File Locking

• Like a traffic light for processes

• Only one street has a green light at any time

• Only one process has a file lock at any time

        use Fcntl ':flock';

• Wait until lock is available and then get the lock:

        flock(FILEHANDLE, LOCK_EX) or die ...;

• Try to get lock, return immediately:

        if (flock(FILEHANDLE, LOCK_EX | LOCK_NB)) {
          # I have the lock
        } else {
          # I don't
        }

• Release lock:

        flock(FILEHANDLE, LOCK_UN);

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Copyright © 2003 M. J. Dominus