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