[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 1.14 2003/09/08 19:57:15 ru Exp $
.\"
.Dd May 25, 1999
.Dt RAND 3
.Os
.Sh NAME
.Nm rand ,
.Nm rand_r ,
.Nm srand ,
.Nm sranddev
.Nd bad random number generator
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft int
.Fo rand
.Fa void
.Fc
.Ft int
.Fo rand_r
.Fa "unsigned *seed"
.Fc
.Ft void
.Fo srand
.Fa "unsigned seed"
.Fc
.Ft void
.Fo sranddev
.Fa void
.Fc
.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
.In 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
The
.Fn rand_r
function
provides the same functionality as
.Fn rand .
A pointer to the context value
.Fa seed
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
224c7076	1	.\" Copyright (c) 1990, 1991, 1993
e9ce8d39 A	2	.\" The Regents of the University of California. All rights reserved.
e9ce8d39 A	3	.\"
224c7076 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	.\"
224c7076 A	36	.\" @(#)rand.3 8.1 (Berkeley) 6/4/93
224c7076 A	37	.\" $FreeBSD: src/lib/libc/stdlib/rand.3,v 1.14 2003/09/08 19:57:15 ru Exp $
e9ce8d39	38	.\"
224c7076 A	39	.Dd May 25, 1999
224c7076 A	40	.Dt RAND 3
e9ce8d39 A	41	.Os
e9ce8d39 A	42	.Sh NAME
224c7076 A	43	.Nm rand ,
	44	.Nm rand_r ,
	45	.Nm srand ,
	46	.Nm sranddev
	47	.Nd bad random number generator
e9ce8d39 A	48	.Sh LIBRARY
	49	.Lb libc
	50	.Sh SYNOPSIS
224c7076 A	51	.In stdlib.h
	52	.Ft int
	53	.Fo rand
	54	.Fa void
	55	.Fc
e9ce8d39	56	.Ft int
224c7076 A	57	.Fo rand_r
	58	.Fa "unsigned *seed"
	59	.Fc
	60	.Ft void
	61	.Fo srand
	62	.Fa "unsigned seed"
	63	.Fc
	64	.Ft void
	65	.Fo sranddev
	66	.Fa void
	67	.Fc
e9ce8d39	68	.Sh DESCRIPTION
224c7076 A	69	.Bf -symbolic
	70	These interfaces are obsoleted by
	71	.Xr random 3 .
	72	.Ef
	73	.Pp
e9ce8d39	74	The
224c7076 A	75	.Fn rand
	76	function computes a sequence of pseudo-random integers in the range
	77	of 0 to
	78	.Dv RAND_MAX
	79	(as defined by the header file
	80	.In stdlib.h ) .
	81	.Pp
e9ce8d39	82	The
224c7076 A	83	.Fn srand
	84	function sets its argument
	85	.Fa seed
	86	as the seed for a new sequence of
	87	pseudo-random numbers to be returned by
	88	.Fn rand .
	89	These sequences are repeatable by calling
	90	.Fn srand
	91	with the same seed value.
	92	.Pp
	93	If no
	94	.Fa seed
	95	value is provided, the functions are automatically
	96	seeded with a value of 1.
5b2abdfb	97	.Pp
5b2abdfb	98	The
224c7076 A	99	.Fn sranddev
	100	function initializes a seed, using the
	101	.Xr random 4
	102	random number device which returns good random numbers,
	103	suitable for cryptographic use.
	104	.Pp
	105	The
	106	.Fn rand_r
5b2abdfb	107	function
224c7076 A	108	provides the same functionality as
	109	.Fn rand .
	110	A pointer to the context value
	111	.Fa seed
	112	must be supplied by the caller.
e9ce8d39	113	.Sh SEE ALSO
224c7076 A	114	.Xr random 3 ,
	115	.Xr random 4
	116	.Sh STANDARDS
e9ce8d39	117	The
224c7076 A	118	.Fn rand
	119	and
	120	.Fn srand
	121	functions
	122	conform to
	123	.St -isoC .
	124	.Pp
5b2abdfb	125	The
224c7076 A	126	.Fn rand_r
224c7076 A	127	function is as proposed in the POSIX.4a Draft #6 document.