atomically creating a file lock in MATLAB (file mutex)

Question

I am looking for a simple already implemented solution for atomically creating a file lock in MATLAB.

Something like:

file_lock(\'create\', \'mylockf         


        

Answer 1

Depending on which Java version you're using, perhaps this will work (translated from: http://www.javabeat.net/2007/10/locking-files-using-java/)

classdef FileLock < handle
    properties (Access = private)
        fileLock = []
        file
    end

    methods
        function this = FileLock(filename)
            this.file = java.io.RandomAccessFile(filename,'rw');
            fileChannel = this.file.getChannel();
            this.fileLock = fileChannel.tryLock();
        end

        function val = hasLock(this)
            if ~isempty(this.fileLock) && this.fileLock.isValid()
                val = true;
            else
                val = false;
            end
        end

        function delete(this)
            this.release();
        end

        function release(this)
            if this.hasLock
                this.fileLock.release();
            end
            this.file.close
        end
    end
end

Usage would be:

lock = FileLock('my_lock_file');
if lock.hasLock
    %// do something here
else
    %// I guess not
end
%// Manually release the lock, or just delete (or let matlab clean it up)

I like the obj wrapping pattern for IO so that releasing happens even in exceptions

EDIT: The file ref must be kept around and manually closed or you won't be able to edit this. That means this code is only really useful for pure lock files, I think.