Readdb is an alias for org.apache.nutch.crawl.CrawlDbReader
Nutch 1.x
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.
Nutch 2.x
Usage: WebTableReader (-stats | -url [url] | -dump <out_dir> [-regex regex])
[-crawlId <id>] [-content] [-headers] [-links] [-text]
-crawlId <id> - the id to prefix the schemas to operate on,
(default: storage.crawl.id)
-stats [-sort] - print overall statistics to System.out
[-sort] - list status sorted by host
-url <url> - print information on <url> to System.out
-dump <out_dir> [-regex regex] - dump the webtable to a text file in
<out_dir>
-content - dump also raw content
-headers - dump protocol headers
-links - dump links
-text - dump extracted text
[-regex] - filter on the URL of the webtable entry