Yearly Archive December 18, 2017

#powershell Get-Date v.s. [datetime] Format and System Locale III

On a non-US system locale Windows machine[1], running this statement in a #powershell script will fail:

[datetime]$dt1 = (Get-Date).DateTime
Cannont convert value “Dienstag, 12. Dezember 2017 22:20:20” to type “System.DateTime”. Error: “The string was not recognized as a valid DateTime. There is an unknown word starting at index 0.”
At line:1 char:1
+[datetime]$dt1 = (Get-Date).DateTime
+
+ CategoryInfo : MetadataError: (:) [], ArgumentTransformationMetadataException
+ FullyQualifiedErrorId : RuntimeException

To resolve this,

#powershell Get a List of Windows Update Hotfixes & Patches

To retrieve a comprehensive list of installed quick fix engineering hotfixes and patches[1] in Windows Update, you export into a format such as CSV with the help of the perennial $env:windir\Windows\System32\Wbem\WMIC.exe tool:

$file = “qfe.csv”
wmic qfe list full /format:csv > $file
#optionally run in MS-DOS
#wmic qfe list full /format:”%windir%\system32\wbem\en-us\csv.xsl” > “qfe.csv”

Subsequently, you can import the Comma Separated Variable file and…

#powershell Get-EventLog <-> Get-WinEvent

Inspecting the Event Log (eventvwr.exe) can provide clues to the startup (Event ID 6005*) and shutdown (Event ID 6006) date/time of a Windows machine. To do this, one common approach is with Get-EventLog:

#requires -version 3.0
Get-EventLog -LogName system -ComputerName FS01 | ? EventId -eq 6006

Instead, a more efficient way without the #powershell pipeline can be achieved using Get-WinEvent:

Get-WinEvent -ComputerName FS01 -FilterHashtable @{ LogName=’system’; Id=6006 }

Look out for Event ID 6008 which records the date/time of unexpected system shutdown.

* Event ID: 12 Provider (Source): Kernel-General contains actual operating system start time.

#powershell -version is not recognized

Note that powershell.exe /? shows the syntax to execute PowerShell from a command prompt. Nevertheless, running

C:\> powershell -noprofile -version 2.0
-version : The term ‘-version’ is not recognized as the name of a cmdlet, function, script file, or operable program.
Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ -version 2.0
+ ~~~~~~~~
+ CategoryInfo : ObjectNotFound: (-version:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException

fails …

#powershell Temporary Files

Introduced in PowerShell 5.0, the New-TemporaryFile cmdlet creates a single ‘scratch’ file with the tmp file extension in a user’s $env:temp directory. For previous #powershell versions, you can do this directly with .NET Framework:

$tempfile = [system.io.path]::GetTempFileName()

Likewise, this has the tmp file extension and is automatically placed in $env:temp. Assigning to a variable permits quick access.

Alternatively, you can create a unique file name for temporary usage by taking advantage of your system date/time as depicted:

$d = Get-Date
$d1 = $d.date.ToShortDateString() -replace “:|/|-|\.”
$d2 = $d.TimeOfDay.ToString() -replace “:|\|-|\.”
$tempfile = “$env:temp\” + $d1 + $d2 + “.tmp”
$tempfile

#powershell Auto Type Conversion – String Array Concatenation

$a1 = “apple”
$a2 = “pear”, “guava”

# add/join 2 string arrays together
[array]$fruits = $a1 + $a2
$fruits
# applepear guava
# $a1 is a simple string type;
# $a2 string array auto expanded and added to same string object

$fruits.count #1 unique string
$fruits.GetType() #a single unit of string array

# one correct way to add/join 2 string arrays together
# force conversion of $a1 simple string to a string array
$fruits = @($a1) + $a2
$fruits
<#
apple
pear
guava
#>

$fruits.count #3 items in array
$fruits.GetType() #an array of strings

$fruits[1]
# pear

#alternative if the order is not important
$fruits = $a2 + $a1
$fruits
<#
pear
guava
apple
#>

$fruits.GetType() #an array of 3 strings