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332 lines
10 KiB
Markdown
332 lines
10 KiB
Markdown
---
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category: tool
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tool: powershell
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contributors:
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- ["Wouter Van Schandevijl", "https://github.com/laoujin"]
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filename: LearnPowershell.ps1
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---
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PowerShell is the Windows scripting language and configuration management
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framework from Microsoft built on the .NET Framework. Windows 7 and up ship
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with PowerShell.
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Nearly all examples below can be a part of a shell script or executed directly
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in the shell.
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A key difference with Bash is that it is mostly objects that you manipulate
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rather than plain text.
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[Read more here.](https://technet.microsoft.com/en-us/library/bb978526.aspx)
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If you are uncertain about your environment:
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```powershell
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Get-ExecutionPolicy -List
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Set-ExecutionPolicy AllSigned
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# Execution policies include:
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# - Restricted: Scripts won't run.
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# - RemoteSigned: Downloaded scripts run only if signed by a trusted publisher.
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# - AllSigned: Scripts need to be signed by a trusted publisher.
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# - Unrestricted: Run all scripts.
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help about_Execution_Policies # for more info
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# Current PowerShell version:
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$PSVersionTable
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```
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Getting help:
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```powershell
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# Find commands
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Get-Command about_* # alias: gcm
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Get-Command -Verb Add
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Get-Alias ps
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Get-Alias -Definition Get-Process
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Get-Help ps | less # alias: help
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ps | Get-Member # alias: gm
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Show-Command Get-EventLog # Display GUI to fill in the parameters
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Update-Help # Run as admin
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```
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The tutorial starts here:
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```powershell
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# As you already figured, comments start with #
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# Simple hello world example:
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echo Hello world!
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# echo is an alias for Write-Output (=cmdlet)
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# Most cmdlets and functions follow the Verb-Noun naming convention
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# Each command starts on a new line, or after a semicolon:
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echo 'This is the first line'; echo 'This is the second line'
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# Declaring a variable looks like this:
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$aString="Some string"
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# Or like this:
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$aNumber = 5 -as [double]
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$aList = 1,2,3,4,5
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$anEmptyList = @()
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$aString = $aList -join '--' # yes, -split exists also
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$aHashtable = @{name1='val1'; name2='val2'}
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# Using variables:
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echo $aString
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echo "Interpolation: $aString"
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echo "$aString has length of $($aString.Length)"
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echo '$aString'
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echo @"
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This is a Here-String
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$aString
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"@
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# Note that ' (single quote) won't expand the variables!
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# Here-Strings also work with single quote
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# Builtin variables:
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# There are some useful builtin variables, like
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echo "Booleans: $TRUE and $FALSE"
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echo "Empty value: $NULL"
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echo "Last program's return value: $?"
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echo "Exit code of last run Windows-based program: $LastExitCode"
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echo "The last token in the last line received by the session: $$"
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echo "The first token: $^"
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echo "Script's PID: $PID"
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echo "Full path of current script directory: $PSScriptRoot"
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echo 'Full path of current script: ' + $MyInvocation.MyCommand.Path
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echo "FUll path of current directory: $Pwd"
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echo "Bound arguments in a function, script or code block: $PSBoundParameters"
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echo "Unbound arguments: $($Args -join ', ')."
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# More builtins: `help about_Automatic_Variables`
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# Inline another file (dot operator)
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. .\otherScriptName.ps1
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### Control Flow
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# We have the usual if structure:
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if ($Age -is [string]) {
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echo 'But.. $Age cannot be a string!'
