Advanced Programming in the UNIX® Environment

ptg10805159

Section 18.3 Special Input Characters 679

Example

Beforedescribing all the special characters in detail, let’s look at a small program that

changes them. The program in Figure18.10 disables the interrupt character and sets the

end-of-file character to Control-B.

#include "apue.h"

#include <termios.h>

int

main(void)

{

struct termios term;

long vdisable;

if (isatty(STDIN_FILENO) == 0)

err_quit("standard input is not a terminal device");

if ((vdisable = fpathconf(STDIN_FILENO, _PC_VDISABLE)) < 0)

err_quit("fpathconf error or _POSIX_VDISABLE not in effect");

if (tcgetattr(STDIN_FILENO, &term) < 0) /* fetch tty state */

err_sys("tcgetattr error");

term.c_cc[VINTR] = vdisable; /* disable INTR character */

term.c_cc[VEOF] = 2; /* EOF is Control-B */

if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &term) < 0)

err_sys("tcsetattr error");

exit(0);

}

Figure 18.10 Disable interrupt character and change end-of-file character

Note the following points regarding this program.

•Wemodify the terminal characters only if standardinput is a terminal device.

We callisatty(Section 18.9) to check this.

•Wefetch the_POSIX_VDISABLEvalue usingfpathconf.

•The functiontcgetattr(Section 18.4) fetches atermiosstructurefromthe

kernel. After we’ve modified this structure, we call tcsetattrto set the

attributes. The only attributes that change arethe ones we specifically modified.

•Disabling the interrupt key is different from ignoring the interrupt signal. The

program in Figure18.10 simply disables the special character that causes the

terminal driver to generateSIGINT.Wecan still use thekillfunction to send

the signal to the process.