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1 | .\" Copyright (C) 2014, Heinrich Schuchardt <xypron.glpk@gmx.de> |
2 | .\" | |
3 | .\" %%%LICENSE_START(VERBATIM) | |
4 | .\" Permission is granted to make and distribute verbatim copies of this | |
5 | .\" manual provided the copyright notice and this permission notice are | |
6 | .\" preserved on all copies. | |
7 | .\" | |
8 | .\" Permission is granted to copy and distribute modified versions of | |
9 | .\" this manual under the conditions for verbatim copying, provided that | |
10 | .\" the entire resulting derived work is distributed under the terms of | |
11 | .\" a permission notice identical to this one. | |
12 | .\" | |
13 | .\" Since the Linux kernel and libraries are constantly changing, this | |
3a6b9445 MK |
14 | .\" manual page may be incorrect or out-of-date. The author(s) assume |
15 | .\" no responsibility for errors or omissions, or for damages resulting | |
16 | .\" from the use of the information contained herein. The author(s) may | |
17 | .\" not have taken the same level of care in the production of this | |
18 | .\" manual, which is licensed free of charge, as they might when working | |
a1cd6a8f HS |
19 | .\" professionally. |
20 | .\" | |
21 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
22 | .\" the source, must acknowledge the copyright and authors of this work. | |
23 | .\" %%%LICENSE_END | |
24 | .TH IOCTl-FAT 2 2015-01-23 "Linux" "Linux Programmer's Manual" | |
25 | .SH "NAME" | |
f54da10e | 26 | ioctl_fat \- manipulating the FAT filesystem |
a1cd6a8f HS |
27 | .SH SYNOPSIS |
28 | .nf | |
29 | .B #include <linux/msdos_fs.h> | |
30 | .br | |
31 | .B #include <sys/ioctl.h> | |
32 | .sp | |
f54da10e MK |
33 | .BI "int ioctl(int " fd ", FAT_IOCTL_GET_ATTRIBUTES, uint32_t * " attr ); |
34 | .BI "int ioctl(int " fd ", FAT_IOCTL_SET_ATTRIBUTES, uint32_t * " attr ); | |
35 | .BI "int ioctl(int " fd ", FAT_IOCTL_GET_VOLUME_ID, uint32_t * " id ); | |
a1cd6a8f | 36 | .BI "int ioctl(int " fd ", VFAT_IOCTL_READDIR_BOTH, |
f54da10e | 37 | .BI " struct __fat_dirent[2] " entry ); |
a1cd6a8f | 38 | .BI "int ioctl(int " fd ", VFAT_IOCTL_READDIR_SHORT, |
f54da10e | 39 | .BI " struct __fat_dirent[2] " entry ); |
a1cd6a8f HS |
40 | .SH DESCRIPTION |
41 | The | |
42 | .BR ioctl (2) | |
f54da10e | 43 | system call can be used to read and write metadata of FAT filesystems that |
a1cd6a8f HS |
44 | are not accessible using other system calls. |
45 | .SS Reading and setting file attributes | |
46 | Files and directories in the FAT filesystem possess an attribute bit mask that | |
47 | can be read with | |
48 | .B FAT_IOCTL_GET_ATTRIBUTES | |
49 | and written with | |
50 | .BR FAT_IOCTL_SET_ATTRIBUTES . | |
51 | .PP | |
52 | The | |
53 | .I fd | |
f54da10e | 54 | argument contains a file descriptor for a file or directory. |
a1cd6a8f HS |
55 | It is sufficient to create the file descriptor by calling |
56 | .BR open (2) | |
57 | with the | |
58 | .B O_RDONLY | |
59 | flag. | |
60 | .PP | |
61 | The | |
62 | .I attr | |
f54da10e MK |
63 | argument contains a pointer to a bit mask. |
64 | The bits of the bit mask are: | |
a1cd6a8f HS |
65 | .TP |
66 | .B ATTR_RO | |
67 | This bit specifies that the file or directory is read-only. | |
68 | .TP | |
69 | .B ATTR_HIDDEN | |
70 | This bit specifies that the file or directory is hidden. | |
