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The 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 awk
, in order from
the highest precedence to the lowest:
- x
+ x
x ^ y
x ** y
x * y
x / y
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 awk
are floating-point,
and that division of integer-looking constants produces a real number,
not an integer.)
x % y
x + y
x - y
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 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.
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