Programs & Examples On #Android service

A Service is an application component representing either an application's desire to perform a longer-running operation while not interacting with the user or to supply functionality for other applications to use.

Broadcast Receiver within a Service

The better pattern is to create a standalone BroadcastReceiver. This insures that your app can respond to the broadcast, whether or not the Service is running. In fact, using this pattern may remove the need for a constant-running Service altogether.

Register the BroadcastReceiver in your Manifest, and create a separate class/file for it.


<receiver android:name=".FooReceiver" >
    <intent-filter >
        <action android:name="android.provider.Telephony.SMS_RECEIVED" />

When the receiver runs, you simply pass an Intent (Bundle) to the Service, and respond to it in onStartCommand().


public class FooReceiver extends BroadcastReceiver {
    public void onReceive(Context context, Intent intent) {
        // do your work quickly!
        // then call context.startService();

getApplication() vs. getApplicationContext()

It seems to have to do with context wrapping. Most classes derived from Context are actually a ContextWrapper, which essentially delegates to another context, possibly with changes by the wrapper.

The context is a general abstraction that supports mocking and proxying. Since many contexts are bound to a limited-lifetime object such as an Activity, there needs to be a way to get a longer-lived context, for purposes such as registering for future notifications. That is achieved by Context.getApplicationContext(). A logical implementation is to return the global Application object, but nothing prevents a context implementation from returning a wrapper or proxy with a suitable lifetime instead.

Activities and services are more specifically associated with an Application object. The usefulness of this, I believe, is that you can create and register in the manifest a custom class derived from Application and be certain that Activity.getApplication() or Service.getApplication() will return that specific object of that specific type, which you can cast to your derived Application class and use for whatever custom purpose.

In other words, getApplication() is guaranteed to return an Application object, while getApplicationContext() is free to return a proxy instead.

Android - implementing startForeground for a service?

@mikebertiean solution almost did the trick, but I had this problem with additional twist -- I use Gingerbread system and I didn't want to add some extra package just to run notification. Finally I found:

then I hit additional problem -- notification simply kills my app when it runs (how to solve this problem: Android: How to avoid that clicking on a Notification calls onCreate()), so in total my code in service looks like this (C#/Xamarin):

Intent notificationIntent = new Intent(this, typeof(MainActivity));
// make the changes to manifest as well
notificationIntent.SetFlags(ActivityFlags.ClearTop | ActivityFlags.SingleTop);
PendingIntent pendingIntent = PendingIntent.GetActivity(this, 0, notificationIntent, 0);
Notification notification = new Notification(Resource.Drawable.Icon, "Starting service");
notification.SetLatestEventInfo(this, "MyApp", "Monitoring...", pendingIntent);
StartForeground(1337, notification);

How to have Android Service communicate with Activity

Besides LocalBroadcastManager , Event Bus and Messenger already answered in this question,we can use Pending Intent to communicate from service.

As mentioned here in my blog post

Communication between service and Activity can be done using PendingIntent.For that we can use createPendingResult().createPendingResult() creates a new PendingIntent object which you can hand to service to use and to send result data back to your activity inside onActivityResult(int, int, Intent) callback.Since a PendingIntent is Parcelable , and can therefore be put into an Intent extra,your activity can pass this PendingIntent to the service.The service, in turn, can call send() method on the PendingIntent to notify the activity via onActivityResult of an event.


public class PendingIntentActivity extends AppCompatActivity
protected void onCreate(@Nullable Bundle savedInstanceState) {

PendingIntent pendingResult = createPendingResult(
100, new Intent(), 0);
Intent intent = new Intent(getApplicationContext(), PendingIntentService.class);
intent.putExtra("pendingIntent", pendingResult);


protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 100 && resultCode==200) {
super.onActivityResult(requestCode, resultCode, data);


public class PendingIntentService extends Service {

    private static final String[] items= { "lorem", "ipsum", "dolor",
            "sit", "amet", "consectetuer", "adipiscing", "elit", "morbi",
            "vel", "ligula", "vitae", "arcu", "aliquet", "mollis", "etiam",
            "vel", "erat", "placerat", "ante", "porttitor", "sodales",
            "pellentesque", "augue", "purus" };
    private PendingIntent data;

    public void onCreate() {

    public int onStartCommand(Intent intent, int flags, int startId) {

        data = intent.getParcelableExtra("pendingIntent");

        new LoadWordsThread().start();
        return START_NOT_STICKY;

    public IBinder onBind(Intent intent) {
        return null;

    public void onDestroy() {

    class LoadWordsThread extends Thread {
        public void run() {
            for (String item : items) {
                if (!isInterrupted()) {

                    Intent result = new Intent();
                    result.putExtra("name", item);
                    try {
                    } catch (PendingIntent.CanceledException e) {



Android 8.0: java.lang.IllegalStateException: Not allowed to start service Intent

i had this problem too

added this library

implementation 'androidx.localbroadcastmanager:localbroadcastmanager:1.0.0'

and reinstalled the app solved this for me

What is the difference between an IntentService and a Service?

See Tejas Lagvankar's post about this subject. Below are some key differences between Service and IntentService and other components.

enter image description here

Get Context in a Service

Since Service is a Context, the variable context must be this:

DataBaseManager dbm = Utils.getDataManager(this);   

How to check if a service is running on Android?

There can be several services with the same class name.

I've just created two apps. The package name of the first app is com.example.mock. I created a subpackage called lorem in the app and a service called Mock2Service. So its fully qualified name is com.example.mock.lorem.Mock2Service.

Then I created the second app and a service called Mock2Service. The package name of the second app is com.example.mock.lorem. The fully qualified name of the service is com.example.mock.lorem.Mock2Service, too.

Here is my logcat output.

03-27 12:02:19.985: D/TAG(32155): Mock-01: com.example.mock.lorem.Mock2Service
03-27 12:02:33.755: D/TAG(32277): Mock-02: com.example.mock.lorem.Mock2Service

A better idea is to compare ComponentName instances because equals() of ComponentName compares both package names and class names. And there can't be two apps with the same package name installed on a device.

The equals() method of ComponentName.

public boolean equals(Object obj) {
    try {
        if (obj != null) {
            ComponentName other = (ComponentName)obj;
            // Note: no null checks, because mPackage and mClass can
            // never be null.
            return mPackage.equals(other.mPackage)
                    && mClass.equals(other.mClass);
    } catch (ClassCastException e) {
    return false;


How to run an android app in background?

You can probably start a Service here if you want your Application to run in Background. This is what Service in Android are used for - running in background and doing longtime operations.


You can use START_STICKY to make your Service running continuously.

public int onStartCommand(Intent intent, int flags, int startId) {
    // We want this service to continue running until it is explicitly
    // stopped, so return sticky.
    return START_STICKY;


  • START_STICKY: It will restart the service in case if it terminated and the Intent data which is passed to the onStartCommand() method is NULL. This is suitable for the service which are not executing commands but running independently and waiting for the job.
  • START_NOT_STICKY: It will not restart the service and it is useful for the services which will run periodically. The service will restart only when there are a pending startService() calls. It’s the best option to avoid running a service in case if it is not necessary.
  • START_REDELIVER_INTENT: It’s same as STAR_STICKY and it recreates the service, call onStartCommand() with last intent that was delivered to the service.

Trying to start a service on boot on Android

Before mounting external storage BOOT_COMPLETE is sent execute.if your app is installed to external storage it won't receive BOOT_COMPLETE broadcast message. To prevent this you can install your application in internal storage. you can do this just adding this line in menifest.xml

<manifest xmlns:android=""
... >

Some HTC devices can enable a "fast boot" feature that is more like a deep hibernation and not a real reboot and therefore should not give the BOOT_COMPLETE intent. To recover this you can add this intent filter inside your receiver:

                <action android:name="android.intent.action.BOOT_COMPLETED" />
                <action android:name="android.intent.action.QUICKBOOT_POWERON" />

Android background music service

Theres an excellent tutorial on this subject at HelloAndroid regarding this very subject. Infact it was the first hit i got on google. You should try googling before asking here, as it is good practice.

Background service with location listener in android

I know I am posting this answer little late, but I felt it is worth using Google's fuse location provider service to get the current location.

Main features of this api are :

1.Simple APIs: Lets you choose your accuracy level as well as power consumption.

2.Immediately available: Gives your apps immediate access to the best, most recent location.

3.Power-efficiency: It chooses the most efficient way to get the location with less power consumptions

4.Versatility: Meets a wide range of needs, from foreground uses that need highly accurate location to background uses that need periodic location updates with negligible power impact.

It is flexible in while updating in location also. If you want current location only when your app starts then you can use getLastLocation(GoogleApiClient) method.

If you want to update your location continuously then you can use requestLocationUpdates(GoogleApiClient,LocationRequest, LocationListener)

You can find a very nice blog about fuse location here and google doc for fuse location also can be found here.


According to developer docs starting from Android O they have added new limits on background location.

If your app is running in the background, the location system service computes a new location for your app only a few times each hour. This is the case even when your app is requesting more frequent location updates. However if your app is running in the foreground, there is no change in location sampling rates compared to Android 7.1.1 (API level 25).

Android – Listen For Incoming SMS Messages

If someone referring how to do the same feature (reading OTP using received SMS) on Xamarin Android like me :

  1. Add this code to your AndroidManifest.xml file :

    <receiver android:name=".listener.BroadcastReveiverOTP">
        <action android:name="android.provider.Telephony.SMS_RECEIVED" />
    <uses-permission android:name="android.permission.RECEIVE_SMS" />
    <uses-permission android:name="android.permission.BROADCAST_SMS" />
    <uses-permission android:name="android.permission.READ_SMS" />
  2. Then create your BroadcastReveiver class in your Android Project.

    [BroadcastReceiver(Enabled = true)] [IntentFilter(new[] { "android.provider.Telephony.SMS_RECEIVED" }, Priority = (int)IntentFilterPriority.HighPriority)] 
    public class BroadcastReveiverOTP : BroadcastReceiver {
            public static readonly string INTENT_ACTION = "android.provider.Telephony.SMS_RECEIVED";
            protected string message, address = string.Empty;
            public override void OnReceive(Context context, Intent intent)
                if (intent.HasExtra("pdus"))
                    var smsArray = (Java.Lang.Object[])intent.Extras.Get("pdus");
                    foreach (var item in smsArray)
                        var sms = SmsMessage.CreateFromPdu((byte[])item);
                        address = sms.OriginatingAddress;
                        if (address.Equals("NotifyDEMO"))
                            message = sms.MessageBody;
                            string[] pin = message.Split(' ');
                            if (!string.IsNullOrWhiteSpace(pin[0]))
                                    // NOTE : Here I'm passing received OTP to Portable Project using MessagingCenter. So I can display the OTP in the relevant entry field.
                                    MessagingCenter.Send<object, string>(this,MessengerKeys.OnBroadcastReceived, pin[0]);
  3. Register this BroadcastReceiver class in your MainActivity class on Android Project:

    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity {
            // Initialize your class
            private BroadcastReveiverOTP _receiver = new BroadcastReveiverOTP ();
            protected override void OnCreate(Bundle bundle) { 
                    global::Xamarin.Forms.Forms.Init(this, bundle);
                    LoadApplication(new App());
                    // Register your receiver :  RegisterReceiver(_receiver, new IntentFilter("android.provider.Telephony.SMS_RECEIVED"));

How to get the current location latitude and longitude in android

Use Location Listener Method

public void onLocationChanged(Location loc) {
Double lat = loc.getLatitude();
Double lng = loc.getLongitude();

Service vs IntentService in the Android platform

Android IntentService vs Service


  • A Service is invoked using startService().
  • A Service can be invoked from any thread.
  • A Service runs background operations on the Main Thread of the Application by default. Hence it can block your Application’s UI.
  • A Service invoked multiple times would create multiple instances.
  • A service needs to be stopped using stopSelf() or stopService().
  • Android service can run parallel operations.

2. IntentService

  • An IntentService is invoked using Intent.
  • An IntentService can in invoked from the Main thread only.
  • An IntentService creates a separate worker thread to run background operations.
  • An IntentService invoked multiple times won’t create multiple instances.
  • An IntentService automatically stops after the queue is completed. No need to trigger stopService() or stopSelf().
  • In an IntentService, multiple intent calls are automatically Queued and they would be executed sequentially.
  • An IntentService cannot run parallel operation like a Service.

Refer from Here

Determining the current foreground application from a background task or service

i had to figure out the right solution the hard way. the below code is part of cyanogenmod7 (the tablet tweaks) and is tested on android 2.3.3 / gingerbread.


  • getForegroundApp - returns the foreground application.
  • getActivityForApp - returns the activity of the found app.
  • isStillActive - determines if a earlier found app is still the active app.
  • isRunningService - a helper function for getForegroundApp

this hopefully answers this issue in all extend (:

private RunningAppProcessInfo getForegroundApp() {
    RunningAppProcessInfo result=null, info=null;

        mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
    List <RunningAppProcessInfo> l = mActivityManager.getRunningAppProcesses();
    Iterator <RunningAppProcessInfo> i = l.iterator();
        info =;
        if(info.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND
                && !isRunningService(info.processName)){
    return result;

private ComponentName getActivityForApp(RunningAppProcessInfo target){
    ComponentName result=null;
    ActivityManager.RunningTaskInfo info;

        return null;

        mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
    List <ActivityManager.RunningTaskInfo> l = mActivityManager.getRunningTasks(9999);
    Iterator <ActivityManager.RunningTaskInfo> i = l.iterator();


    return result;

private boolean isStillActive(RunningAppProcessInfo process, ComponentName activity)
    // activity can be null in cases, where one app starts another. for example, astro
    // starting rock player when a move file was clicked. we dont have an activity then,
    // but the package exits as soon as back is hit. so we can ignore the activity
    // in this case
        return false;

    RunningAppProcessInfo currentFg=getForegroundApp();
    ComponentName currentActivity=getActivityForApp(currentFg);

    if(currentFg!=null && currentFg.processName.equals(process.processName) &&
            (activity==null || currentActivity.compareTo(activity)==0))
        return true;

    Slog.i(TAG, "isStillActive returns false - CallerProcess: " + process.processName + " CurrentProcess: "
            + (currentFg==null ? "null" : currentFg.processName) + " CallerActivity:" + (activity==null ? "null" : activity.toString())
            + " CurrentActivity: " + (currentActivity==null ? "null" : currentActivity.toString()));
    return false;

private boolean isRunningService(String processname){
    if(processname==null || processname.isEmpty())
        return false;

    RunningServiceInfo service;

        mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
    List <RunningServiceInfo> l = mActivityManager.getRunningServices(9999);
    Iterator <RunningServiceInfo> i = l.iterator();
        service =;
            return true;

    return false;

Launch Android application without main Activity and start Service on launching application

Yes you can do that by just creating a BroadcastReceiver that calls your Service when your Application boots. Here is a complete answer given by me.
Android - Start service on boot

If you don't want any icon/launcher for you Application you can do that also, just don't create any Activity with

    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.LAUNCHER" />

Just declare your Service as declared normally.

