Ethereal-users: Re: [Ethereal-users] Tethereal question

Note: This archive is from the project's previous web site, ethereal.com. This list is no longer active.

From: Guy Harris <gharris@xxxxxxxxx>
Date: Fri, 6 Jul 2001 18:02:25 -0700
On Fri, Jul 06, 2001 at 05:54:51PM -0700, Anthony Abby wrote:
> Sorry to bother you all again, but could someone
> explain what I did wrong with this tethereal
> statement?

You didn't put the argument to "-f" in quotes.

In the command

> /usr/sbin/tethereal -c 0 -f ip host 192.168.1.3 -i
> eth0 -t ad -w /root/ethereal-caps/test

the argument to the "-f" flag is just "ip" - the standard command-line
argument parsing code on UNIX-flavored OSes (such as Linux) assumes that
the *next* token on the command line is the argument to a command-line
flag that takes an argument; that code does not attempt to infer that
you really meant to make "ip host 192.168.1.3" the argument.

Try

	tethereal -c 0 -f "ip host 192.168.1.3" -i eth0 -t ad -w /root/ethereal-caps/test

instead, or try

	tethereal -i eth0 -w /root/ethereal-caps/test ip host 192.168.1.3

as

	1) "-c 0" is meaningless - it would mean "stop after capturing
	   no packets", which is pointless, so a packet count of 0 means
	   "keep capturing until interrupted", but that's the default,
	   so there's no need to supply "-c 0";

	2) "-t" only applies if Tethereal is *printing* packets rather
	   than saving them to a file, and you're using the "-w" flag to
	   save them to a file, so "-t ad" does nothing and can be
	   omitted in your example;

	3) any command-line arguments after the command-line flags are
	   concatenated and used as a capture filter if you're
	   capturing, so you can just put the filter at the end.