reverse grep

Gavin Cameron ggcameron at
Sat Nov 3 17:53:51 PDT 2007

On 11/4/07, deeptech71 at <deeptech71 at> wrote:
> How is it possible to select lines that do NOT match a specific pattern?
> For example, I'm connecting to via telnet (port 23), and
> do tcpdump -nli rl0. This cyclic traffic, becuase when tcpdump outputs
> something, the system sends me some packets, which generates output in
> tcpdump, and vice versa. I want to filter out packets of telnet access
> to the FreeBSD machine, that is, something like:
>      tcpdump -nli rl0 | grep --non-matching-lines

grep -v

man grep

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