pmgetoptions(3) — Linux manual page


PMGETOPTIONS(3)         Library Functions Manual         PMGETOPTIONS(3)

NAME         top

       pmgetopt_r, pmGetOptions, pmGetContextOptions, pmFreeOptions,
       pmUsageMessage - command line handling for PMAPI tools

C SYNOPSIS         top

       #include <pcp/pmapi.h>

       int pmgetopt_r(int argc, char *const *argv, pmOptions *opts);
       int pmGetOptions(int argc, char *const *argv, pmOptions *opts);
       int pmGetContextOptions(int ctx, pmOptions *opts);
       void pmUsageMessage(pmOptions *opts);
       void pmFreeOptions(pmOptions *opts);

       cc ... -lpcp

DESCRIPTION         top

       The pmGetOptions function provides command line option processing
       services for both monitor and collector PMAPI(3) tools.  It is
       modelled on the thread-safe variants of the GNU getopt_long(3)
       API, and primarily differs in its focus on providing generalised
       processing for the (de-facto) standard PCP command line options
       described in PCPIntro(1).  These common options include the host
       and archive specification, time windows, timezones, sample
       counts, time intervals, and so on.

       The primary interface is pmGetOptions, which should be passed the
       argc argument count and argv array, as passed to the main()
       function on program invocation.  The final opts argument
       describes the set of long and short options the tools is prepared
       to process, and other metadata regarding how those options should
       be processed.

       The pmgetopt_r interface, used internally by pmGetOptions,
       behaves in a similar fashion, but it does not perform any common
       option processing.  It is more suited to PCP collector processes,
       whereas PCP monitor tools tend to use pmGetOptions.

       The opts argument consists of an array of pmLongOpts entries
       describing the arguments, as well as the enclosing pmOptions
       struct, which are defined as follows (internal fields are not
       presented, for brevity):

         typedef struct {
             const char *        long_opt;
             int                 has_arg;
             int                 short_opt;
             const char *        argname;
             const char *        message;
         } pmLongOptions;

         typedef struct {
             int                 version;
             int                 flags;
             const char *        short_options;
             pmLongOptions *     long_options;
             const char *        short_usage;
             pmOptionOverride    override;

             int                 index;
             int                 optind;
             int                 opterr;
             int                 optopt;
             char                *optarg;
             /* [internal fields, undocumented] */

             int                 errors;
             int                 context; /* PM_CONTEXT_{HOST,ARCHIVE,LOCAL} */
             int                 nhosts;
             int                 narchives;
             char **             hosts;
             char **             archives;
             struct timeval      unused[4];
             struct timeval      start;
             struct timeval      finish;
             struct timeval      origin;
             struct timeval      interval;
             char *              align_optarg;
             char *              start_optarg;
             char *              finish_optarg;
             char *              origin_optarg;
             char *              guiport_optarg;
             char *              timezone;
             int                 samples;
             int                 guiport;
             int                 padding;
             unsigned int        guiflag : 1;
             unsigned int        tzflag  : 1;
             unsigned int        nsflag  : 1;
             unsigned int        Lflag   : 1;
             unsigned int        zeroes  : 28;
             struct timespec     start;
             struct timespec     finish;
             struct timespec     origin;
             struct timespec     interval;
         } pmOptions;

       The initial flags and version fields describe how the rest of the
       pmOptions structure is to be interpreted.  These fields can be
       zeroed, specifying a default interpretation.  Alternatively, the
       PMAPI_VERSION macro can be used to specify the API level to use
       (currently, values of 3 or less are allowed).  Version 2 is the
       default, version 3 introduces high resolution time window and
       interval fields (i.e. using struct timespec as opposed to struct
       timeval).  When using the latter form, before including
       <pcp/pmapi.h> the PMAPI_VERSION macro must be set to 3 to ensure
       the correct layout of pmOptions structure is used by the
       application.  The flags field can be used to modify option
       processing behaviour as described in the ``FLAGS VALUES'' section

