Re: What about a new `mib' command?

Juergen Schoenwaelder (schoenw@cs.utwente.nl)
Wed, 22 Jan 1997 23:51:56 +0100

Buz Owen <ado@bbn.com> said:

Buz> Sure. I can always convert scripts I still have under my control
Buz> anyway, especially if the conversion is mechanical. (Will I
Buz> be able to execute the following twice, with the same value of
Buz> x,

Buz> [ mib node $x ] syntax

Buz> without error?)

Yes. The mib node command will in fact reuse the handle that is
created the first time you evaluate this command.

Buz> But scripts can sometimes find their way into the hands of people
Buz> who didn't write them, who don't know (maybe don't still employ)
Buz> the original author, and maybe don't have full control of their
Buz> environment. They are happily using some script, and one day it
Buz> breaks when someone deletes the oldest copy of scotty. This then
Buz> reflects on the system that they think broke their scripts by not
Buz> maintaining backward compatibility.

This is a version management problem. Every script that uses the
current version of the Tnm extension should start with a package
require command:

package require Tnm 2.1

This command will fail with an error message if your environment is
not able to provide the requested package. I know, this does not solve
the problem (because it is difficult to find out if there is still
someone around who is using an old version), but it makes it easy to
deal with the problem (you get a clear error message and not some
obscure script behaviour) and it gives the package a way to evolve.

Systems that are trying to be backward compatibility across version
number changes end up to be ugly and difficult to maintain. Look at
some MicroSoft operating systems if you need examples. :-)

Juergen

--
!! This message is brought to you via the `tkined & scotty' mailing list.
!! Please do not reply to this message to unsubscribe. To subscribe or
!! unsubscribe, send a mail message to <tkined-request@ibr.cs.tu-bs.de>.
!! See http://wwwsnmp.cs.utwente.nl/~schoenw/scotty/ for more information.