LinuxGuruz
  • Last 5 Forum Topics
    Replies
    Views
    Last post


The Web Only This Site
  • BOOKMARK

  • ADD TO FAVORITES

  • REFERENCES


  • MARC

    Mailing list ARChives
    - Search by -
     Subjects
     Authors
     Bodies





    FOLDOC

    Computing Dictionary




  • Text Link Ads






  • LINUX man pages
  • Linux Man Page Viewer


    The following form allows you to view linux man pages.

    Command:

    rand_r

    
    
    

    SYNOPSIS

           #include <stdlib.h>
    
           int rand(void);
    
           int rand_r(unsigned int *seedp);
    
           void srand(unsigned int seed);
    
       Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
    
           rand_r(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE
    
    
    

    DESCRIPTION

           The  rand()  function returns a pseudo-random integer in the range 0 to
           RAND_MAX inclusive (i.e., the mathematical range [0, RAND_MAX]).
    
           The srand() function sets its argument as the seed for a  new  sequence
           of  pseudo-random  integers  to be returned by rand().  These sequences
           are repeatable by calling srand() with the same seed value.
    
           If no seed value is provided,  the  rand()  function  is  automatically
           seeded with a value of 1.
    
           The function rand() is not reentrant or thread-safe, since it uses hid-
           den state that is modified on each call.  This might just be  the  seed
           value to be used by the next call, or it might be something more elabo-
           rate.  In order to get reproducible behavior in a threaded application,
           this  state must be made explicit; this can be done using the reentrant
           function rand_r().
    
           Like rand(), rand_r() returns a  pseudo-random  integer  in  the  range
           [0, RAND_MAX].  The seedp argument is a pointer to an unsigned int that
           is used to store state between calls.  If rand_r() is called  with  the
           same  initial value for the integer pointed to by seedp, and that value
           is not modified between calls, then  the  same  pseudo-random  sequence
           will result.
    
           The  value pointed to by the seedp argument of rand_r() provides only a
           very small amount of state, so this function will be a weak pseudo-ran-
           dom generator.  Try drand48_r(3) instead.
    
    
    

    RETURN VALUE

           The rand() and rand_r() functions return a value between 0 and RAND_MAX
           (inclusive).  The srand() function returns no value.
    
    
    

    CONFORMING TO

           The functions rand() and srand() conform to  SVr4,  4.3BSD,  C89,  C99,
           POSIX.1-2001.     The   function   rand_r()   is   from   POSIX.1-2001.
           POSIX.1-2008 marks rand_r() as obsolete.
    
    
    

    NOTES

    
               /* RAND_MAX assumed to be 32767 */
               int myrand(void) {
                   next = next * 1103515245 + 12345;
                   return((unsigned)(next/65536) % 32768);
               }
    
               void mysrand(unsigned int seed) {
                   next = seed;
               }
    
           The following program can be used to display the pseudo-random sequence
           produced by rand() when given a particular seed.
    
               #include <stdlib.h>
               #include <stdio.h>
    
               int
               main(int argc, char *argv[])
               {
                   int j, r, nloops;
                   unsigned int seed;
    
                   if (argc != 3) {
                       fprintf(stderr, "Usage: %s <seed> <nloops>\n", argv[0]);
                       exit(EXIT_FAILURE);
                   }
    
                   seed = atoi(argv[1]);
                   nloops = atoi(argv[2]);
    
                   srand(seed);
                   for (j = 0; j < nloops; j++) {
                       r =  rand();
                       printf("%d\n", r);
                   }
    
                   exit(EXIT_SUCCESS);
               }
    
    
    

    SEE ALSO

           drand48(3), random(3)
    
                                      2014-01-18                           RAND(3)
    
  • MORE RESOURCE


  • Linux

    The Distributions





    Linux

    The Software





    Linux

    The News



  • MARKETING






  • Toll Free

webmaster@linuxguruz.com
Copyright © 1999 - 2016 by LinuxGuruz