In computing, the process identifier (normally referred to as the process ID or just PID) is a number used by some operating system kernels (such as that of UNIX or Windows NT) to uniquely identify a process.

Under Unix, the PID of a newly created child process is returned by the fork() system call to the parent.

The PID can be passed to waitpid() or kill() to perform actions on the given process, and the files in /proc/pid/ can be queried for information about the process.

See also

• UID
• GID

Operating system technology

Process ID | Pid | Identifiant de processus | PID (informatyka) | PID