exit

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  addi-
       tional  function  to be executed during exit processing; the new regis-
       tration 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, flush-
       ing of stdio(3) streams) is abandoned.  If a function has  been  regis-
       tered  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 at-
       tributes(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  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 the file <sysex-
       its.h>.

       After exit(), the  exit  status  must  be  transmitted  to  the  parent
       process.  There are three cases:

       o  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.

       o  If the parent was waiting on the child, it is notified of  the  exit
          status and the child dies immediately.

       o  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 statis-
          tics) is retained in process table.  This allows the parent to  sub-
          sequently  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  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  chil-
       dren  of  the terminating process, termination of a process does not in
       general cause a signal to be sent to children of  that  process.   How-
       ever,  a process can use the prctl(2) PR_SET_PDEATHSIG operation to ar-
       range 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)