Can you take food on a plane?

I'm flying with United, whether that matters or not. Anyway I wanted to know if I could bring food on the plane with me. I know that I can bring food that you buy at the airport, but I wanted to take a sandwhich or something from home. Same with drinks. I'm flying to Hawaii from Philadelphia so it's gonna be a long flight and a lot of people tell me the food you buy on the plane sucks.

Thanks
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LOL i got two different answers. If I can bring food how do bring it on?