A process identifier (PID) identifying a process requesting a cryptographic operation is received.

Since init is always the first process run on a system, it always has a process ID of 1.

Because init is always the first process on a system, its process ID is always 1.

The other process, the parent, receives from fork the process identifier of the child, which is always a positive number.

The file must consist of the process identifier in ASCII-encoded decimal, followed by a newline character.