WMLUG January 2017

PowerShell on Linux

Patrick TenHoopen

PowerShell on Linux

On August 18, 2016, Microsoft announced that it would make PowerShell open source and release it for Linux and Mac OS using one code base under the MIT license. It is still in an alpha stage though.

Why Run PowerShell on Linux?

● Language is easily readable and is self-documenting

● Optimized for structured data● Good at "gluing" systems together● Provides an interactive shell as well as being

scriptable●

Comparing PowerShell to Bash

Command Input/Output Piping

Bash uses text while PowerShell uses objects (does require that you know the object methods and properties). PowerShell doesn’t support input redirection.

Available Commands

Bash has ~150 built-in commands and helper functions (less to learn) compared to PowerShell's 300+ (on Windows) methods and cmdlets.

Windows System Integration

PowerShell has many cmdlets written for administering Microsoft products while bash has none.

Integrated Scripting Environment (ISE)

PowerShell on Windows provides an integrated scripting environment.

PowerShell's Use of Objects

The output of a PowerShell command is an object.

The object can be passed to the next command (object pipeline) for input.

Running on Linux

Not all of PowerShell's features work on Linux like in Windows due to bugs and the difference in frameworks (.NET Core on Linux vs full .NET on Windows).

Some examples of issues:● Remote management is not available● Case-sensitivity of file names● Aliases were removed for native commands (ls, cp,

etc.) so the native commands are used but they return text rather than objects

Running on Linux

● Output from native commands is sent in total after command is done rather than as it is generated

● Redirected output contains the UTF-8 byte order mark (BOM) unless ASCII encoding is specified

● Job control doesn’t work● Doesn’t do wildcard expansion (globbing) for the

native commands but does for built-in/internal commands

Installation

Supported distros: Ubuntu 16.04, Ubuntu 14.04, CentOS 7, Red Hat Enterprise Linux 7

https://github.com/PowerShell/PowerShell/releases

Installing on Ubuntu 16.04:sudo apt-get install libunwind8 libicu55

sudo dpkg -i /path/to/powershell_6.0.0-alpha.14-1ubuntu1.16.04.1_amd64.deb

Running PowerShell

Starting the interactive PowerShell shell:

powershell

The PowerShell prompt is PS followed by the current directory:

PS /home/user>

PowerShell Basics

● Commenting Code● Variables● Some String Methods and Properties● Casting● Arrays● Getting Help● Getting Members and Properties● User Input● Screen Output● Functions● Conditional Branching● Loops● XML Parsing● Running Scripts

Commenting Code

Comments use #

# This is a comment

"Hello" # This is an inline comment

<#

This is a

multi-line comment.

#>

Variables

Common Data Types: string, int, long, bool

Variables - Integer

# Integer

$Item1 = 5

$Item2 = 2

$Total = $Item1 + $Item2

$Total

7

Variables - String

# String

$MyString = "Hello"

$MyString

Hello

Variables - Boolean

#Boolean uses $True or $False

$Done = $False

$TrueOrFalse = 1 -gt 2

Variable Scope

Scopes: Global vs Local

Some String Methods and Properties

$Alphabet = "abcdefghijklmnopqrstuvwxyz"

$Alphabet.Length #26

$Alphabet[0] # a

$Alphabet.IndexOf("c") # 2

$Alphabet.Substring(2,3) # cde

$Alphabet.ToUpper() # ABCDEFGHIJKLMNOPQRSTUVWXYZ

Splitting Strings

$phone = "616-867-5309"

$phone.Split("-")

616

867

5309

Casting

# Cast a string as an integer

[Int] $Number = "3"

$Number.GetType().Name

Int32

Arrays

$array1 = @() # Create an empty array

$array1 += 1

$array1 += “two”

# Create an array with 3 elements

$array2 = @("One", "Two", "Three")

Iterating an Array with Foreach

$ColorList = @("Red", "Green", "Blue")

