CMD.exe compatibility

CMD.exe compatibility

  • Comments 18

A few weeks ago I was getting Mark Russinovich up and running on PowerShell. While he liked the power the new model afforded him, he was frustrated because a bunch of things that were simple in CMD.EXE where now either hard or not available. I forget what the specific was but I think he wanted to know how to do the CMD.EXE equivalent of "dir /q". This command shows the owners of the files. Here is the output from a CMD.EXE session:

C:\Documents and Settings\jsnover.ntdev>dir /q
Volume in drive C is PowerShell Rocks
Volume Serial Number is 14B2-8C76

Directory of C:\Documents and Settings\jsnover.ntdev

05/10/2007 07:57 AM <DIR> BUILTIN\Administrators .
05/10/2007 07:57 AM <DIR> BUILTIN\Administrators ..
04/16/2006 10:26 AM <DIR> NTDEV\jsnover .freemind
06/18/2006 07:54 PM 4,608 NTDEV\jsnover custom
11/05/2005 05:34 PM 24,498 NTDEV\jsnover err.txt
11/05/2005 05:36 PM 49,283 NTDEV\jsnover err1.txt
11/05/2005 05:37 PM 923 NTDEV\jsnover err2.txt
01/21/2007 01:45 PM <DIR> NTDEV\jsnover Favorites
06/16/2006 04:26 PM 6,219 NTDEV\jsnover foo
05/21/2007 11:31 AM 7,340,032 BUILTIN\Administrators NTUSER.DAT
06/30/2006 10:30 PM <DIR> NTDEV\jsnover PowerShell
05/10/2007 08:00 AM <DIR> NTDEV\jsnover SecurityScans
01/19/2006 03:28 PM <DIR> NTDEV\jsnover Start Menu
11/05/2005 05:50 PM 213 NTDEV\jsnover t.msh
05/27/2006 08:25 AM 13 NTDEV\jsnover t.txt
06/14/2006 06:18 PM 19 NTDEV\jsnover t1.bat
09/21/2006 07:33 PM 10,678 NTDEV\jsnover t1.txt
06/15/2001 05:42 AM 4,081 NTDEV\jsnover testroot.cer
01/19/2006 03:36 PM <DIR> NTDEV\jsnover Tracing
02/06/2006 09:41 PM <DIR> NTDEV\jsnover WINDOWS
11 File(s) 7,440,567 bytes
9 Dir(s) 16,137,601,024 bytes free

Doing the same in PowerShell is quite difficult because the underlying .NET objects do not make this simple.

Out of the box, we provide an alias DIR which maps to Get-ChildItem and that works fine for those of use that usually just type "dir" but it doesn't work well for those people that want to use the "native" parameters for DIR (e.g. "dir /q").

There are a few commands that fall into the same category and we've been thinking about whether we should provide better DOS emulations for these. The thinking was that maybe we should get rid of the alias and write a function which supports the CMD.exe syntax and then does mostly the same thing. We brainstormed that for a while and we didn't like the idea of spending a lot of time on a path that in the end, we wanted people to migrate off of. If we spend calories on that, that will rob you of other great features (and we have a BUCKETLOAD of great features we want to deliver for the next release).

We thought maybe we should provide a function "Get-DosOptions" which would work like UNIX getopts() but work against a DOS syntax. We'd provide this and then you could use it to write a front end function to those CMD.EXE commands that you miss the most. I decided to ask Bruce whether this was feasible and he reminded me that this was simple to do in PowerShell and we were thinking about it all wrong.