71 | .TP | |
72 | .B ATTR_SYS | |
73 | This bit specifies that the file is a system file. | |
74 | .TP | |
75 | .B ATTR_VOLUME | |
76 | This bit specifies that the file is a volume label. | |
77 | This attribute is read-only. | |
78 | .TP | |
79 | .B ATTR_DIR | |
80 | This bit specifies that this is a directory. | |
81 | This attribute is read-only. | |
82 | .TP | |
83 | .B ATTR_ARCH | |
84 | This bit indicates that this file or directory should be archived. | |
85 | It is set when a file is created or modified. | |
86 | It is reset by an archiving system. | |
87 | .PP | |
88 | The zero value | |
89 | .B ATTR_NONE | |
90 | can be used to indicate that no attribute bit is set. | |
91 | .SS Reading the volume label | |
f54da10e | 92 | FAT filesystems are identified by a volume label. |
a1cd6a8f HS |
93 | The volume label can be read with |
94 | .BR FAT_IOCTL_GET_VOLUME_ID . | |
95 | .PP | |
96 | The | |
97 | .I fd | |
98 | argument can be a file descriptor for any file or directory of the | |
99 | filesystem. | |
100 | It is sufficient to create the file descriptor by calling | |
101 | .BR open (2) | |
102 | with the | |
103 | .B O_RDONLY | |
104 | flag. | |
105 | .PP | |
106 | The | |
107 | .I id | |
108 | argument is a pointer to the field that will be filled with the volume ID. | |
109 | Typically the volume label is displayed to the user as a group of two | |
f54da10e | 110 | 16-bit fields: |
a1cd6a8f HS |
111 | .PP |
112 | .in +4n | |
113 | .nf | |
114 | printf("Volume ID %4x-%4x\\n", id >> 16, id & 0xFFFF); | |
115 | .fi | |
116 | .in | |
117 | .SS Reading short file names of a directory | |
118 | A file or directory on a FAT filesystem always has a short filename | |
119 | consisting of up to 8 capital letters, optionally followed by a period | |
120 | and up to 3 capital letters for the file extension. | |
121 | If the actual filename does not fit into this scheme, it is stored | |
122 | as a long filename of up to 255 UTF-16 characters. | |
123 | .PP | |
124 | The short filenames in a directory can be read with | |
125 | .BR VFAT_IOCTL_READDIR_SHORT . | |
126 | .B VFAT_IOCTL_READDIR_BOTH | |
127 | reads both the short and the long filenames. | |
128 | .PP | |
129 | The | |
130 | .I fd | |
131 | argument must be a file descriptor for a directory. | |
132 | It is sufficient to create the file descriptor by calling | |
133 | .BR open (2) | |
134 | with the | |
135 | .B O_RDONLY | |
136 | flag. | |
f54da10e | 137 | The file descriptor can be used only once to iterate over the directory |
a1cd6a8f HS |
138 | entries by calling |
139 | .BR ioctl (2) | |
140 | repeatedly. | |
141 | .PP | |
142 | The | |
143 | .I entry | |
f54da10e | 144 | argument is a two-element array of the following structures: |
a1cd6a8f HS |
145 | |
146 | .in +4n | |
147 | .nf | |
148 | struct __fat_dirent { | |
149 | long d_ino; | |
150 | __kernel_off_t d_off; | |
151 | uint32_t short d_reclen; | |
152 | char d_name[256]; | |
153 | }; | |
154 | .fi | |
155 | .in | |
156 | .PP | |
157 | The first entry in the array is for the short filename. | |
158 | The second entry is for the long filename. | |
159 | .PP | |
432cdf0d HS |
160 | Fields |
161 | .I d_ino | |
162 | and | |
163 | .I d_off | |
164 | are only filled for long filenames. | |
165 | Field | |
166 | .I d_ino | |
