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.\"	$OpenBSD: rand.3,v 1.13 2013/07/18 10:14:50 schwarze Exp $
.\"
.Dd $Mdocdate: July 18 2013 $
.Dt RAND 3
.Os
.Sh NAME
.Nm rand ,
.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 .
.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
.Aq Pa 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 .