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libtracefs(3)
=============
NAME
----
tracefs_file_exists, tracefs_dir_exists,
tracefs_instance_get_file, tracefs_instance_get_dir - Work with files directories in tracing instances.
SYNOPSIS
--------
[verse]
--
*#include <tracefs.h>*
bool *tracefs_file_exists*(struct tracefs_instance pass:[*]_instance_, char pass:[*]_name_);
bool *tracefs_dir_exists*(struct tracefs_instance pass:[*]_instance_, char pass:[*]_name_);
char pass:[*]*tracefs_instance_get_file*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_);
char pass:[*]*tracefs_instance_get_dir*(struct tracefs_instance pass:[*]_instance_);
--
DESCRIPTION
-----------
This set of APIs can be used to work with trace files in all trace instances.
Each of these APIs take an _instance_ argument, that can be NULL to act
on the top level instance. Otherwise, it acts on an instance created with
*tracefs_insance_create*(3)
The *tracefs_file_exists()* function checks if a file with _name_ exists in _instance_.
The *tracefs_dir_exists()* function checks if a directory with _name_ exists in _instance_.
The *tracefs_instance_get_file()* function returns the full path of the file
with given _name_ in _instance_. Note, it does not check if the file exists in
the instance.
The *tracefs_instance_get_dir()* function returns the full path of the directory
with given _name_ in _instance_. Note, it does not check if the directory exists
in the instance.
RETURN VALUE
------------
The *tracefs_file_exists()* and *tracefs_dir_exists()* functions return true if the
file / directory exist in the given instance or false if it does not exist.
The *tracefs_instance_get_file()* and *tracefs_instance_get_dir()* functions return
a string or NULL in case of an error. The returned string must be freed with
*tracefs_put_tracing_file()*.
EXAMPLE
-------
[source,c]
--
#include <tracefs.h>
struct tracefs_instance *inst = tracefs_instance_create("foo");
if (!inst) {
/* Error creating a new trace instance */
...
}
if (tracefs_file_exists(inst,"trace_clock")) {
/* The instance foo supports trace clock */
char *path, *clock;
int size;
path = = tracefs_instance_get_file(inst, "trace_clock")
if (!path) {
/* Error getting the path to trace_clock file in instance foo */
...
}
...
tracefs_put_tracing_file(path);
clock = tracefs_instance_file_read(inst, "trace_clock", &size);
if (!clock) {
/* Failed to read trace_clock file in instance foo */
...
}
...
free(clock);
if (tracefs_instance_file_write(inst, "trace_clock", "global") != strlen("global")) {
/* Failed to set gloabl trace clock in instance foo */
...
}
} else {
/* The instance foo does not support trace clock */
}
if (tracefs_dir_exists(inst,"options")) {
/* The instance foo supports trace options */
char *path = tracefs_instance_get_file(inst, "options");
if (!path) {
/* Error getting the path to options directory in instance foo */
...
}
tracefs_put_tracing_file(path);
} else {
/* The instance foo does not support trace options */
}
...
if (tracefs_instance_is_new(inst))
tracefs_instance_destroy(inst);
else
tracefs_instance_free(inst);
...
long long int res;
if (tracefs_instance_file_read_number(NULL, "tracing_on", &res) == 0) {
if (res == 0) {
/* tracing is disabled in the top instance */
} else if (res == 1) {
/* tracing is enabled in the top instance */
} else {
/* Unknown tracing state of the top instance */
}
} else {
/* Failed to read integer from tracing_on file */
}
...
int fd;
fd = tracefs_instance_file_open(NULL, "tracing_on", O_WRONLY);
if (fd >= 0) {
/* Got file descriptor to the tracing_on file from the top instance for writing */
...
close(fd);
}
--
FILES
-----
[verse]
--
*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
------
[verse]
--
*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).
|
