Working with your OS

Working with Your OS

• Console started as hardware like a typewriter connecting to a mainframe
• The console ran terminal software, communicating with the mainframe
• A terminal emulator combines the console and terminal functions
• The terminal, provides the CLI environment, accepting commands and passing them to a shell
• PowerShell has cmdlets

Shell Prompts

• The shell controls the prompt
• PS C:\Users\Miles McDonald> indicates PowerShell
• C:\Users\Miles McDonald> indicates cmd
• The prompt can be changed and is followed by the command line

VS Code Intro

• Create a folder structure, for example a folder named ‘OS’ with an internal folder named 'Week 9 Scripts'
• Open VS Code, and open the created folder
• Create new scripts with the icon or by pressing Ctrl+N
• Select PowerShell 7 as the language by clicking the bottom right-hand side corner
• You can get auto-complete by typing: Get-Process
• Right-click and choose ‘Run Selection’ will execute the current line

Displaying and Stopping Processes

• Running Get-Process will display the processes on your device in the terminal window
• Running Get-Process -Name Notepad will display Notepad details; if not running, it gives a red line
• Use Stop-Process -Name Notepad to close Notepad
• Use Control + ~ to Open/close the terminal window in VS Code
• Press F1 to change the colour theme etc

PowerShell Overview

• PowerShell is based on the .Net Framework and incorporates technologies like WMI
• PowerShell is both a shell and a scripting language
• Learning PowerShell is essential for network administrators
• Open PowerShell 7 as administrator and type Get-Help
• Press 'Return'

PowerShell Scripts

• PowerShell is built upon objects
• Important commands include those to filter, sort, and select objects
• Uses the '$_.', syntax familiar with the environment

PowerShell 7 vs. CLI

• CLI (bash or Command Prompt) commands return text
• Using PowerShell CLI commands you can pipe text to another command

Objects

• PowerShell commands return objects
• Objects have properties like name, path, and extension

PowerShell and the 'ls' Command

• Run 'ls' in PowerShell to see results similar to 'bash'
• 'ls' produces a table showing objects in a text format
• Use a pipe (|) to pass the object over for the command Format-List
• Is was taken by PowerShell and formatted via pipe internally as: Is | Format-Table

Get-Process Command

• It lists all the processes running
• Get-Process | Format-List shows the same processes in a different format

Measure Cmdlet

• Measure is short for Measure-Object which tells you the number of objects you get back
• Example: ls | Measure

Important Commands

• Where command limits responses to objects matching the command's restrictions

The $_ Syntax

• 'Where' can run conditions on every item
• $_ refers to the indicated item, telling the computer to fill in the blank
• Dot (.) tells PowerShell to access a specific property on the object

ForEach Cmdlet

• ForEach is used in two different ways
• Ls provides the three objects, which are then given to ForEach
• ForEach runs the code specified for each of the files found

Basic Exercise

• To get processes with an ID above 4000 and calculate the average CPU time, use: Get-Process | where { $.ID -gt 4000} | Sort {$.CPU} | ForEach {$_.CPU} | Measure -Average

Navigating Folders

• Use Set-Location to change the current directory

Aliases

• Aliases are shortcuts for commands
• example, where is an alias for where-object
• Ls is an alias for Get-ChildItem, listing child parts of the current location

PS Drives

• PowerShell organizes everything into drives
• Windows hard disks and devices show up as drives
• Navigate entry to the registry drive using cd HKCU:
• Run find a list Is to show the listing of all the registry entries

Cmdlets

• Cmdlets are PowerShell commands which are objects, using a verb-noun format

New-Item Cmdlet

• Creates new items and sets their value, depending on the location
• Use get-help cmdlet to get information about the New-Item cmdlet

Creating a New File

• Example: New-Item -Path -Name "tcp.txt" -ItemType "file" -Value "transmission control protocol"
• It creates files with the date and length

Content Cmdlets

• Add-Content cmdlet adds to text files
• Get-Content cmdlet gets the content of text files

Discovering Parameters

• Parameters provide details for commands
• The Syntax is: Get-Help (followed by) ‘some command'
• Optional parameters reside within square brackets

Standard and Non-Standard Filtering

• For standard filtering: Is | where { $_.Extension -eq '.txt'}
• Using non-standard filtering is: Ls *.txt

Discovering Cmdlets

• Cmdlet names are logical, following a verb-noun structure
• Complete using tab: Get-Network(tab here)
• This will complete for you if it is right: Get-NetworkSwitchEthernetPort

