Question, How portable are "off the shelf" unix applications?

[Doug Gwyn <gwyn>]

>  1. On the average, with 1 programmer of 2 years UNIX and C experience how
>     long will it take to port an 'off the shelf' UNIX business package? If
>     you have a justification for your statement I'd be interested.

There is an excellent article in the November 1984 UNIX/WORLD (Vol 1 No 6,
pp. 44-49) describing one business software house's experience in this.
They changed from using IBM business systems to UNIX-based ones and improved
their situation tremendously.

My estimate is that porting a major package like a spreadsheet from one UNIX
to ANY other UNIX implementation should take such a programmer no more than
a few weeks.  Sometimes it takes only hours, if the software is well-written
and if the UNIXes are similar versions (e.g. both UNIX System V).

>  2. What factors must I consider if I want to buy an 'off the self' application
>     and be sure I'll minimize (whatever minimization is) my porting efforts?

This is hard to answer in a few words.  Basically, stick to portable C and
separate system-dependent functions out into carefully-chosen modules.  Use
libcurses for video screen manipulation.  Avoid things that may not be
supported on other target systems (e.g., shared memory, sockets, database
managers, etc.); if you need these facilities, provide your own or be
prepared to limit your porting to systems that provide them.  As UNIX System V
spreads more widely, it would make sense to expect its facilities to be there.

If you're buying an "off the shelf" application, why would you be doing the
porting work?

>  3. What do you think of the statement "I can port any UNIX application in
>     2 weeks"?

Change that to "most applications" and I could believe it.

>  4. What do you think of the statement "Porting any UNIX application will   
>     take at least a man year of effort"?

Porting any application that makes significant use of UNIX facilities
to an obsolete OS could easily take a man-year.  Porting from one UNIX
to another is pretty easy; an application could probably be totally rewritten
in less than a man-year!