1#include <signal.h>
2
3void (*sigset(int sig, void (*handler)(int)))(int)
4{
5 struct sigaction sa, sa_old;
6 sigset_t mask, mask_old;
7
8 sigemptyset(&mask);
9 if (sigaddset(&mask, sig) < 0)
10 return SIG_ERR;
11
12 if (handler == SIG_HOLD) {
13 if (sigaction(sig, 0, &sa_old) < 0)
14 return SIG_ERR;
15 if (sigprocmask(SIG_BLOCK, &mask, &mask_old) < 0)
16 return SIG_ERR;
17 } else {
18 sa.sa_handler = handler;
19 sa.sa_flags = 0;
20 sigemptyset(&sa.sa_mask);
21 if (sigaction(sig, &sa, &sa_old) < 0)
22 return SIG_ERR;
23 if (sigprocmask(SIG_UNBLOCK, &mask, &mask_old) < 0)
24 return SIG_ERR;
25 }
26 return sigismember(&mask_old, sig) ? SIG_HOLD : sa_old.sa_handler;
27}