RANDOM (3)
random number generator.
SYNOPSIS
#include <stdlib.h>
long int random(void);
void srandom(unsigned int seed );
char *initstate(unsigned int seed , char * state , int n );
char *setstate(char * state );
DESCRIPTION
The random() function uses a non-linear additive feedback random
number generator employing a default table of size 31 long integers to
return successive pseudo-random numbers in the range from 0 to RAND_MAX.
The period of this random number generator is very large, approximately
16*((2**31)-1).
The srandom() function sets its argument as the seed for a new
sequence of pseudo-random integers to be returned by random().
These sequences are repeatable by calling srandom() with the same
seed value. If no seed value is provided, the random() function
is automatically seeded with a value of 1.
The initstate() function allows a state array state to
be initialized for use by random(). The size of the state array
n is used by initstate() to decide how sophisticated a
random number generator it should use the larger the state array,
the better the random numbers will be. seed is the seed for the
initialization, which specifies a starting point for the random number
sequence, and provides for restarting at the same point.
The setstate() function changes the state array used by the
random() function. The state array state is used for
random number generation until the next call to initstate()
or setstate(). state must first have been initialized
using initstate().
RETURN VALUE
The random() function returns a value between 0 and RAND_MAX.
The srandom() function returns no value. The initstate()
and setstate() functions return a pointer to the previous state
array.
ERRORS
EINVAL
A state array of less than 8 bytes was specified to initstate().
NOTES
Current "optimal" values for the size of the state array n are
8, 32, 64, 128, and 256 bytes; other amounts will be rounded down to
the nearest known amount. Using less than 8 bytes will cause an
error.
CONFORMING TO
SEE ALSO
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