Introduction to REXX

REXX is a high level programming language designed to perform in two important roles as an agent for computer users and system administrators:

• As an integrator of system commands and other programs into composites intended to handle specific higher level functions
• As an embeded macro language for customization or augmentation of system commands such as the system editor

REXX has been available for nearly a decade from IBM and other vendors for operating systems ranging from PCDOS, OS/2, and the Amiga on the desk top thru UNIX(tm) to IBM mainframe VM and MVS systems in the glass house. It biggest defect has probably been its ease of application to production problems where a traditional compiled high-level might have been more appropriate.

The purpose of these pages is to introduce S/REXX, Benaroya's implementation of REXX for UNIX environments with an overview of those features which differentiate S/REXX from other implementations. There is an extensive set of REXX references maintained by Mike Cowlishaw (the creator of REXX) for more information about the REXX language and its application.

S/REXX with a Graphical Debugger from Benaroya

S/REXX is a UNIX and Microsoft Windows implementation of REXX which supports all features of the second edition of The Rexx Language by Mike Cowlishaw except the numeric digit specification which is limited to 15 digits. It is is available for many UNIX platforms including Linux as well as current versions of Microsoft Windows.

S/REXX Compatibility

S/REXX is designed to be compabile with other implementations of IBM SAA REXX. In particular:

• Thre are no implementation size or shape limits which are likely to impact your REXX programs. For example, if your system has enough memory, there are no limits on:
  • Procedure size
  • Expression complexity
  • Parenthesis nesting
  • Number of variables or content
  • Recursive function depth
  • Argument number and size
• When a S/REXX program file begins with the standard UNIX magic number record:
  #! /home/xed/srexx
  it becomes a system command which can be executed by simply typing its name.
• Full support by SEDIT permits writing of edit macros in REXX, many of which will be directly compatible with REXX macros written for IBM's XEDIT (IBM/VM) and Mansfield Software's KEDIT (PCDOS and OS/2).
• An EXECIO command is included to facilitate porting of REXX programs from IBM's VM/CMS to UNIX. EXECIO reads and writes files and prints on native UNIX printers. All options of the CMS EXECIO are supported.

Leveraging the UNIX Environment

S/REXX includes a number of extensions designed to meet the expectations of UNIX users experienced with the idioms of classical UNIX scripting languages.

• Dynamic loading of external procedures
• Traditional use of backquote (`) to retrieve the result of executing UNIX commands
• A new DO instruction iterator to control loop interation based on the number of words in an expression
• Square bracket ([]) indexing of character strings
• Many new built-in functions which provide access to UNIX facilities
• The REXX Graphical Debugger extends the clasical REXX support for Trace with a GUI providing interactive source level debugging of REXX programs.
• Optional use of the dollar sign ($) in REXX programs to refer to UNIX system environment variables.
• Braces (curly brackets - {}) may be used as they are in C in lieu of REXX DO/END to enclose blocks of code.

Traditional REXX Environmental Integration

S/REXX provides the traditional facilities for integration of REXX programs into your computing environment. As discussed previously, REXX is a single language designed for integration into other programs as a MACRO processor and for integrating other programs via command scripts. S/REXX performs both roles:

• S/REXX is fully integrated into Benaroya's SEDIT editor (An XEDIT [and ISPF/PDF] like editor for UNIX). You can write SEDIT macros which build MOTIF or OpenLook dialog boxes with input fields, toggles, and buttons in addition to the more traditional XEDIT use of REXX to automate complex editing tasks.
• Within SEDIT, S/REXX can be used to manage ISPF-like project control table files.
• User programs can include S/REXX as a MACRO processor exposing subcommands to the REXX MACRO. The S/REXX API supports use of the REXX Address instruction to trigger user specified subroutines included in the C program with which S/REXX has been integrated.
• User written built-in functions can be added to S/REXX.

Select an Overview of Benaroya Products including SEDIT.