Variables value gets lost in subshell

Question

This bash script concatenates the names for jar files to a classpath (variable CP), in the while loop the value is correct but is lost in the subshell as descibed in this re

Answer 1

None of these answers seem to get into actually returning the value properly, echoing out the answer is fine with a very simple routine, but say you want output of the script in action, this is useless. I don't have the best answer but I don't have much time to figure it out either, so I'm just going to suggest to output exactly what you want to a temp file and read that (surprised it hasn't been mentioned to date) :

#!/bin/bash
CP="AAA"
func() {
  ls -1 | (
    while read JAR
    do
      if [ ! -z "$CP" ]; then
        CP=${CP}':'
      fi
      CP=${CP}${JAR}
    done
    echo "$CP" > /tmp/cp-value-file
  )
}

func
CP=$(cat /tmp/cp-value-file)
echo $CP

Downside: will in some cases need to write to the disk every iteration of the loop.