Environment variables in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an environment variable in Linux?

An environment variable is a named value stored by the operating system that programs can use to get information about the system or user settings. It acts like a note that programs can read to know how to behave.

beginner

How do you display all environment variables in a Linux shell?

You can use the command printenv or env to list all environment variables currently set in your shell session.

beginner

How do you set a new environment variable for the current shell session?

Use the command export NAME=value. For example, export MYVAR=hello sets an environment variable named MYVAR with the value 'hello' for the current session.

intermediate

What happens to environment variables when you close the terminal?

Environment variables set in a terminal session are lost when you close that terminal unless saved in configuration files like ~/.bashrc or ~/.profile to load automatically on new sessions.

beginner

How can you use an environment variable inside a shell script?

You can access an environment variable in a shell script by prefixing its name with a dollar sign, like $VARIABLE_NAME. For example, echo $HOME prints the home directory path.

Which command shows all environment variables in Linux?

A mkdir

B ls

C cd

D printenv

The printenv command lists all environment variables. Other commands like ls, cd, and mkdir do not show environment variables.

How do you set an environment variable named PATH to '/usr/bin' for the current session?

A export PATH=/usr/bin

B set PATH=/usr/bin

C PATH=/usr/bin

D env PATH=/usr/bin

Use export PATH=/usr/bin to set and export the variable so child processes can see it. Just PATH=/usr/bin sets it only for the current shell, not exported.

What symbol do you use to access the value of an environment variable in a shell script?

A #

B $

C &

D *

The dollar sign $ is used to access the value of an environment variable, e.g., $HOME.

Where should you save environment variable settings to make them permanent for your user?

A /tmp

B /etc/passwd

C ~/.bashrc

D /var/log

User-specific environment variables are often saved in ~/.bashrc or ~/.profile to load automatically on new shell sessions.

If you set an environment variable in one terminal, will it be available in a new terminal window automatically?

A No, unless saved in config files

B Only if you reboot

C Yes, always

D Only if you use sudo

Environment variables set in one terminal session are not available in new terminals unless saved in configuration files like ~/.bashrc.

Explain what environment variables are and how they are used in Linux.

Think about how programs know about your system or preferences.

Describe the steps to create a new environment variable that lasts across terminal sessions.

Consider both temporary and permanent ways.