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diff --git a/doc/info/bus.texinfo b/doc/info/bus.texinfo deleted file mode 100644 index be50cea..0000000 --- a/doc/info/bus.texinfo +++ /dev/null @@ -1,2079 +0,0 @@ -\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}. -* Interface:: Using @command{libbus}. -* Protocol:: How communication over @command{bus} works internally. -* Rationale:: Why @command{bus}? -* Examples:: Usecase examples and API-demonstration. -* GNU Free Documentation License:: Copying and sharing this manual. - -@detailmenu - --- The Detailed Node Listing --- - -Invoking - -* 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. - -Examples - -* Audio-volume control:: -* Telephony and music:: -* Timed:: -* Nonblocking:: -* Daemon-dependencies:: - -@end detailmenu -@end menu - - - -@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 Interface -@chapter Interface - -To use @command{libbus} in your C program, include the -header file @file{<bus.h>} and link with the flag -@option{-lbus}. - -With exception to @code{bus_poll} and @code{bus_poll_timed}, -all functions return @code{0} upon successful completion, -and @code{-1} in case of failure. @code{bus_poll} and -@code{bus_poll_timed} return @code{NULL} on failure. -On failure on all functions set @code{errno} to indicate -what went wrong. - -@file{<bus.h>} defines the following functions: - -@table @code -@item int bus_create(const char *file, int flags, char **out_file) -This function creates a bus with the asscoiated pathname -specifed by the value of the parameter @code{file}. If -@code{file} is @code{NULL} a random pathname is selected. -This pathname adheres to the convention set forth by -in @ref{Standard}. - -If @code{file} is not @code{NULL} the function fails if the -file already exists if @code{flags} contains @code{BUS_EXCL}. -Otherwise if @code{file} is not @code{NULL}, the function -does nothing if the file already exists. - -If @code{flags} contains @code{BUS_INTR}, the function fails -if it is interrupted. - -Unless @code{out_file} is NULL, the pathname of the bus -should be stored in a new char array stored in @code{*out_file}. -The caller must free the allocated stored in @code{*out_file}. - -If the processes cannot allocate enough memory to perform -the action, the function sets @code{errno} to @code{ENOMEM} -and fails. It may also fail and set @code{errno} to any of -the errors specified for the system calls @code{open} and -@code{write}. - -@item int bus_unlink(const char *file) -This function removes the bus assoicated with the pathname -stored in the parameter @code{file}. The function also -unlinks the file. - -The function may set @code{errno} to any of the following -values and fail for the specified reasons: -@table @code -@item EINVAL -The bus does not exist. -@item EACCES -Operation permission is denied to the calling process. -@item EPERM -The user does not have permission to remove the bus. -@end table -@noindent -It may also fail and set @code{errno} to any of the errors -specified for the system calls @code{unlink} and @code{open}, -and the functions @code{semget} and @code{shmget}. - -@item int bus_open(bus_t *bus, const char *file, int flags) -This function acquires resources required for the process -to use the bus associated with the filename stored in the -parameter @code{file}. The function also stores the resources -in @code{bus} for use by other @command{bus} functions. - -Values for @code{flags} are constructed by a bitwise -inclusive @sc{or} of flags from the following list. -@table @code -@item BUS_RDONLY -The process will only be using the bus for receiving messages. -@item BUS_WRONLY -The process will only be using the bus for sending messages. -@item BUS_RDWR -The process will use the bus for both receiving and sending -messages. -@end table - -The function may set @code{errno} to any of the following -values and fail for the specified reasons: -@table @code -@item ENOMEM -The process cannot allocate enough memory to perform the -action. -@item EACCES -Operation permission is denied to the calling process. -@item EINVAL -The described bus does not exist. -@end table -@noindent -It may also fail and set @code{errno} to any of the errors -specified for the system call @code{open}. - -@item int bus_close(bus_t *bus) -This function disposes of resources allocated to the -process, as referenced in the parameter @code{bus}. - -The function fails and sets @code{errno} to @code{EINVAL} -if the bus does not exist. - -@item int bus_write(const bus_t *bus, const char *message, int flags) -This function broadcasts a message on the bus whose -information is stored in the parameter @code{bus}. The -message read by the function is stored in the parameter -@code{message}. It may not exceeed 2048 bytes, including -NUL termination. - -The function shall fail, and set @code{errno} to -@code{EAGAIN}, if the call would suspend the process and -@code{flags} contains @code{BUS_NOWAIT}. - -The function may fail and set @code{errno} to any of the -errors specified for the function @code{semop}. - -@item int bus_write_timed(const bus_t *bus, const char *message, const struct timespec *timeout, clockid_t clockid) -This function behaves like @code{bus_write}, except if it -is not able to write the message within the specified time, -it will fail and set @code{errno} to @code{EAGAIN}. The -time is specified as an absolute time using the parameter -@code{timeout}. The behaviour is unspecified if @code{timeout} -is @code{NULL}. @code{timeout} is measured with the clock whose -identifier is specified by the parameter @code{clockid}. This -clock must be a predicitable clock@footnote{There are probably -other, undocumented, seemingly arbitrary restrictions too.