read_data using fix keyword

Hi,

in the documentation of the method read_data (http://www.cfdem.com/media/DEM/docu/read_data.html) it is mentioned how the fix keyword can be used to process a specific portion of the data file through a pre-defined fix.

Trying to apply this functionality, however, fails. When I look through the source code I end up at the function ReadData::fix :

/* ----------------------------------------------------------------------
read fix section, pass lines to fix to process
n = index of fix
------------------------------------------------------------------------- */

void ReadData::fix(int ifix, char *keyword)
{
int nchunk,eof;

bigint nlines = modify->fix[ifix]->read_data_skip_lines(keyword);

bigint nread = 0;
while (nread < nlines) {
nchunk = MIN(nlines-nread,CHUNK);
eof = comm->read_lines_from_file(fp,nchunk,MAXLINE,buffer);
if (eof) error->all(FLERR,"Unexpected end of data file");
modify->fix[ifix]->read_data_section(keyword,nchunk,buffer);
nread += nchunk;
}
}

This function contains read_data_skip_lines and read_data_section, but the only occurrences I found for these functions are in fix.h, where they are just defined (or return 0 resp.).

So, is this a bug and the functionality of using read_data with the fix keyword not applicable in LIGGGHTS?

Best,
Tobias