Script Kiddie Format (-oS <logfilename>)
The "script kiddie" format (-oS) has very little practical functionality. Fyodor added this output format to nmap as a joke, since most users of "leet speak" (or l33t 5p34k) are considered to be technically immature. Fyodor considers the use of nmap to be for serious security purposes, and his sarcastic dig at the less technical script kiddies is intended to be as pointed as it is accurate.


clock
There actually is some practical use to this format, since it takes advantage of a flexible output system that could be used in the future for other purposes. Fyodor's opinion of this format can be found at this nmap-hackers mailing list archive page:

http://seclists.org/lists/nmap-hackers/2000/Jan-Mar/0005.html


HTML Format (-oH)
The HTML format command line is included in the nmap source, but it does not include any supporting code. This format isn't currently supported, and if the option is used in the command line this message will display:
HTML output is not yet supported
QUITTING!
Considering that XML format has now been integrated into nmap with cooresponding XSL stylesheets, a separate HTML format will probably be unnecessary.


Resume Scan (--resume <logfilename>)
A scan can be interrupted during processing with the control-C key combination. The --resume option allows the nmap scan to restart without reprocessing previously scanned devices.

The resume scan option works by parsing a normal (-oN) or grepable (-oG) output file to determine the last successful scanned device. Since the original nmap options are also included in the log file, no additional nmap parameters are required or allowed on the command line when resuming a scan.

Once the previously saved output file has been parsed, the --resume option can determine the last successfully scanned device and continue the scanning process from that point. If a device was partially scanned prior to the interruption, it will be scanned again from the very beginning of the process.

clock
Ironically, the recommended output format for post-processing of nmap scans is the XML output (-oX), but the --resume option will not work with an XML file. If both XML output and the ability to resume a scan is required, consider using the all formats (-oA) output option.

If a scan is interrupted that used the --randomize_hosts option, nmap has no method to recreate the same randomness that was used in the initial scan. If this type of scan is resumed, nmap will provide this message:

WARNING: You are attempting to resume a scan which used
--randomize_hosts. Some hosts in the last randomized batch
make (sic) be missed and others may be repeated once

Append Output (--append_output)
If a single log file is required from multiple nmap scans, the --append_output option will append the output the to the log filename used on the nmap command line. If this option isn't specified, nmap will overwrite an existing logfile without any warning or message.