phpman > perldoc > Net::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 AT seamons.com)

    Rob B Brown (rob AT 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.