That file over there.

What this file-locking interview question tests

This is an easy operating-systems question that probes whether you understand the difference between advisory and mandatory locking mechanisms on Linux, and which synchronization primitives actually prevent concurrent writes to a shared file. It appears in interviews where candidates will work with multi-process systems or shared resources.

The question asks you to reason about the guarantees offered by different locking strategies—file descriptor operations, filesystem-level locks, and inter-process synchronization tools—and to identify which approach sounds plausible but offers no real serialization. A strong answer requires knowing not just which locks exist, but what each one actually protects and under what conditions they fail.

• Advisory vs. mandatory file locking on POSIX systems
• File descriptor scope and inheritance across processes
• Inode-level vs. user-space synchronization
• Race conditions in cooperative locking protocols