'\" t
.\"     Title: libtracefs
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 01/13/2024
.\"    Manual: libtracefs Manual
.\"    Source: libtracefs 1.8.0
.\"  Language: English
.\"
.TH "LIBTRACEFS" "3" "01/13/2024" "libtracefs 1\&.8\&.0" "libtracefs Manual"
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.SH "NAME"
tracefs_instance_get_name, tracefs_instance_get_trace_dir, tracefs_instances_walk, tracefs_instance_exists, tracefs_instance_get_buffer_size, tracefs_instance_set_buffer_size, tracefs_instance_get_buffer_percent, tracefs_instance_set_buffer_percent \- Helper functions for working with tracing instances\&.
.SH "SYNOPSIS"
.sp
.nf
\fB#include <tracefs\&.h>\fR

const char *\fBtracefs_instance_get_name\fR(struct tracefs_instance *\fIinstance\fR);
const char *\fBtracefs_instance_get_trace_dir\fR(struct tracefs_instance *\fIinstance\fR);
int \fBtracefs_instances_walk\fR(int (*\fIcallback\fR)(const char *, void *), void *\fIcontext)\fR;
bool \fBtracefs_instance_exists\fR(const char *\fIname\fR);
size_t \fBtracefs_instance_get_buffer_size\fR(struct tracefs_instance *\fIinstance\fR, int \fIcpu\fR);
int \fBtracefs_instance_set_buffer_size\fR(struct tracefs_instance *\fIinstance\fR, size_t \fIsize\fR, int \fIcpu\fR);
int \fBtracefs_instance_get_buffer_percent\fR(struct tracefs_instance *\fIinstance\fR);
int \fBtracefs_instance_set_buffer_percent\fR(struct tracefs_instance *\fIinstance\fR, int \fIval\fR);
.fi
.SH "DESCRIPTION"
.sp
Helper functions for working with trace instances\&.
.sp
The \fBtracefs_instance_get_name()\fR function returns the name of the given \fIinstance\fR\&. Note that the top instance has no name, the function returns NULL for it\&.
.sp
The \fBtracefs_instance_get_trace_dir()\fR function returns the tracing directory, where the given \fIinstance\fR is configured\&.
.sp
The \fBtracefs_instances_walk()\fR function walks through all configured tracing instances in the system and calls \fIcallback\fR for each one of them\&. The \fIcontext\fR argument is passed to the \fIcallback\fR, together with the instance name\&. If the \fIcallback\fR returns non\-zero, the iteration stops\&. Note, the \fIcallback\fR is not called for the top top instance\&.
.sp
The \fBtracefs_instance_exists()\fR function checks if an instance with the given \fIname\fR exists in the system\&.
.sp
The \fBtracefs_instace_get_buffer_size()\fR returns the size of the ring buffer\&. If \fIcpu\fR is negative, it returns the total size of all the per CPU ring buffers, otherwise it returns the size of the per CPU ring buffer for \fIcpu\fR\&.
.sp
The \fBtracefs_instance_set_buffer_size()\fR function sets the size of the ring buffer\&. If \fIcpu\fR is negative, then it sets all the per CPU ring buffers to \fIsize\fR (note the total size is the number of CPUs * \fIsize\fR)\&. If \fIcpu\fR is specified, then it only sets the size of the per CPU ring buffer\&.
.sp
The \fBtracefs_instance_set_buffer_percent()\fR sets the buffer percent value of the tracing ring buffer for \fIinstance\fR or the top level buffer if \fIinstance\fR is NULL\&. The buffer percent decides when readers on \fBtracefs_cpu_read\fR(3), \fBtracefs_cpu_buffered_read\fR(3), \fBtracefs_cpu_write\fR(3) and \fBtracefs_cpu_pipe\fR(3) will block when O_NONBLOCK is not set\&. The value of \fIval\fR must be between 0 and 100, where:
.sp
.if n \{\
.RS 4
.\}
.nf
  0   \- block until there\(cqs any data in the ring buffer
  1   \- block until 1% of the ring buffer sub\-buffers are filled
  50  \- block until 50% of the ring buffer sub\-buffers are filled
  100 \- block until the entire ring buffer is filled
.fi
.if n \{\
.RE
.\}
.sp
Note, any number from 0 to 100 can be used where it is the percentage of the ring buffer that must be filled before a blocked reader will be notified that there\(cqs data to be retrieved\&.
.sp
The \fBtracefs_instance_get_buffer_percent()\fR retrieves the current buffer percent setting of the tracing ring buffer for \fIinstance\fR or the top level buffer if \fIinstance\fR is NULL\&.
.SH "RETURN VALUE"
.sp
The \fBtracefs_instance_get_name()\fR returns a string or NULL in case of the top instance\&. The returned string must \fInot\fR be freed\&.
.sp
The \fBtracefs_instance_get_trace_dir()\fR returns a string or NULL in case of an error\&. The returned string must \fInot\fR be freed\&.
.sp
The \fBtracefs_instances_walk()\fR function returns 0, if all instances were iterated, 1 if the iteration was stopped by the \fIcallback\fR, or \-1 in case of an error\&.
.sp
The \fBtracefs_instance_exists()\fR returns true if an instance with the given \fIname\fR exists in the system or false otherwise\&.
.sp
The \fBtracefs_instance_get_buffer_size()\fR returns the size of the ring buffer depending on the \fIcpu\fR value passed in, or \-1 on error\&.
.sp
The \fBtracefs_instance_set_buffer_size()\fR returns zero on success and \-1 on error\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#include <tracefs\&.h>

struct tracefs_instance *inst;
\&.\&.\&.\&.
char *name = tracefs_instance_get_name(inst);
        if(name) {
                /* Got name of the instance */
        }
char *dir = tracefs_instance_get_trace_dir(inst);
        if(dir) {
                /* Got tracing directory of the instance */
        }
\&.\&.\&.
static int instance_walk(char *name, void *context)
{
        /* Got instance with name */
        return 0;
}
\&.\&.\&.
        if (tracefs_instances_walk(instance_walk, NULL) < 0) {
                /* Error walking through the instances */
        }
\&.\&.\&.
        if (tracefs_instance_exists("foo")) {
                /* There is instance with name foo in the system */
        } else {
                /* There is no instance with name foo in the system */
        }
.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) 2020 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