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Bitbake Cheat Sheet

Revision as of 20:46, 30 October 2012 by Tim Bird (Talk | contribs)

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Here are some quick notes on bitbake syntax and rules. For an exhaustive list of functionality, and longer descriptions, see the bitbake manual at: (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

.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 = "foo"
VAR_string1 = "bar"

alternate/override value if string1 is listed in OVERRIDES, use "bar" for value of VAR, otherwise use "foo"

VAR = "foo"
VAR_appends_string1 = " bar"

conditional appending if string1 is in OVERRIDES, then append " bar" to the value of VAR
BBVERSIONS="1.0 1.8 string"


range-specific conditional If the version of the package is in the specified range, the 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)