Programs & Examples On #Scrapy

Scrapy is a fast open-source high-level screen scraping and web crawling framework written in Python, used to crawl websites and extract structured data from their pages. It can be used for a wide range of purposes, from data mining to monitoring and automated testing.

pip is not able to install packages correctly: Permission denied error

It looks like you're having a permissions error, based on this message in your output: error: could not create '/lib/python2.7/site-packages/lxml': Permission denied.

One thing you can try is doing a user install of the package with pip install lxml --user. For more information on how that works, check out this StackOverflow answer. (Thanks to Ishaan Taylor for the suggestion)

You can also run pip install as a superuser with sudo pip install lxml but it is not generally a good idea because it can cause issues with your system-level packages.


This terminal command:

open /Applications/Python\ 3.7/Install\ Certificates.command

Found here:

Resolved it for me. With my config

pip install --upgrade certifi

had no impact.

"OSError: [Errno 1] Operation not permitted" when installing Scrapy in OSX 10.11 (El Capitan) (System Integrity Protection)

install python again:

brew install python

try it again:

sudo pip install scrapy

works for me, hope it can help

Can scrapy be used to scrape dynamic content from websites that are using AJAX?

Webkit based browsers (like Google Chrome or Safari) has built-in developer tools. In Chrome you can open it Menu->Tools->Developer Tools. The Network tab allows you to see all information about every request and response:

enter image description here

In the bottom of the picture you can see that I've filtered request down to XHR - these are requests made by javascript code.

Tip: log is cleared every time you load a page, at the bottom of the picture, the black dot button will preserve log.

After analyzing requests and responses you can simulate these requests from your web-crawler and extract valuable data. In many cases it will be easier to get your data than parsing HTML, because that data does not contain presentation logic and is formatted to be accessed by javascript code.

Firefox has similar extension, it is called firebug. Some will argue that firebug is even more powerful but I like the simplicity of webkit.

TypeError: Object of type 'bytes' is not JSON serializable

I guess the answer you need is referenced here Python sets are not json serializable

Not all datatypes can be json serialized . I guess pickle module will serve your purpose.

Numpy `ValueError: operands could not be broadcast together with shape ...`

If X and beta do not have the same shape as the second term in the rhs of your last line (i.e. nsample), then you will get this type of error. To add an array to a tuple of arrays, they all must be the same shape.

I would recommend looking at the numpy broadcasting rules.

Android SQLite SELECT Query

Try trimming the string to make sure there is no extra white space:

Cursor c = db.rawQuery("SELECT * FROM tbl1 WHERE TRIM(name) = '"+name.trim()+"'", null);

Also use c.moveToFirst() like @thinksteep mentioned.

This is a complete code for select statements.

SQLiteDatabase db = this.getReadableDatabase();
Cursor c = db.rawQuery("SELECT column1,column2,column3 FROM table ", null);
if (c.moveToFirst()){
    do {
        // Passing values 
        String column1 = c.getString(0);
        String column2 = c.getString(1);
        String column3 = c.getString(2); 
        // Do something Here with values
    } while(c.moveToNext());

Visual Studio 2015 or 2017 does not discover unit tests

I would just like to add that I found an entirely different solution to the ones above.

I had declared my test class as below:

class ClassificationTests
   //unit tests

As soon as I added the public modifier to the class, it worked as expected!

Is it safe to clean docker/overlay2/

adding to above comment, in which people are suggesting to prune system like clear dangling volumes, images, exit containers etc., Sometime your app become culprit, it generated too much logs in a small time and if you using empty directy volume (local volumes) this fill the /var partitions. In that case I found below command very interesting to figure out, what is consuming space on my /var partition disk.

du -ahx /var/lib | sort -rh | head -n 30

This command will list top 30, which is consuming most space on a single disk. Means if you are using external storage with your containers, it consumes a lot of time to run du command. This command will not count mount volumes. And is much faster. You will get the exact directories/files which are consuming space. Then you can go to those directories and check which files are useful or not. if these files are required then you can move them to some persistent storage by making change in app to use persistent storage for that location or change location of that files. And for rest you can clear them.

Select multiple rows with the same value(s)

This may work for you:

select t1.*
from table t1
join (select t2.Chromosome, t2.Locus
    from table2
    group by t2.Chromosome, t2.Locus
    having count(*) > 1) u on u.Chromosome = t1.Chromosome and u.Locus = t1.Locus

Hidden Features of C#?

Just learned, anonymous types can infer property names from the variable name:

string hello = "world";
var o = new { hello };

Using GSON to parse a JSON array

Gson gson = new Gson();
Wrapper[] arr = gson.fromJson(str, Wrapper[].class);

class Wrapper{
    int number;
    String title;       

Seems to work fine. But there is an extra , Comma in your string.

        "number" : "3",
        "title" : "hello_world"
        "number" : "2",
        "title" : "hello_world"

ValueError: math domain error

Your code is doing a log of a number that is less than or equal to zero. That's mathematically undefined, so Python's log function raises an exception. Here's an example:

>>> from math import log
>>> log(-1)
Traceback (most recent call last):
  File "<pyshell#59>", line 1, in <module>
ValueError: math domain error

Without knowing what your newtonRaphson2 function does, I'm not sure I can guess where the invalid x[2] value is coming from, but hopefully this will lead you on the right track.

Creating a file name as a timestamp in a batch job

This works well with (my) German locale, should be possible to adjust it to your needs...

forfiles /p *PATH* /m *filepattern* /c "cmd /c ren @file 

Display number with leading zeros

Use a format string -

For example:

python -c 'print "%(num)02d" % {"num":5}'

Error "initializer element is not constant" when trying to initialize variable with const

Just for illustration by compare and contrast The code is from /The code fails in gcc and passes in g++/

int initializer(void)
    return 50;

int main()
    int j;
    for (j=0;j<10;j++)
        static int i = initializer();
        /*The variable i is only initialized to one*/
        printf(" value of i = %d ", i);
    return 0;

Two HTML tables side by side, centered on the page

The problem is that the DIV that should center your tables has no width defined. By default, DIVs are block elements and take up the entire width of their parent - in this case the entire document (propagating through the #outer DIV), so the automatic margin style has no effect.

For this technique to work, you simply have to set the width of the div that has margin:auto to anything but "auto" or "inherit" (either a fixed pixel value or a percentage).

How to pass anonymous types as parameters?

Normally, you do this with generics, for example:

MapEntToObj<T>(IQueryable<T> query) {...}

The compiler should then infer the T when you call MapEntToObj(query). Not quite sure what you want to do inside the method, so I can't tell whether this is useful... the problem is that inside MapEntToObj you still can't name the T - you can either:

  • call other generic methods with T
  • use reflection on T to do things

but other than that, it is quite hard to manipulate anonymous types - not least because they are immutable ;-p

Another trick (when extracting data) is to also pass a selector - i.e. something like:

Foo<TSource, TValue>(IEnumerable<TSource> source,
        Func<TSource,string> name) {
    foreach(TSource item in source) Console.WriteLine(name(item));
Foo(query, x=>x.Title);

Python: list of lists

Time traveller here

List_of_list =[([z for z in range(x-2,x+1) if z >= 0],y) for y in range(10) for x in range(10)]

This should do the trick. And the output is this:

[([0], 0), ([0, 1], 0), ([0, 1, 2], 0), ([1, 2, 3], 0), ([2, 3, 4], 0),  ([3, 4, 5], 0), ([4, 5, 6], 0), ([5, 6, 7], 0), ([6, 7, 8], 0), ([7, 8, 9], 0), ([0], 1), ([0, 1], 1), ([0, 1, 2], 1), ([1, 2, 3], 1), ([2, 3, 4], 1), ([3, 4, 5], 1), ([4, 5, 6], 1), ([5, 6, 7], 1), ([6, 7, 8], 1), ([7, 8, 9], 1), ([0], 2), ([0, 1], 2), ([0, 1, 2], 2), ([1, 2, 3], 2), ([2, 3, 4], 2), ([3, 4, 5], 2), ([4, 5, 6], 2), ([5, 6, 7], 2), ([6, 7, 8], 2), ([7, 8, 9], 2), ([0], 3), ([0, 1], 3), ([0, 1, 2], 3), ([1, 2, 3], 3), ([2, 3, 4], 3), ([3, 4, 5], 3), ([4, 5, 6], 3), ([5, 6, 7], 3), ([6, 7, 8], 3), ([7, 8, 9], 3), ([0], 4), ([0, 1], 4), ([0, 1, 2], 4), ([1, 2, 3], 4), ([2, 3, 4], 4), ([3, 4, 5], 4), ([4, 5, 6], 4), ([5, 6, 7], 4), ([6, 7, 8], 4), ([7, 8, 9], 4), ([0], 5), ([0, 1], 5), ([0, 1, 2], 5), ([1, 2, 3], 5), ([2, 3, 4], 5), ([3, 4, 5], 5), ([4, 5, 6], 5), ([5, 6, 7], 5), ([6, 7, 8], 5), ([7, 8, 9], 5), ([0], 6), ([0, 1], 6), ([0, 1, 2], 6), ([1, 2, 3], 6), ([2, 3, 4], 6), ([3, 4, 5], 6), ([4, 5, 6], 6), ([5, 6, 7], 6), ([6, 7, 8], 6), ([7, 8, 9], 6), ([0], 7), ([0, 1], 7), ([0, 1, 2], 7), ([1, 2, 3], 7), ([2, 3, 4], 7), ([3, 4, 5], 7), ([4, 5, 6], 7), ([5, 6, 7], 7), ([6, 7, 8], 7), ([7, 8, 9], 7), ([0], 8), ([0, 1], 8), ([0, 1, 2], 8), ([1, 2, 3], 8), ([2, 3, 4], 8), ([3, 4, 5], 8), ([4, 5, 6], 8), ([5, 6, 7], 8), ([6, 7, 8], 8), ([7, 8, 9], 8), ([0], 9), ([0, 1], 9), ([0, 1, 2], 9), ([1, 2, 3], 9), ([2, 3, 4], 9), ([3, 4, 5], 9), ([4, 5, 6], 9), ([5, 6, 7], 9), ([6, 7, 8], 9), ([7, 8, 9], 9)]    

This is done by list comprehension(which makes looping elements in a list via one line code possible). The logic behind this one-line code is the following:

(1) for x in range(10) and for y in range(10) are employed for two independent loops inside a list

(2) (a list, y) is the general term of the loop, which is why it is placed before two for's in (1)

(3) the length of the list in (2) cannot exceed 3, and the list depends on x, so

[z for z in range(x-2,x+1)] 

is used

(4) because z starts from zero but range(x-2,x+1) starts from -2 which isn't what we want, so a conditional statement if z >= 0 is placed at the end of the list in (2)

[z for z in range(x-2,x+1) if z >= 0] 

What does numpy.random.seed(0) do?

Imagine you are showing someone how to code something with a bunch of "random" numbers. By using numpy seed they can use the same seed number and get the same set of "random" numbers.

So it's not exactly random because an algorithm spits out the numbers but it looks like a randomly generated bunch.

What is the difference between Bootstrap .container and .container-fluid classes?

From a display perspective .container gives you more control over the what the users are seeing, and makes it easier to see what the users will see as you only have 4 variations of display (5 in the case of bootstrap 5) because the sizes relate to the same as the grid sizes. e.g. .col-xs, .col-sm, .col, and .col-lg.

What this means, is that when you are doing user testing if you test on a displays with the 4 different sizes you see all the veriations in display.

When using .container-fluid because the witdh is related to the viewport width the display is dynamic, so the varations are much greater and users with very large screens or uncommon screen widths may see results you weren't expecting.

Best practices for API versioning?

This is a good and a tricky question. The topic of URI design is at the same time the most prominent part of a REST API and, therefore, a potentially long-term commitment towards the users of that API.

Since evolution of an application and, to a lesser extent, its API is a fact of life and that it's even similar to the evolution of a seemingly complex product like a programming language, the URI design should have less natural constraints and it should be preserved over time. The longer the application's and API's lifespan, the greater the commitment to the users of the application and API.

On the other hand, another fact of life is that it is hard to foresee all the resources and their aspects that would be consumed through the API. Luckily, it is not necessary to design the entire API which will be used until Apocalypse. It is sufficient to correctly define all the resource end-points and the addressing scheme of every resource and resource instance.

Over time you may need to add new resources and new attributes to each particular resource, but the method that API users follow to access a particular resources should not change once a resource addressing scheme becomes public and therefore final.

This method applies to HTTP verb semantics (e.g. PUT should always update/replace) and HTTP status codes that are supported in earlier API versions (they should continue to work so that API clients that have worked without human intervention should be able to continue to work like that).

Furthermore, since embedding of API version into the URI would disrupt the concept of hypermedia as the engine of application state (stated in Roy T. Fieldings PhD dissertation) by having a resource address/URI that would change over time, I would conclude that API versions should not be kept in resource URIs for a long time meaning that resource URIs that API users can depend on should be permalinks.

Sure, it is possible to embed API version in base URI but only for reasonable and restricted uses like debugging a API client that works with the the new API version. Such versioned APIs should be time-limited and available to limited groups of API users (like during closed betas) only. Otherwise, you commit yourself where you shouldn't.

A couple of thoughts regarding maintenance of API versions that have expiration date on them. All programming platforms/languages commonly used to implement web services (Java, .NET, PHP, Perl, Rails, etc.) allow easy binding of web service end-point(s) to a base URI. This way it's easy to gather and keep a collection of files/classes/methods separate across different API versions.

From the API users POV, it's also easier to work with and bind to a particular API version when it's this obvious but only for limited time, i.e. during development.

From the API maintainer's POV, it's easier to maintain different API versions in parallel by using source control systems that predominantly work on files as the smallest unit of (source code) versioning.

However, with API versions clearly visible in URI there's a caveat: one might also object this approach since API history becomes visible/aparent in the URI design and therefore is prone to changes over time which goes against the guidelines of REST. I agree!

The way to go around this reasonable objection, is to implement the latest API version under versionless API base URI. In this case, API client developers can choose to either:

  • develop against the latest one (committing themselves to maintain the application protecting it from eventual API changes that might break their badly designed API client).

  • bind to a specific version of the API (which becomes apparent) but only for a limited time

For example, if API v3.0 is the latest API version, the following two should be aliases (i.e. behave identically to all API requests):


In addition, API clients that still try to point to the old API should be informed to use the latest previous API version, if the API version they're using is obsolete or not supported anymore. So accessing any of the obsolete URIs like these:


should return any of the 30x HTTP status codes that indicate redirection that are used in conjunction with Location HTTP header that redirects to the appropriate version of resource URI which remain to be this one:


There are at least two redirection HTTP status codes that are appropriate for API versioning scenarios:

  • 301 Moved permanently indicating that the resource with a requested URI is moved permanently to another URI (which should be a resource instance permalink that does not contain API version info). This status code can be used to indicate an obsolete/unsupported API version, informing API client that a versioned resource URI been replaced by a resource permalink.

  • 302 Found indicating that the requested resource temporarily is located at another location, while requested URI may still supported. This status code may be useful when the version-less URIs are temporarily unavailable and that a request should be repeated using the redirection address (e.g. pointing to the URI with APi version embedded) and we want to tell clients to keep using it (i.e. the permalinks).

  • other scenarios can be found in Redirection 3xx chapter of HTTP 1.1 specification

ASP.Net which user account running Web Service on IIS 7?

