Memoize in the shell

So, one day at work, me and my fried David were complaining about how slow requests to AWS can be, using the cli, and what a pain it is to iterate on a slow feedback loop. David remarked, "I wish we could memoize this". That stopped me in my tracks. "Yeah, why don't we?"

A flash later, we had memoize as a shell function.

It doesn't have any testing rig, but if it did, there are a few cases we have considered:

• The return code, stdout and stderr should all be replicated.

• The whole of the command is used in the cache key. That is, invokations with different arguments are cached separately.

• Waiting to read something from either stdout or stderr before reading the other should not block.

• Cache entries can be cleared individually.

• Cache can age out with a TTL

• Removing empty files in cache does not affect results

• Removing cache completely does not cause a crash