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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |EXAMPLE |FILES |SEE ALSO |AUTHOR |REPORTING BUGS |LICENSE |RESOURCES |COPYING |NOTES |COLOPHON | |
LIBTRACEFS(3) libtracefs ManualLIBTRACEFS(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); inttracefs_event_enable(struct tracefs_instance *instance, const char *system, const char *event); inttracefs_event_disable(struct tracefs_instance *instance, const char *system, const char *event); enum tracefs_enable_statetracefs_event_is_enabled(struct tracefs_instance *instance, const char *system, const char *event);Trace systems and events related APIs. Thetracefs_event_systems()function returns array of strings with the names of all registered trace systems, located in the giventracing_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 withtracefs_list_free()API. Thetracefs_system_events()function returns array of strings with the names of all registered trace events for given trace system specified bysystem, located in the giventracing_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 withtracefs_list_free()API. Thetracefs_event_enable()function enables a given event based on thesystem andevent passed in for the giveninstance. Ifinstance is NULL, then the top level tracing directory is used. Ifsystem andevent are both NULL, then all events are enabled for theinstance. Ifevent is NULL then all events within thesystem are enabled. Ifsystem is NULL, then all systems are searched and any event within a system that matchesevent is enabled. Bothsystem andevent may be regular expressions as defined byregex(3). Thetracefs_event_disable()function disables the events that match thesystem andevent parameters for the giveninstance. What events are disable follow the same rules astracefs_event_enable() for matching events. That is, ifinstance is NULL, then the top level tracing directory is used. If bothsystem andevent are NULL then all events are disabled for the giveninstance, and so on. Thetracefs_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 bothsystem andevent are NULL, then it returns the enable state of all events. Ifsystem is not NULL andevent is NULL, then it will check if all the events in all the systems thatsystem and return the enable state of those events. Ifsystem is NULL andevent is not NULL, then it will match all the events in all systems that matchevent and return their enabled state. If bothsystem andevent 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.
Thetracefs_event_systems()andtracefs_system_events()functions return an array of strings. The last element in that array is a NULL pointer. The array must be freed withtracefs_list_free() API. In case of an error, NULL is returned. Bothtracefs_event_enable()andtracefs_event_disable()return 0 if they found any matching events (Note it does not check the previous status of the event. Iftracefs_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 thesystem andevent parameters, then -1 is returned and errno is not set. Thetracefs_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 thelibtracefs (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 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-06-02.) 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 isnot part of the original manual page), send a mail to man-pages@man7.orglibtracefs 1.7.0 12/22/2023LIBTRACEFS(3)HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |