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28 .\" @(#)vfork.2 8.1 (Berkeley) 6/4/93
29 .\" $FreeBSD: src/lib/libc/sys/vfork.2,v 1.12.2.6 2002/12/29 16:35:34 schweikh Exp $
36 .Nd spawn new process in a virtual memory efficient way
45 can be used to create new processes without fully copying the address
46 space of the old process, which is horrendously inefficient in a paged
47 environment. It is useful when the purpose of
49 would have been to create a new system context for an
54 in that the child borrows the parent's memory and thread of
55 control until a call to
57 or an exit (either by a call to
60 The parent process is suspended while the child is using its resources.
63 returns 0 in the child's context and (later) the pid of the child in
67 can normally be used just like
69 It does not work, however, to return while running in the child's context
70 from the procedure that called
72 since the eventual return from
74 would then return to a no longer existent stack frame.
75 Be careful, also, to call
83 will flush and close standard I/O channels, and thereby mess up the
84 parent processes standard I/O data structures.
89 since buffered data would then be flushed twice.)
104 function call appeared in
107 This system call will be eliminated when proper system sharing
108 mechanisms are implemented.
109 Users should not depend on the memory
112 as it will, in that case, be made synonymous to
115 To avoid a possible deadlock situation,
116 processes that are children in the middle
128 and input attempts result in an end-of-file indication.