What Is POSIX Shell?

What is POSIX Shell under UNIX / Linux operating systems?

POSIX is an acronym for “Portable Operating System Interface”. POSIX shell is based on the standard defined in Portable Operating System Interface (POSIX) – IEEE P1003.2. It is a set of standards codified by the IEEE and issued by ANSI and ISO. POSIX makes task of cross-platform software development easy. There are various POSIX versions, but the most important are POSIX.1 and POSIX.2, which define system calls and command-line interface.

Tutorial details
Difficulty level Easy
Root privileges No
Requirements None
Est. reading time 1 minutes

What is POSIX?

POSIX defines the application programming interface (API), along with Unix command line shells and utility interfaces. This ensure software compatibility with flavors of Unix and other operating systems. The POSIX shell is implemented for many UNIX like operating systems. The POSIX standard is designed to be used by both application programmers and system administrators. Most of the POSIX Shell features are similar to the Korn Shell. The following perating systems are 100% compliant with various POSIX standards:

  • A/UX
  • AIX
  • HP-UX
  • INTEGRITY
  • IRIX
  • OS X
  • QNX
  • Solaris
  • Tru64
  • UnixWare

Please note that GNU/Linux (most distributions) and *BSD operating systems are not officially certified as POSIX compatible, but comply in large part. For more information see the following ulrs:

  1. A joint technical committee of ISO and IEC – POSIX page
  2. POSIX page at opengroup.org

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