[Detroit-pm] Trying to stick a fork in it!

[Scott Webster Wood]

OK, I briefly tried threading with some success until I found out the final tool was going to be on a machine running a pre-5.8 version of perl so I went back to pipes and sockets and here's what I came up with in case anyone is curious.

I stripped out the bidirectional communication as I'm only talking from-child-to-parent but if anyone wants to see the two-directional code, just let me know (basically just imagine adding the code after the variable initialization from 'sub parent' to 'sub child' and vice versa and changing the verbage)


--------------------------- cut here -----------------------------
#!/usr/bin/perl

use Socket;
use IO::Handle;

my (@c, at p, at pid); # c=child handle, p=parent handle, pid=process ID
for(my $s=0; $s<5; $s++) {
  $c[$s] = new IO::Handle;
  $p[$s] = new IO::Handle;

  socketpair($c[$s], $p[$s], AF_UNIX, SOCK_STREAM, PF_UNSPEC)
    or  die "socketpair: $!";

  $c[$s]->autoflush(1);
  $p[$s]->autoflush(1);


  if ($pid[$s] = fork()) { # is the parent
    close $p[$s];        # close unused parent stream
    &parent($c[$s], $s);
    close $c[$s];        # close the stream coming back from the child
    waitpid($pid[$s],0); # wait for child process to terminate
  } else {                   # is the child
    die "cannot fork: $!" unless defined $pid[$s];          # make sure pid == 0
    close $c[$s];        # close the unused child stream
    &child($p[$s], $s);
    close $p[$s];        # close stream that was talking to the parent
    exit(0);
  }
}

sub parent() { # read data coming from child process(es)
  my $fh = shift;
  my $s  = shift;
  while ($line = <$fh>) { # read data from child line by line until done
    chomp($line);
    print "Parent $s Pid $$ just read this: `$line'\n";
  };
}

sub child() { # send data back to parent through filehandle
  my $fh = shift;
  print $fh "Child Pid $$ is sending this\n";
  print $fh "Child Pid $$ sends some more\n";
}

# filehandles didn't behave well using array references and my ultimate solution
#  is going to create functions to perform tasks anyway so I just passed the
#  handles to subroutines

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$ ./test.pl
Parent 0 Pid 25960 just read this: `Child Pid 25961 is sending this'
Parent 0 Pid 25960 just read this: `Child Pid 25961 sends some more'
Parent 1 Pid 25960 just read this: `Child Pid 25962 is sending this'
Parent 1 Pid 25960 just read this: `Child Pid 25962 sends some more'
Parent 2 Pid 25960 just read this: `Child Pid 25963 is sending this'
Parent 2 Pid 25960 just read this: `Child Pid 25963 sends some more'
Parent 3 Pid 25960 just read this: `Child Pid 25964 is sending this'
Parent 3 Pid 25960 just read this: `Child Pid 25964 sends some more'
Parent 4 Pid 25960 just read this: `Child Pid 25965 is sending this'
Parent 4 Pid 25960 just read this: `Child Pid 25965 sends some more'




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