Tiny C program that takes text in from stdin, replaces {{ key.name.tokens }} with data from a JSON file (passed by argument), and outputs the result.
Very simple. One argument: JSON file.
./jsonsubst data.json <input.txt >output.txt
Or, in a pipeline of some kind...
cat input.txt | ./jsonsubst data.json | tee output.txt
If you're cool and already have a good working C build environment on your system, just run make build.
I'm not cool though, so I use Docker for this kind of thing, which is why it's the default make target. Just run make on a system with Docker running on it, and a build image will be created, make build executed within the container where all the prerequisites exist, and the build image will be removed after it's done.
No external runtime dependencies, so it should run anywhere. Which means it'll run inside your quick-and-dirty Docker stuff without complaint.