TOUCH
Section: User Commands (1)
Updated: August 1998
NAME
touch - change file timestamps
SYNOPSIS
touch
[-acm][-r ref_file|-t time] file...
Obsolescent version:
touch
[-acm][ugly_time] file...
GNU version:
touch
[-acfm] [-r file] [-t decimtime]
[-d time] [--time={atime,access,use,mtime,modify}]
[--date=time] [--reference=file]
[--no-create] [--help] [--version] [--] file...
DESCRIPTION
touch
changes the access and/or modification timestamps of each
specified
file.
These timestamps are changed to the current time, unless
the -r option is specified, in which case they are changed
to the corresponding timestamps of the file
ref_file,
or the -t option is specified, in which case they are changed
to the specified
time.
Both times are changed when neither or both of the -a and -m
options are given. Only the access or only the modification time
is changed when one of the options -a and -m is given.
If the file did not exist yet, it is created (as an empty file
with mode 0666, modified by the umask), unless the -c option is given.
POSIX OPTIONS
- -a
-
Change the access time of
file.
- -c
-
Do not create
file.
- -m
-
Change the modification time of
file.
- -r ref_file
-
Use the corresponding timestamp of
ref_file
as the new value for the changed timestamp(s).
- -t time
-
Use the specified time as the new value for the changed timestamp(s).
The argument is a decimal number of the form
[[CC]YY]MMDDhhmm[.SS]
with the obvious meaning. If CC is not specified, the year CCYY
is taken to be in the range 1969-2068.
If SS is not specified, it is taken to be 0. It may be specified
in the range 0-61 so that it is possible to refer to leap seconds.
The resulting time is taken as a time for the time zone specified by
the environment variable TZ. It is an error if the resulting time
precedes 1 January 1970.
POSIX DETAILS
The second form of invocation has the disadvantage that there is
some ambiguity as to whether
ugly_time
is a time or a file argument. It is taken to be a time when
no -r or -t option is present, there are at least two arguments,
and the first argument is an eight- or ten-digit decimal integer.
The format of
ugly_time
is MMDDhhmm[yy], where an yy in the range 69-99 denotes a year
in the range 1969-1999, and an unspecified yy denotes the current year.
This form is obsolete.
GNU DETAILS
If the first
file
would be a valid argument to the
-t
option and no timestamp is given with any of the
-d,
-r
or
-t
options and the `--' argument is not given, that argument is
interpreted as the time for the other files instead of as a file name.
If changing both the access and modification times to the current
time,
touch
can change the timestamps for files that the user running it does
not own but has write permission for. Otherwise, the user must
own the files.
GNU OPTIONS
- -a, --time=atime, --time=access, --time=use
-
Change the access time only.
- -c, --no-create
-
Do not create files that do not exist.
- -d, --date=time
-
Use
time
instead of the current time. It can contain month names,
timezones, `am' and `pm', etc.
- -f
-
Ignored; for compatibility with BSD versions of
touch(1).
- -m, --time=mtime, --time=modify
-
Change the modification time only.
- -r file, --reference=file
-
Use the times of the reference
file
instead of the current time.
- -t decimtime
-
Here
decimtime
has the format MMDDhhmm[[CC]YY][.ss]
Use the argument (months, days, hours, minutes, optional century
and years, optional seconds) instead of the current time.
Note that this format violates the POSIX specification.
GNU STANDARD OPTIONS
- --help
-
Print a usage message on standard output and exit successfully.
- --version
-
Print version information on standard output, then exit successfully.
- --
-
Terminate option list.
ENVIRONMENT
The variable TZ is used to interpret explicitly given times.
The variables LANG, LC_ALL, LC_CTYPE and LC_MESSAGES have the
usual meaning.
CONFORMING TO
POSIX 1003.2 describes a syntax for the argument of the -t option
that differs from that used by the GNU implementation.
EXAMPLE OF USE
The command `touch foo' will create the file foo
if it didn't exist, and change the time of last modification to now.
It is often used to guide the actions of
make.
NOTES
This page describes
touch
as found in the fileutils-3.16 package;
other versions may differ slightly. Mail corrections and additions to
aeb@cwi.nl and aw@mail1.bet1.puv.fi and ragnar@lightside.ddns.org .
Report bugs in the program to fileutils-bugs@gnu.ai.mit.edu.