In the program reading this data file, you may want to 'skip' the lines containing comments. One way of doing this is reading the entire line, until end-of-line character.
This can easily be done using
fscanf(fs, "\n%[^\n]", dummy);
where fs is file handlers, and dummy a (large enough) string to hold the line.
Idea was found on programmers heaven. As it took me quite some searching for a solution, henceforth this post.