Setting and Exporting Variables

Learn how to create, modify, and export environment variables to customize your shell environment.

Setting Variables

Basic syntax:

VARIABLE_NAME=value

Important: No spaces around the = sign!

Variable Naming Rules

• Start with letter or underscore
• Can contain letters, numbers, underscores
• Case sensitive (convention: UPPERCASE for env vars)
• No spaces in names

# Good
MY_VAR=value
_private=secret
CONFIG_PATH=/etc

# Bad
my-var=value     # Hyphens not allowed
1stVar=value     # Can't start with number
my var=value     # Spaces not allowed

export - Make Variables Available

export makes variables available to child processes:

MY_VAR="local only"           # Shell variable
export MY_VAR                  # Now exported
export OTHER_VAR="value"       # Set and export

Exercise: Set a Variable

Create and display an environment variable:

Viewing Exported Variables

export              # List all exports
export -p           # Same, with 'declare -x' prefix

Unsetting Variables

Remove a variable:

unset VARIABLE_NAME

Temporary Variables

Set a variable for one command only:

DEBUG=1 ./script.sh
LANG=C sort file.txt

Variable Expansion

Use variables in strings:

echo "Hello, $USER"
echo "Home: ${HOME}/documents"
echo "Date: $(date)"

Modifying Variables

# Append to variable
PATH=$PATH:/new/path
PATH="${PATH}:/another/path"

# Prepend to variable
PATH=/new/path:$PATH

Making Variables Permanent

Add to shell config file:

For Current User

# Add to ~/.bashrc
export MY_VAR="value"

For All Users (requires root)

# Add to /etc/environment
MY_VAR="value"

Common Use Cases

Set Editor

export EDITOR=vim
export VISUAL=vim

Set Language

export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8

Application Config

export NODE_ENV=production
export DATABASE_URL="postgres://..."

Exercise: Export a Variable

Export a variable and verify it's in the environment:

Key Takeaways

• Set variables with NAME=value (no spaces!)
• Use export to make available to child processes
• Use unset to remove variables
• Add to ~/.bashrc for persistence
• Variables are case-sensitive (use UPPERCASE)