The Windows NT POSIX subsystem is designed to run POSIX applications and meets the requirements of POSIX.1.
POSIX (Portable Operating System Interface for Computing Environments) is a set of standards being drafted by the Institute of Electrical and Electronic Engineers (IEEE). It defines various aspects of an operating system, including topics such as programming interface, security, networking, and graphical interface. So far, only one of these standards, POSIX.1 (also called IEEE Standard 1003.1-1990), has made the transition from draft to final form and gained a base of customer acceptance.
POSIX.1 defines C-language API calls between applications and the operating system. It is an API based on ideas drawn from the UNIX file system and process model. Because POSIX.1 addresses only API-level issues, most applications written to the POSIX.1 API must rely on non-POSIX operating system extensions to provide services such as security and networking.
POSIX applications need certain file-system functionality, such as support for case-sensitive filenames and support for files with multiple names (or hard links). The new file system, NTFS, supports these POSIX requirements. Any POSIX application requiring access to file system resources must have access to an NTFS partition. POSIX applications that do not access file system resources can run on any supported file system.
For more information about using POSIX applications on Windows NT, see Chapter 29, "POSIX Compatibility."