termios, tcgetattr, tcsetattr, tcsendbreak, tcdrain, tcflush, tcflow,
cfmakeraw, cfgetospeed, cfgetispeed, cfsetispeed, cfsetospeed, tcgetpgrp,
tcsetpgrp - get and set terminal attributes, line control, get and
set baud rate, get and set terminal foreground process group ID
#include <termios.h>
#include <unistd.h>
int tcgetattr ( int fd, struct termios *termios_p );
int tcsetattr ( int fd, int optional_actions, struct termios *termios_p
);
int tcsendbreak ( int fd, int duration );
int tcdrain ( int fd );
int tcflush ( int fd, int queue_selector );
int tcflow ( int fd, int action );
int cfmakeraw ( struct termios *termios_p );
speed_t cfgetospeed ( struct termios *termios_p );
int cfsetospeed ( struct termios *termios_p, speed_t speed );
speed_t cfgetispeed ( struct termios *termios_p );
int cfsetispeed ( struct termios *termios_p, speed_t speed );
pid_t tcgetpgrp ( int fd );
int tcsetpgrp ( int fd, pid_t pgrpid );
The termios functions describe a general terminal interface that is
provided to control asynchronous communications ports.
Many of the functions described here have a termios_p argument that is
a pointer to a termios structure. This structure contains the following
members:
tcflag_t c_iflag; /* input modes */
tcflag_t c_oflag; /* output modes */
tcflag_t c_cflag; /* control modes */
tcflag_t c_lflag; /* local modes */
cc_t c_cc[NCCS]; /* control chars */
c_iflag flag constants:
IGNBRK ignore BREAK condition on input
BRKINT If IGNBRK is not set, generate SIGINT on BREAK condition, else
read BREAK as character \0.
IGNPAR ignore framing errors and parity errors.
PARMRK if IGNPAR is not set, prefix a character with a parity error or
framing error with \377 \0. If neither IGNPAR nor PARMRK is
set, read a character with a parity error or framing error as
\0.
INPCK enable input parity checking
ISTRIP strip off eighth bit
INLCR translate NL to CR on input
IGNCR ignore carriage return on input
ICRNL translate carriage return to newline on input (unless IGNCR is
set)
IUCLC map uppercase characters to lowercase on input
IXON enable XON/XOFF flow control on output
IXANY enable any character to restart output
IXOFF enable XON/XOFF flow control on input
IMAXBEL [Toc] [Back]
ring bell when input queue is full
c_oflag flag constants:
OPOST enable implementation-defined output processing
OLCUC map lowercase characters to uppercase on output
ONLCR map NL to CR-NL on output
OCRNL map CR to NL on output
ONOCR don't output CR at column 0
ONLRET don't output CR
OFILL send fill characters for a delay, rather than using a timed
delay
OFDEL fill character is ASCII DEL. If unset, fill character is ASCII
NUL
NLDLY newline delay mask. Values are NL0 and NL1.
CRDLY carriage return delay mask. Values are CR0, CR1, CR2, or CR3.
TABDLY horizontal tab delay mask. Values are TAB0, TAB1, TAB2, TAB3,
or XTABS. A value of XTABS expands tabs to spaces (with tab
stops every eight columns).
BSDLY backspace delay mask. Values are BS0 or BS1.
VTDLY vertical tab delay mask. Values are VT0 or VT1.
FFDLY form feed delay mask. Values are FF0 or FF1.
c_cflag flag constants:
CSIZE character size mask. Values are CS5, CS6, CS7, or CS8.
CSTOPB set two stop bits, rather than one.
CREAD enable receiver.
PARENB enable parity generation on output and parity checking for
input.
PARODD parity for input and output is odd.
HUPCL lower modem control lines after last process closes the device
(hang up).
CLOCAL ignore modem control lines
CIBAUD mask for input speeds (not used).
