shell-patterns

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name: shell-patterns description: Shell scripting patterns - portability, explicit error handling, readability over cleverness

Philosophy

• Shell scripts should be obvious
• Portability matters - your script will run on systems you don't control
• Explicit error handling - scripts shouldn't silently fail halfway through

Shebang and Compatibility

• Use #!/usr/bin/env bash for portability, not #!/bin/bash
• If you need bash-specific features, use bash - don't try to make it POSIX when it's not
• For truly portable scripts, stick to POSIX sh and test on different shells
• Target systems will always be Linux by default unless explicitly told otherwise

Functions

• Use functions for repeated logic - don't copy-paste the same shit
• Name functions clearly - backup_config not bc
• Keep functions focused - one job per function
• Return meaningful exit codes (0 for success, non-zero for failure)

Variables

• Use "${var}" instead of $var - quote everything unless you want word splitting
• UPPER_CASE for environment/global vars, lower_case for local/function vars
• local keyword for function variables - don't pollute global scope
• Check if vars are set before using: ${var:-default} or explicit checks

Commands and Tools

• Never assume a non-default tool exists - ask user before
• Prefer common POSIX tools over GNU-specific extensions when possible
• Use command substitution $(command) instead of backticks - it's more readable

Loops and Arrays

• Use while read for processing command output line by line
• Arrays in bash: arr=("one" "two") - but remember they're bash-specific
• Loop over files safely: for file in *.txt; do [[ -e "$file" ]] || continue
• Avoid parsing ls output - use globs or find with -print0 and while read -d ''

Output and Logging

• Use echo for simple output, printf when you need formatting
• stderr for errors: echo "Error message" >&2

Anti-Patterns

• Not quoting variables - guaranteed to break with spaces
• Parsing ls output instead of using proper tools
• Ignoring error codes and letting scripts continue after failures
• Using cd without checking if it succeeded
• Not cleaning up temporary files