1DBUS-LAUNCH(1)                   User Commands                  DBUS-LAUNCH(1)
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NAME

6       dbus-launch - Utility to start a message bus from a shell script
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SYNOPSIS

9       dbus-launch [--version] [--help] [--sh-syntax] [--csh-syntax]
10                   [--auto-syntax] [--binary-syntax] [--close-stderr]
11                   [--exit-with-session] [--exit-with-x11]
12                   [--autolaunch=MACHINEID] [--config-file=FILENAME] [PROGRAM]
13                   [ARGS...]
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DESCRIPTION

17       The dbus-launch command is used to start a session bus instance of
18       dbus-daemon from a shell script. It would normally be called from a
19       user's login scripts. Unlike the daemon itself, dbus-launch exits, so
20       backticks or the $() construct can be used to read information from
21       dbus-launch.
22
23       With no arguments, dbus-launch will launch a session bus instance and
24       print the address and PID of that instance to standard output.
25
26       You may specify a program to be run; in this case, dbus-launch will
27       launch a session bus instance, set the appropriate environment
28       variables so the specified program can find the bus, and then execute
29       the specified program, with the specified arguments. See below for
30       examples.
31
32       If you launch a program, dbus-launch will not print the information
33       about the new bus to standard output.
34
35       When dbus-launch prints bus information to standard output, by default
36       it is in a simple key-value pairs format. However, you may request
37       several alternate syntaxes using the --sh-syntax, --csh-syntax,
38       --binary-syntax, or --auto-syntax options. Several of these cause
39       dbus-launch to emit shell code to set up the environment.
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41       With the --auto-syntax option, dbus-launch looks at the value of the
42       SHELL environment variable to determine which shell syntax should be
43       used. If SHELL ends in "csh", then csh-compatible code is emitted;
44       otherwise Bourne shell code is emitted. Instead of passing
45       --auto-syntax, you may explicitly specify a particular one by using
46       --sh-syntax for Bourne syntax, or --csh-syntax for csh syntax. In
47       scripts, it's more robust to avoid --auto-syntax and you hopefully know
48       which shell your script is written in.
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50       See http://www.freedesktop.org/software/dbus/ for more information
51       about D-Bus. See also the man page for dbus-daemon.
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EXAMPLES

54       Distributions running dbus-launch as part of a standard X session
55       should run dbus-launch --exit-with-session after the X server has
56       started and become available, as a wrapper around the "main" X client
57       (typically a session manager or window manager), as in these examples:
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59       dbus-launch --exit-with-session gnome-session
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61       dbus-launch --exit-with-session openbox
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63       dbus-launch --exit-with-session ~/.xsession
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65       If your distribution does not do this, you can achieve similar results
66       by running your session or window manager in the same way in a script
67       run by your X session, such as ~/.xsession, ~/.xinitrc or ~/.Xclients.
68
69       To start a D-Bus session within a text-mode session, do not use
70       dbus-launch. Instead, see dbus-run-session(1).
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72             ## test for an existing bus daemon, just to be safe
73             if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
74                 ## if not found, launch a new one
75                 eval `dbus-launch --sh-syntax`
76                 echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
77             fi
78
79       Note that in this case, dbus-launch will exit, and dbus-daemon will not
80       be terminated automatically on logout.
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AUTOMATIC LAUNCHING

