'awk', nawk', sed'? Not sure 2

[mwesticle]

OK. Here's my dilemma... I have a file with a bunch of 12-byte "ID's" on it. It looks like this:

111111111111
999999999999
222222222222
999999999999
333333333333
222222222222

...and so on.

Anyway, here's the criteria: I want to take this file, do "something" to it, and, when that "something" is done, I want a file that contains just the duplicated ID's from this file. So in the example above, the output file would look like this:

999999999999
222222222222

The duplication in this file is sometimes non-consecutive, so a "sort" may have to happen first. Anyway, what's the best way to go about this, do you think? I figured I'd solicit some expert opinions... Thanks for the input!

 

[hoinz]

sort your_file | uniq -d

 

[adamcpng]

how about

sort -u filename, i think it is almost the same as sort filename|uniq

 

[CaKiwi]

But not the same as sort filename | uniq -d which outputs only duplicate lines

CaKiwi

 

[PHV]

adamcpng, sort -u is the same as sort | uniq but not the same as sort | uniq -d.
The goal is to retrieve only the duplicates lines.

Hope This Help, PH.
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