Function: string-prefix-p

string-prefix-p is a byte-compiled function defined in subr.el.gz.

Signature

(string-prefix-p PREFIX STRING &optional IGNORE-CASE)

Documentation

Return non-nil if STRING begins with PREFIX.

PREFIX should be a string; the function returns non-nil if the characters at the beginning of STRING compare equal with PREFIX. If IGNORE-CASE is non-nil, the comparison is done without paying attention to letter-case differences.

Other relevant functions are documented in the string group.

View in manual

Probably introduced at or before Emacs version 24.1.

Shortdoc

;; string
(string-prefix-p "foo" "foobar")
    => t

Source Code

;; Defined in /usr/src/emacs/lisp/subr.el.gz
(defun string-prefix-p (prefix string &optional ignore-case)
  "Return non-nil if STRING begins with PREFIX.
PREFIX should be a string; the function returns non-nil if the
characters at the beginning of STRING compare equal with PREFIX.
If IGNORE-CASE is non-nil, the comparison is done without paying attention
to letter-case differences."
  (declare (side-effect-free t))
  (let ((prefix-length (length prefix)))
    (if (> prefix-length (length string)) nil
      (eq t (compare-strings prefix 0 prefix-length string
			     0 prefix-length ignore-case)))))