Server 2008

Start Task Manager Find w3wp.exe process (description IIS Worker Process) Check User Name column to find who you're IIS process is running as.

In the IIS GUI you can configure your application pool to run as a specific user: Application Pool default Advanced Settings Identity

Here's the info from Microsoft on setting up Application Pool Identites:

How can I read input from the console using the Scanner class in Java?

Reading Data From The Console

  • BufferedReader is synchronized, so read operations on a BufferedReader can be safely done from multiple threads. The buffer size may be specified, or the default size(8192) may be used. The default is large enough for most purposes.

    readLine() « just reads data line by line from the stream or source. A line is considered to be terminated by any one these: \n, \r (or) \r\n

  • Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace(\s) and it is recognised by Character.isWhitespace.

    « Until the user enters data, the scanning operation may block, waiting for input. « Use Scanner(BUFFER_SIZE = 1024) if you want to parse a specific type of token from a stream. « A scanner however is not thread safe. It has to be externally synchronized.

    next() « Finds and returns the next complete token from this scanner. nextInt() « Scans the next token of the input as an int.


String name = null;
int number; in = new BufferedReader(new InputStreamReader(;
name = in.readLine(); // If the user has not entered anything, assume the default value.
number = Integer.parseInt(in.readLine()); // It reads only String,and we need to parse it.
System.out.println("Name " + name + "\t number " + number);

java.util.Scanner sc = new Scanner("\\s");
name =;  // It will not leave until the user enters data.
number = sc.nextInt(); // We can read specific data.
System.out.println("Name " + name + "\t number " + number);

// The Console class is not working in the IDE as expected. cnsl = System.console();
if (cnsl != null) {
    // Read a line from the user input. The cursor blinks after the specified input.
    name = cnsl.readLine("Name: ");
    System.out.println("Name entered: " + name);

Inputs and outputs of Stream

Reader Input:     Output:
Yash 777          Line1 = Yash 777
     7            Line1 = 7

Scanner Input:    Output:
Yash 777          token1 = Yash
                  token2 = 777

How to find a number in a string using JavaScript?

I like @jesterjunk answer, however, a number is not always just digits. Consider those valid numbers: "123.5, 123,567.789, 12233234+E12"

So I just updated the regular expression:

var regex = /[\d|,|.|e|E|\+]+/g;

var string = "you can enter maximum 5,123.6 choices";
var matches = string.match(regex);  // creates array from matches

document.write(matches); //5,123.6

How do I use NSTimer?

The answers are missing a specific time of day timer here is on the next hour:

NSCalendarUnit allUnits = NSCalendarUnitYear   | NSCalendarUnitMonth |
                          NSCalendarUnitDay    | NSCalendarUnitHour  |
                          NSCalendarUnitMinute | NSCalendarUnitSecond;

NSCalendar *calendar = [[ NSCalendar alloc]  

NSDateComponents *weekdayComponents = [calendar components: allUnits 
                                                  fromDate: [ NSDate date ] ];

[ weekdayComponents setHour: weekdayComponents.hour + 1 ];
[ weekdayComponents setMinute: 0 ];
[ weekdayComponents setSecond: 0 ];

NSDate *nextTime = [ calendar dateFromComponents: weekdayComponents ];

refreshTimer = [[ NSTimer alloc ] initWithFireDate: nextTime
                                          interval: 0.0
                                            target: self
                                          selector: @selector( doRefresh )
                                          userInfo: nil repeats: NO ];

[[NSRunLoop currentRunLoop] addTimer: refreshTimer forMode: NSDefaultRunLoopMode];

Of course, substitute "doRefresh" with your class's desired method

try to create the calendar object once and make the allUnits a static for efficiency.

adding one to hour component works just fine, no need for a midnight test (link)

Javascript array sort and unique

A way to use a custom sort function

//func has to return 0 in the case in which they are equal
sort_unique = function(arr,func) {
        func = func || function (a, b) {
            return a*1 - b*1;
        arr = arr.sort(func);
        var ret = [arr[0]];
        for (var i = 1; i < arr.length; i++) {
            if (func(arr[i-1],arr[i]) != 0) 
        return ret;

Example: desc order for an array of objects

MyArray = sort_unique(MyArray , function(a,b){
            return  b.iterator_internal*1 - a.iterator_internal*1;

How to use Console.WriteLine in ASP.NET (C#) during debug?

Make sure you start your application in Debug mode (F5), not without debugging (Ctrl+F5) and then select "Show output from: Debug" in the Output panel in Visual Studio.

What is the use of adding a null key or value to a HashMap in Java?

Another example : I use it to group Data by date. But some data don't have date. I can group it with the header "NoDate"

How to get the first element of an array?

The previous examples work well when the array index begins at zero. thomax's answer did not rely on the index starting at zero, but relied on Array.prototype.find to which I did not have access. The following solution using jQuery $.each worked well in my case.

let haystack = {100: 'first', 150: 'second'},
    found = null;

$.each(haystack, function( index, value ) {
    found = value;  // Save the first array element for later.
    return false;  // Immediately stop the $.each loop after the first array element.

console.log(found); // Prints 'first'.

How do I get information about an index and table owner in Oracle?

According to the docs, you can just do:




if you want all indexes...

ENOENT, no such file or directory

Another possibility is that you are missing an .npmrc file if you are pulling any packages that are not publicly available.

You will need to add an .npmrc file at the root directory and add the private/internal registry inside of the .npmrc file like this:


Creating Scheduled Tasks

This works for me

It is nicely designed Fluent API.

//This will create Daily trigger to run every 10 minutes for a duration of 18 hours
SchedulerResponse response = WindowTaskScheduler
    .CreateTask("TaskName", "C:\\Test.bat")
    .RunDurationFor(new TimeSpan(18, 0, 0))
    .SetStartDate(new DateTime(2015, 8, 8))
    .SetStartTime(new TimeSpan(8, 0, 0))

How do I fix the "You don't have write permissions into the /usr/bin directory" error when installing Rails?

To fix your specific error you need to run that command as sudo, ie:

sudo gem install rails --pre

How to update array value javascript?

How about;

function keyValue(key, value){
    this.Key = key;
    this.Value = value;
keyValue.prototype.updateTo = function(newKey, newValue) {
    this.Key = newKey;
    this.Value = newValue;  

array[1].updateTo("xxx", "999");   

How to process SIGTERM signal gracefully?

Here is a simple example without threads or classes.

import signal

run = True

def handler_stop_signals(signum, frame):
    global run
    run = False

signal.signal(signal.SIGINT, handler_stop_signals)
signal.signal(signal.SIGTERM, handler_stop_signals)

while run:
    pass # do stuff including other IO stuff

MySQL: #1075 - Incorrect table definition; autoincrement vs another key?

I think i understand what the reason of your error. First you click auto AUTO INCREMENT field then select it as a primary key.

The Right way is First You have to select it as a primary key then you have to click auto AUTO INCREMENT field.

Very easy. Thanks

Tracking Google Analytics Page Views with AngularJS

I suggest using the Segment analytics library and following our Angular quickstart guide. You’ll be able to track page visits and track user behavior actions with a single API. If you have an SPA, you can allow the RouterOutlet component to handle when the page renders and use ngOnInit to invoke page calls. The example below shows one way you could do this:

  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.css']
export class HomeComponent implements OnInit {
  ngOnInit() {'Home');

I’m the maintainer of With Segment, you’ll be able to switch different destinations on-and-off by the flip of a switch if you are interested in trying multiple analytics tools (we support over 250+ destinations) without having to write any additional code.

Limit the height of a responsive image with css

You can use inline styling to limit the height:

<img src="" class="img-responsive" alt="" style="max-height: 400px;">

Are dictionaries ordered in Python 3.6+?

To fully answer this question in 2020, let me quote several statements from official Python docs:

Changed in version 3.7: Dictionary order is guaranteed to be insertion order. This behavior was an implementation detail of CPython from 3.6.

Changed in version 3.7: Dictionary order is guaranteed to be insertion order.

Changed in version 3.8: Dictionaries are now reversible.

Dictionaries and dictionary views are reversible.

A statement regarding OrderedDict vs Dict:

Ordered dictionaries are just like regular dictionaries but have some extra capabilities relating to ordering operations. They have become less important now that the built-in dict class gained the ability to remember insertion order (this new behavior became guaranteed in Python 3.7).

Detect changes in the DOM

MutationObserver = window.MutationObserver || window.WebKitMutationObserver;

var observer = new MutationObserver(function(mutations, observer) {
    // fired when a mutation occurs
    console.log(mutations, observer);
    // ...

// define what element should be observed by the observer
// and what types of mutations trigger the callback
observer.observe(document, {
  subtree: true,
  attributes: true

Complete explanations:

Extract time from date String

Use SimpleDateFormat to convert between a date string and a real Date object. with a Date as starting point, you can easily apply formatting based on various patterns as definied in the javadoc of the SimpleDateFormat (click the blue code link for the Javadoc).

Here's a kickoff example:

String originalString = "2010-07-14 09:00:02";
Date date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse(originalString);
String newString = new SimpleDateFormat("H:mm").format(date); // 9:00

how to delete the content of text file without deleting itself

Just write:

FileOutputStream writer = new FileOutputStream("file.txt");

dyld: Library not loaded: /usr/local/lib/libpng16.16.dylib with anything php related

I got this problem after updating MAMP, and the custom $PATH I had set was wrong because of the new php version, so the wrong version of php was loaded first, and it was that version of php that triggered the error.

Updating the path in my .bash_profile fixed my issue.

Counting the number of files in a directory using Java

Unfortunately, I believe that is already the best way (although list() is slightly better than listFiles(), since it doesn't construct File objects).

cURL POST command line on WINDOWS RESTful service

We can use below Curl command in Windows Command prompt to send the request. Use the Curl command below, replace single quote with double quotes, remove quotes where they are not there in below format and use the ^ symbol.

curl http://localhost:7101/module/url ^
  -d @D:/request.xml ^
  -H "Content-Type: text/xml" ^
  -H "SOAPAction: process" ^
  -H "Authorization: Basic xyz" ^

PHP - Move a file into a different folder on the server

shell_exec('mv filename dest_filename');

Pure Javascript listen to input value change

This is what events are for.

HTMLInputElementObject.addEventListener('input', function (evt) {

Disable a Button

You can enable/disable a button using isEnabled or isUserInteractionEnabled property.

The difference between two is :

  • isEnabled is a property of UIControl (super class of UIButton) and it has visual effects (i.e. grayed out) of enable/disable

  • isUserInteractionEnabled is a property of UIView (super class of UIControl) and has no visual effect although but achieves the purpose

Usage :

myButton.isEnabled = false // Recommended approach

myButton.isUserInteractionEnabled = false // Alternative approach

Rails params explained?

As others have pointed out, params values can come from the query string of a GET request, or the form data of a POST request, but there's also a third place they can come from: The path of the URL.

As you might know, Rails uses something called routes to direct requests to their corresponding controller actions. These routes may contain segments that are extracted from the URL and put into params. For example, if you have a route like this:

match 'products/:id', ...

Then a request to a URL like will set params[:id] to 42.

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

It looks like the original answer was for pre Apache 2.4. It did not work for me. Here's what I had to change to make it work in 2.4. This will work for any depth of subdomain of

SetEnvIf Host ^((?:.+\.)*yourcompany\.com?)$    CORS_ALLOW_ORIGIN=$1
Header append Access-Control-Allow-Origin  %{REQUEST_SCHEME}e://%{CORS_ALLOW_ORIGIN}e    env=CORS_ALLOW_ORIGIN
Header merge  Vary "Origin"

Specify sudo password for Ansible

This worked for me... Created file /etc/sudoers.d/90-init-users file with NOPASSWD

echo "user ALL=(ALL)       NOPASSWD:ALL" > 90-init-users

where "user" is your userid.

undefined reference to WinMain@16 (codeblocks)

Open the project you want to add it.

Right click on the name. Then select, add in the active project. Then the cpp file will get its link to cbp.

ArrayList or List declaration in Java

Possibly you can refer to this link

List is an interface.ArrayList,LinkedList etc are classes which implement list.Whenyou are using List Interface,you have to itearte elements using ListIterator and can move forward and backward,in the List where as in ArrayList Iterate using Iterator and its elements can be accessed unidirectional way.

How to parse XML using shellscript?

Try sgrep. It's not clear exactly what you are trying to do, but I surely would not attempt writing an XML parser in bash.

connecting to phpMyAdmin database with PHP/MySQL

Set up a user, a host the user is allowed to talk to MySQL by using (e.g. localhost), grant that user adequate permissions to do what they need with the database .. and presto.

The user will need basic CRUD privileges to start, that's sufficient to store data received from a form. The rest of the permissions are self explanatory, i.e. permission to alter tables, etc. Give the user no more, no less power than it needs to do its work.

Cropping an UIImage

Here is my UIImage crop implementation which obeys the imageOrientation property. All orientations were thoroughly tested.

inline double rad(double deg)
    return deg / 180.0 * M_PI;

UIImage* UIImageCrop(UIImage* img, CGRect rect)
    CGAffineTransform rectTransform;
    switch (img.imageOrientation)
        case UIImageOrientationLeft:
            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(90)), 0, -img.size.height);
        case UIImageOrientationRight:
            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(-90)), -img.size.width, 0);
        case UIImageOrientationDown:
            rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(-180)), -img.size.width, -img.size.height);
            rectTransform = CGAffineTransformIdentity;
    rectTransform = CGAffineTransformScale(rectTransform, img.scale, img.scale);

    CGImageRef imageRef = CGImageCreateWithImageInRect([img CGImage], CGRectApplyAffineTransform(rect, rectTransform));
    UIImage *result = [UIImage imageWithCGImage:imageRef scale:img.scale orientation:img.imageOrientation];
    return result;

Error in data frame undefined columns selected

Are you meaning?

data2 <- data1[good,]



you're selecting columns in a wrong way (using a logical vector of complete rows).

Consider that parameter pollutant is not used; is it a column name that you want to extract? if so it should be something like

data2 <- data1[good, pollutant]

Furthermore consider that you have to rbind the data.frames inside the for loop, otherwise you get only the last data.frame (its completed.cases)

And last but not least, i'd prefer generating filenames eg with

id <- 1:322
paste0( directory, "/", gsub(" ", "0", sprintf("%3d",id)), ".csv")

A little modified chunk of ?sprintf

The string fmt (in our case "%3d") contains normal characters, which are passed through to the output string, and also conversion specifications which operate on the arguments provided through .... The allowed conversion specifications start with a % and end with one of the letters in the set aAdifeEgGosxX%. These letters denote the following types:

  • d: integer

Eg a more general example

    sprintf("I am %10d years old", 25)
[1] "I am         25 years old"
          |        |
          1       10

How to get cell value from DataGridView in VB.Net?

In you want to know the data from de selected row, you can try this snippet code:


Replace multiple strings at once

String.prototype.replaceArray = function (find, replace) {
    var replaceString = this;
    for (var i = 0; i < find.length; i++) {
        // global replacement
        var pos = replaceString.indexOf(find[i]);
        while (pos > -1) {
            replaceString = replaceString.replace(find[i], replace[i]);
            pos = replaceString.indexOf(find[i]);
    return replaceString;

var textT = "Hello world,,,,, hello people.....";
var find = [".",","];
var replace = ['2', '5'];
textT = textT.replaceArray(find, replace);
// result: Hello world55555 hello people22222

Post multipart request with Android SDK

Here is a Simple approach if you are using the AOSP library Volley.

