Power Shell – Developer Blog

Cheat Sheet 1

Get-Command                                    # List of all the commands available to PowerShell
                                               # (native binaries in $env:PATH + cmdlets / functions from PowerShell modules)
Get-Command -Module Microsoft*                 # Lst of all the PowerShell commands exported from modules named Microsoft*
Get-Command -Name *item                        # List of all commands ending in "item"

Get-Help                                       # Get all help topics
Get-Help -Name about_Variables                 # Get help for a specific about_* topic (aka. man page)
Get-Help -Name Get-Command                     # Get help for a specific PowerShell function
Get-Help -Name Get-Command -Parameter Module   # Get help for a specific parameter on a specific command

###################################################
# Operators
###################################################

$a = 2                                                    # Basic variable assignment operator
$a += 1                                                   # Incremental assignment operator
$a -= 1                                                   # Decrement assignment operator

$a -eq 0                                                  # Equality comparison operator
$a -ne 5                                                  # Not-equal comparison operator
$a -gt 2                                                  # Greater than comparison operator
$a -lt 3                                                  # Less than comparison operator

$FirstName = 'Trevor'
$FirstName -like 'T*'                                     # Perform string comparison using the -like operator, which supports the wildcard (*) character. Returns $true

$BaconIsYummy = $true
$FoodToEat = $BaconIsYummy ? 'bacon' : 'beets'            # Sets the $FoodToEat variable to 'bacon' using the ternary operator

'Celery' -in @('Bacon', 'Sausage', 'Steak', 'Chicken')    # Returns boolean value indicating if left-hand operand exists in right-hand array
'Celery' -notin @('Bacon', 'Sausage', 'Steak')            # Returns $true, because Celery is not part of the right-hand list

5 -is [string]                                            # Is the number 5 a string value? No. Returns $false.
5 -is [int32]                                             # Is the number 5 a 32-bit integer? Yes. Returns $true.
5 -is [int64]                                             # Is the number 5 a 64-bit integer? No. Returns $false.
'Trevor' -is [int64]                                      # Is 'Trevor' a 64-bit integer? No. Returns $false.
'Trevor' -isnot [string]                                  # Is 'Trevor' NOT a string? No. Returns $false.
'Trevor' -is [string]                                     # Is 'Trevor' a string? Yes. Returns $true.
$true -is [bool]                                          # Is $true a boolean value? Yes. Returns $true.
$false -is [bool]                                         # Is $false a boolean value? Yes. Returns $true.
5 -is [bool]                                              # Is the number 5 a boolean value? No. Returns $false.
/pre>

###################################################
# Regular Expressions
###################################################

'Trevor' -match '^T\w*'                                   # Perform a regular expression match against a string value. # Returns $true and populates $matches variable
$matches[0]                                               # Returns 'Trevor', based on the above match

@('Trevor', 'Billy', 'Bobby') -match '^B'                 # Perform a regular expression match against an array of string values. Returns Billy, Bobby

$regex = [regex]'(\w{3,8})'
$regex.Matches('Trevor Bobby Dillon Joe Jacob').Value     # Find multiple matches against a singleton string value.
/pre>

###################################################
# Flow Control
###################################################

if (1 -eq 1) { }                                          # Do something if 1 is equal to 1

do { 'hi' } while ($false)                                # Loop while a condition is true (always executes at least once)

while ($false) { 'hi' }                                   # While loops are not guaranteed to run at least once
while ($true) { }                                         # Do something indefinitely
while ($true) { if (1 -eq 1) { break } }                  # Break out of an infinite while loop conditionally

for ($i = 0; $i -le 10; $i++) { Write-Host $i }           # Iterate using a for..loop
foreach ($item in (Get-Process)) { }                      # Iterate over items in an array

switch ('test') { 'test' { 'matched'; break } }           # Use the switch statement to perform actions based on conditions. Returns string 'matched'
switch -regex (@('Trevor', 'Daniel', 'Bobby')) {          # Use the switch statement with regular expressions to match inputs
  'o' { $PSItem; break }                                  # NOTE: $PSItem or $_ refers to the "current" item being matched in the array
}
switch -regex (@('Trevor', 'Daniel', 'Bobby')) {          # Switch statement omitting the break statement. Inputs can be matched multiple times, in this scenario.
  'e' { $PSItem }
  'r' { $PSItem }
}
/pre>

###################################################
# Variables
###################################################


$a = 0                                                    # Initialize a variable
[int] $a = 'Trevor'                                       # Initialize a variable, with the specified type (throws an exception)
[string] $a = 'Trevor'                                    # Initialize a variable, with the specified type (doesn't throw an exception)

Get-Command -Name *varia*                                 # Get a list of commands related to variable management

Get-Variable                                              # Get an array of objects, representing the variables in the current and parent scopes 
Get-Variable | ? { $PSItem.Options -contains 'constant' } # Get variables with the "Constant" option set
Get-Variable | ? { $PSItem.Options -contains 'readonly' } # Get variables with the "ReadOnly" option set

New-Variable -Name FirstName -Value Trevor
New-Variable FirstName -Value Trevor -Option Constant     # Create a constant variable, that can only be removed by restarting PowerShell
New-Variable FirstName -Value Trevor -Option ReadOnly     # Create a variable that can only be removed by specifying the -Force parameter on Remove-Variable

