How do I add environment variables?

To set variable only for current shell:

VARNAME="my value"

To set it for current shell and all processes started from current shell:

export VARNAME="my value"      # shorter, less portable version

To set it permanently for all future bash sessions add such line to your .bashrc file in your $HOME directory.

To set it permanently, and system wide (all users, all processes) add set variable in /etc/environment:

sudo -H gedit /etc/environment

This file only accepts variable assignments like:

VARNAME="my value"

Do not use the export keyword here.

You need to logout from current user and login again so environment variables changes take place.

To set an environment variable once, use the export command in the prompt, not in a shell script:

$ export THEVAR=/example

The variable will be set for the rest of the shell session or until unset.

To set an environment variable everytime, use the export command in the .bashrc file (or the appropriate initialization file for your shell).

To set an environment variable from a script, use the export command in the script, and then source the script. If you execute the script it will not work.

For an explanation of the difference between sourcing and executing see this answer:

• What is the difference between executing a Bash script vs sourcing it?

To permanently add a new environment variable in Ubuntu (tested only in 14.04), use the following steps:

1. Open a terminal (by pressing CtrlAltT)
2. sudo -H gedit /etc/environment
3. Type your password
4. Edit the text file just opened:
   e.g. if you want to add FOO=bar, then just write FOO=bar in a new line
5. Save it
6. Once saved, logout and login again.
7. Your required changes are made.

To get the environment/var changes to persist after the script has completed, you have to usesource ./script.sh or the shorthand notation for source, ".", like . ./script.sh

Source will execute the commands in the script as if you have typed them in... so it does change some aspects of the script, such as exiting... so if your script checks something and decides to exit if false, for instance, via calling exit 0, it will terminate your current terminal / shell session.

I know it's pretty late, but if you want to add an environment variable for all users (e.g. JAVA usage) - you can do the following:

1) Open /etc/bash.bashrc using nano (you can use whatever editor, I do not prefer VIM as it's the worst when it comes to user friendliness - nothing personal).

2) Append to the file:

export VAR=path export PATH=$PATH:/bin 3) (Better if you can bounce the box) - or simply open a new SSH session and confirm using `env' command.

BUT IF you want each user to have a separate setting for this, you have to make a change (scripted) to .bashrc file under ~/.bashrc (or /home/$USER/ if you are new to Linux systems)

If you are doing things via script, one easy way to set environment variable permanently is put below statement in your script,

if [[ ! -d "$MyVar" ]]; then 
    export MyVar="abc"
    echo 'export MyVar="abc"' >> ~/.bashrc
fi

If you need to evaluage expressions like pwd, you can use this, for example,

echo "export EIGEN_ROOT=\"$(pwd)/eigen\"" >> ~/.bashrc

If you are using Ubuntu or any Unix-based system then export the variables in the ~/.bashrc file. It's a hidden file and you can get there through the terminal or by unhiding hidden files in the file system.

Then edit the file and set export THEVAR=/example there, save and it's done.

If you are deploying JAVA aplication using TOMCAT you can set environment variables the following way:

1.sudo su and cd to /var/lib/tomcat8/bin/ (or whichever is your tomcat bin path)

2. touch setenv.sh(if it doesn't exist), if file present already do 'vi setenv.sh'

3. chmod 777 setenv.sh (make file executable)

4. vi setenv.sh and set following line in setenv.sh export key=value

5. sudo systemctl restart tomcat.service

In your java file you can use the following code to check if the variable is set

private static void printEnv() {
    System.out.println("******************************Environment Vars*****************************");
    Map<String, String> enviorntmentVars = System.getenv();
    enviorntmentVars.entrySet().forEach(System.out::println);

    System.out.println("******************************system Vars*****************************");
    Properties enviorntmentProperties = System.getProperties();
    enviorntmentVars.entrySet().forEach(System.out::println);
}