Programs & Examples On #Avmutablecomposition

AVMutableComposition is a mutable subclass of AVComposition you use when you want to create a new composition from existing assets. You can add and remove tracks, and you can add, remove, and scale time ranges.

DBCC CHECKIDENT Sets Identity to 0

It seems ridiculous that you can't set/reset an identity column with a single command to cover both cases of whether or not the table has had records inserted. I couldn't understand the behavior I was experiencing until I stumbled across this question on SO!

My solution (ugly but works) is to explicitly check the sys.identity_columns.last_value table (which tells you whether or not the table has had records inserted) and call the appropriate DBCC CHECKIDENT command in each case. It is as follows:

DECLARE @last_value INT = CONVERT(INT, (SELECT last_value FROM sys.identity_columns WHERE OBJECT_NAME(OBJECT_ID) = 'MyTable'));
IF @last_value IS NULL
        -- Table newly created and no rows inserted yet; start the IDs off from 1
        DBCC CHECKIDENT ('MyTable', RESEED, 1);
        -- Table has rows; ensure the IDs continue from the last ID used
        DECLARE @lastValUsed INT = (SELECT ISNULL(MAX(ID),0) FROM MyTable);
        DBCC CHECKIDENT ('MyTable', RESEED, @lastValUsed);

How to stop Python closing immediately when executed in Microsoft Windows

I couldn't find anywhere on the internet a true non-script specific, double click and the window doesn't close solution. I guess I'm too lazy to drag and drop or type when I don't need to so after some experimentation I came up with a solution.

The basic idea is to reassociate .py files so they run a separate initial script before running the intended script. The initial script launches a new command prompt window with the /k parameter which keeps the command prompt open after completion and runs your intended script in the new window.

Maybe there are good reasons not to do this, those with more knowledge please comment if so, but I figure if I run into any it is easy to revert back if needed. One possibly undesirable side effect is dragging and dropping or typing and running from a command prompt now opens a second command prompt rather than running in the command prompt you dragged or typed in.

Now, for the implementation, I call the initial python script python_cmd_k.pyw. I'm using Python 3.7. The code required may differ for other versions. Change the path C:\Python37\python.exe to the location of your python installation. Associate .pyw files to pythonw.exe (not python.exe) through Windows if they aren't already.

import subprocess
import sys

#Run a python script in a new command prompt that does not close
command = 'start cmd /k C:\Python37\python.exe "' + sys.argv[1] + '"', shell=True)

This runs every time you double click any .py script and launches a new command prompt to run the script you double clicked. Running through pythonw.exe suppresses the command prompt window when this initial script runs. Otherwise if you run it through python.exe an annoying blink of a command prompt appear as a result of the first window showing briefly each time. The intended script displays because the code in the initial script above runs the intended script with python.exe.

Now associate .py files with python.exe (not pythonw.exe) through Windows if they are not already and edit the registry entry for this association (Disclaimer: Always back up your registry before editing it if you are unsure of what you are doing). I do not know if there are different paths in the registry for file association for different versions of Windows but for me it is at:


Change the data to the pythonw.exe path (not python.exe) and add the path to the ptyhon script above and "%1" as arguments ("%1" passes the full path of the doubled clicked file). For example if pythonw.exe and python_cmd_k.pyw are at C:\Python37\ then:

"C:\Python37\pythonw.exe" "C:\Python37\python_cmd_k.pyw" "%1"

It is not necessary to put python_cmd_k.pyw in the same directory as pythonw.exe as long as you provide the correct path for both. You can put these in .reg files for easy switching back and forth between using the script and the default behavior. Change the paths as needed in the examples below (location in the registry, your installation of python, the location you put your python_cmd_k.pyw script).

With ptyhon_cmd_k.pyw (change paths as needed):

Windows Registry Editor Version 5.00

@="\"C:\\Python37\\pythonw.exe\" \"C:\\Python37\\python_cmd_k.pyw\" \"%1\""

Default version (change paths as needed):

Windows Registry Editor Version 5.00

@="\"C:\\Python37\\python.exe\" \"%1\""

Fastest way to convert an iterator to a list

@Robino was suggesting to add some tests which make sense, so here is a simple benchmark between 3 possible ways (maybe the most used ones) to convert an iterator to a list:

  1. by type constructor


  1. by unpacking


  1. using list comprehension

[e for e in my_iterator]

I have been using simple_bechmark library

from simple_benchmark import BenchmarkBuilder
from heapq import nsmallest

b = BenchmarkBuilder()

def convert_by_type_constructor(size):

def convert_by_list_comprehension(size):
    [e for e in iter(range(size))]

def convert_by_unpacking(size):

@b.add_arguments('Convert an iterator to a list')
def argument_provider():
    for exp in range(2, 22):
        size = 2**exp
        yield size, size

r =

enter image description here

As you can see there is very hard to make a difference between conversion by the constructor and conversion by unpacking, conversion by list comprehension is the “slowest” approach.

I have been testing also across different Python versions (3.6, 3.7, 3.8, 3.9) by using the following simple script:

import argparse
import timeit

parser = argparse.ArgumentParser(
    description='Test convert iterator to list')
    '--size', help='The number of elements from iterator')

args = parser.parse_args()

size = int(args.size)
repeat_number = 10000

# do not wait too much if the size is too big
if size > 10000:
    repeat_number = 100

def test_convert_by_type_constructor():

def test_convert_by_list_comprehension():
    [e for e in iter(range(size))]

def test_convert_by_unpacking():

def get_avg_time_in_ms(func):
    avg_time = timeit.timeit(func, number=repeat_number) * 1000 / repeat_number
    return round(avg_time, 6)

funcs = [test_convert_by_type_constructor,
         test_convert_by_unpacking, test_convert_by_list_comprehension]

print(*map(get_avg_time_in_ms, funcs))

The script will be executed via a subprocess from a Jupyter Notebook (or a script), the size parameter will be passed through command-line arguments and the script results will be taken from standard output.

from subprocess import PIPE, run

import pandas

simple_data = {'constructor': [], 'unpacking': [], 'comprehension': [],
        'size': [], 'python version': []}

size_test = 100, 1000, 10_000, 100_000, 1_000_000
for version in ['3.6', '3.7', '3.8', '3.9']:
    print('test for python', version)
    for size in size_test:
        command = [f'python{version}', '', f'--size={size}']
        result = run(command, stdout=PIPE, stderr=PIPE, universal_newlines=True)
        constructor, unpacking,  comprehension = result.stdout.split()
        simple_data['python version'].append(version)

df_ = pandas.DataFrame(simple_data)

enter image description here

You can get my full notebook from here.

In most of the cases, in my tests, unpacking shows to be faster, but the difference is so small that the results may change from a run to the other. Again, the comprehension approach is the slowest, in fact, the other 2 methods are up to ~ 60% faster.

How do I write output in same place on the console?

Print the backspace character \b several times, and then overwrite the old number with the new number.

What is the difference between `new Object()` and object literal notation?

They both do the same thing (unless someone's done something unusual), other than that your second one creates an object and adds a property to it. But literal notation takes less space in the source code. It's clearly recognizable as to what is happening, so using new Object(), you are really just typing more and (in theory, if not optimized out by the JavaScript engine) doing an unnecessary function call.


person = new Object() /*You should put a semicolon here too.  
It's not required, but it is good practice.*/ 

person = {
    property1 : "Hello"

technically do not do the same thing. The first just creates an object. The second creates one and assigns a property. For the first one to be the same you then need a second step to create and assign the property.

The "something unusual" that someone could do would be to shadow or assign to the default Object global:

// Don't do this
Object = 23;

In that highly-unusual case, new Object will fail but {} will work.

In practice, there's never a reason to use new Object rather than {} (unless you've done that very unusual thing).


The code was most likely compiled with a later JDK (without using cross-compilation options) and is being run on an earlier JRE. While upgrading the JRE is one solution, it would be better to use the cross-compilation options to ensure the code will run on whatever JRE is intended as the minimum version for the app.

<meta charset="utf-8"> vs <meta http-equiv="Content-Type">

While not contesting the other answers, I think the following is worthy of mentioning.

  1. The “long” (http-equiv) notation and the “short” one are equal, whichever comes first wins;
  2. Web server headers will override all the <meta> tags;
  3. BOM (Byte order mark) will override everything, and in many cases it will affect html 4 (and probably other stuff, too);
  4. If you don't declare any encoding, you will probably get your text in “fallback text encoding” that is defined your browser. Neither in Firefox nor in Chrome it's utf-8;
  5. In absence of other clues the browser will attempt to read your document as if it was in ASCII to get the encoding, so you can't use any weird encodings (utf-16 with BOM should do, though);
  6. While the specs say that the encoding declaration must be within the first 512 bytes of the document, most browsers will try reading more than that.

You can test by running echo 'HTTP/1.1 200 OK\r\nContent-type: text/html; charset=windows-1251\r\n\r\n\xef\xbb\xbf<!DOCTYPE html><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta charset="windows-1251"><title>??????</title></head><body>??????</body></html>' | nc -lp 4500 and pointing your browser at localhost:4500. (Of course you will want to change or remove parts. The BOM part is \xef\xbb\xbf. Be wary of the encoding of your shell.)

Please mind that it's very important that you explicitly declare the encoding. Letting browsers guess can lead to security issues.

When do you use POST and when do you use GET?

Gorgapor, mod_rewrite still often utilizes GET. It just allows to translate a friendlier URL into a URL with a GET query string.

R: numeric 'envir' arg not of length one in predict()

There are several problems here:

  1. The newdata argument of predict() needs a predictor variable. You should thus pass it values for Coupon, instead of Total, which is the response variable in your model.

  2. The predictor variable needs to be passed in as a named column in a data frame, so that predict() knows what the numbers its been handed represent. (The need for this becomes clear when you consider more complicated models, having more than one predictor variable).

  3. For this to work, your original call should pass df in through the data argument, rather than using it directly in your formula. (This way, the name of the column in newdata will be able to match the name on the RHS of the formula).

With those changes incorporated, this will work:

model <- lm(Total ~ Coupon, data=df)
new <- data.frame(Coupon = df$Coupon)
predict(model, newdata = new, interval="confidence")

Using git commit -a with vim

See this thread for an explanation: VIM for Windows - What do I type to save and exit from a file?

As I wrote there: to learn Vimming, you could use one of the quick reference cards:

Also note How can I set up an editor to work with Git on Windows? if you're not comfortable in using Vim but want to use another editor for your commit messages.

If your commit message is not too long, you could also type

git commit -a -m "your message here"

how to convert a string date into datetime format in python?

The particular format for strptime:

datetime.datetime.strptime(string_date, "%Y-%m-%d %H:%M:%S.%f")
#>>> datetime.datetime(2013, 9, 28, 20, 30, 55, 782000)

How to set TextView textStyle such as bold, italic

The easiest way you can do based on the style selection criteria is:

String pre = "", post = "";

    pre += "<b>"; post += "</b>";
    pre += "<i>"; post += "</i>";
    pre += "<u>"; post += "</u>";

textView.setText(Html.fromHtml(pre + editText.getText().toString()+ post));
// you can also use it with EidtText
editText.setText(Html.fromHtml(pre + editText.getText().toString()+ post));

MySQL error 1449: The user specified as a definer does not exist

For future googlers: I got a similar message trying to update a table in a database that contained no views. After some digging, it turned out I had imported triggers on that table, and those were the things defined by the non-existant user. Dropping the triggers solved the problem.

Copying sets Java

Another way to do this is to use the copy constructor:

Collection<E> oldSet = ...
TreeSet<E> newSet = new TreeSet<E>(oldSet);

Or create an empty set and add the elements:

Collection<E> oldSet = ...
TreeSet<E> newSet = new TreeSet<E>();

Unlike clone these allow you to use a different set class, a different comparator, or even populate from some other (non-set) collection type.

Note that the result of copying a Set is a new Set containing references to the objects that are elements if the original Set. The element objects themselves are not copied or cloned. This conforms with the way that the Java Collection APIs are designed to work: they don't copy the element objects.

When should you use constexpr capability in C++11?

Your basic example serves he same argument as that of constants themselves. Why use

static const int x = 5;
int arr[x];


int arr[5];

Because it's way more maintainable. Using constexpr is much, much faster to write and read than existing metaprogramming techniques.

Adding form action in html in laravel

Your form is also missing '{{csrf_field()}}'

CSS - how to make image container width fixed and height auto stretched

What you're looking for is min-height and max-height.

img {
    max-width: 100%;
    height: auto;

.item {
    width: 120px;
    min-height: 120px;
    max-height: auto;
    float: left;
    margin: 3px;
    padding: 3px;

Regex to replace multiple spaces with a single space

Here is an alternate solution if you do not want to use replace (replace spaces in a string without using replace javascript)

var str="The dog      has a long   tail, and it     is RED!";
var rule=/\s{1,}/g;

str = str.split(rule).join(" "); 


selected value get from db into dropdown select box option using php mysql error

The easiest way I can think of is the following:


$selection = array('PHP', 'ASP');
echo '<select>
      <option value="0">Please Select Option</option>';

foreach ($selection as $selection) {
    $selected = ($options == $selection) ? "selected" : "";
    echo '<option '.$selected.' value="'.$selection.'">'.$selection.'</option>';

echo '</select>';

The code basically places all of your options in an array which are called upon in the foreach loop. The loop checks to see if your $options variable matches the current selection it's on, if it's a match then $selected will = selected, if not then it is set as blank. Finally the option tag is returned containing the selection from the array and if that particular selection is equal to your $options variable, it's set as the selected option.

How do I tell Maven to use the latest version of a dependency?

MY solution in maven 3.5.4 ,use nexus, in eclipse:


then in eclipse: atl + F5, and choose the force update of snapshots/release

it works for me.

How do I keep jQuery UI Accordion collapsed by default?

Add the active: false option (documentation)..

$("#accordion").accordion({ header: "h3", collapsible: true, active: false });

Add button to a layout programmatically

This line:

layout = (LinearLayout) findViewById(;

Looks for the "statsviewlayout" id in your current 'contentview'. Now you've set that here:

setContentView(new GraphTemperature(getApplicationContext()));

And i'm guessing that new "graphTemperature" does not set anything with that id.

It's a common mistake to think you can just find any view with findViewById. You can only find a view that is in the XML (or appointed by code and given an id).

