[9fans] watch command

[9fans] watch command

[YAMANASHI Takeshi]

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?
-- 

Re: [9fans] watch command

[Kenji Okamoto]

> 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?

I've heard a Japanese talked on automatic counting of craters, where
it can, probably, recognise the crater right(?), actually which is the
problem here.   By the way, he is a programmer probably, and not a
Planetary geologist, and had thought it might be usefull.   Is it usefull?
No.

In your example, are you going to have a huge list of files to be watched?

Kenji

Re: [9fans] watch command

[Fco. J. Ballesteros]

[-- Attachment #1: Type: text/plain, Size: 820 bytes --]

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)

[-- Attachment #2: Type: message/rfc822, Size: 3182 bytes --]

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?
-- 

Re: [SPAM] [9fans] watch command

[vdharani]

> 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}
>
i dont think it will work.

let us say i just saved an intermediate version of a.c while doing a
bigger change. then the above script will kick mk process that is neither
needed nor useful. the same is the case when i save a.c but i need to
change 10 other files to reflect the change in all relevant files.

thanks
dharani

Re: [SPAM] [9fans] watch command

[Ronald G. Minnich]

On Tue, 19 Apr 2005 vdharani@infernopark.com wrote:

> >
> > 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}
> >
> i dont think it will work.
> 
> let us say i just saved an intermediate version of a.c while doing a
> bigger change. then the above script will kick mk process that is neither
> needed nor useful. the same is the case when i save a.c but i need to
> change 10 other files to reflect the change in all relevant files.
> 

the specific example may not be useful but ... you have no idea how many 
times people want this stuff. 

But what about a file that the server can provide that provides info about
metadata changes, i.e. you are reading a
/srv/fsstatus
and as things change you get twstat messages?

ron

Re: [SPAM] [9fans] watch command

[YAMANASHI Takeshi]

> let us say i just saved an intermediate version of a.c while doing a
> bigger change. then the above script will kick mk process that is neither
> needed nor useful.

sounds reasonable.  I wonder what was the experience in the original
watch command about intermediate modifications...

In my case, I might be going to just ignore the mk error messages
for such mk run. :)
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