Listing Unique Projects Used by MailTags

Spurred to see if I could become more efficient than I am currently, I’ve been experimenting with some GTD-style applications.  As a result of my experiments, I found that I needed a list of all the MailTags projects I’ve ever used in any of my mailboxes.  (To make a long story short, I want to use the same project names across all applications—Mail, GTD application, Spotlight comments for files, etc.)  While you can see a list of projects in the Preferences, that list does not include all projects that might ever have been used.

It only took a few minutes of experimentation in the Terminal to come across the mdls command, which lists metadata for a file (or group of files).  Perfect!  Using mdls, I listed the metadata for an e-mail message, and found that it was the kMDItemProjects attribute that was used by MailTags.  With that information in hand, I hacked together this quick process for listing all the projects in use across all my mailboxes (I’ve used a backslash to indicate line continuation; lines are wrapped here for readability):

mdls <mailbox path>/*.emlx | grep kMDItemProjects >> \
~/all-projects.txt

Repeat this command for each mailbox (for example, I have a separate archive mailbox for each year).  Once you’ve enumerated the information for all the mailboxes, then parse it down like this:

sort all-projects.txt > sorted-projects.txt
uniq sorted-projects.txt > unique-projects.txt

Now the file “unique-projects.txt” contains all the unique project names that are in use across all your mailboxes.  Very handy!  Now, if only obtaining a unique list of all the MailTags keywords were as easy…