also check out the PLINQO set of code generation templates, based on CodeSmith, which allow you to do a lot of neat things for and with Linq-to-SQL:

  • generate one file per class (instead of a single, huge file)
  • update your model as needed
  • many more features

Check out the PLINQO site at and have a look at the intro videos.

The second tool I know of are the Huagati DBML/EDMX tools, which allow update of DBML (Linq-to-SQL) and EDMX (Entity Framework) mapping files, and more (like naming conventions etc.).


Cannot perform runtime binding on a null reference, But it is NOT a null reference

This error happens when you have a ViewBag Non-Existent in your razor code calling a method.


public ActionResult Accept(int id)
    return View();


<div class="form-group">
      @Html.LabelFor(model => model.ToId, "To", htmlAttributes: new { @class = "control-label col-md-2" })
     <div class="col-md-10">
<div class="form-group">
     <div class="col-md-10">
          <input value="@ViewBag.MaximounAmount.ToString()" />@* HERE is the error *@ 

For some reason, the .net aren't able to show the error in the correct line.

Normally this causes a lot of wasted time.

Convert JSON to Map

With google's Gson 2.7 (probably earlier versions too, but I tested 2.7) it's as simple as:

Map map = gson.fromJson(json, Map.class);

Which returns a Map of type class and works recursively on nested objects.

How to remove margin space around body or clear default css styles

Go with this

body {

How to concatenate strings in django templates?

extends has no facility for this. Either put the entire template path in a context variable and use that, or copy the exist template tag and modify it appropriately.

MS-DOS Batch file pause with enter key

The only valid answer would be the pause command.

Though this does not wait specifically for the 'ENTER' key, it waits for any key that is pressed.

And just in case you want it convenient for the user, pause is the best option.

What is the most compatible way to install python modules on a Mac?

If you use Python from MacPorts, it has it's own easy_install located at: /opt/local/bin/easy_install-2.6 (for py26, that is). It's not the same one as simply calling easy_install directly, even if you used python_select to change your default python command.

Creating a JSON response using Django and Python

from django.http import HttpResponse
import json

class JsonResponse(HttpResponse):
    def __init__(self, content={}, mimetype=None, status=None,
        super(JsonResponse, self).__init__(json.dumps(content), mimetype=mimetype,
                                           status=status, content_type=content_type)

And in the view:

resp_data = {'my_key': 'my value',}
return JsonResponse(resp_data)

Extracting columns from text file with different delimiters in Linux

You can use cut with a delimiter like this:

with space delim:

cut -d " " -f1-100,1000-1005 infile.csv > outfile.csv

with tab delim:

cut -d$'\t' -f1-100,1000-1005 infile.csv > outfile.csv

I gave you the version of cut in which you can extract a list of intervals...

Hope it helps!

Angular - "has no exported member 'Observable'"

You are using RxJS 6. Just replace

import { Observable } from 'rxjs/Observable';
import { of } from 'rxjs/observable/of';


import { Observable, of } from 'rxjs';

Is it possible to declare a public variable in vba and assign a default value?

Little-Known Fact:
A named range can refer to a value instead of specific cells.

This could be leveraged to act like a "global variable", plus you can refer to the value from VBA and in a worksheet cell, and the assigned value will even persist after closing & re-opening the workbook!

  • To "declare" the name myVariable and assign it a value of 123:

    ThisWorkbook.Names.Add "myVariable", 123
  • To retrieve the value (for example to display the value in a MsgBox):

      MsgBox [myVariable]
  • Alternatively, you could refer to the name with a string: (identical result as square brackets)

    MsgBox Evaluate("myVariable")
  • To use the value on a worksheet just use it's name in your formula as-is:

  • In fact, you could even store function expressions: (sort of like in JavaScript)
    (Admittedly, I can't actually think of a situation where this would be beneficial - but I don't use them in JS either.)

    ThisWorkbook.Names.Add "myDay", "=if(isodd(day(today())),""on day"",""off day"")"

Square brackets are just a shortcut for the Evaluate method. I've heard that using them is considered messy or "hacky", but I've had no issues and their use in Excel is supported by Microsoft.

There is probably also a way use the Range function to refer to these names, but I don't see any advantage so I didn't look very deeply into it.

More info:

Check if a class is derived from a generic class

Here's a little method I created for checking that a object is derived from a specific type. Works great for me!

internal static bool IsDerivativeOf(this Type t, Type typeToCompare)
    if (t == null) throw new NullReferenceException();
    if (t.BaseType == null) return false;

    if (t.BaseType == typeToCompare) return true;
    else return t.BaseType.IsDerivativeOf(typeToCompare);

How to execute AngularJS controller function on page load?

Try this?

$scope.$on('$viewContentLoaded', function() {
    //call it here

How do I declare class-level properties in Objective-C?

If you have many class level properties then a singleton pattern might be in order. Something like this:

// Foo.h
@interface Foo

+ (Foo *)singleton;

@property 1 ...
@property 2 ...
@property 3 ...



// Foo.m

#import "Foo.h"

@implementation Foo

static Foo *_singleton = nil;

+ (Foo *)singleton {
    if (_singleton == nil) _singleton = [[Foo alloc] init];

    return _singleton;

@synthesize property1;
@synthesize property2;
@synthesise property3;


Now access your class-level properties like this:

[Foo singleton].property1 = value;
value = [Foo singleton].property2;

select2 onchange event only works once

Apparently the change event is not fired if a selection already exists when using data. I ended up updating the data manually on select to resolve the problem.

$("#search_code").on("select2-selecting", function(e) {

I know this is pretty late but hopefully this answer will save others time.

How does Django's Meta class work?

Class Meta is the place in your code logic where your model.fields MEET With your form.widgets. So under Class Meta() you create the link between your model' fields and the different widgets you want to have in your form.

How can I get a list of repositories 'apt-get' is checking?

It's not a format suitable for blindly copying to another machine, but users who wish to work out whether they've added a repository yet or not (like I did), you can just do:

sudo apt update

When apt is updating, it outputs a list of repositories it fetches. It seems obvious, but I've just realised what the GET URLs are that it spits out.

The following awk-based expression could be used to generate a sources.list file:

 cat /tmp/apt-update.txt | awk '/http/ { gsub("/", " ", $3); gsub("^\s\*$", "main", $3); printf("deb "); if($4 ~ "^[a-z0-9]$") printf("[arch=" $4 "] "); print($2 " " $3) }' | sort | uniq

Alternatively, as other answers suggest, you could just cat all the pre-existing sources like this:

cat /etc/apt/sources.list /etc/apt/sources.list.d/*

Since the disabled repositories are commented out with hash, this should work as intended.

What is the equivalent of "!=" in Excel VBA?

In VBA, the != operator is the Not operator, like this:

If Not strTest = "" Then ...

Angular 2: How to access an HTTP response body?

This is work for me 100% :

let data:Observable<any> =, postData);
  data.subscribe((data) => {

  let d = data.json();
  console.log("result = " + d.result);
  console.log("url = " + d.image_url);      

Javascript button to insert a big black dot (•) into a html textarea

Just access the element and append it to the value.

     onclick="document.getElementById('myTextArea').value += '•'" 
     value="Add •">

See a live demo.

For the sake of keeping things simple, I haven't written unobtrusive JS. For a production system you should.

Also it needs to be a UTF8 character.

Browsers generally submit forms using the encoding they received the page in. Serve your page as UTF-8 if you want UTF-8 data submitted back.

Multiple dex files define Landroid/support/v4/accessibilityservice/AccessibilityServiceInfoCompat

This is an annoying problem, that can take some time to find out the root case. The way you should proceed is @CommonsWare answer.

I faced this problem recently and found it hard to resolve.

My problem was i was including a library by "+" version in build.gradle. Latest version of library contained one of older dex and bang.

I reverted to older version of library and solved it.

It is good to run your androidDependencies and see what is really happening. Its also good to search in your build folder.

Above all Android Studio 2.2 provide in build features to track this problem.

Happy Coding Guys

How to send POST in angularjs with multiple params?

var name = $scope.username;
var pwd = $scope.password;

var req = {
    method: 'POST',
    url: '../Account/LoginAccount',
    headers: {
        'Content-Type': undefined
    params: { username: name, password: pwd }

$http(req).then(function (responce) {
    // success function
}, function (responce) {
    // Failure Function

PHP isset() with multiple parameters

The parameter(s) to isset() must be a variable reference and not an expression (in your case a concatenation); but you can group multiple conditions together like this:

if (isset($_POST['search_term'], $_POST['postcode'])) {

This will return true only if all arguments to isset() are set and do not contain null.

Note that isset($var) and isset($var) == true have the same effect, so the latter is somewhat redundant.


The second part of your expression uses empty() like this:

empty ($_POST['search_term'] . $_POST['postcode']) == false

This is wrong for the same reasons as above. In fact, you don't need empty() here, because by that time you would have already checked whether the variables are set, so you can shortcut the complete expression like so:

isset($_POST['search_term'], $_POST['postcode']) && 
    $_POST['search_term'] && 

Or using an equivalent expression:

!empty($_POST['search_term']) && !empty($_POST['postcode'])

Final thoughts

You should consider using filter functions to manage the inputs:

$data = filter_input_array(INPUT_POST, array(
    'search_term' => array(
        'filter' => FILTER_UNSAFE_RAW,
        'flags' => FILTER_NULL_ON_FAILURE,
    'postcode' => array(
        'filter' => FILTER_UNSAFE_RAW,
        'flags' => FILTER_NULL_ON_FAILURE,

if ($data === null || in_array(null, $data, true)) {
    // some fields are missing or their values didn't pass the filter
    die("You did something naughty");

// $data['search_term'] and $data['postcode'] contains the fields you want

Btw, you can customize your filters to check for various parts of the submitted values.

Java using scanner enter key pressed

Scanner scan = new Scanner(;
        int i = scan.nextInt();
        Double d = scan.nextDouble();

        String newStr = "";
        Scanner charScanner = new Scanner( ).useDelimiter( "(\\b|\\B)" ) ;
        while( charScanner.hasNext() ) { 
            String  c =;

            if (c.equalsIgnoreCase("\r")) {
            else {
                newStr += c;    

        System.out.println("String: " + newStr);
        System.out.println("Int: " + i);
        System.out.println("Double: " + d);

This code works fine

I don't understand -Wl,-rpath -Wl,

You could also write


To get rid of that pesky space. It's arguably more readable than adding extra commas (it's exactly what gets passed to ld).

Execute action when back bar button of UINavigationController is pressed

If you are using navigationController then add the UINavigationControllerDelegate protocol to class and add the delegate method as follows:

class ViewController:UINavigationControllerDelegate {

    func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController,
animated: Bool) {
        if viewController === self {
            // do here what you want

This method is called whenever the navigation controller will slide to a new screen. If the back button was pressed, the new view controller is ViewController itself.

How to get the selected value from drop down list in jsp?

I've got one more additional option to get value by id:

var idElement = document.getElementById("idName");
var selectedValue = idElement.options[idElement.selectedIndex].value;

It's a simple JavaScript solution.

How to loop through an array of objects in swift

Your userPhotos array is option-typed, you should retrieve the actual underlying object with ! (if you want an error in case the object isn't there) or ? (if you want to receive nil in url):

let userPhotos = currentUser?.photos

for var i = 0; i < userPhotos!.count ; ++i {
    let url = userPhotos![i].url

But to preserve safe nil handling, you better use functional approach, for instance, with map, like this:

let urls = userPhotos?.map{ $0.url }

Defining private module functions in python

This is an ancient question, but both module private (one underscore) and class-private (two underscores) mangled variables are now covered in the standard documentation:

The Python Tutorial » Classes » Private Variables

How to enable SOAP on CentOS

On CentOS 7, the following works:

yum install php-soap

This will automatically create a soap.ini under /etc/php.d.

The extension itself for me lives in /usr/lib64/php/modules. You can confirm your extension directory by doing:

php -i | grep extension_dir

Once this has been installed, you can simply restart Apache using the new service manager like so:

systemctl restart httpd

Thanks to Matt Browne for the info about /etc/php.d.

How to create an AVD for Android 4.0

This answer is for creating AVD in Android Studio.

  1. First click on AVD button on your Android Studio top bar.

image 1

  1. In this window click on Create Virtual Device

image 2

  1. Now you will choose hardware profile for AVD and click Next.

image 3

  1. Choose Android Api Version you want in your AVD. Download if no api exist. Click next.

image 4

  1. This is now window for customizing some AVD feature like camera, network, memory and ram size etc. Just keep default and click Finish.

image 5

  1. You AVD is ready, now click on AVD button in Android Studio (same like 1st step). Then you will able to see created AVD in list. Click on Play button on your AVD.

image 6

  1. Your AVD will start soon.

image 7

How to take a first character from the string

"ABCDEFG".First returns "A"

Dim s as string

s = "Rajan"

s = "Sajan"

How to put the legend out of the plot

Short answer: you can use bbox_to_anchor + bbox_extra_artists + bbox_inches='tight'.

Longer answer: You can use bbox_to_anchor to manually specify the location of the legend box, as some other people have pointed out in the answers.

