POSIX shell compatibility

The Interix Korn shell follows traditional Korn shell behavior, which is almost identical to POSIX behavior. If you need strict POSIX conformance, which some work environments require, see the differences between the Korn shell and POSIX in ksh(1) under the heading "POSIX Mode."

To get full POSIX.2 conformance from the Korn shell, you must run it in POSIX mode. To run the Korn shell in POSIX mode, either invoke the Korn shell with the -o posix option, run the command set -o posix from within the shell, or set the POSIXLY_CORRECT shell parameter.

You cannot get POSIX conformance from the C shell. The C shell has no POSIX-mode command options like the Korn shell.