Function: TRIM-STRING

Source

(defun trim-string (string &optional (char '(#\Space #\Tab #\Newline
                                             #\Return #\Linefeed)))
  (let ((chars (ensure-list char)))
    (subseq string 
	    (loop for index upfrom 0 below (length string)
		  when (not (member (aref string index) chars)) 
		    do (return index)
		  ;; if we get here we're trimming the entire string
                  finally (return-from trim-string ""))
	    (loop for index downfrom (length string)
		  when (not (member (aref string (1- index)) chars))
		    do (return index)))))