An XARGS question

[Les Mikesell]

On Tue, 2006-07-18 at 16:50, Bill Rugolsky Jr. wrote:
> On Tue, Jul 18, 2006 at 11:31:00PM +0200, Alexander Dalloz wrote:
> > Even shorter:
> > 
> > lastb -ai | awk '/Jul 18/ {print $10}' | sort -u | fgrep -x -f - blacklist
> 
> Of course, in the way that I wrote it, if blacklist really only contains
> IP addresses, and is not huge, then one should reverse the order:
> 
> 	| fgrep -x -f blacklist
> 
> If blacklist is huge, and the output of the pipeline is not, or e.g., blacklist
> has multiple fields, say IP address, reason for blacklisting, etc., and one
> wants the whole record, then the order that I gave is useful.

If blacklist is sorted, why not:
lastb -ai |awk '/Jul 18/ {print $10}' |sort -u |comm -23 - blacklist
that will get you the new entries in one pass.

-- 
  Les Mikesell
   lesmikesell at gmail.com