Programs & Examples On #Compose

Setting default checkbox value in Objective-C?

Documentation on UISwitch says:

[mySwitch setOn:NO]; 

In Interface Builder, select your switch and in the Attributes inspector you'll find State which can be set to on or off.

Axios Delete request with body and headers?

For Delete, you will need to do as per the following

axios.delete("/<your endpoint>", { data:<"payload object">})

It worked for me.

E: gnupg, gnupg2 and gnupg1 do not seem to be installed, but one of them is required for this operation

I faced the same issue:

E: gnupg, gnupg2 and gnupg1 do not seem to be installed, but one of them is required for this operation

I resolved by using the following commands:

apt-get update
apt-get install gnupg

How to upgrade docker-compose to latest version

Based on @eric-johnson's answer, I'm currently using this in a script:

compose_version=$(curl | jq .name -r)
curl -L$compose_version/docker-compose-$(uname -s)-$(uname -m) -o $output
chmod +x $output
echo $(docker-compose --version)

it grabs the latest version from the GitHub api.

How to fix docker: Got permission denied issue

You can always try Manage Docker as a non-root user paragraph in the docs.

After doing this also if the problem persists then you can run the following command to solve it:

sudo chmod 666 /var/run/docker.sock

How to change PHP version used by composer

You can change php version of composer without uninstalling it, follow these steps :

  1. Search for system environment variables in cortana.
  2. Click on the button "Environment variables".
  3. Under "System variables" select path and click on edit, you will see one entry like this "C:\wamp\bin\php\php5.6.13".
  4. Just change this to the folder name of the php located at your wamp/bin/php7.1.9, here php7.1.9 is folder name.
  5. Replace php5.6.13 with bin7.1.9, it will look like these "C:\wamp\bin\php\php7.1.9", just click ok on all the boxes.
  6. You are done.
  7. To verify, first close all the cmd windows, than open cmd and type php -v, press enter and you should see php7.1.9.
  8. If you don't see change in php version than just restart your pc and run php -v again in cmd , it will work.

Script @php artisan package:discover handling the post-autoload-dump event returned with error code 1

You have added the service provider in config/app.php for the package that is not installed in the system.

You must have this line in your config/app.php. You can either remove it or install the package GeneaLabs\LaravelCaffeine\LaravelCaffeineServiceProvider


Run the line below via CLI to install the package.

 composer require genealabs/laravel-caffeine

Can't install laravel installer via composer

For PHP7.1 install this

sudo apt-get install php7.1-zip

Docker: How to delete all local Docker images

You can try like this:

docker system prune

Do I commit the package-lock.json file created by npm 5?

To the people complaining about the noise when doing git diff:

git diff -- . ':(exclude)*package-lock.json' -- . ':(exclude)*yarn.lock'

What I did was use an alias:

alias gd="git diff --ignore-all-space --ignore-space-at-eol --ignore-space-change --ignore-blank-lines -- . ':(exclude)*package-lock.json' -- . ':(exclude)*yarn.lock'"

To ignore package-lock.json in diffs for the entire repository (everyone using it), you can add this to .gitattributes:

package-lock.json binary
yarn.lock binary

This will result in diffs that show "Binary files a/package-lock.json and b/package-lock.json differ whenever the package lock file was changed. Additionally, some Git services (notably GitLab, but not GitHub) will also exclude these files (no more 10k lines changed!) from the diffs when viewing online when doing this.

Cannot connect to the Docker daemon on macOS

This problem:

$ brew install docker docker-machine
$ docker ps

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

This apparently meant do the following:

$ docker-machine create default # default driver is apparently vbox:
Running pre-create checks...
Error with pre-create check: "VBoxManage not found. Make sure VirtualBox is installed and VBoxManage is in the path"
$  brew cask install virtualbox
$ docker-machine create default 
# works this time
$ docker ps
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
$ eval "$(docker-machine env default)"
$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

It finally works.

You can use the “xhyve” driver if you don’t want to install virtual box. Also you can install the “docker app” (then run it) which apparently makes it so you don’t have to run some of the above. brew cask install docker then run the app, see the other answers. But apparently isn't necessary per se.

Import data.sql MySQL Docker Container

Another option if you don't wanna mount a volume, but wanna dump a file from your local machine, is to pipe cat yourdump.sql. Like so:

cat dump.sql | docker exec -i mysql-container mysql -uuser -ppassword db_name


Docker "ERROR: could not find an available, non-overlapping IPv4 address pool among the defaults to assign to the network"

I fixed this issue by steps :

  1. turn off your network (wireless or wired...).

  2. reboot your system.

  3. before turning on your network on PC, execute command docker-compose up, it's going to create new network.

  4. then you can turn network on and go on ...

How to run docker-compose up -d at system start up?

If your docker.service enabled on system startup

$ sudo systemctl enable docker

and your services in your docker-compose.yml has

restart: always

all of the services run when you reboot your system if you run below command only once

docker-compose up -d

PHP7 : install ext-dom issue

I faced this exact same issue with Laravel 8.x on Ubuntu 20. I run: sudo apt install php7.4-xml and composer update within the project directory. This fixed the issue.

How to create a DB for MongoDB container on start up?

The official mongo image has merged a PR to include the functionality to databases and admin users at startup.

The database initialisation will run scripts in /docker-entrypoint-initdb.d/ when there is nothing populated in the /data/db directory.

Database Initialisation

The mongo container image provides the /docker-entrypoint-initdb.d/ path to deploy custom .js or .sh setup scripts that will be run once on database initialisation. .js scripts will be run against test by default or MONGO_INITDB_DATABASE if defined in the environment.

COPY /docker-entrypoint-initdb.d/


COPY mysetup.js /docker-entrypoint-initdb.d/

A simple initialisation mongo shell javascript file that demonstrates setting up the container collection with data, logging and how to exit with an error (for result checking).

let error = true

let res = [
  db.container.createIndex({ myfield: 1 }, { unique: true }),
  db.container.createIndex({ thatfield: 1 }),
  db.container.createIndex({ thatfield: 1 }),
  db.container.insert({ myfield: 'hello', thatfield: 'testing' }),
  db.container.insert({ myfield: 'hello2', thatfield: 'testing' }),
  db.container.insert({ myfield: 'hello3', thatfield: 'testing' }),
  db.container.insert({ myfield: 'hello3', thatfield: 'testing' })


if (error) {
  print('Error, exiting')

Admin User Setup

The environment variables to control "root" user setup are



docker run -d \

or Dockerfile


You don't need to use --auth on the command line as the docker script adds this in when it detects the environment variables exist.

How to use local docker images with Minikube?

There is one essay and effective way to push your local Docker image directly to minikube, which will save time from building the images in minikube again.

minikube cache add <Image name>

More details here

All possible method to push images to minikube are mention here:

How to specify Memory & CPU limit in docker compose version 3

      cpus: '0.001'
      memory: 50M
      cpus: '0.0001'
      memory: 20M


In you specific case:

version: "3"
    image: USER/Your-Pre-Built-Image
      - VIRTUAL_HOST=localhost
      - logs:/app/out/
    command: ["npm","start"]
      - NET_ADMIN
      - SYS_ADMIN
          cpus: '0.001'
          memory: 50M
          cpus: '0.0001'
          memory: 20M

  - logs

    driver: overlay


  • Expose is not necessary, it will be exposed per default on your stack network.
  • Images have to be pre-built. Build within v3 is not possible
  • "Restart" is also deprecated. You can use restart under deploy with on-failure action
  • You can use a standalone one node "swarm", v3 most improvements (if not all) are for swarm

Also Note: Networks in Swarm mode do not bridge. If you would like to connect internally only, you have to attach to the network. You can 1) specify an external network within an other compose file, or have to create the network with --attachable parameter (docker network create -d overlay My-Network --attachable) Otherwise you have to publish the port like this:

  - 80:80

How to mount a single file in a volume

I have same issue on my Windows 8.1

It turned out that it was due to case-sensitivity of path. I called docker-compose up from directory cd /c/users/alex/ and inside container a file was turned into directory.

But when I did cd /c/Users/alex/ (not Users capitalized) and called docker-compose up from there, it worked.

In my system both Users dir and Alex dir are capitalized, though it seems like only Users dir matter.

ARG or ENV, which one to use in this case?

So if want to set the value of an environment variable to something different for every build then we can pass these values during build time and we don't need to change our docker file every time.

While ENV, once set cannot be overwritten through command line values. So, if we want to have our environment variable to have different values for different builds then we could use ARG and set default values in our docker file. And when we want to overwrite these values then we can do so using --build-args at every build without changing our docker file.

For more details, you can refer this.

How to persist data in a dockerized postgres database using volumes

Strangely enough, the solution ended up being to change

  - ./postgres-data:/var/lib/postgresql


  - ./postgres-data:/var/lib/postgresql/data

Pandas Split Dataframe into two Dataframes at a specific row


df1 = datasX.iloc[:, :72]
df2 = datasX.iloc[:, 72:]

(iloc docs)

PHP error: "The zip extension and unzip command are both missing, skipping."

PHP-ZIP needs some dependancies or library missing, depends on the image from Dockerfile you need to install them first

RUN set -eux \
   && apt-get update \
   && apt-get install -y libzip-dev zlib1g-dev \
   && docker-php-ext-install zip

Composer: file_put_contents(./composer.json): failed to open stream: Permission denied

To resolve this, you should open up a terminal window and type this command:

sudo chown -R user ~/.composer (with user being your current user, in your case, kramer65)

After you have ran this command, you should have permission to run your composer global require command.

You may also need to remove the .composer file from the current directory, to do this open up a terminal window and type this command:

sudo rm -rf .composer

require(vendor/autoload.php): failed to open stream

If you get the error also when you run

composer install

Just run this command first

composer dump-autoload

This command will clean up all compiled files and their paths.

How to install a specific version of package using Composer?

just use php composer.phar require

For example :

php composer.phar require doctrine/mongodb-odm-bundle 3.0

Also available with install.

How do I mount a host directory as a volume in docker compose

It was two things:

I added the volume in docker-compose.yml:

    - ./node:/app

I moved the npm install && nodemon app.js pieces into a CMD because RUN adds things to the Union File System, and my volume isn't part of UFS.

# Set the base image to Ubuntu
FROM    node:boron

# File Author / Maintainer
MAINTAINER Amin Shah Gilani <[email protected]>

# Install nodemon
RUN npm install -g nodemon

# Add a /app volume
VOLUME ["/app"]

# Define working directory

# Expose port
EXPOSE  8080

# Run npm install
CMD npm install && nodemon app.js

What is the difference between docker-compose ports vs expose


The ports section will publish ports on the host. Docker will setup a forward for a specific port from the host network into the container. By default this is implemented with a userspace proxy process (docker-proxy) that listens on the first port, and forwards into the container, which needs to listen on the second point. If the container is not listening on the destination port, you will still see something listening on the host, but get a connection refused if you try to connect to that host port, from the failed forward into your container.

Note, the container must be listening on all network interfaces since this proxy is not running within the container's network namespace and cannot reach inside the container. The IPv4 method for that is to configure your application to listen on

Also note that published ports do not work in the opposite direction. You cannot connect to a service on the host from the container by publishing a port. Instead you'll find docker errors trying to listen to the already-in-use host port.


Expose is documentation. It sets metadata on the image, and when running, on the container too. Typically you configure this in the Dockerfile with the EXPOSE instruction, and it serves as documentation for the users running your image, for them to know on which ports by default your application will be listening. When configured with a compose file, this metadata is only set on the container. You can see the exposed ports when you run a docker inspect on the image or container.

There are a few tools that rely on exposed ports. In docker, the -P flag will publish all exposed ports onto ephemeral ports on the host. There are also various reverse proxies that will default to using an exposed port when sending traffic to your application if you do not explicitly set the container port.

Other than those external tools, expose has no impact at all on the networking between containers. You only need a common docker network, and connecting to the container port, to access one container from another. If that network is user created (e.g. not the default bridge network named bridge), you can use DNS to connect to the other containers.

Brew install docker does not include docker engine?

Please try running

brew install docker

This will install the Docker engine, which will require Docker-Machine (+ VirtualBox) to run on the Mac.

If you want to install the newer Docker for Mac, which does not require virtualbox, you can install that through Homebrew's Cask:

brew install --cask docker 
open /Applications/

Docker for Windows error: "Hardware assisted virtualization and data execution protection must be enabled in the BIOS"

I have tried many suggestions above but docker keeps complaining about hardware assisted virtualization error. Virtualization is enabled in BIOS, and also Hyper-V is installed and enabled. After a few try and errors, I eventually downloaded coreinfo tool and found out that Hypervisor was not actually enabled. Using ISE (64 bit) as admin and run command from above Solution B and that enables Hypervisor successfully (checked via coreinfo -v again). After restart, docker is now running successfully.

Provide static IP to docker containers via docker-compose

Note that I don't recommend a fixed IP for containers in Docker unless you're doing something that allows routing from outside to the inside of your container network (e.g. macvlan). DNS is already there for service discovery inside of the container network and supports container scaling. And outside the container network, you should use exposed ports on the host. With that disclaimer, here's the compose file you want:

version: '2'

    container_name: mysql
    image: mysql:latest
    restart: always
     - "3306:3306"

    container_name: apigw-tomcat
    build: tomcat/.
     - "8080:8080"
     - "8009:8009"
     - mysql

    driver: bridge
       - subnet:

Extension gd is missing from your system - laravel composer Update

if you are working in PHP version 7.2 then you have to install

sudo apt-get install php7.2-gd

Copying files to a container with Docker Compose


      - /dir/on/host:/var/www/html

if /dir/on/host doesn't exist, it is created on the host and the empty content is mounted in the container at /var/www/html. Whatever content you had before in /var/www/html inside the container is inaccessible, until you unmount the volume; the new mount is hiding the old content.

Docker-Compose persistent data MySQL

Actually this is the path and you should mention a valid path for this to work. If your data directory is in current directory then instead of my-data you should mention ./my-data, otherwise it will give you that error in mysql and mariadb also.


sudo: docker-compose: command not found

If you have tried installing via the official docker-compose page, where you need to download the binary using curl:

curl -L`uname -s`-`uname -m` > /usr/local/bin/docker-compose

Then do not forget to add executable flag to the binary:

chmod +x /usr/local/bin/docker-compose

If docker-compose is installed using python-pip

sudo apt-get -y install python-pip
sudo pip install docker-compose

try using pip show --files docker-compose to see where it is installed.

If docker-compose is installed in user path, then try:

sudo "PATH=$PATH" docker-compose

As I see from your updated post, docker-compose is installed in user path /home/user/.local/bin and if this path is not in your local path $PATH, then try:

sudo "PATH=$PATH:/home/user/.local/bin" docker-compose

"Please provide a valid cache path" error in laravel

I solved this problem by adding this line in my index.php:

$app['config']['view.compiled'] = "storage/framework/cache";

Communication between multiple docker-compose projects

UPDATE: As of compose file version 3.5:

This now works:

version: "3.5"
    image: hello-world
      - "80:80"
      - proxynet

    name: custom_network

docker-compose up -d will join a network called 'custom_network'. If it doesn't exist, it will be created!

root@ubuntu-s-1vcpu-1gb-tor1-01:~# docker-compose up -d
Creating network "custom_network" with the default driver
Creating root_proxy_1 ... done

Now, you can do this:

version: "2"
    image: hello-world
      - my-proxy-net
      name: custom_network

This will create a container that will be on the external network.

I can't find any reference in the docs yet but it works!

Docker Error bind: address already in use

In my case it was

Error starting userland proxy: listen tcp bind: address already in use

And all that I need is turn off debug listening in php storm icon

how to get docker-compose to use the latest image from repository

Since 2020-05-07, the docker-compose spec also defines the "pull_policy" property for a service:

version: '3.7'

    image: someimage/somewhere
    pull_policy: always

The docker-compose spec says:

pull_policy defines the decisions Compose implementations will make when it starts to pull images.

Possible values are (tl;dr, check spec for more details):

  • always: always pull
  • never: don't pull (breaks if the image can not be found)
  • missing: pulls if the image is not cached
  • build: always build or rebuild

How to pass arguments to entrypoint in docker-compose.yml

You can use docker-compose run instead of docker-compose up and tack the arguments on the end. For example:

docker-compose run dperson/samba arg1 arg2 arg3

If you need to connect to other docker containers, use can use --service-ports option:

docker-compose run --service-ports dperson/samba arg1 arg2 arg3

How to view log output using docker-compose run?

If you want to see output logs from all the services in your terminal.

docker-compose logs -t -f --tail <no of lines> 

Eg.: Say you would like to log output of last 5 lines from all service

docker-compose logs -t -f --tail 5

If you wish to log output from specific services then it can be done as below:

docker-compose logs -t -f --tail <no of lines> <name-of-service1> <name-of-service2> ... <name-of-service N>


Eg. say you have API and portal services then you can do something like below :

docker-compose logs -t -f --tail 5 portal api

Where 5 represents last 5 lines from both logs.


Docker-Compose with multiple services

The thing is that you are using the option -t when running your container.

Could you check if enabling the tty option (see reference) in your docker-compose.yml file the container keeps running?

version: '2'
        build: .
        container_name: ubuntu
            - ~/sph/laravel52:/www/laravel
          - "80:80"
        tty: true

How to pass boolean parameter value in pipeline to downstream jobs?

Things are much easier nowadays: the builtin Snippet Generator supports the 'build' step (I don't know since when though).

getting error while updating Composer

A lot of good answers already for Ubuntu. I'm on Linux and had the same problem but none of the commands above worked for me.

With Linux and php70 I used the following command which worked great:

sudo yum install php70-mbstring -y

How to rebuild docker container in docker-compose.yml?

Simply use :

docker-compose build [yml_service_name]

Replace [yml_service_name] with your service name in docker-compose.yml file. You can use docker-compose restart to make sure changes are effected. You can use --no-cache to ignore the cache.

Docker is installed but Docker Compose is not ? why?

On Linux, you can download the Docker Compose binary from the Compose repository release page on GitHub. Follow the instructions from the link, which involve running the curl command in your terminal to download the binaries. These step-by-step instructions are also included below.

1:Run this command to download the current stable release of Docker Compose:

sudo curl -L "$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

To install a different version of Compose, substitute 1.26.2 with the version of Compose you want to use.

2:Apply executable permissions to the binary:

sudo chmod +x /usr/local/bin/docker-compose

Note: If the command docker-compose fails after installation, check your path. You can also create a symbolic link to /usr/bin or any other directory in your path.

Interactive shell using Docker Compose

This question is very interesting for me because I have problems, when I run container after execution finishes immediately exit and I fixed with -it:

docker run -it -p 3000:3000 -v /app/node_modules -v $(pwd):/app <your_container_id>

And when I must automate it with docker compose:

version: '3'
        stdin_open: true
        tty: true
            context: .
            - "3000:3000"
            - /app/node_modules
            - .:/app

This makes the trick: stdin_open: true, tty: true

This is a project generated with create-react-app it looks this that:

FROM node:alpine

WORKDIR '/app'

COPY package.json .
RUN npm install

COPY . . 

CMD ["npm", "run", "start"]

Hope this example will help other to run a frontend(react in example) into docker container.

Composer update memory limit

When you run composer update, the OS will look into the configured paths and try to locate an executable file with that name.

When running php composer update, the composer string is treated as a parameter to PHP, which is not searched in any paths. You have to provide the full path in order to run it.

Running which composer will tell you where the OS finds the composer executable, and then you simply use the full path in the PHP command:

$>which composer

$>php -d memory_limit=512M /usr/local/bin/composer update

Note that 512MB might be too few. My perception is that it will happily take 1GB or more, depending on the number of dependencies you use and the variety of versions that you theoretically allow, i.e. if you allow Symfony ~2.3, then you make Composer deal with a lot more possible versions compared to using ~2.7.

Also note that running Composer on the production machine is not the best idea. You would have to have access to Github, maybe provide access credentials, have VCS tools installed, and you will easily break your site if any of the remote hosting servers is offline during your update. It is a better idea to use Composer on a deployment system that does all the preparation, and then moves all the files onto the production server.


It's the year 2020 now, and the way Composer manages its memory has changed quite a bit. The most important thing is that Composer will increase the memory limit by itself if it encounters a limit set too low. This however immediately triggers the problem of running out of memory on machines that have too few memory installed. You can make Composer use less memory by setting the environment variable like COMPOSER_MEMORY_LIMIT=512M, but this will create problems if Composer would need more memory to correctly operate.

My main point remains true: Do not run Composer on machines that have too few memory installed. You potentially need 1.5 GB of free memory to be able to update everything.

Docker compose, running containers in net:host

Those documents are outdated. I'm guessing the 1.6 in the URL is for Docker 1.6, not Compose 1.6. Check out the correct syntax here: You are looking for network_mode when using the v2 YAML format.

Cannot create cache directory .. or directory is not writable. Proceeding without cache in Laravel

Run this command :

    sudo chown -R yourUser /home/yourUser/.composer

Difference between links and depends_on in docker_compose.yml

[Update Sep 2016]: This answer was intended for docker compose file v1 (as shown by the sample compose file below). For v2, see the other answer by @Windsooon.

[Original answer]:

It is pretty clear in the documentation. depends_on decides the dependency and the order of container creation and links not only does these, but also

Containers for the linked service will be reachable at a hostname identical to the alias, or the service name if no alias was specified.

For example, assuming the following docker-compose.yml file:

  image: example/my_web_app:latest
    - db
    - cache

  image: postgres:latest

  image: redis:latest

With links, code inside web will be able to access the database using db:5432, assuming port 5432 is exposed in the db image. If depends_on were used, this wouldn't be possible, but the startup order of the containers would be correct.

To enable extensions, verify that they are enabled in those .ini files - Vagrant/Ubuntu/Magento 2.0.2

Updated....For ubuntu users

sudo apt-get install libapache2-mod-php php-common php-gd php-mysql php-curl php-intl php-xsl php-mbstring php-zip php-bcmath php-soap php-xdebug php-imagick

Docker compose port mapping

It's important to point out that all of the above solutions map the port to every interface on your machine. This is less than desirable if you have a public IP address, or your machine has an IP on a large network. Your application may be exposed to a much wider audience than you'd hoped.

    dockerfile: Dockerfile-redis
    - "" is the ip address that maps to the hostname localhost on your machine. So now your application is only exposed over that interface and since is only accessible via your machine, you're not exposing your containers to the entire world.

The documentation explains this further and can be found here:

Note: If you're using Docker for mac this will make the container listen on on the Docker for Mac VM and will not be accessible from your localhost. If I recall correctly.

The openssl extension is required for SSL/TLS protection

enter image description here You are running Composer with SSL/TLS protection disabled.

 composer config --global disable-tls true
 composer config --global disable-tls false

Android Studio Gradle: Error:Execution failed for task ':app:processDebugGoogleServices'. > No matching client found for package

For me, I had to check the google-services.json file and make sure "package_name" was correctly set to the package name of my android app. The auto generated services file had .backend appended to it in my case.

Docker is in volume in use, but there aren't any Docker containers

Volume can be in use by one of stopped containers. You can remove such containers by command:

docker container prune

then you can remove not used volumes

docker volume prune

Docker-Compose can't connect to Docker Daemon

I had this problem and did not want to mess things up using sudo. When investigating, I tried to get some info :

docker info

Surprinsingly, I had the following error :

Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http:///var/run/docker.sock/v1.38/info: dial unix /var/run/docker.sock: connect: permission denied

For some reason I did not have enough privileges, the following command solved my problem :

sudo chown $USER /var/run/docker.sock

Et voilà !

Laravel 5.2 not reading env file

Not sure whether is it already posted, but this combo worked for me:

php artisan clear-compiled 
composer dump-autoload
php artisan optimize

android : Error converting byte to dex

For me was very easy. Just add:

//noinspection GradleDependency,GradleCompatible implementation ''

... and the magic happens.

How to pass arguments within docker-compose?

This can now be done as of docker-compose v2+ as part of the build object;


version: '2'
            context: . #current dir as build context
                var1: 1
                var2: c

See the docker compose docs.

In the above example "var1" and "var2" will be sent to the build environment.

