RE: STDIN, STDOUT, STDERR in RPG

[James Rich <james@xxxxxxxxxxx>]

On Mon, 15 Apr 2002, Peter Connell wrote:

> Forgive me for mentioning this again. You may have spotted a recent question
> I posed that asks if stdout (not stdin) can be read into an RPGLE pgm after
> some previous process has already populated it via an api like QtmhWrStout.
> Can this be done?

I know I'm not Scott but you get to hear from me anyway :)

I believe the straightforward answer to this is no.  For a more in depth
discussion on how stdin and friends work see the reply I just wrote to
David's question.

Using pipes one program's stdout can be read by another program's stdin.
I think you are trying to accomplish this reading without using a pipe,
which I believe cannot be done.  But there is a bigger problem with your
question.  stdout is not something that can be populated.  If there is
something to read it (using a pipe) then fine, or it can be printed on the
screen, or it can be redirected to a file.  But stdout is not saved or
stored anywhere.  It never fills up or gets empty.  So you can't have one
program write some stuff to its stdout and then fire up another program
and read the first's stdout.  stdin, stdout, and stderr aren't real files.
They only exist in the mind of the operating system.  To do what you want
you should use a pipe.

James Rich
james@eaerich.com