[apple/libc.git] / stdlib / rand.3

.\" Copyright (c) 1990, 1991, 1993
.\"	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. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. 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.
.\"
.\"     @(#)rand.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/stdlib/rand.3,v 1.12 2001/09/07 14:46:36 asmodai Exp $
.\"
.Dd May 25, 1999
.Dt RAND 3
.Os
.Sh NAME
.Nm rand ,
.Nm srand ,
.Nm sranddev ,
.Nm rand_r
.Nd bad random number generator
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft void
.Fn srand "unsigned seed"
.Ft void
.Fn sranddev void
.Ft int
.Fn rand void
.Ft int
.Fn rand_r "unsigned *ctx"
.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
.Fa seed
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
.Fa seed
value is provided, the functions are automatically
seeded with a value of 1.
.Pp
The
.Fn sranddev
function initializes a seed using the
.Xr random 4
random number device which returns good random numbers,
suitable for cryptographic use.
.Pp
.Fn rand_r
provides the same functionality as
.Fn rand .
A pointer to the context value
.Fa ctx
must be supplied by the caller.
.Sh SEE ALSO
.Xr random 3 ,
.Xr random 4
.Sh STANDARDS
The
.Fn rand
and
.Fn srand
functions
conform to
.St -isoC .
.Pp
The
.Fn rand_r
function is as proposed in the POSIX.4a Draft #6 document.
Commit	Line	Data
5b2abdfb	1	.\" Copyright (c) 1990, 1991, 1993
e9ce8d39 A	2	.\" The Regents of the University of California. All rights reserved.
e9ce8d39 A	3	.\"
5b2abdfb A	4	.\" This code is derived from software contributed to Berkeley by
	5	.\" the American National Standards Committee X3, on Information
	6	.\" Processing Systems.
	7	.\"
e9ce8d39 A	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	.\"
5b2abdfb A	36	.\" @(#)rand.3 8.1 (Berkeley) 6/4/93
5b2abdfb A	37	.\" $FreeBSD: src/lib/libc/stdlib/rand.3,v 1.12 2001/09/07 14:46:36 asmodai Exp $
e9ce8d39	38	.\"
5b2abdfb A	39	.Dd May 25, 1999
5b2abdfb A	40	.Dt RAND 3
e9ce8d39 A	41	.Os
e9ce8d39 A	42	.Sh NAME
5b2abdfb A	43	.Nm rand ,
	44	.Nm srand ,
	45	.Nm sranddev ,
	46	.Nm rand_r
	47	.Nd bad random number generator
e9ce8d39 A	48	.Sh LIBRARY
	49	.Lb libc
	50	.Sh SYNOPSIS
5b2abdfb A	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
e9ce8d39	58	.Ft int
5b2abdfb	59	.Fn rand_r "unsigned *ctx"
e9ce8d39	60	.Sh DESCRIPTION
5b2abdfb A	61	.Bf -symbolic
	62	These interfaces are obsoleted by
	63	.Xr random 3 .
	64	.Ef
	65	.Pp
e9ce8d39	66	The
5b2abdfb A	67	.Fn rand
	68	function computes a sequence of pseudo-random integers in the range
	69	of 0 to
	70	.Dv RAND_MAX
	71	(as defined by the header file
	72	.Aq Pa stdlib.h ) .
	73	.Pp
e9ce8d39	74	The
5b2abdfb A	75	.Fn srand
	76	function sets its argument
	77	.Fa seed
	78	as the seed for a new sequence of
	79	pseudo-random numbers to be returned by
	80	.Fn rand .
	81	These sequences are repeatable by calling
	82	.Fn srand
	83	with the same seed value.
	84	.Pp
	85	If no
	86	.Fa seed
	87	value is provided, the functions are automatically
	88	seeded with a value of 1.
	89	.Pp
	90	The
	91	.Fn sranddev
	92	function initializes a seed using the
	93	.Xr random 4
	94	random number device which returns good random numbers,
	95	suitable for cryptographic use.
	96	.Pp
	97	.Fn rand_r
	98	provides the same functionality as
	99	.Fn rand .
	100	A pointer to the context value
	101	.Fa ctx
	102	must be supplied by the caller.
e9ce8d39	103	.Sh SEE ALSO
5b2abdfb A	104	.Xr random 3 ,
	105	.Xr random 4
	106	.Sh STANDARDS
	107	The
	108	.Fn rand
	109	and
	110	.Fn srand
	111	functions
	112	conform to
	113	.St -isoC .
	114	.Pp
e9ce8d39	115	The
5b2abdfb A	116	.Fn rand_r
5b2abdfb A	117	function is as proposed in the POSIX.4a Draft #6 document.