127 lines
3.3 KiB
Groff
127 lines
3.3 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)rand.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd October 6, 2010
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.Dt RAND 3
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.Os
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.Sh NAME
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.Nm rand ,
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.Nm srand ,
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.Nm sranddev ,
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.Nm rand_r
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.Nd bad random number generator
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.Ft void
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.Fn srand "unsigned seed"
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.Ft void
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.Fn sranddev void
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.Ft int
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.Fn rand void
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.Ft int
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.Fn rand_r "unsigned *ctx"
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.Sh DESCRIPTION
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.Bf -symbolic
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These interfaces are obsoleted by
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.Xr random 3 .
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.Ef
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.Pp
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The
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.Fn rand
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function computes a sequence of pseudo-random integers in the range
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of 0 to
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.Dv RAND_MAX
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(as defined by the header file
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.In stdlib.h ) .
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.Pp
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The
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.Fn srand
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function sets its argument
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.Fa seed
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as the seed for a new sequence of
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pseudo-random numbers to be returned by
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.Fn rand .
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These sequences are repeatable by calling
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.Fn srand
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with the same seed value.
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.Pp
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If no
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.Fa seed
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value is provided, the functions are automatically
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seeded with a value of 1.
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.Pp
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The
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.Fn sranddev
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function initializes a seed using the
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.Xr random 4
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random number device which returns good random numbers.
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However, the
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.Fn rand
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function still remains unsuitable for cryptographic use.
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.Pp
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The
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.Fn rand_r
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function
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provides the same functionality as
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.Fn rand .
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A pointer to the context value
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.Fa ctx
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must be supplied by the caller.
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.Pp
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For better generator quality, use
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.Xr random 3
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or
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.Xr lrand48 3 .
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Applications requiring cryptographic quality randomness should use
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.Xr arc4random 3 .
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.Sh SEE ALSO
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.Xr arc4random 3 ,
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.Xr lrand48 3 ,
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.Xr random 3 ,
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.Xr random 4
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.Sh STANDARDS
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The
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.Fn rand
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and
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.Fn srand
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functions
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conform to
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.St -isoC .
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.Pp
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The
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.Fn rand_r
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function is as proposed in the POSIX.4a Draft #6 document.
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