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} elseif ($Age -lt 12 -and $Age -gt 0) {
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echo 'Child (Less than 12. Greater than 0)'
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} else {
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echo 'Adult'
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}
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# Switch statements are more powerful compared to most languages
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$val = "20"
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switch($val) {
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{ $_ -eq 42 } { "The answer equals 42"; break }
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'20' { "Exactly 20"; break }
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{ $_ -like 's*' } { "Case insensitive"; break }
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{ $_ -clike 's*'} { "clike, ceq, cne for case sensitive"; break }
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{ $_ -notmatch '^.*$'} { "Regex matching. cnotmatch, cnotlike, ..."; break }
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{ 'x' -contains 'x'} { "FALSE! -contains is for lists!"; break }
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default { "Others" }
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}
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# The classic for
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for($i = 1; $i -le 10; $i++) {
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"Loop number $i"
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}
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# Or shorter
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1..10 | % { "Loop number $_" }
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# PowerShell also offers
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foreach ($var in 'val1','val2','val3') { echo $var }
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# while () {}
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# do {} while ()
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# do {} until ()
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# Exception handling
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try {} catch {} finally {}
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try {} catch [System.NullReferenceException] {
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echo $_.Exception | Format-List -Force
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}
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### Providers
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# List files and directories in the current directory
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ls # or `dir`
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cd ~ # goto home
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Get-Alias ls # -> Get-ChildItem
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# Uh!? These cmdlets have generic names because unlike other scripting
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# languages, PowerShell does not only operate in the current directory.
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cd HKCU: # go to the HKEY_CURRENT_USER registry hive
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# Get all providers in your session
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Get-PSProvider
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### Pipeline
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# Cmdlets have parameters that control their execution:
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Get-ChildItem -Filter *.txt -Name # Get just the name of all txt files
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# Only need to type as much of a parameter name until it is no longer ambiguous
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ls -fi *.txt -n # -f is not possible because -Force also exists
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# Use `Get-Help Get-ChildItem -Full` for a complete overview
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# Results of the previous cmdlet can be passed to the next as input.
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# `$_` is the current object in the pipeline object.
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ls | Where-Object { $_.Name -match 'c' } | Export-CSV export.txt
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ls | ? { $_.Name -match 'c' } | ConvertTo-HTML | Out-File export.html
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# If you get confused in the pipeline use `Get-Member` for an overview
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# of the available methods and properties of the pipelined objects:
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ls | Get-Member
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Get-Date | gm
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# ` is the line continuation character. Or end the line with a |
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Get-Process | Sort-Object ID -Descending | Select-Object -First 10 Name,ID,VM `
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| Stop-Process -WhatIf
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Get-EventLog Application -After (Get-Date).AddHours(-2) | Format-List
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# Use % as a shorthand for ForEach-Object
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(a,b,c) | ForEach-Object `
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-Begin { "Starting"; $counter = 0 } `
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-Process { "Processing $_"; $counter++ } `
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-End { "Finishing: $counter" }
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# Get-Process as a table with three columns
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# The third column is the value of the VM property in MB and 2 decimal places
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# Computed columns can be written more verbose as:
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# `@{name='lbl';expression={$_}`
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ps | Format-Table ID,Name,@{n='VM(MB)';e={'{0:n2}' -f ($_.VM / 1MB)}} -autoSize
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### Functions
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# The [string] attribute is optional.
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function foo([string]$name) {
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echo "Hey $name, have a function"
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}
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# Calling your function
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foo "Say my name"
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# Functions with named parameters, parameter attributes, parsable documentation
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<#
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.SYNOPSIS
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Setup a new website
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.DESCRIPTION
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Creates everything your new website needs for much win
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.PARAMETER siteName
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The name for the new website
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.EXAMPLE
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New-Website -Name FancySite -Po 5000
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New-Website SiteWithDefaultPort
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New-Website siteName 2000 # ERROR! Port argument could not be validated
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('name1','name2') | New-Website -Verbose
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#>
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function New-Website() {
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[CmdletBinding()]
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param (
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[Parameter(ValueFromPipeline=$true, Mandatory=$true)]
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[Alias('name')]
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[string]$siteName,
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[ValidateSet(3000,5000,8000)]
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[int]$port = 3000
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)
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BEGIN { Write-Verbose 'Creating new website(s)' }
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PROCESS { echo "name: $siteName, port: $port" }
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END { Write-Verbose 'Website(s) created' }
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}
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### It's all .NET
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# A PS string is in fact a .NET System.String
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# All .NET methods and properties are thus available
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'string'.ToUpper().Replace('G', 'ggg')
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# Or more powershellish
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'string'.ToUpper() -replace 'G', 'ggg'
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# Unsure how that .NET method is called again?
