RPC (remote procedure calls) in BASH over SSH

An example is if you have something inside a KVM instance or a docker container, and you need to ssh outside of it when it boots up (or a service starts) to play with IPtables settings on the base server.

For most cases, you would use a higher level language, that has clean remote procedure execution (in modern terms, doing "curl" to a remote node.js served API). This however is when you have a need to do everything in BASH scripts.

The purpose of this technique is if you have a script running on, say, a master host, has a bunch of functions, but has a couple functions that need to run somewhere else (like a backup script that needs to put a remote database server in hot backup mode). You can either write the remote commands to a file, sync it to the remote host (somewhere), then execute it. Or, use this technique to pass the function "live" to the remote environment and run it unmodified.

I personally use it in the front-end client script (snebu-client) for the Snebu backup system.