```
```**
let**

```
```*
expressions*

or
```
```**
((**

```
```*
expressions*

```
```**
))**

Korn shell only. Perform arithmetic as specified by one or more integer ```
```*
expressions*

.
```
```*
expressions*

consist of numbers, operators, and
shell variables (which don't need a preceding ```
$
```

).
Expressions must be quoted if they contain spaces or other special characters.
The **
(( ))**
form does the quoting for you.
For more information and examples,
see "Arithmetic Expressions" earlier in this section.
See also **
expr**
in Section 2.

Each example below adds 1 to variable **
i**
.

i=`expr $i + 1`
let i=i+1
let "i = i + 1"
(( i = i + 1 ))