tty_raw.c

Linux Kernel Programming by Examples(1)[Xeroo]

/* @file tty_raw.c
 *
 * R. Stevens Adv. Prog. in UNIX Env. p.355
 *
 */
#include <stdio.h>   // printf
#include <stdlib.h>  // exit
#include <signal.h>
#include <termios.h>
#include <unistd.h>

static struct termios termios_save;
static int    ttysavefd = -1;
static enum { RESET, RAW, CBREAK } ttystate = RESET;

int tty_reset( int fd );

static void
sig_catch( int signo )
{
  printf("signal caught. No %d\n", signo );
  tty_reset( STDIN_FILENO );
  exit(0);
}

int
tty_raw( int fd )
{
  struct termios buf;
  if ( tcgetattr( fd, &termios_save ) < 0 ) 
    return -1;
  buf = termios_save; // struct copy
  buf.c_lflag &= ~( ECHO | ICANON | IEXTEN | ISIG );
  buf.c_iflag &= ~( BRKINT | ICRNL | INPCK | ISTRIP | IXON );
  buf.c_cflag &= ~( CSIZE | PARENB );
  buf.c_cflag |= CS8;
  buf.c_oflag &= ~( OPOST );
  buf.c_cc[VMIN] = 1;
  buf.c_cc[VTIME] = 0;

  if ( tcsetattr( fd, TCSAFLUSH, &buf ) < 0 )
    return -1;

  ttysavefd = fd;
  ttystate  = RAW;
  return 0;
}
 
int
tty_reset( int fd )
{
  if ( ttystate != RAW )
    return 0;
  if ( tcsetattr( fd, TCSAFLUSH, &termios_save) < 0 )
    return -1;
  ttystate = RESET;
  return 0;
}

void
tty_atexit( void )
{
  if ( ttysavefd >= 0 )
    tty_reset( ttysavefd );
}

struct termios *
tty_termios( void )
{
  return &termios_save;
}

int
main( int argc, char ** argv )
{
  int  i;
  char c;
  
  if ( signal( SIGINT, sig_catch ) == SIG_ERR ) {
    printf("signal(SIGINT) error\n");
    exit(1);
  }
  if ( signal( SIGTERM, sig_catch ) == SIG_ERR ) {
    printf("signal(SIGTERM) error\n");
    exit(1);
  }
  if ( signal( SIGQUIT, sig_catch ) == SIG_ERR ) {
    printf("signal(SIGQUIT) error\n");
    exit(1);
  }

  if ( tty_raw( STDIN_FILENO ) < 0 ) {
    printf("tty_raw(STDIN) error\n");
    exit(2);
  }
  printf("Enter raw mode characters. Terminate with DELETE\n");
  while ( (i = read(STDIN_FILENO, &c, 1)) == 1) {
    if ( (c &= 255) == 0177 ) {
      break;
    }
    printf("%o\n", c );
  }
  if ( tty_reset( STDIN_FILENO ) < 0 ) {
    printf("tty_reset(STDIN) error\n");
  }
  if ( i <= 0 ) {
    printf("read error %d\n", i );
  }

  exit(0);
}