rexx programing

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Rexx ProgrammingRexx Programming 1 1

REXX Programming REXX Programming


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INTRODUCTIONINTRODUCTION

What is REXX ?

REstructured eXtended eXecuter

Simple Programming Language

Can run Inside / Outside of a

TSO/E Address Space


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Fe atur e s of REXXFe atur e s of REXX Ease to Use

Free Format

Convenient Built - in Functions

Debugging Capabilities

Interpreted Language

Extensive Parsing capabilities


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Compon e nts of REXXCompon e nts of REXX

Instructions

Built in Functions TSO/E External Functions Data Stack Functions


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W riting a REXX Exec W riting a REXX Exec


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What is a REXX Ex ec ?What is a REXX Ex ec ?

Contains REXX language Instructions andCommands

Starts with the comment line with the wordREXX

Exampl e :/* REXX */Say This is my First REXX program


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Sy ntax of REXX Instru c tionsSy ntax of REXX Instru c tions

Lit e ral S tring Using Single quotes

Using double quotes

F ormat of a REXX Instru c tion Can begin in any column on any line Comma (,) used as a continuation

character Semi colon (;) indicates the end of an

Instruction


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Typ e s of REXX Instru c tionsTyp e s of REXX Instru c tions

Ke yw ordAssignm e nt

Lab e lNullCommand


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Op e ratorsOp e rators

Comparison Op e rators

Logi c al (Bool e an) Op e rators

Con c at e nation Op e rators


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Controlling th e F lo w Within an Ex ecControlling th e F lo w Within an Ex ec

Conditional Instru c tion

IF / THEN / ELSE Instruction SELECT / WHEN / OTHERWISE / END Instruction

Looping Instru c tion

Repetitive LoopsLEAVEITERATE

Conditional Loops

Int e rrupt Instru c tion

EXIT SIGNAL CALL / RETURN


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S ubroutin e s & F un c tionsS ubroutin e s & F un c tions

Made up of sequence of instruction that can receive data , processthe data and return a value (Optional for Subroutine & Mandatory for Functions)

Passing the Information

RESULT

PROCEDURE Instruction

PROCEDURE EXPOSE Instruction


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BuiltBuilt--In F un c tionsIn F un c tions

Arithm e tic F un c tions

ABS - Returns the Absolute value of the input number

MAX - Returns the largest number from the list specified

MIN - Returns the smallest number from the list specified

RANDOM - Returns a quasi-random, non-negative whole

number in the range Specified


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BuiltBuilt--In F un c tions ..In F un c tions .. ContdContd

Comparison F un c tion:

COMPARE :

Returns 0 if the two input strings are identical. Otherwisereturns the position of the first character that doesnt match.

DATATYPE :

Returns a String indicating the input data type of the inputstring such as Number or Character.


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Conv e rsion F un c tions :

B2X Binary to Hexadecimal

C2D Character to Decimal

F ormatting F un c tions:

CENTER / CENTRE Returns a String of a specifiedlength with the input string centeredin it.

COPIES Returns the specified number of concatenatedcopies of the input string.

LEFT / RIGHT Returns a String of the specified lengthtruncated or padded on the Right / Left asneeded.


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S tring Manipulating F un c tion:

INDEX Returns the character position of the first character of the specified string found in the input string.

LENGTH Returns the Length of the Input String.

STRIP Returns a character String after removing leading or

trailing character or both from the Input String.

SUBSTR Returns a portion of the Input String beginning ata specified character position.


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S tring Manipulating F un c tionsS tring Manipulating F un c tions.... ContdContd

WORD Returns a word from the Input String as indicatedby a specified number.

WORDS Returns a number of words in the Input String.

VERIFY Returns a number indicating whether an inputString is composed only of characters fromanother input string or returns the character position of the first unmatched character.


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y Mis ce llan e ous fun c tions:

DATE Returns the date in the default format(dd mon yyyy) or inone of the various optional format.

