The variable $var is blank when I run this script:
function FOO { write-output "HEY" }
$var = Start-Job -ScriptBlock { ${function:FOO} } | Wait-Job | Receive-Job
$var
How do I get output from receive-job?
Start-Job
spawns a new PowerShell instance in the background and as such has no knowledge of your function FOO
which is defined in your initial instance
There is an additional parameter InitializationScript
which is called upfront executing your script block in the new instance which you can use to define FOO
like so
$var = Start-Job -InitializationScript { function FOO { write-output "HEY" } } -ScriptBlock ...
BTW: I guess you want to execute the function instead of getting the function object itself so you may want to change your script block to this
-ScriptBlock { FOO }