Extend the class Request<T> as follows-

public class MultipartRequest extends Request<String> {
    private static final String FILE_PART_NAME = "file";
    private final Response.Listener<String> mListener;
    private final Map<String, File> mFilePart;
    private final Map<String, String> mStringPart;
    MultipartEntityBuilder entity = MultipartEntityBuilder.create();
    HttpEntity httpentity;

    public MultipartRequest(String url, Response.ErrorListener errorListener,
                            Response.Listener<String> listener, Map<String, File> file,
                            Map<String, String> mStringPart) {
        super(Method.POST, url, errorListener);
        mListener = listener;
        mFilePart = file;
        this.mStringPart = mStringPart;

    public void addStringBody(String param, String value) {
        mStringPart.put(param, value);

    private void buildMultipartEntity() {
        for (Map.Entry<String, File> entry : mFilePart.entrySet()) {
            // entity.addPart(entry.getKey(), new FileBody(entry.getValue(), ContentType.create("image/jpeg"), entry.getKey()));
            try {
                entity.addBinaryBody(entry.getKey(), Utils.toByteArray(new FileInputStream(entry.getValue())), ContentType.create("image/jpeg"), entry.getKey() + ".JPG");
            } catch (FileNotFoundException e) {
        for (Map.Entry<String, String> entry : mStringPart.entrySet()) {
            if (entry.getKey() != null && entry.getValue() != null) {
                entity.addTextBody(entry.getKey(), entry.getValue());

    public String getBodyContentType() {
        return httpentity.getContentType().getValue();

    public byte[] getBody() throws AuthFailureError {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        try {
            httpentity =;
        } catch (IOException e) {
            VolleyLog.e("IOException writing to ByteArrayOutputStream");
        return bos.toByteArray();

    protected Response<String> parseNetworkResponse(NetworkResponse response) {
        Log.d("Response", new String(;
        return Response.success(new String(, getCacheEntry());

    protected void deliverResponse(String response) {

You can create and add a request like-

Map<String, String> params = new HashMap<>();
        params.put("name", name.getText().toString());
        params.put("email", email.getText().toString());
        params.put("user_id", appPreferences.getInt( Utils.PROPERTY_USER_ID, -1) + "");
        params.put("password", password.getText().toString());
        params.put("imageName", pictureName);
        Map<String, File> files = new HashMap<>();
        files.put("photo", new File(Utils.LOCAL_RESOURCE_PATH + pictureName));
        MultipartRequest multipartRequest = new MultipartRequest(Utils.BASE_URL + "editprofile/" + appPreferences.getInt(Utils.PROPERTY_USER_ID, -1), new Response.ErrorListener() {
            public void onErrorResponse(VolleyError error) {
                // TODO Auto-generated method stub
                Log.d("Error: ", error.toString());
        }, new Response.Listener<String>() {
            public void onResponse(String jsonResponse) {
                JSONObject response = null;
                try {
                    Log.d("jsonResponse: ", jsonResponse);
                    response = new JSONObject(jsonResponse);

                } catch (JSONException e) {
                try {
                    if (response != null && response.has("statusmessage") && response.getBoolean("statusmessage")) {

                } catch (JSONException e) {

        }, files, params);
        RequestQueue queue = Volley.newRequestQueue(this);

Padding In bootstrap

I have not used Bootstrap but I worked on Zurb Foundation. On that I used to add space like this.

<div id="main" class="container" role="main">
    <div class="row">

        <div class="span5 offset1">
            <p>Hello and welcome to my website.</p>
        <div class="span6">
            Image Here (TODO)

Visit this link: and read the section: Offsetting columns.

I think I know what you are doing wrong. If you are applying padding to the span6 like this:

<div class="span6" style="padding-left:5px;">
    <p>Hello and welcome to my website.</p>

It is wrong. What you have to do is add padding to the elements inside:

<div class="span6">
    <h2 style="padding-left:5px;">Welcome</h2>
    <p  style="padding-left:5px;">Hello and welcome to my website.</p>

How generate unique Integers based on GUIDs

Here is the simplest way:

Guid guid = Guid.NewGuid();
Random random = new Random();
int i = random.Next();

You'll notice that guid is not actually used here, mainly because there would be no point in using it. Microsoft's GUID algorithm does not use the computer's MAC address any more - GUID's are actually generated using a pseudo-random generator (based on time values), so if you want a random integer it makes more sense to use the Random class for this.

Update: actually, using a GUID to generate an int would probably be worse than just using Random ("worse" in the sense that this would be more likely to generate collisions). This is because not all 128 bits in a GUID are random. Ideally, you would want to exclude the non-varying bits from a hashing function, although it would be a lot easier to just generate a random number, as I think I mentioned before. :)

How to convert Calendar to java.sql.Date in Java?

Did you try cal.getTime()? This gets the date representation.

You might also want to look at the javadoc.

How do I test for an empty JavaScript object?

export function isObjectEmpty(obj) {
  return (
    Object.keys(obj).length === 0 &&
    Object.getOwnPropertySymbols(obj).length === 0 &&
    obj.constructor === Object

This include checking for objects containing symbol properties.

Object.keys does not retrieve symbol properties.

jQuery animate backgroundColor

I had the same problem and fixed it by including jQuery UI. Here is the complete script :

<!-- include Google's AJAX API loader -->
<script src=""></script>
<!-- load JQuery and UI from Google (need to use UI to animate colors) -->
<script type="text/javascript">
google.load("jqueryui", "1.5.2");

<script type="text/javascript">
$(document).ready(function() {
$('#menu ul li.item').hover(
    function() {
        $(this).stop().animate({backgroundColor:'#4E1402'}, 300);
        }, function () {
        $(this).stop().animate({backgroundColor:'#943D20'}, 100);

On Windows, running "import tensorflow" generates No module named "_pywrap_tensorflow" error

In case you are trying to install tensorflow GPU in Windows, you can find this easy interesting tutorial.

Note: If you are using PyCharm for example, you have to change the interpreter to the created conda environment.

Case insensitive access for generic dictionary

There is much simpler way:

using System;
using System.Collections.Generic;
var caseInsensitiveDictionary = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

How do I create/edit a Manifest file?

Go to obj folder in you app folder, then Debug. In there delete the manifest file and build again. It worked for me.

Fastest way to download a GitHub project

Downloading with Git using Windows CMD from a GitHub project

You can get download the link from GitHub <b>HTTPS clone URL</b>

Download with Window Command Prompt cmd for above picture HTTPS clone URL

  1. Copy the HTTPS clone URL shown in picture 1

  2. Open CMD

  3. git clone //paste the URL show in picture 2

grep without showing path/file:line

Just replace -H with -h. Check man grep for more details on options

find . -name '*.bar' -exec grep -hn FOO {} \;

JQuery string contains check

You can use javascript's indexOf function.

var str1 = "ABCDEFGHIJKLMNOP";_x000D_
var str2 = "DEFG";_x000D_
if(str1.indexOf(str2) != -1){_x000D_
    console.log(str2 + " found");_x000D_

Checking if date is weekend PHP

This works for me and is reusable.

function isThisDayAWeekend($date) {

    $timestamp = strtotime($date);

    $weekday= date("l", $timestamp );

    if ($weekday =="Saturday" OR $weekday =="Sunday") { return true; } 
    else {return false; }


Python: find position of element in array

Suppose if the list is a collection of objects like given below:

obj =  [

            "subjectId" : "577a54c09c57916109142248", 
            "evaluableMaterialCount" : 0, 
            "subjectName" : ""


            "subjectId" : "56645cd63c43a07b61c2c650", 
            "subjectName" : ".NET",         

            "subjectId" : "5656a2ec3c43a07b61c2bd83", 
            "subjectName" : "Python",


            "subjectId" : "5662add93c43a07b61c2c58c", 
            "subjectName" : "HTML"

You can use the following method to find the index. Suppose the subjectId is 5662add93c43a07b61c2c58c then to get the index of the object in the list,

subjectId = "5662add93c43a07b61c2c58c"

for i, subjobj in enumerate(obj):
    if(subjectId == subjobj['subjectId']):

how to add button click event in android studio

Start your OnClickListener, but when you get to the first set up parenthesis, type new, then View, and press enter. Should look like this when you're done:

Button btn1 = (Button)findViewById(;

btn1.setOnClickListener(new View.OnClickListener() {            
    public void onClick(View v) {
//your stuff here.

XMLHttpRequest cannot load an URL with jQuery

Fiddle with 3 working solutions in action.

Given an external JSON:

myurl = '|zh-hant|fr&props=sitelinks|labels|aliases|descriptions&format=json'

Solution 1: $.ajax() + jsonp:

  dataType: "jsonp",
  url: myurl ,
  }).done(function ( data ) {
  // do my stuff

Solution 2: $.ajax()+json+&calback=?:

  dataType: "json",
  url: myurl + '&callback=?',
  }).done(function ( data ) {
  // do my stuff

Solution 3: $.getJSON()+calback=?:

$.getJSON( myurl + '&callback=?', function(data) {
  // do my stuff

Documentations: ,

Why Java Calendar set(int year, int month, int date) not returning correct date?

Selected date at the example is interesting. Example code block is:

Calendar c1 = GregorianCalendar.getInstance();
c1.set(2000, 1, 30);  //January 30th 2000
Date sDate = c1.getTime();


and output Wed Mar 01 19:32:21 JST 2000.

When I first read the example i think that output is wrong but it is true:)

  • Calendar.Month is starting from 0 so 1 means February.
  • February last day is 28 so output should be 2 March.
  • But selected year is important, it is 2000 which means February 29 so result should be 1 March.

Implode an array with JavaScript?

For future reference, if you want to mimic the behaviour of PHP's implode() when no delimiter is specified (literally just join the pieces together), you need to pass an empty string into Javascript's join() otherwise it defaults to using commas as delimiters:

var bits = ['H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd'];
alert(bits.join());    // H,e,l,l,o, ,W,o,r,l,d
alert(bits.join(''));  // Hello World

How can I add a PHP page to WordPress?

The best way to add PHP pages in WordPress to Page Template in the child-theme folder.

How to create Page Template in WordPress.

Create a file named template-custom.php and put it in /wp-content/theme/my-theme/.

 * Template Name: Custom Template
 * Custom template used for custom php code display
 * @package   Portafolio WordPress Theme
 * @author    Gufran Hasan
 * @copyright Copyright
 * @link
<?php get_header(); ?>
  //write code here


<?php get_footer(); ?>

For more details

List all indexes on ElasticSearch server?

People here have answered how to do it in curl and sense, some people might need to do this in java.

Here it goes

client.admin().indices().stats(new IndicesStatsRequest()).actionGet().getIndices().keySet()

Python 2.7 getting user input and manipulating as string without quotations

The function input will also evaluate the data it just read as python code, which is not really what you want.

The generic approach would be to treat the user input (from sys.stdin) like any other file. Try

import sys

If you want to keep it short, you can use raw_input which is the same as input but omits the evaluation.

Sort Go map values by keys

The Go blog: Go maps in action has an excellent explanation.

When iterating over a map with a range loop, the iteration order is not specified and is not guaranteed to be the same from one iteration to the next. Since Go 1 the runtime randomizes map iteration order, as programmers relied on the stable iteration order of the previous implementation. If you require a stable iteration order you must maintain a separate data structure that specifies that order.

Here's my modified version of example code:

package main

import (

func main() {
    // To create a map as input
    m := make(map[int]string)
    m[1] = "a"
    m[2] = "c"
    m[0] = "b"

    // To store the keys in slice in sorted order
    keys := make([]int, len(m))
    i := 0
    for k := range m {
        keys[i] = k

    // To perform the opertion you want
    for _, k := range keys {
        fmt.Println("Key:", k, "Value:", m[k])


Key: 0 Value: b
Key: 1 Value: a
Key: 2 Value: c

Better way to check if a Path is a File or a Directory?

I came across this when facing a similar problem, except I needed to check if a path is for a file or folder when that file or folder may not actually exist. There were a few comments on answers above that mentioned they would not work for this scenario. I found a solution (I use VB.NET, but you can convert if you need) that seems to work well for me:

Dim path As String = "myFakeFolder\ThisDoesNotExist\"
Dim bIsFolder As Boolean = (IO.Path.GetExtension(path) = "")
'returns True

Dim path As String = "myFakeFolder\ThisDoesNotExist\File.jpg"
Dim bIsFolder As Boolean = (IO.Path.GetExtension(path) = "")
'returns False

Hopefully this can be helpful to someone!

Retrieving the output of

I recently just figured out how to do this, and here's some example code from a current project of mine:

#Getting the random picture.
#First find all pictures:
import shlex, subprocess
cmd = 'find ../Pictures/ -regex ".*\(JPG\|NEF\|jpg\)" '
#cmd = raw_input("shell:")
args = shlex.split(cmd)
output,error = subprocess.Popen(args,stdout = subprocess.PIPE, stderr= subprocess.PIPE).communicate()
#Another way to get output
#output = subprocess.Popen(args,stdout = subprocess.PIPE).stdout
ber = raw_input("search complete, display results?")
print output
#... and on to the selection process ...

You now have the output of the command stored in the variable "output". "stdout = subprocess.PIPE" tells the class to create a file object named 'stdout' from within Popen. The communicate() method, from what I can tell, just acts as a convenient way to return a tuple of the output and the errors from the process you've run. Also, the process is run when instantiating Popen.

How to give a pattern for new line in grep?

As for the workaround (without using non-portable -P), you can temporary replace a new-line character with the different one and change it back, e.g.:

grep -o "_foo_" <(paste -sd_ file) | tr -d '_'

Basically it's looking for exact match _foo_ where _ means \n (so __ = \n\n). You don't have to translate it back by tr '_' '\n', as each pattern would be printed in the new line anyway, so removing _ is enough.

set background color: Android

This question is a old one but it can help for others too.

Try this :





    li.setBackgroundColor(Color.rgb(226, 11, 11));


Is this very likely to create a memory leak in Tomcat?

This problem appears when we are using any third party solution, without using the handlers for the cleanup activitiy. For me this was happening for EhCache. We were using EhCache in our project for caching. And often we used to see following error in the logs

 SEVERE: The web application [/products] appears to have started a thread named [products_default_cache_configuration] but has failed to stop it. This is very likely to create a memory leak.
Aug 07, 2017 11:08:36 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/products] appears to have started a thread named [Statistics Thread-products_default_cache_configuration-1] but has failed to stop it. This is very likely to create a memory leak.

And we often noticed tomcat failing for OutOfMemory error during development where we used to do backend changes and deploy the application multiple times for reflecting our changes.

This is the fix we did


So point I am trying to make is check the documentation of the third party libraries which you are using. They should be providing some mechanisms to clean up the threads during shutdown. Which you need to use in your application. No need to re-invent the wheel unless its not provided by them. The worst case is to provide your own implementation.

Reference for EHCache Shutdown

How to test an Oracle Stored Procedure with RefCursor return type?

In Toad I use:

variable salida refcursor
exec MY_PKG.MY_PRC(1, 2, 3, :salida)  -- 1, 2, 3 are params
print salida

Then, Execute as Script.