Remove-Variable -Name firstname                           # Remove a variable, with the specified name
Remove-Variable -Name firstname -Force                    # Remove a variable, with the specified name, that has the "ReadOnly" option set
/pre>

###################################################
# Functions
###################################################

function add ($a, $b) { $a + $b }                         # A basic PowerShell function

function Do-Something {                                   # A PowerShell Advanced Function, with all three blocks declared: BEGIN, PROCESS, END
  [CmdletBinding]()]
  param ()
  begin { }
  process { }
  end { }
}
/pre>

###################################################
# Working with Modules
###################################################

Get-Command -Name *module* -Module mic*core                 # Which commands can I use to work with modules?

Get-Module -ListAvailable                                   # Show me all of the modules installed on my system (controlled by $env:PSModulePath)
Get-Module                                                  # Show me all of the modules imported into the current session

$PSModuleAutoLoadingPreference = 0                          # Disable auto-loading of installed PowerShell modules, when a command is invoked

Import-Module -Name NameIT                                  # Explicitly import a module, from the specified filesystem path or name (must be present in $env:PSModulePath)
Remove-Module -Name NameIT                                  # Remove a module from the scope of the current PowerShell session

New-ModuleManifest                                          # Helper function to create a new module manifest. You can create it by hand instead.

New-Module -Name trevor -ScriptBlock {                      # Create an in-memory PowerShell module (advanced users)
  function Add($a,$b) { $a + $b } }

New-Module -Name trevor -ScriptBlock {                      # Create an in-memory PowerShell module, and make it visible to Get-Module (advanced users)
  function Add($a,$b) { $a + $b } } | Import-Module
/pre>

###################################################
# Module Management
###################################################

Get-Command -Module PowerShellGet                           # Explore commands to manage PowerShell modules

Find-Module -Tag cloud                                      # Find modules in the PowerShell Gallery with a "cloud" tag
Find-Module -Name ps*                                       # Find modules in the PowerShell Gallery whose name starts with "PS"

Install-Module -Name NameIT -Scope CurrentUser -Force       # Install a module to your personal directory (non-admin)
Install-Module -Name NameIT -Force                          # Install a module to your personal directory (admin / root)
Install-Module -Name NameIT -RequiredVersion 1.9.0          # Install a specific version of a module

Uninstall-Module -Name NameIT                               # Uninstall module called "NameIT", only if it was installed via Install-Module

Register-PSRepository -Name <repo> -SourceLocation <uri>    # Configure a private PowerShell module registry
Unregister-PSRepository -Name <repo>                        # Deregister a PowerShell Repository
/pre>

###################################################
# Filesystem
###################################################

New-Item -Path c:\test -ItemType Directory                  # Create a directory
mkdir c:\test2                                              # Create a directory (short-hand)

New-Item -Path c:\test\myrecipes.txt                        # Create an empty file
Set-Content -Path c:\test.txt -Value ''                     # Create an empty file
[System.IO.File]::WriteAllText('testing.txt', '')           # Create an empty file using .NET Base Class Library

Remove-Item -Path testing.txt                               # Delete a file
[System.IO.File]::Delete('testing.txt')                     # Delete a file using .NET Base Class Library
/pre>

###################################################
# Hashtables (Dictionary)
###################################################

$Person = @{
  FirstName = 'Trevor'
  LastName = 'Sullivan'
  Likes = @(
    'Bacon',
    'Beer',
    'Software'
  )
}                                                           # Create a PowerShell HashTable

$Person.FirstName                                           # Retrieve an item from a HashTable
$Person.Likes[-1]                                           # Returns the last item in the "Likes" array, in the $Person HashTable (software)
$Person.Age = 50                                            # Add a new property to a HashTable
/pre>

###################################################
# Windows Management Instrumentation (WMI) (Windows only)
###################################################

Get-CimInstance -ClassName Win32_BIOS                       # Retrieve BIOS information
Get-CimInstance -ClassName Win32_DiskDrive                  # Retrieve information about locally connected physical disk devices
Get-CimInstance -ClassName Win32_PhysicalMemory             # Retrieve information about install physical memory (RAM)
Get-CimInstance -ClassName Win32_NetworkAdapter             # Retrieve information about installed network adapters (physical + virtual)
Get-CimInstance -ClassName Win32_VideoController            # Retrieve information about installed graphics / video card (GPU)

Get-CimClass -Namespace root\cimv2                          # Explore the various WMI classes available in the root\cimv2 namespace
Get-CimInstance -Namespace root -ClassName __NAMESPACE      # Explore the child WMI namespaces underneath the root\cimv2 namespace
/pre>


###################################################
# Asynchronous Event Registration
###################################################

#### Register for filesystem events
$Watcher = [System.IO.FileSystemWatcher]::new('c:\tmp')
Register-ObjectEvent -InputObject $Watcher -EventName Created -Action {
  Write-Host -Object 'New file created!!!'
}                                                           

