'\" t
.\"     Title: libtracecmd
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 01/22/2023
.\"    Manual: libtracefs Manual
.\"    Source: libtracefs
.\"  Language: English
.\"
.TH "LIBTRACECMD" "3" "01/22/2023" "libtracefs" "libtracefs Manual"
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.nh
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.\" * MAIN CONTENT STARTS HERE *
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.SH "NAME"
tracecmd_get_first_ts, tracecmd_add_ts_offset \- Handle time stamps from a trace file\&.
.SH "SYNOPSIS"
.sp
.nf
\fB#include <trace\-cmd\&.h>\fR

unsigned long long \fBtracecmd_get_first_ts\fR(struct tracecmd_input *\fIhandle\fR);
void \fBtracecmd_add_ts_offset\fR(struct tracecmd_input *\fIhandle\fR, long long \fIoffset\fR);
.fi
.SH "DESCRIPTION"
.sp
This set of APIs can be used to read tracing data from a trace file opened with \fItracecmd_open()(3)\fR, \fItracecmd_open_fd()(3)\fR or \fItracecmd_open_head()(3)\fR\&.
.sp
The \fBtracecmd_get_first_ts()\fR function returns the time stamp of the first record in the \fIhandle\fR\&.
.sp
The \fBtracecmd_add_ts_offset()\fR function adds an offset to each of the records in the \fIhandle\fR 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)\&.
.SH "RETURN VALUE"
.sp
The \fBtracecmd_get_first_ts()\fR function returns the timestamp of the first record in a trace file for the given \fIhandle\fR\&.
.SH "EXAMPLE"
.sp
.if n \{\
.RS 4
.\}
.nf
#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\en",
                        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 \&.\&.\&.]\en", 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);
}
.fi
.if n \{\
.RE
.\}
.SH "FILES"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBtrace\-cmd\&.h\fR
        Header file to include in order to have access to the library APIs\&.
\fB\-ltracecmd\fR
        Linker switch to add when building a program that uses the library\&.
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fIlibtracefs(3)\fR, \fIlibtraceevent(3)\fR, \fItrace\-cmd(1)\fR \fItrace\-cmd\&.dat(5)\fR
.SH "AUTHOR"
.sp
.if n \{\
.RS 4
.\}
.nf
\fBSteven Rostedt\fR <\m[blue]\fBrostedt@goodmis\&.org\fR\m[]\&\s-2\u[1]\d\s+2>
\fBTzvetomir Stoyanov\fR <\m[blue]\fBtz\&.stoyanov@gmail\&.com\fR\m[]\&\s-2\u[2]\d\s+2>
.fi
.if n \{\
.RE
.\}
.SH "REPORTING BUGS"
.sp
Report bugs to <\m[blue]\fBlinux\-trace\-devel@vger\&.kernel\&.org\fR\m[]\&\s-2\u[3]\d\s+2>
.SH "LICENSE"
.sp
libtracecmd is Free Software licensed under the GNU LGPL 2\&.1
.SH "RESOURCES"
.sp
\m[blue]\fBhttps://git\&.kernel\&.org/pub/scm/utils/trace\-cmd/trace\-cmd\&.git/\fR\m[]
.SH "COPYING"
.sp
Copyright (C) 2020 VMware, Inc\&. Free use of this software is granted under the terms of the GNU Public License (GPL)\&.
.SH "NOTES"
.IP " 1." 4
rostedt@goodmis.org
.RS 4
\%mailto:rostedt@goodmis.org
.RE
.IP " 2." 4
tz.stoyanov@gmail.com
.RS 4
\%mailto:tz.stoyanov@gmail.com
.RE
.IP " 3." 4
linux-trace-devel@vger.kernel.org
.RS 4
\%mailto:linux-trace-devel@vger.kernel.org
.RE