#!/bin/csh -f
if ( $#argv != 2) then
	echo $0 usage:
	echo "	$0 file-1 file-2"
	exit 1
endif
set noclobber
mv $1 $1.swap$$ &&   ( mv $2 $1 &&  mv $1.swap$$ $2 || mv $1.swap$$ $1 )