Retrieve parameters from file - Windows PowerShell

Question

I am writing a super-easy script in PowerShell. The target of this script is to read a list of server names from a txt file and a command block from another txt file. The result of the operation shold be a third txt file containing the information.

Here some code:

cls
$usr = Read-Host "Please insert username, you'll be asked for password later"
$path = Read-Host "Insert a valid path for ServerList.txt file"
$serverList = Get-Content -Path $path | Out-String

$path = Read-Host "Insert a valid path fom Command.txt file"
$commandBlock = Get-Content -Path $path | Out-String


echo "Command: " $commandBlock "will be executed on " $serverList
echo "Press CTRL+Z to abort or"
pause

Invoke-Command -ComputerName $serverList -ScriptBlock { $commandBlock } -credential $usr

Serverlist.txt is a plain text containing something like "server1,server2,server3" and command.txt contain only this "Get-WmiObject Win32_BIOS | Select-Object SerialNumber"

Why the error is Invoke-Command : One or more computer names are not valid. If you are trying to pass a URI, use the -ConnectionUri parameter, or pass URI objects instead of strings. ?

I even tried to substitute $serverlist with $serverlist.toString() but it's not working. I read somewhere that in this case $serverlist is an Array, how do I do to make everything work?

Consider that https://technet.microsoft.com/en-us/library/hh849719.aspx Invoke-Commands work with "server1,server2,server3" format if you put the string via console.

Vesper · Accepted Answer · 2015-07-20 13:37:57Z

2

Your $serverList isn't a list, it's a single string of server1,server2 etc. To make it into an array, you can use -split to split the string by commas.

$serverList = Get-Content -Path $path | Out-String
$serverList = $serverList -split ","

answered Jul 20, 2015 at 13:37

Vesper

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10 Comments

BlacK Over a year ago

The thing is that "server1,server2,server3" is what the invoke-command needs to work properly. I don't need to split! Don't I?

Mathias R. Jessen Over a year ago

@BlacK When you input server1,server2,server3 as a naked argument, the PowerShell parser recognizes that it should be treated as three individual strings, not a single string. This is not the case when you pass a variable to it

Vesper Over a year ago

You do, as if you're passing a variable, its value is used unparsed, so that your gwmi command searches a computer named server1,server2,server3 instead of going for three computers server1, server2, server3. But if your $serverList would be an array, then gwmi will see it and do a call on each computer.

Mathias R. Jessen Over a year ago

@BlacK the last entry still has a trailing newline thanks to Out-String, see my answer below

user4003407 Over a year ago

@Vesper, you can get this "[`r`n]" by using this ``"[`r`n]"``.

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Mathias R. Jessen · Accepted Answer · 2015-07-20 14:00:15Z

For further understanding of why this doesn't work as you expect, please see the parsing and command syntax help files:

Get-Help about_Parsing
Get-Help about_Command_Syntax

$serverlist

When your text file contains the line server1,server2,server3, this command:

Get-Content -Path .\file.txt | Out-String

Just results in the string server1,server2,server3 and a newline - that's not a valid hostname.

Either format your text file like this (Get-Content automatically splits on line breaks):

server1
server2
server3

or split the string(s) from the file yourself:

$Serverlist = Get-Content -Path $Path | ForEach-Object { $_ -split "," }

$commandblock

For the command block part to work, you can't just drop a string into a ScriptBlock and expect it to execute - you need to recreate it as executable code:

$Code = Get-Content -Path $path -Raw
$CommandBlock = [scriptblock]::Create($Code)

# Now you can do this
Invoke-Command -ScriptBlock $CommandBlock

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