巴什阵列和负下标，是或否？ [英] Bash arrays and negative subscripts, yes or no?

问题描述

借助 GNU bash的手动告诉我

如果任何变量分配的索引数组会自动创建
  使用语法

An indexed array is created automatically if any variable is assigned to using the syntax

name[subscript]=value

  
  

下标作为一个算术前pression处理必须
  计算为一个数字。如果标计算为一个数字小于
  零，它被用作从一个偏移大于阵列的
  最大指数（所以-1 subcript指的最后一个元素
  阵列）。

The subscript is treated as an arithmetic expression that must evaluate to a number. If subscript evaluates to a number less than zero, it is used as an offset from one greater than the array’s maximum index (so a subcript of -1 refers to the last element of the array).

所以我想我会给它一个尝试，得到以下结果：

So I figure I will give it a try and get the following result:

$ muh=(1 4 'a' 'bleh' 2)
$ echo $muh
1
$ echo ${muh[*]}
1 4 a bleh 2    # so far so good so now I'll try a negative ...
$ echo ${muh[-1]}
-bash: muh: bad array subscript  # didn't go as planned!

难道我做错了什么，或者是网站错误的，或者是GNU的bash，从我的CentOS下运行bash的有什么不同？谢谢！

Did I do something wrong, or is the website wrong, or is gnu bash that different from the bash I am running under CentOS? Thanks!

推荐答案

如果你只是想在最后一个元素

If you just want the last element

$ echo ${muh[*]: -1}
2

如果你想倒数第二个元素

If you want next to last element

$ echo ${muh[*]: -2:1}
bleh

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