The nullpointer will be thrown because the layout you're looking for isn't found, so


Throws that exception.

addition: Now if you want to get that view from an XML, you should use an inflater:

layout = (LinearLayout) View.inflate(this, R.layout.yourXMLYouWantToLoad, null);

assuming that you have your linearlayout in a file called "yourXMLYouWantToLoad.xml"

Recommendation for compressing JPG files with ImageMagick

Here's a complete solution for those using Imagick in PHP:

$im = new \Imagick($filePath);

// Try between 0 or 5 radius. If you find radius of 5 
// produces too blurry  pictures decrease to 0 until you 
// find a good balance between size and quality. 
$im->gaussianBlurImage(0.05, 5);

// Include this part if you also want to specify a maximum size for the images

$size = $im->getImageGeometry();
$maxWidth = 1920;
$maxHeight = 1080;

// ----------
// |        |
// ----------
if($size['width'] >= $size['height']){
  if($size['width'] > $maxWidth){
    $im->resizeImage($maxWidth, 0, \Imagick::FILTER_LANCZOS, 1);

// ------
// |    |
// |    |
// |    |
// |    |
// ------
  if($size['height'] > $maxHeight){
    $im->resizeImage(0, $maxHeight, \Imagick::FILTER_LANCZOS, 1);

Can not find the tag library descriptor for ""

You may try to make the folder which include jsp-s become the source folder of eclipse, that solved the same problem of mine. As below:

  1. open project's properties.(right click project, then choose the Properties)
  2. choose Java Build Path, select the Source tab, click Add Folder and choose the folder including your jsp-s, OK

npm start error with create-react-app

I have faced the following issue.

enter image description here

Please find the solution:

  1. Add "C:\Windows\System32" to the global PATH environment variable.

  2. Check whether the environment variables has been created for nodejs,npm and composer. if not create one

enter image description here

  1. Run your app.

Create database from command line


sudo -u postgres psql -c 'create database test;'

How do I convert a double into a string in C++?

If you use C++, avoid sprintf. It's un-C++y and has several problems. Stringstreams are the method of choice, preferably encapsulated as in Boost.LexicalCast which can be done quite easily:

template <typename T>
std::string to_string(T const& value) {
    stringstream sstr;
    sstr << value;
    return sstr.str();


string s = to_string(42.5);

React : difference between <Route exact path="/" /> and <Route path="/" />

The shortest answer is

Please try this.

   <Route exact path="/" component={Home} />
   <Route path="/about" component={About} />
   <Route path="/shop" component={Shop} />

Generic Interface

As an answer strictly in line with your question, I support cleytus's proposal.

You could also use a marker interface (with no method), say DistantCall, with several several sub-interfaces that have the precise signatures you want.

  • The general interface would serve to mark all of them, in case you want to write some generic code for all of them.
  • The number of specific interfaces can be reduced by using cleytus's generic signature.

Examples of 'reusable' interfaces:

    public interface DistantCall {

    public interface TUDistantCall<T,U> extends DistantCall {
      T execute(U... us);

    public interface UDistantCall<U> extends DistantCall {
      void execute(U... us);

    public interface TDistantCall<T> extends DistantCall {
      T execute();

    public interface TUVDistantCall<T, U, V> extends DistantCall {
      T execute(U u, V... vs);

UPDATED in response to OP comment

I wasn't thinking of any instanceof in the calling. I was thinking your calling code knew what it was calling, and you just needed to assemble several distant call in a common interface for some generic code (for example, auditing all distant calls, for performance reasons). In your question, I have seen no mention that the calling code is generic :-(

If so, I suggest you have only one interface, only one signature. Having several would only bring more complexity, for nothing.

However, you need to ask yourself some broader questions :
how you will ensure that caller and callee do communicate correctly?

That could be a follow-up on this question, or a different question...

Using partial views in MVC 4

You're passing the same model to the partial view as is being passed to the main view, and they are different types. The model is a DbSet of Notes, where you need to pass in a single Note.

You can do this by adding a parameter, which I'm guessing as it's the create form would be a new Note

@Html.Partial("_CreateNote", new QuickNotes.Models.Note())

How to have Java method return generic list of any type?

No need to even pass the class:

public <T> List<T> magicalListGetter() {
    return new ArrayList<T>();

Decimal separator comma (',') with numberDecimal inputType in EditText

You can use the following workaround to also include comma as a valid input:-

Through XML:

    android:digits="0123456789.," />


EditText input = new EditText(THE_CONTEXT);

In this way Android system will show the numbers' keyboard and allow the input of comma. Hope this answers the question :)

ng-model for `<input type="file"/>` (with directive DEMO)

I create a directive and registered on bower.

This lib will help you modeling input file, not only return file data but also file dataurl or base 64.

    "lastModified": 1438583972000,
    "lastModifiedDate": "2015-08-03T06:39:32.000Z",
    "name": "gitignore_global.txt",
    "size": 236,
    "type": "text/plain",
    "data": "data:text/plain;base64,DQojaWdub3JlIHRodW1ibmFpbHMgY3JlYXRlZCBieSB3aW5kb3dz…xoDQoqLmJhaw0KKi5jYWNoZQ0KKi5pbGsNCioubG9nDQoqLmRsbA0KKi5saWINCiouc2JyDQo="

How to use nan and inf in C?

I usually use

#define INFINITY (1e999)


const double INFINITY = 1e999

which works at least in IEEE 754 contexts because the highest representable double value is roughly 1e308. 1e309 would work just as well, as would 1e99999, but three nines is sufficient and memorable. Since this is either a double literal (in the #define case) or an actual Inf value, it will remain infinite even if you're using 128-bit (“long double”) floats.

How to remove focus without setting focus to another control?

What about just adding android:windowSoftInputMode="stateHidden" on your activity in the manifest.

Taken from a smart man commenting on this:

How to get href value using jQuery?

**Replacing  href attribut value to other** 
 <div class="cpt">
   <a href="/ref/ref/testone.html">testoneLink</a>

  <div class="test" >
      <a href="/ref/ref/testtwo.html">testtwoLInk</a>

 <!--Remove first default Link from href attribut -->
     Remove first default Link from href attribut
    $(".cpt a").removeAttr("href");
    Add  Link to same href attribut
    var testurl= $(".test").find("a").attr("href");
    $(".test a").attr('href', testurl);

Jquery date picker z-index issue

I had this issue as well, since the datepicker uses the input's z-index, I added the following css

#dialogID input,.modal-dialog input, .modal-dialog .input-group .form-control{

Just take the rule that applies to yours, either by parent id, class, or in my case a bootstrap dialog, using their input-group and form-control.

How to set background color of view transparent in React Native

Surprisingly no one told about this, which provides some !clarity:

backgroundColor: 'white',
opacity: 0.7

Count the number of occurrences of each letter in string

One simple possibility would be to make an array of 26 ints, each is a count for a letter a-z:

int alphacount[26] = {0}; //[0] = 'a', [1] = 'b', etc

Then loop through the string and increment the count for each letter:

for(int i = 0; i<strlen(mystring); i++)      //for the whole length of the string
        alphacount[tolower(mystring[i])-'a']++;  //make the letter lower case (if it's not)
                                                 //then use it as an offset into the array
                                                 //and increment

It's a simple idea that works for A-Z, a-z. If you want to separate by capitals you just need to make the count 52 instead and subtract the correct ASCII offset

How do I import from Excel to a DataSet using Microsoft.Office.Interop.Excel?

Years after everyone's answer, I too want to present how I did it for my project

    /// <summary>
    /// /Reads an excel file and converts it into dataset with each sheet as each table of the dataset
    /// </summary>
    /// <param name="filename"></param>
    /// <param name="headers">If set to true the first row will be considered as headers</param>
    /// <returns></returns>
    public DataSet Import(string filename, bool headers = true)
        var _xl = new Excel.Application();
        var wb = _xl.Workbooks.Open(filename);
        var sheets = wb.Sheets;
        DataSet dataSet = null;
        if (sheets != null && sheets.Count != 0)
            dataSet = new DataSet();
            foreach (var item in sheets)
                var sheet = (Excel.Worksheet)item;
                DataTable dt = null;
                if (sheet != null)
                    dt = new DataTable();
                    var ColumnCount = ((Excel.Range)sheet.UsedRange.Rows[1, Type.Missing]).Columns.Count;
                    var rowCount = ((Excel.Range)sheet.UsedRange.Columns[1, Type.Missing]).Rows.Count;

                    for (int j = 0; j < ColumnCount; j++)
                        var cell = (Excel.Range)sheet.Cells[1, j + 1];
                        var column = new DataColumn(headers ? cell.Value : string.Empty);

                    for (int i = 0; i < rowCount; i++)
                        var r = dt.NewRow();
                        for (int j = 0; j < ColumnCount; j++)
                            var cell = (Excel.Range)sheet.Cells[i + 1 + (headers ? 1 : 0), j + 1];
                            r[j] = cell.Value;

        return dataSet;

Error using eclipse for Android - No resource found that matches the given name

Eclipse doesn't seem to like imported programs. What worked for me is renaming strings.xml to string.xml, save (without error) and then rename it back to strings.xml, save again and error doesn't show up again.

Eclipse would be sooo good if it wasn't for those tiny little errors all the time :(

Check for internet connection with Swift

To solve the 4G issue mentioned in the comments I have used @AshleyMills reachability implementation as a reference and rewritten Reachability for Swift 3.1:

updated: Xcode 10.1 • Swift 4 or later

Reachability.swift file

import Foundation
import SystemConfiguration

class Reachability {
    var hostname: String?
    var isRunning = false
    var isReachableOnWWAN: Bool
    var reachability: SCNetworkReachability?
    var reachabilityFlags = SCNetworkReachabilityFlags()
    let reachabilitySerialQueue = DispatchQueue(label: "ReachabilityQueue")
    init(hostname: String) throws {
        guard let reachability = SCNetworkReachabilityCreateWithName(nil, hostname) else {
            throw Network.Error.failedToCreateWith(hostname)
        self.reachability = reachability
        self.hostname = hostname
        isReachableOnWWAN = true
        try start()
    init() throws {
        var zeroAddress = sockaddr_in()
        zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
        zeroAddress.sin_family = sa_family_t(AF_INET)
        guard let reachability = withUnsafePointer(to: &zeroAddress, {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                SCNetworkReachabilityCreateWithAddress(nil, $0)
        }) else {
            throw Network.Error.failedToInitializeWith(zeroAddress)
        self.reachability = reachability
        isReachableOnWWAN = true
        try start()
    var status: Network.Status {
        return  !isConnectedToNetwork ? .unreachable :
                isReachableViaWiFi    ? .wifi :
                isRunningOnDevice     ? .wwan : .unreachable
    var isRunningOnDevice: Bool = {
        #if targetEnvironment(simulator)
            return false
            return true
    deinit { stop() }

extension Reachability {

    func start() throws {
        guard let reachability = reachability, !isRunning else { return }
        var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil) = Unmanaged<Reachability>.passUnretained(self).toOpaque()
        guard SCNetworkReachabilitySetCallback(reachability, callout, &context) else { stop()
            throw Network.Error.failedToSetCallout
        guard SCNetworkReachabilitySetDispatchQueue(reachability, reachabilitySerialQueue) else { stop()
            throw Network.Error.failedToSetDispatchQueue
        reachabilitySerialQueue.async { self.flagsChanged() }
        isRunning = true

    func stop() {
        defer { isRunning = false }
        guard let reachability = reachability else { return }
        SCNetworkReachabilitySetCallback(reachability, nil, nil)
        SCNetworkReachabilitySetDispatchQueue(reachability, nil)
        self.reachability = nil

    var isConnectedToNetwork: Bool {
        return isReachable &&
               !isConnectionRequiredAndTransientConnection &&
               !(isRunningOnDevice && isWWAN && !isReachableOnWWAN)

    var isReachableViaWiFi: Bool {
        return isReachable && isRunningOnDevice && !isWWAN

    /// Flags that indicate the reachability of a network node name or address, including whether a connection is required, and whether some user intervention might be required when establishing a connection.
    var flags: SCNetworkReachabilityFlags? {
        guard let reachability = reachability else { return nil }
        var flags = SCNetworkReachabilityFlags()
        return withUnsafeMutablePointer(to: &flags) {
            SCNetworkReachabilityGetFlags(reachability, UnsafeMutablePointer($0))
            } ? flags : nil

    /// compares the current flags with the previous flags and if changed posts a flagsChanged notification
    func flagsChanged() {
        guard let flags = flags, flags != reachabilityFlags else { return }
        reachabilityFlags = flags .flagsChanged, object: self)

    /// The specified node name or address can be reached via a transient connection, such as PPP.
    var transientConnection: Bool { return flags?.contains(.transientConnection) == true }

    /// The specified node name or address can be reached using the current network configuration.
    var isReachable: Bool { return flags?.contains(.reachable) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. If this flag is set, the kSCNetworkReachabilityFlagsConnectionOnTraffic flag, kSCNetworkReachabilityFlagsConnectionOnDemand flag, or kSCNetworkReachabilityFlagsIsWWAN flag is also typically set to indicate the type of connection required. If the user must manually make the connection, the kSCNetworkReachabilityFlagsInterventionRequired flag is also set.
    var connectionRequired: Bool { return flags?.contains(.connectionRequired) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. Any traffic directed to the specified name or address will initiate the connection.
    var connectionOnTraffic: Bool { return flags?.contains(.connectionOnTraffic) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established.
    var interventionRequired: Bool { return flags?.contains(.interventionRequired) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. The connection will be established "On Demand" by the CFSocketStream programming interface (see CFStream Socket Additions for information on this). Other functions will not establish the connection.
    var connectionOnDemand: Bool { return flags?.contains(.connectionOnDemand) == true }

    /// The specified node name or address is one that is associated with a network interface on the current system.
    var isLocalAddress: Bool { return flags?.contains(.isLocalAddress) == true }

    /// Network traffic to the specified node name or address will not go through a gateway, but is routed directly to one of the interfaces in the system.
    var isDirect: Bool { return flags?.contains(.isDirect) == true }

    /// The specified node name or address can be reached via a cellular connection, such as EDGE or GPRS.
    var isWWAN: Bool { return flags?.contains(.isWWAN) == true }

    /// The specified node name or address can be reached using the current network configuration, but a connection must first be established. If this flag is set
    /// The specified node name or address can be reached via a transient connection, such as PPP.
    var isConnectionRequiredAndTransientConnection: Bool {
        return (flags?.intersection([.connectionRequired, .transientConnection]) == [.connectionRequired, .transientConnection]) == true

func callout(reachability: SCNetworkReachability, flags: SCNetworkReachabilityFlags, info: UnsafeMutableRawPointer?) {
    guard let info = info else { return }
    DispatchQueue.main.async {

extension Notification.Name {
    static let flagsChanged = Notification.Name("FlagsChanged")

struct Network {
    static var reachability: Reachability!
    enum Status: String {
        case unreachable, wifi, wwan
    enum Error: Swift.Error {
        case failedToSetCallout
        case failedToSetDispatchQueue
        case failedToCreateWith(String)
        case failedToInitializeWith(sockaddr_in)


Initialize it in your AppDelegate.swift didFinishLaunchingWithOptions method and handle any errors that might occur:

import UIKit
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        do {
            try Network.reachability = Reachability(hostname: "")
        catch {
            switch error as? Network.Error {
            case let .failedToCreateWith(hostname)?:
                print("Network error:\nFailed to create reachability object With host named:", hostname)
            case let .failedToInitializeWith(address)?:
                print("Network error:\nFailed to initialize reachability object With address:", address)
            case .failedToSetCallout?:
                print("Network error:\nFailed to set callout")
            case .failedToSetDispatchQueue?:
                print("Network error:\nFailed to set DispatchQueue")
            case .none:
        return true

And a view controller sample:

import UIKit
class ViewController: UIViewController {
    override func viewDidLoad() {
                         selector: #selector(statusManager),
                         name: .flagsChanged,
                         object: nil)
    func updateUserInterface() {
        switch Network.reachability.status {
        case .unreachable:
            view.backgroundColor = .red
        case .wwan:
            view.backgroundColor = .yellow
        case .wifi:
            view.backgroundColor = .green
        print("Reachability Summary")
        print("Status:", Network.reachability.status)
        print("HostName:", Network.reachability.hostname ?? "nil")
        print("Reachable:", Network.reachability.isReachable)
        print("Wifi:", Network.reachability.isReachableViaWiFi)
    @objc func statusManager(_ notification: Notification) {

Sample Project

How do I set up NSZombieEnabled in Xcode 4?

