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termios(4)
NAME
termios, termios.h - Defines the structure of the termios file, which
provides the terminal interface for POSIX compatibility.
DESCRIPTION
The /usr/include/termios.h header file is used to obtain and modify
attributes required by the terminal driver. These attributes control input
and output processing. The definition values and structure in the
/usr/include/termios.h file are required for P1003.1 POSIX compliance.
The primary mechanism for obtaining and setting terminal driver parameters
is through the following POSIX functions:
· tcgetattr()
· tcsetattr()
· cfgetispeed()
· cfgetospeed()
· cfsetospeed()
· cfsetispeed()
Optionally the termios values can be obtained or set using the termios
ioctls. See the tty(7) reference page. For compatibility the system
supports BSD and System V ioctls, but they are internally translated into
termios ioctls.
The termios structure in the <termios.h> header file contains the following
fields:
c_iflag Describes the basic terminal input control. The possible input
modes are:
IGNBRK Ignores the break condition. If set, the break
condition is not put on the input queue and is
therefore not read by any process.
BRKINT Interrupts signal on the break condition. If set, the
break condition generates an interrupt signal and
flushes both the input and output queues.
IGNPAR Ignores characters with parity errors. If set,
characters with other framing and parity errors are
ignored.
PARMRK Marks parity errors. If set, a character with a framing
or parity error that is not ignored is read as the 3-
character sequence: 0377, 0, x, where the x variable is
the data of the character received in error. If the
ISTRIP mode is not set, then a valid character of 0377
is read as 0377, 0377 to avoid ambiguity. If the PARMRK
mode is clear, a framing or parity error that is not
ignored is read as the null character.
INPCK Enables input parity checking. If set, input parity
checking is enabled. If clear, input parity checking is
disabled. This allows for output parity generation
without input parity errors.
ISTRIP Strips characters. If set, valid input characters are
first stripped to 7 bits; otherwise all 8 bits are
processed.
INLCR Maps new-line character (NL) to carriage return (CR) on
input. If set, a received NL character is translated
into a CR character.
IGNCR Ignores CR character. If set, a received CR character
is ignored (not read).
ICRNL Maps CR character to NL character on input. If set, a
received CR character is translated into a NL
character.
IUCLC Maps uppercase to lowercase on input. If set, a
received uppercase, alphabetic character is translated
into the corresponding lowercase character.
IXON Enables start and stop output control. If set, a
received STOP character suspends output, and a received
START character restarts output. The START and STOP
characters perform flow control functions but are not
read.
IXANY Enables any character to restart output. If set, any
input character restarts output that was suspended.
IXOFF Enables start and stop input control. If set, the
system transmits a STOP character when the input queue
is nearly full and a START character when enough input
has been read that the queue is nearly empty again.
IMAXBEL Echoes the ASCII BEL character if the input stream
overflows. Further input is not stored, but any input
received prior to the overflow condition is retained.
If clear, the BEL character is not echoed, and the
input in the input queue is discarded if the input
stream overflows.
c_oflag Specifies how the system treats output. The possible output
modes are:
OPOST Postprocesses output. If set, output characters are
processed as indicated by the remaining flags;
otherwise, characters are transmitted without change.
OLCUC Maps lowercase to uppercase on output. If set, a
lowercase alphabetic character is transmitted as the
corresponding uppercase character. This function is
often used in conjunction with the IUCLC input mode.
ONLCR Maps NL to CR-NL on output. If set, the NL character is
transmitted as the CR-NL character pair.
OCRNL Maps CR to NL on output. If set, the CR character is
transmitted as the NL character.
ONOCR Indicates no CR output at column 0. If set, no CR
character is transmitted at column 0 (first position).
ONLRET NL performs CR function. If set, the NL character is
assumed to do the carriage return function. The column
pointer is set to a value of 0 and the delay specified
for carriage return is used. Otherwise the NL character
is assumed to do the line feed function only; the
column pointer remains unchanged. The column pointer is
also set to a value of 0 if the CR character is
actually transmitted.
The delay bits specify how long a transmission stops to
allow for mechanical or other movement when certain
characters are sent to the terminal. The actual delays
depend on line speed and system load.
OFILL Uses fill characters for delay. If set, fill characters
are transmitted for a delay instead of a timed delay.
This is useful for high baud rate terminals that need
only a minimal delay.