However, the usual issue is that the legend box is cropped, e.g.:

import matplotlib.pyplot as plt

# data 
all_x = [10,20,30]
all_y = [[1,3], [1.5,2.9],[3,2]]

# Plot
fig = plt.figure(1)
ax = fig.add_subplot(111)
ax.plot(all_x, all_y)

# Add legend, title and axis labels
lgd = ax.legend( [ 'Lag ' + str(lag) for lag in all_x], loc='center right', bbox_to_anchor=(1.3, 0.5))
ax.set_xlabel('x label')
ax.set_ylabel('y label')

fig.savefig('image_output.png', dpi=300, format='png')

enter image description here

In order to prevent the legend box from getting cropped, when you save the figure you can use the parameters bbox_extra_artists and bbox_inches to ask savefig to include cropped elements in the saved image:

fig.savefig('image_output.png', bbox_extra_artists=(lgd,), bbox_inches='tight')

Example (I only changed the last line to add 2 parameters to fig.savefig()):

import matplotlib.pyplot as plt

# data 
all_x = [10,20,30]
all_y = [[1,3], [1.5,2.9],[3,2]]

# Plot
fig = plt.figure(1)
ax = fig.add_subplot(111)
ax.plot(all_x, all_y)

# Add legend, title and axis labels
lgd = ax.legend( [ 'Lag ' + str(lag) for lag in all_x], loc='center right', bbox_to_anchor=(1.3, 0.5))
ax.set_xlabel('x label')
ax.set_ylabel('y label')    

fig.savefig('image_output.png', dpi=300, format='png', bbox_extra_artists=(lgd,), bbox_inches='tight')

enter image description here

I wish that matplotlib would natively allow outside location for the legend box as Matlab does:

x = 0:.2:12;
hleg = legend('First','Second','Third',...
% Make the text of the legend italic and color it brown

enter image description here

How can I show three columns per row?

Even though the above answer appears to be correct, I wanted to add a (hopefully) more readable example that also stays in 3 columns form at different widths:

.flex-row-container {_x000D_
    background: #aaa;_x000D_
    display: flex;_x000D_
    flex-wrap: wrap;_x000D_
    align-items: center;_x000D_
    justify-content: center;_x000D_
.flex-row-container > .flex-row-item {_x000D_
    flex: 1 1 30%; /*grow | shrink | basis */_x000D_
    height: 100px;_x000D_
.flex-row-item {_x000D_
  background-color: #fff4e6;_x000D_
  border: 1px solid #f76707;_x000D_
<div class="flex-row-container">_x000D_
  <div class="flex-row-item">1</div>_x000D_
  <div class="flex-row-item">2</div>_x000D_
  <div class="flex-row-item">3</div>_x000D_
  <div class="flex-row-item">4</div>_x000D_
  <div class="flex-row-item">5</div>_x000D_
  <div class="flex-row-item">6</div>_x000D_

Hope this helps someone else.

Double quotes within php script echo

if you need to access your variables for an echo statement within your quotes put your variable inside curly brackets

echo "i need to open my lock with its: {$array['key']}";

Warning: Cannot modify header information - headers already sent by ERROR

There is likely whitespace outside of your php tags.

Opening a SQL Server .bak file (Not restoring!)

It doesn't seem possible with SQL Server 2008 alone. You're going to need a third-party tool's help.

It will help you make your .bak act like a live database:

Transactions in .net

It also depends on what you need. For basic SQL transactions you could try doing TSQL transactions by using BEGIN TRANS and COMMIT TRANS in your code. That is the easiest way but it does have complexity and you have to be careful to commit properly (and rollback).

I would use something like

SQLTransaction trans = null;
using(trans = new SqlTransaction)
    Do SQL stuff here passing my trans into my various SQL executers
    trans.Commit  // May not be quite right

Any failure will pop you right out of the using and the transaction will always commit or rollback (depending on what you tell it to do). The biggest problem we faced was making sure it always committed. The using ensures the scope of the transaction is limited.

Python class input argument

Remove the name param from the class declaration. The init method is used to pass arguments to a class at creation.

class Person(object):
  def __init__(self, name): = name

me = Person("TheLazyScripter")

Scanner doesn't read whole sentence - difference between next() and nextLine() of scanner class

I would use Scanner#nextLine opposed to next for your address attribute.

This method returns the rest of the current line, excluding any line separator at the end.

Since this returns the entire line, delimited by a line separator, it will allow the user to enter any address without any constraint.

docker container ssl certificates

I am trying to do something similar to this. As commented above, I think you would want to build a new image with a custom Dockerfile (using the image you pulled as a base image), ADD your certificate, then RUN update-ca-certificates. This way you will have a consistent state each time you start a container from this new image.

# Dockerfile
FROM some-base-image:0.1
ADD you_certificate.crt:/container/cert/path
RUN update-ca-certificates

Let's say a docker build against that Dockerfile produced IMAGE_ID. On the next docker run -d [any other options] IMAGE_ID, the container started by that command will have your certificate info. Simple and reproducible.

Filter output in logcat by tagname

use this:

adb logcat -s "TAGNAME"

get user timezone

This will get you the timezone as a PHP variable. I wrote a function using jQuery and PHP. This is tested, and does work!

On the PHP page where you are want to have the timezone as a variable, have this snippet of code somewhere near the top of the page:

    $timezone = $_SESSION['time'];

This will read the session variable "time", which we are now about to create.

On the same page, in the <head> section, first of all you need to include jQuery:

<script type="text/javascript" src=""></script>

Also in the <head> section, paste this jQuery:

<script type="text/javascript">
    $(document).ready(function() {
        if("<?php echo $timezone; ?>".length==0){
            var visitortime = new Date();
            var visitortimezone = "GMT " + -visitortime.getTimezoneOffset()/60;
                type: "GET",
                url: "",
                data: 'time='+ visitortimezone,
                success: function(){

You may or may not have noticed, but you need to change the url to your actual domain.

One last thing. You are probably wondering what the heck timezone.php is. Well, it is simply this: (create a new file called timezone.php and point to it with the above url)

    $_SESSION['time'] = $_GET['time'];

If this works correctly, it will first load the page, execute the JavaScript, and reload the page. You will then be able to read the $timezone variable and use it to your pleasure! It returns the current UTC/GMT time zone offset (GMT -7) or whatever timezone you are in.

You can read more about this on my blog

What exactly is Python's file.flush() doing?

It flushes the internal buffer, which is supposed to cause the OS to write out the buffer to the file.[1] Python uses the OS's default buffering unless you configure it do otherwise.

But sometimes the OS still chooses not to cooperate. Especially with wonderful things like write-delays in Windows/NTFS. Basically the internal buffer is flushed, but the OS buffer is still holding on to it. So you have to tell the OS to write it to disk with os.fsync() in those cases.


Color picker utility (color pipette) in Ubuntu

You can install the package gcolor2 for this:

sudo apt-get install gcolor2


Applications -> Graphics -> GColor2

Saving lists to txt file

@Jon's answer is great and will get you where you need to go. So why is your code printing out what it is. The answer: You're not writing out the contents of your list, but the String representation of your list itself, by an implicit call to Lists.verbList.ToString(). Object.ToString() defines the default behavior you're seeing here.

How to call base.base.method()?

If you want to access to base class data you must use "this" keyword or you use this keyword as reference for class.

namespace thiskeyword
    class Program
        static void Main(string[] args)
            I i = new I();
            int res = i.m1();

    public class E
        new public int x = 3;

    public class F:E
        new public int x = 5;

    public class G:F
        new public int x = 50;

    public class H:G
        new public int x = 20;

    public class I:H
        new public int x = 30;

        public int m1()
           // (this as <classname >) will use for accessing data to base class

            int z = (this as I).x + base.x + (this as G).x + (this as F).x + (this as E).x; // base.x refer to H
            return z;

Package Manager Console Enable-Migrations CommandNotFoundException only in a specific VS project

Just simply re-starting Visual Studio worked for me. No need to install packages, etc.

async for loop in node.js

I like to use the recursive pattern for this scenario. For example, something like this:

// If config is an array of queries
var config = JSON.parse(queries.querrryArray);   

// Array of results
var results;


function processQueries(queries) {
    var searchQuery;

    if (queries.length == 0) {
        // All queries complete
        res.writeHead(200, {'content-type': 'application/json'});
        res.end(JSON.stringify({results: results}));

    searchQuery = queries.pop();

    search(searchQuery, function(result) {
        results.push(JSON.stringify({result: result}); 


processQueries is a recursive function that will pull a query element out of an array of queries to process. Then the callback function calls processQueries again when the query is complete. The processQueries knows to end when there are no queries left.

It is easiest to do this using arrays, but it could be modified to work with object key/values I imagine.

Origin http://localhost is not allowed by Access-Control-Allow-Origin

You've got two ways to go forward:


If this API supports JSONP, the easiest way to fix this issue is to add &callback to the end of the URL. You can also try &callback=. If that doesn't work, it means the API does not support JSONP, so you must try the other solution.

Proxy Script

You can create a proxy script on the same domain as your website in order to avoid the cross-origin issues. This will only work with HTTP URLs, not HTTPS URLs, but it shouldn't be too difficult to modify if you need that.

// File Name: proxy.php
if (!isset($_GET['url'])) {
    die(); // Don't do anything if we don't have a URL to work with
$url = urldecode($_GET['url']);
$url = 'http://' . str_replace('http://', '', $url); // Avoid accessing the file system
echo file_get_contents($url); // You should probably use cURL. The concept is the same though

Then you just call this script with jQuery. Be sure to urlencode the URL.

    url      : 'proxy.php?',
    type     : 'GET',
    dataType : 'json'
}).done(function(data) {
    console.log(data.results.result[1].category); // Do whatever you want here

The Why

You're getting this error because of XMLHttpRequest same origin policy, which basically boils down to a restriction of ajax requests to URLs with a different port, domain or protocol. This restriction is in place to prevent cross-site scripting (XSS) attacks.

More Information

Our solutions by pass these problems in different ways.

JSONP uses the ability to point script tags at JSON (wrapped in a javascript function) in order to receive the JSON. The JSONP page is interpreted as javascript, and executed. The JSON is passed to your specified function.

The proxy script works by tricking the browser, as you're actually requesting a page on the same origin as your page. The actual cross-origin requests happen server-side.

How can I select multiple columns from a subquery (in SQL Server) that should have one record (select top 1) for each record in the main query?

You'll have to make a join:

SELECT A.SalesOrderID, B.Foo
JOIN B bo ON = (
     SELECT TOP 1 id
     FROM B bi
     WHERE bi.SalesOrderID = a.SalesOrderID
     ORDER BY bi.whatever
WHERE A.Date BETWEEN '2000-1-4' AND '2010-1-4'

, assuming that is a PRIMARY KEY on B

In MS SQL 2005 and higher you may use this syntax:

SELECT SalesOrderID, Foo
  SELECT A.SalesOrderId, B.Foo,
         ROW_NUMBER() OVER (PARTITION BY B.SalesOrderId ORDER BY B.whatever) AS rn
  JOIN B ON B.SalesOrderID = A.SalesOrderID
  WHERE A.Date BETWEEN '2000-1-4' AND '2010-1-4'
) i

This will select exactly one record from B for each SalesOrderId.

How to search images from private 1.0 registry in docker?

Was able to get everything in my private registry back by searching just for 'library':

docker search []:[port]/library

Returns (e.g.):

library/custom-image                  0                    
library/another-image                 0                    
library/hello-world                   0

Has anyone ever got a remote JMX JConsole to work?

These are the steps that worked for me (debian behind firewall on the server side, reached over VPN from my local Mac):

check server ip

hostname -i

use JVM params:[jmx port]
-Djava.rmi.server.hostname=[server ip from step 1]

run application

find pid of the running java process

check all ports used by JMX/RMI

netstat -lp | grep [pid from step 4]

open all ports from step 5 on the firewall


Moving Average Pandas

The rolling mean returns a Series you only have to add it as a new column of your DataFrame (MA) as described below.

For information, the rolling_mean function has been deprecated in pandas newer versions. I have used the new method in my example, see below a quote from the pandas documentation.

Warning Prior to version 0.18.0, pd.rolling_*, pd.expanding_*, and pd.ewm* were module level functions and are now deprecated. These are replaced by using the Rolling, Expanding and EWM. objects and a corresponding method call.

df['MA'] = df.rolling(window=5).mean()

#             Value    MA
# Date                   
# 1989-01-02   6.11   NaN
# 1989-01-03   6.08   NaN
# 1989-01-04   6.11   NaN
# 1989-01-05   6.15   NaN
# 1989-01-09   6.25  6.14
# 1989-01-10   6.24  6.17
# 1989-01-11   6.26  6.20
# 1989-01-12   6.23  6.23
# 1989-01-13   6.28  6.25
# 1989-01-16   6.31  6.27

Get all rows from SQLite

Update queueAll() method as below:

public Cursor queueAll() {

     String selectQuery = "SELECT * FROM " + MYDATABASE_TABLE;
     Cursor cursor = sqLiteDatabase.rawQuery(selectQuery, null);

     return cursor;

Update readFileFromSQLite() method as below:

public ArrayList<String> readFileFromSQLite() {

    fileName = new ArrayList<String>();

    fileSQLiteAdapter = new FileSQLiteAdapter(FileChooser.this);

    cursor = fileSQLiteAdapter.queueAll();

    if (cursor != null) {
        if (cursor.moveToFirst()) {
                String name = cursor.getString(cursor.getColumnIndex(FileSQLiteAdapter.KEY_CONTENT1));
            } while (cursor.moveToNext());


    return fileName;

How can I make window.showmodaldialog work in chrome 37?