CRTSCTS [Toc] [Back]
flow control.
c_lflag flag constants:
ISIG when any of the characters INTR, QUIT, SUSP, or DSUSP are
received, generate the corresponding signal.
ICANON enable canonical mode. This enables the special characters EOF,
EOL, EOL2, ERASE, KILL, REPRINT, STATUS, and WERASE, and buffers
by lines.
XCASE if ICANON is also set, terminal is uppercase only. Input is
converted to lowercase, except for characters preceded by \. On
output, uppercase characters are preceded by \ and lowercase
characters are converted to uppercase.
ECHO echo input characters.
ECHOE if ICANON is also set, the ERASE character erases the preceding
input character, and WERASE erases the preceding word.
ECHOK if ICANON is also set, the KILL character erases the current
line.
ECHONL if ICANON is also set, echo the NL character even if ECHO is not
set.
ECHOCTL [Toc] [Back]
if ECHO is also set, ASCII control signals other than TAB, NL,
START, and STOP are echoed as ^X, where X is the character with
ASCII code 0x40 greater than the control signal. For example,
character 0x08 (BS) is echoed as ^H.
ECHOPRT [Toc] [Back]
if ICANON and IECHO are also set, characters are printed as they
are being erased.
ECHOKE if ICANON is also set, KILL is echoed by erasing each character
on the line, as specified by ECHOE and ECHOPRT.
FLUSHO output is being flushed. This flag is toggled by typing the
DISCARD character.
NOFLSH disable flushing the input and output queues when generating the
SIGINT and SIGQUIT signals, and flushing the input queue when
generating the SIGSUSP signal.
TOSTOP send the SIGTTOU signal to the process group of a background
process which tries to write to its controlling terminal.
PENDIN all characters in the input queue are reprinted when the next
character is read. (bash handles typeahead this way.)
IEXTEN enable implementation-defined input processing.
The c_cc array defines the special control characters. The symbolic
indices (and meaning: initial values) are: VINTR (interrupt character:
0177, DEL, rubout), VQUIT (quit character: 034, FS, Ctrl-\), VERASE
(erase character: 010, BS, Ctrl-H), VKILL (kill character: 025, NAK,
Ctrl-U), VEOF (end-of-file character: 004, EOT, Ctrl-D), VMIN, VEOL
(additional end-of-line character: 0, NUL), VTIME, VEOL2 (yet another
end-of-line character: 0, NUL), VSWTCH (switch character: 0, NUL),
VSTART (start character: 021, DC1, Ctrl-Q), VSTOP (stop character: 023,
DC3, Ctrl-S), VSUSP (suspend character: 032, SUB, Ctrl-Z), VDSUSP
(delayed suspend character: 031, EM, Ctrl-Y), VLNEXT (literal next:
026, SYN, Ctrl-V), VWERASE (word erase: 027, ETB, Ctrl-W), VREPRINT
(reprint unread characters: 022, DC2, Ctrl-R), VDISCARD (discard pending
output: 017, SI, Ctrl-O).
These symbolic subscript values are all different, except that VTIME,
VMIN may have the same value as VEOL, VEOF, respectively. (In noncanonical
mode the special character meaning is replaced by the timeout
meaning. MIN represents the minimum number of characters that should be
received to satisfy the read. TIME is a decisecond-valued timer. When
both are set, a read will wait until at least one character has been
received, and then return as soon as either MIN characters have been
received or time TIME has passed since the last character was received.
If only MIN is set, the read will not return before MIN characters have
been received. If only TIME is set, the read will return as soon as
either at least one character has been received, or the timer times
out. If neither is set, the read will return immediately, only giving
the currently already available characters.)
tcgetattr() gets the parameters associated with the object referred by
fd and stores them in the termios structure referenced by termios_p.
This function may be invoked from a background process; however, the
terminal attributes may be subsequently changed by a foreground
process.
tcsetattr() sets the parameters associated with the terminal (unless
support is required from the underlying hardware that is not available)
from the termios structure referred to by termios_p. optional_actions
specifies when the changes take effect:
TCSANOW [Toc] [Back]
the change occurs immediately.
