If an open or write error is detected on the device or file specified by the swcons command, the console device driver switches all output back to the device or file providing console support when the system started. This command does not affect the current console selection, but becomes effective when the system is started again. This action ensures that the swcons command does not effect the console device being used for login. These subroutines are redirected to the device or file serving as the current system console device by the console device driver. When an open subroutine call is issued to the console device driver, it is redirected to the device or file currently chosen as the console device.
Subsequent opens have no effect when the console selection is a file.
However, the opens are then passed to the device driver supporting the device chosen as the console. If the console selection has been temporarily switched using the swcons command and the first open of the new underlying device fails, the console device driver switches back to the console device or file with which the system was booted. This prevents important system messages from being lost. An ext parameter passed using the openx subroutine is passed to the device driver supporting the console target or else ignored. The close subroutine support is standard.