ForEach ($Color in $ColorList) {

Write-Host $Color -ForeGroundColor $Color

}

Getting Help

Get-Help date

Get-Help Get-Date

Get-Help Get-Date -examples

Get-Help Get-Process

Find Object Members and Properties

Get-ChildItem | Get-Member

Get-Process | Get-Member

Get-Date | Get-Member

$TestString = "Test"

$TestString | Get-Member

Acting on Objects with ForEach-Object

Get-ChildItem | ForEach-Object {

Write-Host "Name is $_.Name, size $_.Length"

}

Note: $_ is the current object in the pipeline

Filtering with Where-Object

Get-ChildItem | Where-Object {$_ -Like "*.txt"} | ForEach-Object {

Write-Host "Text file name is $_.”

Write-Host “Last updated on $($_.LastWriteTime)."

}

Listing Processes

Example raw output of Get-ProcessNPM(K) PM(K) WS(K) CPU(s) Id SI ProcessName

------ ----- ----- ------ -- -- -----------

0 0 0 0.000 1326 324 (sd-pam)

0 0 2 1.100 925 925 accounts-daemon

0 0 0 0.000 64 0 acpi_thermal_pm

0 0 0 4.640 942 942 acpid

0 0 0 0.000 1095 095 agetty

0 0 2 0.000 1671 574 at-spi-bus-laun

0 0 1 3.280 1678 574 at-spi2-registr

0 0 0 0.000 37 0 ata_sff

0 0 1 0.830 911 911 avahi-daemon

0 0 0 0.000 950 911 avahi-daemon

0 0 10 32.860 1692 692 bamfdaemon

0 0 1 0.040 4009 009 bash

0 0 0 0.000 35 0 bioset

0 0 0 0.000 70 0 bioset

Filtering Processes with Where-Object

Get-Process | Where-Object {$_.Name -Like “fire*”}

User Input

$Name = Read-Host "What is your name?"

Screen Output

Write-Host "Hello $Name"

Hello Pat

$Greeting = "Hello"

Write-Host "$Greeting my friend, $Name!"

Simple Function

Function SayHello {

Write-Host "Hello"

}

PS> SayHello

Hello

Function with Parameter

Function SayHelloTo ($Name) {

Write-Host "Hello $Name"

}

PS> SayHelloTo "Sheldon"

Hello Sheldon

Comparison Operators

-lt -- Less than

-le -- Less than or equal to

-gt -- Greater than

-ge -- Greater than or equal to

-eq -- Equal to

-ne -- Not equal to

-like - Like; uses wildcards for pattern matching

Logical operators

-and -- Logical And

-or -- Logical Or

-not -- Logical Not

! -- Logical Not

Conditional Branching with If

$Dollars = 5

$TacoPrice = 3

If ($Dollars -ge $TacoPrice) { Write-Host "Tacos for dinner!" }

$Day = (Get-Date).DayOfWeek

If ($Day -eq "Friday") {

Write-Host "TGIF!"

}

Else {

Write-Host "Sorry, it's not Friday yet :("

}

While Loop

$Done = $False

$Count = 3

While (!$Done) {

Write-Host $Count

$Count--

If ($Count -eq 0) {

$Done = $True

Write-Host "Done!"

}

}

For Loop

For ($Count = 3; $Count -ne 0; $Count--) {

Write-Host $Count

}

Write-Host "Done!"

XML Parsing

[xml] $MovieList = Get-Content sample.xml

$MovieList.movies.movie

$MovieList.movies.movie.title

CSV Output

$MovieList.movies.movie | Export-CSV sample.csv

Running Scripts

If PowerShell is not running:

powershell -file /path/to/ScriptName.ps1

If PowerShell is running:

/path/to/ScriptName.ps1

Additional Resources

● Daily PowerShell tips– http://community.idera.com/powershell/powertips/

● Windows PowerShell Survival Guide– https://social.technet.microsoft.com/wiki/contents/a

rticles/183.windows-powershell-survival-guide.aspx● Scripting with Windows PowerShell

– https://technet.microsoft.com/en-us/library/bb978526.aspx