167 | holds the inode number of the directory. | |
168 | Field | |
169 | .I d_off | |
170 | holds the offset of the file entry in the directory. | |
171 | As these values are not available for short filenames, the user code should | |
172 | simply ignore them. | |
173 | .PP | |
f54da10e | 174 | The field |
a1cd6a8f | 175 | .I d_reclen |
f54da10e | 176 | contains the length of the filename in the field |
a1cd6a8f | 177 | .IR d_name . |
432cdf0d HS |
178 | To keep backwards compatibility a length of 0 for the short filename signals |
179 | that the end of the directory has been reached. | |
180 | The user code should rely on the return value to identify the end of the | |
181 | directory. | |
182 | If no long filename exists, field | |
183 | .I d_reclen | |
184 | is set to 0 and | |
185 | .I d_name | |
186 | is a character string of length 0 for the long filename. | |
a1cd6a8f | 187 | .SH RETURN VALUE |
f54da10e MK |
188 | On error, \-1 is returned, and |
189 | .I errno | |
190 | is set to indicate the error. | |
432cdf0d HS |
191 | .PP |
192 | For | |
193 | .B VFAT_IOCTL_READDIR_BOTH | |
194 | and | |
195 | .B VFAT_IOCTL_READDIR_SHORT | |
196 | a return value of 1 signals that a new directory entry has been read and | |
197 | a return value of 0 signals that the end of the directory has been reached. | |
a1cd6a8f HS |
198 | .SH ERRORS |
199 | .TP | |
432cdf0d | 200 | .B ENOENT |
a1cd6a8f | 201 | This error is returned by |
432cdf0d HS |
202 | .B VFAT_IOCTL_READDIR_BOTH |
203 | and | |
a1cd6a8f | 204 | .B VFAT_IOCTL_READDIR_SHORT |
432cdf0d HS |
205 | if the file descriptor |
206 | .I fd | |
207 | refers to a removed, but still open directory. | |
208 | .TP | |
209 | .B ENOTDIR | |
210 | This error is returned by | |
211 | .B VFAT_IOCTL_READDIR_BOTH | |
a1cd6a8f HS |
212 | and |
213 | .B VFAT_IOCTL_READDIR_SHORT | |
432cdf0d | 214 | if the file descriptor |
f54da10e MK |
215 | .I fd |
216 | does not refer to a directory. | |
a1cd6a8f HS |
217 | .TP |
218 | .B ENOTTY | |
f54da10e MK |
219 | The file descriptor |
220 | .I fd | |
221 | does not refer to an object in a FAT filesystem. | |
a1cd6a8f | 222 | .PP |
f54da10e | 223 | For further error values, see |
a1cd6a8f HS |
224 | .BR ioctl (2). |
225 | .SH VERSIONS | |
3289445e MK |
226 | .BR VFAT_IOCTL_READDIR_BOTH |
227 | and | |
228 | .B VFAT_IOCTL_READDIR_SHORT | |
229 | first appeared in Linux 2.0. | |
230 | ||
231 | .BR FAT_IOCTL_GET_ATTRIBUTES | |
232 | and | |
233 | .BR FAT_IOCTL_SET_ATTRIBUTES | |
234 | first appeared | |
235 | .\" just before we got Git history | |
236 | in Linux 2.6.12. | |
237 | ||
a1cd6a8f | 238 | .B FAT_IOCTL_GET_VOLUME_ID |
f54da10e MK |
239 | was introduced in version 3.11 |
240 | .\" commit 6e5b93ee55d401f1619092fb675b57c28c9ed7ec | |
241 | of the Linux kernel. | |
a1cd6a8f HS |
242 | .SH "CONFORMING TO" |
243 | This API is Linux-specific. | |
244 | .SH EXAMPLE | |
245 | .SS Toggling the archive flag | |
f54da10e MK |
246 | The following program demonstrates the usage of |
247 | .BR ioctl () | |
248 | to manipulate file attributes. | |
249 | The program reads and displays the archive attribute of a file. | |
250 | After inverting the value of the attribute, | |
251 | the program reads and displays the attribute again. | |
a1cd6a8f HS |
252 | .PP |
253 | The following was recorded when applying the program for the file | |
