Windows PowerShell promises to revolutionize the world of system management and command-line shells. From its object-based pipelines, to its administrator focus, to its enormous reach into other Microsoft management technologies, PowerShell drastically improves the productivity of administrators and power users alike.
When learning a new technology, it is natural to feel bewildered at first by all the unfamiliar features and functionality. This perhaps rings especially true for users new to Windows PowerShell because it may be their first experience with a fully featured command-line shell. Or worse, they’ve heard stories of PowerShell’s fantastic integrated scripting capabilities and fear being forced into a world of programming that they’ve actively avoided until now.
Fortunately, these fears are entirely misguided; PowerShell is a shell that both grows with you and grows on you. Let’s take a tour to see what it is capable of:
PowerShell works with standard Windows commands and applications. You don’t have to throw away what you already know and use.
PowerShell introduces a powerful new type of command. PowerShell commands (called cmdlets) share a common
Verb-Nounsyntax and offer many usability improvements over standard commands.PowerShell understands objects. Working directly with richly structured objects makes working with (and combining) PowerShell commands immensely easier than working in the plain-text world of traditional shells.
PowerShell caters to administrators. Even with all its advances, PowerShell focuses strongly on its use as an interactive shell: the experience of entering commands in a running PowerShell application.
PowerShell supports discovery. Using three simple commands, you can learn and discover almost anything PowerShell has to offer.
PowerShell enables ubiquitous scripting. With a fully fledged scripting language that works directly from the command line, PowerShell lets you automate tasks with ease.
PowerShell bridges many technologies. By letting you work with .NET, COM, WMI, XML, and Active Directory, PowerShell makes working with these previously isolated technologies easier than ever before.
PowerShell simplifies management of data stores. Through its provider model, PowerShell lets you manage data stores using the same techniques you already use to manage files and folders.
We’ll explore each of these pillars in this introductory tour of PowerShell. If you are running Windows 7 or Windows 2008 R2, version two of PowerShell is already installed. If not, visit the download link at http://www.microsoft.com/PowerShell to install it. PowerShell and its supporting technologies are together referred to as the Windows Management Framework.
At its core, PowerShell is first and foremost an interactive shell. While it supports scripting and other powerful features, its focus as a shell underpins everything.
Getting started in PowerShell is a simple matter of launching PowerShell.exe rather than cmd.exe—the shells begin to diverge as you explore the intermediate and advanced functionality, but you can be productive in PowerShell immediately.
To launch Windows PowerShell, do one of the following:
Click Start→All Programs→Accessories→Windows PowerShell
Click Start→Run, and then type “PowerShell”
A PowerShell prompt window opens that’s nearly identical to the traditional command
prompt window of Windows XP, Windows Server 2003, and their many
ancestors. The PS C:\Documents and
Settings\Lee> prompt indicates that PowerShell is ready for
input, as shown in Figure 1.
Once you’ve launched your PowerShell prompt, you can enter
DOS-style and Unix-style commands to navigate around the filesystem just as you would with
any Windows or Unix command prompt—as in the interactive session shown in
Example 1. In this
example, we use the pushd, cd, dir,
pwd, and popd commands to store the current location,
navigate around the filesystem, list items in the current directory, and
then return to the original location. Try it!
Example 1. Entering many standard DOS- and Unix-style file manipulation commands produces the same results you get when you use them with any other Windows shell
PS C:\Documents and Settings\Lee> function Prompt { "PS > " }
PS > pushd .
PS > cd \
PS > dir
Directory: C:\
Mode LastWriteTime Length Name
---- ------------- ------ ----
d---- 11/2/2006 4:36 AM $WINDOWS.~BT
d---- 5/8/2007 8:37 PM Blurpark
d---- 11/29/2006 2:47 PM Boot
d---- 11/28/2006 2:10 PM DECCHECK
d---- 10/7/2006 4:30 PM Documents and Settings
d---- 5/21/2007 6:02 PM F&SC-demo
d---- 4/2/2007 7:21 PM Inetpub
d---- 5/20/2007 4:59 PM Program Files
d---- 5/21/2007 7:26 PM temp
d---- 5/21/2007 8:55 PM Windows
-a--- 1/7/2006 10:37 PM 0 autoexec.bat
-ar-s 11/29/2006 1:39 PM 8192 BOOTSECT.BAK
-a--- 1/7/2006 10:37 PM 0 config.sys
-a--- 5/1/2007 8:43 PM 33057 RUU.log
-a--- 4/2/2007 7:46 PM 2487 secedit.INTEG.RAW
PS > popd
PS > pwd
Path
----
C:\Documents and Settings\LeeIn this example, our first command customizes
the prompt. In cmd.exe, customizing the prompt looks
like prompt $P$G. In bash, it looks like
PS1="[\h] \w> ". In PowerShell, you define a
function that returns whatever you want displayed. Write a Function introduces functions and how to write
them.
