POSIX.2, the shell and utilities standard, is most important for users, as opposed to application developers. Its principal purpose is to specify the semantics of a shell (based on the Korn Shell) and a collection of utilities that you can use to develop portable shell scripts. A secondary purpose is to promote user portability. This term refers to a standard specification for utilities, such as vi, man, and who, that are not very useful for scripts but are typically used interactively.

POSIX.2 is independent of POSIX.1, and a system can claim conformance to POSIX.2 without claiming conformance to POSIX.1. This is not true of most of the other POSIX standards, which take POSIX.1 as a base. In practice you can expect virtually all UNIX ...

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