Shell Script Question

[Mike Reinehr]

On Thursday 02 June 2005 08:12 am, Brad De Vries wrote:
> On 6/1/05, David Bandel <david.bandel at gmail.com> wrote:
> > Wonder why this reply didn't go to the list?
> >
> > On 6/1/05, Alma J Wetzker <almaw at ieee.org> wrote:
> > > I don't do much scripting beyond expect, can you have more than one
> > > return value to a script?  I counted three desired variables.  Is there
> > > a way to get all three out without going to global?
> > >
> > > In C, I would pass two by reference and return the third.  Can you do
> > > weird stuff like that in a script?
> >
> > Good question.  And the answer is:  I don't have a clue.  And it could
> > be different between ksh, bash, bash2, and bash3.  As soon as
> > something really needs more than very simple scripting, I drop into
> > Perl mode.  In Perl I can pass several variables to a subroutine, no
> > reference needed (although Perl can do all those memory tricks of
> > passing a memory address of a variable).  And there are ways to get
> > them back out, too.
> >
> > Brad, what shell are you calling and have you tried calling a
> > different one?  Last time I worked on AIX and HP-UX, they didn't have
> > bash.  They had borne and korn shells and that was about it (unless
> > you liked to abuse yourself with a C-shell -- which should only be
> > sold down by the sea shore).
> >
> > Ciao,
> >
> > David A. Bandel
>
> I use the bourne shell (#!/bin/sh) for virtually all my scripts
> because I deal with several UNIX variants (including cygwin and MKS
> Toolkit, UNIX environments on Windows.)  I would love to use perl for
> many of my projects but I can't always guarantee that it will be
> installed and trying to get a sys-admin to install perl when they've
> gone without it for 10+ years is a little like trying to push a rope.
> Sadly I don't push too hard because I know shell scripting but my perl
> skills are pretty weak.
>
> I would guess that 90-95% of all my scripts work perfectly everywhere
> I go with the one big exception of this looping issue.  Stuff I wrote
> in the late 80's worked this way and when I started working with Linux
> and bash I found it worked differently.  Now I know why.
>
> To answer Alma's question about passing variables by reference, I'd
> have to say that the shell does not have that ability.  Actually,
> until I started working with AIX and ksh, I'd never even heard of that
> concept of local variables in shell scripts.  Ksh and bash, there may
> be others, allow the you to define local variables but in sh and csh
> every variable that you create is global.
>
> Brad.
>

Brad,

Your scripting skills appear to be far past mine, but my experience with sh 
has been that all variables are global. I just ran a quick test of a script 
similar to yours and, in fact, they were. A couple of differences that might 
be significant:

I initialized my variables the old fashioned way:

export TEMP=0 TEMP1=1 TEMP2=2

and used the expr command to do the calculations:

TEMP=`expr $TEMP + 1`

etc, ...

When I broke from the for/do loop all values were retained as expected.

HTH's!

cmr

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