Programs & Examples On #Apk

An .apk file extension denotes an Android Package (APK) file. This file format, a variant of the JAR format, is used for distributing and installing bundled components onto the Android operating system.

APK signing error : Failed to read key from keystore

In my case, while copying the text from other source it somehow included the space at the end of clipboard entry. That way the key password had a space at the end.

Difference between signature versions - V1 (Jar Signature) and V2 (Full APK Signature) while generating a signed APK in Android Studio?

I think this represents a good answer.

APK Signature Scheme v2 verification

  1. Locate the APK Signing Block and verify that:
    1. Two size fields of APK Signing Block contain the same value.
    2. ZIP Central Directory is immediately followed by ZIP End of Central Directory record.
    3. ZIP End of Central Directory is not followed by more data.
  2. Locate the first APK Signature Scheme v2 Block inside the APK Signing Block. If the v2 Block if present, proceed to step 3. Otherwise, fall back to verifying the APK using v1 scheme.
  3. For each signer in the APK Signature Scheme v2 Block:
    1. Choose the strongest supported signature algorithm ID from signatures. The strength ordering is up to each implementation/platform version.
    2. Verify the corresponding signature from signatures against signed data using public key. (It is now safe to parse signed data.)
    3. Verify that the ordered list of signature algorithm IDs in digests and signatures is identical. (This is to prevent signature stripping/addition.)
    4. Compute the digest of APK contents using the same digest algorithm as the digest algorithm used by the signature algorithm.
    5. Verify that the computed digest is identical to the corresponding digest from digests.
    6. Verify that SubjectPublicKeyInfo of the first certificate of certificates is identical to public key.
  4. Verification succeeds if at least one signer was found and step 3 succeeded for each found signer.

Note: APK must not be verified using the v1 scheme if a failure occurs in step 3 or 4.

JAR-signed APK verification (v1 scheme)

The JAR-signed APK is a standard signed JAR, which must contain exactly the entries listed in META-INF/MANIFEST.MF and where all entries must be signed by the same set of signers. Its integrity is verified as follows:

  1. Each signer is represented by a META-INF/<signer>.SF and META-INF/<signer>.(RSA|DSA|EC) JAR entry.
  2. <signer>.(RSA|DSA|EC) is a PKCS #7 CMS ContentInfo with SignedData structure whose signature is verified over the <signer>.SF file.
  3. <signer>.SF file contains a whole-file digest of the META-INF/MANIFEST.MF and digests of each section of META-INF/MANIFEST.MF. The whole-file digest of the MANIFEST.MF is verified. If that fails, the digest of each MANIFEST.MF section is verified instead.
  4. META-INF/MANIFEST.MF contains, for each integrity-protected JAR entry, a correspondingly named section containing the digest of the entry’s uncompressed contents. All these digests are verified.
  5. APK verification fails if the APK contains JAR entries which are not listed in the MANIFEST.MF and are not part of JAR signature. The protection chain is thus <signer>.(RSA|DSA|EC) ? <signer>.SF ? MANIFEST.MF ? contents of each integrity-protected JAR entry.

How to Sign an Already Compiled Apk

create a key using

keytool -genkey -v -keystore my-release-key.keystore -alias alias_name -keyalg RSA -keysize 2048 -validity 10000

then sign the apk using :

jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore my-release-key.keystore my_application.apk alias_name

check here for more info

Where can I find the .apk file on my device, when I download any app and install?

You can use a file browser with an backup function, for example the ES File Explorer Long tap a item and select create backup

How to create a release signed apk file using Gradle?

Adding my way to do it in React-Native using react-native-config package.
Create a .env file:


note this should not be part of the version control.

in your build.gradle:

signingConfigs {
        debug {
        release {
            storeFile file(RELEASE_STORE_FILE)
            storePassword project.env.get('RELEASE_STORE_PASSWORD')
            keyAlias RELEASE_KEY_ALIAS
            keyPassword project.env.get('RELEASE_KEY_PASSWORD')

The APK file does not exist on disk

In my case, I was using a special character in my app file path. I closed the Android Studio and removed the ' character from my app file path. Everything worked fine when I reopned the project.

Is there a way to get the source code from an APK file?

There are lots of applications and methods in the market to decompile the apk file into java class but if the app is compiled with ProGuard rule then you are in a big trouble because this rule will shrink all the dex files into a small character name and then you can not trace back the implementation. see for mode clarification.

Happy Coding...

unsigned APK can not be installed

Just follow these steps to transfer the apk onto the real device(with debugger key) and which is just for testing purpose. (Note: For proper distribution to the market you may need to sign your app with your keys and follow all the steps.)

  1. Install your app onto the emulator.
  2. Once it is installed goto DDMS, select the current running app under the devices window. This will then show all the files related to it under the file explorer.
  3. Under file explorer go to data->app and select your APK (which is the package name of the app).
  4. Select it and click on 'Pull a file from the device' button (the one with the save symbol).
  5. This copies the APK to your system. From there you can copy the file to your real device, install and test it.

Good luck !

How to convert .pfx file to keystore with private key?

jarsigner can use your pfx file as the keystore for signing your jar. Be sure that your pfx file has the private key and the cert chain when you export it. There is no need to convert to other formats. The trick is to obtain the Alias of your pfx file:

 keytool -list -storetype pkcs12 -keystore your_pfx_file -v | grep Alias

Once you have your alias, signing is easy

jarsigner.exe -storetype pkcs12 -keystore pfx_file jar_file "your alias"

The above two commands will prompt you for the password you specified at pfx export. If you want to have your password hang out in clear text use the -storepass switch before the -keystore switch

Once signed, admire your work:

jarsigner.exe -verify -verbose -certs  yourjarfile

Session 'app': Error Installing APK

I changed my USB port and that fixed it for me.

How do I get the APK of an installed app without root access?

On Nougat(7.0) Android version run adb shell pm list packages to list the packages installed on the device. Then run adb shell pm path your-package-name to show the path of the apk. After use adb to copy the package to Downloads adb shell cp /data/app/com.test-1/base.apk /storage/emulated/0/Download. Then pull the apk from Downloads to your machine by running adb pull /storage/emulated/0/Download/base.apk.

Android Studio: Application Installation Failed

Happened to me as well: At the first time, it says- Failure [INSTALL_FAILED_CONFLICTING_PROVIDER] At the second time, it says- DELETE_FAILED_INTERNAL_ERROR

This because of the new '' version 8.3.0

Changing it back to 8.1.0 solved the problem in my case

How to edit an Android app?

You would need to decompile the apk as Davis suggested, can use tools such as apkTool , then if you need to change the source code you would need other tools to do that.

You would then need to put the apk back together and sign it, if you don't have the original key used to sign the apk this means the new apk will have a different signature.

If the developer employed any obfuscation or other techniques to protect the app then it gets more complicated.

In short its a pretty complex and technical procedure, so if the developer is really just out of reach, its better to wait until he is in reach. And ask for the source code next time.

How to sign an android apk file

The manual is clear enough. Please specify what part you get stuck with after you work through it, I'd suggest:

Okay, a small overview without reference or eclipse around, so leave some space for errors, but it works like this

  • Open your project in eclipse
  • Press right-mouse - > tools (android tools?) - > export signed application (apk?)
  • Go through the wizard:
  • Make a new key-store. remember that password
  • Sign your app
  • Save it etc.

Also, from the link:

Compile and sign with Eclipse ADT

If you are using Eclipse with the ADT plugin, you can use the Export Wizard to export a signed .apk (and even create a new keystore, if necessary). The Export Wizard performs all the interaction with the Keytool and Jarsigner for you, which allows you to sign the package using a GUI instead of performing the manual procedures to compile, sign, and align, as discussed above. Once the wizard has compiled and signed your package, it will also perform package alignment with zip align. Because the Export Wizard uses both Keytool and Jarsigner, you should ensure that they are accessible on your computer, as described above in the Basic Setup for Signing.

To create a signed and aligned .apk in Eclipse:

  1. Select the project in the Package Explorer and select File > Export.
  2. Open the Android folder, select Export Android Application, and click Next.

    The Export Android Application wizard now starts, which will guide you through the process of signing your application, including steps for selecting the private key with which to sign the .apk (or creating a new keystore and private key).

  3. Complete the Export Wizard and your application will be compiled, signed, aligned, and ready for distribution.

Get Android .apk file VersionName or VersionCode WITHOUT installing apk

final PackageManager pm = getPackageManager();
String apkName = "example.apk";
String fullPath = Environment.getExternalStorageDirectory() + "/" + apkName;        
PackageInfo info = pm.getPackageArchiveInfo(fullPath, 0);
Toast.makeText(this, "VersionCode : " + info.versionCode + ", VersionName : " + info.versionName , Toast.LENGTH_LONG).show();

How to view the contents of an Android APK file?

Actually the apk file is just a zip archive, so you can try to rename the file to and extract it with any zip utility (e.g. 7zip).

The androidmanifest.xml file and the resources will be extracted and can be viewed whereas the source code is not in the package - just the compiled .dex file ("Dalvik Executable")

Is it possible to run .APK/Android apps on iPad/iPhone devices?

It is not natively possible to run Android application under iOS (which powers iPhone, iPad, iPod, etc.)

This is because both runtime stacks use entirely different approaches. Android runs Dalvik (a "variant of Java") bytecode packaged in APK files while iOS runs Compiled (from Obj-C) code from IPA files. Excepting time/effort/money and litigations (!), there is nothing inherently preventing an Android implementation on Apple hardware, however.

It looks to package a small Dalvik VM with each application and targeted towards developers.

See iPhoDroid:

Looks to be a dual-boot solution for 2G/3G jailbroken devices. Very little information available, but there are some YouTube videos.

See iAndroid:

iAndroid is a new iOS application for jailbroken devices that simulates the Android operating system experience on the iPhone or iPod touch. While it’s still very far from completion, the project is taking shape.

I am not sure the approach(es) it uses to enable this: it could be emulation or just a simulation (e.g. "looks like"). The requirement of being jailbroken makes it sound like emulation might be used ..

See BlueStacks, per the Holo Dev's comment:

It looks to be an "Android App Player" for OS X (and Windows). However, afaik, it does not [currently] target iOS devices ..


Application Installation Failed in Android Studio

Faced same issues on MIUI phone resolved by making MIUI account and enable install by USB.

How to check programmatically if an application is installed or not in Android?

Cleaner solution (without try-catch) than the accepted answer (based on AndroidRate Library):

public static boolean isPackageExists(@NonNull final Context context, @NonNull final String targetPackage) {
    List<ApplicationInfo> packages = context.getPackageManager().getInstalledApplications(0);
    for (ApplicationInfo packageInfo : packages) {
        if (targetPackage.equals(packageInfo.packageName)) {
            return true;
    return false;


It's throwing this error for me today because I have an app with a min sdk of 28 and am hitting play on an emulator with an SDK version of 23. Usually this is not possible (AS gray's out the play button), but today not so much.

Reverse engineering from an APK file to a project

There is a new way to do this.

Android Studio 2.2 has APK Analyzer it will give lot of info about apk, checkout it here :-


The apk must be signed with the same certificates as the previous version

Nothing - Google says it clearly that the application is identified by the keys used to sign it. Consequently if you've lost the keys, you need to create a new application.

How do I get an apk file from an Android device?

I haven't used code to pull .apk file from mobile but i have been using software to extract .apk file from mobile and software i have used are below with google play link:

  1. ES File Explorer File Manager
  2. ASTRO Cloud & File Manager 3.Software Data Cable

Hope it helps You.

Does Android keep the .apk files? if so where?

If you're looking for the path of a specific app, a quick and dirty solution is to just grep the bugreport:

$ adb bugreport | grep 'dir=/data/app' 

I don't know that this will provide an exhaustive list, so it may help to run the app first.

Build and Install unsigned apk on device without the development server?

You need to manually create the bundle for a debug build.

Bundle debug build:

#React-Native 0.59
react-native bundle --dev false --platform android --entry-file index.js --bundle-output ./android/app/src/main/assets/ --assets-dest ./android/app/src/main/res

#React-Native 0.49.0+
react-native bundle --dev false --platform android --entry-file index.js --bundle-output ./android/app/build/intermediates/assets/debug/ --assets-dest ./android/app/build/intermediates/res/merged/debug

#React-Native 0-0.49.0
react-native bundle --dev false --platform android --entry-file --bundle-output ./android/app/build/intermediates/assets/debug/ --assets-dest ./android/app/build/intermediates/res/merged/debug

Then to build the APK's after bundling:

$ cd android
#Create debug build:
$ ./gradlew assembleDebug
#Create release build:
$ ./gradlew assembleRelease #Generated `apk` will be located at `android/app/build/outputs/apk`

P.S. Another approach might be to modify gradle scripts.

How to build an APK file in Eclipse?

We can a make a signed and unsigned APK file. A signed APK file can install in your device.

For creating a signed APK file:

  1. Right-click the project in the Package Explorer

  2. Select Android Tools -> Export Signed Application Package.

  3. Then specify the file location for the signed .apk.

For creating an unsigned APK file:

  1. Right-click the project in the Package Explorer

  2. Select Android Tools -> Export Unsigned Application Package.

  3. Then specify the file location for the unsigned APK file.

Read the package name of an Android APK

aapt list -a "path_to_apk"

I recommend you save it in a .txt, because it can be very long. So:

aapt list -a "path_to_apk" > file.txt

Then see the file.txt in your current directory.

install / uninstall APKs programmatically (PackageManager vs Intents)

If you're using Kotlin, API 14+, and just wish to show uninstall dialog for your app:

startActivity(Intent(Intent.ACTION_UNINSTALL_PACKAGE).apply {
    data = Uri.parse("package:$packageName")

You can change packageName to any other package name if you want to prompt the user to uninstall another app on the device

This version of the application is not configured for billing through Google Play

This will happen if you use a different version of the apk than the one in the google play.

Upload failed You need to use a different version code for your APK because you already have one with version code 2

In my app/build.gradle file , version code was like this:-

build.gradle(app module) file

In place of versionCode flutterVersionCode.toInteger() , i replaced it with as versionCode 2

Android Studio - local path doesn't exist

In case you hit this issue after an upgrade to studio 0.3.4do a rm android-studio/plugins/gradle/lib/gradle-*-1.8.jar. There is a 1.9-rc-2 release of gradle available there. Make sure your gradle path is set to automatic. If set manually change to automatic or manually point it to the latest gradle release.

Also make sure you run ./gradlew clean packageDebug in your project root.


Android - How to decode and decompile any APK file?

