]> git.saurik.com Git - apple/xnu.git/blob - bsd/man/man2/fcntl.2
xnu-2782.30.5.tar.gz
[apple/xnu.git] / bsd / man / man2 / fcntl.2
1 .\"
2 .\" Copyright (c) 2011 Apple Inc. All rights reserved.
3 .\"
4 .\" @APPLE_LICENSE_HEADER_START@
5 .\"
6 .\" This file contains Original Code and/or Modifications of Original Code
7 .\" as defined in and that are subject to the Apple Public Source License
8 .\" Version 2.0 (the 'License'). You may not use this file except in
9 .\" compliance with the License. Please obtain a copy of the License at
10 .\" http://www.opensource.apple.com/apsl/ and read it before using this
11 .\" file.
12 .\"
13 .\" The Original Code and all software distributed under the License are
14 .\" distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
15 .\" EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
16 .\" INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
17 .\" FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
18 .\" Please see the License for the specific language governing rights and
19 .\" limitations under the License.
20 .\"
21 .\" @APPLE_LICENSE_HEADER_END@
22 .\"
23 .\"
24 .\" $NetBSD: fcntl.2,v 1.6 1995/02/27 12:32:29 cgd Exp $
25 .\"
26 .\" Copyright (c) 1983, 1993
27 .\" The Regents of the University of California. All rights reserved.
28 .\"
29 .\" Redistribution and use in source and binary forms, with or without
30 .\" modification, are permitted provided that the following conditions
31 .\" are met:
32 .\" 1. Redistributions of source code must retain the above copyright
33 .\" notice, this list of conditions and the following disclaimer.
34 .\" 2. Redistributions in binary form must reproduce the above copyright
35 .\" notice, this list of conditions and the following disclaimer in the
36 .\" documentation and/or other materials provided with the distribution.
37 .\" 3. All advertising materials mentioning features or use of this software
38 .\" must display the following acknowledgement:
39 .\" This product includes software developed by the University of
40 .\" California, Berkeley and its contributors.
41 .\" 4. Neither the name of the University nor the names of its contributors
42 .\" may be used to endorse or promote products derived from this software
43 .\" without specific prior written permission.
44 .\"
45 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
46 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
47 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
48 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
49 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
50 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
51 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
52 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
53 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
54 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
55 .\" SUCH DAMAGE.
56 .\"
57 .\" @(#)fcntl.2 8.2 (Berkeley) 1/12/94
58 .\"
59 .Dd February 17, 2011
60 .Dt FCNTL 2
61 .Os BSD 4.2
62 .Sh NAME
63 .Nm fcntl
64 .Nd file control
65 .Sh SYNOPSIS
66 .Fd #include <fcntl.h>
67 .Ft int
68 .Fo fcntl
69 .Fa "int fildes"
70 .Fa "int cmd"
71 .Fa "..."
72 .Fc
73 .Sh DESCRIPTION
74 .Fn Fcntl
75 provides for control over descriptors.
76 The argument
77 .Fa fildes
78 is a descriptor to be operated on by
79 .Fa cmd
80 as follows:
81 .Bl -tag -width F_WRITEBOOTSTRAPX
82 .It Dv F_DUPFD
83 Return a new descriptor as follows:
84 .Pp
85 .Bl -bullet -compact -offset 4n
86 .It
87 Lowest numbered available descriptor greater than or equal to
88 .Fa arg .
89 .It
90 Same object references as the original descriptor.
91 .It
92 New descriptor shares the same file offset if the object
93 was a file.
94 .It
95 Same access mode (read, write or read/write).
96 .It
97 Same file status flags (i.e., both file descriptors
98 share the same file status flags).
99 .It
100 The close-on-exec flag associated with the new file descriptor
101 is cleared so that the descriptor remains open across an
102 .Xr execv 2
103 system call.
104 .El
105 .It Dv F_DUPFD_CLOEXEC
106 Like
107 .Dv F_DUPFD ,
108 except that the close-on-exec flag associated with the new file descriptor
109 is set.
110 .It Dv F_GETFD
111 Get the flags associated with the file descriptor
112 .Fa fildes ,
113 as described below
114 .Fa ( arg
115 is ignored).
