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From: ado@elsie.UUCP (Arthur David Olson)
Newsgroups: net.unix-wizards
Subject: Re: comm '! sort file1' '! sort file2'
Message-ID: <7028@elsie.UUCP>
Date: Fri, 10-Oct-86 13:26:40 EDT
Article-I.D.: elsie.7028
Posted: Fri Oct 10 13:26:40 1986
Date-Received: Sat, 11-Oct-86 19:59:03 EDT
References: <830003@hpcnoe.UUCP> <35@pixutl.UUCP> <3724@umcp-cs.UUCP> <264@desint.UUCP>
Organization: NIH-LEC, Bethesda, MD
Lines: 33
Summary: Three steps back

On the floor:  allowing something such as
	comm '! sort file1' '! sort file2'
to set up multiple pipes into a command.

In article <830003@hpcnoe.UUCP>, jason@hpcnoe.UUCP (Jason Zions) writes:
> It can be done easily on SYSV, using fifo's. . .This is what you do,
> after creating the fifo (mknod -p ~/fifo).
>
> sort file1 > ~/fifo & sort file2 | comm - ~/fifo

In article <3724@umcp-cs.UUCP> chris@umcp-cs.UUCP (Chris Torek) writes:
> Unfortunately, one must be root to create a fifo, no?

In article <264@desint.UUCP>, geoff@desint.UUCP (Geoff Kuenning) writes:
> . . .I just did "mknod fifo p" from a normal account, and it worked. . .

And in this article I write:
Even if a normal can create a fifo, it may not be the wisest thing to do.
Think of the havoc that results if I put a
	sort "$1" > ~/fifo & sort "$2" | comm - ~/fifo
command into a shell script (named, for example, "scomm") and then,
six months from now when I've forgotten the implementation details,
type in
	scomm firstfile secondfile > results &
	scomm thirdfile fourthfile > moreresults &

The "/dev/fd/n" mechanism discussed in other recent postings doesn't suffer
from this defect.
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