Android Error Building Signed APK: keystore.jks not found for signing config 'externalOverride'

File -> Invalidate Caches & Restart...

Build -> Build signed APK -> check the path in the dialog

Check the key store path

How can I select rows with most recent timestamp for each key value?

I had mostly the same problem and ended up a a different solution that makes this type of problem trivial to query.

I have a table of sensor data (1 minute data from about 30 sensors)


and I have a sensor table that has lots of mostly static stuff about the sensor but the relevant fields are these:


The tvLastupdate and tvLastValue are set in a trigger on inserts to the SensorReadings table. I always have direct access to these values without needing to do any expensive queries. This does denormalize slightly. The query is trivial:

SELECT idSensor,Description,tvLastUpdate,tvLastValue 
FROM Sensors

I use this method for data that is queried often. In my case I have a sensor table, and a large event table, that have data coming in at the minute level AND dozens of machines are updating dashboards and graphs with that data. With my data scenario the trigger-and-cache method works well.

Passing a varchar full of comma delimited values to a SQL Server IN function

-- select * from dbo.Split_ID('77,106')  

    ALTER FUNCTION dbo.Split_ID(@String varchar(8000))     
    returns @temptable TABLE (ID varchar(8000))     
        declare @idx int     
        declare @slice varchar(8000)     
        declare @Delimiter char(1)
         set @Delimiter =','

        select @idx = 1     
            if len(@String)<1 or @String is null  return     

        while @idx!= 0     
            set @idx = charindex(@Delimiter,@String)     
            if @idx!=0     
                set @slice = left(@String,@idx - 1)     
                set @slice = @String     

                insert into @temptable(ID) values(@slice)     

            set @String = right(@String,len(@String) - @idx)     
            if len(@String) = 0 break     

How many concurrent requests does a single Flask process receive?

When running the development server - which is what you get by running, you get a single synchronous process, which means at most 1 request is being processed at a time.

By sticking Gunicorn in front of it in its default configuration and simply increasing the number of --workers, what you get is essentially a number of processes (managed by Gunicorn) that each behave like the development server. 4 workers == 4 concurrent requests. This is because Gunicorn uses its included sync worker type by default.

It is important to note that Gunicorn also includes asynchronous workers, namely eventlet and gevent (and also tornado, but that's best used with the Tornado framework, it seems). By specifying one of these async workers with the --worker-class flag, what you get is Gunicorn managing a number of async processes, each of which managing its own concurrency. These processes don't use threads, but instead coroutines. Basically, within each process, still only 1 thing can be happening at a time (1 thread), but objects can be 'paused' when they are waiting on external processes to finish (think database queries or waiting on network I/O).

This means, if you're using one of Gunicorn's async workers, each worker can handle many more than a single request at a time. Just how many workers is best depends on the nature of your app, its environment, the hardware it runs on, etc. More details can be found on Gunicorn's design page and notes on how gevent works on its intro page.

How to change indentation mode in Atom?

See Soft Tabs and Tab Length under Settings > Editor Settings.

To toggle indentation modes quickly you can use Ctrl-Shift-P and search for Editor: Toggle Soft Tabs.

How to round float numbers in javascript?

Number((6.688689).toFixed(1)); // 6.7

var number = 6.688689;
var roundedNumber = Math.round(number * 10) / 10;

Use toFixed() function.

(6.688689).toFixed(); // equal to "7"
(6.688689).toFixed(1); // equal to "6.7"
(6.688689).toFixed(2); // equal to "6.69"

javascript regex for password containing at least 8 characters, 1 number, 1 upper and 1 lowercase

Your regex only allows exactly 8 characters. Use {8,} to specify eight or more instead of {8}.

But why would you limit the allowed character range for your passwords? 8-character alphanumeric passwords can be bruteforced by my phone within minutes.

How to secure phpMyAdmin

The simplest approach would be to edit the webserver, most likely an Apache2 installation, configuration and give phpmyadmin a different name.

A second approach would be to limit the IP addresses from where phpmyadmin may be accessed (e.g. only local lan or localhost).

How to fetch Java version using single line command in Linux

Since (at least on my linux system) the version string looks like "1.8.0_45":

 function checkJavaVers {
    for token in $(java -version 2>&1)
        if [[ $token =~ \"([[:digit:]])\.([[:digit:]])\.(.*)\" ]]
            export JAVA_MAJOR=${BASH_REMATCH[1]}
            export JAVA_MINOR=${BASH_REMATCH[2]}
            export JAVA_BUILD=${BASH_REMATCH[3]}
            return 0
    return 1

checkJavaVers || { echo "check failed" ; exit; }

How do you add a JToken to an JObject?

TL;DR: You should add a JProperty to a JObject. Simple. The index query returns a JValue, so figure out how to get the JProperty instead :)

The accepted answer is not answering the question as it seems. What if I want to specifically add a JProperty after a specific one? First, lets start with terminologies which really had my head worked up.

  • JToken = The mother of all other types. It can be A JValue, JProperty, JArray, or JObject. This is to provide a modular design to the parsing mechanism.
  • JValue = any Json value type (string, int, boolean).
  • JProperty = any JValue or JContainer (see below) paired with a name (identifier). For example "name":"value".
  • JContainer = The mother of all types which contain other types (JObject, JValue).
  • JObject = a JContainer type that holds a collection of JProperties
  • JArray = a JContainer type that holds a collection JValue or JContainer.

Now, when you query Json item using the index [], you are getting the JToken without the identifier, which might be a JContainer or a JValue (requires casting), but you cannot add anything after it, because it is only a value. You can change it itself, query more deep values, but you cannot add anything after it for example.

What you actually want to get is the property as whole, and then add another property after it as desired. For this, you use JOjbect.Property("name"), and then create another JProperty of your desire and then add it after this using AddAfterSelf method. You are done then.

For more info:

This is the code I modified.

public class Program
  public static void Main()
      string jsonText = @"
        ""food"": {
          ""fruit"": {
            ""apple"": {
              ""colour"": ""red"",
              ""size"": ""small""
            ""orange"": {
              ""colour"": ""orange"",
              ""size"": ""large""

      var foodJsonObj = JObject.Parse(jsonText);
      var bananaJson = JObject.Parse(@"{ ""banana"" : { ""colour"": ""yellow"", ""size"": ""medium""}}");

      var fruitJObject = foodJsonObj["food"]["fruit"] as JObject;
      fruitJObject.Property("orange").AddAfterSelf(new JProperty("banana", fruitJObject));

    catch (Exception ex)
      Console.WriteLine(ex.GetType().Name + ": " + ex.Message);

Difference between two dates in Python

pd.date_range('2019-01-01', '2019-02-01').shape[0]

Ruby - ignore "exit" in code

One hackish way to define an exit method in context:

class Bar; def exit; end; end 

This works because exit in the initializer will be resolved as self.exit1. In addition, this approach allows using the object after it has been created, as in: b =

But really, one shouldn't be doing this: don't have exit (or even puts) there to begin with.

(And why is there an "infinite" loop and/or user input in an intiailizer? This entire problem is primarily the result of poorly structured code.)

1 Remember Kernel#exit is only a method. Since Kernel is included in every Object, then it's merely the case that exit normally resolves to Object#exit. However, this can be changed by introducing an overridden method as shown - nothing fancy.

How to install JSTL? The absolute uri: cannot be resolved

jstl-1.2.jar --> <%@ taglib prefix="c" uri="" %>
jstl-1.1.jar --> <%@ taglib prefix="c" uri="" %>

also please check for the dependency jars that you have added javax.servlet.jar and javax.servlet.jsp.jstl-1.2.1.jar or not in your WEB-INF/lib folder. In my case these two solved the issue.

Check if string contains only whitespace

Check the length of the list given by of split() method.

if len(your_string.split()==0:

Or Compare output of strip() method with null.

if your_string.strip() == '':

What are the differences between using the terminal on a mac vs linux?

If you did a new or clean install of OS X version 10.3 or more recent, the default user terminal shell is bash.

Bash is essentially an enhanced and GNU freeware version of the original Bourne shell, sh. If you have previous experience with bash (often the default on GNU/Linux installations), this makes the OS X command-line experience familiar, otherwise consider switching your shell either to tcsh or to zsh, as some find these more user-friendly.

If you upgraded from or use OS X version 10.2.x, 10.1.x or 10.0.x, the default user shell is tcsh, an enhanced version of csh('c-shell'). Early implementations were a bit buggy and the programming syntax a bit weird so it developed a bad rap.

There are still some fundamental differences between mac and linux as Gordon Davisson so aptly lists, for example no useradd on Mac and ifconfig works differently.

The following table is useful for knowing the various unix shells.

sh      The original Bourne shell   Present on every unix system 
ksh     Original Korn shell         Richer shell programming environment than sh 
csh     Original C-shell            C-like syntax; early versions buggy 
tcsh    Enhanced C-shell            User-friendly and less buggy csh implementation 
bash    GNU Bourne-again shell      Enhanced and free sh implementation 
zsh     Z shell                     Enhanced, user-friendly ksh-like shell

You may also find these guides helpful:

On a final note, I am on Linux (Ubuntu 11) and Mac osX so I use bash and the thing I like the most is customizing the .bashrc (source'd from .bash_profile on OSX) file with aliases, some examples below. I now placed all my aliases in a separate .bash_aliases file and include it with:

if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases

in the .bashrc or .bash_profile file.

Note that this is an example of a mac-linux difference because on a Mac you can't have the --color=auto. The first time I did this (without knowing) I redefined ls to be invalid which was a bit alarming until I removed --auto-color !

You may also find useful

# ~/.bash_aliases
# ls variants
#alias l='ls -CF' 
alias la='ls -A' 
alias l='ls -alFtr' 
alias lsd='ls -d .*' 
# Various
alias h='history | tail'
alias hg='history | grep'
alias mv='mv -i' 
alias zap='rm -i'
# One letter quickies:
alias p='pwd'
alias x='exit'
alias {ack,ak}='ack-grep'
# Directories
alias s='cd ..'
alias play='cd ~/play/'
# Rails
alias src='script/rails console'
alias srs='script/rails server'
alias raked='rake db:drop db:create db:migrate db:seed' 
alias rvm-restart='source '\''/home/durrantm/.rvm/scripts/rvm'\'''
alias rrg='rake routes | grep '
alias rspecd='rspec --drb '
# DropBox - syncd
alias work="cd $WORKBASE"
alias code="cd $WORKBASE/ror/code"
# DropNot - NOT syncd !
alias {dropnot,not}="cd $WORKBASE_GIT"
alias {webs,ww}="cd $WORKBASE_GIT/webs"
alias {setups,docs}="cd $WORKBASE_GIT/setups_and_docs"
alias {linker,lnk}="cd $WORKBASE_GIT/webs/rails_v3/linker"
# git
alias {gsta,gst}='git status' 
# Warning: gst conflicts with gnu-smalltalk (when used).
alias {gbra,gb}='git branch'
alias {gco,go}='git checkout'
alias {gcob,gob}='git checkout -b '
alias {gadd,ga}='git add '
alias {gcom,gc}='git commit'
alias {gpul,gl}='git pull '
alias {gpus,gh}='git push '
alias glom='git pull origin master'
alias ghom='git push origin master'
alias gg='git grep '
# vim
alias v='vim'
# tmux
alias {ton,tn}='tmux set -g mode-mouse on'
alias {tof,tf}='tmux set -g mode-mouse off'
# dmc
alias {dmc,dm}='cd ~/Dropnot/webs/rails_v3/dmc/'
alias wf='cd ~/Dropnot/webs/rails_v3/dmc/dmWorkflow'
alias ws='cd ~/Dropnot/webs/rails_v3/dmc/dmStaffing'

Check if an element has event listener on it. No jQuery

You don't need to. Just slap it on there as many times as you want and as often as you want. MDN explains identical event listeners:

If multiple identical EventListeners are registered on the same EventTarget with the same parameters, the duplicate instances are discarded. They do not cause the EventListener to be called twice, and they do not need to be removed manually with the removeEventListener method.

Appending a line to a file only if it does not already exist

Using sed: It will insert at the end of line. You can also pass in variables as usual of course.

grep -qxF "port=9033" $light.conf
if [ $? -ne 0 ]; then
  sed -i "$ a port=9033" $light.conf
    echo "port=9033 already added"

Using oneliner sed

grep -qxF "port=9033" $lightconf || sed -i "$ a port=9033" $lightconf

Using echo may not work under root, but will work like this. But it will not let you automate things if you are looking to do it since it might ask for password.

I had a problem when I was trying to edit from the root for a particular user. Just adding the $username before was a fix for me.

grep -qxF "port=9033" light.conf
if [ $? -ne 0 ]; then
  sudo -u $user_name echo "port=9033" >> light.conf
    echo "already there"    

Why do I get access denied to data folder when using adb?

The problem could be that we need to specifically give adb root access in the developnent options in the latest CMs.. Here is what i did.

abc@abc-L655:~$ sudo adb kill-server
abc@abc-L655:~$ sudo adb root start-server * daemon not running. starting it now on port 5037 * * daemon started successfully * root access is disabled by system setting - enable in settings -> development options

after altering the development options...

abc@abc-L655:~$ sudo adb kill-server
abc@abc-L655:~$ sudo adb root start-server
* daemon not running. starting it now on port 5037 *
* daemon started successfully *
restarting adbd as root
abc@abc-L655:~$ adb shell
root@android:/ # ls /data/ .... good to go.. 

Iterating through a string word by word

for word in string.split():
    print word

mysql query result in php variable

$query="SELECT * FROM contacts";

HTML5 Number Input - Always show 2 decimal places

You can't really, but you a halfway step might be:

<input type='number' step='0.01' value='0.00' placeholder='0.00' />

How to verify a method is called two times with mockito verify()

build gradle:

testImplementation "com.nhaarman.mockitokotlin2:mockito-kotlin:2.2.0"


interface MyCallback {
  fun someMethod(value: String)

class MyTestableManager(private val callback: MyCallback){
  fun perform(){


import com.nhaarman.mockitokotlin2.times
import com.nhaarman.mockitokotlin2.verify
import com.nhaarman.mockitokotlin2.mock
val callback: MyCallback = mock()
val manager = MyTestableManager(callback)

val captor: KArgumentCaptor<String> = com.nhaarman.mockitokotlin2.argumentCaptor<String>()

verify(callback, times(3)).someMethod(captor.capture())

assertTrue(captor.allValues[0] == "first")
assertTrue(captor.allValues[1] == "second")
assertTrue(captor.allValues[2] == "third")

java.lang.NoClassDefFoundError: org.slf4j.LoggerFactory

get the compatible version of this jar slf4j-jdk14 and add it as a dependency. this solved the problem for me.

Getting specified Node values from XML document

Just like you do for getting something from the CNode you also need to do for the ANode

XmlNodeList xnList = xml.SelectNodes("/Element[@*]");
foreach (XmlNode xn in xnList)
  XmlNode anode = xn.SelectSingleNode("ANode");
    if (anode!= null)
        string id = anode["ID"].InnerText;
        string date = anode["Date"].InnerText;
        XmlNodeList CNodes = xn.SelectNodes("ANode/BNode/CNode");
        foreach (XmlNode node in CNodes)
         XmlNode example = node.SelectSingleNode("Example");
         if (example != null)
            string na = example["Name"].InnerText;
            string no = example["NO"].InnerText;

Find character position and update file name

The string is a .NET string so you can use .NET methods. In your case:

$index = "The string".IndexOf(" ")

will return 3, which is the first occurrence of space in the string. For more information see:

For your need try something like:

$s.SubString($s.IndexOf("_") + 1, $s.LastIndexOf(".") - $s.IndexOf("_") - 1)

Or you could use regexps:

if ($s -Match '(_)(.*)(\.)[^.]*$') {  $matches[2] }

(has to be adjusted depending on exactly what you need).

