Practical UNIX

Arithmetic Integer Calculations

The expr command performs simple integer arithmetic:

$ expr 8 / 3
2
$

Notice that any fractional result is ignored. The general syntax is as follows:

expr integer1 operand integer2

Possible operands for this command are given in Table 6.1.

Table 6.1. expr Operands

Operand	Description
+	Addition
-	Subtraction
\*	Multiplication
/	Integer division (any fraction in the result is dropped)
%	Remainder from a division operation (also called the modulus function)

Notice that the * sign must be enclosed in quotation marks to prevent shell expansion (see the section “Quoting,” in Chapter 4, “Rules for Entering UNIX Commands”), but the spaces around the * sign must not be quoted, as in the following example:

$ expr 3 \* 5
15
$

The remainder ...