Programs & Examples On #System.printing

Setting multiple attributes for an element at once with JavaScript

You might be able to use Object.assign(...) to apply your properties to the created element. See comments for additional details.

Keep in mind that height and width attributes are defined in pixels, not percents. You'll have to use CSS to make it fluid.

var elem = document.createElement('img')_x000D_
Object.assign(elem, {_x000D_
  className: 'my-image-class',_x000D_
  src: '',_x000D_
  height: 120, // pixels_x000D_
  width: 160, // pixels_x000D_
  onclick: function () {_x000D_
// One-liner:_x000D_
// document.body.appendChild(Object.assign(document.createElement(...), {...}))
.my-image-class {_x000D_
  height: 100%;_x000D_
  width: 100%;_x000D_
  border: solid 5px transparent;_x000D_
  box-sizing: border-box_x000D_
.my-image-class:hover {_x000D_
  cursor: pointer;_x000D_
  border-color: red_x000D_
body { margin:0 }

To show only file name without the entire directory path

I prefer the base name which is already answered by fge. Another way is :

ls /home/user/new/*.txt|awk -F"/" '{print $NF}'

one more ugly way is :

ls /home/user/new/*.txt| perl -pe 's/\//\n/g'|tail -1

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

Anyone using AUSKEY from the Australian Tax Office (ATO) should uninstall AUSKEY. This sorted out my JAVA_HOME issues.

It is also no longer required for MAC users. Yah!

SyntaxError: missing ; before statement

I got this error, hope this will help someone:

const firstName = 'Joe';
const lastName = 'Blogs';
const wholeName = firstName + ' ' lastName + '.';

The problem was that I was missing a plus (+) between the empty space and lastName. This is a super simplified example: I was concatenating about 9 different parts so it was hard to spot the error.

Summa summarum: if you get "SyntaxError: missing ; before statement", don't look at what is wrong with the the semicolon (;) symbols in your code, look for an error in syntax on that line.

Node.js global variables

In Node.js, you can set global variables via the "global" or "GLOBAL" object:

GLOBAL._ = require('underscore'); // But you "shouldn't" do this! (see note below)

or more usefully...

GLOBAL.window = GLOBAL;  // Like in the browser

From the Node.js source, you can see that these are aliased to each other:

28:     global = this;
128:    global.GLOBAL = global;

In the code above, "this" is the global context. With the CommonJS module system (which Node.js uses), the "this" object inside of a module (i.e., "your code") is not the global context. For proof of this, see below where I spew the "this" object and then the giant "GLOBAL" object.


/* Outputs ...


{ ArrayBuffer: [Function: ArrayBuffer],
  Int8Array: { [Function] BYTES_PER_ELEMENT: 1 },
  Uint8Array: { [Function] BYTES_PER_ELEMENT: 1 },
  Int16Array: { [Function] BYTES_PER_ELEMENT: 2 },
  Uint16Array: { [Function] BYTES_PER_ELEMENT: 2 },
  Int32Array: { [Function] BYTES_PER_ELEMENT: 4 },
  Uint32Array: { [Function] BYTES_PER_ELEMENT: 4 },
  Float32Array: { [Function] BYTES_PER_ELEMENT: 4 },
  Float64Array: { [Function] BYTES_PER_ELEMENT: 8 },
  DataView: [Function: DataView],
  global: [Circular],
   { EventEmitter: [Function: EventEmitter],
     title: 'node',
     assert: [Function],
     version: 'v0.6.5',
     _tickCallback: [Function],
      [ 'Binding evals',
        'Binding natives',
        'NativeModule events',
        'NativeModule buffer',
        'Binding buffer',
        'NativeModule assert',
        'NativeModule util',
        'NativeModule path',
        'NativeModule module',
        'NativeModule fs',
        'Binding fs',
        'Binding constants',
        'NativeModule stream',
        'NativeModule console',
        'Binding tty_wrap',
        'NativeModule tty',
        'NativeModule net',
        'NativeModule timers',
        'Binding timer_wrap',
        'NativeModule _linklist' ],
      { node: '0.6.5',
        v8: '',
        ares: '1.7.5-DEV',
        uv: '0.6',
        openssl: '0.9.8n' },
     nextTick: [Function],
     stdout: [Getter],
     arch: 'x64',
     stderr: [Getter],
     platform: 'darwin',
     argv: [ 'node', '/workspace/zd/zgap/darwin-js/index.js' ],
     stdin: [Getter],
      { TERM_PROGRAM: '',
        TERM: 'xterm',
        SHELL: '/bin/bash',
        TMPDIR: '/var/folders/2h/2hQmtmXlFT4yVGtr5DBpdl9LAiQ/-Tmp-/',
        Apple_PubSub_Socket_Render: '/tmp/launch-9Ga0PT/Render',
        USER: 'ddopson',
        COMMAND_MODE: 'unix2003',
        SSH_AUTH_SOCK: '/tmp/launch-sD905b/Listeners',
        __CF_USER_TEXT_ENCODING: '0x12D732E7:0:0',
        PATH: '/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:~/bin:/usr/X11/bin',
        PWD: '/workspace/zd/zgap/darwin-js',
        LANG: 'en_US.UTF-8',
        ITERM_PROFILE: 'Default',
        SHLVL: '1',
        COLORFGBG: '7;0',
        HOME: '/Users/ddopson',
        ITERM_SESSION_ID: 'w0t0p0',
        LOGNAME: 'ddopson',
        DISPLAY: '/tmp/launch-l9RQXI/org.x:0',
        OLDPWD: '/workspace/zd/zgap/darwin-js/external',
        _: './index.js' },
     openStdin: [Function],
     exit: [Function],
     pid: 10321,
      { debug: false,
        uv: true,
        ipv6: true,
        tls_npn: false,
        tls_sni: true,
        tls: true },
     kill: [Function],
     execPath: '/usr/local/bin/node',
     addListener: [Function],
     _needTickCallback: [Function],
     on: [Function],
     removeListener: [Function],
     reallyExit: [Function],
     chdir: [Function],
     debug: [Function],
     error: [Function],
     cwd: [Function],
     watchFile: [Function],
     umask: [Function],
     getuid: [Function],
     unwatchFile: [Function],
     mixin: [Function],
     setuid: [Function],
     setgid: [Function],
     createChildProcess: [Function],
     getgid: [Function],
     inherits: [Function],
     _kill: [Function],
     _byteLength: [Function],
      { id: '.',
        exports: {},
        parent: null,
        filename: '/workspace/zd/zgap/darwin-js/index.js',
        loaded: false,
        exited: false,
        children: [],
        paths: [Object] },
     _debugProcess: [Function],
     dlopen: [Function],
     uptime: [Function],
     memoryUsage: [Function],
     uvCounters: [Function],
     binding: [Function] },
  GLOBAL: [Circular],
  root: [Circular],
   { [Function: Buffer]
     poolSize: 8192,
     isBuffer: [Function: isBuffer],
     byteLength: [Function],
     _charsWritten: 8 },
  setTimeout: [Function],
  setInterval: [Function],
  clearTimeout: [Function],
  clearInterval: [Function],
  console: [Getter],
  window: [Circular],
  navigator: {} }

** Note: regarding setting "GLOBAL._", in general you should just do var _ = require('underscore');. Yes, you do that in every single file that uses Underscore.js, just like how in Java you do import;. This makes it easier to figure out what your code is doing because the linkages between files are 'explicit'. It is mildly annoying, but a good thing. .... That's the preaching.

There is an exception to every rule. I have had precisely exactly one instance where I needed to set "GLOBAL._". I was creating a system for defining "configuration" files which were basically JSON, but were "written in JavaScript" to allow a bit more flexibility. Such configuration files had no 'require' statements, but I wanted them to have access to Underscore.js (the entire system was predicated on Underscore.js and Underscore.js templates), so before evaluating the "configuration", I would set "GLOBAL._". So yeah, for every rule, there's an exception somewhere. But you had better have a darn good reason and not just "I get tired of typing 'require', so I want to break with the convention".

Seeing the console's output in Visual Studio 2010?

Here are a couple of things to check:

  1. For console.Write/WriteLine, your app must be a console application. (right-click the project in Solution Explorer, choose Properties, and look at the "Output Type" combo in the Application Tab -- should be "Console Application" (note, if you really need a windows application or a class library, don't change this to Console App just to get the Console.WriteLine).

  2. You could use System.Diagnostics.Debug.WriteLine to write to the output window (to show the output window in VS, got to View | Output) Note that these writes will only occur in a build where the DEBUG conditional is defined (by default, debug builds define this, and release builds do not)

  3. You could use System.Diagnostics.Trace.Writeline if you want to be able to write to configurable "listeners" in non-debug builds. (by default, this writes to the Output Window in Visual Studio, just like Debug.Writeline)

Simulate delayed and dropped packets on Linux

You can try It's quite old NIST project (last release 2005), but it works for me.

not None test in Python

if val is not None:
    # ...

is the Pythonic idiom for testing that a variable is not set to None. This idiom has particular uses in the case of declaring keyword functions with default parameters. is tests identity in Python. Because there is one and only one instance of None present in a running Python script/program, is is the optimal test for this. As Johnsyweb points out, this is discussed in PEP 8 under "Programming Recommendations".

As for why this is preferred to

if not (val is None):
    # ...

this is simply part of the Zen of Python: "Readability counts." Good Python is often close to good pseudocode.

how to use html2canvas and jspdf to export to pdf in a proper and simple way

Changing this line:

var doc = new jsPDF('L', 'px', [w, h]);
var doc = new jsPDF('L', 'pt', [w, h]);

To fix the dimensions.

jQuery checkbox change and click event

Try this:

    let checkbox = document.getElementById('checkboxId');
    if (checkbox.checked != true)
        alert("select checkbox");

error while loading shared libraries:

error while loading shared libraries:

If you see this, your distro probably has a newer version of libncurse installed. First find out what version of libncurses your distro has:

$ ls -1 /usr/lib/libncurses*

In this case, we are dealing with version 6, so we make two symlinks:

$ sudo ln -s /usr/lib/ /usr/lib/
$ sudo ln -s /usr/lib/ /usr/lib/

After this, the program should run normally.

Save the plots into a PDF

For multiple plots in a single pdf file you can use PdfPages

In the plotGraph function you should return the figure and than call savefig of the figure object.

------ plotting module ------

def plotGraph(X,Y):
      fig = plt.figure()
      ### Plotting arrangements ###
      return fig

------ plotting module ------

----- mainModule ----

from matplotlib.backends.backend_pdf import PdfPages

plot1 = plotGraph(tempDLstats, tempDLlabels)
plot2 = plotGraph(tempDLstats_1, tempDLlabels_1)
plot3 = plotGraph(tempDLstats_2, tempDLlabels_2)

pp = PdfPages('foo.pdf')

Python append() vs. + operator on lists, why do these give different results?

To explain "why":

The + operation adds the array elements to the original array. The array.append operation inserts the array (or any object) into the end of the original array, which results in a reference to self in that spot (hence the infinite recursion).

The difference here is that the + operation acts specific when you add an array (it's overloaded like others, see this chapter on sequences) by concatenating the element. The append-method however does literally what you ask: append the object on the right-hand side that you give it (the array or any other object), instead of taking its elements.

An alternative

Use extend() if you want to use a function that acts similar to the + operator (as others have shown here as well). It's not wise to do the opposite: to try to mimic append with the + operator for lists (see my earlier link on why).

Little history

For fun, a little history: the birth of the array module in Python in February 1993. it might surprise you, but arrays were added way after sequences and lists came into existence.

show icon in actionbar/toolbar with AppCompat-v7 21

In Kotlin I did the following to just show the icon:


Javascript replace with reference to matched group?

For the replacement string and the replacement pattern as specified by $. here a resume:

enter image description here

link to doc : here

"hello _there_".replace(/_(.*?)_/g, "<div>$1</div>")


If you want to have a $ in the replacement string use $$. Same as with vscode snippet system.

Plot a bar using matplotlib using a dictionary

For future reference, the above code does not work with Python 3. For Python 3, the D.keys() needs to be converted to a list.

import matplotlib.pyplot as plt

D = {u'Label1':26, u'Label2': 17, u'Label3':30}, D.values(), align='center')
plt.xticks(range(len(D)), list(D.keys()))

Detecting an "invalid date" Date instance in JavaScript

Generally I'd stick with whatever Date implantation is in the browser stack. Which means you will always get "Invalid Date" when calling toDateString() in Chrome, Firefox, and Safari as of this reply's date.

  Date.prototype.isValidDate = function(){
    return this.toDateString().toLowerCase().lastIndexOf('invalid') == -1;

I did not test this in IE though.

How can I show an image using the ImageView component in javafx and fxml?


    Parent root =new StackPane();
    ImageView imageView=new ImageView(new Image(getClass().getResourceAsStream("images/shopp.png")));
    ((StackPane) root).getChildren().add(imageView);


How to hide .php extension in .htaccess

The other option for using PHP scripts sans extension is

Options +MultiViews

Or even just following in the directories .htaccess:

DefaultType application/x-httpd-php

The latter allows having all filenames without extension script being treated as PHP scripts. While MultiViews makes the webserver look for alternatives, when just the basename is provided (there's a performance hit with that however).

