Programs & Examples On #Geolocation

Geolocation is the identification of the real-world geographic location of an object, such as a cell phone or an Internet-connected computer terminal. Use [w3c-geolocation] for questions about the W3C Geolocation API.

J2ME/Android/BlackBerry - driving directions, route between two locations

J2ME Map Route Provider has a navigation service which can provide you route information in KML format.

To get kml file we need to form url with start and destination locations:

public static String getUrl(double fromLat, double fromLon,
                            double toLat, double toLon) {// connect to map web service
    StringBuffer urlString = new StringBuffer();
    urlString.append("&saddr=");// from
    urlString.append("&daddr=");// to
    return urlString.toString();

Next you will need to parse xml (implemented with SAXParser) and fill data structures:

public class Point {
    String mName;
    String mDescription;
    String mIconUrl;
    double mLatitude;
    double mLongitude;

public class Road {
    public String mName;
    public String mDescription;
    public int mColor;
    public int mWidth;
    public double[][] mRoute = new double[][] {};
    public Point[] mPoints = new Point[] {};

Network connection is implemented in different ways on Android and Blackberry, so you will have to first form url:

 public static String getUrl(double fromLat, double fromLon,
     double toLat, double toLon)

then create connection with this url and get InputStream.
Then pass this InputStream and get parsed data structure:

 public static Road getRoute(InputStream is) 

Full source code


class MapPathScreen extends MainScreen {
    MapControl map;
    Road mRoad = new Road();
    public MapPathScreen() {
        double fromLat = 49.85, fromLon = 24.016667;
        double toLat = 50.45, toLon = 30.523333;
        String url = RoadProvider.getUrl(fromLat, fromLon, toLat, toLon);
        InputStream is = getConnection(url);
        mRoad = RoadProvider.getRoute(is);
        map = new MapControl();
        add(new LabelField(mRoad.mName));
        add(new LabelField(mRoad.mDescription));
    protected void onUiEngineAttached(boolean attached) {
        if (attached) {
    private InputStream getConnection(String url) {
        HttpConnection urlConnection = null;
        InputStream is = null;
        try {
            urlConnection = (HttpConnection);
            is = urlConnection.openInputStream();
        } catch (IOException e) {
        return is;

See full code on J2MEMapRouteBlackBerryEx on Google Code


Android G1 screenshot

public class MapRouteActivity extends MapActivity {
    LinearLayout linearLayout;
    MapView mapView;
    private Road mRoad;
    public void onCreate(Bundle savedInstanceState) {
        mapView = (MapView) findViewById(;
        new Thread() {
            public void run() {
                double fromLat = 49.85, fromLon = 24.016667;
                double toLat = 50.45, toLon = 30.523333;
                String url = RoadProvider
                        .getUrl(fromLat, fromLon, toLat, toLon);
                InputStream is = getConnection(url);
                mRoad = RoadProvider.getRoute(is);

    Handler mHandler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            TextView textView = (TextView) findViewById(;
            textView.setText(mRoad.mName + " " + mRoad.mDescription);
            MapOverlay mapOverlay = new MapOverlay(mRoad, mapView);
            List<Overlay> listOfOverlays = mapView.getOverlays();

    private InputStream getConnection(String url) {
        InputStream is = null;
        try {
            URLConnection conn = new URL(url).openConnection();
            is = conn.getInputStream();
        } catch (MalformedURLException e) {
        } catch (IOException e) {
        return is;
    protected boolean isRouteDisplayed() {
        return false;

See full code on J2MEMapRouteAndroidEx on Google Code

Get current location of user in Android without using GPS or internet

Here possible to get the User current location Without the use of GPS and Network Provider.

1 . Convert cellLocation to real location (Latitude and Longitude), using ""

2.Click Here For Your Reference

How to display my location on Google Maps for Android API v2

Java code:

public class MapActivity extends FragmentActivity implements LocationListener  {

    GoogleMap googleMap;
    LatLng myPosition;

    protected void onCreate(Bundle savedInstanceState) {

        // Getting reference to the SupportMapFragment of activity_main.xml
        SupportMapFragment fm = (SupportMapFragment)

        // Getting GoogleMap object from the fragment
        googleMap = fm.getMap();

        // Enabling MyLocation Layer of Google Map

        // Getting LocationManager object from System Service LOCATION_SERVICE
        LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

        // Creating a criteria object to retrieve provider
        Criteria criteria = new Criteria();

        // Getting the name of the best provider
        String provider = locationManager.getBestProvider(criteria, true);

        // Getting Current Location
        Location location = locationManager.getLastKnownLocation(provider);

        if (location != null) {
            // Getting latitude of the current location
            double latitude = location.getLatitude();

            // Getting longitude of the current location
            double longitude = location.getLongitude();

            // Creating a LatLng object for the current location
            LatLng latLng = new LatLng(latitude, longitude);

            myPosition = new LatLng(latitude, longitude);

            googleMap.addMarker(new MarkerOptions().position(myPosition).title("Start"));


<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android=""

You will get your current location in a blue circle.

Get Country of IP Address with PHP

You can get country from IP address with this location API


    echo file_get_contents('');



Here's a fiddle. Response is text when you query a specific field e.g. country here. No decoding needed, just plug it into your code.

P.S. If you want all the fields e.g., the response is JSON.

How does Google calculate my location on a desktop?

They use a combination of IP geolocation, as well as comparing the results of a scan for nearby wireless networks with a database on their side (which is built by collecting GPS coordinates alongside wifi scan data when Android phone users use their GPS)

Where am I? - Get country

This will get the country code set for the phone (phones language, NOT user location):

 String locale = context.getResources().getConfiguration().locale.getCountry(); 

can also replace getCountry() with getISO3Country() to get a 3 letter ISO code for the country. This will get the country name:

 String locale = context.getResources().getConfiguration().locale.getDisplayCountry();

This seems easier than the other methods and rely upon the localisation settings on the phone, so if a US user is abroad they probably still want Fahrenheit and this will work :)

Editors note: This solution has nothing to do with the location of the phone. It is constant. When you travel to Germany locale will NOT change. In short: locale != location.

What is the simplest and most robust way to get the user's current location on Android?

I have created small application with step by step description to gets current locations GPS co-ordinates.

enter image description here

Complete example source code in below URL:

Get Current Location coordinates , City name - in Android

See How it works :

  • All we need to do is add this permission in manifest file

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION">  
  • and create LocationManager instance like this

    LocationManager locationManager = (LocationManager) 
  • Check GPS is enabled or not

  • then implement LocationListener and Get Coordinates

    LocationListener locationListener = new MyLocationListener();  
    LocationManager.GPS_PROVIDER, 5000, 10, locationListener);
  • here is the sample code to do

/*----------Listener class to get coordinates ------------- */
private class MyLocationListener implements LocationListener {

    public void onLocationChanged(Location loc) {
            "Location changed: Lat: " + loc.getLatitude() + " Lng: "
                + loc.getLongitude(), Toast.LENGTH_SHORT).show();
        String longitude = "Longitude: " + loc.getLongitude();
        Log.v(TAG, longitude);
        String latitude = "Latitude: " + loc.getLatitude();
        Log.v(TAG, latitude);
        /*-------to get City-Name from coordinates -------- */
        String cityName = null;
        Geocoder gcd = new Geocoder(getBaseContext(), Locale.getDefault());
        List<Address> addresses;
        try {
            addresses = gcd.getFromLocation(loc.getLatitude(),
                loc.getLongitude(), 1);
            if (addresses.size() > 0)
            cityName = addresses.get(0).getLocality();
        } catch (IOException e) {
        String s = longitude + "\n" + latitude + "\n\nMy Current City is: "
            + cityName;

    public void onProviderDisabled(String provider) {}

    public void onProviderEnabled(String provider) {}

    public void onStatusChanged(String provider, int status, Bundle extras) {}

getCurrentPosition() and watchPosition() are deprecated on insecure origins

Because switching to HTTPS can be painful or impossible depending on your architecture, I found a workaround solution: you can use the Google Maps Geolocation API. Although it has usage limits, it does the job. You will need an browser API key, so don't forget to limit it's usage to your page hostname.

I use it as a fallback method to the getCurrentPosition() method if it fails. It allows me to make it work until I switch to HTTPS.

Here's the JSFiddles:

  • HTTP: getCurrentPosition() will fail and fall back to the API
  • HTTPS: getCurrentPosition() will succeed

Google Maps: how to get country, state/province/region, city given a lat/long value?

@Szkíta Had a great solution by creating a function that gets the address parts in a named array. Here is a compiled solution for those who want to use plain JavaScript.

Function to convert results to the named array:

function getAddressParts(obj) {

    var address = [];

    obj.address_components.forEach( function(el) {
        address[el.types[0]] = el.short_name;

    return address;

} //getAddressParts()

Geocode the LAT/LNG values:

geocoder.geocode( { 'location' : latlng }, function(results, status) {

    if (status == google.maps.GeocoderStatus.OK) {
        var addressParts =  getAddressParts(results[0]);

        // the city
        var city = addressParts.locality;

        // the state
        var state = addressParts.administrative_area_level_1;


How to convert latitude or longitude to meters?

There are quite a few ways to calculate this. All of them use aproximations of spherical trigonometry where the radius is the one of the earth.

try for a bit of methods and code in different languages.

Can we locate a user via user's phone number in Android?

I checked They are not locating the user's current location at all. So based on the number itself they are judging the location of the user. Like if the number starts from 240 ( in US) they they are saying location is Maryland but the person can be in California. So i don't think they are getting the user's location through LocationListner of Java at all.

How to get the exact local time of client?

You can also make your own nodeJS endpoint, publish it with something like heroku, and access it

require("http").createServer(function (q,r) {
}).listen(process.env.PORT || 80)

Then just access it on JS

fetch ("http://someGerokuApp")
. then (r=>console.log(r))

This will still be relative to whatever computer the node app is hosted on, but perhaps you can get the location somehow and provide different endpoints fit the other timezones based on the current one (for example if the server happens to be in California then for a new York timezone just add 1000*60*60*3 milliseconds to to add 3 hours)

For simplicity, if it's possible to get the location from the server and send it as a response header, you can just do the calculations for the different time zones in the client side

In fact using heroku they allow you to specify a region that it should be deployed at you can use this as reference..

EDIT just realized the timezone is in the date string itself, can just pay the whole thing as a header to be read by the client

require("http").createServer(function (q,r) {
    var d= new Date()
    r.setHeader("zman", d.toString())
}).listen(process.env.PORT || 80)

How to get Latitude and Longitude of the mobile device in android?

Use the LocationManager.

LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE); 
Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
double longitude = location.getLongitude();
double latitude = location.getLatitude();

The call to getLastKnownLocation() doesn't block - which means it will return null if no position is currently available - so you probably want to have a look at passing a LocationListener to the requestLocationUpdates() method instead, which will give you asynchronous updates of your location.

private final LocationListener locationListener = new LocationListener() {
    public void onLocationChanged(Location location) {
        longitude = location.getLongitude();
        latitude = location.getLatitude();

lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 2000, 10, locationListener);

You'll need to give your application the ACCESS_FINE_LOCATION permission if you want to use GPS.

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

You may also want to add the ACCESS_COARSE_LOCATION permission for when GPS isn't available and select your location provider with the getBestProvider() method.

How do I get the current GPS location programmatically in Android?

Here is additional information for other answers.

Since Android has


you can register to both and start fetch events from onLocationChanged(Location location) from two at the same time. So far so good. Now the question do we need two results or we should take the best. As I know GPS_PROVIDER results have better accuracy than NETWORK_PROVIDER.

Let's define Location field:

private Location currentBestLocation = null;

Before we start listen on Location change we will implement the following method. This method returns the last known location, between the GPS and the network one. For this method newer is best.

 * @return the last know best location
private Location getLastBestLocation() {
    Location locationGPS = mLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    Location locationNet = mLocationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

    long GPSLocationTime = 0;
    if (null != locationGPS) { GPSLocationTime = locationGPS.getTime(); }

    long NetLocationTime = 0;

    if (null != locationNet) {
        NetLocationTime = locationNet.getTime();

    if ( 0 < GPSLocationTime - NetLocationTime ) {
        return locationGPS;
    else {
        return locationNet;

Each time when we retrieve a new location we will compare it with our previous result.

static final int TWO_MINUTES = 1000 * 60 * 2;

I add a new method to onLocationChanged:

public void onLocationChanged(Location location) {


    if(currentBestLocation == null){
        currentBestLocation = location;


 * This method modify the last know good location according to the arguments.
 * @param location The possible new location.
void makeUseOfNewLocation(Location location) {
    if ( isBetterLocation(location, currentBestLocation) ) {
        currentBestLocation = location;


/** Determines whether one location reading is better than the current location fix
 * @param location  The new location that you want to evaluate
 * @param currentBestLocation  The current location fix, to which you want to compare the new one.
protected boolean isBetterLocation(Location location, Location currentBestLocation) {
    if (currentBestLocation == null) {
        // A new location is always better than no location
        return true;

    // Check whether the new location fix is newer or older
    long timeDelta = location.getTime() - currentBestLocation.getTime();
    boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
    boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
    boolean isNewer = timeDelta > 0;

    // If it's been more than two minutes since the current location, use the new location,
    // because the user has likely moved.
    if (isSignificantlyNewer) {
        return true;
        // If the new location is more than two minutes older, it must be worse.
    } else if (isSignificantlyOlder) {
        return false;

    // Check whether the new location fix is more or less accurate
    int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
    boolean isLessAccurate = accuracyDelta > 0;
    boolean isMoreAccurate = accuracyDelta < 0;
    boolean isSignificantlyLessAccurate = accuracyDelta > 200;

    // Check if the old and new location are from the same provider
    boolean isFromSameProvider = isSameProvider(location.getProvider(),

    // Determine location quality using a combination of timeliness and accuracy
    if (isMoreAccurate) {
        return true;
    } else if (isNewer && !isLessAccurate) {
        return true;
    } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
        return true;
    return false;

// Checks whether two providers are the same
private boolean isSameProvider(String provider1, String provider2) {
    if (provider1 == null) {
        return provider2 == null;
    return provider1.equals(provider2);


navigator.geolocation.getCurrentPosition sometimes works sometimes doesn't

This is the hacky way that I am getting around this, at least it works in all current browsers (on Windows, I don't own a Mac):

if (navigator.geolocation) {
    var location_timeout = setTimeout("geolocFail()", 10000);

    navigator.geolocation.getCurrentPosition(function(position) {

        var lat = position.coords.latitude;
        var lng = position.coords.longitude;

        geocodeLatLng(lat, lng);
    }, function(error) {
} else {
    // Fallback for no geolocation

This will also work if someone clicks the close or chooses no or chooses the Never Share option on Firefox.

Clunky, but it works.

Given the lat/long coordinates, how can we find out the city/country?

If you are using Google's Places API, this is how you can get country and city from the place object using Javascript:

function getCityAndCountry(location) {
  var components = {};
  for(var i = 0; i < location.address_components.length; i++) {
    components[location.address_components[i].types[0]] = location.address_components[i].long_name;

  if(!components['country']) {
    console.warn('Couldn\'t extract country');
    return false;

  if(components['locality']) {
    return [components['locality'], components['country']];
  } else if(components['administrative_area_level_1']) {
    return [components['administrative_area_level_1'], components['country']];
  } else {
    console.warn('Couldn\'t extract city');
    return false;

Address validation using Google Maps API

Validate it against FedEx's api. They have an API to generate labels from XML code. The process involves a step to validate the address.

How to get a time zone from a location using latitude and longitude coordinates?

