Looping over pairs of values in bash

Question

I have 10 text files and I want to paste each file with its pair, such that I have 5 total files.

I tried the following:

for i in 4_1 5_         


        

Answer 1

There is difference between using read -r x y and read x && read y

while read -r x y; do
    echo "$x and $y"
done <<'____HERE'
    A B
    C D
____HERE

will print

A and B
C and D

whereas,

while read x && read y; do
    echo "$x and $y"
done <<'____HERE'
    A B
    C D
____HERE

will print

A B and C D

First example splits on space, while second splits on newline.