These Nmap scripts were created to make parsing Nmap files much more convenient. For example, with nmap_parser.py, it simply creates a text file, named whatever port that was found to be opened, and it contains a list of IP addresses that has that port open. It's much easier to feed other tools a list of IP addresses that have a port opened this way.
With the nmapscrape.rb script, this allows for you to parse a greppable Nmap output into a nicely formatted table.
With regards to the Nmap parser script, here's an example of the usage menu:
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nmapparse 1.0 - Nmap Output Parser, Alton Johnson ([email protected])
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Usage: ./nmapparse.py results.gnmap
Note: This script must point to a grepable output file from nmap to work properly.
With regards to the Nmap scrape script, here's an example of the usage menu:
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Nmap Parser v1.0, Alton Johnson ([email protected])
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Usage: nmapscrape.py <gnmap file>