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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