execs

#! /bin/sh


case "$1" in
    ( -h | --help )
        printf "%s\n" \
            "execs: Print the external commands called by a shell script." \
            "" \
            "usage:" \
            "  execs [-h|--help]    Show this help." \
            "  execs <scripts>      Print all external commands called by <scripts>."

        exit;;
esac


#   Functions.

err () { printf "${0##*/}: \e[31merror:\e[0m %s\n" "$*" >&2; exit 1; }

_list_cmds () {
    sed '/^#/d
         /^$/d
         /^[ \t]*/d
         s:(:\n:g
         s:{:\n:g
         s:`:\n:g
         s:|:\n:g
         s:&:\n:g
         s:;:\n:g
         s:exec:\n:g
         s:eval:\n:g' "$@"
}

_get_path () {
    while read f; do
        type "$f" | grep -Eq 'function|builtin' && continue
        which -- "$f" && continue
        test -f "$f" && printf "%s\n" "$f"
    done 2> /dev/null
}


#   Get the list.

_list_cmds "$@" \
    | awk '{print $1}' \
    | sort -u \
    | _get_path