To decompile APK Use APKTool.
You can learn how APKTool works on or by reading the documentation.

How to retrieve Key Alias and Key Password for signed APK in android studio(migrated from Eclipse)

On the Mac, I found the keystore file path, password, key alias and key password in an earlier log report before I updated Android Studio.

I launched the Console utility and scrolled down to ~/Library/Logs -> AndroidStudioBeta ->idea.log.1 (or any old log number)

Then I searched for “” and found this from an earlier date:,, 

On Windows

you can find your lost key password in below path

Project\.gradle\2.14.1\taskArtifacts\taskArtifacts.bin or ..taskHistory\taskHistory.bin

Here is the image for path view in folder structure

open the file using appropriate tools e.g. NotePad++ and search with the part of the password that you remember. You will find it definitely. Else, try searching with this string "signingConfig.storePassword".

Note: I have experienced the same and i am able to find it. In case if you didn't find may be you cleared all the cache and temp files.

Android error: Failed to install *.apk on device *: timeout

don't use USB 3.0 ports for connection beetwen PC and Android phone!

USB 3.0 - Port with blue tongue

USB 2.0 - Port with black tongue

Apk location in New Android Studio

The Android build system is the toolkit you use to build, test, run and package your apps. The build system can run as an integrated tool from the Android Studio menu and independently from the command line. You can use the features of the build system to:

  1. Customize, configure, and extend the build process.
  2. Create multiple APKs for your app with different features using the same project and modules.

The build process involves many tools and processes that generate intermediate files on the way to producing an .apk. If you are developing in Android Studio, the complete build process is done every time you run the Gradle build task for your project or modules.

The build process is very flexible so it's useful, however, to understand what is happening under the hood since much of the build process is configurable and extensible. The following diagram depicts the different tools and processes that are involved in a build:

Build a release version

You can now use the Build menu options to build the release version of your application for distribution.

The build generates an APK for each build variant: the app/build/apk/ (or app/build/outputs/apk) directory contains packages named app--.apk; for example, app-full-release.apk and app-demo-debug.apk.

enter image description here

Build output

The build generates an APK for each build variant in the app/build folder: the app/build/outputs/apk/ directory contains packages named app--.apk; for example, app-full-release.apk and app-demo-debug.apk.

Courtesy goes to Build System Overview


In my case was by uploading an APK, that although it was signed with production certificate and was a release variant, was generated by the run play button from Android studio. Problem solved after generating APK from Gradle or from Build APK menu option.

Is it possible to decompile an Android .apk file?

Download this jadx tool

Unzip it and than in lib folder run jadx-gui-0.6.1.jar file now browse your apk file. It's done. Automatically apk will decompile and save it by pressing save button. Hope it will work for you. Thanks

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

I have same problem, because i don't have keystore path then i see solutions and had a new problem In my Android Studio 3.1 for mac had a windows dialog problem when trying create new keystore path, it's like this

enter image description here

if u have the same problem, don't worried about the black windows it's just typing your new keystore and then save.

How do you install an APK file in the Android emulator?

From Windows 7 Onwards ,

Shift + Right click in your apk file folder.

Select Open Command Window Here

Type & Hit "adb install AppName.apk"

Install an apk file from command prompt?

Commands for install APK files like it does in Android Studio you can see below.

1) To push your app:

adb push /pathOfApk/ /data/local/tmp/

where is your package.

2) To install:

adb shell pm install -t -r "/data/local/tmp/"


I got this error even after uninstalling the original APK, which was mystifying. Finally I realized that I had set up multiple users on my Nexus 7 for testing and that the app was still installed for one of the other users. Once I uninstalled it for all users the error went away.

Install Application programmatically on Android

I just want to share the fact that my apk file was saved to my app "Data" directory and that I needed to change the permissions on the apk file to be world readable in order to allow it to be installed that way, otherwise the system was throwing "Parse error: There is a Problem Parsing the Package"; so using solution from @Horaceman that makes:

File file = new File(dir, "App.apk");
file.setReadable(true, false);
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.fromFile(file), "application/");

How do I verify that an Android apk is signed with a release certificate?

Use console command:

apksigner verify --print-certs application-development-release.apk

You could find apksigner in ../sdk/build-tools/24.0.3/apksigner.bat. Only for build tools v. 24.0.3 and higher.

Also read google docs:

Build unsigned APK file with Android Studio

I would recommend you to build your APK file with Gradle:

  • Click the dropdown menu in the toolbar at the top (Open 'Edit Run/Debug configurations' dialog)
  • Select "Edit Configurations"
  • Click the "+"
  • Select "Gradle"
  • Choose your module as a Gradle project
  • In Tasks: enter assemble
  • Press Run

Your unsigned APK is now located in


For detailed information on how to use Gradle, this tutorial is good to go: Building with Gradle in Android Studio. I also wrote a blog post on how to build an unsigned APK with Gradle.

If you moved your project from the other IDE and don't want to recompile, you may find your APK file that was already built in the IDE you moved from:

  • If you generated the Project with Android Studio, the APK file will be found in ProjectName/ProjectName/build/apk/...

  • Imported the project from eclipse: File should be in the same directory. Go to Project - Show in Explorer. There you should find the bin folder where your APK file is located in.

  • Imported from IntelliJ, the location would be ProjectName/out/production/...

Side note: As Chris Stratton mentioned in his comment:

Technically, what you want is an APK signed with a debug key. An APK that is actually unsigned will be refused by the device.

How to run .APK file on emulator

You need to install the APK on the emulator. You can do this with the adb command line tool that is included in the Android SDK.

adb -e install -r yourapp.apk

Once you've done that you should be able to run the app.

The -e and -r flags might not be necessary. They just specify that you are using an emulator (if you also have a device connected) and that you want to replace the app if it already exists.

Decompile .smali files on an APK

I second that.

Dex2jar will generate a WORKING jar, which you can add as your project source, with the xmls you got from apktool.

However, JDGUI generates .java files which have ,more often than not, errors.

It has got something to do with code obfuscation I guess.

How to view AndroidManifest.xml from APK file?

aapt d xmltree com.package.apk AndroidManifest.xml

will dump the AndroidManifest.xml from the specified APK. It's not in XML form, but you can still read it.

aapt (Android Asset Packaging Tool) is a built in tool that comes with the Android SDK.

Returning data from Axios API

I know this post is old. But i have seen several attempts of guys trying to answer using async and await but getting it wrong. This should clear it up for any new references

async function axiosTest() {
      try {
        const {data:response} = await axios.get(url) //use data destructuring to get data from the promise object
        return response

      catch (error) {

On npm install: Unhandled rejection Error: EACCES: permission denied

as per npm community

sudo npm cache clean --force --unsafe-perm

and then npm install goes normally.

source: npm community-unhandled-rejection-error-eacces-permission-denied

How to get a random value from dictionary?

Try this:

import random
a = dict(....) # a is some dictionary
random_key = random.sample(a, 1)[0]

This definitely works.

How to get the difference between two arrays of objects in JavaScript

let obj1 =[
                 { id: 1, submenu_name: 'login' },
                 { id: 2, submenu_name: 'Profile',}, 
                 { id: 3, submenu_name: 'password',  },  
                 { id: 4, submenu_name: 'reset',}
               ] ;
 let obj2 =[
                 { id: 2}, 
                 { id: 3 },
               ] ;
// Need Similar obj 
const result1 = obj1.filter(function(o1){
 return obj2.some(function(o2){
    return ==;          // id is unnique both array object

// Need differnt obj 
 const result2 = obj1.filter(function(o1){
 return !obj2.some(function(o2){    //  for diffrent we use NOT (!) befor obj2 here
    return ==;          // id is unnique both array object

Insert an element at a specific index in a list and return the updated list

l.insert(index, obj) doesn't actually return anything. It just updates the list.

As ATO said, you can do b = a[:index] + [obj] + a[index:]. However, another way is:

a = [1, 2, 4]
b = a[:]
b.insert(2, 3)

Javascript: Easier way to format numbers?

Also try dojo.number which has built-in localization support. It is a much closer analog to Java's NumberFormat/DecimalFormat

multiple where condition codeigniter

$wherecond = "( ( ( username ='" . $username . "' OR status='" . $status . "') AND (id='" . $id . "') ) )"; $this->db->where($wherecond);

If you want to add AND and OR conditions at a time. this will work.

Get the current fragment object

This will give you the current fragment class name -->

String fr_name = getSupportFragmentManager().findFragmentById(;

Set width to match constraints in ConstraintLayout

I found one more answer when there is a constraint layout inside the scroll view then we need to put


to the scroll view



in the constraint layout


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


// Rest of the views



JSONResult to String

json = " { \"success\" : false, \"errors\": { \"text\" : \"??????!\" } }";            
return new MemoryStream(Encoding.UTF8.GetBytes(json));

How to print Unicode character in Python?

To include Unicode characters in your Python source code, you can use Unicode escape characters in the form \u0123 in your string. In Python 2.x, you also need to prefix the string literal with 'u'.

Here's an example running in the Python 2.x interactive console:

>>> print u'\u0420\u043e\u0441\u0441\u0438\u044f'

In Python 2, prefixing a string with 'u' declares them as Unicode-type variables, as described in the Python Unicode documentation.

In Python 3, the 'u' prefix is now optional:

>>> print('\u0420\u043e\u0441\u0441\u0438\u044f')

If running the above commands doesn't display the text correctly for you, perhaps your terminal isn't capable of displaying Unicode characters.

These examples use Unicode escapes (\u...), which allows you to print Unicode characters while keeping your source code as plain ASCII. This can help when working with the same source code on different systems. You can also use Unicode characters directly in your Python source code (e.g. print u'??????' in Python 2), if you are confident all your systems handle Unicode files properly.

For information about reading Unicode data from a file, see this answer:

Character reading from file in Python

one line if statement in php

Use ternary operator:

echo (($test == '') ? $redText : '');
echo $test == '' ? $redText : ''; //removed parenthesis

But in this case you can't use shorter reversed version because it will return bool(true) in first condition.

echo (($test != '') ?: $redText); //this will not work properly for this case

Check if multiple strings exist in another string

You should be careful if the strings in a or str gets longer. The straightforward solutions take O(S*(A^2)), where S is the length of str and A is the sum of the lenghts of all strings in a. For a faster solution, look at Aho-Corasick algorithm for string matching, which runs in linear time O(S+A).

HTML: How to limit file upload to be only images?

HTML5 says <input type="file" accept="image/*">. Of course, never trust client-side validation: Always check again on the server-side...

Can you force Visual Studio to always run as an Administrator in Windows 8?

Also, you can check the compatibility troubleshooting

  • Right-click on Visual Studio > select Troubleshoot compatibility.
  • Select Troubleshoot Program.
  • Check The program requires additional permissions.
  • Click on Test the program.
  • Wait for a moment until the program launch. Click Next.
  • Select Yes, save these settings for this program.
  • Wait for resolving the issue.
  • Make sure the final status is fixed. Click Close.

Check the detail steps, and other ways to always open VS as Admin at Visual Studio requires the application to have elevated permissions.

Backporting Python 3 open(encoding="utf-8") to Python 2

This may do the trick:

import sys
if sys.version_info[0] > 2:
    # py3k
    # py2
    import codecs
    import warnings
    def open(file, mode='r', buffering=-1, encoding=None,
             errors=None, newline=None, closefd=True, opener=None):
        if newline is not None:
            warnings.warn('newline is not supported in py2')
        if not closefd:
            warnings.warn('closefd is not supported in py2')
        if opener is not None:
            warnings.warn('opener is not supported in py2')
        return, mode=mode, encoding=encoding,
                    errors=errors, buffering=buffering)

Then you can keep you code in the python3 way.

Note that some APIs like newline, closefd, opener do not work

Combining Two Images with OpenCV

in OpenCV 3.0 you can use it easily as follow:

#combine 2 images same as to concatenate images with two different sizes
h1, w1 = img1.shape[:2]
h2, w2 = img2.shape[:2]
#create empty martrix (Mat)
res = np.zeros(shape=(max(h1, h2), w1 + w2, 3), dtype=np.uint8)
# assign BGR values to concatenate images
for i in range(res.shape[2]):
    # assign img1 colors
    res[:h1, :w1, i] = np.ones([img1.shape[0], img1.shape[1]]) * img1[:, :, i]
    # assign img2 colors
    res[:h2, w1:w1 + w2, i] = np.ones([img2.shape[0], img2.shape[1]]) * img2[:, :, i]

output_img = res.astype('uint8')

Facebook API "This app is in development mode"

I have the same problem while integrating the Facebook SDK for login.

I'm suggesting below approach for development mode > you can test all things if you are login with same account, which is used for '' and if you want to use another accounts then you need to add Roles for that particular app, for that you can add developer or testers by using fid or facebook username.

Eg: - Select the particular app > Roles and then add developer or testers.

enter image description here

How to view DLL functions?

You may try the Object Browser in Visual Studio.

Select Edit Custom Component Set. From there, you can choose from a variety of .NET, COM or project libraries or just import external dlls via Browse.

Convert String to Float in Swift

In swift 4

let Totalname = "10.0" //Now it is in string

let floatVal  = (Totalname as NSString).floatValue //Now converted to float

How to get the ASCII value of a character

The accepted answer is correct, but there is a more clever/efficient way to do this if you need to convert a whole bunch of ASCII characters to their ASCII codes at once. Instead of doing:

for ch in mystr:
    code = ord(ch)

or the slightly faster:

for code in map(ord, mystr):

you convert to Python native types that iterate the codes directly. On Python 3, it's trivial:

for code in mystr.encode('ascii'):

and on Python 2.6/2.7, it's only slightly more involved because it doesn't have a Py3 style bytes object (bytes is an alias for str, which iterates by character), but they do have bytearray:

# If mystr is definitely str, not unicode
for code in bytearray(mystr):

# If mystr could be either str or unicode
for code in bytearray(mystr, 'ascii'):

Encoding as a type that natively iterates by ordinal means the conversion goes much faster; in local tests on both Py2.7 and Py3.5, iterating a str to get its ASCII codes using map(ord, mystr) starts off taking about twice as long for a len 10 str than using bytearray(mystr) on Py2 or mystr.encode('ascii') on Py3, and as the str gets longer, the multiplier paid for map(ord, mystr) rises to ~6.5x-7x.

