# libtracefs(3) Manual Page

## NAME

tracefs_instance_get_name, tracefs_instance_get_trace_dir, tracefs_instances_walk, tracefs_instance_exists - Helper functions for working with tracing instances.

## SYNOPSIS

    #include <tracefs.h>

    const char *tracefs_instance_get_name(struct tracefs_instance *instance);
    const char *tracefs_instance_get_trace_dir(struct tracefs_instance *instance);
    int tracefs_instances_walk(int (*callback)(const char *, void *), void *context);
    bool tracefs_instance_exists(const char *name);

## DESCRIPTION

Helper functions for working with trace instances.

The tracefs_instance_get_name() function returns the name of the given instance. Note that the top instance has no name, the function returns NULL for it.

The tracefs_instance_get_trace_dir() function returns the tracing directory, where the given instance is configured.

The tracefs_instances_walk() function walks through all configured tracing instances in the system and calls callback for each one of them. The context argument is passed to the callback, together with the instance name. If the callback returns non-zero, the iteration stops. Note, the callback is not called for the top top instance.

The tracefs_instance_exists() function checks if an instance with the given name exists in the system.

## RETURN VALUE

The tracefs_instance_get_name() returns a string or NULL in case of the top instance. The returned string must not be freed.

The tracefs_instance_get_trace_dir() returns a string or NULL in case of an error. The returned string must not be freed.

The tracefs_instances_walk() function returns 0, if all instances were iterated, 1 if the iteration was stopped by the callback, or -1 in case of an error.

The tracefs_instance_exists() returns true if an instance with the given name exists in the system or false otherwise.

## EXAMPLE

    #include <tracefs.h>

    struct tracefs_instance *inst;
    ....
    char *name = tracefs_instance_get_name(inst);
            if(name) {
                    /* Got name of the instance */
            }
    char *dir = tracefs_instance_get_trace_dir(inst);
            if(dir) {
                    /* Got tracing directory of the instance */
            }
    ...
    static int instance_walk(char *name, void *context)
    {
            /* Got instance with name */
            return 0;
    }
    ...
            if (tracefs_instances_walk(instance_walk, NULL) < 0) {
                    /* Error walking through the instances */
            }
    ...
            if (tracefs_instance_exists("foo")) {
                    /* There is instance with name foo in the system */
            } else {
                    /* There is no instance with name foo in the system */
            }

## 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), libtraceevent(3), trace-cmd(1)

## AUTHOR

    Steven Rostedt <rostedt@goodmis.org>
    Tzvetomir Stoyanov <tz.stoyanov@gmail.com>

## REPORTING BUGS

Report bugs to <linux-trace-devel@vger.kernel.org>

## 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).