CLIST (Command List) (pronounced "C-List") is a Procedural programming, procedural programming language for Time Sharing Option, TSO in MVS systems. It originated in OS/360 Release 20 and has assumed a secondary role since the availability of Rexx in TSO/E Version 2. The term CLIST is also used for command lists written by users of Tivoli Management Framework#NetView, NetView.
In its basic form, a CLIST program (or "CLIST" for short) can take the form of a simple list of command (computing), commands to be executed in strict sequence (like a DOS batch file (*.bat) file). However, CLIST also features If-Then-Else logic as well as loop constructs.
CLIST is an interpreted language. That is, the computer must translate a CLIST every time the program is executed. CLISTs therefore tend to be slower than programs written in compiled languages such as COBOL, FORTRAN, or PL/I, PL/1. (A program written in a compiled language is translated once to create a "load module" or executable.)
CLIST can read/write MVS files and read/write from/to a TSO terminal. It can read parameters from the caller and also features a function to hold global variables and pass them between CLISTs. A CLIST can also call an MVS application program (written in COBOL or PL/I, for example). CLISTs can be run in background (by running Job Control Language, JCL which executes the TSO control program (IKJEFT01)). TSO I/O screens and menus using ISPF dialog services can be displayed by CLISTs.
Compare the function of CLIST with that provided by REXX.
Example programs
PROC 0
WRITE HELLO WORLD!
Adding If-Then-Else logic:
/********************************************************************/
/* MULTI-LINGUAL "HELLO WORLD" PROGRAM. */
/* */
/* THIS CLIST, STORED AS USERID.TSO.CLIST(TEST), CAN BE INVOKED */
/* FROM THE ISPF COMMAND LINE AS SHOWN IN THE FOLLOWING EXAMPLE: */
/* */
/* COMMAND > TSO TEST SPANISH */
/* */
/********************************************************************/
PROC 1 LANGUAGE
IF &LANGUAGE = SPANISH THEN +
WRITE HOLA, MUNDO
ELSE IF &LANGUAGE = FRENCH THEN +
WRITE BONJOUR, MONDE
ELSE +
WRITE HELLO, WORLD
EXIT
See also
* Rexx
Footnotes
References
IBM mainframe operating systems
Procedural programming languages
Command shells
Text-oriented programming languages
Scripting languages
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