FAQ 8.13 How do I trap control characters/signals?

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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 = sub { syswrite(STDERR, "ouch\n", 5 ) };

            # or a reference to a function

            $SIG = \&ouch;

            # or the name of the function as a string

            $SIG = "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.


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