The only downside is that the conversion is all at once, so your first result might take a little longer, and a truly enormous str would have a proportionately large temporary bytes/bytearray, but unless this forces you into page thrashing, this isn't likely to matter.

jQuery selector for inputs with square brackets in the name attribute

If the selector is contained within a variable, the code below may be helpful:

selector_name = $this.attr('name');
//selector_name = users[0][first:name]

escaped_selector_name = selector_name.replace(/(:|\.|\[|\])/g,'\\$1');
//escaped_selector_name = users\\[0\\]\\[first\\:name\\]

In this case we prefix all special characters with double backslash.

How to append strings using sprintf?

Why do you want to use sprintf for string concatenation when there are methods intended specifically for what you need such as strcat and strncat?

Spring @Autowired and @Qualifier

@Autowired to autowire(or search) by-type
@Qualifier to autowire(or search) by-name
Other alternate option for @Qualifier is @Primary

public class A{}

public class B{

public B(@Qualifier("beanname")A a){...} //  you need to add @autowire also 

private A a;


//If you don't want to add the two annotations, we can use @Resource
public class B{

private A a;

//Importing properties is very similar
@Value("${}")  //@Value know how to interpret ${}
private String name;

more about @value

Change value of input placeholder via model?

Since AngularJS does not have directive DOM manipulations as jQuery does, a proper way to modify attributes of one element will be using directive. Through link function of a directive, you have access to both element and its attributes.

Wrapping you whole input inside one directive, you can still introduce ng-model's methods through controller property.

This method will help to decouple the logic of ngmodel with placeholder from controller. If there is no logic between them, you can definitely go as Wagner Francisco said.

Call Python script from bash with argument

Embedded option:

Wrap python code in a bash function.


function current_datetime {
python - <<END
import datetime

# Call it

# Call it and capture the output
echo Current date and time: $DT

Use environment variables, to pass data into to your embedded python script.


function line {
PYTHON_ARG="$1" python - <<END
import os
line_len = int(os.environ['PYTHON_ARG'])
print '-' * line_len

# Do it one way
line 80

# Do it another way
echo $(line 80)

Is it possible to serialize and deserialize a class in C++?

If you want simple and best performance and don't care about backward data compatibility, try HPS, it's lightweight, much faster than Boost, etc, and much easier to use than Protobuf, etc.


std::vector<int> data({22, 333, -4444});
std::string serialized = hps::serialize_to_string(data);
auto parsed = hps::parse_from_string<std::vector<int>>(serialized);

Eclipse: How do I add the javax.servlet package to a project?

Go to


include JAR


For me it worked

How to display default text "--Select Team --" in combo box on pageload in WPF?

I believe a watermark as mentioned in this post would work well in this case

There's a bit of code needed but you can reuse it for any combobox or textbox (and even passwordboxes) so I prefer this way

Resolving MSB3247 - Found conflicts between different versions of the same dependent assembly

Use a dependency reader

Using dep.exe you can list out all the nested dependencies of an entire folder. Combined with unix tools like grep or awk, it can help you to solve your problem

Finding assemblies being referenced in more than one version

$ dep | awk '{ print $1 " " $2; print $4 " " $5 }' | awk '{ if (length(versions[$1]) == 0) versions[$1] = $2; if (versions[$1] != $2) errors[$1] = $1; }  END{ for(e in errors) print e } ' 

This obscure command line runs dep.exe then pipes the output twice to awk to

  • put the parent and child in a single column (by default each line contains one parent and a child to express the fact that this parent depends of that child)
  • then do a kind of 'group by' using an associative array

Understanding how this assembly got pulled in your bin

$ dep myproject/bin | grep -i System\.Web\.Http
MyProject- >> System.Web.Http.Web- 2 ( FooLib- )
MyProject- >> System.Web.Http.Web- 2 ( BarLib- )
FooLib- > System.Web.Http.Web- 1
BarLib- > System.Web.Http.Web- 1 

In this example, the tool would show you that System.Web.Http 5.2.3 comes from your dependency to FooLib whereas the version 4.0.0 comes from BarLib.

Then you have the choice between

  • convincing the owners of the libs to use the same version
  • stop using one them
  • adding binding redirects in your config file to use the latest version

How to run these thing in Windows

If you don't have a unix type shell you'll need to download one before being able to run awkand grep. Try one of the following

showing that a date is greater than current date

In sql server, you can do

FROM table t
WHERE > DATEADD(dd,90,now())

App store link for "rate/review this app"

quote from Apple Developer Documentation

In addition, you can continue to include a persistent link in the settings or configuration screens of your app that deep-links to your App Store product page. To automatically open a page on which users can write a review in the App Store, append the query parameter action=write-review to your product URL.

So the URL would be the following:


jQuery SVG vs. Raphael

Oh Raphael has moved on significantly since June. There is a new charting library that can work with it and these are very eye catching. Raphael also supports full SVG path syntax and is incorporating really advanced path methods. Come see 1.2.8+ at my site (Shameless plug) and then bounce over to the Dmitry's site from there.

Resource interpreted as Document but transferred with MIME type application/zip

I could not find anywhere just an explanation of the message by itself. Here is my interpretation.

As far as I understand, Chrome was expecting some material it could possibly display (a document), but it obtained something it could not display (or something it was told not to display).

This is both a question of how the document was declared at the HTML page level in href (see the download attribute in Roy's message) and how it is declared within the server's answer by the means of HTTP headers (in particular Content-Disposition). This is a question of contract, as opposed to hope and expectation.

To continue on Evan's way, I've experienced that:

Content-type: application/pdf
Content-disposition: attachment; filename=some.pdf

is just inconsistent with:

<a href='some.pdf'>

Chrome will cry Resource interpreted as document but transferred…

Actually, the attachment disposition just means this: the browser shall not interpret the link, but rather store it somewhere for other—hidden—purposes. Here above, either download is missing beside href, or Content-disposition must be removed from the headers. It depends on whether we want the browser to render the document or not.

Hope this helps.

How to run Python script on terminal?

You can execute your file by using this:

python /Users/luca/Documents/python/

You can also run the file by moving to the path of the file you want to run and typing:


How to fix height of TR?

Try putting the height into one of the cells, like this:

<table class="tableContainer" cellspacing="10px">
  <td style="height:15px;">NHS Number</td>

Note however, that you won't be able to make the cell smaller than the content requires it to be. In that case you would have to make the text smaller first.

Can I give the col-md-1.5 in bootstrap?

The short answer is no (technically you can give whatever name of the class you want, but this will have no effect, unless you define your own CSS class - and remember - no dots in the class selector). The long answer is again no, because Bootstrap includes a responsive, mobile first fluid grid system that appropriately scales up to 12 columns as the device or view port size increases.

Rows must be placed within a .container (fixed-width) or .container-fluid (full-width) for proper alignment and padding.

  • Use rows to create horizontal groups of columns.
  • Content should be placed within columns, and only columns may be immediate children of rows.
  • Predefined grid classes like .row and .col-xs-4 are available for quickly making grid layouts. Less mixins can also be used for more semantic layouts.
  • Columns create gutters (gaps between column content) via padding. That padding is offset in rows for the first and last column via negative margin on .rows.
  • Grid columns are created by specifying the number of twelve available columns you wish to span. For example, three equal columns would use three .col-xs-4.
  • If more than 12 columns are placed within a single row, each group of extra columns will, as one unit, wrap onto a new line.
  • Grid classes apply to devices with screen widths greater than or equal to the breakpoint sizes, and override grid classes targeted at smaller devices. Therefore, e.g. applying any .col-md-* class to an element will not only affect its styling on medium devices but also on large devices if a .col-lg-* class is not present.

A possible solution to your problem is to define your own CSS class with desired width, let's say .col-half{width:XXXem !important} then add this class to elements you want along with original Bootstrap CSS classes.

What does "hashable" mean in Python?

Hashable = capable of being hashed.

Ok, what is hashing? A hashing function is a function which takes an object, say a string such as “Python,” and returns a fixed-size code. For simplicity, assume the return value is an integer.

When I run hash(‘Python’) in Python 3, I get 5952713340227947791 as the result. Different versions of Python are free to change the underlying hash function, so you will likely get a different value. The important thing is that no matter now many times I run hash(‘Python’), I’ll always get the same result with the same version of Python.

But hash(‘Java’) returns 1753925553814008565. So if the object I am hashing changes, so does the result. On the other hand, if the object I am hashing does not change, then the result stays the same.

Why does this matter?

Well, Python dictionaries, for example, require the keys to be immutable. That is, keys must be objects which do not change. Strings are immutable in Python, as are the other basic types (int, float, bool). Tuples and frozensets are also immutable. Lists, on the other hand, are not immutable (i.e., they are mutable) because you can change them. Similarly, dicts are mutable.

So when we say something is hashable, we mean it is immutable. If I try to pass a mutable type to the hash() function, it will fail:

>>> hash('Python')
>>> hash('Java')
>>> hash([1, 2])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
>>> hash({1, 2})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'set'
>>> hash({1 : 2})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'dict'
>>> hash(frozenset({1, 2}))
>>> hash((1, 2))

How to clear text area with a button in html using javascript?

You need to attach a click event handler and clear the contents of the textarea from that handler.


<input type="button" value="Clear" id="clear"> 
<textarea id='output' rows=20 cols=90></textarea>


var input = document.querySelector('#clear');
var textarea = document.querySelector('#output');

input.addEventListener('click', function () {
    textarea.value = '';
}, false);

and here's the working demo.

How do I replace text in a selection?

You can use ctrl+F to find the text.
ctrl+h to enter the replacement text. Then ctrl+shift+h to replace the current selected text and move to next matched text.

This is for windows. But you can check in mac also for which you might want to check the key bindings under Preferences.

Send PHP variable to javascript function

If I understand you correctly, you should be able to do something along the lines of the following:

function clicked() {
    var someVariable="<?php echo $phpVariable; ?>";

Simple If/Else Razor Syntax

I would just go with

<tr @(if (count++ % 2 == 0){<text>class="alt-row"</text>})>

Or even better

<tr class="alt-row@(count++ % 2)">

this will give you lines like

<tr class="alt-row0">
<tr class="alt-row1">
<tr class="alt-row0">
<tr class="alt-row1">

Format SQL in SQL Server Management Studio

Late answer, but hopefully worthwhile: The Poor Man's T-SQL Formatter is an open-source (free) T-SQL formatter with complete T-SQL batch/script support (any DDL, any DML), SSMS Plugin, command-line bulk formatter, and other options.

It's available for immediate/online use at, and just today graduated to "version 1.0" (it was in beta version for a few months), having just acquired support for MERGE statements, OUTPUT clauses, and other finicky stuff.

The SSMS Add-in allows you to set your own hotkey (default is Ctrl-K, Ctrl-F, to match Visual Studio), and formats the entire script or just the code you have selected/highlighted, if any. Output formatting is customizable.

In SSMS 2008 it combines nicely with the built-in intelli-sense, effectively providing more-or-less the same base functionality as Red Gate's SQL Prompt (SQL Prompt does, of course, have extra stuff, like snippets, quick object scripting, etc).

Feedback/feature requests are more than welcome, please give it a whirl if you get the chance!

Disclosure: This is probably obvious already but I wrote this library/tool/site, so this answer is also shameless self-promotion :)

Oracle listener not running and won't start

I had the same problem on 11.201 on Windows. After: additional install 11.203 64bit server and client in new folders. PATH environment variable was changed right after install. Error in listener appeared after listener service restart. In my case there was a night time and number of windows updates, so windows server restart helped us. Also I cleaned listener.log file according to, it was surprisingly big.

How do I parse a URL into hostname and path in javascript?

a simple hack with the first answer

var getLocation = function(href=window.location.href) {
    var l = document.createElement("a");
    l.href = href;
    return l;

this can used even without argument to figure out the current hostname getLocation().hostname will give current hostname

Convert String (UTF-16) to UTF-8 in C#

    private static string Utf16ToUtf8(string utf16String)
         * Every .NET string will store text with the UTF16 encoding, *
         * known as Encoding.Unicode. Other encodings may exist as    *
         * Byte-Array or incorrectly stored with the UTF16 encoding.  *
         *                                                            *
         * UTF8 = 1 bytes per char                                    *
         *    ["100" for the ansi 'd']                                *
         *    ["206" and "186" for the russian '?']                   *
         *                                                            *
         * UTF16 = 2 bytes per char                                   *
         *    ["100, 0" for the ansi 'd']                             *
         *    ["186, 3" for the russian '?']                          *
         *                                                            *
         * UTF8 inside UTF16                                          *
         *    ["100, 0" for the ansi 'd']                             *
         *    ["206, 0" and "186, 0" for the russian '?']             *
         *                                                            *
         * We can use the convert encoding function to convert an     *
         * UTF16 Byte-Array to an UTF8 Byte-Array. When we use UTF8   *
         * encoding to string method now, we will get a UTF16 string. *
         *                                                            *
         * So we imitate UTF16 by filling the second byte of a char   *
         * with a 0 byte (binary 0) while creating the string.        *

        // Get UTF16 bytes and convert UTF16 bytes to UTF8 bytes
        byte[] utf16Bytes = Encoding.Unicode.GetBytes(utf16String);
        byte[] utf8Bytes = Encoding.Convert(Encoding.Unicode, Encoding.UTF8, utf16Bytes);
        char[] chars = (char[])Array.CreateInstance(typeof(char), utf8Bytes.Length);

        for (int i = 0; i < utf8Bytes.Length; i++)
            chars[i] = BitConverter.ToChar(new byte[2] { utf8Bytes[i], 0 }, 0);

        // Return UTF8
        return new String(chars);

In the original post author concatenated strings. Every sting operation will result in string recreation in .Net. String is effectively a reference type. As a result, the function provided will be visibly slow. Don't do that. Use array of chars instead, write there directly and then convert result to string. In my case of processing 500 kb of text difference is almost 5 minutes.

How to get the IP address of the server on which my C# application is running on?

namespace NKUtilities 
    using System;
    using System.Net;

    public class DNSUtility
        public static int Main (string [] args)

          String strHostName = new String ("");
          if (args.Length == 0)
              // Getting Ip address of local machine...
              // First get the host name of local machine.
              strHostName = Dns.GetHostName ();
              Console.WriteLine ("Local Machine's Host Name: " +  strHostName);
              strHostName = args[0];

          // Then using host name, get the IP address list..
          IPHostEntry ipEntry = DNS.GetHostByName (strHostName);
          IPAddress [] addr = ipEntry.AddressList;

          for (int i = 0; i < addr.Length; i++)
              Console.WriteLine ("IP Address {0}: {1} ", i, addr[i].ToString ());
          return 0;

Python conditional assignment operator

I think what you are looking for, if you are looking for something in a dictionary, is the setdefault method:

(Pdb) we=dict()
(Pdb) we.setdefault('e',14)
(Pdb) we['e']
(Pdb) we['r']="p"
(Pdb) we.setdefault('r','jeff')
(Pdb) we['r']
(Pdb) we[e]
*** NameError: name 'e' is not defined
(Pdb) we['e']
(Pdb) we['q2']

*** KeyError: 'q2' (Pdb)

The important thing to note in my example is that the setdefault method changes the dictionary if and only if the key that the setdefault method refers to is not present.

