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

What is an environment variable?

Environment variables are variables used by the operating system to store information about the runtime environment, providing a way to share configuration data between programs. They affect process behavior and their child processes and play an important role in the OS.

Common environment variables

PATH : Specifies the search path for executable files.

HOME : The current user's home directory.

USER : The username of the currently logged‑in user.

SHELL : The type of shell currently in use.

LANG : System language and character set settings.

PWD : The current working directory.

Viewing environment variables

In Linux you can use the following commands to view the current environment variables: printenv or env To view the value of a specific variable, use the echo command, for example:

echo $PATH

Setting environment variables

Temporary setting

Temporary environment variables are only valid for the current terminal session. Set them with: export VARIABLE_NAME="value" Example:

export MY_VARIABLE="Hello, World!"

Permanent setting

To make environment variables persist across all sessions, add them to configuration files. Common files include:

/etc/profile : System‑wide environment variable settings.

~/.bashrc : Current user's Bash shell configuration file.

~/.bash_profile : Current user's login shell configuration file.

~/.profile : General configuration file for the current user's shell.

Example: edit ~/.bashrc and add the following line: export MY_VARIABLE="Hello, World!" Save and close the file, then apply the changes:

source ~/.bashrc

Deleting environment variables

Use the unset command. Example:

unset MY_VARIABLE

Examples: Setting and using environment variables

Example 1: Temporary environment variable

export MY_VAR="temporary value"
echo $MY_VAR

Output:

temporary value

Example 2: Permanently set PATH variable

Edit ~/.bashrc and add: export PATH=$PATH:/my/custom/path Save and apply:

source ~/.bashrc

Example 3: Use environment variable in a script

Create a simple Bash script, e.g., myscript.sh:

#!/bin/bash
echo "My variable is: $MY_VAR"

Make the script executable: chmod +x myscript.sh Set the variable and run the script:

export MY_VAR="Hello from script"
./myscript.sh

Output:

My variable is: Hello from script

Summary

Environment variables are crucial in Linux, providing a flexible way to configure the system and programs. By learning how to view, set, and delete them, users can better manage and optimize their Linux environment.