create read/write environment using named pipes - bash

Question

I am using RedHat EL 4. I am using Bash 3.00.15.
I am writing SystemVerilog and I want to emulate stdin and stdout. I can only use files as the normal stdin and stdout is not supported in the environment. I would like to use named pipes to emulate stdin and stdout.
I understand how to create a to_sv and from_sv file using mkpipe, and how to open them and use them in SystemVerilog.
By using "cat > to_sv" I can output strings to the SystemVerilog simulation. But that also outputs what I'm typing in the shell.
I would like, if possible, a single shell where it acts almost like a UART terminal. Whatever I type goes directly out to "to_sv", and whatever is written to "from_sv" gets printed out.
If I am going about this completely wrong, then by all means suggest the correct way! Thank you so much,
Nachum Kanovsky

Answer 1

Edit: You can output to a named pipe and read from an other one in the same terminal. You can also disable keys to be echoed to the terminal using stty -echo.
mkfifo /tmp/from
mkfifo /tmp/to
stty -echo
cat /tmp/from & cat > /tmp/to
Whit this command everything you write goes to /tmp/to and is not echoed and everything written to /tmp/from will be echoed.
Update: I have found a way to send every chars inputed to the /tmp/to one at a time. Instead of cat > /tmp/to use this command:
while IFS= read -n1 c;
do
if [ -z "$c" ]; then
printf "\n" >> /tmp/to;
fi;
printf "%s" "$c" >> /tmp/to;
done

Answer 2

You probably want to use exec as in:
exec > to_sv
exec < from_sv
See sections 19.1. and 19.2. in the Advanced Bash-Scripting Guide - I/O Redirection

Answer 3

Instead of cat /tmp/from & you may use tail -f /tmp/from & (at least here on Mac OS X 10.6.7 this prevented a deadlock if I echo more than once to /tmp/from).
Based on Lynch's code:
# terminal window 1
(
rm -f /tmp/from /tmp/to
mkfifo /tmp/from
mkfifo /tmp/to
stty -echo
#cat -u /tmp/from &
tail -f /tmp/from &
bgpid=$!
trap "kill -TERM ${bgpid}; stty echo; exit" 1 2 3 13 15
while IFS= read -n1 c;
do
if [ -z "$c" ]; then
printf "\n" >> /tmp/to
fi;
printf "%s" "$c" >> /tmp/to
done
)
# terminal window 2
(
tail -f /tmp/to &
bgpid=$!
trap "kill -TERM ${bgpid}; stty echo; exit" 1 2 3 13 15
wait
)
# terminal window 3
echo "hello from /tmp/from" > /tmp/from