6.22. Built-In Arithmetic Functions

Table 6.13 lists the built-in arithmetic functions, where x and y are arbitrary expressions.

Table 6.13. Arithmetic Functions
Function
Value Returned
atan2(x,y)
Arctangent of y/x in the range
cos(x)
Cosine of x (x in radians)
exp(x)
Exponential function e to the power of x
int(x)
Integer portion of x; truncated toward 0 when x > 0
log(x)
Natural (base e) logarithm of x
rand( )
Random number r, where 0 < r< 1
sin(x)
Sine of x (with x in radians)
sqrt(x)
Square root of x
srand(x)
x is a new seed for rand( )

6.22.1 Integer Function

The int function truncates any digits to the right of the decimal point to create a whole number. There is no rounding off.

Example 6.156.


1   % awk 'END{print 31/3}' filename

    10.3333

2   % awk 'END{print int(31/3})' filename

    10

EXPLANATION

In the END block, the result of the division is to print a floating-point number.
In the END block, the int function causes the result of the division to be truncated at the decimal point. A whole number is displayed.

6.22.2 Random Number Generator

The `rand` Function

The rand function generates a pseudorandom floating-point number greater than or equal to 0 and less than 1.

Example 6.157.


% nawk '{print rand()}' filename

0.513871

0.175726

0.308634



% nawk '{print rand()}' filename

0.513871

0.175726

0.308634

EXPLANATION

Each time the program runs, the same set of numbers is printed. The srand function can be used to seed the rand function with a new starting value. Otherwise, as in this example, the same sequence is repeated each time rand is called.

The `srand` Function

The srand function without an argument uses the time of day to generate the seed for the rand function. Srand(x) uses x as the seed. Normally, x should vary during the run of the program.

Example 6.158.


% nawk 'BEGIN{srand()};{print rand()}' filename

0.508744

0.639485

0.657277



% nawk 'BEGIN{srand()};{print rand()}' filename

0.133518

0.324747

0.691794

EXPLANATION

The srand function sets a new seed for rand. The starting point is the time of day. Each time rand is called, a new sequence of numbers is printed.

Example 6.159.


% nawk 'BEGIN{srand()};{print 1 + int(rand() * 25)}' filename

6

24

14

EXPLANATION

The srand function sets a new seed for rand. The starting point is the time of day. The rand function selects a random number between 0 and 25 and casts it to an integer value.

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