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termios.h File
Purpose
Defines the structure of the termios file, which
provides the terminal interface for POSIX compatibility.
Description
The /usr/include/termios.h file contains information
used by subroutines that apply to terminal files. The definitions, values,
and structures in this file are required for compatibility with the POSIX
standard. The termios.h file also supports ioctl modem-control operations.
The general terminal interface information is contained in the termio.h file. The termio structure in the termio.h 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 file
is implemented. Window and terminal size operations use the winsize structure, which is defined in the ioctl.h
file. The termios structure in the termios.h file contains the following fields:
- c_iflag
- c_oflag
- c_cflag
- c_lflag
- c_cc
The termios.h file also defines the values for the following parameters of the tcsetattr subroutine:
- OptionalActions
- QueueSelector
- Action
The termios.h file also supports ioctl modem-control operations.
- Field Descriptions
-
- 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. In the context of asynchronous serial
data transmission, a break condition is defined as
a sequence of zero-valued bits that continues for more than the time required
to send one byte. The entire sequence of zero-valued bits is interpreted as
a single break condition, even if it continues for an amount of time equivalent
to more than one byte. If the IGNBRK flag is set, a
break condition detected on input is ignored, which means that it is not put
on the input queue and therefore not read by any process.
- BRKINT
- Signal interrupt on the break condition. If the IGNBRK flag is not set and the BRKINT flag is set,
the break condition flushes the input and output queues. If the terminal is
the controlling terminal of a foreground process group, the break condition
generates a SIGINT signal to that foreground process
group. If neither the IGNBRK nor the BRKINT flag is set, a break condition is read as a single \0, or if the PARMRK flag is set, as \377, \0, \0.
- IGNPAR
- Ignores characters with parity errors. If this flag is set, a byte
with a framing or parity error (other than break) is ignored.
- PARMRK
- Marks parity errors. If the PARMRK flag is set,
and the IGNPAR flag is not set, a byte with a framing
or parity error (other than break) is given to the application as the three-character
sequence \377, \0, x, where \377, \0 is a two-character
flag preceding each sequence and x is the data of
the character received in error. To avoid ambiguity in this case, if the ISTRIP flag is not set, a valid character of \377 is given
to the application as \377, \377. If neither the IGNPAR
nor the PARMRK flag is set, a framing or parity error
(other than break) is given to the application as a single character \0.
- INPCK
- Enables input parity checking. If this flag is 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 this flag is set, valid input characters are
first stripped to 7 bits. Otherwise, all 8 bits are processed.
- INLCR
- Maps a new-line character (NL) to a carriage return (CR) on input.
If this flag is set, a received NL character is translated into a CR character.
- IGNCR
- Ignores CR character. If this flag is set, a received CR character
is ignored and not read.
- ICRNL
- Maps a CR character to the NL character on input. If the ICRNL flag is set and the IGNCR flag is not set,
a received CR character is translated into a NL character.
- IUCLC
- Maps uppercase to lowercase on input. If this flag is set, a received
uppercase, alphabetic character is translated into the corresponding lowercase
character.
- IXON
- Enables start and stop output control. If this flag is set, a received
STOP character suspends output and a received START character restarts output.
When the IXON flag is set, START and STOP characters
are not read, but merely perform flow-control functions. When the IXON flag is not set, the START and STOP characters are read.
- IXANY
- Enables any character to restart output. If this flag is set, any
input character restarts output that was suspended.
- IXOFF
- Enables start-and-stop input control. If this flag is 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 input already present in the input stream is not
lost. If this flag is not set, no BEL character is echoed; the input in the
input queue is discarded if the input stream overflows. This function also
requires the IEXTEN bit to be set.
- 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 this flag is set, output characters are
post-processed as indicated by the remaining flags. Otherwise, characters
are transmitted without change.
- OLCUC
- Maps lowercase to uppercase on output. If this flag is set, a lowercase
alphabetic character is transmitted as the corresponding uppercase character.
This flag is often used in conjunction with the IUCLC
input mode.
- ONLCR
- Maps NL to CR-NL on output. If this flag is set, the NL character
is transmitted as the CR-NL character pair.
- OCRNL
- Maps CR to NL on output. If this flag is set, the CR character is
transmitted as the NL character.
