dbus-launch(1) User Commands dbus-launch(1)NAMEdbus-launch - Utility to start a message bus from a shell script
SYNOPSISdbus-launch [--auto-syntax] [--config-file=filename] [--close-stderr]
[--csh-syntax] [--exit-with-session] [--help] [--sh-syntax] [--version]
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.
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‐
ples.
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-syn‐
tax, you may explicity specify a particular one by using --sh-syntax
for Bourne syntax, or --csh-syntax for csh syntax. In scripts, it is
more robust to avoid --auto-syntax and you hopefully know which shell
your script is written in.
EXTENDED DESCRIPTION
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 application and
what it tries to do.
There are two common reasons for autolaunch. One is ssh(1) 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(1m). 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 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 is no real
reason to use it outside of the libdbus implementation anyhow.
OPTIONS
The following options are supported:
--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 exclu‐
sive use of libdbus, you do not want to use it manually. It may
change in the future.
--auto-syntax
Choose --csh-syntax or --sh-syntax based on the SHELL environment
variable.
--binary-syntax
Write to stdout a null-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 do not 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 connec‐
tion, it kills the message bus daemon.
-?, --help
Show help information on standard output and exit.
--sh-syntax
Emit Bourne-shell compatible code to set up environment variables.
--version
Print the version of dbus-launch.
EXAMPLES
Example 1: How to use dbus-launch with a 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"
fi
Example 2: Use dbus-launch to run your main session program
example% dbus-launch--exit-with-session gnome-session
The above would likely be appropriate for ~/.xsession or ~/.Xclients.
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables:
DBUS_SESSION_BUS_ADDRESS
The address of the login session message bus. If this variable is
not set, applications may also try to read the address from the X
Window System root window property _DBUS_SESSION_BUS_ADDRESS. The
root window property must have type STRING. The environment vari‐
able should have precedence over the root window property.
DBUS_VERBOSE
Set DBUS_VERSION=1 to enable debugging, if D-Bus was compiled with
verbose debug mode enabled.
SHELL
When the --auto-syntax is used, then dbus-launch checks the SHELL
environment variable. If it ends in "csh", then the --csh-syntax
option will be used, otherwise the --sh-syntax will be used.
EXIT STATUS
The following exit values are returned:
0 Application exited successfully
>0 Application exited with failure
FILES
The following files are used by this application:
/usr/bin/dbus-launch Executable for dbus-launch
/etc/dbus-1/session.conf Configuration file for D-Bus session
services.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │system/library/dbus │
├─────────────────────────────┼─────────────────────────────┤
│Interface stability │Volatile │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSO
More information can be found at:
http://www.freedesktop.org/software/dbus/
dbus-cleanup-sockets(1), dbus-daemon(1), dbus-monitor(1), dbus-send(1),
dbus-uuidgen(1), libdbus-glib-1(3), attributes(5), environ(5)NOTES
For authorship information refer to http://www.freedesktop.org/soft‐
ware/dbus/doc/AUTHORS. Updated by Brian Cameron, Sun Microsystems
Inc., 2007.
Please send bug reports to the D-Bus mailing list or bug tracker, see
http://www.freedesktop.org/software/dbus/
SunOS 5.11 25 Feb 2009 dbus-launch(1)
