in reply to Windows weirdness after fork, dup2

Instead of dup2(), use this 
open STDOUT, ">&SOCK_WRITE" or die "STDOUT: $!\n";

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The "fork" in ActivePerl is not a real fork, it just creates a separate thread. I think by using dup2() you are bypassing the logic that makes them work like separate processes with separate file descriptors.

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Re: Re: Windows weirdness after fork, dup2
by sgifford (Prior) on Mar 05, 2004 at 20:23 UTC
    Thanks Thelonius, but no luck. If I use: 
    open STDOUT, ">&SOCK_WRITE" or die "STDOUT: $!\n";
warn "fileno(STDOUT)=",fileno(STDOUT),"\n";

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    I find that it's not using the right file descriptor: 
    fileno(STDOUT)=3

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    so when I exec a new process it doesn't have the file handles hooked up right. For example, if I change the infinite sleep loop to actually run something: 
    exec('perl','-e','$|=1; while(1) { sleep(5); print q:The time is now :
+,time,qq:\n:; };')
  or die "exec error: $!\n";

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    the output from the child goes to the console, not the socket. With dup2, it goes to the socket.
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[d/l]
[select]
      What you can do is set up the child to forward the output of the command to the main parent through the socket:
          # child
  close(SOCK_READ);
  open CMD, "ipconfig|" or die "ipconfig: $!\n";
  print SOCK_WRITE while <CMD>;
  exit(0);

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[reply]
[d/l]
        Ah, great idea! That worked. I had to add some kludginess to get CTRL-C to kill the grandchild process (and for some reason an INT signal wasn't enough, so I had to use KILL), but here's a final working version.

        Read more... (2 kB)
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[d/l]

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