'\" t
.\" Title: libtracefs
.\" Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\" Date: 07/27/2024
.\" Manual: libtracefs Manual
.\" Source: libtracefs 1.8.1
.\" Language: English
.\"
.TH "LIBTRACEFS" "3" "07/27/2024" "libtracefs 1\&.8\&.1" "libtracefs Manual"
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.SH "NAME"
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\&.
.SH "SYNOPSIS"
.sp
.nf
\fB#include <tracefs\&.h>\fR
int \fBtracefs_trace_is_on\fR(struct tracefs_instance *\fIinstance\fR);
int \fBtracefs_trace_on\fR(struct tracefs_instance *\fIinstance\fR);
int \fBtracefs_trace_off\fR(struct tracefs_instance *\fIinstance\fR);
int \fBtracefs_trace_on_get_fd\fR(struct tracefs_instance *\fIinstance\fR);
int \fBtracefs_trace_on_fd\fR(int \fIfd\fR);
int \fBtracefs_trace_off_fd\fR(int \fIfd\fR);
.fi
.SH "DESCRIPTION"
.sp
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\&.
.sp
The \fBtracefs_trace_is_on()\fR function checks if tracing is enabled for the given \fIinstance\fR\&. If \fIinstance\fR is NULL, the top instance is used\&.
.sp
The \fBtracefs_trace_on()\fR and \fBtracefs_trace_off()\fR functions set the tracing in the \fIinstance\fR to enable or disable state\&. If \fIinstance\fR is NULL, the top instance is used\&.
.sp
The \fBtracefs_trace_on_get_fd()\fR function returns a file descriptor to the "tracing_on" file from the given \fIinstance\fR\&. If \fIinstance\fR is NULL, the top trace instance is used\&. The returned descriptor can be used for fast enabling or disabling the tracing of the instance\&.
.sp
The \fBtracefs_trace_on_fd()\fR and \fBtracefs_trace_off_fd()\fR functions set the tracing state to enable or disable using the given \fIfd\fR\&. This file descriptor must be opened for writing with \fBtracefs_trace_on_get_fd\fR(3) of the desired trace instance\&. These functions are faster than \fBtracefs_trace_on\fR and \fBtracefs_trace_off\fR\&.
.SH "RETURN VALUE"
.sp
The \fBtracefs_trace_is_on()\fR function returns 0 if tracing is disable, 1 if it is enabled or \-1 in case of an error\&.
.sp
The \fBtracefs_trace_on_get_fd()\fR 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\&.
.sp
The \fBtracefs_trace_on()\fR, \fBtracefs_trace_off()\fR, \fBtracefs_trace_on_fd()\fR and \fBtracefs_trace_off_fd()\fR functions return \-1 in case of an error or 0 otherwise\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#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);
.fi
.if n \{\
.RE
.\}
.SH "FILES"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBtracefs\&.h\fR
Header file to include in order to have access to the library APIs\&.
\fB\-ltracefs\fR
Linker switch to add when building a program that uses the library\&.
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBlibtracefs\fR(3), \fBlibtraceevent\fR(3), \fBtrace\-cmd\fR(1)
.SH "AUTHOR"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBSteven Rostedt\fR <\m[blue]\fBrostedt@goodmis\&.org\fR\m[]\&\s-2\u[1]\d\s+2>
\fBTzvetomir Stoyanov\fR <\m[blue]\fBtz\&.stoyanov@gmail\&.com\fR\m[]\&\s-2\u[2]\d\s+2>
.fi
.if n \{\
.RE
.\}
.SH "REPORTING BUGS"
.sp
Report bugs to <\m[blue]\fBlinux\-trace\-devel@vger\&.kernel\&.org\fR\m[]\&\s-2\u[3]\d\s+2>
.SH "LICENSE"
.sp
libtracefs is Free Software licensed under the GNU LGPL 2\&.1
.SH "RESOURCES"
.sp
\m[blue]\fBhttps://git\&.kernel\&.org/pub/scm/libs/libtrace/libtracefs\&.git/\fR\m[]
.SH "COPYING"
.sp
Copyright (C) 2021 VMware, Inc\&. Free use of this software is granted under the terms of the GNU Public License (GPL)\&.
.SH "NOTES"
.IP " 1." 4
rostedt@goodmis.org
.RS 4
\%mailto:rostedt@goodmis.org
.RE
.IP " 2." 4
tz.stoyanov@gmail.com
.RS 4
\%mailto:tz.stoyanov@gmail.com
.RE
.IP " 3." 4
linux-trace-devel@vger.kernel.org
.RS 4
\%mailto:linux-trace-devel@vger.kernel.org
.RE