Well that makes it more difficult.

If you're running Solaris 8 or 9, or 10 if you have root, the command /usr/ucb/ps -aeguxwwwww <pid of java ExternalPG> should show you the complete command-line and environment variables. With that you could try calling open3 directly on java ExternalPG ... to bypass whatever IO redirection external.sh is doing.

update - missed the 'e' in the ps command