Shell Programming and Scripting

$ cat fA
DOWNLOAD_REPOSITORY=E:/download_repository/
DOWNLOAD_PROCESS_LOG=E:/download_repository/process_logs/
DOWNLOAD_ARTICLE_FOLDER=article
DOWNLOAD_SUBSIDARY_FOLDER=subsidiary
$ cat fB
DOWNLOAD_REPOSITORY=/opt/download_repository/
DOWNLOAD_PROCESS_LOG=/opt/download_repository/process_logs/
$ cat replace.sh 
awk '
BEGIN {
   FS="="
   i=0
   COMMAND="cat fA"
}

   {
   ARR[i,0]=$1
   ARR[i,1]=$2
   i++
   }

END {
   while (( COMMAND | getline ) > 0)
      {
      f=0
      for (b=0;b<=i;b++)
         {
         if ( $1 == ARR[b,0])
            {
            print ARR[b,0]"="ARR[b,1]
            f=1
            break
            }
         }
       if ( f == 0 )
          print $0
       }
}'<fB
$ replace.sh 
DOWNLOAD_REPOSITORY=/opt/download_repository/
DOWNLOAD_PROCESS_LOG=/opt/download_repository/process_logs/
DOWNLOAD_ARTICLE_FOLDER=article
DOWNLOAD_SUBSIDARY_FOLDER=subsidiary

#! /usr/bin/ksh

awk -F"=" '{print $1" "$2}' filea | while read iden temp
do
  found=0
  awk -F"=" '{print $1" "$2}' fileb | while read line val
  do
     if [ $iden = $line ]
     then
        echo $iden"="$val
        found=1
        break
     fi
  done
  if [ $found -eq 0 ]
  then
     echo $iden"="$temp
  fi
done

exit 0