Android Fatal signal 11 (SIGSEGV) at 0x636f7d89 (code=1). How can it be tracked down?

Try disabling Android hardware acceleration in your manifest.


android start activity from service

If you need to recal an Activity that is in bacgrounde, from your service, I suggest the following link. Intent.FLAG_ACTIVITY_NEW_TASK is not the solution.

Example: Communication between Activity and Service using Messaging

Everything is fine.Good example of activity/service communication using Messenger.

One comment : the method MyService.isRunning() is not required.. bindService() can be done any number of times. no harm in that.

If MyService is running in a different process then the static function MyService.isRunning() will always return false. So there is no need of this function.

How to read json file into java with simple JSON library

your json file look like this

enter image description here

import java.util.*;
import org.json.simple.*;
import org.json.simple.parser.*;
public class JSONReadFromTheFileTest {
   public static void main(String[] args) {
      JSONParser parser = new JSONParser();
      try {
         Object obj = parser.parse(new FileReader("/Users/User/Desktop/course.json"));
         JSONObject jsonObject = (JSONObject)obj;
         String name = (String)jsonObject.get("Name");
         String course = (String)jsonObject.get("Course");
         JSONArray subjects = (JSONArray)jsonObject.get("Subjects");
         System.out.println("Name: " + name);
         System.out.println("Course: " + course);
         Iterator iterator = subjects.iterator();
         while (iterator.hasNext()) {
      } catch(Exception e) {

the output is

Name: Raja
Course: MCA
subject1: MIS
subject2: DBMS
subject3: UML

took it from here

How to use java.String.format in Scala?

Instead of looking at the source code, you should read the javadoc String.format() and Formatter syntax.

You specify the format of the value after the %. For instance for decimal integer it is d, and for String it is s:

String aString = "world";
int aInt = 20;
String.format("Hello, %s on line %d",  aString, aInt );


Hello, world on line 20

To do what you tried (use an argument index), you use: *n*$,

String.format("Line:%2$d. Value:%1$s. Result: Hello %1$s at line %2$d", aString, aInt );


Line:20. Value:world. Result: Hello world at line 20

how to print a string to console in c++

All you have to do is add:

#include <string>
using namespace std;

at the top. (BTW I know this was posted in 2013 but I just wanted to answer)

I want to convert std::string into a const wchar_t *

You can use the ATL text conversion macros to convert a narrow (char) string to a wide (wchar_t) one. For example, to convert a std::string:

#include <atlconv.h>
std::string str = "Hello, world!";
CA2W pszWide(str.c_str());

You can also specify a code page, so if your std::string contains UTF-8 chars you can use:

CA2W pszWide(str.c_str(), CP_UTF8);

Very useful but Windows only.

iOS 8 removed "minimal-ui" viewport property, are there other "soft fullscreen" solutions?

It is possible to get a web application running in full screen in both iOS and Android, it is called a PWA and after mucha hard work, it was the only way around this issue.

PWAs open a number of interesting options for development that should not be missed. I've made a couple already, check out this Public and Private Tender Manual For Designers (Spanish). And here is an English explanation from the CosmicJS site

What is FCM token in Firebase?

What is it exactly?

An FCM Token, or much commonly known as a registrationToken like in . As described in the GCM FCM docs:

An ID issued by the GCM connection servers to the client app that allows it to receive messages. Note that registration tokens must be kept secret.

How can I get that token?

Update: The token can still be retrieved by calling getToken(), however, as per FCM's latest version, the FirebaseInstanceIdService.onTokenRefresh() has been replaced with FirebaseMessagingService.onNewToken() -- which in my experience functions the same way as onTokenRefresh() did.

Old answer:

As per the FCM docs:

On initial startup of your app, the FCM SDK generates a registration token for the client app instance. If you want to target single devices or create device groups, you'll need to access this token.

You can access the token's value by extending FirebaseInstanceIdService. Make sure you have added the service to your manifest, then call getToken in the context of onTokenRefresh, and log the value as shown:

public void onTokenRefresh() {
    // Get updated InstanceID token.
    String refreshedToken = FirebaseInstanceId.getInstance().getToken();
    Log.d(TAG, "Refreshed token: " + refreshedToken);

    // TODO: Implement this method to send any registration to your app's servers.

The onTokenRefreshcallback fires whenever a new token is generated, so calling getToken in its context ensures that you are accessing a current, available registration token. FirebaseInstanceID.getToken() returns null if the token has not yet been generated.

After you've obtained the token, you can send it to your app server and store it using your preferred method. See the Instance ID API reference for full detail on the API.

Convert list to dictionary using linq and not worrying about duplicates

A Linq-solution using Distinct() and and no grouping is:

var _people = personList
    .Select(item => new { Key = item.Key, FirstAndLastName = item.FirstAndLastName })
    .ToDictionary(item => item.Key, item => item.FirstFirstAndLastName, StringComparer.OrdinalIgnoreCase);

I don't know if it is nicer than LukeH's solution but it works as well.

Uncaught TypeError: .indexOf is not a function

I was getting is not a function error, after debugging it, I found that it was actually a TypeError, which meant, indexOf() being a function is applicable to strings, so I typecasted the data like the following and then used the indexOf() method to make it work'<stringToBeMatchedToPosition>')

Not sure if my answer was accurate to the question, but yes shared my opinion as i faced a similar kind of situation.

python encoding utf-8

Unfortunately, the string.encode() method is not always reliable. Check out this thread for more information: What is the fool proof way to convert some string (utf-8 or else) to a simple ASCII string in python

Converting a Date object to a calendar object

it's so easy...converting a date to calendar like this:

Calendar cal=Calendar.getInstance();
DateFormat format=new SimpleDateFormat("yyyy/mm/dd");

Rails 4: before_filter vs. before_action

before_filter/before_action: means anything to be executed before any action executes.

Both are same. they are just alias for each other as their behavior is same.

When to use "new" and when not to, in C++?

Take a look at this question and this question for some good answers on C++ object instantiation.

This basic idea is that objects instantiated on the heap (using new) need to be cleaned up manually, those instantiated on the stack (without new) are automatically cleaned up when they go out of scope.

void SomeFunc()
    Point p1 = Point(0,0);
} // p1 is automatically freed

void SomeFunc2()
    Point *p1 = new Point(0,0);
    delete p1; // p1 is leaked unless it gets deleted

MySQL Results as comma separated list

Instead of using group concat() you can use just concat()

Select concat(Col1, ',', Col2) as Foo_Bar from Table1;

edit this only works in mySQL; Oracle concat only accepts two arguments. In oracle you can use something like select col1||','||col2||','||col3 as foobar from table1; in sql server you would use + instead of pipes.

How do I validate a date in this format (yyyy-mm-dd) using jquery?

Here's the JavaScript rejex for YYYY-MM-DD format


MySQL Database won't start in XAMPP Manager-osx

Try running these two commands in the terminal:

  1. sudo killall mysqld sudo
  2. /Applications/XAMPP/xamppfiles/bin/mysql.server start

Escape string Python for MySQL


See MySQL C API function mapping:

symbol(s) not found for architecture i386

Another situation that can cause this problem is if your code calls into C++, or is called by C++ code. I had a problem with my own .c file's utility function showing up as "symbol not found" when called from Obj-C. The fix was to change the file type: in Xcode 4, use the extended info pane to set the file type to "Objective-C++ Source"; in Xcode 3, use "Get Info" to change file type to "source.cpp.objcpp".

how to make a html iframe 100% width and height?

Answering this just in case if someone else like me stumbles upon this post among many that advise use of JavaScripts for changing iframe height to 100%.

I strongly recommend that you see and try this option specified at How do you give iframe 100% height before resorting to a JavaScript based option. The referenced solution works perfectly for me in all of the testing I have done so far. Hope this helps someone.

Incorrect integer value: '' for column 'id' at row 1

For the same error in wamp/phpmyadmin, I have edited my.ini, commented the original :


and added sql_mode = "".

ASP.NET MVC: Html.EditorFor and multi-line text boxes

Use data type 'MultilineText':

public string Text { get; set; }

See ASP.NET MVC3 - textarea with @Html.EditorFor

Is it possible to start activity through adb shell?

For example this will start XBMC:

adb shell am start -a android.intent.action.MAIN -n org.xbmc.xbmc/

(More general answers are already posted, but I missed a nice example here.)

Storing integer values as constants in Enum manner in java

I found this to be helpful:

public enum Difficulty

    * Value for this difficulty
    public final int Value;

    private Difficulty(int value)
        Value = value;

    // Mapping difficulty to difficulty id
    private static final Map<Integer, Difficulty> _map = new HashMap<Integer, Difficulty>();
        for (Difficulty difficulty : Difficulty.values())
            _map.put(difficulty.Value, difficulty);

    * Get difficulty from value
    * @param value Value
    * @return Difficulty
    public static Difficulty from(int value)
        return _map.get(value);

Convert String to Uri

Java's parser in is going to fail if the URI isn't fully encoded to its standards. For example, try to parse:|dog. An exception will be thrown for the vertical bar.

urllib makes it easy to convert a string to a It will pre-process and escape the URL.


$.browser is undefined error

The .browser call has been removed in jquery 1.9 have a look at for more details.

Creating a procedure in mySql with parameters

I figured it out now. Here's the correct answer

   brugernavn1 varchar(64),
   password varchar(64)
   SELECT COUNT(*) FROM bruger 
   WHERE bruger.brugernavn=brugernavn1 
   AND bruger.pass=password; 

@ points to a global var in mysql. The above syntax is correct.

unix diff side-to-side results?

You can use vimdiff.


vimdiff file1 file2

Regex Match all characters between two strings

In case anyone is looking for an example of this within a Jenkins context. It parses the build.log and if it finds a match it fails the build with the match.

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

        def file = readFile 'build.log'

        def regex = ~"(?s)(firstStringToUse(.*)secondStringToUse)"
        Matcher match = regex.matcher(file)
        match.find() {
            capturedText =

Messagebox with input field

You can reference Microsoft.VisualBasic.dll.

Then using the code below.

Microsoft.VisualBasic.Interaction.InputBox("Question?","Title","Default Text");

Alternatively, by adding a using directive allowing for a shorter syntax in your code (which I'd personally prefer).

using Microsoft.VisualBasic;
Interaction.InputBox("Question?","Title","Default Text");

Or you can do what Pranay Rana suggests, that's what I would've done too...

Bootstrap 3 hidden-xs makes row narrower

How does it work if you only are using visible-md at Col4 instead? Do you use the -lg at all? If not this might work.

<div class="container">
    <div class="row">
        <div class="col-xs-4 col-sm-2 col-md-1" align="center">
        <div class="col-xs-4 col-sm-2" align="center">
        <div class="hidden-xs col-sm-6 col-md-5" align="center">
        <div class="visible-md col-md-3 " align="center">
        <div class="col-xs-4 col-sm-2 col-md-1" align="center">

How to export JSON from MongoDB using Robomongo

  1. make your search
  2. push button view results in JSON mode
  3. copy te result to word
  4. print the result from word


select * from sqlite_master where type = 'table' and tbl_name = 'TableName' and sql like '%ColumnName%'

Logic: sql column in sqlite_master contains table definition, so it certainly contains string with column name.

As you are searching for a sub-string, it has its obvious limitations. So I would suggest to use even more restrictive sub-string in ColumnName, for example something like this (subject to testing as '`' character is not always there):

select * from sqlite_master where type = 'table' and tbl_name = 'MyTable' and sql like '%`MyColumn` TEXT%'

How to print variables without spaces between values

print(*objects, sep=' ', end='\n', file=sys.stdout)

Note: This function is not normally available as a built-in since the name print is recognized as the print statement. To disable the statement and use the print() function, use this future statement at the top of your module:

from future import print_function

How does JavaScript .prototype work?

The Definitive Guide to Object-Oriented JavaScript - a very concise and clear ~30min video explanation of the asked question (Prototypal Inheritance topic begins from 5:45, although I'd rather listen to the whole video). The author of this video also made JavaScript object visualizer website image description here enter image description here

Background position, margin-top?

 background-image: url(/images/poster.png);
 background-position: center;
 background-position-y: 50px;
 background-repeat: no-repeat;

Height of status bar in Android

Since multi-window mode is available now, your app may not have statusbar on top.

Following solution handle all the cases automatically for you.


or programatically


you may also get root view by


For more details on getting root-view refer -

Difference between jQuery .hide() and .css("display", "none")


The display property can have many possible values, among which are block, inline, inline-block, and many more.

The .show() method doesn't set it necessarily to block, but rather resets it to what you defined it (if at all).

In the jQuery source code, you can see how they're setting the display property to "" (an empty string) to check what it was before any jQuery manipulation: little link.

On the other hand, hiding is done via display: none;, so you can consider .hide() and .css("display", "none") equivalent to some point.

It's recommended to use .show() and .hide() anyway to avoid any gotcha's (plus, they're shorter).

How to specify preference of library path?

If one is used to work with DLL in Windows and would like to skip .so version numbers in linux/QT, adding CONFIG += plugin will take version numbers out. To use absolute path to .so, giving it to linker works fine, as Mr. Klatchko mentioned.

