Powershell: Setting an environment variable for a single command only

Question

On Linux, I can do:

$ FOO=BAR ./myscript

to call "myscript" with the environment variable FOO being set.

Is something similar possible in Powershell, i.e. without having to first set the variable, call the command, and then unset the variable again?

To be more clear about my use case - I don't want to use this as part of a script. Rather, I have a third party script whose behavior I can control using environment variables, but, in this case, not command line arguments. So being able to alternate between typing

$ OPTION=1 ./myscript

and

$ ./myscript

would just be very handy.

Answer 1

You can scope variables to functions and scripts.

$script:foo = "foo"
$foo
$function:functionVariable = "v"
$functionVariable

New-Variable also has a -scope parameter if you want to be formal and declare your variable using new-variable.

Answer 2

Generally it would be better to pass info to the script via a parameter rather than a global variable. But if that is what you need to do and you want automatic cleanup of the variable then introduce a new scope like so:

& { $foo = 'bar'; $env:foo = 'bar'; ./myscript }

A couple of things to note about this. First, when the scope (scriptblock) is exited, $foo no longer exists. It existed only within the context of the scriptblock. However the environment variable $env:foo still exists because that truly is a global change. You can delete that variable like so:

Remove-Item Env:\foo