man2/utime.2

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   3 .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
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  25 .\" Modified by Michael Haardt <michael@moria.de>
  26 .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
  27 .\" Modified 1995-06-10 by Andries Brouwer <aeb@cwi.nl>
  28 .\" Modified 2004-06-23 by Michael Kerrisk <mtk-manpages@gmx.net>
  29 .\" Modified 2004-10-10 by Andries Brouwer <aeb@cwi.nl>
  30 .\"
  31 .TH UTIME 2 2004-10-10 "Linux" "Linux Programmer's Manual"
  32 .SH NAME
  33 utime, utimes \- change access and/or modification times of an inode
  34 .SH SYNOPSIS
  35 .nf
  36 .B #include <sys/types.h>
  37 .br
  38 .B #include <utime.h>
  39 .sp
  40 .BI "int utime(const char *" filename ", const struct utimbuf *" buf );
  41 .sp
  42 .B #include <sys/time.h>
  43 .sp
  44 .BI "int utimes(const char *" filename ", const struct timeval " times [2]);
  45 .fi
  46 .SH DESCRIPTION
  47 .BR utime ()
  48 changes the access and modification times of the inode specified by
  49 .I filename
  50 to the
  51 .IR actime " and " modtime
  52 fields of
  53 .I buf
  54 respectively.
  55
  56 If
  57 .I buf
  58 is NULL, then the access and modification times of the file are set
  59 to the current time.
  60
  61 Changing time stamps is permitted when: either
  62 the process has appropriate privileges (Linux: has the
  63 .B CAP_FOWNER
  64 capability), or the effective user ID equals the user ID
  65 of the file, or
  66 .I buf
  67 must is NULL and the process has write permission to the file.
  68
  69 The
  70 .I utimbuf
  71 structure is:
  72
  73 .RS
  74 .nf
  75 struct utimbuf {
  76     time_t actime;       /* access time */
  77     time_t modtime;      /* modification time */
  78 };
  79 .fi
  80 .RE
  81
  82 The function
  83 .BR utime ()
  84 allows specification of time stamps with a resolution of 1 second.
  85 The function
  86 .BR utimes ()
  87 is similar, but allows a resolution of 1 microsecond.
  88 Here
  89 .IR times [0]
  90 refers to access time, and
  91 .IR times [1]
  92 to modification time.
  93
  94 The
  95 .I timeval
  96 structure is:
  97
  98 .RS
  99 .nf
 100 struct timeval {
 101     long tv_sec;        /* seconds */
 102     long tv_usec;       /* microseconds */
 103 };
 104 .fi
 105 .RE
 106 .SH "RETURN VALUE"
 107 On success, zero is returned.
 108 On error, \-1 is returned, and
 109 .I errno
 110 is set appropriately.
 111 .SH ERRORS
 112 .TP
 113 .B EACCES
 114 Search permission is denied for one of the directories in
 115 the path prefix of
 116 .I path
 117 (see also
 118 .BR path_resolution (7)),
 119 or
 120 .I buf
 121 is NULL and the process does not have permission to change the time stamps
 122 (see above).
 123 .TP
 124 .B ENOENT
 125 .I filename
 126 does not exist.
 127 .TP
 128 .B EPERM
 129 .I buf
 130 is not NULL and the process does not have permission to change the time stamps.
 131 .TP
 132 .B EROFS
 133 .I path
 134 resides on a read-only file system.
 135 .SH "CONFORMING TO"
 136 .BR utime ():
 137 SVr4, POSIX.1-2001.
 138 .\" SVr4 documents additional error conditions EFAULT,
 139 .\" EINTR, ELOOP, EMULTIHOP, ENAMETOOLONG, ENOLINK, ENOLINK, ENOTDIR.
 140 .br
 141 .BR utimes ():
 142 4.3BSD
 143 .SH NOTES
 144 Linux does not allow changing the time stamps on an immutable file,
 145 or setting the time stamps to something other than the current time
 146 on an append-only file.
 147
 148 In libc4 and libc5,
 149 .BR utimes ()
 150 is just a wrapper for
 151 .BR utime ()
 152 and hence does not allow a subsecond resolution.
 153
 154 POSIX.1-2001 marks
 155 .BR utimes ()
 156 legacy, which is strange since it provides more functionality than
 157 .BR utime ().
 158 .SH BUGS
 159 Linux is not careful to distinguish between the
 160 .B EACCES
 161 and
 162 .B EPERM
 163 error returns.
 164 On the other hand, POSIX.1-2001 is buggy in its error description for
 165 .BR utimes ().
 166 .SH "SEE ALSO"
 167 .BR chattr (1),
 168 .BR futimesat (2),
 169 .BR stat (2),
 170 .BR futimes (3)