I will put together a sample directory and post it.

The -v method works for the comments and replace line, no matter if there are special characters or spaces. It is the $look_for line that is the problem. This version of the code does not work. The $look_for line is never found.

Code:

#! /bin/bash

# value determined elsewhere
total_outputs_p1=100
# file being modified
filename='./common_depend/UTILPARAMS.DAT'
# comment lines to ignore
comment_ch="C"
# line being searched for to replace
look_for="      PARAMETER \(SIZEXX = "
# value of replacement line
replace_with="      PARAMETER (SIZEXX = $total_outputs_p1)"

# process file with awk to find $look_for and replace with $replace_with
awk -v comment="$comment_ch" \
    -v find_line="$look_for" \
    -v replace_line="$replace_with" \
' { if( substr($0,1,1) == comment || if( substr($0,1,2) == comment )
       print $0;
    else if($0 ~ find_line)
       print replace_line;
    else
       print $0;
  } ' $filename > tmp
# overwrite original file
mv tmp $filename

If you replace,

else if($0 ~ find_line)

with,

else if($0 ~ / PARAMETER \(SIZEXX = /)

then it will function. This is hard coding specifically for each item to find and so can't be used in a function. I read that the -v option presented difficulties when using characters that need to be escaped and that is when I switched to the temporary environment variables that I read about on a stackexchange post (I think). I don't understand why it works, but not in the function.

I will post some samples in a few minutes. I need another cup of coffee.

LMHmedchem