_exit(2) - f37

1_EXIT(2)                   Linux Programmer's Manual                  _EXIT(2)
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NAME

6       _exit, _Exit - terminate the calling process
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SYNOPSIS

9       #include <unistd.h>
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11       noreturn void _exit(int status);
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13       #include <stdlib.h>
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15       noreturn void _Exit(int status);
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       _Exit():
20           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
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DESCRIPTION

23       _exit()  terminates  the  calling process "immediately".  Any open file
24       descriptors belonging to the process are closed.  Any children  of  the
25       process are inherited by init(1) (or by the nearest "subreaper" process
26       as defined through the use of the prctl(2) PR_SET_CHILD_SUBREAPER oper‐
27       ation).  The process's parent is sent a SIGCHLD signal.
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29       The  value  status  &  0xFF  is  returned  to the parent process as the
30       process's exit status, and can be collected by the parent using one  of
31       the wait(2) family of calls.
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33       The function _Exit() is equivalent to _exit().
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RETURN VALUE

36       These functions do not return.
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CONFORMING TO

39       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.  The function _Exit() was in‐
40       troduced by C99.
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NOTES

43       For a discussion on the effects of an exit, the  transmission  of  exit
44       status, zombie processes, signals sent, and so on, see exit(3).
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46       The  function  _exit() is like exit(3), but does not call any functions
47       registered with atexit(3) or on_exit(3).  Open stdio(3) streams are not
48       flushed.   On the other hand, _exit() does close open file descriptors,
49       and this may cause an unknown delay, waiting for pending output to fin‐
50       ish.   If  the  delay  is undesired, it may be useful to call functions
51       like tcflush(3) before calling _exit().  Whether  any  pending  I/O  is
52       canceled, and which pending I/O may be canceled upon _exit(), is imple‐
53       mentation-dependent.
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55   C library/kernel differences
56       In glibc up to version 2.3, the _exit() wrapper  function  invoked  the
57       kernel  system  call  of  the  same name.  Since glibc 2.3, the wrapper
58       function invokes exit_group(2),  in  order  to  terminate  all  of  the
59       threads in a process.
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61       The raw _exit() system call terminates only the calling thread, and ac‐
62       tions such as reparenting child processes or  sending  SIGCHLD  to  the
63       parent  process  are  performed  only if this is the last thread in the
64       thread group.
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COLOPHON

71       This  page  is  part of release 5.13 of the Linux man-pages project.  A
72       description of the project, information about reporting bugs,  and  the
73       latest     version     of     this    page,    can    be    found    at
74       https://www.kernel.org/doc/man-pages/.
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78Linux                             2021-03-22                          _EXIT(2)