dup2

fn dup2(ev: *Evented, old_fd: c.fd_t, new_fd: c.fd_t) DupError!void {
    _ = ev;
    while (true) switch (c.errno(c.dup2(old_fd, new_fd))) {
        .SUCCESS => return,
        .BUSY, .INTR => {},
        .INVAL => |err| return errnoBug(err), // invalid parameters
        .BADF => |err| return errnoBug(err), // use after free
        .MFILE => return error.ProcessFdQuotaExceeded,
        .NOMEM => return error.SystemResources,
        else => |err| return unexpectedErrno(err),
    };
}