Section (3) exit
exit — cause normal process termination
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.
The C standard specifies two constants,
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).
||Thread safety||MT-Unsafe race:exit|
exit() function uses a
global variable that is not protected, so it is not
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_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
exit(), the exit
status must be transmitted to the parent process. There are
If the parent has set
SA_NOCLDWAIT, or has set the
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.
This page is part of release 5.04 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
Copyright (C) 2001 Andries Brouwer <aebcwi.nl>.
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
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Since the Linux kernel and libraries are constantly changing, this
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the use of the information contained herein. The author(s) may not
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which is licensed free of charge, as they might when working
Formatted or processed versions of this manual, if unaccompanied by
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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.