#### Perform a task on a timer (ie. every 5000 milliseconds)
$Timer = [System.Timers.Timer]::new(5000)
Register-ObjectEvent -InputObject $Timer -EventName Elapsed -Action {
  Write-Host -ForegroundColor Blue -Object 'Timer elapsed! Doing some work.'
}
$Timer.Start()
/pre>

###################################################
# PowerShell Drives (PSDrives)
###################################################

Get-PSDrive                                                 # List all the PSDrives on the system
New-PSDrive -Name videos -PSProvider Filesystem -Root x:\data\content\videos  # Create a new PSDrive that points to a filesystem location
New-PSDrive -Name h -PSProvider FileSystem -Root '\\storage\h$\data' -Persist # Create a persistent mount on a drive letter, visible in Windows Explorer
Set-Location -Path videos:                                  # Switch into PSDrive context
Remove-PSDrive -Name xyz                                    # Delete a PSDrive
/pre>

###################################################
# Data Management
###################################################

Get-Process | Group-Object -Property Name                   # Group objects by property name
Get-Process | Sort-Object -Property Id                      # Sort objects by a given property name
Get-Process | Where-Object -FilterScript { $PSItem.Name -match '^c' } # Filter objects based on a property matching a value
gps | where Name -match '^c'                                # Abbreviated form of the previous statement
/pre>

###################################################
# PowerShell Classes
###################################################

class Person {
  [string] $FirstName                                       # Define a class property as a string
  [string] $LastName = 'Sullivan'                           # Define a class property with a default value
  [int] $Age                                                # Define a class property as an integer
  
  Person() {                                                # Add a default constructor (no input parameters) for a class
  }
  
  Person([string] $FirstName) {                             # Define a class constructor with a single string parameter
    $this.FirstName = $FirstName
  }
  
  [string] FullName() {
    return '{0} {1}' -f $this.FirstName, $this.LastName
  }
}
$Person01 = [Person]::new()                                 # Instantiate a new Person object.
$Person01.FirstName = 'Trevor'                              # Set the FirstName property on the Person object.
$Person01.FullName()                                        # Call the FullName() method on the Person object. Returns 'Trevor Sullivan'


class Server {                                              # Define a "Server" class, to manage remote servers. Customize this based on your needs.
  [string] $Name
  [System.Net.IPAddress] $IPAddress                         # Define a class property as an IPaddress object
  [string] $SSHKey = "$HOME/.ssh/id_rsa"                    # Set the path to the private key used to authenticate to the server
  [string] $Username                                        # Set the username to login to the remote server with
  
  RunCommand([string] $Command) {                           # Define a method to call a command on the remote server, via SSH
    ssh -i $this.SSHKey $this.Username@$this.Name $this.Command
  }
}

$Server01 = [Server]::new()                                 # Instantiate the Server class as a new object
$Server01.Name = 'webserver01.local'                        # Set the "name" of the remote server
$Server01.Username = 'root'                                 # Set the username property of the "Server" object
$Server01.RunCommand("hostname")                            # Run a command on the remote server
/pre>

###################################################
# REST APIs
###################################################

$Params = @{
  Uri = 'https://api.github.com/events'
  Method = 'Get'
}
Invoke-RestMethod @Params                                   # Call a REST API, using the HTTP GET method

Learning Powershell in 5 Minutes

Comments

# Single line comments start with a number symbol.

<#
  Multi-line comments
  like so
#>
/pre>

Primitive Datatypes and Operators

####################################################
## 1. Primitive Datatypes and Operators
####################################################

# Numbers
3 # => 3

# Math
1 + 1   # => 2
8 - 1   # => 7
10 * 2  # => 20
35 / 5  # => 7.0

# Powershell uses banker's rounding,
# meaning [int]1.5 would round to 2 but so would [int]2.5
# Division always returns a float. 
# You must cast result to [int] to round.
[int]5 / [int]3       # => 1.66666666666667
[int]-5 / [int]3      # => -1.66666666666667
5.0 / 3.0   # => 1.66666666666667
-5.0 / 3.0  # => -1.66666666666667
[int]$result = 5 / 3 
$result # => 2

# Modulo operation
7 

# Exponentiation requires longform or the built-in [Math] class.
[Math]::Pow(2,3)  # => 8

# Enforce order of operations with parentheses.
1 + 3 * 2  # => 7
(1 + 3) * 2  # => 8

# Boolean values are primitives (Note: the $)
$True  # => True
$False  # => False

# negate with !
!$True   # => False
!$False  # => True

# Boolean Operators
# Note "-and" and "-or" usage
$True -and $False  # => False
$False -or $True   # => True

# True and False are actually 1 and 0 but only support limited arithmetic.
# However, casting the bool to int resolves this.
$True + $True # => 2
$True * 8    # => '[System.Boolean] * [System.Int32]' is undefined
[int]$True * 8 # => 8
$False - 5   # => -5

# Comparison operators look at the numerical value of True and False.
0 -eq $False  # => True
1 -eq $True   # => True
2 -eq $True   # => False
-5 -ne $False # => True

# Using boolean logical operators on ints casts to booleans for evaluation.
# but their non-cast value is returned
# Don't mix up with bool(ints) and bitwise -band/-bor
[bool](0)     # => False
[bool](4)     # => True
[bool](-6)    # => True
0 -band 2     # => 0
-5 -bor 0     # => -5

