Signal handling and sigemptyset()

c process signals posix
user2644819 picture user2644819 · Dec 19, 2013 · Viewed 16.1k times · Source

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. From what i gather it tracks the signals that are being used for blocking purposes? I'm not really sure i understand why that would be useful. Is it so we do not get that specific signal recursively?

Basic example where sigemptyset() is used:

#include <signal.h>
#include <stdio.h>
#include <unistd.h>

int main(){

struct sigaction act;
sigemptyset(&act.sa_mask);
act.sa_handler=function_name;
act.sa_flags=0;

sigaction(SIGINT, &act, 0);

}

Answer

Devolus picture Devolus · Dec 19, 2013

sigemptyset simply initializes the signalmask to empty, such that it is guaranteed that no signal would be masked. (that is, all signals will be received) Basically it is similar to a memset(0) but you don't have to know the details of the implementation. So if the sa_mask member is changed you don't need to adjust your code because it will be taken care of by sigemptyset.

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