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} 28