.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
.\"
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.\" manual provided the copyright notice and this permission notice are
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.\" 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.\" manual page may be incorrect or out-of-date.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
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.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
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.\" 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@gmx.net>
.\" Modified 2004-10-10 by Andries Brouwer <aeb@cwi.nl>
.\"
.TH UTIME 2 2004-10-10 "Linux 2.6.8" "Linux Programmer's Manual"
.SH NAME
utime, utimes \- change access and/or modification times of an inode
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.br
.B #include <utime.h>
.sp
.BI "int utime(const char *" filename ", const struct utimbuf *" buf );
.sp 2
.B #include <sys/time.h>
.sp
.BI "int utimes(const char *" filename ", const struct timeval " tv [2]);
.fi
.SH DESCRIPTION
.BR utime ()
changes the access and modification times of the inode specified by
.I filename
to the
.IR actime " and " modtime
fields of 
.I buf
respectively.

If
.I 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
.B CAP_FOWNER
capability), or the effective user ID equals the user ID
of the file, or
.I buf
must is NULL and the process has write permission to the file.

The
.I utimbuf
structure is:

.RS
.nf
struct utimbuf {
        time_t actime;  /* access time */
        time_t modtime; /* modification time */
};
.fi
.RE

The function
.BR utime ()
allows specification of time stamps with a resolution of 1 second.
The function
.BR utimes ()
is similar, but allows a resolution of 1 microsecond.
Here
.IR tv [0]
refers to access time, and
.IR tv [1]
to modification time.

The
.I timeval
structure is:

.RS
.nf
struct timeval {
        long    tv_sec;         /* seconds */
        long    tv_usec;        /* microseconds */
};
.fi
.RE
.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 (2)),
or
.I buf
is NULL and the process does not have permission to change the time stamps
(see above).
.TP
.B ENOENT
.I filename
does not exist.
.TP
.B EPERM
.I buf
is not NULL and the process does not have permission to change the time stamps.
.TP
.B EROFS
.I path
resides on a read-only file system.
.SH 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,
.BR utimes ()
is just a wrapper for
.BR utime ()
and hence does not allow a subsecond resolution.

POSIX calls
.BR utimes ()
legacy.
.SH BUGS
Linux is not careful to distinguish between the EACCES and EPERM error returns.
On the other hand, POSIX 1003.1-2003 is buggy in its error description for
.BR utimes ().
.SH "CONFORMING TO"
.BR utime ():
SVr4, SVID, POSIX.  SVr4 documents additional error conditions EFAULT,
EINTR, ELOOP, EMULTIHOP, ENAMETOOLONG, ENOLINK, ENOLINK, ENOTDIR.
.br
.BR utimes ():
4.3BSD
.SH "SEE ALSO"
.BR chattr (1),
.BR stat (2)