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

This solution allows you to keep the same formatting in the ouput file

Copy and paste the following lines in your script

cat $1 | while read line
do
  eval $line
  echo $line
  eval echo $line
done | uniq | grep -v '\$'

this will read the file passed as argument line by line, and then process to try and print each line twice: - once without substitution - once with substitution of the variables. then remove the duplicate lines then remove the lines containing visible variables ($)