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| author |   Scott Rifenbark <srifenbark@gmail.com> | 2019-04-18 10:37:07 -0700 |
|---|---|---|
| committer |   Richard Purdie <richard.purdie@linuxfoundation.org> | 2019-04-23 16:34:03 +0100 |
| commit | f0d4ef3cdcf803aab2acf3c40dea8bfec44dc01c (patch) | |
| tree | b9b1c57d66937a99fef8bdec95c4c5dc10e5c2d2 /bitbake | |
| parent | c23c8ebc7f66a92110bfc9e3c4d633a432d1353b (diff) | |
| download | openembedded-core-contrib-f0d4ef3cdcf803aab2acf3c40dea8bfec44dc01c.tar.gz | |
bitbake: bitbake-user-manual: Added section on modifying variables
Fixes [YOCTO #12548]
I created a new section titled "Modifying Variable Values" that
provides instruction on how to use the "bitbake -e" command to
be sure your configuration and variable values are as expected.
(Bitbake rev: 5a697957d7687fe2c730896e178f7e1e054fe724)
Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Diffstat (limited to 'bitbake')
| -rw-r--r-- | bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml index 199ab23095..a125ad332e 100644 --- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml +++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml @@ -61,6 +61,78 @@ </para> </section> + <section id='modifying-existing-variables'> + <title>Modifying Existing Variables</title> + + <para> + Sometimes you need to modify existing variables. + Following are some cases where you might find you want to + modify an existing variable: + <itemizedlist> + <listitem><para> + Customize a recipe that uses the variable. + </para></listitem> + <listitem><para> + Change a variable's default value used in a + <filename>*.bbclass</filename> file. + </para></listitem> + <listitem><para> + Change the variable in a <filename>*.bbappend</filename> + file to override the variable in the original recipe. + </para></listitem> + <listitem><para> + Change the variable in a configuration file so that the + value overrides an existing configuration. + </para></listitem> + </itemizedlist> + </para> + + <para> + Changing a variable value can sometimes depend on how the + value was originally assigned and also on the desired + intent of the change. + In particular, when you append a value to a variable that + has a default value, the resulting value might not be what + you expect. + In this case, the value you provide might replace the value + rather than append to the default value. + </para> + + <para> + If after you have changed a variable's value and something + unexplained occurs, you can use BitBake to check the actual + value of the suspect variable. + You can make these checks for both configuration and recipe + level changes: + <itemizedlist> + <listitem><para> + For configuration changes, use the following: + <literallayout class='monospaced'> + $ bitbake -e + </literallayout> + This command displays variable values after the + configuration files (i.e. <filename>local.conf</filename>, + <filename>bblayers.conf</filename>, + <filename>bitbake.conf</filename> and so forth) have + been parsed. + <note> + Variables that are exported to the environment are + preceded by the string "export" in the command's + output. + </note> + </para></listitem> + <listitem><para> + For recipe changes, use the following: + <literallayout class='monospaced'> + $ bitbake <replaceable>recipe</replaceable> -e | grep VARIABLE=" + </literallayout> + This command checks to see if the variable actually + makes it into a specific recipe. + </para></listitem> + </itemizedlist> + </para> + </section> + <section id='line-joining'> <title>Line Joining</title> |