PowerShell Revisited - Running Commands

Running PowerShell Commands

The command Get-Verb is an example of a cmdlet (pronounced “command-let”). Cmdlets are structured verb-noun, where the noun is singular.

Below we will get a list of approved verbs in PowerShell, then format the results to fill the screen from left to right:

PS C:\> Get-Verb | Format-Wide -AutoSize Add Clear Close Copy Enter Exit Find Format Get Hide Join Lock Move New Open Optimize Pop Push Redo Remove Rename Reset Resize Search Select Set Show Skip Split Step Switch Undo Unlock Watch Backup Checkpoint Compare Compress Convert ConvertFrom ConvertTo Dismount Edit Expand Export Group Import Initialize Limit Merge Mount Out Publish Restore Save Sync Unpublish Update Approve Assert Complete Confirm Deny Disable Enable Install Invoke Register Request Restart Resume Start Stop Submit Suspend Uninstall Unregister Wait Debug Measure Ping Repair Resolve Test Trace Connect Disconnect Read Receive Send Write Block Grant Protect Revoke Unblock Unprotect Use

Microsoft has provided a nice page on the verb naming rules which can be found here.

The commands you use in cmd.exe can also be used within PowerShell since they are either aliased, new functions, or the external executable is called.

• dir is an alias for Get-ChildItem
• md is an alias for mkdir which is a function for New-Item
• rmdir is an alias for Remove-Item

Some easy commands that just work:

• Get-Process
• Get-Service
• Get-Date
• Get-HotFix
• Get-History
• Start-Transcript, Stop-Transcript
• Get-ChildItem

Now you may be wondering why the names seem so generic. The idea is that if the names are consistent then you can easily discover new commands. In addition, some commands can be reused in multiple areas such as managing the registry and filesystem. Here is a good example with Get-PSDrive:

PS C:\> Get-PSDrive

Name Used (GB) Free (GB) Provider Root CurrentLocation

---

Alias Alias C 81.37 151.42 FileSystem C:\ Cert Certificate \ E FileSystem E:\ Env Environment Function Function HKCU Registry HKEY_CURRENT_USER HKLM Registry HKEY_LOCAL_MACHINE I 1112.16 305.87 FileSystem \\chs-fs01_users\Users\Michael.West Variable Variable WSMan WSMan Y 8.88 3.12 FileSystem \\chs\data

PowerShell uses a variety of providers such as those for connecting to the file system and the registry. This design allows one to use for example, the Remove-Item command to delete a file or delete a registry key. Sweet!

PS C:\> $item = New-Object -TypeName PSObject -Property @{Name=“Michael”;Height=73;} PS C:\> $item | Format-List

Height : 73 Name : Michael

Here I created a new PSObject to contains some details about my name and height. Let’s see the member information.

PS C:\> $item | Get-Member

TypeName: System.Management.Automation.PSCustomObject

Name MemberType Definition

---

Equals Method bool Equals(System.Object obj) GetHashCode Method int GetHashCode() GetType Method type GetType() ToString Method string ToString() Height NoteProperty System.Int32 Height=73 Name NoteProperty System.String Name=Michael

As you can see, the TypeName is “System.Management.Automation.PSCustomObject” and the new properties “Name” and “Height” are listed. The object type will be relevant to whatever object is piped in to Get-Member.

Get-PSDrive

Gets the Windows PowerShell drives in the current session.

Example:

# Displays details about the local disk C.
Get-PSDrive C

Random fact:

Try this: (Get-PSDrive)[0].Name <# Returns the name of the first object. #>

Try this: (Get-PSDrive)[0].GetType() <# Returns the type of the first object. #>

Set-Location

Sets the current working location to a specified location.

Example:

# Changes the location to the registry hive HKEY_LOCAL_MACHINE. The colon is required.
Set-Location HKLM:

PS C:\> Set-Location HKLM: PS HKLM:\> Set-Location C: PS C:\> Set-Location Alias: PS Alias:\> dir | more

CommandType Name ModuleName

---

Alias % -> ForEach-Object Alias ? -> Where-Object Alias ac -> Add-Content Alias asnp -> Add-PSSnapin Alias cat -> Get-Content Alias cd -> Set-Location Alias chdir -> Set-Location Alias clc -> Clear-Content Alias clear -> Clear-Host Alias clhy -> Clear-History Alias cli -> Clear-Item

As you can see in the image above, I changed to the registry, then the C drive, then to Alias. In all of these locations, you can run the standard commands such as dir, ls, cd and so on. In the image you can also see that cd is an alias for Set-Location.

Below are some command aliases common in other environments.

Command

Aliases

Copy-Item

cpi, cp, copy

ForEach-Object

foreach, %

Get-ChildItem

dir, ls

Get-Command

gcm

Get-Content

gc, type, cat

Get-Help

help

Get-Location

gl, pwd

Move-Item

mi, mv, move

Rename-Item

rni, ren

Set-Location

cd, chdir

Where-Object

where, ?

Remove-Item

ri, rd, del, rm, rmdir

Random fact:

To count the number of items return, use Measure-Object. Use additional switch parameters such as -Sum and -Average.

Try this: Get-Process | Measure-Object <# Returns a table with the results of Measure-Object. #>

Try this: (Get-Process | Measure-Object).Count <# Returns the count value. #>

Get-Content

Gets the content of the item at the specified location.

Example:

# Reads the entire contents of the file.
Get-Content -Path C:\log.txt

Add-Content

Adds content to the specified items, such as adding words to a file.

Example:

# Appends the text to the file log.txt.
Add-Content -Path C:\log.txt -Value "The quick brown fox jumps over the lazy dog."

Out-File

Sends output to a file.

Example:

# The first command takes a snapshot of all the running processes. 
# The list passed through pipeline to Out-File which is then written to log.txt.
Get-Process | Out-File -FilePath C:\log.txt

Write-Host

Writes customized output to a host. The information is not kept in the pipeline.

Example:

# The text is written to the console window.
Write-Host "This text is written to the host, such as the console window."

Write-Output

Sends the specified objects to the next command in the pipeline. If the command is the last command in the pipeline, the objects are displayed in the console.

Example:

# The snapshot of running processes is saved into the variable p. The variable p is then written to the console window.
$p = Get-Process; Write-Output -InputObject $p

Write-Verbose

The text is written to the verbose message stream. This is commonly used in PowerShell scripts.

Example:

# The text is written to the verbose stream. If the switch -Verbose is used, the text will be written to the console window.
Write-Verbose -Message "The quick brown fox jumps over the lazy dog."

New-Item

Creates a new item. The item can be a new registry key, file, directory, etc. The type of item created depends on which provider you are connected to.

Example:

# A new file is created with the specified text.
New-Item -Path C:\ -Name log.txt -ItemType "file"
New-Item -Path C:\log.txt -ItemType "file" -Value "The quick brown fox jumps over the lazy dog."