STDIN, STDOUT, STDERR in RPG

Group,

While testing these files in an RPG program I came upon something
strange. First, here are some assumptions that may not be valid:

STDIN should be assigned a handle of 0, STDOUT 1, and STDERR 2. At least
that is what the PASE manual says.

You should close these if you open them when your process is completed,
this just seems like a good practice.

I found something strange. With QSH it opens a single file at 0 if
possible, but it will use anything if 0 is not available. QSH closes
this file when you press F3. Debug does not operate this way. Debug
appears to 0,1,2 and never close them.

How does a unix utility like grep locate STDIN, STDOUT, and STDERR? Does
it use the file handle 0,1,2 or some other means?

Thanks,

David Morris