If you want to use then use this code. (But is very slow sometimes)

String get_time_zone_time_geonames(GeoPoint gp){

        String erg = "";

        double Longitude = gp.getLongitudeE6()/1E6;
        double Latitude = gp.getLatitudeE6()/1E6;

        String request = ""+Latitude+"&lng="+ Longitude+ "&style=full";

        URL time_zone_time = null;

        InputStream input;
       // final StringBuilder sBuf = new StringBuilder();

        try {
            time_zone_time = new URL(request);

        try {
            input = time_zone_time.openConnection().getInputStream();

        final BufferedReader reader = new BufferedReader(new InputStreamReader(input));
            final StringBuilder sBuf = new StringBuilder();

            String line = null;
            try {
                while ((line = reader.readLine()) != null) {
            } catch (IOException e) {
                    Log.e(e.getMessage(), "XML parser, stream2string 1");
            } finally {
                try {
                } catch (IOException e) {
                    Log.e(e.getMessage(), "XML parser, stream2string 2");

             String xmltext = sBuf.toString();

             int startpos = xmltext.indexOf("<geonames");
             xmltext = xmltext.substring(startpos);

            XmlPullParser parser;
            try {
                parser = XmlPullParserFactory.newInstance().newPullParser();

            parser.setInput(new StringReader (xmltext));

            int eventType = parser.getEventType();  

            String tagName = "";

            while(eventType != XmlPullParser.END_DOCUMENT) {
                switch(eventType) {

                    case XmlPullParser.START_TAG:

                          tagName = parser.getName();


                    case XmlPullParser.TEXT :

                        if  (tagName.equalsIgnoreCase("time"))
                          erg = parser.getText();  



                try {
                    eventType =;
                } catch (IOException e) {



            } catch (XmlPullParserException e) {

                erg += e.toString();

            } catch (IOException e1) {


            } catch (MalformedURLException e1) {


        return erg;


And use it with:

GeoPoint gp = new GeoPoint(39.6034810,-119.6822510);
String Current_TimeZone_Time = get_time_zone_time_geonames(gp);

Get GPS location from the web browser


  function geo_success(position) {
    do_something(position.coords.latitude, position.coords.longitude);

  function geo_error() {
    alert("Sorry, no position available.");

  var geo_options = {
    enableHighAccuracy: true,
    maximumAge        : 30000,
    timeout           : 27000

  var wpid = navigator.geolocation.watchPosition(geo_success, geo_error, geo_options);
  getLocation(): Observable<Position> {
    return Observable.create((observer) => {
      const watchID = navigator.geolocation.watchPosition((position: Position) => {;
      return () => {

  ngOnDestroy() {

Good way of getting the user's location in Android

To select the right location provider for your app, you can use Criteria objects:

Criteria myCriteria = new Criteria();
// let Android select the right location provider for you
String myProvider = locationManager.getBestProvider(myCriteria, true); 

// finally require updates at -at least- the desired rate
long minTimeMillis = 600000; // 600,000 milliseconds make 10 minutes

Read the documentation for requestLocationUpdates for more details on how the arguments are taken into account:

The frequency of notification may be controlled using the minTime and minDistance parameters. If minTime is greater than 0, the LocationManager could potentially rest for minTime milliseconds between location updates to conserve power. If minDistance is greater than 0, a location will only be broadcasted if the device moves by minDistance meters. To obtain notifications as frequently as possible, set both parameters to 0.

More thoughts

  • You can monitor the accuracy of the Location objects with Location.getAccuracy(), which returns the estimated accuracy of the position in meters.
  • the Criteria.ACCURACY_HIGH criterion should give you errors below 100m, which is not as good as GPS can be, but matches your needs.
  • You also need to monitor the status of your location provider, and switch to another provider if it gets unavailable or disabled by the user.
  • The passive provider may also be a good match for this kind of application: the idea is to use location updates whenever they are requested by another app and broadcast systemwide.

Get user's current location

An IP gives you an quite unreliable location, you could Ajax the location upon load with JS if it isn't critical to have the location at first. (Also, the user need's to give you it's permission to access it.)

Html5 Geolocation

Simple calculations for working with lat/lon and km distance?

Interesting that I didn't see a mention of UTM coordinates.

At least if you want to add km to the same zone, it should be straightforward (in Python : )

utm.from_latlon and utm.to_latlon.

How to emulate GPS location in the Android Emulator?

The already mentioned multiple times answer to use the shell command "geo fix..." is the correct answer. But in case you use LocationClient.getLastLocation() to retrieve your data it is worth to mention that it will not work at first. The LocationClient class uses the Google Play Service to retrieve the coordinates. For me this started working after running the emulators maps app once. During the first start you are asked to allow google apps access to your location, which I guess does the trick.

Get the distance between two geo points

Look into distanceTo or distanceBetween. You can create a Location object from a latitude and longitude:

Location location = new Location("");

How to simulate browsing from various locations?

This is a bit of self promotion, but I built a tool to do just this that you might find useful, called GeoPeeker.

It remotely accesses a site from servers spread around the world, renders the page with webkit and sends back an image. It will also report the IP address and DNS information of the site as it appears from that location.

There are no ads, and it's very stream-lined to serve this one purpose. It's still in development, and feedback is welcome. Here's hoping somebody besides myself finds it useful!

Google API for location, based on user IP address

It looks like Google actively frowns on using IP-to-location mapping:

That article encourages using the W3C geolocation API. I was a little skeptical, but it looks like almost every major browser already supports the geolocation API:

What is meaning of negative dbm in signal strength?

At ms end Rx lev ranges 0 to -120 dbm Mean antenna power which received at ms end alway less than 1mW.

Thats why it always -ve.

Identifying country by IP address

Amazon's CloudFront content delivery network can now be configured to pass this information through as a header. Given Amazon's size (they're big and stable, not going anywhere) and this is configuration over code (no third-party API to learn or code to maintain), all around believe this to be the best option.

If you do not use AWS CloudFront, I'd look into seeing if your CDN has a similar header option that can be turned on. Usually the large providers are quick to push for feature parity. And if you are not using a CDN, you could put CloudFront in front of your infrastructure and simply set the origin to resolve to whatever you are currently using.

Additionally, it also makes sense to resolve this at the CDN level. Your CDN is already having to figure out geo location to route the user to the nearest content node, might as well pass this information along and not figure it out twice through a third party API (this becomes chokepoint for your app, waiting for a geo location lookup to resolve). No need to do this work twice (and the second time, arguably less resilient [e.g., 3rd party geo lookup]).

Geo-Targeting – CloudFront will detect the user’s country of origin and pass along the county code to you in the CloudFront-Viewer-Country header. You can use this information to customize your responses without having to use URLs that are specific to each country.

Does GPS require Internet?

I've found out that GPS does not need Internet, BUT of course if you need to download maps, you will need a data connection or wifi.

Calculate distance between 2 GPS coordinates

If you need something more accurate then have a look at this.

Vincenty's formulae are two related iterative methods used in geodesy to calculate the distance between two points on the surface of a spheroid, developed by Thaddeus Vincenty (1975a) They are based on the assumption that the figure of the Earth is an oblate spheroid, and hence are more accurate than methods such as great-circle distance which assume a spherical Earth.

The first (direct) method computes the location of a point which is a given distance and azimuth (direction) from another point. The second (inverse) method computes the geographical distance and azimuth between two given points. They have been widely used in geodesy because they are accurate to within 0.5 mm (0.020") on the Earth ellipsoid.

Get city name using geolocation

You can get the name of the city, country, street name and other geodata using the Google Maps Geocoding API

<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <script type="text/javascript" src=""></script>
    <script type="text/javascript">
        navigator.geolocation.getCurrentPosition(success, error);

        function success(position) {

            var GEOCODING = '' + position.coords.latitude + '%2C' + position.coords.longitude + '&language=en';

            $.getJSON(GEOCODING).done(function(location) {


        function error(err) {

and to display this data on the page using jQuery

<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <script type="text/javascript" src=""></script>

    <p>Country: <span id="country"></span></p>
    <p>State: <span id="state"></span></p>
    <p>City: <span id="city"></span></p>
    <p>Address: <span id="address"></span></p>

    <p>Latitude: <span id="latitude"></span></p>
    <p>Longitude: <span id="longitude"></span></p>

    <script type="text/javascript">
        navigator.geolocation.getCurrentPosition(success, error);

        function success(position) {

            var GEOCODING = '' + position.coords.latitude + '%2C' + position.coords.longitude + '&language=en';

            $.getJSON(GEOCODING).done(function(location) {


        function error(err) {

Getting the location from an IP address

PHP has an extension for that.


The GeoIP extension allows you to find the location of an IP address. City, State, Country, Longitude, Latitude, and other information as all, such as ISP and connection type can be obtained with the help of GeoIP.

For example:

$record = geoip_record_by_name($ip);
echo $record['city'];

How to get visitor's location (i.e. country) using geolocation?

You can use my service,, for this. It will give you the client IP, hostname, geolocation information (city, region, country, area code, zip code etc) and network owner. Here's a simple example that logs the city and country:

$.get("", function(response) {
}, "jsonp");

Here's a more detailed JSFiddle example that also prints out the full response information, so you can see all of the available details:

The location will generally be less accurate than the native geolocation details, but it doesn't require any user permission.

How to calculate distance from Wifi router using Signal Strength?

FSPL depends on two parameters: First is the frequency of radio signals;Second is the wireless transmission distance. The following formula can reflect the relationship between them.

FSPL (dB) = 20log10(d) + 20log10(f) + K

d = distance
f = frequency
K= constant that depends on the units used for d and f
If d is measured in kilometers, f in MHz, the formula is:

FSPL (dB) = 20log10(d)+ 20log10(f) + 32.44

From the Fade Margin equation, Free Space Path Loss can be computed with the following equation.

Free Space Path Loss=Tx Power-Tx Cable Loss+Tx Antenna Gain+Rx Antenna Gain - Rx Cable Loss - Rx Sensitivity - Fade Margin

With the above two Free Space Path Loss equations, we can find out the Distance in km.

Distance (km) = 10(Free Space Path Loss – 32.44 – 20log10(f))/20

The Fresnel Zone is the area around the visual line-of-sight that radio waves spread out into after they leave the antenna. You want a clear line of sight to maintain strength, especially for 2.4GHz wireless systems. This is because 2.4GHz waves are absorbed by water, like the water found in trees. The rule of thumb is that 60% of Fresnel Zone must be clear of obstacles. Typically, 20% Fresnel Zone blockage introduces little signal loss to the link. Beyond 40% blockage the signal loss will become significant.


d = distance [km]
f = frequency [GHz]
r = radius [m]

Source :

Algorithm to find all Latitude Longitude locations within a certain distance from a given Lat Lng location

As biziclop mentioned, some sort of metric space tree would probably be your best option. I have experience using kd-trees and quad trees to do these sorts of range queries and they're amazingly fast; they're also not that hard to write. I'd suggest looking into one of these structures, as they also let you answer other interesting questions like "what's the closest point in my data set to this other point?"

How to get current location in Android

You need to write code in the OnLocationChanged method, because this method is called when the location has changed. I.e. you need to save the new location to return it if getLocation is called.

If you don't use the onLocationChanged it always will be the old location.

Getting visitors country from their IP

I am using api and getting exactly what you are looking for.

Its completely free, you just need to register with them to get your api key. You can include their php class by downloading from their website or you can use url format to retrieve information.

Here's what I am doing:

I included their php class in my script and using the below code:

$ipLite = new ip2location_lite;
if(!$_COOKIE["visitorCity"]){ //I am using cookie to store information
  $visitorCity = $ipLite->getCity($_SERVER['REMOTE_ADDR']);
  if ($visitorCity['statusCode'] == 'OK') {
    $data = base64_encode(serialize($visitorCity));
    setcookie("visitorCity", $data, time()+3600*24*7); //set cookie for 1 week
$visitorCity = unserialize(base64_decode($_COOKIE["visitorCity"]));
echo $visitorCity['countryName'].' Region'.$visitorCity['regionName'];

Thats it.

How to edit binary file on Unix systems

For small changes, I have used hexedit:

Simple but fast and useful.

Find all storage devices attached to a Linux machine

you can also try lsblk ... is in util-linux ... but i have a question too

fdisk -l /dev/sdl

no result

grep sdl /proc/partitions      
   8      176   15632384 sdl
   8      177   15628288 sdl1

lsblk | grep sdl
sdl       8:176  1  14.9G  0 disk  
`-sdl1    8:177  1  14.9G  0 part  

fdisk is good but not that good ... seems like it cannot "see" everything

in my particular example i have a stick that have also a card reader build in it and i can see only the stick using fdisk:

fdisk -l /dev/sdk

Disk /dev/sdk: 15.9 GB, 15931539456 bytes
255 heads, 63 sectors/track, 1936 cylinders, total 31116288 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xbe24be24

   Device Boot      Start         End      Blocks   Id  System
/dev/sdk1   *        8192    31116287    15554048    c  W95 FAT32 (LBA)

but not the card (card being /dev/sdl)

also, file -s is inefficient ...

file -s /dev/sdl1
/dev/sdl1: sticky x86 boot sector, code offset 0x52, OEM-ID "NTFS    ", sectors/cluster 8, reserved sectors 0, Media descriptor 0xf8, heads 255, hidden sectors 8192, dos < 4.0 BootSector (0x0)

that's nice ... BUT

fdisk -l /dev/sdb
/dev/sdb1            2048   156301487    78149720   fd  Linux raid autodetect
/dev/sdb2       156301488   160086527     1892520   82  Linux swap / Solaris

file -s /dev/sdb1
/dev/sdb1: sticky \0

to see information about a disk that cannot be accesed by fdisk, you can use parted:

parted /dev/sdl print

Model: Mass Storage Device (scsi)
Disk /dev/sdl: 16.0GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      4194kB  16.0GB  16.0GB  primary  ntfs

arted /dev/sdb print 
Model: ATA Maxtor 6Y080P0 (scsi)
Disk /dev/sdb: 82.0GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system     Flags
 1      1049kB  80.0GB  80.0GB  primary                  raid
 2      80.0GB  82.0GB  1938MB  primary  linux-swap(v1)

ImportError: No module named xlsxwriter

I am not sure what caused this but it went all well once I changed the path name from Lib into lib and I was finally able to make it work.

How to do multiline shell script in Ansible

Ansible uses YAML syntax in its playbooks. YAML has a number of block operators:

  • The > is a folding block operator. That is, it joins multiple lines together by spaces. The following syntax:

    key: >
      This text
      has multiple

    Would assign the value This text has multiple lines\n to key.

  • The | character is a literal block operator. This is probably what you want for multi-line shell scripts. The following syntax:

    key: |
      This text
      has multiple

    Would assign the value This text\nhas multiple\nlines\n to key.

You can use this for multiline shell scripts like this:

- name: iterate user groups
  shell: |
    groupmod -o -g {{ item['guid'] }} {{ item['username'] }} 
  with_items: "{{ users }}"

There is one caveat: Ansible does some janky manipulation of arguments to the shell command, so while the above will generally work as expected, the following won't:

- shell: |
    cat <<EOF
    This is a test.

Ansible will actually render that text with leading spaces, which means the shell will never find the string EOF at the beginning of a line. You can avoid Ansible's unhelpful heuristics by using the cmd parameter like this:

- shell:
    cmd: |
      cat <<EOF
      This is a test.

How to get package name from anywhere?

PackageInfo pinfo = this.getPackageManager().getPackageInfo(getPackageName(), 0);
         String sVersionCode = pinfo.versionCode; // 1
         String sVersionName = pinfo.versionName; // 1.0
         String sPackName = getPackageName(); // cz.okhelp.my_app
         int nSdkVersion = Integer.parseInt(Build.VERSION.SDK); 
         int nSdkVers = Build.VERSION.SDK_INT; 

Hope it will work.

Why doesn't calling a Python string method do anything unless you assign its output?

This is because strings are immutable in Python.

Which means that X.replace("hello","goodbye") returns a copy of X with replacements made. Because of that you need replace this line:

X.replace("hello", "goodbye")

with this line:

X = X.replace("hello", "goodbye")

More broadly, this is true for all Python string methods that change a string's content "in-place", e.g. replace,strip,translate,lower/upper,join,...

You must assign their output to something if you want to use it and not throw it away, e.g.

X  = X.strip(' \t')
X2 = X.translate(...)
Y  = X.lower()
Z  = X.upper()
A  = X.join(':')
B  = X.capitalize()
C  = X.casefold()

and so on.

How to update PATH variable permanently from Windows command line?

You can use:

setx PATH "%PATH%;C:\\Something\\bin"

However, setx will truncate the stored string to 1024 bytes, potentially corrupting the PATH.

/M will change the PATH in HKEY_LOCAL_MACHINE instead of HKEY_CURRENT_USER. In other words, a system variable, instead of the user's. For example:

SETX /M PATH "%PATH%;C:\your path with spaces"

You have to keep in mind, the new PATH is not visible in your current cmd.exe.

But if you look in the registry or on a new cmd.exe with "set p" you can see the new value.

How do I print the elements of a C++ vector in GDB?

To view vector std::vector myVector contents, just type in GDB:

(gdb) print myVector

This will produce an output similar to:

$1 = std::vector of length 3, capacity 4 = {10, 20, 30}

To achieve above, you need to have gdb 7 (I tested it on gdb 7.01) and some python pretty-printer. Installation process of these is described on gdb wiki.

What is more, after installing above, this works well with Eclipse C++ debugger GUI (and any other IDE using GDB, as I think).

What does the "at" (@) symbol do in Python?

What does the “at” (@) symbol do in Python?

In short, it is used in decorator syntax and for matrix multiplication.

In the context of decorators, this syntax:

def decorated_function():
    """this function is decorated"""

is equivalent to this:

def decorated_function():
    """this function is decorated"""

decorated_function = decorator(decorated_function)

In the context of matrix multiplication, a @ b invokes a.__matmul__(b) - making this syntax:

a @ b

equivalent to

dot(a, b)


a @= b

equivalent to

a = dot(a, b)

where dot is, for example, the numpy matrix multiplication function and a and b are matrices.

