Powershell function unexpectedly returns no object

Question

I want to have in a .ps1 file some code that creates a PSSession that can be used in other .ps1 scripts (in order to avoid code duplication).

At first I thought i need a function that creates a PSSession and returns it but I am confused about how they the function outputs work.

Here is my function:

function newRemoteSession
{
    param([string]$ipAddress)

    $accountName = 'admin'
    $accountPassword = 'admin'
    $accountPasswordSecure = ConvertTo-SecureString $accountPassword -AsPlainText -Force
    $accountCredential = New-Object System.Management.Automation.PSCredential ($accountName, $accountPasswordSecure)

    Try
    {
        $remoteSession = New-PSSession -ComputerName $ipAddress -UseSSL -Credential $accountCredential -SessionOption (New-PSSessionOption -SkipCACheck -SkipCNCheck) -ErrorAction Stop
    }
    Catch [System.Management.Automation.RuntimeException] #PSRemotingTransportException
    {
        Write-Host 'Could not connect with default credentials. Please enter credentials...'    
        $remoteSession = New-PSSession -ComputerName $ipAddress -UseSSL -Credential (Get-Credential) -SessionOption (New-PSSessionOption -SkipCACheck -SkipCNCheck) -ErrorAction Stop
        Break
    }

    return $remoteSession
}

However when I call $s = newRemoteSession(192.168.1.10), $s is empty.

When I run a script with

Write-Host '00'
$s = newRemoteSession('192.168.1.10')
$s
Write-Host '02'

function newRemoteSession
{
        ........
    Write-Host '01'
    $remoteSession
}

I get only '00' in the console, but I know the function runs because I get the credential prompt.

EDIT:

Ok, now it works:

The Break in the Catch was stopping everything.
The function call must be without parenthesis.
The second code was wrong because the function must be defined before the call.

If you place the function in the same file where you are trying to call it does it work? — EBGreen, Mar 01 '18 at 20:43
Run `$s = newRemoteSession '192.168.1.10'` **without parentheses**. — JosefZ, Mar 01 '18 at 21:02
I get the same results with `$s = newRemoteSession '192.168.1.10' ` and with `$s = newRemoteSession -ipAddress '192.168.1.10'` — Axel Williot, Mar 01 '18 at 21:06
The code that you posted should error the first time that it is run. — EBGreen, Mar 01 '18 at 21:08
Also, if you get the prompt and you do not see the write host, then only a portion of the function code is running. — EBGreen, Mar 01 '18 at 21:09
Is your second block your complete script? the function needs to be defined before the call. As @JosefZ said, you also need to remove the parenthesis from the function call. Try writing your script in PowerShell_ISE if possible, then step through debugging. You also don't need the break in the `catch` block. — Matthew Wetmore, Mar 01 '18 at 21:20
You do not trap `New-PSSession … -ErrorAction Stop` **inside** `Catch` block. — JosefZ, Mar 01 '18 at 21:28
@JozefZ The Catch is for the first New-PSSession: if it fails (because wrong default credentials) I recall it with credential prompt. — Axel Williot, Mar 01 '18 at 21:37

score 2 · Answer 1 · answered Mar 01 '18 at 22:34

You've found the problems yourself, but since they're common pitfalls, let me elaborate a little:

Only ever use break / continue inside a loop (for, foreach, while, do) or in the branch handlers of a switch statement.
- Otherwise, PowerShell looks up the call stack for an enclosing loop and, in the absence of one, exits the script.
- This is what happened with the break in your catch block.

Do not use (...) to enclose the list of function (command) arguments and do not separate arguments with ,:

In PowerShell, functions - just like cmdlets - are called with shell-like syntax, without parentheses and with whitespace-separated arguments (, is only used to construct an array to be passed as a single argument)^[1] .

# WRONG: method-invocation syntax does NOT apply to *functions*
# (It *happens* to work *in this case*, however, because only a
# a *single* argument is passed and the (...) is a no-op in this case,
# but this syntax should never be used.)
newRemoteSession('192.168.1.10')

# OK: Shell-like syntax, which PowerShell calls *argument mode*:
# Note that the argument needn't be quoted, because it 
# contains no shell metacharacters.
# If there were additional arguments, you'd separate them with *whitespace*
newRemoteSession 192.168.1.10

# BETTER: You can even use *parameter names* (again, as with cmdlets),
# which helps readability.
newRemoteSession -ipAddress 192.168.1.10

In PowerShell, functions must be defined before you can call them.
- You initially didn't notice, because a previous definition of your newRemoteSession function happened to exist.

^{[1] For more information about PowerShell's two fundamental parsing modes -
argument mode and expression mode - see this answer of mine.}

Powershell function unexpectedly returns no object

1 Answers1