www.unix.org.ua/orelly/perl/cookbook/ch16_16.htm
Installing a Signal Handler Problem You want to control how your program responds to signals. You need to do this if you want to catch Ctrl-C, avoid accumulating finished subprocess es, or prevent your process from dying when it writes to a child that ha s gone away. Solution Use the %SIG hash to install your own handler by name or by code referenc e: $SIG{QUIT} = \&got_sig_quit; Each value is the action to take when Perl receives the corresponding signal. Perl provides two spec ial behaviors: "IGNORE" to take no action when a particular signal is re ceived, and "DEFAULT" to perform the default Unix action for that signal . Although a C programmer might think of a signal as SIGINT, Perl uses just INT. Perl figures you only use signal names in functions that deal with signals, so the SIG prefix is redundant. This means that you'll assign to $SIG{CHLD} to change what your process does when it gets a SIGCHLD. If you want to run your own code when a given signal is received, you hav e two choices of what to put in the hash: either a code reference or a s ubroutine name. A code reference refers to a subroutine in a particular package, so it i s a better choice. Perl calls your handler code with a single argument: the name of the sign al that triggered it, like "INT" or "USR1". Returning from a signal hand ler takes you back to whatever you were doing when the signal hit. Perl defines two special signals, __DIE__ and __WARN__, whose handlers ar e called whenever a Perl program emits warnings through warn or dies thr ough die. This lets you catch such warnings, and selectively trap or pro pagate them. The die and warn handlers are disabled while they run, so y ou can safely die from a __DIE__ handler or warn from a __WARN__ handler without fear of recursion.
|
http://csua.com/feed/