Chapter 1: The POSIX Shell and Command-Line Utilities
Chris F. A. Johnson, Jayant Varma · Apress eBooks · 2015
The POSIX shell is a descendant of the KornShell, which is a descendant of the Bourne shell. The basic syntax has remained the same, and Bourne shell scripts will usually run successfully in a POSIX shell. Not all of the KornShell features are included in POSIX (there are no arrays, for example), but the most important ones are. Those, which would be important to many developers, are string manipulation and arithmetic. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.