How to use shell variables

Overview

Shell variables give names to text values. Environment variables are exported so programs started by the shell can read them.

Examples

course='Linux basics'
echo "$course"
file="$HOME/notes.txt"
printf '%s\n' "$file"
export EDITOR=nano
unset course

Rules and expansions

• Do not put spaces around = in an assignment
• Use $name or ${name} to expand a value
• Double quotes allow expansion while preserving spaces
• Single quotes keep text literal
• $HOME, $PATH, and $? are common shell values
• export passes a variable to child processes

Tips and safety

Quote variable expansions as "$file" unless you specifically need word splitting or wildcard expansion.

Do not store secrets in shell history or commit them in scripts. Environment variables can also be visible to processes and diagnostic tools.