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

I've settled on a pretty simple solution for combining error/logging messages from multiple worker threads into a single file. Every time I want to write to that file, I first write the output to the thread's own temporary file. Next, I append that temporary file to the "master" log file using flock. Skipping over some details here, the idea is:

fid=fopen(threadtemp, 'w');
fprintf(fid, 'Error message goes here');
fclose(fid);

runme = sprintf('flock -x %s -c ''cat %s >> %s''', LOGFILE, threadtemp, LOGFILE);
system(runme);

See the flock man page for details, but the call above is acquiring an eXclusive lock on the logfile, running the provided Command under the lock, and then releasing it.

This obviously only works if you're on a system which has flock (Linux/OS X, and only certain types of file systems at that) and you're doing something that can be done from the command line, but I'd bet that it's a pretty common use-case.