diff options
Diffstat (limited to 'bitbake/doc')
-rw-r--r-- | bitbake/doc/user-manual/user-manual-metadata.xml | 61 |
1 files changed, 49 insertions, 12 deletions
diff --git a/bitbake/doc/user-manual/user-manual-metadata.xml b/bitbake/doc/user-manual/user-manual-metadata.xml index 23b3fa6..55b59eb 100644 --- a/bitbake/doc/user-manual/user-manual-metadata.xml +++ b/bitbake/doc/user-manual/user-manual-metadata.xml @@ -409,22 +409,59 @@ </note> </section> - <section> - <title>Defining executable metadata</title> - <para><emphasis>NOTE:</emphasis> This is only supported in .bb and .bbclass files. + <section id='functions'> + <title>Functions</title> + + <note> + This is only supported in <filename>.bb</filename> + and <filename>.bbclass</filename> files. + </note> + + <para> + As with most languages, functions are the building blocks + that define operations. + Bitbake supports shell and Python functions. + An example shell function definition is: + <literallayout class='monospaced'> + some_function () { + echo "Hello World" + } + </literallayout> + An example Python function definition is: <literallayout class='monospaced'> -do_mytask () { - echo "Hello, world!" -} + python some_python_function () { + d.setVar("TEXT", "Hello World") + print d.getVar("TEXT", True) + } </literallayout> - This is essentially identical to setting a variable, except that this variable happens to be executable shell code. + In python functions, the "bb" and "os" modules are already + imported, there is no need to import those modules. + The datastore, "d" is also a global variable and always + available to these functions automatically. + </para> + + <para> + Bitbake will execute functions of this form using + the <filename>bb.build.exec_func()</filename>, which can also be + called from Python functions to execute other functions, + either shell or Python based. + Shell functions can only execute other shell functions. + </para> + + <para> + There is also a second way to declare python functions with + parameters which takes the form: <literallayout class='monospaced'> -python do_printdate () { - import time - print time.strftime('%Y%m%d', time.gmtime()) -} + def some_python_function(arg1, arg2): + print arg1 + " " + arg2 </literallayout> - This is the similar to the previous, but flags it as Python so that BitBake knows it is Python code. + The difference is that the second form takes parameters, + the datastore is not available automatically + and must be passed as a parameter and these functions are + not called with the <filename>exec_func()</filename> but are + executed with direct Python function calls. + The "bb" and "os" modules are still automatically available + and there is no need to import them. </para> </section> |