standards-shell

Shell/Bash Coding Standards

Core Principles

1. Simplicity: Simple, understandable scripts
2. Readability: Readability over cleverness
3. Maintainability: Scripts that are easy to maintain
4. Testability: Scripts that are easy to test
5. DRY: Don't Repeat Yourself - but don't overdo it
6. Defensiveness: Fail early, fail loudly

General Rules

• Defensive Header: Always use set -euo pipefail
• Quote Variables: Always quote variables "$var"
• Descriptive Names: Meaningful names for variables and functions
• Minimal Changes: Only change relevant code parts
• No Over-Engineering: No unnecessary complexity
• ShellCheck Clean: All scripts must pass ShellCheck

Naming Conventions

Element	Convention	Example
Variables	snake_case	user_name, file_count
Functions	snake_case	get_user_by_id, validate_input
Constants	UPPER_SNAKE_CASE	MAX_RETRIES, DEFAULT_TIMEOUT
Files	kebab-case or snake_case	deploy-app.sh, run_tests.sh
Environment Vars	UPPER_SNAKE_CASE	API_URL, DATABASE_HOST

Script Template

#!/bin/bash
set -euo pipefail

readonly SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
readonly SCRIPT_NAME="$(basename "${BASH_SOURCE[0]}")"

# Cleanup on exit
cleanup() {
    rm -f "$SCRIPT_DIR"/*.tmp 2>/dev/null || true
}
trap cleanup EXIT

# Error handler
error_handler() {
    echo "Error on line $1" >&2
    exit 1
}
trap 'error_handler $LINENO' ERR

main() {
    # Script logic here
    echo "Running $SCRIPT_NAME"
}

main "$@"

Defensive Scripting

# REQUIRED: Always start with this
set -euo pipefail
# -e: Exit on error
# -u: Error on undefined variables
# -o pipefail: Pipe fails if any command fails

# RECOMMENDED: Safer IFS
IFS=$'\n\t'

# REQUIRED: Quote all variables
echo "$var"                     # Good
echo $var                       # Bad - word splitting

# REQUIRED: Use [[ ]] for conditionals (Bash)
if [[ -f "$file" ]]; then       # Good
if [ -f "$file" ]; then         # POSIX only