Math Extensions in Bash

Bash supports only integer operations and does not support floating-point operations. If you need a floating point operation, you need to use the BC program.
There are two types of mathematical extensions in bash:
$[expression]
Or
$ ((expression))

Example:
$echo $[5+4-2]
7

$echo $[5* (6-2)]
20

var1=100
Var2=50
Var3=45
var4=$ ((var1* (VAR2-VAR3))) #注意: There is no need to add $ in parentheses, as is the case with mathematical operations, it is recommended this way
$echo $var 4

You can also use program/usr/bin/expr to perform integer operations
$EXPR 8 + 3//Note that operators and operands must be separated by spaces

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Math Extensions in Bash