The window.returnValue property does not work directly when you are opening a window using while it does work when you are using window.showModalDialog()

So in your case you have two options to achieve what you are trying to do.

Option 1 - Using window.showModalDialog()

In your parent page

var answer = window.showModalDialog(<your page and other arguments>)
if (answer == 1)
 { do some thing with answer }

and inside your child page you can make use of the window.returnValue directly like

window.returnValue = 'value that you want to return';

showModalDialog halts the executions of the JavaScript until the dialog box is closed and can get a return value from the opened dialog box when its closing.But the problem with showModalDialog is that it is not supported on many modern browsers. In contrast just opens a window asynchronously (User can access both the parent window and the opened window). And the JavaScript execution will continue immediately. Which bring us to Option 2

Option 2 - Using In your parent page write a function that deals with opening of your dialog.

function openDialog(url, width, height, callback){
    options = 'dialogHeight: '+ height + '; dialogWidth: '+ width + '; scroll=no'
    var returnValue = window.showModalDialog(url,this,options);
else {
    options ='toolbar=no, directories=no, location=no, status=yes, menubar=no, resizable=yes, scrollbars=no, width=' + width + ', height=' + height; 
        var childWindow =,"",options);
            if (childWindow.isOpened == null) {
                childWindow.isOpened = 1;
            else {


And whenever you want to use open a dialog. Write a callback that deals with the return value and pass it as a parameter to openDialog function

function callback(returnValue){
    do something nice with the returnValue

And when calling the function

openDialog(<your page>, 'width px', 'height px', callbak);

Check out an article on how to replace window.showModalDialog with

Remove HTML tags from a String

HTML Escaping is really hard to do right- I'd definitely suggest using library code to do this, as it's a lot more subtle than you'd think. Check out Apache's StringEscapeUtils for a pretty good library for handling this in Java.

jQuery - determine if input element is textbox or select list

You could do this:

if( ctrl[0].nodeName.toLowerCase() === 'input' ) {
    // it was an input

or this, which is slower, but shorter and cleaner:

if('input') ) {
    // it was an input

If you want to be more specific, you can test the type:

if('input:text') ) {
    // it was an input

Why is there no SortedList in Java?

I think all the above do not answer this question due to following reasons,

  1. Since same functionality can be achieved by using other collections such as TreeSet, Collections, PriorityQueue..etc (but this is an alternative which will also impose their constraints i.e. Set will remove duplicate elements. Simply saying even if it does not impose any constraint, it does not answer the question why SortedList was not created by java community)
  2. Since List elements do not implements compare/equals methods (This holds true for Set & Map also where in general items do not implement Comparable interface but when we need these items to be in sorted order & want to use TreeSet/TreeMap,items should implement Comparable interface)
  3. Since List uses indexing & due to sorting it won't work (This can be easily handled introducing intermediate interface/abstract class)

but none has told the exact reason behind it & as I believe these kind of questions can be best answered by java community itself as it will have only one & specific answer but let me try my best to answer this as following,

As we know sorting is an expensive operation and there is a basic difference between List & Set/Map that List can have duplicates but Set/Map can not. This is the core reason why we have got a default implementation for Set/Map in form of TreeSet/TreeMap. Internally this is a Red Black Tree with every operation (insert/delete/search) having the complexity of O(log N) where due to duplicates List could not fit in this data storage structure.

Now the question arises we could also choose a default sorting method for List also like MergeSort which is used by Collections.sort(list) method with the complexity of O(N log N). Community did not do this deliberately since we do have multiple choices for sorting algorithms for non distinct elements like QuickSort, ShellSort, RadixSort...etc. In future there can be more. Also sometimes same sorting algorithm performs differently depending on the data to be sorted. Therefore they wanted to keep this option open and left this on us to choose. This was not the case with Set/Map since O(log N) is the best sorting complexity.

TLS 1.2 in .NET Framework 4.0

Make the following changes in your Registry and it should work:

1.) .NET Framework strong cryptography registry keys



2.) Secure Channel (Schannel) TLS 1.2 registry keys

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2]

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client]

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server]

Remove Array Value By index in jquery

Your example code is wrong and will throw a SyntaxError. You seem to have confused the syntax of creating an object Object with creating an Array.

The correct syntax would be: var arr = [ "abc", "def", "ghi" ];

To remove an item from the array, based on its value, use the splice method:

arr.splice(arr.indexOf("def"), 1);

To remove it by index, just refer directly to it:

arr.splice(1, 1);

What is the Python 3 equivalent of "python -m SimpleHTTPServer"

From the docs:

The SimpleHTTPServer module has been merged into http.server in Python 3.0. The 2to3 tool will automatically adapt imports when converting your sources to 3.0.

So, your command is python -m http.server, or depending on your installation, it can be:

python3 -m http.server

R data formats: RData, Rda, Rds etc

In addition to @KenM's answer, another important distinction is that, when loading in a saved object, you can assign the contents of an Rds file. Not so for Rda

> x <- 1:5
> save(x, file="x.Rda")
> saveRDS(x, file="x.Rds")
> rm(x)

> new_x1 <- readRDS("x.Rds")
> new_x1
[1] 1 2 3 4 5

## 'ASSIGN' USING load -- note the result
> new_x2 <- load("x.Rda")
loading in to  <environment: R_GlobalEnv> 
> new_x2
[1] "x"
# NOTE: `load()` simply returns the name of the objects loaded. Not the values. 
> x
[1] 1 2 3 4 5

How to link html pages in same or different folders?

Answer below is what I created to link html contents from another shared drive to the html page I would send out to managers. Of course, the path is relative to your using, but in my case, I would just send them the html, and everything else that is updated from load runner dynamically would be updated for me. Saves tons of paper, and they can play with the numbers as they see fit instead of just a hard copy this way.

SRC="file://///shareddrive/shareddrive-folder/username/scripting/testReport\contents.html" NAME="contents_frame" title="Table of Contents"

Making a PowerShell POST request if a body param starts with '@'

Use Invoke-RestMethod to consume REST-APIs. Save the JSON to a string and use that as the body, ex:

$JSON = @'
 "username":"[email protected]",

$response = Invoke-RestMethod -Uri "" -Method Post -Body $JSON -ContentType "application/json"

If you use Powershell 3, I know there have been some issues with Invoke-RestMethod, but you should be able to use Invoke-WebRequest as a replacement:

$response = Invoke-WebRequest -Uri "" -Method Post -Body $JSON -ContentType "application/json"

If you don't want to write your own JSON every time, you can use a hashtable and use PowerShell to convert it to JSON before posting it. Ex.

$JSON = @{
    "@type" = "login"
    "username" = "[email protected]"
    "password" = "yyy"
} | ConvertTo-Json

What are the benefits of learning Vim?

The amazing ubiquity of Vim, and the even more amazing ubiquity of Vi-clones in general, on Unix systems alone is enough to make it worth learning.

Besides that, the whole Vi-style thinking is something that I really think has made me a bit more productive. For a person not used to modes such as the command mode and insert mode, it seems a bit excessive to have to enter a mode just to insert text. But, when one has been using Vim for a few months, and has learned quite a few tips and tricks, Vim seems to be an asset that seems to be worth it.

Of course, the Emacs crowd says the same thing regarding Emacs-style thinking, but I gave up on learning Emacs because Vim was simpler and did the job for me.

Custom Cell Row Height setting in storyboard is not responding

I have recently been wrestling with this. My issue was the solutions posted above using the heightForRowAtIndexPath: method would work for iOS 7.1 in the Simulator but then have completely screwed up results by simply switching to iOS 8.1.

I began reading more about self-sizing cells (introduced in iOS 8, read here). It was apparent that the use of UITableViewAutomaticDimension would help in iOS 8. I tried using that technique and deleted the use of heightForRowAtIndexPath: and voila, it was working perfect in iOS 8 now. But then iOS 7 wasn't. What was I to do? I needed heightForRowAtIndexPath: for iOS 7 and not for iOS 8.

Here is my solution (trimmed up for brevity's sake) which borrow's from the answer @JosephH posted above:

- (void)viewDidLoad {
    [super viewDidLoad];

    self.tableView.estimatedRowHeight = 50.;
    self.tableView.rowHeight = UITableViewAutomaticDimension;

    // ...

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
        return UITableViewAutomaticDimension;

    } else {
        NSString *cellIdentifier = [self reuseIdentifierForCellAtIndexPath:indexPath];
        static NSMutableDictionary *heightCache;
        if (!heightCache)
            heightCache = [[NSMutableDictionary alloc] init];
        NSNumber *cachedHeight = heightCache[cellIdentifier];
        if (cachedHeight)
            return cachedHeight.floatValue;

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    CGFloat height = cell.bounds.size.height;
    heightCache[cellIdentifier] = @(height);
    return height;

- (NSString *)reuseIdentifierForCellAtIndexPath:(NSIndexPath *)indexPath {
    NSString * reuseIdentifier;
    switch (indexPath.row) {
        case 0:
            reuseIdentifier = EventTitleCellIdentifier;
        case 2:
            reuseIdentifier = EventDateTimeCellIdentifier;
        case 4:
            reuseIdentifier = EventContactsCellIdentifier;
        case 6:
            reuseIdentifier = EventLocationCellIdentifier;
        case 8:
            reuseIdentifier = NotesCellIdentifier;
            reuseIdentifier = SeparatorCellIdentifier;

    return reuseIdentifier;

SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0") is actually from a set of macro definitions I am using which I found somewhere (very helpful). They are defined as:

#define SYSTEM_VERSION_EQUAL_TO(v)                  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedSame)
#define SYSTEM_VERSION_GREATER_THAN(v)              ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedDescending)
#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN(v)                 ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(v)     ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedDescending)

How to redirect to another page using PHP

Assuming you're using cookies for login, just call it after your setcookie call -- after all, you must be calling that one before any output too.

Anyway in general you could check for the presence of your form's submit button name at the beginning of the script, do your logic, and then output stuff:

if(isset($_POST['mySubmit'])) {
    // the form was submitted

    // ...
    // perform your logic

    // redirect if login was successful
    header('Location: /somewhere');

// output your stuff here

How can I hash a password in Java?

You can actually use a facility built in to the Java runtime to do this. The SunJCE in Java 6 supports PBKDF2, which is a good algorithm to use for password hashing.

byte[] salt = new byte[16];
KeySpec spec = new PBEKeySpec("password".toCharArray(), salt, 65536, 128);
SecretKeyFactory f = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
byte[] hash = f.generateSecret(spec).getEncoded();
Base64.Encoder enc = Base64.getEncoder();
System.out.printf("salt: %s%n", enc.encodeToString(salt));
System.out.printf("hash: %s%n", enc.encodeToString(hash));

Here's a utility class that you can use for PBKDF2 password authentication:

import java.util.Arrays;
import java.util.Base64;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;

 * Hash passwords for storage, and test passwords against password tokens.
 * Instances of this class can be used concurrently by multiple threads.
 * @author erickson
 * @see <a href="">StackOverflow</a>
public final class PasswordAuthentication

   * Each token produced by this class uses this identifier as a prefix.
  public static final String ID = "$31$";

   * The minimum recommended cost, used by default
  public static final int DEFAULT_COST = 16;

  private static final String ALGORITHM = "PBKDF2WithHmacSHA1";

  private static final int SIZE = 128;

  private static final Pattern layout = Pattern.compile("\\$31\\$(\\d\\d?)\\$(.{43})");

  private final SecureRandom random;

  private final int cost;

  public PasswordAuthentication()

   * Create a password manager with a specified cost
   * @param cost the exponential computational cost of hashing a password, 0 to 30
  public PasswordAuthentication(int cost)
    iterations(cost); /* Validate cost */
    this.cost = cost;
    this.random = new SecureRandom();

  private static int iterations(int cost)
    if ((cost < 0) || (cost > 30))
      throw new IllegalArgumentException("cost: " + cost);
    return 1 << cost;

   * Hash a password for storage.
   * @return a secure authentication token to be stored for later authentication 
  public String hash(char[] password)
    byte[] salt = new byte[SIZE / 8];
    byte[] dk = pbkdf2(password, salt, 1 << cost);
    byte[] hash = new byte[salt.length + dk.length];
    System.arraycopy(salt, 0, hash, 0, salt.length);
    System.arraycopy(dk, 0, hash, salt.length, dk.length);
    Base64.Encoder enc = Base64.getUrlEncoder().withoutPadding();
    return ID + cost + '$' + enc.encodeToString(hash);

   * Authenticate with a password and a stored password token.
   * @return true if the password and token match
  public boolean authenticate(char[] password, String token)
    Matcher m = layout.matcher(token);
    if (!m.matches())
      throw new IllegalArgumentException("Invalid token format");
    int iterations = iterations(Integer.parseInt(;
    byte[] hash = Base64.getUrlDecoder().decode(;
    byte[] salt = Arrays.copyOfRange(hash, 0, SIZE / 8);
    byte[] check = pbkdf2(password, salt, iterations);
    int zero = 0;
    for (int idx = 0; idx < check.length; ++idx)
      zero |= hash[salt.length + idx] ^ check[idx];
    return zero == 0;

  private static byte[] pbkdf2(char[] password, byte[] salt, int iterations)
    KeySpec spec = new PBEKeySpec(password, salt, iterations, SIZE);
    try {
      SecretKeyFactory f = SecretKeyFactory.getInstance(ALGORITHM);
      return f.generateSecret(spec).getEncoded();
    catch (NoSuchAlgorithmException ex) {
      throw new IllegalStateException("Missing algorithm: " + ALGORITHM, ex);
    catch (InvalidKeySpecException ex) {
      throw new IllegalStateException("Invalid SecretKeyFactory", ex);

   * Hash a password in an immutable {@code String}. 
   * <p>Passwords should be stored in a {@code char[]} so that it can be filled 
   * with zeros after use instead of lingering on the heap and elsewhere.
   * @deprecated Use {@link #hash(char[])} instead
  public String hash(String password)
    return hash(password.toCharArray());

   * Authenticate with a password in an immutable {@code String} and a stored 
   * password token. 
   * @deprecated Use {@link #authenticate(char[],String)} instead.
   * @see #hash(String)
  public boolean authenticate(String password, String token)
    return authenticate(password.toCharArray(), token);


How do I read image data from a URL in Python?

