'\" t
.\" Title: libtracefs
.\" Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot
.\" Date: 05/25/2021
.\" Manual: libtracefs Manual
.\" Source: libtracefs 1.2.0
.\" Language: English
.\"
.TH "LIBTRACEFS" "3" "05/25/2021" "libtracefs 1\&.2\&.0" "libtracefs Manual"
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.\" * MAIN CONTENT STARTS HERE *
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.SH "NAME"
tracefs_file_exists, tracefs_dir_exists, tracefs_instance_get_file, tracefs_instance_get_dir \- Work with files directories in tracing instances\&.
.SH "SYNOPSIS"
.sp
.nf
\fB#include \fR
bool \fBtracefs_file_exists\fR(struct tracefs_instance *\fIinstance\fR, char *\fIname\fR);
bool \fBtracefs_dir_exists\fR(struct tracefs_instance *\fIinstance\fR, char *\fIname\fR);
char *\fBtracefs_instance_get_file\fR(struct tracefs_instance *\fIinstance\fR, const char *\fIfile\fR);
char *\fBtracefs_instance_get_dir\fR(struct tracefs_instance *\fIinstance\fR);
.fi
.SH "DESCRIPTION"
.sp
This set of APIs can be used to work with trace files in all trace instances\&. Each of these APIs take an \fIinstance\fR argument, that can be NULL to act on the top level instance\&. Otherwise, it acts on an instance created with \fBtracefs_insance_create\fR(3)
.sp
The \fItracefs_file_exists()\fR function checks if a file with \fIname\fR exists in \fIinstance\fR\&.
.sp
The \fItracefs_dir_exists()\fR function checks if a directory with \fIname\fR exists in \fIinstance\fR\&.
.sp
The \fItracefs_instance_get_file()\fR function returns the full path of the file with given \fIname\fR in \fIinstance\fR\&. Note, it does not check if the file exists in the instance\&.
.sp
The \fItracefs_instance_get_dir()\fR function returns the full path of the directory with given \fIname\fR in \fIinstance\fR\&. Note, it does not check if the directory exists in the instance\&.
.SH "RETURN VALUE"
.sp
The \fItracefs_file_exists()\fR and \fItracefs_dir_exists()\fR functions return true if the file / directory exist in the given instance or false if it does not exist\&.
.sp
The \fItracefs_instance_get_file()\fR and \fItracefs_instance_get_dir()\fR functions return a string or NULL in case of an error\&. The returned string must be freed with \fItracefs_put_tracing_file()\fR\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#include
struct tracefs_instance *inst = tracefs_instance_create("foo");
if (!inst) {
/* Error creating a new trace instance */
\&.\&.\&.
}
if (tracefs_file_exists(inst,"trace_clock")) {
/* The instance foo supports trace clock */
char *path, *clock;
int size;
path = = tracefs_instance_get_file(inst, "trace_clock")
if (!path) {
/* Error getting the path to trace_clock file in instance foo */
\&.\&.\&.
}
\&.\&.\&.
tracefs_put_tracing_file(path);
clock = tracefs_instance_file_read(inst, "trace_clock", &size);
if (!clock) {
/* Failed to read trace_clock file in instance foo */
\&.\&.\&.
}
\&.\&.\&.
free(clock);
if (tracefs_instance_file_write(inst, "trace_clock", "global") != strlen("global")) {
/* Failed to set gloabl trace clock in instance foo */
\&.\&.\&.
}
} else {
/* The instance foo does not support trace clock */
}
if (tracefs_dir_exists(inst,"options")) {
/* The instance foo supports trace options */
char *path = tracefs_instance_get_file(inst, "options");
if (!path) {
/* Error getting the path to options directory in instance foo */
\&.\&.\&.
}
tracefs_put_tracing_file(path);
} else {
/* The instance foo does not support trace options */
}
\&.\&.\&.
if (tracefs_instance_is_new(inst))
tracefs_instance_destroy(inst);
else
tracefs_instance_free(inst);
\&.\&.\&.
long long int res;
if (tracefs_instance_file_read_number(NULL, "tracing_on", &res) == 0) {
if (res == 0) {
/* tracing is disabled in the top instance */
} else if (res == 1) {
/* tracing is enabled in the top instance */
} else {
/* Unknown tracing state of the top instance */
}
} else {
/* Failed to read integer from tracing_on file */
}
\&.\&.\&.
int fd;
fd = tracefs_instance_file_open(NULL, "tracing_on", O_WRONLY);
if (fd >= 0) {
/* Got file descriptor to the tracing_on file from the top instance for writing */
\&.\&.\&.
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
\fIlibtracefs(3)\fR, \fIlibtraceevent(3)\fR, \fItrace\-cmd(1)\fR
.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