What a brilliant idea: del.icio.us-style file tagging.

Stephen Hahn has written a perl script tag(1) which lets you associate tags with your files and query them later. The syntax is easy to remember:

$ tag -a <tagname> <filename> - for adding a tag to a file
$ tag -d <tagname> <filename> - for removing a tag from a file
$ tag -q <tagname> - for listing all files associated with a tag
$ tag <filename> - for listing all tags associated with a file