exit, _exit - terminate process
void exit(int status);
void _exit(int status);
The C library routine exit, which is discussed at the end of this
section, invokes the system routine _exit upon completion of its own
cleanup chores. _exit terminates the calling process with the following
All of the file descriptors, directory streams and message catalogue
descriptors open in the calling process are closed. If the process
is sharing file descriptors via an sproc, other members of the share
group do NOT have their file descriptors closed.
A SIGCHLD signal is sent to the calling process's parent process.
If the parent process of the calling process has not specified the
SA_NOCLDWAIT flag [see sigaction(2)], 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 the times
The parent process ID of all of the calling process's existing child
processes and zombie processes is set to 1. This means the
initialization process [see intro(2)] inherits each of these
If the process belongs to a share group, it is removed from that
group. Its stack segment is deallocated and removed from the share
group's virtual space. All other virtual space that was shared with
the share group is left untouched. If the prctl (PR_SETEXITSIG)
option has been enabled for the share group, than the specified
signal is sent to all remaining share group members.
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)]. If the process has any pages locked, they
are unlocked [see mpin(2)].
An accounting record is written on the accounting file if the
system's accounting routine is enabled [see acct(2)].
If the process is a controlling process, SIGHUP is sent to the
foreground process group of its controlling terminal and its
controlling terminal is deallocated.
If the calling process has any stopped children whose process group
will be orphaned when the calling process exits, or if the calling
process is a member of a process group that will be orphaned when
the calling process exits, that process group will be sent SIGHUP
and SIGCONT signals. Note that these signals are not sent if the
process became the process group leader through the invocation of
the setpgrp(2) system call.
In all cases, if the calling process is a process group leader and
has an associated controlling terminal, the controlling terminal is
disassociated from the process allowing it to be acquired by another
process group leader.
Any mapped files are closed and any written pages flushed to disk.
The C function exit(3C) calls any functions registered through the atexit
function in the reverse order of their registration. It then causes each
buffered file stream to be flushed, and, unless an sproc has been
executed, closed. The function _exit circumvents all such functions and
The symbols EXIT_SUCCESS and EXIT_FAILURE are defined in stdlib.h and may
be used as the value of status to indicate successful or unsuccessful
acct(2), intro(2), plock(2), semop(2), sigaction(2), signal(2), mmap(2),
mpin(2), prctl(2), sigprocmask(2), sigvec(3B), sigblock(3B),
sigsetmask(3B), times(2), wait(2), atexit(3C).
See signal(2) NOTES.
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