IBM SC34-5764-01 Manuale utente

CICS Transaction Server for VSE/ESA

REXX Guide

SC34-5764-01



CICS Transaction Server for VSE/ESA

REXX Guide

SC34-5764-01



Note!

Before using this information and the product it supports, be sure to read the general information under “Notices” on page

443.

Second edition (September 2000)

This edition applies to Release 1 of CICS Transaction Server for VSE/ESA, program number 5648-054, and to all

subsequent versions, releases, and modifications until otherwise indicated in new editions. Make sure you are using

the correct edition for the level of the product.

US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract

with IBM Corp.

Contents

Preface ....................................xix

What this book is about ..............................xix

Who this book is for ...............................xix

What you need to know to understand this book .....................xix

Prerequisites .................................xix

Part 1. User's Guide..............................1

Chapter 1. Introduction ..............................3

What is REXX?..................................3

Features of REXX.................................3

Ease of use ..................................3

Free format ..................................3

Convenient built-in functions ............................3

Debugging capabilities ..............................3

Interpreted language ...............................3

Extensive parsing capabilities ...........................3

Components of REXX ...............................4

Chapter 2. Writing and Running a REXX Program ....................5

What you need to run a REXX Program? ........................5

What is a REXX Program? .............................5

Syntax of REXX Instructions .............................6

The Format of REXX Instructions ..........................6

The Letter Case of REXX Instructions ........................6

Types of REXX Clauses .............................9

Programs Using Double-Byte Character Set Names ....................10

Typing in a Program ...............................11

Running a Program ...............................11

Interpreting Error Messages ............................12

How to Prevent Translation to Uppercase .......................13

Characters within a program ...........................13

Characters Input to a program...........................14

Exercises - Running and Modifying the Example Programs ................14

Passing Information to a program ..........................14

Getting Information from the Program Stack or Terminal Input Device ............14