In Python3 the StringIO and cStringIO modules are gone.

In Python3 you should use:

from PIL import Image
import requests
from io import BytesIO

response = requests.get(url)
img =

Convert DataTable to IEnumerable<T>

Simple method using System.Data.DataSetExtensions:

table.AsEnumerable().Select(row => new TankReading{
        TankReadingsID = Convert.ToInt32(row["TRReadingsID"]),
        TankID = Convert.ToInt32(row["TankID"]),
        ReadingDateTime = Convert.ToDateTime(row["ReadingDateTime"]),
        ReadingFeet = Convert.ToInt32(row["ReadingFeet"]),
        ReadingInches = Convert.ToInt32(row["ReadingInches"]),
        MaterialNumber = row["MaterialNumber"].ToString(),
        EnteredBy = row["EnteredBy"].ToString(),
        ReadingPounds = Convert.ToDecimal(row["ReadingPounds"]),
        MaterialID = Convert.ToInt32(row["MaterialID"]),
        Submitted = Convert.ToBoolean(row["Submitted"]),


TankReading TankReadingFromDataRow(DataRow row){
    return new TankReading{
        TankReadingsID = Convert.ToInt32(row["TRReadingsID"]),
        TankID = Convert.ToInt32(row["TankID"]),
        ReadingDateTime = Convert.ToDateTime(row["ReadingDateTime"]),
        ReadingFeet = Convert.ToInt32(row["ReadingFeet"]),
        ReadingInches = Convert.ToInt32(row["ReadingInches"]),
        MaterialNumber = row["MaterialNumber"].ToString(),
        EnteredBy = row["EnteredBy"].ToString(),
        ReadingPounds = Convert.ToDecimal(row["ReadingPounds"]),
        MaterialID = Convert.ToInt32(row["MaterialID"]),
        Submitted = Convert.ToBoolean(row["Submitted"]),

// Now you can do this
table.AsEnumerable().Select(row => return TankReadingFromDataRow(row));

Or, better yet, create a TankReading(DataRow r) constructor, then this becomes:

    table.AsEnumerable().Select(row => return new TankReading(row));

Regex for not empty and not whitespace

/^$|\s+/ This matches when empty or white spaces

/(?!^$)([^\s])/ This matches when its not empty or white spaces

How can I find the first and last date in a month using PHP?

Simple one

  • Y - A full numeric representation of a year, 4 digits
  • m - Numeric representation of a month, with leading zeros
  • t - Number of days in the given month

Reference -

    echo 'First Date    = ' . date('Y-m-01') . '<br />';
    echo 'Last Date     = ' . date('Y-m-t')  . '<br />';

How to maintain a Unique List in Java?

You can use a Set implementation:

Some info from the JAVADoc:

A collection that contains no duplicate elements. More formally, sets contain no pair of elements e1 and e2 such that e1.equals(e2), and at most one null element. As implied by its name, this interface models the mathematical set abstraction.

Note: Great care must be exercised if mutable objects are used as set elements. The behavior of a set is not specified if the value of an object is changed in a manner that affects equals comparisons while the object is an element in the set. A special case of this prohibition is that it is not permissible for a set to contain itself as an element.`

These are the implementations:

  • HashSet

    This class offers constant time performance for the basic operations (add, remove, contains and size), assuming the hash function disperses the elements properly among the buckets. Iterating over this set requires time proportional to the sum of the HashSet instance's size (the number of elements) plus the "capacity" of the backing HashMap instance (the number of buckets). Thus, it's very important not to set the initial capacity too high (or the load factor too low) if iteration performance is important.

    When iterating a HashSet the order of the yielded elements is undefined.

  • LinkedHashSet

    Hash table and linked list implementation of the Set interface, with predictable iteration order. This implementation differs from HashSet in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is the order in which elements were inserted into the set (insertion-order). Note that insertion order is not affected if an element is re-inserted into the set. (An element e is reinserted into a set s if s.add(e) is invoked when s.contains(e) would return true immediately prior to the invocation.)

    So, the output of the code above...

     Set<Integer> linkedHashSet = new LinkedHashSet<>();
     for (int i : linkedHashSet) {

    ...will necessarily be

  • TreeSet

    This implementation provides guaranteed log(n) time cost for the basic operations (add, remove and contains). By default he elements returned on iteration are sorted by their "natural ordering", so the code above...

     Set<Integer> treeSet = new TreeSet<>();
     for (int i : treeSet) {

    ...will output this:


    (You can also pass a Comparator instance to a TreeSet constructor, making it sort the elements in a different order.)

    Note that the ordering maintained by a set (whether or not an explicit comparator is provided) must be consistent with equals if it is to correctly implement the Set interface. (See Comparable or Comparator for a precise definition of consistent with equals.) This is so because the Set interface is defined in terms of the equals operation, but a TreeSet instance performs all element comparisons using its compareTo (or compare) method, so two elements that are deemed equal by this method are, from the standpoint of the set, equal. The behavior of a set is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Set interface.

mysql after insert trigger which updates another table's column

With your requirements you don't need BEGIN END and IF with unnecessary SELECT in your trigger. So you can simplify it to this

CREATE TRIGGER occupy_trig AFTER INSERT ON occupiedroom 
  UPDATE BookingRequest
     SET status = 1
   WHERE idRequest = NEW.idRequest;

How can I confirm a database is Oracle & what version it is using SQL?

For Oracle use:

Select * from v$version;

For SQL server use:

Select @@VERSION as Version

and for MySQL use:

Show variables LIKE "%version%";

Adding an identity to an existing column

I don't believe you can alter an existing column to be an identity column using tsql. However, you can do it through the Enterprise Manager design view.

Alternatively you could create a new row as the identity column, drop the old column, then rename your new column.

ADD BarColumn INT IDENTITY(1, 1)
               NOT NULL

How to sort ArrayList<Long> in decreasing order?

A more general approach to implement our own Comparator as below

Collections.sort(lst,new Comparator<Long>(){
                public int compare(Long o1, Long o2) {
                    return o2.compareTo(o1);

Using OpenGl with C#?

Tao is supposed to be a nice framework.

From their site:

The Tao Framework for .NET is a collection of bindings to facilitate cross-platform media application development utilizing the .NET and Mono platforms.

Can someone explain the dollar sign in Javascript?

My answer is here lacks technomalogical sophistication to the extent it even employs words like "technomalogical" which are one of those words which aren't actually in the dictionary but have infrequent usage such as the word "gullible" which also cannot be found in the dictionary either.

All that aside: here's me simple answer to a simple question in a simple way to answer a question like this one which is very complicated to ask and the simple wishy washy answer to the wishy washy question like this is thus:

The $('#ident') thing says "document.getElementById('ident').

The $('.classname') thing says "document.getElementByClass('classname').

Yes I know there is no getElementByClass but thats kind of what people are saying when they use the $ symbol like that which is a jQuery syntax. Now you know the answer, I bet you are still lost for how to ask the question. Well now you dont have to learn jQuery just to understand jQuery babel a bit right? Give me a +10 please!

SQL - using alias in Group By

SQL is implemented as if a query was executed in the following order:

  1. FROM clause
  2. WHERE clause
  3. GROUP BY clause
  4. HAVING clause
  5. SELECT clause
  6. ORDER BY clause

For most relational database systems, this order explains which names (columns or aliases) are valid because they must have been introduced in a previous step.

So in Oracle and SQL Server, you cannot use a term in the GROUP BY clause that you define in the SELECT clause because the GROUP BY is executed before the SELECT clause.

There are exceptions though: MySQL and Postgres seem to have additional smartness that allows it.

Has an event handler already been added?

From outside the defining class, as @Telos mentions, you can only use EventHandler on the left-hand side of a += or a -=. So, if you have the ability to modify the defining class, you could provide a method to perform the check by checking if the event handler is null - if so, then no event handler has been added. If not, then maybe and you can loop through the values in Delegate.GetInvocationList. If one is equal to the delegate that you want to add as event handler, then you know it's there.

public bool IsEventHandlerRegistered(Delegate prospectiveHandler)
    if ( this.EventHandler != null )
        foreach ( Delegate existingHandler in this.EventHandler.GetInvocationList() )
            if ( existingHandler == prospectiveHandler )
                return true;
    return false;

And this could easily be modified to become "add the handler if it's not there". If you don't have access to the innards of the class that's exposing the event, you may need to explore -= and +=, as suggested by @Lou Franco.

However, you may be better off reexamining the way you're commissioning and decommissioning these objects, to see if you can't find a way to track this information yourself.

JPA Hibernate One-to-One relationship

This should be working too using JPA 2.0 @MapsId annotation instead of Hibernate's GenericGenerator:

public class Person {

    public int id;

    public OtherInfo otherInfo;

    rest of attributes ...

public class OtherInfo {

    public int id;

    public Person person;

    rest of attributes ...

More details on this in Hibernate 4.1 documentation under section

width:auto for <input> fields

Answer 1 - "response" gave a nice answer/link for it. To put it in short, "auto" is the default, so it is like removing any changes in the width of an element

Answer 2 - use width: 100% instead. It will fill the 100% of the parent container, in this case, the "form".

Read XML file using javascript

The code below will convert any XMLObject or string to a native JavaScript object. Then you can walk on the object to extract any value you want.

 * Tries to convert a given XML data to a native JavaScript object by traversing the DOM tree.
 * If a string is given, it first tries to create an XMLDomElement from the given string.
 * @param {XMLDomElement|String} source The XML string or the XMLDomElement prefreably which containts the necessary data for the object.
 * @param {Boolean} [includeRoot] Whether the "required" main container node should be a part of the resultant object or not.
 * @return {Object} The native JavaScript object which is contructed from the given XML data or false if any error occured.
Object.fromXML = function( source, includeRoot ) {
    if( typeof source == 'string' )
            if ( window.DOMParser )
                source = ( new DOMParser() ).parseFromString( source, "application/xml" );
            else if( window.ActiveXObject )
                var xmlObject = new ActiveXObject( "Microsoft.XMLDOM" );
                xmlObject.async = false;
                xmlObject.loadXML( source );
                source = xmlObject;
                xmlObject = undefined;
                throw new Error( "Cannot find an XML parser!" );
        catch( error )
            return false;

    var result = {};

    if( source.nodeType == 9 )
        source = source.firstChild;
    if( !includeRoot )
        source = source.firstChild;

    while( source ) {
        if( source.childNodes.length ) {
            if( source.tagName in result ) {
                if( result[source.tagName].constructor != Array ) 
                    result[source.tagName] = [result[source.tagName]];
                result[source.tagName].push( Object.fromXML( source ) );
                result[source.tagName] = Object.fromXML( source );
        } else if( source.tagName )
            result[source.tagName] = source.nodeValue;
        else if( !source.nextSibling ) {
            if( source.nodeValue.clean() != "" ) {
                result = source.nodeValue.clean();
        source = source.nextSibling;
    return result;

String.prototype.clean = function() {
    var self = this;
    return this.replace(/(\r\n|\n|\r)/gm, "").replace(/^\s+|\s+$/g, "");

Angular - Can't make ng-repeat orderBy work

You're going to have to reformat your releases object to be an array of objects. Then you'll be able to sort them the way you're attempting.

How do I access store state in React Redux?

You should create separate component, which will be listening to state changes and updating on every state change:

import store from '../reducers/store';

class Items extends Component {
  constructor(props) {

    this.state = {
      items: [],

    store.subscribe(() => {
      // When state will be updated(in our case, when items will be fetched), 
      // we will update local component state and force component to rerender 
      // with new data.

        items: store.getState().items;

  render() {
    return (
        { => <p> {item.title} </p> )}

render(<Items />, document.getElementById('app'));

What does the question mark in Java generics' type parameter mean?

Perhaps a contrived "real world" example would help.

At my place of work we have rubbish bins that come in different flavours. All bins contain rubbish, but some bins are specialist and do not take all types of rubbish. So we have Bin<CupRubbish> and Bin<RecylcableRubbish>. The type system needs to make sure I can't put my HalfEatenSandwichRubbish into either of these types, but it can go into a general rubbish bin Bin<Rubbish>. If I wanted to talk about a Bin of Rubbish which may be specialised so I can't put in incompatible rubbish, then that would be Bin<? extends Rubbish>.

