pmAddDerivedText - add help text for a derived metric

#include <pcp/pmapi.h>

int pmAddDerivedText(const char *name, int type, const char *text);

cc ... -lpcp

Derived metrics provide a way of extending the Performance Metrics Name Space (PMNS) with new metrics defined at the PCP client-side using expressions over the existing performance metrics. Global derived metrics are defined using pmRegisterDerived(3) or pmRegisterDerivedMetric(3) or pmLoadDerivedConfig(3), and per-context derived metrics are defined using pmAddDerived(3) or pmAddDerivedMetric(3).

Once a derived metric has been defined, pmAddDerivedText may be used to associate the help text with the derived metric identified by name.

Help text may be a ``one line'' summary or a more verbose ``multi-line'' block of text, and type should be PM_TEXT_ONELINE or PM_TEXT_HELP respectively. To associate both styles of help text with a derived metric, pmAddDerivedText would need to be called twice with different values for type.

Once a particular type of help text has been associated with a derived metric it cannot be deleted or redefined.

Applications using the Performance Metrics Application Programming Interface (PMAPI) are able to retrieve help text for specific metrics using pmLookupText(3).

pmAddDerivedText returns zero on success, else an error code.

The return value PM_ERR_NAME indicates name does not correspond to a previously defined derived metric.

Repeated calls for the same name and type will result a return value of PM_ERR_TEXT.

A return value of PM_ERR_ARG indicates that type is not one of the expected values.

PCPIntro(1), pmAddDerived(3), pmAddDerivedMetric(3), PMAPI(3), pmLoadDerivedConfig(3), pmLookupText(3), pmRegisterDerived(3), pmRegisterDerivedMetric(3) and PMNS(5).

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