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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 <&lt;stdlib.h>&gt;

       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 initial-
       izes  the state in the object pointed to by buf, rather than initializ-
       ing 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  init-
              state_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 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



GNU                               2008-03-07                       RANDOM_R(3)