I think one way to learn C is to work through a short tutorial with varied examples, such as this one: http://vergil.chemistry.gatech.edu/resources/programming/c-tutorial/toc.html

Anyway, good references are always handy, so here are two links that I found. They describe the C language but also the Unix programming environment: http://www.its.strath.ac.uk/courses/c/ http://publications.gbdirect.co.uk/c_book/

Finally, there is a C and C++ -related site at http://www.cprogramming.com/ -- it has annoying popups and the quality of the content varies, but maybe there is some usable information, particularly in the forums.