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In this lesson, you’ll learn how to view, customize, and persist environment variables on Linux. We cover session-level tweaks, system-wide settings, and automating tasks at login.

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What Are Environment Variables?

Environment variables are key–value pairs that your shell and applications use to determine behavior, file locations, and settings. You can list all of them with either:
Example output:

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Modifying Bash History Size

By default, HISTSIZE=1000 limits your Bash history to 1 000 commands. To increase it for the current session:
Verify:
Sample:

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Common Environment Variables

Here are a few variables you’ll encounter frequently: To display a variable’s value:
Use these expansions for platform-independent scripting:
Each user running this command will create saved_file in their own home directory.

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Setting Persistent Environment Variables

User-specific variables can go in ~/.bashrc or ~/.profile, but for system-wide settings, use /etc/environment.
Line-based syntax only—no shell expansions or functions.
Example entries look like KEY="value".

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Edit /etc/environment

  1. Open the file with root privileges:
  2. Add your variable:
  3. Save and exit.
  4. Log out and back in, then verify:
Changes in /etc/environment affect all users and services.
Always back up /etc/environment before editing.

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Automating Commands on Login

To execute commands for every user at login, place shell scripts in /etc/profile.d/. For instance, record the last login time:
  1. Create a script file:
  2. Add the following (no shebang required):
  3. Save and exit.
  4. Log out and back in, then check:
This script uses $HOME and demonstrates how to run tasks automatically upon user login.

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