regex - Perl 字符串模式匹配的负正则表达式

Question

我有这个正则表达式:

if($string =~ m/^(Clinton|[^Bush]|Reagan)/i)
  {print "$string\n"};

我想与克林顿和里根匹配，但不想与布什匹配。

它不起作用。

Answer 1

你的正则表达式不起作用，因为 [] 定义了一个字符类，但你想要的是一个前瞻:

(?=) - Positive look ahead assertion foo(?=bar) matches foo when followed by bar
(?!) - Negative look ahead assertion foo(?!bar) matches foo when not followed by bar
(?<=) - Positive look behind assertion (?<=foo)bar matches bar when preceded by foo
(?<!) - Negative look behind assertion (?<!foo)bar matches bar when NOT preceded by foo
(?>) - Once-only subpatterns (?>\d+)bar Performance enhancing when bar not present
(?(x)) - Conditional subpatterns
(?(3)foo|fu)bar - Matches foo if 3rd subpattern has matched, fu if not
(?#) - Comment (?# Pattern does x y or z)

所以尝试一下:(？!布什)