---
name: "tracefs_tracers"
section: "3"
platform: "linux"
package: "libtracefs"
version: "1.8.4-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/tracefs_tracers"
---

# tracefs\_tracers(3)

Helper functions for working with trace file system.

## NAME

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.

## SYNOPSIS

```
#include <tracefs.h>
char **tracefs_tracers(const char *tracing_dir);
bool tracefs_tracer_available(const char *tracing_dir, const char *tracer);
char *tracefs_get_clock(struct tracefs_instance *instance);
void tracefs_list_free(char **list);
char **tracefs_list_add(char *list, const char *string);
int *tracefs_list_size(char **list);
```

## DESCRIPTION

Various useful functions for working with trace file system.

The **tracefs\_tracers()** function returns array of strings with the names of supported tracer plugins, 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\_tracer\_available()** returns true if the *tracer* is available in the given *tracing\_dir\_director*, and false otherwise.

The **tracefs\_get\_clock()** function returns name of the current trace clock, used in the given *instance*. If *instance* is NULL, the clock of the main trace instance is returned. The returned string must be freed with free().

The **tracefs\_list\_free()** function frees an array of strings, returned by **tracefs\_event\_systems()**, **tracefs\_system\_events()** and **tracefs\_tracers()** APIs.

The **tracefs\_list\_add()** function adds *string* to the string *list*. If *list* is NULL, then a new list is created with the first element a copy of *string*, and the second element will be a NULL pointer. If *list* 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.

The **tracefs\_list\_size()** is a fast way to find out the number of elements in a string array that is to be freed with **tracefs\_list\_free()**. Note, this depends on meta data that is created for these lists and will not work on normal string arrays like argv.

## RETURN VALUE

The **tracefs\_tracers()** returns 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.

The **tracefs\_tracer\_available()** returns true if the *tracer* is available, and false otherwise.

The **tracefs\_get\_clock()** returns string, that must be freed with free(), or NULL in case of an error.

The **tracefs\_list\_add()** returns an allocated string array that must be freed with **tracefs\_list\_free()** on success or NULL on error. If NULL is returned, then the passed in *list* is untouched. Thus, **tracefs\_list\_add()** should be treated similarly to [**realloc**(3)](/realloc/3.md).

The **tracefs\_list\_size()** returns the number of strings in the *list*. The passed in list must be one that is to be freed with **tracefs\_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.

## EXAMPLE

```
#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);
        }
```

## FILES

```
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.
```

## SEE ALSO

[**libtracefs**(3)](/libtracefs/3.md), [**libtraceevent**(3)](/libtraceevent/3.md), [**trace-cmd**(1)](/trace-cmd/1.md)

## AUTHOR

```
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
```

## REPORTING BUGS

Report bugs to \<**linux-trace-devel@vger.kernel.org**\[3\]\>

## LICENSE

libtracefs is Free Software licensed under the GNU LGPL 2.1

## RESOURCES

**https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/**

## COPYING

Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).

## NOTES

- 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