This is assuan.info, produced by makeinfo version 4.6 from assuan.texi.

INFO-DIR-SECTION GNU Libraries
START-INFO-DIR-ENTRY
* Assuan: (assuan).        An IPC library for non-persistent servers.
END-INFO-DIR-ENTRY
   This file documents the use and the internals of Assuan.

   This is Edition 0.6.9, last updated 27 September 2004, of `The
`Developing with Assuan' Manual', for Version 0.6.9.

   Published by the Free Software Foundation
59 Temple Place - Suite 330
Boston, MA 02111-1307 USA

   Copyright (C) 2002, 2003 Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version. The text of the license can be found in the
section entitled "Copying".


File: assuan.info,  Node: Top,  Next: Introduction,  Up: (dir)

Introduction
************

This manual documents how to exploit the Assuan library, a simple
interprocess communcation library.

* Menu:

* Introduction::        An introduction to and the motivation behind Assuan.
* Assuan::              Description of the Assuan protocol.
* Implementation::      Overview of the implementation.

Miscellaneous

* Library Copying::     GNU Lesser General Public License says
                        how you can copy and share Assuan.
* Copying::             How you can copy and share this manual.

Indices

* Option Index::        Index to command line options.
* Index::	        Index of concepts and symbol names.


File: assuan.info,  Node: Introduction,  Next: Assuan,  Prev: Top,  Up: Top

Introduction to Assuan
**********************

In an ideal world, Assuan is irrelevant.  Assuan's primary use is to
allow a client to interact with a non-persistent server.  Using Assuan,
this is accomplished by forking a subprocess and communicating with it
via, for example, a pipe or unix domain socket.  This method is neither
elegant nor efficient especially when there is a lot of data spread
across several transactions: not only is there a penalty for an
increased number of context switches, but also a significant amount of
data is MEMCPYed from the client to a file descriptor and from the file
descriptor to the server.  Despite these and other disadvantages, this
type of client/server communication can be useful: the client is
completely separate from the server; they are in different address
spaces.  This is especially important in situations where the server
must have a known degree of reliability and data must be protected: as
the Assuan protocol is well defined and clients cannot corrupt the
servers' address space, auditing become much easier.

   Assuan was developed for use by the GNU Privacy Guard, GnuPG, to
prevent potentially buggy clients from unwittingly corrupting sensitive
transactions or compromising data such as a secret key.  Assuan permits
the servers, which do the actual work, e.g. encryption and decryption
of data using a secret key, to be developed independently of the user
interfaces, e.g. mail clients and other encryption front ends.  Like a
shared library, the interface is well defined and any number of front
ends can use it; however, unlike a shared library, the client cannot
see or touch the server's data.  As with any modular system, Assuan
helps keep the servers small and understandable help to make code more
understandable and less error prone.

   Assuan is not, however, limited to use with GnuPG servers and
clients: it was design to be flexible enough to meet the demands of
almost any transaction based environment with non-persistent servers.


File: assuan.info,  Node: Assuan,  Next: Implementation,  Prev: Introduction,  Up: Top

Description of the Assuan protocol.
***********************************

The architecture of the modular GnuPG system is based on several highly
specialized modules which compose a network of client/server
communication.  A common framework for intermodule communication is
therefore needed and should be implemented in a library.

   Goals:

   * Common framework for module communication

   * Easy debugging

   * Easy module testing

   * Extendible

   * Optional authentication and encryption facility

   * Usable by access external hardware

   Design criteria:

   * Client server with back channel

   * Use a mainly text based protocol

   * Escape certain control characters

   * Allow indefinite data length

   * Request confidentiality for parts of the communication

   * Dummy module to allow direct linking of client and server

   * Inline data or descriptor passing for bulk data

   * No protection against DoS needed

   * Subliminal channels are not an issue


File: assuan.info,  Node: Implementation,  Next: Library Copying,  Prev: Assuan,  Up: Top

Implementation
**************

The implementation is line based with a maximum line size of 1000
octects.  The default IPC mechanism are Unix Domain Sockets.

   On a connect request the server responds either with an okay or an
error status.  For authentication check the server may send an Inquiry
Response prior to the first Okay, it may also issue Status messages.
The server must check that the client is allowed to connect, this is
done by requesting the credentials for the peer and comparing them to
those of the server.  This avoids attacks based on wrong socket
permissions.