Can't connect to docker from docker-compose

$sudo docker-compose up

I did follow the steps as it is in the above answer to add $USER to group docker. i didn't want to add a new group docker because in my docker installation a group named docker automatically created.

Docker CE is installed and running. The docker group is created but no users are added to it. You need to use sudo to run Docker commands. Continue to Linux postinstall to allow non-privileged users to run Docker commands and for other optional configuration steps.

but using docker-compose up didn't work either. It gave the same previous error. So in my case(Ubuntu 18.10) sudo docker-compose up fixed the issue.

ps: @Tiw thanks for the advice.

Set CSS property in Javascript?

That's actually quite simple with vanilla JavaScript: = "100px";

Python TypeError must be str not int

Python comes with numerous ways of formatting strings:

New style .format(), which supports a rich formatting mini-language:

>>> temperature = 10
>>> print("the furnace is now {} degrees!".format(temperature))
the furnace is now 10 degrees!

Old style % format specifier:

>>> print("the furnace is now %d degrees!" % temperature)
the furnace is now 10 degrees!

In Py 3.6 using the new f"" format strings:

>>> print(f"the furnace is now {temperature} degrees!")
the furnace is now 10 degrees!

Or using print()s default separator:

>>> print("the furnace is now", temperature, "degrees!")
the furnace is now 10 degrees!

And least effectively, construct a new string by casting it to a str() and concatenating:

>>> print("the furnace is now " + str(temperature) + " degrees!")
the furnace is now 10 degrees!

Or join()ing it:

>>> print(' '.join(["the furnace is now", str(temperature), "degrees!"]))
the furnace is now 10 degrees!

How can I find my php.ini on wordpress?

Create a file yourself php.ini anywhere in your root or wp-admin folder and add the necessary code to the file it should work

Execute bash script from URL

Is some unattended scripts I use the following command:

sh -c "$(curl -fsSL <URL>)"

I recommend to avoid executing scripts directly from URLs. You should be sure the URL is safe and check the content of the script before executing, you can use a SHA256 checksum to validate the file before executing.

How to get the width and height of an android.widget.ImageView?

The reason the ImageView's dimentions are 0 is because when you are querying them, the view still haven't performed the layout and measure steps. You only told the view how it would "behave" in the layout, but it still didn't calculated where to put each view.

How do you decide the size to give to the image view? Can't you simply use one of the scaling options natively implemented?

CodeIgniter: How to use WHERE clause and OR clause

You can use or_where() for that - example from the CI docs:

$this->db->where('name !=', $name);

$this->db->or_where('id >', $id); 

// Produces: WHERE name != 'Joe' OR id > 50

Execute a shell script in current shell with sudo permission

The answers here explain why it happens but I thought I'd add my simple way around the issue. First you can cat the file into a variable with sudo permissions. Then you can evaluate the variable to execute the code in the file in your current shell.

Here is an example of reading and executing an .env file (ex Docker)

 sensitive_stuff=$(sudo cat ".env")
 eval "${sensitive_stuff}"

What does template <unsigned int N> mean?

You templatize your class based on an 'unsigned int'.


template <unsigned int N>
class MyArray
        double    data[N]; // Use N as the size of the array

int main()
    MyArray<2>     a1;
    MyArray<2>     a2;

    MyArray<4>     b1;

    a1 = a2;  // OK The arrays are the same size.
    a1 = b1;  // FAIL because the size of the array is part of the
              //      template and thus the type, a1 and b1 are different types.
              //      Thus this is a COMPILE time failure.

html select option SELECTED

foreach($array as $value=>$name)
    if($value == $_GET['sel'])
         echo "<option selected='selected' value='".$value."'>".$name."</option>";
         echo "<option value='".$value."'>".$name."</option>";

How to clear input buffer in C?

But I cannot explain myself how it works? Because in the while statement, we use getchar() != '\n', that means read any single character except '\n'?? if so, in the input buffer still remains the '\n' character??? Am I misunderstanding something??

The thing you may not realize is that the comparison happens after getchar() removes the character from the input buffer. So when you reach the '\n', it is consumed and then you break out of the loop.

iTunes Connect: How to choose a good SKU?

SKU stands for Stock-keeping Unit. It's more for inventory tracking purpose.

The purpose of having an SKU is so that you can tie the app sales to whatever internal SKU number that your accounting is using.

What's an Aggregate Root?

Aggregate is where you protect your invariants and force consistency by limiting its access thought aggregate root. Do not forget, aggregate should design upon your project business rules and invariants, not database relationship. you should not inject any repository and no queries are not allowed.

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

That's because the color input only accepts three attributes: "primary", "accent" or "warn". Hence, you'll have to style the icons the CSS way:

  1. Add a class to style your icon:

    .white-icon {
        color: white;
    /* Note: If you're using an SVG icon, you should make the class target the `<svg>` element */
    .white-icon svg {
        fill: white;
  2. Add the class to your icon:

    <mat-icon class="white-icon">menu</mat-icon>

how to install gcc on windows 7 machine?

EDIT Since not so recently by now, MinGW-w64 has "absorbed" one of the toolchain building projects. The downloads can be found here. The installer should work, and allow you to pick a version that you need.

Note the Qt SDK comes with the same toolchain. So if you are developing in Qt and using the SDK, just use the toolchain it comes with.

Another alternative that has up to date toolchains comes from... harhar... a Microsoft developer, none other than STL (Stephan T. Lavavej, isn't that a spot-on name for the maintainer of MSVC++ Standard Library!). You can find it here. It includes Boost.

Another option which is highly useful if you care for prebuilt dependencies is MSYS2, which provides a Unix shell (a Cygwin fork modified to work better with Windows pathnames and such), also provides a GCC. It usually lags a bit behind, but that is compensated for by its good package management system and stability. They also provide a functional Clang with libc++ if you care for such thing.

I leave the below for reference, but I strongly suggest against using, due to limitations detailed below. TDM-GCC (the MinGW-w64 version) provides some hacks that you may find useful in your specific situation, although I recommend using vanilla GCC at all times for maximum compatibility.

GCC for Windows is provided by two projects currently. They both provide a very own implementation of the Windows SDK (headers and libraries) which is necessary because GCC does not work with Visual Studio files.

  1. The older, which @Mat already pointed you to. They provide only a 32-bit compiler. See here for the downloads you need:

    • Binutils is the linker and resource compiler etc.
    • GCC is the compiler, and is split in core and language packages
    • GDB is the debugger.
    • runtime library is required only for
    • You might need to download mingw32-make seperately.
    • For support, you can try (don't expect friendly replies) [email protected]

    Alternatively, download mingw-get and use that.

  2. The newer mingw-w64, which as the name predicts, also provides a 64-bit variant, and in the future hopefully some ARM support. I use it and built toolchains with their CRT. Personal and auto builds are found under "Toolchains targetting Win32/64" here. They also provide Linux to Windows cross-compilers. I suggest you try a personal build first, they are more complete. Try mine (rubenvb) for GCC 4.6 to 4.8, or use sezero's for GCC 4.4 and 4.5. Both of us provide 32-bit and 64-bit native toolchains. These packages include everything listed above. I currently recommend the "MinGW-Builds" builds, as these are currently sanctioned as "official builds", and come with an installer (see above).

    For support, send an email to [email protected] or post on the forum via

Both projects have their files listed on sourceforge, and all you have to do is either run the installer (in case of or download a suitable zipped package and extract it (in the case of mingw-w64).

There are a lot of "non-official" toolchain builders, one of the most popular is TDM-GCC. They may use patches that break binary compatibility with official/unpatched toolchains, so be careful using them. It's best to use the official releases.

intelliJ IDEA 13 error: please select Android SDK

You have to Select Build Tool Version from your project setting.

  1. Select Project App Folder
  2. Press F4 OR Right Click on Project App Folder and open Module Settings In The Properties tab select Build Tool Version from List

This will work on my side i hope it will help you.

How to list files and folder in a dir (PHP)

You may use Directory Functions:

Simple example from opendir() function description:

$dir_path = "/path/to/your/dir";

if (is_dir($dir_path)) {
    if ($dir_handler = opendir($dir_path)) {
        while (($file = readdir($dir_handler)) !== false) {
            echo "filename: $file : filetype: " . filetype($dir_path . $file) . "\n";

How to comment multiple lines in Visual Studio Code?

visual studio 2017 we do a: Comment Selection

Ctrl+K, Ctrl+C

press Ctrl+K to get shortcut. press Ctrl+C to confirm

How to convert a private key to an RSA private key?

Newer versions of OpenSSL say BEGIN PRIVATE KEY because they contain the private key + an OID that identifies the key type (this is known as PKCS8 format). To get the old style key (known as either PKCS1 or traditional OpenSSL format) you can do this:

openssl rsa -in server.key -out server_new.key

Alternately, if you have a PKCS1 key and want PKCS8:

openssl pkcs8 -topk8 -nocrypt -in privkey.pem

CSS: Truncate table cells, but fit as much as possible

Don't know if this will help anyone, but I solved a similar problem by specifying specific width sizes in percentage for each column. Obviously, this would work best if each column has content with width that doesn't vary too widely.

Inner Joining three tables

Just do the same thing agin but then for TableC

FROM dbo.tableA A 
INNER JOIN dbo.TableB B ON A.common = B.common
INNER JOIN dbo.TableC C ON A.common = C.common

Delete a dictionary item if the key exists

You can use dict.pop:

 mydict.pop("key", None)

Note that if the second argument, i.e. None is not given, KeyError is raised if the key is not in the dictionary. Providing the second argument prevents the conditional exception.

__init__() got an unexpected keyword argument 'user'

I got the same error.

On my view I was overriding get_form_kwargs() like this:

class UserAccountView(FormView):
    form_class = UserAccountForm
    success_url = '/'
    template_name = 'user_account/user-account.html'

def get_form_kwargs(self):
    kwargs = super(UserAccountView, self).get_form_kwargs()
    kwargs.update({'user': self.request.user})
    return kwargs

But on my form I failed to override the init() method. Once I did it. Problem solved

class UserAccountForm(forms.Form):
    first_name = forms.CharField(label='Your first name', max_length=30)
    last_name = forms.CharField(label='Your last name', max_length=30)
    email = forms.EmailField(max_length=75)

    def __init__(self, *args, **kwargs):
        user = kwargs.pop('user')
        super(UserAccountForm, self).__init__(*args, **kwargs)

When using SASS how can I import a file from a different directory?

You could use the -I command line switch or :load_paths option from Ruby code to add sub_directory_a to Sass's load path. So if you're running Sass from root_directory, do something like this:

sass -I sub_directory_a --watch sub_directory_b:sub_directory_b

Then you can simply use @import "common" in more_styles.scss.

C compiler for Windows?

I use either BloodShed's DEV C++, CygWin, or Visual C++ Express. All of which are free and work well. I have found that for me, DEV C++ worked the best and was the least quirky. Each compiler has it's own quirks and deifferences, you need to try out a few and find the one with which you are most comfortable. I also liked the fact that DEV C++ allowed me to change the fonts that are used in the editor. I like Proggy Programming fonts!

How to iterate a table rows with JQuery and access some cell values?

try this

var value = iterate('tr.item span.value');
var quantity = iterate('tr.item span.quantity');

function iterate(selector)
  var result = '';
  if ($(selector))
    $(selector).each(function ()
      if (result == '')
        result = $(this).html();
        result = result + "," + $(this).html();

Does JavaScript have the interface type (such as Java's 'interface')?

This is an old question, nevertheless this topic never ceases to bug me.

As many of the answers here and across the web focus on "enforcing" the interface, I'd like to suggest an alternative view:

I feel the lack of interfaces the most when I'm using multiple classes that behave similarly (i.e. implement an interface).

For example, I have an Email Generator that expects to receive Email Sections Factories, that "know" how to generate the sections' content and HTML. Hence, they all need to have some sort of getContent(id) and getHtml(content) methods.

The closest pattern to interfaces (albeit it's still a workaround) I could think of is using a class that'll get 2 arguments, which will define the 2 interface methods.

The main challenge with this pattern is that the methods either have to be static, or to get as argument the instance itself, in order to access its properties. However there are cases in which I find this trade-off worth the hassle.

class Filterable {_x000D_
  constructor(data, { filter, toString }) {_x000D_ = data;_x000D_
    this.filter = filter;_x000D_
    this.toString = toString;_x000D_
    // You can also enforce here an Iterable interface, for example,_x000D_
    // which feels much more natural than having an external check_x000D_
const evenNumbersList = new Filterable(_x000D_
  [1, 2, 3, 4, 5, 6], {_x000D_
    filter: (lst) => {_x000D_
      const evenElements = => x % 2 === 0);_x000D_ = evenElements;_x000D_
    toString: lst => `< ${} >`,_x000D_
console.log('The whole list:    ', evenNumbersList.toString(evenNumbersList));_x000D_
console.log('The filtered list: ', evenNumbersList.toString(evenNumbersList));

package does not exist ; in Android studio 0.8



Then sync gradle to build project.

Java - get index of key in HashMap?

Posting this as an equally viable alternative to @Binil Thomas's answer - tried to add it as a comment, but was not convinced of the readability of it all.

int index = 0;

for (Object key : map.keySet()) {
   Object value = map.get(key);

Probably doesn't help the original question poster since this is the literal situation they were trying to avoid, but may aid others searching for an easy answer.

Model Binding to a List MVC 4

A clean solution could be create a generic class to handle the list, so you don't need to create a different class each time you need it.

public class ListModel<T>
    public List<T> Items { get; set; }

    public ListModel(List<T> list) {
        Items = list;

and when you return the View you just need to simply do:

List<customClass> ListOfCustomClass = new List<customClass>();
//Do as needed...
return View(new ListModel<customClass>(ListOfCustomClass));

then define the list in the model:

@model ListModel<customClass>

and ready to go:

@foreach(var element in Model.Items) {
  //do as needed...

Replace HTML Table with Divs

Basically it boils down to using a fixed-width page and setting the width for those labels and controls. This is the most common way in which table-less layouts are implemented.

There are many ways to go about setting widths. Blueprint.css is a very popular css framework which can help you set up columns/widths.