TIME Returns the local time in the default 24 hour clock format(hh:mm:ss) or in one of the various optional formats.

USERID Returns the TSO/E user id, if the REXX exec is runningTSO/E address space.


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Passing InformationPassing Information

S AY Passing Information to th e Te rminal

PULL Ge tting Information from th e Te rminal

ARG S p ec if ying th e inputs w hil e invoking th e e xec s P e riods (.) w ill a c t as th e dumm y variabl e s

PAR S E Pr e ve nting th e translation of Upp e r c as e


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Compound Variabl e s & S te msCompound Variabl e s & S te ms

Compound Variables

a way to create a multi dimensional array or a list of variablesin REXX.

Stems

First variable name and the first period of a compound variable Every compound variable begins with a stem


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Parsing DataParsing Data

PARSE UPPER PULLPARSE UPPER ARGPARSE UPPER VAR

For Examplequote = Knowledge is powerPARSE UPPER VAR quote word1 word2 word3

PARSE UPPER VALUE For Example

PARSE UPPER VALUE Knowledge is power WITH word1word2 word3.


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Commands from an Ex ecCommands from an Ex ec

TSO/E REXX COMMANDS

Provided with the TSO/E implementation of the language Will do the REXX related tasks in an execs. For Example

EXECIO Controls the I/O operations to and from the dataset

NEWSTACK & DELSTACK Perform data stack services

SUBCOM Checks for the existence of a host commandEnvironment.


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Commands from an Ex ec .Commands from an Ex ec . ContdContd

Host Commands :

Recognized by the Host Environment in which an exec runs.

RC is set to the return code of the Host Command issued Enclose the Command within single or double quotation marks For Example

ALLOC DA(NEW.DATA) LIKE(OLD.DATA) NEW

name = myrexx.execLISTDS name STATUS


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Host Command Environm e ntsHost Command Environm e nts

TSO Default Host command EnvironmentISPEXEC The environment in which the ISPF commands execute.ISREDIT The environment in which ISPF/PDF EDIT commands execute.

ADDRESS The command used to change the Host Command Environment. For Example

ADDRESS ISPEXECEDIT DATASET(datasetname)


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Data S ta c kData S ta c k

Expandable data structure to store the informationSTACK - Last In First Out (LIFO)QUEUE First In First Out (FIFO)PUSH Puts one item of data on the top of the Data StackQUEUE - puts one item of data on the bottom of the Data StackQUEUED() Total number of elements in a Data Stack

PARSE EXTERNAL Gets the input directly from the terminal andby pass the data stack.


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TS O/E Ext e rnal F un c tionsTS O/E Ext e rnal F un c tions

LISTDSI To retrieve the detailed information about a datasets attribute. The attribute information will be stored in a system variables. For Example

x = LISTDSI(proj5.rexx.exec)

SYSDSNAME - Dataset nameSYSUNIT - Device unit

SYSDSORG - Dataset OrganizationSYSRECFM - Record FormatSYSLRECL - Logical Record Length


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TS O/E Ext e rnal F un c tions.TS O/E Ext e rnal F un c tions. ContdContd

OUTTRAP Puts lines of command output into a series of numbered

variables each with the same prefix. These variables will save the command output. Specify the variable name in parentheses following the function

call. For Example

X = OUTTRAP(var.)

LISTCX = OUTTRAP(OFF)


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PROMPT Prompting the user for the valid input for the TSO/E commands TSO/E Profile - For the terminal session

TSO PROFILE PROMPT

TSO PROFILE NOPROMPT TSO/E EXEC commandWhen invoking an exec with the EXEC command, can specify thePROMPT operand to set prompting on for the TSO commandsIssued within the exec.The default value is NOPROMPT

PROMPT External FunctionPROMPT(ON) to set the PROMPT optionPROMPT(OFF) to set the NOPROMPT option


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SYSDSN Determines if a specified dataset is available or not For Example

X = SYSDSN(myrexx.exec)The value of X will be OK if it is available for use otherwiseThe value of the X will be

