bash

name	bash
description	Create, edit, and improve bash scripts with automated linting and formatting. Use when working with shell scripts (.sh files), writing bash functions, fixing script errors, or when the user asks to create or modify any bash/shell script.

Bash

Write robust, well-formatted bash scripts with automated quality checks.

Workflow

1. Before writing: Format with shfmt -w <file> if available
2. After writing: Lint with shellcheck <file> if available
3. Iterate: Fix errors, re-format if needed

Formatting with shfmt

Always format before writing if shfmt is installed:

shfmt -w script.sh

Default style (POSIX-compatible):

• Indent with tabs
• Simplify code where possible
• Add spaces around operators

Options:

• -i 4 - 4-space indent instead of tabs
• -ci - indent switch cases
• -bn - binary operators start lines

Linting with shellcheck

Run after writing/modifying scripts:

shellcheck script.sh

Common issues to address:

• SC2086: Double quote variables to prevent globbing
• SC2034: Unused variables
• SC2164: Use cd ... || exit for error handling
• SC2181: Check exit status directly instead of $?

Best Practices

Shebang and Headers

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

Error Handling

# Check command success
if ! command -v foo &>/dev/null; then
    echo "error: foo not found" >&2
    exit 1
fi

# Safe cd
cd "$DIR" || exit 1

Variables

# Quote all variables
"$VAR"
"${ARRAY[@]}"

# Prefer local
local var="value"

# Defaults
: "${VAR:=default}"

Functions

my_func() {
    local arg1="$1"
    # ...
}

Conditionals

# Prefer [[ ]] over [ ]
[[ -f "$file" ]]

# String matching
[[ "$str" == *pattern* ]]

Pipes

# Use pipefail to catch errors in pipelines
set -o pipefail
cmd1 | cmd2