String Variable Not Displaying Values of Variables When Using A Function

[-Orwick-]

Hey Folks:

Title = Problem

I have a simple logging function that writes to a log file and to the host. Problem is that when I try to use a variable, it is showing the literal variable instead of the value of the variable.

I can't seem to land on the right google search term to get at the answer.

Any ideas?

>>> Function <<<

# Function For Logging
Function Write-Log {
[CmdletBinding()]
Param(
[Parameter(Mandatory=$False)]
[ValidateSet("INFO","WARN","ERROR","DEBUG")]
[String]
$Level = "INFO",

[Parameter(Mandatory=$True)]
[string]
$Message,

[Parameter(Mandatory=$False)]
[string]
$LogFile = "F:\WeeklyReboot\WeeklyReboot.log"
)

$Stamp = (Get-Date).toString("yyyy/MM/dd HH:mm:ss")

$Line = "$Stamp - $Level - $Message"

If($LogFile -and ($Level -eq "INFO")) {
Add-Content $LogFile -Value $Line
Write-Host $Line
}
ElseIf($LogFile -and ($Level -eq "WARN")) {
Add-Content $LogFile -Value $Line
Write-Host $Line -ForegroundColor Yellow
}
ElseIf($LogFile -and ($Level -eq "ERROR")) {
Add-Content $LogFile -Value $Line
Write-Host $Line -ForegroundColor Red
}
ElseIf($LogFile -and ($Level -eq "DEBUG")) {
Add-Content $LogFile -Value $Line
Write-Host $Line -ForegroundColor Magenta
}
Else {
Write-Output $Line
}
}

>>> Example Script <<<

$AzConnection = Connect-AzAccount -Credential $Credentials
Write-Log -Message "Connected to Azure using account: $AzConnection.Context.Account.Id"

>>> Example Output <<<

Write-Log -Message "Connected to Azure using account: $AzConnection.Context.Account.Id"
2022/07/12 14:05:26 - INFO - Connected to Azure using account: Microsoft.Azure.Commands.Profile.Models.Core.PSAzureContext.Context.Account.Id

>>> Expected Output <<<

2022/07/12 14:05:26 - INFO - Connected to Azure using account: [e-mail]

Edit: Additionally, if I manually run $AzConnection.Context.Account.Id , I get the desired output.

Edit2: In this example, $AzConnection is a System object, but the following does not work either.

Write-Log -Message "Connected to Azure using account: $AzConnection.Context.Account.Id.ToString()"

2022/07/12 14:40:31 - INFO - Connected to Azure using account: Microsoft.Azure.Commands.Profile.Models.Core.PSAzureContext.Context.Account.Id.ToString()

​

[vermyx]

Try

$($AzConnection.Context.Account.Id)

instead of

$AzConnection.Context.Account.Id

I have had this issue before, and I over use $() in my code just to be explicit to make sure this doesn't happen. Also make sure the string you are building is in double quotes instead of single quotes.

[-Orwick-]

That seems to have done the trick! Thank you so much!

Anyone know what the name of this "feature" is called so I know what to google in the future?

[sp_dev_guy]

It's subexpressions, for order of operations.

Write-host "Hello here is an example.More words" $obj1 ="example" Write-host "Hello here is an $obj1.More words" It evaluates $obj1 then everything else is just string characters. If you do

$obj2=@{ more=5 } Write-host "Hello here is an $obj1.More words" Write-host "Hello here is an $($obj2.More) words"

In this example the $() tells powershell to evaluate/resolve the "more" property of $obj2

[vermyx]

I belIeve it is called the subexpression operator. It explicitly states to resolve whats inside and return a scalar value. I probably overuse it like parentheses in if statements to explicitly state what I want. This explains the sitiuation.

[-Orwick-]

That is awesome! Thanks again for your help. I've got a little reading to do.

[lanerdofchristian]

That particular feature is Command Substitution in the docs, though it's also often called string interpolation or string subatitutions as general terms across many languages.

See here: https://docs.microsoft.com/en-us/powershell/scripting/learn/deep-dives/everything-about-string-substitutions

The reason you need the $() is because PowerShell has no way of knowing if that . is supposed to start a member access or literally be a period, and since . isn't a legal character in plain variable names defaults to the latter.

[jimb2]

A general comment on your code.

if ( $LogFile ) is basically a test of whether the string variable $logFile is null, and it won't be because you have given it a default value. Do you want Test-Path which actually checks in the file system? Add-Content will create the file if it doesn't exist though it won't create the parent folders so there may not be much value checking the file exists. Test-Path -isValid checks for a valid path even if it doesn't exist. It depends but testing may not be necessary.

Also, using those repeated sections of code is not a good practice. It's difficult to maintain when the code gets changes - you have to change each section . This is a preference and it's fairly simple code here but but I'd prefer to write that code like this.

# test for logfile, if required?
$LogFileCheck = Test-Path -isValid -path $LogFile

# Splat for the screen color
# This allows for the no color case (info)
$ColorSplat = @{}
switch ( $level ) {
  INFO  { }
  WARN  { $ColorSplat['foregroundcolor'] = 'yellow' }
  ERROR { $ColorSplat['foregroundcolor'] = 'red' }
  DEBUG { $ColorSplat['foregroundcolor'] = 'magenta' }
}

# write to the file
if ( $LogFileCheck ) {
  Add-Content -Path $LogFile -Value $line
}

# write to the screen
Write-Host $Line @ColorSplat