tracecmd_buffer_instances - Man Page

Read tracing instances from a trace file.

Synopsis

#include <trace-cmd.h>

int tracecmd_buffer_instances(struct tracecmd_input *handle);
const char *tracecmd_buffer_instance_name(struct tracecmd_input *handle, int indx);
struct tracecmd_input *tracecmd_buffer_instance_handle(struct tracecmd_input *handle, int indx);

Description

This set of APIs can be used to get information and read tracing data from tracing instances stored in a trace file.

The tracecmd_buffer_instances() function gets the number of tracing instances recorded in a trace file. The top instance is not counted. The handle is a tracecmd_input handler returned by tracecmd_open_head().

The tracecmd_buffer_instance_name() function gets the name of the tracing instance with given index indx, recorded in a trace file. The indx is a number in the interval [0 .. count-1], where count is the number returned by tracecmd_buffer_instances(). The handle is a tracecmd_input handler returned by tracecmd_open_head().

The tracecmd_buffer_instance_handle() allocates and initializes a tracecmd_input handle, associated with trace instance with index indx from a trace file. The handle is a tracecmd_input handler returned by tracecmd_open_head(). The indx is a number in the interval [0 .. count-1], where count is the number returned by tracecmd_buffer_instances().

Return Value

The tracecmd_buffer_instances() function returns the number of tracing instances recorded in a trace file.

The tracecmd_buffer_instance_name() function returns a string, the name of a tracing instance, or NULL in case of an error The string must not be freed.

The tracecmd_buffer_instance_handle() function returns a pointer to newly allocated tracecmd_input handler or NULL in case if an error. The returned handler must be closed by tracecmd_close()(3)

Example

#include <trace-cmd.h>
...
struct tracecmd_input *handle = tracecmd_open_head("trace.dat");
        if (!handle) {
                /* Failed to open trace.dat file */
        }
...
int num = tracecmd_buffer_instances(handle);

        while(num) {
                struct tracecmd_input *h;
                char *name;

                name = tracecmd_buffer_instance_name(handle, num);
                if (!name) {
                        /* Failed to get name of instance num */
                }
                h = tracecmd_buffer_instance_handle(handle, num);
                if (!h) {
                        /* Failed to initialize handler for instance num */
                }

                ...
                tracecmd_close(h);
                num--;
        }
...
        tracecmd_close(handle);

Files

trace-cmd.h
        Header file to include in order to have access to the library APIs.
-ltracecmd
        Linker switch to add when building a program that uses the library.

See Also

libtracefs(3), libtraceevent(3), trace-cmd(1) trace-cmd.dat(5)

Author

Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>

Reporting Bugs

Report bugs to <linux-trace-devel@vger.kernel.org[3]>

License

libtracecmd is Free Software licensed under the GNU LGPL 2.1

Resources

https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/

Copying

Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).

Notes

  1. rostedt@goodmis.org
    mailto:rostedt@goodmis.org
  2. tz.stoyanov@gmail.com
    mailto:tz.stoyanov@gmail.com
  3. linux-trace-devel@vger.kernel.org
    mailto:linux-trace-devel@vger.kernel.org

Referenced By

The man pages tracecmd_buffer_instance_handle(3) and tracecmd_buffer_instance_name(3) are aliases of tracecmd_buffer_instances(3).

03/29/2021 libtracefs Manual