f54da10e MK |
254 | .IR /mnt/user/foo : |
255 | ||
a1cd6a8f HS |
256 | .in +4n |
257 | .nf | |
11a86b15 | 258 | # ./toggle_fat_archive_flag /mnt/user/foo |
a1cd6a8f HS |
259 | Archive flag is set |
260 | Toggling archive flag | |
261 | Archive flag is not set | |
262 | .fi | |
263 | .in | |
11a86b15 | 264 | .SS Program source (toggle_fat_archive_flag.c) |
a1cd6a8f HS |
265 | .in +4n |
266 | .nf | |
267 | #include <fcntl.h> | |
268 | #include <linux/msdos_fs.h> | |
269 | #include <stdint.h> | |
270 | #include <stdio.h> | |
271 | #include <stdlib.h> | |
272 | #include <sys/ioctl.h> | |
273 | #include <unistd.h> | |
274 | ||
275 | /* | |
276 | * Read file attributes of a file on a FAT filesystem. | |
277 | * Output the state of the archive flag. | |
278 | */ | |
279 | static uint32_t | |
280 | readattr(int fd) | |
281 | { | |
282 | uint32_t attr; | |
283 | int ret; | |
284 | ||
285 | ret = ioctl(fd, FAT_IOCTL_GET_ATTRIBUTES, &attr); | |
286 | if (ret == \-1) { | |
287 | perror("ioctl"); | |
288 | exit(EXIT_FAILURE); | |
289 | } | |
290 | ||
291 | if (attr & ATTR_ARCH) | |
292 | printf("Archive flag is set\\n"); | |
293 | else | |
294 | printf("Archive flag is not set\\n"); | |
295 | ||
296 | return attr; | |
297 | } | |
298 | ||
299 | int | |
300 | main(int argc, char *argv[]) | |
301 | { | |
302 | uint32_t attr; | |
303 | int fd; | |
304 | int ret; | |
305 | ||
306 | if (argc != 2) { | |
307 | printf("Usage: %s FILENAME\\n", argv[0]); | |
308 | exit(EXIT_FAILURE); | |
309 | } | |
310 | ||
311 | fd = open(argv[1], O_RDONLY); | |
312 | if (fd == \-1) { | |
313 | perror("open"); | |
314 | exit(EXIT_FAILURE); | |
315 | } | |
316 | ||
317 | /* | |
318 | * Read and display the FAT file attributes. | |
319 | */ | |
320 | attr = readattr(fd); | |
321 | ||
322 | /* | |
323 | * Invert archive attribute. | |
324 | */ | |
325 | printf("Toggling archive flag\\n"); | |
326 | attr ^= ATTR_ARCH; | |
327 | ||
328 | /* | |
329 | * Write the changed FAT file attributes. | |
330 | */ | |
331 | ret = ioctl(fd, FAT_IOCTL_SET_ATTRIBUTES, &attr); | |
332 | if (ret == \-1) { | |
333 | perror("ioctl"); | |
334 | exit(EXIT_FAILURE); | |
335 | } | |
336 | ||
337 | /* | |
338 | * Read and display the FAT file attributes. | |
339 | */ | |
340 | readattr(fd); | |
341 | ||
342 | close(fd); | |
343 | ||
3b4f9570 | 344 | exit(EXIT_SUCCESS); |
a1cd6a8f HS |
345 | } |
346 | .fi | |
347 | .in | |
348 | .SS Reading the volume label | |
f54da10e MK |
349 | The following program demonstrates the use of |
350 | .BR ioctl (2) | |
351 | to display the volume label of a FAT filesystem. | |
a1cd6a8f HS |
352 | .PP |
353 | The following output was recorded when applying the program for | |
354 | directory | |
f54da10e MK |
355 | .IR /mnt/user : |
356 | ||
a1cd6a8f HS |
357 | .in +4n |
358 | .nf | |
11a86b15 | 359 | $ ./display_fat_volume_id /mnt/user |
a1cd6a8f HS |
360 | Volume ID 6443-6241 |
361 | .fi | |
362 | .in | |
11a86b15 | 363 | .SS Program source (display_fat_volume_id.c) |
a1cd6a8f HS |
364 | .in +4n |
365 | .nf | |
366 | #include <fcntl.h> | |
367 | #include <linux/msdos_fs.h> | |
368 | #include <stdint.h> | |
369 | #include <stdio.h> | |
370 | #include <stdlib.h> | |
371 | #include <sys/ioctl.h> | |
372 | #include <unistd.h> | |
373 | ||
374 | int | |
