What is a pid number?

A PID (Process ID) number is a unique identifier assigned to each running process on a computer system. This number is used by the operating system to track and manage processes, allowing it to identify and control individual programs and services.

Each process on a system is assigned a PID number, which is typically a non-negative integer. The first process created by the operating system is usually assigned a PID of 1, and subsequent processes are assigned incrementally increasing numbers.

PID numbers are important for performing various system administration tasks, such as monitoring and controlling processes, identifying and troubleshooting issues with specific programs, and managing system resources.

In Unix-based operating systems, the ps command can be used to view a list of running processes along with their corresponding PID numbers. Additionally, the kill command can be used to send signals to processes, allowing users to stop or restart them as needed.