}. - -The function may fail and set @code{errno} to any of the -errors specified for the functions @code{semop} and -@code{clock_gettime}. - -@item int bus_read(const bus_t *bus, int (*callback)(const char *message, void *user_data), void *user_data) -This function waits for new message to be sent on the bus -specified in the @code{bus} parameter, as provieded by a -previous call to the function @code{bus_open}. Once a -message is received, the parameter-function @code{callback} -is invoked. The parameter @code{message} in @code{callback} -is the received message, and @code{user_data} in -@code{callback} should be @code{user_data} from @code{bus_read}. -However, once the function [@code{bus_read}] has ensured -that it will receive any message sent on the bus, it shall -invoke the parameter-function @code{callback} with -@code{message} set to @code{NULL}, to notify the process that -it can perform any action that requires that it is listening -on the bus. - -After @code{callback} returns, @code{message} may be override. -Therefore @code{callback} should copy message and start a new -thread that uses the copy of @code{message}. @code{callback} -shall return @code{-1} on failure, @code{0} if the function -[@code{bus_read}] should stop listening, or @code{1} if -the function should continue listening. - -The function may fail and set @code{errno} to any of the -errors specified for the function @code{semop}. - -@item int bus_read_timed(const bus_t *bus, int (*callback)(const char *message, void *user_data), void *user_data, const struct timespec *timeout, clockid_t clockid) -This function behaves like @code{bus_read}, except it will -automatically fail and set @code{errno} to @code{EAGAIN} when -the specified time has passed. The time is specified as an -absolute time using the parameter @code{timeout}. The -behaviour is unspecified if @code{timeout} is @code{NULL}. -@code{timeout} is measured with the clock whose identifier -is specified by the parameter @code{clockid}. This clock -must be a predicitable clock@footnote{There are probably -other, undocumented, seemingly arbitrary restrictions too.}. - -The function may fail and set @code{errno} to any of the -errors specified for the functions @code{semop} and -@code{clock_gettime}. - -@item int bus_poll_start(bus_t *bus) -@itemx int bus_poll_stop(const bus_t *bus) -@itemx const char *bus_poll(bus_t *bus, int flags) -@itemx const char *bus_poll_timed(bus_t *bus, const struct timespec *timeout, clockid_t clockid) -The function @code{bus_poll} waits for a message to be -broadcasted on the bus, and return the message it receives. -The function fails if @code{flags} contains @code{BUS_NOWAIT} -and there is not already a message waiting on the bus. -Received messages shall be copied and parsed, and acted -upon, in a separate thread, and the function @code{bus_poll} -or the function @code{bus_poll_stop} called again as soon -as possible. - -The funcion @code{bus_poll_start} must be called before -@code{bus_poll} is called for the first time. When the -process is done listening on the bus, it must call the -function @code{bus_poll_stop}. - -The function @code{bus_poll_timed} behaves like the function -@code{bus_poll}, except if it is not able to read a message -within the specified time, it will fail and set @code{errno} -to @code{EAGAIN}. The time is specified as an absolute time -using the parameter @code{timeout}. The behaviour is -unspecified if @code{timeout} is @code{NULL}. @code{timeout} -is measured with the clock whose identifier is specified by -the parameter @code{clockid}. This clock must be a predicitable -clock@footnote{There are probably other, undocumented, -seemingly arbitrary restrictions too.}. - -Upon successful completion, the functions @code{bus_poll} and -@code{bus_poll_timed} returns the received message. - -These functions may fail and set @code{errno} to any of the -errors specified for the function @code{semop}. The function -@code{bus_poll_timed} may also set @code{errno} to any of -the errors specified for @code{clock_gettime}. - -@item int bus_chown(const char *file, uid_t owner, gid_t group) -This function changes the owner and the group of the bus, -associated with the file whose pathname is stored in the -parameter @code{file}, to the owner and group specified by -the parameters @code{owner} and @code{group}, respectively. - -The current ownership of a bus can be retrieved by calling -@code{stat} over the pathname of the bus. - -The function may fail and set @code{errno} to any of the -errors specified for the functions @code{bus_open}, -@code{chown}, @code{semget}, @code{shmget}, and @code{shmctl} -as well as any errors specified for the commands -@code{IPC_STAT} and @code{IPC_SET} for the function -@code{semctl}. - -@item int bus_chmod(const char *file, mode_t mode) -This function gives access to the bus associated with the -file whose pathname is stored in the parameter @code{file} -according to the following rules: - -@itemize @bullet{} -@item -If @code{mode} contains any of the bits @code{S_IRWXU} -contains, the owner should be given full access to the -bus. Otherwise the owner should have no access. -@item -If @code{mode} contains any of the bits @code{S_IRWXG} -contains, the group should be given read and write -access to the bus. Otherwise the group should have no -access. -@item -If @code{mode} contains any of the bits @code{S_IRWXO} -contains, users that are neither the owner nor member -of the group should be given read and write access to -the bus. Otherwise they should have no access. -@end itemize - -The current permissions of a bus can be retrieved by calling -@code{stat} over the pathname of the bus. - -The function may fail and set @code{errno} to any of the -errors specified for the functions @code{bus_open}, -@code{chmode}, @code{semget}, @code{shmget}, and @code{shmctl} -as well as any errors specified for the commands -@code{IPC_STAT} and @code{IPC_SET} for the function -@code{semctl}. -@end table - -There is not reason for poking around in @code{bus_t} -(@code{struct bus}). It should be considered opaque. -You can read the documentation in @file{<bus.h>} if -you want to know what is in it. - - - - -@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 Examples -@chapter Examples - -This chapter contains usecase examples and -API-demonstrations. You will find that they are (on -a standard installation) installed on your system. - -@menu -* Audio-volume control:: -* Telephony and music:: -* Timed:: -* Nonblocking:: -* Daemon-dependencies:: -@end menu - - - - -@node Audio-volume control -@section Audio-volume control - -Assume you have program that display the audio volume. -This program checks every second third if the volume -have changed. - -Also assume that you use @command{amixer} to change the -volume, most often by using keybindings via @command{xbindkeys}. - -To reduce the delay, you want to send a signal to the -monitor program that the volume have changed. For this -more primitive IPC is sufficient, but lets assume there -are other programs interested in this information too. - -To accomplish this, you create a wrapper for @command{amixer} -that broadcasts updates on a bus. This wrapper is -installed as @command{~/.local/bin/amixer}, and -@command{~/.local/bin/} is included in @env{$PATH} -before @command{/usr/bin}. -@* - -@noindent -Before starting run @command{./init}, this code is -should be run from your profile file if you want to -implement this on your system. After running -@command{./init}, you can start one or more listeners -by running @command{./alsa-monitor}. - -To change the volume run -@code{./amixer -c 0 -- set Master 5%+} or similar. - -When you are done run @command{./cleanup}. - - -@subsubheading @file{./amixer} -@example -#!/bin/sh -/usr/bin/amixer "$@@" -for arg in "$@@"; do - if [ "$@{arg@}" = "set" ] || \ - [ "$@{arg@}" = "sset" ] || \ - [ "$@{arg@}" = "cset" ]; then - exec bus broadcast "/tmp/example-bus" '0 volume-changed *' - fi -done -@end example - - -@subsubheading @file{./cleanup} -@example -#!/bin/sh -exec bus remove "/tmp/example-bus" -@end example - - -@subsubheading @file{./init} -@example -#!/bin/sh -bus create "/tmp/example-bus" - -# @w{@xrm{}The following code is more suitable in the real world,@xtt{}} -# @w{@xrm{}if used, the other files should use @xtt{}"$@{BUS_AUDIO@}"} -# @w{@xrm{}instead of @xtt{}"/tmp/example-bus"@xrm{}.@xtt{}} -# -# export BUS_AUDIO="$@{XDG_RUNTIME_DIR@}/bus/audio" -# if [ ! -f "$@{BUS_AUDIO@}" ]; then -# bus create "$@{BUS_AUDIO@}" -# fi -@end example - - -@subsubheading @file{./monitor} -@example -#!/bin/sh -if [ $# = 1 ]; then - if [ "$(echo "$@{1@}" | cut -d ' ' -f 2)" = "volume-changed" ]; then - printf '\e[H\e[2J' - amixer get Master - fi - exit 0 -fi - -exec 2>/dev/null - -printf '\e[?1049h\e[H\e[2J' -trap -- "printf '\e[?1049l'" SIGINT -bus listen "/tmp/example-bus" \'"$@{0/\'/\'\\\'\'@}"\'' "$@{msg@}"' -@end example - - - -@node Telephony and music -@section Telephony and music - -Assume you have a music player and a telephony program. -You might like it if the music player pauses whenever -you make or receive a call. You may also like it, if -the music resumed when the call ended. - -In this example we will assume you the have @command{mocp} -(@command{moc} package) running. And we will use the shell to -simulate a telephony program. -@* - -@noindent -First of, run make to build this example. Before -starting run @command{./init}. And when you are -done run @command{./cleanup}. - -In one terminal run @command{./monitor}. This program -will pause @command{mocp} when you make or receive a call, -it will also resume @command{mocp} when all calls have -ended if it did pause @command{mocp}. - -Then