FAQ 8.13 How do I trap control characters/signals?
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From: PerlFAQ Server on 2 Jul 2010 00:00 This is an excerpt from the latest version perlfaq8.pod, which comes with the standard Perl distribution. These postings aim to reduce the number of repeated questions as well as allow the community to review and update the answers. The latest version of the complete perlfaq is at http://faq.perl.org . -------------------------------------------------------------------- 8.13: How do I trap control characters/signals? You don't actually "trap" a control character. Instead, that character generates a signal which is sent to your terminal's currently foregrounded process group, which you then trap in your process. Signals are documented in "Signals" in perlipc and the section on "Signals" in the Camel. You can set the values of the %SIG hash to be the functions you want to handle the signal. After perl catches the signal, it looks in %SIG for a key with the same name as the signal, then calls the subroutine value for that key. # as an anonymous subroutine $SIG{INT} = sub { syswrite(STDERR, "ouch\n", 5 ) }; # or a reference to a function $SIG{INT} = \&ouch; # or the name of the function as a string $SIG{INT} = "ouch"; Perl versions before 5.8 had in its C source code signal handlers which would catch the signal and possibly run a Perl function that you had set in %SIG. This violated the rules of signal handling at that level causing perl to dump core. Since version 5.8.0, perl looks at %SIG after the signal has been caught, rather than while it is being caught. Previous versions of this answer were incorrect. -------------------------------------------------------------------- The perlfaq-workers, a group of volunteers, maintain the perlfaq. They are not necessarily experts in every domain where Perl might show up, so please include as much information as possible and relevant in any corrections. The perlfaq-workers also don't have access to every operating system or platform, so please include relevant details for corrections to examples that do not work on particular platforms. Working code is greatly appreciated. If you'd like to help maintain the perlfaq, see the details in perlfaq.pod. |