That one formats nicely. It does have a quirk with regards to always printing the "value" of the first find next to the current find for each of multiple repeats. That's a mouthful, let me demonstrate with a contrived data set: 

file1.....

test1 abc
test2 def
test3 ghi
test4 jkl

file2.....
test1 ghi
test3 jkl
test3 mno

[download]

And the output.....

test1 abc ghi
test3 ghi jkl
test3 ghi mno

[download]

As you can see, test3's "ghi" (the first sequence found) gets repeated for each 'test3' found. Not that there's anything wrong with that. ;)

If you use the -a switch, you will shave off a few more keystrokes from your solution though, and that's got to be worth something!

perl -ane '($a,$b)=@F;!$h{$a}?$h{$a}=$b:print"$a $h{$a} $b\n"' file1 f
+ile2

[download]

I do like your solution since it preserves order and formats nicely. Good job.


Dave

In reply to Re^3: comparing two files for duplicate entries by davido
in thread comparing two files for duplicate entries by Angharad

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