join two files using linux command

Question

I have two unix files A and B.

A is like

100
101
102

B is like

ABC
DEF
GHI

How do I have one single consolidated like

 100   ABC
 101   DEF
 102   GHI

like the first column joined with first column of other file.

Answer 1

You use paste.

 NAME
   paste - merge lines of files

SYNOPSIS
   paste [OPTION]... [FILE]...

DESCRIPTION
   Write  lines consisting of the sequentially corresponding lines from each FILE, separated by TABs, to standard output.  With no FILE, or when FILE is -, read standard
   input.

The following command should do the trick

paste A B

Answer 2

use a scripting language, like python?

>>> fina = open("a")
>>> finb = open("b")
>>> for i in fina.readlines():
...     j = finb.readline()
...     print (i.strip() + " " + j.strip())
...