# man(1) Manual page archive

```
RAND(2)                                                   RAND(2)

NAME
rand, lrand, frand, nrand, lnrand, srand - random number
generator

SYNOPSIS
int    rand(void)

long   lrand(void)

double frand(void)

int    nrand(int val)

long   lnrand(long val)

void   srand(long seed)

DESCRIPTION
Rand returns a uniform pseudo-random number x, 0<=x<2^15.

Lrand returns a uniform long x, 0<=x<2^31.

Frand returns a uniform double x, 0.0<=x<1.0.  This function
calls lrand twice to generate a number with as many as 62
significant bits of mantissa.

Nrand returns a uniform integer x, 0<=x<val.  Lnrand is the
same, but returns a long.

The algorithm is additive feedback with:

x[n] = (x[n-273] + x[n-607]) mod 2^31.

giving a period of 2^30 * (2^607 - 1).

The generators are initialized by calling srand with what-
ever you like as argument.  To get a different starting
value each time,

srand(time(0))

will work as long as it is not called more often than once
per second.  Calling

srand(1)

will initialize the generators to their starting state.

```