libtracefs(3)
=============

NAME
----
tracefs_event_systems, tracefs_system_events, tracefs_iterate_raw_events -
Work with trace systems and events.

SYNOPSIS
--------
[verse]
--
*#include <tracefs.h>*

char pass:[*]pass:[*]*tracefs_event_systems*(const char pass:[*]_tracing_dir_);
char pass:[*]pass:[*]*tracefs_system_events*(const char pass:[*]_tracing_dir_, const char pass:[*]_system_);
int *tracefs_iterate_raw_events*(struct tep_handle pass:[*]_tep_, struct tracefs_instance pass:[*]_instance_, cpu_set_t pass:[*]_cpus_, int _cpu_size_, int (pass:[*]_callback_)(struct tep_event pass:[*], struct tep_record pass:[*], int, void pass:[*]), void pass:[*]_callback_context_);

--

DESCRIPTION
-----------
Trace systems and events related APIs.

The _tracefs_event_systems()_ function returns array of strings with the
names of all registered trace systems, located in the given _tracing_dir_
directory. This could be NULL or the location of the tracefs mount point
for the trace systems of the local machine, or it may be a path to a copy
of the tracefs directory from another machine. The last entry in the array
is a NULL pointer. The array must be freed with _tracefs_list_free()_ API.

The _tracefs_system_events()_ function returns array of strings with the
names of all registered trace events for given trace system specified by
_system_, located in the given _tracing_dir_ directory. This could be NULL
or the location of the tracefs mount point for the trace systems of the
local machine, or it may be a path to a copy of the tracefs directory
from another machine. The last entry in the array as a NULL pointer.
The array must be freed with _tracefs_list_free()_ API.

The _tracefs_interate_raw_events()_ function will read the tracefs raw
data buffers and call the specified _callback_ function for every event it
encounters. An initialized _tep_ handler is required (See
_tracefs_local_events_(3)). If _instance_ is NULL, then the toplevel
tracefs buffer is used, otherwise the buffer for the corresponding
_instance_ is read. To filter only on a subset of CPUs, _cpus_ and
_cpu_size_ may be set to only call _callback_ with events that occurred on
the CPUs specified, otherwise if _cpus_ is NULL then the _callback_
function will be called for all events, and _cpu_size_ is ignored. The
_callback_ function will be called with the following parameters: A
pointer to a struct tep_event that corresponds to the type of event the
record is; The record representing the event; The CPU that the event
occurred on; and a pointer to user specified _callback_context_. If the _callback_
returns non-zero, the iteration stops.


RETURN VALUE
------------
The _tracefs_event_systems()_ and __tracefs_system_events()_ functions return
an array of strings. The last element in that array is a NULL pointer. The array
must be freed with _tracefs_list_free()_ API. In case of an error, NULL is returned.

The _tracefs_iterate_raw_events()_ function returns -1 in case of an error or
0 otherwise.

EXAMPLE
-------
[source,c]
--
#include <tracefs.h>

char **systems = tracefs_event_systems(NULL);

	if (systems) {
		int i = 0;
		/* Got registered trace systems from the top trace instance */
		while (systems[i]) {
			char **events = tracefs_system_events(NULL, systems[i]);
			if (events) {
				/* Got registered events in system[i] from the top trace instance */
				int j = 0;

				while (events[j]) {
					/* Got event[j] in system[i] from the top trace instance */
					j++;
				}
				tracefs_list_free(events);
			}
			i++;
		}
		tracefs_list_free(systems);
	}
....
static int records_walk(struct tep_event *tep, struct tep_record *record, int cpu, void *context)
{
	/* Got recorded event on cpu */
	return 0;
}
...
struct tep_event *tep = tracefs_local_events(NULL);

	if (!tep) {
		/* Failed to initialise tep handler with local events */
		...
	}
	if (tracefs_iterate_raw_events(tep, NULL, NULL, 0, records_walk, NULL) < 0) {
		/* Error walking through the recorded raw events */
	}
	tep_free(tep);
--
FILES
-----
[verse]
--
*tracefs.h*
	Header file to include in order to have access to the library APIs.
*-ltracefs*
	Linker switch to add when building a program that uses the library.
--

SEE ALSO
--------
_libtracefs(3)_,
_libtraceevent(3)_,
_trace-cmd(1)_

AUTHOR
------
[verse]
--
*Steven Rostedt* <rostedt@goodmis.org>
*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>
--
REPORTING BUGS
--------------
Report bugs to  <linux-trace-devel@vger.kernel.org>

LICENSE
-------
libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES
---------
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

COPYING
-------
Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under
the terms of the GNU Public License (GPL).
