Manual Reference Pages  - <termios.h> (P)


This manual page is part of the POSIX Programmer’s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


     The termios Structure
     Input Modes
     Output Modes
     Baud Rate Selection
     Control Modes
     Local Modes
     Attribute Selection
     Line Control
Application Usage
Future Directions
See Also


termios.h - define values for termios


#include <termios.h>


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.
  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 ModeNon-Canonical ModeDescription
VEOF EOF character.
VEOL EOL character.
VERASE ERASE character.
VKILL KILL character.
VMINMIN 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 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 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.
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.
  Change attributes when output has drained.
  Change attributes when output has drained; also flush pending input.

    Line Control

The following symbolic constants for use with tcflush() shall be defined:
  Flush pending input.
  Flush both pending input and untransmitted output.
  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 *);

pid_t tcgetsid(int);

int tcsendbreak(int, int); int tcsetattr(int, int, const struct termios *);

The following sections are informative.


The following names are reserved for XSI-conformant systems to use as an extension to the above; therefore strictly conforming applications shall not use them:







The System Interfaces volume of IEEE Std 1003.1-2001, cfgetispeed(), cfgetospeed(), cfsetispeed(), cfsetospeed(), confstr(), tcdrain(), tcflow(), tcflush(), tcgetattr(), tcgetsid(), tcsendbreak(), tcsetattr(), the Shell and Utilities volume of IEEE Std 1003.1-2001, getconf, General Terminal Interface


Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at .

IEEE/The Open Group <termios.h> (P) 2003
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