Linux manual pages Section 3: Subroutines  

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);
 
[Note] Note
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. On error, −1 is returned, with errno set to indicate the cause of the error.

ERRORS

EINVAL

A state array of less than 8 bytes was specified to initstate_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 3.52 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/.


  Copyright 2008 Michael Kerrisk <mtk.manpagesgmail.com>

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