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domlao
domlao

Reputation: 16029

Detect Keyboard Event in C

How can I detect keyboard event in C language without using third party libraries? Should I use signal handling?

Upvotes: 12

Views: 24657

Answers (5)

ill
ill

Reputation: 1

I'm a little late to answer, but:

The basic idea is to set the terminal to non-canonical mode so that you can read each keypress individually.

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

void setNonCanonicalMode() {
    struct termios term;
    tcgetattr(STDIN_FILENO, &term);
    term.c_lflag &= ~(ICANON | ECHO);
    tcsetattr(STDIN_FILENO, TCSANOW, &term);
}

void resetCanonicalMode() {
    struct termios term;
    tcgetattr(STDIN_FILENO, &term);
    term.c_lflag |= ICANON | ECHO;
    tcsetattr(STDIN_FILENO, TCSANOW, &term);
}

This should suffice.

Upvotes: 0

Ilya
Ilya

Reputation: 3138

What about good old kbhit ? If I understand the question correctly this will work. Here is the kbhit implementation on Linux.

Upvotes: 4

Mark Harrison
Mark Harrison

Reputation: 304434

There's not a standard way, but these should get you started.

Windows:

getch();

Unix:

Use this code from W. Richard Stevens' Unix Programming book to set your terminal in raw mode, and then use read().

static struct termios   save_termios;
static int              term_saved;

int tty_raw(int fd) {       /* RAW! mode */
    struct termios  buf;

    if (tcgetattr(fd, &save_termios) < 0) /* get the original state */
        return -1;

    buf = save_termios;

    buf.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
                    /* echo off, canonical mode off, extended input
                       processing off, signal chars off */

    buf.c_iflag &= ~(BRKINT | ICRNL | ISTRIP | IXON);
                    /* no SIGINT on BREAK, CR-toNL off, input parity
                       check off, don't strip the 8th bit on input,
                       ouput flow control off */

    buf.c_cflag &= ~(CSIZE | PARENB);
                    /* clear size bits, parity checking off */

    buf.c_cflag |= CS8;
                    /* set 8 bits/char */

    buf.c_oflag &= ~(OPOST);
                    /* output processing off */

    buf.c_cc[VMIN] = 1;  /* 1 byte at a time */
    buf.c_cc[VTIME] = 0; /* no timer on input */

    if (tcsetattr(fd, TCSAFLUSH, &buf) < 0)
        return -1;

    term_saved = 1;

    return 0;
}


int tty_reset(int fd) { /* set it to normal! */
    if (term_saved)
        if (tcsetattr(fd, TCSAFLUSH, &save_termios) < 0)
            return -1;

    return 0;
}

Upvotes: 12

Adam Rosenfield
Adam Rosenfield

Reputation: 400174

You really should use third party libraries. There's definitely no platform-independent way to do it in ANSI C. Signal handling is not the way.

Upvotes: 3

JesperE
JesperE

Reputation: 64404

Standard C does not have any facilities for detecting keyboard events, unfortunately. You have to rely on platform-specific extensions. Signal handling wont help you.

Upvotes: 3

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