'\" t
.\"     Title: libtracefs
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      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_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 <tracefs\&.h>\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 \fBtracefs_file_exists()\fR function checks if a file with \fIname\fR exists in \fIinstance\fR\&.
.sp
The \fBtracefs_dir_exists()\fR function checks if a directory with \fIname\fR exists in \fIinstance\fR\&.
.sp
The \fBtracefs_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 \fBtracefs_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 \fBtracefs_file_exists()\fR and \fBtracefs_dir_exists()\fR functions return true if the file / directory exist in the given instance or false if it does not exist\&.
.sp
The \fBtracefs_instance_get_file()\fR and \fBtracefs_instance_get_dir()\fR functions return a string or NULL in case of an error\&. The returned string must be freed with \fBtracefs_put_tracing_file()\fR\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#include <tracefs\&.h>

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
\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