116 .It Dv F_SETFD
117 Set the file descriptor flags to
118 .Fa arg .
119 .It Dv F_GETFL
120 Get descriptor status flags, as described below
121 .Fa ( arg
122 is ignored).
123 .It Dv F_SETFL
124 Set descriptor status flags to
125 .Fa arg .
126 .It Dv F_GETOWN
127 Get the process ID or process group
128 currently receiving
129 .Dv SIGIO
130 and
131 .Dv SIGURG
132 signals; process groups are returned
133 as negative values
134 .Fa ( arg
135 is ignored).
136 .It Dv F_SETOWN
137 Set the process or process group
138 to receive
139 .Dv SIGIO
140 and
141 .Dv SIGURG
142 signals;
143 process groups are specified by supplying
144 .Fa arg
145 as negative, otherwise
146 .Fa arg
147 is interpreted as a process ID.
148 .It Dv F_GETPATH
149 Get the path of the file descriptor
150 .Fa Fildes .
151 The argument must be a buffer of size
152 .Sy MAXPATHLEN
153 or greater.
154 .It Dv F_PREALLOCATE
155 Preallocate file storage space. Note: upon success,
156 the space that is allocated can be the same size or
157 larger than the space requested.
158 .It Dv F_SETSIZE
159 Truncate a file without zeroing space.
160 The calling process must have root privileges.
161 .It Dv F_RDADVISE
162 Issue an advisory read async with no copy to user.
163 .It Dv F_RDAHEAD
164 Turn read ahead off/on.
165 A zero value in
166 .Fa arg
167 disables read ahead.
168 A non-zero value in
169 .Fa arg
170 turns read ahead on.
171 .It Dv F_READBOOTSTRAP
172 Read bootstrap from disk.
173 .It Dv F_WRITEBOOTSTRAP
174 Write bootstrap on disk.
175 The calling process must have root privileges.
176 .It Dv F_NOCACHE
177 Turns data caching off/on. A non-zero value in
178 .Fa arg
179 turns data caching off.
180 A value of zero in
181 .Fa arg
182 turns data caching on.
183 .It Dv F_LOG2PHYS
184 Get disk device information.
185 Currently this only includes the
186 disk device address that corresponds
187 to the current file offset. Note that if the
188 file offset is not backed by physical blocks
189 we can return -1 as the offset. This is subject
190 to change.
191 .It Dv F_LOG2PHYS_EXT
192 Variant of F_LOG2PHYS that uses the passed in
193 file offset and length.
194 .It Dv F_FULLFSYNC
195 Does the same thing as
196 .Xr fsync 2
197 then asks the drive to
198 flush all buffered data to
199 the permanent storage device
200 .Fa ( arg
201 is ignored).
202 This is currently implemented on HFS, MS-DOS (FAT),
203 and Universal Disk Format (UDF) file systems.
204 The operation may take quite a while to complete.
205 Certain FireWire drives have also been known
206 to ignore the request to flush their buffered data.
207 .It Dv F_SETNOSIGPIPE
208 Determines whether a
209 .Dv SIGPIPE
210 signal will be generated when a write fails on a pipe or socket for
211 which there is no reader. If
212 .Fa arg
213 is non-zero,
214 .Dv SIGPIPE
215 generation is disabled for descriptor
216 .Fa fildes ,
217 while an
218 .Fa arg
219 of zero enables it (the default).
220 .It Dv F_GETNOSIGPIPE
221 Returns whether a
222 .Dv SIGPIPE
223 signal will be generated when a write fails on a pipe or socket
224 for which there is no reader. The semantics of the return value
225 match those of the
226 .Fa arg
227 of
228 .Dv F_SETNOSIGPIPE .
229 .El
230 .Pp
231 The flags for the
232 .Dv F_GETFD
233 and
234 .Dv F_SETFD
235 commands are as follows:
236 .Bl -tag -width FD_CLOEXECX -offset indent
237 .It Dv FD_CLOEXEC
238 Close-on-exec; the given file descriptor will be automatically
239 closed in the successor process image when one of the
240 .Xr execv 2
241 or
242 .Xr posix_spawn 2
243 family of system calls is invoked.
