LIBTRACECMD(3) libtracefs Manual LIBTRACECMD(3)

tracecmd_buffer_instances, tracecmd_buffer_instance_name, tracecmd_buffer_instance_handle - Read tracing instances from a trace file.

#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);

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().

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)

#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);

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.

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

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

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

libtracecmd is Free Software licensed under the GNU LGPL 2.1

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

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

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
11/11/2021 libtracefs