start any positive number of terminals. -We will pretend that each of them are telephony -programs. To make or receive a call, run -@command{./receive-or-make-call}, when you want to -end the pretend call, run @command{./end-call} from -the terminal (or more accurately, from the same -process.) - - -@subsubheading @file{./Makefile} -@example -COMMANDS = init cleanup monitor end-call receive-or-make-call - -all: $@{COMMANDS@} -%: %.c - $@{CC@} -Wall -Wextra -pedantic -std=c99 -lbus -o $@@ $< -clean: - -rm $@{COMMANDS@} - -.PHONY: all clean -@end example - - -@subsubheading @file{./cleanup.c} -@example -#include <bus.h> -#include <stdio.h> - -int main() -@{ - return bus_unlink("/tmp/example-bus") && (perror("cleanup"), 1); -@} -@end example - - -@subsubheading @file{./end-call.c} -@example -#include <bus.h> -#include <stdio.h> -#include <unistd.h> -#include <stdint.h> - -#define t(stmt) if (stmt) goto fail - -static char message[BUS_MEMORY_SIZE]; - -int main() -@{ - bus_t bus; - sprintf(message, "%ji unforce-pause", (intmax_t)getppid()); - /* @w{@xrm{}Yes, PPID; in this example we pretend the shell is the telephony process.@xtt{}} */ - t (bus_open(&bus, "/tmp/example-bus", BUS_WRONLY)); - t (bus_write(&bus, message, 0)); - bus_close(&bus); - return 0; - -fail: - perror("end-call"); - bus_close(&bus); - return 1; -@} -@end example - - -@subsubheading @file{./init.c} -@example -#include <bus.h> -#include <stdio.h> - -int main() -@{ - return bus_create("/tmp/example-bus", 0, NULL) && (perror("init"), 1); -@} -@end example - - -@subsubheading @file{./monitor.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> -#include <string.h> - -static size_t pauser_count = 0; -static size_t pausers_size = 0; -static char* pausers = NULL; - -static int is_moc_playing(void) -@{ - return !WEXITSTATUS(system("env LANG=C mocp -i 2>/dev/null |" - "grep 'State: PLAY' >/dev/null")); -@} - -/* @w{@xrm{}In a proper implementation, message whould be copyied, and then@xtt{}} - * @w{@xrm{}a new thread would be created that parsed the copy. But that is@xtt{}} - * @w{@xrm{}too much for an example, especially since it would also require@xtt{}} - * @w{@xrm{}a mutex to make sure two threads do not modify data at the same@xtt{}} - * @w{@xrm{}time, causing chaos.@xtt{}} */ -static int callback(const char *message, void *user_data) -@{ - char *msg = NULL; - size_t len = 0; - if (message == 0) - return 1; - while ((len < 2047) && message[len]) - len++; - msg = malloc((len + 1) * sizeof(char)); - t (msg == NULL); - memcpy(msg, message, len * sizeof(char)); - msg[len] = 0; - /* @w{@xrm{}BEGIN run as in a separate thread@xtt{}} */ - if (pauser_count || is_moc_playing()) @{ - char *begin = strchr(msg, ' '); - ssize_t pid; - int requests_pause; - if (begin == NULL) - goto done; - *begin++ = 0; - pid = (ssize_t)atoll(msg); - if (pid < 1) /* @w{@xrm{}We need a real PID, too bad there is@xtt{}} - * @w{@xrm{}no convient way to detect if it dies.@xtt{}} */ - goto done; - if ((strstr(begin, "force-pause ") == begin) || - !strcmp(begin, "force-pause")) - requests_pause = 1; - else if ((strstr(begin, "unforce-pause ") == begin) || - !strcmp(begin, "unforce-pause")) - requests_pause = 0; - else - goto done; - if ((size_t)pid >= pausers_size) @{ - pausers = realloc(pausers, (size_t)(pid + 1) * sizeof(char)); - t (pausers == NULL); /* @w{@xrm{}Let's ignore the memory leak.@xtt{}} */ - memset(pausers + pausers_size, 0, - ((size_t)(pid + 1) - pausers_size) * sizeof(char)); - pausers_size = (size_t)(pid + 1); - @} - if (pausers[pid] ^ requests_pause) @{ - pauser_count += requests_pause ? 1 : -1; - pausers[pid] = requests_pause; - if (pauser_count == (size_t)requests_pause) - system(requests_pause ? "mocp -P" : "mocp -U"); - @} - @} - /* @w{@xrm{}END run as in a separate thread@xtt{}} */ - goto done; - (void) user_data; - -fail: - perror("monitor"); - return -1; - -done: - free(msg); - return 1; -@} - -int main() -@{ - bus_t bus; - t (bus_open(&bus, "/tmp/example-bus", BUS_RDONLY)); - t (bus_read(&bus, callback, NULL)); - bus_close(&bus); - free(pausers); - return 0; - -fail: - perror("monitor"); - bus_close(&bus); - free(pausers); - return 1; -@} -@end example - - -@subsubheading @file{./receive-or-make-call.c} -@example -#include <bus.h> -#include <stdio.h> -#include <unistd.h> -#include <stdint.h> - -#define t(stmt) if (stmt) goto fail - -static char message[BUS_MEMORY_SIZE]; - -int main() -@{ - bus_t bus; - sprintf(message, "%ji force-pause", (intmax_t)getppid()); - /* @w{@xrm{}Yes, PPID; in this example we pretend the shell is the telephony process.