=head1 DESCRIPTION
-The B<update> function feeds new data values into an B<RRD>. The
-data gets time aligned according to the properties of the B<RRD> to
-which the data is written.
+The B<update> function feeds new data values into an B<RRD>. The data
+is time aligned (interpolated) according to the properties of the
+B<RRD> to which the data is written.
=over 8
=item B<--template>|B<-t> I<ds-name>[B<:>I<ds-name>]...
-by default, the B<update> function expects the data input in the order
-the data sources are defined in the RRD, excluding any COMPUTE data sources
-(i.e. if the third data source B<DST> is COMPUTE, the third input value
-will be mapped to the fourth data source in the B<RRD>). This is not very
-error resistant, as you might be sending the wrong data into a RRD.
+By default, the B<update> function expects its data input in the order
+the data sources are defined in the RRD, excluding any COMPUTE data
+sources (i.e. if the third data source B<DST> is COMPUTE, the third
+input value will be mapped to the fourth data source in the B<RRD> and
+so on). This is not very error resistant, as you might be sending the
+wrong data into an RRD.
The template switch allows you to specify which data sources you are
going to update and in which order. If the data sources specified in
asynchronously, B<RRDtool> implicitly assigns non-COMPUTE data sources missing
from the template the I<*UNKNOWN*> value.
-Do not specify a value for a COMPUTE B<DST> in the B<update> function. If
-this is done accidentally (and this can only be done using the template switch),
-B<RRDtool> will ignore the value specified for the COMPUTE B<DST>.
+Do not specify a value for a COMPUTE B<DST> in the B<update>
+function. If this is done accidentally (and this can only be done
+using the template switch), B<RRDtool> will ignore the value specified
+for the COMPUTE B<DST>.
=item B<N>|I<timestamp>B<:>I<value>[B<:>I<value>...]
-The data used for updating the RRD was acquired at a certain time. This
-time can either be defined in seconds since 1970-01-01. Or by using the
-letter 'N' the update time is set to be the current time. Negative time
-values are subtracted from the current time.
-An AT_STYLE TIME SPECIFICATION (see the I<rrdfetch> documentation) may
-also be used by delimiting the end of the time specification with the '@' character
-instead of a ':'.
-Getting the timing right to the second is especially
-important when you are working with data-sources of type B<COUNTER>,
-B<DERIVE> or B<ABSOLUTE>.
-
-The remaining elements of the argument are DS updates. The order of this list is
-the same as the order the data sources were defined in the RRA.
-If there is no data for a certain data-source, the letter
-B<U> (e.g., N:0.1:U:1) can be defined.
-
-The format of the value acquired from the data source is dependent of the
-data source type chosen. Normally it will be numeric, but the data acquisition
-modules may impose their very own parsing of this parameter as long as the colon
-(B<:>) remains the data source value separator.
+The data used for updating the RRD was acquired at a certain
+time. This time can either be defined in seconds since 1970-01-01 or
+by using the letter 'N', in which case the update time is set to be
+the current time. Negative time values are subtracted from the current
+time. An AT_STYLE TIME SPECIFICATION (see the I<rrdfetch>
+documentation) may also be used by delimiting the end of the time
+specification with the '@' character instead of a ':'. Getting the
+timing right to the second is especially important when you are
+working with data-sources of type B<COUNTER>, B<DERIVE> or
+B<ABSOLUTE>.
+
+The remaining elements of the argument are DS updates. The order of
+this list is the same as the order the data sources were defined in
+the RRA. If there is no data for a certain data-source, the letter
+B<U> (e.g., N:0.1:U:1) can be specified.
+
+The format of the value acquired from the data source is dependent on
+the data source type chosen. Normally it will be numeric, but the data
+acquisition modules may impose their very own parsing of this
+parameter as long as the colon (B<:>) remains the data source value
+separator.
=back
Update the database file demo2.rrd which expects data from a single
data-source, three times. First with an I<*UNKNOWN*> value then with two
-normal readings. The update interval seems to be around 300 seconds.
+regular readings. The update interval seems to be around 300 seconds.
=head1 AUTHOR
projects / rrdtool.git / blobdiff