For one or more
files, update the access time and modification time
(and dates) to the current time and date, or update to the optional
date is a date and time
in the format
touch is useful in forcing other commands to handle files a certain
way; e.g., the operation of make, and sometimes find,
relies on a file's access and modification time.
Update only the access time.
Do not create nonexistent files.
Update only the modification time.