How could you discover this on your own?

I also do not know what to search for as searching Python docs or Google does not return relevant results when the @ symbol is included.

If you want to have a rather complete view of what a particular piece of python syntax does, look directly at the grammar file. For the Python 3 branch:

~$ grep -C 1 "@" cpython/Grammar/Grammar 

decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
decorators: decorator+
testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']
augassign: ('+=' | '-=' | '*=' | '@=' | '/=' | '%=' | '&=' | '|=' | '^=' |
            '<<=' | '>>=' | '**=' | '//=')
arith_expr: term (('+'|'-') term)*
term: factor (('*'|'@'|'/'|'%'|'//') factor)*
factor: ('+'|'-'|'~') factor | power

We can see here that @ is used in three contexts:

  • decorators
  • an operator between factors
  • an augmented assignment operator

Decorator Syntax:

A google search for "decorator python docs" gives as one of the top results, the "Compound Statements" section of the "Python Language Reference." Scrolling down to the section on function definitions, which we can find by searching for the word, "decorator", we see that... there's a lot to read. But the word, "decorator" is a link to the glossary, which tells us:


A function returning another function, usually applied as a function transformation using the @wrapper syntax. Common examples for decorators are classmethod() and staticmethod().

The decorator syntax is merely syntactic sugar, the following two function definitions are semantically equivalent:

def f(...):
f = staticmethod(f)

def f(...):

The same concept exists for classes, but is less commonly used there. See the documentation for function definitions and class definitions for more about decorators.

So, we see that

def bar():

is semantically the same as:

def bar():

bar = foo(bar)

They are not exactly the same because Python evaluates the foo expression (which could be a dotted lookup and a function call) before bar with the decorator (@) syntax, but evaluates the foo expression after bar in the other case.

(If this difference makes a difference in the meaning of your code, you should reconsider what you're doing with your life, because that would be pathological.)

Stacked Decorators

If we go back to the function definition syntax documentation, we see:

def func(): pass

is roughly equivalent to

def func(): pass
func = f1(arg)(f2(func))

This is a demonstration that we can call a function that's a decorator first, as well as stack decorators. Functions, in Python, are first class objects - which means you can pass a function as an argument to another function, and return functions. Decorators do both of these things.

If we stack decorators, the function, as defined, gets passed first to the decorator immediately above it, then the next, and so on.

That about sums up the usage for @ in the context of decorators.

The Operator, @

In the lexical analysis section of the language reference, we have a section on operators, which includes @, which makes it also an operator:

The following tokens are operators:

+       -       *       **      /       //      %      @
<<      >>      &       |       ^       ~
<       >       <=      >=      ==      !=

and in the next page, the Data Model, we have the section Emulating Numeric Types,

object.__add__(self, other)
object.__sub__(self, other) 
object.__mul__(self, other) 
object.__matmul__(self, other) 
object.__truediv__(self, other) 
object.__floordiv__(self, other)

[...] These methods are called to implement the binary arithmetic operations (+, -, *, @, /, //, [...]

And we see that __matmul__ corresponds to @. If we search the documentation for "matmul" we get a link to What's new in Python 3.5 with "matmul" under a heading "PEP 465 - A dedicated infix operator for matrix multiplication".

it can be implemented by defining __matmul__(), __rmatmul__(), and __imatmul__() for regular, reflected, and in-place matrix multiplication.

(So now we learn that @= is the in-place version). It further explains:

Matrix multiplication is a notably common operation in many fields of mathematics, science, engineering, and the addition of @ allows writing cleaner code:

S = (H @ beta - r).T @ inv(H @ V @ H.T) @ (H @ beta - r)

instead of:

S = dot((dot(H, beta) - r).T,
        dot(inv(dot(dot(H, V), H.T)), dot(H, beta) - r))

While this operator can be overloaded to do almost anything, in numpy, for example, we would use this syntax to calculate the inner and outer product of arrays and matrices:

>>> from numpy import array, matrix
>>> array([[1,2,3]]).T @ array([[1,2,3]])
array([[1, 2, 3],
       [2, 4, 6],
       [3, 6, 9]])
>>> array([[1,2,3]]) @ array([[1,2,3]]).T
>>> matrix([1,2,3]).T @ matrix([1,2,3])
matrix([[1, 2, 3],
        [2, 4, 6],
        [3, 6, 9]])
>>> matrix([1,2,3]) @ matrix([1,2,3]).T

Inplace matrix multiplication: @=

While researching the prior usage, we learn that there is also the inplace matrix multiplication. If we attempt to use it, we may find it is not yet implemented for numpy:

>>> m = matrix([1,2,3])
>>> m @= m.T
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: In-place matrix multiplication is not (yet) supported. Use 'a = a @ b' instead of 'a @= b'.

When it is implemented, I would expect the result to look like this:

>>> m = matrix([1,2,3])
>>> m @= m.T
>>> m

How do I find Waldo with Mathematica?

I've found Waldo!

waldo had been found

How I've done it

First, I'm filtering out all colours that aren't red

waldo = Import[""];
red = Fold[ImageSubtract, #[[1]], Rest[#]] &@ColorSeparate[waldo];

Next, I'm calculating the correlation of this image with a simple black and white pattern to find the red and white transitions in the shirt.

corr = ImageCorrelate[red, 
   Image@Join[ConstantArray[1, {2, 4}], ConstantArray[0, {2, 4}]], 

I use Binarize to pick out the pixels in the image with a sufficiently high correlation and draw white circle around them to emphasize them using Dilation

pos = Dilation[ColorNegate[Binarize[corr, .12]], DiskMatrix[30]];

I had to play around a little with the level. If the level is too high, too many false positives are picked out.

Finally I'm combining this result with the original image to get the result above

found = ImageMultiply[waldo, ImageAdd[ColorConvert[pos, "GrayLevel"], .5]]

Implementing a simple file download servlet

That depends. If said file is publicly available via your HTTP server or servlet container you can simply redirect to via response.sendRedirect().

If it's not, you'll need to manually copy it to response output stream:

OutputStream out = response.getOutputStream();
FileInputStream in = new FileInputStream(my_file);
byte[] buffer = new byte[4096];
int length;
while ((length = > 0){
    out.write(buffer, 0, length);

You'll need to handle the appropriate exceptions, of course.

DOS: find a string, if found then run another script

C:\test>find /c "string" file | find ": 0" 1>nul && echo "execute command here"

Setting DIV width and height in JavaScript

The onclick attribute of a button takes a string of JavaScript, not an href like you provided. Just remove the "javascript:" part.

SQL Server Configuration Manager not found

If you don't have any version of SQLServerManagerXX.msc, then you simply do not have it installed. I noticed it does not come with SQL server management studio 2019.

It's available (client-connectivity tools) in the SQL Server Express edition or SQL Server Developer edition which is good for dev/test (non-production) usage.

Move column by name to front of table in pandas

Here is a generic set of code that I frequently use to rearrange the position of columns. You may find it useful.

cols = df.columns.tolist()
n = int(cols.index('Mid'))
cols = [cols[n]] + cols[:n] + cols[n+1:]
df = df[cols]

Cannot push to Git repository on Bitbucket

I am using macOS and although i had setup my public key in bitbucket the next time i tried to push i got

repository access denied.

fatal: Could not read from remote repository.

Please make sure you have the correct access rights and the repository exists.

What i had to do was Step 2. Add the key to the ssh-agent as described in Bitbucket SSH keys setup guide and especially the 3rd step:

(macOS only) So that your computer remembers your password each time it restarts, open (or create) the ~/.ssh/config file and add these lines to the file:

Host *
UseKeychain yes

Hope it helps a mac user with the same issue.

How to run a script as root on Mac OS X?

As in any unix-based environment, you can use the sudo command:

$ sudo script-name

It will ask for your password (your own, not a separate root password).

100% width Twitter Bootstrap 3 template

In BOOTSTRAP 4 you can use

<div class="row m-0">
my fullwidth div

... if you just use a .row without the .m-0 as a top level div, you will have unwanted margin, which makes the page wider than the browser window and cause a horizontal scrollbar.

How do you run your own code alongside Tkinter's event loop?

Another option is to let tkinter execute on a separate thread. One way of doing it is like this:

import Tkinter
import threading

class MyTkApp(threading.Thread):
    def __init__(self):
        self.s = Tkinter.StringVar()
        l = Tkinter.Label(self.root,textvariable=self.s)

    def run(self):

app = MyTkApp()

# Now the app should be running and the value shown on the label
# can be changed by changing the member variable s.
# Like this:
# app.s.set('Bar')

Be careful though, multithreaded programming is hard and it is really easy to shoot your self in the foot. For example you have to be careful when you change member variables of the sample class above so you don't interrupt with the event loop of Tkinter.

How do I include a pipe | in my linux find -exec command?

The job of interpreting the pipe symbol as an instruction to run multiple processes and pipe the output of one process into the input of another process is the responsibility of the shell (/bin/sh or equivalent).

In your example you can either choose to use your top level shell to perform the piping like so:

find -name 'file_*' -follow -type f -exec zcat {} \; | agrep -dEOE 'grep'

In terms of efficiency this results costs one invocation of find, numerous invocations of zcat, and one invocation of agrep.

This would result in only a single agrep process being spawned which would process all the output produced by numerous invocations of zcat.

If you for some reason would like to invoke agrep multiple times, you can do:

find . -name 'file_*' -follow -type f \
    -printf "zcat %p | agrep -dEOE 'grep'\n" | sh

This constructs a list of commands using pipes to execute, then sends these to a new shell to actually be executed. (Omitting the final "| sh" is a nice way to debug or perform dry runs of command lines like this.)

In terms of efficiency this results costs one invocation of find, one invocation of sh, numerous invocations of zcat and numerous invocations of agrep.

The most efficient solution in terms of number of command invocations is the suggestion from Paul Tomblin:

find . -name "file_*" -follow -type f -print0 | xargs -0 zcat | agrep -dEOE 'grep'

... which costs one invocation of find, one invocation of xargs, a few invocations of zcat and one invocation of agrep.

Search all of Git history for a string?

Git can search diffs with the -S option (it's called pickaxe in the docs)

git log -S password

This will find any commit that added or removed the string password. Here a few options:

  • -p: will show the diffs. If you provide a file (-p file), it will generate a patch for you.
  • -G: looks for differences whose added or removed line matches the given regexp, as opposed to -S, which "looks for differences that introduce or remove an instance of string".
  • --all: searches over all branches and tags; alternatively, use --branches[=<pattern>] or --tags[=<pattern>]

Component is not part of any NgModule or the module has not been imported into your module

In Some case the same may happen when you have created a module for HomeComponent and in app-routing.module you directly given both

component: HomeComponent, loadChildren:"./modules/.../HomeModule.module#HomeModule" in Routes array.

when we try lazy loading we do give loadChildren attribute only.

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

for your example:

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

you will have to do something of this effect:

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

this returns the array object.

Then iterating will be as follows:

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

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

//The end...

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

Hope this helps.

In TensorFlow, what is the difference between and Tensor.eval()?

If you have a Tensor t, calling t.eval() is equivalent to calling tf.get_default_session().run(t).

You can make a session the default as follows:

t = tf.constant(42.0)
sess = tf.Session()
with sess.as_default():   # or `with sess:` to close on exit
    assert sess is tf.get_default_session()
    assert t.eval() ==

The most important difference is that you can use to fetch the values of many tensors in the same step:

t = tf.constant(42.0)
u = tf.constant(37.0)
tu = tf.mul(t, u)
ut = tf.mul(u, t)
with sess.as_default():
   tu.eval()  # runs one step
   ut.eval()  # runs one step[tu, ut])  # evaluates both tensors in a single step

Note that each call to eval and run will execute the whole graph from scratch. To cache the result of a computation, assign it to a tf.Variable.

What is the Java equivalent for LINQ?

you can use scala, it is similar in syntax and it's actually probably more powerful than linq.

How to quickly drop a user with existing privileges

The accepted answer resulted in errors for me when attempting REASSIGN OWNED BY or DROP OWNED BY. The following worked for me:

DROP USER username;

The user may have privileges in other schemas, in which case you will have to run the appropriate REVOKE line with "public" replaced by the correct schema. To show all of the schemas and privilege types for a user, I edited the \dp command to make this query:

  n.nspname as "Schema",
  CASE c.relkind 
    WHEN 'r' THEN 'table' 
    WHEN 'v' THEN 'view' 
    WHEN 'm' THEN 'materialized view' 
    WHEN 'S' THEN 'sequence' 
    WHEN 'f' THEN 'foreign table' 
  END as "Type"
FROM pg_catalog.pg_class c
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE pg_catalog.array_to_string(c.relacl, E'\n') LIKE '%username%';

I'm not sure which privilege types correspond to revoking on TABLES, SEQUENCES, or FUNCTIONS, but I think all of them fall under one of the three.

Does PHP have threading?

Ever heard about appserver from techdivision?

It is written in php and works as a appserver managing multithreads for high traffic php applications. Is still in beta but very promesing.

What is the $$hashKey added to my JSON.stringify result

Here is how you can easily remove the $$hashKey from the object:

$scope.myNewObject = JSON.parse(angular.toJson($scope.myObject))

$scope.myObject - Refers to the Object that you want to perform the operation upon i.e. remove the $$hashKey from

$scope.myNewObject - Assign the modified original object to the new object so it can be used as necessary

How to load local html file into UIWebView

by this you can load html file which is in your project Assets(bundle) to webView.

 UIWebView *web = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
    [web loadRequest:[NSURLRequest requestWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] 
                                pathForResource:@"test" ofType:@"html"]isDirectory:NO]]];

may be this is useful to you.

see if two files have the same content in python

I'm not sure if you want to find duplicate files or just compare two single files. If the latter, the above approach (filecmp) is better, if the former, the following approach is better.

There are lots of duplicate files detection questions here. Assuming they are not very small and that performance is important, you can

  • Compare file sizes first, discarding all which doesn't match
  • If file sizes match, compare using the biggest hash you can handle, hashing chunks of files to avoid reading the whole big file

Here's is an answer with Python implementations (I prefer the one by nosklo, BTW)

Using parameters in batch files at Windows command line

@Jon's :parse/:endparse scheme is a great start, and he has my gratitude for the initial pass, but if you think that the Windows torturous batch system would let you off that easy… well, my friend, you are in for a shock. I have spent the whole day with this devilry, and after much painful research and experimentation I finally managed something viable for a real-life utility.

Let us say that we want to implement a utility foobar. It requires an initial command. It has an optional parameter --foo which takes an optional value (which cannot be another parameter, of course); if the value is missing it defaults to default. It also has an optional parameter --bar which takes a required value. Lastly it can take a flag --baz with no value allowed. Oh, and these parameters can come in any order.

In other words, it looks like this:

foobar <command> [--foo [<fooval>]] [--bar <barval>] [--baz]

Complicated? No, that seems pretty typical of real life utilities. (git anyone?)

Without further ado, here is a solution:

REM FooBar parameter demo
REM By Garret Wilson


IF "%CMD%" == "" (
  GOTO usage

IF "%PARAM%" == "--foo" (
  IF NOT "%ARG%" == "" (
    IF NOT "%ARG:~0,2%" == "--" (
      SET FOO=%ARG%
    ) ELSE (
  ) ELSE (
) ELSE IF "%PARAM%" == "--bar" (
  IF NOT "%ARG%" == "" (
  ) ELSE (
    ECHO Missing bar value. 1>&2
    GOTO usage
) ELSE IF "%PARAM%" == "--baz" (
  SET BAZ=true
) ELSE IF "%PARAM%" == "" (
  GOTO endargs
) ELSE (
  ECHO Unrecognized option %1. 1>&2
  GOTO usage
GOTO args

ECHO Command: %CMD%
IF NOT "%FOO%" == "" (
  ECHO Foo: %FOO%
IF NOT "%BAR%" == "" (
  ECHO Bar: %BAR%
IF "%BAZ%" == "true" (
  ECHO Baz

REM TODO do something with FOO, BAR, and/or BAZ
GOTO :eof

ECHO Usage: foobar ^<command^> [--foo [^<fooval^>]] [--bar ^<barval^>] [--baz]

Yes, it really is that bad. See my similar post at, where I provide more analysis of what is going on in the logic, and why I used certain constructs.

Hideous. Most of that I had to learn today. And it hurt.

Generics in C#, using type of a variable as parameter

I'm not sure whether I understand your question correctly, but you can write your code in this way:

bool DoesEntityExist<T>(T instance, ....)

You can call the method in following fashion:

DoesEntityExist(myTypeInstance, ...)

This way you don't need to explicitly write the type, the framework will overtake the type automatically from the instance.

