'\" t
.\" Title: libtracefs
.\" Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot
.\" Date: 10/08/2022
.\" Manual: libtracefs Manual
.\" Source: libtracefs 1.5.0
.\" Language: English
.\"
.TH "LIBTRACEFS" "3" "10/08/2022" "libtracefs 1\&.5\&.0" "libtracefs Manual"
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.SH "NAME"
tracefs_tracers, tracefs_tracer_available, tracefs_get_clock, tracefs_list_free, tracefs_list_add, tracefs_list_size \- Helper functions for working with trace file system\&.
.SH "SYNOPSIS"
.sp
.nf
\fB#include \fR
char **\fBtracefs_tracers\fR(const char *\fItracing_dir\fR);
bool \fBtracefs_tracer_available\fR(const char *\fItracing_dir\fR, const char *\fItracer\fR);
char *\fBtracefs_get_clock\fR(struct tracefs_instance *\fIinstance\fR);
void \fBtracefs_list_free\fR(char **\fIlist\fR);
char **\fBtracefs_list_add\fR(char \fB*\fR\fB\fIlist\fR\fR\fB, const char *\fR\fB\fIstring\fR\fR\fB);
int *tracefs_list_size\fR(char **\fIlist\fR);
.fi
.SH "DESCRIPTION"
.sp
Various useful functions for working with trace file system\&.
.sp
The \fBtracefs_tracers()\fR function returns array of strings with the names of supported tracer plugins, located in the given \fItracing_dir\fR directory\&. This could be NULL or the location of the tracefs mount point for the trace systems of the local machine, or it may be a path to a copy of the tracefs directory from another machine\&. The last entry in the array as a NULL pointer\&. The array must be freed with \fBtracefs_list_free()\fR API\&.
.sp
The \fBtracefs_tracer_available()\fR returns true if the \fItracer\fR is available in the given \fItracing_dir_director\fR, and false otherwise\&.
.sp
The \fBtracefs_get_clock()\fR function returns name of the current trace clock, used in the given \fIinstance\fR\&. If \fIinstance\fR is NULL, the clock of the main trace instance is returned\&. The returned string must be freed with free()\&.
.sp
The \fBtracefs_list_free()\fR function frees an array of strings, returned by \fBtracefs_event_systems()\fR, \fBtracefs_system_events()\fR and \fBtracefs_tracers()\fR APIs\&.
.sp
The \fBtracefs_list_add()\fR function adds \fIstring\fR to the string \fIlist\fR\&. If \fIlist\fR is NULL, then a new list is created with the first element a copy of \fIstring\fR, and the second element will be a NULL pointer\&. If \fIlist\fR is not NULL, then it is reallocated to include a new element and a NULL terminator, and the new allocated array is returned\&. The list passed in should be ignored, as it wil be freed if a new one was allocated\&.
.sp
The \fBtracefs_list_size()\fR is a fast way to find out the number of elements in a string array that is to be freed with \fBtracefs_list_free()\fR\&. Note, this depends on meta data that is created for these lists and will not work on normal string arrays like argv\&.
.SH "RETURN VALUE"
.sp
The \fBtracefs_tracers()\fR returns array of strings\&. The last element in that array is a NULL pointer\&. The array must be freed with \fBtracefs_list_free()\fR API\&. In case of an error, NULL is returned\&.
.sp
The \fBtracefs_tracer_available()\fR returns true if the \fItracer\fR is available, and false otherwise\&.
.sp
The \fBtracefs_get_clock()\fR returns string, that must be freed with free(), or NULL in case of an error\&.
.sp
The \fBtracefs_list_add()\fR returns an allocated string array that must be freed with \fBtracefs_list_free()\fR on success or NULL on error\&. If NULL is returned, then the passed in \fIlist\fR is untouched\&. Thus, \fBtracefs_list_add()\fR should be treated similarly to \fBrealloc\fR(3)\&.
.sp
The \fBtracefs_list_size()\fR returns the number of strings in the \fIlist\fR\&. The passed in list must be one that is to be freed with \fBtracefs_list_free()\fR as the list has meta data that is used to determine the size and this does not work on any normal string array like argv\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#include
char **tracers = tracefs_tracers(NULL);
if (tracers) {
/* Got tracer plugins from the top trace instance */
\&.\&.\&.
tracefs_list_free(tracers);
}
\&.\&.\&.\&.
char *clock = tracefs_get_clock(NULL);
if (clock) {
/* Got current trace clock of the top trace instance */
\&.\&.\&.
free(clock);
}
.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