Background: On Linux, there are two locking APIs: FLOCK and the POSIX lockf. Locking using one API appears to have no effect locks used with the other API.
sudo can be built to use either flock or lockf, but there is no way to select after compile time. There is a command line utility for flock but no comparable one for lockf. Therefore by default there is no fail-proof way to interact with the sudoers file both from scripts and visudo. This script wraps the call to visudo in a call to flock such that locking can be performed between command line scripts and visudo.