freebsd-dev/games/factor/factor.6

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.\" This code is derived from software contributed to Berkeley by
.\" Landon Curt Noll.
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.\"	@(#)factor.6	8.1 (Berkeley) 5/31/93
.\"
.\" $FreeBSD$
.\"
.\" By: Landon Curt Noll   chongo@toad.com,   ...!{sun,tolsoft}!hoptoad!chongo
.\"
.\"   chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
.\"
.Dd October 10, 2002
.Dt FACTOR 6
.Os
.Sh NAME
.Nm factor , primes
.Nd factor a number, generate primes
.Sh SYNOPSIS
.Nm
.Op Fl h
.Op Ar number ...
.Nm primes
.Op Fl h
.Op Ar start Op Ar stop
.Sh DESCRIPTION
The
.Nm
utility will factor positive integers.
When a number is factored, it is printed, followed by a
.Ql \&: ,
and the list of factors on a single line.
Factors are listed in ascending order, and are preceded by a space.
If a factor divides a value more than once, it will be printed more than once.
.Pp
When
.Nm
is invoked with one or more arguments, each argument will be factored.
.Pp
When
.Nm
is invoked with no arguments,
.Nm
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
.Ql + .
Numbers are terminated by a non-digit character (such as a newline).
After a number is read, it is factored.
.Pp
The
.Nm primes
utility prints primes in ascending order, one per line, starting at or above
.Ar start
and continuing until, but not including
.Ar stop .
The
.Ar start
value must be at least 0 and not greater than
.Ar stop .
The
.Ar stop
value must not be greater than the maximum.
The default and maximum value of
.Ar stop
is 4294967295 on 32-bit architectures
and 18446744073709551615 on 64-bit ones.
.Pp
When the
.Nm primes
utility is invoked with no arguments,
.Ar start
is read from standard input and
.Ar stop
is taken to be the maximum.
The
.Ar start
value may be preceded by a single
.Ql + .
The
.Ar start
value is terminated by a non-digit character (such as a newline).
.Sh DIAGNOSTICS
.Bl -diag
.It "negative numbers aren't permitted"
.It "illegal numeric format"
.It "start value must be less than stop value"
.It "Result too large"
.El
.Sh BUGS
.Nm
cannot handle the
.Dq "10 most wanted"
factor list,
.Nm primes
will not get you a world record.