Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!pprg.unm.edu!hc!ames!oliveb!pyramid!ncc!myrias!cg
From: cg@myrias.UUCP (Chris Gray)
Newsgroups: comp.sys.amiga
Subject: Re: Using PIPE: device
Summary: PIPE: depends on the Open mode
Keywords: PIPE:
Message-ID: <815@myrias.UUCP>
Date: 31 Jan 89 01:29:27 GMT
References: <167@nrl-cmf.UUCP>
Organization: Myrias Research Corporation
Lines: 35

In article <167@nrl-cmf.UUCP> healy@nrl-cmf.UUCP (Liam Healy) writes:
>I am having trouble using the PIPE: device.
>I am writing a file in DME, and I want to feed the finished
>file into Proff.  So, I saveas PIPE:a, go to a CLI, and then
>run proff PIPE:a foo.fmt.  No output, DME locks up.  So I do it
>the other way around, i.e., run proff first then save from DME.
>A little better this time ... I get a file foo.fmt, but it is
>empty.  Am I doing something stupid?  By the way, I can use the
>PIPE: device without problems with e.g.
>  run copy file PIPE:a
>  proff PIPE:a foo.fmt
>but that defeats the idea of a pipe.
>Thanks for the help.

Well, it just so happens that I spent a couple hours over the weekend in
messing with PIPE: w.r.t. my Draco library (should go out tomorrow??).
The PIPE: device is sort of picky about what mode is used to Open it.

    MODE_NEWFILE - should be used by the write end.
    MODE_OLDFILE - should be used by the read end.

Other modes will SEEM to work (in fact, either end can read or write), but
the end-of-file signal when the writer closes the PIPE: will only get to the
reader if the above modes were used.

Thus, I suspect that DME is using (at a guess), MODE_READWRITE, which can
indeed cause one end or the other to hang. Thus, there is probably not much
that you, a user, can do about it. The only fix is to change DME. This would
have to be kludgey, since you want different modes for PIPE: than you would
normally use for files (MODE_NEWFILE for a file empties the file). I ended
up putting some specific tests for "pipe:" in my Draco I/O library. (Ugh!)

-- 
Chris Gray		Myrias Research, Edmonton	+1 403 428 1616
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