man_3_exit.txt

EXIT(3)                            Linux Programmer's Manual                           EXIT(3)

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 & 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  re‐
       moved.

       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).

       ┌──────────┬───────────────┬─────────────────────┐
       │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.

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 envi‐
       ronments) 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  (termi‐
          nation status, resource usage statistics) is retained in process table.  This allows
          the parent to subsequently use waitpid(2) (or similar) to learn the termination sta‐
          tus 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 control‐
       ling 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 SIG‐
       CONT  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  termi‐
       nating  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
       This page is part of release 5.05 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/.

Linux                                     2020-02-09                                   EXIT(3)