This happens to me all the time: I type a long command line and forget to specify some options. For example:
$ tcpdump host foo.com and port 8080
Hmm, I should be seeing some output. Ah! Forgot to listen on a different interface.
At this point I'd hit the up-arrow to bring back the previous command, then either scroll back to the first argument or press C-a to jump to the start of the command and scroll forward to the first argument.
Is there a quicker way to jump to the first argument so I can insert the
-i eth1 option?