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1 | .\" Copyright (c) 1999 Andries Brouwer (aeb@cwi.nl), 1 Nov 1999 |
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14 | .\" manual page may be incorrect or out-of-date.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 |
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24 | .\" |
25 | .\" 1999-11-10: Merged text taken from the page contributed by | |
26 | .\" Reed H. Petty (rhp@draper.net) | |
27 | .\" | |
97986708 | 28 | .TH VFORK 2 2016-03-15 "Linux" "Linux Programmer's Manual" |
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29 | .SH NAME |
30 | vfork \- create a child process and block parent | |
31 | .SH SYNOPSIS | |
32 | .B #include <sys/types.h> | |
33 | .br | |
34 | .B #include <unistd.h> | |
35 | .sp | |
36 | .B pid_t vfork(void); | |
cc4615cc MK |
37 | .sp |
38 | .in -4n | |
39 | Feature Test Macro Requirements for glibc (see | |
40 | .BR feature_test_macros (7)): | |
41 | .in | |
42 | .sp | |
43 | .BR vfork (): | |
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44 | .ad l |
45 | .RS 4 | |
46 | .PD 0 | |
47 | .TP 4 | |
48 | Since glibc 2.12: | |
49 | .nf | |
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50 | (_XOPEN_SOURCE\ >=\ 500) && ! (_POSIX_C_SOURCE\ >=\ 200809L) |
51 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
52 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE | |
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53 | .TP 4 |
54 | .fi | |
55 | Before glibc 2.12: | |
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56 | _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 |
57 | .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED | |
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58 | .PD |
59 | .RE | |
60 | .ad b | |
8c87824d | 61 | .SH DESCRIPTION |
73d8cece | 62 | .SS Standard description |
f9f81237 | 63 | (From POSIX.1) |
fea681da | 64 | The |
bed66765 | 65 | .BR vfork () |
fea681da | 66 | function has the same effect as |
0bfa087b | 67 | .BR fork (2), |
d9bfdb9c | 68 | except that the behavior is undefined if the process created by |
bed66765 | 69 | .BR vfork () |
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70 | either modifies any data other than a variable of type |
71 | .I pid_t | |
70cbdedf | 72 | used to store the return value from |
bed66765 | 73 | .BR vfork (), |
fea681da | 74 | or returns from the function in which |
bed66765 | 75 | .BR vfork () |
fea681da | 76 | was called, or calls any other function before successfully calling |
0bfa087b | 77 | .BR _exit (2) |
fea681da | 78 | or one of the |
d806e103 | 79 | .BR exec (3) |
fea681da | 80 | family of functions. |
73d8cece | 81 | .SS Linux description |
bed66765 | 82 | .BR vfork (), |
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83 | just like |
84 | .BR fork (2), | |
85 | creates a child process of the calling process. | |
86 | For details and return value and errors, see | |
87 | .BR fork (2). | |
88 | .PP | |
bed66765 | 89 | .BR vfork () |
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90 | is a special case of |
91 | .BR clone (2). | |
92 | It is used to create new processes without copying the page tables of | |
c13182ef | 93 | the parent process. |
600c9aa9 | 94 | It may be useful in performance-sensitive applications |