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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_tracers, tracefs_tracer_available, tracefs_get_clock, tracefs_list_free, tracefs_list_add, tracefs_list_size - Helper functions for working with trace file system.
#include <tracefs.h> char **tracefs_tracers(const char *tracing_dir); booltracefs_tracer_available(const char *tracing_dir, const char *tracer); char *tracefs_get_clock(struct tracefs_instance *instance); voidtracefs_list_free(char **list); char **tracefs_list_add(char*list, const char *string);int *tracefs_list_size(char **list);
Various useful functions for working with trace file system. Thetracefs_tracers()function returns array of strings with the names of supported tracer plugins, 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_tracer_available()returns true if thetracer is available in the giventracing_dir_director, and false otherwise. Thetracefs_get_clock()function returns name of the current trace clock, used in the giveninstance. Ifinstance is NULL, the clock of the main trace instance is returned. The returned string must be freed with free(). Thetracefs_list_free()function frees an array of strings, returned bytracefs_event_systems(),tracefs_system_events()andtracefs_tracers()APIs. Thetracefs_list_add()function addsstring to the stringlist. Iflist is NULL, then a new list is created with the first element a copy ofstring, and the second element will be a NULL pointer. Iflist is not NULL, then it is reallocated to include a new element and a NULL terminator, and the new allocated array is returned. The list passed in should be ignored, as it wil be freed if a new one was allocated. Thetracefs_list_size()is a fast way to find out the number of elements in a string array that is to be freed withtracefs_list_free(). Note, this depends on meta data that is created for these lists and will not work on normal string arrays like argv.
Thetracefs_tracers()returns 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. Thetracefs_tracer_available()returns true if thetracer is available, and false otherwise. Thetracefs_get_clock()returns string, that must be freed with free(), or NULL in case of an error. Thetracefs_list_add()returns an allocated string array that must be freed withtracefs_list_free()on success or NULL on error. If NULL is returned, then the passed inlist is untouched. Thus,tracefs_list_add()should be treated similarly torealloc(3). Thetracefs_list_size()returns the number of strings in thelist. The passed in list must be one that is to be freed withtracefs_list_free()as the list has meta data that is used to determine the size and this does not work on any normal string array like argv.
#include <tracefs.h> char **tracers = tracefs_tracers(NULL); if (tracers) { /* Got tracer plugins from the top trace instance */ ... tracefs_list_free(tracers); } .... char *clock = tracefs_get_clock(NULL); if (clock) { /* Got current trace clock of the top trace instance */ ... free(clock); }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)Pages that refer to this page:tracefs_instance_create(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. | |