A co-worker of mine is trying to write a simple unidirectional named pipe script where the parent process will assign tasks to several child processes. The idea was to have each child read only one line from the pipe, which he tells me can be done in C. But apparently in Perl the first child to connect is reading the entire buffer.

Since he's out today I thought I would try my very inexperienced hand at this. The closest I could get is below, which is based on an exmaple in Network Programming with Perl. Since I'm not really familair with this type of programming I used pipe() instead of named pipes.

To reitierate, the question is is there a way to have each child process actually read just one line from the pipe? Any pointers (and other terrible C puns) are appreciated!! 

#!/usr/local/bin/perl
use strict;
use warnings;
sub child {
    my( $child ) = @_;
    if( fork == 0 ) {  # Child
        close  WRITER;
        select STDOUT;  $| = 1;
        select READER;  $| = 1;
        while( 1 )  { 
            my $line = <READER>;
            print STDOUT "$child: $line";
            sleep 1;
        }
    }
    return;
}
pipe( READER, WRITER ) or die "Can't open pipe: $!";

# Create children
child( 'a' ); child( 'b' );
child( 'c' ); child( 'd' );
child( 'e' );
    
# Parent
close  READER;
select WRITER;  $| = 1;
my $str = "";
foreach ( 0..50 ) { $str .= "$_\n"; }
while( 1 ) { print WRITER $str; }

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Update: Put the sleep 1 in and merged some of the child() lines.

In reply to Pipes: Is it possible for a child to just read one line? by Argel

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