In Xcode 4.x press


(or click Menubar > Product > Scheme > Edit Scheme)

select the "Diagnostics" tab and click "Enable Zombie Objects":

Click "Enable Zombie Objects"

This turns released objects into NSZombie instances that print console warnings when used again. This is a debugging aid that increases memory use (no object is really released) but improves error reporting.

A typical case is when you over-release an object and you don't know which one:

  • With zombies: -[UITableView release]: message sent to deallocated instance
  • Without zombies: EXC_BAD_ACCESS

This Xcode setting is ignored when you archive the application for App Store submission. You don't need to touch anything before releasing your application.

Pressing ??R is the same as selecting Product > Run while keeping the Alt key pressed.
Clicking the "Enable Zombie Objects" checkbox is the same as manually adding "NSZombieEnabled = YES" in the section "Environment Variables" of the tab Arguments.

Slack URL to open a channel from browser

Referencing a channel within a conversation

To create a clickable reference to a channel in a Slack conversation, just type # followed by the channel name. For example: #general.

# mention of a channel

To grab a link to a channel through the Slack UI

To share the channel URL externally, you can grab its link by control-clicking (Mac) or right-clicking (Windows) on the channel name:

grabbing a channel's URL

The link would look like this:

Note that this link doesn't change even if you change the name of the channel. So, it is better to use this link rather than the one based on channel's name.

To compose a URL for a channel based on channel name<channel_name>

Opening the above URL from a browser would launch the Slack client (if available) or open the slack channel on the browser itself.

To compose a URL for a direct message (DM) channel to a user<username>

Read file from resources folder in Spring Boot

stuck in the same issue, this helps me

URL resource = getClass().getClassLoader().getResource("jsonschema.json");
JsonNode jsonNode = JsonLoader.fromURL(resource);

Most simple code to populate JTable from ResultSet

I think this is the Easiest way to populate a table with ResultSet with a method like

FillTable(MyTable, "select * Customers;");

And a very simple method can be made as

public void FillTable(JTable table, String Query)
        Statement stat = conn.createStatement();
        ResultSet rs = stat.executeQuery(Query);

        //To remove previously added rows
        while(table.getRowCount() > 0) 
            ((DefaultTableModel) table.getModel()).removeRow(0);
        int columns = rs.getMetaData().getColumnCount();
            Object[] row = new Object[columns];
            for (int i = 1; i <= columns; i++)
                row[i - 1] = rs.getObject(i);
            ((DefaultTableModel) table.getModel()).insertRow(rs.getRow()-1,row);

    catch(InstantiationException | IllegalAccessException | SQLException e)

When should I use git pull --rebase?

Perhaps the best way to explain it is with an example:

  1. Alice creates topic branch A, and works on it
  2. Bob creates unrelated topic branch B, and works on it
  3. Alice does git checkout master && git pull. Master is already up to date.
  4. Bob does git checkout master && git pull. Master is already up to date.
  5. Alice does git merge topic-branch-A
  6. Bob does git merge topic-branch-B
  7. Bob does git push origin master before Alice
  8. Alice does git push origin master, which is rejected because it's not a fast-forward merge.
  9. Alice looks at origin/master's log, and sees that the commit is unrelated to hers.
  10. Alice does git pull --rebase origin master
  11. Alice's merge commit is unwound, Bob's commit is pulled, and Alice's commit is applied after Bob's commit.
  12. Alice does git push origin master, and everyone is happy they don't have to read a useless merge commit when they look at the logs in the future.

Note that the specific branch being merged into is irrelevant to the example. Master in this example could just as easily be a release branch or dev branch. The key point is that Alice & Bob are simultaneously merging their local branches to a shared remote branch.

Customize list item bullets using CSS

Based on @dzimney answer and similar to @Crisman answer (but different)

That answer is good but has indention problem (bullets appear inside of li scope). Probably you don't want this. See simple example list below (this is a default HTML list):

  • Lorem ipsum dolor sit amet, ei cum offendit partiendo iudicabit. At mei quaestio honestatis, duo dicit affert persecuti ei. Etiam nusquam cu his, nec alterum posidonium philosophia te. Nec an purto iudicabit, no vix quod clita expetendis.

  • Quem suscipiantur no eos, sed impedit explicari ea, falli inermis comprehensam est in. Vide dicunt ancillae cum te, habeo delenit deserunt mei in. Tale sint ex his, ipsum essent appellantur et cum.

But if you use the mentioned answer the list will be like below (ignoring the size of the bullets):

Lorem ipsum dolor sit amet, ei cum offendit partiendo iudicabit. At mei quaestio honestatis, duo dicit affert persecuti ei. Etiam nusquam cu his, nec alterum posidonium philosophia te. Nec an purto iudicabit, no vix quod clita expetendis.

Quem suscipiantur no eos, sed impedit explicari ea, falli inermis comprehensam est in. Vide dicunt ancillae cum te, habeo delenit deserunt mei in. Tale sint ex his, ipsum essent appellantur et cum.

So I recommend this approach that resolves the issue:

li {_x000D_
    list-style-type: none;_x000D_
    position: relative;    /* It's needed for setting position to absolute in the next rule. */_x000D_
li::before {_x000D_
    content: '¦';_x000D_
    position: absolute;_x000D_
    left: -0.8em;          /* Adjust this value so that it appears where you want. */_x000D_
    font-size: 1.1em;      /* Adjust this value so that it appears what size you want. */_x000D_
    <li>Lorem ipsum dolor sit amet, ei cum offendit partiendo iudicabit. At mei quaestio honestatis, duo dicit affert persecuti ei. Etiam nusquam cu his, nec alterum posidonium philosophia te. Nec an purto iudicabit, no vix quod clita expetendis.</li>_x000D_
    <li>Quem suscipiantur no eos, sed impedit explicari ea, falli inermis comprehensam est in. Vide dicunt ancillae cum te, habeo delenit deserunt mei in. Tale sint ex his, ipsum essent appellantur et cum.</li>_x000D_

How do I add python3 kernel to jupyter (IPython)

sudo apt-get install python3-pip python3-dev
pip3 install -U jupyter

How to count lines in a document?

Use wc:

wc -l <filename>

PHP - Get key name of array value

Here is another option

$array = [1=>'one', 2=>'two', 3=>'there'];
$array = array_flip($array);
echo $array['one']; 

Purpose of Activator.CreateInstance with example?

You can also do this -

var handle = Activator.CreateInstance("AssemblyName", 
                "Full name of the class including the namespace and class name");
var obj = handle.Unwrap();

Can I call curl_setopt with CURLOPT_HTTPHEADER multiple times to set multiple headers?

Other type of format :

$headers[] = 'Accept: application/json';
$headers[] = 'Content-Type: application/json';
$headers[] = 'Content-length: 0';

curl_setopt($curlHandle, CURLOPT_HTTPHEADER, $headers);

Repeat a string in JavaScript a number of times

These days, the repeat string method is implemented almost everywhere. (It is not in Internet Explorer.) So unless you need to support older browsers, you can simply write:


Before repeat, we used this hack:

Array(11).join("a") // create string with 10 a's: "aaaaaaaaaa"

(Note that an array of length 11 gets you only 10 "a"s, since Array.join puts the argument between the array elements.)

Simon also points out that according to this jsperf, it appears that it's faster in Safari and Chrome (but not Firefox) to repeat a character multiple times by simply appending using a for loop (although a bit less concise).

Hide Show content-list with only CSS, no javascript used

I've got another simple solution:


<a href="#alert" class="span3" tabindex="0">Hide Me</a>
<a href="#" class="span2" tabindex="0">Show Me</a>
<p id="alert" class="alert" >Some alarming information here</p>


body { display: block; }
p.alert:target { display: none; }


How to format numbers?

This will get you your comma seperated values as well as add the fixed notation to the end.

    nStr += '';
    x = nStr.split('.');
    x1 = x[0];
    x2 = x.length > 1 ? '.' + x[1] : '';
    var rgx = /(\d+)(\d{3})/;
    while (rgx.test(x1)) {
        x1 = x1.replace(rgx, '$1' + ',' + '$2');
    commaSeperated = x1 + x2 + ".00";


Vibrate and Sound defaults on notification

For Kotlin you can Try this.

var builder = NotificationCompat.Builder(this,CHANNEL_ID)
     .setVibrate(longArrayOf(1000, 1000, 1000, 1000, 1000))

PermissionError: [WinError 5] Access is denied python using moviepy to write gif

If you're encountering this in Jupyter/Jupyerlab while trying to pip install foo, you can sometimes work around it by using !python -m pip install foo instead.

Passing javascript variable to html textbox

Pass the variable to the form element like this

your form element

<input type="text" id="mytext">


var test = "Hello";
document.getElementById("mytext").value = test;//Now you get the js variable inside your form element

REST API Best practice: How to accept list of parameter values as input

First case:

A normal product lookup would look like this

So Im thinking that best practice would be for you to do this,7267261

Second Case

Search with querystring parameters - fine like this. I would be tempted to combine terms with AND and OR instead of using [].

PS This can be subjective, so do what you feel comfortable with.

The reason for putting the data in the url is so the link can pasted on a site/ shared between users. If this isnt an issue, by all means use a JSON/ POST instead.

EDIT: On reflection I think this approach suits an entity with a compound key, but not a query for multiple entities.

Difference between @Mock and @InjectMocks

This is a sample code on how @Mock and @InjectMocks works.

Say we have Game and Player class.

class Game {

    private Player player;

    public Game(Player player) {
        this.player = player;

    public String attack() {
        return "Player attack with: " + player.getWeapon();


class Player {

    private String weapon;

    public Player(String weapon) {
        this.weapon = weapon;

    String getWeapon() {
        return weapon;

As you see, Game class need Player to perform an attack.

class GameTest {

    Player player;

    Game game;

    public void attackWithSwordTest() throws Exception {

        assertEquals("Player attack with: Sword", game.attack());


Mockito will mock a Player class and it's behaviour using when and thenReturn method. Lastly, using @InjectMocks Mockito will put that Player into Game.

Notice that you don't even have to create a new Game object. Mockito will inject it for you.

// you don't have to do this
Game game = new Game(player);

We will also get same behaviour using @Spy annotation. Even if the attribute name is different.

public class GameTest {

  @Mock Player player;

  @Spy List<String> enemies = new ArrayList<>();

  @InjectMocks Game game;

  @Test public void attackWithSwordTest() throws Exception {


    assertEquals(2, game.numberOfEnemies());

    assertEquals("Player attack with: Sword", game.attack());

class Game {

  private Player player;

  private List<String> opponents;

  public Game(Player player, List<String> opponents) {
    this.player = player;
    this.opponents = opponents;

  public int numberOfEnemies() {
    return opponents.size();

  // ...

That's because Mockito will check the Type Signature of Game class, which is Player and List<String>.

Rails: How to list database tables/objects using the Rails console?

To get a list of all model classes, you can use ActiveRecord::Base.subclasses e.g. { |cl| }
ActiveRecord::Base.subclasses.find { |cl| == "Foo" }

How to check if a view controller is presented modally or pushed on a navigation stack?

self.navigationController != nil would mean it's in a navigation stack.

When is it practical to use Depth-First Search (DFS) vs Breadth-First Search (BFS)?

Depth-first Search

Depth-first searches are often used in simulations of games (and game-like situations in the real world). In a typical game you can choose one of several possible actions. Each choice leads to further choices, each of which leads to further choices, and so on into an ever-expanding tree-shaped graph of possibilities.

enter image description here

For example in games like Chess, tic-tac-toe when you are deciding what move to make, you can mentally imagine a move, then your opponent’s possible responses, then your responses, and so on. You can decide what to do by seeing which move leads to the best outcome.

Only some paths in a game tree lead to your win. Some lead to a win by your opponent, when you reach such an ending, you must back up, or backtrack, to a previous node and try a different path. In this way you explore the tree until you find a path with a successful conclusion. Then you make the first move along this path.

Breadth-first search

The breadth-first search has an interesting property: It first finds all the vertices that are one edge away from the starting point, then all the vertices that are two edges away, and so on. This is useful if you’re trying to find the shortest path from the starting vertex to a given vertex. You start a BFS, and when you find the specified vertex, you know the path you’ve traced so far is the shortest path to the node. If there were a shorter path, the BFS would have found it already.

Breadth-first search can be used for finding the neighbour nodes in peer to peer networks like BitTorrent, GPS systems to find nearby locations, social networking sites to find people in the specified distance and things like that.

How to create a DataFrame of random integers with Pandas?

The recommended way to create random integers with NumPy these days is to use numpy.random.Generator.integers. (documentation)

import numpy as np
import pandas as pd

rng = np.random.default_rng()
df = pd.DataFrame(rng.integers(0, 100, size=(100, 4)), columns=list('ABCD'))
      A    B    C    D
 0   58   96   82   24
 1   21    3   35   36
 2   67   79   22   78
 3   81   65   77   94
 4   73    6   70   96
... ...  ...  ...  ...
95   76   32   28   51
96   33   68   54   77
97   76   43   57   43
98   34   64   12   57
99   81   77   32   50
100 rows × 4 columns

Horizontal Scroll Table in Bootstrap/CSS

You can also check for bootstrap datatable plugin as well for above issue.

It will have a large column table scrollable feature with lot of other options

$(document).ready(function() {
    $('#example').dataTable( {
        "scrollX": true
    } );
} );

for more info with example please check out this link

Convert True/False value read from file to boolean

If you need quick way to convert strings into bools (that functions with most strings) try.

def conv2bool(arg):
     res= (arg[0].upper()) == "T"
   except Exception,e:
     res= False
   return res # or do some more processing with arg if res is false

How can I open the interactive matplotlib window in IPython notebook?

You can use

%matplotlib qt

If you got the error ImportError: Failed to import any qt binding then install PyQt5 as: pip install PyQt5 and it works for me.

Adding to an ArrayList Java

thanks for the help, I've solved my problem :) Here is the code if anyone else needs it :D

import java.util.*;

public class HelloWorld {

public static void main(String[] Args) {

Map<Integer,List<Integer>> map = new HashMap<Integer,List<Integer>>();
List<Integer> list = new ArrayList<Integer>();

    int First = list.get(1);
    int Second = list.get(2);

    if (First < Second) {

        System.out.println("One or more of your items have been restocked. The current stock is: " + First);

        Random rn = new Random();
int answer = rn.nextInt(99) + 1;

System.out.println("You are buying " + answer + " New stock");

First = First + answer;
list.set(1, First);
System.out.println("There are now " + First + " in stock");

Add (insert) a column between two columns in a data.frame

Create an example data.frame and add a column to it.

df = data.frame(a = seq(1, 3), b = seq(4,6), c = seq(7,9))
df['d'] <- seq(10,12)

  a b c  d
1 1 4 7 10
2 2 5 8 11
3 3 6 9 12

Rearrange by column index

df[, colnames(df)[c(1:2,4,3)]]

or by column name

df[, c('a', 'b', 'd', 'c')]

The result is

  a b  d c
1 1 4 10 7
2 2 5 11 8
3 3 6 12 9

How can I get stock quotes using Google Finance API?

