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man pages section 3: Library Interfaces and Headers

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Updated: Thursday, June 13, 2019
 
 

termios.h(3HEAD)

Name

termios.h, termios - define values for termios

Synopsis

#include <termios.h>

Description

The <termios.h> header contains the definitions used by the terminal I/O interfaces. See termios(3C) and termio(4I) for an overview of the terminal interface.

The termios Structure

The following data types are 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 are all unsigned integer types.

The implementation supports 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(3C) function or the getconf(1) utility.

The termios structure is defined and includes 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 is provided for:

NCCS

size of the array c_cc for control characters

The following subscript names for the array c_cc are defined:

Subscript Usage
Canonical Mode
Subscript Usage
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 are unique, except that the VMIN and VTIME subscripts can have the same values as the VEOF and VEOL subscripts, respectively.

The header file provides the flags described below.

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

Enable any character to restart output.

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

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 are 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

1 200 baud

B1800

1 800 baud

B2400

2 400 baud

B4800

4 800 baud

B9600

9 600 baud

B19200

19 200 baud

B38400

38 400 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 supports 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() are 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() are 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.

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
Standard

See Also

getconf(1), cfgetispeed(3C), cfsetispeed(3C), confstr(3C), tcdrain(3C), tcflow(3C), tcflush(3C), tcgetattr(3C), tcgetsid(3C), tcsendbreak(3C), tcsetattr(3C), attributes(7), standards(7)