VBA vlookup reference in different sheet

try this:

Dim ws as Worksheet

Set ws = Thisworkbook.Sheets("Sheet2")

With ws
    .Range("E2").Formula = "=VLOOKUP(D2,Sheet1!$A:$C,1,0)"
End With

End Sub

This just the simplified version of what you want.
No need to use Application if you will just output the answer in the Range("E2").

If you want to stick with your logic, declare the variables.
See below for example.

Sub Test()

Dim rng As Range
Dim ws1, ws2 As Worksheet
Dim MyStringVar1 As String

Set ws1 = ThisWorkbook.Sheets("Sheet1")
Set ws2 = ThisWorkbook.Sheets("Sheet2")
Set rng = ws2.Range("D2")

With ws2
    On Error Resume Next 'add this because if value is not found, vlookup fails, you get 1004
    MyStringVar1 = Application.WorksheetFunction.VLookup(rng, ws1.Range("A1:C65536").Value, 1, False)
    On Error GoTo 0
    If MyStringVar1 = "" Then MsgBox "Item not found" Else MsgBox MyStringVar1
End With

End Sub

Hope this get's you started.

Disable Scrolling on Body

Set height and overflow:

html, body {margin: 0; height: 100%; overflow: hidden}

Increase Tomcat memory settings

try setting this

CATALINA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 
-server -Xms1536m -Xmx1536m
-XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=256m 
-XX:MaxPermSize=256m -XX:+DisableExplicitGC"

in {$tomcat-folder}\bin\ (create it if necessary).

See for more details.

paint() and repaint() in Java

The paint() method supports painting via a Graphics object.

The repaint() method is used to cause paint() to be invoked by the AWT painting thread.

Get the string representation of a DOM node

I have wasted a lot of time figuring out what is wrong when I iterate through DOMElements with the code in the accepted answer. This is what worked for me, otherwise every second element disappears from the document:

_getGpxString: function(node) {
          clone = node.cloneNode(true);
          var tmp = document.createElement("div");
          return tmp.innerHTML;

String.Format alternative in C++

The C++ way would be to use a std::stringstream object as:

std::stringstream fmt;
fmt << a << " " << b << " > " << c;

The C way would be to use sprintf.

The C way is difficult to get right since:

  • It is type unsafe
  • Requires buffer management

Of course, you may want to fall back on the C way if performance is an issue (imagine you are creating fixed-size million little stringstream objects and then throwing them away).

Manually adding a Userscript to Google Chrome

Update 2016: seems to be working again.

Update August 2014: No longer works as of recent Chrome versions.

Yeah, the new state of affairs sucks. Fortunately it's not so hard as the other answers imply.

  1. Browse in Chrome to chrome://extensions
  2. Drag the .user.js file into that page.

Voila. You can also drag files from the downloads footer bar to the extensions tab.

Chrome will automatically create a manifest.json file in the extensions directory that Brock documented.

<3 Freedom.

Do I need to close() both FileReader and BufferedReader?

I'm late, but:

public BufferedReader(Reader in) {
  this(in, defaultCharBufferSize);


public void close() throws IOException {
    synchronized (lock) {
        if (in == null)
        try {
        } finally {
            in = null;
            cb = null;

Initialize a string in C to empty string

Assuming your array called 'string' already exists, try

string[0] = '\0';

\0 is the explicit NUL terminator, required to mark the end of string.

How to use Elasticsearch with MongoDB?

Using river can present issues when your operation scales up. River will use a ton of memory when under heavy operation. I recommend implementing your own elasticsearch models, or if you're using mongoose you can build your elasticsearch models right into that or use mongoosastic which essentially does this for you.

Another disadvantage to Mongodb River is that you'll be stuck using mongodb 2.4.x branch, and ElasticSearch 0.90.x. You'll start to find that you're missing out on a lot of really nice features, and the mongodb river project just doesn't produce a usable product fast enough to keep stable. That said Mongodb River is definitely not something I'd go into production with. It's posed more problems than its worth. It will randomly drop write under heavy load, it will consume lots of memory, and there's no setting to cap that. Additionally, river doesn't update in realtime, it reads oplogs from mongodb, and this can delay updates for as long as 5 minutes in my experience.

We recently had to rewrite a large portion of our project, because its a weekly occurrence that something goes wrong with ElasticSearch. We had even gone as far as to hire a Dev Ops consultant, who also agrees that its best to move away from River.

UPDATE: Elasticsearch-mongodb-river now supports ES v1.4.0 and mongodb v2.6.x. However, you'll still likely run into performance problems on heavy insert/update operations as this plugin will try to read mongodb's oplogs to sync. If there are a lot of operations since the lock(or latch rather) unlocks, you'll notice extremely high memory usage on your elasticsearch server. If you plan on having a large operation, river is not a good option. The developers of ElasticSearch still recommend you to manage your own indexes by communicating directly with their API using the client library for your language, rather than using river. This isn't really the purpose of river. Twitter-river is a great example of how river should be used. Its essentially a great way to source data from outside sources, but not very reliable for high traffic or internal use.

Also consider that mongodb-river falls behind in version, as its not maintained by ElasticSearch Organization, its maintained by a thirdparty. Development was stuck on v0.90 branch for a long time after the release of v1.0, and when a version for v1.0 was released it wasn't stable until elasticsearch released v1.3.0. Mongodb versions also fall behind. You may find yourself in a tight spot when you're looking to move to a later version of each, especially with ElasticSearch under such heavy development, with many very anticipated features on the way. Staying up on the latest ElasticSearch has been very important as we rely heavily on constantly improving our search functionality as its a core part of our product.

All in all you'll likely get a better product if you do it yourself. Its not that difficult. Its just another database to manage in your code, and it can easily be dropped in to your existing models without major refactoring.

Calculating Page Load Time In JavaScript

Don't ever use the setInterval or setTimeout functions for time measuring! They are unreliable, and it is very likely that the JS execution scheduling during a documents parsing and displaying is delayed.

Instead, use the Date object to create a timestamp when you page began loading, and calculate the difference to the time when the page has been fully loaded:

<doctype html>
        <script type="text/javascript">
            var timerStart =;
        <!-- do all the stuff you need to do -->
        <!-- put everything you need in here -->

        <script type="text/javascript">
             $(document).ready(function() {
                 console.log("Time until DOMready: ",;
             $(window).load(function() {
                 console.log("Time until everything loaded: ",;

How can I use an array of function pointers?

This simple example for multidimensional array with function pointers":

void one( int a, int b){    printf(" \n[ ONE ]  a =  %d   b = %d",a,b);}
void two( int a, int b){    printf(" \n[ TWO ]  a =  %d   b = %d",a,b);}
void three( int a, int b){    printf("\n [ THREE ]  a =  %d   b = %d",a,b);}
void four( int a, int b){    printf(" \n[ FOUR ]  a =  %d   b = %d",a,b);}
void five( int a, int b){    printf(" \n [ FIVE ]  a =  %d   b = %d",a,b);}
void(*p[2][2])(int,int)   ;
int main()
    int i,j;
    printf("multidimensional array with function pointers\n");

    p[0][0] = one;    p[0][1] = two;    p[1][0] = three;    p[1][1] = four;
    for (  i  = 1 ; i >=0; i--)
        for (  j  = 0 ; j <2; j++)
            (*p[i][j])( (i, i*j);
    return 0;

Angular2 handling http response

Update alpha 47

As of alpha 47 the below answer (for alpha46 and below) is not longer required. Now the Http module handles automatically the errores returned. So now is as easy as follows

  .get('Some Url')
  .map(res => res.json())
    (data) => = data,
    (err) => this.error = err); // Reach here if fails

Alpha 46 and below

You can handle the response in the map(...), before the subscribe.

  .get('Some Url')
  .map(res => {
    // If request fails, throw an Error that will be caught
    if(res.status < 200 || res.status >= 300) {
      throw new Error('This request has failed ' + res.status);
    // If everything went fine, return the response
    else {
      return res.json();
    (data) => = data, // Reach here if res.status >= 200 && <= 299
    (err) => this.error = err); // Reach here if fails

Here's a plnkr with a simple example.

Note that in the next release this won't be necessary because all status codes below 200 and above 299 will throw an error automatically, so you won't have to check them by yourself. Check this commit for more info.

How do you create optional arguments in php?

Give the optional argument a default value.

function date ($format, $timestamp='') {

Java and HTTPS url connection without downloading certificate

A simple, but not pure java solution, is to shell out to curl from java, which gives you complete control over how the request is done. If you're just doing this for something simple, this allows you to ignore certificate errors at times, by using this method. This example shows how to make a request against a secure server with a valid or invalid certificate, pass in a cookie, and get the output using curl from java.


public class MyTestClass
  public static void main(String[] args) 
    String url = "";
    String sessionId = "faf419e0-45a5-47b3-96d1-8c62b2a3b558";

    // Curl options are:
    // -k: ignore certificate errors
    // -L: follow redirects
    // -s: non verbose
    // -H: add a http header

    String[] command = { "curl", "-k", "-L", "-s", "-H", "Cookie: MYSESSIONCOOKIENAME=" + sessionId + ";", "-H", "Accept:*/*", url };
    String output = executeShellCmd(command, "/tmp", true, true);

  public String executeShellCmd(String[] command, String workingFolder, boolean wantsOutput, boolean wantsErrors)
      ProcessBuilder pb = new ProcessBuilder(command);
      File wf = new File(workingFolder);;

      Process proc = pb.start();
      BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));
      BufferedReader stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream()));

      StringBuffer sb = new StringBuffer();
      String newLine = System.getProperty("line.separator");
      String s;

      // read stdout from the command
      if (wantsOutput)
        while ((s = stdInput.readLine()) != null)

      // read any errors from the attempted command
      if (wantsErrors)
        while ((s = stdError.readLine()) != null)

      String result = sb.toString();

      return result;
    catch (IOException e)
      throw new RuntimeException("Problem occurred:", e);


How to trigger event in JavaScript?

The most efficient way is to call the very same function that has been registered with addEventListener directly.

You can also trigger a fake event with CustomEvent and co.

Finally some elements such as <input type="file"> support a .click() method.

How do I get column datatype in Oracle with PL-SQL with low privileges?

ALL_TAB_COLUMNS should be queryable from PL/SQL. DESC is a SQL*Plus command.

SQL> desc all_tab_columns;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 OWNER                                     NOT NULL VARCHAR2(30)
 TABLE_NAME                                NOT NULL VARCHAR2(30)
 COLUMN_NAME                               NOT NULL VARCHAR2(30)
 DATA_TYPE                                          VARCHAR2(106)
 DATA_TYPE_MOD                                      VARCHAR2(3)
 DATA_TYPE_OWNER                                    VARCHAR2(30)
 DATA_LENGTH                               NOT NULL NUMBER
 DATA_PRECISION                                     NUMBER
 DATA_SCALE                                         NUMBER
 NULLABLE                                           VARCHAR2(1)
 COLUMN_ID                                          NUMBER
 DEFAULT_LENGTH                                     NUMBER
 DATA_DEFAULT                                       LONG
 NUM_DISTINCT                                       NUMBER
 LOW_VALUE                                          RAW(32)
 HIGH_VALUE                                         RAW(32)
 DENSITY                                            NUMBER
 NUM_NULLS                                          NUMBER
 NUM_BUCKETS                                        NUMBER
 LAST_ANALYZED                                      DATE
 SAMPLE_SIZE                                        NUMBER
 CHARACTER_SET_NAME                                 VARCHAR2(44)
 CHAR_COL_DECL_LENGTH                               NUMBER
 GLOBAL_STATS                                       VARCHAR2(3)
 USER_STATS                                         VARCHAR2(3)
 AVG_COL_LEN                                        NUMBER
 CHAR_LENGTH                                        NUMBER
 CHAR_USED                                          VARCHAR2(1)
 V80_FMT_IMAGE                                      VARCHAR2(3)
 DATA_UPGRADED                                      VARCHAR2(3)
 HISTOGRAM                                          VARCHAR2(15)

Python PDF library

The two that come to mind are:

Conditional statement in a one line lambda function in python?

Yes, you can use the shorthand syntax for if statements.

rate = lambda(t): (200 * exp(-t)) if t > 200 else (400 * exp(-t))

Note that you don't use explicit return statements inlambdas either.

Declare a variable as Decimal

The best way is to declare the variable as a Single or a Double depending on the precision you need. The data type Single utilizes 4 Bytes and has the range of -3.402823E38 to 1.401298E45. Double uses 8 Bytes.

You can declare as follows:

Dim decAsdf as Single


Dim decAsdf as Double

Here is an example which displays a message box with the value of the variable after calculation. All you have to do is put it in a module and run it.

Sub doubleDataTypeExample()
Dim doubleTest As Double

doubleTest = 0.0000045 * 0.005 * 0.01

MsgBox "doubleTest = " & doubleTest
End Sub

Convert dictionary values into array

There is a ToArray() function on Values:

Foo[] arr = new Foo[dict.Count];    
dict.Values.CopyTo(arr, 0);

But I don't think its efficient (I haven't really tried, but I guess it copies all these values to the array). Do you really need an Array? If not, I would try to pass IEnumerable:

IEnumerable<Foo> foos = dict.Values;

How to see indexes for a database or table in MySQL?

Why not show create table myTable ?

Someone told me this but I didn't see anyone mention here, anything bad?

It's neat if you just want to take a glance at the indexes along with column infomations.

How to call a PHP function on the click of a button

To show $message in your input:

        $message= "The insert function is called.";
        $message="The select function is called.";

<form  method="post">
    <input type="text" name="txt" value="<?php if(isset($message)){ echo $message;}?>" >
    <input type="submit" name="insert" value="insert">
    <input type="submit" name="select" value="select" >

To use functioncalling.php as an external file you have to include it somehow in your HTML document.

Failed to execute 'postMessage' on 'DOMWindow': The target origin provided does not match the recipient window's origin ('null')

In my case SSL certificate was invalid for iframe domain, so make sure that iframe URL you're trying to send messages to is opening w/o any issues (in case you load your iframe over https).

