HUMANIZE_NUMBER(3)     FreeBSD Library Functions Manual     HUMANIZE_NUMBER(3)

NAME
     humanize_number - format a number into a human readable form

LIBRARY
     System Utilities Library (libutil, -lutil)

SYNOPSIS
     #include <libutil.h>

     int
     humanize_number(char *buf, size_t len, int64_t number,
         const char *suffix, int scale, int flags);

DESCRIPTION
     The humanize_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_1000 is 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
     expand_number(3)

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.

FreeBSD 13.1-RELEASE-p6         October 7, 2013        FreeBSD 13.1-RELEASE-p6