Note: any env variables (specified by using the environment block) which have the same name as args variable(s) will override that variable.

Composer: Command Not Found

Step 1 : Open Your terminal

Step 2 : Run bellow command

          curl -sS | php

Step 3 : After installation run bellow command

          sudo mv composer.phar /usr/local/bin/

Step 4 : Open bash_profile file create alias follow bellow steps

           vim ~/.bash_profile

Step 5 : Add bellow line in bash_profile file

          alias composer="php /usr/local/bin/composer.phar"

Step 6 : Close your terminal and reopen your terminal and run bellow command composer

Why do I have to run "composer dump-autoload" command to make migrations work in laravel?

Short answer: classmaps are static while PSR autoloading is dynamic.

If you don't want to use classmaps, use PSR autoloading instead.

MySQL error - #1932 - Table 'phpmyadmin.pma user config' doesn't exist in engine

I had the same error and it occured when changing the mysql/data folder to another folder.
I just copied all folders inside mysql/data folder to a new location except for two files. Those are ib_logfile0 and ib_logfile1; those are automatically created when starting the MySQL server. That worked for me.

How to tag docker image with docker-compose

Original answer Nov 20 '15:

No option for a specific tag as of Today. Docker compose just does its magic and assigns a tag like you are seeing. You can always have some script call docker tag <image> <tag> after you call docker-compose.

Now there's an option as described above or here

build: ./dir
image: webapp:tag

How do I install the ext-curl extension with PHP 7?

First Login to your server and check the PHP version which is installed on your server.

And then run the following commands:

sudo apt-get install php7.2-curl

sudo service apache2 restart

Replace the PHP version ( php7.2 ), with your PHP version.

Docker Networking - nginx: [emerg] host not found in upstream

Had the same problem and solved it. Please add the following line to docker-compose.yml nginx section:

  - php:waapi_php_1

Host in nginx config fastcgi_pass section should be linked inside docker-compose.yml nginx configuration.

Where is a log file with logs from a container?

To see the size of logs per container, you can use this bash command :

for cont_id in $(docker ps -aq); do cont_name=$(docker ps | grep $cont_id | awk '{ print $NF }') && cont_size=$(docker inspect --format='{{.LogPath}}' $cont_id | xargs sudo ls -hl | awk '{ print $5 }') && echo "$cont_name ($cont_id): $cont_size"; done

Example output:

container_name (6eed984b29da): 13M
elegant_albattani (acd8f73aa31e): 2.3G

How to get docker-compose to always re-create containers from fresh images?

docker-compose up --build


docker-compose build --no-cache

Composer - the requested PHP extension mbstring is missing from your system

sudo apt-get install php-mbstring

# if your are using php 7.1
sudo apt-get install php7.1-mbstring

# if your are using php 7.2
sudo apt-get install php7.2-mbstring

Ubuntu: Using curl to download an image

For ones who got permission denied for saving operation, here is the command that worked for me:

$ curl --output py.png

How do I define the name of image built with docker-compose

As per docker-compose 1.6.0:

You can now specify both a build and an image key if you're using the new file format. docker-compose build will build the image and tag it with the name you've specified, while docker-compose pull will attempt to pull it.

So your docker-compose.yml would be

version: '2'
      build: /path/to/dir/Dockerfile
      image: wildfly_server
       - 9990:9990
       - 80:8080

To update docker-compose

sudo pip install -U docker-compose==1.6.0

Composer could not find a composer.json

You could try updating the composer:

sudo composer self-update

If that doest works remove composer files & then use: SSH into terminal & type :

$ cd ~
$ sudo curl -sS | sudo php
$ sudo mv composer.phar /usr/local/bin/composer
$ sudo ln -s /usr/local/bin/composer /usr/bin/composer

If you face an error that says: PHP Fatal error: Uncaught exception 'ErrorException' with message 'proc_open(): fork failed - Cannot allocate memory' in phar

/bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=1024
/sbin/mkswap /var/swap.1
/sbin/swapon /var/swap.1

To install package use:

composer global require "package-name"

Docker Compose wait for container X before starting Y

In version 3 of a Docker Compose file, you can use RESTART.

For example:


    build: myapp/.
    - myapp/.:/usr/src/app:ro
    restart: on-failure
    - rabbitmq
    image: rabbitmq:3-management

Note that I used depends_on instead of links since the latter is deprecated in version 3.

Even though it works, it might not be the ideal solution since you restart the docker container at every failure.

Have a look to RESTART_POLICY as well. it let you fine tune the restart policy.

When you use Compose in production, it is actually best practice to use the restart policy :

Specifying a restart policy like restart: always to avoid downtime

How to restart a single container with docker-compose

It is very simple: Use the command:

docker-compose restart worker

You can set the time to wait for stop before killing the container (in seconds)

docker-compose restart -t 30 worker

Note that this will restart the container but without rebuilding it. If you want to apply your changes and then restart, take a look at the other answers.

SQLSTATE[HY000] [1045] Access denied for user 'root'@'localhost' (using password: YES) symfony2

database_password: password would between quotes: " or '.

like so:

database_password: "password"

How do I make a Docker container start automatically on system boot?

The default restart policy is no.

For the created containers use docker update to update restart policy.

docker update --restart=always 0576df221c0b

0576df221c0b is the container id.

Remove composer

Additional information about removing/uninstalling composer

Answers above did not help me, but what did help me is removing:

  1. ~/.cache/composer
  2. ~/.local/share/composer
  3. ~/.config/composer

Hope this helps.

docker-compose up for only certain containers

Oh, just with this:

$ docker-compose up client server database

How do I get into a Docker container's shell?

To exec into a running container named test, below is the following commands

If the container has bash shell

docker exec -it test /bin/bash

If the container has bourne shell and most of the cases it's present

docker run -it test /bin/sh

Using Docker-Compose, how to execute multiple commands

Another idea:

If, as in this case, you build the container just place a startup script in it and run this with command. Or mount the startup script as volume.

Docker-compose: node_modules not present in a volume after npm install succeeds

If you don't use docker-compose you can do it like this:

FROM node:10

WORKDIR /usr/src/app

RUN npm install -g @angular/cli

COPY package.json ./
RUN npm install


CMD ng serve --port 5000 --host

Then you build it: docker build -t myname . and you run it by adding two volumes, the second one without source: docker run --rm -it -p 5000:5000 -v "$PWD":/usr/src/app/ -v /usr/src/app/node_modules myname

How do I set hostname in docker-compose?

This seems to work correctly. If I put your config into a file:

$ cat > compose.yml <<EOF
  image: phensley/docker-dns
  hostname: affy
    - /var/run/docker.sock:/docker.sock

And then bring things up:

$ docker-compose -f compose.yml up
Creating tmp_dns_1...
Attaching to tmp_dns_1
dns_1 | 2015-04-28T17:47:45.423387 [dockerdns] table.add tmp_dns_1.docker ->

And then check the hostname inside the container, everything seems to be fine:

$ docker exec -it stack_dns_1 hostname

How to generate .env file for laravel?

in console (cmd), go to app root path and execute:

type .env.example > .env

How to correctly link php-fpm and Nginx Docker containers?

I think we also need to give the fpm container the volume, dont we? So =>

    image: php:fpm
        - ./:/var/www/test/

If i dont do this, i run into this exception when firing a request, as fpm cannot find requested file:

[error] 6#6: *4 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client:, server: localhost, request: "GET / HTTP/1.1", upstream: "fastcgi://", host: "localhost"

Fatal error: Class 'Illuminate\Foundation\Application' not found

i was having same problem with this error. It turn out my Kenel.php is having a wrong syntax when i try to comply with wrong php8 syntax

The line should be

protected $commands = [

instead of

protected array $commands = [

What's the difference between Docker Compose vs. Dockerfile

Dockerfiles are to build an image for example from a bare bone Ubuntu, you can add mysql called mySQL on one image and mywordpress on a second image called mywordpress.

Compose YAML files are to take these images and run them cohesively. For example, if you have in your docker-compose.yml file a service called db:

     image: mySQL  --- image that you built.

and a service called wordpress such as:

    image: mywordpress

then inside the mywordpress container you can use db to connect to your mySQL container. This magic is possible because your docker host create a network bridge (network overlay).

How to use environment variables in docker compose

I have a simple bash script I created for this it just means running it on your file before use:

Basically just create your compose file using double curly braces to denote environment variables e.g:

    build: "{{APP_PATH}}"
    - "{{APP_PORT_MAP}}"

Anything in double curly braces will be replaced with the environment variable of the same name so if I had the following environment variables set:


on running subber docker-compose.yml the resulting file would look like:

    build: "~/my_app/build"
    - "5000:5000"

How can I resolve "Your requirements could not be resolved to an installable set of packages" error?

I use Windows 10 machine working with PHP 8 and Lavarel 8 and I got the same error, I used the following command :-

composer update --ignore-platform-reqs

to update all the packages regardless of the version conflicts.

Can't connect to docker from docker-compose

If you are on Linux you may not have docker-machine installed since it is only installed by default on Windows and Mac computers.

If so you will need to got to: to find instructions for how to install it on your version of Linux.

After installing, retry running docker-compose up before trying anything listed above.

Hope this helps someone. This worked for my devilbox installation in Fedora 25.

Using --add-host or extra_hosts with docker-compose

I have great news: this will be in Compose 1.3!

I'm using it in the current RC (RC1) like this:

  build: rng

Whoops, looks like something went wrong. Laravel 5.0

This worked for me:

  1. Go to the .env file and be sure APP_DEBUG=true
  2. Here (in .env file) change reemplace for localhost for check if your DB credential are corrects.
  3. Go to the config folder and do. the step #2.

Laravel 5 Class 'form' not found

Form isn't included in laravel 5.0 as it was on 4.0, steps to include it:

Begin by installing laravelcollective/html package through Composer. Edit your project's composer.json file to require:

"require": {
    "laravelcollective/html": "~5.0"

Next, update composer from the Terminal:

composer update

Next, add your new provider to the providers array of config/app.php:

'providers' => [
  // ...
  // ...

Finally, add two class aliases to the aliases array of config/app.php:

'aliases' => [
// ...
  'Form' => 'Collective\Html\FormFacade',
  'Html' => 'Collective\Html\HtmlFacade',
// ...

At this point, Form should be working


Update Laravel 5.8 (2019-04-05):

In Laravel 5.8, the providers in the config/app.php can be declared as:


instead of:


This notation is the same for the aliases.

Laravel 5 Failed opening required bootstrap/../vendor/autoload.php

In my case I had to enable another extension, namely php_mbstring.dll in the php.ini file before it could work. It's listed under extension=php_mbstring.dll. Find it in the php.ini file and remove the semi-colon (;) in front of it and save the file.

After this run install composer again in the root directory of your Laravel applcication and is should work.

How to remove unused dependencies from composer?

following commands will do the same perfectly

rm -rf vendor

composer install 

how can I connect to a remote mongo server from Mac OS terminal

With Mongo 3.2 and higher just use your connection string as is:

mongo mongodb://username:[email protected]:10011/my_database

Undefined symbols for architecture x86_64 on Xcode 6.1

I just had this error when I opened a (quite) old project, created in Xcode 4~ish, in Xcode 6.4. While the linked Frameworks were visible in the Project sidebar, I overlooked that there were no linked libraries in the Target Build Phases tab. Once I fixed that, it compiled fine.

How can I rename column in laravel using migration?

Follow these steps, respectively for rename column migration file.

1- Is there Doctrine/dbal library in your project. If you don't have run the command first

composer require doctrine/dbal

2- create update migration file for update old migration file. Warning (need to have the same name)

php artisan make:migration update_oldFileName_table

for example my old migration file name: create_users_table update file name should : update_users_table

3- update_oldNameFile_table.php

Schema::table('users', function (Blueprint $table) {
$table->renameColumn('from', 'to');

'from' my old column name and 'to' my new column name

4- Finally run the migrate command

php artisan migrate

Source link: laravel document

Laravel PHP Command Not Found

1) First, download the Laravel installer using Composer:

composer global require "laravel/installer"

2) Make sure to place the ~/.composer/vendor/bin directory in your PATH so the laravel executable can be located by your system.

  set PATH=%PATH%;%USERPROFILE%\AppData\Roaming\Composer\vendor\bin

  eg: “C:\Users\\AppData\Roaming\Composer\vendor\bin” 

3) Once installed, the simple laravel new command will create a fresh Laravel installation in the directory you specify.

eG:  laravel new blog

CakePHP 3.0 installation: intl extension missing from system

For Ubuntu terminal:

Please follow the steps:


cd ~

Step -2: Run the following commands

sudo apt-get install php5-intl

Step -3: You then need to restart Apache

sudo service apache2 restart

For Windows(XAMPP) :

Find the Php.ini file:


Update the php.ini file with remove (;) semi colon like mentioned below:

;extension=php_intl.dll to extension=php_intl.dll

and save the php.ini file.

After that you need to

Restart the xampp using xampp control.

Laravel 5 - artisan seed [ReflectionException] Class SongsTableSeeder does not exist

SongsTableSeeder.php should be in database/seeds directory

Console command steps:

composer dump-autoload

and then:

php artisan cache:clear

and then:

php artisan optimize

and then:

php artisan db:seed


php artisan db:seed --class=SongsTableSeeder

plot different color for different categorical levels using matplotlib

You can pass plt.scatter a c argument which will allow you to select the colors. The code below defines a colors dictionary to map your diamond colors to the plotting colors.

import matplotlib.pyplot as plt
import pandas as pd

carat = [5, 10, 20, 30, 5, 10, 20, 30, 5, 10, 20, 30]
price = [100, 100, 200, 200, 300, 300, 400, 400, 500, 500, 600, 600]
color =['D', 'D', 'D', 'E', 'E', 'E', 'F', 'F', 'F', 'G', 'G', 'G',]

df = pd.DataFrame(dict(carat=carat, price=price, color=color))

fig, ax = plt.subplots()

colors = {'D':'red', 'E':'blue', 'F':'green', 'G':'black'}

ax.scatter(df['carat'], df['price'], c=df['color'].apply(lambda x: colors[x]))

df['color'].apply(lambda x: colors[x]) effectively maps the colours from "diamond" to "plotting".

(Forgive me for not putting another example image up, I think 2 is enough :P)

With seaborn

You can use seaborn which is a wrapper around matplotlib that makes it look prettier by default (rather opinion-based, I know :P) but also adds some plotting functions.

For this you could use seaborn.lmplot with fit_reg=False (which prevents it from automatically doing some regression).

The code below uses an example dataset. By selecting hue='color' you tell seaborn to split your dataframe up based on your colours and then plot each one.

import matplotlib.pyplot as plt
import seaborn as sns

import pandas as pd

carat = [5, 10, 20, 30, 5, 10, 20, 30, 5, 10, 20, 30]
price = [100, 100, 200, 200, 300, 300, 400, 400, 500, 500, 600, 600]
color =['D', 'D', 'D', 'E', 'E', 'E', 'F', 'F', 'F', 'G', 'G', 'G',]

df = pd.DataFrame(dict(carat=carat, price=price, color=color))

sns.lmplot('carat', 'price', data=df, hue='color', fit_reg=False)

enter image description here

Without seaborn using pandas.groupby

If you don't want to use seaborn then you can use pandas.groupby to get the colors alone and then plot them using just matplotlib, but you'll have to manually assign colors as you go, I've added an example below:

fig, ax = plt.subplots()

colors = {'D':'red', 'E':'blue', 'F':'green', 'G':'black'}

grouped = df.groupby('color')
for key, group in grouped:
    group.plot(ax=ax, kind='scatter', x='carat', y='price', label=key, color=colors[key])

This code assumes the same DataFrame as above and then groups it based on color. It then iterates over these groups, plotting for each one. To select a color I've created a colors dictionary which can map the diamond color (for instance D) to a real color (for instance red).

enter image description here

AngularJS ng-click to go to another page (with Ionic framework)

If you simply want to go to another page, then what you might need is a link that looks like a button with a href like so:

<a href="/#/somepage.html" class="button">Back to Listings</a>

Hope this helps.

How to place the ~/.composer/vendor/bin directory in your PATH?

For Ubuntu 16.04

echo 'export PATH="$PATH:$HOME/.config/composer/vendor/bin"' >> ~/.bashrc

source ~/.bashrc

Using a PagedList with a ViewModel ASP.Net MVC

I modified the code as follow:


using System.Collections.Generic;
using ContosoUniversity.Models;

namespace ContosoUniversity.ViewModels
    public class InstructorIndexData
     public PagedList.IPagedList<Instructor> Instructors { get; set; }
     public PagedList.IPagedList<Course> Courses { get; set; }
     public PagedList.IPagedList<Enrollment> Enrollments { get; set; }


public ActionResult Index(int? id, int? courseID,int? InstructorPage,int? CoursePage,int? EnrollmentPage)
 int instructPageNumber = (InstructorPage?? 1);
 int CoursePageNumber = (CoursePage?? 1);
 int EnrollmentPageNumber = (EnrollmentPage?? 1);
 var viewModel = new InstructorIndexData();
 viewModel.Instructors = db.Instructors
    .Include(i => i.OfficeAssignment)
    .Include(i => i.Courses.Select(c => c.Department))
    .OrderBy(i => i.LastName).ToPagedList(instructPageNumber,5);

 if (id != null)
    ViewBag.InstructorID = id.Value;
    viewModel.Courses = viewModel.Instructors.Where(
        i => i.ID == id.Value).Single().Courses.ToPagedList(CoursePageNumber,5);

 if (courseID != null)
    ViewBag.CourseID = courseID.Value;
    viewModel.Enrollments = viewModel.Courses.Where(
        x => x.CourseID == courseID).Single().Enrollments.ToPagedList(EnrollmentPageNumber,5);

 return View(viewModel);


   Page @(Model.Instructors.PageCount < Model.Instructors.PageNumber ? 0 : Model.Instructors.PageNumber) of @Model.Instructors.PageCount

   @Html.PagedListPager(Model.Instructors, page => Url.Action("Index", new {InstructorPage=page}))


I hope this would help you!!

OSX -bash: composer: command not found

Composer is avialble and install the packages in the global path but they are not available in the shell, Mac in my case. I managed to fix this by adding the global bin to the path at my bash file.


First, check what is your home directory by typing in the shell:

cd ~

this will tell you the home path

The next step is to verify that composer set the global directory there:

ls -al .composer

If you got list of files that's mean composer set up the directory, if not - look above or in the documentation.

The next step is to edit the bash profile. Mine is ~/.bash_profile but other can ~/.zshrc. If you don't have any one like this try to see how to set up aliases and place the the code in aliases file:

export PATH

That's it! just reload the file with


And you good to go!

Composer Update Laravel

The following works for me:

composer update --no-scripts

Using Laravel Homestead: 'no input file specified'

I edited homestead.yaml and hosts according to this laracast tutorial and restarted homestead using vagrant suspend, vagrant halt, etc. /vagrant up; I tried to vagrant provision as well, but no file specified only went away after I restarted my computer (I'm on Windows 7 PC) after doing all of the above. It is certainly a time consuming and tricky error.

This is what my working homestead.yaml looks like for two laravel projects:

ip: ""
memory: 2048
cpus: 1
provider: virtualbox

authorize: ~/.ssh/

- ~/.ssh/id_rsa

    - map: D:\Projects
      to: /home/vagrant/Projects

    - map:
      to: /home/vagrant/Projects/ProjectOne/public
    - map:
      to: /home/vagrant/Projects/ProjectTwo/public

    - laraveldb

and here is my hosts file:

...       localhost

Note, there are two separate installations of laravel in D:\Projects\ProjectOne and D:\Projects\ProjectTwo

I then access the first project by typing in the browser and for the second project.

P.S. I tested this for Laravel 5.2 on Windows

Installing specific laravel version with composer create-project

composer create-project laravel/laravel=4.1.27 your-project-name --prefer-dist

And then you probably need to install all of vendor packages, so

composer install

How to get root directory in yii2

Use "getAlias" in Yii2


How to remove a package from Laravel using composer?

In case the given answers still don't help you remove that, try this:

  • Manually delete the line in require from composer.json

  • Run composer update

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

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

Updating the path in my .bash_profile fixed my issue.

Composer: The requested PHP extension ext-intl * is missing from your system

I have solved this problem by adding --ignore-platform-reqs command with composer install in ubuntu.

composer install --ignore-platform-reqs

How to deploy correctly when using Composer's develop / production switch?

Actually, I would highly recommend AGAINST installing dependencies on the production server.

My recommendation is to checkout the code on a deployment machine, install dependencies as needed (this includes NOT installing dev dependencies if the code goes to production), and then move all the files to the target machine.


  • on shared hosting, you might not be able to get to a command line
  • even if you did, PHP might be restricted there in terms of commands, memory or network access
  • repository CLI tools (Git, Svn) are likely to not be installed, which would fail if your lock file has recorded a dependency to checkout a certain commit instead of downloading that commit as ZIP (you used --prefer-source, or Composer had no other way to get that version)
  • if your production machine is more like a small test server (think Amazon EC2 micro instance) there is probably not even enough memory installed to execute composer install
  • while composer tries to no break things, how do you feel about ending with a partially broken production website because some random dependency could not be loaded during Composers install phase

Long story short: Use Composer in an environment you can control. Your development machine does qualify because you already have all the things that are needed to operate Composer.

What's the correct way to deploy this without installing the -dev dependencies?

The command to use is

composer install --no-dev

This will work in any environment, be it the production server itself, or a deployment machine, or the development machine that is supposed to do a last check to find whether any dev requirement is incorrectly used for the real software.

The command will not install, or actively uninstall, the dev requirements declared in the composer.lock file.

If you don't mind deploying development software components on a production server, running composer install would do the same job, but simply increase the amount of bytes moved around, and also create a bigger autoloader declaration.

Running Composer returns: "Could not open input file: composer.phar"

I had the same problem on Windows and used a different solution. I used the Composer_Setup.exe installation file supplied by the composer website and it does a global install.

After installing, make sure your PATH variable points to the directory where composer.phar is stored. This is usually C:\ProgramData\ComposerSetup\bin (ProgramData might be a hidden directory). It goes without saying, but also be sure that the PHP executable is also in your PATH variable.

You can then simply call

composer install

instead of

php composer.phar install

How do I install Composer on a shared hosting?

You can do it that way:

  • Create a directory where you want to install composer (let's say /home/your_username/composer)
  • Go to this directory - cd /home/your_username/composer
  • Then run the following command:

    php -r "readfile('');" | php

  • After that if you want to run composer, you can do it this way (in this caseyou must be in the composer's dir): php composer.phar

  • As a next step, you can do this:

    alias composer="/home/your_username/composer/composer.phar".

    And run commands like you do it normally: $ composer install

Hope that helps

Could not open input file: composer.phar

I had the same issue when trying to use php composer install in a local directory on my Apache server for a laravel project I cloned from Github. My problem was I had already setup composer globally on my Ubuntu 18 machine.
Adding sudo instead of php started the install of a whole slew of packages listed in the json.lock file i.e. sudo composer install.

Composer killed while updating

Solved on Laravel/Homestead (Vagrant Windows)

  1. Edit Homestead.yaml and increase memory from 2048 to 4096

  2. vagrant up

  3. vagrant ssh

  4. Install Symfony with this line on the folder you choose (must be without files)

    COMPOSER_MEMORY_LIMIT=-1 composer create-project symfony/website-skeleton . -s dev

What are the Differences Between "php artisan dump-autoload" and "composer dump-autoload"?

composer dump-autoload

PATH vendor/composer/autoload_classmap.php
  • Composer dump-autoload won’t download a thing.
  • It just regenerates the list of all classes that need to be included in the project (autoload_classmap.php).
  • Ideal for when you have a new class inside your project.
  • autoload_classmap.php also includes the providers in config/app.php

php artisan dump-autoload

  • It will call Composer with the optimize flag
  • It will 'recompile' loads of files creating the huge bootstrap/compiled.php

How to force composer to reinstall a library?

First execute composer clearcache

Then clear your vendors folder

rm -rf vendor/*

or better yet just remove the specific module which makes problems to avoid having to download all over again.