The pushd command is an
alternative name (alias) to the much more descriptively named PowerShell
command Push-Location. Likewise, the
cd, dir, popd,
and pwd commands all have more
memorable counterparts.
Although navigating around the filesystem is helpful, so is running
the tools you know and love, such as ipconfig and notepad. Type the command name and you’ll see
results like those shown in Example 2.
Example 2. Windows tools and applications such as ipconfig run in PowerShell just as they do in cmd.exe
PS > ipconfig
Windows IP Configuration
Ethernet adapter Wireless Network Connection 4:
Connection-specific DNS Suffix . : hsd1.wa.comcast.net.
IP Address. . . . . . . . . . . . : 192.168.1.100
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
PS > notepad
(notepad launches)Entering ipconfig displays the IP addresses of your
current network connections. Entering notepad runs—as you’d expect—the Notepad editor
that ships with Windows. Try them both on your own machine.
In addition to supporting traditional Windows
executables, PowerShell introduces a powerful new type of command called a
cmdlet (pronounced
command-let). All cmdlets are named in a Verb-Noun pattern, such as
Get-Process, Get-Content, and
Stop-Process.
PS > Get-Process -Name lsass
Handles NPM(K) PM(K) WS(K) VM(M) CPU(s) Id ProcessName
------- ------ ----- ----- ----- ------ -- -----------
668 13 6228 1660 46 932 lsassIn this example, you provide a value to the
ProcessName parameter to get a specific
process by name.
Note
Once you know the handful of common verbs in
PowerShell, learning how to work with new nouns becomes much easier.
While you may never have worked with a certain object before (such as a
Service), the standard Get, Set, Start,
and Stop actions still apply. For a
list of these common verbs, see Table J-1 in Appendix J.
You don’t always have to type these full cmdlet
names, however. PowerShell lets you use the Tab key to auto-complete cmdlet names and parameter names:
PS > Get-Pr<TAB> -N<TAB> lsass
For quick interactive use, even that may be too
much typing. To help improve your efficiency, PowerShell defines aliases
for all common commands and lets you define your own. In addition to alias
names, PowerShell only requires that you type enough of the parameter name
to disambiguate it from the rest of the parameters in that cmdlet.
PowerShell is also case-insensitive. Using the built-in gps alias (which represents the Get-Process cmdlet) along with parameter
shortening, you can instead type:
PS > gps -n lsass
Going even further, PowerShell supports
positional parameters on cmdlets.
Positional parameters let you provide parameter values in a certain
position on the command line, rather than having to specify them by name.
The Get-Process cmdlet takes a process
name as its first positional parameter. This parameter even supports
wildcards:
PS > gps l*s
PowerShell begins to flex more of its muscle as you explore the way it handles structured data and richly functional objects. For example, the following command generates a simple text string. Since nothing captures that output, PowerShell displays it to you:
PS > "Hello World" Hello World
The string you just generated is, in fact, a
fully functional object from the .NET Framework. For example, you can
access its Length property, which
tells you how many characters are in the string. To access a property, you
place a dot between the object and its property name:
PS > "Hello World".Length 11
All PowerShell commands that produce output
generate that output as objects as well. For example, the Get-Process cmdlet
generates a System.Diagnostics.Process
object, which you can store in a variable. In PowerShell, variable names
start with a $ character. If you have an instance of
Notepad running, the following command stores a reference to it:
$process = Get-Process notepad
Since this is a fully functional Process object from the .NET Framework, you can
call methods on that object to perform actions on it. This command calls
the Kill() method, which
stops a process. To access a method, you place a dot between the object and its
method name:
$process.Kill()
PowerShell supports this functionality more
directly through the Stop-Process cmdlet, but
this example demonstrates an important point about your ability to
interact with these rich objects.
While PowerShell’s support for objects from the
.NET Framework quickens the pulse of most users, PowerShell
continues to focus strongly on administrative tasks. For example, PowerShell supports
MB (for megabyte) and GB (for gigabyte) as some of its standard
administrative constants. For example, how many disks will it take to back
up a 40 GB hard drive to CD-ROM?
PS > 40GB / 650MB 63.0153846153846
Although the .NET Framework is traditionally a development platform, it contains a wealth of functionality useful for administrators too! In fact, it makes PowerShell a great calendar. For example, is 2008 a leap year? PowerShell can tell you:
PS > [DateTime]::IsLeapYear(2008) True
Going further, how might you determine how much
time remains until summer? The following command converts "06/21/2011" (the start of summer) to a date,
and then subtracts the current date from that. It stores the result in the
$result variable, and then accesses the
TotalDays property.
