determine if the file is empty and separate them into different file - matlab

Question

The goal of my code is to look into a certain folder and create a new text file with a list of names of all the files that aren't empty in that folder written to a new file, and the list of names of all the empty files (no text) into another folder. My current code is only able to create a new text file with a list of names of all the files (regardless of its content) written to a new file. I want to know how to set up if statement regarding the content of the file (array).
function ListFile
dirName = '';
files = dir(fullfile(dirName,'*.txt'));
files = {files.name};
[fid,msg] = fopen(sprintf('output.txt'),'w+t');
assert(fid>=0,msg)
fprintf(fid,'%s\n',files{:});
fclose(fid);

Answer 1

EDIT: The linked solution in Stewie Griffin's comment is way better. Use this!
A simple approach would be to iterate all files, open them, and check their content. Caveat: If you have large files, this approach might be memory intensive.
A possible code for that could look like this:
function ListFile
dirName = '';
files = dir(fullfile(dirName, '*.txt'));
files = {files.name};
fidEmpty = fopen(sprintf('output_empty_files.txt'), 'w+t');
fidNonempty = fopen(sprintf('output_nonempty_files.txt'), 'w+t');
for iFile = 1:numel(files)
content = fileread(files{iFile})
if (isempty(content))
fprintf(fidEmpty, '%s\n', files{iFile});
else
fprintf(fidNonempty, '%s\n', files{iFile});
end
end
fclose(fidEmpty);
fclose(fidNonempty);
I have two non-empty files nonempty1.txt and nonempty2.txt as well as two empty files empty1.txt and empty2.txt. Running this code, I get the following outputs.
Debugging output from fileread:
content =
content =
content = Test
content = Another test
Content of output_empty_files.txt:
empty1.txt
empty2.txt
Content of output_nonempty_files.txt:
nonempty1.txt
nonempty2.txt

Answer 2

Matlab isn't really the optimal tool for this task (although it is capable). To generate the files you're looking for, a command line tool would be much more efficient.
For example, using GNU find you could do
find . -type f -not -empty -ls > notemptyfiles.txt
find . -type f -empty -ls > emptyfiles.txt
to create the text files you desire. Here's a link for doing something comparable using the windows command line. You could also call these functions from within Matlab if you want to using the system command. This would be much faster than iterating over the files from within Matlab.