1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)rand.3 8.1 (Berkeley) 6/4/93 37.\" $FreeBSD: src/lib/libc/stdlib/rand.3,v 1.14 2003/09/08 19:57:15 ru Exp $ 38.\" $DragonFly: src/lib/libc/stdlib/rand.3,v 1.6 2007/06/29 19:34:41 swildner Exp $ 39.\" 40.Dd May 25, 1999 41.Dt RAND 3 42.Os 43.Sh NAME 44.Nm rand , 45.Nm srand , 46.Nm sranddev , 47.Nm rand_r 48.Nd bad random number generator 49.Sh LIBRARY 50.Lb libc 51.Sh SYNOPSIS 52.In stdlib.h 53.Ft void 54.Fn srand "unsigned seed" 55.Ft void 56.Fn sranddev void 57.Ft int 58.Fn rand void 59.Ft int 60.Fn rand_r "unsigned *ctx" 61.Sh DESCRIPTION 62.Bf -symbolic 63These interfaces are obsoleted by 64.Xr random 3 . 65.Ef 66.Pp 67The 68.Fn rand 69function computes a sequence of pseudo-random integers in the range 70of 0 to 71.Dv RAND_MAX 72(as defined by the header file 73.In stdlib.h ) . 74.Pp 75The 76.Fn srand 77function sets its argument 78.Fa seed 79as the seed for a new sequence of 80pseudo-random numbers to be returned by 81.Fn rand . 82These sequences are repeatable by calling 83.Fn srand 84with the same seed value. 85.Pp 86If no 87.Fa seed 88value is provided, the functions are automatically 89seeded with a value of 1. 90.Pp 91The 92.Fn sranddev 93function initializes a seed using the 94.Xr random 4 95random number device which returns good random numbers, 96suitable for cryptographic use. 97.Pp 98The 99.Fn rand_r 100function 101provides the same functionality as 102.Fn rand . 103A pointer to the context value 104.Fa ctx 105must be supplied by the caller. 106.Sh SEE ALSO 107.Xr arc4random 3 , 108.Xr random 3 , 109.Xr random 4 110.Sh STANDARDS 111The 112.Fn rand 113and 114.Fn srand 115functions 116conform to 117.St -isoC . 118.Pp 119The 120.Fn rand_r 121function is as proposed in the POSIX.4a Draft #6 document. 122