The New KornShell Command And Programming Language by Morris I. Bolsky
For both new users with little computer or shell experience, and for experienced computer users who are familiar with ksh and/or other shells.
This is a Second Edition of the best-selling guide to the KornShell command and programming languge by the original inventors of the language. It provides a specification for the KornShell language, tutorial material for those new to ksh (the program that implements the KornShell language), and a comprehensive reference and for all ksh users.