Create a SQL query to retrieve most recent records

Another easy way:

SELECT Date, User, Status, Notes  
FROM Test_Most_Recent 
WHERE Date in ( SELECT MAX(Date) from Test_Most_Recent group by User)

jQuery scrollTop not working in Chrome but working in Firefox

If it work all fine for Mozilla, with html,body selector, then there is a good chance that the problem is related to the overflow, if the overflow in html or body is set to auto, then this will cause chrome to not work well, cause when it is set to auto, scrollTop property on animate will not work, i don't know exactly why! but the solution is to omit the overflow, don't set it! that solved it for me! if you are setting it to auto, take it off!

if you are setting it to hidden, then do as it is described in "user2971963" answer (ctrl+f to find it). hope this is useful!

Get skin path in Magento?

To get that file use the below code.


But it is not a correct way. To add your custom functions you can use the below file.


Kindly avoid to use the PHP function under skin dir.

Create a custom callback in JavaScript

When calling the callback function, we could use it like below:



// Callback function only know the action,
// but don't know what's the data.
function callbackFunction(unknown) {

// This is a consuming function.
function getInfo(thenCallback) {
  // When we define the function we only know the data but not
  // the action. The action will be deferred until excecuting.
  var info = 'I know now';
  if (typeof thenCallback === 'function') {

// Start.
getInfo(callbackFunction); // I know now

This is the Codepend with full example.

Python: subplot within a loop: first panel appears in wrong position

The problem is the indexing subplot is using. Subplots are counted starting with 1! Your code thus needs to read

fig=plt.figure(figsize=(15, 6),facecolor='w', edgecolor='k')
for i in range(10):

    #this part is just arranging the data for contourf 
    ind2 = py.find(zz==i+1)
    sfr_mass_mat = np.reshape(sfr_mass[ind2],(pixmax_x,pixmax_y))
    sfr_mass_sub = sfr_mass[ind2]
    zi = griddata(massloclist, sfrloclist, sfr_mass_sub,xi,yi,interp='nn')

    temp = 251+i  # this is to index the position of the subplot
    plt.subplots_adjust(hspace = .5,wspace=.001)

    #just annotating where each contour plot is being placed

Note the change in the line where you calculate temp

Convert Java Date to UTC String

If XStream is a dependency, try:

new com.thoughtworks.xstream.converters.basic.DateConverter().toString(date)

Pass parameter from a batch file to a PowerShell script

Assuming your script is something like the below snippet and named testargs.ps1

param ([string]$w)
Write-Output $w

You can call this at the commandline as:

PowerShell.Exe -File C:\scripts\testargs.ps1 "Test String"

This will print "Test String" (w/o quotes) at the console. "Test String" becomes the value of $w in the script.

What's the environment variable for the path to the desktop?

you could also open a DOS command prompt and execute the set command.

This will give you an idea what environment variables are available on your system.

E.g. - since you where specifically asking for a non-english Windows - heres is an example of my own German Edition (Window7-64bit) :

set > env.txt
type env.txt

CommonProgramFiles=C:\Program Files\Common Files
CommonProgramFiles(x86)=C:\Program Files (x86)\Common Files
CommonProgramW6432=C:\Program Files\Common Files
Path=C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Program Files\TortoiseSVN\bin;C:\Program Files (x86)\CMake 2.8\bin;C:\Program Files (x86)\emacs-22.3\bin;C:\Program Files (x86)\GnuWin32\bin;
PROCESSOR_IDENTIFIER=AMD64 Family 15 Model 67 Stepping 3, AuthenticAMD
ProgramFiles=C:\Program Files
ProgramFiles(x86)=C:\Program Files (x86)
ProgramW6432=C:\Program Files
VBOX_INSTALL_PATH=C:\Program Files\Sun\VirtualBox\
VS90COMNTOOLS=C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\Tools\

Android getting value from selected radiobutton

Thanks a lot to Chris.

This is my solution:

RadioGroup radgroup_opcionesEventos = null;

 private static String[] arrayEventos = {
            "Congestión", "Derrumbe", "Accidente"
    protected void onCreate(Bundle savedInstanceState)
        radgroup_opcionesEventos = (RadioGroup)findViewById(;
        int i=0;//
        for(String evento : arrayEventos) {
            //RadioButton nuevoRadio = crearRadioButton(evento);//a.old.ln
            RadioButton nuevoRadio = crearRadioButton(evento,i);//

        RadioButton primerRadio = (RadioButton) radgroup_opcionesEventos.getChildAt(0);

private RadioButton crearRadioButton(String evento, int n)
        //RadioButton nuevoRadio = new RadioButton(this);//a.old.ln
        RadioButton nuevoRadio = new RadioButton(getApplicationContext());//

        LinearLayout.LayoutParams params = new RadioGroup.LayoutParams(
        return nuevoRadio;

    protected void onResume()
        radgroup_opcionesEventos.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            public void onCheckedChanged(RadioGroup group, int checkedId) {
                RadioButton radioButton = (RadioButton) group.findViewById(checkedId);
                //int mySelectedIndex = (int) radioButton.getTag();
                String mySelectedIndex = radioButton.getTag().toString();

How do I catch an Ajax query post error?

In case you want to utilize .then() which has a subtle difference in comparison with .done() :

return $.post(url, payload)
    function (result, textStatus, jqXHR) {
        return result;
    function (jqXHR, textStatus, errorThrown) {
        return console.error(errorThrown);

You seem to not be depending on "@angular/core". This is an error

Try to run

npm install

in the project folder

When does Java's Thread.sleep throw InterruptedException?

The InterruptedException is usually thrown when a sleep is interrupted.

jQuery click not working for dynamically created items

I faced this problem a few days ago - the solution for me was to use .bind() to bind the required function to the dynamically created link.

var catLink = $('<a href="#" id="' + i + '" class="lnkCat">' + category.category + '</a>');
catLink.bind("click", function(){

getSubCategories : function(obj) {
 //do something

I hope this helps.

Fitting a histogram with python

Starting Python 3.8, the standard library provides the NormalDist object as part of the statistics module.

The NormalDist object can be built from a set of data with the NormalDist.from_samples method and provides access to its mean (NormalDist.mean) and standard deviation (NormalDist.stdev):

from statistics import NormalDist

# data = [0.7237248252340628, 0.6402731706462489, -1.0616113628912391, -1.7796451823371144, -0.1475852030122049, 0.5617952240065559, -0.6371760932160501, -0.7257277223562687, 1.699633029946764, 0.2155375969350495, -0.33371076371293323, 0.1905125348631894, -0.8175477853425216, -1.7549449090704003, -0.512427115804309, 0.9720486316086447, 0.6248742504909869, 0.7450655841312533, -0.1451632129830228, -1.0252663611514108]
norm = NormalDist.from_samples(data)
# NormalDist(mu=-0.12836704320073597, sigma=0.9240861018557649)
# -0.12836704320073597
# 0.9240861018557649

How to detect a docker daemon port

  1. Prepare extra configuration file. Create a file named /etc/systemd/system/docker.service.d/docker.conf. Inside the file docker.conf, paste below content:
ExecStart=/usr/bin/dockerd -H tcp:// -H unix:///var/run/docker.sock

Note that if there is no directory like docker.service.d or a file named docker.conf then you should create it.

  1. Restart Docker. After saving this file, reload the configuration by systemctl daemon-reload and restart Docker by systemctl restart docker.service.

  2. Check your Docker daemon. After restarting docker service, you can see the port in the output of systemctl status docker.service like /usr/bin/dockerd -H tcp:// -H unix:///var/run/docker.sock.

Hope this may help

Thank you!

How to log in to phpMyAdmin with WAMP, what is the username and password?


Username: root


(No password set)

In Java, how do I convert a byte array to a string of hex digits while keeping leading zeros?

String result = String.format("%0" + messageDigest.length + "s", hexString.toString())

That's the shortest solution given what you already have. If you could convert the byte array to a numeric value, String.format can convert it to a hex string at the same time.

Finding rows containing a value (or values) in any column

If you want to find the rows that have any of the values in a vector, one option is to loop the vector (lapply(v1,..)), create a logical index of (TRUE/FALSE) with (==). Use Reduce and OR (|) to reduce the list to a single logical matrix by checking the corresponding elements. Sum the rows (rowSums), double negate (!!) to get the rows with any matches.

indx1 <- !!rowSums(Reduce(`|`, lapply(v1, `==`, df)), na.rm=TRUE)

Or vectorise and get the row indices with which with arr.ind=TRUE

indx2 <- unique(which(Vectorize(function(x) x %in% v1)(df),


I didn't use @kristang's solution as it is giving me errors. Based on a 1000x500 matrix, @konvas's solution is the most efficient (so far). But, this may vary if the number of rows are increased

val <- paste0('M0', 1:1000)
df1 <-, NA), 1000*500, 
  replace=TRUE), ncol=500), stringsAsFactors=FALSE) 
v1 <- sample(val, 200, replace=FALSE)

 konvas <- function() {apply(df1, 1, function(r) any(r %in% v1))}
 akrun1 <- function() {!!rowSums(Reduce(`|`, lapply(v1, `==`, df1)),
 akrun2 <- function() {unique(which(Vectorize(function(x) x %in% 

 microbenchmark(konvas(), akrun1(), akrun2(), unit='relative', times=20L)
 #Unit: relative
 #   expr       min         lq       mean     median         uq      max   neval
 # konvas()   1.00000   1.000000   1.000000   1.000000   1.000000  1.00000    20
 # akrun1() 160.08749 147.642721 125.085200 134.491722 151.454441 52.22737    20
 # akrun2()   5.85611   5.641451   4.676836   5.330067   5.269937  2.22255    20
 # cld
 #  a 
 #  b
 #  a 

For ncol = 10, the results are slighjtly different:

expr       min        lq     mean    median        uq       max    neval
 konvas()  3.116722  3.081584  2.90660  2.983618  2.998343  2.394908    20
 akrun1() 27.587827 26.554422 22.91664 23.628950 21.892466 18.305376    20
 akrun2()  1.000000  1.000000  1.00000  1.000000  1.000000  1.000000    20


 v1 <- c('M017', 'M018')
 df <- structure(list(datetime = c("04.10.2009 01:24:51",
"04.10.2009 01:24:53", 
"04.10.2009 01:24:54", "04.10.2009 01:25:06", "04.10.2009 01:25:07", 
"04.10.2009 01:26:07", "04.10.2009 01:26:27", "04.10.2009 01:27:23", 
"04.10.2009 01:27:30", "04.10.2009 01:27:32", "04.10.2009 01:27:34"
), col1 = c("M017", "M018", "M051", "<NA>", "<NA>", "<NA>", "<NA>", 
"<NA>", "<NA>", "M017", "M051"), col2 = c("<NA>", "<NA>", "<NA>", 
"M016", "M015", "M017", "M017", "M017", "M017", "<NA>", "<NA>"
), col3 = c("<NA>", "<NA>", "<NA>", "<NA>", "<NA>", "<NA>", "<NA>", 
"<NA>", "<NA>", "<NA>", "<NA>"), col4 = c(NA, NA, NA, NA, NA, 
NA, NA, NA, NA, NA, NA)), .Names = c("datetime", "col1", "col2", 
"col3", "col4"), class = "data.frame", row.names = c("1", "2", 
"3", "4", "5", "6", "7", "8", "9", "10", "11"))

How do I display the current value of an Android Preference in the Preference summary?

According to Android docs you can use app:useSimpleSummaryProvider="true" in ListPreference and EditTextPreference components.

map vs. hash_map in C++

The C++ spec doesn't say exactly what algorithm you must use for the STL containers. It does, however, put certain constraints on their performance, which rules out the use of hash tables for map and other associative containers. (They're most commonly implemented with red/black trees.) These constraints require better worst-case performance for these containers than hash tables can deliver.

Many people really do want hash tables, however, so hash-based STL associative containers have been a common extension for years. Consequently, they added unordered_map and such to later versions of the C++ standard.

How to "test" NoneType in python?

Not sure if this answers the question. But I know this took me a while to figure out. I was looping through a website and all of sudden the name of the authors weren't there anymore. So needed a check statement.

if type(author) == type(None):
     my if body
    my else body

Author can be any variable in this case, and None can be any type that you are checking for.

Why is HttpContext.Current null?

In IIS7 with integrated mode, Current is not available in Application_Start. There is a similar thread here.

How do I set up IntelliJ IDEA for Android applications?

Just in case someone is lost. For both new application or existing ones go to File->Project Structure. Then in Project settings on the left pane select Project for the Java SDK and select Modules for Android SDK.

How to add new item to hash

Create hash as:

h =
=> {}

Now insert into hash as:

h = Hash["one" => 1]

How to bind Close command to a button

Actually, it is possible without C# code. The key is to use interactions:

<Button Content="Close">
    <i:EventTrigger EventName="Click">
      <ei:CallMethodAction TargetObject="{Binding ElementName=window}" MethodName="Close"/>

In order for this to work, just set the x:Name of your window to "window", and add these two namespaces:


This requires that you add the Expression Blend SDK DLL to your project, specifically Microsoft.Expression.Interactions.

In case you don't have Blend, the SDK can be downloaded here.

How can we print line numbers to the log in java

I use this little method that outputs the trace and line number of the method that called it.

 Log.d(TAG, "Where did i put this debug code again?   " + Utils.lineOut());

Double click the output to go to that source code line!

You might need to adjust the level value depending on where you put your code.

public static String lineOut() {
    int level = 3;
    StackTraceElement[] traces;
    traces = Thread.currentThread().getStackTrace();
    return (" at "  + traces[level] + " " );

Can I run multiple programs in a Docker container?

I had similar requirement of running a LAMP stack, Mongo DB and my own services

Docker is OS based virtualisation, which is why it isolates its container around a running process, hence it requires least one process running in FOREGROUND.

So you provide your own startup script as the entry point, thus your startup script becomes an extended Docker image script, in which you can stack any number of the services as far as AT LEAST ONE FOREGROUND SERVICE IS STARTED, WHICH TOO TOWARDS THE END

So my Docker image file has two line below in the very end:

COPY /usr/local/myscripts/
CMD ["/bin/bash", "/usr/local/myscripts/"]

In my script I run all MySQL, MongoDB, Tomcat etc. In the end I run my Apache as a foreground thread.

source /etc/apache2/envvars
/usr/sbin/apache2 -DFOREGROUND

This enables me to start all my services and keep the container alive with the last service started being in the foreground

Hope it helps

UPDATE: Since I last answered this question, new things have come up like Docker compose, which can help you run each service on its own container, yet bind all of them together as dependencies among those services, try knowing more about docker-compose and use it, it is more elegant way unless your need does not match with it.

