Listing 2. uio.c

#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>

size_t
writeuio(int fd, struct iovec *iov, int cnt)
{
        size_t pos = 0;
        ssize_t res;
        n = iov[0].iov_cnt;
        while (n > pos) {
                poll_wait(fd, POLLOUT | POLLERR);
                res = writev (fd, iov[0].iov_base + pos, n - pos);
                switch ((int)res) {
                        case -1:
                                if (errno == EINTR || errno == EAGAIN)
                                        continue;
                                return 0;
                        case 0:
                                errno = EPIPE;
                                return pos;
                        default:
                                pos += (size_t)res;
                }
        }
        return (pos);

}