Modem disconnect

If the carrier signal is lost, i.e. a modem disconnect is detected by the terminal interface for a controlling terminal, and if CLOCAL is not set in c_cflag (see section “Control modes”), the hangup signal SIGHUP is sent to the controlling process associated with the terminal. Unless other arrangements have been made, this causes the controlling process to terminate (see exit()). All subsequent read operations from this terminal device return with an end-of-file indication. Thus, processes that read a terminal file and test for end-offile can terminate appropriately after a disconnect. Any subsequent write() to the terminal device returns -1, with errno set to EIO, until the file is closed.