Bash: Poor mans code generation

When it comes to generating code, I often find that the simplest code generation only needs variable replacement. There’s a cli utility that already facilitates this with environment variables, named envsubst, part of the gettext suite of tools.

In it’s most simple form, it takes a template file and replaces any variables contained within, and outputs the resulting text. It’s not super great if you have any dangling $ characters in your template, but for most purposes...