bash_starter.sh

bash_starter.sh

#!/bin/bash
# Template for a multi-command bash script with online help by convention
# based on $0-dispatch pattern described here:
#    https://www.oilshell.org/blog/2020/02/good-parts-sketch.html#the-0-dispatch-pattern-solves-three-important-problems
set -o nounset
set -o pipefail
set -o errexit

__describe() {
	echo "a global description for the tool"
}

__describe_help() {
    echo "show global help or help <command> for details"
}

__help_help() {
    echo "usage: $(basename "$0") help"
    echo ""
    echo " print the global usage help and exit"
    echo ""
    echo "usage: $(basename "$0") help <command>"
    echo ""
    echo " provide usage hep for <command>"
}

help() {
    local cmd
    if [[ "$#" -eq 0 ]]; then
        "$0" _globalusage
    else
        cmd="$1"
        shift
        if declare -F | grep -q "^declare -f __help_${cmd}\$"; then
            "$0" "__help_${cmd}" "$@"
        else
            echo "no help available for ${cmd} $*"
        fi
    fi
}

_globalusage() {
    echo "$(basename "$0"): $("$0" __describe)"
    echo ""
    echo " usage: $(basename "$0") <command>"
    echo ""
    "$0" _listcommands | xargs -L 1 "$0" _describecommand
}

_listcommands() {
    declare -F | sed -n 's/^declare -f \([^_]\)/\1/ip'
}

_describecommand() {
    local cmd
    local desc
    desc=""

    local spacing
    spacing="              " # cool trick
    if [ "$#" -gt 0 ]; then
        cmd="$1"
        shift
        if declare -F | grep -q "^declare -f __describe_${cmd}\$" ; then
            desc="$("$0" "__describe_${cmd}")"
        fi
        echo "  ${cmd}${spacing:${#cmd}}${desc}" # cool trick, pt.2
    fi
}

if [ "$#" -eq 0 ]; then
    help >&2
    exit 1
fi

"$@"