1.\" Copyright (c) 1990, 1991 The Regents of the University of California. 2.\" 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. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $OpenBSD: rand.3,v 1.15 2014/04/07 17:57:56 schwarze Exp $ 33.\" 34.Dd $Mdocdate: April 7 2014 $ 35.Dt RAND 3 36.Os 37.Sh NAME 38.Nm rand , 39.Nm rand_r , 40.Nm srand 41.Nd bad random number generator 42.Sh SYNOPSIS 43.In stdlib.h 44.Ft void 45.Fn srand "unsigned int seed" 46.Ft int 47.Fn rand void 48.Ft int 49.Fn rand_r "unsigned int *seed" 50.Sh DESCRIPTION 51.Bf -symbolic 52These interfaces are obsoleted by 53.Xr random 3 . 54.Ef 55.Pp 56The 57.Fn rand 58function computes a sequence of pseudo-random integers in the range 59of 0 to 60.Dv RAND_MAX 61(as defined by the header file 62.In stdlib.h ) . 63.Pp 64The 65.Fn srand 66function sets its argument as the seed for a new sequence of 67pseudo-random numbers to be returned by 68.Fn rand . 69These sequences are repeatable by calling 70.Fn srand 71with the same seed value. 72.Pp 73If no seed value is provided, the functions are automatically 74seeded with a value of 1. 75.Pp 76The 77.Fn rand_r 78is a thread-safe version of 79.Fn rand . 80Storage for the seed must be provided through the 81.Fa seed 82argument, and needs to have been initialized by the caller. 83.Sh SEE ALSO 84.Xr arc4random 3 , 85.Xr rand48 3 , 86.Xr random 3 87.Sh STANDARDS 88The 89.Fn rand 90and 91.Fn srand 92functions conform to 93.St -ansiC . 94.Pp 95The 96.Fn rand_r 97function conforms to 98.St -p1003.1-2008 . 99.Sh HISTORY 100The functions 101.Fn rand 102and 103.Fn srand 104first appeared in 105.At v3 . 106