Family of standards by IEEE, enabling compatibility of software between different operating systems.
Porting software between operating systems used to be a lot of work until POSIX was born. POSIX is a standardization of a UNIX like operating systems, but not limited to UNIX.
POSIX adds more functions on top of ANSI C standars, around:
- File operations
- Processes, threads, shared memory and scheduling parameters
- Networking
- Memory management
- Regular Expressions
General rules over how to write a software.
Rules for formatting strings that we use in files, STDOUT, STDIN, STDERR.
Reserved Environment Variables in standard utilities
[C Locale is POSIX locale][https://en.cppreference.com/w/c/locale]
- Character Sets
- Regular Expressions
- Directory Structure
- Utilities such as CLIs
Most operating except Windows, are partly POSIX compliant. There are several OSes that are fully compliant including new versions of MacOS.
https://developer.huaweicloud.com/ict/en/site-euleros/euleros
https://www.opengroup.org/openbrand/register/brand3555.htm
Earlier versions of Bash was POSIX compliant but now it became partially compliant.