Unknown discipline ':utf8' w/ maint perl w/o perlio

[p5sagit/p5-mst-13.2.git] / pod / perlipc.pod

diff --git a/pod/perlipc.pod b/pod/perlipc.pod
index 637030c..5f8af22 100644 (file)
--- a/pod/perlipc.pod
+++ b/pod/perlipc.pod
@@ -95,13 +95,22 @@ it doesn't kill itself):
     }
 
 Another interesting signal to send is signal number zero.  This doesn't
-actually affect another process, but instead checks whether it's alive
+actually affect a child process, but instead checks whether it's alive
 or has changed its UID.
 
     unless (kill 0 => $kid_pid) {
        warn "something wicked happened to $kid_pid";
     }
 
+When directed at a process whose UID is not identical to that
+of the sending process, signal number zero may fail because
+you lack permission to send the signal, even though the process is alive.
+You may be able to determine the cause of failure using C<%!>.
+
+    unless (kill 0 => $pid or $!{EPERM}) {
+       warn "$pid looks dead";
+    }
+
 You might also want to employ anonymous functions for simple signal
 handlers:
 
@@ -279,7 +288,7 @@ to find out whether anyone (or anything) has accidentally removed our fifo.
        sleep 2;    # to avoid dup signals
     }
 
-=head2 Deferred Signals (Safe signals)
+=head2 Deferred Signals (Safe Signals)
 
 In Perls before Perl 5.7.3 by installing Perl code to deal with
 signals, you were exposing yourself to danger from two things.  First,