HTML table with fixed headers?

By applying the StickyTableHeaders jQuery plugin to the table, the column headers will stick to the top of the viewport as you scroll down.


$(function () {_x000D_
/*! Copyright (c) 2011 by Jonas Mosbech -
 MIT license info: */_x000D_
(function ($, window, undefined) {_x000D_
    'use strict';_x000D_
    var name = 'stickyTableHeaders',_x000D_
        id = 0,_x000D_
        defaults = {_x000D_
            fixedOffset: 0,_x000D_
            leftOffset: 0,_x000D_
            marginTop: 0,_x000D_
            scrollableArea: window_x000D_
    function Plugin(el, options) {_x000D_
        // To avoid scope issues, use 'base' instead of 'this'_x000D_
        // to reference this class from internal events and functions._x000D_
        var base = this;_x000D_
        // Access to jQuery and DOM versions of element_x000D_
        base.$el = $(el);_x000D_
        base.el = el;_x000D_ = id++;_x000D_
        base.$window = $(window);_x000D_
        base.$document = $(document);_x000D_
        // Listen for destroyed, call teardown_x000D_
        $.proxy(base.teardown, base));_x000D_
        // Cache DOM refs for performance reasons_x000D_
        base.$clonedHeader = null;_x000D_
        base.$originalHeader = null;_x000D_
        // Keep track of state_x000D_
        base.isSticky = false;_x000D_
        base.hasBeenSticky = false;_x000D_
        base.leftOffset = null;_x000D_
        base.topOffset = null;_x000D_
        base.init = function () {_x000D_
            base.$el.each(function () {_x000D_
                var $this = $(this);_x000D_
                // remove padding on <table> to fix issue #7_x000D_
                $this.css('padding', 0);_x000D_
                base.$originalHeader = $('thead:first', this);_x000D_
                base.$clonedHeader = base.$originalHeader.clone();_x000D_
                $this.trigger('clonedHeader.' + name, [base.$clonedHeader]);_x000D_
                base.$clonedHeader.css('display', 'none');_x000D_
                base.$printStyle = $('<style type="text/css" media="print">' +_x000D_
                    '.tableFloatingHeader{display:none !important;}' +_x000D_
                    '.tableFloatingHeaderOriginal{position:static !important;}' +_x000D_
        base.destroy = function () {_x000D_
            base.$el.unbind('destroyed', base.teardown);_x000D_
        base.teardown = function () {_x000D_
            if (base.isSticky) {_x000D_
                base.$originalHeader.css('position', 'static');_x000D_
            $.removeData(base.el, 'plugin_' + name);_x000D_
            base.$originalHeader.css('visibility', 'visible');_x000D_
            base.el = null;_x000D_
            base.$el = null;_x000D_
        base.bind = function () {_x000D_
            base.$scrollableArea.on('scroll.' + name, base.toggleHeaders);_x000D_
            if (!base.isWindowScrolling) {_x000D_
                base.$window.on('scroll.' + name +, base.setPositionValues);_x000D_
                base.$window.on('resize.' + name +, base.toggleHeaders);_x000D_
            base.$scrollableArea.on('resize.' + name, base.toggleHeaders);_x000D_
            base.$scrollableArea.on('resize.' + name, base.updateWidth);_x000D_
        base.unbind = function () {_x000D_
            // unbind window events by specifying handle so we don't remove too much_x000D_
            base.$'.' + name, base.toggleHeaders);_x000D_
            if (!base.isWindowScrolling) {_x000D_
                base.$'.' + name +, base.setPositionValues);_x000D_
                base.$'.' + name +, base.toggleHeaders);_x000D_
            base.$'.' + name, base.updateWidth);_x000D_
        base.toggleHeaders = function () {_x000D_
            if (base.$el) {_x000D_
                base.$el.each(function () {_x000D_
                    var $this = $(this),_x000D_
                        newTopOffset = base.isWindowScrolling ? (_x000D_
                        isNaN(base.options.fixedOffset) ? base.options.fixedOffset.outerHeight() : base.options.fixedOffset) : base.$scrollableArea.offset().top + (!isNaN(base.options.fixedOffset) ? base.options.fixedOffset : 0),_x000D_
                        offset = $this.offset(),_x000D_
                        scrollTop = base.$scrollableArea.scrollTop() + newTopOffset,_x000D_
                        scrollLeft = base.$scrollableArea.scrollLeft(),_x000D_
                        scrolledPastTop = base.isWindowScrolling ? scrollTop > : newTopOffset >,_x000D_
                        notScrolledPastBottom = (base.isWindowScrolling ? scrollTop : 0) < ( + $this.height() - base.$clonedHeader.height() - (base.isWindowScrolling ? 0 : newTopOffset));_x000D_
                    if (scrolledPastTop && notScrolledPastBottom) {_x000D_
                        newLeft = offset.left - scrollLeft + base.options.leftOffset;_x000D_
                            'position': 'fixed',_x000D_
                                'margin-top': base.options.marginTop,_x000D_
                                'left': newLeft,_x000D_
                                'z-index': 3 // #18: opacity bug_x000D_
                        base.leftOffset = newLeft;_x000D_
                        base.topOffset = newTopOffset;_x000D_
                        base.$clonedHeader.css('display', '');_x000D_
                        if (!base.isSticky) {_x000D_
                            base.isSticky = true;_x000D_
                            // make sure the width is correct: the user might have resized the browser while in static mode_x000D_
                    } else if (base.isSticky) {_x000D_
                        base.$originalHeader.css('position', 'static');_x000D_
                        base.$clonedHeader.css('display', 'none');_x000D_
                        base.isSticky = false;_x000D_
                        base.resetWidth($('td,th', base.$clonedHeader), $('td,th', base.$originalHeader));_x000D_
        base.setPositionValues = function () {_x000D_
            var winScrollTop = base.$window.scrollTop(),_x000D_
                winScrollLeft = base.$window.scrollLeft();_x000D_
            if (!base.isSticky || winScrollTop < 0 || winScrollTop + base.$window.height() > base.$document.height() || winScrollLeft < 0 || winScrollLeft + base.$window.width() > base.$document.width()) {_x000D_
                'top': base.topOffset - (base.isWindowScrolling ? 0 : winScrollTop),_x000D_
                    'left': base.leftOffset - (base.isWindowScrolling ? 0 : winScrollLeft)_x000D_
        base.updateWidth = function () {_x000D_
            if (!base.isSticky) {_x000D_
            // Copy cell widths from clone_x000D_
            if (!base.$originalHeaderCells) {_x000D_
                base.$originalHeaderCells = $('th,td', base.$originalHeader);_x000D_
            if (!base.$clonedHeaderCells) {_x000D_
                base.$clonedHeaderCells = $('th,td', base.$clonedHeader);_x000D_
            var cellWidths = base.getWidth(base.$clonedHeaderCells);_x000D_
            base.setWidth(cellWidths, base.$clonedHeaderCells, base.$originalHeaderCells);_x000D_
            // Copy row width from whole table_x000D_
            base.$originalHeader.css('width', base.$clonedHeader.width());_x000D_
        base.getWidth = function ($clonedHeaders) {_x000D_
            var widths = [];_x000D_
            $clonedHeaders.each(function (index) {_x000D_
                var width, $this = $(this);_x000D_
                if ($this.css('box-sizing') === 'border-box') {_x000D_
                    width = $this[0].getBoundingClientRect().width; // #39: border-box bug_x000D_
                } else {_x000D_
                    var $origTh = $('th', base.$originalHeader);_x000D_
                    if ($origTh.css('border-collapse') === 'collapse') {_x000D_
                        if (window.getComputedStyle) {_x000D_
                            width = parseFloat(window.getComputedStyle(this, null).width);_x000D_
                        } else {_x000D_
                            // ie8 only_x000D_
                            var leftPadding = parseFloat($this.css('padding-left'));_x000D_
                            var rightPadding = parseFloat($this.css('padding-right'));_x000D_
                            // Needs more investigation - this is assuming constant border around this cell and it's neighbours._x000D_
                            var border = parseFloat($this.css('border-width'));_x000D_
                            width = $this.outerWidth() - leftPadding - rightPadding - border;_x000D_
                    } else {_x000D_
                        width = $this.width();_x000D_
                widths[index] = width;_x000D_
            return widths;_x000D_
        base.setWidth = function (widths, $clonedHeaders, $origHeaders) {_x000D_
            $clonedHeaders.each(function (index) {_x000D_
                var width = widths[index];_x000D_
                    'min-width': width,_x000D_
                        'max-width': width_x000D_
        base.resetWidth = function ($clonedHeaders, $origHeaders) {_x000D_
            $clonedHeaders.each(function (index) {_x000D_
                var $this = $(this);_x000D_
                    'min-width': $this.css('min-width'),_x000D_
                        'max-width': $this.css('max-width')_x000D_
        base.setOptions = function (options) {_x000D_
            base.options = $.extend({}, defaults, options);_x000D_
            base.$scrollableArea = $(base.options.scrollableArea);_x000D_
            base.isWindowScrolling = base.$scrollableArea[0] === window;_x000D_
        base.updateOptions = function (options) {_x000D_
            // scrollableArea might have changed_x000D_
        // Run initializer_x000D_
    // A plugin wrapper around the constructor,_x000D_
    // preventing against multiple instantiations_x000D_
    $.fn[name] = function (options) {_x000D_
        return this.each(function () {_x000D_
            var instance = $.data(this, 'plugin_' + name);_x000D_
            if (instance) {_x000D_
                if (typeof options === 'string') {_x000D_
                } else {_x000D_
            } else if (options !== 'destroy') {_x000D_
                $.data(this, 'plugin_' + name, new Plugin(this, options));_x000D_
})(jQuery, window);
body {_x000D_
    margin: 0 auto;_x000D_
    padding: 0 20px;_x000D_
    font-family: Arial, Helvetica, sans-serif;_x000D_
    font-size: 11px;_x000D_
    color: #555;_x000D_
table {_x000D_
    border: 0;_x000D_
    padding: 0;_x000D_
    margin: 0 0 20px 0;_x000D_
    border-collapse: collapse;_x000D_
th {_x000D_
    padding: 5px;_x000D_
    /* NOTE: th padding must be set explicitly in order to support IE */_x000D_
    text-align: right;_x000D_
    line-height: 2em;_x000D_
    color: #FFF;_x000D_
    background-color: #555;_x000D_
tbody td {_x000D_
    padding: 10px;_x000D_
    line-height: 18px;_x000D_
    border-top: 1px solid #E0E0E0;_x000D_
tbody tr:nth-child(2n) {_x000D_
    background-color: #F7F7F7;_x000D_
tbody tr:hover {_x000D_
    background-color: #EEEEEE;_x000D_
td {_x000D_
    text-align: right;_x000D_
td:first-child, th:first-child {_x000D_
    text-align: left;_x000D_
<script src=""></script>_x000D_
<div style="width:3000px">some really really wide content goes here</div>_x000D_
            <th colspan="9">Companies listed on NASDAQ OMX Copenhagen.</th>_x000D_
            <th>Full name</th>_x000D_
            <td>A.P. Møller...</td>_x000D_
            <td>A.P. Møller...</td>_x000D_
            <td>Carlsberg A</td>_x000D_
            <td>Carlsberg B</td>_x000D_
            <td>Chr. Hansen...</td>_x000D_
            <td>Coloplast B</td>_x000D_
            <td>D/S Norden</td>_x000D_
            <td>Danske Bank</td>_x000D_
            <td>FLSmidth &amp; Co.</td>_x000D_
            <td>G4S plc</td>_x000D_
            <td>Jyske Bank</td>_x000D_
            <td>Københavns ...</td>_x000D_
            <td>Nordea Bank</td>_x000D_
            <td>Novo Nordisk B</td>_x000D_
            <td>Novozymes B</td>_x000D_
            <td>Rockwool In...</td>_x000D_
            <td>Rockwool In...</td>_x000D_
            <td>Vestas Wind...</td>_x000D_
            <td>William Dem...</td>_x000D_
<div style="height: 4000px">lots of content down here...</div>

C/C++ macro string concatenation

Hint: The STRINGIZE macro above is cool, but if you make a mistake and its argument isn't a macro - you had a typo in the name, or forgot to #include the header file - then the compiler will happily put the purported macro name into the string with no error.

If you intend that the argument to STRINGIZE is always a macro with a normal C value, then


will expand it once and check it for validity, discard that, and then expand it again into a string.

It took me a while to figure out why STRINGIZE(ENOENT) was ending up as "ENOENT" instead of "2"... I hadn't included errno.h.

Always pass weak reference of self into block in ARC?

It helps not to focus on the strong or weak part of the discussion. Instead focus on the cycle part.

A retain cycle is a loop that happens when Object A retains Object B, and Object B retains Object A. In that situation, if either object is released:

  • Object A won't be deallocated because Object B holds a reference to it.
  • But Object B won't ever be deallocated as long as Object A has a reference to it.
  • But Object A will never be deallocated because Object B holds a reference to it.
  • ad infinitum

Thus, those two objects will just hang around in memory for the life of the program even though they should, if everything were working properly, be deallocated.

So, what we're worried about is retain cycles, and there's nothing about blocks in and of themselves that create these cycles. This isn't a problem, for example:

[myArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop){
   [self doSomethingWithObject:obj];

The block retains self, but self doesn't retain the block. If one or the other is released, no cycle is created and everything gets deallocated as it should.

Where you get into trouble is something like:

//In the interface:
@property (strong) void(^myBlock)(id obj, NSUInteger idx, BOOL *stop);

//In the implementation:
[self setMyBlock:^(id obj, NSUInteger idx, BOOL *stop) {
  [self doSomethingWithObj:obj];     

Now, your object (self) has an explicit strong reference to the block. And the block has an implicit strong reference to self. That's a cycle, and now neither object will be deallocated properly.

Because, in a situation like this, self by definition already has a strong reference to the block, it's usually easiest to resolve by making an explicitly weak reference to self for the block to use:

__weak MyObject *weakSelf = self;
[self setMyBlock:^(id obj, NSUInteger idx, BOOL *stop) {
  [weakSelf doSomethingWithObj:obj];     

But this should not be the default pattern you follow when dealing with blocks that call self! This should only be used to break what would otherwise be a retain cycle between self and the block. If you were to adopt this pattern everywhere, you'd run the risk of passing a block to something that got executed after self was deallocated.

__weak MyObject *weakSelf = self;
[[SomeOtherObject alloc] initWithCompletion:^{
  //By the time this gets called, "weakSelf" might be nil because it's not retained!
  [weakSelf doSomething];

How can I get the last day of the month in C#?

DateTime.DaysInMonth(DateTime.Now.Year, DateTime.Now.Month) vs onClick


There are already many good answers here however, authors sometimes mention about performance but actually nobody investigate it yet - so I will focus on this aspect here. Today I perform test on Chrome 83.0, Safari 13.1 and Firefox 77.0 for solutions mention in question and additionally few alternative solutions (some of them was mention in other answers).


