Net::Server::SIG(3)					User Contributed Perl Documentation				       Net::Server::SIG(3)

NAME

       Net::Server::SIG - adpf - Safer signal handling

SYNOPSIS

	 use Net::Server::SIG qw(register_sig check_sigs);
	 use IO::Select ();
	 use POSIX qw(WNOHANG);

	 my $select = IO::Select->new();

	 register_sig(PIPE => 'IGNORE',
		      HUP  => 'DEFAULT',
		      USR1 => sub { print "I got a SIG $_[0]
"; },
		      USR2 => sub { print "I got a SIG $_[0]
"; },
		      CHLD => sub { 1 while (waitpid(-1, WNOHANG) > 0); },
		      );

	 ### add some handles to the select
	 $select->add(*STDIN);

	 ### loop forever trying to stay alive
	 while ( 1 ){

	   ### do a timeout to see if any signals got passed us
	   ### while we were processing another signal
	   my @fh = $select->can_read(10);

	   my $key;
	   my $val;

	   ### this is the handler for safe (fine under unsafe also)
	   if( &check_sigs() ){
	     # or my @sigs = &check_sigs();
	     next unless @fh;
	   }

	   my $handle = $fh[@fh];

	   ### do something with the handle

	 }

DESCRIPTION

       Signals in Perl 5 are unsafe.  Some future releases may be able to fix some of this (ie Perl 5.8 or 6.0), but it would be nice to have some
       safe, portable signal handling now.  Clarification - much of the time, signals are safe enough.	However, if the program employs forking or
       becomes a daemon which can receive many simultaneous signals, then the signal handling of Perl is normally not sufficient for the task.

       Using a property of the select() function, Net::Server::SIG attempts to fix the unsafe problem.	If a process is blocking on select() any
       signal will short circuit the select.  Using this concept, Net::Server::SIG does the least work possible (changing one bit from 0 to 1).
       And depends upon the actual processing of the signals to take place immediately after the the select call via the "check_sigs" function.
       See the example shown above and also see the sigtest.pl script located in the examples directory of this distribution.

FUNCTIONS

       "register_sig($SIG => &code_ref)"
	   Takes key/value pairs where the key is the signal name, and the argument is either a code ref, or the words 'DEFAULT' or 'IGNORE'.  The
	   function register_sig must be used in conjuction with check_sigs, and with a blocking select() function call -- otherwise, you will
	   observe the registered signal mysteriously vanish.

       "unregister_sig($SIG)"
	   Takes the name of a signal as an argument.  Calls register_sig with a this signal name and 'DEFAULT' as arguments (same as
	   register_sig(SIG,'DEFAULT')

       "check_sigs()"
	   Checks to see if any registered signals have occured.  If so, it will play the registered code ref for that signal.	Return value is
	   array containing any SIGNAL names that had occured.

AUTHORS

       Paul Seamons (paul@seamons.com)

       Rob B Brown (rob@roobik.com) - Provided a sounding board and feedback in creating Net::Server::SIG and sigtest.pl.

LICENSE

	 This package may be distributed under the terms of either the
	 GNU General Public License
	   or the
	 Perl Artistic License

	 All rights reserved.

perl v5.12.1							    2007-02-03						       Net::Server::SIG(3)