Originální popis anglicky:
termios, tcgetattr, tcsetattr, tcsendbreak, tcdrain, tcflush, tcflow, cfmakeraw,
cfgetospeed, cfgetispeed, cfsetispeed, cfsetospeed, cfsetspeed - get and set
terminal attributes, line control, get and set baud rate
Návod, kniha: Linux Programmer's Manual
#include <termios.h>
#include <unistd.h>
int tcgetattr(int fd, struct termios
*termios_p);
int tcsetattr(int fd, int optional_actions, const
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);
void cfmakeraw(struct termios *termios_p);
speed_t cfgetispeed(const struct termios *termios_p);
speed_t cfgetospeed(const struct termios *termios_p);
int cfsetispeed(struct termios *termios_p, speed_t
speed);
int cfsetospeed(struct termios *termios_p, speed_t
speed);
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 at least 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 set, a BREAK is ignored. If it is not
set but BRKINT is set, then a BREAK causes the input and output
queues to be flushed, and if the terminal is the controlling terminal of a
foreground process group, it will cause a SIGINT to be sent to this
foreground process group. When neither IGNBRK nor BRKINT are
set, a BREAK reads as a NUL character, except when PARMRK is set,
in which case it reads as the sequence \377 \0 \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
- (not in POSIX) Map uppercase characters to lowercase on
input.
- IXON
- Enable XON/XOFF flow control on output.
- IXANY
- (not in POSIX.1; XSI) Enable any character to restart
output.
- IXOFF
- Enable XON/XOFF flow control on input.
- IMAXBEL
- (not in POSIX) Ring bell when input queue is full. Linux
does not implement this bit, and acts as if it is always set.
c_oflag flag constants defined in POSIX.1:
- OPOST
- Enable implementation-defined output processing.
The remaining
c_oflag flag constants are defined in POSIX 1003.1-2001,
unless marked otherwise.
- OLCUC
- (not in POSIX) Map lowercase characters to uppercase on
output.
- ONLCR
- (XSI) 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
- (not in POSIX) Fill character is ASCII DEL (0177). 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 TAB3,
that is, XTABS, expands tabs to spaces (with tab stops every eight
columns).
- BSDLY
- Backspace delay mask. Values are BS0 or BS1.
(Has never been implemented.)
- VTDLY
- Vertical tab delay mask. Values are VT0 or
VT1.
- FFDLY
- Form feed delay mask. Values are FF0 or
FF1.
c_cflag flag constants:
- CBAUD
- (not in POSIX) Baud speed mask (4+1 bits).
- CBAUDEX
- (not in POSIX) Extra baud speed mask (1 bit), included in
CBAUD.
(POSIX says that the baud speed is stored in the termios structure without
specifying where precisely, and provides
cfgetispeed() and
cfsetispeed() for getting at it. Some systems use bits selected by
CBAUD in
c_cflag, other systems use separate fields, e.g.
sg_ispeed and
sg_ospeed.)
- 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.
- LOBLK
- (not in POSIX) Block output from a noncurrent shell layer.
(For use by shl.)
- CIBAUD
- (not in POSIX) Mask for input speeds. The values for the
CIBAUD bits are the same as the values for the CBAUD bits, shifted left
IBSHIFT bits.
- CRTSCTS
- (not in POSIX) Enable RTS/CTS (hardware) 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, LNEXT, REPRINT, STATUS, and WERASE, and
buffers by lines.
- XCASE
- (not in POSIX; not supported under Linux) 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
- (not in POSIX) 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
- (not in POSIX) If ICANON and IECHO are also
set, characters are printed as they are being erased.
- ECHOKE
- (not in POSIX) If ICANON is also set, KILL is echoed
by erasing each character on the line, as specified by ECHOE and
ECHOPRT.
- DEFECHO
- (not in POSIX) Echo only when a process is reading.
- FLUSHO
- (not in POSIX; not supported under Linux) 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, SIGQUIT and SIGSUSP signals.
- TOSTOP
- Send the SIGTTOU signal to the process group of a
background process which tries to write to its controlling terminal.
- PENDIN
- (not in POSIX; not supported under Linux) 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. This flag,
as well as ICANON must be enabled for the special characters EOL2,
LNEXT, REPRINT, WERASE to be interpreted, and for the IUCLC flag to
be effective.
