The <termios.h> header contains the definitions used by the terminal I/O interfaces (see General Terminal Interface for the structures and names defined).
The termios Structure
The following data types shall be defined through typedef:
- cc_t
- Used for terminal special characters.
- speed_t
- Used for terminal baud rates.
- tcflag_t
- Used for terminal modes.
The above types shall be all unsigned integer types.
The implementation shall support one or more programming environments in which the widths of cc_t, speed_t, and tcflag_t are no greater than the width of type long. The names of these programming environments can be obtained using the confstr() function or the getconf utility.
The termios structure shall be defined, and shall include at least the following members:
tcflag_t c_iflag Input modes. tcflag_t c_oflag Output modes. tcflag_t c_cflag Control modes. tcflag_t c_lflag Local modes. cc_t c_cc[NCCS] Control characters.
A definition shall be provided for:
- NCCS
- Size of the array c_cc for control characters.
The following subscript names for the array c_cc shall be defined:
|
Subscript Usage |
|
|
|---|---|---|
|
Canonical Mode |
Non-Canonical Mode |
Description |
|
VEOF |
|
EOF character. |
|
VEOL |
|
EOL character. |
|
VERASE |
|
ERASE character. |
|
VINTR |
VINTR |
INTR character. |
|
VKILL |
|
KILL character. |
|
|
VMIN |
MIN value. |
|
VQUIT |
VQUIT |
QUIT character. |
|
VSTART |
VSTART |
START character. |
|
VSTOP |
VSTOP |
STOP character. |
|
VSUSP |
VSUSP |
SUSP character. |
|
|
VTIME |
TIME value. |
The subscript values shall be unique, except that the VMIN and VTIME subscripts may have the same values as the VEOF and VEOL subscripts, respectively.
The following flags shall be provided.
Input Modes
The c_iflag field describes the basic terminal input control:
- BRKINT
- Signal interrupt on break.
- ICRNL
- Map CR to NL on input.
- IGNBRK
- Ignore break condition.
- IGNCR
- Ignore CR.
- IGNPAR
- Ignore characters with parity errors.
- INLCR
- Map NL to CR on input.
- INPCK
- Enable input parity check.
- ISTRIP
- Strip character.
- IXANY
- [XSI]
![[Option Start]](../images/opt-start.gif)
Enable any character to restart output. ![[Option End]](../images/opt-end.gif)
- IXOFF
- Enable start/stop input control.
- IXON
- Enable start/stop output control.
- PARMRK
- Mark parity errors.
Output Modes
The c_oflag field specifies the system treatment of output:
- OPOST
- Post-process output.
- ONLCR
- [XSI]
Map NL to CR-NL on output.
- OCRNL
- Map CR to NL on output.
- ONOCR
- No CR output at column 0.
- ONLRET
- NL performs CR function.
- OFILL
- Use fill characters for delay.
- NLDLY
- Select newline delays:
- NL0
- Newline type 0.
- NL1
- Newline type 1.
- CRDLY
- Select carriage-return delays:
- CR0
- Carriage-return delay type 0.
- CR1
- Carriage-return delay type 1.
- CR2
- Carriage-return delay type 2.
- CR3
- Carriage-return delay type 3.
- TABDLY
- Select horizontal-tab delays:
- TAB0
- Horizontal-tab delay type 0.
- TAB1
- Horizontal-tab delay type 1.
- TAB2
- Horizontal-tab delay type 2.
- TAB3
- Expand tabs to spaces.
- BSDLY
- Select backspace delays:
- BS0
- Backspace-delay type 0.
- BS1
- Backspace-delay type 1.
- VTDLY
- Select vertical-tab delays:
- VT0
- Vertical-tab delay type 0.
- VT1
- Vertical-tab delay type 1.
- FFDLY
- Select form-feed delays:
- FF0
- Form-feed delay type 0.
- FF1
- Form-feed delay type 1.
Baud Rate Selection
The input and output baud rates are stored in the termios structure. These are the valid values for objects of type speed_t. The following values shall be defined, but not all baud rates need be supported by the underlying hardware.
- B0
- Hang up
- 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
Control Modes
The c_cflag field describes the hardware control of the terminal; not all values specified are required to be supported by the underlying hardware:
- CSIZE
- Character size:
- CS5
- 5 bits
- CS6
- 6 bits
- CS7
- 7 bits
- CS8
- 8 bits
- CSTOPB
- Send two stop bits, else one.
- CREAD
- Enable receiver.
- PARENB
- Parity enable.
- PARODD
- Odd parity, else even.
- HUPCL
- Hang up on last close.
- CLOCAL
- Ignore modem status lines.
The implementation shall support the functionality associated with the symbols CS7, CS8, CSTOPB, PARODD, and PARENB.
Local Modes
The c_lflag field of the argument structure is used to control various terminal functions:
- ECHO
- Enable echo.
- ECHOE
- Echo erase character as error-correcting backspace.
- ECHOK
- Echo KILL.
- ECHONL
- Echo NL.
- ICANON
- Canonical input (erase and kill processing).
- IEXTEN
- Enable extended input character processing.
- ISIG
- Enable signals.
- NOFLSH
- Disable flush after interrupt or quit.
- TOSTOP
- Send SIGTTOU for background output.
Attribute Selection
The following symbolic constants for use with tcsetattr() are defined:
- TCSANOW
- Change attributes immediately.
- TCSADRAIN
- Change attributes when output has drained.
- TCSAFLUSH
- Change attributes when output has drained; also flush pending input.
Line Control
The following symbolic constants for use with tcflush() shall be defined:
- TCIFLUSH
- Flush pending input.
- TCIOFLUSH
- Flush both pending input and untransmitted output.
- TCOFLUSH
- Flush untransmitted output.
The following symbolic constants for use with tcflow() shall be defined:
- TCIOFF
- Transmit a STOP character, intended to suspend input data.
- TCION
- Transmit a START character, intended to restart input data.
- TCOOFF
- Suspend output.
- TCOON
- Restart output.
The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.
speed_t cfgetispeed(const struct termios *); speed_t cfgetospeed(const struct termios *); int cfsetispeed(struct termios *, speed_t); int cfsetospeed(struct termios *, speed_t); int tcdrain(int); int tcflow(int, int); int tcflush(int, int); int tcgetattr(int, struct termios *); [XSI]