bash - bash中括号${}、$()、$[]的区别及用法

Question

Bash 包含不同的大括号，它们的使用方式也不同。您能否全面解释一下和之间${}的区别？它们在 bash 中用在哪里？他们的主要目的是什么？$()$[]

Answer 1

The keyword is shell expansion! So i highly recommend you to read the section Shell Expansions in your bash reference manual.

You can access this section online [1].

The names of the following stated forms are:

• ${} Parameter expansion
• $() Command substitution

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