How to write to a text file several times without overwriting the old values

I write the output values from a simulation to a txt file using.

outputFile = fopen('output.txt','w'); fprintf(outputFile,'values');........

I would like to run the simulation several times with different output and store each simulation output without overwriting the old values. Is there some easy way to append the old values?

Answer 1

[Tigersnooze]

I think if you do

outputFile = fopen('output.txt', 'a+');

It would work when put in a loop. 'a' will append, where 'w' will discard existing contents.

Answer 2

[the cyclist]

One way:

for nf = 1:3
   % Other stuff
   outputFile = fopen(['output',num2str(nf),'.txt'],'w');
   fprintf(outputFile,'values');
end

[the cyclist]

I didn't read your question carefully enough. My method will create multiple output files, not one file with appended data.

Answer 3

[Walter Roberson]

You want to append the old values after the new ones, or you want to append the new values after the old?

Appending the old values after the new requires opening the file with 'a+' access, seeking to the beginning of the file with fseek(fid,0,0), reading and recording the old values, seeking back to the beginning of the file, writing the new values, then writing the recorded old values. There is no built-in mechanism to "insert" text "moving over" the existing text automatically.

Appending the new values after the old values requires opening the file with 'a' or 'a+' access, and writing the new values. This is easier and more robust.