4 Environment. Currently in use on Debian 10 (Buster).
13 - `ls` and `tree` (primary)
14 - `pcmanfm` (secondary)
15 - `ranger` (occasional)
32 - `ncmpc` (to delete from playlist, which doesn't work in `ncmpcpp`)
34 - [soma fm](http://somafm.com/) (primary) (via `mpd`)
35 - `spotify` (occasional)
56 - `qutebrowser` (primary)
57 - `chromium` (fallback)
61 - `khatus` (currently x2)
66 - `hsetroot` (background color)
67 - `feh` (background image)
73 - [doodle](https://grothoff.org/christian/doodle/)