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From: katzung@laidbak.UUCP (Brian Katzung)
Newsgroups: comp.unix.questions
Subject: Re: C-shell idiosyncracy ??
Message-ID: <1248@laidbak.UUCP>
Date: Sat, 14-Nov-87 00:35:15 EST
Article-I.D.: laidbak.1248
Posted: Sat Nov 14 00:35:15 1987
Date-Received: Mon, 16-Nov-87 05:14:34 EST
References: <33414@sun.uucp> <9316@mimsy.UUCP>
Reply-To: katzung@laidbak.UUCP (Brian Katzung)
Organization: Lachman Associates, Inc., Naperville, Illinois
Lines: 23

In article <9316@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
>In article <33414@sun.uucp> vipin%samsun@Sun.COM (Vipin Samar) writes:
...
>>So, for some reasons I just cannot pipe the output of "jobs".
>To see why this happens, consider how pipes are implemented.
>After creating a pipe, it is necessary to fork.

It is necessary to fork to create the read end of the pipe, but
not for the write end of the pipe (and the write end of the pipe
is the supplier of jobs information).  It is just as easy to
write to the file descriptor for a pipe as it is to write to
the file descriptor for a file.  His shell and the several I just
tested are broken because they chose to take the lazy approach by
forking instead of juggling file descriptors in the current shell.
IT CAN BE DONE RIGHT, and from the responses, I gather the HPUX
people did do it right.

Actually, in a degenerate case, you could pipe from one built-in
to another, as long as you didn't ever send more than 4K before
you read it (ie, "history -hr 8 | source -h" would append your
last 8 events in reverse order onto your history list if source
accepted input from the standard input).
-- Brian Katzung   ihnp4!laidbak!katzung