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44f01c419d
Since so many programs don't check return value, always NUL terminate the buf... fix rounding when using base 1024 (the bug that started it all)... add a set of test cases so we can make sure that things don't break in the future... Thanks to Clifton Royston for testing and the test program... Approved by: re (hrs, glebius) MFC after: 1 week
203 lines
5.5 KiB
Groff
203 lines
5.5 KiB
Groff
.\" $NetBSD: humanize_number.3,v 1.4 2003/04/16 13:34:37 wiz Exp $
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.\" $FreeBSD$
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.\"
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.\" Copyright (c) 1999, 2002 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Luke Mewburn and by Tomas Svensson.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd October 7, 2013
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.Dt HUMANIZE_NUMBER 3
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.Os
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.Sh NAME
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.Nm humanize_number
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.Nd format a number into a human readable form
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.Sh LIBRARY
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.Lb libutil
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.Sh SYNOPSIS
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.In libutil.h
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.Ft int
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.Fo humanize_number
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.Fa "char *buf" "size_t len" "int64_t number" "const char *suffix"
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.Fa "int scale" "int flags"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn humanize_number
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function formats the signed 64-bit quantity given in
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.Fa number
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into
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.Fa buf .
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A space and then
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.Fa suffix
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is appended to the end.
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The buffer pointed to by
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.Fa buf
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must be at least
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.Fa len
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bytes long.
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.Pp
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If the formatted number (including
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.Fa suffix )
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would be too long to fit into
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.Fa buf ,
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then divide
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.Fa number
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by 1024 until it will.
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In this case, prefix
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.Fa suffix
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with the appropriate designator.
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The
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.Fn humanize_number
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function follows the traditional computer science conventions by
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default, rather than the IEE/IEC (and now also SI) power of two
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convention or the power of ten notion.
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This behaviour however can be altered by specifying the
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.Dv HN_DIVISOR_1000
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and
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.Dv HN_IEC_PREFIXES
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flags.
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.Pp
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The traditional
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.Pq default
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prefixes are:
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.Bl -column "Prefix" "Description" "1000000000000000000" -offset indent
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.It Sy "Prefix" Ta Sy "Description" Ta Sy "Multiplier" Ta Sy "Multiplier 1000x"
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.It Li (note) Ta No kilo Ta 1024 Ta 1000
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.It Li M Ta No mega Ta 1048576 Ta 1000000
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.It Li G Ta No giga Ta 1073741824 Ta 1000000000
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.It Li T Ta No tera Ta 1099511627776 Ta 1000000000000
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.It Li P Ta No peta Ta 1125899906842624 Ta 1000000000000000
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.It Li E Ta No exa Ta 1152921504606846976 Ta 1000000000000000000
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.El
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.Pp
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Note:
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An uppercase K indicates a power of two, a lowercase k a power of ten.
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.Pp
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The IEE/IEC (and now also SI) power of two prefixes are:
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.Bl -column "Prefix" "Description" "1000000000000000000" -offset indent
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.It Sy "Prefix" Ta Sy "Description" Ta Sy "Multiplier"
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.It Li Ki Ta No kibi Ta 1024
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.It Li Mi Ta No mebi Ta 1048576
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.It Li Gi Ta No gibi Ta 1073741824
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.It Li Ti Ta No tebi Ta 1099511627776
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.It Li Pi Ta No pebi Ta 1125899906842624
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.It Li Ei Ta No exbi Ta 1152921504606846976
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.El
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.Pp
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The
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.Fa len
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argument must be at least 4 plus the length of
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.Fa suffix ,
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in order to ensure a useful result is generated into
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.Fa buf .
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To use a specific prefix, specify this as
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.Fa scale
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.Po multiplier = 1024 ^ scale;
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when
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.Dv HN_DIVISOR_1000
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is specified,
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multiplier = 1000 ^ scale
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.Pc .
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This cannot be combined with any of the
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.Fa scale
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flags below.
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.Pp
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The following flags may be passed in
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.Fa scale :
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.Bl -tag -width ".Dv HN_DIVISOR_1000" -offset indent
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.It Dv HN_AUTOSCALE
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Format the buffer using the lowest multiplier possible.
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.It Dv HN_GETSCALE
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Return the prefix index number (the number of times
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.Fa number
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must be divided to fit) instead of formatting it to the buffer.
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.El
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.Pp
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The following flags may be passed in
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.Fa flags :
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.Bl -tag -width ".Dv HN_DIVISOR_1000" -offset indent
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.It Dv HN_DECIMAL
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If the final result is less than 10, display it using one decimal place.
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.It Dv HN_NOSPACE
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Do not put a space between
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.Fa number
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and the prefix.
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.It Dv HN_B
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Use
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.Ql B
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(bytes) as prefix if the original result does not have a prefix.
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.It Dv HN_DIVISOR_1000
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Divide
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.Fa number
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with 1000 instead of 1024.
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.It Dv HN_IEC_PREFIXES
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Use the IEE/IEC notion of prefixes (Ki, Mi, Gi...).
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This flag has no effect when
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.Dv HN_DIVISOR_1000
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is also specified.
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.El
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.Sh RETURN VALUES
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Upon success, the
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.Nm
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function returns the number of characters that would have been stored in
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.Fa buf
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(excluding the terminating
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.Dv NUL )
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if
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.Fa buf
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was large enough, or \-1 upon failure.
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Even upon failure, the contents of
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.Fa buf
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may be modified.
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If
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.Dv HN_GETSCALE
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is specified, the prefix index number will be returned instead.
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.Sh SEE ALSO
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.Xr expand_number 3
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.Sh STANDARDS
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The
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.Dv HN_DIVISOR_1000
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and
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.Dv HN_IEC_PREFIXES
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flags
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conform to
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.Tn ISO/IEC
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Std\~80000-13:2008
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and
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.Tn IEEE
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Std\~1541-2002.
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.Sh HISTORY
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The
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.Fn humanize_number
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function first appeared in
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.Nx 2.0
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and then in
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.Fx 5.3 .
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The
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.Dv HN_IEC_PREFIXES
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flag was introduced in
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.Fx 9.0 .
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