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. |  |
NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |EXAMPLE |FILES |SEE ALSO |AUTHOR |REPORTING BUGS |LICENSE |RESOURCES |COPYING |NOTES |COLOPHON | |
LIBTRACEFS(3) libtracefs ManualLIBTRACEFS(3)tracefs_instance_create, tracefs_instance_destroy, tracefs_instance_alloc, tracefs_instance_free, tracefs_instance_is_new, tracefs_instances, tracefs_instance_clear, tracefs_instance_reset - Manage trace instances.
#include <tracefs.h> struct tracefs_instance *tracefs_instance_create(const char *name); inttracefs_instance_destroy(struct tracefs_instance *instance); struct tracefs_instance *tracefs_instance_alloc(const char *tracing_dir, const char *name); voidtracefs_instance_free(struct tracefs_instance *instance); booltracefs_instance_is_new(struct tracefs_instance *instance); char **tracefs_instances(const char *regex); voidtracefs_instance_clear(struct tracefs_instance *instance); voidtracefs_instance_reset(struct tracefs_instance *instance);
This set of functions can be used to manage trace instances. A trace instance is a sub buffer used by the Linux tracing system. Given a unique name, the events enabled in an instance do not affect the main tracing system, nor other instances, as events enabled in the main tracing system or other instances do not affect the given instance. Thetracefs_instance_create()function allocates and initializes a new tracefs_instance structure and returns it. If the instance withname does not yet exist in the system, it will be created. Thename could be NULL, then the new tracefs_instance structure is initialized for the top instance. Note that the top instance cannot be created in the system, if it does not exist. Thetracefs_instance_destroy()removes the instance from the system, but does not free the structure.tracefs_instance_free() must still be called oninstance. The tracefs_instance_alloc()* function allocates a new tracefs_instance structure for existing trace instance. If the instance does not exist in the system, the function fails. Thetracing_dir parameter points to the system trace directory. It can be NULL, then default system trace directory is used. This parameter is useful to allocate instances to trace directories, copied from another machine. Thename is the name of the instance, or NULL for the top instance in the giventracing_dir. Thetracefs_instance_free()function frees the tracefs_instance structure, without removing the trace instance from the system. Thetracefs_instance_is_new()function checks if the giveninstance is newly created bytracefs_instance_create(), or it has been in the system before that. Thetracefs_instances() function returns a list of instances that exist in the system that match the regular expressionregex. Ifregex is NULL, then it will match all instances that exist. The returned list must be freed withtracefs_list_free(3). Note, if no instances are found an empty list is returned and that too needs to be free withtracefs_list_free(3). Thetracefs_instance_clear()function clears the ring buffer of the giveninstance or the top level ring buffer ifinstance is NULL. Thetracefs_instance_reset() function resets the giveninstance to its default state.
Thetracefs_instance_create()andtracefs_instance_alloc() functions return a pointer to a newly allocated tracefs_instance structure. It must be freed withtracefs_instance_free(). Thetracefs_instance_destroy()function returns 0 if it succeeds to remove the instance, otherwise it returns -1 if the instance does not exist or it fails to remove it. Thetracefs_instance_is_new()function returns true if thetracefs_instance_create()that allocatedinstance also created the trace instance in the system, or false if the trace instance already existed in the system wheninstance was allocated bytracefs_instance_create()ortracefs_instance_alloc(). Thetracefs_instances()returns a list of instance names that exist on the system. The list must be freed withtracefs_list_free(3). An empty list is returned if no instance exists that matchesregex, and this needs to be freed withtracefs_list_free(3) as well. NULL is returned on error. Thetracefs_instance_clear()returns 0 if it successfully cleared the ring buffer, or -1 on error.
#include <tracefs.h> struct tracefs_instance *inst = tracefs_instance_create("foo"); if (!inst) { /* Error creating a new trace instance */ ... } ... if (tracefs_instance_is_new(inst)) tracefs_instance_destroy(inst); tracefs_instance_free(inst); ... struct tracefs_instance *inst = tracefs_instance_alloc(NULL, "bar"); if (!inst) { /* Error allocating 'bar' trace instance */ ... } ... tracefs_instance_reset(inst); tracefs_instance_free(inst);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 1.8.1 01/02/2025LIBTRACEFS(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. | |