FAT_IOCTL_GET_VOLUME_ID(2const) - Linux manual page (original) (raw)

FATIOCTLGETVOLUMEID(2const) FATIOCTLGETVOLUMEID(2const)

NAME top

   FAT_IOCTL_GET_VOLUME_ID - read the volume ID in a FAT filesystem

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#include <linux/msdos_fs.h>** /* Definition of **FAT_*** constants */
   **#include <sys/ioctl.h>**

   **int ioctl(int** _fd_**, FAT_IOCTL_GET_VOLUME_ID, uint32_t ***_id_**);**

DESCRIPTION top

   FAT filesystems are identified by a volume ID.  The volume ID can
   be read with **FAT_IOCTL_GET_VOLUME_ID**.

   The _fd_ argument can be a file descriptor for any file or directory
   of the filesystem.  It is sufficient to create the file descriptor
   by calling [open(2)](../man2/open.2.html) with the **O_RDONLY** flag.

   The _id_ argument is a pointer to the field that will be filled with
   the volume ID.  Typically the volume ID is displayed to the user
   as a group of two 16-bit fields:

       printf("Volume ID %04x-%04x\n", id >> 16, id & 0xFFFF);

RETURN VALUE top

   On success, 0 is returned.  On error, -1 is returned, and _[errno](../man3/errno.3.html)_ is
   set to indicate the error.

STANDARDS top

   Linux.

HISTORY top

   Linux 3.11.

EXAMPLES top

   The following program demonstrates the use of [ioctl(2)](../man2/ioctl.2.html) to display
   the volume ID of a FAT filesystem.

   The following output was recorded when applying the program for
   directory _/mnt/user_:

       $ ./display_fat_volume_id /mnt/user
       Volume ID 6443-6241

Program source (display_fat_volume_id.c)

   #include <fcntl.h>
   #include <linux/msdos_fs.h>
   #include <stdint.h>
   #include <stdio.h>
   #include <stdlib.h>
   #include <sys/ioctl.h>
   #include <unistd.h>

   int
   main(int argc, char *argv[])
   {
       int       fd;
       int       ret;
       uint32_t  id;

       if (argc != 2) {
           printf("Usage: %s FILENAME\n", argv[0]);
           exit(EXIT_FAILURE);
       }

       fd = open(argv[1], O_RDONLY);
       if (fd == -1) {
           perror("open");
           exit(EXIT_FAILURE);
       }

       /*
        * Read volume ID.
        */
       ret = ioctl(fd, FAT_IOCTL_GET_VOLUME_ID, &id);
       if (ret == -1) {
           perror("ioctl");
           exit(EXIT_FAILURE);
       }

       /*
        * Format the output as two groups of 16 bits each.
        */
       printf("Volume ID %04x-%04x\n", id >> 16, id & 0xFFFF);

       close(fd);

       exit(EXIT_SUCCESS);
   }

SEE ALSO top

   [ioctl(2)](../man2/ioctl.2.html), [ioctl_fat(2)](../man2/ioctl%5Ffat.2.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23_FATIOCTLGETVOLUMEID_(2const)

Pages that refer to this page:ioctl_fat(2)