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2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
3                   "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
4<!-- lifted from troff+man by doclifter -->
5<refentry id='dbuslaunch1'>
6<!--   -->
7<!--  dbus\-launch manual page. -->
8<!--  Copyright (C) 2003 Red Hat, Inc. -->
9
10<refmeta>
11<refentrytitle>dbus-launch</refentrytitle>
12<manvolnum>1</manvolnum>
13</refmeta>
14<refnamediv id='name'>
15<refname>dbus-launch</refname>
16<refpurpose>Utility to start a message bus from a shell script</refpurpose>
17</refnamediv>
18<!-- body begins here -->
19<refsynopsisdiv id='synopsis'>
20<cmdsynopsis>
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>
30    <sbr/>
31</cmdsynopsis>
32</refsynopsisdiv>
33
34
35<refsect1 id='description'><title>DESCRIPTION</title>
36<para>The <command>dbus-launch</command> command is used to start a session bus
37instance of <emphasis remap='I'>dbus-daemon</emphasis> from a shell script.
38It would normally be called from a user's login
39scripts. Unlike the daemon itself, <command>dbus-launch</command> exits, so
40backticks or the $() construct can be used to read information from
41<command>dbus-launch</command>.</para>
42
43<para>With no arguments, <command>dbus-launch</command> will launch a session bus
44instance and print the address and pid of that instance to standard
45output.</para>
46
47<para>You may specify a program to be run; in this case, <command>dbus-launch</command>
48will launch a session bus instance, set the appropriate environment
49variables so the specified program can find the bus, and then execute the
50specified program, with the specified arguments.  See below for
51examples.</para>
52
53<para>If you launch a program, <command>dbus-launch</command> will not print the
54information about the new bus to standard output.</para>
55
56<para>When <command>dbus-launch</command> prints bus information to standard output, by
57default it is in a simple key-value pairs format. However, you may
58request several alternate syntaxes using the --sh-syntax, --csh-syntax,
59--binary-syntax, or
60--auto-syntax options. Several of these cause <command>dbus-launch</command> to emit shell code
61to set up the environment.</para>
62
63<para>With the --auto-syntax option, <command>dbus-launch</command> looks at the value
64of the SHELL environment variable to determine which shell syntax
65should be used.  If SHELL ends in "csh", then csh-compatible code is
66emitted; otherwise Bourne shell code is emitted.  Instead of passing
67--auto-syntax, you may explicity specify a particular one by using
68--sh-syntax for Bourne syntax, or --csh-syntax for csh syntax.
69In scripts, it's more robust to avoid --auto-syntax and you hopefully
70know which shell your script is written in.</para>
71
72
73<para>See <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink> for more information
74about D-Bus. See also the man page for <emphasis remap='I'>dbus-daemon</emphasis>.</para>
75
76
77<para>Here is an example of how to use <command>dbus-launch</command> with an
78sh-compatible shell to start the per-session bus daemon:</para>
79<literallayout remap='.nf'>
80
81  ## test for an existing bus daemon, just to be safe
82  if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
83      ## if not found, launch a new one
84      eval `dbus-launch --sh-syntax --exit-with-session`
85      echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
86  fi
87
88</literallayout> <!-- .fi -->
89<para>You might run something like that in your login scripts.</para>
90
91
92<para>Another way to use <command>dbus-launch</command> is to run your main session
93program, like so:</para>
94<literallayout remap='.nf'>
95
96dbus-launch gnome-session
97
98</literallayout> <!-- .fi -->
99<para>The above would likely be appropriate for ~/.xsession or ~/.Xclients.</para>
100
101</refsect1>
102
103<refsect1 id='automatic_launching'><title>AUTOMATIC LAUNCHING</title>
104<para>If DBUS_SESSION_BUS_ADDRESS is not set for a process that tries to use
105D-Bus, by default the process will attempt to invoke dbus-launch with
106the --autolaunch option to start up a new session bus or find the
107existing bus address on the X display or in a file in
108~/.dbus/session-bus/</para>
109
110
111<para>Whenever an autolaunch occurs, the application that had to
112start a new bus will be in its own little world; it can effectively
113end up starting a whole new session if it tries to use a lot of
114bus services. This can be suboptimal or even totally broken, depending
115on the app and what it tries to do.</para>
116
117
118<para>There are two common reasons for autolaunch. One is ssh to a remote
119machine. The ideal fix for that would be forwarding of
120DBUS_SESSION_BUS_ADDRESS in the same way that DISPLAY is forwarded.
