PowerShell One-Liners: Help, Syntax, Display and Files

04 April 2014
by Michael Sorens

Powershell is designed to be used by busy IT professionals who want to get things done, and don't necessarily enjoy programming. PowerShell tackles this paradox by providing its own help and command-line intellisense. We aim to assist by providing a series of collections of general-purpose one-liners to cover most of what you'll need to get useful scripting done.

Well, yes, it would be an onerous task indeed to deliver everything. But per the Pareto principle, roughly  eighty percent of what you could want to know about PowerShell is here in this series of articles; possibly more!  You will tend to learn the other twenty percent  as you go, and you may not need  it for quite a ways into your PowerShell explorations.  I feel compelled to confess that some of the entries are not, strictly speaking, on one physical line, but  are written in such a way that, if you really want to run them in one line, you can just remove the line breaks and they will work. (Note that that is not generally true of PowerShell syntax.)

This series of articles evolved out of my own notes on PowerShell as I poked and prodded it to show me more. As my collection  burgeoned, I began to organize them until I had one-line recipes for most any simple PowerShell task. Simple, though, does not mean trivial. You can do quite a lot in one line of PowerShell, such as grabbing the contents of specific elements of a web page or converting a CSV file into a collection of PowerShell objects.

This collection of PowerShell one-liners is organized as follows:

Part 1
begins by showing you how to have PowerShell itself help you figure out what you need to do to accomplish a task, covering the help system as well as its handy command-line intellisense. The next sections deal with locations, files, and paths: the basic currency of any shell. You are introduced to some basic but key syntactic constructs and then ways to cast your output in list, table, grid, or chart form.
Part 2
moves into details on variables, parameters, properties, and objects, providing insight into the richness of the PowerShell programming language. Part 2 is rounded out with a few other vital bits on leveraging the PowerShell environment.
Part 3
covers the two fundamental data structures of PowerShell: the collection (array) and the hash table (dictionary), examining everything from creating, accessing, iterating, ordering, and selecting. Part 3 also covers converting between strings and arrays, and rounds out with techniques for searching, most commonly applicable to files (searching both directory structures as well as file contents).
Part 4
is your information source for a variety of input and output techniques: reading and writing files; writing the various output streams; file housekeeping operations; and various techniques related to CSV, JSON, database, network, and XML.

Each part of this series is available as both an online reference here at Simple-Talk.com as well as a downloadable wallchart in PDF format for those who prefer a printed copy near at hand. Please keep in mind though that this is a quick reference, not a tutorial. So while there are a few brief introductory remarks for each section, there is very little explanation for any given incantation. But do not let that scare you off—jump in and try things! You should find more than a few “aha!” moments ahead of you!

Notes on using the tables:

  • A command will typically use full names of cmdlets but the examples will often use aliases for brevity. Example: Get-Help has aliases man and help. This has the side benefit of showing you both long and short names to invoke many commands.
  • Most tables contain either 3 or 4 columns: a description of an action; the generic command syntax to perform that action; an example invocation of that command; and optionally an output column showing the result of that example where feasible.
  • For clarity, embedded newlines (`n) and embedded return/newline combinations (`r`n) are highlighted as shown.
  • Many actions in PowerShell can be performed in more than one way. The goal here is to show just the simplest which may mean displaying more than one command if they are about equally straightforward. In such cases the different commands are numbered with square brackets (e.g. "[1]"). Multiple commands generally mean multiple examples, which are similarly numbered.
  • Most commands will work with PowerShell version 2 and above, though some require at least version 3. So if you are still running v2 and encounter an issue that is likely your culprit.
  • The vast majority of commands are built-in, i.e. supplied by Microsoft. There are a few sprinkled about that require loading an additional module or script, but their usefulness makes them worth including in this compendium. These "add-ins" will be demarcated with angle brackets, e.g. <<pscx>> denotes the popular PowerShell Community Extensions (http://pscx.codeplex.com/).
  • There are many links included for further reading; these are active hyperlinks that you may select if you are working online, but the URLs themselves are also explicitly provided (as in the previous bullet) in case you have a paper copy.

