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 generator 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.  On error, -1 is returned, with errno set to
       indicate the cause of the 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.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The random_r(), srandom_r(), initstate_r(), and setstate_r() functions are thread-safe.

CONFORMING TO
       These functions are nonstandard glibc extensions.

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

COLOPHON
       This page is part of release 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.



GNU                                         2014-03-25                                RANDOM_R(3)