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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | EXAMPLES | SEE ALSO | COLOPHON |
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VFAT_IOCTL_READDIR_BOTH(2const) VFAT_IOCTL_READDIR_BOTH(2const)
VFAT_IOCTL_READDIR_BOTH, VFAT_IOCTL_READDIR_SHORT - read
filenames of a directory in a FAT filesystem
Standard C library (libc, -lc)
#include <linux/msdos_fs.h> /* Definition of VFAT_* constants */
#include <sys/ioctl.h>
int ioctl(int fd, VFAT_IOCTL_READDIR_BOTH,
struct __fat_dirent entry[2]);
int ioctl(int fd, VFAT_IOCTL_READDIR_SHORT,
struct __fat_dirent entry[2]);
A file or directory on a FAT filesystem always has a short
filename consisting of up to 8 capital letters, optionally
followed by a period and up to 3 capital letters for the file
extension. If the actual filename does not fit into this scheme,
it is stored as a long filename of up to 255 UTF-16 characters.
The short filenames in a directory can be read with
VFAT_IOCTL_READDIR_SHORT. VFAT_IOCTL_READDIR_BOTH reads both the
short and the long filenames.
The fd argument must be a file descriptor for a directory. It is
sufficient to create the file descriptor by calling open(2) with
the O_RDONLY flag. The file descriptor can be used only once to
iterate over the directory entries by calling ioctl(2)
repeatedly.
The entry argument is a two-element array of the following
structures:
struct __fat_dirent {
long d_ino;
__kernel_off_t d_off;
uint32_t short d_reclen;
char d_name[256];
};
The first entry in the array is for the short filename. The
second entry is for the long filename.
The d_ino and d_off fields are filled only for long filenames.
The d_ino field holds the inode number of the directory. The
d_off field holds the offset of the file entry in the directory.
As these values are not available for short filenames, the user
code should simply ignore them.
The field d_reclen contains the length of the filename in the
field d_name. To keep backward compatibility, a length of 0 for
the short filename signals that the end of the directory has been
reached. However, the preferred method for detecting the end of
the directory is to test the ioctl(2) return value. If no long
filename exists, field d_reclen is set to 0 and d_name is a
character string of length 0 for the long filename.
A return value of 1 signals that a new directory entry has been
read and a return value of 0 signals that the end of the
directory has been reached.
On error, -1 is returned, and errno is set to indicate the error.
ENOENT fd refers to a removed, but still open directory.
ENOTDIR
fd does not refer to a directory.
Linux.
Linux 2.0.
The following program demonstrates the use of ioctl(2) to list a
directory.
The following was recorded when applying the program to the
directory /mnt/user:
$ ./fat_dir /mnt/user
. -> ''
.. -> ''
ALONGF~1.TXT -> 'a long filename.txt'
UPPER.TXT -> ''
LOWER.TXT -> 'lower.txt'
Program source
#include <fcntl.h>
#include <linux/msdos_fs.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <unistd.h>
int
main(int argc, char *argv[])
{
int fd;
int ret;
struct __fat_dirent entry[2];
if (argc != 2) {
printf("Usage: %s DIRECTORY\n", argv[0]);
exit(EXIT_FAILURE);
}
/*
* Open file descriptor for the directory.
*/
fd = open(argv[1], O_RDONLY | O_DIRECTORY);
if (fd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
for (;;) {
/*
* Read next directory entry.
*/
ret = ioctl(fd, VFAT_IOCTL_READDIR_BOTH, entry);
/*
* If an error occurs, the return value is -1.
* If the end of the directory list has been reached,
* the return value is 0.
* For backward compatibility the end of the directory
* list is also signaled by d_reclen == 0.
*/
if (ret < 1)
break;
/*
* Write both the short name and the long name.
*/
printf("%s -> '%s'\n", entry[0].d_name, entry[1].d_name);
}
if (ret == -1) {
perror("VFAT_IOCTL_READDIR_BOTH");
exit(EXIT_FAILURE);
}
/*
* Close the file descriptor.
*/
close(fd);
exit(EXIT_SUCCESS);
}
ioctl(2), ioctl_fat(2)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
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part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.9.1 2024-06-15VFAT_IOCTL_READDIR_BOTH(2const)
Pages that refer to this page: ioctl_fat(2)
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HTML rendering created 2024-06-26 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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