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.\" ========================================================================
.\"
.IX Title "Net::Server::SIG 3pm"
.TH Net::Server::SIG 3pm "2023-06-11" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
Net::Server::SIG \- adpf \- Safer signal handling
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 3
\&    use Net::Server::SIG qw(register_sig check_sigs);
\&    use IO::Select ();
\&    use POSIX qw(WNOHANG);
\&
\&    my $select = IO::Select\->new();
\&
\&    register_sig(PIPE => \*(AqIGNORE\*(Aq,
\&                 HUP  => \*(AqDEFAULT\*(Aq,
\&                 USR1 => sub { print "I got a SIG $_[0]\en"; },
\&                 USR2 => sub { print "I got a SIG $_[0]\en"; },
\&                 CHLD => sub { 1 while waitpid(\-1, WNOHANG) > 0; },
\&                 );
\&
\&    # add some handles to the select
\&    $select\->add(\e*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 = $fh[@fh];
\&
\&        # do something with the handle
\&
\&    }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Signals prior in Perl prior to 5.7 were unsafe.  Since then signals
have been implemented in a more safe algorithm.  Net::Server::SIG
provides backwards compatibility, while still working reliably with
newer releases.
.PP
Using a property of the \fBselect()\fR function, Net::Server::SIG attempts
to fix the unsafe problem.  If a process is blocking on \fBselect()\fR any
signal will short circuit the select.  Using this concept,
Net::Server::SIG does the least work possible (changing one bit from 0
to 1).  And depends upon the actual processing of the signals to take
place immediately after the select call via the \*(L"check_sigs\*(R"
function.  See the example shown above and also see the sigtest.pl
script located in the examples directory of this distribution.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.ie n .IP """register_sig($SIG => \e&code_ref)""" 4
.el .IP "\f(CWregister_sig($SIG => \e&code_ref)\fR" 4
.IX Item "register_sig($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 '\s-1DEFAULT\s0' or '\s-1IGNORE\s0'.
The function register_sig must be used in conjunction with check_sigs,
and with a blocking \fBselect()\fR function call \*(-- otherwise, you will
observe the registered signal mysteriously vanish.
.ie n .IP """unregister_sig($SIG)""" 4
.el .IP "\f(CWunregister_sig($SIG)\fR" 4
.IX Item "unregister_sig($SIG)"
Takes the name of a signal as an argument.  Calls register_sig with a
this signal name and '\s-1DEFAULT\s0' as arguments (same as
register_sig(\s-1SIG,\s0'\s-1DEFAULT\s0')
.ie n .IP """check_sigs()""" 4
.el .IP "\f(CWcheck_sigs()\fR" 4
.IX Item "check_sigs()"
Checks to see if any registered signals have occurred.  If so, it will
play the registered code ref for that signal.  Return value is array
containing any \s-1SIGNAL\s0 names that had occurred.
.ie n .IP """sig_is_registered($SIG)""" 4
.el .IP "\f(CWsig_is_registered($SIG)\fR" 4
.IX Item "sig_is_registered($SIG)"
Takes a signal name and returns any registered code_ref for that signal.
.SH "AUTHORS"
.IX Header "AUTHORS"
Paul Seamons (paul@seamons.com)
.PP
Rob B Brown (rob@roobik.com) \- Provided a sounding board and feedback
in creating Net::Server::SIG and sigtest.pl.
.SH "LICENSE"
.IX Header "LICENSE"
.Vb 4
\&  This package may be distributed under the terms of either the
\&  GNU General Public License
\&    or the
\&  Perl Artistic License
\&
\&  All rights reserved.
.Ve