The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘PowerShell’ Category

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PowerShell: count the Windows EventLog entries for Applications over the last 10 minutes

Posted by jpluimers on 2019/09/25

In production, somehow an application started to misbehave, so would spit out a lot of Windows EventLog entries for Applications you can see in the EventViewer. This small script helped counting it (it takes about 10 seconds on a log having a total of 77k entries):

$tenMinutes = New-TimeSpan -Minutes 10
$now = Get-Date
$tenMinutesAgo = $now - $tenMinutes
$eventLogEntries = Get-EventLog -After $tenMinutesAgo -LogName "Application"
$count = ($eventLogEntries | Measure-Object).Count
Write-Host $count

Related:

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | 1 Comment »

how to filter name/value pairs under a registry key by name and value in PowerShell?

Posted by jpluimers on 2019/09/03

A very concise way for [WayBack] how to filter name/value pairs under a registry key by name and value in PowerShell?:

$path = 'hkcu:\Software\Microsoft\Windows\CurrentVersion\Extensions'
(Get-ItemProperty $path).PSObject.Properties |
  Where-Object { $_.Name -match '^xls' ` -or $_.Value -match 'msaccess.exe$' } |
  Select-Object Name, Value

Thanks montonero for getting me on that path and pointing me to the hidden PSObject property which by itself has Properties, and making me find these links with background information:

More in-depth information:

  • [WayBack] Get-Member (Microsoft.PowerShell.Utility)
    • The Get-Member cmdlet gets the members, the properties and methods, of objects. To specify the object, use the InputObject parameter or pipe an object to Get-Member. To get information about static members, the members of the class, not of the instance, use the Static parameter. To get only certain types of members, such as NoteProperties, use the MemberType parameter.
    • -Force

      Adds the intrinsic members (PSBase, PSAdapted, PSObject, PSTypeNames) and the compiler-generated get_ and set_ methods to the display. By default, Get-Member gets these properties in all views other than Base and Adapted, but it does not display them.

      The following list describes the properties that are added when you use the Force parameter:

      • PSBase: The original properties of the .NET Framework object without extension or adaptation. These are the properties defined for the object class and listed in MSDN.
      • PSAdapted. The properties and methods defined in the Windows PowerShell extended type system.
      • PSExtended. The properties and methods that were added in the Types.ps1xml files or by using the Add-Member cmdlet.
      • PSObject. The adapter that converts the base object to a Windows PowerShell PSObject object.
      • PSTypeNames. A list of object types that describe the object, in order of specificity. When formatting the object, Windows PowerShell searches for the types in the Format.ps1xml files in the Windows PowerShell installation directory ($pshome). It uses the formatting definition for the first type that it finds.
  • [WayBack] PSObject Class (System.Management.Automation)
    • Wraps an object providing alternate views of the available members and ways to extend them. Members can be methods, properties, parameterized properties, etc.
  • [WayBack] PSObject.Properties Property (System.Management.Automation)
    • Gets the Property collection, or the members that are actually properties.
      Is of type PSMemberInfoCollection<PSPropertyInfo>
  • [WayBack] PSMemberInfoCollection<T> Class
    • Serves as the collection of members in an PSObject or MemberSet
  • [WayBack] PSPropertyInfo Class (System.Management.Automation)
    • Serves as a base class for all members that behave like properties.
  • [WayBack] Difference between PSObject, Hashtable and PSCustomObject
  • [WayBack] Combining Objects Efficiently – Use a Hash Table to Index a Collection of Objects
    • With objects objects everywhere it may not seem apparent, but hash tables are still needed.  When the PowerShell mind sets to work it can be very easy to use where and selects everywhere to get you…
  • [Archive.is] Custom objects default display in PowerShell 3.0
  • [WayBack] Using PSObject to store data in PowerShell | 9to5IT
    • PowerShell’s PSObject is a powerful tool which is used to store, retrieve, sort and export data. Here is how to use PSObject to store data in PowerShell.

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

When Powershell function won’t work: you define them with commas and parentheses, but call them with spaces and no parentheses

Posted by jpluimers on 2019/08/15

The function or command was called as if it were a method. 
Parameters should be separated by spaces. For information about 
parameters, see the about_Parameters Help topic.

