typeset/$[ ] operation notes

typeset can also implement calculations

[root@linhexiao shellTest]# typeset -i a=1 b=3
[root@linhexiao shellTest]# a=a+b
[root@linhexiao shellTest]# echo $a
4
[root@linhexiao shellTest]# a=a*b
[root@linhexiao shellTest]# echo $a
12

 $[ ] can also be calculated

1) As long as the expression is legal, it can be calculated
[root@linhexiao shellTest]# echo $[2+3]
5
[root@linhexiao shellTest]# echo $[2+ 3]
5
[root@linhexiao shellTest]# echo $[ 2+ 3]
5
2) $[] cannot calculate decimals
[root@linhexiao shellTest]# echo $[ 2.2+ 3]
bash: 2.2+ 3: syntax error: invalid arithmetic operator (error token is ".2+ 3")
[root@linhexiao shellTest]# echo $[ 2+ 3]
5
[root@linhexiao shellTest]# echo $[ 2- 3]
-1
[root@linhexiao shellTest]# echo $[ 2* 3]
6
[root@linhexiao shellTest]# echo $[ 2** 3]
8
[root@linhexiao shellTest]# echo $[ 2/ 3]
0