#include "apue.h"/* Reliable version of signal(), using POSIX sigaction().  */Sigfunc *signal(int signo, Sigfunc *func){	struct sigaction	act, oact;	act.sa_handler = func;	sigemptyset(&act.sa_mask);	act.sa_flags = 0;	if (signo == SIGALRM) {#ifdef	SA_INTERRUPT		act.sa_flags |= SA_INTERRUPT;#endif	} else {#ifdef	SA_RESTART		act.sa_flags |= SA_RESTART;#endif	}	if (sigaction(signo, &act, &oact) < 0)		return(SIG_ERR);	return(oact.sa_handler);}