# Equality is -eq (equals)
1 -eq 1  # => True
2 -eq 1  # => False

# Inequality is -ne (notequals)
1 -ne 1  # => False
2 -ne 1  # => True

# More comparisons
1 -lt 10  # => True
1 -gt 10  # => False
2 -le 2  # => True
2 -ge 2  # => True

# Seeing whether a value is in a range
1 -lt 2 -and 2 -lt 3  # => True
2 -lt 3 -and 3 -lt 2  # => False

# (-is vs. -eq) -is checks if two objects are the same type.
# -eq checks if the objects have the same values.
# Note: we called '[Math]' from .NET previously without the preceeding
# namespaces. We can do the same with [Collections.ArrayList] if preferred.
[System.Collections.ArrayList]$a = @()  # Point a at a new list
$a = (1,2,3,4)
$b = $a                                 # => Point b at what a is pointing to
$b -is $a.GetType()                     # => True, a and b equal same type
$b -eq $a                               # => True, a and b values are equal
[System.Collections.Hashtable]$b = @{}  # => Point a at a new hash table
$b = @{'one' = 1 
       'two' = 2}
$b -is $a.GetType()                     # => False, a and b types not equal

# Strings are created with " or ' but " is required for string interpolation
"This is a string."
'This is also a string.'

# Strings can be added too! But try not to do this.
"Hello " + "world!"  # => "Hello world!"

# A string can be treated like a list of characters
"Hello world!"[0]  # => 'H'

# You can find the length of a string
("This is a string").Length  # => 16

# You can also format using f-strings or formatted string literals.
$name = "Steve"
$age = 22
"He said his name is $name." 
# => "He said his name is Steve"
"{0} said he is {1} years old." -f $name, $age 
# => "Steve said he is 22 years old"
"$name's name is $($name.Length) characters long." 
# => "Steve's name is 5 characters long."

# Escape Characters in Powershell
# Many languages use the '\', but Windows uses this character for 
# file paths. Powershell thus uses '`' to escape characters
# Take caution when working with files, as '`' is a
# valid character in NTFS filenames.
"Showing`nEscape Chars" # => new line between Showing and Escape
"Making`tTables`tWith`tTabs" # => Format things with tabs

# Negate pound sign to prevent comment
# Note that the function of '#' is removed, but '#' is still present
`#Get-Process # => Fail: not a recognized cmdlet

# $null is not an object
$null  # => None

# $null, 0, and empty strings and arrays all evaluate to False.
# All other values are True
function Test-Value ($value) {
  if ($value) {
    Write-Output 'True'
  }
  else {
    Write-Output 'False'
  }
}

Test-Value ($null) # => False
Test-Value (0)     # => False
Test-Value ("")    # => False
Test-Value []      # => True 
# *[] calls .NET class; creates '[]' string when passed to function
Test-Value ({})    # => True
Test-Value @()     # => False

/pre>

####################################################
## 2. Variables and Collections
####################################################

# Powershell uses the "Write-Output" function to print
Write-Output "I'm Posh. Nice to meet you!"  # => I'm Posh. Nice to meet you!

# Simple way to get input data from console
$userInput = Read-Host "Enter some data: " # Returns the data as a string

# There are no declarations, only assignments.
# Convention is to use camelCase or PascalCase, whatever your team uses.
$someVariable = 5
$someVariable  # => 5

# Accessing a previously unassigned variable does not throw exception.
# The value is $null by default

# Ternary Operators exist in Powershell 7 and up
0 ? 'yes' : 'no'  # => no


# The default array object in Powershell is an fixed length array.
$defaultArray = "thing","thing2","thing3"
# you can add objects with '+=', but cannot remove objects.
$defaultArray.Add("thing4") # => Exception "Collection was of a fixed size."
# To have a more workable array, you'll want the .NET [ArrayList] class
# It is also worth noting that ArrayLists are significantly faster

# ArrayLists store sequences
[System.Collections.ArrayList]$array = @()
# You can start with a prefilled ArrayList
[System.Collections.ArrayList]$otherArray = @(4, 5, 6)

# Add to the end of a list with 'Add' (Note: produces output, append to $null)
$array.Add(1) > $null    # $array is now [1]
$array.Add(2) > $null    # $array is now [1, 2]
$array.Add(4) > $null    # $array is now [1, 2, 4]
$array.Add(3) > $null    # $array is now [1, 2, 4, 3]
# Remove from end with index of count of objects-1; array index starts at 0
$array.RemoveAt($array.Count-1) # => 3 and array is now [1, 2, 4]
# Let's put it back
$array.Add(3) > $null   # array is now [1, 2, 4, 3] again.

