#include "apue.h"Sigfunc *signal_intr(int signo, Sigfunc *func){	struct sigaction	act, oact;	act.sa_handler = func;	sigemptyset(&act.sa_mask);	act.sa_flags = 0;#ifdef	SA_INTERRUPT	act.sa_flags |= SA_INTERRUPT;#endif	if (sigaction(signo, &act, &oact) < 0)		return(SIG_ERR);	return(oact.sa_handler);}