Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!st-andy!larry
From: larry@st-andy.uucp (Larry Martell)
Newsgroups: comp.unix.shell
Subject: Re: Passing a var thru a file
Message-ID: <1991Jun18.193237.20647@st-andy.uucp>
Date: 18 Jun 91 19:32:37 GMT
References: <1991Jun18.153222.20836@cid.aes.doe.CA>
Reply-To: uunet!st-andy!larry (Larry Martell)
Distribution: na
Organization: RMJ Securities Corp.
Lines: 26

In article <1991Jun18.153222.20836@cid.aes.doe.CA> afsipmh@cidsv01.cid.aes.doe.CA () writes:
>Say i have a file that (just for the sake of this question) contains
>just one word:
>$ENVAR
>
>Say $ENVAR is an environmental variable
>
>What is it about the shell that prevents interpretation:
>
>#!/bin/sh
>var=`cat file`
>echo $var     #gives (literally) $ENVAR
>echo `echo $var`  #also gives (literally) $ENVAR

You need to tell the shell to re-evaluate the expression. The shell IS 
expanding $var (it equals $ENVAR), but you want it to expand $var, and
then expand it again.  You do this using eval:

#!/bin/sh
var=`cat file`
eval echo $var

-- 
Larry Martell                  "Opinions are like assholes; everybody has one, 
212-668-9478		        but nobody wants to look at the other guys"
uunet!st-andy!larry