How do I set path while saving a cookie value in JavaScript?

See for more documentation:

 setItem: function (sKey, sValue, vEnd, sPath, sDomain, bSecure) {  
     if (!sKey || /^(?:expires|max\-age|path|domain|secure)$/.test(sKey)) { return; }  
     var sExpires = "";  
     if (vEnd) {  
       switch (typeof vEnd) {  
         case "number": sExpires = "; max-age=" + vEnd; break;  
         case "string": sExpires = "; expires=" + vEnd; break;  
         case "object": if (vEnd.hasOwnProperty("toGMTString")) { sExpires = "; expires=" + vEnd.toGMTString(); } break;  
     document.cookie = escape(sKey) + "=" + escape(sValue) + sExpires + (sDomain ? "; domain=" + sDomain : "") + (sPath ? "; path=" + sPath : "") + (bSecure ? "; secure" : "");  

CSS3 transition on click using pure CSS

You can also affect differente DOM elements using :target pseudo class. If an element is the destination of an anchor target it will get the :target pseudo element.

p { color:black; }
p:target { color:red; }

<a href="#elem">Click me</a>
<p id="elem">And I will change</p>

Here is a fiddle :

Is there an XSLT name-of element?

<xsl:value-of select="name(.)" /> : <xsl:value-of select="."/>

How to set the context path of a web application in Tomcat 7.0

Simplest and flexible solution is below: Inside ${Tomcat_home}/config/server.xml

Change the autoDeploy="false" deployOnStartup="false" under Host element like below This is must.

<Host name="localhost"  appBase="webapps"
        unpackWARs="true" autoDeploy="false" deployOnStartup="false">

Add below line under Host element.

<Context path="" docBase="ServletInAction.war"  reloadable="true">

With the above approach we can add as many applications under webapps with different context path names.

How can I format my grep output to show line numbers at the end of the line, and also the hit count?

Or use awk instead:

awk '/null/ { counter++; printf("%s%s%i\n",$0, " - Line number: ", NR)} END {print "Total null count: " counter}' file

Remove credentials from Git

This error appears when you are using multiple Git accounts on the same machine.

If you are using macOS then you can remove the saved credentials of

Please follow below steps to remove the credentials.

  1. Open Keychain Access
  2. Find github
  3. Select the and Right click on it
  4. Delete ""
  5. Try again to Push or Pull to git and it will ask for the credentials.
  6. Enter valid credentials for repository account.
  7. Done

    enter image description here

Undocumented NSURLErrorDomain error codes (-1001, -1003 and -1004) using StoreKit

see NSURLError.h Define

NSURLErrorUnknown =             -1,
NSURLErrorCancelled =           -999,
NSURLErrorBadURL =              -1000,
NSURLErrorTimedOut =            -1001,
NSURLErrorUnsupportedURL =          -1002,
NSURLErrorCannotFindHost =          -1003,
NSURLErrorCannotConnectToHost =         -1004,
NSURLErrorNetworkConnectionLost =       -1005,
NSURLErrorDNSLookupFailed =         -1006,
NSURLErrorHTTPTooManyRedirects =        -1007,
NSURLErrorResourceUnavailable =         -1008,
NSURLErrorNotConnectedToInternet =      -1009,
NSURLErrorRedirectToNonExistentLocation =   -1010,
NSURLErrorBadServerResponse =       -1011,
NSURLErrorUserCancelledAuthentication =     -1012,
NSURLErrorUserAuthenticationRequired =  -1013,
NSURLErrorZeroByteResource =        -1014,
NSURLErrorCannotDecodeRawData =             -1015,
NSURLErrorCannotDecodeContentData =         -1016,
NSURLErrorCannotParseResponse =             -1017,
NSURLErrorAppTransportSecurityRequiresSecureConnection NS_ENUM_AVAILABLE(10_11, 9_0) = -1022,
NSURLErrorFileDoesNotExist =        -1100,
NSURLErrorFileIsDirectory =         -1101,
NSURLErrorNoPermissionsToReadFile =     -1102,
NSURLErrorDataLengthExceedsMaximum NS_ENUM_AVAILABLE(10_5, 2_0) =   -1103,

// SSL errors
NSURLErrorSecureConnectionFailed =      -1200,
NSURLErrorServerCertificateHasBadDate =     -1201,
NSURLErrorServerCertificateUntrusted =  -1202,
NSURLErrorServerCertificateHasUnknownRoot = -1203,
NSURLErrorServerCertificateNotYetValid =    -1204,
NSURLErrorClientCertificateRejected =   -1205,
NSURLErrorClientCertificateRequired =   -1206,
NSURLErrorCannotLoadFromNetwork =       -2000,

// Download and file I/O errors
NSURLErrorCannotCreateFile =        -3000,
NSURLErrorCannotOpenFile =          -3001,
NSURLErrorCannotCloseFile =         -3002,
NSURLErrorCannotWriteToFile =       -3003,
NSURLErrorCannotRemoveFile =        -3004,
NSURLErrorCannotMoveFile =          -3005,
NSURLErrorDownloadDecodingFailedMidStream = -3006,
NSURLErrorDownloadDecodingFailedToComplete =-3007,

NSURLErrorInternationalRoamingOff NS_ENUM_AVAILABLE(10_7, 3_0) =         -1018,
NSURLErrorCallIsActive NS_ENUM_AVAILABLE(10_7, 3_0) =                    -1019,
NSURLErrorDataNotAllowed NS_ENUM_AVAILABLE(10_7, 3_0) =                  -1020,
NSURLErrorRequestBodyStreamExhausted NS_ENUM_AVAILABLE(10_7, 3_0) =      -1021,

NSURLErrorBackgroundSessionRequiresSharedContainer NS_ENUM_AVAILABLE(10_10, 8_0) = -995,
NSURLErrorBackgroundSessionInUseByAnotherProcess NS_ENUM_AVAILABLE(10_10, 8_0) = -996,
NSURLErrorBackgroundSessionWasDisconnected NS_ENUM_AVAILABLE(10_10, 8_0)= -997,

What is the official name for a credit card's 3 digit code?

It is called the Card Security Code (CSC) according to Wikipedia, but has also been known as other things, such as the Card Verification Value (CVV) or Card Verfication Code (CVC).

The second code, and the most cited, is CVV2 or CVC2. This CSC (also known as a CCID or Credit Card ID) is often asked for by merchants for them to secure "card not present" transactions occurring over the Internet, by mail, fax or over the phone. In many countries in Western Europe, due to increased attempts at card fraud, it is now mandatory to provide this code when the cardholder is not present in person.

Because this seems to be known by multiple names, and its name doesn't seem to be printed on the card itself, you'll probably (unfortunately) still need to tell your users how to find the code - ie by describing it as the "3 digit code on back of card".

2018 update

The situation has not improved, and is now worse - there are even more different names now. However, you can if you like use different terms depending on the card type:

  • "CVC2" or "Card Validation Code" – MasterCard
  • "CVV2" or "Card Verification Value 2" – Visa
  • "CSC" or "Card Security Code" – American Express

Note that some American Express and Discover cards use a 4-digit code on the front of the card. See the above linked Wikipedia article for more.

How do I add a .click() event to an image?

<!DOCTYPE html>
<script src=""></script> 
<script type="text/javascript" src="jquery-2.1.0.js"></script> 
<script type="text/javascript" >
function openOnImageClick()
//alert("Jai Sh Raam");
// document.getElementById("images").src = "fruits.jpg";
 var img = document.createElement('img');
 img.setAttribute('src', 'tiger.jpg');
  img.setAttribute('width', '200');
   img.setAttribute('height', '150');



<h1>Screen Shot View</h1>
<p>Click the Tiger to display the Image</p>

<div id="images" >

<img src="tiger.jpg" width="100" height="50" alt="unfinished bingo card" onclick="openOnImageClick()" />
<img src="Logo1.jpg" width="100" height="50" alt="unfinished bingo card" onclick="openOnImageClick()" />


Index was outside the bounds of the Array. (Microsoft.SqlServer.smo)

It's very old problem with cashed content. MS planning to remove diagrams from SSMS, so they don't care about this. Anyway, solution exists.

Just close Diagrams tab and open it again. Works with SSMS 18.2.

Why dict.get(key) instead of dict[key]?

It allows you to provide a default value if the key is missing:

dictionary.get("bogus", default_value)

returns default_value (whatever you choose it to be), whereas


would raise a KeyError.

If omitted, default_value is None, such that

dictionary.get("bogus")  # <-- No default specified -- defaults to None

returns None just like

dictionary.get("bogus", None)


How can I check if a background image is loaded?

pure JS solution that will add preloader, set the background-image and then set it up for garbage collection along with it's event listener:

Short version:

const imageUrl = "";_x000D_
let bgElement = document.querySelector("body");_x000D_
let preloaderImg = document.createElement("img");_x000D_
preloaderImg.src = imageUrl;_x000D_
preloaderImg.addEventListener('load', (event) => {_x000D_ = `url(${imageUrl})`;_x000D_
    preloaderImg = null;_x000D_

A bit longer with nice opacity transition:

const imageUrl = "";_x000D_
let bgElement = document.querySelector(".bg-lazy");_x000D_
let preloaderImg = document.createElement("img");_x000D_
preloaderImg.src = imageUrl;_x000D_
preloaderImg.addEventListener('load', (event) => {_x000D_
  bgElement.classList.remove("bg-loading");_x000D_ = `url(${imageUrl})`;_x000D_
  preloaderImg = null;_x000D_
.bg-lazy {_x000D_
  height: 100vh;_x000D_
  width: 100vw;_x000D_
  transition: opacity 1s ease-out;_x000D_
.bg-loading {_x000D_
  opacity: 0;_x000D_
<div class="bg-lazy"></div>

What is the backslash character (\\)?

Imagine you are designing a programming language. You decide that Strings are enclosed in quotes ("Apple"). Then you hit your first snag: how to represent quotation marks since you've already used them ? Just out of convention you decide to use \" to represent quotation marks. Then you have a second problem: how to represent \ ? Again, out of convention you decide to use \\ instead. Thankfully, the process ends there and this is sufficient. You can also use what is called an escape sequence to represent other characters such as the carriage return (\n).

How to listen to the window scroll event in a VueJS component?

I think the best approach is just add ".passive"


No suitable driver found for 'jdbc:mysql://localhost:3306/mysql

A typographical error in the string describing the database driver can also produce the error.

A string specified as:


can result in a "no suitable driver found" error. The colon following "mysql" is missing in this example.

The correct driver string would be:


Loading another html page from javascript

Yes. In the javascript code:

window.location.href = "";

ImportError: No module named PIL

On windows, try checking the path to the location of the PIL library. On my system, I noticed the path was

\Python26\Lib\site-packages\pil instead of \Python26\Lib\site-packages\PIL  

after renaming the pil folder to PIL, I was able to load the PIL module.

Excel VBA, error 438 "object doesn't support this property or method

The Error is here

lastrow = wsPOR.Range("A" & Rows.Count).End(xlUp).Row + 1

wsPOR is a workbook and not a worksheet. If you are working with "Sheet1" of that workbook then try this

lastrow = wsPOR.Sheets("Sheet1").Range("A" & _
          wsPOR.Sheets("Sheet1").Rows.Count).End(xlUp).Row + 1


wsPOR.Range("A2:G" & lastrow).Select

should be

wsPOR.Sheets("Sheet1").Range("A2:G" & lastrow).Select

Batch file to copy files from one folder to another folder

If you want to copy file not using absolute path, relative path in other words:

Don't forget to write backslash in the path AND NOT slash


copy children-folder\file.something .\other-children-folder

PS: absolute path can be retrieved using these wildcards called "batch parameters"

@echo off
echo %%~dp0 is "%~dp0"
echo %%0 is "%0"
echo %%~dpnx0 is "%~dpnx0"
echo %%~f1 is "%~f1"
echo %%~dp0%%~1 is "%~dp0%~1"

Check documentation here about copy:

And also here for batch parameters documentation:

Replace tabs with spaces in vim

Once you've got expandtab on as per the other answers, the extremely convenient way to convert existing files according to your new settings is:


It will work on the current buffer.

Using TortoiseSVN how do I merge changes from the trunk to a branch and vice versa?

The behavior depends on which version your repository has. Subversion 1.5 allows 4 types of merge:

  1. merge sourceURL1[@N] sourceURL2[@M] [WCPATH]
  2. merge sourceWCPATH1@N sourceWCPATH2@M [WCPATH]
  3. merge [-c M[,N...] | -r N:M ...] SOURCE[@REV] [WCPATH]
  4. merge --reintegrate SOURCE[@REV] [WCPATH]

Subversion before 1.5 only allowed the first 2 formats.

Technically you can perform all merges with the first two methods, but the last two enable subversion 1.5's merge tracking.

TortoiseSVN's options merge a range or revisions maps to method 3 when your repository is 1.5+ or to method one when your repository is older.

When merging features over to a release/maintenance branch you should use the 'Merge a range of revisions' command.

Only when you want to merge all features of a branch back to a parent branch (commonly trunk) you should look into using 'Reintegrate a branch'.

And the last command -Merge two different trees- is only usefull when you want to step outside the normal branching behavior. (E.g. Comparing different releases and then merging the differenct to yet another branch)

Make body have 100% of the browser height




Print Combining Strings and Numbers

Using print function without parentheses works with older versions of Python but is no longer supported on Python3, so you have to put the arguments inside parentheses. However, there are workarounds, as mentioned in the answers to this question. Since the support for Python2 has ended in Jan 1st 2020, the answer has been modified to be compatible with Python3.

You could do any of these (and there may be other ways):

(1)  print("First number is {} and second number is {}".format(first, second))
(1b) print("First number is {first} and number is {second}".format(first=first, second=second)) 


(2) print('First number is', first, 'second number is', second) 

(Note: A space will be automatically added afterwards when separated from a comma)


(3) print('First number %d and second number is %d' % (first, second))


(4) print('First number is ' + str(first) + ' second number is' + str(second))

Using format() (1/1b) is preferred where available.

