.\" .\" This manual page is taken directly from Plan9, and modified to .\" describe the actual OpenBSD implimentation. Permission for .\" use of this page comes from Rob Pike <rob@plan9.att.com>. .\" .Dd Jan 12, 1996 .Dt RFORK 2 .Os .Sh NAME .Nm rfork .Nd manipulate process resources .Sh SYNOPSIS .Fd #include <sys/param.h> .Fd #include <unistd.h> .Ft int .Fn rfork "int flags" .Sh DESCRIPTION Forking, vforking or rforking is the only way new processes are created. The .Fa flags argument to .Fn rfork selects which resources of the invoking process (parent) are shared by the new process (child) or initialized to their default values. The resources include the open file descriptor table (which, when shared, permits processes to open and close files for other processes), and open files. .Fa Flags is the logical OR of some subset of .Bl -tag -width "RFCNAMEG" -compact -offset indent .It RFPROC If set a new process is created; otherwise changes affect the current process. The current implementation requires this flag to always be set. .It RFNOWAIT If set, the child process will be dissociated from the parent. Upon exit the child will not leave a status for the parent to collect. See .Xr wait 2 . This is not currently implemented. .It RFNAMEG, RFCNAMEG, RFENVG, RFCENVG, RFNOTEG These are Plan 9 specific flags, and not implimented. .It RFFDG If set, the invoker's file descriptor table (see .Xr intro 2 ) is copied; otherwise the two processes share a single table. .It RFCFDG If set, the new process starts with a clean file descriptor table. Is mutually exclusive with .Dv RFFDG . .It RFMEM If set, the kernel will force sharing of the entire address space. The child will then inherit all the shared segments the parent process owns. Other segment types will be unaffected. Subsequent forks by the parent will then propagate the shared data and bss between children. The stack segment is always split. May be set only with .Dv RFPROC . .El .Pp File descriptors in a shared file descriptor table are kept open until either they are explicitly closed or all processes sharing the table exit. .Pp If .Dv RFPROC is set, the value returned in the parent process is the process id of the child process; the value returned in the child is zero. Without .Dv RFPROC , the return value is zero. Process ids range from 1 to the maximum integer .Ft ( int ) value. .Fn Rfork will sleep, if necessary, until required process resources are available. .Pp .Fn Fork can be implemented as a call to .Xr rfork "RFFDG|RFPROC" but isn't for backwards compatibility. .Sh ERRORS .Fn Rfork will fail and no child process will be created if: .Bl -tag -width Er .It Bq Er EAGAIN The system-imposed limit on the total number of processes under execution would be exceeded. This limit is configuration-dependent. .It Bq Er EAGAIN The system-imposed limit .Dv MAXUPRC .Pq Aq Pa sys/param.h on the total number of processes under execution by a single user would be exceeded. .It Bq Er ENOMEM There is insufficient swap space for the new process. .El .Sh SEE ALSO .Xr intro 2 , .Xr fork 2 , .Xr vfork 2 , .Xr minherit 2 .Sh HISTORY The .Fn rfork function first appeared in Plan9.