pmdaGetOpt(3) get options from arguments, parsing generic PMDA options

Other Alias



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

int pmdaGetOptions(int argc, char *const *argv, pmdaOptions *opts, pmdaInterface *dispatch);

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

cc ... -lpcp_pmda -lpcp


These functions are wrappers for pmgetopt_r(3). The behavior of each function is that certain options are assumed to have a predefined behavior which initializes several fields in the pmdaInterface structure. The pmdaGetOptions interface allows both short and long options to be given, whereas pmdaGetOpt allows for short form options only.

The options that both pmdaGetOptions and 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).
Expect PMCD to connect on ipv6 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.

The pmdaGetOptions interface will also capture the following options, and store them within the opts parameter:

Set the user account name under which the PMDA should execute.

Only one of -i, -6, -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 either the opts or optstring argument. To accept all the options, the PMDA should call pmdaGetOptions with the short_options field of the opts structure set to the PMDA_OPTIONS macro, or pmdaGetOpt with the option string "D:d:h:i:l:pu:". Any PMDA specific options should be added to these strings in the style of getopt(3), and will be returned by both pmdaGetOptions and pmdaGetOpt if encountered.

When a command line option usage error is detected in the pmdaGetOptions interface, the error field of the opts structure will contain a non-zero error count.

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.

Neither pmdaGetOptions nor pmdaGetOpt modify their argc or argv parameters.

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

On the other hand, the pmdaGetOptions interface does not utilize global variables at all (neither reading nor modifying them). Instead, these variables can be access via the opts fields of the same name.


Both pmdaGetOptions and 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, unless using the override method provided by the pmdaGetOptions interface, which operates in the same way as described for the pmGetOptions(3) interface used by PMAPI client tools.

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