Path: utzoo!attcan!uunet!husc6!uwvax!oddjob!mimsy!eneevax!umd5!uvaarpa!mcnc!rti!xyzzy!meissner
From: meissner@xyzzy.UUCP (Michael Meissner)
Newsgroups: comp.sources.wanted
Subject: Re: BSD43 pushd/popd compatible progs on sysV
Message-ID: <875@xyzzy.UUCP>
Date: 16 May 88 21:51:24 GMT
References: <792@miraculix.liu.se> <730001@hpmtlx.HP.COM>
Reply-To: meissner@xyzzy.UUCP (Michael Meissner)
Organization: Data General (Languages @ Research Triangle Park, NC.)
Lines: 27

In article <730001@hpmtlx.HP.COM> kwb@hpmtlx.HP.COM (Keith Blackwell) writes:
| 
| My understanding is that pushd and popd are commands built in to the
| shell (csh only?) --- they *HAVE* to be built in since it is the shell's
| working directory you want to change (stack-wise).  Executable
| programs can't do the job.  So maybe what you
| really want is a more useful shell!  Note: if your shell
| has command aliasing and array variables, you can build your own
| version of pushd/popd with aliases.
| 					Keith Blackwell
| 					hplabs!hpmtlkb!kwb
| BTW, I would be really interested (and surprised) in hearing about any
| 	exceptions to my explanation!
| 

One particularly grungy way of supporting pushd/popd just occurred to
me.  Basically pushd would spawn a subshell in the pushed directory.
It would also stuff somewhere (like the environment) it's process id.
Popd would then send a signal to popd, which would kill the subshell
(and presumably popd).  Each pushd would consume 1-2 processes, and
you would have to do as many popd's as you did pushd's.  Before you
flame me, I did warn you it was grungy, and is more proof of concept.

-- 
Michael Meissner, Data General.

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