This item was added on: 2003/03/07
Most UNIX-like operating systems aim at POSIX-conformance. POSIX, the Portable Operating System Standard, defines various documents about terminal, shell and standard tool behaviour, as well as a system API (Application Programming Interface) that covers file, directory and terminal handling, process creation, process environments and interprocess communication, sockets, program execution, signals, threads, timers, the system password database and realtime extensions.
The API builds on ANSI C, X/Open's UNIX95/UNIX98 standards build on POSIX.
Of course, all systems offer additional, nonportable, extensions - use them sparingly if you can't get the job done without.