       The array of long_options pmLongOpts structures must be
       terminated by a sentinel and the PMAPI_OPTIONS_END macro can be
       used to effect this termination.  Individual records within the
       long_options array can be of two types - options headers, or
       actual options.  An options header is constructed using the
       PMAPI_OPTIONS_HEADER macro, and is used for usage message option
       grouping.  Free form text can be inserted into the usage message
       at any point using the PMAPI_OPTIONS_TEXT macro - this is
       intended for additional explanatory text covering detailed usage
       that is beyond the scope of the individual headers or options.
       Otherwise, the array entry specifies an option.  These should be
       named (long_opt) if a long-option form is allowed, specify
       whether or not they take an argument (has_arg), specify the
       single character variant argument (short_opt) if a short-option
       form is allowed, and finally specify how to present the option in
       the usage message.  This latter component consists of a short,
       one-word description of the optional argument (argname) and a
       one-line description of what the command-line option does

       The short_usage string is also used only when constructing the
       usage message.  It forms the component of the usage message that
       follows the program name (i.e. argv[0]).

       The optional short_options string is the normal getopt command-
       line option specification string, using individual characters
       (those with arguments are designated as such using the ':'
       character) - as used by all getopt implementations.

       A facility is provided to extend the existing set of common
       options with additional options, as well as to re-task the
       standard options into non-standard roles for individual tools.
       The latter is achieved using the override method, which allows a
       callback function to be provided which will be called on receipt
       of every argument, prior to common processing.  If this callback
       returns a non-zero value the common processing will be short-
       circuited for that option, otherwise processing continues.  Thus,
       aach client tool is free to choose exactly which of the standard
       options they wish to support - this can be all, some, or none,
       and no matter what they choose, each tool always has access to
       the long option parsing capability and the usage message
       generation facility.

       The remaining pmOptions structure fields are filled in as a
       result of processing the arguments, and are largely self-
       explanatory.  Further discussion of these is deferred to the
       ``FLAGS VALUES'' section below.  The error field contains a count
       of errors detected during option processing.  These can be either
       usage or runtime errors, as indicated by the flags field (set,
       and passed out to the caller).  Typically, a command line tool
       will fail to start successfully and will produce an error message
       (e.g. via pmUsageMessage) if the error field is non-zero at the
       end of either pmGetOptions or pmGetContextOptions.

       Some command line option post-processing can only be performed
       once the tool has established a PMAPI context via
       pmNewContext(3).  This processing includes use of context-aware
       timezones (-z), and time window processing (-A, -O, -S, -T) that
       may be affected by the timezone, for example.  The
       pmGetContextOptions function is available for such situations,
       and it completes any remaining processing of opts with respect to
       the ctx context identifier given.

       The pmUsageMessage function generates a usage message for the
       tool, and included both standard PCP options and custom options
       for each tool, as specified by the pmLongOptions array.  It
       supports grouping of options (via PMAPI_OPTIONS_HEADER) as well
       as neat formatting of all options - short and long - their
       arguments, and individual explanatory messages.  It will build
       this usage message using pmprintf(3) upon which it will issue a
       single pmflush(3) before returning to the caller, provided the
       PM_OPTFLAG_USAGE_ERR flag is set in flags, which will happen
       automatically during option parsing, when usage errors are

       In certain situations, such as recording lists of host
       specifications or PCP archive paths, the pmGetOptions routine may
       allocate memory, and store pointers to it within opts.  Should a
       program wish to free this memory before exiting, it can use the
       pmFreeOptions routine to do so.  This is safe to call
       irrespective of whether memory was allocated dynamically,
       provided that opts was zeroed initially.

FLAGS VALUES         top

              Used internally within the library to indicate
              initialisation has been done, so that on subsequent calls
              it will not be done again.

              Used primarily internally within the library to indicate
              that the final option processing has been completed.  This
              processing involves cross-referencing a number of the
              options, to check for mutual exclusion, for example.
              There may be other post-processing at this stage also,
              provided it does not require a PMAPI context.

              Allow more than one host or set of archives to be
              specified.  The default is to allow one source of metrics
              only, however some of the more sophisticated tools permit
              multiple metric sources, each of which is handled within a
              separate context.  See also PM_OPTFLAG_MIXED.

