"=~"是什么含义吗？

GB_juno

今天看到shell里面有这么=~符号，但是找来找去也没找到出处（貌似在ABS里面也没有），好像跟正则表达式有关

1. [[ ! ${DISTRO} =~ (precise|saucy|trusty|7.0|wheezy|sid|testing|jessie|f19|f20|rhel6) ]]

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这个符号是什么意思吗？从哪里能够找到最新的符号解释文档?

bikkuri

[[ ! ${DISTRO} =~ (precise|saucy|trusty|7.0|wheezy|sid|testing|jessie|f19|f20|rhel6) ]]
字符串$DISTRO中不含有precise|saucy|trusty|7.0|wheezy|sid|testing|jessie|f19|f20|rhel6这11个字符串中的任何一个

rdcwayx

这个是具体解释：

1. An additional binary operator, ‘=~’, is available, with the same precedence as ‘==’ and ‘!=’. When it is used, the string to the right of the operator is considered an extended regular expression and matched accordingly (as in regex3)). The return value is 0 if the string matches the pattern, and 1 otherwise. If the regular expression is syntactically incorrect, the conditional expression’s return value is 2. If the shell option nocasematch (see the description of shopt in The Shopt Builtin) is enabled, the match is performed without regard to the case of alphabetic characters. Any part of the pattern may be quoted to force it to be matched as a string. Substrings matched by parenthesized subexpressions within the regular expression are saved in the array variable BASH_REMATCH. The element of BASH_REMATCH with index 0 is the portion of the string matching the entire regular expression. The element of BASH_REMATCH with index n is the portion of the string matching the nth parenthesized subexpression.

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如果你看过我的另一个帖子的话，就对=~ 不会陌生了。

http://bbs.chinaunix.net/thread-4125147-1-1.html

seesea2517

它是bash内建测试命令的操作符，所以要在bash man里找：
man bash:

1.        [[ expression ]]
   
2.               Return a status of 0 or 1 depending on the evaluation of the conditional expression expression.  Expres-
   
3.               sions are composed of the primaries described below under CONDITIONAL EXPRESSIONS.  Word  splitting  and
   
4.               pathname  expansion are not performed on the words between the [[ and ]]; tilde expansion, parameter and
   
5.               variable expansion, arithmetic expansion, command substitution, process substitution, and quote  removal
   
6.               are performed.  Conditional operators such as -f must be unquoted to be recognized as primaries.
   
7. 
   
8.               When used with [[, The < and > operators sort lexicographically using the current locale.
   
9. 
   
10.               When  the  == and != operators are used, the string to the right of the operator is considered a pattern
    
11.               and matched according to the rules described below under Pattern Matching.  If the shell option  nocase-
    
12.               match  is  enabled,  the  match  is  performed without regard to the case of alphabetic characters.  The
    
13.               return value is 0 if the string matches (==) or does not match (!=) the pattern, and 1  otherwise.   Any
    
14.               part of the pattern may be quoted to force it to be matched as a string.
    
15. 
    
16.               An  additional  binary  operator,  =~,  is available, with the same precedence as == and !=.  When it is
    
17.               used, the string to the right of the operator is considered an extended regular expression  and  matched
    
18.               accordingly (as in regex(3)).  The return value is 0 if the string matches the pattern, and 1 otherwise.
    
19.               If the regular expression is syntactically incorrect, the conditional expression鈥檚 return  value  is  2.
    
20.               If  the shell option nocasematch is enabled, the match is performed without regard to the case of alpha-
    
21.               betic characters.  Any part of the pattern may be quoted to force it to be matched as  a  string.   Sub-
    
22.               strings  matched  by  parenthesized  subexpressions within the regular expression are saved in the array
    
23.               variable BASH_REMATCH.  The element of BASH_REMATCH with index 0 is the portion of the  string  matching
    
24.               the  entire  regular  expression.  The element of BASH_REMATCH with index n is the portion of the string
    
25.               matching the nth parenthesized subexpression.

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GB_juno

@bikkuri
@rdcwayx
@seesea2517

谢谢三位大神指点~，已经明白了。
找了很多资料都没找到，还是CU多大神

jason680

回复 5# GB_juno

study basic shell skill in top of this forum


http://bbs.chinaunix.net/forum-24-1.html

Shell版新手导航    Shell基础二十篇    Shell十三问    Shell综合水平测试    Linux相关书籍    Shell版精华帖合集    Shell索引树


Linux相关书籍  http://bbs.chinaunix.net/thread-1776727-1-1.html
(中文版)  ABS_Guide_cn.pdf(pdf格式).tar.bz2
  
  ...
  =~ 用于正则表达式,这个操作将在正则表达式匹配部分讲解,只有version3 才支持.
  ...
  =~ 正则表达式(Regular Expression) 匹配操作符在双方括号(double brackets)
测试表达式中使用. (Perl 也有一个相似的操作符.)
   

英文版（6.2）：
Advanced Bash-Scripting Guide_6.2.pdf

=~
regular expression match. This operator was introduced with version 3 of Bash.

GB_juno

@jason680
谢谢，之前在ABS里面没有看到后面37章..惭愧