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false positives for products of primes larger than 2^16. For example, before this commit: $ /usr/games/primes 4295360521 4295360522 4295360521 but $ /usr/games/factor 4295360521 4295360521: 65539 65539 or $ /usr/games/primes 3825123056546413049 3825123056546413050 3825123056546413049 yet $ /usr/games/factor 3825123056546413049 3825123056546413049: 165479 23115459100831 or $ /usr/games/primes 18446744073709551577 18446744073709551577 although $ /usr/games/factor 18446744073709551577 18446744073709551577: 139646831 132095686967 Incidentally, the above examples show the smallest and largest cases that were erroneously stated as prime in the range 2^32 .. 3825123056546413049 .. 2^64; the primes(6) program now stops at 3825123056546413050 as primality tests on larger integers would be by brute force factorization. In addition, special to the NetBSD version: . for -d option, skip first difference when start is >65537 as it is incorrect . corrected usage to mention both the existing -d as well as the new -h option For original FreeBSD commit message by Colin Percival, see: http://svnweb.freebsd.org/base?view=revision&revision=272166
93 lines
3.2 KiB
Groff
93 lines
3.2 KiB
Groff
.\" $NetBSD: factor.6,v 1.13 2014/10/02 21:36:37 ast Exp $
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.\"
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.\" Copyright (c) 1989, 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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.\" Landon Curt Noll.
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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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.\" 3. 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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.\" @(#)factor.6 8.1 (Berkeley) 5/31/93
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.\"
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.\"
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.\" By Landon Curt Noll, http://www.isthe.com/chongo/index.html /\oo/\
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.\"
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.Dd May 15, 2010
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.Dt FACTOR 6
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.Os
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.Sh NAME
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.Nm factor
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.Nd factor a number
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.Sh SYNOPSIS
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.Nm
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.Op Ar number ...
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.Sh DESCRIPTION
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The
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.Nm
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utility factors integers larger than 1.
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When a number is factored, it is printed, followed by a
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.Dq \&: ,
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and the list of
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.Pq prime
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factors on a single line.
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Factors are listed in ascending order, and are preceded by a space.
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If a factor divides a value more than once, it will be printed more than once.
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.Pp
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When
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.Nm
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is invoked with one or more arguments, each argument will be factored.
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.Pp
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When
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.Nm
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is invoked with no arguments,
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.Nm
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reads numbers, one per line, from standard input, until end of file or error.
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Leading white-space and empty lines are ignored.
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Numbers may be preceded by a single +.
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Integer less than 2 are rejected.
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Numbers are terminated by a non-digit character (such as a newline).
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After a number is read, it is factored.
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Input lines must not be longer than
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.Dv LINE_MAX \- 1
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(currently 2047) characters.
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.Pp
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By default,
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.Nm
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is compiled against the OpenSSL bignum implementation
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.Xr openssl_bn 3 ,
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which lets it handle arbitrarily large values.
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.Pq Note however that very large values can take a very long time to factor.
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If
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.Nm
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is compiled without OpenSSL it is limited to the maximum value of
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.Vt unsigned long .
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.Sh DIAGNOSTICS
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Out of range or invalid input results in
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an appropriate error message to standard error.
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.Sh AUTHORS
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Originally by
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.An Landon Curt Noll .
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