**@**

*variable*
**=**

*expression*
**@**

*variable*
**[**

*n*
**] =**

*expression*
**@**

Assign the value of the arithmetic *expression*
to *variable*
, or to the *n*
th element of *variable*
if the index *n*
is specified. With no *variable*
or *expression*
specified, print the values of all shell variables (same as `set`
). Expression operators as well as examples are listed in the earlier section "Expressions." Two special forms are also valid:

**@**

*variable*
**++**

Increment *variable*
by one.

**@**

*variable*
**--**

Decrement *variable*
by one.