RegExp:在另一个模式之前发生的模式的最后一次出现

Question

我想采用在另一个文本模式之前发生的文本模式.

例如,我有这样的文字:

code 4ab6-7b5
Another lorem ipsum
Random commentary.

code f6ee-304
Lorem ipsum text 
Dummy text

code: ebf6-649
Other random text
id-x: 7662dd41-29b5-9646-a4bc-1f6e16e8095e

code: abcd-ebf
Random text
id-x: 7662dd41-29b5-9646-a4bc-1f6e16e8095e

我想采取在第一次code出现之前发生的最后一次id-x(这意味着我想获取代码ebf6-649)

我怎么能用regexp做到这一点？

Answer 1

如果你的正则表达式支持前瞻,你可以使用这样的解决方案

^code:[ ]([0-9a-f-]+)(?:(?!^code:[ ])[\s\S])*id-x

你可以在捕获号码中找到你的结果1.

它是如何工作的？

^code:[ ]           # match "code: " at the beginning of a line, the square 
                    # brackets are just to aid readability. I recommend always
                    # using them for literal spaces.

(                   # capturing group 1, your key
  [0-9a-f-]+        # match one or more hex-digits or hyphens
)                   # end of group 1

(?:                 # start a non-capturing group; each "instance" of this group
                    # will match a single arbitrary character that does not start
                    # a new "code: " (hence this cannot go beyond the current
                    # block)

  (?!               # negative lookahead; this does not consume any characters,
                    # but causes the pattern to fail, if its subpattern could
                    # match here

    ^code:[ ]       # match the beginning of a new block (i.e. "code: " at the
                    # beginning of another line

  )                 # end of negative lookahead, if we've reached the beginning
                    # of a new block, this will cause the non-capturing group to
                    # fail. otherwise just ignore this.

  [\s\S]            # match one arbitrary character
)*                  # end of non-capturing group, repeat 0 or more times
id-x                # match "id-x" literally

这个(?:(?!stopword)[\s\S])*模式让你尽可能地匹配,而不会超越另一个事件stopword.

请注意,您可能必须使用某种形式的多行模式^来匹配行的开头.该^避免假阴性,如果你是很重要的random text包含open:.

工作演示(使用Ruby的正则表达式,因为我不确定你最终将使用哪一个)