dbus-launch man page on ElementaryOS

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dbus-launch(1)							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  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 vari‐
       ables so the specified program can find the bus, and then  execute  the
       specified  program,  with the specified arguments.  See below for exam‐

       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 sev‐
       eral   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-syn‐
       tax,  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, you can run	 dbus-
       launch in the background. For instance, in a sh-compatible shell:

	 ## 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 ~/.dbus/ses‐

       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_SES‐
       SION_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 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_SES‐
       SION_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_SES‐
       SION_BUS_ADDRESS="something:,autolaunch:"  -  in that case if the first
       address doesn't work, processes will autolaunch. (The bus address vari‐
       able 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 environ‐
	      ment 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 pass‐
	      ing 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 previ‐
	      ously-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	 vari‐

	      Print the version of dbus-launch

       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.

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

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


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