The Linux Programming Interface

1306 Chapter 62

passed to the reading process instead. If none of IGNPAR, PARMRK, or INPCK is set, then

the character is passed as is to the reading process.

Example program

Listing 62-2 demonstrates the use of tcgetattr() and tcsetattr() to turn off the ECHO flag,

so that input characters are not echoed. Here is an example of what we see when

running this program:

$ ./no_echo

Enter text: We type some text, which is not echoed,

Read: Knock, knock, Neo. but was nevertheless read

Listing 62-2: Disabling terminal echoing

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––tty/no_echo.c

#include <termios.h>

#include "tlpi_hdr.h"

#define BUF_SIZE 100

int

main(int argc, char *argv[])

{

struct termios tp, save;

char buf[BUF_SIZE];

/* Retrieve current terminal settings, turn echoing off */

if (tcgetattr(STDIN_FILENO, &tp) == -1)

errExit("tcgetattr");

save = tp; /* So we can restore settings later */

tp.c_lflag &= ~ECHO; /* ECHO off, other bits unchanged */

if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &tp) == -1)

errExit("tcsetattr");

/* Read some input and then display it back to the user */

printf("Enter text: ");

fflush(stdout);

if (fgets(buf, BUF_SIZE, stdin) == NULL)

printf("Got end-of-file/error on fgets()\n");

else

printf("\nRead: %s", buf);

/* Restore original terminal settings */

if (tcsetattr(STDIN_FILENO, TCSANOW, &save) == -1)

errExit("tcsetattr");

exit(EXIT_SUCCESS);

}

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––tty/no_echo.c