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'string' | gm
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# Syntax for calling static .NET methods
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[System.Reflection.Assembly]::LoadWithPartialName('Microsoft.VisualBasic')
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# Note that .NET functions MUST be called with parentheses
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# while PS functions CANNOT be called with parentheses.
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# If you do call a cmdlet/PS function with parentheses,
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# it is the same as passing a single parameter list
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$writer = New-Object System.IO.StreamWriter($path, $true)
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$writer.Write([Environment]::NewLine)
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$writer.Dispose()
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### IO
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# Reading a value from input:
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$Name = Read-Host "What's your name?"
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echo "Hello, $Name!"
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[int]$Age = Read-Host "What's your age?"
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# Test-Path, Split-Path, Join-Path, Resolve-Path
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# Get-Content filename # returns a string[]
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# Set-Content, Add-Content, Clear-Content
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Get-Command ConvertTo-*,ConvertFrom-*
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### Useful stuff
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# Refresh your PATH
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$env:PATH = [System.Environment]::GetEnvironmentVariable("Path", "Machine") +
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";" + [System.Environment]::GetEnvironmentVariable("Path", "User")
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# Find Python in path
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$env:PATH.Split(";") | Where-Object { $_ -like "*python*"}
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# Change working directory without having to remember previous path
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Push-Location c:\temp # change working directory to c:\temp
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Pop-Location # change back to previous working directory
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# Aliases are: pushd and popd
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# Unblock a directory after download
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Get-ChildItem -Recurse | Unblock-File
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# Open Windows Explorer in working directory
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ii .
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# Any key to exit
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$host.UI.RawUI.ReadKey()
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return
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# Create a shortcut
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$WshShell = New-Object -comObject WScript.Shell
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$Shortcut = $WshShell.CreateShortcut($link)
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$Shortcut.TargetPath = $file
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$Shortcut.WorkingDirectory = Split-Path $file
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$Shortcut.Save()
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```
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Configuring your shell
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```powershell
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# $Profile is the full path for your `Microsoft.PowerShell_profile.ps1`
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# All code there will be executed when the PS session starts
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if (-not (Test-Path $Profile)) {
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New-Item -Type file -Path $Profile -Force
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notepad $Profile
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}
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# More info: `help about_profiles`
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# For a more useful shell, be sure to check the project PSReadLine below
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```
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Interesting Projects
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* [Channel9](https://channel9.msdn.com/Search?term=powershell%20pipeline#ch9Search&lang-en=en) PowerShell tutorials
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* [PSGet](https://github.com/psget/psget) NuGet for PowerShell
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* [PSReadLine](https://github.com/lzybkr/PSReadLine/) A bash inspired readline implementation for PowerShell (So good that it now ships with Windows10 by default!)
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* [Posh-Git](https://github.com/dahlbyk/posh-git/) Fancy Git Prompt (Recommended!)
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* [PSake](https://github.com/psake/psake) Build automation tool
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* [Pester](https://github.com/pester/Pester) BDD Testing Framework
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* [Jump-Location](https://github.com/tkellogg/Jump-Location) Powershell `cd` that reads your mind
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* [PowerShell Community Extensions](http://pscx.codeplex.com/) (Dead)
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Not covered
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* WMI: Windows Management Intrumentation (Get-CimInstance)
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* Multitasking: Start-Job -scriptBlock {...},
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* Code Signing
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* Remoting (Enter-PSSession/Exit-PSSession; Invoke-Command)
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