use tab-completion rules extracted from man page

[joey@hwi.ath.cx]

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Greetings elite shell hackers!

I wrote this script to extract all the - and -- options of any program
from its man page, and use them as possible words for completion.

I saw the good work in /etc/bash_completion, and in zsh/.../Completion,
and I thought you might be interested in this slant.

It doesn't display the meanings of the options, but it does work in the
general case, without human-defined rules.

-- Joey [ who likes writing shellscripts: http://hwi.ath.cx/jsh ]

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## autocomplete_from_man: Adds to bash or zsh the ability to use tab-completion for the - and -- options of the current command (provided it has a man page installed).
## eg.: source this script with ". ./autocomplete_from_man", then type: tar --<Tab>
## Documented code available from http://hwi.ath.cx

extractregex () {
if [ "$1" = -atom ]
then shift; EXPR="$@"
else EXPR="(""$@"")"
fi
perl -n -e ' while ( /'"$EXPR"'/g ) { print("$1\n"); } '
}

extractpossoptsfrommanpage () {
'man' "$@" 2> /dev/null | col -bx | extractregex -atom "[ 	]((-|--)[A-Za-z0-9-=]+)"
}

if [ "$BASH" ]
then
	function joeyComplete {
		COMMAND="$1"
		CURRENT=${COMP_WORDS[COMP_CWORD]}
		WORDS="--help "` extractpossoptsfrommanpage "$COMMAND" `
		complete -W "$WORDS" -a -b -c -d -f -g -j -k -s -u "$COMMAND"
		COMPREPLY=(`compgen -W "$WORDS" -a -b -c -d -f -g -j -k -s -u -- "$CURRENT"`)
	}
	complete -F joeyComplete ` echo "$PATH" | tr ':' '\n' | while read DIR; do find "$DIR" -type f -maxdepth 1; done | sed 's+.*/++' `
fi

if [ "$ZSH_NAME" ]
then
	mkdir -p /tmp/completion_options
	function joeyComplete {
		read -c COMMAND ARGS
		if [ ! "$ARGS" ]
		then reply=
		else
			MEMOFILE=/tmp/completion_options/"$COMMAND".cached
			if [ ! -f "$MEMOFILE" ] || [ "$REMEMO" ]
			then extractpossoptsfrommanpage "$COMMAND" > "$MEMOFILE"
			fi
			reply=(--help `cat "$MEMOFILE"`)
		fi
	}
	compctl -f -c -u -r -K joeyComplete -H 0 '' "*" -tn
fi