RFORK(3) RFORK(3)
NAME
rfork - manipulate process state
SYNOPSIS
#include <u.h>
#include <libc.h>
int rfork(int flags)
DESCRIPTION
Rfork is a partial implementation of the Plan 9 system call.
It can be used to manipulate some process state and to cre-
ate new processes a la fork(2). It cannot be used to create
shared-memory processes (Plan 9's RFMEM flag); for that
functionality use proccreate (see thread(3)).
The flags argument to rfork selects which resources of the
invoking process (parent) are shared by the new process
(child) or initialized to their default values. Flags is
the logical OR of some subset of
RFPROC If set a new process is created; otherwise changes
affect the current process.
RFNOWAIT If set, the child process will be dissociated from
the parent. Upon exit the child will leave no
Waitmsg (see wait(3)) for the parent to collect.
RFNOTEG Each process is a member of a group of processes
that all receive notes when a note is sent to the
group (see postnote(3) and signal(2)). The group
of a new process is by default the same as its
parent, but if RFNOTEG is set (regardless of
RFPROC), the process becomes the first in a new
group, isolated from previous processes. In Plan
9, a process can call rfork(RFNOTEG) and then be
sure that it will no longer receive console inter-
rupts or other notes. Unix job-control shells put
each command in its own process group and then
relay notes to the current foreground command,
making the idiom less useful.
RFFDG If set, the invoker's file descriptor table (see
intro()) is copied; otherwise the two processes
share a single table.
File descriptors in a shared file descriptor table are kept
open until either they are explicitly closed or all pro-
cesses sharing the table exit.
If 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 RFPROC, the return value is
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RFORK(3) RFORK(3)
zero. Process ids range from 1 to the maximum integer (int)
value. Rfork will sleep, if necessary, until required pro-
cess resources are available.
Calling rfork(RFFDG|RFPROC) is equivalent to calling
fork(2).
SOURCE
/usr/local/plan9/src/lib9/rfork.c
DIAGNOSTICS
Rfork sets errstr.
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