NAME
humanize_number —
format a number into a human readable
form
LIBRARY
library “libutil”
SYNOPSIS
#include
<libutil.h>
int
humanize_number(char *buf,
size_t len, int64_t number,
const char *suffix, int scale,
int flags);
DESCRIPTION
Thehumanize_number()
function formats the signed 64-bit quantity given in
number into buf. A space and then
suffix is appended to the end. The buffer pointed to by
buf must be at least len bytes
long.
If the formatted number (including
suffix) would be too long to fit into
buf, then divide number by 1024
until it will. In this case, prefix suffix with the
appropriate designator. The
humanize_number()
function follows the traditional computer science conventions by default,
rather than the IEE/IEC (and now also SI) power of two convention or the
power of ten notion. This behaviour however can be altered by specifying the
HN_DIVISOR_1000 and
HN_IEC_PREFIXES flags.
The traditional (default) prefixes are:
| Prefix | Description | Multiplier | Multiplier 1000x |
(note) |
kilo | 1024 | 1000 |
M |
mega | 1048576 | 1000000 |
G |
giga | 1073741824 | 1000000000 |
T |
tera | 1099511627776 | 1000000000000 |
P |
peta | 1125899906842624 | 1000000000000000 |
E |
exa | 1152921504606846976 | 1000000000000000000 |
Note: An uppercase K indicates a power of two, a lowercase k a power of ten.
The IEE/IEC (and now also SI) power of two prefixes are:
| Prefix | Description | Multiplier |
Ki |
kibi | 1024 |
Mi |
mebi | 1048576 |
Gi |
gibi | 1073741824 |
Ti |
tebi | 1099511627776 |
Pi |
pebi | 1125899906842624 |
Ei |
exbi | 1152921504606846976 |
The len argument must be at least 4 plus the
length of suffix, in order to ensure a useful result
is generated into buf. To use a specific prefix,
specify this as scale (multiplier = 1024 ^ scale; when
HN_DIVISOR_1000 is specified, multiplier = 1000 ^
scale). This cannot be combined with any of the scale
flags below.
The following flags may be passed in scale:
HN_AUTOSCALE- Format the buffer using the lowest multiplier possible.
HN_GETSCALE- Return the prefix index number (the number of times number must be divided to fit) instead of formatting it to the buffer.
The following flags may be passed in flags:
HN_DECIMAL- If the final result is less than 10, display it using one decimal place.
HN_NOSPACE- Do not put a space between number and the prefix.
HN_B- Use ‘
B’ (bytes) as prefix if the original result does not have a prefix. HN_DIVISOR_1000- Divide number with 1000 instead of 1024.
HN_IEC_PREFIXES- Use the IEE/IEC notion of prefixes (Ki, Mi, Gi...). This flag has no
effect when
HN_DIVISOR_1000is also specified.
RETURN VALUES
Upon success, the humanize_number function
returns the number of characters that would have been stored in
buf (excluding the terminating
NUL) if buf was large enough,
or -1 upon failure. Even upon failure, the contents of
buf may be modified. If
HN_GETSCALE is specified, the prefix index number
will be returned instead.
SEE ALSO
STANDARDS
The HN_DIVISOR_1000 and
HN_IEC_PREFIXES flags conform to ISO/IEC
Std 80000-13:2008 and IEEE Std 1541-2002.
HISTORY
The humanize_number() function first
appeared in NetBSD 2.0 and then in
FreeBSD 5.3. The
HN_IEC_PREFIXES flag was introduced in
FreeBSD 9.0.
CAVEATS
For numbers greater than 999 using buffer length of 4 and less can
cause rounding errors. When using HN_IEC_PREFIXES
the same error occurs for buffer length of 5 or less.