This extension provides a Tcl interface to the mmap(2) POSIX system call. It provides a Tcl package that allows Tcl scripts to: 1) Memory map files for improved access efficiency; 2) Share memory between related processes; 3) Easily implement cyclic persistent log files. The functionality of 'mmap' is exported from this extension in the form of a new Tcl channel type, named "mmap". A memory mapping is established with the 'mmap' command. Following 'mmap' execution, access to the memory mapped file is done via the standard Tcl commands: puts/gets/seek/flush/close/fconfigure, only that this time these commands operate on memory, rather than on a file.