Every now and then I bump into the above error. The reason is this:

  1. Functions are defined with commas between parameters and parentheses around them
  2. One-parameter functions can be called with one parameter surrounded by parentheses
  3. Multi-parameter functions need to be called with spaces between parameters and no parentheses surrounding them

Confused? #MeToo

The problem: [WayBack] about_Parameters_Default_Values | Microsoft Docs

Based on [WayBack] Powershell function won’t work.

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

PowerShell: be careful using `-ReadCount` on `Get-Content`

Posted by jpluimers on 2019/08/14

I learned this the hard way: [WayBack] Different result when using -ReadCount with Get-Content: because -ReadCount delivers data in chunks, the filter after [WayBack] Get-Content (Microsoft.PowerShell.Management) it will only filter on those chunks. If the filter isn’t prepared for that, it might only filter the last chunk.

So do not use for instance [WayBack] Select-String (Microsoft.PowerShell.Utility) on it, but perform your own [WayBack] ForEach-Object (Microsoft.PowerShell.Core) aliased as foreach like in [WayBack] Get all lines containing a string in a huge text file – as fast as possible?:

Get-Content myfile.txt -ReadCount 1000 |
  foreach { $_ -match "my_string" }

A more elaborate example is at [WayBack] How can I make this PowerShell script parse large files faster?.

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

Powershell: what kind of data type is [string[]] and when would you use it?

Posted by jpluimers on 2019/08/13

[WayBack] In Powershell, what kind of data type is [string[]] and when would you use it? (thanks cignul9 and arco444!): basically it forces an array of string.

It defines an array of strings. Consider the following ways of initialising an array:

[PS] > [string[]]$s1 = "foo","bar","one","two",3,4
[PS] > $s2 = "foo","bar","one","two",3,4

[PS] > $s1.gettype()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     String[]                                 System.Array

[PS] > $s2.gettype()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Object[]                                 System.Array

By default, a powershell array is an array of objects that it will cast to a particular type if necessary. Look at how it’s decided what types the 5th element of each of these are:

[PS] > $s1[4].gettype()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     String                                   System.Object


[PS] > $s2[4].gettype()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Int32                                    System.ValueType


[PS] > $s1[4]
3
[PS] > $s2[4]
3

The use of [string[]] when creating $s1 has meant that a raw 3 passed to the array has been converted to a String type in contrast to an Int32 when stored in an Object array.

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

.NET and PowerShell: Getting proper version info from a PE file like EXE, DLL, assembly

Posted by jpluimers on 2019/08/01

I’ve learned the hard way that both .NET and PowerShell version information isn’t always accurate or usable for two reasons which I later found in various other blog and forum posts:

The easiest is to use these numbers to create a [WayBack] Version Class (System) instance using the [WayBack] Version Constructor (Int32, Int32, Int32, Int32) constructor. This has the added benefit that you directly compare versions with each other.

Sometimes it makes even sense to take the highest version from Product and File.

In PowerShell, this is the way to do that, assuming $imagePath points to a [WayBack] Portable Executable:

try {
  $VersionInfo = (Get-Item $imagePath).VersionInfo
  $FileVersion = [version]("{0}.{1}.{2}.{3}" -f $VersionInfo.FileMajorPart, $VersionInfo.FileMinorPart, $VersionInfo.FileBuildPart, $VersionInfo.FilePrivatePart)
  $ProductVersion = [version]("{0}.{1}.{2}.{3}" -f $VersionInfo.ProductMajorPart, $VersionInfo.ProductMinorPart, $VersionInfo.ProductBuildPart, $VersionInfo.ProductPrivatePart)
  $ActualVersion = $(if ($ProductVersion -gt $FileVersion) { $ProductVersion } else { $FileVersion })
}
catch {
  $ActualVersion = [version]("0.0.0.0")
}

Background information:

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

Ternary operator in PowerShell – Stack Overflow

Posted by jpluimers on 2019/07/31

I like this built-in construct by fbehrens most:

$result = If ($condition) {"true"} Else {"false"}

Everything else is incidental complexity and thus to be avoided.

