iOS Manual Pages

This document is a Mac OS X manual page. Manual pages are a command-line technology for providing documentation. You can view these manual pages locally using the man(1) command. These manual pages come from many different sources, and thus, have a variety of writing styles.

For more information about the manual page format, see the manual page for manpages(5).

RAND(3)                  BSD Library Functions Manual                  RAND(3)

NAME
     rand, rand_r, srand, sranddev -- bad random number generator

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdlib.h>

     int
     rand(void);

     int
     rand_r(unsigned *seed);

     void
     srand(unsigned seed);

     void
     sranddev(void);

DESCRIPTION
     These interfaces are obsoleted by random(3).

     The rand() function computes a sequence of pseudo-random integers in the
     range of 0 to RAND_MAX (as defined by the header file <stdlib.h>).

     The srand() function sets its argument seed as the seed for a new
     sequence of pseudo-random numbers to be returned by rand().  These
     sequences are repeatable by calling srand() with the same seed value.

     If no seed value is provided, the functions are automatically seeded with
     a value of 1.

     The sranddev() function initializes a seed, using the random(4) random
     number device which returns good random numbers, suitable for crypto-graphic cryptographic
     graphic use.

     The rand_r() function provides the same functionality as rand().  A
     pointer to the context value seed must be supplied by the caller.

SEE ALSO
     random(3), random(4)

STANDARDS
     The rand() and srand() functions conform to ISO/IEC 9899:1990
     (``ISO C90'').

     The rand_r() function is as proposed in the POSIX.4a Draft #6 document.

BSD                              May 25, 1999                              BSD