Building upon the shoulders of's a one-liner I wrote to zap all of Google's current stock data into local Bash shell variables:


# Fetch from Google Finance API, put into local variables
eval $(curl -s "$stock"|sed 's/</\n</g' |sed '/data=/!d; s/ data=/=/g; s/\/>/; /g; s/</GF_/g' |tee /tmp/stockprice.tmp.log)

echo "$stock,$(date +%Y-%m-%d),$GF_open,$GF_high,$GF_low,$GF_last,$GF_volume"

Then you will have variables like $GF_last $GF_open $GF_volume etc. readily available. Run env or see inside /tmp/stockprice.tmp.log by itself returns:

<?xml version="1.0"?>
<xml_api_reply version="1">
<finance module_id="0" tab_id="0" mobile_row="0" mobile_zipped="1" row="0" section="0" >
<symbol data="TVIX"/>
<pretty_symbol data="TVIX"/>
<symbol_lookup_url data="/finance?client=ig&amp;q=TVIX"/>
<company data="VelocityShares Daily 2x VIX Short Term ETN"/>
<exchange data="AMEX"/>
<exchange_timezone data="ET"/>
<exchange_utc_offset data="+05:00"/>
<exchange_closing data="960"/>
<divisor data="2"/>
<currency data="USD"/>
<last data="57.45"/>
<high data="59.70"/>
<low data="56.85"/>


So for stock="FBM" /tmp/stockprice.tmp.log (and your environment) will contain:

GF_company="Focus Morningstar Basic Materials Index ETF"; 
GF_trade_timestamp="8 hours ago"; 

"Line contains NULL byte" in CSV reader (Python)

If you want to replace the nulls with something you can do this:

def fix_nulls(s):
    for line in s:
        yield line.replace('\0', ' ')

r = csv.reader(fix_nulls(open(...)))

Convert String To date in PHP

If you're up for it, use the DateTime class

Adding a SVN repository in Eclipse

Necropost, but helpful: I came across this problem with an RA request failed since the files "already existed on the server" but wouldn't sync with my repository. I went to the source on my disk, deleted there, refreshed my Eclipse view, and updated the source. Error gone.

What is the recommended way to delete a large number of items from DynamoDB?

What I ideally want to do is call LogTable.DeleteItem(user_id) - Without supplying the range, and have it delete everything for me.

An understandable request indeed; I can imagine advanced operations like these might get added over time by the AWS team (they have a history of starting with a limited feature set first and evaluate extensions based on customer feedback), but here is what you should do to avoid the cost of a full scan at least:

  1. Use Query rather than Scan to retrieve all items for user_id - this works regardless of the combined hash/range primary key in use, because HashKeyValue and RangeKeyCondition are separate parameters in this API and the former only targets the Attribute value of the hash component of the composite primary key..

    • Please note that you''ll have to deal with the query API paging here as usual, see the ExclusiveStartKey parameter:

      Primary key of the item from which to continue an earlier query. An earlier query might provide this value as the LastEvaluatedKey if that query operation was interrupted before completing the query; either because of the result set size or the Limit parameter. The LastEvaluatedKey can be passed back in a new query request to continue the operation from that point.

  2. Loop over all returned items and either facilitate DeleteItem as usual

    • Update: Most likely BatchWriteItem is more appropriate for a use case like this (see below for details).


As highlighted by ivant, the BatchWriteItem operation enables you to put or delete several items across multiple tables in a single API call [emphasis mine]:

To upload one item, you can use the PutItem API and to delete one item, you can use the DeleteItem API. However, when you want to upload or delete large amounts of data, such as uploading large amounts of data from Amazon Elastic MapReduce (EMR) or migrate data from another database in to Amazon DynamoDB, this API offers an efficient alternative.

Please note that this still has some relevant limitations, most notably:

  • Maximum operations in a single request — You can specify a total of up to 25 put or delete operations; however, the total request size cannot exceed 1 MB (the HTTP payload).

  • Not an atomic operation — Individual operations specified in a BatchWriteItem are atomic; however BatchWriteItem as a whole is a "best-effort" operation and not an atomic operation. That is, in a BatchWriteItem request, some operations might succeed and others might fail. [...]

Nevertheless this obviously offers a potentially significant gain for use cases like the one at hand.

How to get base URL in Web API controller?

  1. Add a reference to System.Web using System.Web;

  2. Get the host or any other component of the url you want string host = HttpContext.Current.Request.Url.Host;

Sending and Parsing JSON Objects in Android

GSON is easiest to use and the way to go if the data have a definite structure.

Download gson.

Add it to the referenced libraries.

package com.tut.JSON;

import org.json.JSONException;
import org.json.JSONObject;

import android.os.Bundle;
import android.util.Log;


public class SimpleJson extends Activity {
    /** Called when the activity is first created. */
    public void onCreate(Bundle savedInstanceState) {

        String jString = "{\"username\": \"tom\", \"message\": \"roger that\"}  ";

        GsonBuilder gsonb = new GsonBuilder();
        Gson gson = gsonb.create();
        Post pst;

        try {
            pst = gson.fromJson(jString,  Post.class);

        } catch (JSONException e) {

Code for Post class

package com.tut.JSON;

public class Post {

    String message;
    String time;
    String username;
    Bitmap icon;

Why does range(start, end) not include end?

Consider the code

for i in range(10):
    print "You'll see this 10 times", i

The idea is that you get a list of length y-x, which you can (as you see above) iterate over.

Read up on the python docs for range - they consider for-loop iteration the primary usecase.

Java - Search for files in a directory

I tried many ways to find the file type I wanted, and here are my results when done.

public static void main( String args[]){
final String dir2 = System.getProperty(""); \\get user name 
String path = "C:\\Users\\" + dir2; 
digFile(new File(path)); \\ path is file start to dig
   for (int i = 0; i < StringFile.size(); i++) {

private void digFile(File dir) {

    FilenameFilter filter = new FilenameFilter() {
        public boolean accept(File dir, String name) {
            return name.endsWith(".mp4");
    String[] children = dir.list(filter);

    if (children == null) {
    } else {
        for (int i = 0; i < children.length; i++) {


    File[] directories;
    directories = dir.listFiles(new FileFilter() {
        public boolean accept(File file) {
            return file.isDirectory();
        public boolean accept(File dir, String name) {
            return !name.endsWith(".mp4");
       for (File directory : directories) {

How to delete a module in Android Studio

In Android Studio 1.0 - 1.1b4, I found this to be the easiest way to remove a module:

  1. Open settings.gradle found under Gradle Scripts

  2. Delete module's name from the include statement

  3. Sync Project with Gradle Files

  4. Optionally, delete it manually from the project folder



include ':app', ':greendao'


include ':app'

Get Base64 encode file-data from Input Form

After struggling with this myself, I've come to implement FileReader for browsers that support it (Chrome, Firefox and the as-yet unreleased Safari 6), and a PHP script that echos back POSTed file data as Base64-encoded data for the other browsers.

Reading in from - Java

You can call java myProg arg1 arg2 ... :

public static void main (String args[]) {
    BufferedReader in = new BufferedReader(new FileReader(args[0]));

Automatic confirmation of deletion in powershell

You just need to add a /A behind the line.


get-childitem C:\temp\ -exclude *.svn-base,".svn" -recurse | foreach ($_) {remove-item $_.fullname} /a

Create SQLite database in android

Why not refer to the documentation or the sample code shipping with the SDK? There's code in the samples on how to create/update/fill/read databases using the helper class described in the document I linked.

Convert UTF-8 to base64 string

It's a little difficult to tell what you're trying to achieve, but assuming you're trying to get a Base64 string that when decoded is abcdef==, the following should work:

byte[] bytes = Encoding.UTF8.GetBytes("abcdef==");
string base64 = Convert.ToBase64String(bytes);

This will output: YWJjZGVmPT0= which is abcdef== encoded in Base64.


To decode a Base64 string, simply use Convert.FromBase64String(). E.g.

string base64 = "YWJjZGVmPT0=";
byte[] bytes = Convert.FromBase64String(base64);

At this point, bytes will be a byte[] (not a string). If we know that the byte array represents a string in UTF8, then it can be converted back to the string form using:

string str = Encoding.UTF8.GetString(bytes);

This will output the original input string, abcdef== in this case.

Declare a dictionary inside a static class

The problem with your initial example was primarily due to the use of const rather than static; you can't create a non-null const reference in C#.

I believe this would also have worked:

public static class ErrorCode
    public static IDictionary<string, string> ErrorCodeDic
        = new Dictionary<string, string>()
            { {"1", "User name or password problem"} };

Also, as Y Low points out, adding readonly is a good idea as well, and none of the modifiers discussed here will prevent the dictionary itself from being modified.

What are Covering Indexes and Covered Queries in SQL Server?

A covering index is one which can satisfy all requested columns in a query without performing a further lookup into the clustered index.

There is no such thing as a covering query.

Have a look at this Simple-Talk article: Using Covering Indexes to Improve Query Performance.

How to declare a variable in a PostgreSQL query

You could also try this in PLPGSQL:

DO $$
DECLARE myvar integer;
    SELECT 5 INTO myvar;

    DROP TABLE IF EXISTS tmp_table;
    CREATE TABLE tmp_table AS
    SELECT * FROM yourtable WHERE   id = myvar;
END $$;

SELECT * FROM tmp_table;

The above requires Postgres 9.0 or later.

Python: Converting string into decimal number

use the built in float() function in a list comprehension.

A2 = [float(v.replace('"','').strip()) for v in A1]

Redirect within component Angular 2

@kit's answer is okay, but remember to add ROUTER_PROVIDERS to providers in the component. Then you can redirect to another page within ngOnInit method:

import {Component, OnInit} from 'angular2/core';
import {Router, ROUTER_PROVIDERS} from 'angular2/router'

    selector: 'loginForm',
    templateUrl: 'login.html',
    providers: [ROUTER_PROVIDERS]

export class LoginComponent implements OnInit {

    constructor(private router: Router) { }

    ngOnInit() {


Error while installing json gem 'mkmf.rb can't find header files for ruby'

For Ubuntu 18, after checking log file mentioned while install

Results logged to /var/canvas/vendor/bundle/ruby/2.5.0/extensions/x86_64-linux/2.5.0/nio4r-2.5.2/gem_make.out


less /var/canvas/vendor/bundle/ruby/2.5.0/extensions/x86_64-linux/2.5.0/nio4r-2.5.2/gem_make.out

I noticed that make is not found. So installed make by

sudo apt-get install make

everything worked.

Filter an array using a formula (without VBA)

Today, in Office 365, Excel has so called 'array functions'. The filter function does exactly what you want. No need to use CTRL+SHIFT+ENTER anymore, a simple enter will suffice.

In Office 365, your problem would be simply solved by using:

=VLOOKUP(A3, FILTER(A2:C6, B2:B6="B"), 3, FALSE)

How to convert PDF files to images

The NuGet package Pdf2Png is available for free and is only protected by the MIT License, which is very open.

I've tested around a bit and this is the code to get it to convert a PDF file to an image (tt does save the image in the debug folder).

using cs_pdf_to_image;
using PdfToImage;

private void BtnConvert_Click(object sender, EventArgs e)
    if(openFileDialog1.ShowDialog() == DialogResult.OK)
            string PdfFile = openFileDialog1.FileName;
            string PngFile = "Convert.png";
            List<string> Conversion = cs_pdf_to_image.Pdf2Image.Convert(PdfFile, PngFile);
            Bitmap Output = new Bitmap(PngFile);
            PbConversion.Image = Output;
        catch(Exception E)

Add image in pdf using jspdf

Though I'm not sure, the image might not be added because you create the output before you add it. Try:

function convert(){
    var doc = new jsPDF();
    var imgData = 'data:image/jpeg;base64,'+ Base64.encode('Koala.jpeg');
    doc.text(30, 20, 'Hello world!');
    doc.addImage(imgData, 'JPEG', 15, 40, 180, 160);

How to workaround 'FB is not defined'?

It's pretty strange for FB not to be loaded in your javascript if you have the script tag there correctly. Check that you don't have any javascript blockers, ad blockers, tracking blockers etc installed in your browser that are neutralizing your FB Connect code.

Add shadow to custom shape on Android

I would suggest a small improvement to Bruce's solution which is to prevent overdrawing the same shape on top of each other and to simply use stroke instead of solid. It would look like this:

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="">
    <!-- Drop Shadow Stack -->
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <stroke android:color="#02000000" android:width="1dp"  />
            <corners android:radius="8dp" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <stroke android:color="#05000000" android:width="1dp" />
            <corners android:radius="7dp" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <stroke android:color="#10000000" android:width="1dp" />
            <corners android:radius="6dp" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <stroke android:color="#15000000" android:width="1dp" />
            <corners android:radius="5dp" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <stroke android:color="#20000000" android:width="1dp" />
            <corners android:radius="4dp" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <stroke android:color="#25000000" android:width="1dp" />
            <corners android:radius="3dp" />
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <stroke android:color="#30000000" android:width="1dp" />
            <corners android:radius="3dp" />

    <!-- Background -->
            <solid android:color="#FFF" />
            <corners android:radius="3dp" />

screenshot of the rendering of the shadow Lastly I wanted to point out for people who would like a shadow in a specific direction that all you have to do is set the top, bottom, left or right to 0dp (for a solid line) or -1dp (for nothing)

SQL server query to get the list of columns in a table along with Data types, NOT NULL, and PRIMARY KEY constraints

Throwing another answer into the ring, this will give you those columns and more:

     , col.TABLE_SCHEMA AS Owner
     , col.TABLE_NAME AS TableName
     , col.COLUMN_NAME AS ColumnName
     , col.ORDINAL_POSITION AS OrdinalPosition
     , col.COLUMN_DEFAULT AS DefaultSetting
     , col.DATA_TYPE AS DataType
     , col.DATETIME_PRECISION AS DatePrecision
                WHEN 'NO' THEN 0
                ELSE 1
            END AS bit)AS IsNullable
     , COLUMNPROPERTY(OBJECT_ID('[' + col.TABLE_SCHEMA + '].[' + col.TABLE_NAME + ']'), col.COLUMN_NAME, 'IsIdentity')AS IsIdentity
     , COLUMNPROPERTY(OBJECT_ID('[' + col.TABLE_SCHEMA + '].[' + col.TABLE_NAME + ']'), col.COLUMN_NAME, 'IsComputed')AS IsComputed
     , CAST(ISNULL(pk.is_primary_key, 0)AS bit)AS IsPrimaryKey
                      , AS TABLE_NAME
                      , AS COLUMN_NAME
                      , i.is_primary_key
                   FROM sys.indexes AS i JOIN sys.index_columns AS ic ON i.object_id = ic.object_id
                                                                     AND i.index_id = ic.index_id
                                         JOIN sys.objects AS o ON i.object_id = o.object_id
                                         LEFT JOIN sys.columns AS c ON ic.object_id = c.object_id
                                                                   AND c.column_id = ic.column_id
                  WHERE i.is_primary_key = 1)AS pk ON col.TABLE_NAME = pk.TABLE_NAME
                                                  AND col.TABLE_SCHEMA = pk.TABLE_SCHEMA
                                                  AND col.COLUMN_NAME = pk.COLUMN_NAME
 WHERE col.TABLE_NAME = 'YourTableName'
   AND col.TABLE_SCHEMA = 'dbo'

Aligning textviews on the left and right edges in Android layout

    android:text="Hello world" />

    android:layout_weight="1" />

    android:text="Gud bye" />

What does "exec sp_reset_connection" mean in Sql Server Profiler?