OFDEL Sets fill characters to the DEL value. If set, the fill
character is DEL. If this flag is clear, the fill
character is null.
NLDLY Selects the newline character delays. This is a mask to
use before comparing to NL0 and NL1.
ONL0 Specifies no delay.
NL1 Specifies one delay of approximately 0.10
seconds. If ONLRET is set, the carriage
return delays are used instead of the newline
delays. If OFILL is set, two fill characters
are transmitted.
CRDLY Selects the carriage return delays. This is a mask to
use before comparing to CR0, CR1, CR2, and CR3.
CR0 Specifies no delay.
CR1 Specifies that the delay is dependent on the
current column position. If OFILL is set,
this delay transmits two fill characters.
CR2 Specifies one delay of approximately 0.10
seconds. If OFILL is set, this delay
transmits four fill characters.
CR3 Specifies one delay of approximately 0.15
seconds.
TABDLY Selects the horizontal tab delays. This is a mask to
use before comparing to TAB0, TAB1, TAB2, and TAB3. If
OFILL is set, any of these delays transmit two fill
characters.
TAB0 Specifies no delay.
TAB1 Specifies that the delay is dependent on the
current column position. If OFILL is set, two
fill characters are transmitted.
TAB2 Specifies one delay of approximately 0.10
seconds.
TAB3 Specifies that tabs are to be expanded into
spaces.
BSDLY Selects the backspace delays. This is a mask to use
before comparing to BS0 and BS1.
BS0 Specifies no delay.
BS1 Specifies one delay of approximately 0.05
seconds. If OFILL is set, this delay
transmits one fill character.
VTDLY Selects the vertical-tab delays. This is a mask to use
before comparing to VT0 and VT1.
VT0 Specifies no delay.
VT1 Specifies one delay of approximately 2
seconds.
FFDLY Selects the formfeed delays. This is a mask to use
before comparing to FF0 and FF1.
FF0 Specifies no delay.
FF1 Specifies one delay of approximately 2
seconds.
c_cflag Describes the hardware control of the terminal. In addition to
the basic control modes, this field uses the following control
characters:
CRTSCTS Enables hardware flow control using the Request to Sent
(RTS) and Clear to Send (CTS) signals.
CSIZE Specifies the character size. These bits specify the
character size in bits for both transmit and receive
operations. This size does not include the parity bit,
if any.
CS5 5 bits.
CS6 6 bits.
CS7 7 bits.
CS8 8 bits.
CSTOPB Specifies number of stop bits. If set, 2 stop bits are
sent; otherwise, only 1 stop bit is sent. Higher baud
rates require 2 stop bits. (At 110 baud, for example, 2
stop bits are required.)
CREAD Enables receiver. If set, the receiver is enabled.
Otherwise, characters are not received.
PARENB Enables parity. If set, parity generation and detection
is enabled and a parity bit is added to each character.
PARODD Specifies odd parity. If parity is enabled, this
specifies odd parity. If clear, even parity is used.
HUPCL Hangs up on last close. If set, the line is
disconnected when the last process closes the line or
when the process terminates (when the `data terminal
ready' signal drops).
CLOCAL Specifies a local line. If set, the line is assumed to
have a local, direct connection with no modem control.
If clear, modem control (dialup) is assumed. The
initial hardware control value after an open is CS8 and
CREAD.
c_lflag Controls various terminal functions. In addition to the basic
modes, this field uses the following mask name symbols:
ISIG Enables signals. If set, each input character is
checked against the INTR and QUIT special control
characters. If a character matches one of these control
characters, the function associated with that character
is performed. If the ISIG function is clear, checking
is not done.
ICANON Enables canonical input. If set, turns on canonical
processing, which enables the erase and kill edit
functions as well as the assembly of input characters
into lines delimited by NL, EOF, and EOL.
If the ICANON function is clear, read requests are
satisfied directly from the input queue. In this case,
a read request is not satisfied until one of the
following conditions is met: a) the minimum number of
characters specified by MIN are received; or b) the
timeout value specified by TIME has expired since the
last character was received. This allows bursts of
input to be read, while still allowing single character
input. The MIN and TIME values are stored in the VMIN
and VTIME positions, respectively. The time value
represents tenths of seconds.
XCASE Enables canonical uppercase and lowercase presentation.
If set along with the ICANON function, an uppercase
letter (or the uppercase letter translated to lowercase
by the IUCLC input mode) is accepted on input by
preceding it with a \ (backslash) character. The
output is then preceded by a backslash character.
