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RANDOM_R(3)                Linux Programmer's Manual               RANDOM_R(3)



NAME
       random_r, srandom_r, initstate_r, setstate_r - reentrant random number generator

SYNOPSIS
       #include <stdlib.h>

       int random_r(struct random_data *buf, int32_t *result);

       int srandom_r(unsigned int seed, struct random_data *buf);

       int initstate_r(unsigned int seed, char *statebuf,
                       size_t statelen, struct random_data *buf);
       int setstate_r(char *statebuf, struct random_data *buf);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       random_r(), srandom_r(), initstate_r(), setstate_r(): _SVID_SOURCE || _BSD_SOURCE

DESCRIPTION
       These  functions  are the reentrant equivalents of the functions described in random(3).  They are suitable for
       use in multithreaded programs where each thread needs to obtain an independent, reproducible sequence of random
       numbers.

       The  random_r()  function  is  like  random(3),  except that instead of using state information maintained in a
       global variable, it uses the state information in the argument pointed to by buf.  The generated random  number
       is returned in the argument result.

       The  srandom_r() function is like srandom(3), except that it initializes the seed for the random number genera-
       tor whose state is maintained in the object pointed to by buf, instead of the seed associated with  the  global
       state variable.

       The  initstate_r()  function is like initstate(3) except that it initializes the state in the object pointed to
       by buf, rather than initializing the global state variable.

       The setstate_r() function is like setstate(3) except that it modifies the state in the  object  pointer  to  by
       buf, rather than modifying the global state variable.

RETURN VALUE
       All of these functions return 0 on success, or -1 on error.

ERRORS
       EINVAL A state array of less than 8 bytes was specified to initstate_r().

       EINVAL The statebuf or buf argument to setstate_r() was NULL.

       EINVAL The buf or result argument to random_r() was NULL.

CONFORMING TO
       These functions are non-standard glibc extensions.

SEE ALSO
       drand48(3), rand(3), random(3)

COLOPHON
       This  page  is part of release 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                               2008-03-07                       RANDOM_R(3)