Like the other answers said, sp_reset_connection indicates that connection pool is being reused. Be aware of one particular consequence!

Jimmy Mays' MSDN Blog said:

sp_reset_connection does NOT reset the transaction isolation level to the server default from the previous connection's setting.

UPDATE: Starting with SQL 2014, for client drivers with TDS version 7.3 or higher, the transaction isolation levels will be reset back to the default.

ref: SQL Server: Isolation level leaks across pooled connections

Here is some additional information:

What does sp_reset_connection do?

Data access API's layers like ODBC, OLE-DB and System.Data.SqlClient all call the (internal) stored procedure sp_reset_connection when re-using a connection from a connection pool. It does this to reset the state of the connection before it gets re-used, however nowhere is documented what things get reset. This article tries to document the parts of the connection that get reset.

sp_reset_connection resets the following aspects of a connection:

  • All error states and numbers (like @@error)

  • Stops all EC's (execution contexts) that are child threads of a parent EC executing a parallel query

  • Waits for any outstanding I/O operations that is outstanding

  • Frees any held buffers on the server by the connection

  • Unlocks any buffer resources that are used by the connection

  • Releases all allocated memory owned by the connection

  • Clears any work or temporary tables that are created by the connection

  • Kills all global cursors owned by the connection

  • Closes any open SQL-XML handles that are open

  • Deletes any open SQL-XML related work tables

  • Closes all system tables

  • Closes all user tables

  • Drops all temporary objects

  • Aborts open transactions

  • Defects from a distributed transaction when enlisted

  • Decrements the reference count for users in current database which releases shared database locks

  • Frees acquired locks

  • Releases any acquired handles

  • Resets all SET options to the default values

  • Resets the @@rowcount value

  • Resets the @@identity value

  • Resets any session level trace options using dbcc traceon()

  • Resets CONTEXT_INFO to NULL in SQL Server 2005 and newer [ not part of the original article ]

sp_reset_connection will NOT reset:

  • Security context, which is why connection pooling matches connections based on the exact connection string

  • Application roles entered using sp_setapprole, since application roles could not be reverted at all prior to SQL Server 2005. Starting in SQL Server 2005, app roles can be reverted, but only with additional information that is not part of the session. Before closing the connection, application roles need to be manually reverted via sp_unsetapprole using a "cookie" value that is captured when sp_setapprole is executed.

Note: I am including the list here as I do not want it to be lost in the ever transient web.

Running javascript in Selenium using Python

Use execute_script, here's a python example:

from selenium import webdriver
driver = webdriver.Firefox()

How to delete large data of table in SQL without log?

@Francisco Goldenstein, just a minor correction. The COMMIT must be used after you set the variable, otherwise the WHILE will be executed just once:

DECLARE @Deleted_Rows INT;
SET @Deleted_Rows = 1;

WHILE (@Deleted_Rows > 0)

    -- Delete some small number of rows at a time
    DELETE TOP (10000)  LargeTable 
    WHERE readTime < dateadd(MONTH,-7,GETDATE())

    SET @Deleted_Rows = @@ROWCOUNT;

    CHECKPOINT -- for simple recovery model


Java - How to access an ArrayList of another class?

import java.util.ArrayList;
public class numbers {
   private int number1 = 50;
   private int number2 = 100;
   private List<Integer> list;

   public numbers() {
       list = new ArrayList<Integer>();

   public List<Integer> getList() {
       return list;

And the test class:

import java.util.ArrayList;
public class test {
   private numbers number;

   public test() {
     number = new numbers();
     List<Integer> list = number.getList();
     //hurray !

Set encoding and fileencoding to utf-8 in Vim


In the first case with set encoding=utf-8, you'll change the output encoding that is shown in the terminal.

In the second case with set fileencoding=utf-8, you'll change the output encoding of the file that is written.

As stated by @Dennis, you can set them both in your ~/.vimrc if you always want to work in utf-8.

More details

From the wiki of VIM about working with unicode

"encoding sets how vim shall represent characters internally. Utf-8 is necessary for most flavors of Unicode."

"fileencoding sets the encoding for a particular file (local to buffer); :setglobal sets the default value. An empty value can also be used: it defaults to same as 'encoding'. Or you may want to set one of the ucs encodings, It might make the same disk file bigger or smaller depending on your particular mix of characters. Also, IIUC, utf-8 is always big-endian (high bit first) while ucs can be big-endian or little-endian, so if you use it, you will probably need to set 'bomb" (see below)."

How to set a CMake option() at command line

Delete the CMakeCache.txt file and try this:


You have to enter all your command-line definitions before including the path.

How to remove padding around buttons in Android?

It doesn't seem to be padding, margin, or minheight/width. Setting android:background="@null" the button loses its touch animation, but it turns out that setting the background to anything at all fixes that border.

I am currently working with:

minSdkVersion 19
targetSdkVersion 23

How to get terminal's Character Encoding

To my knowledge, no.

Circumstantial indications from $LC_CTYPE, locale and such might seem alluring, but these are completely separated from the encoding the terminal application (actually an emulator) happens to be using when displaying characters on the screen.

They only way to detect encoding for sure is to output something only present in the encoding, e.g. ä, take a screenshot, analyze that image and check if the output character is correct.

So no, it's not possible, sadly.

Create a OpenSSL certificate on Windows

To create a self signed certificate on Windows 7 with IIS 6...

  1. Open IIS

  2. Select your server (top level item or your computer's name)

  3. Under the IIS section, open "Server Certificates"

  4. Click "Create Self-Signed Certificate"

  5. Name it "localhost" (or something like that that is not specific)

  6. Click "OK"

You can then bind that certificate to your website...

  1. Right click on your website and choose "Edit bindings..."

  2. Click "Add"

    • Type: https
    • IP address: "All Unassigned"
    • Port: 443
    • SSL certificate: "localhost"
  3. Click "OK"

  4. Click "Close"

Html- how to disable <a href>?


This will prevent the default action.

H.264 file size for 1 hr of HD video

It is whatever size you want it to be, the only thing that changes is quality. If you intend it to be played back on a non-PC device (or a slow PC), you may need to respect a certain profile (standardized set of compression settings that ensure a fixed device can play back the content).

You can see the main H.264 profiles at Wikipedia

While it is highly subjective (and highly dependent on the content being compressed), it is claimed that H.264 can achieve the same quality as DVD MPEG2 using half the bitrate.

jQuery Validate Required Select

It's simple, you need to get the Select field value and it cannot be "default".

    alert('Please, choose an option');
    return false;

Selecting rows where remainder (modulo) is 1 after division by 2?

At least some versions of SQL (Oracle, Informix, DB2, ISO Standard) support:

WHERE MOD(value, 2) = 1

MySQL supports '%' as the modulus operator:

WHERE value % 2 = 1

How to format font style and color in echo

Are you trying to echo out a style or an inline style? An inline style would be like

echo "<p style=\"font-color: #ff0000;\">text here</p>";

What is difference between Axios and Fetch?

According to mzabriskie on GitHub:

Overall they are very similar. Some benefits of axios:

  • Transformers: allow performing transforms on data before a request is made or after a response is received

  • Interceptors: allow you to alter the request or response entirely (headers as well). also, perform async operations before a request is made or before Promise settles

  • Built-in XSRF protection

please check Browser Support Axios

enter image description here

I think you should use axios.

ImportError: No module named 'django.core.urlresolvers'

You need replace all occurrences of:

from django.core.urlresolvers import reverse


from django.urls import reverse

enter image description here

NOTE: The same apply to reverse_lazy

in Pycharm Cmd+Shift+R for starting replacment in Path.

For loop for HTMLCollection elements

As of March 2016, in Chrome 49.0, for...of works for HTMLCollection:

this.headers = this.getElementsByTagName("header");

for (var header of this.headers) {

See here the documentation.

But it only works if you apply the following workaround before using the for...of:

HTMLCollection.prototype[Symbol.iterator] = Array.prototype[Symbol.iterator];

The same is necessary for using for...of with NodeList:

NamedNodeMap.prototype[Symbol.iterator] = Array.prototype[Symbol.iterator];

I believe/hope for...of will soon work without the above workaround. The open issue is here:

Update: See Expenzor's comment below: This has been fixed as of April 2016. You don't need to add HTMLCollection.prototype[Symbol.iterator] = Array.prototype[Symbol.iterator]; to iterate over an HTMLCollection with for...of

Node.JS: Getting error : [nodemon] Internal watch failed: watch ENOSPC

in my case closing the visual studio code then starting the server did the trick

Operating system - ubuntu 16.4 lts

node.js version - 8.11.1

npm version - 6.0.0

How to retrieve the current version of a MySQL database management system (DBMS)?

For UBUNTU you can try the following command to check mysql version :

mysql --version

Why does my Spring Boot App always shutdown immediately after starting?

Resolution: the app is not a webapp because it doesn't have an embedded container (e.g. Tomcat) on the classpath. Adding one fixed it. If you are using Maven, then add this in pom.xml:


For Gradle (build.gradle) it looks like

dependencies {
    compile 'org.springframework.boot:spring-boot-starter-web'

Java ArrayList of Arrays?

ArrayList<String[]> action = new ArrayList<String[]>();

Don't need String[2];

Concatenate strings from several rows using Pandas groupby

For me the above solutions were close but added some unwanted /n's and dtype:object, so here's a modified version:

df.groupby(['name', 'month'])['text'].apply(lambda text: ''.join(text.to_string(index=False))).str.replace('(\\n)', '').reset_index()

Get protocol, domain, and port from URL

None of these answers seem to completely address the question, which calls for an arbitrary url, not specifically the url of the current page.

Method 1: Use the URL API (caveat: no IE11 support)

You can use the URL API (not supported by IE11, but available everywhere else).

This also makes it easy to access search params. Another bonus: it can be used in a Web Worker since it doesn't depend on the DOM.

const url = new URL('');

Method 2 (old way): Use the browser's built-in parser in the DOM

Use this if you need this to work on older browsers as well.

//  Create an anchor element (note: no need to append this element to the document)
const url = document.createElement('a');
//  Set href to any path
url.setAttribute('href', '');

That's it!

The browser's built-in parser has already done its job. Now you can just grab the parts you need (note that this works for both methods above):

//  Get any piece of the url you're interested in
url.hostname;  //  ''
url.port;      //  12345;    //  '?startIndex=1&pageSize=10'
url.pathname;  //  '/blog/foo/bar'
url.protocol;  //  'http:'

Bonus: Search params

Chances are you'll probably want to break apart the search url params as well, since '?startIndex=1&pageSize=10' isn't too useable on its own.

If you used Method 1 (URL API) above, you simply use the searchParams getters:

url.searchParams.get('startIndex');  // '1'

Or to get all parameters:

function searchParamsToObj(searchParams) {
  const paramsMap = Array
    .reduce((params, [key, val]) => params.set(key, val), new Map());
  return Object.fromEntries(paramsMap);
// -> { startIndex: '1', pageSize: '10' }

If you used Method 2 (the old way), you can use something like this:

// Simple object output (note: does NOT preserve duplicate keys).
var params =; // remove '?' prefix
    .reduce((accum, keyval) => {
        const [key, val] = keyval.split('=');
        accum[key] = val;
        return accum;
    }, {});
// -> { startIndex: '1', pageSize: '10' }

SQL SERVER: Get total days between two dates

PRINT DATEDIFF(DAY, '1/1/2011', '3/1/2011') will give you what you're after.

This gives the number of times the midnight boundary is crossed between the two dates. You may decide to need to add one to this if you're including both dates in the count - or subtract one if you don't want to include either date.

Edit and Continue: "Changes are not allowed when..."

what worked for me was unchecking "Use Managed Compatibility Mode" under

Tools -> Options -> Debugging

TBN: checking or unchecking "Require source file to exactly match the original version" seems not influences the E&C

Hope this can help.

Spring profiles and testing

Looking at Biju's answer I found a working solution.

I created an extra context-file test-context.xml:

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

Containing the profile:

And loading the test with:

@ActiveProfiles(profiles = "localtest")
@ContextConfiguration(locations = {
    "classpath:config/test-context.xml" })
public class TestContext {

  public void testContext(){


This saves some work when creating multiple test-cases.

How to put a symbol above another in LaTeX?

Use \overset{above}{main} in math mode. In your case, \overset{a}{\#}.

Check number of arguments passed to a Bash script

Check out this bash cheatsheet, it can help alot.

To check the length of arguments passed in, you use "$#"

To use the array of arguments passed in, you use "$@"

An example of checking the length, and iterating would be:

myFunc() {
  if [[ "$#" -gt 0 ]]; then
    for arg in "$@"; do
      echo $arg

myFunc "$@"

This articled helped me, but was missing a few things for me and my situation. Hopefully this helps someone.

Resize font-size according to div size

In regards to your code, see @Coulton. You'll need to use JavaScript.

Checkout either FitText (it does work in IE, they just ballsed their site somehow) or BigText.

FitText will allow you to scale some text in relation to the container it is in, while BigText is more about resizing different sections of text to be the same width within the container.

BigText will set your string to exactly the width of the container, whereas FitText is less pixel perfect. It starts by setting the font-size at 1/10th of the container element's width. It doesn't work very well with all fonts by default, but it has a setting which allows you to decrease or increase the 'power' of the re-size. It also allows you to set a min and max font-size. It will take a bit of fiddling to get working the first time, but does work great. <- playing with it currently here. As far as I understand, BigText wouldn't work in my context at all.

For those of you using Angularjs, here's an Angular version of FitText I've made.

Here's a LESS mixin you can use to make @humanityANDpeace's solution a little more pretty:

@mqIterations: 19;
.fontResize(@i) when (@i > 0) {
    @media all and (min-width: 100px * @i) { body { font-size:0.2em * @i; } }
    .fontResize((@i - 1));

And an SCSS version thanks to @NIXin!

$mqIterations: 19;
@mixin fontResize($iterations) { 
    $i: 1; 
    @while $i <= $iterations { 
        @media all and (min-width: 100px * $i) { body { font-size:0.2em * $i; } } 
        $i: $i + 1; 
@include fontResize($mqIterations);

What's the HTML to have a horizontal space between two objects?