How to include route handlers in multiple files in Express?


const express = require("express");
const app = express();
const http = require('http');
const server = http.createServer(app).listen(3000);
const router = (global.router = (express.Router()));
app.use('/books', require('./routes/books'))
app.use('/users', require('./routes/users'))


const router = global.router
router.get('/', (req, res) => {
    res.jsonp({name: 'John Smith'})

module.exports = router


const router = global.router
router.get('/', (req, res) => {
    res.jsonp({name: 'Dreams from My Father by Barack Obama'})

module.exports = router

if you have your server running local (http://localhost:3000) then

// Users
curl --request GET 'localhost:3000/users' => {name: 'John Smith'}

// Books
curl --request GET 'localhost:3000/users' => {name: 'Dreams from My Father by Barack Obama'}

How can I remove the outline around hyperlinks images?

I hope this is useful to some of you, it can be used to remove outline from links, images and flash and from MSIE 9:

    a, a:hover, a:active, a:focus, a img, object, embed {
    outline: none;
    ie-dummy: expression(this.hideFocus=true); /* MSIE - Microsoft Internet Explorer 9 remove outline */

The code below is able to hide image border:

    img {
    border: 0;

If you would like to support Firefox 3.6.8 but not Firefox 4... Clicking down on an input type=image can produce a dotted outline as well, to remove it in the old versions of firefox the following will do the trick:

   input::-moz-focus-inner { 
   border: 0; 

IE 9 doesn't allow in some cases to remove the dotted outline around links unless you include this meta tag between and in your pages:

     <meta http-equiv="X-UA-Compatible" content="IE=9" />

How to specify jdk path in eclipse.ini on windows 8 when path contains space

All above answers didn't work for me. My Eclipse mars is x64 but I need to set registry dll to x86 for another software.

At the end I put -vm argument at the end of shortcut and this did the trick.

D:\mars\eclipse\eclipse.exe -vm "C:\Program Files\Java\jre7\bin\server\jvm.dll"

According to this doc jvm.dll also work for some cases.

SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed

What worked for me is a combination of answers, namely:

# Reinstall OpenSSL
brew update
brew remove openssl
brew install openssl
# Download CURL CA bundle
cd /usr/local/etc/openssl/certs
# Reinstall Ruby from source
rvm reinstall 2.2.3 --disable-binary

How to stop/shut down an elasticsearch node?

use the following command to know the pid of the node already running.

curl -XGET 'http://localhost:9200/_nodes/process'

It took me an hour to find out the way to kill the node and could finally do it after using this command in the terminal window.

HTML5 Video Autoplay not working correctly

Try autoplay="autoplay" instead of the "true" value. That's the documented way to enable autoplay. That sounds weirdly redundant, I know.

Setting a width and height on an A tag

You need to make your anchor display: block or display: inline-block; and then it will accept the width and height values.

iloc giving 'IndexError: single positional indexer is out-of-bounds'

This error is caused by:

Y = Dataset.iloc[:,18].values

Indexing is out of bounds here most probably because there are less than 19 columns in your Dataset, so column 18 does not exist. The following code you provided doesn't use Y at all, so you can just comment out this line for now.

HTML5 Canvas: Zooming

One option is to use css zoom feature:


How to print_r $_POST array?

Because you have nested arrays, then I actually recommend a recursive approach:

function recurse_into_array( $in, $tabs = "" )
    foreach( $in as $key => $item )
        echo $tabs . $key . ' => ';
        if( is_array( $item ) )
            recurse_into_array( $item, $tabs . "\t" );
            echo $tabs . "\t" . $key;

recurse_into_array( $_POST );

Applying Comic Sans Ms font style

You need to use quote marks.

font-family: "Comic Sans MS", cursive, sans-serif;

Although you really really shouldn't use comic sans. The font has massive stigma attached to it's use; it's not seen as professional at all.

Generate random numbers using C++11 random library

Stephan T. Lavavej (stl) from Microsoft did a talk at Going Native about how to use the new C++11 random functions and why not to use rand(). In it, he included a slide that basically solves your question. I've copied the code from that slide below.

You can see his full talk here:

#include <random>
#include <iostream>

int main() {
    std::random_device rd;
    std::mt19937 mt(rd());
    std::uniform_real_distribution<double> dist(1.0, 10.0);

    for (int i=0; i<16; ++i)
        std::cout << dist(mt) << "\n";

We use random_device once to seed the random number generator named mt. random_device() is slower than mt19937, but it does not need to be seeded because it requests random data from your operating system (which will source from various locations, like RdRand for example).

Looking at this question / answer, it appears that uniform_real_distribution returns a number in the range [a, b), where you want [a, b]. To do that, our uniform_real_distibution should actually look like:

std::uniform_real_distribution<double> dist(1, std::nextafter(10, DBL_MAX));

Git push error pre-receive hook declined

Seems the problem is with some services, like sidekiq. Running sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production outputs all the problems with config.

How to perform element-wise multiplication of two lists?

you can multiplication using lambda

l=map(lambda x,y:x*y,foo,bar)

Convert Json Array to normal Java list

We can simply convert the JSON into readable string, and split it using "split" method of String class.

String jsonAsString = yourJsonArray.toString();
//we need to remove the leading and the ending quotes and square brackets
jsonAsString = jsonAsString.substring(2, jsonAsString.length() -2);
//split wherever the String contains ","
String[] jsonAsStringArray = jsonAsString.split("\",\"");

How can I remove the string "\n" from within a Ruby string?

When you want to remove a string, rather than replace it you can use String#delete (or its mutator equivalent String#delete!), e.g.:

x = "foo\nfoo"

x now equals "foofoo"

In this specific case String#delete is more readable than gsub since you are not actually replacing the string with anything.

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

Handling multiple extensions

In the case where you have multiple extensions this one-liner using pathlib and str.replace works a treat:

Remove/strip extensions

>>> from pathlib import Path
>>> p = Path("/path/to/myfile.tar.gz")
>>> extensions = "".join(p.suffixes)

# any python version
>>> str(p).replace(extensions, "")

# python>=3.9
>>> str(p).removesuffix(extensions)

Replace extensions

>>> p = Path("/path/to/myfile.tar.gz")
>>> extensions = "".join(p.suffixes)
>>> new_ext = ".jpg"
>>> str(p).replace(extensions, new_ext)

If you also want a pathlib object output then you can obviously wrap the line in Path()

>>> Path(str(p).replace("".join(p.suffixes), ""))

Wrapping it all up in a function

from pathlib import Path
from typing import Union

PathLike = Union[str, Path]

def replace_ext(path: PathLike, new_ext: str = "") -> Path:
    extensions = "".join(Path(path).suffixes)
    return Path(str(p).replace(extensions, new_ext))

p = Path("/path/to/myfile.tar.gz")
new_ext = ".jpg"

assert replace_ext(p, new_ext) == Path('/path/to/myfile.jpg')
assert replace_ext(str(p), new_ext) == Path('/path/to/myfile.jpg')
assert replace_ext(p) == Path('/path/to/myfile')

Find first and last day for previous calendar month in SQL Server Reporting Services (VB.Net)

These functions have been very helpful to me - especially in setting up subscription reports; however, I noticed when using the Last Day of Current Month function posted above, it works as long as the proceeding month has the same number of days as the current month. I have worked through and tested these modifications and hope they help other developers in the future:

Date Formulas: Find the First Day of Previous Month:

DateAdd("m", -1, DateSerial(Year(Today()), Month(Today()), 1))

Find Last Day of Previous Month:

DateSerial(Year(Today()), Month(Today()), 0)

Find First Day of Current Month:


Find Last Day of Current Month:

DateSerial(Year(Today()),Month(DateAdd("m", 1, Today())),0)

What is the Swift equivalent of isEqualToString in Objective-C?

Actually, it feels like swift is trying to promote strings to be treated less like objects and more like values. However this doesn't mean under the hood swift doesn't treat strings as objects, as am sure you all noticed that you can still invoke methods on strings and use their properties.

For example:-

//example of calling method (String to Int conversion)
let intValue = ("12".toInt())
println("This is a intValue now \(intValue)")

//example of using properties (fetching uppercase value of string)
let caUpperValue = "ca".uppercaseString
println("This is the uppercase of ca \(caUpperValue)")

In objectC you could pass the reference to a string object through a variable, on top of calling methods on it, which pretty much establishes the fact that strings are pure objects.

Here is the catch when you try to look at String as objects, in swift you cannot pass a string object by reference through a variable. Swift will always pass a brand new copy of the string. Hence, strings are more commonly known as value types in swift. In fact, two string literals will not be identical (===). They are treated as two different copies.

let curious = ("ca" === "ca")
println("This will be false.. and the answer is..\(curious)")

As you can see we are starting to break aways from the conventional way of thinking of strings as objects and treating them more like values. Hence .isEqualToString which was treated as an identity operator for string objects is no more a valid as you can never get two identical string objects in Swift. You can only compare its value, or in other words check for equality(==).

 let NotSoCuriousAnyMore = ("ca" == "ca")
 println("This will be true.. and the answer is..\(NotSoCuriousAnyMore)")

This gets more interesting when you look at the mutability of string objects in swift. But thats for another question, another day. Something you should probably look into, cause its really interesting. :) Hope that clears up some confusion. Cheers!

Inverse of matrix in R

Note that if you care about speed and do not need to worry about singularities, solve() should be preferred to ginv() because it is much faster, as you can check:

mat <- matrix(rnorm(1e6),nrow=1e3,ncol=1e3)

t0 <- proc.time()
inv0 <- ginv(mat)
proc.time() - t0 

t1 <- proc.time()
inv1 <- solve(mat)
proc.time() - t1 

how to change default python version?

According to a quick google search, this update only applies to the current shell you have open. It can probably be fixed by typing python3, as mac and linux are similar enough for things like this to coincide. Link to the result of google search.

Also, as ninjagecko stated, most programs have not been updated to 3.x yet, so having the default python as 3.x would break many python scripts used in applications.

Editor does not contain a main type

The correct answer is: the Scala library needs to before the JRE library in the buildpath.

Go to Java Buildpath > Order and Export and move Scala library to the top

"Multiple definition", "first defined here" errors

The problem here is that you are including commands.c in commands.h before the function prototype. Therefore, the C pre-processor inserts the content of commands.c into commands.h before the function prototype. commands.c contains the function definition. As a result, the function definition ends up before than the function declaration causing the error.

The content of commands.h after the pre-processor phase looks like this:

#ifndef COMMANDS_H_
#define COMMANDS_H_

// function definition
void f123(){


// function declaration
void f123();

#endif /* COMMANDS_H_ */

This is an error because you can't declare a function after its definition in C. If you swapped #include "commands.c" and the function declaration the error shouldn't happen because, now, the function prototype comes before the function declaration.

However, including a .c file is a bad practice and should be avoided. A better solution for this problem would be to include commands.h in commands.c and link the compiled version of command to the main file. For example:


#ifndef COMMANDS_H_
#define COMMANDS_H_

void f123(); // function declaration



#include "commands.h"

void f123(){} // function definition

Checking if a field contains a string

As of version 2.4, you can create a text index on the field(s) to search and use the $text operator for querying.

First, create the index:

db.users.createIndex( { "username": "text" } )

Then, to search:

db.users.find( { $text: { $search: "son" } } )

Benchmarks (~150K documents):

  • Regex (other answers) => 5.6-6.9 seconds
  • Text Search => .164-.201 seconds


  • A collection can have only one text index. You can use a wildcard text index if you want to search any string field, like this: db.collection.createIndex( { "$**": "text" } ).
  • A text index can be large. It contains one index entry for each unique post-stemmed word in each indexed field for each document inserted.
  • A text index will take longer to build than a normal index.
  • A text index does not store phrases or information about the proximity of words in the documents. As a result, phrase queries will run much more effectively when the entire collection fits in RAM.

Xcode stuck on Indexing

I had a similar problem where Xcode would spend lots of time indexing and would frequently hang building the project, at which point I had to force-quit and relaunch Xcode. It was very annoying.

Then I noticed a warning in the project about improperly assigning self as a delegate. Sure enough, there was a missing protocol in the class declaration. Note that there is a similar assignment in the OP's sample code (though it is impossible to tell from the sample whether the correct protocol is declared):

leaderboardController.leaderboardDelegate == self;

After resolving that warning (by correctly declaring the implemented protocol), Xcode stopped misbehaving. Also, I should note that the project did execute correctly since the protocol methods were implemented. It was just that Xcode could not confirm that the protocol should in fact implemented by the class.

Format a BigDecimal as String with max 2 decimal digits, removing 0 on decimal part

If its money use:


how to display full stored procedure code?

SELECT prosrc FROM pg_proc WHERE proname = 'function_name';

This tells the function handler how to invoke the function. It might be the actual source code of the function for interpreted languages, a link symbol, a file name, or just about anything else, depending on the implementation language/call convention

SQL Server: Is it possible to insert into two tables at the same time?

Before being able to do a multitable insert in Oracle, you could use a trick involving an insert into a view that had an INSTEAD OF trigger defined on it to perform the inserts. Can this be done in SQL Server?

How to create a cron job using Bash automatically without the interactive editor?

You can probably change the default editor to ed and use a heredoc to edit.

export EDITOR

crontab -e << EOF
> a
> * * * * * Myscript
> * * * * * AnotherScript
> * * * * * MoreScript
> .
> w
> q

Note the leading > in that code means the return/enter key is pressed to create a new line.

The a means APPEND so it will not overwrite anything.

The . means you're done editing.

The w means WRITE the changes.

The q means QUIT or exit ed.

you can check it out

crontab -l

You can delete an entry too.

export EDITOR

crontab -e << EOF
> /Myscript/
> d
> .
> w
> q

That will delete the crontab entry with Myscript in it.

The d means delete the pattern inside the / /.

No check it again

crontab -l

This solution works inside a script too less the > of course :-)

How to add a custom button to the toolbar that calls a JavaScript function?

