.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"	$OpenBSD: rand.3,v 1.16 2014/07/17 23:12:28 deraadt Exp $
.\"
.Dd $Mdocdate: July 17 2014 $
.Dt RAND 3
.Os
.Sh NAME
.Nm rand ,
.Nm rand_r ,
.Nm srand
.Nd bad random number generator
.Sh SYNOPSIS
.In stdlib.h
.Ft void
.Fn srand "unsigned int seed"
.Ft int
.Fn rand void
.Ft int
.Fn rand_r "unsigned int *seed"
.Sh DESCRIPTION
.Bf -symbolic
These interfaces are obsoleted by
.Xr random 3 ,
which is also unsafe.
Consider using
.Xr arc4random 3 .
.Ef
.Pp
The
.Fn rand
function computes a sequence of pseudo-random integers in the range
of 0 to
.Dv RAND_MAX
(as defined by the header file
.In stdlib.h ) .
.Pp
The
.Fn srand
function sets its argument as the seed for a new sequence of
pseudo-random numbers to be returned by
.Fn rand .
These sequences are repeatable by calling
.Fn srand
with the same seed value.
.Pp
If no seed value is provided, the functions are automatically
seeded with a value of 1.
.Pp
The
.Fn rand_r
is a thread-safe version of
.Fn rand .
Storage for the seed must be provided through the
.Fa seed
argument, and needs to have been initialized by the caller.
.Sh SEE ALSO
.Xr arc4random 3 ,
.Xr rand48 3 ,
.Xr random 3
.Sh STANDARDS
The
.Fn rand
and
.Fn srand
functions conform to
.St -ansiC .
.Pp
The
.Fn rand_r
function conforms to
.St -p1003.1-2008 .
.Sh HISTORY
The functions
.Fn rand
and
.Fn srand
first appeared in
.At v3 .