I compare here solutions A-H because they operate on elements id. I also show results for solutions which use class (I,J,K) as reference.

  • solution based on html-inline handler binding (B) is fast and fastest for Chrome and fastest for small number of elements
  • solutions based on getElementById (C,D) are fast, and for big number of elements fastest on Safari and Firefox
  • referenced solutions I,J based are fastest for big num of elements so It is worth to consider use class instead id approach in this case
  • solution based on (A) is slowest

enter image description here


Actually It was not easy to design performance test for this question. I notice that for all tested solutions, performance of triggering events for 10K div-s was fast and manually I was not able to detect any differences between them (you can run below snippet to check it yourself). So I focus on measure execution time of generate html and bind event handlers for two cases

  • 10 divs - you can run test HERE
  • 1000 divs - you can run test HERE

let a= [...Array(10000)];

function clean() { test.innerHTML = ''; console.clear() }

function divFunction(el) {
  console.log(`clicked on: ${}`);

function initA() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;,i)=> $(`#myDiv${i}`).click(e=> divFunction(;

function initB() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box" onclick="divFunction(this)">${i}</div>`).join``;

function initC() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;,i)=> document.getElementById(`myDiv${i}`).onclick = e=> divFunction( );

function initD() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;,i)=> document.getElementById(`myDiv${i}`).addEventListener('click', e=> divFunction( ));

function initE() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;,i)=> document.querySelector(`#myDiv${i}`).onclick = e=> divFunction( );

function initF() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;,i)=> document.querySelector(`#myDiv${i}`).addEventListener('click', e=> divFunction( ));

function initG() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;,i)=> window[`myDiv${i}`].onclick = e=> divFunction( );

function initH() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;,i)=> window[`myDiv${i}`].addEventListener('click',e=> divFunction(;

function initI() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;
  [...document.querySelectorAll(`.box`)].map(el => el.onclick = e=> divFunction(;

function initJ() {
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;
  [...document.querySelectorAll(`.box`)].map(el => el.addEventListener('click', e=> divFunction(;

function initK() {  
  test.innerHTML =,i)=> `<div id="myDiv${i}" class="box">${i}</div>`).join``;
  $(`.box`).click(e=> divFunction(;

function measure(f) {  
  console.time("measure ";
  console.timeEnd("measure "
#test {
  display: flex;
  flex-wrap: wrap;

.box {
  margin: 1px;
  height: 10px;
  background: red;
  font-size: 10px;
  cursor: pointer;
<script src=""></script>
<div>This snippet only presents used solutions. Click to solution button and then click on any red box to trigger its handler</div>
<button onclick="measure(initA)">A</button>
<button onclick="measure(initB)">B</button>
<button onclick="measure(initC)">C</button>
<button onclick="measure(initD)">D</button>
<button onclick="measure(initE)">E</button>
<button onclick="measure(initF)">F</button>
<button onclick="measure(initG)">G</button>
<button onclick="measure(initH)">H</button>
<button onclick="measure(initI)">I</button>
<button onclick="measure(initJ)">J</button>
<button onclick="measure(initK)">K</button>
<button onclick="clean()">Clean</button>

<div id="test"></div>

Here is example test for Chrome

enter image description here

Recursive query in SQL Server

Sample of the Recursive Level:

enter image description here


--SET @VALUE_CODE = 'A' -- Specify a level

WITH ViewValue AS
    SELECT ValueCode
    , ValueDesc
    , PrecedingValueCode
    FROM ValuesTable
    WHERE PrecedingValueCode IS NULL
    SELECT A.ValueCode
    , A.ValueDesc
    , A.PrecedingValueCode 
    FROM ValuesTable A
    INNER JOIN ViewValue V ON
        V.ValueCode = A.PrecedingValueCode

SELECT ValueCode, ValueDesc, PrecedingValueCode

FROM ViewValue

--WHERE PrecedingValueCode  = @VALUE_CODE -- Specific level

--WHERE PrecedingValueCode  IS NULL -- Root

Multiple WHERE Clauses with LINQ extension methods

Just use the && operator like you would with any other statement that you need to do boolean logic.

if (useAdditionalClauses)
  results = results.Where(
                  o => o.OrderStatus == OrderStatus.Open 
                  && o.CustomerID == customerID)     

Initial bytes incorrect after Java AES/CBC decryption

The IV that your using for decryption is incorrect. Replace this code

//Decrypt cipher
Cipher decryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec ivParameterSpec = new IvParameterSpec(aesKey.getEncoded());
decryptCipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);

With this code

//Decrypt cipher
Cipher decryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec ivParameterSpec = new IvParameterSpec(encryptCipher.getIV());
decryptCipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);

And that should solve your problem.

Below includes an example of a simple AES class in Java. I do not recommend using this class in production environments, as it may not account for all of the specific needs of your application.

import java.nio.charset.StandardCharsets;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;

public class AES 
    public static byte[] encrypt(final byte[] keyBytes, final byte[] ivBytes, final byte[] messageBytes) throws InvalidKeyException, InvalidAlgorithmParameterException
        return AES.transform(Cipher.ENCRYPT_MODE, keyBytes, ivBytes, messageBytes);

    public static byte[] decrypt(final byte[] keyBytes, final byte[] ivBytes, final byte[] messageBytes) throws InvalidKeyException, InvalidAlgorithmParameterException
        return AES.transform(Cipher.DECRYPT_MODE, keyBytes, ivBytes, messageBytes);

    private static byte[] transform(final int mode, final byte[] keyBytes, final byte[] ivBytes, final byte[] messageBytes) throws InvalidKeyException, InvalidAlgorithmParameterException
        final SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
        final IvParameterSpec ivSpec = new IvParameterSpec(ivBytes);
        byte[] transformedBytes = null;

            final Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding");

            cipher.init(mode, keySpec, ivSpec);

            transformedBytes = cipher.doFinal(messageBytes);
        catch (NoSuchAlgorithmException | NoSuchPaddingException | IllegalBlockSizeException | BadPaddingException e) 
        return transformedBytes;

    public static void main(final String[] args) throws InvalidKeyException, InvalidAlgorithmParameterException
        //Retrieved from a protected local file.
        //Do not hard-code and do not version control.
        final String base64Key = "ABEiM0RVZneImaq7zN3u/w==";

        //Retrieved from a protected database.
        //Do not hard-code and do not version control.
        final String shadowEntry = "AAECAwQFBgcICQoLDA0ODw==:ZtrkahwcMzTu7e/WuJ3AZmF09DE=";

        //Extract the iv and the ciphertext from the shadow entry.
        final String[] shadowData = shadowEntry.split(":");        
        final String base64Iv = shadowData[0];
        final String base64Ciphertext = shadowData[1];

        //Convert to raw bytes.
        final byte[] keyBytes = Base64.getDecoder().decode(base64Key);
        final byte[] ivBytes = Base64.getDecoder().decode(base64Iv);
        final byte[] encryptedBytes = Base64.getDecoder().decode(base64Ciphertext);

        //Decrypt data and do something with it.
        final byte[] decryptedBytes = AES.decrypt(keyBytes, ivBytes, encryptedBytes);

        //Use non-blocking SecureRandom implementation for the new IV.
        final SecureRandom secureRandom = new SecureRandom();

        //Generate a new IV.

        //At this point instead of printing to the screen, 
        //one should replace the old shadow entry with the new one.
        System.out.println("Old Shadow Entry      = " + shadowEntry);
        System.out.println("Decrytped Shadow Data = " + new String(decryptedBytes, StandardCharsets.UTF_8));
        System.out.println("New Shadow Entry      = " + Base64.getEncoder().encodeToString(ivBytes) + ":" + Base64.getEncoder().encodeToString(AES.encrypt(keyBytes, ivBytes, decryptedBytes)));

Note that AES has nothing to do with encoding, which is why I chose to handle it separately and without the need of any third party libraries.

php delete a single file in directory

Simply You Can Use It

    $sql="select * from tbl_publication where id='5'";
    //Getting File Name From DB
    $pdfname = $res1['pdfname'];
    //pdf is directory where file exist

What is the best (idiomatic) way to check the type of a Python variable?

type(dict()) says "make a new dict, and then find out what its type is". It's quicker to say just dict. But if you want to just check type, a more idiomatic way is isinstance(x, dict).

Note, that isinstance also includes subclasses (thanks Dustin):

class D(dict):

d = D()
print("type(d) is dict", type(d) is dict)  # -> False
print("isinstance (d, dict)", isinstance(d, dict))  # -> True

How can I update a row in a DataTable in VB.NET?

The problem you're running into is that you're trying to replace an entire row object. That is not allowed by the DataTable API. Instead you have to update the values in the columns of a row object. Or add a new row to the collection.

To update the column of a particular row you can access it by name or index. For instance you could write the following code to update the column "Foo" to be the value strVerse

dtResult.Rows(i)("Foo") = strVerse

Getting text from td cells with jQuery

I would give your tds a specific class, e.g. data-cell, and then use something like this:

$("").each(function () {
    // 'this' is now the raw td DOM element
    var txt = $(this).html();

Is there a format code shortcut for Visual Studio?

Try Ctrl + K + D (don't lift the Ctrl key in between).

How do I remove documents using Node.js Mongoose?

If you don't feel like iterating, try FBFriendModel.find({ id:333 }).remove( callback ); or FBFriendModel.find({ id:333 }).remove().exec();

mongoose.model.find returns a Query, which has a remove function.

Update for Mongoose v5.5.3 - remove() is now deprecated. Use deleteOne(), deleteMany() or findOneAndDelete() instead.

How can you sort an array without mutating the original array?

You can use slice with no arguments to copy an array:

var foo,
foo = [3,1,2];
bar = foo.slice().sort();

Web API Put Request generates an Http 405 Method Not Allowed error

Add this to your web.config. You need to tell IIS what PUT PATCH DELETE and OPTIONS means. And which IHttpHandler to invoke.

    <remove name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" />
    <remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
    <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
    <add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness32" responseBufferLimit="0" />
    <add name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness64" responseBufferLimit="0" />
    <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />

Also check you don't have WebDAV enabled.

Is there an effective tool to convert C# code to Java code?

Although this is an old-ish question, take a look at xmlVM, I'm not sure if it's mature enough yet, although it has been around for several years now. XMLvm was made, I believe, primarily for translating Android Java apps to the iPhone, however, its XML-code-translation-based framework is flexible enough to do other combinations (see the diagrams on the site).

As for a reason to do this conversion, maybe there is a need to 'hijack' some of the highly abundant oss code out there and use it within his/their own [Java] project.



Best way to style a TextBox in CSS

You could target all text boxes with input[type=text] and then explicitly define the class for the textboxes who need it.

You can code like below :

input[type=text] {_x000D_
  padding: 0;_x000D_
  height: 30px;_x000D_
  position: relative;_x000D_
  left: 0;_x000D_
  outline: none;_x000D_
  border: 1px solid #cdcdcd;_x000D_
  border-color: rgba(0, 0, 0, .15);_x000D_
  background-color: white;_x000D_
  font-size: 16px;_x000D_
.advancedSearchTextbox {_x000D_
  width: 526px;_x000D_
  margin-right: -4px;_x000D_
<input type="text" class="advancedSearchTextBox" />

Passing HTML input value as a JavaScript Function Parameter

You can get the values with use of ID. But ID should be Unique.

<h1>Adding 'a' and 'b'</h1>
  a: <input type="number" name="a" id="a"><br>
  b: <input type="number" name="b" id="b"><br>
  <button onclick="add()">Add</button>
  function add() {
    a = $('#a').val();
    b = $('#b').val();
    var sum = a + b;

Delete duplicate records from a SQL table without a primary key

It is very simple. I tried in SQL Server 2008

 FROM Employee) SUB
WHERE SUB.cnt > 1

Chrome extension: accessing localStorage in content script

Sometimes it may be better to use API. It's better then localStorage because you can:

  • store information from your content script without the need for message passing between content script and extension;
  • store your data as JavaScript objects without serializing them to JSON (localStorage only stores strings).

Here's a simple code demonstrating the use of Content script gets the url of visited page and timestamp and stores it, popup.js gets it from storage area.


(function () {
    var visited = window.location.href;
    var time = +new Date();{'visitedPages':{pageUrl:visited,time:time}}, function () {
        console.log("Just visited",visited)


(function () { (changes,areaName) {
        console.log("New item in storage",changes.visitedPages.newValue);

"Changes" here is an object that contains old and new value for a given key. "AreaName" argument refers to name of storage area, either 'local', 'sync' or 'managed'.

Remember to declare storage permission in manifest.json.


"permissions": [

Genymotion, "Unable to load VirtualBox engine." on Mavericks. VBox is setup correctly

I had the same problem and solved it by running the following command:

sudo /Library/StartupItems/VirtualBox/VirtualBox restart

In later versions, the command is

sudo /Library/Application\ Support/VirtualBox/LaunchDaemons/ restart

Make sure you've unblocked VirtualBox's kernel extensions in System Preferences->Security and Privacy->General (You'll get a popup when you install VirtualBox).

Configuration Error: <compilation debug="true" targetFramework="4.0"> ASP.NET MVC3

Make sure that you are building your web app as "Any CPU". Right click your web project --> Properties --> Build --> and look for the "Platform Target". Choose "Any CPU" or play around with it.

Hope this helps!

Oracle PL/SQL string compare issue

As Phil noted, the empty string is treated as a NULL, and NULL is not equal or unequal to anything. If you expect empty strings or NULLs, you'll need to handle those with NVL():

 str1  varchar2(4000);
 str2  varchar2(4000);
-- Provide an alternate null value that does not exist in your data:
   IF(NVL(str1,'X') != NVL(str2,'Y')) THEN
    dbms_output.put_line('The two strings are not equal');
   END IF;

Concerning null comparisons:

According to the Oracle 12c documentation on NULLS, null comparisons using IS NULL or IS NOT NULL do evaluate to TRUE or FALSE. However, all other comparisons evaluate to UNKNOWN, not FALSE. The documentation further states:

A condition that evaluates to UNKNOWN acts almost like FALSE. For example, a SELECT statement with a condition in the WHERE clause that evaluates to UNKNOWN returns no rows. However, a condition evaluating to UNKNOWN differs from FALSE in that further operations on an UNKNOWN condition evaluation will evaluate to UNKNOWN. Thus, NOT FALSE evaluates to TRUE, but NOT UNKNOWN evaluates to UNKNOWN.

A reference table is provided by Oracle:

Condition       Value of A    Evaluation
a IS NULL       10            FALSE
a IS NOT NULL   10            TRUE        
a IS NULL       NULL          TRUE
a = NULL        10            UNKNOWN
a != NULL       10            UNKNOWN
a = NULL        NULL          UNKNOWN
a != NULL       NULL          UNKNOWN
a = 10          NULL          UNKNOWN
a != 10         NULL          UNKNOWN

I also learned that we should not write PL/SQL assuming empty strings will always evaluate as NULL:

Oracle Database currently treats a character value with a length of zero as null. However, this may not continue to be true in future releases, and Oracle recommends that you do not treat empty strings the same as nulls.

