[Nutch Wiki] Update of "bin/nutch readdb" by kiranchitturi

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The "bin/nutch readdb" page has been changed by kiranchitturi:
http://wiki.apache.org/nutch/bin/nutch%20readdb

New page:
Readdb is an alias for org.apache.nutch.crawl.CrawlDbReader

The CrawlDbReader implements all the read-only parts of accessing our web database. It provides us with a read utility for the crawldb.

Usage: 

{{{
bin/nutch readdb <crawldb> (-stats | -dump <out_dir> | -topN <nnnn> <out_dir> [<min>] | -url <url>)
}}} 

'''<crawldb>''': The location of the crawldb directory we wish to read and obtain information from.

'''-stats''': This prints the overall statistics to System.out.

'''-dump <out_dir>''': Enables us to dump the whole crawldb to a text file in any <out_dir> we wish to specify.

'''[-regex <expr>]''': filter records with a regular expression

'''[-status <status>]''': filter records by CrawlDatum status

'''-topN <nnnn> <out_dir> [<min>]''': This dumps the top <nnnn> urls sorted by score relevance to any <out_dir> we wish to specify. If the [<min>] parameter is passed in the command the reader will skip records with scores below this particluar value. This can significantly improve retrieval performance of statistics or crawldb dump results.

'''-url <url>''': This simply prints information of any particular <url> to System.out.



CommandLineOptions