Commands

Helpful Information

• If you type the beginning of a command and press tab, options for that command will print out in the terminal. For example you can type Get- and all the options for Get will be printed out.

• PowerShell scripts will end in .ps1

Cmdlet	Description
Write-Host	Used within scripts to create output for the user and display data being processed.
Get-Date	Outputs the current date in the terminal.
Get-Command	Will output all available CmdLets.
Get-Command -Verb Get	Output all Get commands. We use the -Verb
Get-Command -Noun Host	outputs all commands acting on host in the terminal
Get-Content	Used to access file content, reads the file line by line
Select-String	Used to return lines with specific content
Clear-Host	Use this to clear the terminal session
Get-History	Access the terminal command history
Get-Help	Displays help about Powershell cmdlets and concepts
Get-Host	Output information about your host
Get-Timezone	Outputs your timezone
-Prompt	Outputs a string and then waits for the user to press enter.
Read-Host	Allows you to prompt the user for input.

Variables and Operators

Data comes in various forms:

• Numbers (integers): 1,-99,42

• Text (strings): "Hello", "BF1991"

• Booleans (True/False)

How Variables Work

In computer programming, variables are used to store a piece of data. In PowerShell variables can store the results of commands and expressions like values, names, paths, and settings.

To create a variable, we must assign it a value. Variables in PowerShell are referenced using a dollar sign ($) followed by a variable name. After a variable reference, we use an equal sign followed by the value we are assigning to it.

• $my_string_variable = "Hello, World"

• Variable names:

  • Not case-sensitive

  • Can include spaces and special characters when enclosed in curly brackets.

• If you assign a variable and want to know its variable you can use the following command:

  • Write-Host $my_input

• To figure out what data type a variable is we can add the following to the end of the variable:

  • $my_input = "Hello World!"

  • $my_input.GetType().Name

  • The output will then be "string"

Constrained Variables

If we want to enforce a certain type on a variable, we can create a constrained variable via casting.

PS > [Int]$age = 25
PS > $age 
25 

PS > [Int]$age = "twenty five"
Cannot convert value "age" to type "System.Int32". Error: "Input string was not in a correct format."

Create Multiple Variables

//creating multiple variables with the same value
$i = $j = $k = 0

// assign multiple values to multiple variables 
$number, $color, $bool = 25, "red", $false  

Environmental Variables

Environmental variables store information related to the current environment, like the OS and user sessions in the terminal. They are global variables, which means we can access them across commands and programs. They are usually created by the operating system, but we can use them to configure our production environment.

• Environment Variables are stored as strings

• To get all existing environmental variables, we can use the following:

  • Get-ChildItem Env:

• Use the following:

(Get-ChildItem Env:EIN_IMAGE).Value
> ubuntu
$Env:EIN_IMAGE
> ubuntu  

• The PATH variable is a popular environment variable that includes all directories where applications look for executables.

• The HOME variable is another popular environmental variable that specifies the current user's home directory.

• The following is the syntax to create an environmental variable:

  • The variable names are usually fully capitalized

$Env:EXAMPLE_ENV_VAR = "custom value"

Arithmetic Operators

Operators are used to perform specific operations on data often stored in variables. PowerShell has multiple types of operators:

Operators are best used with variables!

Arithmetic Operators

• Add +

• Subtract -

• Multiply *

• Divide /

• Modulus %

PS > 5 + 5
10

PS > 25 % 3  # 25/3 = 8 remainder 1
1

//manipulating strings with operators! 

PS > $best_learning_platform = "Code" + "cademy"
PS > $punctuation = "!" * 3
PS > $best_learning_platform + $punctuation
Codecademy!!!

Assignment Operators

The Following are compound assignment operators:

= is the default assignment operator that we know

/ +=, -=, *=, /=,%=

PS > $number = 75
PS > $number_1 = $number / 3
PS > $number_1
25
PS > $number_2 = $number
PS > $number_2 /= 3
PS > $number_2
25

//ENV variable example 
PS > $Env:EXAMPLE_ENV_VAR = "custom value"
PS > $Env:EXAMPLE_ENV_VAR += "; another value"
PS > $Env:EXAMPLE_ENV_VAR
custom value; another value

• Unary Operators

  • ++ increases the value of a variable by 1

  • -- decreases the value of a variable by 1

Comparison Operators

Comparison operators are used to compare values, test conditions, or filter elements of a collection such as an array. They return a boolean operators (true or false)

Operator	Description
-eq	Checks if the two operand values are an exact match
-ne	Checks if the two operand values are NOT an exact match
-gt	Checks if the value of the left operand is greater than the value of the right operand
-lt	Checks if the value of the left operand is less than the value of the right operand
-ge	Checks if the value of the left operand is greater OR equal to the value of the right operand
-le	Checks if the value of the left operand is less OR equal to the value of the right operand

PS > $my_num = 5
PS > $my_num -eq 5
True

PS > $my_num -ne 5
False

Logical Operators

Logical operators allow us to combine multiple True/False expressions and statements into complex conditionals.

-and, -or, -xor, -not, !, 

Truth Table

x	y	x -and y	x -or y	x -xor y	-not x
T	T	T	T	F	F
T	F	F	T	T	F
F	T	F	T	T	T
F	F	F	F	F	T