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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | COPYING | NOTES | COLOPHON |
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LIBTRACEFS(3) libtracefs Manual LIBTRACEFS(3)
tracefs_print_init, tracefs_print_close, tracefs_printf,
tracefs_vprintf - Open, close and write formated strings in the
trace buffer.
#include <tracefs.h>
int tracefs_print_init(struct tracefs_instance *instance);
int tracefs_printf(struct tracefs_instance *instance, const char *fmt, ...);
int tracefs_vprintf(struct tracefs_instance *instance, const char *fmt, va_list ap);
void tracefs_print_close(struct tracefs_instance *instance);
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.
The tracefs_print_init(), tracefs_printf(), and tracefs_vprintf()
functions return 0 if the operation is successful, or -1 in case
of an error.
#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();
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.
libtracefs(3), libtraceevent(3), trace-cmd(1),
Documentation/trace/ftrace.rst from the Linux kernel tree
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
libtracefs is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
Copyright (C) 2021 VMware, Inc. Free use of this software is
granted under the terms of the GNU Public License (GPL).
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
This page is part of the libtracefs (Linux kernel trace file
system library) project. Information about the project can be
found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report
for this manual page, see ⟨https://www.trace-cmd.org/⟩. This
page was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git⟩ on
2023-12-22. (At that time, the date of the most recent commit
that was found in the repository was 2023-07-05.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
libtracefs 1.7.0 12/22/2023 LIBTRACEFS(3)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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