VFAT_IOCTL_READDIR_BOTH(2const) - Linux manual page (original) (raw)
VFATIOCTLREADDIRBOTH(2const) VFATIOCTLREADDIRBOTH(2const)
NAME top
VFAT_IOCTL_READDIR_BOTH, VFAT_IOCTL_READDIR_SHORT - read filenames
of a directory in a FAT filesystemLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#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]);**DESCRIPTION top
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)](../man2/open.2.html) with
the **O_RDONLY** flag. The file descriptor can be used only once to
iterate over the directory entries by calling [ioctl(2)](../man2/ioctl.2.html) 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 _dino_ and _doff_ fields are filled only for long filenames.
The _dino_ field holds the inode number of the directory. The
_doff_ 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 _dreclen_ contains the length of the filename in the
field _dname_. 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)](../man2/ioctl.2.html) return value. If no long
filename exists, field _dreclen_ is set to 0 and _dname_ is a
character string of length 0 for the long filename.RETURN VALUE top
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](../man3/errno.3.html)_ is set to indicate the error.ERRORS top
**ENOENT** _fd_ refers to a removed, but still open directory.
**ENOTDIR**
_fd_ does not refer to a directory.STANDARDS top
Linux.HISTORY top
Linux 2.0.EXAMPLES top
The following program demonstrates the use of [ioctl(2)](../man2/ioctl.2.html) 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);
}SEE ALSO top
[ioctl(2)](../man2/ioctl.2.html), [ioctl_fat(2)](../man2/ioctl%5Ffat.2.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23_VFATIOCTLREADDIRBOTH_(2const)
Pages that refer to this page:ioctl_fat(2)