1 .\" Copyright (c) 1980, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. Neither the name of the University nor the names of its contributors
13 .\" may be used to endorse or promote products derived from this software
14 .\" without specific prior written permission.
16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" @(#)open.2 8.2 (Berkeley) 11/16/93
36 .Nd open or create a file for reading, writing or executing
42 .Fn open "const char *path" "int flags" "..."
44 .Fn openat "int fd" "const char *path" "int flags" "..."
46 The file name specified by
49 for either execution or reading and/or writing as specified by the
52 and the file descriptor returned to the calling process.
55 argument may indicate the file is to be
56 created if it does not exist (by specifying the
63 require an additional argument
65 and the file is created with mode
69 and modified by the process' umask value (see
74 function is equivalent to the
76 function except in the case where the
78 specifies a relative path, or the
85 the file to be opened is determined relative to the directory
86 associated with the file descriptor
88 instead of the current working directory.
91 parameter and the optional fourth parameter correspond exactly to
96 is passed the special value
100 parameter, the current working directory is used
101 and the behavior is identical to a call to
106 is called with an absolute
115 is specified with an absolute
117 a directory passed by the
119 argument is used as the topping point for the resolution.
120 See the definition of the
133 must be strictly relative to a file descriptor
136 .Pa sys/kern/vfs_lookup.c .
138 must not be an absolute path and must not contain ".." components
139 which cause the path resolution to escape the directory hierarchy
142 Additionally, no symbolic link in
144 may target absolute path or contain escaping ".." components.
150 .Dv vfs.lookup_cap_dotdot
152 MIB is set to zero, ".." components in the paths,
153 used in capability mode, or with the
155 flag, are completely disabled.
157 .Dv vfs.lookup_cap_dotdot_nonlocal
158 MIB is set to zero, ".." is not allowed if found on non-local filesystem.
160 The flags specified are formed by
164 .Bd -literal -offset indent -compact
165 O_RDONLY open for reading only
166 O_WRONLY open for writing only
167 O_RDWR open for reading and writing
168 O_EXEC open for execute only
169 O_NONBLOCK do not block on open
170 O_APPEND append on each write
171 O_CREAT create file if it does not exist
172 O_TRUNC truncate size to 0
173 O_EXCL error if create and file exists
174 O_SHLOCK atomically obtain a shared lock
175 O_EXLOCK atomically obtain an exclusive lock
176 O_DIRECT eliminate or reduce cache effects
177 O_FSYNC synchronous writes
178 O_SYNC synchronous writes
179 O_NOFOLLOW do not follow symlinks
182 O_DIRECTORY error if file is not a directory
183 O_CLOEXEC set FD_CLOEXEC upon open
184 O_VERIFY verify the contents of the file
185 O_BENEATH require path to be strictly relative to topping directory
190 set causes each write on the file
191 to be appended to the end.
195 file exists, the file is truncated to zero length.
205 implement a simple exclusive access locking mechanism.
208 is set and the last component of the pathname is
211 will fail even if the symbolic
212 link points to a non-existent name.
215 flag is specified and the
217 system call would result
218 in the process being blocked for some reason (e.g., waiting for
219 carrier on a dialup line),
222 The descriptor remains in non-blocking mode for subsequent operations.
226 is used in the mask, all writes will
227 immediately be written to disk,
228 the kernel will not cache written data
229 and all writes on the descriptor will not return until
230 the data to be written completes.
240 is used in the mask and the target file passed to
242 is a symbolic link then the
246 When opening a file, a lock with
248 semantics can be obtained by setting
250 for a shared lock, or
252 for an exclusive lock.
253 If creating a file with
255 the request for the lock will never fail
256 (provided that the underlying file system supports locking).
259 may be used to minimize or eliminate the cache effects of reading and writing.
260 The system will attempt to avoid caching the data you read or write.
261 If it cannot avoid caching the data,
262 it will minimize the impact the data has on the cache.
263 Use of this flag can drastically reduce performance if not used with care.
266 may be used to ensure the OS does not assign this file as the
267 controlling terminal when it opens a tty device.
268 This is the default on
275 system call will not assign controlling terminals on
279 may be used to ensure the OS restores the terminal attributes when
280 initially opening a TTY.
281 This is the default on
288 on a TTY will always restore default terminal attributes on
292 may be used to ensure the resulting file descriptor refers to a
294 This flag can be used to prevent applications with elevated privileges
295 from opening files which are even unsafe to open with
297 such as device nodes.
302 flag for the newly returned file descriptor.
305 may be used to indicate to the kernel that the contents of the file should
306 be verified before allowing the open to proceed.
309 means is implementation specific.