You should put a padding in each object. For example, you want a space between images, you can use the following:

   padding: 5px;

That means 5px paddin for ALL sides. Read more at By the way, studying a lot before attempting to program will make things easier for you (and for us).

Allow click on twitter bootstrap dropdown toggle link?

Here's a little hack that switched from data-hover to data-toggle depending the screen width:

 * Bootstrap nav menu hack
$(window).on('load', function () {
    // On page load
    if ($(window).width() < 768) {
        $('.navbar-nav > li > .dropdown-toggle').removeAttr('data-hover').attr('data-toggle', 'dropdown');

    // On window resize
    $(window).resize(function () {
        if ($(window).width() < 768) {
            $('.navbar-nav > li > .dropdown-toggle').removeAttr('data-hover').attr('data-toggle', 'dropdown');
        } else {
            $('.navbar-nav > li > .dropdown-toggle').removeAttr('data-toggle').attr('data-hover', 'dropdown');

Angular ngClass and click event for toggling class

If you're looking for an HTML only way of doing this in angular...

<div #myDiv class="my_class" (click)="myDiv.classList.toggle('active')">
  Some content

The important bit is the #myDiv part.

It's a HTML Node reference, so you can use that variable as if it was assigned to document.querySelector('.my_class')

NOTE: this variable is scope specific, so you can use it in *ngFor statements

Does JavaScript guarantee object property order?

The iteration order for objects follows a certain set of rules since ES2015, but it does not (always) follow the insertion order. Simply put, the iteration order is a combination of the insertion order for strings keys, and ascending order for number-like keys:

// key order: 1, foo, bar
const obj = { "foo": "foo", "1": "1", "bar": "bar" }

Using an array or a Map object can be a better way to achieve this. Map shares some similarities with Object and guarantees the keys to be iterated in order of insertion, without exception:

The keys in Map are ordered while keys added to object are not. Thus, when iterating over it, a Map object returns keys in order of insertion. (Note that in the ECMAScript 2015 spec objects do preserve creation order for string and Symbol keys, so traversal of an object with ie only string keys would yield keys in order of insertion)

As a note, properties order in objects weren’t guaranteed at all before ES2015. Definition of an Object from ECMAScript Third Edition (pdf):

4.3.3 Object

An object is a member of the type Object. It is an unordered collection of properties each of which contains a primitive value, object, or function. A function stored in a property of an object is called a method.

How can I specify my .keystore file with Spring Boot and Tomcat?

If you don't want to implement your connector customizer, you can build and import the library ( which provides predefined connector customizer. According to the README, you only have to create your keystore, configure connector.https.*, import the library and add @ComponentScan("org.ycavatars.sboot.kit"). Then you'll have HTTPS connection.

The opposite of Intersect()


Nonintersect such operator is not present in Linq you should do

except -> union -> except


Removing padding gutter from grid columns in Bootstrap 4

Bootstrap4: Comes with .no-gutters out of the box. source:


Requires custom CSS.

Stylesheet: {
  margin-right: 0;
  margin-left: 0;

  & > [class^="col-"],
  & > [class*=" col-"] {
    padding-right: 0;
    padding-left: 0;

Then to use:

<div class="row no-gutters">
  <div class="col-xs-4">...</div>
  <div class="col-xs-4">...</div>
  <div class="col-xs-4">...</div>

It will:

  • Remove margin from the row
  • Remove padding from all columns directly beneath the row

Java String.split() Regex

You could also do something like:

String str = "a + b - c * d / e < f > g >= h <= i == j";
String[] arr = str.split("(?<=\\G(\\w+(?!\\w+)|==|<=|>=|\\+|/|\\*|-|(<|>)(?!=)))\\s*");

It handles white spaces and words of variable length and produces the array:

[a, +, b, -, c, *, d, /, e, <, f, >, g, >=, h, <=, i, ==, j]

How to Compare two strings using a if in a stored procedure in sql server 2008?

declare @temp as varchar
  set @temp='Measure'
  if(@temp = 'Measure')
Select Measure from Measuretable
Select OtherMeasure from Measuretable

How to Empty Caches and Clean All Targets Xcode 4 and later

Command-Option-Shift-K to clean out the build folder. Even better, quit Xcode and clean out ~/Library/Developer/Xcode/DerivedData manually. Remove all its contents because there's a bug where Xcode will run an old version of your project that's in there somewhere. (Xcode 4.2 will show you the Derived Data folder: choose Window > Organizer and switch to the Projects tab. Click the right-arrow to the right of the Derived Data folder name.)

In the simulator, choose iOS Simulator > Reset Content and Settings.

Finally, for completeness, you can delete the contents of /var/folders; some caching happens there too.

WARNING: Deleting /var/folders can cause issues, and you may need to repair or reinstall your operating system after doing so.

EDIT: I have just learned that if you are afraid to grapple with /var/folders/ you can use the following command in the Terminal to delete in a more targeted way:

rm -rf "$(getconf DARWIN_USER_CACHE_DIR)/org.llvm.clang/ModuleCache"

EDIT: For certain Swift-related problems I have found it useful to delete ~/Library/Caches/ You lose a lot when you do this, like your spare copies of the downloaded documentation doc sets, but it can be worth it.

How to write data to a JSON file using Javascript

You have to be clear on what you mean by "JSON".

Some people use the term JSON incorrectly to refer to a plain old JavaScript object, such as [{a: 1}]. This one happens to be an array. If you want to add a new element to the array, just push it, as in

var arr = [{a: 1}];
arr.push({b: 2});

< [{a: 1}, {b: 2}]

The word JSON may also be used to refer to a string which is encoded in JSON format:

var json = '[{"a": 1}]';

Note the (single) quotation marks indicating that this is a string. If you have such a string that you obtained from somewhere, you need to first parse it into a JavaScript object, using JSON.parse:

var obj = JSON.parse(json);

Now you can manipulate the object any way you want, including push as shown above. If you then want to put it back into a JSON string, then you use JSON.stringify:

var new_json = JSON.stringify(obj.push({b: 2}));
'[{"a": 1}, {"b": 1}]'

JSON is also used as a common way to format data for transmission of data to and from a server, where it can be saved (persisted). This is where ajax comes in. Ajax is used both to obtain data, often in JSON format, from a server, and/or to send data in JSON format up to to the server. If you received a response from an ajax request which is JSON format, you may need to JSON.parse it as described above. Then you can manipulate the object, put it back into JSON format with JSON.stringify, and use another ajax call to send the data to the server for storage or other manipulation.

You use the term "JSON file". Normally, the word "file" is used to refer to a physical file on some device (not a string you are dealing with in your code, or a JavaScript object). The browser has no access to physical files on your machine. It cannot read or write them. Actually, the browser does not even really have the notion of a "file". Thus, you cannot just read or write some JSON file on your local machine. If you are sending JSON to and from a server, then of course, the server might be storing the JSON as a file, but more likely the server would be constructing the JSON based on some ajax request, based on data it retrieves from a database, or decoding the JSON in some ajax request, and then storing the relevant data back into its database.

Do you really have a "JSON file", and if so, where does it exist and where did you get it from? Do you have a JSON-format string, that you need to parse, mainpulate, and turn back into a new JSON-format string? Do you need to get JSON from the server, and modify it and then send it back to the server? Or is your "JSON file" actually just a JavaScript object, that you simply need to manipulate with normal JavaScript logic?

How do I stop/start a scheduled task on a remote computer programmatically?

Note: "schtasks" (see the other, accepted response) has replaced "at". However, "at" may be of use if the situation calls for compatibility with older versions of Windows that don't have schtasks.

Command-line help for "at":

C:\>at /?
The AT command schedules commands and programs to run on a computer at
a specified time and date. The Schedule service must be running to use
the AT command.

AT [\\computername] [ [id] [/DELETE] | /DELETE [/YES]]
AT [\\computername] time [/INTERACTIVE]
    [ /EVERY:date[,...] | /NEXT:date[,...]] "command"

\\computername     Specifies a remote computer. Commands are scheduled on the
                   local computer if this parameter is omitted.
id                 Is an identification number assigned to a scheduled
/delete            Cancels a scheduled command. If id is omitted, all the
                   scheduled commands on the computer are canceled.
/yes               Used with cancel all jobs command when no further
                   confirmation is desired.
time               Specifies the time when command is to run.
/interactive       Allows the job to interact with the desktop of the user
                   who is logged on at the time the job runs.
/every:date[,...]  Runs the command on each specified day(s) of the week or
                   month. If date is omitted, the current day of the month
                   is assumed.
/next:date[,...]   Runs the specified command on the next occurrence of the
                   day (for example, next Thursday).  If date is omitted, the
                   current day of the month is assumed.
"command"          Is the Windows NT command, or batch program to be run.

PHP new line break in emails

If you output to html or an html e-mail you will need to use <br> or <br /> instead of \n.

If it's just a text e-mail: Are you perhaps using ' instead of "? Although then your values would not be inserted either...

What is the difference between printf() and puts() in C?

In simple cases, the compiler converts calls to printf() to calls to puts().

For example, the following code will be compiled to the assembly code I show next.

#include <stdio.h>
main() {
    printf("Hello world!");
    return 0;
push rbp
mov rbp,rsp
mov edi,str.Helloworld!
call dword imp.puts
mov eax,0x0
pop rbp

In this example, I used GCC version 4.7.2 and compiled the source with gcc -o hello hello.c.

Error:Cannot fit requested classes in a single dex file.Try supplying a main-dex list. # methods: 72477 > 65536

modify your app's or module's build.gradle

android {
    defaultConfig {
        minSdkVersion 21 <----- *here
        targetSdkVersion 26
        multiDexEnabled true <------ *here

According to official documentation

Multidex support for Android 5.0 and higher

Android 5.0 (API level 21) and higher uses a runtime called ART which natively supports loading multiple DEX files from APK files. ART performs pre-compilation at app install time which scans for classesN.dex files and compiles them into a single .oat file for execution by the Android device. Therefore, if your minSdkVersion is 21 or higher, you do not need the multidex support library.

For more information on the Android 5.0 runtime, read ART and Dalvik.

using if else with eval in aspx page

You can try c#

public string ProcessMyDataItem(object myValue)
  if (myValue == null)
   return "0 %"";
     if(Convert.ToInt32(myValue) < 50)
       return "0";
      return myValue.ToString() + "%";



 <div class="tooltip" style="display: none">                                                                  
      <div style="text-align: center; font-weight: normal">
   Value =<%# ProcessMyDataItem(Eval("Percentage")) %> </div>

How to use conditional breakpoint in Eclipse?

Put your breakpoint. Right-click the breakpoint image on the margin and choose Breakpoint Properties:

enter image description here

Configure condition as you see fit:

enter image description here

CSS3 transform: rotate; in IE9

Standard CSS3 rotate should work in IE9, but I believe you need to give it a vendor prefix, like so:

  -ms-transform: rotate(10deg);

It is possible that it may not work in the beta version; if not, try downloading the current preview version (preview 7), which is a later revision that the beta. I don't have the beta version to test against, so I can't confirm whether it was in that version or not. The final release version is definitely slated to support it.

I can also confirm that the IE-specific filter property has been dropped in IE9.

People have asked for some further documentation. As they say, this is quite limited, but I did find this page: which is useful for testing various CSS3 features in all browsers.

But testing the rotate feature on this page in IE9 preview caused it to crash fairly spectacularly.

However I have done some independant tests using -ms-transform:rotate() in IE9 in my own test pages, and it is working fine. So my conclusion is that the feature is implemented, but has got some bugs, possibly related to setting it dynamically.

Another useful reference point for which features are implemented in which browsers is -- see

Reviving this old answer because I recently found out about a hack called CSS Sandpaper which is relevant to the question and may make things easier.

The hack implements support for the standard CSS transform for for old versions of IE. So now you can add the following to your CSS:

-sand-transform: rotate(10deg);

...and have it work in IE 6/7/8, without having to use the filter syntax. (of course it still uses the filter syntax behind the scenes, but this makes it a lot easier to manage because it's using similar syntax to other browsers)

How to check if running as root in a bash script

As @wrikken mentioned in his comments, id -u is a much better check for root.

In addition, with proper use of sudo, you could have the script check and see if it is running as root. If not, have it recall itself via sudo and then run with root permissions.

Depending on what the script does, another option may be to set up a sudo entry for whatever specialized commands the script may need.

Add border-bottom to table row <tr>


border-collapse:collapse as Nathan wrote and you need to set

td { border-bottom: 1px solid #000; }

MVC4 HTTP Error 403.14 - Forbidden

Perhaps... If you happen to use the Publish Wizard (like I did) and select the "Precompile during publishing" checkbox (like I did) and see the same symptoms...

Yeah, I beat myself over the head, but after unchecking this box, a seemingly unrelated setting, all the symptoms described go away after redeploying.

Hopefully this fixes some folks.

iPhone 6 Plus resolution confusion: Xcode or Apple's website? for development

The answer is that older apps run in 2208 x 1242 Zoomed Mode. But when an app is built for the new phones the resolutions available are: Super Retina HD 5.8 (iPhone X) 1125 x 2436 (458ppi), Retina HD 5.5 (iPhone 6, 7, 8 Plus) 1242 x 2208 and Retina HD 4.7 (iPhone 6) 750 x 1334. This is causing the confusion mentioned in the question. To build apps that use the full screen size of the new phones add LaunchImages in the sizes: 1125 x 2436, 1242 x 2208, 2208 x 1242 and 750 x 1334.

Updated for the new iPhones 12, 12 mini, 12 Pro, 12 Pro Max

Size for iPhone 12 Pro Max with @3x scaling, coordinate space: 428 x 926 points and 1284 x 2778 pixels, 458 ppi, device physical size is 3.07 x 6.33 in or 78.1 x 160.8 mm. 6.7" Super Retina XDR display.

Size for iPhone 12 Pro with @3x scaling, coordinate space: 390 x 844 points and 1170 x 2532 pixels, 460 ppi, device physical size is 2.82 x 5.78 in or 71.5 x 146.7 mm. 6.1" Super Retina XDR display.

Size for iPhone 12 with @2x scaling, coordinate space: 585 x 1266 points and 1170 x 2532 pixels, 460 ppi, device physical size is 2.82 x 5.78 in or 71.5 x 146.7 mm. 6.1" Super Retina XDR display.

Size for iPhone 12 mini with @2x scaling, coordinate space: 540 x 1170 points and 1080 x 2340 pixels, 476 ppi, device physical size is 2.53 x 5.18 in or 64.2 x 131.5 mm. 5.4" Super Retina XDR display.

Size for iPhone 11 Pro Max with @3x scaling, coordinate space: 414 x 896 points and 1242 x 2688 pixels, 458 ppi, device physical size is 3.06 x 6.22 in or 77.8 x 158.0 mm. 6.5" Super Retina XDR display.

Size for iPhone 11 Pro with @3x scaling, coordinate space: 375 x 812 points and 1125 x 2436 pixels, 458 ppi, device physical size is 2.81 x 5.67 in or 71.4 x 144.0 mm. 5.8" Super Retina XDR display.

