What are Parameters?

Parameters are variables used in programming that allow you to pass data or values into functions, methods, or procedures to enable them to perform tasks with varying inputs. When you define a function or method, you can specify parameters in its declaration, which are placeholders for the values that will be passed when the function is called. Parameters act as input data for the function and allow it to process different values each time it is executed.

Parameters are essential in making functions reusable and dynamic. By defining parameters, functions can perform tasks based on the values passed to them, without having to hard-code specific data. They serve as a critical component of function-based programming and are used in many programming languages such as Python, Java, JavaScript, C, C++, and more.

In many cases, parameters are also referred to as arguments, though there is a subtle distinction between the two:

• Parameter: The variable in the function definition.
• Argument: The actual value passed to the parameter when the function is called.

For example, consider a simple function that adds two numbers:

def add_numbers(a, b):
    return a + b

Here, a and b are parameters. When you call the function with actual values, those values are arguments:

add_numbers(3, 5)

In this case, 3 and 5 are arguments passed to the a and b parameters of the add_numbers function.

What are the Major Use Cases of Parameters?

Parameters are used in a wide range of programming scenarios. Below are the major use cases:

1. Dynamic Function Behavior

Parameters allow functions to behave dynamically by taking input values that determine the function’s behavior. Instead of hardcoding values, parameters allow the same function to be executed with different inputs, making the function reusable for different scenarios.

Example:

• A sum function can be reused for adding any two numbers, and the numbers are passed as parameters to define the function’s behavior.

2. Encapsulation of Complex Operations

Functions that perform complex operations (e.g., calculations, data processing) often require different values for each operation. Parameters encapsulate the input data, allowing the function to work on a variety of inputs without modifying the core logic.

Example:

• A file processing function can take parameters for the file path, encoding, and output format, enabling the same function to process different files.

3. Code Reusability

Parameters increase code reusability by allowing functions to work with different inputs and perform similar operations without writing multiple versions of the same function.

Example:

• A data sorting function can be reused with different datasets and sort orders by passing the dataset and order type as parameters.

4. Configuration of Functions

Parameters allow functions to be configured and customized without changing their internal logic. This allows greater flexibility, as parameters control aspects of the function’s execution, like timeouts, limits, and environment settings.

Example:

• A server connection function might take parameters for the server address, port, and authentication details, allowing the function to connect to various servers with different configurations.

5. Control Flow and Decision Making

Parameters can control the flow of a program, allowing developers to implement decision-making logic within functions based on the input values. This can help in implementing conditional operations and branching logic.

Example:

• A payment processing function could take a payment_method parameter to determine whether the payment is processed via credit card, PayPal, or another method.

6. Interfacing with External Systems

In distributed systems or when working with external APIs, parameters serve as the mechanism to pass data between different services, applications, or system layers. They act as data carriers that transport necessary information across systems.

Example:

• An API request might take parameters like user_id, action_type, and time_range to request specific data from a server.

How Parameters Work Along with Architecture?

In programming, parameters fit into the overall architecture of functions, methods, and procedures. Below is an explanation of how parameters are used within the architecture of a function and the general software architecture.

1. Function Declaration

When you define a function or method, you specify the parameters within the function’s declaration. These parameters act as placeholders for the values that will be passed when the function is invoked.

Example in Python:

def greet_user(username):
    print(f"Hello, {username}!")

Here, username is a parameter that is used in the function greet_user. When you call the function, you pass an argument to this parameter:

greet_user("Alice")

2. Function Call

When a function is invoked, you pass values, known as arguments, to the parameters in the function definition. These arguments replace the parameters with specific data when the function executes. The argument values are assigned to the corresponding parameters, and the function uses them to perform its operations.

3. Parameter Scope

The scope of a parameter is local to the function or method in which it is defined. This means the parameter can only be used inside the function or method where it is declared. Once the function execution is complete, the parameter value is discarded.

Example:

def calculate_area(radius):
    area = 3.14 * radius * radius  # radius is a parameter
    return area

# radius is not accessible outside the function

4. Default Parameters

Some programming languages allow default parameter values, which are used when no argument is passed to the function. This makes parameters optional.

Example in Python:

def greet_user(username="Guest"):
    print(f"Hello, {username}!")

greet_user()  # Uses the default value "Guest"
greet_user("Alice")  # Uses the provided argument "Alice"

5. Varied Number of Parameters (Arbitrary Arguments)

Some languages support functions that accept a variable number of parameters, often using a special syntax. In Python, this is achieved using *args for non-keyword arguments or **kwargs for keyword arguments.

