I have several files, namely a.txt, b.txt, c.txt, d.txt, in the same format (3 columns, separated with tab). Let's take the first 3 lines of a.txt and b.txt for example:
$head -3 a.txt
id_1 59 4
id_4 89 43
id_5 8 90
$head -3 b.txt
id_1 9 4
id_4 39 43
id_5 81 9
c.txt and d.txt are similar to that.
I want to check if the first columns from them are all the same. Is there any easy way in shell to do this?