Composer install error - requires ext_curl when it's actually enabled

I have Archlinux with php 7.2, which has Curl integrated, so no amount of configuration voodoo would make Composer see ext-curl, that PHP could see and work with happily. Work around is to use Composer with --ignore-platform-reqs.

eg composer update --ignore-platform-reqs

Reference =

What is the difference between require and require-dev sections in composer.json?

From the composer site (it's clear enough)


Lists packages required by this package. The package will not be installed unless those requirements can be met.

require-dev (root-only)#

Lists packages required for developing this package, or running tests, etc. The dev requirements of the root package are installed by default. Both install or update support the --no-dev option that prevents dev dependencies from being installed.

Using require-dev in Composer you can declare the dependencies you need for development/testing the project but don't need in production. When you upload the project to your production server (using git) require-dev part would be ignored.

Also check this answer posted by the author and this post as well.

composer laravel create project

Dont write with stability stable in the command ,
in your composer.json file, put
"minimum-stability": "stable" before the closing curly bracket.

PHP Composer update "cannot allocate memory" error (using Laravel 4)

you can use the following to check your free (swap) memory

free -m

total used free shared buffers cached

Mem: 2048 357 1690 0 0 237
-/+ buffers/cache: 119 1928
Swap: 0 0 0

To enable the swap you can use for example:

/bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=1024
/sbin/mkswap /var/swap.1
/sbin/swapon /var/swap.1

How to enable PHP's openssl extension to install Composer?


Browse to the line that reads:


and remove the semicolon preceding the line. Restart your WAMP server services (click in your icon tray > 'Restart All Services'

PHP parse/syntax errors; and how to solve them

Unexpected $end

When PHP talks about an "unexpected $end", it means that your code ended prematurely. (The message is a bit misleading when taken literally. It's not about a variable named "$end", as sometimes assumed by newcomers. It refers to the "end of file", EOF.)

Cause: Unbalanced { and } for code blocks / and function or class declarations.

It's pretty much always about a missing } curly brace to close preceding code blocks.

  • Again, use proper indentation to avoid such issues.

  • Use an IDE with bracket matching, to find out where the } is amiss. There are keyboard shortcuts in most IDEs and text editors:

    • NetBeans, PhpStorm, Komodo: Ctrl[ and Ctrl]
    • Eclipse, Aptana: CtrlShiftP
    • Atom, Sublime: Ctrlm - Zend Studio CtrlM
    • Geany, Notepad++: CtrlB - Joe: CtrlG - Emacs: C-M-n - Vim: %

Most IDEs also highlight matching braces, brackets and parentheses. Which makes it pretty easy to inspect their correlation:

Bracket matching in an IDE

Unterminated expressions

And Unexpected $end syntax/parser error can also occur for unterminated expressions or statements:

  • $var = func(1, ?>EOF

So, look at the end of scripts first. A trailing ; is often redundant for the last statement in any PHP script. But you should have one. Precisely because it narrows such syntax issues down.

Indented HEREDOC markers

Another common occurrence appears with HEREDOC or NOWDOC strings. The terminating marker goes ignored with leading spaces, tabs, etc.:

print <<< END
# ? terminator isn't exactly at the line start

Therefore the parser assumes the HEREDOC string to continue until the end of the file (hence "Unexpected $end"). Pretty much all IDEs and syntax-highlighting editors will make this obvious or warn about it.

Escaped Quotation marks

If you use \ in a string, it has a special meaning. This is called an "Escape Character" and normally tells the parser to take the next character literally.

Example: echo 'Jim said \'Hello\''; will print Jim said 'hello'

If you escape the closing quote of a string, the closing quote will be taken literally and not as intended, i.e. as a printable quote as part of the string and not close the string. This will show as a parse error commonly after you open the next string or at the end of the script.

Very common error when specifiying paths in Windows: "C:\xampp\htdocs\" is wrong. You need "C:\\xampp\\htdocs\\".

Alternative syntax

Somewhat rarer you can see this syntax error when using the alternative syntax for statement/code blocks in templates. Using if: and else: and a missing endif; for example.

See also:

Laravel view not found exception

Just in the controller call

return View('index');



PHP Composer behind http proxy

You can use the standard HTTP_PROXY environment var. Simply set it to the URL of your proxy. Many operating systems already set this variable for you.

Just export the variable, then you don't have to type it all the time.

export HTTP_PROXY=""

Then you can do composer update normally.

<Django object > is not JSON serializable

From version 1.9 Easier and official way of getting json

from django.http import JsonResponse
from django.forms.models import model_to_dict

return JsonResponse(  model_to_dict(modelinstance) )

How to update a single library with Composer?

You can use the following command to update any module with its dependencies

composer update vendor-name/module-name --with-dependencies

Bootstrap Carousel Full Screen

Update Bootstrap 4

Bootstrap 4 has utility classes that make it easier to create a full screen carousel. For example, use the min-vh-100 class on the carousel-item content...

<div class="carousel slide" data-ride="carousel">
      <div class="carousel-inner bg-info" role="listbox">
            <div class="carousel-item active">
                <div class="d-flex align-items-center justify-content-center min-vh-100">
                    <h1 class="display-1">ONE</h1>

Full screen carousel demo

This works to make the carousel items full screen, but carousel items that contain images or videos that have a specific size & aspect ratio require further consideration.

Since the viewport h/w ratio is likely to be different than the image or video h/w ratio, usually background images or object-fit are commonly used to size images and videos to "full screen". For videos, use the Bootstrap responsive embed classes as needed for the video ratio (21:9, 19:9, etc...).

Full screen videos demo

Also see:

Original answer (Bootstrap 3)

Make sure the img inside the carousel item is set to height and width 100%. You also have to make sure the carousel and any of the .item containers (html,body) are 100%...


Boostrap 3 Full Screen Carousel Demo

Here's an example for Bootstrap 3.x:

Sending email from Command-line via outlook without having to click send

Send SMS/Text Messages from Command Line with VBScript!

If VBA meets the rules for VB Script then it can be called from command line by simply placing it into a text file - in this case there's no need to specifically open Outlook.

I had a need to send automated text messages to myself from the command line, so I used the code below, which is just a compressed version of @Geoff's answer above.

Most mobile phone carriers worldwide provide an email address "version" of your mobile phone number. For example in Canada with Rogers or Chatr Wireless, an email sent to <YourPhoneNumber> will be immediately delivered to your Rogers/Chatr phone as a text message.

* You may need to "authorize" the first message on your phone, and some carriers may charge an additional fee for theses message although as far as I know, all Canadian carriers provide this little-known service for free. Check your carrier's website for details.

There are further instructions and various compiled lists of worldwide carrier's Email-to-Text addresses available online such as this and this and this.

Code & Instructions

  1. Copy the code below and paste into a new file in your favorite text editor.
  2. Save the file with any name with a .VBS extension, such as TextMyself.vbs.

That's all!
Just double-click the file to send a test message, or else run it from a batch file using START.

Sub SendMessage()
    Const EmailToSMSAddy = "[email protected]"
    Dim objOutlookRecip
    With CreateObject("Outlook.Application").CreateItem(0)
        Set objOutlookRecip = .Recipients.Add(EmailToSMSAddy)
        objOutlookRecip.Type = 1
        .Subject = "The computer needs your attention!"
        .Body = "Go see why Windows Command Line is texting you!"
    End With
End Sub

Example Batch File Usage:

START x:\mypath\TextMyself.vbs

Of course there are endless possible ways this could be adapted and customized to suit various practical or creative needs.

Using moment.js to convert date to string "MM/dd/yyyy"

StartDate = moment(StartDate).format('MM-YYYY');

...and MySQL date format:

StartDate = moment(StartDate).format('YYYY-MM-DD');

Composer: how can I install another dependency without updating old ones?

To install a new package and only that, you have two options:

  1. Using the require command, just run:

    composer require new/package

    Composer will guess the best version constraint to use, install the package, and add it to composer.lock.

    You can also specify an explicit version constraint by running:

    composer require new/package ~2.5


  1. Using the update command, add the new package manually to composer.json, then run:

    composer update new/package

If Composer complains, stating "Your requirements could not be resolved to an installable set of packages.", you can resolve this by passing the flag --with-dependencies. This will whitelist all dependencies of the package you are trying to install/update (but none of your other dependencies).

Regarding the question asker's issues with Laravel and mcrypt: check that it's properly enabled in your CLI php.ini. If php -m doesn't list mcrypt then it's missing.

Important: Don't forget to specify new/package when using composer update! Omitting that argument will cause all dependencies, as well as composer.lock, to be updated.

How to get list of all installed packages along with version in composer?

The behaviour of this command as been modified so you don't have to pass the -i option:

[10:19:05] coil@coil:~/workspace/api$ composer show -i
You are using the deprecated option "installed". 
Only installed packages are shown by default now. 
The --all option can be used to show all packages.

Truncate string in Laravel blade templates

Edit: This answer is was posted during the Laravel 4 beta, when Str class did not exist. There is now a better way to do it in Laravel 4 - which is Dustin's answer below. I cannot delete this answer due to SO rules (it wont let me)

Blade itself does not have that functionality.

In Laravel 3 there was the Str class - which you could do:

{{ Str::limit($myVariable, 10) }}

At this stage I do not believe the Str class is in Laravel 4 - but here is a port of it that you can include in composer to add to your own project

You must enable the openssl extension to download files via https

Uttam, if your issue is not solved then try the follwoing 3 step approach. It worked for me as I had exactly same issue.

step1: click on wamp tray icon.

step2: goto menu apache->apache modules

step3: click on menu item "ssl_module"

it will automatically restart wamp. if wamp not restarted automatically then restart it through wamp tray menu-> Restart All services. After restart confirm that "ssl_module" coming as ticked under menu apache->apache modules

after that just attempt the php composer.phar install from going through the response shared by you, php.ini file contains extension=php_openssl.dll and the php/ext directory also have file "php_openssl.dll"

good luck

Composer Warning: openssl extension is missing. How to enable in WAMP

All those answers are good, but in fact, if you want to understand, the extension directory need to be right if you want all you uncommented extensions to work. Can write a physical or relative path like

extension_dir = "C:/myStack/php/ext"


extension_dir = "../../php/ext"

It's relative to the httpd.exe Apache web server (C:\myStack\apache\bin) But if you want it to work with Composer or anything you need the physical path because the cli mode doesn't use the web server !

Where can I find Android's default icons?

You can find the default Android menu icons here - link is broken now.

Update: You can find Material Design icons here.

Use PHP composer to clone git repo

At the time of writing in 2013, this was one way to do it. Composer has added support for better ways: See @igorw 's answer


Git, Mercurial and SVN is supported by Composer.




If you have a repository you can write to: Add a composer.json file, or fix the existing one, and DON'T use the solution below.

Go to @igorw 's answer


This will override everything that Composer may be able to read from the original repository's composer.json, including the dependencies of the package and the autoloading.

Using the package type will transfer the burden of correctly defining everything onto you. The easier way is to have a composer.json file in the repository, and just use it.

This solution really only is for the rare cases where you have an abandoned ZIP download that you cannot alter, or a repository you can only read, but it isn't maintained anymore.

"repositories": [
        "package": {
          "name": "l3pp4rd/doctrine-extensions",
          "source": {
              "url": "",
              "type": "git",
"require": {
    "l3pp4rd/doctrine-extensions": "master"

Should composer.lock be committed to version control?

After doing it both ways for a few projects my stance is that composer.lock should not be committed as part of the project.

composer.lock is build metadata which is not part of the project. The state of dependencies should be controlled through how you're versioning them (either manually or as part of your automated build process) and not arbitrarily by the last developer to update them and commit the lock file.

If you are concerned about your dependencies changing between composer updates then you have a lack of confidence in your versioning scheme. Versions (1.0, 1.1, 1.2, etc) should be immutable and you should avoid "dev-" and "X.*" wildcards outside of initial feature development.

Committing the lock file is a regression for your dependency management system as the dependency version has now gone back to being implicitly defined.

Also, your project should never have to be rebuilt or have its dependencies reacquired in each environment, especially prod. Your deliverable (tar, zip, phar, a directory, etc) should be immutable and promoted through environments without changing.

Using Composer's Autoload

The autoload config does start below the vendor dir. So you might want change the vendor dir, e.g.

    "config": {
        "vendor-dir": "../vendor/"
    "autoload": {
        "psr-0": {"AppName": "src/"}

Or isn't this possible in your project?

Why am I getting error for apple-touch-icon-precomposed.png

I finally solved!! It's a Web Clip feature on Mac Devices. If a user want to add your website in Dock o Desktop it requests this icon.

You may want users to be able to add your web application 
or webpage link to the Home screen. These links, represented 
by an icon, are called Web Clips. Follow these simple steps 
to specify an icon to represent your web application or webpage
on iOS.

more info:

how to solve?: Add a icon to solve problem.

Moq, SetupGet, Mocking a property

ColumnNames is a property of type List<String> so when you are setting up you need to pass a List<String> in the Returns call as an argument (or a func which return a List<String>)

But with this line you are trying to return just a string

input.SetupGet(x => x.ColumnNames).Returns(temp[0]);

which is causing the exception.

Change it to return whole list:

input.SetupGet(x => x.ColumnNames).Returns(temp);

Is there any way to install Composer globally on Windows?

A bit more generic if you put the batch in the same folder as composer.phar:

php %SUBDIR%/composer.phar %*

I'd write it as a comment, but code isn't avail there

Add custom icons to font awesome

In Font Awesome 5, you can create custom icons with your own SVG data. Here's a demo GitHub repo that you can play with. And here's a CodePen that shows how something similar might be done in <script> blocks.

In either case, it simply involves using library.add() to add an object like this:

export const faSomeObjectName = {
  // Use a prefix like 'fac' that doesn't conflict with a prefix in the standard Font Awesome styles
  // (So avoid fab, fal, fas, far, fa)
  prefix: string,
  iconName: string, // Any name you like
  icon: [
    number, // width
    number, // height
    string[], // ligatures
    string, // unicode (if relevant)
    string // svg path data

Note that the element labelled by the comment "svg path data" in the code sample is what will be assigned as the value of the d attribute on a <path> element that is a child of the <svg>. Like this (leaving out some details for clarity):

  <path d=SVG_PATH_DATA></path>

(Adapted from my similar answer here:

How to run composer from anywhere?

Just move it to /usr/local/bin folder and remove the extension

sudo mv composer.phar /usr/local/bin/composer

SSLHandshakeException: No subject alternative names present

Thanks,Bruno for giving me heads up on Common Name and Subject Alternative Name. As we figured out certificate was generated with CN with DNS name of network and asked for regeneration of new certificate with Subject Alternative Name entry i.e. san=ip: which is the actual solution.

But, we managed to find out a workaround with which we can able to run on development phase. Just add a static block in the class from which we are making ssl connection.

static {
    HttpsURLConnection.setDefaultHostnameVerifier(new HostnameVerifier()
            public boolean verify(String hostname, SSLSession session)
                // ip address of the service URL(like.
                if (hostname.equals(""))
                    return true;
                return false;

If you happen to be using Java 8, there is a much slicker way of achieving the same result:

static {
    HttpsURLConnection.setDefaultHostnameVerifier((hostname, session) -> hostname.equals(""));

Send a SMS via intent

Create the Intent like this:

   Uri uriSms = Uri.parse("smsto:1234567899");   
   Intent intentSMS = new Intent(Intent.ACTION_SENDTO, uriSms);   
   intentSMS.putExtra("sms_body", "The SMS text");   

What's the difference between primitive and reference types?

These are the primitive types in Java:

  • boolean
  • byte
  • short
  • char
  • int
  • long
  • float
  • double

All the other types are reference types: they reference objects.

This is the first part of the Java tutorial about the basics of the language.

How do I find Waldo with Mathematica?

My guess at a "bulletproof way to do this" (think CIA finding Waldo in any satellite image any time, not just a single image without competing elements, like striped shirts)... I would train a Boltzmann machine on many images of Waldo - all variations of him sitting, standing, occluded, etc.; shirt, hat, camera, and all the works. You don't need a large corpus of Waldos (maybe 3-5 will be enough), but the more the better.

This will assign clouds of probabilities to various elements occurring in whatever the correct arrangement, and then establish (via segmentation) what an average object size is, fragment the source image into cells of objects which most resemble individual people (considering possible occlusions and pose changes), but since Waldo pictures usually include a LOT of people at about the same scale, this should be a very easy task, then feed these segments of the pre-trained Boltzmann machine. It will give you probability of each one being Waldo. Take one with the highest probability.

This is how OCR, ZIP code readers, and strokeless handwriting recognition work today. Basically you know the answer is there, you know more or less what it should look like, and everything else may have common elements, but is definitely "not it", so you don't bother with the "not it"s, you just look of the likelihood of "it" among all possible "it"s you've seen before" (in ZIP codes for example, you'd train BM for just 1s, just 2s, just 3s, etc., then feed each digit to each machine, and pick one that has most confidence). This works a lot better than a single neural network learning features of all numbers.

Format output string, right alignment

Here is another way how you can format using 'f-string' format:

    f"\n{'Win/Loss Ratio:':<15}{win_r:>10}",
    f"\n{'Mean Win:':<15}{mean_w:>10}",
    f"\n{'Mean Loss:':<15}{mean_l:>10}",
    f"\n{'Std Dev:':<15}{sd:>10}",
    f"\n{'Max Loss:':<15}{max_l:>10}",
    f"\n{'Max Win:':<15}{max_w:>10}",
    f"\n{'Sharpe Ratio:':<15}{sharpe_r:>10}",

This will provide the following output:

Trades:              2304
Wins:                1232
Losses:              1035
Breakeven:             37
Win/Loss Ratio:      1.19
Mean Win:           0.381
Mean Loss:         -0.395
Mean:               0.026
Std Dev:             0.56
Max Loss:          -3.406
Max Win:             4.09
Sharpe Ratio:      0.7395

What you are doing here is you are saying that the first column is 15 chars long and it's left justified and second column (values) is 10 chars long and it's right justified.

Replace Fragment inside a ViewPager

tl;dr: Use a host fragment that is responsible for replacing its hosted content and keeps track of a back navigation history (like in a browser).

As your use case consists of a fixed amount of tabs my solution works well: The idea is to fill the ViewPager with instances of a custom class HostFragment, that is able to replace its hosted content and keeps its own back navigation history. To replace the hosted fragment you make a call to the method hostfragment.replaceFragment():

public void replaceFragment(Fragment fragment, boolean addToBackstack) {
    if (addToBackstack) {
        getChildFragmentManager().beginTransaction().replace(, fragment).addToBackStack(null).commit();
    } else {
        getChildFragmentManager().beginTransaction().replace(, fragment).commit();

All that method does is to replace the frame layout with the id with the fragment provided to the method.

Check my tutorial on this topic for further details and a complete working example on GitHub!

UIView bottom border?

Or, the most performance-friendly way is to overload drawRect, simply like that:

@interface TPActionSheetButton : UIButton

@property (assign) BOOL drawsTopLine;
@property (assign) BOOL drawsBottomLine;
@property (assign) BOOL drawsRightLine;
@property (assign) BOOL drawsLeftLine;
@property (strong, nonatomic) UIColor * lineColor;


@implementation TPActionSheetButton

- (void) drawRect:(CGRect)rect
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    CGContextSetLineWidth(ctx, 0.5f * [[UIScreen mainScreen] scale]);
    CGFloat red, green, blue, alpha;
    [self.lineColor getRed:&red green:&green blue:&blue alpha:&alpha];
    CGContextSetRGBStrokeColor(ctx, red, green, blue, alpha);

    if(self.drawsTopLine) {
        CGContextMoveToPoint(ctx, CGRectGetMinX(rect), CGRectGetMinY(rect));
        CGContextAddLineToPoint(ctx, CGRectGetMaxX(rect), CGRectGetMinY(rect));
    if(self.drawsBottomLine) {
        CGContextMoveToPoint(ctx, CGRectGetMinX(rect), CGRectGetMaxY(rect));
        CGContextAddLineToPoint(ctx, CGRectGetMaxX(rect), CGRectGetMaxY(rect));
    if(self.drawsLeftLine) {
        CGContextMoveToPoint(ctx, CGRectGetMinX(rect), CGRectGetMinY(rect));
        CGContextAddLineToPoint(ctx, CGRectGetMinX(rect), CGRectGetMaxY(rect));
    if(self.drawsRightLine) {
        CGContextMoveToPoint(ctx, CGRectGetMaxX(rect), CGRectGetMinY(rect));
        CGContextAddLineToPoint(ctx, CGRectGetMaxX(rect), CGRectGetMaxY(rect));

    [super drawRect:rect];


Android getText from EditText field

Try out this will solve ur problem ....

EditText etxt = (EditText)findviewbyid(;
String str_value = etxt.getText().toString();

URL to compose a message in Gmail (with full Gmail interface and specified to, bcc, subject, etc.)

For Chrome:

  1. Set your email manager to Gmail

gmail handler

  1. Write mailto: in the address bar and press enter.


  1. Edit search engines:

Edit search engines

Edit search engines

  1. Write mt and enter in address bar.

How Should I Declare Foreign Key Relationships Using Code First Entity Framework (4.1) in MVC3?

If you have an Order class, adding a property that references another class in your model, for instance Customer should be enough to let EF know there's a relationship in there:

public class Order
    public int ID { get; set; }

    // Some other properties

    // Foreign key to customer
    public virtual Customer Customer { get; set; }

You can always set the FK relation explicitly:

public class Order
    public int ID { get; set; }

    // Some other properties

    // Foreign key to customer
    public string CustomerID { get; set; }
    public virtual Customer Customer { get; set; }

The ForeignKeyAttribute constructor takes a string as a parameter: if you place it on a foreign key property it represents the name of the associated navigation property. If you place it on the navigation property it represents the name of the associated foreign key.

What this means is, if you where to place the ForeignKeyAttribute on the Customer property, the attribute would take CustomerID in the constructor:

public string CustomerID { get; set; }
public virtual Customer Customer { get; set; }

EDIT based on Latest Code You get that error because of this line:

public Patient Patient { get; set; }

EF will look for a property called Parent to use it as the Foreign Key enforcer. You can do 2 things:

1) Remove the ForeignKeyAttribute and replace it with the RequiredAttribute to mark the relation as required:

public virtual Patient Patient { get; set; }

Decorating a property with the RequiredAttribute also has a nice side effect: The relation in the database is created with ON DELETE CASCADE.

I would also recommend making the property virtual to enable Lazy Loading.

2) Create a property called Parent that will serve as a Foreign Key. In that case it probably makes more sense to call it for instance ParentID (you'll need to change the name in the ForeignKeyAttribute as well):

public int ParentID { get; set; }

In my experience in this case though it works better to have it the other way around:

public int ParentID { get; set; }

public virtual Patient Patient { get; set; }

String length in bytes in JavaScript

Another very simple approach using Buffer (only for NodeJS):

Buffer.byteLength(string, 'utf8')


How to hide status bar in Android

protected void onCreate(Bundle savedInstanceState) {


    , WindowManager.LayoutParams.FLAG_FULLSCREEN);


How can I get the height and width of an uiimage?

There are a lot of helpful solutions out there, but there is no simplified way with extension. Here is the code to solve the issue with an extension:

extension UIImage {

    var getWidth: CGFloat {
        get {
            let width = self.size.width
            return width

    var getHeight: CGFloat {
        get {
            let height = self.size.height
            return height

Splitting a C++ std::string using tokens, e.g. ";"

I find std::getline() is often the simplest. The optional delimiter parameter means it's not just for reading "lines":

#include <sstream>
#include <iostream>
#include <vector>

using namespace std;

int main() {
    vector<string> strings;
    istringstream f("denmark;sweden;india;us");
    string s;    
    while (getline(f, s, ';')) {
        cout << s << endl;

How to make a HTTP PUT request?

protected void UpdateButton_Click(object sender, EventArgs e)
            var values = string.Format("Name={0}&Family={1}&Id={2}", NameToUpdateTextBox.Text, FamilyToUpdateTextBox.Text, IdToUpdateTextBox.Text);
            var bytes = Encoding.ASCII.GetBytes(values);
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(string.Format("http://localhost:51436/api/employees"));
            request.Method = "PUT";
            request.ContentType = "application/x-www-form-urlencoded";
            using (var requestStream = request.GetRequestStream())
                requestStream.Write(bytes, 0, bytes.Length);
            var response =  (HttpWebResponse) request.GetResponse();

            if (response.StatusCode == HttpStatusCode.OK)
                UpdateResponseLabel.Text = "Update completed";
                UpdateResponseLabel.Text = "Error in update";

Show compose SMS view in Android

This will definitely work, In this, Send message without using any intent .