121In the meantime, you can edit the session.conf config file to
122have your session bus listen on TCP, and manually set
123DBUS_SESSION_BUS_ADDRESS, if you like.</para>
124
125
126<para>The second common reason for autolaunch is an su to another user, and
127display of X applications running as the second user on the display
128belonging to the first user. Perhaps the ideal fix in this case
129would be to allow the second user to connect to the session bus of the
130first user, just as they can connect to the first user's display.
131However, a mechanism for that has not been coded.</para>
132
133
134<para>You can always avoid autolaunch by manually setting
135DBUS_SESSION_BUS_ADDRESS. Autolaunch happens because the default
136address if none is set is "autolaunch:", so if any other address is
137set there will be no autolaunch. You can however include autolaunch in
138an explicit session bus address as a fallback, for example
139DBUS_SESSION_BUS_ADDRESS="something:,autolaunch:" - in that case if
140the first address doesn't work, processes will autolaunch. (The bus
141address variable contains a comma-separated list of addresses to try.)</para>
142
143
144<para>The --autolaunch option is considered an internal implementation
145detail of libdbus, and in fact there are plans to change it. There's
146no real reason to use it outside of the libdbus implementation anyhow.</para>
147
148</refsect1>
149
150<refsect1 id='options'><title>OPTIONS</title>
151<para>The following options are supported:</para>
152<variablelist remap='TP'>
153  <varlistentry>
154  <term><option>--auto-syntax</option></term>
155  <listitem>
156<para>Choose --csh-syntax or --sh-syntax based on the SHELL environment variable.</para>
157
158<para><option>--binary-syntax</option>
159Write to stdout a nul-terminated bus address, then the bus PID as a
160binary integer of size sizeof(pid_t), then the bus X window ID as a
161binary integer of size sizeof(long). Integers are in the machine's
162byte order, not network byte order or any other canonical byte order.</para>
163
164  </listitem>
165  </varlistentry>
166  <varlistentry>
167  <term><option>--close-stderr</option></term>
168  <listitem>
169<para>Close the standard error output stream before starting the D-Bus
170daemon. This is useful if you want to capture dbus-launch error
171messages but you don't want dbus-daemon to keep the stream open to
172your application.</para>
173
174  </listitem>
175  </varlistentry>
176  <varlistentry>
177  <term><option>--config-file=FILENAME</option></term>
178  <listitem>
179<para>Pass --config-file=FILENAME to the bus daemon, instead of passing it
180the --session argument. See the man page for dbus-daemon</para>
181
182  </listitem>
183  </varlistentry>
184  <varlistentry>
185  <term><option>--csh-syntax</option></term>
186  <listitem>
187<para>Emit csh compatible code to set up environment variables.</para>
188
189  </listitem>
190  </varlistentry>
191  <varlistentry>
192  <term><option>--exit-with-session</option></term>
193  <listitem>
194<para>If this option is provided, a persistent "babysitter" process will be
195created that watches stdin for HUP and tries to connect to the X
196server. If this process gets a HUP on stdin or loses its X connection,
197it kills the message bus daemon.</para>
198
199  </listitem>
200  </varlistentry>
201  <varlistentry>
202  <term><option>--autolaunch=MACHINEID</option></term>
203  <listitem>
204<para>This option implies that <command>dbus-launch</command> should scan for a
205previously-started session and reuse the values found there. If no
206session is found, it will start a new session. The
207--exit-with-session option is implied if --autolaunch is given.
208This option is for the exclusive use of libdbus, you do not want to
209use it manually. It may change in the future.</para>
210
211  </listitem>
212  </varlistentry>
213  <varlistentry>
214  <term><option>--sh-syntax</option></term>
215  <listitem>
216<para>Emit Bourne-shell compatible code to set up environment variables.</para>
217
218  </listitem>
219  </varlistentry>
220  <varlistentry>
221  <term><option>--version</option></term>
222  <listitem>
223<para>Print the version of dbus-launch</para>
224
225  </listitem>
226  </varlistentry>
227</variablelist>
228</refsect1>
229
230<refsect1 id='author'><title>AUTHOR</title>
231<para>See <ulink url='http://www.freedesktop.org/software/dbus/doc/AUTHORS'>http://www.freedesktop.org/software/dbus/doc/AUTHORS</ulink></para>
232
233</refsect1>
234
235<refsect1 id='bugs'><title>BUGS</title>
236<para>Please send bug reports to the D-Bus mailing list or bug tracker,
237see <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink></para>
238</refsect1>
239</refentry>
240
241