Provided by: libpcp3-dev_5.3.6-1build1_amd64 
NAME
pmgetopt_r, pmGetOptions, pmGetContextOptions, pmFreeOptions, pmUsageMessage - command line handling for
PMAPI tools
C SYNOPSIS
#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
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 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;
} 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 2 or less are
allowed). The flags field can be used to modify option processing behaviour as described in the ``FLAGS
VALUES'' section below.
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 (message).
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
detected.
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
PM_OPTFLAG_INIT
Used internally within the library to indicate initialisation has been done, so that on subsequent
calls it will not be done again.
PM_OPTFLAG_DONE
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.
PM_OPTFLAG_MULTI
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.
PM_OPTFLAG_USAGE_ERR
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).
PM_OPTFLAG_RUNTIME_ERR
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 option).
PM_OPTFLAG_EXIT
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 macro).
PM_OPTFLAG_POSIX
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 case.
PM_OPTFLAG_MIXED
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.
PM_OPTFLAG_ENV_ONLY
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).
PM_OPTFLAG_LONG_ONLY
Only process long options, not short options.
PM_OPTFLAG_BOUNDARIES
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 archives.
PM_OPTFLAG_STDOUT_TZ
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.
PM_OPTFLAG_NOFLUSH
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.
PM_OPTFLAG_QUIET
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).
OPTIONS VIA ENVIRONMENT VARIABLES
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 ``win'').
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 time │
│ $ORIGIN_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
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.
PCP ENVIRONMENT
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
PCPIntro(1), pmcd(1), pminfo(1), pmstat(1), getopt(3), getopt_long(3), pmNewContext(3), pmGetConfig(3),
pmprintf(3), pmflush(3) and PMAPI(3).