   It may choose to delay the first response in case of an error.  The
server never closes the connection - however the lower protocol may do
so after some time of inactivity or when the connection is in an error
state.

   All textual messages are assumed to be in UTF-8 unless otherwise
noted.

* Menu:

* Server responses::    Description of server responses.
* Client requests::     Description of client requests.
* Error codes::         List of error and status codes.


File: assuan.info,  Node: Server responses,  Next: Client requests,  Up: Implementation

Server responses
================

`OK  [<arbitary debugging information>]'
     Request was successful.

`ERR ERRORCODE [<human readable error description>]'
     Request could not be fulfilled.  The error codes are mostly
     application specific except for a few common ones.

`S KEYWORD <status information depending on keyword>'
     Informational output by the server, still processing the request.

`# <string>'
     Comment line issued only for debugging purposes.  Totally ignored.

`D <raw data>'
     Raw data returned to client. There must be exactly one space after
     the 'D'.  The values for '%', CR and LF must be percent escaped;
     this is encoded as %25, %0D and %0A.  Only uppercase letters
     should be used in the hexadecimal representation.  Other
     characters may be percent escaped for easier debugging.  All these
     Data lines are considered one data stream up to the OK or ERR
     response.  Status and Inquiry Responses may be mixed with the Data
     lines.

`INQUIRE KEYWORD> <parameters>'
     Server needs further information from the client.  The client
     should answer with a command which is allowed after an inquiry.
     Note that the server does not confirm that client command but
     either continues processing or ends processing with an error
     status.  Not all commands are allowed.

   A client should only check the first letter of each line and then
skip over to the next token (except for data lines where the raw data
starts exactly after 2 bytes).  Lines larger than 1000 bytes should be
treated as a communication error. (The rationale for having a line
length limit is to allow for easier multiplexing of multiple channels).


File: assuan.info,  Node: Client requests,  Next: Error codes,  Prev: Server responses,  Up: Implementation

Client requests
===============

The server waits for client requests after he sent an Okay or Error.
The client should not issue a request in other cases.

     COMMAND <parameters>

   COMMAND is a one word string without preceding white space.
Parameters are command specific, CR, LF and the percent signs should be
percent escaped as described above.  To send a backslash as the last
character it should also be percent escaped.  Percent escaping is
allowed anywhere in the parameters but not in the command.  The line
ends with a CR, LF or just a LF.

   Not yet implemented feature: If there is a need for a parameter list
longer than the line length limit (1000 characters including command and
CR, LF), the last character of the line (right before the CR/LF or LF)
must be a non-escape encoded backslash. The following line is then
expected to be a continuation of the line with the backslash replaced by
a blank and the line ending removed.

     D <raw data>

   Raw data to the server. There must be exactly one space after the
'D'.  The values for '%', CR and LF must be percent escaped; this is
encoded as %25, %0D and %0A.  Only uppercase letters should be used in
the hexadecimal representation.  Other characters may be percent
escaped for easier debugging.  All these Data lines are considered one
data stream up to the OKAY or ERROR response.  Status and Inquiry
Responses may be mixed with the Data lines.

     END

   Lines beginning with a `#' or empty lines are ignored.  This is
useful to comment test scripts.

   Although the commands are application specific, some of them are
used by all protocols and partly directly supported by the Assuan
library:

`CANCEL'
     This command is used for future extenxions.  It may today be used
     to cancel outstanding requests in an asynchronous protocol.

`BYE'
     Close the connect, the server will reply with an `OK'.

`AUTH'
     Not yet specified as we don't implement it in the first phase.
     See my mail to gpa-dev on 2001-10-25 about the rationale for
     measurements against local attacks.

`RESET'
     Reset the connection but not any existing authentication.  The
     server should release all resources associated with the connection.

`END'
     Used by a client to mark the end of raw data.  The server may send
     END to indicate a partial end of data.

`HELP'
     Reserved for future extensions.

`QUIT'
     Reserved for future extensions.



File: assuan.info,  Node: Error codes,  Prev: Client requests,  Up: Implementation

Error codes
===========

Here we keep a list of error codes used in any Assuan based protocol.
The format is the string `ERR', white space, the error number, white
space, a textual description of the error.

