This might very well be a race condition. If the reader process tries to read() from the pipe before a writer opens it, the read() will fail with an EOF condition.

To avoid this scenario, open two filedescriptors in the parent, before the fork(). After the fork() close the appropiate end of the pipe. This code will probably do what you want:


#!/usr/bin/perl -w
use strict;

# Lots of nice code here...

open RFIFO, "< $ENV{HOME}/.fifopipe" 
  or die "Cannot open read pipe: $!\n";

open WFIFO, "> $ENV{HOME}/.fifopipe" 
  or die "Cannot open write pipe: $!\n";

if (fork()) { # Parent

  close WFIFO;

  # Your parent code, which can now safely block on
  # <RFIFO>

}
else { # Child

  close RFIFO;

  # Your child code, which can take its time to write()
  # to the pipe.

  exit 0;
}

[download]
Hope this helps.

In reply to Re: multiple processes by fokat
in thread multiple processes by Mirage

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.