如何使用Perl regexp匹配字符串末尾/开头的空格或环绕的单词? [英] How to match word surronded by spaces OR at the end / beginning of the string using Perl regexp?

问题描述

我想找到与我的正则表达式匹配的序列，如果它们位于由空格包围的字符串中间、结尾或开头，或者是字符串中唯一的内容.

I want to find sequences matching my regexp should they be in the middle of the string surrounded by spaces, in the end or beginning or be the only thing in a string.

示例:让我们假设序列 'qwe45rty' 是我们正在寻找的.我希望能够对所有这些字符串都有积极的态度:

Example: Let's assume the sequence 'qwe45rty' is what we are looking for. I want to be able to get positive on all of these strings:

'qwe45rty' 'qwe45rty blabla' 'smth qwe45rty blabla' 'smth qwe45rty' ' qwe45rty '

但这些都不是:

'aaqwe45rty' 'qwe45rtybb' 'aaqwe45rtybb'

我想出的最好的东西是这样的:

Best what I came up with is smth like this:

if ( ($a =~ /\s+$re\s+/) or
     ($a =~ /^$re\s+/)   or
     ($a =~ /\s+$re$/)   or
     ($a =~ /^$re$/)        )
{
    # do stuff
}

这不是最好的方法:)

有什么建议吗?

推荐答案

您可以在正则表达式中执行或:

You can do the or inside the regex:

/(^|\s+)qwe45rty(?=\s+|$)/

regex101

请注意，第二组是正向前瞻 (?=)，因此它检查是否有空格，但不会消耗它.这样，正则表达式可以匹配字符串的两次连续出现并给出准确的匹配计数.

Note that the second group is a positive lookahead (?=) so it checks for whitespace, but doesn't consume it. That way the regex can match two consecutive occurrences of the string and give an accurate match count.

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