APUE中关于controlling terminal的一点疑问
static void
sig_hup(int signo)
{
printf("SIGHUP received, pid = %d\n", getpid());
}
static void
pr_ids(char *name)
{
printf("%s: pid = %d, ppid = %d, pgrp = %d, tpgrp = %d\n",
name, getpid(), getppid(), getpgrp(), tcgetpgrp(STDIN_FILENO));
fflush(stdout);
}
int
main(void)
{
char c;
pid_t pid;
pr_ids("parent");
if ((pid = fork()) < 0) {
printf("fork error");
}
else if (pid > 0) {
sleep(5);
exit(0);
}
else {
pr_ids("child");
signal(SIGHUP, sig_hup);
kill(getpid(), SIGTSTP);
pr_ids("child"); //这里调用pr_ids时，父进程已经关闭，但是调用printf却可以向原来的controlling terminal写
if (read(STDIN_FILENO, &c, 1) != 1) //但是这里向原来的terminal读却有问题
printf("read error from controlling TTY, errno = %d\n",
errno); //这里也可以向原来的controlling terminal写
exit(0);
}
}
