tracefs_trace_is_on(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | COPYING | NOTES | COLOPHON

LIBTRACEFS(3)               libtracefs Manual              LIBTRACEFS(3)

NAME         top

       tracefs_trace_is_on, tracefs_trace_on, tracefs_trace_off,
       tracefs_trace_on_get_fd, tracefs_trace_on_fd,
       tracefs_trace_off_fd - Functions to enable or disable tracing.

SYNOPSIS         top

       #include <tracefs.h>

       int tracefs_trace_is_on(struct tracefs_instance *instance);
       int tracefs_trace_on(struct tracefs_instance *instance);
       int tracefs_trace_off(struct tracefs_instance *instance);
       int tracefs_trace_on_get_fd(struct tracefs_instance *instance);
       int tracefs_trace_on_fd(int fd);
       int tracefs_trace_off_fd(int fd);

DESCRIPTION         top

       This set of functions can be used to check, enable or disable
       writing to the ring buffer in the given trace instance. The
       tracing is enabled when writing to the ring buffer is enabled.

       The tracefs_trace_is_on() function checks if tracing is enabled
       for the given instance. If instance is NULL, the top instance is
       used.

       The tracefs_trace_on() and tracefs_trace_off() functions set the
       tracing in the instance to enable or disable state. If instance
       is NULL, the top instance is used.

       The tracefs_trace_on_get_fd() function returns a file descriptor
       to the "tracing_on" file from the given instance. If instance is
       NULL, the top trace instance is used. The returned descriptor can
       be used for fast enabling or disabling the tracing of the
       instance.

       The tracefs_trace_on_fd() and tracefs_trace_off_fd() functions
       set the tracing state to enable or disable using the given fd.
       This file descriptor must be opened for writing with
       tracefs_trace_on_get_fd(3) of the desired trace instance. These
       functions are faster than tracefs_trace_on and tracefs_trace_off.

RETURN VALUE         top

       The tracefs_trace_is_on() function returns 0 if tracing is
       disable, 1 if it is enabled or -1 in case of an error.

       The tracefs_trace_on_get_fd() function returns a file descriptor
       to "tracing_on" file for reading and writing, which must be
       closed wuth close(). In case of an error -1 is returned.

       The tracefs_trace_on(), tracefs_trace_off(),
       tracefs_trace_on_fd() and tracefs_trace_off_fd() functions return
       -1 in case of an error or 0 otherwise.

EXAMPLE         top

           #include <tracefs.h>

                   int ret;

                   ret = tracefs_trace_is_on(NULL);
                   if (ret == 0) {
                           /* Tracing is disabled in the top instance */
                   } else if (ret == 1) {
                           /* Tracing is enabled in the top instance */
                   } else {
                           /* Error getting tracing state of the top instance */
                   }

                   ...

                   if (!tracefs_trace_on(NULL)) {
                       /* Enabled tracing in the top instance */

                       ...

                       if (!tracefs_trace_off(NULL)) {
                           /* Disabled tracing in the top instance */
                       } else {
                           /* Error disabling tracing in the top instance */
                       }
                   } else {
                           /* Error enabling tracing in the top instance */
                   }

                   ...

                   int fd = tracefs_trace_on_get_fd(NULL);

                   if (fd < 0) {
                           /* Error opening tracing_on file */
                   }
                   ...
                   if (!tracefs_trace_on_fd(fd)) {
                       /* Enabled tracing in the top instance */

                       ...

                       if (!tracefs_trace_off_fd(fd)) {
                           /* Disabled tracing in the top instance */
                       } else {
                           /* Error disabling tracing in the top instance */
                       }
                   } else {
                           /* Error enabling tracing in the top instance */
                   }

                   ...

                   close(fd);

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)

AUTHOR         top

           Steven Rostedt <[email protected][1]>
           Tzvetomir Stoyanov <[email protected][2]>

REPORTING BUGS         top

       Report bugs to <[email protected][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. [email protected]
           mailto:[email protected]

        2. [email protected]
           mailto:[email protected]

        3. [email protected]
           mailto:[email protected]

COLOPHON         top

       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
       2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2024-05-17.)  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 [email protected]

libtracefs 1.7.0               12/22/2023                  LIBTRACEFS(3)

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