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