PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

FUTIMENS(3P)              POSIX Programmer's Manual             FUTIMENS(3P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       futimens, utimensat, utimes — set file access and modification times

SYNOPSIS         top

       #include <sys/stat.h>

       int futimens(int fd, const struct timespec times[2]);
       int utimensat(int fd, const char *path, const struct timespec times[2],
           int flag);

       #include <sys/time.h>

       int utimes(const char *path, const struct timeval times[2]);

DESCRIPTION         top

       The futimens() and utimensat() functions shall set the access and
       modification times of a file to the values of the times argument. The
       futimens() function changes the times of the file associated with the
       file descriptor fd.  The utimensat() function changes the times of
       the file pointed to by the path argument, relative to the directory
       associated with the file descriptor fd.  Both functions allow time
       specifications accurate to the nanosecond.

       For futimens() and utimensat(), the times argument is an array of two
       timespec structures. The first array member represents the date and
       time of last access, and the second member represents the date and
       time of last modification. The times in the timespec structure are
       measured in seconds and nanoseconds since the Epoch. The file's
       relevant timestamp shall be set to the greatest value supported by
       the file system that is not greater than the specified time.

       If the tv_nsec field of a timespec structure has the special value
       UTIME_NOW, the file's relevant timestamp shall be set to the greatest
       value supported by the file system that is not greater than the
       current time. If the tv_nsec field has the special value UTIME_OMIT,
       the file's relevant timestamp shall not be changed. In either case,
       the tv_sec field shall be ignored.

       If the times argument is a null pointer, both the access and
       modification timestamps shall be set to the greatest value supported
       by the file system that is not greater than the current time. If
       utimensat() is passed a relative path in the path argument, the file
       to be used shall be relative to the directory associated with the
       file descriptor fd instead of the current working directory. If the
       file descriptor was opened without O_SEARCH, the function shall check
       whether directory searches are permitted using the current
       permissions of the directory underlying the file descriptor. If the
       file descriptor was opened with O_SEARCH, the function shall not
       perform the check.

       If utimensat() is passed the special value AT_FDCWD in the fd
       parameter, the current working directory shall be used.

       Only a process with the effective user ID equal to the user ID of the
       file, or with write access to the file, or with appropriate
       privileges may use futimens() or utimensat() with a null pointer as
       the times argument or with both tv_nsec fields set to the special
       value UTIME_NOW. Only a process with the effective user ID equal to
       the user ID of the file or with appropriate privileges may use
       futimens() or utimensat() with a non-null times argument that does
       not have both tv_nsec fields set to UTIME_NOW and does not have both
       tv_nsec fields set to UTIME_OMIT. If both tv_nsec fields are set to
       UTIME_OMIT, no ownership or permissions check shall be performed for
       the file, but other error conditions may still be detected (including
       [EACCES] errors related to the path prefix).

       Values for the flag argument of utimensat() are constructed by a
       bitwise-inclusive OR of flags from the following list, defined in
       <fcntl.h>:

       AT_SYMLINK_NOFOLLOW
             If path names a symbolic link, then the access and modification
             times of the symbolic link are changed.

       Upon completion, futimens() and utimensat() shall mark the last file
       status change timestamp for update.

       The utimes() function shall be equivalent to the utimensat() function
       with the special value AT_FDCWD as the fd argument and the flag
       argument set to zero, except that the times argument is a timeval
       structure rather than a timespec structure, and accuracy is only to
       the microsecond, not nanosecond, and rounding towards the nearest
       second may occur.

RETURN VALUE         top

       Upon successful completion, these functions shall return 0.
       Otherwise, these functions shall return −1 and set errno to indicate
       the error. If −1 is returned, the file times shall not be affected.

ERRORS         top

       These functions shall fail if:

       EACCES The times argument is a null pointer, 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 write access is denied.