ECHO Enables echo. If set, characters are displayed on the
terminal screen as they are received.
ECHOE Echoes erase character as BS-SP-BS. If the ECHO and
ECHOE functions are both set and ECHOPRT is clear, the
erase character is implemented as a backspace, a space,
and then another backspace (ASCII BS-SP-BS). This
clears the last character from the screen. If ECHOE is
set, but ECHO is clear, the erase character is
implemented as ASCII SP-BS.
ECHOK Echoes NL after kill. If ECHOK is set and ECHOKE is
clear, a newline function is performed to clear the
line after a KILL character is received. This
emphasizes that the line is deleted. Note that an
escape character preceding the ERASE or KILL character
removes any special function.
ECHONL Echoes NL. If ECHONL is set, the line is cleared when a
newline function is performed whether or not the ECHO
function is set. This is useful for terminals that are
set to local echo (also referred to as half-duplex).
Unless an escape character precedes an EOF, the EOF
character is not displayed. Because the ASCII EOT
character is the default end-of-file character, this
prevents terminals that respond to the EOT character
from hanging up.
NOFLSH Disables queue flushing. If set, the normal flushing of
the input and output queues associated with the quit
and interrupt characters is not done.
The ICANON, XCASE, ECHO, ECHOE, ECHOK, ECHONL, and
NOFLSH special input functions are possible only if the
ISIG function is set. These functions can be disabled
individually by changing the value of the control
character to an unlikely or impossible value (for
example, 0377 octal or 0xFF)
ECHOCTL Echoes control characters as ^X, where the X variable
is the character given by adding 100 octal to the code
of the control character. The ASCII DEL character is
echoed as ^? and the ASCII TAB, NL, and START
characters are not echoed.
Unless an escape character precedes an EOF, the EOF
character is not displayed. Because the ASCII EOT
character is the default End-of-File character, this
mask prevents terminals that respond to the EOT
character from hanging up.
ECHOPRT Echoes the first ERASE and WERASE character in a
sequence as a \ (backslash), and then erases the
characters. Subsequent ERASE and WERASE characters echo
the characters being erased (in reverse order).
ECHOKE Echoes the kill character by erasing from the screen
each character on the line.
FLUSHO Flushes the output. When this bit is set by typing the
FLUSH character, data written to the terminal is
discarded. A terminal can cancel the effect of typing
the FLUSH character by clearing this bit.
PENDIN Reprints any input that has not yet been read when the
next character arrives as input.
IEXTEN Enables extended (implementation-defined) functions to
be recognized from the input data. If this bit is
clear, implementation-defined functions are not
recognized, and the corresponding input characters are
processed as described for ICANON, ISIG, IXON, and
IXOFF.
TOSTOP Sends a SIGTTOU signal when a process in a background
process group tries to write to its controlling
terminal. The SIGTTOU signal stops the members of the
process group. If job control is not supported, this
symbol is ignored.
c_cc Specifies an array that defines the special control characters.
The relative positions and initial values for each function are:
VINTR Indexes the INTR control character (Ctrl-Backspace),
which sends a SIGINT signal to stop all processes
controlled by this terminal.
VQUIT Indexes the QUIT control character (Ctrl-v or Ctrl-|),
which sends a SIGQUIT signal to stop all processes
controlled by this terminal and writes a core image
file into the current working directory.
VERASE Indexes the ERASE control character (Backspace), which
erases the preceding character. The ERASE character
does not erase beyond the beginning of the line
(delimited by a NL, EOL, EOF, or EOL2 character).
VKILL Indexes the KILL control character (Ctrl-u), which
deletes the entire line (delimited by a NL, EOL, EOF,
or EOL2 character).
VEOF Indexes the EOF control character (Ctrl-d), which can
be used at the terminal to generate an end-of-file.
When this character is received, all characters waiting
to be read are immediately passed to the program
without waiting for a new line, and the EOF is
discarded. If the EOF is at the beginning of a line (no
characters are waiting), zero characters are passed
back, which is the standard End-of-File.
VEOL Indexes the EOL control character (Ctrl-@ or ASCII
null), which is an additional line delimiter that is
not normally used.
VEOL2 Indexes the EOL2 control character (Ctrl-@ or ASCII
null), which is an additional line delimiter that is
not normally used.
