mention how to look up perllocal.pod (from Michael G Schwern)

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

diff --git a/pod/perlipc.pod b/pod/perlipc.pod
index 3649e4f..8760257 100644 (file)
--- a/pod/perlipc.pod
+++ b/pod/perlipc.pod
@@ -453,8 +453,8 @@ doesn't actually work:
 
     open(PROG_FOR_READING_AND_WRITING, "| some program |")
 
-and if you forget to use the B<-w> flag, then you'll miss out
-entirely on the diagnostic message:
+and if you forget to use the C<use warnings> pragma or the B<-w> flag,
+then you'll miss out entirely on the diagnostic message:
 
     Can't do bidirectional pipe at -e line 1.
 
@@ -1024,7 +1024,7 @@ something to the server before fetching the server's response.
 The web server handing the "http" service, which is assumed to be at
 its standard port, number 80.  If your the web server you're trying to
 connect to is at a different port (like 1080 or 8080), you should specify
-as the named-parameter pair, C<PeerPort =E<gt> 8080>.  The C<autoflush>
+as the named-parameter pair, C<< PeerPort => 8080 >>.  The C<autoflush>
 method is used on the socket because otherwise the system would buffer
 up the output we sent it.  (If you're on a Mac, you'll also need to
 change every C<"\n"> in your code that sends data over the network to
@@ -1142,7 +1142,7 @@ well.
 As always, setting up a server is little bit more involved than running a client.
 The model is that the server creates a special kind of socket that
 does nothing but listen on a particular port for incoming connections.
-It does this by calling the C<IO::Socket::INET-E<gt>new()> method with
+It does this by calling the C<< IO::Socket::INET->new() >> method with
 slightly different arguments than the client did.
 
 =over
@@ -1305,16 +1305,16 @@ you weren't wanting it to.
 
 Here's a small example showing shared memory usage.
 
-    use IPC::SysV qw(IPC_PRIVATE IPC_RMID S_IRWXU S_IRWXG S_IRWXO);
+    use IPC::SysV qw(IPC_PRIVATE IPC_RMID S_IRWXU);
 
     $size = 2000;
-    $key = shmget(IPC_PRIVATE, $size, S_IRWXU|S_IRWXG|S_IRWXO) || die "$!";
-    print "shm key $key\n";
+    $id = shmget(IPC_PRIVATE, $size, S_IRWXU) || die "$!";
+    print "shm key $id\n";
 
     $message = "Message #1";
-    shmwrite($key, $message, 0, 60) || die "$!";
+    shmwrite($id, $message, 0, 60) || die "$!";
     print "wrote: '$message'\n";
-    shmread($key, $buff, 0, 60) || die "$!";
+    shmread($id, $buff, 0, 60) || die "$!";
     print "read : '$buff'\n";
 
     # the buffer of shmread is zero-character end-padded.
@@ -1322,16 +1322,16 @@ Here's a small example showing shared memory usage.
     print "un" unless $buff eq $message;
     print "swell\n";
 
-    print "deleting shm $key\n";
-    shmctl($key, IPC_RMID, 0) || die "$!";
+    print "deleting shm $id\n";
+    shmctl($id, IPC_RMID, 0) || die "$!";
 
 Here's an example of a semaphore:
 
     use IPC::SysV qw(IPC_CREAT);
 
     $IPC_KEY = 1234;
-    $key = semget($IPC_KEY, 10, 0666 | IPC_CREAT ) || die "$!";
-    print "shm key $key\n";
+    $id = semget($IPC_KEY, 10, 0666 | IPC_CREAT ) || die "$!";
+    print "shm key $id\n";
 
 Put this code in a separate file to be run in more than one process.
 Call the file F<take>:
@@ -1339,8 +1339,8 @@ Call the file F<take>:
     # create a semaphore
 
     $IPC_KEY = 1234;
-    $key = semget($IPC_KEY,  0 , 0 );
-    die if !defined($key);
+    $id = semget($IPC_KEY,  0 , 0 );
+    die if !defined($id);
 
     $semnum = 0;
     $semflag = 0;
@@ -1348,14 +1348,14 @@ Call the file F<take>:
     # 'take' semaphore
     # wait for semaphore to be zero
     $semop = 0;
-    $opstring1 = pack("sss", $semnum, $semop, $semflag);
+    $opstring1 = pack("s!s!s!", $semnum, $semop, $semflag);
 
     # Increment the semaphore count
     $semop = 1;
-    $opstring2 = pack("sss", $semnum, $semop,  $semflag);
+    $opstring2 = pack("s!s!s!", $semnum, $semop,  $semflag);
     $opstring = $opstring1 . $opstring2;
 
-    semop($key,$opstring) || die "$!";
+    semop($id,$opstring) || die "$!";
 
 Put this code in a separate file to be run in more than one process.
 Call this file F<give>:
@@ -1365,22 +1365,53 @@ Call this file F<give>:
     # that the second process continues
 
     $IPC_KEY = 1234;
-    $key = semget($IPC_KEY, 0, 0);
-    die if !defined($key);
+    $id = semget($IPC_KEY, 0, 0);
+    die if !defined($id);
 
     $semnum = 0;
     $semflag = 0;
 
     # Decrement the semaphore count
     $semop = -1;
-    $opstring = pack("sss", $semnum, $semop, $semflag);
+    $opstring = pack("s!s!s!", $semnum, $semop, $semflag);
 
-    semop($key,$opstring) || die "$!";
+    semop($id,$opstring) || die "$!";
 
 The SysV IPC code above was written long ago, and it's definitely
 clunky looking.  For a more modern look, see the IPC::SysV module
 which is included with Perl starting from Perl 5.005.
 
+A small example demonstrating SysV message queues:
+
+    use IPC::SysV qw(IPC_PRIVATE IPC_RMID IPC_CREAT S_IRWXU);
+
+    my $id = msgget(IPC_PRIVATE, IPC_CREAT | S_IRWXU);
+
+    my $sent = "message";
+    my $type = 1234;
+    my $rcvd;
+    my $type_rcvd;
+
+    if (defined $id) {
+        if (msgsnd($id, pack("l! a*", $type_sent, $sent), 0)) {
+            if (msgrcv($id, $rcvd, 60, 0, 0)) {
+                ($type_rcvd, $rcvd) = unpack("l! a*", $rcvd);
+                if ($rcvd eq $sent) {
+                    print "okay\n";
+                } else {
+                    print "not okay\n";
+                }
+            } else {
+                die "# msgrcv failed\n";
+            }
+        } else {
+            die "# msgsnd failed\n";
+        }
+        msgctl($id, IPC_RMID, 0) || die "# msgctl failed: $!\n";
+    } else {
+        die "# msgget failed\n";
+    }
+
 =head1 NOTES
 
 Most of these routines quietly but politely return C<undef> when they