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From: leres@ucbvax.UUCP
Newsgroups: comp.os.eunice
Subject: Re: vms format files and unix format files
Message-ID: <17989@ucbvax.BERKELEY.EDU>
Date: Tue, 24-Mar-87 00:58:20 EST
Article-I.D.: ucbvax.17989
Posted: Tue Mar 24 00:58:20 1987
Date-Received: Wed, 25-Mar-87 05:31:48 EST
References: <1250@uwmacc.UUCP>
Reply-To: leres@ucbarpa.Berkeley.EDU (Craig Leres)
Organization: University of California at Berkeley
Lines: 16


There's a reason why exec() works the way it does under Eunice; it's
faster for the 99% case. If the file is fixed length, exec() simply
tries to execute it as a VMS image. If it's a variable length file, it
reads a record to extract the name of the shell to use. Those who know
how slow file I/O is under VMS will see why you want to avoid the read.
It may not seem like much overhead, but Unix programs use exec()
extensively and it quickly adds up.

I disagree with the statement that random seeks only work with Unix
files; although not efficient, random seeks work fine. They are slow
when dealing with a variable length file is because you must seek to
the beginning of the file and read until you get to the right place.
So make sure /etc/termcap is a fixed length file!

		Craig