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docs: Update wireshark-filter man page about "!=" 

Update man page to remove obsolete information about "!=".
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João Valverde 2021-10-25 19:31:01 +01:00 committed by Wireshark GitLab Utility
parent 10352d552e
commit c9abbde287
1 changed files with 17 additions and 39 deletions
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doc/wireshark-filter.adoc
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@ -387,56 +387,34 @@ Remember that whenever a protocol or field name occurs in an expression, the
priority. This means that the first filter expression must be read as "show me
the packets for which tcp.port exists and equals 80, and ip.src exists and
equals 192.168.2.1". The second filter expression means "show me the packets
where not (llc exists)", or in other words "where llc does not exist" and hence
where not exists llc", or in other words "where llc does not exist" and hence
will match all packets that do not contain the llc protocol.
The third filter expression includes the constraint that offset 199 in the
frame exists, in other words the length of the frame is at least 200.
A special caveat must be given regarding fields that occur more than
once per packet. "ip.addr" occurs twice per IP packet, once for the
source address, and once for the destination address. Likewise,
"tr.rif.ring" fields can occur more than once per packet. The following
two expressions are not equivalent:
ip.addr ne 192.168.4.1
not ip.addr eq 192.168.4.1
The first filter says "show me packets where an ip.addr exists that
does not equal 192.168.4.1". That is, as long as one ip.addr in the
packet does not equal 192.168.4.1, the packet passes the display
filter. The other ip.addr could equal 192.168.4.1 and the packet would
still be displayed.
The second filter says "don't show me any packets that have an
ip.addr field equal to 192.168.4.1". If one ip.addr is 192.168.4.1,
the packet does not pass. If *neither* ip.addr field is 192.168.4.1,
then the packet is displayed.
It is easy to think of the 'ne' and 'eq' operators as having an implicit
"exists" modifier when dealing with multiply-recurring fields. "ip.addr
ne 192.168.4.1" can be thought of as "there exists an ip.addr that does
not equal 192.168.4.1". "not ip.addr eq 192.168.4.1" can be thought of as
"there does not exist an ip.addr equal to 192.168.4.1".
Be careful with multiply-recurring fields; they can be confusing.
Care must also be taken when using the display filter to remove noise
from the packet trace. If, for example, you want to filter out all IP
Each comparison has an implicit exists test for any field value. Care must
be taken when using the display filter to remove noise from
the packet trace. If, for example, you want to filter out all IP
multicast packets to address 224.1.2.3, then using:
ip.dst ne 224.1.2.3
may be too restrictive. Filtering with "ip.dst" selects only those
*IP* packets that satisfy the rule. Any other packets, including all
non-IP packets, will not be displayed. To display the non-IP
packets as well, you can use one of the following two expressions:
may be too restrictive. This is the same as writing:
not ip or ip.dst ne 224.1.2.3
not ip.addr eq 224.1.2.3
ip.dst and ip.dst ne 224.1.2.3
The first filter uses "not ip" to include all non-IP packets and then
The filter selects only frames that have the "ip.dst" field. Any
other frames, including all non-IP packets, will not be displayed. To
display the non-IP packets as well, you can use one of the following
two expressions:
not ip.dst or ip.dst ne 224.1.2.3
not ip.dst eq 224.1.2.3
The first filter uses "not ip.dst" to include all non-IP packets and then
lets "ip.dst ne 224.1.2.3" filter out the unwanted IP packets. The
second filter has already been explained above where filtering with
multiply occurring fields was discussed.
second filter also negates the implicit existance test and so is
a shorter way to write the first.
== FILTER FIELD REFERENCE