Print list without brackets in a single row

For array of integer type, we need to change it to string type first and than use join function to get clean output without brackets.

    arr = [1, 2, 3, 4, 5]    
    print(', '.join(map(str, arr)))

OUTPUT - 1, 2, 3, 4, 5

For array of string type, we need to use join function directly to get clean output without brackets.

    arr = ["Ram", "Mohan", "Shyam", "Dilip", "Sohan"]
    print(', '.join(arr)

OUTPUT - Ram, Mohan, Shyam, Dilip, Sohan

Javascript "Cannot read property 'length' of undefined" when checking a variable's length


You asked why it happens, let's see:

The official language specificaion dictates a call to the internal [[GetValue]] method. Your .attr returns undefined and you're trying to access its length.

If Type(V) is not Reference, return V.

This is true, since undefined is not a reference (alongside null, number, string and boolean)

Let base be the result of calling GetBase(V).

This gets the undefined part of myVar.length .

If IsUnresolvableReference(V), throw a ReferenceError exception.

This is not true, since it is resolvable and it resolves to undefined.

If IsPropertyReference(V), then

This happens since it's a property reference with the . syntax.

Now it tries to convert undefined to a function which results in a TypeError.

Difference between int32, int, int32_t, int8 and int8_t

The _t data types are typedef types in the stdint.h header, while int is an in built fundamental data type. This make the _t available only if stdint.h exists. int on the other hand is guaranteed to exist.

C# : 'is' keyword and checking for Not

if(!(child is IContainer))

is the only operator to go (there's no IsNot operator).

You can build an extension method that does it:

public static bool IsA<T>(this object obj) {
    return obj is T;

and then use it to:

if (!child.IsA<IContainer>())

And you could follow on your theme:

public static bool IsNotAFreaking<T>(this object obj) {
    return !(obj is T);

if (child.IsNotAFreaking<IContainer>()) { // ...

Update (considering the OP's code snippet):

Since you're actually casting the value afterward, you could just use as instead:

public void Update(DocumentPart part) {
    IContainer containerPart = part as IContainer;
    if(containerPart == null) return;
    foreach(DocumentPart child in containerPart.Children) { // omit the cast.

Get json value from response

var results = {"id":"2231f87c-a62c-4c2c-8f5d-b76d11942301"}

results is now an object.

Remove ListView items in Android

I think if u add the following code, it will work


To remove an item, Just remove that item from the arraylist that we passed to the adapter and do listview.invalidateViews();
This will refresh the listview

An invalid XML character (Unicode: 0xc) was found

Today, I've got a similar error:

Servlet.service() for servlet [remoting] in context with path [/***] threw exception [Request processing failed; nested exception is java.lang.RuntimeException: buildDocument failed.] with root cause org.xml.sax.SAXParseException; lineNumber: 19; columnNumber: 91; An invalid XML character (Unicode: 0xc) was found in the value of attribute "text" and element is "label".

After my first encouter with the error, I had re-typed the entire line by hand, so that there was no way for a special character to creep in, and Notepad++ didn't show any non-printable characters (black on white), nevertheless I got the same error over and over.

When I looked up what I've done different than my predecessors, it turned out it was one additional space just before the closing /> (as I've heard was recommended for older parsers, but it shouldn't make any difference anyway, by the XML standards):

<label text="this label's text" layout="cell 0 0, align left" />

When I removed the space:

<label text="this label's text" layout="cell 0 0, align left"/>

everything worked just fine.

So it's definitely a misleading error message.

Absolute vs relative URLs

Should I use absolute or relative URLs?

If by absolute URLs you mean URLs including scheme (e.g. http / https) and the hostname (e.g. don't ever do that (for local resources) because it will be terrible to maintain and debug.

Let's say you have used absolute URL everywhere in your code like <img src="">. Now what will happen when you are going to:

  • switch to another scheme (e.g. http -> https)
  • switch domain names ( ->

In the first example what will happen is that you will get warnings about unsafe content being requested on the page. Because all your URLs are hardcoded to use http(:// And when running your pages over https the browser expects all resources to be loaded over https to prevent leaking of information.

In the second example when putting your site live from the test environment it would mean all resources are still pointing to your test domain instead of your live domain.

So to answer your question about whether to use absolute or relative URLs: always use relative URLs (for local resources).

What are the differences between the different URLs?

First lets have a look at the different types of urls that we can use:

  • //
  • /images/example.png
  • images/example.png

What resources do these URLs try to access on the server?

In the examples below I assume the website is running from the following location on the server /var/www/mywebsite.

The above (absolute) URL tries to access the resource /var/www/website/images/example.png. This type of URL is something you would always want to avoid for requesting resources from your own website for reason outlined above. However it does have its place. For example if you have a website and you want to request a resource from an external domain over https you should use this. E.g.


This URL is relative based on the current scheme used and should almost always be used when including external resources (images, javascripts etc).

What this type of URL does is use the current scheme of the page it is on. This means that you are on the page and on that page is an image tag <img src="//"> the URL of the image would resolve in
When you would have been on the page http**s**:// and on that page is an image tag <img src="//"> the URL of the image would resolve in

This prevent loading resources over https when it is not needed and automatically makes sure the resource is requested over https when it is needed.

The above URL resolves in the same manner on the server side as the previous URL:

The above (absolute) URL tries to access the resource /var/www/website/images/example.png.


For local resources this is the prefered way of referencing them. This is a relative URL based on the document root (/var/www/mywebsite) of your website. This means when you have <img src="/images/example.png"> it will always resolve to /var/www/mywebsite/images/example.png.

If at some point you decide to switch domain it will still work because it is relative.


This is also a relative URL although a bit different than the previous one. This URL is relative to the current path. What this means is that it will resolve to different paths depending on where you are in the site.

For example when you are on the page and you use <img src="images/example.png"> it would resolve on the server to /var/www/mywebsite/images/example.png as expected, however when your are on the page and you use the exact same image tag it suddenly will resolve to /var/www/mywebsite/some/path/images/example.png.

When to use what?

When requesting external resources you most likely want to use an URL relative to the scheme (unless you want to force a different scheme) and when dealing with local resources you want to use relative URLs based on the document root.

An example document:

<!DOCTYPE html>
        <link href='//,700italic,300,700' rel='stylesheet' type='text/css'>
        <link href="/style/style.css" rel="stylesheet" type="text/css" media="screen"></style>
        <img src="/images/some/localimage.png" alt="">
        <script src="//" ></script>

Some (kinda) duplicates

Trigger Change event when the Input value changed programmatically?

Vanilla JS solution:

var el = document.getElementById('changeProgramatic');
el.value='New Value'
el.dispatchEvent(new Event('change'));

Note that dispatchEvent doesn't work in old IE (see: caniuse). So you should probably only use it on internal websites (not on websites having wide audience).

So as of 2019 you just might want to make sure your customers/audience don't use Windows XP (yes, some still do in 2019). You might want to use conditional comments to warn customers that you don't support old IE (pre IE 11 in this case), but note that conditional comments only work until IE9 (don't work in IE10). So you might want to use feature detection instead. E.g. you could do an early check for: typeof document.body.dispatchEvent === 'function'.

How can I run specific migration in laravel

use this command php artisan migrate --path=/database/migrations/my_migration.php it worked for me..

Redirect all output to file using Bash on Linux?

Though not POSIX, bash 4 has the &> operator:

command &> alloutput.txt

Deserialize a JSON array in C#

This should work...

JavaScriptSerializer ser = new JavaScriptSerializer();
var records = new ser.Deserialize<List<Record>>(jsonData);

public class Person
    public string Name;
    public int Age;
    public string Location;
public class Record
    public Person record;

How do I list all cron jobs for all users?

Building on top of @Kyle

for user in $(tail -n +11 /etc/passwd | cut -f1 -d:); do echo $user; crontab -u $user -l; done

to avoid the comments usually at the top of /etc/passwd,

And on macosx

for user in $(dscl . -list /users | cut -f1 -d:); do echo $user; crontab -u $user -l; done    

Uncaught TypeError: (intermediate value)(...) is not a function

The error is a result of the missing semicolon on the third line:

window.Glog = function(msg) {
}; // <--- Add this semicolon

(function(win) {
  // ...

The ECMAScript specification has specific rules for automatic semicolon insertion, however in this case a semicolon isn't automatically inserted because the parenthesised expression that begins on the next line can be interpreted as an argument list for a function call.

This means that without that semicolon, the anonymous window.Glog function was being invoked with a function as the msg parameter, followed by (window) which was subsequently attempting to invoke whatever was returned.

This is how the code was being interpreted:

window.Glog = function(msg) {
}(function(win) {
  // ...

How do you hide the Address bar in Google Chrome for Chrome Apps?

2016-05-04-03:59A - Windows 7 - Google Chrome [Version 50.0.2661.94]

wanted this done for a 'YouTube Pop-out Player' without Chrome Address / Toolbar or Bookmarks Bar; solution ended up being a small edit of MarkHu's answer (because of new updates, i guess?)

Go to the page you want altered, select Chrome Toolbar's 'Hamburger button' (3 horizontal lines).

From there: More tools > Add to desktop... > Open as window (tick box) > Add (button).

... and, simply open your page from the new desktop shortcut, adjust as needed, and enjoy!

equivalent of vbCrLf in c#

I think that "\r\n" should work fine

jquery - disable click

If you're using jQuery versions 1.4.3+:


If not:

$('selector').click(function(){return false;});

Decorators with parameters?

In my instance, I decided to solve this via a one-line lambda to create a new decorator function:

def finished_message(function, message="Finished!"):

    def wrapper(*args, **kwargs):
        output = function(*args,**kwargs)
        return output

    return wrapper

def func():

my_finished_message = lambda f: finished_message(f, "All Done!")

def my_func():

if __name__ == '__main__':

When executed, this prints:

All Done!

Perhaps not as extensible as other solutions, but worked for me.

How to add pandas data to an existing csv file?

You can specify a python write mode in the pandas to_csv function. For append it is 'a'.

In your case:

df.to_csv('my_csv.csv', mode='a', header=False)

The default mode is 'w'.

How do I download NLTK data?

Please Try

import nltk

After running this you get something like this

NLTK Downloader
   d) Download   l) List    u) Update   c) Config   h) Help   q) Quit

Then, Press d

Do As Follows:

Downloader> d all

You will get following message on completion, and Prompt then Press q Done downloading collection all

What is `git push origin master`? Help with git's refs, heads and remotes

Or as a single command:

git push -u origin master:my_test

Pushes the commits from your local master branch to a (possibly new) remote branch my_test and sets up master to track origin/my_test.

find: missing argument to -exec

Just in case anyone sees a similar "missing -exec args" in Amazon Opsworks Chef bash scripts, I needed to add another backslash to escape the \;

bash 'remove_wars' do
  user 'ubuntu'
  cwd '/'
  code <<-EOH
    find /home/ubuntu/wars -type f -name "*.war" -exec rm {} \\;
  ignore_failure true

Convert char to int in C#

Has anyone considered using int.Parse() and int.TryParse() like this

int bar = int.Parse(foo.ToString());

Even better like this

int bar;
if (!int.TryParse(foo.ToString(), out bar))
    //Do something to correct the problem

It's a lot safer and less error prone

Keep background image fixed during scroll using css

Just add background-attachment to your code

body {
    background-position: center;
    background-image: url(../images/images5.jpg);
    background-attachment: fixed;

How to use S_ISREG() and S_ISDIR() POSIX Macros?

You're using S_ISREG() and S_ISDIR() correctly, you're just using them on the wrong thing.

In your while((dit = readdir(dip)) != NULL) loop in main, you're calling stat on currentPath over and over again without changing currentPath:

if(stat(currentPath, &statbuf) == -1) {
    return errno;

Shouldn't you be appending a slash and dit->d_name to currentPath to get the full path to the file that you want to stat? Methinks that similar changes to your other stat calls are also needed.

Internal Error 500 Apache, but nothing in the logs?

Why are the 500 Internal Server Errors not being logged into your apache error logs?

The errors that cause your 500 Internal Server Error are coming from a PHP module. By default, PHP does NOT log these errors. Reason being you want web requests go as fast as physically possible and it's a security hazard to log errors to screen where attackers can observe them.

These instructions to enable Internal Server Error Logging are for Ubuntu 12.10 with PHP 5.3.10 and Apache/2.2.22.

Make sure PHP logging is turned on:

  1. Locate your php.ini file:

    el@apollo:~$ locate php.ini
  2. Edit that file as root:

    sudo vi /etc/php5/apache2/php.ini
  3. Find this line in php.ini:

    display_errors = Off
  4. Change the above line to this:

    display_errors = On
  5. Lower down in the file you'll see this:

    ;   Default Value: Off
    ;   Development Value: On
    ;   Production Value: Off
    ;   Default Value: E_ALL & ~E_NOTICE
    ;   Development Value: E_ALL | E_STRICT
    ;   Production Value: E_ALL & ~E_DEPRECATED
  6. The semicolons are comments, that means the lines don't take effect. Change those lines so they look like this:

    display_startup_errors = On
    ;   Default Value: Off
    ;   Development Value: On
    ;   Production Value: Off
    error_reporting = E_ALL
    ;   Default Value: E_ALL & ~E_NOTICE
    ;   Development Value: E_ALL | E_STRICT
    ;   Production Value: E_ALL & ~E_DEPRECATED

    What this communicates to PHP is that we want to log all these errors. Warning, there will be a large performance hit, so you don't want this enabled on production because logging takes work and work takes time, time costs money.

  7. Restarting PHP and Apache should apply the change.

  8. Do what you did to cause the 500 Internal Server error again, and check the log:

    tail -f /var/log/apache2/error.log
  9. You should see the 500 error at the end, something like this:

    [Wed Dec 11 01:00:40 2013] [error] [client] PHP Fatal error:  
    Call to undefined function Foobar\\byob\\penguin\\alert() in /yourproject/
    your_src/symfony/Controller/MessedUpController.php on line 249, referer:

How to filter a data frame

Another method utilizing the dplyr package:

df <- mtcars %>%
        filter(mpg > 25)

Without the chain (%>%) operator:

df <- filter(mtcars, mpg > 25)

react button onClick redirect page

First, import it:

import { useHistory } from 'react-router-dom';

Then, in function or class:

const history = useHistory();

Finally, you put it in the onClick function:

<Button onClick={()=> history.push("/mypage")}>Click me!</Button>

Position last flex item at the end of container

This flexbox principle also works horizontally

During calculations of flex bases and flexible lengths, auto margins are treated as 0.
Prior to alignment via justify-content and align-self, any positive free space is distributed to auto margins in that dimension.

Setting an automatic left margin for the Last Item will do the work.

.last-item {
  margin-left: auto;

Code Example:

.container {_x000D_
  display: flex;_x000D_
  width: 400px;_x000D_
  outline: 1px solid black;_x000D_
p {_x000D_
  height: 50px;_x000D_
  width: 50px;_x000D_
  margin: 5px;_x000D_
  background-color: blue;_x000D_
.last-item {_x000D_
  margin-left: auto;_x000D_
<div class="container">_x000D_
  <p class="last-item"></p>_x000D_

Codepen Snippet

This can be very useful for Desktop Footers.

As Envato did here with the company logo.

Codepen Snippet

Build Step Progress Bar (css and jquery)

I had the same requirements to create a kind of step progress tracker so I created a JavaScript plugin for that purpose. Here is the JsFiddle for the demo for this step progress tracker. You can access its code on GitHub as well.

What it basically does is, it takes the json data(in a particular format described below) as input and creates the progress tracker based on that. Highlighted steps indicates the completed steps.

It's html will somewhat look like shown below with default CSS but you can customize it as per the theme of your application. There is an option to show tool-tip text for each steps as well.

Here is some code snippet for that:

//container div 
<div id="tracker1" style="width: 700px">

//sample JSON data
var sampleJson1 = {
ToolTipPosition: "bottom",
data: [{ order: 1, Text: "Foo", ToolTipText: "Step1-Foo", highlighted: true },
    { order: 2, Text: "Bar", ToolTipText: "Step2-Bar", highlighted: true },
    { order: 3, Text: "Baz", ToolTipText: "Step3-Baz", highlighted: false },
    { order: 4, Text: "Quux", ToolTipText: "Step4-Quux", highlighted: false }]

//Invoking the plugin
$(document).ready(function () {

Hopefully it will be useful for somebody else as well!

enter image description here

SQL update statement in C#

If you don't want to use the SQL syntax (which you are forced to), then switch to a framework like Entity Framework or Linq-to-SQL where you don't write the SQL statements yourself.

Set folder for classpath

If you are using Java 6 or higher you can use wildcards of this form:

java -classpath ".;c:\mylibs\*;c:\extlibs\*" MyApp

If you would like to add all subdirectories: lib\a\, lib\b\, lib\c\, there is no mechanism for this in except:

java -classpath ".;c:\lib\a\*;c:\lib\b\*;c:\lib\c\*" MyApp

There is nothing like lib\*\* or lib\** wildcard for the kind of job you want to be done.

