mirror of https://github.com/mkerrisk/man-pages
220 lines
5.9 KiB
Groff
220 lines
5.9 KiB
Groff
.\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.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.\" manual page may be incorrect or out-of-date.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.
|
|
.\"
|
|
.TH EXIT 3 2021-03-22 "Linux" "Linux Programmer's Manual"
|
|
.SH NAME
|
|
exit \- cause normal process termination
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.B #include <stdlib.h>
|
|
.PP
|
|
.BI "noreturn void exit(int " status );
|
|
.fi
|
|
.SH DESCRIPTION
|
|
The
|
|
.BR exit ()
|
|
function causes normal process termination and the least significant byte of
|
|
.I status
|
|
(i.e., \fIstatus & 0xFF\fP) is returned to the parent (see
|
|
.BR wait (2)).
|
|
.PP
|
|
All functions registered with
|
|
.BR atexit (3)
|
|
and
|
|
.BR on_exit (3)
|
|
are called, in the reverse order of their registration.
|
|
(It is possible for one of these functions to use
|
|
.BR atexit (3)
|
|
or
|
|
.BR 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
|
|
.BR _exit (2),
|
|
or kills itself with a signal),
|
|
then none of the remaining functions is called,
|
|
and further exit processing (in particular, flushing of
|
|
.BR stdio (3)
|
|
streams) is abandoned.
|
|
If a function has been registered multiple times using
|
|
.BR atexit (3)
|
|
or
|
|
.BR on_exit (3),
|
|
then it is called as many times as it was registered.
|
|
.PP
|
|
All open
|
|
.BR stdio (3)
|
|
streams are flushed and closed.
|
|
Files created by
|
|
.BR tmpfile (3)
|
|
are removed.
|
|
.PP
|
|
The C standard specifies two constants,
|
|
\fBEXIT_SUCCESS\fP and \fBEXIT_FAILURE\fP,
|
|
that may be passed to
|
|
.BR exit ()
|
|
to indicate successful or unsuccessful
|
|
termination, respectively.
|
|
.SH RETURN VALUE
|
|
The
|
|
.BR exit ()
|
|
function does not return.
|
|
.SH ATTRIBUTES
|
|
For an explanation of the terms used in this section, see
|
|
.BR attributes (7).
|
|
.ad l
|
|
.nh
|
|
.TS
|
|
allbox;
|
|
lbx lb lb
|
|
l l l.
|
|
Interface Attribute Value
|
|
T{
|
|
.BR exit ()
|
|
T} Thread safety MT-Unsafe race:exit
|
|
.TE
|
|
.hy
|
|
.ad
|
|
.sp 1
|
|
.PP
|
|
The
|
|
.BR exit ()
|
|
function uses a global variable that is not protected,
|
|
so it is not thread-safe.
|
|
.SH CONFORMING TO
|
|
POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
|
|
.SH NOTES
|
|
The behavior is undefined if one of the functions registered using
|
|
.BR atexit (3)
|
|
and
|
|
.BR on_exit (3)
|
|
calls either
|
|
.BR exit ()
|
|
or
|
|
.BR longjmp (3).
|
|
Note that a call to
|
|
.BR execve (2)
|
|
removes registrations created using
|
|
.BR atexit (3)
|
|
and
|
|
.BR on_exit (3).
|
|
.PP
|
|
The use of
|
|
.B EXIT_SUCCESS
|
|
and
|
|
.B 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.
|
|
.PP
|
|
BSD has attempted to standardize exit codes
|
|
(which some C libraries such as the GNU C library have also adopted);
|
|
see the file
|
|
.IR <sysexits.h> .
|
|
.PP
|
|
After
|
|
.BR exit (),
|
|
the exit status must be transmitted to the
|
|
parent process.
|
|
There are three cases:
|
|
.IP \(bu 3
|
|
If the parent has set
|
|
.BR SA_NOCLDWAIT ,
|
|
or has set the
|
|
.B SIGCHLD
|
|
handler to
|
|
.BR SIG_IGN ,
|
|
the status is discarded and the child dies immediately.
|
|
.IP \(bu
|
|
If the parent was waiting on the child,
|
|
it is notified of the exit status and the child dies immediately.
|
|
.IP \(bu
|
|
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
|
|
.BR waitpid (2)
|
|
(or similar) to learn the termination status of the child;
|
|
at that point the zombie process slot is released.
|
|
.PP
|
|
If the implementation supports the
|
|
.B SIGCHLD
|
|
signal, this signal
|
|
is sent to the parent.
|
|
If the parent has set
|
|
.BR SA_NOCLDWAIT ,
|
|
it is undefined whether a
|
|
.B SIGCHLD
|
|
signal is sent.
|
|
.\"
|
|
.SS 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
|
|
.B SIGHUP
|
|
signal, and the terminal is disassociated
|
|
from this session, allowing it to be acquired by a new controlling
|
|
process.
|
|
.PP
|
|
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
|
|
.B SIGHUP
|
|
signal followed by a
|
|
.B SIGCONT
|
|
signal will be
|
|
sent to each process in this process group.
|
|
See
|
|
.BR setpgid (2)
|
|
for an explanation of orphaned process groups.
|
|
.PP
|
|
Except in the above cases,
|
|
where the signalled processes may be children of the terminating process,
|
|
termination of a process does
|
|
.I not
|
|
in general cause a signal to be sent to children of that process.
|
|
However, a process can use the
|
|
.BR prctl (2)
|
|
.B PR_SET_PDEATHSIG
|
|
operation to arrange that it receives a signal if its parent terminates.
|
|
.SH SEE ALSO
|
|
.BR _exit (2),
|
|
.BR get_robust_list (2),
|
|
.BR setpgid (2),
|
|
.BR wait (2),
|
|
.BR atexit (3),
|
|
.BR on_exit (3),
|
|
.BR tmpfile (3)
|