- ONOCR
- Indicates no CR output at column 0. If this flag is set, no CR character
is transmitted when at column 0 (first position).
- ONLRET
- NL performs CR function. If this flag is set, the NL character is
assumed to do the carriage-return function. The column pointer is set to 0,
and the delay specified for carriage return is used. If neither the ONLCR, OCRNL, ONOCR, nor ONLRET flag is set, the NL character is assumed to do the
line-feed function only. The column pointer remains unchanged. The column
pointer is set to 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 this flag is 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
- If this flag is set, the fill character is DEL. If this flag is not
set, the fill character is NULL.
- NLDLY
- Selects the new-line character delays. This is the mask to use before
comparing to NL0 and NL1:
- NL0
- Specifies no delay.
- NL1
- Specifies a delay of approximately 0.10 seconds. If the ONLRET flag is set, the carriage-return delays are used instead of the
new-line delays. If the OFILL flag is set, two fill
characters are transmitted.
- CRDLY
- Selects the carriage-return delays. This is the 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 the OFILL flag is set, this delay transmits two
fill characters.
- CR2
- Specifies a delay of approximately 0.10 seconds. If the OFILL flag is set, this delay transmits four fill characters.
- CR3
- Specifies a delay of approximately 0.15 seconds.
- TABDLY
- Selects the horizontal-tab delays. This is the mask to use before
comparing to TAB0, TAB1, TAB2, and TAB3. If the OFILL
flag is set, any of these delays (except TAB3) transmit two fill characters.
- TAB0
- Specifies no delay.
- TAB1
- Specifies that the delay is dependent on the current column position.
If the OFILL flag is set, two fill characters are transmitted.
- TAB2
- Specifies a delay of approximately 0.10 seconds.
- TAB3
- Specifies that tabs are to be expanded into spaces.
- BSDLY
- Selects the backspace delays. This is the mask to use before comparing
to BS0 and BS1:
- BS0
- Specifies no delay.
- BS1
- Specifies a delay of approximately 0.05 seconds. If the OFILL flag is set, this delay transmits one fill character.
- VTDLY
- Selects the vertical-tab delays. This is the mask to use before comparing
to VT0 and VT1:
- VT0
- Specifies no delay.
- VT1
- Specifies a delay of approximately 2 seconds.
- FFDLY
- Selects the form-feed delays. This is the mask to use before comparing
to FF0 and FF1:
- FF0
- Specifies no delay.
- FF1
- Specifies a 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.
- 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. The character size does
not include the parity bit, if one is used:
- CS5
- 5 bits
- CS6
- 6 bits
- CS7
- 7 bits
- CS8
- 8 bits.
- CSTOPB
- Specifies number of stop bits. If this flag is set, 2 stop bits are
sent; otherwise, only 1 stop bit is sent.
- CREAD
- Enables receiver. If this flag is set, the receiver is enabled. Otherwise,
characters are not received.
- PARENB
- Enables parity. If this flag is set, parity generation and detection
is enabled and a parity bit is added to each character.
- PARODD
- Specifies odd parity. If parity is enabled, the PARODD flag specifies odd parity if set. If parity is enabled and the PARODD flag is not set, even parity is used.
- HUPCL
- Hangs up on last close. If this flag is 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 this flag is set, the line is assumed to
have a local, direct connection with no modem control. If not set, modem
control (dial-up) is assumed.
- CIBAUD
- Specifies the input baud rate if different from the output rate.
- PAREXT
- Specifies extended parity for mark and space parity.
- 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 this flag is set, each input character is checked
against the INTR, QUIT, SUSP, and DSUSP special control characters. If an
input character matches one of these control characters, the function associated
with that character is performed. If the ISIG flag
is not set, checking is not done.
- ICANON
- Enables canonical input. If this flag is set, it 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 characters.
If the ICANON flag 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:
- The minimum number of characters specified by MIN
are received.
- 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 character values of MIN and TIME are converted to their ascii equivalents to get the numeric value.
The time value represents tenths of seconds.
- XCASE
- Enables canonical uppercase and lowercase presentation. If this flag
is set along with the ICANON flag, 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 also preceded by a backslash character. In
this mode, the output generates and the input accepts the following escape
sequences:
- For
- Use
- ` (grave)
- \ `
- |
- \ !