# Access a list like you would any array
$array[0]   # => 1
# Look at the last element
$array[-1]  # => 3

# Looking out of bounds returns nothing
$array[4]  # blank line returned

# You can look at ranges with slice syntax.
# The start index is included, the end index is not
# (It's a closed/open range for you mathy types.)
$array[1..3]   # Return array from index 1 to 3 => [2, 4]
$array[2..-1]    # Return array starting from index 2 => [4, 3]
$array[0..3]    # Return array from beginning until index 3  => [1, 2, 4]
$array[0..2]   # Return array selecting every second entry => [1, 4]
$array.Reverse()  # mutates array to reverse order => [3, 4, 2, 1]
# Use any combination of these to make advanced slices

# Remove arbitrary elements from a array with "del"
$array.Remove($array[2])  # $array is now [1, 2, 3]

# Insert an element at a specific index
$array.Insert(1, 2)  # $array is now [1, 2, 3] again

# Get the index of the first item found matching the argument
$array.IndexOf(2)  # => 1
$array.IndexOf(6)  # Returns -1 as "outside array" 

# You can add arrays
# Note: values for $array and for $otherArray are not modified.
$array + $otherArray  # => [1, 2, 3, 4, 5, 6]

# Concatenate arrays with "AddRange()"
$array.AddRange($otherArray)  # Now $array is [1, 2, 3, 4, 5, 6]

# Check for existence in a array with "in"
1 -in $array  # => True

# Examine length with "Count" (Note: "Length" on arrayList = each items length)
$array.Count  # => 6


# Tuples are like arrays but are immutable.
# To use Tuples in powershell, you must use the .NET tuple class.
$tuple = [System.Tuple]::Create(1, 2, 3)
$tuple.Item(0)      # => 1
$tuple.Item(0) = 3  # Raises a TypeError

# You can do some of the array methods on tuples, but they are limited.
$tuple.Length       # => 3
$tuple + (4, 5, 6)  # => Exception
$tuple[0..2]        # => $null
2 -in $tuple        # => False


# Hashtables store mappings from keys to values, similar to Dictionaries.
$emptyHash = @{}
# Here is a prefilled dictionary
$filledHash = @{"one"= 1 
                "two"= 2 
                "three"= 3}

# Look up values with []
$filledHash["one"]  # => 1

# Get all keys as an iterable with ".Keys".
# items maintain the order at which they are inserted into the dictionary.
$filledHash.Keys  # => ["one", "two", "three"]

# Get all values as an iterable with ".Values".
$filledHash.Values  # => [1, 2, 3]

# Check for existence of keys or values in a hash with "-in"
"one" -in $filledHash.Keys  # => True
1 -in $filledHash.Values    # => False

# Looking up a non-existing key returns $null
$filledHash["four"]  # $null

# Adding to a dictionary
$filledHash.Add("five",5)  # $filledHash["five"] is set to 5
$filledHash.Add("five",6)  # exception "Item with key "five" has already been added"
$filledHash["four"] = 4 # $filledHash["four"] is set to 4, running again does nothing

# Remove keys from a dictionary with del
$filledHash.Remove("one") # Removes the key "one" from filled dict

/pre>

####################################################
## 3. Control Flow and Iterables
####################################################

# Let's just make a variable
$someVar = 5

# Here is an if statement.
# This prints "$someVar is smaller than 10"
if ($someVar -gt 10) {
    Write-Output "$someVar is bigger than 10."
}
elseif ($someVar -lt 10) {    # This elseif clause is optional.
    Write-Output "$someVar is smaller than 10."
}
else {                        # This is optional too.
    Write-Output "$someVar is indeed 10."
}


<#
Foreach loops iterate over arrays
prints:
    dog is a mammal
    cat is a mammal
    mouse is a mammal
#>
foreach ($animal in ("dog", "cat", "mouse")) {
    # You can use -f to interpolate formatted strings
    "{0} is a mammal" -f $animal
}

<#
For loops iterate over arrays and you can specify indices
prints:
   0 a
   1 b
   2 c
   3 d
   4 e
   5 f
   6 g
   7 h
#>
$letters = ('a','b','c','d','e','f','g','h')
for($i=0; $i -le $letters.Count-1; $i++){
    Write-Host $i, $letters[$i]
}

<#
While loops go until a condition is no longer met.
prints:
    0
    1
    2
    3
#>
$x = 0
while ($x -lt 4) {
    Write-Output $x
    $x += 1  # Shorthand for x = x + 1
}

# Switch statements are more powerful compared to most languages
$val = "20"
switch($val) {
  { $_ -eq 42 }           { "The answer equals 42"; break }
  '20'                    { "Exactly 20"; break }
  { $_ -like 's*' }       { "Case insensitive"; break }
  { $_ -clike 's*'}       { "clike, ceq, cne for case sensitive"; break }
  { $_ -notmatch '^.*$'}  { "Regex matching. cnotmatch, cnotlike, ..."; break }
  default                 { "Others" }
}

# Handle exceptions with a try/catch block
try {
    # Use "throw" to raise an error
    throw "This is an error"
}
catch {
    Write-Output $Error.ExceptionMessage
}
finally {
    Write-Output "We can clean up resources here"
}


# Writing to a file
$contents = @{"aa"= 12 
             "bb"= 21}
$contents | Export-CSV "$env:HOMEDRIVE\file.csv" # writes to a file

$contents = "test string here"
$contents | Out-File "$env:HOMEDRIVE\file.txt" # writes to another file

# Read file contents and convert to json
Get-Content "$env:HOMEDRIVE\file.csv" | ConvertTo-Json

/pre>

####################################################
## 4. Functions
####################################################

