括号$ {} $(),$ []在bash区别和用法 [英] Brackets ${}, $(), $[] difference and usage in bash
问题描述
猛砸包含不同的括号和他们用不同的方式。能否请您解释一下COM prehensively是 $ {}
, $()
和<$ C之间的差异$ C> $ [] ?
在那里他们在bash使用吗?什么是他们的主要目的是什么?
Bash contains different braces and they used differently. Could you please explain comprehensively what is difference between ${}
, $()
and $[]
?
Where they are used in bash? What is their main purpose?
推荐答案
关键词是 shell扩展
!所以我强烈建议你看看在你的bash参考手册中的部分 shell扩展
。
The keyword is shell expansion
! So i highly recommend you to read the section Shell Expansions
in your bash reference manual.
您可以在线访问这一部分[1]。
You can access this section online [1].
的下列规定形式的名称是:
The names of the following stated forms are:
-
$ {}
参数扩展 -
$()
命令替换
${}
Parameter expansion$()
Command substitution
表格 $ []
未在说明书中说明实际,所以我不会使用它。
the form $[]
isn't actually stated in the manual so i wouldn't use it.
[1] http://www.gnu.org /software/bash/manual/bashref.html#Shell-Expansions
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