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

6       tep_print_field, tep_print_fields, tep_print_num_field,
7       tep_print_func_field - Print the field content.
8

SYNOPSIS

10       #include <event-parse.h>
11       #include <trace-seq.h>
12
13       void tep_print_field(struct trace_seq *s, void *data, struct tep_format_field *field);
14       void tep_print_fields(struct trace_seq *s, void *data, int size, struct tep_event *event);
15       int tep_print_num_field(struct trace_seq *s, const char *fmt, struct tep_event *event, const char *name, struct tep_record *record, int err);
16       int tep_print_func_field(struct trace_seq *s, const char *fmt, struct tep_event *event, const char *name, struct tep_record *record, int err);
17

DESCRIPTION

19       These functions print recorded field’s data, according to the field’s
20       type.
21
22       The tep_print_field() function extracts from the recorded raw data
23       value of the field and prints it into s, according to the field type.
24
25       The tep_print_fields() prints each field name followed by the record’s
26       field value according to the field’s type:
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28           "field1_name=field1_value field2_name=field2_value ..."
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30       It iterates all fields of the event, and calls tep_print_field() for
31       each of them.
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33       The tep_print_num_field() function prints a numeric field with given
34       format string. A search is performed in the event for a field with
35       name. If such field is found, its value is extracted from the record
36       and is printed in the s, according to the given format string fmt. If
37       the argument err is non-zero, and an error occures - it is printed in
38       the s.
39
40       The tep_print_func_field() function prints a function field with given
41       format string. A search is performed in the event for a field with
42       name. If such field is found, its value is extracted from the record.
43       The value is assumed to be a function address, and a search is perform
44       to find the name of this function. The function name (if found) and its
45       address are printed in the s, according to the given format string fmt.
46       If the argument err is non-zero, and an error occures - it is printed
47       in s.
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RETURN VALUE

50       The tep_print_num_field() and tep_print_func_field() functions return 1
51       on success, -1 in case of an error or 0 if the print buffer s is full.
52

EXAMPLE

54           #include <event-parse.h>
55           #include <trace-seq.h>
56           ...
57           struct tep_handle *tep = tep_alloc();
58           ...
59           struct trace_seq seq;
60           trace_seq_init(&seq);
61           struct tep_event *event = tep_find_event_by_name(tep, "timer", "hrtimer_start");
62           ...
63           void process_record(struct tep_record *record)
64           {
65                   struct tep_format_field *field_pid = tep_find_common_field(event, "common_pid");
66
67                   trace_seq_reset(&seq);
68
69                   /* Print the value of "common_pid" */
70                   tep_print_field(&seq, record->data, field_pid);
71
72                   /* Print all fields of the "hrtimer_start" event */
73                   tep_print_fields(&seq, record->data, record->size, event);
74
75                   /* Print the value of "expires" field with custom format string */
76                   tep_print_num_field(&seq, " timer expires in %llu ", event, "expires", record, 0);
77
78                   /* Print the address and the name of "function" field with custom format string */
79                   tep_print_func_field(&seq, " timer function is %s ", event, "function", record, 0);
80            }
81            ...
82

FILES

84           event-parse.h
85                   Header file to include in order to have access to the library APIs.
86           trace-seq.h
87                   Header file to include in order to have access to trace sequences related APIs.
88                   Trace sequences are used to allow a function to call several other functions
89                   to create a string of data to use.
90           -ltraceevent
91                   Linker switch to add when building a program that uses the library.
92

SEE ALSO

94       libtraceevent(3), trace-cmd(1)
95

AUTHOR

97           Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
98           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.
99

REPORTING BUGS

101       Report bugs to <linux-trace-devel@vger.kernel.org[3]>
102

LICENSE

104       libtraceevent is Free Software licensed under the GNU LGPL 2.1
105

RESOURCES

107       https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
108

NOTES

110        1. rostedt@goodmis.org
111           mailto:rostedt@goodmis.org
112
113        2. tz.stoyanov@gmail.com
114           mailto:tz.stoyanov@gmail.com
115
116        3. linux-trace-devel@vger.kernel.org
117           mailto:linux-trace-devel@vger.kernel.org
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121libtraceevent 1.2.1               07/22/2021                  LIBTRACEEVENT(3)
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