(Note: ? extends does not mean read-only. For instance, I can with proper precautions take out a piece of rubbish from a bin of unknown speciality and later put it back in a different place.)

Not sure how much that helps. Pointer-to-pointer in presence of polymorphism isn't entirely obvious.

How can I force component to re-render with hooks in React?

For regular React Class based components, refer to React Docs for the forceUpdate api at this URL. The docs mention that:

Normally you should try to avoid all uses of forceUpdate() and only read from this.props and this.state in render()

However, it is also mentioned in the docs that:

If your render() method depends on some other data, you can tell React that the component needs re-rendering by calling forceUpdate().

So, although use cases for using forceUpdate might be rare, and I have not used it ever, however I have seen it used by other developers in some legacy corporate projects that I have worked on.

So, for the equivalent functionality for Functional Components, refer to the React Docs for HOOKS at this URL. Per the above URL, one can use the "useReducer" hook to provide a forceUpdate functionality for Functional Components.

A working code sample that does not use state or props is provided below, which is also available on CodeSandbox at this URL

import React, { useReducer, useRef } from "react";
import ReactDOM from "react-dom";

import "./styles.css";

function App() {
  // Use the useRef hook to store a mutable value inside a functional component for the counter
  let countref = useRef(0);

  const [, forceUpdate] = useReducer(x => x + 1, 0);

  function handleClick() {
    console.log("Count = ", countref.current);
    forceUpdate(); // If you comment this out, the date and count in the screen will not be updated

  return (
    <div className="App">
      <h1> {new Date().toLocaleString()} </h1>
      <h2>You clicked {countref.current} times</h2>
        onClick={() => {

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

NOTE: An alternate approach using the useState hook (instead of useReducer) is also available at this URL.

Numpy, multiply array with scalar

You can multiply numpy arrays by scalars and it just works.

>>> import numpy as np
>>> np.array([1, 2, 3]) * 2
array([2, 4, 6])
>>> np.array([[1, 2, 3], [4, 5, 6]]) * 2
array([[ 2,  4,  6],
       [ 8, 10, 12]])

This is also a very fast and efficient operation. With your example:

>>> a_1 = np.array([1.0, 2.0, 3.0])
>>> a_2 = np.array([[1., 2.], [3., 4.]])
>>> b = 2.0
>>> a_1 * b
array([2., 4., 6.])
>>> a_2 * b
array([[2., 4.],
       [6., 8.]])

How do I get the max and min values from a set of numbers entered?

This is what I did and it works try and play around with it. It calculates total,avarage,minimum and maximum.

public static void main(String[] args) {
   int[] score= {56,90,89,99,59,67};
   double avg;
   int sum=0;
   int maxValue=0;
   int minValue=100;

   for(int i=0;i<6;i++){
System.out.print("Max: "+maxValue+"," +" Min: "+minValue+","+" Avarage: "+avg+","+" Sum: "+sum);}


Best way to move files between S3 buckets?

We had this exact problem with our ETL jobs at Snowplow, so we extracted our parallel file-copy code (Ruby, built on top of Fog), into its own Ruby gem, called Sluice:

Sluice also handles S3 file delete, move and download; all parallelised and with automatic re-try if an operation fails (which it does surprisingly often). I hope it's useful!

Does reading an entire file leave the file handle open?

The answer to that question depends somewhat on the particular Python implementation.

To understand what this is all about, pay particular attention to the actual file object. In your code, that object is mentioned only once, in an expression, and becomes inaccessible immediately after the read() call returns.

This means that the file object is garbage. The only remaining question is "When will the garbage collector collect the file object?".

in CPython, which uses a reference counter, this kind of garbage is noticed immediately, and so it will be collected immediately. This is not generally true of other python implementations.

A better solution, to make sure that the file is closed, is this pattern:

with open('Path/to/file', 'r') as content_file:
    content =

which will always close the file immediately after the block ends; even if an exception occurs.

Edit: To put a finer point on it:

Other than file.__exit__(), which is "automatically" called in a with context manager setting, the only other way that file.close() is automatically called (that is, other than explicitly calling it yourself,) is via file.__del__(). This leads us to the question of when does __del__() get called?

A correctly-written program cannot assume that finalizers will ever run at any point prior to program termination.


In particular:

Objects are never explicitly destroyed; however, when they become unreachable they may be garbage-collected. An implementation is allowed to postpone garbage collection or omit it altogether — it is a matter of implementation quality how garbage collection is implemented, as long as no objects are collected that are still reachable.


CPython currently uses a reference-counting scheme with (optional) delayed detection of cyclically linked garbage, which collects most objects as soon as they become unreachable, but is not guaranteed to collect garbage containing circular references.


(Emphasis mine)

but as it suggests, other implementations may have other behavior. As an example, PyPy has 6 different garbage collection implementations!

What is an .axd file?

from Google

An .axd file is a HTTP Handler file. There are two types of .axd files.

  1. ScriptResource.axd
  2. WebResource.axd

These are files which are generated at runtime whenever you use ScriptManager in your Web app. This is being generated only once when you deploy it on the server.

Simply put the ScriptResource.AXD contains all of the clientside javascript routines for Ajax. Just because you include a scriptmanager that loads a script file it will never appear as a ScriptResource.AXD - instead it will be merely passed as the .js file you send if you reference a external script file. If you embed it in code then it may merely appear as part of the html as a tag and code but depending if you code according to how the ToolKit handles it - may or may not appear as as a ScriptResource.axd. ScriptResource.axd is only introduced with AJAX and you will never see it elsewhere

And ofcourse it is necessary

How many socket connections can a web server handle?

I think that the number of concurrent socket connections one web server can handle largely depends on the amount of resources each connection consumes and the amount of total resource available on the server barring any other web server resource limiting configuration.

To illustrate, if every socket connection consumed 1MB of server resource and the server has 16GB of RAM available (theoretically) this would mean it would only be able to handle (16GB / 1MB) concurrent connections. I think it's as simple as that... REALLY!

So regardless of how the web server handles connections, every connection will ultimately consume some resource.

How do you specify a byte literal in Java?

You have to cast, I'm afraid:


I believe that will perform the appropriate conversion at compile-time instead of execution time, so it's not actually going to cause performance penalties. It's just inconvenient :(

SELECT using 'CASE' in SQL

Change to:


Isn't the size of character in Java 2 bytes?

Java allocates 2 of 2 bytes for character as it follows UTF-16. It occupies minimum 2 bytes while storing a character, and maximum of 4 bytes. There is no 1 byte or 3 bytes of storage for character.

align textbox and text/labels in html?

You have two boxes, left and right, for each label/input pair. Both boxes are in one row and have fixed width. Now, you just have to make label text float to the right with text-align: right;

Here's a simple example:

How to align a div inside td element using CSS class

div { margin: auto; }

This will center your div.

Div by itself is a blockelement. Therefor you need to define the style to the div how to behave.

Generating a random password in php

Tiny code with 2 line.


function rand_string( $length ) {

    $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    return substr(str_shuffle($chars),0,$length);


echo rand_string(8);

with rand_string you can define how much character will be create.

Is it possible to capture a Ctrl+C signal and run a cleanup function, in a "defer" fashion?

Death is a simple library that uses channels and a wait group to wait for shutdown signals. Once the signal has been received it will then call a close method on all of your structs that you want to cleanup.

Select values of checkbox group with jQuery

You can have a javascript variable which stores the number of checkboxes that are emitted, i.e in the <head> of the page:

<script type="text/javascript">
var num_cboxes=<?php echo $number_of_checkboxes;?>;

So if there are 10 checkboxes, starting from user_group-1 to user_group-10, in the javascript code you would get their value in this way:

var values=new Array();
for (x=1; x<=num_cboxes; x++)
   values[x]=$("#user_group-" + x).val();

Java: Simplest way to get last word in a string

Get the last word in Kotlin:

String.substringAfterLast(" ")

Difference Between Schema / Database in MySQL

PostgreSQL supports schemas, which is a subset of a database:

A database contains one or more named schemas, which in turn contain tables. Schemas also contain other kinds of named objects, including data types, functions, and operators. The same object name can be used in different schemas without conflict; for example, both schema1 and myschema can contain tables named mytable. Unlike databases, schemas are not rigidly separated: a user can access objects in any of the schemas in the database they are connected to, if they have privileges to do so.

Schemas are analogous to directories at the operating system level, except that schemas cannot be nested.

In my humble opinion, MySQL is not a reference database. You should never quote MySQL for an explanation. MySQL implements non-standard SQL and sometimes claims features that it does not support. For example, in MySQL, CREATE schema will only create a DATABASE. It is truely misleading users.

This kind of vocabulary is called "MySQLism" by DBAs.

How to receive POST data in django

res = request.GET['paymentid'] will raise a KeyError if paymentid is not in the GET data.

Your sample php code checks to see if paymentid is in the POST data, and sets $payID to '' otherwise:

$payID = isset($_POST['paymentid']) ? $_POST['paymentid'] : ''

The equivalent in python is to use the get() method with a default argument:

payment_id = request.POST.get('payment_id', '')

while debugging, this is what I see in the response.GET: <QueryDict: {}>, request.POST: <QueryDict: {}>

It looks as if the problem is not accessing the POST data, but that there is no POST data. How are you are debugging? Are you using your browser, or is it the payment gateway accessing your page? It would be helpful if you shared your view.

Once you are managing to submit some post data to your page, it shouldn't be too tricky to convert the sample php to python.

How can I sort one set of data to match another set of data in Excel?

You could also simply link both cells, and have an =Cell formula in each column like, =Sheet2!A2 in Sheet 1 A2 and =Sheet2!B2 in Sheet 1 B2, and drag it down, and then sort those two columns the way you want.

  • If they don't sort the way you want, put the order you want to sort them in another column and sort all three columns by that.
  • If you drag it down further and get zeros you can edit the =Cell formula to show "" IF there is nothing. =(if(cell="","",cell)
  • Cutting, pasting, deleting, and inserting rows is something to be weary of. #REF! errors could occur.

This would be better if your unique items change also, then all you would do is sort and be done.

Docker Repository Does Not Have a Release File on Running apt-get update on Ubuntu

Linux Mint 20 Ulyana users need to change "ulyana" to "bionic" in


like so:

deb [arch=amd64]    bionic    stable

DB2 Query to retrieve all table names for a given schema

    type = 'T'
    creator = 'MySchema'
    name LIKE 'book_%';

Call a Subroutine from a different Module in VBA

Prefix the call with Module2 (ex. Module2.IDLE). I'm assuming since you asked this that you have IDLE defined multiple times in the project, otherwise this shouldn't be necessary.

re.sub erroring with "Expected string or bytes-like object"

The simplest solution is to apply Python str function to the column you are trying to loop through.

If you are using pandas, this can be implemented as:


Usage of __slots__?

Another somewhat obscure use of __slots__ is to add attributes to an object proxy from the ProxyTypes package, formerly part of the PEAK project. Its ObjectWrapper allows you to proxy another object, but intercept all interactions with the proxied object. It is not very commonly used (and no Python 3 support), but we have used it to implement a thread-safe blocking wrapper around an async implementation based on tornado that bounces all access to the proxied object through the ioloop, using thread-safe concurrent.Future objects to synchronise and return results.

By default any attribute access to the proxy object will give you the result from the proxied object. If you need to add an attribute on the proxy object, __slots__ can be used.

from peak.util.proxies import ObjectWrapper

class Original(object):
    def __init__(self): = 'The Original'

class ProxyOriginal(ObjectWrapper):

    __slots__ = ['proxy_name']

    def __init__(self, subject, proxy_name):
        # proxy_info attributed added directly to the
        # Original instance, not the ProxyOriginal instance
        self.proxy_info = 'You are proxied by {}'.format(proxy_name)

        # proxy_name added to ProxyOriginal instance, since it is
        # defined in __slots__
        self.proxy_name = proxy_name

        super(ProxyOriginal, self).__init__(subject)

if __name__ == "__main__":
    original = Original()
    proxy = ProxyOriginal(original, 'Proxy Overlord')

    # Both statements print "The Original"
    print " ",
    print " ",

    # Both statements below print 
    # "You are proxied by Proxy Overlord", since the ProxyOriginal
    # __init__ sets it to the original object 
    print "original.proxy_info: ", original.proxy_info
    print "proxy.proxy_info: ", proxy.proxy_info

    # prints "Proxy Overlord"
    print "proxy.proxy_name: ", proxy.proxy_name
    # Raises AttributeError since proxy_name is only set on 
    # the proxy object
    print "original.proxy_name: ", proxy.proxy_name

MySQL Great Circle Distance (Haversine formula)

$greatCircleDistance = acos( cos($latitude0) * cos($latitude1) * cos($longitude0 - $longitude1) + sin($latitude0) * sin($latitude1));

with latitude and longitude in radian.


      cos(radians( $latitude0 ))
    * cos(radians( $latitude1 ))
    * cos(radians( $longitude0 ) - radians( $longitude1 ))
    + sin(radians( $latitude0 )) 
    * sin(radians( $latitude1 ))
  ) AS greatCircleDistance 
 FROM yourTable;

is your SQL query

to get your results in Km or miles, multiply the result with the mean radius of Earth (3959 miles,6371 Km or 3440 nautical miles)

The thing you are calculating in your example is a bounding box. If you put your coordinate data in a spatial enabled MySQL column, you can use MySQL's build in functionality to query the data.

