1DBUS-LAUNCH(1) User Commands DBUS-LAUNCH(1)
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6 dbus-launch - Utility to start a message bus from a shell script
7
9 dbus-launch [--version] [--help] [--sh-syntax] [--csh-syntax]
10 [--auto-syntax] [--binary-syntax] [--close-stderr]
11 [--exit-with-session] [--autolaunch=MACHINEID]
12 [--config-file=FILENAME] [PROGRAM] [ARGS...]
13
16 The dbus-launch command is used to start a session bus instance of
17 dbus-daemon from a shell script. It would normally be called from a
18 user's login scripts. Unlike the daemon itself, dbus-launch exits, so
19 backticks or the $() construct can be used to read information from
20 dbus-launch.
21 With no arguments, dbus-launch will launch a session bus instance and
23 print the address and PID of that instance to standard output.
24 If the environment variable HOME is set, it is used as the current
26 working directory. Otherwise, the root directory (/) is used.
27 You may specify a program to be run; in this case, dbus-launch will
29 launch a session bus instance, set the appropriate environment
30 variables so the specified program can find the bus, and then execute
31 the specified program, with the specified arguments. See below for
32 examples.
33 If you launch a program, dbus-launch will not print the information
35 about the new bus to standard output.
36 When dbus-launch prints bus information to standard output, by default
38 it is in a simple key-value pairs format. However, you may request
39 several alternate syntaxes using the --sh-syntax, --csh-syntax,
40 --binary-syntax, or --auto-syntax options. Several of these cause
41 dbus-launch to emit shell code to set up the environment.
42 With the --auto-syntax option, dbus-launch looks at the value of the
44 SHELL environment variable to determine which shell syntax should be
45 used. If SHELL ends in "csh", then csh-compatible code is emitted;
46 otherwise Bourne shell code is emitted. Instead of passing
47 --auto-syntax, you may explicitly specify a particular one by using
48 --sh-syntax for Bourne syntax, or --csh-syntax for csh syntax. In
49 scripts, it's more robust to avoid --auto-syntax and you hopefully know
50 which shell your script is written in.
51 See http://www.freedesktop.org/software/dbus/ for more information
53 about D-Bus. See also the man page for dbus-daemon.
54
56 Distributions running dbus-launch as part of a standard X session
57 should run dbus-launch --exit-with-session after the X server has
58 started and become available, as a wrapper around the "main" X client
59 (typically a session manager or window manager), as in these examples:
60 dbus-launch --exit-with-session gnome-session
62 dbus-launch --exit-with-session openbox
64 dbus-launch --exit-with-session ~/.xsession
66 If your distribution does not do this, you can achieve similar results
68 by running your session or window manager in the same way in a script
69 run by your X session, such as ~/.xsession, ~/.xinitrc or ~/.Xclients.
70 To start a D-Bus session within a text-mode session, do not use
72 dbus-launch. Instead, see dbus-run-session(1).
73 ## test for an existing bus daemon, just to be safe
75 if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
76 ## if not found, launch a new one
77 eval `dbus-launch --sh-syntax`
78 echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
79 fi
80 Note that in this case, dbus-launch will exit, and dbus-daemon will not
82 be terminated automatically on logout.
83
85 If DBUS_SESSION_BUS_ADDRESS is not set for a process that tries to use
86 D-Bus, by default the process will attempt to invoke dbus-launch with
87 the --autolaunch option to start up a new session bus or find the
88 existing bus address on the X display or in a file in
89 ~/.dbus/session-bus/
90 Whenever an autolaunch occurs, the application that had to start a new
92 bus will be in its own little world; it can effectively end up starting
93 a whole new session if it tries to use a lot of bus services. This can
94 be suboptimal or even totally broken, depending on the app and what it
95 tries to do.
96 There are two common reasons for autolaunch. One is ssh to a remote
98 machine. The ideal fix for that would be forwarding of
99 DBUS_SESSION_BUS_ADDRESS in the same way that DISPLAY is forwarded. In
100 the meantime, you can edit the session.conf config file to have your
101 session bus listen on TCP, and manually set DBUS_SESSION_BUS_ADDRESS,
102 if you like.
103 The second common reason for autolaunch is an su to another user, and
105 display of X applications running as the second user on the display
106 belonging to the first user. Perhaps the ideal fix in this case would
107 be to allow the second user to connect to the session bus of the first
108 user, just as they can connect to the first user's display. However, a
109 mechanism for that has not been coded.
110 You can always avoid autolaunch by manually setting
112 DBUS_SESSION_BUS_ADDRESS. Autolaunch happens because the default
113 address if none is set is "autolaunch:", so if any other address is set
114 there will be no autolaunch. You can however include autolaunch in an
115 explicit session bus address as a fallback, for example
116 DBUS_SESSION_BUS_ADDRESS="something:,autolaunch:" - in that case if the
117 first address doesn't work, processes will autolaunch. (The bus address
118 variable contains a comma-separated list of addresses to try.)
119 The --autolaunch option is considered an internal implementation detail
121 of libdbus, and in fact there are plans to change it. There's no real
122 reason to use it outside of the libdbus implementation anyhow.
123
125 The following options are supported:
126 --auto-syntax
128 Choose --csh-syntax or --sh-syntax based on the SHELL environment
129 variable.
130 --binary-syntax
132 Write to stdout a nul-terminated bus address, then the bus PID as a
133 binary integer of size sizeof(pid_t), then the bus X window ID as a
134 binary integer of size sizeof(long). Integers are in the machine's
135 byte order, not network byte order or any other canonical byte
136 order.
137 --close-stderr
139 Close the standard error output stream before starting the D-Bus
140 daemon. This is useful if you want to capture dbus-launch error
141 messages but you don't want dbus-daemon to keep the stream open to
142 your application.
143 --config-file=FILENAME
145 Pass --config-file=FILENAME to the bus daemon, instead of passing
146 it the --session argument. See the man page for dbus-daemon
147 --csh-syntax
149 Emit csh compatible code to set up environment variables.
150 --exit-with-session
152 If this option is provided, a persistent "babysitter" process will
153 be created that watches stdin for HUP and tries to connect to the X
154 server. If this process gets a HUP on stdin or loses its X
155 connection, it kills the message bus daemon.
156 --autolaunch=MACHINEID
158 This option implies that dbus-launch should scan for a
159 previously-started session and reuse the values found there. If no
160 session is found, it will start a new session. The
161 --exit-with-session option is implied if --autolaunch is given.
162 This option is for the exclusive use of libdbus, you do not want to
163 use it manually. It may change in the future.
164 --sh-syntax
166 Emit Bourne-shell compatible code to set up environment variables.
167 --version
169 Print the version of dbus-launch
170 --help
172 Print the help info of dbus-launch
173
175 If you run dbus-launch myapp (with any other options), dbus-daemon will
176 not exit when myapp terminates: this is because myapp is assumed to be
177 part of a larger session, rather than a session in its own right.
178
180 See http://www.freedesktop.org/software/dbus/doc/AUTHORS
181
183 Please send bug reports to the D-Bus mailing list or bug tracker, see
184 http://www.freedesktop.org/software/dbus/
185D-Bus 1.10.24 03/14/2019 DBUS-LAUNCH(1)