What's What and What's Where

This is your starting point when you are staring at a PowerShell prompt, knowing not what to do. Find out what commands are available, read help on PowerShell concepts, learn about auto-completion of cmdlets and parameters, see what command an alias refers to, and more.  Before even going to the first entry, though, it is useful to learn one thing: PowerShell has help available on both commands and concepts. You can look up a command simply with, for example, Get-Help Get-ChildItem (# 1 below). Or you can search for a command with a substring, e.g. Get-Help file (#3). But as with any programming language you have to know syntax, semantics, structures, … in short all those conceptual items that let you work with commands. If you want to know about variables, for example, you have merely to say Get-Help about_variables. All conceptual topics begin with the “about_” prefix (#11).

Not at first, but in short order, you will want to be able to find meta-details about commands as well. By that, I mean to answer questions like: What type of objects does a cmdlet return? Does a cmdlet have one or multiple sets of parameters available?  Where does a cmdlet come from? All of those meta-details can be seen from entry 20 below.

1Basic help for xGet-Help cmd (cmd is a full name)help Get-ChildItem
2Help in separate windowShow-Command cmd; then select the help iconShow-Command Get-ChildItem
3List help topics containing xGet-Help string (string is a prefix or uses wildcards)[1a] help Get
[1b] help Get-*
4Help for parameter y of cmdlet xGet-Help cmd -parameter yhelp Get-Date -param month
5Help for multiple parametersGet-Help cmd -parameter y* (i.e. use wildcards)help Get-Date -param m*
6List allowed values for parameter y of cmdlet xGet-Help cmd -parameter yhelp Out-File -parameter Encoding
7Intellisense for parameter names [in ISE]cmdlet -paramNamePrefixOut-File -enc
8Intellisense for parameter values [in ISE]cmdlet -paramName<space> paramValuePrefixOut-File -enc<space>
9Auto-completion for parameter namescmdlet - paramNamePrefix <tab>[1a] Out-File -<tab>
[1b] Out-File -enc<tab>
10Auto-completion for parameter valuescmdlet -paramName<space> paramValuePrefix <tab>[1a] Out-File -enc<space><tab>
[1b] Out-File -enc<space>u<tab>
11List all ‘conceptual’ topics (see text above)Get-Help about_*same
12Filter help output by regexGet-Help topic | Out-String -stream | sls -pattern regexhelp ls | Out-String -Stream | Select-String recurse
13Filter help output by constantGet-Help topic | Out-String -stream | sls -simple texthelp ls | Out-String -Stream | sls -SimpleMatch "[-recurse]"
14Send help text to a file[1] Get-Help topic| Out-String | Set-Content file
[2] Get-Help topic > file
[1] help Get-ChildItem | Out-String | sc help.txt
[2] help Get-ChildItem > help.txt
15List all cmdlets and functionsGet-Commandsame
16List all cmdlets/functions beginning with charactersGet-Command string*gcm wr*
17List all cmdlets/functions filtered by nounGet-Command -noun string*gcm -noun type*
18List all exported items from module xGet-Command -Module moduleGet-Command -Module BitLocker
19List properties and methods of cmdletcmdlet | Get-MemberGet-ChildItem | gm
20List meta-details of cmdlet (see text above)Get-Command cmdlet | Select-Object *gcm Get-ChildItem | select *
21Display module containing cmdlet(Get-Command cmdlet).ModuleName(gcm Get-ChildItem).ModuleName
22Display assembly containing cmdlet (for compiled cmdlets)( Get-Command cmdlet ).dll(gcm Get-ChildItem).dll
23Display underlying command for alias xGet-Alias -name xGet-Alias -name gci
24Display aliases for command xGet-Alias -definition xGet-Alias -def Get-ChildItem
25Get general help for PS Community ExtensionsImport-Module pscx; Get-Help pscx <<pscx>>same
26List all functions in PSCXGet-Command -Module Pscx* -CommandType Function <<pscx>>same

Location, Location, Location

See where you are or where you have been and navigate to where you want to be; understand the difference between your PowerShell current location and your Windows working directory; get relative or absolute paths for files or directories.

