How to directly append columns of one file to another file

Requirement: Only grep/cut/join/cat/regex/for/while.

I am a beginner at shell utilities.

I have fileA and fileB containing equal number of rows. I want to append columns of fileB into fileA.

I am trying this (cat fileA && cat fileB) > fileC. But it isn't working as required.

Expected:

fileA:

1
2
3

fileB:

1
2
3

then fileC should have:

1 1
2 2
3 3

Solution

With bash:

#!/bin/bash

while true; do
  read -r f1 <&3 || break
  read -r f2 <&4 || break
  echo "$f1 $f2"
done 3<fileA 4<fileB >fileC

Output to fileC:

1 1
2 2
3 3