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X11R7.4 - man page for dbus-launch (x11r4 section 1)

dbus-launch(1)			     General Commands Manual			   dbus-launch(1)

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

       dbus-launch [--version] [--sh-syntax] [--csh-syntax] [--auto-syntax] [--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  informa-
       tion 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.

       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 pass-
       ing --auto-syntax, you may explicity 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.

       Here is an example of how to use dbus-launch with an sh-compatible shell to start the per-
       session bus daemon:

	 ## 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 --exit-with-session`
	     echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"

       You might run something like that in your login scripts.

       Another way to use dbus-launch is to run your main session program, like so:

       dbus-launch gnome-session

       The above would likely be appropriate for ~/.xsession or ~/.Xclients.

       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  ses-
       sion 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 appli-
       cations 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  mecha-
       nism 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="some-
       thing:,autolaunch:" - in that case if the first address doesn't work, processes will auto-
       launch. (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 variable.

	      --binary-syntax 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 order.

	      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 ses-
	      sion. 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

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

       Please send bug reports to the D-Bus mailing list or bug tracker, see http://www.freedesk-


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