docs: mention regexps for the interface plugin

It is very useful to collect data (or ignore) from a group of interfaces
that are similarly named - especially if the list is dynamic and it's
not feasible to update configuration each time an interface shows up or
disappears. It's possible to use regexps to specify interfaces to
collect data from (or ignore), but it's not clearly stated anywhere in
the documentation.
This is an attempt to improve documentation in this area.

Signed-off-by: Jakub Jankowski <shasta@toxcorp.com>

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index 25e2b77..f4bd32a 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -2002,6 +2002,23 @@ do that: By setting B<IgnoreSelected> to I<true> the effect of
 B<Interface> is inverted: All selected interfaces are ignored and all
 other interfaces are collected.
 
+It is possible to use regular expressions to match interface names, if the
+name is surrounded by I</.../> and collectd was compiled with support for
+regexps. This is useful if there's a need to collect (or ignore) data
+for a group of interfaces that are similarly named, without the need to
+explicitly list all of them (especially useful if the list is dynamic).
+Example:
+
+ Interface "lo"
+ Interface "/^veth/"
+ Interface "/^tun[0-9]+/"
+ IgnoreSelected "true"
+
+This will ignore the loopback interface, all interfaces with names starting
+with I<veth> and all interfaces with names starting with I<tun> followed by
+at least one digit.
+
+
 =back
 
 =head2 Plugin C<ipmi>