PS > $result = [DateTime] "06/21/2011" - [DateTime]::Now PS > $result.TotalDays 283.0549285662616
Whenever a command generates output, you can use a pipeline character (|) to pass that output directly to another command as input. If the second command understands the objects produced by the first command, it can operate on the results. You can chain together many commands this way, creating powerful compositions out of a few simple operations. For example, the following command gets all items in the Path1 directory and moves them to the Path2 directory:
Get-Item Path1\* | Move-Item -Destination Path2
You can create even more complex commands by
adding additional cmdlets to the pipeline. In Example 3, the first command
gets all processes running on the system. It passes those to the
Where-Object cmdlet,
which runs a comparison against each incoming item. In this case, the
comparison is $_.Handles -ge 500, which
checks whether the Handles property of
the current object (represented by the $_ variable) is greater than or equal to
500. For each object in which this
comparison holds true, you pass the results to the Sort-Object cmdlet,
asking it to sort items by their Handles property. Finally, you pass the objects
to the Format-Table cmdlet to
generate a table that contains the Handles,
Name, and Description of the process.
Example 3. You can build more complex PowerShell commands by using pipelines to link cmdlets, as shown in this example with Get-Process, Where-Object, Sort-Object, and Format-Table
PS > Get-Process |
Where-Object { $_.Handles -ge 500 } |
Sort-Object Handles |
Format-Table Handles,Name,Description -Auto
Handles Name Description
------- ---- -----------
588 winlogon
592 svchost
667 lsass
725 csrss
742 System
964 WINWORD Microsoft Office Word
1112 OUTLOOK Microsoft Office Outlook
2063 svchostWhile aliases, wildcards, and composable pipelines are powerful, their use in commands that modify system information can easily be nerve-wracking. After all, what does this command do? Think about it, but don’t try it just yet:
PS > gps [b-t]*[c-r] | Stop-Process
It appears to stop all processes that begin
with the letters b through t and end with the letters c through r.
How can you be sure? Let PowerShell tell you. For commands that modify
data, PowerShell supports -WhatIf and -Confirm parameters that
let you see what a command would do:
PS > gps [b-t]*[c-r] | Stop-Process -whatif What if: Performing operation "Stop-Process" on Target "ctfmon (812)". What if: Performing operation "Stop-Process" on Target "Ditto (1916)". What if: Performing operation "Stop-Process" on Target "dsamain (316)". What if: Performing operation "Stop-Process" on Target "ehrecvr (1832)". What if: Performing operation "Stop-Process" on Target "ehSched (1852)". What if: Performing operation "Stop-Process" on Target "EXCEL (2092)". What if: Performing operation "Stop-Process" on Target "explorer (1900)". (...)
In this interaction, using the -WhatIf parameter with the Stop-Process pipelined command lets you preview
which processes on your system will be stopped before you actually carry
out the operation.
Note that this example is not a dare! In the words of one reviewer:
While reading through a guided tour is helpful,
I find that most learning happens in an ad hoc fashion. To find all
commands that match a given wildcard, use the Get-Command cmdlet. For example, by entering the following, you can
find out which PowerShell commands (and Windows applications) contain the
word process.
PS > Get-Command *process* CommandType Name Definition ----------- ---- ---------- Cmdlet Get-Process Get-Process [[-Name] <Str... Application qprocess.exe c:\windows\system32\qproc... Cmdlet Stop-Process Stop-Process [-Id] <Int32...
To see what a command such as Get-Process does, use the Get-Help cmdlet, like
this:
PS > Get-Help Get-Process
Since PowerShell lets you work with objects
from the .NET Framework, it provides the Get-Member cmdlet to retrieve information about the
properties and methods that an object, such as a .NET System.String, supports. Piping a string to the
Get-Member command displays its type
name and its members:
PS > "Hello World" | Get-Member
TypeName: System.String
Name MemberType Definition
---- ---------- ----------
(...)
PadLeft Method System.String PadLeft(Int32 tota...
PadRight Method System.String PadRight(Int32 tot...
Remove Method System.String Remove(Int32 start...
Replace Method System.String Replace(Char oldCh...
Split Method System.String[] Split(Params Cha...
StartsWith Method System.Boolean StartsWith(String...
Substring Method System.String Substring(Int32 st...
ToCharArray Method System.Char[] ToCharArray(), Sys...
ToLower Method System.String ToLower(), System....