# Use "function" to create new functions
# Keep the Verb-Noun naming convention for functions
function Add-Numbers {
 $args[0] + $args[1]
}

Add-Numbers 1 2 # => 3

# Calling functions with parameters
function Add-ParamNumbers {
 param( [int]$firstNumber, [int]$secondNumber )
 $firstNumber + $secondNumber
}

Add-ParamNumbers -FirstNumber 1 -SecondNumber 2 # => 3 

# Functions with named parameters, parameter attributes, parsable documentation
<#
.SYNOPSIS
Setup a new website
.DESCRIPTION
Creates everything your new website needs for much win
.PARAMETER siteName
The name for the new website
.EXAMPLE
New-Website -Name FancySite -Po 5000
New-Website SiteWithDefaultPort
New-Website siteName 2000 # ERROR! Port argument could not be validated
('name1','name2') | New-Website -Verbose
#>
function New-Website() {
    [CmdletBinding()]
    param (
        [Parameter(ValueFromPipeline=$true, Mandatory=$true)]
        [Alias('name')]
        [string]$siteName,
        [ValidateSet(3000,5000,8000)]
        [int]$port = 3000
    )
    BEGIN { Write-Output 'Creating new website(s)' }
    PROCESS { Write-Output "name: $siteName, port: $port" }
    END { Write-Output 'Website(s) created' }
}
/pre>

####################################################
## 5. Modules
####################################################

# You can import modules and install modules
# The Install-Module is similar to pip or npm, pulls from Powershell Gallery
Install-Module dbaTools
Import-Module dbaTools

$query = "SELECT * FROM dbo.sometable"
$queryParams = @{
    SqlInstance = 'testInstance'
    Database    = 'testDatabase'
    Query       = $query
}
Invoke-DbaQuery @queryParams

# You can get specific functions from a module
Import-Module -Function Invoke-DbaQuery


# Powershell modules are just ordinary Posh files. You
# can write your own, and import them. The name of the
# module is the same as the name of the file.

# You can find out which functions and attributes
# are defined in a module.
Get-Command -module dbaTools
Get-Help dbaTools -Full

/pre>

####################################################
## 6. Classes
####################################################

# We use the "class" statement to create a class
class Instrument {
    [string]$Type
    [string]$Family
}

$instrument = [Instrument]::new()
$instrument.Type = "String Instrument"
$instrument.Family = "Plucked String"

$instrument

<# Output:
Type              Family        
----              ------        
String Instrument Plucked String
#>

/pre>

####################################################
## 6.1 Inheritance
####################################################

# Inheritance allows new child classes to be defined that inherit 
# methods and variables from their parent class.

class Guitar : Instrument
{
    [string]$Brand
    [string]$SubType
    [string]$ModelType
    [string]$ModelNumber
}

$myGuitar = [Guitar]::new()
$myGuitar.Brand       = "Taylor"
$myGuitar.SubType     = "Acoustic"
$myGuitar.ModelType   = "Presentation"
$myGuitar.ModelNumber = "PS14ce Blackwood"

$myGuitar.GetType()

<#
IsPublic IsSerial Name                                     BaseType                                               
-------- -------- ----                                     --------                                               
True     False    Guitar                                   Instrument  
#>

/pre>

####################################################
## 7. Advanced
####################################################

# The powershell pipeline allows things like High-Order Functions.

# Group-Object is a handy cmdlet that does incredible things.
# It works much like a GROUP BY in SQL.

<#
 The following will get all the running processes,
 group them by Name,
 and tell us how many instances of each process we have running.
 Tip: Chrome and svcHost are usually big numbers in this regard.
#>
Get-Process | Foreach-Object ProcessName | Group-Object

# Useful pipeline examples are iteration and filtering.
1..10 | ForEach-Object { "Loop number $PSITEM" }
1..10 | Where-Object { $PSITEM -gt 5 } | ConvertTo-Json

# A notable pitfall of the pipeline is it's performance when
# compared with other options.
# Additionally, raw bytes are not passed through the pipeline,
# so passing an image causes some issues.
# See more on that in the link at the bottom.

<#
 Asynchronous functions exist in the form of jobs.
 Typically a procedural language,
 Powershell can operate non-blocking functions when invoked as Jobs.
#>

# This function is known to be non-optimized, and therefore slow.
$installedApps = Get-CimInstance -ClassName Win32_Product

# If we had a script, it would hang at this func for a period of time.
$scriptBlock = {Get-CimInstance -ClassName Win32_Product}
Start-Job -ScriptBlock $scriptBlock

# This will start a background job that runs the command.
# You can then obtain the status of jobs and their returned results.
$allJobs = Get-Job
$jobResponse = Get-Job | Receive-Job


# Math is built in to powershell and has many functions.
$r=2
$pi=[math]::pi
$r2=[math]::pow( $r, 2 )
$area = $pi*$r2
$area

# To see all possibilities, check the members.
[System.Math] | Get-Member -Static -MemberType All


<#
 This is a silly one:
 You may one day be asked to create a func that could take $start and $end
 and reverse anything in an array within the given range
 based on an arbitrary array without mutating the original array.
 Let's see one way to do that and introduce another data structure.
#>