- ~
- \ ^
- {
- \ (
- }
- \ )
- \
- \ \
For example, A is input as \a, \n as \\n, and \N as \\\n.
- NOFLSH
- Disables queue flushing. If this flag is set, the normal flushing
of the input and output queues associated with the INTR, QUIT, and SUSP characters
is not done.
- 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 pending input. If this flag is set, any input that is pending
after a switch from raw to canonical mode is re-input the next time a read
operation becomes pending or the next time input arrives. The PENDIN flag is an internal-state bit.
- IEXTEN
- Enables extended (implementation-defined) functions to be recognized
from the input data. If this flag is not set, implementation-defined functions
are not recognized, and the corresponding input characters are processed
as described for the ICANON, ISIG,
IXON, and IXOFF flags. Recognition
of the following special control characters requires the IEXTEN flag to be set:
- VEOL2
- VDSUSP
- VREPRINT
- VDISCRD
- VWERSE
- VLNEXT
The functions associated with the following bits also require the
IEXTEN flag to be set:
- IMAXBEL
- ECHOKE
- ECHOPRT
- ECHOCTL
- 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.
- ECHO
- Enables echo. If this flag is set, characters are echoed as they are
received.
When the ICANON is set, the following echo functions
are also possible:
- ECHOE
- Echoes the erase character as Backspace-Space-Backspace. If the ECHO and ECHOE flags are both set
and the ECHOPRT flag is not set, the ERASE and WERASE
characters are echoed as one or more ASCII Backspace-Space-Backspace sequences,
which clears the last characters from the screen.
- ECHOPRT
- If the ECHO and ECHOPRT
flags are both set, the first ERASE and WERASE character in a sequence are
echoed as a \ (backslash), followed by the characters being erased. Subsequent
ERASE and WERASE characters echo the characters being erased, in reverse order.
The next non-erase character causes a / (slash) to be typed before the nonerase
character is echoed. This function also requires the IEXTEN bit to be set.
- ECHOKE
- Backspace-Space-Backspace entire line on line kill. If this flag is
set, the kill character is echoed by erasing the entire line from the screen
(using the mechanism selected by the ECHOE and ECHOPRT flags). This function also requires the IEXTEN flag to be set.
- ECHOK
- Echoes the NL character after kill. If the ECHOK flag is set and the ECHOKE flag is not set, the
NL character is echoed after the kill character is received. This emphasizes
that the line is deleted.
- ECHONL
- Echoes the NL character. If the ECHONL flag
is set, the NL character is echoed even if the ECHO
flag is not set. This is useful for terminals that are set to "local echo"
(also referred to as "half-duplex").
- ECHOCTL
- Echoes control characters (with codes between 0 and 37 octal) as ^X, where X is the character that
results from adding 100 octal to the code of the control character. (For
example, the character with octal code 1 is echoed as ^A). The ASCII DEL character (code 177 octal) is echoed as ^?. The ASCII TAB, NL, and START characters are not echoed. Unless escaped
(preceded by a backslash), the EOF character is not echoed. As a result,
because EOT is the default EOF character, terminals that respond to EOT are
prevented from hanging up. This function also requires the IEXTEN flag to be set.
- 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 special character (Ctrl-c), which is recognized on
input if the ISIG flag is set. The INTR character generates
a SIGINT signal, which is sent to all processes in
the foreground process group for which the terminal is the controlling terminal.
If the ISIG flag is set, the INTR character is discarded
when processed.
- VQUIT
- Indexes the QUIT special character (Ctrl-\), which is recognized on
input if the ISIG flag is set. The QUIT character generates
a SIGQUIT signal, which is sent to all processes in
the foreground process group for which the terminal is the controlling terminal,
and writes a core image file into the current working
directory. If the ISIG flag is set, the QUIT character
is discarded when processed.
- VERASE
- Indexes the ERASE special character (Backspace), which is recognized
on input if the ICANON flag is set. The ERASE character
does not erase beyond the beginning of the line as delimited by a NL, EOL,
EOF, or EOL2 character. If the ICANON flag is set, the
ERASE character is discarded when processed.
- VKILL
- Indexes the KILL special character (Ctrl-u), which is recognized on
input if the ICANON flag is set. The KILL character
deletes the entire line, as delimited by a NL, EOL, EOF, or EOL2 character.
