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4 <!-- lifted from troff+man by doclifter -->
5 <refentry id='dbuslaunch1'>
7 <!-- dbus\-launch manual page.
8 Copyright (C) 2003 Red Hat, Inc. -->
11 <refentrytitle>dbus-launch</refentrytitle>
12 <manvolnum>1</manvolnum>
15 <refname>dbus-launch</refname>
16 <refpurpose>Utility to start a message bus from a shell script</refpurpose>
18 <!-- body begins here -->
19 <refsynopsisdiv id='synopsis'>
21 <command>dbus-launch</command> <arg choice='opt'>--version </arg>
22 <arg choice='opt'>--sh-syntax </arg>
23 <arg choice='opt'>--csh-syntax </arg>
24 <arg choice='opt'>--auto-syntax </arg>
25 <arg choice='opt'>--exit-with-session </arg>
26 <arg choice='opt'>--autolaunch=<replaceable>MACHINEID</replaceable></arg>
27 <arg choice='opt'>--config-file=<replaceable>FILENAME</replaceable></arg>
28 <arg choice='opt'><replaceable>PROGRAM</replaceable></arg>
29 <arg choice='opt' rep='repeat'><replaceable>ARGS</replaceable></arg>
35 <refsect1 id='description'><title>DESCRIPTION</title>
36 <para>The <command>dbus-launch</command> command is used to start a session bus
37 instance of <emphasis remap='I'>dbus-daemon</emphasis> from a shell script.
38 It would normally be called from a user's login
39 scripts. Unlike the daemon itself, <command>dbus-launch</command> exits, so
40 backticks or the $() construct can be used to read information from
41 <command>dbus-launch</command>.</para>
43 <para>With no arguments, <command>dbus-launch</command> will launch a session bus
44 instance and print the address and PID of that instance to standard
47 <para>You may specify a program to be run; in this case, <command>dbus-launch</command>
48 will launch a session bus instance, set the appropriate environment
49 variables so the specified program can find the bus, and then execute the
50 specified program, with the specified arguments. See below for
53 <para>If you launch a program, <command>dbus-launch</command> will not print the
54 information about the new bus to standard output.</para>
56 <para>When <command>dbus-launch</command> prints bus information to standard output, by
57 default it is in a simple key-value pairs format. However, you may
58 request several alternate syntaxes using the --sh-syntax, --csh-syntax,
60 --auto-syntax options. Several of these cause <command>dbus-launch</command> to emit shell code
61 to set up the environment.</para>
63 <para>With the --auto-syntax option, <command>dbus-launch</command> looks at the value
64 of the SHELL environment variable to determine which shell syntax
65 should be used. If SHELL ends in "csh", then csh-compatible code is
66 emitted; otherwise Bourne shell code is emitted. Instead of passing
67 --auto-syntax, you may explicitly specify a particular one by using
68 --sh-syntax for Bourne syntax, or --csh-syntax for csh syntax.
69 In scripts, it's more robust to avoid --auto-syntax and you hopefully
70 know which shell your script is written in.</para>
73 <para>See <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink> for more information
74 about D-Bus. See also the man page for <emphasis remap='I'>dbus-daemon</emphasis>.</para>
78 <refsect1 id='examples'><title>EXAMPLES</title>
79 <para>Distributions running
80 <command>dbus-launch</command>
81 as part of a standard X session should run
82 <emphasis remap='B'>dbus-launch --exit-with-session</emphasis>
83 after the X server has started and become available, as a wrapper around
84 the "main" X client (typically a session manager or window manager), as in
85 these examples:</para>
87 <blockquote remap='RS'>
88 <para><emphasis remap='B'>dbus-launch --exit-with-session gnome-session</emphasis></para>
90 <para><emphasis remap='B'>dbus-launch --exit-with-session openbox</emphasis></para>
92 <para><emphasis remap='B'>dbus-launch --exit-with-session ~/.xsession</emphasis>
93 </para></blockquote> <!-- remap='RE' -->
95 <para>If your distribution does not do this, you can achieve similar results
96 by running your session or window manager in the same way in a script
97 run by your X session, such as
98 <filename>~/.xsession</filename>,
99 <filename>~/.xinitrc</filename>
101 <filename>~/.Xclients</filename>.</para>
103 <para>To start a D-Bus session within a text-mode session, you can run
104 dbus-launch in the background. For instance, in a sh-compatible shell:</para>
106 <literallayout remap='.nf'>
107 ## test for an existing bus daemon, just to be safe
108 if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
109 ## if not found, launch a new one
110 eval `dbus-launch --sh-syntax`
111 echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
113 </literallayout> <!-- .fi -->
114 <para>Note that in this case, dbus-launch will exit, and dbus-daemon will not be
