Mailinglist Archive: opensuse-programming (98 mails)

[Jerry Feldman <gaf@xxxxxxx>]

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On Tue, 17 Feb 2004 20:51:53 -1000
"Ryan Walsh" <walshfam@xxxxxxxxxxxxx> wrote:

> I'm just getting back into programming, and this is my first
> introduction to LINUX.  I was wondering if anyone had a basic C
> program on how to read input from the keyboard one character at a time
> (without having to press enter)...
This is not part of standard C, but here is a program that I've had
hanging around. The Unix/C FAQ also includes something similar. 
I've been using this for a while. Essentially, you set the terminal to
raw mode, (stdin is file descriptor 0). You should use the basic I/O
(eg. read(2) not the stdio routines like getc(3)).
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <termio.h>
#include <sys/ioctl.h>
static struct termio save_term;
void
SetRaw(int fd)
{
  struct termio s;
  
    /*
     * Get terminal modes.
     */
    (void)ioctl(fd, TCGETA, &s);
    
    /*
     * Save modes and set certain variables dependent on modes.
     */
    save_term = s;
      
      /*
       * Set the modes to the way we want them.
       */
      s.c_lflag &= ~(ICANON|ECHO|ECHOE|ECHOK|ECHONL);
      s.c_oflag |=  (OPOST|ONLCR|TAB3);
      s.c_oflag &= ~(OCRNL|ONOCR|ONLRET);
      s.c_cc[VMIN] = 1;
      s.c_cc[VTIME] = 0;
	(void)ioctl(fd, TCSETAW, &s);
}
static void 
TermRestore(int fd)
{
	/*
	 * Restore saved modes.
	 */
	s = save_term;
  (void)ioctl(fd, TCSETAW, &s);
}
int main(int argc, char **argv)
{
  int fd, n;
  char buf;
  fd = 0;
  /Set Term to raw mode */
  SetRaw(fd);
  printf("Enter a digit, q or x to quit\n");
  while(1) {
    n = read(fd, &buf, 1);
    if (n == 1) {
      switch(buf) {
      case 'q':
      case 'Q':
      case 'x':
      case 'X':
	printf("done\n");
        TermRestore(fd);
	return 0;
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
      case '8':
      case '9':
	printf(" %c ", buf);
	fflush(stdout);
      }
    } else if (n == 0) {
      printf("no input\n");
      TermRestore(fd);
      return 0;
    } else {
      TermRestore(fd);
      perror("read\n");
      return -1;
    }
  }
}



- -- 
Jerry Feldman <gaf@xxxxxxx>
Boston Linux and Unix user group
http://www.blu.org PGP key id:C5061EA9
PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9
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