1Display current location (non-UNC paths)[1] Get-Location
[2] $pwd
[3] $pwd.Path
[1] cd c:\foo; pwd
[2] cd c:\foo; $pwd
[3] cd c:\foo; $pwd.Path
2Display current location (UNC paths)$pwd.ProviderPathcd \\localhost\c$; $pwd.ProviderPath
3Change current location (to drive or folder or data store)Set-Location target[1a] cd variable:
[1b] sl c:\documents\me
[1c] chdir foo\bar
4Get absolute path of file in current locationResolve-Path fileResolve-Path myfile.txt
5Get name without path for file or directory[1] (Get-Item filespec).Name
[2] Split-Path filespec -Leaf
[1] (Get-Item \users\me\myfile.txt).Name
[2] Split-Path \users\me -Leaf
6Get parent path for file(Get-Item filespec).DirectoryName(Get-Item \users\me\myfile.txt).DirectoryName
7Get parent path for directory(Get-Item filespec).Parent(Get-Item \users\me).Parent
8Get parent path for file or directorySplit-Path filespec –Parent[1a] Split-Path \users\me\myfile.txt -Parent
[1b] Split-Path \users\me -Parent
9Get parent name without path for file(Get-Item filespec).Directory.Name(Get-Item \users\me\myfile.txt).Directory.Name
10Get parent name without path for file or directory[1] (Get-Item (Split-Path filespec -Parent)).Name

[2] Split-Path (Split-Path filespec -Parent) -Leaf
[3] "filespec".split("\")[-2]
[1] (Get-Item (Split-Path \users\me\myfile.txt -Parent)).Name
[2] Split-Path (Split-Path \users\me -Parent) -Leaf
[3a] "\users\me\myfile.txt".split("\")[-2]
[3b] "\users\me".split("\")[-2]
11Display working directory (see http://bit.ly/1j4uomr)[Environment]::CurrentDirectorysame
12Change current location and stack itPush-Location pathpushd \projects\stuff
13Return to last stacked location Pop-Locationpopd
14View directory stackGet-Location –stacksame
15View directory stack depth(Get-Location -stack).Countsame

Files and Paths and Things

You can list contents of disk folders with Get-ChildItem just as you could use dir from DOS. But Get-ChildItem also lets you examine environment variables, local variables, aliases, registry paths, even database objects with the same syntax! See about_providers (http://bit.ly/1ghdcvb) and PS Provider Help (http://bit.ly/1dHlC7r) for more details.

1List contents of location
(location may be on any supported PSDrive—see list datastores below).
[1] Get-ChildItem path

[2] Get-ChildItem psdrive:path

[3] Get-ChildItem psdrive:
[1a] Get-ChildItem
[1b] Get-ChildItem .
[2a] gci c:\users\me\documents
[2b] ls SQLSERVER:\SQL­\localhost­\SQLEXPRESS\­Databases
[3a] dir env:
[3b] dir variable:
[3c] ls alias:
2List names of files in current directory[1] Get-ChildItem | select -ExpandProperty name
[2] dir | % { $_.Name }
[3] (dir).Name
3List names of files recursively[1] dir -Recurse | select -ExpandProperty Name
[2] (dir -Recurse).Name
4List full paths of files recursively[1] dir -Recurse | select -ExpandProperty FullName
[2] (dir -Recurse).FullName
5List full paths of files recursively with directory markerdir -r | % { $_.FullName + $(if ($_.PsIsContainer) {'\'}) }same
6List relative paths of files recursively with directory markerdir -r | % { $_.FullName.substring($pwd.Path.length+1) + $(if ($_.PsIsContainer) {'\'}) }same
List file and directory sizes
(see http://stackoverflow.com/a/14031005)
dir | % { New-Object PSObject -Property @{ Name = $_.Name; Size = if($_.PSIsContainer) { (gci $_.FullName -Recurse | Measure Length -Sum).Sum } else {$_.Length}; Type = if($_.PSIsContainer) {'Directory'} else {'File'} } }same
8List datastores (regular filesystem drives plus drives from other providers)[1] Get-PSDrive
[2] Get-PSDrive -PSProvider provider
[1] Get-PSDrive
[2] gdr -PSProvider FileSystem
9List providers (suppliers of datastores)[1] Get-PSProvider
[2] Get-PSProvider -PSProvider provider
[1] Get-PSProvider
[2] Get-PSProvider -PSProvider registry
10List processesGet-Processsame

Basic Syntactic Elements

Like with learning most things, you need to learn to crawl before you can learn to run. This section shows you how to do some of the most basic but important things, things that will soon become second nature: knowing what is true and what is false; adding comments; continuing a command across multiple lines or, contrariwise, combining multiple commands on one line; and so forth. Arguably there should be one other important group of items included here: PowerShell operators. But I already published a wallchart on a set of common operators for strings and string arrays. See Harnessing PowerShell's String Comparison and List-Filtering Features (http://bit.ly/1c20itX) for details on -eq, -like, -match, and -contains operators and their variations.

