This is how we do it.

   POLL(1)               Plan B — 3rd edition                POLL(1)

     NAME
          poll - poll files for changes

     SYNOPSIS
          poll [ -1 ] [ -i ival ] cmd file...

     DESCRIPTION
          Poll monitors the given files each ival seconds (one by
          default) and runs cmd when any of the files change. It uses
          fstat(2) to generate a single stat(5) request for each poll
          and file. If -1 is given, the program exits after the first
          change noticed; otherwise, it keeps on polling the files.

          The command is assumed to be at /bin and is executing using
          the list of files as arguments.

     SOURCE
          /sys/src/cmd/poll.c

     Page 1                Plan B User's Manual      (printed 4/19/05)