1fcntl.h(0P) POSIX Programmer's Manual fcntl.h(0P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 fcntl.h — file control options
14
16 #include <fcntl.h>
17
19 The <fcntl.h> header shall define the following symbolic constants for
20 the cmd argument used by fcntl(). The values shall be unique and shall
21 be suitable for use in #if preprocessing directives.
22 F_DUPFD Duplicate file descriptor.
24 F_DUPFD_CLOEXEC
26 Duplicate file descriptor with the close-on-exec flag
27 FD_CLOEXEC set.
28 F_GETFD Get file descriptor flags.
30 F_SETFD Set file descriptor flags.
32 F_GETFL Get file status flags and file access modes.
34 F_SETFL Set file status flags.
36 F_GETLK Get record locking information.
38 F_SETLK Set record locking information.
40 F_SETLKW Set record locking information; wait if blocked.
42 F_GETOWN Get process or process group ID to receive SIGURG signals.
44 F_SETOWN Set process or process group ID to receive SIGURG signals.
46 The <fcntl.h> header shall define the following symbolic constant used
48 for the fcntl() file descriptor flags, which shall be suitable for use
49 in #if preprocessing directives.
50 FD_CLOEXEC Close the file descriptor upon execution of an exec family
52 function.
53 The <fcntl.h> header shall also define the following symbolic constants
55 for the l_type argument used for record locking with fcntl(). The val‐
56 ues shall be unique and shall be suitable for use in #if preprocessing
57 directives.
58 F_RDLCK Shared or read lock.
60 F_UNLCK Unlock.
62 F_WRLCK Exclusive or write lock.
64 The <fcntl.h> header shall define the values used for l_whence,
66 SEEK_SET, SEEK_CUR, and SEEK_END as described in <stdio.h>.
67 The <fcntl.h> header shall define the following symbolic constants as
69 file creation flags for use in the oflag value to open() and openat().
70 The values shall be bitwise-distinct and shall be suitable for use in
71 #if preprocessing directives.
72 O_CLOEXEC The FD_CLOEXEC flag associated with the new descriptor
74 shall be set to close the file descriptor upon execution of
75 an exec family function.
76 O_CREAT Create file if it does not exist.
78 O_DIRECTORY Fail if not a directory.
80 O_EXCL Exclusive use flag.
82 O_NOCTTY Do not assign controlling terminal.
84 O_NOFOLLOW Do not follow symbolic links.
86 O_TRUNC Truncate flag.
88 O_TTY_INIT Set the termios structure terminal parameters to a state
90 that provides conforming behavior; see Section 11.2, Param‐
91 eters that Can be Set.
92 The O_TTY_INIT flag can have the value zero and in this case it need
94 not be bitwise-distinct from the other flags.
95 The <fcntl.h> header shall define the following symbolic constants for
97 use as file status flags for open(), openat(), and fcntl(). The values
98 shall be suitable for use in #if preprocessing directives.
99 O_APPEND Set append mode.
101 O_DSYNC Write according to synchronized I/O data integrity comple‐
103 tion.
104 O_NONBLOCK Non-blocking mode.
106 O_RSYNC Synchronized read I/O operations.
108 O_SYNC Write according to synchronized I/O file integrity comple‐
110 tion.
111 The <fcntl.h> header shall define the following symbolic constant for
113 use as the mask for file access modes. The value shall be suitable for
114 use in #if preprocessing directives.
115 O_ACCMODE Mask for file access modes.
117 The <fcntl.h> header shall define the following symbolic constants for
119 use as the file access modes for open(), openat(), and fcntl(). The
120 values shall be unique, except that O_EXEC and O_SEARCH may have equal
121 values. The values shall be suitable for use in #if preprocessing
122 directives.
123 O_EXEC Open for execute only (non-directory files). The result is
125 unspecified if this flag is applied to a directory.
126 O_RDONLY Open for reading only.
128 O_RDWR Open for reading and writing.
130 O_SEARCH Open directory for search only. The result is unspecified
132 if this flag is applied to a non-directory file.
133 O_WRONLY Open for writing only.
135 The <fcntl.h> header shall define the symbolic constants for file modes
137 for use as values of mode_t as described in <sys/stat.h>.
138 The <fcntl.h> header shall define the following symbolic constant as a
140 special value used in place of a file descriptor for the *at() func‐
141 tions which take a directory file descriptor as a parameter:
142 AT_FDCWD Use the current working directory to determine the target
144 of relative file paths.