How to check for empty array in vba macro

if Ubound(yourArray)>-1 then
 debug.print "The array is not empty"
 debug.print "EMPTY"
end if

CodeIgniter activerecord, retrieve last insert id?

After your insert query, use this command $this->db->insert_id(); to return the last inserted id.

For example:

$this->db->insert('Your_tablename', $your_data);

$last_id =  $this->db->insert_id();

echo $last_id // assume that the last id from the table is 1, after the insert query this value will be 2.

How to disable keypad popup when on edittext?

Try this answer,


Note: only for API 11+

Getting the names of all files in a directory with PHP

Recursive code to explore all the file contained in a directory ('$path' contains the path of the directory):

function explore_directory($path)
    $scans = scandir($path);

    foreach($scans as $scan)
        $new_path = $path.$scan;

            $new_path = $new_path."/";
        else // A file
                  Body of code

Embed a PowerPoint presentation into HTML

I was looking for a solution for similar problem.

I looked into

But they have no better documentation, and even no demo page I could see over there and it was seemingly difficult.

What I came up with is: SkyDrive by Microsoft.

All you need is an account with them and upload your PPT and embed them straightaway. PPT player is quite clean to use and I like it.

Sort an array of objects in React and render them

Chrome browser considers integer value as return type not boolean value so,, b) => a.item.timeM > b.item.timeM ? 1:-1).map(
    (item, i) => <div key={i}> {item.matchID} {item.timeM} {item.description}</div>

Crystal Reports - Adding a parameter to a 'Command' query

Try this:

Select Project_Name, ReleaseDate, TaskName
From DB_Table
Where Project_Name like '{?Pm-?Proj_Name}'
  And ReleaseDate >= currentdate

currentdate should be a valid database function or field to work. If you are using MS SQL Server, use GETDATE() instead.

If all you want is to filter records in a subreport based on a parameter from the main report, it might be easier to simply add the table to the subreport, and then create a Project_Name link between the main report and subreport. You can then use the Select Expert to filter the ReleaseDate as well.

How to include a child object's child object in Entity Framework 5

With EF Core in .NET Core you can use the keyword ThenInclude :

return DatabaseContext.Applications
 .Include(a => a.Children).ThenInclude(c => c.ChildRelationshipType);

Include childs from childrens collection :

return DatabaseContext.Applications
 .Include(a => a.Childrens).ThenInclude(cs => cs.ChildRelationshipType1)
 .Include(a => a.Childrens).ThenInclude(cs => cs.ChildRelationshipType2);

Importing packages in Java

You don't import methods in Java, only types:

import Dan.Vik;
class Kab
    public static void main(String args[])
        Vik Sam = new Vik();

The exception is so-called "static imports", which let you import class (static) methods from other types.

Convert string to datetime in

You can try with ParseExact method


Dim format As String  
format = "d" 
Dim provider As CultureInfo = CultureInfo.InvariantCulture
result = Date.ParseExact(DateString, format, provider)

How to parse a JSON and turn its values into an Array?

for your example:

{'profiles': [{'name':'john', 'age': 44}, {'name':'Alex','age':11}]}

you will have to do something of this effect:

JSONObject myjson = new JSONObject(the_json);
JSONArray the_json_array = myjson.getJSONArray("profiles");

this returns the array object.

Then iterating will be as follows:

    int size = the_json_array.length();
    ArrayList<JSONObject> arrays = new ArrayList<JSONObject>();
    for (int i = 0; i < size; i++) {
        JSONObject another_json_object = the_json_array.getJSONObject(i);
            //Blah blah blah...

JSONObject[] jsons = new JSONObject[arrays.size()];

//The end...

You will have to determine if the data is an array (simply checking that charAt(0) starts with [ character).

Hope this helps.

Change the size of a JTextField inside a JBorderLayout

Try to play with


These method are used by layout when it decide what should be the size of current element. The layout manager calls setSize() and actually overrides your values.

Can I apply multiple background colors with CSS3?

You can only use one color but as many images as you want, here is the format:

background: [ <bg-layer> , ]* <final-bg-layer>

<bg-layer> = <bg-image> || <bg-position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box>{1,2}

<final-bg-layer> = <bg-image> || <bg-position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box>{1,2} || <background-color>

or background: url(image1.png) center bottom no-repeat, url(image2.png) left top no-repeat;

If you need more colors, make an image of a solid color and use it. I know it’s not what you want to hear, but I hope it helps.

The format is from

How to get last inserted row ID from WordPress database?

Something like this should do it too :

$last = $wpdb->get_row("SHOW TABLE STATUS LIKE 'table_name'");
$lastid = $last->Auto_increment;

Regex matching in a Bash if statement

I'd prefer to use [:punct:] for that. Also, a-zA-Z09-9 could be just [:alnum:]:

[[ $TEST =~ ^[[:alnum:][:blank:][:punct:]]+$ ]]

Declare a Range relative to the Active Cell with VBA

There is an .Offset property on a Range class which allows you to do just what you need

ActiveCell.Offset(numRows, numCols)

follow up on a comment:

Dim newRange as Range
Set newRange = Range(ActiveCell, ActiveCell.Offset(numRows, numCols))

and you can verify by MsgBox newRange.Address

and here's how to assign this range to an array

Reading values from DataTable

I think it will work

for (int i = 1; i <= broj_ds; i++ ) 

     QuantityInIssueUnit_value = dr_art_line_2[i]["Column"];
     QuantityInIssueUnit_uom  = dr_art_line_2[i]["Column"];


Assigning default values to shell variables with a single command in bash

Then there's the way of expressing your 'if' construct more tersely:

[ -n "${VARIABLE}" ] && FOO=${VARIABLE}

NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference

This issue is due to ArrayList variable not being instantiated. Need to declare "recordings" variable like following, that should solve the issue;

ArrayList<String> recordings = new ArrayList<String>();

this calls default constructor and assigns empty string to the recordings variable so that it is not null anymore.

Pythonic way to add and datetime.time objects

It's in the python docs.

import datetime
datetime.datetime.combine(, 1, 1), 
                          datetime.time(10, 23))


datetime.datetime(2011, 1, 1, 10, 23)

Set icon for Android application

Add an application launcher icon with automatic sizing.

(Android studio)

Go to menu File* ? New ? Image Assets ? select launcher icon ? choose image file.

It will automatically re-size.


"git rm --cached x" vs "git reset head --? x"?

There are three places where a file, say, can be - the (committed) tree, the index and the working copy. When you just add a file to a folder, you are adding it to the working copy.

When you do something like git add file you add it to the index. And when you commit it, you add it to the tree as well.

It will probably help you to know the three more common flags in git reset:

git reset [--<mode>] [<commit>]

This form resets the current branch head to <commit> and possibly updates the index (resetting it to the tree of <commit>) and the working tree depending on <mode>, which must be one of the following:

Does not touch the index file nor the working tree at all (but resets the head to <commit>, just like all modes do). This leaves all your changed files "Changes to be committed", as git status would put it.


Resets the index but not the working tree (i.e., the changed files are preserved but not marked for commit) and reports what has not been updated. This is the default action.


Resets the index and working tree. Any changes to tracked files in the working tree since <commit> are discarded.

Now, when you do something like git reset HEAD, what you are actually doing is git reset HEAD --mixed and it will "reset" the index to the state it was before you started adding files / adding modifications to the index (via git add). In this case, no matter what the state of the working copy was, you didn't change it a single bit, but you changed the index in such a way that is now in sync with the HEAD of the tree. Whether git add was used to stage a previously committed but changed file, or to add a new (previously untracked) file, git reset HEAD is the exact opposite of git add.

git rm, on the other hand, removes a file from the working directory and the index, and when you commit, the file is removed from the tree as well. git rm --cached, however, removes the file from the index alone and keeps it in your working copy. In this case, if the file was previously committed, then you made the index to be different from the HEAD of the tree and the working copy, so that the HEAD now has the previously committed version of the file, the index has no file at all, and the working copy has the last modification of it. A commit now will sync the index and the tree, and the file will be removed from the tree (leaving it untracked in the working copy). When git add was used to add a new (previously untracked) file, then git rm --cached is the exact opposite of git add (and is pretty much identical to git reset HEAD).

Git 2.25 introduced a new command for these cases, git restore, but as of Git 2.28 it is described as “experimental” in the man page, in the sense that the behavior may change.

JSON post to Spring Controller

You need to include the getters and setters for all the fields that have been defined in the model Test class --

public class Test implements Serializable {

    private static final long serialVersionUID = -1764970284520387975L;

    public String name;

    public Test() {


    public String getName() {
        return name;

    public void setName(String name) { = name;


@AspectJ pointcut for all methods of a class with specific annotation

I share with you a code that can be useful, it is to create an annotation that can be used either in a class or a method.

@Target({TYPE, METHOD})
public @interface AnnotationLogger {
     * It is the parameter is to show arguments in the method or the class.
    boolean showArguments() default false;

public class AnnotationLoggerAspect {
    private Logger logger;  
    private static final String METHOD_NAME   = "METHOD NAME: {} ";
    private static final String ARGUMENTS     = "ARGS: {} ";
    @Before(value = "@within( || @annotation(")
    public void logAdviceExecutionBefore(JoinPoint joinPoint){  
        CodeSignature codeSignature = (CodeSignature) joinPoint.getSignature();
        AnnotationLogger annotationLogger = getAnnotationLogger(joinPoint);
        if(annotationLogger!= null) {
            StringBuilder annotationLoggerFormat = new StringBuilder();
            List<Object> annotationLoggerArguments = new ArrayList<>();
            if (annotationLogger.showArguments()) {
                List<?> argumentList = Arrays.asList(joinPoint.getArgs());
            logger.error(annotationLoggerFormat.toString(), annotationLoggerArguments.toArray());
    private AnnotationLogger getAnnotationLogger(JoinPoint joinPoint) {
        AnnotationLogger annotationLogger = null;
        try {
            MethodSignature signature = (MethodSignature) joinPoint.getSignature();
            Method method = joinPoint.getTarget().getClass().
                    getMethod(signature.getMethod().getName(), signature.getMethod().getParameterTypes());
            if (method.isAnnotationPresent(AnnotationLogger.class)){
                annotationLogger = method.getAnnotation(AnnotationLoggerAspect.class);
            }else if (joinPoint.getTarget().getClass().isAnnotationPresent(AnnotationLoggerAspect.class)){
                annotationLogger = joinPoint.getTarget().getClass().getAnnotation(AnnotationLoggerAspect.class);
            return annotationLogger;
        }catch(Exception e) {
            return annotationLogger;

Aren't Python strings immutable? Then why does a + " " + b work?


>>> a='asdf'
>>> a.__repr__
<method-wrapper '__repr__' of str object at 0x1091aab90>
>>> a='asdf'
>>> a.__repr__
<method-wrapper '__repr__' of str object at 0x1091aab90>
>>> a='qwer'
>>> a.__repr__
<method-wrapper '__repr__' of str object at 0x109198490>

Notice that the hex memory location did not change when I stored the same value in the variable twice. It did change when I stored a different value. The string is immutable. Not because of zealotry, but because you pay the performance penalty of creating a new object in memory. The variable a is just a label pointing to that memory address. It can be altered to point to anything.

SQL string value spanning multiple lines in query

SQL Server allows the following (be careful to use single quotes instead of double)

SET UserId = 12345
   , Name = 'J Doe'
   , Location = 'USA'
   , Bio='my bio
WHERE UserId = 12345

initializing strings as null vs. empty string

Empty-ness and "NULL-ness" are two different concepts. As others mentioned the former can be achieved via std::string::empty(), the latter can be achieved with boost::optional<std::string>, e.g.:

boost::optional<string> myStr;
if (myStr) { // myStr != NULL
    // ...

difference between primary key and unique key

  • Think the table name is employe.
  • Primary key
  • Primary key can not accept null values. primary key enforces uniqueness of a column. We can have only one Primary key in a table.
  • Unique key
  • Unique key can accept null values. unique key also enforces uniqueness of a can think if unique key contains null values then why it can be unique ? yes, though it can accept null values it enforces uniqueness of a column. just have a look on the Emp_ID is primary and Citizen ID is unique. Hope you understand. We can use multiple unique key in a table. enter image description here

HTML: Image won't display?

Just to expand niko's answer:

You can reference any image via its URL. No matter where it is, as long as it's accesible you can use it as the src. Example:

Relative location:

<img src="images/image.png">

The image is sought relative to the document's location. If your document is at, then your images folder should be on the same directory where your document.html file is.

Absolute location:

<img src="/site/images/image.png">
<img src="">


<img src="">

In this case, your image will be sought from the document site's root, so, if your document.html is at, the root would be at (or it's respective directory on the server's filesystem, commonly www/). The first two examples are the same, since both point to the same host, Think of the first / as an alias for your server's root. In the second case, the image is located in another host, so you'd have to specify the complete URL of the image.

Regarding /, . and ..:

The / symbol will always return the root of a filesystem or site.

The single point ./ points to the same directory where you are.

And the double point ../ will point to the upper directory, or the one that contains the actual working directory.

So you can build relative routes using them.