SmsManager smsManager =     SmsManager.getDefault();
smsManager.sendTextMessage("Phone Number", null, "Message", null, null);

This code is used for send message in background (Not showing message composer), It can also work inside the Broadcast receiver. If you want to send a message from Broadcast receiver.

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

Send auto email programmatically

Sending email programmatically with Kotlin.

  • simple email sending, not all the other features (like attachments).
  • TLS is always on
  • Only 1 gradle email dependency needed also.

I also found this list of email POP services really helpful:

How to use:

    val auth = EmailService.UserPassAuthenticator("yourUser", "yourPass")
    val to = listOf(InternetAddress("[email protected]"))
    val from = InternetAddress("[email protected]")
    val email = EmailService.Email(auth, to, from, "Test Subject", "Hello Body World")
    val emailService = EmailService("yourSmtpServer", 587)

    GlobalScope.launch { // or however you do background threads

The code:

import java.util.*
import javax.mail.*
import javax.mail.internet.InternetAddress
import javax.mail.internet.MimeBodyPart
import javax.mail.internet.MimeMessage
import javax.mail.internet.MimeMultipart

class EmailService(private var server: String, private var port: Int) {

    data class Email(
        val auth: Authenticator,
        val toList: List<InternetAddress>,
        val from: Address,
        val subject: String,
        val body: String

    class UserPassAuthenticator(private val username: String, private val password: String) : Authenticator() {
        override fun getPasswordAuthentication(): PasswordAuthentication {
            return PasswordAuthentication(username, password)

    fun send(email: Email) {
        val props = Properties()
        props["mail.smtp.auth"] = "true"
        props["mail.user"] = email.from
        props[""] = server
        props["mail.smtp.port"] = port
        props["mail.smtp.starttls.enable"] = "true"
        props[""] = server
        props["mail.mime.charset"] = "UTF-8"
        val msg: Message = MimeMessage(Session.getDefaultInstance(props, email.auth))
        msg.sentDate = Calendar.getInstance().time
        msg.setRecipients(Message.RecipientType.TO, email.toList.toTypedArray())
//      msg.setRecipients(Message.RecipientType.CC, email.ccList.toTypedArray())
//      msg.setRecipients(Message.RecipientType.BCC, email.bccList.toTypedArray())
        msg.replyTo = arrayOf(email.from)

        msg.addHeader("X-Mailer", CLIENT_NAME)
        msg.addHeader("Precedence", "bulk")
        msg.subject = email.subject

        msg.setContent(MimeMultipart().apply {
            addBodyPart(MimeBodyPart().apply {
                setText(email.body, "iso-8859-1")
                //setContent(email.htmlBody, "text/html; charset=UTF-8")

    companion object {
        const val CLIENT_NAME = "Android StackOverflow programmatic email"


dependencies {
    implementation 'com.sun.mail:android-mail:1.6.4'
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.3"


<uses-permission name="android.permission.INTERNET" />

Android ListView Text Color

I needed to make a ListView with items of different colors. I modified Shardul's method a bit and result in this:

ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                this, android.R.layout.simple_list_item_1, colorString) {
            public View getView(int position, View convertView, ViewGroup parent) {
                TextView textView = (TextView) super.getView(position, convertView, parent);
                return textView;

assignBackgroundColor() and assignTextColor() are methods that assign color you want. They can be replaced with int[] arrays.

How to change color of ListView items on focus and on click

<selector xmlns:android="" >    
    <item android:state_pressed="true" android:drawable="@drawable/YOUR DRAWABLE XML" /> 
    <item android:drawable="@drawable/YOUR DRAWABLE XML" />

MySQL Foreign Key Error 1005 errno 150 primary key as foreign key

Give attention to CHARSET and COLLATE parameters when you create a table. In terms of FOREIGN KEY problems something like that:

CREATE TABLE yourTableName (
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

In my case i couldn´t create the table with FOREIGN KEY references. First i got the Error Code 1005 which pretty much says nothing. Then i added COLLATE and finally the error message complaining about CHARSET.

Error Code: 1253. COLLATION 'utf8_unicode_ci' is not valid for CHARACTER SET 'latin1'

After that correction my issue was solved.

How to store a list in a column of a database table

I was very reluctant to choose the path I finally decide to take because of many answers. While they add more understanding to what is SQL and its principles, I decided to become an outlaw. I was also hesitant to post my findings as for some it's more important to vent frustration to someone breaking the rules rather than understanding that there are very few universal truthes.

I have tested it extensively and, in my specific case, it was way more efficient than both using array type (generously offered by PostgreSQL) or querying another table.

Here is my answer: I have successfully implemented a list into a single field in PostgreSQL, by making use of the fixed length of each item of the list. Let say each item is a color as an ARGB hex value, it means 8 char. So you can create your array of max 10 items by multiplying by the length of each item:

ALTER product ADD color varchar(80)

In case your list items length differ you can always fill the padding with \0

NB: Obviously this is not necessarily the best approach for hex number since a list of integers would consume less storage but this is just for the purpose of illustrating this idea of array by making use of a fixed length allocated to each item.

The reason why: 1/ Very convenient: retrieve item i at substring i*n, (i +1)*n. 2/ No overhead of cross tables queries. 3/ More efficient and cost-saving on the server side. The list is like a mini blob that the client will have to split.

While I respect people following rules, many explanations are very theoretical and often fail to acknowledge that, in some specific cases, especially when aiming for cost optimal with low-latency solutions, some minor tweaks are more than welcome.

"God forbid that it is violating some holy sacred principle of SQL": Adopting a more open-minded and pragmatic approach before reciting the rules is always the way to go. Else you might end up like a candid fanatic reciting the Three Laws of Robotics before being obliterated by Skynet

I don't pretend that this solution is a breakthrough, nor that it is ideal in term of readability and database flexibility, but it can certainly give you an edge when it comes to latency.

Replace transparency in PNG images with white background

The only one that worked for me was a mix of all the answers:

convert in.png -background white -alpha remove -flatten -alpha off out.png

How to style UITextview to like Rounded Rect text field?

I don't think that it is possible. but you can do UITableView(grouped) with 1 section and 1 empty cell and use it as a container for your UITextView.

Extract only right most n letters from a string

Without resorting to the bit converter and bit shifting (need to be sure of encoding) this is fastest method I use as an extension method 'Right'.

string myString = "123456789123456789";

if (myString > 6)

        char[] cString = myString.ToCharArray();
        Array.Resize(ref myString, 6);
        string val = new string(myString);

Intercept page exit event

See this article. The feature you are looking for is the onbeforeunload

sample code:

  <script language="JavaScript">
  window.onbeforeunload = confirmExit;
  function confirmExit()
    return "You have attempted to leave this page.  If you have made any changes to the fields without clicking the Save button, your changes will be lost.  Are you sure you want to exit this page?";

How to send HTTP request in java?

You can use

Example (from here), with improvements. Included in case of link rot:

public static String executePost(String targetURL, String urlParameters) {
  HttpURLConnection connection = null;

  try {
    //Create connection
    URL url = new URL(targetURL);
    connection = (HttpURLConnection) url.openConnection();

    connection.setRequestProperty("Content-Language", "en-US");  


    //Send request
    DataOutputStream wr = new DataOutputStream (

    //Get Response  
    InputStream is = connection.getInputStream();
    BufferedReader rd = new BufferedReader(new InputStreamReader(is));
    StringBuilder response = new StringBuilder(); // or StringBuffer if Java version 5+
    String line;
    while ((line = rd.readLine()) != null) {
    return response.toString();
  } catch (Exception e) {
    return null;
  } finally {
    if (connection != null) {

Generate random string/characters in JavaScript

This works for sure

<script language="javascript" type="text/javascript">
function randomString() {
 var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz";
 var string_length = 8;
 var randomstring = '';
 for (var i=0; i<string_length; i++) {
  var rnum = Math.floor(Math.random() * chars.length);
  randomstring += chars.substring(rnum,rnum+1);
 document.randform.randomfield.value = randomstring;

How to make a <ul> display in a horizontal row

List items are normally block elements. Turn them into inline elements via the display property.

In the code you gave, you need to use a context selector to make the display: inline property apply to the list items, instead of the list itself (applying display: inline to the overall list will have no effect):

#ul_top_hypers li {
    display: inline;

Here is the working example:

#div_top_hypers {_x000D_
    display:inline;      _x000D_
#ul_top_hypers li{_x000D_
    display: inline;_x000D_
<div id="div_top_hypers">_x000D_
    <ul id="ul_top_hypers">_x000D_
        <li>&#8227; <a href="" class="a_top_hypers"> Inbox</a></li>_x000D_
        <li>&#8227; <a href="" class="a_top_hypers"> Compose</a></li>_x000D_
        <li>&#8227; <a href="" class="a_top_hypers"> Reports</a></li>_x000D_
        <li>&#8227; <a href="" class="a_top_hypers"> Preferences</a></li>_x000D_
        <li>&#8227; <a href="" class="a_top_hypers"> logout</a></li>_x000D_

Making a UITableView scroll when text field is selected

Combining and filling in the blanks from several answers (in particular Ortwin Gentz, user 98013) and another post, this will work out of the box for SDK 4.3 on an iPad in Portrait or Landscape mode:

@implementation UIView (FindFirstResponder)
- (UIResponder *)findFirstResponder
  if (self.isFirstResponder) {        
    return self;     

  for (UIView *subView in self.subviews) {
    UIResponder *firstResponder = [subView findFirstResponder];
    if (firstResponder != nil) {
      return firstResponder;

  return nil;

@implementation MyViewController

- (UIResponder *)currentFirstResponder {
  return [self.view findFirstResponder];

- (IBAction)editingEnded:sender {
  [sender resignFirstResponder];

- (BOOL)textFieldShouldReturn:(UITextField *)textField {
  [textField resignFirstResponder];
  return NO;

- (void)textFieldDidBeginEditing:(UITextField *)textField {
  UITableViewCell *cell = (UITableViewCell*) [[textField superview] superview];
  [_tableView scrollToRowAtIndexPath:[_tableView indexPathForCell:cell] atScrollPosition:UITableViewScrollPositionTop animated:YES];

- (void)keyboardWillShow:(NSNotification*)notification {
  if ([self currentFirstResponder] != nil) {
    NSDictionary* userInfo = [notification userInfo];

    // we don't use SDK constants here to be universally compatible with all SDKs = 3.0
    NSValue* keyboardFrameValue = [userInfo objectForKey:@"UIKeyboardBoundsUserInfoKey"];
    if (!keyboardFrameValue) {
      keyboardFrameValue = [userInfo objectForKey:@"UIKeyboardFrameEndUserInfoKey"];

    // Reduce the tableView height by the part of the keyboard that actually covers the tableView
    CGRect windowRect = [[UIApplication sharedApplication] keyWindow].bounds;
    CGRect viewRectAbsolute = [_tableView convertRect:_tableView.bounds toView:[[UIApplication sharedApplication] keyWindow]];
    CGRect frame = _tableView.frame;
    if (UIInterfaceOrientationLandscapeLeft == self.interfaceOrientation ||UIInterfaceOrientationLandscapeRight == self.interfaceOrientation ) {
      windowRect = CGRectMake(windowRect.origin.y, windowRect.origin.x, windowRect.size.height, windowRect.size.width);
      viewRectAbsolute = CGRectMake(viewRectAbsolute.origin.y, viewRectAbsolute.origin.x, viewRectAbsolute.size.height, viewRectAbsolute.size.width);
    frame.size.height -= [keyboardFrameValue CGRectValue].size.height - CGRectGetMaxY(windowRect) + CGRectGetMaxY(viewRectAbsolute);

    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:[[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue]];
    [UIView setAnimationCurve:[[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue]];
    _tableView.frame = frame;
    [UIView commitAnimations];

    UITableViewCell *textFieldCell = (id)((UITextField *)self.currentFirstResponder).superview.superview;
    NSIndexPath *textFieldIndexPath = [_tableView indexPathForCell:textFieldCell];

    // iOS 3 sends hide and show notifications right after each other
    // when switching between textFields, so cancel -scrollToOldPosition requests
    [NSObject cancelPreviousPerformRequestsWithTarget:self];
    _topmostRowBeforeKeyboardWasShown = [[_tableView indexPathsForVisibleRows] objectAtIndex:0];
    [_tableView scrollToRowAtIndexPath:textFieldIndexPath atScrollPosition:UITableViewScrollPositionMiddle animated:YES];

- (void) scrollToOldPosition {
  [_tableView scrollToRowAtIndexPath:_topmostRowBeforeKeyboardWasShown atScrollPosition:UITableViewScrollPositionTop animated:YES];

- (void)keyboardWillHide:(NSNotification*)notification {
  if ([self currentFirstResponder] != nil) {

    NSDictionary* userInfo = [notification userInfo];

    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:[[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue]];
    [UIView setAnimationCurve:[[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue]];
    _tableView.frame = self.view.bounds;
    [UIView commitAnimations];

    [self performSelector:@selector(scrollToOldPosition) withObject:nil afterDelay:0.1];


Javascript: how to validate dates in format MM-DD-YYYY?

DateFormat = DD.MM.YYYY or D.M.YYYY

function dateValidate(val){ 
var dateStr = val.split('.'); 
  var date = new Date(dateStr[2], dateStr[1]-1, dateStr[0]); 
  if(date.getDate() == dateStr[0] && date.getMonth()+1 == dateStr[1] && date.getFullYear() == dateStr[2])
  { return date; }
  else{ return 'NotValid';} 

How do I iterate over the words of a string?

I've been searching for a way to split a string by a separator of any length, so I started writing it from scratch, as existing solutions didn't suit me.

Here is my little algorithm, using only STL:

//use like this
//std::vector<std::wstring> vec = Split<std::wstring> (L"Hello##world##!", L"##");

template <typename valueType>
static std::vector <valueType> Split (valueType text, const valueType& delimiter)
    std::vector <valueType> tokens;
    size_t pos = 0;
    valueType token;

    while ((pos = text.find(delimiter)) != valueType::npos) 
        token = text.substr(0, pos);
        tokens.push_back (token);
        text.erase(0, pos + delimiter.length());
    tokens.push_back (text);

    return tokens;

It can be used with separator of any length and form, as far as I've tested. Instantiate with either string or wstring type.

All the algorithm does is it searches for the delimiter, gets the part of the string that is up to the delimiter, deletes the delimiter and searches again until it finds it no more.

Of course, you can use any number of whitespaces for the delimiter.

I hope it helps.

Vue.js toggle class on click

If you need more than 1 class

You can do this:

<i id="icon" 
  v-bind:class="{ 'fa fa-star': showStar }"
  v-on:click="showStar = !showStar"

data: {
  showStar: true

Notice the single quotes ' around the classes!

Thanks to everyone else's solutions.

How to obtain Telegram chat_id for a specific user?

Straight out from the documentation:

Suppose the website would like to send notifications to its users via a Telegram bot. Here's what they could do to enable notifications for a user with the ID 123.

  1. Create a bot with a suitable username, e.g. @ExampleComBot
  2. Set up a webhook for incoming messages
  3. Generate a random string of a sufficient length, e.g. $memcache_key = "vCH1vGWJxfSeofSAs0K5PA"
  4. Put the value 123 with the key $memcache_key into Memcache for 3600 seconds (one hour)
  5. Show our user the button
  6. Configure the webhook processor to query Memcached with the parameter that is passed in incoming messages beginning with /start. If the key exists, record the chat_id passed to the webhook as telegram_chat_id for the user 123. Remove the key from Memcache.
  7. Now when we want to send a notification to the user 123, check if they have the field telegram_chat_id. If yes, use the sendMessage method in the Bot API to send them a message in Telegram.

How to extract filename.tar.gz file

Check to make sure that the file is complete. This error message can occur if you only partially downloaded a file or if it has major issues. Check the MD5sum.

Can we pass model as a parameter in RedirectToAction?

Yes you can pass the model that you have shown using

return RedirectToAction("GetStudent", "Student", student1 );

assuming student1 is an instance of Student

which will generate the following url (assuming your using the default routes and the value of student1 are ID=4 and Name="Amit")


Internally the RedirectToAction() method builds a RouteValueDictionary by using the .ToString() value of each property in the model. However, binding will only work if all the properties in the model are simple properties and it fails if any properties are complex objects or collections because the method does not use recursion. If for example, Student contained a property List<string> Subjects, then that property would result in a query string value of


and binding would fail and that property would be null

What port is a given program using?

netstat -b -a lists the ports in use and gives you the executable that's using each one. I believe you need to be in the administrator group to do this, and I don't know what security implications there are on Vista.

I usually add -n as well to make it a little faster, but adding -b can make it quite slow.

Edit: If you need more functionality than netstat provides, vasac suggests that you try TCPView.

how to use concatenate a fixed string and a variable in Python

I'm guessing that you meant to do this:

msg['Subject'] = "Auto Hella Restart Report " + sys.argv[1]
# To concatenate strings in python, use       ^ 

Display back button on action bar

Official solution

Add those two code snippets to your SubActivity

public void onCreate(Bundle savedInstanceState) {

public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    // Respond to the action bar's Up/Home button
        return true;
    return super.onOptionsItemSelected(item);

add meta-data and parentActivity to manifest to support lower sdk.

 <application ... >
    <!-- The main/home activity (it has no parent activity) -->
        android:name="com.example.myfirstapp.MainActivity" ...>
    <!-- A child of the main activity -->
        android:parentActivityName="com.example.myfirstapp.MainActivity" >
        <!-- Parent activity meta-data to support 4.0 and lower -->
            android:value="com.example.myfirstapp.MainActivity" />

Reference here:

How do I set the default font size in Vim?

For the first one remove the spaces. Whitespace matters for the set command.

set guifont=Monaco:h20

For the second one it should be (the h specifies the height)

set guifont=Monospace:h20

My recommendation for setting the font is to do (if your version supports it)

set guifont=*

This will pop up a menu that allows you to select the font. After selecting the font, type

set guifont?

To show what the current guifont is set to. After that copy that line into your vimrc or gvimrc. If there are spaces in the font add a \ to escape the space.

set guifont=Monospace\ 20

Preprocessing in scikit learn - single sample - Depreciation warning

Just listen to what the warning is telling you:

Reshape your data either X.reshape(-1, 1) if your data has a single feature/column and X.reshape(1, -1) if it contains a single sample.

For your example type(if you have more than one feature/column):

temp = temp.reshape(1,-1) 

For one feature/column:

temp = temp.reshape(-1,1)

How to get records randomly from the oracle database?

( SELECT column, dbms_random.value FROM table ORDER BY 2 )
where rownum <= 20;

How to uninstall/upgrade Angular CLI?

I always use the following commands before upgrading to latest . If it is for Ubuntu prefix : 'sudo'

npm uninstall -g angular-cli
npm cache clean
npm install -g angular-cli@latest

Bootstrap 4 multiselect dropdown

Because the bootstrap-select is a bootstrap component and therefore you need to include it in your code as you did for your V3

NOTE: this component only works in since version 1.13.0

<link rel="stylesheet" href="">_x000D_
<link rel="stylesheet" href="" />_x000D_
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<select class="selectpicker" multiple data-live-search="true">_x000D_

Getting an object array from an Angular service

Take a look at your code :

 getUsers(): Observable<User[]> {
        return Observable.create(observer => {
            this.http.get('').map(response => response.json();

and code from (BTW. really good tutorial, you should check it out)

 getHeroes(): Promise<Hero[]> {
    return this.http.get(this.heroesUrl)
               .then(response => response.json().data as Hero[])

The HttpService inside Angular2 already returns an observable, sou don't need to wrap another Observable around like you did here:

   return Observable.create(observer => {
        this.http.get('').map(response => response.json()

Try to follow the guide in link that I provided. You should be just fine when you study it carefully.


First of all WHERE you log the this.users variable? JavaScript isn't working that way. Your variable is undefined and it's fine, becuase of the code execution order!

Try to do it like this:

  getUsers(): void {
            .then(users => {
               this.users = users
               console.log('this.users=' + this.users);


See where the console.log(...) is!

Try to resign from toPromise() it's seems to be just for ppl with no RxJs background.

Catch another link: Build your service once again with RxJs observables.

Reading integers from binary file in Python

As of Python 3.2+, you can also accomplish this using the from_bytes native int method:

file_size = int.from_bytes(, byteorder='big')

Note that this function requires you to specify whether the number is encoded in big- or little-endian format, so you will have to determine the endian-ness to make sure it works correctly.

how to add super privileges to mysql database?

You can add super privilege using phpmyadmin:

Go to PHPMYADMIN > privileges > Edit User > Under Administrator tab Click SUPER. > Go

If you want to do it through Console, do like this:

 mysql> GRANT SUPER ON *.* TO user@'localhost' IDENTIFIED BY 'password';

After executing above code, end it with:


You should do in on *.* because SUPER is not the privilege that applies just to one database, it's global.

How to get main window handle from process id?

Though it may be unrelated to your question, take a look at GetGUIThreadInfo Function.

How to access at request attributes in JSP?

EL expression:


There are several implicit objects in JSP EL. See Expression Language under the "Implicit Objects" heading.

Use of the MANIFEST.MF file in Java

Manifest.MF contains information about the files contained in the JAR file.

Whenever a JAR file is created a default file is created inside META-INF folder and it contains the default entries like this:

Manifest-Version: 1.0
Created-By: 1.7.0_06 (Oracle Corporation)

These are entries as “header:value” pairs. The first one specifies the manifest version and second one specifies the JDK version with which the JAR file is created.

Main-Class header: When a JAR file is used to bundle an application in a package, we need to specify the class serving an entry point of the application. We provide this information using ‘Main-Class’ header of the manifest file,

Main-Class: {fully qualified classname}

The ‘Main-Class’ value here is the class having main method. After specifying this entry we can execute the JAR file to run the application.

Class-Path header: Most of the times we need to access the other JAR files from the classes packaged inside application’s JAR file. This can be done by providing their fully qualified paths in the manifest file using ‘Class-Path’ header,

Class-Path: {jar1-name jar2-name directory-name/jar3-name}

This header can be used to specify the external JAR files on the same local network and not inside the current JAR.

Package version related headers: When the JAR file is used for package versioning the following headers are used as specified by the Java language specification:

Headers in a manifest
Header                  | Definition
Name                    | The name of the specification.
Specification-Title     | The title of the specification.
Specification-Version   | The version of the specification.
Specification-Vendor    | The vendor of the specification.
Implementation-Title    | The title of the implementation.
Implementation-Version  | The build number of the implementation.
Implementation-Vendor   | The vendor of the implementation.

Package sealing related headers:

We can also specify if any particular packages inside a JAR file should be sealed meaning all the classes defined in that package must be archived in the same JAR file. This can be specified with the help of ‘Sealed’ header,

Name: {package/some-package/} Sealed:true

Here, the package name must end with ‘/’.

Enhancing security with manifest files:

We can use manifest files entries to ensure the security of the web application or applet it packages with the different attributes as ‘Permissions’, ‘Codebae’, ‘Application-Name’, ‘Trusted-Only’ and many more.

META-INF folder:

This folder is where the manifest file resides. Also, it can contain more files containing meta data about the application. For example, in an EJB module JAR file, this folder contains the EJB deployment descriptor for the EJB module along with the manifest file for the JAR. Also, it contains the xml file containing mapping of an abstract EJB references to concrete container resources of the application server on which it will be run.


How to initialize a list of strings (List<string>) with many string values

List<string> mylist = new List<string>(new string[] { "element1", "element2", "element3" });

How to change angular port from 4200 to any other

Just Run

ng serve --port yourport


ng serve --port 4401

Why do people use Heroku when AWS is present? What distinguishes Heroku from AWS?

