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Variables
=========
We already have seen some variables in :ref:`device_parameters`. But
there is more to variables.
.. _global_device:
The ``global`` device
---------------------
The ``global`` device is a special purpose device. It only exists as a
storage for global variables. Some global variables are created internally
in barebox (see :ref:`magicvars`). Additional variables can be created with
the :ref:`command_global` command::
global myvar
This creates the ``global.myvar`` variable which now can be used like any
other variable. You can also directly assign a value during creation::
global myvar1=foobar
**NOTE:** creating a variable with ``global myvar1=foobar`` looks very similar
to assigning a value with ``global.myvar1=foobar``, but the latter fails when
a variable has not been created before.
.. _magicvars:
Magic variables
---------------
Some variables have special meanings and influence the behaviour
of barebox. Most but not all of them are consolidated in the :ref:`global_device`
Since it's hard to remember which variables these are and if the current
barebox has support for them the :ref:`command_magicvar` command can print a list
of all variables with special meaning along with a short description::
barebox:/ magicvar
OPTARG optarg for hush builtin getopt
PATH colon separated list of pathes to search for executables
PS1 hush prompt
armlinux_architecture ARM machine ID
armlinux_system_rev ARM system revision
armlinux_system_serial ARM system serial
automount_path mountpath passed to automount scripts
bootargs Linux Kernel parameters
bootsource The source barebox has been booted from
bootsource_instance The instance of the source barebox has been booted from
global.boot.default default boot order
...
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