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From: reschly@BRL.MIL (Robert J. Reschly Jr.)
Newsgroups: comp.unix.questions
Subject: Re: which/type & built-ins
Message-ID: <21912@adm.BRL.MIL>
Date: 1 Jan 90 23:17:07 GMT
Sender: news@adm.BRL.MIL
Lines: 41


      Richard,
You say:
> Does anyone know why the C shell command "which" (ok, /usr/ucb/which)
> and the Bourne shell command "type" don't understand built-in commands?

   The "which" command is an independent program (actually a C-shell
script) which can be called from any command interpreter.  Since the
various command interpreters offer differing sets of built-in commands,
"which" cannot presume to know anything about built-in commands.
Additionally there is no reasonable way for "which" to learn this
information.

> I don't quite see why; surely it would be easy for /usr/ucb/which to
> execute an appropriate switch() after everything else has failed.

   Resulting in "which blurfle" responding with "blurfle is a shell
built-in"?  What action would you have the switch() branch take?  Note
that another failure mode for "which" involves using a shell other than
/bin/csh while having a .cshrc in your home directory.  If this .cshrc
defines any aliases, "which" will gladly report them even though they are
probably inappropriate.

   As for "type", I have no good answers.  Given that "type type"
reports itself as a shell built-in it should be able to report on other
built-ins. My current shell of choice, "tcsh" handles this operation
correctly.

				Later,
				    Bob 
   --------
Internet: reschly@BRL.MIL (or BRL.ARMY.MIL)  Phone: (301)278-6808  AV: 298
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Postal:   Robert J. Reschly Jr.
          U.S. Army Ballistic Research Laboratory
          Systems Engineering and Concepts Analysis Division
          Networking and Systems Development Team
          ATTN: SLCBR-SE-A  (Reschly)
          APG, MD  21005-5066             (Hey, *I* don't make 'em up!)

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