sed.exe replace new line character

sed ':a;N;$!ba;s/\n/ /g'

:a create a label 'a'
N append the next line to the pattern space
$! if not the last line, ba branch (go to) label 'a'
s substitute, /\n/ regex for new line, / / by a space, /g global match (as many times as it can)

sed will loop through step 1 to 3 until it reach the last line, getting all lines fit in the pattern space where sed will substitute all \n characters

Copied from:
https://stackoverflow.com/questions/1251999/how-can-i-replace-a-newline-n-using-sed