Indispensable Bash script skeleton: never forget

skeleton

#!/usr/bin/env bash
# Shell script skeleton. Try each of these:
#     ./skeleton
#     ./skeleton one
#     ENVIRONMENTAL=x ./skeleton one
#     ENVIRONMENTAL=x ./skeleton one two

set -o errexit
set -o nounset
set -o pipefail

readonly global=g

main() {
    local -r required=$1
    local -r optional=${2:-default}

    printf '<%s> <%s> <%s> <%s>\n' \
           "${ENVIRONMENTAL}" "${global}" "${required}" "${optional}"
}

main "$@"