7. Variables

We already have seen some variables in Device parameters. But there is more to variables.

7.1. 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 Magic variables). Additional variables can be created with the global (create or set global variables) 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.

7.2. Magic variables

Some variables have special meanings and influence the behaviour of barebox. Most but not all of them are consolidated in the The global device. Since it’s hard to remember which variables these are and if the current barebox has support for them the magicvar (list information about magic variables) 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
...