If the ICANON flag is set, the KILL character is discarded
when processed.
- VEOF
- Indexes the EOF special character (Ctrl-d), which is recognized on
input if the ICANON flag is set. When EOF is received,
all the characters waiting to be read are immediately passed to the process,
without waiting for a new line, and the EOF is discarded. If the EOF is received
at the beginning of a line (no characters are waiting), a character count
of zero is returned from the read, indicating an end-of-file. If the ICANON flag is set, the EOF character is discarded when
processed.
- VEOL
- Indexes the EOL special character (Ctrl-@ or ASCII NULL), which is
recognized on input if the ICANON flag is set. EOL
is an additional line delimiter, like NL, and is not normally used.
- VEOL2
- Indexes the EOL2 special character (Ctrl-@ or ASCII NULL), which is
recognized on input if the ICANON and IEXTEN flags are set. EOL2 is an additional line delimiter, like NL,
and is not normally used.
- VSTART
- Indexes the START special character (Ctrl-q), which is recognized
on input if the IXON flag is set, and generated on
output if the IXOFF flag is set. The START character
can be used to resume output that has been suspended by a STOP character.
If the IXON flag is set, the START character is discarded
when processed. While output is not suspended, START characters are ignored
and not read. VSTRT is an alias for VSTART.
- VSTOP
- Indexes the STOP special character (Ctrl-s), which is recognized on
input if the IXON flag is set, and generated on output
if the IXOFF flag is set. The STOP character can be
used to with terminals to prevent output from disappearing before it can be
read. If the IXON flag is set, the STOP character is
discarded when processed. While output is suspended, STOP characters are
ignored and not read.
- VSUSP
- Indexes the SUSP special character (Ctrl-z), which is recognized on
input if the ISIG flag is set. The SUSP character generates
a SIGTSTP signal, which is sent to all processes in
the foreground process group for which the terminal is the controlling terminal.
If the ISIG flag is set, the SUSP character is discarded
when processed.
- VDSUSP
- Indexes the DSUSP special character (Ctrl-y), which is recognized
on input if the ISIG and IEXTEN
flags are set. The DSUSP character generates a SIGTSTP
signal as the SUSP character does, but the signal is sent when a process
in the foreground process group attempts to read the DSUSP character, rather
than when DSUSP is typed. If the ISIG and IEXTEN flags are set, the DSUSP character is discarded when processed.
- VREPRINT
- Indexes the REPRINT special character (Ctrl-r), which is recognized
on input if the ICANON and IEXTEN flags are set. The REPRINT character reprints all characters, preceded
by a new line, that have not been read. If the ICANON
and IEXTEN flags are set, the REPRINT character is
discarded when processed.
- VDISCRD
- Indexes the DISCARD special character (Ctrl-o), which is recognized
on input if the ICANON and IEXTEN flags are set. The DISCARD character causes subsequent output to be
discarded until another DISCARD character is typed, more input arrives, or
the condition is cleared by a program. If the ICANON
and IEXTEN flags are set, the DISCARD character is
discarded when processed.
- VWERSE
- Indexes the WERASE special character (Ctrl-w), which is recognized
on input if the ICANON and IEXTEN flags are set. The WERASE character causes the preceding word to be
erased. The WERASE character does not erase beyond the beginning of the line
as delimited by a NL, EOL, EOF, or EOL2 character. If the ICANON and IEXTEN flags are set, the WERASE character
is discarded when processed.
- VLNEXT
- Indexes the LNEXT (literal next) special character (Ctrl-v), which
is recognized on input if the ICANON and IEXTEN flags are set. The LNEXT character causes the special meaning
of the next character to be ignored so that characters can be input without
being interpreted by the system. If the ICANON, ECHO, and IEXTEN flags are set, the
LNEXT character is replaced by a ^-Backspace sequence when processed.
- VMIN
- Indexes the MIN value, which is not a special
character. The use of the MIN value is described in
the discussion of noncanonical mode input processing in "ldterm Line Discipline" in AIX 5L Version 5.2 General Programming Concepts: Writing and Debugging Programs.
