collectd.conf(5): Document he "Derive*" and "AbsoluteSet" DSTypes of the tail plugin.

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index ec68c44..be7d99c 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -3803,25 +3803,37 @@ Use the last number found.
 
 =item B<CounterSet>
 
-The matched number is a counter. Simply sets the internal counter to this
-value.
+=item B<DeriveSet>
+
+=item B<AbsoluteSet>
+
+The matched number is a counter. Simply I<sets> the internal counter to this
+value. Variants exist for C<COUNTER>, C<DERIVE>, and C<ABSOLUTE> data sources.
 
 =item B<CounterAdd>
 
-Add the matched value to the internal counter.
+=item B<DeriveAdd>
+
+Add the matched value to the internal counter. In case of B<DeriveAdd>, the
+matched number may be negative, which will effectively subtract from the
+internal counter.
 
 =item B<CounterInc>
 
-Increase the internal counter by one. This B<DSType> is the only one that does
-not use the matched subexpression, but simply counts the number of matched
+=item B<DeriveInc>
+
+Increase the internal counter by one. These B<DSType> are the only ones that do
+not use the matched subexpression, but simply count the number of matched
 lines. Thus, you may use a regular expression without submatch in this case.
 
 =back
 
 As you'd expect the B<Gauge*> types interpret the submatch as a floating point
-number, using L<strtod(3)>. The B<CounterSet> and B<CounterAdd> interpret the
-submatch as an integer using L<strtoll(3)>. B<CounterInc> does not use the
-submatch at all and it may be omitted in this case.
+number, using L<strtod(3)>. The B<Counter*> and B<AbsoluteSet> types interpret
+the submatch as an unsigned integer using L<strtoull(3)>. The B<Derive*> types
+interpret the submatch as a signed integer using L<strtoll(3)>. B<CounterInc>
+and B<DeriveInc> do not use the submatch at all and it may be omitted in this
+case.
 
 =item B<Type> I<Type>