POSIX.1-2008 defines a standard operating system interface and environment, including a command interpreter (or ‘‘shell’’), and common utility programs to support applications portability at the source code level. It is intended to be used by both application developers and system implementors.POSIX.1-2008 comprises four major components (each in an associated volume):1. General terms, concepts, and interfaces common to all volumes of POSIX.1-2008, including utility conventions and C-language header definitions, are included in the Base Definitions volume of POSIX.1-2008.2. Definitions for system service functions and subroutines, language-specific system s