#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
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.