touch -- change file access and modification times

touch [-acfm] [-r referenceFile] [-t [[CC]YY]MMDDhhmm[.SS]] file

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.

-m Change the modification time only
-a Change the access time only
-c Do not create the file if it does not exist and do not treat this as an error. No error messages are displayed and the exit value is not affected.
-f Attempt to force the update, even if the file permissions do not currently permit it.
-r Use the times of referenceFile
-t Change the access and modification times. [[CC]YY]MMDDhhmm[.SS]
CC first two digits of the year (the century).
YY second two digits of the 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 1-12 DD 1-31
hh 0-23 mm 0-59 SS 0-61
Century defaults to the current year. seconds defaults to 0.

Time may be specified as the first argument.
When no -r or -t is specified, there are at least two arguments, and the first argument is either 8 or 10 digits, of the form

MMDDhhmm[YY].
If YY is in the range 39 to 99, the year is set to 1939-1999, otherwise, the year is set to 20YY
Notice that this is different from the ranges if -t is specified.

The touch utility exits 0 on success, and >0 if an error occurs.

SEE utimes BSD April 28, 1995