正则表达式多个字符但没有特定字符串 [英] Regex multiple characters but without specific string

问题描述

我有以下几行:

• 可选:否"，
• 可选:两个非空白字符，
• 几个非空白字符.

我想从包含以下内容的每一行中捕获字符串:

I want to capture string from each line which consist of:

• 可选:两个非空白字符(但不是无"部分)，
• 几个非空白字符.

示例行:

ab123
ab 123
no abc123
no ab 123

我想捕捉:

ab123
ab 123
abc123
ab 123

我的正则表达式(仅适用于没有no"的示例).

My regexp (works only for examples without "no ").

^
  (?! no \s) # not "no "
  ( # match it
    (?: \S{1,2} \s )? # optional: 1-2 non whitespace characters and one space, BUT NOT GET "no " (it doesn't works)
    \S+ # non whitespace characters
  )
$

在线示例(4 个单元测试):https://regex101.com/r/70soe2/1

Example online (4 unit tests): https://regex101.com/r/70soe2/1

也许我应该以某种方式使用否定前瞻(?! no \\s) 或否定(?<! no \\s)?但是不知道怎么用.

Maybe should I use negative look ahead (?! no \\s) or negative look behind (?<! no \\s) in some way? But I don't know how to use it.

推荐答案

在这里你不能真正依赖环视，你需要使用可选的 no + 字符串的空白部分.

You cannot actually rely on lookarounds here, you need to consume the optional no + whitespace part of the string.

最好在开始时使用非捕获可选组:

^
  (?: no \s)? # not "no "
  ( # capture it
    (?: \S{1,2} \s )? # optional: 1-2 non whitespace characters and one space, BUT NOT GET "no " (it doesn't works)
    \S+ # non whitespace characters
  )
$

查看正则表达式演示

您需要的值在第 1 组内.

The value you need is inside Group 1.

如果您的正则表达式引擎支持 \K 构造，您可以使用它来代替:

If your regex engine supports \K construct, you may use this instead:

^
  (?:no \s \K)? # not "no "
  ( # match it
    (?: \S{1,2} \s )? # optional: 1-2 non whitespace characters and one space, BUT NOT GET "no " (it doesn't works)
    \S+ # non whitespace characters
  )
$

(?:no \s \K)? 中的 \K 将省略匹配值中消耗的字符串部分，您将得到预期的结果一个完整的匹配值.

The \K in (?:no \s \K)? will omit the consumed string part from the match value, and you will get the expected result as a whole match value.

查看正则表达式演示

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