Google Maps API V3 : How show the direction from a point A to point B (Blue line)?

Use the directions API.

Make an ajax call i.e.

and then parse the responce

Replace transparency in PNG images with white background

It appears that your command is correct so the problem might be due to missing support for PNG (). You can check with convert -list configure or just try the following:

sudo yum install libpng libpng-devel

MYSQL Truncated incorrect DOUBLE value

Try replacing the AND with ,

UPDATE shop_category 
SET name = 'Secolul XVI - XVIII', name_eng = '16th to 18th centuries' 
WHERE category_id = 4768

The UPDATE Syntax shows comma should be used as the separator.

Converting string to byte array in C#

If the result of, 'searchResult.Properties [ "user" ] [ 0 ]', is a string:

if ( ( searchResult.Properties [ "user" ].Count > 0 ) ) {

   profile.User = System.Text.Encoding.UTF8.GetString ( searchResult.Properties [ "user" ] [ 0 ].ToCharArray ().Select ( character => ( byte ) character ).ToArray () );


The key point being that converting a string to a byte [] can be done using LINQ:

.ToCharArray ().Select ( character => ( byte ) character ).ToArray () )

And the inverse:

.Select ( character => ( char ) character ).ToArray () )

How do I find the version of Apache running without access to the command line?

httpd -v will give you the version of Apache running on your server (if you have SSH/shell access).

The output should be something like this:

Server version: Apache/2.2.3
Server built:   Oct 20 2011 17:00:12

As has been suggested you can also do apachectl -v which will give you the same output, but will be supported by more flavours of Linux.

JavaScript sleep/wait before continuing

JS does not have a sleep function, it has setTimeout() or setInterval() functions.

If you can move the code that you need to run after the pause into the setTimeout() callback, you can do something like this:

//code before the pause
    //do what you need here
}, 2000);

see example here :

This won't halt the execution of your script, but due to the fact that setTimeout() is an asynchronous function, this code

    console.log("THIS IS");
}, 2000);

will print this in the console:


(note that DOG is printed before THIS IS)

You can use the following code to simulate a sleep for short periods of time:

function sleep(milliseconds) {
  var start = new Date().getTime();
  for (var i = 0; i < 1e7; i++) {
    if ((new Date().getTime() - start) > milliseconds){

now, if you want to sleep for 1 second, just use:



please note that this code will keep your script busy for n milliseconds. This will not only stop execution of Javascript on your page, but depending on the browser implementation, may possibly make the page completely unresponsive, and possibly make the entire browser unresponsive. In other words this is almost always the wrong thing to do.

How to re-create database for Entity Framework?

Just want to add to the excellent answer of @Lin:

5) B. If you don't have SQL Management Studio, go to "SQL Server Object Explorer". If you cannot see your project db in the localdb "SQL Server Object Explorer", then click on "Add SQL server" button to add it to the list manually. Then you can delete the db from the list.

How to set the From email address for mailx command?

You can use the "-r" option to set the sender address:

mailx -r [email protected] -s ...

How to force a UIViewController to Portrait orientation in iOS 6

If you want all of our navigation controllers to respect the top view controller you can use a category so you don't have to go through and change a bunch of class names.

@implementation UINavigationController (Rotation_IOS6)

    return [[self.viewControllers lastObject] shouldAutorotate];

    return [[self.viewControllers lastObject] supportedInterfaceOrientations];

- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation
    return [[self.viewControllers lastObject] preferredInterfaceOrientationForPresentation];


As a few of the comments point to, this is a quick fix to the problem. A better solution is subclass UINavigationController and put these methods there. A subclass also helps for supporting 6 and 7.

sql searching multiple words in a string

Oracle SQL :

select * 
where REGEXP_LIKE (company , 'Microsodt industry | goglge auto car | oracles    database')
  • company - is the database column name.
  • results - this SQL will show you if company column rows contain one of those companies (OR phrase) please note that : no wild characters are needed, it's built in.

more info at :

sweet-alert display HTML code in text

As of 2018, the accepted answer is out-of-date:

Sweetalert is maintained, and you can solve the original question's issue with use of the content option.

How to get a ListBox ItemTemplate to stretch horizontally the full width of the ListBox?

Since the border is used just for visual appearance, you could put it into the ListBoxItem's ControlTemplate and modify the properties there. In the ItemTemplate, you could place only the StackPanel and the TextBlock. In this way, the code also remains clean, as in the appearance of the control will be controlled via the ControlTemplate and the data to be shown will be controlled via the DataTemplate.

How to Convert JSON object to Custom C# object?

A good way to use JSON in C# is with JSON.NET

Quick Starts & API Documentation from JSON.NET - Official site help you work with it.

An example of how to use it:

public class User
    public User(string json)
        JObject jObject = JObject.Parse(json);
        JToken jUser = jObject["user"];
        name = (string) jUser["name"];
        teamname = (string) jUser["teamname"];
        email = (string) jUser["email"];
        players = jUser["players"].ToArray();

    public string name { get; set; }
    public string teamname { get; set; }
    public string email { get; set; }
    public Array players { get; set; }

// Use
private void Run()
    string json = @"{""user"":{""name"":""asdf"",""teamname"":""b"",""email"":""c"",""players"":[""1"",""2""]}}";
    User user = new User(json);

    Console.WriteLine("Name : " +;
    Console.WriteLine("Teamname : " + user.teamname);
    Console.WriteLine("Email : " +;

    foreach (var player in user.players)

The term "Add-Migration" is not recognized

It's so simple.

Just install Microsoft.EntityFrameworkCore.Tools package from nuget:

Install-Package Microsoft.EntityFrameworkCore.Tools -Version 3.1.5

You can also use this link to install the latest version: Nuget package link

.NET CLI command:

dotnet add package Microsoft.EntityFrameworkCore.Tools

How Do I Convert an Integer to a String in Excel VBA?

Another way to do it is to splice two parsed sections of the numerical value together:

Cells(RowNum, ColumnNum).Value = Mid(varNumber,1,1) & Mid(varNumber,2,Len(varNumber))

I have found better success with this than CStr() because CStr() doesn't seem to convert decimal numbers that came from variants in my experience.

Invalid column name sql error

Change this line:

cmd.CommandText = "INSERT INTO Data (Name,PhoneNo,Address) VALUES (" + txtName.Text + "," + txtPhone.Text + "," + txtAddress.Text + ");";

to this:

cmd.CommandText = "INSERT INTO Data (Name,PhoneNo,Address) VALUES ('" + txtName.Text + "','" + txtPhone.Text + "','" + txtAddress.Text + "');";

Your insert command is expecting text, and you need single quotes (') between the actual value so SQL can understand it as text.

EDIT: For those of you who aren't happy with this answer, I would like to point out that there is an issue with this code in regards to SQL Injection. When I answered this question I only considered the question in point which was the missing single-quote on his code and I pointed out how to fix it. A much better answer has been posted by Adam (and I voted for it), where he explains the issues with injection and shows a way to prevent. Now relax and be happy guys.

How to get current user, and how to use User class in MVC5?

In .Net MVC5 core 2.2, I use HttpContext.User.Identity.Name . It worked for me.

Reverting to a specific commit based on commit id with Git?

I think, bwawok's answer is wrong at some point:

if you do

git reset --soft c14809fa

It will make your local files changed to be like they were then, but leave your history etc. the same.

According to manual: git-reset, "git reset --soft"...

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

So it will "remove" newer commits from the branch. This means, after looking at your old code, you cannot go to the newest commit in this branch again, easily. So it does the opposide as described by bwawok: Local files are not changed (they look exactly as before "git reset --soft"), but the history is modified (branch is truncated after the specified commit).

The command for bwawok's answer might be:

git checkout <commit>

You can use this to peek at old revision: How did my code look yesterday?

(I know, I should put this in comments to this answer, but stackoverflow does not allow me to do so! My reputation is too low.)

How to activate the Bootstrap modal-backdrop?

Just append a div with that class to body, then remove it when you're done:

// Show the backdrop
$('<div class="modal-backdrop"></div>').appendTo(document.body);

// Remove it (later)

Live Example:

$("input").click(function() {_x000D_
  var bd = $('<div class="modal-backdrop"></div>');_x000D_
  setTimeout(function() {_x000D_
  }, 2000);_x000D_
<link href="//" rel="stylesheet" type="text/css" />_x000D_
<script src="//"></script>_x000D_
<script src="//"></script>_x000D_
<p>Click the button to get the backdrop for two seconds.</p>_x000D_
<input type="button" value="Click Me">

How to print a string multiple times?

It amazes me that this simple answer did not occur in the previous answers.

In my viewpoint, the easiest way to print a string on multiple lines, is the following :

print("Random String \n" * 100), where 100 stands for the number of lines to be printed.

How to correct indentation in IntelliJ

Solution of unchecking comment at first column is partially working, because it works for line comments, but not block comments.

So, with lines like:

/* first line
 * second line
 * ...


// line 1
// line 2
// line 3

they are indented with "Auto reformat", but lines like:

/* first line
   second line

the identation will not be fixed.

So you should:

  • add * or // before each line of comments
  • then uncheck Keep when reformatting -> comment at first column
  • and Auto reformat.

How to properly add cross-site request forgery (CSRF) token using PHP

Security Warning: md5(uniqid(rand(), TRUE)) is not a secure way to generate random numbers. See this answer for more information and a solution that leverages a cryptographically secure random number generator.

Looks like you need an else with your if.

if (!isset($_SESSION['token'])) {
    $token = md5(uniqid(rand(), TRUE));
    $_SESSION['token'] = $token;
    $_SESSION['token_time'] = time();
    $token = $_SESSION['token'];

Run a vbscript from another vbscript

As Martin's Answer didn't work at all for me ("File not found") and atesio's Answer does not allow to call two scripts which include repeating variable definitions, here is another alternative which finally worked for me:

filepath =  Chr(34) & "C:\...\helloworld.vbs" & Chr(34)
Set objshell= CreateObject("WScript.Shell") 
objshell.Run "wscript " & filepath, , True
Set objshell= Nothing

(Windows 8.1)

Git Remote: Error: fatal: protocol error: bad line length character: Unab

TL;DR: Do not omit username@ in your remote URLs when on Windows.

On Linux and on Windows with the default ssh, you can omit the username from remote URLs, like so:

git clone server-name:/srv/git/repo-name

Because ssh's default behavior is to just use whatever username you're currently logged in with. If you're on Windows and have set up git to use plink.exe so that you can use the key loaded in your pageant, then this will not work, because plink does not have this same automatic username behavior, resulting in those cryptic error messages, because it will prompt for the username:

$ plink server-name
login as: _


$ plink username@server-name
...logs you in...

If you already cloned a repository somehow you can fix the remotes in your .git/config by adding the username@ to the remote URL.

Javascript ES6/ES5 find in array and change

worked for me

let returnPayments = [ ...this.payments ];

returnPayments[this.payments.findIndex(x => ==] = this.payment;

Java character array initializer

Here's how you convert a String to a char array:

String str = "someString"; 
char[] charArray = str.toCharArray();

I'd recommend that you use an IDE when programming, to easily see which methods a class contains (in this case you'd be able to find toCharArray()) and compile errors like the one you have above. You should also familiarize yourself with the documentation, which in this case would be this String documentation.

Also, always post which compile errors you're getting. In this case it was easy to spot, but when it isn't you won't be able to get any answers if you don't include it in the post.

How to hide axes and gridlines in Matplotlib (python)

# Hide grid lines

# Hide axes ticks

Note, you need matplotlib>=1.2 for set_zticks() to work.

Insert 2 million rows into SQL Server quickly

You can try with SqlBulkCopy class.

Lets you efficiently bulk load a SQL Server table with data from another source.

There is a cool blog post about how you can use it.

How to get root directory of project in core. Directory.GetCurrentDirectory() doesn't seem to work correctly on a mac

If you are using ASP.NET MVC Core 3 or newer, IHostingEnvironment has been deprecated and replaced with IWebHostEnvironment

public Startup(IWebHostEnvironment webHostEnvironment)
    var webRootPath = webHostEnvironment.WebRootPath;

how to pass data in an hidden field from one jsp page to another?

To pass the value you must included the hidden value value="hiddenValue" in the <input> statement like so:

<input type="hidden" id="thisField" name="inputName" value="hiddenValue">

Then you recuperate the hidden form value in the same way that you recuperate the value of visible input fields, by accessing the parameter of the request object. Here is an example:

This code goes on the page where you want to hide the value.

<form action="anotherPage.jsp" method="GET">
    <input type="hidden" id="thisField" name="inputName" value="hiddenValue">
<input type="submit">   

Then on the 'anotherPage.jsp' page you recuperate the value by calling the getParameter(String name) method of the implicit request object, as so:

<% String hidden = request.getParameter("inputName"); %>
The Hidden Value is <%=hidden %>

The output of the above script will be:

The Hidden Value is hiddenValue 

How to get a unique device ID in Swift?

if (UIDevice.current.identifierForVendor?.uuidString) != nil
            self.lblDeviceIdValue.text = UIDevice.current.identifierForVendor?.uuidString

Java2D: Increase the line width

What is Stroke:

The BasicStroke class defines a basic set of rendering attributes for the outlines of graphics primitives, which are rendered with a Graphics2D object that has its Stroke attribute set to this BasicStroke.

Note that the Stroke setting:

Graphics2D g2 = (Graphics2D) g;
g2.setStroke(new BasicStroke(10));

is setting the line width,since BasicStroke(float width):

Constructs a solid BasicStroke with the specified line width and with default values for the cap and join styles.

And, it also effects other methods like Graphics2D.drawLine(int x1, int y1, int x2, int y2) and Graphics2D.drawRect(int x, int y, int width, int height):

The methods of the Graphics2D interface that use the outline Shape returned by a Stroke object include draw and any other methods that are implemented in terms of that method, such as drawLine, drawRect, drawRoundRect, drawOval, drawArc, drawPolyline, and drawPolygon.

Safely casting long to int in Java

A new method has been added with Java 8 to do just that.

import static java.lang.Math.toIntExact;

long foo = 10L;
int bar = toIntExact(foo);

Will throw an ArithmeticException in case of overflow.

See: Math.toIntExact(long)

Several other overflow safe methods have been added to Java 8. They end with exact.


  • Math.incrementExact(long)
  • Math.subtractExact(long, long)
  • Math.decrementExact(long)
  • Math.negateExact(long),
  • Math.subtractExact(int, int)

Delete newline in Vim

Certainly. Vim recognizes the \n character as a newline, so you can just search and replace. In command mode type:


Disable future dates after today in Jquery Ui Datepicker

In case you are appending Dtpicker,use the following code

    "dateOnly": true,
    "dateFormat": "YYYY-MM-DD",
    "closeOnSelected": true,
    maxDate: new Date()         

Is there any pythonic way to combine two dicts (adding values for keys that appear in both)?

def merge_with(f, xs, ys):
    xs = a_copy_of(xs) # dict(xs), maybe generalizable?
    for (y, v) in ys.iteritems():
        xs[y] = v if y not in xs else f(xs[x], v)

merge_with((lambda x, y: x + y), A, B)

You could easily generalize this:

def merge_dicts(f, *dicts):
    result = {}
    for d in dicts:
        for (k, v) in d.iteritems():
            result[k] = v if k not in result else f(result[k], v)

Then it can take any number of dicts.

returning a Void object

Java 8 has introduced a new class, Optional<T>, that can be used in such cases. To use it, you'd modify your code slightly as follows:

interface B<E>{ Optional<E> method(); }

class A implements B<Void>{

    public Optional<Void> method(){
        // do something
        return Optional.empty();

This allows you to ensure that you always get a non-null return value from your method, even when there isn't anything to return. That's especially powerful when used in conjunction with tools that detect when null can or can't be returned, e.g. the Eclipse @NonNull and @Nullable annotations.

How do I best silence a warning about unused variables?

An even cleaner way is to just comment out variable names:

int main(int /* argc */, char const** /* argv */) {
  return 0;

Significance of ios_base::sync_with_stdio(false); cin.tie(NULL);

The two calls have different meanings that have nothing to do with performance; the fact that it speeds up the execution time is (or might be) just a side effect. You should understand what each of them does and not blindly include them in every program because they look like an optimization.


This disables the synchronization between the C and C++ standard streams. By default, all standard streams are synchronized, which in practice allows you to mix C- and C++-style I/O and get sensible and expected results. If you disable the synchronization, then C++ streams are allowed to have their own independent buffers, which makes mixing C- and C++-style I/O an adventure.

Also keep in mind that synchronized C++ streams are thread-safe (output from different threads may interleave, but you get no data races).


This unties cin from cout. Tied streams ensure that one stream is flushed automatically before each I/O operation on the other stream.

