ioctl: Operation not supported

xiaoruoax

程序如下：
/*
* setext2.c - Set ext2 special flags
*/
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/ext2_fs.h>
#include <sys/ioctl.h>
#include <errno.h>

int main(int argc, char *argv[])
{
    int fd;
    long flags;

    /* Usage nag */
    if (argc != 2) {
        puts("USAGE:setext2 {filename}");
        exit(EXIT_FAILURE);
    }

    if ((fd = open(argv[1], O_RDONLY)) < 0) {
        perror("open");
        exit(EXIT_FAILURE);
    }
    /* These are the flags we'll set on the file */
    flags = EXT2_SYNC_FL | EXT2_NODUMP_FL;
    if (ioctl(fd, EXT2_IOC_SETFLAGS, &flags)) {
        perror("ioctl");
        close(fd);
        exit(EXIT_FAILURE);
    }

    if (flags & EXT2_SYNC_FL)
        puts("SYNC flag set");
    if (flags & EXT2_NODUMP_FL)
        puts("NODUMP flag set");

    close(fd);
    exit(EXIT_SUCCESS);
}


為什么編譯的時候報錯ioctl: Operation not supported

seaquester

你說的這個錯誤信息“ioctl: Operation not supported” 不像是編譯是的錯誤信息，反倒像執(zhí)行是的錯誤信息。

我在CentOS 6.3下編譯是下面的錯誤：
$ gcc -Wall -o setext2 setext2.c
In file included from setext2.c:10:
/usr/include/linux/ext2_fs.h: In function ‘ext2_mask_flags’:
/usr/include/linux/ext2_fs.h:182: error: ‘FS_DIRSYNC_FL’ undeclared (first use in this function)
/usr/include/linux/ext2_fs.h:182: error: (Each undeclared identifier is reported only once
/usr/include/linux/ext2_fs.h:182: error: for each function it appears in.)
/usr/include/linux/ext2_fs.h:182: error: ‘FS_TOPDIR_FL’ undeclared (first use in this function)
/usr/include/linux/ext2_fs.h:184: error: ‘FS_NODUMP_FL’ undeclared (first use in this function)
/usr/include/linux/ext2_fs.h:184: error: ‘FS_NOATIME_FL’ undeclared (first use in this function)
setext2.c: In function ‘main’:
setext2.c:30: error: ‘FS_SYNC_FL’ undeclared (first use in this function)
setext2.c:30: error: ‘FS_NODUMP_FL’ undeclared (first use in this function)
setext2.c:31: error: ‘FS_IOC_SETFLAGS’ undeclared (first use in this function)

在 #include <linux/ext2_fs.h>之前，include 另外一個頭文件 fs.h 之后就可以編譯了。
#include <linux/fs.h>

seaquester

回復(fù) 1# xiaoruoax

經(jīng)過嘗試發(fā)現(xiàn)，解決方法很簡單。
只需要，先通過EXT2_IOC_GETFLAGS獲取 ext2 flags，然后，將要設(shè)置的flag通過 “|” 操作附加上去，然后通過EXT2_IOC_SETFLAGS設(shè)置就可以成功，在CentOS 6.3 （x86_64）上面測試通過。設(shè)置完成后，通過lsattr可以查看設(shè)置的結(jié)果（chattr可以設(shè)置flags）。

示例代碼如下：

1. 
   
2. #include <sys/types.h>
   
3. #include <unistd.h>
   
4. #include <stdlib.h>
   
5. #include <stdio.h>
   
6. #include <fcntl.h>
   
7. #include <linux/fs.h>
   
8. #include <linux/ext2_fs.h>
   
9. #include <sys/ioctl.h>
   
10. #include <errno.h>
    
11. 
    
12. 
    
13. int main(int argc, char *argv[])
    
14. {
    
15.     int fd;
    
16.     long flags;
    
17. 
    
18.     if (argc != 2) {
    
19.         printf("Usage: %s <filename>\n", argv[0]);
    
20.         exit(EXIT_FAILURE);
    
21.     }
    
22. 
    
23.     if ((fd = open(argv[1], O_RDONLY)) < 0) {
    
24.         perror("open");
    
25.         exit(EXIT_FAILURE);
    
26.     }
    
27. 
    
28.     /* Get attributes from the file */
    
29.     if (ioctl(fd, EXT2_IOC_GETFLAGS, &flags)) {
    
30.         perror("ioctl");
    
31.         exit(EXIT_FAILURE);
    
32.     }
    
33. 
    
34.     /* Set attributes to the file */
    
35.     flags |= (EXT2_SYNC_FL | EXT2_NODUMP_FL);
    
36.     if (ioctl(fd, EXT2_IOC_SETFLAGS, &flags)) {
    
37.         perror("ioctl");
    
38.         close(fd);
    
39.         exit(EXIT_FAILURE);
    
40.     }
    
41. 
    
42.     if (flags & EXT2_SYNC_FL) {
    
43.         puts("SYNC flag set");
    
44.     }
    
45.     if (flags & EXT2_NODUMP_FL) {
    
46.         puts("NODUMP flag set");
    
47.     }
    
48. 
    
49.     close(fd);
    
50.     exit(EXIT_SUCCESS);
    
51. }
    

復(fù)制代碼

xiaoruoax

不好意思，修改一下，是執(zhí)行的時候的報錯

seaquester

回復(fù) 4# xiaoruoax


    試試我修改的那份代碼，在我這邊可以執(zhí)行，沒錯誤。

xiaoruoax

回復(fù) 5# seaquester


    果然好了！謝謝O(∩_∩)O