ReGex，如何找到字符串的第二个实例

Question

如果我想获取“for”和“;”之间的名称这是 NISHER HOSE，你能帮我找到正确的正则表达式吗，因为有不止一个“for”和“;”在字符串中

访问请求需要数据所有者批准#：NISHER HOSE 为 2137352；承包商;经理：MUILLER, TIM (TWM0069)

使用正则表达式 (?<=for).*(?=;) 我得到了错误的匹配 Access Request #: 2137352 for NISHER HOSE; CONTRACTOR - 参见 screenshot on https://www.regextester.com/

谢谢

Answer 1

这里的主要问题是有两个“for”。如果要捕获名称，请使用“:”作为分隔符来捕获第二个“for”:

正则表达式：/:.*for(.+?);/gm
演示：https://regex101.com/r/p3QY0o/1

名称将在第 1 组中捕获。如果您决定使用 lookahead/lookbehind 请记住，这些名称可能受支持也可能不受支持，具体取决于正则表达式引擎。

Answer 2

如果你只想在左边断言 for ，你应该并确保不再匹配 for 和你应该排除匹配; 同时断言右边有一个。

(?<=\bfor )(?:(?!\bfor\b)[^;])+(?=;)

说明

(?<=\bfor ) 在左侧断言 for
(?:(?!\bfor\b)[^;])! 匹配 1+ 次除 ; 之外的任何字符，如果从当前位置开始不直接跟随 for 被单词边界包围
(?=;)直接在右边断言;

Regex demo

Answer 3

使用

(?<=\bfor )(?![^;]*\bfor\b)[^;]+

参见proof。

说明

--------------------------------------------------------------------------------
  (?<=                     look behind to see if there is:
--------------------------------------------------------------------------------
    \b                       the boundary between a word char (\w)
                             and something that is not a word char
--------------------------------------------------------------------------------
    for                      'for '
--------------------------------------------------------------------------------
  )                        end of look-behind
--------------------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
    [^;]*                    any character except: ';' (0 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    \b                       the boundary between a word char (\w)
                             and something that is not a word char
--------------------------------------------------------------------------------
    for                      'for'
--------------------------------------------------------------------------------
    \b                       the boundary between a word char (\w)
                             and something that is not a word char
--------------------------------------------------------------------------------
  )                        end of look-ahead
--------------------------------------------------------------------------------
  [^;]+                    any character except: ';' (1 or more times
                           (matching the most amount possible))

ReGex，如何找到字符串的第二个实例

ReGex, How to find second instance of string

regex

regex-greedy