Python: get key of index in dictionary

Python dictionaries have a key and a value, what you are asking for is what key(s) point to a given value.

You can only do this in a loop:

[k for (k, v) in i.iteritems() if v == 0]

Note that there can be more than one key per value in a dict; {'a': 0, 'b': 0} is perfectly legal.

If you want ordering you either need to use a list or a OrderedDict instance instead:

items = ['a', 'b', 'c']
items.index('a') # gives 0
items[0]         # gives 'a'

How to get current date in 'YYYY-MM-DD' format in ASP.NET?

Might be worthwhile using the CultureInfo to apply DateTime formatting throughout the website. Insteado f running around formatting whever you have to.

CultureInfo.CurrentUICulture.DateTimeFormat.SetAllDateTimePatterns( ...


CultureInfo.CurrentUICulture.DateTimeFormat.ShortDatePattern = "yyyy-MM-dd"; 

Code should go somewhere in your Global.asax file

protected void Application_Start(){ ...

@Resource vs @Autowired

With @Resource you can do bean self-injection, it might be needed in order to run all extra logic added by bean post processors like transactional or security related stuff.

With Spring 4.3+ @Autowired is also capable of doing this.

Twitter Bootstrap add active class to li

None of these worked for me. My Bootstrap setup navigates to separate pages (so I can't do it on a click action, but the active class is removed on the navigation to a new page), and my urls don't match exactly. So here's what I did, based on my exception-based situation. Hope it helps others:

//Adding the active class to Twitter bootstrap navs, with a few alternate approaches

$(document).ready(function() {
  var rawhref = window.location.href; //raw current url 
  var newpage = ((window.location.href.match(/([^\/]*)\/?$/)[1]).substring(1)); //take only the last part of the url, and chop off the first char (substring), since the contains method below is case-sensitive. Don't need to do this if they match exactly.
  if (newpage == 'someNonMatchingURL') {  //deal with an exception literally
    newpage = 'matchingNavbarText'
  if (rawhref.indexOf('somePartofURL') != -1) { //look for a consistent part of the path in the raw url to deal with variable urls, etc.
    newpage = "moreMatchingNavbarText"
  $(".nav li a:contains('" + newpage + "')").parent().addClass('active'); //add the active class. Note that the contains method requires the goofy quote syntax to insert a variable.


CSS - Expand float child DIV height to parent's height

I have recently done this on my website using jQuery. The code calculates the height of the tallest div and sets the other divs to the same height. Here's the technique:

I don't believe height:100% will work, so if you don't explicitly know the div heights I don't think there is a pure CSS solution.

Can't open config file: /usr/local/ssl/openssl.cnf on Windows

The solution is running this command:

set OPENSSL_CONF=C:\OpenSSL-Win32\bin\openssl.cfg   


set OPENSSL_CONF=[path-to-OpenSSL-install-dir]\bin\openssl.cfg

in the command prompt before using openssl command.

Let openssl know for sure where to find its .cfg file.

Alternatively you could set the same variable OPENSSL_CONF in the Windows environment variables.

NOTE: This can happen when using the OpenSSL binary distribution from Shining Light Productions (a compiled + installer version of the official OpenSSL that is free to download & use). This distribution is "semi-officially" linked from OpenSSL's site as a "service primarily for operating systems where there are no pre-compiled OpenSSL packages".

ReferenceError: $ is not defined

Use Google CDN for fast loading:

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

How to measure elapsed time

When the game starts:

long tStart = System.currentTimeMillis();

When the game ends:

long tEnd = System.currentTimeMillis();
long tDelta = tEnd - tStart;
double elapsedSeconds = tDelta / 1000.0;

C#: Assign same value to multiple variables in single statement

Your example would be:

int num1 = 1;
int num2 = 1;

num1 = num2 = 5;

HTML button calling an MVC Controller and Action method

In case if you are getting an error as "unterminated string constant", use the following razor syntax :

<input type="button" onclick="@("location.href='"+ Url.Action("Index","Test")+ "'")" />

How do I change the UUID of a virtual disk?

Same solution as @Al3x for Windows x64, in cmd.exe:

cd %programfiles%\Oracle\VirtualBox

VBoxManage internalcommands sethduuid "full/path/to/.vdi"

This randomizes the UUID of the disk. Pro tip: Right click the .vdi file while holding shift and select "Copy as path" to obtain "full/path/to/.vdi" and enable quick edit in cmd.exe, then right click to paste.

scp from remote host to local host

There must be a user in the AllowUsers section, in the config file /etc/ssh/ssh_config, in the remote machine. You might have to restart sshd after editing the config file.

And then you can copy for example the file "test.txt" from a remote host to the local host

scp [email protected]:test.txt /local/dir

@cool_cs you can user ~ symbol ~/Users/djorge/Desktop if it's your home dir.

In UNIX, absolute paths must start with '/'.

html - table row like a link

The usual way is to assign some JavaScript to the onClick attribute of the TR element.

If you can't use JavaScript, then you must use a trick:

  1. Add the same link to each TD of the same row (the link must be the outermost element in the cell).

  2. Turn links into block elements: a { display: block; width: 100%; height: 100%; }

The latter will force the link to fill the whole cell so clicking anywhere will invoke the link.

TensorFlow not found using pip

You need a 64-bit version of Python and in your case are using a 32-bit version. As of now Tensorflow only supports 64-bit versions of Python 3.5.x and 3.8.x on Windows. See the install docs to see what is currently supported

To check which version of Python you are running, type python or python3 to start the interpreter, and then type import struct;print(struct.calcsize("P") * 8) and that will print either 32 or 64 to tell you which bit version of Python you are running.

From comments:

To download a different version of Python for Windows, go to and scroll down until you see the version you want that ends in a "64". That will be the 64 bit version that should work with tensorflow

Exercises to improve my Java programming skills

When learning a new language, there are some nice problem sets you can use to learn the language better.

  • Project Euler has some nice problems with a strong mathematical twist.
  • Practice on Google Code Jam past problems, stick to the qualification rounds for the easier problems

ggplot2 line chart gives "geom_path: Each group consist of only one observation. Do you need to adjust the group aesthetic?"

You get this error because one of your variables is actually a factor variable . Execute


to check this. Then do this double variable change to keep the year numbers instead of transforming into "1,2,3,4" level numbers:

df$year <- as.numeric(as.character(df$year))

EDIT: it appears that your data.frame has a variable of class "array" which might cause the pb. Try then:

df <- data.frame(apply(df, 2, unclass))

and plot again?

How to remove extension from string (only real extension!)

I found many examples on the Google but there are bad because just remove part of string with "."

Actually that is absolutely the correct thing to do. Go ahead and use that.

The file extension is everything after the last dot, and there is no requirement for a file extension to be any particular number of characters. Even talking only about Windows, it already comes with file extensions that don't fit 3-4 characters, such as eg. .manifest.

Using cURL with a username and password?

curl -X GET -u username:password  {{ }} -O

Floating point inaccuracy examples

Another example, in C

printf (" %.20f \n", 3.6);

incredibly gives


Removing duplicates from rows based on specific columns in an RDD/Spark DataFrame

This is my Df contain 4 is repeated twice so here will remove repeated values.

|    1|
|    4|
|    3|
|    5|
|    4|
|   18|

scala> val newdf=df.dropDuplicates

|    1|
|    3|
|    5|
|    4|
|   18|

Is it possible to install both 32bit and 64bit Java on Windows 7?

Yes, it is absolutely no problem. You could even have multiple versions of both 32bit and 64bit Java installed at the same time on the same machine.

In fact, i have such a setup myself.

Eclipse : Failed to connect to remote VM. Connection refused.

I faced the same issue. But i resolved it by changing my port numbers to different one.

How do I convert a string to enum in TypeScript?

If you provide string values to your enum, a straight cast works just fine.

enum Color {
  Green = "Green",
  Red = "Red"

const color = "Green";
const colorEnum = color as Color;

List of macOS text editors and code editors

My vote would be for BBedit's free little brother TextWrangler.

How to install MySQLdb package? (ImportError: No module named setuptools)

I resolved this issue on centos5.4 by running the following command to install setuptools

yum install python-setuptools

I hope that helps.

CLEAR SCREEN - Oracle SQL Developer shortcut?

Ctrl+Shift+D, but you have to put focus on the script output panel first...which you can do via the KB.

Run script.

Alt+PgDn     -  puts you in Script Output panel.
Ctrl+Shift+D -  clears panel.
Alt+PgUp     -  puts you back in editor panel. 

equivalent of rm and mv in windows .cmd

If you want to see a more detailed discussion of differences for the commands, see the Details about Differences section, below.

From the website1 (archived), specifically the Windows and Unix command line equivalents page (archived), I found the following2. There's a better/more complete table in the next edit.

Windows command     Unix command
rmdir               rmdir
rmdir /s            rm -r
move                mv

I'm interested to hear from @Dave and @javadba to hear how equivalent the commands are - how the "behavior and capabilities" compare, whether quite similar or "woefully NOT equivalent".

All I found out was that when I used it to try and recursively remove a directory and its constituent files and subdirectories, e.g.

(Windows cmd)>rmdir /s C:\my\dirwithsubdirs\

gave me a standard Windows-knows-better-than-you-do-are-you-sure message and prompt

dirwithsubdirs, Are you sure (Y/N)?

and that when I typed Y, the result was that my top directory and its constituent files and subdirectories went away.


I'm looking back at this after finding this answer. I retried each of the commands, and I'd change the table a little bit.

Windows command     Unix command
rmdir               rmdir
rmdir /s /q         rm -r
rmdir /s /q         rm -rf
rmdir /s            rm -ri
move                mv
del <file>          rm <file>

If you want the equivalent for

rm -rf

you can use

rmdir /s /q

or, as the author of the answer I sourced described,

But there is another "old school" way to do it that was used back in the day when commands did not have options to suppress confirmation messages. Simply ECHO the needed response and pipe the value into the command.

echo y | rmdir /s

Details about Differences

I tested each of the commands using Windows CMD and Cygwin (with its bash).

Before each test, I made the following setup.

Windows CMD

>mkdir this_directory
>echo some text stuff > this_directory/some.txt
>mkdir this_empty_directory

Cygwin bash

$ mkdir this_directory
$ echo "some text stuff" > this_directory/some.txt
$ mkdir this_empty_directory

That resulted in the following file structure for both.

|-- this_directory
|   `-- some.txt
`-- this_empty_directory

Here are the results. Note that I'll not mark each as CMD or bash; the CMD will have a > in front, and the bash will have a $ in front.


>rmdir this_directory
The directory is not empty.

>tree /a /f .
Folder PATH listing for volume Windows
Volume serial number is ¦¦¦¦¦¦¦¦ ¦¦¦¦:¦¦¦¦
|       some.txt

> rmdir this_empty_directory

>tree /a /f .
$ rmdir this_directory
rmdir: failed to remove 'this_directory': Directory not empty

$ tree --charset=ascii
|-- this_directory
|   `-- some.txt
`-- this_empty_directory

2 directories, 1 file

$ rmdir this_empty_directory

$ tree --charset=ascii
`-- this_directory
    `-- some.txt

RMDIR /S /Q and RM -R ; RM -RF

>rmdir /s /q this_directory

>tree /a /f

>rmdir /s /q this_empty_directory

>tree /a /f
No subfolders exist
$ rm -r this_directory

$ tree --charset=ascii
`-- this_empty_directory

$ rm -r this_empty_directory

$ tree --charset=ascii
0 directories, 0 files
$ rm -rf this_directory

$ tree --charset=ascii
`-- this_empty_directory

$ rm -rf this_empty_directory

$ tree --charset=ascii
0 directories, 0 files

RMDIR /S AND RM -RI Here, we have a bit of a difference, but they're pretty close.

>rmdir /s this_directory
this_directory, Are you sure (Y/N)? y

>tree /a /f

>rmdir /s this_empty_directory
this_empty_directory, Are you sure (Y/N)? y

>tree /a /f
No subfolders exist
$ rm -ri this_directory
rm: descend into directory 'this_directory'? y
rm: remove regular file 'this_directory/some.txt'? y
rm: remove directory 'this_directory'? y

$ tree --charset=ascii
`-- this_empty_directory

$ rm -ri this_empty_directory
rm: remove directory 'this_empty_directory'? y

$ tree --charset=ascii
0 directories, 0 files



  1. I know almost nothing about the LeMoDa website, other than the fact that the info is

Copyright © Ben Bullock 2009-2018. All rights reserved.

(archived copyright notice)

and that there seem to be a bunch of useful programming tips along with some humour (yes, the British spelling) and information on how to fix Japanese toilets. I also found some stuff talking about the "Ibaraki Report", but I don't know if that is the website.

I think I shall go there more often; it's quite useful. Props to Ben Bullock, whose email is on his page. If he wants me to remove this info, I will.

I will include the disclaimer (archived) from the site:

Disclaimer Please read the following disclaimer before using any of the computer program code on this site.

There Is No Warranty For The Program, To The Extent Permitted By Applicable Law. Except When Otherwise Stated In Writing The Copyright Holders And/Or Other Parties Provide The Program “As Is” Without Warranty Of Any Kind, Either Expressed Or Implied, Including, But Not Limited To, The Implied Warranties Of Merchantability And Fitness For A Particular Purpose. The Entire Risk As To The Quality And Performance Of The Program Is With You. Should The Program Prove Defective, You Assume The Cost Of All Necessary Servicing, Repair Or Correction.

In No Event Unless Required By Applicable Law Or Agreed To In Writing Will Any Copyright Holder, Or Any Other Party Who Modifies And/Or Conveys The Program As Permitted Above, Be Liable To You For Damages, Including Any General, Special, Incidental Or Consequential Damages Arising Out Of The Use Or Inability To Use The Program (Including But Not Limited To Loss Of Data Or Data Being Rendered Inaccurate Or Losses Sustained By You Or Third Parties Or A Failure Of The Program To Operate With Any Other Programs), Even If Such Holder Or Other Party Has Been Advised Of The Possibility Of Such Damages.

  1. Actually, I found the information with a Google search for "cmd equivalent of rm"

The information I'm sharing came up first.

