man2/_exit.2

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   2 .\"             and Copyright (C) 1993 Michael Haardt, Ian Jackson.
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  26 .\" Modified Wed Jul 21 23:02:38 1993 by Rik Faith <faith@cs.unc.edu>
  27 .\" Modified 2001-11-17, aeb
  28 .\"
  29 .TH _EXIT 2 2016-03-15 "Linux" "Linux Programmer's Manual"
  30 .SH NAME
  31 _exit, _Exit \- terminate the calling process
  32 .SH SYNOPSIS
  33 .B #include <unistd.h>
  34 .sp
  35 .BI "void _exit(int " status );
  36 .sp
  37 .B #include <stdlib.h>
  38 .sp
  39 .BI "void _Exit(int " status );
  40 .sp
  41 .in -4n
  42 Feature Test Macro Requirements for glibc (see
  43 .BR feature_test_macros (7)):
  44 .in
  45 .sp
  46 .ad l
  47 .BR _Exit ():
  48 .RS 4
  49 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  50 .RE
  51 .ad
  52 .SH DESCRIPTION
  53 The function
  54 .BR _exit ()
  55 terminates the calling process "immediately".
  56 Any open file descriptors
  57 belonging to the process are closed; any children of the process are
  58 inherited by process 1,
  59 .IR init ,
  60 and the process's parent is sent a
  61 .B SIGCHLD
  62 signal.
  63 .LP
  64 The value
  65 .I status
  66 is returned to the parent process as the process's exit status, and
  67 can be collected using one of the
  68 .BR wait (2)
  69 family of calls.
  70 .LP
  71 The function
  72 .BR _Exit ()
  73 is equivalent to
  74 .BR _exit ().
  75 .SH RETURN VALUE
  76 These functions do not return.
  77 .SH CONFORMING TO
  78 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
  79 The function
  80 .BR _Exit ()
  81 was introduced by C99.
  82 .SH NOTES
  83 For a discussion on the effects of an exit, the transmission of
  84 exit status, zombie processes, signals sent, and so on, see
  85 .BR exit (3).
  86 .LP
  87 The function
  88 .BR _exit ()
  89 is like
  90 .BR exit (3),
  91 but does not call any
  92 functions registered with
  93 .BR atexit (3)
  94 or
  95 .BR on_exit (3).
  96 Open
  97 .BR stdio (3)
  98 streams are not flushed.
  99 On the other hand,
 100 .BR _exit ()
 101 does close open file descriptors, and this may cause an unknown delay,
 102 waiting for pending output to finish.
 103 If the delay is undesired,
 104 it may be useful to call functions like
 105 .BR tcflush (3)
 106 before calling
 107 .BR _exit ().
 108 Whether any pending I/O is canceled, and which pending I/O may be
 109 canceled upon
 110 .BR _exit (),
 111 is implementation-dependent.
 112 .SS C library/kernel differences
 113 In glibc up to version 2.3, the
 114 .BR _exit ()
 115 wrapper function invoked the kernel system call of the same name.
 116 Since glibc 2.3, the wrapper function invokes
 117 .BR exit_group (2),
 118 in order to terminate all of the threads in a process.
 119 .SH SEE ALSO
 120 .BR execve (2),
 121 .BR exit_group (2),
 122 .BR fork (2),
 123 .BR kill (2),
 124 .BR wait (2),
 125 .BR wait4 (2),
 126 .BR waitpid (2),
 127 .BR atexit (3),
 128 .BR exit (3),
 129 .BR on_exit (3),
 130 .BR termios (3)