[gmx-users] Select one molecule closest to another molecule for all snapshots

[Apramita Chand]

Dear Gromacs Users,
I have two kinds of molecules in my system. I want to know the coordinates
of the molecule A that is found closest to molecule B at every snapshot of
the MD trajectory. I am using gromacs 5.1.
I dont have a cutoff, I just want to generate coordinates of the  single
one molecule that is closest at any given snapshot.(for all frames0

How do I do so? Is there any gmx tool?
I tried '-select' statements but am not able to hit upon the right
combination.

Regards,
Apramita