1libtraceevent(3)
  2================
  3
  4NAME
  5----
  6tep_get_any_field_val, tep_get_common_field_val, tep_get_field_val,
  7tep_get_field_raw - Get value of a field.
  8
  9SYNOPSIS
 10--------
 11[verse]
 12--
 13*#include <event-parse.h>*
 14*#include <trace-seq.h>*
 15
 16int *tep_get_any_field_val*(struct trace_seq pass:[*]_s_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, unsigned long long pass:[*]_val_, int _err_);
 17int *tep_get_common_field_val*(struct trace_seq pass:[*]_s_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, unsigned long long pass:[*]_val_, int _err_);
 18int *tep_get_field_val*(struct trace_seq pass:[*]_s_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, unsigned long long pass:[*]_val_, int _err_);
 19void pass:[*]*tep_get_field_raw*(struct trace_seq pass:[*]_s_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, int pass:[*]_len_, int _err_);
 20--
 21
 22DESCRIPTION
 23-----------
 24These functions can be used to find a field and retrieve its value.
 25
 26The _tep_get_any_field_val()_ function searches in the _record_ for a field
 27with _name_, part of the _event_. If the field is found, its value is stored in
 28_val_. If there is an error and _err_ is not zero, then an error string is
 29written into _s_.
 30
 31The _tep_get_common_field_val()_ function does the same as
 32_tep_get_any_field_val()_, but searches only in the common fields. This works
 33for any event as all events include the common fields.
 34
 35The _tep_get_field_val()_ function does the same as _tep_get_any_field_val()_,
 36but searches only in the event specific fields.
 37
 38The _tep_get_field_raw()_ function searches in the _record_ for a field with
 39_name_, part of the _event_. If the field is found, a pointer to where the field
 40exists in the record's raw data is returned. The size of the data is stored in
 41_len_. If there is an error and _err_ is not zero, then an error string is
 42written into _s_.
 43
 44RETURN VALUE
 45------------
 46The _tep_get_any_field_val()_, _tep_get_common_field_val()_ and
 47_tep_get_field_val()_ functions return 0 on success, or -1 in case of an error.
 48
 49The _tep_get_field_raw()_ function returns a pointer to field's raw data, and
 50places the length of this data in _len_. In case of an error NULL is returned.
 51
 52EXAMPLE
 53-------
 54[source,c]
 55--
 56#include <event-parse.h>
 57#include <trace-seq.h>
 58...
 59struct tep_handle *tep = tep_alloc();
 60...
 61struct tep_event *event = tep_find_event_by_name(tep, "kvm", "kvm_exit");
 62...
 63void process_record(struct tep_record *record)
 64{
 65	int len;
 66	char *comm;
 67	struct tep_event_format *event;
 68	unsigned long long val;
 69
 70	event = tep_find_event_by_record(pevent, record);
 71	if (event != NULL) {
 72		if (tep_get_common_field_val(NULL, event, "common_type",
 73					     record, &val, 0) == 0) {
 74			/* Got the value of common type field */
 75		}
 76		if (tep_get_field_val(NULL, event, "pid", record, &val, 0) == 0) {
 77			/* Got the value of pid specific field */
 78		}
 79		comm = tep_get_field_raw(NULL, event, "comm", record, &len, 0);
 80		if (comm != NULL) {
 81			/* Got a pointer to the comm event specific field */
 82		}
 83	}
 84}
 85--
 86
 87FILES
 88-----
 89[verse]
 90--
 91*event-parse.h*
 92	Header file to include in order to have access to the library APIs.
 93*trace-seq.h*
 94	Header file to include in order to have access to trace sequences
 95	related APIs. Trace sequences are used to allow a function to call
 96	several other functions to create a string of data to use.
 97*-ltraceevent*
 98	Linker switch to add when building a program that uses the library.
 99--
100
101SEE ALSO
102--------
103_libtraceevent(3)_, _trace-cmd(1)_
104
105AUTHOR
106------
107[verse]
108--
109*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
110*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
111--
112REPORTING BUGS
113--------------
114Report bugs to  <linux-trace-devel@vger.kernel.org>
115
116LICENSE
117-------
118libtraceevent is Free Software licensed under the GNU LGPL 2.1
119
120RESOURCES
121---------
122https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git