DSSP Analysis with GROMACS

GROMACS version: 2019.6-amd

Hello,

I’d like to do dssp analysis with GROMACS do_dssp. However when I do it, I always get the same weird pattern in my .dat file. It always looks like this (for all systems!):
10
~=~=~=~=~=~=~=~=~=~
~=~=~=~=~=~=~=~=~=~
~=~=~=~=~=~=~=~=~=~
~=~=~=~=~=~=~=~=~=~
~=~=~=~=~=~=~=~=~=~
~=~=~=~=~=~=~=~=~=~

I can’t figure out what can be the cause. My code seems to be OK:
gmx do_dssp -f trajectory.xtc -s structure.pdb -n index.ndx -ssdump file.dat -dt 1000

My index file specifies 10 amino acids for which I want to use the DSSP analysis.
I use this version of dssp: dssp-2.0.4-linux-amd64

Have someone ever experienced this type of error and could give me an advice, please? Thank You

I’m not familiar with the format of this data file, but ~ means coil and = indicates a chain separator.