From a-close-date on, Twitter won't let you into their API without having an OAuth key. But as a workaround you can use Search API. It is RESTful, so you can use curl to retrieve search results in JSON format. For example, if you want to retrieve @java's tweets, and save it to file ~/.tweets, this line of code can be used:
curl http://search.twitter.com/search.json?q=from:java&page=1&rpp=10&callback=? >> $HOME/.tweets
And you can parse the file, using any JSON parser.
The
rpp parameter is number af tweets to be retrieved.
callback is javascript function to be executed on the resulting JSON. In case you're not using JavaScript with the api, you can leave it ?, but don't remove it. I will cause an error. More guidance on Search api can be found on
https://dev.twitter.com/docs/api/1/get/search
There are tools to parse JSON from command line interface. Although I've never used one, I'll put some links to some resources, to help you find out the best suited tool:
http://stackoverflow.com/questions/3858671/unix-command-line-json-parser
http://www.conigliaro.org/2011/01/24/jazor-a-simple-command-line-json-parsing-tool/
http://stackoverflow.com/questions/1955505/parsing-json-with-sed-and-awk
http://kmkeen.com/jshon/
And as a little note, it is quicker to use some Python or Ruby (or others).