The touch utility shall change the modification times, access times, or
both of files. The modification time shall be equivalent to the value
of the st_mtime member of the stat structure for a file, as described
in the System Interfaces volume of IEEE Std 1003.1-2001; the access
time shall be equivalent to the value of st_atime.
The time used can be specified by the -t time option-argument, the
corresponding time fields of the file referenced by the -r ref_file
option-argument, or the date_time operand, as specified in the
following sections. If none of these are specified, touch shall use the
current time (the value returned by the equivalent of the time()
function defined in the System Interfaces volume of
IEEE Std 1003.1-2001).
For each file operand, touch shall perform actions equivalent to the
following functions defined in the…