bash ${^^}

hbmhalley

1. 
   
2. $ b=abcd
   
3. 
   
4. $ echo ${b^a} # O
   
5. Abcd
   
6. 
   
7. $ echo ${b^ab} # X
   
8. abcd
   
9. 
   
10. $ echo ${b^d} # X
    
11. abcd
    
12. 
    
13. $ echo ${b^^d} # O
    
14. abcD
    
15. 
    
16. $ echo ${b^^cd} # X
    
17. abcd
    
18. 
    
19. $ echo ${b%d} # O
    
20. abc
    
21. 
    
22. $ bash --version
    
23. GNU bash, version 4.1.10(4)-release (i686-pc-cygwin)
    

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为什么三个标 X 的没有成功替换成大写？

seesea2517

这么高级的功能没用过呢，看来我是没机会用了……

1. [seesea@UC ~]$ b=abcd
   
2. [seesea@UC ~]$ echo ${b^a}
   
3. -bash: ${b^a}: bad substitution
   
4. [seesea@UC ~]$ echo ${b^^a}
   
5. -bash: ${b^^a}: bad substitution
   
6. [seesea@UC ~]$ bash --version
   
7. GNU bash, version 3.2.25(1)-release (i686-redhat-linux-gnu)
   
8. Copyright (C) 2005 Free Software Foundation, Inc.
   
9. 
   

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1. seesea@UC ~/桌面
   
2. $ b=abcde
   
3. 
   
4. seesea@UC ~/桌面
   
5. $ echo ${b^a}
   
6. bash: ${b^a}: bad substitution
   
7. 
   
8. seesea@UC ~/桌面
   
9. $ bash --version
   
10. GNU bash, version 2.05b.0(1)-release (i686-pc-cygwin)
    
11. Copyright (C) 2002 Free Software Foundation, Inc.

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V_客

1. 站个楼 下个bash 4看看去

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blackold

bash 4 新功能吧，还没用过。

hbmhalley

@seesea2517
@V_客
@blackold

大家平时都在什么环境下？如果有包管理工具的话应该不会长时间不更新吧

Shell_HAT

${parameter^pattern}        ${parameter^^pattern}        ${parameter,pattern}        ${parameter,,pattern}               Case modification.  This expansion modifies the case of alphabetic characters in parameter.  The pattern is expanded to produce  a  pattern  just  as  in  pathname               expansion.   The  ^ operator converts lowercase letters matching pattern to uppercase; the , operator converts matching uppercase letters to lowercase.  The ^^ and               ,, expansions convert each matched character in the expanded value; the ^ and , expansions match and convert only the first character in the expanded  value..   If               pattern  is  omitted, it is treated like a ?, which matches every character.  If parameter is @ or *, the case modification operation is applied to each positional               parameter in turn, and the expansion is the resultant list.  If parameter is an array variable subscripted with @ or *, the case modification operation is  applied               to each member of the array in turn, and the expansion is the resultant list.

首先要搞清楚什么是pathname expansion，这一点很关键。
其次要分清^和^^，前者是first，后者是each
你先仔细想想，实在不明白再问。

blackold

回复 5# hbmhalley


    我只是玩，工作很少用到。
   
    之前还及时更新，后来觉得没有必要，就改为必要时才更新——不更新不行了，或者有问题了。

hbmhalley

回复 6# Shell_HAT


    其实我还真不是太清楚，一直当成弱版正则
    但:

       ${parameter%word}
       ${parameter%%word}
              Remove matching suffix pattern.  The word is expanded to produce  a  pattern
              just as in pathname expansion.  If the pattern matches a trailing portion of
              the expanded value of parameter, then the result of  the  expansion  is  the
              expanded  value  of  parameter with the shortest matching pattern (the ``%''
              case) or the longest matching pattern (the ``%%'' case) deleted.  If parame‐
              ter  is  @ or *, the pattern removal operation is applied to each positional
              parameter in turn, and the expansion is the resultant list.  If parameter is
              an  array variable subscripted with @ or *, the pattern removal operation is
              applied to each member of the array in turn, and the expansion is the resul‐
              tant list.

    这也是上面把 ${%}作为参照的原因
    而且 ${b^^abcd} 同样不成功

Shell_HAT

回复 8# hbmhalley


    大小写转换时的pattern只能是一个character，不像子串删除或者替换的时候pattern可以是一个string

hbmhalley

回复 9# Shell_HAT


    这样啊!
    但为什么手册里没发现 .. 难道我E文捉急了?
    &为什么要这么规定? 尤其是 ^^ 好像更适合匹配并替换字符串吧