2 .\" This manual page is taken directly from Plan 9, 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 $
7 .\" $DragonFly: src/lib/libc/sys/rfork.2,v 1.5 2006/03/22 10:18:47 swildner Exp $
14 .Nd manipulate process resources
22 Forking, vforking or rforking are the only ways new processes are created.
27 selects which resources of the
28 invoking process (parent) are shared
29 by the new process (child) or initialized to
32 the open file descriptor table (which, when shared, permits processes
33 to open and close files for other processes),
36 is the logical OR of some subset of:
37 .Bl -tag -width "RFCNAMEG" -compact -offset indent
39 If set a new process is created; otherwise changes affect the
41 The current implementation requires this flag to always be set.
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. The stack segment is
63 not split (both the parent and child return on the same stack) and thus
65 with the RFMEM flag may not generally be called directly from high level
66 languages including C.
69 A helper function is provided to assist with this problem and will cause
70 the new process to run on the provided stack. See
74 If set, the kernel will force sharing the sigacts structure between the
77 If set, the kernel will return SIGUSR1 instead of SIGCHILD upon thread
78 exit for the child. This is intended to mimic certain Linux clone behaviour.
81 File descriptors in a shared file descriptor table are kept
82 open until either they are explicitly closed
83 or all processes sharing the table exit.
88 value returned in the parent process
90 of the child process; the value returned in the child is zero.
93 the return value is zero.
94 Process id's range from 1 to the maximum integer
98 will sleep, if necessary, until required process resources are available.
101 can be implemented as a call to
102 .Fn rfork "RFFDG | RFPROC"
103 but isn't for backwards compatibility.
105 Upon successful completion,
108 of 0 to the child process and returns the process ID of the child
109 process to the parent process. Otherwise, a value of -1 is returned
110 to the parent process, no child process is created, and the global
113 is set to indicate the error.
116 will fail and no child process will be created if:
119 The system-imposed limit on the total
120 number of processes under execution would be exceeded.
121 The limit is given by the
125 (The limit is actually ten less than this
126 except for the super user).
128 The user is not the super user, and
129 the system-imposed limit
130 on the total number of
131 processes under execution by a single user would be exceeded.
132 The limit is given by the
135 .Dv KERN_MAXPROCPERUID .
137 The user is not the super user, and
138 the soft resource limit corresponding to the resource parameter
140 would be exceeded (see
143 The RFPROC flag was not specified.
145 Both the RFFDG and the RFCFDG flags were specified.
147 There is insufficient swap space for the new process.
158 function call first appeared in Plan 9.
161 does not yet implement a native
163 library call, and the current pthreads implementation does not use
165 with RFMEM. A native port of the linux threads library,
166 .Pa /usr/ports/devel/linuxthreads ,
169 call that utilizes RFMEM.
172 library call can often be used instead of