The open call will return when the process exits
This is not true on operating systems I'm familiar with and I doubt it's true on Windows, either. The open call returns when the process starts not when it exits. You can then have the child process talking with the parent process while both are running at the same time.

Here's proof: 

perl -e 'open F, "sleep 60 |" or die "$!\n"; print "done\n"'

[download]

I know that "sleep 60" takes about 60 seconds to run, but my top perl program prints "done" right away and exits. It does not wait for the "sleep 60" to exit.

The related system call does wait for the child return when the child process exits.

-- Eric Hammond

In reply to Re: Re: When starting a process, at what point does "open()" return? by esh
in thread When starting a process, at what point does "open()" return? by tid

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.