145 The <fcntl.h> header shall define the following symbolic constant as a
147 value for the flag used by faccessat():
148 AT_EACCESS Check access using effective user and group ID.
150 The <fcntl.h> header shall define the following symbolic constant as a
152 value for the flag used by fstatat(), fchmodat(), fchownat(), and uti‐
153 mensat():
154 AT_SYMLINK_NOFOLLOW
156 Do not follow symbolic links.
157 The <fcntl.h> header shall define the following symbolic constant as a
159 value for the flag used by linkat():
160 AT_SYMLINK_FOLLOW
162 Follow symbolic link.
163 The <fcntl.h> header shall define the following symbolic constant as a
165 value for the flag used by unlinkat():
166 AT_REMOVEDIR
168 Remove directory instead of file.
169 The <fcntl.h> header shall define the following symbolic constants for
171 the advice argument used by posix_fadvise():
172 POSIX_FADV_DONTNEED
174 The application expects that it will not access the specified
175 data in the near future.
176 POSIX_FADV_NOREUSE
178 The application expects to access the specified data once and
179 then not reuse it thereafter.
180 POSIX_FADV_NORMAL
182 The application has no advice to give on its behavior with
183 respect to the specified data. It is the default characteristic
184 if no advice is given for an open file.
185 POSIX_FADV_RANDOM
187 The application expects to access the specified data in a random
188 order.
189 POSIX_FADV_SEQUENTIAL
191 The application expects to access the specified data sequentially
192 from lower offsets to higher offsets.
193 POSIX_FADV_WILLNEED
195 The application expects to access the specified data in the near
196 future.
197 The <fcntl.h> header shall define the flock structure describing a file
199 lock. It shall include the following members:
200 short l_type Type of lock; F_RDLCK, F_WRLCK, F_UNLCK.
202 short l_whence Flag for starting offset.
203 off_t l_start Relative offset in bytes.
204 off_t l_len Size; if 0 then until EOF.
205 pid_t l_pid Process ID of the process holding the lock; returned with F_GETLK.
206 The <fcntl.h> header shall define the mode_t, off_t, and pid_t types as
208 described in <sys/types.h>.
209 The following shall be declared as functions and may also be defined as
211 macros. Function prototypes shall be provided.
212 int creat(const char *, mode_t);
214 int fcntl(int, int, ...);
215 int open(const char *, int, ...);
216 int openat(int, const char *, int, ...);
217 int posix_fadvise(int, off_t, off_t, int);
218 int posix_fallocate(int, off_t, off_t);
219 Inclusion of the <fcntl.h> header may also make visible all symbols
221 from <sys/stat.h> and <unistd.h>.
222 The following sections are informative.
224
226 Although no existing implementation defines AT_SYMLINK_FOLLOW and
227 AT_SYMLINK_NOFOLLOW as the same numeric value, POSIX.1‐2008 does not
228 prohibit that as the two constants are not used with the same inter‐
229 faces.
230
232 While many of the symbolic constants introduced in the <fcntl.h> header
233 do not strictly need to be used in #if preprocessor directives, wide‐
234 spread historic practice has defined them as macros that are usable in
235 such constructs, and examination of existing applications has shown
236 that they are occasionally used in such a way. Therefore it was decided
237 to retain this requirement on an implementation in POSIX.1‐2008.
238
240 None.
241
243 <stdio.h>, <sys_stat.h>, <sys_types.h>, <unistd.h>
244 The System Interfaces volume of POSIX.1‐2008, creat(), exec, fcntl(),
246 futimens(), open(), posix_fadvise(), posix_fallocate(), posix_madvise()
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249 Portions of this text are reprinted and reproduced in electronic form
250 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
251 -- Portable Operating System Interface (POSIX), The Open Group Base
252 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
253 cal and Electronics Engineers, Inc and The Open Group. (This is
254 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
255 event of any discrepancy between this version and the original IEEE and
256 The Open Group Standard, the original IEEE and The Open Group Standard
257 is the referee document. The original Standard can be obtained online
258 at http://www.unix.org/online.html .
259 Any typographical or formatting errors that appear in this page are
261 most likely to have been introduced during the conversion of the source
262 files to man page format. To report such errors, see https://www.ker‐
263 nel.org/doc/man-pages/reporting_bugs.html .
264IEEE/The Open Group 2013 fcntl.h(0P)