Well! I observer Heroku is famous in budding and newly born developers while AWS has advanced developer persona. DigitalOcean is also a major player in this ground. Cloudways has made it much easy to create Lamp stack in a click on DigitalOcean and AWS. Having all services and packages updates in a click is far better than doing all thing manually.

You can check out completely here:

How to get a matplotlib Axes instance to plot to?

Use the gca ("get current axes") helper function:

ax = plt.gca()


import matplotlib.pyplot as plt
quotes = [(1, 5, 6, 7, 4), (2, 6, 9, 9, 6), (3, 9, 8, 10, 8), (4, 8, 8, 9, 8), (5, 8, 11, 13, 7)]
ax = plt.gca()
h =, quotes)

enter image description here

What is context in _.each(list, iterator, [context])?

context is where this refers to in your iterator function. For example:

var person = {};
person.friends = {
  name1: true,
  name2: false,
  name3: true,
  name4: true

_.each(['name4', 'name2'], function(name){
  // this refers to the friends property of the person object
}, person.friends);

How do you change Background for a Button MouseOver in WPF?

To remove the default MouseOver behaviour on the Button you will need to modify the ControlTemplate. Changing your Style definition to the following should do the trick:

<Style TargetType="{x:Type Button}">
    <Setter Property="Background" Value="Green"/>
    <Setter Property="Template">
            <ControlTemplate TargetType="{x:Type Button}">
                <Border Background="{TemplateBinding Background}" BorderBrush="Black" BorderThickness="1">
                    <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
        <Trigger Property="IsMouseOver" Value="True">
            <Setter Property="Background" Value="Red"/>

EDIT: It's a few years late, but you are actually able to set the border brush inside of the border that is in there. Idk if that was pointed out but it doesn't seem like it was...

Check if an object exists

If the user exists you can get the user in user_object else user_object will be None.

    user_object = User.objects.get(email = cleaned_info['username'])
except User.DoesNotExist:
    user_object = None
if user_object:
    # user exist
    # user does not exist

What is the maximum length of data I can put in a BLOB column in MySQL?

A BLOB can be 65535 bytes maximum. If you need more consider using a MEDIUMBLOB for 16777215 bytes or a LONGBLOB for 4294967295 bytes.

Hope, it will help you.

Initializing multiple variables to the same value in Java

Works for primitives and immutable classes like String, Wrapper classes Character, Byte.

int i=0,j=2   
String s1,s2  
s1 = s2 = "java rocks"

For mutable classes

Reference r1 = Reference r2 = Reference r3 = new Object();`  

Three references + one object are created. All references point to the same object and your program will misbehave.

What's the difference between an argument and a parameter?

Parameters are the variables received by a function.Hence they are visible in function declaration.They contain the variable name with their data type. Arguments are actual values which are passed to another function. thats why we can see them in function call. They are just values without their datatype

docker command not found even though installed with apt-get

The Ubuntu package docker actually refers to a GUI application, not the beloved DevOps tool we've come out to look for.

The instructions for docker can be followed per instructions on the docker page here:

=== UPDATED (thanks @Scott Stensland) ===

You now run the following install script to get docker:

`sudo curl -sSL | sh`
  • Note: review the script on the website and make sure you have the right link before continuing since you are running this as sudo.

This will run a script that installs docker. Note the last part of the script:

If you would like to use Docker as a non-root user, you should now consider
adding your user to the "docker" group with something like:

  `sudo usermod -aG docker stens`

Remember that you will have to log out and back in for this to take effect!

To update Docker run:

`sudo apt-get update && sudo apt-get upgrade`

For more details on what's going on, See the docker install documentation or @Scott Stensland's answer below


=== UPDATE: For those uncomfortable w/ sudo | sh ===

Some in the comments have mentioned that it a risk to run an arbitrary script as sudo. The above option is a convenience script from docker to make the task simple. However, for those that are security-focused but don't want to read the script you can do the following:

  1. Add Dependencies
sudo apt-get update; \
sudo apt-get install \
 apt-transport-https \
 ca-certificates \
 curl \
 gnupg-agent \
  1. Add docker gpg key

curl -fsSL | sudo apt-key add -

(Security check, verify key fingerprint 9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88

$ sudo apt-key fingerprint 0EBFCD88

pub   rsa4096 2017-02-22 [SCEA]
      9DC8 5822 9FC7 DD38 854A  E2D8 8D81 803C 0EBF CD88
uid           [ unknown] Docker Release (CE deb) <[email protected]>
sub   rsa4096 2017-02-22 [S]


  1. Setup Repository
sudo add-apt-repository \
   "deb [arch=amd64] \
   $(lsb_release -cs) \
  1. Install Docker
sudo apt-get update; \
sudo apt-get install docker-ce docker-ce-cli

If you want to verify that it worked run: sudo docker run hello-world

The following explains why it is named like this: Why install docker on ubuntu should be `sudo apt-get install`?

Sending emails in Node.js?

Complete Code to send Email Using nodemailer Module

var mailer = require("nodemailer");

// Use Smtp Protocol to send Email
var smtpTransport = mailer.createTransport("SMTP",{
    service: "Gmail",
    auth: {
        user: "[email protected]",
        pass: "gmail_password"

var mail = {
    from: "Yashwant Chavan <[email protected]>",
    to: "[email protected]",
    subject: "Send Email Using Node.js",
    text: "Node.js New world for me",
    html: "<b>Node.js New world for me</b>"

smtpTransport.sendMail(mail, function(error, response){
        console.log("Message sent: " + response.message);


How do I determine the current operating system with Node.js

Works fine for me

if (/^win/i.test(process.platform)) {
    // TODO: Windows
} else {
    // TODO: Linux, Mac or something else

The i modifier is used to perform case-insensitive matching.

How do I reference a local image in React?

I found another way to implement this (this is a functional component):

const Image = ({icon}) => {
   const Img = require(`./path_to_your_file/${icon}.svg`).ReactComponent;
   return <Img />

Hope it helps!

How to check if one DateTime is greater than the other in C#

You can use the overloaded < or > operators.

For example:

DateTime d1 = new DateTime(2008, 1, 1);
DateTime d2 = new DateTime(2008, 1, 2);
if (d1 < d2) { ...

How do I wait for an asynchronously dispatched block to finish?

Here's a nifty trick that doesn't use a semaphore:

dispatch_queue_t serialQ = dispatch_queue_create("serialQ", DISPATCH_QUEUE_SERIAL);
dispatch_async(serialQ, ^
    [object doSomething];
dispatch_sync(serialQ, ^{ });

What you do is wait using dispatch_sync with an empty block to Synchronously wait on a serial dispatch queue until the A-Synchronous block has completed.

Typescript export vs. default export

I was trying to solve the same problem, but found an interesting advice by Basarat Ali Syed, of TypeScript Deep Dive fame, that we should avoid the generic export default declaration for a class, and instead append the export tag to the class declaration. The imported class should be instead listed in the import command of the module.

That is: instead of

class Foo {
    // ...
export default Foo;

and the simple import Foo from './foo'; in the module that will import, one should use

export class Foo {
    // ...

and import {Foo} from './foo' in the importer.

The reason for that is difficulties in the refactoring of classes, and the added work for exportation. The original post by Basarat is in export default can lead to problems

Timer for Python game

New to the python world!
I need a System Time independent Stopwatch so I did translate my old C++ class into Python:

from ctypes.wintypes import DWORD
import win32api
import datetime

class Stopwatch:

    def __init__(self):

    def Restart(self):
        self.__ulStartTicks = DWORD(win32api.GetTickCount()).value

    def ElapsedMilliSecs(self):
        return DWORD(DWORD(win32api.GetTickCount()).value-DWORD(self.__ulStartTicks).value).value

    def ElapsedTime(self):
        return datetime.timedelta(milliseconds=self.ElapsedMilliSecs())

This has no 49 days run over issue due to DWORD math but NOTICE that GetTickCount has about 15 milliseconds granularity so do not use this class if your need 1-100 milliseconds elapsed time ranges.

Any improvement or feedback is welcome!

How to check if a directory containing a file exist?

EDIT: as of Java8 you'd better use Files class:

Path resultingPath = Files.createDirectories('A/B');

I don't know if this ultimately fixes your problem but class File has method mkdirs() which fully creates the path specified by the file.

File f = new File("/A/B/");

Java logical operator short-circuiting

boolean a = (x < z) && (x == x);

This kind will short-circuit, meaning if (x < z) evaluates to false then the latter is not evaluated, a will be false, otherwise && will also evaluate (x == x).

& is a bitwise operator, but also a boolean AND operator which does not short-circuit.

You can test them by something as follows (see how many times the method is called in each case):

public static boolean getFalse() {
    return false;

public static void main(String[] args) {
    if(getFalse() && getFalse()) { }        
    if(getFalse() & getFalse()) { }

git ahead/behind info between master and branch?

After doing a git fetch, you can run git status to show how many commits the local branch is ahead or behind of the remote version of the branch.

This won't show you how many commits it is ahead or behind of a different branch though. Your options are the full diff, looking at github, or using a solution like Vimhsa linked above: Git status over all repo's

How can I remove an element from a list, with lodash?

Here is the simple lodash function with array and deleting it with the index number.

index_tobe_delete = 1

fruit = [{a: "apple"}, {b: "banana"}, {c: "choco"}]
_.filter(fruit, (value, key)=> {
return (key !== index_tobe_delete)

How to check a channel is closed or not without reading it?

If you listen this channel you always can findout that channel was closed.

case state, opened := <-ws:
    if !opened {
         // channel was closed 
         // return or made some final work
    switch state {
        case Stopped:

But remember, you can not close one channel two times. This will raise panic.

Difference between window.location.href and top.location.href

window.location.href returns the location of the current page.

top.location.href (which is an alias of returns the location of the topmost window in the window hierarchy. If a window has no parent, top is a reference to itself (in other words, window ===

top is useful both when you're dealing with frames and when dealing with windows which have been opened by other pages. For example, if you have a page called test.html with the following script:


The resulting alert will have the full path to test.html – not about:blank, which is what window.location.href would return.

To answer your question about redirecting, go with window.location.assign(url);

Inline CSS styles in React: how to implement a:hover?

The simple way is using ternary operator

var Link = React.createClass({
  getInitialState: function(){
    return {hover: false}
  toggleHover: function(){
    this.setState({hover: !this.state.hover})
  render: function() {
    var linkStyle;
    if (this.state.hover) {
      linkStyle = {backgroundColor: 'red'}
    } else {
      linkStyle = {backgroundColor: 'blue'}
        <a style={this.state.hover ? {"backgroundColor": 'red'}: {"backgroundColor": 'blue'}} onMouseEnter={this.toggleHover} onMouseLeave={this.toggleHover}>Link</a>

Eclipse keyboard shortcut to indent source code to the left?

For Mac Users who using Eclipse Use Cmd + I(Indent) and Cmd + F(Format). But I had worst experience with Cmd + F which breaks the code in to several lines as follows

String A = MyClass.getA(x, y);
if (A != null) {
    A = Long.parseLong(0);

Where my original code is as follows

String A = MyClass.get(x, y);
if (A != null) {
    A = Long.parseLong(0);

jQuery: how to scroll to certain anchor/div on page load?

I have tried some hours now and the easiest way to stop browsers to jump to the anchor instead of scrolling to it is: Using another anchor (an id you do not use on the site). So instead of linking to "http://#YourActualID" you link to "http://#NoIDonYourSite". Poof, browsers won’t jump anymore.

Then just check if an anchor is set (with the script provided below, that is pulled out of the other thread!). And set your actual id you want to scroll to.


    // Remove the # from the hash, as different browsers may or may not include it
    var hash = location.hash.replace('#','');

    if(hash != ''){

       // Clear the hash in the URL
       // location.hash = '';   // delete front "//" if you want to change the address bar
        $('html, body').animate({ scrollTop: $('#YourIDtoScrollTo').offset().top}, 1000);


See for a working example.

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

Easy and without LINQ:

while (parameterList.Remove(null)) {};

Why does JavaScript only work after opening developer tools in IE once?

If you are using AngularJS version 1.X you could use the $log service instead of using console.log directly.

Simple service for logging. Default implementation safely writes the message into the browser's console (if present).$log

So if you have something similar to

angular.module('logExample', [])
  .controller('LogController', ['$scope', function($scope) {
    console.log('Hello World!');

you can replace it with

angular.module('logExample', [])
  .controller('LogController', ['$scope', '$log', function($scope, $log) {
    $log.log('Hello World!');

Angular 2+ does not have any built-in log service.

How to test the `Mosquitto` server?

If you wish to have an GUI based broker testing without installing any tool you can use Hive Mqtt web socket for testing your Mosquitto server

just visit and enter server connection details.

If you got connected means your server is configured properly.

You can also test publish and subscribe of messages using this mqtt web socket

PHPmailer sending HTML CODE

In version 5.2.7 I use this to send plain text: $mail->set('Body', $Body);

How to set initial value and auto increment in MySQL?

SET GLOBAL auto_increment_offset=1;

SET GLOBAL auto_increment_increment=5;

auto_increment_offset: interval between successive column values

auto_increment_offset: determines the starting point for the AUTO_INCREMENT column value. The default value is 1.

read more here

How to create a sticky navigation bar that becomes fixed to the top after scrolling

For Bootstrap 4, a new class was released for this. According to the utilties docs:

Apply the class sticky-top.

<div class="sticky-top">...</div>

For further navbar position options, visit here. Also, keep in mind that position: sticky; is not supported in every browser so this may not be the best solution for you if you need to support older browsers.

java.lang.NoSuchMethodError: javax.servlet.ServletContext.getContextPath()Ljava/lang/String;

java.lang.NoSuchMethodError: javax.servlet.ServletContext.getContextPath()Ljava/lang/String;

That method was added in Servlet 2.5.

So this problem can have at least 3 causes:

  1. The servlet container does not support Servlet 2.5.
  2. The web.xml is not declared conform Servlet 2.5 or newer.
  3. The webapp's runtime classpath is littered with servlet container specific JAR files of a different servlet container make/version which does not support Servlet 2.5.

To solve it,

  1. Make sure that your servlet container supports at least Servlet 2.5. That are at least Tomcat 6, Glassfish 2, JBoss AS 4.1, etcetera. Tomcat 5.5 for example supports at highest Servlet 2.4. If you can't upgrade Tomcat, then you'd need to downgrade Spring to a Servlet 2.4 compatible version.
  2. Make sure that the root declaration of web.xml complies Servlet 2.5 (or newer, at least the highest whatever your target runtime supports). For an example, see also somewhere halfway our servlets wiki page.
  3. Make sure that you don't have any servlet container specific libraries like servlet-api.jar or j2ee.jar in /WEB-INF/lib or even worse, the JRE/lib or JRE/lib/ext. They do not belong there. This is a pretty common beginner's mistake in an attempt to circumvent compilation errors in an IDE, see also How do I import the javax.servlet API in my Eclipse project?.

How to test if a double is zero?

Yes; all primitive numeric types default to 0.

However, calculations involving floating-point types (double and float) can be imprecise, so it's usually better to check whether it's close to 0:

if (Math.abs(foo.x) < 2 * Double.MIN_VALUE)

You need to pick a margin of error, which is not simple.

difference between $query>num_rows() and $this->db->count_all_results() in CodeIgniter & which one is recommended

There are two ways to count total number of records that the query will return. First this

$query = $this->db->query('select blah blah');  
return $query->num_rows();

This will return number of rows the query brought.


return $this->db->count_all_results('select blah blah');

Simply count_all_results will require to run the query again.

Create space at the beginning of a UITextField

Put this code in your viewDidLoad():

textField.delegate = self

let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: 20, height: self.textField.frame.height))
textField.leftView = paddingView
textField.leftViewMode = UITextFieldViewMode.always

It works for me :)

Deep copy in ES6 using the spread syntax

function deepclone(obj) {
    let newObj = {};

    if (typeof obj === 'object') {
        for (let key in obj) {
            let property = obj[key],
                type = typeof property;
            switch (type) {
                case 'object':
                    if( property ) === '[object Array]' ) {
                        newObj[key] = [];
                        for (let item of property) {
                    } else {
                        newObj[key] = deepclone(property);
                    newObj[key] = property;

        return newObj
    } else {
        return obj;

generate model using user:references vs user_id:integer

how does rails know that user_id is a foreign key referencing user?

Rails itself does not know that user_id is a foreign key referencing user. In the first command rails generate model Micropost user_id:integer it only adds a column user_id however rails does not know the use of the col. You need to manually put the line in the Micropost model

class Micropost < ActiveRecord::Base
  belongs_to :user

class User < ActiveRecord::Base
  has_many :microposts

the keywords belongs_to and has_many determine the relationship between these models and declare user_id as a foreign key to User model.

The later command rails generate model Micropost user:references adds the line belongs_to :user in the Micropost model and hereby declares as a foreign key.

Declaring the foreign keys using the former method only lets the Rails know about the relationship the models/tables have. The database is unknown about the relationship. Therefore when you generate the EER Diagrams using software like MySql Workbench you find that there is no relationship threads drawn between the models. Like in the following pic enter image description here

However, if you use the later method you find that you migration file looks like:

def change
    create_table :microposts do |t|
      t.references :user, index: true

      t.timestamps null: false
    add_foreign_key :microposts, :users

Now the foreign key is set at the database level. and you can generate proper EER diagrams. enter image description here

Generate a random number in the range 1 - 10

To summarize and a bit simplify, you can use:

-- 0 - 9
select floor(random() * 10);
-- 0 - 10
SELECT floor(random() * (10 + 1));
-- 1 - 10
SELECT ceil(random() * 10);

And you can test this like mentioned by @user80168

-- 0 - 9
SELECT min(i), max(i) FROM (SELECT floor(random() * 10) AS i FROM generate_series(0, 100000)) q;
-- 0 - 10
SELECT min(i), max(i) FROM (SELECT floor(random() * (10 + 1)) AS i FROM generate_series(0, 100000)) q;
-- 1 - 10
SELECT min(i), max(i) FROM (SELECT ceil(random() * 10) AS i FROM generate_series(0, 100000)) q;

CAML query with nested ANDs and ORs for multiple fields

Since you are not allowed to put more than two conditions in one condition group (And | Or) you have to create an extra nested group (MSDN). The expression A AND B AND C looks like this:


Your SQL like sample translated to CAML (hopefully with matching XML tags ;) ):

                <FieldRef Name='FirstName' />
                <Value Type='Text'>John</Value>
                    <FieldRef Name='LastName' />
                    <Value Type='Text'>John</Value>
                    <FieldRef Name='Profile' />
                    <Value Type='Text'>John</Value>
                    <FieldRef Name='FirstName' />
                    <Value Type='Text'>Doe</Value>
                        <FieldRef Name='LastName' />
                        <Value Type='Text'>Doe</Value>
                        <FieldRef Name='Profile' />
                        <Value Type='Text'>Doe</Value>
                    <FieldRef Name='FirstName' />
                    <Value Type='Text'>123</Value>
                        <FieldRef Name='LastName' />
                        <Value Type='Text'>123</Value>
                        <FieldRef Name='Profile' />
                        <Value Type='Text'>123</Value>

adding a datatable in a dataset

I assume that you haven't set the TableName property of the DataTable, for example via constructor:

var tbl = new DataTable("dtImage");

If you don't provide a name, it will be automatically created with "Table1", the next table will get "Table2" and so on.

Then the solution would be to provide the TableName and then check with Contains(nameOfTable).

To clarify it: You'll get an ArgumentException if that DataTable already belongs to the DataSet (the same reference). You'll get a DuplicateNameException if there's already a DataTable in the DataSet with the same name(not case-sensitive).

SQL Server Error : String or binary data would be truncated

You're trying to write more data than a specific column can store. Check the sizes of the data you're trying to insert against the sizes of each of the fields.

In this case transaction_status is a varchar(10) and you're trying to store 19 characters to it.

Run a .bat file using python code

This has already been answered in detail on SO. Check out this thread, It should answer all your questions: Executing a subprocess fails

I've tried it myself with this code:

from subprocess import Popen
p = Popen("batch.bat", cwd=r"C:\Path\to\batchfolder")
stdout, stderr = p.communicate()


echo Hello World!

I've got the example from the aforementioned thread.

VBA paste range

This is what I came up to when trying to copy-paste excel ranges with it's sizes and cell groups. It might be a little too specific for my problem but...:

'** 'Copies a table from one place to another 'TargetRange: where to put the new LayoutTable 'typee: If it is an Instalation Layout table(1) or Package Layout table(2) '**

Sub CopyLayout(TargetRange As Range, typee As Integer)
    Application.ScreenUpdating = False
        Dim ncolumn As Integer
        Dim nrow As Integer

    If (typee = 1) Then 'is installation
        Range("installationlayout").Copy Destination:=TargetRange '@SHEET2 TEM DE PASSAR A SER A SHEET DO PROJECT PLAN!@@@@@
    ElseIf (typee = 2) Then 'is package
        Range("PackageLayout").Copy Destination:=TargetRange '@SHEET2 TEM DE PASSAR A SER A SHEET DO PROJECT PLAN!@@@@@
    End If


    If typee = 1 Then
       nrow = SheetLayout.Range("installationlayout").Rows.Count
       ncolumn = SheetLayout.Range("installationlayout").Columns.Count

       Call RowHeightCorrector(SheetLayout.Range("installationlayout"), TargetRange.CurrentRegion, typee, nrow, ncolumn)
    ElseIf typee = 2 Then
       nrow = SheetLayout.Range("PackageLayout").Rows.Count
       ncolumn = SheetLayout.Range("PackageLayout").Columns.Count
       Call RowHeightCorrector(SheetLayout.Range("PackageLayout"), TargetRange.CurrentRegion, typee, nrow, ncolumn)
    End If
    Range("A1").Select 'Deselect the created table

    Application.CutCopyMode = False
    Application.ScreenUpdating = True
End Sub

'** 'Receives the Pasted Table Range and rearranjes it's properties 'accordingly to the original CopiedTable 'typee: If it is an Instalation Layout table(1) or Package Layout table(2) '**

Function RowHeightCorrector(CopiedTable As Range, PastedTable As Range, typee As Integer, RowCount As Integer, ColumnCount As Integer)
    Dim R As Long, C As Long

    For R = 1 To RowCount
        PastedTable.Rows(R).RowHeight = CopiedTable.CurrentRegion.Rows(R).RowHeight
        If R >= 2 And R < RowCount Then
            PastedTable.Rows(R).Group 'Main group of the table
        End If
        If R = 2 Then
            PastedTable.Rows(R).Group 'both type of tables have a grouped section at relative position "2" of Rows
        ElseIf (R = 4 And typee = 1) Then
            PastedTable.Rows(R).Group 'If it is an installation materials table, it has two grouped sections...
        End If
    Next R

    For C = 1 To ColumnCount
        PastedTable.Columns(C).ColumnWidth = CopiedTable.CurrentRegion.Columns(C).ColumnWidth
    Next C
End Function

Sub test ()
    Call CopyLayout(Sheet2.Range("A18"), 2)
end sub

How to detect internet speed in JavaScript?

It's possible to some extent but won't be really accurate, the idea is load image with a known file size then in its onload event measure how much time passed until that event was triggered, and divide this time in the image file size.