   General error codes pertaining to the actual Assuan operations:

`0  Success'

`1  General error'

`2  Out of core'

`3  Invalid value'

`4  Timeout'

`5  Read error'

`6  Write error'

`7  Problem starting server'

`8  Not a server'

`9  Not a client'

`10 Nested commands'

`11 Invalid response'

`12 No data callback'

`13 No inquire callback'

`14 Connect failed'

`15 Accept failed'

   Error codes used as status codes in the Assuan protocol:

`100 Not implemented'

`101 Server fault (catch all error code)'

`102 Invalid command'

`103 Unknown command'

`104 Syntax error'

`105 Parameter error'

`106 Parameter conflict'

`107 Line too long'

`108 Line not terminated'

`109 No input'

`110 No output'

`111 Canceled'

`112 Unsupported algorithm'

`113 Server resource problem'

`114 Server I/O error'

`115 Server bug'

`116 No data available'

`117 Invalid data'

`118 Unexpected command'

`119 Too much data'

`120 Inquire unknown'

`121 Inquire error'

`122 Invalid option'

`123 Invalid index'

`124 Unexpected status'

`125 Unexpected data'

`126 Invalid status'

`128 Not confirmed'

   For historical reasons a few more error codes are defined in
`assuan.h'; they should not be used be new applications.

   Errror codes in the range ASSUAN_USER_ERROR_FIRST to
ASSUAN_USER_ERROR_LAST may be used at the applications own discretion.
Error codes greater than 65535 are not defined by Assuan and may also
be used by applications -- note that the GnuPG system maps libgpg-error
codes into this range.


File: assuan.info,  Node: Library Copying,  Next: Copying,  Prev: Implementation,  Up: Top

GNU LESSER GENERAL PUBLIC LICENSE
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     under any particular circumstance, the balance of the section is
     intended to apply, and the section as a whole is intended to apply
     in other circumstances.

     It is not the purpose of this section to induce you to infringe any
     patents or other property right claims or to contest validity of
     any such claims; this section has the sole purpose of protecting
     the integrity of the free software distribution system which is
     implemented by public license practices.  Many people have made
     generous contributions to the wide range of software distributed
     through that system in reliance on consistent application of that
     system; it is up to the author/donor to decide if he or she is
     willing to distribute software through any other system and a
     licensee cannot impose that choice.

     This section is intended to make thoroughly clear what is believed
     to be a consequence of the rest of this License.

 12. If the distribution and/or use of the Library is restricted in
     certain countries either by patents or by copyrighted interfaces,
     the original copyright holder who places the Library under this
     License may add an explicit geographical distribution limitation
     excluding those countries, so that distribution is permitted only
     in or among countries not thus excluded.  In such case, this
     License incorporates the limitation as if written in the body of
     this License.

 13. The Free Software Foundation may publish revised and/or new
     versions of the Lesser General Public License from time to time.
     Such new versions will be similar in spirit to the present version,
     but may differ in detail to address new problems or concerns.

     Each version is given a distinguishing version number.  If the
     Library specifies a version number of this License which applies
     to it and "any later version", you have the option of following
     the terms and conditions either of that version or of any later
     version published by the Free Software Foundation.  If the Library
     does not specify a license version number, you may choose any
     version ever published by the Free Software Foundation.

 14. If you wish to incorporate parts of the Library into other free
     programs whose distribution conditions are incompatible with these,
     write to the author to ask for permission.  For software which is
     copyrighted by the Free Software Foundation, write to the Free
     Software Foundation; we sometimes make exceptions for this.  Our
     decision will be guided by the two goals of preserving the free
     status of all derivatives of our free software and of promoting
     the sharing and reuse of software generally.

                                NO WARRANTY

 15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO
     WARRANTY FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE
     LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
     HOLDERS AND/OR OTHER PARTIES PROVIDE THE LIBRARY "AS IS" WITHOUT
     WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT
     NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
     FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS TO THE
     QUALITY AND PERFORMANCE OF THE LIBRARY IS WITH YOU.  SHOULD THE
     LIBRARY PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY
     SERVICING, REPAIR OR CORRECTION.

 16. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY
     MODIFY AND/OR REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE
     LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL,
     INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR
     INABILITY TO USE THE LIBRARY (INCLUDING BUT NOT LIMITED TO LOSS OF
     DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU
     OR THIRD PARTIES OR A FAILURE OF THE LIBRARY TO OPERATE WITH ANY
     OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN
     ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

                      END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Libraries
----------------------------------------------

If you develop a new library, and you want it to be of the greatest
possible use to the public, we recommend making it free software that
everyone can redistribute and change.  You can do so by permitting
redistribution under these terms (or, alternatively, under the terms of
the ordinary General Public License).

