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-.\" Copyright (C) 2014, Heinrich Schuchardt <xypron.glpk@gmx.de>
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.TH ioctl_fat 2 2023-10-31 "Linux man-pages 6.7"
-.SH NAME
-ioctl_fat \- manipulating the FAT filesystem
-.SH LIBRARY
-Standard C library
-.RI ( libc ", " \-lc )
-.SH SYNOPSIS
-.nf
-.BR "#include <linux/msdos_fs.h>" " /* Definition of [" V ] FAT_* " and"
-.BR " ATTR_* " constants */"
-.B #include <sys/ioctl.h>
-.P
-.BI "int ioctl(int " fd ", FAT_IOCTL_GET_ATTRIBUTES, uint32_t *" attr );
-.BI "int ioctl(int " fd ", FAT_IOCTL_SET_ATTRIBUTES, uint32_t *" attr );
-.BI "int ioctl(int " fd ", FAT_IOCTL_GET_VOLUME_ID, uint32_t *" id );
-.BI "int ioctl(int " fd ", VFAT_IOCTL_READDIR_BOTH,"
-.BI " struct __fat_dirent " entry [2]);
-.BI "int ioctl(int " fd ", VFAT_IOCTL_READDIR_SHORT,"
-.BI " struct __fat_dirent " entry [2]);
-.fi
-.SH DESCRIPTION
-The
-.BR ioctl (2)
-system call can be used to read and write metadata of FAT filesystems that
-are not accessible using other system calls.
-.SS Reading and setting file attributes
-Files and directories in the FAT filesystem possess an attribute bit mask that
-can be read with
-.B FAT_IOCTL_GET_ATTRIBUTES
-and written with
-.BR FAT_IOCTL_SET_ATTRIBUTES .
-.P
-The
-.I fd
-argument contains a file descriptor for a file or directory.
-It is sufficient to create the file descriptor by calling
-.BR open (2)
-with the
-.B O_RDONLY
-flag.
-.P
-The
-.I attr
-argument contains a pointer to a bit mask.
-The bits of the bit mask are:
-.TP
-.B ATTR_RO
-This bit specifies that the file or directory is read-only.
-.TP
-.B ATTR_HIDDEN
-This bit specifies that the file or directory is hidden.
-.TP
-.B ATTR_SYS
-This bit specifies that the file is a system file.
-.TP
-.B ATTR_VOLUME
-This bit specifies that the file is a volume label.
-This attribute is read-only.
-.TP
-.B ATTR_DIR
-This bit specifies that this is a directory.
-This attribute is read-only.
-.TP
-.B ATTR_ARCH
-This bit indicates that this file or directory should be archived.
-It is set when a file is created or modified.
-It is reset by an archiving system.
-.P
-The zero value
-.B ATTR_NONE
-can be used to indicate that no attribute bit is set.
-.SS Reading the volume ID
-FAT filesystems are identified by a volume ID.
-The volume ID can be read with
-.BR FAT_IOCTL_GET_VOLUME_ID .
-.P
-The
-.I 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
-.BR open (2)
-with the
-.B O_RDONLY
-flag.
-.P
-The
-.I 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:
-.P
-.in +4n
-.EX
-printf("Volume ID %04x\-%04x\en", id >> 16, id & 0xFFFF);
-.EE
-.in
-.SS Reading short filenames of a directory
-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.
-.P
-The short filenames in a directory can be read with
-.BR VFAT_IOCTL_READDIR_SHORT .
-.B VFAT_IOCTL_READDIR_BOTH
-reads both the short and the long filenames.
-.P
-The
-.I fd
-argument must be a file descriptor for a directory.
-It is sufficient to create the file descriptor by calling
-.BR open (2)
-with the
-.B O_RDONLY
-flag.
-The file descriptor can be used only once to iterate over the directory
-entries by calling
-.BR ioctl (2)
-repeatedly.
-.P
-The
-.I entry
-argument is a two-element array of the following structures:
-.P
-.in +4n
-.EX
-struct __fat_dirent {
- long d_ino;
- __kernel_off_t d_off;
- uint32_t short d_reclen;
- char d_name[256];
-};
-.EE
-.in
-.P
-The first entry in the array is for the short filename.
-The second entry is for the long filename.
-.P
-The
-.I d_ino
-and
-.I d_off
-fields are filled only for long filenames.
-The
-.I d_ino
-field holds the inode number of the directory.
-The
-.I 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.
-.P
-The field
-.I d_reclen
-contains the length of the filename in the field
-.IR 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
-.BR ioctl (2)
-return value.
-If no long filename exists, field
-.I d_reclen
-is set to 0 and
-.I d_name
-is a character string of length 0 for the long filename.
-.SH RETURN VALUE
-On error, \-1 is returned, and
-.I errno
-is set to indicate the error.
-.P
-For
-.B VFAT_IOCTL_READDIR_BOTH
-and
-.B VFAT_IOCTL_READDIR_SHORT
-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.
-.SH ERRORS
-.TP
-.B ENOENT
-This error is returned by
-.B VFAT_IOCTL_READDIR_BOTH
-and
-.B VFAT_IOCTL_READDIR_SHORT
-if the file descriptor
-.I fd
-refers to a removed, but still open directory.
