1FUTIMENS(3P) POSIX Programmer's Manual FUTIMENS(3P)
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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.
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13 futimens, utimensat, utimes — set file access and modification times
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16 #include <sys/stat.h>
17 int futimens(int fd, const struct timespec times[2]);
19 int utimensat(int fd, const char *path, const struct timespec times[2],
20 int flag);
21 #include <sys/time.h>
23 int utimes(const char *path, const struct timeval times[2]);
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27 The futimens() and utimensat() functions shall set the access and modi‐
28 fication times of a file to the values of the times argument. The futi‐
29 mens() function changes the times of the file associated with the file
30 descriptor fd. The utimensat() function changes the times of the file
31 pointed to by the path argument, relative to the directory associated
32 with the file descriptor fd. Both functions allow time specifications
33 accurate to the nanosecond.
34 For futimens() and utimensat(), the times argument is an array of two
36 timespec structures. The first array member represents the date and
37 time of last access, and the second member represents the date and time
38 of last modification. The times in the timespec structure are measured
39 in seconds and nanoseconds since the Epoch. The file's relevant time‐
40 stamp shall be set to the greatest value supported by the file system
41 that is not greater than the specified time.
42 If the tv_nsec field of a timespec structure has the special value
44 UTIME_NOW, the file's relevant timestamp shall be set to the greatest
45 value supported by the file system that is not greater than the current
46 time. If the tv_nsec field has the special value UTIME_OMIT, the file's
47 relevant timestamp shall not be changed. In either case, the tv_sec
48 field shall be ignored.
49 If the times argument is a null pointer, both the access and modifica‐
51 tion timestamps shall be set to the greatest value supported by the
52 file system that is not greater than the current time. If utimensat()
53 is passed a relative path in the path argument, the file to be used
54 shall be relative to the directory associated with the file descriptor
55 fd instead of the current working directory. If the file descriptor was
56 opened without O_SEARCH, the function shall check whether directory
57 searches are permitted using the current permissions of the directory
58 underlying the file descriptor. If the file descriptor was opened with
59 O_SEARCH, the function shall not perform the check.
60 If utimensat() is passed the special value AT_FDCWD in the fd parame‐
62 ter, the current working directory shall be used.
63 Only a process with the effective user ID equal to the user ID of the
65 file, or with write access to the file, or with appropriate privileges
66 may use futimens() or utimensat() with a null pointer as the times
67 argument or with both tv_nsec fields set to the special value
68 UTIME_NOW. Only a process with the effective user ID equal to the user
69 ID of the file or with appropriate privileges may use futimens() or
70 utimensat() with a non-null times argument that does not have both
71 tv_nsec fields set to UTIME_NOW and does not have both tv_nsec fields
72 set to UTIME_OMIT. If both tv_nsec fields are set to UTIME_OMIT, no
73 ownership or permissions check shall be performed for the file, but
74 other error conditions may still be detected (including [EACCES] errors
75 related to the path prefix).
76 Values for the flag argument of utimensat() are constructed by a bit‐
78 wise-inclusive OR of flags from the following list, defined in
79 <fcntl.h>:
80 AT_SYMLINK_NOFOLLOW
82 If path names a symbolic link, then the access and modification
83 times of the symbolic link are changed.
84 Upon completion, futimens() and utimensat() shall mark the last file
86 status change timestamp for update.
87 The utimes() function shall be equivalent to the utimensat() function
89 with the special value AT_FDCWD as the fd argument and the flag argu‐
90 ment set to zero, except that the times argument is a timeval structure
91 rather than a timespec structure, and accuracy is only to the microsec‐
92 ond, not nanosecond, and rounding towards the nearest second may occur.
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95 Upon successful completion, these functions shall return 0. Otherwise,
96 these functions shall return −1 and set errno to indicate the error. If
97 −1 is returned, the file times shall not be affected.
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100 These functions shall fail if:
101 EACCES The times argument is a null pointer, or both tv_nsec values are
103 UTIME_NOW, and the effective user ID of the process does not
104 match the owner of the file and write access is denied.
105 EINVAL Either of the times argument structures specified a tv_nsec
107 value that was neither UTIME_NOW nor UTIME_OMIT, and was a value
108 less than zero or greater than or equal to 1000 million.
