How to expand shell variables in a text file?

Question

Consider a ASCII text file (lets say it contains code of a non-shell scripting language):

Text_File.msh:

spool on to \'$LOG_FILE_PATH/lo         


        

Answer 1

One limitation of the above answers is that they both require the variables to be exported to the environment. Here's what i came up with that would allow the variables to be local to the current shell script:

#!/bin/sh
FOO=bar;
FILE=`mktemp`; # Let the shell create a temporary file
trap 'rm -f $FILE' 0 1 2 3 15;   # Clean up the temporary file 

(
  echo 'cat < $FILE
. $FILE

The above example allows the variable $FOO to be substituted in the files named on the command line. I'm sure it can be improved, but this works for me so far.

Thanks to both previous answers for their ideas!