Howard Abrams has a nifty bit of Elisp that allows you to filter on file tags in eshell. As an example of his idea, suppose I want to list all my blog posts with a tag of “Emacs”. I can use the eshell filtering mechanism with Abrams’ custom code to write
ls ~/org/blog/*.org(T'Emacs')
This will list only those files that have a #+TAGS: line with Emacs as one of the tags.
Abrams has added the code to his EShell Tutorial. I’ve written about that tutorial before but this addition is new. If, like me, you use eshell and work a lot with Org files, you’re apt to find this very useful.