Tag Archives: Where-Object

View Current PowerShell.org Q&A Forum Topics

Note: Update added at the bottom on this post on August, 9, 2016. Please read.

Sometimes you don’t always have the time to finish something you’ve started. For me, it was this function. I pounded this out in a quick few minutes, and while I don’t see myself investing in it any further, I didn’t want to forget the function, and thought I would hang on to it somewhere. Well, that’s why it’s here, especially as someone may find it useful, or helpful.

The function, which I called Get-PowerShell.orgForumTopic, runs out to PowerShell.org and grabs the current topics (page one) from the PowerShell Q&A forum (http://powershell.org/wp/forums/forum/windows-powershell-qa). It only returns the Thread name and the URL, because, well, that’s what seemed useful and relevant at the time I wrote it (which was many months ago).

Function Get-PowerShell.orgForumTopic {
    [CmdletBinding()]
    Param ()

    Begin {
    } # End Begin.

    Process {
        (Invoke-WebRequest -Uri 'http://powershell.org/wp/forums/forum/windows-powershell-qa/' |
            Select-Object -ExpandProperty Links |
            Where-Object {$_.outerHTML -like '*http://powershell.org/wp/forums/topic*'} |
            Select-Object @{N='Thread';E={$_.innerHTML}},@{N='Url';E={$_.href}} |
            Select-Object -First 30)[(0..30 |
                ForEach-Object {
                    If (-not($_ % 2)) {
                        $_
                    }
                 }
            )]
    } # End Process.

    End {
    } # End End.
} # End Function: Get-PowerShell.orgForumTopic

Here’s what the results looked like in the ConsoleHost, near in time to when this post was published.

current-powershell.org-qa-forum-topics-01

While I never added any more to this function, I had some ideas: add the thread status, add the “started by user,” add the user that made the last post, add the number of posts per topic, and allow it to run against other PowerShell.org forum topics. It might’ve also been helpful to include additional pages, if requested by the user of the function, such as adding a -Pages parameter (-Pages 4).

Anyway, here it is. Beside being helpful to see the top PowerShell.org Q&A forum posts at a specific point in time, it’s an interesting example of reading from a webpage, of which I had minimal experience. So yeah, I probably learned something by doing this exercise.

If you want to do the same, then start by running the first command, Invoke-WebRequest -Uri ‘http://powershell.org/wp/forums/forum/windows-powershell-qa/’. Then add the pipe and first Select-Object command and run that. Then add the Where-Object command, and so on. This will allow you to see how I finally got to only returning the “Threads” and “Urls.” Take care.

Update: Since a site redesign at PowerShell.org, this function, no longer functions. I’m not sure that I’ll bother to update it — I don’t get the feeling that it was ever used by anyone — but I’ll keep this post up for anything else it may offer, that may be helpful in learning PowerShell.

An Improved Measure-Command: Multiple Commands, Multiple Repetitions, Calculated Averages, and Pauses Between Runs

Download the Measure-TMCommand function here: https://gallery.technet.microsoft.com/Measure-Command-with-52158178

In Windows PowerShell, there are often several ways to complete the same task. With that in mind, it makes sense that we might want to determine how long commands and scripts take to complete. Until now, Measure-Command has been the cmdlet we’ve used.

While Measure-Command has been helpful, I’ve often thought it should include some additional functionality. Therefore, I’ve written an advanced function, Measure-TMCommand, that adds all the benefits listed below:

– Continually measure the execution time of a single command and/or script, up to a user-defined number of repetitions.

– Continually measure the execution time of multiple commands and/or scripts, up to a user-defined number of repetitions.

– Calculate the average time a command(s), and/or a script(s)  takes to execute.

– Display limited hardware information about the computer where the command and/or script is being measured.

– Includes an option to display the output of the command and/or script, as well as the measurement results.

