2 .\" This manual page is taken directly from Plan9, and modified to
3 .\" describe the actual BSD implementation. Permission for
4 .\" use of this page comes from Rob Pike <rob@plan9.att.com>.
13 .Nd manipulate process resources
21 Forking, vforking or rforking are the only ways new processes are created.
26 selects which resources of the
27 invoking process (parent) are shared
28 by the new process (child) or initialized to
31 the open file descriptor table (which, when shared, permits processes
32 to open and close files for other processes),
37 is the logical OR of some subset of:
38 .Bl -tag -width ".Dv RFLINUXTHPN"
40 If set a new process is created; otherwise changes affect the
43 If set, the child process will be dissociated from the parent.
45 exit the child will not leave a status for the parent to collect.
49 If set, the invoker's file descriptor table (see
51 is copied; otherwise the two processes share a
54 If set, the new process starts with a clean file descriptor table.
55 Is mutually exclusive with
58 If set, the kernel will force sharing of the entire address space,
59 typically by sharing the hardware page table directly.
61 will thus inherit and share all the segments the parent process owns,
62 whether they are normally shareable or not.
64 not split (both the parent and child return on the same stack) and thus
66 with the RFMEM flag may not generally be called directly from high level
67 languages including C.
70 A helper function is provided to assist with this problem and will cause
71 the new process to run on the provided stack.
76 If set, the kernel will force sharing the sigacts structure between the
79 If set, the kernel will return SIGUSR1 instead of SIGCHILD upon thread
81 This is intended to mimic certain Linux clone behaviour.
84 File descriptors in a shared file descriptor table are kept
85 open until either they are explicitly closed
86 or all processes sharing the table exit.
91 value returned in the parent process
93 of the child process; the value returned in the child is zero.
96 the return value is zero.
97 Process id's range from 1 to the maximum integer
103 will sleep, if necessary, until required process resources are available.
108 can be implemented as a call to
109 .Fn rfork "RFFDG | RFPROC"
110 but is not for backwards compatibility.
112 Upon successful completion,
115 of 0 to the child process and returns the process ID of the child
116 process to the parent process.
117 Otherwise, a value of -1 is returned
118 to the parent process, no child process is created, and the global
121 is set to indicate the error.
126 will fail and no child process will be created if:
129 The system-imposed limit on the total
130 number of processes under execution would be exceeded.
131 The limit is given by the
135 (The limit is actually ten less than this
136 except for the super user).
138 The user is not the super user, and
139 the system-imposed limit
140 on the total number of
141 processes under execution by a single user would be exceeded.
142 The limit is given by the
145 .Dv KERN_MAXPROCPERUID .
147 The user is not the super user, and
148 the soft resource limit corresponding to the
152 would be exceeded (see
155 Both the RFFDG and the RFCFDG flags were specified.
157 Any flags not listed above were specified.
159 There is insufficient swap space for the new process.
170 function first appeared in Plan9.
173 does not yet implement a native
175 library call, and the current pthreads implementation does not use
178 A native port of the linux threads library,
179 .Pa /usr/ports/devel/linuxthreads ,
182 call that utilizes RFMEM.
185 function can often be used instead of