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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
By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo
chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\
.Dd April 22, 2010 .Dt FACTOR 6 .Os .Sh NAME .Nm factor .Nd factor a number .Sh SYNOPSIS .Nm .Op Ar number ... .Sh DESCRIPTION The .Nm utility factors positive integers. When a number is factored, it is printed, followed by a .Dq : , and the list of
q prime 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.
p When .Nm is invoked with one or more arguments, each argument will be factored.
p 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 - or +, although negative numbers are rejected. 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.
p By default, .Nm is compiled against the OpenSSL bignum implementation .Xr openssl_bn 3 , which lets it handle arbitrarily large values.
q Note however that very large values can take a very long time to factor.
If
.Nm
is compiled without OpenSSL it is limited to the maximum value of
.Vt unsigned long .
.Sh DIAGNOSTICS
Out of range or invalid input results in
an appropriate error message
being written to standard error.
.Sh BUGS
.Nm
cannot handle the
.Dq 10 most wanted
factor list.