Calling a specific PowerShell function from the command line

You would typically "dot" the script into scope (global, another script, within a scriptblock). Dotting a script will both load and execute the script within that scope without creating a new, nested scope. With functions, this has the benefit that they stick around after the script has executed. You could do what Tomer suggests except that you would need to dot the script e.g.:

powershell -command "& { . <path>\script1.ps1; My-Func }"

If you just want to execute the function from your current PowerShell session then do this:

. .\script.ps1
My-Func

Just be aware that any script not in a function will be executed and any script variables will become global variables.

This solution works with powershell core:

powershell -command "& { . .\validate.ps1; Validate-Parameters }"