Powershell Notes

This is an ongoing collection of notes related to my learning of Powershell. Warning - These notes aren’t structured yet.

Powershell unlike other CLI’s is object based not string based, even though the output may appear to be a string sometimes.

Powershell has something called PS drives which are providers to allow interaction to components whether it be Filesystems, Registry, Variables, etc though see them as you would a filesystem. These are only Powershell drives and drive names must follow with a colon.*

Show what PS drives are available

get-psdrive

Either will show system variables. This is using a PSDrive. The end colon is important.

ls variable:
dir variable:

This would change your current ‘drive’ to HKey Current User registry.

cd hkcu

Creates a new PSDrive called Demo as a filesystem provider going to C:demo

New-PSDrive -name Demo -PSProvider FileSystem -Root C:Demo

If you run items like Net Use for example, behind the scenes Powershell will run CMD.exe, run the command and return the output to Powershell.

cmdlets are always a Verbal followed a dash then a singular noun.

This will search powershell help for any help topics that names matches the work. The ‘man’ command also works like Linux. (I prefer ‘man’ command).

help *word*

i.e
help *mail*

If in the help, the parameter name is in squared brackets, this means the parameter name is optional and therefore based on the order. parameter names can be shortened though need to take into account common parameter too as may need to provide more detail (length of shortened name).

For string[] arrays, you can just use comma separated lists. It’s important to wrap each parameter in single quotes only if contains a space, not the whole string array.

Get all commands containing word. Great way to discover new commands. Third example gets all references though only cmdlets as without it would return external applications too.

Get-Command -noun *word*
Get-Command -verb *word*
Get-Command *word* -CommandType cmdlet

You can pipe output into a range of different outputs

command | out-file filename.txt
command | out-gridview
command | out-print
command | Export-Clixml C:filename.xml

Compare files

diff (Compare-object)

Compare XML of processes to current processes based on name

Compare-Object -ReferenaceObject (import-clixml C:filename.xml) -DifferenceObject (Get-Process) -property Name

Convert to HTML

command | convertto-html | out-file test.html

Snapin’s are the old way in Powershell 2. Now it’s called Modules.

See what modules are available

Get-Module -ListAvailable

Get commands within a module

Get-Command -Module *ModuleName*

Gets Services On Machine

Get-Service

Columns are trimmed depending on screen size. Can use Get-Member so see what properties are available.

To sort on propertyName

Command | Sort-Object -Property *PropertyName* -Descending

Filter to single property and rename it. Useful if piping output into another command to bind on property name. The command to bind, must ‘Accept pipeline input’ which is visable in the help file

COMMAND | Select @{name='MyNewPropertyName'; expression={$_.OldPropteryName}}

Filter to all properties and rename/add property to another properties value. Useful if piping output into another command to bind on property name

COMMAND | Select *,@{name='MyNewPropertyName'; expression={$_.OldPropteryName}}

If a command doesn’t allow piping, you can still provide input, eg. This will get all properties when running Get-AdComputer and only pull the value from the name

Get-WMIObject -Class win32_bios -ComputerName (Get-AdComputer -Filter * | select -expand Name)

Where clause

# $_ Allows you to access a row at a time that was passed into the where clause
# $_. Allows you to access a column from the data row
# You don't need to type FilterScript if the first parameter is the filter in {}
Get-Service | Where-Object -FilterScript { $_.Status -eq 'Running' }
Get-Service | Where-Object -FilterScript { $_.Status -eq 'Running' and $_.Name -like '*VMWARE*' }

Just like in SQL, it’s best to reduce the dataset before doing sorting (I.e Ordering in SQL). This reduces the dataset that needs to be sorted as we might not need them. This might be called Filter Left. You should also check to see if the command can filter itself.

# Gets services beginning with C
Get-Service -Name C*

Neat like trick, is powershell knows what kb, mb, gb, tb or pt are. I.e 1000mb / 5mb

You can run scripts or code blocks on remote computers by enabling psremoting

Enable-PSRemoting

# For remote commands
invoke-command -scriptblock {} -computer localhost

# For remote script
invoke-command -FilePath H:PowershellScriptsscript1.ps1 -computer localhost

#Throttle connections as will spawn a new powershell instance on your machine too
invoke-command -FilePath H:PowershellScriptsscript1.ps1 -computer localhost,server01,server02 -ThrottleLimtit 2

Start an interactive session with a remote computer

# connect to server01
enter-pssession -computer server01

# Exit
exit-pssession

Due to kerberos, you cannot start a remote session from a remote session as kerberos wont allow your credentials to be delegated again. Also, you cannot connect to localhost with different credentials, at least for WMI.

Child Jobs If you run invoke commands on a group of computers, you can break down the output after to view any session.

# Returns list of jobs with ID (Parent ID)
Get-Job

# Get sub jobs of parent id 2 and expand each child
Get-Job -id 2 | Select -ExpandProperty childjobs

# Now you've got the list of child id's, you can now retrieve the output
received-job 3

# Now you've got the list of child id's, you can now retrieve the output though this time tell Powershell to keep the output until the parent shell is closed. Else, one read you cannot read it again.
received-job 3 -keep

WMI Example

Get-WMI -Name WIN32_BIOS -Computer server01

http://www.youtube.com/watch?v=tyjiOn-QBTE&list=PL6D474E721138865A

Posted in DevOps, Programming with : PowerShell