UNIX for Dummies Questions & Answers

Hi,

I am having a file which contains many duplicate lines. I wanted to redirect these duplicate lines into another file.

Suppose I have a file called file_dup.txt which contains some line as

file_dup.txt

A100-R1
ACCOUNTING-CONTROL
ACTONA-ACTASTOR
ADMIN-AUTH-STATS
ACTONA-ACTASTOR
ADMIN-AUTH-STATS

If you see the above file contents the 3 and 4 numbered lines are duplicated. I want to redirect the lines which are duplicated in to another file say file_nodup.txt. So the file_nodup.txt will contain the line as follows

file_nodup.txt

ACTONA-ACTASTOR
ADMIN-AUTH-STATS

Is there any command in UNIX which will give me the above work done?
Or any AWK way to solve it.

Thanks in advance...

Regards...
zing_foru

Code:

awk ' ++arr[$0] > 1 ' file_dup.txt > file_nodup.txt

I think it can work by this way also:
sort file1 |uniq -d > file2
this will extract the duplicated lines and redirects them to file2

you can also specify the number of duplication of every line at the begining of the line:
sort file1 |uniq -c > file2

Hey thanks for all of you who suggested very good options to solve my problem.