Shell arithmetic calculation $ (())

From shell 13

 

Well, let's introduce the purpose of $ (): it is used for integer calculation.
In bash, the integer operators of $ () generally include the following:
+-*/: Add, subtract, multiply, and divide respectively ".
%: Remainder operation
& | ^! : "And, Or, XOR, not" operations.

 

~ # A = 1
~ # B = 2
~ # Echo $ (a + B ))
3
~ # Echo $ ($ A + $ B ))
3

 

 

~ # Echo $ (a-B ))
-1
~ # Echo $ (A/B ))
0
~ # Echo $ (A * B ))
2

~ # Echo $ (a % B ))
1

 

 

~ # A = 1
~ # B = 3
~ # Echo $ (A & B ))
1
~ # Echo $ (A | B ))
3
~ # Echo $ (a ^ B ))
2
~ # Echo $ ((! B ))
0
~ # Echo $ ((! A ))
0

 

Example:
[Code] $ A = 5; B = 7; C = 2
$ Echo $ (a + B * C ))
19
$ Echo $ (A + B)/C ))
6
$ Echo $ (A * B) % C ))
1 [/Code]
The variable name in $ () can be replaced by the $ symbol before it or not (which can be supported in busybox)Such:
$ ($ A + $ B * $ C) returns 19 results.

 

In addition, $ () can also be used for different carry (such as binary, octal, and hexadecimal) operations, but the output results are all in decimal format (busybox is not supported ):
Echo $(16 # 2a) returns 42 (hexadecimal to decimal)