rand(2) [plan9 man page]

RAND(2) 							System Calls Manual							   RAND(2)

NAME

       rand, lrand, frand, nrand, lnrand, srand - random number generator

SYNOPSIS

       #include <u.h>
       #include <libc.h>

       int    rand(void)

       long   lrand(void)

       double frand(void)

       int    nrand(int val)

       long   lnrand(long val)

       void   srand(long seed)

DESCRIPTION

       Rand returns a uniform pseudo-random number x, 0<=x<215.

       Lrand returns a uniform long x, 0<=x<231.

       Frand  returns  a uniform double x, 0.0<=x<1.0, This function calls lrand twice to generate a number with as many as 62 significant bits of
       mantissa.

       Nrand returns a uniform integer x, 0<=x<val.  Lnrand is the same, but returns a long.

       The algorithm is additive feedback with:

	      x[n] = (x[n-273] + x[n-607]) mod 2^31

       giving a period of 2^30 x (2^607 - 1).

       The generators are initialized by calling srand with whatever you like as argument.  To get a different starting value each time,

	      srand(time(0))

       will work as long as it is not called more often than once per second.  Calling

	      srand(1)

       will initialize the generators to their starting state.

   Alef
       There is no rand in Alef.

SOURCE

       /sys/src/libc/port/rand.c

																	   RAND(2)

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 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