@xtt{}} */ - t (bus_open(&bus, "/tmp/example-bus", BUS_WRONLY)); - t (bus_write(&bus, message, 0)); - bus_close(&bus); - return 0; - -fail: - perror("receive-or-make-call"); - bus_close(&bus); - return 1; -@} -@end example - - - -@node Timed -@section Timed - -This example shows how to use timed operations. - -First of, run make to build this example. - -To start the example run @command{./init}. When you are -done run @command{./cleanup}. - -Running instances of @command{./poll} will wait for new -messages continuously, but with one second timeouts. - -@command{./slow-poll} works like @command{./poll}, except -it will sleep for one second every time it receives -a message. - -Running instances of @command{./read} will read for ten -seconds and then time out. - -@command{./poll}, @command{./read}, and @command{./slow-poll} -will stop if the message "stop" is broadcasted. - -@command{./write} will wait for atmost a tenth of a -seconds before failing. This means that if two instances -of @command{./write} is started at the same time one of -them will fail if @command{./slow-poll} is running. - -@command{./poll}, @command{./read}, @command{./init} and -@command{./cleanup} are run without any additional -arguments. @command{./write} is run with the message -as the second argument. - - -@subsubheading @file{./Makefile} -@example -COMMANDS = init cleanup write poll read slow-poll - -all: $@{COMMANDS@} -%: %.c - $@{CC@} -Wall -Wextra -pedantic -std=c99 -lbus -o $@@ $< -clean: - -rm $@{COMMANDS@} - -.PHONY: all clean -@end example - - -@subsubheading @file{./cleanup.c} -@example -#include <bus.h> -#include <stdio.h> - -int main() -@{ - return bus_unlink("/tmp/example-bus") && (perror("cleanup"), 1); -@} -@end example - - -@subsubheading @file{./init.c} -@example -#include <bus.h> -#include <stdio.h> - -int main() -@{ - return bus_create("/tmp/example-bus", 0, NULL) && (perror("init"), 1); -@} -@end example - - -@subsubheading @file{./poll.c} -@example -#include <bus.h> -#include <stdio.h> -#include <unistd.h> -#include <string.h> -#include <errno.h> - -#define t(stmt) if (stmt) goto fail - -int main() -@{ - bus_t bus; - const char *message; - long long tick = 0; - struct timespec timeout; - t (bus_open(&bus, "/tmp/example-bus", BUS_RDONLY)); - t (bus_poll_start(&bus)); - for (;;) @{ - t (clock_gettime(CLOCK_MONOTONIC, &timeout)); - timeout.tv_sec += 1; - message = bus_poll_timed(&bus, &timeout, CLOCK_MONOTONIC); - if (message == NULL) @{ - t (errno != EAGAIN); - printf("waiting... %lli\n", ++tick); - continue; - @} - tick = 0; - message = strchr(message, ' ') + 1; - if (!strcmp(message, "stop")) - break; - printf("\033[01m%s\033[21m\n", message); - @} - t (bus_poll_stop(&bus)); - bus_close(&bus); - return 0; - -fail: - perror("poll"); - bus_poll_stop(&bus); - bus_close(&bus); - return 1; -@} -@end example - - -@subsubheading @file{./read.c} -@example -#include <bus.h> -#include <stdio.h> -#include <unistd.h> -#include <string.h> -#include <errno.h> - -#define t(stmt) if (stmt) goto fail - -static int callback(const char *message, void *user_data) -@{ - (void) user_data; - - if (message == NULL) - return 1; - - message = strchr(message, ' ') + 1; - if (!strcmp(message, "stop")) - return 0; - printf("%s\n", message); - return 1; -@} - -int main() -@{ - bus_t bus; - struct timespec timeout; - t (bus_open(&bus, "/tmp/example-bus", BUS_RDONLY)); - t (clock_gettime(CLOCK_MONOTONIC, &timeout)); - timeout.tv_sec += 10; - t (bus_read_timed(&bus, callback, NULL, &timeout, CLOCK_MONOTONIC)); - bus_close(&bus); - return 0; - -fail: - perror("poll"); - bus_poll_stop(&bus); - bus_close(&bus); - return 1; -@} -@end example - - -@subsubheading @file{./slow-poll.c} -@example -#include <bus.h> -#include <stdio.h> -#include <unistd.h> -#include <string.h> -#include <errno.h> - -#define t(stmt) if (stmt) goto fail - -int main() -@{ - bus_t bus; - const char *message; - long long tick = 0; - struct timespec timeout; - t (bus_open(&bus, "/tmp/example-bus", BUS_RDONLY)); - t (bus_poll_start(&bus)); - for (;;) @{ - t (clock_gettime(CLOCK_MONOTONIC, &timeout)); - timeout.tv_sec += 1; - message = bus_poll_timed(&bus, &timeout, CLOCK_MONOTONIC); - if (message == NULL) @{ - t (errno != EAGAIN); - printf("waiting... %lli\n", ++tick); - continue; - @} - tick = 0; - message = strchr(message, ' ') + 1; - if (!strcmp(message, "stop")) - break; - printf("\033[01m%s\033[21m\n", message); - sleep(1); - @} - t (bus_poll_stop(&bus)); - bus_close(&bus); - return 0; - -fail: - perror("poll"); - bus_poll_stop(&bus); - bus_close(&bus); - return 1; -@} -@end example - - -@subsubheading @file{./write.c} -@example -#include <bus.h> -#include <stdio.h> -#include <unistd.h> -#include <stdint.h> - -#define t(stmt) if (stmt) goto fail - -static char message[BUS_MEMORY_SIZE]; - -int main(int argc, char *argv[]) -@{ - bus_t bus; - struct timespec timeout; - if (argc < 2) @{ - fprintf(stderr, "%s: USAGE: %s message\n", argv[0], argv[0]); - return 2; - @} - sprintf(message, "0 %s", argv[1]); - t (bus_open(&bus, "/tmp/example-bus", BUS_WRONLY)); - t (clock_gettime(CLOCK_MONOTONIC, &timeout)); - timeout.tv_nsec += 100000000L; - t (bus_write_timed(&bus, message, &timeout, CLOCK_MONOTONIC)); - bus_close(&bus); - return 0; - -fail: - perror("write"); - bus_close(&bus); - return 1; -@} -@end example - - - -@node Nonblocking -@section Nonblocking - -This example shows how to use bus_poll instead of bus_read, -and how to do non-blocking polling and non-blocking writing. - -First of, run make to build this example. - -To start the example run @command{./init}. When you are done -run @command{./cleanup}. - -Running instances of @command{./poll} will check every second -if there is a new inbound message. Between