Readline.output=

static VALUE
readline_s_set_output(VALUE self, VALUE output)
{
    rb_io_t *ofp;
    int fd;
    FILE *f;

    if (NIL_P(output)) {
        clear_rl_outstream();
    }
    else {
        Check_Type(output, T_FILE);
        GetOpenFile(output, ofp);
        clear_rl_outstream();
        fd = rb_cloexec_dup(ofp->fd);
        if (fd == -1)
            rb_sys_fail("dup");
        f = fdopen(fd, "w");
        if (f == NULL) {
            int save_errno = errno;
            close(fd);
            rb_syserr_fail(save_errno, "fdopen");
        }
        rl_outstream = readline_rl_outstream = f;
        readline_outstream = output;
    }
    return output;
}