NAME
dbus-launch - Utility to start a message bus from a shell script SYNOPSIS
dbus-launch [version] [help] [sh-syntax] [csh-syntax]
[auto-syntax] [binary-syntax] [close-stderr]
[exit-with-session] [autolaunch=MACHINEID]
[config-file=FILENAME] [PROGRAM] [ARGS...] DESCRIPTION
The dbus-launch command is used to start a session bus instance of
dbus-daemon from a shell script. It would normally be called from a
user's login scripts. Unlike the daemon itself, dbus-launch exits, so
backticks or the $() construct can be used to read information from
dbus-launch.
With no arguments, dbus-launch will launch a session bus instance and print the address and PID of that instance to standard output. If the environment variable HOME is set, it is used as the current working directory. Otherwise, the root directory (/) is used.
You may specify a program to be run; in this case, dbus-launch will launch a session bus instance, set the appropriate environment variables so the specified program can find the bus, and then execute the specified program, with the specified arguments. See below for examples.
If you launch a program, dbus-launch will not print the information about the new bus to standard output.
When dbus-launch prints bus information to standard output, by default
it is in a simple key-value pairs format. However, you may request
several alternate syntaxes using the sh-syntax, csh-syntax,
binary-syntax, or auto-syntax options. Several of these cause
dbus-launch to emit shell code to set up the environment.
With the auto-syntax option, dbus-launch looks at the value of the SHELL environment variable to determine which shell syntax should be
used. If SHELL ends in "csh", then csh-compatible code is emitted; otherwise Bourne shell code is emitted. Instead of passing
auto-syntax, you may explicitly specify a particular one by using
sh-syntax for Bourne syntax, or csh-syntax for csh syntax. In
scripts, it's more robust to avoid auto-syntax and you hopefully know which shell your script is written in. See http://www.freedesktop.org/software/dbus/ for more information
about D-Bus. See also the man page for dbus-daemon. EXAMPLES
Distributions running dbus-launch as part of a standard X session
should run dbus-launch exit-with-session after the X server has started and become available, as a wrapper around the "main" X client (typically a session manager or window manager), as in these examples:
dbus-launch exit-with-session gnome-session
dbus-launch exit-with-session openbox
dbus-launch exit-with-session ~/.xsession If your distribution does not do this, you can achieve similar results by running your session or window manager in the same way in a script run by your X session, such as ~/.xsession, ~/.xinitrc or ~/.Xclients.
To start a D-Bus session within a text-mode session, do not use
dbus-launch. Instead, see dbus-run-session(1).
## test for an existing bus daemon, just to be safe
if test -z "$DBUSSESSIONBUSADDRESS" ; then
## if not found, launch a new one
eval `dbus-launch sh-syntax`
echo "D-Bus per-session daemon address is: $DBUSSESSIONBUSADDRESS" fi
Note that in this case, dbus-launch will exit, and dbus-daemon will not be terminated automatically on logout. AUTOMATIC LAUNCHING If DBUSSESSIONBUSADDRESS is not set for a process that tries to use
D-Bus, by default the process will attempt to invoke dbus-launch with the autolaunch option to start up a new session bus or find the existing bus address on the X display or in a file in
~/.dbus/session-bus/ Whenever an autolaunch occurs, the application that had to start a new bus will be in its own little world; it can effectively end up starting a whole new session if it tries to use a lot of bus services. This can be suboptimal or even totally broken, depending on the app and what it tries to do. There are two common reasons for autolaunch. One is ssh to a remote machine. The ideal fix for that would be forwarding of DBUSSESSIONBUSADDRESS in the same way that DISPLAY is forwarded. In the meantime, you can edit the session.conf config file to have your session bus listen on TCP, and manually set DBUSSESSIONBUSADDRESS, if you like. The second common reason for autolaunch is an su to another user, and display of X applications running as the second user on the display belonging to the first user. Perhaps the ideal fix in this case would be to allow the second user to connect to the session bus of the first user, just as they can connect to the first user's display. However, a mechanism for that has not been coded. You can always avoid autolaunch by manually setting DBUSSESSIONBUSADDRESS. Autolaunch happens because the default address if none is set is "autolaunch:", so if any other address is set there will be no autolaunch. You can however include autolaunch in an explicit session bus address as a fallback, for example
DBUSSESSIONBUSADDRESS="something:,autolaunch:" - in that case if the first address doesn't work, processes will autolaunch. (The bus address
variable contains a comma-separated list of addresses to try.) The autolaunch option is considered an internal implementation detail of libdbus, and in fact there are plans to change it. There's no real reason to use it outside of the libdbus implementation anyhow. OPTIONS The following options are supported:
auto-syntax
Choose csh-syntax or sh-syntax based on the SHELL environment variable.
binary-syntax
Write to stdout a nul-terminated bus address, then the bus PID as a binary integer of size sizeof(pidt), then the bus X window ID as a binary integer of size sizeof(long). Integers are in the machine's byte order, not network byte order or any other canonical byte order.
close-stderr
Close the standard error output stream before starting the D-Bus
daemon. This is useful if you want to capture dbus-launch error
messages but you don't want dbus-daemon to keep the stream open to your application.
config-file=FILENAME
Pass config-file=FILENAME to the bus daemon, instead of passing
it the session argument. See the man page for dbus-daemon
csh-syntax Emit csh compatible code to set up environment variables.
exit-with-session If this option is provided, a persistent "babysitter" process will be created that watches stdin for HUP and tries to connect to the X server. If this process gets a HUP on stdin or loses its X connection, it kills the message bus daemon. autolaunch=MACHINEID
This option implies that dbus-launch should scan for a
previously-started session and reuse the values found there. If no session is found, it will start a new session. The
exit-with-session option is implied if autolaunch is given. This option is for the exclusive use of libdbus, you do not want to use it manually. It may change in the future.
sh-syntax
Emit Bourne-shell compatible code to set up environment variables. version
Print the version of dbus-launch help
Print the help info of dbus-launch NOTES
If you run dbus-launch myapp (with any other options), dbus-daemon will not exit when myapp terminates: this is because myapp is assumed to be part of a larger session, rather than a session in its own right. AUTHOR See http://www.freedesktop.org/software/dbus/doc/AUTHORS BUGS
Please send bug reports to the D-Bus mailing list or bug tracker, see http://www.freedesktop.org/software/dbus/
D-Bus 1.10.24 11/02/2018 DBUS-LAUNCH(1)