Document what the backtick returns if the command fails.

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

diff --git a/pod/perlipc.pod b/pod/perlipc.pod
index 475271d..47556a5 100644 (file)
--- a/pod/perlipc.pod
+++ b/pod/perlipc.pod
@@ -234,8 +234,7 @@ prepared to clean up core dumps now and again.
 
 To forbid signal handlers altogether would bars you from
 many interesting programs, including virtually everything in this manpage,
-since you could no longer even write SIGCHLD handlers.  Their dodginess
-is expected to be addresses in the 5.005 release.
+since you could no longer even write SIGCHLD handlers.  
 
 
 =head1 Using open() for IPC
@@ -837,7 +836,7 @@ domain sockets can show up in the file system with an ls(1) listing.
 You can test for these with Perl's B<-S> file test:
 
     unless ( -S '/dev/log' ) {
-       die "something's wicked with the print system";
+       die "something's wicked with the log system";
     }
 
 Here's a sample Unix-domain client:
@@ -1247,6 +1246,11 @@ find yourself overly concerned about reliability and start building checks
 into your message system, then you probably should use just TCP to start
 with.
 
+Note that UDP datagrams are I<not> a bytestream and should not be treated
+as such. This makes using I/O mechanisms with internal buffering
+like stdio (i.e. print() and friends) especially cumbersome. Use syswrite(),
+or better send(), like in the example below.
+
 Here's a UDP program similar to the sample Internet TCP client given
 earlier.  However, instead of checking one host at a time, the UDP version
 will check many of them asynchronously by simulating a multicast and then
@@ -1297,6 +1301,11 @@ with TCP, you'd have to use a different socket handle for each host.
        $count--;
     }
 
+Note that this example does not include any retries and may consequently
+fail to contact a reachable host. The most prominent reason for this
+is congestion of the queues on the sending host if the number of
+list of hosts to contact is sufficietly large.
+
 =head1 SysV IPC
 
 While System V IPC isn't so widely used as sockets, it still has some