Re: [9fans] watch command

["Fco. J. Ballesteros" <nemo@lsub.org>]

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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)

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From: YAMANASHI Takeshi <9.nashi@gmail.com>
To: 9fans@cse.psu.edu
Subject: [9fans] watch command
Date: Tue, 19 Apr 2005 15:17:29 +0900
Message-ID: <fba2c2927e6c4dd58cd8a6ebd5ec1d86@orthanc.cc.titech.ac.jp>

I read about "watch" command in the mpx paper (*) and thought
it's interesting.  The paper mentions the commandline:
	watch fig1.pic | pic | troff | proof
and the pipe line runs whenever fig1.pic is modified.
Does anyone have a similar program in his pocket?

(*) hget http://cm.bell-labs.com/cm/cs/doc/83/mpx.ps.gz | gunzip | page


I'm thinking of writing a file server (watchfs) which will serve:
  /n/watch/ctl
  /n/watch/data/a.c
  /n/watch/data/b.c

Whenever a.c and b.c are changed, a text will appear on the ctl file.
Thus, you can do something like:
	% while(){read /n/watch/ctl; mk}

How's this idea?
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