For use in or as an expression, not just an assignment, wrap it in $(), thus:

write-host $(If ($condition) {"true"} Else {"false"})

There are even more elegant constructs, but those require setting up an alias before using them.

Source: [WayBack] Ternary operator in PowerShell – Stack Overflow

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

scripting – Run Multiple Powershell Scripts Sequentially – on a Folder – Combine Scripts into a Master Script – Stack Overflow

Posted by jpluimers on 2019/07/30

Cool tip by mjolinor to execute the scripts 1.ps1, 2.ps1 and 3.ps1 from a master.ps1 script in the same directory:

&"$PSScriptroot\1.ps1"
&"$PSScriptroot\2.ps1"
&"$PSScriptroot\3.ps1"

Source: [WayBack] scripting – Run Multiple Powershell Scripts Sequentially – on a Folder – Combine Scripts into a Master Script – Stack Overflow.

It uses $PSScriptroot which got introduced in PowerShell 2 in modules and extended in PowerShell 3 to be available in all scripts. More information in [WayBack] about_Automatic_Variables | Microsoft Docs

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

powershell – How do I use join-path to combine more than two strings into a file path? – Stack Overflow

Posted by jpluimers on 2019/07/25

I love the solution with piped Join-Path constructs answered by David Keaveny in [WayBack] powershell – How do I use join-path to combine more than two strings into a file path? – Stack Overflow:

Since Join-Path can be piped its path value, you can pipe multiple Join-Path statements together:

Join-Path "C:" -ChildPath "Windows" | Join-Path -ChildPath "system32" | Join-Path -ChildPath "drivers"

Of course you could replace the built-in [WayBack] Join-Path by using using the .NET Framework [WayBack] Path.Combine Method (System.IO), but then you loose code completion.

If you do like that, here is how:

[System.IO.Path]::Combine("C:", "Windows", "system32", "drivers")

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

PowerShell script header to be as strict as possible and always throw exceptions

Posted by jpluimers on 2019/07/24

This is my default PowerShell script header from now on:

Set-StrictMode -Version Latest
$ErrorActionPreference = 'Stop'
$PSDefaultParameterValues['*:ErrorAction']='Stop'

This might sound like overkill, but it solves these problems:

The above helped me tremendously with for instance [WayBack] powershell – Why does the exception not get me in the catch block? – Stack Overflow:

I’m trying to interrogate some service information. Sometimes the installer of the application fails to correctly install, so the registry does not contain a service entry. I want to find out which installer steps did get executed correctly, even on systems that do not have proper logging in the installer.

If MyService does not exist, the script below does not go to the catch block even though the exception handling documentation suggests a bare catch should be enough:

try {
    $path = 'hklm:\SYSTEM\CurrentControlSet\services\MyService'
    $key = Get-Item $path
    $namevalues = $key | Select-Object -ExpandProperty Property |
        ForEach-Object {
        [PSCustomObject] @{
            Name = $_;
            Value = $key.GetValue($_)
        }
    }
    $namevalues | Format-Table
}
catch {
    $ProgramFilesX86 = [System.Environment]::GetFolderPath("ProgramFilesX86");
    $ProgramFiles = [System.Environment]::GetFolderPath("ProgramFiles");
    Write-Host $ProgramFilesX86
    Write-Host $ProgramFiles
}

Why is that and how should I force it to end up in the catch?

This is what PowerShell outputs:

Get-Item : Cannot find path 'HKLM:\SYSTEM\CurrentControlSet\services\MyService' because it does not exist.
At C:\Users\Developer\...\GetMyServiceInfo.ps1:17 char:12
+     $key = Get-Item $path
+            ~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (HKLM:\SYSTEM\Cu...vices\MyService:String) [Get-Item], ItemNotFoundException
    + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetItemCommand

For which I edited the answer to become this:

Force the error to be terminating:

$key = Get-Item $path -ErrorAction Stop

That way it will throw and catch will get it.

Explanation and links to the official Microsoft documentation:

What is missing there is the link to the $PSDefaultParameterValues documentation at [WayBack] about_Parameters_Default_Values | Microsoft Docs

–jeroen

Posted in CommandLine, Development, PowerShell, PowerShell, Scripting, Software Development | Leave a Comment »

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