Path: utzoo!utgpu!watmath!att!pacbell!ames!henry.jpl.nasa.gov!elroy.jpl.nasa.gov!hacgate!tcville!sed170!lee
From: lee@sed170.HAC.COM (John Lee)
Newsgroups: comp.sys.amiga
Subject: Re: Relying on ARP (was Re: My AmigaDOS 1.4 wishlist (one among thousands!))
Message-ID: <309@sed170.HAC.COM>
Date: 8 Aug 89 02:00:45 GMT
References: <12878@well.UUCP> <26758@agate.BERKELEY.EDU> <20904@cup.portal.com> <26915@agate.BERKELEY.EDU> <11107@polya.Stanford.EDU>
Reply-To: lee@sed170.UUCP (John Lee)
Distribution: na
Organization: Hughes Aircraft Co., El Segundo, CA
Lines: 53

In article <11107@polya.Stanford.EDU> rokicki@polya.Stanford.EDU (Tomas G. Rokicki) writes:
[...]
>I've always wanted to be able to fopen("|lpr", "w"), for instance, to
>spool things automatically, or anything else with pipes.  Why hasn't
>any operating system (that I know of) allowed file names to also specify
>new processes?  I mean, I can open `par:' or `ser:' or even `speak:'.
>Just a thought.
[...]

Well, I can think of several reasons, not all real justifications, but
they're better than "because the system designers/programmers were
lazy."  :-)  First of all, "|lpr" is a legal filename in many filesystems,
include UNIX and AmigaDOS.  I've used filesnames like that on occasion,
or used other funny characters (e.g., "~" or "$") for filenames.  Not
everybody names their files the same way or for the same reasons.

Secondly, redirection operators/symbols are usually in the domain of
the shell/user interface, since usually they define the semantics of
operation rather than the operating system.  Redirection can mean
different things depending on the source and/or destination.  This is
best left up to the shell, although the operating system must have the
capabilities or generality to implement various piping/redirection
schemes.  Remember, even UNIX doesn't have redirection built-in, just
a mechanism ("pipes") that shells use to implement redirection.

Thirdly, it depends on the design and meaning of "a filename" and the
"filespace".  In some operating systems, a filename can indeed mean a
process.  Opening such a "file" actually creates a pipe to and/or from
the process like you want.  AmigaDos even has little flavor of this,
since the filename "CON:100/100/20/50/Test" means open a CON: window
of a certain size named "Test".  Usually, however, a "filename" is the
name of a file on a mass-storage device, and then "|lpr" is inappropriate
for a function designed to open a file.  It's whatever was decided upon
by the designer.

Fourthly, there is nothing preventing one from writing a smartopen()
which does what you want, depending on the operating system.  The
resultant code would probably be very similar to that written if it were
built into the operating system.

Like I said, not exactly concrete reasons.  It's more of a stylistic
judgement made by the system designers of whether or not the operating
system should support redirection directly or to just provide a general
mechanism.  Personally, I don't think fopen() should support it.

--John Lee
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