FROM spatialEnabledTable
  MBRWithin(ogc_point, GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))'))

Symfony2 Setting a default choice field selection

If you use Cristian's solution, you'll need to inject the EntityManager into your FormType class. Here is a simplified example:

class EntityType extends AbstractType{
    public function __construct($em) {
        $this->em = $em;

    public function buildForm(FormBuilderInterface $builder, array $options){
             ->add('MyEntity', 'entity', array(
                     'class' => 'AcmeDemoBundle:Entity',
                     'property' => 'name',
                     'query_builder' => function(EntityRepository $er) {
                         return $er->createQueryBuilder('e')
                             ->orderBy('', 'ASC');
                     'data' => $this->em->getReference("AcmeDemoBundle:Entity", 3)

And your controller:

 // ...    

 $form = $this->createForm(new EntityType($this->getDoctrine()->getManager()), $entity);

// ...

From Doctrine Docs:

The method EntityManager#getReference($entityName, $identifier) lets you obtain a reference to an entity for which the identifier is known, without loading that entity from the database. This is useful, for example, as a performance enhancement, when you want to establish an association to an entity for which you have the identifier.

How do you add an ActionListener onto a JButton in Java

I'm didn't totally follow, but to add an action listener, you just call addActionListener (from Abstract Button). If this doesn't totally answer your question, can you provide some more details?

Spring @PropertySource using YAML

From Spring Boot 1.4, you can use the new @SpringBootTest annotation to achieve this more easily (and to simplify your integration test setup in general) by bootstrapping your integration tests using Spring Boot support.

Details on the Spring Blog.

As far as I can tell, this means you get all the benefits of Spring Boot's externalized config goodness just like in your production code, including automatically picking up YAML config from the classpath.

By default, this annotation will

... first attempt to load @Configuration from any inner-classes, and if that fails, it will search for your primary @SpringBootApplication class.

but you can specify other configuration classes if required.

For this particular case, you can combine @SpringBootTest with @ActiveProfiles( "test" ) and Spring will pick up your YAML config, provided it follows the normal Boot naming standards (i.e. application-test.yml).

@RunWith( SpringRunner.class )
@ActiveProfiles( "test" )
public class SpringBootITest {

    private String username;

    private MyBean myBean;



Note: SpringRunner.class is the new name for SpringJUnit4ClassRunner.class

Python circular importing?

If you run into this issue in a fairly complex app it can be cumbersome to refactor all your imports. PyCharm offers a quickfix for this that will automatically change all usage of the imported symbols as well.

enter image description here

Short description of the scoping rules?

Python resolves your variables with -- generally -- three namespaces available.

At any time during execution, there are at least three nested scopes whose namespaces are directly accessible: the innermost scope, which is searched first, contains the local names; the namespaces of any enclosing functions, which are searched starting with the nearest enclosing scope; the middle scope, searched next, contains the current module's global names; and the outermost scope (searched last) is the namespace containing built-in names.

There are two functions: globals and locals which show you the contents two of these namespaces.

Namespaces are created by packages, modules, classes, object construction and functions. There aren't any other flavors of namespaces.

In this case, the call to a function named x has to be resolved in the local name space or the global namespace.

Local in this case, is the body of the method function Foo.spam.

Global is -- well -- global.

The rule is to search the nested local spaces created by method functions (and nested function definitions), then search global. That's it.

There are no other scopes. The for statement (and other compound statements like if and try) don't create new nested scopes. Only definitions (packages, modules, functions, classes and object instances.)

Inside a class definition, the names are part of the class namespace. code2, for instance, must be qualified by the class name. Generally Foo.code2. However, self.code2 will also work because Python objects look at the containing class as a fall-back.

An object (an instance of a class) has instance variables. These names are in the object's namespace. They must be qualified by the object. (variable.instance.)

From within a class method, you have locals and globals. You say self.variable to pick the instance as the namespace. You'll note that self is an argument to every class member function, making it part of the local namespace.

See Python Scope Rules, Python Scope, Variable Scope.

Assembly code vs Machine code vs Object code?

Machine code is binary (1's and 0's) code that can be executed directly by the CPU. If you open a machine code file in a text editor you would see garbage, including unprintable characters (no, not those unprintable characters ;) ).

Object code is a portion of machine code not yet linked into a complete program. It's the machine code for one particular library or module that will make up the completed product. It may also contain placeholders or offsets not found in the machine code of a completed program. The linker will use these placeholders and offsets to connect everything together.

Assembly code is plain-text and (somewhat) human read-able source code that mostly has a direct 1:1 analog with machine instructions. This is accomplished using mnemonics for the actual instructions, registers, or other resources. Examples include JMP and MULT for the CPU's jump and multiplication instructions. Unlike machine code, the CPU does not understand assembly code. You convert assembly code to machine code with the use of an assembler or a compiler, though we usually think of compilers in association with high-level programming language that are abstracted further from the CPU instructions.

Building a complete program involves writing source code for the program in either assembly or a higher level language like C++. The source code is assembled (for assembly code) or compiled (for higher level languages) to object code, and individual modules are linked together to become the machine code for the final program. In the case of very simple programs the linking step may not be needed. In other cases, such as with an IDE (integrated development environment) the linker and compiler may be invoked together. In other cases, a complicated make script or solution file may be used to tell the environment how to build the final application.

There are also interpreted languages that behave differently. Interpreted languages rely on the machine code of a special interpreter program. At the basic level, an interpreter parses the source code and immediately converts the commands to new machine code and executes them. Modern interpreters are now much more complicated: evaluating whole sections of source code at a time, caching and optimizing where possible, and handling complex memory management tasks.

One final type of program involves the use of a runtime-environment or virtual machine. In this situation, a program is first pre-compiled to a lower-level intermediate language or byte code. The byte code is then loaded by the virtual machine, which just-in-time compiles it to native code. The advantage here is the virtual machine can take advantage of optimizations available at the time the program runs and for that specific environment. A compiler belongs to the developer, and therefore must produce relatively generic (less-optimized) machine code that could run in many places. The runtime environment or virtual machine, however, is located on the end user's computer and therefore can take advantage of all the features provided by that system.

The Android emulator is not starting, showing "invalid command-line parameter"

There is currently a problem with R12 where the SDK location cannot contain any spaces.

The default installation location is: C:\Programme Files(x86)\Android\android-sdk. They are currently fixing the problem but you can currently work around it by changing the SDK location path in eclipse to C:\PROGRA~2\Android\android-sdk.

If you are running 32-bit Windows, change the path to C:\PROGRA~1\Android\android-sdk.

how to remove json object key and value.?

Follow this, it can be like what you are looking:

var obj = {_x000D_
    Objone: 'one',_x000D_
    Objtwo: 'two'_x000D_
var key = "Objone";_x000D_
delete obj[key];_x000D_
console.log(obj); // prints { "objtwo": two}

How to POST JSON data with Python Requests?

From requests 2.4.2 (, the "json" parameter is supported. No need to specify "Content-Type". So the shorter version:'', json={'test': 'cheers'})

Why there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT clause?

Well a fix for you could be to put it on the UpdatedDate field and have a trigger that updates the AddedDate field with the UpdatedDate value only if AddedDate is null.

Select the top N values by group

If there were a tie at the fourth position for mtcars$mpg then this should return all the ties:

top_mpg <- mtcars[ mtcars$mpg >= mtcars$mpg[order(mtcars$mpg, decreasing=TRUE)][4] , ]

> top_mpg
                mpg cyl disp  hp drat    wt  qsec vs am gear carb
Fiat 128       32.4   4 78.7  66 4.08 2.200 19.47  1  1    4    1
Honda Civic    30.4   4 75.7  52 4.93 1.615 18.52  1  1    4    2
Toyota Corolla 33.9   4 71.1  65 4.22 1.835 19.90  1  1    4    1
Lotus Europa   30.4   4 95.1 113 3.77 1.513 16.90  1  1    5    2

Since there is a tie at the 3-4 position you can test it by changing 4 to a 3, and it still returns 4 items. This is logical indexing and you might need to add a clause that removes the NA's or wrap which() around the logical expression. It's not much more difficult to do this "by" cyl:

 Reduce(rbind,  by(mtcars, mtcars$cyl, 
        function(d) d[ d$mpg >= d$mpg[order(d$mpg, decreasing=TRUE)][4] , ]) )
                   mpg cyl  disp  hp drat    wt  qsec vs am gear carb
Fiat 128          32.4   4  78.7  66 4.08 2.200 19.47  1  1    4    1
Honda Civic       30.4   4  75.7  52 4.93 1.615 18.52  1  1    4    2
Toyota Corolla    33.9   4  71.1  65 4.22 1.835 19.90  1  1    4    1
Lotus Europa      30.4   4  95.1 113 3.77 1.513 16.90  1  1    5    2
Mazda RX4         21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
Mazda RX4 Wag     21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
Hornet 4 Drive    21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
Ferrari Dino      19.7   6 145.0 175 3.62 2.770 15.50  0  1    5    6
Hornet Sportabout 18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2
Merc 450SE        16.4   8 275.8 180 3.07 4.070 17.40  0  0    3    3
Merc 450SL        17.3   8 275.8 180 3.07 3.730 17.60  0  0    3    3
Pontiac Firebird  19.2   8 400.0 175 3.08 3.845 17.05  0  0    3    2

Incorporating my suggestion to @Ista:

Reduce(rbind,  by(mtcars, mtcars$cyl, function(d) d[ d$mpg <= sort( d$mpg )[3] , ]) )

builder for HashMap

Here is a very simple one ...

public class FluentHashMap<K, V> extends java.util.HashMap<K, V> {
  public FluentHashMap<K, V> with(K key, V value) {
    put(key, value);
    return this;

  public static <K, V> FluentHashMap<K, V> map(K key, V value) {
    return new FluentHashMap<K, V>().with(key, value);


import static;

HashMap<String, Integer> m = map("a", 1).with("b", 2);


When to use a View instead of a Table?

According to Wikipedia,

Views can provide many advantages over tables:

  • Views can represent a subset of the data contained in a table.
  • Views can limit the degree of exposure of the underlying tables to the outer world: a given user may have permission to query the view, while denied access to the rest of the base table.

  • Views can join and simplify multiple tables into a single virtual table.

  • Views can act as aggregated tables, where the database engine aggregates data (sum, average, etc.) and presents the calculated results as part of the data.

  • Views can hide the complexity of data. For example, a view could appear as Sales2000 or Sales2001, transparently partitioning the actual underlying table.

  • Views take very little space to store; the database contains only the definition of a view, not a copy of all the data that it presents.

  • Views can provide extra security, depending on the SQL engine used.

Increasing the timeout value in a WCF service

Are you referring to the server side or the client side?

For a client, you would want to adjust the sendTimeout attribute of a binding element. For a service, you would want to adjust the receiveTimeout attribute of a binding elemnent.

      <binding name="longTimeoutBinding"
        receiveTimeout="00:10:00" sendTimeout="00:10:00">
        <security mode="None"/>

    <service name="longTimeoutService"
      <endpoint address="net.tcp://localhost/longtimeout/"
        binding="netTcpBinding" bindingConfiguration="longTimeoutBinding" />

Of course, you have to map your desired endpoint to that particular binding.

Build an iOS app without owning a mac?

Most framework like React Native and Ionic allows you to built on their server. Meaning that they can help you compile and provide you with and .ipa file.

The problem is you need Xcode or Application loader to submit your app to Apple App Store Connect. Both of these are only available on OSX. To overcome this solution you have 2 options that I am aware of

  1. Rent mac virtually.
  2. Use website that helps you to upload your app (You need to have .ipa file).

LF will be replaced by CRLF in git - What is that and is it important?

In Unix systems the end of a line is represented with a line feed (LF). In windows a line is represented with a carriage return (CR) and a line feed (LF) thus (CRLF). when you get code from git that was uploaded from a unix system they will only have an LF.

If you are a single developer working on a windows machine, and you don't care that git automatically replaces LFs to CRLFs, you can turn this warning off by typing the following in the git command line

git config core.autocrlf true

If you want to make an intelligent decision how git should handle this, read the documentation

Here is a snippet

Formatting and Whitespace

Formatting and whitespace issues are some of the more frustrating and subtle problems that many developers encounter when collaborating, especially cross-platform. It’s very easy for patches or other collaborated work to introduce subtle whitespace changes because editors silently introduce them, and if your files ever touch a Windows system, their line endings might be replaced. Git has a few configuration options to help with these issues.


If you’re programming on Windows and working with people who are not (or vice-versa), you’ll probably run into line-ending issues at some point. This is because Windows uses both a carriage-return character and a linefeed character for newlines in its files, whereas Mac and Linux systems use only the linefeed character. This is a subtle but incredibly annoying fact of cross-platform work; many editors on Windows silently replace existing LF-style line endings with CRLF, or insert both line-ending characters when the user hits the enter key.

Git can handle this by auto-converting CRLF line endings into LF when you add a file to the index, and vice versa when it checks out code onto your filesystem. You can turn on this functionality with the core.autocrlf setting. If you’re on a Windows machine, set it to true – this converts LF endings into CRLF when you check out code:

$ git config --global core.autocrlf true

If you’re on a Linux or Mac system that uses LF line endings, then you don’t want Git to automatically convert them when you check out files; however, if a file with CRLF endings accidentally gets introduced, then you may want Git to fix it. You can tell Git to convert CRLF to LF on commit but not the other way around by setting core.autocrlf to input:

$ git config --global core.autocrlf input

This setup should leave you with CRLF endings in Windows checkouts, but LF endings on Mac and Linux systems and in the repository.

