[lammps-users] if command problem

Dear colleague

Currently I’m using If command in LAMMPS, but only to get ambiguous error messages. :ERROR: Illegal if command

I tried several kind of modified commands, but neither of them works properly.
I’m using 2010 Dec 21 version of lammps, and here is part of my script.

I would try the most current version of LAMMPS, which
is what matched the WWW page docs. If that still fails,
then post your entire input script. No one can run the
lines below by themselves. And making the input script
you post as simple as possible, while still reproducing the
problem is very helpful.