TCSADRAIN [Toc] [Back]
the change occurs after all output written to fd has been transmitted.
This function should be used when changing parameters
that affect output.
TCSAFLUSH [Toc] [Back]
the change occurs after all output written to the object
referred by fd has been transmitted, and all input that has been
received but not read will be discarded before the change is
made.
tcsendbreak() transmits a continuous stream of zero-valued bits for a
specific duration, if the terminal is using asynchronous serial data
transmission. If duration is zero, it transmits zero-valued bits for
at least 0.25 seconds, and not more that 0.5 seconds. If duration is
not zero, it sends zero-valued bits for duration*N seconds, where N is
at least 0.25, and not more than 0.5.
If the terminal is not using asynchronous serial data transmission,
tcsendbreak() returns without taking any action.
tcdrain() waits until all output written to the object referred to by
fd has been transmitted.
tcflush() discards data written to the object referred to by fd but not
transmitted, or data received but not read, depending on the value of
queue_selector:
TCIFLUSH [Toc] [Back]
flushes data received but not read.
TCOFLUSH [Toc] [Back]
flushes data written but not transmitted.
TCIOFLUSH [Toc] [Back]
flushes both data received but not read, and data written but
not transmitted.
tcflow() suspends transmission or reception of data on the object
referred to by fd, depending on the value of action:
TCOOFF suspends output.
TCOON restarts suspended output.
TCIOFF transmits a STOP character, which stops the terminal device from
transmitting data to the system.
TCION transmits a START character, which starts the terminal device
transmitting data to the system.
The default on open of a terminal file is that neither its input nor
its output is suspended.
The baud rate functions are provided for getting and setting the values
of the input and output baud rates in the termios structure. The new
values do not take effect until tcsetattr() is successfully called.
Setting the speed to B0 instructs the modem to "hang up". The actual
bit rate corresponding to B38400 may be altered with setserial(8).
The input and output baud rates are stored in the termios structure.
cfmakeraw sets the terminal attributes as follows:
termios_p->c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP
|INLCR|IGNCR|ICRNL|IXON);
termios_p->c_oflag &= ~OPOST;
termios_p->c_lflag &= ~(ECHO|ECHONL|ICANON|ISIG|IEXTEN);
termios_p->c_cflag &= ~(CSIZE|PARENB);
termios_p->c_cflag |= CS8;
cfgetospeed() returns the output baud rate stored in the termios structure
pointed to by termios_p.
cfsetospeed() sets the output baud rate stored in the termios structure
pointed to by termios_p to speed, which must be one of these constants:
B0
B50
B75
B110
B134
B150
B200
B300
B600
B1200
B1800
B2400
B4800
B9600
B19200
B38400
B57600
B115200
B230400
The zero baud rate, B0, is used to terminate the connection. If B0 is
specified, the modem control lines shall no longer be asserted. Normally,
this will disconnect the line. CBAUDEX is a mask for the speeds
beyond those defined in POSIX.1 (57600 and above). Thus, B57600 &
CBAUDEX is nonzero.
cfgetispeed() returns the input baud rate stored in the termios structure.
cfsetispeed() sets the input baud rate stored in the termios structure
to speed. If the input baud rate is set to zero, the input baud rate
will be equal to the output baud rate.
tcgetpgrp() returns process group ID of foreground processing group, or
-1 on error.
tcsetpgrp() sets process group ID to pgrpid. pgrpid must be the ID of
a process group in the same session.
cfgetispeed() returns the input baud rate stored in the termios structure.
cfgetospeed() returns the output baud rate stored in the termios structure.
tcgetpgrp() returns process group ID of foreground processing group, or
-1 on error.
All other functions return:
0 on success.
-1 on failure and set errno to indicate the error.
setserial(8)
Linux 1995-09-02 TERMIOS(3)
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