Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mit-eddie!apollo!nazgul
From: nazgul@apollo.COM (Kee Hinckley)
Newsgroups: comp.sys.apollo
Subject: Re: go to old directory == 'back' ??
Keywords: Aegis shell levels
Message-ID: <443447ef.1b147@apollo.COM>
Date: 3 Jul 89 19:43:00 GMT
References: <678@idacom.UUCP>
Reply-To: nazgul@apollo.COM (Kee Hinckley)
Organization: Apollo Computer, Chelmsford, MA
Lines: 58

In article <678@idacom.UUCP> danny@idacom.UUCP (Danny Wilson) writes:
>I thought this would be a great function for the Aegis shell. I made
>the following shell scripts:
>
>file: wd
>	eon
>	if eqs ^1 "" then
>		/com/wd		# no parameters, just print where we are
>		return
>	endif
>	old := ^"/com/wd" 
>	export old
>	/com/wd ^1
>
>file: back
>	eon
>	back := ^old
>	old := ^"/com/wd"
>	/com/wd ^back
>	dlvar back
>	/com/wd
>
>However, because the variable 'old' gets set at a lower shell level it
>is undefined within program 'back'. Has anyone got a solution for
>a (seemingly) easy problem like this?

First of all you should probably stop using /com/wd, and just use wd.
wd is a builtin at SR10 (one program per process and all that).  The version
in /com is a shell script, so it will still work, it's just slower.

Now for the problem.  There is no way to have a shell script change
a variable above it unless you "source" the shell script.  To do what
you want I think the best solution would be:

wd:
    #!/com/sh
    eon
    if eqs ^1 "" then
	wd
    else
	wd > ^HOME/.olddir
	wd ^1
    endif
back:
    #!/com/sh
    eon
    read back < ^HOME/.olddir
    wd > ^HOME/.olddir
    wd ^back

Note that I haven't tested this!

						    -kee
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