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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 @@ | |||
| 61 | </para> | 61 | </para> |
| 62 | </section> | 62 | </section> |
| 63 | 63 | ||
| 64 | <section id='modifying-existing-variables'> | ||
| 65 | <title>Modifying Existing Variables</title> | ||
| 66 | |||
| 67 | <para> | ||
| 68 | Sometimes you need to modify existing variables. | ||
| 69 | Following are some cases where you might find you want to | ||
| 70 | modify an existing variable: | ||
| 71 | <itemizedlist> | ||
| 72 | <listitem><para> | ||
| 73 | Customize a recipe that uses the variable. | ||
| 74 | </para></listitem> | ||
| 75 | <listitem><para> | ||
| 76 | Change a variable's default value used in a | ||
| 77 | <filename>*.bbclass</filename> file. | ||
| 78 | </para></listitem> | ||
| 79 | <listitem><para> | ||
| 80 | Change the variable in a <filename>*.bbappend</filename> | ||
| 81 | file to override the variable in the original recipe. | ||
| 82 | </para></listitem> | ||
| 83 | <listitem><para> | ||
| 84 | Change the variable in a configuration file so that the | ||
| 85 | value overrides an existing configuration. | ||
| 86 | </para></listitem> | ||
| 87 | </itemizedlist> | ||
| 88 | </para> | ||
| 89 | |||
| 90 | <para> | ||
| 91 | Changing a variable value can sometimes depend on how the | ||
| 92 | value was originally assigned and also on the desired | ||
| 93 | intent of the change. | ||
| 94 | In particular, when you append a value to a variable that | ||
| 95 | has a default value, the resulting value might not be what | ||
| 96 | you expect. | ||
| 97 | In this case, the value you provide might replace the value | ||
| 98 | rather than append to the default value. | ||
| 99 | </para> | ||
| 100 | |||
| 101 | <para> | ||
| 102 | If after you have changed a variable's value and something | ||
| 103 | unexplained occurs, you can use BitBake to check the actual | ||
| 104 | value of the suspect variable. | ||
| 105 | You can make these checks for both configuration and recipe | ||
| 106 | level changes: | ||
| 107 | <itemizedlist> | ||
| 108 | <listitem><para> | ||
| 109 | For configuration changes, use the following: | ||
| 110 | <literallayout class='monospaced'> | ||
| 111 | $ bitbake -e | ||
| 112 | </literallayout> | ||
| 113 | This command displays variable values after the | ||
| 114 | configuration files (i.e. <filename>local.conf</filename>, | ||
| 115 | <filename>bblayers.conf</filename>, | ||
| 116 | <filename>bitbake.conf</filename> and so forth) have | ||
| 117 | been parsed. | ||
| 118 | <note> | ||
| 119 | Variables that are exported to the environment are | ||
| 120 | preceded by the string "export" in the command's | ||
| 121 | output. | ||
| 122 | </note> | ||
| 123 | </para></listitem> | ||
| 124 | <listitem><para> | ||
| 125 | For recipe changes, use the following: | ||
| 126 | <literallayout class='monospaced'> | ||
| 127 | $ bitbake <replaceable>recipe</replaceable> -e | grep VARIABLE=" | ||
| 128 | </literallayout> | ||
| 129 | This command checks to see if the variable actually | ||
| 130 | makes it into a specific recipe. | ||
| 131 | </para></listitem> | ||
| 132 | </itemizedlist> | ||
| 133 | </para> | ||
| 134 | </section> | ||
| 135 | |||
| 64 | <section id='line-joining'> | 136 | <section id='line-joining'> |
| 65 | <title>Line Joining</title> | 137 | <title>Line Joining</title> |
| 66 | 138 | ||