Rexx Programmer's Reference

Chapter 5. Input and Output

Overview

Input/output, or I/O, is how a program interacts with its environment. Input may come from what a user types in, an input file, or another program. Program output might be written to the display, to an output file, or to a communication mechanism such as a pipe. These are just a few of the possibilities.

Rexx provides a simple-to-use, high-level I/O interface. At the same time, Rexx aims for standardization and portability across platforms. Unfortunately, this latter goal is difficult to achieve—I/O is inherently platform-dependent, because it relies upon the file systems and drivers the operating system provides for data management. These vary by operating system.

This chapter describes the Rexx I/O model at a conceptual level. Then it explores examples and how to code I/O. The last part of the chapter discusses some of the problems that any programming language confronts when trying to standardize I/O across platforms, some of the trade-offs involved, and how this tension has been resolved in Rexx and its many implementations.

Rexx provides an I/O model that is easy to use and as portable as possible. Section II explores the I/O extensions that many versions of Rexx offer for more sophisticated (but less portable) I/O. Chapter 15 illustrates database I/O and how to interface scripts to popular database management systems such as SQL Server, Oracle, DB2, and MySQL.

The Conceptual I/O Model

Rexx views both input and output as streams—a sequence of ...