If you have customized the ckeditor toolbar then use this method:

var editor = CKEDITOR.replace("da_html", {_x000D_
  disableNativeSpellChecker: false,_x000D_
  toolbar: [{_x000D_
      name: "clipboard",_x000D_
      items: ["Cut", "Copy", "Paste", "PasteText", "PasteFromWord", "-", "Undo", "Redo"]_x000D_
      name: "basicstyles",_x000D_
      items: ["Italic"]_x000D_
      name: "paragraph",_x000D_
      items: ["BulletedList"]_x000D_
      name: "insert",_x000D_
      items: ["Table"]_x000D_
      name: "styles",_x000D_
      items: ["Styles", "Format", "Font", "FontSize"]_x000D_
      name: "colors",_x000D_
      items: ["TextColor", "BGColor"]_x000D_
      name: "tools",_x000D_
      items: ["Maximize", "saveButton"]_x000D_
editor.addCommand("mySaveCommand", { // create named command_x000D_
  exec: function(edt) {_x000D_
editor.ui.addButton("saveButton", { // add new button and bind our command_x000D_
  label: "Click me",_x000D_
  command: "mySaveCommand",_x000D_
  toolbar: "insert",_x000D_
  icon: ""_x000D_
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<textarea id="da_html">How are you!</textarea>

Working code in jsfiddle due to some security issue of stackoverflow:

No resource found - Theme.AppCompat.Light.DarkActionBar

make sure there is a v7 directory in your sdk, I thought having the 'Android Support Library' (in Extras) was sufficient. Turns out I was missing the 'Local Maven repository for Support Libraries (extras;android;m2repository)' Studio found that actually and fixed the gradle dependencies. using gradle to build then worked. $ cat app/build.gradle

apply plugin: ''

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.2"

    defaultConfig {
        applicationId ""
        minSdkVersion 15
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), ''

dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
    compile ''

Filtering Sharepoint Lists on a "Now" or "Today"

If you want to filter only items that are less than 7 days old then you just use


  • Created

  • is greater than or equal to

  • [Today]-7

Note - the screenshot is incorrect.

New items - created in last 7 days

[Today] is fully supported in view filters in 2007 and onwards (just keep the spaces out!) and you only need to muck around with calculated columns in 2003.

What is console.log in jQuery?

it will print log messages in your developer console (firebug/webkit dev tools/ie dev tools)

How to form tuple column from two columns in Pandas

Pandas has the itertuples method to do exactly this:

list(df[['lat', 'long']].itertuples(index=False, name=None))

How can I make a menubar fixed on the top while scrolling

 #header {

    #content {

How to run python script with elevated privilege on windows

It worth mentioning that if you intend to package your application with PyInstaller and wise to avoid supporting that feature by yourself, you can pass the --uac-admin or --uac-uiaccess argument in order to request UAC elevation on start.

py2exe - generate single executable file

I'm told bbfreeze will create a single file .EXE, and is newer than py2exe.

Vertically centering Bootstrap modal window

Use this simple script that centers the modals.

If you want you can set a custom class (ex: .modal.modal-vcenter instead of .modal) to limit the functionality only to some modals.

var modalVerticalCenterClass = ".modal";

function centerModals($element) {
    var $modals;
    if ($element.length) {
      $modals = $element;
    } else {
    $modals = $(modalVerticalCenterClass + ':visible');
$modals.each( function(i) {
    var $clone = $(this).clone().css('display', 'block').appendTo('body');
    var top = Math.round(($clone.height() - $clone.find('.modal-content').height()) / 2);
    top = top > 0 ? top : 0;
    $(this).find('.modal-content').css("margin-top", top);
$(modalVerticalCenterClass).on('', function(e) {
$(window).on('resize', centerModals);

Also add this CSS fix for the modal's horizontal spacing; we show the scroll on the modals, the body scrolls is hidden automatically by Bootstrap:

/* scroll fixes */
.modal-open .modal {
  padding-left: 0px !important;
  padding-right: 0px !important;
  overflow-y: scroll;

Can I scale a div's height proportionally to its width using CSS?

If you want vertical sizing proportional to a width set in pixels on an enclosing div, I believe you need an extra element, like so:


<div class="ptest">
    <div class="ptest-wrap">
        <div class="ptest-inner">
            Put content here

.ptest {
  width: 200px;
  position: relative;

.ptest-wrap {
    padding-top: 60%;
.ptest-inner {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: #333;

Here's the 2 div solution that doesn't work. Note the 60% vertical padding is proportional to the window width, not the div.ptest width:

Here's the example with the code above, which does work:

How Does Modulus Divison Work

I would like to add one more thing:

it's easy to calculate modulo when dividend is greater/larger than divisor

dividend = 5 divisor = 3

5 % 3 = 2


but what if divisor is smaller than dividend

dividend = 3 divisor = 5

3 % 5 = 3 ?? how

This is because, since 5 cannot divide 3 directly, modulo will be what dividend is

How do I pass a unique_ptr argument to a constructor or a function?

Here are the possible ways to take a unique pointer as an argument, as well as their associated meaning.

(A) By Value

Base(std::unique_ptr<Base> n)
  : next(std::move(n)) {}

In order for the user to call this, they must do one of the following:

Base newBase(std::move(nextBase));
Base fromTemp(std::unique_ptr<Base>(new Base(...));

To take a unique pointer by value means that you are transferring ownership of the pointer to the function/object/etc in question. After newBase is constructed, nextBase is guaranteed to be empty. You don't own the object, and you don't even have a pointer to it anymore. It's gone.

This is ensured because we take the parameter by value. std::move doesn't actually move anything; it's just a fancy cast. std::move(nextBase) returns a Base&& that is an r-value reference to nextBase. That's all it does.

Because Base::Base(std::unique_ptr<Base> n) takes its argument by value rather than by r-value reference, C++ will automatically construct a temporary for us. It creates a std::unique_ptr<Base> from the Base&& that we gave the function via std::move(nextBase). It is the construction of this temporary that actually moves the value from nextBase into the function argument n.

(B) By non-const l-value reference

Base(std::unique_ptr<Base> &n)
  : next(std::move(n)) {}

This has to be called on an actual l-value (a named variable). It cannot be called with a temporary like this:

Base newBase(std::unique_ptr<Base>(new Base)); //Illegal in this case.

The meaning of this is the same as the meaning of any other use of non-const references: the function may or may not claim ownership of the pointer. Given this code:

Base newBase(nextBase);

There is no guarantee that nextBase is empty. It may be empty; it may not. It really depends on what Base::Base(std::unique_ptr<Base> &n) wants to do. Because of that, it's not very evident just from the function signature what's going to happen; you have to read the implementation (or associated documentation).

Because of that, I wouldn't suggest this as an interface.

(C) By const l-value reference

Base(std::unique_ptr<Base> const &n);

I don't show an implementation, because you cannot move from a const&. By passing a const&, you are saying that the function can access the Base via the pointer, but it cannot store it anywhere. It cannot claim ownership of it.

This can be useful. Not necessarily for your specific case, but it's always good to be able to hand someone a pointer and know that they cannot (without breaking rules of C++, like no casting away const) claim ownership of it. They can't store it. They can pass it to others, but those others have to abide by the same rules.

(D) By r-value reference

Base(std::unique_ptr<Base> &&n)
  : next(std::move(n)) {}

This is more or less identical to the "by non-const l-value reference" case. The differences are two things.

  1. You can pass a temporary:

    Base newBase(std::unique_ptr<Base>(new Base)); //legal now..
  2. You must use std::move when passing non-temporary arguments.

The latter is really the problem. If you see this line:

Base newBase(std::move(nextBase));

You have a reasonable expectation that, after this line completes, nextBase should be empty. It should have been moved from. After all, you have that std::move sitting there, telling you that movement has occurred.

The problem is that it hasn't. It is not guaranteed to have been moved from. It may have been moved from, but you will only know by looking at the source code. You cannot tell just from the function signature.


  • (A) By Value: If you mean for a function to claim ownership of a unique_ptr, take it by value.
  • (C) By const l-value reference: If you mean for a function to simply use the unique_ptr for the duration of that function's execution, take it by const&. Alternatively, pass a & or const& to the actual type pointed to, rather than using a unique_ptr.
  • (D) By r-value reference: If a function may or may not claim ownership (depending on internal code paths), then take it by &&. But I strongly advise against doing this whenever possible.

How to manipulate unique_ptr

You cannot copy a unique_ptr. You can only move it. The proper way to do this is with the std::move standard library function.

If you take a unique_ptr by value, you can move from it freely. But movement doesn't actually happen because of std::move. Take the following statement:

std::unique_ptr<Base> newPtr(std::move(oldPtr));

This is really two statements:

std::unique_ptr<Base> &&temporary = std::move(oldPtr);
std::unique_ptr<Base> newPtr(temporary);

(note: The above code does not technically compile, since non-temporary r-value references are not actually r-values. It is here for demo purposes only).

The temporary is just an r-value reference to oldPtr. It is in the constructor of newPtr where the movement happens. unique_ptr's move constructor (a constructor that takes a && to itself) is what does the actual movement.

If you have a unique_ptr value and you want to store it somewhere, you must use std::move to do the storage.

Disable color change of anchor tag when visited

You can solve this issue by calling a:link and a:visited selectors together. And follow it with a:hover selector.

a:link, a:visited
{color: gray;}
{color: skyblue;}

Count all duplicates of each value

SELECT   col,
         COUNT(dupe_col) AS dupe_cnt
HAVING   COUNT(dupe_col) > 1

Class method decorator with self arguments?

I know this is an old question, but this solution has not been mentioned yet, hopefully it may help someone even today, after 8 years.

So, what about wrapping a wrapper? Let's assume one cannot change the decorator neither decorate those methods in init (they may be @property decorated or whatever). There is always a possibility to create custom, class-specific decorator that will capture self and subsequently call the original decorator, passing runtime attribute to it.

Here is a working example (f-strings require python 3.6):

import functools

# imagine this is at some different place and cannot be changed
def check_authorization(some_attr, url):
        def decorator(func):
                def wrapper(*args, **kwargs):
                        print(f"checking authorization for '{url}'...")
                        return func(*args, **kwargs)
                return wrapper
        return decorator

# another dummy function to make the example work
def do_work():
        print("work is done...")

# wrapped wrapper #
def custom_check_authorization(some_attr):
        def decorator(func):
                # assuming this will be used only on this particular class
                def wrapper(self, *args, **kwargs):
                        # get url
                        url = self.url
                        # decorate function with original decorator, pass url
                        return check_authorization(some_attr, url)(func)(self, *args, **kwargs)
                return wrapper
        return decorator
# original example, updated #
class Client(object):
        def __init__(self, url):
                self.url = url
        def get(self):

# create object
client = Client(r"")

# call decorated function


checking authorisation for ''...
work is done...

How to create enum like type in TypeScript?

TypeScript 0.9+ has a specification for enums:

enum AnimationType {

The final comma is optional.

Symfony2 and date_default_timezone_get() - It is not safe to rely on the system's timezone settings

The current accepted answer by crack is deprecated in Symfony 2.3 and will be removed by 3.0. It should be moved to the constructor:

public function __construct($environment, $debug) {
    parent::__construct($environment, $debug);

MySQL error code: 1175 during UPDATE in MySQL Workbench

No need to set SQL_SAFE_UPDATES to 0, I would really discourage it to do it that way. SAFE_UPDATES is by default on for a REASON. You can drive a car without safety belts and other things if you know what I mean ;) Just add in the WHERE clause a KEY-value that matches everything like a primary-key comparing to 0, so instead of writing:

UPDATE customers SET countryCode = 'USA'
    WHERE country = 'USA';               -- which gives the error, you just write:

UPDATE customers SET countryCode = 'USA'
    WHERE (country = 'USA' AND customerNumber <> 0); -- Because customerNumber is a primary key you got no error 1175 any more.

Now you can be assured every record is (ALWAYS) updated as you expect.

How do I use reflection to call a generic method?

With C# 4.0, reflection isn't necessary as the DLR can call it using runtime types. Since using the DLR library is kind of a pain dynamically (instead of the C# compiler generating code for you), the open source framework Dynamitey (.net standard 1.5) gives you easy cached run-time access to the same calls the compiler would generate for you.

var name = InvokeMemberName.Create;
Dynamic.InvokeMemberAction(this, name("GenericMethod", new[]{myType}));

var staticContext = InvokeContext.CreateStatic;
Dynamic.InvokeMemberAction(staticContext(typeof(Sample)), name("StaticMethod", new[]{myType}));

How do I implement basic "Long Polling"?

This is a nice 5-minute screencast on how to do long polling using PHP & jQuery:

Code is quite similar to dbr's example above.

Index of element in NumPy array

Use np.where to get the indices where a given condition is True.


For a 2D np.ndarray called a:

i, j = np.where(a == value) # when comparing arrays of integers

i, j = np.where(np.isclose(a, value)) # when comparing floating-point arrays

For a 1D array:

i, = np.where(a == value) # integers

i, = np.where(np.isclose(a, value)) # floating-point

Note that this also works for conditions like >=, <=, != and so forth...

You can also create a subclass of np.ndarray with an index() method:

class myarray(np.ndarray):
    def __new__(cls, *args, **kwargs):
        return np.array(*args, **kwargs).view(myarray)
    def index(self, value):
        return np.where(self == value)


a = myarray([1,2,3,4,4,4,5,6,4,4,4])
#(array([ 3,  4,  5,  8,  9, 10]),)

How to get the current directory in a C program?

Have you had a look at getcwd()?

#include <unistd.h>
char *getcwd(char *buf, size_t size);

Simple example:

#include <unistd.h>
#include <stdio.h>
#include <limits.h>

int main() {
   char cwd[PATH_MAX];
   if (getcwd(cwd, sizeof(cwd)) != NULL) {
       printf("Current working dir: %s\n", cwd);
   } else {
       perror("getcwd() error");
       return 1;
   return 0;

Change Tomcat Server's timeout in Eclipse

This problem can occur if you have altogether too much stuff being started when the server is started -- or if you are in debug mode and stepping through the initialization sequence. In eclipse, changing the start-timeout by 'opening' the tomcat server entry 'Servers view' tab of the Debug Perspective is convenient. In some situations it is useful to know where this setting is 'really' stored.

Tomcat reads this setting from the element in the element in the servers.xml file. This file is stored in the .metatdata/.plugins/org.eclipse.wst.server.core directory of your eclipse workspace, ie:


There are other juicy configuration files for Eclipse plugins in other directories under .metadata/.plugins as well.

Here's an example of the servers.xml file, which is what is changed when you edit the tomcat server configuration through the Eclipse GUI:

Note the 'start-timeout' property that is set to a good long 1200 seconds above.

mysql - move rows from one table to another

INSERT INTO persons_table select * from customer_table where person_name = 'tom';
DELETE FROM customer_table where person_name = 'tom';

How can I get the current network interface throughput statistics on Linux/UNIX?

iftop does for network usage what top(1) does for CPU usage --

I don't know how "standard" iftop is, but I was able to install it with yum install iftop on Fedora.

How to use OpenSSL to encrypt/decrypt files?

