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 = $fh[@fh];
# do something with the handle
}
DESCRIPTION¶
Signals prior in Perl prior to 5.7 were unsafe. Since then signals have been
implemented in a more safe algorithm. Net::Server::SIG provides backwards
compatibility, while still working reliably with newer releases.
Using a property of the
select() function, Net::Server::SIG attempts to
fix the unsafe problem. If a process is blocking on
select() any signal
will short circuit the select. Using this concept, Net::Server::SIG does the
least work possible (changing one bit from 0 to 1). And depends upon the
actual processing of the signals to take place immediately after the the
select call via the "check_sigs" function. See the example shown
above and also see the sigtest.pl script located in the examples directory of
this distribution.
FUNCTIONS¶
- "register_sig($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 conjunction with check_sigs, and
with a blocking select() function call -- otherwise, you will
observe the registered signal mysteriously vanish.
- "unregister_sig($SIG)"
- Takes the name of a signal as an argument. Calls
register_sig with a this signal name and 'DEFAULT' as arguments (same as
register_sig(SIG,'DEFAULT')
- "check_sigs()"
- Checks to see if any registered signals have occured. If
so, it will play the registered code ref for that signal. Return value is
array containing any SIGNAL names that had occured.
- "sig_is_registered($SIG)"
- Takes a signal name and returns any registered code_ref for
that signal.
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.