Path: utzoo!attcan!uunet!zephyr.ens.tek.com!uw-beaver!sumax!nwnexus!golder
From: golder@nwnexus.WA.COM (Warren Jones)
Newsgroups: comp.unix.questions
Subject: How to prevent execution of $ENV file in Korn shell scripts ?
Keywords: Korn shell environment
Message-ID: <392@nwnexus.WA.COM>
Date: 4 Oct 90 15:49:59 GMT
Organization: Golder Associates
Lines: 46


When writing a C shell script, you can start off with:

#! /bin/csh -f

... where the "-f" flag insures that the user's $HOME/.cshrc file
is not read.  Efficiency is a secondary consideration here.  More
important is making sure that the shell environment is predictable,
and that you don't unwittingly use an alias that was defined in .cshrc.

Does anyone know a way to avoid reading the user's $ENV file in
Korn shell scripts?  I'm puzzled that a shell with so many features
apparently neglects this question.

Of course, you can always make the behavior of a script predictable
by writing all commands as fully qualified pathnames (e.g. "/bin/sed",
rather than just "sed").  But:

   1.  This is tiresome to write and makes scripts hard to read.
   2.  Who wants to have to remember which commands are in /bin,
       which are in /usr/bin, and which are in /usr/ucb ?  (Do
       you have some other directories on your system ?)
   3.  I suspect that the distribution of commands among these
       directories is not portable between various flavors of **ix.

Suggestions?

A related question:  When working on an HP-UX system a while back,
I remember seeing in one of the manuals a trick for defining ENV
so that the variable expands to the desired file name for interactive
shells, but to a null string if the shell is not interactive.

NOTE:  this is a different question, and does involve efficiency
(though I'm sure not in any critical way).  After all, you don't
need to read the ENV file when the shell is simply being used
to glob some file names for an editor.  The trick involved checking
the "$-" flags variable for the presence of the letter "i"
(indicating an interactive shell).  I remember marveling at the
time how wonderfully obscure and arcane it was, but I can't quite
seem to reproduce it.  Can anyone out there provide the answer?

-- 
----------------------------------------------------------------
Warren Jones <golder@nwnexus.wa.com>      Golder Associates Inc.
(uucp: uunet!nwnexus!golder)              4104 148th Avenue NE
(206) 883-0777                            Redmond, WA 98052, USA