.\" 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 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 .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 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.