TOUCH(1) User Commands TOUCH(1)


NAME


touch, settime - change file access and modification times

SYNOPSIS


touch [-acm] [-r ref_file | -t time | -d date_time] file...


touch [-acm] [time_spec] file...


settime [-f ref_file] [time_spec] file...


DESCRIPTION


The touch utility sets the access and modification times of each file.
The file operand is created if it does not already exist.


The time used can be specified by -t time, by -d date_time, by the
corresponding time fields of the file referenced by -r ref_file, or by
the time_spec operand. If none of these are specified, touch uses the
current time.


If neither the -a nor -m options are specified, touch updates both the
modification and access times.


A user with write access to a file, but who is not the owner of the file
or a super-user, can change the modification and access times of that
file only to the current time. Attempts to set a specific time with touch
results in an error.


The settime utility is equivalent to touch -c [time_spec] file.

OPTIONS


The following options are supported in the touch and settime utilities:

touch
The following options are supported for the touch utility:

-a

Changes the access time of file. Does not change the modification
time unless -m is also specified.


-c

Does not create a specified file if it does not exist. Does not write
any diagnostic messages concerning this condition.


-d date_time

Uses the specified date_time instead of the current time. The option-
argument must be a string of the form:

YYYY-MM-DDThh:mm:SS[.frac][tz]


or

YYYY-MM-DDThh:mm:SS[,frac][tz]


where

o YYYY is at least four decimal digits giving the year

o MM, DD, hh, mm, and SS are as with -t time

o T is either the letter T or a single SPACE character

o [.frac] and [,frac] are either empty, or a period (.) or a
comma (,) respectively, followed by one or more decimal
digits, specifying a fractional second

o [tz] is either empty, signifying local time, or the letter
Z, signifying UTC. If [tz] is empty, the resulting time is
affected by the value of the TZ environment variable


-m

Changes the modification time of file. Does not change the access
time unless -a is also specified.


-r ref_file

Uses the corresponding times of the file named by ref_file instead of
the current time.


-t time

Uses the specified time instead of the current time. time is a
decimal number of the form:

[[CC]YY]MMDDhhmm[.SS]


where each two digits represent the following:

MM

The month of the year [01-12].


DD

The day of the month [01-31].


hh

The hour of the day [00-23].


mm

The minute of the hour [00-59].


CC

The first two digits of the year.


YY

The second two digits of the year.


SS

The second of the minute [00-61].

Both CC and YY are optional. If neither is given, the current year is
assumed. If YY is specified, but CC is not, CC is derived as follows:


+------------------------+
|If YY is: CC becomes: |
+------------------------+
|69-99 19 |
|00-38 20 |
|39-68 ERROR |
+------------------------+
The resulting time is affected by the value of the TZ environment
variable. If the resulting time value precedes the Epoch, touch exits
immediately with an error status. The range of valid times is the
Epoch to January 18, 2038.

The range for SS is [00-61] rather than [00-59] because of leap
seconds. If SS is 60 or 61, and the resulting time, as affected by
the TZ environment variable, does not refer to a leap second, the
resulting time is one or two seconds after a time where SS is 59. If
SS is not given, it is assumed to be 0.


settime
The following option is supported for the settime utility:

-f ref_file

Uses the corresponding times of the file named by ref_file instead of
the current time.


OPERANDS


The following operands are supported for the touch and settime utilities:

file

A path name of a file whose times are to be modified.


time_spec

Uses the specified time_spec instead of the current time. This
operand is a decimal number of the form:

MMDDhhmm[YY]


where each two digits represent the following:

MM

The month of the year [01-12].


DD

The day of the month [01-31].


hh

The hour of the day [00-23].


mm

The minute of the hour [00-59].


YY

The second two digits of the year.

YY is optional. If it is omitted, the current year is assumed. If
YY is specified, the year is derived as follows:


+---------------------------+
| YY Corresponding Year |
|69-99 1969-1999 |
|00-38 2000-2038 |
|39-68 ERROR |
+---------------------------+
If no -d, -r, or -toption is specified, at least two operands are
specified, and the first operand is an eight- or ten-digit decimal
integer, the first operand is assumed to be a time_spec operand.
Otherwise, the first operand is assumed to be a file operand.


USAGE


See largefile(5) for the description of the behavior of touch when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).

ENVIRONMENT VARIABLES


See environ(5) for descriptions of the following environment variables
that affect the execution of touch: LANG, LC_ALL, LANG, LC_ALL, LC_CTYPE,
LC_MESSAGES, and NLSPATH.

TZ

Determine the timezone to be used for interpreting the time or
date_time option-argument or the time_spec operand.


EXIT STATUS


The following exit values are returned:

0

The touch utility executed successfully and all requested changes
were made.


>0

An error occurred. The touch utility returned the number of files for
which the times could not be successfully modified.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|CSI | Enabled |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|Standard | See standards(5). |
+--------------------+-------------------+

SEE ALSO


futimens(2), stat(2), attributes(5), environ(5), largefile(5),
standards(5)

NOTES


Users familiar with the BSD environment find that for the touch utility,
the -f option is accepted but ignored. The -f option is unnecessary
because touch succeeds for all files owned by the user regardless of the
permissions on the files.


September 9, 2009 TOUCH(1)