factor/factor.6

   1 .\"     $NetBSD: factor.6,v 1.15 2020/10/03 22:27:00 christos Exp $
   2 .\"
   3 .\" Copyright (c) 1989, 1993
   4 .\"     The Regents of the University of California.  All rights reserved.
   5 .\"
   6 .\" This code is derived from software contributed to Berkeley by
   7 .\" Landon Curt Noll.
   8 .\"
   9 .\" Redistribution and use in source and binary forms, with or without
  10 .\" modification, are permitted provided that the following conditions
  11 .\" are met:
  12 .\" 1. Redistributions of source code must retain the above copyright
  13 .\"    notice, this list of conditions and the following disclaimer.
  14 .\" 2. Redistributions in binary form must reproduce the above copyright
  15 .\"    notice, this list of conditions and the following disclaimer in the
  16 .\"    documentation and/or other materials provided with the distribution.
  17 .\" 3. Neither the name of the University nor the names of its contributors
  18 .\"    may be used to endorse or promote products derived from this software
  19 .\"    without specific prior written permission.
  20 .\"
  21 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31 .\" SUCH DAMAGE.
  32 .\"
  33 .\"     @(#)factor.6    8.1 (Berkeley) 5/31/93
  34 .\"
  35 .\"
  36 .\" By Landon Curt Noll, http://www.isthe.com/chongo/index.html /\oo/\
  37 .\"
  38 .Dd October 3, 2020
  39 .Dt FACTOR 6
  40 .Os
  41 .Sh NAME
  42 .Nm factor
  43 .Nd factor a number
  44 .Sh SYNOPSIS
  45 .Nm
  46 .Op Fl hx
  47 .Op Ar number ...
  48 .Sh DESCRIPTION
  49 The
  50 .Nm
  51 utility factors integers larger than 1.
  52 When a number is factored, it is printed, followed by a
  53 .Dq \&: ,
  54 and the list of
  55 .Pq prime
  56 factors on a single line.
  57 Factors are listed in ascending order, and are preceded by a space.
  58 By default, if a factor divides a value more than once, it will be
  59 printed more than once.
  60 .Pp
  61 When
  62 .Nm
  63 is invoked with one or more
  64 .Ar number
  65 arguments, each argument will be factored.
  66 .Pp
  67 When
  68 .Nm
  69 is invoked with no
  70 .Ar number
  71 arguments,
  72 .Nm
  73 reads numbers, one per line, from standard input, until end of file or error.
  74 Leading white-space and empty lines are ignored.
  75 Numbers may be preceded by a single +.
  76 Integer less than 2 are rejected.
  77 Numbers are terminated by a non-digit character (such as a newline).
  78 After a number is read, it is factored.
  79 Input lines must not be longer than
  80 .Dv LINE_MAX \- 1
  81 (currently 2047) characters.
  82 .Pp
  83 By default,
  84 .Nm
  85 is compiled against the OpenSSL bignum implementation
  86 .Xr openssl_bn 3 ,
  87 which lets it handle arbitrarily large values.
  88 .Pq Note however that very large values can take a very long time to factor.
  89 If
  90 .Nm
  91 is compiled without OpenSSL it is limited to the maximum value of
  92 .Vt unsigned long .
  93 .Pp
  94 The following option is available:
  95 .Bl -tag -width flag
  96 .It Fl h
  97 If the
  98 .Fl h
  99 flag is specified, factors will be printed in "human-readable" format.
 100 If a factor x divides a value n (>1) times, it will appear as x^n.
 101 .It Fl x
 102 If the
 103 .Fl x
 104 flag is specified, factors will be printed int hexadecimal format.
 105 .El
 106 .Sh DIAGNOSTICS
 107 Out of range or invalid input results in
 108 an appropriate error message to standard error.
 109 .Sh AUTHORS
 110 Originally by
 111 .An Landon Curt Noll .