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authorRobert P. J. Day <rpjday@crashcourse.ca>2014-07-10 10:12:09 +0300
committerRichard Purdie <richard.purdie@linuxfoundation.org>2014-07-21 11:00:36 +0100
commita18cc69c2fef6484a6acd78ea008d1da71198e68 (patch)
treeb60e1499eb2f2abcdd3f9ff6b416558166f00841
parent877c4c9a466e26953abd6fe416c2cba092607dac (diff)
downloadbitbake-a18cc69c2fef6484a6acd78ea008d1da71198e68.tar.gz
bitbake-user-manual-metadata.xml: Adding some flag examples.
As long as i've understood everything correctly, this is just throwing in some physical examples of a couple concepts. Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
-rw-r--r--doc/bitbake-user-manual/bitbake-user-manual-metadata.xml25
1 files changed, 24 insertions, 1 deletions
diff --git a/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml b/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
index b8a77e1fa..5e1a381fa 100644
--- a/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
+++ b/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
@@ -293,6 +293,17 @@
The flags are immediately set to "abc" and "123", respectively.
The <filename>a</filename> flag becomes "abc456".
</para>
+
+ <para>
+ No need exists to pre-define variable flags.
+ You can simply start using them.
+ One extremely common application
+ is to attach some brief documentation to a BitBake variable as
+ follows:
+ <literallayout class='monospaced'>
+ CACHE[doc] = "The directory holding the cache of the metadata."
+ </literallayout>
+ </para>
</section>
<section id='inline-python-variable-expansion'>
@@ -306,7 +317,19 @@
DATE = "${@time.strftime('%Y%m%d',time.gmtime())}"
</literallayout>
This example results in the <filename>DATE</filename>
- variable becoming the current date.
+ variable being set to the current date.
+ </para>
+
+ <para>
+ Probably the most common use of this feature is to extract
+ the value of variables from BitBake's internal data dictionary,
+ <filename>d</filename>.
+ The following lines select the values of a package name
+ and its version number, respectively:
+ <literallayout class='monospaced'>
+ PN = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE'),d)[0] or 'defaultpkgname'}"
+ PV = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE'),d)[1] or '1.0'}"
+ </literallayout>
</para>
</section>