244 .El
245 .Pp
246 The flags for the
247 .Dv F_GETFL
248 and
249 .Dv F_SETFL
250 commands are as follows:
251 .Bl -tag -width O_NONBLOCKX -offset indent
252 .It Dv O_NONBLOCK
253 Non-blocking I/O; if no data is available to a
254 .Xr read
255 call, or if a
256 .Xr write
257 operation would block,
258 the read or write call returns -1 with the error
259 .Er EAGAIN .
260 .It Dv O_APPEND
261 Force each write to append at the end of file;
262 corresponds to the
263 .Dv O_APPEND
264 flag of
265 .Xr open 2 .
266 .It Dv O_ASYNC
267 Enable the
268 .Dv SIGIO
269 signal to be sent to the process group
270 when I/O is possible, e.g.,
271 upon availability of data to be read.
272 .El
273 .Pp
274 Several commands are available for doing advisory file locking;
275 they all operate on the following structure:
276 .ne 7v
277 .Bd -literal
278 struct flock {
279 off_t l_start; /* starting offset */
280 off_t l_len; /* len = 0 means until end of file */
281 pid_t l_pid; /* lock owner */
282 short l_type; /* lock type: read/write, etc. */
283 short l_whence; /* type of l_start */
284 };
285 .Ed
286 .Pp
287 The commands available for advisory record locking are as follows:
288 .Bl -tag -width F_SETLKWX
289 .It Dv F_GETLK
290 Get the first lock that blocks the lock description pointed to by the
291 third argument,
292 .Fa arg ,
293 taken as a pointer to a
294 .Fa "struct flock"
295 (see above).
296 The information retrieved overwrites the information passed to
297 .Nm fcntl
298 in the
299 .Fa flock
300 structure.
301 If no lock is found that would prevent this lock from being created,
302 the structure is left unchanged by this function call except for the
303 lock type which is set to
304 .Dv F_UNLCK .
305 .It Dv F_SETLK
306 Set or clear a file segment lock according to the lock description
307 pointed to by the third argument,
308 .Fa arg ,
309 taken as a pointer to a
310 .Fa "struct flock"
311 (see above).
312 .Dv F_SETLK
313 is used to establish shared (or read) locks
314 .Dv (F_RDLCK)
315 or exclusive (or write) locks,
316 .Dv (F_WRLCK) ,
317 as well as remove either type of lock
318 .Dv (F_UNLCK) .
319 If a shared or exclusive lock cannot be set,
320 .Nm fcntl
321 returns immediately with
322 .Er EAGAIN .
323 .It Dv F_SETLKW
324 This command is the same as
325 .Dv F_SETLK
326 except that if a shared or exclusive lock is blocked by other locks,
327 the process waits until the request can be satisfied.
328 If a signal that is to be caught is received while
329 .Nm fcntl
330 is waiting for a region, the
331 .Nm fcntl
332 will be interrupted if the signal handler has not specified the
333 .Dv SA_RESTART
334 (see
335 .Xr sigaction 2 ) .
336 .El
337 .Pp
338 When a shared lock has been set on a segment of a file,
339 other processes can set shared locks on that segment
340 or a portion of it.
341 A shared lock prevents any other process from setting an exclusive
342 lock on any portion of the protected area.
343 A request for a shared lock fails if the file descriptor was not
344 opened with read access.
345 .Pp
346 An exclusive lock prevents any other process from setting a shared lock or
347 an exclusive lock on any portion of the protected area.
348 A request for an exclusive lock fails if the file was not
349 opened with write access.
350 .Pp
351 The value of
352 .Fa l_whence
353 is
354 .Dv SEEK_SET ,
355 .Dv SEEK_CUR ,
356 or
357 .Dv SEEK_END
358 to indicate that the relative offset,
359 .Fa l_start
360 bytes, will be measured from the start of the file,
361 current position, or end of the file, respectively.
362 The value of
363 .Fa l_len
364 is the number of consecutive bytes to be locked.
365 If
366 .Fa l_len
367 is negative, the result is undefined.
368 The
369 .Fa l_pid
370 field is only used with
371 .Dv F_GETLK
372 to return the process ID of the process holding a blocking lock.
