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-rw-r--r--doc/man/bus-create.16
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+\input texinfo @c -*-texinfo-*-
+
+@c %**start of header
+@setfilename bus.info
+@settitle bus
+@afourpaper
+@documentencoding UTF-8
+@documentlanguage en
+@finalout
+@c %**end of header
+
+
+@dircategory Interprorcess Communication
+@direntry
+* bus: (bus). A simple daemonless system for broadcasting messages locally
+@end direntry
+
+
+@copying
+Copyright @copyright{} 2015 Mattias Andrée
+
+@quotation
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts. A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+@end quotation
+@end copying
+
+@ifnottex
+@node Top
+@top bus -- A simple daemonless system for broadcasting messages locally
+@insertcopying
+@end ifnottex
+
+@titlepage
+@title bus
+@subtitle A simple daemonless system for broadcasting messages locally
+@author by Mattias Andrée (maandree)
+
+@page
+@vskip 0pt plus 1filll
+@insertcopying
+@page
+@end titlepage
+
+@contents
+
+
+@iftex
+@macro xrm{}
+@rm{}
+@end macro
+@macro xtt{}
+@tt{}
+@end macro
+@end iftex
+
+@ifnottex
+@macro xrm{}
+@end macro
+@macro xtt{}
+@end macro
+@end ifnottex
+
+
+
+@menu
+* Overview:: Brief overview of @command{bus}.
+* Standard:: How to use @command{bus} properly.
+* Invoking:: Executing @command{bus}.
+* Protocol:: How communication over @command{bus} works internally.
+* Rationale:: Why @command{bus}?
+* GNU Free Documentation License:: Copying and sharing this manual.
+@end menu
+@c TODO @detailmenu (`C-c C-u m`)
+
+
+
+@node Overview
+@chapter Overview
+
+@command{bus} is a stupid-simple, thrilless, daemonless interprocess
+communication system for broadcasting messages. It is a lightweight
+alternative to a two-phase interprocess flexible barrier.
+
+@command{bus} uses a System V semaphore array and System V shared
+memory. Buses are named; the key of the semaphore array and the
+shared memory is stored in a regular file.
+
+The shared memory used by @command{bus} is always 2048 bytes.
+Additionally all messages should be encoded in UTF-8 and not contain
+any NULL characters, except they @emph{must} always end with a NULL
+byte. Furthermore messages should be prefixed with the process
+identifer of the process whence the message originated, followed
+by a space. If the process is ephemeral@footnote{The process exits
+after the broadcast, or shortly thereafter.}, 0 should be used
+instead of the process identifier.
+
+Communication over @command{bus} is synchronous. The broadcast call
+does not return until all listeners have received (and copied) the
+message. A malfunctioning program can lock the bus.
+
+This software package contains a C library and a command line
+utility. The package python-bus provides a Python 3 module.
+
+
+
+@node Standard
+@chapter Standard
+
+The command @command{bus create} can be used to create new buses. By
+convention, buses should be stored in @file{$XDG_RUNTIME_DIR/bus},
+this is what @command{bus create} does if no pathname is given. The
+pathname of the bus should be tracked using @env{BUS_X}, where @env{X}
+is replaced with either:
+
+@table @env
+@item GENERIC
+For the bus used in generic cases. That is all but the cases
+of the buses listed below.
+@item AUDIO
+For the bus used in with the audio subsystem is involved.
+@item VIDEO
+For the bus used in with the video subsystem is involved.
+@item INPUT
+For the bus used in with the input subsystem is involved.
+@item FILES
+For the bus used in with the storage subsystem is involved.
+@end table
+
+This list may be extended in the future. Therefore, and for
+other conventions, project-private buses should be tracked
+using @env{X_BUS}, where @env{X} is the project name.
+
+Messages broadcasted on a bus cannot be longer than 2047 bytes,
+excluding NUL termination. Message should be encoded in UTF-8,
+and most not contain the NUL character.
+
+Broadcasted message should start with the process ID whence
+the message originated, followed by a single regular space.
+If the process is ephemeral@footnote{The process exits after
+the broadcast, or shortly thereafter.}, 0 should be used instead
+of the process identifier.
+
+
+
+@node Invoking
+@chapter Invoking
+
+@command{bus} includes the following commands:
+
+@table @command
+@item create
+Create a bus.
+See @ref{bus create} for more information.
+@item remove
+Remove a bus.
