touch —
change file access and modification times
touch |
[-acm] [-d
ccyy-mm-ddTHH:MM:SS[.frac][Z]]
[-r file]
[-t
[[cc]yy]mmddHHMM[.SS]]
file ... |
The
touch utility sets the modification and access times
of files to the current time of day. If the file doesn't exist, it is created
with default permissions.
The options are as follows:
-a- Change the access time of the file. The modification time of the file is
not changed unless the
-m flag is also
specified.
-c- Do not create the file if it does not exist. The
touch utility does not treat this as an error. No
error messages are displayed and the exit value is not affected.
-d
ccyy-mm-ddTHH:MM:SS[.frac][Z]- Change the access and modification times to the specified time, in a
format compliant with the ISO 8601 standard. The
parts of the argument represent the following:
- ccyy
- Year.
- mm
- Month: a number from 1 to 12.
- dd
- Day: a number from 1 to 31.
- T
- Either the capital letter ‘T’ or a single space.
- HH
- Hour: a number from 0 to 23.
- MM
- Minute: a number from 0 to 59.
- SS
- Second: a number from 0 to 60 (permitting a leap second).
- frac
- The decimal fraction of the second, either a period or comma, followed
by one or more decimal digits.
- Z
- The timezone specifier, a capital letter ‘Z’ indicating
that the time is in UTC. If not specified, the time is in the local
timezone.
-m- Change the modification time of the file. The access time of the file is
not changed unless the
-a flag is also
specified.
-r
file- Use the access and modification times from the specified file instead of
the current time of day.
-t
[[cc]yy]mmddHHMM[.SS]- Change the access and modification times to the specified time, where the
parts of the argument represent the following:
- ccyy
- Year. If yy is specified, but cc is not, a value for yy between 69 and
99 results in a cc value of 19. Otherwise, a cc value of 20 is
used.
- mm
- Month: a number from 1 to 12.
- dd
- Day: a number from 1 to 31.
- HH
- Hour: a number from 0 to 23.
- MM
- Minute: a number from 0 to 59.
- SS
- Second: a number from 0 to 60 (permitting a leap second), preceded by
a period. The default is 0.
The touch utility exits 0 on success,
and >0 if an error occurs.
The touch utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
specification.
The obsolescent form of touch, where a
time format is specified as the first argument, is supported. When no
-d, -r, or
-t option is specified, there are at least two
arguments, and the first argument is a string of digits either eight or ten
characters in length, the first argument is interpreted as a time
specification of the form “mmddHHMM[yy]”.
A touch utility appeared in
Version 7 AT&T UNIX.
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