getch

/****************************************************************
 * getch() implementation                                       *
 * On windows, we have getch() in <conio.h> to get a char from  *
 * keyboard without echoing it out to stdout. But Unix has no   *
 * <conio.h>, it is not standard though. If we want to use      *
 * getch() on Unix, we have to implement it by ourselves.       *
 * As <termios.h> is defined in POSIX.1 standard, the code will *
 * be portable and be able to port to ANY Unix-like systems     *
 * e.g. Linux, mac, BSD, Solarix, HP-UX, AIX, IRIX, etc.        *
 * without any changes in source code.                          *
 ****************************************************************/

#include <unistd.h>     /* STDIN_FILENO */
#include <termios.h>    /* tcgetattr(3), tcsetattr(3) */
#include <stdio.h>
#include <stdlib.h>     /* exit(3) */

int getch(void);        /* Prototype */

int main(void)
{
    char c; /* Local variable */

    printf("Starting getch(), press space to quit.\n");
    while ((c = (int)getch()) != 0x20)  /* Invoke our getch().  */
        printf("You type %c.\n", c);
        /* Once you type a key, it will not be echoed on stdout *
         * directly. It is our choice whether we want to print  *
         * it out or not. We prefer to  printing the sentence   *
         * mentioning what key you have typed.  */

    return 0;
}

int getch(void)         /* Implementation */
{
    int c; /* Local variable */
    struct termios oldt, newt; /* Declare old and new terminal. */

    /* Get attribute of stdin and store it in "oldt". */
    if (tcgetattr(STDIN_FILENO, &oldt) != 0) {
        fprintf(stderr, "tcgetattr error\n");
        exit(EXIT_FAILURE);
    }

    /* Copy "oldt" to "newt" */
    newt = oldt;

    /* Bitwise-and to turn of canonical mode (ICANON) and echo.*/
    newt.c_lflag &= ~(ICANON | ECHO);

    /* newt.c_cc[VTIME] == 0, so the time is not significant.   *
     * Only newt.c_cc[VMIN] is significant.                     *
     * The read is satisfied when VMIN byte(s), 1 for this case *
     * is received. That is it waits for one byte input, within *
     * indefinite time. Read termios(4) for more information.   */
    newt.c_cc[VMIN] = 1;
    newt.c_cc[VTIME] = 0;

    /* Set attribute to "newt", and take effect immediately. */
    if (tcsetattr(STDIN_FILENO, TCSANOW, &newt) != 0) {
        fprintf(stderr, "tcsetattr error\n");
        exit(EXIT_FAILURE);
    }

    /* Since we disabled ECHO and we take input char by char    *
     * not canonical (line by line). getchar() will request for *
     * input from a terminal. But now it will not be echoed.    */
    c = getchar();

    /* Restore "oldt" prior to ending the function. */
    tcsetattr(STDIN_FILENO, TCSANOW, &oldt);

    return c; /* return a char we have read, but not echod. */
}