File sysconf_addword of Package apache2

#!/bin/bash

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.

debug=false

function usage() {
	cat <<-EOF
	usage: $(basename $0) [-r] FILE VAR WORD

Add word WORD to variable VAR in file FILE, or remove 
	it if the -r option is given.
	
	Example:
	$(basename $0) /etc/sysconfig/apache2 APACHE_SERVER_FLAGS asdf
	leads to the change:
	-APACHE_SERVER_FLAGS="SSL STATUS ruby"
	+APACHE_SERVER_FLAGS="SSL STATUS ruby asdf"

If multiple lines matching ^VAR= are found (which happens to be a habit of 
	mine), only the last one is manipulated.

It does not work for WORD starting with characters like a dash which
	prevent word boundary matching.
	
	EOF
}

function find_last_occurrence () {
	# takes two arguments, FILE and VAR
	# and return the number of the last line where
	# VAR occurs in FILE (not commented)
	grep -n -- "^[[:space:]]*$1" $2 | tail -n 1 | cut -d: -f1
}

function word_present () {
	. $file
	case " ${!var} " in
	*" $word "*) true;;
	*) false;;
	esac
}

function add_word() {
	local word=$1
	local word_quoted=$2
	if ! word_present; then
		$debug && cp $file $tmpf
		sed -i -e "${lineno} { 
			s/^[[:space:]]*$$var=\".*$$\".*$/\1 $word_quoted\2/; 
			s/=\" /=\"/ 
			}" $file
		$debug && diff -u $tmpf $file
	else
		echo \"$word\" already present
	fi
	# some balancing for vim"s syntax highlighting
}

function remove_word() {
	local word=$1
	local word_quoted=$2
	if word_present; then
		$debug && cp $file $tmpf
		sed -i -e "${lineno} { 
			s/$['\" 	]$$word_quoted$['\" 	]$/\1 \2/g
			s/  / /g
			}" $file
		$debug && diff -u $tmpf $file
	else
		echo \"$word\" not present
	fi
	# some balancing for vim"s syntax highlighting

}

# poor man's option parsing

case "$1" in
-h) usage; exit 0;;
esac

if [ $# -lt 3 ]; then
	echo not enough arguments
	echo
	usage; exit 1
fi

action=add
case "$1" in 
-r) action=remove; shift;;
esac

file=$1; shift
var=$1; shift
word=$1
word_quoted=${1//\//\\\/}

if $debug; then
	echo FILE: $file
	echo VAR: $var
	echo WORD: $word
	echo current content:
	grep "^$var=" $file | tail -n 1
	echo
fi

if ! [ -r $file ]; then
	echo ${0##*/}: file $file is not a readable file
	exit 1
fi

lineno=$(find_last_occurrence $var $file)
if [ -z $lineno ]; then
	echo ${0##*/}: variable $var does not occur in $file 
	exit 1
fi

$debug && tmpf=$(mktemp /tmp/$(basename $0).XXXXXX)

if [ $action = add ]; then
	add_word $word $word_quoted $lineno
else
	remove_word $word $word_quoted $lineno
fi

$debug && rm -f $tmpf

exit 0