Show and hide divs at a specific time interval using jQuery

here is a jQuery plugin I came up with:

$.fn.cycle = function(timeout){
    var $all_elem = $(this)

    show_cycle_elem = function(index){
        if(index == $all_elem.length) return; //you can make it start-over, if you want
        setTimeout(function(){show_cycle_elem(++index)}, timeout);

You need to have a common classname for all the divs you wan to cycle, use it like this:


Does the 'mutable' keyword have any purpose other than allowing the variable to be modified by a const function?

Mutable is for marking specific attribute as modifiable from within const methods. That is its only purpose. Think carefully before using it, because your code will probably be cleaner and more readable if you change the design rather than use mutable.

So if the above madness isn't what mutable is for, what is it for? Here's the subtle case: mutable is for the case where an object is logically constant, but in practice needs to change. These cases are few and far between, but they exist.

Examples the author gives include caching and temporary debugging variables.

Linq select to new object

Read : 101 LINQ Samples in that LINQ - Grouping Operators from Microsoft MSDN site

var x = from t in types  group t by t.Type
         into grp    
         select new { type = grp.key, count = grp.Count() };

forsingle object make use of stringbuilder and append it that will do or convert this in form of dictionary

    // fordictionary 
  var x = (from t in types  group t by t.Type
     into grp    
     select new { type = grp.key, count = grp.Count() })
   .ToDictionary( t => t.type, t => t.count); 

   //for stringbuilder not sure for this 
  var x = from t in types  group t by t.Type
         into grp    
         select new { type = grp.key, count = grp.Count() };
  StringBuilder MyStringBuilder = new StringBuilder();

  foreach (var res in x)
       //: is separator between to object
       MyStringBuilder.Append(result.Type +" , "+ result.Count + " : ");

How to finish Activity when starting other activity in Android?

Intent i = new Intent(this,Here is your first activity.Class);

"Missing return statement" within if / for / while

This will return the string only if the condition is true.

public String myMethod()
       return x;
       return "";

How to set a default value with Html.TextBoxFor?

This should work for MVC3 & MVC4

 @Html.TextBoxFor(m => m.Age, new { @Value = "12" }) 

If you want it to be a hidden field

 @Html.TextBoxFor(m => m.Age, new { @Value = "12",@type="hidden" }) 

How to make an anchor tag refer to nothing?

There are a few less than perfect solutions:

1. Link to a fake anchor

<a href="#">

Problem: clicking the link jumps back to the top of the page

2. Using a tag other than 'a'

Use a span tag and use the jquery to handle the click

Problem: breaks keyboard navigation, have to manually change the hover cursor

3. Link to a javascript void function

<a href="javascript:void(0);">
<a href="javascript:;">

Problem: breaks when linking images in IE


Since these all have their problems, the solution I've settled on is to link to a fake anchor, and then return false from the onClick method:

<a href="#" onClick="return false;">

Not the most concise of solutions, but it solves all the problems with the above methods.

Convert a binary NodeJS Buffer to JavaScript ArrayBuffer

No dependencies, fastest, Node.js 4.x and later

Buffers are Uint8Arrays, so you just need to slice (copy) its region of the backing ArrayBuffer.

// Original Buffer
let b = Buffer.alloc(512);
// Slice (copy) its segment of the underlying ArrayBuffer
let ab = b.buffer.slice(b.byteOffset, b.byteOffset + b.byteLength);

The slice and offset stuff is required because small Buffers (less than 4 kB by default, half the pool size) can be views on a shared ArrayBuffer. Without slicing, you can end up with an ArrayBuffer containing data from another Buffer. See explanation in the docs.

If you ultimately need a TypedArray, you can create one without copying the data:

// Create a new view of the ArrayBuffer without copying
let ui32 = new Uint32Array(b.buffer, b.byteOffset, b.byteLength / Uint32Array.BYTES_PER_ELEMENT);

No dependencies, moderate speed, any version of Node.js

Use Martin Thomson's answer, which runs in O(n) time. (See also my replies to comments on his answer about non-optimizations. Using a DataView is slow. Even if you need to flip bytes, there are faster ways to do so.)

Dependency, fast, Node.js = 0.12 or iojs 3.x

You can use to go in either direction (Buffer to ArrayBuffer and back). It's faster than the other answers posted here and is a well-written library. Node 0.12 through iojs 3.x require ngossen's fork (see this).

How to get the date 7 days earlier date from current date in Java

You can use this to continue using the type Date and a more legible code, if you preffer:

import org.apache.commons.lang.time.DateUtils;
Date yourDate = DateUtils.addDays(new Date(), *days here*);

Python 101: Can't open file: No such file or directory

I resolved this problem by navigating to C:\Python27\Scripts folder and then run file instead of C:\Python27 folder

jquery select option click handler

The problem that I had with the change handler was that it triggered on every keypress that I scrolled up and down the <select>.

I wanted to get the event for whenever an option was clicked or when enter was pressed on the desired option. This is how I ended up doing it:

let blockChange = false;

$element.keydown(function (e) {

    const keycode = (e.keyCode ? e.keyCode : e.which);

    // prevents select opening when enter is pressed
    if (keycode === 13) {

    // lets the change event know that these keypresses are to be ignored
    if([38, 40].indexOf(keycode) > -1){
        blockChange = true;


$element.keyup(function(e) {

    const keycode = (e.keyCode ? e.keyCode : e.which);
    // handle enter press
    if(keycode === 13) {


$element.change(function(e) {

    // this effective handles the click only as preventDefault was used on enter
    if(!blockChange) {
    blockChange = false;


C# equivalent to Java's charAt()?

please try to make it as a character

string str = "Tigger";
//then str[0] will return 'T' not "T"

How to use Angular2 templates with *ngFor to create a table out of nested arrays?

You can use the template syntax of ngFor on groups and the usual syntax inside it for the actual rows like:

  <template let-group ngFor [ngForOf]="groups">
    <tr *ngFor="let row of group.items">{{row}}</tr>

Check this plunk

How can I get device ID for Admob

Something similar to Google Ads, from the documentation:

public AdRequest.Builder addTestDevice (String deviceId)

Causes a device to receive test ads. The deviceId can be obtained by viewing the logcat output after creating a new ad. For emulators, use DEVICE_ID_EMULATOR.

for example my Test Device id displayed in LogCat is "B86BC9402A69B031A516BC57F7D3063F":

AdRequest adRequest = new AdRequest.Builder() 

Maven: How to include jars, which are not available in reps into a J2EE project?

@Ric Jafe's solution is what worked for me.

This is exactly what I was looking for. A way to push it through for research test code. Nothing fancy. Yeah I know that that's what they all say :) The various maven plugin solutions seem to be overkill for my purposes. I have some jars that were given to me as 3rd party libs with a pom file. I want it to compile/run quickly. This solution which I trivially adapted to python worked wonders for me. Cut and pasted into my pom. Python/Perl code for this task is in this Q&A: Can I add jars to maven 2 build classpath without installing them?

def AddJars(jarList):
  s1 = ''
  for elem in jarList:
   s1+= """
     </dependency>\n"""%(elem, elem)
  return s1

Can I add a custom attribute to an HTML tag?

You can add custom attributes to your elements at will. But that will make your document invalid.

In HTML 5 you will have the opportunity to use custom data attributes prefixed with data-.

How to remove all the null elements inside a generic list in one go?

There is another simple and elegant option:


This will remove all elements that are not of type EmailParameterClass which will obviously filter out any elements of type null.

Here's a test:

class Test { }
class Program
    static void Main(string[] args)
        var list = new List<Test>();
        Console.WriteLine(list.OfType<Test>().Count());// 0
        list.Add(new Test());
        Console.WriteLine(list.OfType<Test>().Count());// 1
        Test test = null;
        Console.WriteLine(list.OfType<Test>().Count());// 1

UnsatisfiedDependencyException: Error creating bean with name 'entityManagerFactory'

The MySQL dependency should be like the following syntax in the pom.xml file.


Make sure the syntax, groupId, artifactId, Version has included in the dependancy.

Best practices for circular shift (rotate) operations in C++

Below is a slightly improved version of Dídac Pérez's answer, with both directions implemented, along with a demo of these functions' usages using unsigned char and unsigned long long values. Several notes:

  1. The functions are inlined for compiler optimizations
  2. I used a cout << +value trick for tersely outputting an unsigned char numerically that I found here:
  3. I recommend using the explicit <put the type here> syntax for clarity and safety.
  4. I used unsigned char for the shiftNum parameter because of what I found in the Additional Details section here:

The result of a shift operation is undefined if additive-expression is negative or if additive-expression is greater than or equal to the number of bits in the (promoted) shift-expression.

Here's the code I'm using:

#include <iostream>

using namespace std;

template <typename T>
inline T rotateAndCarryLeft(T rotateMe, unsigned char shiftNum)
    static const unsigned char TBitCount = sizeof(T) * 8U;

    return (rotateMe << shiftNum) | (rotateMe >> (TBitCount - shiftNum));

template <typename T>
inline T rotateAndCarryRight(T rotateMe, unsigned char shiftNum)
    static const unsigned char TBitCount = sizeof(T) * 8U;

    return (rotateMe >> shiftNum) | (rotateMe << (TBitCount - shiftNum));

void main()
    //00010100 == (unsigned char)20U
    //00000101 == (unsigned char)5U == rotateAndCarryLeft(20U, 6U)
    //01010000 == (unsigned char)80U == rotateAndCarryRight(20U, 6U)

    cout << "unsigned char " << 20U << " rotated left by 6 bits == " << +rotateAndCarryLeft<unsigned char>(20U, 6U) << "\n";
    cout << "unsigned char " << 20U << " rotated right by 6 bits == " << +rotateAndCarryRight<unsigned char>(20U, 6U) << "\n";

    cout << "\n";

    for (unsigned char shiftNum = 0U; shiftNum <= sizeof(unsigned char) * 8U; ++shiftNum)
        cout << "unsigned char " << 21U << " rotated left by " << +shiftNum << " bit(s) == " << +rotateAndCarryLeft<unsigned char>(21U, shiftNum) << "\n";

    cout << "\n";

    for (unsigned char shiftNum = 0U; shiftNum <= sizeof(unsigned char) * 8U; ++shiftNum)
        cout << "unsigned char " << 21U << " rotated right by " << +shiftNum << " bit(s) == " << +rotateAndCarryRight<unsigned char>(21U, shiftNum) << "\n";

    cout << "\n";

    for (unsigned char shiftNum = 0U; shiftNum <= sizeof(unsigned long long) * 8U; ++shiftNum)
        cout << "unsigned long long " << 3457347ULL << " rotated left by " << +shiftNum << " bit(s) == " << rotateAndCarryLeft<unsigned long long>(3457347ULL, shiftNum) << "\n";

    cout << "\n";

    for (unsigned char shiftNum = 0U; shiftNum <= sizeof(unsigned long long) * 8U; ++shiftNum)
        cout << "unsigned long long " << 3457347ULL << " rotated right by " << +shiftNum << " bit(s) == " << rotateAndCarryRight<unsigned long long>(3457347ULL, shiftNum) << "\n";

    cout << "\n\n";

How do I ignore ampersands in a SQL script running from SQL Plus?

set define off <- This is the best solution I found

I also tried...

set define }

I was able to insert several records containing ampersand characters '&' but I cannot use the '}' character into the text So I decided to use "set define off" and everything works as it should.

Twitter Bootstrap Form File Element Upload Button



<input type="file" class="filestyle" data-input="false">

How to select id with max date group by category in PostgreSQL?

Try this one:

SELECT t1.* FROM Table1 t1
   SELECT category, MAX(date) AS MAXDATE
   FROM Table1
   GROUP BY category
) t2
ON T1.category = t2.category

See this SQLFiddle

splitting a string into an array in C++ without using vector

Here's a suggestion: use two indices into the string, say start and end. start points to the first character of the next string to extract, end points to the character after the last one belonging to the next string to extract. start starts at zero, end gets the position of the first char after start. Then you take the string between [start..end) and add that to your array. You keep going until you hit the end of the string.

Can an XSLT insert the current date?

Late answer, but my solution works in Eclipse XSLT. Eclipse uses XSLT 1 at time of this writing. You can install an XSLT 2 engine like Saxon. Or you can use the XSLT 1 solution below to insert current date and time.

<xsl:value-of select=""/>

This will call Java's Data class to output the date. It will not work unless you also put the following "java:" definition in your <xsl:stylesheet> tag.

<xsl:stylesheet [...snip...]

I hope that helps someone. This simple answer was difficult to find for me.

How to Run a jQuery or JavaScript Before Page Start to Load

This should do the trick:

window.onload = function(event) {

Good luck  ;)

ProgressDialog in AsyncTask

AsyncTask is very helpful!

class QueryBibleDetail extends AsyncTask<Integer, Integer, String>{
        private Activity activity;
        private ProgressDialog dialog;
        private Context context;

        public QueryBibleDetail(Activity activity){
            this.activity = activity;
            this.context = activity;
            this.dialog = new ProgressDialog(activity);

        protected String doInBackground(Integer... params) {

            if(sectionFromID > sectionToID){
                return "";

            String queryBible = "action=query_bible&article="+chapterID+"&id="+tomeID+"&verse_start="+sectionFromID+"&verse_stop="+sectionToID+"";
                String bible = (Json.getRequest(HOST+queryBible)).trim();
                bible = android.text.Html.fromHtml(bible).toString();
                return bible;
            }catch(Exception e){
            return null;

        protected void onPostExecute(String bible){
            TextView bibleBox = (TextView) findViewById(;

How to play YouTube video in my Android application?


  1. Create a new Activity, for your player(fullscreen) screen with menu options. Run the mediaplayer and UI in different threads.

  2. For playing media - In general to play audio/video there is mediaplayer api in android. FILE_PATH is the path of file - may be url(youtube) stream or local file path

     MediaPlayer mp = new MediaPlayer();

Also check: Android YouTube app Play Video Intent have already discussed this in detail.

how do you insert null values into sql server


What exactly are iterator, iterable, and iteration?

