Termios functions

The termios functions allow to control terminals and asynchronous communications ports. The DJGPP implementation currently supports the termios functionality for console devices only. It does that by reading the keyboard via the BIOS Int 16h and writes to the screen via the direct output interrupt 29h. This I/O redirection is performed by the special hook internal to the library.

Many of the termios functions accept a termiosp argument which is a pointer to a struct termios variable. Here's the description of this structure:

#define NCCS 12 struct termios { cc_t c_cc[NCCS]; /* control characters */ tcflag_t c_cflag; /* control modes */ tcflag_t c_iflag; /* input modes */ tcflag_t c_lflag; /* local modes */ tcflag_t c_oflag; /* output modes */ speed_t c_ispeed; /* input baudrate */ speed_t c_ospeed; /* output baudrate */ }

The array c_cc[] defines the special control characters. the following table lists the supported control functions the default characters which invoke those functions, and the default values for MIN and TIME parameters:

Index	Name	Function	Default Value
1	VEOF	Signal End-Of-Input	Ctrl-D
2	VEOL	Signal End-Of-Line	[Disabled]
3	VERASE	Delete previous character	Backspace
4	VINTR	Generate SIGINT	Ctrl-C
5	VKILL	Erase current line	Ctrl-U
6	VMIN	The MIN value	1
7	VQUIT	Generate SIGQUIT	Ctrl-\
8	VSTART	Resume output	Ctrl-Q
9	VSTOP	Suspend output	Ctrl-S
10	VSUSP	Suspend program	Ctrl-Z
11	VTIME	TIME value	0

The special characters (like VEOL, VKILL, etc.) produce their effect only under the canonical input processing, that is, when the ICANON bit in the c_lflag member of struct termios (see below) is set. If ICANON is not set, all characters are processed as regular characters and returned to the caller; only the VMIN and VTIME parameters are meaningful in the non-canonical processing mode.

The VEOL character can be used to signal end of line (and thus end of input in the canonical mode) in addition to the normal RET key. In the non-canonical mode, input ends as soon as at least VMIN characters are received.

Note that the values of VMIN and VTIME are currently ignored; termios functions always work as if VMIN were 1 and VTIME were zero. Other parameters are supported (for console devices only), except that VSTOP and VSTART characters are not inserted to the input, but otherwise produce no effect.

The c_cflag member of struct termios describes the hardware terminal control, as follows:

Symbol	Function
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
CSIZE	Character size:
CS5	5-bit characters
CS6	6-bit characters
CS7	7-bit characters
CS8	8-bit characters
CSTOPB	If set, send two stop bits
CREAD	Enable reading
PARENB	Enable parity
PARODD	If set, use odd parity
HUPCL	Hang up on last close
CLOCAL	If set, line is local

Note that since the DOS terminal doesn't use asynchronous ports, the above parameters are always ignored by the implementation. The default value of c_cflag is (CS8|CREAD|CLOCAL).

The c_lflag member of struct termios defines the local modes that control the terminal functions:

Symbol	Function
ISIG	If set, enable signals SIGINT and SIGQUIT
ICANON	If set, enable canonical input processing
ECHO	If set, enable echoing
ECHOE	Erase character deletes
ECHOK	Output newline after the kill character
ECHONL	Echo the newline
NOFLSH	[Ignored]
TOSTOP	[Ignored]
ECHOCTL	Echo control characters as ^X
ECHOKE	Erase killed line
IEXTEN	[Ignored]

The default value of c_lflag is (ISIG|ICANON|ECHO|IEXTEN|ECHOE|ECHOKE|ECHOCTL).

The c_iflag member of struct termios describes the input control:

Symbol	Function
IGNBRK	Ignore Ctrl-BREAK
BRKINT	Generate SIGINT on Ctrl-BREAK
IGNPAR	[Ignored]
PARMRK	[Ignored]
INPCK	[Ignored]
ISTRIP	Strip the 8th bit from input
INLCR	Map NL to CR on input
IGNCR	Ignore CR characters
ICRNL	Map CR to NL on input
IXON	[Ignored]
IXOFF	Enable start/stop input control
IMAXBEL	Ring the bell if input line too long

The default value of c_iflag is (BRKINT|ICRNL|IMAXBEL).

The c_oflag member of struct termios specifies the output handling:

Symbol	Function
OPOST	If not set, output characters verbatim
ONLCR	Map newline to CR-LF pair on output
OCRNL	Map CR to NL on output
ONOEOT	Don't output EOT characters

Note that if the OPOST bit is not set, all the other flags are ignored and the characters are output verbatim. The default value of c_oflag is (OPOST|ONLCR|ONOEOT).

The c_ispeed and c_ospeed members specify, respectively, the input and output baudrate of the terminal. They are set by default to 9600 baud, but the value is always ignored by this implementation, since no asynchronous ports are used.