Example in Python:

def sum_numbers(*args):
    return sum(args)

print(sum_numbers(1, 2, 3))  # Output: 6

Here, *args allows the function to accept an arbitrary number of arguments.

Basic Workflow of Parameters

The basic workflow for using parameters in functions follows a few simple steps:

1. Define Parameters in Function Declaration
   • Define the function and specify the parameters inside the parentheses.
2. Call the Function and Pass Arguments
   • When calling the function, pass values (arguments) that correspond to the parameters defined in the function.
3. Use Parameters Inside the Function
   • Inside the function, use the parameter values to perform computations or execute specific tasks based on the input.
4. Return Results (If Applicable)
   • The function can return a value based on the parameters, which can be used elsewhere in the program.
5. Handle Optional or Variable Parameters
   • Define default values for parameters or use variable argument techniques (like *args or **kwargs) to make the function more flexible.

Step-by-Step Getting Started Guide for Parameters

Here’s a step-by-step guide to help you understand and implement parameters in your programs:

Step 1: Define a Simple Function

Start by creating a simple function that accepts a single parameter:

def say_hello(name):
    print(f"Hello, {name}!")

This function takes name as a parameter and prints a greeting.

Step 2: Call the Function with an Argument

Now, call the function and pass an argument to the parameter:

say_hello("Alice")

This will output:

Hello, Alice!

Step 3: Add More Parameters

You can add more parameters to the function to make it more versatile. For example, let’s define a function to calculate the area of a rectangle:

def calculate_area(length, width):
    area = length * width
    return area

Step 4: Call the Function with Multiple Arguments

Pass multiple arguments to the function:

result = calculate_area(5, 3)
print(result)  # Output: 15

Step 5: Use Default Parameters

Let’s add a default value to a parameter. This makes it optional:

def greet_user(username="Guest"):
    print(f"Hello, {username}!")

You can call it with or without an argument:

greet_user()  # Output: Hello, Guest!
greet_user("Bob")  # Output: Hello, Bob!

Step 6: Use Variable-Length Arguments

If you want to accept an arbitrary number of arguments, use *args or **kwargs:

def add_numbers(*args):
    return sum(args)

print(add_numbers(1, 2, 3, 4))  # Output: 10

This allows you to pass any number of arguments to the function.

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Immediately Invoked Function Expression (IIFE)

• Avoid Creating Global variable and Functions
• As it doesn‟t define variable and function globally so there will be no name conflicts
• Scope is limited to that particular function

Pass by Value

• JavaScript arguments are passed by value: The function only gets to know the values, not the argument’s locations.
• If a function changes an argument’s value, it does not change the parameter’s original value.
• Changes to arguments are not visible (reflected) outside the function.

Pass by reference

• In JavaScript, object references are values.
• Because of this, objects will behave like they are passed by reference:
• If a function changes an object property, it changes the original value.
• Changes to object properties are visible (reflected) outside the function.

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When we create a function and assign it to a variable, known as a function expression.

Note: –

• You can‟t call function expression before the function definition.
• Function expressions in JavaScript are not hoisted, unlike function declarations.

Anonymous Functions

Anonymous functions allow the creation of functions that have no specified name.

• Can be stored in a Variable
• Can be Returned in a Function
• Can be pass in a Function

Store Anonymous Function in Variable

Passing Anonymous Function as Argument

Returning Anonymous Function

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JavaScript has two scopes: –

• Global
• Local

Global Scope

A variable that is declared outside a function definition is a global variable, and its value is accessible and modifiable throughout your program. In a web browser, global variables are deleted when you close the browser window (or tab) but remain available to new pages loaded into the same window.

Local Scope

A variable that is declared inside a function definition is local. It is created and destroyed every time the function is executed, and it cannot be accessed by any code outside the function. Inside a function, if a variable has not been declared with var it is created as a global variable.

Local Scope

If there is a function inside a function the inner function can access outer function‟s variables but the outer function can not access inner function‟s variables. Function arguments (parameters) work as local variables inside functions.

Block Scope

Variables declared with var do not have block scope.

Block Scope

Identifiers declared with let and const do have block scope.

Variable Hoisting

Hoisting is JavaScript’s default behavior of moving declaration to the top of the function, if defined in a function, or the top of the global context, if outside a function.

Variable Hoisting

A variable can be used before it has been declared. Only variable declarations are hoisted to the top, not variable initialization.

Closure

A closure is a function having access to the parent scope. It preserves the data from the outside.

A closure is an inner function that has access to the outer (enclosing) function‟s variables.

