parser.add_argument('select',help='selected components separated by coma')
parser.add_argument('id_file',help='input file with particles\'s id (aka glnemo2 index file)')
parser.add_argument('--bits',help='specify which array you want to proces\nexample:\nbits=\"mxvIU\" (pos,mass,vel,id,internal energy)\nbits=\"\" (every array, default)',default="")