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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | STANDARDS | HISTORY | EXAMPLES | SEE ALSO | COLOPHON |
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FAT_IOCTL_GET_VOLUME_ID(2const) FAT_IOCTL_GET_VOLUME_ID(2const)
FAT_IOCTL_GET_VOLUME_ID - read the volume ID in a FAT filesystem
Standard C library (libc, -lc)
#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);
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);
On success, 0 is returned. On error, -1 is returned, and errno is
set to indicate the error.
Linux.
Linux 3.11.
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);
}
ioctl(2), ioctl_fat(2)
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Linux man-pages 6.15 2025-05-17FAT_IOCTL_GET_VOLUME_ID(2const)
Pages that refer to this page: ioctl_fat(2)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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