For one or more
files, updates the access time and modification time (and dates) to the current time and date. 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. If a file doesn't exist, touch creates it with a file size of 0.
Update only the access time.
Don't create any file that doesn't already exist.
Try to update even if you don't have permissions.
Update only the modification time.
Change times to be the same as those of the specified
file, instead of the current time.
Use the time specified in
time instead of the current time. This argument must be of the format
[[cc]yy]mmddhhmm[.ss], indicating optional century and year, month, date, hours, minutes, and optional seconds.