Example can be found here: Calculate speed using javascript

Test case applying the fix suggested there:

var imageAddr = ""; _x000D_
var downloadSize = 4995374; //bytes_x000D_
function ShowProgressMessage(msg) {_x000D_
    if (console) {_x000D_
        if (typeof msg == "string") {_x000D_
        } else {_x000D_
            for (var i = 0; i < msg.length; i++) {_x000D_
    var oProgress = document.getElementById("progress");_x000D_
    if (oProgress) {_x000D_
        var actualHTML = (typeof msg == "string") ? msg : msg.join("<br />");_x000D_
        oProgress.innerHTML = actualHTML;_x000D_
function InitiateSpeedDetection() {_x000D_
    ShowProgressMessage("Loading the image, please wait...");_x000D_
    window.setTimeout(MeasureConnectionSpeed, 1);_x000D_
};    _x000D_
if (window.addEventListener) {_x000D_
    window.addEventListener('load', InitiateSpeedDetection, false);_x000D_
} else if (window.attachEvent) {_x000D_
    window.attachEvent('onload', InitiateSpeedDetection);_x000D_
function MeasureConnectionSpeed() {_x000D_
    var startTime, endTime;_x000D_
    var download = new Image();_x000D_
    download.onload = function () {_x000D_
        endTime = (new Date()).getTime();_x000D_
    download.onerror = function (err, msg) {_x000D_
        ShowProgressMessage("Invalid image, or error downloading");_x000D_
    startTime = (new Date()).getTime();_x000D_
    var cacheBuster = "?nnn=" + startTime;_x000D_
    download.src = imageAddr + cacheBuster;_x000D_
    function showResults() {_x000D_
        var duration = (endTime - startTime) / 1000;_x000D_
        var bitsLoaded = downloadSize * 8;_x000D_
        var speedBps = (bitsLoaded / duration).toFixed(2);_x000D_
        var speedKbps = (speedBps / 1024).toFixed(2);_x000D_
        var speedMbps = (speedKbps / 1024).toFixed(2);_x000D_
            "Your connection speed is:", _x000D_
            speedBps + " bps", _x000D_
            speedKbps + " kbps", _x000D_
            speedMbps + " Mbps"_x000D_
<h1 id="progress">JavaScript is turned off, or your browser is realllllly slow</h1>

Quick comparison with "real" speed test service showed small difference of 0.12 Mbps when using big picture.

To ensure the integrity of the test, you can run the code with Chrome dev tool throttling enabled and then see if the result matches the limitation. (credit goes to user284130 :))

Important things to keep in mind:

  1. The image being used should be properly optimized and compressed. If it isn't, then default compression on connections by the web server might show speed bigger than it actually is. Another option is using uncompressible file format, e.g. jpg. (thanks Rauli Rajande for pointing this out and Fluxine for reminding me)

  2. The cache buster mechanism described above might not work with some CDN servers, which can be configured to ignore query string parameters, hence better setting cache control headers on the image itself. (thanks orcaman for pointing this out))

Options for embedding Chromium instead of IE WebBrowser control with WPF/C#

I had same issue with my WPF RSS reader, I originally went with Awesomium (I think version 1.6) Awesomium is great. You get a lot of control for caching (images and HTML content), JavaScript execution, intercepting downloads and so forth. It's also super fast. The process isolation means when browser crashes it does not crash the app.

But it's also heavy, even release build adds about 10-15mb (can't remember exact number) and hence a slight start-up penalty. I then realized, only problem I had with IE browser control was that it would throw the JavaScript errors every now and again. But that was fixed with the following snippet.

I hardly used my app on XP or Vista but on Win 7 and above it never crashed (at least not because I used IE browser control)

IOleServiceProvider sp = browser.Document as IOleServiceProvider;
if (sp != null)
    IID_IWebBrowserApp = new Guid("0002DF05-0000-0000-C000-000000000046");
    Guid IID_IWebBrowser2 = new Guid("D30C1661-CDAF-11d0-8A3E-00C04FC9E26E");

    sp.QueryService(ref IID_IWebBrowserApp, ref IID_IWebBrowser2, out webBrowser);
    if (webBrowser != null)
                BindingFlags.Instance | BindingFlags.Public | BindingFlags.PutDispProperty, null, webBrowser, new object[] { silent });

SQLSTATE[42S22]: Column not found: 1054 Unknown column - Laravel

Try to change where Member class

public function users() {
    return $this->hasOne('User');

return $this->belongsTo('User');

How can I add items to an empty set in python

D = {} is a dictionary not set.

>>> d = {}
>>> type(d)
<type 'dict'>

Use D = set():

>>> d = set()
>>> type(d)
<type 'set'>
>>> d.update({1})
>>> d.add(2)
>>> d.update([3,3,3])
>>> d
set([1, 2, 3])

Could not resolve all dependencies for configuration ':classpath'

Right, I'm not sure if it will work for others but worked for me.

I changed proxyPort to 8080 and used jcenter instead of Maven. But I had to apply expeption to use HTTP instead of HTTPS. This is what I have in my build.gradle for build script and allprojects

buildscript {
  repositories {
    jcenter {
        url ""

allprojects {
repositories {
    jcenter {
        url ""

UPDATE: 06/08

I have recently updated Gradle and plugin version and had some problems. It was complaining about plugin

I did some digging around and changed

 jcenter {
    url ""


repositories {
    maven { url '' }

C++: How to round a double to an int?

Casting is not a mathematical operation and doesn't behave as such. Try

int y = (int)round(x);

How to check if element is visible after scrolling?

I was looking for a way to see if the element is going to come into view soon, so by extending the snippets above i managed to do it. thought i would leave this here just in case it will help someone

elm = is the element you want to check is in the view

scrollElement = you can pass window or a parent element that has a scroll

offset = if you want it to fire when the element is 200px away before its in the screen then pass 200

function isScrolledIntoView(elem, scrollElement, offset)_x000D_
            var $elem = $(elem);_x000D_
            var $window = $(scrollElement);_x000D_
            var docViewTop = $window.scrollTop();_x000D_
            var docViewBottom = docViewTop + $window.height();_x000D_
            var elemTop = $elem.offset().top;_x000D_
            var elemBottom = elemTop + $elem.height();_x000D_
            return (((elemBottom+offset) >= docViewBottom) && ((elemTop-offset) <= docViewTop)) || (((elemBottom-offset) <= docViewBottom) && ((elemTop+offset) >= docViewTop));_x000D_

What is "Signal 15 received"

This indicates the linux has delivered a SIGTERM to your process. This is usually at the request of some other process (via kill()) but could also be sent by your process to itself (using raise()). This signal requests an orderly shutdown of your process.

If you need a quick cheatsheet of signal numbers, open a bash shell and:

$ kill -l
63) SIGRTMAX-1  64) SIGRTMAX    

You can determine the sender by using an appropriate signal handler like:

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>

void sigterm_handler(int signal, siginfo_t *info, void *_unused)
  fprintf(stderr, "Received SIGTERM from process with pid = %u\n",

int main (void)
  struct sigaction action = {
    .sa_handler = NULL,
    .sa_sigaction = sigterm_handler,
    .sa_mask = 0,
    .sa_flags = SA_SIGINFO,
    .sa_restorer = NULL

  sigaction(SIGTERM, &action, NULL);

  return 0;

Notice that the signal handler also includes a call to exit(). It's also possible for your program to continue to execute by ignoring the signal, but this isn't recommended in general (if it's a user doing it there's a good chance it will be followed by a SIGKILL if your process doesn't exit, and you lost your opportunity to do any cleanup then).

Order a MySQL table by two columns

Default sorting is ascending, you need to add the keyword DESC to both your orders:

ORDER BY article_rating DESC, article_time DESC

How to change JDK version for an Eclipse project

Eclipse - specific Project change JDK Version -

If you want to change any jdk version of A specific project than you have to click ---> Project --> JRE System Library --> Properties ---> Inside Classpath Container (JRE System Library) change the Execution Environment to which ever version you want e.g. 1.7 or 1.8.

Automatically run %matplotlib inline in IPython Notebook

In your file, search for the following lines

# c.InteractiveShellApp.matplotlib = None


# c.InteractiveShellApp.pylab = None

and uncomment them. Then, change None to the backend that you're using (I use 'qt4') and save the file. Restart IPython, and matplotlib and pylab should be loaded - you can use the dir() command to verify which modules are in the global namespace.

How to check if anonymous object has a method?

typeof myObj.prop2 === 'function'; will let you know if the function is defined.

if(typeof myObj.prop2 === 'function') {
    alert("It's a function");
} else if (typeof myObj.prop2 === 'undefined') {
    alert("It's undefined");
} else {
    alert("It's neither undefined nor a function. It's a " + typeof myObj.prop2);

How to change app default theme to a different app theme?

To change your application to a different built-in theme, just add this line under application tag in your app's manifest.xml file.






If you set style to DeviceDefault it will require min SDK version 14, but if you won't add a style, it will set to the device default anyway.


How to overcome TypeError: unhashable type: 'list'

    python 3.2

    with open("d://test.txt") as f:
              k=(((i.split("\n"))[0].rstrip()).split() for i in f.readlines())
              for i,_,v in k:

How can I remove a commit on GitHub?

To delete the commit from the remote repository:

 git push -f origin last_known_good_commit:branch_name

In order delete the commit from your local repository:

git reset --hard HEAD~1


How to change color and font on ListView

Even better, you do not need to create separate android xml layout for list cell view. You can just use "android.R.layout.simple_list_item_1" if the list only contains textview.

private class ExampleAdapter extends ArrayAdapter<String>{

    public ExampleAdapter(Context context, int textViewResourceId, String[] objects) {
        super(context, textViewResourceId, objects);

    public View getView(int position, View convertView, ViewGroup parent) {

        View view =  super.getView(position, convertView, parent);

        TextView tv = (TextView) view.findViewById(;

        return view;

Getting IP address of client

I use the following static helper method to retrieve the IP of a client:

public static String getClientIpAddr(HttpServletRequest request) {  
    String ip = request.getHeader("X-Forwarded-For");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("Proxy-Client-IP");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("WL-Proxy-Client-IP");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_X_FORWARDED_FOR");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_X_FORWARDED");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_X_CLUSTER_CLIENT_IP");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_CLIENT_IP");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_FORWARDED_FOR");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_FORWARDED");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("HTTP_VIA");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getHeader("REMOTE_ADDR");  
    if (ip == null || ip.length() == 0 || ip.equalsIgnoreCase("unknown")) {  
        ip = request.getRemoteAddr();  
    return ip;  

SQLSTATE[HY000] [1045] Access denied for user 'username'@'localhost' using CakePHP

If you use MAMP, you might have to set the socket: unix_socket: /Applications/MAMP/tmp/mysql/mysql.sock

Onclick javascript to make browser go back to previous page?




Put this to the button onclick handle. It should look like this:

<input name="action" onclick="history.back()" type="submit" value="Cancel"/>

How to use Google fonts in React.js?

In some cases your font resource maybe somewhere in your project directory. So you can load it like this using SCSS

 $list: (
    @mixin setRobotoFonts {
      @each $var in $list {
        @font-face {
          font-family: "Roboto-#{$var}";
          src: url("../fonts/Roboto-#{$var}.ttf") format("ttf");
@include setRobotoFonts();

Declaring an enum within a class

In general, I always put my enums in a struct. I have seen several guidelines including "prefixing".

enum Color

Always thought this looked more like C guidelines than C++ ones (for one because of the abbreviation and also because of the namespaces in C++).

So to limit the scope we now have two alternatives:

  • namespaces
  • structs/classes

I personally tend to use a struct because it can be used as parameters for template programming while a namespace cannot be manipulated.

Examples of manipulation include:

template <class T>
size_t number() { /**/ }

which returns the number of elements of enum inside the struct T :)

How to get html table td cell value by JavaScript?

You can use:

<td onclick='javascript:someFunc(this);'></td>

With passing this you can access the DOM object via your function parameters.

How to make sure that a certain Port is not occupied by any other process

netstat -ano|find ":port_no" will give you the list.
a: Displays all connections and listening ports.
n: Displays addresses and port numbers in numerical form.
o: Displays the owning process ID associated with each connection .

example : netstat -ano | find ":1900" This gives you the result like this.

UDP   *:*                                    1324  
UDP         *:*                                    1324  
UDP    [::1]:1900             *:*                                    1324  
UDP    [fe80::8db8:d9cc:12a8:2262%13]:1900  *:*                      1324

How to move/rename a file using an Ansible task on a remote system

Another Option that has worked well for me is using the synchronize module . Then remove the original directory using the file module.

Here is an example from the docs:

- synchronize:
    src: /first/absolute/path
    dest: /second/absolute/path
    archive: yes
  delegate_to: "{{ inventory_hostname }}"

How to dump raw RTSP stream to file?

If you are reencoding in your ffmpeg command line, that may be the reason why it is CPU intensive. You need to simply copy the streams to the single container. Since I do not have your command line I cannot suggest a specific improvement here. Your acodec and vcodec should be set to copy is all I can say.

EDIT: On seeing your command line and given you have already tried it, this is for the benefit of others who come across the same question. The command:

ffmpeg -i rtsp://@ -acodec copy -vcodec copy c:/abc.mp4

will not do transcoding and dump the file for you in an mp4. Of course this is assuming the streamed contents are compatible with an mp4 (which in all probability they are).

Lotus Notes email as an attachment to another email

Click on email which you want to forward

Edit - > Copy As -> Document Link

create new mail and paste.

it will work

How to hide Bootstrap previous modal when you opening new one?

You hide Bootstrap modals with:


Saying $().hide() makes the matched element invisible, but as far as the modal-related code is concerned, it's still there. See the Methods section in the Modals documentation.

LINQ: Select where object does not contain items from list

In general, you're looking for the "Except" extension.

var rejectStatus = GenerateRejectStatuses();
var fullList = GenerateFullList();
var rejectList = fullList.Where(i => rejectStatus.Contains(i.Status));
var filteredList = fullList.Except(rejectList);

In this example, GenerateRegectStatuses() should be the list of statuses you wish to reject (or in more concrete terms based on your example, a List<int> of IDs)

How do I count unique values inside a list

How about:

import pandas as pd
#List with all words

#Code for adding words

#When Input equals blank:

It returns how many unique values are in a list

Insert picture into Excel cell

Now we can add a picture to Excel directly and easely. Just follow these instructions:

  1. Go to the Insert tab.
  2. Click on the Pictures option (it’s in the illustrations group). image1
  3. In the ‘Insert Picture’ dialog box, locate the pictures that you want to insert into a cell in Excel. image2
  4. Click on the Insert button. image3
  5. Re-size the picture/image so that it can fit perfectly within the cell. image4
  6. Place the picture in the cell. A cool way to do this is to first press the ALT key and then move the picture with the mouse. It will snap and arrange itself with the border of the cell as soon it comes close to it.

If you have multiple images, you can select and insert all the images at once (as shown in step 4).

You can also resize images by selecting it and dragging the edges. In the case of logos or product images, you may want to keep the aspect ratio of the image intact. To keep the aspect ratio intact, use the corners of an image to resize it.

When you place an image within a cell using the steps above, it will not stick with the cell in case you resize, filter, or hide the cells. If you want the image to stick to the cell, you need to lock the image to the cell it’s placed n.

To do this, you need to follow the additional steps as shown below.

  1. Right-click on the picture and select Format Picture. image5
  2. In the Format Picture pane, select Size & Properties and with the options in Properties, select ‘Move and size with cells’. image6

Now you can move cells, filter it, or hide it, and the picture will also move/filter/hide.


This answer was taken from this link: Insert Picture into a Cell in Excel.

document.getElementById().value and document.getElementById().checked not working for IE

Jin Yong - IE has an issue with polluting the global scope with object references to any DOM elements with a "name" or "id" attribute set on the "initial" page load.

Thus you may have issues due to your variable name.

Try this and see if it works.

var someOtherName="abc";
//  ^^^^^^^^^^^^^
document.getElementById('msg').value = someOtherName;
document.getElementById('sp_100').checked = true;

There is a chance (in your original code) that IE attempts to set the value of the input to a reference to that actual element (ignores the error) but leaves you with no new value.

Keep in mind that in IE6/IE7 case doesn't matter for naming objects. IE believes that "foo" "Foo" and "FOO" are all the same object.

Local file access with JavaScript

If you're deploying on Windows, the Windows Script Host offers a very useful JScript API to the file system and other local resources. Incorporating WSH scripts into a local web application may not be as elegant as you might wish, however.

Passing data between view controllers

Pure Combine solution for UIKit and AppKit

Let's take a simple example of passing an Int value of count between ViewControllers.

A parent ViewController (VC) has a variable named count, and child ViewController can let the user change the value of count. Once the user is done changing the value, they will dismiss the child controller and parent VC should have the updated value after that.

Parent View Controller

ParentVC gets the updated value of count from the ChildVC

class ParentVC: UIViewController {
    var count = 1
    var countObserver: AnyCancellable! // 1

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        let childVC = segue.destination as! ChildVC
        childVC.sliderValue = count // 2
        countObserver = childVC.$sliderValue // 3
            .assign(to: \.count, on: self)
  1. countObserver will retain the observer that would observe changes made by ChildVC

  2. When the child appears, we assign the current count value from parent to a control (here UISlider) in the ChildVC, which becomes a starting point for modifying the value of count.

  3. We observe sliderValue (which is a publisher) that would emit the value of count that the user would change by dragging the slider. Note that we used $sliderValue instead of just sliderValue.

Child View Controller

ChildVC is the one that would emit values that ParentVC is interested in:

class ChildVC: UIViewController {
    @Published var sliderValue: Int = 0 // 1

    @IBOutlet var sliderOutlet: UISlider!

    @IBAction func slided(_ sender: UISlider) {
        sliderValue = Int(sender.value)
  1. @Published is Publisher that stores value and emits a signal when the value changes. It behaves just like a regular var but can publish values that can be accessed by prepending $ sign to it.

CurrentValueSubject and PassthroughSubject vs @Published

  1. CurrentValueSubject can also be used instead of @Published. The only difference is, you would have to manually emit the signal. It is useful in cases where you want to control when to emit. For example, you can emit the value, but only if it falls in a specific range.

  2. PassthroughSubject also can be used instead of @Published or CurrentValueSubject. Here, the difference is PassthroughSubject cannot hold a value, it can just emit a signal. This can be useful when the value cannot be concretely represented in a variable.

How to remove leading and trailing spaces from a string

Or you can split your string to string array, splitting by space and then add every item of string array to empty string.
May be this is not the best and fastest method, but you can try, if other answer aren't what you whant.

Docker for Windows error: "Hardware assisted virtualization and data execution protection must be enabled in the BIOS"

I have tried many suggestions above but docker keeps complaining about hardware assisted virtualization error. Virtualization is enabled in BIOS, and also Hyper-V is installed and enabled. After a few try and errors, I eventually downloaded coreinfo tool and found out that Hypervisor was not actually enabled. Using ISE (64 bit) as admin and run command from above Solution B and that enables Hypervisor successfully (checked via coreinfo -v again). After restart, docker is now running successfully.

Meaning of "n:m" and "1:n" in database design

1:n means 'one-to-many'; you have two tables, and each row of table A may be referenced by any number of rows in table B, but each row in table B can only reference one row in table A (or none at all).

n:m (or n:n) means 'many-to-many'; each row in table A can reference many rows in table B, and each row in table B can reference many rows in table A.

A 1:n relationship is typically modelled using a simple foreign key - one column in table A references a similar column in table B, typically the primary key. Since the primary key uniquely identifies exactly one row, this row can be referenced by many rows in table A, but each row in table A can only reference one row in table B.

A n:m relationship cannot be done this way; a common solution is to use a link table that contains two foreign key columns, one for each table it links. For each reference between table A and table B, one row is inserted into the link table, containing the IDs of the corresponding rows.

Transport security has blocked a cleartext HTTP

Using NSExceptionDomains may not apply an effect simultaneously due to target site may load resources (e.g. js files) from external domains over http. It can be resolved by adding these external domains to NSExceptionDomains as well.

To inspect which resources cannot be loaded try to use Remote debugging. Here is a tutorial:

Background service with location listener in android

Background location service. It will be restarted even after killing the app.

public class MainActivity extends AppCompatActivity {
    AlarmManager alarmManager;
    Button stop;
    PendingIntent pendingIntent;

    protected void onCreate(Bundle savedInstanceState) {

        if (alarmManager == null) {
            alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
            Intent intent = new Intent(this, AlarmReceive.class);
            pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0);
            alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 30000,

public class BookingTrackingService extends Service implements LocationListener {

    private static final String TAG = "BookingTrackingService";
    private Context context;
    boolean isGPSEnable = false;
    boolean isNetworkEnable = false;
    double latitude, longitude;
    LocationManager locationManager;
    Location location;
    private Handler mHandler = new Handler();
    private Timer mTimer = null;
    long notify_interval = 30000;

    public double track_lat = 0.0;
    public double track_lng = 0.0;
    public static String str_receiver = "servicetutorial.service.receiver";
    Intent intent;

    public IBinder onBind(Intent intent) {
        return null;

    public void onCreate() {

        mTimer = new Timer();
        mTimer.schedule(new TimerTaskToGetLocation(), 5, notify_interval);
        intent = new Intent(str_receiver);

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

        this.context = this;

        return START_NOT_STICKY;

    public void onDestroy() {
        Log.e(TAG, "onDestroy <<");
        if (mTimer != null) {

    private void trackLocation() {
        Log.e(TAG, "trackLocation");
        String TAG_TRACK_LOCATION = "trackLocation";
        Map<String, String> params = new HashMap<>();
        params.put("latitude", "" + track_lat);
        params.put("longitude", "" + track_lng);

        Log.e(TAG, "param_track_location >> " + params.toString());



    public void onLocationChanged(Location location) {


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


    public void onProviderEnabled(String provider) {


    public void onProviderDisabled(String provider) {



    private void fn_getlocation() {
        locationManager = (LocationManager) getApplicationContext().getSystemService(LOCATION_SERVICE);
        isGPSEnable = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
        isNetworkEnable = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        if (!isGPSEnable && !isNetworkEnable) {
            Log.e(TAG, "CAN'T GET LOCATION");
        } else {
            if (isNetworkEnable) {
                location = null;
                locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 1000, 0, this);
                if (locationManager != null) {
                    location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                    if (location != null) {

                        Log.e(TAG, "isNetworkEnable latitude" + location.getLatitude() + "\nlongitude" + location.getLongitude() + "");
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                        track_lat = latitude;
                        track_lng = longitude;
//                        fn_update(location);

            if (isGPSEnable) {
                location = null;
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 0, this);
                if (locationManager != null) {
                    location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                    if (location != null) {
                        Log.e(TAG, "isGPSEnable latitude" + location.getLatitude() + "\nlongitude" + location.getLongitude() + "");
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                        track_lat = latitude;
                        track_lng = longitude;
//                        fn_update(location);

            Log.e(TAG, "START SERVICE");


    private class TimerTaskToGetLocation extends TimerTask {
        public void run() {

   Runnable() {
                public void run() {


//    private void fn_update(Location location) {
//        intent.putExtra("latutide", location.getLatitude() + "");
//        intent.putExtra("longitude", location.getLongitude() + "");
//        sendBroadcast(intent);
//    }
} (BroadcastReceiver)

public class AlarmReceive extends BroadcastReceiver {

    public void onReceive(Context context, Intent intent) {
        Log.e("Service_call_"  , "You are in AlarmReceive class.");
        Intent background = new Intent(context, BookingTrackingService.class);
//        Intent background = new Intent(context, GoogleService.class);
        Log.e("AlarmReceive ","testing called broadcast called");


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

            android:enabled="true" />

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

Default value in an mvc view model

Create a base class for your ViewModels with the following constructor code which will apply the DefaultValueAttributeswhen any inheriting model is created.

public abstract class BaseViewModel
    protected BaseViewModel()
        // apply any DefaultValueAttribute settings to their properties
        var propertyInfos = this.GetType().GetProperties();
        foreach (var propertyInfo in propertyInfos)
            var attributes = propertyInfo.GetCustomAttributes(typeof(DefaultValueAttribute), true);
            if (attributes.Any())
                var attribute = (DefaultValueAttribute) attributes[0];
                propertyInfo.SetValue(this, attribute.Value, null);

And inherit from this in your ViewModels:

public class SearchModel : BaseViewModel
    public bool IsMale { get; set; }
    public bool IsFemale { get; set; }

How to enable C++11 in Qt Creator?

According to this site add

CONFIG += c++11

to your .pro file (see at the bottom of that web page). It requires Qt 5.

The other answers, suggesting

QMAKE_CXXFLAGS += -std=c++11 (or QMAKE_CXXFLAGS += -std=c++0x)

also work with Qt 4.8 and gcc / clang.

Docker - Cannot remove dead container

I had the following error when removing a dead container (docker 17.06.1-ce on CentOS 7):

Error response from daemon: driver "overlay" failed to remove root filesystem for <some-id>: 
remove /var/lib/docker/overlay/<some-id>/merged: device or resource busy

Here is how I fixed it:

1. Check which other processes are also using docker resources

$ grep docker /proc/*/mountinfo

which outputs something like this, where the number after /proc/ is the pid:

/proc/12345/mountinfo:159 149 0:36 / /var/lib/docker/overlay/...