these checks -@command{./write} will wait for all @command{./poll}:s to -receive the message. This means that @command{./write} blocks -while @command{./poll} sleeps. If two or more instances of -@command{./write} is started at approximately the same time, -only one will continue to write a message on the bus, the -others will fail. - -@command{./poll} will stop if the message ``stop'' is -broadcasted. - -@command{./poll}, @command{./init} and @command{./cleanup} -are run without any additional arguments. @command{./write} -is run with the message as the second argument. - - -@subsubheading @file{./Makefile} -@example -COMMANDS = init cleanup write poll - -all: $@{COMMANDS@} -%: %.c - $@{CC@} -Wall -Wextra -pedantic -std=c99 -lbus -o $@@ $< -clean: - -rm $@{COMMANDS@} - -.PHONY: all clean -@end example - - -@subsubheading @file{./cleanup.c} -@example -#include <bus.h> -#include <stdio.h> - -int main() -@{ - return bus_unlink("/tmp/example-bus") && (perror("cleanup"), 1); -@} -@end example - - -@subsubheading @file{./init.c} -@example -#include <bus.h> -#include <stdio.h> - -int main() -@{ - return bus_create("/tmp/example-bus", 0, NULL) && (perror("init"), 1); -@} -@end example - - -@subsubheading @file{./poll.c} -@example -#include <bus.h> -#include <stdio.h> -#include <unistd.h> -#include <string.h> -#include <errno.h> - -#define t(stmt) if (stmt) goto fail - -int main() -@{ - bus_t bus; - const char *message; - long long tick = 0; - t (bus_open(&bus, "/tmp/example-bus", BUS_RDONLY)); - t (bus_poll_start(&bus)); - for (;;) @{ - message = bus_poll(&bus, BUS_NOWAIT); - if (message == NULL) @{ - t (errno != EAGAIN); - printf("waiting... %lli\n", ++tick); - sleep(1); - continue; - @} - tick = 0; - message = strchr(message, ' ') + 1; - if (!strcmp(message, "stop")) - break; - printf("\033[01m%s\033[21m\n", message); - @} - t (bus_poll_stop(&bus)); - bus_close(&bus); - return 0; - -fail: - perror("poll"); - bus_poll_stop(&bus); - bus_close(&bus); - return 1; -@} -@end example - - -@subsubheading @file{./write.c} -@example -#include <bus.h> -#include <stdio.h> -#include <unistd.h> -#include <stdint.h> - -#define t(stmt) if (stmt) goto fail - -static char message[BUS_MEMORY_SIZE]; - -int main(int argc, char *argv[]) -@{ - bus_t bus; - if (argc < 2) @{ - fprintf(stderr, "%s: USAGE: %s message\n", argv[0], argv[0]); - return 2; - @} - sprintf(message, "0 %s", argv[1]); - t (bus_open(&bus, "/tmp/example-bus", BUS_WRONLY)); - t (bus_write(&bus, message, BUS_NOWAIT)); - bus_close(&bus); - return 0; - -fail: - perror("write"); - bus_close(&bus); - return 1; -@} -@end example - - - -@node Daemon-dependencies -@section Daemon-dependencies - -This example shows how bus can be used in an init system -to provide ``aggressivly'' parallel startup of daemons. - -First of, run make to build this example. - -To start the example run @command{./init}. It will print in -red export-statement you may want to run i other terminals. -You will need to select at least one daemon, for example -you can run @code{./init d-ntp}. The available pretend -daemons are: @command{d-network}, @command{d-ntp}, and -@command{d-ssh}. - -When you are done run @command{./cleanup} with @env{BUS_INIT} -exported with the value printed by @command{./init}. - - -@subsubheading @file{./Makefile} -@example -COMMANDS = announce await-ready await-started cleanup \ - init require start-daemon test-daemon - -all: $@{COMMANDS@} -%: %.c - $@{CC@} -Wall -Wextra -pedantic -std=c99 -lbus -o $@@ $< -clean: - -rm $@{COMMANDS@} - -rm -r run - -.PHONY: all clean -@end example - - -@subsubheading @file{./announce.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> -#include <stdint.h> -#include <unistd.h> - -#define t(stmt) if (stmt) goto fail - -static char arg[4098]; - -int main(int argc, char *argv[]) -@{ - bus_t bus; - if (argc < 3) - return fprintf(stderr, "USAGE: %s state daemon", *argv), 2; - t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY)); - sprintf(arg, "%ji %s %s", (intmax_t)getppid(), argv[1], argv[2]); - t (bus_write(&bus, arg, 0)); - t (bus_close(&bus)); - return 0; - -fail: - perror("announce"); - return 1; -@} -@end example - - -@subsubheading @file{./await-ready.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> -#include <stdint.h> -#include <unistd.h> -#include <string.h> -#include <sys/wait.h> - -#define t(stmt) if (stmt) goto fail - -static char arg[4098]; -static int argc; -static char **argv; -static int remaining = 0; -static char *started = NULL; -static char msg[BUS_MEMORY_SIZE]; - -static void announce_wait(pid_t pid) -@{ - bus_t bus; - int i; - t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY)); - for (i = 1; i < argc; i++) @{ - if (!started[i]) @{ - sprintf(arg, "%ji awaiting-ready %s", (intmax_t)pid, argv[i]); - t (bus_write(&bus, arg, 0)); - @} - @} - t (bus_close(&bus)); - return; - -fail: - perror("await-ready"); -@} - -static int callback(const char *message, void *user_data) -@{ - int i; - char *arg2; - char *arg3; - pid_t pid; - pid_t ppid; - - if (!message) @{ - ppid = getppid(); - pid = fork(); - if (pid == 0) @{ - if (fork() == 0) - announce_wait(ppid); - exit(0); - @} else @{ - (void) waitpid(pid, NULL, 0); - /* @w{@xrm{}Let's pretend everything will go swimmingly.