An error using fprintf

Hello, 

I am currently getting an error while trying to save. This is what I currently have

function saveline(filename,line,mode)
    fid = fopen(filename,mode);
    fprintf(fid,line);
    fclose(fid);
end

Then I get

Error using fprintf

Invalid file identifier. Use fopen to generate a valid file identifier.

Error in saveline (line 11)

fprintf(fid,line);

Any suggestions?

Answer 1

[Guillaume]

Any suggestions?

Yes, for some reason, fopen failed to open the file. There can be many reasons, the most likely being that the file doesn't exist but other reasons are possible (permission problem, etc.)

You never check that the fopen succeeds which is never a good idea.

[fid, errmsg] = fopen(filename, mode);
if fid < 0
    error('Failed to open "%s", the error message was: %s');
end
%...

would at least tell you what the problem is.