1EXIT(3)                    Linux Programmer's Manual                   EXIT(3)
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3
4

NAME

6       exit - cause normal process termination
7

SYNOPSIS

9       #include <stdlib.h>
10
11       void exit(int status);
12

DESCRIPTION

14       The  exit() function causes normal process termination and the value of
15       status & 0377 is returned to the parent (see wait(2)).
16
17       All functions registered with atexit(3) and on_exit(3) are  called,  in
18       the  reverse  order  of their registration.  (It is possible for one of
19       these functions to use atexit(3) or on_exit(3)  to  register  an  addi‐
20       tional  function  to be executed during exit processing; the new regis‐
21       tration is added to the front of the list of functions that  remain  to
22       be  called.)  If one of these functions does not return (e.g., it calls
23       _exit(2), or kills itself with a signal), then none  of  the  remaining
24       functions is called, and further exit processing (in particular, flush‐
25       ing of stdio(3) streams) is abandoned.  If a function has  been  regis‐
26       tered  multiple  times using atexit(3) or on_exit(3), then it is called
27       as many times as it was registered.
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29       All open stdio(3) streams are flushed and  closed.   Files  created  by
30       tmpfile(3) are removed.
31
32       The  C standard specifies two constants, EXIT_SUCCESS and EXIT_FAILURE,
33       that may be passed to exit() to  indicate  successful  or  unsuccessful
34       termination, respectively.
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RETURN VALUE

37       The exit() function does not return.
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ATTRIBUTES

40       For   an   explanation   of   the  terms  used  in  this  section,  see
41       attributes(7).
42
43       ┌──────────┬───────────────┬─────────────────────┐
44Interface Attribute     Value               
45       ├──────────┼───────────────┼─────────────────────┤
46exit()    │ Thread safety │ MT-Unsafe race:exit │
47       └──────────┴───────────────┴─────────────────────┘
48       The exit() function uses a global variable that is not protected, so it
49       is not thread-safe.
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CONFORMING TO

52       POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
53

NOTES

55       The  behavior  is  undefined  if  one of the functions registered using
56       atexit(3) and on_exit(3) calls either exit() or longjmp(3).  Note  that
57       a  call  to execve(2) removes registrations created using atexit(3) and
58       on_exit(3).
59
60       The use of EXIT_SUCCESS and EXIT_FAILURE is slightly more portable  (to
61       non-UNIX  environments) than the use of 0 and some nonzero value like 1
62       or -1.  In particular, VMS uses a different convention.
63
64       BSD has attempted to standardize exit codes  (which  some  C  libraries
65       such  as  the  GNU  C  library have also adopted); see the file <sysex‐
66       its.h>.
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68       After exit(), the  exit  status  must  be  transmitted  to  the  parent
69       process.  There are three cases:
70
71       ·  If  the  parent has set SA_NOCLDWAIT, or has set the SIGCHLD handler
72          to SIG_IGN, the status is discarded and the child dies immediately.
73
74       ·  If the parent was waiting on the child, it is notified of  the  exit
75          status and the child dies immediately.
76
77       ·  Otherwise, the child becomes a "zombie" process: most of the process
78          resources are recycled, but a slot  containing  minimal  information
79          about  the child process (termination status, resource usage statis‐
80          tics) is retained in process table.  This allows the parent to  sub‐
81          sequently  use waitpid(2) (or similar) to learn the termination sta‐
82          tus of the child; at that point the zombie process slot is released.
83
84       If the implementation supports the SIGCHLD signal, this signal is  sent
85       to  the  parent.   If  the parent has set SA_NOCLDWAIT, it is undefined
86       whether a SIGCHLD signal is sent.
87
88   Signals sent to other processes
89       If the exiting process is a session leader and its controlling terminal
90       is  the  controlling  terminal of the session, then each process in the
91       foreground process group of this controlling terminal is sent a  SIGHUP
92       signal,  and  the terminal is disassociated from this session, allowing
93       it to be acquired by a new controlling process.
94
95       If the exit of the process causes a process group to  become  orphaned,
96       and  if any member of the newly orphaned process group is stopped, then
97       a SIGHUP signal followed by a SIGCONT  signal  will  be  sent  to  each
98       process  in  this  process group.  See setpgid(2) for an explanation of
99       orphaned process groups.
100
101       Except in the above cases, where the signalled processes may  be  chil‐
102       dren  of  the terminating process, termination of a process does not in
103       general cause a signal to be sent to children of  that  process.   How‐
104       ever,  a  process  can  use  the prctl(2) PR_SET_PDEATHSIG operation to
105       arrange that it receives a signal if its parent terminates.
106

SEE ALSO

108       _exit(2),   get_robust_list(2),   setpgid(2),    wait(2),    atexit(3),
109       on_exit(3), tmpfile(3)
110

COLOPHON

112       This  page  is  part of release 5.02 of the Linux man-pages project.  A
113       description of the project, information about reporting bugs,  and  the
114       latest     version     of     this    page,    can    be    found    at
115       https://www.kernel.org/doc/man-pages/.
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119Linux                             2019-03-06                           EXIT(3)
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