=head1 NAME

rrdxport - Export data in XML format based on data from one or several RRD

=head1 SYNOPSIS

B<rrdtool> B<xport>
S<[B<-s>|B<--start> I<seconds>]>
S<[B<-e>|B<--end> I<seconds>]>
S<[B<-m>|B<--maxrows> I<rows>]>
S<[B<--step> I<value>]>
S<[B<--json>]>
S<[B<-t>|B<--showtime>]>
S<[B<--enumds>]>
S<[B<--daemon>|B<-d> I<address>]>
S<[B<DEF:>I<vname>B<=>I<rrd>B<:>I<ds-name>B<:>I<CF>]>
S<[B<CDEF:>I<vname>B<=>I<rpn-expression>]>
S<[B<XPORT>B<:>I<vname>[B<:>I<legend>]]>

=head1 DESCRIPTION

The B<xport> function's main purpose is to write an XML formatted
representation of the data stored in one or several B<RRD>s. It
can also extract numerical reports.

If no I<XPORT> statements are found, there will be no output.

=over

=item B<-s>|B<--start> I<seconds> (default end-1day)

The time when the exported range should begin. Time in seconds since
epoch (1970-01-01) is required. Negative numbers are relative to the
current time. By default one day worth of data will be printed.
See also L<rrdfetch/"AT-STYLE TIME SPECIFICATION"> for a detailed explanation
on how to specify time.

See L<"OUTPUT FORMAT"> below for details on how this affects the output.

=item B<-e>|B<--end> I<seconds> (default now)

The time when the exported range should end. Time in seconds since epoch.
See also L<rrdfetch/"AT-STYLE TIME SPECIFICATION"> for a detailed explanation
on how to specify time.

See L<"OUTPUT FORMAT"> below for details on how this affects the output.

=item B<-m>|B<--maxrows> I<rows> (default 400 rows)

This works like the B<-w>|B<--width> parameter of I<rrdgraph>.
In fact it is exactly the same, but the parameter was renamed to
describe its purpose in this module. See I<rrdgraph> documentation
for details.

=item B<--step> I<value> (default automatic)

See L<rrdgraph> documentation.

=item B<--daemon>|B<-d> I<address>

Address of the L<rrdcached> daemon. If specified, a C<flush> command is sent
to the server before reading the RRD files. This allows B<rrdtool> to return
fresh data even if the daemon is configured to cache values for a long time.
For a list of accepted formats, see the B<-l> option in the L<rrdcached> manual.

  rrdtool xport --daemon unix:/var/run/rrdcached.sock ...

=item B<-t>|B<--showtime>

include the time into each data row.

=item B<--json>

produce json formatted output (instead of xml)

=item B<--enumds>

The generated xml should contain the data values in enumerated tags.

 <v0>val</v0><v1>val</v1>

=item B<DEF:>I<vname>B<=>I<rrd>B<:>I<ds-name>B<:>I<CF>

See I<rrdgraph> documentation.

=item B<CDEF:>I<vname>B<=>I<rpn-expression>

See I<rrdgraph> documentation.

=item B<XPORT:>I<vname>[B<:>I<legend>]

At least one I<XPORT> statement should be present. The values
referenced by I<vname> are printed. Optionally add a legend.

=back

=head1 OUTPUT FORMAT

The output is enclosed in an B<xport> element and contains two
blocks. The first block is enclosed by a B<meta> element and
contains some meta data. The second block is enclosed by a
B<data> element and contains the data rows.

Let's assume that the I<xport> command looks like this:

  rrdtool xport \
          --start now-1h --end now \
          DEF:xx=host-inout.lo.rrd:output:AVERAGE \
	  DEF:yy=host-inout.lo.rrd:input:AVERAGE \
          CDEF:aa=xx,yy,+,8,* \
          XPORT:xx:"out bytes" \
          XPORT:aa:"in and out bits"

The resulting meta data section is (the values will depend on the
RRD characteristics):

  <meta>
    <start>1020611700</start>
    <step>300</step>
    <end>1020615600</end>
    <rows>14</rows>
    <columns>2</columns>
    <legend>
      <entry>out bytes</entry>
      <entry>in and out bits</entry>
    </legend>
  </meta>

The resulting data section is:

  <data>
    <row><t>1020611700</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020612000</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020612300</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020612600</t><v>3.4113333333e+00</v><v>5.4581333333e+01</v></row>
    <row><t>1020612900</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020613200</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020613500</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020613800</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020614100</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020614400</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020614700</t><v>3.7333333333e+00</v><v>5.9733333333e+01</v></row>
    <row><t>1020615000</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020615300</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>
    <row><t>1020615600</t><v>NaN</v><v>NaN</v></row>
  </data>

All the statistics in the output will use the same step. The first sample will
be the first sample starting immediately after B<--start>. The last
sample will be the one ending at or immediately after B<--end>.

Each sample has a timestamp and one or more values. The timestamps associated
with a value in RRDtool ALWAYS represent the time the sample was taken. Since
any value you sample will represent some sort of past state your sampling
apparatus has gathered, the timestamp will always be at the end of the sampling
period.

RRDtool does not store the actual samples, but does internal resampling of the
values presented to it. Nevertheless when a data value is presented with a
single timestamp the timestamp is at the end of the period the value
represents. Note that the timestamp itself is outside the period the sample is
valid for. For more details about this, see L<PDP calculation
explanation|rrd_pdpcalc>.

So the time range for a sample with a timestamp is actually
from C<timestamp - step> inclusive to C<timestamp> exclusive.

The first line of the sample output:

    <row><t>1020611700</t><v>3.4000000000e+00</v><v>5.4400000000e+01</v></row>

therefore means that the values for the interval 1020611400 to 1020611699 were
3.4 and 54.4 for "out bytes" and "in and out bits" respectively, because the
value was taken at 1020611700.

=head1 EXAMPLE 1

  rrdtool xport \
          DEF:out=if1-inouts.rrd:outoctets:AVERAGE \
          XPORT:out:"out bytes"

=head1 EXAMPLE 2

  rrdtool xport \
          DEF:out1=if1-inouts.rrd:outoctets:AVERAGE \
          DEF:out2=if2-inouts.rrd:outoctets:AVERAGE \
	  CDEF:sum=out1,out2,+ \
          XPORT:out1:"if1 out bytes" \
          XPORT:out2:"if2 out bytes" \
	  XPORT:sum:"output sum"

=head1 ENVIRONMENT VARIABLES

The following environment variables may be used to change the behavior of
C<rrdtoolE<nbsp>xport>:

=over 4

=item B<RRDCACHED_ADDRESS>

If this environment variable is set it will have the same effect as specifying
the C<--daemon> option on the command line. If both are present, the command
line argument takes precedence.

=back

=head1 AUTHOR

Tobias Oetiker E<lt>tobi@oetiker.chE<gt>
