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{{Short description|Programming language}}
{{one source |date=April 2024}}
'''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]].<ref name="clist">{{cite web | url=https://www.ibm.com/support/knowledgecenter/SSLTBW_2.1.0/com.ibm.zos.v2r1.ikjb800/toc.htm | title=z/OS TSO/E CLISTs | publisher=IBM | work=z/OS 2.1.0 | date=14 June 2013 | accessdate=12 May 2016}}</ref>

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 language]]s 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{{efn-lr|by running [[Job Control Language|JCL]] that executes a TSO terminal monitor program{{efn-lr|Usually IKJEFT01}} (TMP)}}{{efn-lr|This capability was added by the program product Time Sharing Option/Extensions (TSO/E), which is a standard part of [[OS/390]] and [[z/OS]].}}. CLISTs can display TSO I/O screens and menus by using [[ISPF]] dialog services.

Compare the function of CLIST with that provided by [[REXX]].

== Example programs ==

 PROC 0
 WRITE HELLO WORLD!

Adding If-Then-Else logic:
<syntaxhighlight lang="rexx" line highlight="10">
   /********************************************************************/
   /*  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
</syntaxhighlight>{{efn-lr|Here PROC is treated as a separate routine.}}

== See also ==

* [[Rexx]]

== Footnotes ==

{{notelist-lr}}

== References ==
{{Reflist}}

{{IBM}}
{{Authority control}}

{{DEFAULTSORT:Clist}}
[[Category:IBM mainframe operating systems]]
[[Category:Procedural programming languages]]
[[Category:Command shells]]
[[Category:Text-oriented programming languages]]
[[Category:Scripting languages]]


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