Terminal device control

Special control characters

The array c_cc specifies the special control-characters that affect the operation of the communication-port and the processing of terminal input and output as described in the ``Special characters'' section below. For each entry of the control-character array c_cc, the following are typical default values:

Terminal device control character array

Subscript value Subscript name Character value Character description

0 VINTR ASCII DEL INTR character

1 VNUIT ASCII FS QUIT character

2 VERASE ^h ERASE character

3 VKILL ^u KILL character

4 VEOF ASCII EOT EOF character

5 VEOL ASCII NUL EOL character

6 reserved

7 reserved

8 VSTART ASCII DC1 START character

9 VSTOP ASCII DC3 STOP character

10 VSUSP ASCII SUB SUSP character

Subscript value	Subscript name	Character value	Character description
0	VINTR	ASCII DEL	INTR character
1	VNUIT	ASCII FS	QUIT character
2	VERASE	^h	ERASE character
3	VKILL	^u	KILL character
4	VEOF	ASCII EOT	EOF character
5	VEOL	ASCII NUL	EOL character
6	reserved
7	reserved
8	VSTART	ASCII DC1	START character
9	VSTOP	ASCII DC3	STOP character
10	VSUSP	ASCII SUB	SUSP character

The subscript values are unique, except that the VMIN and VTIME subscripts may have the same value as the VEOF and VEOL subscripts respectively. The <termios.h> header file defines the relative positions, subscript names and default values for the control-character array c_cc (see ``Special control characters'' in termio(7)).

The NL and CR character cannot be changed. The INTR, QUIT, ERASE, KILL, EOF, EOL, SUSP, STOP and START characters can be changed as follows:

   struct termios term;
   term.c_cc[VINTR] = `a';
   term.c_cc[VQUIT] = `b';
   term.c_cc[VERASE] = `c';
   term.c_cc[VKILL] = `d';
   term.c_cc[VEOF] = `e';
   term.c_cc[VEOL] = `f';
   term.c_cc[VSUSP] = `g';
   term.c_cc[VSTOP] = `h';
   term.c_cc[VSTART] = `i';

where a, b, c, d, e, f, g, h and i are the INTR, QUIT, ERASE, KILL, EOF, EOL, SUSP, STOP and START characters respectively.

Implementations which prohibit changing the START and STOP characters may ignore the character values in the c_cc array indexed by the VSTART and VSTOP subscripts when tcsetattr is called, but return the character value when tcsetattr is called (see tcsetattr in termios(3C)).

If _POSIX_VDISABLE is defined for the terminal-device-file, and the value of one of the changeable special control-characters equals _POSIX_VDISABLE, that function is disabled; that is, the special character is ignored on input and is not recognized (see ``Special characters'' section below). If ICANON is clear, the value of _POSIX_VDISABLE lacks any special meaning for the VMIN and VTIME entries of the c_cc array.