NAME¶

pmUnitsStr, pmUnitsStr_r - convert a performance metric's units into a string

C SYNOPSIS¶

#include <pcp/pmapi.h>

const char *pmUnitsStr(const pmUnits *pu);
char *pmUnitsStr_r(const pmUnits *pu, char *buf, int buflen);

cc ... -lpcp

DESCRIPTION¶

The encoding of a performance metric's dimensionality and scale uses a pmUnits structure; see pmLookupDesc(3).

As an aid to labeling graphs and tables, or for error messages, pmUnitsStr will take a dimension and scale specification as per pu, and return the corresponding text string. The pmUnitsStr_r function does the same, but stores the result in a user-supplied buffer buf of length buflen, which should have room for at least 60 bytes. If buflen is less than 60 then pmUnitsStr_r returns NULL and buf is not changed.

For example {1, -2, 0, PM_SPACE_MBYTE, PM_TIME_SEC, 0}, as the value of *pu gives the result string Mbyte / sec^2.

The string value result from pmUnitsStr is held in a single static buffer, so the returned value is only valid until the next call to pmUnitsStr.

If the ``count'' dimension is non-zero, and the ``count'' scale is not zero, then the text string will include a decimal scaling factor, eg. count x 10^6.

As a special case, if all components of the dimension are zero, then the ``count'' scale is used to produce the text. If this scale is zero the result is an empty string, otherwise the result is of the form x1 0^2.

NOTES¶

pmUnitsStr returns a pointer to a static buffer and hence is not thread-safe. Multi-threaded applications should use pmUnitsStr_r instead.

SEE ALSO¶

PMAPI(3), pmAtomStr(3), pmConvScale(3), pmExtractValue(3), pmLookupDesc(3), pmPrintValue(3) and pmTypeStr(3).