The Public Domain Korn Shell, or pdksh, is a free, public domain version of the Korn shell. It’s compatible with most any version of Unix such as SCO, BSD, Solaris, HP-UX, but is mostly used on Linux-based systems. It has most of the features of ksh88, as well as some ksh93 and additional features that are not in either. Here are a few of the features not in pdksh:
Exported aliases and functions
Signals/traps not cleared during functions
Trap DEBUG, local ERR and EXIT traps in functions
Float and structure datatypes
Compound and nameref variables
Search, replace, and substring operators
The source distribution contains more details on features not found in pdksh as well as current ...