Thanks for your reply. I found controlling the environment outside org is much better and stopped thinking this direction.

Cheers,

Zhihao

On 15 November 2015 at 14:03, Grant Rettke <gcr@wisdomandwonder.com> wrote:

On Thu, Nov 5, 2015 at 7:16 PM, Zhihao Ding <zhihao.ding@gmail.com> wrote:
> Is it a good idea to use environment variables in the links referenced in a
> org file? e.g.
>
> [[$mydata/myfigure.pdf]]

How do you want Org to behave when the user clicks the link?

> If so how to achieve this?

I would try in-line source blocks.

Regards,
Zhihao Ding