@xtt{}} */ - @} - return 1; - @} - - strncpy(msg, message, BUS_MEMORY_SIZE - 1); - msg[BUS_MEMORY_SIZE - 1] = 0; - - arg2 = strchr(msg, ' '); - if (!arg2) - return 1; - arg3 = strchr(++arg2, ' '); - if (!arg3) - return 1; - *arg3++ = 0; - - if (strcmp(arg2, "ready")) - return 1; - - for (i = 1; i < argc; i++) - if (!started[i] && !strcmp(argv[i], arg3)) - started[i] = 1, remaining--; - - return !!remaining; - (void) user_data; -@} - -int main(int argc_, char *argv_[]) -@{ - bus_t bus; - int i; - - argc = argc_; - argv = argv_; - - if (argc < 2) - return fprintf(stderr, "USAGE: %s daemon...", *argv), 2; - t (bus_open(&bus, getenv("BUS_INIT"), BUS_RDONLY)); - started = calloc(argc, sizeof(char)); - t (started == NULL); - - started[0] = 1; - for (i = 1; i < argc; i++) @{ - sprintf(arg, "grep '^%s$'" - " <\"$@{XDG_RUNTIME_DIR@}/ready-daemons\"" - " >/dev/null", - argv[i]); - if (!WEXITSTATUS(system(arg))) - started[i] = 1; - else - remaining++; - @} - - if (remaining) - bus_read(&bus, callback, NULL); - - bus_close(&bus); - free(started); - return 0; - -fail: - perror("await-ready"); - bus_close(&bus); - free(started); - return 1; -@} -@end example - - -@subsubheading @file{./await-started.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> -#include <stdint.h> -#include <unistd.h> -#include <string.h> -#include <sys/wait.h> - -#define t(stmt) if (stmt) goto fail - -static char arg[4098]; -static int argc; -static char **argv; -static int remaining = 0; -static char *started = NULL; -static char msg[BUS_MEMORY_SIZE]; - -static void announce_wait(pid_t pid) -@{ - bus_t bus; - int i; - t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY)); - for (i = 1; i < argc; i++) @{ - if (!started[i]) @{ - sprintf(arg, "%ji awaiting-started %s", (intmax_t)pid, argv[i]); - t (bus_write(&bus, arg, 0)); - @} - @} - t (bus_close(&bus)); - return; - -fail: - perror("await-started"); -@} - -static int callback(const char *message, void *user_data) -@{ - int i; - char *arg2; - char *arg3; - pid_t pid; - pid_t ppid; - - if (!message) @{ - ppid = getppid(); - pid = fork(); - if (pid == 0) @{ - if (fork() == 0) - announce_wait(ppid); - exit(0); - @} else @{ - (void) waitpid(pid, NULL, 0); - /* @w{@xrm{}Let's pretend everything will go swimmingly.@xtt{}} */ - @} - return 1; - @} - - strncpy(msg, message, BUS_MEMORY_SIZE - 1); - msg[BUS_MEMORY_SIZE - 1] = 0; - - arg2 = strchr(msg, ' '); - if (!arg2) - return 1; - arg3 = strchr(++arg2, ' '); - if (!arg3) - return 1; - *arg3++ = 0; - - if (strcmp(arg2, "started") && strcmp(arg2, "ready")) - return 1; - - for (i = 1; i < argc; i++) - if (!started[i] && !strcmp(argv[i], arg3)) - started[i] = 1, remaining--; - - return !!remaining; - (void) user_data; -@} - -int main(int argc_, char *argv_[]) -@{ - bus_t bus; - int i; - - argc = argc_; - argv = argv_; - - if (argc < 2) - return fprintf(stderr, "USAGE: %s daemon...", *argv), 2; - t (bus_open(&bus, getenv("BUS_INIT"), BUS_RDONLY)); - started = calloc(argc, sizeof(char)); - t (started == NULL); - - started[0] = 1; - for (i = 1; i < argc; i++) @{ - sprintf(arg, "grep '^%s$'" - " <\"$@{XDG_RUNTIME_DIR@}/started-daemons\"" - " >/dev/null", - argv[i]); - if (!WEXITSTATUS(system(arg))) @{ - started[i] = 1; - @} else @{ - sprintf(arg, "grep '^%s$'" - " <\"$@{XDG_RUNTIME_DIR@}/ready-daemons\"" - " >/dev/null", - argv[i]); - if (!WEXITSTATUS(system(arg))) - started[i] = 1; - else - remaining++; - @} - @} - - if (remaining) - bus_read(&bus, callback, NULL); - - bus_close(&bus); - free(started); - return 0; - -fail: - perror("await-started"); - bus_close(&bus); - free(started); - return 1; -@} -@end example - - -@subsubheading @file{./cleanup.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> - -#define t(stmt) if (stmt) goto fail - -int main() -@{ - char *bus_address = getenv("BUS_INIT"); - if (!bus_address || !*bus_address) @{ - fprintf(stderr, "$BUS_INIT has not been set, its export statement " - "should have been printed in bold red by ./init\n"); - return 1; - @} - t (bus_unlink(bus_address)); - return 0; - -fail: - perror("cleanup"); - return 1; -@} -@end example - - -@subsubheading @file{./d-network} -@example -#!/bin/sh -PATH=.:$PATH -d=d-network - -echo $d: starting -sleep 2 -echo $d: ready -announce ready $d -@end example - - -@subsubheading @file{./d-ntp} -@example -#!/bin/sh -PATH=.:$PATH -d=d-ntp - -require d-network -echo $d: started -announce started $d -await-ready d-network -echo $d: ready -announce ready $d -@end example - - -@subsubheading @file{./d-ssh} -@example -#!/bin/sh -PATH=.:$PATH -d=d-ssh - -require d-network -echo $d: starting -sleep 1 -echo $d: started -announce started $d -sleep 1 -echo $d: ready -announce ready $d -@end example - - -@subsubheading @file{./init.