Where can I download POSIX standard ?

1 . Thanks everyone who reads the post .
2 . I want to know where can I download POSIX standard ,because I want to migrate my programe from Linux to ohter platform .

The POSIX standard if you really want it you can get from IEEE for a few hundred dollars. But, now POSIX has been merged into Open Group, and they have a terrifically useful site that you can access for free at:

http://www.opengroup.org/onlinepubs/007904975/toc.htm