If you’re a Windows programmer doing a Windows-only project, then you can turn off this functionality, recording the carriage returns in the repository by setting the config value to false:

$ git config --global core.autocrlf false

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

Using read_delim function, which is part of readr library, you can specify additional parameter:

locale = locale(decimal_mark = ",")

read_delim("filetoread.csv", ';", locale = locale(decimal_mark = ","))

*Semicolon in second line means that read_delim will read csv semicolon separated values.

This will help to read all numbers with a comma as proper numbers.


Mateusz Kania

Is it possible to install iOS 6 SDK on Xcode 5?

I downloaded XCode 4 and took iOS 6.1 SDK from it to the XCode 5 as described in other answers. Then I also installed iOS 6.1 Simulator (it was available in preferences). I also switched Base SDK to iOS 6.1 in project settings.

After all these manipulations the project with 6.1 base sdk runs in comp ability mode in iOS 7 Simulator.

How to redirect user's browser URL to a different page in Nodejs?

OP: "I would love if there were a way to do it where I didn't have to know the host address..."

response.writeHead(301, {
  Location: "http" + (request.socket.encrypted ? "s" : "") + "://" + + newRoom

This declaration has no storage class or type specifier in C++

This is a mistake:


That code has to go inside a function. Your class definition can only contain declarations and functions.

Classes don't "run", they provide a blueprint for how to make an object.

The line Message m; means that an Orderbook will contain Message called m, if you later create an Orderbook.

Padding between ActionBar's home icon and title

For my case, it was with Toolbar i resolved it like this:


<layer-list xmlns:android="">

In my Fragment, i check the api :


Good luck!

Unable to Git-push master to Github - 'origin' does not appear to be a git repository / permission denied

VonC's answer is best, but the part that worked for me was super simple and is kind of buried among a lot of other possible answers. If you are like me, you ran into this issue while running a "getting started with rails" tutorial and you had NOT setup your public/private SSH keys.

If so, try this:

  1. $>cd ~/.ssh

  2. $>ls

  3. If the output of ls is known_hosts and nothing else, visit: and start following the instructions from the "Generating a key" section and down.

After running those instructions, my "git push origin master" command worked.

How do you get the magnitude of a vector in Numpy?

You can do this concisely using the toolbelt vg. It's a light layer on top of numpy and it supports single values and stacked vectors.

import numpy as np
import vg

x = np.array([1, 2, 3, 4, 5])
mag1 = np.linalg.norm(x)
mag2 = vg.magnitude(x)
print mag1 == mag2
# True

I created the library at my last startup, where it was motivated by uses like this: simple ideas which are far too verbose in NumPy.

How to escape % in String.Format?

This is a stronger regex replace that won't replace %% that are already doubled in the input.

str = str.replaceAll("(?:[^%]|\\A)%(?:[^%]|\\z)", "%%");

How to cancel/abort jQuery AJAX request?

jQuery: Use this as a starting point - as inspiration. I solved it like this: (this is not a perfect solution, it just aborts the last instance and is WIP code)

var singleAjax = function singleAjax_constructor(url, params) {
    // remember last jQuery's get request
    if (this.lastInstance) {
        this.lastInstance.abort();  // triggers .always() and .fail()
        this.lastInstance = false;

    // how to use Deferred :
    var $def = new $.Deferred();

    // pass the deferrer's request handlers into the get response handlers
    this.lastInstance = $.get(url, params)
        .fail($def.reject)         // triggers .always() and .fail()
        .success($def.resolve);    // triggers .always() and .done()

    // return the deferrer's "control object", the promise object
    return $def.promise();

// initiate first call
singleAjax('/ajax.php', {a: 1, b: 2})
    .always(function(a,b,c) {console && console.log(a,b,c);});

// second call kills first one
singleAjax('/ajax.php', {a: 1, b: 2})
    .always(function(a,b,c) {console && console.log(a,b,c);});
    // here you might use .always() .fail() .success() etc.

Editable 'Select' element

Another sort of workaround might be...

Use the HTML:

<input type="text" id="myselect"/>
<datalist id="myselect">
<option>option 1</option>
<option>option 2</option>
<option>option 3</option>
<option>option 4</option>

In Firefox at least a focus followed by a click drops down the list of known valid values as the <datalist> elements IFF the field happens to be empty. Otherwise, one must clear the field to see valid choices as one types in data. A new value is accepted as typed. One must handle new values in JS or other to persist them.

This is not perfect, but it suffices for my minimalist needs, so I thought I would share.

In PowerShell, how do I test whether or not a specific variable exists in global scope?

There's an even easier way:

if ($variable)
    Write-Host "bar exist"
    Write-Host "bar does not exists"

What does the @Valid annotation indicate in Spring?

It's for validation purposes.

Validation It is common to validate a model after binding user input to it. Spring 3 provides support for declarative validation with JSR-303. This support is enabled automatically if a JSR-303 provider, such as Hibernate Validator, is present on your classpath. When enabled, you can trigger validation simply by annotating a Controller method parameter with the @Valid annotation: After binding incoming POST parameters, the AppointmentForm will be validated; in this case, to verify the date field value is not null and occurs in the future.

Look here for more info:

How to center a button within a div?

Updated Answer

Updating because I noticed it's an active answer, however Flexbox would be the correct approach now.

Live Demo

Vertical and horizontal alignment.

#wrapper {
  display: flex;
  align-items: center;
  justify-content: center;

Just horizontal (as long as the main flex axis is horizontal which is default)

#wrapper {
  display: flex;
  justify-content: center;

Original Answer using a fixed width and no flexbox

If the original poster wants vertical and center alignment its quite easy for fixed width and height of the button, try the following

Live Demo


    margin: -20px -50px; 

for just horizontal alignment use either

    margin: 0 auto;



iPhone App Development on Ubuntu

I found one interesting site which seems pretty detailed on how you could setup a ubuntu for iPhone development. But it's a little old from November 2008 for the SDK 2.0.

Ubuntu 8.10 for iPhone open toolchain SDK2.0

The instructions also include something about the Android SDK/Emulator which you can leave out.

Android Studio - local path doesn't exist

For me uninstalling the app from the device works. :)

Which characters are valid in CSS class names/selectors?

To my surprise most answers here are wrong. It turns out that:

Any character except NUL is allowed in CSS class names in CSS. (If CSS contains NUL (escaped or not), the result is undefined. [CSS-characters])

Mathias Bynens' answer links to explanation and demos showing how to use these names. Written down in CSS code, a class name may need escaping, but that doesn’t change the class name. E.g. an unnecessarily over-escaped representation will look different from other representations of that name, but it still refers to the same class name.

Most other (programming) languages don’t have that concept of escaping variable names (“identifiers”), so all representations of a variable have to look the same. This is not the case in CSS.

Note that in HTML there is no way to include space characters (space, tab, line feed, form feed and carriage return) in a class name attribute, because they already separate classes from each other.

So, if you need to turn a random string into a CSS class name: take care of NUL and space, and escape (accordingly for CSS or HTML). Done.

Missing XML comment for publicly visible type or member

In your solution, once you check the option to generate XML Document file, it start checking your public members, for having the XMLDoc, if they don't, you'll receive a warning per each element. if you don't really want to release your DLL, and also you don't need documentations then, go to your solution, build section, and turn it off, else if you need it, so fill them, and if there are unimportant properties and fields, just surpass them with pre-compiler instruction #pragma warning disable 1591 you can also restore the warning : #pragma warning restore 1591

pragma usage: any where in code before the place you get compiler warning for... (for file, put it in header, and you do not need to enable it again, for single class wrap around a class, or for method wrap around a method, or ... you do not either need to wrap it around, you can call it and restore it casually (start in begin of file, and end inside a method)), write this code:

#pragma warning disable 1591 and in case you need to restore it, use: #pragma warning restore 1591

Here an example:

using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using MongoDB.Bson;
using MongoDB.Bson.Serialization.Attributes;
using RealEstate.Entity.Models.Base;

namespace RealEstate.Models.Base
    public class CityVM

#pragma warning disable 1591

        public string Id { get; set; }

        public string Name { get; set; }

        public List<LanguageBasedName> LanguageBasedNames { get; set; }

        public string CountryId { get; set; }

#pragma warning restore 1591

        /// <summary>
        /// Some countries do not have neither a State, nor a Province
        /// </summary>
        public string StateOrProvinceId { get; set; }

Note that pragma directive start at the begin of line

What is the difference between .text, .value, and .value2?

.Text is the formatted cell's displayed value; .Value is the value of the cell possibly augmented with date or currency indicators; .Value2 is the raw underlying value stripped of any extraneous information.

range("A1") = Date
range("A1").numberformat = "yyyy-mm-dd"
debug.print range("A1").text
debug.print range("A1").value
debug.print range("A1").value2

'results from Immediate window

range("A1") = "abc"
range("A1").numberformat = "_(_(_(@"
debug.print range("A1").text
debug.print range("A1").value
debug.print range("A1").value2

'results from Immediate window

range("A1") = 12
range("A1").numberformat = "0 \m\m"
debug.print range("A1").text
debug.print range("A1").value
debug.print range("A1").value2

'results from Immediate window
12 mm

If you are processing the cell's value then reading the raw .Value2 is marginally faster than .Value or .Text. If you are locating errors then .Text will return something like #N/A as text and can be compared to a string while .Value and .Value2 will choke comparing their returned value to a string. If you have some custom cell formatting applied to your data then .Text may be the better choice when building a report.

Cannot kill Python script with Ctrl-C

I think it's best to call join() on your threads when you expect them to die. I've taken some liberty with your code to make the loops end (you can add whatever cleanup needs are required to there as well). The variable die is checked for truth on each pass and when it's True then the program exits.

import threading
import time

class MyThread (threading.Thread):
    die = False
    def __init__(self, name):
        threading.Thread.__init__(self) = name

    def run (self):
        while not self.die:
            print (

    def join(self):
        self.die = True

if __name__ == '__main__':
    f = MyThread('first')
    s = MyThread('second')
        while True:
    except KeyboardInterrupt:

How do I set headers using python's urllib?

For both Python 3 and Python 2, this works:

    from urllib.request import Request, urlopen  # Python 3
except ImportError:
    from urllib2 import Request, urlopen  # Python 2

req = Request('')
req.add_header('apikey', 'xxx')
content = urlopen(req).read()


Removing Data From ElasticSearch

For mass-delete by query you may use special delete by query API:

$ curl -XDELETE 'http://localhost:9200/twitter/tweet/_query' -d '{
    "query" : {
        "term" : { "user" : "kimchy" }

In history that API was deleted and then reintroduced again

Who interesting it has long history.

  1. In first version of that answer I refer to documentation of elasticsearch version 1.6. In it that functionality was marked as deprecated but works good.
  2. In elasticsearch version 2.0 it was moved to separate plugin. And even reasons why it became plugin explained.
  3. And it again appeared in core API in version 5.0!

Easiest way to pass an AngularJS scope variable from directive to controller?

Wait until angular has evaluated the variable

I had a lot of fiddling around with this, and couldn't get it to work even with the variable defined with "=" in the scope. Here's three solutions depending on your situation.

Solution #1

I found that the variable was not evaluated by angular yet when it was passed to the directive. This means that you can access it and use it in the template, but not inside the link or app controller function unless we wait for it to be evaluated.

If your variable is changing, or is fetched through a request, you should use $observe or $watch:

app.directive('yourDirective', function () {
    return {
        restrict: 'A',
        // NB: no isolated scope!!
        link: function (scope, element, attrs) {
            // observe changes in attribute - could also be scope.$watch
            attrs.$observe('yourDirective', function (value) {
                if (value) {
                    // pass value to app controller
                    scope.variable = value;
        // the variable is available in directive controller,
        // and can be fetched as done in link function
        controller: ['$scope', '$element', '$attrs',
            function ($scope, $element, $attrs) {
                // observe changes in attribute - could also be scope.$watch
                $attrs.$observe('yourDirective', function (value) {
                    if (value) {
                        // pass value to app controller
                        $scope.variable = value;
.controller('MyCtrl', ['$scope', function ($scope) {
    // variable passed to app controller
    $scope.$watch('variable', function (value) {
        if (value) {

And here's the html (remember the brackets!):

<div ng-controller="MyCtrl">
    <div your-directive="{{ someObject.someVariable }}"></div>
    <!-- use ng-bind in stead of {{ }}, when you can to avoids FOUC -->
    <div ng-bind="variable"></div>

Note that you should not set the variable to "=" in the scope, if you are using the $observe function. Also, I found that it passes objects as strings, so if you're passing objects use solution #2 or scope.$watch(attrs.yourDirective, fn) (, or #3 if your variable is not changing).

