如何在正则表达式中使用双括号? [英] How to use double brackets in a regular expression?

问题描述

双方括号在正则表达式中是什么意思?我对以下示例感到困惑:

What do double square brackets mean in a regex? I am confused about the following examples:

/[[^abc]]/

/[^abc]/

我正在使用 Rubular 进行测试，但我没有看到双括号和单括号之间的任何区别.

I was testing using Rubular, but I didn't see any difference between the one with double brackets and single brackets.

推荐答案

Posix 字符类

Posix character classes use a [:alpha:] notation, which are used inside a regular expression like:

a> 使用 [:alpha:] 表示法，在正则表达式中使用，例如:

/[[:alpha:][:digit:]]/

You'll need to scroll down a ways to get to the Posix information in the link above. From the docs:

您需要向下滚动以获取以上链接中的 Posix 信息.来自文档:

POSIX bracket expressions are also similar to character classes. They provide a portable alternative to the above, with the added benefit that they encompass non-ASCII characters. For instance, /\d/ matches only the ASCII decimal digits (0-9); whereas /[[:digit:]]/ matches any character in the Unicode Nd category.

POSIX 括号表达式也类似于字符类.它们为上述提供了一种可移植的替代方案，并具有包含非 ASCII 字符的额外好处.例如，/\d/只匹配 ASCII 十进制数字 (0-9)；而/[[:digit:]]/匹配 Unicode Nd 类别中的任何字符.

<块引用>

Ruby 还支持以下非 POSIX 字符类:

Ruby also supports the following non-POSIX character classes:

/[[:word:]]/ - A character in one of the following Unicode general categories Letter, Mark, Number, Connector_Punctuation
/[[:ascii:]]/ - A character in the ASCII character set
# U+06F2 is "EXTENDED ARABIC-INDIC DIGIT TWO"

/[[:digit:]]/.match("\u06F2")    #=> #<MatchData "\u{06F2}">
/[[:upper:]][[:lower:]]/.match("Hello") #=> #<MatchData "He">
/[[:xdigit:]][[:xdigit:]]/.match("A6")  #=> #<MatchData "A6">

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