Terminal device control

Pseudo-tty emulation module -- ptem

Because the pseudo-tty subsystem has no hardware driver downstream from the ldterm module to process the terminal ioctl calls, another module that understands the ioctl commands is placed downstream from the ldterm. This module, known as ptem, processes all the terminal ioctl commands and mediates the passage of control information downstream.

ldterm and ptem together behave like a real terminal. Because there is no real terminal or modem in the pseudo-tty subsystem, some of the ioctl commands are ignored and cause only an acknowledgement of the command. The ptem module keeps track of the terminal parameters set by the various ``set'' commands such as TCSETA or TCSETAW but does not usually perform any action. For example, if one of the ``set'' ioctls is called, none of the bits in the c_cflag field of termio has any effect on the pseudo-terminal except if the baud rate is set to 0. When setting the baud rate to 0, it has the effect of hanging up the pseudo-terminal.

The pseudo-terminal has no concept of parity so none of the flags in the c_iflag that control the processing of parity errors have any effect. The delays specified in the c_oflag field are not also supported.

The ptem module does the following:

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UnixWare 7 Release 7.1.4 - 27 April 2004