Man page - tracefs_list_free(3)

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Manual

LIBTRACEFS

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
EXAMPLE
FILES
SEE ALSO
AUTHOR
REPORTING BUGS
LICENSE
RESOURCES
COPYING
NOTES

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).

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

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