How can I keep track of a constantly updating text file's latest string

I'm currently new to matlab and would appreciate some help with my current code. I'm currently constantly updating a text file saved in the same spot as the code that is opening it. The updating is being done with Unity and involves constantly updating the most recent console logs to the text file. Is there any way I could continuously keep track of the latest log in a variable or something?

If it helps, this is how my current text file is set up. Basically my unity code constantly adds logs below the last log.

Answer 1

[Voss]

The following function returns a string containing the last non-empty line of text in the file (or "" if there are none).

Call it by passing in the name of your text file whenever you want to see what the latest event is.

As for checking in synchrony with Unity, I don't know.

As for "continuously" checking, you could call this function in a while loop, e.g., this would keep checking until an event starting with "escape" is the latest event:

evt = "";

while ~startsWith(evt,"escape")

evt = get_latest_event(filename);

end

But note that nothing would prevent multiple events from being written to the file in between the times when you check it, so you could miss the event you're looking for, i.e., the event happens but it's not ever the last event in the file when you check.

function out = get_latest_event(filename)
L = readlines(filename)
idx = numel(L);
if idx == 0
    out = "";
    return
end
while idx > 0
    out = L(idx);
    if ~strcmp(out,"")
        return
    end
    idx = idx-1;
end
end

[Geoffrey]

Thanks for the explanation and example code. I'll try and see what I can do!

[Voss]

You're welcome!

It occurred to me after I wrote my answer that the text file might be very large, and if that's the case, then a different approach (not reading the entire file with readlines) will be faster. Something like this:

function out = get_latest_event(filename)
fid = fopen(filename,'rt');
fseek(fid,0,'eof');
filesize = ftell(fid);
offset = min(100,filesize);
while true
    fseek(fid,-offset,'eof');
    txt = deblank(fread(fid,[1 Inf],'*char'));
    if any(txt == newline()) || offset == filesize
        break
    end
    offset = min(offset+100,filesize);
end
fclose(fid);
if isempty(txt)
    out = "";
else
    out = string(regexp(txt,'([^\r\n]+)$','tokens','once'));
end
end