Examples given the route and your calling document being inside three/:


or just


Will try to find a directory named pictures inside


Will try to find a directory named pictures inside


Will try to find a directory named pictures directly at / or (which are the same), on the same level as directory.

Javascript wait() function

You shouldn't edit it, you should completely scrap it.

Any attempt to make execution stop for a certain amount of time will lock up the browser and switch it to a Not Responding state. The only thing you can do is use setTimeout correctly.

Java System.out.print formatting

Since you are using Java, printf is available from version 1.5

You may use it like this

System.out.printf("%03d ", x);

For Example:

System.out.printf("%03d ", 5);
System.out.printf("%03d ", 55);
System.out.printf("%03d ", 555);

Will Give You

005 055 555

as output

See: System.out.printf and Format String Syntax

jQuery selector for the label of a checkbox

Thanks Kip, for those who may be looking to achieve the same using $(this) whilst iterating or associating within a function:

$("label[for="+$(this).attr("id")+"]").addClass( "orienSel" );

I looked for a while whilst working this project but couldn't find a good example so I hope this helps others who may be looking to resolve the same issue.

In the example above, my objective was to hide the radio inputs and style the labels to provide a slicker user experience (changing the orientation of the flowchart).

You can see an example here

If you like the example, here is the css:

.orientation {      position: absolute; top: -9999px;   left: -9999px;}
    .orienlabel{background:#1a97d4 url('') no-repeat 2px 5px; background-size: 40px auto;color:#fff; width:50px;height:50px;display:inline-block; border-radius:50%;color:transparent;cursor:pointer;}
    .orR{   background-position: 9px -57px;}
    .orT{   background-position: 2px -120px;}
    .orB{   background-position: 6px -177px;}

    .orienSel {background-color:#323232;}

and the relevant part of the JavaScript:

function changeHandler() {
    $(".orienSel").removeClass( "orienSel" );
    if(this.checked) {
        $("label[for="+$(this).attr("id")+"]").addClass( "orienSel" );

An alternate root to the original question, given the label follows the input, you could go with a pure css solution and avoid using JavaScript altogether...:

input[type=checkbox]:checked+label {}

Comparing Dates in Oracle SQL

31-DEC-95 isn't a string, nor is 20-JUN-94. They're numbers with some extra stuff added on the end. This should be '31-DEC-95' or '20-JUN-94' - note the single quote, '. This will enable you to do a string comparison.

However, you're not doing a string comparison; you're doing a date comparison. You should transform your string into a date. Either by using the built-in TO_DATE() function, or a date literal.


select employee_id
  from employee
 where employee_date_hired > to_date('31-DEC-95','DD-MON-YY')

This method has a few unnecessary pitfalls

  • As a_horse_with_no_name noted in the comments, DEC, doesn't necessarily mean December. It depends on your NLS_DATE_LANGUAGE and NLS_DATE_FORMAT settings. To ensure that your comparison with work in any locale you can use the datetime format model MM instead
  • The year '95 is inexact. You know you mean 1995, but what if it was '50, is that 1950 or 2050? It's always best to be explicit
select employee_id
  from employee
 where employee_date_hired > to_date('31-12-1995','DD-MM-YYYY')

Date literals

A date literal is part of the ANSI standard, which means you don't have to use an Oracle specific function. When using a literal you must specify your date in the format YYYY-MM-DD and you cannot include a time element.

select employee_id
  from employee
 where employee_date_hired > date '1995-12-31'

Remember that the Oracle date datatype includes a time elemement, so the date without a time portion is equivalent to 1995-12-31 00:00:00.

If you want to include a time portion then you'd have to use a timestamp literal, which takes the format YYYY-MM-DD HH24:MI:SS[.FF0-9]

select employee_id
  from employee
 where employee_date_hired > timestamp '1995-12-31 12:31:02'

Further information

NLS_DATE_LANGUAGE is derived from NLS_LANGUAGE and NLS_DATE_FORMAT is derived from NLS_TERRITORY. These are set when you initially created the database but they can be altered by changing your inialization parameters file - only if really required - or at the session level by using the ALTER SESSION syntax. For instance:

alter session set nls_date_format = 'DD.MM.YYYY HH24:MI:SS';

This means:

  • DD numeric day of the month, 1 - 31
  • MM numeric month of the year, 01 - 12 ( January is 01 )
  • YYYY 4 digit year - in my opinion this is always better than a 2 digit year YY as there is no confusion with what century you're referring to.
  • HH24 hour of the day, 0 - 23
  • MI minute of the hour, 0 - 59
  • SS second of the minute, 0-59

You can find out your current language and date language settings by querying V$NLS_PARAMETERSs and the full gamut of valid values by querying V$NLS_VALID_VALUES.

Further reading

Incidentally, if you want the count(*) you need to group by employee_id

select employee_id, count(*)
  from employee
 where employee_date_hired > date '1995-12-31'
 group by employee_id

This gives you the count per employee_id.

Best way to parse command line arguments in C#?

There is a command line argument parser at

It can parse arguments using
1. attributes
2. explicit calls
3. single line of multiple arguments OR string array

It can handle things like the following:

-config:Qa -startdate:${today} -region:'New York' Settings01

It's very easy to use.

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

Starting with arcseldon's answer, I found that the team name was needed in the URL like so:

npm install --save "git+https://myteamname@[email protected]/myteamname/myprivate.git"

And note that the API key is only available for the team, not individual users.

Difference between attr_accessor and attr_accessible

Many people on this thread and on google explain very well that attr_accessible specifies a whitelist of attributes that are allowed to be updated in bulk (all the attributes of an object model together at the same time) This is mainly (and only) to protect your application from "Mass assignment" pirate exploit.

This is explained here on the official Rails doc : Mass Assignment

attr_accessor is a ruby code to (quickly) create setter and getter methods in a Class. That's all.

Now, what is missing as an explanation is that when you create somehow a link between a (Rails) model with a database table, you NEVER, NEVER, NEVER need attr_accessor in your model to create setters and getters in order to be able to modify your table's records.

This is because your model inherits all methods from the ActiveRecord::Base Class, which already defines basic CRUD accessors (Create, Read, Update, Delete) for you. This is explained on the offical doc here Rails Model and here Overwriting default accessor (scroll down to the chapter "Overwrite default accessor")

Say for instance that: we have a database table called "users" that contains three columns "firstname", "lastname" and "role" :

SQL instructions :

  firstname string,
  lastname string
  role string

I assumed that you set the option config.active_record.whitelist_attributes = true in your config/environment/production.rb to protect your application from Mass assignment exploit. This is explained here : Mass Assignment

Your Rails model will perfectly work with the Model here below :

class User < ActiveRecord::Base


However you will need to update each attribute of user separately in your controller for your form's View to work :

def update
    @user = User.find_by_id(params[:id])
    @user.firstname = params[:user][:firstname]
    @user.lastname = params[:user][:lastname]

        # Use of I18 internationalization t method for the flash message
        flash[:success] = t('activerecord.successful.messages.updated', :model => User.model_name.human)


Now to ease your life, you don't want to make a complicated controller for your User model. So you will use the attr_accessible special method in your Class model :

class User < ActiveRecord::Base

  attr_accessible :firstname, :lastname


So you can use the "highway" (mass assignment) to update :

def update
    @user = User.find_by_id(params[:id])

    if @user.update_attributes(params[:user])
        # Use of I18 internationlization t method for the flash message
        flash[:success] = t('activerecord.successful.messages.updated', :model => User.model_name.human)


You didn't add the "role" attributes to the attr_accessible list because you don't let your users set their role by themselves (like admin). You do this yourself on another special admin View.

Though your user view doesn't show a "role" field, a pirate could easily send a HTTP POST request that include "role" in the params hash. The missing "role" attribute on the attr_accessible is to protect your application from that.

You can still modify your user.role attribute on its own like below, but not with all attributes together.

@user.role = DEFAULT_ROLE

Why the hell would you use the attr_accessor?

Well, this would be in the case that your user-form shows a field that doesn't exist in your users table as a column.

For instance, say your user view shows a "please-tell-the-admin-that-I'm-in-here" field. You don't want to store this info in your table. You just want that Rails send you an e-mail warning you that one "crazy" ;-) user has subscribed.

To be able to make use of this info you need to store it temporarily somewhere. What more easy than recover it in a user.peekaboo attribute ?

So you add this field to your model :

class User < ActiveRecord::Base

  attr_accessible :firstname, :lastname
  attr_accessor :peekaboo


So you will be able to make an educated use of the user.peekaboo attribute somewhere in your controller to send an e-mail or do whatever you want.

ActiveRecord will not save the "peekaboo" attribute in your table when you do a because she don't see any column matching this name in her model.

How do I finish the merge after resolving my merge conflicts?

After all files have been added, the next step is a "git commit".

"git status" will suggest what to do: files yet to add are listed at the bottom, and once they are all done, it will suggest a commit at the top, where it explains the merge status of the current branch.

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

git ahead/behind info between master and branch?

After doing a git fetch, you can run git status to show how many commits the local branch is ahead or behind of the remote version of the branch.

This won't show you how many commits it is ahead or behind of a different branch though. Your options are the full diff, looking at github, or using a solution like Vimhsa linked above: Git status over all repo's

Electron: jQuery is not defined

I face the same issue and this worked for me!

Install jQuery using npm

$ npm install jquery

Then include jQuery in one of the following ways.

Using script tag

<script>window.$ = window.jQuery = require('jquery');</script>

Using Babel

import $ from 'jquery';

Using Webpack

const $ = require('jquery');

How to search if dictionary value contains certain string with Python

Klaus solution has less overhead, on the other hand this one may be more readable

myDict = {'age': ['12'], 'address': ['34 Main Street, 212 First Avenue'],
          'firstName': ['Alan', 'Mary-Ann'], 'lastName': ['Stone', 'Lee']}

def search(myDict, lookup):
    for key, value in myDict.items():
        for v in value:
            if lookup in v:
                return key

search(myDict, 'Mary')

Populating VBA dynamic arrays

in your for loop use a Redim on the array like here:

For i = 0 to 3
  ReDim Preserve test(i)
  test(i) = 3 + i
Next i

Starting a shell in the Docker Alpine container

Nowadays, Alpine images will boot directly into /bin/sh by default, without having to specify a shell to execute:

$ sudo docker run -it --rm alpine  
/ # echo $0  

This is since the alpine image Dockerfiles now contain a CMD command, that specifies the shell to execute when the container starts: CMD ["/bin/sh"].

In older Alpine image versions (pre-2017), the CMD command was not used, since Docker used to create an additional layer for CMD which caused the image size to increase. This is something that the Alpine image developers wanted to avoid. In recent Docker versions (1.10+), CMD no longer occupies a layer, and so it was added to alpine images. Therefore, as long as CMD is not overridden, recent Alpine images will boot into /bin/sh.

For reference, see the following commit to the official Alpine Dockerfiles by Glider Labs:

HTML list-style-type dash

In my case adding this code to CSS

ul {
    list-style-type: '- ';

was enough. Simple as it is.

How to change to an older version of Node.js

One way is to use NVM, the Node Version Manager.

Use following command to get nvm

curl -o- | bash

You can find it at

It allows you to easily install and manage multiple versions of node. Here's a snippet from the help:

nvm install <version>       Download and install a <version>
nvm use <version>           Modify PATH to use <version>
nvm ls                      List versions (installed versions are blue)

ListView with Add and Delete Buttons in each Row in android

public class UserCustomAdapter extends ArrayAdapter<User> {
 Context context;
 int layoutResourceId;
 ArrayList<User> data = new ArrayList<User>();

 public UserCustomAdapter(Context context, int layoutResourceId,
   ArrayList<User> data) {
  super(context, layoutResourceId, data);
  this.layoutResourceId = layoutResourceId;
  this.context = context; = data;

 public View getView(int position, View convertView, ViewGroup parent) {
  View row = convertView;
  UserHolder holder = null;

  if (row == null) {
   LayoutInflater inflater = ((Activity) context).getLayoutInflater();
   row = inflater.inflate(layoutResourceId, parent, false);
   holder = new UserHolder();
   holder.textName = (TextView) row.findViewById(;
   holder.textAddress = (TextView) row.findViewById(;
   holder.textLocation = (TextView) row.findViewById(;
   holder.btnEdit = (Button) row.findViewById(;
   holder.btnDelete = (Button) row.findViewById(;
  } else {
   holder = (UserHolder) row.getTag();
  User user = data.get(position);
  holder.btnEdit.setOnClickListener(new OnClickListener() {

   public void onClick(View v) {
    // TODO Auto-generated method stub
    Log.i("Edit Button Clicked", "**********");
    Toast.makeText(context, "Edit button Clicked",
  holder.btnDelete.setOnClickListener(new OnClickListener() {

   public void onClick(View v) {
    // TODO Auto-generated method stub
    Log.i("Delete Button Clicked", "**********");
    Toast.makeText(context, "Delete button Clicked",
  return row;


 static class UserHolder {
  TextView textName;
  TextView textAddress;
  TextView textLocation;
  Button btnEdit;
  Button btnDelete;

Hey Please have a look here-

I have same answer here on my blog ..

