[nflug] Unix Command / Bash Question...

[Robert Meyer]

>From the 'uniq' man page:
Discard  all but one of successive identical lines from INPUT (or stan-
dard input), writing to OUTPUT (or standard output).

The usual pipe process is:

someprogram | sort | uniq ... whatever else

So this is expected behaviour...

Cheers!

Bob

--- DANIEL MAGNUSZEWSKI <dmagnuszewski at mandtbank.com> wrote:

> Ahhh yes...there lies the problem!
> 
> Thanks.
> 
> >>> rao3 at buffalo.edu 01/27/06 10:35 AM >>>
> Could it have to do with adjacency?
> 
> Example:
> a
> b
> a
> 
> uniq will not see lines a and a to be the same, since the line with b 
> 
> is intervening.
> 
> But, should you grep first, then b is filtered out:
> 
> uniq then grep:
> input:
> a
> b
> a
> 
> after uniq:
> a
> b
> a
> 
> after grep:
> a
> a
> 
> 
> grep then uniq:
> input:
> a
> b
> a
> 
> after grep
> a
> a
> 
> after uniq:
> a
> 
> Maybe you want to throw in a sort in the pipe?
> 
> 
> On Jan 27, 2006, at 10:25 AM, DANIEL MAGNUSZEWSKI wrote:
> 
> > All,
> >
> > I wrote a Perl script to parse a file for ip addresses and
> hostnames,
> > and to print out in the format of:
> >
> > $ip,$hostname
> >
> > There are some duplicates in the list, so I was just using some Unix
> > commands and pipes to rid them from the output. While doing this, I 
> 
> > ran
> > into something interesting.
> >
> > If I do:
> >
> > user at server:/opt/cwscripts# ./dcraudit.pl | uniq | grep -i
> '10.x.x.x'
> >
> > I get the output of:
> >
> > 10.x.x.x,router1
> > 10.x.x.x,router1
> >
> > If I switch the 'uniq' and 'grep' and run:
> >
> > user at server:/opt/cwscripts# ./dcraudit.pl |  grep -i '10.x.x.x' |
> uniq
> >
> > I get the output of:
> >
> > 10.x.x.x,router1
> >
> > What is the technical reason for this? I assumed that it would work
> > either way.
> >
> > Thanks.
> >
> > -Dan
> >
> > _______________________________________________
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> >
> 
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