NAME
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
SYNOPSIS
#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 );
DESCRIPTION
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 argu-
ment that is a pointer to a termios structure. This struc-
ture 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 condi-
tion, 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
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
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 char-
acters 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
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
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 typ-
ing the DISCARD character.
NOFLSH
disable flushing the input and output queues when gen-
erating 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 back-
ground 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.
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
the change occurs immediately.
TCSADRAIN
the change occurs after all output written to fd has
been transmitted. This function should be used when
changing parameters that affect output.
TCSAFLUSH
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 dis-
carded before the change is made.
tcsendbreak() transmits a continuous stream of zero-valued
bits for a specific duration, if the terminal is using asyn-
chronous 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
flushes data received but not read.
TCOFLUSH
flushes data written but not transmitted.
TCIOFLUSH
flushes both data received but not read, and data writ-
ten 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 ter-
mios 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 ter-
mios 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 process-
ing 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.
RETURN VALUES
cfgetispeed() returns the input baud rate stored in the ter-
mios structure.
cfgetospeed() returns the output baud rate stored in the
termios structure.
tcgetpgrp() returns process group ID of foreground process-
ing group, or -1 on error.
All other functions return:
0 on success.
-1 on failure and set errno to indicate the error.
SEE ALSO
setserial(8)