Add in perldelta changes about unpack A and trailing whitespace, trie

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

diff --git a/pod/perlipc.pod b/pod/perlipc.pod
index 8412bfd..5bf4f6c 100644 (file)
--- a/pod/perlipc.pod
+++ b/pod/perlipc.pod
@@ -105,9 +105,9 @@ or has changed its UID.
 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<$!>.
+You may be able to determine the cause of failure using C<%!>.
 
-    unless (kill 0 => $pid or $! == $!{EPERM}) {
+    unless (kill 0 => $pid or $!{EPERM}) {
        warn "$pid looks dead";
     }
 
@@ -288,7 +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,
@@ -355,11 +355,16 @@ with your timeouts.  If you are having problems with such functions,
 you can try using the POSIX sigaction() function, which bypasses the
 Perl safe signals (note that this means subjecting yourself to
 possible memory corruption, as described above).  Instead of setting
-C<$SIG{ALRM}> try something like the following:
+C<$SIG{ALRM}>:
 
-    use POSIX;
-    sigaction SIGALRM, new POSIX::SigAction sub { die "alarm\n" }
-        or die "Error setting SIGALRM handler: $!\n";
+   local $SIG{ALRM} = sub { die "alarm" };
+
+try something like the following:
+
+    use POSIX qw(SIGALRM);
+    POSIX::sigaction(SIGALRM,
+                     POSIX::SigAction->new(sub { die "alarm" }))
+          or die "Error setting SIGALRM handler: $!\n";
 
 =item Restartable system calls
 
@@ -388,7 +393,7 @@ will generate the signal again. The result of this is a rather odd
 "loop". In future Perl's signal mechanism may be changed to avoid this
 - perhaps by simply disallowing %SIG handlers on signals of that
 type. Until then the work-round is not to set a %SIG handler on those
-signals. (Which signals they are is operating system dependant.)
+signals. (Which signals they are is operating system dependent.)
 
 =item Signals triggered by operating system state
 
@@ -616,7 +621,7 @@ the syntax
 
 forks the ps(1) command (without spawning a shell, as there are more than
 three arguments to open()), and reads its standard output via the
-C<KID_PS> filehandle.  The corresponding syntax to read from command
+C<KID_PS> filehandle.  The corresponding syntax to write to command
 pipes (with C<"|-"> in place of C<"-|">) is also implemented.
 
 Note that these operations are full Unix forks, which means they may not be
@@ -1030,7 +1035,7 @@ Here's a sample Unix-domain client:
     use strict;
     my ($rendezvous, $line);
 
-    $rendezvous = shift || '/tmp/catsock';
+    $rendezvous = shift || 'catsock';
     socket(SOCK, PF_UNIX, SOCK_STREAM, 0)      || die "socket: $!";
     connect(SOCK, sockaddr_un($rendezvous))    || die "connect: $!";
     while (defined($line = <SOCK>)) {
@@ -1051,7 +1056,7 @@ to be on the localhost, and thus everything works right.
     sub spawn;  # forward declaration
     sub logmsg { print "$0 $$: @_ at ", scalar localtime, "\n" }
 
-    my $NAME = '/tmp/catsock';
+    my $NAME = 'catsock';
     my $uaddr = sockaddr_un($NAME);
     my $proto = getprotobyname('tcp');
 
@@ -1610,7 +1615,7 @@ A small example demonstrating SysV message queues:
     my $id = msgget(IPC_PRIVATE, IPC_CREAT | S_IRWXU);
 
     my $sent = "message";
-    my $type = 1234;
+    my $type_sent = 1234;
     my $rcvd;
     my $type_rcvd;
 
@@ -1658,15 +1663,6 @@ signals and to stick with simple TCP and UDP socket operations; e.g., don't
 try to pass open file descriptors over a local UDP datagram socket if you
 want your code to stand a chance of being portable.
 
-As mentioned in the signals section, because few vendors provide C
-libraries that are safely re-entrant, the prudent programmer will do
-little else within a handler beyond setting a numeric variable that
-already exists; or, if locked into a slow (restarting) system call,
-using die() to raise an exception and longjmp(3) out.  In fact, even
-these may in some cases cause a core dump.  It's probably best to avoid
-signals except where they are absolutely inevitable.  This
-will be addressed in a future release of Perl.
-
 =head1 AUTHOR
 
 Tom Christiansen, with occasional vestiges of Larry Wall's original