table of contents
|UTIMENSAT(2)||System Calls Manual||UTIMENSAT(2)|
utimensat — set file access
and modification times
Standard C Library (libc, -lc)
fd, const struct timespec
const char *path, const struct
timespec times, int flag);
The access and modification times of the file named by path or referenced by fd are changed as specified by the argument times. The inode-change-time of the file is set to the current time.
If path specifies a relative path, it is
relative to the current working directory if fd is
AT_FDCWD and otherwise relative to the directory
associated with the file descriptor fd.
The tv_nsec field of a
timespec structure can be set to the special value
UTIME_NOW to set the current time, or to
UTIME_OMIT to leave the time unchanged. In either
case, the tv_sec field is ignored.
If times is
NULL, it is assumed to
point to an array of two timespec structures. The access time is set to the
value of the first element, and the modification time is set to the value of
the second element. For file systems that support file birth (creation)
times (such as
UFS2), the birth time will be set to
the value of the second element if the second element is older than the
currently set birth time. To set both a birth time and a modification time,
two calls are required; the first to set the birth time and the second to
set the (presumably newer) modification time. Ideally a new system call will
be added that allows the setting of all three times at once. If
NULL, this is
equivalent to passing a pointer to an array of two timespec structures with
both tv_nsec fields set to
If both tv_nsec fields are
UTIME_OMIT, the timestamps remain unchanged and no
permissions are needed for the file itself, although search permissions may
be required for the path prefix. The call may or may not succeed if the
named file does not exist.
If both tv_nsec fields are
UTIME_NOW, the caller must be the owner of the file,
have permission to write the file, or be the super-user.
For all other values of the timestamps, the caller must be the owner of the file or be the super-user.
The values for the flag
argument of the
system call are constructed by a bitwise-inclusive OR of flags from the
following list, defined in
- If path names a symbolic link, the symbolic link's
times are changed. By default,
utimensat() changes the times of the file referenced by the symbolic link.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
If the running kernel does not support this system call, a wrapper
emulates it using fstatat(2),
futimesat(2) and lutimes(2). As a
result, timestamps will be rounded down to the nearest microsecond,
UTIME_OMIT is not atomic and
AT_SYMLINK_NOFOLLOW is not available with a path
relative to a file descriptor.
These system calls will fail if:
- The times argument is
NULL, or both tv_nsec values are
UTIME_NOW, and the effective user ID of the process does not match the owner of the file, and is not the super-user, and write access is denied.
- The times argument points outside the process's allocated address space.
- The tv_nsec component of at least one of the values
specified by the times argument has a value less
than 0 or greater than 999999999 and is not equal to
- An I/O error occurred while reading or writing the affected inode.
- Corrupted data was detected while reading from the file system.
- The times argument is not
NULLnor are both tv_nsec values
UTIME_NOW, nor are both tv_nsec values
UTIME_OMITand the calling process's effective user ID does not match the owner of the file and is not the super-user.
- The named file has its immutable or append-only flag set, see the chflags(2) manual page for more information.
- The file system containing the file is mounted read-only.
futimens() system call will fail
- The fd argument does not refer to a valid descriptor.
utimensat() system call will fail
- Search permission is denied for a component of the path prefix.
- The path argument does not specify an absolute path
and the fd argument is neither
AT_FDCWDnor a valid file descriptor.
- The path argument points outside the process's allocated address space.
- Too many symbolic links were encountered in translating the pathname.
- A component of a pathname exceeded
NAME_MAXcharacters, or an entire path name exceeded
- The named file does not exist.
- A component of the path prefix is not a directory.
- The path argument is not an absolute path and
fd is neither
AT_FDCWDnor a file descriptor associated with a directory.
chflags(2), stat(2), symlink(2), utimes(2), utime(3), symlink(7)
utimensat() system calls are expected to conform to
IEEE Std 1003.1-2008 (“POSIX.1”).
utimensat() system calls appeared in
|March 30, 2020||Debian|