Process identifier

A process identifier (process ID, PID, German Process Identifier) ​​is a unique key, which is used for unique identification of processes in computer science. The PID does not change during the lifetime of the process. After finishing the process of a zombie process and the parent process is (identified by the Parent Process ID ) may query the status. Only after the PID is available again for new processes.

Most operating systems ( such as UNIX, Windows, etc.) use for a natural number. Process IDs are mainly required for interprocess communication.

A Parent Process ID ( PPID ) is the PID of the parent process.

Example

The bash is running as a process on a Unix system. This process is a unique process ID assigned ( for example: 3139 ). If you now start from this process another so-called child process, so this is now running with its own PID ( for example: 4071 ) under the PPID of the parent process ( 3139 ). Unix command for process overview with PID and PPID: $ ps- l or $ ps -f