Unix one liner: Combine 2 headed files

Question

If I have 2 files where the first lines contain identical headings:

A.txt:

A
1
aa

B.txt

A
ee
7

I want to combine them like so:

C.txt

A
1
aa
ee
7

Is there a one liner to do this?

Do you want this to happen only if the header is the same?
Not necessary.. I'm thinking of a simple case when I know the headers are the same. Handling the case where the headers can be slightly different might be the subject of another question :-)

Ignacio Vazquez-Abrams · Answer 1 · 2010-12-03 11:42:24Z

up vote 3 down vote accepted

tail -n +2 B.txt | cat A.txt - > C.txt

answered Dec 3 '10 at 11:42

Thank you Ignacio; – StamfordBingo Dec 3 '10 at 13:29

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shaktale · Answer 2 · 2010-12-03 13:01:37Z

up vote 0 down vote

If order is not a problem:

sort A.txt B.txt | uniq

answered Dec 3 '10 at 13:01

1

How will this result in the desired output? – Ignacio Vazquez-Abrams Dec 3 '10 at 13:06

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Dennis Williamson · Answer 3 · 2010-12-03 16:56:36Z

up vote 0 down vote

Here's another way that's easily scalable to any number of input files (just add them as additional arguments:

awk 'FNR!=NR&&FNR==1{next}{print}' A.txt B.txt > C.txt

answered Dec 3 '10 at 16:56

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3 Answers