NAME

POSIX::1003::Signals - POSIX using signals

SYNOPSIS

use POSIX::1003::Signals qw(:functions SIGPOLL SIGHUP);
sigaction($signal, $action, $oldaction);
sigpending($sigset);
sigprocmask($how, $sigset, $oldsigset)
sigsuspend($signal_mask);

kill SIGPOLL//SIGHUP, $$;

use POSIX::1003::Signals '%signals';
my $number = $signals{SIGHUP};
$signals{SIGNEW} = $number;

DESCRIPTION

This manual page explains the access to the POSIX sigaction functions and its relatives. This module uses two helper objects: POSIX::SigSet and POSIX::SigAction.

FUNCTIONS

These functions are implemened in POSIX.xs

Standard POSIX

kill($signal, $process)

Simply "kill" in perlfunc.

Be warned the order of parameters is reversed in the kill exported by POSIX!

CORE::kill($signal, $pid);
::Signals::kill($signal, $pid);
POSIX::kill($pid, $signal);

raise($signal)

Send a signal to the executing process.

sigaction( $signal, $action, [$oldaction] )

Detailed signal management. The signal must be a number (like SIGHUP), not a string (like "SIGHUP"). The action and oldaction arguments are POSIX::SigAction objects. Returns undef on failure.

If you use the SA_SIGINFO flag, the signal handler will in addition to the first argument (the signal name) also receive a second argument: a hash reference, inside which are the following keys with the following semantics, as defined by POSIX/SUSv3:

signo   the signal number
errno   the error number
code    if this is zero or less, the signal was sent by
        a user process and the uid and pid make sense,
        otherwise the signal was sent by the kernel

The following are also defined by POSIX/SUSv3, but unfortunately not very widely implemented:

pid     the process id generating the signal
uid     the uid of the process id generating the signal
status  exit value or signal for SIGCHLD
band    band event for SIGPOLL

A third argument is also passed to the handler, which contains a copy of the raw binary contents of the siginfo structure: if a system has some non-POSIX fields, this third argument is where to unpack() them from.

Note that not all siginfo values make sense simultaneously (some are valid only for certain signals, for example), and not all values make sense from Perl perspective.

signal( $signal, <CODE|'IGNORE'|'DEFAULT'> )

Set the CODE (subroutine reference) to be called when the $signal appears. See "%SIG" in perlvar.

signal(SIGINT, \&handler);
$SIG{SIGINT} = \&handler;  # same

sigpending($sigset)

Examine signals that are blocked and pending. This uses POSIX::SigSet objects for the sigset argument. Returns undef on failure.

sigprocmask( $how, $sigset, [$oldsigset] )

Change and/or examine calling process's signal mask. This uses POSIX::SigSet objects for the sigset and oldsigset arguments. Returns undef on failure.

Note that you can't reliably block or unblock a signal from its own signal handler if you're using safe signals. Other signals can be blocked or unblocked reliably.

sigsuspend($sigset)

Install a signal mask and suspend process until signal arrives. This uses POSIX::SigSet objects for the signal_mask argument. Returns undef on failure.

strsignal($signal)

Returns a string reprentation of the $signal. When the $signal is unknown, a standard string is returned (never undef)

Additional

sigaction_names()

Returns a list with all known sigaction names, unsorted.

signal_names()

Returns a list with all known signal names, unsorted.

CONSTANTS

%signals

This exported variable is a (tied) HASH which maps SIG* and SA_* names to their numbers.

Export tag :signals

The following constants are exported, shown here with the values discovered during installation of this module:

During installation, a symbol table will get inserted here.

Export tag :actions

During installation, a symbol table will get inserted here.

Export tag :handlers

During installation, a symbol table will get inserted here.

SEE ALSO

This module is part of POSIX-1003 distribution version 1.02, built on November 10, 2020. Website: http://perl.overmeer.net/CPAN. The code is based on POSIX, which is released with Perl itself. See also POSIX::Util for additional functionality.

COPYRIGHTS

Copyrights 2011-2020 on the perl code and the related documentation by [Mark Overmeer]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See http://dev.perl.org/licenses/