bash-development

Bash Development

Core patterns and best practices for Bash 5.1+ script development. Provides modern bash idioms, error handling, argument parsing, and pure-bash alternatives to external commands.

Script Foundation

Every script starts with the essential header:

#!/usr/bin/env bash
set -euo pipefail

set options explained:

• -e - Exit immediately on command failure
• -u - Treat unset variables as errors
• -o pipefail - Pipeline fails if any command fails

Script Metadata Pattern

SCRIPT_NAME=$(basename "${BASH_SOURCE[0]}")
SCRIPT_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
readonly SCRIPT_VERSION="1.0.0"
readonly SCRIPT_NAME SCRIPT_DIR

Error Handling

Implement trap-based error handling for robust scripts.

Code examples

Argument Parsing

Standard argument parsing template.

Code examples

Variable Best Practices

Always use curly braces and quote variables:

# Correct
"${variable}"
"${array[@]}"

# Incorrect
$variable
${array[*]}  # Use [@] for proper iteration

Use readonly for constants:

readonly CONFIG_FILE="/etc/app/config"
readonly -a VALID_OPTIONS=("opt1" "opt2" "opt3")

Note: Never use readonly in sourced scripts - it causes errors on re-sourcing.

String Operations (Pure Bash)

Prefer native bash parameter expansion over external tools:

# Trim whitespace
trimmed="${string#"${string%%[![:space:]]*}"}"
trimmed="${trimmed%"${trimmed##*[![:space:]]}"}"

# Lowercase/Uppercase (Bash 4+)
lower="${string,,}"
upper="${string^^}"

# Substring extraction
substring="${string:0:10}"      # First 10 chars
suffix="${string: -5}"          # Last 5 chars

# Replace patterns
replaced="${string//old/new}"   # Replace all
replaced="${string/old/new}"    # Replace first

# Strip prefix/suffix
no_prefix="${string#prefix}"    # Shortest match
no_prefix="${string##*/}"       # Longest match (basename)
no_suffix="${string%suffix}"    # Shortest match
no_suffix="${string%%/*}"       # Longest match