Transcript No Slide Title

REXX
Saravanan Desingh
REXX
• An abbreviation of IBMs Restructured EXtended
eXecutor (REXX) Language, which allows system
command to be used or combined in a routine.
Topics
1 REXX ENVIRONMENT
2 CODING PROGRAM & DATA INSTRUCTIONS
3 DEBUGGING & STORAGE FACILITIES
4 REXX AS A COMMAND LANGUAGE
1. REXX ENVIRONMENT
1.1
Creating a REXX program.
1.2
Coding Simple variables and Expressions
1.3
Using Built-in functions
1.1 Creating a REXX program
1.1.1 Beginning a REXX Program and using
comments
1.1.2 Structuring a REXX Program
1.1.3 Using Basic Terminal I/O
1.1.4 Running a REXX Program
1.1.1 Beginning a REXX program and using
comments
• Start with Keyword REXX
• Comments /* and */
1.1.2 Structuring a REXX program
• Free-Formatted Language
• A Space to separate the arguments
• Not Case-Sensitive
1.1.2 Structuring a REXX program
; Separate 2 Instructions
, Continue an Instruction
1.1.3 Basic terminal input and output instruction
• SAY
– Display Text on Screen
• PULL
– Retrieves User Input
1.1.4 How to Run a REXX program?
• Explicit Command
– TSO Environment
exec ‘DSN’ exec
• Implicit Command
– SYSPROC or SYSEXEC
TSO member-name
1.2 Coding Simple variables and Expressions
1.2.1
Using Dynamic Typing
1.2.2
Assigning simple variable
1.2.3
Using Character String Expressions and
Operations
1.2.4
Using Arithmetic Expressions and
Operations
1.2.5
Using Logical Expression and Operations
1.2.1 Using Dynamic Typing
• Implicit Defining of Variables
• Defined Dynamically
1.2.2 Assigning simple variables
• Variable Characteristics:
– Length 1 to 255 characters
– A-Z, a-z, 0-9
– !,@,#,$,?,_
– Should not begin with Digits
1.2.3 Using Character String Expressions and
Operations
• All Constants & Variables referred as
Alphanumeric Character Strings.
• Character Strings - “” and ‘’
• Concatenation - ||
1.2.4 Using Arithmetic Expressions and Operations
• Denoted with or without Quotes
12,’12.0’,”12.00”
• Arithmetic Operators
+,-,*,/
1.2.5 Using Logical Expressions and Operations
=
>
<
== (Identical to)
&
|
\ (Not)
1.3 Using Built-in functions
1.3.1
Using string manipulation function
1.3.2
Formatting numbers
1.3.3
Using Arithmetic Functions
1.3.4
Using Miscellaneous functions
1.3.1 Using String Manipulation Functions
• LENGTH(string)
– No.of characters in the string
• LEFT(string,no.of chars)
– Isolate a string within a string
• SUBSTR(string,startpos,no.of chars)
• RIGHT(string,no.of chars)
1.3.1 Using String Manipulation Functions
• POS(lookfor,seach)
• INDEX(search,lookfor)
– searches one string (search) to see if
another string (lookfor) is contained in it
1.3.2 Formatting Numbers
• FORMAT(nn,ninteger,ndecimal)
nn
- Number or numeric expression to format
ninterger-Number of digits or blanks to the left of the
decimal point.
ndecimal-Number of places to the right of the
decimal point
• Ex:
A=123.44
FORMAT(A,3,1)=123.4
1.3.2 Formatting Numbers
• TRUNC(number,numberofplaces)
• Ex:
TRUNC(56.7777,1)=56.7
1.3.3 Using Arithmetic Functions
• DATATYPE(variable)
– NUM
– CHAR
1.3.3 Using Arithmetic Functions
• Additional Function:
– ABS(n)
– MAX(n1, n2, n3...)
– MIN(n1, n2, n3….)