373 After a successful
374 .Dv F_GETLK
375 request, the value of
376 .Fa l_whence
377 is
378 .Dv SEEK_SET .
379 .Pp
380 Locks may start and extend beyond the current end of a file,
381 but may not start or extend before the beginning of the file.
382 A lock is set to extend to the largest possible value of the
383 file offset for that file if
384 .Fa l_len
385 is set to zero. If
386 .Fa l_whence
387 and
388 .Fa l_start
389 point to the beginning of the file, and
390 .Fa l_len
391 is zero, the entire file is locked.
392 If an application wishes only to do entire file locking, the
393 .Xr flock 2
394 system call is much more efficient.
395 .Pp
396 There is at most one type of lock set for each byte in the file.
397 Before a successful return from an
398 .Dv F_SETLK
399 or an
400 .Dv F_SETLKW
401 request when the calling process has previously existing locks
402 on bytes in the region specified by the request,
403 the previous lock type for each byte in the specified
404 region is replaced by the new lock type.
405 As specified above under the descriptions
406 of shared locks and exclusive locks, an
407 .Dv F_SETLK
408 or an
409 .Dv F_SETLKW
410 request fails or blocks respectively when another process has existing
411 locks on bytes in the specified region and the type of any of those
412 locks conflicts with the type specified in the request.
413 .Pp
414 This interface follows the completely stupid semantics of System V and
415 .St -p1003.1-88
416 that require that all locks associated with a file for a given process are
417 removed when \fIany\fP file descriptor for that file is closed by that process.
418 This semantic means that applications must be aware of any files that
419 a subroutine library may access.
420 For example if an application for updating the password file locks the
421 password file database while making the update, and then calls
422 .Xr getpwname 3
423 to retrieve a record,
424 the lock will be lost because
425 .Xr getpwname 3
426 opens, reads, and closes the password database.
427 The database close will release all locks that the process has
428 associated with the database, even if the library routine never
429 requested a lock on the database.
430 Another minor semantic problem with this interface is that
431 locks are not inherited by a child process created using the
432 .Xr fork 2
433 function.
434 The
435 .Xr flock 2
436 interface has much more rational last close semantics and
437 allows locks to be inherited by child processes.
438 .Xr Flock 2
439 is recommended for applications that want to ensure the integrity
440 of their locks when using library routines or wish to pass locks
441 to their children.
442 Note that
443 .Xr flock 2
444 and
445 .Xr fcntl 2
446 locks may be safely used concurrently.
447 .Pp
448 All locks associated with a file for a given process are
449 removed when the process terminates.
450 .Pp
451 A potential for deadlock occurs if a process controlling a locked region
452 is put to sleep by attempting to lock the locked region of another process.
453 This implementation detects that sleeping until a locked region is unlocked
454 would cause a deadlock and fails with an
455 .Er EDEADLK
456 error.
457 .Pp
458 The
459 .Dv F_PREALLOCATE
460 command operates on the following structure:
461 .ne 7v
462 .Bd -literal
463 typedef struct fstore {
464 u_int32_t fst_flags; /* IN: flags word */
465 int fst_posmode; /* IN: indicates offset field */
466 off_t fst_offset; /* IN: start of the region */
467 off_t fst_length; /* IN: size of the region */
468 off_t fst_bytesalloc; /* OUT: number of bytes allocated */
469 } fstore_t;
470 .Ed
471 .Pp
472 The flags (fst_flags) for the
473 .Dv F_PREALLOCATE
474 command are as follows:
475 .Bl -tag -width F_ALLOCATECONTIGX -offset indent
476 .It Dv F_ALLOCATECONTIG
477 Allocate contiguous space.
478 .It Dv F_ALLOCATEALL
479 Allocate all requested space or no space at all.
480 .El
481 .Pp
482 The position modes (fst_posmode) for the
483 .Dv F_PREALLOCATE
484 command indicate how to use the offset field.
