Process Creation and Execution Manager
######################################

Introduction
============

The process creation and execution manager provides the
functionality associated with the creation and termination
of processes.

The directives provided by the process creation and execution manager are:

- ``fork`` - Create a Process

- ``execl`` - Execute a File

- ``execv`` - Execute a File

- ``execle`` - Execute a File

- ``execve`` - Execute a File

- ``execlp`` - Execute a File

- ``execvp`` - Execute a File

- ``pthread_atfork`` - Register Fork Handlers

- ``wait`` - Wait for Process Termination

- ``waitpid`` - Wait for Process Termination

- ``_exit`` - Terminate a Process

Background
==========

POSIX process functionality can not be completely
supported by RTEMS.  This is because RTEMS provides no memory
protection and implements a *single process, multi-threaded
execution model*.  In this light, RTEMS provides none of the
routines that are associated with the creation of new processes.
However, since the entire RTEMS application (e.g. executable)
is logically a single POSIX process, RTEMS is able to provide
implementations of many operations on processes.  The rule of
thumb is that those routines provide a meaningful result.
For example, ``getpid()`` returns the node number.

Operations
==========

The only functionality method defined by this manager which is
supported by RTEMS is the ``_exit`` service.  The
implementation of ``_exit`` shuts the application down and
is equivalent to invoking either ``exit`` or``rtems_shutdown_executive``.

Directives
==========

This section details the process creation and execution manager's directives.
A subsection is dedicated to each of this manager's directives
and describes the calling sequence, related constants, usage,
and status codes.

fork - Create a Process
-----------------------
.. index:: fork
.. index:: create a process

**CALLING SEQUENCE:**

.. code:: c

    #include <sys/types.h>
    int fork( void );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

execl - Execute a File
----------------------
.. index:: execl
.. index:: execute a file

**CALLING SEQUENCE:**

.. code:: c

    int execl(
    const char \*path,
    const char \*arg,
    ...
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

execv - Execute a File
----------------------
.. index:: execv
.. index:: execute a file

**CALLING SEQUENCE:**

.. code:: c

    int execv(
    const char \*path,
    char const \*argv[],
    ...
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

execle - Execute a File
-----------------------
.. index:: execle
.. index:: execute a file

**CALLING SEQUENCE:**

.. code:: c

    int execle(
    const char \*path,
    const char \*arg,
    ...
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

execve - Execute a File
-----------------------
.. index:: execve
.. index:: execute a file

**CALLING SEQUENCE:**

.. code:: c

    int execve(
    const char \*path,
    char \*const argv[],
    char \*const envp[]
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

execlp - Execute a File
-----------------------
.. index:: execlp
.. index:: execute a file

**CALLING SEQUENCE:**

.. code:: c

    int execlp(
    const char \*file,
    const char \*arg,
    ...
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

execvp - Execute a File
-----------------------
.. index:: execvp
.. index:: execute a file

**CALLING SEQUENCE:**

.. code:: c

    int execvp(
    const char \*file,
    char \*const argv[]
    ...
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

pthread_atfork - Register Fork Handlers
---------------------------------------
.. index:: pthread_atfork
.. index:: register fork handlers

**CALLING SEQUENCE:**

.. code:: c

    #include <sys/types.h>
    int pthread_atfork(
    void (\*prepare)(void),
    void (\*parent)(void),
    void (\*child)(void)
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

wait - Wait for Process Termination
-----------------------------------
.. index:: wait
.. index:: wait for process termination

**CALLING SEQUENCE:**

.. code:: c

    #include <sys/types.h>
    #include <sys/wait.h>
    int wait(
    int \*stat_loc
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

waitpid - Wait for Process Termination
--------------------------------------
.. index:: waitpid
.. index:: wait for process termination

**CALLING SEQUENCE:**

.. code:: c

    int wait(
    pid_t  pid,
    int   \*stat_loc,
    int    options
    );

**STATUS CODES:**

*ENOSYS*
    This routine is not supported by RTEMS.

**DESCRIPTION:**

This routine is not supported by RTEMS.

**NOTES:**

NONE

_exit - Terminate a Process
---------------------------
.. index:: _exit
.. index:: terminate a process

**CALLING SEQUENCE:**

.. code:: c

    void _exit(
    int status
    );

**STATUS CODES:**

NONE

**DESCRIPTION:**

The ``_exit()`` function terminates the calling process.

**NOTES:**

In RTEMS, a process is equivalent to the entire application on a single
processor. Invoking this service terminates the application.

.. COMMENT: COPYRIGHT (c) 1988-2002.

.. COMMENT: On-Line Applications Research Corporation (OAR).

.. COMMENT: All rights reserved.