utime, utimes — change access and/or modification times of an inode
#include <sys/types.h> #include <utime.h>
int
utime( |
const char * | filename, |
| const struct utimbuf * | buf); |
#include <sys/time.h>
int
utimes( |
const char * | filename, |
| const struct timeval | times[2]); |
utime() changes the access
and modification times of the inode specified by filename to the actime and modtime fields of buf respectively.
If buf is NULL,
then the access and modification times of the file are set to
the current time.
Changing time stamps is permitted when: either the process
has appropriate privileges (Linux: has the CAP_FOWNER capability), or the effective
user ID equals the user ID of the file, or buf is NULL and the process has
write permission to the file.
The utimbuf structure is:
struct utimbuf { time_t actime;time_t modtime;};
The function utime() allows
specification of time stamps with a resolution of 1
second.
The function utimes() is
similar, but the times argument allows a
resolution of 1 microsecond for the timestamps. The
timeval structure is:
struct timeval { long tv_sec;long tv_usec;};
times[0]
specifies the new access time, and times[1] specifies the new
modification time. If times is NULL, then
analogously to utime(), the
access and modification times of the file are set to the
current time.
On success, zero is returned. On error, −1 is
returned, and errno is set
appropriately.
Search permission is denied for one of the
directories in the path prefix of path (see also
path_resolution(7)),
or buf is NULL
and the process does not have permission to change the
time stamps (see above).
filename
does not exist.
buf is not
NULL and the process does not have permission to change
the time stamps.
path
resides on a read-only file system.
Linux does not allow changing the time stamps on an immutable file, or setting the time stamps to something other than the current time on an append-only file.
In libc4 and libc5, utimes()
is just a wrapper for utime()
and hence does not allow a subsecond resolution.
POSIX.1-2001 marks utimes()
legacy, which is strange since it provides more functionality
than utime().
Linux is not careful to distinguish between the
EACCES and EPERM error returns. On the other hand,
POSIX.1-2001 is buggy in its error description for
utimes().