Note that the OpenSSL CLI uses a weak non-standard algorithm to convert the passphrase to a key, and installing GPG results in various files added to your home directory and a gpg-agent background process running. If you want maximum portability and control with existing tools, you can use PHP or Python to access the lower-level APIs and directly pass in a full AES Key and IV.

Example PHP invocation via Bash:


ENCRYPTED=$(php -r "print(openssl_encrypt('$INPUT','aes-256-ctr',base64_decode('$KEY'),OPENSSL_ZERO_PADDING,base64_decode('$IV')));")
DECRYPTED=$(php -r "print(openssl_decrypt('$ENCRYPTED','aes-256-ctr',base64_decode('$KEY'),OPENSSL_ZERO_PADDING,base64_decode('$IV')));")

This outputs:


You could also use PHP's openssl_pbkdf2 function to convert a passphrase to a key securely.

MySQL select query with multiple conditions

Lets suppose there is a table with following describe command for table (hello)- name char(100), id integer, count integer, city char(100).

we have following basic commands for MySQL -

select * from hello;
select name, city from hello;

select name from hello where id = 8;
select id from hello where name = 'GAURAV';

now lets see multiple where condition -

select name from hello where id = 3 or id = 4 or id = 8 or id = 22;

select name from hello where id =3 and count = 3 city = 'Delhi';

This is how we can use multiple where commands in MySQL.

What are the undocumented features and limitations of the Windows FINDSTR command?

When several commands are enclosed in parentheses and there are redirected files to the whole block:

< input.txt (
   . . .
) > output.txt

... then the files remains open as long as the commands in the block be active, so the commands may move the file pointer of the redirected files. Both MORE and FIND commands move the Stdin file pointer to the beginning of the file before process it, so the same file may be processed several times inside the block. For example, this code:

more < input.txt >  output.txt
more < input.txt >> output.txt

... produce the same result than this one:

< input.txt (
) > output.txt

This code:

find    "search string" < input.txt > matchedLines.txt
find /V "search string" < input.txt > unmatchedLines.txt

... produce the same result than this one:

< input.txt (
   find    "search string" > matchedLines.txt
   find /V "search string" > unmatchedLines.txt

FINDSTR is different; it does not move the Stdin file pointer from its current position. For example, this code insert a new line after a search line:

call :ProcessFile < input.txt
goto :EOF

   rem Read the next line from Stdin and copy it
   set /P line=
   echo %line%
   rem Test if it is the search line
   if "%line%" neq "search line" goto ProcessFile
rem Insert the new line at this point
echo New line
rem And copy the rest of lines
findstr "^"
exit /B

We may make good use of this feature with the aid of an auxiliary program that allow us to move the file pointer of a redirected file, as shown in this example.

This behavior was first reported by jeb at this post.

EDIT 2018-08-18: New FINDSTR bug reported

The FINDSTR command have a strange bug that happen when this command is used to show characters in color AND the output of such a command is redirected to CON device. For details on how use FINDSTR command to show text in color, see this topic.

When the output of this form of FINDSTR command is redirected to CON, something strange happens after the text is output in the desired color: all the text after it is output as "invisible" characters, although a more precise description is that the text is output as black text over black background. The original text will appear if you use COLOR command to reset the foreground and background colors of the entire screen. However, when the text is "invisible" we could execute a SET /P command, so all characters entered will not appear on the screen. This behavior may be used to enter passwords.

@echo off

set /P "=_" < NUL > "Enter password"
findstr /A:1E /V "^$" "Enter password" NUL > CON
del "Enter password"
set /P "password="
color 07
echo The password read is: "%password%"

How to exit an if clause

Here's another way to handle this. It uses a single item for loop that enables you to just use continue. It prevents the unnecessary need to have extra functions for no reason. And additionally eliminates potential infinite while loops.

if something:
    for _ in [0]:
        # Get x
        if not x:

        # Get y
        if not y:

        # Get z
        if not z:

        # Stuff that depends on x, y, and z

How to quickly test some javascript code?

Install firebug: . You can use its console to test Javascript code. Google Chrome comes with Web Inspector in which you can do the same. IE and Safari also have Web Developer tools in which you can test Javascript.

Best HTTP Authorization header type for JWT

Short answer

The Bearer authentication scheme is what you are looking for.

Long answer

Is it related to bears?

Errr... No :)

According to the Oxford Dictionaries, here's the definition of bearer:

bearer /'b??r?/

  1. A person or thing that carries or holds something.

  2. A person who presents a cheque or other order to pay money.

The first definition includes the following synonyms: messenger, agent, conveyor, emissary, carrier, provider.

And here's the definition of bearer token according to the RFC 6750:

1.2. Terminology

Bearer Token

A security token with the property that any party in possession of the token (a "bearer") can use the token in any way that any other party in possession of it can. Using a bearer token does not require a bearer to prove possession of cryptographic key material (proof-of-possession).

The Bearer authentication scheme is registered in IANA and originally defined in the RFC 6750 for the OAuth 2.0 authorization framework, but nothing stops you from using the Bearer scheme for access tokens in applications that don't use OAuth 2.0.

Stick to the standards as much as you can and don't create your own authentication schemes.

An access token must be sent in the Authorization request header using the Bearer authentication scheme:

2.1. Authorization Request Header Field

When sending the access token in the Authorization request header field defined by HTTP/1.1, the client uses the Bearer authentication scheme to transmit the access token.

For example:

GET /resource HTTP/1.1
Authorization: Bearer mF_9.B5f-4.1JqM


Clients SHOULD make authenticated requests with a bearer token using the Authorization request header field with the Bearer HTTP authorization scheme. [...]

In case of invalid or missing token, the Bearer scheme should be included in the WWW-Authenticate response header:

3. The WWW-Authenticate Response Header Field

If the protected resource request does not include authentication credentials or does not contain an access token that enables access to the protected resource, the resource server MUST include the HTTP WWW-Authenticate response header field [...].

All challenges defined by this specification MUST use the auth-scheme value Bearer. This scheme MUST be followed by one or more auth-param values. [...].

For example, in response to a protected resource request without authentication:

HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer realm="example"

And in response to a protected resource request with an authentication attempt using an expired access token:

HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer realm="example",
                         error_description="The access token expired"

How to add an element to Array and shift indexes?

Try this

public static int [] insertArry (int inputArray[], int index, int value){
    for(int i=0; i< inputArray.length-1; i++) {

        if (i == index){

            for (int j = inputArray.length-1; j >= index; j-- ){
                inputArray[j]= inputArray[j-1];


    return inputArray;

Undefined symbols for architecture arm64

None of the solutions fix this error in my case(Xcode 9), with TesseractOCRiOS. After hours of trial and error, I came up with a good solution. I just delete 'pod 'TesseractOCRiOS', '~> 4.0.0' in the Podfile, run pod install. And then, add pod 'TesseractOCRiOS', '~> 4.0.0' back to Podfile and run pod install again.

Bang! It works!

"make clean" results in "No rule to make target `clean'"

You have fallen victim to the most common of errors in Makefiles. You always need to put a Tab at the beginning of each command. You've put spaces before the $(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS) and @rm -f $(PROGRAMS) *.o core lines. If you replace them with a Tab, you'll be fine.

However, this error doesn't lead to a "No rule to make target ..." error. That probably means your issue lies beyond your Makefile. Have you checked this is the correct Makefile, as in the one you want to be specifying your commands? Try explicitly passing it as a parameter to make, make -f Makefile and let us know what happens.

Current Subversion revision command

Nobody mention for Windows world SubWCRev, which, properly used, can substitute needed data into the needed places automagically, if script call SubWCRev in form SubWCRev WC_PATH TPL-FILE READY-FILE

Sample of my post-commit hook (part of)

SubWCRev.exe CustomLocations Builder.tpl  z:\Builder.bat
call z:\Builder.bat

where my Builder.tpl is

svn.exe export trunk z:\trunk$WCDATE=%Y%m%d$-r$WCREV$

as result, I have every time bat-file with variable part - name of dir - which corresponds to the metadata of Working Copy

Could not reserve enough space for object heap

Combined with -Xmx512M use -d64 to make sure you're running 64-bit VM. On a 64-bit machine I thought for sure I was running 64-bit virtual machine, but no. After installing 64-bit Java the -d64 option works and -Xmx allows much larger memory sizes.

java -d64 -Xmx512M mypackage.Test

cd into directory without having permission

@user812954's answer was quite helpful, except I had to do this this in two steps:

sudo su
cd directory

Then, to exit out of "super user" mode, just type exit.

Bulk create model objects in django

Using create will cause one query per new item. If you want to reduce the number of INSERT queries, you'll need to use something else.

I've had some success using the Bulk Insert snippet, even though the snippet is quite old. Perhaps there are some changes required to get it working again.

Mythical man month 10 lines per developer day - how close on large projects?

Good planning, good design and good programmers. You get all that togheter and you will not spend 30 minutes to write one line. Yes, all projects require you to stop and plan,think over,discuss, test and debug but at two lines per day every company would need an army to get tetris to work...

Bottom line, if you were working for me at 2 lines per hours, you'd better be getting me a lot of coffes andmassaging my feets so you didn't get fired.

remove duplicates from sql union

If you are using T-SQL then it appears from previous posts that UNION removes duplicates. But if you are not, you could use distinct. This doesn't quite feel right to me either but it could get you the result you are looking for

select * from calls
left join users a on calls.assigned_to= a.user_id
where a.dept = 4 
select * from calls
left join users r on calls.requestor_id= r.user_id
where r.dept = 4

Determine version of Entity Framework I am using?

if you are using EF core this command below could help

dotnet ef --version

How to select lines between two marker patterns which may occur multiple times with awk/sed

I tried to use awk to print lines between two patterns while pattern2 also match pattern1. And the pattern1 line should also be printed.

e.g. source

package AAA
package BBB
package CCC
package DDD

should has an ouput of

package BBB

Where pattern1 is package BBB, pattern2 is package \w*. Note that CCC isn't a known value so can't be literally matched.

In this case, neither @scai 's awk '/abc/{a=1}/mno/{print;a=0}a' file nor @fedorqui 's awk '/abc/{a=1} a; /mno/{a=0}' file works for me.

Finally, I managed to solve it by awk '/package BBB/{flag=1;print;next}/package \w*/{flag=0}flag' file, haha

A little more effort result in awk '/package BBB/{flag=1;print;next}flag;/package \w*/{flag=0}' file, to print pattern2 line also, that is,

package BBB
package CCC

Pointers in JavaScript?

You refer to 'x' from window object

var x = 0;

function a(key, ref) {
    ref = ref || window;  // object reference - default window

a('x');                   // string

Django: save() vs update() to update the database?

There are several key differences.

update is used on a queryset, so it is possible to update multiple objects at once.

As @FallenAngel pointed out, there are differences in how custom save() method triggers, but it is also important to keep in mind signals and ModelManagers. I have build a small testing app to show some valuable differencies. I am using Python 2.7.5, Django==1.7.7 and SQLite, note that the final SQLs may vary on different versions of Django and different database engines.

Ok, here's the example code.

from __future__ import print_function
from django.db import models
from django.db.models import signals
from django.db.models.signals import pre_save, post_save
from django.dispatch import receiver

__author__ = 'sobolevn'

class CustomManager(models.Manager):
    def get_queryset(self):
        super_query = super(models.Manager, self).get_queryset()
        print('Manager is called', super_query)
        return super_query

class ExtraObject(models.Model):
    name = models.CharField(max_length=30)

    def __unicode__(self):

class TestModel(models.Model):

    name = models.CharField(max_length=30)
    key = models.ForeignKey('ExtraObject')
    many = models.ManyToManyField('ExtraObject', related_name='extras')

    objects = CustomManager()

    def save(self, *args, **kwargs):
        print('save() is called.')
        super(TestModel, self).save(*args, **kwargs)

    def __unicode__(self):
        # Never do such things (access by foreing key) in real life,
        # because it hits the database.
        return u'{} {} {}'.format(,, self.many.count())

@receiver(pre_save, sender=TestModel)
@receiver(post_save, sender=TestModel)
def reicever(*args, **kwargs):
    print('signal dispatched')

def index(request):
    if request and request.method == 'GET':

        from models import ExtraObject, TestModel

        # Create exmple data if table is empty:
        if TestModel.objects.count() == 0:
            for i in range(15):
                extra = ExtraObject.objects.create(name=str(i))
                test = TestModel.objects.create(key=extra, name='test_%d' % i)
                print test

        to_edit = TestModel.objects.get(id=1) = 'edited_test'
        to_edit.key = ExtraObject.objects.create(name='new_for')

        new_key = ExtraObject.objects.create(name='new_for_update')
        to_update = TestModel.objects.filter(id=2).update(name='updated_name', key=new_key)
        # return any kind of HttpResponse

That resuled in these SQL queries:

# to_edit = TestModel.objects.get(id=1):
QUERY = u'SELECT "main_testmodel"."id", "main_testmodel"."name", "main_testmodel"."key_id" 
FROM "main_testmodel" 
WHERE "main_testmodel"."id" = %s LIMIT 21' 
- PARAMS = (u'1',)

QUERY = u'UPDATE "main_testmodel" SET "name" = %s, "key_id" = %s 
WHERE "main_testmodel"."id" = %s' 
- PARAMS = (u"'edited_test'", u'2', u'1')

# to_update = TestModel.objects.filter(id=2).update(name='updated_name', key=new_key):
QUERY = u'UPDATE "main_testmodel" SET "name" = %s, "key_id" = %s 
WHERE "main_testmodel"."id" = %s' 
- PARAMS = (u"'updated_name'", u'3', u'2')

We have just one query for update() and two for save().

Next, lets talk about overriding save() method. It is called only once for save() method obviously. It is worth mentioning, that .objects.create() also calls save() method.

But update() does not call save() on models. And if no save() method is called for update(), so the signals are not triggered either. Output:

Starting development server at
Quit the server with CONTROL-C.

# TestModel.objects.get(id=1):
Manager is called [<TestModel: edited_test new_for 0>]
Manager is called [<TestModel: edited_test new_for 0>]
save() is called.
signal dispatched
signal dispatched

# to_update = TestModel.objects.filter(id=2).update(name='updated_name', key=new_key):
Manager is called [<TestModel: edited_test new_for 0>]

As you can see save() triggers Manager's get_queryset() twice. When update() only once.

Resolution. If you need to "silently" update your values, without save() been called - use update. Usecases: last_seen user's field. When you need to update your model properly use save().

