In a recent note, "Shmuel Metz (Seymour J.)" said:
> Date: Wed, 13 Dec 2006 07:09:22 -0500
>
> >Does FTP client under Unix Services perform I/O directly to stdin
> >and stdout, or does it ALLOCATE INPUT and OUTPUT to the paths?
>
> I don't understand the question. The Unix process gets control with
> whatever stdin and stdout the caller specifies. It doesn't and
> shouldn't allocate anything as long as stdin and stdout are all it
> wants. Those names refer to pre-opened files, not to ddnames.
>
In the diachronic view, many strange things are possible. Suppose
the archetypal MVS FTP client was written (in Pascal?) long before
Unix System Services to do QSAM I/O to DD names INPUT and OUTPUT.
The most economical accommodation to UNIX might then have been
to add DYNALLOCs:
alloc dd(INPUT) path('/dev/fd/0') ...
alloc dd(OUTPUT) path('/dev/fd/1') ...
and leave the rest of the code unchanged. But then concurrent
invocations of FTP with _BPX_SHAREAS=YES would contend for the
DD names.
> Think of stdin, stdout and stderr as being open DCB's passed to the
> process. It's not a perfect analogy, but it conveys the flavor.
>
I do.
-- gil
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