mask.c

UNIX编程高级环境（第二版）的信号部分的程序源码

#include    <signal.h>
#include    <setjmp.h>
#include    <time.h>
#include    "ourhdr.h"

static void                        sig_usr1(int), sig_alrm(int);
static sigjmp_buf                jmpbuf;
static volatile sig_atomic_t    canjump;

int
main(void)
{
    if (signal(SIGUSR1, sig_usr1) == SIG_ERR)
        err_sys("signal(SIGUSR1) error");
    if (signal(SIGALRM, sig_alrm) == SIG_ERR)
        err_sys("signal(SIGALRM) error");
    pr_mask("starting main: ");        /* {Prog prmask} */

    if (sigsetjmp(jmpbuf, 0)) {
        pr_mask("ending main: ");
        exit(0);
    }
    canjump = 1;    /* now sigsetjmp() is OK */

    for ( ; ; )
        pause();
}
static void
sig_usr1(int signo)
{
    time_t    starttime;

    if (canjump == 0)
        return;        /* unexpected signal, ignore */

    pr_mask("starting sig_usr1: ");

    alarm(3);                /* SIGALRM in 3 seconds */

    starttime = time(NULL);
    for ( ; ; )                /* busy wait for 5 seconds */
        if (time(NULL) > starttime + 5)
            break;

    pr_mask("finishing sig_usr1: ");

    canjump = 0;
    siglongjmp(jmpbuf, 1);    /* jump back to main, don't return */
}

static void
sig_alrm(int signo)
{
    pr_mask("in sig_alrm: ");
    return;
}