PowerShell running a system command with arguments that include "/"

I'm trying to run a simple system command: dir c:\Temp /ar from a PowerShell script using "&", Invoke-Expression, Invoke-Command but looks like PowerShell does not really like the forward slash "/". I've also tries to escape it using "" or "`" but to no avail...

Any idea?

dir is neither a PowerShell command nor a native executable - it's a built-in command in cmd.exe - so you need to invoke cmd.exe:

& cmd /c dir c:\Temp /ar

PowerShell aliases dir to its own Get-ChildItem command - and Get-ChildItem will interpret /ar as a rooted path argument, thus attempting to list the directory contents at /ar (or C:\ar on Windows), which is probably what you're currently experiencing.

To list read-only items with the Get-ChildItem command, use the -Attributes parameter:

Get-ChildItem -Attributes ReadOnly

Which can conveniently be shortened to:

Get-ChildItem -ar

So you can also solve your problem by simply using -ar instead of /ar:

dir c:\Temp -ar