Command Discovery

• To list potential commands run: Get-Command
• To search commands using wildcards (), run: Get-Command | where {$_.Name -like ‘Get-'}

PowerShell Modules

• PowerShell's internal structure includes modules, libraries, .NET Framework, and CLR

Variables and Operators

• Use variables to perform function results once to reuse them

Creating Variables

• Create variables using $var
• Create an inquiry for Get-Process for CPU usage over 20: $heavyProcesses
• Set variable equal to the return from our Get-Process enquiry

Variable Reuse

• This variable now contains the entire table identified we can reuse this information

ForEach and Variables

• $_ is a variable that allows pulling each (CPU in this case) in turn within ForEach

Turning Text into Numbers

• If $t = "123", it is text
• By running [int] $t it becomes an integer

Further Conversion

• You can convert variables like $students with mathsScore from text to numbers using $students | ForEach {$.mathsScore = [int]$.mathsScore }

Expanded Note Property

• An object is composed of properties
• A ScriptProperty runs a script
• A NoteProperty allows adding after a process is created

PowerShell Script and Columns

• Example of adding a column to a CSV file called ‘students.csv'
  • Create a CSV file ‘students.csv' with 3 columns, Name, Maths and English.
  • Load the CSV and change text to numbers
  • Add a 'sum' column to all objects in the file
  • Fill in all those properties
  • Save the CSV file

NoTypeInformation

• Without -NoTypeInformation a resultant CSV will have PSCustom type info
• -NoTypeInformation instructs the code to not include the type
• Therefore the data returned to a csv is usable in outside tools

Object Typing

• An Object always has a type attached to it which describes its members, for examples:
• Get-Process delivers processes
• Each process here is an object and each object has same property labels
• Types come from the central areas of the system

Variable data types

• CmdletInfo type is from PowerShell Core
• Process info type is from .NET library

Object Types

• Object types are:
  • Property
  • NoteProperty
  • Method

Common Methods

• GetType() is a common method which returns the type of an object

Methods vs. Commands

• Command is designed specifically for PowerShell
• Method is designed for all .NET things

Commands and Parameters

• bool WaitForExit(int milliseconds); method which returns a bool type of object
• The parameter is an integer and is named 'milliseconds'
• void M(string a, int b); has two parameters, separated by a comma

C# and PowerShell

• Most of .NET and PowerShell is written in C#
• Example Code: string A {get; set;}, the code shows how to look what is in it, and change what's in it

Get-Member and Objects

• Run Get-Member gives one object and will give a clear list of all the members on an object
• Gives a list of all the members on the object if one object is provided, otherwise lists members on the first object.

Member Information

• In get-member, we retrieves the Name, MemberType and the Definitions
• The list is cut off but further down are the methods and Properties listed too.
• Methods can have different variants, example: overloads. moveTO()
• PS C:\Users\Miles McDonald> ls -Directory; Lists directories in current path

Primitive Number Datatypes

• byte (Byte)
• sbyte (SByte)
• short (Int16)
• ushort (UInt16)
• int (Int32)
• uint (UInt32)
• long (Int64)
• ulong (UInt64)

Primitive Decimal Datatypes

• float (Single) - 32 bit
• double (Double) - 64 bit
  • Note that Doubles are more precise (because they are bigger)

Boolean Datatype

• isPrimitive Returns: True

String Datatype

• isPrimitive Returns 'False'

One property on the string.

• Int Length {get;}; The length is one property of all strings

Single Quotes vs. Double Quotes

• To break out of the regular usage for quotes, use single quotes
• For example:
  • $age = 50'I am $age years old'Will return I am $age years old “I am $($age + 5) years old"Will return I am 55 years old

Concatenation

• $str = 'abc'$str + ''; returns abc
• $str += ''; Returns abc. $str has changed its value to abc.

Arrays

• $myArray = @(), is an empty array, Notice the naming is the same as a variable
• $myArray.count, this will return 0 (zero)
• A string is also an array.
• An array can be considered a list of objects. @('Joe', 'Fred', 'John') is an array with three items.

Array Type

• The type displayed is Object [];is an array containing objects
• [Int] is an array with only integers in it. When you create a strongly typed array, it can only contain values or objects of the specified type.

Open scripts

• A script is a file with some code in it.
• Make a file with the extension ps1
• Two ways to open:1-PSDemoscript.ps1, 2-Rt click on file and select PowerShell 7.
• You can use Visual Studio Code