Simple multi command bash scripts

example-commands.sh

#!/usr/bin/env bash

SELF=$(basename "${BASH_SOURCE[0]}")

describe() {
    cat <<EOF
Some Descriptive words...
EOF
}

### Commands

cmd_foo() {
    HELP="
Do foo never forget to do before bar

SOME PROSA

BLAH
"
    echo "FOO CMD"
}

cmd_bar() {
    HELP="
Barify ARGS
"
    echo "BAR"
}

### Generic stuff

__main() {
    (( $# > 0 )) || {
        printf 'Error: missing command argument\n\n'
        cmd_help
        exit 1
    } >&2

    cmd="cmd_${1}"
    if [[ $(type -t "$cmd") != 'function' ]]; then
        {
            printf 'Error: no command named %s\n\n' "$1"
            cmd_help
            exit 1
        } >&2
    else
        "$cmd" "${@:2}"
    fi
}

cmd_help() {
    HELP="
Print this message
"
    echo "Usage: $SELF COMMAND ARG..."
    echo ""
    describe
    echo ""
    echo "List of available commands: "
    echo ""
    # shellcheck disable=SC2034
    declare -F | while read -r _declare _flag cmd; do
        shopt -s extglob
        [[ $cmd = cmd_* ]] || continue
        unset HELP
        eval "$(type "$cmd" | awk '/^ *HELP="/, /^";/ { print; } /^";/ { exit 0}')"
        HELP="${HELP#$'\n'}"
        help_lns=( )
        readarray -t help_lns <<<"${HELP%$'\n'}"
        printf '  %-8s  %s\n' "${cmd//cmd_/}" "${help_lns[0]}"
        for ln in "${help_lns[@]:1}"; do
            printf '  %8s  %s\n' '' "${ln%%+([[:space:]])}"
        done
        echo ""
    done
}

__main "$@"