Signal handling and sigemptyset()

Question

Could anyone please explain in a really easy way to understand what sigemptyset() does? Why is it useful? I\'ve read a bunch of definitions but i just don\'t understand. Fro

Answer 1

The name says it all. sigemptyset() empties (a variable describing) a set of signals.

That is

sigset_t ss;
sigemptyset(&ss);

initialises a variable of type sigset_t (ss here) to "contain" no signals.

From man sigemptyset (Linux):

sigemptyset() initializes the signal set given by set to empty, with all signals excluded from the set.

[...]

Objects of type sigset_t must be initialized by a call to either sigemptyset() or sigfillset() before being passed to the functions sigaddset(), sigdelset() and sigismember() [...]

From the POSIX specs:

int sigemptyset(sigset_t *set); 

[...]

The sigemptyset() function initializes the signal set pointed to by set, such that all signals defined in POSIX.1-2008 are excluded.