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28 .\" @(#)vfork.2 8.1 (Berkeley) 6/4/93
35 .Nd create a new process without copying the address space
44 Since this function is hard to use correctly from application software,
45 it is recommended to use
55 can be used to create new processes without fully copying the address
56 space of the old process, which is inefficient in a paged
58 It is useful when the purpose of
60 would have been to create a new system context for an
67 in that the child borrows the parent process's address space and the
68 calling thread's stack
71 or an exit (either by a call to
74 The calling thread is suspended while the child is using its resources.
75 Other threads continue to run.
80 returns 0 in the child's context and (later) the pid of the child in
83 Many problems can occur when replacing
87 For example, it does not work to return while running in the child's context
88 from the procedure that called
90 since the eventual return from
92 would then return to a no longer existent stack frame.
93 Also, changing process state which is partially implemented in user space
94 such as signal handlers with
96 will corrupt the parent's state.
98 Be careful, also, to call
106 will flush and close standard I/O channels, and thereby mess up the
107 parent processes standard I/O data structures.
112 since buffered data would then be flushed twice.)
128 system call appeared in
131 To avoid a possible deadlock situation,
132 processes that are children in the middle
144 and input attempts result in an end-of-file indication.