Find a file with a certain extension in folder

Use this code for read file with all type of extension file.

string[] sDirectoryInfo = Directory.GetFiles(SourcePath, "*.*");

How to pass in password to pg_dump?

You can pass a password into pg_dump directly by using the following:

pg_dump "host=localhost port=5432 dbname=mydb user=myuser password=mypass" > mydb_export.sql

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

Two things:

  1. Only need one (1) equals sign to evaluate
  2. You need to specify a length on the VARCHAR - the default is a single character.


    SET @temp = 'm'

IF @temp = 'm'
  SELECT 'yes'
  SELECT 'no'

VARCHAR(10) means the VARCHAR will accommodate up to 10 characters. More examples of the behavior -

    SET @temp = 'm'

IF @temp = 'm'
  SELECT 'yes'
  SELECT 'no'

...will return "yes"

    SET @temp = 'mtest'

IF @temp = 'm'
  SELECT 'yes'
  SELECT 'no'

...will return "no".

Is it possible to change the content HTML5 alert messages?


<input required title="Enter something OR ELSE." /> 

The title attribute will be used to notify the user of a problem.

How to set the title text color of UIButton?

Example in setting button title color

btnDone.setTitleColor(.black, for: .normal)

HTTP could not register URL http://+:8000/HelloWCF/. Your process does not have access rights to this namespace

Unfortunately the link in the exception text,, is broken. However, it used to lead to which explains how to set the permissions.

It basically informs you to use the following command:

netsh http add urlacl url=http://+:80/MyUri user=DOMAIN\user

You can get more help on the details using the help of netsh

For example: netsh http add ?

Gives help on the http add command.


I think that parse_str is what you're looking for, something like this should do the trick for you:

parse_str($_SERVER['QUERY_STRING'], $vars);

Then the $vars array will hold all the passed arguments.

MySQL SELECT only not null values

Following query working for me

when i have set default value of column 'NULL' then

select * from table where column IS NOT NULL

and when i have set default value nothing then

select * from table where column <>''

How do I move a table into a schema in T-SQL

ALTER SCHEMA TargetSchema 
    TRANSFER SourceSchema.TableName;

If you want to move all tables into a new schema, you can use the undocumented (and to be deprecated at some point, but unlikely!) sp_MSforeachtable stored procedure:

exec sp_MSforeachtable "ALTER SCHEMA TargetSchema TRANSFER ?"


SQL 2008: How do I change db schema to dbo

HTML not loading CSS file

Your css file should be defined as UTF-8. Put this in the first line of you css file.

@charset "UTF-8";

How to uninstall downloaded Xcode simulator?

Run this command in terminal to remove simulators that can't be accessed from the current version of Xcode in use.

xcrun simctl delete unavailable

Also if you're looking to reclaim simulator related space Michael Tsai found that deleting sim logs saved him 30 GB.


Create Map in Java

There is even a better way to create a Map along with initialization:

Map<String, String> rightHereMap = new HashMap<String, String>()
        put("key1", "value1");
        put("key2", "value2");

For more options take a look here How can I initialise a static Map?

Node.js – events js 72 throw er unhandled 'error' event

I had the same problem. I closed terminal and restarted node. This worked for me.

What, exactly, is needed for "margin: 0 auto;" to work?

It will also work with display:table - a useful display property in this case because it doesn't require a width to be set. (I know this post is 5 years old, but it's still relevant to passers-by ;)

Regular Expressions and negating a whole character group

Simplest way is to pull the negation out of the regular expression entirely:

if (!userName.matches("^([Ss]ys)?admin$")) { ... }

deleting folder from java

I found this piece of code more understadable and working:

public static boolean deleteDir(File dir) {
    if (dir.isDirectory()) {
        String[] children = dir.list();
        for (int i = 0; i < children.length; i++) {
            boolean success = deleteDir(new File(dir, children[i]));
            if (!success) {
                return false;

    return dir.delete(); // The directory is empty now and can be deleted.

perform an action on checkbox checked or unchecked event on html form

If you debug your code using developer tools, you will notice that this refers to the window object and not the input control. Consider using the passed in id to retrieve the input and check for checked value.

function doalert(id){
  if(document.getElementById(id).checked) {

Check if a value exists in ArrayList

Just use .contains. For example, if you were checking if an ArrayList arr contains a value val, you would simply run arr.contains(val), which would return a boolean representing if the value is contained. For more information, see the docs for .contains.

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '''')' at line 2

I was getting the same error when I used this code to update the record:

@mysqli_query($dbc,$query or die()))

After removing or die, it started working properly.

How to ignore conflicts in rpm installs

From the context, the conflict was caused by the version of the package.
Let's take a look the manual about rpm:

    Same as using --replacepkgs, --replacefiles, and --oldpackage.

    Allow an upgrade to replace a newer package with an older one.

So, you can execute the command rpm -Uvh info-4.13a-2.rpm --force to solve your issue.

Fast query runs slow in SSRS

Add this to the end of your proc: option(recompile)

This will make the report run almost as fast as the stored procedure

How to print matched regex pattern using awk?

Off topic, this can be done using the grep also, just posting it here in case if anyone is looking for grep solution

echo 'xxx yyy zzze ' | grep -oE 'yyy'

javascript: calculate x% of a number

Best thing is to memorize balance equation in natural way.

Amount / Whole = Percentage / 100

usually You have one variable missing, in this case it is Amount

Amount / 10000 = 35.8 / 100

then you have high school math (proportion) to multiple outer from both sides and inner from both sides.

Amount * 100 = 358 000

Amount = 3580

It works the same in all languages and on paper. JavaScript is no exception.

How to create range in Swift?

I want to do this:

// out: Error

But unfortunately, I can't write a subscript of my own because the loathed one takes up the name space.

We can do this however:

print("Hello"[range: 1...3])
// out: ell 

Just add this to your project:

extension String {
    subscript(range: ClosedRange<Int>) -> String {
        get {
            let start = String.Index(utf16Offset: range.lowerBound, in: self)
            let end = String.Index(utf16Offset: range.upperBound, in: self)
            return String(self[start...end])

How can I maintain fragment state when added to the back stack?

I would suggest a very simple solution.

Take the View reference variable and set view in OnCreateView. Check if view already exists in this variable, then return same view.

   private View fragmentView;

   public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);

        if (fragmentView != null) {
            return fragmentView;
        View view = inflater.inflate(R.layout.yourfragment, container, false);
        fragmentView = view;
        return view;

MySQL: update a field only if condition is met

found the solution with AND condition:

  $trainstrength = "UPDATE user_character SET strength_trains = strength_trains + 1, trained_strength = trained_strength +1, character_gold = character_gold - $gold_to_next_strength WHERE ID = $currentUser AND character_gold > $gold_to_next_strength";

Missing .map resource?

I had similar expirience like yours. I have Denwer server. When I loaded my local site without using via script src jquery.min.js file at index.php in Chrome I got error 500 in console. I resolved this problem simply - I disabled extension Wunderlist in Chrome and voila - I never see this error more. Although, No, I found this error again - when Wunderlist have been on again. So, check your extensions and try to disable all of them or some of them or one by one. Good luck!

org.glassfish.jersey.servlet.ServletContainer ClassNotFoundException

I had the same problem with eclipse, the WA solution was to copy the libs to WEB-INF/lib

How to determine the Boost version on a system?

Include #include <boost/version.hpp>

std::cout << "Using Boost "     
          << BOOST_VERSION / 100000     << "."  // major version
          << BOOST_VERSION / 100 % 1000 << "."  // minor version
          << BOOST_VERSION % 100                // patch level
          << std::endl;

Possible output: Using Boost 1.75.0

Tested with Boost 1.51.0 to 1.63, 1.71.0 and 1.75.0:

How to my "exe" from PyCharm project

You cannot directly save a Python file as an exe and expect it to work -- the computer cannot automatically understand whatever code you happened to type in a text file. Instead, you need to use another program to transform your Python code into an exe.

I recommend using a program like Pyinstaller. It essentially takes the Python interpreter and bundles it with your script to turn it into a standalone exe that can be run on arbitrary computers that don't have Python installed (typically Windows computers, since Linux tends to come pre-installed with Python).

To install it, you can either download it from the linked website or use the command:

pip install pyinstaller

...from the command line. Then, for the most part, you simply navigate to the folder containing your source code via the command line and run:


You can find more information about how to use Pyinstaller and customize the build process via the documentation.

You don't necessarily have to use Pyinstaller, though. Here's a comparison of different programs that can be used to turn your Python code into an executable.

127 Return code from $?

If you're trying to run a program using a scripting language, you may need to include the full path of the scripting language and the file to execute. For example:

exec('/usr/local/bin/node /usr/local/lib/node_modules/uglifycss/uglifycss in.css > out.css');

How to modify a specified commit?

If for some reason you don't like interactive editors, you can use git rebase --onto.

Say you want to modify Commit1. First, branch from before Commit1:

git checkout -b amending [commit before Commit1]

Second, grab Commit1 with cherry-pick:

git cherry-pick Commit1

Now, amend your changes, creating Commit1':

git add ...
git commit --amend -m "new message for Commit1"

And finally, after having stashed any other changes, transplant the rest of your commits up to master on top of your new commit:

git rebase --onto amending Commit1 master

Read: "rebase, onto the branch amending, all commits between Commit1 (non-inclusive) and master (inclusive)". That is, Commit2 and Commit3, cutting the old Commit1 out entirely. You could just cherry-pick them, but this way is easier.

Remember to clean up your branches!

git branch -d amending

jQuery-UI datepicker default date

You can try with the code that is below.

It will make the default date become the date you are looking for.

$('#birthdate').datepicker("setDate", new Date(1985,01,01) );

What is the difference between active and passive FTP?

I recently run into this question in my work place so I think I should say something more here. I will use image to explain how the FTP works as an additional source for previous answer.

Active mode:

active mode

Passive mode:

enter image description here

In an active mode configuration, the server will attempt to connect to a random client-side port. So chances are, that port wouldn't be one of those predefined ports. As a result, an attempt to connect to it will be blocked by the firewall and no connection will be established.

enter image description here

A passive configuration will not have this problem since the client will be the one initiating the connection. Of course, it's possible for the server side to have a firewall too. However, since the server is expected to receive a greater number of connection requests compared to a client, then it would be but logical for the server admin to adapt to the situation and open up a selection of ports to satisfy passive mode configurations.

So it would be best for you to configure server to support passive mode FTP. However, passive mode would make your system vulnerable to attacks because clients are supposed to connect to random server ports. Thus, to support this mode, not only should your server have to have multiple ports available, your firewall should also allow connections to all those ports to pass through!

To mitigate the risks, a good solution would be to specify a range of ports on your server and then to allow only that range of ports on your firewall.

For more information, please read the official document.

Get client IP address via third party web service

        url: '//',
        type: 'POST',
        dataType: 'jsonp',
        success: function(location) {

This will work https too

How to do a background for a label will be without color?

this.label1.BackColor = System.Drawing.Color.Transparent;

Does WGET timeout?

Prior to version 1.14, wget timeout arguments were not adhered to if downloading over https due to a bug.

Turn off textarea resizing

this will do your job


enter image description here

Delete a row from a SQL Server table

As you have stated that all column names are of TEXT type, So, there is need to use IDNumber as Text by using single quote around IDNumber.....

    public static void deleteRow(string table, string columnName, string IDNumber)
    using (SqlConnection con = new SqlConnection(Global.connectionString))
         using (SqlCommand command = new SqlCommand("DELETE FROM " + table + " WHERE " + columnName + " = '" + IDNumber+"'", con))
    catch (SystemException ex)
       MessageBox.Show(string.Format("An error occurred: {0}", ex.Message));

How to position the Button exactly in CSS

Try using absolute positioning, rather than relative positioning

this should get you close - you can adjust by tweaking margins or top/left positions

#play_button {
    transition: .5s ease;
    top: 50%;
    left: 50%;

jquery: get elements by class name and add css to each of them

You can try this

 $('div.easy_editor').css({'border-width':'9px', 'border-style':'solid', 'border-color':'red'});

The $('div.easy_editor') refers to a collection of all divs that have the class easy editor already. There is no need to use each() unless there was some function that you wanted to run on each. The css() method actually applies to all the divs you find.

How to convert hex string to Java string?

First of all read in the data, then convert it to byte array:

 byte b = Byte.parseByte(str, 16); 

and then use String constructor:

new String(byte[] bytes) 

or if the charset is not system default then:

new String(byte[] bytes, String charsetName) 

C# Debug - cannot start debugging because the debug target is missing

I had the same problems. I had to change file rights. Unmark "read only" in their properties.

How to cancel a local git commit

The first thing you should do is to determine whether you want to keep the local changes before you delete the commit message.

Use git log to show current commit messages, then find the commit_id before the commit that you want to delete, not the commit you want to delete.

If you want to keep the locally changed files, and just delete commit message:

git reset --soft commit_id

If you want to delete all locally changed files and the commit message:

git reset --hard commit_id

That's the difference of soft and hard

Get each line from textarea

Use PHP DOM to parse and add <br/> in it. Like this:

$html = '<textarea> put returns between paragraphs
for linebreak add 2 spaces at end
indent code by 4 spaces
quote by placing > at start of line

//parsing begins here:
$doc = new DOMDocument();
$nodes = $doc->getElementsByTagName('textarea');

//get text and add <br/> then remove last <br/>
$lines = $nodes->item(0)->nodeValue;

//split it by newlines
$lines = explode("\n", $lines);

//add <br/> at end of each line
foreach($lines as $line)
    $output .= $line . "<br/>";

//remove last <br/>
$output = rtrim($output, "<br/>");

//display it

This outputs:

string ' put returns between paragraphs
<br/>for linebreak add 2 spaces at end
<br/>indent code by 4 spaces
<br/>quote by placing > at start of line
' (length=141)

Convert list to tuple in Python

You might have done something like this:

>>> tuple = 45, 34  # You used `tuple` as a variable here
>>> tuple
(45, 34)
>>> l = [4, 5, 6]
>>> tuple(l)   # Will try to invoke the variable `tuple` rather than tuple type.

Traceback (most recent call last):
  File "<pyshell#10>", line 1, in <module>
TypeError: 'tuple' object is not callable
>>> del tuple  # You can delete the object tuple created earlier to make it work
>>> tuple(l)
(4, 5, 6)

Here's the problem... Since you have used a tuple variable to hold a tuple (45, 34) earlier... So, now tuple is an object of type tuple now...

It is no more a type and hence, it is no more Callable.

Never use any built-in types as your variable name... You do have any other name to use. Use any arbitrary name for your variable instead...