Graphic Timer

/* The utility is a graphic timer. It should be launched in a terminal
 * emulator. It determines the size of the terminal window and then
 * fills all of it with the character "W", in the number of minutes
 * indicated in the definition of the macro SESSION_DURATION_MINS. */

#include <stdio.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <stdlib.h>

#define SESSION_DURATION_MINS 20
#define MICROSECS_IN_A_MINUTE 60000000

int main() {
    struct winsize w;

    // Get the number of columns and the number of lines of the terminal window
    if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &w) == -1) {
        perror("ioctl failed!");
        return 1;
    }

    int char_places_number = (int)(w.ws_row * w.ws_col);
    if (char_places_number <= 0) {
        fprintf(stderr, "Invalid terminal size.\n");
        return 1;
    }

    useconds_t timeout_microsecs = (useconds_t)(SESSION_DURATION_MINS * MICROSECS_IN_A_MINUTE / char_places_number);

    // Clear the screen
    printf("\033[H\033[J");

    for (int i = 0; i < char_places_number; i++) {
        (void) putchar(87);
        (void) fflush(stdout);
        (void) usleep(timeout_microsecs);
    }
    return 0;
}