sub compare_avs  {
	
	# find the name of the file created at last running

open(DIFF_OLD, $path.$agent."/AVS/DIFF_OLD.txt") || die "ERROR: Unable to open ".$agent." - DIFF_OLD_FILE.txt";
	$DIFF_OLD = <DIFF_OLD>;
	close DIFF_OLD;

        # check if file exists if not, write contents of new file to $data
	
	if ($DIFF_OLD eq "")  {
		print "DIFF_OLD file - Does not exist\n"; 
		open(DIFF, "$EMAILfile") || die "ERROR: Unable to open ".$agent." - ".$EMAILfile;
		while(my @AVSn = split/\n/, <DIFF>) {
			foreach $AVn(@AVSn) {
				$data = $data.$AVn."\n";
			}
		}
		close DIFF;
	}  else  {
		print "DIFF_OLD file - ".$DIFF_OLD."\n"; sleep(5);
		
                # write contents of old file to an array

		open(CHECK, $path.$agent."/AVS/".$DIFF_OLD) || die  "ERROR: Unable to open ".$agent." - ".$DIFF_OLD;
		@AVSo = <CHECK>;
		close CHECK;
		
		# write contents of new file to array and loop through it

                open(DIFF, "$EMAILfile") || die "ERROR: Unable to open ".$agent." - ".$EMAILfile;
		while(my @AVSn = split/\n/, <DIFF>) {
			foreach $AVn(@AVSn) {
				$AVSchecked = 0;
				($SIDn,$DATEn,$AVSn,$NOTHINGn,$EPOCHDATEn,$SERIALn) = split/::/,$AVn;
				        # compare contents of old list with new list

                                        foreach $AVo(@AVSo)  {
					$AVo =~ s/\n|\r//g;
					($SIDo,$DATEo,$AVSo) = split/::/,$AVo;
					if ($SIDn eq $SIDo && $DATEn eq $DATEo && $AVSn ne $AVSo)  {
						$data = $data.$SIDn."::".$DATEn."::".$AVSn."::::".$EPOCHDATEn."::".$SERIALn."\n";
						print $SIDn."::".$DATEn."::".$AVSn."::::".$EPOCHDATEn."::".$SERIALn."\n";
						$AVSchecked = 1;
					}  elsif  ($SIDn eq $SIDo && $DATEn eq $DATEo && $AVSn eq $AVSo)  {
						$AVSchecked = 1;
					}
				}
				if ($AVSchecked == 0)  {
					$data = $data.$SIDn."::".$DATEn."::".$AVSn."::::".$EPOCHDATEn."::".$SERIALn."\n";
					print $SIDn."::".$DATEn."::".$AVSn."::::".$EPOCHDATEn."::".$SERIALn."\n";
				}
			}
		}
		close DIFF;
	}
	
	$DIFF_OLD_filex = $path.$agent."/AVS/DIFF_OLD.txt";
	open(DIFF_OLD,">".$path.$agent."/AVS/DIFF_OLD.txt") || die "ERROR: Unable to open ".$agent." - DIFF_OLD_FILE.txt to update";
	print DIFF_OLD $agent.$$.".AVS";
	close DIFF_OLD;
	
}