Normail format
Plain text, very clean screen output
-oN
nmap -oN normal.nmap 192.168.1.1
Grepable format
-oG
XML format
-oX
scan ip range 202.21.178.1 to 50 and save to xml format
nmap -v -oX test.xml 202.21.178.1-50
All formats
-oA (log filename>
Network Scanning using Nmap