MEMBER SPECIFIED, BUT DATASET IS NOT PARTITIONED

MEMBER NOT FOUNDDATASET NOT FOUND

PROTECTED DATASETUNAVAILABLE DATASETINVALID DATASET NAME, data-set-name:

MISSING DATASET NAME


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SYSVAR Retrieves the information about the MVS , TSO/E and the

current session, such as logon procedure and the user id. Information retrieved depends upon the argument specified. For example

Argument Value DescriptionSYSPREF Prefix as defined in user profile

SYSPROC Logon procedure of current sessionSYSUID User id of the current session


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Dynami c Modifi c ation of a S ingl e REXXDynami c Modifi c ation of a S ingl e REXXExpr e ssionExpr e ssion

INTERPRET Instruction

Evaluate the expression and also treat it as an instruction after itis evaluated

For Exampleaction = DO 3 ; SAY HELLO ; END INTERPRET action


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Pro ce ss Information to and from th e Pro ce ss Information to and from th e Data S e tsData S e ts

Using EXECIO reads information from a data set to the data stack (or a list of variables) and

writes information from the data stack (or list of variables) back to a data set. The dataset must be either sequential or a single member of a PDS. OPTIONS with DISKR / DISKRU

OPENFINISSTEMSKIPLIFOFIFO

OPTIONS with DISKW

OPENFINISSTEM

QUEUE Used to queue a null line at the bottom of the stack to indicate theend of the information


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EXECIO ..EXECIO .. ContdContd

Re turn Cod e s from EXECIO Command

0 - Normal Completion1 - Data was truncated during the DISKW

operation.2 - End of file Reached before the number of lines

were read during DISKR / DISKRU operation.4 - An empty dataset was found during the DISKR

/ DISKRU operation.20 - Severe error .


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Executing a REXX Exec


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Ex ec uting th e REXX Ex ecEx ec uting th e REXX Ex ec

Explicit Execution

EXEC command runs the non-compiled REXX programs in

TSO/E. Enter EXEC command followed by the dataset name thatcontains the exec and keyword exec to distinguish it from theCLIST.

For Example

EXEC SHRTEST.SHREXB.EXEC(SEARCH) execEXEC SHREXB(SEARCH) exec


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Ex ec uting th e REXX Ex ec .Ex ec uting th e REXX Ex ec . ContdContd

Implicit Execution Running the Exec by simply entering the member name of the

dataset that contains the exec. Allocate the PDS that contains the execs to the system file

SYSPROC or SYSEXEC SYSPROC

Is a system file whose dataset can contain both CLISTS and EXEC SYSEXEC

Is a system file whose dataset can contain only the EXECs. If both the system files are available, SYSEXEC will be

searched first.


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Ex ec uting th e REXX Ex ec .Ex ec uting th e REXX Ex ec . ContdContd

Through Batch Mode

Program IKJEFT01 will be used to submit the REXX execs inBatch mode

The member name and the arguments will be passed thru thePARM parameter.

The PDS that contains the member exec will be mentioned inSYSEXEC DD statement.

The output (if any) from the REXX exec will be stored inthe dataset mentioned in the SYSTSPRT DD statement.


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D ebugging the REXX Exec


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De bugging th e REXX Ex ecDe bugging th e REXX Ex ec

TRACE

Displays how the language processor evaluates eachoperations.

TRACE I (Trace Intermediates)Will Trace the Intermediate states of the Expression or anInstruction.

TRACE R (Trace Results)Will Trace the Result or Output of the Expression or an Instruction.


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De bugging th e REXX Ex ec .De bugging th e REXX Ex ec . ContdContd

SPECIAL VARIABLES

RC Will contain the Return code the latest command

SIGL The line number from which there was a transfer of control because of the function call, a SIGNALinstruction , or a call instruction.

Interactive Debug Facility

EXECUTIL TS(TRACE Start)EXECUTIL TE(TRACE End)

Option within Interactive Trace


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Thank You..

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