#!/bin/bash
# Try to list debian packages required for any shell script
# <C> 2023 F-Hauri -- http://f-hauri.ch
# Version 0.00.001
# Depend on grep, sed.

declare -Ai ExtExec Depends
while read -r wrd1 _ ; do
    case $wrd1 in
	*[!a-zA-Z0-9_+-]*) ;;
	[1-9:*] ) ;;
	* ) read -r typ < <(type "$wrd1" 2>/dev/null)
	    case $typ in
		*/*) bin=${typ#*/};
		     bin=${bin#usr/}
		     ExtExec["/${bin%\)}"]+=1
		     ;;
	    esac ;;
    esac
done < <( sed <"$1" '/^[^(]*).*\(OPTARG\|;;\)/d;s/(/\n/g' ) 

for Executable in "${!ExtExec[@]}"; do
    mapfile -t packt < <(grep -l "$Executable$" /var/lib/dpkg/info/*list)
    packt=("${packt[@]##*/}")    packt=("${packt[@]%.list}")
    case ${#packt[@]} in
	0 ) printf 'External: "%s" (%dx) not found!\n' \
		"${Executable##*/}" ${ExtExec["$Executable"]} ;;
	1 ) printf 'External: "%s" (%dx) depend on "%s"\n' \
		   "${Executable##*/}" ${ExtExec["$Executable"]} "${packt[0]}"
	    Depends["${packt[0]}"]+=1
	    ;;
	* ) printf 'External: "%s" (%dx) depend on more than 1??:\n  "%s"\n' \
		   "${Executable##*/}" ${ExtExec["$Executable"]} "${packt[*]}"
	    for pack in "${packt[@]}"; do
		Depends["$pack"]+=1
	    done
	    ;;
    esac
done
echo "$1 depends on: ${!Depends[*]}."