83       If DBUS_SESSION_BUS_ADDRESS is not set for a process that tries to use
84       D-Bus, by default the process will attempt to invoke dbus-launch with
85       the --autolaunch option to start up a new session bus or find the
86       existing bus address on the X display or in a file in
87       ~/.dbus/session-bus/
88
89       Whenever an autolaunch occurs, the application that had to start a new
90       bus will be in its own little world; it can effectively end up starting
91       a whole new session if it tries to use a lot of bus services. This can
92       be suboptimal or even totally broken, depending on the app and what it
93       tries to do.
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95       There are two common reasons for autolaunch. One is ssh to a remote
96       machine. The ideal fix for that would be forwarding of
97       DBUS_SESSION_BUS_ADDRESS in the same way that DISPLAY is forwarded. In
98       the meantime, you can edit the session.conf config file to have your
99       session bus listen on TCP, and manually set DBUS_SESSION_BUS_ADDRESS,
100       if you like.
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102       The second common reason for autolaunch is an su to another user, and
103       display of X applications running as the second user on the display
104       belonging to the first user. Perhaps the ideal fix in this case would
105       be to allow the second user to connect to the session bus of the first
106       user, just as they can connect to the first user's display. However, a
107       mechanism for that has not been coded.
108
109       You can always avoid autolaunch by manually setting
110       DBUS_SESSION_BUS_ADDRESS. Autolaunch happens because the default
111       address if none is set is "autolaunch:", so if any other address is set
112       there will be no autolaunch. You can however include autolaunch in an
113       explicit session bus address as a fallback, for example
114       DBUS_SESSION_BUS_ADDRESS="something:,autolaunch:" - in that case if the
115       first address doesn't work, processes will autolaunch. (The bus address
116       variable contains a comma-separated list of addresses to try.)
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118       The --autolaunch option is considered an internal implementation detail
119       of libdbus, and in fact there are plans to change it. There's no real
120       reason to use it outside of the libdbus implementation anyhow.
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OPTIONS

123       The following options are supported:
124
125       --auto-syntax
126           Choose --csh-syntax or --sh-syntax based on the SHELL environment
127           variable.
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129       --binary-syntax
130           Write to stdout a nul-terminated bus address, then the bus PID as a
131           binary integer of size sizeof(pid_t), then the bus X window ID as a
132           binary integer of size sizeof(long). Integers are in the machine's
133           byte order, not network byte order or any other canonical byte
134           order.
135
136       --close-stderr
137           Close the standard error output stream before starting the D-Bus
138           daemon. This is useful if you want to capture dbus-launch error
139           messages but you don't want dbus-daemon to keep the stream open to
140           your application.
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142       --config-file=FILENAME
143           Pass --config-file=FILENAME to the bus daemon, instead of passing
144           it the --session argument. See the man page for dbus-daemon
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146       --csh-syntax
147           Emit csh compatible code to set up environment variables.
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149       --exit-with-x11
150           If this option is provided, a persistent "babysitter" process will
151           be created, and will connect to the X server. If it cannot do so,
152           launching fails. If the "babysitter" process loses its X
153           connection, it kills the message bus daemon, disconnecting all of
154           its clients (which should exit in response). This avoids having
155           leftover daemon processes from a user X session, after the X
156           session has ended.
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158       --exit-with-session
159           If this option is provided, a persistent "babysitter" process will
160           be created, as if for --exit-with-x11. If it cannot connect to the
161           X server, it will monitor the terminal from which dbus-launch was
162           started instead, and if it gets a HUP on stdin, the message bus
163           daemon will be killed. This option is not recommended, since it
164           will consume input from the terminal where it was started; it is
165           mainly provided for backwards compatibility.
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167       --autolaunch=MACHINEID
168           This option implies that dbus-launch should scan for a
169           previously-started session and reuse the values found there. If no
170           session is found, it will start a new session. The
171           --exit-with-session option is implied if --autolaunch is given.
172           This option is for the exclusive use of libdbus, you do not want to
173           use it manually. It may change in the future.
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175       --sh-syntax
176           Emit Bourne-shell compatible code to set up environment variables.
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178       --version
179           Print the version of dbus-launch
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181       --help
182           Print the help info of dbus-launch
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NOTES

185       If you run dbus-launch myapp (with any other options), dbus-daemon will
186       not exit when myapp terminates: this is because myapp is assumed to be
187       part of a larger session, rather than a session in its own right.
188

AUTHOR

190       See http://www.freedesktop.org/software/dbus/doc/AUTHORS
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BUGS

193       Please send bug reports to the D-Bus mailing list or bug tracker, see
194       http://www.freedesktop.org/software/dbus/
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198D-Bus 1.12.20                     10/01/2021                    DBUS-LAUNCH(1)
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