#!/usr/bin/perl

print "Content-type: text/html\n\n";

#List14_09
#Read fixed length records from a file
#1 Verify the record length
$NL = "\n";
$DC = sprintf("%c", 236);   #Special character
$TW = 63;                  #Line with
$DL = sprintf( "%63s", $NL . $DC x $TW); #top and bottom lines

$Record = "A3 A20 A20 A20";
$RecordLength = length(pack($Record));
print "$NL  Record length: $RecordLength";

#2 Open the data file--read only
open(FILE, "lab8_tcpdump2.txt") || die "\n Cannot access file.";

#3  Set the file at the end (option 2)
    seek(FILE, 0 , 2);
#  Obtain the length
    $FileLength =  tell(FILE);
    print "$NL  The length of the file is $FileLength";
    $NumOfRecords = int($FileLength/$RecordLength);
    print("$NL  $NumOfRecords records are in the file.");
  print($DL);
    print "$NL>>Press <Enter>";

#4 Use seek and read to obtain records by multiplying by length
    for($Itr = 0; $Itr < $NumOfRecords; $Itr++){
       $Count = $Itr + 1;
       $AnyChar = <STDIN>;
       seek(FILE, $Itr * $RecordLength, 0);
       read(FILE, $LineRead, $RecordLength, 0);
       print(" >> $Count $LineRead");
    }
 print($DL);

#5 Use seek and record length to find a record for display
    seek(FILE, 0, 0);
    print("$NL $NL Enter a record number. $NL  >>");
    $LineNumber = <STDIN>;
    # print "$NL The record length: $RecordLength $NL";
    $SeekPoint = ($LineNumber - 1)* $RecordLength;
    seek(FILE, $SeekPoint, 0);
    read(FILE, $LineRead, $RecordLength);
    # print "$NL The line read is: $NL";
    print "$LineRead\n";

    close(FILE) || "Cannot close file: $!";

print "\n";
print "\n";

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