– RANDOM(low, high)
– SIGN(n)
-1, 0 , 1
1.3.4 Using Miscellaneous Function
– USERID()
– TIME()
Format hh:mm:ss
– DATE()
Format dd mmm yyyy
– DATE(J)
Format yyddd
– DATE(U)
Format mm/dd/yy
2 CODING PROGRAM & DATA INSTRUCTIONS
2.1
Using Compound variables
2.2
Coding Conditional and Looping Constructs
2.3
Implementing Subroutines, Procedures, and
Functions
2.4
Parsing Data
2.1 Using Compound variables
• Implementing Arrays and Records
– Stem
– No. of Elements
– Maximum Variable Name Length - 250 Characters
– Mixed types and Lengths
– Ex:
arr.1=“25”
arr.2=“Steeple-Reach Building”
• Initialize array:
– array.=0
– arr.=‘’
• Single and Multi dimension array.
– Ex:
single.var
matrix.row.col
• Compound Variables can be used as Data
Structures.
• Ex:
emprec.empname=‘Bharath’
emprec.empno=5508
emprec.sex=‘M’
• Record like structure.
2.2 Coding Conditional and Looping
Constructs
2.2.1
Using Conditional Constructs and
Compound Statements
2.2.2
Using Looping Constructs
2.2.3
Bypassing and Terminating Loops
2.2.4
Branching on errors
2.2.1 Using Conditional constructs and Compound
statements
• Conditional group:
IF-THEN-ELSE
• Format:
IF expression THEN
statement
ELSE
statement
• ELSE optional
2.2.1 Using Conditional constructs and Compound
statements
• Grouping the statements:
DO-END
Ex:
DO
Statement1
Statement2
END
2.2.1 Using Conditional constructs and Compound
statements
• Selecting several conditions:
SELECT-WHEN-THEN-OTHERWISE
* OTHERWISE optional
2.2.2 Using Looping Constructs
• Repeating a sequence of instructions.
• Conditional Looping.
• DO-WHILE
• DO-UNTIL
2.2.2 Using Looping Constructs
• Format:
DO WHILE condition
Stmts
END
• Executes when condition is True.
2.2.2 Using Looping Constructs
• Format:
DO UNTIL condition
stmts
END
• Executes when condition is False.
2.2.2 Using Looping Constructs
• Numerically Controlled Repetitive Loop:
– Format:
DO nooftimes
stmts
END
– Ex:
DO 5
say ‘It will be displayed for 5 times’
END
2.2.2 Using Looping Constructs
• Numerically Controlled Repetitive Loop:(Infinite Looping)
– Format:
DO FOREVER
stmts
END
– Ex:
DO FOREVER
say ‘Your System is locked by the User’
END
2.2.2 Using Looping Constructs
• Numerically Controlled Repetitive Loop:
– Format:
DO var = initial T0 final
stmts
END
– Ex:
DO I=1 to 10
s=s+I
END
2.2.2 Using Looping Constructs
• BY Clause:
– Additional variations.
Ex:
DO I=1 T0 99 BY 2
SUM=SUM+I
END
‘I’ will have the values 1,3,5,…99
2.2.2 Using Looping Constructs
• FOR Clause:
– Controls Maximum no. of Execution.
Ex:
DO I=0 BY 5 FOR 20
SAY I
END
‘I’ will have the values 0,5,10,..95
2.2.2 Using Looping Constructs
• Nested Looping:
DO …
DO …
…….
END
END
2.2.3 Bypassing and Terminating Loops
• LEAVE:
–
Terminating explicitly.
• Ex:
DO FOREVER
SAY ‘Enter a String (Exit : X)’
PULL STR
IF STR == ‘X’ THEN
LEAVE
ELSE
SAY STR
END
2.2.3 Bypassing and Terminating Loops
• ITERATE:
–
Bypass instructions.
• Ex:
DO count = 1 TO 10
IF count = 8 THEN
ITERATE
ELSE
SAY 'Number' count
END
2.2.4 Branching on Errors
• SIGNAL:
• Ex:
IF RC\=0 THEN
SIGNAL handle-error
…….
handle-error:
….
2.3 Implementing Subroutines, Procedures,
and Functions
2.3.1 Defining Subroutines, Procedures and Functions
2.3.2 Using Subroutines
2.3.3 Using Procedures
2.3.4 Using Functions
2.3.1 Defining Subroutines, Procedures, and
Functions
• In REXX, use a
Subroutine for a simple branch and return within a
program. All main program variables are available
to a subroutine.