2. Check the process name of the above pid

$ ps -p 10001 -o comm=
$ ps -p 10002 -o comm=
$ ps -p 12345 -o comm=
nginx   <<<-- This is suspicious!!!

So, nginx with pid 12345 seems to also be using /var/lib/docker/overlay/..., which is why we cannot remove the related container and get the device or resource busy error. (See here for a discussion on how nginx shares the same mount namespace with docker containers thus prevents its deletion.)

3. Stop nginx and then I can remove the container successfully.

$ sudo service nginx stop
$ docker rm <container-id>

Array of an unknown length in C#

A little background information:

As said, if you want to have a dynamic collection of things, use a List<T>. Internally, a List uses an array for storage too. That array has a fixed size just like any other array. Once an array is declared as having a size, it doesn't change. When you add an item to a List, it's added to the array. Initially, the List starts out with an array that I believe has a length of 16. When you try to add the 17th item to the List, what happens is that a new array is allocated, that's (I think) twice the size of the old one, so 32 items. Then the content of the old array is copied into the new array. So while a List may appear dynamic to the outside observer, internally it has to comply to the rules as well.

And as you might have guessed, the copying and allocation of the arrays isn't free so one should aim to have as few of those as possible and to do that you can specify (in the constructor of List) an initial size of the array, which in a perfect scenario is just big enough to hold everything you want. However, this is micro-optimization and it's unlikely it will ever matter to you, but it's always nice to know what you're actually doing.

Oracle SQL - DATE greater than statement

As your query string is a literal, and assuming your dates are properly stored as DATE you should use date literals:

SELECT * FROM OrderArchive
WHERE OrderDate <= DATE '2015-12-31'

If you want to use TO_DATE (because, for example, your query value is not a literal), I suggest you to explicitly set the NLS_DATE_LANGUAGE parameter as you are using US abbreviated month names. That way, it won't break on some localized Oracle Installation:

SELECT * FROM OrderArchive
WHERE OrderDate <= to_date('31 Dec 2014', 'DD MON YYYY',
                           'NLS_DATE_LANGUAGE = American');

Convert JS object to JSON string

With JSON.stringify() found in json2.js or native in most modern browsers.

   JSON.stringify(value, replacer, space)
        value       any JavaScript value, usually an object or array.

       replacer    an optional parameter that determines how object
                    values are stringified for objects. It can be a
                    function or an array of strings.

       space       an optional parameter that specifies the indentation
                    of nested structures. If it is omitted, the text will
                    be packed without extra whitespace. If it is a number,
                    it will specify the number of spaces to indent at each
                    level. If it is a string (such as '\t' or '&nbsp;'),
                    it contains the characters used to indent at each level.

       This method produces a JSON text from a JavaScript value.

make bootstrap twitter dialog modal draggable

In my own case, i had to set backdrop and set the top and left properties before i could apply draggable function on the modal dialog. Maybe it might help someone ;)

if (!($('').length)) {       
     top: 0,
     left: 0
  backdrop: false,
   show: true

  handle: ".modal-header"

Java NoSuchAlgorithmException - SunJSSE,$DefaultSSLContext

I had the similar issue. The problem was in the passwords: the Keystore and private key used different passwords. (KeyStore explorer was used)

After creating Keystore with the same password as private key had the issue was resolved.

Missing MVC template in Visual Studio 2015

I'm going to add my 2 cents in case someone finds himself in a position like mine. I too was looking for an MVC project type and could not see it. All I saw is a "Web Application Project". So I freaked out and rushed into trying all solutions listed on this page.



enter image description here

Just go with the "Web application" project and it will give you the MVC option on the next step.

Download File Using Javascript/jQuery

Note: Not supported in all browsers.

I was looking for a way to download a file using jquery without having to set the file url in the href attribute from the beginning.

jQuery('<a/>', {_x000D_
    id: 'downloadFile',_x000D_
    href: '[email protected]',_x000D_
    style: 'display:hidden;',_x000D_
    download: ''_x000D_
<script src=""></script>

RecyclerView - Get view at particular position

If you want the View, make sure to access the itemView property of the ViewHolder like so: myRecyclerView.findViewHolderForAdapterPosition(pos).itemView;

Google Drive as FTP Server

I couldn't find a direct GDrive/DropBox solution. I'm also surprised there's no lazy solution for a free ftp host. Windows azure offers a ftp server "FTP connector" that's fairly easy to turn on at:

You can get a free 1 GB account by selecting "View All" machine types during your deployment.

Command to delete all pods in all kubernetes namespaces

K8s completely works on the fundamental of the namespace. if you like to release all the resource related to specified namespace.

you can use the below mentioned :

kubectl delete namespace k8sdemo-app

Response Buffer Limit Exceeded

The reason this is happening is because buffering is turned on by default, and IIS 6 cannot handle the large response.

In Classic ASP, at the top of your page, after <%@Language="VBScript"%> add: <%Response.Buffer = False%>

In ASP.NET, you would add Buffer="False" to your Page directive. For example: <%@Page Language="C#" Buffer="False"%>

How to add element into ArrayList in HashMap

HashMap<String, ArrayList<Item>> items = new HashMap<String, ArrayList<Item>>();

public synchronized void addToList(String mapKey, Item myItem) {
    List<Item> itemsList = items.get(mapKey);

    // if list does not exist create it
    if(itemsList == null) {
         itemsList = new ArrayList<Item>();
         items.put(mapKey, itemsList);
    } else {
        // add if item is not already in list
        if(!itemsList.contains(myItem)) itemsList.add(myItem);

Maximum on http header values?

HTTP does not place a predefined limit on the length of each header field or on the length of the header section as a whole, as described in Section 2.5. Various ad hoc limitations on individual header field length are found in practice, often depending on the specific field semantics.

HTTP Header values are restricted by server implementations. Http specification doesn't restrict header size.

A server that receives a request header field, or set of fields, larger than it wishes to process MUST respond with an appropriate 4xx (Client Error) status code. Ignoring such header fields would increase the server's vulnerability to request smuggling attacks (Section 9.5).

Most servers will return 413 Entity Too Large or appropriate 4xx error when this happens.

A client MAY discard or truncate received header fields that are larger than the client wishes to process if the field semantics are such that the dropped value(s) can be safely ignored without changing the message framing or response semantics.

Uncapped HTTP header size keeps the server exposed to attacks and can bring down its capacity to serve organic traffic.


Speed tradeoff of Java's -Xms and -Xmx options

This was always the question I had when I was working on one of my application which created massive number of threads per request.

So this is a really good question and there are two aspects of this:
1. Whether my Xms and Xmx value should be same
       - Most websites and even oracle docs suggest it to be the same. However, I suggest to have some 10-20% of buffer between those values to give heap resizing an option to your application in case sudden high traffic spikes OR a incidental memory leak.

2. Whether I should start my Application with lower heap size
       - So here's the thing - no matter what GC Algo you use (even G1), large heap always has some trade off. The goal is to identify the behavior of your application to what heap size you can allow your GC pauses in terms of latency and throughput.
              - For example, if your application has lot of threads (each thread has 1 MB stack in native memory and not in heap) but does not occupy heavy object space, then I suggest have a lower value of Xms.
              - If your application creates lot of objects with increasing number of threads, then identify to what value of Xms you can set to tolerate those STW pauses. This means identify the max response time of your incoming requests you can tolerate and according tune the minimum heap size.

Sieve of Eratosthenes - Finding Primes Python

You're not quite implementing the correct algorithm:

In your first example, primes_sieve doesn't maintain a list of primality flags to strike/unset (as in the algorithm), but instead resizes a list of integers continuously, which is very expensive: removing an item from a list requires shifting all subsequent items down by one.

In the second example, primes_sieve1 maintains a dictionary of primality flags, which is a step in the right direction, but it iterates over the dictionary in undefined order, and redundantly strikes out factors of factors (instead of only factors of primes, as in the algorithm). You could fix this by sorting the keys, and skipping non-primes (which already makes it an order of magnitude faster), but it's still much more efficient to just use a list directly.

The correct algorithm (with a list instead of a dictionary) looks something like:

def primes_sieve2(limit):
    a = [True] * limit                          # Initialize the primality list
    a[0] = a[1] = False

    for (i, isprime) in enumerate(a):
        if isprime:
            yield i
            for n in range(i*i, limit, i):     # Mark factors non-prime
                a[n] = False

(Note that this also includes the algorithmic optimization of starting the non-prime marking at the prime's square (i*i) instead of its double.)

no suitable HttpMessageConverter found for response type

In addition to all the answers, if you happen to receive in response text/html while you've expected something else (i.e. application/json), it may suggest that an error occurred on the server side (say 404) and the error page was returned instead of your data.

So it happened in my case. Hope it will save somebody's time.

Special characters like @ and & in cURL POST data

cURL > 7.18.0 has an option --data-urlencode which solves this problem. Using this, I can simply send a POST request as

curl -d name=john --data-urlencode passwd=@31&3*J

The character encoding of the plain text document was not declared - mootool script

I got this error using Spring Boot (in Mozilla),

because I was just testing some basic controller -> service -> repository communication by directly returning some entities from the database to the browser (as JSON).

I forgot to put data in the database, so my method wasn't returning anything... and I got this error.

Now that I put some data in my db, it works fine (the error is removed). :D

Access properties file programmatically with Spring?

Create a class like below

    package com.tmghealth.common.util;

    import java.util.Properties;

    import org.springframework.beans.BeansException;

    import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

    import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;

    import org.springframework.context.annotation.Configuration;

    import org.springframework.context.annotation.PropertySource;

    import org.springframework.stereotype.Component;

    @PropertySource(value = { "classpath:/spring/" })
    public class PropertiesReader extends PropertyPlaceholderConfigurer {

        protected void processProperties(
                ConfigurableListableBeanFactory beanFactory, Properties props)
                throws BeansException {
            super.processProperties(beanFactory, props);



Then wherever you want to access a property use

        private Environment environment;
    and getters and setters then access using 

                    + ".letter.fdi.letterdetails.restServiceUrl");

-- write getters and setters in the accessor class

    public Environment getEnvironment() {
            return environment;
        }`enter code here`

        public void setEnvironment(Environment environment) {
            this.environment = environment;

How can I fill a div with an image while keeping it proportional?

Consider using background-size: cover (IE9+) in conjunction with background-image. For IE8-, there is a polyfill.

Safe String to BigDecimal conversion

The following sample code works well (locale need to be obtained dynamically)

import java.math.BigDecimal;
import java.text.NumberFormat;
import java.text.DecimalFormat;
import java.text.ParsePosition;
import java.util.Locale;

class TestBigDecimal {
    public static void main(String[] args) {

        String str = "0,00";
        Locale in_ID = new Locale("in","ID");
        //Locale in_ID = new Locale("en","US");

        DecimalFormat nf = (DecimalFormat)NumberFormat.getInstance(in_ID);

        BigDecimal bd = (BigDecimal)nf.parse(str, new ParsePosition(0));

        System.out.println("bd value : " + bd);

Powershell script to check if service is started, if not then start it

A potentially simpler solution:

get-service "servicename*" | Where {$_.Status -eq 'Stopped'} | start-service

Git - Ignore node_modules folder everywhere

it will automatically create a .gitignore file if not then create a file name .gitignore and add copy & paste the below code

# dependencies

# testing

# production

# misc


these below are all unnecessary files

See for more about ignoring files.

and save the .gitignore file and you can upload

How to restore the permissions of files and directories within git if they have been modified?

The easiest thing to do is to just change the permissions back. As @kroger noted git only tracks executable bits. So you probably just need to run chmod -x filename to fix it (or +x if that's what's needed.

How to get current html page title with javascript

One option from DOM directly:


Tested only on chrome & IE9, but logically should work on all browsers.

Or more generic

var title = document.getElementsByTagName("title")[0].innerHTML;

How to specify Memory & CPU limit in docker compose version 3

Docker Compose does not support the deploy key. It's only respected when you use your version 3 YAML file in a Docker Stack.

This message is printed when you add the deploy key to you docker-compose.yml file and then run docker-compose up -d

WARNING: Some services (database) use the 'deploy' key, which will be ignored. Compose does not support 'deploy' configuration - use docker stack deploy to deploy to a swarm.

The documentation ( says:

Specify configuration related to the deployment and running of services. This only takes effect when deploying to a swarm with docker stack deploy, and is ignored by docker-compose up and docker-compose run.

Setting up a git remote origin

Using SSH

git remote add origin ssh://login@IP/path/to/repository

Using HTTP

git remote add origin http://IP/path/to/repository

However having a simple git pull as a deployment process is usually a bad idea and should be avoided in favor of a real deployment script.

How do I write stderr to a file while using "tee" with a pipe?

why not simply:

./ 2>&1 | tee -a log

This simply redirects stderr to stdout, so tee echoes both to log and to screen. Maybe I'm missing something, because some of the other solutions seem really complicated.

Note: Since bash version 4 you may use |& as an abbreviation for 2>&1 |:

./ |& tee -a log

Using File.listFiles with FileNameExtensionFilter

One-liner in java 8 syntax:

pdfTestDir.listFiles((dir, name) -> name.toLowerCase().endsWith(".txt"));

How to set UTF-8 encoding for a PHP file

PHP, by default, always returns the following header: "Content-Type: text/html" (notice no charset), therefore you must use

<?php header('Content-type: text/plain; charset=utf-8'); ?>

How do I activate a virtualenv inside PyCharm's terminal?

I had the same problem with venv in PyCharm. But It is not big problem! Just do:

  1. enter in your terminal venv directory( cd venv/Scripts/ )
  2. You will see activate.bat
  3. Just enter activate.bat in your terminal after this you will see YOUR ( venv )

Sleep function in Windows, using C


#include <windows.h>

Sleep(sometime_in_millisecs); // Note uppercase S

And here's a small example that compiles with MinGW and does what it says on the tin:

#include <windows.h>
#include <stdio.h>

int main() {
    printf( "starting to sleep...\n" );
    Sleep(3000); // Sleep three seconds
    printf("sleep ended\n");

Why can't I enter a string in Scanner(, when calling nextLine()-method?

if you don't want to use parser :

int a;
String s;
Scanner scan = new Scanner(;

System.out.println("enter a no");
a = scan.nextInt();
System.out.println("no is =" + a);
scan.nextLine(); // This line you have to add (It consumes the \n character)
System.out.println("enter a string");
s = scan.nextLine();
System.out.println("string is=" + s);

How to subtract hours from a date in Oracle so it affects the day also


A day consists of 24 hours. So, to subtract 2 hours from a day you need to divide it by 24:

DATE_value - 2/24

Using interval for the same:

DATE_value - interval '2' hour

var functionName = function() {} vs function functionName() {}

The two code snippets you've posted there will, for almost all purposes, behave the same way.

However, the difference in behaviour is that with the first variant (var functionOne = function() {}), that function can only be called after that point in the code.

With the second variant (function functionTwo()), the function is available to code that runs above where the function is declared.

This is because with the first variant, the function is assigned to the variable foo at run time. In the second, the function is assigned to that identifier, foo, at parse time.

More technical information

JavaScript has three ways of defining functions.

  1. Your first snippet shows a function expression. This involves using the "function" operator to create a function - the result of that operator can be stored in any variable or object property. The function expression is powerful that way. The function expression is often called an "anonymous function", because it does not have to have a name,
  2. Your second example is a function declaration. This uses the "function" statement to create a function. The function is made available at parse time and can be called anywhere in that scope. You can still store it in a variable or object property later.
  3. The third way of defining a function is the "Function()" constructor, which is not shown in your original post. It's not recommended to use this as it works the same way as eval(), which has its problems.

How to add column to numpy array

If you have an array, a of say 210 rows by 8 columns:

a = numpy.empty([210,8])

and want to add a ninth column of zeros you can do this:

b = numpy.append(a,numpy.zeros([len(a),1]),1)

What is the difference between Scrum and Agile Development?


SCRUM is a type of Agile approach. It is a Framework not a Methodology.

It does not provide detailed instructions to what needs to be done rather most of it is dependent on the team that is developing the software. Because the developing the project knows how the problem can be solved that is why much is left on them

Cross-functional and self-organizing teams are essential in case of scrum. There is no team leader in this case who will assign tasks to the team members rather the whole team addresses the issues or problems. It is cross-functional in a way that everyone is involved in the project right from the idea to the implementation of the project.

The advantage of scrum is that a project’s direction to be adjusted based on completed work, not on speculation or predictions.

Roles Involved : Product Owner, Scrum Master, Team Members

Agile Methodology :

Build Software applications that are unpredictable in nature

Iterative and incremental work cadences called sprints are used in this methodology.

Both Agile and SCRUM follows the system -- some of the features are developed as a part of the sprint and at the end of each sprint; the features are completed right from coding, testing and their integration into the product. A demonstration of the functionality is provided to the owner at the end of each sprint so that feedback can be taken which can be helpful for the next sprint.

Manifesto for Agile Development :

  1. Individuals and interactions over processes and tools
  2. Working software over comprehensive documentation
  3. Customer collaboration over contract negotiation
  4. Responding to change over following a plan

That is, while there is value in the items on the right, we value the items on the left more.

Loading PictureBox Image from resource file with path (Part 3)

The path should be something like: "Images\a.bmp". (Note the lack of a leading slash, and the slashes being back slashes.)

And then:

pictureBox1.Image = Image.FromFile(@"Images\a.bmp");

I just tried it to make sure, and it works. This is besides the other answer that you got - to "copy always".

Get pixel's RGB using PIL

With numpy :

im ='image.gif')
im_matrix = np.array(im)

Give RGB vector of the pixel in position (0,0)

Using ALTER to drop a column if it exists in MySQL

There is no language level support for this in MySQL. Here is a work-around involving MySQL information_schema meta-data in 5.0+, but it won't address your issue in 4.0.18.

drop procedure if exists schema_change;

delimiter ';;'
create procedure schema_change() begin

    /* delete columns if they exist */
    if exists (select * from information_schema.columns where table_schema = schema() and table_name = 'table1' and column_name = 'column1') then
        alter table table1 drop column `column1`;
    end if;
    if exists (select * from information_schema.columns where table_schema = schema() and table_name = 'table1' and column_name = 'column2') then
        alter table table1 drop column `column2`;
    end if;

    /* add columns */
    alter table table1 add column `column1` varchar(255) NULL;
    alter table table1 add column `column2` varchar(255) NULL;


delimiter ';'
call schema_change();

drop procedure if exists schema_change;

I wrote some more detailed information in a blog post.

Named regular expression group "(?P<group_name>regexp)": what does "P" stand for?

Pattern! The group names a (sub)pattern for later use in the regex. See the documentation here for details about how such groups are used.

Bad Gateway 502 error with Apache mod_proxy and Tomcat

You can avoid global timeouts or having to virtual hosts by specifying the proxy timeouts in the ProxyPass directive as follows:

ProxyPass /svc timeout=600
ProxyPassReverse /svc timeout=600

Notice timeout=600 seconds.

However this does not always work when you have load balancer. In that case you must add the timeouts in both the places (tested in Apache 2.2.31)

Load Balancer example:

<Proxy "balancer://mycluster">
     BalancerMember "http://member1:8080/svc" timeout=600
     BalancerMember "http://member2:8080/svc" timeout=600

ProxyPass /svc "balancer://mycluster" timeout=600
ProxyPassReverse /svc "balancer://mycluster" timeout=600

A side note: the timeout=600 on ProxyPass was not required when Chrome was the client (I don;t know why) but without this timeout on ProxyPass Internet Explorer (11) aborts saying connection reset by server.

My theory is that the :

ProxyPass timeout is used between the client(browser) and the Apache.

BalancerMember timeout is used between the Apache and the backend.

To those who use Tomcat or other backed you may also want to pay attention to the HTTP Connector timeouts.

How to capitalize the first character of each word in a string

This one works for the surname case...

With different types of separators, and it keeps the same separator:

  • jean-frederic --> Jean-Frederic

  • jean frederic --> Jean Frederic

The code works with the GWT client side.

public static String capitalize (String givenString) {
    String Separateur = " ,.-;";
    StringBuffer sb = new StringBuffer(); 
    boolean ToCap = true;
    for (int i = 0; i < givenString.length(); i++) {
        if (ToCap)              

        if (Separateur.indexOf(givenString.charAt(i)) >=0) 
            ToCap = true;
            ToCap = false;
    return sb.toString().trim();

Convert php array to Javascript

Is very simple I use this way:


var arrayJavascript = <?php echo json_encode($arrayPhp) ?>;

Convert PHP array to Javascript


Is it possible to sort a ES6 map object?

Perhaps a more realistic example about not sorting a Map object but preparing the sorting up front before doing the Map. The syntax gets actually pretty compact if you do it like this. You can apply the sorting before the map function like this, with a sort function before map (Example from a React app I am working on using JSX syntax)

Mark that I here define a sorting function inside using an arrow function that returns -1 if it is smaller and 0 otherwise sorted on a property of the Javascript objects in the array I get from an API.

report.ProcedureCodes.sort((a, b) => a.NumericalOrder < b.NumericalOrder ? -1 : 0).map((item, i) =>
                        <TableRow key={i}>

                            {/* <TableCell>{item.NumericalOrder}</TableCell> */}

Could not load dynamic library 'cudart64_101.dll' on tensorflow CPU-only installation

This answer might be helpful if you see above error but actually you have CUDA 10 installed:

pip install tensorflow-gpu==2.0.0


I tensorflow/stream_executor/platform/default/] Successfully opened dynamic library cudart64_100.dll

which was the solution for me.

Printing Python version in output

If you are using jupyter notebook Try:

!python --version

If you are using terminal Try:

 python --version

Webfont Smoothing and Antialiasing in Firefox and Opera


font-weight: normal;

To your @font-face fonts will fix the bold appearance in Firefox.

sys.stdin.readline() reads without prompt, returning 'nothing in between'

will not return when you press one character - it will wait for '\n'. The problem is that the second character is buffered in standard input, and the moment you call another input - it will return immediately because it gets its input from buffer.

Django URL Redirect

If you are stuck on django 1.2 like I am and RedirectView doesn't exist, another route-centric way to add the redirect mapping is using:

(r'^match_rules/$', 'django.views.generic.simple.redirect_to', {'url': '/new_url'}),  

You can also re-route everything on a match. This is useful when changing the folder of an app but wanting to preserve bookmarks:

(r'^match_folder/(?P<path>.*)', 'django.views.generic.simple.redirect_to', {'url': '/new_folder/%(path)s'}),  

This is preferable to django.shortcuts.redirect if you are only trying to modify your url routing and do not have access to .htaccess, etc (I'm on Appengine and app.yaml doesn't allow url redirection at that level like an .htaccess).

Convert Difference between 2 times into Milliseconds?

Try the following:

   DateTime dtStart;
   DateTime dtEnd;

   if (DateTime.TryParse( tb1.Text, out dtStart ) && DateTime.TryParse(tb2.Text, out dtEnd ))
      TimeSpan ts = dtStart - dtEnd;
      double difference = ts.TotalMilliseconds;

How do I generate random number for each row in a TSQL Select?

Take a look at SQL Server - Set based random numbers which has a very detailed explanation.

To summarize, the following code generates a random number between 0 and 13 inclusive with a uniform distribution:

ABS(CHECKSUM(NewId())) % 14

To change your range, just change the number at the end of the expression. Be extra careful if you need a range that includes both positive and negative numbers. If you do it wrong, it's possible to double-count the number 0.

A small warning for the math nuts in the room: there is a very slight bias in this code. CHECKSUM() results in numbers that are uniform across the entire range of the sql Int datatype, or at least as near so as my (the editor) testing can show. However, there will be some bias when CHECKSUM() produces a number at the very top end of that range. Any time you get a number between the maximum possible integer and the last exact multiple of the size of your desired range (14 in this case) before that maximum integer, those results are favored over the remaining portion of your range that cannot be produced from that last multiple of 14.

