Distance b/w 2 group of atoms

User discussions
1

GROMACS version:2023
GROMACS modification: No

i am trying to compute dist. of 2 group of atoms in a single .gro file using the following command line script;
gmx distance -f step4.gro -s topol.tpr -n index2.ndx -oall dist.xvg -select ‘com of group “gama” plus com of group “beta”’
i receive following error msg :

Error in user input:
Invalid command-line options
In command-line option -select
Invalid selection ‘‘com’
Near ‘’’
syntax error
In command-line option -select
Invalid selection ‘group’
Near ‘group’
syntax error
In command-line option -select
Invalid selection ‘plus’
Near ‘plus’
syntax error
In command-line option -select
Invalid selection ‘com’
While parsing ‘com’
‘of’ is missing
In command-line option -select
Invalid selection ‘group’
Near ‘group’
syntax error
In command-line option -select
Invalid selection ‘beta’’
Near ‘’’
syntax error