+See @ref{bus remove} for more information.
+@item listen
+Listen for new message on a bus.
+See @ref{bus listen} for more information.
+@item wait
+Listen for one new message only on a bus.
+See @ref{bus wait} for more information.
+@item broadcast
+Broadcast a message on a bus.
+See @ref{bus broadcast} for more information.
+@item chmod
+Change permissions on a bus.
+See @ref{bus chmod} for more information.
+@item chown
+Change ownership of a bus.
+See @ref{bus chown} for more information.
+@item chgrp
+Change group ownership of a bus.
+See @ref{bus chgrp} for more information.
+@end table
+
+Upon successful completion, these commands exit with the value
+0. On failure, they exit with the value 1. If the command is
+not recognised the exit value is 2.
+
+@menu
+* bus create:: Create a bus.
+* bus remove:: Remove a bus.
+* bus listen:: Listen for new message on a bus.
+* bus wait:: Listen for one new message only on a bus.
+* bus broadcast:: Broadcast a message on a bus.
+* bus chmod:: Change permissions on a bus.
+* bus chown:: Change ownership of a bus.
+* bus chgrp:: Change group ownership of a bus.
+@end menu
+
+
+
+@node bus create
+@section @command{bus create}
+
+The syntax for invocation of @command{bus create} is
+@example
+bus create [-x] [--] [@var{PATHNAME}]
+@end example
+
+The command creates a bus and stores the key to it in the
+file @var{PATHNAME}. If @var{PATHNAME} is omitted, a
+random pathname in @file{$XDG_RUNTIME_DIR/bus} will be
+used and printed to stdout.
+
+If @option{-x} is used, the command will fail if
+the file @var{PATHNAME} already exists.
+
+
+
+
+@node bus remove
+@section @command{bus remove}
+
+The syntax for invocation of @command{bus remove} is
+@example
+bus remove [--] @var{PATHNAME}
+@end example
+
+The command removes the bus whose key is stored in
+the file @var{PATHNAME}. The file holding the
+key is also unlinked.
+
+
+
+@node bus listen
+@section @command{bus listen}
+
+The syntax for invocation of @command{bus command} is
+@example
+bus listen [--] @var{PATHNAME} @var{COMMAND}
+@end example
+
+The command listens for new messages on the bus whose
+key is stored in the file @var{PATHNAME}. Once a message
+is received, @var{COMMAND} will be spawned with the
+environment variable @env{msg} (lowercased) set to the
+received message. @sc{POSIX} shell syntax applies to
+@var{COMMAND}.
+
+
+@node bus wait
+@section @command{bus wait}
+
+The syntax for invocation of @command{bus wait} is
+@example
+bus wait [--] @var{PATHNAME} @var{COMMAND}
+@end example
+
+The command listens for a new message on the bus whose
+key is stored in the file @var{PATHNAME}. Once a message
+is received, the process will stop listening for more
+messages and @var{COMMAND} will be spawned with the
+environment variable @env{msg} (lowercased) set to the
+received message. @sc{POSIX} shell syntax applies to
+@var{COMMAND}.
+
+
+
+@node bus broadcast
+@section @command{bus broadcast}
+
+The syntax for invocation of @command{bus broadcast} is
+@example
+bus broadcast [-n] [--] @var{PATHNAME} @var{MESSAGE}
+@end example
+
+The command broadcasts the message @var{MESSAGE} on the
+bus whose key is stored in the file @var{PATHNAME}.
+
+
+
+@node bus chmod
+@section @command{bus chmod}
+
+The syntax for invocation of @command{bus chmod} is
+@example
+bus chmod [--] @var{PERMISSIONS} @var{PATHNAME}
+@end example
+
+This command changes who have access to the bus whose key
+is stored in the file @var{PATHNAME}. In the permissions,
+the owner, the group, and others (not in tgroup) are
+represented by the symbols @code{u}@footnote{@code{u}
+stands for `user'.}, @code{g}, and @code{o}, respectively.
+The permissions string is imagined to have always be
+prefixed with an @code{=}. This symbols means that all user
+classes list after it, and only those classes, as permission
+to use the bus. Similarly the symbols @code{+} and @code{-}
+can be used to grant and revoke access, respectively. The
+symbols @code{=}, @code{+}, and @code{-} can be mixed, and
+are interpreted from left to right. Alternatively the
+permissions string can be a octal number, where the owner
+is represented by any bit in 700 (100, 200, or 400, or any
+combination thereof), the group is represented by any bit
+in 70, and others (not in the group) is represented by any
+bit in 7.
