.\" $NetBSD: factor.6,v 1.18 2020/10/12 13:53:43 christos Exp $
.\" Copyright (c) 1989, 1993
.\" The Regents of the University of California. All rights reserved.
.\" This code is derived from software contributed to Berkeley by
.\" Landon Curt Noll.
.\" 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. 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.
.\" @(#)factor.6 8.1 (Berkeley) 5/31/93
.\" By Landon Curt Noll, http://www.isthe.com/chongo/index.html /\oo/\
.Dd October 12, 2020
.Dt FACTOR 6
.Nd factor a number
.Op Fl hx
.Op Ar number ...
utility factors integers larger than
.Dv 0 .
When a number is factored, it is printed, followed by a
.Dq \&: ,
and the list of
factors on a single line.
Factors are listed in ascending order, and are preceded by a space.
By default, if a factor divides a value more than once, it will be
printed more than once.
is invoked with one or more
arguments, each argument will be factored.
is invoked with no
reads numbers, one per line, from standard input, until end of file or error.
Leading white-space and empty lines are ignored.
Numbers may be preceded by a single +.
Numbers that start with
are interpreted as hexadecimal.
input exits the program.
Negative numbers are not allowed.
Numbers are terminated by a non-digit character (such as a newline).
After a number is read, it is factored.
Input lines must not be longer than
.Dv LINE_MAX \- 1
(currently 2047) characters.
is compiled against the OpenSSL bignum implementation
.Xr openssl_bn 3 ,
which lets it handle arbitrarily large values.
.Pq Note however that very large values can take a very long time to factor.
is compiled without OpenSSL it is limited to the maximum value of
.Vt unsigned long .
The following option is available:
.Bl -tag -width flag
.It Fl h
flag is specified, factors will be printed in "human-readable" format.
If a factor x divides a value n (>1) times, it will appear as x^n.
.It Fl x
flag is specified, factors will be printed in hexadecimal format.
Out of range or invalid input results in
an appropriate error message to standard error.
.An Landon Curt Noll .