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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | COPYING | NOTES | COLOPHON |
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LIBTRACEFS(3) libtracefs Manual LIBTRACEFS(3)
tracefs_event_systems, tracefs_system_events,
tracefs_event_enable, tracefs_event_disable,
tracefs_event_is_enabled - Work with trace systems and events.
#include <tracefs.h>
enum tracefs_event_state {
TRACEFS_ERROR = -1,
TRACEFS_ALL_DISABLED = 0,
TRACEFS_ALL_ENABLED = 1,
TRACEFS_SOME_ENABLED = 2,
};
char **tracefs_event_systems(const char *tracing_dir);
char **tracefs_system_events(const char *tracing_dir, const char *system);
int tracefs_event_enable(struct tracefs_instance *instance, const char *system,
const char *event);
int tracefs_event_disable(struct tracefs_instance *instance, const char *system,
const char *event);
enum tracefs_enable_state tracefs_event_is_enabled(struct tracefs_instance *instance,
const char *system, const char *event);
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_event_enable() function enables a given event based on
the system and event passed in for the given instance. If instance
is NULL, then the top level tracing directory is used. If system
and event are both NULL, then all events are enabled for the
instance. If event is NULL then all events within the system are
enabled. If system is NULL, then all systems are searched and any
event within a system that matches event is enabled. Both system
and event may be regular expressions as defined by regex(3).
The tracefs_event_disable() function disables the events that
match the system and event parameters for the given instance. What
events are disable follow the same rules as tracefs_event_enable()
for matching events. That is, if instance is NULL, then the top
level tracing directory is used. If both system and event are NULL
then all events are disabled for the given instance, and so on.
The tracefs_event_is_enabled() returns if an event is enabled, a
set of events are enabled, a system is enabled, or all events are
enabled. If both system and event are NULL, then it returns the
enable state of all events. If system is not NULL and event is
NULL, then it will check if all the events in all the systems that
system and return the enable state of those events. If system is
NULL and event is not NULL, then it will match all the events in
all systems that match event and return their enabled state. If
both system and event are not NULL, then it will return the
enabled state of all matching events. The enabled state is defined
as:
TRACEFS_ERROR - An error occurred including no event were matched.
TRACEFS_ALL_DISABLED - All matching events are disabled.
TRACEFS_ALL_ENABLED - All matching events are enabled.
TRACEFS_SOME_ENABLED - Some matching events were enabled while
others were not.
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.
Both tracefs_event_enable() and tracefs_event_disable() return 0
if they found any matching events (Note it does not check the
previous status of the event. If tracefs_event_enable() finds an
event that is already enabled, and there are no other errors, then
it will return 0). If an error occurs, even if other events were
found, it will return -1 and errno will be set. If no errors
occur, but no events are found that match the system and event
parameters, then -1 is returned and errno is not set.
The tracefs_event_is_enabled() returns the enabled status of the
matching events or TRACEFS_ERROR on error.
#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_handle *tep = tracefs_local_events(NULL);
if (!tep) {
/* Failed to initialise tep handler with local events */
...
}
errno = 0;
ret = tracefs_event_enable(NULL, "sched", NULL);
if (ret < 0 && !errno)
printf("Could not find 'sched' events\n");
tracefs_event_enable(NULL, "irq", "irq_handler_\(enter\|exit\)");
if (tracefs_iterate_raw_events(tep, NULL, NULL, 0, records_walk, NULL) < 0) {
/* Error walking through the recorded raw events */
}
/* Disable all events */
tracefs_event_disable(NULL, NULL, NULL);
tep_free(tep);
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.
libtracefs(3), libtraceevent(3), trace-cmd(1)
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
libtracefs is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
Copyright (C) 2020 VMware, Inc. Free use of this software is
granted under the terms of the GNU Public License (GPL).
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
2. tz.stoyanov@gmail.com
mailto:tz.stoyanov@gmail.com
3. linux-trace-devel@vger.kernel.org
mailto:linux-trace-devel@vger.kernel.org
This page is part of the libtracefs (Linux kernel trace file
system library) project. Information about the project can be
found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report
for this manual page, see ⟨https://www.trace-cmd.org/⟩. This page
was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git⟩ on
2025-02-02. (At that time, the date of the most recent commit
that was found in the repository was 2024-11-22.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
libtracefs 1.7.0 12/22/2023 LIBTRACEFS(3)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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