UNIX环境高级编程第10章信号10.3singal函数

// signals/sigusr.c 10-1
#include "apue.h"

static void sig_usr(int); /* one handler for both signals */

int main(void)
{
    if (signal(SIGUSR1, sig_usr) == SIG_ERR)
    {
        err_sys("can‘t catch SIGUSR1");
    }
    if (signal(SIGUSR2, sig_usr) == SIG_ERR)
    {
        err_sys("can‘t catch SIGUSR2");
    }
    /* SIGKILL is not available for this function
    if (signal(SIGKILL, sig_usr) == SIG_ERR)
    {
        err_sys("can‘t catch SIGKILL");
    }
    */
    for ( ; ; )
    {
        pause();
    }
}

static void sig_usr(int signo) /* argument is signal number */
{
    if (signo == SIGUSR1)
    {
        printf("received SIGUSR1\n");
    }
    else if (signo == SIGUSR2)
    {
        printf("received SIGUSR2\n");
    }
    else
    {
        err_dump("received signal %d\n", signo);
    }
}

// lib/signal.c
#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);
}