After creating a folder structure and .m file, I want to write to the file, but the fid keeps coming back as -1. What should i be doing that I'm not?

% Here are the variable name string values:
%   outputFileName = "Aaron.m"
%  outputFilePath = "./folder/yayy/"
% currentSection is a string with a bunch of data
% ===================================
file = fullfile(outputFilePath, outputFileName);
mkdir(file);
[fid, msg] = fopen(file, 'w');
if fid == -1
    error('Could not open file "%s" for writing.', file, msg);
end
% Write the content of the current section to the new .m file
fprintf(fid, '%s\n', currentSection);
% Close the file
fclose(fid);

[Stephen23]

"What should i be doing that I'm not?"

It is the other way around, you are doing something that you shouldn't: you create a folder with the value of file... which you then try to FOPEN. It is not possible to FOPEN a folder.

Answer 1

[dpb]

file = fullfile(outputFilePath, outputFileName);
mkdir(file);

You created the directory with the fully qualified file name, not the folder...

% Here are the variable name string values:
%   outputFileName = "Aaron.m"
%  outputFilePath = "./folder/yayy/"
% currentSection is a string with a bunch of data
% ===================================
file = fullfile(outputFilePath, outputFileName);
if exist(outputFilePath)~=7   % see if already exists, if not create it but not multiple times
  mkdir(outputFilePath);
end
[fid, msg] = fopen(file, 'w');
if fid == -1
    error('Could not open file "%s" for writing.', file, msg);
end
% Write the content of the current section to the new .m file
fprintf(fid, '%s\n', currentSection);
% Close the file
fclose(fid);

[Aaron]

That makes sense. Thanks for your help!

[dpb]

If that resovled your issue, go ahead and Accept an Answer to let folks know if nothing else...