regex - elisp 中的匹配字符串不返回与字符串匹配匹配的字符串

Question

我有一个问题，在字符串匹配后我无法获得匹配字符串。我认为字符串匹配有效，至少它返回非零，但是当我尝试获取匹配字符串时出现错误。我该怎么做？

失败的功能:

(defun small-test ()
  (string-match "\\([0-9]+\\)-v\\([0-9]+\\).txt" "2011-v9.txt")
  (message (match-string 1))
  )

Answer 1

从 C-h f match-string，我建议你阅读底线:

(match-string NUM &optional STRING)

Return string of text matched by last search. NUM specifies which parenthesized expression in the last regexp. Value is nil if NUMth pair didn't match, or there were less than NUM pairs. Zero means the entire text matched by the whole regexp or whole string. STRING should be given if the last search was by `string-match' on STRING.