Plugin org.apache.maven.plugins:maven-clean-plugin:2.5 or one of its dependencies could not be resolved

The error is due to maven official repository being not accessible. This repo ( is not accessible so follow these steps:

  1. Firstly delete your /home/user/.m2 folder
  2. create .m2 folder at user home and repository folder within .m2
  3. copy the default settings.xml to .m2 folder
  4. Change mirrors as follows in the settings.xml as shown in below snap mirror_settings

    <name>UK Central</name>_x000D_

  1. Execute the mvn clean commands now .....

How to get a function name as a string?


There are also other fun properties of functions. Type dir(func_name) to list them. func_name.func_code.co_code is the compiled function, stored as a string.

import dis

will display the code in almost human readable format. :)

Why does git revert complain about a missing -m option?

I had this problem, the solution was to look at the commit graph (using gitk) and see that I had the following:

*   commit I want to cherry-pick (x)
| * branch I want to cherry-pick to (y)
* | 
* common parent (x)

I understand now that I want to do

git cherry-pick -m 2 mycommitsha

This is because -m 1 would merge based on the common parent where as -m 2 merges based on branch y, that is the one I want to cherry-pick to.

Xcode project not showing list of simulators

Looks like Xcode hides that menu when the window is a certain size. You have to make your window quite large before it comes back.

Remove URL parameters without refreshing page

None of these solutions really worked for me, here is a IE11-compatible function that can also remove multiple parameters:

* Removes URL parameters
* @param removeParams - param array
function removeURLParameters(removeParams) {
  const deleteRegex = new RegExp(removeParams.join('=|') + '=')

  const params ='&')
  let search = []
  for (let i = 0; i < params.length; i++) if (deleteRegex.test(params[i]) === false) search.push(params[i])

  window.history.replaceState({}, document.title, location.pathname + (search.length ? '?' + search.join('&') : '') + location.hash)

removeURLParameters(['param1', 'param2'])

NSInternalInconsistencyException', reason: 'Could not load NIB in bundle: 'NSBundle

I've got some subprojects.

I solved this problem via adding xib file to Copy Bundle Resources build phase of main project.

Font Awesome & Unicode

It does not work, because <i>&#xf015;</i> simply asks the browser to display the Private Use code point U+F015 using an italic typeface. The Font Awesome CSS code has nothing that would affect this. If you add class=icon-home to the tag, you will get the glyph assigned to U+F015 in the FontAwesome font, but you will get it twice, due to the way the Font Awesome trickery works.

To get the glyph just once, you need to use CSS that asks for the use of the FontAwesome font without triggering the rules that add a glyph via generated content. A simple trick is to use a class name that starts with icon- but does not match any of the predefined names in Font Awesome or any name otherwise used in your CSS or JavaScript code. E.g.,

<i class=icon-foo>&#xf015;</i>

Alternatively, use CSS code that sets font-family: FontAwesome and font-style: normal on the i element.

PS. Note that Private Use code points such as U+F015 have, by definition, no interoperable meaning. Consequently, when style sheets are disabled, &#xf015; will not be displayed as any character; the browser will use its way of communicating the presence of undefined data, such as a small box, possibly containing the code point number.

Compare two data.frames to find the rows in data.frame 1 that are not present in data.frame 2

The following code uses both data.table and fastmatch for increased speed.


a1 <- setDT(data.frame(a = 1:5, b=letters[1:5]))
a2 <- setDT(data.frame(a = 1:3, b=letters[1:3]))

compare_rows <- a1$a %fin% a2$a
# the %fin% function comes from the `fastmatch` package

added_rows <- a1[which(compare_rows == FALSE)]


#    a b
# 1: 4 d
# 2: 5 e

Post request with Wget?

Wget currently only supports x-www-form-urlencoded data. --post-file is not for transmitting files as form attachments, it expects data with the form: key=value&otherkey=example.

--post-data and --post-file work the same way: the only difference is that --post-data allows you to specify the data in the command line, while --post-file allows you to specify the path of the file that contain the data to send.

Here's the documentation:

           Use POST as the method for all HTTP requests and send the specified data
           in the request body.  --post-data sends string as data, whereas
           --post-file sends the contents of file.  Other than that, they work in
           exactly the same way. In particular, they both expect content of the
           form "key1=value1&key2=value2", with percent-encoding for special
           characters; the only difference is that one expects its content as a
           command-line parameter and the other accepts its content from a file. In
           particular, --post-file is not for transmitting files as form
           attachments: those must appear as "key=value" data (with appropriate
           percent-coding) just like everything else. Wget does not currently
           support "multipart/form-data" for transmitting POST data; only
           "application/x-www-form-urlencoded". Only one of --post-data and
           --post-file should be specified.

Regarding your authentication token, it should either be provided in the header, in the path of the url, or in the data itself. This must be indicated somewhere in the documentation of the service you use. In a POST request, as in a GET request, you must specify the data using keys and values. This way the server will be able to receive multiple information with specific names. It's similar with variables.

Hence, you can't just send a magic token to the server, you also need to specify the name of the key. If the key is "token", then it should be token=YOUR_TOKEN.

wget --post-data 'user=foo&password=bar'

Also, you should consider using curl if you can because it is easier to send files using it. There are many examples on the Internet for that.

How to get the last characters in a String in Java, regardless of String size

String inputstr = "abcd: efg: 1006746"
int startindex = inputstr.length() - 10;
String outputtendigitstr = inputstr.substring(startindex);

Make sure you check string length is more than 10.

UICollectionView cell selection and cell reuse

UICollectionView has changed in iOS 10 introducing some problems to solutions above.

Here is a good guide:

Cells now stay around for a bit after going off-screen. Which means that sometimes we might not be able to get hold of a cell in didDeselectItemAt indexPath in order to adjust it. It can then show up on screen un-updated and un-recycled. prepareForReuse does not help this corner case.

The easiest solution is disabling the new scrolling by setting isPrefetchingEnabled to false. With this, managing the cell's display with cellForItemAt didSelect didDeselect works as it used to.

However, if you'd rather keep the new smooth scrolling behaviour it's better to use willDisplay :

func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
    let customCell = cell as! CustomCell
    if customCell.isSelected {
    } else {

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CustomCell", for: indexPath) as! CustomCell
    //Don't even need to set selection-specific things here as recycled cells will also go through willDisplay
    return cell

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath) as? CustomCell

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath) as? CustomCell
    cell?.unselect() // <----- this can be null here, and the cell can still come back on screen!

With the above you control the cell when it's selected, unselected on-screen, recycled, and just re-displayed.

Select last N rows from MySQL

You can do it with a sub-query:

) sub

This will select the last 50 rows from table, and then order them in ascending order.

Error: Cannot access file bin/Debug/... because it is being used by another process

I have faced the same issue, but none of the answers above helped me! I just simply closed my Visual Studio 2017 then re-run it, and It worked!

Telegram Bot - how to get a group chat id?

If you are implementing your bot, keep stored a group name -> id table, and ask it with a command. Then you can also send per name.

How to hide status bar in Android

Add this to your Activity class

protected void onCreate(Bundle savedInstanceState) {
    // some your code

UILabel Align Text to center

IO6.1 [lblTitle setTextAlignment:NSTextAlignmentCenter];

How do you stop tracking a remote branch in Git?

git branch --unset-upstream stops tracking all the local branches, which is not desirable.

Remove the [branch "branch-name"] section from the .git/config file followed by

git branch -D 'branch-name' && git branch -D -r 'origin/branch-name'

works out the best for me.

How can I have linebreaks in my long LaTeX equations?

If it is inline equation, then use \allowbreak. Use it like:

$x_1,x_2,x_3,\allowbreak x_4,x_5$.

Latex will break equation in this place only if necessary.

Example: Communication between Activity and Service using Messaging

Great tutorial, fantastic presentation. Neat, simple, short and very explanatory. Although, notification.setLatestEventInfo(this, getText(R.string.service_label), text, contentIntent); method is no more. As trante stated here, good approach would be:

private static final int NOTIFICATION_ID = 45349;

private void showNotification() {
    NotificationCompat.Builder builder =
            new NotificationCompat.Builder(this)
                    .setContentTitle("My Notification Title")
                    .setContentText("Something interesting happened");

    Intent targetIntent = new Intent(this, MainActivity.class);
    PendingIntent contentIntent = PendingIntent.getActivity(this, 0, targetIntent, PendingIntent.FLAG_UPDATE_CURRENT);
    _nManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

public void onDestroy() {
    if (_timer != null) {_timer.cancel();}
    _nManager.cancel(NOTIFICATION_ID); // Cancel the persistent notification.
    Log.i("PlaybackService", "Service Stopped.");
    _isRunning = false;

Checked myself, everything works like a charm (activity and service names may differ from original).

JavaScript: How to pass object by value?

As a consideration to jQuery users, there is also a way to do this in a simple way using the framework. Just another way jQuery makes our lives a little easier.

var oShallowCopy = jQuery.extend({}, o);
var oDeepCopy    = jQuery.extend(true, {}, o); 

references :

Parse JSON with R

The function fromJSON() in RJSONIO, rjson and jsonlite don't return a simple 2D data.frame for complex nested json objects.

To overcome this you can use tidyjson. It takes in a json and always returns a data.frame. It is currently not availble in CRAN, you can get it here:

Update: tidyjson is now available in cran, you can install it directly using install.packages("tidyjson")

Vagrant error : Failed to mount folders in Linux guest

Try like it:

vagrant plugin install vagrant-vbguest

In Vagrantfile add:

config.vbguest.iso_path = ""
config.vbguest.auto_update = false
config.vbguest.installer_arguments = %w{--nox11 -- --force}


vagrant vbguest --do install -f -b

vagrant reload

Lock, mutex, semaphore... what's the difference?

A lock allows only one thread to enter the part that's locked and the lock is not shared with any other processes.

A mutex is the same as a lock but it can be system wide (shared by multiple processes).

A semaphore does the same as a mutex but allows x number of threads to enter, this can be used for example to limit the number of cpu, io or ram intensive tasks running at the same time.

For a more detailed post about the differences between mutex and semaphore read here.

You also have read/write locks that allows either unlimited number of readers or 1 writer at any given time.

PreparedStatement with list of parameters in a IN clause

You don't want use PreparedStatment with dynamic queries using IN clause at least your sure you're always under 5 variable or a small value like that but even like that I think it's a bad idea ( not terrible, but bad ). As the number of elements is large, it will be worse ( and terrible ).

Imagine hundred or thousand possibilities in your IN clause :

  1. It's counter-productive, you lost performance and memory because you cache every time a new request, and PreparedStatement are not just for SQL injection, it's about performance. In this case, Statement is better.

  2. Your pool have a limit of PreparedStatment ( -1 defaut but you must limit it ), and you will reach this limit ! and if you have no limit or very large limit you have some risk of memory leak, and in extreme case OutofMemory errors. So if it's for your small personnal project used by 3 users it's not dramatic, but you don't want that if you're in a big company and that you're app is used by thousand people and million request.

Some reading. IBM : Memory utilization considerations when using prepared statement caching

String method cannot be found in a main class method

It seem like your Resort method doesn't declare a compareTo method. This method typically belongs to the Comparable interface. Make sure your class implements it.

Additionally, the compareTo method is typically implemented as accepting an argument of the same type as the object the method gets invoked on. As such, you shouldn't be passing a String argument, but rather a Resort.

Alternatively, you can compare the names of the resorts. For example

if (resortList[mid].getResortName().compareTo(resortName)>0)  

multiple packages in context:component-scan, spring config

You can add multiple base packages (see axtavt's answer), but you can also filter what's scanned inside the base package:

<context:component-scan base-package="x.y.z">
   <context:include-filter type="regex" expression="(service|controller)\..*"/>

Problems with Android Fragment back stack

I know it's a old quetion but i got the same problem and fix it like this:

First, Add Fragment1 to BackStack with a name (e.g "Frag1"):

frag = new Fragment1();

transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(, frag);

And then, Whenever you want to go back to Fragment1 (even after adding 10 fragments above it), just call popBackStackImmediate with the name:

getSupportFragmentManager().popBackStackImmediate("Frag1", 0);

Hope it will help someone :)

Convert YYYYMMDD string date to a datetime value

You should have to use DateTime.TryParseExact.

var newDate = DateTime.ParseExact("20111120", 


string str = "20111021";
string[] format = {"yyyyMMdd"};
DateTime date;

if (DateTime.TryParseExact(str, 
                           out date))

How to implement custom JsonConverter in JSON.NET to deserialize a List of base class objects?

Here's another solution that avoids the use of jObject.CreateReader(), and instead creates a new JsonTextReader (which is the behavior used by the default JsonCreate.Deserialze method:

public abstract class JsonCreationConverter<T> : JsonConverter
    protected abstract T Create(Type objectType, JObject jObject);

    public override bool CanConvert(Type objectType)
        return typeof(T).IsAssignableFrom(objectType);

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        if (reader.TokenType == JsonToken.Null)
            return null;

        // Load JObject from stream
        JObject jObject = JObject.Load(reader);

        // Create target object based on JObject
        T target = Create(objectType, jObject);

        // Populate the object properties
        StringWriter writer = new StringWriter();
        serializer.Serialize(writer, jObject);
        using (JsonTextReader newReader = new JsonTextReader(new StringReader(writer.ToString())))
            newReader.Culture = reader.Culture;
            newReader.DateParseHandling = reader.DateParseHandling;
            newReader.DateTimeZoneHandling = reader.DateTimeZoneHandling;
            newReader.FloatParseHandling = reader.FloatParseHandling;
            serializer.Populate(newReader, target);

        return target;

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        serializer.Serialize(writer, value);

How to test code dependent on environment variables using JUnit?

