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

       random_r,  srandom_r, initstate_r, setstate_r - reentrant random number

       #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

       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, which must have been
       previously initialized by initstate_r().  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, which must have been previously initial-
       ized by initstate_r(), 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.

       All  of these functions return 0 on success.  On error, -1 is returned,
       with errno set to indicate the cause of the error.

       EINVAL A state array of less  than  8  bytes  was  specified  to  init-

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

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

       For   an   explanation   of   the  terms  used  in  this  section,  see

       |Interface                   | Attribute     | Value            |
       |random_r(), srandom_r(),    | Thread safety | MT-Safe race:buf |
       |initstate_r(), setstate_r() |               |                  |
       These functions are nonstandard glibc extensions.

       drand48(3), rand(3), random(3)

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GNU                               2015-12-28                       RANDOM_R(3)
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