exit — cause normal process termination
#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.
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.
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.
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.
This page is part of release 5.11 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/.
|
Copyright (C) 2001 Andries Brouwer <aebcwi.nl>. %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END FIXME . There are a lot of other process termination actions that could be listed on this page. See, for example, the list in the POSIX exit(3p) page. |