   To apply these terms, attach the following notices to the library.
It is safest to attach them to the start of each source file to most
effectively convey the exclusion of warranty; and each file should have
at least the "copyright" line and a pointer to where the full notice is
found.

     ONE LINE TO GIVE THE LIBRARY'S NAME AND AN IDEA OF WHAT IT DOES.
     Copyright (C) YEAR  NAME OF AUTHOR
     
     This library is free software; you can redistribute it and/or modify it
     under the terms of the GNU Lesser General Public License as published by
     the Free Software Foundation; either version 2.1 of the License, or (at
     your option) any later version.
     
     This library is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.
     
     You should have received a copy of the GNU Lesser General Public
     License along with this library; if not, write to the Free Software
     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307,
     USA.

   Also add information on how to contact you by electronic and paper
mail.

   You should also get your employer (if you work as a programmer) or
your school, if any, to sign a "copyright disclaimer" for the library,
if necessary.  Here is a sample; alter the names:

     Yoyodyne, Inc., hereby disclaims all copyright interest in the library
     `Frob' (a library for tweaking knobs) written by James Random Hacker.
     
     SIGNATURE OF TY COON, 1 April 1990
     Ty Coon, President of Vice

   That's all there is to it!


File: assuan.info,  Node: Copying,  Next: Option Index,  Prev: Library Copying,  Up: Top

GNU GENERAL PUBLIC LICENSE
**************************

                         Version 2, June 1991
     Copyright (C) 1989, 1991 Free Software Foundation, Inc.
     59 Temple Place -- Suite 330, Boston, MA 02111-1307, USA
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

Preamble
--------

The licenses for most software are designed to take away your freedom
to share and change it.  By contrast, the GNU General Public License is
intended to guarantee your freedom to share and change free
software--to make sure the software is free for all its users.  This
General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to
using it.  (Some other Free Software Foundation software is covered by
the GNU Library General Public License instead.)  You can apply it to
your programs, too.

   When we speak of free software, we are referring to freedom, not
price.  Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish), that you receive source code or can get it
if you want it, that you can change the software or use pieces of it in
new free programs; and that you know you can do these things.

   To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.

   For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have.  You must make sure that they, too, receive or can get the
source code.  And you must show them these terms so they know their
rights.

   We protect your rights with two steps: (1) copyright the software,
and (2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

   Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software.  If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.

   Finally, any free program is threatened constantly by software
patents.  We wish to avoid the danger that redistributors of a free
program will individually obtain patent licenses, in effect making the
program proprietary.  To prevent this, we have made it clear that any
patent must be licensed for everyone's free use or not licensed at all.

   The precise terms and conditions for copying, distribution and
modification follow.

    TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
  1. This License applies to any program or other work which contains a
     notice placed by the copyright holder saying it may be distributed
     under the terms of this General Public License.  The "Program",
     below, refers to any such program or work, and a "work based on
     the Program" means either the Program or any derivative work under
     copyright law: that is to say, a work containing the Program or a
     portion of it, either verbatim or with modifications and/or
     translated into another language.  (Hereinafter, translation is
     included without limitation in the term "modification".)  Each
     licensee is addressed as "you".

     Activities other than copying, distribution and modification are
     not covered by this License; they are outside its scope.  The act
     of running the Program is not restricted, and the output from the
     Program is covered only if its contents constitute a work based on
     the Program (independent of having been made by running the
     Program).  Whether that is true depends on what the Program does.

  2. You may copy and distribute verbatim copies of the Program's
     source code as you receive it, in any medium, provided that you
     conspicuously and appropriately publish on each copy an appropriate
     copyright notice and disclaimer of warranty; keep intact all the
     notices that refer to this License and to the absence of any
     warranty; and give any other recipients of the Program a copy of
     this License along with the Program.

     You may charge a fee for the physical act of transferring a copy,
     and you may at your option offer warranty protection in exchange
     for a fee.