310 The run-time linker (rtld) uses this flag to ensure shared objects have
311 been verified before operating on them.
316 if the specified relative path, after resolving all symlinks and ".."
317 references, does not reside in the directory hierarchy of
318 children beneath the topping directory.
319 Topping directory is the process current directory if relative
323 and the directory referenced by the
327 If the specified path is absolute,
329 allows arbitrary prefix that ends up at the topping directory,
330 after which all further resolved components must be under it.
334 returns a non-negative integer, termed a file descriptor.
335 It returns \-1 on failure.
336 The file pointer used to mark the current position within the
337 file is set to the beginning of the file.
339 If a sleeping open of a device node from
341 is interrupted by a signal, the call always fails with
345 flag is set for the signal.
346 A sleeping open of a fifo (see
348 is restarted as normal.
350 When a new file is created it is given the group of the directory
356 the new descriptor is set to remain open across
365 The system imposes a limit on the number of file descriptors
366 open simultaneously by one process.
369 system call returns the current system limit.
375 return a non-negative integer, termed a file descriptor.
376 They return \-1 on failure, and set
378 to indicate the error.
380 The named file is opened unless:
383 A component of the path prefix is not a directory.
384 .It Bq Er ENAMETOOLONG
385 A component of a pathname exceeded 255 characters,
386 or an entire path name exceeded 1023 characters.
389 is not set and the named file does not exist.
391 A component of the path name that must exist does not exist.
393 Search permission is denied for a component of the path prefix.
395 The required permissions (for reading and/or writing)
396 are denied for the given flags.
399 is specified and write permission is denied.
403 the file does not exist,
404 and the directory in which it is to be created
405 does not permit writing.
408 is specified, the file does not exist, and the directory in which it is to be
409 created has its immutable flag set, see the
411 manual page for more information.
413 The named file has its immutable flag set and the file is to be modified.
415 The named file has its append-only flag set, the file is to be modified, and
421 Too many symbolic links were encountered in translating the pathname.
423 The named file is a directory, and the arguments specify
424 it is to be modified.
426 The named file resides on a read-only file system,
427 and the file is to be modified.
430 is specified and the named file would reside on a read-only file system.
432 The process has already reached its limit for open file descriptors.
434 The system file table is full.
437 was specified and the target is a symbolic link.
439 The named file is a character special or block
440 special file, and the device associated with this special file
444 is set, the named file is a fifo,
446 is set, and no process has the file open for reading.
450 operation was interrupted by a signal.
455 is specified but the underlying file system does not support locking.
457 The named file is a special file mounted through a file system that
458 does not support access to it (e.g.\& NFS).
459 .It Bq Er EWOULDBLOCK
465 is specified and the file is locked.
469 the file does not exist,
470 and the directory in which the entry for the new file is being placed
471 cannot be extended because there is no space left on the file
472 system containing the directory.
476 the file does not exist,
477 and there are no free inodes on the file system on which the
478 file is being created.
482 the file does not exist,
483 and the directory in which the entry for the new file
484 is being placed cannot be extended because the
485 user's quota of disk blocks on the file system
486 containing the directory has been exhausted.
490 the file does not exist,
491 and the user's quota of inodes on the file system on
492 which the file is being created has been exhausted.
494 An I/O error occurred while making the directory entry or
495 allocating the inode for
498 The file is a pure procedure (shared text) file that is being
501 system call requests write access.
506 points outside the process's allocated address space.
511 were specified and the file exists.
513 An attempt was made to open a socket (not currently implemented).
515 An attempt was made to open a descriptor with an illegal combination
525 argument does not specify an absolute path and the
530 nor a valid file descriptor open for searching.
534 argument is not an absolute path and
538 nor a file descriptor associated with a directory.
541 is specified and the file is not a directory.
544 is specified and the process is in capability mode.
547 was called and the process is in capability mode.
548 .It Bq Er ENOTCAPABLE
551 or contained a ".." component leading to a
552 directory outside of the directory hierarchy specified by
554 and the process is in capability mode.
555 .It Bq Er ENOTCAPABLE
558 flag was provided, and the absolute
560 does not have its tail fully contained under the topping directory,
571 .Xr getdtablesize 2 ,
581 These functions are specified by
587 .Er EMLINK instead of
593 is set in flags and the final component of pathname is a symbolic link
594 to distinguish it from the case of too many symbolic link traversals
595 in one of its non-final components.
603 function was introduced in
606 The Open Group Extended API Set 2 specification requires that the test
609 is searchable is based on whether
611 is open for searching, not whether the underlying directory currently
613 The present implementation of the
615 checks the current permissions of directory instead.