#include	<signal.h>#include	"ourhdr.h"static volatile sig_atomic_t	sigflag;								/* set nonzero by signal handler */static sigset_t			newmask, oldmask, zeromask;static voidsig_usr(int signo)	/* one signal handler for SIGUSR1 and SIGUSR2 */{	sigflag = 1;	return;}voidTELL_WAIT(){	if (signal(SIGUSR1, sig_usr) == SIG_ERR)		err_sys("signal(SIGINT) error");	if (signal(SIGUSR2, sig_usr) == SIG_ERR)		err_sys("signal(SIGQUIT) error");	sigemptyset(&zeromask);	sigemptyset(&newmask);	sigaddset(&newmask, SIGUSR1);	sigaddset(&newmask, SIGUSR2);		/* block SIGUSR1 and SIGUSR2, and save current signal mask */	if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)		err_sys("SIG_BLOCK error");}voidTELL_PARENT(pid_t pid){	kill(pid, SIGUSR2);		/* tell parent we're done */}voidWAIT_PARENT(void){	while (sigflag == 0)		sigsuspend(&zeromask);	/* and wait for parent */	sigflag = 0;			/* reset signal mask to original value */	if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)		err_sys("SIG_SETMASK error");}voidTELL_CHILD(pid_t pid){	kill(pid, SIGUSR1);			/* tell child we're done */}voidWAIT_CHILD(void){	while (sigflag == 0)		sigsuspend(&zeromask);	/* and wait for child */	sigflag = 0;			/* reset signal mask to original value */	if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)		err_sys("SIG_SETMASK error");}