How to use 'coproc' to interact with another command driven program

Question

Ok, obviously I am NOT a bash guru and am in need of one!

I have never used \'coproc\' before, but it seems to be just what I need. But, I have to admit that I can not

Answer 1

result = $(echo 'command' <&${bkgndProc[0]})    ### Doesn't work for me

wouldn't work at least basically since you have spaces on it

result=$(echo 'command' <&${bkgndProc[0]})

---- Update ----

A simple concept could be shown in a script like this:

#!/bin/bash

# create the co-process
coproc myproc {
    bash
}

# send a command to it (echo a)
echo 'echo a' >&"${myproc[1]}"

# read a line from its output
read line <&"${myproc[0]}"

# show the line
echo "$line"

Outputs:

a

Another which reads multiple lines using a timeout:

#!/bin/bash

coproc myproc {
    bash
}

# send a command to message 4 random numbers in 4 lines
echo 'echo "$RANDOM"; echo "$RANDOM"; echo "$RANDOM"; echo "$RANDOM"' >&"${myproc[1]}"

# keep reading the line until it times out
while read -t 1 -u "${myproc[0]}" line; do
    echo "$line"
done

Output:

17393
1423
8368
1782

If we use cat, it would no longer quit since the other end is still alive and connected, and EOF is not yet reached. It's the reason why we used timeouts.

cat <&"${myproc[0]}"