If you want to retrieve informations about the environment variable in Java, you can call the method : System.getenv();. As the properties, this method returns a Map containing the variable names as keys and the variable values as the map values. Here is an example :

    import java.util.Map;

public class EnvMap {
    public static void main (String[] args) {
        Map<String, String> env = System.getenv();
        for (String envName : env.keySet()) {
            System.out.format("%s=%s%n", envName, env.get(envName));

The method getEnv() can also takes an argument. For instance :

String myvalue = System.getEnv("MY_VARIABLE");

For testing, I would do something like this :

public class Environment {
    public static String getVariable(String variable) {
       return  System.getenv(variable);

 public class EnvVariableTest {

     @Test testVariable1(){
         String value = Environment.getVariable("MY_VARIABLE1");

    @Test testVariable2(){
       String value2 = Environment.getVariable("MY_VARIABLE2");

How to set a Javascript object values dynamically?

simple as this = value;

Display a decimal in scientific notation

My decimals are too big for %E so I had to improvize:

def format_decimal(x, prec=2):
    tup = x.as_tuple()
    digits = list(tup.digits[:prec + 1])
    sign = '-' if tup.sign else ''
    dec = ''.join(str(i) for i in digits[1:])
    exp = x.adjusted()
    return '{sign}{int}.{dec}e{exp}'.format(sign=sign, int=digits[0], dec=dec, exp=exp)

Here's an example usage:

>>> n = decimal.Decimal(4.3) ** 12314
>>> print format_decimal(n)
>>> print '%e' % n

How do I activate a Spring Boot profile when running from IntelliJ?

I use the Intellij Community Edition. Go to the "Run/Debug Configurations" > Runner tab > Environment variables > click button "...". Add: SPRING_PROFILES_ACTIVE = local

Exception in thread "main" java.lang.Error: Unresolved compilation problems

Your problem is in this line: Message messageObject = new Message ();
This error says that the Message class is not known at compile time.

So you need to import the Message class.

Something like this:

import package1.package2.Message;

Check this out.

How to establish a connection pool in JDBC?

If you need a standalone connection pool, my preference goes to C3P0 over DBCP (that I've mentioned in this previous answer), I just had too much problems with DBCP under heavy load. Using C3P0 is dead simple. From the documentation:

ComboPooledDataSource cpds = new ComboPooledDataSource();
cpds.setDriverClass( "org.postgresql.Driver" ); //loads the jdbc driver
cpds.setJdbcUrl( "jdbc:postgresql://localhost/testdb" );

// the settings below are optional -- c3p0 can work with defaults

// The DataSource cpds is now a fully configured and usable pooled DataSource 

But if you are running inside an application server, I would recommend to use the built-in connection pool it provides. In that case, you'll need to configure it (refer to the documentation of your application server) and to retrieve a DataSource via JNDI:

DataSource ds = (DataSource) new InitialContext().lookup("jdbc/myDS");

Interesting 'takes exactly 1 argument (2 given)' Python error

If a non-static method is member of a class, you have to define it like that:

def Method(self, atributes..)

So, I suppose your 'e' is instance of some class with implemented method that tries to execute and has too much arguments.

Get index of element as child relative to parent

Delegate and Live are easy to use but if you won't have any more li:s added dynamically you could use event delagation with normal bind/click as well. There should be some performance gain using this method since the DOM won't have to be monitored for new matching elements. Haven't got any actual numbers but it makes sense :)

$("#wizard").click(function (e) {
    var source = $(;
        // alert index of li relative to ul parent

You could test it at jsFiddle:

Trigger a Travis-CI rebuild without pushing a commit?

I should mention here that we now have a means of triggering a new build on the web. See for details.

TL;DR Click on "More options", and choose "Trigger build".

set pythonpath before import statements

This will add a path to your Python process / instance (i.e. the running executable). The path will not be modified for any other Python processes. Another running Python program will not have its path modified, and if you exit your program and run again the path will not include what you added before. What are you are doing is generally correct.

import sys

import sys
import time
while True:
  print sys.path

run: python &

This will run, connected to your STDOUT, and it will continue to run in the background. You can then run python Each has a different set of environment variables. Observe that the output from does not change because does not change's environment.

A note on importing

Python imports are dynamic, like the rest of the language. There is no static linking going on. The import is an executable line, just like sys.path.append....

awk without printing newline

The ORS (output record separator) variable in AWK defaults to "\n" and is printed after every line. You can change it to " " in the BEGIN section if you want everything printed consecutively.

How to run a single test with Mocha?

Looking into we see that simply use

mocha test/myfile

will work. You can omit the '.js' at the end.

How to get WordPress post featured image URL

I think this is the easiest solution and the updated one:

<?php the_post_thumbnail('single-post-thumbnail'); ?>

Entity Framework is Too Slow. What are my options?

If you're purely fetching data, it's a big help to performance when you tell EF to not keep track of the entities it fetches. Do this by using MergeOption.NoTracking. EF will just generate the query, execute it and deserialize the results to objects, but will not attempt to keep track of entity changes or anything of that nature. If a query is simple (doesn't spend much time waiting on the database to return), I've found that setting it to NoTracking can double query performance.

See this MSDN article on the MergeOption enum:

Identity Resolution, State Management, and Change Tracking

This seems to be a good article on EF performance:

Performance and the Entity Framework

How to catch integer(0)?

Maybe off-topic, but R features two nice, fast and empty-aware functions for reducing logical vectors -- any and all:

if(any(x=='dolphin')) stop("Told you, no mammals!")

How does python numpy.where() work?

np.where returns a tuple of length equal to the dimension of the numpy ndarray on which it is called (in other words ndim) and each item of tuple is a numpy ndarray of indices of all those values in the initial ndarray for which the condition is True. (Please don't confuse dimension with shape)

For example:

array([[0, 1, 2],
      [3, 4, 5],
      [6, 7, 8]])
y = np.where(x>4)
array([1, 2, 2, 2], dtype=int64), array([2, 0, 1, 2], dtype=int64))

y is a tuple of length 2 because x.ndim is 2. The 1st item in tuple contains row numbers of all elements greater than 4 and the 2nd item contains column numbers of all items greater than 4. As you can see, [1,2,2,2] corresponds to row numbers of 5,6,7,8 and [2,0,1,2] corresponds to column numbers of 5,6,7,8 Note that the ndarray is traversed along first dimension(row-wise).



will return a tuple of length 3 because x has 3 dimensions.

But wait, there's more to np.where!

when two additional arguments are added to np.where; it will do a replace operation for all those pairwise row-column combinations which are obtained by the above tuple.

y = np.where(x>4, 1, 0)
array([[0, 0, 0],
   [0, 0, 1],
   [1, 1, 1]])

SQLSTATE[HY000] [1698] Access denied for user 'root'@'localhost'

Users for mysql and for server are 2 different things, look how to add user to database and login with these credentials

Using Auto Layout in UITableView for dynamic cell layouts & variable row heights

I had to use dynamic views (setup views and constraints by code) and when I wanted to set preferredMaxLayoutWidth label's width was 0. So I've got wrong cell height.

Then I added

[cell layoutSubviews];

before executing

[cell setNeedsUpdateConstraints];
[cell updateConstraintsIfNeeded];

After that label's width was as expected and dynamic height was calculating right.

How do you remove a Cookie in a Java Servlet

This is code that I have effectively used before, passing "/" as the strPath parameter.

public static Cookie eraseCookie(String strCookieName, String strPath) {
    Cookie cookie = new Cookie(strCookieName, "");

    return cookie;

SQL where datetime column equals today's date?

Easy way out is to use a condition like this ( use desired date > GETDATE()-1)

your sql statement "date specific" > GETDATE()-1

Load CSV file with Spark

If you are having any one or more row(s) with less or more number of columns than 2 in the dataset then this error may arise.

I am also new to Pyspark and trying to read CSV file. Following code worked for me:

In this code I am using dataset from kaggle the link is:

1. Without mentioning the schema:

from pyspark.sql import SparkSession  
scSpark = SparkSession \
    .builder \
    .appName("Python Spark SQL basic example: Reading CSV file without mentioning schema") \
    .config("spark.some.config.option", "some-value") \

sdfData ="data.csv", header=True, sep=",")

Now check the columns: sdfData.columns

Output will be:

['InvoiceNo', 'StockCode','Description','Quantity', 'InvoiceDate', 'CustomerID', 'Country']

Check the datatype for each column:


This will give the data frame with all the columns with datatype as StringType

2. With schema: If you know the schema or want to change the datatype of any column in the above table then use this (let's say I am having following columns and want them in a particular data type for each of them)

from pyspark.sql import SparkSession  
from pyspark.sql.types import StructType, StructField
from pyspark.sql.types import DoubleType, IntegerType, StringType
    schema = StructType([\
        StructField("InvoiceNo", IntegerType()),\
        StructField("StockCode", StringType()), \
        StructField("Description", StringType()),\
        StructField("Quantity", IntegerType()),\
        StructField("InvoiceDate", StringType()),\
        StructField("CustomerID", DoubleType()),\
        StructField("Country", StringType())\

scSpark = SparkSession \
    .builder \
    .appName("Python Spark SQL example: Reading CSV file with schema") \
    .config("spark.some.config.option", "some-value") \

sdfData ="data.csv", header=True, sep=",", schema=schema)

Now check the schema for datatype of each column:



Edited: We can use the following line of code as well without mentioning schema explicitly:

sdfData ="data.csv", header=True, inferSchema = True)

The output is:


The output will look like this:

|InvoiceNo|StockCode|         Description|Quantity|   InvoiceDate|CustomerID|Country|
|   536365|   85123A|WHITE HANGING HEA...|       6|12/1/2010 8:26|      2.55|  17850|
|   536365|    71053| WHITE METAL LANTERN|       6|12/1/2010 8:26|      3.39|  17850|
|   536365|   84406B|CREAM CUPID HEART...|       8|12/1/2010 8:26|      2.75|  17850|
|   536365|   84029G|KNITTED UNION FLA...|       6|12/1/2010 8:26|      3.39|  17850|
|   536365|   84029E|RED WOOLLY HOTTIE...|       6|12/1/2010 8:26|      3.39|  17850|
|   536365|    22752|SET 7 BABUSHKA NE...|       2|12/1/2010 8:26|      7.65|  17850|
|   536365|    21730|GLASS STAR FROSTE...|       6|12/1/2010 8:26|      4.25|  17850|
|   536366|    22633|HAND WARMER UNION...|       6|12/1/2010 8:28|      1.85|  17850|
|   536366|    22632|HAND WARMER RED P...|       6|12/1/2010 8:28|      1.85|  17850|
|   536367|    84879|ASSORTED COLOUR B...|      32|12/1/2010 8:34|      1.69|  13047|
|   536367|    22745|POPPY'S PLAYHOUSE...|       6|12/1/2010 8:34|       2.1|  13047|
|   536367|    22748|POPPY'S PLAYHOUSE...|       6|12/1/2010 8:34|       2.1|  13047|
|   536367|    22749|FELTCRAFT PRINCES...|       8|12/1/2010 8:34|      3.75|  13047|
|   536367|    22310|IVORY KNITTED MUG...|       6|12/1/2010 8:34|      1.65|  13047|
|   536367|    84969|BOX OF 6 ASSORTED...|       6|12/1/2010 8:34|      4.25|  13047|
|   536367|    22623|BOX OF VINTAGE JI...|       3|12/1/2010 8:34|      4.95|  13047|
|   536367|    22622|BOX OF VINTAGE AL...|       2|12/1/2010 8:34|      9.95|  13047|
|   536367|    21754|HOME BUILDING BLO...|       3|12/1/2010 8:34|      5.95|  13047|
|   536367|    21755|LOVE BUILDING BLO...|       3|12/1/2010 8:34|      5.95|  13047|
|   536367|    21777|RECIPE BOX WITH M...|       4|12/1/2010 8:34|      7.95|  13047|
only showing top 20 rows

jQuery - Appending a div to body, the body is the object?

    $('body').append($('<div/>', {
        id: 'holdy' 


Standard SQL syntax is

DROP TABLE table_name;

IF EXISTS is not standard; different platforms might support it with different syntax, or not support it at all. In PostgreSQL, the syntax is


The first one will throw an error if the table doesn't exist, or if other database objects depend on it. Most often, the other database objects will be foreign key references, but there may be others, too. (Views, for example.) The second will not throw an error if the table doesn't exist, but it will still throw an error if other database objects depend on it.

To drop a table, and all the other objects that depend on it, use one of these.


Use CASCADE with great care.

Missing XML comment for publicly visible type or member

I wanted to add something to the answers listed here:

As Isak pointed out, the XML documentation is useful for Class Libraries, as it provides intellisense to any consumer within Visual Studio. Therefore, an easy and correct solution is to simply turn off documentation for any top-level project (such as UI, etc), which is not going to be implemented outside of its own project.

