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tracefs_print_init(3) — Linux manual page

LIBTRACEFS(3)               libtracefs ManualLIBTRACEFS(3)

NAME        top

       tracefs_print_init, tracefs_print_close, tracefs_printf,       tracefs_vprintf - Open, close and write formated strings in the       trace buffer.

SYNOPSIS        top

#include <tracefs.h>       inttracefs_print_init(struct tracefs_instance *instance);       inttracefs_printf(struct tracefs_instance *instance, const char *fmt,...);       inttracefs_vprintf(struct tracefs_instance *instance, const char *fmt, va_listap);       voidtracefs_print_close(struct tracefs_instance *instance);

DESCRIPTION        top

       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 haveinstance as a first argument. If NULL       is passed asinstance, the top trace instance is used.       Thetracefs_print_init()function initializes the library for       writing into the trace buffer of the selectedinstance. 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 callingtracefs_print_init()in advance will       speed up the writing.       Thetracefs_printf()function writes a formatted string in the       trace buffer of the selectedinstance. Thefmt argument is a       string in printf format, followed by variable arguments....       Thetracefs_vprintf()function writes a formatted string in the       trace buffer of the selectedinstance. Thefmt argument is a       string in printf format, followed by listap of arguments.       Thetracefs_print_close()function closes the resources, used by       the library for writing in the trace buffer of the selected       instance.

RETURN VALUE        top

       Thetracefs_print_init(),tracefs_printf(), andtracefs_vprintf()       functions return 0 if the operation is successful, or -1 in case       of an error.

EXAMPLE        top

           #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        top

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        top

libtracefs(3),libtraceevent(3),trace-cmd(1),       Documentation/trace/ftrace.rst from the Linux kernel tree

AUTHOR        top

Steven Rostedt<rostedt@goodmis.org[1]>Tzvetomir Stoyanov<tz.stoyanov@gmail.com[2]>

REPORTING BUGS        top

       Report bugs to <linux-trace-devel@vger.kernel.org[3]>

LICENSE        top

       libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES        top

https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

COPYING        top

       Copyright (C) 2021 VMware, Inc. Free use of this software is       granted under the terms of the GNU Public License (GPL).

NOTES        top

        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

COLOPHON        top

       This page is part of thelibtracefs (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       2025-08-11.  (At that time, the date of the most recent commit       that was found in the repository was 2025-06-02.)  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 isnot part of the original manual page), send a       mail to man-pages@man7.orglibtracefs 1.7.0                12/22/2023LIBTRACEFS(3)

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