+
+The current permission of the bus can be retrieved by
+running @command{stat} over the file @var{PATHNAME}.
+
+
+
+@node bus chown
+@section @command{bus chown}
+
+The syntax for invocation of @command{bus chown} is
+@example
+bus chown [--] @var{OWNER}[:@var{GROUP}] @var{PATHNAME}
+@end example
+
+This command changes the owner, that owns the bus whose
+key is stored in the file @var{PATHNAME}, to the specified
+owner. The owner can be specified either with a numerical
+user identifier or with a user name. If a group is
+specified, the bus's owner-group will be set to that group,
+otherwise the group will remain unchanged (not changed
+to the group of the new owner.) The group can be specified
+either with a numerical group identifier or with a group
+name.
+
+The current ownership of the bus can be retrieved by
+running @command{stat} over the file @var{PATHNAME}.
+
+
+
+@node bus chgrp
+@section @command{bus chgrp}
+
+The syntax for invocation of @command{bus chgrp} is
+@example
+bus chgrp [--] @var{GROUP} @var{PATHNAME}
+@end example
+
+This command changes the group, that owns the bus whose
+key is stored in the file @var{PATHNAME}, to the specified
+group. The group can be specified either with a numerical
+group identifier or with a group name.
+
+The current ownership of the bus can be retrieved by
+running @command{stat} over the file @var{PATHNAME}.
+
+
+
+@node Protocol
+@chapter Protocol
+
+@command{bus} is built upon following three procedures.
+
+@noindent
+@code{create}
+@example
+@w{@xrm{}Select a filename.@xtt{}}
+
+@w{@xrm{}Create XSI semaphore array @{@code{S} = 0, @code{W} = 0, @code{X} = 1, @code{Q} = 0, @code{N} = 0@}@xtt{}}
+@w{@xrm{}with random key. Store the semaphore array's key in decimal form@xtt{}}
+@w{@xrm{}on the first line in the selected file.@xtt{}}
+
+@w{@xrm{}Create XSI shared memory, with an allocation of 2048 bytes, with@xtt{}}
+@w{@xrm{}a random key. Store the shared memory's key in decimal form on@xtt{}}
+@w{@xrm{}the second line in the selected file.@xtt{}}
+@end example
+
+@noindent
+@code{broadcast}
+@example
+with P(X):
+ Z(W)
+ @w{@xrm{}Write NUL-terminate message to shared memory@xtt{}}
+ with V(N): -- (1)
+ Q := 0
+ Z(S)
+
+-- (1) @w{@xrm{}may be omitted if semaphores are known that@xtt{}}
+ @w{P()@xrm{}, @xtt{}Z()@xrm{}, @xtt{}V()@xrm{} cannot create a race condition@xtt{}}
+ @w{@xrm{}with a processes running @xtt{}Z()@xrm{}.@xtt{}}
+@end example
+
+@noindent
+@code{listen}
+@example
+with V(S):
+ forever:
+ V(Q)
+ Z(Q)
+ @w{@xrm{}Read NUL-terminated message from shared memory@xtt{}}
+ if breaking:
+ break
+ with V(W):
+ with P(S):
+ Z(S)
+ Z(N)
+@end example
+
+@noindent
+@code{V(a)} means that semaphore a is released.@*
+@code{P(a)} means that semaphore a is acquired.@*
+@code{Z(a)} means that the process waits for semaphore a to become 0.@*
+@code{with P(a)} that @code{P(a)} is done before the entering the scope,
+and @code{V(a)} is done when exiting the scope. It also means that
+these actions [@code{P(a)} and @code{V(a)}] are undone when the process
+exits, or if the call fails.@*
+@code{with V(a)} is to @code{V(a)} as @code{with P(a)} is to @code{P(a)}.
+
+
+
+@node Rationale
+@chapter Rationale
+
+We need an interprocess communication system similar to message queues.
+But we need broadcasting rather than anycasting, so we have a fast,
+simple and daemonless system for announcing events to any processes that
+might be interested.
+
+
+
+@node GNU Free Documentation License
+@appendix GNU Free Documentation License
+@include fdl.texinfo
+
+@bye
+
diff --git a/doc/info/fdl.texinfo b/doc/info/fdl.texinfo
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+@c The GNU Free Documentation License.
