C Programming

The C programming language is at the heart of GNU/Linux - it is the programming language most of the Linux Kernel and GNU tools is written in.

There are many outstanding books and online resources where you can learn C and as such this site will not try and duplicate these efforts.

What I will try to do here is try to complement other sources, trying to explain parts which are easily overlooked by beginners or are difficult to remember. I hope that you like what is on offer and if you do, please bookmark these pages and spread the word.

The C Language

Standard Library

The Standard Headers

stdarg.h - variadic functions

Macros:
va_start             enables access to variadic function arguments (function macro)
va_arg               accesses the next variadic function argument(function macro)
va_copy              (C99) makes a copy of the variadic function arguments (function macro)
va_end               ends traversal of the variadic function arguments (function macro)

Type:
va_list              holds the information needed by va_start, va_arg, va_end, and va_copy (typedef)

#include <stdio.h>
#include <stdarg.h>

void simple_printf(const char* fmt, ...)
{
    va_list args;
    va_start(args, fmt);

    while (*fmt != '0') {
        if (*fmt == 'd') {
            int i = va_arg(args, int);
            printf("%dn", i);
        } else if (*fmt == 'c') {
            // A 'char' variable will be promoted to 'int'
            // A character literal in C is already 'int' by itself
            int c = va_arg(args, int);
            printf("%cn", c);
        } else if (*fmt == 'f') {
            double d = va_arg(args, double);
            printf("%fn", d);
        }
        ++fmt;
    }

    va_end(args);
    }

Functions at a Glance

Basic Tools
- Compiling with GCC
- Using make to Build C Programs
- Debugging C Programs with GDB
- Using an IDE with C
- Unicode in C
Problem Solving

C Programming

Videos

Books

Other External Links