VSTART Indexes the START control character (Ctrl-q), which
resumes output that has been suspended by a STOP
character. START characters are ignored if the output
is not suspended.
VSUSP Indexes the SUSP control character (Ctrl-z), which
causes a SIGTSTP signal to be sent to all foreground
processes controlled by this terminal. This character
is recognized during input if the ISIG flag is enabled.
If job control is not supported, this character is
ignored.
VDSUSP Indexes the DSUSP control character (Ctrl-y), which
causes a SIGTSTP signal to be sent to all foreground
processes controlled by this terminal. This character
is recognized when the process attempts to read the
DSUSP character. If job control is not supported, this
character is ignored.
VSTOP Indexes the STOP control character (Ctrl-s), which can
be used to temporarily suspend output. This character
is recognized during both input and output if the IXOFF
(input control) or IXON (output control) flag is set.
VREPRINT Indexes the REPRINT control character (Ctrl-r), which
reprints all characters that are preceded by a NL
character and that have not been read.
VDISCARD Indexes the DISCARD control character (Ctrl-o), which
causes all output to be discarded until another DISCARD
character is typed, more input is received, or the
condition is cleared by a program.
VWERASE Indexes the WERASE control character (Ctrl-w), which
erases the preceding word. The WERASE character does
not erase beyond the beginning of the line (delimited
by a NL, EOL, EOF, or EOL2 character).
VLNEXT Indexes the LNEXT (literal next) control character
(Ctrl-v), which causes the special meaning of the next
character to be ignored, so that characters can be
input without being interpreted by the system.
The character values for INTR, QUIT, SWTCH, ERASE,
KILL, EOF, and EOL can be changed. The ERASE, KILL, and
EOF characters can also be escaped (preceded with a
backslash) so that no special processing is done.
VMIN Indexes the minimum read value. This value is used for
noncanonical processing. See the previous description
of the ICANON flag.
VTIME Indexes the time value. This value is used for
noncanonical processing. See the previous description
of the ICANON flag.
c_ispeed Specifies the input baud rate.
The default input baud rate is 9600. However, the input baud
rate can be specified to be one of the following:
B0 Hangs up. The zero baud rate is used to hang up the
connection. If B0 is specified, the `data terminal
ready' signal is not asserted. Normally, this
disconnects the line.
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.
B600 600 baud.
B1200 1200 baud.
B1800 1800 baud.
B2400 2400 baud.
B4800 4800 baud.
B9600 9600 baud.
B19200 19200 baud.
B38400 38400 baud.
B57600 57600 baud.
B115200 115200 baud.
EXTA External A.
EXTB External B.
c_ospeed Specifies the output baud rate.
The default output baud rate is 9600. However, the possible
output baud rate values are the same as for the input baud rate
values listed above.
The following values for the optional-actions parameter of the tcsetattr()
function are also defined in the termios.h header file:
TCSANOW Immediately sets the parameters associated with the terminal from
the referenced termios structure.
TCSADRAIN Waits until all output written to the object file has been
transmitted before setting the terminal parameters from the
termios structure.
TCSAFLUSH Waits until all output written to the object file has been
transmitted and all input received but not read has been
discarded before setting the terminal parameters from the termios
structure.
The following values for the queue-selector parameter of the tcflush()
function are also defined in this header file:
TCIFLUSH Flushes data that is received but not read.
TCOFLUSH Flushes data that is written but not transmitted.
TCIOFLUSH Flushes both data that is received but not read and data that is
written but not transmitted.
The following values for the action parameter of the tcflow() system call
are also defined in the termios.h header file:
TCOOFF Suspends the output of data by the object file named in the
tcflow() function.
TCOON Restarts data output that was suspended by the TCOOFF parameter.
TCIOFF Transmits a stop character to stop data transmission by the
terminal device.
TCION Transmits a start character to start or restart data transmission
by the terminal device.
FILES
/usr/include/sys/termios.h
The path to the termios.h header file.
RELATED INFORMATION
Files: ace(7), scc(7), tty(7).
Functions: ioctl(2), cfgetispeed(3), cfgetospeed(3), cfsetispeed(3),
cfsetospeed(3), tcsetattr(3), tcgetattr(3), tcflow(3), tcflush(3).
Commands: csh(1), sh(1), stty(1), tset(1), getty(8).
|
Index for
Section 4 |
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Alphabetical
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Top of
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