From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <45219fb00709061317x594e82a6vb43d136767f245ab@mail.gmail.com>
Date: Thu,  6 Sep 2007 22:17:39 +0200
From: "=?ISO-8859-1?Q?Llu=EDs_Batlle?=" <viriketo@gmail.com>
To: "Fans of the OS Plan 9 from Bell Labs" <9fans@cse.psu.edu>
Subject: Re: [9fans] Pipes on UNIX
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I better explain my problem. :)
I have a CGI for Apache. I wrote it in C, and it simply parses text
from a html textarea, giving another html in output. I made it as a
state machine which outputs and outputs according to the input
characters.

Apache communicates with the CGI process with two pipes linked to the
process' stdin and stdout.
But I think that apache code is like this:
while()
{
  read(socket,buffer)
  write(pipe_process1, buffer)
}
while()
{
  read(pipe_process2, buffer)
  write(socket,buffer)
}

Therefore, if I had a CGI similar to 'cat' (and I have), it would
deadlock due to the pipe_process2 not being read by apache if it gets
filled, the process blocks, and then pipe_process1 gets filled.

As I want the CGI to accept input from almost any length, I need a
"pipe buffer" big enough.

Then, based on Gorka suggestion (which I didn't understand as a
9pserver ;), I finally agreed on the easiest solution wrapping the CGI
with a sh script:
#!/bin/sh
head -n 10000000 > inputfile   # limiting the disk ussage to 10MB, raw cutt=
ing.
mycgi < inputfile
#EOF

That's all. I will not write any "superpipe" program, or any 9pserver,
because at the end I need the disk. The sh wrapper works well enough.

Thank you for your help in this non-plan9-related problem! Simply the
unicon documentation pointed to something strange in named pipes which
I couldn't check anywhere. :)

Regards,
Llu=EDs

2007/9/6, Gorka Guardiola <paurea@gmail.com>:
> I wrote it without coffee... would be more like:
>
> generate_data > input &
> data_eater < output
>
> :-).
>
> And input and output can come from a stupid fileserver like pipefs...
> or pipebackedbyaharddiskfs :-).
> --
> - curiosity sKilled the cat
>