2.3.1 Defining Subroutines, Procedures, and
Functions
• In REXX, use a
Procedures the same way as you use a subroutine,
but use it when you need a routine with its own
local variables ‘hidden’ from the main program.
2.3.1 Defining Subroutines, Procedures, and
Functions
• In REXX, use a
Functions to return data to use in the main program.
REXX allows functions to either access main
program variables or local variables.
2.3.2 Using Subroutines
Main pgm,
…..
CALL subrtn
……
EXIT
subrtn:
……..
RETURN
2.3.3 Using Procedures
Main pgm,
…..
CALL subrtn
…...
EXIT
subrtn: PROCEDURE
……..
RETURN
2.3.3 Using Procedures
• Ex:
i=4
call num
say i
num: PROCEDURE
i=3
RETURN
•
Output is 4.
2.3.3 Using Procedures
• EXPOSE:
– To expose caller Variables.
• Format:
– ProcName: PROCEDURE EXPOSE arg1 arg2…
• Argument variables can be constants, expressions or
variables
2.3.3 Using Procedures
• Ex:
n1=5
n2=4
avg=0
call calc
say avg
calc: PROCEDURE EXPOSE n1 n2 avg
avg=(n1+n2)/2
RETURN
2.3.3 Using Procedures
• To pass value, code
– A CALL with up to 20 Arguments.
• The ARG, PARSE UPPER ARG and PARSE ARG
instruction as the first line in the PROCEDURE.
2.3.3 Using Procedures
• Ex:
CALL exproc name1 ecode1
exproc: PROCEDURE
ARG name2 ecode2
say name2
say ecode2
RETURN
2.3.3 Using Procedures
• RESULT:
– Last value returned from the Procedure or
Subroutine
• Ex:
RETURN 10
- 10 is assigned to RESULT.
2.3.4 Using Functions
• User-defined Functions:
– Like Built-in function.
– Substitutes Expressions.
– Subroutines or Procedures returns a value can
be used as function
• Format:
– FunctionName()
2.3.4 Using Functions
• Ex:
n1=1
n2=2
say average(n1 n2)
average:PROCEDURE
ARG n1 n2
RETURN (n1+n2)/2
2.4 Parsing Data
2.4.1 Parsing from Terminal Input and Passed Values
2.4.2 Using Additional Parsing Instructions
2.4.1 Parsing from terminal input
• Format:
PULL var
or
PARSE UPPER PULL var
2.4.1 Parsing from terminal input
PULL var1 var2…
PARSE UPPER PULL var1 var2..
PARSE PULL var1 var2..
2.4.1 Parsing from passed values
• Receiving data from the another routine
• Format:
ARG var1 var2..
or
PARSE UPPER ARG var1 var2 ..
• Without converting to uppercase,
PARSE ARG var1 var2 …
2.4.2 Using additional Parsing Instructions
• PARSE VAR varname var1 var2 …
• PARSE VALUE expression WITH var1 var2..
2.4.2 Using additional Parsing Instructions
Ex:
PARSE VALUE “hello” || “world”,
WITH var1 var2
Var1=”hello”
Var2=”world”
To Trap and disregard dummy words
PARSE VALUE “This is a REXX program” WITH var1 . . var2 .
Var1=”This”
Var2=”REXX”
PARSE VALUE “Hi , Everybody” WITH var1 ‘,’ var2
Var1=”Hi ”
Var2=” Everybody”
3 DEBUGGING & STORAGE FACILITIES
3.1
Processing Data on a Stack
3.2
Manipulating Data sets
3.3
Debugging with REXX Facilities
3.1 Processing Data on a Stack
3.1.1 Defining the stack
3.1.2 Implementing LIFO and FIFO lists with the stack
3.1.1 Defining the stack
• Storage Facility in Memory for lists of Data.
• Access is Sequential.
3.1.2 Implementing LIFO and FIFO lists with the
stack
• LIFO- Last In First Out
• FIFO- First In First Out
• Default is LIFO
3.1.2 Implementing LIFO and FIFO lists with the
stack
PUSH:
To implement a LIFO list on the stack,
PUSH expression
3.1.2 Implementing LIFO and FIFO lists with the
stack
• PULL:
– As long as the stack contains data lines, PULL
accesses the stack. When the stack is empty,
PULL accesses the keyboard.