Additionally I wanted to point out that the warning only expresses on publicly visible members. So, if you setup your class library to only expose what it needs to, you can get by without documenting private and internal members.


I have noticed that @Eyo Okon Eyo solution works as long as MySQL server is not restarted, then defaults settings are restored. Here is a permanent solution that worked for me:

To remove particular SQL mode (in this case ONLY_FULL_GROUP_BY), find the current SQL mode:

SELECT @@GLOBAL.sql_mode;

copy the result and remove from it what you don't need (ONLY_FULL_GROUP_BY)





create and open this file:


and write and past into it your new SQL mode:


restart MySQL:

sudo service mysql restart

Or you can use ANY_VALUE() to suppress ONLY_FULL_GROUP_BY value rejection, you can read more about it here

Types in Objective-C on iOS

Note that you can also use the C99 fixed-width types perfectly well in Objective-C:

#import <stdint.h>
int32_t x; // guaranteed to be 32 bits on any platform

The wikipedia page has a decent description of what's available in this header if you don't have a copy of the C standard (you should, though, since Objective-C is just a tiny extension of C). You may also find the headers limits.h and inttypes.h to be useful.

How do I do an initial push to a remote repository with Git?

@Josh Lindsey already answered perfectly fine. But I want to add some information since I often use ssh.

Therefore just change:

git remote add origin [email protected]:/path/to/my_project.git


git remote add origin ssh://[email protected]/path/to/my_project

Note that the colon between domain and path isn't there anymore.

Error sending json in POST to web API service

another tip...where to add "content-type: application/json" the textbox field on the Composer/Parsed tab. There are 3 lines already filled in there, so I added this Content-type as the 4th line. That made the Post work.

Better way to check variable for null or empty string?

Beware false negatives from the trim() function — it performs a cast-to-string before trimming, and thus will return e.g. "Array" if you pass it an empty array. That may not be an issue, depending on how you process your data, but with the code you supply, a field named question[] could be supplied in the POST data and appear to be a non-empty string. Instead, I would suggest:

$question = $_POST['question'];

if (!is_string || ($question = trim($question))) {
    // Handle error here

// If $question was a string, it will have been trimmed by this point

How can I programmatically get the MAC address of an iphone

#import <sys/socket.h>
#import <net/if_dl.h>
#import <ifaddrs.h>
#import <sys/xattr.h>
#define IFT_ETHER 0x6


- (NSString*)macAddress
    NSString* result = nil;

    char* macAddressString = (char*)malloc(18);
    if (macAddressString != NULL)
        strcpy(macAddressString, "");

        struct ifaddrs* addrs = NULL;
        struct ifaddrs* cursor;

        if (getifaddrs(&addrs) == 0)
            cursor = addrs;

            while (cursor != NULL)
                if ((cursor->ifa_addr->sa_family == AF_LINK) && (((const struct sockaddr_dl*)cursor->ifa_addr)->sdl_type == IFT_ETHER) && strcmp("en0", cursor->ifa_name) == 0)
                    const struct sockaddr_dl* dlAddr = (const struct sockaddr_dl*) cursor->ifa_addr;
                    const unsigned char* base = (const unsigned char*)&dlAddr->sdl_data[dlAddr->sdl_nlen];

                    for (NSInteger index = 0; index < dlAddr->sdl_alen; index++)
                        char partialAddr[3];

                        sprintf(partialAddr, "%02X", base[index]);
                        strcat(macAddressString, partialAddr);

                cursor = cursor->ifa_next;


        result = [[[NSString alloc] initWithUTF8String:macAddressString] autorelease];


    return result;

JavaScript array to CSV

for a simple csv one map() and a join() are enough:

var csv ={
    return d.join();

/* Results in 

This method also allows you to specify column separator other than a comma in the inner join. for example a tab: d.join('\t')

On the other hand if you want to do it properly and enclose strings in quotes "", then you can use some JSON magic:

var csv ={
   return JSON.stringify(d);
.replace(/(^\[)|(\]$)/mg, ''); // remove opening [ and closing ] brackets from each line 

/* would produce

if you have array of objects like :

var data = [
  {"title": "Book title 1", "author": "Name1 Surname1"},
  {"title": "Book title 2", "author": "Name2 Surname2"},
  {"title": "Book title 3", "author": "Name3 Surname3"},
  {"title": "Book title 4", "author": "Name4 Surname4"}

// use
var csv ={
    return JSON.stringify(Object.values(d));
.replace(/(^\[)|(\]$)/mg, '');

WCF named pipe minimal example

Check out my highly simplified Echo example: It is designed to use basic HTTP communication, but it can easily be modified to use named pipes by editing the app.config files for the client and server. Make the following changes:

Edit the server's app.config file, removing or commenting out the http baseAddress entry and adding a new baseAddress entry for the named pipe (called net.pipe). Also, if you don't intend on using HTTP for a communication protocol, make sure the serviceMetadata and serviceDebug is either commented out or deleted:

            <service name="">
                        <add baseAddress="net.pipe://localhost/EchoService"/>

Edit the client's app.config file so that the basicHttpBinding is either commented out or deleted and a netNamedPipeBinding entry is added. You will also need to change the endpoint entry to use the pipe:

                <binding name="NetNamedPipeBinding_IEchoService"/>
            <endpoint address              = "net.pipe://localhost/EchoService"
                      binding              = "netNamedPipeBinding"
                      bindingConfiguration = "NetNamedPipeBinding_IEchoService"
                      contract             = "EchoServiceReference.IEchoService"
                      name                 = "NetNamedPipeBinding_IEchoService"/>

The above example will only run with named pipes, but nothing is stopping you from using multiple protocols to run your service. AFAIK, you should be able to have a server run a service using both named pipes and HTTP (as well as other protocols).

Also, the binding in the client's app.config file is highly simplified. There are many different parameters you can adjust, aside from just specifying the baseAddress...

Returning binary file from controller in ASP.NET Web API

For those using .NET Core:

You can make use of the IActionResult interface in an API controller method, like so...

    public async Task<IActionResult> GetReportData(int year)
        // Render Excel document in memory and return as Byte[]
        Byte[] file = await this._reportDao.RenderReportAsExcel(year);

        return File(file, "application/vnd.openxmlformats", "fileName.xlsx");

This example is simplified, but should get the point across. In .NET Core this process is so much simpler than in previous versions of .NET - i.e. no setting response type, content, headers, etc.

Also, of course the MIME type for the file and the extension will depend on individual needs.

Reference: SO Post Answer by @NKosi

Importing the private-key/public-certificate pair in the Java KeyStore

A keystore needs a keystore file. The KeyStore class needs a FileInputStream. But if you supply null (instead of FileInputStream instance) an empty keystore will be loaded. Once you create a keystore, you can verify its integrity using keytool.

Following code creates an empty keystore with empty password

  KeyStore ks2 = KeyStore.getInstance("jks");
  FileOutputStream out = new FileOutputStream("C:\\mykeytore.keystore");, "".toCharArray());

Once you have the keystore, importing certificate is very easy. Checkout this link for the sample code.

Comparing two files in linux terminal

You can also use: colordiff: Displays the output of diff with colors.

About vimdiff: It allows you to compare files via SSH, for example :

vimdiff /var/log/secure scp://

Extracted from:

Comparison of Android Web Service and Networking libraries: OKHTTP, Retrofit and Volley

And yet another option:

  • It is modular like Volley, but more extended and documentation is improving, supporting different HTTP stacks and converters out of the box
  • It has a module to generate server API interface mappings like Retrofit
  • It also has JavaRx support

And many other handy features like markers, transformers, etc.

Make a nav bar stick

Give headercss position fixed.

.headercss {
    width: 100%;
    height: 320px;
    background-color: #000000;
    position: fixed;

Then give the content container a 320px padding-top, so it doesn't get behind the header.

Why should text files end with a newline?

I personally like new lines at the end of source code files.

It may have its origin with Linux or all UNIX systems for that matter. I remember there compilation errors (gcc if I'm not mistaken) because source code files did not end with an empty new line. Why was it made this way one is left to wonder.

phpMyAdmin is throwing a #2002 cannot log in to the mysql server phpmyadmin

Just in case anyone has anymore troubles, this is a pretty sure fix.

check your etc/hosts file make sure you have a root user for every host.



Therefore I will have 2 or more users as root for mysql:

[email protected]

this is how I fixed my problem.

How to redirect to another page in node.js

You should return the line that redirects

return res.redirect('/UserHomePage');

How to run a Powershell script from the command line and pass a directory as a parameter

try this:

powershell "C:\Dummy Directory 1\Foo.ps1 'C:\Dummy Directory 2\File.txt'"

SQL UPDATE with sub-query that references the same table in MySQL

Some reference for you

UPDATE user_account student 
INNER JOIN user_account teacher ON
   teacher.user_account_id = student.teacher_id 
   AND teacher.user_type = 'ROLE_TEACHER'
SET student.student_education_facility_id = teacher.education_facility_id

Column count doesn't match value count at row 1

You can resolve the error by providing the column names you are affecting.

> INSERT INTO table_name (column1,column2,column3)
 `VALUES(50,'Jon Snow','Eye');`

please note that the semi colon should be added only after the statement providing values

How to install libusb in Ubuntu

Here is what worked for me.

Install the userspace USB programming library development files

sudo apt-get install libusb-1.0-0-dev
sudo updatedb && locate libusb.h

The path should appear as (or similar)


Include the header to your C code

#include <libusb-1.0/libusb.h>

Compile your C file

gcc -o example example.c -lusb-1.0

Change Placeholder Text using jQuery

$(this).val() is a string. Use parseInt($(this).val(), 10) or check for '1'. The ten is to denote base 10.

$(function () {
    $('input[placeholder], textarea[placeholder]').blur();
    $('#serMemdd').change(function () {
        var k = $(this).val();
        if (k == '1') {
            $("#serMemtb").attr("placeholder", "Type a name (Lastname, Firstname)").blur();
        else if (k == '2') {
            $("#serMemtb").attr("placeholder", "Type an ID").blur();
        else if (k == '3') {
            $("#serMemtb").attr("placeholder", "Type a Location").blur();


$(function () {
    $('input[placeholder], textarea[placeholder]').placeholder();
    $('#serMemdd').change(function () {
        var k = parseInt($(this).val(), 10);
        if (k == 1) {
            $("#serMemtb").attr("placeholder", "Type a name (Lastname, Firstname)").blur();
        else if (k == 2) {
            $("#serMemtb").attr("placeholder", "Type an ID").blur();
        else if (k == 3) {
            $("#serMemtb").attr("placeholder", "Type a Location").blur();

Other Plugins

ori has brought to my attention that the plugin you are using does not overcome IEs HTML failure.

Try something like this:

How do you parse and process HTML/XML in PHP?

There are many ways to process HTML/XML DOM of which most have already been mentioned. Hence, I won't make any attempt to list those myself.

I merely want to add that I personally prefer using the DOM extension and why :

  • iit makes optimal use of the performance advantage of the underlying C code
  • it's OO PHP (and allows me to subclass it)
  • it's rather low level (which allows me to use it as a non-bloated foundation for more advanced behavior)
  • it provides access to every part of the DOM (unlike eg. SimpleXml, which ignores some of the lesser known XML features)
  • it has a syntax used for DOM crawling that's similar to the syntax used in native Javascript.

And while I miss the ability to use CSS selectors for DOMDocument, there is a rather simple and convenient way to add this feature: subclassing the DOMDocument and adding JS-like querySelectorAll and querySelector methods to your subclass.

For parsing the selectors, I recommend using the very minimalistic CssSelector component from the Symfony framework. This component just translates CSS selectors to XPath selectors, which can then be fed into a DOMXpath to retrieve the corresponding Nodelist.

You can then use this (still very low level) subclass as a foundation for more high level classes, intended to eg. parse very specific types of XML or add more jQuery-like behavior.

The code below comes straight out my DOM-Query library and uses the technique I described.

For HTML parsing :

namespace PowerTools;

use \Symfony\Component\CssSelector\CssSelector as CssSelector;

class DOM_Document extends \DOMDocument {
    public function __construct($data = false, $doctype = 'html', $encoding = 'UTF-8', $version = '1.0') {
        parent::__construct($version, $encoding);
        if ($doctype && $doctype === 'html') {
        } else {

    public function querySelectorAll($selector, $contextnode = null) {
        if (isset($this->doctype->name) && $this->doctype->name == 'html') {
        } else {
        $xpath = new \DOMXpath($this);
        return $xpath->query(CssSelector::toXPath($selector, 'descendant::'), $contextnode);


    public function loadHTMLFile($filename, $options = 0) {
        $this->loadHTML(file_get_contents($filename), $options);

    public function loadHTML($source, $options = 0) {
        if ($source && $source != '') {
            $data = trim($source);
            $html5 = new HTML5(array('targetDocument' => $this, 'disableHtmlNsInDom' => true));
            $data_start = mb_substr($data, 0, 10);
            if (strpos($data_start, '<!DOCTYPE ') === 0 || strpos($data_start, '<html>') === 0) {
            } else {
                @$this->loadHTML('<!DOCTYPE html><html><head><meta charset="' . $encoding . '" /></head><body></body></html>');
                $t = $html5->loadHTMLFragment($data);
                $docbody = $this->getElementsByTagName('body')->item(0);
                while ($t->hasChildNodes()) {


See also Parsing XML documents with CSS selectors by Symfony's creator Fabien Potencier on his decision to create the CssSelector component for Symfony and how to use it.

