G'day italdesign,

This technique may be suitable for your needs.

Parent:
  1. Waits (up to a specified timeout period) for the child to create a (uniquely) named pipe.
  2. Writes an unordered list of records to the named pipe.
  3. Waits for the child to exit.
  4. Deletes the named pipe.
Child:
  1. Opens an anonymous pipe to sort.
  2. Creates a (uniquely) named pipe.
  3. Reads all records from the named pipe and writes them to the anonymous (sort) pipe. 
#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

use POSIX qw{mkfifo};
use Time::HiRes qw{usleep};

my $named_pipe = "pm_1085515_$$.fifo";
unlink $named_pipe if -e $named_pipe;

if (fork) {
    my $timeout = 2;
    local $SIG{ALRM} = sub { die "Timed out after $timeout seconds" };
    alarm $timeout;
    usleep 1e3 until -p $named_pipe;
    alarm 0;

    open my $writer, '>', $named_pipe;
    print $writer "$_\n" for qw{B D C A};
    close $writer;
    wait;
    unlink $named_pipe;
}
else {
    open my $sorter, '|-', 'sort';
    mkfifo $named_pipe, 0600;
    open my $reader, '<', $named_pipe;
    print $sorter $_ while <$reader>;
    close $reader;
    close $sorter;
}

[download]

Input:

B
D
C
A

[download]

Output:

A
B
C
D

[download]

-- Ken

In reply to Re: Filehandle reference lost between parent and child by kcott
in thread Filehandle reference lost between parent and child by italdesign

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