485 The modes are as follows:
486 .Bl -tag -width F_PEOFPOSMODEX -offset indent
487 .It Dv F_PEOFPOSMODE
488 Allocate from the physical end of file.
489 .It Dv F_VOLPOSMODE
490 Allocate from the volume offset.
491 .El
492 .Pp
493 The
494 .Dv F_RDADVISE
495 command operates on the following structure
496 which holds information passed from the
497 user to the system:
498 .ne 7v
499 .Bd -literal
500 struct radvisory {
501 off_t ra_offset; /* offset into the file */
502 int ra_count; /* size of the read */
503 };
504 .Ed
505 .Pp
506 The
507 .Dv F_READBOOTSTRAP and F_WRITEBOOTSTRAP
508 commands operate on the following structure.
509 .ne 7v
510 .Bd -literal
511 typedef struct fbootstraptransfer {
512 off_t fbt_offset; /* IN: offset to start read/write */
513 size_t fbt_length; /* IN: number of bytes to transfer */
514 void *fbt_buffer; /* IN: buffer to be read/written */
515 } fbootstraptransfer_t;
516 .Ed
517 .Pp
518 The
519 .Dv F_LOG2PHYS
520 command operates on the following structure:
521 .ne 7v
522 .Bd -literal
523 struct log2phys {
524 u_int32_t l2p_flags; /* unused so far */
525 off_t l2p_contigbytes; /* unused so far */
526 off_t l2p_devoffset; /* bytes into device */
527 };
528 .Ed
529 .Pp
530 The
531 .Dv F_LOG2PHYS_EXT
532 command operates on the same structure as F_LOG2PHYS but treats it as an in/out:
533 .ne 7v
534 .Bd -literal
535 struct log2phys {
536 u_int32_t l2p_flags; /* unused so far */
537 off_t l2p_contigbytes; /* IN: number of bytes to be queried;
538 OUT: number of contiguous bytes allocated at this position */
539 off_t l2p_devoffset; /* IN: bytes into file;
540 OUT: bytes into device */
541 };
542 .Ed
543 .Pp
544 If
545 .Fa fildes
546 is a socket, then the
547 .Dv F_SETNOSIGPIPE
548 and
549 .Dv F_GETNOSIGPIPE
550 commands are directly analogous, and fully interoperate with the
551 .Dv SO_NOSIGPIPE
552 option of
553 .Xr setsockopt 2
554 and
555 .Xr getsockopt 2
556 respectively.
557 .Sh RETURN VALUES
558 Upon successful completion, the value returned depends on
559 .Fa cmd
560 as follows:
561 .Bl -tag -width F_GETOWNX -offset indent
562 .It Dv F_DUPFD
563 A new file descriptor.
564 .It Dv F_GETFD
565 Value of flag (only the low-order bit is defined).
566 .It Dv F_GETFL
567 Value of flags.
568 .It Dv F_GETOWN
569 Value of file descriptor owner.
570 .It other
571 Value other than -1.
572 .El
573 .Pp
574 Otherwise, a value of -1 is returned and
575 .Va errno
576 is set to indicate the error.
577 .Sh ERRORS
578 The
579 .Fn fcntl
580 system call will fail if:
581 .Bl -tag -width Er
582 .\" ==========
583 .It Bq Er EAGAIN
584 The argument
585 .Fa cmd
586 is
587 .Dv F_SETLK ,
588 the type of lock
589 .Fa (l_type)
590 is a shared lock
591 .Dv (F_RDLCK)
592 or exclusive lock
593 .Dv (F_WRLCK) ,
594 and the segment of a file to be locked is already
595 exclusive-locked by another process;
596 or the type is an exclusive lock and some portion of the
597 segment of a file to be locked is already shared-locked or
598 exclusive-locked by another process.
599 .It Bq Er EACCESS
600 The argument
601 .Fa cmd
602 is either
603 .Dv F_SETSIZE
604 or
605 .Dv F_WRITEBOOTSTRAP
606 and the calling process does not have root privileges.
607 .\" ==========
608 .It Bq Er EBADF
609 .Fa Fildes
610 is not a valid open file descriptor.
611 .Pp
612 The argument
613 .Fa cmd
614 is
615 .Dv F_SETLK
616 or
617 .Dv F_SETLKW ,
618 the type of lock
619 .Fa (l_type)
620 is a shared lock
621 .Dv (F_RDLCK) ,
622 and
623 .Fa fildes
624 is not a valid file descriptor open for reading.
