1LIBTRACEEVENT(3)             libtraceevent Manual             LIBTRACEEVENT(3)
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NAME

6       tep_get_any_field_val, tep_get_common_field_val, tep_get_field_val,
7       tep_get_field_raw - Get value of a field.
8

SYNOPSIS

10       #include <event-parse.h>
11       #include <trace-seq.h>
12
13       int tep_get_any_field_val(struct trace_seq *s, struct tep_event *event, const char *name, struct tep_record *record, unsigned long long *val, int err);
14       int tep_get_common_field_val(struct trace_seq *s, struct tep_event *event, const char *name, struct tep_record *record, unsigned long long *val, int err);
15       int tep_get_field_val(struct trace_seq *s, struct tep_event *event, const char *name, struct tep_record *record, unsigned long long *val, int err);
16       void *tep_get_field_raw(struct trace_seq *s, struct tep_event *event, const char *name, struct tep_record *record, int *len, int err);
17

DESCRIPTION

19       These functions can be used to find a field and retrieve its value.
20
21       The tep_get_any_field_val() function searches in the record for a field
22       with name, part of the event. If the field is found, its value is
23       stored in val. If there is an error and err is not zero, then an error
24       string is written into s.
25
26       The tep_get_common_field_val() function does the same as
27       tep_get_any_field_val(), but searches only in the common fields. This
28       works for any event as all events include the common fields.
29
30       The tep_get_field_val() function does the same as
31       tep_get_any_field_val(), but searches only in the event specific
32       fields.
33
34       The tep_get_field_raw() function searches in the record for a field
35       with name, part of the event. If the field is found, a pointer to where
36       the field exists in the record’s raw data is returned. The size of the
37       data is stored in len. If there is an error and err is not zero, then
38       an error string is written into s.
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RETURN VALUE

41       The tep_get_any_field_val(), tep_get_common_field_val() and
42       tep_get_field_val() functions return 0 on success, or -1 in case of an
43       error.
44
45       The tep_get_field_raw() function returns a pointer to field’s raw data,
46       and places the length of this data in len. In case of an error NULL is
47       returned.
48

EXAMPLE

50           #include <event-parse.h>
51           #include <trace-seq.h>
52           ...
53           struct tep_handle *tep = tep_alloc();
54           ...
55           struct tep_event *event = tep_find_event_by_name(tep, "kvm", "kvm_exit");
56           ...
57           void process_record(struct tep_record *record)
58           {
59                   int len;
60                   char *comm;
61                   struct tep_event_format *event;
62                   unsigned long long val;
63
64                   event = tep_find_event_by_record(pevent, record);
65                   if (event != NULL) {
66                           if (tep_get_common_field_val(NULL, event, "common_type",
67                                                        record, &val, 0) == 0) {
68                                   /* Got the value of common type field */
69                           }
70                           if (tep_get_field_val(NULL, event, "pid", record, &val, 0) == 0) {
71                                   /* Got the value of pid specific field */
72                           }
73                           comm = tep_get_field_raw(NULL, event, "comm", record, &len, 0);
74                           if (comm != NULL) {
75                                   /* Got a pointer to the comm event specific field */
76                           }
77                   }
78           }
79

FILES

81           event-parse.h
82                   Header file to include in order to have access to the library APIs.
83           trace-seq.h
84                   Header file to include in order to have access to trace sequences
85                   related APIs. Trace sequences are used to allow a function to call
86                   several other functions to create a string of data to use.
87           -ltraceevent
88                   Linker switch to add when building a program that uses the library.
89

SEE ALSO

91       libtraceevent(3), trace-cmd(1)
92

AUTHOR

94           Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
95           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.
96

REPORTING BUGS

98       Report bugs to <linux-trace-devel@vger.kernel.org[3]>
99

LICENSE

101       libtraceevent is Free Software licensed under the GNU LGPL 2.1
102

RESOURCES

104       https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
105

NOTES

107        1. rostedt@goodmis.org
108           mailto:rostedt@goodmis.org
109
110        2. tz.stoyanov@gmail.com
111           mailto:tz.stoyanov@gmail.com
112
113        3. linux-trace-devel@vger.kernel.org
114           mailto:linux-trace-devel@vger.kernel.org
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118libtraceevent 1.5.3               04/15/2022                  LIBTRACEEVENT(3)
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