"=~"是什么含義嗎？

GB_juno

今天看到shell里面有這么=~符號，但是找來找去也沒找到出處（貌似在ABS里面也沒有），好像跟正則表達式有關(guān)

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

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這個符號是什么意思嗎？從哪里能夠找到最新的符號解釋文檔?

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這11個字符串中的任何一個

rdcwayx

這個是具體解釋：

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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如果你看過我的另一個帖子的話，就對=~ 不會陌生了。

http://72891.cn/thread-4125147-1-1.html

seesea2517

它是bash內(nèi)建測試命令的操作符，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

謝謝三位大神指點~，已經(jīng)明白了。
找了很多資料都沒找到，還是CU多大神

jason680

回復(fù) 5# GB_juno

study basic shell skill in top of this forum


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(中文版)  ABS_Guide_cn.pdf(pdf格式).tar.bz2
  
  ...
  =~ 用于正則表達式,這個操作將在正則表達式匹配部分講解,只有version3 才支持.
  ...
  =~ 正則表達式(Regular Expression) 匹配操作符在雙方括號(double brackets)
測試表達式中使用. (Perl 也有一個相似的操作符.)
   

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
謝謝，之前在ABS里面沒有看到后面37章..慚愧