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>.
6 .\" $FreeBSD: src/lib/libc/sys/rfork.2,v 1.11.2.11 2002/07/30 19:04:25 silby Exp $
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),
35 is the logical OR of some subset of:
36 .Bl -tag -width "RFCNAMEG" -compact -offset indent
38 If set a new process is created; otherwise changes affect the
40 The current implementation requires this flag to always be set.
42 If set, the child process will be dissociated from the parent.
44 exit the child will not leave a status for the parent to collect.
48 If set, the invoker's file descriptor table (see
50 is copied; otherwise the two processes share a
53 If set, the new process starts with a clean file descriptor table.
54 Is mutually exclusive with
57 If set, the kernel will force sharing of the entire address space,
58 typically by sharing the hardware page table directly.
60 will thus inherit and share all the segments the parent process owns,
61 whether they are normally shareable or not. The stack segment is
62 not split (both the parent and child return on the same stack) and thus
64 with the RFMEM flag may not generally be called directly from high level
65 languages including C.
68 A helper function is provided to assist with this problem and will cause
69 the new process to run on the provided stack. See
73 If set, the kernel will force sharing the sigacts structure between the
76 If set, the kernel will return SIGUSR1 instead of SIGCHILD upon thread
77 exit for the child. This is intended to mimic certain Linux clone behaviour.
80 File descriptors in a shared file descriptor table are kept
81 open until either they are explicitly closed
82 or all processes sharing the table exit.
87 value returned in the parent process
89 of the child process; the value returned in the child is zero.
92 the return value is zero.
93 Process id's range from 1 to the maximum integer
97 will sleep, if necessary, until required process resources are available.
100 can be implemented as a call to
101 .Fn rfork "RFFDG | RFPROC"
102 but isn't for backwards compatibility.
104 Upon successful completion,
107 of 0 to the child process and returns the process ID of the child
108 process to the parent process. Otherwise, a value of -1 is returned
109 to the parent process, no child process is created, and the global
112 is set to indicate the error.
115 will fail and no child process will be created if:
118 The system-imposed limit on the total
119 number of processes under execution would be exceeded.
120 The limit is given by the
124 (The limit is actually ten less than this
125 except for the super user).
127 The user is not the super user, and
128 the system-imposed limit
129 on the total number of
130 processes under execution by a single user would be exceeded.
131 The limit is given by the
134 .Dv KERN_MAXPROCPERUID .
136 The user is not the super user, and
137 the soft resource limit corresponding to the resource parameter
139 would be exceeded (see
142 The RFPROC flag was not specified.
144 Both the RFFDG and the RFCFDG flags were specified.
146 There is insufficient swap space for the new process.
156 does not yet implement a native
158 library call, and the current pthreads implementation does not use
160 with RFMEM. A native port of the linux threads library,
161 .Pa /usr/ports/devel/linuxthreads ,
164 call that utilizes RFMEM.
167 library call can often be used instead of
172 function call first appeared in Plan9.