#!/bin/bash
#<pre><b>
# Script     : idiff
# Version    : 1.0
# Author     : Roland Rashleigh-Berry
# Date       : 21-Oct-2004
# Purpose    : To compare files with "diff" but saying which lines to ignore
# SubScripts : none
# Notes      : Refer to documentation on diff (man diff). Note that this utility
#              has pattern matching and substitution in it to mask lines you
#              wish not to compare. You need to supply this to the -i option.
#              You should supply a regular expression and this would normally
#              start with the ^ character signifying the beginning of a line.
#              The rest of the line will be automatically ignored. See usage
#              notes.
# Usage      : idiff -i "^OUTPUT" file1.ext file2.ext > differ.txt
#              idiff -i "^Report No" file1.ext file2.ext > differ.txt
#===============================================================================
# OPTIONS:
#-opt- -------------------------------description-------------------------------
#  i   (value)  Ignore lines matching this regular expression
#===============================================================================
# PARAMETERS:
#-pos- -------------------------------description-------------------------------
#  1   First file to compare
#  2   Second file to compare
#===============================================================================
# AMENDMENT HISTORY:
# init --date-- mod-id ----------------------description------------------------
# 
#===============================================================================
# This is public domain software. No guarantee as to suitability or accuracy is
# given or implied. User uses this code entirely at their own risk.
#===============================================================================

usage () {
  echo "Usage: idiff -i <regular expression for lines to ignore> file1.ext file2.ext" 1>&2
  exit 1
}

# Default value for Ignore lines regular expression
valuei=


# "case" statement for action to take on selected options
while getopts "i:" param ; do
  case $param in
   "?") # bad option supplied
        usage
        ;;
   "i") # (value) Ignore these lines
        valuei=$OPTARG
        ;;
  esac
done


# shift to bring first parameter to position 1
shift $(($OPTIND - 1))


if [ $# -ne 2 ] ; then
  echo "Error: (idiff) You must specify two files to compare" 1>&2
  usage
fi


echo 
echo '============================================================================================='
echo " < = $1    > = $2"
echo '============================================================================================='
if [ -n "$valuei" ] ; then
  sed "s/${valuei}.*//"    $1 > ~/file1_$$.tmp
  sed "s/${valuei}.*//"    $2 > ~/file2_$$.tmp
else
  cp    $1 ~/file1_$$.tmp
  cp    $2 ~/file2_$$.tmp
fi
diff -b ~/file1_$$.tmp ~/file2_$$.tmp

rm -f ~/file1_$$.tmp ~/file2_$$.tmp