fileno

/*
 *  call-seq:
 *     ios.fileno    => fixnum
 *     ios.to_i      => fixnum
 *  
 *  Returns an integer representing the numeric file descriptor for
 *  <em>ios</em>.
 *     
 *     $stdin.fileno    #=> 0
 *     $stdout.fileno   #=> 1
 */

static VALUE
rb_io_fileno(io)
    VALUE io;
{
    OpenFile *fptr;
    int fd;

    GetOpenFile(io, fptr);
    fd = fileno(fptr->f);
    return INT2FIX(fd);
}