tramp-process-alive-regexp

tramp-process-alive-regexp is a variable defined in `tramp.el'.
Its value is

""

Documentation:
Regular expression indicating a process has finished.
In fact this expression is empty by intention, it will be used only to
check regularly the status of the associated process.
The answer will be provided by `tramp-action-process-alive',
`tramp-action-out-of-band', which see.

You can customize this variable.