As an example, imagine the entire range of the Int type is only 19. 19 is the largest possible integer you can hold. When CHECKSUM() results in 14-19, these correspond to results 0-5. Those numbers would be heavily favored over 6-13, because CHECKSUM() is twice as likely to generate them. It's easier to demonstrate this visually. Below is the entire possible set of results for our imaginary integer range:

Checksum Integer: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Range Result:     0 1 2 3 4 5 6 7 8 9 10 11 12 13  0  1  2  3  4  5

You can see here that there are more chances to produce some numbers than others: bias. Thankfully, the actual range of the Int type is much larger... so much so that in most cases the bias is nearly undetectable. However, it is something to be aware of if you ever find yourself doing this for serious security code.

Position Relative vs Absolute?

Another thing to note is that if you want a absolute element to be confined to a parent element then you need to set the parent element's position to relative. That will keep the child element contained within the parent element and it won't be "relative" to the entire window.

I wrote a blog post that gives a simple example that creates the following affect:

enter image description here

That has a green div that is absolutely positioned to the bottom of the parent yellow div.


How to delete columns that contain ONLY NAs?

It seeems like you want to remove ONLY columns with ALL NAs, leaving columns with some rows that do have NAs. I would do this (but I am sure there is an efficient vectorised soution:

#set seed for reproducibility
set.seed <- 103
df <- data.frame( id = 1:10 , nas = rep( NA , 10 ) , vals = sample( c( 1:3 , NA ) , 10 , repl = TRUE ) )
#      id nas vals
#   1   1  NA   NA
#   2   2  NA    2
#   3   3  NA    1
#   4   4  NA    2
#   5   5  NA    2
#   6   6  NA    3
#   7   7  NA    2
#   8   8  NA    3
#   9   9  NA    3
#   10 10  NA    2

#Use this command to remove columns that are entirely NA values, it will elave columns where only some vlaues are NA
df[ , ! apply( df , 2 , function(x) all( ) ]
#      id vals
#   1   1   NA
#   2   2    2
#   3   3    1
#   4   4    2
#   5   5    2
#   6   6    3
#   7   7    2
#   8   8    3
#   9   9    3
#   10 10    2

If you find yourself in the situation where you want to remove columns that have any NA values you can simply change the all command above to any.

How to sort in mongoose?

with the current version of mongoose (1.6.0) if you only want to sort by one column, you have to drop the array and pass the object directly to the sort() function:

Content.find().sort('created', 'descending').execFind( ... );

took me some time, to get this right :(

Difference between Date(dateString) and new Date(dateString)

I know this is old but by far the easier solution is to just use

var temp = new Date("2010-08-17T12:09:36");

Getting only response header from HTTP POST using curl

While the other answers have not worked for me in all situations, the best solution I could find (working with POST as well), taken from here:

curl -vs '' 1> /dev/null

Callback to a Fragment from a DialogFragment

Kotlin guys here we go!

So the problem we have is that we created an activity, MainActivity, on that activity we created a fragment, FragmentA and now we want to create a dialog fragment on top of FragmentA call it FragmentB. How do we get the results from FragmentB back to FragmentA without going through MainActivity?


  1. FragmentA is a child fragment of MainActivity. To manage fragments created in FragmentA we will use childFragmentManager which does that!
  2. FragmentA is a parent fragment of FragmentB, to access FragmentA from inside FragmentB we will use parenFragment.

Having said that, inside FragmentA,

class FragmentA : Fragment(), UpdateNameListener {
    override fun onSave(name: String) {
        toast("Running save with $name")

    // call this function somewhere in a clickListener perhaps
    private fun startUpdateNameDialog() {
        FragmentB().show(childFragmentManager, "started name dialog")

Here is the dialog fragment FragmentB.

class FragmentB : DialogFragment() {

    private lateinit var listener: UpdateNameListener

    override fun onAttach(context: Context) {
        try {
            listener = parentFragment as UpdateNameListener
        } catch (e: ClassCastException) {
            throw ClassCastException("$context must implement UpdateNameListener")

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
        return activity?.let {
            val builder = AlertDialog.Builder(it)
            val binding = UpdateNameDialogFragmentBinding.inflate(LayoutInflater.from(context))
            binding.btnSave.setOnClickListener {
                val name =
            return builder.create()
        } ?: throw IllegalStateException("Activity can not be null")

Here is the interface linking the two.

interface UpdateNameListener {
    fun onSave(name: String)

That's it.

Bootstrap modal link

Please remove . from your target it should be a id

<a href="#bannerformmodal" data-toggle="modal" data-target="#bannerformmodal">Load me</a>

Also you have to give your modal id like below

<div class="modal fade bannerformmodal" tabindex="-1" role="dialog" aria-labelledby="bannerformmodal" aria-hidden="true" id="bannerformmodal">

Here is the solution in a fiddle.

Select from one table matching criteria in another?

You should make tags their own table with a linking table.

id    object
1     lamp  
2     table   
3     stool  
4     bench 

id     tag
1      furniture
2      chair

item_id tag_id
1       1
2       1
3       1
4       1
3       2
4       2

Convert a JSON string to object in Java ME?

You have many JSON parsers for Java:

    A JSONObject is an unordered collection of name/value pairs. Its external form is a string wrapped in curly braces with colons between the names and values, and commas between the values and names. The internal form is an object having get() and opt() methods for accessing the values by name, and put() methods for adding or replacing values by name. The values can be any of these types: Boolean, JSONArray, JSONObject, Number, and String, or the JSONObject.NULL object.

    A JSONArray is an ordered sequence of values. Its external form is a string wrapped in square brackets with commas between the values. The internal form is an object having get() and opt() methods for accessing the values by index, and put() methods for adding or replacing values. The values can be any of these types: Boolean, JSONArray, JSONObject, Number, and String, or the JSONObject.NULL object.

    A JSONStringer is a tool for rapidly producing JSON text.

    A JSONWriter is a tool for rapidly writing JSON text to streams.

    A JSONTokener takes a source string and extracts characters and tokens from it. It is used by the JSONObject and JSONArray constructors to parse JSON source strings.

    A JSONException is thrown when a syntax or procedural error is detected.

    The JSONString is an interface that allows classes to implement their JSON serialization.

Redirect to new Page in AngularJS using $location

If you want to change ng-view you'll have to use the '#'

$window.location.href= "#operation";

XML Error: There are multiple root elements

You can do it without modifying the XML stream: Tell the XmlReader to not be so picky. Setting the XmlReaderSettings.ConformanceLevel to ConformanceLevel.Fragment will let the parser ignore the fact that there is no root node.

        XmlReaderSettings settings = new XmlReaderSettings();
        settings.ConformanceLevel = ConformanceLevel.Fragment;
        using (XmlReader reader = XmlReader.Create(tr,settings))

Now you can parse something like this (which is an real time XML stream, where it is impossible to wrap with a node).

  <payload type='80'>7d1300786a0000000bf9458b0518000000000000000000000000000000000c0c030306001b</payload>
  <payload type='80'>fd1260780912ff3028fea5ffc0387d640fa550f40fbdf7afffe001fff8200fff00f0bf0e000042201421100224ff40312300111400004f000000e0c0fbd1e0000f10e0fccc2ff0000f0fe00f00f0eed00f11e10d010021420401</payload>
  <payload type='80'>fd126078ad11fc4015fefdf5b042ff1010223500000000000000003007ff00f20e0f01000e0000dc0f01000f000000000000004f000000f104ff001000210f000013010000c6da000000680ffa807800200000000d00c0f0</payload>

Xcode couldn't find any provisioning profiles matching

You can get this issue if Apple update their terms. Simply log into your dev account and accept any updated terms and you should be good (you will need to goto Xcode -> project->signing and capabilities and retry the certificate check. This should get you going if terms are the issue.

How may I reference the script tag that loaded the currently-executing script?

To get the script, that currently loaded the script you can use

var thisScript = document.currentScript;

You need to keep a reference at the beginning of your script, so you can call later

var url = thisScript.src

correct way to define class variables in Python

I think this sample explains the difference between the styles:

#!/usr/bin/env python

class MyClass:
    element1 = "Hello"

    def __init__(self):
        self.element2 = "World"

obj = MyClass()

print dir(MyClass)
print "--"
print dir(obj)
print "--"
print obj.element1 
print obj.element2
print MyClass.element1 + " " + MyClass.element2
['__doc__', '__init__', '__module__', 'element1']
['__doc__', '__init__', '__module__', 'element1', 'element2']
Hello World
Traceback (most recent call last):
  File "./", line 17, in <module>
    print MyClass.element2
AttributeError: class MyClass has no attribute 'element2'

element1 is bound to the class, element2 is bound to an instance of the class.

What does the colon (:) operator do?

It's used in for loops to iterate over a list of objects.

for (Object o: list)
    // o is an element of list here

Think of it as a for <item> in <list> in Python.


You did the right thing by checking from query plans. But I have 100% confidence in version 2. It is faster when the number off records are on the very high side.

My database has around 1,000,000 records and this is exactly the scenario where the query plan shows the difference between both the queries. Further, instead of using a where clause, if you use it in the join itself, it makes the query faster :
SELECT p.Name, s.OrderQty
FROM Product p
INNER JOIN (SELECT ProductID, OrderQty FROM SalesOrderDetail) s on p.ProductID = s.ProductID WHERE p.isactive = 1

The better version of this query is :

SELECT p.Name, s.OrderQty
FROM Product p
INNER JOIN (SELECT ProductID, OrderQty FROM SalesOrderDetail) s on p.ProductID = s.ProductID AND p.isactive = 1

(Assuming isactive is a field in product table which represents the active/inactive products).

Link a photo with the cell in excel

Hold down the Alt key and drag the pictures to snap to the upper left corner of the cell.

Format the picture and in the Properties tab select "Move but don't size with cells"

Now you can sort the data table by any column and the pictures will stay with the respective data.

This post at SuperUser has a bit more background and screenshots:

Get screenshot on Windows with Python?

This can be done with PIL. First, install it, then you can take a full screenshot like this:

import PIL.ImageGrab

im = PIL.ImageGrab.grab()

Check if multiple strings exist in another string

Just some more info on how to get all list elements availlable in String

a = ['a', 'b', 'c']
str = "a123" 
list(filter(lambda x:  x in str, a))

Failed to install android-sdk: "java.lang.NoClassDefFoundError: javax/xml/bind/annotation/XmlSchema"

set JAVA_OPTS=-XX:+IgnoreUnrecognizedVMOptions --add-modules

This fixed the problem on Windows for me.

Source 1, source 2

How to change status bar color in Flutter?

Change status bar color when you are not using AppBar

First Import this

import 'package:flutter/services.dart';

Now use below code to change status bar color in your application when you are not using the AppBar


    statusBarColor: AppColors.statusBarColor,/* set Status bar color in Android devices. */
    statusBarIconBrightness: Brightness.dark,/* set Status bar icons color in Android devices.*/
    statusBarBrightness: Brightness.dark)/* set Status bar icon color in iOS. */

To change the status bar color in iOS when you are using SafeArea

  body: Container(
    color:, /* Set your status bar color here */
    child: SafeArea(child: Container(
      /* Add your Widget here */

Pull request vs Merge request

There is a subtle difference in terms of conflict management. In case of conflicts, a pull request in Github will result in a merge commit on the destination branch. In Gitlab, when a conflict is found, the modifications made will be on a merge commit on the source branch.


"GitLab resolves conflicts by creating a merge commit in the source branch that is not automatically merged into the target branch. This allows the merge commit to be reviewed and tested before the changes are merged, preventing unintended changes entering the target branch without review or breaking the build."

Difference between == and ===

Just a minor contribution related to the Any object.

I was working with unit tests around NotificationCenter, which makes use of Any as a parameter that I wanted to compare for equality.

However, since Any cannot be used in an equality operation, it was necessary to change it. Ultimately, I settled on the following approach, which allowed me to get equality in my specific situation, shown here with a simplistic example:

func compareTwoAny(a: Any, b: Any) -> Bool {
    return ObjectIdentifier(a as AnyObject) == ObjectIdentifier(b as AnyObject)

This function takes advantage of ObjectIdentifier, which provides a unique address for the object, allowing me to test.

One item to note though about ObjectIdentifier per Apple at the above link:

In Swift, only class instances and metatypes have unique identities. There is no notion of identity for structs, enums, functions, or tuples.

Moment.js - tomorrow, today and yesterday

I use a combination of add() and endOf() with moment

const today = moment().endOf('day')
const tomorrow = moment().add(1, 'day').endOf('day')

if (date < today) return 'today'
if (date < tomorrow) return 'tomorrow'
return 'later'

How do I add slashes to a string in Javascript?

var str = "This is a single quote: ' and so is this: '";

var replaced = str.replace(/'/g, "\\'");

Gives you:

This is a single quote: ' and so is this: '
This is a single quote: \' and so is this: \'

CASE (Contains) rather than equal statement

CASE WHEN ', ' + dbo.Table.Column +',' LIKE '%, lactulose,%' 
  THEN 'BP Medication' ELSE '' END AS [BP Medication]

The leading ', ' and trailing ',' are added so that you can handle the match regardless of where it is in the string (first entry, last entry, or anywhere in between).

That said, why are you storing data you want to search on as a comma-separated string? This violates all kinds of forms and best practices. You should consider normalizing your schema.

In addition: don't use 'single quotes' as identifier delimiters; this syntax is deprecated. Use [square brackets] (preferred) or "double quotes" if you must. See "string literals as column aliases" here:

EDIT If you have multiple values, you can do this (you can't short-hand this with the other CASE syntax variant or by using something like IN()):

  WHEN ', ' + dbo.Table.Column +',' LIKE '%, lactulose,%' 
  WHEN ', ' + dbo.Table.Column +',' LIKE '%, amlodipine,%' 
  THEN 'BP Medication' ELSE '' END AS [BP Medication]

If you have more values, it might be worthwhile to use a split function, e.g.

USE tempdb;

       ( SELECT Item = x.i.value('(./text())[1]', 'nvarchar(max)')
         FROM ( SELECT [XML] = CONVERT(XML, '<i>'
         + REPLACE(@List,',', '</i><i>') + '</i>').query('.')
           ) AS a CROSS APPLY [XML].nodes('i') AS x(i) ) AS y

CREATE TABLE dbo.[Table](ID INT, [Column] VARCHAR(255));

(1,'lactulose, Lasix (furosemide), oxazepam, propranolol, rabeprazole, sertraline,'),
(2,'lactulite, Lasix (furosemide), lactulose, propranolol, rabeprazole, sertraline,'),
(3,'lactulite, Lasix (furosemide), oxazepam, propranolol, rabeprazole, sertraline,'),
(4,'lactulite, Lasix (furosemide), lactulose, amlodipine, rabeprazole, sertraline,');

  FROM dbo.[Table] AS t
  INNER JOIN dbo.SplitStrings('lactulose,amlodipine') AS s
  ON ', ' + t.[Column] + ',' LIKE '%, ' + s.Item + ',%'



Define global constants

This is my recent experience with this scenario:

  • @angular/cli: 1.0.0
  • node: 6.10.2
  • @angular/core: 4.0.0

I've followed the official and updated docs here:!#dependency-injection-tokens

Seems OpaqueToken is now deprecated and we must use InjectionToken, so these are my files running like a charm:


export interface IAppConfig {

  STORE_KEY: string;



import { InjectionToken } from "@angular/core";
import { IAppConfig } from "./app-config.interface";

export const APP_DI_CONFIG: IAppConfig = {

  STORE_KEY: 'l@_list@'


export let APP_CONFIG = new InjectionToken< IAppConfig >( 'app.config' );


import { APP_CONFIG, APP_DI_CONFIG } from "./app-config/app-config.constants";

@NgModule( {
  declarations: [ ... ],
  imports: [ ... ],
  providers: [
      provide: APP_CONFIG,
      useValue: APP_DI_CONFIG
  bootstrap: [ ... ]
} )
export class AppModule {}


  constructor( ...,
               @Inject( APP_CONFIG ) private config: IAppConfig) {

    console.log("This is the App's Key: ", this.config.STORE_KEY);
    //> This is the App's Key:  l@_list@


The result is clean and there's no warnings on console thank's to recent comment of John Papa in this issue:

The key was implement in a different file the interface.

Anaconda-Navigator - Ubuntu16.04

To run anaconda-navigator:

$ source ~/anaconda3/bin/activate root
$ anaconda-navigator

refresh leaflet map: map container is already initialized

For refresh leaflet map you can use this code:;

How to make custom error pages work in ASP.NET MVC 4

I do something that requires less coding than the other solutions posted.

First, in my web.config, I have the following:

<customErrors mode="On" defaultRedirect="~/ErrorPage/Oops">
   <error redirect="~/ErrorPage/Oops/404" statusCode="404" />
   <error redirect="~/ErrorPage/Oops/500" statusCode="500" />

And the controller (/Controllers/ErrorPageController.cs) contains the following:

public class ErrorPageController : Controller
    public ActionResult Oops(int id)
        Response.StatusCode = id;

        return View();

And finally, the view contains the following (stripped down for simplicity, but it can conta:

@{ ViewBag.Title = "Oops! Error Encountered"; }_x000D_
<section id="Page">_x000D_
  <div class="col-xs-12 well">_x000D_
    <table cellspacing="5" cellpadding="3" style="background-color:#fff;width:100%;" class="table-responsive">_x000D_
          <td valign="top" align="left" id="tableProps">_x000D_
            <img width="25" height="33" src="~/Images/PageError.gif" id="pagerrorImg">_x000D_
          <td width="360" valign="middle" align="left" id="tableProps2">_x000D_
            <h1 style="COLOR: black; FONT: 13pt/15pt verdana" id="errortype"><span id="errorText">@Response.Status</span></h1>_x000D_
          <td width="400" colspan="2" id="tablePropsWidth"><font style="COLOR: black; FONT: 8pt/11pt verdana">Possible causes:</font>_x000D_
          <td width="400" colspan="2" id="tablePropsWidth2">_x000D_
            <font style="COLOR: black; FONT: 8pt/11pt verdana" id="LID1">_x000D_
                                <li id="list1">_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Baptist explanation: </strong>There_x000D_
                                        must be sin in your life. Everyone else opened it fine.<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Presbyterian explanation: </strong>It's_x000D_
                                        not God's will for you to open this link.<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong> Word of Faith explanation:</strong>_x000D_
                                        You lack the faith to open this link. Your negative words have prevented_x000D_
                                        you from realizing this link's fulfillment.<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Charismatic explanation: </strong>Thou_x000D_
                                        art loosed! Be commanded to OPEN!<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Unitarian explanation:</strong> All_x000D_
                                        links are equal, so if this link doesn't work for you, feel free to_x000D_
                                        experiment with other links that might bring you joy and fulfillment.<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Buddhist explanation:</strong> .........................<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Episcopalian explanation:</strong>_x000D_
                                        Are you saying you have something against homosexuals?<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Christian Science explanation: </strong>There_x000D_
                                        really is no link.<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Atheist explanation: </strong>The only_x000D_
                                        reason you think this link exists is because you needed to invent it.<br>_x000D_
                                    <span class="infotext">_x000D_
                                        <strong>Church counselor's explanation:</strong>_x000D_
                                        And what did you feel when the link would not open?_x000D_
                            <h2 style="font:8pt/11pt verdana; color:black" id="ietext">_x000D_
                                <img width="16" height="16" align="top" src="~/Images/Search.gif">_x000D_
                                HTTP @Response.StatusCode - @Response.StatusDescription <br>_x000D_

It's just as simple as that. It could be easily extended to offer more detailed error info, but ELMAH handles that for me & the statusCode & statusDescription is all that I usually need.

How to improve performance of ngRepeat over a huge dataset (angular.js)?

If all your rows have equal height, you should definitely take a look at the virtualizing ng-repeat:

This demo looks very promising (and it supports inertial scrolling)

React prevent event bubbling in nested components on click

I had issues getting event.stopPropagation() working. If you do too, try moving it to the top of your click handler function, that was what I needed to do to stop the event from bubbling. Example function:

  toggleFilter(e) {
    e.stopPropagation(); // If moved to the end of the function, will not work
    let target =;
    let i = 10; // Sanity breaker

    while(true) {
      if (--i === 0) { return; }
      if (target.classList.contains("filter")) {
      target = target.parentNode;

What’s the best way to load a JSONObject from a json text file?

With java 8 you can try this:

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

import java.nio.file.Files;
import java.nio.file.Paths;

public class JSONUtil {

    public static JSONObject parseJSONFile(String filename) throws JSONException, IOException {
        String content = new String(Files.readAllBytes(Paths.get(filename)));
        return new JSONObject(content);

    public static void main(String[] args) throws IOException, JSONException {
        String filename = "path/to/file/abc.json";
        JSONObject jsonObject = parseJSONFile(filename);

        //do anything you want with jsonObject

What do I do when my program crashes with exception 0xc0000005 at address 0?

Exception code 0xc0000005 is an Access Violation. An AV at fault offset 0x00000000 means that something in your service's code is accessing a nil pointer. You will just have to debug the service while it is running to find out what it is accessing. If you cannot run it inside a debugger, then at least install a third-party exception logger framework, such as EurekaLog or MadExcept, to find out what your service was doing at the time of the AV.

Get last field using awk substr

I know I'm like 3 years late on this but.... you should consider parameter expansion, it's built-in and faster.

if your input is in a var, let's say, $var1, just do ${var1##*/}. Look below

$ var1='/home/parent/child1/filename'
$ echo ${var1##*/}
$ var1='/home/parent/child1/child2/filename'
$ echo ${var1##*/}
$ var1='/home/parent/child1/child2/child3/filename'
$ echo ${var1##*/}

Linux - Install redis-cli only


tar xvzf redis-stable.tar.gz
cd redis-stable
make redis-cli
sudo cp src/redis-cli /usr/local/bin/

With Docker I normally use If I need to add redis-cli to an image I use the following snippet.

RUN cd /tmp &&\
    curl | tar xz &&\
    make -C redis-stable &&\
    cp redis-stable/src/redis-cli /usr/local/bin &&\
    rm -rf /tmp/redis-stable

HTML img scaling

I think the best solution is resize the images via script or locally and upload them again. Remember, you're forcing your viewers to download larger files than they need

Oracle comparing timestamp with date

to_date format worked for me. Please consider the date formats: MON-, MM, ., -.

t.start_date >= to_date('14.11.2016 04:01:39', 'DD.MM.YYYY HH24:MI:SS')
t.start_date <=to_date('14.11.2016 04:10:07', 'DD.MM.YYYY HH24:MI:SS')

Grab a segment of an array in Java without creating a new array on heap

How about a thin List wrapper?

List<Byte> getSubArrayList(byte[] array, int offset, int size) {
   return new AbstractList<Byte>() {
      Byte get(int index) {
         if (index < 0 || index >= size) 
           throw new IndexOutOfBoundsException();
         return array[offset+index];
      int size() {
         return size;


How do I get specific properties with Get-AdUser

using select-object for example:

Get-ADUser -Filter * -SearchBase 'OU=Users & Computers, DC=aaaaaaa, DC=com' -Properties DisplayName | select -expand displayname | Export-CSV "ADUsers.csv" 

Difference between TCP and UDP?

Run into this thread and let me try to express it in this way.


3-way handshake

Bob: Hey Amy, I'd like to tell you a secret
Amy: OK, go ahead, I'm ready
Bob: OK

Bob: 'I', this is the first letter
Amy: First letter received, please send me the second letter
Bob: ' ', this is the second letter
Amy: Second letter received, please send me the third letter
Bob: 'L', this is the third letter
After a while
Bob: 'L', this the third letter
Amy: Third letter received, please send me the fourth letter
Bob: 'O', this the forth letter
Amy: ...

4-way handshake
Bob: My secret is exposed, now, you know my heart.
Amy: OK. I have nothing to say.
Bob: OK.


Amy received: OVI L E

TCP is more reliable than UDP with even message order guaranteed, that's no doubt why UDP is more lightweight and efficient.

Python function attributes - uses and abuses

I use them sparingly, but they can be pretty convenient:

def log(msg):

Now I can use log throughout my module, and redirect output simply by setting log.logfile. There are lots and lots of other ways to accomplish that, but this one's lightweight and dirt simple. And while it smelled funny the first time I did it, I've come to believe that it smells better than having a global logfile variable.