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man pages section 1: User Commands

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Updated: Wednesday, February 9, 2022

dbus-launch (1)


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


dbus-launch [--version] [--help] [--sh-syntax] [--csh-syntax]
[--auto-syntax] [--binary-syntax] [--close-stderr]
[--exit-with-session] [--autolaunch=MACHINEID]
[--config-file=FILENAME] [PROGRAM] [ARGS...]


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

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

       dbus-launch [--version] [--help] [--sh-syntax] [--csh-syntax]
                   [--auto-syntax] [--binary-syntax] [--close-stderr]
                   [--exit-with-session] [--autolaunch=MACHINEID]
                   [--config-file=FILENAME] [PROGRAM] [ARGS...]

       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

       With no arguments, dbus-launch will launch a session bus instance and
       print the address and PID of that instance to standard output.

       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

       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.

       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 "$DBUS_SESSION_BUS_ADDRESS" ; then
                 ## if not found, launch a new one
                 eval `dbus-launch --sh-syntax`
                 echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"

       Note that in this case, dbus-launch will exit, and dbus-daemon will not
       be terminated automatically on logout.

       If DBUS_SESSION_BUS_ADDRESS 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

       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
       DBUS_SESSION_BUS_ADDRESS 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 DBUS_SESSION_BUS_ADDRESS,
       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
       DBUS_SESSION_BUS_ADDRESS. 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
       DBUS_SESSION_BUS_ADDRESS="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.

       The following options are supported:

           Choose --csh-syntax or --sh-syntax based on the SHELL environment

           Write to stdout a nul-terminated bus address, then the bus PID as a
           binary integer of size sizeof(pid_t), 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

           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.

           Pass --config-file=FILENAME to the bus daemon, instead of passing
           it the --session argument. See the man page for dbus-daemon

           Emit csh compatible code to set up environment variables.

           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.

           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.

           Emit Bourne-shell compatible code to set up environment variables.

           Print the version of dbus-launch

           Print the help info of dbus-launch

       See attributes(7) for descriptions of the following attributes:

       |Availability   | system/library/dbus |
       |Stability      | Uncommitted         |

       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.

       Source code for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-

       This software was built from source available at
       https://github.com/oracle/solaris-userland.  The original community
       source was downloaded from

       Further information about this software can be found on the open source
       community website at http://dbus.freedesktop.org.

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

       Please send bug reports to the D-Bus mailing list or bug tracker, see

D-Bus 1.10.32                     12/21/2021                    DBUS-LAUNCH(1)