// fifo-select - does select(2) work with FIFO?

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

#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define FIFO_MSGMAX 127U

inline static void
set_blocking(int fd)
{
	int flags;
	flags = fcntl(fd, F_GETFL, 0);
	if (flags == -1) err(1, "fcntl");
	flags &= ~(O_NONBLOCK);
	if (fcntl(fd, F_SETFL, flags) == -1) err(1, "fcntl");
}

int
main(int argc, char *argv[])
{
	char buf[FIFO_MSGMAX + 1], *fname;
	const int nfd = 1;
	fd_set fds;
	int fd, ret;

	if (argc != 2) {
		fputs("Usage: fifo-select fifo-name\n", stderr);
		exit(1);
	}
	fname = argv[1];

	ret = mkfifo(fname, 0600);
	if (ret == -1 && errno != EEXIST) err(1, "mkfifo");
	if ((fd = open(fname, O_RDONLY | O_NONBLOCK)) == -1)
		err(1, "open '%s'", fname);

	FD_ZERO(&fds);
	FD_SET(fd, &fds);
	//set_blocking(fd);
	while (1) {
		fprintf(stderr, "DBG select...\n");
		// Always wedges here on OpenBSD, regardless of how I
		// fiddle with the blocking. I'm guessing that FIFO
		// don't work(TM) with select(2).
		ret = select(nfd, &fds, NULL, NULL, NULL);
		if (ret == -1) err(1, "select");
		if (ret == 0) {
			warnx("select timeout??");
			continue;
		}
		if (FD_ISSET(fd, &fds)) {
			ssize_t amount = read(fd, buf, FIFO_MSGMAX);
			if (amount == -1) {
				err(1, "read");
			} else if (amount == 0) {
				warnx("read EOF");
			} else if (amount > 0) {
				fprintf(stderr, "MSG %.*s\n", (int) amount,
				        buf);
			} else {
				errx(1, "read negative??");
			}
		}
	}
}