115 terminated automatically on logout.</para>
119 <refsect1 id='automatic_launching'><title>AUTOMATIC LAUNCHING</title>
120 <para>If DBUS_SESSION_BUS_ADDRESS is not set for a process that tries to use
121 D-Bus, by default the process will attempt to invoke dbus-launch with
122 the --autolaunch option to start up a new session bus or find the
123 existing bus address on the X display or in a file in
124 ~/.dbus/session-bus/</para>
127 <para>Whenever an autolaunch occurs, the application that had to
128 start a new bus will be in its own little world; it can effectively
129 end up starting a whole new session if it tries to use a lot of
130 bus services. This can be suboptimal or even totally broken, depending
131 on the app and what it tries to do.</para>
134 <para>There are two common reasons for autolaunch. One is ssh to a remote
135 machine. The ideal fix for that would be forwarding of
136 DBUS_SESSION_BUS_ADDRESS in the same way that DISPLAY is forwarded.
137 In the meantime, you can edit the session.conf config file to
138 have your session bus listen on TCP, and manually set
139 DBUS_SESSION_BUS_ADDRESS, if you like.</para>
142 <para>The second common reason for autolaunch is an su to another user, and
143 display of X applications running as the second user on the display
144 belonging to the first user. Perhaps the ideal fix in this case
145 would be to allow the second user to connect to the session bus of the
146 first user, just as they can connect to the first user's display.
147 However, a mechanism for that has not been coded.</para>
150 <para>You can always avoid autolaunch by manually setting
151 DBUS_SESSION_BUS_ADDRESS. Autolaunch happens because the default
152 address if none is set is "autolaunch:", so if any other address is
153 set there will be no autolaunch. You can however include autolaunch in
154 an explicit session bus address as a fallback, for example
155 DBUS_SESSION_BUS_ADDRESS="something:,autolaunch:" - in that case if
156 the first address doesn't work, processes will autolaunch. (The bus
157 address variable contains a comma-separated list of addresses to try.)</para>
160 <para>The --autolaunch option is considered an internal implementation
161 detail of libdbus, and in fact there are plans to change it. There's
162 no real reason to use it outside of the libdbus implementation anyhow.</para>
166 <refsect1 id='options'><title>OPTIONS</title>
167 <para>The following options are supported:</para>
168 <variablelist remap='TP'>
170 <term><option>--auto-syntax</option></term>
172 <para>Choose --csh-syntax or --sh-syntax based on the SHELL environment variable.</para>
174 <para><option>--binary-syntax</option>
175 Write to stdout a nul-terminated bus address, then the bus PID as a
176 binary integer of size sizeof(pid_t), then the bus X window ID as a
177 binary integer of size sizeof(long). Integers are in the machine's
178 byte order, not network byte order or any other canonical byte order.</para>
183 <term><option>--close-stderr</option></term>
185 <para>Close the standard error output stream before starting the D-Bus
186 daemon. This is useful if you want to capture dbus-launch error
187 messages but you don't want dbus-daemon to keep the stream open to
188 your application.</para>
193 <term><option>--config-file=FILENAME</option></term>
195 <para>Pass --config-file=FILENAME to the bus daemon, instead of passing it
196 the --session argument. See the man page for dbus-daemon</para>
201 <term><option>--csh-syntax</option></term>
203 <para>Emit csh compatible code to set up environment variables.</para>
208 <term><option>--exit-with-session</option></term>
210 <para>If this option is provided, a persistent "babysitter" process will be
211 created that watches stdin for HUP and tries to connect to the X
212 server. If this process gets a HUP on stdin or loses its X connection,
213 it kills the message bus daemon.</para>
218 <term><option>--autolaunch=MACHINEID</option></term>
220 <para>This option implies that <command>dbus-launch</command> should scan for a
221 previously-started session and reuse the values found there. If no
222 session is found, it will start a new session. The
223 --exit-with-session option is implied if --autolaunch is given.
224 This option is for the exclusive use of libdbus, you do not want to
225 use it manually. It may change in the future.</para>
230 <term><option>--sh-syntax</option></term>
232 <para>Emit Bourne-shell compatible code to set up environment variables.</para>
237 <term><option>--version</option></term>
239 <para>Print the version of dbus-launch</para>
246 <refsect1 id='notes'><title>NOTES</title>
248 <emphasis remap='B'>dbus-launch myapp</emphasis>
249 (with any other options), dbus-daemon will
250 <emphasis remap='I'>not</emphasis>
252 <emphasis remap='B'>myapp</emphasis>
253 terminates: this is because
254 <emphasis remap='B'>myapp</emphasis>
255 is assumed to be part of a larger session, rather than a session in its
260 <refsect1 id='author'><title>AUTHOR</title>
261 <para>See <ulink url='http://www.freedesktop.org/software/dbus/doc/AUTHORS'>http://www.freedesktop.org/software/dbus/doc/AUTHORS</ulink></para>
265 <refsect1 id='bugs'><title>BUGS</title>
266 <para>Please send bug reports to the D-Bus mailing list or bug tracker,
267 see <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink></para>