I want to get latest news content for my web portal. I plan to put news content more than RSS headlines.. I'm thinking to get automatic news content by using cURL.. My important concern is that if I get the news automatically by using cURL or simply copy/paste, and I provide link the original source clearly.. will it be legal? Please reply?
With a few exceptions, as long as you don't claim the content to be yours and link to the source, yes.
It depends on the source and their terms, but generally no, quoting the source does not give you permission and reprinting the story in its entirety without express permission is copyright infringement. Many do not let you use their rss feed if your site is commercial (i.e. runs ads or take in any type of revenue). They "own" the rights and get to determine who, in any, gets to reprint it.
Fair Use is a very gray area. It does say that the amount of the original work copied does have a bearing if its fair use or not - but it does not say how much that amount is, or does it define original work as one web page, or the entire site. Its very much open to interpretation.
Copying an article on a commercial site without express permission isn't in a "gray area" - it's infringement. Even google has been sued (and lost) and also pays for using some of news on its site. There have been lawsuits for the use of just the news headline - and that could be considered a "gray area" - but in reality, no small publisher wants to claim "Fair use" and then spend six figures in legal fees proving you were right. Get permission or take the risk of being sued.