By default cin is tied to cout to ensure a sensible user interaction. For example:

std::cout << "Enter name:";
std::cin >> name;

If cin and cout are tied, you can expect the output to be flushed (i.e., visible on the console) before the program prompts input from the user. If you untie the streams, the program might block waiting for the user to enter their name but the "Enter name" message is not yet visible (because cout is buffered by default, output is flushed/displayed on the console only on demand or when the buffer is full).

So if you untie cin from cout, you must make sure to flush cout manually every time you want to display something before expecting input on cin.

In conclusion, know what each of them does, understand the consequences, and then decide if you really want or need the possible side effect of speed improvement.

Why can I not push_back a unique_ptr into a vector?

std::unique_ptr has no copy constructor. You create an instance and then ask the std::vector to copy that instance during initialisation.

error: deleted function 'std::unique_ptr<_Tp, _Tp_Deleter>::uniqu
e_ptr(const std::unique_ptr<_Tp, _Tp_Deleter>&) [with _Tp = int, _Tp_D
eleter = std::default_delete<int>, std::unique_ptr<_Tp, _Tp_Deleter> =

The class satisfies the requirements of MoveConstructible and MoveAssignable, but not the requirements of either CopyConstructible or CopyAssignable.

The following works with the new emplace calls.

std::vector< std::unique_ptr< int > > vec;
vec.emplace_back( new int( 1984 ) );

See using unique_ptr with standard library containers for further reading.

Tensorflow installation error: not a supported wheel on this platform

It means that the version of your default python (python -V) and the version of your default pip (pip -V) do not match. You have built tensorflow with your default python and trying to use a different pip version to install it. In mac, delete /usr/local/bin/pip and rename(copy) pipx.y (whatever x.y version that matches your python version) to pip in that folder.

Missing XML comment for publicly visible type or member

Add XML comments to the publicly visible types and members of course :)

/// Gets the answer
public int MyMethod()
   return 42;

You need these <summary> type comments on all members - these also show up in the intellisense popup menu.

The reason you get this warning is because you've set your project to output documentation xml file (in the project settings). This is useful for class libraries (.dll assemblies) which means users of your .dll are getting intellisense documentation for your API right there in visual studio.

I recommend you get yourself a copy of the GhostDoc Visual Studio AddIn.. Makes documenting much easier.

Adding a caption to an equation in LaTeX

The \caption command is restricted to floats: you will need to place the equation in a figure or table environment (or a new kind of floating environment). For example:

\[ E = m c^2 \]
\caption{A famous equation}

The point of floats is that you let LaTeX determine their placement. If you want to equation to appear in a fixed position, don't use a float. The \captionof command of the caption package can be used to place a caption outside of a floating environment. It is used like this:

\[ E = m c^2 \]
\captionof{figure}{A famous equation}

This will also produce an entry for the \listoffigures, if your document has one.

To align parts of an equation, take a look at the eqnarray environment, or some of the environments of the amsmath package: align, gather, multiline,...

Passive Link in Angular 2 - <a href=""> equivalent

Here is a simple way

  <div (click)="$event.preventDefault()">
            <a href="#"></a>

capture the bubbling event and shoot it down

Rails formatting date

Try this:


It's a time formatting function which provides you a way to present the string representation of the date. (

From APIdock:

%Y%m%d           => 20071119                  Calendar date (basic)
%F               => 2007-11-19                Calendar date (extended)
%Y-%m            => 2007-11                   Calendar date, reduced accuracy, specific month
%Y               => 2007                      Calendar date, reduced accuracy, specific year
%C               => 20                        Calendar date, reduced accuracy, specific century
%Y%j             => 2007323                   Ordinal date (basic)
%Y-%j            => 2007-323                  Ordinal date (extended)
%GW%V%u          => 2007W471                  Week date (basic)
%G-W%V-%u        => 2007-W47-1                Week date (extended)
%GW%V            => 2007W47                   Week date, reduced accuracy, specific week (basic)
%G-W%V           => 2007-W47                  Week date, reduced accuracy, specific week (extended)
%H%M%S           => 083748                    Local time (basic)
%T               => 08:37:48                  Local time (extended)
%H%M             => 0837                      Local time, reduced accuracy, specific minute (basic)
%H:%M            => 08:37                     Local time, reduced accuracy, specific minute (extended)
%H               => 08                        Local time, reduced accuracy, specific hour
%H%M%S,%L        => 083748,000                Local time with decimal fraction, comma as decimal sign (basic)
%T,%L            => 08:37:48,000              Local time with decimal fraction, comma as decimal sign (extended)
%H%M%S.%L        => 083748.000                Local time with decimal fraction, full stop as decimal sign (basic)
%T.%L            => 08:37:48.000              Local time with decimal fraction, full stop as decimal sign (extended)
%H%M%S%z         => 083748-0600               Local time and the difference from UTC (basic)
%T%:z            => 08:37:48-06:00            Local time and the difference from UTC (extended)
%Y%m%dT%H%M%S%z  => 20071119T083748-0600      Date and time of day for calendar date (basic)
%FT%T%:z         => 2007-11-19T08:37:48-06:00 Date and time of day for calendar date (extended)
%Y%jT%H%M%S%z    => 2007323T083748-0600       Date and time of day for ordinal date (basic)
%Y-%jT%T%:z      => 2007-323T08:37:48-06:00   Date and time of day for ordinal date (extended)
%GW%V%uT%H%M%S%z => 2007W471T083748-0600      Date and time of day for week date (basic)
%G-W%V-%uT%T%:z  => 2007-W47-1T08:37:48-06:00 Date and time of day for week date (extended)
%Y%m%dT%H%M      => 20071119T0837             Calendar date and local time (basic)
%FT%R            => 2007-11-19T08:37          Calendar date and local time (extended)
%Y%jT%H%MZ       => 2007323T0837Z             Ordinal date and UTC of day (basic)
%Y-%jT%RZ        => 2007-323T08:37Z           Ordinal date and UTC of day (extended)
%GW%V%uT%H%M%z   => 2007W471T0837-0600        Week date and local time and difference from UTC (basic)
%G-W%V-%uT%R%:z  => 2007-W47-1T08:37-06:00    Week date and local time and difference from UTC (extended)

jQuery .scrollTop(); + animation

Try this code:

    $("html, body").animate({ scrollTop: 0 }, 600);
    return false;

Differences between Emacs and Vim

I have worked with spacemacs for about 2 years and neovim for about a year now in a production/research environment. Spacemacs is emacs with couple of nice extra features like layers etc. And neovim is a fork of vim again with some extra features.

I am quite unsatisfied with both of them in terms of experience. And I am still on the look out for a long term solution for my text editing needs.

Here is a simple comparison:

  • Neovim, vim, emacs, spacemacs, etc all of those editors consume less ressources compared to most of the editors out there.

  • Neovim/vim is slightly faster than emacs, noticably faster than spacemacs.

  • In terms of editing experience. I can easily say that emacs packages feel superior. I think that's because they blend in better with the core of emacs.

  • Vimscript is nice and there are certainly great projects in the vim ecosystem as well. The good thing is they are better documented than most emacs projects I have seen so far.

  • Both can be glitchy depending on the package you are using. Spacemacs tend to freeze, and neovim tend to display scary error messages, so pick your poison there.

  • Modal editing in vim, is not an intuitive concept, but once you get used to it, you want it anywere. Both of the editor provide that.

How can I change the default credentials used to connect to Visual Studio Online (TFSPreview) when loading Visual Studio up?

I had a very similiar problem as I was not able to connect to TFS with my own credentials. Turned out that the user who had created the image (I was using Hyper-V) stored his account in Credential Manager. There was no way to change this in Visual Studio. To solve the issue, I opened Credential Manager in Control Panel and edited the Generic Credentials to be my own account. I closed and opened Visual Studio 2012, and reconnected to TFS. It prompted me for my credentials, but it connected with my account from then on.

hope this helps, sivilian

How to make sure docker's time syncs with that of the host?

With docker for windows I had to tick

MobyLinuxVM > Settings > Integration Services > Time synchronization 

in Hyper-V manager and it worked

'console' is undefined error for Internet Explorer

In IE9, if console is not opened, this code:

alert(typeof console);

will show "object", but this code

alert(typeof console.log);

will throw TypeError exception, but not return undefined value;

So, guaranteed version of code will look similar to this:

try {
    if (window.console && window.console.log) {
        my_console_log = window.console.log;
} catch (e) {
    my_console_log = function() {};

How to get the primary IP address of the local machine on Linux and OS X?

I have to add to Collin Andersons answer that this method also takes into account if you have two interfaces and they're both showing as up.

ip route get 1 | awk '{print $NF;exit}'

I have been working on an application with Raspberry Pi's and needed the IP address that was actually being used not just whether it was up or not. Most of the other answers will return both IP address which isn't necessarily helpful - for my scenario anyway.

How to create a sub array from another array in Java?

You can use

JDK > 1.5

Arrays.copyOfRange(Object[] src, int from, int to)


JDK <= 1.5

System.arraycopy(Object[] src, int srcStartIndex, Object[] dest, int dstStartIndex, int lengthOfCopiedIndices); 


How can I force browsers to print background images in CSS?

You can use borders for fixed colors.

 borderTop: solid 15px black;

and for gradient background you can use:

    box-sizing: border-box;
    border-style: solid;
    border-top: 0px;
    border-left: 0px;
    border-right: 0px;
    border-image: linear-gradient(to right, red, blue) 100%;
    border-image-slice: 1;
    border-width: 18px;

Error when deploying an artifact in Nexus

400 Bad Request will be returned if you attempt to:

  1. Deploy a snapshot artifact (or version) ending in -SNAPSHOT to a release repository
  2. Deploy a release artifact (version not ending in -SNAPSHOT) to a snapshot repository
  3. Deploy the same version of a release artifact more than once to a release repository

laravel 5.5 The page has expired due to inactivity. Please refresh and try again

I know this question has been satisfactorily answered, but I wanted to mention a fix that worked in my case. I added {{ csrf_field() }} and it still didn't work.

Then I remembered that I blocked all cookies for development purposes, which can be nice when you change the page and want to refresh it.

Once I changed the settings to stop blocking all cookies in MS Edge browser the problem went away.

How do I implement JQuery.noConflict() ?

In addition to that, passing true to $.noConflict(true); will also restore previous (if any) global variable jQuery, so that plugins can be initialized with correct jQuery version when multiple versions are being used.

How to determine the current language of a wordpress page when using polylang?

This plugin is documented rather good in

Switching post language

The developers documentation states the following logic as a means to generate URL's for different translations of the same post

<?php while ( have_posts() ) : the_post(); ?>
<ul class='translations'><?php pll_the_languages(array('post_id' =>; $post->ID)); ?></ul>
<?php the_content(); ?>
<?php endwhile; ?>

If you want more influence on what is rendered, inspet pll_the_languages function and copy it's behaviour to your own output implementation

Switching site language

As you want buttons to switch language, this page: will give you the required info.

An implementation example:

<ul><?php pll_the_languages();?></ul>

Then style with CSS to create buttons, flags or whatever you want. It is also possible to use a widget for this, provided by te plugin

Getting current language

All plugins functions are explained here:

In this case use:


Convert string to number field

Within Crystal, you can do it by creating a formula that uses the ToNumber function. It might be a good idea to code for the possibility that the field might include non-numeric data - like so:

If NumericText ({field}) then ToNumber ({field}) else 0

Alternatively, you might find it easier to convert the field's datatype within the query used in the report.

Changing the resolution of a VNC session in linux

Interestingly no one answered this. In TigerVNC, when you are logged into the session. Go to System > Preference > Display from the top menu bar ( I was using Cent OS as my remote Server). Click on the resolution drop down, there are various settings available including 1080p. Select the one that you like. It will change on the fly.

enter image description here

Make sure you Apply the new setting when a dialog is prompted. Otherwise it will revert back to the previous setting just like in Windows

const char* concatenation

const char* one = "one";
const char* two = "two";
char result[40];
sprintf(result, "%s%s", one, two);

find all unchecked checkbox in jquery

You can use like this :


How to access the first property of a Javascript object?

To get the first key name in the object you can use:

var obj = { first: 'someVal' };
Object.keys(obj)[0]; //returns 'first'

Returns a string, so you cant access nested objects if there were, like:

var obj = { first: { someVal : { id : 1} }; Here with that solution you can't access id.

The best solution if you want to get the actual object is using lodash like:


To return the value of the first key, (if you don't know exactly the first key name):

var obj = { first: 'someVal' };
obj[Object.keys(obj)[0]]; //returns 'someVal'

if you know the key name just use:




sequelize findAll sort order in nodejs

If you want to sort data either in Ascending or Descending order based on particular column, using sequlize js, use the order method of sequlize as follows

// Will order the specified column by descending order
order: sequelize.literal('column_name order')
e.g. order: sequelize.literal('timestamp DESC')

Show div #id on click with jQuery

The problem you're having is that the event-handlers are being bound before the elements are present in the DOM, if you wrap the jQuery inside of a $(document).ready() then it should work perfectly well:

        $("#music").click(function () {


An alternative is to place the <script></script> at the foot of the page, so it's encountered after the DOM has been loaded and ready.

To make the div hide again, once the #music element is clicked, simply use toggle():

        $("#music").click(function () {

JS Fiddle demo.

And for fading:

        $("#music").click(function () {

JS Fiddle demo.

Max retries exceeded with URL in requests

What happened here is that itunes server refuses your connection (you're sending too many requests from same ip address in short period of time)

Max retries exceeded with url: /in/app/adobe-reader/id469337564?mt=8

error trace is misleading it should be something like "No connection could be made because the target machine actively refused it".

There is an issue at about python.requests lib at Github, check it out here

To overcome this issue (not so much an issue as it is misleading debug trace) you should catch connection related exceptions like so:

    page1 = requests.get(ap)
except requests.exceptions.ConnectionError:
    r.status_code = "Connection refused"

Another way to overcome this problem is if you use enough time gap to send requests to server this can be achieved by sleep(timeinsec) function in python (don't forget to import sleep)

from time import sleep

All in all requests is awesome python lib, hope that solves your problem.

Add new column with foreign key constraint in one command

You can do it like below in SQL Server

ADD two_id int foreign key

How to remove focus without setting focus to another control?


using the following in the activity with some layout options below seemed to work as desired.


in connection with the following parameters on the root view.

    android:descendantFocusability="beforeDescendants" />

Answer thanks to:

About windowSoftInputMode

There's yet another point of contention to be aware of. By default, Android will automatically assign initial focus to the first EditText or focusable control in your Activity. It naturally follows that the InputMethod (typically the soft keyboard) will respond to the focus event by showing itself. The windowSoftInputMode attribute in AndroidManifest.xml, when set to stateAlwaysHidden, instructs the keyboard to ignore this automatically-assigned initial focus.


great reference

SQL Server equivalent to Oracle's CREATE OR REPLACE VIEW

For reference from SQL Server 2016 SP1+ you could use CREATE OR ALTER VIEW syntax.


CREATE [ OR ALTER ] VIEW [ schema_name . ] view_name [ (column [ ,...n ] ) ]   
[ WITH <view_attribute> [ ,...n ] ]   
AS select_statement   
[ ; ]


Conditionally alters the view only if it already exists.

db<>fiddle demo

How to read the Stock CPU Usage data

So far this has been the most helpful source of information regarding this I could find. Apparently the numbers do NOT reperesent load average in %:

Clear text area

This works:


Change the background color of a pop-up dialog

You can use a custom style:

  <!-- Alert Dialog -->
  <style name="ThemeOverlay.MaterialComponents.MaterialAlertDialog_Background" parent="@style/ThemeOverlay.MaterialComponents.MaterialAlertDialog">
    <!-- Background Color-->
    <item name="android:background">@color/.....</item>
    <!-- Text Color for title and message -->
    <item name="colorOnSurface">@color/......</item>
    <!-- Style for positive button -->
    <item name="buttonBarPositiveButtonStyle">@style/PositiveButtonStyle</item>
    <!-- Style for negative button -->
    <item name="buttonBarNegativeButtonStyle">@style/NegativeButtonStyle</item>

  <style name="PositiveButtonStyle" parent="@style/Widget.MaterialComponents.Button">
    <!-- text color for the button -->
    <item name="android:textColor">@color/.....</item>
    <!-- Background tint for the button -->
    <item name="backgroundTint">@color/primaryDarkColor</item>

And just use the default MaterialAlertDialogBuilder:

    new MaterialAlertDialogBuilder(AlertDialogActivity.this,
        .setMessage("Message...  ....")
        .setPositiveButton("Ok", /* listener = */ null)

enter image description here

SQL update trigger only when column is modified

One should check if QtyToRepair is updated at first.

