Bash — Environment Variables

Common environment variables

echo $HOME         # Home directory
echo $USER         # Current user
echo $SHELL        # Current shell
echo $PATH         # Executable path
echo $PWD          # Current directory
echo $LANG         # Language
echo $EDITOR       # Default editor

Setting variables

#!/bin/bash

# Local variable (only in current shell)
my_var="hello"

# Export to environment
export MY_VAR="hello"

# Set and export
export NAME="Alice"

PATH manipulation

#!/bin/bash

# Add to PATH
export PATH="$PATH:/new/path"

# Prepend to PATH
export PATH="/new/path:$PATH"

# Remove from PATH
export PATH=$(echo "$PATH" | sed 's|/old/path:||')

Shell configuration files

File	Purpose
~/.bashrc	Interactive shell config
~/.bash_profile	Login shell config
~/.profile	Login shell config (POSIX)
/etc/bash.bashrc	System-wide config
/etc/profile	System-wide login config

Aliases

# Create alias
alias ll='ls -la'
alias gs='git status'
alias gp='git push'

# Remove alias
unalias ll

# Make permanent (add to ~/.bashrc)
echo "alias ll='ls -la'" >> ~/.bashrc

Mini Practice

Write Bash code that:

1. Prints common environment variables
2. Sets and exports a custom variable
3. Adds a directory to PATH
4. Creates an alias

Up Next

In the next lesson, you'll learn about Regular Expressions — pattern matching in Bash.