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> -#include <string.h> -#include <unistd.h> -#include <sys/wait.h> - -#define t(stmt) if (stmt) goto fail -#define _2(...) __VA_ARGS__, __VA_ARGS__ - -static char msg[BUS_MEMORY_SIZE]; -static int argc; -static char **argv; -static char arg[4098]; - -static void start_daemons() -@{ - int i; - for (i = 1; i < argc; i++) - if (fork() == 0) - execl("./start-daemon", "./start-daemon", argv[i], NULL); -@} - -static int callback(const char *message, void *user_data) -@{ - pid_t pid; - char *arg2; - char *arg3; - if (!message) @{ - pid = fork(); - t (pid == -1); - if (pid == 0) @{ - if (fork() == 0) @{ - start_daemons(); - @} - exit(0); - @} else @{ - (void) waitpid(pid, NULL, 0); - /* @w{@xrm{}Let's pretend everything will go swimmingly.@xtt{}} */ - @} - return 1; - @} - - strncpy(msg, message, BUS_MEMORY_SIZE - 1); - msg[BUS_MEMORY_SIZE - 1] = 0; - - pid = fork(); - t (pid == -1); - - if (pid == 0) @{ - if (fork() == 0) @{ - arg2 = strchr(msg, ' '); - if (arg2 == NULL) - exit(0); - arg3 = strchr(++arg2, ' '); - if (arg3 == NULL) - exit(0); - *arg3++ = 0; - if (!strcmp(arg2, "require")) @{ - execl(_2("./start-daemon"), arg3, NULL); - @} else if (!strcmp(arg2, "awaiting-started")) @{ - execl(_2("./test-daemon"), arg3, "started", NULL); - @} else if (!strcmp(arg2, "awaiting-ready") || - !strcmp(arg2, "awaiting")) @{ - execl(_2("./test-daemon"), arg3, "ready", NULL); - @} else if (!strcmp(arg2, "started")) @{ - sprintf(arg, - "grep '^%s\\$' < \"%s\" >/dev/null || echo %s >> \"%s\"", - _2(arg3, "$@{XDG_RUNTIME_DIR@}/started-daemons")); - execlp(_2("sh"), "-c", arg, NULL); - @} else if (!strcmp(arg2, "ready")) @{ - sprintf(arg, - "grep '^%s\\$' < \"%s\" >/dev/null || echo %s >> \"%s\"", - _2(arg3, "$@{XDG_RUNTIME_DIR@}/ready-daemons")); - execlp(_2("sh"), "-c", arg, NULL); - @} - @} - exit(0); - @} else @{ - (void) waitpid(pid, NULL, 0); - /* @w{@xrm{}Let's pretend everything will go swimmingly.@xtt{}} */ - @} - - return 1; - (void) user_data; - -fail: - perror("init"); - return -1; -@} - -int main(int argc_, char *argv_[]) -@{ - char *bus_address = NULL; - bus_t bus; - argv = argv_; - argc = argc_; - if (argc < 2) @{ - fprintf(stderr, "USAGE: %s daemon...\n", *argv); - return 1; - @} - t (setenv("XDG_RUNTIME_DIR", "./run", 1)); - /* @w{@xrm{}Real init systems with not have the period.@xtt{}} */ - system("mkdir -p -- \"$@{XDG_RUNTIME_DIR@}\""); - system("truncate -s 0 -- \"$@{XDG_RUNTIME_DIR@}/started-daemons\""); - system("truncate -s 0 -- \"$@{XDG_RUNTIME_DIR@}/ready-daemons\""); - t (bus_create(NULL, 1, &bus_address)); - fprintf(stderr, "\033[00;01;31mexport BUS_INIT=%s\033[00m\n", - bus_address); - fprintf(stderr, "\033[00;31mexport XDG_RUNTIME_DIR=./run\033[00m\n"); - t (setenv("BUS_INIT", bus_address, 1)); - t (bus_open(&bus, bus_address, BUS_RDONLY)); - t (bus_read(&bus, callback, NULL)); - bus_close(&bus); - free(bus_address); - return 0; - -fail: - perror("init"); - bus_close(&bus); - free(bus_address); - return 1; -@} -@end example - - -@subsubheading @file{./require.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> -#include <stdint.h> -#include <unistd.h> - -#define t(stmt) if (stmt) goto fail - -static char arg[4098]; - -int main(int argc, char *argv[]) -@{ - bus_t bus; - int i; - if (argc < 2) - return fprintf(stderr, "USAGE: %s daemon...", *argv), 2; - t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY)); - - for (i = 1; i < argc; i++) @{ - sprintf(arg, "grep '^%s$' <\"%s\" >/dev/null", - argv[i], "$@{XDG_RUNTIME_DIR@}/started-daemons"); - if (WEXITSTATUS(system(arg))) @{ - sprintf(arg, "%ji require %s", (intmax_t)getppid(), argv[i]); - t (bus_write(&bus, arg, 0)); - @} - @} - - bus_close(&bus); - return 0; - -fail: - perror("require"); - bus_close(&bus); - return 1; -@} -@end example - - -@subsubheading @file{./start-daemon.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> -#include <stdlib.h> -#include <string.h> -#include <unistd.h> - -static char arg[4098]; - -int main(int argc, char *argv[]) -@{ - if (argc != 2) @{ - fprintf(stderr, "This program should be called from ./init\n"); - return 2; - @} - - sprintf(arg, "grep '^%s$' <\"%s\" >/dev/null", - argv[1], "$@{XDG_RUNTIME_DIR@}/started-daemons"); - if (!WEXITSTATUS(system(arg))) - return 0; - sprintf(arg, "grep '^%s$' <\"%s\" >/dev/null", - argv[1], "$@{XDG_RUNTIME_DIR@}/ready-daemons"); - if (!WEXITSTATUS(system(arg))) - return 0; - - sprintf(arg, "./%s", argv[1]); - execlp(arg, arg, NULL); - perror("start-daemon"); - return 1; -@} -@end example - - -@subsubheading @file{./test-daemon.c} -@example -#include <bus.h> -#include <stdio.h> -#include <stdlib.h> -#include <string.h> - -#define t(stmt) if (stmt) goto fail - -static char arg[4098]; - -int main(int argc, char *argv[]) -@{ - bus_t bus; - if (argc != 3) @{ - fprintf(stderr, "This program should be called from ./init\n"); - return 2; - @} - -retry: - sprintf(arg, "grep '^%s$'" - " <\"$@{XDG_RUNTIME_DIR@}/%s-daemons\"" - " >/dev/null", - argv[1], argv[2]); - if (!WEXITSTATUS(system(arg))) @{ - t (bus_open(&bus, getenv("BUS_INIT"), BUS_WRONLY)); - sprintf(arg, "0 %s %s", argv[2], argv[1]); - t (bus_write(&bus, arg, 0)); - bus_close(&bus); - @} else if (!strcmp(argv[2], "started")) @{ - argv[2] = "ready"; - goto retry; - @} - return 0; - -fail: - perror("test-daemon"); - return 1; -@} -@end example - - - -@node GNU Free Documentation License -@appendix GNU Free Documentation License -@include fdl.texinfo - -@bye - |