if [ $# -lt "3" ]
then
	echo Usage: gres pattern replacement file
	exit 1
fi
pattern=$1
replacement=$2
if [ -f $3 ]
then
	file=$3
else
	echo $3 is not a file
	exit 1
fi
A="`echo | tr '\012' '\001' `" # generates ctl-A
sed -e "s$A$pattern$A$replacement$A" $file