For me, Python's glossery was most helpful for these questions, e.g. for iterable it says:

An object capable of returning its members one at a time. Examples of iterables include all sequence types (such as list, str, and tuple) and some non-sequence types like dict, file objects, and objects of any classes you define with an iter() method or with a getitem() method that implements Sequence semantics.

Iterables can be used in a for loop and in many other places where a sequence is needed (zip(), map(), …). When an iterable object is passed as an argument to the built-in function iter(), it returns an iterator for the object. This iterator is good for one pass over the set of values. When using iterables, it is usually not necessary to call iter() or deal with iterator objects yourself. The for statement does that automatically for you, creating a temporary unnamed variable to hold the iterator for the duration of the loop. See also iterator, sequence, and generator.

SQL Server : SUM() of multiple rows including where clauses

Try this:

   SUM(Amount) as TOTAL_COSTS
   EndDate IS NULL

What is Options +FollowSymLinks?

You might try searching the internet for ".htaccess Options not allowed here".

A suggestion I found (using google) is:

Check to make sure that your httpd.conf file has AllowOverride All.

A .htaccess file that works for me on Mint Linux (placed in the Laravel /public folder):

# Apache configuration file

# Turning on the rewrite engine is necessary for the following rules and
# features. "+FollowSymLinks" must be enabled for this to work symbolically.

<IfModule mod_rewrite.c>
    Options +FollowSymLinks
    RewriteEngine On

# For all files not found in the file system, reroute the request to the
# "index.php" front controller, keeping the query string intact

<IfModule mod_rewrite.c>
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ index.php/$1 [L]

Hope this helps you. Otherwise you could ask a question on the Laravel forum (, there are some really helpful people hanging around there.

How do I install and use the ASP.NET AJAX Control Toolkit in my .NET 3.5 web applications?

You can easily install it by writing

Install-Package AjaxControlToolkit in package manager console.

for more information you can check this link

Django CSRF Cookie Not Set

from django.http import HttpResponse
from django.views.decorators.csrf import csrf_exempt

def your_view(request):
    if request.method == "POST":
        # do something
    return HttpResponse("Your response")

Hibernate: How to fix "identifier of an instance altered from X to Y"?

In my case, a template had a typo so instead of checking for equivalency (==) it was using an assignment equals (=).

So I changed the template logic from:

if ( = ...


if ( == ...

and now everything is fine. So, check your views as well!

git - pulling from specific branch

Laravel documentation example:

git pull 5.8

based on the command format:

git pull origin <branch>

How would I get everything before a : in a string Python

You don't need regex for this

>>> s = "Username: How are you today?"

You can use the split method to split the string on the ':' character

>>> s.split(':')
['Username', ' How are you today?']

And slice out element [0] to get the first part of the string

>>> s.split(':')[0]

How to install Python package from GitHub?

You need to use the proper git URL:

pip install git+

Also see the VCS Support section of the pip documentation.

Don’t forget to include the egg=<projectname> part to explicitly name the project; this way pip can track metadata for it without having to have run the script.

How does a Linux/Unix Bash script know its own PID?

The variable '$$' contains the PID.

What is an example of the Liskov Substitution Principle?

Long story short, let's leave rectangles rectangles and squares squares, practical example when extending a parent class, you have to either PRESERVE the exact parent API or to EXTEND IT.

Let's say you have a base ItemsRepository.

class ItemsRepository
    * @return int Returns number of deleted rows
    public function delete()
        // perform a delete query
        $numberOfDeletedRows = 10;

        return $numberOfDeletedRows;

And a sub class extending it:

class BadlyExtendedItemsRepository extends ItemsRepository
     * @return void Was suppose to return an INT like parent, but did not, breaks LSP
    public function delete()
        // perform a delete query
        $numberOfDeletedRows = 10;

        // we broke the behaviour of the parent class

Then you could have a Client working with the Base ItemsRepository API and relying on it.

 * Class ItemsService is a client for public ItemsRepository "API" (the public delete method).
 * Technically, I am able to pass into a constructor a sub-class of the ItemsRepository
 * but if the sub-class won't abide the base class API, the client will get broken.
class ItemsService
     * @var ItemsRepository
    private $itemsRepository;

     * @param ItemsRepository $itemsRepository
    public function __construct(ItemsRepository $itemsRepository)
        $this->itemsRepository = $itemsRepository;

     * !!! Notice how this is suppose to return an int. My clients expect it based on the
     * ItemsRepository API in the constructor !!!
     * @return int
    public function delete()
        return $this->itemsRepository->delete();

The LSP is broken when substituting parent class with a sub class breaks the API's contract.

class ItemsController
     * Valid delete action when using the base class.
    public function validDeleteAction()
        $itemsService = new ItemsService(new ItemsRepository());
        $numberOfDeletedItems = $itemsService->delete();

        // $numberOfDeletedItems is an INT :)

     * Invalid delete action when using a subclass.
    public function brokenDeleteAction()
        $itemsService = new ItemsService(new BadlyExtendedItemsRepository());
        $numberOfDeletedItems = $itemsService->delete();

        // $numberOfDeletedItems is a NULL :(

You can learn more about writing maintainable software in my course:

SPA best practices for authentication and session management

You can increase security in authentication process by using JWT (JSON Web Tokens) and SSL/HTTPS.

The Basic Auth / Session ID can be stolen via:

  • MITM attack (Man-In-The-Middle) - without SSL/HTTPS
  • An intruder gaining access to a user's computer
  • XSS

By using JWT you're encrypting the user's authentication details and storing in the client, and sending it along with every request to the API, where the server/API validates the token. It can't be decrypted/read without the private key (which the server/API stores secretly) Read update.

The new (more secure) flow would be:


  • User logs in and sends login credentials to API (over SSL/HTTPS)
  • API receives login credentials
  • If valid:
    • Register a new session in the database Read update
    • Encrypt User ID, Session ID, IP address, timestamp, etc. in a JWT with a private key.
  • API sends the JWT token back to the client (over SSL/HTTPS)
  • Client receives the JWT token and stores in localStorage/cookie

Every request to API

  • User sends a HTTP request to API (over SSL/HTTPS) with the stored JWT token in the HTTP header
  • API reads HTTP header and decrypts JWT token with its private key
  • API validates the JWT token, matches the IP address from the HTTP request with the one in the JWT token and checks if session has expired
  • If valid:
    • Return response with requested content
  • If invalid:
    • Throw exception (403 / 401)
    • Flag intrusion in the system
    • Send a warning email to the user.

Updated 30.07.15:

JWT payload/claims can actually be read without the private key (secret) and it's not secure to store it in localStorage. I'm sorry about these false statements. However they seem to be working on a JWE standard (JSON Web Encryption).

I implemented this by storing claims (userID, exp) in a JWT, signed it with a private key (secret) the API/backend only knows about and stored it as a secure HttpOnly cookie on the client. That way it cannot be read via XSS and cannot be manipulated, otherwise the JWT fails signature verification. Also by using a secure HttpOnly cookie, you're making sure that the cookie is sent only via HTTP requests (not accessible to script) and only sent via secure connection (HTTPS).

Updated 17.07.16:

JWTs are by nature stateless. That means they invalidate/expire themselves. By adding the SessionID in the token's claims you're making it stateful, because its validity doesn't now only depend on signature verification and expiry date, it also depends on the session state on the server. However the upside is you can invalidate tokens/sessions easily, which you couldn't before with stateless JWTs.

How can I easily switch between PHP versions on Mac OSX?

Example: Let us switch from php 7.4 to 7.3

brew unlink [email protected]
brew install [email protected]
brew link [email protected]

If you get Warning: [email protected] is keg-only and must be linked with --force Then try with:

brew link [email protected] --force

How do I detect unsigned integer multiply overflow?

You can't access the overflow flag from C/C++.

I don't agree with this. You could write some inline assembly language and use a jo (jump overflow) instruction assuming you are on x86 to trap the overflow. Of course, your code would no longer be portable to other architectures.

Look at info as and info gcc.

Foreach loop in java for a custom object list

You can fix your example with the iterator pattern by changing the parametrization of the class:

List<Room> rooms = new ArrayList<Room>();
for(Iterator<Room> i = rooms.iterator(); i.hasNext(); ) {
  String item =;

or much simpler way:

List<Room> rooms = new ArrayList<Room>();
for(Room room : rooms) {

Restrict SQL Server Login access to only one database

For anyone else out there wondering how to do this, I have the following solution for SQL Server 2008 R2 and later:

USE master

This will address exactly the requirement outlined above..

How to decode JWT Token?

new JwtSecurityTokenHandler().ReadToken("") will return a SecurityToken

new JwtSecurityTokenHandler().ReadJwtToken("") will return a JwtSecurityToken

If you just change the method you are using you can avoid the cast in the above answer

handle textview link click in my android app

I changed the TextView's color to blue by using for example:


in the xml file. How to make it underlined is explained here.

Then use its onClick property to specify a method (I'm guessing you could call setOnClickListener(this) as another way), e.g.:

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

In that method, I can do whatever I want as normal, such as launch an intent. Note that you still have to do the normal myTextView.setMovementMethod(LinkMovementMethod.getInstance()); thing, like in your acitivity's onCreate() method.

TypeScript - Append HTML to container element in Angular 2

When working with Angular the recent update to Angular 8 introduced that a static property inside @ViewChild() is required as stated here and here. Then your code would require this small change:

@ViewChild('one') d1:ElementRef;


// query results available in ngOnInit
@ViewChild('one', {static: true}) foo: ElementRef;


// query results available in ngAfterViewInit
@ViewChild('one', {static: false}) foo: ElementRef;

Pandas df.to_csv("file.csv" encode="utf-8") still gives trash characters for minus sign

Your "bad" output is UTF-8 displayed as CP1252.

On Windows, many editors assume the default ANSI encoding (CP1252 on US Windows) instead of UTF-8 if there is no byte order mark (BOM) character at the start of the file. While a BOM is meaningless to the UTF-8 encoding, its UTF-8-encoded presence serves as a signature for some programs. For example, Microsoft Office's Excel requires it even on non-Windows OSes. Try:


That encoder will add the BOM.

javascript getting my textbox to display a variable

Even if this is already answered (1 year ago) you could also let the fields be calculated automatically.


        <td><input type="text" value="" ></td>
        <td><input type="text" class="class_name" placeholder="bla bla"/></td>
        <td><input type="text" value="" ></td>
        <td><input type="text" class="class_name" placeholder="bla bla."/></td>

The script

            function calculateSum(){
                var sum=0;
                    if(!isNaN(this.value) && this.value.length!=0){
                    else if(isNaN(this.value)) {
                        alert("Maybe an alert if they type , instead of .");

Ansible - read inventory hosts and variables to group_vars/all file

If you want to have your vars in files under group_vars, just move them here. Vars can be in the inventory ([group:vars] section) but also (and foremost) in files under group_vars or hosts_vars.

For instance, with your example above, you can move your vars for group tests in the file group_vars/tests :

Inventory file :







group_vars/tests file :


Fragments within Fragments

I've faced with the same problem, have struggled a couple of day with it and should say that the most easiest way to overcome I found this is to use fragment.hide() / when tab is selected/unselected().

public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft)
    if (mFragment != null)

When screen rotation occurs all parent and child fragments get correctly destroyed.

This approach has also one additional advantage - using hide()/show() does not cause fragment views to loose their state, so there is no need to restore the previous scroll position for ScrollViews for example.

The problem is that I don't know whether it is correct to not detach fragments when they are not visible. I think the official example of TabListener is designed with a thought in mind that fragments are reusable and you should not pollute with them memory, however, I think if you have just a few tabs and you know that users will be switching between them frequently it will be appropriate to keep them attached to the current activity.

I would like to hear comments from more experienced developers.

MySQL JOIN with LIMIT 1 on joined table

I would try something like this:

      (SELECT, P.title 
       FROM products as P
       WHERE P.category_id =
       LIMIT 1)
FROM categories C

Sass calculate percent minus px

There is a calc function in both SCSS [compile-time] and CSS [run-time]. You're likely invoking the former instead of the latter.

For obvious reasons mixing units won't work compile-time, but will at run-time.

You can force the latter by using unquote, a SCSS function.

.selector { height: unquote("-webkit-calc(100% - 40px)"); }

Android Studio marks R in red with error message "cannot resolve symbol R", but build succeeds

The solution is simple:

Go to File > Project Structure > app and choose the Flavours tab, select API 21: Android 5.0 (Lollipop) in the drop down list for Min Sdk Version.

How can I determine the direction of a jQuery scroll event?

Why nobody use the event object returned by jQuery on scroll ?

$window.on('scroll', function (event) {'Scroll');'Scroll event:', event);'Position:', this.pageYOffset);'Direction:', event.originalEvent.dir); // Here is the direction

I'm using chromium and I didn't checked on other browsers if they have the dir property.

how to set JAVA_OPTS for Tomcat in Windows?

This is because, the amount of memory you wish to assign for JVM is not available or may be you are assigning more than available memory. Try small size then u can see the difference.

set JAVA_OPTS=-Xms128m -Xmx512m -XX:PermSize=128m

How to set custom header in Volley Request

public class CustomJsonObjectRequest  extends JsonObjectRequest
    public CustomJsonObjectRequest(int method, String url, JSONObject jsonRequest,Response.Listener listener, Response.ErrorListener errorListener)
        super(method, url, jsonRequest, listener, errorListener);

public Map getHeaders() throws AuthFailureError {
    Map headers = new HashMap();
    headers.put("AppId", "xyz");

    return headers;


How to pass parameters using ui-sref in ui-router to controller

You simply misspelled $stateParam, it should be $stateParams (with an s). That's why you get undefined ;)

How to implement a confirmation (yes/no) DialogPreference?

That is a simple alert dialog, Federico gave you a site where you can look things up.

Here is a short example of how an alert dialog can be built.

new AlertDialog.Builder(this)
.setMessage("Do you really want to whatever?")
.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {

    public void onClick(DialogInterface dialog, int whichButton) {
        Toast.makeText(MainActivity.this, "Yaay", Toast.LENGTH_SHORT).show();
 .setNegativeButton(, null).show();

gitbash command quick reference

from within the git bash shell type:

>cd /bin
>ls -l

You will then see a long listing of all the unix-like commands available. There are lots of goodies in there.