man2/utime.2

.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.\" Modified by Michael Haardt <michael@moria.de>
.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 1995-06-10 by Andries Brouwer <aeb@cwi.nl>
.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
.\" Modified 2004-10-10 by Andries Brouwer <aeb@cwi.nl>
.\"
.TH UTIME 2 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
utime, utimes \- change file last access and modification times
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.B #include <utime.h>
.PP
.BI "int utime(const char *" filename ", const struct utimbuf *" times );
.PP
.B #include <sys/time.h>
.PP
.BI "int utimes(const char *" filename ", const struct timeval " times [2]);
.fi
.SH DESCRIPTION
.B Note:
modern applications may prefer to use the interfaces described in
.BR utimensat (2).
.PP
The
.BR utime ()
system call
changes the access and modification times of the inode specified by
.I filename
to the
.IR actime " and " modtime
fields of
.I times
respectively.
.PP
If
.I times
is NULL, then the access and modification times of the file are set
to the current time.
.PP
Changing timestamps is permitted when: either
the process has appropriate privileges,
or the effective user ID equals the user ID
of the file, or
.I times
is NULL and the process has write permission for the file.
.PP
The
.I utimbuf
structure is:
.PP
.in +4n
.EX
struct utimbuf {
    time_t actime;       /* access time */
    time_t modtime;      /* modification time */
};
.EE
.in
.PP
The
.BR utime ()
system call
allows specification of timestamps with a resolution of 1 second.
.PP
The
.BR utimes ()
system call
is similar, but the
.I times
argument refers to an array rather than a structure.
The elements of this array are
.I timeval
structures, which allow a precision of 1 microsecond for specifying timestamps.
The
.I timeval
structure is:
.PP
.in +4n
.EX
struct timeval {
    long tv_sec;        /* seconds */
    long tv_usec;       /* microseconds */
};
.EE
.in
.PP
.IR times [0]
specifies the new access time, and
.IR times [1]
specifies the new modification time.
If
.I times
is NULL, then analogously to
.BR utime (),
the access and modification times of the file are
set to the current time.
.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EACCES
Search permission is denied for one of the directories in
the path prefix of
.I path
(see also
.BR path_resolution (7)).
.TP
.B EACCES
.I times
is NULL,
the caller's effective user ID does not match the owner of the file,
the caller does not have write access to the file,
and the caller is not privileged
(Linux: does not have either the
.B CAP_DAC_OVERRIDE
or the
.B CAP_FOWNER
capability).
.TP
.B ENOENT
.I filename
does not exist.
.TP
.B EPERM
.I times
is not NULL,
the caller's effective UID does not match the owner of the file,
and the caller is not privileged
(Linux: does not have the
.B CAP_FOWNER
capability).
.TP
.B EROFS
.I path
resides on a read-only filesystem.
.SH CONFORMING TO
.BR utime ():
SVr4, POSIX.1-2001.
POSIX.1-2008 marks
.BR utime ()
as obsolete.
.PP
.BR utimes ():
4.3BSD, POSIX.1-2001.
.SH NOTES
Linux does not allow changing the timestamps on an immutable file,
or setting the timestamps to something other than the current time
on an append-only file.
.\"
.\" In libc4 and libc5,
.\" .BR utimes ()
.\" is just a wrapper for
.\" .BR utime ()
.\" and hence does not allow a subsecond resolution.
.SH SEE ALSO
.BR chattr (1),
.BR touch (1),
.BR futimesat (2),
.BR stat (2),
.BR utimensat (2),
.BR futimens (3),
.BR futimes (3),
.BR inode (7)