Net::Server::SIG(3pm) User Contributed Perl DocumentationNet::Server::SIG(3pm)
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 = $fh[@fh];
# do something with the handle
}
DESCRIPTION
Signals prior in Perl prior to 5.7 were unsafe. Since then signals
have been implemented in a more safe algorithm. Net::Server::SIG
provides backwards compatibility, while still working reliably with
newer releases.
Using a property of the select() function, Net::Server::SIG attempts to
fix the unsafe problem. If a process is blocking on select() any
signal will short circuit the select. Using this concept,
Net::Server::SIG does the least work possible (changing one bit from 0
to 1). And depends upon the actual processing of the signals to take
place immediately after the select call via the "check_sigs" function.
See the example shown above and also see the sigtest.pl script located
in the examples directory of this distribution.
FUNCTIONS
"register_sig($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($SIG)"
Takes the name of a signal as an argument. Calls register_sig with
a this signal name and 'DEFAULT' as arguments (same as
register_sig(SIG,'DEFAULT')
"check_sigs()"
Checks to see if any registered signals have occurred. If so, it
will play the registered code ref for that signal. Return value is
array containing any SIGNAL names that had occurred.
"sig_is_registered($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.
perl v5.30.0 2020-04-03 Net::Server::SIG(3pm)
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