patch for daemonization docs in perlipc

	Message-ID: <17625.909690618@eeyore.ibcinc.com>

p4raw-id: //depot/perl@2149

1 files changed, 25 insertions, 38 deletions

diff --git a/pod/perlipc.pod b/pod/perlipc.pod
index 59c5ad9f01..cc2a1a9d81 100644
--- a/pod/perlipc.pod
+++ b/pod/perlipc.pod
@@ -317,46 +317,33 @@ details).
 =head2 Complete Dissociation of Child from Parent
 
 In some cases (starting server processes, for instance) you'll want to
-complete dissociate the child process from the parent.    The easiest 
-way is to use:
-
-    use POSIX qw(setsid);
-    setsid() 		or die "Can't start a new session: $!";
-
-However, you may not be on POSIX.  The following process is reported
-to work on most Unixish systems.  Non-Unix users should check their
-Your_OS::Process module for other solutions.
-
-=over 4
-
-=item *
-
-Open /dev/tty and use the TIOCNOTTY ioctl on it.  See L<tty(4)>
-for details.
-
-=item *
-
-Change directory to /
-
-=item *
-
-Reopen STDIN, STDOUT, and STDERR so they're not connected to the old
-tty.
-
-=item *
-
-Background yourself like this:
-
-    fork && exit;
-
-=item *
-
-Ignore hangup signals in case you're running on a shell that doesn't
-automatically no-hup you:
+completely dissociate the child process from the parent.  This is
+often called daemonization.  A well behaved daemon will also chdir()
+to the root directory (so it doesn't prevent unmounting the filesystem
+containing the directory from which it was launched) and redirect its
+standard file descriptors from and to F</dev/null> (so that random
+output doesn't wind up on the user's terminal).
+
+    use POSIX 'setsid';
+
+    sub daemonize {
+	chdir '/'		or die "Can't chdir to /: $!";
+	open STDIN, '/dev/null' or die "Can't read /dev/null: $!";
+	open STDOUT, '>/dev/null'
+				or die "Can't write to /dev/null: $!";
+	defined(my $pid = fork)	or die "Can't fork: $!";
+	exit if $pid;
+	setsid			or die "Can't start a new session: $!";
+	open STDERR, '>&STDOUT'	or die "Can't dup stdout: $!";
+    }
 
-    $SIG{HUP} = 'IGNORE';	# or whatever you'd like
+The fork() has to come before the setsid() to ensure that you aren't a
+process group leader (the setsid() will fail if you are).  If your
+system doesn't have the setsid() function, open F</dev/tty> and use the
+C<TIOCNOTTY> ioctl() on it instead.  See L<tty(4)> for details.
 
-=back
+Non-Unix users should check their Your_OS::Process module for other
+solutions.
 
 =head2 Safe Pipe Opens