sábado, 30 de enero de 2021

Shell Oneliner Compression

I'm back to Lisp. Now, Clojure. For real. But this post is about zsh

Part of my relearning of clojure is to read and watch everything clojure that crosses my path. And I discovered https://github.com/clojure-cookbook/clojure-cookbook , which seems super useful.  But I have too many open tabs and books already. So I thought I'd do a 'Tip Of The Day' like thing, and I'd pop a different page every day.

 Relevant files have .asciidoc  extension. And the ones with content start with a number. The other ones are index pages or headers/footers.

Here's a version of what I typed. and it worked (at the second try!)

random-clojure() {
   e $(ls ~/clojure-cookbook/**/*asciidoc(.) | awk -F/ '$NF ~ /^[0-9]/' | shuf -n1 | xargs realpath)

Quite a lot of things going on there, so I'm gonna explain the oneliner, because there's a lot of compression there.

  • e. e is my shellscript that opens files in emacs, moving to the line, and massaging input. in this case, it's the same as emacs, vi, $EDITOR.
  • ~/clojure-cookbook/**/*asciidoc(.). This one expands recursively files that contain 'asciidoc'. excluding directories. '**/' means 'recursively' in zsh, and the '(.)' globbing is for files only.
  • awk. '-F/' makes slash a field separator. Then, we pick the latest field, and we regex match it with '/^[0-9]/', beginning with a number. Cool!
  • shuf -n1 picks a line at random
  • xargs realpath. As we'll be running this function from all kinds of directories, expand the file path to an absolute path. as realpath asks for a parameter, we either nest the whole thing or use the xargs trick.


While writing this, I noticed that the whole thing is much simpler than that:

 e $(ls ~/clojure-cookbook/**/[0-9]*asciidoc(.)|shuf -n1| xargs realpath)

Master-ing git