How to read user input without pressing ENTER?-CodePudding

I'm writing code where I need to get input without the user pressing ENTER. The code is basically that I need to get 4 numbers from 1-6 without the user pressing ENTER all in one line.

I tried doing so with getchar(), but it doesn't work.

How do I do that?

Here's that part of the code:

int p1 = 0;
int p2 = 0;
int p3 = 0;
int p4 = 0;
p1 = getchar() - 48;
p2 = getchar() - 48;
p3 = getchar() - 48;
p4 = getchar() - 48;

CodePudding user response：

This is a C FAQ: 12.5 How can I read one character at a time, without waiting for the RETURN key?

To quote:

Depending on which operating system you're using and what libraries you have available, you may be able to use one (or more!) of the following techniques:

If you can use the curses library, you can call cbreak [footnote] (and perhaps noecho), after which calls to getch will return characters immediately.
If all you're trying to do is read a short password without echo, you may be able to use a function called getpass, if it's available. (Another possibility for hiding typed passwords is to select black characters on a black background.)
Under classic versions of Unix, use ioctl and the TIOCGETP and TIOCSETP (or TIOCSETN) requests on file descriptor 0 to manipulate the sgttyb structure, defined in <sgtty.h> and documented in tty(4). In the sg_flags field, set the CBREAK (or RAW) bit, and perhaps clear the ECHO bit.
Under System V Unix, use ioctl and the TCGETAW and TCSETAW requests on file descriptor 0 to manipulate the termio structure, defined in <termio.h>. In the c_lflag field, clear the ICANON (and perhaps ECHO) bits. Also, set c_cc[VMIN] to 1 and c_cc[VTIME] to 0.
Under any operating system (Unix or otherwise) offering POSIX compatibility, use the tcgetattr and tcsetattr calls on file descriptor 0 to manipulate the termios structure, defined in <termios.h>. In the c_lflag field, clear the ICANON (and perhaps ECHO) bits. Also, set c_cc[VMIN] to 1 and c_cc[VTIME] to 0.
In a pinch, under Unix, use system (see question 19.27) to invoke the stty command to set terminal driver modes (as in the preceding three items).
Under MS-DOS, use getch or getche, or the corresponding BIOS interrupts.
Under VMS, try the Screen Management (SMG$) routines, or curses, or issue low-level $QIO's with the IO$_READVBLK function code (and perhaps IO$M_NOECHO, and others) to ask for one character at a time. (It's also possible to set character-at-a-time or ``pass through'' modes in the VMS terminal driver.)
Under other operating systems, you're on your own.

CodePudding user response：

There is no standard function for this.

There are some custom solutions e.g. https://www.cs.uleth.ca/~holzmann/C/system/ttyraw.c But your mileage may vary.

However if this kind of dynamic use of the terminal is core to your program I would recommend using ncurses or something similar.