1End-of-line comment# (octothorp)52 # number of weeks in a year52
2Block comment or documentation comment<# … #> <# multi-line
comment here #>
3Continue command on multiple lines (required unless break after pipe or curly bracket)` (backquote as last character on line)"hello " + `
hello world
4Combine commands on a single line; (semicolon)$a = 25; $b = -9; "$a, $b"25, -9
5Escape next character` (backquote)$a = 25; "value of `$a is $a"value of $a is 25
6Non-printable characters (newline, tab, etc.)`n, `t"line one`n line two"line one
line two
7Boolean constant TRUE
(see here
and http://bit.ly/1iGhXOW)
[1] $TRUE
[2] Any string of length > 0
[3] Any number not equal to 0
[4] Array of length > 1
[5] Array of length 1 whose element is true
[6] A reference to any object
[1] if ($TRUE) { "true" } else { "not true" }
[2] if ("abc") { "true" } else { "not true" }
[3] if (-99.5) { "true" } else { "not true" }
[4] if ((1, 2)) { "true" } else { "not true" }
[5] if ((1)) { "true" } else { "not true" }
[6] $a = 25; if ([ref]$a) { "true" } else { "not true" }
8Boolean constant FALSE
(see here)
[1] $FALSE
[2] Empty string
[3] Any number = 0 (e.g. 0, 0.0, 0x0, 0mb, 0D, …)
[4] Array of length 0
[5] Array of length 1 whose element is false
[6] $NULL
[1] if ($FALSE) { "true" } else { "not true" }
[2] if ("") { "true" } else { "not true" }
[3] if (0x0) { "true" } else { "not true" }

[4] if (@()) { "true" } else { "not true" }
[5] if (("")) { "true" } else { "not true" }
[6] if ($NULL) { "true" } else { "not true" }
not true
not true
not true
not true
not true
not true
10Iterate each element in a listForEach-Object1..3 | % { $_ * 2 }2
11Ternary operator, scalar
(e.g. result = a > b ? x : y; )
[1] $result = switch (boolExpr) { $true { $x } $false { $y } }
[2] $result = if (boolExpr) { $x } else { $y }
[3] $result = ?: {boolExpr} {$x} {$y} <<pscx>>
[1] $result = switch (25 -gt 10) { $true { "yes" } $false { "no" } }
[2] $result = if (25 -gt 10) { "yes" } else { "no" }
12Coalesce (evaluate 2nd block if 1st block is null)
Define Coalesce-Args as:
function Coalesce-Args  { (@($args | ?{$_}) + $null)[0] }; Set-Alias ?? Coalesce-Args
[1] Invoke-NullCoalescing block1 block2 <<pscx>>

[2] Coalesce-Args block1 block2
<<code from http://bit.ly/KhMkwO>>
[1a] Invoke-NullCoalescing {$env:dummy} {"\usr\tmp"}
[1b] ?? {$env:dummy} {"\usr\tmp"}
[2a] Coalesce-Args $env:dummy "\usr\tmp"
[2b] ?? $env:dummy "\usr\tmp"

Display Options

According to Using Format Commands to Change Output View (http://bit.ly/N8b7oe) each format cmdlet (i.e. Format-Table and Format-List) has default properties that will be used if you do not specify specific properties to display. But the documentation does not reveal what those defaults are or how they vary depending on the type of input object. Also, the default properties differ between Format-Table and Format-List. Finally, keep in mind that if Select-Object is the last cmdlet in your command sequence, it implicitly uses Format-Table or Format-List selecting one or the other based on the number and width of output fields. (And while the included images were not designed for you to make out the actual text, you can discern the representation of the data from those thumbnails.)

