xref: /freebsd/usr.bin/factor/factor.6 (revision 49b49cda41feabe3439f7318e8bf40e3896c7bf4)
1.\" Copyright (c) 1989, 1993
2.\"	The Regents of the University of California.  All rights reserved.
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4.\" This code is derived from software contributed to Berkeley by
5.\" Landon Curt Noll.
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31.\"	@(#)factor.6	8.1 (Berkeley) 5/31/93
32.\"
33.\" $FreeBSD$
34.\"
35.\" By: Landon Curt Noll   chongo@toad.com,   ...!{sun,tolsoft}!hoptoad!chongo
36.\"
37.\"   chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
38.\"
39.Dd October 10, 2002
40.Dt FACTOR 6
41.Os
42.Sh NAME
43.Nm factor , primes
44.Nd factor a number, generate primes
45.Sh SYNOPSIS
46.Nm
47.Op Fl h
48.Op Ar number ...
49.Nm primes
50.Op Fl h
51.Op Ar start Op Ar stop
52.Sh DESCRIPTION
53The
54.Nm
55utility will factor positive integers.
56When a number is factored, it is printed, followed by a
57.Ql \&: ,
58and the list of factors on a single line.
59Factors are listed in ascending order, and are preceded by a space.
60If a factor divides a value more than once, it will be printed more than once.
61.Pp
62When
63.Nm
64is invoked with one or more arguments, each argument will be factored.
65.Pp
66When
67.Nm
68is invoked with no arguments,
69.Nm
70reads numbers, one per line, from standard input, until end of file or error.
71Leading white-space and empty lines are ignored.
72Numbers may be preceded by a single
73.Ql + .
74Numbers are terminated by a non-digit character (such as a newline).
75After a number is read, it is factored.
76.Pp
77The
78.Nm primes
79utility prints primes in ascending order, one per line, starting at or above
80.Ar start
81and continuing until, but not including
82.Ar stop .
83The
84.Ar start
85value must be at least 0 and not greater than
86.Ar stop .
87The
88.Ar stop
89value must not be greater than the maximum.
90The default and maximum value of
91.Ar stop
92is 3825123056546413050.
93.Pp
94When the
95.Nm primes
96utility is invoked with no arguments,
97.Ar start
98is read from standard input and
99.Ar stop
100is taken to be the maximum.
101The
102.Ar start
103value may be preceded by a single
104.Ql + .
105The
106.Ar start
107value is terminated by a non-digit character (such as a newline).
108.Sh DIAGNOSTICS
109.Bl -diag
110.It "negative numbers aren't permitted"
111.It "illegal numeric format"
112.It "start value must be less than stop value"
113.It "Result too large"
114.El
115.Sh BUGS
116.Nm
117cannot handle the
118.Dq "10 most wanted"
119factor list,
120.Nm primes
121will not get you a world record.
122.Pp
123.Nm primes
124is unable to list primes between 3825123056546413050 and 18446744073709551615
125since it relies on strong pseudoprime tests after sieving, and nobody has
126proven how many strong pseudoprime tests are required to prove primality for
127integers larger than 3825123056546413050.
128