Clarify which filter expressions on the command line are capture filters

and which are display filters.

svn path=/trunk/; revision=2857

doc/ethereal.pod.template

@@ -8,7 +8,7 @@ Ethereal - Interactively browse network traffic
 B<ethereal>
 S<[ B<-B> byte view height ]>
 S<[ B<-c> count ]>
-S<[ B<-f> filter expression ]>
+S<[ B<-f> capture filter expression ]>
 S<[ B<-h> ]>
 S<[ B<-i> interface ]> 
 S<[ B<-k> ]>
@@ -19,7 +19,7 @@ S<[ B<-p> ]>
 S<[ B<-P> packet list height ]>
 S<[ B<-Q> ]>
 S<[ B<-r> infile ]>
-S<[ B<-R> filter expression ]>
+S<[ B<-R> display filter expression ]>
 S<[ B<-S> ]>
 S<[ B<-s> snaplen ]>
 S<[ B<-T> tree view height ]>

doc/tethereal.pod.template

@@ -7,7 +7,7 @@ Tethereal - Dump and analyze network traffic
 
 B<tethereal>
 S<[ B<-c> count ]>
-S<[ B<-f> filter expression ]>
+S<[ B<-f> capture filter expression ]>
 S<[ B<-F> file format ]>
 S<[ B<-h> ]>
 S<[ B<-i> interface ]> 
@@ -16,7 +16,7 @@ S<[ B<-n> ]>
 S<[ B<-o> preference setting ] ...>
 S<[ B<-p> ]>
 S<[ B<-r> infile ]>
-S<[ B<-R> filter expression ]>
+S<[ B<-R> display filter expression ]>
 S<[ B<-s> snaplen ]>
 S<[ B<-t> time stamp format ]>
 S<[ B<-v> ]>
@@ -93,7 +93,11 @@ option, respectively, in which case the entire filter expression must be
 specified as a single argument (which means that if it contains spaces,
 it must be quoted), or can be specified with command-line arguments
 after the option arguments, in which case all the arguments after the
-filter arguments are treated as a filter expression.
+filter arguments are treated as a filter expression.  If the filter is
+specified with command-line arguments after the option arguments, it's a
+capture filter if a capture is being done (i.e., if no B<-r> flag was
+specified) and a read filter if a capture file is being read (i.e., if a
+B<-r> flag was specified).
 
 =head1 OPTIONS