Shell numerical calculation

In the shell, especially in the shell loop, some expressions may be used to operate

This requirement can be accomplished using the expr command, such as:

x=$ (expr $a + 1)

Completed the calculation of the sum of $ A and 1 and assigned the value to X

Similar operators also have

$a | $b if $ A nonzero then the result of the operation takes a $ A value, otherwise take $b value

$a & $b As long as one expression is 0, the result of the operation is 0, otherwise equal to $ A

Plus +,-, *,/,%, =, <=, >=,! = etc Operations

Note that the $a + $b is illegal and must be strictly spaced on both sides of the operator: $a + $b to get the results.

Shell numerical calculation