#! /usr/bin/mira -exec
main :: [sys_message]
main = map f (tl $*),          if # $* > 1 ||$* is equivalent to argv
     = [Stdout (revlines $-)], otherwise   ||no files, use stdin ($-)

f :: [char]->sys_message
f fil = Stderr ("mrev: cannot open "++fil++"\n"), if badfile
      = Stdout (revlines (read fil)), otherwise
	where
	badfile = ~ member (filemode fil) 'r'

revlines :: [char]->[char]
revlines = lay.map reverse.lines

||The usage of this command (from a UNIX shell) is
||	mrev [file] ...
||If no files given, takes data from stdin.  This is a  Miranda  version
||of the UNIX command `rev' which reverses each line of its input.

||This example is a template for turning any Miranda  function  of  type
||[char]->[char]  into  a  UNIX filter.  Replace `revlines' in the above
||text, by your chosen function.