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1 | .\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>. |
2 | .\" | |
93015253 | 3 | .\" %%%LICENSE_START(VERBATIM) |
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4 | .\" Permission is granted to make and distribute verbatim copies of this |
5 | .\" manual provided the copyright notice and this permission notice are | |
6 | .\" preserved on all copies. | |
7 | .\" | |
8 | .\" Permission is granted to copy and distribute modified versions of this | |
9 | .\" manual under the conditions for verbatim copying, provided that the | |
10 | .\" entire resulting derived work is distributed under the terms of a | |
11 | .\" permission notice identical to this one. | |
c13182ef | 12 | .\" |
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13 | .\" Since the Linux kernel and libraries are constantly changing, this |
14 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
15 | .\" responsibility for errors or omissions, or for damages resulting from | |
16 | .\" the use of the information contained herein. The author(s) may not | |
17 | .\" have taken the same level of care in the production of this manual, | |
18 | .\" which is licensed free of charge, as they might when working | |
19 | .\" professionally. | |
c13182ef | 20 | .\" |
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21 | .\" Formatted or processed versions of this manual, if unaccompanied by |
22 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 23 | .\" %%%LICENSE_END |
fea681da | 24 | .\" |
bea08fec | 25 | .\" FIXME . There are a lot of other process termination actions that |
0d44d05f MK |
26 | .\" could be listed on this page. See, for example, the list in the |
27 | .\" POSIX exit(3p) page. | |
28 | .\" | |
9ba01802 | 29 | .TH EXIT 3 2019-03-06 "Linux" "Linux Programmer's Manual" |
fea681da | 30 | .SH NAME |
54221c6a | 31 | exit \- cause normal process termination |
fea681da MK |
32 | .SH SYNOPSIS |
33 | .nf | |
34 | .B #include <stdlib.h> | |
68e4db0a | 35 | .PP |
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36 | .BI "void exit(int " status ); |
37 | .fi | |
38 | .SH DESCRIPTION | |
60a90ecd MK |
39 | The |
40 | .BR exit () | |
41 | function causes normal process termination and the | |
a210091c | 42 | value of \fIstatus & 0377\fP is returned to the parent |
fea681da MK |
43 | (see |
44 | .BR wait (2)). | |
dd3568a1 | 45 | .PP |
a210091c | 46 | All functions registered with |
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47 | .BR atexit (3) |
48 | and | |
49 | .BR on_exit (3) | |
a210091c MK |
50 | are called, in the reverse order of their registration. |
51 | (It is possible for one of these functions to use | |
60a90ecd MK |
52 | .BR atexit (3) |
53 | or | |
54 | .BR on_exit (3) | |
55 | to register an additional | |
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56 | function to be executed during exit processing; |
57 | the new registration is added to the front of the list of functions | |
58 | that remain to be called.) | |
65b70abf MK |
59 | If one of these functions does not return |
60 | (e.g., it calls | |
61 | .BR _exit (2), | |
62 | or kills itself with a signal), | |
63 | then none of the remaining functions is called, | |
64 | and further exit processing (in particular, flushing of | |
65 | .BR stdio (3) | |
66 | streams) is abandoned. | |
67 | If a function has been registered multiple times using | |
68 | .BR atexit (3) | |
69 | or | |
70 | .BR on_exit (3), | |
71 | then it is called as many times as it was registered. | |
dd3568a1 | 72 | .PP |
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73 | All open |
74 | .BR stdio (3) | |
75 | streams are flushed and closed. | |
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76 | Files created by |
77 | .BR tmpfile (3) | |
78 | are removed. | |
dd3568a1 | 79 | .PP |
a210091c | 80 | The C standard specifies two constants, |
3b46efc3 | 81 | \fBEXIT_SUCCESS\fP and \fBEXIT_FAILURE\fP, |
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82 | that may be passed to |
83 | .BR exit () | |
84 | to indicate successful or unsuccessful | |
fea681da | 85 | termination, respectively. |
47297adb | 86 | .SH RETURN VALUE |
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87 | The |
88 | .BR exit () | |
89 | function does not return. | |
d0e96150 | 90 | .SH ATTRIBUTES |
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91 | For an explanation of the terms used in this section, see |
92 | .BR attributes (7). | |
93 | .TS | |
94 | allbox; | |
95 | lb lb lb | |
96 | l l l. | |
97 | Interface Attribute Value | |
98 | T{ | |
99 | .BR exit () | |
ef38f354 | 100 | T} Thread safety MT-Unsafe race:exit |
2a2948ab MK |
101 | .TE |
102 | .PP | |
d0e96150 PH |
103 | The |
104 | .BR exit () | |
105 | function uses a global variable that is not protected, | |
