5 A sensor writes to a file, bar reads it.
8 - Race condition: a sensor's message needs multiple `write` calls to complete
9 and bar reads in between those calls.
11 This might not be so bad in practice, since we expect sensor messages to be
12 small and this to complete in a single `write` call.
16 A sensor produces a message to a named pipe, bar consumes it.
19 - Cannot accommodate multiple readers (besides bar, I want other tools to be
20 able to read sensor data, like the `today` script (akin to `motd`));
21 - Writer blocked when no consumers, though this is irrelevant since only 1
22 consumer is possible :)
25 ### N pipes per sensor
26 A sensor monitors a `subscribers` directory for named pipes and produces
27 messages for all subscribers.
30 - Reader blocked (which is fine for bar, but not for today/motd)
33 ### 1 file + lock per sensor
39 ### 1 pipe + 1 file per sensor
40 A sensor writes message to file, then to pipe, bar reads pipe, others can read