Array of arrays (Python/NumPy)



tolist method mentioned above will return the nested Python list

How to get the user input in Java?

This is a simple code that uses the function. This code just writes out whatever was typed. You can get rid of the while loop if you just want to take input once, and you could store answers in a character array if you so choose.

package main;


public class Root 
    public static void main(String[] args)
        new Root();

    public Root()
                for(int y = 0; y <; ++y)
            catch(IOException ex)

Python xml ElementTree from a string source?

If you're using xml.etree.ElementTree.parse to parse from a file, then you can use xml.etree.ElementTree.fromstring to parse from text.

See xml.etree.ElementTree

Rebasing remote branches in Git

You can disable the check (if you're really sure you know what you're doing) by using the --force option to git push.

multiple where condition codeigniter

you can use both use array like :

$array = array('tlb_account.crid' =>$value , 'tlb_request.sign'=> 'FALSE' );

and direct assign like:

$this->db->where('tlb_account.crid' =>$value , 'tlb_request.sign'=> 'FALSE');

I wish help you.

Date ticks and rotation in matplotlib

An easy solution which avoids looping over the ticklabes is to just use


This command automatically rotates the xaxis labels and adjusts their position. The default values are a rotation angle 30° and horizontal alignment "right". But they can be changed in the function call

fig.autofmt_xdate(bottom=0.2, rotation=30, ha='right')

The additional bottom argument is equivalent to setting plt.subplots_adjust(bottom=bottom), which allows to set the bottom axes padding to a larger value to host the rotated ticklabels.

So basically here you have all the settings you need to have a nice date axis in a single command.

A good example can be found on the matplotlib page.

Save ArrayList to SharedPreferences

You can convert it to JSON String and store the string in the SharedPreferences.

How to convert "Mon Jun 18 00:00:00 IST 2012" to 18/06/2012?

Just need to add: new SimpleDateFormat("bla bla bla", Locale.US)

public static void main(String[] args) throws ParseException {
    java.util.Date fecha = new java.util.Date("Mon Dec 15 00:00:00 CST 2014");
    DateFormat formatter = new SimpleDateFormat("EEE MMM dd HH:mm:ss Z yyyy", Locale.US);
    Date date;
    date = (Date)formatter.parse(fecha.toString());

    Calendar cal = Calendar.getInstance();
    String formatedDate = cal.get(Calendar.DATE) + "/" + 
            (cal.get(Calendar.MONTH) + 1) + 
            "/" +         cal.get(Calendar.YEAR);
    System.out.println("formatedDate : " + formatedDate);

Spark - repartition() vs coalesce()

One additional point to note here is that, as the basic principle of Spark RDD is immutability. The repartition or coalesce will create new RDD. The base RDD will continue to have existence with its original number of partitions. In case the use case demands to persist RDD in cache, then the same has to be done for the newly created RDD.

scala> pairMrkt.repartition(10)
res16: org.apache.spark.rdd.RDD[(String, Array[String])] =MapPartitionsRDD[11] at repartition at <console>:26

scala> res16.partitions.length
res17: Int = 10

scala>  pairMrkt.partitions.length
res20: Int = 2

JavaFX FXML controller - constructor vs initialize method

The initialize method is called after all @FXML annotated members have been injected. Suppose you have a table view you want to populate with data:

class MyController { 
    TableView<MyModel> tableView; 

    public MyController() {
        tableView.getItems().addAll(getDataFromSource()); // results in NullPointerException, as tableView is null at this point. 

    public void initialize() {
        tableView.getItems().addAll(getDataFromSource()); // Perfectly Ok here, as FXMLLoader already populated all @FXML annotated members. 

Difference between char* and const char*?


char *str = "Hello";
str[0] = 'M'  //Warning may be issued by compiler, and will cause segmentation fault upon running the programme

The above sets str to point to the literal value "Hello" which is hard-coded in the program's binary image, which is flagged as read-only in memory, means any change in this String literal is illegal and that would throw segmentation faults.


const char *str = "Hello";
str[0] = 'M'  //Compile time error


char str[] = "Hello";
str[0] = 'M'; // legal and change the str = "Mello".

How to add headers to a multicolumn listbox in an Excel userform using VBA

I was searching for quite a while for a solution to add a header without using a separate sheet and copy everything into the userform.

My solution is to use the first row as header and run it through an if condition and add additional items underneath.

Like that:

If lborowcount = 0 Then_x000D_
 With lboorder_x000D_
 .ColumnCount = 5_x000D_
 .Column(0, lborowcount) = "Item"_x000D_
 .Column(1, lborowcount) = "Description"_x000D_
 .Column(2, lborowcount) = "Ordered"_x000D_
 .Column(3, lborowcount) = "Rate"_x000D_
 .Column(4, lborowcount) = "Amount"_x000D_
 End With_x000D_
 lborowcount = lborowcount + 1_x000D_
End If_x000D_
With lboorder_x000D_
 .ColumnCount = 5_x000D_
 .Column(0, lborowcount) = itemselected_x000D_
 .Column(1, lborowcount) = descriptionselected_x000D_
 .Column(2, lborowcount) = orderedselected_x000D_
 .Column(3, lborowcount) = rateselected_x000D_
 .Column(4, lborowcount) = amountselected_x000D_
 End With_x000D_
lborowcount = lborowcount + 1

in that example lboorder is the listbox, lborowcount counts at which row to add the next listbox item. It's a 5 column listbox. Not ideal but it works and when you have to scroll horizontally the "header" stays above the row.

Delete all Duplicate Rows except for One in MySQL?

If you want to keep the row with the lowest id value:

                    FROM (SELECT MIN(
                            FROM NAMES n
                        GROUP BY x)

If you want the id value that is the highest:

                    FROM (SELECT MAX(
                            FROM NAMES n
                        GROUP BY x)

The subquery in a subquery is necessary for MySQL, or you'll get a 1093 error.

C++ equivalent of StringBuffer/StringBuilder?

The Rope container may be worth if have to insert/delete string into the random place of destination string or for a long char sequences. Here is an example from SGI's implementation:

crope r(1000000, 'x');          // crope is rope<char>. wrope is rope<wchar_t>
                                // Builds a rope containing a million 'x's.
                                // Takes much less than a MB, since the
                                // different pieces are shared.
crope r2 = r + "abc" + r;       // concatenation; takes on the order of 100s
                                // of machine instructions; fast
crope r3 = r2.substr(1000000, 3);       // yields "abc"; fast.
crope r4 = r2.substr(1000000, 1000000); // also fast.
reverse(r2.mutable_begin(), r2.mutable_end());
                                // correct, but slow; may take a
                                // minute or more.

Get local IP address

To get local Ip Address:

public static string GetLocalIPAddress()
    var host = Dns.GetHostEntry(Dns.GetHostName());
    foreach (var ip in host.AddressList)
        if (ip.AddressFamily == AddressFamily.InterNetwork)
            return ip.ToString();
    throw new Exception("No network adapters with an IPv4 address in the system!");

To check if you're connected or not:


How to get the current location latitude and longitude in android

Here is Android Location library you can find your current location without using Google account or subscription.

Find this link and download repository

Take care and Enjoy...

How to display the string html contents into webbrowser control?

Simple solution, I've tested is

var str = "<html><head></head><body>" + sender.ToString() + "</body></html>";
webBrowser1.DocumentText = str;

Best way to store a key=>value array in JavaScript?

That's just what a JavaScript object is:

var myArray = {id1: 100, id2: 200, "tag with spaces": 300};
myArray.id3 = 400;
myArray["id4"] = 500;

You can loop through it using loop:

for (var key in myArray) {
  console.log("key " + key + " has value " + myArray[key]);

See also: Working with objects (MDN).

In ECMAScript6 there is also Map (see the browser compatibility table there):

  • An Object has a prototype, so there are default keys in the map. This could be bypassed by using map = Object.create(null) since ES5, but was seldomly done.

  • The keys of an Object are Strings and Symbols, where they can be any value for a Map.

  • You can get the size of a Map easily while you have to manually keep track of size for an Object.

Cannot insert explicit value for identity column in table 'table' when IDENTITY_INSERT is set to OFF

There are basically 2 different ways to INSERT records without having an error:



As per the following example from the same Table created with an IDENTITY PRIMARY KEY:

CREATE TABLE [dbo].[Persons] (    
    LastName VARCHAR(40) NOT NULL,
    FirstName VARCHAR(40)

1) In the first example, you can insert new records into the table without getting an error when the IDENTITY_INSERT is OFF. The PRIMARY KEY "ID" MUST NOT BE PRESENT from the "INSERT INTO" Statements and a unique ID value will be added automatically:. If the ID is present from the INSERT in this case, you will get the error "Cannot insert explicit value for identify column in table..."

INSERT INTO [dbo].[Persons] (FirstName,LastName)
INSERT INTO Persons (FirstName,LastName) 

OUTPUT of TABLE [dbo].[Persons] will be:

ID    LastName   FirstName
1     DOE        Jane
2     BROWN      JOE

2) In the Second example, you can insert new records into the table without getting an error when the IDENTITY_INSERT is ON. The PRIMARY KEY "ID" MUST BE PRESENT from the "INSERT INTO" Statements as long as the ID value does not already exist: If the ID is NOT present from the INSERT in this case, you will get the error "Explicit value must be specified for identity column table..."

INSERT INTO [dbo].[Persons] (ID,FirstName,LastName)
INSERT INTO [dbo].[Persons] (ID,FirstName,LastName)

OUTPUT of TABLE [dbo].[Persons] will be:

ID    LastName   FirstName
1     DOE        Jane
2     BROWN      JOE
3     BLACK      JACK
5     WHITE      JOHN

The type cannot be resolved. It is indirectly referenced from required .class files

Something happened in Java 8 Update 91 that broke existing JSP code. That seems pretty clear. Here is a sample of similar questions and bug reports:

All these are about problems with Java 8 Update 91 (or later) that are not present when using earlier JRE/JDK versions.

The following OpenJDK changeset from 22 January 2016 appears to be related: (commit message "8144430: Improve JMX connections"). The changeset seems to be related to this vulnerability,, which is mentioned in a comment to this Red Hat bug report,

The Update 91 release notes document mentions JDK-8144430 (non-public ticket):

In "Oracle Critical Patch Update Advisory - April 2016", the CVE-2016-3427 vulnerability is mentioned:

How to escape the equals sign in properties files

In Spring or Spring boot file here is the way to escape the special characters;

table.whereclause=where id'\='100

Multiple Errors Installing Visual Studio 2015 Community Edition

If no other option in this thread works, you can try the steps given in this guide (see below):

  1. Download and install (Note: new site These are general-purpose PowerShell cmdlets I created for all sorts of development and troubleshooting operations for Windows Installer-based installs. You do not need to elevate to install them, though if you pre-elevate you can install them per-machine (by default they are per-user).
  2. Open an elevated PowerShell command prompt and run the following to discover which products have installed the key shared component:

    get-msicomponentinfo '{777CBCAC-12AB-4A57-A753-4A7D23B484D3}' | get-msiproductinfo

  3. If you’re fine with uninstalling all the listed products (especially given that you’re probably going to install RTM next), run the following:

    get-msicomponentinfo '{777CBCAC-12AB-4A57-A753-4A7D23B484D3}' | get-msiproductinfo | uninstall-msiproduct -properties IGNOREDEPENDENCIES=ALL

Personally, this worked for me. I forgot that I had some old files laying around on an old drive, which appearantly later on messed something up in the registry (I think..?). Anyway, with everything clean, it installed just fine!

Note: if you have issues with importing the PSMSI-tools in PowerShell, check this out:

In summary, you may need to run the command Set-ExecutionPolicy RemoteSigned to be allowed to import the software.

Hope this helps someone in need!

Should I use SVN or Git?

I would opt for SVN since it is more widely spread and better known.

I guess, Git would be better for Linux user.

How to Validate on Max File Size in Laravel?

Edit: Warning! This answer worked on my XAMPP OsX environment, but when I deployed it to AWS EC2 it did NOT prevent the upload attempt.

I was tempted to delete this answer as it is WRONG But instead I will explain what tripped me up

My file upload field is named 'upload' so I was getting "The upload failed to upload.". This message comes from this line in validation.php:

in resources/lang/en/validaton.php:

'uploaded' => 'The :attribute failed to upload.',

And this is the message displayed when the file is larger than the limit set by PHP.

I want to over-ride this message, which you normally can do by passing a third parameter $messages array to Validator::make() method.

However I can't do that as I am calling the POST from a React Component, which renders the form containing the csrf field and the upload field.

So instead, as a super-dodgy-hack, I chose to get into my view that displays the messages and replace that specific message with my friendly 'file too large' message.

