src/libmp/port/reduce - plan9 - Git at Google

 O=$1
 shift
 objtype=$1
 shift

 reduce="("`ls -p ../$objtype/*.[cs] 2>/dev/null | sed 's/..$//' | sed 's/^.*\///' | tr '\012' '|' | sed 's/.$//'`")"

 echo $* | tr ' ' '\012' | egrep -v $reduce | tr \012 ' '
	O=$1
	shift
	objtype=$1
	shift

	reduce="("`ls -p ../$objtype/.[cs] 2>/dev/null \| sed 's/..$//' \| sed 's/^.\///' \| tr '\012' '\|' \| sed 's/.$//'`")"

	echo $* \| tr ' ' '\012' \| egrep -v $reduce \| tr \012 ' '