How to change the current active partition slot?

How to automate slot selection after android AB-Update fastboot get active slot But I want without fastboot command My usecase is the bootloader need to check the currect active slot and set the proper suffix How can I do fastboot get active slot If the bootloader implements fastboot, it should support the command set_active slot> that sets the current active slot to the given slot (this

fastboot getvar currentslot stack trace: Error: failed to set active slot: Error: {error:{code:1,cmd:fastboot --set-active=b},stderr: waiting for any device >