Specifying Values When Calling a program ......................15

Preventing Translation of Input to Uppercase .....................16

Passing Arguments ...............................17

Chapter 3. Using Variables and Expressions .....................19

Program Variables ................................19

Using Variables .................................19

Variable Names ................................19

Variable Values ................................20

Using Expressions ................................21

Arithmetic Operators ..............................21

Comparison Operators .............................23

Logical (Boolean) Operators ...........................25

Concatenation Operators.............................27

Priority of Operators ..............................28

Tracing Expressions with the TRACE Instruction .....................29

Tracing Operations ...............................29

Tracing Results ................................30

Exercises - Using the TRACE Instruction .......................30

Chapter 4. Controlling the Flow within a program ...................33

Conditional, Looping, and Interrupt Instructions .....................33

Using Conditional Instructions ............................33

IF...THEN...ELSE Instructions ...........................33

Nested IF...THEN...ELSE Instructions ........................34

SELECT WHEN...OTHERWISE...END Instruction....................37

Using Looping Instructions .............................39

Repetitive Loops ................................39

Conditional Loops ...............................42

Combining Types of Loops ............................46

Nested DO Loops ...............................46

Using Interrupt Instructions .............................48

EXIT Instruction ................................48

CALL and RETURN Instructions ..........................49

SIGNAL Instruction ...............................50

Chapter 5. Using Functions ............................51

What is a Function? ...............................51

Example of a Function .............................51

Built-In Functions ................................52

Arithmetic Functions ..............................53

Comparison Functions..............................53

Conversion Functions ..............................53

Formatting Functions ..............................54

String Manipulating Functions ...........................54

Miscellaneous Functions .............................55

Testing Input with Built-In Functions.........................55

Chapter 6. Writing Subroutines and Functions.....................57

What are Subroutines and Functions? .........................57

When to Write Subroutines Rather Than Functions ...................57

Writing Subroutines and Functions ..........................58

When to Use Internal Versus External Subroutines or Functions ..............60

Passing Information ..............................60

Receiving Information from a Subroutine or Function ..................66

Subroutines and Functions—Similarities and Differences ..................70

Chapter 7. Manipulating Data ...........................71

Using Compound Variables and Stems ........................71

What Is a Compound Variable? ..........................71

Using Stems .................................72

Parsing Data ..................................73

Parsing Instructions...............................73

More about Parsing into Words ..........................75

Parsing with Patterns ..............................75

Parsing Multiple Strings as Arguments ........................78

Chapter 8. Using Commands from a program .....................81

Types of Commands ...............................81

Using Quotations Marks in Commands .......................81

Using Variables in Commands ...........................81

Calling Another REXX Program as a Command ....................82

Issuing Commands from a program ..........................82

iv CICS TS for VSE/ESA: REXX Guide

What is a Host Command Environment? .......................82

How Is a Command Passed to the Host Environment?..................83

Changing the Host Command Environment ......................83

Chapter 9. Diagnosing Problems within a program ...................85

Debugging Programs ...............................85

Tracing Commands with the TRACE Instruction ....................85

Using REXX Special Variables RC and SIGL .....................85

Tracing with the Interactive Debug Facility ......................86

Saving Interactive TRACE Output .........................87

Chapter 10. Programming Style and Techniques ....................89

Consider the Data ................................89

Test Yourself... ................................89

Happy Hour ..................................90

Designing a Program ...............................92

Methods for Designing Loops ...........................93

The Conclusion ................................93

What Do We Have So Far?............................94

Stepwise Refinement: An Example .........................94

Reconsider the Data ..............................95

Correcting Your Program ..............................95

Modifying Your Program .............................95

Tracing Your Program ..............................95

Coding Style ..................................96

Part 2. Reference ..............................101

Chapter 11. Introduction .............................103

Who Should Read This Reference..........................103

How to Use This Reference ............................103

Overview of Product Features ...........................104

SAA Level 2 REXX Language Support Under REXX/CICS ................104

Support for the Interpretive Execution of REXX Execs .................104

CICS-Based Text Editor for REXX Execs and Data ..................104

VSAM-Based File System for REXX Execs and Data ..................104

VSE Librarian Sublibraries............................104

Dynamic Support for EXEC CICS Commands ....................105

REXX Interface to CEDA and CEMT Transaction Programs ...............105

High-level Client/Server Support .........................105

Support for Commands Written in REXX ......................105

Command Definition of REXX Commands ......................105

Support for System and User Profile Execs .....................105

Shared Execs in Virtual Storage .........................105

SQL Interface ................................106

How to Read the Syntax Diagrams .........................106

Chapter 12. REXX General Concepts ........................109

Structure and General Syntax ...........................109

Characters .................................110

Comments .................................110

Tokens ...................................111

Implied Semicolons ..............................114

Continuations ................................115

Expressions and Operators ............................115

Expressions .................................115

Contents v

Operators ..................................115

Parentheses and Operator Precedence .......................118

Clauses and Instructions .............................120

Null Clauses .................................120

Labels ...................................120

Instructions .................................120

Assignments .................................120

Keyword Instructions ..............................120

Commands .................................120

Assignments and Symbols.............................121

Constant Symbols ...............................121

Simple Symbols ...............................122

Compound Symbols ..............................122

Stems ...................................123

Commands to External Environments ........................124

Environment .................................124

