Go to the first, previous, next, last section, table of contents.

Arithmetic Operators

The @command{awk} language uses the common arithmetic operators when evaluating expressions. All of these arithmetic operators follow normal precedence rules and work as you would expect them to.

The following example uses a file named `grades', which contains a list of student names as well as three test scores per student (it's a small class):

Pat   100 97 58
Sandy  84 72 93
Chris  72 92 89

This programs takes the file `grades' and prints the average of the scores:

$ awk '{ sum = $2 + $3 + $4 ; avg = sum / 3
>        print $1, avg }' grades
-| Pat 85
-| Sandy 83
-| Chris 84.3333

The following list provides the arithmetic operators in @command{awk}, in order from the highest precedence to the lowest:

- x

Negation.

+ x

Unary plus; the expression is converted to a number.

x ^ y

x ** y

Exponentiation; x raised to the y power. `2 ^ 3' has the value eight; the character sequence `**' is equivalent to `^'.

x * y

Multiplication.

x / y

Division; because all numbers in @command{awk} are floating-point numbers, the result is not rounded to an integer---`3 / 4' has the value 0.75. (It is a common mistake, especially for C programmers, to forget that all numbers in @command{awk} are floating-point, and that division of integer-looking constants produces a real number, not an integer.)

x % y

Remainder; further discussion is provided in the text, just after this list.

x + y

Addition.

x - y

Subtraction.

Unary plus and minus have the same precedence, the multiplication operators all have the same precedence, and addition and subtraction have the same precedence.

When computing the remainder of x % y, the quotient is rounded toward zero to an integer and multiplied by y. This result is subtracted from x; this operation is sometimes known as "trunc-mod." The following relation always holds:

b * int(a / b) + (a % b) == a

One possibly undesirable effect of this definition of remainder is that x % y is negative if x is negative. Thus:

-17 % 8 = -1

In other @command{awk} implementations, the signedness of the remainder may be machine dependent.

Note: The POSIX standard only specifies the use of `^' for exponentiation. For maximum portability, do not use the `**' operator.

Go to the first, previous, next, last section, table of contents.