Master Linux Environment Variables: View, Set, and Delete Them

Environment Variables in Linux

What is an environment variable?

Environment variables are key‑value pairs maintained by the operating system. They are inherited by child processes and influence program behavior, such as search paths, user information, locale settings, and other configuration data.

Common environment variables

PATH : List of directories searched for executable files.

HOME : Current user's home directory.

USER : Logged‑in username.

SHELL : Path to the current shell program.

LANG : System language and character set.

PWD : Present working directory.

Viewing environment variables

Use any of the following commands in a terminal: printenv or env To display a specific variable, use echo $VARIABLE_NAME, for example:

echo $PATH

Setting environment variables

Temporary setting

Temporary variables exist only for the current shell session. Define them with export: export VARIABLE_NAME="value" Example:

export MY_VARIABLE="Hello, World!"

Permanent setting

To make a variable persist across sessions, add an export line to one of the shell initialization files. Typical files are: /etc/profile: System‑wide configuration. ~/.bashrc: Interactive Bash sessions for the current user. ~/.bash_profile: Login Bash sessions for the current user. ~/.profile: General user shell configuration.

Example – add a variable to ~/.bashrc: nano ~/.bashrc Append the line: export MY_VARIABLE="Hello, World!" Apply the changes without restarting the shell:

source ~/.bashrc

Deleting environment variables

Remove a variable from the current environment with unset:

unset MY_VARIABLE

Practical examples

Example 1 – Set a temporary variable

export MY_VAR="temporary value"
echo $MY_VAR

Output:

temporary value

Example 2 – Permanently add a directory to PATH

nano ~/.bashrc   # open the file for editing
# Append the following line at the end
export PATH=$PATH:/my/custom/path
source ~/.bashrc   # reload the file

Example 3 – Use an environment variable in a Bash script

#!/bin/bash
# myscript.sh

echo "My variable is: $MY_VAR"

Make the script executable and run it:

chmod +x myscript.sh
export MY_VAR="Hello from script"
./myscript.sh

Output:

My variable is: Hello from script