Updated 4/15/2015 (v1.2.1): Added a parameter -TimeInBetweenSeconds with a parameter alias of -Pause. This will pause the function between executions, allowing the ability to test at different times between a set time. For instance, let’s say you want to measure a command every 1/2 hour for six hours: 12 repetitions with 30 minute pauses. You would then run the command with the -Repetitions parameter with a value of 12 and the -TimeInBetweenSeconds (or -Pause) with a value of 1800 (as in 1800 seconds, or 30 minutes).

Here’s the function in action:

Measure-TMCommand1.2.1

In the example, above, we can easily determine that using the -Name parameter of the Get-Service cmdlet, is faster then piping the entire result set to the Where-Object cmdlet, and then filtering on the name. Notice that not all properties were returned — only the ones in which I was interested.

With the addition of the -TimeBetweenInSeconds, or -Pause, parameter I have considered that this function might be better served to also have an -AsJob parameter. I’ll look into it, but no promises. Thanks, and enjoy.

Download the Measure-TMCommand function here: https://gallery.technet.microsoft.com/Measure-Command-with-52158178

about_Aliases

This post is the help rewrite for about_Aliases. While the help files for Windows PowerShell are invaluable, the idea behind a rewrite is so true beginners might even better understand the help file concepts. At times, some things discussed in the Windows PowerShell help file will not be included in a help rewrite. Therefore, it is always best to read the actual help file after reading this post. (PS3.0)

An Alias in Windows PowerShell is a simplified, or quicker, way to type a cmdlet using an alternate name. Get-Alias (or the alias for Get-Alias, gal) will display a list of all of the aliases that the Windows PowerShell session knows about. This includes both built-in aliases and any additional aliases created or imported. The first two examples below, indicate two ways to accomplish the same thing – listing all the aliases. These examples only show the first four results.

PS C:\> Get-Alias

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Alias           % -> ForEach-Object
Alias           ? -> Where-Object
Alias           ac -> Add-Content
Alias           asnp -> Add-PSSnapin

This example uses the alias for the Get-Alias cmdlet, gal.

PS C:\> gal

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Alias           % -> ForEach-Object
Alias           ? -> Where-Object
Alias           ac -> Add-Content
Alias           asnp -> Add-PSSnapin

In order to find the cmdlet associated with a single alias, the alias needs to be provided, as the value for the -Name parameter, to the Get-Alias cmdlet.

PS C:\> gal -Name gc

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Alias           gc -> Get-Content

The name parameter (-Name) is not required to use it. This means that if there is something after the Get-Alias cmdlet, such as gc in this example, then it will default to using the -Name parameter.

PS C:\> gal gc

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Alias           gc -> Get-Content

Windows PowerShell will error if the -Name parameter is supplied with a cmdlet name, or another value that is not an alias.

