Bridge Unix domain socket with a FIFO and log file

Question

I need to write a script - preferably a bash script - that will listen on a Unix domain socket and pipe the output to a log file while receiving input through a FIFO. The FIFO / log end is supposed to mimic the style of ii. The script also be able to monitor and react to the input from the FIFO (e.g. for a "stop" function).

This is as far as I got:

if [[ ! -p "in" ]]; then mkfifo "in"; fi

while true; do
  nc -Ul sock >> "out"
done

I'm stuck on how to get the input from the FIFO into netcat. When I add < "in" and try to connect to the socket from another shell the connection is refused. Strangely enough, it works just fine when I replace "in" with a regular file.

What's the easiest / correct way to do this?

Edit: Using the pipes on the whole while block has the same effect.

Answer 1

Try use some "proxy" to input. For example "cat":

if [[ ! -p "in" ]]; then mkfifo "in"; fi

(while true; do cat in; done) | (while true; do
  nc -Ul sock >> "out"
done)