How to paste 2 files in unix

Question

I have 2 files below are the values and expected output,could anyone please help.

File 1 :

A
B
C
D
E
F

FIle 2

1
2
3

Expected output:

1
A
B
C
2
E
F
G

Answer 1

The output of this awk script happens to produce the expected output,

but it's unclear if this is a correct answer to your question:

awk 'NR==FNR{ a[NR]=$0 }NR!=FNR{ if(FNR%3==1) { print a[++i] } print $0 }' file2 file1

• NR==FNR see: an explanation of NR and FNR, the array a[] is filled with the values found in file file2
• NR!=FNR see: an explanation of NR and FNR, here file file1 is read
• if(FNR%3==1) {...} When the value if FNR%3 equals 1, print the first member of the array a[], and i is incremented

This happens to print a line from file2, and then print 3 lines from file1. After this again 1 line from file2, and 3 lines of file1. Then the process stops. Nothing is done with the 3rd line of file2.