PS C:\> gal Get-Content

gal : This command cannot find a matching alias because an alias with the name ‘Get-Content’ does not exist.
At line:1 char:1
+ gal Get-Content
+ ~~~~~~~~~~~~~~~
+ CategoryInfo          : ObjectNotFound: (Get-Content:String) [Get-Alias], ItemNotFoundException
+ FullyQualifiedErrorId : ItemNotFoundException,Microsoft.PowerShell.Commands.GetAliasCommand

In order to get an alias (or aliases, if there is more than one) for a cmdlet, the -Definition parameter must be used.

PS C:\> gal -Definition Get-Content

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Alias           cat -> Get-Content
Alias           gc -> Get-Content
Alias           type -> Get-Content

The Get-Service cmdlet returns the computer’s services, the Get-Process cmdlet return the processes running on the computer, and the Get-ChildItem cmdlet returns the directories and/or files from the root of a drive or from a folder. Here is how a user can get the aliases for multiple cmdlets at the same time.

PS C:\> gal -Definition Get-Service,Get-Process,Get-ChildItem

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Alias           gsv -> Get-Service
Alias           gps -> Get-Process
Alias           ps -> Get-Process
Alias           dir -> Get-ChildItem
Alias           gci -> Get-ChildItem
Alias           ls -> Get-ChildItem

There are a few other cmdlets that allow a user to work with aliases. By using the Get-Command cmdlet (or its alias – if it has one), additional cmdlets can be returned that all end with -Alias.

PS C:\> Get-Command *-Alias

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Cmdlet          Export-Alias                                       Microsoft.PowerShell.Utility
Cmdlet          Get-Alias                                          Microsoft.PowerShell.Utility
Cmdlet          Import-Alias                                       Microsoft.PowerShell.Utility
Cmdlet          New-Alias                                          Microsoft.PowerShell.Utility
Cmdlet          Set-Alias                                          Microsoft.PowerShell.Utility

Export-Alias: Exports information about currently defined aliases to a file.

PS C:\> Export-Alias -Path 'C:\aliases.txt'

Import-Alias: Imports an alias, or aliases, from a file.

PS C:\> Import-Alias -Path 'C:\ImportedAliases.txt'

Trying to import aliases that already exists will cause an error for every alias Windows PowerShell tries to import (that already exists).

PS C:\> Export-Alias -Path 'C:\aliases.txt'
PS C:\> Import-Alias -Path 'C:\aliases.txt'
Import-Alias : The alias is not allowed, because an alias with the name ‘ac’ already exists.
At line:1 char:1
+ Import-Alias -Path ‘C:\aliases.txt’
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ResourceExists: (ac:String) [Import-Alias], SessionStateException
    + FullyQualifiedErrorId : AliasAlreadyExists,Microsoft.PowerShell.Commands.ImportAliasCommand

New-Alias: Creates a new alias.
Set-Alias: Changes an existing alias, or creates an alias if it does not already exist.

PS C:\> New-Alias -Name MyAlias -Value Get-Process
PS C:\> MyAlias | select -First 4

Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)     Id ProcessName
-------  ------    -----      ----- -----   ------     -- -----------
    224      19     3440        772   110    16.50   4612 ALMon
    164      14     2476       2108    44     5.36   2744 ALsvc
     77       9     1336       5288    75   137.55   4076 ApMsgFwd
     90       8     1372       5788    76   162.11   4324 ApntEx

PS C:\> Set-Alias -Name MyAlias -Value Get-Service
PS C:\> MyAlias | select -First 4

Status   Name               DisplayName
------   ----               -----------
Running  AdobeARMservice    Adobe Acrobat Update Service
Stopped  AdobeFlashPlaye... Adobe Flash Player Update Service
Stopped  AeLookupSvc        Application Experience
Stopped  ALG                Application Layer Gateway Service

Bonus Information

Use the Measure-Object cmdlet, or the count property, to find out how many aliases Windows PowerShell knows about.

PS C:\> Get-Alias | Measure-Object

Count    : 182
Average  :
Sum      :
Maximum  :
Minimum  :
Property :

PS C:\> gal | measure

Count    : 182
Average  :
Sum      :
Maximum  :
Minimum  :
Property :

PS C:\> (gal | measure).count
182
PS C:\> (gal).count
182

Real World

While aliases are helpful in the console, the belief is that they should not be used in a script file (.ps1 file). Using full cmdlet names in a script is preferred for script readability. There are plenty of people writing Windows PowerShell who adhere to this best practice even while using aliases for the object cmdlets (select for Select-Object, where for Where-Object, etc.).

Learn More

This information, and more, is stored in the help file about_Aliases that comes with Windows PowerShell. This information can be read by typing any of the commands below. The first example will display the help file in the Windows PowerShell console, the second example will open the full help in it’s own window, the third example will send the contents of the help file to the clipboard (so it can be pasted into Word, Notepad, etc.), and the fourth example will open the help file in Notepad.

PS C:\> Get-Help about_aliases
PS C:\> Get-Help about_aliases -ShowWindow
PS C:\> Get-Help about_aliases | clip
PS C:\> Notepad C:\Windows\System32\WindowsPowerShell\v1.0\en-US\about_Aliases.help.txt

There is a built-in, automatic variable, $PSHOME, that stores the installation path of Windows PowerShell. This means that the third example above could have been partially written using that variable.

PS C:\> Notepad $PSHOME\en-us\about_Aliases.help.txt