UTIME(2)

NAME
utime, utimes - change access and/or modification times of an inode

SYNOPSIS
#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]);

DESCRIPTION
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;       /* access time */
        time_t modtime;      /* modification time */
    };
The function utime() allows specification of time stamps with a resolution of 1 second.

  utimes()
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;        /* seconds */
        long tv_usec;       /* microseconds */
    };

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.

RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

ERRORS

EACCES
    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).

ENOENT
    filename does not exist.

EPERM
    buf is not NULL and the process does not have permission to change the time stamps.

EROFS
    path resides on a read-only file system.

CONFORMING TO
utime(): SVr4, POSIX.1-2001.
utimes(): 4.3BSD

NOTES
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().

BUGS
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().

SEE ALSO
chattr(1), futimesat(2), stat(2), futimes(3)