Bitbake Cheat Sheet

Here are some quick notes on bitbake syntax and rules. For an exhaustive list of functionality, and longer descriptions, see the bitbake manual at: http://docs.openembedded.org/bitbake/html/ (note that this link goes to the OpenEmbedded version of the bitbake manual, which is a version from 2006 as of this writing. A separate (yocto-specific?) bitbake manual is included in source form in the yocto project source directory, under bitbake/doc.)

Command Line options

Here are a few commonly-used command line options.

Option	Meaning
-c <task>	execute <task> for the image or recipe being built. ex: bitbake -c fetch busybox. Some of the possible tasks are: fetch, configure, compile, package, clean
-f	force execution of the operation, even if not required
-v	show verbose output
-DDD	show lots of debug information
-s	show recipe version information
--help	get usage help
-c listtasks <image-or-recipe-name>	show the tasks associated with an image or individual recipe
-g <recipe>	output dependency tree in graphviz format

user interfaces

Bitbake can be used with several different user interfaces. Here are some options:

User interface	Type	NOTES
bitbake <nothing> or "bitbake -u knotty"	scrolling text interface	This is the default user interface
bitbake -u knotty2	fancier text-based interface	This interface updates concurrently processed recipes in-place on text lines
bitbake -u ncurses	text-window based interface	I couldn't figure out how to control or exit this interface
bitbake -u hob	graphical interface
bitbake -u goggle	???

.bb file syntax

This table lists some of the syntax found in recipe (.bb) files.

Syntax	Meaning	NOTES
VAR = "foo"	simple assignment
VAR ?= "foo"	assign if no other value is already assigned (default assignment)
VAR ??=foo	weak default assignment	takes lower precedence than ?=
VAR = "stuff ${OTHER_VAR} more"	variable expansion	OTHER_VAR expanded at time of reference to VAR
VAR := "stuff ${OTHER_VAR} more"	immediate variable expansion	OTHER_VAR expanded at time of parsing this line
VAR += "foo"	append with space
VAR =+ "foo"	prepend with space
VAR .= "foo"	append without space
VAR =. "foo"	prepend without space
VAR_append = "foo"	append without space
OVERRIDES="string1:string2" VAR = "foo" VAR_string1 = "bar"	alternate/override value	if string1 is listed in OVERRIDES, use "bar" for value of VAR, otherwise use "foo"
OVERRIDES="string1:string2" VAR = "foo" VAR_append_string1 = " bar"	conditional append	if string1 is in OVERRIDES, then append " bar" to the value of VAR
BBVERSIONS="1.0 1.8 string" VAR="foo" VAR_string="bar"	range-specific conditional	If the version of the package is in the specified range (1.0-1.8 in this example), then perform an override on the indicated variable
VAR = "foo ${@<line-of-python-code>}"	python code expansion	ex: VAR = "the date is: ${@time.strftime(’%Y%m%d’,time.gmtime())}"
include foo	include file	include file named "foo", search BBPATH
require [<path>]foo	require file	include file named "foo", failing if not found exactly where specified
inherit foo	inherit classes	include definitions from foo.bbclass
do_sometask() { <shell code> }	define a task using shell code
python do_sometask { <python code> }	define a task using python code
addtask sometask (before|after) other_task	add a task	adds a defined task to the list of tasks, with the ordering specified. Zero or more 'before' or 'after' clauses can be used.
VAR[some_flag]="foo"	associate a subsidiary flag value to a variable	a few subsidiary flag value names are well-defined: "dirs", "cleandirs", "noexec", "nostamp", "fakeroot", "umask", "deptask", "rdeptask", "recdeptask", "recrdeptask" Flag values appear to be used exclusively with task definitions (i.e. do_sometask)

additional bitbake-related commands

Command	Description	NOTES
bitbake-layers	Show information about layers and recipes	Included in the bitbake/bin directory in yocto.
bitbake-env	Show invidividual bitbake variable values	see: http://www.crashcourse.ca/wiki/index.php/OE_bitbake-env_utility
bitbake -u depexp	Show dependency information in a graphical interface	}