All about using memory mapped files. Questions on programming should be asked on Stack Overflow SE.
mmap() is a system call that allows for very fast and convenient file I/O. A file that is mapped into memory can be accessed like any memory region.
mmap() can also be used for inter-process communication: a process that creates an anonymous mapping that is not backed by any file can share this region with any child process since memory mappings are preserved across
Note that pipes and socket cannot be mapped.