TERMIOS(4) Domain/OS BSD TERMIOS(4)
NAME
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 contains information used by
system calls that apply to terminal files. The definitions, values, and
structure in this file are required for compatibility with the Institute
of Electrical and Electronics Engineers (IEEE) P1003.1 Portable Operating
System Interface for Computer Environments (POSIX) standard.
The general terminal interface information is contained in the termio.h
header file. The termio structure in the termio.h header file defines the
basic input, output, control, and line discipline modes. If a calling
program is identified as requiring POSIX compatibility, the termios
structure and additional, POSIX control packet information in the
termios.h header file is implemented. Window and terminal size operations
use the winsize structure, which is defined in the ioctl.h header
file.The termios structure in the termios.h header file contains the
following fields:
c_iflag
Describes the basic terminal input control. The initial input
control value is all bits clear. 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 not
set, 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 not set, 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
present in the input stream is not lost. If not set, 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 initial output control
value is all bits clear. The possible output modes are:
OPOST Post-processes 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 not set, the fill
character is null.
NLDLY Selects the newline character delays. This is a mask to
use before comparing to NL0 and NL1.
NL0 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:
CBAUD Specifies baud rate. These bits specify the baud rate for
a connection. For any particular hardware, impossible
speed changes are ignored.
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.
B1200 1200 baud.
B1800 1800 baud.
B2400 2400 baud.
B4800 4800 baud.
B9600 9600 baud.
B19200 19200 baud.
B38400 38400 baud.
EXTA External A.
EXTB External B.
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 not set, 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
not set, modem control (dialup) is assumed.
CIBAUD Specifies the input baud rate if it is different than the
output rate.
PAREXT Specifies extended parity for mark and space parity.
The initial hardware control value after an open is B300, CS8,
CREAD, and HUPCL
c_lflag
Controls various terminal functions. The initial value after an open
is all bits clear. 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 not set, 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 not set, 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 time-out 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 positions for the EOF and EOL
characters, 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 not set, 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
not set, the erase character is implemented as ASCII SP-
BS.
ECHOK Echoes NL after kill. If ECHOK is set and ECHOKE is not
set, 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 not set,
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 ouput 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.
VDISCRD 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.
The following values for the optional_actions argument of the tcsetattr()
function are also defined in the termios.h header file:
TCSANOW Immediately sets the arguments 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 arguments 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 arguments from the
termios structure.
The following values for the queue_selector argument 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 argument 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 argument.
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/termios.h
SEE ALSO
ioctl(2), sigvec(2)
Commands: getty(1), sh(1), stty(1),