1RANDOM_R(3)                Linux Programmer's Manual               RANDOM_R(3)
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NAME

6       random_r,  srandom_r, initstate_r, setstate_r - reentrant random number
7       generator
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SYNOPSIS

10       #include <stdlib.h>
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12       int random_r(struct random_data *buf, int32_t *result);
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14       int srandom_r(unsigned int seed, struct random_data *buf);
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16       int initstate_r(unsigned int seed, char *statebuf,
17                       size_t statelen, struct random_data *buf);
18       int setstate_r(char *statebuf, struct random_data *buf);
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20   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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22       random_r(), srandom_r(), initstate_r(), setstate_r(): _SVID_SOURCE ||
23       _BSD_SOURCE
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DESCRIPTION

26       These   functions  are  the  reentrant  equivalents  of  the  functions
27       described in random(3).  They are suitable  for  use  in  multithreaded
28       programs where each thread needs to obtain an independent, reproducible
29       sequence of random numbers.
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31       The random_r() function is like random(3), except that instead of using
32       state  information  maintained  in a global variable, it uses the state
33       information in the argument pointed to by buf.   The  generated  random
34       number is returned in the argument result.
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36       The srandom_r() function is like srandom(3), except that it initializes
37       the seed for the random number generator whose state is  maintained  in
38       the  object  pointed to by buf, instead of the seed associated with the
39       global state variable.
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41       The initstate_r() function is like initstate(3) except that it initial‐
42       izes  the state in the object pointed to by buf, rather than initializ‐
43       ing the global state variable.
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45       The setstate_r() function is like setstate(3) except that  it  modifies
46       the  state  in  the object pointer to by buf, rather than modifying the
47       global state variable.
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RETURN VALUE

50       All of these functions return 0 on success, or -1 on error.
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ERRORS

53       EINVAL A state array of less  than  8  bytes  was  specified  to  init‐
54              state_r().
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56       EINVAL The statebuf or buf argument to setstate_r() was NULL.
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58       EINVAL The buf or result argument to random_r() was NULL.
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CONFORMING TO

61       These functions are non-standard glibc extensions.
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SEE ALSO

64       drand48(3), rand(3), random(3)
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COLOPHON

67       This  page  is  part of release 3.22 of the Linux man-pages project.  A
68       description of the project, and information about reporting  bugs,  can
69       be found at http://www.kernel.org/doc/man-pages/.
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73GNU                               2008-03-07                       RANDOM_R(3)
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