While I'm not completely sure of what you want, it appears to me you are looking for something like a "datawaiting()" call instead of an end-of-file.
Here's a (somewhat) minimal change to your program with the end-of-file replaced :)
#!/usr/bin/perl
use diagnostics;
use strict 'subs';
use strict 'refs';
use Socket;
use IO::Handle;
my $child; #filehandle to child process
my $parent; #filehandle to parent process
my $pid; #Process ID of child process
socketpair($child, $parent, AF_UNIX, SOCK_STREAM, PF_UNSPEC)
or die "socketpair: $!
+";
$child->autoflush(1);
$parent->autoflush(1);
if ($pid = fork()) { #parent
close $parent or die "close: $!\n";
sleep 1;
print STDOUT time%1000, ": polling child\n";
if (not datawaiting($child)) { ##### CHANGE
+D
print STDOUT time%1000, ": no input from child yet\n";
} else {
my $line = <$child>;
chomp $line;
print STDOUT time%1000, ": received <$line>\n";
}
} else { #child
die "cannot fork: $!" unless defined $pid;
close $child or die "close: $!\n";
print STDOUT time%1000, ": child started\n";
sleep 5;
print {$parent} time%1000, ": child printed\n";
close $parent or die "close: $!\n";
exit;
}
sub datawaiting ####### CHANGED see perldoc -f select
{
my $rin = my $win = my $ein = '';
vec($rin, fileno(shift), 1) = 1;
return scalar select my $rout = $rin, my $wout = $win, my $eout = $e
+in, 0;
}
Outputs:
277: child started
278: polling child
278: no input from child yet
Is that what you were looking for ?
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