The
c_cc array defines the special control characters. The symbolic
indices (initial values) and meaning are:
- VINTR
- (003, ETX, Ctrl-C, or also 0177, DEL, rubout) Interrupt
character. Send a SIGINT signal. Recognized when ISIG is set, and then not
passed as input.
- VQUIT
- (034, FS, Ctrl-\) Quit character. Send SIGQUIT signal.
Recognized when ISIG is set, and then not passed as input.
- VERASE
- (0177, DEL, rubout, or 010, BS, Ctrl-H, or also #) Erase
character. This erases the previous not-yet-erased character, but does not
erase past EOF or beginning-of-line. Recognized when ICANON is set, and
then not passed as input.
- VKILL
- (025, NAK, Ctrl-U, or Ctrl-X, or also @) Kill character.
This erases the input since the last EOF or beginning-of-line. Recognized
when ICANON is set, and then not passed as input.
- VEOF
- (004, EOT, Ctrl-D) End-of-file character. More precisely:
this character causes the pending tty buffer to be sent to the waiting
user program without waiting for end-of-line. If it is the first character
of the line, the read() in the user program returns 0, which
signifies end-of-file. Recognized when ICANON is set, and then not passed
as input.
- VMIN
- Minimum number of characters for non-canonical read.
- VEOL
- (0, NUL) Additional end-of-line character. Recognized when
ICANON is set.
- VTIME
- Timeout in deciseconds for non-canonical read.
- VEOL2
- (not in POSIX; 0, NUL) Yet another end-of-line character.
Recognized when ICANON is set.
- VSWTCH
- (not in POSIX; not supported under Linux; 0, NUL) Switch
character. (Used by shl only.)
- VSTART
- (021, DC1, Ctrl-Q) Start character. Restarts output stopped
by the Stop character. Recognized when IXON is set, and then not passed as
input.
- VSTOP
- (023, DC3, Ctrl-S) Stop character. Stop output until Start
character typed. Recognized when IXON is set, and then not passed as
input.
- VSUSP
- (032, SUB, Ctrl-Z) Suspend character. Send SIGTSTP signal.
Recognized when ISIG is set, and then not passed as input.
- VDSUSP
- (not in POSIX; not supported under Linux; 031, EM, Ctrl-Y)
Delayed suspend character: send SIGTSTP signal when the character is read
by the user program. Recognized when IEXTEN and ISIG are set, and the
system supports job control, and then not passed as input.
- VLNEXT
- (not in POSIX; 026, SYN, Ctrl-V) Literal next. Quotes the
next input character, depriving it of a possible special meaning.
Recognized when IEXTEN is set, and then not passed as input.
- VWERASE
- (not in POSIX; 027, ETB, Ctrl-W) Word erase. Recognized
when ICANON and IEXTEN are set, and then not passed as input.
- VREPRINT
- (not in POSIX; 022, DC2, Ctrl-R) Reprint unread characters.
Recognized when ICANON and IEXTEN are set, and then not passed as
input.
- VDISCARD
- (not in POSIX; not supported under Linux; 017, SI, Ctrl-O)
Toggle: start/stop discarding pending output. Recognized when IEXTEN is
set, and then not passed as input.
- VSTATUS
- (not in POSIX; not supported under Linux; status request:
024, DC4, Ctrl-T).
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 some implementation-defined length of
time.
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 "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.
cfsetspeed() is a 4.4 BSD extension. It will set both input and output
speed.
cfgetispeed() returns the input baud rate stored in the
termios
structure.
cfgetospeed() returns the output baud rate stored in the
termios
structure.
All other functions return:
- 0
- on success.
- -1
- on failure and set errno to indicate the error.
Note that
tcsetattr() returns success if
any of the requested
changes could be successfully carried out. Therefore, when making multiple
changes it may be necessary to follow this call with a further call to
tcgetattr() to check that all changes have been performed successfully.
Unix V7 and several later systems have a list of baud rates where after the
fourteen values B0, ..., B9600 one finds the two constants EXTA, EXTB
("External A" and "External B"). Many systems extend the
list with much higher baud rates.
The effect of a nonzero
duration with
tcsendbreak varies. SunOS
specifies a break of
duration*N seconds, where
N
is at least 0.25, and not more than 0.5. Linux, AIX, DU, Tru64 send a break of
duration milliseconds. FreeBSD and NetBSD and HP-UX and MacOS ignore
the value of
duration. Under Solaris and Unixware,
tcsendbreak
with nonzero
duration behaves like
tcdrain.
stty(1),
setserial(8)
