What is a REXX Exec?

The REstructured eXtended eXecutor (REXX) language is a high-level interpretive language that enables you to write programs in a clear and structured way. You can use the REXX language to write programs, called execs, that perform a given task, or tasks, or group of tasks.

REXX execs have many characteristics that are similar to CLISTs. For example, using either the REXX or CLIST language, you can:

Perform numerous tasks, including issuing multiple TSO/E commands and invoking programs written in other languages.
Write structured programs, perform I/O and process arithmetic and character data.
Write interactive applications by issuing commands of the Interactive System Productivity Facility (ISPF) to display full-screen panels.
Provide easy-to-use interfaces to applications written in other languages. Execs can prompt the terminal user for information on the tasks the user requests, set up the environment needed for the application, and then issue the commands needed to invoke the application program.

However, a significant difference between REXX execs and CLISTs is that you can execute CLISTs only in a TSO/E environment. REXX execs do not require a TSO/E environment, and can execute in any MVS™ address space.

TSO/E REXX is the implementation of the Systems Application Architecture® (SAA) Procedures Language on the MVS system. By using the instructions and functions defined for the SAA Procedures Language, you can write REXX execs that will run in any of the supported SAA environments, such as VM/SP (CMS). SAA Common Programming Interface Procedures Language Level 2 Reference describes the instructions and functions the SAA Procedures Language offers.

You can also write APPC/MVS transaction programs in the REXX language. The host command environments, CPICOMM, LU62, and APPCMVS, allow you to invoke the SAA common programming interface (CPI) Communications calls and APPC/MVS calls, which are based on the SNA LU 6.2 architecture, respectively. The CPICOMM host command environment allows transaction programs written in the REXX language to be ported across Systems Application Architecture (SAA) environments. The LU62 host command environment allows you to use specific features of MVS in conversations with transaction programs on other systems.

Note: APPC/MVS calls that are based on the SNA LU 6.2 architecture are referred to as APPC/MVS calls throughout the document.

For information about writing APPC/MVS transaction programs, see z/OS MVS Programming: Writing Transaction Programs for APPC/MVS. For information about writing and executing REXX execs, see z/OS TSO/E REXX User's Guide and z/OS TSO/E REXX Reference.

Another advantage to using REXX is that TSO/E provides support for a REXX compiler and run-time library, such as the IBM® Compiler and Library for REXX/370. Using a compiler provides significant benefit for programmers during program development and for users when a program is run.