How to run a command correct for CMD in remote box using PowerShell?

Question

I need to run a remote command with help of PowerShell from CMD. This is the command I call from CMD:

powershell -command "$encpass=convertto-securestring -asplaintext mypass -force;$cred = New-Object System.Management.Automation.PSCredential -ArgumentList myuser,$encpass; invoke-command -computername "REMOTE_COMPUTER_NAME" -scriptblock {<command>} -credential $cred;"

in place of <command> (including < and > signs) can be any command which can be run in cmd.exe. For example there can be perl -e "print $^O;" or echo "Hello World!" (NOTE: There cannot be perl -e 'print $^O;', because it is incorrect command for CMD due to the single quotes). So it appears the command perl -e "print $^O;" and any other command which contains double quotes doesn't handled as expected. Here I expect it to return OS name of remote box from perl's point of view, but it prints nothing due to obscure handling of double quotes by PowerShell and/or CMD.

So the question is following, how to run command correct for CMD in remote box using PowerShell?

Are you sure it isn't an effect of unescaped quotes (") near REMOTE_COMPUTER_NAME? — user268396
– user268396, Commented Jul 17, 2013 at 14:38
@user268396 Yes I am. Generally I've tried with single-quoted REMOTE_COMPUTER_NAME and it doesn't affect to the result of any operation. I can surely tell that the problem is in <command>. — Mihran Hovsepyan
– Mihran Hovsepyan, Commented Jul 18, 2013 at 8:26

Χpẘ · Accepted Answer · 2013-07-18 02:32:00Z

1

There are several possible problems with the command line in the OP. If the command line in the OP is being executed from Powershell itself the $encpass and $cred will get substituted before the (sub-instance) of powershell is invoked. You need to use single quotes or else escape the $ signs, for example:

powershell -command "`$encpass=2"
powershell -command '$encpass=2'

If, instead of using Powershell, the command line is executed from CMD, then ^ has to be escaped, because it is the CMD escape character.

And quoting " is a good idea as well. In a few tests that I did I had to use unbalanced quotes to get a command to work, for example, from powershell:

powershell -command "`$encpass=`"`"a`"`"`"; write-host `$encpass"

worked, but balanced quotes didn't.

To avoid all this, probably the most robust way to do this is given in powershell command line help: powershell -?:

# To use the -EncodedCommand parameter:
$command = 'dir "c:\program files" '
$bytes = [System.Text.Encoding]::Unicode.GetBytes($command)
$encodedCommand = [Convert]::ToBase64String($bytes)
powershell.exe -encodedCommand $encodedCommand

However there is a new feature in PS 3.0 that is also supposed to help, but I don't think it will be as robust. Described here: http://blogs.msdn.com/b/powershell/archive/2012/06/14/new-v3-language-features.aspx, near the middle of the blog.

edited Jul 18, 2013 at 2:32

answered Jul 17, 2013 at 20:43

Χpẘ

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1 Comment

Mihran Hovsepyan Over a year ago

This is not what I want. But it helps me to figure out the problem. So I have written perl -e """print `$^O;""" instead of perl -e "print $^O;" and it works.

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