exit.2 (2010 09)

e
exit(2) exit(2)
NAME
exit(), _exit(), _Exit() - terminate a process
SYNOPSIS
#include <stdlib.h>
void exit(int status);
void _Exit(int status);
#include <unistd.h>
void _exit(int status);
Parameters
status The values of status can be EXIT_SUCCESS
or EXIT_FAILURE, as described in
<stdlib.h>, or any other value, although only the least significant 8 bits (that is,
status & 0377) is available to a waiting parent process.
DESCRIPTION
The
exit() function first calls all functions registered by
atexit(), in the reverse order of their regis-
tration. Each function is called as many times as it was registered. If a function registered by a call to
atexit() fails to return, the remaining registered functions are called and the rest of the exit()
pro-
cessing is not completed.
exit() terminates the calling process and passes status to the system for
inspection {see wait (2)}. Returning from main in a C program has the same effect as
exit(); the status
value is the function value returned by main (this value is undefined if main does not take care to return
a value or to call
exit() explicitly).
If the calling process is multithreaded, all threads/lightweight process in the process will be terminated.
exit() cannot return to its caller. The result of an exit() call during exit processing is undefined.
The functions
exit() and _exit(), are equivalent, except that exit() calls functions registered by
atexit() and flushes standard I/O buffers, while _exit() does not.
The function
_Exit() is equivalent to _exit().
The functions
exit(), _exit(), and _Exit() terminate the calling process with the following conse-
quences. The exact order of these consequences is unspecified.
All file descriptors, directory streams, conversion descriptors, and message catalog descriptors open
in the calling process are closed.
All files created by
tmpfile() are removed (see tmpfile (3S)).
If the parent process of the calling process is executing a
wait(), wait3(),orwaitpid()
,itis
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(), wait3(),orwaitpid(),
and does not have SIGCLD set to SIG_IGN, the calling process is transformed into a zombie pro-
cess.Azombie 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. Time accounting information is recorded for use by
times() (see times (2)).
The parent process ID is set to the process ID of the initialization process (aka
init) for all of the
calling process’s existing child processes and zombie processes. This means the initialization process
inherits each of these processes.
Threads/LWPs terminated by a call to
exit() shall not invoke their cancellation cleanup handlers
or their thread specific data destructor functions.
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 (see shmop(2)).
For each semaphore for which the calling process has set a semadj value (see semop(2)), that semadj
value is added to the value 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)).
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