how can I combine these lines

Question

How can I combine these lines (NOTE: this is just an excerpt from a much larger file):

interface GigabitEthernet0/0
 no ip proxy-arp
interface GigabitEthernet0/0         


        

Answer 1

while IFS= read line1 && IFS= read line2; do
    printf "%s | %s\n" "$line1" "$line2"
done < file.txt