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16 <H2><A NAME="s2">2. Filtering (Old Style upto v1.44)</A></H2>
18 <P>Filters can be set for spots, announcements and WWV. You will find the
19 directories for these under /spider/filter. You will find some examples in
20 the directories with the suffix <EM>.issue</EM>. There are two types of
21 filter, one for incoming information and one for outgoing information.
22 Outgoing filters are in the form <EM>CALLSIGN.pl</EM> and incoming filters
23 are in the form <EM>in_CALLSIGN.pl</EM>. Filters can be set for both nodes
26 <P>All filters work in basically the same way. There are several elements
27 delimited by commas. There can be many lines in the filter and they are
28 read from the top by the program. When writing a filter you need to think
29 carefully about just what you want to achieve. You are either going to write
30 a filter to <EM>accept</EM> or to <EM>reject</EM>. Think of a filter as
31 having 2 main elements. For a reject filter, you would have a line or multiple
32 lines rejecting the things you do not wish to receive and then a default line
33 accepting everything else that is not included in the filter. Likewise, for an
34 accept filter, you would have a line or multiple lines accepting the things you
35 wish to receive and a default line rejecting everthing else.
37 <P>In the example below, a user requires a filter that would only return SSB spots
38 posted in Europe on the HF bands. This is achieved by first rejecting the CW
39 section of each HF band and rejecting all of VHF, UHF etc based on frequency.
40 Secondly, a filter rule is set based on CQ zones to only accept spots posted in
41 Europe. Lastly, a default filter rule is set to reject anything outside the filter.
46 [ 0, 0, 'r', # reject all CW spots
56 30000.0, 49000000000.0,
58 [ 1, 11, 'n', [ 14, 15, 16, 20, 33, ], 15 ], #accept EU
59 [ 0, 0, 'd', 0, 1 ], # 1 = want, 'd' = everything else
64 <P>The actual elements of each filter are described more fully in the following
67 <H2><A NAME="ss2.1">2.1 Spots</A>
70 <P>The elements of the Spot filter are ....
74 [action, field_no, sort, possible_values, hops]
78 <P>There are 3 elements here to look at. Firstly, the action element. This is
79 very simple and only 2 possible states exist, accept (1) or drop (0).
81 <P>The second element is the field_no. There are 13 possiblities to choose from
88 2 = date in unix format
91 5 = spotted dxcc country
92 6 = spotter's dxcc country
98 12 = callsign of the channel on which the spot has appeared
102 <P>The third element tells us what to expect in the fourth element. There are
107 n - numeric list of numbers e.g. [ 1,2,3 ]
108 r - ranges of pairs of numbers e.g. between 2 and 4 or 10 to 17 - [ 2,4, 10,17 ]
109 a - an alphanumeric regex
114 <P>The fifth element is simply the hops to set in this filter. This would only
115 be used if the filter was for a node of course and overrides the hop count in
118 <P>So, let's look at an example spot filter. It does not matter in the example
119 who the filter is to be used for. So, what do we need in the filter? We need
120 to filter the spots the user/node requires and also set a default rule for
121 anything else outside the filter. Below is a simple filter that stops spots
122 arriving from outside Europe.
127 [ 0, 4, 'a', '^(K|N|A|W|VE|VA|J)'], # 0 = drop, 'a' = alphanumeric
128 [ 1, 0, 'd', 0, 1 ], # 1 = want, 'd' = everything else
133 <P>So the filter is wrapped in between a pair of square brackets. This tells
134 Spider to look in between these limits. Then each line is contained within
135 its own square brackets and ends with a comma. Lets look carefully at the first
136 line. The first element is 0 (drop). Therefore anything we put on this line
137 will not be accepted. The next element is 4. This means we are filtering by
138 the spotter. The third element is the letter "a" which tells the program to
139 expect an alphanumeric expression in the fourth element. The fourth element
140 is a list of letters separated by the pipe symbol.
142 <P>What this line does is tell the program to drop any spots posted by anyone in
143 the USA, Canada or Japan.
145 <P>The second line is the default rule for anything else. The "d" tells us this
146 and the line simply reads... accept anything else.
148 <P>You can add as many lines as you need to complete the filter but if there are
149 several lines of the same type it is neater to enclose them all as one line.
150 An example of this is where specific bands are set. We could write this like
155 [ 0,0,'r',[1800.0, 2000.0], 1],
156 [ 0,0,'r',[10100.0, 10150.0], 1],
157 [ 0,0,'r',[14000.0, 14350.0], 1],
158 [ 0,0,'r',[18000.0, 18200.0], 1],
162 <P>But the line below achieves the same thing and is more efficient ....
168 1800.0, 2000.0, # top band
169 10100.0, 10150.0, # WARC
170 14000.0, 14350.0, # 20m
171 18000.0, 18200.0, # WARC
177 <H2><A NAME="ss2.2">2.2 Announcements</A>
184 # This is an example announce or filter allowing only West EU announces
186 # The element list is:-
187 # 0 - callsign of announcer
188 # 1 - destination * = all, <callsign> = routed to the node
190 # 3 - * - sysop, <some text> - special list eg 6MUK, ' ', normal announce
192 # 5 - 0 - announce, 1 - wx
193 # 6 - channel callsign (the interface from which this spot came)
196 [ 1, 0, 'a', '^(P[ABCDE]|DK0WCY|G|M|2|EI|F|ON)' ],
201 <P>In this example, only the prefixes listed will be allowed. It is possible to
202 be quite specific. The Dutch prefix "P" is followed by several secondary
203 identifiers which are allowed. So, in the example, "PA" or "PE" would be ok
204 but not "PG". It is even possible to allow information from a single callsign.
205 In the example this is DK0WCY, to allow the posting of his Aurora Beacon.
207 <H2><A NAME="ss2.3">2.3 WWV</A>
214 # This is an example WWV filter
216 # The element list is:-
217 # 0 - nominal unix date of spot (ie the day + hour:13)
225 # 8 - incoming interface callsign
227 # this one doesn't filter, it just sets the hop count to 6 and is
228 # used mainly just to override any isolation from WWV coming from
237 <P>It should be noted that the filter will start to be used only once a user/node
238 has logged out and back in again.
239 <P>I am not going to spend any more time on these filters now as they will become
240 more "comprehensive" in the near future.
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