Control modes

The control modes described below have no significance for BS2000 computers.
The c_cflag field describes the hardware control of the terminal. The following elements are supported for character-oriented terminals:

Mask name	Definition
CLOCAL	Ignore modem status
CREAD	Enable receiver
CSIZE CS5 CS6 CS7 CS8	Character size (number of bits per byte): 5 bits 6 bits 7 bits 8 bits
CS5	5 bits
CS6	6 bits
CS7	7 bits
CS8	8 bits
CSTOPB	Send 2 stop bits (else 1)
HUPCL	Hang up on last close()
PARENB	Enable parity detection
PARODD	Enable odd parity

In addition, the input and output baud rates are stored in the termios structure. The following values are supported:

Name	Definition
B0	Hang up
B50	50 baud
B75	75 baud
B110	110 baud
B134	134.5 baud
B150	150 baud
B200	200 baud
B300	300 baud
B600	600 baud
B1200	1200 baud
B1800	1800 baud
B2400	2400 baud
B4800	4800 baud
B9600	9600 baud
B19200	19200 baud
B38400	38400 baud

The following interfaces are provided for getting and setting the values of the input and output baud rates in the termios structure:
cfgetispeed(), cfgetospeed(), cfsetispeed() and cfsetospeed().

The CSIZE bits specify the character size in bits per byte for both transmission and reception. This size does not include the parity bit, if any. If CSTOPB is set, two stop bits are used, otherwise one stop bit. For example, at 110 baud, two stop bits are normally used.

If CREAD is set, the receiver is enabled. If CREAD is not set, no characters are received.

If PARENB is set, parity generation and detection is enabled, i.e. a parity bit is added to each character. If parity is enabled, the PARODD bit specifies odd parity be used; otherwise, even parity is used.

If HUPCL is set, the line will be disconnected when the last process to use the line closes it or terminates. This means that the Data-Terminal-Ready (DTR) signal will be disabled, thus breaking the modem connection.

If CLOCAL is set, the existing line is assumed to be a local, direct connection with no modem control. The connection does not depend on line signals in this case. Otherwise, modem control is assumed, and the modem status lines are monitored.

Under normal circumstances, a call to the open() function waits for the modem connection to complete. However, if the O_NONBLOCK flag is set when calling open(), or if the CLOCAL bit is set, the open() function returns immediately without waiting for the connection.

If the object for which the control modes are set is not an asynchronous serial connection, some of the modes may be ignored; e.g., if an attempt is made to set the baud rate on a network connection to a terminal on another host, the baud rate may or may not be set on the connection between that terminal and the machine to which it is directly connected.

The initial value for the control modes (value of c_oflag) after a call to open() is that no flag is set.