In the pseudo-tty subsystem (see ``Pseudo-tty subsystem architecture''), the line discipline module ldterm is pushed on the slave side to present the user with the terminal interface.
ldterm may turn off the processing of the c_iflag, c_oflag, and c_lflag fields to allow processing to take place elsewhere. The ldterm module may also turn off all canonical processing when it receives an M_CTL message with the MC_NO_CANON command to support remote mode. Although ldterm passes through messages without processing them, the appropriate flags are set when a ``get'' ioctl, such as TCGETA or TCGETS, is issued to show that canonical processing is being performed.
Pseudo-tty subsystem architecture