ALTER TRIGGER [dbo].[tr_SCHEDULE_Modified]
   ON [dbo].[SCHEDULE]
    IF UPDATE (QtyToRepair) 
        SET modified = GETDATE()
           , ModifiedUser = SUSER_NAME()
           , ModifiedHost = HOST_NAME()
            ON S.OrderNo = I.OrderNo and S.PartNumber =    I.PartNumber
        WHERE S.QtyToRepair <> I.QtyToRepair

Android device is not connected to USB for debugging (Android studio)

If you are on windows, many times it will not recognize the device fully and because of driver issues, the device won't show up.

  • go to settings
  • control panel
  • hardware and sound
  • device manager

And look for any devices showing an error. Many androids will show as an unknown USB device. Select that device and try to update the drivers for it.

Can Flask have optional URL parameters?

@user.route('/<user_id>', defaults={'username': default_value})
def show(user_id, username):

How can I pass an argument to a PowerShell script?

Create a PowerShell script with the following code in the file.

Get-ChildItem $path | Where-Object {$_.LinkType -eq 'SymbolicLink'} | select name, target

This creates a script with a path parameter. It will list all symbolic links within the path provided as well as the specified target of the symbolic link.

Install gitk on Mac

As of macOS Catalina 10.15.6, I run:

brew install git
brew install git-gui

and it worked for me.

Query based on multiple where clauses in Firebase

I've written a personal library that allows you to order by multiple values, with all the ordering done on the server.

Meet Querybase!

Querybase takes in a Firebase Database Reference and an array of fields you wish to index on. When you create new records it will automatically handle the generation of keys that allow for multiple querying. The caveat is that it only supports straight equivalence (no less than or greater than).

const databaseRef = firebase.database().ref().child('people');
const querybaseRef = querybase.ref(databaseRef, ['name', 'age', 'location']);

// Automatically handles composite keys
  name: 'David',
  age: 27,
  location: 'SF'

// Find records by multiple fields
// returns a Firebase Database ref
const queriedDbRef = querybaseRef
   name: 'David',
   age: 27

// Listen for realtime updates
queriedDbRef.on('value', snap => console.log(snap));

Thymeleaf: Concatenation - Could not parse as expression

But from what I see you have quite a simple error in syntax

<p th:text="${bean.field} + '!' + ${bean.field}">Static content</p>

the correct syntax would look like

<p th:text="${bean.field + '!' + bean.field}">Static content</p>

As a matter of fact, the syntax th:text="'static part' + ${bean.field}" is equal to th:text="${'static part' + bean.field}".

Try it out. Even though this is probably kind of useless now after 6 months.

Getting the count of unique values in a column in bash

Here is a way to do it in the shell:

cut -f $FIELD * | sort| uniq -c |sort -nr

This is the sort of thing bash is great at.

Specify JDK for Maven to use

Using this command below also worked for me, using it right after installation of Java 8 from here

export JAVA_HOME=$(/usr/libexec/java_home)

Convert pandas data frame to series

You can retrieve the series through slicing your dataframe using one of these two methods:

import pandas as pd
import numpy as np
df = pd.DataFrame(data=np.random.randn(1,8))


How to fetch Java version using single line command in Linux

This way works for me.

# java -version 2>&1|awk '/version/ {gsub("\"","") ; print $NF}'


XML Error: Extra content at the end of the document

You need a root node

<?xml version="1.0" encoding="ISO-8859-1"?>    
        <name>Sample Document</name>


Powershell: convert string to number

Simply casting the string as an int won't work reliably. You need to convert it to an int32. For this you can use the .NET convert class and its ToInt32 method. The method requires a string ($strNum) as the main input, and the base number (10) for the number system to convert to. This is because you can not only convert to the decimal system (the 10 base number), but also to, for example, the binary system (base 2).

Give this method a try:

[string]$strNum = "1.500"
[int]$intNum = [convert]::ToInt32($strNum, 10)


Calling async method synchronously

Well I am using this approach:

    private string RunSync()
        var task = Task.Run(async () => await GenerateCodeService.GenerateCodeAsync());
        if (task.IsFaulted && task.Exception != null)
            throw task.Exception;

        return task.Result;

Alternative to file_get_contents?

Yes, if you have URL wrappers disabled you should use sockets or, even better, the cURL library.

If it's part of your site then refer to it with the file system path, not the web URL. /var/www/..., rather than http://domain.tld/....

How to show text on image when hovering?

<img id="close" className="fa fa-close" src="" alt="" title="Close Me" />

#close[title]:hover:after {
  color: red;
  content: attr(title);
  position: absolute;
  left: 50px;

How to make Unicode charset in cmd.exe by default?

Open an elevated Command Prompt (run cmd as administrator). query your registry for available TT fonts to the console by:

    REG query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Console\TrueTypeFont"

You'll see an output like :

    0    REG_SZ    Lucida Console
    00    REG_SZ    Consolas
    936    REG_SZ    *???
    932    REG_SZ    *MS ????

Now we need to add a TT font that supports the characters you need like Courier New, we do this by adding zeros to the string name, so in this case the next one would be "000" :

    REG ADD "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Console\TrueTypeFont" /v 000 /t REG_SZ /d "Courier New"

Now we implement UTF-8 support:

    REG ADD HKCU\Console /v CodePage /t REG_DWORD /d 65001 /f

Set default font to "Courier New":

    REG ADD HKCU\Console /v FaceName /t REG_SZ /d "Courier New" /f

Set font size to 20 :

    REG ADD HKCU\Console /v FontSize /t REG_DWORD /d 20 /f

Enable quick edit if you like :

    REG ADD HKCU\Console /v QuickEdit /t REG_DWORD /d 1 /f

Android: How to programmatically access the device serial number shown in the AVD manager (API Version 8)

Up to Android 7.1 (SDK 25)

Until Android 7.1 you will get it with:


From Android 8 (SDK 26)

On Android 8 (SDK 26) and above, this field will return UNKNOWN and must be accessed with:


which requires the dangerous permission android.permission.READ_PHONE_STATE.

From Android Q (SDK 29)

Since Android Q using Build.getSerial() gets a bit more complicated by requiring:

android.Manifest.permission.READ_PRIVILEGED_PHONE_STATE (which can only be acquired by system apps), or for the calling package to be the device or profile owner and have the READ_PHONE_STATE permission. This means most apps won't be able to uses this feature. See the Android Q announcement from Google.

See Android SDK reference

Best Practice for Unique Device Identifier

If you just require a unique identifier, it's best to avoid using hardware identifiers as Google continuously tries to make it harder to access them for privacy reasons. You could just generate a UUID.randomUUID().toString(); and save it the first time it needs to be accessed in e.g. shared preferences. Alternatively you could use ANDROID_ID which is a 8 byte long hex string unique to the device, user and (only Android 8+) app installation. For more info on that topic, see Best practices for unique identifiers.

Adding rows to dataset

To add rows to existing DataTable in Dataset:

DataRow drPartMtl = DSPartMtl.Tables[0].NewRow();
drPartMtl["Group"] = "Group";
drPartMtl["BOMPart"] = "BOMPart";

Installing Oracle Instant Client

I was able to setup Oracle Instant Client (Basic) 11g2 and Oracle ODBC (32bit) drivers on my 32bit Windows 7 PC. Note: you'll need a 'tnsnames.ora' file because it doesn't come with one. You can Google examples and copy/paste into a text file, change the parameters for your environment.

Setting up Oracle Instant Client-Basic 11g2 (Win7 32-bit)
(I think there's another step or two if your using 64-bit)

Oracle Instant Client

  • Unzip Oracle Instant Client - Basic
  • Put contents in folder like "C:\instantclient"
  • Edit PATH evironment variable, add path to Instant Client folder to the Variable Value.
  • Add new Variable called "TNS_ADMIN" point to same folder as Instant Client.
  • I had to create a "tnsnames.ora" file because it doesn't come with one. Put it in same folder as the client.
  • reboot or use Task Manager to kill "explorer.exe" and restart it to refresh the PATH environment variables.

ODBC Drivers

  • Unzip ODBC drivers
  • Copy all files into same folder as client "C:\instantclient"
  • Use command prompt to run "odbc_install.exe" (should say it was successful)

Note: The "un-documented" things that were hanging me up where...
- All files (Client and Drivers) needed to be in the same folder (nothing in sub-folders).
- Running the ODBC driver from the command prompt will allow you to see if it installs successfully. Double-clicking the installer just flashed a box on the screen, no idea it was failing because no error dialog.

After you've done this you should be able to setup a new DSN Data Source using the Oracle ODBC driver.
-Hope this helps someone else.

Send Post Request with params using Retrofit


      compile ''

      compile 'com.squareup.retrofit2:retrofit:2.1.0'// compulsory

      compile 'com.squareup.retrofit2:converter-gson:2.1.0' //for retrofit conversion

Login APi Put Two Parameters

        "UserId": "1234",

Login Response

        "UserId": "1234",
        "FirstName": "Keshav",
        "LastName": "Gera",
        "ProfilePicture": "312.113.221.1/GEOMVCAPI/Files/1.500534651736E12p.jpg"

    import retrofit2.Retrofit;
    import retrofit2.converter.gson.GsonConverterFactory;

    class APIClient {

        public static final String BASE_URL = "Your Base Url ";
        private static Retrofit retrofit = null;

        public static Retrofit getClient() {
            if (retrofit == null) {
                retrofit = new Retrofit.Builder()
            return retrofit;

APIInterface interface

    interface APIInterface {

        Call<LoginResponse> createUser(@Body LoginResponse login);

Login Pojo

    package pojos;


    public class LoginResponse {

        public String UserId;
        public String FirstName;
        public String LastName;
        public String ProfilePicture;
        public String Password;
        public String ResponseCode;
        public String ResponseMessage;

        public LoginResponse(String UserId, String Password) {
            this.UserId = UserId;
            this.Password = Password;

        public String getUserId() {
            return UserId;

        public String getFirstName() {
            return FirstName;

        public String getLastName() {
            return LastName;

        public String getProfilePicture() {
            return ProfilePicture;

        public String getResponseCode() {
            return ResponseCode;

        public String getResponseMessage() {
            return ResponseMessage;


    package com.keshav.retrofitloginexampleworkingkeshav;

    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;
    import android.widget.Toast;

    import pojos.LoginResponse;
    import retrofit2.Call;
    import retrofit2.Callback;
    import retrofit2.Response;
    import utilites.CommonMethod;

    public class MainActivity extends AppCompatActivity {

        TextView responseText;
        APIInterface apiInterface;

        Button loginSub;
        EditText et_Email;
        EditText et_Pass;
        private Dialog mDialog;
        String userId;
        String password;

        protected void onCreate(Bundle savedInstanceState) {

            apiInterface = APIClient.getClient().create(APIInterface.class);

            loginSub = (Button) findViewById(;
            et_Email = (EditText) findViewById(;
            et_Pass = (EditText) findViewById(;

            loginSub.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                    if (checkValidation()) {
                        if (CommonMethod.isNetworkAvailable(MainActivity.this))
                            loginRetrofit2Api(userId, password);
                            CommonMethod.showAlert("Internet Connectivity Failure", MainActivity.this);

        private void loginRetrofit2Api(String userId, String password) {
            final LoginResponse login = new LoginResponse(userId, password);
            Call<LoginResponse> call1 = apiInterface.createUser(login);
            call1.enqueue(new Callback<LoginResponse>() {
                public void onResponse(Call<LoginResponse> call, Response<LoginResponse> response) {
                    LoginResponse loginResponse = response.body();

                    Log.e("keshav", "loginResponse 1 --> " + loginResponse);
                    if (loginResponse != null) {
                        Log.e("keshav", "getUserId          -->  " + loginResponse.getUserId());
                        Log.e("keshav", "getFirstName       -->  " + loginResponse.getFirstName());
                        Log.e("keshav", "getLastName        -->  " + loginResponse.getLastName());
                        Log.e("keshav", "getProfilePicture  -->  " + loginResponse.getProfilePicture());

                        String responseCode = loginResponse.getResponseCode();
                        Log.e("keshav", "getResponseCode  -->  " + loginResponse.getResponseCode());
                        Log.e("keshav", "getResponseMessage  -->  " + loginResponse.getResponseMessage());
                        if (responseCode != null && responseCode.equals("404")) {
                            Toast.makeText(MainActivity.this, "Invalid Login Details \n Please try again", Toast.LENGTH_SHORT).show();
                        } else {
                            Toast.makeText(MainActivity.this, "Welcome " + loginResponse.getFirstName(), Toast.LENGTH_SHORT).show();

                public void onFailure(Call<LoginResponse> call, Throwable t) {
                    Toast.makeText(getApplicationContext(), "onFailure called ", Toast.LENGTH_SHORT).show();

        public boolean checkValidation() {
            userId = et_Email.getText().toString();
            password = et_Pass.getText().toString();

            Log.e("Keshav", "userId is -> " + userId);
            Log.e("Keshav", "password is -> " + password);

            if (et_Email.getText().toString().trim().equals("")) {
                CommonMethod.showAlert("UserId Cannot be left blank", MainActivity.this);
                return false;
            } else if (et_Pass.getText().toString().trim().equals("")) {
                CommonMethod.showAlert("password Cannot be left blank", MainActivity.this);
                return false;
            return true;

    public class CommonMethod {

        public static final String DISPLAY_MESSAGE_ACTION =

        public static final String EXTRA_MESSAGE = "message";

        public  static boolean isNetworkAvailable(Context ctx) {
            ConnectivityManager connectivityManager
                    = (ConnectivityManager)ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
            return activeNetworkInfo != null && activeNetworkInfo.isConnected();

        public static void showAlert(String message, Activity context) {

            final AlertDialog.Builder builder = new AlertDialog.Builder(context);
                    .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {

            try {
            } catch (Exception e) {



    <LinearLayout android:layout_width="wrap_content"


                android:text="Holostik Track and Trace"
                android:visibility="gone" />


                    android:hint="Login ID"




                    android:singleLine="true" />



                    android:textColor="#ffffff" />    


How to obtain Signing certificate fingerprint (SHA1) for OAuth 2.0 on Android?

I know this question has been answered but this is how I found my signature for the default keystore. In Eclipse, if you go to Windows -> Preferences -> Android -> Build

enter image description here

How can I get the order ID in WooCommerce?

I didnt test it and dont know were you need it, but:

$order = new WC_Order(post->ID);
echo $order->get_order_number();

Let me know if it works. I belive order number echoes with the "#" but you can split that if only need only the number.

Subdomain on different host

sub domain is part of the domain, it's like subletting a room of an apartment. A records has to be setup on the dns for the domain e.g has IP 123.456.789.999 and hosted with Godaddy. Now to get the sub domain

of which the site is actually on another server then

login to Godaddy and add an A record dnsimple and point the IP to the other server

And that's it.

how to get the base url in javascript

var baseTags = document.getElementsByTagName("base");
var basePath = baseTags.length ? 
    baseTags[ 0 ].href.substr( location.origin.length, 999 ) : 

How to export/import PuTTy sessions list?

For those who don't want to mess with the registry, a variation of putty that saves to file has been created. It is located here:

It would be nice if the putty team would take this as an option into the main distribution.

What is the difference between Class.getResource() and ClassLoader.getResource()?

The first call searches relative to the .class file while the latter searches relative to the classpath root.

To debug issues like that, I print the URL:

System.out.println( getClass().getResource(getClass().getSimpleName() + ".class") );

Check if AJAX response data is empty/blank/null/undefined/0


This is an assignment statement, not a comparison. Also, "undefined" is a string, it's a property. Checking it is like this: if (data === undefined) (no quotes, otherwise it's a string value)

If it's not defined, you may be returning an empty string. You could try checking for a falsy value like if (!data) as well

No module named 'openpyxl' - Python 3.4 - Ubuntu

If you're using Python3, then install:

python3 -m pip install --user xlsxwriter

This will run pip with the appropriate version of Python3. If you run bare pip3 and have many versions of Python install, it will still fail leading to more confusion.

The --user flag will allow to install as a regular user and no require root.

How to uninstall pip on OSX?

The first thing you should try is:

sudo pip uninstall pip

On many environments that doesn't work. So given the lack of info on that problem, I ended up removing pip manually from /usr/local/bin.

Calculate row means on subset of columns

You can create a new row with $ in your data frame corresponding to the Means

DF$Mean <- rowMeans(DF[,2:4])

What is "String args[]"? parameter in main method Java

Even tho OP is only talking about the String[] args, i want to give a complete example of the public static void main(String[] args).

Public : is an Access Modifier, which defines who can access this Method. Public means that this Method will be accessible by any Class(If other Classes are able to access this Class.).

Static : is a keyword which identifies the class related thing. This means the given Method or variable is not instance related but Class related. It can be accessed without creating the instance of a Class.

Void : is used to define the Return Type of the Method. It defines what the method can return. Void means the Method will not return any value.

main: is the name of the Method. This Method name is searched by JVM as a starting point for an application with a particular signature only.

