IEEE 1003.1-2013 pdf download Standard for Information Technology— Portable Operating System Interface (POSIX®) Base Specifications, Issue 7
For an implementation that conforms to POSIX.1-2008, describes a feature or behavior thatis mandatory. An application can rely on the existence of the feature or behavior.
For an application or user, describes a behavior that is mandatory.should
For an implementation that conforms to POSIX.1-2008, describes a feature or behavior thatis recommended but not mandatory. An application should not rely on the existence of thefeature or behavior. An application that relies on such a feature or behavior cannot beassured to be portable across conforming implementations.
For an application, describes a feature or behavior that is recommended programmingpractice for optimum portability.
undefined
Describes the nature of a value or behavior not defined by POSIX1-2008 which results fromuse of an invalid program construct or invalid data input.
The value or behavior may vary among implementations that conform to POSIX.1-2008. Anapplication should not rely on the existence or validity of the value or behavior. Anapplication that relies on any particular value or behavior cannot be assured to be portableacross conforming implementations.
unspecifiedDescribes the nature of a value or behavior not specified by POSIX.1-2008 which resultsfrom use of a valid program construct or valid data input.
The value or behavior may vary among implementations that conform to POSIX.1-2008. Anapplication should not rely on the existence or validity of the value or behavior. Anapplication that relies on any particular value or behavior cannot be assured to be portableacross conforming implementations.
Definitions and Concepts
Definitions and concepts are defined in Chapter 3 (on page 33) and Chapter 4 (on page 107)
Portability
Some of the utilities in the Shell and Utilities volume of POSIX.1-2008 and functions in theSystem Interfaces volume of POSIX.1-2008 describe functionality that might not be fully portableto systems meeting the requirements for POSIX conformance (see Chapter 2, on page 15).Where optional, enhanced, or reduced functionality is specified, the text is shaded and a code inthe margin identifies the nature of the option, extension, or warning (see Section 1.7.1, on page7). For maximum portability, an application should avoid such functionality.
Unless the primary task of a utility is to produce textual material on its standard outputapplication developers should not rely on the format or content of any such material that may beproduced. Where the primary task is to provide such material, but the output format isincompletely specified, the description is marked with the OF margin code and shadingApplication developers are warned not to expect that the output of such an interface on one