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pmdaGetOpt − get options from argument vector, trapping generic PMDA options


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

int pmdaGetOpt(int argc, char *const *argv, const char *optstring, pmdaInterface *dispatch, int *err);

cc ... −lpcp_pmda −lpcp


This function is a wrapper for getopt(3). The behavior of the function is identical except that certain options are assumed to have a predefined behavior which initializes several fields in the pmdaInterface structure.

The options that pmdaGetOpt will trap are:


Set the PMAPI(3) debug control variable (pmDebug) to trace. Used for controlling levels of trace output while debugging.


Set the domain number of this agent.


Obtain the help text (see pmdaText(3)) for the metrics from this file rather than from the path specified with pmdaDSO(3) or pmdaDaemon(3).


Expect PMCD to connect on inet port (number or name).


Redirect diagnostics and trace output to logfile.


Expect PMCD to supply stdin/stdout pipe.


Expect PMCD to connect on unix domain socket.

Only one of −i, −p and −u may be specified. If none of these three options is given, a pipe (−p) is assumed. When these options are encountered by pmdaGetOpt, the option is processed and the next option is examined. Therefore, pmdaGetOpt will only return when an option other than those listed above is found, or the end of the list is reached. The returned value will be the argument or EOF, respectively.

A PMDA can control which of these options the program will accept with the optstring argument. To accept all the options, the PMDA should call pmdaGetOpt with the option string "D:d:h:i:l:pu:". Any PMDA specific options should be added to this string in the style of getopt(3), and returned by pmdaGetOpt if encountered. However, the PMDA cannot reuse any of the options specified above.

pmdaGetOpt takes a pointer to an int, err, which is used as an error count. This variable should be initialized to zero before pmdaGetOpt is first called, and tested when pmdaGetOpt returns EOF.

pmdaGetOpt does not modify argc or argv.


A PMDA which takes the additional argument −n and does not use pmDebug might call pmdaGetOpt like this:

    pmdaInterface dispatch;
    int           err = 0;
    int           c = 0;

    while ((c = pmdaGetOpt(argv, argc, "d:h:i:l:pu:n:",
                           dispatch &err)) != EOF) {
        /* process argument ’n’, may use optarg etc. */

    if (err)

The global variables used by getopt (3) may be used by the caller of pmdaGetOpt within the argument parsing loop.


pmdaGetOpt will display the same error messages as getopt.


The options −D, −d, −i, −l, −p and −u cannot be reused for other purposes by the PMDA.

The PMDA must be using PMDA_INTERFACE_2 or later, as specified in the call to pmdaDSO(3) or pmdaDaemon(3).


pmdbg(1), getopt(3), PMAPI(3), PMDA(3), pmdaDaemon(3), pmdaDSO(3) and pmdaText(3).