.\"	$NetBSD: humanize_number.9,v 1.9 2010/08/07 16:41:34 jruoho Exp $
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.Dd August 7, 2010
.Dt HUMANIZE_NUMBER 9
.Os
.Sh NAME
.Nm humanize_number ,
.Nm format_bytes
.Nd human readable numbers
.Sh SYNOPSIS
.Ft int
.Fn humanize_number \
"char *buf" "size_t len" "uint64_t number" "const char *suffix" "int divisor"
.Ft int
.Fn format_bytes "char *buf" "size_t len" "uint64_t number"
.Sh DESCRIPTION
The
.Fn humanize_number
function formats the unsigned 64-bit quantity given in
.Fa number
into
.Fa buf .
A space and then
.Fa suffix
is appended to the end.
The supplied
.Fa buf
must be at least
.Fa len
bytes long.
.Pp
If the formatted number (including
.Fa suffix )
is too long to fit into
.Fa buf ,
.Fn humanize_number
divides
.Fa number
by
.Fa divisor
until it will fit.
In this case,
.Fa suffix
is prefixed with the appropriate SI designator.
Suitable values of
.Fa divisor
are 1024 or 1000 to remain consistent with the common meanings of the
SI designator prefixes.
.Pp
The prefixes are:
.Bl -column "Prefix" "Description" "Multiplier" -offset indent
.It Sy "Prefix" Ta Sy "Description" Ta Sy "Multiplier"
.It k	kilo	1024
.It M	mega	1048576
.It G	giga	1073741824
.It T	tera	1099511627776
.It P	peta	1125899906842624
.It E	exa	1152921504606846976
.El
.Pp
The
.Fa len
argument must be at least 4 plus the length of
.Fa suffix ,
in order to ensure a useful result in
.Fa buf .
.Pp
The
.Fn format_bytes
function
is a front-end to
.Fn humanize_number .
It calls the latter with a
.Fa suffix
of
.Dq B .
Also, if the suffix in the returned
.Fa buf
would not have a prefix, the suffix is removed.
This means that a result of
.Dq 100000
occurs, instead of
.Dq 100000 B .
.Sh RETURN VALUES
Both functions return the number of characters stored in
.Fa buf
(excluding the terminating NUL) upon success, or \-1 upon failure.
.Sh SEE ALSO
.Xr humanize_number 3
.Sh HISTORY
These functions first appeared in
.Nx 1.5 .