Copies input.txt into output.txt using mmap
This program copies an arbitrary sized file into stdout and output.txt.
This uses mmap() function to create a new mapping in the "memory mapping region" of the calling process' virtual space.
The fstat system call retrieves information on a file based on its file descriptor, and stores it into a data-structure. In the case of this small script, the struct is named "mystat"
Like any instance of a system call, one must always check the return case.
To run: -have an input.txt file with any sort of text -compile: gcc mmaptest.c -direct stdout to output.txt -run: ./a.out input.txt output.txt