1MMV_STATS_INIT(3)          Library Functions Manual          MMV_STATS_INIT(3)
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NAME

6       mmv_stats_init - create and initialize Memory Mapped Value file
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C SYNOPSIS

9       #include <pcp/pmapi.h>
10       #include <pcp/mmv_stats.h>
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12       void *mmv_stats_init(const char *name, int cluster,
13               mmv_stats_flags_t flags, const mmv_metric_t *stats, int nstats,
14               mmv_indom_t *indoms, int nindoms);
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16       cc ... -lpcp_mmv -lpcp
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DESCRIPTION

19       mmv_stats_init  creates and initializes the content of the MMV(5) file,
20       returning a handle that is used in subsequent MMV API calls.
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22       mmv_stats_stop performs an orderly shutdown of the mapping  handle  re‐
23       turned by an earlier initialization call.
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25       The file is created in the $PCP_TMP_DIR/mmv directory, name argument is
26       expected to be a basename of the file, not the full path.  The metadata
27       content of the file does not change after the file has been created.
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29       The old file is removed unconditionally unless there was an error.
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31       cluster is the preferred MMV PMDA cluster ID to be used for the metrics
32       originating from this call to mmv_stats_init.  The flags provide  addi‐
33       tional  control  over  the  behaviour  of  the  MMV  PMDA - e.g. use of
34       MMV_FLAG_PROCESS will ensure values are only exported when the  instru‐
35       mented  application  is  running - this is verified on each request for
36       new values.
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38       stats is the array of mmv_metric_t elements of length nstats. Each ele‐
39       ment of the array describes one PCP metric.
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41               typedef struct {
42                   char name[MMV_NAMEMAX];     /* Name of the metric */
43                   __uint32_t item;            /* Item component of PMID */
44                   mmv_metric_type_t type;     /* Type of the metric */
45                   mmv_metric_sem_t semantics; /* Semantics of the metric */
46                   pmUnits dimension;          /* Dimensions (TIME,SPACE,etc) */
47                   __uint32_t indom;           /* Instance domain identifier */
48                   char *shorttext;            /* Optional, one-line help */
49                   char *helptext;             /* Optional, full help text */
50               } mmv_metric_t;
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52       If  indom is not zero and not PM_INDOM_NULL, then the metric has multi‐
53       ple values and there must be a corresponding indom entry in  the  indom
54       list (uniquely identified by serial number).
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56       The  stats  array cannot contain any elements which have no name - this
57       is considered an error and no metrics will be exported in this case.
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59       indoms is the array of mmv_indom_t elements of length nindoms. Each el‐
60       ement of the array describes one PCP instance domain.
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62               typedef struct {
63                   __int32_t internal;
64                   char external[MMV_NAMEMAX];
65               } mmv_instances_t;
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67               typedef struct {
68                   __uint32_t serial;          /* Unique serial number */
69                   __uint32_t count;           /* Number of instances */
70                   mmv_instances_t *instances; /* Internal/external IDs */
71                   char *shorttext;            /* Short help text */
72                   char *helptext;             /* Long help text */
73               } mmv_indom_t;
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RETURNS

76       The function returns the address of the memory mapped region on success
77       or NULL on failure.
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SEE ALSO

80       mmv_inc_value(3), mmv_lookup_value_desc(3) and mmv(5).
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