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® Version 7.1 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 Version 7.1 General Programming Concepts: Writing and Debugging Programs.
The character values for the following control
characters can be changed:
Item |
Description |
Value |
Value |
INTR |
EOF |
STOP |
DISCARD |
QUIT |
EOL |
SUSP |
WERASE |
ERASE |
EOL2 |
DSUSP |
LNEXT |
KILL |
START |
REPRINT |
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:
Item |
Description |
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:
Item |
Description |
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:
Item |
Description |
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.
Item |
Description |
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.
|