What are lock files?
A lock is a file placed in a special directory that should prevent other applications from using a serial port or other resource. The concept is that applications wishing to use a serial port should check for the existence of a lock file prior to opening the port. Unfortunately, there is no standard for where locks should be written and what they should contain. Therefore, some applications do not check for the existence of a lock while others misinterpret what locks they do happen to find. For example, on SCO Unix, neither getty nor login create a lock file when a user dials in on a port. The uucp program writes a lock file in directory /usr/spool/uucp. Other applications write their locks in /usr/spool/locks. BLAST puts locks in the most common places for locks to be found on any given Unix operating system. Common directories for locks are /usr/spool/uucp, /usr/spool/locks/, /var/spool/locks, /var/spool/uucp and /etc/locks.
