CLISTs

CLISTs, short for command lists, are a scripting language historically used in IBM mainframe environments to automate tasks within the TSO/ISPF and MVS/ z/OS environments. A CLIST is a plain-text script that issues host commands, coordinates dataset handling, and performs basic data processing. They were designed to simplify repetitive work and reduce manual command entry by combining sequences of TSO commands into reusable procedures.

Originating in the 1970s, CLISTs gained widespread use through the 1980s as a lightweight automation tool. They run in the CLIST processor provided by the TSO environment and can interact with the external world via commands issued through an ADDRESS instruction targeted at TSO, ISPF, SDSF, or other subsystems. CLISTs support simple control structures, variables, and subroutine-like organization, enabling conditional logic, looping, and modular scripts. Variables commonly carry values between lines and can be passed to CLISTs at invocation time.

Typical CLIST tasks include preparing datasets for processing, allocating and freeing datasets, invoking other programs or CLISTs, formatting and printing output, and performing routine system checks. Because CLISTs operate by issuing native TSO commands, they are tightly coupled to the environment in which they run, and their portability is limited to similar TSO/ISPF contexts.

In modern practice, CLISTs have largely been superseded by REXX scripts, which offer more powerful language constructs and better portability. Nevertheless, CLISTs remain part of many legacy systems, where they continue to support automation of long-standing operational tasks. Related languages and topics include REXX, ISPF CLISTs, and mainframe automation.