PowerShell for beginners

When working with PowerShell, the first thing we encounter is commands (Cmdlets).
The command invocation looks like this:

Verb-Noun -Parameter1 ValueType1 -Parameter2 ValueType2[]

Help

To access help in PowerShell, use the Get-Help command. You can specify one of the parameters: example, detailed, full, online, showWindow.

Get-Help Get-Service -full will return a complete description of how the Get-Service command works.
Get-Help Get-S* will show all available commands and functions starting with Get-S*

There is also detailed documentation on the official Microsoft site.

Here is an example of help for the Get-EventLog command.

If parameters are enclosed in square brackets [], then they are optional.
So in this example, the log name is mandatory, while the parameter name is not. If the parameter type and its name are enclosed in brackets together, then this parameter is optional.

Looking at the EntryType parameter, we see values that are enclosed in curly braces. For this parameter, we can only use predefined values in curly braces.

Information on whether a parameter is mandatory can be found in the description below in the Required field. In the example above, the After attribute is optional, as false is indicated next to Required. Then we see the Position field, next to which it says Named. This indicates that the parameter can only be accessed by name, that is:

Get-EventLog -LogName Application -After 2020.04.26

Since the LogName parameter was indicated with 0 instead of Named, this means we can access the parameter without a name, specifying it in the correct order:

Get-EventLog Application -After 2020.04.26

Let's suppose this order:

Get-EventLog -Newest 5 Application

Alias

To use familiar commands from the console in PowerShell, there are aliases.

An example of an alias for the Set-Location command is cd.

So instead of invoking the command

Set-Location “D:”

we can use

cd “D:”

History

To see the history of command calls, you can use Get-History.

Run a command from the history Invoke-History 1; Invoke-History 2

Clear history Clear-History

Pipeline

The pipeline in PowerShell is when the result of the first function is passed to the second. Here is an example of using the pipeline:

Get-Verb | Measure-Object

But to better understand the pipeline, let's take a simpler example. There is a command

Get-Verb "get"

If you call Get-Help Get-Verb -Full, you will see that the Verb parameter accepts pipeline input and it is noted in parentheses as ByValue.

This means that we can rewrite Get-Verb "get" to "get" | Get-Verb.
Thus, the result of the first expression is a string that is passed to the Verb parameter of the Get-Verb command through pipeline input by value.
Additionally, pipeline input can be ByPropertyName. In this case, we will be passing an object that has a property with a similar name to Verb.

Variables

Variables are not strictly typed and are defined with a $ sign in front.

$example = 4

The symbol > means to place data into
For example, $example > File.txt
This expression places the data from the $example variable into a file.
Similar to the command Set-Content -Value $example -Path File.txt

Arrays

Array initialization:

$ArrayExample = @(“First”, “Second”)

Initializing an empty array:

$ArrayExample = @()

Getting a value by index:

$ArrayExample[0]

Get the entire array:

$ArrayExample

Adding an element:

$ArrayExample += “Third”

$ArrayExample += @(“Fourth”, “Fifth”)

Sorting:

$ArrayExample | Sort

$ArrayExample | Sort -Descending

But the array itself remains unchanged during this sorting. If we want the array to contain sorted data, we need to assign the sorted values:

$ArrayExample = $ArrayExample | Sort

In fact, there is no concept of deleting an element from the array in PowerShell, but it can be done like this:

$ArrayExample = $ArrayExample | where { $_ -ne “First” }

$ArrayExample = $ArrayExample | where { $_ -ne $ArrayExample[0] }

Deleting the array:

$ArrayExample = $null

Loops

Loop syntax:

for($i = 0; $i -lt 5; $i++){}

$i = 0
while($i -lt 5){}

$i = 0
do{} while($i -lt 5)

$i = 0
do{} until($i -lt 5)

ForEach($item in $items){}

Exit from the loop break.

Skip an element continue.

Conditional Statements

if () {} elseif () {} else

switch($someIntValue){
  1 { “Option 1” }
  2 { “Option 2” }
  default { “Not set” }
}

Function

Function definition:

function Example () {
  echo &args
}

Calling the function:

Example “First argument” “Second argument”

Defining arguments in the function:

function Example () {
  param($first, $second)
}

function Example ($first, $second) {}

Calling the function:

Example -first “First argument” -second “Second argument”

Exception

try{
} catch [System.Net.WebException],[System.IO.IOException]{
} catch {
} finally{
}

Source: habr.com