Question

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What is the difference between sigaction and signal?

It seems to me that both of them can be used to register a callback for a specific signal.

How do you choose which one to use?

Answer 1

TLPI

UNIX systems provide two ways of
changing the disposition of a signal:
signal() and sigaction(). The
sigaction() system call is an
alternative to signal() for setting
the disposition of a signal. Although
sigaction() is somewhat more complex
to use than signal(), in return it
provides greater flexibility.

sigaction is also more portable than signal. Also, with sigaction you can specify signal handlers that receive additional arguments (sa_sigaction versus sa_handler).

/* can be installed by signal / sigaction */
void(*) (int);

/* can be installed by sigaction only */
void(*) (int, siginfo_t *, void *);