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1 | .\" Copyright (c) 1999 Andries Brouwer (aeb@cwi.nl), 1 Nov 1999 |
2 | .\" | |
3 | .\" Permission is granted to make and distribute verbatim copies of this | |
4 | .\" manual provided the copyright notice and this permission notice are | |
5 | .\" preserved on all copies. | |
6 | .\" | |
7 | .\" Permission is granted to copy and distribute modified versions of this | |
8 | .\" manual under the conditions for verbatim copying, provided that the | |
9 | .\" entire resulting derived work is distributed under the terms of a | |
10 | .\" permission notice identical to this one. | |
c13182ef | 11 | .\" |
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12 | .\" Since the Linux kernel and libraries are constantly changing, this |
13 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
14 | .\" responsibility for errors or omissions, or for damages resulting from | |
15 | .\" the use of the information contained herein. The author(s) may not | |
16 | .\" have taken the same level of care in the production of this manual, | |
17 | .\" which is licensed free of charge, as they might when working | |
18 | .\" professionally. | |
c13182ef | 19 | .\" |
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20 | .\" Formatted or processed versions of this manual, if unaccompanied by |
21 | .\" the source, must acknowledge the copyright and authors of this work. | |
22 | .\" | |
23 | .\" 1999-11-10: Merged text taken from the page contributed by | |
24 | .\" Reed H. Petty (rhp@draper.net) | |
25 | .\" | |
608bf950 | 26 | .TH VFORK 2 2012-08-05 "Linux" "Linux Programmer's Manual" |
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27 | .SH NAME |
28 | vfork \- create a child process and block parent | |
29 | .SH SYNOPSIS | |
30 | .B #include <sys/types.h> | |
31 | .br | |
32 | .B #include <unistd.h> | |
33 | .sp | |
34 | .B pid_t vfork(void); | |
cc4615cc MK |
35 | .sp |
36 | .in -4n | |
37 | Feature Test Macro Requirements for glibc (see | |
38 | .BR feature_test_macros (7)): | |
39 | .in | |
40 | .sp | |
41 | .BR vfork (): | |
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42 | .ad l |
43 | .RS 4 | |
44 | .PD 0 | |
45 | .TP 4 | |
46 | Since glibc 2.12: | |
47 | .nf | |
48 | _BSD_SOURCE || | |
98dbe7af | 49 | (_XOPEN_SOURCE\ >=\ 500 || |
7b072c4d | 50 | _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED) && |
98dbe7af | 51 | !(_POSIX_C_SOURCE\ >=\ 200809L || _XOPEN_SOURCE\ >=\ 700) |
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52 | .TP 4 |
53 | .fi | |
54 | Before glibc 2.12: | |
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55 | _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 || |
56 | _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED | |
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57 | .PD |
58 | .RE | |
59 | .ad b | |
8c87824d | 60 | .SH DESCRIPTION |
73d8cece | 61 | .SS Standard description |
f9f81237 | 62 | (From POSIX.1) |
fea681da | 63 | The |
bed66765 | 64 | .BR vfork () |
fea681da | 65 | function has the same effect as |
0bfa087b | 66 | .BR fork (2), |
d9bfdb9c | 67 | except that the behavior is undefined if the process created by |
bed66765 | 68 | .BR vfork () |
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69 | either modifies any data other than a variable of type |
70 | .I pid_t | |
70cbdedf | 71 | used to store the return value from |
bed66765 | 72 | .BR vfork (), |
fea681da | 73 | or returns from the function in which |
bed66765 | 74 | .BR vfork () |
fea681da | 75 | was called, or calls any other function before successfully calling |
0bfa087b | 76 | .BR _exit (2) |
fea681da | 77 | or one of the |
d806e103 | 78 | .BR exec (3) |
fea681da | 79 | family of functions. |
73d8cece | 80 | .SS Linux description |
bed66765 | 81 | .BR vfork (), |
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82 | just like |
83 | .BR fork (2), | |
84 | creates a child process of the calling process. | |
85 | For details and return value and errors, see | |
86 | .BR fork (2). | |
87 | .PP | |
bed66765 | 88 | .BR vfork () |
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89 | is a special case of |
90 | .BR clone (2). | |
91 | It is used to create new processes without copying the page tables of | |
c13182ef | 92 | the parent process. |
600c9aa9 | 93 | It may be useful in performance-sensitive applications |