TERMIOS
NAME SYNOPSIS DESCRIPTION RETURN VALUE SEE ALSO
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
int tcgetattr ( int fd__, struct termios
int tcsetattr ( int fd, int optional_actions__, struct termios
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
__int cfsetospeed ( struct termios
);
__speed_t cfgetispeed ( struct termios
__int cfsetispeed ( struct termios
);
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
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 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
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 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 non-canonical 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
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 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
flushes data received but not read.
TCOFLUSH
flushes data written but not transmitted.
TCIOFLUSH
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 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
termios_p-
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.
on failure and set errno to indicate the error.
One page links to cfsetispeed(3):
