BASH: Best architecture for reading from two input streams

Question

Simple script here:

a) constantly read from a socket and store values in an associative array
b) constantly read values from s

Answer 1

Don't know if this is fully practical and atomic enough in the described context, but using a client / server model and named pipes it's possible to create a while-loop that can distinguish between lines coming from a fifo or stdin.

The server constantly reads lines from a socket (/tmp/to) as well as lines from stdin (which is being redirected to the server via /tmp/to).

However, lines from stdin get marked by the del byte (\177) to be the first byte of the line.

Then the (backgrounded) client while-loop uses this first-byte-of-line to distinguish lines of different origin.

# terminal window 1

# server
(
rm -f /tmp/to /tmp/from
mkfifo /tmp/to /tmp/from
while true; do 
  while IFS="" read -r -d $'\n' line; do 
    printf '%s\n' "${line}"
  done /tmp/from &
  bgpid=$!
  exec 3>/tmp/to
  exec 4/tmp/to;
exec 4&3
) 
#kill -TERM $serverpid


# terminal window 2
echo hello > /tmp/to