$targetArray = 'a','b','c','d','e','f','g','h','i','j','k','l','m'

function Format-Range ($start, $end, $array) {
    [System.Collections.ArrayList]$firstSectionArray = @()
    [System.Collections.ArrayList]$secondSectionArray = @()
    [System.Collections.Stack]$stack = @()
    for ($index = 0; $index -lt $array.Count; $index++) {
        if ($index -lt $start) {
            $firstSectionArray.Add($array[$index]) > $null
        }
        elseif ($index -ge $start -and $index -le $end) {
            $stack.Push($array[$index])
        }
        else {
            $secondSectionArray.Add($array[$index]) > $null
        }
    }
    $finalArray = $firstSectionArray + $stack.ToArray() + $secondSectionArray
    return $finalArray
}

Format-Range 2 6 $targetArray 
# => 'a','b','g','f','e','d','c','h','i','j','k','l','m'

# The previous method works, but uses extra memory by allocating new arrays.
# It's also kind of lengthy.
# Let's see how we can do this without allocating a new array.
# This is slightly faster as well.

function Format-Range ($start, $end) {
  while ($start -lt $end)
  {
      $temp = $targetArray[$start]
      $targetArray[$start] = $targetArray[$end]
      $targetArray[$end] = $temp
      $start++
      $end--
  }
  return $targetArray
}

Format-Range 2 6 # => 'a','b','g','f','e','d','c','h','i','j','k','l','m'

# Find commands
Get-Command about_* # alias: gcm
Get-Command -Verb Add
Get-Alias ps
Get-Alias -Definition Get-Process

Get-Help ps | less # alias: help
ps | Get-Member # alias: gm

Show-Command Get-WinEvent # Display GUI to fill in the parameters

Update-Help # Run as admin

Get-ExecutionPolicy -List
Set-ExecutionPolicy AllSigned
# Execution policies include:
# - Restricted: Scripts won't run.
# - RemoteSigned: Downloaded scripts run only if signed by a trusted publisher. 
# - AllSigned: Scripts need to be signed by a trusted publisher.
# - Unrestricted: Run all scripts.
help about_Execution_Policies # for more info

# Current PowerShell version:
$PSVersionTable

# Calling external commands, executables, 
# and functions with the call operator.
# Exe paths with arguments passed or containing spaces can create issues.
C:\Program Files\dotnet\dotnet.exe
# The term 'C:\Program' is not recognized as a name of a cmdlet,
# function, script file, or executable program.
# Check the spelling of the name, or if a path was included, 
# verify that the path is correct and try again

"C:\Program Files\dotnet\dotnet.exe"
C:\Program Files\dotnet\dotnet.exe    # returns string rather than execute

&"C:\Program Files\dotnet\dotnet.exe --help"   # fail
&"C:\Program Files\dotnet\dotnet.exe" --help   # success
# Alternatively, you can use dot-sourcing here
."C:\Program Files\dotnet\dotnet.exe" --help   # success

# the call operator (&) is similar to Invoke-Expression, 
# but IEX runs in current scope.
# One usage of '&' would be to invoke a scriptblock inside of your script.
# Notice the variables are scoped
$i = 2
$scriptBlock = { $i=5; Write-Output $i }
& $scriptBlock # => 5
$i # => 2

invoke-expression ' $i=5; Write-Output $i ' # => 5
$i # => 5

# Alternatively, to preserve changes to public variables
# you can use "Dot-Sourcing". This will run in the current scope.
$x=1
&{$x=2};$x # => 1

.{$x=2};$x # => 2


# Remoting into computers is easy.
Enter-PSSession -ComputerName RemoteComputer

# Once remoted in, you can run commands as if you're local.
RemoteComputer\PS> Get-Process powershell

<#
Handles  NPM(K)    PM(K)      WS(K)     CPU(s)     Id  SI ProcessName                                             
-------  ------    -----      -----     ------     --  -- -----------                                             
   1096      44   156324     179068      29.92  11772   1 powershell                                              
    545      25    49512      49852             25348   0 powershell 
#>
RemoteComputer\PS> Exit-PSSession

<#
 Powershell is an incredible tool for Windows management and Automation.
 Let's take the following scenario:
 You have 10 servers.
 You need to check whether a service is running on all of them.
 You can RDP and log in, or PSSession to all of them, but why?
 Check out the following
#>

$serverList = @(
    'server1',
    'server2',
    'server3',
    'server4',
    'server5',
    'server6',
    'server7',
    'server8',
    'server9',
    'server10'
)

[scriptblock]$script = {
    Get-Service -DisplayName 'Task Scheduler'
}

foreach ($server in $serverList) {
    $cmdSplat = @{
        ComputerName  = $server
        JobName       = 'checkService'
        ScriptBlock   = $script
        AsJob         = $true
        ErrorAction   = 'SilentlyContinue'
    }
    Invoke-Command @cmdSplat | Out-Null
}

<#
 Here we've invoked jobs across many servers.
 We can now Receive-Job and see if they're all running.
 Now scale this up 100x as many servers :)
#>

Cheat Sheet 2

PowerShell Commands Cheat Sheet

cmdlets

Cmdlets are PowerShell’s internal commands. These cmdlets will return one or more objects to the pipeline where at the end of that pipeline, we mention some properties of the objects in the following table to see their values displayed on the screen.

