I am writing a script to do a backup of files. I need to get only files
which are newer than the last backup. Unfortunately I have deleted all
the .tar.Z files because they were huge files and they filled up the
disk. If I still had them I could work out which files I needed to
find /dir/to/look/at -newer lastbackup.tar.Z
So, my solution is to create a dummy file called lastbackup, and set the
last modified time to, say, two weeks ago, then do my first
'incremental' backup, then 'touch' it after every backup.
How do I change the date on the file to two weeks ago today? Changing
the system's date then 'touch'ing the file is not an option.