PMPARSEUNITSSTR(3)

NAME
pmParseUnitsStr - parse units specification

C SYNOPSIS
#include <pcp/pmapi.h>

int pmParseUnitsStr(const char *string, struct pmUnits *out, double *outMult, char **errMsg);

cc ... -lpcp

DESCRIPTION
pmParseUnitsStr is designed to encapsulate the interpretation of a units (dimension and scale) specification in command line switches for use by the PCP client tools.

This function expects to be called with the unit/scale specification as string. This specification takes the general form produced by pmUnitsStr(3). Briefly, the format allows /-separated divisor and dividend, each listing space-separated dimensions/scales along the space, time, and count axes. There are also a few extra possibilities:

First, multiple equivalent sets of keywords are accepted for the time and space dimensions, insensitive to case. For example, "microseconds", "microsecond", "microsec", "us" are considered synonymous, as are "kilobytes", "KB", "KiB", "kiloByte", and so on.

Second, units may be offered in any order, e.g., ms kb count x 10^3 or count x 10^3 kb ms. They may not be repeated within the denominator or within the numerator. Each scale/unit keyword may be immediately followed by positive or negative exponents, e.g., ^-4.

Third, numerical scaling factors may be supplied. These are factored together with implicit scale conversions into the final outMult result.

The out and outMult values must both be allocated before calling pmParseUnitsStr(3). If the conversion is successful, pmParseUnitsStr returns 0, and fills in out and outMult with the unit/scales defined by the input parameter. If the argument strings could not be parsed, it returns a negative status code.

EXAMPLES
string | out | outMult
2 count | {0,1,0,0,0,0} | 0.5
count / 7.5 nanosecond | {0,1,-1,0,0,0} | 7.5
10 kilobytes / 2.5e2 count x 10^3 | {1,-1,0,1,3,0} | 25
millisecond / second^2 | {0,0,-1,0,0,3} | 1000
mib/s | {1,0,-1,2,0,3} | 1

BUGS
For backward compatibility, this interface interprets several traditional computer science interpretations of space units incorrectly according to the International System of Units (SI) standard.

The accepted unit string - in either singular or plural form - and the pmParseUnitsStr interpretation for each are: megabyte (is really mebibyte), gigabyte (is really gibibyte), terabyte (is really tebibyte), petabyte (is really pebibyte), exabyte (is really exbibyte), zettabyte (is really zebibyte) and yottabyte (is really yobibyte).

RETURN VALUE
A zero status indicates success. A negative status indicates an error, in which case the errMsg pointer will contain a textual error message, which the caller should later free(3).

SEE ALSO
PMAPI(3), pmUnitsStr(3), pmConvScale(3), and pmLookupDesc(3).