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    Command:

    initstate

    
    
    

    SYNOPSIS

           #include <stdlib.h>
    
           long int random(void);
    
           void srandom(unsigned int seed);
    
           char *initstate(unsigned int seed, char *state, size_t n);
           char *setstate(char *state);
    
       Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
    
           random(), srandom(), initstate(), setstate():
               _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
               _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
    
    
    

    DESCRIPTION

           The random() function uses a nonlinear 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 init-
           state() 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() or be the result of a previous
           call of setstate().
    
    
    

    RETURN VALUE

           The random() function returns a value  between  0  and  RAND_MAX.   The
           srandom() function returns no value.
    
           The initstate() function returns a pointer to the previous state array.
           On error, errno is set to indicate the cause.
    
           On success, setstate() returns a pointer to the previous  state  array.
           On  error, it returns NULL, with errno set to indicate the cause of the
    
           This  function  should  not be used in cases where multiple threads use
           random() and the behavior should be reproducible.  Use random_r(3)  for
           that purpose.
    
           Random-number  generation  is a complex topic.  Numerical Recipes in C:
           The Art of Scientific Computing (William H. Press, Brian  P.  Flannery,
           Saul  A.  Teukolsky, William T. Vetterling; New York: Cambridge Univer-
           sity Press, 2007, 3rd ed.)  provides an excellent discussion of practi-
           cal random-number generation issues in Chapter 7 (Random Numbers).
    
           For  a  more  theoretical  discussion  which also covers many practical
           issues in depth, see Chapter 3 (Random Numbers) in  Donald  E.  Knuth's
           The  Art  of Computer Programming, volume 2 (Seminumerical Algorithms),
           2nd ed.; Reading,  Massachusetts:  Addison-Wesley  Publishing  Company,
           1981.
    
    
    

    BUGS

           According  to  POSIX,  initstate() should return NULL on error.  In the
           glibc implementation, errno is (as specified) set  on  error,  but  the
           function does not return NULL.
    
    
    

    SEE ALSO

           drand48(3), rand(3), random_r(3), srand(3)
    
    
    

    GNU 2013-04-19 RANDOM(3)

    
    
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