375 | main(int argc, char *argv[]) | |
376 | { | |
377 | uint32_t id; | |
378 | int fd; | |
379 | int ret; | |
380 | ||
381 | if (argc != 2) { | |
382 | printf("Usage: %s FILENAME\\n", argv[0]); | |
383 | exit(EXIT_FAILURE); | |
384 | } | |
385 | ||
386 | fd = open(argv[1], O_RDONLY); | |
387 | if (fd == \-1) { | |
388 | perror("open"); | |
389 | exit(EXIT_FAILURE); | |
390 | } | |
391 | ||
392 | /* | |
393 | * Read volume ID. | |
394 | */ | |
395 | ret = ioctl(fd, FAT_IOCTL_GET_VOLUME_ID, &id); | |
396 | if (ret == \-1) { | |
397 | perror("ioctl"); | |
398 | exit(EXIT_FAILURE); | |
399 | } | |
400 | ||
401 | /* | |
402 | * Format the output as two groups of 16 bits each. | |
403 | */ | |
404 | printf("Volume ID %4x\-%4x\\n", id >> 16, id & 0xFFFF); | |
405 | ||
406 | close(fd); | |
407 | ||
3b4f9570 | 408 | exit(EXIT_SUCCESS); |
a1cd6a8f HS |
409 | } |
410 | .fi | |
411 | .in | |
412 | .SS Listing a directory | |
f54da10e MK |
413 | The following program demonstrates the use of |
414 | .BR ioctl (2) | |
415 | to list a directory. | |
a1cd6a8f | 416 | .PP |
f54da10e MK |
417 | The following was recorded when applying the program to the directory |
418 | .IR /mnt/user : | |
419 | ||
a1cd6a8f HS |
420 | .in +4n |
421 | .nf | |
422 | $ ./fat_dir /mnt/user | |
423 | \[char46] -> '' | |
424 | \[char46]. -> '' | |
425 | ALONGF~1.TXT -> 'a long filename.txt' | |
426 | UPPER.TXT -> '' | |
427 | LOWER.TXT -> 'lower.txt' | |
428 | .fi | |
429 | .in | |
430 | .SS Program source | |
431 | .in +4n | |
432 | .nf | |
433 | #include <fcntl.h> | |
434 | #include <linux/msdos_fs.h> | |
435 | #include <stdio.h> | |
436 | #include <stdlib.h> | |
437 | #include <sys/ioctl.h> | |
438 | #include <unistd.h> | |
439 | ||
440 | int | |
441 | main(int argc, char *argv[]) | |
442 | { | |
443 | struct __fat_dirent entry[2]; | |
444 | int fd; | |
445 | int ret; | |
446 | ||
447 | if (argc != 2) { | |
448 | printf("Usage: %s DIRECTORY\\n", argv[0]); | |
449 | exit(EXIT_FAILURE); | |
450 | } | |
451 | ||
452 | /* | |
453 | * Open file descriptor for the directory. | |
454 | */ | |
455 | fd = open(argv[1], O_RDONLY | O_DIRECTORY); | |
456 | if (fd == \-1) { | |
457 | perror("open"); | |
458 | exit(EXIT_FAILURE); | |
459 | } | |
460 | ||
461 | for (;;) { | |
462 | ||
463 | /* | |
464 | * Read next directory entry. | |
465 | */ | |
466 | ret = ioctl( fd, VFAT_IOCTL_READDIR_BOTH, entry); | |
467 | ||
468 | /* | |
469 | * If an error occurs, the return value is \-1. | |
432cdf0d HS |
470 | * If the end of the directory list has been reached, |
471 | * the return value is 0. | |
472 | * For backward compatibility the end of the directory | |
473 | * list is also signaled by d_reclen == 0. | |
a1cd6a8f | 474 | */ |
432cdf0d | 475 | if (ret < 1) |
a1cd6a8f HS |
476 | break; |
477 | ||
478 | /* | |
479 | * Write both the short name and the long name. | |
480 | */ | |
481 | printf("%s \-> '%s'\\n", entry[0].d_name, entry[1].d_name); | |
482 | } | |
f54da10e | 483 | |
a1cd6a8f HS |
484 | if (ret == \-1) { |
485 | perror("VFAT_IOCTL_READDIR_BOTH"); | |
486 | exit(EXIT_FAILURE); | |
487 | } | |
488 | ||
489 | /* | |
490 | * Close the file descriptor. | |
491 | */ | |
492 | close(fd); | |
493 | ||
3b4f9570 | 494 | exit(EXIT_SUCCESS); |
a1cd6a8f HS |
495 | } |
496 | .fi | |
497 | .in | |
498 | .SH SEE ALSO | |
499 | .BR ioctl (2) |