Quoting

Bash · Reference cheat sheet

📋 Overview

Quoting controls word-splitting, globbing, and expansion. Double quotes allow $, `, and \ escapes; single quotes are literal; $'' enables ANSI-C escapes. Correct quoting prevents most bash bugs.

🔧 Core concepts

Word-splitting uses IFS (default space/tab/newline) on unquoted expansions. Globbing (*, ?, []) also applies only when unquoted.

💡 Examples

Preserve spaces:

file="my document.txt"
rm -- "$file"          # good
# rm -- $file          # bad: two words

Literal vs expanded:

echo 'Home is $HOME'   # Home is $HOME
echo "Home is $HOME"   # Home is /home/you

ANSI-C quotes:

printf '%s\n' $'line1\nline2'
path=$'C:\\Users\\name'   # backslashes as written

Nested / mixed:

sql="SELECT * FROM users WHERE name='${name//\'/\'\'}'"
msg="He said \"hello\""

Here-docs:

cat <<'EOF'
No expansion: $HOME stays literal
EOF

cat <<EOF
Expanded: $HOME
EOF

⚠️ Pitfalls

• "$@" keeps args separate; "$*" joins with first IFS char.
• Empty "$var" is one empty argument; unquoted $var vanishes.
• Globs inside quotes are literal: "*.txt" is not a pattern.
• Backticks nest poorly; prefer $(...).
• JSON/YAML in scripts: prefer single quotes or heredocs to avoid escape hell.
• echo + escapes is non-portable; use printf.

🔗 Related

• variables.md
• globbing.md
• string_ops.md
• arrays.md
• scripts_best_practices.md