Size for iPhone 11 with @2x scaling, coordinate space: 414 x 896 points and 828 x 1792 pixels, 326 ppi, device physical size is 2.98 x 5.94 in or 75.7 x 150.9 mm. 6.1" Liquid Retina HD display.

Size for iPhone X Max with @3x scaling (Apple name: Super Retina HD 6.5 display"), coordinate space: 414 x 896 points and 1242 x 2688 pixels, 458 ppi, device physical size is 3.05 x 6.20 in or 77.4 x 157.5 mm.

let screen = UIScreen.main
print("Screen bounds: \(screen.bounds), Screen resolution: \(screen.nativeBounds), scale: \(screen.scale)")
//iPhone X Max Screen bounds: (0.0, 0.0, 414.0, 896.0), Screen resolution: (0.0, 0.0, 1242.0, 2688.0), scale: 3.0

Size for iPhone X with @2x scaling (Apple name: Super Retina HD 6.1" display), coordinate space: 414 x 896 points and 828 x 1792 pixels, 326 ppi, device physical size is 2.98 x 5.94 in or 75.7 x 150.9 mm.

let screen = UIScreen.main
print("Screen bounds: \(screen.bounds), Screen resolution: \(screen.nativeBounds), scale: \(screen.scale)")
//iPhone X Screen bounds: (0.0, 0.0, 414.0, 896.0), Screen resolution: (0.0, 0.0, 828.0, 1792.0), scale: 2.0

Size for iPhone X and iPhone X with @3x scaling (Apple name: Super Retina HD 5.8" display), coordinate space: 375 x 812 points and 1125 x 2436 pixels, 458 ppi, device physical size is 2.79 x 5.65 in or 70.9 x 143.6 mm.

let screen = UIScreen.main
print("Screen bounds: \(screen.bounds), Screen resolution: \(screen.nativeBounds), scale: \(screen.scale)")
//iPhone X and X Screen bounds: (0.0, 0.0, 375.0, 812.0), Screen resolution: (0.0, 0.0, 1125.0, 2436.0), scale: 3.0

enter image description here

Size for iPhone 6, 6S, 7 and 8 with @3x scaling (Apple name: Retina HD 5.5), coordinate space: 414 x 736 points and 1242 x 2208 pixels, 401 ppi, screen physical size is 2.7 x 4.8 in or 68 x 122 mm. When running in Zoomed Mode, i.e. without the new LaunchImages or choosen in Setup on iPhone 6 Plus, the native scale is 2.88 and the screen is 320 x 568 points, which is the iPhone 5 native size:

Screen bounds: {{0, 0}, {414, 736}}, Screen resolution: <UIScreen: 0x7f97fad330b0; bounds = {{0, 0}, {414, 736}};
mode = <UIScreenMode: 0x7f97fae1ce00; size = 1242.000000 x 2208.000000>>, scale: 3.000000, nativeScale: 3.000000

Size for iPhone 6 and iPhone 6S with @2x scaling (Apple name: Retina HD 4.7), coordinate space: 375 x 667 points and 750 x 1334 pixels, 326 ppi, screen physical size is 2.3 x 4.1 in or 58 x 104 mm. When running in Zoomed Mode, i.e. without the new LaunchImages, the screen is 320 x 568 points, which is the iPhone 5 native size:

Screen bounds: {{0, 0}, {375, 667}}, Screen resolution: <UIScreen: 0x7fa01b5182d0; bounds = {{0, 0}, {375, 667}};
mode = <UIScreenMode: 0x7fa01b711760; size = 750.000000 x 1334.000000>>, scale: 2.000000, nativeScale: 2.000000

And iPhone 5 for comparison is 640 x 1136, iPhone 4 640 x 960.

Here is the code I used to check this out (note that nativeScale only runs on iOS 8):

UIScreen *mainScreen = [UIScreen mainScreen];
NSLog(@"Screen bounds: %@, Screen resolution: %@, scale: %f, nativeScale: %f",
          NSStringFromCGRect(mainScreen.bounds), mainScreen.coordinateSpace, mainScreen.scale, mainScreen.nativeScale);

Note: Upload LaunchImages otherwise the app will run in Zoomed Mode and not show the correct scaling, or screen sizes. In Zoomed Mode the nativeScale and scale will not be the same. On an actual device the scale can be 2.608 on the iPhone 6 Plus, even when it is not running in Zoomed Mode, but it will show scale of 3.0 when running on the simulator.

Comparing iPhone 6 and 6 Plus

What is WebKit and how is it related to CSS?

Addition to what @KennyTM said:

  • IE
  • Edge
  • Firefox
    • Engine: Gecko
    • CSS-prefix: -moz
  • Opera
    • Engine: Presto ? Blink1
    • CSS-prefix: -o (Presto) and -webkit (Blink)
  • Safari
    • Engine: WebKit
    • CSS-prefix: -webkit
  • Chrome

1) On February 12 2013 Opera (version 15+) announces they moving away from their own engine Presto to WebKit named Blink.

2) On April 3 2013 Google (Chrome version 28+) announces they are going to use the WebKit-based Blink engine.

3) On December 6 2018 Microsoft (Microsoft Edge 79+ stable) announces they are going to use the WebKit-based Blink engine.

Boolean operators && and ||

&& and || are what is called "short circuiting". That means that they will not evaluate the second operand if the first operand is enough to determine the value of the expression.

For example if the first operand to && is false then there is no point in evaluating the second operand, since it can't change the value of the expression (false && true and false && false are both false). The same goes for || when the first operand is true.

You can read more about this here: From the table on that page you can see that && is equivalent to AndAlso in VB.NET, which I assume you are referring to.

Embed youtube videos that play in fullscreen automatically

This was pretty well answered over here: How to make a YouTube embedded video a full page width one?

If you add '?rel=0&autoplay=1' to the end of the url in the embed code (like this)

<iframe id="video" src="//" frameborder="0" allowfullscreen></iframe>

of the video it should play on load. Here's a demo over at jsfiddle.

SQL Server: Invalid Column Name

I just tried. If you execute the statement to generate your local table, the tool will accept that this column name exists. Just mark the table generation statement in your editor window and click execute.

How do you use script variables in psql?

Another approach is to (ab)use the PostgreSQL GUC mechanism to create variables. See this prior answer for details and examples.

You declare the GUC in postgresql.conf, then change its value at runtime with SET commands and get its value with current_setting(...).

I don't recommend this for general use, but it could be useful in narrow cases like the one mentioned in the linked question, where the poster wanted a way to provide the application-level username to triggers and functions.

What is the single most influential book every programmer should read?

alt text

This last year I took a number of classes. I read

The Innovator's Dilemma (disruptive tech)
The Mythical Man Month (managing software)
Crossing the Chasm (startup)
Database Management Systems, The COW Book
Programming C#, The OSTRICH Book
Beginning iPhone Developmen, The GRAPEFRUIT Book

Each book was amazing but the Innovator's Dilemma by Clayton Christensen (1997!!!) is really a fantastic book, and it got me really thinking about the modern software world. The challenge addressed is disruptive technology, and how disk drive companies and non-technical companies are always disrupted by new, game changing technology. It gives one a new perspective when thinking about Google, probably the biggest 'web' company. Why do they have their hands in EVERYTHING? It's because they don't want to have their position disrupted by something new. The preview on google is plenty to get the idea. Read it!

How do I specify the columns and rows of a multiline Editor-For in ASP.MVC?

in mvc 5

              @Html.EditorFor(x => x.Address, 
              new {htmlAttributes = new {@class = "form-control", 
                   @placeholder = "Complete Address", @cols = 10, @rows = 10 } })

How to set default text for a Tkinter Entry widget

Use Entry.insert. For example:

    from tkinter import *  # Python 3.x
except Import Error:
    from Tkinter import *  # Python 2.x

root = Tk()
e = Entry(root)
e.insert(END, 'default text')

Or use textvariable option:

    from tkinter import *  # Python 3.x
except Import Error:
    from Tkinter import *  # Python 2.x

root = Tk()
v = StringVar(root, value='default text')
e = Entry(root, textvariable=v)

accessing a file using [NSBundle mainBundle] pathForResource: ofType:inDirectory:

Are you attempting to do this inside of an XCTest and on the verge of smashing your laptop? This is the thread for you: Why can't code inside unit tests find bundle resources?

socket.emit() vs. socket.send()

socket.send // Sends a message event

socket.emit(eventName[, ...args][, ack]) // you can custom eventName

What is EOF in the C programming language?

int c;

while((c = getchar())!= 10)
    if( getchar() == EOF )

     printf(" %d\n", c);

Maven Installation OSX Error Unsupported major.minor version 51.0

The problem is because you haven't set JAVA_HOME in Mac properly. In order to do that, you should do set it like this:

export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_40.jdk/Contents/Home

In my case my JDK installation is jdk1.8.0_40, make sure you type yours.

Then you can use maven commands.


How to declare a structure in a header that is to be used by multiple files in c?

if this structure is to be used by some other file func.c how to do it?

When a type is used in a file (i.e. func.c file), it must be visible. The very worst way to do it is copy paste it in each source file needed it.

The right way is putting it in an header file, and include this header file whenever needed.

shall we open a new header file and declare the structure there and include that header in the func.c?

This is the solution I like more, because it makes the code highly modular. I would code your struct as:


struct a
    int i;
    struct b
        int j;


I would put functions using this structure in the same header (the function that are "semantically" part of its "interface").

And usually, I could name the file after the structure name, and use that name again to choose the header guards defines.

If you need to declare a function using a pointer to the struct, you won't need the full struct definition. A simple forward declaration like:

struct a ;

Will be enough, and it decreases coupling.

or can we define the total structure in header file and include that in both source.c and func.c?

This is another way, easier somewhat, but less modular: Some code needing only your structure to work would still have to include all types.

In C++, this could lead to interesting complication, but this is out of topic (no C++ tag), so I won't elaborate.

then how to declare that structure as extern in both the files. ?

I fail to see the point, perhaps, but Greg Hewgill has a very good answer in his post How to declare a structure in a header that is to be used by multiple files in c?.

shall we typedef it then how?

  • If you are using C++, don't.
  • If you are using C, you should.

The reason being that C struct managing can be a pain: You have to declare the struct keyword everywhere it is used:

struct MyStruct ; /* Forward declaration */

struct MyStruct
   /* etc. */
} ;

void doSomething(struct MyStruct * p) /* parameter */
   struct MyStruct a ; /* variable */
   /* etc */

While a typedef will enable you to write it without the struct keyword.

struct MyStructTag ; /* Forward declaration */

typedef struct MyStructTag
   /* etc. */
} MyStruct ;

void doSomething(MyStruct * p) /* parameter */
   MyStruct a ; /* variable */
   /* etc */

It is important you still keep a name for the struct. Writing:

typedef struct
   /* etc. */
} MyStruct ;

will just create an anonymous struct with a typedef-ed name, and you won't be able to forward-declare it. So keep to the following format:

typedef struct MyStructTag
   /* etc. */
} MyStruct ;

Thus, you'll be able to use MyStruct everywhere you want to avoid adding the struct keyword, and still use MyStructTag when a typedef won't work (i.e. forward declaration)


Corrected wrong assumption about C99 struct declaration, as rightfully remarked by Jonathan Leffler.

Edit 2018-06-01:

Craig Barnes reminds us in his comment that you don't need to keep separate names for the struct "tag" name and its "typedef" name, like I did above for the sake of clarity.

Indeed, the code above could well be written as:

typedef struct MyStruct
   /* etc. */
} MyStruct ;

IIRC, this is actually what C++ does with its simpler struct declaration, behind the scenes, to keep it compatible with C:

// C++ explicit declaration by the user
struct MyStruct
   /* etc. */
} ;
// C++ standard then implicitly adds the following line
typedef MyStruct MyStruct;

Back to C, I've seen both usages (separate names and same names), and none has drawbacks I know of, so using the same name makes reading simpler if you don't use C separate "namespaces" for structs and other symbols.

Recommended way of making React component/div draggable

I've updated the class using refs as all the solutions I see on here have things that are no longer supported or will soon be depreciated like ReactDOM.findDOMNode. Can be parent to a child component or a group of children :)

import React, { Component } from 'react';

class Draggable extends Component {

    constructor(props) {
        this.myRef = React.createRef();
        this.state = {
            counter: this.props.counter,
            pos: this.props.initialPos,
            dragging: false,
            rel: null // position relative to the cursor

    /*  we could get away with not having this (and just having the listeners on
     our div), but then the experience would be possibly be janky. If there's
     anything w/ a higher z-index that gets in the way, then you're toast,
    componentDidUpdate(props, state) {
        if (this.state.dragging && !state.dragging) {
            document.addEventListener('mousemove', this.onMouseMove);
            document.addEventListener('mouseup', this.onMouseUp);
        } else if (!this.state.dragging && state.dragging) {
            document.removeEventListener('mousemove', this.onMouseMove);
            document.removeEventListener('mouseup', this.onMouseUp);

    // calculate relative position to the mouse and set dragging=true
    onMouseDown = (e) => {
        if (e.button !== 0) return;
        let pos = { left: this.myRef.current.offsetLeft, top: this.myRef.current.offsetTop }
            dragging: true,
            rel: {
                x: e.pageX - pos.left,
                y: e.pageY -

    onMouseUp = (e) => {
        this.setState({ dragging: false });

    onMouseMove = (e) => {
        if (!this.state.dragging) return;

            pos: {
                x: e.pageX - this.state.rel.x,
                y: e.pageY - this.state.rel.y

    render() {
        return (
            <span ref={this.myRef} onMouseDown={this.onMouseDown} style={{ position: 'absolute', left: this.state.pos.x + 'px', top: this.state.pos.y + 'px' }}>

export default Draggable;

How to use sha256 in php5.3.0

First of all, sha256 is a hashing algorithm, not a type of encryption. An encryption would require having a way to decrypt the information back to its original value (collisions aside).

Looking at your code, it seems it should work if you are providing the correct parameter.

  • Try using a literal string in your code first, and verify its validity instead of using the $_POST[] variable

  • Try moving the comparison from the database query to the code (get the hash for the given user and compare to the hash you have just calculated)

But most importantly before deploying this in any kind of public fashion, please remember to sanitize your inputs. Don't allow arbitrary SQL to be insert into the queries. The best idea here would be to use parameterized queries.

Installing OpenCV for Python on Ubuntu, getting ImportError: No module named

Its complete installation nightmare, but I'll give one more hope you can avoid building opencv from source:

pip install opencv-contrib-python

ng-mouseover and leave to toggle item using mouse in angularjs

I'd probably change your example to look like this:

<ul ng-repeat="task in tasks">
  <li ng-mouseover="enableEdit(task)" ng-mouseleave="disableEdit(task)">{{}}</li>
  <span ng-show="task.editable"><a>Edit</a></span>

$scope.enableEdit = function(item){
  item.editable = true;

$scope.disableEdit = function(item){
  item.editable = false;

I know it's a subtle difference, but makes the domain a little less bound to UI actions. Mentally it makes it easier to think about an item being editable rather than having been moused over.

Example jsFiddle.

How to set the color of an icon in Angular Material?

