Why does a continue in this ForEach-Object loop cause Powershell to error

Question

When piping the output of a command to a ForEach-Object loop in PowerShell, using a continue statement causes it to error out.

Works as expected:

ipconfig | ForEach-Object {
  $_
} 

Errors:

ipconfig | ForEach-Object {
  $_
  continue
} 

The error is

Program 'ipconfig.exe' failed to run: System error.At C:\Users\test\ps.ps1:1 char:1
+ nslookup google.com | ForEach-Object {
+ ~~~~~~~~~~~~~~~~~~~.
At C:\Users\test\ps.ps1:1 char:1
+ nslookup google.com | ForEach-Object {
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ResourceUnavailable: (:) [], ApplicationFailedException
    + FullyQualifiedErrorId : NativeCommandFailed

This seems to happen with any external command, such as nslookup and net

I thought maybe this had to do with some type conversion, but the object inside the loop is always a string. Saving the command output to a variable, and then doing a $var | ForEach-Object works.

Answer 1

continue statements in PowerShell can only be used within loop constructs. While ForEach-Object seems like a loop, it's not.

In PowerShell, you can technically use continue outside of a loop, but it causes PowerShell to not find a loop, and just terminate the current runspace.¹

This means PowerShell can actually terminate the caller¹, and looking at the callstack, that caller is the "parent" line and so it is terminated.

Callstack right before the continue executes:

ScriptLineNumber : 4
Position         : continue
FunctionName     : <ScriptBlock>


ScriptLineNumber : 1
Position         : net help | ForEach-Object {
                       $_.GetType()
                       continue
                   }
FunctionName     : <ScriptBlock>

Instead, use a return statement.

---

Reference

1 - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_continue?view=powershell-5.1