Unix Prog: sigaction function(2)

1. sigaction example

sigaction.c:

 #include<stdio.h>  
 #include<stdlib.h>  
 #include<unistd.h>  
 #include<signal.h>  
   
 // We can also use:  
 // typedef void (*SigFunc)(int);  
 int my_signal(int signo, void (*func)(int))  
 {  
  struct sigaction act, oact;  
   
  act.sa_handler = func;  
  sigemptyset(&act.sa_mask);  
  act.sa_flags = 0;  
   
  // Setup SIGALRM to interrupt any other system call  
  if(signo == SIGALRM) {  
   act.sa_flags |= SA_INTERRUPT;  
  }  
  else {  
   act.sa_flags |= SA_RESTART;  
  }  
   
  if(sigaction(signo, &act, &oact) < 0) {  
   printf("sigaction error!\n");  
   return 1;  
  }  
  return 0;  
 }  
   
 void sig_quit(int signo)  
 {  
  printf("caught SIGQUIT signal!\n");  
 }  
   
 int main(int argc, char* argv[])  
 {  
  if(my_signal(SIGQUIT, sig_quit) < 0) {  
   printf("my_signal error!\n");  
   exit(1);  
  }  
   
  pause();  
   
  exit(0);  
 }  

shell:
The program setup the SIGQUIT signal handler with our self-defined my_signal function, which uses sigaction system call to setup the signal handler. Inside the my_signal, we zero out all sa_mask , indicating that we don't turn off any other signals when executing the signal handler. If the signo is SIGALRM, we setup flags to be SA_INTERRUPT, to make it be able to interrupt any other system calls without re-starting it.

After running the program, we type in Ctrl + \, to send out SIGQUIT signal. And the handler caught signal well.

 ubuntu@ip-172-31-23-227:~$ ./mysignal.out  
 ^\caught SIGQUIT signal!