String[] args : is the parameter to the main Method.

If you look into JDK source code (jdk-src\j2se\src\share\bin\java.c):

/* Get the application's main method */
mainID = (*env)->GetStaticMethodID(env, mainClass, "main",
{    /* Make sure the main method is public */
mods = (*env)->CallIntMethod(env, obj, mid);
if ((mods & 1) == 0) { /* if (!Modifier.isPublic(mods)) ... */
    message = "Main method not public.";
    messageDest = JNI_TRUE;
    goto leave;

You can see that the starting method in java must be named main and must have the specific signature public static void main(String[] args)

The code also tells us that the public static void main(String[] args) is not fixed, if you change the code in (jdk-src\j2se\src\share\bin\java.c) to another signature, it will work but changing this will give you other possible problems because of the java specs

Offtopic: It's been 7 years since OP asked this question, my guess is that OP can answer his own question by now.

How to disable/enable a button with a checkbox if checked

You will have to use javascript, or the JQuery framework to do that. her is an example using Jquery

   $('#toggle').click(function () {
        //check if checkbox is checked
        if ($(this).is(':checked')) {

            $('#sendNewSms').removeAttr('disabled'); //enable input

        } else {
            $('#sendNewSms').attr('disabled', true); //disable input


How to get value from form field in django framework?

To retrieve data from form which send post request you can do it like this

def login_view(request):
        login_data = request.POST.dict()
        username = login_data.get("username")
        password = login_data.get("password")
        user_type = login_data.get("user_type")
        print(user_type, username, password)
        return HttpResponse("This is a post request")
        return render(request, "base.html")

How to resolve git's "not something we can merge" error

I had this issue as well. The branch looked like 'username/master' which seemed to confuse git as it looked like a remote address I defined. For me using this

git merge origin/username/master

worked perfectly fine.

file path Windows format to java format

String path = "C:\\Documents and Settings\\Manoj\\Desktop";
path = path.replace("\\", "/");
// or
path = path.replaceAll("\\\\", "/");

Find more details in the Docs

Task continuation on UI thread

Got here through google because i was looking for a good way to do things on the ui thread after being inside a Task.Run call - Using the following code you can use await to get back to the UI Thread again.

I hope this helps someone.

public static class UI
    public static DispatcherAwaiter Thread => new DispatcherAwaiter();

public struct DispatcherAwaiter : INotifyCompletion
    public bool IsCompleted => Application.Current.Dispatcher.CheckAccess();

    public void OnCompleted(Action continuation) => Application.Current.Dispatcher.Invoke(continuation);

    public void GetResult() { }

    public DispatcherAwaiter GetAwaiter()
        return this;


... code which is executed on the background thread...
await UI.Thread;
... code which will be run in the application dispatcher (ui thread) ...

How to uninstall a windows service and delete its files without rebooting

Should it be necessary to manually remove a service:

  1. Run Regedit or regedt32.
  2. Find the registry key entry for your service under the following key: HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services
  3. Delete the Registry Key

You will have to reboot before the list gets updated in services

Circle-Rectangle collision detection (intersection)

There are only two cases when the circle intersects with the rectangle:

  • Either the circle's centre lies inside the rectangle, or
  • One of the edges of the rectangle has a point in the circle.

Note that this does not require the rectangle to be axis-parallel.

Some different ways a circle and rectangle may intersect

(One way to see this: if none of the edges has a point in the circle (if all the edges are completely "outside" the circle), then the only way the circle can still intersect the polygon is if it lies completely inside the polygon.)

With that insight, something like the following will work, where the circle has centre P and radius R, and the rectangle has vertices A, B, C, D in that order (not complete code):

def intersect(Circle(P, R), Rectangle(A, B, C, D)):
    S = Circle(P, R)
    return (pointInRectangle(P, Rectangle(A, B, C, D)) or
            intersectCircle(S, (A, B)) or
            intersectCircle(S, (B, C)) or
            intersectCircle(S, (C, D)) or
            intersectCircle(S, (D, A)))

If you're writing any geometry you probably have the above functions in your library already. Otherwise, pointInRectangle() can be implemented in several ways; any of the general point in polygon methods will work, but for a rectangle you can just check whether this works:

0 = AP·AB = AB·AB and 0 = AP·AD = AD·AD

And intersectCircle() is easy to implement too: one way would be to check if the foot of the perpendicular from P to the line is close enough and between the endpoints, and check the endpoints otherwise.

The cool thing is that the same idea works not just for rectangles but for the intersection of a circle with any simple polygon — doesn't even have to be convex!

How to run a C# console application with the console hidden

You can use the FreeConsole API to detach the console from the process :

static extern bool FreeConsole();

(of course this is applicable only if you have access to the console application's source code)

How to add 10 days to current time in Rails

Use + 10.days

or even


Both definitely work. Are you sure you're in Rails and not just Ruby?

If you definitely are in Rails, where are you trying to run this from? Note that Active Support has to be loaded.

FPDF error: Some data has already been output, can't send PDF

For fpdf to work properly, there cannot be any output at all beside what fpdf generates. For example, this will work:

$pdf = new FPDF();
$pdf->Cell(40,10,'Hello World!');

While this will not (note the leading space before the opening <? tag)

$pdf = new FPDF();
$pdf->Cell(40,10,'Hello World!');

Also, this will not work either (the echo will break it):

echo "About to create pdf";
$pdf = new FPDF();
$pdf->Cell(40,10,'Hello World!');

I'm not sure about the drupal side of things, but I know that absolutely zero non-fpdf output is a requirement for fpdf to work.

add ob_start (); at the top and at the end add ob_end_flush();

    $pdf = new FPDF();
    $pdf->Cell(40,10,'Hello World!');

give me an error as below:
FPDF error: Some data has already been output, can't send PDF

to over come this error: go to fpdf.php in that,goto line number 996

function Output($name='', $dest='')

after that make changes like this:

function Output($name='', $dest='') {   
    ob_clean();     //Output PDF to so

Hi do you have a session header on the top of your page. or any includes If you have then try to add this codes on top pf your page it should works fine.


while (ob_get_level())
header("Content-Encoding: None", true);


cheers :-)

In my case i had set:

ini_set('display_errors', 'on');
error_reporting(E_ALL | E_STRICT);

When i made the request to generate the report, some warnings were displayed in the browser (like the usage of deprecated functions).
Turning off the display_errors option, the report was generated successfully.

Execute cmd command from VBScript

Set oShell = WScript.CreateObject("") "cmd cd /d C:dir_test\file_test & sanity_check_env.bat arg1"

Invariant Violation: Objects are not valid as a React child

In my case it was i forgot to return a html element frm the render function and i was returning an object . What i did was i just wrapped the {items} with a html element - a simple div like below


Finding what methods a Python object has there at least an easy way to check if it has a particular method other than simply checking if an error occurs when the method is called

While "Easier to ask for forgiveness than permission" is certainly the Pythonic way, you may be looking for:

d={'foo':'bar', 'spam':'eggs'}
if 'get' in dir(d):
# OUT: 'bar'

How to style readonly attribute with CSS?

input[readonly], input:read-only {
    /* styling info here */

Shoud cover all the cases for a readonly input field...

The data-toggle attributes in Twitter Bootstrap

The presence of this data-attribute tells Bootstrap to switch between visual or a logical states of another element on user interaction.

It is used to show modals, tab content, tooltips and popover menus as well as setting a pressed-state for a toggle-button. It is used in multiple ways without a clear documentation.

Where do I configure log4j in a JUnit test class?

The LogManager class determines which log4j config to use in a static block which runs when the class is loaded. There are three options intended for end-users:

  1. If you specify log4j.defaultInitOverride to false, it will not configure log4j at all.
  2. Specify the path to the configuration file manually yourself and override the classpath search. You can specify the location of the configuration file directly by using the following argument to java:

    -Dlog4j.configuration=<path to properties file>

    in your test runner configuration.

  3. Allow log4j to scan the classpath for a log4j config file during your test. (the default)

See also the online documentation.

How to use BigInteger?

sum = sum.add(BigInteger.valueOf(i))

The BigInteger class is immutable, hence you can't change its state. So calling "add" creates a new BigInteger, rather than modifying the current.

Java string to date conversion

DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date;
try {
    date = dateFormat.parse("2013-12-4");
    System.out.println(date.toString()); // Wed Dec 04 00:00:00 CST 2013

    String output = dateFormat.format(date);
    System.out.println(output); // 2013-12-04
catch (ParseException e) {

It works fine for me.

How to find array / dictionary value using key?

It's as simple as this :


Set value to currency in <input type="number" />

The browser only allows numerical inputs when the type is set to "number". Details here.

You can use the type="text" and filter out any other than numerical input using JavaScript like descripted here

How to toggle font awesome icon on click?

You can toggle the class of the i element within the clicked anchor like

<i class="fa fa-plus-circle"></i>


$('#category-tabs li a').click(function(){
    $(this).find('i').toggleClass('fa-plus-circle fa-minus-circle')

Demo: Fiddle

Android ADB devices unauthorized

  1. First Remove the adbkey and from the .android directory in your Home directory.
  2. Make .android directory in your home with 710 permissions: $ chmod 710 .android/ and ownership as: chown -R <user>:<user> .android/. Ex:

    $ chmod 710 .android/
    $ chown -R ashan:ashan .android/
  3. Go to developer options in your mobile and tap option Revoke USB debugging authorizations

  4. Turn off all USB Debugging and Developer Options in the device and disconnect the device from your machine.

  5. Connect the device again and at first turn on the Developer Options. Then Turn on the USB debugging.

  6. At this point in your mobile, you will get a prompt for asking permission from you. Note: you must check the checkbox always accept from this …. option and click ok.

  7. Now in you machine, start the adb server: adb start-server.

  8. Hopefully when you issue the command: adb devices now, you will see your device ready authorized.

Sublime Text 3 how to change the font size of the file sidebar?

On Ubuntu, for versions of Sublime older than 3.2, what worked for me was changing the dpi scale in Preferences > Settings — User by adding this line:

"dpi_scale": 1.10 

For Sublime 3.2, you can use the following line instead:

"ui_scale": 1.10

Adjust the scale value as needed. After this change, you have to restart Sublime Text for it to take effect.

How to perform a for loop on each character in a string in Bash?

I believe there is still no ideal solution that would correctly preserve all whitespace characters and is fast enough, so I'll post my answer. Using ${foo:$i:1} works, but is very slow, which is especially noticeable with large strings, as I will show below.

My idea is an expansion of a method proposed by Six, which involves read -n1, with some changes to keep all characters and work correctly for any string:

while IFS='' read -r -d '' -n 1 char; do
        # do something with $char
done < <(printf %s "$string")

How it works:

  • IFS='' - Redefining internal field separator to empty string prevents stripping of spaces and tabs. Doing it on a same line as read means that it will not affect other shell commands.
  • -r - Means "raw", which prevents read from treating \ at the end of the line as a special line concatenation character.
  • -d '' - Passing empty string as a delimiter prevents read from stripping newline characters. Actually means that null byte is used as a delimiter. -d '' is equal to -d $'\0'.
  • -n 1 - Means that one character at a time will be read.
  • printf %s "$string" - Using printf instead of echo -n is safer, because echo treats -n and -e as options. If you pass "-e" as a string, echo will not print anything.
  • < <(...) - Passing string to the loop using process substitution. If you use here-strings instead (done <<< "$string"), an extra newline character is appended at the end. Also, passing string through a pipe (printf %s "$string" | while ...) would make the loop run in a subshell, which means all variable operations are local within the loop.

Now, let's test the performance with a huge string. I used the following file as a source:
The following script was called through time command:


# Saving contents of the file into a variable named `string'.
# This is for test purposes only. In real code, you should use
# `done < "filename"' construct if you wish to read from a file.
# Using `string="$(cat makefiles.txt)"' would strip trailing newlines.
IFS='' read -r -d '' string < makefiles.txt

while IFS='' read -r -d '' -n 1 char; do
        # remake the string by adding one character at a time
done < <(printf %s "$string")

# confirm that new string is identical to the original
diff -u makefiles.txt <(printf %s "$new_string")

And the result is:

$ time ./

real    0m1.161s
user    0m1.036s
sys     0m0.116s

As we can see, it is quite fast.
Next, I replaced the loop with one that uses parameter expansion:

for (( i=0 ; i<${#string}; i++ )); do

The output shows exactly how bad the performance loss is:

$ time ./

real    2m38.540s
user    2m34.916s
sys     0m3.576s

The exact numbers may very on different systems, but the overall picture should be similar.

How to insert a line break <br> in markdown

I know this post is about adding a single line break but I thought I would mention that you can create multiple line breaks with the backslash (\) character:


This would result in 3 new lines after "Hello". To clarify, that would mean 2 empty lines between "Hello" and "World!". It would display like this:



Personally I find this cleaner for a large number of line breaks compared to using <br>.

Note that backslashes are not recommended for compatibility reasons. So this may not be supported by your Markdown parser but it's handy when it is.

What is an idiomatic way of representing enums in Go?

Here is an example that will prove useful when there are many enumerations. It uses structures in Golang, and draws upon Object Oriented Principles to tie them all together in a neat little bundle. None of the underlying code will change when a new enumeration is added or deleted. The process is:

  • Define an enumeration structure for enumeration items: EnumItem. It has an integer and string type.
  • Define the enumeration as a list of enumeration items: Enum
  • Build methods for the enumeration. A few have been included:
    • enum.Name(index int): returns the name for the given index.
    • enum.Index(name string): returns the name for the given index.
    • enum.Last(): returns the index and name of the last enumeration
  • Add your enumeration definitions.

Here is some code:

type EnumItem struct {
    index int
    name  string

type Enum struct {
    items []EnumItem

func (enum Enum) Name(findIndex int) string {
    for _, item := range enum.items {
        if item.index == findIndex {
    return "ID not found"

func (enum Enum) Index(findName string) int {
    for idx, item := range enum.items {
        if findName == {
            return idx
    return -1

func (enum Enum) Last() (int, string) {
    n := len(enum.items)
    return n - 1, enum.items[n-1].name

var AgentTypes = Enum{[]EnumItem{{0, "StaffMember"}, {1, "Organization"}, {1, "Automated"}}}
var AccountTypes = Enum{[]EnumItem{{0, "Basic"}, {1, "Advanced"}}}
var FlagTypes = Enum{[]EnumItem{{0, "Custom"}, {1, "System"}}}

ExecutorService, how to wait for all tasks to finish

I will just wait for the executor to terminate with a specified timeout that you think it is suitable for the tasks to complete.

 try {  
         //do stuff here 
    } finally {
    boolean result = exe.awaitTermination(4, TimeUnit.HOURS);
    if (!result)

        LOGGER.error("It took more than 4 hour for the executor to stop, this shouldn't be the normal behaviour.");

How Best to Compare Two Collections in Java and Act on Them?

public static boolean doCollectionsContainSameElements(
        Collection<Integer> c1, Collection<Integer> c2){

    if (c1 == null || c2 == null) {
        return false;
    else if (c1.size() != c2.size()) {
        return false;
    } else {    
        return c1.containsAll(c2) && c2.containsAll(c1);

CSS horizontal scroll

You can use display:inline-block with white-space:nowrap. Write like this:

.scrolls {
    overflow-x: scroll;
    overflow-y: hidden;
    height: 80px;
.imageDiv img {
    box-shadow: 1px 1px 10px #999;
    margin: 2px;
    max-height: 50px;
    cursor: pointer;
    *display:inline;/* For IE7*/
    *zoom:1;/* For IE7*/

Check this

Populate data table from data reader

If you're trying to load a DataTable, then leverage the SqlDataAdapter instead:

DataTable dt = new DataTable();

using (SqlConnection c = new SqlConnection(cString))
using (SqlDataAdapter sda = new SqlDataAdapter(sql, c))
    sda.SelectCommand.CommandType = CommandType.StoredProcedure;
    sda.SelectCommand.Parameters.AddWithValue("@parm1", val1);


You don't even need to define the columns. Just create the DataTable and Fill it.

Here, cString is your connection string and sql is the stored procedure command.

how to use "tab space" while writing in text file

Use "\t". That's the tab space character.

You can find a list of many of the Java escape characters here:

How to remove multiple indexes from a list at the same time?

If you can use numpy, then you can delete multiple indices:

>>> import numpy as np
>>> a = np.arange(10)
>>> np.delete(a,(1,3,5))
array([0, 2, 4, 6, 7, 8, 9])

and if you use np.r_ you can combine slices with individual indices:

>>> np.delete(a,(np.r_[0:5,7,9]))
array([5, 6, 8])

However, the deletion is not in place, so you have to assign to it.

Angularjs error Unknown provider

Make sure you are loading those modules ( and myApp.directives) as dependencies of your main app module, like this:

angular.module('myApp', ['myApp.directives', '']);