This section describes the terminal flags and fields that control
parameters usually associated with asynchronous serial data
transmission. These flags may not make sense for other kinds of
terminal ports (such as a network connection pseudo-terminal). All of
these are contained in the
c_cflag member of the
c_cflag member itself is an integer, and you change the flags
and fields using the operators
try to specify the entire value for
only specific flags and leave the rest untouched (see Setting Modes).
If this bit is set, it indicates that the terminal is connected “locally” and that the modem status lines (such as carrier detect) should be ignored.
On many systems if this bit is not set and you call
O_NONBLOCK flag set,
open blocks until a modem
connection is established.
If this bit is not set and a modem disconnect is detected, a
SIGHUP signal is sent to the controlling process group for the
terminal (if it has one). Normally, this causes the process to exit;
see Signal Handling. Reading from the terminal after a disconnect
causes an end-of-file condition, and writing causes an
to be returned. The terminal device must be closed and reopened to
clear the condition.
If this bit is set, a modem disconnect is generated when all processes that have the terminal device open have either closed the file or exited.
If this bit is set, input can be read from the terminal. Otherwise, input is discarded when it arrives.
If this bit is set, two stop bits are used. Otherwise, only one stop bit is used.
If this bit is set, generation and detection of a parity bit are enabled. See Input Modes, for information on how input parity errors are handled.
If this bit is not set, no parity bit is added to output characters, and input characters are not checked for correct parity.
This bit is only useful if
PARENB is set. If
PARODD is set,
odd parity is used, otherwise even parity is used.
The control mode flags also includes a field for the number of bits per
character. You can use the
CSIZE macro as a mask to extract the
value, like this:
settings.c_cflag & CSIZE.
This is a mask for the number of bits per character.
This specifies five bits per byte.
This specifies six bits per byte.
This specifies seven bits per byte.
This specifies eight bits per byte.
The following four bits are BSD extensions; these exist only on BSD systems and GNU/Hurd systems.
If this bit is set, enable flow control of output based on the CTS wire (RS232 protocol).
If this bit is set, enable flow control of input based on the RTS wire (RS232 protocol).
If this bit is set, enable carrier-based flow control of output.
If this bit is set, it says to ignore the control modes and line speed
values entirely. This is only meaningful in a call to
c_cflag member and the line speed values returned by
cfgetospeed will be unaffected by the
CIGNORE is useful if you want to set all the software
modes in the other members, but leave the hardware details in
c_cflag unchanged. (This is how the
TCSASOFT flag to
This bit is never set in the structure filled in by