Or simply

add to your element

[ngStyle]="{'color': myVariableColor}"


<mat-icon [ngStyle]="{'color': myVariableColor}">{{ getActivityIcon() }}</mat-icon>

Where color can be defined at another component etc

Find element's index in pandas Series

>>> myseries[myseries == 7]
3    7
dtype: int64
>>> myseries[myseries == 7].index[0]

Though I admit that there should be a better way to do that, but this at least avoids iterating and looping through the object and moves it to the C level.

How do I call a function inside of another function?

function function_one() {_x000D_
    function_two(); // considering the next alert, I figured you wanted to call function_two first_x000D_
    alert("The function called 'function_one' has been called.");_x000D_
function function_two() {_x000D_
    alert("The function called 'function_two' has been called.");_x000D_

A little bit more context: this works in JavaScript because of a language feature called "variable hoisting" - basically, think of it like variable/function declarations are put at the top of the scope (more info).

Why doesn't catching Exception catch RuntimeException?

I faced similar scenario. It was happening because classA's initilization was dependent on classB's initialization. When classB's static block faced runtime exception, classB was not initialized. Because of this, classB did not throw any exception and classA's initialization failed too.

class A{//this class will never be initialized because class B won't intialize
    }catch(Exception e){
      sysout("This comment will never be printed");

class B{//this class will never be initialized
    int i = 1/0;//throw run time exception 

 public static void someStaticMethod(){}

And yes...catching Exception will catch run time exceptions as well.

How to start http-server locally

When you're running npm install in the project's root, it installs all of the npm dependencies into the project's node_modules directory.

If you take a look at the project's node_modules directory, you should see a directory called http-server, which holds the http-server package, and a .bin folder, which holds the executable binaries from the installed dependencies. The .bin directory should have the http-server binary (or a link to it).

So in your case, you should be able to start the http-server by running the following from your project's root directory (instead of npm start):

./node_modules/.bin/http-server -a localhost -p 8000 -c-1

This should have the same effect as running npm start.

If you're running a Bash shell, you can simplify this by adding the ./node_modules/.bin folder to your $PATH environment variable:

export PATH=./node_modules/.bin:$PATH

This will put this folder on your path, and you should be able to simply run

http-server -a localhost -p 8000 -c-1

mysqli::mysqli(): (HY000/2002): Can't connect to local MySQL server through socket 'MySQL' (2)

If 'localhost' doesn't work but does. Make sure your local hosts file points to the correct location. (/etc/hosts for linux/mac, C:\Windows\System32\drivers\etc\hosts for windows).

Also, make sure your user is allowed to connect to whatever database you're trying to select.

How to add Options Menu to Fragment in Android

I had the same problem, but I think it's better to summarize and introduce the last step to get it working:

  1. Add setHasOptionsMenu(true) method in your Fragment's onCreate(Bundle savedInstanceState) method.

  2. Override onCreateOptionsMenu(Menu menu, MenuInflater inflater) (if you want to do something different in your Fragment's menu) and onOptionsItemSelected(MenuItem item) methods in your Fragment.

  3. Inside your onOptionsItemSelected(MenuItem item) Activity's method, make sure you return false when the menu item action would be implemented in onOptionsItemSelected(MenuItem item) Fragment's method.

An example:


public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getSupportMenuInflater();
    inflater.inflate(, menu);
    return true;

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {


            // Do Activity menu item stuff here
            return true;


            // Not implemented here
            return false;

    return false;


public void onCreate(Bundle savedInstanceState) {

public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    // Do something that differs the Activity's menu here
    super.onCreateOptionsMenu(menu, inflater);

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {


            // Not implemented here
            return false;

            // Do Fragment menu item stuff here
            return true;


    return false;

Multiple linear regression in Python

sklearn.linear_model.LinearRegression will do it:

from sklearn import linear_model
clf = linear_model.LinearRegression()[[getattr(t, 'x%d' % i) for i in range(1, 8)] for t in texts],
        [t.y for t in texts])

Then clf.coef_ will have the regression coefficients.

sklearn.linear_model also has similar interfaces to do various kinds of regularizations on the regression.

How to declare strings in C

Strings in C are represented as arrays of characters.

char *p = "String";

You are declaring a pointer that points to a string stored some where in your program (modifying this string is undefined behavior) according to the C programming language 2 ed.

char p2[] = "String";

You are declaring an array of char initialized with the string "String" leaving to the compiler the job to count the size of the array.

char p3[5] = "String";

You are declaring an array of size 5 and initializing it with "String". This is an error be cause "String" don't fit in 5 elements.

char p3[7] = "String"; is the correct declaration ('\0' is the terminating character in c strings).

Efficient method to generate UUID String in JAVA (UUID.randomUUID().toString() without the dashes)

Ended up writing something of my own based on implementation. Note that I'm not generating a UUID, instead just a random 32 bytes hex string in the most efficient way I could think of.


import java.util.UUID;

public class RandomUtil {
    // Maxim: Copied from UUID implementation :)
    private static volatile SecureRandom numberGenerator = null;
    private static final long MSB = 0x8000000000000000L;

    public static String unique() {
        SecureRandom ng = numberGenerator;
        if (ng == null) {
            numberGenerator = ng = new SecureRandom();

        return Long.toHexString(MSB | ng.nextLong()) + Long.toHexString(MSB | ng.nextLong());




Some of the inputs I've tested to make sure it's working:

public static void main(String[] args) {

    System.out.println(Long.toHexString(0x8000000000000000L |21));
    System.out.println(Long.toBinaryString(0x8000000000000000L |21));
    System.out.println(Long.toHexString(Long.MAX_VALUE + 1));

How to delete a certain row from mysql table with same column values?

Add a limit to the delete query

delete from orders 
where id_users = 1 and id_product = 2
limit 1

How can I create an Asynchronous function in Javascript?

here you have simple solution (other write about it)

And here you have above ready solution:

function async(your_function, callback) {
    setTimeout(function() {
        if (callback) {callback();}
    }, 0);

TEST 1 (may output '1 x 2 3' or '1 2 x 3' or '1 2 3 x'):

async(function() {console.log('x')}, null);

TEST 2 (will always output 'x 1'):

async(function() {console.log('x');}, function() {console.log(1);});

This function is executed with timeout 0 - it will simulate asynchronous task

Run as java application option disabled in eclipse

Run As > Java Application wont show up if the class that you want to run does not contain the main method. Make sure that the class you trying to run has main defined in it.

How do I convert a C# List<string[]> to a Javascript array?

Many of these answers do work, but I have found the easiest way by far is to send data through ViewData or ViewBag and let JSON.Net serialize it.

I use this technique when Javascript is needed for HTML generation before the page load or when AJAX overhead needs to be avoided:

In the controller:

public ActionResult MyController()
    var addresses = myAddressesGetter();
    ViewData["addresses"] = addresses ;
    return View();

In the view:

@section scripts {
<script type="text/javascript">
    var MyjavascriptAddresses: @Html.Raw(JsonConvert.SerializeObject(ViewData["addresses"])),

You can always rely on JSON.NET whereas some browsers have poor JSON deserialization support. Another benefit over some methods in that you can see the Javascript using your browser's View --> Source, since it is simply text generated server-side.

Note that In most situations, Web API a more elegant way to get JSON to the client.

How to send email by using javascript or jquery

You can send Email by Jquery just follow these steps 

include this link : <script src=""></script>
after that use this code :

$( document ).ready(function() {
Host : "",
Username : "username",
Password : "password",
To : '[email protected]',
From : "[email protected]",
Subject : "This is the subject",
Body : "And this is the body"}).then( message => alert(message));});

Write to UTF-8 file in Python

I believe the problem is that codecs.BOM_UTF8 is a byte string, not a Unicode string. I suspect the file handler is trying to guess what you really mean based on "I'm meant to be writing Unicode as UTF-8-encoded text, but you've given me a byte string!"

Try writing the Unicode string for the byte order mark (i.e. Unicode U+FEFF) directly, so that the file just encodes that as UTF-8:

import codecs

file ="lol", "w", "utf-8")

(That seems to give the right answer - a file with bytes EF BB BF.)

EDIT: S. Lott's suggestion of using "utf-8-sig" as the encoding is a better one than explicitly writing the BOM yourself, but I'll leave this answer here as it explains what was going wrong before.

Vim delete blank lines

work with perl in vim:

:%!perl -pi -e s/^\s*$//g

Can I get div's background-image url?

I'm using this one

  function getBackgroundImageUrl($element) {
    if (!($element instanceof jQuery)) {
      $element = $($element);

    var imageUrl = $element.css('background-image');
    return imageUrl.replace(/(url\(|\)|'|")/gi, ''); // Strip everything but the url itself

keycode and charcode

keyCode and which represent the actual keyboard key pressed in the form of a numeric value. The reason both exist is that keyCode is available within Internet Explorer while which is available in W3C browsers like FireFox.

charCode is similar, but in this case you retrieve the Unicode value of the character pressed. For example, the letter "A."

The JavaScript expression:

var keyCode = e.keyCode ? e.keyCode : e.charCode;

Essentially says the following:

If the e.keyCode property exists, set variable keyCode to its value. Otherwise, set variable keyCode to the value of the e.charCode property.

Note that retrieving the keyCode or charCode properties typically involve figuring out differences between the event models in IE and in W3C. Some entails writing code like the following:

 get the event object: either window.event for IE 
 or the parameter e for other browsers
var evt = window.event ? window.event : e;
 get the numeric value of the key pressed: either 
 event.keyCode for IE for e.which for other browsers
var keyCode = evt.keyCode ? evt.keyCode : e.which;

EDIT: Corrections to my explanation of charCode as per Tor Haugen's comments.

How to have a a razor action link open in a new tab?

Looks like you are confusing Html.ActionLink() for Url.Action(). Url.Action has no parameters to set the Target, because it only returns a URL.

Based on your current code, the anchor should probably look like:

<a href="@Url.Action("RunReport", "Performance", new { reportView = Model.ReportView.ToString() })" 
   class="button Secondary">

Insert php variable in a href

echo '<a href="' . $folder_path . '">Link text</a>';

Please note that you must use the path relative to your domain and, if the folder path is outside the public htdocs directory, it will not work.

EDIT: maybe i misreaded the question; you have a file on your pc and want to insert the path on the html page, and then send it to the server?

Difference between string and StringBuilder in C#

From the StringBuilder Class documentation:

The String object is immutable. Every time you use one of the methods in the System.String class, you create a new string object in memory, which requires a new allocation of space for that new object. In situations where you need to perform repeated modifications to a string, the overhead associated with creating a new String object can be costly. The System.Text.StringBuilder class can be used when you want to modify a string without creating a new object. For example, using the StringBuilder class can boost performance when concatenating many strings together in a loop.

Jquery bind double click and single click separately

You could probably write your own custom implementation of click/dblclick to have it wait for an extra click. I don't see anything in the core jQuery functions that would help you achieve this.

Quote from .dblclick() at the jQuery site

It is inadvisable to bind handlers to both the click and dblclick events for the same element. The sequence of events triggered varies from browser to browser, with some receiving two click events before the dblclick and others only one. Double-click sensitivity (maximum time between clicks that is detected as a double click) can vary by operating system and browser, and is often user-configurable.

Get current index from foreach loop

You can't, because IEnumerable doesn't have an index at all... if you are sure your enumerable has less than int.MaxValue elements (or long.MaxValue if you use a long index), you can:

  1. Don't use foreach, and use a for loop, converting your IEnumerable to a generic enumerable first:

    var genericList = list.Cast<object>();
    for(int i = 0; i < genericList.Count(); ++i)
       var row = genericList.ElementAt(i);
       /* .... */
  2. Have an external index:

    int i = 0;
    foreach(var row in list)
       /* .... */
  3. Get the index via Linq:

    foreach(var rowObject in list.Cast<object>().Select((r, i) => new {Row=r, Index=i}))
      var row = rowObject.Row;
      var i = rowObject.Index;
      /* .... */    

In your case, since your IEnumerable is not a generic one, I'd rather use the foreach with external index (second method)... otherwise, you may want to make the Cast<object> outside your loop to convert it to an IEnumerable<object>.

Your datatype is not clear from the question, but I'm assuming object since it's an items source (it could be DataGridRow)... you may want to check if it's directly convertible to a generic IEnumerable<object> without having to call Cast<object>(), but I'll make no such assumptions.

All this said:

The concept of an "index" is foreign to an IEnumerable. An IEnumerable can be potentially infinite. In your example, you are using the ItemsSource of a DataGrid, so more likely your IEnumerable is just a list of objects (or DataRows), with a finite (and hopefully less than int.MaxValue) number of members, but IEnumerable can represent anything that can be enumerated (and an enumeration can potentially never end).

Take this example:

public static IEnumerable InfiniteEnumerable()
  var rnd = new Random();
    yield return rnd.Next();

So if you do:

foreach(var row in InfiniteEnumerable())
  /* ... */

Your foreach will be infinite: if you used an int (or long) index, you'll eventually overflow it (and unless you use an unchecked context, it'll throw an exception if you keep adding to it: even if you used unchecked, the index would be meaningless also... at some point -when it overflows- the index will be the same for two different values).

So, while the examples given work for a typical usage, I'd rather not use an index at all if you can avoid it.

Should I add the Visual Studio .suo and .user files to source control?

This appears to be Microsoft's opinion on the matter:

Adding (and editing) .suo files to source control

I don't know why your project stores the DebuggingWorkingDirectory in the suo file. If that is a user specific setting you should consider storing that in the *.proj.user filename. If that setting is shareable between all users working on the project you should consider storing it in the project file itself.

Don't even think of adding the suo file to source control! The SUO (soluton user options) file is meant to contain user-specific settings, and should not be shared amongst users working on the same solution. If you'd be adding the suo file in the scc database I don't know what other things in the IDE you'd break, but from source control point of view you will break web projects scc integration, the Lan vs Internet plugin used by different users for VSS access, and you could even cause the scc to break completely (VSS database path stored in suo file that may be valid for you may not be valid for another user).

Alin Constantin (MSFT)

Multiple aggregate functions in HAVING clause

For your example query, the only possible value greater than 2 and less than 4 is 3, so we simplify:

GROUP BY meetingID

In your general case:

GROUP BY meetingID
HAVING COUNT(caseID) > x AND COUNT(caseID) < 7

Or (possibly easier to read?),

GROUP BY meetingID

javac : command not found

Install same version javac as your JRE

yum install java-devel

How can I make a CSS table fit the screen width?

Instead of using the % unit – the width/height of another element – you should use vh and vw.
Your code would be:

your table {
  width: 100vw;
  height: 100vh;

But, if the document is smaller than 100vh or 100vw, then you need to set the size to the document's size.

(table).style.width = window.innerWidth;
(table).style.height = window.innerHeight;

CSS transition fade on hover

This will do the trick


  transition: opacity .2s ease-out;
  -moz-transition: opacity .2s ease-out;
  -webkit-transition: opacity .2s ease-out;
  -o-transition: opacity .2s ease-out;

Specific Time Range Query in SQL Server

I (using PostgrSQL on PGadmin4) queried for results that are after or on 21st Nov 2017 at noon, like this (considering the display format of hours on my database):

select * from Table1 where FIELD >='2017-11-21 12:00:00'