LIBTRACECMD

NAME

tracecmd_get_first_ts, tracecmd_add_ts_offset - Handle time stamps from a trace file.

SYNOPSIS

#include <trace-cmd.h>

unsigned long long tracecmd_get_first_ts(struct tracecmd_input *handle);
void tracecmd_add_ts_offset(struct tracecmd_input *handle, long long offset);

DESCRIPTION

This set of APIs can be used to read tracing data from a trace file opened with tracecmd_open()(3), tracecmd_open_fd()(3) or tracecmd_open_head()(3).

The tracecmd_get_first_ts() function returns the time stamp of the first record in the handle.

The tracecmd_add_ts_offset() function adds an offset to each of the records in the handle that represents a trace file. This is useful for associating two different tracing files by their offset (for example a trace file from a host and a trace file from a guest that were not synchronized when created).

RETURN VALUE

The tracecmd_get_first_ts() function returns the timestamp of the first record in a trace file for the given handle.

EXAMPLE

#include <stdlib.h>
#include <trace-cmd.h>

static int print_events(struct tracecmd_input *handle, struct tep_record *record, int cpu, void *data)
{
static struct trace_seq seq;
struct tep_handle *tep = tracecmd_get_tep(handle);
const char *file = tracecmd_get_private(handle);

if (!seq.buffer)
trace_seq_init(&seq);

trace_seq_reset(&seq);
trace_seq_printf(&seq, "%s: ", file);
tep_print_event(tep, &seq, record, "%6.1000d [%03d] %s-%d %s: %s\n",
TEP_PRINT_TIME, TEP_PRINT_CPU, TEP_PRINT_COMM, TEP_PRINT_PID,
TEP_PRINT_NAME, TEP_PRINT_INFO);
trace_seq_terminate(&seq);
trace_seq_do_printf(&seq);
return 0;
}

int main(int argc, char **argv)
{
struct tracecmd_input **handles = NULL;
unsigned long long ts, first_ts = 0;
int nr_handles = 0;
int i;

if (argc < 2) {
printf("usage: %s trace.dat [trace.dat ...]\n", argv[0]);
exit(-1);
}

for (i = 1; i < argc; i++) {
handles = realloc(handles, sizeof(*handles) * (nr_handles + 1));
if (!handles)
exit(-1);
handles[nr_handles] = tracecmd_open(argv[i], 0);
if (!handles[nr_handles])
exit(-1);
tracecmd_set_private(handles[nr_handles], argv[i]);
ts = tracecmd_get_first_ts(handles[nr_handles]);
if (!first_ts || ts < first_ts)
first_ts = ts;
nr_handles++;
}

/* Set the time stamp to start at the first record found */
for (i = 0; i < nr_handles; i++)
tracecmd_add_ts_offset(handles[i], -first_ts);

tracecmd_iterate_events_multi(handles, nr_handles, print_events, NULL);

for (i = 0; i < nr_handles; i++)
tracecmd_close(handles[i]);
free(handles);
}

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