For every closure we have three scopes:-

• Local Scope ( Own scope)
• Outer Functions Scope
• Global Scope

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In JavaScript, we do not need to specify the type of the variable because it is dynamically used by the JavaScript engine.
We can use var data type. It can hold any type of data like String, Number, Boolean, etc.

Primitive Data Type Non-Primitive Data type

String Object
Number Array
Boolean RegExp
Undefine

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A variable is an identifier or a name which is used to refer a value. A variable is written with a combination of letters, numbers and special characters _ (underscore) and $ (dollar) with the first letter being an alphabet.

Ex-

c, fact, b33, total_amount etc.

Rules

• Variable can contain combination of letters, digits, underscores ( _ ), and
dollar signs ( $ ).
• Must begin with a letter A-Z or a-z or underscore or dollar sign
• A variable name cannot start with a number
• Must not contain any space characters
• JavaScript is case-sensitive
• Can‟t use reserved keywords

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<script type="text/javascript">
	document.write("Hello DevOpSchool");  
</script>

<script src="devops.js" type="text/javascript"></script>

<script> – Opening Script Tag.

src – It’s an attribute of the script.

name.js – This is our script file, which we created. The code of javascript is written inside devops.js.
In which DevOps is the file name, .js is the extension. Javascript has an extension of .js

Type – This is also an attribute of the script tag, it tells the browser that it is javascript. Now it is not necessary to write it, you can leave it if you want.

Text/javascript – It defines what type these documents are.

document.write(“Hello World”); – This is a function which is displaying the data.

</script> – Closing Script tag.

How to link more than one External?

You can link more than one JavaScript file to a single document. Just need to write different script tags for that.

<script src="devops1.js" type="text/javascript"></script>
<script src="devops2.js" type="text/javascript"></script>
<script src="devops2.js" type="text/javascript"></script>
<script src="devops3.js" type="text/javascript"></script>

How to use inline and External together in javascript?

No, both cannot be written together. But both inline and external can be written separately.

<!DOCTYPR>
<HTML>
    <head><title></title>
        
            
        </script>
    </head>
    <body>
        <h1>I am Heading</h1>
        <p>I am Paragharph</p>
        
        <script type="text/javascript">
			document.write("Hello Vijay");  
		</script>
        <br>
        
        <script src="devops.js" type="text/javascript"></script>
        
    </body>
</html>

Write funtion

This function is used to write arbitrary HTML and content into the page. If we use this function after an HTML document is fully loaded, will delete all existing HTML. It is used only for testing purposes.

Ex:-    document.write("Hello world");
	    document.write(variable);
	    document.write(4+2);
	    document.write("hello world . <br>");
	    document.write("hello world . <br>" + variable +"<br>");

Alert function in JavaScript

The data that will be displayed in it will be in the dialog box. You forcefully want to see this thing, then only this work will be done. In that case, you use a window. alert

Ex:- window.alert("Hello World");
	 window.alert(variable);
	 window.alert(4+2);
	 window.alert("hello world"+ variable);

<html>
	<head><title>Hello JS</title>
		<script>
			window.alert("Hello");
		</script>
	</head>
	</body>
`		<h1>I am heading</h1>
		<p>I am Paraghraph</p>
		
		<script src="name.js" type="text/javascript">
		</script>
	</body>
</html>

Identifier

An identifier is a name having a few letters, numbers, and special characters _(underscore). It is used to identify a variable, function, symbolic constants, and so on.

Ex:- X2
PI
Sigma
Matadd

Veriable in JavaScript

Variable can be any name, in which a combination of letters, numbers, and special characters can be written _()(underscore) and $(dollar). It is not necessary that there should be only a combination, it can only be a letter.

Ex:- c, fact, b33, total_amount ect.

Rules of Veriable in JavaScript

• Variable can contain a combination of letters, digits, _()(underscore), and dollar signs($).
• Must begin with a letter A-Z or a-z or underscore or dollar sign.
• A variable name cannot start a number.
• Must not contain any space characters.
• JavaScript is case-sensitive
• Can’t use reserved keywords.

Reserved Keyword in javascript

Keyword or Reserved words

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Object Oriented Progrmming

Object-Oriented Programming is a Technic that solves the problem. In this, the code breaks the object. And you see your problem on the side of the object. In which you find your problem similar to the real-world problem and it is easy to maintain, and it has to be solved.

Class

The PHP class has a group of values. To manipulate whatever value you write inside the class, you also write operations in it. The class gives you this facility, that if the user does not need to know the information. So you can also hide the information. To use the application, you can keep it hidden for security purposes. Or if it will be accessed from the outside users or from an outside viewer then your application may be damaged. That’s why you can keep your application hidden, it gives class facility. You can define type using class.