625 .Pp
626 The argument
627 .Fa cmd
628 is
629 .Dv F_SETLK
630 or
631 .Dv F_SETLKW ,
632 the type of lock
633 .Fa (l_type)
634 is an exclusive lock
635 .Dv (F_WRLCK) ,
636 and
637 .Fa fildes
638 is not a valid file descriptor open for writing.
639 .Pp
640 The argument
641 .Fa cmd
642 is
643 .Dv F_PREALLOCATE
644 and the calling process does not have
645 file write permission.
646 .Pp
647 The argument
648 .Fa cmd
649 is
650 .Dv F_LOG2PHYS
651 or
652 .Dv F_LOG2PHYS_EXT
653 and
654 .Fa fildes
655 is not a valid file descriptor open for reading.
656 .\" ==========
657 .It Bq Er EDEADLK
658 The argument
659 .Fa cmd
660 is
661 .Dv F_SETLKW ,
662 and a deadlock condition was detected.
663 .\" ==========
664 .It Bq Er EINTR
665 The argument
666 .Fa cmd
667 is
668 .Dv F_SETLKW ,
669 and the function was interrupted by a signal.
670 .\" ==========
671 .It Bq Er EINVAL
672 .Fa Cmd
673 is
674 .Dv F_DUPFD
675 and
676 .Fa arg
677 is negative or greater than the maximum allowable number
678 (see
679 .Xr getdtablesize 2 ) .
680 .Pp
681 The argument
682 .Fa cmd
683 is
684 .Dv F_GETLK ,
685 .Dv F_SETLK ,
686 or
687 .Dv F_SETLKW
688 and the data to which
689 .Fa arg
690 points is not valid, or
691 .Fa fildes
692 refers to a file that does not support locking.
693 .Pp
694 The argument
695 .Fa cmd
696 is
697 .Dv F_PREALLOCATE
698 and the
699 .Fa fst_posmode
700 is not a valid mode,
701 or when
702 .Dv F_PEOFPOSMODE
703 is set and
704 .Fa fst_offset
705 is a non-zero value,
706 or when
707 .Dv F_VOLPOSMODE
708 is set and
709 .Fa fst_offset
710 is a negative or zero value.
711 .Pp
712 The argument
713 .Fa cmd
714 is either
715 .Dv F_READBOOTSTRAP
716 or
717 .Dv F_WRITEBOOTSTRAP
718 and the operation was attempted on a non-HFS disk type.
719 .\" ==========
720 .It Bq Er EMFILE
721 .Fa Cmd
722 is
723 .Dv F_DUPFD
724 and the maximum allowed number of file descriptors are currently
725 open.
726 .\" ==========
727 .It Bq Er EMFILE
728 The argument
729 .Fa cmd
730 is
731 .Dv F_DUPED
732 and the maximum number of file descriptors permitted for the
733 process are already in use,
734 or no file descriptors greater than or equal to
735 .Fa arg
736 are available.
737 .\" ==========
738 .It Bq Er ENOLCK
739 The argument
740 .Fa cmd
741 is
742 .Dv F_SETLK
743 or
744 .Dv F_SETLKW ,
745 and satisfying the lock or unlock request would result in the
746 number of locked regions in the system exceeding a system-imposed limit.
747 .\" ==========
748 .It Bq Er EOVERFLOW
749 A return value would overflow its representation.
750 For example,
751 .Fa cmd
752 is F_GETLK, F_SETLK, or F_SETLKW
753 and the smallest (or, if l_len is non-zero, the largest) offset
754 of a byte in the requested segment
755 will not fit in an object of type off_t.
756 .\" ==========
757 .It Bq Er ESRCH
758 .Fa Cmd
759 is
760 .Dv F_SETOWN
761 and
762 the process ID given as argument is not in use.
763 .El
764 .Sh SEE ALSO
765 .Xr close 2 ,
766 .Xr execve 2 ,
767 .Xr flock 2 ,
768 .Xr getdtablesize 2 ,
769 .Xr open 2 ,
770 .Xr pipe 2 ,
771 .Xr socket 2 ,
772 .Xr setsockopt 2 ,
773 .Xr sigaction 3
774 .Sh HISTORY
775 The
776 .Fn fcntl
777 function call appeared in
778 .Bx 4.2 .