How to Use Environment Variables in Bash: Syntax and Examples

In Bash, you set an environment variable using export VAR_NAME=value and access it with $VAR_NAME. These variables store data that scripts and commands can use during execution.

Syntax

To create or update an environment variable, use export VAR_NAME=value. To read the variable, use $VAR_NAME in your script or command.

• export: Makes the variable available to child processes.
• VAR_NAME: The name of your variable (uppercase by convention).
• value: The data you want to store.
• $VAR_NAME: Accesses the value stored in the variable.

bash

export MY_VAR="Hello World"
echo $MY_VAR

Output

Hello World

Example

This example shows how to set an environment variable and then use it in a script to print a greeting message.

bash

#!/bin/bash
export GREETING="Hello"
export NAME="Alice"
echo "$GREETING, $NAME!"

Output

Hello, Alice!

Common Pitfalls

Common mistakes include not exporting the variable, which means child processes won't see it, or forgetting to use $ when accessing the variable.

Also, avoid spaces around the = sign when assigning values.

bash

# Wrong: variable not exported, child processes can't access it
MY_VAR="No export"
echo $MY_VAR

# Right: export variable to make it available
export MY_VAR="Exported"
echo $MY_VAR

Output

No export
Exported

Quick Reference

Command	Description
export VAR=value	Set and export an environment variable
echo $VAR	Access and print the variable's value
unset VAR	Remove the variable from environment
VAR=value command	Set variable only for a single command execution

Key Takeaways

Use 'export VAR=value' to create environment variables accessible to child processes.

Access variables with '$VAR' to use their stored values in scripts or commands.

Always avoid spaces around '=' when assigning variables in Bash.

Export variables if you want them available to other programs or scripts.

Use 'unset VAR' to remove environment variables when no longer needed.