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NAME

       exit - cause normal process termination

SYNOPSIS

       #include <stdlib.h>

       void exit(int status);

DESCRIPTION

       The 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.

       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.

RETURN VALUE

       The exit() function does not return.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────┬───────────────┬─────────────────────┐
       │InterfaceAttributeValue               │
       ├──────────┼───────────────┼─────────────────────┤
       │exit()    │ Thread safety │ MT-Unsafe race:exit │
       └──────────┴───────────────┴─────────────────────┘
       The exit() function uses a global variable that is not protected, so it is not thread-safe.

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

NOTES

       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; 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.

SEE ALSO

       _exit(2), get_robust_list(2), setpgid(2), wait(2), atexit(3), on_exit(3), tmpfile(3)

COLOPHON

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