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 1.10 2007/05/31 19:19:31 jmc Exp $ 33.\" 34.Dd $Mdocdate: May 31 2007 $ 35.Dt RAND 3 36.Os 37.Sh NAME 38.Nm rand , 39.Nm srand 40.Nd bad random number generator 41.Sh SYNOPSIS 42.Fd #include <stdlib.h> 43.Ft void 44.Fn srand "unsigned int seed" 45.Ft int 46.Fn rand void 47.Ft int 48.Fn rand_r "unsigned int *seed" 49.Sh DESCRIPTION 50.Bf -symbolic 51These interfaces are obsoleted by 52.Xr random 3 . 53.Ef 54.Pp 55The 56.Fn rand 57function computes a sequence of pseudo-random integers in the range 58of 0 to 59.Dv RAND_MAX 60(as defined by the header file 61.Aq Pa stdlib.h ) . 62.Pp 63The 64.Fn srand 65function sets its argument as the seed for a new sequence of 66pseudo-random numbers to be returned by 67.Fn rand . 68These sequences are repeatable by calling 69.Fn srand 70with the same seed value. 71.Pp 72If no seed value is provided, the functions are automatically 73seeded with a value of 1. 74.Pp 75The 76.Fn rand_r 77is a thread-safe version of 78.Fn rand . 79Storage for the seed must be provided through the 80.Fa seed 81argument, and needs to have been initialized by the caller. 82.Sh SEE ALSO 83.Xr arc4random 3 , 84.Xr rand48 3 , 85.Xr random 3 86.Sh STANDARDS 87The 88.Fn rand 89and 90.Fn srand 91functions conform to 92.St -ansiC . 93.Pp 94The 95.Fn rand_r 96function conforms to ISO/IEC 9945-1 ANSI/IEEE 97.Pq Dq Tn POSIX 98Std 1003.1c Draft 10. 99