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libtracefs(3)
=============
NAME
----
tracefs_print_init, tracefs_print_close, tracefs_printf, tracefs_vprintf -
Open, close and write formated strings in the trace buffer.
SYNOPSIS
--------
[verse]
--
*#include <tracefs.h>*
int *tracefs_print_init*(struct tracefs_instance pass:[*]_instance_);
int *tracefs_printf*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_fmt_, _..._);
int *tracefs_vprintf*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_fmt_, va_list _ap_);
void *tracefs_print_close*(struct tracefs_instance pass:[*]_instance_);
--
DESCRIPTION
-----------
Set of functions to write formated strings in the trace buffer.
See Documentation/trace/ftrace.rst from the Linux kernel tree for more information about writing
data from user space in the trace buffer. All these APIs have _instance_ as a first argument. If
NULL is passed as _instance_, the top trace instance is used.
The *tracefs_print_init()* function initializes the library for writing into the trace buffer of
the selected _instance_. It is not mandatory to call this API before writing strings, any of
the printf APIs will call it automatically, if the library is not yet initialized. But calling
*tracefs_print_init()* in advance will speed up the writing.
The *tracefs_printf()* function writes a formatted string in the trace buffer of the selected
_instance_. The _fmt_ argument is a string in printf format, followed by variable arguments _..._.
The *tracefs_vprintf()* function writes a formatted string in the trace buffer of the selected
_instance_. The _fmt_ argument is a string in printf format, followed by list _ap_ of arguments.
The *tracefs_print_close()* function closes the resources, used by the library for writing in
the trace buffer of the selected instance.
RETURN VALUE
------------
The *tracefs_print_init()*, *tracefs_printf()*, and *tracefs_vprintf()* functions return 0 if
the operation is successful, or -1 in case of an error.
EXAMPLE
-------
[source,c]
--
#include <tracefs.h>
if (tracefs_print_init(NULL) < 0) {
/* Failed to initialize the library for writing in the trace buffer of the top trace instance */
}
void foo_print(char *format, ...)
{
va_list ap;
va_start(ap, format);
if (tracefs_vprintf(NULL, format, ap) < 0) {
/* Failed to print in the trace buffer */
}
va_end(ap);
}
void foo_print_string(char *message)
{
if (tracefs_printf(NULL, "Message from user space: %s", message) < 0) {
/* Failed to print in the trace buffer */
}
}
tracefs_print_close();
--
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),
Documentation/trace/ftrace.rst from the Linux kernel tree
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) 2021 VMware, Inc. Free use of this software is granted under
the terms of the GNU Public License (GPL).
|
