pmdaGetInDomHelp(3) help text support for a PMDA

Other Alias

pmdaOpenHelp, pmdaGetHelp, pmdaCloseHelp


#include <pcp/pmapi.h>
#include <pcp/impl.h>
#include <pcp/pmda.h>

int pmdaOpenHelp(char *fname);
char *pmdaGetHelp(int handle, pmID pmid, int type);
char *pmdaGetInDomHelp(int handle, pmInDom indom, int type);
void pmdaCloseHelp(int handle);

cc ... -lpcp_pmda -lpcp


As part of the Performance Metrics Domain Agent (PMDA) API (see PMDA(3)), this group of routines is used to implement the processing of a PMDA's metric help information.

These routines are really intended for internal use, and should not need to be called directly from any PMDA code.

Briefly, the base name of the help text file (as created by newhelp(1)) is passed in via a -h command line option for a daemon PMDA or as an argument to pmdaDaemon(3) or pmdaDSO(3). Then pmdaOpenHelp is called from pmdaInit(3) and returns a handle that is used in subsequent calls to identify a particular help text collection (each PMDA typically has only one such collection).

Requests for help text are passed to pmdaText(3) which calls pmdaGetHelp or pmdaGetInDomHelp as required.

Other than error cases in pmdaOpenHelp, pmdaCloseHelp is not called.


pmdaOpenHelp returns a negative value for failure, suitable for decoding with pmErrStr(3). pmdaGetHelp and pmdaGetInDomHelp return NULL if the corresponding help text does not exist.


The PMDA must be using PMDA_PROTOCOL_2 or later, as specified in the call to pmdaDSO(3) or pmdaDaemon(3).