Using mysql_real_escape_string

OK this should be really obvious but I just can't figure it out. I have a script that opens a file, reads it line by line and inserts the contents into a database. I know I need to use mysql_real_escape_string to properly escape the contents but I don't know where exactly to place it in the script. Any pointers, liks, guidance etc gratefully received! Alan *CODE:* //Input check file $filename="input/w2wcheck.txt"; echo "<h2>$filename</h2>"; # Open file $fptr = fopen($filename, "r"); # Check if file is open if($fptr) { $current_line = fgets($fptr,4096); $retval = TRUE;

       echo "open";
       while($current_line && $retval)

{

       list(
$UNIQUEID    ,

$ASSETID , $CNF

                     ) = explode(",",$current_line);
         $query = "insert into invw2wcheck (
UNIQUEID    ,

ASSETID , CNF

          )

values ( '$UNIQUEID', '$ASSETID ', '$CNF' )";

                  $result = mysql_query($query);
                                                                                                        if(!$result)
           {
                echo "<h1>Processing halted due to Error No:";
               echo mysql_errno().": ";
               echo mysql_error()."<BR>";
               echo "</h1>";
               $retval = FALSE;
               die;
           }
           elseif(mysql_affected_rows() == 0)
       {
         $retval = FALSE;
               die;
       }

     $current_line = fgets($fptr,4096);

}

}     

fclose($fptr);