Environment variables in Linux are dynamic values that affect how running processes behave. They are used to store configuration settings that can be accessed by applications and scripts to modify their behavior based on the environment they run in.
To view all currently set environment variables, use the env command:
karchunt@kcserver:~$ env
SHELL=/bin/bash
WSL2_GUI_APPS_ENABLED=1
WSL_DISTRO_NAME=Ubuntu
NAME=kcserver
PWD=/home/karchunt
LOGNAME=karchunt
HOME=/home/karchunt
LANG=C.UTF-8
USER=karchunt
TERM=xterm-256color
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
...
Creating Environment Variables
Use the export command to create an environment variable in the current shell session:
karchunt@kcserver:~$ export MY_VARIABLE="Hello, World!"
karchunt@kcserver:~$ echo $MY_VARIABLE
Hello, World!
Variables created with export only persist for the current session. When you close the terminal, they are lost.
export command to your shell’s configuration file:
| Scope | File |
|---|
| Current user | ~/.bashrc, ~/.profile, or ~/.bash_profile |
| All users (system-wide) | /etc/environment or a new file in /etc/profile.d/ |
Removing Environment Variables
Use the unset command to remove an environment variable:
karchunt@kcserver:~$ unset MY_VARIABLE
karchunt@kcserver:~$ echo $MY_VARIABLE
unset, echoing the variable returns an empty string.
The PATH Variable
The PATH environment variable is a special variable that tells the shell where to look for executable files when you run a command. It contains a colon-separated list of directories that the shell searches through in order.
View the current PATH:
karchunt@kcserver:~$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
which:
karchunt@kcserver:~$ which python3
/usr/bin/python3
Adding a Directory to PATH
If a command isn’t found, its directory may not be in PATH. Append a new directory using export:
karchunt@kcserver:~$ export PATH=$PATH:/new/directory/path
Avoid overwriting PATH entirely (e.g. PATH=/new/path). Always append to the existing value using $PATH:/new/path to preserve access to system commands.
To make changes to PATH permanent, add the export command to your ~/.bashrc or ~/.profile file.