C Programming, Keyboard input, ncurses.

Joshu · 09-30-2015, 12:52 AM

Hi there everyone, first time poster, very long time reader. I'm trying to understand how I can get user input from the keyboard. For example if the user presses the letter 'a' the object moves to the left and if they press 'f' they move the object to the right. The following elementary code just shows the word TARGET move across the screen from left to right and then back again and repeats. I've tried googling and have been through a few stackoverflow threads but still can't seem to find an answer. My thinking is that I somehow use getch() to somehow scan for a '97/65' for the letter 'a/A'? If anyone could give me a helping hand or point me in the right direction that'd be great. Thankyou, and I look forward to contributing to the LQ community in the future.

Code:

#include <stdio.h>
#include <unistd.h>
#include <ncurses.h>
#define DELAY 60000

int main(int argc, char *argv[])
{
    int y, x = 0;
    int max_y, max_x, next_x = 0;
    int direction_x = 1;
    
    initscr();
    noecho();
    curs_set(FALSE);
    
    while (1) {
        getmaxyx(stdscr, max_y, max_x);
        clear();
        mvprintw(y, x, "TARGET");
        refresh();
        usleep(DELAY);
        
        next_x = x + direction_x;
        
        if (next_x >= max_x || next_x < 0) {
            direction_x*= -1;
        } else {
            x += direction_x;
        }
    }
    endwin();
}

NevemTeve · 09-30-2015, 02:54 AM

I couldn't find any getch in your code

Joshu · 09-30-2015, 04:18 AM

Thanks for the reply NevemTeve. I've tried to get getch() working multiple times and failed. It may not be possible, i've been searching for hours and have found no solution.
Edit. I could do this, but it would be good to have a getAsciCode() or something similar. I can just do this i suppose.

Code:

#headers

int main()
{
        char c;
        printf("Enter a character ");
        c = getchar();

        if (c == 'b') {
                printf("You hit the letter 'b'\n");
                printf("Now run this code\n");
        }
        else {
                printf("You didn't hit 'b'\n");
        }
}

NevemTeve · 09-30-2015, 04:33 AM

Well, actually calling 'getch' is an important part of using it.

Code:

    int ch;
...
    while ((ch = getch()) != ERR) {
	printw("Keycode %d\n", ch);
	if      (ch=='A') printw("Upper-case 'A'\n");
	else if (ch=='a') printw("Lower-case 'a'\n");
	clrtoeol();
	refresh();
    }

rtmistler · 09-30-2015, 07:08 AM

I would use the getc() and getchar() functions, they conform to the standards. There seem to be too many exceptions and special considerations for using getch(). When I search I find a lot more references back to Microsoft's NCurses library. They did something for their purposes and not a general C language case. I say stick with the more universal functions and use NevemTeve's example.

ntubski · 09-30-2015, 09:12 AM

Quote:

Originally Posted by rtmistler

When I search I find a lot more references back to Microsoft's NCurses library.

Huh? GNU is Not Unix, but it's not Microsoft either.

http://www.gnu.org/software/ncurses/ncurses.html

@NevemTeve: your % got eaten.

NevemTeve · 09-30-2015, 09:18 AM

> I would use the getc() and getchar() functions, they conform to the standards.

Also termios, I have to add, because the OP wants to read in raw mode. Plus, if he wants to interpret ESC-sequences generated by terminal then he has to reinvent ncurses... So it might be easier to use ncurses.

metaschima · 10-03-2015, 10:08 PM

Get rid of 'stdio.h', you do not need it here.