Input without hitting enter

[petteyg]

code from this blog

int kbhit()
{
    struct timeval tv;
    fd_set fds;
    tv.tv_sec = 0;
    tv.tv_usec = 0;
    FD_ZERO(&fds);
    FD_SET(STDIN_FILENO, &fds); //STDIN_FILENO is 0
    select(STDIN_FILENO+1, &fds, NULL, NULL, &tv);
    return FD_ISSET(STDIN_FILENO, &fds);
}

void nonblock(int state)
{
    struct termios ttystate;

    //get the terminal state
    tcgetattr(STDIN_FILENO, &ttystate);

    if (state==NB_ENABLE)
    {
        //turn off canonical mode
        ttystate.c_lflag &= ~ICANON;
        //minimum of number input read.
        ttystate.c_cc[VMIN] = 1;
    }
    else if (state==NB_DISABLE)
    {
        //turn on canonical mode
        ttystate.c_lflag |= ICANON;
    }
    //set the terminal attributes.
    tcsetattr(STDIN_FILENO, TCSANOW, &ttystate);

}

int main()
{
    char c;
    int i=0;

    nonblock(NB_ENABLE);
    while(!i)
    {
        usleep(1);
        i=kbhit();
        if (i!=0)
        {
            c=fgetc(stdin);
            if (c=='q')
                i=1;
            else
                i=0;
        }

        fprintf(stderr,"%d ",i);
    }
    printf("\n you hit %c. \n",c);
    nonblock(NB_DISABLE);

    return 0;
}

This is the only example of "non-enter" input I've been able to find. Is this code portable between operating systems and compilers? Any reason why it wouldn't be a good idea to use?

[Ancient Dragon]

>>s this code portable between operating systems

No. Works only on MS-Windows because it appears to be using win32 api functions. There is no portable way to do what you want using any standard C or C++ functions. There are non-standard functions, such as ncurses which I know has been ported between MS-Windows and *nix. Functions in conio.h may also do it, but that is not only os dependent but also compiler dependent.

>>Any reason why it wouldn't be a good idea to use?
Depends on the compiler you are using. Since you brought up portability then you probably don't want to use that.

[WaltP]

No it's not portable at all. That's why it's not recommended.

C/C++ does not have a standard way to accept input without a Return.

[nezachem]

The code is not portable. It is very linux-specific. It uses termios, and it assumes that stdin is selectable.
Another problem is that it doesn't test the select error code. When select returns -1, the fds is undefined, and kbhit would return garbage.
Otherwise, it is a fairly standard way to achieve the goal, although I prefer a portable setvbuf(stdin, 0, _IONBF, 0) .

[petteyg]

setvbuf does not produce the same result. It doesn't remove the need hit enter/return. Suppose I'll deal with ncurses.