Advanced UNIX Programming

Creating Memory Mappings

A memory mapping is established with the help of the mmap(2) function call. The function synopsis for it is as follows:

#include <sys/types.h>
#include <sys/mman.h>

void *mmap(void *addr,size_t len,int prot,int flags,int fd,off_t offset);

The argument addr is normally specified as a null pointer unless a specific mapping address must be used. When addr is null, the mmap(2) call returns the system-selected memory address.

When addr is not null, the argument flags influences the final result: The MAP_FIXED flag indicates that the specified address must be used, or an error indication is to be returned instead. When the flag MAP_FIXED is not present and addr is not null, the mmap(2) function will attempt to accommodate ...