Tribblix: manual page: exit.2

EXIT(2) System Calls EXIT(2)

NAME

exit, _Exit, _exit - terminate process

SYNOPSIS

#include <stdlib.h>

void exit(int status);

void _Exit(int status);

#include <unistd.h>

void _exit(int status);

DESCRIPTION

The exit() function first calls all functions registered by
atexit(3C), in the reverse order of their registration, except that a
function is called after any previously registered functions that had
already been called at the time it was registered. Each function is
called as many times as it was registered. If, during the call to any
such function, a call to the longjmp(3C) function is made that would
terminate the call to the registered function, the behavior is
undefined.

If a function registered by a call to atexit(3C) fails to return, the
remaining registered functions are not called and the rest of the
exit() processing is not completed. If exit() is called more than
once, the effects are undefined.

The exit() function then flushes all open streams with unwritten
buffered data, closes all open streams, and removes all files created
by tmpfile(3C).

The _Exit() and _exit() functions are functionally equivalent. They
do not call functions registered with atexit(), do not call any
registered signal handlers, and do not flush open streams.

The _exit(), _Exit(), and exit() functions terminate the calling
process with the following consequences:

o All of the file descriptors, directory streams, conversion
descriptors and message catalogue descriptors open in the
calling process are closed.

o If the parent process of the calling process is executing
a wait(3C), wait3(3C), waitid(2), or waitpid(3C), and has
neither set its SA_NOCLDWAIT flag nor set SIGCHLD to
SIG_IGN, it is notified of the calling process's
termination and the low-order eight bits (that is, bits
0377) of status are made available to it. If the parent
is not waiting, the child's status will be made available
to it when the parent subsequently executes wait(),
wait3(), waitid(), or waitpid().

o If the parent process of the calling process is not
executing a wait(), wait3(), waitid(), or waitpid(), and
has not set its SA_NOCLDWAIT flag, or set SIGCHLD to
SIG_IGN, the calling process is transformed into a zombie
process. A zombie process is an inactive process and it
will be deleted at some later time when its parent process
executes wait(), wait3(), waitid(), or waitpid(). A zombie
process 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 the times(2) function.

o Termination of a process does not directly terminate its
children. The sending of a SIGHUP signal as described
below indirectly terminates children in some
circumstances.

o A SIGCHLD will be sent to the parent process.

o The parent process ID of all of the calling process's
existing child processes and zombie processes is set to 1.
That is, these processes are inherited by the
initialization process (see Intro(2)).

o Each mapped memory object is unmapped.

o Each attached shared-memory segment is detached and the
value of shm_nattch (see shmget(2)) in the data structure
associated with its shared memory ID is decremented by 1.

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

o If the process is a controlling process, the SIGHUP signal
will be sent to each process in the foreground process
group of the controlling terminal belonging to the calling
process.

o If the process is a controlling process, the controlling
terminal associated with the session is disassociated from
the session, allowing it to be acquired by a new
controlling process.

o If the exit of the process causes a process group to
become orphaned, and if any member of the newly-orphaned
process group is stopped, then a SIGHUP signal followed by
a SIGCONT signal will be sent to each process in the
newly-orphaned process group.

o If the parent process has set its SA_NOCLDWAIT flag, or
set SIGCHLD to SIG_IGN, the status will be discarded, and
the lifetime of the calling process will end immediately.

o If the process has process, text or data locks, an UNLOCK
is performed (see plock(3C) and memcntl(2)).

o All open named semaphores in the process are closed as if
by appropriate calls to sem_close(3C). All open message
queues in the process are closed as if by appropriate
calls to mq_close(3C). Any outstanding asynchronous I/O
operations may be cancelled.

o An accounting record is written on the accounting file if
the system's accounting routine is enabled (see acct(2)).

o An extended accounting record is written to the extended
process accounting file if the system's extended process
accounting facility is enabled (see acctadm(8)).

o If the current process is the last process within its task
and if the system's extended task accounting facility is
enabled (see acctadm(8)), an extended accounting record is
written to the extended task accounting file.

RETURN VALUES

These functions do not return.

ERRORS

No errors are defined.

USAGE

Normally applications should use exit() rather than _exit().

ATTRIBUTES