ftok

ftok is a function found in some Unix-like operating systems. Its primary purpose is to generate a unique key identifier based on a file path and a project identifier. This key is then used to access shared memory segments. Shared memory is a mechanism for inter-process communication (IPC) where multiple processes can access the same region of memory.

The function takes two arguments: a string representing the file path and an integer representing the project ID. The file path is typically a path to a file that exists on the system, though its content is not directly used. The project ID is a numerical value that helps to namespace the shared memory segments, preventing conflicts between different applications.

ftok combines these two inputs using a specific algorithm to produce a unique 32-bit integer. This integer, often referred to as a "key" or "ftok key," is then passed to other IPC functions, such as `shmget`, to request or access a shared memory segment. The deterministic nature of ftok ensures that as long as the file path and project ID remain the same, the generated key will also be the same, allowing different processes to consistently find and utilize the same shared memory. This makes ftok a common method for establishing shared memory connections between related processes.