Lab - stock prices

getprice (stock symbol)
Get the price of that stock.
Usage like: getprice GOOG

1. Download quote page. Parse to extract price.
2. See Parsing XML / HTML

3. Hard to parse: http://bigcharts.marketwatch.com/quickchart/quickchart.asp?symb=SYMBOL
   • grep "Last:" | head -1 | various sed's

4. Easier to parse: http://finance.yahoo.com/q?s=SYMBOL because stock price is delimited by tags.
   • grep "Last Trade:"
   • grep "yfs_l10_SYMBOL"
   • Something like:
     <span id="yfs_l10_goog">540.30</span>

   • If clean up HTML first to make it well-formed XHTML, can use xpath to parse it properly:

      
     # search for <span tag(s) with attribute id="yfs_l10_goog"  
     cat cleanedupfile.xhtml | xpath '//span[@id="yfs_l10_goog"]'     
     
     # get first one    
     cat cleanedupfile.xhtml | xpath '(//span[@id="yfs_l10_goog"])[1]'      
     
     # get contents    
     cat cleanedupfile.xhtml | xpath '(//span[@id="yfs_l10_goog"])[1]/text()'    > outputfile 
     

5. In general, remote HTML page may not be written to allow a machine easily find the stock price.
6. Downside of script - has to be re-written if HTML format changes.
7. Web scraping issues.