How to merge every two lines into one from the command line?

Question

I have a text file with the following format. The first line is the \"KEY\" and the second line is the \"VALUE\".

KEY 4048:1736 string
3
KEY 0:1772 string
1         


        

Answer 1

If Perl is an option, you can try:

perl -0pe 's/(.*)\n(.*)\n/$1 $2\n/g' file.txt