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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]\n"; },
		 USR2 => sub { print "I got a SIG $_[0]\n"; },
		 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.

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