PULL var
• QUEUE:
To implement a FIFO list on the stack,
QUEUE expression
3.1.2 Implementing LIFO and FIFO lists with the
stack
QUEUED():
Built-in function used to determine the
no. of items in the stack.
n=QUEUED()
3.2 Manipulating Data sets
3.2.1 Reading information from Data sets
3.2.2 Writing information to Datasets
3.2.3 Updating Data sets
ALLOC – allocation
EXECIO – input/output operations
3.2.1 Reading information from data sets
 Allocate dataset to a file.
– “ALLOC F(file) DA(‘DSN’) SHR REUSE”
file -> Logical File
DSN-> Physical File
3.2.1 Reading information from data sets
 Read data into a stack or an array using EXECIO
with the DISKR option.
– “EXECIO * DISKR file(FINIS”
• using stack
– “EXECIO * DISKR file(STEM arr. FINIS”
• using array
* - all lines.
 FINIS- close dataset after processing
3.2.1 Reading information from data sets
“EXECIO nooflines DISKR file startlineno (FINIS”
nooflines – no. of lines to read.
Startlineno - starting line to read.
Ex:
“EXECIO 10 DISKR file 100(FINIS”
3.2.1 Reading information from data sets
stack:
“EXECIO * DISKR file(LIFO FINIS”
-PUSH command
“EXECIO * DISKR file(FIFO FINIS”
-QUEUE command
- Default is FIFO.
3.2.2 Writing information to data sets
DISKW in EXECIO
Stack:
EXECIO will continue to pull from the
stack until it locates a null line.
3.2.3 Updating a data sets
• DISKRU:
– Disk read for updating.
• Ex:
– “EXECIO 1 DISKRU file(LIFO ”
3.3 Debugging with REXX Facilities
3.3.1 Tracing Program Flow
3.3.2 Using Special Variables
3.3.1 Tracing Program Flow
TRACE:
Initiate trace from REXX
TRACE C – Commands
TRACE R - Results
TRACE E - Errors
TRACE N - Normal
3.3.1 Tracing Program Flow
Interactive Tracing:
TRACE ?option
option- C,R or E.
3.3.2 Using Special Variables
SIGL (Signal Line):
Whenever control transfers within a REXX
program (usually due to CALL, SIGNAL, or a
Function call), SIGL is set to the line number
where the branch occurred.
3.3.2 Using Special Variables
Ex:
000003
CALL subrtn
000004
EXIT
000005
000006 subrtn:
000007
000008
say “This is call from line” SIGL
RETURN
O/p:
This is call from line 3
3.3.2 Using Special Variables
RC (Return Code):
Retains the return code of the REXX
command executed last.
Ex:
“EXECIO * DISKR f1(FINIS”
readcode=RC
3.3.2 Using Special Variables
• SIGNAL ON ERROR:
– Any subsequent nonzero RC cause control to
pass to a subroutine named ERROR.
3.3.2 Using Special Variables
SIGNAL ON ERROR:
Ex:
SIGNAL ON ERROR
…..
ERROR:
Say ‘Error no.’ RC ‘occurred at line’ SIGL
EXIT
4 REXX AS A COMMAND LANGUAGE
4.1
Interacting with the Command Host
Environment
4.2
Interacting with TSO/E
4.1 Interacting with the Command Host
Environment
• Directing Commands to the Command Host
Environment
To change the command Host Environment for all
subsequent commands, use the format,
“ADDRESS environment”
Environments:
MVS, TSO, ISPEXEC, ISREDIT, LINK, ATTACH,
or NETVIEW.
Ex:
“address MVS”
Verify Environment:
Format:
“SUBCOM environment”
Sets RC to zero if the environment is present,
else set to one.
4.2 Interacting with TSO/E
4.2.1
TSO Commands
4.2.2
Using OUTTRAP to Pass Data
4.2.1 TSO Commands
• Commonly used TSO Commands
– ALLOCATE
– DELETE
– DSAT
– EXEC
– LISTDS
4.2.2 Using OUTTRAP to pass Data
Traps the output of the subsequent commands and
places the trapped lines into an array
Format:
OUTTRAP(“stem.”,Maxnoof lines)
“command”
Ex:
OUTTRAP(“output.”,5)
THE END