  3. You may modify your copy or copies of the Program or any portion
     of it, thus forming a work based on the Program, and copy and
     distribute such modifications or work under the terms of Section 1
     above, provided that you also meet all of these conditions:

       a. You must cause the modified files to carry prominent notices
          stating that you changed the files and the date of any change.

       b. You must cause any work that you distribute or publish, that
          in whole or in part contains or is derived from the Program
          or any part thereof, to be licensed as a whole at no charge
          to all third parties under the terms of this License.

       c. If the modified program normally reads commands interactively
          when run, you must cause it, when started running for such
          interactive use in the most ordinary way, to print or display
          an announcement including an appropriate copyright notice and
          a notice that there is no warranty (or else, saying that you
          provide a warranty) and that users may redistribute the
          program under these conditions, and telling the user how to
          view a copy of this License.  (Exception: if the Program
          itself is interactive but does not normally print such an
          announcement, your work based on the Program is not required
          to print an announcement.)

     These requirements apply to the modified work as a whole.  If
     identifiable sections of that work are not derived from the
     Program, and can be reasonably considered independent and separate
     works in themselves, then this License, and its terms, do not
     apply to those sections when you distribute them as separate
     works.  But when you distribute the same sections as part of a
     whole which is a work based on the Program, the distribution of
     the whole must be on the terms of this License, whose permissions
     for other licensees extend to the entire whole, and thus to each
     and every part regardless of who wrote it.

     Thus, it is not the intent of this section to claim rights or
     contest your rights to work written entirely by you; rather, the
     intent is to exercise the right to control the distribution of
     derivative or collective works based on the Program.

     In addition, mere aggregation of another work not based on the
     Program with the Program (or with a work based on the Program) on
     a volume of a storage or distribution medium does not bring the
     other work under the scope of this License.

  4. You may copy and distribute the Program (or a work based on it,
     under Section 2) in object code or executable form under the terms
     of Sections 1 and 2 above provided that you also do one of the
     following:

       a. Accompany it with the complete corresponding machine-readable
          source code, which must be distributed under the terms of
          Sections 1 and 2 above on a medium customarily used for
          software interchange; or,

       b. Accompany it with a written offer, valid for at least three
          years, to give any third party, for a charge no more than your
          cost of physically performing source distribution, a complete
          machine-readable copy of the corresponding source code, to be
          distributed under the terms of Sections 1 and 2 above on a
          medium customarily used for software interchange; or,

       c. Accompany it with the information you received as to the offer
          to distribute corresponding source code.  (This alternative is
          allowed only for noncommercial distribution and only if you
          received the program in object code or executable form with
          such an offer, in accord with Subsection b above.)

     The source code for a work means the preferred form of the work for
     making modifications to it.  For an executable work, complete
     source code means all the source code for all modules it contains,
     plus any associated interface definition files, plus the scripts
     used to control compilation and installation of the executable.
     However, as a special exception, the source code distributed need
     not include anything that is normally distributed (in either
     source or binary form) with the major components (compiler,
     kernel, and so on) of the operating system on which the executable
     runs, unless that component itself accompanies the executable.

     If distribution of executable or object code is made by offering
     access to copy from a designated place, then offering equivalent
     access to copy the source code from the same place counts as
     distribution of the source code, even though third parties are not
     compelled to copy the source along with the object code.

  5. You may not copy, modify, sublicense, or distribute the Program
     except as expressly provided under this License.  Any attempt
     otherwise to copy, modify, sublicense or distribute the Program is
     void, and will automatically terminate your rights under this
     License.  However, parties who have received copies, or rights,
     from you under this License will not have their licenses
     terminated so long as such parties remain in full compliance.

  6. You are not required to accept this License, since you have not
     signed it.  However, nothing else grants you permission to modify
     or distribute the Program or its derivative works.  These actions
     are prohibited by law if you do not accept this License.
     Therefore, by modifying or distributing the Program (or any work
     based on the Program), you indicate your acceptance of this
     License to do so, and all its terms and conditions for copying,
     distributing or modifying the Program or works based on it.

  7. Each time you redistribute the Program (or any work based on the
     Program), the recipient automatically receives a license from the
     original licensor to copy, distribute or modify the Program
     subject to these terms and conditions.  You may not impose any
     further restrictions on the recipients' exercise of the rights
     granted herein.  You are not responsible for enforcing compliance
     by third parties to this License.

  8. If, as a consequence of a court judgment or allegation of patent
     infringement or for any other reason (not limited to patent
     issues), conditions are imposed on you (whether by court order,
     agreement or otherwise) that contradict the conditions of this
     License, they do not excuse you from the conditions of this
     License.  If you cannot distribute so as to satisfy simultaneously
     your obligations under this License and any other pertinent
     obligations, then as a consequence you may not distribute the
     Program at all.  For example, if a patent license would not permit
     royalty-free redistribution of the Program by all those who
     receive copies directly or indirectly through you, then the only
     way you could satisfy both it and this License would be to refrain
     entirely from distribution of the Program.

