FAT_IOCTL_GET_VOLUME_ID(2const) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | STANDARDS | HISTORY | EXAMPLES | SEE ALSO | COLOPHON

FAT_IOCTL_GET_VOLUME_ID(2const)          FAT_IOCTL_GET_VOLUME_ID(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) 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
       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) 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), ioctl_fat(2)

COLOPHON         top

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Linux man-pages 6.9.1          2024-06-15FAT_IOCTL_GET_VOLUME_ID(2const)

Pages that refer to this page: ioctl_fat(2)