Solution #2

If your variable is created in e.g. another controller, but just need to wait until angular has evaluated it before sending it to the app controller, we can use $timeout to wait until the $apply has run. Also we need to use $emit to send it to the parent scope app controller (due to the isolated scope in the directive):

app.directive('yourDirective', ['$timeout', function ($timeout) {
    return {
        restrict: 'A',
        // NB: isolated scope!!
        scope: {
            yourDirective: '='
        link: function (scope, element, attrs) {
            // wait until after $apply
                // use scope.$emit to pass it to controller
                scope.$emit('notification', scope.yourDirective);
        // the variable is available in directive controller,
        // and can be fetched as done in link function
        controller: [ '$scope', function ($scope) {
            // wait until after $apply
                // use $scope.$emit to pass it to controller
                $scope.$emit('notification', scope.yourDirective);
.controller('MyCtrl', ['$scope', function ($scope) {
    // variable passed to app controller
    $scope.$on('notification', function (evt, value) {
        $scope.variable = value;

And here's the html (no brackets!):

<div ng-controller="MyCtrl">
    <div your-directive="someObject.someVariable"></div>
    <!-- use ng-bind in stead of {{ }}, when you can to avoids FOUC -->
    <div ng-bind="variable"></div>

Solution #3

If your variable is not changing and you need to evaluate it in your directive, you can use the $eval function:

app.directive('yourDirective', function () {
    return {
        restrict: 'A',
        // NB: no isolated scope!!
        link: function (scope, element, attrs) {
            // executes the expression on the current scope returning the result
            // and adds it to the scope
            scope.variable = scope.$eval(attrs.yourDirective);

        // the variable is available in directive controller,
        // and can be fetched as done in link function
        controller: ['$scope', '$element', '$attrs',
            function ($scope, $element, $attrs) {
                // executes the expression on the current scope returning the result
                // and adds it to the scope
                scope.variable = scope.$eval($attrs.yourDirective);
.controller('MyCtrl', ['$scope', function ($scope) {
    // variable passed to app controller
    $scope.$watch('variable', function (value) {
        if (value) {

And here's the html (remember the brackets!):

<div ng-controller="MyCtrl">
    <div your-directive="{{ someObject.someVariable }}"></div>
    <!-- use ng-bind instead of {{ }}, when you can to avoids FOUC -->
    <div ng-bind="variable"></div>

Also, have a look at this answer:

Reference for FOUC (flash of unstyled content) issue:

For the interested: here's an article on the angular life cycle

ImportError: No module named six

For Mac OS X:

pip install --ignore-installed six

Import multiple csv files into pandas and concatenate into one DataFrame

import os

os.system("awk '(NR == 1) || (FNR > 1)' file*.csv > merged.csv")

Where NR and FNR represent the number of the line being processed.

FNR is the current line within each file.

NR == 1 includes the first line of the first file (the header), while (FNR > 1) skips the first line of each subsequent file.

How to create a blank/empty column with SELECT query in oracle?

In DB2, using single quotes instead of your double quotes will work. So that could translate the same in Oracle..

SELECT CustomerName AS Customer, '' AS Contact 
FROM Customers;

C#: List All Classes in Assembly

I'd just like to add to Jon's example. To get a reference to your own assembly, you can use:

Assembly myAssembly = Assembly.GetExecutingAssembly();

System.Reflection namespace.

If you want to examine an assembly that you have no reference to, you can use either of these:

Assembly assembly = Assembly.ReflectionOnlyLoad(fullAssemblyName);
Assembly assembly = Assembly.ReflectionOnlyLoadFrom(fileName);

If you intend to instantiate your type once you've found it:

Assembly assembly = Assembly.Load(fullAssemblyName);
Assembly assembly = Assembly.LoadFrom(fileName);

See the Assembly class documentation for more information.

Once you have the reference to the Assembly object, you can use assembly.GetTypes() like Jon already demonstrated.

geom_smooth() what are the methods available?

The method argument specifies the parameter of the smooth statistic. You can see stat_smooth for the list of all possible arguments to the method argument.

How to configure custom PYTHONPATH with VM and PyCharm?

An update to the correct answer phil provided, for more recent versions of Pycharm (e.g. 2019.2).

Go to File > Settings and find your project, then select Project Interpreter. Now click the button with a cog to the right of the selected project interpreter (used to be a ...).

enter image description here

From the drop-down menu select Show All... and in the dialog that opens click the icon with a folder and two sub-folders.

enter image description here

You are presented with a dialog with the current interpreter paths, click on + to add one more.

BeautifulSoup getText from between <p>, not picking up subsequent paragraphs

You are getting close!

# Find all of the text between paragraph tags and strip out the html
page = soup.find('p').getText()

Using find (as you've noticed) stops after finding one result. You need find_all if you want all the paragraphs. If the pages are formatted consistently ( just looked over one), you could also use something like


to zero in on the body of the article.

Is having an 'OR' in an INNER JOIN condition a bad idea?

You can use UNION ALL instead.

SELECT mt.ID, mt.ParentID, ot.MasterID FROM dbo.MainTable AS mt Union ALL SELECT mt.ID, mt.ParentID, ot.MasterID FROM dbo.OtherTable AS ot

What is the difference between Left, Right, Outer and Inner Joins?

Simple Example: Let's say you have a Students table, and a Lockers table. In SQL, the first table you specify in a join, Students, is the LEFT table, and the second one, Lockers, is the RIGHT table.

Each student can be assigned to a locker, so there is a LockerNumber column in the Student table. More than one student could potentially be in a single locker, but especially at the beginning of the school year, you may have some incoming students without lockers and some lockers that have no students assigned.

For the sake of this example, let's say you have 100 students, 70 of which have lockers. You have a total of 50 lockers, 40 of which have at least 1 student and 10 lockers have no student.

INNER JOIN is equivalent to "show me all students with lockers".
Any students without lockers, or any lockers without students are missing.
Returns 70 rows

LEFT OUTER JOIN would be "show me all students, with their corresponding locker if they have one".
This might be a general student list, or could be used to identify students with no locker.
Returns 100 rows

RIGHT OUTER JOIN would be "show me all lockers, and the students assigned to them if there are any".
This could be used to identify lockers that have no students assigned, or lockers that have too many students.
Returns 80 rows (list of 70 students in the 40 lockers, plus the 10 lockers with no student)

FULL OUTER JOIN would be silly and probably not much use.
Something like "show me all students and all lockers, and match them up where you can"
Returns 110 rows (all 100 students, including those without lockers. Plus the 10 lockers with no student)

CROSS JOIN is also fairly silly in this scenario.
It doesn't use the linked lockernumber field in the students table, so you basically end up with a big giant list of every possible student-to-locker pairing, whether or not it actually exists.
Returns 5000 rows (100 students x 50 lockers). Could be useful (with filtering) as a starting point to match up the new students with the empty lockers.

Pick images of root folder from sub-folder

../ takes you one folder up the directory tree. Then, select the appropriate folder and its contents.


Mongoose.js: Find user by username LIKE value

if I want to query all record at some condition,I can use this:

if (userId == 'admin')
  userId = {'$regex': '.*.*'};
User.where('status', 1).where('creator', userId);

Number of days in particular month of particular year?

Code for java.util.Calendar

If you have to use java.util.Calendar, I suspect you want:

int days = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);

Code for Joda Time

Personally, however, I'd suggest using Joda Time instead of java.util.{Calendar, Date} to start with, in which case you could use:

int days = chronology.dayOfMonth().getMaximumValue(date);

Note that rather than parsing the string values individually, it would be better to get whichever date/time API you're using to parse it. In java.util.* you might use SimpleDateFormat; in Joda Time you'd use a DateTimeFormatter.

Using CSS in Laravel views?

Use {!! in new laravel

{!! asset('js/app.min.js') !!}

<script type="text/javascript" src="{!! asset('js/app.min.js') !!}"></script>

jQuery Validate - Enable validation for hidden fields

Just find the text ignore: ":hidden" in your jquery validation file and comment it. After comment this it will never loss any hidden elements to validate...


Two constructors

The first line of a constructor is always an invocation to another constructor. You can choose between calling a constructor from the same class with "this(...)" or a constructor from the parent clas with "super(...)". If you don't include either, the compiler includes this line for you: super();

Calculate time difference in Windows batch file

Aacini's latest code showcases an awesome variable substitution method.
It's a shame it's not Regional format proof - it fails on so many levels.
Here's a short fix that keeps the substitution+math method intact:

@echo off
setlocal EnableDelayedExpansion

set "startTime=%time: =0%" & rem AveYo: fix single digit hour

set /P "=Any process here..."

set "endTime=%time: =0%" & rem AveYo: fix single digit hour

rem Aveyo: Regional format fix with just one aditional line
for /f "tokens=1-3 delims=0123456789" %%i in ("%endTime%") do set "COLON=%%i" & set "DOT=%%k" 

rem Get elapsed time:
set "end=!endTime:%DOT%=%%100)*100+1!" & set "start=!startTime:%DOT%=%%100)*100+1!"
set /A "elap=((((10!end:%COLON%=%%100)*60+1!%%100)-((((10!start:%COLON%=%%100)*60+1!%%100)"

rem Aveyo: Fix 24 hours 
set /A "elap=!elap:-=8640000-!"

rem Convert elapsed time to HH:MM:SS:CC format:
set /A "cc=elap%%100+100,elap/=100,ss=elap%%60+100,elap/=60,mm=elap%%60+100,hh=elap/60+100"

echo Start:    %startTime%
echo End:      %endTime%
echo Elapsed:  %hh:~1%%COLON%%mm:~1%%COLON%%ss:~1%%DOT%%cc:~1% & rem AveYo: display as regional


"Lean and Mean" TIMER with Regional format, 24h and mixed input support
Adapting Aacini's substitution method body, no IF's, just one FOR (my regional fix)

1: File timer.bat placed somewhere in %PATH% or the current dir

@echo off & rem :AveYo: compact timer function with Regional format, 24-hours and mixed input support
if not defined timer_set (if not "%~1"=="" (call set "timer_set=%~1") else set "timer_set=%TIME: =0%") & goto :eof
(if not "%~1"=="" (call set "timer_end=%~1") else set "timer_end=%TIME: =0%") & setlocal EnableDelayedExpansion
for /f "tokens=1-6 delims=0123456789" %%i in ("%timer_end%%timer_set%") do (set CE=%%i&set DE=%%k&set CS=%%l&set DS=%%n)
set "TE=!timer_end:%DE%=%%100)*100+1!"     & set "TS=!timer_set:%DS%=%%100)*100+1!"
set/A "T=((((10!TE:%CE%=%%100)*60+1!%%100)-((((10!TS:%CS%=%%100)*60+1!%%100)" & set/A "T=!T:-=8640000-!"
set/A "cc=T%%100+100,T/=100,ss=T%%60+100,T/=60,mm=T%%60+100,hh=T/60+100"
set "value=!hh:~1!%CE%!mm:~1!%CE%!ss:~1!%DE%!cc:~1!" & if "%~2"=="" echo/!value!
endlocal & set "timer_end=%value%" & set "timer_set=" & goto :eof

timer & echo start_cmds & timeout /t 3 & echo end_cmds & timer
timer & timer "23:23:23,00"
timer "23:23:23,00" & timer
timer "13.23.23,00" & timer "03:03:03.00"
timer & timer "0:00:00.00" no & cmd /v:on /c echo until midnight=!timer_end!
Input can now be mixed, for those unlikely, but possible time format changes during execution

2: Function :timer bundled with the batch script (sample usage below):

@echo off
set "TIMER=call :timer" & rem short macro
call :timer
timeout /t 3 >nul & rem Any process here..
call :timer
%TIMER% & timeout /t 1 & %TIMER% 
set "start=22:04:04.58"
set "end=04.22.44,22"
echo %start% ~ start & echo %end% ~ end
call :timer "%start%"
call :timer "%end%"
%TIMER% & %TIMER% "00:00:00.00" no 
echo UNTIL MIDNIGHT: %timer_end%
exit /b

:: to test it, copy-paste both above and below code sections

rem :AveYo: compact timer function with Regional format, 24-hours and mixed input support 
:timer Usage " call :timer [input - optional] [no - optional]" :i Result printed on second call, saved to timer_end 
if not defined timer_set (if not "%~1"=="" (call set "timer_set=%~1") else set "timer_set=%TIME: =0%") & goto :eof
(if not "%~1"=="" (call set "timer_end=%~1") else set "timer_end=%TIME: =0%") & setlocal EnableDelayedExpansion
for /f "tokens=1-6 delims=0123456789" %%i in ("%timer_end%%timer_set%") do (set CE=%%i&set DE=%%k&set CS=%%l&set DS=%%n)
set "TE=!timer_end:%DE%=%%100)*100+1!"     & set "TS=!timer_set:%DS%=%%100)*100+1!"
set/A "T=((((10!TE:%CE%=%%100)*60+1!%%100)-((((10!TS:%CS%=%%100)*60+1!%%100)" & set/A "T=!T:-=8640000-!"
set/A "cc=T%%100+100,T/=100,ss=T%%60+100,T/=60,mm=T%%60+100,hh=T/60+100"
set "value=!hh:~1!%CE%!mm:~1!%CE%!ss:~1!%DE%!cc:~1!" & if "%~2"=="" echo/!value!
endlocal & set "timer_end=%value%" & set "timer_set=" & goto :eof

What is a callback URL in relation to an API?

Another use case could be something like OAuth, it's may not be called by the API directly, instead the callback URL will be called by the browser after completing the authencation with the identity provider.

Normally after end user key in the username password, the identity service provider will trigger a browser redirect to your "callback" url with the temporary authroization code, e.g.

Then your application could use this authorization code to request a access token with the identity provider which has a much longer lifetime.