24. Status of Implementation — RTEMS POSIX API Guide 5.4-rc2 (21st August 2026) documentation

# 24. Status of Implementation

This chapter provides an overview of the status of the implementation of the POSIX API for RTEMS. The POSIX 1003.1b Compliance Guide provides more detailed information regarding the implementation of each of the numerous functions, constants, and macros specified by the POSIX 1003.1b standard.

RTEMS supports many of the process and user/group oriented services in a “single user/single process” manner. This means that although these services may be of limited usefulness or functionality, they are provided and do work in a coherent manner. This is significant when porting existing code from UNIX to RTEMS.

- Implementation

  - The current implementation of `dup()` is insufficient.

  - FIFOs `mkfifo()` are not currently implemented.

  - Asynchronous IO is not implemented.

  - The `flockfile()` family is not implemented

  - getc/putc unlocked family is not implemented

  - Mapped Memory is partially implemented

  - NOTES:

    - For Shared Memory and Mapped Memory services, it is unclear what level of support is appropriate and possible for RTEMS.

- Functional Testing

  - Tests for unimplemented services

- Performance Testing

  - There are no POSIX Performance Tests.

- Documentation

  - Many of the service description pages are not complete in this manual. These need to be completed and information added to the background and operations sections.

  - Example programs (not just tests) would be very nice.