Possible Duplicate:
Good book on Programming C in Unix environment?
Can you suggest me some books for C programming on linux...
Possible Duplicate:
Good book on Programming C in Unix environment?
Can you suggest me some books for C programming on linux...
The standard textbook in many universities is Advanced Programming in the Unix environment.
Search for books on the standard C library, or on POSIX. These will describe the functions available in Linux under C.
Also, here is an online book: http://www.cs.cf.ac.uk/Dave/C/
For pure C, don't look further than this: http://en.wikipedia.org/wiki/The_C_Programming_Language_(book)
Once you've read this one, you'll be set.
K&R - The Bible, everyone should read it at least once.
C Programming - A Modern Approch - A good companion to K&R
Advanced Programming in the Unix Environment - everything you need to know about unix/linux programming
Programming in C by Kernighan and ritchie http://www.goldfish.org/books/The%20C%20Programming%20Language%20-%20K&R/kandr.html
Not especially focused on C programming, but a sum of wisdom for UNIX/Linux programming in C is Eric Raymond's: The ART of UNIX programming.