How to multiplex named pipe / fifo

Question

Say we have a named pipe:

mkfifo my_named_pipe

say there are multiple writers writing to this named pipe:

node x.js > ${my_named_pipe} &
node y.js > ${my_named_pipe} &
node z.js > ${my_named_pipe} &

something like that - is there a reliable way to multiplex it, so that one whole message gets through each time, or can a named pipe reliable read from only one writer?

It leads me to wonder how we multiplex ports/sockets etc, I don't know how it's done.

looks like we can't multiplex named pipes....https://gist.github.com/thinkerbot/6406361 — Alexander Mills, Apr 20 '18 at 09:26
I guess I don't understand how sockets can be multiplexed but named pipes can't — Alexander Mills, Apr 20 '18 at 09:26

score 1 · Answer 1 · answered Jun 22 '18 at 16:48

This might be a bit of a naïve answer, but this works for me.

If you have multiple writers to a single FIFO and you don't want their output to be mangled then you can use stdbuf but only if the output is line-based. Whole paragraphs will still be interleaved.

stdbuf -oL node x.js > ${my_named_pipe} &
stdbuf -oL node y.js > ${my_named_pipe} &
stdbuf -oL node z.js > ${my_named_pipe} &

man stdbuf: stdbuf - Run COMMAND, with modified buffering operations for its standard streams.

This will only work when your original program does not adjusts its buffering of the standard output stream.

How to multiplex named pipe / fifo

1 Answers1