The System Interfaces volume of POSIX.1-2017 describes the interfaces offered to application programs by POSIX-conformant systems.
Great care has been taken to ensure that this volume of POSIX.1-2017 is fully aligned with the following standards:
Parts of the ISO/IEC 9899:1999 standard (hereinafter referred to as the ISO C standard) are referenced to describe requirements also mandated by this volume of POSIX.1-2017. Some functions and headers included within this volume of POSIX.1-2017 have a version in the ISO C standard; in this case CX markings are added as appropriate to show where the ISO C standard has been extended (see Codes). Any conflict between this volume of POSIX.1-2017 and the ISO C standard is unintentional.
This volume of POSIX.1-2017 also allows, but does not require, mathematics functions to support IEEE Std 754-1985 and IEEE Std 854-1987.
The entries in System Interfaces are based on a common format as follows. The only sections relating to conformance are the SYNOPSIS, DESCRIPTION, RETURN VALUE, and ERRORS sections.
If the implementation can detect errors, "successful completion" means that no error has been detected during execution of the function. If the implementation does detect an error, the error is indicated.
For functions where no errors are defined, "successful completion" means that if the implementation checks for errors, no error has been detected. If the implementation can detect errors, and an error is detected, the indicated return value is returned and errno may be set.
``No errors are defined" means that error values returned by a function or stored into a variable accessed through the symbol errno, if any, depend on the implementation.
This section gives examples of usage, where appropriate. In the event of conflict between an example and a normative part of this volume of POSIX.1-2017, the normative material is to be taken as correct.
This section gives warnings and advice to application developers about the entry. In the event of conflict between warnings and advice and a normative part of this volume of POSIX.1-2017, the normative material is to be taken as correct.
This section contains historical information concerning the contents of this volume of POSIX.1-2017 and why features were included or discarded by the standard developers.
This section provides comments which should be used as a guide to current thinking; there is not necessarily a commitment to adopt these future directions.
This section gives references to related information.
This section shows the derivation of the entry and any significant changes that have been made to it.
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