(with-open-file (ifile "key.html" :direction :input)
  (loop for line = (read-line ifile nil)
        while line
        counting 1))

If the loop implementation of your CL system supports extending loop
paths you can even write a loop path that gives you each line in the
file. I have such a thing in my .clinit.

Then you can do:

(loop for line being each line of ifile
      count 1)

If you use the simple loop, you might consider do:

(with-open-file (ifile "/etc/passwd" :direction :input)
  (do ((line (read-line ifile nil) (read-line ifile nil))
       (count 0))
      ((null line) count)
    (incf count)))