little-things/base64url

#!/bin/bash
# Like base64 but for the URL-safe alphabet A-Za-z0-9-_ (instead of A-Za-z0-9+/).
# This works by replacing occurrences of - with + and vice-versa, and likewise with _ and /.
# Does not support passing the filename by argument.
tr -- '\-_+/' '+/\-_' | base64 "$@"