ToLowerInvariant Method System.String ToLowerInvariant()
ToString Method System.String ToString(), System...
ToUpper Method System.String ToUpper(), System....
ToUpperInvariant Method System.String ToUpperInvariant()
Trim Method System.String Trim(Params Char[]...
TrimEnd Method System.String TrimEnd(Params Cha...
TrimStart Method System.String TrimStart(Params C...
Chars ParameterizedProperty System.Char Chars(Int32 index) {...
Length Property System.Int32 Length {get;}PowerShell makes no distinction between the
commands typed at the command line and the commands written in a script.
Your favorite cmdlets work in scripts and your favorite scripting techniques
(e.g., the foreach statement) work
directly on the command line. For example, to add up the handle count for
all running processes:
PS > $handleCount = 0
PS > foreach($process in Get-Process) { $handleCount += $process.Handles }
PS > $handleCount
19403While PowerShell provides a command (Measure-Object) to measure statistics about
collections, this short example shows how PowerShell lets you apply
techniques that normally require a separate scripting or programming
language.
In addition to using PowerShell scripting keywords, you can also create and work directly with objects from the .NET Framework that you may be familiar with. PowerShell becomes almost like the C# immediate mode in Visual Studio. Example 4 shows how PowerShell lets you easily interact with the .NET Framework.
Example 4. Using objects from the .NET Framework to retrieve a web page and process its content
PS > $webClient = New-Object System.Net.WebClient
PS > $content = $webClient.DownloadString("http://blogs.msdn.com/PowerShell/rss.aspx")
PS > $content.Substring(0,1000)
<?xml version="1.0" encoding="UTF-8" ?>
<?xml-stylesheet type="text/xsl" href="http://blogs.msdn.com/utility/FeedS
tylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://pu
rl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slas
h/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>Windo
(...)By blurring the lines between interactive
administration and writing scripts, the history buffers of PowerShell
sessions quickly become the basis for ad hoc script development. In this
example, you call the Get-History cmdlet to
retrieve the history of your session. For each item, you get its CommandLine property (the thing you typed) and
send the output to a new script file.
PS > Get-History | Foreach-Object { $_.CommandLine } > c:\temp\script.ps1
PS > notepad c:\temp\script.ps1
(save the content you want to keep)
PS > c:\temp\script.ps1Note
If this is the first time you’ve run a script in PowerShell, you will need to configure your Execution Policy. For more information about selecting an execution policy, see Enable Scripting Through an Execution Policy.
For more detail about saving your session history into a script, see Program: Create Scripts from Session History.
We’ve seen how PowerShell lets you fully leverage the .NET Framework in your tasks, but its support for common technologies stretches even further. As Example 5 (continued from Example 4) shows, PowerShell supports XML.
Example 5. Working with XML content in PowerShell
PS > $xmlContent = [xml] $content PS > $xmlContent xml xml-stylesheet rss --- -------------- --- version="1.0" encoding... type="text/xsl" href="... rss PS > $xmlContent.rss version : 2.0 dc : http://purl.org/dc/elements/1.1/ slash : http://purl.org/rss/1.0/modules/slash/ wfw : http://wellformedweb.org/CommentAPI/ channel : channel PS > $xmlContent.rss.channel.item | select Title title ----- CMD.exe compatibility Time Stamping Log Files Microsoft Compute Cluster now has a PowerShell Provider and Cmdlets The Virtuous Cycle: .NET Developers using PowerShell (...)
PowerShell also lets you work with Windows Management Instrumentation (WMI):
PS > Get-WmiObject Win32_Bios SMBIOSBIOSVersion : ASUS A7N8X Deluxe ACPI BIOS Rev 1009 Manufacturer : Phoenix Technologies, LTD Name : Phoenix - AwardBIOS v6.00PG SerialNumber : xxxxxxxxxxx Version : Nvidia - 42302e31
Or, as Example 6 shows, Active Directory Service Interfaces (ADSI).
Example 6. Working with Active Directory in PowerShell
PS > [ADSI] "WinNT://./Administrator" | Format-List *
UserFlags : {66113}
MaxStorage : {-1}
PasswordAge : {19550795}
PasswordExpired : {0}
LoginHours : {255 255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255}
FullName : {}
Description : {Built-in account for administering the compu
ter/domain}
BadPasswordAttempts : {0}
LastLogin : {5/21/2007 3:00:00 AM}
HomeDirectory : {}
LoginScript : {}
Profile : {}
HomeDirDrive : {}
Parameters : {}
PrimaryGroupID : {513}
Name : {Administrator}
MinPasswordLength : {0}
MaxPasswordAge : {3710851}
MinPasswordAge : {0}
PasswordHistoryLength : {0}
AutoUnlockInterval : {1800}
LockoutObservationInterval : {1800}
MaxBadPasswordsAllowed : {0}
RasPermissions : {1}
objectSid : {1 5 0 0 0 0 0 5 21 0 0 0 121 227 252 83 122
130 50 34 67 23 10 50 244 1 0 0}Or, as Example 7 shows, even scripting traditional COM objects.
