comment on

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

Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
Want more info? How to link or How to display code and escape characters are good places to start.


Perl: the Markov chain saw
	PerlMonks