       EINVAL Either of the times argument structures specified a tv_nsec
              value that was neither UTIME_NOW nor UTIME_OMIT, and was a
              value less than zero or greater than or equal to 1000 million.

       EINVAL A new file timestamp would be a value whose tv_sec component
              is not a value supported by the file system.

       EPERM  The times argument is not a null pointer, does not have both
              tv_nsec fields set to UTIME_NOW, does not have both tv_nsec
              fields set to UTIME_OMIT, the calling process' effective user
              ID does not match the owner of the file, and the calling
              process does not have appropriate privileges.

       EROFS  The file system containing the file is read-only.

       The futimens() function shall fail if:

       EBADF  The fd argument is not a valid file descriptor.

       The utimensat() function shall fail if:

       EACCES fd was not opened with O_SEARCH and the permissions of the
              directory underlying fd do not permit directory searches.

       EBADF  The path argument does not specify an absolute path and the fd
              argument is neither AT_FDCWD nor a valid file descriptor open
              for reading or searching.

       ENOTDIR
              The path argument is not an absolute path and fd is a file
              descriptor associated with a non-directory file.

       The utimensat() and utimes() functions shall fail if:

       EACCES Search permission is denied by a component of the path prefix.

       ELOOP  A loop exists in symbolic links encountered during resolution
              of the path argument.

       ENAMETOOLONG
              The length of a component of a pathname is longer than
              {NAME_MAX}.

       ENOENT A component of path does not name an existing file or path is
              an empty string.

       ENOTDIR
              A component of the path prefix names an existing file that is
              neither a directory nor a symbolic link to a directory, or the
              path argument contains at least one non-<slash> character and
              ends with one or more trailing <slash> characters and the last
              pathname component names an existing file that is neither a
              directory nor a symbolic link to a directory.

       The utimensat() and utimes() functions may fail if:

       ELOOP  More than {SYMLOOP_MAX} symbolic links were encountered during
              resolution of the path argument.

       ENAMETOOLONG
              The length of a pathname exceeds {PATH_MAX}, or pathname
              resolution of a symbolic link produced an intermediate result
              with a length that exceeds {PATH_MAX}.

       The utimensat() function may fail if:

       EINVAL The value of the flag argument is not valid.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       The purpose of the utimensat() function is to set the access and
       modification time of files in directories other than the current
       working directory without exposure to race conditions. Any part of
       the path of a file could be changed in parallel to a call to
       utimes(), resulting in unspecified behavior. By opening a file
       descriptor for the target directory and using the utimensat()
       function it can be guaranteed that the changed file is located
       relative to the desired directory.

       The standard developers considered including a special case for the
       permissions required by utimensat() when one tv_nsec field is
       UTIME_NOW and the other is UTIME_OMIT. One possibility would be to
       include this case in with the cases where times is a null pointer or
       both fields are UTIME_NOW, where the call is allowed if the process
       has write permission for the file. However, associating write
       permission with an update to just the last data access timestamp
       (which is normally updated by read()) did not seem appropriate. The
       other possibility would be to specify that this one case is allowed
       if the process has read permission, but this was felt to be too great
       a departure from the utime() and utimes() functions on which
       utimensat() is based. If an application needs to set the last data
       access timestamp to the current time for a file on which it has read
       permission but is not the owner, it can do so by opening the file,
       reading one or more bytes (or reading a directory entry, if the file
       is a directory), and then closing it.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       read(3p), utime(3p)

       The Base Definitions volume of POSIX.1‐2008, fcntl.h(0p),
       sys_stat.h(0p), sys_time.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) In the event of any discrepancy between this version and
       the original IEEE and The Open Group Standard, the original IEEE and
       The Open Group Standard is the referee document. The original
       Standard can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                        FUTIMENS(3P)

Pages that refer to this page: fcntl.h(0p)sys_stat.h(0p)sys_time.h(0p)utime.h(0p)touch(1p)time(3p)utime(3p)utimensat(3p)