[moiziaig] Usefully accessed timestamp

This Linux filesystem automatically records access time (atime) but I really want is when the last "useful" access was.  Perhaps for auditing who accessed what when.  This is a fuzzy problem.

I probably don't want accesses by search (grep).  Unless it was a successful search (a match in that file).  However, not successful searches could be "useful", too. Cache search results and/or usually only search an index?  Perhaps grep can run under special permissions that allow it to avoid modifying atime.

Or, disk is cheap, so just record all accesses (and meta information about them such as the program and user), and sort out "usefulness" later.