EXIT
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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NAME
exit - cause normal process termination
SYNOPSIS
#include <stdlib.h>
void exit(int status);
DESCRIPTION
The
exit()
function causes normal process termination and the
value of
status & 0377 is returned to the parent
(see
wait(2)).
All functions registered with
atexit(3)
and
on_exit(3)
are called, in the reverse order of their registration.
(It is possible for one of these functions to use
atexit(3)
or
on_exit(3)
to register an additional
function to be executed during exit processing;
the new registration is added to the front of the list of functions
that remain to be called.)
If one of these functions does not return
(e.g., it calls
_exit(2),
or kills itself with a signal),
then none of the remaining functions is called,
and further exit processing (in particular, flushing of
stdio(3)
streams) is abandoned.
If a function has been registered multiple times using
atexit(3)
or
on_exit(3),
then it is called as many times as it was registered.
All open
stdio(3)
streams are flushed and closed.
Files created by
tmpfile(3)
are removed.
The C standard specifies two constants,
EXIT_SUCCESS and EXIT_FAILURE,
that may be passed to
exit()
to indicate successful or unsuccessful
termination, respectively.
RETURN VALUE
The
exit()
function does not return.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
exit()
| Thread safety | MT-Unsafe race:exit
|
The
exit()
function uses a global variable that is not protected,
so it is not thread-safe.
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
NOTES
The behavior is undefined if one of the functions registered using
atexit(3)
and
on_exit(3)
calls either
exit()
or
longjmp(3).
Note that a call to
execve(2)
removes registrations created using
atexit(3)
and
on_exit(3).
The use of
EXIT_SUCCESS
and
EXIT_FAILURE
is slightly more portable
(to non-UNIX environments) than the use of 0 and some nonzero value
like 1 or -1.
In particular, VMS uses a different convention.
BSD has attempted to standardize exit codes; see the file
<sysexits.h>.
After
exit(),
the exit status must be transmitted to the
parent process.
There are three cases:
- *
-
If the parent has set
SA_NOCLDWAIT,
or has set the
SIGCHLD
handler to
SIG_IGN,
the status is discarded and the child dies immediately.
- *
-
If the parent was waiting on the child,
it is notified of the exit status and the child dies immediately.
- *
-
Otherwise,
the child becomes a "zombie" process:
most of the process resources are recycled,
but a slot containing minimal information about the child process
(termination status, resource usage statistics) is retained in process table.
This allows the parent to subsequently use
waitpid(2)
(or similar) to learn the termination status of the child;
at that point the zombie process slot is released.
If the implementation supports the
SIGCHLD
signal, this signal
is sent to the parent.
If the parent has set
SA_NOCLDWAIT,
it is undefined whether a
SIGCHLD
signal is sent.
Signals sent to other processes
If the exiting process is a session leader and its controlling terminal
is the controlling terminal of the session, then each process in
the foreground process group of this controlling terminal
is sent a
SIGHUP
signal, and the terminal is disassociated
from this session, allowing it to be acquired by a new controlling
process.
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 this process group.
See
setpgid(2)
for an explanation of orphaned process groups.
Except in the above cases,
where the signalled processes may be children of the terminating process,
termination of a process does
not
in general cause a signal to be sent to children of that process.
However, a process can use the
prctl(2)
PR_SET_PDEATHSIG
operation to arrange that it receives a signal if its parent terminates.
SEE ALSO
_exit(2),
get_robust_list(2),
setpgid(2),
wait(2),
atexit(3),
on_exit(3),
tmpfile(3)
COLOPHON
This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- Signals sent to other processes
-
- SEE ALSO
-
- COLOPHON
-
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