tracecmd_get_first_ts - Man Page

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

Referenced By

The man page tracecmd_add_ts_offset(3) is an alias of tracecmd_get_first_ts(3).

10/11/2022 libtracefs Manual