106 | so it is not thread-safe. | |
47297adb | 107 | .SH CONFORMING TO |
7a475b7c | 108 | POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD. |
fea681da | 109 | .SH NOTES |
dd3568a1 | 110 | .PP |
cffa7950 | 111 | The behavior is undefined if one of the functions registered using |
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112 | .BR atexit (3) |
113 | and | |
114 | .BR on_exit (3) | |
115 | calls either | |
116 | .BR exit () | |
117 | or | |
118 | .BR longjmp (3). | |
5eab557e MK |
119 | Note that a call to |
120 | .BR execve (2) | |
121 | removes registrations created using | |
122 | .BR atexit (3) | |
123 | and | |
124 | .BR on_exit (3). | |
dd3568a1 | 125 | .PP |
8bd58774 MK |
126 | The use of |
127 | .B EXIT_SUCCESS | |
128 | and | |
129 | .B EXIT_FAILURE | |
130 | is slightly more portable | |
008f1ecc | 131 | (to non-UNIX environments) than the use of 0 and some nonzero value |
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132 | like 1 or \-1. |
133 | In particular, VMS uses a different convention. | |
dd3568a1 | 134 | .PP |
946bdf72 MF |
135 | BSD has attempted to standardize exit codes |
136 | (which some C libraries such as the GNU C library have also adopted); | |
137 | see the file | |
fea681da | 138 | .IR <sysexits.h> . |
dd3568a1 | 139 | .PP |
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140 | After |
141 | .BR exit (), | |
142 | the exit status must be transmitted to the | |
c13182ef | 143 | parent process. |
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144 | There are three cases: |
145 | .IP \(bu 3 | |
c13182ef | 146 | If the parent has set |
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147 | .BR SA_NOCLDWAIT , |
148 | or has set the | |
149 | .B SIGCHLD | |
150 | handler to | |
151 | .BR SIG_IGN , | |
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152 | the status is discarded and the child dies immediately. |
153 | .IP \(bu | |
2a825954 | 154 | If the parent was waiting on the child, |
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155 | it is notified of the exit status and the child dies immediately. |
156 | .IP \(bu | |
71e87683 MK |
157 | Otherwise, |
158 | the child becomes a "zombie" process: | |
159 | most of the process resources are recycled, | |
160 | but a slot containing minimal information about the child process | |
161 | (termination status, resource usage statistics) is retained in process table. | |
162 | This allows the parent to subsequently use | |
163 | .BR waitpid (2) | |
164 | (or similar) to learn the termination status of the child; | |
165 | at that point the zombie process slot is released. | |
dd3568a1 | 166 | .PP |
8bd58774 | 167 | If the implementation supports the |
0daa9e92 | 168 | .B SIGCHLD |
8bd58774 | 169 | signal, this signal |
c13182ef | 170 | is sent to the parent. |
8bd58774 MK |
171 | If the parent has set |
172 | .BR SA_NOCLDWAIT , | |
173 | it is undefined whether a | |
174 | .B SIGCHLD | |
175 | signal is sent. | |
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176 | .\" |
177 | .SS Signals sent to other processes | |
178 | If the exiting process is a session leader and its controlling terminal | |
37894cb3 | 179 | is the controlling terminal of the session, then each process in |
fea681da | 180 | the foreground process group of this controlling terminal |
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181 | is sent a |
182 | .B SIGHUP | |
183 | signal, and the terminal is disassociated | |
fea681da MK |
184 | from this session, allowing it to be acquired by a new controlling |
185 | process. | |
dd3568a1 | 186 | .PP |
fea681da | 187 | If the exit of the process causes a process group to become orphaned, |
54221c6a | 188 | and if any member of the newly orphaned process group is stopped, |
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189 | then a |
190 | .B SIGHUP | |
191 | signal followed by a | |
192 | .B SIGCONT | |
193 | signal will be | |
fea681da | 194 | sent to each process in this process group. |
aec4704f MK |
195 | See |
196 | .BR setpgid (2) | |
197 | for an explanation of orphaned process groups. | |
ee7c8e26 MK |
198 | .PP |
199 | Except in the above cases, | |
200 | where the signalled processes may be children of the terminating process, | |
201 | termination of a process does | |
202 | .I not | |
203 | in general cause a signal to be sent to children of that process. | |
204 | However, a process can use the | |
205 | .BR prctl (2) | |
206 | .B PR_SET_PDEATHSIG | |
207 | operation to arrange that it receives a signal if its parent terminates. | |
47297adb | 208 | .SH SEE ALSO |
fea681da | 209 | .BR _exit (2), |
18523cfc | 210 | .BR get_robust_list (2), |
aec4704f | 211 | .BR setpgid (2), |
fea681da MK |
212 | .BR wait (2), |
213 | .BR atexit (3), | |
214 | .BR on_exit (3), | |
215 | .BR tmpfile (3) |