#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

#define TIMEOUT 5
#define BUF_LEN 1024

int main(void) {
	struct timeval tv;
	fd_set readfds;
	int ret;

	/* Wait on stdin for intput. */
	FD_ZERO(&readfds);
	FD_SET(STDIN_FILENO, &readfds);
	
	/* Wait up to file seconds */
	tv.tv_sec = TIMEOUT;
	tv.tv_usec = 0;

	/* All right, now block! */
	ret = select(
		STDIN_FILENO + 1,
		&readfds,
		NULL,
		NULL,
		&tv
	);
	if (ret == -1) {
		perror("select");
		return 1;
	} else if (!ret) {
		printf("%d seconds elapsed.\n", TIMEOUT);
		return 0;
	}

	/*
	 * Is our file descriptor ready to read?
	 * (It must be, as it was the only fd that
	 * we provided and the call returned
	 * nonzero, but we will humor ourselves.)
	 */
	if (FD_ISSET(STDIN_FILENO, &readfds)) {
		char buf[BUF_LEN+1];
		int len;

		/* guaranteed to not block */
		len = read(STDIN_FILENO, buf, BUF_LEN);
		if (len == -1) {
			perror("read");
			return 1;
		}

		if (len) {
			buf[len] = '\0';
			printf("read: %s\n", buf);
		}
		
		return 0;
	}

	fprintf(stderr, "This should not happen!\n");
	return 1;
}