-.TP
-.B ENOTDIR
-This error is returned by
-.B VFAT_IOCTL_READDIR_BOTH
-and
-.B VFAT_IOCTL_READDIR_SHORT
-if the file descriptor
-.I fd
-does not refer to a directory.
-.TP
-.B ENOTTY
-The file descriptor
-.I fd
-does not refer to an object in a FAT filesystem.
-.P
-For further error values, see
-.BR ioctl (2).
-.SH STANDARDS
-Linux.
-.SH HISTORY
-.TP
-.B VFAT_IOCTL_READDIR_BOTH
-.TQ
-.B VFAT_IOCTL_READDIR_SHORT
-Linux 2.0.
-.TP
-.B FAT_IOCTL_GET_ATTRIBUTES
-.TQ
-.B FAT_IOCTL_SET_ATTRIBUTES
-.\" just before we got Git history
-Linux 2.6.12.
-.TP
-.B FAT_IOCTL_GET_VOLUME_ID
-Linux 3.11.
-.\" commit 6e5b93ee55d401f1619092fb675b57c28c9ed7ec
-.SH EXAMPLES
-.SS Toggling the archive flag
-The following program demonstrates the usage of
-.BR ioctl (2)
-to manipulate file attributes.
-The program reads and displays the archive attribute of a file.
-After inverting the value of the attribute,
-the program reads and displays the attribute again.
-.P
-The following was recorded when applying the program for the file
-.IR /mnt/user/foo :
-.P
-.in +4n
-.EX
-# ./toggle_fat_archive_flag /mnt/user/foo
-Archive flag is set
-Toggling archive flag
-Archive flag is not set
-.EE
-.in
-.SS Program source (toggle_fat_archive_flag.c)
-\&
-.\" SRC BEGIN (toggle_fat_archive_flag.c)
-.EX
-#include <fcntl.h>
-#include <linux/msdos_fs.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <sys/ioctl.h>
-#include <unistd.h>
-\&
-/*
- * Read file attributes of a file on a FAT filesystem.
- * Output the state of the archive flag.
- */
-static uint32_t
-readattr(int fd)
-{
- int ret;
- uint32_t attr;
-\&
- ret = ioctl(fd, FAT_IOCTL_GET_ATTRIBUTES, &attr);
- if (ret == \-1) {
- perror("ioctl");
- exit(EXIT_FAILURE);
- }
-\&
- if (attr & ATTR_ARCH)
- printf("Archive flag is set\en");
- else
- printf("Archive flag is not set\en");
-\&
- return attr;
-}
-\&
-int
-main(int argc, char *argv[])
-{
- int fd;
- int ret;
- uint32_t attr;
-\&
- if (argc != 2) {
- printf("Usage: %s FILENAME\en", argv[0]);
- exit(EXIT_FAILURE);
- }
-\&
- fd = open(argv[1], O_RDONLY);
- if (fd == \-1) {
- perror("open");
- exit(EXIT_FAILURE);
- }
-\&
- /*
- * Read and display the FAT file attributes.
- */
- attr = readattr(fd);
-\&
- /*
- * Invert archive attribute.
- */
- printf("Toggling archive flag\en");
- attr \[ha]= ATTR_ARCH;
-\&
- /*
- * Write the changed FAT file attributes.
- */
- ret = ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &attr);
- if (ret == \-1) {
- perror("ioctl");
- exit(EXIT_FAILURE);
- }
-\&
- /*
- * Read and display the FAT file attributes.
- */
- readattr(fd);
-\&
- close(fd);
-\&
- exit(EXIT_SUCCESS);
-}
-.EE
-.\" SRC END
-.SS Reading the volume ID
-The following program demonstrates the use of
-.BR ioctl (2)
-to display the volume ID of a FAT filesystem.
-.P
-The following output was recorded when applying the program for
-directory
-.IR /mnt/user :
-.P
-.in +4n
-.EX
-$ ./display_fat_volume_id /mnt/user
-Volume ID 6443\-6241
-.EE
-.in
-.SS Program source (display_fat_volume_id.c)
-\&
-.\" SRC BEGIN (display_fat_volume_id.c)
-.EX
-#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\en", 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\en", id >> 16, id & 0xFFFF);
-\&
- close(fd);
-\&
- exit(EXIT_SUCCESS);
-}
-.EE
-.\" SRC END
-.SS Listing a directory
-The following program demonstrates the use of
-.BR ioctl (2)
-to list a directory.
-.P
-The following was recorded when applying the program to the directory
-.IR /mnt/user :
-.P
-.in +4n
-.EX
-$ \fB./fat_dir /mnt/user\fP
-\&. \-> \[aq]\[aq]
-\&.. \-> \[aq]\[aq]
-ALONGF\[ti]1.TXT \-> \[aq]a long filename.txt\[aq]
-UPPER.TXT \-> \[aq]\[aq]
-LOWER.TXT \-> \[aq]lower.txt\[aq]
-.EE
-.in
-.\"
-.SS Program source
-.in +4n
-.\" SRC BEGIN (ioctl_fat.c)
-.EX
-#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\en", 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 \-> \[aq]%s\[aq]\en", 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);
-}
-.EE
-.\" SRC END
-.in
-.SH SEE ALSO
-.BR ioctl (2)
generated by cgit v1.2.3 (git 2.39.1) at 2024-10-31 11:06:10 +0000