     If any portion of this section is held invalid or unenforceable
     under any particular circumstance, the balance of the section is
     intended to apply and the section as a whole is intended to apply
     in other circumstances.

     It is not the purpose of this section to induce you to infringe any
     patents or other property right claims or to contest validity of
     any such claims; this section has the sole purpose of protecting
     the integrity of the free software distribution system, which is
     implemented by public license practices.  Many people have made
     generous contributions to the wide range of software distributed
     through that system in reliance on consistent application of that
     system; it is up to the author/donor to decide if he or she is
     willing to distribute software through any other system and a
     licensee cannot impose that choice.

     This section is intended to make thoroughly clear what is believed
     to be a consequence of the rest of this License.

  9. If the distribution and/or use of the Program is restricted in
     certain countries either by patents or by copyrighted interfaces,
     the original copyright holder who places the Program under this
     License may add an explicit geographical distribution limitation
     excluding those countries, so that distribution is permitted only
     in or among countries not thus excluded.  In such case, this
     License incorporates the limitation as if written in the body of
     this License.

 10. The Free Software Foundation may publish revised and/or new
     versions of the General Public License from time to time.  Such
     new versions will be similar in spirit to the present version, but
     may differ in detail to address new problems or concerns.

     Each version is given a distinguishing version number.  If the
     Program specifies a version number of this License which applies
     to it and "any later version", you have the option of following
     the terms and conditions either of that version or of any later
     version published by the Free Software Foundation.  If the Program
     does not specify a version number of this License, you may choose
     any version ever published by the Free Software Foundation.

 11. If you wish to incorporate parts of the Program into other free
     programs whose distribution conditions are different, write to the
     author to ask for permission.  For software which is copyrighted
     by the Free Software Foundation, write to the Free Software
     Foundation; we sometimes make exceptions for this.  Our decision
     will be guided by the two goals of preserving the free status of
     all derivatives of our free software and of promoting the sharing
     and reuse of software generally.

                                NO WARRANTY

 12. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO
     WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE
     LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
     HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT
     WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT
     NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
     FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS TO THE
     QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
     PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY
     SERVICING, REPAIR OR CORRECTION.

 13. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY
     MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE
     LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL,
     INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR
     INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
     DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU
     OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY
     OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN
     ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

                      END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs
=============================================

If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.

   To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.

     ONE LINE TO GIVE THE PROGRAM'S NAME AND AN IDEA OF WHAT IT DOES.
     Copyright (C) 19YY  NAME OF AUTHOR
     
     This program is free software; you can redistribute it and/or
     modify it under the terms of the GNU General Public License
     as published by the Free Software Foundation; either version 2
     of the License, or (at your option) any later version.
     
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
     
     You should have received a copy of the GNU General Public License along
     with this program; if not, write to the Free Software Foundation, Inc.,
     59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.

   Also add information on how to contact you by electronic and paper
mail.

   If the program is interactive, make it output a short notice like
this when it starts in an interactive mode:

     Gnomovision version 69, Copyright (C) 19YY NAME OF AUTHOR
     Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
     type `show w'.  This is free software, and you are welcome
     to redistribute it under certain conditions; type `show c'
     for details.

   The hypothetical commands `show w' and `show c' should show the
appropriate parts of the General Public License.  Of course, the
commands you use may be called something other than `show w' and `show
c'; they could even be mouse-clicks or menu items--whatever suits your
program.

   You should also get your employer (if you work as a programmer) or
your school, if any, to sign a "copyright disclaimer" for the program,
if necessary.  Here is a sample; alter the names:

     Yoyodyne, Inc., hereby disclaims all copyright
     interest in the program `Gnomovision'
     (which makes passes at compilers) written
     by James Hacker.
     
     SIGNATURE OF TY COON, 1 April 1989
     Ty Coon, President of Vice

   This General Public License does not permit incorporating your
program into proprietary programs.  If your program is a subroutine
library, you may consider it more useful to permit linking proprietary
applications with the library.  If this is what you want to do, use the
GNU Library General Public License instead of this License.


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************

* Menu:

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*****

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Tag Table:
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