#!/bin/bash
 
set -e
 
INPIPE=/tmp/pipe_in
OUTPIPE=/tmp/pipe_out
 
rm -f "$INPIPE" "$OUTPIPE" 2>/dev/null
if ! mkfifo "$INPIPE" "$OUTPIPE"; then 
  exit 1;
fi
 
process_cmd() {
  echo $@
  sleep 4
}
 
while IFS="" read -r -d $'\n' line; do
  printf '%s\n' "${line}"
done <$INPIPE >$OUTPIPE &
bgproxy=$!
 
exec 3>$INPIPE
exec 4<$OUTPIPE
 
while IFS="" read -r -d $'\n' <&4 line; do
  process_cmd $line
done &
bgreader=$!
 
trap "kill -TERM $bgproxy; kill -TERM $bgreader; echo 'bgproxy=$bgproxy bgreader=$bgreader'; rm -f '$PIPE'; exit" 0 1 2 3 13 15
wait "$bgproxy"