Wireshark-users: Re: [Wireshark-users] Filtering a very large capture file

From: Seymour Dupa <grumpy_44134@xxxxxxxxx>
Date: Fri, 26 Jan 2007 08:12:40 -0800 (PST)
What about 'grep'?
I used it a lot in my DOS days.  I'm sure there is/are
Windows versions.  It's quite powerful with many
wildcard characters and search patterns.  It will do a
lot of filtering for you.
You mauy have to run it several times for the
different search parameters.

John

--- Guy Harris <guy@xxxxxxxxxxxx> wrote:

> 
> On Jan 25, 2007, at 8:23 PM, Stuart MacDonald wrote:
> 
> > I've read the man pages on the tools that come
> with Wireshark. I was
> > hoping to find a tool that opens a capture,
> applies a filter and
> > outputs matching packets to a new file. Here's a
> sample run of the
> > hypothetical filtercap tool:
> > # filtercap -r very-large.eth -w
> only-infrequent.eth -f  
> > "tcp.port==50000"
> 
> 	tcpdump -r very-large.eth -w only-infrequent.eth
> tcp port 50000
> 
> That can't do arbitrary display filtering, but truly
> *arbitrary*  
> display filtering has problems with reassembly
> (i.e., a filter that  
> matches something in the reassembled portion of the
> packet can't match  
> anything but the last packet).  It also can't handle
> non-libpcap  
> capture files, but given that your capture file is
> *from* tcpdump,  
> it's obviously readable by tcpdump....
> 
> 
> > tshark is almost the right thing, except that
> tshark also tries to
> > read in the whole capture first instead of
> processing it like editcap.
> 
> No, actually, it *does* process it like editcap;
> neither it nor  
> Wireshark read the entire capture file into memory. 
> They *do* keep  
> reassembled data in memory, but that's another
> matter.
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