Shellcheck specifically supports POSIX, BASH, and Korn. Each of these has an important role in scripting. Development of the formal ksh93 was halted and rewoun

Shellcheck specifically supports POSIX, BASH, and Korn. Each of these has an important role in scripting. Development of the formal ksh93 was halted and rewound by AT&T after David Korn's departure, precisely because the user community remains extremely intolerant to changes in functionality and/or performance. Korn shell development that requires a "living" shell should likely target both ksh93 and the MirBSD Korn shell (the default shell in Android). BASH has diverged from the Korn shell in a few (annoying) ways, but remains core to the GNU movement and rightly commands its own audience. It is much larger than the MirBSD Korn shell. POSIX shells were developed to target truly minimal systems - POSIX rejected Korn likely due to (Microsoft) XENIX on 80286 systems that only allowed 64K text segments. Korn was able to run on such machines, but the code was not maintainable. Clean C source for a POSIX shell is far easier to achieve for XENIX, and remains a better fit for embedded environments. This is likely why POSIX is not Korn.