sigtrap(3perl) Perl Programmers Reference Guide sigtrap(3perl)
NAME
sigtrap - Perl pragma to enable simple signal handling
SYNOPSIS
use sigtrap;
use sigtrap qw(stack-trace old-interface-signals); # equivalent
use sigtrap qw(BUS SEGV PIPE ABRT);
use sigtrap qw(die INT QUIT);
use sigtrap qw(die normal-signals);
use sigtrap qw(die untrapped normal-signals);
use sigtrap qw(die untrapped normal-signals
stack-trace any error-signals);
use sigtrap 'handler' => \&my_handler, 'normal-signals';
use sigtrap qw(handler my_handler normal-signals
stack-trace error-signals);
DESCRIPTION
The sigtrap pragma is a simple interface to installing signal handlers.
You can have it install one of two handlers supplied by sigtrap itself
(one which provides a Perl stack trace and one which simply die()s), or
alternately you can supply your own handler for it to install. It can
be told only to install a handler for signals which are either untrapped
or ignored. It has three lists of signals to trap, plus you can supply
your own list of signals.
The arguments passed to the "use" statement which invokes sigtrap are
processed in order. When a signal name or the name of one of sigtrap's
signal lists is encountered a handler is immediately installed, when an
option is encountered it affects subsequently installed handlers.
OPTIONS
SIGNAL HANDLERS
These options affect which handler will be used for subsequently
installed signals.
stack-trace
The handler used for subsequently installed signals outputs a Perl
stack trace to STDERR and then tries to dump core. This is the
default signal handler.
die The handler used for subsequently installed signals calls "die"
(actually "croak") with a message indicating which signal was
caught.
handler your-handler
your-handler will be used as the handler for subsequently installed
signals. your-handler can be any value which is valid as an
assignment to an element of %SIG. See perlvar for examples of
handler functions.
SIGNAL LISTS
sigtrap has a few built-in lists of signals to trap. They are:
normal-signals
These are the signals which a program might normally expect to
encounter and which by default cause it to terminate. They are HUP,
INT, PIPE and TERM.
error-signals
These signals usually indicate a serious problem with the Perl
interpreter or with your script. They are ABRT, BUS, EMT, FPE, ILL,
QUIT, SEGV, SYS and TRAP.
old-interface-signals
These are the signals which were trapped by default by the old
sigtrap interface, they are ABRT, BUS, EMT, FPE, ILL, PIPE, QUIT,
SEGV, SYS, TERM, and TRAP. If no signals or signals lists are
passed to sigtrap, this list is used.
For each of these three lists, the collection of signals set to be
trapped is checked before trapping; if your architecture does not
implement a particular signal, it will not be trapped but rather
silently ignored.
OTHER
untrapped
This token tells sigtrap to install handlers only for subsequently
listed signals which aren't already trapped or ignored.
any This token tells sigtrap to install handlers for all subsequently
listed signals. This is the default behavior.
signal
Any argument which looks like a signal name (that is,
"/^[A-Z][A-Z0-9]*$/") indicates that sigtrap should install a
handler for that name.
number
Require that at least version number of sigtrap is being used.
EXAMPLES
Provide a stack trace for the old-interface-signals:
use sigtrap;
Ditto:
use sigtrap qw(stack-trace old-interface-signals);
Provide a stack trace on the 4 listed signals only:
use sigtrap qw(BUS SEGV PIPE ABRT);
Die on INT or QUIT:
use sigtrap qw(die INT QUIT);
Die on HUP, INT, PIPE or TERM:
use sigtrap qw(die normal-signals);
Die on HUP, INT, PIPE or TERM, except don't change the behavior for
signals which are already trapped or ignored:
use sigtrap qw(die untrapped normal-signals);
Die on receipt one of any of the normal-signals which is currently
untrapped, provide a stack trace on receipt of any of the error-signals:
use sigtrap qw(die untrapped normal-signals
stack-trace any error-signals);
Install my_handler() as the handler for the normal-signals:
use sigtrap 'handler', \&my_handler, 'normal-signals';
Install my_handler() as the handler for the normal-signals, provide a
Perl stack trace on receipt of one of the error-signals:
use sigtrap qw(handler my_handler normal-signals
stack-trace error-signals);
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