apue习题8.7

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <dirent.h>
#include <fcntl.h>

int main(void)
{
    DIR *dp;
    struct dirent *dirp;
    int fd;
    int val;
    pid_t pid;
    char fdstr[10];
    dp = opendir("/");
    fd = dirfd(dp);  /*注意函数*/
    val = fcntl(fd, F_GETFD, 0);
    if (val)
        printf("close-on-exec is on in test\n");
    else
        printf("close-on-exec is off in test\n");
    sprintf(fdstr, "%d\0", fd);
    if ((pid = fork()) < 0) {
        printf("fork error\n");
        exit(1);
    } else if (pid == 0) {
        execl("/home/shyan/study/test/child", "child", fdstr, (char *)0);
        exit(0);
    }
    exit(0);
}

child程序代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>

int main(int argc, char *argv[])
{
    int val;
    int fd;
    sscanf(argv[1], "%d", &fd);
    if ((val = fcntl(fd, F_GETFD, 0)) < 0) {
        perror("fcntl error");
        exit(1);
    }
    if (val)
        printf("close-on-exec is off\n");
    else
        printf("close-on-exec if off\n");
    exit(0);
}