Difference between revisions of "Bitbake Cheat Sheet"

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Revision as of 19:16, 29 November 2012

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 This is a full graphical interface which includes selecting machine, distro, etc. and performing a build
bitbake -u goggle simple graphical interface This is a simple graphical wrapper over the streaming text output of bitbake. It's nice in that it shows collapsible trees for the logs for sub-tasks for each recipe.

.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

}