[nflug] Unix Command / Bash Question...

DANIEL MAGNUSZEWSKI dmagnuszewski at mandtbank.com
Fri Jan 27 10:38:35 EST 2006


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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