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man: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 & 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  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
     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  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:
     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
     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 4.16 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 2017-09-15 EXIT(3)

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