Use jquery click to handle anchor onClick()

<div class = "solTitle"> <a href = "#"  id = "solution0" onClick = "openSolution();">Solution0 </a></div> <br>

<div class= "solTitle"> <a href = "#"  id = "solution1" onClick = "openSolution();">Solution1 </a></div> <br>

    $('.solTitle a').click(function(e) {
        alert('here in');
         var divId = 'summary' +$(this).attr('id');

        document.getElementById(divId).className = ''; /* or $('#'+divid).removeAttr('class'); */


I changed few things:

  1. remove the onclick attr and bind click event inside the document.ready
  2. changed solTitle to be an ID to a CLASS: id cant be repeated

Java: parse int value from a char

Using binary AND with 0b1111:

String element = "el5";

char c = element.charAt(2);

System.out.println(c & 0b1111); // => '5' & 0b1111 => 0b0011_0101 & 0b0000_1111 => 5

// '0' & 0b1111 => 0b0011_0000 & 0b0000_1111 => 0
// '1' & 0b1111 => 0b0011_0001 & 0b0000_1111 => 1
// '2' & 0b1111 => 0b0011_0010 & 0b0000_1111 => 2
// '3' & 0b1111 => 0b0011_0011 & 0b0000_1111 => 3
// '4' & 0b1111 => 0b0011_0100 & 0b0000_1111 => 4
// '5' & 0b1111 => 0b0011_0101 & 0b0000_1111 => 5
// '6' & 0b1111 => 0b0011_0110 & 0b0000_1111 => 6
// '7' & 0b1111 => 0b0011_0111 & 0b0000_1111 => 7
// '8' & 0b1111 => 0b0011_1000 & 0b0000_1111 => 8
// '9' & 0b1111 => 0b0011_1001 & 0b0000_1111 => 9

regular expression for anything but an empty string

You could also use:

public static bool IsWhiteSpace(string s) 
    return s.Trim().Length == 0;

How to get date, month, year in jQuery UI datepicker?

You can use method getDate():

    dateFormat: 'yy-m-d',
    inline: true,
    onSelect: function(dateText, inst) { 
        var date = $(this).datepicker('getDate'),
            day  = date.getDate(),  
            month = date.getMonth() + 1,              
            year =  date.getFullYear();
        alert(day + '-' + month + '-' + year);


Select N random elements from a List<T> in C#

Here you have one implementation based on Fisher-Yates Shuffle whose algorithm complexity is O(n) where n is the subset or sample size, instead of the list size, as John Shedletsky pointed out.

public static IEnumerable<T> GetRandomSample<T>(this IList<T> list, int sampleSize)
    if (list == null) throw new ArgumentNullException("list");
    if (sampleSize > list.Count) throw new ArgumentException("sampleSize may not be greater than list count", "sampleSize");
    var indices = new Dictionary<int, int>(); int index;
    var rnd = new Random();

    for (int i = 0; i < sampleSize; i++)
        int j = rnd.Next(i, list.Count);
        if (!indices.TryGetValue(j, out index)) index = j;

        yield return list[index];

        if (!indices.TryGetValue(i, out index)) index = i;
        indices[j] = index;

Why "Data at the root level is invalid. Line 1, position 1." for XML Document?

I can give you two advices:

  1. It seems you are using "LoadXml" instead of "Load" method. In some cases, it helps me.
  2. You have an encoding problem. Could you check the encoding of the XML file and write it?

How to generate a Makefile with source in sub-directories using just one makefile

The reason is that your rule

%.o: %.cpp

expects the .cpp file to reside in the same directory as the .o your building. Since test.exe in your case depends on build/widgets/apple.o (etc), make is expecting apple.cpp to be build/widgets/apple.cpp.

You can use VPATH to resolve this:

VPATH = src/widgets

BUILDDIR = build/widgets

$(BUILDDIR)/%.o: %.cpp

When attempting to build "build/widgets/apple.o", make will search for apple.cpp in VPATH. Note that the build rule has to use special variables in order to access the actual filename make finds:

$(BUILDDIR)/%.o: %.cpp
        $(CC) $< -o $@

Where "$<" expands to the path where make located the first dependency.

Also note that this will build all the .o files in build/widgets. If you want to build the binaries in different directories, you can do something like

build/widgets/%.o: %.cpp

build/ui/%.o: %.cpp

build/tests/%.o: %.cpp

I would recommend that you use "canned command sequences" in order to avoid repeating the actual compiler build rule:

define cc-command
$(CC) $(CFLAGS) $< -o $@

You can then have multiple rules like this:

build1/foo.o build1/bar.o: %.o: %.cpp

build2/frotz.o build2/fie.o: %.o: %.cpp

What are the sizes used for the iOS application splash screen?

Here I can add Resolutions and Display Specifications for iphone 6 & 6+ size:

iPhone 6+ - Asset Resolution (@3x) - Resolution (2208 x 1242)px

iPhone 6 - Asset Resolution (@2x) - Resolution (1334 x 750)px

iPad Air / Retina iPad (1st & 2nd Generation / 3rd & 4th) - Asset Resolution (@2x) - Resolution (2048 x 1536)px

iPad Mini (2nd & 3rd Generation) - Asset Resolution (@2x) - Resolution (2048 x 1536)px

iPhone (6, 5S, 5, 5C, 4S, 4) - App Icon (120x120 px) - AppStore Icon (1024x1024 px) - Spotlight (80x80 px) - Settings (58x58 px)

iPhone (6+) - App Icon (180x180 px) - AppStore Icon (1024x1024 px) - Spotlight (120x120 px) - Settings (87x87 px)

Unable to simultaneously satisfy constraints, will attempt to recover by breaking constraint

I had a hard time figuring out what constraints were causing this error. Here is a simpler way to do it.

I'm using Xcode 6.1.1

  1. "Command + A" to select all the UILabels, UIImages etc.
  2. Click Editor -> Pin > (Select...) to Superview
  3. again click Editor -> Resolve Auto Layout Issues -> Add Missing Constraints or Reset to Suggested Constraints. It depends on your case.

How to save MySQL query output to excel or .txt file?

From Save MySQL query results into a text or CSV file:

MySQL provides an easy mechanism for writing the results of a select statement into a text file on the server. Using extended options of the INTO OUTFILE nomenclature, it is possible to create a comma separated value (CSV) which can be imported into a spreadsheet application such as OpenOffice or Excel or any other application which accepts data in CSV format.

Given a query such as

SELECT order_id,product_name,qty FROM orders

which returns three columns of data, the results can be placed into the file /tmp/orders.txt using the query:

SELECT order_id,product_name,qty FROM orders
INTO OUTFILE '/tmp/orders.txt'

This will create a tab-separated file, each row on its own line. To alter this behavior, it is possible to add modifiers to the query:

SELECT order_id,product_name,qty FROM orders
INTO OUTFILE '/tmp/orders.csv'

In this example, each field will be enclosed in double quotes, the fields will be separated by commas, and each row will be output on a new line separated by a newline (\n). Sample output of this command would look like:

"1","Tech-Recipes sock puppet","14.95" "2","Tech-Recipes chef's hat","18.95"

Keep in mind that the output file must not already exist and that the user MySQL is running as has write permissions to the directory MySQL is attempting to write the file to.


   SELECT Your_Column_Name
    FROM Your_Table_Name
    INTO OUTFILE 'Filename.csv'

Or you could try to grab the output via the client:

You could try executing the query from the your local client and redirect the output to a local file destination:

mysql -user -pass -e "select cols from table where cols not null" > /tmp/output

Hint: If you don't specify an absoulte path but use something like INTO OUTFILE 'output.csv' or INTO OUTFILE './output.csv', it will store the output file to the directory specified by show variables like 'datadir';.

What is the meaning of Bus: error 10 in C

For one, you can't modify string literals. It's undefined behavior.

To fix that you can make str a local array:

char str[] = "First string";

Now, you will have a second problem, is that str isn't large enough to hold str2. So you will need to increase the length of it. Otherwise, you will overrun str - which is also undefined behavior.

To get around this second problem, you either need to make str at least as long as str2. Or allocate it dynamically:

char *str2 = "Second string";
char *str = malloc(strlen(str2) + 1);  //  Allocate memory
//  Maybe check for NULL.

strcpy(str, str2);

//  Always remember to free it.

There are other more elegant ways to do this involving VLAs (in C99) and stack allocation, but I won't go into those as their use is somewhat questionable.

As @SangeethSaravanaraj pointed out in the comments, everyone missed the #import. It should be #include:

#include <stdio.h>
#include <string.h>

TypeError: a bytes-like object is required, not 'str' in python and CSV

You are opening the csv file in binary mode, it should be 'w'

import csv

# open csv file in write mode with utf-8 encoding
with open('output.csv','w',encoding='utf-8',newline='')as w:
    fieldnames = ["SNo", "States", "Dist", "Population"]
    writer = csv.DictWriter(w, fieldnames=fieldnames)
    # write list of dicts
    writer.writerows(list_of_dicts) #writerow(dict) if write one row at time

Difference between Big-O and Little-O Notation

f ? O(g) says, essentially

For at least one choice of a constant k > 0, you can find a constant a such that the inequality 0 <= f(x) <= k g(x) holds for all x > a.

Note that O(g) is the set of all functions for which this condition holds.

f ? o(g) says, essentially

For every choice of a constant k > 0, you can find a constant a such that the inequality 0 <= f(x) < k g(x) holds for all x > a.

Once again, note that o(g) is a set.

In Big-O, it is only necessary that you find a particular multiplier k for which the inequality holds beyond some minimum x.

In Little-o, it must be that there is a minimum x after which the inequality holds no matter how small you make k, as long as it is not negative or zero.

These both describe upper bounds, although somewhat counter-intuitively, Little-o is the stronger statement. There is a much larger gap between the growth rates of f and g if f ? o(g) than if f ? O(g).

One illustration of the disparity is this: f ? O(f) is true, but f ? o(f) is false. Therefore, Big-O can be read as "f ? O(g) means that f's asymptotic growth is no faster than g's", whereas "f ? o(g) means that f's asymptotic growth is strictly slower than g's". It's like <= versus <.

More specifically, if the value of g(x) is a constant multiple of the value of f(x), then f ? O(g) is true. This is why you can drop constants when working with big-O notation.

However, for f ? o(g) to be true, then g must include a higher power of x in its formula, and so the relative separation between f(x) and g(x) must actually get larger as x gets larger.

To use purely math examples (rather than referring to algorithms):

The following are true for Big-O, but would not be true if you used little-o:

  • x² ? O(x²)
  • x² ? O(x² + x)
  • x² ? O(200 * x²)

The following are true for little-o:

  • x² ? o(x³)
  • x² ? o(x!)
  • ln(x) ? o(x)

Note that if f ? o(g), this implies f ? O(g). e.g. x² ? o(x³) so it is also true that x² ? O(x³), (again, think of O as <= and o as <)

How to replace (or strip) an extension from a filename in Python?

Try os.path.splitext it should do what you want.

import os
print os.path.splitext('/home/user/somefile.txt')[0]+'.jpg'

How to properly make a http web GET request

Another way is using 'HttpClient' like this:

using System;
using System.Net;
using System.Net.Http;

namespace Test
    class Program
        static void Main(string[] args)
            Console.WriteLine("Making API Call...");
            using (var client = new HttpClient(new HttpClientHandler { AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate }))
                client.BaseAddress = new Uri("");
                HttpResponseMessage response = client.GetAsync("answers?order=desc&sort=activity&site=stackoverflow").Result;
                string result = response.Content.ReadAsStringAsync().Result;
                Console.WriteLine("Result: " + result);

Check HttpClient vs HttpWebRequest from stackoverflow and this from other.

Update June 22, 2020: It's not recommended to use httpclient in a 'using' block as it might cause port exhaustion.

private static HttpClient client = null;
   if(client == null)
        HttpClientHandler handler = new HttpClientHandler()
            AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate
        client = new HttpClient(handler);
   client.BaseAddress = new Uri("");
   HttpResponseMessage response = client.GetAsync("answers?order=desc&sort=activity&site=stackoverflow").Result;
   string result = response.Content.ReadAsStringAsync().Result;
            Console.WriteLine("Result: " + result);           

If using .Net Core 2.1+, consider using IHttpClientFactory and injecting like this in your startup code.

 var timeout = Policy.TimeoutAsync<HttpResponseMessage>(

 services.AddHttpClient<XApiClient>().ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler
            AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate
        }).AddPolicyHandler(request => timeout);

What does "commercial use" exactly mean?

I suggest this discriminative question:

Is the open-source tool necessary in your process of making money?

  • a blog engine on your commercial web site is necessary: commercial use.
  • winamp for listening to music is not necessary: non-commercial use.

Java: How to convert a File object to a String object in java?

Use a library like Guava or Commons / IO. They have oneliner methods.


Files.toString(file, charset);

Commons / IO:

FileUtils.readFileToString(file, charset);

Without such a library, I'd write a helper method, something like this:

public String readFile(File file, Charset charset) throws IOException {
    return new String(Files.readAllBytes(file.toPath()), charset);

How to increase MaximumErrorCount in SQL Server 2008 Jobs or Packages?

It is important to highlight that the Property (MaximumErrorCount) that needs to be changed must be set as more than 0 (which is the default) in the Package level and not in the specific control that is showing the error (I tried this and it does not work!)

Be sure that in the Properties Window, the Pull down menu is set to "Package", then look for the property MaximumErrorCount to change it.

7-zip commandline

Instead of the option a use option x, this will create the directories but only for extraction, not compression.

Javascript to export html table to Excel

ShieldUI's export to excel functionality should already support all special chars.

How to write and save html file in python?

You can create multi-line strings by enclosing them in triple quotes. So you can store your HTML in a string and pass that string to write():

html_str = """
<table border=1>
     <% for i in range(10): %>
         <td><%= i %></td>
         <td><%= i**2 %></td>

Html_file= open("filename","w")

How to send email attachments?

You can also specify the type of attachment you want in your e-mail, as an example I used pdf:

def send_email_pdf_figs(path_to_pdf, subject, message, destination, password_path=None):
    ## credits:
    from socket import gethostname
    #import email
    from email.mime.application import MIMEApplication
    from email.mime.multipart import MIMEMultipart
    from email.mime.text import MIMEText
    import smtplib
    import json

    server = smtplib.SMTP('', 587)
    with open(password_path) as f:
        config = json.load(f)
        server.login('[email protected]', config['password'])
        # Craft message (obj)
        msg = MIMEMultipart()

        message = f'{message}\nSend from Hostname: {gethostname()}'
        msg['Subject'] = subject
        msg['From'] = '[email protected]'
        msg['To'] = destination
        # Insert the text to the msg going by e-mail
        msg.attach(MIMEText(message, "plain"))
        # Attach the pdf to the msg going by e-mail
        with open(path_to_pdf, "rb") as f:
            #attach = email.mime.application.MIMEApplication(,_subtype="pdf")
            attach = MIMEApplication(,_subtype="pdf")
        # send msg

inspirations/credits to:

Is Java a Compiled or an Interpreted programming language ?

The terms "interpreted language" or "compiled language" don't make sense, because any programming language can be interpreted and/or compiled.

As for the existing implementations of Java, most involve a compilation step to bytecode, so they involve compilation. The runtime also can load bytecode dynamically, so some form of a bytecode interpreter is always needed. That interpreter may or may not in turn use compilation to native code internally.

These days partial just-in-time compilation is used for many languages which were once considered "interpreted", for example JavaScript.

