problem to edit a text file

Dear all,

I am having some difficulties to edit my text file. I have an input file which I need to modify certain lines (11844 lines) in each iteration. The input file is a mixture of text, numbers. the numbers are the coordinates of my object in 3D space. So I open the file and rewrite the new coordinates but when it writes it down it pushes the have of previous coordinates and just replace half of it with my new data. So at the end I have correctly started place for my new points but then at the end I see some residue of the previous coordinates.

find_line = '*Node';

    InputFID=fopen([file,'.inp'],'r+');
    j = 0; count=0;
while j==0
    count = count+1;
    tline = fgetl(InputFID);
    j = strcmp(tline, find_line);
end

    n = 1;
    format = '   %5.0f,      %.4f,       %.4f,     %.4f    \n';
    fseek(InputFID,0, 'cof');

 for n = 1:size(newdata,1)

    m = [newdata(n,1), newdata(n,2), newdata(n,3), newdata(n,4)];
    fprintf(InputFID,format,m);
 end 
    fclose(InputFID);

I will appreciate any idea, Thanks Sareh

[Cedric]

Please attach your file or part of it if it is too large.

[per isakson]

My first idea is

    str = fileread( [file,'.inp'] );
    str = regexprep( str, ...

and hope there are keywords in the file to locate the coordinates of interest

[sareh]

Dear all,

Thank you very much, I made it work by:

 A = regexp( fileread('data.txt'), '\n', 'split');
then copy and paste the rows I wanted to change in this array then wrote it out:
 fid = fopen('data.txt', 'w');
    for i = 1:size(A1,2)
        fprintf(fid, '%s\n', A{i});
    end
    fclose(fid);

Thank you very much, My best regards, Sareh