Join two files on Linux

Question

I have two files; I want to join them.

$cat t1
 1 1.2
 2 2.2
$cat t2
 1
 2
 1

I want to have the output below

$cat joind.tx         


        

Answer 1

join requires that both files to be sorted. If you sort them first, you'll get all your output

$ sort t1 > t1.sorted
$ sort t2 > t2.sorted
$ join -j1 -o 1.1,1.2 t1.sorted t2.sorted
1 1.2
1 1.2
2 2.2

Without the sort:

$ join -j1 -o 1.1,1.2 t1 t2
1 1.2
2 2.2

This assumes that the order of your inputs don't need to be preserved; if they do, you will need a custom script like other answers have provided.