TIL: multiple bash coprocs with dynamic names

coprocs.sh

#!/usr/bin/bash
PID_MAIN=$$

# notify subshells on ctrl-c
trap "kill 0" SIGINT

function wrk() {  while read data; do echo $1 _${data}_; done  }

function shw() {  
   pid=$1
   fd=$2
   while IFS= read result; do 
    echo out: $result  
  done < /proc/${pid}/fd/${fd}
}

# return worker names like "wrk0"
function workers() {
  for i in {1..5}; do
    echo wrk${i}
  done
}

# spawn worker and printer processes
for worker in $(workers); do
 eval "coproc  ${worker} { wrk $worker; }"
 fdname="${worker}[0]"
 ( shw ${PID_MAIN} ${!fdname} )  &
done


echo Filedescriptors of main process:
ls -lFh /proc/$$/fd/

echo List of processes in processgroup:
jobs -l

echo feeding some test data to the workers
for worker in $(workers); do
   fdname="${worker}[1]"
   echo $fdname
   echo test > /proc/$PID_MAIN/fd/${!fdname}
done

sleep 100
kill 0
exit

Using multiple coprocs works nice but shows warnings like:

./coprocs.sh: Zeile 26: Warnung: execute_coproc: coproc [21535:wrk1] still exists