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, 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 nonstandard glibc extensions.
SEE ALSO
drand48(3), rand(3), random(3)
COLOPHON
- This page is part of release 3.25 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/.