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sigtrap(3pm) Perl Programmers Reference Guide sigtrap(3pm)

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' => \&myhandler, 'normal-signals';

use sigtrap qw(handler myhandler normal-signals

stack-trace error-signals);

DESCRIPTION

The ssiiggttrraapp pragma is a simple interface to installing signal handlers. You can have it install one of two handlers supplied by ssiiggttrraapp 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 a couple of lists of signals to trap, plus you can supply your own list of signals. The arguments passed to the "use" statement which invokes ssiiggttrraapp are processed in order. When a signal name or the name of one of ssiiggttrraapp's signal lists is encountered a handler is immediately installed, when an option is encountered it affects subsequently installed handlers. OOPPTTIIOONNSS SSIIGGNNAALL HHAANNDDLLEERRSS These options affect which handler will be used for subsequently installed signals.

ssttaacckk-ttrraaccee

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. ddiiee The handler used for subsequently installed signals calls "die" (actually "croak") with a message indicating which signal was caught.

hhaannddlleerr 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.

SSIIGGNNAALL LLIISSTTSS

ssiiggttrraapp has a few built-in lists of signals to trap. They are:

nnoorrmmaall-ssiiggnnaallss

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.

eerrrroorr-ssiiggnnaallss

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.

oolldd-iinntteerrffaaccee-ssiiggnnaallss

These are the signals which were trapped by default by the old ssiigg-

ttrraapp interface, they are ABRT, BUS, EMT, FPE, ILL, PIPE, QUIT, SEGV, SYS, TERM, and TRAP. If no signals or signals lists are passed to ssiiggttrraapp, 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. OOTTHHEERR uunnttrraappppeedd This token tells ssiiggttrraapp to install handlers only for subsequently listed signals which aren't already trapped or ignored. aannyy This token tells ssiiggttrraapp 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 ssiiggttrraapp should install a han-

dler for that name. number Require that at least version number of ssiiggttrraapp is being used. EEXXAAMMPPLLEESS

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 an of the nnoorrmmaall-ssiiggnnaallss which is currently

uunnttrraappppeedd, provide a stack trace on receipt of aannyy of the eerrrroorr-ssiigg-

nnaallss:

use sigtrap qw(die untrapped normal-signals

stack-trace any error-signals);

Install myhandler() as the handler for the nnoorrmmaall-ssiiggnnaallss:

use sigtrap 'handler', \&myhandler, 'normal-signals';

Install myhandler() as the handler for the normal-signals, provide a

Perl stack trace on receipt of one of the error-signals:

use sigtrap qw(handler myhandler normal-signals

stack-trace error-signals);