Example 7. Working with COM objects in PowerShell
PS > $firewall = New-Object -com HNetCfg.FwMgr
PS > $firewall.LocalPolicy.CurrentProfile
Type : 1
FirewallEnabled : True
ExceptionsNotAllowed : False
NotificationsDisabled : False
UnicastResponsesToMulticastBroadcastDisabled : False
RemoteAdminSettings : System.__ComObject
IcmpSettings : System.__ComObject
GloballyOpenPorts : {Media Center Extender Serv
ice, Remote Media Center Ex
perience, Adam Test Instanc
e, QWAVE...}
Services : {File and Printer Sharing,
UPnP Framework, Remote Desk
top}
AuthorizedApplications : {Remote Assistance, Windows
Messenger, Media Center, T
rillian...}Another avenue PowerShell offers for working with the system is providers. PowerShell providers let you navigate and manage data stores using the same techniques you already use to work with the filesystem, as illustrated in Example 8.
Example 8. Navigating the filesystem
PS > Set-Location c:\
PS > Get-ChildItem
Directory: C:\
Mode LastWriteTime Length Name
---- ------------- ------ ----
d---- 11/2/2006 4:36 AM $WINDOWS.~BT
d---- 5/8/2007 8:37 PM Blurpark
d---- 11/29/2006 2:47 PM Boot
d---- 11/28/2006 2:10 PM DECCHECK
d---- 10/7/2006 4:30 PM Documents and Settings
d---- 5/21/2007 6:02 PM F&SC-demo
d---- 4/2/2007 7:21 PM Inetpub
d---- 5/20/2007 4:59 PM Program Files
d---- 5/21/2007 11:47 PM temp
d---- 5/21/2007 8:55 PM Windows
-a--- 1/7/2006 10:37 PM 0 autoexec.bat
-ar-s 11/29/2006 1:39 PM 8192 BOOTSECT.BAK
-a--- 1/7/2006 10:37 PM 0 config.sys
-a--- 5/1/2007 8:43 PM 33057 RUU.log
-a--- 4/2/2007 7:46 PM 2487 secedit.INTEG.RAWThis also works on the registry, as shown in Example 9.
Example 9. Navigating the registry
PS > Set-Location HKCU:\Software\Microsoft\Windows\
PS > Get-ChildItem
Hive: HKEY_CURRENT_USER\Software\Microsoft\Windows
SKC VC Name Property
--- -- ---- --------
30 1 CurrentVersion {ISC}
3 1 Shell {BagMRU Size}
4 2 ShellNoRoam {(default), BagMRU Size}
PS > Set-Location CurrentVersion\Run
PS > Get-ItemProperty .
(...)
FolderShare : "C:\Program Files\FolderShare\FolderShare.exe" /
background
TaskSwitchXP : d:\lee\tools\TaskSwitchXP.exe
ctfmon.exe : C:\WINDOWS\system32\ctfmon.exe
Ditto : C:\Program Files\Ditto\Ditto.exe
(...)Or even the machine’s certificate store, as Example 10 illustrates.
Example 10. Navigating the certificate store
PS > Set-Location cert:\CurrentUser\Root
PS > Get-ChildItem
Directory: Microsoft.PowerShell.Security\Certificate::CurrentUser\Root
Thumbprint Subject
---------- -------
CDD4EEAE6000AC7F40C3802C171E30148030C072 CN=Microsoft Root Certificate...
BE36A4562FB2EE05DBB3D32323ADF445084ED656 CN=Thawte Timestamping CA, OU...
A43489159A520F0D93D032CCAF37E7FE20A8B419 CN=Microsoft Root Authority, ...
9FE47B4D05D46E8066BAB1D1BFC9E48F1DBE6B26 CN=PowerShell Local Certifica...
7F88CD7223F3C813818C994614A89C99FA3B5247 CN=Microsoft Authenticode(tm)...
245C97DF7514E7CF2DF8BE72AE957B9E04741E85 OU=Copyright (c) 1997 Microso...
(...)As exciting as this guided tour was, it barely scratches the surface of how you can use PowerShell to improve your productivity and systems management skills. For more information about getting started in PowerShell, see Chapter 1.
Get Windows PowerShell Cookbook, 2nd Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