So here it goes, I'm going to show you how to get the native CMD.EXE semantics for DIR. You can use the same technique to get the native semantics for most CMD.EXE commands. The first thing you'll want to do is to remove any alias that we've set up for you:

PS> Remove-Item Alias:dir
PS>

Now define a function as follows and then run it:

PS> function dir {cmd /c dir $args}
PS> dir /ad /q
Volume in drive C is PowerShell Rocks
Volume Serial Number is 14B2-8C76

Directory of C:\Documents and Settings\jsnover.ntdev

05/10/2007 07:57 AM <DIR> BUILTIN\Administrators .
05/10/2007 07:57 AM <DIR> BUILTIN\Administrators ..
04/16/2006 10:26 AM <DIR> NTDEV\jsnover .freemind
05/15/2007 10:56 PM <DIR> NTDEV\jsnover Application Data
05/21/2007 07:53 PM <DIR> NTDEV\jsnover Cookies
01/21/2007 01:45 PM <DIR> NTDEV\jsnover Favorites
11/09/2005 05:00 PM <DIR> NTDEV\jsnover Local Settings
06/06/2006 12:54 PM <DIR> NTDEV\jsnover NetHood
06/30/2006 10:30 PM <DIR> NTDEV\jsnover PowerShell
08/10/2004 10:57 AM <DIR> NTDEV\jsnover PrintHood
05/21/2007 07:37 PM <DIR> NTDEV\jsnover Recent
05/10/2007 08:00 AM <DIR> NTDEV\jsnover SecurityScans
09/30/2006 08:26 PM <DIR> NTDEV\jsnover SendTo
01/19/2006 03:28 PM <DIR> NTDEV\jsnover Start Menu
06/11/2006 04:21 PM <DIR> NTDEV\jsnover Templates
01/19/2006 03:36 PM <DIR> NTDEV\jsnover Tracing
10/29/2005 10:01 PM <DIR> NTDEV\jsnover UserData
02/06/2006 09:41 PM <DIR> NTDEV\jsnover WINDOWS
0 File(s) 0 bytes
18 Dir(s) 16,440,205,312 bytes free

You can do this for all your CMD.EXE favorites:

PS> function assoc {cmd /c assoc $args}
PS> assoc .ps1
.ps1=Microsoft.PowerShellScript.1
PS> function vol {cmd /c vol $args}
PS> vol /?
Displays the disk volume label and serial number, if they exist.

VOL [drive:]
PS> vol c:
Volume in drive C is PowerShell Rocks
Volume Serial Number is 14B2-8C76
PS>

You gotta love it! Enjoy!

Jeffrey Snover [MSFT]
Windows Management Partner Architect
Visit the Windows PowerShell Team blog at: http://blogs.msdn.com/PowerShell
Visit the Windows PowerShell ScriptCenter at: http://www.microsoft.com/technet/scriptcenter/hubs/msh.mspx

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  • Please add 3 and 6 and type the answer here:
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  • Here's what I do.  I define a file named

    "~.bat" in the PATH as these two lines

    @echo off

    %*

    Thereafter I can just do

    ~ dir /q

    at a Powershell prompt.

    There's nothing magic about the name "~", but I find it conveniently terse.  It allows me access to all the cmd.exe supported internal commands.

    - Larry Weiss, lfw@airmail.net

  • Thanks for the tip.  

    What approach would you use to allow this to work with a transcript (start-transcipt and stop-transcript)?  

    When I begin and end the transcript, the results of the dir command are not recorded to the transcript.

    Do you have any creative ideas on how to get the results of a shell'ed command to record to the transcript?

    I've tried piping the cmd.exe output using the '>' but this is disconnected and cumbersome:

    function dir {cmd /c dir $args >log.txt}

    Do you have any tips on how to append the results of a cmd.exe to a transcript?

  • Nice tricks!  As an old CMD dog from DOS 1.0 days, I still struggle with the right way to do things in PowerShell vs. what I can easily recall via CMD way.  One idea to really help bridge/migrate over more to use Powershell is for not only emulating the CMD commands, but perhaps also providing example PS commands to achieve the same (or near same) effect.

    Example:

    function dir {

       Write-Output "PS Command (alias): Get-Children (gci)`n";

       cmd /c dir $args;

    }

    Of course this is a very simple PS tutor example.  More advanced ones I suppose could analyze the $args passed in and then provide different Write-Output commands depending on the $args analysis.

    Cheers,

    JD

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