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.\" $FreeBSD$ 38.\" 39.Dd May 25, 1999 40.Dt RAND 3 41.Os 42.Sh NAME 43.Nm rand , 44.Nm srand , 45.Nm sranddev , 46.Nm rand_r 47.Nd bad random number generator 48.Sh LIBRARY 49.Lb libc 50.Sh SYNOPSIS 51.In stdlib.h 52.Ft void 53.Fn srand "unsigned seed" 54.Ft void 55.Fn sranddev void 56.Ft int 57.Fn rand void 58.Ft int 59.Fn rand_r "unsigned *ctx" 60.Sh DESCRIPTION 61.Bf -symbolic 62These interfaces are obsoleted by 63.Xr random 3 . 64.Ef 65.Pp 66The 67.Fn rand 68function computes a sequence of pseudo-random integers in the range 69of 0 to 70.Dv RAND_MAX 71(as defined by the header file 72.In stdlib.h ) . 73.Pp 74The 75.Fn srand 76function sets its argument 77.Fa seed 78as the seed for a new sequence of 79pseudo-random numbers to be returned by 80.Fn rand . 81These sequences are repeatable by calling 82.Fn srand 83with the same seed value. 84.Pp 85If no 86.Fa seed 87value is provided, the functions are automatically 88seeded with a value of 1. 89.Pp 90The 91.Fn sranddev 92function initializes a seed using the 93.Xr random 4 94random number device which returns good random numbers. 95However, the 96.Fn rand 97function still remains unsuitable for cryptographic use. 98.Pp 99The 100.Fn rand_r 101function 102provides the same functionality as 103.Fn rand . 104A pointer to the context value 105.Fa ctx 106must be supplied by the caller. 107.Sh SEE ALSO 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