+@center Version 1.3, 3 November 2008
+
+@c This file is intended to be included within another document,
+@c hence no sectioning command or @node.
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+@uref{http://fsf.org/}
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+Everyone is permitted to copy and distribute verbatim copies
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+@end display
+
+@enumerate 0
+@item
+PREAMBLE
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+If the Modified Version includes new front-matter sections or
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+
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+
+@item
+COMBINING DOCUMENTS
+
+You may combine the Document with other documents released under this
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+Invariant Sections of all of the original documents, unmodified, and
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+Make the same adjustment to the section titles in the list of
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+sections Entitled ``Endorsements.''
+
+@item
+COLLECTIONS OF DOCUMENTS
+
+You may make a collection consisting of the Document and other documents
+released under this License, and replace the individual copies of this
+License in the various documents with a single copy that is included in
+the collection, provided that you follow the rules of this License for
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+
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+
+@item
+AGGREGATION WITH INDEPENDENT WORKS
+
+A compilation of the Document or its derivatives with other separate
+and independent documents or works, in or on a volume of a storage or
+distribution medium, is called an ``aggregate'' if the copyright
+resulting from the compilation is not used to limit the legal rights
+of the compilation's users beyond what the individual works permit.
+When the Document is included in an aggregate, this License does not
+apply to the other works in the aggregate which are not themselves
+derivative works of the Document.
+
+If the Cover Text requirement of section 3 is applicable to these
+copies of the Document, then if the Document is less than one half of
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+covers that bracket the Document within the aggregate, or the
+electronic equivalent of covers if the Document is in electronic form.
+Otherwise they must appear on printed covers that bracket the whole
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+
+@item
+TRANSLATION
+
+Translation is considered a kind of modification, so you may
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+Replacing Invariant Sections with translations requires special
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+translations of some or all Invariant Sections in addition to the
+original versions of these Invariant Sections. You may include a
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+Document, and any Warranty Disclaimers, provided that you also include
+the original English version of this License and the original versions
+of those notices and disclaimers. In case of a disagreement between
+the translation and the original version of this License or a notice
+or disclaimer, the original version will prevail.
+
+If a section in the Document is Entitled ``Acknowledgements'',
+``Dedications'', or ``History'', the requirement (section 4) to Preserve
+its Title (section 1) will typically require changing the actual
+title.
+
+@item
+TERMINATION
+
+You may not copy, modify, sublicense, or distribute the Document
+except as expressly provided under this License. Any attempt
+otherwise to copy, modify, sublicense, or distribute it is void, and
+will automatically terminate your rights under this License.
+
+However, if you cease all violation of this License, then your license
+from a particular copyright holder is reinstated (a) provisionally,
+unless and until the copyright holder explicitly and finally
+terminates your license, and (b) permanently, if the copyright holder
+fails to notify you of the violation by some reasonable means prior to
+60 days after the cessation.
+
+Moreover, your license from a particular copyright holder is
+reinstated permanently if the copyright holder notifies you of the
+violation by some reasonable means, this is the first time you have
+received notice of violation of this License (for any work) from that
+copyright holder, and you cure the violation prior to 30 days after
+your receipt of the notice.
+
+Termination of your rights under this section does not terminate the
+licenses of parties who have received copies or rights from you under
+this License. If your rights have been terminated and not permanently
+reinstated, receipt of a copy of some or all of the same material does
+not give you any rights to use it.
+
+@item
+FUTURE REVISIONS OF THIS LICENSE
+
+The Free Software Foundation may publish new, revised versions
+of the GNU Free Documentation 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. See
+@uref{http://www.gnu.org/copyleft/}.
+
+Each version of the License is given a distinguishing version number.
+If the Document specifies that a particular numbered version of this
+License ``or any later version'' applies to it, you have the option of
+following the terms and conditions either of that specified version or
+of any later version that has been published (not as a draft) by the
+Free Software Foundation. If the Document does not specify a version
+number of this License, you may choose any version ever published (not
+as a draft) by the Free Software Foundation. If the Document
+specifies that a proxy can decide which future versions of this
+License can be used, that proxy's public statement of acceptance of a
+version permanently authorizes you to choose that version for the
+Document.
+
+@item
+RELICENSING
+
+``Massive Multiauthor Collaboration Site'' (or ``MMC Site'') means any
+World Wide Web server that publishes copyrightable works and also
+provides prominent facilities for anybody to edit those works. A
+public wiki that anybody can edit is an example of such a server. A
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+site means any set of copyrightable works thus published on the MMC
+site.
