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.
POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
NOTES¶
It is undefined what happens 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. If the
parent was waiting on the child, it is notified of the exit status. In both
cases the exiting process dies immediately. If the parent has not indicated
that it is not interested in the exit status, but is not waiting, the exiting
process turns into a "zombie" process (which is nothing but a
container for the single byte representing the exit status) so that the parent
can learn the exit status when it later calls one of the
wait(2)
functions.
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.
If the 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.
SEE ALSO¶
_exit(2),
setpgid(2),
wait(2),
atexit(3),
on_exit(3),
tmpfile(3)
COLOPHON¶
This page is part of release 4.10 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/.