Rule

• The class name can be any valid label.
• It can’t be PHP reserved world.
• The class name must start with a letter or an underscore. Following by any number of letters, numbers, or underscore all this will work. Lwkin should not start with number.

class Classname
{
	var $variable_name;  (It is also called Data Member/Properties or Attribute.)
	var $variable_name;
	
	function Method_name()
	{
		Body of method;
	}
	function Method_name(parameter_list)     (And these methods are called methods or member functions.)
	{
		Body of Method;
	}

}

See your problem in the real world.

class Mobile
{
	public $model;
	function show Model (Sumber)
	{
		$this->model = $number;
		echo "Model Number: $this->model";
	}
	
}

Object

The object is a variable of class data type. Whenever you create an object, for that object, whatever is proper inside the class, a copy of it is prepared and it is prepared for that object. If there are 2 objects then 2 copies of that variable or that property will be created and one copy for the first object and a second copy for the second object. Whatever object you make, its copy will be ready and one copy will be distributed. But this is not the case with the member function. The member function is the same, all the objects share with it.

The new Operator is used to create an object.

Syntax:

class Mobile
{
	public $model;
	function show Model (Sumber)
	{
		$this->model = $number;
		echo "Model Number: $this->model";
	}
	
}
$samsung = new Mobile;
$samsung->showModel('A5');

$lg = new Mobile;
$lg->showModel('M30');

You will not need to write the class, again and again, you just have to create an object of it. And call this method with the help of that object. It will show its own model number.

Important thing

A class is of no importance unless it has an object.

Accessing class member using object

How would you make accessing a member of a class into a user object?

-> This operator is used to access the member of the class.

object_name->variable_name;
$samsung->model;

access to method
Object_name->method_name();
$samsung->showModel();

in parameter
Object_name->method_name(parameter_list)
$samsung->showModel(‘A8’);

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We will see the explanation by a example:

Form.html

Testform.php

In this form we have used “get” method and we will see the output below:

As we can see we have used the method “get” in the form and in the output page of testform.php we can see the input given, also with that in the URL box we can see the details which we have provided in the form.html.

If we use “post” method in the form.html we will see the difference below:

As we can see in the URL box there is no such details provided which we can see while using “post” method.

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Initially we will see what is local variable and global variable with examples.

Here if we see the variable is declared inside the function “local” so it will work inside the local function only until we return the value inside the function.

In this we can see that the variable “a” is declared outside the function local, so it won’t work inside the function until we call it.

If we see the output for this we will see an error since “a” is a local variable and it will not work beyond the function “test”.

Now in this code if we see, variable “a” is declared globally and we will get an error if we call it inside any function.

To execute the global variable in the function we need to use predefined variable “global” inside the function.

We will see now that it will return value inside the function as well as outside the function.

References:

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Another major use of variables is running a command and using the result of that command to save the result into a variable

- hosts: all
  tasks:
  - name: Ansible register variable basic example
    shell: "find *.txt"
    args:
      chdir: "/Users/mdtutorials2/Documents/Ansible"
    register: find_output

  - debug:
      var: find_output

#
- hosts: all
  tasks:
  - name: Ansible register with_items example
    shell: "find *.txt"
    args:
      chdir: "/Users/mdtutorials2/Documents/Ansible"
    register: with_output

  - shell: "cp {{ item }} {{item}}_bkp"
    with_items:
      - "{{ with_output.stdout_lines }}"

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InstallAnywhere Variables are the key to any InstallAnywhere based installation. They
allow developers to control the flow of information, and the flow of the installation.
They let developers store information from the system and information input by endusers,
then create rules to determine operations based on that information.
Developers can even output that information to configuration files or other resources
to be used by the application.

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Environment variables and properties defined in jenkins

Jenkins Set Environment Variables

When a Jenkins job executes, it sets some environment variables that you may use in your shell script, batch command, Ant script or Maven POM 1. The following table contains a list of all of these environment variables.

Promoted Build Plugin Environment Variables

If you are using the Promoted Build Plugin, you will have access to the following environment variables. This allows you to access information about your Jenkins build since certain environment variables stated above (such as BUILD_TAG now refer to the Promoted Build Plugin’s job.

System Properties

Environment Variables

Plugins

Useful Plugins

https://wiki.jenkins-ci.org/display/JENKINS/EnvInject+Plugin

Reference

https://wiki.jenkins-ci.org/display/JENKINS/Building+a+software+project
http://jenkins:8080/systemInfo

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