Command	Description
`Get-Help`	This command allows you to get support with PowerShell.
`Get-PSdrive`	This command offers you a list of available PSDrives, such as c, env, hklm, hkcu, alias, etc.
`Get-ChildItem`	In any registry, children are the subkeys of the current key. To get the required details, you can use the following command.
`Get-ChildItem -recurse`	Run this command to list all the children recursively of the current PSdrive, folder, or registry key.
`Get-ChildItem -rec -force`	Use this command To include the hidden folders (directories).
`(Get-ChildItem).name or Get-ChildItem -name`	Run any of these commands to get the list file and directory names in the current folder.
`(Get-ChildItem).count`	Use this command to get the number of entries in the collection of objects returned by the Get-Children.

PSdrives

PSdrives are the collection of entities grouped together so they can be accessed as a filesystem drive. The “PSprovider” does this grouping.

By default, a PS session can access several PSdrives including c:, env:, alias:, and HKLM:, where c: refers to the usual Windows c-drive; env: is the space of Windows environmental variables; alias: is the collection of cmdlet aliases; and HKLM is a hive in the registry.

Any PS session will enter the user’s home folder. If you want to switch from a PS session to another PSdrive and retrieve the information from that drive, consider the following commands:

Commands	Description
`Switching to env-`	The prompt character will change to the “ENV:\>”. Set-Location env by running the following command: `Set-Location env-`
`Env:\> Get-Childitem`	This command will get you all the environment variables.
`Env:\> Get-Childitem userprofile`	Use this command to get the environment variables of “userprofile.”
`Env:\> Set-Location alias:`	Run the following command to change the prompt character to “Alias.”
`Alias:\> Get-Childitem`	Run this command to get all the children of all aliases.
`Alias:\> Set-Location C:\`	Use this command to get the “C:/>” prompt again, back to the default drive.
`C:\Users\user_name>$alias:ls`	Run this command to find what alias “ls” stands for.

Pipelines

Cmdlets uses the pipelines to pass the objects but not the character streams like Unix. The pipeline character is | (ASCII 124), followed by a command that handles the output passed through the pipeline. The pipeline consists of the following three stages.

Get-ChildItem *.txt | Where-Object length -lt 1000 | Sort-Object length

The following table highlights some of the basic pipeline commands:

Command	Description
`(Get-Item /Users/praashibansal/Desktop).lastwritetime.year`	Easily sets the value of the ‘lastwritetime.year’ property to the present date and time without affecting the file’s content.
`(Get-ChildItem data.txt.rtf -name).name # -> null`	Provides an empty result
`"data.txt.rtf" \| Rename-Item -NewName "data_new.txt.rtf"`	Changes the old file names and file extensions to the new ones
`Get-ChildItem data.txt \| Rename-Item -new {$_.name}`	A trivial renaming command that invokes an automatic variable
`Get-ChildItem data.txt.rtf -name \| Rename-Item -new {$_.name}`	If the piped object $_ doesn’t have the member property (name), you will receive an error, as parameter $_.name is null
`Get-ChildItem \| Select-Object basename \| Sort-Object *`	Displays the list of the names of all the files that are present in the current folder sorted in alphabetical order.
`Move-Item *.txt subdirectory`	Moves all the files to the folder subdirectory
`Get-ChildItem *.txt \| Move-Item ..\`	Gives the error message that Move-Item lacks input

Alias

Cmdlets come with several aliases. The following table highlights a few of aliases, along with their descriptions:

Command	Description
`Add-Content`	Appends value to a file
`Get-Content`	Finds file content in an array
`Set-Location`	Changes folder, key, or PS drive
`Clear-Host`	Clears console
`Remove-Item`	Delete files
`Get-ChildItem -Path .\`	Lists Folder, Key, or PSDrive Children
`Write-Output`	Sends the array to the console, pipeline, or redirect it to the file
`Foreach-Object`	Traverses each object in a pipeline
`Format-Table`	Formats the table with selected properties for each object in each column
`Format-List`	Formats the process properties by name
`Get-Alias`	Provides Cmdlet Alias
`Get-Command`	Provides you with commands from the current session only
`Get-Member`	Retrieves all the object members
`Get-ItemProperty .\data.txt \| Format-List`	Provides the specified item’s properties
`Get-ItemPropertyValue -Path '.\data.txt' -Name LastWriteTime`	Gives the current value for a specified property while using the name parameter
`Get-Variable m*`	Finds session variable names and sessions
`New-Item -Path .\ -Name "testfile1.txt" -ItemType "file" -Value "This is a text string."`	Creates a new file, directory, symbolic link, registry key, or registry entry
`Get-Process`	Gives the entire list of all the running processes
`Get-Location`	Provides the current directory’s or registry key’s location
`Rename-Item -Path “old_name” -NewName “new_name”`	Renames the old item name with the new name
`Remove-Item .\testfile1.txt`	Removes the specified directory, files, or registry keys
`Remove-Variable`	Removes the specified variable
`Start-Sleep`	Suspends an activity for a specified period of time