簡易メニューシェルスクリプト。do_* というfunctionの*部分を引数に指定して実行できる。

app.sh

#!/bin/bash
set -eu

do_cmd1() {
    echo "cmd1"
}

do_cmd2() {
    echo "cmd2"
}

# -------------------------------------------------
COMMAND_LISTS=$(declare -F | awk '{ print $3 }' | grep -e '^do_')
usage() {
    echo "USAGE: $0 [COMMAND]"
    echo " COMMANDS:"
    for i in $COMMAND_LISTS; do
        echo "  ${i#do_}"
    done
    exit 1
}
if [ -z "${1:-}" ]; then usage; fi
for i in $COMMAND_LISTS; do
    if [ "${i#do_}" == "$1" ]; then
        "$i"
        exit 0
    fi
done
usage