Bash的最后一个索引

问题描述：

对不起，我很抱歉，但是我似乎无法解决这个问题.

Sorry for the lame bash question, but I can't seem to be able to work it out.

我有以下简单情况:

我有像artifact-1.2.3.zip

我想在连字符和点的最后一个索引(都是排他的)之间得到一个子字符串.

I would like to get a sub-string between the hyphen and the last index of the dot (both exclusive).

我的bash技能不太强.我有以下内容:

My bash skill are not too strong. I have the following:

a="artifact-1.2.3.zip"; b="-"; echo ${a:$(( $(expr index "$a" "$b" + 1) - $(expr length "$b") ))}

制作:

1.2.3.zip

如何也删除.zip部分?

答

$ a="artifact-1.2.3.zip"; a="${a#*-}"; echo "${a%.*}"

只要

"# 模式"与$a的开始相匹配，就会删除模式. pattern 的语法类似于文件名匹配中使用的语法. 就我们而言，

‘#pattern’ removes pattern so long as it matches the beginning of $a. The syntax of pattern is similar to that used in filename matching. In our case,

*是任意字符序列.
-表示文字破折号.
因此，#*-匹配直到 first 破折号的所有内容.
因此${a#*-}可以扩展为$a可以扩展的范围，除了从扩展中删除了artifact-之外，留下我们1.2.3.zip.

* is any sequence of characters.
- means a literal dash.
Thus #*- matches everything up to, and including, the first dash.
Thus ${a#*-} expands to whatever $a would expand to, except that artifact- is removed from the expansion, leaving us with 1.2.3.zip.

类似地，只要与扩展的 end 相匹配，"% 模式"就会删除模式. 就我们而言，

Similarly, ‘%pattern’ removes pattern so long as it matches the end of the expansion. In our case,

.文字点.
*任何字符序列.
因此%.*是包括字符串末尾的 last 点在内的所有内容.
因此，如果$a扩展为1.2.3.zip，然后${a%.*}扩展为1.2.3.

. a literal dot.
* any sequence of characters.
Thus %.* is everything including the last dot up to the end of the string.
Thus if $a expands to 1.2.3.zip, then ${a%.*} expands to 1.2.3.

工作完成.

此手册页的内容如下(至少在我的计算机上为YMMV):

The man page content for this is as follows (at least on my machine, YMMV):


       ${parameter#word}
       ${parameter##word}
              The word is expanded to produce a pattern just  as  in  pathname
              expansion.  If the pattern matches the beginning of the 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 parameter 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 resultant
              list.

       ${parameter%word}
       ${parameter%%word}
              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 pat-
              tern (the ``%'' case)  or  the  longest  matching  pattern  (the
              ``%%''  case)  deleted.   If  parameter  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 resultant list.

HTH！

编辑

对@ x4d表示感谢，以获取详细的答案. 仍然认为人们应该使用RTFM. 如果他们不理解手册，然后发布另一个问题.

Kudos to @x4d for the detailed answer. Still think people should RTFM though. If they don't understand the manual, then post another question.

Bash的最后一个索引

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