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 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
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 an 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);