How to use select() to read input from keyboard in C

Question

I am trying to use select() to read keyboard input and I got stuck in that I do not know how to read from keyboard and use a file descriptor to do so. I've been told to use STDIN and STDIN_FILENO to approach this problem but I am still confused.
How can I do it?

Answer 1

Youre question sounds a little confused. select() is used to block until input is available. But you do the actual reading with normal file-reading functions (like read,fread,fgetc, etc.).

Here's a quick example. It blocks until stdin has at least one character available for reading. But of course unless you change the terminal to some uncooked mode, it blocks until you press enter, when any characters typed are flushed into the file buffer (from some terminal buffer).

#include <stdio.h>
#include <sys/select.h>

int main(void) {
    fd_set s_rd, s_wr, s_ex;
    FD_ZERO(&s_rd);
    FD_ZERO(&s_wr);
    FD_ZERO(&s_ex);
    FD_SET(fileno(stdin), &s_rd);
    select(fileno(stdin)+1, &s_rd, &s_wr, &s_ex, NULL);
    return 0;
}