Allan’s Musings

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Archive for August, 2009

Why Windows Powershell Is Next To Useless

Posted by Allan Peda on August 21, 2009

So a few weeks ago I decide to learn some powershell in order to set up a backup routine for some mission critical systems. One would expect that Microsoft would have put something together that was useful to *nix heads, in fact all they did was succeed in frustrating me.

Why is this? Well here in a nutshell are my complaints:

  • Powershell uses pipes are used for intra process communication. They move objects around. That’s all well and good, but pipes are historically used by shells for inter process communication.
  • Redirection locks files so that you cannot read them as they are being written. Terrific, so I cannot monitor powershell process that are launched in the background.
  • Redirection of standard error mangles the output. Why is it that such a good thing?

Here

1# ruby -e "STDERR.puts %Q[I AM AN ERROR]" 2> file
2# cat file
ruby.exe : I AM AN ERROR
At line:1 char:5
+ ruby <<<< -e "STDERR.puts %Q[I AM AN ERROR]" 2> file

So what the hell is going on here? But that’s not the end of it:

  • I cannot (easily) launch process in the background, so forget launching something that writes to a log, then tailing the log. This really hinders whating the progress of scheduled tasks. As to shell transcripts; yeah I tried that. Big failure.
  • This last one I think really put me over the edge. If I use Mark Russinovich’s psexec.exe to launch a terminal session, I get nothing, zip.

C:\>psexec \\appserver cmd.exe
PsExec v1.94 – Execute processes remotely
Copyright (C) 2001-2008 Mark Russinovich
Sysinternals – http://www.sysinternals.com
Microsoft Windows [Version 5.2.3790]
(C) Copyright 1985-2003 Microsoft Corp.
C:\WINDOWS\system32>powershell -command "echo hello"
*nothing*

Yes, where I typed the word “*nothing*” is where nothing is returned. It just hangs there. Some shell! Obviously powershell does not want to play well with others. I’ll be this is a feature!

  • Shell transcripts do not capture standout output of child process. I didn’t bother trying to work around this. By this time I decided to redo everything in perl or ruby if I ever have the chance.

Lets look at the powershell answer to *nix "find"

1# get-childitem C:\windows\system32 | where {$_.extension -eq ".log"}
Directory: Microsoft.PowerShell.Core\FileSystem::C:\windows\system32
Mode LastWriteTime Length Name
—- ————- —— —-
-a— 8/10/2009 12:35 PM 90 spupdwxp.log
-a— 4/16/2009 2:32 PM 211792 TZLog.log

Good luck trying to pipe that into pkzip or 7zip as a list of input filenames! As to the commandlets to format this stuff, I don’t want to do extra work to coerce my output into a simple format. (POSIX calls them builtins, but why not come up with a trademarked term. What a great idea!)

At this point I rest my case. Powershell exists only as a platform to prevent stringing programs together, which is contrary to the essential purpose of a shell. I am sure the party line response is to re-write everything in dotNet. Well sure, but the point of a shell is to allow you to quickly get work done, not to force you to re-write everything. Or maybe Microsoft doesn’t see it quite that way?

Powershell is a terrific example of "embrace and extend" and then break it as cleverly as possible!

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