Do you mean Matlab should watch the file to detect when the file edit date&time changes?
I am not aware of any listeners that can do that, but you could have a loop running to track this every few seconds. You can either use the OS tools to determine the date&time, but you could also use some hash function. I have included my draft below. This is still work in progress and given that it relies on ComputeNonCryptHash (and ETA_disp) this is not a secure or fool-proof method.
function H=HashFile(filename,varargin)
%Compute the hash of a file.
%
% The file is read as uint16, after which the optional parameters are forwarded to the
% ComputeNonCryptHash function.
%
% On a reasonably powerfull machine this will process a file at about 3MB/s (7 on a fast machine).
% For ML6.5 you should expect 1/8 the performance of a modern release.
%
%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%
%| Author: H.J. Wisselink |%
%| Licence: CC by-nc-sa 4.0 ( creativecommons.org/licenses/by-nc-sa/4.0 ) |%
%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%/%
% Because fread(fid,inf,'*uint16') might cause memory errors on large file, this function uses a
% looped system, where the file is read in chunks. The hash for each chunk is computed and stored
% in an array. When this array is full, the hash of the entire block is computed. This resultant
% hash is stored as the last line of a new block. This idea is similar to salting of hashes or to
% how a blockchain can work.
bytes_per_chunk = 1024*1024; % Number of bytes used for each line in the block
chuncks_per_block = 25; % Number of lines in the block (excluding the salt line)
fid = fopen(filename,'r');
if fid<0 || ftell(fid)<0
error('HJW:HashFile:FileReadFailed',...
'The file could not be read. Check if it exists and if it allows reading.')
end
% Compute the null hash and parse input options.
[N,HashOpts] = ComputeNonCryptHash(uint8([]),varargin{:});
% Set up variables for ETA_disp/waitbar.
sz = dir(filename);sz=sz.bytes;
N_blocks = ceil(sz/(bytes_per_chunk*chuncks_per_block));
N_block = 0;then = now; %#ok<TNOW1>
uint16_per_chunk = round(bytes_per_chunk/2);
counter = 0;X = repmat(N,chuncks_per_block+1,1); % Use null hash as initial salt.
while ~feof(fid)
% Read the next chunk of the file as uint16.
x = fread(fid,uint16_per_chunk,'*uint16');
% If the ledger is full, compute the hash over the entire block and use it as salt for the
% remainder of the file.
if counter==chuncks_per_block
salt = ComputeNonCryptHash(X,HashOpts);
X = [repmat(N,chuncks_per_block,1);salt];
counter = 0;
N_block = N_block+1;ETA_disp(N_blocks,N_block,then)
end
counter = counter+1;
X(counter,:) = ComputeNonCryptHash(x,HashOpts);
end
fclose(fid);
% Only post the 100% update if there was a previous call to ETA_disp.
if N_block~=0,ETA_disp(1,1,then),end
% Compute final hash.
H = ComputeNonCryptHash(X,HashOpts);
end