Here is what works if the file to smaller than the PHP file size limit:

In case anyone else is using Laravel FormRequest class, here is what worked for me on Laravel 5.7:

This is how I set a custom error message and maximum file size:

I have an input field <input type="file" name="upload">. Note the CSRF token is required also in the form (google laravel csrf_field for what this means).

namespace App\Http\Requests;
use Illuminate\Foundation\Http\FormRequest;
class Upload extends FormRequest
  public function rules() {
    return [
      'upload' => 'required|file|max:8192',
  public function messages()
    return [            
      'upload.required' => "You must use the 'Choose file' button to select which file you wish to upload",
      'upload.max' => "Maximum file size to upload is 8MB (8192 KB). If you are uploading a photo, try to reduce its resolution to make it under 8MB"

iOS: UIButton resize according to text length

The way to do this in code is:

[button sizeToFit];

If you are subclassing and want to add extra rules you can override:

- (CGSize)sizeThatFits:(CGSize)size;

Apache SSL Configuration Error (SSL Connection Error)

A common cause I wanted to suggest for this situation:

Sometimes a customer is running Skype, which is using port 443 without their realizing it. When they go to start Tomcat or Apache, it appears to start but cannot bind with port 443. This is the exact message that the user would receive in the browser. The fix is to stop what was running on port 443 and re-start the webserver so it can bind with port 443.

The customer can re-start Skype after starting the webserver, and Skype will detect that port 443 is in use and choose a different port to use.

How do I redirect a user when a button is clicked?

<li class="nav-item">
    <a class="nav-link text-dark" asp-area="" asp-page="/UsersPage">Users</a>

Try this

Can HTTP POST be limitless?

Different IIS web servers can process different amounts of data in the 'header', according to this (now deleted) article;;

Note that there is no limit on the number of FORM elements you can pass via POST, but only on the aggregate size of all name/value pairs. While GET is limited to as low as 1024 characters, POST data is limited to 2 MB on IIS 4.0, and 128 KB on IIS 5.0. Each name/value is limited to 1024 characters, as imposed by the SGML spec. Of course this does not apply to files uploaded using enctype='multipart/form-data' ... I have had no problems uploading files in the 90 - 100 MB range using IIS 5.0, aside from having to increase the server.scriptTimeout value as well as my patience!

Convert a video to MP4 (H.264/AAC) with ffmpeg

You can also try adding the Motumedia PPA to your apt sources and update your ffmpeg packages.

How to change a PG column to NULLABLE TRUE?

From the fine manual:


There's no need to specify the type when you're just changing the nullability.

"Not allowed to load local resource: file:///C:....jpg" Java EE Tomcat

The concept of http location and disk location is different. What you need to do is:

  1. for uploaded file summer.jpg
  2. move that under a known (to the application) location to disk, e.g c:\images\summer.jpg
  3. insert into db record representing the image with text summer.jpg
  4. to display it use plain <img src="images/summer.jpg" />
  5. you need something (e.g apache) that will serve c:\images\ under your application's /images. If you cannot do this then in step #2 you need to save somewhere under your web root, e.g c:\my-applications\demo-app\build\images

Hash Map in Python

It's built-in for Python. See dictionaries.

Based on your example:

streetno = {"1": "Sachine Tendulkar",
            "2": "Dravid",
            "3": "Sehwag",
            "4": "Laxman",
            "5": "Kohli" }

You could then access it like so:

sachine = streetno["1"]

Also worth mentioning: it can use any non-mutable data type as a key. That is, it can use a tuple, boolean, or string as a key.

Double.TryParse or Convert.ToDouble - which is faster and safer?

Personally, I find the TryParse method easier to read, which one you'll actually want to use depends on your use-case: if errors can be handled locally you are expecting errors and a bool from TryParse is good, else you might want to just let the exceptions fly.

I would expect the TryParse to be faster too, since it avoids the overhead of exception handling. But use a benchmark tool, like Jon Skeet's MiniBench to compare the various possibilities.

How to modify PATH for Homebrew?

open bash profile in textEdit

open -e .bash_profile

Edit file or paste in front of PATH export PATH=/usr/bin:/usr/sbin:/bin:/sbin:/usr/local/bin:/usr/local/sbin:~/bin

save & close the file

*To open .bash_profile directly open textEdit > file > recent

javax.xml.bind.JAXBException: Class *** nor any of its super class is known to this context

I have the same problem and I solved it by adding package to explore to the Jaxb2marshaller. For spring will be define a bean like this:

    public Jaxb2Marshaller marshaller() {
        Jaxb2Marshaller marshaller = new Jaxb2Marshaller();
        String[] packagesToScan= {"<packcge which contain the department class>"};
        return marshaller;

By this way if all your request and response classes are in the same package you do not need to specifically indicate the classes on the JAXBcontext

Could not find or load main class

Here is my working env path variables after much troubleshooting


.;C:\Program Files (x86)\Java\jre7\lib\ext\;C:\Program Files (x86)\Java\jdk1.6.0_27\bin

PATH <---sometimes this PATH fills up with too many paths and you can't add a path(which was my case!)

bunchofpaths;C:\Program Files (x86)\Java\jdk1.6.0_27\bin

Additionally, when you try to use the cmd to execute the file...make sure your in the local directory as the file your trying to execute (which you did.)

Just a little checklist for people that have this problem still.

TypeError: document.getElementbyId is not a function

Case sensitive: document.getElementById (notice the capital B).

Convert JS object to JSON string

if you have a json string and it's not wrapped with [] then wrap it up first

var str = '{"city": "Tampa", "state": "Florida"}, {"city": "Charlotte", "state": "North Carolina"}';
str = '[' + str + ']';
var jsonobj = $.parseJSON(str);


var jsonobj = eval('(' + str + ')');

ASP.Net Download file to client browser

Just a slight addition to the above solution if you are having problem with downloaded file's name...

Response.AddHeader("Content-Disposition", "attachment; filename=\"" + file.Name + "\"");

This will return the exact file name even if it contains spaces or other characters.

How to fix Warning Illegal string offset in PHP


 if(1 == @$manta_option['iso_format_recent_works']){
      $theme_img = 'recent_works_thumbnail';
 } else {
      $theme_img = 'recent_works_iso_thumbnail';


if(isset($manta_option['iso_format_recent_works']) && 1 == $manta_option['iso_format_recent_works']){
    $theme_img = 'recent_works_thumbnail';
} else {
    $theme_img = 'recent_works_iso_thumbnail';


if (!empty($manta_option['iso_format_recent_works']) && $manta_option['iso_format_recent_works'] == 1){

Accessing AppDelegate from framework?

If you're creating a framework the whole idea is to make it portable. Tying a framework to the app delegate defeats the purpose of building a framework. What is it you need the app delegate for?

Convert hex string to int in Python

Without the 0x prefix, you need to specify the base explicitly, otherwise there's no way to tell:

x = int("deadbeef", 16)

With the 0x prefix, Python can distinguish hex and decimal automatically.

>>> print(int("0xdeadbeef", 0))
>>> print(int("10", 0))

(You must specify 0 as the base in order to invoke this prefix-guessing behavior; if you omit the second parameter int() will assume base-10.)

Oracle - How to create a readonly user

A user in an Oracle database only has the privileges you grant. So you can create a read-only user by simply not granting any other privileges.

When you create a user


the user doesn't even have permission to log in to the database. You can grant that


and then you can go about granting whatever read privileges you want. For example, if you want RO_USER to be able to query SCHEMA_NAME.TABLE_NAME, you would do something like

GRANT SELECT ON schema_name.table_name TO ro_user

Generally, you're better off creating a role, however, and granting the object privileges to the role so that you can then grant the role to different users. Something like

Create the role

CREATE ROLE ro_role;

Grant the role SELECT access on every table in a particular schema

  FOR x IN (SELECT * FROM dba_tables WHERE owner='SCHEMA_NAME')
    EXECUTE IMMEDIATE 'GRANT SELECT ON schema_name.' || x.table_name || 
                                  ' TO ro_role';

And then grant the role to the user

GRANT ro_role TO ro_user;

Sharepoint: How do I filter a document library view to show the contents of a subfolder?

With Sharepoint Designer you can edit the CAML of your XSLT List View.

If you set the Scope attribute of the View element to Recursive or RecursiveAll, which returns all Files and Folders, you can filter the documents by FileDirRef:

      <FieldRef Name='FileDirRef' />
      <Value Type='Lookup'>MyFolder</Value>

This returns all documents which contain the string 'MyFolder' in their path.

I found infos about this on and useful information abouts fields at

How to delete columns in numpy.array

In your situation, you can extract the desired data with:

a[:, -z]

"-z" is the logical negation of the boolean array "z". This is the same as:

a[:, logical_not(z)]

How to transfer paid android apps from one google account to another google account

You should be able to transfer the Application to another Username. You would need all your old user information to transfer it. The application would remove it's self from old account to new account. Also you could put a limit on how many times you where allowed to transfer it. If you transfer it to the application could expire after a year and force to buy update.

Disable back button in react navigation

In Latest Version (v2) works headerLeft:null. you can add in controller's navigationOptions as bellow

static navigationOptions = {
    headerLeft: null,

How to generate a random alpha-numeric string

You can use an Apache Commons library for this, RandomStringUtils:


How to access share folder in virtualbox. Host Win7, Guest Fedora 16?

I just figured. You need to add a shared folder using VirtualBox before you access it with the guest.

Click "Device" in the menu bar--->Shared File--->add a directory and name it

then in the guest terminal, use:

sudo mount -t vboxsf myFileName ~/destination

Dont directly refer to the host directory

How to find the length of an array list?


Since no elements are in the list

output => 0

myList.add("newString");  // use myList.add() to insert elements to the arraylist

Since one element is added to the list

output => 1

With ' N ' no of nodes, how many different Binary and Binary Search Trees possible?

I recommend this article by my colleague Nick Parlante (from back when he was still at Stanford). The count of structurally different binary trees (problem 12) has a simple recursive solution (which in closed form ends up being the Catalan formula which @codeka's answer already mentioned).

I'm not sure how the number of structurally different binary search trees (BSTs for short) would differ from that of "plain" binary trees -- except that, if by "consider tree node values" you mean that each node may be e.g. any number compatible with the BST condition, then the number of different (but not all structurally different!-) BSTs is infinite. I doubt you mean that, so, please clarify what you do mean with an example!

Setting network adapter metric priority in Windows 7

I had the same problem on Windows 7 64-bit Pro. I adjusted network adapters binding using Control panel but nothing changed. Also metrics where showing that Win should use Ethernet adapter as primary, but it didn't.

Then a tried to uninstall Ethernet adapter driver and then install it again (without restart) and then I checked metrics for sure.

After this, Windows started prioritize Ethernet adapter.

Export MySQL data to Excel in PHP

Posts by John Peter and Dileep kurahe helped me to develop what I consider as being a simpler and cleaner solution, just in case anyone else is still looking. (I am not showing any database code because I actually used a $_SESSION variable.)

The above solutions invariably caused an error upon loading in Excel, about the extension not matching the formatting type. And some of these solutions create a spreadsheet with the data across the page in columns where it would be more traditional to have column headings and list the data down the rows. So here is my simple solution:

$filename = "webreport.csv";
header("Content-Type: application/xls");    
header("Content-Disposition: attachment; filename=$filename");  
header("Pragma: no-cache"); 
header("Expires: 0");
foreach($results as $x => $x_value){
    echo '"'.$x.'",' . '"'.$x_value.'"' . "\r\n";
  1. Change to .csv (which Excel instantly updates to .xls and there is no error upon loading.)
  2. Use the comma as delimiter.
  3. Double quote the Key and Value to escape any commas in the data.
  4. I also prepended column headers to $results so the spreadsheet looked even nicer.

I do not understand how execlp() works in Linux

this prototype:

  int execlp(const char *file, const char *arg, ...);

Says that execlp ìs a variable argument function. It takes 2 const char *. The rest of the arguments, if any, are the additional arguments to hand over to program we want to run - also char * - all these are C strings (and the last argument must be a NULL pointer)

So, the file argument is the path name of an executable file to be executed. arg is the string we want to appear as argv[0] in the executable. By convention, argv[0] is just the file name of the executable, normally it's set to the same as file.

The ... are now the additional arguments to give to the executable.

Say you run this from a commandline/shell:

$ ls

That'd be execlp("ls", "ls", (char *)NULL); Or if you run

$ ls -l /

That'd be execlp("ls", "ls", "-l", "/", (char *)NULL);

So on to execlp("/bin/sh", ..., "ls -l /bin/??", ...);

Here you are going to the shell, /bin/sh , and you're giving the shell a command to execute. That command is "ls -l /bin/??". You can run that manually from a commandline/shell:

 $ ls -l /bin/??

Now, how do you run a shell and tell it to execute a command ? You open up the documentation/man page for your shell and read it.

What you want to run is:

$ /bin/sh -c "ls -l /bin/??"

This becomes

  execlp("/bin/sh","/bin/sh", "-c", "ls -l /bin/??", (char *)NULL);

Side note: The /bin/?? is doing pattern matching, this pattern matching is done by the shell, and it expands to all files under /bin/ with 2 characters. If you simply did

  execlp("ls","ls", "-l", "/bin/??", (char *)NULL);

Probably nothing would happen (unless there's a file actually named /bin/??) as there's no shell that interprets and expands /bin/??