Hi monks,

I'm having troubles deciphering exactly what is going on in some fork open pipe code, despite reading perlopentut and perlipc slowly and repeatedly. I have stripped out as much as I can and added some comment-questions:

   open(P, "|-") or                # fork a process using fh 
                                   # P as STDIN to the child.
      do {                         # huh? Why would open P fail...
                                   # and we launch child?!?
           open(STDERR,">&=$err"); # alias STDERR to output
                                   # to the $err filehandle
           open(STDOUT,">&=$out"); # alias STDOUT to output
                                   # to the $out filehandle
           exec(@cmd);             # run command. How to
                                   # capture @cmd errors gracefully?
           exit 9                  # what is 9's special
                                   # meaning here?
         };
   close($err);
   close($out);

   print P "test input to child" or die ("Mein Leiben! $!");
   close(P) or die("Stella! $!");

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Admittedly, I'm most puzzled by the "open or do". I find that a very strange way to fork open a child process. Since this subroutine is called many times, how might the open fail and prompt the opening of the child? I would expect the open to be mandatory - AND - the do to be mandatory. Urg.

Thank you very much for your time and help.

Thanks!

In reply to Forked pipe open...or do??? by blahblah

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