Linux环境编程--lseek ioctl

时间：2010-12-25 来源：willwwei

willisway1: #include <stdio.h> #include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h> int main(int argc, char *argv[])
{
    int fd;
    int ret;     if (argc < 2)
    {
        fprintf(stderr, "Usage: %s filename\n", argv[0]);
        return -1;
    }     fd = open(argv[1], O_RDWR);
    if (fd == -1)
    {
        perror("open");
        return -1;
    }     ret = lseek(fd, 1 * 1024 * 1024 * 1024, SEEK_END);
    printf("ret = %d\n", ret);
    ret = write(fd, "", 1);
    printf("ret = %d\n", ret);     close(fd);     return -1;
}
分析：移动文件读/写指针 willisway2: #include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h> #include <sys/ioctl.h>
#include <linux/cdrom.h> int main(void)
{
    int fd, ret;     fd = open("/dev/cdrom", O_RDONLY | O_NONBLOCK);
    if (fd == -1)
    {
        perror("open");
        return -1;
    }     ret = ioctl(fd, CDROMEJECT);
    if (ret == -1)
    {
        perror("ioctl");
        return -1;
    }     close(fd);     return 0;
}
分析：控制I/O设备 willisway3: #include <unistd.h> #define FILENAME "./test" int main(void)
{
    int fd;
    int ret;
    int flag;     fd = open(FILENAME, O_WRONLY);
    printf("fd = %d\n");     ret = write(fd, "1", 1);
    if (ret == -1)
    {
        printf("ret = -1\n");
        perror("write");
    }     flag = fcntl(fd, F_GETFL);
    flag |= O_APPEND;
    ret = fcntl(fd, F_SETFL, flag);

    printf("fcntl ret = %d\n");     ret = write(fd, "2", 1);
    printf("ret = %d\n", ret);     flag = fcntl(fd, F_GETFL);
    flag &= ~(O_APPEND);
    fcntl(fd, F_SETFL, flag);     return 0;
} 分析：控制I/O设备