NAME

exit, _exit − terminate process

SYNOPSIS

void exit (status)
int status;
void _exit (status)
int status;

DESCRIPTION

exit terminates the calling process with the following consequences:

All of the file descriptors open in the calling process are closed. 

If the parent process of the calling process is executing a wait, it is notified of the calling process’s termination and the low order eight bits (i.e., bits 0377) of status are made available to it [see wait(2)].

If the parent process of the calling process is not executing a wait, the calling process is transformed into a zombie process. A zombie process is a process that only occupies a slot in the process table.  It has no other space allocated either in user or kernel space.  The process table slot that it occupies is partially overlaid with time accounting information (see <sys/proc.h>) to be used by times. 

The parent process ID of all of the calling processes’ existing child processes and zombie processes is set to 1.  This means the initialization process [see intro(2)] inherits each of these processes.

Each attached shared memory segment is detached and the value of shm_nattach in the data structure associated with its shared memory identifier is decremented by 1. 

For each semaphore for which the calling process has set a semadj value [see semop(2)], that semadj value is added to the semval of the specified semaphore.

If the process has a process, text, or data lock, an unlock is performed [see plock(2)].

An accounting record is written on the accounting file if the system’s accounting routine is enabled [see acct(2)].

If the process ID, tty group ID, and process group ID of the calling process are equal, the SIGHUP signal is sent to each process that has a process group ID equal to that of the calling process. 

A death of child signal is sent to the parent. 

The C function exit may cause cleanup actions before the process exits.  The function _exit circumvents all cleanup. 

In a multi-threaded process, a thread that calls exit or (_exit) causes all other threads of the process to join before exiting. The process itself then effectively calls exit.

SEE ALSO

acct(2), intro(2), plock(2), semop(2), signal(2), sigset(2), thread(2), wait(2). 

WARNING

See WARNING in signal(2).

DIAGNOSTICS

None.  There can be no return from an exit system call. 

September 29, 2021