+
+``CC-BY-SA'' means the Creative Commons Attribution-Share Alike 3.0
+license published by Creative Commons Corporation, a not-for-profit
+corporation with a principal place of business in San Francisco,
+California, as well as future copyleft versions of that license
+published by that same organization.
+
+``Incorporate'' means to publish or republish a Document, in whole or
+in part, as part of another Document.
+
+An MMC is ``eligible for relicensing'' if it is licensed under this
+License, and if all works that were first published under this License
+somewhere other than this MMC, and subsequently incorporated in whole
+or in part into the MMC, (1) had no cover texts or invariant sections,
+and (2) were thus incorporated prior to November 1, 2008.
+
+The operator of an MMC Site may republish an MMC contained in the site
+under CC-BY-SA on the same site at any time before August 1, 2009,
+provided the MMC is eligible for relicensing.
+
+@end enumerate
+
+@page
+@heading ADDENDUM: How to use this License for your documents
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and
+license notices just after the title page:
+
+@smallexample
+@group
+ Copyright (C) @var{year} @var{your name}.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+ Texts. A copy of the license is included in the section entitled ``GNU
+ Free Documentation License''.
+@end group
+@end smallexample
+
+If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
+replace the ``with@dots{}Texts.''@: line with this:
+
+@smallexample
+@group
+ with the Invariant Sections being @var{list their titles}, with
+ the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
+ being @var{list}.
+@end group
+@end smallexample
+
+If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of
+free software license, such as the GNU General Public License,
+to permit their use in free software.
+
+@c Local Variables:
+@c ispell-local-pdict: "ispell-dict"
+@c End:
diff --git a/doc/man/bus-chmod.1 b/doc/man/bus-chmod.1
index 24f97e6..3a44423 100644
--- a/doc/man/bus-chmod.1
+++ b/doc/man/bus-chmod.1
@@ -7,7 +7,7 @@ bus chmod - Change permissions on a bus
.IR permissions
.IR pathname
.SH DESCRIPTION
-Change whom as access to a bus with an associated \fIpathname\fP.
+Change who have access to a bus with an associated \fIpathname\fP.
In the \fIpermissions\fP, the owner, the group, and others (not
in group) are represented by the symbols \fBu\fP, \fBg\fP, and
\fBo\fP, respectively. The \fIpermissions\fP string is imagined
@@ -15,7 +15,7 @@ to have always be prefixed with an \fB=\fP. This symbols means
that all user classes list after it, and only those classes, as
permission to use the bus. Similarly the symbols \fB+\fP and
\fB\-\fP can be used to grant and revoke access, respectively.
-The symbols \fB=\fP, \fB+\fP, and \fB\-\fP can be maked, and are
+The symbols \fB=\fP, \fB+\fP, and \fB\-\fP can be mixed, and are
interpreted from left to right. Alternatively the \fIpermissions\fP
string can be a octal number, where the owner is represented by any
bit in 700 (100, 200, or 400, or any combination thereof), the
diff --git a/doc/man/bus-create.1 b/doc/man/bus-create.1
index d0cc27d..91041cf 100644
--- a/doc/man/bus-create.1
+++ b/doc/man/bus-create.1
@@ -7,9 +7,9 @@ bus create - Create a bus
[--]
.IR [pathname]
.SH DESCRIPTION
-Create a bus with an associated \fIpathname\fP. If \fIpathname\fP,
-a random pathname in \fI$XDG_RUNTIME_DIR/bus\fP will be created and
-printed to stdout.
+Create a bus with an associated \fIpathname\fP. If \fIpathname\fP
+is omitted, a random pathname in \fI$XDG_RUNTIME_DIR/bus\fP will be
+created and printed to stdout.
.SH OPTIONS
.TP
.B \-x
diff --git a/doc/protocol b/doc/protocol
index a846581..f45799e 100644
--- a/doc/protocol
+++ b/doc/protocol
@@ -44,6 +44,5 @@ listen:
and `V(a)` is done when exiting the scope. It also means that
these actions [P(a) and V(a)] are undone when the process exits,
or if the call fails.
-`with V(a)` that `V(a)` is like `with P(a)` that `P(a)` and
-`V(a)` are exchanged.
+`with V(a)` is to `V(a)` as `with P(a)` is to `P(a)`.