正则表达式求解

chenzhanyiczy

man regex

       Within  a  bracket  expression, a collating element (a character, a multi-character sequence that collates as if it were a single character, or a collating-sequence name
       for either) enclosed in "[." and ".]" stands for the sequence of characters of that collating element.  The sequence is a single  element  of  the  bracket  expression’s
       list.  A bracket expression containing a multi-character collating element can thus match more than one character, for example, if the collating sequence includes a "ch"
       collating element, then the RE "[[.ch.]]*c" matches the first five characters of "chchcc".


       Within a bracket expression, a collating element enclosed in "[=" and "=]" is an equivalence class, standing for the sequences of characters of  all  collating  elements
       equivalent  to  that  one,  including itself.  (If there are no other equivalent collating elements, the treatment is as if the enclosing delimiters were "[." and ".]".)
       For example, if o and ^ are the members of an equivalence class, then "[[=o=]]", "[[=^=]]", and "[o^]" are all synonymous.  An equivalence class may not(!)  be  an  end-
       point of a range.


一直没搞懂这个[..]是怎么用的？

"collating element" 如果看中文的man翻译就是"归并元素"

egrep、grep、sed、awk貌似都不支持。

以egrep来说：

regex.log：
0000ee0000ll000
0000ex0000ll000

egrep "[[.ee.]]" regex.log
egrep: Invalid collation character

egrep "[[.e.]]" regex.log
0000ee0000ll000
0000ex0000ll000

如果不支持多个字符的形式(即[.多个字符.])，那粗体部分描述的意思是什么？貌似就没有什么意义了。

ps：下面那段的"等价类"就更难理解了，更晦涩。