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dbus-launch(1)									   dbus-launch(1)

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

SYNOPSIS
       dbus-launch [--version] [--sh-syntax] [--csh-syntax] [--auto-syntax] [--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  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
       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 pass-
       ing --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, you can run dbus-launch in the  back-
       ground. 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"
	 fi
       Note  that  in  this  case,  dbus-launch will exit, and dbus-daemon will not be terminated
       automatically on logout.

AUTOMATIC LAUNCHING
       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/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 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.

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(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-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 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.

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

       --version
	      Print the version 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.freedesk-
       top.org/software/dbus/

										   dbus-launch(1)
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