ScraperWiki Ruby library

This is a Ruby library for scraping web pages and saving data. It is a fork/rewrite of the original scraperwiki-ruby gem, extracting the SQLite utility methods into the sqlite_magic gem.

It is a work in progress (for example, it doesn't yet create indices automatically), but should allow ScraperWiki classic scripts to be run locally.

Installing

Add this line to your application's Gemfile:

gem 'scraperwiki'

And then execute:

$ bundle

Scraping

ScraperWiki.scrape(url[, params])

Returns the downloaded string from the given url. params are sent as a POST if set.

Saving data

Helper functions for saving and querying an SQL database. Updates the schema automatically according to the data you save.

Currently only supports SQLite. It will make a local SQLite database.

ScraperWiki.save_sqlite(unique_keys, data[, table_name = "swdata"],verbose)

Saves a data record into the datastore into the table given by table_name.

data is a hash with field names as keys (can be strings or symbols).

unique_keys is a subset of data.keys() which determines when a record is overwritten.

For large numbers of records data can be an array of hashes.

verbose, kept for smooth migration from classic, doesn't do anything yet.

ScraperWiki.sqliteexecute(query,[params],verbose)

Executes provided query with the parameters against the database and returns the results in key value pairs

query is a sql statement

params, if prepared statement will contains an array of values

ScraperWiki.save_var(name,value,verbose)

Allows the user to save a single variable (at a time) to carry state across runs of the scraper.

name, the variable name

value, the value of the variable

verbose, verbosity level

ScraperWiki.get_var(name,default,verbose)

Allows the user to retrieve a previously saved variable

name, The variable name to fetch

value, The value to use if the variable name is not found

verbose, verbosity level

ScraperWiki.select(partial_query,[params],verbose)

Allows for a simplified select statement

partial_query, A valid select statement, without the select keyword

params Any data provided for ? replacements in the query

verbose, verbosity level

Usage

Run your Ruby scraper and any data saved will be put in an SQLite database in the current directory called scraperwiki.sqlite.

If you're using scrapers from ScraperWiki Classic, remember to add require 'scraperwiki' to your file if it's not already there.

Development

You need the sqlite3 program installed to run tests. To install run sudo apt-get install sqlite3 on Ubuntu.