X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlfork.pod;h=d930e9396e87565c874374ffcf1c2763f18e2acc;hb=cb50131aab68ac6dda048612c6e853b8cb08701e;hp=533dcfab31a35338b5dd633e4942e0f69c82409e;hpb=8560c20dd6b2f3dfec719d4b500be45742de4507;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perlfork.pod b/pod/perlfork.pod
index 533dcfa..d930e93 100644
--- a/pod/perlfork.pod
+++ b/pod/perlfork.pod
@@ -172,6 +172,73 @@ the seek position in the parent will change it in the child and vice-versa.
 One can avoid this by opening files that need distinct seek pointers
 separately in the child.
 
+=item Forking pipe open() not yet implemented
+
+The C<open(FOO, "|-")> and C<open(BAR, "-|")> constructs are not yet
+implemented.  This limitation can be easily worked around in new code
+by creating a pipe explicitly.  The following example shows how to
+write to a forked child:
+
+    # simulate open(FOO, "|-")
+    sub pipe_to_fork ($) {
+	my $parent = shift;
+	pipe my $child, $parent or die;
+	my $pid = fork();
+	die "fork() failed: $!" unless defined $pid;
+	if ($pid) {
+	    close $child;
+	}
+	else {
+	    close $parent;
+	    open(STDIN, "<&=" . fileno($child)) or die;
+	}
+	$pid;
+    }
+
+    if (pipe_to_fork('FOO')) {
+	# parent
+	print FOO "pipe_to_fork\n";
+	close FOO;
+    }
+    else {
+	# child
+	while (<STDIN>) { print; }
+	close STDIN;
+	exit(0);
+    }
+
+And this one reads from the child:
+
+    # simulate open(FOO, "-|")
+    sub pipe_from_fork ($) {
+	my $parent = shift;
+	pipe $parent, my $child or die;
+	my $pid = fork();
+	die "fork() failed: $!" unless defined $pid;
+	if ($pid) {
+	    close $child;
+	}
+	else {
+	    close $parent;
+	    open(STDOUT, ">&=" . fileno($child)) or die;
+	}
+	$pid;
+    }
+
+    if (pipe_from_fork('BAR')) {
+	# parent
+	while (<BAR>) { print; }
+	close BAR;
+    }
+    else {
+	# child
+	print "pipe_from_fork\n";
+	close STDOUT;
+	exit(0);
+    }
+
+Forking pipe open() constructs will be supported in future.
+
 =item Global state maintained by XSUBs 
 
 External subroutines (XSUBs) that maintain their own global state may
@@ -217,6 +284,8 @@ representation for pseudo-process IDs will be implemented in future.
 
 This document may be incomplete in some respects.
 
+=back
+
 =head1 AUTHOR
 
 Support for concurrent interpreters and the fork() emulation was implemented