stdin v.s. tty

stdin-vs-tty.c

#include <stdio.h>
#include <stdlib.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <unistd.h>

#include <string.h>
#include <errno.h>

#include <poll.h>

#include <termios.h>

int main(void)
{
    char buf[1024];
    int len;
    int i, j;

    struct pollfd pfds[2] = {0};

    struct termios flags = {0};

    pfds[1].fd = open("/dev/tty", O_RDONLY);
    if (pfds[1].fd < 0) {
        printf("open(2): %s\n", strerror(errno));
        return EXIT_FAILURE;
    }
    pfds[1].events = POLLIN;

    if (tcgetattr(pfds[1].fd, &flags) < 0) {
        printf("tcgetattr(3): %s\n", strerror(errno));
        close(pfds[1].fd);
        return EXIT_FAILURE;
    }

    flags.c_lflag &= ~ICANON;
    if (tcsetattr(pfds[1].fd, TCSANOW, &flags) < 0) {
        printf("tcsetattr(3): %s\n", strerror(errno));
        close(pfds[1].fd);
        return EXIT_FAILURE;
    }

    pfds[0].fd = fileno(stdin);
    if (pfds[0].fd < 0) {
        printf("open(2): %s\n", strerror(errno));
        close(pfds[1].fd);
        return EXIT_FAILURE;
    }
    pfds[0].events = POLLIN;

    while (1) {
        for (i = 0; i < sizeof(pfds)/sizeof(pfds[0]); ++i)
            pfds[i].revents = 0;

        len = poll(pfds, sizeof(pfds)/sizeof(pfds[0]), -1);
        if (len < 0) {
            if (errno == -EAGAIN)
                continue;
            printf("poll(2): %s\n", strerror(errno));
            break;
        }

        if (len == 0)
            continue;

        for (i = 0; i < sizeof(pfds)/sizeof(pfds[0]); ++i) {
            if (!(pfds[i].revents & POLLIN))
                continue;

            len = read(pfds[i].fd, buf, sizeof(buf));
            if (len < 0) {
                printf("read(2): %s\n", strerror(errno));
                break;
            }
            if (len == 0)
                break;
            for (j = 0; j < len; ++j) {
                printf("%d: %d: %c\n", pfds[i].fd, j, buf[j]);
                fflush(stdout);
            }
        }
    }

    flags.c_lflag |= ICANON;
    if (tcsetattr(pfds[0].fd, TCSANOW, &flags) < 0) {
        printf("tcsetattr(3): %s\n", strerror(errno));
        close(pfds[0].fd);
        return EXIT_FAILURE;
    }

    close(pfds[0].fd);
    close(pfds[1].fd);

    return EXIT_SUCCESS;
}