Commands .................................124

Basic Structure of REXX Running Under CICS .....................125

REXX Exec Invocation .............................125

Where Execs Execute .............................126

Locating and Loading Execs ...........................126

Editing Execs ................................126

REXX File System ..............................127

Control of Exec Execution Search Order ......................127

Adding User Written Commands .........................127

Support of Standard REXX Features .........................127

SAY and TRACE Statements...........................127

PULL and PARSE EXTERNAL Statements......................127

REXX Stack Support..............................127

REXX Function Support ............................127

REXX Command Environment Support ........................128

Adding REXX Host Command Environments .....................128

Support of Standard CICS Features/Facilities......................128

CICS Mapped I/O Support............................128

Dataset I/O Services ..............................128

Interfaces to CICS Facilities and Services ......................128

Issuing User Applications From Execs .......................128

REXX Interfaces to CICS Storage Queues......................128

Pseudo-conversational Transaction Support .....................129

Interfaces to Other Programming Languages ......................129

DBCS Support ................................129

Miscellaneous Features.............................129

Chapter 13. Keyword Instructions .........................131

ADDRESS ..................................132

ARG.....................................134

CALL ....................................135

DO.....................................138

DROP ....................................142

EXIT.....................................143

IF......................................144

INTERPRET ..................................145

ITERATE ...................................147

LEAVE....................................148

NOP.....................................149

NUMERIC...................................150

vi CICS TS for VSE/ESA: REXX Guide

OPTIONS ...................................151

PARSE ....................................152

PROCEDURE .................................155

PULL ....................................158

PUSH ....................................159

QUEUE ...................................160

RETURN ...................................161

SAY.....................................162

SELECT ...................................163

SIGNAL ...................................164

TRACE....................................166

UPPER....................................170

Chapter 14. Functions ..............................171

Syntax ....................................171

Functions and Subroutines ............................171

Search Order ................................172

Errors During Execution ............................173

Built-in Functions ................................174

ABBREV (Abbreviation).............................175

ABS (Absolute Value) .............................175

ADDRESS .................................175

ARG (Argument) ...............................175

BITAND (Bit by Bit AND) ............................176

BITOR (Bit by Bit OR) .............................177

BITXOR (Bit by Bit Exclusive OR) .........................177

B2X (Binary to Hexadecimal)...........................177

CENTER/CENTRE ..............................178

COMPARE .................................178

CONDITION .................................178

COPIES ..................................179

C2D (Character to Decimal) ...........................179

C2X (Character to Hexadecimal) .........................180

DATATYPE .................................180

DATE...................................181

DBCS (Double-Byte Character Set Functions) ....................183

DELSTR (Delete String) ............................183

DELWORD (Delete Word) ............................183

DIGITS ...................................183

D2C (Decimal to Character) ...........................183

D2X (Decimal to Hexadecimal) ..........................184

ERRORTEXT ................................184

EXTERNALS ................................185

FIND ...................................185

FORM ...................................185

FORMAT ..................................185

FUZZ ...................................186

INDEX ...................................187

INSERT ..................................187

JUSTIFY ..................................187

LASTPOS (Last Position) ............................188

LEFT ...................................188

LENGTH ..................................188

LINESIZE ..................................188

MAX (Maximum) ...............................188

MIN (Minimum) ................................189

Contents vii

OVERLAY..................................189

POS (Position) ................................189

QUEUED ..................................190

RANDOM ..................................190

REVERSE .................................191

RIGHT ...................................191

SIGN ...................................191

SOURCELINE ................................191

SPACE...................................191

STORAGE .................................192

STRIP ...................................192

SUBSTR (Substring) ..............................192

SUBWORD .................................193

SYMBOL ..................................193

TIME ...................................193

TRACE...................................195

TRANSLATE.................................195

TRUNC (Truncate) ..............................195

USERID ..................................196

VALUE ...................................196

VERIFY ..................................197

WORD ...................................197

WORDINDEX ................................198

WORDLENGTH ...............................198

WORDPOS (Word Position) ...........................198

WORDS ..................................198

XRANGE (Hexadecimal Range)..........................198

X2B (Hexadecimal to Binary)...........................199

X2C (Hexadecimal to Character) .........................199

X2D (Hexadecimal to Decimal) ..........................199

External Functions Provided in REXX/CICS ......................200

STORAGE .................................200

SYSSBA ..................................201

Chapter 15. Parsing...............................203

General Description ...............................203

Simple Templates for Parsing into Words ......................203

Templates Containing String Patterns........................205

Templates Containing Positional (Numeric) Patterns ..................206

Parsing with Variable Patterns ..........................209

Using UPPER ................................209

Parsing Instructions Summary ..........................210

Parsing Instructions Examples ..........................210

Advanced Topics in Parsing ............................211

Parsing Multiple Strings .............................211

Combining String and Positional Patterns: A Special Case ................212

Parsing with DBCS Characters ..........................213

Details of Steps in Parsing ...........................213

Chapter 16. Numbers and Arithmetic ........................217

Introduction ..................................217

Definition ...................................218

Numbers ..................................218

Precision ..................................218

Arithmetic Operators ..............................218

Arithmetic Operation Rules—Basic Operators.....................219

viii CICS TS for VSE/ESA: REXX Guide

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