CODEWITHSUNDEEP
sedawkuniq
Jamie
Jamie

Reputation: 7421

How can I emulate `uniq -d` in awk?

I've got a busybox system which doesn't have uniq and I'd like to generate a unique list of duplicated lines.

A plain uniq emulated in awk would be:

sort <filename> | awk '!($0 in a){a[$0]; print}'

How can I use awk (or sed for that matter, not perl) to accomplish:

sort <filename> | uniq -d

Upvotes: 3

Views: 1873

Answers (3)

potong
potong

Reputation: 58401

This might work for you:

# make some test data
seq 25 >/tmp/a
seq 3 3 25 >>/tmp/a
seq 5 5 25 >>/tmp/a
# run old command
sort -n /tmp/a | uniq -d
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# run sed command 
sort -n /tmp/a | 
sed ':a;$bb;N;/^\([^\n]*\)\(\n\1\)*$/ba;:b;/^\([^\n]*\)\(\n\1\)*/{s//\1/;P};D' 
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Upvotes: 0

Dennis Williamson
Dennis Williamson

Reputation: 360065

On a busybox system, you might need to save bytes. ;-)

awk ++a[\$0]==2

Upvotes: 6

Benoit
Benoit

Reputation: 79185

Could do this (needn't sort it):

awk '{++a[$0]; if(a[$0] == 2) print}'

Upvotes: 3

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