well, I have solved the problem to get out of the loop. but to answer your question, Im trying to to read the file "'abaqus_data_aux3.txt'" which has data I need to plot on a graph. The data is stored as strings, so i need to extract this data into numerics so that I can plot the graph. I am trying to sort this out now. my code looks like this now:

fid3=fopen('abaqus_data3.txt','r+')

i=0
kk=0;
fid4= fopen('results.wri','w+')

data_line=fgetl(fid3)

while(fid3>=0)&& kk==0
if(i>2)

end

while ~feof(fid3)

i=i+1
data_line=fgetl(fid3)
a=str2num(data_line)


if length(data_line)==0,
kk=1
end
fprintf(fid4,'%s\n',data_line)
end

end

I am stuck at the point where I want the variable "a" to store all the values, and not just the last one. any input from you is welcome. thanks!

Regards,
Raul