pmDerivedErrStr(3) return error message from failure to parse derived metric definition

C SYNOPSIS

#include <pcp/pmapi.h>

char *pmDerivedErrStr(void);

cc ... -lpcp

DESCRIPTION

When pmRegisterDerived(3) is called to add a new derived metric definition and an error occurs, pmDerivedErrStr may be called to return the associated error message.

The pmRegisterDerivedMetric interface provides a convenience wrapper around both pmRegisterDerived and pmDerivedErrStr.