| 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). |
