Shared Memory: Solaris vs. Linux

[Chris Richard Adams]

I am reading some material on Shared Memory - it states, "In the Solaris
2.x operating system, the most efficient way to implement shared memory
applications is to rely on the mmap() function and on the system's
native virtual memory facility. Solaris 2.x also supports System V
shared memory, which is another way to let multiple processes attach a
segment of physical memory to their virtual address spaces. When write
access is allowed for more than one process, an outside protocol or
mechanism such as a semaphore can be used to prevent inconsistencies and
collisions. "

Question: I assume Linux has the same support - a version of mmap()?
Does Linux also support System V shared memory?


I also read: POSIX shared memory is actually a variation of mapped
memory. The major differences are to use shm_open() to open the shared
memory object (instead of calling open()) and use shm_unlink() to close
and delete the object (instead of calling close() which does not remove
the object). The options in shm_open() are substantially fewer than the
number of options provided in open(). 

Question: Can someone explain..what is POSIX? Also is there the same
support on Linux?

Thanks!