109 EINVAL A new file timestamp would be a value whose tv_sec component is
111 not a value supported by the file system.
112 EPERM The times argument is not a null pointer, does not have both
114 tv_nsec fields set to UTIME_NOW, does not have both tv_nsec
115 fields set to UTIME_OMIT, the calling process' effective user ID
116 does not match the owner of the file, and the calling process
117 does not have appropriate privileges.
118 EROFS The file system containing the file is read-only.
120 The futimens() function shall fail if:
122 EBADF The fd argument is not a valid file descriptor.
124 The utimensat() function shall fail if:
126 EACCES fd was not opened with O_SEARCH and the permissions of the
128 directory underlying fd do not permit directory searches.
129 EBADF The path argument does not specify an absolute path and the fd
131 argument is neither AT_FDCWD nor a valid file descriptor open
132 for reading or searching.
133 ENOTDIR
135 The path argument is not an absolute path and fd is a file
136 descriptor associated with a non-directory file.
137 The utimensat() and utimes() functions shall fail if:
139 EACCES Search permission is denied by a component of the path prefix.
141 ELOOP A loop exists in symbolic links encountered during resolution of
143 the path argument.
144 ENAMETOOLONG
146 The length of a component of a pathname is longer than
147 {NAME_MAX}.
148 ENOENT A component of path does not name an existing file or path is an
150 empty string.
151 ENOTDIR
153 A component of the path prefix names an existing file that is
154 neither a directory nor a symbolic link to a directory, or the
155 path argument contains at least one non-<slash> character and
156 ends with one or more trailing <slash> characters and the last
157 pathname component names an existing file that is neither a
158 directory nor a symbolic link to a directory.
159 The utimensat() and utimes() functions may fail if:
161 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
163 resolution of the path argument.
164 ENAMETOOLONG
166 The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
167 tion of a symbolic link produced an intermediate result with a
168 length that exceeds {PATH_MAX}.
169 The utimensat() function may fail if:
171 EINVAL The value of the flag argument is not valid.
173 The following sections are informative.
175
177 None.
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180 None.
181
183 The purpose of the utimensat() function is to set the access and modi‐
184 fication time of files in directories other than the current working
185 directory without exposure to race conditions. Any part of the path of
186 a file could be changed in parallel to a call to utimes(), resulting in
187 unspecified behavior. By opening a file descriptor for the target
188 directory and using the utimensat() function it can be guaranteed that
189 the changed file is located relative to the desired directory.
190 The standard developers considered including a special case for the
192 permissions required by utimensat() when one tv_nsec field is UTIME_NOW
193 and the other is UTIME_OMIT. One possibility would be to include this
194 case in with the cases where times is a null pointer or both fields are
195 UTIME_NOW, where the call is allowed if the process has write permis‐
196 sion for the file. However, associating write permission with an update
197 to just the last data access timestamp (which is normally updated by
198 read()) did not seem appropriate. The other possibility would be to
199 specify that this one case is allowed if the process has read permis‐
200 sion, but this was felt to be too great a departure from the utime()
201 and utimes() functions on which utimensat() is based. If an application
202 needs to set the last data access timestamp to the current time for a
203 file on which it has read permission but is not the owner, it can do so
204 by opening the file, reading one or more bytes (or reading a directory
205 entry, if the file is a directory), and then closing it.
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208 None.
209
211 read(), utime()
212 The Base Definitions volume of POSIX.1‐2008, <fcntl.h>, <sys_stat.h>,
214 <sys_time.h>
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217 Portions of this text are reprinted and reproduced in electronic form
218 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
219 -- Portable Operating System Interface (POSIX), The Open Group Base
220 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
221 cal and Electronics Engineers, Inc and The Open Group. (This is
222 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
223 event of any discrepancy between this version and the original IEEE and
224 The Open Group Standard, the original IEEE and The Open Group Standard
225 is the referee document. The original Standard can be obtained online
226 at http://www.unix.org/online.html .
227 Any typographical or formatting errors that appear in this page are
229 most likely to have been introduced during the conversion of the source
230 files to man page format. To report such errors, see https://www.ker‐
231 nel.org/doc/man-pages/reporting_bugs.html .
232IEEE/The Open Group 2013 FUTIMENS(3P)