Rexx - Overview

Rexx (Restructured Extended Executor) is designed to be a scripting language. Its goal is to make scripting as easy, fast, reliable, and error-free as possible. Many programming languages are designed for compatibility with older languages, and are written for specific audiences or platforms.

Rexx - Environment

Try it Option Online

We have set up the Rexx Programming environment on-line, so that you can compile and execute all the available examples on line. It gives you confidence in what you are reading and enables you to verify the programs with different options. Feel free to modify any example and execute it on-line.

Rexx - Installation

The following steps will explain in detail how Rexx can be installed on a Windows system.
Step 1 − Launch the Installer downloaded in the earlier section. After the installer starts, click on the Run button.

Rexx - Installation of Plugin-Ins

In this chapter, we will discuss on how to install plug-ins on popular IDE’s (Integrated Development Environment). Rexx as a programming language is also available in popular IDE’s such as Eclipse. Let’s look at how we can get the required plugin’s in these IDE’s, so that you have more choices in working with Rexx.

Rexx - Basic Syntax

In order to understand the basic syntax of Rexx, let us first look at a simple Hello World program.

Example

/* Main program */ 
say "Hello World"

Rexx - DataTypes

In any programming language, you need to use various variables to store various types of information. Variables are nothing but reserved memory locations to store values. This means that when you create a variable you reserve some space in the memory to store the value associated with that variable.

Rexx - Variables

In Rexx, all variables are bound with the ‘=’ statement. Variable names are sometimes referred to as symbols. They may be composed of Letters, Digits, and Characters such as ‘. ! ? _’. A variable name you create must not begin with a digit or a period. A simple variable name does not include a period. A variable name that includes a period is called a compound variable and represents an array or table.

Rexx - Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations.
Rexx has various types of operators which are also explained in detail as follows −

Rexx - Arrays

Arrays in any programming language allow you to group a list of values of the same type. The use of arrays is that it allows you to build a list of similar type of values which are sortable, searchable and can be easily manipulated. Rexx also allows one to define arrays. These arrays can be one dimensional or multidimensional.

Rexx - Loops

So far we have seen statements which have been executed one after the other in a sequential manner. Additionally, statements are provided in Rexx to alter the flow of control in a program’s logic. They are then classified into a flow of control statements which we will study in detail.

Rexx - Decision Making

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program.
The following diagram shows the general form of a typical decision-making structure found in most of the programming languages.

Rexx - Numbers

Rexx has the following data types when it comes to numbers.

• Integer − A string of numerics that does not contain a decimal point or exponent identifier. The first character can be a plus (+) or minus (-) sign. The number that is represented must be between -2147483648 and 2147483647, inclusive.
  

Rexx - Strings

Strings in Rexx are denoted by a sequence of characters. The following program is an example of strings −

/* Main program */ 
a = "This is a string" 
say a

The output of the above program is as follows −

This is a string 

Rexx - Functions

The code in Rexx is normally divided into Functions and Subroutines. Using functions helps in segregating the code into many more logical units. Let’s look at these functions in detail.

Rexx - Stacks

The stack is sometimes called the external data queue, but we follow common usage and refer to it as the stack. It is a block of memory that is logically external to Rexx. Instructions like push and queue place data into the stack, and instructions like pull and parse pull extract data from it.

Rexx - File I/O

Rexx provides a number of methods when working with I/O. Rexx provides easier classes to provide the following functionalities for files.

• Reading files
• Writing to files
• Seeing whether a file is a file or directory

Rexx - Functions For Files

In this chapter, we will discuss regarding some of the other functions that are available for files.

S.No.	Functions for Files
1	Lines This function returns either the value 1 or the number of lines left to read in an input stream. The filename is given as the input to the function.

Rexx - Subroutines

In any programming language, the entire program is broken into logical modules. This makes it easier to write code that can be maintained easily. This is a basic requirement for any programming language.
In Rexx, modules can be written using Subroutines and functions. Let’s look at the subroutines in detail.

Rexx - Built-In Functions

Every programming language has some built-in functions that help the programmer do some routine tasks. Rexx also has a lot of built in functions.
Let’s look at all of these functions available in Rexx.

Rexx - System Commands

One of the biggest advantages in Rexx is the ability to create re-usable scripts. Often in organizations nowadays, having re-usable scripts is a big value add in saving time to do common repetitive tasks.
For example, technology teams in an IT organization can have the need to have scripts which do common everyday tasks.