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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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exit(3) Library Functions Manual exit(3)
exit - cause normal process termination
Standard C library (libc, -lc)
#include <stdlib.h>
[[noreturn]] void exit(int status);
The exit() function causes normal process termination and the
least significant byte of status (i.e., status & 0xFF) 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.
The exit() function does not return.
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.
C11, POSIX.1-2008.
C89, POSIX.1-2001, SVr4, 4.3BSD.
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 (which some C
libraries such as the GNU C library have also adopted); 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.
_exit(2), get_robust_list(2), setpgid(2), wait(2), atexit(3),
on_exit(3), tmpfile(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 exit(3)
Pages that refer to this page: man(1), _exit(2), kill(2), vfork(2), wait(2), abort(3), assert(3), assert_perror(3), atexit(3), err(3), error(3), EXIT_SUCCESS(3const), on_exit(3), pthread_create(3), pthread_detach(3), pthread_exit(3), sd_bus_set_exit_on_disconnect(3), setjmp(3), stdin(3), stdio(3), sysexits.h(3head), tmpfile(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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