#! /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)"
# temporarily add variable values to environment varialbes
export comment_ch  look_for  replace_with

# process file with awk to find $look_for and replace with $replace_with
# if the first character(s) are are a comment, print the unmodified line
# if the line contains the string we are looking for, print the replacement line
# in all other cases, print the unmodified line
awk ' { if( substr($0,1,1) == ENVIRON["comment_ch"] || if( substr($0,1,2) == ENVIRON["comment_ch"] )
           print $0;
        else if($0 ~ ENVIRON["look_for"])
           print ENVIRON["replace_with"];
        else
           print $0;
      } ' $filename > tmp
# overwrite original file
mv tmp $filename

# clear variables set for this call to awk
unset ENVIRON["comment_ch"]
unset ENVIRON["look_for"]
unset ENVIRON["replace_with"]

#! /bin/bash

# function to call awk and implement find and replace
function find_and_replace () {

   # leading comment character (ignore line and print)
   local f_comment_ch=$1
   # line in file to find and replace
   local f_look_for=$2
   # replacement line
   local f_replace_with=$3
   # original filename
   local f_filename=$4

echo "     in function"
echo "  f_comment_ch: " $f_comment_ch
echo "    f_look_for: " $f_look_for
echo "f_replace_with: " $f_replace_with
echo "    f_filename: " $f_filename
echo ""

   # add variables to ENVIRON
   export f_comment_ch  f_look_for  f_replace_with

   # process file with awk to find $look_for and replace with $replace_with
   awk ' { if( substr($0,1,1) == ENVIRON["comment_ch"] || if( substr($0,1,2) == ENVIRON["comment_ch"] )
              print $0;
           else if($0 ~ ENVIRON["f_look_for"])
              print ENVIRON["f_replace_with"];
           else
              print $0;
         } ' $f_filename > tmp
   # overwrite original file
   mv tmp $f_filename

   # clear variables set for this call to awk
   unset ENVIRON["f_comment_ch"]
   unset ENVIRON["f_look_for"]
   unset ENVIRON["f_replace_with"]

}

# 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)"

# call find and replace
find_and_replace  "$comment_ch"  "$look_for"  "$replace_with"  "$filename"