thing-at-point库用来快去获取光标下的元素，比如symbol, list, sexp, defun,
filename, url, email, word, sentence, whitespace,
line, and page。

(require 'thingatpt)
(thing-at-point 'sentence)

这样就可以获取光标下的句子了。

thing-at-point还有很多实用函数，比如thing-at-point-url-at-point可以获取光标下的链接。

参考地址