Parsing all posts of a wordpress blog by tag. RSS or plugin?

I'm complete new to wordpress but I have to parse a complete blog into a another website. This should happen on a hourly base.

My question now is what should I use for this? The posts I need to parse are marked by a specific tag.

Can I use the RSS-Feed for this or is it limited and will on开发者_StackOverflow社区ly return me like the last 20 posts? Or is there any plugin out there which can return me all posts of a tag or category in an XML or JSON?

Thanks guys!

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You can use RSS for this. You can set the feed limit on RSS in your Wordpress Blog Settings. The feed URL would be:

http://example.com/tag/tagname/feed

Check this page on the codex.