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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_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);
int tracefs_instance_destroy(struct tracefs_instance *instance);
struct tracefs_instance *tracefs_instance_alloc(const char *tracing_dir, const char *name);
void tracefs_instance_free(struct tracefs_instance *instance);
bool tracefs_instance_is_new(struct tracefs_instance *instance);
char **tracefs_instances(const char *regex);
void tracefs_instance_clear(struct tracefs_instance *instance);
void tracefs_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.
The tracefs_instance_create() function allocates and initializes a
new tracefs_instance structure and returns it. If the instance
with name does not yet exist in the system, it will be created.
The name 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.
The tracefs_instance_destroy() removes the instance from the
system, but does not free the structure. tracefs_instance_free()
must still be called on instance.
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. The
tracing_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. The name is the name of the instance,
or NULL for the top instance in the given tracing_dir.
The tracefs_instance_free() function frees the tracefs_instance
structure, without removing the trace instance from the system.
The tracefs_instance_is_new() function checks if the given
instance is newly created by tracefs_instance_create(), or it has
been in the system before that.
The tracefs_instances() function returns a list of instances that
exist in the system that match the regular expression regex. If
regex is NULL, then it will match all instances that exist. The
returned list must be freed with tracefs_list_free(3). Note, if no
instances are found an empty list is returned and that too needs
to be free with tracefs_list_free(3).
The tracefs_instance_clear() function clears the ring buffer of
the given instance or the top level ring buffer if instance is
NULL.
The tracefs_instance_reset() function resets the given instance to
its default state.
The tracefs_instance_create() and tracefs_instance_alloc()
functions return a pointer to a newly allocated tracefs_instance
structure. It must be freed with tracefs_instance_free().
The tracefs_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.
The tracefs_instance_is_new() function returns true if the
tracefs_instance_create() that allocated instance also created the
trace instance in the system, or false if the trace instance
already existed in the system when instance was allocated by
tracefs_instance_create() or tracefs_instance_alloc().
The tracefs_instances() returns a list of instance names that
exist on the system. The list must be freed with
tracefs_list_free(3). An empty list is returned if no instance
exists that matches regex, and this needs to be freed with
tracefs_list_free(3) as well. NULL is returned on error.
The tracefs_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 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
2025-08-11. (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 is not part of the original manual page), send a
mail to man-pages@man7.org
libtracefs 1.8.1 01/02/2025 LIBTRACEFS(3)
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HTML rendering created 2025-09-06 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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