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Bash Standards

Compatibility and readability conventions for shell scripts.

Shebang

• Use #!/usr/bin/env bash for portability, not hardcoded /bin/bash
• Use #!/bin/sh only when the script genuinely works with POSIX sh

Strict Mode

Start scripts with:

#!/usr/bin/env bash
set -euo pipefail
IFS=$'\n\t'

• -e - exit on error
• -u - error on unset variables
• -o pipefail - fail if any command in a pipeline fails
• IFS - only split on newlines and tabs, avoids word-splitting surprises

Style

• 2-space indent (4-space is too deep for shell, especially with nested conditionals)
• snake_case for variables and functions
• UPPER_SNAKE_CASE for environment variables and readonly globals
• Opening braces on the same line as the keyword:

if [[ -f "$file" ]]; then
    echo "exists"
fi

for item in "${list[@]}"; do
    process "$item"
done

Conditionals

• Use [[ ]] over [ ] - fewer quoting issues, more features (regex, pattern matching)
• Quote all variable expansions: "$var", not $var
• Quote command substitutions: "$(command)"

Functions

• Declare with name() { … } - no function keyword (POSIX-compatible)
• Keep functions small, one task each
• Use local for all function-scoped variables:

greet() {
    local name="$1"
    echo "Hello, $name"
}

Error Handling

• Print error messages to stderr:

die() {
    echo "$*" >&2
    exit 1
}

• Check command exit codes explicitly when set -e isn’t enough
• Use trap for cleanup on exit:

cleanup() {
    rm -f "$tmpfile"
}
trap cleanup EXIT

Input Validation

• Check argument count before accessing positional params:

if [[ $# -lt 1 ]]; then
    die "Usage: $0 <file>"
fi

• Validate file existence before reading/writing
• Use ${var:-default} for optional variables with fallbacks

Output

• printf over echo for anything beyond plain strings (more portable)
• Use heredocs for multi-line blocks:

cat <<EOF > config.ini
[default]
path=$target_dir
mode=0755
EOF

Organization

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

# ── Constants ──────────────────────────────
readonly APP_NAME="my-tool"
readonly CONFIG_DIR="${XDG_CONFIG_HOME:-$HOME/.config}/$APP_NAME"

# ── Helpers ────────────────────────────────
die() { echo "$*" >&2; exit 1; }

# ── Main ───────────────────────────────────
main() { ... }
main "$@"

• Constants at the top, then helpers, then the main function
• main "$@" at the bottom - keeps the global scope clean
• Section comments with dividers for longer scripts