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1 perry 1 !!NAME
2
3
4 random, srandom, initstate, setstate - random number generator.
5 !!SYNOPSIS
4 StuartYeates 6 #include <stdlib.h>
7 long int random(void);
8 void srandom(unsigned int __''seed''__);
9 char *initstate(unsigned int __''seed''__, char *state, size_t __''n''__);
10 char *setstate(char *__''state''__);
1 perry 11
12 !!DESCRIPTION
13
14
15 The __random()__ function uses a non-linear additive
16 feedback random number generator employing a default table
17 of size 31 long integers to return successive pseudo-random
18 numbers in the range from 0 to __RAND_MAX__. The period
19 of this random number generator is very large, approximately
20 16*((2**31)-1).
21
22
23 The __srandom()__ function sets its argument as the seed
24 for a new sequence of pseudo-random integers to be returned
25 by __random()__. These sequences are repeatable by
26 calling __srandom()__ with the same seed value. If no
27 seed value is provided, the __random()__ function is
28 automatically seeded with a value of 1.
29
30
31 The __initstate()__ function allows a state array
32 ''state'' to be initialized for use by __random()__.
33 The size of the state array ''n'' is used by
34 __initstate()__ to decide how sophisticated a random
35 number generator it should use -- the larger the state
36 array, the better the random numbers will be. ''seed'' is
37 the seed for the initialization, which specifies a starting
38 point for the random number sequence, and provides for
39 restarting at the same point.
40
41
42 The __setstate()__ function changes the state array used
43 by the __random()__ function. The state array
44 ''state'' is used for random number generation until the
45 next call to __initstate()__ or __setstate()__.
46 ''state'' must first have been initialized using
47 __initstate()__ or be the result of a previous call of
48 __setstate()__.
49 !!RETURN VALUE
50
51
52 The __random()__ function returns a value between 0 and
53 RAND_MAX. The __srandom()__ function returns no value.
54 The __initstate()__ and __setstate()__ functions
55 return a pointer to the previous state array, or NULL on
56 error.
57 !!ERRORS
58
59
60 __EINVAL__
61
62
63 A state array of less than 8 bytes was specified to
64 __initstate()__.
65 !!NOTES
66
67
68 Current
69 n'' are 8, 32, 64, 128, and 256 bytes; other
70 amounts will be rounded down to the nearest known amount.
71 Using less than 8 bytes will cause an error.
72 !!CONFORMING TO
73
74
75 BSD 4.3
76 !!SEE ALSO
77
78
2 StuartYeates 79 rand(3), srand(3), [random(3)], [random(4)], [srandom(3)] and [urandom(4)]
1 perry 80 ----
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