              Indicates that the library has detected a command-line
              usage error.  This is an error such as when an option
              requires an argument but none is supplied, or conflicting
              options are specified (such as -s and -T).

              Indicates that the library has detected an error at run
              time.  This is an error such as failing to retrieve
              timezone information from pmcd(1) or failing to load an
              alternate metric namespace from a local file (via the -n

              Indicates a suggestion from the library that the tool exit
              cleanly.  This is used when the version number is
              requested, for example (the -V option and PMOPT_VERSION

              Use strict POSIX command line argument handling.  This
              means options and following arguments will not be
              reordered, so additional options cannot follow command
              line arguments.  This may be important for tools where the
              arguments can be negative numbers, for example, as these
              should not be treated as command line options in this

              Allow both live and archive metric sources to be
              specified.  The default is to allow one type of metric
              context only, however some of the more sophisticated tools
              permit multiple context types.  See also PM_OPTFLAG_MULTI.

              Many options can be specified through the either the
              command line or from similarly-named environment
              variables.  This flag disables all argument parsing, and
              only changes opts based on the environment variables.
              This may be useful for tools wishing to ensure no command
              line option conflicts occur between their own set and the
              standard PCP option set (such as an existing tool,
              reimplemented using PMAPI services).

              Only process long options, not short options.

              The default pmGetOptions behaviour is to parse the time
              window options (namely, -A, -O, -S and -T), only if one of
              those options has been specified on the command line.
              However, this flag can be used (particularly with archive
              contexts) to find the start and finish times associated
              with the context(s) even if no time window options were
              specified.  In the case of multiple archives, the time
              window is defined as the time window spanning all of the

              The timezone being used will be reported on the standard
              output stream during option parsing.  The default
              behaviour is to not report, but simply return timezone
              information via the timezone (-Z) and tzflag (-z) fields
              in the opts structure.

              The final pmflush call issued by pmUsageMessage will be
              skipped if this flag is set.  This is useful in situations
              where the caller wishes to append additional test to the
              generated usage message before flushing.

              Suppress messages from pmgetopt_r about unrecognised
              command line options.  This is the equivalent to setting
              the opterr field in the opt parameter (which mimics the
              getopt variable of the same name).


       Some environment variables may be used as an alternative to the
       command line options.  The use of these mechanisms is primarily
       for internal use by PCP tools.  General users should choose the
       command line options as this provides a clearer indication of
       intent, makes debugging issues easier and avoids confusion over
       possible conflicts between the command line options and the
       environment variables (where the command line options usually

       The following table describes the environment variables that may
       be used to set values as an alternative to command line options.

