man(1) Manual page archive

     FORK(2)                                                   FORK(2)

          fork, rfork - manipulate process resources

          int fork(void)

          int rfork(int flags)

          Forking is the only way new processes are created.  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.  The
          resources include the file name space, the open file
          descriptor table (which, when shared, permits processes to
          open and close files for other processes), the set of envi-
          ronment variables (see env(3)), the note group (the set of
          processes that receive notes written to a member's notepg
          file; see proc(3)), and open files.  Flags is the logical OR
          of some subset of 336168.if 432.sp40u
               If set a new process is created; otherwise changes
               affect the current process.  360192.if 456.sp40u
               If set, the new process inherits a copy of the parent's
               name space; otherwise the new process shares the
               parent's name space.  Is mutually exclusive with

               If set, the child process will be disassociated from
               the parent. Upon exit the child will leave no Waitmsg
               (see wait(2)) for the parent to collect.

               If set, the new process starts with a clean name space.
               A new name space must be built from a mount of an open
               file descriptor.  Is mutually exclusive with RFNAMEG.

               If set, the environment variables are copied; otherwise
               the two processes share environment variables.  Is
               mutually exclusive with RFCENVG.

               If set, the new process starts with an empty environ-
               ment.  Is mutually exclusive with RFENVG.

               Each process is a member of a group of processes that

     FORK(2)                                                   FORK(2)

               all receive notes when a note is written to any of
               their notepg files (see proc(3)). 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 previ-
               ous processes.

               If set, the invoker's file descriptor table (see
               intro(2)) is copied; otherwise the two processes share
               a single table.

               If set, the new process starts with a clean file
               descriptor table.  Is mutually exclusive with RFCFDG.

               If set, the kernel will mark segments of type data and
               bss as shared. The child will then inherit all the
               shared segments the parent process owns. Other segment
               types will be unaffected.  Subsequent forks by the par-
               ent will then propagate the shared data and bss between
               children.  The stack segment is always split.  May be
               set only with RFPROC.

          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
          zero.  Process ids range from 1 to the maximum integer (int)
          value.  Rfork will sleep, if necessary, until required pro-
          cess resources are available.

          Fork is just a call of rfork(RFFDG|RFPROC).

          intro(2), proc(3),

          These functions set errstr.