1Format list of objects with each field on a separate lineany | Format-Listls C:\Windows\temp | select name,length | Format-ListName   : fwtsqmfile08.sqm
Length : 608

Name   : MpCmdRun.log
Length : 270630
. . .
2Format list of objects with all fields on one lineany | Format-Tablels C:\Windows\temp | select name,length | Format-TableName             length
----             ------
fwtsqmfile08.sqm 608
MpCmdRun.log     270630
MpSigStub.log   189120
. . .
3Format list of objects in an interactive gridany | Out-GridViewls C:\Windows\temp | select name,length | Out-GridView
4Format list as console graphany | Out-ConsoleGraph -property quantityPropertyName <<code from http://bit.ly/1jJN4tG>>ls C:\Windows\temp | select name,length | Out-ConsoleGraph -property length
5Format list as gridview graphany | Out-ConsoleGraph -GridView -property quantityPropertyName
<<code from http://bit.ly/1jJN4tG>>
ls C:\Windows\temp | select name,length | Out-ConsoleGraph -property length –grid
6Send table-formatted output to file[1] any | Format-Table -AutoSize |
Out-File file -Encoding ascii
[2] any | Format-Table -AutoSize |
Out-String | Set-Content file
[1] ps | ft -auto |Out-File process.txt -enc ascii
[2] ps | ft -auto |Out-String | sc process.txt
7Send trimmed table-formatted output to file (removes trailing spaces on fields as well as blank lines)any | Format-Table -AutoSize | Out-String -Stream | ForEach { $_.TrimEnd() } |where { $PSItem } |
Set-Content file
ps | ft -auto| Out-String -Stream | %{ $_.TrimEnd() } | ? { $_ } | sc file

Prompts and Pauses

Some basic interactivity entries, showing how to get input from a user, how to pause and resume, and how to clear the window contents.

1Prompt user for inputRead-Host prompt$userValue = Read-Host "Enter name"
2Pause for a specific time periodStart-Sleep seconds"before"; Start-Sleep 5; "after"
3Pause a script and resume with Enter keyRead-Host -Prompt promptString Read-Host -Prompt "Press enter to continue..."
4Pause a script and resume with any key
(does not work in PowerShell ISE)
Write-Host "Press any key to continue ...";
$x = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyDown")
5Clear screenClear-Host
6Display progress barWrite-Progress -Activity title -status event -percentComplete percentagefor ($i = 0; $i -lt $stuff.Count; $i++)
# primary code here
Write-Progress -Activity $title -status $label[$i] -percent (($i + 1) / $stuff.Count*100)

Casts, Type Accelerators, and .NET Classes

You are no doubt familiar with type casting in .NET languages. PowerShell provides the same casting capability but enhances it with a new concept, type accelerators. Type accelerators are simply aliases for .NET framework classes. Note that in PowerShell you can always omit the “System.” prefix of a class if it has one to save typing, so you could use, say, DateTime rather than System.DateTime. But with type accelerators you can get a lot more concise than that. For example, you can just use [wmi] instead of System.Management.ManagementObject. As far as casting, in PowerShell you can cast to any .NET type that has either a cast operator or a constructor that accepts the source type (see the Net.IpAddress entry below). Finally, you can use .NET type names to access static members of .NET classes (see the DateTime.Now entry below).

1List all type accelerators (see here)[1] [accelerators]::get <<pscx>>
[2] [psobject].assembly.gettype( "System.Management.Automation.TypeAccelerators")::Get
2Cast string to IPAddress object[System.Net.IpAddress]"ip-address”[Net.IpAddress]''Address : 16777408
AddressFamily : InterNetwork
. . .
IsIPv4MappedToIPv6 : False
IPAddressToString :
3Create new DateTime object with constructorNew-Object -TypeName DateTime
-ArgumentList constructor-argument-list
New-Object -TypeName DateTime
-ArgumentList 2014,10,10
Friday, October 10, 2014 12:00:00 AM
4Cast string to a DateTime object[DateTime]"date-time value"[DateTime]"10/10/2014" |
select Year, DayOfWeek, Ticks
Year DayOfWeek Ticks
---- --------- -----
2014 Friday    635484960000000000
5Cast string to XML without accelerator[System.Xml.XmlDocument] "XML text"[System.Xml.XmlDocument] "<root>text</root>"root
6Cast string to XML with accelerator[xml] "XML text"[xml] "<root>text</root>"root
7Access static member of .NET class[class]::member$currentTime = [datetime]::Now
8Cast integer to Boolean # [bool]2 yields True; [bool]0 yields False

That’s it for part 1; keep an eye out for more in the near future! While I have been over the recipes presented numerous times to weed out errors and inaccuracies, I think I may have missed one. If you locate it, please share your findings in the comments below!