Exit (operating system)

On many computer operating systems, a computer process terminates its execution by making an exit system call. More generally, an exit in a multithreading environment means that a thread of execution has stopped running. For resource management, the operating system reclaims resources (memory, files, etc.) that were used by the process. The process is said to be a dead process after it terminates.

Under Unix and Unix-like operating systems, a process is started when its parent process executes a fork system call. The parent process may then wait for the child process to terminate, or may continue execution (possibly forking off other child processes). When the child process terminates ("dies"), either normally by calling exit, or abnormally due to a fatal error or signal (e.g., SIGTERM, SIGINT, SIGKILL), an exit status is returned to the operating system and a SIGCHLD signal is sent to the parent process. The exit status can then be retrieved by the parent process via the wait system call.

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