#include <assert.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/select.h>
#include <sys/stat.h>

#define FIFO "fifo"

int main()
{
	int fd;
	int pid;
	int flags;
	fd_set set;
	struct timeval tv;

	assert(unlink(FIFO) == 0 || errno == ENOENT);
	assert(mkfifo(FIFO, DEFFILEMODE) == 0);
	signal(SIGCHLD, SIG_IGN);
	pid = fork();
	if (pid == 0) {
		char c;
		int ret;

		fd = open(FIFO, O_WRONLY);
		flags = fcntl(fd, F_GETFL);
		assert(flags != -1);
		flags |= O_NONBLOCK;
		assert(fcntl(fd, F_SETFL, flags) == 0);
		/* fill the pipe */
		for (;;) {
			c = 'a';
			ret = write(fd, &c, 1);
			if (ret == -1 && errno == EAGAIN)
				break;
		}
		FD_ZERO(&set);
		FD_SET(fd, &set);
		tv.tv_sec = 4;
		tv.tv_usec = 0;
		ret = select(fd+1, NULL, &set, NULL, &tv);
		if (ret == 0)
			printf("child: select() timeout\n");
		else
			printf("child: number writeable of files: %d\n", ret);
		exit(0);
	} else {
		fd = open(FIFO, O_RDONLY);
		sleep(2);
		printf("parent: exit\n");
	}
	return (0);
}