请解释这个正则表达式

Question

  ^[[:space:]]*@

我无法弄清楚[[:space:]]*上面正则表达式的含义.请帮忙,谢谢!

Answer 1

[:space:]是一个POSIX character class匹配All whitespace characters, including line breaks的单词.

换句话说[:space:]是相同的\s(因为Perl 5.18 ^[1])

http://www.regular-expressions.info/posixbrackets.html

1. 在5.18之前,垂直标签(U + 000B)未包括在内\s.

   $ diff -u <( unichars -au '\s' ) <( unichars -au '[[:space:]]' ) \
       && echo 'no difference'
   --- /dev/fd/63  2013-05-21 22:08:03.000000000 -0400
   +++ /dev/fd/62  2013-05-21 22:08:03.000000000 -0400
   @@ -1,5 +1,6 @@
     ---- U+00009 CHARACTER TABULATION
     ---- U+0000A LINE FEED (LF)
   + ---- U+0000B LINE TABULATION
     ---- U+0000C FORM FEED (FF)
     ---- U+0000D CARRIAGE RETURN (CR)
     ---- U+00020 SPACE