- VTIME
- Indexes the TIME value, which is not a special
character. The use of the TIME value is described in
the discussion of noncanonical mode input processing in "ldterm Line Discipline" in AIX 5L Version 5.2 General Programming Concepts: Writing and Debugging Programs.
The character values for the following control characters can be
changed:
INTR |
EOF |
STOP |
DISCARD |
QUIT |
EOL |
SUSP |
WERASE |
ERASE |
EOL2 |
DSUSP |
LNEXT |
KILL |
START |
REPRINT |
The ERASE, KILL, and EOF characters can also be escaped (preceded
by a backslash) so that no special processing is done.
Parameter Value Definitions
The following values for the OptionalActions parameter
of the tcsetattr subroutine are also defined in the termios.h 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 until all input received but not read has been discarded before setting
the terminal parameters from the termios structure. |
The following values for the QueueSelector parameter
of the tcflush subroutine 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 data that is received but not read as well as data that is
written but not transmitted. |
The following values for the Action parameter of
the tcflow subroutine are also defined in the termios.h file:
TCOOFF |
Suspends the output of data by the object file named in the tcflow subroutine. |
TCOON |
Restarts data output that was suspended by the TCOOFF action. |
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. |
Modem Control Operations
The following ioctl operations, used for modem control, are an extension
to the POSIX line discipline interface. To use these operations in a program,
the program must contain an #include statement for the ioctl.h file.
TIOCMBIS |
The argument to this command is a pointer to an integer that turns
on the control lines specified by the integer mask value. No other control
lines are affected. |
TIOCMBIC |
The argument to this command is a pointer to an integer that turns
off the control lines specified by the integer mask value. No other control
lines are affected. |
TIOCMGET |
Gets all modem bits. The argument to this command is a pointer to an
integer where the current state of the modem status lines is stored. Which
modem status and modem control lines are supported depends on the capabilities
of the hardware and the hardware's device driver. |
TIOCMSET |
Sets all modem bits. The argument to this command is a pointer to an
integer containing a new set of modem bits. The modem control bits use these
bits to turn the modem control lines on or off, depending on whether the
bit for that line is set or clear. Any modem status bits are ignored. The
actual modem control lines which are supported depend on the capabilities
of the hardware and the hardware's device driver.
The integer specifies
one of the following modem control or status lines on which the modem control ioctl command operates:
- TIOCM_LE
- Line enable
- TIOCM_DTR
- Data terminal ready
- TIOCM_RTS
- Request to send
- TIOCM_ST
- Secondary transmit
- TIOCM_SR
- Secondary receive
- TIOCM_CTS
- Clear to send
- TIOCM_CAR
- Carrier detect
- TIOCM_CD
- TIOCM_CAR
- TIOCM_RNG
- Ring
- TIOCM_RI
- TIOCM_RNG
- TIOCM_DSR
- Data set ready.
|
TIOCMIWAIT |
Wait for modem status line to change status.
The
argument is a pointer to an integer mask value specifying the modem status
line(s) on which to wait for a status change, and can consist of one or more
of the following values:
- TIOCM_CTS
- Clear to send
- TIOCM_CAR
- Carrier detect
- TIOCM_CD
- TIOCM_CAR
- TIOCM_RNG
- Ring
- TIOCM_RI
- TIOCM_RNG
- TIOCM_DSR
- Data set ready.
The request blocks until one of the specified lines changes status, then
returns to the caller. Note that this ioctl blocks even
if O_NDELAY or O_NONBLOCK is set.
If none of the specified lines changes status, the ioctl can block indefinitely, so it should be used in conjunction with
an alarm() timer.
If TIOCM_RNG or TIOCM_RI is specified, the transition is reported
only when the status line transitions from on to off
due to hardware restrictions.
Note
Correct operation of this ioctl depends on correct cabling. |
Related Information
The termiox.h file,
types.h file.
The csh command, getty command, ksh command, stty command, tset
command.
The cfgetispeed, cfgetospeed, cfsetispeed, cfsetospeed subroutine, ioctl
subroutine, sigvec subroutine,
tcdrain subroutine, tcflow subroutine, tcflush subroutine, tcgetattr subroutine, tcsendbreak subroutine, tcsetattr subroutine.
tty Subsystem Overview in AIX 5L Version 5.2 General Programming Concepts: Writing and Debugging Programs.
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