      │    Environment    │Short   │     Long       │      Meaning       │
      │                   │Option  │    Option      │                    │
      │ $PCP_ALIGN_TIME   -A      --align         │ align sample       │
      │                   │        │                │ times on           │
      │                   │        │                │ natural            │
      │                   │        │                │ boundaries         │
      │ $PCP_ARCHIVE      -a      --archive       │ metrics source     │
      │                   │        │                │ is a PCP           │
      │                   │        │                │ archive            │
      │ $PCP_ARCHIVE_LIST │        │--archive-list  │ comma-             │
      │                   │        │                │ separated list     │
      │                   │        │                │ of metric          │
      │                   │        │                │ source             │
      │                   │        │                │ archives           │
      │ $PCP_FOLIO        │        │--archive-folio │ metric source      │
      │                   │        │                │ is a mkaf(1)       │
      │                   │        │                │ archives folio     │
      │ $PCP_DEBUG        -D      --debug         │ a comma-           │
      │                   │        │                │ separated list     │
      │                   │        │                │ of                 │
      │                   │        │                │ pmSetDebug(3)      │
      │                   │        │                │ debugging          │
      │                   │        │                │ options            │
      │ $PCP_GUIMODE      -g      --guimode       │ start in GUI       │
      │                   │        │                │ mode with new      │
      │                   │        │                │ pmtime(1) time     │
      │                   │        │                │ control            │
      │ $PCP_HOST         -h      --host          │ metrics source     │
      │                   │        │                │ is pmcd(1) on      │
      │                   │        │                │ a host             │
      │ $PCP_HOST_LIST    │        │--host-list     │ comma-             │
      │                   │        │                │ separated list     │
      │                   │        │                │ of metric          │
      │                   │        │                │ source hosts       │
      │ $PCP_SPECLOCAL    -K      --spec-local    │ optional           │
      │                   │        │                │ additional DSO     │
      │                   │        │                │ PMDA               │
      │                   │        │                │ specification      │
      │                   │        │                │ for local          │
      │                   │        │                │ connection,        │
      │                   │        │                │ see                │
      │                   │        │                │ pmSpecLocalPMDA(3) │
      │ $PCP_LOCALPMDA or │-L      --local-PMDA    │ metrics source is  │
      │ $PCP_LOCALMODE    │        │                │ local connection   │
      │                   │        │                │ to a DSO PMDA      │
      │ $PCP_NAMESPACE    -n      --namespace     │ use an alternative │
      │                   │        │                │ Performance        │
      │                   │        │                │ Metrics Name Space │
      │                   │        │                │ (PMNS)             │
      │ $PCP_UNIQNAMES    -N      --uniqnames     │ like -n but only   │
      │                   │        │                │ one name allowed   │
      │                   │        │                │ for each metric in │
      │                   │        │                │ the PMNS           │
      │ $PCP_ORIGIN or    │-O      --origin        │ initial sample     │
      │ $ORIGIN_TIME      │        │                │ time within the    │
      │                   │        │                │ time window        │
      │ $PCP_GUIPORT      -p      --guiport       │ port for           │
      │                   │        │                │ connection to an   │
      │                   │        │                │ existing pmtime(1) │
      │                   │        │                │ time control       │
      │ $PCP_START_TIME   -S      --start         │ start of the time  │
      │                   │        │                │ window             │
      │ $PCP_SAMPLES      -s      --samples       │ terminate after    │
      │                   │        │                │ this many samples  │
      │ $PCP_FINISH_TIME  -T      --finish        │ end of the time    │
      │                   │        │                │ window             │
      │ $PCP_INTERVAL     -t      --interval      │ sampling interval  │
      │ $PCP_TIMEZONE     -Z      --timezone      │ set reporting      │
      │                   │        │                │ timezone           │
      │ $PCP_HOSTZONE     -z      --hostzone      │ set reporting      │
      │                   │        │                │ timezone to local  │
      │                   │        │                │ time of metrics    │
      │                   │        │                │ source             │

RETURN VALUE         top

       The pmGetOptions function returns either when it detects a
       command-line option that is not one of the standard PCP set, or
       when the end of the command line options has been reached (at
       which point -1 is returned).  Both the pmgetopt_r and
       pmGetOptions routines return control to the caller in the same
       way that a regular getopt call would, with the return value
       indicating either the end of all processing (-1), or the single
       character form of the option currently being processed, or zero
       for the special long-option-only case.  For all option-processing
       cases, the opts structure is returned containing filled out
       optarg, opterr, optopt, optind, and index fields as normal (do
       NOT use the global optarg or optind from your platform C library,
       these will NOT be modified).

       pmGetOptions does not return to the caller when any of the
       standard PCP options are being processed (although the override
       mechanism can be used to still detect such options if needed).

       The pmGetContextOptions function returns zero on success, or a
       negative PCP error code on failure.  The error field within the
       opts parameter will also be non-zero in the latter case.


       Environment variables with the prefix PCP_ are used to
       parameterize the file and directory names used by PCP.  On each
       installation, the file /etc/pcp.conf contains the local values
       for these variables.  The $PCP_CONF variable may be used to
       specify an alternative configuration file, as described in
       pcp.conf(5).  Values for these variables may be obtained
       programmatically using the pmGetOptions(3) function.

SEE ALSO         top

       PCPIntro(1), pmcd(1), pminfo(1), pmstat(1), getopt(3),
       getopt_long(3), pmNewContext(3), pmGetConfig(3), pmprintf(3),
       pmflush(3) and PMAPI(3).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨⟩ on 2023-12-22.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-12-16.)  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

Performance Co-Pilot               PCP                   PMGETOPTIONS(3)

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