How can I print script block content in PowerShell

Question

Hi guys, I want to create a function that will be checking execution of selected commands and in case of catched failure retry 3 times and display the command name with the retry message. I placed a test command "Test Connection" between the function brackets to be evaluted, retry seems to be working, however I can not get the command name to be printed. I tried with "$($MyInvocation.MyCommand.ScriptBlock)", but it prints out the whole function intead of that executed line that I'm checking. Can anyone please advice here? Thanks a lot in advance

function Execute-WithRetry([ScriptBlock]$command) {

    $Stoploop = $false
    $count = 0
 
    do {
        try {
            & $command
            Write-Host "Download completed"
            $Stoploop = $true
        }
        catch {
            if ($count -eq 3) {
               
                Write-Host "Could not download after 3 retries."
                $Stoploop = $true
            }
            else {
                Write-Host "Could not download the files retrying in 5 seconds..."
                Write-Host "Executing: $($MyInvocation.MyCommand.ScriptBlock)"
                Start-Sleep -Seconds 5
            }
        }
        $count++
    }
    While  ($Stoploop -eq $false)
    pause

    }


Execute-WithRetry {
  Test-Connection -ComputerName 192.10.129.15 -ErrorAction Stop
}

Answer 1

As mentioned in the comments, if you want just the "offending" line from the script block, grab the invocation info from the error record inside the catch block (as opposed to $MyInvocation) and use the Line property to get the line on which the statement that failed starts:

function Invoke-Retry {
  param([scriptblock]$Command)

  $stop = $false
  $count = 0

  $ErrorActionPreference = 'Stop'

  do {
    try {
      &$Command

      Write-Host "Download completed"
      $stop = $true
    }
    catch {
      if ($count -ge 3) {
        Write-Host "Could not download after 3 retries."
        $stop = $true
      }
      else {
        Write-Host "Could not download the files, retrying in 5 seconds"
        Write-Host "Error occurred while executing: `n>> $($_.InvocationInfo.Line)" -ForegroundColor Red
        Start-Sleep -Seconds 5
      }
    }
    $count++
  } while (-not $stop)
  pause
}

Which should give you the actual line from the script block:

PS ~> Invoke-Retry {
  Test-Connection -ComputerName doesntexist
}
Could not download the files retrying in 5 seconds
Error occurred while executing:
>>   Test-Connection -ComputerName doesntexist

Could not download the files retrying in 5 seconds
Error occurred while executing:
>>   Test-Connection -ComputerName doesntexist

Could not download the files retrying in 5 seconds
Error occurred while executing:
>>   Test-Connection -ComputerName doesntexist

Could not download after 3 retries.
Press Enter to continue...:

Note: starting with version 7.4, the invocation info class also exposes the full extent of any multiline statements via the Statement property

Answer 2

Preface:

• This answer addresses the question as asked: how to obtain the entire source-code representation of the script block whose invocation triggered an error.

• Mathias' helpful answer demonstrates how to extract the specific line inside the script block's source code that triggered the error.

---

It looks like you're looking for the source-code representation of the script block stored in $command.

Calling .ToString() on a script block returns just that (without the enclosing { and }) and, therefore, simply referencing a script block inside "...", an expandable string has the same effect.

Therefore, this should do what you want (the surrounding { and } are solely to give the full appearance of the original script-block literal):

Write-Host "Executing: {$command}"

Note:

• The string representation is exactly what you place inside {...}, i.e. a script-block literal, and can therefore include newlines.

---

A simplified example:

# Sample function that prints the source code of a given script block.
function Foo { param([scriptblock] $Command) "Source code: {$Command}" }

# Sample call
# ->
#  "Source code: { Get-Date -Format 'yyyy' }" 
Foo -Command { Get-Date -Format 'yyyy' }

Calling .ToString() directly on a script-block literal makes the behavior obvious:

# -> " Get-Date -Format 'yyyy' "
{ Get-Date -Format 'yyyy' }.ToString()