How to view method information in Android Studio?

If you need only Parameter info then:

On Mac, it's assigned to Command+P

On Windows, it's assigned to Ctrl+P

If you need document info then:

On Mac, it's assigned to Command+Q

On Windows, it's assigned to Ctrl+Q

Django error - matching query does not exist

You can use this:

comment = Comment.objects.filter(pk=comment_id)

Hide all warnings in ipython

For jupyter lab this should work (@Alasja)

from IPython.display import HTML
var code_show_err = false; 
var code_toggle_err = function() {
 var stderrNodes = document.querySelectorAll('[data-mime-type="application/vnd.jupyter.stderr"]')
 var stderr = Array.from(stderrNodes)
 if (code_show_err){
     stderr.forEach(ele => = 'block');
 } else {
     stderr.forEach(ele => = 'none');
 code_show_err = !code_show_err
document.addEventListener('DOMContentLoaded', code_toggle_err);
To toggle on/off output_stderr, click <a onclick="javascript:code_toggle_err()">here</a>.''')

sql select with column name like

SELECT * FROM SysColumns WHERE Name like 'a%'

Will get you a list of columns, you will want to filter more to restrict it to your target table

From there you can construct some ad-hoc sql

How to determine a Python variable's type?

Examples of simple type checking in Python:

assert type(variable_name) == int

assert type(variable_name) == bool

assert type(variable_name) == list

Properties private set;

Or you can do

public class Person
    public Person(int id)

    public string Name { get;  set; }
    public int Id { get; private set; }
    public int Age { get; set; }

Protect .NET code from reverse engineering?

The best answer is the first one from the small developer speaking from his own expierence, all the anti-reversing techniques discussed above are 101 textbook cases for any serious reverse-engineer.

Some commercial DRM solutions are pretty decent, but they crack every triple AAA game with custom DRM solutions all the time within hours (or days). Only the introduction of a completely new DRM solution - sometimes - delays in inevitable for perhaps a couple of weeks.

Getting the most out of the DRM costs a lot of time & money and can easily hurt performance, reliability, compatibility/portability and customer-relations in general. Either stick with some decent commercial DRM without trying to be too smart about and take your (less) losses or just forget about it totally ...

One example of a DRM solution which dug it's own (commercial) grave:

Android Studio does not show layout preview

Choose another theme (other than Holo, for example Theme)

Solution Image

When you create the style incorrectly or from an existing style, this problem usually occurs. So select the "Graphical Layout" select "AppTheme" (The tab with a blue star). And select any of the predefined style. In my case "Light" which should resolve the problem.

Try to 'Invalidate caches & restart'.

how to invalidate cache & restart

Restart your Android Studio by choosing this option. It may take some time.

Then, if still doesn't work try to rebuild your project.

Laravel 5 How to switch from Production mode

Laravel 5 gets its enviroment related variables from the .env file located in the root of your project. You just need to set APP_ENV to whatever you want, for example:


This is used to identify the current enviroment. If you want to display errors, you'll need to enable debug mode in the same file:


The role of the .env file is to allow you to have different settings depending on which machine you are running your application. So on your production server, the .env file settings would be different from your local development enviroment.

Prevent Bootstrap Modal from disappearing when clicking outside or pressing escape?

Works too, data-backdrop="static" to click out and data-keyboard="false" to Esc in your div modal:

<div id="idModal" class="modal hide" data-backdrop="static" data-keyboard="false">

What is the difference between MOV and LEA?

Basically ... "Move into REG ... after computing it..." it seems to be nice for other purposes as well :)

if you just forget that the value is a pointer you can use it for code optimizations/minimization ...what ever..


;//with 1 instruction you got result of 2 registers in 3rd one ...

EAX = 8

originaly it would be:


error: ORA-65096: invalid common user or role name in oracle

In Oracle 12c and above, we have two types of databases:

  1. Container DataBase (CDB), and
  2. Pluggable DataBase (PDB).

If you want to create an user, you have two possibilities:

  1. You can create a "container user" aka "common user".
    Common users belong to CBDs as well as to current and future PDBs. It means they can perform operations in Container DBs or Pluggable DBs according to assigned privileges.

    create user c##username identified by password;

  2. You can create a "pluggable user" aka "local user".
    Local users belong only to a single PDB. These users may be given administrative privileges, but only for that PDB inside which they exist. For that, you should connect to pluggable datable like that:

    alter session set container = nameofyourpluggabledatabase;

    and there, you can create user like usually:

    create user username identified by password;

Don't forget to specify the tablespace(s) to use, it can be useful during import/export of your DBs. See this for more information about it

WPF Timer Like C# Timer

The usual WPF timer is the DispatcherTimer, which is not a control but used in code. It basically works the same way like the WinForms timer:

System.Windows.Threading.DispatcherTimer dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
dispatcherTimer.Tick += dispatcherTimer_Tick;
dispatcherTimer.Interval = new TimeSpan(0,0,1);

private void dispatcherTimer_Tick(object sender, EventArgs e)
  // code goes here

More on the DispatcherTimer can be found here

if, elif, else statement issues in Bash

You have some syntax issues with your script. Here is a fixed version:


if [ "$seconds" -eq 0 ]; then
elif [ "$seconds" -gt 0 ]; then
   timezone_string=$(printf "%02d:%02d" $((seconds/3600)) $(((seconds / 60) % 60)))
   echo "Unknown parameter"

Calling stored procedure with return value

I had a similar problem with the SP call returning an error that an expected parameter was not included. My code was as follows.
Stored Procedure:

@Result int OUTPUT

And C#:

            SqlParameter result = cmd.Parameters.Add(new SqlParameter("@Result", DbType.Int32));
            result.Direction = ParameterDirection.ReturnValue;

In troubleshooting, I realized that the stored procedure was ACTUALLY looking for a direction of "InputOutput" so the following change fixed the problem.


Result.Direction = ParameterDirection.InputOutput;

Get current URL with jQuery?

If you need the hash parameters present in the URL, window.location.href may be a better choice.

=> /search


ValueError: object too deep for desired array while using convolution

The Y array in your screenshot is not a 1D array, it's a 2D array with 300 rows and 1 column, as indicated by its shape being (300, 1).

To remove the extra dimension, you can slice the array as Y[:, 0]. To generally convert an n-dimensional array to 1D, you can use np.reshape(a, a.size).

Another option for converting a 2D array into 1D is flatten() function from numpy.ndarray module, with the difference that it makes a copy of the array.

Angular2 handling http response

The service :

import 'rxjs/add/operator/map';

import { Http } from '@angular/http';
import { Observable } from "rxjs/Rx"
import { Injectable } from '@angular/core';

export class ItemService {
  private api = "your_api_url";

  constructor(private http: Http) {


  toSaveItem(item) {
    return new Promise((resolve, reject) => {
        .post(this.api + '/items', { item: item })
        .map(res => res.json())
        // This catch is very powerfull, it can catch all errors
        .catch((err: Response) => {
          // The err.statusText is empty if server down (err.type === 3)
          console.log((err.statusText || "Can't join the server."));
          // Really usefull. The app can't catch this in "(err)" closure
          reject((err.statusText || "Can't join the server."));
          // This return is required to compile but unuseable in your app
          return Observable.throw(err);
        // The (err) => {} param on subscribe can't catch server down error so I keep only the catch
        .subscribe(data => { resolve(data) })

In the app :

  (res) => { console.log('success', res) },
  (err) => { console.log('error', err) }

Please initialize the log4j system properly warning

None of answered method solve the problem which file is not found for non-maven jsf web project in NetBeans. So the answer is:

  1. Create a folder named resources in project root folder (outermost folder).
  2. Right click project in projects explorer in left menu, select properties.
  3. Open Sources in Categories, add that folder in Source Package Folders.
  4. Open Run in Categories and add this to VM options: Dlog4j.configuration=resources/
  5. Click Ok, build and deploy project as you like, that's it.

I wrote special pattern in log4j file to check whether log4j is used my file:

# Root Logger Option
log4j.rootLogger=INFO, console

# Redirect Log Messages To Console
log4j.appender.console.layout.ConversionPattern=%-5p | %d{yyyy-MM-dd HH:mm:ss} | [%t] %C{2} xxxx (%F:%L) - %m%n

I checked it because if you use BasicConfigurator.configure(); in your code in log4j use predefined pattern.

Convert string to variable name in JavaScript

let me make it more clear

function changeStringToVariable(variable, value){
changeStringToVariable("name", "john doe");
//this outputs: john doe
let file="newFile";
changeStringToVariable(file, "text file");
//this outputs: text file

jQuery changing css class to div


If you'd like to add it on an event, you can do so easily as well. An example with the click event:

$(".first").click(function() {

How can a Javascript object refer to values in itself?

You can also reference the obj once you are inside the function instead of this.

var obj = {
    key1: "it",
    key2: function(){return obj.key1 + " works!"}

iOS UIImagePickerController result image orientation after upload

Here is the Swift-4.2 code for automatic fix your image orientation Returns UIImage

func AutofixImageOrientation(_ image: UIImage)->UIImage {


    image.draw(at: .zero)

    let newImage = UIGraphicsGetImageFromCurrentImageContext()


    return newImage ?? image

Logical XOR operator in C++?

For a true logical XOR operation, this will work:

if(!A != !B) {
    // code here

Note the ! are there to convert the values to booleans and negate them, so that two unequal positive integers (each a true) would evaluate to false.

Global Variable from a different file Python

from file2 import * is making copies. You want to do this:

import file2
print file2.SomeClass()

Posting array from form

Give each input a name in array format:

<input type="hidden" name="data[EstPriceInput]" value="" />

Then the in PHP $_POST['data']; will be an array:

  print_r($_POST);         // print out the whole post
  print_r($_POST['data']); // print out only the data array

What does "javax.naming.NoInitialContextException" mean?

In extremely non-technical terms, it may mean that you forgot to put "ejb:" or "jdbc:" or something at the very beginning of the URI you are trying to connect.

What is the meaning of "$" sign in JavaScript

In addition to the above answers, $ has no special meaning in javascript,it is free to be used in object naming. In jQuery, it is simply used as an alias for the jQuery object and jQuery() function. However, you may encounter situations where you want to use it in conjunction with another JS library that also uses $, which would result a naming conflict. There is a method in JQuery just for this reason, jQuery.noConflict().

Here is a sample from jQuery doc's:

<script src="other_lib.js"></script>
<script src="jquery.js"></script>
// Code that uses other library's $ can follow here.

Alternatively, you can also use a like this

(function ($) {
// Code in which we know exactly what the meaning of $ is
} (jQuery));


Changing background color of ListView items on Android

Did you mean to change the background color of the custom listitems when you click on it?

If so:

You just add the following code to your listview layout in xml.

android:drawSelectorOnTop="true" android:listSelector="@android:drawable/list_selector_background"

The list selector here uses default selector which has a dark grey color. You can make your own drawable and assign it to the list selector as above.

Hope this is what you wanted.

In Python, how do I loop through the dictionary and change the value if it equals something?

for k, v in mydict.iteritems():
    if v is None:
        mydict[k] = ''

In a more general case, e.g. if you were adding or removing keys, it might not be safe to change the structure of the container you're looping on -- so using items to loop on an independent list copy thereof might be prudent -- but assigning a different value at a given existing index does not incur any problem, so, in Python 2.any, it's better to use iteritems.

In Python3 however the code gives AttributeError: 'dict' object has no attribute 'iteritems' error. Use items() instead of iteritems() here.

Refer to this post.

Perform curl request in javascript?

curl is a command in linux (and a library in php). Curl typically makes an HTTP request.

What you really want to do is make an HTTP (or XHR) request from javascript.

Using this vocab you'll find a bunch of examples, for starters: Sending authorization headers with jquery and ajax

Essentially you will want to call $.ajax with a few options for the header, etc.

        url: '',
        beforeSend: function(xhr) {
             xhr.setRequestHeader("Authorization", "Bearer 6QXNMEMFHNY4FJ5ELNFMP5KRW52WFXN5")
        }, success: function(data){
            //process the JSON data etc

Get selected value from combo box in C# WPF

I had a similar issue and tried a number of solutions suggested in this thread but found that the SelectionChanged Event was firing before the ComboBox item had actually updated to show the new selection (i.e. so it always gave the contents of the combobox prior to the change occurring).

In order to overcome this, I found that it was better to use the e parameter that is automatically passed to the event handler rather than trying to load the value directly from the combo box.


    <x:Array x:Key="Combo" Type="sys:String">
        <sys:String>Item 1</sys:String>
        <sys:String>Item 2</sys:String>
    <ComboBox Name="myCombo" ItemsSource="{StaticResource Combo}" SelectionChanged="ComboBox_SelectionChanged" />
    <TextBlock Name="MyTextBlock"></TextBlock>


private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    string chosenValue = e.AddedItems[0].ToString();

How can I print variable and string on same line in Python?

use String formatting

print("If there was a birth every 7 seconds, there would be: {} births".format(births))
 # Will replace "{}" with births

if you doing a toy project use:

print('If there was a birth every 7 seconds, there would be:' births'births) 


print('If there was a birth every 7 seconds, there would be: %d births' %(births))
# Will replace %d with births

What is a View in Oracle?

regular view----->short name for a query,no additional space is used here

Materialised view---->similar to creating table whose data will refresh periodically based on data query used for creating the view

What is the difference between a schema and a table and a database?

schema : database : table :: floor plan : house : room

Select all child elements recursively in CSS

Use a white space to match all descendants of an element:

div.dropdown * {
    color: red;

x y matches every element y that is inside x, however deeply nested it may be - children, grandchildren and so on.

The asterisk * matches any element.

Official Specification: CSS 2.1: Chapter 5.5: Descendant Selectors

Combine multiple results in a subquery into a single comma-separated value

I think you are on the right track with COALESCE. See here for an example of building a comma-delimited string:

Why is 1/1/1970 the "epoch time"?


The earliest versions of Unix time had a 32-bit integer incrementing at a rate of 60 Hz, which was the rate of the system clock on the hardware of the early Unix systems. The value 60 Hz still appears in some software interfaces as a result. The epoch also differed from the current value. The first edition Unix Programmer's Manual dated November 3, 1971 defines the Unix time as "the time since 00:00:00, Jan. 1, 1971, measured in sixtieths of a second".

Which mime type should I use for mp3

Your best bet would be using the RFC defined mime-type audio/mpeg.

How to add new item to hash

hash[key]=value Associates the value given by value with the key given by key.

hash[:newKey] = "newValue"

From Ruby documentation:

What is middleware exactly?

It is just a piece of software or a tool on which your application executes and rapplication capabilities with respect to high availability,scalability,integrating with other softwares or systems without you bothering about your application level code changes .

For example : The operating system on which your application runs requires an I.P change , you do not have to worry about it in your code , it is the middleware stack on which you can simple update the configuration.

Example 2 : You experience problems with your runtime memory allocation and feel that the your application usage has increased , you do not have to much about it unless you have a bug or bottleneck in your code , it is easily achievable by tuning middleware software configuration on which your application runs.

Example 3 : You have multiple disparate software and you need them to talk to each other or send data in a common format which is understandable by all the systems then this is where middleware systems comes handy.

Hope the information provided helps.

How to set editable true/false EditText in Android programmatically?

try this,

EditText editText=(EditText)findViewById(;


It works fine...