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.\" $OpenBSD: fmt_scaled.3,v 1.8 2016/07/16 16:10:44 jca Exp $
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.\" Copyright (c) 2001, 2003 Ian Darwin. All rights reserved.
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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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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: July 16 2016 $
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.Dt FMT_SCALED 3
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.Os
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.Sh NAME
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.Nm fmt_scaled ,
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.Nm scan_scaled
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.Nd handle numbers with a human-readable scale
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.Sh SYNOPSIS
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.In util.h
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.Ft int
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.Fn scan_scaled "char *number_w_scale" "long long *result"
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.Ft int
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.Fn fmt_scaled "long long number" "char *result"
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.Sh DESCRIPTION
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The
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.Fn scan_scaled
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function scans the given number and looks for a terminal scale multiplier
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of B, K, M, G, T, P or E
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.Pq in either upper or lower case
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for Byte, Kilobyte, Megabyte, Gigabyte, Terabyte, Petabyte, Exabyte
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.Po computed using powers of two, i.e., Megabyte = 1024*1024
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.Pc .
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The number can have a decimal point, as in 1.5K, which returns 1536
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.Pq 1024+512 .
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If no scale factor is found, B is assumed.
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.Pp
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The
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.Fn fmt_scaled
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function formats a number for display using the same
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"human-readable" format, that is, a number with one of the above scale factors.
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Numbers will be printed with a maximum of four digits (preceded by
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a minus sign if the value is negative); values such
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as 0B, 100B, 1023B, 1K, 1.5K, 5.5M, and so on, will be generated.
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The
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.Qq result
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buffer must be allocated with at least
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.Dv FMT_SCALED_STRSIZE
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bytes.
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The result will be left-justified in the given space, and NUL-terminated.
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.Sh RETURN VALUES
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The
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.Fn scan_scaled
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and
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.Fn fmt_scaled
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functions
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return 0 on success.
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In case of error, they return \-1, leave
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.Va *result
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as is, and set
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.Va errno
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to one of the following values:
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.Dv ERANGE
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if the input string represents a number that is too large to represent.
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.Dv EINVAL
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if an unknown character was used as scale factor, or
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if the input to
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.Fn scan_scaled
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was malformed, e.g., too many '.' characters.
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.Sh EXAMPLES
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.Bd -literal -offset indent
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char *cinput = "1.5K";
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long long result;
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if (scan_scaled(cinput, &result) == 0)
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printf("%s -> %lld\en", cinput, result);
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else
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fprintf(stderr, "%s - invalid\en", cinput);
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char buf[FMT_SCALED_STRSIZE];
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long long ninput = 10483892;
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if (fmt_scaled(ninput, buf) == 0)
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printf("%lld -> %s\en", ninput, buf);
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else
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fprintf(stderr, "fmt scaled failed (errno %d)", errno);
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.Ed
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.Sh SEE ALSO
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.Xr printf 3 ,
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.Xr scanf 3
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.Sh HISTORY
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The functions
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.Fn fmt_scaled
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and
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.Fn scan_scaled
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first appeared in
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.Ox 3.4 .
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.Sh AUTHORS
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.An -nosplit
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.An Ken Stailey
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wrote the first version of the code that became
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.Fn fmt_scaled ,
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originally inside
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.Ox
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.Xr df 1 .
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.An Ian Darwin
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excerpted this and made it into a library routine
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(with significant help from
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.An Paul Janzen ) ,
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and wrote
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.Fn scan_scaled .
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.Sh BUGS
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Some of the scale factors have misleading meanings in lower case
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(p for P is incorrect; p should be pico- and P for Peta-).
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However, we bend the SI rules in favor of common sense here.
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A person creating a disk partition of "100m" is unlikely to require
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100 millibytes (i.e., 0.1 byte) of storage in the partition;
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100 megabytes is the only reasonable interpretation.
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.Pp
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Cannot represent the larger scale factors on all architectures.
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.Pp
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Ignores the current locale.
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