CMD command in Windows to switch to an already open application

Solution 1:

How do I switch to an already open application from the command line?

You can use nircmd from nirsoft to do this.

Example:

nircmd win activate title "Calculator"

Notes:

See NirCmd Command Reference - win

What is nircmd?

NirCmd is a small command-line utility that allows you to do some useful tasks without displaying any user interface. By running NirCmd with simple command-line option, you can write and delete values and keys in the Registry, write values into INI file, dial to your internet account or connect to a VPN network, restart windows or shut down the computer, create shortcut to a file, change the created/modified date of a file, change your display settings, turn off your monitor, open the door of your CD-ROM drive, and more...

Source nircmd

Disclaimer

I am not affiliated with nirsoft in any way, I am just an end user of the software.

Solution 2:

The solution with 1 line of initialisation and 1 line calling. The calling is %tmp%\switch.vbs ... used twice below.

Title %vTitle%
:: preparation (initialisation)
@echo WScript.CreateObject("WScript.Shell").AppActivate(WScript.Arguments.Item(0))>%tmp%\switch.vbs
:: some cmd lines exposing other windows
:: ...
:: just as an example to start the notepad
start "" notepad
:: use 1: focus back on this cmd window
%tmp%\switch.vbs %vTitle%
:: ...
:: use 2: focus to an application with <application name> 
%tmp%\switch.vbs "<application name>"