exit - cause normal process termination
void exit(int status);
() 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)
in the reverse order of their registration. (It is possible for one of these
functions to use atexit(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
, or kills itself with a signal), then none of the remaining
functions is called, and further exit processing (in particular, flushing of
streams) is abandoned. If a function has been registered
multiple times using atexit(3)
, then it is called
as many times as it was registered.
All open stdio(3)
streams are flushed and closed. Files created by
The C standard specifies two constants, EXIT_SUCCESS
, that may be passed to exit
() to indicate
successful or unsuccessful termination, respectively.
() function does not return.
For an explanation of the terms used in this section, see attributes(7)
() 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.
The behavior is undefined if one of the functions registered using
calls either exit
. Note that a call to execve(2)
created using atexit(3)
The use of EXIT_SUCCESS
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
(), 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
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
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
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
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.
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