bash

Bash / Shell: Idiomatic Efficiency Reference

When to Use

• Use this skill when the task matches this description: Language-specific super-code guidelines for bash.

Table of Contents

1. [Quoting & Word Splitting](#quoting)
2. [Conditionals & Tests](#conditionals)
3. [Loops & Iteration](#loops)
4. [Pipes & Process Substitution](#pipes)
5. [Functions & Return Values](#functions)
6. [Error Handling](#errors)
7. [Anti-patterns specific to Bash](#antipatterns)

---

1. Quoting & Word Splitting {#quoting}

# ❌ Unquoted variable (word splitting + globbing)
for f in $files; do rm $f; done

# ✅
for f in "${files[@]}"; do rm -- "$f"; done

# ❌ Unquoted command substitution
path=$(find . -name config)
cat $path  # breaks on spaces

# ✅
path="$(find . -name config)"
cat "$path"

# ❌ Using backticks for command substitution
result=`echo hello`

# ✅ — $() nests cleanly
result=$(echo hello)

# ❌ String comparison without quotes
if [ $var = "hello" ]; then  # breaks if var is empty or has spaces

# ✅
if [[ "$var" = "hello" ]]; then

Rule: double-quote every $variable and $(command) unless you specifically need splitting.

---

2. Conditionals & Tests {#conditionals}

# ❌ Single bracket test (POSIX but fragile)
if [ -f "$file" -a -r "$file" ]; then

# ✅ — [[ is safer, supports &&/||, no word splitting inside
if [[ -f