NAME
exit, _exit — terminate process
SYNOPSIS
#include <stdlib.h>
void exit(int status);
#include <unistd.h>
void _exit(int status);
DESCRIPTION
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.
Both
exit()
and
_exit()
terminate the calling process with the following consequences.
The exact order of these consequences is unspecified.
Functions registered by
atexit()
(see
atexit(2))
are called in reverse order of registration.
All file 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(),
or
waitpid(),
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(),
wait3(),
or
waitpid(),
and does not have
SIGCLD
set to
SIG_IGN,
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.
Time accounting information is recorded for use by
times()
(see
times(2)).
The parent process
ID
is set to 1 for all of the calling process's
existing child processes and zombie processes.
This means the initialization process (proc1)
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 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)).
A
SIGCHLD
signal is sent to the parent process.
If the calling process is a controlling process,
the
SIGHUP
signal is sent to each process in the foreground process group
of the controlling terminal belonging to the calling process.
The controlling terminal associated with the session is
disassociated from the session,
allowing it to be acquired by a new controlling process.
If the exit of the calling process causes a process group to become orphaned,
and if any member of the newly-orphaned process group is stopped,
all processes in the newly-orphaned process group are sent
SIGHUP
and
SIGCONT
signals.
If the current process has any child processes that are being traced,
they are sent a
SIGKILL
signal.
AUTHOR
exit()
was developed by
HP, AT&T, and the University of California, Berkeley.
SEE ALSO
Exit conditions
(
$?
)
in
sh(1),
acct(2),
plock(2),
pthread_cancel(3T),
pthread_exit(3T),
pthread_key_create(3T),
semop(2),
shmop(2),
times(2),
vfork(2),
wait(2),
signal(5).
STANDARDS CONFORMANCE
exit(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C
_exit(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1
