pmlookupname(3) — Linux manual page

NAME | C SYNOPSIS | DESCRIPTION | EXAMPLE | DIAGNOSTICS | SEE ALSO | COLOPHON

PMLOOKUPNAME(3)          Library Functions Manual         PMLOOKUPNAME(3)

NAME         top

       pmLookupName - translate performance metric names into PMIDs

C SYNOPSIS         top

       #include <pcp/pmapi.h>

       int pmLookupName(int numpmid, const char **namelist,
                        pmID *pmidlist);

       cc ... -lpcp

DESCRIPTION         top

       Given  a  list  in  namelist containing numpmid full pathnames for
       performance metrics from a Performance Metrics Name Space  (PMNS),
       pmLookupName  returns  the  list  of associated Performance Metric
       Identifiers (PMIDs) via pmidlist.

       The result from pmLookupName depends on the presence of any lookup
       failures, their severity and the number of  metrics  being  looked
       up.

       1.  If there are no lookup failures, the return value will be
           numpmid.

       2.  If a fatal error is encountered, the return value will be less
           than 0.  For example PM_ERR_TOOSMALL, PM_ERR_NOPMNS or
           PM_ERR_IPC.

       3.  If numpmid is greater than one and non-fatal error(s) are en‐
           countered, the return value is the number of metric names that
           have successfully been looked up (greater than or equal to ze‐
           ro and less than or equal to numpmid).

       4.  If numpmid is one and a non-fatal error is encountered, the
           return value is the error code (less than zero).

       When errors are encountered, any metrics that cannot be looked up
       result in the corresponding element of pmidlist being set to
       PM_ID_NULL.

       The slightly convoluted error protocol allows bulk lookups, then
       probing for more error details in the case of a specific failure,
       as shown in the EXAMPLES section below.

       Note that the error protocol guarantees there is a 1:1 relation‐
       ship between the elements of namelist and pmidlist, hence both
       lists contain exactly numpmid elements.  For this reason, the
       caller is expected to have preallocated a suitably sized array for
       pmidlist.

EXAMPLE         top

       #include <pcp/pmapi.h>

       #define NUMPMID (sizeof(names)/sizeof(const char *))
       const char *names[] = {
                      "sample.bin",
                      "sample",
                      "sample.bog",
                      "sample.secret.bar",
                      "sample.secret.bar.bad"
                    };
       pmID pmids[NUMPMID];

       int
       main(int argc, char **argv)
       {
           int  sts;
           int  numpmid = NUMPMID;

           pmNewContext(PM_CONTEXT_HOST, "local:");

           sts = pmLookupName(numpmid, names, pmids);

           if (sts < 0) {
            fprintf(stderr, "pmLookupName failed: %s0, pmErrStr(sts));
            exit(1);
           }
           if (sts != numpmid) {
            /*
             * some of the lookups failed ... report the reason(s)
             */
            int  i;

            for (i = 0; i < numpmid; i++) {
                if (pmids[i] != PM_ID_NULL) continue;
                /* this one failed */
                sts = pmLookupName(1, &names[i], &pmids[i]);
                fprintf(stderr, "%s: lookup failed: %s0, names[i], pmErrStr(sts));
            }
            exit(1);
           }

           /* all good ... */
           ...
       }

DIAGNOSTICS         top

       PM_ERR_TOOSMALL
              numpmid must be at least 1

       PM_ERR_NOPMNS
              Failed to access a PMNS for operation.  Note that if the
              application hasn't a priori called pmLoadNameSpace(3) and
              wants to use the distributed PMNS, then a call to pmLookup‐
              Name must be made after the creation of a context (see
              pmNewContext(3)).

       PM_ERR_NAME
              namelist[0] does not correspond to a valid metric name in
              the PMNS.

       PM_ERR_NONLEAF
              namelist[0] refers to a node in the PMNS but it was not a
              leaf node.

       PM_ERR_*
              Other diagnostics are for protocol failures when accessing
              the distributed PMNS.

SEE ALSO         top

       PMAPI(3), pmGetChildren(3), pmGetChildrenStatus(3),
       pmGetConfig(3), pmLoadNameSpace(3), pmNameID(3), pmNewContext(3),
       pcp.conf(5) and pcp.env(5).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.  In‐
       formation about the project can be found at ⟨http://www.pcp.io/⟩.
       If you have a bug report for this manual page, send it to
       pcp@groups.io.  This page was obtained from the project's upstream
       Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ on
       2025-08-11.  (At that time, the date of the most recent commit
       that was found in the repository was 2025-08-11.)  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a
       mail to man-pages@man7.org

Performance Co-Pilot               PCP                    PMLOOKUPNAME(3)

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