这里是计算

$[ ... ]
integer expansion.
Evaluate integer expression between $[ ].

a=3
b=7
echo $[$a+$b] # 10
echo $[$a*$b] # 21

Note that this usage is deprecated, and has been replaced by the (( ... )) construct


【 在 Dazzy 的大作中提到: 】
: 很多shell里，[ 其实就是test的别名，$[]就是判断方括号中表达式是否为真。
: #发自zSMTH@Redmi Note 11
--
FROM 117.173.158.*