The C Programming Language,
by Brian Kernighan and Dennis Ritchie,
Prentice Hall, 1988 (2nd edition).
A Book on C,
by Al Kelley and Ira Pohl,
Addison-Wesley, 1997 (4th edition).
On to C,
by Charlie McDowell,
Addison-Wesley, 2001.
Just Enough Unix,
by Paul K. Andersen,
McGraw Hill, 2003 (4th edition).
Unix Power Tools,
by Jerry D. Peek, Tim O'Reilly, Mike Loukides,
O'Reilly & Associates, 1997, (2nd edition).